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1

Digitale Medien

Effect of ionic interactions on the rates of reduction of Cu(II) with H2O2 in aqueous solutions (1992)

Millero, F. J. ; Johnson, R. L. ; Vega, C. A. ; [weitere]

Springer

Journal of solution chemistry 21 (1992), S. 1271-1287

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ISSN: 1572-8927

Schlagwort(e): Cu(II) ; kinetics ; reduction ; temperature dependence ; H2O2, NaCl, NaBr, NaClO4

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract The rates of reduction of Cu(II) with H2O2 have been measured in NaCl and NaBr solutions and mixtures with NaClO4 as a function of pH (6 to 9), temperature (5 to 45°C) and ionic composition (0.1 to 6M). The effect of pH on the rates was found to be independent of temperature and ionic composition. The rates increased as a function of [H+] raised to the power of 1.3 to 1.6. Speciation calculations indicate that this pH dependence can be attributed to Cu(OH)2 being the reactive species. The rate constants in NaCl and NaBr and mixtures with NaClO4 were independent of ionic strength, but proportional to the halide concentration raised to the power of 2.0 (0.2 to 2.6M). These results can be attributed to Cu(OH)2Cl 2 2− being the reactive species to reduction with H2O2. The Cu(I) halide complexes formed from the reduction are not easily oxidized with O2 or H2O2. The faster rates in Br− solutions, which form stronger complexes with Cu+, support this contention. Measurements made in NaCl with added NaHCO3, NaB(OH)4 EDTA, NTA and glycine were also made. These measurements indicate that the CuL complexes (L=B(OH) 4 − , CO 3 2− , EDTA, NTA, and glycine) are not very reactive to reduction with H2O2. The addition of Mg2+ or Ca2+ caused the rates to increase due to the formation of MgL or CaL complexes and the resultant release of reactive Cu2+.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00667222

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2

Digitale Medien

Increased sensitivity of an enzyme immunoassay (ELISA) for the determination of triazine herbicides by variation of tracer incubation time (1992)

Weller, Michael G. ; Weil, Ludwig ; Niessner, Reinhard

Springer

Microchimica acta 108 (1992), S. 29-40

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ISSN: 1436-5073

Schlagwort(e): atrazine ; terbuthylazine ; sequential binding ; kinetics ; cross-reactivity

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract Immunoassays for triazine herbicides were tested for their reaction to the variation of the tracer incubation time. By application of a sequential technique the measuring range of atrazine could be expanded to five decades and the total duration of the test could be reduced to about 30 min. In an optimized version a lower detection limit of 9 pmol/l (2 ng/l) was achieved. The detection limit of a sensitive immunoassay for terbuthylazine is also below the concentration limit demanded of the German drinking water regulation (100 ng/l) and reaches 130 pmol/l (30 ng/l). Short tracer incubation times did not lead to increased cross-reactivities in contrast to theoretical models [1, 2]. Different mechanisms, which could cause a shift of the center point of the calibration curve, are discussed, including kinetic considerations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01240369

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3

Digitale Medien

Genetic approaches to the study of mitochondrial biogenesis in yeast (1992)

Bolotin-Fukuhara, M. ; Grivell, L. A.

Springer

Antonie van Leeuwenhoek 62 (1992), S. 131-153

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ISSN: 1572-9699

Schlagwort(e): mitochondrial DNA ; mutational analysis ; nucleo-mitochondrial interactions ; gene expression ; membrane assembly ; respiratory deficiency

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract In contrast to most other organisms, the yeastSaccharomyces cerevisiae can survive without functional mitochondria. This ability has been exploited in genetic approaches to the study of mitochondrial biogenesis. In the last two decades, mitochondrial genetics have made major contributions to the identification of genes on the mitochondrial genome, the mapping of these genes and the establishment of structure-function relationships in the products they encode. In parallel, more than 200 complementation groups, corresponding to as many nuclear genes necessary for mitochondrial function or biogenesis have been described. Many of the latter are required for post-transcriptional events in mitochondrial gene expression, including the processing of mitochondrial pre-RNAs, the translation of mitochondrial mRNAs, or the assembly of mitochondrial translation products into the membrane. The aim of this review is to describe the genetic approaches used to unravel the intricacies of mitochondrial biogenesis and to summarize recent insights gained from their application.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00584467

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4

Digitale Medien

Absorption of intramuscular phenobarbitone in children with severe falciparum malaria (1992)

Kuile, F. ; Nosten, F. ; Chongsuphajaisiddhi, T. ; [weitere]

Springer

European journal of clinical pharmacology 42 (1992), S. 107-110

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ISSN: 1432-1041

Schlagwort(e): Phenobarbitone ; Cerebral malaria ; P.falciparum ; kinetics ; drug absorption ; children

