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  • Angiosperms
  • Protein Conformation
  • kinetics
  • Springer  (43)
  • American Association for the Advancement of Science (AAAS)  (17)
  • 1975-1979  (53)
  • 1970-1974  (7)
Collection
Publisher
  • Springer  (43)
  • American Association for the Advancement of Science (AAAS)  (17)
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 77-88 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The solid-state reaction between barium carbonate and rutile powders to form barium metatitanate BaTiO3 was studied by thermogravimetric analysis, X rays, and microscopy. Phase-stability domains were drawn in a temperature— $${\text{p}}_{CO_2 } $$ , diagram. The dependence of the reaction kinetics on $${\text{p}}_{CO_2 } $$ , $${\text{p}}_{O_2 } $$ or $${\text{p}}_{N_2 } $$ is discussed. In particular, the rate continuously decreases when $${\text{p}}_{CO_2 } $$ , or $${\text{p}}_{N_2 } $$ increases, but it reaches a maximum as a function of $${\text{p}}_{O_2 } $$ .
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 283-298 
    ISSN: 1573-4889
    Keywords: oxidation ; surface alloys ; Fe-Cr alloys ; iron ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of several surface and bulk Fe-Cr alloys and iron at 300°C and 4×10−6 Torr oxygen was studied. The surface alloys were fabricated by implantation of 25 keV Cr ions into the outermost 300Å of polycrystalline iron samples. The oxide thickness as a function of oxygen exposure was obtained using proton-excited X-ray analysis, and composition profiles of oxide films were obtained using Auger electron spectroscopy and ion sputtering. The addition of Cr to Fe by surface and bulk alloying caused the oxidation rate to decrease and changed the oxidation kinetics from parabolic (for Fe) to logarithmic (for Cr concentrations ≥4.7at.%). Interpretation of the data in terms of simple oxidation theories indicates that the Cr additions may reduce the oxidation rate by altering the electronic properties of the metal-oxide interface.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 255-272 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; graphite deposition ; nonadherent oxide ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Fe-C alloys containing 0.5 and 1.0% C was studied in 1 atm O2 at 700° C. The oxidation rate is considerably slower than for pure Fe. The oxide scale formed is detached, multilayered, and overoxidized, containing little or no FeO. A thin film of graphite was identified at the metal-oxide interface by electron diffraction. It is proposed that the slow oxidation and abnormal scale are caused by a residue of graphite left at the metal surface from the oxidation of Fe3C. This inhibition of the oxidation of Fe by carbon at 700°C is in contrast to the stimulation observed at 500°C.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 301-309 
    ISSN: 1573-4889
    Keywords: NiO ; Electrical conductivity ; gas-solid equilibria ; kinetics ; equivalent circuit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In a previous work it has been stated that the NiO electrical conductivity changes connected to the oxygen pressure changes may be considered as a transitory phenomenon. A mixed kinetics case controlled by the formation of surface cation vacancies and their diffusion in the bulk is proposed to explain the reaction process. By means of an equivalent electrical circuit in good agreement with the kinetics model it was possible to reproduce the experimental phenomenon.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 481-504 
    ISSN: 1573-4889
    Keywords: kinetics ; sulfidation ; Fe-Cr-Al alloys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of aluminium on the kinetics and mechanism of high-temperature sulfidation of Fe-Cr alloys containing 20 at.% chromium has been investigated. It has been found that the addition of aluminum greatly improves the scaling resistance of Fe-Cr alloys against attack by sulfur vapors at high temperatures.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 437-456 
    ISSN: 1573-4889
    Keywords: Fe-Cr ; oxidation ; kinetics ; oxide morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ferritic polycrystalline Fe-24 wt.% Cr was oxidized in pure oxygen at 190 ≤ T≤490° C and pressures in the range 5.3×10−2–13.3 Pa for periods of up to 5 hr. The reaction proceeded in three stages. An initial period of accelerating rate was accompanied by oxide island nucleation and growth. Following island coalescence the rate was approximately logarithmic at low temperatures and somewhat slower than parabolic at high temperatures. Rate control during this period was thought to be due to mass transport through the oxide grain boundaries left by the island impingement process. During these first two stages the oxide formed was γ-M2O3 with possibly some spinel. The final stage of reaction involved the appearance of α-M2O3 on the outer oxide surface and a substantial slowing of the oxidation rate due to the low diffusivity in this phase.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 89-104 
    ISSN: 1573-4889
    Keywords: BaTiO3 ; kinetics ; solid state ; mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The authors propose a mechanism for the solid-solid reaction BaCO3+ TiO2→BaTiO3+CO2. This mechanism is based on the real structure of the present semiconductors. The reactions at different interfaces and the diffusing species are identified. The reaction rates are calculated and the dependence of the reaction rate upon O2, N2, and CO2 gas pressure is interpreted and discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 13 (1979), S. 119-158 
    ISSN: 1573-4889
    Keywords: nickel-chromium alloys ; oxidation ; high temperature ; kinetics ; mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of binary Ni-Cr alloys containing 44 and 50 wt. % Cr has been studied over a range of oxygen partial pressures at temperatures between 800 and 1100°C. The effects of cold work, surface preparation, and distribution of the Cr-rich second phase have been studied. The oxidation behavior is complex and cannot be described by a single model. The oxide grows by short-circuit diffusion as well as bulk transport through Cr 2 O 3 scales. The scale-growth mechanism includes extensive metal-oxide separation requiring Cr vapor transport to the scale, compressive stresses within the oxide which result in scale bulging and cracking, and the formation of a second oxide layer which results in voids being incorporated into the scale. Any factor which reduces the oxide grain size, such as cold work, finer distribution of the Cr-rich α phase or reduced oxygen pressure, results in an increased oxidation rate of binary alloys because of an increased number of grain-boundary short-circuit diffusion paths.
