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  • 1980-1984
  • 1975-1979  (267)
  • 1977  (267)
  • Engineering General  (234)
  • pharmacokinetics
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 283-286 
    ISSN: 1432-1041
    Keywords: Paracetamol ; Acetaminophen ; pharmacokinetics ; first-pass elimination ; intravenous administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma paracetamol concentrations were measured in 6 volunteers after single intravenous (1000 mg) and oral (500 mg, 1000 mg and 2000 mg) doses of the drug. Paracetamol levels declined multiphasically with a mean clearance after intravenous administration of 352±40 ml/min. A two-compartment open model appeared to describe the decline adequately. Comparison of the areas under the plasma concentration-time curves (AUC) indicated that oral bioavailability increased from 0.63±0.02 after 500 mg, to 0.89±0.04 and 0.87±0.08 after 1000 mg and 2000 mg, respectively. As a consequence of the incomplete bioavailability of paracetamol, as well as its multicompartmental distribution, accurate estimates of its distribution volume and clearance cannot be obtained if the drug is given orally. However, an estimate of its total plasma clearance may be derived from the AUC after a 500 mg oral dose.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 329-335 
    ISSN: 1432-1041
    Keywords: Digoxin ; pharmacokinetics ; two-compartment model ; radioimmunoassay ; neonates ; infants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The distribution and elimination of intravenous digoxin were investigated in seven neonates and infants with heart failure. Serum digoxin concentrations during a 24 h period were determined by radioimmunoassay, using125I as tracer. The serum values declined biexponentially after the injection and could be fitted to a two-compartment open model by non-linear least-squares regression. The calculated mean half-lives of the distribution (alpha) phase in neonates and infants were 37 and 28 min, respectively. The mean half-life of the elimination (beta) phase in neonates was 44 h, as compared to 19 h in infants. The mean volume of the central compartment and the mean volume of distribution at steady-state were calculated to be 1.3 and 9.9 l/kg, respectively; no significant differences between neonates and infants were found. The relation between these volumes indicates that digoxin is extensively distributed in tissues. The steady-state distribution volumes of digoxin in neonates and infants exceed those reported in adults. The larger volume of distribution might explain in part why infants with cardiac insufficiency require larger doses of digoxin than adults (on a mg/kg body weight basis) to obtain the same serum concentrations. Elimination of digoxin from the body was slower in neonates than in infants.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 351-358 
    ISSN: 1432-1041
    Keywords: Phenprocoumon ; protein binding ; pharmacokinetics ; pharmacodynamics ; drug therapy ; myocardial infarction ; chronic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In nine patients, the synthesis rate Rsyn of the vitamin K-dependent clotting factors was calculated from changes in prothrombin-complex activity after intravenous administration of a synthesis-blocking dose of phenprocoumon (PPC). The biological half-life of PPC was between 2.70 and 7.01 days. No correlation was found between the level of the free fraction of this strongly protein-bound drug and its biological half-life. There was a positive correlation (p〈0.01) between the size of the free fraction of PPC and the apparent volume of distribution of the drug. Four of the patients had had an acute myocardial infarction and they showed increased sensitivity to PPC. In them the plasma level of PPC sufficient to reduce Rsyn to 50% of R°syn was significantly lower, and the depression of individual vitamin K-dependent coagulation factors was more pronounced and prolonged, than in five other patients with chronic disease. The degradation rate of coagulation factors was also found to be higher in the patients with acute myocardial infarction. In four patients with chronic disease, anticoagulant therapy with PPC was continued in the out-patient clinic. The calculated oral maintenance dose of PPC, assuming complete absorption, first-order elimination kinetics and a linear relationship between the pharmacological effect and the logarithm of the PPC-plasma concentration, showed good agreement with the dose actually found to produce the desired PP% level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 367-375 
    ISSN: 1432-1041
    Keywords: Acenocoumarol ; excretory balance man ; pharmacokinetics ; biotransformation ; plasma protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption, biotransformation and elimination of the anticoagulant acenocoumarol, 3-[α- (4′-nitrophenyl)-β-acetylethyl]-4-hydroxycoumarin, have been studied by oral administration of 12 mg of a14C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and the plasma concentration of unchanged drug reached a maximum of 169 and 412 ng/ml, respectively, after 3 hours. The elimination half-life in the two subjects, calculated from the decline between 6 and 24 h, was 8.7 and 8.2 hours. A constant proportion of 98.7% of the drug was bound in vitro to serum proteins over a concentration range of 0.021–8.34 µg/ml, with little interindividual variation. The major portion of the binding was to human serum albumin (97.5%) at two classes of binding sites: association constant K1=1.04×105 l/mole (n1=1) and K2=5.55×103 l/mole (n2=4). In addition to unchanged acenocoumarol, four metabolites were determined in plasma by isotope dilution techniques: the amino-, acetamido-, alcohol1- and alcohol2-metabolites. Of them, the amino-metabolite showed the highest concentration, namely 278 ng/ml, after 6 h in Subject A, and 163 ng/ml after 10 hours in Subject B. Judged from the integrated concentrations, the compounds analyzed accounted for 76 and 89%, respectively, of the total radioactivity in plasma. All the metabolites detected in plasma showed anticoagulant activity when tested in mice. The quantities of the metabolites excreted in urine from 0–120 hours were (Subject A/Subject B): acenocoumarol 0.3/0.2%, amino-metabolite 12.3/7.7%, acetamido-metabolite 19.0/11.1%, alcohol1-metabolite 4.6/9.0%, alcohol2-metabolite 1.7/4.4%, 6-hydroxy-metabolite 6.9/18.3% and 7-hydroxy-metabolite 14.0/22.2%.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 51-56 
    ISSN: 1432-1041
    Keywords: Antidepressive agent ; protriptyline ; plasma concentration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels of protriptyline have been determined in 30 depressed female patients undergoing antidepressant therapy. After 3 1/2 weeks treatment at dosage levels of 40 mg/day, protriptyline plasma levels ranged from 430 to 1430 nmol/l. During this period only two-thirds of the subjects had definitely achieved asymptotic concentrations. Single dose studies in 5 volunteers suggest that the volume of distribution of protriptyline shows little intersubject variation. The half life of the drug, however, may vary appreciably from subject to subject, ranging from 54 to 198 h. The effects of two sedatives on mean protriptyline plasma levels have been determined. Mean plasma levels for nitrazepam recipients are indistinguishable from those for patients receiving no night sedation. The mean plasma levels for a group of patients receiving sodium amylobarbitone were significantly reduced. The problem of choice and early adjustment of dosages in order to achieve satisfactory plasma levels is discussed. For practical purposes it is suggested that early values may be of predictive significance in allowing early dosage adjustments to be made.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 473-477 
    ISSN: 1432-1041
    Keywords: Salicylate ; aspirin ; indomethacin ; pharmacokinetics ; coeliac disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of salicylate and indomethacin were measured after a single oral dose of aspirin (600 mg) and indomethacin (50 mg) in twelve starved normal subjects and twelve adult patients with coeliac disease. The absorption of salicylate in the coeliac patients was faster than in the normal subjects. The plasma concentration/time curve of indomethacin in both groups was similar during the absorption phase, but there were significant differences between the groups in its elimination. The abnormal absorption pattern of salicylate in coeliac disease does not appear to be related to its pKa. Possible causes of the difference in salicylate absorption include changes in gastric emptying or altered small intestinal permeability.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 297-303 
    ISSN: 1432-1041
    Keywords: Hydrochlorothiazide ; pharmacokinetics ; dose/response relationship ; natriuresis ; kaliuresis ; calciuresis ; magnesiuresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Hydrochlorothiazide (hct) was administered orally in four different doses (12.5, 25, 50 and 75 mg), to eight healthy volunteers. Plasma and urine concentrations of hct were determined by GLC. Maximal plasma levels were found at 1.5–5 h, and averaged 70, 142, 260 and 376 ng × ml−1 respectively. The peak plasma levels and AUC0→9h of hct were highly correlated (p〈0.001) with the dose. The decline in the plasma curve was biphasic in those experiments in which the plasma levels of hct could be determined for at least 24 h. The half life of the slower phase lay between 5.6 and 14.8 h. The urinary recovery of hct, which represented the gastrointestinal absorption, averaged 65 to 72 per cent of the dose. The mean renal plasma clearance did not vary with the dose and averaged 319 to 345 ml × min−1. The diuresis during the 10 h after hct 12.5 mg exceeded that after placebo by a mean of 800 ml. The diureses was not increased further after higher doses of hct. The maximal natriuretic effect (+ 100 mmol), too, was found after the 12.5 mg dose. The excretion of potassium, however, rose with increasing doses; the maximal increment, after 75 mg hct, averaged 25 mmol. The excretion of calcium was significantly increased after 50 mg hct (+ 0.6 mmol). The maximal effect on magnesium excretion occurred after 25 mg hct (+ 0.5 mmol). In healthy volunteers there was no correlation between peak plasma level of hct or AUC0→9h and the renal excretion of water and electrolytes.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 305-310 
    ISSN: 1432-1041
    Keywords: Phenobarbital ; pharmacokinetics ; neonates ; infancy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In 14 neonates 1–4 weeks old, 30 babies aged 1–12 months, and 7 infants of 1–5 years of age, the serum levels of phenobarbital were determined by a gas chromatographic micro-method after intravenous injection of phenobarbital 5–10 mg per kg body weight. It was possible to calculate the pharmacokinetic parameters using a two compartment open model. The distribution volumes within the individual age groups and the rate constants k12 and k21 showed no significant differences, but the elimination half-life was significantly longer in neonates (118.6±16.1 h) than in babies (62.9±5.2 h) or infants (68.5±3.2 h).
