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  • 101
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    European journal of clinical pharmacology 12 (1977), S. 153-158 
    ISSN: 1432-1041
    Keywords: Fentanyl ; radioimmunoassay ; cross-reaction ; plasma level ; dog ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Antiserum to fentanyl was obtained in rabbits repeatedly injected with carboxyfentanyl conjugated to bovine serum albumin. Using the antiserum, a highly sensitive radioimmunoassay has been developed, based on the dextran-coated charcoal method. It proved possible to assay the drug directly in plasma, in amounts as small as 30 picogram in 0.5 ml. The antibody was highly specific for fentanyl and no cross-reaction was observed with its major metabolites. This sensitive and specific radioimmunoassay method was employed to determine fentanyl in plasma from six volunteers after an intravenous bolus of 0.2 mg, and in plasma from dogs treated both intravenously and subcutaneously with 0.02 mg/kg. The plasma level of fentanyl could be followed for up to 6 h after a therapeutic dose in dogs and man.
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  • 102
    ISSN: 1432-1041
    Keywords: Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
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  • 103
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    European journal of clinical pharmacology 13 (1978), S. 213-218 
    ISSN: 1432-1041
    Keywords: Activated charcoal ; acute intoxication ; digoxin ; phenytoin ; aspirin ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The inhibitory effect of activated charcoal 50 g suspended in water on the absorption of digoxin, phenytoin and aspirin was studied in six healthy volunteers in a cross-over manner. The absorption of digoxin and phenytoin were almost completely prevented (about 98%) when activated charcoal was ingested immediately after the drug. The total absorption of aspirin was inhibited by 70%, with clear postponement of absorption and partial release of aspirin from the charcoal in the gut: The peak serum concentration of aspirin was reduced by 95% by charcoal. When activated charcoal was ingested 1 hour after the drugs the inhibition of absorption was considerably less. However, since the absorption of larger doses of the drugs is often slow, the administration of an adequate dose of activated charcoal will be of definite value in the treatment of acute intoxication, even if delayed for several hours.
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  • 104
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    European journal of clinical pharmacology 14 (1978), S. 129-131 
    ISSN: 1432-1041
    Keywords: Tetracycline absorption ; EDTA ; milk ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of tetracycline in man under the influence of concomitantly administered EDTA, milk and a combination of EDTA and milk has been investigated. Urinary excretion of the drug was measured for 30 h. The inhibitory effect of milk could be counteracted by simultaneous ingestion of EDTA, which resulted in almost equivalent urinary excretion of tetracycline compared to experiments done in the fasting state. Administration of EDTA alone, in a neutral dosage form, did not significantly change absorption of the drug, which contradicted previous findings. The possible use of EDTA during tetracycline therapy is discussed.
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  • 105
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    European journal of clinical pharmacology 14 (1978), S. 277-280 
    ISSN: 1432-1041
    Keywords: Doxycycline ; iron ; charcoal ; enteral cycling ; man ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In order to study the intestinal interactions of doxycycline (DC) with Fe++ and charcoal, two groups of healthy volunteers were given either 200 mg or 100 mg DC in capsules at 2 p. m. and 9 p. m., and blood samples for fluorimetric assay of DC were collected for 24 h starting at 8.30 a. m. on the following morning. A 24-h-urine was also collected. The test was subsequently repeated at one-week intervals, when the volunteers also ingested either ferrous sulphate (80 mg Fe++) or charcoal (4.0 g) immediately after the zero-time sample of DC and at 3, 8 and 12 h. Charcoal completely adsorbed DC in vitro in an artificial small intestinal fluid. Ferrous sulphate or charcoal did not modify the serum level or urinary excretion of DC after the 200 mg+200 mg dose, but ferrous sulphate did reduce the 24-h urinary excretion of DC after the 100 mg+100 mg dose. The serum half-life and AUC of DC were reduced by ferrous sulphate given after the 100 mg+100 mg dose of DC. Charcoal did not modify any parameter, even after the 100 mg+100 mg dose of DC. The results do not support existence of important enteral cycling of DC. Although oral ferrous sulphate can lower the serum level and shorten the serum half-life of DC, the acute experiment suggested that a therapeutic serum level of DC can be maintained despite treatment with iron in the doses used in iron-deficiency, and charcoal in the doses used in diarrhoeic states, if the drugs are administered several hours apart.
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  • 106
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    European journal of clinical pharmacology 15 (1979), S. 187-192 
    ISSN: 1432-1041
    Keywords: quinidine ; plasma protein binding ; pharmacokinetics ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition and plasma protein binding of quinidine after intravenous administration were studied in 13 healthy subjects. Plasma protein binding, expressed as the fraction of quinidine unbound ranged from 0.134–0.303 (mean 0.221). Elimination rate constant (β) varied from 0.071 to 0.146 h−1 (mean 0.113), and apparent volume of distribution (Vβ) varied from 1.39–3.20 l · kg−1β (mean 2.27). Total body clearance was 2.32–6.49 ml min−1 · kg−1. There was a positive linear correlation between the plasma fraction of unbound quinidine and both Vβ (r=0.885, p〈0.01) and total body clearance (r=0.668, p〈0.05). No significant correlation existed between the fraction of unbound quinidine in plasma and the elimination rate constant. The results show that both the apparent volume of distribution and total body clearance of quinidine are proportional to the unbound fraction in plasma. This implies that the total plasma concentration of quinidine at steady state will change with alterations in plasma binding, whilst the concentration of unbound compund and its elimination rate will remain unaffected.
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  • 107
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    European journal of clinical pharmacology 14 (1978), S. 69-73 
    ISSN: 1432-1041
    Keywords: Citalopram ; pharmacokinetics ; man ; steady state levels ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of citalopram, a potent serotonin reuptake inhibitor, and its demethylated metabolite have been determined by a specific fluorescence coupling technique during single dose experiments in volunteers and in clinical tests. Citalopram was found to have linear kinetics within the dose range investigated, which were characterized by fairly rapid absorption and slow elimination (biological half-life 1–21/2 days). Steady state levels in the range 120–340 nM (i.e. slightly above those associated with pharmacodynamic activity in animals) were attained within a week. A drug/metabolite ratio of 2–3 was recorded.
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  • 108
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    European journal of clinical pharmacology 14 (1978), S. 425-430 
    ISSN: 1432-1041
    Keywords: Penta-acetyl-gitoxin ; 16-acetyl-gitoxin ; gitoxin ; mass spectrometry ; species-specific deacylation ; man ; rabbit ; guinea-pig ; rat ; blood ; intestinal mucosa ; liver homogenate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Penta-acetyl-gitoxin (PAG) shows species-specific deacylation to 16-acetyl-gitoxin (16-AG; I and III) or gitoxin (II and IV) by homogenates of liver and intestinal mucosa of man (I), rabbit (II), guinea-pig (III) and rat (IV), whereas it is degraded into tri- and tetra-acetates by homogenates of guinea-pig myocardium as well as by human blood and serum. The identity of the principal and chloroform-extractable metabolites in human urine after PAG administration with 16-AG has been demonstrated by mass spectrometry.
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  • 109
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    European journal of clinical pharmacology 15 (1979), S. 73-81 
    ISSN: 1432-1041
    Keywords: simulation model ; diazoxide hypotension ; haemodynamics ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The acute haemodynamic effects of injected diazoxide (Hyperstat® Schering) have been studied in 8 hypertensive subjects. Aortic blood pressure was measured and cardiac output and peripheral conductance were assessed continuously using a simulation model. In six of the patients pulmonary artery end-diastolic pressure was also measured. Blood pressure fell in all subjects 5–10 min after injection of the drug cardiac output increased in all patients studied. However, the initial change in cardiac output differed, as it decreased in two subjects and did not change in one. The largest initial increases in cardiac output were seen in the subjects with the highest pulmonary artery end-diastolic pressure. Patients with an initial decrease in cardiac output were those with the least compliant (stiffest) aortas. We consider that the responsiveness of the baroreceptors determines the size of the increase in cardiac output immediately after reduction of blood pressure by diazoxide. Thus in a patient with a stiff aorta, particularly at low cardiac filling pressure, diazoxide might cause a fall in blood pressure to an unacceptable level.
