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  • kinetics  (107)
  • Springer  (107)
  • American Meteorological Society
  • Institute of Physics
  • 1995-1999  (70)
  • 1990-1994  (37)
  • 1940-1944
  • 1996  (70)
  • 1994  (37)
Collection
Keywords
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  • Springer  (107)
  • American Meteorological Society
  • Institute of Physics
  • Wiley-Blackwell  (58)
Years
  • 1995-1999  (70)
  • 1990-1994  (37)
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    The kinetics of the solvolysis of chloropentacyanocobaltate(III) ions in water containing 2-methoxyethanol or diethylene glycol: A contrast with the effect of more hydrophobic cosolvents (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 1089-1100 
    Details
    ISSN: 1572-8927
    Keywords: Solvolysis ; kinetics ; aqueous solvent mixtures ; Co(III) complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the solvolysis of [Co(CN)5Cl]3− have been investigated in water +2-methoxyethanol and water + diethylene glycol mixtures. Although the addition of these linear hydrophilic cosolvent molecules to water produces curvature in the variation of log(rate constant) with the reciprocal of the dielectric constant, their effect on the enthalpy and entropy of activation is minimal, unlike the effect of hydrophobic cosolvents. The application of a Gibbs energy cycle to the solvolysis in water and in the mixtures using either solvent-sorting or TATB values for the Gibbs energy of transfer of the chloride ion between water and the mixture shows that the relative stability of the emergent solvated Co(III) ion in the transition state compared to that of Co(CN)5Cl3− in the initial state increases with increasing content of cosolvent in the mixture. By comparing the effects of other cosolvents on the solvolysis, this differential increase in the relative stabilities of the two species increases with the degree of hydrophobicity of the cosolvent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00976258
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  • 2
    Electronic Resource
    Electronic Resource
    Thermodynamics of coupled reactions by the method of dynamic titration: the Nickel(II)-salicylate ion system (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 483-500 
    Details
    ISSN: 1572-8927
    Keywords: Thermodynamics ; kinetics ; chemical relaxation ; temperature-jump ; amplitudes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amplitudes of chemical relaxation signals can provide useful information as to the thermodynamics of coupled chemical reactions. The temperature-jump technique has been used to investigate the thermodynamic behavior of the Nickel(II)-3,5-dinitrosalicylate system in buffer solution, where complex formation steps are coupled to proton transfer steps. The analysis of the relaxation curves is based on the transformation of a set of coupled elementary reactions into a set of uncoupled ‘normal reactions.’ By analogy with classical titrations, the experiments have been performed by changing the metal ion concentration at constant ligand concentration and pH. Each measured amplitude is associated in this way to a point of a ‘dynamic titration’ and a procedure is formulated by which the values of the equilibrium constants and enthalpies of the normal reactions are simultaneously obtained by simple linear plots. From the dependence of these parameters on suitable functions of the concentrations of the reactants the values of ΔG° and ΔH° of the individual steps are derived. It is shown that the addition of a buffer (instead of an indicator) influences the stoichiometric coefficients of the normal reaction in such a way that measurable amplitudes are produced in systems that, as the presently investigated, in unbuffered solution would remain insensitive to the external perturbation. The circumstances under which the dynamic method offers advantages over the classical techniques are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00972614
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  • 3
    Electronic Resource
    Electronic Resource
    Frequency response analysis of a closed diffusion cell with two resonators (1996)
    Springer
    Adsorption 2 (1996), S. 265-277 
    Details
    ISSN: 1572-8757
    Keywords: frequency response ; diffusion cell ; kinetics ; diffusion ; heat effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This paper deals with frequency response (FR) analysis of a closed diffusion cell system with two resonators, that is both the LHS and RHS volumes are modulated. The analysis is made for a homogeneous particle described by a single effective diffusivity as well as a biporous pellet described by macropore and micropore diffusions. It is shown that if the perturbation of the volume of the reservoir #2 is lagged behind that of the reservoir #1 by 3π/2, the pressure response in reservoir #1 is significantly enhanced with larger amplitude as well as phase angle. When the perturbations of the two reservoirs are out of phase, the heat effect is reduced and can become insignificant when the two perturbations are completely out of phase (ψ = π). Under such a condition, the pressure difference between the two reservoirs could be doubled. In the case of biporous pellets, it is shown that the FR behaviours obtained for micropore diffusion control and macropore diffusion control are well distinguished. In the former case, the FR system reduces to a traditional batch adsorber one while in the latter case, the FR behaviour is the same as for a two resonator system with homogeneous particles. This difference can be used for the discrimination of micropore and macropore diffusion processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879541
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  • 4
    Electronic Resource
    Electronic Resource
    The dissociation kinetics of H2S over an alumina supported Co-Mo sulphide catalyst (1996)
    Springer
    Catalysis letters 37 (1996), S. 167-172 
    Details
    ISSN: 1572-879X
    Keywords: dissociation ; kinetics ; Co-Mo sulphide ; H2S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, a high surface area 4Co∶6Mo∶100γ-Al2O3 sulphide prepared using precipitation from homogeneous solution (PFHS) has been used for the catalytic splitting of hydrogen sulphide into H2 and elemental sulphur. The activity of this new formulation was significantly better than previously reported recipes. Kinetic data collected over a wide range of H2S partial pressures between 883 and 983 K revealed that, although the decomposition followed a first-order law, a mechanism involving H2S adsorption on co-ordinative unsaturation sites of the Co-Mo sulphide catalyst gave a Langmuir-Hinshelwood rate expression that yielded satisfactory model parameters. In particular, the scission of the surface H-S bond appeared to be the rate determining step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807749
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  • 5
    Electronic Resource
    Electronic Resource
    Kinetics and mechanisms of the low-temperature degradation of cellulose (1994)
    Springer
    Cellulose 1 (1994), S. 26-56 
    Details
    ISSN: 1572-882X
    Keywords: low-temperature degradation ; kinetics ; mechanisms ; electrical insulation ; transformers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A critical review is given of the degradation of cellulose in the low-temperature region (below about 300°C) of power transformer operation. The large number of kinetic studies, under a variety of environmental conditions from Kraft paper in insulating oil, to cotton and paper in oxygen, are considered in terms of a first-order polymer chain scission model. In many cases, the data are replotted to suit the model. A common activation energy of 111±6 kjmol−1 is calculated and it is shown that the pre-exponential factor, rather than the activation energy, is sensitive to the oxidizing nature of the environment and the susceptibility to degradation of the material. The chemical mechanisms of degradation are reviewed, and conclusions and recommendations are made regarding chemical condition monitoring and life prediction of electrical insulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00818797
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of potassium on the high pressure kinetics of ammonia synthesis over fused iron catalyst (1996)
    Springer
    Catalysis letters 37 (1996), S. 173-179 
    Details
    ISSN: 1572-879X
    Keywords: ammonia synthesis ; iron catalysts ; potassium promotion ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Measurements were performed of reaction rate in the process of ammonia synthesis (T=370–470°C) on doubly promoted (DP) (Al2O3, CaO) and triply promoted (TP) (K2O, Al2O3, CaO) iron catalysts. The latter were obtained by impregnation of the reduced and subsequently passivated DP precursors with alcoholic solution of KOH. The studies were carried out under high total pressure (10 MPa) in a wide range of ammonia partial pressure in the gas phase: from 0.25 to about 7 bar. The results are shown to be authoritative for the so-called kinetic regime. The effect of the presence of K+ cations in the catalyst was the stronger, as the temperature of the reaction was the lower and, in particular, the ammonia pressure in the gas phase the higher. The obtained results are in good accordance with the results of Somorjai's studies on activity of iron single crystal surfaces both clean and covered with (K+O) adlayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807750
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation of carbidic carbon on a rhodium surface (1994)
    Springer
    Catalysis letters 27 (1994), S. 79-90 
    Details
    ISSN: 1572-879X
    Keywords: kinetics ; carbon ; oxygen ; recombination ; rhodium ; surface characterisation ; XPS ; AES
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different mechanisms of atomic carbon and oxygen recombination on a rhodium surface are studied with Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The kinetics of adsorbed carbidic carbon oxidation (carbon coverageθ c ≈ 0.1–0.3 ML) by gas-phase oxygen that proceeds by a Langmuir-Hinshelwood reaction mechanism, provides the value of the activation energy for recombination (E rec ⇂t ≈ 170±20 kJ/mol).E rec ⇂t depends slightly on the carbon coverage. An Eley-Rideal type of reaction was observed for adsorbed oxygen and atomic gas-phase carbon recombination which occurs in a dynamic regime. The low value found for the activation energy (near zero) is consistent with the mechanism that this exothermic reaction is too fast for energy dissipation into the substrate; the energy is mainly transferred into translational, vibrational and rotational energy of CO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806980
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  • 8
    Electronic Resource
    Electronic Resource
    Prediction of paper permanence by accelerated aging II. Comparison of the predictions with natural aging results (1996)
    Springer
    Cellulose 3 (1996), S. 269-279 
    Details
    ISSN: 1572-882X
    Keywords: accelerated tests ; aging tests ; cellulose degradation ; durability ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Accelerated aging tests are credible and useful to predict paper permanence only if such tests can be shown to correlate with natural aging. In the first part of this study, a kinetic model was developed based on the accelerated aging results. In this report, we have shown that this kinetic model can indeed predict the natural aging results of lignin-free sheets with a statistical confidence. This is the first quantitative comparison of accelerated aging with natural aging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02228806
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  • 9
    Electronic Resource
    Electronic Resource
    Prediction of paper permanence by accelerated aging I. Kinetic analysis of the aging process (1996)
    Springer
    Cellulose 3 (1996), S. 243-267 
    Details
    ISSN: 1572-882X
    Keywords: aging tests ; cellulose degradation ; durability ; kinetics ; paper properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The validity of accelerated aging tests to predict and rank papers on their permanence has been under question, preventing the development of performance-based standards for permanent paper. We conducted a general kinetic analysis to investigate the aging process of paper. A general kinetic model is proposed to describe the depolymerization of cellulose. Experimentally it was shown that in the case of aging, cellulose degradation follows classic first-order kinetics as a special case of our general kinetic model. The Arrhenius equation was critically re-examined for the case of a multiple reaction system. It was shown analytically that the Arrhenius equation is still applicable when certain conditions are met. This was convincingly supported by experimental results. We also analysed the dependence of the degradation rate on the moisture content and hydrogen ion concentration. By conducting systematic experiments on these two factors, a general and quantitative relationship was established to explain the contribution of each factor and their interactions. Finally, based on this kinetic analysis, the effects of storage conditions on the life expectancy of paper were estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02228805
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  • 10
    Electronic Resource
    Electronic Resource
    Dynamics and self-organization of catalytic systems (1994)
    Springer
    Topics in catalysis 1 (1994), S. 305-314 
    Details
    ISSN: 1572-9028
    Keywords: non-Langmuir ; kinetics ; non-linear dynamics ; oscillations ; chaos ; self-organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of a catalytic reaction is frequently formulated in terms of simple concepts of the Langmuir type. Apart from limitations arising from the non-uniformity of the catalyst's surface and from the coverage dependence of the rate “constants”, several other complications may come into play. These may arise on the “quantum level” where energy flow between the various degrees of freedom may cause failure of simple transition state theory, as well as on the “continuum level” where formulation of rate equations in terms of coupled non-linear differential equations may give rise to a rich scenario of spatio-temporal self-organization, including kinetic oscillations, chaos, and formation of concentration patterns. Several of these phenomena are illustrated by selected examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01492284
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  • 11
    Electronic Resource
    Electronic Resource
    The influence of sulfur dioxide on propane oxidation activity over supported platinum and palladium (1994)
    Springer
    Catalysis letters 30 (1994), S. 41-51 
    Details
    ISSN: 1572-879X
    Keywords: propane ; oxidation ; platinum ; palladium ; sulfur dioxide ; alumina ; zirconia ; activity ; acidity ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Earlier studies have shown that sulfur dioxide and metal-support interaction can strongly influence propane oxidation over platinum. In particular, oxidation activity is enhanced when platinum is supported on sulfated γ-alumina or zirconia compared to γ-alumina. Therefore, it is of interest to compare the performance of palladium under the same experimental conditions. Four model catalysts were examined: Pt/γ-alumina, Pt/zirconia, Pd/γ-alumina and Pd/zirconia. The metal loading was kept at or below 0.05 wt% to emphasize changes in activity attributable to metal-support interaction. Reaction rates were measured with and without sulfur dioxide. Surface sulfation was analyzed by measuring acid strength and evaluating spectra obtained by Fourier-transform infrared spectroscopy. In contrast to platinum, sulfation does not promote propane oxidation on Pd/γ-alumina, and Pd/zirconia is less active than Pd/γ-alumina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813671
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  • 12
    Electronic Resource
    Electronic Resource
    Non-uniform surface kinetics with two types of sites: the case of ethanol oxidation on molybdenum oxide (1996)
    Springer
    Catalysis letters 39 (1996), S. 67-71 
    Details
    ISSN: 1572-879X
    Keywords: non-uniform surface ; kinetics ; ethanol ; oxidation ; molybdenum oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Temkin's theory of rates of catalytic reactions on non-uniform surfaces is extended to the MoO3-catalyzed oxidation of ethanol to acetaldehyde. Two types of sites are assumed to be present, an oxygen atom site that can be modeled with uniform properties and a metal atom site characterized by non-uniform properties both for ethanol chemisorption to an ethoxide intermediate and the conversion of this intermediate to acetaldehyde. The rate-limiting step is the cleavage of a C-H bond in the absorbed ethoxide intermediate. Non-uniform surface kinetics leads to a kinetic rate expression of the form $$v = kP_{C_2 H_5 OH}^{1 - m} P_{O_2 }^{(1 - m)/4} P_{H_2 O}^{ - (1 - m)/2} $$ . Such a rate expression, withm=0.14, is shown to provide a good fit to kinetic data for the selective oxidation of ethanol on a silica supported molybdenum oxide catalyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813732
