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  • 1980-1984
  • 1975-1979  (773)
  • 1978  (401)
  • 1977  (372)
  • Engineering General  (491)
  • Molecular Cell Biology  (208)
  • pharmacokinetics
Material
Years
  • 1980-1984
  • 1975-1979  (773)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 275-284 
    ISSN: 1432-1041
    Keywords: Diazepam ; pharmacokinetics ; pregnant women ; plasma clearance ; blood/plasma concentration ratio ; placental transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of diazepam has been studied in pregnant women at parturition. The plasma concentration of diazepam was monitored for at least 3 days in 18 women who received a single intravenous injection of 10 mg during the 10 h-period prior to delivery. Fourteen mothers had uneventful puerperia (Group I) and in 13 of these cases there was a pronounced postnatal increase in the plasma concentration of diazepam. The terminal phase half-life (t1/2) was significantly greater for Group I (mean = 65 h; range = 24–114 h) than for age-matched non-pregnant patients (mean = 29 h; range = 18–44 h from literature). The prolonged t1/2 appeared to be related to changes in the distribution of diazepam and not to a reduction in hepatic elimination since the total plasma clearance (Cltp) in these 14 pregnant patients (mean = 28 ml/min; range = 18–43 ml/min) was not reduced compared to that reported for non-pregnant controls (mean = 30 ml/min; range = 22–45 ml/min). Four mothers underwent postnatal surgery for tubal ligation (Group II) and the plasma concentration-time profiles for this group did not show the same postnatal phenomenon as did the profiles obtained for Group I. The t1/2 for Group II was shorter (mean = 31 h; range = 24–37 h) than for Group I and similar to that for the non-pregnant controls. The Cltp for Group II was greater (mean = 56 ml/min; range = 48–63 ml/min) than for both Group I and non-pregnant controls. These results suggest that delivery alters the disposition of diazepam and is generally associated with a postnatal re-distribution of diazepam into the systemic circulation. The blood/plasma concentration ratio was determined in 9 patients (mean = 0.62; range = 0.54–0.77). There was no difference in the total blood clearance between the pregnant patients of Group I and the non-pregnant controls. In most cases the umbilical venous plasma concentration (Cpuv) of diazepam was greater than the peripheral maternal venous plasma concentration (Cpmv) at delivery. The foetus appears to constitute a slowly equilibrating tissue-group in which diazepam does not reach equilibrium with the maternal systemic circulation for at least 5–10 h at which time the diazepam concentration in maternal and foetal plasma is similar.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations and bioavailability of clofibrinic acid have been estimated under conditions approaching the steady-state during a ten-day period of administration as clofibrate or as a calcium clofibrinate-carbonate combination (1:1 w/w) at a dosage interval of 12 h. Formulation — related differences in bioavailability were not significant, and the 95% confidence limits of these differences were within −2% to +8% of the mean for the reference formulation of clofibrate. The mean steadystate plasma concentrations of clofibrinic acid measured on the tenth day of dosing were 116 µg/ml±22 S.D. and 119 µg/ml±23 S.D. after administration of 885 mg as clofibrate and the calcium clofibrinate-carbonate combination respectively. The peaks of mean plasma concentrations were 70 µg/ml±15 S.D., 119 µg/ml±32 S.D. and 131 µg/ml±26 S.D. on the first, fifth and tenth day of dosing with clofibrate, and 62 µg/ml±13 S.D., 127 µg/ml±S.D. and 143 µg/ml±25 S.D. on the corresponding days of dosing with the calcium clofibrinate-carbonate combination. After the last dose on the tenth day of dosing, the mean apparent half-lives of elimination of clofibrinic acid from plasma were 24.2 h±4.4 S.D. and 25.5 h±3.2 S.D. after administration of clofibrate and the calcium clofibrinate-carbonate combination respectively.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 69-72 
    ISSN: 1432-1041
    Keywords: Phenazone ; pharmacokinetics ; hydrocortisone ; elimination rate ; distribution volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of a high plasma concentration of hydrocortisone on the metabolism of phenazone in humans has been studied. Two series of experiments were carried out, Group A to demonstrate any enzyme-inducing effect of hydrocortisone, and Group B to study the immediate effect of hydrocortisone on the metabolism of phenazone. 9 subjects (Group A) received a total 250–400 mg hydrocortisone i.m. twice daily for three days and the 24-hour elimination of phenazone was studied before and afterwards. In a further 5 subjects (Group B) the elimination of phenazone was examined during administration of hydrocortisone or placebo. The elimination rate and the apparent volume of distribution of phenazone remained unchanged under both experimental conditions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 97-101 
    ISSN: 1432-1041
    Keywords: Clonidine ; plasma level ; pharmacokinetics ; steady state ; urinary excretion ; side-effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single oral dose of clonidine 300 µg was administered to 8 healthy, normotensive subjects and the time course of its plasma concentrations was followed for 24 h. The plasma concentration of clonidine rose to a peak of 1.17±0.12 ng/ml at about 2 h: the absorption half-life was 0.6±0.2 h. Elimination followed first order kinetics with a half-life of 7.7±2.0 h. The correlation between the two most common side-effects of clonidine, sedation and dryness of the mouth, with the time course of its plasma concentrations was highly significant, p〈0.01. All the subjects complained of severe sedation. During continuous administration of clonidine (75 µg t.i.d.) for one week a steady state serum level of 0.30–0.35 ng/ml was achieved. One 75 µg tablet of clonidine raised the serum level to about 0.69±0.13 ng/ml in two hours. After cessation of dosing, the serum level declined with a half-life of 7.5±1.5 h. The urinary excretion of unchanged clonidine was found to be about onethird of the administered dose in 24 h during continuous administration and in the first 24 h after the single oral dose.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 203-212 
    ISSN: 1432-1041
    Keywords: Mepivacaine ; pharmacokinetics ; neonates ; healthy adults ; metabolism ; renal excretion ; lignocaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and metabolism of mepivacaine has been studied in premature neonates dosed subcutaneously and in healthy adults dosed intravenously. The pharmacokinetics of mepivacaine in four neonates (N) was compared with that in six adults (A). Newborns had a significantly longer terminal phase half-life than adults (N mean 8.69 h; A mean 3.17 h). Total plasma clearance normalized on body weight was significantly smaller in neonates (mean 2.34 ml/min/kg) than in adults (mean 5.47 ml/min/kg), as was the hepatic blood clearance (N mean 1.37 ml/min/kg; A mean 5.10 ml/min/kg). The renal plasma clearance, however, was significantly greater in neonates (mean 0.76 ml/min/kg) than adults (mean 0.20 ml/min/kg). There was an average six-fold increase in the fraction of the dose excreted unchanged in newborns (mean 43.3%) compared to adults (mean 7.1%) with acidified urine (pH 5.5–6.0). There was significantly more of the mono-N-demethylated metabolite of mepivacaine excreted by newborns (mean 11.4%) than by adults (mean 2.2%), but their capacity to carry out aromatic hydroxylation of mepivacaine was negligible. These results for mepivacaine were compared with those previously reported for lignocaine in premature infants. The immaturity of hepatic function appears to have diminished more profoundly the ability of premature infants to metabolize mepivacaine than lignocaine. These findings are discussed in terms of perfusion theory of hepatic drug elimination.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 143-147 
    ISSN: 1432-1041
    Keywords: Children ; leukemia ; high-dose methotrexate ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intravenous high-dose methotrexate were studied in two groups of children being treated for malignant diseases, mostly acute lymphatic leukemia. The peak serum level of methotrexate of 2.32·10−5 mol/l was found in children given 500 mg methotrexate/m2 by a 24 h infusion, and another group given 2790 mg/m2 during a 6 h infusion had serum levels as high as 2.16·10−4 mol/l. The decay of serum concentration of methotrexate after completion of the infusion followed a diphasic curve, with an initial serum half-life of 4.8 h, followed by a second half-life of 34.4 h at distribution equilibrium. The apparent volume of distribution was 56.8 litres/m2. Significant levels of methotrexate were found in cerebrospinal fluid, but penetration into cerebrospinal fluid was slow. Urinary excretion of methotrexate was considerable. Four to five days after commencement of the infusion, urinary concentrations of methotrexate still exceeded the serum levels.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 335-340 
    ISSN: 1432-1041
    Keywords: Drug binding to muscle ; interindividual differences ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Binding of 22 drugs to human muscle tissue has been determined by ultrafiltration. All drugs tested were bound, the bound fraction ranging from 13% (aminophenazone) to 〉98% (desipramine). Both linear and nonlinear binding was observed. For chemically related substances, binding to muscle tissue correlated with plasma binding and lipid solubility. There were significant differences in binding to muscle from different individuals. With respect to pharmacokinetics of drugs, it is suggested that binding to muscle tissue may be at least as important as plasma binding.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 41-48 
