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  • Gas chromatography  (108)
  • kinetics
  • phosphorus
  • Springer  (235)
  • American Institute of Physics
  • American Meteorological Society
  • Annual Reviews
  • Frontiers Media SA
  • Periodicals Archive Online (PAO)
  • 1980-1984  (235)
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  • Springer  (235)
  • American Institute of Physics
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 261 (1983), S. 188-189 
    ISSN: 1435-1536
    Schlagwort(e): Polymerization ; kinetics ; redox polymerization ; acrylamide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 262 (1984), S. 366-373 
    ISSN: 1435-1536
    Schlagwort(e): kinetics ; isothermal crystallization ; polymer ; spherulite ; differential scanning calorimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In the DSC technique, isothermal crystallization experiments are usually performed on thin flat specimens, but their interpretation generally uses theories developed for an unbounded volume. In this paper, isothermal crystallization of spherical entities in the volume limited by two parallel infinite planes is considered. Our model, derived from Avrami's theory, gives an analytical expression for the transformed volume fraction as a function of time. It is shown that the influence of thickness becomes important when thickness becomes of the order of or smaller than the average spherulite radius. The main effects of a decreasing thickness are a slower crystallization kinetics and a decrease in the Avrami exponent. These results can be used to interpret experimental data obtained in isothermal polymer crystallization.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 261 (1983), S. 621-625 
    ISSN: 1435-1536
    Schlagwort(e): Polyamide 6 ; crystallisation ; kinetics ; titania
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The kinetics of isothermal and nonisothermal crystallization of polyamide-6 (PA6) containing titania was studied by means of DSC. It was found thatTiO 2 causes an acceleration in the crystallization of polyamide-6 and lowers the value of the Avrami exponent,n. The presence of TiO2 does not affect equilibrium melting pointT m 0 , glass temperatureT g, or surface free energiesσ e andσ of the basal and lateral surfaces.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Fire technology 20 (1984), S. 47-63 
    ISSN: 1572-8099
    Schlagwort(e): Extinguishment ; fire modeling ; mass loss ; heat release ; char ; reflash ; sprinklers ; radiant flux ; kinetics ; reaction rate ; heat loss ; ash ; latent heat ; spray density ; extinguishing agents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung
    Notizen: Abstract The Ad Hoc Mathematical Fire Modeling Working Group was organized about seven years ago to facilitate voluntary cooperation and coordination in developing mathematical fire modeling capability. The group has a steering committee of representatives of agencies that support fire modeling and related research. These include the National Bureau of Standards' Center for Fire Research, Factory Mutual Research Corp., the Naval Research Laboratory, NASA, and the Federal Aviation Agency. The Group holds plenary meetings when it seems desirable to do so (about once each 1 1/2 years), and workshops on topical subjects. Three workshops were held in 1983. Normally, Group meetings are held before or after other meetings at which a number of interested personnel would likely be present. Minutes are mailed to those who attended and to others (including European and Japanese personnel) who have indicated interest. This workshop was arranged by Ron Alpert of Factory Mutual Research Corp. and held at their facilities at Norwood, MA, in November 1983.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 11 (1982), S. 339-346 
    ISSN: 1572-8927
    Schlagwort(e): Carbon dioxide ; hydrolysis ; aqueous solution ; kinetics ; activation volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pressure dependence of the dehydration reaction of H2CO3 was measured in acidic aqueous solution for pressures up to 1 kbar using a high-pressure stopped-flow instrument. The corresponding volume of activation was found to be 6.4±0.4 cm3-mol−1 at 25°C and 0.5 ionic strength. Volume equation calculations result in a value of −9.9±1.9cm3-mol−1 for the volume of activation for the hydrolysis of CO2 under the same conditions. For the first time, the reaction mechanism can be interpreted in terms of dissociative and associative modes, respectively. These data are used to construct an overall reaction volume profile.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1572-8927
    Schlagwort(e): Temperature jump ; kinetics ; thermodynamics ; TRIS ; iminodiacetic acid ; magnesium ion ; phenol red
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Equations describing the temperature jump amplitudes associated with a system of two coupled reactions (TRIS-phenol red) as well as the ternary system (Mg2+-iminodiacetic acid-phenol red) are presented. The termodynamic parameters calculated from experimentally measured temperature perturbation amplitudes using a multiparametric curve fitting procedure are found to be in good agreement with those determined from pH- and costant rate thermometric titrations. For phenol red, pK I =7.55, ΔH I =3.45 kcal, and for Mg2+ iminodiacetic acid, log K M =2.84, ΔH M =3.25 kcal, were obtained. It is shown that this method can be used to determine accurate thermodynamic enthalpy changes over a narrow temperature interval of less than 1.0°C from a single experiment requiring about 50 μl of sample solution.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 12 (1983), S. 771-781 
    ISSN: 1572-8927
    Schlagwort(e): Ultrasonics ; kinetics ; aqueous solution ; iso-butyl cellosolve
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Ultrasonic absorption and velocity measurements in aqueous solution of iso-butyl cellosolve (ethylene glycol iso-butyl ether) as a function of the concentration are reported. The two relaxational absorptions have been attributed to the perturbation of the equilibria expressed by AB⇌A+B and Aα(1/n)An where A is the solute, B is the solvent, AB is the complex and A n is the solute aggregate. The rate constants for each step have been determined. From the concentration dependence of the maximum excess absorption per wave length, the enthalpy change and the volume change for the reaction between the solute and the solvent have been determined for aqueous solutions of butyl cellosolve (ethylene glycol n-butyl ether), iso-butyl cellosolve and propyl cellosolve (ethylene glycol n-propyl ether). The results are consistent with a hydrogen bonding reaction. The effect of the ethers on water structure are considered and it is clear that the fraction of water molecules which can hydrogen bond to the solute decreases with the increasing hydrophobicity of the solute.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1572-8927
    Schlagwort(e): Enthalpies of reaction ; heats of reaction ; kinetics ; ester hydrolysis ; microcalorimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The conditions under which the Picker flow microcalorimeter can be used to measure enthalpies and rates of reactions were investigated. For this purpose, systematic studies were made of the enthalpies of neutralization of HCl, HBr, HNO 3 , acetic, proprionic, and butyric acids with NaOH, enthalpies of hydrolysis of methyl and ethyl acetate with NaOH, and the reaction rates of the ester hydrolysis with NaOH. The general procedure and various sources of error are discussed and it is concluded that enthalpies of slow reactions can be measured to about 1% when the calorimeter is operated in the quasi-isothermal mode and the reaction rates to about 3% when operated in the quasi-adiabatic mode.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 34 (1983), S. 20-26 
    ISSN: 1570-7458
    Schlagwort(e): Dioryctria abietella ; Cone pyralid ; Lepidoptera ; Pyralidae ; Sex pheromone, (Z,E)-9,11-tetradecadienyl acetate ; Single sensillum recordings ; Electroantennography ; Gas chromatography ; Mass spectrometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Résumé L'analyse en chromatographie gazeuse associée à une détection électroantennographique a montré que l'acétate (Z,E)-9,11-tétradécadiényle (Z,E)-9,11–14:Ac est l'un des composants de la phéromone de Dioryctria abietella Schiff (Lepid.: Pyralidae). Couplage chromatographie en phase gazeuse spectrometrie de masse a montré la présence d'acétate tétradécadiényle avec un spectre de masse et un indice de rétention identiques au Z,E-9,11–14:Ac Un récepteur cellulaire sensible à la fois au Z,E-9,11–14:Ac et à un extrait de la femelle a été identifié sous l'antenne du mâle. Les analyses des antennogrammes et de la cellule isolée ont étayé la caractérisation du composant de la phéromone comme étant Z,E-9,11–14:Ac. Un récepteur cellulaire additionnel sensible à l'acétate (Z.)-9-tétradécadiényle et à l'acétate (Z.E.)-9,12-tétradécadiényle a été trouvé sur l'antenne du mâle, mais il n'était pas activé par l'extrait de la femelle. Sur le terrain Z,E-9,11–14:Ac, présenté seul, attirait des nombres importants de mâles de D. abietella. L'addition de l'acétate (Z)-9-tétradécényle a inhibé l'attraction des mâles par les pièges.
    Notizen: Summary Gas chromatographic analyses coupled with electro-antennographic detection indicated that (Z,E)-9,11-tetradecadienyl acetate (Z,E-9, 11–14:Ac) is a pheromone component of the cone pyralid Dioryctria abietella. Gas chromatographic-mass spectrometric analyses confirmed the presence of a tetradecadienyl acetate with mass spectrum and retention index identical to Z,E-9,11–14:Ac. A receptor cell sensitive to both Z,E-9,11–14:Ac and the female extract was identified on the male antenna. An additional receptor cell sensitive to (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate was found on the male antenna but was not activated by the female extract. In the field Z,E-9,11–14:Ac presented alone attracted significant numbers of male D. abietella. Addition of (Z)-9-tetradecenyl acetate inhibited the attraction of males to traps.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 1 (1980), S. 95-101 
    ISSN: 1573-0867
    Schlagwort(e): soil fertility ; phosphorus ; potassium ; green manure ; crop rotation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Changes in the soil phosphorus and potassium status on three farming systems in the Northeast Polder during 25 years are related to the fertilizer regime over this period. The changes in the nutrient status of the soil are reflected in fertilizer policy. High rates of phosphate dressings markedly increased the phosphate status of the soil and built up a reserve of phosphate. In contrast, the potassium status decreased by about half, because only potatoes in the rotation were dressed with potassium. Methods of fertilization are discussed and suggestions are made with regard to possible improvements.
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 3 (1982), S. 13-16 
    ISSN: 1573-0867
    Schlagwort(e): cocoa ; nitrogen ; phosphorus ; soil analysis ; Nigeria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract No extensive investigation on the effect of fertilizers on Amazon cocoa variety (Theobroma cacao L.) has been performed in Nigeria. Therefore eight fertilizer treatments involving nitrogen and phosphorus, replicated six times at four locations across southern Nigeria, were established in 1973. The four N levels (N0, N1, N2, N3) involved were 0, 80, 160 and 240 kg ha−1 y−1, and the two P levels (P0, P1) were 0 and 67 kg ha−1 y−1. Results of the first 5 years of fertilizer application are reported. Response to P was observed at all locations, and the response was statistically significant at 2 of the locations. There was no response to the application of nitrogen. The data suggest, however, that there is only a response to phosphorus when nitrogen is applied.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 5 (1984), S. 371-382 
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; phosphorus ; dry areas ; apparent recovery fraction ; fertilizer management
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Agronomic efficiency (AE) is defined as the increase in economic yield of a crop per unit fertilizer applied. Components of AE are physiological efficiency and apparent recovery fraction. The latter can be further separated into uptake efficiency and availability index. Ways to increase the nitrogen fertilizer use efficiency in rainfed agriculture through fertilizer management are discussed.