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  • 110
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    European journal of clinical pharmacology 10 (1976), S. 1-7 
    ISSN: 1432-1041
    Keywords: 3H-terbutaline sulphate ; aerosol ; man ; absorption ; excretion ; spirometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six asthmatic patients and two healthy volunteers inhaled tritiated terbutaline sulphate delivered by a pressurized aerosol inhaler. Spirometric measurements were performed and the amounts of total radioactivity in plasma, urine and faeces were determined. The analysis of urine included determination of radioactivity due to metabolized drug. Depending on the amount of drug inhaled the peak plasma level varied from undetectable to 3.8 ng/ml. An early plasma peak was found in 7 out of 8 subjects. The main plasma peaks were observed 1 – 6 hours after administration. The results of urinalysis showed a metabolic profile similar to that after parenteral administration. Disregarding the amount of inhaled drug and sampling time, 3 – 35% of the delivered drug was recovered in the urine and 2 – 37% in the faeces. Immediately after treatment 4 subjects rinsed their mouths with water and it was found to contain 14.5 – 50% of the delivered dose. The adapters from the aerosol canisters contained 14 – 27.5% of the delivered dose of drug.
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  • 111
    ISSN: 1432-1041
    Keywords: H 80/62 ; haemodynamic effects ; noninvasive techniques ; selectivity ; β1-adrenoceptor agonist ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The selective β1-adrenoceptor agonist H 80/62 was administered intravenously and orally to healthy subjects and its effects on systolic time intervals, arterial blood pressure and heart rate were studied. Side-effects were noted too, and continuous ECG-recordings were made in order to study its arrhythmogenic effect. After i.v. administration of H 80/62 20 µg/kg body weight there was shortening of total electromechanical systole, the pre-ejection period and of the left ventricular ejection time, systolic blood pressure tended to increase, and diastolic blood pressure and heart rate were essentially unchanged. When administered orally as a sustained-release preparation in doses between 20 and 40 mg the haemodynamic effects were qualitatively the same as after i.v. administration, but in some studies there was a slight increase in heart rate. During exercise the systolic blood pressure and heart rate were identical after H 80/62 and placebo. The effect of the drug was maximal immediately after cessation of the i.v. infusion and basal values were regained within 60 min. After oral administration of a sustained-release formulation the effect was maximal after one hour and persisted for at least five to seven hours. The drug was well tolerated on repeated administration. The incidence of ventricular extrasystoles was possibly increased in one subject out of eight (11 ventricular extrasystoles during 18 h). The results of this Phase I study of H 80/62 warrant further evaluation of the drug in man.
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  • 112
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    European journal of clinical pharmacology 14 (1978), S. 445-447 
    ISSN: 1432-1041
    Keywords: Activated charcoal ; tricyclic antidepressants ; nortriptyline ; poisoning ; antidote ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Activated charcoal is known to reduce the absorption of therapeutic doses of nortriptyline in vivo when administered 30 min after drug ingestion. In a group of volunteers, one sachet (10 g) of a new activated charcoal preparation, ‘Medicoal’ was found to produce a highly significant reduction in nortriptyline absorption when given as long as four hours after nortriptyline dosing. Activated charchoal may therefore be useful in the treatment of tricyclic antide-pressant poisoning even if a delay of several hours ensues before medical help is sought.
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  • 113
    ISSN: 1432-1041
    Keywords: Intramuscular Clindamycin Phosphate ; serum levels ; half-lives ; renal Failure ; haemodialysis ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Serum levels of clindamycin bioactivity and total clindamycin were studied after single intramuscular injections of 300 mg of clindamycin phosphate in a group of 6 normal subjects and a group of 6 maintenance haemodialysis patients. The patients were studied during a non-dialysis period and then again during haemodialysis. Peak levels tended to be higher and elimination half-lives shorter in the patients than in the normal subjects. Possible reasons for these differences are discussed. There was no evidence that haemodialysis per se influenced the pharmacokinetics of clindamycin phosphate. The proportion of unhydrolysed clindamycin phosphate tended to be higher in the renal failure patients and the reason for this is not apparent. Little, if any, dosage modification is necessary in severe renal failure although there is probably little point in exceeding a dose of 300 mg intramuscularly every 8 h even in severe infections in patients with severe renal failure. The higher peak levels in patients with advanced renal failure indicate the need for further studies with repeated doses.
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  • 114
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    European journal of clinical pharmacology 8 (1975), S. 317-322 
    ISSN: 1432-1041
    Keywords: Verapamil ; haemodynamics ; exercise ; man ; vascular resistance ; negative inotropism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Verapamil, 0.1 mg/kg body wt, was injected i.v. over 2 minutes in 8 subjectively healthy middle-aged men, followed by a continuous infusion of 0.007 mg/kg body wt per minute. Prior to the injection several of the subjects had raised pulmonary or systemic arterial pressures. At rest, the central pressures increased slightly, which was taken as a sign of a moderate negative inotropic effect, but there was no change in pre-ejection period or maximal dp/dt of the aortic pressure. The heart rate increased and there was a small decrease in systemic arterial pressure, probably due to a fall of systemic vascular resistance. The PQ time was prolonged. During exercise, with its positive inotropic stimulation, the moderate negative inotropic effect of verapamil disappeared, whereas the increase in heart rate and decrease in aortic pressures persisted. Some variables that reflected the oxygen demand of the heart decreased. The slight negative inotropic effect does not appear to be a particular contraindication to the use of verapamil, but it should be employed cautiously in conditions with a compensatory rise in systemic vascular resistance, or if atrioventricular conduction is impaired.
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  • 115
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    European journal of clinical pharmacology 8 (1975), S. 337-341 
    ISSN: 1432-1041
    Keywords: Carbamazepine ; carbamamazepine-10,11-epoxide ; pharmacokinetics ; induction of metabolism ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Carbamazepine (Tegretol®) was administered orally to four patients as a single dose, and one week later three times daily for 15–21 days. The plasma half-lives of the drug were shorter in all patients after multiple doses (20.9±5.0 hours) than after the initial single dose (35.6±15.3 hours). During multiple doses the plasma concentrations of the metabolite carbamazepine-10,11-epoxide followed those of the parent drug. The steady-state plasma concentrations expected during multiple doses were calculated from the pharmacokinetic parameters obtained in the single dose studies. The calculated levels were higher (17.2±7.2 µg/ml) than the observed maximal concentrations (8.4±1.6 µg/ml on day 4), which were obtained 3–4 days after starting the multiple doses. The levels tended to decrease further during the experimental period. The results suggest that carbamazepine induces its own metabolism in man.
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  • 116
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    European journal of clinical pharmacology 8 (1975), S. 427-432 
    ISSN: 1432-1041
    Keywords: Methylproscillaridin ; urinary and faecal excretion ; polar and non-polar metabolites ; man ; glucuronides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 0.5 mg3H-proscillaridin-4-methylether was administered orally to 5 healthy males. Maximum plasma levels of total radioactivity were reached after one to two hours. In two subjects a second peak was observed between 6 and 12 hours. The plasma half life of total radioactivity was 51 hours. 20% and 56% respectively of the dose were eliminated in urine and faeces during the following 7 days. 55% of the total radioactivity in plasma, 80% in urine and 20% in faeces consisted of CHCl3-insoluble compounds. 50 – 60% of the latter in plasma and urine could be hydrolysed by β-glucuronidase. More than 90% of the split products were identified as conjugates of methylproscillaridin. TLC-separation of the CHCl3-soluble fractions of plasma and urine yielded two unidentified metabolites, P2 and P3, as the main compounds, besides methylproscillaridin, proscillaridin and scillarenin. In faeces more than 90% of the non-polar fraction was identified as methylproscillaridin. Shortly after administration of3H-methylproscillaridin, the radioactivity in plasma consisted mainly of CHCl3-in-soluble conjugates and of the metabolite P2.