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  • 9
    ISSN: 1615-6110
    Keywords: Angiosperms ; Winteraceae ; Drimys s. str. ; D. brasiliensis (with subsp. and comb. nov.) ; D. roraimensis ; comb. nov. ; D. angustifolia ; Population variation ; eco-geographical differentiation ; epidermis ultrastructure ; Systematics and history of the S. American flora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Statistical analyses and scatter diagrams illustrate for the polymorphic E. and SE. BrazilianDrimys brasiliensis a clear correlation between morphological variation and eco-geographical differentiation. This is backed by data on the (ultra)structure of the lower leaf surface. A new infraspecific taxonomy is proposed, andD. roraimensis andD. angustifolia are recognized as distinct species of the Guyana Highlands and S. Brazil, respectively. The affinities between these and other taxa of the paleopolyploid genus, its evolution and its position within the family are discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 557-578 
    ISSN: 1573-8744
    Keywords: kinetics ; enzyme induction ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Equations were derived to describe the time course of drug levels during auto- and heteroinduction under a variety of input conditions. These equations were based on a pharmacokinetic theory of induction which assumes that metabolic clearance increases exponentially to a maximum value and that the rate of this increase is governed by the degradation rate constant of the induced enzyme (k′). Closed form solutions could be obtained only for intravenous single-dose (case I) and multiple-dose (case IV) administration. For each of the other cases, constant-rate intravenous infusion (case III), oral single-dose administration (case II), and multiple-dose administration (case V), an exact solution (not closed form) and an approximation (closed form) were derived. Two sets of equations were derived for each of the five cases to take into consideration the possibility of a latency term (λ).Plots of drug amount X(or concentration C) vs. time (t) were constructed. In case I, a log Xvs. tplot was convex, the slope increasing with time. In case II, Xincreased,reached a peak, and decayed as in case I. In case III (λ 〉 5In 2V/Q) Creached a preinduction steady state before decreasing to a lower (induced) steady state. When λ=0, Creached a maximum before decreasing to the same induced steady state. The behavior of Cvs. tfor cases IV and V was similar to that for case III. Determination of parameters was attempted in case III. Nonlinear least-square fitting of generated data with 3–9% error yielded reasonable estimates of k′.
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  • 11
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-03-30
    Description: Human erythrocytes have been freeze-fractured, and the polypeptides associated with the separate halves of the membrane bilayer have been analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The transmembrane proteins were differentially separated by the fracture process. Although sialoglycoproteins associated with the outer half of the membrane, the anion transport protein (band 3) mainly remained with the inner half of the membrane. Well-defined fragments of the sialoglycoproteins were produced by the freeze-fracture procedure, indicating that selected covalent bonds of these transmembrane proteins were broken.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Edwards, H H -- Mueller, T J -- Morrison, M -- New York, N.Y. -- Science. 1979 Mar 30;203(4387):1343-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/424755" target="_blank"〉PubMed〈/a〉
    Keywords: Erythrocyte Membrane/*ultrastructure ; Erythrocytes/*ultrastructure ; Freeze Fracturing/methods ; Glycoproteins/blood ; Humans ; Macromolecular Substances ; *Membrane Proteins/blood ; Molecular Weight ; Polylysine ; Protein Binding ; Protein Conformation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 12
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-11-30
    Description: The tertiary structures of all liganded hemoglobins in the R state differ in detail. Steric hindrance arising from nonbonded ligand-globin interactions affects the binding of ligands such as CO and cyanide which preferentially form linear axial complexes to heme; these ligands bind in a strained off-axis configuration. Ligands such as O2 and NO, which preferentially form bent complexes, encounter less steric hindrance and can bind in their (preferred) unstrained configuration. Linear complexes distort the ligand pockets in the R state (and by inference, in the T state) more than bent complexes. These structural differences between linear and bent complexes are reflected in the kinetic behavior of hemoglobin. Structural interpretation of this kinetic behavior indicates that the relative contributions of nonbonded ligand-globin interactions and nonbonded heme interactions to transition state free energies differ for linear and bent ligands. The relative contributions of these interactions to the free energy of cooperativity may also differ for linear and bent ligands. Thus the detailed molecular mechanism by which the affinity of heme is regulated differs for different ligands.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moffat, K -- Deatherage, J F -- Seybert, D W -- New York, N.Y. -- Science. 1979 Nov 30;206(4422):1035-42.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/493990" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Animals ; Heme/*metabolism ; Hemoglobins/metabolism ; Horses ; Kinetics ; Ligands ; Oxygen/*metabolism ; Oxyhemoglobins/*metabolism ; Protein Conformation ; Stereoisomerism ; Structure-Activity Relationship
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 13
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-04-27
    Description: Space-filling models of yeast hexokinase, adenylate kinase, and phosphoglycerate kinase drawn by computer clearly portray the bilobal character of these phosphoryl transfer enzymes, and the deep cleft which is formed between the lobes. A dramatic conformational change occurs in hexokinase as glucose binds to the bottom of the cleft, which causes the two lobes of hexokinase to come together. A substrate-induced closing of the active site cleft is postulated to occur in other kinases as well. This change may provide a mechanism by which some of these enzymes reduce their inherent adenosine triphosphatase activity and could be a general requirement of the kinase reaction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Anderson, C M -- Zucker, F H -- Steitz, T A -- New York, N.Y. -- Science. 1979 Apr 27;204(4391):375-80.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/220706" target="_blank"〉PubMed〈/a〉
    Keywords: Adenylate Kinase ; Binding Sites ; Catalysis ; Hexokinase ; Models, Molecular ; Phosphoglycerate Kinase ; *Phosphotransferases ; Protein Conformation ; Saccharomyces cerevisiae/enzymology ; Structure-Activity Relationship
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 14
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-04-20
    Description: Infrared absorption of purple membrane reveals an amide I frequency that falls outside the range normally found for alpha helices. This may indicate along with x-ray diffraction the existence of bacteriorhodopsin alpha helices with unusual structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rothschild, K J -- Clark, N A -- New York, N.Y. -- Science. 1979 Apr 20;204(4390):311-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/432645" target="_blank"〉PubMed〈/a〉
