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  • 1
    Digitale Medien
    Digitale Medien
    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
    Springer
    Adsorption 6 (2000), S. 137-147 
    Details
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; kinetics ; linear driving force model ; process design
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008965317983
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of K, Cs and Ba on the kinetics of NH3 synthesis over carbon-based ruthenium catalysts (2000)
    Springer
    Catalysis letters 68 (2000), S. 163-168 
    Details
    ISSN: 1572-879X
    Schlagwort(e): ammonia synthesis ; kinetics ; ruthenium catalysts ; promotional effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019024629261
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  • 3
    Digitale Medien
    Digitale Medien
    Mechanism of the hydrodenitrogenation of o-toluidine and methylcyclohexylamine over NiMo/γ-Al2O3 (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 327-333 
    Details
    ISSN: 1572-9028
    Schlagwort(e): hydrodenitrogenation ; toluidine ; methylcyclohexylamine ; kinetics ; nickel-promoted molybdenum sulphide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al2O3 catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1027208200169
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  • 4
    Digitale Medien
    Digitale Medien
    Static and Kinetic Studies on the Adsorption Behavior of Sulfadiazene (2000)
    Springer
    Adsorption 6 (2000), S. 349-357 
    Details
    ISSN: 1572-8757
    Schlagwort(e): sulfadiazene ; adsorption ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026517117239
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  • 5
    Digitale Medien
    Digitale Medien
    NO reduction over La2O3 using methanol (2000)
    Springer
    Catalysis letters 64 (2000), S. 65-75 
    Details
    ISSN: 1572-879X
    Schlagwort(e): NO reduction ; CH3OH ; La2O3 ; methyl nitrite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Nitric oxide (NO) reduction by methanol was studied over La2O3 in the presence and absence of oxygen. In the absence of O2, CH3OH reduced NO to both N2O and N2, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O2 in the feed, rates were 4–8 times higher, but the selectivity to N2 dropped from 50% at 623 K to 10% at 723 K. The specific activities with La2O3 for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 μmol NO/s m2 was obtained whereas that for methanol was 600 μmol NO/s m2. The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH3OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH3OH and a near‐first order in H2. In the absence of O2, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH3OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O2 a homogeneous gas‐phase reaction between O2, NO, and CH3OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O2 present were significantly complicated by this homogeneous reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019036431195
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  • 6
    Digitale Medien
    Digitale Medien
    Oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and p-benzoquinone in the presence of inorganic acid (2000)
    Springer
    Catalysis letters 69 (2000), S. 103-107 
    Details
    ISSN: 1572-879X
    Schlagwort(e): dicyclopentadiene ; Wacker oxidation ; Pd(AcO)2 ; benzoquinone ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and benzoquinone in the presence of perchloric acid was studied. Tricyclodecenone in high selectivity (85–98%) at a conversion of dicyclopentadiene up to 76% was obtained. The kinetic model assumed the significant inhibition complexation between dicyclopentadiene and tricyclodecenone with the catalytic species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019053402854
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  • 7
    Digitale Medien
    Digitale Medien
    A polymorphism of the rat T-cell receptor β-chain variable gene 13 (BV13S1) correlates with the frequency of BV13S1-positive CD4 cells (2000)
    Springer
    Immunogenetics 51 (2000), S. 296-305 
    Details
    ISSN: 1432-1211
    Schlagwort(e): Key words Vβ13 ; CD4/CD8 ratio ; Rat ; Tcrb ; Polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Three rat BV13S1 alleles (T-cell receptor β-chain variable gene 13) were characterized by new BV13S1-allele specific monoclonal antibodies (18B1 and 17D5) and sequence analysis of expressed and genomic BV13S1. Two alleles were functional and designated BV13S1A1 present in strains LEW, BUF, PVG, and BV13S1A2 present in BN and WF. Their products differed by six amino acids, two of them in complementarity-determing region (CDR)1 and one in CDR2. A third nonfunctional allele, BV13S1A3P, was found in strains F344 and DA. Apart from a single nucleotide insertion, it was identical to BV13S1A2. All 12 rat strains tested showed association of TCRBC1 with BV8S2/4 alleles but not with the BV13S1 alleles, which may reflect a different gene order of the rat BV compared to mouse. BV13S1A1-encoded T-cell receptors (TCRs) which bind both monoclonal antibody (mAb) 18B1 and mAb 17D5 are over-represented in the CD4 lymphocyte subset. BV13S1A2-encoded TCRs which are stained by mAb 18B1 but not by mAb 17D5 show a slight CD8-biased expression. Preferential usage of BV13S1A1-positive TCRs by CD4 but not by CD8 cells in (LEW×WF)F1 hybrids and cosegregation of BV13SA1 and increased frequency of BV13S1 TCR-positive CD4 cells in a (LEW×BN)×BN backcross suggest structural differences of the two allelic products as the reason for their contrasting CD4/CD8 subset bias.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002510050623
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  • 8
    Digitale Medien
    Digitale Medien
    Localization of endothelin receptors in bleomycin-induced pulmonary fibrosis in the rat (2000)
    Springer
    Histochemistry and cell biology 122 (2000), S. 507-517 
    Details
    ISSN: 1432-119X
    Schlagwort(e): Endothelin-A receptor ; Endothelin-B receptor ; Rat ; Pulmonary fibrosis ; Immunohistochemistry ; Quantitative PCR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: AbstractPulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ETB receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ETA and ETB receptor mRNA, and ETA receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ETA nor ETB receptor mRNA which were also not induced by bleomycin. We conclude that, while ETB receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ETA receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s00418-004-0708-7
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  • 9
    Digitale Medien
    Digitale Medien
    Kinetic Analysis of the Decomposition of Chelates of Di-alkyldithiocarbamate of Cd(II) (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010120813517
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  • 10
    Digitale Medien
    Digitale Medien
    Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
    Details
    ISSN: 1572-8943
    Schlagwort(e): facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010157821694
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  • 11
    Digitale Medien
    Digitale Medien
    Thermal Decomposition Kinetics of Some Metal Complexes of N,N-diethyl-n '-benzoylthiourea (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
    Details
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; metal complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010171230450
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  • 12
    Digitale Medien
    Digitale Medien