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  • 117
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    European journal of clinical pharmacology 10 (1976), S. 69-72 
    ISSN: 1432-1041
    Keywords: BS 100-141 ; N-amidino-2-(2,6-dichlorphenyl)acetamide hydrochloride ; essential hypertension ; antihypertensive agent ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antihypertensive effect of the guanidine derivative BS 100-141 (N-amidino-2-(2,6-dichlorphenyl)acetamide hydrochloride) has been studied in 11 hospitalized patients suffering from essential hypertension (WHO grade I – II). BS 100-141 1 mg tid was given in the first week and a larger dose in the second week. Mean 24-hour systolic and diastolic blood pressures were significantly lower at the end of the first and second weeks of active treatment than at the end of the placebo-week. The antihypertensive effect of BS 100-141 was stronger in the standing than in the supine position. It significantly reduced the heart rate. Treatment with BS 100-141 was well tolerated, although tiredness and dryness of the mouth appeared more often than during the placebo period. Extensive laboratory tests did not reveal any toxic effect on the liver, kidneys or haemopoietic tissues.
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  • 118
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    European journal of clinical pharmacology 11 (1977), S. 135-140 
    ISSN: 1432-1041
    Keywords: Phenothiazine ; thioridazine ; metabolites ; plasma-level ; metabolic pattern ; half-life ; man ; schizophrenia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels of thioridazine and four of its metabolites were determined in a series of fifteen young acute schizophrenics. Consistent individually different metabolic patterns were detected in a group of patients who had the same value for the sum of thioridazine plus metabolites. The apparent volume of distribution and half life were calculated. Clinical evolution tended to correlate best with the level of mesoridazine.
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  • 119
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    European journal of clinical pharmacology 11 (1977), S. 213-218 
    ISSN: 1432-1041
    Keywords: β-Methyl-digoxin ; digoxin ; intravenous administration ; man ; serum concentration ; renal clearance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of the present investigation was to estimate the ratio of the intravenous doses ofβ-methyl-digoxin and digoxin required to produce identical serum glycoside concentrations in man. 20 patients on intravenous maintenance therapy were changed fromβ-methyl-digoxin to the identical dose of digoxin or vice versa. Each drug was given for 7 days. Serum concentrations 13% higher were found during administration ofβ-methyl-digoxin. Assuming a half life of 60 h after with drawal, the dose of digoxin producing the same minimum serum concentration was estimated to be 1.16 times higher than that ofβ-methyl-digoxin. 18 healthy volunteers received 0.4 mg β-methyldigoxin, and 23 the same dose of digoxin, as an intravenous infusion over 2 h. The serum concentrations and urinary glycoside excretion were measured over a period of 32 hrs. During the first hour after the infusion the serum concentration of digoxin declined more rapidly than that ofβ-methyl-digoxin. Thereafter, the ratio of the serum concentrations did not change appreciably up to the end of the investigation. The area under the serum concentration/time curve was about 13% greater forβ-methyl-digoxin than for digoxin; this difference was not significant. The average renal clearance was 96±9 ml forβ-methyl-digoxin, 151±13 ml for digoxin. Since the total body clearance of digoxin is only about 1.16 times higher than that ofβ-methyl-digoxin, the lower renal clearance ofβ-methyl-digoxin must partly be compensated by higher extrarenal clearance. From the ratios of the areas under the serum concentration/time curves after single doses of β-methyldigoxin and digoxin, and the minimum serum concentrations during maintenance therapy, it was concluded that the dose of digoxin to produce the same average serum concentrations would be about 1.15 times higher than that ofβ-methyl-digoxin. In comparison with the large variations in individual dosage of digoxin andβ-methyl-digoxin, this difference is too small to be of practical importance.
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  • 120
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    European journal of clinical pharmacology 10 (1976), S. 73-76 
    ISSN: 1432-1041
    Keywords: BS 100-141 ; N-amidino-2-(2,6-dichlorphenyl) acetamide hydrochloride ; clonidine ; essential hypertension ; antihypertensive agents ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antihypertensive effect and side effects of the guanidine derivative BS 100-141 (N-amidino-2-(2,6-dichlorphenyl) acetamide hydrochloride) and clonidine were compared in a single-blind, cross-over study. The study consisted of two active treatment periods of 6 weeks each, both preceded by a 2 week placebo period. Thirty ambulant, hypertensive patients, whose blood pressure was of WHO severity grades I – II, were admitted to the study, and the results are based on the 24 patients who completed it. In more than half the patients the optimal daily dose of BS 100-141 was 3 – 4 mg, and of clonidine 0.30 – 0.45 mg. An equally large and significant decrease in blood pressure was produced by both drugs. Both of them also caused bradycardia, but it was of no clinical significance. Both BS 100-141 and clonidine caused tiredness in about half the patients, but it diminished after a few weeks. Dryness of the mouth occurred in more than half the patients taking either drug, and it remained unchanged during the 6 weeks of treatment. A withdrawal syndrome was noted in one patient on discontinuation of clonidine.
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  • 121
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    European journal of clinical pharmacology 12 (1977), S. 81-87 
    ISSN: 1432-1041
    Keywords: Oxprenolol ; smoking ; catecholamines ; coronary circulation ; man ; c-AMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Changes in catecholamine, c-AMP and lactate concentrations in the coronary circulation of man, during smoking, were studied in 12 patients. The heart rate increased from 63±2 beats/min (control) to 74±3 (smoking) (P〈0.01), falling to 70±2 (10 min after smoking) (0.05〉P〉0.01), whilst coronary sinus c-AMP concentrations rose from 11±0.7 nmol/l (smoking) to 11.9±0.8 nmol/l (after smoing) (0.05〉P〉0.01; one tailed ‘t’ test). There was no significant change in blood pressure, catecholamine or lactate concentrations. The study was repeated in eight of the patients following intravenous oxprenolol. Coronary sinus catecholamine concentrations increased from 4.1±0.7 nmol/l (control) to 5.5±1.1 nmol/l (after smoking) (0.05〉P〉0.01; one tailed ‘t’ test), but heart rate and c-AMP concentrations remained unchanged, confirming that smoking-induced tachycardia is a result of a β-adrenergic mechanism, at least part of which is due to a release of cardiac catecholamines. Arterial lactate concentrations increased only following oxprenolol from 0.74±0.07 mmol/l (control) to 0.83±0.09 mmol/l (smoking).
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  • 122
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    European journal of clinical pharmacology 12 (1977), S. 281-284 
    ISSN: 1432-1041
    Keywords: Tetracycline ; bioavailability ; plasma levels ; nutritional state ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Relative bioavailability after oral administration of a single dose and Cmin levels of tetracycline in plasma after multiple doses were determined in groups of well-nourished and undernourished subjects. The relative bioavailability of tetracycline, assessed by the area under serum concentration time-curves, did not differ in undernourished and well-nourished patients. The plasma levels were not different in the two groups after the conventional dose of tetracycline HCl 250 mg at 6 hour intervals. However, in these studies undernourished subjects received a higher dose per kg body weight, which could have compensated for any effect of a shortened half life of the drug. When the dose per kg body weight was reduced, the Cmin levels were lower. On the other hand, with the same dose per kg body weight at more frequent intervals, the plasma concentrations were similar to those in well-nourished subjects. These studies indicate that the dosage regimen should be based both on body weight and on the nutritional status of the individual.