    Materialart: Digitale Medien
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 21 (1981), S. 215-220 
    ISSN: 1432-1041
    Schlagwort(e): phenytoin ; cimetidine ; antipyrine test ; drug interaction ; drug metabolism ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a prospective study in nine patients the effects of phenytoin and of cimetidine (1000mg/day) + phenytoin on the antipyrine test and serum phenytoin concentrations were studied. Serum phenytoin increased from the steady state level of 5.7±1.3 mg/l to 9.1±1.4mg/l after three weeks on cimetidine (p〈0.01), and fell to 5.8±1.2 mg/l within two weeks after withdrawal of cimetidine. The protein binding of phenytoin was not changed by cimetidine. After use of phenytoin for 2–4 months, antipyrine clearance increased from 0.67±0.06ml/min/kg to 1.61±0.22 ml/ min/kg, and antipyrine half-live fell from 10.9±1.3h to 4.5±0.6h as compared to the values before phenytoin treatment (p〈0.01). After three weeks combined use of cimetidine and phenytoin, antipyrine clearance was decreased to 1.01±0.07 ml/min/kg and antipyrine half-life was prolonged to 6.1±0.5h, (p〈0.01) compared to the values on phenytoin alone. The distribution volume of antipyrine was not affected by phenytoin nor by cimetidine + phenytoin. The half-life of cimetidine was 2.8±0.3h in the patients on longterm phenytoin treatment. There was a significant positive correlation (p〈0.001) between the increase in serum phenytoin concentration and the prolongation of antipyrine half-life caused by cimetidine. Thus, cimetidine increases serum phenytoin concentration, very probably by inhibiting its metabolism. Care should be taken in the concomitant use of cimetidine and phenytoin, and the dose of phenytoin should be modified according to the clinical symptoms and serum phenytoin concentrations.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 225-228 
    ISSN: 1432-1041
    Schlagwort(e): pinazepam ; N-desmethyldiazepam ; kinetics ; metabolism ; human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma profile of a single oral dose of pinazepam 10 mg was studied in 6 healthy male volunteers, aged 26 to 31 years. The concentrations of the parent compound and of its metabolite in plasma were measured by gas-chromatography. The peak plasma levels of pinazepam was 36.8±5.1 ng/ml and of N-desmethyldiazepam 150±13.3 ng/ml. The plasma concentration of the metabolite become higher than that of the parent compound shortly after administration, suggesting that pinazepam acts as a prodrug.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 545-551 
    ISSN: 1432-1041
    Schlagwort(e): oxcarbazepine ; kinetics ; disposition ; metabolites ; renal excretion ; volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Oxcarbazepine (oxcarb) 600 and 900 mg (2360 and 3540 µmol) was taken by 3 volunteers (2 ♀, 1 ♂; 45–67 kg; age 22–34 years) after an overnight fast. Blood, saliva and urine were collected for the next 72 h for assay of oxcarb, 10,11-dihydro-10-hydroxy-carbamazepine (OHcarb), and 10,11-dihydrotrans-10,11-dihydroxy-carbamazepine (diol). Oxcarb reached a maximum level of about 1 µg/ml (3.93 µmol/l) within 1 h and dropped below the detection limit (0.1 µg/ml=0.39 µmol/l) within 3 h. The active metabolite OHcarb appeared in the blood before oxcarb and reached the higher maximum level of 7.4 µg/ml (29 µmol/l) after 7 h. Thereafter serum levels decreased with a t1/2 of about 25 h, and after 40 h with a t1/2 of 9 h, the latter agreeing with the renal excretory t1/2 calculated from the urine data (10 h). The ratio of OHcarb concentration in saliva to that in plasma varied considerably (0.3–1.7; median 1; r〉0.9), whereas that of blood to plasma was 1.25 with only small variation (r〉0.98); OHcarb concentrations in erythrocytes were 50% higher than in plasma. Diol was detected in blood (maximum level 0.5 µg/ml=1.84 µmol/l) in 2 volunteers. 45% of the dose could be recovered in urine (Oxcarb 5%, OH-carb 36%, Diol 4%). Whereas Oxcarb was completely conjugated, only 25% of OHcarb was conjugated and diol was unconjugated.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 217-220 
    ISSN: 1432-1041
    Schlagwort(e): metoprolol ; pregnancy ; hypertension ; kinetics ; pre-eclampsia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition of oral metoprolol was studied in 5 women during the last trimester of pregnancy and 3 to 5 months after delivery. After a single oral dose of 100 mg the individual peak plasma concentration in the pregnant state was only 20–40% of that after pregnancy. The plasma half-lives of metoprolol were about the same during (average 1.3 h) and after pregnancy (average 1.7 h). By contrast, the area under the plasma concentration versus time curve was much smallerduring (mean 262 nmol/l×h) thanafter (mean 1298 nmol/l×h) pregnancy, resulting in an average apparent oral clearance (Clo) of metoprolol that was 4.4times higher during (362 ml×kg−1 body-weight×min−1) than after pregnancy. The increased Clo in pregnancy is assumed to be due to enhanced hepatic metabolism of the drug. The possible clinical consequence of the difference in the disposition of metoprolol is discussed.
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  • 17
    ISSN: 1432-1041
    Schlagwort(e): prizidilol ; antihypertensive effect ; acute and long-term blood pressure control ; plasma renin activity ; acetylator phenotype ; antinuclear antibodies ; side effects ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary After an initial placebo period of four weeks 24 patients with primary hypertension were treated with prizidilol, a hydrazinopyridazine derivative with combined vasodilator and non-selective beta-adrenoceptor blocking actions, for a dose titration period of 14 weeks. Prizidilol 200 to 800 mg was given once daily to achieve a target supine diastolic blood pressure (BP)〈90 mmHg. Supine and standing BP recorded 24–27 h after drug intake decreased from 172±17/106±6 mmHg (mean±SD) and 167±18/111±8 mmHg, respectively, after placebo to 159±16/99±8 and 154±18/101±9 mmHg after active treatment for six weeks (mean dose 447 mg), and to 154±16/97±7 and 148±14/97±7 mmHg after treatment for 14 weeks (mean dose 687 mg/day). A slight reduction in HR was seen after treatment for six weeks and in plasma renin activity and urinary methoxycatecholamine excretion after treatment for 14 weeks. A sustained decrease in BP was observed for 10 h after prizidilol 800 mg (n=9), with a maximum antihypertensive effect (mean reduction in supine BP 33/18 mmHg) 2.5 h after dosing, which coincided with the mean peak plasma concentration. The plasma elimination half-life of the drug was 3.9 h (range 2.0–8.9 h). Changing to a twice daily regimen in 17 patients (mean daily dose 748 mg at six months) did not produce any further reduction in the BP (recorded 12–15 h after dosing) as compared to the once daily regimen at 14 weeks. During treatment for up to 24 months, 16 patients did not achieve satisfactory BP control. Eight of them were withdrawn and eight received additional treatment with bendroflumethiazide (2.5–5 mg/day). In 7 of the latter satisfactory BP control was achieved. Side effects were few. Dizziness and tiredness occurred in four patients 2–5 h after prizidilol 600–800 mg once daily. These symptoms partly subsided when the subjects changed to a twice daily regimen. No ocular side-effects were found. Before treatment 13 out of 24 patients had a low titre of IgM antinuclear antibodies (ANA) and one patient also a low titre of IgG ANA. During treatment the frequency of patients with positive ANA-titres became higher, and after treatment for 12 months (n=17) 15 patients had positive IgM and seven patients positive IgG ANA-titres. However, the titres were low and no patient showed a clinical lupus erythematosus syndrome. There was no relation between acetylator phenotype of the patient and acute or longterm effecton BP, pharmacokinetics of the drug or the development of a raised ANA-titre.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 273-276 
    ISSN: 1432-1041
    Schlagwort(e): undernourished ; chlorquine ; kinetics ; plasma levels ; red cell uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma and whole blood kinetics of chloroquine was studied in 7 normal and 8 undernourished subjects following a single oral dose of 600 mg. The terminal half-lives were similar in both groups. The AUC was also similar in the 2 groups, even though a higher dose per kg body weight was administered to the undernourished. This was probably because of faster clearance in this group. Chloroquine uptake by erythrocytes, its main site of action in malaria, was also comparable in the two groups. The plasma concentration of chloroquine over a period of time was found to be similar in 4 normal and 4 undernourished subjects following administration of 1.5 g of the drug in divided doses. The undernourished appear, therefore, to handle chloroquine in such a way that they do not suffer a greater risk of toxicity than normals.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 525-527 
    ISSN: 1432-1041
    Schlagwort(e): theophylline ; airway obstruction ; biotransformation ; kinetics ; oral dosage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Oral theophylline was given to 6 adults with airways obstruction. The initial dose was 125 mg daily and this was increased by 125 mg each week. The final total daily dose reached was determined by side effects and ranged from 500 mg to 1125 mg. At the end of each week and before the next dosage increment steady state, trough plasma theophylline concentrations were measured. For each individual and for the group as a whole there was a highly significant linear correlation between theophylline dose and trough plasma concentration. This indicates that for oral theophylline, in adults, dose-dependent kinetics do not play a significant role and dose may be adjusted without fear of a disproportionate rise in plasma concentration.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 27 (1984), S. 491-494 
    ISSN: 1432-1041
    Schlagwort(e): amiodarone ; kinetics ; volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We studied three healthy volunteers after a single i.v. bolus of amiodarone, during 1 month of chronic oral dosing and after the discontinuation of the drug. Blood concentrations of amiodarone declined rapidly in a bi-exponential fashion after i.v. bolus. The terminal half-life ranged from 10 to 17 h; after discontinuation of chronic treatment the terminal half-lives were 8–21 days. The i.v. data, the trough levels during multiple dosing and the washout phase could be simultaneously fitted using a tri-exponential equation. The subjects were carefully monitored for cardiac and thyroid function. One subject had to stop taking amiodarone because of profound bradycardia. A reduction of serum TT3 and FT3 concentrations and an increase of serum rT3 and FT4 was found.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 17 (1980), S. 285-293 
    ISSN: 1432-1041
    Schlagwort(e): tolbutamide ; chlorpropamide ; kinetics ; food ; age ; blood glucose ; plasma insulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of food intake (standardized breakfast) on the oral single-dose kinetics and effects of tolbutamide (0.5 g) and chlorpropamide (250 mg) was investigated in young, healthy volunteers. The single-dose kinetics of the two drugs was also studied in elderly healthy subjects. There was great interindividual variation in the elimination rate of both drugs, but food intake influenced neither their AUCs nor their rates of absorption and elimination. The peak concentration of chlorpropamide, but not that of tolbutamide, was reduced by food intake. The peak concentrations of serum tolbutamide were approximately doubled by an increase in dose from 0.5 to 1.0 g, and from 1.0 to 2.0 g. At no time did tolbutamide 0.5 g affect the plasma insulin level, neither in the fasting nor in the non-fasting state. However, this dose did reduce the blood glucose level during fasting and the increase in blood glucose in response to the meal. The latter effect was recorded within 30 min, when the serum level of tolbutamide still was close to zero. Plasma insulin concentrations did increase within 30 min after a higher dose of tolbutamide (1.0 g), when the serum concentration of tolbutamide was about 50 µmol/l. Between 2.5 and 8 h after administration of chlorpropamide 250 mg, serum drug concentrations were lower than those following tolbutamide 0.5 g. The blood glucose response was smaller and occurred later, being significant at 2 h, when the serum concentration of the drug was about 70 µmol/l. There was no significant change in plasma insulin. There was no significant pharmacokinetic difference between young and elderly subjects, except that the peak concentration of tolbutamide was higher in the latter. It appears that both for tolbutamide and chlorpropamide there is great interindividual variation in drug disposition, but food intake does not influence the bioavailability of either drug. The effect of any particular drug concentration seems dependent upon the blood glucose level and hence upon the elapsed time since the last meal. Both drugs can reduce blood glucose without an alteration in the peripheral blood concentration of insulin. This may reflect an extrapancreatic effect of the drugs, but it could also be an expression of increased insulin secretion, which is not detected because of enhanced hepatic degradation of the hormone released into the portal circulation. The observations made in young individuals are also probably relevant for elderly subjects.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 21 (1982), S. 403-408 