    Fast Gas Adsorption Measurements For Complicated Adsorption Mechanisms (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010190131304
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  • 13
    Digitale Medien
    Digitale Medien
    Study of Thermal Decomposition Kinetics of Low-temperature Reaction of Ammonium Perchlorate by Isothermal TG (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
    Details
    ISSN: 1572-8943
    Schlagwort(e): activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010136308310
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  • 14
    Digitale Medien
    Digitale Medien
    Theoretical and Experimental Investigations of The Decomposition of 10-methylacridinium Halides (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
    Details
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010160132175
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  • 15
    Digitale Medien
    Digitale Medien
    Thermal Decomposition of Triazine Herbicides. I. 1,2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropionitrile (cyanazine) (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 103-110 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cyanazine ; DSC ; kinetics ; thermal stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010132820788
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  • 16
    Digitale Medien
    Digitale Medien
    Influence of Gas Atmosphere on Removal of Sulphate Groups From Titanium Oxide (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
    Details
    ISSN: 1572-8943
    Schlagwort(e): desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010178130783
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  • 17
    Digitale Medien
    Digitale Medien
    Solid State Coordination Chemistry. The quantitative thermoanalytical study of thermal dissociation reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
    Details
    ISSN: 1572-8943
    Schlagwort(e): coordination compounds ; kinetics ; thermal dissociation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010148028796
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  • 18
    Digitale Medien
    Digitale Medien
    The Effect of Cross-linked Polyethylene As a Surface Modifier on Crystallization of Polypropylene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010129106561
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  • 19
    Digitale Medien
    Digitale Medien
    Formation of Cr(II) Species in the H2/CrO3 System. Parameter control (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
    Details
    ISSN: 1572-8943
    Schlagwort(e): Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010142904261
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  • 20
    Digitale Medien
    Digitale Medien
    Kinetic Modeling of Advanced Inorganic Glass-ceramics Formation by Crystal Growth From Pre-existing Nuclei (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
    Details
    ISSN: 1572-8943
    Schlagwort(e): accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010123805594
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  • 21
    Digitale Medien
    Digitale Medien
    Temperature Modulated DSC. Theoretical interpretation (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    Details
    ISSN: 1572-8943
    Schlagwort(e): base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010148200201
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  • 22
    Digitale Medien
    Digitale Medien
    Practical Thermogravimetry (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
    Details
    ISSN: 1572-8943
    Schlagwort(e): decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010187019979
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  • 23
    Digitale Medien
    Digitale Medien
    The Thermodynamic Driving Force in the Kinetic Evaluation of Thermoanalytical Curves (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
    Details
    ISSN: 1572-8943
    Schlagwort(e): driving force ; kinetics ; rate equation ; reversible reactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010159708593
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  • 24
    Digitale Medien
    Digitale Medien
    Kinetic Analysis of the Thermal Decomposition of Synthetic Malachite by CRTA (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
    Details
    ISSN: 1572-8943
    Schlagwort(e): CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010172111319
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  • 25
    Digitale Medien
    Digitale Medien
    Thermal Studies on Some Lanthanide Complexes (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
    Details
    ISSN: 1572-8943
    Schlagwort(e): complexes ; kinetics ; TG-DTA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010172926826
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  • 26
    Digitale Medien
    Digitale Medien
    Non-isothermal Kinetic Study of the Heterogeneous Thermal Decomposition of a Mannich Compound (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
    Details
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; Mannich compounds ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010197632277
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  • 27
    Digitale Medien
    Digitale Medien
    Polypropylene Crystallization in an Ethylene-propylene-diene Rubber Matrix (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    Details
    ISSN: 1572-8943
    Schlagwort(e): crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010165317028
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  • 28
    Digitale Medien
    Digitale Medien
    TG and DTA Study of the Thermal Dehydration of Metal-exchanged Zeolite-4A Samples (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    Details
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; metal exchange ; thermaldehydration ; zeolite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026725509732
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  • 29
    Digitale Medien
    Digitale Medien
    Kinetic Equations for Thermal Dissociation Processes. Part I. KEKAM equation (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
    Details
    ISSN: 1572-8943
    Schlagwort(e): KEKAM equation ; kinetics ; thermal dissociation of solids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010184224240
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  • 30
    Digitale Medien
    Digitale Medien
    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. II. The activation energy obtained from isothermal data corresponding to two successive reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 465-469 
    Details
    ISSN: 1572-8943
    Schlagwort(e): isoconversional methods ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010100712853
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  • 31
    Digitale Medien
    Digitale Medien
    Kinetics of Thermal Decomposition of Plumbo-jarosite (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
    Details
    ISSN: 1572-8943
    Schlagwort(e): decomposition ; kinetics ; plumbo-jarosite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010122308490
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  • 32
    Digitale Medien
    Digitale Medien
    Thermal Characterization of Passivated Nanometer Size Aluminium Powders (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    Details
    ISSN: 1572-8943
    Schlagwort(e): aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010197115003
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  • 33
    Digitale Medien
    Digitale Medien
