Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999  (1,948)
  • 1990-1994  (3,277)
  • 1980-1984
  • 1930-1934
  • 1880-1889
  • 1998  (460)
  • 1996  (1,488)
  • 1993  (1,703)
  • 1990  (1,574)
  • Inorganic Chemistry  (2,022)
  • Engineering General  (1,839)
  • Physical Chemistry  (667)
  • Nuclear reactions
  • Physics
  • pharmacokinetics
Source
Material
Years
  • 1995-1999  (1,948)
  • 1990-1994  (3,277)
  • 1980-1984
  • 1930-1934
  • 1880-1889
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    High-dose topotecan with granulocyte-colony stimulating factor in fluoropyrimidine-refractory colorectal cancer: A phase II and pharmacodynamic study (1998)
    Springer
    Annals of oncology 9 (1998), S. 173-180 
    Details
    ISSN: 1569-8041
    Keywords: colorectal cancer ; granulocyte-colony stimulating factor ; pharmacokinetics ; phase II ; topotecan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: The premise for the study was that topotecan (TPT) resistance in preclinical studies is associated with low level expression of the p-glycoprotein (Pgp) multi-drug transporter conferred by the multi-drug resistant (MDR) phenotype, which might be overcome in clinical practice by administering moderately (2.3-fold) higher doses of TPT that have been shown to be feasible with granulocyte colony-stimulating factor (G-CSF) support. This phase II study evaluated the anti-tumor activity of TPT administered at its highest possible solid tumor dose with G-CSF in patients with fluoropyrimdine-refractory advanced colorectal carcinoma. The study also sought to identify pharmacodynamic (PD) determinants of both activity and toxicity. Patients and methods: TPT was administered as a 30-minute infusion daily for five days every three weeks at a dose of 3.5 mg/m2/day to patients with advanced colorectal carcinoma who developed progressive disease either during treatment with fluoropyrimidine-based chemotherapy for advanced disease or within six months after receiving fluoropyrimdine-based adjuvant chemotherapy. This dose of TPT was previously determined to be the maximal tolerated dose (MTD) with G-CSF support in a phase I study involving solid tumor patients with similar risk factors for myelosuppression. Plasma sampling was performed during course 1 to characterize the pharmacokinetic (PK) and PD behavior of TPT. Results: Seventeen patients who received 89 courses of TPT and G-CSF were evaluable for toxicity; 16 patients were evaluable for anti-tumor response. Toxicity, particularly myelosuppression, was substantial. At the 3.5 mg/m2/day dose level, absolute neutrophil counts (ANC) were less than 500/µl for longer than five days in 17% of courses involving seven of 17 (41%) patients. Severe neutropenia associated with fever occurred in 12.3% of courses; and platelet counts below 25,000/µl were noted in 26.9% of courses. These toxicities resulted in dose reductions in seven of 17 (41%) patients. Nevertheless, 90% of the planned total dose of TPT was administered. No major responses were observed, though minor activity was noted in several patients. Both the median time to progression and the median survival time were short – 2.5 and four months, respectively. Although interindividual variability in the disposition of total TPT was observed, the lack of objective responses precluded PD assessments related to disease activity. Total TPT exposure was significantly higher than drug exposure achieved in similar patients at an identical dose in a previous phase I study of TPT and G-CSF, which may explain why more severe myelosuppressive effects occurred in the present study. There were no PD relationships evident between relevant PK parameters and the percent decrements in platelets and ANCs during course 1, although patients with severe toxic effects (ANC below 500/µl for more than five days and/or platelets 〈25,000/µl) had higher drug exposure than patients with less severe toxicity (P 〈 0.018 and P = 0.09, respectively). Conclusions: Based on these results, the true response rate of TPT at its solid tumor MTD with G-CSF support is unlikely to approach 20%. Although a response rate of less than 20% might be viewed as significant in this disease setting and might be confirmed with sufficient statistical certainty by treating additional patients, the substantial toxicity, inconvenience, and cost associated with this high dose TPT/G-CSF regimen does not warrant the acceptance of a lower level of anti-tumor activity as a criterion for further development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008266630701
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    UGT1A1 genotypes and glucuronidation of SN-38, the active metabolite of irinotecan (1998)
    Springer
    Annals of oncology 9 (1998), S. 845-847 
    Details
    ISSN: 1569-8041
    Keywords: genetic polymorphism ; glucuronidation ; irinotecan ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Irinotecan (CPT-11) is metabolized by esterase to form a SN-38, which is further conjugated by UGT1A1. Genetic polymorphism has been shown in a promoter region of UGT1A1 and is related to its activity. We investigated whether there might be an inter-individual difference in pharmacokinetics of SN-38 and its glucuronide, depending on the genotypes of UGT1A1. Patients and methods: Nine male patients with lung cancer were treated with irinotecan (50 mg/m2) and carboplatin. Pharmacokinetic parameters were calculated with full sampling plasma data. Genotypes were determined by analyzing the sequence of TATA box of UGT1A1 of genomic DNA from the patients. Results: The genotyping analysis revealed one heterozygote (6/7) and one homozygote (7/7) for (TA)7TAA allele (UGT1A1*28). The remaining seven patients were homozygote for (TA)6TAA allele (6/6, wild type). The metabolic ratios (SN-38/SN-38 glucuronide) in the patient with 7/7 genotype were uncharacteristically higher than those in the patients with other genotypes (6/6 and 6/7). Biliary index was 6980 versus 2180 ± 1110 (range 840–3730) in patients with 7/7 versus 6/6 genotypes, respectively. Conclusion: These results support the idea that the patient with 7/7 genotype has an impaired capacity for glucuronidation of SN-38.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008438109725
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    A phase I and pharmacologic study of DMP 840 administered by 24-hour infusion (1998)
    Springer
    Annals of oncology 9 (1998), S. 101-104 
    Details
    ISSN: 1569-8041
    Keywords: DMP 840 ; pharmacodynamics ; pharmacokinetics ; phase I
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: DMP 840, a novel bisnaphthalimide, has demonstrated promising schedule dependent anti-tumor activity in vitro and in vivo against several tumor cell lines. A phase I study was conducted to evaluate the effect of a 24-hour infusion schedule repeated every three weeks, on the therapeutic efficacy of DMP 840. Patients and methods: Fourteen patients with refractory solid tumor malignancies were treated with DMP 840 at doses of 20, 40, 50 and 60 mg/m2. Results: A combination of neutropenia, thrombocytopenia and stomatitis were dose-limiting at doses of 50 and 60 mg/m2 in both minimally- and extensively-pretreated patients. In contrast, all courses at lower dose levels were well tolerated. Pharmacokinetic analysis demonstrated that DMP 840 had a prolonged terminal half life (median 39 hours; range 25–86) and that dose-limiting events were significantly related to several indices of systemic DMP 840 exposure (P 〈 0.01, Wilcoxon Rank Sum test). Conclusion: The recommended dose of DMP 840 for further disease oriented evaluations is 40 mg/m2 administered over 24 hours every three weeks. The infusion duration evaluated in this study did not result in a substantial increase in the tolerable dose compared to shorter, less cumbersome schedules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008260515869
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Feasibility and pharmacokinetic study of a chimeric anti-CD20 monoclonal antibody (IDEC-C2B8, rituximab) in relapsed B-cell lymphoma (1998)
    Springer
    Annals of oncology 9 (1998), S. 527-534 
    Details
    ISSN: 1569-8041
    Keywords: CD20 ; chimeric IDEC-C2B8 ; lymphoma ; monoclonal antibody ; pharmacokinetics ; feasibility study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: In clinical trials in the USA, IDEC-C2B8 (a mouse-humanchimeric anti-CD20 monoclonal antibody) has demonstrated high response rateswith only mild toxic effects in relapsed B-cell lymphoma at a dose of fourweekly 375 mg/m2 infusions. The aim of the present trial wasto determine whether or not this dose is practically applicable to Japanesepatients with relapsed B-cell lymphoma with respect to safety,pharmacokinetics and efficacy. Patients and methods: Patients with relapsed CD20+ B-cell lymphomareceived intravenous infusions of IDEC-C2B8 once a week for four weeks. Atotal of 12 patients (four at 250 mg/m2 and eight at 375mg/m2) were enrolled. Results: All 11 eligible patients treated with either dose leveltolerated IDEC-C2B8 well. Commonly observed adverse drug reactions weregrades 1 or 2 non-hematologic toxicities during the infusion, consistingmostly of flu-like symptoms and skin reactions. All of the observedhematologic toxicities were of grade 3 or less, and transient. A rapid andsustained B-cell decrease in peripheral blood was observed, but noinfectious episodes were encountered. Human anti-mouse and anti-chimericantibodies were not detected. Of the 11 eligible patients (eight withfollicular, two with diffuse large-cell and one with mantle cell lymphoma),two showed a complete response and five showed a partial response, and allof the seven responders had lymphoma with follicular histology. Apharmacokinetic analysis showed that the elimination half-life (T1/2) ofIDEC-C2B8 was 445 ± 361 hours, and that the serum antibody levelsincreased in parallel with the course of infusions, and in most patients wasstill measurable at three months. Conclusions: The dose of four weekly 375 mg/m2 infusionsof IDEC-C2B8 is safe and effective in Japanese patients with relapsed B-celllymphoma. Further studies evaluating IDEC-C2B8 are warranted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008265313133
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Basal activity profiles of NPH and [Nɛ-palmitoyl Lys (B29)] human insulins in subjects with IDDM (1998)
    Springer
    Diabetologia 41 (1998), S. 116-120 
    Details
    ISSN: 1432-0428
    Keywords: Keywords Insulin ; pharmacokinetics ; acylated insulin ; NPH ; insulin therapy ; glucose turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary [Ne-palmitoyl Lys (B29)] human insulin is a fatty acid-acylated derivative of insulin with extended action compared to unmodified insulin when infused intravenously (i. v.) secondary to its binding to circulating albumin. The duration and activity profile of the acylated (A) and NPH (B) insulins were assessed following subcutaneous (s. c.) doses of (A) 6 nmol/kg and (B) 1.2 nmol/kg (equivalent to 0.2 U/kg) in 9 subjects with IDDM. After overnight i.v infusion of regular human insulin, morning glucose was (A) 6.9 ± 0.1 and (B) 6.8 ± 0.1 mmol/l. After the s. c. injection, i. v. human insulin or glucose was infused to maintain near-basal glycaemia and tracer glucose to assess hepatic glucose production (HGP). An activity profile was deduced for each study by expressing the glucose infusion rate at each time point, as a fraction (%) of the basal (measured) HGP, and the i. v. insulin infusion rate as a fraction (%) of the basal requirement. The two fractions are combined by adding the fractional glucose infusion rate and subtracting the fractional insulin infusion rate. Infusion rates of i. v. insulin in the morning were (A) 0.96 ± 0.096 and (B) 1.22 ± 0.09 pmol · kg–1· min–1. After insulin injection, i.v insulin requirements decreased and were below 10 % of basal between 100 and 150 min. A constant activity profile of 0 % represents a perfect substitution of the basal i. v. insulin infusion by the s. c. dose. The actual profile is defined by deviations from this (above) and was –17 ± 11, 7 ± 10, –9 ± 6 and –18 ± 18 % for [Ne-palmitoyl Lys (B29)] human insulin and 17 ± 12, 5 ± 6, –9 ± 15, 22 ± 18 % for NPH insulin at 3, 6, 9 and 12 h after s. c. injection. HGP was similar for the two insulins, demonstrating similar metabolic actions and profiles both peripherally and at the liver. [Diabetologia (1998) 41: 116–120]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001250050876
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Ultrasound in vascular pathologies (1998)
    Springer
    European radiology 8 (1998), S. 849-857 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Ultrasound ; Physics ; Vascular studies ; Vascular pathologies ; Ultrasonic contrast agents ; Clinical applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The choice of the optimal ultrasonic frequency for vascular studies is determined by the required resolution and penetration. Anatomical real-time two-dimensional imaging and blood flow studies provide complementary information. Intravascular scanning allows high-frequency ultrasound to be used, with correspondingly good spatial resolution. Contrast resolution is degraded by beam side lobes and the limited dynamic range of the ultrasonic pulse. The physics of ultrasonic scattering by blood, pulsed Doppler and duplex scanning and colour flow imaging performances determines the limits of clinical applications. Contrast agents enhance the echogenicity of blood, improving sensitivity and, through second harmonic detection, suppressing solid tissue echoes. Three-dimensional display, with segmentation by the presence of the flow signal, facilitates spatial perception. Clinical applications in vascular pathologies are summarised.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050482
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Impact of early cyclosporin average blood concentration on early kidney transplant failure (1998)
    Springer
    Transplant international 11 (1998), S. 46-52 
    Details
    ISSN: 1432-2277
    Keywords: Key words Cyclosporin ; pharmacokinetics ; kidney transplantation ; Kidney transplantation ; cyclosporin ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This retrospective study served to examine the correlation between the degree of cyclosporin (CyA) exposure, as estimated by a single pharmacokinetic (PK) profile performed at 1 week post-transplant, and the outcome of 290 consecutive renal transplants performed over a 6-year period. For this retrospective analysis patients were stratified into four historical groups based on 12- versus 24-h PK studies and on the use of radioimmunoassay versus fluorescence polarization immunoassay methods for estimates of CyA concentrations. Four PK measures – trough concentration (C0), average concentration values (Cav; i. e., the dosing interval-corrected area under the concentration-time curve), maximum concentration (Cmax), and time to maximum concentration (tmax) – were examined as predictors of patient, graft, and rejection-free survival rates for each of the four groups individually and for all groups combined. Patients with an initial Cav≥ 550 ng/ml had higher 1-year (88 %) and 6-year (66 %) graft survival rates than patients with Cav 〈 550 ng/ml, who had 1- and 6-year graft survival rates of 80 % and 59 %, respectively (P = NS). Statistically significant differences were observed in graft survival rates between patients with Cav 〈 550 versus Cav≥ 550 ng/ml at 30 (88 % vs 96 %; P 〈 0.02), 60 (85 % vs 94 %; P 〈 0.007), 90 (85 % vs 94 %; P 〈 0.02), and 180 (83 % vs 92 %; P 〈 0.05) days. Moreover, patients with Cav 〈 550 ng/ml displayed more severe rejection episodes, as judged by Banff classification, than patients who displayed Cav≥ 550 ng/ml (grades II and III; 71 % vs 50 %; P = 0.036). In contrast, the C0, Cmax, and tmax values did not correlate with patient, graft, or rejection-free survival rates. The pharmacokinetic parameter of Cav correlated strongly with early graft survival and may, therefore, be a useful predictor of those renal transplant patients who may require more intensive post-transplant monitoring of CyA concentrations by serial PK studies to improve graft survival.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001470050101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Pharmacokinetic and phase I studies of brequinar (DUP 785; NSC 368390) in combination with cisplatin in patients with advanced malignancies (1998)
    Springer
    Investigational new drugs 16 (1998), S. 19-27 
    Details
    ISSN: 1573-0646
    Keywords: phase I ; brequinar ; DUP 785 ; cisplatin ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Brequinar (DUP 785; NSC 368390) is a quinoline carboxylic acid derivative that inhibits pyrimidine synthesis at the level of dihydro-orotate dehydrogenase and revealed synergy with cisplatin in preclinical models. In this study investigating the pharmacokinetic and toxicity of brequinar in combination with cisplatin, patients were initially treated with weekly brequinar, in combination with an every-three-week administration of cisplatin. Due to toxicity, the schedule was modified to a 28-day cycle with brequinar given on days 1, 8, 15, and cisplatin on day 1. A total of 24 patients (16 male, 8 female; median age 57; median performance status 1) received 69 courses of therapy. Six dose levels were explored, with cisplatin/ brequinar doses, respectively, of 50/500, 50/650, 50/860, 60/860, 75/650, and 75/860 mg/m2. The serum concentration versus time curves for brequinar were biphasic. A comparison of the pharmacokinetic results after the first and third doses of brequinar indicate that the presence of 50, 60, and 75 mg/m2cisplatin did not change the protein binding and the pharmacokinetics of brequinar in any of the three brequinar-dose groups. Total cisplatin plasma pharmacokinetic followed a triphasic-shape curve and unbound cisplatin decayed at a very rapid rate. Since pharmacokinetic parameters for total cisplatin in this study were similar to those reported in the literature, the presence of brequinar is unlikely to alter the pharmacokinetics of cisplatin. Main dose-limiting toxicities included myelosuppression (including neutropenia and thrombocytopenia) and mucositis. Cisplatin/brequinar doses of 50/500, 50/650, 50/860, 60/860, 75/650, and 75/860 mg/m2, were associated with dose limiting toxicity in 0/3, 1/3, 1/3, 1/3, 2/4, 2/5, and 4/6 patients, respectively. This study shows that co-administration of brequinar and cisplatin does not affect the pharmacokinetic properties of either drug and that the MTDs of cisplatin/brequinar combinations are 60/860 mg/m2 or 75/650 mg/m2. From this study, we conclude that full dose of 75 mg/m2 cisplatin (day 1) can be administered with 650 mg/m2 brequinar (days 1, 8 and 15) without significant modifications of individual drug pharmacokinetic parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016066529642
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Phase I clinical and pharmacokinetic trial of the podophyllotoxin derivative NK611 administered as intravenous short infusion (1998)
    Springer
    Investigational new drugs 16 (1998), S. 319-324 
    Details
    ISSN: 1573-0646
    Keywords: NK611 ; dimethylaminoetoposide ; Phase I ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Background: NK611 is a novel podophyllotoxin derivative. Compared with etoposide, NK611 carries a dimethyl-amino group at the D-glucose moiety. The antitumor activity of NK611 showed to be equal or superior to etoposide in a variety of in vitro and in vivo tumor models. The aim of our present study was to determine the maximum tolerated dose and the dose-limiting toxicities of NK611 administered as intravenous infusion over 30 min every 28 days. Patients and methods: 45 patients (7 female, 38 male; median age 54 [range 37–73]) were enrolled. In a first stage, NK611 was administered without hematopoietic growth factor support; in a second stage, G-CSF was used for further dose escalation. Toxicities were assessed using WHO-criteria. Results: Initially, the dose was escalated from 60 mg/m2 to 120 mg/m2. In a second patient cohort, doses were further escalated with G-CSF support with doses ranging from 140 mg/m2 to 250 mg/m2. Dose-limiting toxicities were granulocytopenia and thrombocytopenia. Non-hematologic toxicities consisted of alopecia, mild nausea, and infection. Four partial responses were observed: two at 200 mg/m2 (pleural mesothelioma, response duration 7 months, and non-small cell lung cancer, response duration 13 months), and two at 250 mg/m2 (hepatocellular carcinoma, response duration 7 months, and non-small cell lung cancer, response duration 2 months). Pharmacokinetic analyses were performed in all patients. Using an open 3-compartment model, the terminal half-life (t1/2γ) was 14.7 ± 3.7 h. The AUC at 250 mg/m2 was determined to be 330 ± 147 μg/mlh, the plasma clearance of NK611 was 16.2 ± 8.2 ml/min · m2 and the Vss was 16.8 ± 3.3 l/m2. Protein binding of NK611 was 98.7%. Conclusion: the recommended dose for clinical Phase II studies is 120 mg/m2 without G-CSF support and 200 mg/m2 with G-CSF support.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006293830585