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Medizin

Notizen: Summary The absorption of intramuscular phenobarbitone 7 mg·kg−1 was studied in 11 Karen children aged between 1.7 and 11 y with severe falciparum malaria. Eight of the children were comatose. Clinical findings were compared with those in 9 further children with severe malaria of similar age range (four of whom were unconscious), who received an identical placebo. One child, who had received placebo, had repeated convulsions and died 1 h after admission to hospital. The remainder made an uncomplicated recovery. There were no convulsions subsequent to treatment, although the study was too small to assess anticonvulsant efficacy. There was no observable toxicity, but phenobarbitone recipients had a significant tendency to deepen in their level of coma or to become sleepy within the 4 h after drug administration. Phenobarbitone was rapidly absorbed, reaching a mean (range) peak concentration of 34.2 [29.3–42.6] μmol·l−1 in a median (range) of 4 (2.5–12) h. These values are comparable to those previously reported in healthy children and in children with febrile convulsions. Intramuscular phenobarbitone is well absorbed in children with severe malaria; the optimum prophylactic anticonvulsant dose remains to be determined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00314929

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5

Digitale Medien

Kinetics of atrial natriuretic peptide in young and elderly subjects (1992)

Tan, A. C. I. T. L. ; Jansen, T. L.Th. A. ; Termond, E. F. S. ; [weitere]

Springer

European journal of clinical pharmacology 42 (1992), S. 449-452

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ISSN: 1432-1041

Schlagwort(e): Atrial natriuretic peptide ; kinetics ; ageing

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Medizin

Notizen: Summary To study the influence of age on the kinetics of atrial natriuretic peptide (ANP) in man, human (99–126) ANP 2.0 μg·min−1 was infused IV for 60 min in 8 healthy young (18 to 25 y) and 9 healthy elderly (71 to 84 y) subjects. Both baseline ANP values and the levels at the end of infusion were higher in the elderly subjects. The mean residence time of ANP in the two age groups was not significantly different, whereas total body clearance (CL) was markedly diminished in the elderly as compared to the young subjects (mean±SD 3.1±1.0 l·min−1 and 6.2±4.1 l·min−1, respectively). The apparent volume of distribution at steady state was lower in the elderly than in the young, but the difference was not significant (mean±SD 44±19 and 103±111, respectively. The decrease in CL largely explained the higher ANP levels found in the elderly subjects. The MRT and the plasma half-life of the terminal phase did not differ between the two groups. In the elderly but not in the young subjects the calculated endogenous creatinine clearance was closely correlated with the CL (r=0.90, P〈0.001), thereby emphasizing the importance of the kidney in the metabolic clearance of ANP in the elderly.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00280134

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6

Digitale Medien

Interaction of talinolol and sulfasalazine in the human gastrointestinal tract (1992)

Terhaag, B. ; Palm, U. ; Sahre, H. ; [weitere]

Springer

European journal of clinical pharmacology 42 (1992), S. 461-462

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ISSN: 1432-1041

Schlagwort(e): Talinolol ; Sulfasalazine ; β-adrenoceptor-blocking drugs ; absorption ; drug interaction ; kinetics

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Medizin

Notizen: Summary The absorption of talinolol (TA) 50 mg was investigated without and together with the co-administration of sulfasalazine (SASP) 4 g in 11 healthy young volunteers, in order to clarify gastrointestinal transit of TA. Without SASP, the tmax of TA was 2.8 h, Cmax was 112 ng·ml−1 and the half life was 12 h; the AUCo-t was 958 ng·ml−1·h. In the case of concomitant administration of SASP, TA was found only in serum from 3 individuals, with a Cmax of 23 ng·ml−1 and a mean AUCo-t of 84 ng·ml−1·h. TA was not detectable in 5 subjects and it was at the limit of detection (2 ng·ml−1) in 3 subjects. Pharmacokinetic analysis was not possible in any of those individuals. The reason for the interaction appears to be the adsorption of TA by SASP. An interval of 2–3 h should elapse between giving SASP and other drugs.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00280137

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7

Digitale Medien

Somewhere between fiction and reality (1992)

Maciejewski, M.

Springer

Journal of thermal analysis and calorimetry 38 (1992), S. 51-70

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ISSN: 1572-8943

Schlagwort(e): kinetics ; solid-state reactions

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wurde der Einflu\ verschiedener experimenteller Bedingungen (z.B. Probenmasse, Atmosphäre, Aufheizgeschwindigkeit) auf die Zersetzung von NH4VO3, CaCO3 und V2O5 untersucht. Die Ergebnisse zeigen eindeutig, da\ Reaktionsweg und kinetische Parameter in Wirklichkeit nicht die einzelne Verbindung charakterisieren, sondern eher die Kombination von experimentellen Bedingungen und untersuchter Verbindung. Hierdurch ist es meistens unmöglich, “Standardbedingungen≓ zur Berechnung kinetischer Parameter zu wählen, da unter verschiedenen Umständen ganz andere Reaktionswege beschritten werden können.