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  • 13
    Electronic Resource
    Electronic Resource
    Platinum particle size effect on the oxidative dehydrogenation of aqueous ethanol (1996)
    Springer
    Catalysis letters 36 (1996), S. 31-36 
    Details
    ISSN: 1572-879X
    Keywords: ethanol ; kinetics ; oxidation ; oxydehydrogenation ; platinum ; structure sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the platinum particle size was investigated for the catalytic oxidative dehydrogenation of aqueous ethanol to ethanal at a temperature of 303 K, an ethanol concentration of 260 mol m−3, a partial oxygen pressure 60 kPa, a pH of 9, and an ethanal and ethanoate concentration of 20 mol m−3. A particle size effect on the turnover frequency was observed but only for particle sizes smaller than 2 nm. Hence, the reaction shows a limited structure sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807202
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  • 14
    Electronic Resource
    Electronic Resource
    Spectrophotometric determination of mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by flow injection analysis (1994)
    Springer
    Microchimica acta 113 (1994), S. 81-89 
    Details
    ISSN: 1436-5073
    Keywords: flow injection analysis (FIA) ; mercury ; porphyrin ; kinetics ; spectro-photometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS4) was synthesized and used for the Spectrophotometric determination of mercury by flow injection analysis. A pseudo-first-order reaction kinetic mechanism was proposed with a rate constant of 0.8 min−1 for Hg(II) withm-Cl-TPPS4 in the presence of 8-hydroxyquinoline in a medium of 1.0M acetic acid and sodium acetate buffer solution (pH 6.22). In the optimum conditions of reaction temperature (85 ° C), stopped-flow time (60 s) and sampling volume (100 μl), the method's relative standard deviation was 0.82% (n = 12) at 5.0 μg ml−1 mercury, with a linear range of 0–12.0 μg ml−1 and an analytical frequency of 60h−1. The detection limit (3σ) was 0.025 μg ml−1. Interference studies showed that most metal ions co-existing with Hg2+ could be tolerated at 100-fold excess levels, but Zn2+, Cu2+ and Mn2+ needed to be masked. The method has been applied to the analysis of water samples with satisfactory results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243140
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  • 15
    Electronic Resource
    Electronic Resource
    Improving the performance of the two-rate parameter by use of the integrating ratemeter and temporal optimization (1996)
    Springer
    Microchimica acta 124 (1996), S. 13-25 
    Details
    ISSN: 1436-5073
    Keywords: kinetics ; rates ; integrating ratemeter ; optimization ; first-order
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The integrating ratemeter is used in concert with the two-rate parameter to form the integrating ratemeter two-rate parameter. Propagation of error theory is applied to the integrating ratemeter two-rate parameter to yield expressions for the precision of rates calculated from the integrating ratemeter two-rate parameter in terms of the precision of the rates measured with the integrating ratemeter. Simulations and experimental results show that in cases where the standard deviation of the rate is relatively constant, the optimum time to make a rate measurement using the integrating ratemeter is also the optimum time to measure either of the rates in the two-rate parameter. If either of the two rates comprising the two-rate parameter is measured at the optimum time, then the precision and accuracy of concentrations measured with this technique are optimized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244952
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  • 16
    Electronic Resource
    Electronic Resource
    Slow release rate: Individual granules and population behaviour (1994)
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 39-42 
    Details
    ISSN: 1573-0867
    Keywords: Controlled release fertilizers ; kinetics ; mechanism ; nutrient supply ; rate of release ; slow release fertilizers (SRF)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual granules within a given granule population of a slow-release fertilizer (SRF) have a different release pattern. The populations studied differed both in relation to the time delay before the start of the release process and to the duration of the release. An association between a short delay period and a rapid release was found. The random reease distribution can be approximated using first-order rate equations. In cases, a term describing a “lag” period should be added. The distribution of release timing among the fertilizer granules may allow a long-lasting nutrient supply to the plant, as long as there are enough granules within the root zone to allow a uniform supply pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750155
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  • 17
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    Effect of concentration and environmental form of tetradecenyl succinic acid on its mineralization in soil (1996)
    Springer
    Biodegradation 7 (1996), S. 377-382 
    Details
    ISSN: 1572-9729
    Keywords: bioavailability ; builders ; detergents ; kinetics ; mineralization ; sewage sludge ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tetradecenyl succinic acid (TSA) is the major component of a detergent builder (C12-C14 alkenyl succinic acid), which is inherently biodegradable. 14C-TSA was dosed as a component of sewage sludge into a soil with a history of sludge amendment at final added concentrations of 1.5 and 30 mg (kg soil)-1. In addition, it was dosed to the soil in an aqueous solution to a final added concentration of 30 mg (kg soil)-1. Dose and form were found to have a pronouced effect on the mineralization kinetics. When dosed in a realistic form and concentration (i.e. 1.5 mg (kg soil)-1 as a component of sludge), TSA was mineralized at its highest rate and to its greatest extent, and the mineralization half-life was 2.4 days. When dosed at 30 mg (kg soil)-1 as a component of sludge, mineralization began immediately, and the half-life was 23 days. In contrast, when dosed at this concentration in aqueous solution, the onset of mineralization was preceded by a 13 day lag period and the mineralization half-life was 69 days. Primary biodegradation and mineralization rates of TSA were very similar. Approximately, half the radioactivity was evolved as 14CO2, while the remaining radioactivity became non-extractable, having presumably been incorporated into biomass or natural soil organic matter (humics). This study demonstrated that TSA is effectively removed from sludge-amended soils as a result of biodegradation. Furthermore, it showed the effect that dose form and concentration have on the biodegradation kinetics and the importance of dosing a chemical not only at a relevant concentration but also in the environmental form in which it enters the soil environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00056421
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  • 18
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    Biodegradability of diesel oil (1996)
    Springer
    Biodegradation 7 (1996), S. 73-81 
    Details
    ISSN: 1572-9729
    Keywords: diesel oil ; biodegradation ; CSTR ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In batch culture diesel oil was degraded rapidly, with a maximum growth rate (for a consortium of microorganisms) of 0.55 h-1. The corresponding yield Y SX was 0.1 Cmol/Cmol. In a continuous stirred tank reactor the maximum dilution rate was about 0.25 h-1, with a yield of 0.3 Cmol/Cmol. With a residence time of 1 day 82% of the influent oil was degraded. In the batch reactor, of the mixture of linear and branched alkanes the linear alkanes were degraded fastest and with the highest yield. Only after most of the linear alkanes had disappeared were the branched alkanes consumed. In a CSTR a large part of the branched alkanes was not degraded.
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    URL: http://dx.doi.org/10.1007/BF00056560
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  • 19
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    Invariant kinetic approach to the description of a rock fracture process and induced seismic events (1996)
    Springer
    Pure and applied geophysics 147 (1996), S. 367-375 
    Details
    ISSN: 1420-9136
    Keywords: Induced seismicity ; kinetics ; rock fracture ; rockburst ; earthquake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Powerful seismic events, such as earthquakes and rockbursts, are caused by the accumulation of energy in rocks and loss of rock mass stability. Usually methods of their forecasting are based on the registration of anomalous behavior of geophysical fields. However an efficiency of this approach is low. The present paper proposes a kinetic approach to the description of rock fracture process, which can be used for the forecasting of seismic events and an investigation of structure and energy distributions in rock. 3-D and 1-D kinetic equations describing a process of cluster formation in rock were obtained. The equations are invariant to deformation conditions and to the scale level of events. They showed a good agreement with the results of field observations and laboratory experiments. It was also shown that these equations well describe the processes of earthquake, rockburst and rock sample failure preparation. Catalogues of rockbursts in mines were analyzed with the use of the kinetic equations to find out evidence of induced seismic events. The proposed approach makes it possible to reveal trends in rock behavior and thus predict the rock failure at different scale levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877489
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  • 20
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    Pharmacokinetics of diphemanil methylsulphate in neonates and in premature infants (1996)
    Springer
    European journal of clinical pharmacology 50 (1996), S. 429-430 
    Details
    ISSN: 1432-1041
    Keywords: Key words Diphemanil methylsulphate ; Neonate; antimuscarinic agent ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050136
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  • 21
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    Assessment of inhibition kinetics of the growth of strain P5 on pentachlorophenol under steady-state conditions in a nutristat (1996)
    Springer
    Archives of microbiology 165 (1996), S. 194-200 
    Details
    ISSN: 1432-072X
    Keywords: Key words Auxostat ; Batch culture ; Chemostat ; Continuous culture ; Fermentation control ; Inhibition ; kinetics ; Nutristat ; On-line measurement ; Pentachlorophenol ; Pollutant ; Sphingomonas ; Steady-state conditions ; Toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bacterium degrading pentachlorophenol (PCP) as the only source of carbon and energy was grown in a “nutristat”, i.e., a continuous culture with on-line measurement and control of the substrate concentration. We improved the PCP nutristat by incorporation of a personal computer with a proportional integral derivative (PID) algorithm for controlling the medium feed pump. The controlled value deviated from the average (set-point) value by 1% maximally. In the PCP nutristat (30°C), the steady-state dilution rate, and hence, specific growth rate, showed a maximum value of 0.142 ± 0.004 h–1 at set-point PCP concentrations between 37 and 168 μM. At PCP concentrations above 168 μM, the steady-state growth rate decreased because of inhibition. The growth yield coefficient was not seriously affected by the PCP concentration, suggesting that uncoupling was not the inhibitory mechanism. It was concluded that the PCP nutristat is very useful for establishing steady-state conditions that maintain growth-inhibitory PCP concentrations and high cell concentrations, conditions for which the chemostat is not suitable.
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    Polymerization kinetics of acrylic bone cements by differential scanning calorimetry (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 35-49 
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    ISSN: 1572-8943
    Keywords: bone cement ; DSC ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Bone cements are widely used for the fixation of metallic prostheses in orthopaedics and to form replacements for skull defects in neurosurgery. Acrylic bone cements are based on a mixture of methyl methacrylate (MMA) and a fine powder of polymethyl methacrylate (PMMA). The polymerization of the bone cement occurs in contact with the bone and the prosthesis which act as the boundaries of a bulk polymerization reactor. The kinetic behaviour of the bone cement plays a fundamental role for the final performance of the implant. In this paper, the isothermal and non-isothermal polymerization behaviour of a commercial bone cement is described. A simple phenomenological model, accounting for the autoacceleration ffect, for a diffusion controlled termination mechanism and for the reaction between inhibitor and initiator, is proposed. The reaction kinetics is analysed by DSC. DSC data are used for the determination of the rates of polymerization under isothermal and non-isothermal conditions. The experimental data are processed to calculate the parameters of the proposed phenomenological kinetic model. The analytical and numerical details related to the integration of the model are discussed.
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    Erfahrungen mit vier Softwarepaketen für Kinetische Auswertungen in der Thermischen Analyse (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 543-557 
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    ISSN: 1572-8943
    Keywords: compensation effect ; DSC ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Four computer programs as well as one demo-version for non-linear evaluation of kinetic data in thermal analysis and calorimetry, were presented. The multi-task program TA-kin meets all mathematical requirements for solving the numerical assignments. It is shown that the so-called compensation effect is due to the mathematical structure of the Arrhenius equation. Several applications of TA-kin to a lot of DSC- and TG-measurements and isoperibolic batch experiments as well as adiabatic semi batch experiments realized by precision calorimetry have been discussed.
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    Kinetics of the decomposition of calcium carbonate in the presence of Bi2O3 (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 569-575 
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    ISSN: 1572-8943
    Keywords: Bi2O3 ; CaCO3 decomposition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3. The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3.
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    Non-enzymatic browning-induced water plasticization (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1437-1450 
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    ISSN: 1572-8943
    Keywords: browning ; crystallization ; glass transition ; kinetics ; milk powder ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An exotherm, observed in differential scanning calorimetry (DSC) scans of amorphous food materials above their glass transition temperature,T g, may occur due to sugar crystallization, nonenzymatic browning, or both. In the present study, this exothermal phenomenon in initially anhydrous skim milk and lactose-hydrolyzed skim milk was considered to occur due to browning during isothermal holding at various temperatures above the initialT g. The nonenzymatic, Maillard browning reaction produces water that in amorphous foods, may plasticize the material and reduceT g. The assumption was that quantification of formation of water from theT g depression, which should not be observed as a result of crystallization under anhydrous conditions, can be used to determine kinetics of the nonenzymatic browning reaction. The formation of water was found to be substantial, and the amount formed could be quantified from theT g measured after isothermal treatment at various temperatures using DSC. The rate of water formation followed zero-order kinetics, and its temperature dependence well aboveT g was Arrhenius-type. Although water plasticization of the material occurred during the reaction, and there was a dynamic change in the temperature differenceT−T g, the browning reaction was probably diffusioncontrolled in anhydrous skim milk in the vicinity of theT g of lactose. This could be observed from a significant increase in activation energy. The kinetics and temperature dependence of the Maillard reaction in skim milk and lactose-hydrolyzed skim milk were of similar type well above the initialT g. The difference in temperature dependence in theT g region of lactose, but above that of lactose-hydrolyzed skim milk, became significant, as the rate in skim milk, but not in lactose-hydrolyzed skim milk, became diffusion-controlled. The results showed that rates of diffusion-controlled reactions may follow the Williams-Landel-Ferry (WLF) equation, as kinetic restrictions become apparent within amorphous materials in reactions exhibiting high rates at the same temperature under non-diffusion-controlled conditions.