    ISSN: 1432-1041
    Schlagwort(e): glibenclamide ; diabetes ; insulin ; kinetics ; blood glucose ; relationship to meals ; absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In an attempt to assess whether intake of glibenclamide before meals would improve its therapeutic capacity, the present investigation compared the effect of glibenclamide 2.5mg t.i.d. given before and together with meals. In addition, these effects were compared with that of glibenclamide given as a single morning dose of 7.5mg. The subjects studied were six Type 2 diabetics not previously exposed to sulphonylurea drugs. Irrespective of dosage and mode of administration, addition of glibenclamide to a standardized breakfast, lunch and dinner enhanced plasma IRI concentrations and reduced blood glucose concentrations as compared to administration of meals without the drug. The different modes of glibenclamide administration did not differ significantly with respect to IRI responses. However, the blood glucose reduction after breakfast was significantly greater when glibenclaimde 2.5mg had been given before the meal than when 2.5 or 7.5mg were given with the meal; a similar, but non-significant tendency was observed after lunch; no consistent difference was seen after dinner. Food intake did not affect glibenclamide kinetics. It appears that administration of glibenclamide 2.5mg before breakfast improved glucose utilization following the breakfast load, due to earlier attainment of an effective concentration of glibenclamide.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 309-314 
    ISSN: 1432-1041
    Schlagwort(e): acetylsalicylic acid ; salicylic acid ; dipyridamol ; bioavailability ; kinetics ; rapid- and slow-release formulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Acetylsalicylic acid (ASA) is a strong, irreversible inhibitor of platelet aggregation, but loses this activity following first-pass deacetylation to salicylic acid (SA). In order to compare the bioavailability of unchanged ASA from rapid- and slow-release formulations, the single-dose concentration profiles of ASA and SA were studied in healthy volunteers following intake of two different rapid-release (conventional and effervescent tablets) and three different slow-release (microencapsulated ASA in tablets and in capsules, and enteric-coated tablets) formulations of ASA, and of one slow-release formulation of sodium salicylate. Since anti-platelet therapy with ASA is often combined with dipyridamol, the influence of this drug was also examined. The concentrations of ASA and SA were measured by high-pressure liquid chromatography. While the bioavailability of SA from the 5 ASA formulations was essentially equal and similar to that of the salicylate formulation, the bioavailability and peak concentrations of ASA appeared to be the much greater after rapid-release than after slow-release formulations. Indeed, ASA was only rarely detected in systemic blood following intake of slow-release ASA. Co-administered dipyridamol did not significantly influence the kinetics of ASA or SA. It appears that rapid-release formulations of ASA should be prefered in anti-platelet therapy, either alone or in combination with dipyridamol.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 41-47 
    ISSN: 1432-1041
    Schlagwort(e): quinidine ; digoxin ; interaction ; kinetics ; absorption ; elimination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary To evaluate the possible effect of quinidine on digoxin bioavailability, the steady state digoxin kinetics was examined with and without concomitant quinidine therapy, in 7 cardiac patients after simultaneous administration of oral digoxin and intravenous [3H]-digoxin. In the presence of quinidine, the absorption rate constant of digoxin (ka) increased from 2.72±1.04 to 3.53±1.34 h−1 (p〈0.05), whereas lag time and peak time decreased from 0.16±0.10 to 0.05±0.04 h (p〈0.05) and from 0.92±0.27 to 0.69±0.19 h (p〈0.02), respectively. Predose plasma digoxin increased from 0.41±0.25 to 0.70±0.31 ng/ml (p〈0.02), while peak plasma digoxin increased from 0.93±0.34 to 1.63±0.46 ng/ml (p〈0.02). The systemic availability of digoxin increased from 68.48±13.35 to 79.09±14.89% (p〈0.05) in the presence of quinidine. Quinidine had no effect on the biotransformation pattern of digoxin, as assessed by thin layer chromatography. Quinidine increases the rate and extent of digoxin absorption, and this interaction contributes significantly to the elevation in plasma digoxin during both its distribution and elimination phases.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 517-519 
    ISSN: 1432-1041
    Schlagwort(e): lorcainide ; oral antiarrhythmic therapy ; nor-lorcainide ; first-pass metabolism ; kinetics ; alternative dosage ; regimens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The feasibility of giving a supplementary starting dose of the antiarrhythmic drug lorcainide, in order to minimalize the impact of the extensive, but saturable first-pass metabolism, was evaluated. Twenty-five adult patients were given 100 mg lorcainide tablets according to one of 3 different dosage schedules: Eight patients took one tablet at 0, 12 and 24h, 8 took 1 tablet at 0, 1, 12 and 24h and 9 took 1 tablet at 0, 2, 12 and 24h. Levels of lorcainide and its metabolite, nor-lorcainide, during treatment were determined by gas-liquid chromatography. The results show that giving a second tablet 1 or 2h after the first may produce faster saturation of the pre-systemic metabolism of lorcainide in the liver.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 801-806 
    ISSN: 1432-1041
    Schlagwort(e): acebutolol ; hydrochlorothiazide ; kinetics ; drug combination ; interaction ; diacetolol ; healthy subjects ; renal clearance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of acebutolol and hydrochlorothiazide (HCT) alone or in combination were studied in 12 healthy subjects in a cross over study. Acebutolol and diacetolol (the main metabolite) in plasma and urine were determined by HPLC and hydrochlorothiazide by GLC. The main pharmacokinetic parameters of acebutolol did not differ significantly: AUC 4492±272 µg l−1 h given alone versus 4118±354 µg l−1 h with HCT, half-life (7,69±0,32 h vs 8,10±0,72 h) and renal clearance (13,1±0,5 lh−1 vs 13,8±0,9 lh−1), respectively. There was no difference in diacetolol pharmacokinetics. HCT values were not significantly different: AUC 784±48 µg l−1 h given alone and 720±42 µg l−1 h with acebutolol, t1/2 (4,79±0,37 h vs 4,73±0,43 h). The renal clearance was slightly higher when HCT was given with acebutolol (26,2±2,6 vs 20,3±2,11 h−1,p〈0,05). This increase, observed during the first four hours, was probably due to competition between the drugs for binding to red blood cells.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 23 (1982), S. 261-266 
    ISSN: 1432-1041
    Schlagwort(e): mexiletine ; rifampicin ; kinetics ; enzyme induction ; excretion ; antipyrine clearance ; dosage adjustment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary To study the effects of enzyme induction on its pharmacokinetics, a single oral dose of the new antiarrhythmic agent mexiletine hydrochloride 400 mg was administered to 8 healthy volunteers before and after treatment with rifampicin 300 mg b.i.d. for ten days. The absorption and distribution of mexiletine were not changed after rifampicin, but its elimination half-life fell from 8.5±0.8 h (mean±SE) to 5.0±0.4 h (p〈0.01), and its nonrenal clearance increased from 435±68 ml/min to 711±101 ml/min (p〈0.01). The mean renal clearance of mexiletine did not change, but it showed an exponential correlation with urinary pH. The amount of unchanged mexiletine excreted in urine over two days decreased from 32±7 to 18±3 mg (p〈0.01). The half-life of antipyrine fell from 11.8±0.4 to 5.5±0.3 h and its clearance increased from 40±3 ml to 74±3 ml/min (p〈0.01). There was a significant (p〈0.05) positive linear correlation between both the half-lives and the clearances of antipyrine and mexiletine. The clearances were positively correlated with serum γ-glutamyl transpeptidase. The results suggest that the dosage of mexiletine should be adjusted when enzyme inducing drugs are started or stopped during therapy with it.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 23 (1982), S. 87-92 
    ISSN: 1432-1041
    Schlagwort(e): phenobarbital ; epilepsy ; kinetics ; bioavailability ; epileptic patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of phenobarbital (PB) were evaluated in six normal subjects and six epileptic patients treated with phenytoin or carbamazepine. Each normal subject received three single doses of PB: PB-sodium 130 mg i.v. (IV), PB sodium 130 mg i.m. (IM), and PB acid 100 mg orally (PO), in random order at least one month apart. After IV PB distributive half-lives varied from 0.13 to 0.70 h, disposition half-lives were 75 to 126 h, steady state volume of distribution (Vss) was 0.54±0.03 l/kg, and clearance (CL) was 3.8±0.77 ml/h/kg. Absolute bioavailability of IM PB was 101±13%, of PO PB (corrected for dose) 100±11%. Peak serum PB concentrations were achieved from 2 to 8 h after IM administration, and from 0.5 to 4 h after PO administration. Epileptic patients exhibited similar PB kinetics: disposition half-lives were 77 to 128 h, Vss 0.61±0.05 l/kg, and Cl 3.9±0.76 ml/h/kg. Phenobarbital appears to represent an exception among antiepileptic drugs, in that pharmacokinetic data obtained in normals can reasonably be extrapolated to the epileptic population.
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  • 29
    ISSN: 1432-1041
    Schlagwort(e): metoprolol ; age ; disposition ; elderly subjects ; kinetics ; metabolism ; alpha-OH-metoprolol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The absorption and disposition of metoprolol have been evaluated in 10 healthy, non-smoking, elderly individuals (mean age 73.1 years) by simultaneous determination of [3H]-metoprolol and unlabelled metoprolol. The labelled drug was given as an intravenous tracer dose, immediately followed by oral metoprolol 25 mg. The experiment was preceded by administration of metoprolol 25 mg b.i.d. for 3 days. The volume of distribution, elimination half-life and total body clearance were almost the same as previously observed in healthy, young subjects. The mean systemic availability was about 39% in the elderly, which is lower than the mean of 55% observed in a control group of young volunteers who received 50 mg b.i.d. In the elderly, the mean plasma concentration of α-OH-metoprolol was about twice as high as that of the parent drug, whereas the opposite was true of the control group. The results indicate that age-related physiological changes have a negligible effect on the pharmacokinetics of metoprolol.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 21 (1981), S. 149-153 
    ISSN: 1432-1041
    Schlagwort(e): cinromide ; epilepsy ; kinetics ; metabolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Cinromide is an experimental anticonvulsant currently in phase II testing. A single oral dose (900 mg) of cinromide was administered to 8 epileptic subjects on phenytoin therapy. Plasma samples drawn during the next 36 h were analyzed for cinromide and its amide and acid metabolites. The absorption rate of cinromide varied widely between subjects producing maximum cinromide concentrations between 0.5 and 2.5 h after the dose. The median elimination half lives of cinromide and the amide and acid metabolites were 0.73, 1.65, and 4.85 h respectively. The oral clearance of cinromide (median=135 l/h) suggests that it is subject to first pass metabolism. In all subjects the area under the curve (AUC) of acid metabolite (632 to 1777 µM/l) was greater than the AUC of amide metabolite (77 to 185 µM/l) which was greater than the AUC of cinromide (5 to 89 µM/l). Steady-state concentration ratios of metabolite to parent drug predicted from the AUC data were 3.8 for the amide and 35.8 for the acid metabolite. The amide metabolite is known to have anticonvulsant properties and, until the relative contributions of metabolites and parent drug to the efficacy of cinromide are resolved, the monitoring of metabolites as well as parent drug is imperative.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 21 (1982), S. 379-384 
    ISSN: 1432-1041
    Schlagwort(e): hyperthyroidism ; propranolol ; methimazole ; metoprolol ; atenolol ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetic profiles of oral methimazole 40mg, propranolol 80mg, metoprolol 100mg and atenolol 100mg were compared in hyperthyroid patients both during the hyper-and euthyroid states. For methimazole, neither the peak concentration (Cmax), the time to reach peak concentration (tmax), the elimination half-life (t1/2) nor the area under the curve (AUC) value was affected by the hyperthyroid state. For propranolol and metoprolol, which undergo extensive presystemic clearance, the AUC values were lower (p〈0.02) when the patients were hyperthyroid than when they had become euthyroid, but the t1/2's were not significantly altered. For atenolol, there were no significant kinetic differences between the hyperthyroid and euthyroid states. The findings are compatible with the assumption that hyperthyroidism does not affect the kinetics of methimazole or atenolol, but that it may enhance presystemic clearance of propranolol and metoprolol.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 27 (1984), S. 233-236 
    ISSN: 1432-1041