Notizen: Abstract The influence of various experimental conditions such as sample weight, atmosphere and heating rate on the decomposition of NH4VO3, CaCO3 and V2O5 has been investigated. Results obtained clearly indicate that the course of the reactions and — in turn — the kinetic parameters, are not intrinsic to the particular compound and that they characterize rather the combination of experimental conditions and investigated compound. Such a situation makes it almost impossible to choose ‘standard conditions’ for the calculation of kinetic parameters, because under different circumstances quite different reaction-pathways can occur.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02109108

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8

Digitale Medien

Possibilities of two non-isothermal procedures (temperature- or rate-controlled) for kinetical studies (1992)

Málek, J. ; šesták, J. ; Rouquerol, F. ; [weitere]

Springer

Journal of thermal analysis and calorimetry 38 (1992), S. 71-87

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ISSN: 1572-8943

Schlagwort(e): CRTA ; kinetics ; TA

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird die Anwendbarkeit von herkömmlicher Thermoanalyse (TA) und geschwindigkeitsgesteuerter Thermoanalyse (CRTA) bei kinetischen Untersuchungen diskutiert. Die TA Technik kann eine zuverlässige kinetische Information und sinnvolle kinetische Parameter besonders bei Feststoffumsetzungen liefern. Die CRTA Technik ist andererseits mehr für Zersetzungsprozesse geeignet, bei denen ein oder mehrere Gase freigesetzt werden. Für beide Techniken wird eine einheitliche und geeignete Methode zu kinetischen Analyse vorgeschlagen. Als Beispiel wird diese Methode zur Analyse des Kristallisationsprozesses von Chalkogenidgläsern sowie der Zersetzung von Dolomit angewendet.

Notizen: Abstract The applicability of both conventional Thermal Analysis (TA) and Controlled Rate Thermal Analysis (CRTA) for kinetic analysis is discussed. It is shown that TA method can give a reliable kinetic information and meaningful kinetic parameters especially for solid state transformation. On the other hand the CRTA method is more suitable for decomposition process where one or more gasses are evolved. A consistent and reliable method of kinetic analysis is proposed for both techniques. This method is illustrated to analyze the crystallization process of chalcogenide glass and the decomposition of dolomite.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02109109

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9

Digitale Medien

Thermodynamic and kinetic properties of hydrogen adsorption on thin iron layers (1992)

Zommer, L. ; Randzio, S. L.

Springer

Journal of thermal analysis and calorimetry 38 (1992), S. 1999-2003

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ISSN: 1572-8943

Schlagwort(e): calorimetry ; hydrogen adsorption ; kinetics ; thermodynamics

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Mittels kalorimetrischer und volumetrischer Messungen im Temperaturbereich von 298 bis 363 K wurden die thermodynamischen Eigenschaften der Wasserstoffadsorption an Eisenschichten untersucht. Die kinetischen Eigenschaften wurden mit Hilfe der Dekonvulotion kalorimetrischer Thermogramme ermittelt und mit Literaturangaben zum Haftkoeffizienten verglichen.

Notizen: Abstract Thermodynamic properties of hydrogen adsorption on iron layers evaporated under UHV conditions have been determined from calorimetric and volumetric measurements over the temperature range from 298 K to 363 K. Kinetic properties have been determined with the help of deconvolution of calorimetric curves and compared with the literature data on the sticking coefficient.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01979610

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10

Digitale Medien

Thermogravimetric analysis of ZnCl2 catalyzed degradation of PVC (1992)

Ahmad, Z. ; Manzoor, W.

Springer

Journal of thermal analysis and calorimetry 38 (1992), S. 2349-2357

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ISSN: 1572-8943

Schlagwort(e): dehydrochlorination process ; kinetics ; PVC ; ZnCh catalyzed degradation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Mittels TG wurden die kinetischen Parameter des Dehydrochlorierungsprozesses (DHCL) von PVC und von mit verschiedenen Mengen von ZnCl2 versetztem PVC bestimmt. Diese Werte wurden mit denjenigen verglichen, die man bei der spektroskopischen Analyse der Zersetzung von ZnCl2-haltigen PVC-Filmen bei verschiedenen Temperaturen im sichtbaren UV-Bereich erhalten hatte. Die Werte der scheinbaren Aktivierungsenergie (E a) sinken mit zunehmendem ZnCl2-Gehalt und die hier erhaltenen Werte sind vergleichbar gut mit denen der vorangehenden Arbeit. Der katalytische Effekt von ZnCl2 auf PVC DHCL-Vorgänge wurde erklärt.

Notizen: Abstract The kinetic parameters of dehydrochlorination (DHCL) process of PVC and PVC mixed with different amount of ZnCl2 have been determined by using thermogravimetric analysis. These values have been compared with those obtained by using UV-visible spectroscopic analysis of PVC film containing ZnCh degraded at different temperatures. The values of apparent activation energy (E a) decreases with the increase of the amount of ZnCl2 and the values obtained in the present work are in reasonable comparison with previous works. The catalytic effect of ZnCl2 on PVC DHCL process is explained here.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02123988

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