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    Analysis of mesophase formation in side-chain liquid crystalline polycarbosilanes (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 795-808 
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    ISSN: 1572-8943
    Keywords: DSC ; kinetics ; liquid crystalline polymer ; optical transmittance ; polycarbosilane ; side-chain mesogen ; transition parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper is concerned with an analysis of the thermodynamics and kinetics of mesophase formation by cooling from the isotropic state of side-chain liquid crystalline polycarbosilanes containing spacers in the range from 3 to 11 CH2-groups. The polymers are characterized by their thermotropic behaviour as far as temperature, enthalpy and entropy of the transitions are concerned. The kinetics was followed by optical and calorimetric methods. Longer spacer length leads to more perfect ordering in the mesophase, higher isotropization temperatures, and lower glass transition temperatures. The Avrami and Ozawa formalism to describe the transition kinetics to the mesophase from the isotropic state cannot be interpreted as the nucleation and growth mechanism known from crystallization.
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    Kinetic compensation effect in the thermal degradation of polymers (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1081-1091 
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    ISSN: 1572-8943
    Keywords: kinetics ; thermal degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic study of thermal degradation takes into account the validity of the Arrhenius equation. From TG data, the activation energy,E a and pre-exponential factor,A, are evaluated. These results are interpreted by using the ‘kinetic compensation effect’ as basis. A linear correlation between In(A) andE a is obtained in all cases studied. However, in a plot of the logarithm of the rate constant as a function of reciprocal temperature for the same series of reactions, the thermal oxidative degradations of Nylon-6 and PVC display a point of concurrence and one isokinetic temperature, whereas those of HIPS and PC do not. Therefore, in the thermal oxidative degradations of Nylon-6 and PVC a ‘true’ compensation effect occurs, which could be related to the bulk properties of metal oxides, such as different valence states, whereas for other polymers it displays only an ‘apparent’ compensation effect. This means that degradation is largely independent of the bulk properties of oxides, but may be related to the distribution of different kinds of active links in the polymer surface having different activation energies.
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    Convexity requirement in the geometric-probabilistic approach to heterogeneous chemical kinetics (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 49-54 
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    ISSN: 1572-8943
    Keywords: kinetics ; solid-phase reactions
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The convexity of localization forms, strictly required by conventional geometric-probabilistic formalism, is not in agreement with many experimental observations concerning solid-phase chemical reactions. In a discussion of the essence of this requirement, it is shown that it may be weakened for non-convex localization forms consistent with the symmetry of a solid reagent and described within the geometric-probabilistic approach in terms of planigons and Wigner-Seitz cells.
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    Spectroscopic and thermal studies on the decomposition of l,3,5-triamino-2,4,6-trinitrobenzene (TATB) (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 225-236 
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    ISSN: 1572-8943
    Keywords: IR ; kinetics ; TG-DTG-DTA ; l,3,5-triamino-2,4,6-trinitrobenzene
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in condensed state has been investigated by high temperature infrared spectroscopy (IR) and thermogravimetry (TG) in conjunction with pyrolysis gas analysis, differential thermal analysis (DTA) and hot stage microscopy. The decomposition proceeds in two main stages under isothermal conditions and the initial stage involving about 24% loss in weight obeys Avrami-Erofe'ev equation (n= 1), and is governed by an activation energy (E) of 150.58 kJ·mol−1 and log(A in s−1) 12.06. The second stage corresponding to 24 to 90% loss in weight gave best fit for Avrami-Erofe'ev equation,n=2, withE=239.56 kJ·mol−1 and log(A in s−1) 19.88 by isothermal TG. The effect of additives, on the initial thermolysis of TATB has also been studied. Evolved gas analysis by IR showed that NH3, CO2, NO2, HCN and H2O are produced in the initial stage of decomposition. The decomposition in KBr matrix in the temperature range 272 to 311.5°C shows relative preferential loss in the -NH2 to -NO2 band intensity which indicates that the rupture of C-NH2 bond, weakened also by the interaction of the NH2 with the neighbouring NO2 group, appears to be the primary step in the thermolysis of TATB.
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    Kinetics and mechanism of processes in the system FeSO4·7H2O-MnO2 (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 285-290 
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    ISSN: 1572-8943
    Keywords: kinetics ; system FeSO4·7H2O-MnO2
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Processes which occur during the thermal treatment of system FeSO4·7H2O-MnO2 are of the interest for obtaining MnSO4, which can be easily soluted in water and separated from impurities in manganese slime in zinc metallurgy. Results of the experimental investigations of such processes are given in this paper. Kinetic parameters for the previously defined mechanism were determined using Borchardt and Daniels method.
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    Non-isothermal crystallization kinetics of hot drawn polyester films (1996)
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    Journal of thermal analysis and calorimetry 46 (1996), S. 377-385 
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    ISSN: 1572-8943
    Keywords: crystallization ; drawing ; kinetics ; Kissinger ; Ozawa ; poly(ethylene terephthalate)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The non-isothermal crystallization kinetics of hot drawn poly(ethylene terephthalate) films were studied using the Kissinger and Ozawa equations. The influence of the initial drawing on the crystallization kinetics was investigated. The values of the apparent activation energy and of the Avrami exponent indicates that the nucleation and growth of crystallites depend greatly on the stress submitted to the samples.
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    Kinetics of thermal dehydroxylation of aluminous goethite (1996)
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    Journal of thermal analysis and calorimetry 46 (1996), S. 1223-1238 
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    ISSN: 1572-8943
    Keywords: dehydroxylation ; goethite ; hematite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of dehydroxylation of synthetic aluminous goethite was studied using isothermal and non-isothermal thermogravimetry. The complete isothermal dehydroxylation can be described by the Johnson-Mehl equation with up to three linear regions in plots of lnln [1/(1−y)]vs. Int Kinetics for the initial stage of dehydroxylation changed from diffusion to first-order through the temperature range 190 to 260°C. The rate of dehydroxylation was reduced by Al-substitution and increased with temperature. Activation energy for dehydroxylation, calculated from the time to achieve a given dehydroxylation extent, varied depending on the extent of dehydroxylation and Al-substitution. Non-stoichiometric OH existed in goethite and some remained in hematite after the complete crystallographic transition.
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    Non-isothermal kinetics of CrO3 decomposition pathways in air (1996)
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    Journal of thermal analysis and calorimetry 46 (1996), S. 1271-1282 
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    ISSN: 1572-8943
    Keywords: CrO3 ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The course of the non-isothermal decomposition of CrO3 in air was explored kinetically, by using a number of widely accepted methods. The credibility of the values obtained from a given kinetic parameter (the reaction order, the activation energy and the frequency factor) was justified on the grounds of (i) a multiple correlation coefficient, and (ii) the merits and demerits of the method adopted. The results obtained may help towards a characterization of the non-isothermal conditions under which the encountered decomposition events and products could be resolved. The study was motivated by the results of previous physicochemical characterization studies [1, 2], in which catalytically important intermediates CrOx(3〈x〈6) were structurally identified.
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    Thermal degradation of a styrenated unsatured polyester resin (1996)
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    Journal of thermal analysis and calorimetry 46 (1996), S. 1313-1324 
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    ISSN: 1572-8943
    Keywords: kinetics ; polyester resin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The isothermal and non-isothermal degradation of a typical styrenated phthalic acid-maleic acid-propylene glycol polyester were measured. Non-isothermal and isothermal kinetic analyses were performed on the various degradation steps observed. The values of the non-isothermal and the isothermal kinetic parameters are in good agreement.
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    Role of metal oxides in the thermal degradation of bisphenol a polycarbonate (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1671-1679 
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    ISSN: 1572-8943
    Keywords: kinetics ; polycarbonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal degradation of poly(2,2′,-propane-bis-4-phenyl carbonate) or bisphenol A polycarbonate (PC) alone and in presence of metal oxide as additives have been discussed. Thermal degradation of PC in presence of metal oxide additives may be surface induced catalytic thermo-oxidative degradation. Some metal oxides retard thermo-oxidative degradation of PC.
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    Kinetic analysis of DSC and thermogravimetric data on combustion of lignite (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1657-1669 
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    ISSN: 1572-8943
    Keywords: activation energy ; combustion ; differential scanning calorimetry ; kinetics ; lignite ; oxidation ; thermogravimetric analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal analysis increasingly being used to obtain kinetic data relating to sample decomposition. This work involves a comparative study of several methods used to analyse DSC and TG/DTG data obtained on the oxidation of Beypazari lignite. A general computer program was developed and the methods are compared with regard to their accuracy and the ease of interpretation of the kinetics of thermal decomposition. For this study, the ratio method was regarded as the preferred method, because it permits the estimation of reaction order, activation energy and Arrhenius constant simultaneously from a single experiment.
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    On the thermal stability and thermal decomposition kinetics of some mono- and disubstituted furan-2,3-dions (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1729-1740 
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    ISSN: 1572-8943
    Keywords: kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of some compounds derived from 5-phenylfuran-2,3-dione was studied. The thermoanalytical data relating to the decomposition steps and intermediates were completed with mass spectrometric analysis and infrared spectroscopy results. For some of the investigated reactions, the kinetic and structural data correlated satisfactorily.
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    Thermal degradation of ethylene (vinyl acetate) (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 247-258 
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    ISSN: 1572-8943
    Keywords: ethylene (vinyl acetate) ; kinetics ; polymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ethylene (vinyl acetate), EVA, is a copolymer which is thermally degraded at high temperatures, with acetic acid release at approximately 620 K. This release can be studied by using thermal methods, and in particular thermogravimetric analysis. The present work was focused on establishing the polymer weight loss with temperature in order to calculate the activation energy of the overall deacetylation process. To obtain the final results, a Mettler TC50 instrument coupled with a Mettler TC11 microprocessor was used. The activation energies of four different industrial EVA formulations were calculated. The results obtained by applying different kinetic methods reported in the literature agreed reasonably well; they were compared in order to select the best method of reporting EVA deacetylation results.
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    The basic processes of polymerization and its real kinetic analysis (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1041-1062 
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    Keywords: kinetics ; polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The method of computer experiments can be successfully applied to radical polymerization with the inclusion of initiation, propagation and termination. The convenient PC-program ‘TAkin’ for non-linear estimation of the parameters of calorimetric and thermoanalytical experiments was applied for determination of the activation parameters of chain propagation and termination. The overall evaluation of three or more data sets was preferred. The determination of the kinetic parameters proceeds satisfactorily of the measured curves are strongly different, e.g. with a changed start temperature of modified application of batch and semi-batch technique, including acceptable experimental errors. Eight recommendations for laboratory experts are given.
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    The basic processes of depolymerization and its real kinetic analysis (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 1063-1080 
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    ISSN: 1572-8943
    Keywords: depolymerization ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The method of computer-experiments can be applied successfully on the radical depolymerization under inclusion of initiation, depropagation and termination. The comfortable PC-program ‘TA-kin’ for the non-linear estimation of parameters for TG- or DSC-experiments was applied to the determination of activation parameters of depropagation and termination. Therefore the overall-evaluation of three or more data sets is a prerequisite. The determination of kinetic parameters runs satisfactory if the measured curves are strongly different, e.g. by varying the heating rate, including acceptable experimental errors. Several recommendations for laboratory experts are given. A great support for a very sufficient estimation is the inclusion of simultaneous analysis of the radical concentration.
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    Thermal stability and non-isothermal decomposition kinetics of a polynuclear coordination compound precursor of copper ferrite (1996)
    Springer
    Journal of thermal analysis and calorimetry 47 (1996), S. 1709-1718 
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    ISSN: 1572-8943
    Keywords: kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Results are presented on the thermal behaviour of [Fe(III)2Cu(C2C4)2(OH)4(H2O)2] precursor of copper ferrite. An investigation of the decomposition steps and intermediates was followed by a non-isothermal kinetic analysis of the processable steps.