    Keywords: Amides ; *Bacteriorhodopsins ; *Carotenoids ; Deuterium ; Halobacterium/ultrastructure ; Membrane Proteins ; Protein Conformation ; Spectrophotometry, Infrared
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 15
    Publication Date: 1979-07-13
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Blundell, T L -- Hearn, L -- Tickle, I J -- Palmer, R A -- Morgan, B A -- Smith, G D -- Griffin, J F -- New York, N.Y. -- Science. 1979 Jul 13;205(4402):220.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/451597" target="_blank"〉PubMed〈/a〉
    Keywords: Crystallography ; *Endorphins ; *Enkephalins ; Protein Conformation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 16
    Publication Date: 1979-09-21
    Description: The bis-acridine ring system forms the basis for new biophysical probes of novel stereochemistry. Spectral data indicate that certain alkylene bridged bis-9-aminoacridines have a parallel plane conformation of predictable interplane distance. The parallel plane conformation is independent of solvent and thus is different from nucleic acid systems. This stable conformation allows these compounds to be used as sensitive "rulers" for describing binding site geometry in cholinergic enzymes and in the delineation of the mechanism of allosteric control in acetylcholinesterase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Himel, C M -- Taylor, J L -- Pape, C -- Millar, D B -- Christopher, J -- Kurlansik, L -- New York, N.Y. -- Science. 1979 Sep 21;205(4412):1277-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/472743" target="_blank"〉PubMed〈/a〉
    Keywords: *Acetylcholinesterase/metabolism ; *Acridines ; Binding Sites ; Kinetics ; Molecular Conformation ; Phosphorylation ; Protein Conformation ; Spectrophotometry, Ultraviolet
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 17
    Publication Date: 1979-01-12
    Description: Human and mouse hypoxanthine-guanine phosphoribosyltransferase subunits combine to form an active heteropolymer. Dimers form the basic subunit structure of the enzymes, yet the dimers can readily associate to form tetramers. The equilibrium between dimers and tetramers is significantly influenced by the ionic strength of the enzyme solvent.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Johnson, G G -- Eisenberg, L R -- Migeon, B R -- New York, N.Y. -- Science. 1979 Jan 12;203(4376):174-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/569362" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Line ; Female ; Genetic Linkage ; Humans ; Hybrid Cells/enzymology ; *Hypoxanthine Phosphoribosyltransferase/genetics ; Macromolecular Substances ; Mice ; Molecular Weight ; Protein Conformation ; X Chromosome
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 18
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1979-11-02
    Description: The absolute affinities of amino acid side chains for solvent water closely match their relative distributions between the surface and the interior of native proteins and are associated with a remarkable bias in the genetic code.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wolfenden, R V -- Cullis, P M -- Southgate, C C -- New York, N.Y. -- Science. 1979 Nov 2;206(4418):575-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/493962" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acids/*genetics ; *Genetic Code ; Mutation ; Protein Conformation ; Solubility ; Thermodynamics ; Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 19
    ISSN: 1432-1041
    Keywords: Theophylline ; kinetics ; apnea ; premature newborns ; developmental pharmacology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1–2 days, and 3 stayed below it. ‘Toxic’ blood levels (≥20 µg/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean : 27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.
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  • 20
    ISSN: 1573-4889
    Keywords: Cu-Si alloys ; oxidation ; kinetics ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of Cu-Si alloys (containing up to 4.75 wt. % Si) in $${\text{p}}_{O_2 } $$ =0.01 atm from 800 to 1000°C has been investigated using thermogravimetry and other techniques. A 0.04% Si alloy followed a parabolic oxidation law with a rate similar to that of pure Cu. As the Si concentration increased the rate decreased and became irregular owing to SiO2 particles or flakes at the alloy-scale interface. It is considered that sintering of SiO2 particles and rupture of the sinter because of contraction during sintering are responsible for the irregular kinetics. A SiO2 layer forms directly on the 4.75% Si alloy which oxidizes uniformly. The SiO2 was always amorphous. In pure CO2 a similar pattern of amorphous SiO2 particles, flakes, and layers occurs.
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  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 12 (1978), S. 215-225 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-Ni alloys ; kinetics ; scale morphology ; EPMA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of an Fe—19.34 wt. % Ni alloy in dry CO2 has been studied at 700—1000°C using thermogravimetry, metallography, and EPMA. Weight gains for oxygen consumption followed a linear-parabolic-linear sequence at all temperatures. During the initial linear stage the scale consisted mainly of magnetite and the activation energy of 133±25 kJ · mole−1 is considered to be due to dissociation of CO2 into CO and adsorbed oxygen on the outer magnetite surface. During the parabolic oxidation stage a continuous Ni-rich layer containing ∼ 70% Ni forms a barrier to the diffusion which has an activation energy of 192±79 kJ · mole−1. The breakdown of the barrier layer causes a return to linear kinetics with an activation energy of 138±42 kJ · mole−1 for dissociation of CO2 on the outer surface. During the final linear stage there is pronounced general and intergranular subscale formation. Detailed information is presented of the Ni redistribution and concentrations during oxidation and its correlation with the kinetics and morphology.
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Oxidation of metals 12 (1978), S. 67-82 
    ISSN: 1573-4889
    Keywords: oxidation ; Fe-C ; kinetics ; oxide grain size ; grain-boundary diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Fe-C alloys containing 0.1, 0.5, and 1.0% C were oxidized in 1 atm O2 at 500°C. Two specimen preparations were used: annealed followed by slow cooling to form coarse pearlite plus proeutectoid ferrite or cementite; and cold-worked by abrading after annealing. The cold-worked alloys oxidize more rapidly. Annealed pearlite oxidizes faster than annealed ferrite. The differences in oxidation rate are caused by differences in the Fe3O4 grain size, that is, by the number of oxide grain boundaries available to act as easy diffusion paths for the outward diffusion of Fe through the Fe3O4. The oxidation rate constant is 10 times larger for fine-grained poly crystalline oxide than for oxide in which the Fe3O4 is monocrystalline.
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 130 (1978), S. 203-207 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Caryophyllaceae ; Silene ; Chromosome numbers ; Flora of Greece ; Crete
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The chromosome numbers of several Greece species of the genusSilene L. from natural habitats are reported for the first time:S. sieberi, S. niederi, S. radicosa subsp.rechingeri, S. oligantha, S. skorpilii, S. schwarzenbergeri andS. fruticulosa. All species are diploid with 2n = 24 chromosomes, including 0, 2 or 4 SAT-chromosomes;S. niederi has B-chromosomes.