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  • 9
    ISSN: 1432-1041
    Keywords: Muzolimine ; pharmacodynamics ; pharmacokinetics ; furosemide ; saluresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a biometrically planned, double-blind study on 12 Oedema-free male patients the saluretic effect of muzolimine 30 mg was compared with furosemide 40 mg. The plasma level of muzolimine was determined and correlated with its pharmacodynamics. In terms of excretion during the 12-hour observation period muzolimine 30 mg had as great a cumulative effect as furosemide 40 mg. There was a significant difference in the time-response curve. During the first two hours furosemide 40 mg had more saluretic effect than muzolimine 30 mg. Between two and four hours there was no significant difference between the two substances. Between four and six hours, however, muzolimine was somewhat more effective than furosemide, although the difference did not reach the level of significance. After 6 h there was no longer any difference between the two compounds. The half-life of the fall in concentration of muzolimine in plasma was 3.7 up to 10 h after its administration. The time-response curve of the increased urine excretion correlated well with the time course of the concentration of muzolimine in plasma.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 19-25 
    ISSN: 1432-1041
    Keywords: Diabetes mellitus ; sulfonylurea ; glibenclamide ; pharmacokinetics ; repeated administration ; deep compartment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six maturity onset diabetic patients took glibenclamide 5 mg by mouth, every morning 10 min before a standard breakfast. Serum levels of immunoreactive glibenclamide, glucose and immunoreactive insulin were measured repeatedly on the first and 15th days of treatment. Measured glibenclamide blood levels were in close agreement with an analogue computer simulation of data obtained from healthy volunteers: there was no accumulation of drug in the blood, but there was strong evidence for the existence of a slowly equilibrating “deep” compartment. Considerable insulin release and correction of the breakfast-induced hyperglycaemia were observed immediately after administration of the drug, as well as 5 h later, at lunch time. The clinical significance of blood levels of glibenclamide, as well as the correlation of pharmacokinetics with pharmacodynamics, are discussed in the light of these results.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 117-123 
    ISSN: 1432-1041
    Keywords: Methyldopa ; radioactive label ; pharmacokinetics ; metabolism ; healthy volunteers ; intravenous and oral administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of 2-14C-L-α-methyldopa have been investigated in five healthy volunteers following intravenous and oral administration. In the intravenous study a bi-phasic plasma concentration curve was found both for chemically determined α-methyldopa and for radioactivity. The plasma level of radioactivity differed significantly from chemically determined drug, a pattern which was also found in urine. This suggests the presence of unidentified metabolite(s). The difference between plasma disappearance and urine recovery of α-methyldopa and radioactivity during the first 4 h after injection suggests distribution to an extravascular compartment. Plasma half-lives of total radioactivity and of unchanged drug were calculated. In three subjects, pharmacokinetic parameters for a two-compartment open body model were calculated from urine and plasma data. Urinary recovery of radioactivity was almost complete within 48 h after intravenous administration. After oral administration, however, only about 40 per cent of the radioactive dose was recovered in the urine, and it contained approximately equal amounts of unconjugated methyldopa, acid-labile conjugated methyldopa and unidentified metabolite(s). The acid-labile conjugate was found only after oral administration, which supports the theory of a mucosal conjugation process. The lack of acid-labile conjugated drug either in the plasma or urine after intravenous injection indicates that there is no enterohepatic circulation of this drug.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 355-357 
    ISSN: 1432-1041
    Keywords: Nitrazepam ; placental transfer ; pharmacokinetics ; plasma levels ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six women from 14 to 17 weeks pregnant, and 12 woman from 36 to 40 weeks pregnant, were given nitrazepam 5 mg orally about 12 h before legal abortion by hysterotomy in the former group and elective caesarean section in the latter group. The concentration of nitrazepam was determined by gas-liquid chromatography. Binding to plasma proteins was evaluated by separation of the protein-free fraction by ultracentrifugation. In the first group (early pregnancy) the level of nitrazepam was found to be lower in the fetal than in the maternal circulation. The concentration in amniotic fluid was still lower. In the latter group (late pregnancy) the concentration both of unbound and total nitrazepam in maternal and fetal plasma were in equilibrium, which indicated an increase in transplacental transfer in late pregnancy. The percentage of unbound nitrazepam in both cases was 12%.