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    Studies on the dehydration and decomposition of calcium and dicalcium magnesium aconttate hydrates (1996)
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 1201-1213 
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    ISSN: 1572-8943
    Keywords: calcium aconitate ; DTA ; EGA ; kinetics ; SEM ; TG/DTG ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of calcium and dicalcium magnesium aconitate hydrates were studied by TG/DTG, DTA, EGA, SEM and other physico-chemical techniques. The decomposition proceeds in four stages: dehydration; oxidation of the carboxylic acid portion of the salt; complete fragmentation of the hydrocarbon portion; and finally, decarboxylation of the metal carbonate to the oxide. The crystal morphologies of the hydrate and anhydrous salts of each compound are very similar. Tricalcium aconitate consists of well-developed twinned crystals and stellate clusters intergrown with flat platy crystals. On the other hand, dicalcium magnesium aconitate crystals are monoclinic with well-developed pinacoidal faces. The activation energy,E d (43±2 kJ mol−1 water), calculated from Borchardt and Daniels' method, for the dehydration process of calcium aconitate trihydrate is of the same order of magnitude as some simple metal salt hydrates. The rate constant, kd increased from 0.04/min at 238°C to greater than 0.86/min at 295°C. It is concluded that the dehydration process is due to cation bound water.
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    Measurement of heterogeneously catalyzed gas reactions by DSC (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 445-452 
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    ISSN: 1572-8943
    Keywords: catalysts ; catalyst activity ; catalyst deactivation ; DSC ; gas reactions ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gas reactions, catalyzed by solid catalysts, can be measured by DSC. In the experimental set-up an open sample pan with catalyst (powder or pellet) is placed on the sample side of the DSC sensor. The reactive gas mixture flows through the cell and reacts on the catalyst surface. The heat effect, caused by this reaction, results into a DSC signal. The calibration procedure is described for quantitative evaluation of the DSC measurements. For illustration four different reaction systems are discussed.
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    Application of complex reaction kinetic models in thermal analysis (1996)
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    Journal of thermal analysis and calorimetry 47 (1996), S. 535-542 
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    ISSN: 1572-8943
    Keywords: cellulose ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The complexity of the phenomena which arise during the heating of the various substances seldom can be described by a single reaction kinetic equation. As a consequence, sophisticated models with several unknown parameters have to be developed. The determination of the unknown parameters and the validation of the models requires the simultaneous evaluation of whole series of experiments. We can accept a model and its parameters if, and only if we get a reasonable fit to several experiments carried out at different experimental conditions. In the field of the thermal analysis the method of least squares alone seldom can select abest model or abest set of parameter values. Nevertheless, the careful evaluation of the experiments may help in the discerning between various chemical or physical assumptions by the quality of the corresponding fit between the experimental and the simulated date. The problem is illustrated by the thermal de-composition of cellulose under various experimental conditions.
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    Comparative studies on species-specific reactivity between renin and angiotensinogen (1994)
    Springer
    Molecular and cellular biochemistry 131 (1994), S. 43-47 
    Details
    ISSN: 1573-4919
    Keywords: angiotensinogen ; kinetics ; recombinant protein ; renin ; species specificity ; transgenic mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The renin-angiotensin system (RAS) is the most important regulator of electrolyte homeostasis and blood pressure. Our recently generated transgenic mice carrying either the human renin (hREN) or human angiotensinogen (hANG) genes did not develop hypertension but dual gene strains obtained by cross-mating separate lines of mice exhibited a chronically sustained increase in blood pressure, suggesting the presence of species-specific reactivity between renin and angiotensinogen. In order to examine this specificity, the present study was designed to perform a strictly comparative study on hydrolysis of hANG by hREN and mouse submandibular renin (mREN)in vitro by using pure proteins. The recombinant hANG (rhANG) and the synthetic human-type tridecapeptide (hTDP), Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His, corresponding to the N-terminal sequences of hANG, were used to determine the species specificity of recombinant hREN (rhREN) and mREN. While hTDP was cleaved by both rhREN with similar Km and with the same order of kcat, rhANG was cleaved by mREN with 16.7-fold higher Km and with 28.2-fold lower kcat than by rhREN. These results showed that kcat/Km value of mREN for rhANG was 468-fold lower than that for rhREN acting on rhANG.
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    URL: http://dx.doi.org/10.1007/BF01075723
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    Occurrence of histone-related oxalate binding in rat liver nucleus (1996)
    Springer
    Molecular and cellular biochemistry 156 (1996), S. 93-100 
    Details
    ISSN: 1573-4919
    Keywords: rat liver nucleus ; oxalate binding protein ; histone III ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The rat liver nuclear oxalate binding protein was isolated, purified by anion and cation exchange column chromatography using Diethyl Amino Ethyl Sephadex, Carboxy Methyl Cellulose and Carboxy Methyl Sephadex C-50 ion exchangers. The purified oxalate binding protein was found to be H1B of H1 fraction of histories. Kinetic analysis of oxalate binding showed the presence of two affinity sites, one with Kd of 133.5 nM and Bmax of 40 pmoles and another with Kd of 262.5 nM and Bmax of 210 pmoles. The optimal oxalate binding was at pH 4.2 and at 28°C. The oxalate binding was specific and reversible and not due to ionic charge interaction. The IC50 of other dicarboxylates was higher than that of oxalate. EGTA had no effect on oxalate binding but di- and tri-carboxylate carrier inhibitors and thiol modifying agents significantly lowered the binding activity. Oxalate binding to histones was significantly reduced in the presence of DNA or nucleotides, but RNA had no effect. ATP completely inhibited the oxalate binding activity at 1 mM concentration. Different tissues exhibited oxalate binding showing ubiquitous nature. Calf thymus H1 showed maximal binding similar to liver histones.
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    Morphological characteristics of the oxidation of niobium II: The role of stresses on high-temperature morphologies (1994)
    Springer
    Oxidation of metals 41 (1994), S. 235-250 
    Details
    ISSN: 1573-4889
    Keywords: niobium ; oxidation ; morphology ; kinetics ; stresses
    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 niobium at high temperature (900°C) leads to reaction products with “exotic” morphologies. Morphological and kinetics analysis have been undertaken with Nb platelets. A growth mechanism of the oxide at the edges of the platelet is proposed.
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    The effect of purity on high-temperature oxidation of zirconium (1994)
    Springer
    Oxidation of metals 42 (1994), S. 223-237 
    Details
    ISSN: 1573-4889
    Keywords: kinetics ; scale ; oxidation ; zirconium ; purity
    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 of zirconium of different purities were studied over the temperature range of 600–1300°C (α- and β-phases). The structure of the oxidized specimens was examined. TGA, XRD, EPMA, SEM, metallographic analysis, and microhardness measurements were carried out. Impurity elements were found to increase the oxidation rate of technical zirconium. The mechanism of the effect of impurity elements on zirconium oxidation was shown to differ for the α- and β-phases. Activation energies were calculated for the parabolic and linear stages of oxidation.
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    The effect of purity on the high-temperature oxidation of hafnium (1994)
    Springer
    Oxidation of metals 42 (1994), S. 249-263 
    Details
    ISSN: 1573-4889
    Keywords: kinetics ; scale ; oxidation ; hafnium ; purity
    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 of hafnium of different purities were studied in the temperature range of 800–1200°C. This paper concerns the structure studies of the oxidized samples. TGA, XRD, SEM methods, and microhardness measurements were used. Hafnium oxidation follows the parabolic rate law, changing with time to the linear one. Oxidation-reaction products are HfO2(moncl) and α-solid solution of oxygen in hafnium. Anomalous oxidation behavior of hafnium having a high impurity content was found in the range 800–950°C. Activation energies for the parabolic and linear oxidation stages were calculated.
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    Enzymology of ADP-ribose polymer synthesis (1994)
    Springer
    Molecular and cellular biochemistry 138 (1994), S. 33-37 
    Details
    ISSN: 1573-4919
    Keywords: poly(ADP-ribose) polymerase ; structure ; chemistry ; kinetics ; automodification ; mechanism(s)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In this minireview, we summarize recent advances on the enzymology of ADP-ribose polymer synthesis. First, a short discussion of the primary structure and cloning of poly(ADP-ribose) polymerase (PARP) [EC 2.4.2.30], the enzyme that catalyzes, the synthesis of poly(ADP-ribose), is presented. A catalytic distinction between the multiple enzymatic activities of PARP is established. The direction of ADP-ribose chain growth as well as the molecular mechanism of the automodification reaction catalyzed by PARP are described. Current approaches to dissect ADP-ribose polymer synthesis into individual reactions of initiation, elongation and branching, as well as a partial mechanistic characterization of the ADP-ribose elongation reaction at he chemical level are also presented. Finally, recent developments in the catalytic characterization of PARP by site-directed mutagensis are also briefly summarized.
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    In vitro inhibition of human erythrocyte acetylcholinesterase (EC3.1.1.7) by an antineoplastic drug methotrexate (1996)
    Springer
    Molecular and cellular biochemistry 159 (1996), S. 47-53 
    Details
    ISSN: 1573-4919
    Keywords: acetylcholinesterase ; kinetics ; inhibition ; methotrexate ; anticancer drugs ; human erythrocyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This work addresses the kinetic analysis of the interaction of methotrexate (MTX) with human erythrocyte membrane-bound acetylcholinesterase (AChE, EC 3.1. 1.7). It was found that the MTX effect was independent of time of incubation with AChE before the addition of substrate which proves its reversible action. The IC50 was determined, by three methods, to be 0.73 mM. The Michaelis-Menten constant (Ks) for the hydrolysis of acetylthiocholine iodide (ASCh) by AChE was 0.13 mM in the control system, a value decreased by 30–61% in the MTX treated systems. The Vmax was 1.27μtmole/min/mg protein for the control system while it was decreased by 44–77% in the MTX treated systems. The Linexveaver-Buck plot, Dixon plot, and their secondary replots indicated that the nature of the inhibition was of the linear mixed type, i.e. uncompetitive and noncompetitive. The values of Ki(slope) and KI(tntecept) were estimated as 1.67 and 0.34 mM, respectively.
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    Conformational changes of Na,K-ATPase probed with eosin Y (1996)
    Springer
    Journal of fluorescence 6 (1996), S. 165-168 
    Details
    ISSN: 1573-4994
    Keywords: Cation binding ; fluorescence decay ; kinetics ; binding constants ; Na,K-ATPase ; eosin Y
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Time-resolved fluorescence and binding studies have been carried out on Na,K-ATPase in the presence of the fluorescent dye eosin Y to obtain thermodynamic and kinetic parameters for the interaction of the enzyme with different cations. Eosin Y binding is indicated by a 3 ns fluorescence decay process and is observed only in the presence of mono- and divalent cations. This type of cation binding is interpreted as a nonselective electrostatic interaction, with negatively charged groups of the enzyme providing a high-affinity eosin Y binding site. Eosin Y binding is observed only under conditions where the enzyme exists in the conformational state F1. The kinetic parameters of eosin Y binding have been determined employing stopped-flow fluorometry.
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    A two-component, non-aqueous route to silica gel (1994)
    Springer
    Journal of sol gel science and technology 2 (1994), S. 35-41 
    Details
    ISSN: 1573-4846
    Keywords: carboxylic acids ; mechanism ; kinetics ; ultrafine porosity ; CO2 adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new means for generating silica gel has been developed. Simple two component systems comprising tetraalkoxysilanes and strong carboxylic acids such as formic acid can react rapidly to give transparent monolithic gels. The acid serves as solvent, water source, and catalyst for both hydrolysis and condensation. Water need not be present as an initial reactant; it is generated in situ during the reaction. The gelation reaction is at least two orders of magnitude faster than those conducted in conventional acid-catalyzed aqueous systems at comparable pH*. Kinetic evidence indicates a lowering of the activation energy of condensation reactions, believed to be associated with reaction of silyl carboxylates and silanol groups. Physical properties of the dry gels such as bulk density more closely resemble conventional acid-catalyzed gels than those associated with other rapidly gelling systems. Dry gels often exhibit porosity so fine that nitrogen (at 77°K) is not absorbed at significant rates. Independent evidence of porosity arises from comparison of skeletal and bulk densities, sample immersion in water and adsorption isotherms of CO2.
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    Inactivation and conformational changes of aminoacyclase in trifluoroethanol solutions (1996)
    Springer
    The protein journal 15 (1996), S. 631-637 
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    ISSN: 1573-4943
    Keywords: Aminocyclase ; denaturation ; inactivation ; conformation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The inactivation and unfolding of aminoacyclase (EC 3.5.1.14) during denaturation by different concentrations of trifluoroethanol (TFE) have been studied. A marked decrease in enzyme activity was observed at low TFE concentrations. The kinetic theory of the substrate reaction during irreversible inhibition of enzyme activity described previously by Tsou [Tsou (1988),Adv. Enzymol. Related Areas Mol. Biol. 61, 381–436] was applied to study the kinetics of the inactivation course of aminoacyclase during denaturation by TFE. The inactivation rate constants for the free enzyme and substrate-enzyme complex were determined by Tsou's method. The inactivation reaction was a monophasic first-order reaction. The kinetics of the unfolding course were a biphasic process consisting of two first-order reactions. At 2% TFE concentration, the inactivation rate of the enzyme was much faster than the unfolding rate. At a higher concentration of TFE (10%), the inactivation rate was too fast to be determined by conventional methods, whereas the unfolding course remained as a biphasic process with fast and slow reactions occurring at measurable rates. The results suggest that the aminoacyclase active site containing Zn2+ ions is situated in a limited and flexible region of the enzyme molecule that is more fragile to the denaturant than the protein as a whole.