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Relative Bioavailability of Carboxyamido-Triazole with Respect to Food and Time of Administration: Use of a Single Model for Simultaneous Determination of Changing Parameters (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 673-687 
    Details
    ISSN: 1573-8744
    Keywords: carboxyamido-triazole ; bioavailability ; chronopharmacology ; pharmacokinetics ; food
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Carboxyamido-triazole (CAI) is an anti-invasive, antimetastatic, antiangiogenic agent in clinical development for cancer treatment. It has been postulated that food might enhance the oral absorption of micronized CAI based on an apparent discrepancy in steady state maximum concentrations when taken without regard to meals vs. fasting. The purpose of this study was to determine if a standardized meal affects the absorption and pharmacokinetics of this agent. Twelve patients with refractory cancers and good end organ function were randomized to receive two doses of CAI (250 mg/m 2 ) with and without a standardized high fat meal. One cohort of 6 patients received these doses at 9 AM, and the remaining 6 patients received CAI at 9 PM. Blood was obtained prior to each dose, and serially thereafter. A series of pharmacokinetic (PK) models were fit to the concentration–time data. PK parameters were ultimately calculated using a model which allows simultaneous estimation of parameters from both test doses using nonlinear least squares analysis with ADAPT II. This model estimates independent absorption rate constants and relative fraction absorbed for each condition. AUC 0–t was determined using the trapezoidal method, extrapolated to infinity, and used to calculate the relative bioavailability. No significant differences in PK parameters were noted between the morning and evening cohorts. However, the relative bioavailability, as measured by AUC 0–∞, of CAI was significantly increased when administered with a high fat meal compared to fasting (138.9 vs. 52.2 μg * hr/ml; p=0.0005). The magnitude of the increase in relative bioavailability of CAI taken with food could have profound implications for patients who may inadvertently take this medication shortly after eating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020750923542
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    A preliminary study of the pharmacokinetics of fenoprofen enantiomers following intravenous administration of the racemate to cats (1998)
    Springer
    Veterinary research communications 22 (1998), S. 203-208 
    Details
    ISSN: 1573-7446
    Keywords: anti-inflammatory ; cat ; enantiomer ; fenoprofen ; NSAID ; pharmacokinetics ; racemic ; stereoselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006077406388
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Some Pharmacokinetic Parameters and Dosage Regimens for a Long-Acting Formulation of Oxytetracycline in 6- to 8-Month-Old Male Calves (1998)
    Springer
    Veterinary research communications 22 (1998), S. 533-544 
    Details
    ISSN: 1573-7446
    Keywords: calves ; dosage regimen ; oxytetracycline ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A two-way crossover study was conducted in crossbred male calves (6–8 months old) to determine the bioavailability, pharmacokinetics and dosage regimens for a long-acting formulation of oxytetracycline (OTC-LA). The half-lives of oxytetracycline after intravenous and intramuscular administration were 7.8 h and 24 h, respectively. The volume of distribution and total body clearance values of the drug were 0.86±0.07 L and 76.1±3.3 (ml/h)/kg, respectively. The maximum concentration of the drug in the serum (4.7–7.4 μg/ml) was achieved 8–10 h after intramuscular administration. The minimum therapeutic serum concentration of drug of ≥0.5 μg/ml was maintained between 15 min and 84 h after intramuscular administration. The intramuscular bioavailability of the drug was 89.1±4.2%. The dosage regimens to maintain the minimum therapeutic serum concentrations of OTC following intramuscular administration of OTC-LA were computed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006193703979
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    The Pharmacokinetics and Efficacy of Long-Term Low-Level and Split-Dose Administration of Albendazole Through In-Feed Formulations against Ovine and Caprine Parasitic Gastroenteritis (1998)
    Springer
    Veterinary research communications 22 (1998), S. 467-477 
    Details
    ISSN: 1573-7446
    Keywords: albendazole ; anthelmintic ; goat ; in-feed ; metabolite ; pharmacokinetics ; sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two trials were conducted against natural and experimentally induced parasitic gastroenteritis in sheep and goats using an in-feed formulation of albendazole to evaluate its therapeutic and prophylactic efficacy. In the first trial, albendazole was incorporated in feed pellets to deliver an average daily dose of 0.7 mg/kg body weight in order to evaluate its prophylactic efficacy. In the second trial, feed pellets were offered to deliver an average total dose of 8.0 mg/kg body weight in two equal split doses in order to evaluate its curative efficacy. Sustained plasma concentrations of the active compound, albendazole sulphoxide, and its metabolite albendazole sulphone, sufficient to prevent establishment of infection, were achieved when the animals were allowed to feed on medicated pellets for 10 consecutive days. The bioavailability of the metabolites of albendazole following the administration of a therapeutic dose in two split doses of the in-feed formulation was sufficient to remove established adult nematodes. The concentrate feed pellets could be used for self-medicating small ruminants for therapeutic use as well as for prophylaxis based on their strategic use appropriate to the epidemiology of the parasitic disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006127132161
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Plasma, Urinary and Biliary Residues in Cattle Following Intramuscular Injection of Nortestosterone Laurate (1998)
    Springer
    Veterinary research communications 22 (1998), S. 479-491 
    Details
    ISSN: 1573-7446
    Keywords: cattle ; nortestosterone ; pharmacokinetics ; residues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The synthetic androgen 19-nortestosterone (β-NT) has been used illegally as a growth promoter in cattle production in the European Union. Elimination of β-NT and its metabolites in plasma, urine and bile was studied in three cattle with cannulated gallbladders following intramuscular injection at a single site of 500 mg of the laurate ester (NTL) containing 300.5 mg β-NT. Using enzyme immunoassay quantification, plasma Cmax of free β-NT was 0.5±0.15 μg/L (mean±SEM). Concentrations of free β-NT in plasma were consistently greater than the assay limit of quantification (0.12 μg/L) for 32.7±13.42 days. Mean residence time for free β-NT in plasma was 68.5±20.75 days. Following sample preparation by immunoaffinity chromatography, high-resolution GC-MS was used to quantify β-NT and α-NT in urine and bile. β-NT was detected irregularly in urine from two of the three animals post injection. The principal metabolite present in the urine, α-NT, was detected for 160.3±22.67 days post injection. Cmax for α-NT in urine was 13.7±5.14 μg/L. Mean urinary AUC0–183 days for α-NT was 845.7±400.90 (μg h)/L. In bile, α-NT was the only metabolite detected for 174.3±8.67 days post treatment. Cmax for α-NT in bile was 40.8±12.70 μg/L and mean biliary AUC0–183 days for α-NT was 1982.6±373.81 (μg h)/L. Concentrations of α-NT in bile samples were greater than those in urine samples taken at the same time. The mean ratio of biliary:urinary AUC0–183 days was 3.0±0.72. It is concluded that bile is a superior fluid for detection of α-NT following injection of NTL, owing to the longer period during which residues may be detected after administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006179116231
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Comparative Disposition Kinetics of Albendazole in Sheep Following Oral and Intraruminal Administration (1998)
    Springer
    Veterinary research communications 22 (1998), S. 545-551 
    Details
    ISSN: 1573-7446
    Keywords: albendazole ; metabolites ; pharmacokinetics ; route of administration ; sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The pharmacokinetics of albendazole was studied in sheep following single oral and intraruminal administration at nematocidal dose rates. The disposition curves of its metabolites indicated increased uptake of the drug in sheep following intraruminal as compared to oral dosing (p〈0.05). The increased bioavailability of benzimidazole anthelmintics given by the intraruminal route could be exploited for optimizing the use of anthelmintic for sustained parasite control in small ruminants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006145820818
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Lumping of Whole-Body Physiologically Based Pharmacokinetic Models (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 21-46 
    Details
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; whole body physiologically based model ; lumping ; system theory ; barbiturates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Lumping is a common pragmatic approach aimed at the reduction of whole-body physiologically based pharmacokinetic (PBPK) model dimensionality and complexity. Incorrect lumping is equivalent to model misspecification with all the negative consequences to the subsequent model implementation. Proper lumping should guarantee that no useful information about the kinetics of the underlying processes is lost. To enforce this guarantee, formal standard lumping procedures and techniques need to be defined and implemented. This study examines the lumping process from a system theory point of view, which provides a formal basis for the derivation of principles and standard procedures of lumping. The lumping principle in PBPK modeling is defined as follows: Only tissues with identical model specification, and occupying identical positions in the system structure should be lumped together at each lumping iteration. In order to lump together parallel tissues, they should have similar or close time constants. In order to lump together serial tissues, they should equilibrate very rapidly with one another. The lumping procedure should include the following stages: (i) tissue specification conversion (when tissues with different model specifications are to be lumped together); (ii) classification of the tissues into classes with significantly different kinetics, according to the basic principle of lumping above; (iii) calculation of the parameters of the lumped compartments; (iv) simulation of the lumped system; (v) lumping of the experimental data; and (vi) verification of the lumped model. The use of the lumping principles and procedures to be adopted is illustrated with an example of a commonly implemented whole-body physiologically based pharmacokinetic model structure to characterize the pharmacokinetics of a homologous series of barbiturates in the rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023272707390
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Population Pharmacokinetic Analysis of Mizolastine and Validation from Sparse Data on Patients Using the Nonparametric Maximum Likelihood Method (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 133-161 
    Details
    ISSN: 1573-8744
    Keywords: mizolastine ; pharmacokinetics ; population analysis ; zero-order absorption ; heteroscedastic variance ; NPML ; validation ; predictive distributions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A population analysis of the kinetics of mizolastine was performed from concentrations on 449 allergic patients, using the nonparametric maximum likelihood method (NPML). A two-compartment open model with zero-order absorption was used to describe the kinetics of mizolastine after oral administration. A heteroscedastic variance model was assumed for the error. To explain the kinetic variability, eight covariates were introduced in the analysis: gender, pharmaceutical dosage form, age, body weight, serum creatinine concentration, creatinine renal clearance, plasma levels of hepatic transaminases ASAT and ALAT. Their relationships to the kinetic parameters were studied by means of the estimated distribution of each kinetic parameter conditional on different levels of each covariate. An important interindividual kinetic variability was found for all parameters. Moreover, several kinetic parameters among which the duration of absorption were found to be influenced by pharmaceutical dosage form and gender. Body weight and creatinine renal clearance were found to have a little influence on the oral clearance and the smallest disposition rate constant. This population analysis was validated on a separate group of 247 other patients. For each observed concentration of this sample, a predictive distribution was computed using the individual covariates. Predicted concentrations and standardized prediction errors were deduced. The mean and variance of the standardized prediction errors were, respectively, 0.21 and 2.79. Moreover, in the validation sample, the predicted cumulative distribution function of each observed concentration was computed. Empirical distribution of these values was not significantly different from a uniform distribution, as expected under the assumption that the population model estimated by NPML is adequate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020505722924
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Rapid Attainment of Steady State Plasma Drug Concentrations Within Precise Limits (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 319-328 
    Details
    ISSN: 1573-8744
    Keywords: anesthetic techniques ; continuous infusion ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We describe a method of rapidly obtaining a specified steady state plasma concentration of an intravenous drug within precise limits. The technique requires an initial bolus to raise the plasma concentration to the upper limit followed by a series of constant-rate infusions each of which is associated with a minimum plasma concentration equal to the tower limit. The infusion rate is stepped down when the plasma concentration returns to the upper limit. Computer simulation, based on the method, is used to generate plasma concentration–time curves with fluctuations of up to 10% about selected steady state concentrations of amrinone, esmolol, lidocaine, midazolam, propofol, and theophylline. The utility of this general approach to intravenous dosing and potential limitations of the method are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023285426388
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Fourth-Generation Model for Corticosteroid Pharmacodynamics: A Model for Methylprednisolone Effects on Receptor/Gene-Mediated Glucocorticoid Receptor Down-Regulation and Tyrosine Aminotransferase Induction in Rat Liver (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 289-317 
    Details
    ISSN: 1573-8744
    Keywords: methylprednisolone ; pharmacokinetics ; pharmacodynamics ; indirect response models ; glucocorticoid receptor ; tyrosine aminotransferase ; Northern hybridization ; mRNA ; down-regulation ; receptor recycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A fourth-generation pharmacokinetic/pharmacodynamic (PK/PD) model for receptor/genemediated effects of corticosteroids was developed. Male adrenalectomized Wistar rats received a 50 mg/kg iv bolus dose of methylprednisolone (MPL). Plasma concentrations of MPL, hepatic glucocorticoid receptor (GR) messenger RNA (mRNA) and GR density, tyrosine aminotransferase (TAT) mRNA, and TAT activity in liver were determined at various time points up to 72 hr after MPL dosing. Down-regulation of GR mRNA and GR density were observed: GR mRNA level declined to 45–50% of the baseline in 8–10 hr, and slowly returned to predose level in about 3 days; GR density fell to 0 soon after dosing and returned to the baseline in two phases. The first phase, occurring in the first 10 hr, entailed recovery from 0 to 30%. The second phase was parallel to the GR mRNA recovery phase. Two indirect response models were applied for GR mRNA dynamics regulated by activated steroid-receptor complex. A full PK/PD model for GR mRNA/GR down-regulation was proposed, including GR recycling theory. TAT mRNA began to increase at about 1.5 hr, reached the maximum at about 5.5 hr, and declined to the baseline at about 14 hr after MPL dosing. TAT induction followed a similar pattern with a delay of about 1–2 hr. A transcription compartment was applied as one of the cascade events leading to TAT mRNA and TAT induction. Pharmacodynamic parameters were obtained by fitting seven differential equations piecewise using the maximum likelihood method in the ADAPT II program. This model can describe GR down-regulation and the precursor/product relationship between TAT mRNA and TAT in receptor/gene-mediated corticosteroid effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023233409550
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Optimal Experimental Design for Precise Estimation of the Parameters of the Axial Dispersion Model of Hepatic Elimination (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 595-615 
    Details
    ISSN: 1573-8744
    Keywords: optimal design ; hepatic elimination models ; parameter estimation ; protein binding ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The axial dispersion model of hepatic drug elimination is characterized by two dimensionless parameters, the dispersion number, DN , and the efficiency number, RN , corresponding to the relative dispersion of material on transit through the organ and the relative efficiency of elimination of drug by the organ, respectively. Optimal design theory was applied to the estimation of these two parameters based on changes in availability (F) of drug at steady state for the closed boundary condition model, with particular attention to variations in the fraction of drug unbound in the perfusate (fuB ). Sensitivity analysis indicates that precision in parameter estimation is greatest when F is low and that correlation between RN and DN is high, which is desirable for parameter estimation, when DN lies between 0.1 and 100. Optimal design points were obtained using D-optimization, taking into account the error variance model. If the error variance model is unknown, it is shown that choosing Poisson error model is reasonable. Furthermore, although not optimal, geometric spacing of fuB values is often reasonable and definitively superior to a uniform spacing strategy. In practice, the range of fuB available for selection may be limited by such practical considerations as assay sensitivity and acceptable concentration range of binding protein. Notwithstanding, optimal design theory provides a rational approach to precise parameter estimation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023229318017
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Single-Dose Pharmacokinetics of Rifapentine in Women (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 75-85 
    Details
    ISSN: 1573-8744
    Keywords: rifapentine ; pharmacokinetics ; gender differences ; female
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gender can be an important variable in the absorption and disposition of some drugs. In this open-label study, 15 healthy, nonsmoking women received a single 600-mg oral dose of rifapentine. Plasma samples were obtained at frequent intervals for up to 72 hr after the dose to determine the pharmacokinetic (PK) parameters of rifapentine and its active metabolite, 25-desacetyl-rifapentine. Peak plasma rifapentine concentrations (Cmax ) were observed 5.9 hr after ingestion of the single dose. The mean area under the rifapentine plasma concentration–time curve [AUC(0 → ∞ )] was 325 μg · hr ml and the mean elimination half-life (t1/2 ) was 16.3 hr. Plasma concentrations for the 25-desacetyl metabolite peaked at 15.4 hr after the rifapentine dose and declined with a terminal half-life of 17.3 hr. These rifapentine and 25-desacetyl-rifapentine PK data in women were compared to data generated previously in healthy men. Striking similarities in the PK profiles of parent drug and metabolite were found in the two populations. Mean differences in rifapentine CL/F (12%) and t1/2 (2%) were small. The only adverse event reported in the female subjects was discoloration of the urine. Based on these PK and safety data, no dosage adjustments for rifapentine based on gender are recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023276808298