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  • 13
    ISSN: 1432-1041
    Keywords: Tolmetin ; pharmacokinetics ; bioavailability ; antacid ; oral dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The purpose of this study was to determine whether a concomitant single dose of antacid or multiple doses of antacid administered prior to, and with tolmetin, alter the pharmacokinetics of tolmetin when the drug was administered as a commercially available tablet containing tolmetin sodium. The possible effects of the antacid on plasma concentrations and urinary excretion of tolmetin and its major metabolite were evaluated following administration of: (a) tolmetin sodium alone; (b) antacid four time a day for three days prior to a single dose of tolmetin sodium, with continuation of the antacid during the day tolmetin was given; and (c) co-administration of single doses of tolmetin sodium and antacid. The twenty-four subject study was of the crossover type. There were no significant differences among treatment means for: (i) peak plasma concentrations of both tolmetin and metabolite, (ii) AUC 0–8 h and AUC 0-∞ for both tolmetin and metabolite, (iii) time to peak plasma concentration for both tolmetin and metabolite, (iv) plasma concentrations of both tolmetin and the metabolite at all sampling times (except for tolmetin at 2 h), (v) renal clearance of both tolmetin and its metabolite, and (vi) the amount of metabolite excreted in the 0–24 h urine. There were small, but significant, differences among amounts of tolmetin excreted in the 0–24 h urine. Semilogarithmic plots of both tolmetin and metabolite plasma concentrations past the peak concentrations were curved over the entire 8-h observation period; although the elimination half-life of tolmetin has been reported to be about one hour, the half-life most probably exceeds 2.6 h in most subjects. The results of this study indicate a lack of a significant drug-drug interaction between the non-steroidal anti-inflammatory agent, tolmetin sodium, and a commonly used antacid, which is a mixture of magnesium and aluminium hydroxides.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 91-99 
    ISSN: 1432-1041
    Keywords: Disopyramide ; plasma concentration ; cardiodepressant drugs ; ventricular arrhythmia ; ventricular tachycardia ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Ten patients with various heart diseases and ventricular arrhythmia received a single oral dose of disopyramide (DE) 200 mg. The ECG was recorded continuously for about 50 h from 2–4 h before drug administration. A statistically significant reduction in the number of ventricular ectopic beats (VEBs) was seen 1.0–3.5 h after drug intake; the average number of VEBs per 30 min decreased from 317 during the control period to 92 by 1.0–3.5 h after treatment and if one patient who did not respond is excluded, the corresponding figures were 272 and 14, respectively. Consecutive VEBs were seen in seven patients before DE was given and decreased significantly (p〈0.05) 1.5–5.5 h after drug administration. There was no change in the PQ interval, the QRS interval showed a slight increase, whereas the QT interval was prolonged 0.5–4 h after administration of DE. A specific gas chromatographic method was used for DE assay in plasma and urine. Absorption was rapid in all patients. Urinary excretion during the first 48 h after drug intake varied between 35 and 75%. The lowest effective antiarrhythmic concentration estimated in six patients ranged from 1.4 to 7.0 µg/ml. β-Phase half-life in five patients was between 10.3 and 22.1 h.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 149-154 
    ISSN: 1432-1041
    Keywords: Hydroflumethiazide ; spectrofluorometry ; pharmacokinetics ; plasma half life ; renal excretion ; renal disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A spectrofluorometric method for determination of hydroflumethiazide in human plasma and urine has been developed. The limit of detection was 10 ng/ml plasma and 100 ng/ml urine. The plasma concentration of hydroflumethiazide was determined for 9–11 hours and excretion in urine for 24–37 hrs after oral administration of about 1 mg/kg body weight to 7 subjects. Plasma half life in healthy subjects was 1.9–2.1 h, and 2.7–8.6 h in patients during the period 4–9 hrs after dosing. Cumulative excretion in urine was 67–79% of the dose during 31–37 hrs in 6 subjects; one patient with renal disease was found to excrete only 25.8% of dose during 24 hours. Renal clearance of hydroflumethiazide was higher in the healthy subjects (0.29–0.44 1 h−1 kg−1) than in the patients (0.040–0.15 l h−1 kg−1). Plasma half life of hydroflumethiazide was not closely correlated with renal clearance of the drug, which suggests that other factors may play a role in determining plasma half life.
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 11 (1977), S. 57-64 
    ISSN: 1432-1041
    Keywords: General equation ; pharmacokinetics ; first pass effect ; extra-hepatic drug elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A general expression for the ratio of areas below the blood concentration-time curves after intravenous and oral drug administration is derived. This derivation does not require the assumption of a specific compartmental model to describe drug distribution within the body. Similarly an expression for the amount of drug metabolised in the liver is derived. The latter expression is used to estimate the extent of extra-hepatic drug elimination from the body.
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 73-76 
    ISSN: 1432-1041
    Keywords: Quinidine ; pharmacokinetics ; non-linearity ; dose-dependent pharmacokinetics ; steady state plasma level ; oral administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Quinidine was administrated orally to five healthy male volunteers. Doses of 0.2 g t. i. d., 0.3 g t. i. d. and 0.4 g t. i. d. were given for five days with at least four weeks between each test period. The plasma concentration of quinidine was measured before the morning dose on Days 2–5 of treatment, and 1, 2, 4 and 8 h after the morning dose on the 5th day. There was not a linear relationship between the increase in dose and the increase in plasma concentration of quinidine. A dose increase of 50% from 0.6 to 0.9 g quinidine sulphate per day resulted in an increase in steady state concentration of 94%. A further 33% increase in dose, from 0.9 to 1.2 g daily, resulted in a 55% increase in the steady stae concentration of quinidine. The results demonstrate dose-dependent pharmacokinetics for quinidine. Possible explanations for the nonlinear pharmacokinetics are discussed.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 137-145 
    ISSN: 1432-1041
    Keywords: Chlormethiazole ; pharmacokinetics ; metabolites ; oral administration ; young and elderly human subjects ; quantitative gas chromatographymass spectrometry ; whole blood distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration of chlormethiazole and two of its metabolites has been measured in three young and three aged human subjects following administration of a single oral dose of chlormethiazole. A sensitive analytical method based on gas chromatography-mass spectrometry using the selective ion monitoring mode of operation was developed to permit quantitation of the plasma levels. The time course of the plasma concentration of chlormethiazole and metabolites showed wide inter-subject variation, particularly between the young and elderly subjects. Absorption of chlormethiazole was rapid in the subjects of both groups as assessed by the time taken to reach the peak plasma concentration. The mean peak plasma level of chlormethiazole was more than five times greater in the elderly (2.90±1.56 µg/ml) than in the young (0.55±0.58 µg/ml) subjects. The plasma level of chlormethiazole was consistently higher in the aged subjects and this was reflected by the larger area under the plasma curve in aged (7.62±5.37 µg.h/ml) than in young (0.94±0.66 µg.h/ml) individuals. Decreased pre-systemic elimination by the liver has been suggested as an important factor contributing to the higher plasma level in the elderly. Estimates of absolute systemic availability, calculated by reference to previous intravenous studies, were greater for the elderly subjects. The distribution of chlormethiazole in whole blood from six young and six elderly human subjects was investigated in vitro. The unbound fraction of chlormethiazole in plasma increased significantly from 0.308±0.035 in young subjects to 0.403±0.067 in the elderly. Distribution of the drug in whole blood was different for the two age groups; the fraction of drug distributed to plasma water was significantly greater and the fraction in blood cells was significantly less in the aged.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 171-174 
    ISSN: 1432-1041
    Keywords: Tolamolol ; hypertension ; pharmacokinetics ; mean steady-state concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Tolamolol was administered in a “double-blind” study to fifteen hypertensive patients by dose-titration against arterial blood pressure. Mean steady-state plasma tolamolol concentrations (Css) were determined for each patient from the area under the plasma concentration — time curve during a dosage interval whilst patients were receiving optimal tolamolol doses. No significant correlation was observed between daily tolamolol dose and Css; the relationship between fall in lying mean arterial pressure and Css also failed to reach conventional levels of statistical significance, but Css was observed to be correlated with the fall in standing pressure. The results suggest that plasma concentrations in excess of 200 ng/ml may be required to achieve an effective hypotensive response with the drug.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 205-208 
    ISSN: 1432-1041
    Keywords: Cetiedil ; vasodilator ; anticholinergic drug ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Cetiedil, a new vasodilating drug with anticholinergic properties, was shown to be metabolised very rapidly in man after intravenous and oral administration of the14C-compound. Higher concentrations of labelled compound after oral than after intravenous administration at the same sampling time, and proportional differences in urinary excretion, suggest that metabolic handling of the drug differs depending on the route of administration. Experiments in which inhibition of saliva secretion was measured indicated that (an) active metabolite(s) probably was (were) responsible for the action of the drug. As an anticholinergic drug, cetiedil is at least 400 times weaker than atropine.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 221-227 
    ISSN: 1432-1041
    Keywords: Cefuroxime ; cephalosporin antibiotics ; intravenous injection ; pharmacokinetics ; volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Cefuroxime, a new cephalosporin antibiotic which is stable to most β-lactamases produced by Gram-negative bacteria, was given by bolus intravenous injection to six volunteers in doses of 500 mg and 750 mg. The concentrations of cefuroxime in serum and urine were measured at pre-determined times after injection and the data analysed by a two-compartment open system model. A serum concentration of 8 µg/ml was exceeded for 100.3 min (±18.3) after a 500 mg dose and for 144.5 min (±19.8) after 750 mg. The ultimate serum half-life was 1.1 h. Excretion of cefuroxime in the urine was almost complete in 24 h, the clearance being 150 ml/min/1.73 m2. About 45% was excreted through the renal tubules. The injections were well tolerated and no changes in haematological or biochemical values were seen. The resulting data are compared with those published for some other cephalosporins. It is concluded that the favourable pharmacokinetics, especially the high concentrations of unbound cefuroxime in the serum, are likely to aid effective therapy of human infection caused by sensitive bacteria.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 12 (1977), S. 383-386 
    ISSN: 1432-1041
    Keywords: Benzodiazepine ; temazepam ; pharmacokinetics ; bioavailability ; hard and soft gelatine capsules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels of temazepam were determined in healthy subjects after single oral administration of soft and hard gelatin capsules, and after 7 consecutive night-time doses in soft capsules. Absorption from soft gelatin capsules was significantly faster and produced earlier and higher peak plasma levels. The two pharmaceutical forms did not show any significant difference in relative availability. The apparent half-life of temazepam after night-time administration was significantly shorter than after morning administration, but no change in half-life was observed between the first and seventh night-time doses.