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    Substitution of the amino acid at position 102 with polar and aromatic residues influences substrate specificity of lactate dehydrogenase (1994)
    Springer
    The protein journal 13 (1994), S. 129-133 
    Details
    ISSN: 1573-4943
    Keywords: Lactate dehydrogenase ; kinetics ; mutagenesis ; specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Gin residue at amino acid position 102 ofBacillus stearothermophilus lactate dehydrogenase was replaced with Ser, Thr, Tyr, or Phe to investigate the effect on substrate recognition. The Q102S and Q102T mutant enzymes were found to have a broader range of substrate specificity (measured byk cat/K m) than the wild-type enzyme. However, it is evident that either Ser or Thr at position 102 are of a size able to accommodate a wide variety of substrates in the active site and substrate specificity appears to rely largely on size discrimination in these mutants. The Q102F and Q102Y mutant enzymes have low catalytic efficiency and do not show this relaxed substrate specificity. However, their activities are restored by the presence of an aromatic substrate. All of the enzymes have a very low catalytic efficiency with branched chain aliphatic substrates.
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    DEDO: A specific, fluorescent inhibitor for spectroscopic investigations of Na,K-ATPase (1994)
    Springer
    Journal of fluorescence 4 (1994), S. 287-290 
    Details
    ISSN: 1573-4994
    Keywords: Na,K-ATPase ; fluorescent inhibitor ; kinetics ; energy transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interaction between the fluorescent ouabain derivative DEDO and purified renal Na,K-ATPase (isolated from different animal species) is investigated. Equilibrium binding studies provide a pK value of about 7.5 and a stoichoimetric coefficient of 1. Nonmodified ouabain exhibits the same affinity to the rabbit enzyme; the enzyme originating from the other sources binds DEDO 10 times less strongly than ouabain. Kinetic studies indicate that this is the consequence of a 10 times higher dissociation rate constant of the complexes formed with DEDO. The fluorescence emission intensity of DEDO is enhanced, being dependent on the enzyme source. The single decay time of DEDO is 3 ns in the absence and 21 ns in the presence of the rabbit enzyme and 14 ns in the presence of the pig renal enzyme. This result suggests that the fluorophore of DEDO is bound to a very hydrophobic environment of the enzyme. Further characterization of the static fluorescence spectra provides evidence for energy transfer between Trp residues of the enzyme and DEDO. Distance estimations suggest that one or two Trp residues are likely to be located in the proximity of the fluorophore.
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    Stopped-flow fluorescence studies of the interaction of a mutant form of cytochrome b5 with lipid vesicles (1994)
    Springer
    Journal of fluorescence 4 (1994), S. 227-233 
    Details
    ISSN: 1573-4994
    Keywords: Cytochrome b5 ; site-directed mutagenesis ; kinetics ; fluorescence ; membrane-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cytochrome b5 binds spontaneously to lipid vescles and also self-associates in aqueous solution. Two mutant proteins have been generated, one has a self-association constant which is less than that of the native protein, while the other has a larger self-association constant. All three proteins have Trp in the membrane-binding domain but as aqueous solutions of these proteins contain differing amounts of monomeric protein, the kinetics of fluorescence enhancement, when the proteins are mixed with lipid vesicles, are complex. Similar complex kinetics are seen when the Trp are quenched by the addition of bromolipid vesicles. The mutant which has Trp 108 and 112 both replaced by Leu does not self-associate and shows monoexponential stopped-flow fluorescence kinetics. Identical rate constants are seen with this mutant for fluorescence enhancement by POPC and fluorescence quenching by three bromolipids with bromines at the 6,7-, 9,10-, and 11,12-positions of thesn-2 acyl chain. This rate constant is only 1% of the calculated collisional rate constant and it is suggested that the reduced rate is caused by a reduction in the number of productive collisions rather than by a slow rate of penetration of the membrane-binding domain into the bilayer.
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    Chemiluminescence in the reduction of XeO3 by europium(II) (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 2760-2762 
    Details
    ISSN: 1573-9171
    Keywords: chemiluminescence ; kinetics ; xenon trioxide ; europium(II,III) ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Chemiluminescence has been observed in the reduction of perchloric aqueous solutions of XeO3 with Eu2+ ions, Fast (several seconds) consumption of EuII occurs when the ratio of the initial concentrations of the reactants (Eu2+]0 : [XeO3]0 〈 6; however, the chemiluminescence remains sufficiently bright and prolonged (up to −10 min after nearly complete oxidation of EuII to EuIII). The assumption was made that intermediates in the reduction of XeO3 participate in the chemiluminescent stages of the process.
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    Kinetics and mechanisms of halide ion catalysis of CO substitution reactions in Os3(CO)12 and Ru3(CO)12 metal carbonyl clusters (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1451-1456 
    Details
    ISSN: 1573-9171
    Keywords: metal carbonyl clusters ; osmium, ruthenium, alkynes ; kinetics ; catalytic effect of halide ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The results of kinetic studies on ligand substitution in [M3(CO)11X]− complexes (M = Ru, Os; X = Cl, Br, I) are summarized. The [Os3(CO)11X]− complexes react with PPh3 under mild conditions to initially yield monosubstituted products [Os3(CO)10(PPh3)X]−. The rate of CO substitution obeys a first-order equation with respect to the concentration of the complex and does not depend on the ligand concentration. The rates of the reactions decrease in the order Cl 〉 Br 〉 I withΔH≠ values increasing from 15 to 18 kcal mol−1 and ΔS ≠ values varying from −19 to −13 cal mol−1 K−1. The enhanced reactivities of these complexes as well as the low activation energies and negative activation entropies are discussed in terms of the effects of μ-X bridge formation on the transition state of the reaction. Reactions of PPN[Ru3(CO)11−x (Cl)] (PPN is the bis(triphenylphosphine)iminium cation;x=0, 1) and PPN[Ru3(CO)9(μ3-I)] with alkynes are also reported. The reactivities of alkynes follow the order BuC≡CH ≥ PhC≡CH ≥ EtC≡CEt ≥ PhC≡CPh. The higher rates of the reactions of monosubstituted acetylenes compared with those of their disubstituted analogs are explained by agostic interaction between the metal atom and the C-H bond in the reaction transition state and by steric effects. The results obtained attest that the reaction with alkynes occursvia intermediates containing halide bridges and that μ3-halide complexes are more reactive than μ2-halide complexes.
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    Kinetics of vapor nitration of cellulose (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 328-334 
    Details
    ISSN: 1573-9171
    Keywords: vapor nitration ; cellulose ; nitric anhydride ; kinetics ; diffusion constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of vapor nitration of cellulose with nitric anhydride at various pressures was studied under conditions of natural convection in the absence of air, using the nonisothermal kinetic method. The process rate was found to be proportional to the N2O5 pressure. The nitration is described by a law of the dη/dt =k 1/(1+βν) type, wherek 1 = 103.82±0.5 exp[-(36000±(RT)]p N 2O5 s−1. β = 10−7.33±1.4exp[(41300±8000)/(RT)] s−1, s−1, within the extents of conversion from 0.04 to 0.4. At high levels of conversion, the nitration occurs with autoacceleration caused by the accumulation of the HNO3 formed. The diffusion mechanism of vapor nitration of cellulose was suggested and discussed. The values of the effective diffusion constant for N2O5 in cellulose and the corresponding activation energy (38.4±2.8 kJ mol−1) have been estimated.
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    Effect of sodium dodecyl sulfate on the reactivity of copper(II) complexes with 2-dimethylaminomethylphenol (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 346-350 
    Details
    ISSN: 1573-9171
    Keywords: complex formation ; kinetics ; sodium dodecyl sulfate ; copper(II) ; 2-dimethylaminomethylphenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of the anionic surfactant sodium dodecyl sulfate on complex formation of 2-dimethylaminomethylphenol (1) with copper(u) in aqueous solutions and on the kinetics of the reactions of copper(n) complexes of 1 with 4-nitrophenylbis(chloromethyl)phosphinate (2) were studied. The reactivities of the complexes in these reactions are higher than that of 1 at all concentrations of SDS studied (0.010–0.200 mol L−1 with pH 7–9.
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    Kinetics, mechanism, and reactivity of an activated carbon-carbon double bond in nitroxyl radicals and their diamagnetic analog in interaction with some secondary amines and polyethyleneimine (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 797-804 
    Details
    ISSN: 1573-9171
    Keywords: unsaturated nitroxyl radicals ; secondary amines ; addition ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Routes for the reaction of a conjugated methylene group of nitroxyl radicals (NR) with secondary amines were suggested and analyzed. Kinetic parameters of the limiting step of this reaction for the NR-amine and diamagnetic analog of NR-amine systems were estimated. The effect of the medium on these reactions was examined. The specific behavior of polyethyleneimine in the reaction with activated methylene groups of 2,2,6,6-tetra methyl-3, 5-dimethylene-4-oxopiperidine-i-oxyl was demonstrated.
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    On the mechanism of the Kharash reaction catalyzed by Fe(CO)5 (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 871-874 
    Details
    ISSN: 1573-9171
    Keywords: Kharash reaction ; catalysis ; iron pentacarbonyl ; kinetics ; thermal stability ; thermal reaction with CCl3X (X = Br, Cl) ; effect of olefin and DMF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fe(CO)5 is sufficiently stable at 80 °C in benzene solution and its thermal decomposition is not accelerated in the presence of phenyl cinnamate or/and DMF. The decomposition is accelerated by CCl3Br (drastically) and by CCl4 (to a lesser extent). DMF accelerates the reaction of Fe(CO)5 with CCl4. The (FeCl(DMF)5]2+[Cl3FeOFeCl3]2− complex has been isolated as a product; its composition and structure have been determined by X-ray analysis. The obtained data indicate the absence of coordination of DMF or/and an olefin with Fe0 species at the stage preceding oxidation. The mechanisms of the generation of CCl3 radicals in thermal and photochemical Kharash reactions in the presence of Fe(CO)5 are basically different. The probable pathways of the effect of DMF on the rate of the oxidative decomposition of Fe(CO)5 are discussed.
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    Chain decomposition of 2,4,6-trinitrotoluene in hydrocarbon solvents (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1875-1878 
    Details
    ISSN: 1573-9171
    Keywords: 2,4,6-trinitrotoluene ; thermal decomposition ; solvent effect ; chain mechanism ; dissociation energy of C-H bond ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constants for the thermal decomposition of 2,4,6-trinitrotoluene have been measured in toluene and other hydrocarbon solvents. The initial, observed rate constant (k i) increases with dilution with toluene. The concentration dependence is described by the chain decomposition scheme with the transfer of the free valence to a solvent molecule. The activation energy and logk i were found to linearly correlate with the dissociation energy of the C-H bond of the solvent.
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    The kinetics of vapor-phase nitration of cellulose 2. Nitration with nitric acid under static conditions (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1879-1882 
    Details
    ISSN: 1573-9171
    Keywords: cellulose ; nitration ; nitric acid ; kinetics ; diffusion coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The regularities of vapor-phase nitration of cellulose with HNO3 under conditions of natural convection and hindered heat removal in the absence of air were studied using the nonisothermal kinetic method. It was established that the nitration rate at the depth of conversion of 0.08 to 0.7 is described by the kinetic law dη/dt =k 1 p/(1+βη), wherek 1 = 104.49±0.6 exp(−A/RT) s−1 atm−1, β = 10−35.5±15.7exp(B/RT),A = 36.6±3.8 kl mol−1, andB = 203±88 kJ mol−1. The diffusion mechanism of vapor-phase nitration of cellulose, which explains the high value of activation energies, is discussed. The effective diffusion coefficient of HNO3 in cellulose at 25 °3.7 · 10−7 cm2 s−1) and the activation energy of diffusion (38.3±4.2 kJ mol−1) were estimated.
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    Heat release kinetics in the reaction of decane with nitric acid (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1883-1888 
    Details
    ISSN: 1573-9171
    Keywords: decane ; nitric acid ; nitrogen dioxide ; oxidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the reaction of decane with nitric acid (25.07–75.53 %) at 57.8 to 119 °C in an acid-decane-gas triphasic system was studied. The main contribution to the rate of heat release is made by the oxidation of decane with nitrogen dioxide in the organic phase proceedingvia the mechanism of a degenerate branched-chain reaction. Nitration plays the role of a chain termination reaction. The acid phase is the source of NO2, whose content increases with oxidation. The equilibrium of the nitrogen dioxide distribution in the triphasic system was analyzed. The kinetic law of the reaction, the dependences of the reaction constants of the initial and catalytic stages on temperature and the acid phase composition were determined. The results allow one to calculate the rate of heat release in the decane-HNO3 system under any conditions of the process.
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    Oxidation of organic amide ions by dioxygen (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 1646-1650 
    Details
    ISSN: 1573-9171
    Keywords: aromatic amines ; amide ions ; oxidation ; dioxygen ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Amide ions generated from secondary aromatic amines with pK a 〉 21 are readily oxidized by dioxygen in the system KOH+18-crown-6+DMSO at room temperature. It was found that the rate limiting stage of the reaction is the interaction of dioxygen with amide ions. The rate of the reaction is determined by two main factors, varying in opposite directions: the degree of ionization of the amine and the reactivity of the amide ions towards dioxygen.