    Thermal and Spectroscopic Studies on the Decomposition of Some Aminoguanidine Nitrates (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010113707251
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  • 34
    Digitale Medien
    Digitale Medien
    Fractal Approach in the Kinetics of Solid-Gas Decompositions. Part II (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
    Details
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; nucleation-growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010175415429
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  • 35
    Digitale Medien
    Digitale Medien
    Study of The Mechanism and Kinetic Parameters of The Thermal Decomposition of Cobalt Sulphate Hexahydrate (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    Details
    ISSN: 1572-8943
    Schlagwort(e): CoSO46H2O ; kinetics ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010186628054
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  • 36
    Digitale Medien
    Digitale Medien
    Kinetic Study of the Accelerating Effect of Coal-burning Additives on the Combustion of Graphite (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
    Details
    ISSN: 1572-8943
    Schlagwort(e): coal-burning additive ; combustion ; graphite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026769323844
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  • 37
    Digitale Medien
    Digitale Medien
    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. I. Theoretical background (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
    Details
    ISSN: 1572-8943
    Schlagwort(e): isoconversional methods ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010148611036
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  • 38
    Digitale Medien
    Digitale Medien
    Modeling of the Phase Transformation Induced by Ball Milling in Anatase TiO2 (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    Details
    ISSN: 1573-4870
    Schlagwort(e): TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011351807629
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  • 39
    Digitale Medien
    Digitale Medien
    Relating Single-Impact Events to Macrokinetic Features in Mechanical Alloying Processes (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 271-277 
    Details
    ISSN: 1573-4870
    Schlagwort(e): Comminution ; kinetics ; mechanical alloying ; phase transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011382008963
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  • 40
    Digitale Medien
    Digitale Medien
    High-Temperature Oxidation Behavior of the Co-Base Superalloy DZ40M in Air (2000)
    Springer
    Oxidation of metals 53 (2000), S. 351-360 
    Details
    ISSN: 1573-4889
    Schlagwort(e): Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004597405809
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  • 41
    Digitale Medien
    Digitale Medien
    Analysis of Aluminum—Yeast Hexokinase Interaction: Modifications on Protein Structure and Functionality (2000)
    Springer
    The protein journal 19 (2000), S. 199-208 
    Details
    ISSN: 1573-4943
    Schlagwort(e): Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007055719926
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  • 42
    Digitale Medien
    Digitale Medien
    A Comparative Study of Human Muscle and Brain Creatine Kinases Expressed in Escherichia coli (2000)
    Springer
    The protein journal 19 (2000), S. 59-66 
    Details
    ISSN: 1573-4943
    Schlagwort(e): Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007047026691
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  • 43
    Digitale Medien
    Digitale Medien
    Stabilization of ammonium dinitramide in the liquid phase (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1974-1976 
    Details
    ISSN: 1573-9171
    Schlagwort(e): ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009555405171
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  • 44
    Digitale Medien
    Digitale Medien
    The kinetics and mechanism of cyclodimerization of alkylthiopropenals (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1977-1980 
    Details
    ISSN: 1573-9171
    Schlagwort(e): 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009507522009
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  • 45
    Digitale Medien
    Digitale Medien
    Cooperative Interactions in Photosensitized Modification of DNA with Oligonucleotide-derived Binary Reagents (2000)
    Springer
    Molecular biology 34 (2000), S. 814-822 
    Details
    ISSN: 1608-3245
    Schlagwort(e): DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026619607955
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  • 46
    Digitale Medien
    Digitale Medien
    Functional Properties of Lactate Dehydrogenase from Dunaliella salina and Its Role in Glycerol Synthesis (2000)
    Springer
    Russian journal of plant physiology 47 (2000), S. 761-771 
    Details
    ISSN: 1608-3407
    Schlagwort(e): Dunaliella salina ; lactate dehydrogenase ; kinetics ; glycerol synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The dependence of the catalytic properties of lactate dehydrogenase (LDH, EC 1.1.1.27) from a halophilic alga Dunaliella salina, a glycophilic alga Chlamydomonas reinhardtii, and from porcine muscle on glycerol concentration, medium pH, and temperature was investigated. Several chemical properties of the enzyme from D. salina differentiated it from the LDH preparation obtained from C. reinhardtii and any homologous enzymes of plant, animal, and bacterial origin. (1) V max of pyruvate reduction manifested low sensitivity to the major intracellular osmolyte, glycerol. (2) The affinity of LDH for its coenzyme NADH dropped in the physiological pH region of 6–8. Above pH 8, NADH virtually did not bind to LDH, while the enzyme affinity for pyruvate did not change considerably. (3) The enzyme thermostability was extremely low: LDH was completely inactivated at room temperature within 30 min. The optimum temperature for pyruvate reduction (32°C) was considerably lower than with the enzyme preparations from C. reinhardtii (52°C) and porcine muscle (61°C). (4) NADH greatly stabilized LDH: the ratio of LDH inactivation constants in the absence of the coenzyme and after NADH addition at the optimum temperature in the preparation from D. salina exceeded the corresponding indices of LDH preparations from C. reinhardtii twelve times and from porcine muscle eight times. The authors believe that these LDH properties match the specific metabolism of D. salina which is set at rapid glycerol synthesis under hyperosmotic stress conditions. The increase of cytoplasmic pH value produced in D. salina by the hyperosmotic shock can switch off the terminal reaction of the glycolytic pathway and thus provide for the most efficient utilization of NADH in the cycle of glycerol synthesis. As LDH is destabilized in the absence of NADH, this reaction is also switched off. In the course of alga adaptation to the hyperosmotic shock, glycerol accumulation and the neutralization of intracellular pH stabilize LDH, thus creating the conditions for restoring the complete glycolytic cycle.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026607211936
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  • 47
    Digitale Medien
    Digitale Medien
    Kinetic study of a thermostable β-glycosidase of Thermus thermophilus. Effects of temperature and glucose on hydrolysis and transglycosylation reactions (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 377-383 
    Details
    ISSN: 1573-4986