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  • 123
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    European journal of clinical pharmacology 13 (1978), S. 35-39 
    ISSN: 1432-1041
    Keywords: Norethindrone ; bioavailability ; man ; competitive protein binding ; sex differences ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A competitive protein binding assay for norethindrone was developed to measure plasma levels in human subjects. The plasma levels were considerably higher in women than in men, especially at low dose levels. The plasma levels were directly related to the dose in men; but greater variations in the plasma levels were observed in women. The plasma half-life was about 5 h in both sexes with single oral doses of 5 to 20 mg. A comparative bioavailability study with norethindrone from 2 different manufacturers, formulated in the same manner, showed no significant differences in absorption characteristics and provided sufficient data for pharmacokinetic analysis.
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  • 124
    ISSN: 1432-072X
    Keywords: Diatom ; Cylindrotheca fusiformis ; Ribosomes ; Ribosomal RNA ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cytoplasmic and chloroplast ribosomes from the marine diatom Cylindrotheca fusiformis were isolated and characterized. The cytoplasmic ribosomes sedimented in sucrose at 84S and dissociated into subunits of 64S and 42S in the absence of Mg2+. It contained ribosomal RNAs with molecular weights of 1.31×106 and 0.70×106. The chloroplast ribosomes sedimented at 70S only in the presence of high Mg2+ concentrations (25–100 mM). No stable subunits were routinely observed and at very high levels of Mg2+ (〉100 mM) the 70S species was converted to a form sedimenting at 55S. At 4°C ribosomal RNAs with molecular weights of 1.1×106 and 0.40×106 were detected on polyacrylamide gel electrophoresis. When the RNAs were resolved at room temperature the large molecular weight component disappeared while RNA with molecular weights of 0.65×106 and 0.53×106 were observed. Apparently the large chloroplast RNAs dissociated into two pieces of unequal molecular weight. These properties of the diatom's chloroplast ribosomes are very similar to those of the counter parts in unicellular green algae, which suggests that both types of algae have a common phylogenetic ancestor.
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    Archives of microbiology 110 (1976), S. 27-36 
    ISSN: 1432-072X
    Keywords: Immunology ; β-Ketoadipate pathway ; Catabolic enzymes ; Antigenic determinants ; Evolution ; Gene transfer ; Pseudomonas ; β-Carboxy-cis,cis-muconate lactonizing enzyme ; γ-Carboxymuconolactone decarboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract β-Carboxy-cis,cis-muconate lactonizing enzyme and γ-carboxymuconolactone decarboxylase catalyze sequential reactions in the β-ketoadipate pathway, the subunit sizes of the enzymes from Pseudomonas putida, biotype A, are 40000 and 13000, respectively. The cross reaction of antisera prepared against the enzymes was tested with the isofunctional enzymes formed by representatives of other bacterial species. Despite the differences in the subunit sizes of the enzymes, the antisera revealed the same general pattern: cross reaction was observed with the corresponding enzymes formed by other strains in the fluorescent Pseudomonas RNA homology group I and generally was not observed with enzymes from other Pseudomonas species or from other bacterial genera. Exceptions were provided by representatives of Pseudomonas cepacia. Members of this species are classified outside the fluorescent Pseudomonas RNA homology group. Nevertheless, the γ-carboxymuconolactone decarboxylases from these organisms formed precipitin bands with antisera prepared against the corresponding enzyme from P. putida, biotype A; the lactonizing enzymes from the two species did not appear to cross react. Immunodiffusion experiments with γ-carboxymuconolactone decarboxylase indicated that a common set of antigenic determinants for the enzyme is conserved among strains that have been classified together by other criteria; the relative immunological distances of the decarboxylases of each taxon from the reference P. putida, biotype A, enzyme were indicated by spurring patterns on Ouchterlony plates. These results suggested that the interspecific transfer of the structural gene for the enzyme is not a common event in Pseudomonas.
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  • 126
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    Archives of microbiology 119 (1978), S. 313-322 
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Anacystis ; Anoxygenic photosynthesis ; Reducing agents ; Electron donors ; Anaerobiosis ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis by Anacystis nidulans was studied in presence of reduced sulfur or nitrogen compounds, or of hydrogen. O2 evolution and CO2 fixation were depressed by sulfide, sulfite, cysteine, thioglycollate, hydroxylamine and hydrazine. Sulfite, cysteine and hydrazine inhibited O2 evolution much more strongly than CO2 fixation, indicating ability to supply electrons for CO2 photoreduction; DCMU suppressed these photoreductions. In contrast, some anoxygenic photosynthetic CO2 fixation insensitive to DCMU was found with sulfide, thiosulfate and hydrogen. Emerson enhancement studies confirmed that sulfite, cysteine and hydrazine acted on photosystem II, while photoreduction supported by sulfide, thiosulfate and hydrogen needed photosystem I only. Sulfite was photooxidized to sulfate, sulfide to elemental sulfur, and thiosulfate to sulfate plus elemental sulfur; the sulfur accumulated inside the cells. Results on the stoichiometries of the photoreductions were consistent with the photooxidation products determined. Inhibitor studies suggested photosynthetic CO2 fixation through the Calvin cycle. While photoreduction by all reductants used was found to be constitutive in Anacystis, the process was stimulated by anaerobic preincubation with the reductants only in the cases of hydrogen and thiosulfate; this adaptation was prevented by chloramphenicol and by O2. Anaerobic photoautotrophic growth of Anacystis was, however, not observed; the increase in dry weight with H2 and thiosulfate was not accompanied by cell multiplication or by an increase in chlorophyll content. Parallel short-term experiments with Chlorella did not reveal any constitutive photoreduction in this eukaryotic alga.
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  • 127
    ISSN: 1432-2242
    Keywords: Key words Cicer species ; Microsatellites ; Zero-allele ; Phylogenetic tree ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The conservation of 90 microsatellite-flanking sequences from chickpea in 39 accessions of eight annual and 1 accession of a perennial species of the genus Cicer was investigated. All of the primer sequences successfully amplified microsatellites in related species, indicating the conservation of microsatellite-flanking sequences in chickpea’s relatives. However, the degree of conservation of the primer sites varied between species depending on their known phylogenetic relationship to chickpea, ranging from 92.2% in C. reticulatum, chickpea’s closest relative and potential ancestor, down to 50% for C. cuneatum. A phylogenetic tree revealed that chickpea and the other members of its crossability group were more closely related to the perennial C. anatolicum than to other annual species of the genus. Considerable variation in size and number of amplification products between and within species was observed. Sequence analysis of highly divergent amplification products proved that variation is either due to large differences in the number of microsatellite repeats or to the amplification of a locus unrelated to the one amplified from chickpea. Sequence information and bootstrapping using PAUP suggested that STMSs derived from chickpea may be efficiently and reliably used for synteny studies in chickpea’s crossability group, including C. anatolicum. However, care should be taken when applying these markers to other species of the genus. Considering the data presented here and the known historical record, the age of section Monocicer, including chickpea, is estimated to be about 100,000 years.
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    Theoretical and applied genetics 100 (2000), S. 1267-1273 
    ISSN: 1432-2242
    Keywords: Keywords Domestication ; Evolution ; QTL ; Map-based cloning ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The seeds of domesticated plants are normally much larger than those of their wild counterparts. This change in seed weight was most likely in response to the selection pressure for yield, uniform germination and seedling vigor which was exerted by humans during domestication. However, despite the evolutionary and agronomic significance of seed weight, very little is know about the genetic and developmental controls of this trait; and, thus far, none of the genes in this pathway have been isolated from any plant species. QTL mapping experiments conducted in tomato during the past decade have allowed the identification of many seed-weight QTLs and have also revealed that only a few loci are responsible for the majority of the seed-weight changes that accompanied the domestication of tomato. This review presents a consensus map for seed weight QTL identified in previously published reports and in unpublished results from our laboratory. This summary of seed-weight QTL data allows for the identification of the major loci controlling this trait in the genus Lycopersicon. It is hoped that this work will allow the elucidation of this important phenotypic transition that occurred during crop-plant domestication and will also provide the starting point for the cloning of a gene responsible for seed-weight variation.