    ISSN: 1432-1041
    Keywords: Furosemide ; pharmacokinetics ; anephric patients ; metabolism ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of furosemide 40 mg i.v. were compared in 7 anephric patients and in 7 normal subjects. The average serum clearance was 66 ml/min in the patients and 219 ml/min in the normal subjects, and the corresponding weight corrected clearances were 1.33 ml/min · kg and 2.96 ml/min · kg. Binding to serum proteins was significantly decreased in the anephric subjects, in whom a significant negative correlation was found between the percentage binding and the volume of distribution VDss. In the patients, but not in the normal subjects, there was a significant positive correlation between $$V_{D_{ss} } $$ and serum clearance. Both in normal and anephric individuals 4-chlor-5-sulphamoylanthranilic-acid (CSA) was found, but there was no evidence of special accumulation either of CSA or anthranilic acid in the anephric patients. In the patients the initial increase in serum concentration of sodium and protein followed by a more conspicuous decrease were more pronounced, but none of the changes were statistically significant.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 29-33 
    ISSN: 1432-1041
    Keywords: Microcrystalline theophylline ; chronic obstructive airways disease ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma theophylline concentrations have been measured in 9 patients with chronic obstructive airways disease following the oral administration of a microcrystalline theophylline preparation. Some measurements of FEV1 were also made. Four patients were given 375 mg as a single dose and then subsequently 375 mg stat and 125 mg 4 times daily for 3 days, (Group I). A further 5 patients took 250 mg as a single dose and then 250 mg 4 times daily for 3 days, (Group II). In both groups, following the single dose and again after the last dose of chronic administration, blood samples were obtained at frequent intervals up to 24 h for plasma drug estimation. During the 3-day course, blood samples were drawn before and 2 h after each morning dose. In Group I patients, substantial plasma theophylline concentrations were seen only after the loading dose. Thereafter, the mean concentrations before or 2 h after the morning doese were always less than 4.0 µg/ml. Trough concentrations were usually below 2.0 µg/ml. In contrast patients in Group II achieved substantially higher plasma theophylline concentrations, with mean peak concentrations always 10 µg/ml or greater, and trough concentrations greater than 5 µg/ml on at least one occasion in every subject. The elimination half-lives after chronic administration in both groups were not significantly different from those obtained after single doses. Mean drug accumulation, measured as AUCss/AUC1, was 0.87±0.07 in Group I and 0.72±0.14 in Group II, indicating that accumulation had not occurred with either regimen. The mean increase in FEV1 2 h after the administration of a single dose was 19.2% after 375 mg and 16.7% after 250 mg. These results indicate that the recommended dosage regimen for microcrystalline theophylline preparation (375 mg stat and 125 mg 4 times daily) produces inadequate plasma theophylline concentrations: 250 mg 4 times daily would appear to be likely to result in satisfactory theophylline levels in more patients.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 365-371 
    ISSN: 1432-1041
    Keywords: Etidocaine ; pharmacokinetics ; metabolism ; neonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The urinary elimination of etidocaine and several of its metabolites was investigated in neonates whose mothers had received one or more doses of etidocaine during labour. The urine collection period ranged among the neonates from 21.4 to 47.0 h post-partum. The total amounts of etidocaine and its metabolites recovered in neonatal urine represented a mean of 0.12 per cent of the maternal dose. Some differences in the pattern of urinary metabolites were observed between neonates and adults. Mean half-life of elimination of etidocaine calculated from sigma-minus plots of the neonatal urinary data was 6.42 h. This is greater than that previously reported following intravenous administration of etidocaine to adults (2.6 h). The slower rate of elimination in neonates is probably due to an increased neonatal volume of distribution since there is evidence to show that etidocaine is extensively metabolised by the neonate.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 379-383 
    ISSN: 1432-1041
    Keywords: Antipyrine ; pharmacokinetics ; phenzone ; posture ; immobilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a single dose of phenazone was studied in six subjects while ambulant and during bed rest for 3 days. Elimination of the drug was followed for 12 h after oral and intravenous administration. The elimination rate constant and total body clearance were significantly increased during bed rest as compared to the ambulant period, but the differences were small. The apparent volume of distribution decreased significantly. No consistent change due to bed rest was found in the rate of absorption or bioavailability of the oral dose.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 209-212 
    ISSN: 1432-1041
    Keywords: Paracetamol ; acetaminophen ; Gilbert's syndrome ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of paracetamol after intravenous and oral administration has been studied in 6 patients with Gilbert's syndrome, and 6 healthy controls. Paracetamol clearance was significantly less in the patients (255 ml/min SE±23 ml/min) than in the normal subjects (352 ml/min SE±40 ml/min). Moreover, whilst paracetamol concentrations declined monoexponentially in the patients, the decline was biexponential in the controls. No difference in the bioavailability of 500 mg paracetamol given orally was observed between the two groups. The results suggest that not only is paracetamol elimination impaired in Gilbert's syndrome, but that its distribution kinetics are also abnormal. Both these findings could be attributed to a decrease in hepatic glucuronyl transferase activity.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-1041
    Keywords: Aminopyrine ; pharmacokinetics ; 14CO2 breath test ; hepatic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-course of aminopyrine in plasma and of14CO2 in breath was determined for 6 hours after oral administration of (14C-methyl) aminopyrine to healthy controls and to patients with hepatitis and hepatic fibrosis, cirrhosis and hepatic bilharziasis.14CO2 in breath declined about 1.8 times more slowly than aminopyrine plasma levels, which suggests the occurrence of metabolite demethylation. This was confirmed by the slow elimination of14C from plasma, the formation of14CO2 after aminopyrine had disappeared and the presence of a considerable amount of monomethyl-aminopyrine in plasma. The mean14CO2 concentration in breath was correlated with but was not proportional to aminopyrine clearance, which was attributed to individual differences in aminopyrine half-life. Both a correlation and proportionality were found when14CO2 extrapolated to zero time was used as a parameter of14CO2 production. Hepatic disease affected aminopyrine clearance to a variable extent. In the hepatitis and fibrosis group, aminopyrine clearance was affected in 2 out of five subjects. In all except one cirrhotic subject aminopyrine clearance was markedly decreased. Moreover, in three out of seven cases aminopyrine absorption was impaired, presumably due to decreased gastrointestinal blood-flow. This may produce an erroneously low14CO2 concentration in breath during the first two hours after aminopyrine administration. Hepatic bilharziasis was accompanied by very low aminopyrine clearance in all four cases. In two patients high apparent Vd values were observed, probably due to “first-pass” metabolism. Patients with ascites had Vd values within normal limits.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 57-67 
    ISSN: 1432-1041
    Keywords: Chemotherapy ; sulfadiazine ; trimethoprim ; pharmacokinetics ; acetylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Sulfadiazine (SDZ) 800 mg and trimethoprim (TMP) 160 mg were given orally to 10 normal subjects and the concentration of SDZ and TMP in serum and urine was followed for 24 h. Both drugs showed a significant negative correlation between individual “peak” concentrations in serum and the body weight of the subject. Twelve hours after dosing the serum concentration was 12 to 25 µg/ml for SDZ and 0.3 to 1.1 µg/ml for TMP. Individual concentration ratios between SDZ and TMP in serum were 4.8 (1 h) – 145 (24 h), and in the urine the ratio was close to 6 throughout the 24 h collection period. The range of urinary concentrations was from 65 to 400 µg/ml for SDZ and from 13.8 to 93.4 µg/ml for TMP. The fraction acetylated SDZ/acetylated SDZ + SDZ was 21% during the 0–8 h period, 33% during the 8–15 h period and 41% during the 15–24 period. The average values for the notional volume of distribution, Vd, were 0.36±0.13 1/kg for SDZ and 1.39±0.25 1/kg for TMP. The average “t1/2” was 15.2±7.4 h for SDZ and 7.4±1.9 h for TMP. Individual subjects showed a significant correlation between the serum clearance of TMP and SDZ (p〈0.01) and also between the renal clearance of the two drugs (p〈0.05). The serum clearance was significantly correlated with the renal clearance for TMP but not for SDZ. For SDZ Vd was significantly negatively correlated with the elimination constant; for TMP no such correlation was found. The serum clearance of SDZ was significantly correlated with the percentage of SDZ which was excreted as the (presumably) acetylated compound. The renal clearance of SDZ was independent of the serum concentration of SDZ. There was a highly significant negative correlation between the renal clearance and serum concentration of TMP, as well as for “acetylated SDZ”. The renal clearance of “acetylated SDZ” averaged more than six times that of unconjugated SDZ. With increased urine flow the renal clearances of TMP and SDZ were significantly increased.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 237-244 