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    Correlation between solvent-reorganization dynamics and the kinetics of metallotropy in polar media (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 368-371 
    Details
    ISSN: 1573-9171
    Keywords: kinetics ; solvent dynamics ; radical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of metallotropy of the 3,6-di-tert-butyl-2-(triphenylstannyl)oxyphenoxyl radical has been studied by ESR. The correlation between chemical exchange time τex, solvent polarity, and longitudinal relaxation time of the solvent corresponds to the model of a process controlled by molecular dynamics. A linear relation between τex and correlation time τc for reorientation movements of the radical is found: τex = α · τc. The coefficient α depends on the dielectric properties of the solvent.
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    Global view of microstructural evolution: Energetics, kinetics and dynamical systems (1996)
    Springer
    Acta mechanica Sinica 12 (1996), S. 144-157 
    Details
    ISSN: 1614-3116
    Keywords: microstructural evolution ; energetics ; kinetics ; dynamic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An evolving material structure is in a non-equilibrium state, with free energy expressed by the generalized coordinates. A global approach leads to robust computations for the generalized thermodynamic forces. Those forces drive various kinetic processes, causing dissipation at spots, along curves, surfaces and interfaces, and within volumetric regions. The actual evolution path, and therefore the final equilibrium state, is determined by the energetics and kinetics. A virtual work principle links the free energy landscape and the kinetic processes, and assigns a viscous environment to every point on the landscape. The approach leads to a dynamical system that governs the evolution of generalized coordinates. The microstructural evolution is globally characterized by a basin map in the coordinate space; and by a diversity map and a variety map in the parameter space. The control of basin boundaries raises the issue of energetic and kinetic bifurcations. The variation of basin boundaries under different sets of controlling parameters provides an analytical way to plot the diversity maps of structural evolution.
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    Muonic atoms and muon-catalyzed fusion in inhomogeneous mixtures of hydrogen isotopes (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 155-162 
    Details
    ISSN: 1572-9540
    Keywords: muon ; muonic hydrogen ; muonic molecule ; deuterium ; tritium ; fusion ; solid target ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The emission of µd and µt atoms from multilayer solid targets consisting of the mixtures of hydrogen isotopes has been investigated with a kinetics model. The methods to study the elastic scattering of muonic atoms, muon transfer, and molecular formation reactions with µ-atomic beams are discussed.
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    Kinetics of muonic hydrogen drift in axial symmetric geometry (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 163-167 
    Details
    ISSN: 1572-9540
    Keywords: muon ; muonic hydrogen ; energy distribution ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The kinetics of muonic atoms of hydrogen isotopes in an axially symmetric trap is studied. The problem of the determination of the initial kinetic energy distribution of µp and µd atoms from time-of-flight spectra is discussed. The effects of the scattering of muonic atoms from gas and of the stopping distribution are evaluated. When the collision length is much larger than the target radius, the moments of the kinetic energy distribution are shown to be determined by the time-of-flight spectrum in a model-independent way.
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    Hybridomas in a bioreactor cascade: modeling and determination of growth and death kinetics (1996)
    Springer
    Cytotechnology 21 (1996), S. 263-277 
    Details
    ISSN: 1573-0778
    Keywords: hybridomas ; serum-free medium ; monoclonal antibodies ; reactor series ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hybridomas were cultured under steady-state conditions in a series of two continuous stirred-tank reactors (CSTRs), using a serum-free medium. The substrate not completely converted in the first CSTR, was transported with the cells to the second one and very low growth rates, high death rates, and lysis of viable cells were observed in this second CSTR. These conditions are hardly accessible in a single vessel, because such experiments would be extremely time-consuming and unstable due to a low viability. In contrast to what is often observed in literature, kinetic parameters could thus be derived without the neccessity for extrapolation to lower growth rates. Good agreement with literature averages for other hybridomas was found. Furthermore, showing that the reactor series is a valuable research tool for kinetic studies under extreme conditions, the possibility to observe cell death under stable and defined steady-state conditions offers interesting opportunities to investigate apoptosis and necrosis. Additionally, a model was developed that describes hybridoma growth and monoclonal antibody production in the bioreactor cascade on the basis of glutamine metabolism. Good agreement between the model and the experiments was found.
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    The Determination of Interfacial Transfer Constants Using Side-by-Side Diffusion Cells (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1325-1329 
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    ISSN: 1573-904X
    Keywords: interfacial transfer ; partition coefficients ; side-by-side diffusion cells ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A side-by-side diffusion cell setup has been used to determine the pH 7.4 buffer-octanol interfacial transfer constants for twelve compounds. The compounds are a diverse selection of pharmaceuticals, amino acids, and small organics which covers a log distribution coefficient (K) range of −3 to 2. A model based on the resistance summation approach, which deals explicitly with the various barriers involves in the transport process, was used to derive transfer constants from the transport data for each compound. The model gave constants that were well behaved in a published model describing the correlation of the forward and reverse transfer constants to equilibrium K values (r2 = 0.999). These studies demonstrate the utility of side-by-side diffusion cells for the determination of interfacial transfer constants. This type of setup offers the advantages of controlled interfacial area, measurable hydrodynamic effects, and a commercially available apparatus.
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    Entrapping Efficiency and Drug Release Profile of an Oil-in-Water (o/w) Emulsion Formulation Using a Polydimethylsiloxane-Coated Glass Bead Assay (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 503-507 
    Details
    ISSN: 1573-904X
    Keywords: drug delivery ; emulsion ; entrapping efficiency ; polydimethylsiloxane ; glass beads ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Evaluation of entrapping efficiency is difficult for an o/w emulsion formulation containing a lipophilic oily drug, isocarbacyclin methyl ester (TEI-9090), by commonly employed techniques (dialysis, ultrafiltration, or gel filtration), because of its adsorption to the system materials. Employing this characteristic of TEI-9090, we developed an adsorption technique with polydimethylsiloxane-coated glass beads (PDMS-GB). The assay is based on the quantitative adsorption of unentrapped TEI-9090 to the PDMS-GB. The entrapping efficiency of a 10% soybean oil emulsion containing [3H]TEI-9090 (1 µg/mL) assayed by this method approached 100%. The PDMS-GB assay was performed for the emulsion diluted 100 times with physiological saline at different time intervals after dilution over a period of 24 hr. A plot of [3H]TEI-9090 in the emulsion particles versus time showed rapid release within 1 hr, followed by very slow release, reaching equilibrium. Applying first-order kinetics, the data were found to fit to a biexponential equation over the first hour of release. The terminal release resembled the first-order release of the drug from the phospholipid-rich infranatant, which was separated from the creamy layer by ultracentrifugation of the emulsion and contained 35% [3H]TEI-9090. These results suggest that the drug is released from two components in the emulsion.
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    Acid-Catalyzed Peptide Bond Hydrolysis of Recombinant Human Interleukin 11 (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 72-76 
    Details
    ISSN: 1573-904X
    Keywords: interleukin 11 (IL-11) ; recombinant human IL-11 ; degradation ; kinetics ; products ; aspartate–proline cleavage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recombinant human interleukin 11 (rhIL-11) is a multispectrum cytokine that plays an important role in megakaryocytopoiesis and platelet production. Probing rhIL-11 chemical reactivity in aqueous solution is an important initial step in developing a dosage form for rhIL-11 clinical trials. This report documents rhIL-11 degradation kinetics at 50°C in solutions adjusted to pH 3.0 to 9.5. Stressed samples were analyzed by reverse-phase HPLC and degradation product peaks were isolated for structural characterization. The results show maximal stability in the region pH 6.5 to 7.0. Degradation product identification shows that the major reaction pathway in acidic solution involves peptide cleavage at aspartate133–proline134. In alkaline solution, protein disappearance proceeds via nonspecific loss to container surfaces. Degradation products at alkaline pH have not been identified.
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    Epimerization and Hydrolysis of Dalvastatin, a New Hydroxymethylglutaryl Coenzyme A (HMG-CoA) Reductase Inhibitor (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 165-170 
    Details
    ISSN: 1573-904X
    Keywords: dalvastatin ; hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor ; epimerization ; hydrolysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In aqueous solutions, dalvastatin (1) undergoes epimerization as well as hydrolysis. The transformation of the drug was studied as a function of pH at 25°C in aqueous solutions containing 20% acetonitrile. At all pH values, first-order plots for the conversion are biphasic, indicating rapid equilibration of 1 with its epimer (2) and slower hydrolysis of 1 to the corresponding β-hydroxy acid (3). Apparent first-order rate constants for the biexponential equation are given as a function of pH. The alkyl–oxygen cleavage of the lactone ring results in the epimerization of 1 to 2, whereas the acyl–oxygen cleavage results in the hydrolysis of 1 to 3. The epimerization is an SN1 reaction reaching an equilibrium of [l] eq/[2] eq = 1.27. The epimerization rate is increased with an increase in the water content of the solvent. The hydrolysis of 1 to 3 is acid and base catalyzed. The hydrolysis is reversible in acidic media and irreversible in neutral and basic media. At pH values greater than 9, the hydrolysis reaction proceeds more rapidly than the epimerization.
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    Entrapping Efficiency of an Oil-in-Water Emulsion Containing Isocarbacyclin Methyl Ester (TEI-9090) in Dog and Human Sera (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1677-1679 
    Details
    ISSN: 1573-904X
    Keywords: o/w emulsion ; serum ; entrapping efficiency ; kinetics ; SDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1023/A:1018938627408
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    Is Stability Prediction Possible for Protein Drugs? Denaturation Kinetics of β- Galactosidase in Solution (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 1721-1725 
    Details
    ISSN: 1573-904X
    Keywords: protein drug ; denaturation ; aggregation ; kinetics ; Eyring equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Denaturation and aggregation kinetics of Aspergillus oryzae β-galactosidase in solution were studied in order to determine whether the stability of protein drugs can be predicted. Denaturation of β-galactosidase, monitored by measuring enzyme activity, conformed to first-order kinetics, whereas aggregation of the denatured form, monitored by high performance size exclusion chromatography, showed a reaction order higher than 1. Denaturation of β-galactosidase was irreversible and exhibited a biphasic kinetic pattern which could be explained by assuming that two isoenzymes denatured irreversibly at different rates. Linear Arrhenius plots were obtained for the estimated rate constants, and ΔH
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    The kinetics of continuously infused indocyanine green in the pig (1996)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 24 (1996), S. 19-44 
    Details
    ISSN: 1573-8744
    Keywords: indocyanine green ; hepatic removal ; liver function test ; organic anions ; kinetics ; protein binding ; physiologically based pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Indocyanine green (ICG) is used in cardiology and hepatology for the estimation of cardiac output, liver function, and splanchnic blood flow. ICG is bound to plasma proteins and ultimately excreted by the liver. We studied the whole body kinetics of ICG during constant infusion in pigs weighing 30–40 kg. The conventional kinetic model (backflux model) assumes that deviations from one-compartmental linear kinetics is caused by backflux from a liver storage to plasma, and that no extravascular, extrahepatic distribution takes place. This model was tested against an alternative (redistribution) model postulating that temporary redistribution of ICG into an extrahepatic extravascular storage was responsible for the deviations while the hepatic uptake was a one-way first-order process. A mathematical analysis of the two models showed that they predicted different time courses of the hepatic extraction fraction of ICG. Thus, with blood sampling from both a peripheral artery and a hepatic vein, a discriminative model-testing experiment was possible. This test required a first-order steady-state hepatic removal of ICG which was confirmed in 7 experiments with infusion rates varied in a stepwise fashion (0.133±0.003, 0.269±0.010, 0.547±0.020 and 0.130±0.003 μmol·min1). In the model-testing experiments (n=10) ICG was infused at a constant rate of 0.135±0.007 μmol·min1. The mean concentration in peripheral artery (μM) was well fitted by the biexponential functionC(t)=0.476·(1–0.632·e0.216–1−0.368·e0.0172–1). The time course of the observed hepatic extraction fraction was significantly different (p=0.004) from that predicted from the backflux model but in agreement (p=0.98) with the new model assuming hepatic removal to be a one-way process and implying temporary ICG redistribution into an extrahepatic, extravascular storage with an apparent volume of 0.144±0.023 L·Kg1. Accordingly, extravascular ICG was demonstrated in a number of different tissues after 4-hr infusion (n=3). If ICG is used to estimate hepatic blood flow according to Fick's principle, the use of a backflux model to correct for non-steady-state conditions will lead to an overestimation of hepatic blood flow of 28% after 25-min infusion, 16% after 50 min, and 6% after 100 min. The study indicated that distribution of ICG between plasma and tissues is not instantaneous, and that the time course of the redistribution itself significantly influences whole body kinetics. Comparison with a previously published study by Ott, Keiding, and Bass of ICG kinetics after bolus injection suggested that a two-compartment model was insufficient and that the kinetics for the exchange of ICG between plasma and the redistribution space may be nonlinear. The study demonstrates how blood sampling on both sides of the eliminating organ can expose the influence of redistribution. The discriminative model test for constant infusion experiments is novel and may be useful with other ligands.