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    Theoretical and applied genetics 101 (2000), S. 379-387 
    ISSN: 1432-2242
    Keywords: Key words Rice ; Isozyme variation ; Multilocus organization ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic organization of isozyme variation in rice (Oryza sativa L.) was investigated based on 17 polymorphic isozyme loci using a sample of 511 accessions of worldwide origin. The genetic diversity within the species was very high (H=0.36 with 4.82 alleles per locus), as compared with most selfing plant species. Three diversity centers were detected for isozyme variation including South Asia, China and Southeast Asia. The accessions were classified into three well-differentiated cultivar groups corresponding to the indica and japonica subspecies, and a new unnamed group. Variation within the cultivar groups accounted for 80% of the total isozyme variation. Within-country variation accounted for 58% of the total variation while among-region and among-country variation within the cultivar groups accounted for only 14% and 8% of the total variation. Analyses using log-linear models revealed that pronounced non-random associations between and among alleles at many unlinked isozyme loci were organized in a non-hierarchical pattern, and subspecific and macro-geographic differentiation was much more pronounced in multilocus phenotype frequencies than in allelic frequencies at individual loci. These results suggest that selection on multilocus gene complexes was largely responsible for the maintenance of the extensive isozyme variation within the species and the indica-japonica differentiation. Our results further suggest the independent domestication of indica and japonica, the dual origins of the indica rice from China and South Asia (India), and the differentiation of the ecotypes ’javanica’ and the ’temperate japonica’ within the japonica subspecies.
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    Theoretical and applied genetics 101 (2000), S. 1259-1268 
    ISSN: 1432-2242
    Keywords: Key words Enriched-library ; SSR ; Repetitive elements ; Allelic diversity ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsatellites have many desirable marker properties. There has been no report of the development and utilization of microsatellite markers in oat. The objectives of the present study were to construct oat microsatellite-enriched libraries, to isolate microsatellite sequences and evaluate their level of polymorphism in Avena species and oat cultivars. One hundred clones were isolated and sequenced from three oat microsatellite-libraries enriched for either (AC/TG) n , (AG/TC) n or (AAG/TTC) n repeats. Seventy eight clones contained microsatellites. A database search showed that 42% of the microsatellite flanking sequences shared significant homology with various repetitive elements. Alu and retrotransposon sequences were the two largest groups associated with the microsatellites. Forty four primer sets were used to amplify the DNA from 12 Avena species and 20 Avena sativa cultivars. Sixty two percent of the primers revealed polymorphism among the Avena species, but only 36% among the cultivars. In the cultivars, the microsatellites associated with repetitive elements were less polymorphic than those not associated with repetitive elements. Only 25% of the microsatellites associated with repetitive elements were polymorphic, while 46% of the microsatellites not associated with repetitive elements showed polymorphism in the cultivars. An average of four alleles with a polymorphism information content (PIC) of 0.57 per primer set was detected among the Avena species, and 3.8 alleles with a PIC of 0.55 among the cultivars. In addition, 54 barley microsatellite primers were tested in Avena species and 26% of the primers amplified microsatellites from oat. Using microsatellite polymorphisms, dendrograms were constructed showing phylogenetic relationships among Avena species and genetic relationships among oat cultivars.
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    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
    ISSN: 1572-8943
    Keywords: cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
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    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
    ISSN: 1572-8943
    Keywords: facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
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    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
    ISSN: 1572-8943
    Keywords: kinetics ; metal complexes
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
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    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
    ISSN: 1572-8943
    Keywords: adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
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    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
    ISSN: 1572-8943
    Keywords: activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
    ISSN: 1572-8943
    Keywords: kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
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  • 137
    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
    ISSN: 1572-8943
    Keywords: desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
    ISSN: 1572-8943
    Keywords: coordination compounds ; kinetics ; thermal dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
    ISSN: 1572-8943
    Keywords: cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
    ISSN: 1572-8943
    Keywords: Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
    ISSN: 1572-8943
    Keywords: accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
    ISSN: 1572-8943
    Keywords: decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
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    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
    ISSN: 1572-8943
    Keywords: driving force ; kinetics ; rate equation ; reversible reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
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    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
    ISSN: 1572-8943
    Keywords: CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
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    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
    ISSN: 1572-8943
    Keywords: complexes ; kinetics ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
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    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
    ISSN: 1572-8943
    Keywords: kinetics ; Mannich compounds ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
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    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    ISSN: 1572-8943
    Keywords: crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
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  • 150
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    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    ISSN: 1572-8943
    Keywords: kinetics ; metal exchange ; thermaldehydration ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
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  • 151
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    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
    ISSN: 1572-8943
    Keywords: KEKAM equation ; kinetics ; thermal dissociation of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
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  • 152
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
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    Topics: Chemistry and Pharmacology
    Notes: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
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  • 153
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    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
    ISSN: 1572-8943
    Keywords: decomposition ; kinetics ; plumbo-jarosite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
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  • 154
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    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    ISSN: 1572-8943
    Keywords: aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
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  • 155
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    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    ISSN: 1572-8943
    Keywords: DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
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    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
    ISSN: 1572-8943
    Keywords: kinetics ; nucleation-growth
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
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  • 157
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    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    ISSN: 1572-8943
    Keywords: CoSO46H2O ; kinetics ; thermal decomposition
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
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  • 158
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    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
    ISSN: 1572-8943
    Keywords: coal-burning additive ; combustion ; graphite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
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  • 159
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    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
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  • 160
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    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    ISSN: 1573-4870
    Keywords: TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
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  • 161
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    Keywords: tantalum alloy ; oxygen ; dissolution ; kinetics ; oxides
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxygen was added to T-111 (Ta-8W-2Hf, wt.%) at 820 and 990°C at an oxygen pressure of about 3×10−4 Torr (4×10−2N/m2). The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at% oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990°C. The vaporization of WO3 has no apparent affect on the doping reaction.
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  • 162
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    Oxidation of metals 11 (1977), S. 127-132 
    ISSN: 1573-4889
    Keywords: Duplex oxides ; copper oxidation ; kinetics ; oxygen partitioning
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The theory for the growth of a double oxide layer proposed by Yurek, Hirth, and Rapp, has been applied to copper using experimental rate-constant data obtained by Valensi. Calculated thicknesses of the layers agree very well with experimentally measured values.
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  • 163
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    Oxidation of metals 9 (1975), S. 459-472 
    ISSN: 1573-4889
    Keywords: Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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  • 164
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    Oxidation of metals 10 (1976), S. 85-95 
    ISSN: 1573-4889
    Keywords: boron carbide ; oxidation ; kinetics ; chromatography method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermogravimetry and gas-adsorption chromatography were used to study the kinetics of formation of solid and gaseous products during the hightemperature oxidation of compact boron carbide in oxygen at 740 Torr. Oxidation resistance was observed at temperatures up to 1200°C. The main oxidation products were B2O3 and CO2. Oxidation was paralinear; the carbon consumption exceeded the consumption of boron as compared to the ratio of these elements in the compound B4C. This difference resulted in carbon depletion of the carbide layer in the substrate near the scale〉.