    ISSN: 1432-1041
    Keywords: Furosemide ; arterial hypertension ; protein binding ; sodium excretion ; renal function ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Furosemide 40 mg was injected intravenously in 7 patients with severe hypertension and vascular complications. A two compartment, open model was used to describe the disappearance of the drug from serum. The mean serum clearance (Cls=1.83 ml/min · kg) was significantly reduced compared to the mean Cls-value of a group of normals (2.96 ml/min · kg). A significant correlation was found between Cls and mean blood pressure, as well as between Cls and renal clearance (mean Clr=0.83 ml/min · kg); extrapolation of the regression line yielded a Cls-value of 50 ml/min for Clr=0. The Clr was also significantly negatively correlated with mean blood pressure. Protein binding of furosemide was normal, except in one patient, who had considerable impairment of renal function. Apparently more than 90% of unchanged furosemide passed in urine was excreted by tubular transport. A highly significant negative correlation was found between Cls and the fraction of furosemide excreted as a glucuronide. During the first two hours, significantly less sodium was excreted by the patients than by a comparable group of normal subjects. The correlation between serum concentration of furosemide and the amount excreted of sodium was not significant, but highly significant correlations were found between the amounts of furosemide and sodium excreted by the kidney in 0–30 and 0–60 min. In all the individual patients an approximately linear relationship with wide variation in the slope was found between the cumulative excretion of furosemide and sodium from 0–30 min to 0–60 and to 0–120 min. After 120 min deviations were observed in the curves from 4 of the patients, which indicated that smaller and smaller additional amounts of sodium were excreted with constant additional amounts of furosemide.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 267-271 
    ISSN: 1432-1041
    Keywords: Lithium ; sustained-release ; pharmacokinetics ; manic patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An ordinary and a sustained-release lithium carbonate preparation were administered acutely at equivalent dosage (1.80 g=24.3 mmol) in a crossover fashion to manic patients. Serum lithium levels were determined by atomic absorption spectroscopy and pharmacokinetic parameters were calculated. Maximum mean serum levels of 1.13 mmol/l and 0.78 mmol/l were achieved at 6 h and 12 h respectively with the ordinary and sustained-release forms. The mean half-lives of absorption, redistribution and elimination were 0.78 h±0.05 (SE), 5.06 h±0.23, 26.8 h±4.5 and 3.73 h±0.37 (SE), 4.42 h±0.28 and 25.6 h±5.5 for the ordinary and sustained-release forms respectively. In healthy volunteers the ordinary preparation was completely absorbed but only 85% of the sustained-release form was absorbed in the manic subjects. Lithium ion distributed into two kinetic compartments and the final compartment appeared to correspond to total body water.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 277-280 
    ISSN: 1432-1041
    Keywords: Doxycycline ; iron ; charcoal ; enteral cycling ; man ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In order to study the intestinal interactions of doxycycline (DC) with Fe++ and charcoal, two groups of healthy volunteers were given either 200 mg or 100 mg DC in capsules at 2 p. m. and 9 p. m., and blood samples for fluorimetric assay of DC were collected for 24 h starting at 8.30 a. m. on the following morning. A 24-h-urine was also collected. The test was subsequently repeated at one-week intervals, when the volunteers also ingested either ferrous sulphate (80 mg Fe++) or charcoal (4.0 g) immediately after the zero-time sample of DC and at 3, 8 and 12 h. Charcoal completely adsorbed DC in vitro in an artificial small intestinal fluid. Ferrous sulphate or charcoal did not modify the serum level or urinary excretion of DC after the 200 mg+200 mg dose, but ferrous sulphate did reduce the 24-h urinary excretion of DC after the 100 mg+100 mg dose. The serum half-life and AUC of DC were reduced by ferrous sulphate given after the 100 mg+100 mg dose of DC. Charcoal did not modify any parameter, even after the 100 mg+100 mg dose of DC. The results do not support existence of important enteral cycling of DC. Although oral ferrous sulphate can lower the serum level and shorten the serum half-life of DC, the acute experiment suggested that a therapeutic serum level of DC can be maintained despite treatment with iron in the doses used in iron-deficiency, and charcoal in the doses used in diarrhoeic states, if the drugs are administered several hours apart.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 69-73 
    ISSN: 1432-1041
    Keywords: Citalopram ; pharmacokinetics ; man ; steady state levels ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of citalopram, a potent serotonin reuptake inhibitor, and its demethylated metabolite have been determined by a specific fluorescence coupling technique during single dose experiments in volunteers and in clinical tests. Citalopram was found to have linear kinetics within the dose range investigated, which were characterized by fairly rapid absorption and slow elimination (biological half-life 1–21/2 days). Steady state levels in the range 120–340 nM (i.e. slightly above those associated with pharmacodynamic activity in animals) were attained within a week. A drug/metabolite ratio of 2–3 was recorded.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 14 (1978), S. 431-434 
    ISSN: 1432-1041
    Keywords: Timolol ; pharmacokinetics ; oral and intravenous dosing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma kinetics of timolol administered orally and intravenously to 5 male subjects were examined. Bioavailability was reduced by 25% when the drug was taken orally. Mean plasma half-life after oral dosing was 4.86 h, and after intravenous administration it was 4.56 h; the difference was not significant. The volume of distribution was 3.5 l/k. It is suggested that timolol is little affected by the ‘first pass effect’, even though there is marked interindividual variation in availability and peak plasma level.
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  • 20
    ISSN: 1432-1041
    Keywords: Lignocaine ; pharmacokinetics ; neonates ; metabolism ; renal excretion ; plasma concentrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and metabolism of lignocaine in premature neonates was studied after subcutaneous administration. The collection of serial urine together with a limited number of blood samples from neonates enabled simultaneous computer fitting of data to a pharmacokinetic model. The disposition kinetics of lignocaine in four neonates were compared with similar data reported for adults. Neonates had prolonged t1/2 (neonate mean: 3.16 h; adult mean: 1.80 h), and an increased total volume of distribution (neonate mean: 2.75 l/kg; adult mean: 1.11 l/kg) compared with adults. Total plasma clearance (Cltp) normalised on body weight showed no significant difference between neonates (mean: 0.610 l/h/kg) and adults (mean: 0.550 l/h/kg). The urinary excretion of lignocaine and several of its metabolites was studied in 8 neonates and 11 adults. Neonates were shown to excrete much more unchanged lignocaine (mean: 19.67%) compared with adults (mean: 4.27%) and the proportion of the dose excreted as 4-hydroxyxylidine is considerably reduced in neonates (neonate mean: 8.89%; adult mean: 63.78%). The use of the two pharmacokinetic parameters, t1/2 and Cltp, as indices of drug elimination ability are discussed.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 13 (1978), S. 219-222 
    ISSN: 1432-1041
    Keywords: Glaziovine ; pharmacokinetics ; plasma levels ; urinary excretion ; biliary excretion ; enteral absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic parameters of Glaziovine, a pro-aporphine alkaloid with neuropharmacological properties, were investigated in healthy human volunteers. Glaziovine-14C 20 mg was administered in capsules (oral route) and in vials (i.v. route). Total radioactivity was measured in plasma, urine and faeces. When administered orally, peak plasma levels were encountered at 2 h. The cumulative urinary excretion of total radioactivity over a 24 h period was 38% after oral and 50% after i.v. administration. Investigation of metabolites in urine revealed Glaziovine glucuronide as the sole metabolite of the drug. By comparing the percentage of urinary excretion or the area under the plasma level-time curve (AUC) obtained in the first 24 hours after i.v. and oral administration, enteral absorption was found to range from 78 to 84%. Thus, glaziovine appears to show very high enteral absorption.