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  • 23
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    European journal of clinical pharmacology 12 (1977), S. 125-132 
    ISSN: 1432-1041
    Keywords: Valproic acid ; pharmacokinetics ; saliva concentration ; urinary excretion ; serum protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of valproic acid (VPA) have been studied in 6 healthy subjects following a single 600 mg dose, and after multiple doses over 12 days (1200 mg daily) of enteric-coated sodium valproate. A time lag before absorption of 1 to 2 h was observed in each subject, and then absorption was rapid, peak concentrations being recorded 3 to 4 h after administration of the dose. The plasma level decline was biphasic with a terminal half-life of 15.9±2.6 h in the single dose and 17.3±3.0 h in the multiple dose experiments. There was no evidence of dose dependent kinetics or autoinduction. Total plasma clearance was 0.0064±0.0011 l/kg×h. The apparent volume of distribution was small at 0.15±0.2 l/kg. The mean steady state plasma concentration (Css) reached after 4 days was 81.3±13.0 µg/ml. Css observed was lower than Css predicted (99.2±14.7 µg/ml) from single dose kinetics (p〈0.001). The difference was probably due to a reduction in plasma protein binding at higher concentrations. VPA concentration in saliva was between 0.4 and 4.5% of the total plasma concentration and was not equal to the concentration of unbound drug in plasma (6.7±0.8% unbound). 3.2% of the dose was excreted in urine as the parent drug and 21.2% as conjugated metabolites.
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  • 24
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    European journal of clinical pharmacology 12 (1977), S. 387-392 
    ISSN: 1432-1041
    Keywords: Digoxin ; β-methyldigoxin ; prolonged administration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Five healthy volunteers received digoxin 0.4 mg or β-methyldigoxin 0.4 mg i. v., daily for 14 days, in a randomized cross-over arrangement. By monitoring minimal plasma concentrations during multiple dosing, it was found that the steady state pharmacokinetics of digoxin and β-methyldigoxin could be estimated even better by a one-compartment than by a two-compartment model. The following mean parameters were calculated: the half life of digoxin of 1.54±0.31 days was significantly shorter than the half life of 2.29±0.34 days for β-methyldigoxin. The distribution volume of 807±187 liters for digoxin was not significantly larger than the 735±227 liters for β-methyldigoxin. Renal digoxin clearance of 191±25 ml/min was significantly higher than both the renal clearance of β-methyldigoxin of 111±23 ml/min and also the creatinine clearance, which indicates tubular secretion of digoxin. There was a 2.8-fold accumulation of β-methyldigoxin injected once a day, which was significantly higher than the 1.8-fold accumulation of digoxin.
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  • 25
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    European journal of clinical pharmacology 12 (1977), S. 451-456 
    ISSN: 1432-1041
    Keywords: Bioavailability ; carbamazepine ; elimination ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-courses of plasma carbamazepine concentrations were followed in six apparently healthy adult subjects who, at different times, took single oral drug doses of 200, 400, 500, 600, 700, 800 and 900 mg. There were some suggestions of impaired bioavailability of the drug when given in tablet form. The following values were obtained for various pharmacokinetic parameters:k abs =0.176±0.209 h−1;k=0.0203±0.0055 h−1; T1/2=37.5±13.1 h; VD=0.825±0.1041 · kg−1; Clearance=0.0163±0.0061 l · kg−1. The elimination rate constant showed a statistically significant increase with increasing drug dose. This may help explain the clinical observation that the rate of rise of steady state plasma carbamazepine concentrations tends to decrease with dose increase in patients taking carbamazepine alone.
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  • 26
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    European journal of clinical pharmacology 12 (1977), S. 367-373 
    ISSN: 1432-1041
    Keywords: Sulphamethizole ; tetracycline ; doxycycline ; rest ; exercise ; pharmacokinetics ; excretion ; absorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The serum level and urinary excretion of sulphamethizole, tetracycline and doxycycline were studied in healthy volunteers subjected to intensive exercise and bed rest in a cross-over trial. Each group consisted of 7–8 subjects. The exercise or bed rest began 15 min before oral administration of the drug and was continued for the following 4 hours. During exercise serum drug concentration and the area under the serum concentration-time curve for each agent was significantly higher (p〈0.05) than the corresponding values at rest. Exercise greatly suppressed the renal excretion of tetracycline and doxycycline, but the decrease alone appeared insufficient to account for the pronounced increase in serum drug concentration. Total drug excretion in urine was unchanged. Thus, it seemed most unlikely that overall absorption from the gastrointestinal tract had been altered by exercise. However, the rate of absorption appeared to be more rapid in the exercise than in the rest period. Marked haemoconcentration was not produced by the exercise. In addition to changes in absorption and elimination rates, alteration in the volume of distribution might contribute to the higher serum drug concentration during exercise. Therefore, the level of physical activity should be considered in the interpretation of pharmacokinetic data both in clinical practice and in pharmacokinetic studies.
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  • 27
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 335-358 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; perfusion models ; sampling ; parameter estimation ; computer program ; Org GB 94 ; mianserin ; Org GC 94
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A mathematical treatment of the influence of sampling on drug kinetics in liver perfusion is presented. Based on the derived equations, a Fortran IV computer program (PERFUS) is given, by which the time course of drug concentrations can be simulated for any sampling scheme. The simulations show that the withdrawal of large samples from the reservoir, i.e., larger than 5% of the reservoir volume, results in substantially biased parameters for drugs that are rapidly distributed and/or metabolized. For the fitting of empirical data, a Fortran IV computer program is given, based on BMDX85 nonlinear least squares by Gauss-Newton iterations. This program (PERFIT) estimates model parameters corrected as if no sampling had occurred, no matter how distorted the drug disappearance curve mày be as a result of sampling or due to degeneration of the two-compartment model into a one-compartment model. The conditions under which this degeneration occurs are discussed.