    Schlagwort(e): glibenclamide ; acarbose ; kinetics ; alpha-glucosidase inhibitor ; blood glucose control ; plasma insulin ; Type 2 diabetes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A single dose of glibenclamide 5 mg was administered to six Type 2 diabetics, randomly treated for 7 days either with acarbose (3×100 mg daily) or with placebo. The serum concentration of the drug was measured for 10 h. Peak concentrations, times-to-peak concentration, elimination half-lives and the extent of bioavailability of the drug were not significantly modified by acarbose. The combined administration of glibenclamide and acarbose resulted in a modest improvement in the blood glucose profile after breakfast and lunch, together with a significant diminution in plasma insulin. Thus, acarbose appears a useful additional treatment for Type 2 diabetics already receiving sulphonylurea derivatives.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 26 (1984), S. 521-530 
    ISSN: 1432-1041
    Schlagwort(e): chloroquine ; malaria ; rheumatoid disease ; kinetics ; major metabolite ; optimal dosage ; therapeutic regime ; monodesethylchloroquine ; bidesethylchloroquine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics and disposition of chloroquine (CQ) and its metabolite monodesethylchloroquine (CQM) were investigated in 5 healthy volunteers after incremental (150–300–600 mg CQ base) single oral doses of CQ. The analytical method used (HPLC and fluorescence detection) is the most sensitive known method for CQ and CQM. Plasma and whole blood concentrations of CQ, CQM and a third metabolite, bidesethylchloroquine (CQMM), were determined. The kinetics of CQ was found to be unique. The best fit was obtained by a multicompartmental model. The biological half-life appeared to be between 30–60 days; the volume of distribution (Vd) was ∼ 800l/kg, and the clearance ∼ 11/h/kg when calculated from plasma data. The whole blood concentrations were ∼ 8–10 times higher than in plasma, and consequently the Vd and whole blood clearance were ∼ 10 times lower. The kinetics changed as the dose was increased. An indication of capacity-limited steps in CQ disposition was found, as the rate constants decreased even though the clearance remained the same. The intrinsic half-life of CQM was 1/4 of that of CQ, but was prolonged after the highest dose of CQ. The present knowledge of CQ kinetics could provide a basis for revision of current dosage regimens in malaria suppression and rheumatoid disease to ensure efficacious and safe therapy.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 27 (1984), S. 367-369 
    ISSN: 1432-1041
    Schlagwort(e): flurbiprofen ; syrup ; suppository ; kinetics ; children ; bioavailability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Eight subjects, aged 6–12 years and weighing 18.8–36.7 kg, received single doses of flurbiprofen 50 or 75 mg (corresponding to 1.4–2.7 mg/kg) as syrup and suppository in a Latin square design. Half-life (2.7–3.2 h), elimination constant (0.22–0.26 h−1), area under the plasma level curve (72.4–77.3 µg·h·ml−1) and time to reach the concentration peak (1–0.75 h) were similar after the syrup and suppository. Flurbiprofen showed equivalent bioavailability after oral and rectal administration and the same pharmacokinetic profile was confirmed in children as observed in adults.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 39-45 
    ISSN: 1432-1041
    Schlagwort(e): furosemide ; neonates ; kinetics ; placental transfer ; intravenous therapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of furosemide was evaluated in 12 newborns who received the drug transplacentally, and in 21 neonates who received it directly for therapeutic reasons. In the first group, the apparent plasma half-lives ranged from 96 to 6.8 h with a significant inverse relationship (p〈0.01) between the gestational age and the elimination rate. In two cases a clear effect on diuresis was also observed. In the neonates receiving the drug i.v. for therapeutic reasons, the elimination kinetics appeared to follow a two-compartment open model, with a significant difference in the therminal plasma half-life between premature (26.8±12.2 h) and full-term newborns (13.4±8.6 h). In this group no relationship was observed between elimination rate and either gestational or conceptional age. In the case of repeated administration, an increase in plasma clearance and reduction in t1/2 β was noticed.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 435-439 
    ISSN: 1432-1041
    Schlagwort(e): azlocillin ; kinetics ; biliary excretion ; liver dysfunction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic of azlocillin was followed in five elderly patients after biliary surgery. Total clearance was 138.6±17.7 ml/min when 2.0 g was given as an i.v. bolus injection. The half-life of the β-phase averaged 110 min. The total clearance and the half-life of azlocillin were influenced by slight impairment of renal function (creatinine clearance 59.4±13.6 ml/min). In patients with normal liver function biliary excretion of the drug amounted to 5.3±2.8% of the dose (n=3) and the kinetics of biliary excretion were linear. In contrast, in two patients with impaired liver function biliary excretion was 0.2% and 0.5% of the dose, and kinetic analysis of biliary excretion rates revealed at least one zero order step in the excretion process. Renal excretion of the drug amounted to 45.0±17.7% of the dose, which means that 50% of the total clearance of azlocillin has to be accounted for by metabolic clearance.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 23 (1982), S. 529-533 
    ISSN: 1432-1041
    Schlagwort(e): beta-blocker ; bufuralol ; enantiomers ; kinetics ; metabolism ; man
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Single oral doses of (+)-, (−)- and (±)-bufuralol were administered to a healthy volunteer to compare the disposition and metabolism of the individual isomers and the racemate. Plasma levels and area under plasma curve (AUC) of the active isomer, (−)-bufuralol, were higher than those of the (+)-isomer; plasma clearance was correspondingly lower. Intermediate values were found for the racemate. The elimination half-life of (−)-bufuralol was shorter than that of (+)-bufuralol, but similar to the racemate. Both isomers were cleared almost entirely by metabolism. The main metabolic pathway for (−)-bufuralol was aromatic hydroxylation, whereas the principal route for (+)-bufuralol was conjugation. Phenol metabolites in the systemic circulation were present mainly as conjugates. Both isomers also underwent aliphatic hydroxylation. This pathway was more favoured by the (+)-isomer, although plasma levels and AUC of the principal product, 2′-hydroxy-bufuralol, were almost identical for the two forms. Major differences in metabolic fate thus had relatively little effect on the disposition of pharmacologically active metabolites.
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 24 (1983), S. 243-246 
    ISSN: 1432-1041
    Schlagwort(e): tolbutamide ; valproate ; intoxication ; activated charcoal ; inhibition of absorption ; sulphonylureas ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The claim that activated charcoal should be ineffective or even contraindicated in intoxication due to tolbutamide is based only on limited in vitro studies. To test the claim, the effect of activated charcoal 50 g on the absorption of tolbutamide and, as a reference, of sodium valproate, was studied in 6 healthy volunteers. Each volunteer swallowed tolbutamide 500 mg and sodium valproate 300 mg with 50 ml water 1 h after a light breakfast, and within 5 min they took in randomized order either a suspension of activated charcoal or water. The absorption of tolbutamide, calculated as the peak concentration and the area under the serum drug concentration-time curve during 0–48 h, was reduced by 90% by charcoal (p〈0.001). The absorption of valproate in these conditions was reduced on average by 65% (p〈0.01). In each subject charcoal had a greater effect on the absorption of tolbutamide than of valproate. According to these findings and preliminary in vitro studies on other sulphonylureas high doses of activated charcoal can be recommended for the preventing the absorption of sulphonylureas in acute intoxications. The poor aqueous solubility of these substances at the gastric pH probably delays their gastrointestinal absorption, so that they may be adsorbed on to charcoal even given several hours later.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 22 (1982), S. 27-32 
    ISSN: 1432-1041
    Schlagwort(e): sulfonylureas ; diabetes ; chlorpropamide ; glipizide ; C-peptide ; insulin ; blood glucose ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of sulfonylurea on the secretion, disposal and effect of insulin was studied in 9 Type 2 diabetics during 3 one-month courses of treatment with a) chlorpropamide (t1/2〉24 h) once daily, b) glipizide (t1/2=2–4 h) once daily, and c) glipizide in divided doses. Food intake by each patient was identical during each period. Blood concentrations of immunoreactive insulin (IRI) and C-peptide (radioimmunoassays), and of glucose (enzymatic assay), chlorpropamide (gas chromatography) and glipizide (high-pressure liquid chromatography) were determined before and after breakfast and lunch on the 4th day of each examination period. All comparisons were intraindividual. Despite the lunch-time dose of glipizide given during the divided dose treatment, once-daily administration of this drug led to higher drug concentrations not only after breakfast but also for the first few hours after lunch. Divided dosage, on the other hand, led to higher concentrations later. In contrast to once-daily dosage, continuous exposure to glipizide was found in most patients. Chlorpropamide gave the most continuous sulfonylurea exposure. The blood glucose levels were inversely related to the concurrent sulfonylurea concentrations; glucose levels after breakfast and lunch were lowest during once-daily glipizide, whereas the fasting level was lowest during chlorpropamide treatment. The IRI response to breakfast was 60%–70% higher during once-daily glipizide than during the other two treatments, but the C-peptide responses to breakfast were almost identical. Thus, the greater after-breakfast availability of peripheral insulin appeared to be due to an effect of glipizide on the extrapancreatic disposal of the hormone.
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  • 40
    ISSN: 1432-1041
    Schlagwort(e): digoxin ; verapamil ; digoxin-verapamil interaction ; kinetics ; plasma level ; renal clearance ; extra-renal clearance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Single-dose investigations in healthy subjects have demonstrated substantial impairment of renal and extrarenal clearance of digoxin during coadministration of verapamil. A longitudinal study has been performed to assess the changes in digoxin disposition during long-term verapamil therapy. After one week of verapamil 240 mg/d mean plasma digoxin had risen from 0.21±0.01 ng/ml (SE) to 0.34±0.01 ng/ml (p〈0.01), and renal digoxin clearance had fallen from 197.57±17.37 ml/min to 128.20±10.33 ml/min (p〈0.001). These changes gradually subsided, and after six weeks, renal digoxin clearance had normalized and plasma digoxin had declined to 0.27±0.02 ng/ml (NS). The 24-h urinary recovery of digoxin increased from 46.46±3.23% before to 69.78±3.69% (p〈0.001) after six weeks of verapamil co-administration, and this elevation persisted throughout the study. The verapamil-induced suppression of renal digoxin elimination disappears over a few weeks of drug exposure, whereas the inhibition of the extrarenal clearance of digoxin seems to persist.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 1 (1981), S. 19-35 
    ISSN: 1572-8986
    Schlagwort(e): Decomposition of NH3 ; kinetics ; optical spectroscopy ; gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract The plasma decomposition of NH3 has been studied as a function of the residence time, power input, and pressure. The process follows apparently zero-order kinetics, which can be interpreted on the basis of a kinetic mechanism involving as initial step the rupture of an N-H bond from vibro-rotationally excited modecules. Simultaneous spectroscopic observations of the emission light due to electronically excited NH2, NH, H, and N2 have been used to confirm the suggested mechanism and to show that NH2 and NH are successive intermediate species and that the final step of the decomposition process is the bimolecular recombination NH+NH→N2+H2.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Plasma chemistry and plasma processing 1 (1981), S. 233-245 
    ISSN: 1572-8986
    Schlagwort(e): Plasma ; kinetics ; polymerization ; propylene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Flowing microwave plasma of propylene and propylene with argon was studied by mass spectrometry. Plasma composition was investigated as a function of external parameters such as pressure, argon/propylene ratio, and microwave-induced power. It was found that the propylene broke down to C2H2 and CH4, or reacted further with propylene. Two main products, leading to the determination of three main chain reactions for the polymerization of propylene by ion-molecule interactions, were observed, namely, C2H2 and CH4. These were the propylene, acetylene, and ethylene chain reactions. It was also found that the propylene disappeared in a pseudo-first-order reaction. Consequently an overall rate constant for the polymerization was determined (50 sec−1 at 1 torr pressure for propylene plasma). This constant is found to be linearly dependent upon the propylene percent concentration, and nonlinearly dependent upon plasma pressure.