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  • 165
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    Oxidation of metals 10 (1976), S. 361-376 
    ISSN: 1573-4889
    Keywords: metals ; scale structure ; epitaxy ; kinetics ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An explanation of the deviation from the parabolic law is the treatment which considers both shortcircuit and lattice diffusion in the oxide scale. In this study we examine how the oxidation kinetics are influenced by changing the structure of the scale of copper oxide in order to confirm the role of short-circuit diffusion in determining the oxidation rate. In addition we explain the oxidation kinetics of copper and nickel by using a model of the scale structure which includes recrystallization and grain growth. Results are as follows: (1) The nucleation and growth behavior of oxide have a direct effect on the structure and in turn the oxidation kinetics due to short-circuit diffusion. (2) A modified treatment is valid in the region where volume diffusion and short-circuit diffusion play an important role in which it is necessary to consider the scale structure such as the grain size distribution and the boundary width. (3) When recrystallization takes place it is necessary to consider the model of a two-layered scale structure which is different in properties and morphology. (4) In this region the rate curves are S-shaped when oxide recrystallization takes place and exhibit a transition from a parabolic to an nth-power relationship (n〉2) when grain growth takes place.
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  • 166
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    Oxidation of metals 11 (1977), S. 225-239 
    ISSN: 1573-4889
    Keywords: tantalum ; oxidation ; high temperature ; kinetics
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
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  • 167
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    Oxidation of metals 11 (1977), S. 365-381 
    ISSN: 1573-4889
    Keywords: cobalt oxidation ; kinetics ; parabolic rate constant
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10−4−0.658 atm). The dependence of the calculated values of parabolic rate constants k″p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy Ek decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.
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  • 168
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    Oxidation of metals 13 (1979), S. 77-88 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The solid-state reaction between barium carbonate and rutile powders to form barium metatitanate BaTiO3 was studied by thermogravimetric analysis, X rays, and microscopy. Phase-stability domains were drawn in a temperature— $${\text{p}}_{CO_2 } $$ , diagram. The dependence of the reaction kinetics on $${\text{p}}_{CO_2 } $$ , $${\text{p}}_{O_2 } $$ or $${\text{p}}_{N_2 } $$ is discussed. In particular, the rate continuously decreases when $${\text{p}}_{CO_2 } $$ , or $${\text{p}}_{N_2 } $$ increases, but it reaches a maximum as a function of $${\text{p}}_{O_2 } $$ .
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  • 169
    ISSN: 1573-4889
    Keywords: Cu-Si alloys ; oxidation ; kinetics ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Cu-Si alloys (containing up to 4.75 wt. % Si) in $${\text{p}}_{O_2 } $$ =0.01 atm from 800 to 1000°C has been investigated using thermogravimetry and other techniques. A 0.04% Si alloy followed a parabolic oxidation law with a rate similar to that of pure Cu. As the Si concentration increased the rate decreased and became irregular owing to SiO2 particles or flakes at the alloy-scale interface. It is considered that sintering of SiO2 particles and rupture of the sinter because of contraction during sintering are responsible for the irregular kinetics. A SiO2 layer forms directly on the 4.75% Si alloy which oxidizes uniformly. The SiO2 was always amorphous. In pure CO2 a similar pattern of amorphous SiO2 particles, flakes, and layers occurs.
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    Oxidation of metals 13 (1979), S. 283-298 
    ISSN: 1573-4889
    Keywords: oxidation ; surface alloys ; Fe-Cr alloys ; iron ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of several surface and bulk Fe-Cr alloys and iron at 300°C and 4×10−6 Torr oxygen was studied. The surface alloys were fabricated by implantation of 25 keV Cr ions into the outermost 300Å of polycrystalline iron samples. The oxide thickness as a function of oxygen exposure was obtained using proton-excited X-ray analysis, and composition profiles of oxide films were obtained using Auger electron spectroscopy and ion sputtering. The addition of Cr to Fe by surface and bulk alloying caused the oxidation rate to decrease and changed the oxidation kinetics from parabolic (for Fe) to logarithmic (for Cr concentrations ≥4.7at.%). Interpretation of the data in terms of simple oxidation theories indicates that the Cr additions may reduce the oxidation rate by altering the electronic properties of the metal-oxide interface.
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    Oxidation of metals 13 (1979), S. 255-272 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; graphite deposition ; nonadherent oxide ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Fe-C alloys containing 0.5 and 1.0% C was studied in 1 atm O2 at 700° C. The oxidation rate is considerably slower than for pure Fe. The oxide scale formed is detached, multilayered, and overoxidized, containing little or no FeO. A thin film of graphite was identified at the metal-oxide interface by electron diffraction. It is proposed that the slow oxidation and abnormal scale are caused by a residue of graphite left at the metal surface from the oxidation of Fe3C. This inhibition of the oxidation of Fe by carbon at 700°C is in contrast to the stimulation observed at 500°C.
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    Oxidation of metals 13 (1979), S. 301-309 
    ISSN: 1573-4889
    Keywords: NiO ; Electrical conductivity ; gas-solid equilibria ; kinetics ; equivalent circuit
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a previous work it has been stated that the NiO electrical conductivity changes connected to the oxygen pressure changes may be considered as a transitory phenomenon. A mixed kinetics case controlled by the formation of surface cation vacancies and their diffusion in the bulk is proposed to explain the reaction process. By means of an equivalent electrical circuit in good agreement with the kinetics model it was possible to reproduce the experimental phenomenon.
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    Oxidation of metals 13 (1979), S. 481-504 
    ISSN: 1573-4889
    Keywords: kinetics ; sulfidation ; Fe-Cr-Al alloys
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of aluminium on the kinetics and mechanism of high-temperature sulfidation of Fe-Cr alloys containing 20 at.% chromium has been investigated. It has been found that the addition of aluminum greatly improves the scaling resistance of Fe-Cr alloys against attack by sulfur vapors at high temperatures.
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  • 174
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    Oxidation of metals 9 (1975), S. 357-365 
    ISSN: 1573-4889
    Keywords: kinetics ; zirconia ; defect structure ; ionic conductivity ; yttria dopant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A Zr-0.5 Y alloy was found to oxidize about 6 times faster than pure zirconium over the temperature range of 400 to 565°C. The activation energies were nearly identical (∼32 kcal/mole). The activation energies correspond to grain boundary diffusion of oxygen through the scale. The higher oxidation rate of the alloy was attributed to a higher anion vacancy concentration and the assumption that diffusion sites in the lattice and boundaries were in local equilibrium. Measurements on yttria-doped zirconia showed that ionic conductivity was increased markedly by yttrium and extended over a wide range of oxygen pressure. The defect structure of the doped oxide was changed to one of oxygen vacancies, even at the high end of the oxygen pressure range, 10−8 to 0.2 atm, over which pure ziconia contains oxygen interstitials. The doped oxide was found to be extrinsic over the entire range of oxygen pressure and, although ionic conductivity predominated, electronic conductivity was still appreciable. The electronic conductivity, however, was still sufficiently high so that electron transport was not rate-controlling in the predominantly ionic-conducting scale.
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  • 175
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    Journal of materials synthesis and processing 8 (2000), S. 271-277 
    ISSN: 1573-4870
    Keywords: Comminution ; kinetics ; mechanical alloying ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
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    Oxidation of metals 10 (1976), S. 97-103 
    ISSN: 1573-4889
    Keywords: silicon carbide ; oxidation ; molecular oxygen ; glow-discharge oxygen plasma ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics and structure of the oxide scales formed on high-density SiC were studied in molecular oxygen at 740 Torr and in a glow-discharge oxygen plasma at 0.1 Torr at temperatures of 1000, 1100, and 1200°C. The monatomic oxygen formed by the glow discharge markedly increased the reaction rate and the vaporization of some of the oxidation products. The marked differences in kinetics suggest that the rate-controlling step during oxidation in molecular oxygen is the dissociation of adsorbed diatomic oxygen to the monatomic species. Films formed in molecular oxygen were mostly amorphous SiO2 with small inclusions of SiC and graphite, whereas films formed in dissociated oxygen were primarily amorphous SiO2 containing SiO, S2O3, and the coesite form of SiO2.