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  • 22
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    European journal of clinical pharmacology 13 (1978), S. 55-60 
    ISSN: 1432-1041
    Keywords: Valproic acid ; pharmacokinetics ; liver disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of valproic acid (di-n-propylacetate; VA) has been studied after a single oral dose of a solution of 450 mg in 7 patients with alcoholic cirrhosis and in 4 patients recovering from acute hepatitis. The diagnosis was based on biochemical function tests and histological findings. The pharmacokinetic parameters were compared with those reported for healthy volunteers. VA in therapeutic concentration (80 µg/ml) in plasma was less bound to plasma proteins in patients with alcoholic cirrhosis (70.7±11.3%) and in patients recovering from acute hepatitis (78.1±14.1%) than in controls (88.7±5.2%). The reduced binding affected the blood/plasma concentration ratio and the apparent distribution volume Vd(β); the latter was increased from the normal value of 0.14±0.05 l/kg to 0.22±0.09 (p〈0.05) in alcoholic cirrhotics, and to 0.20±0.07 (p=0.056) in patients recovering from acute hepatitis. The half-life of elimination T1/2 (β) (controls=12.2±3.7 h) was significantly (p〈0.05) prolonged in cirrhotics (18.9±5.1 h) and in patients recovering from acute hepatitis (17.0±3.7 h). The plasma $$\overline {Cl} $$ of total drug was not impaired, which can best be explained by the lower plasma protein binding, which might have increased the $$\overline {Cl} $$ of this drug which shows restricted clearance. In addition, the plasma $$\overline {Cl} $$ of free drug was significantly (p〈0.02) reduced in alcoholic cirrhotics. During a two day urine collection no measurable amount of unchanged VA was recovered. There was considerable excretion of VA-conjugates, which could be hydrolyzed either by HCl or by β-glucuronidase/arylsulphatase (4–23% of the dose). These percentages were in the same range as in normals (26.7±16.1%). The study indicates that elimination of VA is slightly impaired in patients with dysfunction of the liver.
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  • 23
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    European journal of clinical pharmacology 13 (1978), S. 267-274 
    ISSN: 1432-1041
    Keywords: Chlordiazepoxide ; benzodiazepines ; pharmacokinetics ; bioavailability ; intramuscular injection ; alcohol withdrawal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of oral and intramuscular (i. m.) chlordiazepoxide hydrochloride (CDX · HCl) was compared in two pharmacokinetic studies. In Study One, single 50-mg doses of CDX · HCl were administered orally and by i. m. injection to 14 healthy volunteers using a crossover design. Whole-blood concentrations of chlordiazepoxide (CDX) and its first active metabolite, desmethylchlordiazepoxide (DMCDX), were determined in multiple samples drawn after the dose. Mean pharmacokinetic variables for CDX following oral and i. m. administration, respectively, were: highest measured blood concentration, 1.65 vs 0.87 µg/ml (p〈0.001); time of highest concentration, 2.3 vs 7.6 h after dosing (p〈0.001); apparent absorption half-life, 0.71 vs 3.39 h (p〈0.001). Biphasic absorption after i. m. injection, consistent with precipitation at the injection site, was observed in 9 of 14 subjects. Based upon comparison with previous intravenous data, the completeness of absorption was 100% for oral vs 86% for i. m. CDX · HCl (p〈0.1). In Study Two, 28 male chronic alcoholics with clinical manifestations of the acute alcohol withdrawal syndrome were randomly assigned to one of four treatment conditions: 50 or 100 mg doses of CDX · HCl, by mouth or by i. m. injection. Concentrations of CDX and DMCDX, determined in plasma samples drawn every 20 min for 5 h following the dose, were significantly higher after oral administration of a given dose than at corresponding points in time after i.m. injection after the same dose. Thus absorption of oral CDX is reasonably rapid and complete, whereas the absorption rate of i. m. CDX is slow.
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  • 24
    ISSN: 1432-1041
    Keywords: Phenylbutazone ; pharmacokinetics ; model ; retrospective analysis ; digestive-tract hemorrhage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Phenylbutazone treatment can cause digestive-tract hemorrhages, but its concentration in the blood at the time of hemorrhage is generally not known. In two patients who had had digestive tract hemorrhages, the variation in the serum phenylbutazone concentration throughout treatment and just before hemorrhage was simulated by a two-compartment model based on assays (gas-liquid chromatography) made after the hemorrhage. Identification of the parameters of the model and simulation of changes in concentration during therapy suggested that the phenylbutazone level in serum at the time of hemorrhage was 101 and 125 µg/ml respectively.
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  • 25
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    European journal of clinical pharmacology 14 (1978), S. 29-37 
    ISSN: 1432-1041
    Keywords: Hydroflumethiazide ; pharmacokinetics ; cardiac failure ; renal drug excretion ; metabolism ; 2,4-disulfamyl-5-trifluoro-methylaniline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of hydroflumethiazide (HFT) were investigated after single oral doses of 6 µmoles/ per kg body weight in five healthy subjects and in nine patients with moderate cardiac failure. HFT was excreted in urine together with 2,4-disulfamyl-5-trifluoromethylaniline (DTA), which was also present in the blood after administration of HFT. HFT and DTA were determined by TLC and spectrofluorodensitometry. Mean cumulative urinary excretion of HFT was 46.5 and 47.5 per cent of the dose both in healthy subjects and in patients. Distribution half-life (t1/2α) was about 2 h in both groups of subjects, while biological half-life (t1/2β) ranged from 12.4 to 26.9 h (mean 16.6) in healthy subjects, and from 6.3 to 13.7 h (mean 9.6) in patients. Mean renal clearance was 0.33 and 0.211 · h−1 · kg−1 in normal subjects and patients, respectively, and was almost equal to the total body clearance. HFT had a large apparent volume of distribution (Vβ), with mean values of 6.4 and 3.11 · kg−1 in normal subjects and patients. Mean cumulative urinary excretion of DTA was 1.8 and 1.9 per cent in healthy subjects and patients with cardiac failure. The apparent half-life of DTA, determined from urinary excretion rate in eleven subjects, ranged from 16 to 56 h but half-lives in three others were more than 100 h. The results indicate that HFT is partly metabolized in the body to DTA, and DTA and HFT are excreted in urine. The half-life of DTA was longer than that of the parent drug. The apparent volume of distribution, clearance and biological half-life of HFT were lower in patients with cardiac failure than in healthy subjects.
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  • 26
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    European journal of clinical pharmacology 14 (1978), S. 361-366 
    ISSN: 1432-1041
    Keywords: Furosemide ; gestosis of pregnancy ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Furosemide 50 mg was administered orally and intravenously to twelve gestotic women for brief periods as a part of a randomized, multicentre clinical trial comparing the efficacy of bed rest and pharmacological treatment. The pharmacokinetic profile was investigated using a gas-liquid chromatographic technique. The plasma half-life after oral and intravenous administration was 115±37.1 and 71.8±26.3 min and plasma clearance was 153±48 and 152±23 ml/min, respectively (mean±SD). Comparative data from healthy pregnant women cannot be obtained for ethical reasons. The results show that gestosis has only a marginal if any effect on the kinetics of furosemide in comparison with published kinetic parameters in healthy volunteers and patients with renal failure. The new-born babies where checked for side effects according to a protocol in use in a larger regional surveillance programme. No clinical side-effects were attributable to furosemide, but the small size of the group does not permit any definitive conclusions about this aspect.
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  • 27
    ISSN: 1432-1041
    Keywords: Phase I clinical trial ; complex protocol ; tolerance ; pharmacokinetics ; praziquantel ; anthelmintic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The tolerance of Praziquantel (2-cyclohexylcarbonyl-1, 3, 4, 6, 7, 11b-hexahydro-2H-pyrazino-[2, 1-a]isoquinoline-4-one) in oral doses of 1×20 mg/kg, 1×50 mg/kg, 3×10 mg/kg and 3×25 mg/kg body weight (τ=4 h) was tested in a complex study involving 36 healthy volunteers. In addition to the usual assessment of clinical chemistry, haematology, coagulation physiology, urinalysis, clinico-physiological examination including EEG, and medical examination, clinico-psychological parameters were also recorded and special neurological investigations were performed. No clinically relevant changes were found in any of the laboratory parameters, nor in the medical-neurological or clinico-physiological examinations. Based on a few clinicopsychological parameters and subjective comments, the largest daily dose tested (3×25 mg/kg=75 mg/kg) produced a slight, transient disturbance in general well-being, which was barely detectable on objective clinical examination. The pharmacokinetic behaviour was dominated by rapid metabolism and pronounced first-pass metabolism of praziquantel, which greatly limits the value of results obtained by GC analysis of unchanged drug in serum. The peak concentration in serum was reached after 1– h, and the elimination half-life for the period 2–8 h was 1–1.5 h.