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  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 6 (1978), S. 389-397 
    ISSN: 1573-8744
    Keywords: probenecid ; methotrexate ; cerebrospinal fluid ; kinetics ; interaction ; dogs ; choroid plexus ; intrathecal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Probenecid is known to inhibit the renal excretion of methotrexate (MTX) and the transport of organic anions by the choroid plexus of the brain. The effect of probenecid on the CSF clearance of MTX given by the intrathecal route was examined in anesthetized dogs. Plasma and CSF MTX levels were measured following intrathecal injection of 0.4 mg/kg MTX, with and without pretreatment with probenecid. In the absence of probenecid, the peak plasma MTX concentration of 3.18×10−7±1.09×10−7 M (mean±SD) was reached 5 hr after intrathecal injection. With probenecid pretreatment, the mean peak plasma MTX concentration was lower (2.09×10−7+-0.98×10−7 M) and plasma disappearance was prolonged. A biexponential decay of CSF MTX levels was observed over the duration of sampling. The half-life of the second exponential phase was 21 hr without probenecid pretreatment and was longer after probenecid pretreatment. These results provide strong evidence that probenecid inhibits transfer of MTX from CSF to plasma following intrathecal injection.
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  • 25
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-07-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Marx, J L -- New York, N.Y. -- Science. 1978 Jul 21;201(4352):243-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/663653" target="_blank"〉PubMed〈/a〉
    Keywords: Ferritins ; Hemoglobins ; Ligands ; *Metalloproteins ; Molybdenum ; Nitrogenase ; Oxyhemoglobins ; *Particle Accelerators ; Protein Conformation ; Spectrophotometry, Atomic/methods
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-03-10
    Description: Incubation of ribonuclease with 0.1M mercaptoethanol at pH 8.5 can increase the enzyme's hydrolytic activity toward cytidine 2',3'-monophosphate (cyclic CMP) under standard assay conditions. Cation-exchange chromatography of the ribonuclease-thiol reaction mixture revealed seven fractions. The fraction with the highest activity had an approximate tenfold decrease in the apparent Michaelis constant for cyclic CMP with respect to native ribonuclease. The enhanced activity is a metastable property since this fraction reverts back to the control activity and chromatographic behavior of native ribonuclease on standing in solution at room temperature.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Watkins, J B -- Benz, F W -- New York, N.Y. -- Science. 1978 Mar 10;199(4333):1084-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/564548" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cattle ; Disulfides/pharmacology ; Enzyme Activation/drug effects ; Glutathione/pharmacology ; Kinetics ; Mercaptoethanol/*pharmacology ; Oxidation-Reduction ; Pancreas/enzymology ; Protein Conformation ; Ribonucleases/*metabolism ; Structure-Activity Relationship
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 27
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-06-02
    Description: Biological organization may be viewed as consisting of two stages: biosynthesis and assembly. The assembly process is largely under thermodynamic control; that is, as a first approximation it represents a search by each structural molecule for its state of lowest chemical potential. The hydrophobic effect is a unique organizing force, based on repulsion by the solvent instead of attractive forces at the site of organization. It is responsible for assembly of membranes of cells and intracellular compartments, and the absence of strong attractive forces makes the membranes fluid and deformable. The spontaneous folding of proteins, however, involves directed polar bonds, leading to more rigid structures. Intercellular organization probably involves polar bonds between cell surface proteins.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tanford, C -- New York, N.Y. -- Science. 1978 Jun 2;200(4345):1012-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/653353" target="_blank"〉PubMed〈/a〉
    Keywords: Cell Compartmentation ; Cells/*ultrastructure ; Chemistry, Physical ; Membrane Proteins ; Membranes/ultrastructure ; Micelles ; *Models, Biological ; Phospholipids ; Physicochemical Phenomena ; Protein Conformation ; Solubility ; *Thermodynamics ; Water
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  • 28
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-02-03
    Description: Small-angle x-ray and neutron diffraction patterns have been obtained from the annulus fibrosus of porcine intervertebral disk. These show that the collagen in this tissue is modified compared with that in tendon.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Berthet, C -- Hulmes, D J -- Miller, A -- Timmins, P A -- New York, N.Y. -- Science. 1978 Feb 3;199(4328):547-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/622556" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Collagen ; Glycosaminoglycans ; Intervertebral Disc/*ultrastructure ; Neutrons ; Protein Conformation ; Proteoglycans ; Scattering, Radiation ; Swine ; X-Ray Diffraction
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  • 29
    Publication Date: 1978-04-28
    Description: Succinyl derivatives of gramicidin were tested for their ability to form channels in planar artificial lipid bilayers. Both N-succinyldeformylgramicidin methyl ester and charged O-succinylgramicidin formed channels, but the channels had markedly different sizes and lifetimes. This implies that gramicidin forms channels by end-to-end association. However, the doubly charged N,O-bissuccinyldeformylgramicidin was inactive, which suggests that only end-to-end association of gramicidin may result in channel formation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bradley, R J -- Urry, D W -- Okamoto, K -- Rapaka, R -- New York, N.Y. -- Science. 1978 Apr 28;200(4340):435-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/77040" target="_blank"〉PubMed〈/a〉
    Keywords: Electric Conductivity ; *Gramicidin ; Hydrogen Bonding ; Ionophores ; Membranes, Artificial ; Protein Conformation ; Structure-Activity Relationship
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  • 30
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1978-09-29
    Description: Electrostatic effects dominate many aspects of protein behavior. When polypeptide chains fold up, most polar side chains seek the exterior, where they can be solvated. Water bound in the interior has been found between the domains of enzymes of the chymotrypsin family, and between the subunits of hemoglobin and tobacco mosaic virus protein. Assembly of this protein from disk to virus is triggered by electrostatic interactions between neighboring subunits. Lysozyme stabilizes the constellation of charges involved in the transition state of its substrate by both permanent and induced dipoles. All factors that lower the oxygen affinity of hemoglobin act by strengthening the salt bridges that constrain its quaternary deoxy (T) structure. Enzymes of thermophile bacteria owe their extra stability mostly to additional salt bridges. The rate of denaturation of hemoglobins by alkali is determined by the ionization of internal side chains with pK's of about 12.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perutz, M F -- New York, N.Y. -- Science. 1978 Sep 29;201(4362):1187-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/694508" target="_blank"〉PubMed〈/a〉
    Keywords: Allosteric Regulation ; Amino Acid Sequence ; Catalysis ; Ions ; Macromolecular Substances ; Protein Conformation ; Protein Denaturation ; *Proteins ; Salts ; Structure-Activity Relationship ; Temperature ; Viruses/ultrastructure ; Water
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  • 31
    Publication Date: 1978-01-20