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  • 43
    Digitale Medien
    Digitale Medien
    Springer
    Biochemical genetics 19 (1981), S. 881-893 
    ISSN: 1573-4927
    Schlagwort(e): chicken kidney ; ornithine transcarbamylase ; Cochin Bantam ; White Leghorn ; genetics ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Comparisons were made of the renal ornithine transcarbamylase (OTC) activities within different groups of chickens including Japanese native breeds. OTC activities varied markedly within these groups. The Cochin Bantam breed and White Leghorn B line had an especially high activity, about 400 units/g of kidney, in contrast to two Japanese native breeds, Japanese Game (white variety) and Banshuu Gashiwa, and the California Gray breed, which showed a very low activity, the values being almost undetectable. In crossing experiments using the California Gray breed as a tester strain, Cochin Bantam OTC represents a simple autosomal incompletely dominant trait similar to the White Leghorn B line OTC. Kinetic studies using partially purified OTC preparations from the White Leghorn B line and Cochin Bantam breed revealed that both enzymes were identical for a variety of enzymic characteristics. In light of these results, the physiological significance of chick kidney OTC is discussed.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 17 (1982), S. 359-369 
    ISSN: 1573-4889
    Schlagwort(e): Oxidation ; microhardness ; oxide thickness ; kinetics ; oxygen partition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Oxidation kinetics of Ti-1 wt. % Si and Ti-5 wt. % Si alloys in either pure oxygen or air under a pressure of 0.93 bar and in the temperature range of 1171–1473 K are reported. For the exposure period investigated (up to 12 h) both alloys oxidized slower than pure Ti. The amount of oxygen dissolved in the Ti-1 wt. % Si alloy has been calculated. X-ray diffraction analyses indicate that the oxide scale is mainly TiO 2 ,except for the Ti-5 wt. % Si alloy oxidized at 1473 K where some evidence of SiO 2 was obtained. Hardness profiles were taken across the Ti-1 wt. % Si alloy matrix.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 20 (1983), S. 37-65 
    ISSN: 1573-4889
    Schlagwort(e): Alloy oxidation ; cobalt-chromium-tungsten ; scale formation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Oxidation rates in air at 1000–1250°C are reported for a series of Co-Cr-W alloys with 34–40 wt. % Cr and up to 10 wt. % W. Alloys with larger W contents exhibited slower oxidation rates and their parabolic rate constants agreed well with those for binary and ternary, Cr2O3 protected, Ni-base and Co-base alloys in the Co-Cr and Ni-Cr-W systems. The resulting scales were characterized by optical and scanning electron metallography, and electron microprobe analysis. The favorable effect of W additions to a Cr2O3-forming Co-Cr base alloy was the opposite of that reported for Ni-Cr-W alloys. The resupply of Cr to a Cr-depleted matrix beneath a protective CrO3 scale is achieved by the dissolution (denuding) of Cr-rich second phases in the Co-Cr-W alloys. Thus, the internal oxidation of Cr beneath the Cr2O3 scale is avoided for high W alloys. No catastrophic failure by liquid phase formation was observed for high-W alloys oxidized 20 hr at 1250°C.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 64 (1984), S. 45-50 
    ISSN: 1573-4919
    Schlagwort(e): cardiac muscle ; kinetics ; pyruvate kinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Summary The mechanism of activation by inorganic phosphate and ATP of cardiac muscle pyruvate kinase was studied with the aid of steady-state kinetics. The enzyme was purified to homogeneity to a final specific activity of 400 units/ mg (phosphate buffer, pH 7.6, 25 °C). At pH 7.6 the enzyme displays Michaelis-Menten kinetics with respect to both its substrates, phosphoenolpyruvate and ADP. Substrate kinetic constants are: app.Km(phosphoenolpyruvate) −0.04 mM, app.Km(ADP) =0.22 mM. Under the conditions used in the standard assay the specific activity is greatly enhanced by inorganic phosphate (50 mM) or ATP (2.5 mM). Each of these modifiers, acting separately, increases the Vmax without seriously affecting Michaelis constants and Hill coefficients. In the presence of both Pi and ATP, only a decrease in Vmax was observed. The kinetics of activation by inorganic phosphate of pyruvate kinase was examined. Studying the effect of varying concentrations of Pi on the initial rate we obtained a hyperbolic saturation curve with the app. Km(Pi) = 20 mM and Vmax = 167 units/ mg. The evidence is presented that inorganic phosphate is a substrate for a side reaction catalyzed by cardiac pyruvate kinase. It is shown that in the presence of pyruvate, inorganic phosphate and ATP in the assay system, Pi is incorporated into acid-labile products of this reaction, inorganic pyrophosphate being one of them. These findings indicate the existence of an alternative reaction catalyzed by pyruvate kinase by which energy may be stored in the form of inorganic pyrophosphate.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 14 (1980), S. 85-108 
    ISSN: 1573-4889
    Schlagwort(e): alloy oxidation ; nickel-chromium-tungsten ; scale formation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior in air at 1000–1250°C of four Ni-Cr-W alloys containing sufficient chromium content (∼22 at. % Cr) for protective Cr2O3 formation in a binary Ni-Cr alloy is reported. Generally for alloys high in W (10 and 16 at.% W), the rejection of tungsten into the alloy beneath the scale introduced a steep Cr concentration gradient and slower Cr diffusion such that continuous precipitation of Cr2O3 internal oxides prevented the formation of a Cr2O3 protective scale. The alloy most dilute in W (1.6 at. % W) formed a protective scale at short times with little outer NiO scale, but scale fractures led to internal oxidation and rapid nonprotective kinetics. After an initially rapid oxidation increment to form NiO, the 3 at.% Walloy formed a protective Cr2O3 scale with about the same steady-state parabolic kinetics as a binary Ni-30Cr alloy. The effect of ternary Wadditions on the development of Cr2O3 scales on Ni-Cr-W alloys is considered as a ternary analog to Wagner's description of the oxidation of Cu-Pt or Cu-Pd alloys.
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  • 48
    ISSN: 1573-4889
    Schlagwort(e): titanium ; oxidation ; oxide scale ; solid state diffusion ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of titanium was studied over the temperature range of 600 to 800°C in a pure oxygen atmosphere. A parabolic kinetics period is made up of a succession of short parts whose weight gain is nearly constant and whose beginning is characterized by an alteration of the oxidation rate. The kinetics curve is closely correlated with the morphology of the oxide scale which contains several layers separated by short cracks. These cracks decrease the diffusional flows of oxygen and titanium and alter the oxidation rate. A parabolic-linear kinetics transition is attributed to the formation of a continuous crack between the oxide scale and the matrix. The oxide scale then forms a porous barrier of constant thickness which induces a linear rate law due to the steady-state oxygen diffusion. Titanium cannot diffuse across the continuous crack. During the linear kinetics period several layers of constant thickness, separated by a continuous crack, spread out.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 15 (1981), S. 437-445 
    ISSN: 1573-4889
    Schlagwort(e): chromium nitriding ; kinetics ; parabolic rate constant ; diffusivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Parabolic rate constants of the reaction of chromium with nitrogen gas under oxygen-free conditions have been determined over a range of temperature (1000–1250°C) and nitrogen pressure (0.265–101.33 kPa). The growth rate of the subnitride was measured by a thermogravimetric technique using a single specimen. Wagner's oxidation theory is used to calculate the self-diffusivity and intrinsic diffusivity of nitrogen in the subnitride from a theoretical analysis of the parabolic rate constant. The calculated diffusivities varied with the composition of the subnitride, having minimum values at intermediate compositions of the nonstoichiometric chromium nitride “Cr2N.”
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 16 (1981), S. 175-191 
    ISSN: 1573-4889
    Schlagwort(e): Sulfidation ; Fe-Cr alloy ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The scaling of an Fe-20Cr alloy has been studied in H2-H2O-H2S mixtures between 973 and 1223 K. According to a simplified phase diagram, Cr2O3 and FeS should be the thermodynamically stable compounds in the gas mixtures chosen. The reaction followed a mixed rate law between linear and parabolic, indicating that the reaction rate at the scale-gas interface was comparable with the diffusion rate in the scale. At a constant H2/H2S ratio the scaling rate initially decreased slightly with increasing water-vapor pressure. A further increase of the water-vapor pressure resulted in localized sulfide formation, while the other parts of the surface were covered with a Cr2O3 film. Only Cr2O3 formed above a critical water-vapor content. Three zones could be distinguished when a sulfide scale is formed. The outer zone consisted of practically pure FeS; the intermediate zone was a solid solution of (Fe,Cr)S, partially decomposed to FeCr2S4 and metal during cooling; and the inner zone contained small Cr2O3 inclusions in an (Fe,Cr)S matrix.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 21 (1984), S. 21-37 
    ISSN: 1573-4889
    Schlagwort(e): internal oxidation ; kinetics ; alloy ; silver ; precipitation ; coalescence ; ageing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The internal oxidation mechanism in silver alloys was studied by residual resistivity, gravimetric, and calorimetric measurements, and by transmission electron microscopy. If the flux, of oxygen atoms is very large with respect to the oxide formation, the mechanism of internal oxidation includes two stages. The first one is the fixation of oxygen in the form of oxidized elementary species, including only one solute atom. These species are stable and keep a certain mobility. The second one is the coalescence process of these elementary species with the formation of the first clusters. When the flux of oxygen atoms is slowed down, the oxide formation mechanisms are more complicated. The initially formed species can include more than one solute atom because of their diffusion. The two stages are not separate.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 21 (1984), S. 103-118 
    ISSN: 1573-4889
    Schlagwort(e): duplex steels ; sulfidation ; kinetics ; transport processes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Two austeno-ferritic stainless steels were sulfidized at temperatures of 783, 873, and 963 K under sulfur pressures in the range 4×10−12 to 3×10−5 atm. In all cases a triplex scale developed, consisting of an outermost layer of (Fe, Cr)1−xS, an intermediate layer of FeCr2S4, and an innermost layer of porous (Cr, Fe)1−xS containing particles of Mo2S3. Parabolic kinetics were observed except at the lowest temperature where one of the steels reacted according to irregular kinetics. The Mo2S3 particles in the innermost layer acted as inert markers, imaging the former positions of the steels' ferrite phase in which Mo is enriched. The lamellar microstructure of the steel was thus reproduced in the innermost sulfide layer. The positions of the Mo2S3 particles together with the porosity of the inner layer are taken to imply inward sulfur transport through this layer and outward metal transport through all three layers.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 14 (1980), S. 147-165 
    ISSN: 1573-4889
    Schlagwort(e): oxidation in air or oxygen ; kinetics ; oxide identification ; oxygen diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation kinetics of Ti-4.32 wt.% Nb (2.27 at.%) alloy in either air or oxygen under 1 bar pressure have been investigated in the temperature range of 1255–1471 K. For oxidation in oxygen the kinetics follow consecutively decreasing parabolic rate laws. The kinetics become nonparabolic after prolonged oxidation in air. X-ray data reveal the presence of TiO2 (rutile) as the main oxide. The presence of Ti2O, δ-TiN, and ɛ-TiN is found on the metal surface after oxidation in air. Microhardness and electron microprobe measurements are used to determine Ti, Nb, O, and N profiles across the oxidized alloy. The oxygen diffusion coefficient in the alloy can be expressed byD=65.6 exp(−234.3/RT) with the activation energy in kilojoules per mole. The oxidation behavior of the alloy is explained.