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  • 28
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    European journal of clinical pharmacology 13 (1978), S. 35-39 
    ISSN: 1432-1041
    Keywords: Norethindrone ; bioavailability ; man ; competitive protein binding ; sex differences ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A competitive protein binding assay for norethindrone was developed to measure plasma levels in human subjects. The plasma levels were considerably higher in women than in men, especially at low dose levels. The plasma levels were directly related to the dose in men; but greater variations in the plasma levels were observed in women. The plasma half-life was about 5 h in both sexes with single oral doses of 5 to 20 mg. A comparative bioavailability study with norethindrone from 2 different manufacturers, formulated in the same manner, showed no significant differences in absorption characteristics and provided sufficient data for pharmacokinetic analysis.
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  • 29
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    European journal of clinical pharmacology 13 (1978), S. 119-124 
    ISSN: 1432-1041
    Keywords: Bendroflumethiazide ; pharmacokinetics ; hypertension ; renal clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After four weeks on placebo treatment, 8 hypertensive patients (WHO stage I) were treated for 2 weeks with bendroflumethiazide (bft) 2.5 mg and KCl 1.5 g daily. Subsequently they received bft 5 mg and KCl 1.5 g daily for a further fortnight. At the end of each period of treatment blood pressure was recorded and blood samples and urine were collected for analysis of bft by GLC. Before taking the daily dose of bft, no trace of the drug was found in plasma. Peak levels of bft were seen after 2.3 h and averaged 23 and 50 ng · ml−1 after 2.5 and 5 mg, respectively. After bft 2.5 mg the plasma level was too low for kinetic analysis. The plasma half-life after 5 mg averaged 4.1 h. The mean apparent volume of distribution was 1.18 l · kg−1. Non-renal clearance averaged 200 ml · min−1. The renal clearance of bft was significantly lower (p〈0.05) after 5 mg (48 ml · min−1) than after 2.5 mg bft (93 ml · min−1), although the creatinine clearance remained unchanged. No correlation was found between the plasma level of bft and its effect on blood pressure.
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  • 30
    ISSN: 1432-1041
    Keywords: Cephacetrile ; pharmacokinetics ; renal Impairment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of cephacetrile, administered as a single i. v. injection of 15 mg/kg, have been determined in 8 patients with normal renal function and in 12 patients with a varying degree of renal impairment. A two-compartment model was used to describe the biphasic decline in serum concentrations and to calculate the amount of antibiotic in the central and peripheral compartments. In patients with normal renal function the following values were obtained for various pharmacokinetic parameters: α=3.971 h−1; β=0.343 h−1; K12=1.745 h−1; K21=0.763 h−1; Kel=1.793 h−1; Vc=8.181; Vp=18.401 and Vdss=26.581. Cephacetrile had some of the highest apparent distribution volumes of all the cephalosporins. Impaired renal function significantly affected α, β, K12, and Kel. A linear relationship between Kel of cephacetrile and creatinine clearance was demonstrated. The elimination of cephacetrile in anuric patients was about ten times slower than in patients with normal renal function.
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  • 31
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    European journal of clinical pharmacology 14 (1978), S. 293-299 
    ISSN: 1432-1041
    Keywords: Breath analysis ; 14CO2 exhalation ; drug metabolism ; glycodiazine ; liquid chromatography ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Exhalation of14CO2 in breath has been used to assess the rate of hepatic demethylation of (14C-dimethyl)aminopyrine, but due to the complexity of aminopyrine metabolism the pharmacokinetics of the procedure are insufficiently understood. Therefore, studies were performed in five individuals after oral administration of (14C-methoxy)glycodiazine, a model substance with relatively simple kinetic properties. Plasma concentrations of the drug and urinary output of its metabolites measured by high pressure liquid chromatography were analysed by a two-compartment open model. The terminal disappearance of14CO2 from breath was practically identical with the terminal disappearance of glycodiazine from plasma, which could be correlated with the plasma clearance of free glycodiazine. The mean transit time of14C-atoms from plasma to breath was 3 h. These results contribute to the pharmacokinetic basis for use of14C-demethylation breath tests. In particular, they are consistent with the hypothesis that14CO2-breath analysis may be used to assess certain pharmacokinetic parameters of appropriately labelled test compounds. These parameters may not necessarily be a direct reflection of the rate of demethylation.
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  • 32
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    European journal of clinical pharmacology 14 (1978), S. 405-412 
    ISSN: 1432-1041
    Keywords: Colloidal plasma substitutes ; cross-linked polypeptides ; Haemaccel® ; pharmacokinetics ; renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Infusions of 3.5% isocyanate cross-linked polypeptide solution 500 ml were given to 52 patients with normal or impaired renal function: glomerular filtration rate (GFR)=0–133 ml/min. The serum concentration and urinary excretion of hydroxyproline were measured and the equivalent polypeptide concentrations were calculated from the results. In patients with normal renal function (GFR〉90 ml/min) the proportion of polypeptide excreted in the urine up to 12 h was 45.4±2.6% ( $$\bar X$$ ±SEM), up to 24 h 47.7±2.9% and up to 48 h 49.3±3.4%. In patients with moderate renal insufficiency (GFR=30–90 ml/min) there was no decrease in polypeptide excretion and even in patients with more serious impairment of GFR (11–30 ml/min) 48-h urinary polypeptide excretion was still 40.6±5.9%. In patients with GFR of 2–10 ml/min polypeptide excretion fell to 10.7±3.2% during the first 12 h, although there was an increase in later collection periods as compared to patients with normal renal function −19.9±3.9% in 24 h and 27.0±3.5% in 48 h. The elimination half-life (t1/2) calculated from serum concentrations was 505±30 min ( $$\bar X$$ ±SEM) in patients with normal renal function (GFR〉90 ml/min). Only when the GFR fell below 30 ml/min did it slowly begin to increase. In patients with minimal residual renal function (GFR=0–0.5 ml/min), who were on haemodialysis, the elimination half-life was 985±49 min, i.e. approximately twice the normal. Twice weekly infusion of 3.5% polypeptide solution 500 ml over a period of 6 weeks did not produce any significant cumulation in haemodialysis patients (GFR=0–0.5 ml/min). A weekly dose of polypeptide 35 g appeared to be quite safe when given for several weeks, even to anuric patients. As no significant amount of polypeptide was lost during haemodialysis, the dose can be chosen without taking into account any effect of intermittent haemodialysis.
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  • 33
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 505-519 
    ISSN: 1573-8744
    Keywords: morphine ; first-pass elimination ; pharmacokinetics ; enterohepatic recirculation ; availability ; routes of administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Morphine was administered to rats by oral, intraportal, and intravenous routes in a dose of 7.6 mg · kg −1.From the serum concentration data after intraportal administration it was calculated that the first-pass elimination of morphine in the liver amounts to 72±2% (sd). The first-pass fraction eliminated after oral administration was 85±7% (sd), thus yielding a contribution by the gut mucosa of 46% to the overall first-pass elimination after an oral dose. The results were obtained with a general compartmental model which included the kinetics of enterohepatic recirculation. The oral availability was also estimated with the aid of pharmacological effect data. This availability was in good agreement with the corresponding value determined from the serum concentration data. The results suggest that morphine is subjected to enterohepatic recirculation and that the slowest phase of decline of morphine concentrations in serum might be due to this physiological process.
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  • 34
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 265-282 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; linear systems analysis ; in vivo dissolution rates ; absorption rates ; metabolic rates ; bioavailability ; numerical desconvolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of certain aspects of linear systems analysis to pharmacokinetic-problems is described. Topics covered include the evaluation of in vivodissolution rates, absorption rates, and metabolic rates, and the use of pharmacological data. Relevant numerical procedures are also discussed.
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  • 35
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 315-325 
    ISSN: 1573-8744
    Keywords: percutaneous penetration ; methotrexate ; compartmental models ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Compartmental models were developed to describe the penetration of a drug from a topically applied vehicle through the skin. Data for in vitro penetration of methotrexate through hairless mouse skin from vehicles varying in PH from 3.5 to 6.5 were computer- fitted to estimate model parameters. Comparison of lag time and the exponential coefficient suggested that parallel penetration pathways exist. The fraction of drug penetrating through the shunt pathway increased as vehicle pH and ionization increased. Penetration curves were quantitatively partitioned into bulk tissue and shunt contributions. At pH 6.5, flux through the shunt pathway predominated.