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    Pharmacokinetic and Pharmacodynamic Evaluation for Tissue-Selective Inhibition of Cholesterol Synthesis by Pravastatin (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 329-347 
    Details
    ISSN: 1573-8744
    Keywords: HMG-CoA reductase inhibitors ; pravastatin ; tissue-selectivity ; cholesterol synthesis ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The tissue-selective inhibition of cholesterol synthesis by pravastatin was evaluated pharmacokinetically and pharmacodynamically. Plasma, tissue, urine, and bile concentrations were measured after iv bolus injection of pravastatin to rats at various doses. The total body clearance and steady state volume of distribution decreased with increasing dose. A saturable biliary excretion was also observed. The time course of plasma and liver concentrations was described by a three-compartment model, consisting of a central compartment, a deep compartment with an nonsaturable uptake process, and a shallow compartment with saturable uptake and nonsaturable elimination processes. It suggests that a mechanism for the decrease in the total body clearance and distribution volume might be explained by a saturation of pravastatin uptake into the liver. Plasma concentration data after oral administration was also fitted to the same model by connecting an absorption compartment to the shallow compartment. The inhibitory activity of pravastatin against cholesterol synthesis in liver could be related to the concentration in the shallow compartment via a sigmoidal Emax model and the obtained pharmacodynamic parameters were comparable to those in vitro. Results suggest that the carrier-mediated hepatic uptake of pravastatin is actually responsible for the hepatoselective inhibition of cholesterol synthesis under physiological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023237510458
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Mathematical Formalism and Characteristics of Four Basic Models of Indirect Pharmacodynamic Responses for Drug Infusions (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 385-408 
    Details
    ISSN: 1573-8744
    Keywords: pharmacodynamics ; pharmacokinetics ; indirect response models ; infusions ; inhibition ; stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Indirect response models require differential equations to describe the nonlinear inhibition or stimulation of the production or loss (kout ) of the response variable. Partially integrated solutions for these models developed previously for iv bolus or biphasic pharmacokinetics were extended to consider drug infusions for limited or extended durations. Qualitative examination was made of the role of infusion rate and duration, type and rate of drug disposition, Imax or Smax capacity factors, IC50 or SC50 sensitivity factors, and kout values. Properties of the response curves characterized include curve shapes, maximum or minimum response, onset rate, steady-state, and return to baseline. Some comparisons were made with behavior of iv bolus doses. These relationships provide both a formal and practical basis for better understanding of the time-course of basic indirect response models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021060000789
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Integrated Pharmacokinetic–Pharmacodynamic Model for Acetaminophen, Ibuprofen, and Placebo Antipyresis in Children (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 559-579 
    Details
    ISSN: 1573-8744
    Keywords: acetaminophen ; age ; antipyretic ; fever ; ibuprofen ; pediatrics ; pharmacokinetics ; pharmacodynamics ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A descriptive profile for antipyretic drug action has been documented for children. However, a linked pharmacokinetic–pharmacodynamic (PK/PD) model is central to the understanding of antipyretic drug action in febrile children. This was examined for previously reported data from 178 febrile children who received a single oral dose of acetaminophen (APAP) (12.5 mg/kg), ibuprofen (IBU) (5 or 10 mg/kg), or placebo. Rectal temperatures and plasma levels (μg/ml) of APAP and IBU were measured for up to 12 hr after drug administration. Nonlinear regression analyses were applied to these measurements and yielded simultaneous solutions of an integrated one-compartment PK, link, and SigmoidEmax effect model in 102/153 febrile children given APAP or IBU. The PK parameters (tlag ,ka , β,T1 / 2β ,AUC0–∞ ,Vd/F,andClp/F) were not different than those reported previously, except the APAPka was significantly lower. The link component yieldedkeo s of 0.58±0.06 (X±SE), 0.70±0.11 and 0.57 ± 0.11 hr -1 for APAP, IBU05, and IBU10, respectively: the SigmoidEmax component yieldedEC50 s (μg/ml) and sigmoidicity (γ) of 4.63±0.39 and 3.98±0.42 for APAP, 11.33±1.35 and 3.97±0.58 for IBU05 and 12.83±1.89 and 4.27±0.63 for IBU10. On visual inspection of the efficacy–time profiles of the febrile children, a number of them had an apparent linear function (slope; Δ°C/hr) and/or a sinusoidal cyclic function “confounding” standard approaches to PD analysis. Thus, the temperature profiles of 91/102 children given APAP or IBU required the addition of a slope (Δ°C/hr) and/or a sinusoidal cyclic function to the SigmoidEmax component to fit the data satisfactorily. All 22 children given a placebo also required a slope and/or a cyclic function in their PD model. The residual Δ°Cs (observed-predicted) of the placebo group were not significantly different from 0. Thus, no placebo antipyretic effect was observed. Dose dependency of IBUAUC0–∞ was confirmed; doubling the dose from 5 to 10 mg/kg increased theAUC0→∞ by only 1.5-fold. The confounding effect of initial temperature (Tempi ) on antipyretic efficacy in all treatment groups except placebo was also confirmed to expose nonlinear pharmacodynamics. A significant (p=0.03) contribution ofTempi (but not age) on the value of the slope function was found. There was no consistent effect of age orTempi , on the cyclic component of the integrated model of antipyresis. In addition, a multiple linear relationship of age andTempi was observed with a large number of the PK, link, and PD variables in those who received IBU. Dose, age, andTempi interacted with β in a significant multiple linear relationship withAUC0–∞ . The effects of IBU dose, age, andTempi are pervasive and cascade down the chain of events leading to the PD response. The etiology of pyresis may create the slope function, the magnitude of which may be partially due to the underlying disease. In some cases, the cyclic function may be explained by temperature regulation. Regardless of their cause, both confound analysis of drug action and make the simple, unmodified SigmoidEMax effect model less than satisfactory for interpretation of antipyretic drug effects. The influence of Tempi on the magnitude of antipyretic drug response is also a finding with major impact on PD investigations of antipyretic medications. In children receiving IBU, dose and age are also confounders, in addition toTempi . A multiplicity of covariables must be taken into account when developing appropriate dosing regimens for these antipyretics in febrile children.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023225217108
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Dose-Dependence and Repeated-Dose Studies for Receptor/Gene-Mediated Pharmacodynamics of Methylprednisolone on Glucocorticoid Receptor Down-Regulation and Tyrosine Aminotransferase Induction in Rat Liver (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 619-648 
    Details
    ISSN: 1573-8744
    Keywords: methylprednisolone ; pharmacokinetics ; pharmacodynamics ; indirect pharmacodynamic response models ; glucocorticoid receptor ; Northern hybridization ; mRNA ; down-regulation ; tyrosine aminotransferase ; dose dependence ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dose-dependent and repeated-dose effects of methylprednisolone (MPL) on down-regulation of glucocorticoid receptor messenger RNA (GR mRNA) and GR density, as well as tyrosine aminotransferase (TAT) mRNA and TAT induction by receptor/gene-mediated mechanisms in rat liver were examined. A previously developed pharmacokinetic/pharmacodynamic (PK/PD) model was used to design these studies which sought to challenge the model. Three groups of male adrenalectomized Wistar rats received MPL by iv injection: low-dose (10 mg/kg at Time 0), high-dose (50 mg/kg at Time 0), and dual-dose (50 mg/kg at Time 0 and 24 hr). Plasma concentrations of MPL, and hepatic content of free GR, GR mRNA, TAT mRNA, and TAT activity were determined. The P-Pharm program was applied for population analysis of MPL PK revealing low interindividual variation in CL and Vc values (3–14%). Two indirect response models were applied to test two competing hypotheses for GR mRNA dynamics. Indirect Pharmacodynamic Response Model I (Model A) where the complex in the nucleus decreases the transcription rate of GR mRNA better described GR mRNA/GR down-regulation. Levels of TAT mRNA began to increase at 1–2 hr, reached a maximum at 5–6 hr, and declined to the baseline at 12–14 hr after MPL dosing. The induction of TAT activity followed a similar pattern with a delay of about 1–2 hr. The low-dose group had 50–60% of the TAT mRNA and TAT induction compared to the high-dose group. Since the GR density returned to about 70% of the baseline level before the second 50 mg/kg dose at 24 hr, tolerance was found for TAT mRNA/TAT induction where only 50–60% of the initial responses were produced. Our fourth-generation model describes the dose dependence and tolerance effects of TAT mRNA/TAT induction by MPL involving multiple-step signal transduction controlled by the steroid regimen, free GR density, and GR occupancy. This model may provide the foundation for studying other induced proteins or enzymes mediated by the similar receptor/nuclear events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020746822634
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Characterization of Pharmacodynamic Recession Slopes for Direct and Indirect Response Models (1998)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 26 (1998), S. 409-436 
    Details
    ISSN: 1573-8744
    Keywords: pharmacodynamic recession slope ; Hill function ; k · m product ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Direct pharmacologic effects are known to recede over time with largely linear slopes (Levy's k · m product, J. Pharm. Sci. 53: 342, 1964) and indirect responses have similar behavior. Pharmacodynamic slope properties were examined mathematically for the Hill function with monoexponential drug disposition and simulations were carried out for other pharmacokinetic functions. Both types of pharmacodynamic profiles exhibit a single terminal inflection point (fp) when drug concentrations exceed the EC50 (that concentration causing one-half maximum effect, Emax ). For direct effects it was found that Cfp (the drug concentration at fp) =EC50 , the determinants of inflection time were identified, and Slopefp = −λzγEmax /4 where λz is the terminal disposition slope and γ is the Hill coefficient. These characteristics were explored for the four basic indirect response models which also exhibit recession profiles with slight sigmoidity and a single terminal inflection point at higher doses. The drug concentration at inflection Cfp is ≤IC50 or SC50 (drug concentrations causing half-maximal inhibition or stimulation), while the inflection response (Rfp ) attains constant values at larger doses. Indirect Response Models I, III, and IV have nearly linear return slopes for a wide range of doses which are governed by the disposition slope λz of the drug, loss constant kout of the response, maximum inhibition (Imax ) or stimulation (Smax ) factors, and a unique fractional constant (0〈G≤1). Model II exhibits more complex behavior with recession slopes which are less likely to be parallel for various doses. Most indirect responses are expected to show nearly linear recession slopes which are parallel for moderate to large doses and mainly governed by an identical combination of pharmacokinetic (λz ), system (kout ), and dynamic capacity factors (Imax or Smax ).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021012117627
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    Effects of Intestinal and Hepatic Metabolism on the Bioavailability of Tacrolimus in Rats (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1609-1613 
    Details
    ISSN: 1573-904X
    Keywords: tacrolimus ; bioavailability ; metabolism ; intestine ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Tacrolimus, an immunosuppressive agent, has poor and variable bioavailability following oral administration in clinical use. We investigated the contribution of intestinal metabolism to the first pass effect of tacrolimus in rats. Methods. Tacrolimus was administered intravenously, intraportally or intraintestinally to rats. Blood samples were collected over a 240-min period, and blood tacrolimus concentrations were measured. The extraction ratios of tacrolimus in the intestine and liver were investigated. In addition, the metabolism of tacrolimus in the everted sacs of the small intestine was examined. Results. The rate of absorption of tacrolimus in the intestine was rapid, and tacrolimus was almost completely absorbed after intestinal administration. The bioavailability of tacrolimus was about 40% and 25% after intraportal and intraintestinal administration, respectively, indicating that tacrolimus is metabolized in both the intestine and the liver. In addition, tacrolimus was significantly metabolized in the everted sacs of the rat intestine. Conclusions. The present study suggested that the metabolism of tacrolimus in the intestine contributes to its extensive and variable first pass metabolism following the oral administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011967519752
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Human Drug Absorption Kinetics and Comparison to Caco-2 Monolayer Permeabilities (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 47-52 
    Details
    ISSN: 1573-904X
    Keywords: permeability ; oral absorption ; Caco-2 cells ; pharmacokinetics ; human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. This study aims to assess the drug absorption kinetics of three drugs and compare their resulting first-order intestinal permeation rate constants to their Caco-2 monolayer permeabilities. Methods. In vitro dissolution — in vivo absorption analysis was conducted on four formulations of each ranitidine HC1, metoprolol tartrate, and piroxicam to yield apparent and "true” human clinical permeation rate constants. Drug permeability coefficients through Caco-2 monolayers were also determined. Results. In vitro dissolution — in vivo absorption analysis revealed different relative and absolute contributions of dissolution and intestinal permeation to overall drug absorption kinetics for various drug formulations and yielded estimates of each drug's true and apparent human intestinal permeation rate constant [k p = 0.225 hr−1, 0.609 hr−l, and 9.00 hr−1 for ranitidine, metoprolol, and piroxicam, respectively]. A rank order relationship was observed for both the apparent and true permeation rate constant with Caco-2 monolayer permeability. The decrease in the true permeation rate constant relative to the apparent permeation rate constant was most significant (almost three-fold) for the least permeable compound, ranitidine. Conclusions. There were marked differences in the permeation kinetics of ranitidine, metoprolol, and piroxicam. The possibility of an association between absorption kinetics from dosage forms in humans and Caco-2 monolayer permeability may allow for a direct kinetic interpretation of human oral absorption from Caco-2 monolayer permeability values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011992518592
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Rapid Determination of Oral Pharmacokinetics and Plasma Free Fraction Using Cocktail Approaches: Methods and Application (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 93-97 
    Details
    ISSN: 1573-904X
    Keywords: cocktail dosing ; pharmacokinetics ; plasma free fraction ; ultrafiltration ; HPLC/APCI/MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To apply cocktail approaches for protein binding (PB) and pharmacokinetics (PK) within a discovery program as a means of providing timely systemic exposure (AUC and Cmax) data. Methods. For PB data, a procedure of cocktail ultrafiltration, mixed matrix sample preparation and single quadrupole atmospheric pressure ionization LC/MS analysis was used. In vivo PK studies consisted of 4 experimental compounds and a control compound dosed orally at 1 mg/kg (5 mg/kg total dose), with plasma samples obtained at 0.5, 1, 2, 4 and 8 h post dose. For PB and in vivo PK analysis, a control compound was tested within each cocktail to ensure consistent reproducibility. Results. Approximately 2 weeks were spent comparing single and cocktail approaches to determine the feasibility of this method for this project. Comparisons of cocktail data with single compound data revealed no significant differences between the approaches. The oral AUC values ranged from 0.01 to 9.28 μg⋅hr/ml and the Cmax values ranged from 0.04 to 2.17 μg/ml. Free fractions of the 44 compounds studied ranged from 0.006 to 0.271. Using the free fraction values to correct for free AUC and Cmax results in ranges of 0.001 to 0.473 μg⋅hr/ml, and 0.001 to 0.119 μg/ml, respectively. Conclusions. All 44 compounds tested had similar potencies in vivo. Thus, these results suggest that a respective 400 and 100-fold range in AUC and Cmax corrected for free fraction exist in the presence of comparable in vivo activity. The ability to generate this type of data in a timely manner allowed the selection of a candidate with low peripheral exposure relative to the effective dose. The free fraction and PK data on the 44 compounds described was collected within three work days by 2 lab scientists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011909022226
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Elucidation of Human Amphotericin B Pharmacokinetics: Identification of a New Potential Factor Affecting Interspecies Pharmacokinetic Scaling (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1630-1636 
    Details
    ISSN: 1573-904X
    Keywords: amphotericin B ; pharmacokinetics ; human ; gender-differences ; disposition function differences ; interspecies scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To elucidate the pharmacokinetics of amphotericin B in rats, mice and humans, and to perform interspecies scaling to humans using allometry. Methods. Plasma concentrations following intravenous bolus administration in rats, and mice were determined by HPLC. Human pharmacokinetic parameters elucidated from literature data were validated in a preliminary study involving a patient receiving daily infusion dose for 27 days. A critical literature review was conducted to identify appropriate pharmacokinetic parameter values in other species for interspecies scale-up. Interspecies allometric scale-up was performed across mice, rats, rabbits and dogs and the resulting predictions in humans were compared to observed values. Results. A triexponential decline in rat, mouse and human plasma concentrations were observed. No gender differences in rat pharmacokinetics were observed. In contrast to allometry, mouse CL was smaller (82 vs 116 ml/h/kg) and T0.5 (33 vs 20 h) was longer compared to rat. In the preliminary human study, Cpeak and Cmin values remained relatively constant over the duration of therapy, and a CL, MRT, T0.5, Vss and Vdarea of 26 ml/h/kg, 10 and 23 days, 6.2 and 20 L/kg, respectively, were estimated. The relative contributions of the terminal phase area in rat, mouse and human were 75%, 92% and 31%, respectively. Interspecies allometric scale-up predictions of human CL (41 ml/h/kg), CLu (467 ml/h/kg) and Vss (3.3 L/kg) were similar to reported values, whereas poor predictions of human Vuss (33 L/kg), Vdarea (4.1 L/kg) and T0.5 (3 days) were obtained. Conclusions. Insignificant accumulation in humans inspite of the long terminal T0.5 was rationalized to be due to the small terminal-phase area contribution. While human CL and Vss were sucessfully predicted in the interspecies scaling, poor predictions of human Vdarea and T0.5 were obtained, which was attributed to disposition pattern differences between humans and other species, a potential new critical factor affecting interspecies scale-up.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011923704731
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    Immediate and Long-Term Effects of 5,7-Dihydroxytryptamine on Rat Striatal Serotonergic Neurons Measured Using In Vivo Voltammetry (1998)