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  • 28
    ISSN: 1573-8744
    Keywords: chlordiazepoxide ; benzodiazepine ; two-compartment model, biopharmaceutics ; pharmacokinetics ; single dose ; routes of administration ; intravenous ; intramuscular ; oral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Single 30- mg doses of chlordiazepoxide HCl were administered to six healthy human subjects by the intravenous, oral, and intramuscular routes. Plasma concentration- time curves following intravenous administration were satisfactorily described by a biexponential equation consistent with a two-compartment open model system. Mean values of half-lives for the so-called distribution and elimination phases were 0.252 and 9.39 hr, respectively. The mean values for the volume of the central compartment (V 1) and volume of distribution $$(V_{d_\beta } )$$ were 18.0 and 30.9% of body weight, respectively. Following oral administration, the drug was rapidly and completely absorbed. Absorption was first order (t1/2≈27 min), and three of the six subjects showed a discernible lag time of approximately 20 min. Drug absorption following intramuscular administration was comparatively slow. A two- compartment “muscle model” comprised of precipitated and solubilized drug in the muscle was found to satisfactorily characterize the absorption process following administration by this route.
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  • 29
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 421-433 
    ISSN: 1573-8744
    Keywords: methotrexate ; pharmacokinetics ; model ; computer ; cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The infusion of high doses of methotrexate followed by folinic acid rescue is clinically useful against a variety of tumors. We studied the plasma pharmacokinetics of high-dose methotrexate infusions in patients with advanced cancer and devised a compartmental, kinetic model. our model is based on an earlier, mathematical model which describes the pharmacokinetics of moderate- to- high-dose methotrexate given as a single, intravenous injection. Mathematical equations for our model were solved on a UNIVAC1108 computer with the SAAM program. Seven compartments represent the distribution spaces for methotrexate and its metabolites. The transport of drug into and out of compartments is described by first-order differential equations. A nonlinear, concentration-dependent function is used for renal excretion with saturation of secretory and reabsorption mechanisms by methotrexate. Our model accurately depicts the pharmacokinetics of nine courses of therapy in five patients. The model can also be used to simulate the kinetics of methotrexate for patients with impaired renal function.
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  • 30
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 111-122 
    ISSN: 1573-8744
    Keywords: hepatic clearance ; extraction ratio ; local anesthetics ; pharmacokinetics ; lidocaine ; bupivacaine ; etidocaine ; cardiovascular effects of local anesthetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two independent methods of calculating hepatic drug clearance were applied to data from studies of the human pharmacokinetics of lidocaine, bupivacaine, and etidocaine. Within experimental limitations, agreement was good between estimates obtained by measurement of areas under blood drug concentration-time curves after rapid intravenous injection and by direct measurement of arterial and hepatic venous drug concentrations. Apparent hepatic extraction ratios of the agents followed the order etidocaine (∼0.73)/s〉lidocaine (∼0.68〉bupivacaine (∼0.37).Pharmacokinetic implications of increases in hepatic blood flow induced by the agents are discussed.
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  • 31
    ISSN: 1573-8744
    Keywords: chlordiazepoxide ; benzodiazepine ; two-compartment model ; multiple dosing ; pharmacokinetics ; biopharmaceutics ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Eight healthy male volunteers received chlordiazepoxide HCl orally at a dosage of 10 mg every 8 hr over a period of 21 days. On day 22, the regimen was changed to 30 mg every 24 hr for an additional 15 days. Plasma concentrations of chlordiazepoxide and its metabolites desmethyl-chlordiazepoxide, demoxepam, and desoxydemoxepam were measured during 14 of the 36 treatment days. Chlordiazepoxide plasma concentration- time data were consistent with first-order absorption and complete bioavailability. The harmonic mean absorption half-life was 12.3 min. Disposition of chlordiazepoxide was described by a two-compartment open model with a harmonic mean terminal exponential half-life of 10.1 hr. Average steady — state plasma levels of chlordiazepoxide, desmethylchlordiazepoxide, and demoxepam were approximately 0.75, 0.54, and 0.36 μg/ml, respectively.
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  • 32
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 513-531 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; nonlinear regression ; curve fitting ; computer program ; time sharing ; modeling ; weighting ; least squares ; parameter estimation ; discrimination between models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The problems of curve fitting and modeling in pharmacokinetics are discussed. A new nonlinear regression program FUNFIT, written for interactive time sharing, is presented which should be more reliable than programs based on the Gauss-Newton or other related gradient methods. The new program and the well-established program NONLIN were tested on two linear models using human plasma drug level data. FUNFIT found a substantially better solution than NONLIN in the majority of the cases.
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  • 33
    ISSN: 1573-8744
    Keywords: gentamicin ; tissue distribution ; pharmacokinetics ; two-compartment modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gentamicin pharmacokinetics was examined in a group of 47 patients with stable renal function treated an average of 10 days for severe infection. Serum concentrations rose continually during treatment, and declined in two phases after the drug was stopped, with a mean half-life of 112hr (range 27–693 hr) in the second phase. A two-compartment model was used to describe the biphasic decline in serum concentrations and to calculate the amount of drug in the tissue compartment at all times during and after treatment. Predicted tissue amounts of gentamicin rose continually on multiple dosing in all patients. In six patients who died, postmortem tissues were obtained to quantitate recovery. In all cases, the predicted amount of gentamicin in tissues was in close agreement with the amount recovered at autopsy. Tissue distribution and accumulation constitute a major reason for variability in gentamicin pharmacokinetics and explain both the rising peak and trough serum concentrations and the prolonged detection of gentamicin in serum and urine after the drug is stopped.
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  • 34
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 194-198 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper contains an algorithm for the ordering of elements in the finite element method, which can be utilized in the Non-assembly Method of the author and in the Frontal Solution Method of B. M. Irons.
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  • 35
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 386-387 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An integration formula for polynomial expressions in terms of the unit triangle co-ordinates is presented.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 247-267 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A Block-Stodola eigensolution method is presented for large algebraic eigensystems of the form AU = λBU where A is real but non-symmetric. The steps in this method parallel those of a previous technique for the case when both A and B were real and symmetric. The essence of the technique is simultaneous iteration using a group of trial vectors instead of only one vector as is the case in the classical Stodola-Vianello iteration method. The problem is then transformed into a subspace where a direct solution of the reduced algebraic eigenvalue problem is sought. The main advantage is the significant reduction of computational effort in extracting a subset of eigenvalues and corresponding eigenvectors. Theorems from linear algebra serve to underlie the basis of the present technique. Complex eigendata that emerge during iteration can be handled without doubling the size of the problem. Higher order eigenvalue problems are reducible to first order form for which this technique is applicable. The treatment of the quadratic eigenvalue problem illustrates the details of this extension.
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  • 37
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 411-417 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We suggest an exercise which illustrates many of the fundamental ideas of finite elements, and is nevertheless easily programmed and quickly solved. It is governed by a partial differential equation on a circular region, but by maintaining symmetry the stiffness matrix becomes small and tridiagonal. The accuracy of linear elements can be studied in detail, and a straightforward extension leads to the eigenvalue problem, elements of higher degree, numerical integration, isoparametric elements, and a simple example in plasticity.