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  • 54
    ISSN: 1573-4889
    Schlagwort(e): oxidation ; titanium ; Ti-Ni alloy ; Ti-Cu alloy ; kinetics ; oxide scale ; solid-state diffusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The kinetics and morphologic oxidation properties of titanium, Ti-1.5Ni and Ti-2.5Cu were compared. Titanium and Ti-1.5Ni have a similar behavior, concerning the kinetics and the oxide micro structure. Copper additions decrease the oxidation rate of titanium. The oxide scales formed on Ti-Cu are thinner and less cracked than those obtained on Ti or Ti-1.5Ni. Copper is found in the oxide scale of Ti-Cu, whereas nickel is not found in the oxide scale of Ti-Ni. The oxidation of titanium and its alloys is controlled chiefly by diffusional phenomena in the oxide scale. Thus the alterations of the oxide scale structure and the slower oxidation rate of Ti-2.5Cu can be attributed to the copper which diffuses towards the gas-oxide interface.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 16 (1981), S. 107-131 
    ISSN: 1573-4889
    Schlagwort(e): Oxidation ; iron ; kinetics ; sulfur ; surface analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The growth of thin (0–200 Å) oxide films on iron at 200 and 300 °C has been studied as a function of time and oxygen partial pressure using proton-induced X-ray emission (PIXE) and Auger electron spectroscopy (AES). Oxidation was found to be initially retarded by sulfur which had segregated onto the iron surfaces during preoxidation annealing, but only if the iron surface contained the maximum or near-maximum sulfur coverage (ca. one-half monolayer). During and immediately following the oxygen-sulfur interaction, oxide buildup appeared to be limited by a surface reaction (adsorption, ionization, or dissociation). For most of the oxidation period, pressure-dependent logarithmic oxide growth was observed at 200°C, and pressure-independent parabolic oxide growth at 300°C. Interpretation of the data indicated that oxide growth at 200°C may be limited by quantum mechanical tunneling of electronic species through the previously formed oxide film, and oxide growth at 300°C may be limited by ionic diffusion through the previously formed oxide film. Comparison of AES and PIXE data indicated that the oxide films formed at 200°C were uniform in thickness over the surface of the metal, whereas films formed at 300°C had relatively thin areas where sulfur had remained.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 17 (1982), S. 43-54 
    ISSN: 1573-4889
    Schlagwort(e): Coatings ; oxidation ; titanium silicide ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Coatings of Ti 5Si3 on titanium have been prepared by means of decomposition of silane SiH4 on heated titanium ribbons. Oxidation of the coated titanium specimens was much slower than that of the noncoated ones. Gravimetric and morphological experiments allowed to propose a mechanism describing the oxidation process.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Oxidation of metals 22 (1984), S. 45-57 
    ISSN: 1573-4889
    Schlagwort(e): Ni-Cr-Mo alloys ; sulfidation ; scale structures ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The effect of molybdenum additions 5, 10, 15, and 20 wt. %, on the sulfidation behavior of Ni-20Cr, and the effect of chromium additions, 5, 10, 15, and 20 wt.%, on the sulfidation of Ni-20Mo were studied in pure sulfur vapor at 700°C. In general, the alloys followed a linear or near-linear rate law, the sulfidation rate of Ni-20Mo being slightly less than that of Ni-20Cr. The alloys having the lowest ternary addition, e.g., Ni-Cr-5Mo and Ni-20Mo-5Cr. exhibited the most rapid reaction rates. The highest alloying additions of 20 wt.% had no appreciable benefit on reaction rates. Scale structures were complex but generally consisted of several layers. The outer layer was always NiS1.03, although both binaries formed Ni3S2 within the NiS1.03. An inner layer of Cr3S4 existed in which there was considerable dissolved molybdenum. A thin, intermediate layer of Cr2S3 generally formed between the Cr3S4 and the outer nickel sulfide. An innermost layer of MoS2 formed on all alloys containing more than 10 wt. % Mo, and a second phase of Mo2S3 formed within the MoS2 on Ni-20Mo. Although the scales changed with alloy composition, no significant changes in reaction rate were observed. Notable differences in both scale structure and reaction kinetics between this study and previous studies were apparent. The differences and possible reaction mechanisms are discussed.
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  • 58
    ISSN: 1573-4927
    Schlagwort(e): alcohol dehydrogenase ; inbred mouse strains ; enzyme structure ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Alcohol dehydrogenase activity in mouse liver homogenate-supernatants is 1.7 times greater in the C57BL/10 strain than in the BALB/c strain, regardless of whether activity is expressed in units per gram liver, total liver, or milligram DNA. The K m values for ethanol and NAD+, approximately 0.4 and 0.03mm, respectively, of enzyme purified from both strains are similar. Moreover, the K i for NADH, 1 µm, the pH optimum for ethanol oxidation, 10.5, and the V max for ethanol oxidation, 160 min−1, for ADH from the C57BL/10 and BALB/c strains are similar. Therefore, the difference in ADH activity in the two strains cannot be due to differences in the catalytic properties of the enzyme. The electrophoretic and isoelectric focusing patterns and two-dimensional tryptic peptide maps of the purified enzyme from both strains are identical. Thus the amino acid sequences of enzyme from C57BL/10 and BALB/c mice must also be identical or very similar. The difference in ADH activity in the two strains is most likely the result of genetic differences in the content of ADH protein in liver.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 69 (1982), S. 35-40 
    ISSN: 1432-1424
    Schlagwort(e): axon ; hydrostatic pressure ; K currents ; kinetics ; activation volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The effect of pressure upon the delayed, K, voltage-clamp currents of giant axons from the squidLoligo vulgaris was studied in axons treated with 300nm TTX to block the early, Na, currents. The effect of TTX remained unaltered by pressure. The major change produced by pressures up to 62 MPa is a slowing down of the rising phase of the K currents by a time scaling factor which depends on pressure according to an apparent activation volume, ΔV∓, of 31 cm3/mole at 15°C; ΔV∓ increased to about 42 cm3/mole at 5°C. Pressure slightly increased the magnitude, but did not produce any obvious major change in the voltage dependence, of the steady-state K conductance estimated from the current jump at the end of step depolarizations of small amplitude (to membrane potentials,E, ≦20 mV) and relatively short duration. At higher depolarizations, pressure produced a more substantial increase of the late membrane conductance, associated with an apparent enhancement of a slow component of the K conductance which could not be described within the framework of the Hodgkin-Huxley (HH)n 4 kinetic scheme. The apparent ΔV∓ values that characterize the pressure dependence of the early component of the K conductance are very close to those that describe the effect of pressure on Na activation kinetics, and it is conceivable that they are related to activation volumes involved in the isomerization of the normal K channels. The enhancement of the slow component of membrane conductance by pressure implies either a large increase in the conductance of the ionic channels that are responsible for it or a strong relative hastening of their turn-on kinetics.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 69 (1982), S. 23-34 
    ISSN: 1432-1424
    Schlagwort(e): axon ; hydrostatic pressure ; Na currents ; kinetics ; temperature ; activation volume
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The effects of hydrostatic pressures up to 62 MPa upon the voltage-clamp currents of intact squid giant axons were measured using mineral oil as the pressure transmitting medium. The membrane resistance and capacitance were not appreciably affected over the whole range of pressures explored. The predominant effect of pressure is to slow the overall kinetics of the voltage-clamp currents. Both the early (Na) currents and the delayed (K) ones were slowed down by approximately the same time scale factor, which was in the range of 2 to 3 when pressure was increased from atmospheric to 62 MPa. Finer details of the effects, most evident at moderate depolarizations, are: the apparent initial delay in the turn-on of Na currents is increased by pressureless than is the phase of steepest time variation, and the later decay is slowedmore than is the rising phase. The initial time course of the currents at high pressures can be made to overlap with that at normal pressure by a constant time compression factor, Θm, together with a small, voltage-dependent delay. In a given axon, Θm was fairly independent of voltage, and it increased exponentially with pressure according to an apparent activation volume, ΔV∓, ranging between 32 and 40 cm3/mole. ΔV∓ tended to decrease with increasing temperature. Contrary to what is observed for moderate or large depolarizations, the kinetics of Na inactivation produced by conditioning prepulses of −50 or −60 mV was little affected over the whole range of pressures explored. Inferences about the pressure dependence of the steady-state Na activation were made from the comparison of the plots of early peak currents,I p, versus membrane potential,E. The Na reversal potential,E Na, and the slope of the plots nearE Na did not change significantly with pressure, but the peak Na conductancevs. E relationship was shifted by about +9 mV upon increasing pressure to 62 MPa. Steady-state Na inactivation,h ∞, was slightly affected by pressure. At 62 MPa the midpoint potential of theh ∞ (E) curve,E h, was shifted negatively by about 4 mV, while the slope atE h decreased by about 38%. Under the tentative assumption that pressure directly affects the gating of Na channels, the Na activation data follows a simple Hodgkin-Huxley scheme if the opening of anm gate involves an activation volume of about 58 Å3 and a net volume increase of about 26 Å3. However, a self-consistent description of the totality of the effects of pressure on Na inactivation cannot be obtained within a similar simple context.
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 74 (1983), S. 85-94 
    ISSN: 1432-1424
    Schlagwort(e): sodium ; lithium ; chloride ; pH ; transport ; kinetics ; ion permeability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Na+, Li+, K+, Rb+, Br−, Cl− and SO 4 2− transport were studied in brush border membrane vesicles isolated from rabbit jejunum., Li+ uptakes were measured by flameless atomic absorption spectroscopy, and all others were measured using isotopic flux and liquid scintillation counting. All uptakes were performed with a rapid filtration procedure. A method is presented for separating various components of ion uptake: 1) passive diffusion, 2) mediated transport and 3) binding. It was concluded that a Na+/H+ exchange mechanism exists in the jejunal brush border. The exchanger was inhibited with 300 μm amiloride or harmaline. The kinetic parameters for sodium transport by this mechanism depend on the pH of the intravesicular solution. The application of a pH gradient (pHin=5.5, pHout=7.5) causes an increase inJ max (50 to 125 pmol/mg protein·sec) with no change inK t (≈4.5mm). Competition experiments show that other monovalent cations, e.g. Li+ and NH 4 + , share the Na+/H+ exchanger. This was confirmed with direct measurements of Li+ uptakes. Saturable uptake mechanisms were also observed for K+, Rb+ and SO 4 2− , but not for Br−. TheJ max for K+ and Rb+ are similar to theJ max for Na+, suggesting that they may share a transporter. The SO 4 2− system appears to be a Na+/SO 4 2− cotransport system. There does not appear to be either a Cl−/OH− transport mechanism of the type observed in ileum or a specific Na+/Cl− symporter.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 74 (1983), S. 175-182 
    ISSN: 1432-1424
    Schlagwort(e): kinetics ; transport inhibition ; noncompetitive ; competitive ; inhibition mechanism ; carrier model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary A new analysis of the conventional carrier model shows that noncompetitive inhibitors can give rise to either competitive, noncompetitive or uncompetitive kinetics; the true mechanism and also the relative affinity of the inhibitor on each surface of the membrane can be decided from the patterns of inhibition observed in different transport experiments. The priciples governing the kinetics of inhibition apply to both reversible and irreversible inhibitors, for in either case the substrate may increase or decrease inhibition or be without effect. Ambiguity arises if the noncompetitive inhibitor acts on only one side of the membrane and if the substrate, in the course of being transported, alters the steady-state distribution of the carrier between inner and outer forms. In facilitated transport systems only equilibrium exchange should give rise to noncompetitive kinetics, whatever the location of the inhibitor. In active systems even the interpretation of exchange in the final steadystate is complicated if the energy-coupling mechanism produces a large displacement in the distribution of the free carrier or the substrate complex: the inhibition could be competitive or uncompetitive, depending on the location of the inhibitor. The actual mechanism is revealed in the uncoupled system.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 79 (1984), S. 41-51 
    ISSN: 1432-1424
    Schlagwort(e): glucose ; brush borders ; sodium cotransport ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Brush border membrane vesicles (BBMV) purified from steer jejunum were used to study the kinetics of sodiumd-glucose cotransport under voltage clamped, zero-trans conditions. When the initial rate of glucose transport (J gluc) was measured over a wide range of glucose concentrations ([S]=0.01–20mm), curvature of the Woolf-Augustinsson-Hofstee plots was seen, compatible with a diffusional and one major, high capacity (maximal transport rateJ max=5.8–8.8 nmol/mg·min) saturable system. Further studies indicated that changes incis [Na] altered theK t , but not theJ max, suggesting the presence of a rapid-equilibrium, ordered bireactant system with sodium adding first.Trans sodium inhibitedJ gluc hyperbolically. KCl-valinomycin diffusion potentials, inner membrane face positive, loweredJ gluc, while potentials of the opposite polarity raiseJ gluc. At low glucose concentrations ([S]〈0.05mm), a second, minor, high affinity transport system was indicated. Further evidence for this second saturable system was provided by sodium activation curves, which were hyperbolic when [S]=0.5mm, but were sigmoidal when [S]=.0.01mm. Simultaneous fluxes of22Na and [3H]glucose at 1mm glucose and 30mm NaCl yielded a cotransport-dependent flux ratio of 2∶1 sodium/glucose, suggestive of 1∶1 (Na/glucose) high capacity, low affinity system and a ∼3∶1 (Na/glucose) high affinity, low capacity system. Kinetic experiments with rabbit jejunal brush borders revealed two major Na-dependent saturable systems. Extravesicular (cis) Na changed theK t , but not theJ max of the major system.