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  • 36
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 521-537 
    ISSN: 1573-8744
    Keywords: compartmental analysis ; doxantrazole ; drug distribution ; mathematical prediction ; pharmacokinetics ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A pharmacokinetic model incorporating 14 compartments and 29 transfer coefficients has been developed from experimental data obtained after intravenous administration of a single dose to describe the distribution of doxantrazole in the rat. The distribution calculated from the model agreed closely with that determined experimentally. In addition, the model was able to predict with considerable accuracy the distribution of doxantrazole after repeated dosing.
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  • 37
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 187-196 
    ISSN: 1573-8744
    Keywords: Chlorpromazine ; pharmacokinetics ; oral absorption ; single dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A single oral dose (120 mg/m2) of Chlorpromazine hydrochloride was administered to four healthy subjects and the blood levels of Chlorpromazine were determined with time. Appropriate equations describing the two-compartment open model with zero-order absorption and the two-compartment model with first-order absorption, both with a lag time, were fitted to the observed data using weighted nonlinear least-squares regression analysis. Fitting the two-compartment model with zero-order absorption and a lag time to the observed data resulted in a significant reduction of the weighted sum of squared deviations, i.e., better correlation between the observed and calculated data, and a closer random scatter of the observed concentration data around the calculated curve with no apparent systematic deviations from the curve. These results suggest that Chlorpromazine absorption is zero order. Chlorpromazine began to appear in the systemic circulation after a mean lag time of 0.4 hr and continued to be absorbed for approximately 2.9 hr. The mean half-lives of the distribution and elimination phases were 1.63 and 17.7 hr, respectively.
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  • 38
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 547-558 
    ISSN: 1573-8744
    Keywords: statistical moments ; network theory ; pharmacokinetics ; bioavailability ; deconvolution ; plasma concentration-time curve ; urinary excretion rate-time curve ; compartment models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Statistical moments are parameters that describe the characteristics of the time courses of plasma concentration (area, mean residence time, and variance of residence time) and of the urinary excretion rate that follow administration of a single dose of a drug. The relationship between the moments of a time-course curve and pharmacokinetic profiles of drug disposition, i.e., absorption, distribution, metabolism, and excretion, is described. The moments are related to the extent and rate of bioavailability, and it is shown that they can be effectively applied to the deconvolution operation.
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  • 39
    ISSN: 1573-8744
    Keywords: trapezoidal rule ; area under the curve ; pharmacokinetics ; clearance ; bioavailability ; integration method ; sulfisoxazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The linear trapezoidal rule method is commonly used for the estimation of the area under the plasma level-time curve. Error analyses are performed when the method is used in first-order absorption and first-order elimination kinetics in the one-compartment system. It is found that significant underestimations and overestimations in area during the absorption phase and postabsorption phase, respectively, can occur when the method is improperly used. During the exponential postabsorption phase the relative error is only a function of the ratio (n)of the time interval over the half-life of the two plasma data points in the interval. The error from the linear trapezoidal rule method at n=0.5 is about 1%. The error increases to 15.5% and 57.1 % when nis increased to 2 and 4, respectively. It is recommended that for most absorption studies the linear trapezoidal method be used for prepeak and plateau plasma data and the logarithmic trapezoidal method for postpeak plasma data.
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  • 40
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 295-303 
    ISSN: 1573-8744
    Keywords: tetracycline ; antibiotics ; Billroth-II gastrectomy ; gastrectomy ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The bioavailability of a single 250-mg oral dose of tetracycline hydroghloride was studied in seven patients following Billroth-II gastrectomy in comparison with seven control subjects matched for age and body weight. There were no significant differences between control subjects and gastrectomized patients in the apparent lag time prior to the start of absorption (23.6 vs. 22.8 min), peak serum tetracycline concentration (1.72 vs. 1.75 μg/ml), the time of attainment of peak concentrations (3.35 vs. 3.42 hr), the apparent first-order absorption half-life (1.8 vs. 1.4hr), or the apparent first-order elimination half-life (8.0 vs. 8.7hr). Completeness of tetracycline absorption, as judged by area under the 24-hr serum concentration curve, did not differ significantly between the two groups, nor did 24-hr urinary excretion of tetracycline. Thus the abnormalities of gastrointestinal structure and function produced by Billroth -II gastrectomy do not result in impairment of the rate and completeness of tetracycline absorption.
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  • 41
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    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 369-387 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; dog ; diethyldithiocarbamate metabolite of disulfiram ; presence of methyl ester ; kinetic evaluation of prior studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Following the intravenous infusion of sodium diethyldithiocarbamate to dogs, the disposition kinetics of diethyldithiocarbamate (DDC), a metabolite of disulfiram, were assessed. Approximately 27% of the administered dose was S-methylated, this process exhibiting a mean first-order rate constant of 0. 0569 min−1 (t1/2=12.2 min), while the remainder was eliminated by other routes having a rate constant of 0.148 min−1 (t1/2=4.68 min). The methyl diethyldithiocarbamate (MeDDC) formed from DDC showed an elimination rate constant of 0.0141 min−1 (t1/2=49.2 min). These observations are discussed in the light of previous investigations where the presence of MeDDC has rarely been sought or reported. A few comparisons with prior studies, in which DDC or disulfiram was administered, are made by retrospective kinetic evaluation of published data. The results are discussed in relation to the duration of action of disulfiram in man.
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  • 42
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 59-65 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This note presents the closed form equations for the stiffness terms in the elastic-plastic stiffness matrix for axisymmetric finite elements. The element considered is a triangular ring element characterized by linear displacement relationships and an averaged state of stress. The physical law is modelled by the incremental theory of plasticity utilizing the Prandtl-Reuss flow rule and von-Mises Yield Criterion. Results are presented comparing stiffness terms as computed by numerical integration to those computed from the closed form equations. Significant errors in stiffness terms arising from numerical integration are observed for axisymmetric elements located near the line of axial symmetry as a result of the logarithmic nature of some of the stiffness terms.
    Additional Material: 2 Ill.
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  • 43
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 85-92 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The compressible potential flow on a blade-to-blade surface of a turbomachine is analysed using the Thomas algorithm. The numerical properties of resulting non-linear simultaneous equations are studied with respect to grid aspect ratios and convergence. The heuristic approach has established which are the important factors that affect the flow solution in typical blade-to-blade configurations.
    Additional Material: 4 Ill.
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  • 44
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 93-99 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This note describes improvements to the Suhara-Fukuda method for generating a triangular finite element network. These are based on the use of a node generation procedure which distributes nodes is a regular pattern across the network area and is sufficiently flexible to permit any variation in element density. Because of the regular node distribution, poorly shaped elements will not arise and so the procedure for connecting the nodes to form elements can be simplified. Examples of networks generaed in this way are given.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 183-185 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In a recent paper, Dr. Frind has formulated a two-dimensional isoparametric finite element based upon the Hermite bicubic interpolation scheme. The present discussion focuses upon certain simplifications in the derivation which appear to have diminished the accuracy of the resulting element, and suggests a simpler approach to the element formulation. This author agrees strongly with Dr. Frind's recommendation of the Hermite parametric element as an efficient and useful tool for general field problems; the present comments are offered to point out that, in fact, the accuracy comparisons presented by Dr. Frind are biased against the Hermite finite element.
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  • 46
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 47
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1-10 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical technique for solving unsteady gas dynamic equations is presented. The technique is based on least squares finite element concepts with elements that are constructed in both space and time. Both linear and quadratic interpolation is used on individual elements. The technique is tested against a problem whose solution is known so that numerical accuracy can be ascertained.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 47-57 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A viscous approximation for steady creeping flow is extended to include the effect of elastic strains. Two examples are presented which illustrate both the method and the need for including elastic strains in the analysis of steady-state visco-plastic flows.
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  • 49
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 101-114 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A finite element formulation for large elasto-plastic deformation of polycrystalline materials is proposed in incremental form. The effect of rotation of crystal axes besides usual element rotaion is taken into account. Some numerical considerations on polycrystalline plasticity (i.e. stress-strain curves for several proportional loadings, effect of change of loading path on stress-strain curve, subsequent yield loci for uniaxial and equi-biaxial loadings and so forth) are given for the case of small deformation by using a plate model which consists of 121 square FCC crystals.