    Schlagwort(e): β-glycosidase ; temperature dependence ; kinetics ; glucose ; transglycosylation ; (Thermus thermophilus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A β-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttβgly) has a broad substrate specificity towards β-D-glucoside, β-D-galactoside and β-D-fucoside derivatives. The thermostability of Ttβgly was exploited to study its kinetic properties within the range 25–80[emsp4 ]°C. Whatever the temperature, except around 60[emsp4 ]°C, the enzyme displayed non-Michaelian kinetic behavior. Ttβgly was inhibited by high concentrations of substrate below 60[emsp4 ]°C and was activated by high concentrations of substrate above 60[emsp4 ]°C. The apparent kinetic parameters (k cat and K m ) were calculated at different temperatures. Both k cat and K m increased with an increase in temperature, but up to 75[emsp4 ]°C the values of k cat increased much more rapidly than the values of K m . The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttβgly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007104030314
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  • 48
    Digitale Medien
    Digitale Medien
    Statistical Properties of Stimulated Raman Scattering in a Nonlinear Regime (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 981-989 
    Details
    ISSN: 1573-8647
    Schlagwort(e): nonlinear regime of stimulated Raman scattering ; fluctuation ; Stokes radiation ; kinetics ; spectrum ; distribution function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Statistical properties of the Raman scattering of an intense step pulse are investigated by numerical solution of the equations of a semi-classical theory with assignment of a random Gaussian distribution of the initial polarization over the sample. The probability density functions of the intensity, energy, delay time, and width of a Stokes pulse and also of the position, height, and width of the spectral peaks of the first incidental Stokes component with the preservation of the phase memory of scattering centers are calculated. The influence of collisional dephasing on the fluctuation of these characteristics is considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004120404710
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  • 49
    Digitale Medien
    Digitale Medien
    Effect of Compaction Scheme on Property Distribution for Cumulative Charge Facings Formed from a Heterogeneous Powder Composite (2000)
    Springer
    Powder metallurgy and metal ceramics 39 (2000), S. 540-544 
    Details
    ISSN: 1573-9066
    Schlagwort(e): compaction ; facing ; cumulative charge ; powder ; composite ; heterogeneous structure ; particle ; kinetics ; surface ; die ; model ; xeroradiogram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract An experimental and numerical (finite element method) study is carried out for the effect of forming scheme on property distribution for cumulative charge facings made from composite heterogeneous powder material. An experimental procedure is developed for studying powder particle flow kinetics. It is shown that use of composite punches and partition of the moulded material into a number of sub-divisions with their successive compaction achieves a more uniform density distribution for an article. It is demonstrated how the direction of the force of friction on the die walls during compaction affects the compaction of articles with faces that are not perpendicular to the direction of the pressing. The results obtained make it possible to select the optimum compaction regime taking account of production features connected with powder material composition as well as service characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011359626701
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  • 50
    Digitale Medien
    Digitale Medien
    Simultaneous Determination of the Heat and the Quantity of Vapor Sorption Using a Novel Microcalorimetric Method (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 701-706 
    Details
    ISSN: 1573-904X
    Schlagwort(e): vapor sorption ; molar heat of adsorption ; kinetics ; isothermal microcalorimetry ; recrystallization ; hydration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. In this study, instrumentation for measuring vapor sorptionenthalpies and sorption uptakes simultaneously with an isothermalmicrocalorimeter is introduced. Various pharmaceutical modelsubstances undergoing phase transitions when exposed to humid conditions(25°C), were employed to evaluate the usefulness and sensitivity ofthe constructed experimental method. Methods. The sample is placed in the sample vessel of a RH cell andthe moisture content of the air flow is controlled. From the RH cellthe air flow is conducted into a subsequent perfusion cell in which asaturated salt solution has been loaded. The RH cell and perfusioncells are positioned in the sample sides of two twin calorimetric units.Depending on the moisture content in the outlet flow leaving thepreceding RH cell, the heat flow signal from the subsequent perfusioncell will vary. By means of blank measurement with identical settings,the rate of water sorption can be calculated and, by integration, theamount of sorbed water is obtained. Results. Amorphous lactose and cefadroxil undergo recrystallizationwhen the moisture level in the surroundings exceeds the thresholdvalues specific to each compound. During the sorption phase, heat isevolved fairly linearly as a function of consumed moisture, and alsoafter the recrystallization, the heats indicate linear behavior. The heatvalues for the desorption phase of amorphous lactose and the adsorptionof crystalline lactose coincide. With the different anhydrous forms oftheophylline, the hydration takes place more rapidly in the metastableform I, and generally, the process is more energetic in form I. In allcases, the gravimetric results agree with the water sorption uptakescalculated from the calorimetric data. Conclusions. The technique introduced offers a rapid and sensitivemethod to gain new insights into the transitions in which vapors areinvolved. In addition, different kinds of surfaces with various energeticscan now be studied more closely.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007530315652
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  • 51
    Digitale Medien
    Digitale Medien
    Modulation of Paired-Pulse Responses in the Dentate Gyrus: Effects of Normal Maturation and Vigilance State (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 128-134 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Hippocampus ; Vigilance states ; Paired-pulse ; Dentate gyrus ; Dentate granule cells ; Evoked response ; Rat ; In vivo studies ; Perforant path ; Maturation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract This study examined the effect of normal development and vigilance state on the modulation of dentate granule cell activity in the freely moving rat at 15, 30, and 90 days of age across three vigilance states: quiet waking, slow-wave sleep, and rapid eye movement sleep. Using paired-pulse stimulation, the paired-pulse index (PPI) was obtained for the dentate evoked field potentials elicited by the stimulation of the medial perforant path. Although significant differences in PPI values were observed during development, no significant vigilance state related changes were obtained. Preweaning infant rats, i.e., 15-day old, exhibited significantly less early (interpulse intervals, IPI= 20–50 ms) and late (IPI = 300–1000 ms) inhibition, and less facilitation (IPI = 50–150 ms) when compared to the 90-day old adult rats during all three vigilance states. PPI values obtained from the 30-day old group fell intermediate between the 15- and 90-day old animals. These changes in PPI values provide a quantitative measure of changes in the modulation of dentate granule cell excitability during normal maturation. They can now can be used to evaluate the impact of various insults, such as prenatal protein malnutrition or neonatal stress, on hippocampal development. © 2000 Biomedical Engineering Society. PAC00: 8717Nn, 8719La, 8719Nn