    Springer
    Neurochemical research 23 (1998), S. 1-6 
    Details
    ISSN: 1573-6903
    Keywords: 5,7-Dihydroxytryptamine ; intracerebroventricular administration ; serotonin release ; in vivo voltammetry ; pharmacokinetics ; striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The immediate and long-term effects of the selective serotonergic neurotoxin 5,7-dihydroxytryp-tamine (5,7-DHT) on rat striatal serotonergic neurons were examined after its intracerebroventricular administration using in vivo voltammetry. Extracellular concentration of 5-hydroxyindoles increased immediately following intracerebroventricular 5,7-DHT injection (200 μg in 24 μl, 18 min), peaked at 1.5-2 h, and returned to normal by 4 h. 5,7-DHT diffused to the contralateral striatum in detectable amounts 9 to 12 min after the start of injection and returned to basal levels by 1.5 h. Three to 6 days after 5,7-DHT lesions, 5-hydroxytryptophan administration produced an increase in striatal 5-hydroxyindoles that was greater than that produced in pre-lesioned rats. This effect was maximal at 14 to 17 days post-lesion, and remained even after 50 days. The short-term effect of 5,7-DHT may be attributable to increased serotonin release, inhibition of uptake, or monoamine oxidase inhibition. The long-term effect of 5,7-DHT lesions may attributable to increased synthesis of serotonin or decreased reuptake in remaining serotonergic neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022460216822
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    Nephrologic complications of drug therapy in the elderly (1998)
    Springer
    Geriatric nephrology and urology 8 (1998), S. 29-44 
    Details
    ISSN: 1573-7306
    Keywords: aged ; contrast sensitivity ; drug toxicity ; hyperkalemia ; pharmacokinetics ; renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008203008239
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Guide for judicious use of the paracetamol absorption technique in a study of gastric emptying rate of liquids (1998)
    Springer
    Journal of gastroenterology 33 (1998), S. 785-791 
    Details
    ISSN: 1435-5922
    Keywords: Key words: gastric emptying rate ; paracetamol (acetaminophen) ; pharmacokinetics ; rate of absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: The paracetamol absorption technique, a widely used method for evaluating the gastric emptying rate of liquids, appears to be performed inappropriately, resulting from a lack of consideration of pharmacokinetics in paracetamol absorption. This review suggests that appropriate study designs and logical choice of the parameters for the rate of paracetamol absorption are the cornerstone of reliable investigation of gastric emptying using the paracetamol method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005350050177
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Mixing in Stars and the Evolution of the 3He Abundance (1998)
    Springer
    Space science reviews 84 (1998), S. 199-206 
    Details
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005027519798
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    A phase I and pharmacokinetic trial of terephthalamidine (NSC 57155) as a 120-hour continuous infusion (1998)
    Springer
    Investigational new drugs 16 (1998), S. 57-67 
    Details
    ISSN: 1573-0646
    Keywords: phase I ; pharmacokinetics ; terephthalamidine ; NSC 57155 ; phthalanilides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract In this phase I study, terephthalamidine was administered as a 120-hour continuous infusion repeated every 21 days. Thirteen patients received 27 courses of terephthalamidine at four dose levels (14, 28, 46, and 70 mg/m2/day). Dose-limiting toxicity consisted of profound and intractable anorexia, weight loss and prostration in all patients. Toxicity was delayed and accompanied by hyponatremia and hypokalemia. No hematologic or other toxicity was documented. One patient with adenocarcinoma of the lung had a 40% decrease in mediastinal lymph nodes and resolution of a pleural effusion lasting 2 months. Pharmacokinetic analysis by HPLC was performed in all patients during their first course. The harmonic mean terminal half-life for terephthalamidine was 23 hours with a plasma clearance of 1.7 l/hr/m2. Both plasma concentrations achieved during infusion (r2 = 0.9) and area under the curve (AUC) (r2 = 0.8) were proportional to increase in dose (p 〈 0.002). Renal excretion accounted for 64% of the total cumulative dose, with an average renal clearance of 1.16 l/hr/m2. Due to the unacceptable toxicity seen at all doses with this schedule, no further studies are recommended unless the mechanism of toxicity is better understood and can be prevented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006003718255
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Effect of Particle Size and Charge on the Disposition of Lipid Carriers After Intratumoral Injection into Tissue-isolated Tumors (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 128-132 
    Details
    ISSN: 1573-904X
    Keywords: pharmacokinetics ; tissue-isolated tumor ; liposome ; emulsion ; intratumoral injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Pharmacokinetic properties of various lipid carriers (liposome and emulsions) after intratumoral injection were studied in perfusion experiments using tissue-isolated tumor preparations of Walker 256 carcinosarcoma. Methods. Four types of lipid carriers, large emulsion (254 nm), small emulsion (85 nm), neutral liposomes (120 nm) and cationic liposomes (125 nm) were prepared. We quantified their recovery from the tumor, leakage from the tumor surface and venous outflow after intratumoral injection into perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model. Results. In contrast to the small emulsion and neutral liposomes, which immediately appeared in the venous outflow perfusate following intratumoral injection, the appearance of the cationic liposomes and the large emulsion was highly restricted, clearly demonstrating that intratumoral clearance of these formulations can be greatly retarded by the cationic charge and large particle size, respectively. The venous appearance rate-time profiles were fitted to equations derived from a two-compartment model by nonlinear regression analysis. When the calculated parameters were compared among these four formulations, the venous appearance rate did not exhibit such a large difference; however, the rate of transfer from the injected site to the compartment which involves clearance by venous outflow was all very different. Conclusions. The results of this study indicate that the determining factor which alters the pharmacokinetic properties of these lipid carriers after intratumoral injection is not the rate of transfer from the interstitial space to the vascular side but the rate of intratumoral transfer from the injection site to the well-vascularized region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011921324952
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Estimation of Oral Bioavailability of a Long Half-Life Drug in Healthy Subjects (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1782-1786 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; pharmacokinetics ; squalene synthase inhibitor ; prodrug
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To estimate and compare the oral bioavailability of a drug (BMS-187745) administered as single doses of oral solution of either the parent drug or its prodrug (BMS-188494). Methods. A single-dose, two-period, three-treatment, control-balanced, residual-effect, incomplete block crossover study was completed in 16 healthy male subjects. All subjects received a 10 mg IV infusion of BMS-187745, and a single oral dose of either BMS-187745 (PO1) or BMS-188494 (PO2). A model is proposed to calculate the oral bioavailability of BMS-187745 which has a long half-life; incomplete data points were available to characterize its elimination phase. The plasma concentration-time data obtained following IV infusion of parent drug, and after administration of either PO1 or PO2 treatment were fitted simultaneously with systemic pharmacokinetic parameters shared by both the oral and IV routes of administration. Results. The best simultaneous fittings of the plasma concentration-time data were obtained by using a biexponential pharmacokinetic model with a first-order absorption rate constant. The mean bioavailability (F) values of BMS-187745 estimated by the proposed model were 26.5% and 2.6% when given as oral solution of its prodrug and as the parent drug. The coefficient of variation (CV) of these F values are reasonable, ranging from 38−40%. In contrast, F calculated by the model-independent AUC method exhibited high CV, ranging from 111−120%. Conclusions. The oral bioavailability values estimated by the proposed model were more reasonable compared to those calculated by the model-independent AUC method. The proposed approach may be useful for estimating bioavailability of long half-life drugs when incomplete data points are available to characterize their elimination phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011977116543
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Risedronate Gastrointestinal Absorption Is Independent of Site and Rate of Administration (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 228-232 
    Details
    ISSN: 1573-904X
    Keywords: risedronate ; gastrointestinal absorption ; gastrointestinal site ; bisphosphonate ; administration rate ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Two studies were conducted to compare the absorption of risedronate administered as a solution to three different gastrointestinal sites (study A) and to determine the extent of absorption of risedronate solution administered by rapid and slow infusion to the second part of the duodenum (study B). Methods. Each study was designed as a single-dose, crossover (three periods, study A; two periods, study B) trial in healthy male subjects, with a 14-day washout period between dosing. Subjects fasted overnight before drug administration and for 4 hours after drug administration. In study A, a risedronate solution of 40 mg in 30 mL of water was administered directly into the stomach, the second part of the duodenum, or the terminal ileum over 1 minute via a nasoenteral tube in a three-period crossover design. In study B, a risedronate solution of 40 mg in 30 mL of water was administered directly into the second part of the duodenum over 1 minute and over 1 hour in a randomized, two-period crossover design. Serum and urine samples were obtained for 48 hours after dosing for risedronate analysis. Results. Eight subjects completed each study. No statistically significant site-specific differences in any pharmacokinetic parameter were observed (study A). Based on the area under the serum concentration-time profile and the amount of drug excreted in the urine unchanged, the extent of risedronate absorption did not differ significantly following a rapid or a slow infusion (study B). Only minor symptomatic complaints were reported by subjects, such as headaches and body aches. Conclusions. These studies indicate that the rate and extent of risedronate absorption are independent of the site of administration along the gastrointestinal tract, and that the extent of absorption is not affected by the rate of administration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011910517200
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    Use of the Stable Isotopes Technique to Evaluate the Bioavailability of a Pharmaceutical Form of Magnesium in Man (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 347-351 
    Details
    ISSN: 1573-904X
    Keywords: magnesium ; absolute bioavailability ; stable isotopes ; pharmacokinetics ; ICP-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011947525377
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Blood-Brain Barrier Equilibration of Codeine in Rats Studied with Microdialysis (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 570-575 
    Details
    ISSN: 1573-904X
    Keywords: microdialysis ; codeine ; morphine ; blood-brain barrier ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of the study was to investigate the distribution of codeine across the blood-brain barrier (BBB) in rats by micro-dialysis (MD). Methods. Rats were administered intravenous infusion of codeine in doses of (1) 10 mg/kg, (2) 20 mg/kg for 10 min, and (3) an exponential infusion for 2 h aiming at a plasma concentration of 2500 ng/ml, in a crossover design (n = 6). Microdialysis was used to determine codeine unbound concentrations in blood and brain extracellular fluid (ECF). Total brain tissue and plasma concentrations were also determined. Nalorphine was used as a calibrator for measurement of in vivo recovery. Results. Relative recovery and retrodialysis loss of codeine and nalorphine were similar both in vitro and in vivo. Codeine was rapidly transported into the brain ECF with identical influx and efflux clearance across the BBB. The AUC ratios of brain to blood were 0.99 ± 0.25 and 0.95 ± 0.16 for Dose 1 and 2, respectively. The Css ratio of brain to blood was 1.06 ± 0.12 for the exponential infusion. The half-lives were 25 ± 4 min, 22 ± 2 min in blood and 27 ± 5 min, 25 ± 5 min in brain for Dose 1 and Dose 2, respectively. Total brain tissue concentrations were 3.6 ± 1.2-fold higher than the unbound concentrations in brain. Codeine was demethylated to morphine with an unbound AUCbIood,morphine/AUCblood,codeine ratio of 7.7 ± 5.1% in blood. No morphine was detected in brain MD, but total concentrations were possible to measure. Conclusions. Codeine rapidly reached a distributional equilibrium with equal unbound concentrations in blood and brain. The brain transport of codeine did not show any dose-dependency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011929910782
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    Pulmonary Bioavailability of a Phosphorothioate Oligonucleotide (CGP 64128A): Comparison with Other Delivery Routes (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 583-591 
    Details
    ISSN: 1573-904X
    Keywords: administration ; antisense ; bioavailability ; gastrointestinal ; intra-peritoneal ; intra-tracheal ; ISIS 3521 ; oligonucleotide ; oral ; pharmacokinetics ; subcutaneous
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Phosphorothioate antisense oligodeoxynucleotides are promising therapeutic candidates. When given systemically in clinical trials they are administered via slow intravenous infusion to avoid their putative plasma concentration-dependent haemodynamic side-effects. In this study, we have evaluated alternative parenteral and non-parenteral administration routes which have the potential to enhance the therapeutic and commercial potential of these agents. Methods. The delivery of CGP 64128A by intravenous, subcutaneous, intra-peritoneal, oral and intra-tracheal (pulmonary) routes was investigated in rats using radiolabelled compound and supported by more specific capillary gel electrophoretic analyses. Results. Intravenously administered CGP 64128A exhibited the rapid blood clearance and distinctive tissue distribution which are typical for phosphorothioate oligodeoxynucleotides. Subcutaneous and intra-peritoneal administration resulted in significant bioavailabilities (30.9% and 28.1% over 360 min, respectively) and reduced peak plasma levels when compared with intravenous dosing. Administration via the gastrointestinal tract gave negligible bioavailability (〈2%). Intra-tracheal administration resulted in significant but dose-dependent bioavailabilities of 3.2, 16.5 and 39.8% at 0.06, 0.6 and 6.0 mg/kg, respectively. Conclusions. Significant bioavailabilities of CGP 64128A were achieved following subcutaneous, intra-peritoneal and intra-tracheal administration. Pulmonary delivery represents a promising mode of non-parenteral dosing for antisense oligonucleotides. The dose-dependent increase in pulmonary bioavailability suggests that low doses may be retained in the lungs for local effects whereas higher doses may be suitable for the treatment of a broader spectrum of systemic diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011934011690
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Skin Mini-Erosion Sampling Technique: Feasibility Study with Regard to Serial Glucose Measurement (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 883-888 
    Details
    ISSN: 1573-904X
    Keywords: transdermal access ; skin erosion ; transdermal ; dermal interstitial fluid ; sampling ; glucose ; monitoring ; diabetes mellitus ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To describe a dermally non-invasive serial sampling technique and to test its clinical feasibility with regard to glucose measurement. Methods. A standardized skin mini-erosion devoid of the epidermal barrier, and covered by an artificial one, was formed by a suctioning technique. Interstitial fluid (IF) was extracted serially by brief application of negative pressure, and its glucose content compared with that in capillary or venous blood samples. Results. The procedure caused no discomfort. The epidermis regenerated rapidly after experimentation. There were no complications. In non-diabetic subjects (n = 13) the mean of all IF values measured daily for 6 days was 6.2 ± 0.1 mmol/1 (±SE). The corresponding capillary blood glucose value was 5.6 ± 0.1 mmol/1, and the venous glucose value was 5.4 ± 0.1 mmol/1. The differences between IF glucose values and invasive control values remained within narrow limits throughout. The 2SD limits of agreement for the differences were 1.44 mmol/1 (IF vs. capillary blood samples) and 1.76 mmol/1 (IF vs venous samples) respectively. The OGTT curves suggested glucose kinetics to be similar in IF and in capillary blood. In diabetic subjects, the mean of IF values determined serially during one day was 15.3 ± 1.0 mmol/1 (range, 6.7−21.8 mmol/1), and the corresponding mean capillary value was 12.0 ± 0.9 mmol/1 (range, 3.3−17.2 mmol/1). The ICC for all paired photometric observations was 0.948. Conclusions. The results suggest the new sampling technique to be a feasible approach for clinical and experimental purposes. A functionally integrated sampling patch is entering the clinical testing stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011924631680
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Biodistribution of a Nucleotide-Based Thrombin Inhibitor in Rats (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 904-910 
    Details
    ISSN: 1573-904X
    Keywords: GS522 ; oligodeoxynucleotide ; pharmacokinetics ; tritiated ; biodistribution ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To characterize the pharmacokinetic and tissue distribution profiles of a nucleotide-based thrombin inhibitor (GS522, phosphodiester oligonucleotide, GGTTGGTGTGGTTGG) following intravenous administration to rats. Methods. Pharmacokinetic study: 10 mg/kg, 20 mg/kg, 30 mg/kg (6 animals/dose) were administered to rats by rapid injection into the femoral vein. Blood samples were collected over a 45 minute period. Plasma concentrations of GS522 were determined using capillary gel electrophoresis with laser-induced fluorescence detection. Biodistribution Study: l0mg/kg (400μl, 31.46 μCi/ml) of 3H-GS522 was administered to rats by rapid injection into the femoral vein. The animals were sacrificed by decapitation at 1, 5, 10, 30, 60, 360 minutes post-dose (3 rats/point). Brain, blood, duodenum, eyes, heart, kidney, liver, lungs, muscle, pancreas, skin, spleen and vein samples were collected, processed and quantitated using liquid scintillation counting. Results. The pharmacokinetic profile declines in multiexponential manner, exhibiting extremely fast distribution and elimination (t1/2 = 7.6−9.0 min, Cl = 22.0−28.0 ml/min, V = 83.9−132.4 ml/kg). GS522 follows linear pharmacokinetics, with the area under the curve being proportional to the dose (Rsq = 0.9744). Highest radioactivity levels were detected in kidney, liver and blood (39.7, 15.7 and 15.3% dose/ respective organ). Less than 1% of the dose was detected in the heart, spleen and lungs, and 〉0.3% of the dose was found in the brain and eyes. The oligonucleotide associated radioactivity was uniformly distributed between the brain regions (left and right lobe and cerebellum). Six hours following the dose administration a statistically significant increase (p 〈 0.05) in radioactivity levels was observed in the brain, eyes, skin, liver, pancreas and vein. Conclusions. The pharmacokinetic and biodistribution profiles of GS522 following intravenous administration to rats at three doses were characterized. The oligonucleotide associated radioactivity was widely distributed in tissues. The amount of radioactivity sharply decreased with time in most tissues. Kidney, liver and muscle were the main sites of accumulation. The oligonucleotide associated radioactivity did not cross the blood brain barrier to an appreciable extent. In addition, a statistically significant increase (p 〈 0.05) in the radioactivity levels observed in select tissues suggested a re-uptake mechanism for intact oligonucleotide or its degradation products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011980716659