    Description: Application of information derived from a three-dimensional model of vasopressin bound to its antidiuretic receptor has resulted in the design and synthesis of a potent analog, [1-deamino, 2-phenylalanine, 7-(3,4-dehydroproline)]-arginine vasopressin; this analog has a specific antidiuretic activity of 13,000 +/- 1,250 units per milligram; noteworthy at these doses is the absence of any detectable pressor activity. Three modifications based on conformational considerations were introduced into the vasopressin molecule in preparing the analog: (i) to enhance binding, a double bond was introduced into the side chain of an amino acid residue occupying a corner position of a beta turn in the vasopressin conformation, (ii) the hydroxyl moiety was deleted from Tyr2, and (iii) to tighten the backbone structure and to enhance the enzymatic resistance of the analog, the NH2-terminal amino group was deleted.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, C W -- Walter, R -- New York, N.Y. -- Science. 1978 Jan 20;199(4326):297-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/619455" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Deamino Arginine Vasopressin/analogs & derivatives ; Diuresis/drug effects ; Heart Rate/drug effects ; Protein Conformation ; Structure-Activity Relationship ; Vasopressins/*analogs & derivatives/pharmacology
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 32
    Publication Date: 1978-02-10
    Description: Covalent light chain dimers (L2) and cysteine-blocked L chain monomers readily react with partially reduced heavy (H) chains. A rapid disappearance of these blocked L chain species is followed by the appearance of covalent intermediates-HL, H2, and H2L-leading to fully assembled H2L2. The mechanism of initial disulfide bond formation between heavy and light chains is disulfide interchange.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kazin, A R -- Beychok, S -- New York, N.Y. -- Science. 1978 Feb 10;199(4329):688-90.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/415360" target="_blank"〉PubMed〈/a〉
    Keywords: Bence Jones Protein/metabolism ; Cysteine/metabolism ; Disulfides ; Humans ; *Immunoglobulin G/biosynthesis ; *Immunoglobulin Heavy Chains/biosynthesis ; *Immunoglobulin Light Chains/biosynthesis ; *Immunoglobulin gamma-Chains/biosynthesis ; *Immunoglobulin kappa-Chains/biosynthesis ; In Vitro Techniques ; Oxidation-Reduction ; Protein Conformation
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 33
    Publication Date: 1978-03-17
    Description: The conformation of [Leu5]enkephalin is produced by a Tyr-Gly-Gly-Phe beta bend stabilized by antiparallel hydrogen bonding between tyrosine and phenylalanine. On the basis of a comparison of the observed structure with the structure of known opiate agonists, three hydrophilic and two hydrophobic regions have been identified as contributing to the recognition of the molecule at the opiate receptor site.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Smith, D -- Griffin, J F -- New York, N.Y. -- Science. 1978 Mar 17;199(4334):1214-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/204006" target="_blank"〉PubMed〈/a〉
    Keywords: *Endorphins/metabolism ; *Enkephalins/metabolism ; Hydrogen Bonding ; Models, Molecular ; Morphine ; Protein Conformation ; Receptors, Opioid/metabolism ; Structure-Activity Relationship ; X-Ray Diffraction
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  • 34
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    Journal of solution chemistry 6 (1977), S. 203-216 
    ISSN: 1572-8927
    Keywords: Glucose ; kinetics ; mixed solvent ; kinetic isotope effect ; enthalpy of activation ; entropy of activation ; tetrahydrofuran ; tert-butanol ; mutarotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mutarotation rates of glucose in aqueous mixtures of tetrahydrofuran andtert-butanol in the mole fraction (xi) range 0〈xi〈0.2 have been measured at 5° intervals in the range 5–35°C. The kinetic deuterium isotope effects have been determined for the same solvent compositions at 25 and 35°C. A statistical analysis of the Arrhenius plots indicates that the experimental errors, although small, are too large for the establishment of any compensation behavior between ΔH
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  • 35
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    Oxidation of metals 11 (1977), S. 127-132 
    ISSN: 1573-4889
    Keywords: Duplex oxides ; copper oxidation ; kinetics ; oxygen partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The theory for the growth of a double oxide layer proposed by Yurek, Hirth, and Rapp, has been applied to copper using experimental rate-constant data obtained by Valensi. Calculated thicknesses of the layers agree very well with experimentally measured values.
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  • 36
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    Oxidation of metals 11 (1977), S. 225-239 
    ISSN: 1573-4889
    Keywords: tantalum ; oxidation ; high temperature ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of tantalum in oxygen-nitrogen and oxygen-inert gas mixtures at925°C has been studied. The oxygen pressure was close to 0.5 atm in all experiments, and partial pressures of the second component of from 0 to 180 Torr were employed. Spherical specimens were used to provide quantitatively significant kinetic data. A model has been proposed which suggests that the oxygen pressure at the reaction interface close to the metal surface is lower than the external pressure because of the finite permeability of the porous outer oxide layer, and that the inert gas effectively reduces the permeability. The model gives good quantitative agreement with the experimental results.
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  • 37
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    Oxidation of metals 11 (1977), S. 365-381 
    ISSN: 1573-4889
    Keywords: cobalt oxidation ; kinetics ; parabolic rate constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Precise values of parabolic rate constants of cobalt oxidation have been determined over a wide range of temperature (950–1300°C) and oxygen pressure (6.58× 10−4−0.658 atm). The dependence of the calculated values of parabolic rate constants k″p on oxygen pressure and temperature can be described by the following empirical equation: $$k''_p = const. \cdot {\text{p}}_{O_2 }^{{\text{1/n}}} \cdot exp ( - {\text{E}}_{\text{k}} /RT)$$ The exponent 1/n decreases with an increase in temperature from 1/3.40 at 950°C to 1/3.96 at 1300°C, whereas the activation energy Ek decreases with an increase in the oxygen pressure from 41.7 to 38.1 kcal/mole.
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  • 38
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    Oxidation of metals 11 (1977), S. 263-276 
    ISSN: 1573-4889
    Keywords: nickel ; sulfidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The reaction between pure nickel and H2S-H2 mixtures containing 1–65% H2S has been studied over the temperature range 450–600°C. The sulfidation of nickel in the temperature range 560–600°C has been found to follow a linear rate law at low concentrations of H2S and a parabolic rate law at higher concentrations (10% and 65% H2S); X-ray examination of the scale formed on the metal showed it to be almost entirely β-Ni3S2. On the basis of the kinetics and marker studies it can be concluded that the sulfide scale on nickel is formed by the outward transport of the metal and the inward transport of sulfur. In the temperature range 450–500°C the sulfidation of nickel follows a parabolic rate law. In mixtures containing 10% H2S the scale formed contains voids, the occurrence of which is connected with formation of Ni7S6. It has also been shown that the rate of transport through the Ni3S2 layer has an essential influence on the formation of a continuous layer of Ni7S6. Marker studies have shown that both nickel and sulfur appear to be mobile in β′-Ni3S2.