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  • 50
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 382-383 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 51
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 405-414 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 52
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 453-469 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A least squares method is presented for computing approximate solutions of indefinite partial differential equations of the mixed type such as those that arise in connection with transonic flutter analysis. The mehod retains the advantages of finite difference schemes namely simplicity and sparsity of the resulting matrix system. However, it offers some great advantages over finite difference schemes. First, the method is insensitive to the value of the forcing frequency i.e., the resulting matrix system is always symmetric and positive definite,. As a result, iterative methods may be successfully employed to solve the matrix system, thus taking full advantage of the sparsity. Furthermore, the method is insensitive to the type of the partial differential equation, i.e., the computational algorithm is the same in elliptic and hyperbolic regions. In this work the method is formulated and numerical results for model problems are presented. Some theoretical aspects of least squares approximations are also discussed.
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  • 53
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1375-1382 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: An optimal steady-state control problem governed by an elliptic state equation is solved by several finite element methods. Finite element discretizations are applied to different variational formulations of the problem yielding accurate numerical results as compared with the given analytical solution. It is sated that, for minimum computational effort and high accuracy, ‘mixed’ finite elements requiring only C° continuity, and approximating the control and state functions simultaneously are better suited to similar ‘fourth order’ problems.
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  • 54
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1367-1373 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A recent paper by Donald Gignac describes some difficulties with a certain matrix eigenvalue problem. This paper shows that the difficulties result from the naturue of the matrix itself. Quantities called condition numbers, which measure the sensitivity of the eigenvalues, are computed, and numerical results given.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1383-1397 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The boundary-integral equation medthod is particularly well suited for solution of stress concentration and elastic fracture mechanics problems. The method was not previously applicable to anisotropic three dimensional problems because no efficient technique existed for calculation of the required point load solution for an infinite body. A technique has been developed to evaluate numerically the anisotropic point load soultions, and used to generate data bases for various materials. An intrpolation technique is used to evaluate the point load solutions efficiently within a higher order boundary-intgral equation code. The effectiveness of the technique is verified by solution of problems involving both uniaxial stress states and stress concentrations.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1473-1477 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 57
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1659-1666 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 59
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1635-1650 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A diagonal lumped mas formulation with non-zero inertia terms is presented for Ahmad's general shell element. The effect of co-ordinate transformation of the mas matrix is demonstrated. Due to arbitray co-ordinate transformation on nodal variables, the diagonal lumped mas matrix becomes a banded matrix of half bandwidth three. It is shown that with some approximations this matrix can be made diagnoal without effecting the results appreciably. Numerical examples are presented to illustrate the accuracy of the formulation. Similar lumped mass matrix formulation is also given for axisymmetric shell elements.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1651-1657 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A Procedure is presented for generating a class of conformal mappings useful in the formulation of finite-difference problems involving curved boundaries. The method provides a systematic approach that is capable, in principle, of reducing the geometry to a nearly-rectangular domain for a wide variety of partical problems. The introduction of sheared co-ordinates in this computational domain then provides for solution of the problem in a nearly-orthogonal (in fact, nearly-conformal) co-ordinate system, with its boundaries corresponding to co-ordinate lines. The method is based upon the Schwarz-Christoffel transformation and is quite simple to apply. Several examples illustrating the types of geometries which can be treated in this manner are presented.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1667-1676 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper presents a thin plate element formulated along parallel lines to the general three-dimensional Semiloof shell element. This plate version possesses only one half of the total number of degrees-of-freedom of the shell element and has the advantqage that the formulation of the strains and other terms is very much simplified. The element is first assessed in static situations and then its performance in the solution of eigenvalue problems is considered.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1697-1704 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper analyses the oscillatory nature of central difference approximations to the heat transport equation when convection is the important mechanism of heat transport. The effects of three different boundary conditions, various heat source profiles, the Peclet Number and the parity of the number of meshes on the amplitudes of these oscillations are described. A boundary condition is presented which suppresses the oscillations to insignificant amplitudes in the one-dimensional situation.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1764-1771 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Upwinded parabolic and cubic elements are derived on a uniform grid of size h for the finite element Galerkin method applied to the solution of the model conduction-convection problem εu″  -  Ku′ = 0, ε, K 〉 0, subject to the boundary conditions u(0) = 1, u (1) = 0. Extension of the results to more complicated problems is indicated. Finally numerical results are given comparing some of the methods derived for a range of L(=Kh/2ε), the grid Peclet number.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1819-1839 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The present paper describes a hybrid stress finite element formulation for geometrically non-linear analysis of thin shell structures. The element properties are derived from an incremental form of Hellinger-Reissner's variational principle in which all quantities are referred to the current configuration of the shell. From this multi-field variational principle, a hybrid stress finite element model is derived using standard matrix notation. Very simple flat triangular and quadrilateral elements are employed in the present study. The resulting non-linear equations are solved by applying the load in finite increments and restoring equilibrium by Newton-Raphson iteratioin. Numerical examples presented in the paper include complete snap-through buckling of cylindrical and spherical shells. It turns out that the present procedure is computationally efficient and accurate for non-linear shell problems of high complexity.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1883-1889 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1890-1896 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Symmetric three point quadrature schemes are at present available for triangles for exact integration of polynomials of degree 2. There are other possible symmetries, which provide higher accuracies. Exact integration of polynomials of a higher degree is possible. General formulations are made and a set of three integration points for improved accuracy is given.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1898-1900 
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 1897-1898 
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  • 69
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    International Journal for Numerical Methods in Engineering 13 (1978), S. 203-228 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A brief review of the structural optimization literature and a description of the present status of optimization methods are presented. The scope of the review is limited and does not profess to cover the entire literature.Results of the optimization of two structures (by the optimality criteria approach) are presented. There are some conclusions and recommendations for future developments in structural optimization.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 11-33 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The discretization of the media at all spatial co-ordinates but one is presented here. This partial discretization leads to continuous finite elements as opposed to fully discrete ones and the problem resolves, for the cases presented here, into a set of linear differential equations rather than algebraic equations. The general problem of first derivative functionals in elastostatics is considered and it is shown, in general, how the continuous finite elements required for the solution may be obtained. Plane states, axisymmetric and three-dimensional continuous elements are obtained to illustrate application to particular cases.Different methods of solution for the set of differential equations are discussed and it is shown that several existing and widely used finite element related techniques are particular cases of this local partial discretization. Three numerical examples are solved to demonstrate the good comparison obtained between the numerical and the exact solutions. The semi-infinite examples included also illustrate the treatment of these types of problems without the use of fictitious boundaries.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 67-76 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: For a wide calss of finite element matrices integrated numerically rather than exactly, a definable number of sampling points is found to be sufficient for keeping their theoretical properties unchanged. A systematic criterion limiting the number of possible point configurations for numerical quadrature formulas on triangles is established. Some new high order formulas are presented. Tables containing optional formulas with respect to minimum number of sampling points and required degrees of accuracy are given. They are arranged so as to assist with selection of suitable quadrature formulas for finite element computer programming.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 115-127 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper presents the finite element method of the analysis of tidal flow. Assuming that tidal flow is periodic, the Galerkin approach is employed as the numerical integration procedure in time using a trigonometric function as the interpolation function. The present method has shown to be suitable for computation especially from the point of computing time and numerical stability.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 169-181 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The visco-plastic model is used in the context of large displacement (geometrically non-linear) analysis. As the process now involves in numerical computation an updating of relevant stiffness matrices, formulation which is stable and computtionally more efficient. The applications shown demonstrate the applicability of the process to large displacement elasto-plastic shell analysis as well as to problems of creep buckling.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 185-186 
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 194-194 
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 229-235 
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    Notes: The approximation of normal derivatives along a curved boundary becomes a major difficulty in obtaining finite difference solutions for irregular regions. A number of authors (for-example, Allen,1 Fox,2 Greenspan3 and Parker and Ma4) have suggested various solutions to this problem. However, most of these suggested methods are fairly cumbersome to use since they require the use of different formulas for various combinations of mesh and boundary geometries. This note shows a different way to approximate a quite general boundary condition along curved boundaries. The method uses a uniformly spaced mesh, is simple, general, relatively easy to program and appears to give accurate results.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 267-278 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In many systems it is known a priori, that some states are ony weakly coupled with others. If such systems are solved on parallel processor it is possible to partition the states in such a way that one set of states is assigned to one processor and the other set of weakly coupled states to another. Computations can then be done in parallel. Because of the weak coupling it may not be necessary for information from the two sets to be communicated to each other for many integration steps. This can result in significant cost savings. In this paper, a partitined Runge - Kutta scheme is formulated for use on weakly coupleld systems of ordinary differential equations. An error expression is derived which provides a means for predicting the number of step sizes over which the partitioned formulas can be used in terms of a prespecified error tolerance. Numerical examples are presented both to verify the error expressions and to compare solutions using partitioned and unpartitioned schemes.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 319-329 
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    Notes: The diferential equations governing two-phase flow through a porous medium are derived and the space discretization is carried out by the Galerkin finite element method. An examination of the eigenvalues of the resulting system follows in order to decide on a suitable stability criterion to be satisfied by the time-stepping algorithm. A class of time-stepping schemes is introduced and their behaviour when applied to a specific problem is analyzed. The aim is to achieve an adequate modelling of the water-oil interface and to preserve reasonable values of the capillary pressure. A technique to clustering the mesh around the interface is used to improved the modelling, and a boundary condition based on the relative mobilities of the two fiuids is imposed to enable the program to calculate the water-oil ratio after breakthrough. The effect of lumping the mass matrix is then examined with a view to reducting the surge in the values obtained for the capillary pressure. Finally an optimum method is suggested for use as a starting algorithm for more sophisticated time-stepping schemes.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 384-384 
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 415-428 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A Finite Element Method using rectangular elements is applied to solve Burgers' non-linear equation in one space dimension. The non-linear algebraic equations thus obtained are solved by an iteration which is equivalent to the generalized Newton method. Numerical experiments indicate that the order of accuracy is equal to 2. In two space dimensions, the method is more efficient than other methods we have tested.