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Lack of In Vivo/In Vitro Correlations for 50 mg and 250 mg Primidone Tablets (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1085-1089 
    Details
    ISSN: 1573-904X
    Keywords: primidone ; bioavailability ; human ; pharmacokinetics ; in vitro dissolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine if large differences in the in vitro dissolution profiles for primidone tablets would result in significant bioavailability differences. Methods. Two separate bioavailability studies were conducted. The first study used 18 healthy subjects and compared the bioavailability of an old 50 mg tablet formulation, a new 50 mg tablet formulation, and a suspension containing 50 mg/ml of primidone. The second study enrolled 24 subjects who were to receive a new 250 mg tablet formulation, two lots of an old 250 mg tablet formulation and a 250 mg tablet from a second manufacturer. In vitro dissolution was conducted over 90 minutes, using USP 23 Apparatus 2 at 50 rpm, with 900 ml of water. Results. Dissolution at 90 minutes for the old and new 50 mg tablets was approximately 20% and 100%, respectively. The dissolution of the four 250 mg tablets ranged from approximately 30% to 100%. The 50 mg tablet that dissolved slower had a longer Tmax and a 14% lower Cmax than the more rapidly dissolving tablet, but the AUC(0−∞) values differed by only 3%. Only nine subjects completed the 250 mg study because of side effects. The differences in Cmax and AUC(0−∞) among the four 250 mg tablets were less than 7%. Conclusions. Even though there were large differences in the in vitro dissolution of the 50 mg and the 250 mg primidone tablets, the two 50 mg tablets were shown to be bioequivalent, as were the four 250 mg tablets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011942530288
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Guar Gum-Based Sustained Release Diltiazem (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1196-1201 
    Details
    ISSN: 1573-904X
    Keywords: guar gum ; sustained release ; extended release ; diltiazem ; dissolution ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. This study was performed to examine the use of guar gum to sustain the release of diltiazem under in vitro and in vivo conditions. Methods. Guar gum tablet formulations were prepared and evaluated under a variety of in vitro dissolution conditions. The formulations, along with Dilacor XR®, were administered to a group of eight fasted, healthy volunteers in a four period crossover study. Results. Varying the lot of guar gum as well as using guar from different suppliers had little effect on diltiazem dissolution. Also, dissolution of diltiazem from guar gum tablets was essentially independent of stir speed under normal conditions (USP Apparatus II). The stability of guar-based formulations under stressed conditions (40°C/75% relative humidity for 3 months) was also established. All four formulations gave similar plasma concentrations over time in the healthy volunteers pharmacokinetic study. Conclusions. Guar gum-based matrix tablets represent a simple and economical alternative to existing diltiazem sustained release dosage forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011931622536
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Pharmacokinetic and Pharmacoimmunodynamic Interactions Between Prednisolone and Sirolimus in Rabbits (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1888-1894 
    Details
    ISSN: 1573-904X
    Keywords: prednisolone ; sirolimus ; immunosuppressant ; interaction ; pharmacokinetics ; pharmacodynamics ; rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To assess pharmacokinetic and pharmacoimmunodynamic interactions between prednisolone (Pred, 1 mg/kg) and sirolimus (Sir, 0.25 mg/kg) in rabbits. Methods. After intravenous administration, plasma concentrations of Pred and corticosterone, and Sir blood concentrations were followed for 24 hours along with blood granulocyte and T-helper cell counts. Ex vivo and in vitro whole blood lymphocyte proliferation marked lymphocyte reactivity. Results. Pred terminal half-life and clearance were 1.1 hr and 0.72 l/ hr/kg with no difference after Sir. Sir values were 13 hr and 0.16 1/hr/ kg and Pred produced no changes. Corticosterone production (0−12hr) was suppressed by 55% after Pred alone or combined, while Sir did not cause adrenal suppression. Blood T-helper cells and granulocytes displayed circadian rhythms after placebo. Over 12 hr, T-helper cell counts were decreased by Pred (40%) and Sir (19%) while granulocyte numbers increased by 56% and 23%. After coadministration, cell numbers were similar to Pred alone. Pred and Sir decreased lymphocyte reactivity by 41% and 56% over 24 hr and their combination reached 85% inhibition with additive interaction. In vitro studies showed antagonistic or synergistic interactions depending on drug concentration ratios. Conclusions. At therapeutic concentrations, Sir and Pred do not significantly interact pharmacokinetically and have additive pharmacoimmunodynamics. Thus, the therapeutic application of this combination is promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011966308791
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and Leukocyte Responses of Recombinant Human Interleukin-10 (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1895-1901 
    Details
    ISSN: 1573-904X
    Keywords: IL-10 ; cytokines ; protein ; immunosuppression ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the pharmacokinetics and ex vivo leukocyte responses of recombinant human IL-10 (rHuIL-10) following single SC and IV dosing. Methods. A randomized two-way cross-over study was undertaken in 17 healthy volunteers in which rHuIL-10 was administered as 25 μg/ kg SC and IV doses. Blood samples were collected for 48 hr after dosing to determine serum IL-10 concentrations. Inhibitory activity of IL-10 on ex vivo production of inflammatory cytokines (TNF-α and IL-1β) by LPS-treated peripheral blood cells were measured over 96 hr. Results. A physiologically-relevant modeling approach was developed to determine the pharmacokinetics for two routes of administration (SC and IV). The IV dose showed polyexponential disposition with CL of 65 mL/kg/hr, Vss of 70 mL/kg, and t1/2 of 1.94 hr. Absolute bioavailability averaged 42% for SC dosing which produced lower but sustained concentrations. Substantial and prolonged suppression of TNF-α and IL-1β production was achieved during IL-10 treatment. The Hill Function was used to account for the joint concentration-dependent immunosuppressive action of rHuIL-10 after both IV and SC doses. The IC50 values were about 0.03 ng/mL and Imax values were about 0.85 for both TNF-α and IL-lβ suppression. The degree of change as well as the duration of leukocyte response was greater after SC administration than after IV administration. Conclusions. rHuIL-10 shows favorable PK/PD characteristics especially by theSC route of administration which produced prolonged suppression of cytokine production (ex vivo) which may be applicable in various immune-related disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011918425629
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    Influence of Different Fat Emulsion-Based Intravenous Formulations on the Pharmacokinetics and Pharmacodynamics of Propofol (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 442-448 
    Details
    ISSN: 1573-904X
    Keywords: propofol ; pharmacokinetics ; pharmacodynamics ; rats ; EEG ; fat emulsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The influence of different intravenous formulations on the pharmacokinetics and pharmacodynamics of propofol was investigated using the effect on the EEG (11.5-30 Hz) as pharmacodynamic endpoint. Methods. Propofol was administered as an intravenous bolus infusion (30 mg/kg in 5 min) or as a continuous infusion (150 mg/kg in 5 hours) in chronically instrumented male rats. Propofol was formulated as a 1% emulsion in an Intralipid 10%®-like fat emulsion (Diprivan-10®, D) or as a 1%- or 6% emulsion in Lipofundin® MCT/LCT-10% (Pl% and P6%, respectively). EEG was recorded continuously and arterial blood samples were collected serially for the determination of propofol concentrations using HPLC. Results. Following bolus infusion, the pharmacokinetics of the various propofol emulsions could adequately be described by a two-compart-mental pharmacokinetic model. The average values for clearance (Cl), volume of distribution at steady-state (Vd,ss) and terminal half-life (t1/2, λ2) were 107 ± 4 ml/min/kg, 1.38 ± 0.06 l/kg and 16 ± 1 min, respectively (mean ± S.E., n = 22). No significant differences were observed between the three propofol formulations. After continuous infusion these values were 112 ± 11 ml/min/kg, 5.19 ± 0.41 l/kg and 45 ± 3 min, respectively (mean±S.E., n = 20) with again no statistically significant differences between the three propofol formulations. Comparison between the bolus- and the continuous infusion revealed a statistically significant difference for both Vd,ss and t1/2, λ2 (p 〈 0.05), whereas Cl remained unchanged. In all treatment groups infusion of propofol resulted in a burst-suppression type of EEG. A profound hysteresis loop was observed between blood concentrations and EEG effect for all formulations. The hysteresis was minimized by a semi-parametric method and resulted in a biphasic concentration-effect relationship of propofol that was described non-parametrically. For P6% a larger rate constant onset of drug effect (t,1/2, keo) was observed compared to the other propofol formulations (p〈0.05). Conclusions. The pharmacokinetics and pharmacodynamics of propofol are not affected by to a large extent the type of emulsion nor by the concentration of propofol in the intravenous formulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011980432646
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    Effect of GF120918, a Potent P-glycoprotein Inhibitor, on Morphine Pharmacokinetics and Pharmacodynamics in the Rat (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 599-605 
    Details
    ISSN: 1573-904X
    Keywords: morphine ; morphine-3-glucuronide ; P-glycoprotein ; pharmacokinetics ; pharmacodynamics ; antinociception ; central nervous system ; analgesia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The objective of this study was to evaluate the effect of a potent P-gp inhibitor, GF120918, on the systemic pharmacokinetics and antinociceptive pharmacodynamics of a single intravenous dose of morphine in rats. Methods. Male Sprague-Dawley rats received either 500 mg base/kg/d GF120918 or vehicle for 4 days by gavage, or no pretreatment. On day 4, morphine was administered as a 1- or 2-mg/kg i.v. bolus. Antinociception, expressed as percent of maximum possible response (%MPR), was evaluated over 300 min after morphine administration. Serial blood samples were collected and analyzed for morphine and morphine-3-glucuronide (M3G) by HPLC. Results. Morphine clearance and distribution volume were not altered significantly by GF120918. M3G AUC in the GF120918-treated rats was approximately 2-fold higher than in vehicle-treated rats. For both morphine doses, %MPR and the area under the effect-time curve at 300 min were significantly higher in the GF120918-treated rats. A pharmacokinetic/pharmacodynamic effect model accurately described the effect-concentration data for the rats that received 1-mg/kg morphine; ke0 was significantly smaller for GF 120918- vs. vehicle-treated and control rats (0.060 ± 0.028 vs. 0.228 ± 0.101 vs. 0.274 ± 0.026 min−1, p=0.0023). EC50 and γ were similar between treatment groups. Conclusions. Pretreatment with GF 120918 enhanced morphine antinociception, as assessed by the hot-lamp tail-flick assay, and elevated systemic M3G concentrations in rats. The differential pharmacologic response to morphine in the GF120918-treated animals could not be attributed to alterations in systemic morphine pharmacokinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011938112599
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    Receptor Occupancy in Myocardium, Adrenal Cortex, and Brain by TH-142177, a Novel AT1 Receptor Antagonist in Rats, in Relation to Its Plasma Concentration and Hypotensive Effect (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 911-917 
    Details
    ISSN: 1573-904X
    Keywords: angiotensin II receptor antagonist ; TH-142177 ; rat tissues ; ex vivo receptor occupancy ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the relationship between angiotensin II (All) receptor occupancy ex vivo in tissues plasma concentration and hypotensive effect of a novel All receptor antagonist, TH-142177 and losartan in rats. Methods. At 2, 8 and 24 hr after oral administration of TH-142177 and losartan in rats, All receptors in myocardium, adrenal cortex and cerebral cortex were determined by radioligand binding assay using [125I]Sar1,Ile8-AII. Plasma concentrations of both drugs and metabolite in rats were also measured using validated HPLC assays. Further, systolic blood pressure (SBP) in conscious renal hypertensive rats treated orally with TH-142177 and losartan were measured by using a tail cuff plethysmographic method. Results. Oral administration of TH-142177 (1.8 and 5.5 μmol/kg) and losartan (6.5 and 21.7 μmol/kg) in rats brought about dose-dependent decreases in [125I]Sar1,Ile8-AII binding sites (Bmax) in myocardium and adrenal cortex. The extent of receptor occupancy by both drugs in adrenal cortex was maximal at 2 hr later but that in myocardium at 8 hr later. Further, the receptor occupancy was more sustained in myocardium than adrenal cortex. The ex vivo binding affinity of TH-142177 for All receptors in these tissues was roughly three times higher than that of losartan. Also, cerebral cortical [125I]Sar1,Ile8-AII binding was significantly reduced by oral administration of losartan but not by TH-142177. The time course of All receptor occupancy by both drugs in adrenal cortex appeared to be in parallel with that of their plasma concentrations, while the time course in myocardium correlated with that of their hypotensive effects rather than plasma concentrations. Conclusions. TH-142177 produced a relatively selective and sustained occupancy ex vivo of All receptors in myocardium and adrenal cortex of rats with approximately three times greater potency than losartan. Its time course of myocardial receptor occupancy was in parallel with that of hypotensive effect rather than plasma concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011932800729
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    Correction for Non-Ideal Tracer Pharmacokinetic Disposition by Disposition Decomposition Analysis (DDA) (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1469-1473 
    Details
    ISSN: 1573-904X
    Keywords: drug tracer ; labeling ; pharmacokinetics ; erythropoietin ; iodination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Pharmacokinetic (PK) studies assume that the tracer's PK is equivalent to the parent compound. This assumption is often violated. The aim of this work is to present a method enabling the ideal tracer PK, i.e. the PK of the parent compound, to be predicted from the non-ideal tracer. Methods. The procedure uses a disposition decomposition-recomposition (DDR) that assumes that the labeling mainly changes the elimination kinetics while the distribution kinetics is not significantly affected. In the DDR procedure an elimination rate constant correction factor (kCOR) is determined from a simultaneously fitting to plasma concentration data resulting from an i.v. injection of both the tracer and the parent compound. The correction factor is subsequently used to predict the ideal tracer PK behavior from the disposition function (i.v. bolus response) of the non ideal tracer. Results. The DDR method when applied to plasma level data of erythropoietin (r-HuEPO) and its iodinated tracer (l25I-r-HuEPO) from a high (4000U/kg) and a low (400U/kg) dosing of r-HuEPO in newborn lambs (n = 13) resulted in excellent agreements in the elimination rate corrected dispositions in all cases (r = 0.995, SD = 0.0095). The correction factor did not show a dose dependence (p 〉 0.05). The correction factors were all larger than 1 (kCOR = 1.94, SD = 0.519) consistent with a reduction in the EPO elimination by the iodination labeling. Conclusions. The DDR tracer correction methodology produces a better differentiation of the PK of endogenously produced compounds by correcting for the non-ideal PK behavior of chemically produced tracers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011922209757
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Correlation of Plasma Clearance of 54 Extensively Metabolized Drugs Between Humans and Rats: Mean Allometric Coefficient of 0.66 (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 1474-1479 
    Details
    ISSN: 1573-904X
    Keywords: plasma clearance ; unbound plasma clearance ; inter-species scale-up in plasma clearance ; allometric analysis ; pharmacokinetics ; rat vs. human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate the distribution of allometric exponents for relationship of total plasma clearance of 54 extensively metabolized drugs, with wide-ranging linear clearance values, between humans and rats, to provide a rationale for the observed data, and to discuss potential significance of the findings. Methods. Human and rat plasma clearance values of 54 drugs with markedly different physicochemical properties were obtained from the literature. Standard allometric analysis was performed for each drug using both rat and human data. Unbound vs. total plasma clearances were obtained for 15 out of 54 drugs and their correlations between humans and rats were compared. Results. The mean ± SD of the allometric exponent for the 54 drugs studied is 0.660 ± 0.190. The median clearance ratio based on unit body weight is 7.41 and the median exponent is 0.645. Excluding two outliers the correlation coefficient of plasma clearance between humans and rats was 0.745 (p 〈 0.0001). For the 15 drugs, use of unbound plasma clearance approach seems to significantly improve the correlation coefficient compared to total plasma clearance (0.940 vs. 0.841). Conclusions. The present study indicates that on average, humans and rats may eliminate extensively metabolized drugs at a rate similar to that expected from the allometric or body surface area relationship of basal metabolic rate between the two species. A simple statistical distribution hypothesis is used to rationalize the species difference in plasma drug clearance. Rat may serve as an useful animal model to predict (unbound) plasma clearance of drugs in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011974226596
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    Combined Use of Carboxyl-Directed Protein Pegylation and Vector-Mediated Blood-Brain Barrier Drug Delivery System Optimizes Brain Uptake of Brain-Derived Neurotrophic Factor Following Intravenous Administration (1998)
    Springer
    Pharmaceutical research 15 (1998), S. 576-582 
    Details
    ISSN: 1573-904X
    Keywords: pegylation ; blood-brain barrier ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Peptide drug delivery to the brain requires optimization of (a) plasma pharmacokinetics and (b) blood-brain barrier (BBB) permeability. In the present studies, plasma pharmacokinetics are improved with protein pegylation and BBB transport is facilitated with the use of vector-mediated drug delivery using the OX26 monoclonal antibody (MAb) to the rat transferrin receptor, which undergoes receptor-mediated transcytosis through the BBB in vivo. Methods. A conjugate of OX26 and streptavidin (SA), designated OX26/SA, was prepared in parallel with the carboxyl-directed pegylation of brain-derived neurotrophic factor (BDNF). A novel bifunctional polyethyleneglycol (PEG) was used in which a hydrazide (Hz) was attached at one end and a biotin moiety was attached to the other end. This allowed for conjugation of BDNF-PEG-biotin to OX26/SA. Results. The brain uptake of BDNF-PEG-biotin was increased following conjugation to OX26/SA to a level of 0.144 ± 0.004% injected dose per g brain and a BBB permeability-surface area product of 2.0 ± 0.2 μL/min/g. Conclusions. These studies demonstrate that peptide drug delivery to the brain can be achieved with advanced formulation of protein-based therapeutics. The formulation is intended to (a) minimize rapid systemic clearance of the peptide, and (b) allow for vector-mediated drug delivery through the BBB in vivo. Following this dual formulation, the brain uptake of a neurotrophin such as BDNF achieves a value that is approximately 2-fold greater than that of morphine, a neuroactive small molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011981927620