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  • 39
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    Journal of pharmacokinetics and pharmacodynamics 5 (1977), S. 183-192 
    ISSN: 1573-8744
    Keywords: propranolol ; kinetics ; volunteers ; bioavailability ; threshold dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of propranolol in blood was studied in healthy volunteers, following intravenous administration of 0.1 mg/kg and increasing oral doses of 10,20, and 40 mg, using a specific and sensitive gas Chromatographie method. The systemic availability of orally administered propranolol varied from 9% to 38% between subjects, but it was constant within each subject. A linear relationship was found between the area under the blood concentration-time curve and the oral dose. At variance with literature data, we could not observe a threshold dose.
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  • 40
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    Journal of solution chemistry 5 (1976), S. 163-169 
    ISSN: 1572-8927
    Keywords: Solvent effects ; tetramethylurea ; hydrolysis ; hydrogen bonding ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetramethylurea was hydrolyzed in aqueous hydrochloric acid at temperatures of 80, 90, and 100°C. All reactions were carried out in an excess of both tetramethylurea and water, with first-order dependence on acid concentration being observed. As the concentration of water was increased, the rate of hydrolysis decreased until equimolar amounts of water and tetramethylurea were present. Subsequent addition of water had no effect on the observed rate.
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  • 41
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    European journal of clinical pharmacology 10 (1976), S. 43-48 
    ISSN: 1432-1041
    Keywords: Spironolactone ; acetylsalicylic acid ; fludrocortisone ; kinetics ; pharmacology ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of 600 mg acetylsalicylic acid (ASA) on the renal excretion and clearance of canrenone, the principal unconjugated metabolite of spironolactone, was examined in a double-blind crossover study in six healthy subjects. ASA significantly reduced the urinary excretion, and the fractional excretion, of canrenone between 4 — 6 hours after administration of 50 mg spironolactone. The pharmacological activity of spironolactone, assessed simultaneously by alterations in fludrocortisone-induced urinary electrolyte changes, was slightly but not significantly reduced. The reductions in urinary canrenone excretion correlated with changes in the urinary log 10 Na/K ratio. The results suggest that canrenone may be actively secreted at the proximal renal tubule, and that secretion is blocked by ASA or its conjugates. This is a possible mechanism for the pharmacological interaction between ASA and spironolactone which has been described previously.
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  • 42
    ISSN: 1573-4889
    Keywords: tantalum alloy ; oxygen ; dissolution ; kinetics ; oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Oxygen was added to T-111 (Ta-8W-2Hf, wt.%) at 820 and 990°C at an oxygen pressure of about 3×10−4 Torr (4×10−2N/m2). The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at% oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990°C. The vaporization of WO3 has no apparent affect on the doping reaction.
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  • 43
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    Oxidation of metals 10 (1976), S. 85-95 
    ISSN: 1573-4889
    Keywords: boron carbide ; oxidation ; kinetics ; chromatography method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermogravimetry and gas-adsorption chromatography were used to study the kinetics of formation of solid and gaseous products during the hightemperature oxidation of compact boron carbide in oxygen at 740 Torr. Oxidation resistance was observed at temperatures up to 1200°C. The main oxidation products were B2O3 and CO2. Oxidation was paralinear; the carbon consumption exceeded the consumption of boron as compared to the ratio of these elements in the compound B4C. This difference resulted in carbon depletion of the carbide layer in the substrate near the scale〉.
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  • 44
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    Oxidation of metals 10 (1976), S. 361-376 
    ISSN: 1573-4889
    Keywords: metals ; scale structure ; epitaxy ; kinetics ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An explanation of the deviation from the parabolic law is the treatment which considers both shortcircuit and lattice diffusion in the oxide scale. In this study we examine how the oxidation kinetics are influenced by changing the structure of the scale of copper oxide in order to confirm the role of short-circuit diffusion in determining the oxidation rate. In addition we explain the oxidation kinetics of copper and nickel by using a model of the scale structure which includes recrystallization and grain growth. Results are as follows: (1) The nucleation and growth behavior of oxide have a direct effect on the structure and in turn the oxidation kinetics due to short-circuit diffusion. (2) A modified treatment is valid in the region where volume diffusion and short-circuit diffusion play an important role in which it is necessary to consider the scale structure such as the grain size distribution and the boundary width. (3) When recrystallization takes place it is necessary to consider the model of a two-layered scale structure which is different in properties and morphology. (4) In this region the rate curves are S-shaped when oxide recrystallization takes place and exhibit a transition from a parabolic to an nth-power relationship (n〉2) when grain growth takes place.
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  • 45
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    Oxidation of metals 10 (1976), S. 97-103 
    ISSN: 1573-4889
    Keywords: silicon carbide ; oxidation ; molecular oxygen ; glow-discharge oxygen plasma ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics and structure of the oxide scales formed on high-density SiC were studied in molecular oxygen at 740 Torr and in a glow-discharge oxygen plasma at 0.1 Torr at temperatures of 1000, 1100, and 1200°C. The monatomic oxygen formed by the glow discharge markedly increased the reaction rate and the vaporization of some of the oxidation products. The marked differences in kinetics suggest that the rate-controlling step during oxidation in molecular oxygen is the dissociation of adsorbed diatomic oxygen to the monatomic species. Films formed in molecular oxygen were mostly amorphous SiO2 with small inclusions of SiC and graphite, whereas films formed in dissociated oxygen were primarily amorphous SiO2 containing SiO, S2O3, and the coesite form of SiO2.
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  • 46
    ISSN: 1573-4889
    Keywords: kinetics ; oxidation ; microcalorimetry ; thermogravimetry
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    Notes: Abstract In the kinetic theories of Bodenstein or Semenov the expression for the rate of a chemical reaction with several elementary stages can be expressed by different physical parameters. If two experimental methods are used, one method of necessity being microcalorimetry to measure the thermal flux produced by the reaction, it is possible to distinguish a pure kinetics case from a mixed one. The two-method technique has been verified by a study of the oxidation of niobium.