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  • 38
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 469-480 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A novel method is proposed for the numerical computation of Fourier coefficients in the range of higher frequencies for which hitherto no practical method was available. The accuracy of the results obtained by application of this method is discussed, and bounds of a correction term are determined accordingly. An example from the field of Diesel engine research is given, and the computed spectrum is compared with the spectrum recorded by an electronic harmonic analyzer.
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  • 39
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 499-520 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents the theoretical and computational procedures which have been applied in the design of a general purpose computer code for static and dynamic response analysis of non-linear structures. A general formulation of the incremental equations of motion for structures undergoing large displacement finite strain deformation is first presented. These equations are based on the Lagrangian frame of reference, in which constitutive models of a variety of types may be introduced. The incremental equations are linearized for computational purposes, and the linearized equations are discretized using isoparametric finite element formulation. Computational techniques, including step-by-step and iterative procedures, for the solution of non-linear equations are discussed, and an acceleration scheme for improving convergence in constant stiffness iteration is reviewed. The equations of motion are integrated using Newmark's generalized operator, and an algorithm with optional iteration is described. A solution strategy defined in terms of a number of solution parameters is implemented in the computer program so that several solution schemes can be obtained by assigning appropriate values to the parameters. The results of analysis of a few non-linear structures are briefly discussed.
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  • 40
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 563-577 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The finite element method is applied to the analysis of a two-dimensional steady flow around a box girder in uniform flow. The local potential principle for an incompressible viscous fluid flow is introduced as a basis for establishing finite element models and a determination is made as to whether or not approximate solutions obtained by the use of the principle give upper or lower bounds of the solution. The boundaries are set so as to be appropriately far from the girder and the velocities are specified at the upstream, upper boundary and the lower boundary and the total stresses are specified at the downstream boundary. The system of non-linear equations is solved by the standard Newton-Raphson method. Integrating the pressures and viscous stresses acting on the surface of the girder, the coefficients of drag, lift and pitching moment are numerically obtained for some Reynolds numbers. The wind tunnel test has been the only means to determine these coefficients for a body with irregular shape. The finite element method presents a new powerful procedure to determine these coefficients.
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  • 41
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 604-604 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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  • 42
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 605-605 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 43
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 611-622 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A complete analytical analysis of three-dimensional, quadratic displacement tetrahedron elements is presented. The results show that the element stiffness can readily be obtained from the much simpler stiffness matrix of the linear displacement element. Thus, the task of obtaining the matrix of the quadratic displacement element is, in effect, reduced to finding that of the linear displacement element.The analysis has been made possible only by using a symbolic manipulation language (PL/I-FORMAC) on a computer. A rather general program for computer-aided basic element analysis is presented. It seems that the extremely effective tool of symbolic manipulation has hardly been used until now in mechanics.
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  • 44
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 766-767 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 45
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 683-708 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A strategy for solving problems involving simultaneously occurring large deflections, elastic-plastic material behaviour, and primary creep is described. The incremental procedure involves a double iteration loop at each load level or time. In the inner loop the material properties are held constant and the non-linear equilibrium equations are solved by the Newton-Raphson method. These equations are formulated in terms of the tangent stiffness. In the outer loop the plastic and creep strains are determined and the tangent stiffness properties are updated with use of a subincremental algorithm. The magnitude of each time subincrement is determined such that the change in effective stress is less than a preset percentage of the effective stress. The strategy is implemented in a computer program, BOSOR 5, for the analysis of shells of revolution. Examples are given of elastic-plastic deformations of a centrally loaded flat plate and elastic-plastic-creep deformations of a beam in bending. The major benefits of the subincremental technique are the increased reliability with which problems involving non-linear plastic and time-dependent material behaviour can be solved and the greatly relaxed requirement on the number of load or time increments needed for satisfactory results.
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  • 46
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 897-900 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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  • 47
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1188-1193 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The application of the finite element method to the supersonic flutter of two parallel elastically coupled flat plates subjected to a pre-stress state of in-plane loadings is presented. Numerical results are given and these are compared with previous analytical solutions. It is shown that, for the coupled plates, the first spanwise modes are not necessarily the critical modes for the flutter boundaries. Previous analytical results do not exhibit such a trend since only the first spanwise modes were considered.
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  • 48
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  • 49
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1235-1250 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Two direct search algorithms for the optimization of non-unimodal systems are presented. One method is interior in nature by using boundary relaxation with pseudo one-dimensional search in the feasible region; the other one is an exterior method which allows the violation of constraints followed by the use of a penalty function to drive the search back into the feasible region. These two methods are usually capable of leaving local optima to reach a better solution if such exists. The application of the proposed approaches to several non-unimodal systems shows that they are better than the existing methods. The proposed methods are also attractive because of the ease of programming and the high probability of reaching the global optimum.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1329-1333 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Temperature load on a shell is usually represented as initial strains in the tangent plane directions of the shell, since strains in shell surface normal directions are neglected. It is shown, however, that this simplification may give rise to significant errors for thick curved shell elements. A procedure to overcome this problem is presented. In particular the eight-node subparametric thick shell element is considered.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1343-1343 
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    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 11 (1977), S. 1379-1389 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Two families of slipline field solutions for extrusion through unsymmetrical square dies, which have hitherto only been suggested qualitatively are computed and their ranges of validity determined. The solutions are of ‘indirect type’ and have been obtained using a technique by which the integral operators are approximated by matrices. The determination of the slipline angles and other field parameters corresponding to any given geometry requires the solution of a set of non-linear algebraic equations. This is accomplished using a non-linear optimization procedure.
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  • 53
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1439-1454 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical scheme with a high degree of accuracy has been developed for the full Navier-Stokes equations. The method utilizes the multi-mesh points for space and time derivatives in order to improve the truncation error. Whereas the existing numerical method employing the finite difference scheme, e.g. the explicit, pure implicit, Crank-Nicolson, and DuFort-Frankel schemes, has the truncation errors of the order (Δx)2, Δx being the spatial mesh length, the one for the present method is generally of the order (Δx)3. A numerical example is shown for a natural convection flow in a square box and the results are compared with those of Cormack et al. One order of magnitude reduction of the computing time for a constant degree of accuracy was attained for the two-dimensional problems. Furthermore, a two order of magnitude reduction is to be expected when the method is applied for the three-dimensional Navier-Stokes equations.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1484-1485 
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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 11 (1977) 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1487-1487 
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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 11 (1977), S. 1559-1577 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the present paper, a finite element technique combined with the collocation method is formulated to obtain numerical solutions of integral equations which determine the airload distributions acting on a wing oscillating sinusoidally in a uniform supersonic flow. This technique, which is formulated by the simultaneous use of two integral equations, is shown to be appropriate especially for the low supersonic regions, i.e., for 1 〈 M 〈 1·3, where M is the Mach number of the uniform flow. Although the formulation is made for a sinusoidally oscillating wing, it is obvious that the corresponding formulation for a stationary wing can be derived as a special case of that for the oscillating wing. Problems of determining the airload distributions for stationary as well as sinusoidally oscillating wings are treated, and it is shown that the accuracy of numerical results obtained by the present finite element technique is encouraging.