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    Oxidation of metals 12 (1978), S. 215-225 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-Ni alloys ; kinetics ; scale morphology ; EPMA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of an Fe—19.34 wt. % Ni alloy in dry CO2 has been studied at 700—1000°C using thermogravimetry, metallography, and EPMA. Weight gains for oxygen consumption followed a linear-parabolic-linear sequence at all temperatures. During the initial linear stage the scale consisted mainly of magnetite and the activation energy of 133±25 kJ · mole−1 is considered to be due to dissociation of CO2 into CO and adsorbed oxygen on the outer magnetite surface. During the parabolic oxidation stage a continuous Ni-rich layer containing ∼ 70% Ni forms a barrier to the diffusion which has an activation energy of 192±79 kJ · mole−1. The breakdown of the barrier layer causes a return to linear kinetics with an activation energy of 138±42 kJ · mole−1 for dissociation of CO2 on the outer surface. During the final linear stage there is pronounced general and intergranular subscale formation. Detailed information is presented of the Ni redistribution and concentrations during oxidation and its correlation with the kinetics and morphology.
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    Oxidation of metals 53 (2000), S. 351-360 
    ISSN: 1573-4889
    Keywords: Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
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    Oxidation of metals 9 (1975), S. 99-116 
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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  • 180
    ISSN: 1573-4889
    Keywords: kinetics ; cobalt and nickel oxidation ; parabolic rate constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new fast method is proposed for the determination of parabolic rate constants of metal oxidation as a function of pressure and temperature. The method consists of determining rate constants by oxidation of a single metal sample in a continuous manner, periodically changing the oxidant pressure or temperature. This method eliminates a number of errors inherent in the classical method which involves the use of a new metal specimen in each experiment and it further shortens the time of evaluating the functions k p '' = f (p, T). The method is particularly suitable for the determination of rate constants of slow processes. To verify the proposed method measurements of the kinetics of oxidation of cobalt and nickel at different oxygen pressures over the temperature range 1000–1300° C were carried out.
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  • 181
    ISSN: 1573-4889
    Keywords: kinetics ; oxidation ; microcalorimetry ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In the kinetic theories of Bodenstein or Semenov the expression for the rate of a chemical reaction with several elementary stages can be expressed by different physical parameters. If two experimental methods are used, one method of necessity being microcalorimetry to measure the thermal flux produced by the reaction, it is possible to distinguish a pure kinetics case from a mixed one. The two-method technique has been verified by a study of the oxidation of niobium.
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  • 182
    ISSN: 1573-4889
    Keywords: titanium ; nitridation ; kinetics ; diffusion ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The nitridation behavior of titanium has been examined in an atmosphere of nitrogen over the temperature range 900–1000° C. In addition to determining the reaction kinetics, microhardness and metallographic studies have been carried out on the nitrided substrates and nitride scales. Overall parabolic kinetics were exhibited, while a linear scaling reaction (associated principally with Ti2N formation) was observed. Extensive dissolution of nitrogen in the substrate was evident from the microhardness studies, and at 950 and 1000° C the growth of the nitrogen-stabilized αTi phase layer followed a parabolic law. Consideration of all the observed processes and derived data suggested that diffusion of nitrogen in the metal substrate was probably the rate-controlling mechanism.
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  • 183
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    Oxidation of metals 11 (1977), S. 263-276 
    ISSN: 1573-4889
    Keywords: nickel ; sulfidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The reaction between pure nickel and H2S-H2 mixtures containing 1–65% H2S has been studied over the temperature range 450–600°C. The sulfidation of nickel in the temperature range 560–600°C has been found to follow a linear rate law at low concentrations of H2S and a parabolic rate law at higher concentrations (10% and 65% H2S); X-ray examination of the scale formed on the metal showed it to be almost entirely β-Ni3S2. On the basis of the kinetics and marker studies it can be concluded that the sulfide scale on nickel is formed by the outward transport of the metal and the inward transport of sulfur. In the temperature range 450–500°C the sulfidation of nickel follows a parabolic rate law. In mixtures containing 10% H2S the scale formed contains voids, the occurrence of which is connected with formation of Ni7S6. It has also been shown that the rate of transport through the Ni3S2 layer has an essential influence on the formation of a continuous layer of Ni7S6. Marker studies have shown that both nickel and sulfur appear to be mobile in β′-Ni3S2.
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  • 184
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    Oxidation of metals 12 (1978), S. 67-82 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; kinetics ; oxide grain size ; grain-boundary diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fe-C alloys containing 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C. Two specimen preparations were used: annealed followed by slow cooling to form coarse pearlite plus proeutectoid ferrite or cementite; and cold-worked by abrading after annealing. The cold-worked alloys oxidize more rapidly. Annealed pearlite oxidizes faster than annealed ferrite. The differences in oxidation rate are caused by differences in the Fe3O4 grain size, that is, by the number of oxide grain boundaries available to act as easy diffusion paths for the outward diffusion of Fe through the Fe3O4. The oxidation rate constant is 10 times larger for fine-grained poly crystalline oxide than for oxide in which the Fe3O4 is monocrystalline.
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  • 185
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    Oxidation of metals 13 (1979), S. 437-456 
    ISSN: 1573-4889
    Keywords: Fe-Cr ; oxidation ; kinetics ; oxide morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ferritic polycrystalline Fe-24 wt.% Cr was oxidized in pure oxygen at 190 ≤ T≤490° C and pressures in the range 5.3×10−2–13.3 Pa for periods of up to 5 hr. The reaction proceeded in three stages. An initial period of accelerating rate was accompanied by oxide island nucleation and growth. Following island coalescence the rate was approximately logarithmic at low temperatures and somewhat slower than parabolic at high temperatures. Rate control during this period was thought to be due to mass transport through the oxide grain boundaries left by the island impingement process. During these first two stages the oxide formed was γ-M2O3 with possibly some spinel. The final stage of reaction involved the appearance of α-M2O3 on the outer oxide surface and a substantial slowing of the oxidation rate due to the low diffusivity in this phase.
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  • 186
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    Oxidation of metals 13 (1979), S. 89-104 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state ; mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The authors propose a mechanism for the solid-solid reaction BaCO3+ TiO2→BaTiO3+CO2. This mechanism is based on the real structure of the present semiconductors. The reactions at different interfaces and the diffusing species are identified. The reaction rates are calculated and the dependence of the reaction rate upon O2, N2, and CO2 gas pressure is interpreted and discussed.
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  • 187
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    Oxidation of metals 13 (1979), S. 119-158 
    ISSN: 1573-4889
    Keywords: nickel-chromium alloys ; oxidation ; high temperature ; kinetics ; mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of binary Ni-Cr alloys containing 44 and 50 wt. % Cr has been studied over a range of oxygen partial pressures at temperatures between 800 and 1100°C. The effects of cold work, surface preparation, and distribution of the Cr-rich second phase have been studied. The oxidation behavior is complex and cannot be described by a single model. The oxide grows by short-circuit diffusion as well as bulk transport through Cr 2 O 3 scales. The scale-growth mechanism includes extensive metal-oxide separation requiring Cr vapor transport to the scale, compressive stresses within the oxide which result in scale bulging and cracking, and the formation of a second oxide layer which results in voids being incorporated into the scale. Any factor which reduces the oxide grain size, such as cold work, finer distribution of the Cr-rich α phase or reduced oxygen pressure, results in an increased oxidation rate of binary alloys because of an increased number of grain-boundary short-circuit diffusion paths.
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  • 188
    ISSN: 1573-4943
    Keywords: Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
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  • 189
    ISSN: 1573-4943
    Keywords: Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
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  • 190
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    Journal of mathematical biology 6 (1978), S. 169-175 
    ISSN: 1432-1416
    Keywords: Selection ; Evolution ; Biological macromolecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary Starting with Eigen's model we discuss some principles pertaining to the selection of biological macromolecules. The principles have a certain analogy to Fisher's fundamental theorem for natural selection.