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.261
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  • 52
    Digitale Medien
    Digitale Medien
    Left Ventricular Contractility is Impaired Following Myocardial Infarction in the Pig and Rat: Assessment by the End Systolic Pressure–Volume Relation Using a Single-Beat Estimation Technique and Cine Magnetic Resonance Imaging (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 484-494 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Heart ; Left ventricle ; LV contractility ; ESPVR ; Pig ; Rat ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The end systolic pressure–volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR $$\left( {E_{es} } \right)$$ decreased significantly following infarction in both species, while the volume-axis intercept $$\left( {V_0 } \right)$$ was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8761Lh, 8719Hh, 8719Rr, 8719Ff
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.289
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  • 53
    Digitale Medien
    Digitale Medien
    Quantifying Coevolution of Nonstationary Biomedical Signals Using Time-Varying Phase Spectra (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 1101-1115 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Time–frequency analysis ; Coherence ; Cross correlation ; Nonstationary persistent signals ; Central pattern generator ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract We present a novel time-varying phase spectrum (TVPS) method to quantify the dynamics of coevolution of two persistent nonstationary coupled signals. Based on the TVPS, an instantaneous intersignal phase shift is defined within the primary frequency range in which the two signals are highly correlated. The TVPS is estimated using a fixed-window method or an adaptive-window method. In the latter method, the window length changes dynamically and automatically as a function of change in frequency of the signals. The effects of altering window types and lengths on the accuracy of the estimation of the primary phase shift is assessed by analyzing synthesized linear chirp signals with decaying amplitude and constant relative phase shift or decaying amplitude and changing relative phase shifts. The methods developed are also used for determining the evolution of the primary phase shift among ventral root activities during fictive locomotion in an in vitro rat spinal cord preparation. The analyses indicate that the TVPS method in conjunction with the determination of the primary frequency range, allows determination of both the evolution of the coupling strength and the evolution of the phase shift between two persistent nonstationary rhythmic signals in the joint time–frequency domain. An adaptive window reduces the estimation bias and the estimation variability. © 2000 Biomedical Engineering Society. PAC00: 0230-f, 8780Tq
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.1313775
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  • 54
    Digitale Medien
    Digitale Medien
    Mercury speciation in natural waters: Measurement of dissolved gaseous mercury with a field analyzer (2000)
    Springer
    Biogeochemistry 48 (2000), S. 237-259 
    Details
    ISSN: 1573-515X
    Schlagwort(e): gaseous ; kinetics ; mercury ; methods ; speciation ; waters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Mercury evasion from water is commonly modeled using measurements of dissolved gaseous mercury (DGM). We developed a method using a recently available automated field-ready mercury vapor analyzer to rapidly measure the concentrations of DGM in surface waters. We summarize here results of laboratory tests of the method, field intercomparisons with a manual method, and selected data from recent sampling campaigns in Florida and Michigan. The method uses the 1.5 lpm flow of a Tekran® Model 2537A mercury analyzer to purge and analyze discrete water samples, generating near real time (5-min) data on DGM in samples and blanks. Application of the Tekran allowed for detailed analysis of DGM removal kinetics and short-term diel studies characterizing the influence of sunlight and precipitation on DGM production in surface waters. Gas removal kinetics for dozens of samples indicates a first-order rate constant, and supports a 20-min. purge time for surface water samples from Florida (40-min for Michigan samples). Blanks are measured during a second such purge. Our results indicate that DGMs determined by both automated and manual methods are generally comparable, and that DGM in Florida samples is unstable during storage (loss rate constant ∼0.1--0.2 h-1), probably due to oxidation. This suggests that rapid in-field analysis is preferred to storage with delayed analysis. Our data indicate that DGM at the Florida site is influenced by inputs of reactive Hg in rainwater, and by production of surface DGM during photoreduction of oxidized Hg in the water column.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006228612872
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  • 55
    Digitale Medien
    Digitale Medien
    The Kinetics of Transposable Element Autoregulation (2000)
    Springer
    Genetica 108 (2000), S. 229-237 
    Details
    ISSN: 1573-6857
    Schlagwort(e): autoregulation ; dimerization ; kinetics ; post-transcriptional regulation ; transposable elements (TEs)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Kinetic modeling of the self-regulatory mechanisms of transposable elements (TEs) involving interactions of one or a few gene products makes predictions that are often at odds with observed results. In particular, explanations of TE autorepression at high copy number that invoke a decrease in number of active monomers through dimerization, amyloidization, and protein-mRNA binding to create an inactive state are not supported by analysis of the corresponding kinetic models. This is also true for similar mRNA–mRNA binding models. Self-repression in marineras well as other TEs can, however, be explained by a host-independent model in which inactive dimers compete with monomers for TE binding sites at the ends of the element. This model would also allow heterodimer poisoning to down-regulate transposition in the presence of divergent nonautonomous elements, since nondivergent monomers would be required at both TE ends for transposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004172703790
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  • 56
    Digitale Medien
    Digitale Medien