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Preliminary observations on the pharmacokinetics of CDRI compound 81/470 in calves (1998)
    Springer
    Veterinary research communications 22 (1998), S. 67-72 
    Details
    ISSN: 1573-7446
    Keywords: anthelmintic ; benzimidazole ; calf ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005939328885
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    The disposition kinetics of albendazole following the administration of single and divided doses to cattle and buffalo (1998)
    Springer
    Veterinary research communications 22 (1998), S. 87-96 
    Details
    ISSN: 1573-7446
    Keywords: anthelmintic ; albendazole ; buffalo ; cattle ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Concentrations of albendazole sulphoxide and its sulphone metabolite in plasma in cattle and buffalo were measured by high-performance liquid chromatography after single and divided intraruminal administration of albendazole at the recommended nematocidal and fasciolicidal dose rates of 7.5 and 15.0 mg/kg body weight, respectively. No significant differences in the plasma concentrations of the metabolites or their pharmacokinetic parameters were observed between cattle or buffalo at either dose rate. Pharmacokinetic analysis and the disposition curve of the metabolites indicated increased uptake of the drug in both cattle and buffalo when the same total amount of the drug was given in divided doses compared to a single dose (p〈0.05). The divided dose schedules of administration could possibly be exploited to extend the life of the available benzimidazole anthelmintics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006023328617
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    The effect of feed quality on the kinetic disposition of orally administered triclabendazole in sheep (1998)
    Springer
    Veterinary research communications 22 (1998), S. 257-263 
    Details
    ISSN: 1573-7446
    Keywords: anthelmintics ; Fasciola ; nutrition ; pharmacokinetics ; sheep ; triclabendazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of two qualities of feed on the kinetic disposition of triclabendazole (TCBZ) metabolites was investigated in sheep (n = 4) following oral administration of TCBZ at 10 mg/kg body weight. The same sheep were given sequentially two qualitatively different diets: a low-quality (LQ) diet based on wheat straw ad libitum, and a high-quality (HQ) diet based on barley+alfalfa. The triclabendazole sulphoxide (TCBZSO) and triclabendazole sulphone (TCBZSO2) concentrations were determined in blood samples taken serially from the jugular vein between 5 min and 9 days after TCBZ administration. The parent drug TCBZ was not detected in any of the samples. The quality of feed affected the kinetics of both TCBZ metabolites. The rate of appearance (Tlag and Tmax) in the jugular blood was slower and the formed amount (AUC) of TCBZSO was slightly higher when the sheep were on the LQ diet (Tlag = 7.74 h; Tmax = 27.91 h; AUC = 1042 μg.h/ml) than when they were offered the HQ diet (Tlag = 1.90 h; Tmax = 16.01 h; AUC = 832.4 μg.h/ml). The MRT of TCBZSO was about 40% longer with the LQ diet than with the HQ diet. Similarly, the rate of appearance of TCBZSO2 in plasma of sheep was slower when they were on the LQ diet than when they were on the HQ diet, suggesting an impairment of the hepatic enzymatic activity involved in the oxidation of TCBZSO to TCBZSO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006095400309
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of antipyrine in rats with different resistance to hypoxia in cold stress (1998)
    Springer
    Bulletin of experimental biology and medicine 126 (1998), S. 1098-1099 
    Details
    ISSN: 1573-8221
    Keywords: pharmacokinetics ; antipyrine ; individual resistance to hypoxia ; cold stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract It is shown that the parameters of antipyrine pharmacokinetics during cold exposure depend on individual resistance to hypoxia. High-resistant rats are characterized by less intense metabolism and more rapid normalization of pharmacokinetic parameters than lowresistant rats characterized by shortened elimination half-time corresponding to a more rapid metabolism of xenobiotics under conditions of cold stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02447243
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Moisture transport studies on newly developed aromatic and aromatic/aliphatic copolyester thin films (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1025-1035 
    Details
    ISSN: 0887-6266
    Keywords: polymer thin films ; thermosets ; microelectronics ; moisture ; physical aging ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In polymers for microelectronics applications, moisture is known to have a deleterious effect upon device reliability. In this paper, the moisture transport behaviors of a newly developed family of all-aromatic and aromatic/aliphatic copolyester thermosetting films were described. The moisture uptake as a function of temperature, relative humidity, sample thickness, and processing conditions were presented via conjugate moisture sorption tests.1 It was found that the post curing near but below Tg resulted in an increase in both total moisture uptake and diffusion coefficient due to the effect of physical aging and the generation of sample defect volume. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1025-1035, 1998
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 59
    Electronic Resource
    Electronic Resource
    Pressure-volume-temperature properties and free volume parameters of PEO/PMMA blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1061-1080 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; dilatometry ; free volume ; specific volume ; excess volume ; compressibility ; thermal expansivity ; equation of state ; scaling parameters ; crystallinity ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Melt-miscible polymer blends of poly(ethylene oxide)/atactic poly(methyl methacrylate (PEO/a-PMMA)) were prepared by melt-mixing and characterized by pressure-volume-temperature (PVT) dilatometry in the pressure and temperature range of 0 to 200 MPa and 20 to 200°C, respectively. The PVT data were analyzed in terms of two equations of state (EOS). The empirical Tait EOS was applied in the glassy, semicrystalline, and equilibrium melt state, and the Simha-Somcynsky EOS theory was applied in the equilibrium melt and glassy state. The Simha-Somcynsky EOS theory contains a free volume function. The temperature, pressure, and composition dependence of the free volume fraction h calculated from the Simha-Somcynsky EOS theory was studied. As a function of blend composition we observe that the free volume fraction, thermal expansivity, and compressibility all deviate mainly positively from linearity while the specific volume deviates mainly negatively from linearity. These findings are reconciled with composition-dependent free volume parameters, the free volume and cell volume as well as with self- and cross-interaction parameters derived from the Simha-Somcynsky EOS theory as applied to polymer mixtures. Moreover, the pressure dependence of glass and melting transitions as well as crystallization kinetics have been investigated. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1061-1080, 1998
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 60
    Electronic Resource
    Electronic Resource
    VTF to arrhenius crossover in temperature dependence of conductivity in (PEG)xNH4ClO4 polymer electrolyte (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1201-1209 
    Details
    ISSN: 0887-6266
    Keywords: polymer electrolytes ; NMR ; conductivity ; glasses ; Arrhenius and VTF dependences ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have studied the temperature variation of conductivity and 1H NMR linewidth of (PEG)xNH4ClO4 (x = 20, 30, 46, 100, 200, & 1000) polymer electrolyte systems. The temperature dependence of the conductivity shows two distinct behaviors, the low temperature VTF dependence crossing over to Arrhenius dependence at higher temperatures. The departure from the VTF behavior is found to be composition dependent. NMR spectra indicate the presence of large fractions of crystalline regions that start to melt around the crossover temperature. We understand the deviation from the VTF behavior as a consequence of this crystalline to elastomer transition. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1201-1209, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 61
    Electronic Resource
    Electronic Resource
    In situ FTIR spectroscopic study on crystallization process of isotactic polystyrene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1227-1233 
    Details
    ISSN: 0887-6266
    Keywords: FTIR spectroscopy ; isotactic polystyrene ; crystallization process ; induction period ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melt crystallization process of isotactic polystyrene (i-PS) was studied by means of in situ Fourier transform infrared (FTIR) spectroscopy, with a focus on the conformational changes during the induction period. The spectra obtained during the induction period suggested the occurrence of some ordered structure that is characterized by higher regularity and packing of the helical moieties than observed in the melt. This ordered structure was clearly different from the amorphous structure, and close to the crystal structure. The Avrami analysis indicated that the formation process of the ordered structure at the late stage of the induction period is similar to the growth process of the crystallites after the induction period. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1227-1233, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 62
    Electronic Resource
    Electronic Resource
    Mechanical and dielectric properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 237-251 
    Details
    ISSN: 0887-6266
    Keywords: segmented ; polyurethanes ; crosslinked ; mechanical ; dielectric properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mechanical and dielectric properties of two series of segmented polyurethanes having soft segment concentration of 50 and 70% and a varying degree of crosslinking through the hard segment were studied. The degree of crosslinking in each series was varied by varying the butane diol/trimethylol propane ratio in the chain extender mixture. Tensile strength, elongation at break decrease, but elastic recovery increases monotonically with increasing crosslinking. The plateau modulus in the dynamic mechanical test decreases and then increases with increasing TMP content. Crosslinking causes broadening of the soft segment glass transition as seen by permittivity and loss factor measurements. It also affects high temperature behavior (above the glass transition of the hard segment); it lowers permittivity, loss factor, and ionic conductivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 237-251, 1998
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 63
    Electronic Resource
    Electronic Resource
    Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2379-2391 
    Details
    ISSN: 0887-6266
    Keywords: block copolymer ; thermoplastic elastomer ; physical gel ; polymer micelle ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379-2391, 1998
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 64
    Electronic Resource
    Electronic Resource
    General matrix formula for the weight-average molecular weights of crosslinked polymer systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2423-2433 
    Details
    ISSN: 0887-6266
    Keywords: gelation theory ; nonlinear polymerization ; nonrandom crosslinking ; molecular weight distribution ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On the basis of the first-order Markovian statistics, we propose a general matrix formula for the weight-average molecular weight of crosslinked polymer systems, explicitly given by M̄w = M̄w,0 + WX0 (I - X)-1 Sf. This equation is valid for both step and chain-growth polymerizations, including those in a nonequilibrium state irrespective of the reactor types used. In the context of the present theory, the onset of gelation is simply stated as a point at which the largest eigenvalue of the matrix X reaches unity (i.e., det(I - X) = 0). The present theory provides a unified point of view for various types of gelling systems. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2423-2433, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 65
    Electronic Resource
    Electronic Resource
    1-Opto-thermal properties of fibers annealing effect on the birefringence variations of polyester fibers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 555-565 
    Details
    ISSN: 0887-6266
    Keywords: polyester ; annealing ; birefringence ; mechanical loss factor ; orientation ; density ; crystalline ; profile ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyester (Egyptian) fibers were annealed at constant temperature (190°C) with different annealing times. Density, crystallinity, mean square density fluctuation, mechanical loss factor, and molecular orientation were calculated. Densities and mechanical loss factor were determined using an acoustic method. Changes in the molecular orientation were evaluated from the resulting optical data using the polarizing Pluta interference microscope. Correlation of data obtained by one method with another leads to relational changes in optothermal properties and in the molecular orientation. Changes of refractive index profiles of annealed PET fibers are provided. Illustrations using graphs and microinterferograms are shown. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 555-565, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 66
    Electronic Resource
    Electronic Resource
    Infrared investigation of the silicon oxide phase in [perfluoro-carboxylate/sulfonate (bilayer)]/[silicon oxide] nanocomposite membranes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 595-606 
    Details
    ISSN: 0887-6266
    Keywords: IR ; perfluoro(sulfonate/carboxylate) bilayer ; sol-gel reactions ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: [Perfluoro-organic]/[silicon oxide] hybrids were formed by conducting sol-gel reactions of tetraethylorthosilicate within a perfluoro(carboxylate/sulfonate) bilayer membrane in the Co+2 form. FTIR and 29Si solid-state NMR spectroscopies were used to probe general aspects of molecular structure within the silicon oxide phase as a function of its relative content. The internal gel structure is considerably unconnected in terms of the population of Si—O—Si groups in cyclic vs. linear substructures and degree of Si atom coordination about bonded SiO4 units. In situ (HO)xSiO2[1-1/4x] intrastructure become increasingly less connected and more strained with regard to bonding geometry with increasing percent silicon oxide. Structural differences are seen between the silicon oxide component incorporated in carboxylate and sulfonate layers. These inorganically modified perfluorinated ionomers have potential as fast-proton conducting membranes for fuel cells and as permselective membranes in liquid pervaporation cells. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 595-606, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 67
    Electronic Resource
    Electronic Resource
    Construction of ternary phase diagrams in nonsolvent/solvent/PMMA systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 607-615 
    Details
    ISSN: 0887-6266
    Keywords: ternary phase diagram ; binodal curve ; Flory-Huggins theory ; interaction parameter ; membrane formation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work, the ternary phase diagrams in three nonsolvent/solvent/PMMA systems (n-hexane/n-butyl acetate/PMMA, water/acetone/PMMA, and n-hexane/acetone/PMMA) were constructed by theoretical calculation and experimental measurement. Binodal curves were calculated by using the Flory-Huggins theory for three-component systems and measured by titrating the PMMA solution with nonsolvent until the onset of turbidity. By using concentration-dependent nonsolvent/solvent and solvent/PMMA interaction parameters and constant nonsolvent/PMMA interaction parameters, good agreement has been obtained between the calculation and the measurement. The values of nonsolvent/solvent interaction parameters were taken from the literature sources, and the values of solvent/PMMA and nonsolvent/PMMA interaction parameters were measured by vapor sorption and swelling equilibrium, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 607-615, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 68
    Electronic Resource
    Electronic Resource
    Atomic level picture of stress relaxation in polymer melts (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 143-154 
    Details
    ISSN: 0887-6266
    Keywords: polymer simulation ; stress relaxation ; molecular dynamics ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have been developing a physical picture on the atomic level of stress relaxation in polymer melts by means of computer simulation of the process in model systems. In this article we treat a melt of freely jointed chains, each with N = 200 bonds and with excluded-volume interactions between all nonbonded atoms, that has been subjected to an initial constant-volume uniaxial extension. We consider both the stress relaxation history σ(t) based on atomic interactions, and the stress history σe(t; NR) based on subdividing the chain into segments with NR bonds each, with each segment regarded as an entropic spring. It is found that at early times σ(t) 〉 σe(t; NR) for all NR, and that, for the remainder of the simulation, there is no value of NR for which σ(t) = σe(t; NR) for an extended period; by the end of the simulation σ(t) has fallen just below the value σe(t; 50). The decay of segment orientation, 〈P2(t; NR)〉, and of bond orientation 〈P2(t; 1)〉, is computed during the simulation. It is found that the decay of the atom-based stress σ(t) is closely related to that of 〈P2(t; 1)〉. This result may be understood through the concept of steric shielding. The change in local structure of the polymer melt during relaxation is also studied. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 143-154, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 69
    Electronic Resource
    Electronic Resource
    The effect of concentration, temperature, and molecular weight on the dynamics of rigid-rod molecules in semi-dilute solutions (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 181-190 
    Details
    ISSN: 0887-6266
    Keywords: dynamics ; rigid-rod ; semidilute ; birefringence ; rotational diffusivity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamics of rigid-rod-like molecules are studied using rheo-optical techniques. Measurements of flow birefringence as a function of shear rate are utilized to understand the scaling behavior of rotational diffusivity with respect to concentration and temperature. The concentration scaling exponent increases with increasing concentration and the scaling laws are valid in narrow concentration windows. The Doi-Edwards (DE) scaling law Dr ∼ c-2, holds at very high concentrations (cL3 〉 150). The concentration scaling exponent decreases dramatically with increasing temperature at concentrations, cL2d 〉 1. Scaling of rotational diffusivity, with respect to temperature and solvent viscosity in the semidilute regime, does not follow the predictions of DE theory (and related caging ideas). On the contrary, a model proposed by Fixman was found to explain both the temperature and concentration dependence of the rotational diffusivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 181-190, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 70
    Electronic Resource
    Electronic Resource
    Structure and physical properties of segmented polyurethane elastomers containing chemical crosslinks in the hard segment (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 221-235 
    Details
    ISSN: 0887-6266
    Keywords: segmented ; polyurethanes ; crosslinked ; properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two series of segmented polyurethanes, one containing 50% soft segments and the other with 70% soft segments were synthesized. Chemical crosslinks were introduced through the hard segment in a controlled way. Chemical polyurethane networks were characterized by swelling. The effect of the degree of crosslinking on properties was examined. It was found that chemical crosslinks in the hard segment reduce the mobility of the soft phase and destroy the crystallinity of the hard phase, but they improve heat stability of the hard domains. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 221-235, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 71