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    International Journal for Numerical Methods in Engineering 11 (1977) 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1681-1697 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple and direct procedure is presented for the formulation of an element stiffness matrix on element co-ordinates for a beam member and a beam-column member including shear deflections. The resulting stiffness matrices are compared with those obtained using the alternative formulation in terms of member flexibilities: The relative effects of axial force and shear force on the stiffness coefficients are presented. The critical buckling loads, considering the effects of shear force, are computed and compared with those available in the literature. Only prismatic members are considered.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1753-1768 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The features of an advanced numerical solution capability for boundary value problems of linear, homogeneous, isotropic, steady-state thermoelasticity theory are outlined. The influence on the stress field of thermal gradient, or comparable mechanical body force, is shown to depend on surface integrals only. Hence discretization for numerical purposes is confined to body surfaces. Several problems are solved, and verification of numerical procedures is obtained by comparison with accepted results from the literature.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1801-1808 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We recognize that established techniques permit two-dimensional interpolation to be accomplished efficiently as well as accurately when the grid of points, on which the data is available, is regular. Existing methods suitable for irregular grids are computationally protracted. We show that by using Lagrange polynomials of a complex variable we can interpolate, almost as conveniently as in one dimension, from an irregular grid onto particular points lying on parallel lines. Standard one-dimensional interpolation schemes can then be used to complete the two-dimensional interpolation. We discuss how, in any particular instance, the order of the Lagrange polynomials is chosen, and we present the results of a computational test of our method.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 11-25 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element method is developed for investigating the propagation of high frequency electromagnetic waves along closed or open (surface) waveguides containing dissipative materials and having a cross section of arbitrary shape. The complex propagation constants and associated complex electromagnetic fields are determined as a function of frequency for possible modes of propagation. The method is verified by applying it to structures of simple shape for which analytical results may be calculated for comparison. Waveguides considered include a waveguide filled with dissipative material, a dissipative dielectric rod, a dielectric coated wire and a conducting wire.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 204-207 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 269-287 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite element formulations based on the Galerkin and variational principles have been developed for the self-adjoint and non-self-adjoint problems represented respectively by the flow and convective-dispersion equations in the cylindrical polar system of co-ordinates. The formulation based on the variational principle is shown to be restricted to dispersion-dominant transports only. The Galerkin method is demonstrated to be more versatile and free from convergence and stability problems. The computational scheme based on the Galerkin principle is shown to be equally valid for both convection and dispersion dominant transports. The numerical results obtained are verified with known analytical solutions. It is concluded that the suggested scheme can be used in solving a variety of field problems involving groundwater dispersion.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 325-344 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In Part I1 of this paper we have established local stability and convergence criteria for the mixed explicit-implicit finite element scheme and have shown that the proposed iterative method converges under certain conditions. Part II describes various practical aspects of the solution strategy such as convergence criteria for terminating the iterations, automatic control of time step size, reclassification of nodes from explicit to implicit during execution, estimation of time derivatives, and automatic adjustment of the implicit weight factor. Several examples are included to demonstrate certain aspects of the theory and illustrate the capabilities of the new approach.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 309-323 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A Galerkin finite element formulation of diffusion processes based on a diagonal capacity matrix is analysed from the standpoint of local stability and convergence. The theoretical analysis assumes that the conductance matrix is locally diagonally dominant, and it is shown that one can always construct a finite element network of linear triangles satisfying this condition. Time derivatives are replaced by finite differences, leading to a mixed explicit-implicit system of algebraic equations which can be efficiently solved by a point iterative technique. In this work the accelerated point iterative method is adopted and is shown to converge when the conductance matrix is locally diagonally dominant. Several examples are included in Part II of this paper to demonstrate the efficiency of the new approach.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 377-382 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 393-395 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 404-405 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 11 (1977) 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 439-445 
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    Notes: The first order partial differential equations of charge flow are commonly differenced in the space co-ordinate, with a view to analogue computation of the resulting ordinary differential equations in time. Defects of orthodox difference formulae are identified. In particular: (a) reversed waves and stability problems arise from central differences and (b) first order errors and a ‘pseudo-viscous’ dispersion effect with accompanying false attenuation results from upwind differences. These difficulties are particularly serious in view of the coarse differencing required for practical analogue computation. A much superior formula is presented which is entirely free of attenuation and is easily implemented. Various other desirable features are reported.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 521-531 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A postbuckling problem of continuous suspension bridges which are used for carrying pipelines is investigated. These are continuous over several bridge towers with pin connections at their base. A geometrically non-linear analysis using the finite element method is performed to study the postbuckling behaviour under increasing loads (for instance by filling up the pipelines with fluid).Two examples are presented which investigate the aspect ratios of constructed continuous suspension bridges.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 883-895 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The analysis of stresses and deformations in concrete structures subjected to temperature gradients is described. As a result of the spatial variation of temperature, the creep compliance is a function of position. Previous work has shown that the constitutive equations for concrete creep can be expressed in a form which is invariable although ageing is included in the analysis. Thus viscoelastic methods can be used and correspondence principles can be developed; emphasis is placed in the present work on those which are based on the Laplace transform. A particular form is described, in which replacement of the elastic modulus by a function of the transformed creep compliance gives transformed values of stress; these values are easily obtained numerically by the finite element method using elastic analyses. The transformed values of stress are then expressed as approximate functions of the transformed creep compliance; inversion of the ensuing functions gives the stress as an approximate function of time. Two applications are given; the first considers a simple axially loaded column with reinforcement and the second deals with a thick cylinder subjected to a temperature gradient.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 908-910 
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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 11 (1977), S. 933-943 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The problem of heat conduction in a multiphase medium is a free boundary problem in which the free boundary is the phase transition line. The solution to this problem is highly irregular in that the temperature gradient is discontinuous at the free boundary. Two-dimensional, discontinuous, space-time finite elements are introduced to obtain a finite element, free boundary formulation for this problem. The jump in heat flux and position of the phase transition line become dependent variables in the finite element model. The resulting models give accurate results while allowing the calculation of free boundary problems with a fixed finite element mesh.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 900-904 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A simple method for solving the matrix equation describing the general active ladder network, is presented. Using Coates flow graphs and continuants the expressions for current, voltage, and also example of application are given.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 911-911 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 915-932 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A technique utilizing the finite element displacement method is developed for the static analysis of structures subjected to non-deterministic thermal loading in which the material properties, assumed isotropic, are temperature dependent. Matrix equations are developed for the first two statistical moments of the displacements using a third order series expansion for the displacements in terms of the random temperatures.Sample problems are included to demonstrate the range of applicability of the third order series solutions. These solutions are compared with results from Monte Carlo analyses and also, for some problems, with solutions obtained by numerically integrating equations for the statistical properties of the displacements. In general, it is shown that the effect of temperature dependent material properties can have a significant effect on the covariances of the displacements.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1041-1043 