    Control of the Mitochondrial Permeability Transition Pore by High-Affinity ADP Binding at the ADP/ATP Translocase in Permeabilized Mitochondria (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 91-96 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Permeability transition ; ADP/ATP translocase ; kinetics ; adenosine diphosphate ; carboxya tractyloside ; bongkekic acid ; mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Low levels of ADP binding at the ADP/ATP translocase caused inhibition of the Ca2+-inducedpermeability transition of the mitochondrial inner membrane, when measured using the shrinkage assay on mitochondria, which have already undergone a transition. Inhibition was preventedby carboxyatractyloside, but potentiated by bongkrekic acid, which increased the affinity forinhibition by ADP. This suggests that inhibition was related to the conformation of thetranslocase. Ca2+ addition was calculated to remove most of the free ADP. Ca2+ added after ADPinduced a slow decay of the inhibition, which probably reflected the dissociation of ADP fromthe translocator. We conclude that the probability of forming a permeability transition pore(PTP) is much greater when the translocase is in the CAT conformation than in the BKAconformation, and, in the absence of CAT and BKA, the translocator is shifted between theBKA and CAT conformations by ADP binding and removal, even in deenergized mitochondria with no nucleotide gradients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005568630151
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  • 57
    Digitale Medien
    Digitale Medien
    The Relationship Between Rate of Administration of an Intubating Dose of Rocuronium and Time to 50% and 90% Block at the Adductor Pollicis Muscle (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 219-222 
    Details
    ISSN: 1573-2614
    Schlagwort(e): Neuromuscular relaxants ; rocuronium ; kinetics ; distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin
    Notizen: Abstract Objective.To determine the relationship between the rate ofrocuronium injection and the onset time of neuromuscular block. Methods.After intravenous induction, 60 female patients (ASA I–II) wereassigned randomly into 3 groups for rocuronium administration within1–15, 15–30 or 30–60 seconds. Acceleromyography of the thumbwas performed using train-of-four (TOF) stimulation. Times to 50% and 90%twitch depression of the first twitch of the TOF stimulation (T1) wererecorded. Results.Injection time significantly influences time to 50%relaxation, but not time to 90% relaxation. Body mass index is negativelycorrelated with time to 50% and 90% relaxation. Conclusions.Weconclude that rate of injection influences only the initial phase ofdevelopment of the block and that slower injection times do not significantlyaffect time to 90% relaxation at the adductor pollicis muscle.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009964305762
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  • 58
    Digitale Medien
    Digitale Medien
    Non-Steady State Monitoring by Respiratory Gas Exchange (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 351-360 
    Details
    ISSN: 1573-2614
    Schlagwort(e): carbon dioxide ; oxygen ; kinetics ; non-steady state ; cardiac output ; PEEP ; pulmonary embolism ; pulmonary gas exchange monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin
    Notizen: Abstract Traditionally, the study of CO2 and O2 kinetics in the body has been mostly confined to equilibrium conditions. However, the peri-anesthesia period and the critical care arena often involve conditions of non-steady state. The detection and explanation of CO2 kinetics during non-steady state pathophysiology have required the development of new methodologies, including the CO2 expirogram, average alveolar expired PCO2, and CO2 volume exhaled per breath. Several clinically relevant examples of non-steady state CO2 kinetics perturbations are examined, including abrupt decrease in cardiac output, application of positive end-expiratory pressure during mechanical ventilation, and occurrence of pulmonary embolism. The lesser known area of non-steady state O2 kinetics is introduced, including the measurement of pulmonary O2 uptake per breath. Future directions include the study of the respiratory quotient per breath, where the anaerobic threshold during anesthesia is identified by increasing respiratory quotient.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011447500984
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  • 59
    Digitale Medien
    Digitale Medien
    Removal of Sulfate, Phosphate and Colored Substances in Wastewater Effluents using Feldspar (2000)
    Springer
    Water resources management 14 (2000), S. 417-434 
    Details
    ISSN: 1573-1650
    Schlagwort(e): adsorption ; feldspar ; industrial effluent ; pollution control ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geographie
    Notizen: Abstract Feldspar, among many natural substances such as termitemount-clay, saw-dust, kaolinite and dolomite, offers asignificant removal ability for sulfate, phosphate, and coloredsubstances. Optimization of experimental parameters such assolution pH and flow rate reveals, that the maximum efficiency forremoval of phosphate, sulfate, and colored substances is about42, 52, and 73% respectively. X-ray diffraction, adsorptionisotherm and recovery studies suggest, that the removal processof anions occurs via ion exchange in conjunction with surfaceadsorption. Furthermore, reaction rate studies indicate thatthe removal of the selected pollutants by feldspar follows first-order kinetics. Although the percent removal, under the optimized conditions, is higher for laboratory prepared solutions, efficiency is a little less for industrial effluentsdue to interferent effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011171330097
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  • 60
    Digitale Medien
    Digitale Medien
    Microbalance and Related Studies of High-temperature Superconductors (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 353-363 
    Details
    ISSN: 1572-8943
    Schlagwort(e): controlled environment ; high-T c superconductors ; kinetics ; microgravimetric investigations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Many properties of oxide superconductors depend on the oxygen concentration and its distribution in the samples. The microgravimetric method is very useful to study of oxide superconductors, as it allows investigations in vacuum and controlled environments in classical applications: thermogravimetric analysis for the study of solid-state reactions, determinations of oxygen contents in redox reactions and the combined measurement of mass and additional parameters, e.g. evolved gas analysis etc. Single-phase samples of high-temperature superconductors were synthesized from stoichiometric mixtures of high-purity oxides and carbonates. Appropriate amounts of the precursor powders were homogenized manually or by a mechanical ball mill and subsequently calcined at temperatures in the 800 to 950°C range with intermediate grinding to ensure homogenous reaction. The lattice parameters of all preparations were controlled, in both initial and final experiments, by the X-ray powder method (CuKα radiation), using a Stadi P (Stoe) diffractometer with a position-sensitive detector. It is well known that temperature and mass can be measured with an accuracy higher by orders of magnitude than it is still possible for the thermoanalyst to determine the transformation temperatures or the mass changes due to overlapping partial reactions. Applications of Cahn microbalance to study of high-temperature superconductors are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010192804471
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  • 61
    Digitale Medien
    Digitale Medien
    Studies on Non-isothermal Kinetics of the Thermal Decomposition of Eu2(BA)6(bipy)2 (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 747-755 
    Details
    ISSN: 1572-8943