    Electronic Resource
    Electronic Resource
    Effect of permeation temperature on permeation and separation of a benzene/cyclohexane mixture through liquid-crystalline polymer membranes (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 281-288 
    Details
    ISSN: 0887-6266
    Keywords: side-chain liquid-crystalline polymer membrane ; pervaporation ; benzene/cyclohexane mixture ; state-transformation ; benzene permselectivity ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: When a benzene/cyclohexane mixture of 10 wt % benzene was permeated through side-chain liquid-crystalline polymer (LCP) membranes by pervaporation at various temperatures, the permeation rate increased with increasing permeation temperature. The LCP membranes also exhibited a benzene permselectivity. The permselectivity for the benzene/cyclohexane mixture through the LCP membrane was different in the glassy, liquid-crystalline, and isotropic states. The LCP membrane had different apparent activation energies for permeation at each state. LCP membrane in the liquid-crystalline state had the highest apparent activation energy of the three states. Results suggest that the benzene permselectivity was influenced by changes in the LCP membrane structure, i.e., a state-transformation. It was found that a balance of the orientation of mesogenic groups and the flexibility of the siloxane chains was very important for benzene permselectivity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 281-288, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 72
    Electronic Resource
    Electronic Resource
    Dispersion polymerization of styrene in ethanol-water media: Monomer partitioning behavior and locus of polymerization (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 325-335 
    Details
    ISSN: 0887-6266
    Keywords: dispersion polymerization ; styrene ; water-ethanol mixtures ; partitioning behavior ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol-water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 325-335, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 73
    Electronic Resource
    Electronic Resource
    Markovian approach to nonlinear polymer formation: Free-radical polymerization with chain transfer to polymer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 357-371 
    Details
    ISSN: 0887-6266
    Keywords: gelation theory ; nonlinear polymerization ; molecular weight distribution ; branched polymers ; polymer modification ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A Markovian model is proposed for nonrandom branching reactions, by using free-radical polymerization that involves chain transfer to polymer as an example. Free-radical polymerizations are kinetically controlled; therefore, each primary polymer molecule experiences different history of branched structure formation. By assuming that the primary chains with the identical birth time conform to the same chain connection probabilities, the nonlinear structural development can be viewed as a system in which the primary chains formed at different birth times are combined into nonlinear polymers in accordance with the first-order Markov chain statistics. An explicit formula for the weight-average chain length is derived in a matrix form. The onset of gelation is simply stated as a point at which the largest eigenvalue of the transition matrix X reaches unity, i.e., det(X - I) = 0. This criterion for the onset of gelation can be considered as an extension of the Flory/Stockmayer theory to a nonequilibrium reaction system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 357-371, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 74
    Electronic Resource
    Electronic Resource
    Copolymerization of hexafluoropropylene and tetrafluoroethylene: Effect on chain conformation and crystal structure (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2811-2819 
    Details
    ISSN: 0887-6266
    Keywords: PTFE/hexafluoropropylene copolymers ; crystal ; disorder ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of new copolymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) containing up to 50 mol % of the hexafluoropropylene comonomer have been investigated with respect to chain conformation and crystal structure using wide-angle X-ray diffraction (WAXD). Increasing HFP content leads to significant departures from the highly ordered crystalline structure of the homopolymer PTFE; the helical conformation of the chain relaxes and untwists to accommodate the larger —CF3 pendant group in the HFP unit. Simultaneously the lateral hexagonal packing of the helices becomes less ordered and the a-dimension of the hexagonal cell increases. The above effects are progressive with increasing HFP content. At 50 mol % HFP incorporation the structure is a disordered crystalline phase. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2811-2819, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 75
    Electronic Resource
    Electronic Resource
    Nonexponentiality parameter in polymethyl(α-n-alkyl) acrylates (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2865-2868 
    Details
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 76
    Electronic Resource
    Electronic Resource
    Near infrared studies of styrene-sodium methacrylate ionomers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2877-2886 
    Details
    ISSN: 0887-6266
    Keywords: ionomers ; NIR ; chemometrics ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Near Infrared (NIR) spectroscopy coupled with chemometrics techniques were utilized to study the composition and properties of styrene-sodium methacrylate ionomers. Predictive models were obtained for mol % ionic content, as well as for the ionic cluster glass transition temperature, storage modulus, and tan δ peak parameters. The results illustrate the feasibility of using NIR and chemometrics algorithms as a property predictive tool, as well as the potential for the development of full calibration models. The chemometric parameters are discussed based on correlations with ionomer NIR spectral features and the role water molecules play as a probe for the associated structure of the ionomer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2877-2886, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 77
    Electronic Resource
    Electronic Resource
    Electrochemical fabrication of all organic heterojunction for polythiophene and its derivatives (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2905-2910 
    Details
    ISSN: 0887-6266
    Keywords: polyalkylthiophenes ; heterojunction ; BF3-diethyl ether ; electropolymerization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new kind of all-organic heterojunction consisting of polythiophene and its derivatives was prepared by the electrochemical method in the presence of boron trifluoride diethyl ether as supporting electrolyte on indium-tin oxide glass electrode. It was observed that sequential-different oxidation potential among layers of polythiophenes is a prerequisite for the heterojunction to show rectification effect. The carrier-flow of the three semiconductors for PBrT/PT/PMT heterojunction was discussed in detail. Its rectification ratio, barrier height, and ideality factor were 392 (±2 V), 0.89 eV, and 8.1, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2905-2910, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 78
    Electronic Resource
    Electronic Resource
    Influence of associations on self-diffusion of styrene-methylmethacrylate random copolymers in semidilute acetone solution (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2931-2939 
    Details
    ISSN: 0887-6266
    Keywords: associations ; random copolymers ; self-diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The self-diffusion of four styrene-methylmethacrylate random copolymers dissolved in acetone, a thermodynamically bad solvent for the styrene sequences in the copolymer, were investigated by pulsed-field gradient NMR. The echo attenuations Sinc(q,t) are dominated by diffusion of clusters. At higher concentrations, physical gelation sets in (formation of a transient network), which is manifested in an anomalous, restricted diffusion at short observation times. The measured fluctuations of the positions of the chain segments in the transient network have an amplitude of about 100 nm. The free long-range diffusion attained at long observation times shows a much stronger concentration dependence than in the nonassociating solvent benzene. The results are in accord with light-scattering investigations. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2931-2939, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 79
    Electronic Resource
    Electronic Resource
    Melting behavior, miscibility, and hydrogen-bonded interactions of poly(ε-caprolactone)/poly(4-hydroxystyrene-co-methoxystyrene) blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 95-104 
    Details
    ISSN: 0887-6266
    Keywords: blends ; melting behavior ; miscibility ; FTIR ; hydrogen bond interactions ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility of poly(4-hydroxystyrene-co-methoxystyrene) (HSMS) and poly(ε-caprolactone) (PCL) was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). HSMS/PCL blends were found to be miscible in the whole composition range by detecting only a glass transition temperature (Tg), for each composition, which could be closely described by the Fox rule. The crystallinity of PCL in the blends was dependent on the Tg of the amorphous phase. The greater the HSMS content in the blends, the lower the crystallinity. The polymer-polymer interaction parameter, χ32, was calculated from melting point depression of PCL using the Nishi-Wang equation. The negative value of χ32 obtained for HSMS/PCL blends has been compared with the value of χ32 for poly(4-hydroxystyrene) (P4HS)/PCL blends. The specific nature, quantitative analysis, and average strength of the intermolecular interactions in HSMS/PCL and P4HS/PCL blends have been determined at room temperature and in the molten state by means of Fourier transform infrared spectroscopy (FTIR) measurements. The FTIR results have been in good correlation with the thermal behavior of the blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 95-104, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 80
    Electronic Resource
    Electronic Resource
    A new approach for estimating the recrystallization rate and equilibrium melting temperature (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 133-141 
    Details
    ISSN: 0887-6266
    Keywords: recrystallization rate ; equilibrium melting temperature ; differential scanning calorimetry (DSC) ; poly(butylene terephthalate) (PBT) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method is described for measuring the heat and rate of recrystallization following partial melting. The method uses a specific sequence of temperatures with a differential scanning calorimeter, and the melting and recrystallization processes were confirmed by optical observations. The method was applied to poly(butylene terephthalate). The rate of recrystallization was found to be roughly two orders of magnitude faster than isothermal crystallization from the melt. The melting temperatures obtained from recrystallization were used in the Hoffman-Weeks equation to deduce 236°C as the equilibrium melting temperature for poly(butylene terephthalate). © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 133-141, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 81
    Electronic Resource
    Electronic Resource
    Interfacial thickness in bilayers of poly(phenylene oxide) and styrenic copolymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 3115-3125 
    Details
    ISSN: 0887-6266
    Keywords: interfacial thickness ; PPO ; SAN ; SMA ; neutron reflectivity NR ; binary interaction energies ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Estimates for the thickness of the interface between poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) and copolymers of styrene-acrylonitrile (SAN) and styrene-maleic anhydride (SMA) based on the theory of Helfand and Tagami are compared to neutron reflectivity (NR) measurements. Good agreement is found between the NR measurements and theoretical predictions that make use of a mean field binary interaction model and previously reported binary interaction energies. The techniques outlined in this work may be used to understand relationships between the mechanical properties of multiphase polymer blends and the fundamental thermodynamics of polymer interactions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3115-3125, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 82
    Electronic Resource
    Electronic Resource
    Compatibilizing effect of isocyanate functional group on polyethylene terephthalate/low density polyethylene blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 447-453 
    Details
    ISSN: 0887-6266
    Keywords: polyethylene terephthalate ; low density polyethylene ; isocyanate functional group ; compatibility ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To evaluate the compatibilizing effects of isocyanate (NCO) functional group on the polyethylene terephthalate/low density polyethylene (PET/LDPE) blends, LDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared and blended with PET. The chemical reaction occurred during the melt blending in the PET/LDPE-g-HI blends was confirmed by the result of IR spectra. In the light of the blend morphology, the dispersions of the PET/LDPE-g-HI blends were very fine over the PET/LDPE blends. DSC thermograms indicated that PET microdispersions produced by the slow cooling of the PET/LDPE-g-HI blends were largely amorphous, with low crystallinity, due to the chemical bonding. The tensile strengths of the PET/LDPE-g-HI blends were higher than those of the PET/LDPE blends having a poor adhesion. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 447-453, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 83
    Electronic Resource
    Electronic Resource
    Polyelectrolytes in shear and extensional flows: Conformation and rheology (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1401-1417 
    Details
    ISSN: 0887-6266
    Keywords: polyelectrolytes ; Brownian dynamics ; shear flow ; extensional flow ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The conformational and rheological dynamics of dilute solutions of polyelectrolyte macromolecules undergoing shear and extensional flow are modeled using Nonequilibrium Brownian Dynamics (NEBD) and Configuration-Biased Monte Carlo (CBMC) simulations. The mathematical model utilizes a bead-spring chain with charged beads that interact through a screened Debye-Hückel potential, and that also interact through stretching and bending forces. The diffusion (or Fokker-Planck) equation for the probability density of the positions of the beads of the chain is converted to a Stochastic Differential Equation (SDE), from which the simulation algorithm for the NEBD is obtained. The CBMC is used in the initial chain generation and in determining steady-state properties in elongational flows. Various conformational and rheological quantities, such as the stress and birefringence, are monitored, under both steady-state and transient conditions, with the primary independent variable being the salt concentration (parametrized through the Debye length) and the strength of interaction q, related to the degree of ionization of the chain. It is found that this model is able to describe qualitatively many of the experimentally observed features in such systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1401-1417, 1998
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 84
    Electronic Resource
    Electronic Resource
    Dynamic mechanical thermal and infrared analyses of polyacrylonitrile “electrografted” onto a metal (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 543-553 
    Details
    ISSN: 0887-6266
    Keywords: polyacrylonitrile ; polyimine ; isotacticity ; dynamic mechanical analysis ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyacrylonitrile (PAN) films have been “grafted” onto copper electrodes by cathodic polarization and analyzed by infrared spectroscopy and dynamic mechanical thermal analysis (DMTA). The dynamic mechanical response shows two or three transitions depending on the film thickness and the potential deposition. The viscoelastic properties of “ungrafted” PAN films, e.g., solvent cast films of commercially available PAN, are deeply different from those of “electrografted” films. The experimental data support that “ungrafted” chains are paracrystalline in contrast to the “grafted” ones which are essentially amorphous. Moreover, the irreversible transformation of the “grafted” PAN chains observed beyond 225°C is confirmed by Fourier transform infrared (FTIR) analysis and ascribed to an intramolecular cyclization of PAN into polyimine. This reaction occurs rapidly and at a comparatively low temperature with respect to “ungrafted” PAN, which suggests that the “grafted” chain configuration might be predominantly isotactic. The isotacticity and the amorphous structure appear to decrease as the thickness of the PAN film is increased. Literature data and the herein reported observations would suggest a dependence of the amorphous structure of PAN on the chain isotacticity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 543-553, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 85
    Electronic Resource
    Electronic Resource
    Enthalpy relaxation in polymethyl(α-n-alkyl)acrylates: Effect of length of alkyl chain (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 583-593 
    Details
    ISSN: 0887-6266
    Keywords: enthalpy relaxation ; differential scanning calorimetry ; peak-shift method ; polymethyl(α-n-alkyl)acrylates ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this work, we have investigated by DSC the structural relaxation of amorphous polymethyl(α-n-alkyl)acrylates in which it is possible to change the length of the alkyl chain. We have evaluated the Narayanaswamy parameter, x, which controls the relative contribution of temperature and of structure to the relaxation time, the apparent activation energy, Δh*, and the nonexponentiality parameter, β, of the stretched exponential response function. The results suggest that x increases while Δh* decreases and β remains constant as the length of the side chain increases. This allows us to comment on the effect of chemical modification on the relaxation kinetics. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 583-593, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 86
    Electronic Resource
    Electronic Resource
    Impedance spectroscopy of reactive polymers. 5. Impedance as a measure of chemical and physical changes in glass formers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 641-653 
    Details
    ISSN: 0887-6266
    Keywords: impedance spectroscopy ; chemical and physical changes ; glass formers ; reactive polymers ; in situ monitoring ; dielectric properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study was conducted aimed at establishing the nature of chemical and physical phenomena in polymeric and nonpolymeric glass formers that can be observed by impedance measurements. Various systems were investigated that undergo a temporal evolution of structure as a result of chemical reactions and physical processes such as crystallization, vitrification, or phase separation. Distinct and systematic changes in impedance during crystallization and vitrification confirmed that these events could be monitored by impedance spectroscopy. Of particular interest was the potential use of impedance measurements in detecting gelation in crosslinking polymers. It was shown that the experimentally observed “knee” in imaginary impedance during reaction shifts with frequency and, hence, cannot be used to measure gelation. But a new insight at the molecular level was obtained by employing a novel experimental approach based on simultaneous dielectric-infrared measurements. Evidence was generated to support the formation of a hydrogen-bonded complex in the vicinity of gel point in polymer networks, which affords a vehicle for the migration of intrinsic charges and provides a contribution to the overall conductivity. This finding should be explored further because it suggests the possibility of correlating dielectric response with gelation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 641-653, 1998
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 87
    Electronic Resource
    Electronic Resource
    Clustering of water molecules during adsorption of water in wood (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 665-671 
    Details
    ISSN: 0887-6266