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    Oxidation of Human Insulin-like Growth Factor I in Formulation Studies: Kinetics of Methionine Oxidation in Aqueous Solution and in Solid State (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 1252-1257 
    Details
    ISSN: 1573-904X
    Keywords: hIGF-I ; oxidation ; methionine ; HPLC ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The aim of this work was to study the kinetics of oxidation of methionine in human Insulin-like Growth Factor I (hIGF-I)1 in aqueous solution and in the solid state by the aid of quantification of oxygen. Methods. The oxidized form of hIGF-I was characterized by tryptic peptide analysis, RP-HPLC and FAB-MS and quantified by RP-HPLC. The oxygen content was quantified polarographically by a Clark-type electrode. Results. Second-order kinetics with respect to amount of protein and dissolved oxygen was found to be appropriate for the oxidation of methionine in hIGF-I. The rate constants ranged from 1 to 280 M−1 month−l and had an activation energy of 95 (+/−4) kJ/mole. Light exposure, storage temperature and oxygen content were found to have a considerable impact on the oxidation rates. No significant difference in reaction rates was found for the oxidation of hIGF-I in aqueous solution or in the solid state. A method for decreasing the oxygen content in aqueous solution without purging is described. Conclusions. Polarographic quantification of dissolved oxygen makes it possible to establish the kinetics for oxidation of proteins. The oxidation of methionine in hIGF-I appears to follow second-order kinetics.
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    Block copolymerization initiated by Mn(III)-poly(ethylene glycol) redox system — general features and kinetics (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 777-783 
    Details
    ISSN: 1435-1536
    Keywords: Mn(III)-poly(ethylene glycol) ; acrylonitrile ; block copolymerization ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The kinetics and mechanism of thermal polymerization of acrylonitrile initiated by Mn(III) pyrophosphate — poly(ethylene glycol) (PEG, molecular weight 6000) redox system in aqueous sulfuric acid medium was studied in the temperature range 30–60°C. The overall rates of polymerization and the disappearance of Mn3+ were determined. The polymerization was initiated by the organic free radical produced from the Mn3+-PEG reaction and the termination was by the metal ions. The rate of polymerization of acrylonitrile was found to be directly proportional to the square of the monomer concentration and first power of PEG concentration, and inversely proportional to the concentration of Mn3+. The rate of manganic ion disappearance was found to be directly proportional to manganic ion concentration and PEG concentration, and independent of the monomer concentration. Based on these observations, a plausible reaction scheme was suggested and suitable kinetic expressions were evaluated.
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    Alternative kinetic laws to describe the turnover of the microbial biomass (1996)
    Springer
    Plant and soil 181 (1996), S. 169-173 
    Details
    ISSN: 1573-5036
    Keywords: kinetics ; microbial biomass ; model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many models that describe the turnover of the microbial biomass in soil use either first order kinetics where the rate of turnover is directly proportional to the microbial mass, or a variant of the Michaelis-Menten law that describes enzyme kinetics. To account for the different rates of microbial turnover observed at different times after the addition of substrate, some authors have suggested the existence of more than one pool of biomass. Each pool obeys the same kinetic law but with a different rate. In other experiments a disproportionately large increase in the turnover of native organisms has been observed relative to the amount of fresh substrate added. A change in the kinetic law describing the turnover of organisms can account for these observations and yet retain the simplicity of a single pool of micro-organisms. However where multiple pools of organisms are justified a mixed kinetic law with both first and second order terms may be more appropriate; in other words one pool of micro-organisms but two rate constants. The advantage of retaining a single pool of microbial biomass is that models may more readily be constructed in relation to the routine measurements of total microbial mass.
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    Are cell redox or lactate dehydrogenase kinetics responsible for the absence of gluconeogenesis from lactate in sea raven, hepatocytes? (1994)
    Springer
    Fish physiology and biochemistry 13 (1994), S. 59-67 
    Details
    ISSN: 1573-5168
    Keywords: fish ; sea raven ; gluconeogensis ; hepatocytes ; redox ; LDH ; isozymes ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have reported very low rates of gluconeogenesis from lactate in sea raven (Hemitripterus americanus) hepatocytes compared to other teleosts studied. This study examines whether hepatic cell redox or lactate dehydrogenase (LDH) characteristics may explain this observation. Sea raven hepatic optimal LDH activities (pyruvate reductase direction) were more than 40 times less compared with rainbow trout liver values (40 vs 1914 μmol·min−1·g−1 protein). The Km(lactate) was 9.24 and 0.86 mM for sea raven and trout hepatic LDH, but the Km(pyruvate) was similar between the two species (0.11 and 0.21 mM, respectively). These results suggested that sea raven liver LDH did not favour lactate use and was more indicative of the mammalian M-isozyme. Gel electrophoresis showed a predominant intermediate isozyme, with a small amount of the M-type LDH. Phosphoenolpyruvate carboxykinase (PEPCK) was localized to the mitochondrial compartment, while there was no apparent mitochondrial glutamate-oxaloacetate transaminase (GOT) activity. No in vitro lactate flux to glucose was found in untreated, 10 mM ethanol-treated, or 3 mM NH4Cl-treated sea raven hepatocytes, although CO2 production from lactate was decreased by ethanol and increased by NH4Cl. These results provide evidence that cell redox does not limit gluconeogenesis from lactate, while low activities and the kinetic characteristics of LDH may partially explain the low lactate gluconeogenesis reported in sea raven hepatocytes.
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    Morphological responses of the rainbow trout (Oncorhynchus mykiss) gill to hyperoxia, base (NaHCO3) and acid (HCl) infusions (1994)
    Springer
    Fish physiology and biochemistry 12 (1994), S. 465-477 
    Details
    ISSN: 1573-5168
    Keywords: fish ; chloride cell ; morphology ; kinetics ; Km ; Jmax ; acid-base
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Marked morphological responses occur in the gills of freshwater rainbow trout in response to experimental acid-base disturbance and these responses play an important role in acid-base correction. Compensated respiratory acidosis induced by 70h exposure to environmental hyperoxia (elevated water PO2) caused a 33% decrease in branchial chloride cell fractional surface area (CCFA). Metabolic alkalosis induced by normoxic recovery (6h) from hyperoxia (72h) caused a 50% increase in CCFA, whereas metabolic alkalosis induced by infusion (19h) of NaHCO3 caused a 70% rise. However, the largest increase (135%) in CCFA was seen in response to infusion (19h) of HCl. NaCl infusion had no effect. A particular goal was to assess the relative importance of changes in CCFA vs. changes in internal substrate (HCO3 −) availability in regulating the activity of the branchial Cl−/HCO3 − exchange system. For each of the experimental treatments, the accompanying blood acid-base status and branchial transport kinetics (Km, Jmax) for Cl− uptake had been determined in earlier studies. In the present study, a positive linear relationship was established between CCFA and JCl− max in individual control fish in the absence of an acid-base disturbance. By reference to this relationship, observed changes in JCl− max during metabolic acid-base disturbances were clearly due to changes in both CCFA and internal substrate levels (plasma [HCO3 −]) with the two factors having approximately equal influence.
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    Transport of calcium by mitochondria (1994)
    Springer
    Journal of bioenergetics and biomembranes 26 (1994), S. 471-485 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; transport ; calcium ; metabolic mediator ; kinetics ; calcium pulses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The identification of intramitochondrial free calcium ([Ca2+ m) as a primary metabolic mediator [see Hansford (this volume) and Gunter, T. E., Gunter, K. K., Sheu, S.-S., and Gavin, C. E. (1994)Am. J. Physiol. 267, C313–C339, for reviews] has emphasized the importance of understanding the characteristics of those mechanisms that control [Ca2+]m. In this review, we attempt to update the descriptions of the mechanisms that mediate the transport of Ca2+ across the mitochondrial inner membrane, emphasizing the energetics of each mechanism. New concepts within this field are reviewed and some older concepts are discussed more completely than in earlier reviews. The mathematical forms of the membrane potential dependence and concentration dependence of the uniporter are interpolated in such a way as to display the convenience of consideringV max to be an explicit function of the membrane potential. Recent evidence for a transient rapid conductance state of the uniporter is discussed. New evidence concerning the energetics and stoichiometries of both Na+-dependent and Na+-independent efflux mechanisms is reviewed. Explicit mathematical expressions are used to describe the energetics of the system and the kinetics of transport via each Ca2+ transport mechanism.
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    URL: http://dx.doi.org/10.1007/BF00762732
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  • 86
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    Binary oscillations in the Kok model of oxygen evolution in oxygenic photosynthesis (1996)
    Springer
    Photosynthesis research 48 (1996), S. 411-417 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll a fluorescence ; kinetics ; Photosystem II ; quinone acceptors ; S-states of oxygen-evolving complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flash-induced kinetics of various characteristics of Photosystem II (PS II) in the thylakoids of oxygenic plants are modulated by a period of two, due to the function of a two-electron gate in the electron acceptor side, and by a period of four, due to the changes in the state of the oxygen-evolving complex. In the absence of inhibitors of PS II, the assignment of measured signal to the oxygen-evolving complex or to quinone acceptor side has frequently been done on the basis of the periodicity of its flash-induced oscillations, i.e. four or two. However, in some circumstances, the period four oscillatory processes of the donor side of PS II can generate period two oscillations. It is shown here that in the Kok model of oxygen evolution (equal misses and equal double hits), the sum of the concentrations of the S 0 and S 2 states (as well as the sum of concentrations of S 1 and S 3 states) oscillates with period of two: S 0+S 2→S 1+S 3→S 0+S 2→S 1+S 3. Moreover, in the generalized Kok model (with specific miss factors and double hits for each S-state) there always exist such ε0, ε1, ε2, ε3 that the sum ε0[S0] + ε1[S1] + ε2[S2] + ε3[S3] oscillates with period of two as a function of flash number. Any other coefficients which are linearly connected with these coefficients, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbew7aLzaaja% aaaa!3917!\[\hat \varepsilon \]i = c1εi + c2, also generate binary oscillations of this sum. Therefore, the decomposition of the flash-induced oscillations of some measured parameters into binary oscillations, depending only on the acceptor side of PS II, and quaternary oscillations, depending only on the donor side of PS II, becomes practically impossible when measured with techniques (such as fluorescence of chlorophyll a, delayed fluorescence, electrochromic shift, transmembrane electrical potential, changes of pH and others) that could not spectrally distinguish the donor and acceptor sides. This property of the Kok cycle puts limits on the simultaneous analysis of the donor and acceptor sides of the RC of PS II in vivo and suggests that binary oscillations are no longer a certain indicator of the origin of a signal in the acceptor side of PS II.
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    URL: http://dx.doi.org/10.1007/BF00029473
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    The effects of flow rate and distance travelled on the mobility of phosphate in soils (1994)
    Springer
    Transport in porous media 16 (1994), S. 237-251 
    Details
    ISSN: 1573-1634
    Keywords: phosphate ; soil ; adsorption ; leaching ; kinetics ; computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Effects of flow rate and distance travelled on average mobilities of phosphate in a soil are estimated from breakthrough curves of phosphate at the outlets of small columns of soil, following step increases in the concentration at the inlets. Experimental results are compared with results from a computer simulation model of leached columns of soil. Average mobilities of phosphate in columns of soil, following a step increase in the input concentration, decrease with decreasing rate of flow and with increasing distance travelled and appear to be linearly correlated on a logarithmic scale with both flow rate and distance travelled. An empirical equation, describing these relationships, is fitted to data from leaching experiments at flow rates between 30 and 600 cm/day in ≈ 10 cm long columns of soil. Coefficients are obtained by curve fitting breakthrough curves, calculated with a numerical computer simulation model, to experimental breakthrough curves. The fitted equation enables extrapolation to flow rates and travel distances that are more relevant to a field situation.
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    URL: http://dx.doi.org/10.1007/BF00617149
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  • 88
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    The atmospheric chemistry of dimethylsulfoxide (DMSO) kinetics and mechanism of the OH+DMSO reaction (1996)
    Springer
    Journal of atmospheric chemistry 24 (1996), S. 23-37 
    Details
    ISSN: 1573-0662
    Keywords: hydroxyl radical ; dimethylsulfoxide ; kinetics ; sulfur cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We have employed a pulsed laser photolysis-pulsed laser induced fluorescence technique to study the kinetics and mechanism of the reaction of OH with dimethylsulfoxide and its deuterated analogue. A rate coefficient of (1.0±0.3)×10-10 cm3 molecule-1 s-1 was obtained ar room temperature. The rate coefficient was independent of pressure over the range 25–700 Torr, showed no dependence on the nature of the buffer gas and showed no kinetic isotope effect. A limited study of the temperature dependence indicated that the reaction displays a negative activation energy. The gas phase ultraviolet absorption spectrum was obtained at room temperature and showed a strong absorption feature in the far ultraviolet. The absolute absorption cross-section at 205 nm, the absorption peak, is (1.0±0.3)×10-17 cm2, where the large uncertainty results from experimental difficulties associated with the low vapor pressure and ‘stickiness’ of DMSO.
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    URL: http://dx.doi.org/10.1007/BF00053821
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  • 89
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    The isothermal crystallization of engineering polymers — POM and PEEK (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 1-16 
    Details
    ISSN: 1435-1536
    Keywords: Polymer crystallization ; kinetics ; modeling ; POM ; PEEK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The isothermal crystallization of two engineering polymers — POM and PEEK — was studied, both theoretically and experimentally. The experiments were performed by means of differential scanning calorimetry (DSC) and polarized light optical microscopy (OM). Building on previously developed theoretical formalisms (Avrami/Evans, Hillier and Tobin), a new procedure is presented, based on Tobin's model coupled with a modification of Hillier's calculation technique, to accurately describe the kinetics and mechanism of the crystallization of polymers from quiescent melts. First, it is shown that Tobin's model alone, without modification, is more accurate than Avrami/Evans model to describe single-mechanism processes, for a wide range of materials and for longer crystallization times, despite having exactly the same nature and number of parameters (the kinetic, nucleation and growth rate-related, parameterK and the dimensionalityn). Then, Hillier's formalism is modified and combined with Tobin's model, to accurately predict the kinetics of dual mechanism crystallization processes; a clear contrast is drawn with Hillier's Avrami-based, original procedure which uses the same number and nature of parameters, but cannot adequately predict the experimental behavior. The parameter values predicted by the model(s) and procedure presented in this work are all given, are then physically interpreted and, in the case of POM, related to independent morphological observations by polarized light optical microscopy. They are also consistent with electron microscopy observations made by other authors on the detailed morphology of the spherulitic crystallization of polymers.