    Schlagwort(e): benzoic acid ; europium complex ; kinetics ; non-isothermal ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal decomposition of Eu2(BA)6(bipy)2 (BA=C2H5N– 2, benzoate; bipy=C10H8N2, 2,2'-bipyridine)and its kinetics were studied under the non-isothermal condition by TG-DTG, IR and SEM methods. The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method, the Madhusudanan-Krishnan-Ninan (MKN) method, the Ozawa method and the Kissinger method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as: dα/dt=Aexp(–E/RT)3(1–α)2/3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026785727479
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  • 62
    Digitale Medien
    Digitale Medien
    Dsc Evaluations in F.c.c. Solid Solutions of Short-range-order Kinetics As Influenced by Bound Vacancies (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 397-413 
    Details
    ISSN: 1572-8943
    Schlagwort(e): Cu–5 at%Zn ; DSC ; F.C.C. (Face Centered Cubic) ; kinetics ; short-range-order ; solute-vacancy complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A modified first order kinetic law, which describes the roles of bound and unbound vacancies, is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. The model has been applied to differential scanning calorimetry (DSC) curves of Cu–5 at%Zn quenched from different temperatures. Activation energy for migration of solute-vacancy complexes was also assessed from the kinetics of short-range-order using DSC traces. A value of 89.5±0.32 kJ mol–1 was obtained. The relative contribution of bound and unbound vacancies to the ordering process as influenced by quenching temperature was determined. In conjunction, a parametric study of the initial total defect concentration and effective energy for defect migration was performed in order to envisage their influence on the calculated DSC profiles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010140409219
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  • 63
    Digitale Medien
    Digitale Medien
    Influence of DSC Measurement Conditions on Kinetic Parameters of Thermal Decomposition of 2,4,6-trinitrotoluene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 25-33 
    Details
    ISSN: 1572-8943
    Schlagwort(e): DSC ; kinetics ; thermal decomposition ; 2,4,6-trinitrotoluene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010108115336
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  • 64
    Digitale Medien
    Digitale Medien
    Positronium Spin-Conversion Reactions Promoted by 3d Complexes in Highand Low-Spin States (2000)
    Springer
    Structural chemistry 11 (2000), S. 341-346 
    Details
    ISSN: 1572-9001
    Schlagwort(e): Positronium chemistry ; kinetics ; spin-exchange reactions ; high- and low-spin 3d complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Continuing in our work on the correlations between the rate constants, k CR, of the ortho into para-positronium conversion reactions, CR, promoted by complexes of various 3d ions and the metal electron delocalization β caused by the ligands, the relationship between the parameters of the correlation lines pertinent to highand low-spin complexes of CrII, MnII, and CoII ions was ascertained. Moreover, it was experimentally verified, for the first time, that the statistical probability of the CR promoted by paramagnetic compounds with S = 1/2 is three times larger than that of the CR caused by compounds with S 〉 1/2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026513904160
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  • 65
    Digitale Medien
    Digitale Medien
    Efficiency of the muon catalyzed fusion in triple H/D/T mixtures (2000)
    Springer
    Hyperfine interactions 128 (2000), S. 481-493 
    Details
    ISSN: 1572-9540
    Schlagwort(e): muon catalyzed fusion ; triple mixture ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper, we solve numerically kinetic equations for the chain reactions of μCF in triple H/D/T mixture. Regarding the computational results, we show that μCF efficiency decreases by adding hydrogen H to D/T mixture. This is in contradiction to the usual belief which expects the increase of μCF efficiency in H/D/T mixture. Our results are confirmed by the first and recent experiment on μdt cycling rate in the triple mixture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1012676825377
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  • 66
    Digitale Medien
    Digitale Medien
    Kinetics of Acetic Acid Esterification with 2-Methoxyethanol Over a Pillared Clay Catalyst (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 169-176 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Al3+-exchanged pillared clay catalyst ; 2-methoxyethanol ; esterification ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pillared clay catalyst, which was obtained by exposing activated clay powder to sulfuric acid and aluminium salts and calcining in air at 373 – 673 K, was found to be highly active for the title reaction. The activity is mainly attributed to the Lewis acid sites and also to a small number of Brönsted acid sites, whose number and strength increases with the extent of pillaring. The kinetic equation of surface esterification is y = 2.57x - 1.47.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005625800341
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  • 67
    Digitale Medien
    Digitale Medien
    The Kinetics of Tenoxicam Photodegradation in Solution (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 119-124 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Tenoxicam ; photodegradation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Photodegradation of tenoxicam was investigated under different reaction conditions. After 60 min of exposure to UV light, the photodegradation was extensive, and the maximum and minimum in the UV-visible spectrum were shifted to shorter and longer wavelengths, respectively. Ethanol exerted a photostabilizing effect on tenoxicam. Tenoxicam is more stable in acidic and basic media than in neutral solution. Increasing light intensity or temperature causes an increase in the rate of photodegradation. The photodegradation of tenoxicam was found to follow first-order kinetics under all these conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010370901272
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  • 68
    Digitale Medien
    Digitale Medien
    Kinetics of the N-Monoalkylation of Aniline with Methanol Over Zn1−XCoXFe2O4 (X = 0, 0.2, 0.5, 0.8 and 1.0)-Type Systems (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Ferrites ; aniline alkylation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Kinetic parameters such as the activation energy (Ea) and Arrhenius frequency factor (A) for the N-methylation of aniline using methanol over Zn-Co ferrites have been calculated. The Ea value is found to be lower than the existing best alkylating systems such as γ-alumina and magnesium oxide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010387304906
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  • 69
    Digitale Medien
    Digitale Medien
    Kinetics and Mechanism of the Oxidative Regeneration of Carbonyl Compounds from Oximes by Pyridinium Fluorochromate (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 343-347 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Deoximination ; chromium (VI) ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Oxidative deoximination of aldoximes and ketoximes by pyridium fluorochromate proceeds by nucleophilic attack of the chromate oxygen on the oxime carbon to give a cyclic intermediate in the rate-determining step.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010391529810
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  • 70
    Digitale Medien
    Digitale Medien