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    The journal of membrane biology 76 (1983), S. 289-297 
    ISSN: 1432-1424
    Schlagwort(e): neuron ; internal perfusion ; Mn current ; kinetics ; Ca blocker
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary Characteristics of currents carried by Mn2+ and other divalent cations were studied in the isolated identified neuron in the circumesophageal ganglia ofHelix aspersa using a suction pipette technique which allows internal perfusion of the cell body and voltage clamp. Increases in [Mn2+] 0 induced not only saturation of the peak ofI Mn but also shifts theI–V relationships along the voltage axis to the more positive potentials. Internal perfusion with F−, which blocks Ca channels, depressedI Mn. Diltiazem, an organic Ca blocker, inhibitedI Mn over the entire range of theI–V relation without shifting the threshold and peak voltage of theI–V relation. Co2+, Ni2+, Cd2+ and La3+ also suppressedI Mn. Relative maximum peak currents of the divalent cations wereI Ba=I Sr〉I Ca〉I Mn=I Zn. Time constants for activation (τ m ) and inactivation (τ h ) of these cations were voltage dependent, and both time constants were greater in the sequence ofI Mn=I Zn〉I Ba=I Sr〉I Ca over the whole voltage range.
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  • 65
    ISSN: 1432-1424
    Schlagwort(e): ion transport ; carriers ; lipid bilayers ; kinetics ; nonactin ; methylation ; macrotetralides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The effects of methylation on the rate constants of carrier-mediated ion transport have been studied on monooleindecane bilayers with K+, Rb+, NH 4 + , and TI+ ions, using the series of homologue carriers, nonactin, monactin, dinactin, trinactin, and tetranactin, each member of the series differing from the previous one by only one methyl group. Measurements of the amplitude and time constant of the current relaxation after a voltage jump over a large domain of voltage and permeant ion concentration, together with a computer curve-fitting procedure, have allowed us, without the help of steady-state current-voltage data, to deduce and compare the values of the various rate constants for ion transport: formation (k Ri) and dissociation (k Di) of the ion-carrier complex at the interface, translocation across the membrane interior of the carrier (k s) and the complex (k is). With the additional information from steady-state low-voltage conductance measurements, we have obtained the value of the aqueous phase-membrane and torus-membrane partition coefficient of the carrier ({ie191-1} and {ie191-2}). From nonactin to tetranactin with the NH 4 + ion,k is, and {ie191-3} are found to increase by factors of 5 and 3, respectively,k Di and {ie191-4} to decrease respectively by factors 8 and 2, whilek Ri andk s are practically invariant. Nearly identical results are found for K+, Rb+, and Tl+ ions.k Ri,k s andk is are quite invariant from one ion to the other except for Tl+ wherek Ri is about five times larger. On the other hand,k Di depends strongly on the ion, indicating that dissociation is the determining step of the ionic selectivity of a given carrier. The systematic variations in the values of the rate constants with increasing methylation are interpreted in terms of modifications of energy barriers induced by the carrier increasing size. Within this framework, we have been able to establish and verify a fundamental relationship between the variations ofk is andk Di with methylation.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Cell & tissue research 211 (1980), S. 73-82 
    ISSN: 1432-0878
    Schlagwort(e): Preputial glands ; Nude mice ; Ultrastructure ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary The preputial glands of male nude (nu/nu) mice were analyzed by a combination of electron microscopy and gas chromatography to determine whether or not they are affected, like developing hairs and nails, by the nu/nu genotype. Results of the analyses revealed no differences between the glands of nude and normal male mice in either their ultrastructural characteristics or lipid secretory products.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Potato research 23 (1980), S. 371-375 
    ISSN: 1871-4528
    Schlagwort(e): nitrogen ; phosphorus ; potassium ; calcium ; sodium ; nitrate ; sulphate ; micronutrients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The specific gravity and dry matter content of 193 tuber samples (cultivars: Arran Banner, Spunta, Up-to-Date, Cara) from crops grown at Kokkinochoria, the major potato growing area of Cyprus, were related to each other as follows: Dry matter (%)=−269.59+268.24×specific gravity. This regression accounted for 82.4% of the variation; the fiducial limits (P〈0.05) for single determinations of specific gravity were±1.54 percentage units. The mineral contents of the tubers were similar to those reported in other countries.
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  • 68
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 203-206 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Carrier gas purity ; Sample stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The amount of oxygen which may be present in the gas volume corresponding to a peak is investigated and compared to the sample amounts. It is shown that even with high purity carrier gases one may have a significant excess of oxygen present at low sample amounts. Attention is drawn to the possibility of impurity build-up by diffusion e.g. through the septum.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 263-270 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Metal complexes ; Enantiomers ; Isotopic composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The high selectivity of complexation gas chromatography has been employed for enantiomer resolution and isotope separation. Thus, a chiral olefin, 3-methylcyclopentene, has been resolved analytically on optically active dicarbonyl-rhodium(I)-3-trifluoroacetyl-1R-camphorate in squalane. The deuterated ethylenes C2H4−nDn have been separated on the same rhodium(I)-containing stationary phase. The chiral aliphatic oxiranes epoxypropane andtrans-2,3-epoxybutane have been resolved on optically active nickel(II)-bis-3-trifluoroacetyl-1R-camphorate in squalane.
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  • 70
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; On-column abstraction ; Aliphatic aldehydes ; Amine antioxidants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The selective on-column abstraction of aliphatic aldehydes by gas chromatographic stationary phases containing N-iso-propyl N′-phenyl-p-phenylenediamine is described.
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  • 71
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 19-22 
    ISSN: 1612-1112
    Schlagwort(e): Teflon columns ; Chemically modified teflon ; Gas chromatography ; Capillary columns
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Wall-coated open tubular columns prepared from chemically modified teflon tubing have been developed for gas chromatography. Chemical reaction of the inner walls of teflon tubing allows bonding of an adhesive layer on which a variety of stationary phaes can be coated. Test mixtures of alkanes and alcohols were used to investigate the chromatographic properties of these columns and the stability and mixing of the adhesive and stationary phae layers. the results in dicate that mixing of the layers is negligible and that the column is stable for a long period of time.
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  • 72
    ISSN: 1612-1112
    Schlagwort(e): Teflon capillary columns ; Chemically modified teflon ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The preparation of teflon capillary columns employing direct coating of the stationary phase to the chemically modified teflon surface and the role of the chemically modified teflon in the separation mechanism are described. Two types of contributions from the modified teflon have been observed: nonspecific adsorption of the carbon surface and specific interactions of polar groups in the carbon skeleton. The use of polar liquid phases can eliminate adsorption due to the presence of polar groups in the modified teflon.
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  • 73
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 55-66 
    ISSN: 1612-1112
    Schlagwort(e): Capillary columns, glass ; Gas chromatography ; Column preparation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Kapillar-Gas-Chromatographie ist heute das sich am stärksten entwickelnde Gebiet der Gas-Chromatographie. Es gibt viele komplexe, neue Fragestellungen in der Analytik, welche den Einsatz spezieller Kapillarsäulen erfordem. Glücklicherweise gibt es aber auch eine große Zahl von Herstellungsverfahren für Kapillarsäulen, welche — noch mehr als bei der Herstellung von gepackten Säulen — eine Anpassung an die gestellten Aufgaben ermöglichen. In diesem Artikel werden die Herstellungsverfahren für Kapillarsäulen zusammengestellt und Anregungen gegeben, wie aufgaben-orientierte Säulen erreicht werden.
    Notizen: Summary Glass capillary column chromatography is the most rapidly growing part of gas chromatography. There are many complex new analytical tasks and they require special capillary columns, Fortunately there is a wide range of column preparation methods available, and they make the preparation of glass capillary columns a more varied job than that of packed columns. In this paper these methods are reviewed and suggestions are given for making task-oriented columns.
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  • 74
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Urea herbicides ; Catalytic hydrolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the rapid catalytic hydrolysis of phenylurea herbicides on silica gel at elevated temperatures. After derivatisation of the anilines produced with heptafluorobutyric acid anhydride final analysis is done on a gas chromatograph equipped with an electroncapture detector. Detection limits are in the 1–5 picogram range. The method has successfully been applied to residue analysis of water samples at the 1 ppb level. The determination of free anilines present in water samples and the potential of various techniques to be used to discriminate between free anilines and parent herbicides are also discussed.
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  • 75
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Graphitised carbon black ; Phenols ; Water pllutants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The fractionation of eleven phenols which may be contaminants in drinking water has been accomplished by using acid-washed graphitised carbon black modified with trimesic acid and PEG 20 M.
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  • 76
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 14 (1981), S. 447-451 
    ISSN: 1612-1112
    Schlagwort(e): Headspace analysis ; Gas chromatography ; Residual analysis of polyethylene terephthalate ; Acetylene reduction assay ; Ethylene evolution in germinating seed ; Acetaldehyde generation in polyester resin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary New application areas for headspace gas chromatography in agricultural and polymer degradation research are described. Specific examples are drawn from the various forms of headspace analysis with emphasis on the automated static equilibrium method.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 13 (1980), S. 35-39 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Nitromethane ; Nitroalkanes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Impurities in commercially available nitromethane have been determined by gas-liquid chromatography using six different column packings. Besides nitromethane, 1-nitropropane, 2-nitropropane, acetonitrile, methanol, small amounts of ethanol and acetaldehyde have been detected. The presence of formaldehyde, ethyl acetate and acetone is probable. Mixtures containing comparable amounts of the four nitroalkanes could be separated on all columns, but plots of logarithms of the retention times vs. carbon number or boiling points of the nitroalkanes or column temperatures were linear only in case of columns packed with Porapak R and Q.
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  • 78
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 60-62 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Amines ; Derivatization ; Chloroformate esters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The gas chromatographic analysis of amines after conversion to electron capture sensitive carbamates in two-phase systems has been studied. Hydrophilic compounds, for instance methylamine, are reacted with 2,2,2-trichloro-tert. butyl chloroformate. Quantitation below 10−7 M can be made by thermionic or electron capture detection. A hydrophobic amine, namely N,N-dimethyl-n-octylamine, was derivatized with 2,4,6-tribromophenyl chloroformate with addition of iodide ion to the aqueous phase. The favorable effect of iodide ion as well as the choice of pH and chloroformate ester is discussed.
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  • 79
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 16 (1982), S. 98-102 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Rectangular channel ; Efficiency ; Capacity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas chromatographic experiments have been performed in a truly rectangular channel with a 60∶1 cross-sectional aspect ratio, constructed according to the field-flow fractionation technology. It is shown that the peak broadening is controlled by the thickness of the channel while the maximum load is determined by the largest cross-sectional dimension. However, even with its elongated configuration, the side walls contribute significantly to the band broadening of solutes with a high diffusivity. Good agreement is found between the experimental plate height data and the recent theoretical calculations of Golay [13] taking into account the side-wall effect.
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  • 80
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 269-284 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Liquid chromatography ; Phenols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Gas and high-performance liquid chromatographic methods in the analysis of phenols are reviewed. Among the great number of phenolic compounds analyzed, alkylphenols, chlorophenols, dihydroxy- and trihydroxybenzenes and biphenols are chiefly considered. The advantages and drawbacks of the methods are discussed, quoting the most important work. Relationships between the structural characteristics of phenols, the stationary phase structure, the mobile phase composition and the retention data are treated. Typical examples of the conditions for GC and HPLC analysis are summarized in tables. The literature comprises over 270 references, most of them recent.
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  • 81
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Average molecular polarizability ; Retention index ; Polycyclic aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The Kováts retention indices of 10 polycyclic aromatic hydrocarbons were determined on SE-30, OV-101, SE-52, OV-7 and OV-17 stationary phases. A significant correlation has been found between the retention indices and the average molecular polarizabilities of the analyzed substances. Equations were derived for the direct determination of the average molecular polarizabilities from the retention index values. The influence of the temperature on this relationship is also indicated.