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  • 47
    ISSN: 1573-4889
    Keywords: titanium ; nitridation ; kinetics ; diffusion ; scaling
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    Notes: Abstract The nitridation behavior of titanium has been examined in an atmosphere of nitrogen over the temperature range 900–1000° C. In addition to determining the reaction kinetics, microhardness and metallographic studies have been carried out on the nitrided substrates and nitride scales. Overall parabolic kinetics were exhibited, while a linear scaling reaction (associated principally with Ti2N formation) was observed. Extensive dissolution of nitrogen in the substrate was evident from the microhardness studies, and at 950 and 1000° C the growth of the nitrogen-stabilized αTi phase layer followed a parabolic law. Consideration of all the observed processes and derived data suggested that diffusion of nitrogen in the metal substrate was probably the rate-controlling mechanism.
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  • 48
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    Oxidation of metals 9 (1975), S. 459-472 
    ISSN: 1573-4889
    Keywords: Cr ; oxidation ; kinetics ; Cr2O3 grain size ; short-circuit diffusion ; surface ; preparation ; Fe-Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cr was oxidized in 1 aim O2 at 980, 1090, and 1200°C. ElectropolishedCr and some orientations of etched Cr oxidize rapidly and develop compressive stress in the growing Cr2O3; other orientations oxidize slowly, apparently free of stress. SEM examination of fracture sections shows that the thick oxide is polycrystalline whereas the thin oxide on etched Cr is monocrystalline. It is deduced that the monocrystalline oxide grows by lattice diffusion of cations outward, and the polycrystalline layer by the two-way transport of cation diffusion outward and anion diffusion inward along oxide grain boundaries. The consequent formation of oxide within the body of the polycrystalline layer generates compressive stress and leads to wrinkling by plastic deformation. The activation energy for oxidation of Cr by cation lattice transport is 58 kcal/mole. Polycrystalline Cr2O3 forms on Fe-26Cr alloy, whether electropolished or etched; oxidation is accordingly rapid and accompanied by compressive stress.
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    Oxidation of metals 9 (1975), S. 357-365 
    ISSN: 1573-4889
    Keywords: kinetics ; zirconia ; defect structure ; ionic conductivity ; yttria dopant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A Zr-0.5 Y alloy was found to oxidize about 6 times faster than pure zirconium over the temperature range of 400 to 565°C. The activation energies were nearly identical (∼32 kcal/mole). The activation energies correspond to grain boundary diffusion of oxygen through the scale. The higher oxidation rate of the alloy was attributed to a higher anion vacancy concentration and the assumption that diffusion sites in the lattice and boundaries were in local equilibrium. Measurements on yttria-doped zirconia showed that ionic conductivity was increased markedly by yttrium and extended over a wide range of oxygen pressure. The defect structure of the doped oxide was changed to one of oxygen vacancies, even at the high end of the oxygen pressure range, 10−8 to 0.2 atm, over which pure ziconia contains oxygen interstitials. The doped oxide was found to be extrinsic over the entire range of oxygen pressure and, although ionic conductivity predominated, electronic conductivity was still appreciable. The electronic conductivity, however, was still sufficiently high so that electron transport was not rate-controlling in the predominantly ionic-conducting scale.
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  • 50
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    Oxidation of metals 9 (1975), S. 99-116 
    ISSN: 1573-4889
    Keywords: oxidation ; kinetics ; ilmenite ; rutile ; pseudobrookite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of ilmenite (FeTiO3) in air and dry oxygen was investigated over the temperature interval 600 to 970°C. Dense platelets of ilmenite crystals as well as powder samples of ilmenite were oxidized. The weight data were recorded employing a thermobalance. The oxidation kinetics of ilmenite platelets were parabolic except for the initial stages during which logarithmic kinetics were observed. For powder samples the logarithmic rate law was followed primarily. The logarithmic rate law was attributed to free penetration of oxygen through cracks and short-circuit paths. The activation energies associated with the logarithmic rate law were nearly one-half of those obtained from parabolic oxidation. The growth morphology of the products of oxidation of ilmenite was observed with a scanning electron microscope. The effect of growth morphology on the kinetics is discussed, and a probable reaction mechanism is suggested for the oxidation of ilmenite.
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  • 51
    ISSN: 1573-4889
    Keywords: kinetics ; cobalt and nickel oxidation ; parabolic rate constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new fast method is proposed for the determination of parabolic rate constants of metal oxidation as a function of pressure and temperature. The method consists of determining rate constants by oxidation of a single metal sample in a continuous manner, periodically changing the oxidant pressure or temperature. This method eliminates a number of errors inherent in the classical method which involves the use of a new metal specimen in each experiment and it further shortens the time of evaluating the functions k p '' = f (p, T). The method is particularly suitable for the determination of rate constants of slow processes. To verify the proposed method measurements of the kinetics of oxidation of cobalt and nickel at different oxygen pressures over the temperature range 1000–1300° C were carried out.
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  • 52
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    Plant systematics and evolution 123 (1975), S. 107-115 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Asteraceae ; Centaurea ; Chromosome numbers ; Flora of the Mediterranean and C. Europe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The chromosome numbers of several Mediterranean and Central European species from the genusCentaurea L. have been studied. The material was collected in natural habitats, exceptC. thracica andC. maxima. The numbers forC. cineraria (2n = 36; tetraploid!),C. subtilis (2n = 22),C. sonchifolia (2n = 44),C. sphaerocephala (2n = 44),C. napifolia (2n = 22),C. achaia (2n = 22),C. thracica (2n = 18), andC. maxima (2n = 28) are reported for the first time. For the following species earlier counts are confirmed:C. cineraria (diploid, 2n = 18),C. maculosa (2n = 18),C. rhenana (2n = 18),C. triumfettii (2n = 22 + 0−1 B; first report of accessory chromosome for this species),C. scabiosa (2n = 20 + 0−3 B),C. crassifolia (2n = 30). B-chromosomes are reported for 3 populations ofCentaurea scabiosa from Berlin; they lack in 2 populations from Bayern and Hessen.