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    URL: http://dx.doi.org/10.1007/BF00653305
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    The molecular basis of potassium nutrition in plants (1996)
    Springer
    Plant and soil 187 (1996), S. 81-89 
    Details
    ISSN: 1573-5036
    Keywords: high-affinity ; kinetics ; low-affinity ; potassium ; regulation ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Over the last five years, the cloning and characterization of K+ transport genes corresponding to K+ channels (KAT1, AKT1, KST1, AKT2), associated subunits (KAB1) and a high-affinity transporter (HKT1) has opened up important new avenues for research on plant K+ nutrition. With the abundance of molecular data now available it seems timely to link this information with the wealth of data previously accumulated on the physiology of plant K+ acquisition. The ultimate goal of all this research is to gain a better understanding of K+ transport and nutrition in the intact plant. Thus it is important to begin to integrate the molecular research with results from biochemical and physiological research conducted at the cellular, root and whole plant levels. This article will focus on describing the features of the cloned K+ transporters and their possible roles in mediating high- and low-affinity K+ uptake from the soil, as well as how K+ acquisition may be regulated.
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    URL: http://dx.doi.org/10.1007/BF00011659
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    The kinetics of reactions around the cytochrome bf complex studied in an isolated system (1994)
    Springer
    Photosynthesis research 40 (1994), S. 199-206 
    Details
    ISSN: 1573-5079
    Keywords: cytochrome bf complex ; electron transfers ; kinetics ; quinol oxidation ; Q-cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of oxidation and reduction of P700, plastocyanin, cytochrome f and cytochrome b-563 were studied in a reconstituted system consisting of Photosystem I particles, cytochrome bf complex and plastocyanin, all derived from pea leaf chloroplasts. Decyl plastoquinol was the reductant of the bf complex. Turnovers of the system were initiated by laser flashes. The reaction between oxidised P700 and plastocyanin was non-homogeneous in that a second-order rate coefficient of c. 5×10−7 M−1 s−1 applied to 80% of the P700+ and c. 0.7×107 M−1 s−1 to the remainder. In the presence of bf complex, but without quinol, the electron transfer between cytochrome f and oxidised plastocyanin could be described by a second-order rate coefficient of c. 4×107 M−1 s−1 (forward), and c. 1.6×107 M−1 s−1 (reverse). The equilibrium coefficient was thus 2.5. Unexpectedly, there was little reduction of cytochrome f + or plastocyanin+ by electrons from the Rieske centre. With added quinol, reduction of cytochrome b-563 occurred. Concomitantly, electrons appeared in the oxidised species. It was inferred that either the Rieske centre was not involved in the high-potential chain of electron transfer events, or that, only in the presence of quinol, electrons were quickly passed from the Rieske centre to cytochrome f +. Additionally, the presence of quinol altered the equilibrium coefficient for the cyt f/PC interaction from 2.5 to c. 5. The reaction between quinol and the bf complex was describable by a second-order rate coefficient of about 3×106 M−1 s−1. The pattern of the redox reactions around the bf complex could be simulated in detail with a Q-cycle model as previously found for chloroplasts.
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    URL: http://dx.doi.org/10.1007/BF00019337
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    Inhibitor binding to isolated chloroplast cytochrome bf complex (1996)
    Springer
    Photosynthesis research 49 (1996), S. 37-48 
    Details
    ISSN: 1573-5079
    Keywords: cytochrome f ; kinetics ; midpoint potential ; plastocyanin ; P700 ; Rieske centre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of three inhibitors of quinol oxidation in the chloroplast cytochrome bf complex (stigmatellin, tridecylstigmatellin and dibromothymoquinone) were studied in an isolated system comprising Photosystem I (PS I) particles, plastocyanin (PC) and cytochrome bf complex, in the absence of quinol or quinone. Addition of these inhibitors increased the extent of cytochrome f oxidation after a laser flash created oxidised PS I reaction centre (P700) and PC, and decreased somewhat the extent of PC oxidation. The re-reduction of oxidised P700 was more complete than when inhibitor was absent. The data were simulated with reactions which included the putative reduction of cytochrome f by the Rieske centre (FeS) and different rate-coefficients according as to whether inhibitor was bound to the bf complex or not. It was concluded that under the conditions studied the Rieske centre donated electrons to oxidised cytochrome f and plastocyanin with an average rate coefficient of 35 s−1. This electron transfer was prevented by any of the three inhibitors, which also increased the equilibrium coefficient for the cytochrome f/PC reaction by a maximum factor of two. This increase corresponded to a decrease in the back reaction coefficient and an increase in the forward rate. The equilibrium coefficient for the reduction of oxidised P700 by PC was about 2 in the absence of inhibitor but increased to about 20 in their presence, but only if cytochrome bf complex was additionally present. This was attributed to the transient formation of complexes between P700 with bound plastocyanin, and bf complex. The operative mid-point potential of FeS, if that of cytochrome f is 370 mV, was 390 mV. Deviations in midpoint potentials (P700/plastocyanin) from solution values were attributed to the bound state of the reactants. Estimates were made of the binding coefficient of each of the three inhibitors to p-sites in the cytochrome bf complex in the absence of competing quinol. A stoichiometry of two inhibitors per bf dimer was necessary to cause the above changes in reduction potential of cyt f and PC. A result of one inhibitor per dimer was statistically unlikely, particularly in the case of tridecylstigmatellin.
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    URL: http://dx.doi.org/10.1007/BF00029426
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    Residual sulfite after dechlorination of water (1996)
    Springer
    Water, air & soil pollution 90 (1996), S. 295-300 
    Details
    ISSN: 1573-2932
    Keywords: dechlorination ; coulometry ; sulfite ; water ; rate ; chloramine ; residual ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The kinetics of dechlorination show that chlorinated organic amines are not completely dechlorinated during typical contact times. Analytical techniques for measuring residual sulfite must maintain pH neutrality in order to represent the actual extent of dechlorination and must allow for rapid and convenient operation near the sampling site in order to minimize errors due to air oxidation during the procedure. A portable, analog circuitry-based instrument using constant current coulometry with amperometric end point detection was developed and evaluated. laboratory and field operation of the instrument showed an analytical range of 0.015-to-25.0 mg sulfite/l. Relative standard deviation was typically 1–2%.
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    URL: http://dx.doi.org/10.1007/BF00619289
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    Qualitative and quantitative strategies of thermal adaptation of grass carp (Ctenopharyngodon idella) cytoplasmic malate dehydrogenases (1996)
    Springer
    Fish physiology and biochemistry 15 (1996), S. 71-81 
    Details
    ISSN: 1573-5168
    Keywords: temperature ; malate dehydrogenase ; acclimation ; adaptation ; grass carp ; Ctenopharyngodon idella ; teleost fish ; thermostability ; isozyme ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Malate dehydrogenase isozymes of grass carp,Ctenopharyngodon idella, were identified by mitochondrial preparation and thermal denaturation. The structural and kinetic characteristics of chromatographically separated thermostable and thermolabile cMDHs were different in (1) half-life at 42°C, 10 min and 24 h, respectively, (2) optimal substrate, oxaloacetate and malate, concentrations, and (3) the apparent Michaelis-Menten constants of NADH and oxaloacetate. Total MDH activity in white muscle of 11°C-acclimated fish was about twice that of the 30°C-acclimated group. In addition, the ratio of the thermostable to thermolabile cMDH activity in white muscle of 30°C-acclimated fish was significantly higher than that of 11°C-acclimated fish. These results suggest that temperature acclimation can induce temperature compensation in MDH activity and differential expression of thermostable and thermolabile cMDH isozymes in freshwater fish.
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    URL: http://dx.doi.org/10.1007/BF01874840
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    Kinetic studies on the cleavage of phthalimide in methylamine buffers (1996)
    Springer
    Reaction kinetics and catalysis letters 58 (1996), S. 97-103 
    Details
    ISSN: 1588-2837
    Keywords: Phthalimide ; methylamine ; aminolysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In aqueous methylamine buffers of pH 10.21–11.25 nucleophilic cleavage of ionized (S−) phthalimide and general base-catalyzed cleavage of nonionized (SH) phthalimide is observed.
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    URL: http://dx.doi.org/10.1007/BF02071111
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    Alkylation of aromatics. Kinetics of phenol alkylation with methanol (1996)
    Springer
    Reaction kinetics and catalysis letters 57 (1996), S. 21-27 
    Details
    ISSN: 1588-2837
    Keywords: Phenol ; alkylation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A kinetic study of phenol alkylation with methanol in the presence of γ-Al2O3 has been carried out. A mechanism involving the reaction of phenol and methanol adsorbed on acid-base pair sites is proposed.
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    URL: http://dx.doi.org/10.1007/BF02076115
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    Kinetics and catalysis by NaY entrapped Pt carbonyl clusters in the CO+NO reaction (1996)
    Springer
    Reaction kinetics and catalysis letters 59 (1996), S. 75-86 
    Details
    ISSN: 1588-2837
    Keywords: Pt carbonyl clusters ; CO+NO reaction ; NaY ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract [Pt12(CO)24]2−/NaY and [Pt9(CO)18]2−/NaY exhibited much higher activities in the CO+NO reaction at 473 K compared with Pt/Al2O3. Kinetic study andin-situ FTIR results suggest that NO adsorption is the rate-limiting step in the CO+NO reaction on intrazeolite Pt carbonyl clusters.
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    URL: http://dx.doi.org/10.1007/BF02067995
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    Degradation of the Antiarthritic Prodrug, 3-Carboxy-5-methyl-N-[4-(trifluoromethoxy)phenyl]-4-isoxazolecarboxamide, in Aqueous Solution (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 345-348 
    Details
    ISSN: 1573-904X
    Keywords: kinetics ; decarboxylation ; leflunomide ; deacetylation ; dissociation constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018940415770
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    Growth characteristics of Geotrichum ingens on propionic acid and acetic acid in batch and continuous culture (1994)
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 505-509 
    Details
    ISSN: 1573-0972
    Keywords: Acetic acid ; chemostat ; Geotrichum ingens ; growth ; inhibition ; kinetics ; monocarboxylic acids ; propionic acid ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Growth of Geotrichum ingens in batch cultures was completely inhibited by 47 g acetic acid/l or 33 g propionic acid/I. With mixtures of acetic and propionic acids, however, growth only ceased at 55 g/l. Acetic acid inhibited growth linearly, whereas propionic acid inhibited growth non-linearly. In continuous culture, two steady states at each dilution rate were observed at high dilution rates for acetic acid and propionic acid. The highest yield coefficient (0.69 g cells/g substrate) was achieved with propionic acid as substrate. On both substrates and their mixtures, the protein content of the biomass increased when the dilution rate was increased.
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    URL: http://dx.doi.org/10.1007/BF00367654
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    Chlorine decay and bacterial inactivation kinetics in drinking water in the tropics (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 549-556 
    Details
    ISSN: 1573-0972
    Keywords: Bacteria inactivation ; chlorine decay ; combined chlorine ; drinking water ; free chlorine ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The decay of free chlorine (Cl2) and combined chlorine (mostly monochloramine: NH2Cl) and the inactivation of bacteria was examined in Dar es Salaam, Tanzania. Batch experiments, pilot-scale pipe experiments and full-scale pipe experiments were carried out to establish the kinetics for both decay and inactivation, and to compare the two disinfectants for use under tropical conditions. The decay of both disinfectants closely followed first order kinetics, with respect to the concentration of both disinfectant and disinfectant-consuming substances. Bacterial densities exhibited a kinetic pattern consisting of first order inactivation with respect to the density of the bacteria and the concentration of the disinfectant, and first order growth with respect to the bacterial density. The disinfection kinetic model takes the decaying concentration of the disinfectant into account. The decay rate constant for free chlorine was 114 lg-1h-1, while the decay rate constant for combined chlorine was 1.84 lg-1h-1 (1.6% of the decay rate for free chlorine). The average concentration of disinfectant consuming substances in the water phase was 2.6 mg Cl2/l for free chlorine and 5.6 mg NH2Cl/l for combined chlorine. The decay rate constant and the concentration of disinfectant consuming substances when water was pumped through pipes, depended on whether or not chlorination was continuous. Combined chlorine especially could clean the pipes of disinfectant consuming substances. The inactivation rate constant λ, was estimated at 3.06×104 lg-1h-1. Based on the inactivation rate constant, and a growth rate constant determined in a previous study, the critical concentration of free chlorine was found to be 0.08 mg Cl2/l. The critical concentration is a value below which growth rates dominate over inactivation.
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    URL: http://dx.doi.org/10.1007/BF00419471
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