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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 11 (1977), S. 1055-1055 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1117-1136 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Two efficient numerical methods for dealing with the stability of linear periodic systems are presented. Both methods combine the use of multivariable Floquet-Liapunov theory with an efficient numerical scheme for computing the transition matrix at the end of one period. The numerical properties of these methods are illustrated by applying them to the simple parametric excitation problem of a fixed end column. The practical value of these methods is shown by applying them to some helicopter rotor blade aeroelastic and structural dynamics problems. It is concluded that these methods are numerically efficient, general and practical for dealing with the stability of large periodic systems.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1155-1174 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The convergence properties of several non-linear solution procedures were examined with respect to the accelerated flow of a fluid in a converging channel (the Hamel problem), using two different finite element computer programs with different elemental construction. The Reynolds number varied from that for creeping flow to 1088 without exceeding the radius of convergence. Special attention was given to the successive substitution and Newton-Raphson solution algorithms, with a significant advantage in rate of convergence noted for the latter.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1137-1154 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A mathematical programming method is presented for solving problems of (i) determining the moments and rotations and (ii) determining the safety factor of reinforced concrete frames. The proposed method is essentially a reformulation of those developed by De Donato and Maier. However, the reformulation results in a new mathematical programming model for which an efficient algorithm is developed. The advantage of the proposed method is mainly computational; in fact it requires roughly one half computer time and storage space as compared with those De Donato and Maier employ to solve the same problem.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1225-1233 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A finite element formulation is described for problems with solution functions known to have local rλ variation (s), 0〈λ〈1, and thus singular gradients. Special 3-node triangular elements encircle the singularity and focus to share a common node at the singular point. The shape function of each triangle has the appropriate r λ mode and a smooth angular mode expressed in element natural co-ordinates. As with standard elements, the unknowns are the nodal values of the function. Even if the precise angular form of the asymptotic solution is known, the formulation makes no attempt to embed it, but instead piecewise approximates it. This allows assembly of the element coefficient matrix using standard procedures without nodeless variables and bandwidth complications.The conditions of continuity, low order solution capability, and accurate numerical integration of the singularity element are discussed with a view towards establishing the general range of applicability of the formulation. Numerical applications to the elastic fracture mechanics problems of composite bondline cracking and crack branching are discussed.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1291-1306 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A stiffness matrix is derived for a rectangular orthotropic sandwich plate element with thick faces by the assumed stress hybrid approach.It will be demonstrated that an independent polynomial can be used for the internal forces of the sandwich plate by the membrane theory (assumption of thin faces) and also for the additional moments and shear forces of the faces.The boundary displacements are approached solutions of the homogeneous differential equation of a sandwich beam.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1507-1518 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The elastohydrodynamic lubrication problem, in which the lubricant pressure and film thickness are sensitive to surface deformation, is solved by using a finite element procedure and the Newton method. The numerical procedure is applied to the point contact problem, in which a thin lubricant film is maintained between two balls loaded together by a high load under conditions of pure rolling. The present analysis shows that pressure spikes are formed near the outlet region, a result which has been found in the line contact problem and which has been conjectured in the present problem.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1627-1630 
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1621-1626 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Using a finite element method, a value of 13.2 per cent is obtained for the die swell of a highly-viscous Newtonian fluid flowing at very low Reynolds number from a circular tube of constant radius. The same method is then used to obtain die swell values for a variety of axisymmetric tube exits. It is found that, in general, conical constrictions at or near the tube exit result in a decrease in die swell, while conical expansions increase the die swell.
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    International Journal for Numerical Methods in Engineering 11 (1977), S. 1635-1651 
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper proposes a straightforward criterion to warrant the displacement functions being used in the finite element approximation of circular arches. The criterion was established by studying the natural shape function, i.e. the exact solution of the deformed shape, of the circular arch element. The exact stiffness matrix [K]exact is derived from the natural shape and is confirmed to be the inverse of the well-known flexibility matrix [F]exact in the curved beam theory. The present paper compares the inverse [K]-1 of the stiffness matrix derived from the assumed displacement function with the [F]exact. It is shown that the procedure also guarantees the implicit inclusion of rigid-body modes in the pertinent stiffness matrix [K]. Case studies on typical approximate displacement functions assure the appropriateness as well as the ease of application of the proposed method.
    Additional Material: 6 Ill.
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  • 91
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 1653-1665 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new finite-difference technique for the numerical solution of boundary value problems for partial differential equations in two space variables is described. Isoparametric finite elements are used in a finite-difference context to derive difference approximations to space derivatives on a locally curvilinear grid. The result is a generalization of a classical finite-difference stencil which is ‘flexible’ in that it is adaptable to variable meshes, such as those arising from regions with curved boundaries. Numerical results presented for a test problem (potential flow past a circle) using a 9 × 10 grid agree with the analytic solution to within one per cent.
    Additional Material: 10 Ill.
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  • 92
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 1769-1773 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this study a method for obtaining the derivatives of eigenvectors of a locally modified structure with respect to a design variable is presented. Eigensolution to the locally modified structure is expressed by equations consisting of the condensed matrices only which refer to the modified part. The analysis presented herein is developed in conjunction with eigensolution to the modified structure, and the derived fundamental equations are also represented by the same type of condensed matrices only. So, advantages are realized both in computational effort and in computer storage, if the modified part is small compared with the unmodified part. To find exact results, complete eigensolution to the unmodified structure needs to be given. Approximate results are obtained from a few lower eigenvectors and eigenvalues. A pin-jointed truss is solved as a numerical example.
    Additional Material: 1 Ill.
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  • 93
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 1879-1892 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An iterative method for numerically solving the time independent Navier-Stokes equations for viscous compressible flows is presented. The method is based upon partial application of the Gauss-Seidel principle in block form to the systems of the non-linear algebraic equations which arise in construction of finite element (Galerkin) models approximating solutions of fluid dynamic problems. The C0-cubic element on triangles is employed for function approximation. Computational results for a free shear flow at Re = 1000 indicate significant achievement of economy in iterative convergence rate over finite element and finite difference models which employ the customary time dependent equations and symptotic time marching procedure to steady solution. Numerical results are in excellent agreement with those obtained for the same test problem employing time marching finite element and finite difference solution techniques.
    Additional Material: 5 Ill.
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  • 94
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977) 
    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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  • 95
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 27-38 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A hierarchical approach is used to construct the simplex elements which permits easy merging of elements of different orders. The explicit interpolation functions and the algorithm of using such elements are presented.
    Additional Material: 4 Ill.
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  • 96
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 85-98 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Triangular and prismatic quadratic isoparametric elements, formed by collapsing one side and placing the mid-side node near the crack tip at the quarter point, are shown to embody the (1/√r) singularity of elastic fracture mechanics and the (1/r) singularity of perfect plasticity. The procedure of performing the fracture analysis for the case of small scale yielding is discussed, and the finite element results are compared with theoretical results.The proposed elements have wide application in the fracture analysis of structures where ductile fracture is investigated. They permit a determination of the relationship between crack tip field parameters, loading, and geometry. And for a given fracture criterion can be applied to the prediction of fracture in structures such as pressure vessels under in service conditions.
    Additional Material: 8 Ill.
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  • 97
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 131-143 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 13 Ill.
    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 11 (1977), S. 145-167 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The Simplified Hybrid Displacement Method, an attractive modification of one of the principles of stationary value of modified potential energy, is examined critically and compared to another form of such variational principles and to the classical principle of minimum of potential energy. The three methods are studied from a theoretical vantage point and through the medium of numerical examples. A non-conforming triangular finite plate bending element serves as the vehicle to solve a number of simple problems, utilizing the classical principle of minimum potential energy, a principle of stationary value of modified potential energy and the Simplified Hybrid Displacement Method.The attraction of this method derives from the fact that no additional independent unknown parameters - Lagrangian multipliers from a mathematical standpoint - enter into the modified energy functional, as is usually the case with hybrid methods.It is demonstrated numcrically that the Simplified Hybrid Displacement Method may become unstable. It is also shown that the stationary values of the modified energy functional for this method may be inconsistent with the corresponding minima of the classical potential energy. Furthermore, it is demonstrated that the Simplified Hybrid Displacement method is, in general, incapable of ‘restoring’ interelement slope continuity in the sense of a principle of stationary value of modified potential energy, that is, at least in an ‘integral sense’.
    Additional Material: 2 Ill.
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  • 99
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 180-184 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 1 Ill.
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  • 100
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 11 (1977), S. 199-200 
    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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