    Keywords: clustering ; water ; wood ; adsorption ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Clustering behavior of water molecules during adsorption of water in wood was studied using the Zimm-Lundberg theory. The average cluster size of water molecules was determined with the help of wood adsorption isotherms at five temperatures. The effects of both relative humidity and temperature on average cluster size were studied. Average cluster size progressively increased with an increase in humidity. At humidities corresponding to fiber saturation, larger clusters were formed. Cluster size increased sharply with an increase in temperature at humidities close to saturation. Formation of large clusters at high temperature and humidities close to saturation is attributed to increased fraction of weakly bonded water and capillary condensation in such conditions. A description of adsorption of water in wood was provided in terms of average cluster size. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 665-671, 1998
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 88
    Electronic Resource
    Electronic Resource
    Modeling molecular weight distribution of comb-branched graft copolymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 705-714 
    Details
    ISSN: 0887-6266
    Keywords: molecular weight distribution ; comb copolymer ; branching ; grafting ; nonlinear polymerization ; modeling ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Grafting one type polymer onto a different polymer type may yield a comb-branched copolymer. The branching density has a significant effect on its overall molecular weight distribution. A general model is derived to describe the bivariate distribution of molecular weight and branching density for such comb copolymers. The model is applicable for various grafting mechanisms provided the side chains are randomly grafted onto the backbone. The determining parameters are the molecular weight distributions of backbone and side chains, and the branching density. Analytical expressions are obtained for the cases of the side chains having uniform and Schulz-Zimm distributions. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 705-714, 1998
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 89
    Electronic Resource
    Electronic Resource
    Surface characterization of ion-implanted polyethylene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 715-725 
    Details
    ISSN: 0887-6266
    Keywords: polyethylene ; ion implantation ; surface structure ; wear ; hardness ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyethylene (PE) film was implanted with 1000-keV Ar+ ions to a fluence of 5 × 1014 ions/cm2 under high vacuum conditions (2.5 × 10-6 torr) and the film surface was investigated by means of microhardness and microwear measurements, and FTIR/ATR, Raman, and XPS techniques. Ion implantation significantly increased the subsurface hardness and also significantly improved the microwear resistance of the polymer. The implanted surface region of the film was found to consist of two distinct layers. One was the outermost carbon layer with a thickness of the order of 10 nm. In this layer, ca. 75% of carbon atoms were combined by graphitic sp2 and diamond-like sp3 bonds, and the remaining 25% had chemical links with oxygen atoms. Spectroscopic data suggested that the sp2-bonded carbons segregated in graphite-like clusters containing imbedded oxygen atoms, interconnected by the sp3-bonded carbons. The other was the subsurface layer resulting from PE oxidation after ion-beam treatment. This layer was characterized by high contents of O—H and C=O groups as well as ester and double bonds. The chemical composition of the layer was uniform and did not vary over the layer thickness of about 1.4 μm. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 715-725, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 90
    Electronic Resource
    Electronic Resource
    Subglass-transition-temperature annealing of poly(ethylene terephthalate) studied by FTIR (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 783-788 
    Details
    ISSN: 0887-6266
    Keywords: poly(ethylene terephthalate) ; sub-Tg ; annealing ; conformation ; infrared spectra ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using FTIR spectroscopy we have examined conformational changes in the quenched and slowly cooled amorphous PET films during physical aging process. It was observed that the amount of trans conformers for quenched sample decreased upon sub-Tg annealing. For the slowly cooled sample that corresponds to a state closer to equilibrium, the amount of trans conformers hardly decreased, but increased gradually during sub-Tg annealing process. The conformational populations of these two samples tend to be identical with annealing time. These results demonstrate that sub-Tg annealing will lead to closer interchain packing and result in the formation of new cohesional entanglements along the chains. In situ FTIR studies on the conformational changes of these samples were also carried out during heating up of the sample through the glass transition region. The results showed that incremental changes of the amount of trans conformers in Samples Q and SC were gradual, while an abrupt change of trans conformers occurred in the sub-Tg annealed samples. These results were in agreement with the formation of the interchain cohesional entanglement due to sub-Tg annealing. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 783-788, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 91
    Electronic Resource
    Electronic Resource
    Equation of state of poly(dimethylsiloxane) melts (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 841-850 
    Details
    ISSN: 0887-6266
    Keywords: specific volume ; Tait equation ; compressibility ; scaling parameter ; hole theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The pressure-volume-temperature (PVT) properties of three commercial samples of poly(dimethylsiloxane) are studied experimentally and theoretically in the temperature range 25-150°C and for pressure to ∼ 3 kbar. The Tait equation is employed to represent the data at elevated pressure. Isothermal compressibilities are computed for the three samples. The melt data are analyzed in terms of the Simha-Somcynsky hole theory, and scaling parameters of pressure, volume, and temperature are obtained. Satisfactory agreement between theory and experiment is found over the entire range of experimental pressures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 841-850, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 92
    Electronic Resource
    Electronic Resource
    Dielectric and dynamic mechanical relaxation studies on poly(aryl ether ketone)s (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 851-859 
    Details
    ISSN: 0887-6266
    Keywords: poly(aryl ether ketone)s ; dielectric relaxation spectroscopy ; dynamic mechanical analysis ; α-relaxation ; β-relaxation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relaxation behavior of four amorphous poly(aryl ether ketone)s was investigated using dielectric relaxation spectroscopy and dynamic mechanical analysis. The temperature dependence of the relaxation times of the glass transition process and the cooperative nature of this process were unaffected by changes in polymer structure. The temperature location of the loss peaks for all polymers progressed smoothly between the low frequency of the mechanical measurements and the higher frequencies of the dielectric probe. Differences were observed in mechanical activation energy and dielectric relaxation strength for one polymer which contained a significant concentration of meta linkages, compared with the para-linked polymers, while relaxation broadness was generally greater in the dynamic mechanical mode. Changes in chemical structure had little effect on the shape, intensity, and location of the β-relaxation peak, the main observation being that the Arrhenius activation energy measured by dynamic mechanical analysis was significantly higher than that calculated from the dielectric data. The dielectric β-relaxation was sensitive to absorbed moisture. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 851-859, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 93
    Electronic Resource
    Electronic Resource
    Application of zone-drawing and zone-annealing method to poly(p-phenylene sulfide) fibers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1731-1738 
    Details
    ISSN: 0887-6266
    Keywords: poly(p-phenylene sulfide) fiber ; zone-drawing ; zone-annealing ; mechanical properties ; DSC thermogram ; viscoelastic properties ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A zone-drawing and zone-annealing treatment was applied to poly(p-phenylene sulfide) fibers in order to improve their mechanical properties. The zone-drawing (ZD) was carried out at a drawing temperature of 90°C under an applied tension of 5.5 MPa, and the zone-annealing (ZA) was carried out at an annealing temperature of 220°C under 138.0 MPa. The differential scanning calorimetry (DSC) thermogram of the ZD fiber had a broad exothermic transition (Tc = 110°C) attributed to cold-crystallization and a melting endotherm peaking at 286°C. The Tc of the ZD fiber was lower than that (Tc = 128°C) of the undrawn fiber. In the temperature dependence of storage modulus (E′) for the ZD fiber, the E′ values decreased with increasing temperature, but increased slightly in the temperature range of 90-100°C, and decreased again. The slight increase in E′ was attributable to the additional increase in the crosslink density of the network, which was caused by strain-induced crystallization during measurement. The resulting ZA fiber had a draw ratio of 6.0, a degree of crystallinity of 38%, a tensile modulus of 8 GPa, and a tensile strength of 0.7 GPa. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1731-1738, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 94
    Electronic Resource
    Electronic Resource
    Molecular theory of solutions and blends of heteropolymers. I. Thermodynamics of amorphous multicomponent polymer systems (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 937-958 
    Details
    ISSN: 0887-6266
    Keywords: thermodynamics ; heteropolymers ; phase diagram ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On the basis of a variational principle a quantitative theory is developed enabling a thermodynamic description in terms of mean field approximation of heteropolymer mixtures of macromolecules with an arbitrary distribution for both degree of polymerization and composition. Rather simple general equations are derived to calculate compositions and volume fractions of spatially homogeneous macroscopic phases as well as to find the cloud-point curve, spinodal, and critical points. Potentialities of general theory are illustrated for copolymers synthesized by traditional methods. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 937-958, 1998
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 95
    Electronic Resource
    Electronic Resource
    Measurement of free-volume hole size distribution in Nafion-117 using positron annihilation spectroscopy (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 983-989 
    Details
    ISSN: 0887-6266
    Keywords: positron annihilation ; free-volume ; Nafion ; free-volume size distribution ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We report a new result of free-volume hole size distribution in water and ethanol-swollen Nafion-117 polymer. With the increase in water content, free-volume hole size decreases, but overall the volume fraction increases. The hole size distribution in dry polymer is seen to be distinctly different from hydrated membranes. The narrow and symmetric distribution in hydrated membrane as compared to dry membrane is believed to be a consequence of crosslinking due to cluster formation. In alcohol-swollen membranes, on the other hand, not only are the free-volume size and fraction seen to be higher, the hole size distribution is seen to be broader compared to dry or hydrated membranes, indicating the effect of penetration of alcohol into the hydrophobic backbone region. We have also examined our results vis-a-vis reported gas diffusion studies in Nafion in the framework of existing free-volume model. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 983-989, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 96
    Electronic Resource
    Electronic Resource
    Effect of sub-Tg relaxations on chromophore reorientation in corona-poled polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1013-1024 
    Details
    ISSN: 0887-6266
    Keywords: nonlinear optical polymer ; pressure ; chromophore reorientation ; poly(alkyl methacrylates) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Activation volumes for chromophore reorientation were measured for a series of guest-host polymeric materials, indicating a significant coupling between chromophore motion and the glassy α and β relaxation dynamics of the polymer host. The specific systems studied were formed by individually dissolving N,N-dimethyl-p-nitroaniline (DpNA), 4-(dimethylamino)-4′-nitrotolane (DMANT), 4-(diethylamino)-4′-nitrotolane (DEANT), and 1-((4-(dimethylamino)phenyl)ethynyl)-4-((4-nitrophenyl)ethynyl)benzene (DMAPEANT) in poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(isobutyl methacrylate) (PiBMA). In each of these systems, the isothermal, sub-Tg decay of the second-order optical susceptibility χ(2) was monitored as a function of pressure using second harmonic generation. In each system, the observed decay of χ(2) was represented by a stretched exponential equation from which the decay time τ0 and decay distribution width βKWW were determined. For each dopant molecule, the decrease in activation volume with the increasing size of the polymer host's alkyl side group and the pressure dependence of βKWW were indicative of partial coupling between chromophore rotation and the glassy β relaxation dynamics of the polymer host. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1013-1024, 1998
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 97
    Electronic Resource
    Electronic Resource
    An electrorheological fluid and siloxane gel based electromechanical actuator: Working toward an artificial muscle (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1091-1094 
    Details
    ISSN: 0887-6266
    Keywords: electrorheological fluids (ERFs) ; poly(dimethyl siloxane) gels ; artificial muscle ; electromechanical actuators ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 98
    Electronic Resource
    Electronic Resource
    Interface characterization in latex blend films by fluorescence energy transfer (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1115-1128 
    Details
    ISSN: 0887-6266
    Keywords: interface structure ; fluorescence energy transfer ; polymer blends ; latex films ; poly(methyl methacrylate) ; poly(butyl methacrylate-co-butyl acrylate) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Immiscible polymer blend films were formed by air drying aqueous dispersions containing mixtures of a high-Tg latex, poly(methyl methacrylate), and a film-forming low-Tg latex, poly(butyl methacrylate-co-butyl acrylate). Fluorescence energy transfer experiments were used to characterize the interfaces in these films, in which one component was labeled with a donor dye and the other with an acceptor. The quantum efficiency of energy transfer (ΦET) between the donors and acceptors is influenced by the interfacial contact area between the two polymer phases. As the amount of soft component in the blend is increased, ΦET approaches an asymptotic value, consistent with complete coverage of the hard polymer surface with soft polymer. This limiting extent of energy transfer is very sensitive to the total surface area in the film, with correspondingly more energy transfer at constant volume fraction for small hard particles. Some of the details of the energy transfer are revealed through a fluorescence lifetime distribution analysis. The presence of ionic surfactant (sodium dodecyl sulfate) in the dispersion from which the latex blend film is prepared reduces the cross-boundary energy transfer by 30%, which implies that in these films the surfactant decreases the interfacial contact. After annealing the surfactant-free blends above 100°C, we observe an increase in energy transfer, consistent with a broader interface between the two polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1115-1128, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 99
    Electronic Resource
    Electronic Resource
    Nylon 6 9 can crystallize with hydrogen bonding in two and in three interchain directions (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1153-1165 
    Details
    ISSN: 0887-6266
    Keywords: even-odd nylons ; lamellar crystals ; structure ; hydrogen-bonding schemes ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nylon 6 9 has been shown to have structures with interchain hydrogen bonds in both two and in three directions. Chain-folded lamellar crystals were studied using transmission electron microscopy and sedimented crystal mats and uniaxially oriented fibers studied by X-ray diffraction. The principal room-temperature structure shows the two characteristic (interchain) diffraction signals at spacings of 0.43 and 0.38 nm, typical of α-phase nylons; however, nylon 6 9 is unable to form the α-phase hydrogen-bonded sheets without serious distortion of the all-trans polymeric backbone. Our structure has c and c* noncoincident and two directions of hydrogen bonding. Optimum hydrogen bonding can only occur if consecutive pairs of amide units alternate between two crystallographic planes. The salient features of our model offer a possible universal solution for the crystalline state of all odd-even nylons. The nylon 6 9 room-temperature structure has a C-centered monoclinic unit cell (β = 108°) with the hydrogen bonds along the C-face diagonals; this structure bears a similarity to that recently proposed for nylons 6 5 and X3. On heating nylon 6 9 lamellar crystals and fibers, the two characteristic diffraction signals converge and meet at 0.42 nm at the Brill temperature, TB · TB for nylon 6 9 lamellar crystals is slightly below the melting point (Tm), whereas TB for nylon 6 9 fibers is ≅ 100°C below Tm. Above TB, nylon 6 9 has a hexagonal unit cell; the alkane segments exist in a mobile phase and equivalent hydrogen bonds populate the three principal (hexagonal) directions. A structure with perturbed hexagonal symmetry, which bears a resemblance to the reported γ-phase for nylons, can be obtained by quenching from the crystalline growth phase (above TB) to room temperature. We propose that this structure is a “quenched-in” perturbed form of the nylon 6 9 high-temperature hexagonal phase and has interchain hydrogen bonds in all three principal crystallographic directions. In this respect it differs importantly from the γ-phase models. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1153-1165, 1998
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 100
    Electronic Resource
    Electronic Resource
    Investigation on the dynamics of aromatic polyesters by means of high resolution solid state CPMAS 13C NMR (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1557-1566 
    Details
    ISSN: 0887-6266
    Keywords: polyesters ; PET ; PEN ; PEI ; 13C NMR ; dynamics ; nuclear relaxation times ; gas diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamics of amorphous aromatic polyesters consisting of poly(ethylene terephthalate) (PET), poly(ethylene isophthalate) (PEI), and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) has been investigated by means of solid state CPMAS 13C NMR. Proton T2, 13C T1ρ, and proton T1ρ decays have been measured in particular, and the experimental data fitted to suitable model functions to determine best relaxation parameters. The fitting results show for proton T2 and 13C T1ρ measurements the presence of two components with different relaxation times and intensities, arising from different motional domains. The proton T1ρ, on the contrary, shows a single component which limits the dimensions of the two regions to less than 20 Angstroms. The dependence of 13C T1ρ values on two different irradiating field strengths (H1 = 38 KHz, H1 = 60 KHz) allowed the assignment of each component to relatively rigid and mobile regions. By comparing the three polymers we observe that PEN and PEI have a similar relaxation behavior, while a higher fraction of mobile components was found for PET. These differences are believed to arise mainly from local motions of the aromatic rings. The relaxation measurements have been evaluated to suggest a correspondence to O2 and CO2 gas permeabilities in PET, PEI, and PEN. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1557-1566, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...