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    International Journal for Numerical Methods in Engineering 12 (1978), S. 471-477 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A global variational method (GVM) not requiring the boundary conditions to be incorporated in the trial functions is described. The method is outlined for a linear differential equation and the extensions necessary to handle the non-linear problem of the indirect design of a compressible fluid channel described. The method requires a suitable estimate of a parameter, but the results obtained for the non-linear problem indicate that the actual value of this parameter is not critical (provided that a sufficeintly large number of trial functions is used). Comparisons are made with the results from an alternative GVM approach described in Davies and Hendry.1
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 479-486 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The problem of confined seepage of water under a hydraulic structure, through a porous medium, is considered in an appropriate abstract space. Existence and uniqueness of the solution are proved. The numerical solution is derived by means of the finite element method. An error estimate is given. A sample problems in included.
    Additional Material: 3 Ill.
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  • 83
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1485-1486 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 84
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1487-1488 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 85
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 86
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1491-1491 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 87
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1492-1492 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 88
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1493-1506 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An iterative algorithm is presented: it builds a continuous stress and displacement solution starting from the solution of a classical displacement finite element analysis. The modified solution satisfies the virtual work principle, and is much better than the starting solution. The algorithm is very easily included in existing programs. A number of examples shows the efficiency of the method.
    Additional Material: 13 Ill.
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  • 89
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1507-1541 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the stressed-skin analysis of metal structures it is vital to have a simple yet accurate treatment of the shear deformation of profiled metal sheeting. A suitable theory is developed in this paper for the two important cases of sheeting fastened to the supporting structure through every and alternate troughs of the corrugations. Various practical factors are taken into account. The results of an extensive series of numerical investigations are presented as a simple equation and a set of tables.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 90
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1677-1696 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents a classification of mathematical commonly encountered in connection with solution of non-linear finite element problems. The principal methods for numerical solution of the non-linear equations are surveyed and discussed. Special emphasis is placed upon the description of an automatic load incrementation procedure with equilibrium iterations. It is shown how this algorithm can be adapted for solving problems involving instabilities, snap-through and snap-back. A simple scalar quantity denoted the current stiffness parameter is suggested; this parameter is used to characterize the overall behaviour of non-linear problems. It can also be used as a steering parameter in the solution process. The use of the present technique is illustrated by several examples.
    Additional Material: 15 Ill.
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  • 91
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1705-1715 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new and efficient method of dynamic condensation is presented. It reduces the order of dynamic matrices without intoroducing further approximation by representing the passive co-ordinates in terms of the active ones exactly. The resulting frequency dependent eigenvalue problem is solved by a combined technique of Sturm sequence and subspace iteration. Examples are given for a space frame and a substructure problem. Results are compared to the complete solution.
    Additional Material: 4 Ill.
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  • 92
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1841-1851 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A common method for numerically approximating two-point parabolic boundary value problems of the form ut = L[u]+f(u) defined of the semi-infinite strip S = [0, 1]×[0, ∞] is to first discretize the spatial operator in the differential equation and then solve for the time evolution. Such an approach typically involves solving a system of algebriaic equations at a sequence of time steps. In this paper we take a different approach and subdivide S into a collection of semi-infinite substrips Si = [xi, xi+1]×[0, ∞], and use blending function techniques to derive finite parameter functions ei(x, t) defined on Si. Spectral matching methods are used in deriving ei to ensure that (u - ei) can be made small on Si. Galerkin's method, with associated integration sover the entire space-time domain S, is then used to generate approximations to u(x, t) based upon the so defined infinite element (ei, Si). Approximations are hence found for all (x, t) in S by solving one well structed system of algebraic equations. We apply the method to several linear and non-linear problms.
    Additional Material: 4 Ill.
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  • 93
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1873-1878 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new and a simple algorithm for approximate calculation of optimal output-constrained feedback regulators is presented. computational simplicity is achieved by using properties of weakly coupled linear systems. The algorithm has been shown to be very effective in solving high dimensional control problems.
    Additional Material: 1 Ill.
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  • 94
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1879-1882 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 95
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1853-1871 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper a technique previously developed for the analysis of rigid-plastic structural frames is adapted to provide a formal procedure for finding the limit load of any structure formed from rigid blocks. In this procedure the load factor is maximized subject to the euilibrium equations of the structure and linear constraints imposed by criteria of failure at the block interfaces.In part I of the paper it is assumed that the limiting shear force associated with sliding at a block interface is independent of the normal component of force across the interface. This assumption means that the normality rule is satisfied, so that the upper- and lower-bound theorems of classical limit analysis apply. This part includes a description of computer program for the collapse analysis of masonry arches with joints incapable of carrying tension.In part II the limit on the Shear force at a block interface is assumed to be that associated with Coulomb friction. It is not difficult to extend the computational algorithm described in part I to deal with this situation. However, the failure mechanism computed by the algorithm will not necessarily satisfy the normality rule. The corresponding limit load may therefore be an over-estimate of the true failure load, even though it is computed by a lower-bound (equilibrium) approach. A criterion is established for testing the validity of a failure load computed in these circumstances.
    Additional Material: 14 Ill.
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  • 96
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 1897-1897 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 97
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 13 (1978) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 98
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 13 (1978), S. 1-16 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents an introduction to two general approaches used in the soluation of coupled structures and fluid systems in which effects of large scale flow are excluded. In the first approach, the Lagrangian, the fluid is simply treated as a ‘solid’ with a negligible shear modulus. In the second method, Eulerian, a single pressure variable is used in the fluid.The numerical problems posed, discretization methods used and possible simplifications are discussed.
    Additional Material: 7 Ill.
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  • 99
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 13 (1978), S. 17-33 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The fluid forces acting on a uniform cylinder with an infinitely long axis, heaving in the free surface or an infinite ideal fluid, are described in terms of its ‘added mass’ and ‘damping coefficient’. The techniques of multipole expansion and multiparameter conformal transformation are adopted for such calculations and applied to shapes which cannot be adequately represented by the conventional, and more rudimentary, ‘Lewis form fit’. The shapes referred to are both relevant to ship bows, one being a ‘fine section’ and the other a ‘bulbous section’. The parameters which influence the accuracy of the solution are examined. Results for these two sections are computed and compared with results based on (a) the ‘Lewis form approximation’ and (b) the ‘Frank's close fit method’ which employs a singularity representation.
    Additional Material: 8 Ill.
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  • 100
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 13 (1978), S. 35-48 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The hydrodynamic mass matrix for a vibrating ship is evaluated using a three-dimensional finite element discretization of the surrounding water. For the important case of vertical vibrations of the ship, values of the added masses obtained in this way are compared with those given by the conventional semi-empirical formulas currently in use in the shipbuilding industry. A numerical example is presented. It is concluded that conventional two-dimensional methods, the usefulness of which is confirmed when the first few modes of the hull girder only are sought, do not apply to higher modes, for which significant deformation of the cross-section may occur. On the other hand, a finite element approach has the advantage of its generality as well as flexibility. Suggestions for future research are given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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