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  • 53
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    Journal of pharmacokinetics and pharmacodynamics 3 (1975), S. 277-290 
    ISSN: 1573-8744
    Keywords: sulfobromophthalein (BSP) ; kinetics ; BSP disposition ; mathematical model ; flow-limited
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A linear, flow-limited mathematical model of drug kinetics was used to simulate total sulfobromophthalein (BSP) kinetics in normal anesthetized rats during intravenous infusions and following rapid intravenous injections. Four parameters were used to characterize the distribution and biliary and urinary excretion of BSP: liver- to- plasma concentration ratio, extrahepatic tissue- to- plasma concentration ratio, liver clearance rate constant, and renal plasma clearance rate constant. The same parameters appear to characterize the kinetics of BSP in man through the successful application of “scale- up” techniques utilizing data from experiments in rats. Plasma levels of BSP corresponding to intravenous infusions and rapid intravenous injections in man are approximated by computer simulation.
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    Journal of solution chemistry 3 (1974), S. 881-887 
    ISSN: 1572-8927
    Keywords: Binary aqueous mixtures ; solubilities ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A treatment which predicts the solubilities of gases in solvent mixtures is examined in the context of the analysis of kinetic data for reactions in aqueous mixtures. The treatment is qualitatively successful to some extent in resolving the effects of changes in the initial state of the reacting substrate in the activation parameters.
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    Biochemical genetics 12 (1974), S. 69-79 
    ISSN: 1573-4927
    Keywords: l-glycerol 3-phosphate dehydrogenase, purified ; inbred mice ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract l-Glycerol 3-phosphate dehydrogenase (E.C. 1.1.1.8) was purified from the muscle of BALB/cJ and C57BL/6J mice. The half-lives of the enzyme at 50 C were 6 and 33 min, respectively, for the BALB/cJ and C57BL/6J strains. Enzyme preparations from the two strains of mice were compared with respect to the following properties and found to be essentially indistinguishable: K m values for dihydroxyacetone phosphate, NADH, l-α-glycerophosphate, and NAD+; maximum velocity; competitive inhibition by inorganic phosphate; pH optimum; energy of activation; electrophoretic mobility; molecular weight and subunit molecular weight. From these data, it is concluded that the kinetic properties of the purified enzyme are not the factors responsible for the differences in activity found in crude homogenates of mouse tissues.
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  • 56
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    Oxidation of metals 8 (1974), S. 379-391 
    ISSN: 1573-4889
    Keywords: oxidation ; sulfidation ; kinetics ; parabolic rate law
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The conditions necessary to determine the oxidation kinetics of metals and alloys are discussed quantitatively, and a new method of calculating the rational rate constants was suggested. It was shown that the size and the shape of a metal sample has an effect on the kinetics of oxidation. Further, it was established that the values of the parabolic rate constants of corrosion, calculated from the empirical Pilling and Bedworth equation, contain a serious systematic error, if changes in the metallic core surface area during the oxidation process are neglected.
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  • 57
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    Biochemical genetics 11 (1974), S. 309-317 
    ISSN: 1573-4927
    Keywords: genetics ; rat ; kinetics ; brain MAO ; serum ChE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This study was performed in order to delineate differences in kinetic enzyme characteristics of brain monoamine oxidase (MAO) and plasma cholinesterase (ChE) derived from the Walker-Walker (Fawn Hooded, FH) rat and from its putative ancestors, the Wistar (W) and Long-Evans (LE). As compared with the enzyme isolated from the other two strains, brain MAO from FH has both a higher V max and increased reaction rate at lower substrate concentrations. It may thus be described as a “more efficient” enzyme. This study confirms previous work which shows that plasma ChE activity of females is higher than that of males. Fluoride ion is a noncompetitive inhibitor of the Wistar ChE, is a competitive inhibitor of the FH enzyme, and has no effect on the LE enzyme. Dibucaine is a competitive inhibitor in all cases except one: ChE derived from the FH female is uncompetitively inhibited. A comparison of the inhibitor constants shows that FH ChE is more resistant to Dibucaine than is that of W, and that LE is the most sensitive. FH cholinesterase is twice as resistant to the action of fluoride as is the Wistar enzyme.
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  • 58
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    Journal of pharmacokinetics and pharmacodynamics 2 (1974), S. 313-335 
    ISSN: 1573-8744
    Keywords: subcutaneous ; absorption ; kinetics ; local anesthetics ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The subcutaneous absorption kinetics of a homologous series of local anesthetics and lidocaine were studied under controlled pH conditions using a previously described in vivorat model. All local anesthetics exhibited biexponential absorption profiles suggesting accumulation into a tissue compartment. Evidence supporting this hypothesis was supplied by back-extraction of lidocaine from subcutaneous tissue into an acidic environment, by multiple dosing experiments, and by movement of compound into subcutaneous tissue of a postmortem rat preparation. A series of interanimal relationships were demonstrated between structure and parameters of a twocompartment open model. Particularly striking were the correlations between in vivopartition and tissue clearance and the octanolwater (pH 7.95)partition coefficients.
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    Journal of solution chemistry 2 (1973), S. 217-238 
    ISSN: 1572-8927
    Keywords: Cation ; energies ; H. S. Frank ; M. Eigen ; R. G. Wilkins ; kinetics ; ligand substitution ; mechanism ; mixed solvents ; nonaqueous ; solvation ; solvent ; solvent structure ; solvent exchange ; transition metal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The role of the solvent in reactions involving ions is considered in relation to the structure of liquids. The rate constants and activation parameters for ligand substitutions at divalent transition metal cations in various solvents are compared with those for solvent exchanges. The differences are related to structural properties of the solvents, represented by their heats of evaporation and fluidities, and interpreted with the aid of a model developed from that of Frank and Wen. Water is not a typical solvent.
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    European journal of clinical pharmacology 5 (1972), S. 111-115 
    ISSN: 1432-1041
    Keywords: Rifampicin ; kinetics ; multicompartmental analysis ; simultaneous serum urine and bile assessment ; one week treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To aid interpretation of the fall in the serum concentrations of rifampicin observed in the early phase of continuous treatment, the distribution of the antibiotic was assessed simultaneously in the serum, bile, and urine of patients treated for one week. Transfer constants between these compartments were calculated on the 1st and 7th day of treatment by multicompartmental kinetic analysis. — The results obtained suggest that the decrease in serum concentrations is due to enhanced biliary excretion; no significant change was observed in the amount of antibiotic excreted in the urine. The increased capacity of the liver to excrete rifampicin in bile might result from enzyme induction by the antibiotic in hepatocytes.
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