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  • 82
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 17 (1983), S. 493-500 
    ISSN: 1612-1112
    Schlagwort(e): Esterification in aqueous solution ; iso butyl esters of C1–C20 fatty acids ; Gas chromatography ; Fatty acid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C1–C20 carboxylic acids have been esterified in aqueous solutions with i-butanol. Gas chromatographic analyses have been performed from a single chromatogram. It has been established that esterification in the concentration range of [H2O]/[i-BuOH]=0.01–10.3 can be utilized for the quantitative determination of these carboxylic acids. The presence of water does not interfere in the range of [H2O]/[i-BuOH]=0.01–1.03. In the cases of [H2O]/[i-BuOH]〉1.03, anhydrous sodium sulfate has been used for binding the water, in an amount of [Na2SO4]anh./[H2O]≥0.2.
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  • 83
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Esterification in aqueous solution ; n-Butyl esters of C2−C16 dicarboxylic acids ; Dicarboxylic acid analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary C2−C16 dicarboxylic acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification in water/n-butanol mixtures with mole ratios between 0.02 and 2.53 can be utilized for the quantitative determination of the dicarboxylic acids by gas chromatography. The presence of water does not interfere at water/n-butanol mole ratios below 0.27. For mole ratios above 0.27 anhydrous sodium sulfate has been used for binding the water. The mole ratio range was 0.25–0.75 for anhydrous sodium sulfate/water, and 0.32–1.3 for sulfuric acid/anhydrous sodium sulfate.
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  • 84
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 663-667 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Gas solubilities ; Enthalpies of solution ; Polar solutions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The gas-liquid chromatographic method has been used to determine the solubilities and partial molar enthalpies of solution of the gases H2S, CO2 and COS in four polar solvents. The results agree well with literature values obtained using conventional techniques, with the one exception of H2S in N-methyl-2-pyrrolidinone. In this case there is some evidence for the occurrence of adsorption at the gas-liquid interface.
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  • 85
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Esterification in aqueous solution ; n-Butyl esters of aromatic polycarboxylic acids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The direct esterification and gas chromatographic analysis of aromatic carboxylic acids as n-butyl esters is described. Derivatization is performed in aqueous solution with n-butanol in the presence of sulfuric acid. The butyl esters of benzoic, phthalic, hemimellitic, trimellitic, trimesic and pyromellitic acids permit their gas chromatographic separation from each other and from fatty acids and alipatic dicarboxylic acids. At mole ratios of [H2O]/ [n-BuOH]≤0.04 the water present does not interfere with the esterification reaction. At mole ratios above 0.04 anhydrous sodium sulfate is used for binding the water, at mole ratios of [Na2SO4 anh.]/[H2O]=0.25–0.75.
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  • 86
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 202-204 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Polysiloxane stationary phases ; Heat of adsorption ; Heat of solution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The changes in the heat of solution of polar compounds and xylene isomers in methylsilicone fluid OV-101 deposited on Chromosorb W AW DMCS were studied. It was shown that the heat of solution increases with an increase of the percentage loading of the OV-101 up to 10%. Solution and adsorption thermodynamic characteristics of the studied system are briefly discussed.
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  • 87
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Metal complexes ; Chemically bonded phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Packings consisting of diphenylphosphine complexes with CoCl2 and CoBr2, chemically bonded to the silica surface, were synthesized and their retention parameters determined. The packings are capable of specifically interacting with electron-donating compounds by forming π-complexes. The interaction is considerably stronger in the case of CoBr2-containing packing than in the case of CoCl2-containing packing.
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  • 88
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 234-238 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Open-tubular columns ; On-column injection ; Stopped-flow operation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A simple, inexpensive, on-column injector of the septum moving-needle kind is described for quantitative analysis using open-tubular columsn. when operated in the stopped-flow mode an improvement incolumn efficiency is observed combined wit a diminished tendency to produce split-top peaks, particularly for late eluting peaks. Using electronic integration a relative error of about 2.7% was observed for peaks spanning a wide range of sample concentrations and volatilities.
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  • 89
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 243-248 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Carrier gas ; Viscosity ; Influence of temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The vicosity-temperature relationship of the three gases (helium, nitrogen and hydrogen) most frequenly used as the carrier gas in gas chromatography is studied. Based on available data, equaitions are derived to describe this relationship. Using these equations viscosity data are tabulated for the chromatographically important temperature range.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 260-264 
    ISSN: 1612-1112
    Schlagwort(e): Parabens and their dissolution ; Pharmaceutical dosage forms ; Derivatization ; Gas chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A specific, sensitive and general applicabla gas chromatographic method is described for the determination of parabens in various liquid pharmaceutical preparations: propylparaben and butylparaben in a liquid antacid dosage form (I); methylparaben, ethylparaben and propylparaben in a syrup (II); methylparaben and propylparaben in a solution for injection (III). Each time one of the parabens is used as internal standard. The parabens are extracted with diethylether and derivatized by silylation. Different columns are used for the analysis of the parabens: 3% SE-30 column, a 3% QF-1 column for different selectivity, a 2% OV-1 column for isothermal operation. Special attention is attributed to the standard: the parabens are dissolved in a minimal amount of 0.1 M sodium hydroxide and extracted in the same way as the pharmaceutical dosage form.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 294-296 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Configuration ; Resolution ; Alcohols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The study of the resolution of sixteen secondary aliphatic alcohols by gas chromatography on (+)-dodecyl (2R, 3R)-tartrate, trapping the ascending part of the peak from a conventional filled column, has allowed the determination in a single operation of the sign and order of emergence of enantiomers. A correlation between the configuration of these secondary alcohols and their order of emergence has been established.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 309-312 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Carboxylic acids ; Acetonyl derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The preparation of the acetonyl esters of nine aliphatic carboxylic acids is described, the general formula of the derivatives being RCOOCH2COCH3 where R=alkyl or H. The derivatives show good chromatographic properties on both packed and capillary columns. The electron impact and chemical ionisation mass spectra of the derivatives are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 93
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 449-455 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Thermodynamic relationships ; Retention index ; Peak identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A thermodynamic criterion, ΔQ, is suggested which permits to estimate the difference in the functional group energy of interactions for two different stationary phases. The linear dependence of ΔQ on the homolog number m of any series Rm X can be used as the thermodynamic criterion for the identification of substances by GC analysis.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Springer
    Chromatographia 18 (1984), S. 477-488 
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Open tubular (capillary) columns ; Sample capacity ; Column comparison ; Film thickness ; Column diameter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Wall-coated, open-tubular (capillary) columns prepared from different diameter tubing, with different liquid phase film thickness, are compared with each other and with packed and support-coated open-tubular columns. The comparison is based on the variation of the phase ratio and the capacity factor, and includes column efficiency (HETP, theoretical plate number), resolution, retention time, and sample capacity. Problems associated with the evaluation of the sample capacity are outlined. The influence of temperature on column performance is discussed in detail. Finally, the possibilities of short, wide-bore open-tubular columns prepared with a thick liquid-phase film are demonstrated.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Springer
    Bulletin of experimental biology and medicine 95 (1983), S. 151-153 
    ISSN: 1573-8221
    Schlagwort(e): antigen-antibody reaction ; kinetics ; laser ; scattering of light
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 9 (1981), S. 181-190 
    ISSN: 1573-8744
    Schlagwort(e): drug displacement ; interaction ; kinetics ; simple model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A simple model simulating the kinetics of drug displacement kinetics is investigated. It is demonstrated that for highly bound, lowly cleared drugs, displacement interactions are transitory. Consequently, the kinetics of the interaction have to be considered as well as the in vitrointeraction. It is possible to have a significant in vitrodisplacement interaction with no in vivocounterpart. Methods of moderating drug displacement by adjusting the rate and the timing of administration of the displacing agent are discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Digitale Medien
    Digitale Medien
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 127-145 
    ISSN: 1573-8744
    Schlagwort(e): warfarin ; dose dependent clearance ; hepatic uptake ; model ; kinetics ; nonlinearity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract To quantify the effects of the liver on the dose dependence of plasma warfarin clearance, an equal number of normal and functionally hepatectomized rats received an intravenous bolus of either 0.01, 0.1, or 1.0 mg/kg body weight of radiolabelled sodium warfarin. Serial samples of plasma and bile collected from each rat during the 1 hr experiment and of hepatic tissue collected at the end of the experiment were analyzed for radioactivity. The disappearance of warfarin from the plasma of hepatectomized rats was not dose dependent and suggested that the apparent dose dependency of plasma warfarin clearance is primarily the result of warfarin's interaction with hepatic tissue. The disappearance of warfarin from the plasma of normal rats was dose dependent with higher doses being cleared less rapidly. This dose dependence, however, was not reflected in the rate of biliary excretion of warfarin's metabolites, which did not show saturation over this dosage range. These results were used to develop a multicompartmental model of warfarin's pharmacokinetics. Plasma warfarin data collected from the hepatectomized rats were used to develop the extrahepatic components of the model, which was then expanded to include hepatic tissues based on data collected from normal rats. To simultaneously fit the plasma, biliary, and hepatic data required that at least two classes of hepatic tissue exchange warfarin with plasma. One tissue exhibited Michaelis-Menten saturation kinetics with Kd and maximum capacity estimated at 1.49E-3μg/ml and 2.72 μg/ml, respectively. The second class exhibited linear exchange kinetics with free plasma warfarin. Warfarin's association with the second class of hepatic tissue leads to its metabolic elimination. Consistent with our experimental findings, the rate of warfarin elimination from the plasma into the bile was linearly related to plasma warfarin concentration. Thus the single hepatic exchange nonlinearity was necessary and sufficient to account for the apparent dose dependency in plasma warfarin's pharmacokinetics. These results suggest that over the range of doses studied, the apparent dose dependent differences in the plasma warfarin concentration profile can be accounted for by saturable hepatic uptake. This mechanism, however, is not related to warfarin's metabolic enzymes, which do not show saturation in the dosage range studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 111 (1984), S. 49-56 
    ISSN: 1573-5117
    Schlagwort(e): nutrient enrichment ; yield coefficient ; nitrogen ; phosphorus ; mass culturing ; phytoplankton ; sea water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Natural phytoplankton of Cabo Frio area was grown in 42 m-deep artificially upwelled seawater enriched with increasing concentrations of nitrogen or phosphorus. Respective values allowing maximum biomass, maximum uptake of initial reserve and maximum yield coefficient are rather conflicting. Notwithstanding, respective values of 75 µg at 1−1 nitrogen and 5 µg at 1−1 phosphorus, and therefore N:P = 15, appeared to be the best compromise for initial nutrient levels.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 112 (1984), S. 131-136 
    ISSN: 1573-5117
    Schlagwort(e): reed ; harvest ; nitrogen ; phosphorus ; redox potential ; oxygen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An investigation of the effects of repeated winter harvest and removal of dry reed culms on water and sediment chemistry was made in a shallow lake dominated by closed, monospecific reed stands. The oxygen concentration and redox potential in the water, as well as temperature, showed regular diurnal fluctuations inside the reed stands. Ammonium and nitrate + nitrite did not exhibit diurnal fluctuations and differences between a harvested and an unharvested reed area were small. Molybdate reactive phosphorus (MRP) concentration was higher in the unharvested area. Because the winter harvest caused an almost doubling of shoot production compared to the unharvested area, net addition of reed litter (leaves, stubble and culms) to the sediment of the harvested area was similar to that of the unharvested area. It is concluded that removal of reed culms in winter has the largest effect on microclimate in spring, and that the rate of mineralization and reducing intensity in the substrate are not immediately affected. Significantly higher summer standing crop of reed after harvest may have caused lower phosphate concentration in the water column and sediment interstitial water.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    ISSN: 1573-5117
    Schlagwort(e): cypress swamp ; nitrogen ; nutrient cycling ; periphytic algae ; phosphorus ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Both periphytic and planktonic algae are found in areas of the seasonally flooded Great Dismal Swamp (Virginia, U.S.A.). The dynamics of these algae were studied in a cypress stand and the periphytic algae appeared to be important as nutrient conservers. Clear temporal patterns in phytoplankton dominance were also observed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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