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  • 191
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    Theoretical and applied genetics 50 (1977), S. 89-101 
    ISSN: 1432-2242
    Keywords: Incompatibility ; Evolution ; Flowering Plants ; Fungi ; Complementarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The restriction of sexual pairing by a specificity gene is considered to be an ancient development in the plant kingdom. The diversity and general parallelism of incompatibility systems seen amongst the phyla at the present time can be rationalized in terms of the association of various derived forms of the ancestral specificity unit with differing spectra of accessory factors controlling sexual physiology in the different phyla. Sexual morphogenesis has become divided into distinct phases under the control of complementary genes. These phases are initiated by a regulatory system of “Co-ordinator genes” which control the order in which groups of morphogenetic genes are expressed during development. The entire sexual cycle will be completed only if all the complementary groups are activated in the appropriate sequence. The present article discusses essential features of the evolution of the breeding locus in different phyla. These features are consistent in themselves with the present data and are not dependent on the proposed ancient origin of the specificity gene. The above hypothesis throws light on the (1) evolution of the complex mating loci in flowering plants and fungi; (2) evolution of complementary incompatibility and heteromorphic incompatibility in flowering plants; (3) anomalous cross-compatibility behaviour of mutants in the fungus Schizophyllum commune; (4) nature of homothallism in higher fungi; (5) mode of origin of new functional self-incompatibility alleles; and (6) “homogenic” and “heterogenic” incompatibility.
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    Theoretical and applied genetics 52 (1978), S. 217-220 
    ISSN: 1432-2242
    Keywords: Page ; Proteins ; Cultivated potatoes ; Evolution ; Taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A recently developed polyacrylamide gel electrophoresis technique for tuber proteins is used to help elucidate the evolution and taxonomy of some cultivated potatoes. The results substantiate the theory that Group Tuberosum evolved from Group Andigena, that Group Andigena evolved from a cultivated diploid × wild diploid hybrid, and that Group Phureja evolved from Group Stenotomum. Furthermore, the results suggest these groups are closely enough related to merit classification within a single species.
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  • 193
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    Behavioral ecology and sociobiology 49 (2000), S. 48-56 
    ISSN: 1432-0762
    Keywords: Keywords Antipredator behavior ; Phylogenetic inertia ; Conflicting selection pressures ; Evolution ; Salamanders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The streamside salamander, Ambystoma barbouri, exhibits ineffective antipredator behavior (high emergence rate from refuge, and high activity while out of refuge) and thus suffers heavy predation in stream pools with sunfish. A. barbouri evolved relatively recently from an ancestor that closely resembled a sister species, A. texanum, which breeds in fishless, ephemeral ponds. Sunfish thus represent a relatively new selection pressure for A. barbouri. Phylogenetic inertia predicts that (1) A. texanum should be very poor at coping with fish and (2) because it has only recently been exposed to fish, A. barbouri should still be poor at avoiding fish, but due to its recent exposure to fish, A. barbouri should be better than A. texanum at coping with sunfish. Experimental results provided mixed support for these predictions. As predicted, A. texanum suffered heavy sunfish predation. Compared to A. texanum, A. barbouri showed a greater tendency to initiate alarm moves that enhanced escape success from fish. However, in both the presence and absence of fish, A. barbouri showed higher emergence rates from refuge and higher movement while out of refuge than A. texanum. These behaviors tend to increase exposure to sunfish, i.e., for these key behaviors, A. barbouri apparently evolved in the wrong direction as far as fish predation is concerned. Due to these offsetting effects (increased exposure to fish, increased escape success), A. barbouri is no better at surviving with sunfish than A. texanum. A possible explanation for the high activity of A. barbouri is its use of highly ephemeral habitats (relative to A. texanum) that favor the evolution of higher activity, feeding, and developmental rates for A. barbouri relative to A. texanum.
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    Cell & tissue research 175 (1977), S. 499-522 
    ISSN: 1432-0878
    Keywords: Muscle ; Audition ; Ultrastructure ; Amphibian ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study characterizes the fine structure of the “opercularis” muscles of selected frogs and salamanders (Genera: Hyla; Desmognathus; Ambystoma). The “opercularis” muscle originates on the shoulder girdle and inserts on the opercular plate in the fenestra ovalis of the otic capsule. Each of the three genera used exhibits one of the major gross dispositions of this muscle found in amphibians. In each case the “opercularis” muscle contains large numbers of tonic fibers: 80% in Hyla; 90% in Desmognathus; 45% in Ambystoma. These fibers correspond to the class-5 tonic fibers of Smith and Ovalle (1973). The remainder of the fibers in the “opercularis” correspond to those in the class-3 “phasic” of Smith and Ovalle. The muscle from which the “opercularis” is derived (levator scapulae in Hyla, cucullaris in Desmognathus) is comprised of fibers which correspond to the class-2 phasic fibers of Smith and Ovalle. The fiber composition of the “opercularis” indicates that it is constructed to sustain contraction over long periods of time. This composition is supportive of the functional role in audition proposed for the muscle by Lombard and Straughan (1974). Evidence is presented that indicates that fiber size may be body size dependent and thus is an inappropriate criterion of fiber type identification.
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  • 195
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    Russian chemical bulletin 49 (2000), S. 1974-1976 
    ISSN: 1573-9171
    Keywords: ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
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  • 196
    ISSN: 1573-9171
    Keywords: 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
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  • 197
    ISSN: 1608-3245
    Keywords: DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
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  • 198
    ISSN: 1617-4623
    Keywords: Key wordsDrosophila melanogaster ; Ceratitis capitata ; Tephritids ; Evolution ; Dacus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alcohol dehydrogenase genes make up one of the best studied gene families in Drosophila, both in terms of expression and evolution. Moreover, alcohol dehydrogenase genes constitute potential versatile markers in insect transformation experiments. However, due to their rapid evolution, these genes cannot be cloned from other insect genera by DNA hybridization or PCR-based strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast genes have evolved independently, acquiring their enzymatic function convergently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementation in yeast can be used to clone alcohol dehydrogenase genes that are unrelated in sequence to those of yeast, thus providing a powerful tool for isolation of dominant insect transformation marker genes.
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  • 199
    ISSN: 1617-4623
    Keywords: Key wordsDictyostelium discoideum ; Mitochondrial DNA ; Genome sequencing ; Genetic map ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identified genes include those for two ribosomal RNAs (rnl and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and five other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used. (2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sufficient to support the synthesis of mitochondrial protein. (4) In total, five group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.
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    Artificial life and robotics 4 (2000), S. 109-118 
    ISSN: 1614-7456
    Keywords: Parallel and distributed processing ; Space navigation ; Evolution ; WAVE model ; Cooperative behavior ; Mobile robots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper modifies the WAVE model for parallel processing in virtual networks to explore and process continuous physical worlds. Expressing distributed activity by cooperative jobs spreading in space and “seeing” each other, rather than as vehicles exchanging messages, the model allows complex missions to be planned in a very flexible manner, with mobile hardware being assigned to the evolving space-conquering programs (waves) dynamically, when required or available. A number of cooperative scenarios in a physical world demonstrate the simplicity and compactness of the wave code. The execution of waves by mobile hardware is discussed, including run-time mapping of waves to vehicles, and supporting multiple distributed jobs in cases of hardware shortages. WAVE can be used efficiently for solving complex problems in space by organized groups of cheap specialized mobile robots, where intelligent behavior is provided by very high level of system organization rather than by the smartness of individual units. In a broader sense, it may also serve as a basic technology for parallel and distributed simulation, and the management of evolution and self-organization of large open systems of different natures.
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