    Homogeneous Catalysis of C-H Bond Activation by a Novel Ruthenium(III)-Complex (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 147-151 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Oxo-functionalization ; [RuIII(amp)(pic)(H2O)] ; t-BuOOH ; kinetics ; cyclohexane cyclohexene ; toluene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A novel mixed-ligand [RuIII(amp)(pic)(H2O)] complex (1) (H2amp = N-(hydroxyphenyl)salicyldimine; pic = picolinate) has been synthesized and characterized by physico-chemical methods. Complex 1has been found to be an effective catalyst in oxo-functionalization of C-H bond of organic substrates by using tert-butyl hydroperoxide (t-BuOOH) as a terminal oxidant. Formation of a high valent Ru(V)-oxo species as catalytic intermediate is proposed to be the source of oxygen atom in the oxidised product.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010331219928
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  • 71
    Digitale Medien
    Digitale Medien
    Study of the Ligand Substitution Reaction [Fe(CN)5(4-tbupy)]3- + Pyrazine in Concentrated Aqueous Electrolyte Solutions: Estimation of the Activation Volume (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 389-394 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Fe(CN)5(4-tbupy)3- ; kinetics ; electrolytes ; substitution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The ligand substitution reaction [Fe(CN)5(4-tbupy)]3- + pyrazine (4-tbupy=4-tertbutylpyridine) was studied in aqueous concentrated electrolyte solutions at 298 K. Plots of ln(k/kw) against (γ-γw), where the subscript w refers to pure water and γ is the surface tension of the appropriate salt solution, gave a common straight line for all the electrolytes studied and permits to estimate the activation volume.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010373823987
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  • 72
    Digitale Medien
    Digitale Medien
    Kinetics of Coke Formation for the Reactions of Light Olefins Ethene, Propene and 1-Butene Over Ushy Zeolite (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 39-46 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Coke formation ; kinetics ; USHY zeolites ; ethene ; propene ; 1-butene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A simplified three-parameter model for the interpretation of the kinetic data of coke formation during transformation of light olefins is presented. This model has been applied to the transformation of ethene, propene and 1-butene over fresh and regenerated zeolite USHY at 623 K. The proposed model covers both the coverage of the acid sites and the autocatalytic growth of coke.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005684524023
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  • 73
    Digitale Medien
    Digitale Medien
    Regioselective Dichlorocyclopropanation of 4-Vinyl-1-Cyclohexene Using the New Diquat, DQ-Br, under Controlled Phase Transfer Catalysis Conditions (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Dichlorocyclopropanation ; 4-vinyl-1-cyclohexene ; phase transfer catalysis ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of regioselective dichlorocyclopropanation of 4-vinyl-1-cyclohexene has been studied under controlled phase transfer catalysis conditions, using aqueous sodium hydroxide as the base and 2-benzylidine-N,N,N,N′,N′,N′-hexaethylpropane-1,3-diammonium dibromide (Dq-Br) as a new phase transfer reagent. The reaction was carried out at 40 °C under pseudo-first order conditions by employing aqueous sodium hydroxide and chloroform in excess and was monitored by gas chromatography. The effect of various experimental parameters on the rate of the reaction has been studied and based on the experimental results, a suitable mechanism is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005673716271
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  • 74
    Digitale Medien
    Digitale Medien
    Kinetics of Oxidation of Phosphinic, Phenylphosphinic and Phosphorous Acid by Benzyltrimethylammonium Chlorobromate (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 247-252 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Phosphorous acid ; oxidation ; kinetics ; mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxidation of lower phosphorus oxyacids by benzyltrimethylammonium chlorobromate (BTMACB) proceeds by a mechanism involving a hydride-ion transfer from oxyacids to the oxidant in the rate-determining step.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005635529900
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  • 75
    Digitale Medien
    Digitale Medien
    Low-Temperature Catalytic Oxidation of Sulfide Ions in Aqueous Solutions on a Ni-Oxide System (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 139-145 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Oxidation of sulfides ; kinetics ; Ni-oxide system ; reaction mechanism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Catalytic oxidation of sulfide ions in aqueous solutions by air oxygen has been investigated using a Ni-oxide system as a catalyst. The kinetics and the selectivity of the oxidation process were studied by varying the pH, catalyst amount and reaction temperature. A reduction/oxidation mechanism of the reaction has been supposed comprising interaction between the surface active oxygen of the catalyst and HS− and reoxidizing of the reduced catalyst by the dissolved oxygen. The results obtained show that the Ni-oxide system is a promising catalyst for practical application.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010379103089
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  • 76
    Digitale Medien
    Digitale Medien
    Coupling of Methanol and Isobutanol to Ethers over γ-Alumina Catalyst. Kinetic Studies (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 235-241 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Methanol ; isobutanol ; ethers ; γ-Al2O3 ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetic of methanol (MeOH) and isobutanol (iBuOH) coupling to ethers has been studied. Catalytic tests were carried out in the gas phase in a fixed-bed flow microreactor, in the temperature range of 463-533 K, under atmospheric pressure, using γ-Al2O3 as the catalyst. The quasi-homogeneous model for the process was assumed. The reaction rates were described by simple kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010320312175
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  • 77
    Digitale Medien
    Digitale Medien
    Rate Constant for the Reaction of the OH-Radical with CH2F2 (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 319-324 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Atmospheric chemistry ; kinetics ; OH-radical ; CH2F2
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The rate constant value of k 1 = (6.05 ± 0.20)×109 cm3 mol−1 s−1 (with ± 1σ error) has been determined for the reaction OH + CH2F2 (1) by applying the discharge-flow/resonance-fluorescence method at 298 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010349118536
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  • 78
    Digitale Medien
    Digitale Medien
    Kinetics and Stereoselectivity in Gas-Phase Hydrogenation of Alkylbenzenes Over Ni/Al2O3 (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 47-54 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Alkylbenzenes ; hydrogenation ; nickel ; kinetics ; stereochemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Experimental data on gas-phase hydrogenation of several alkylbenzenes (toluene, ethlylbenzene, o-, m-, p-xylenes, mesitylene) over nickel catalyst are summarized. Rate dependence as a function of the chemical nature of substituent and position in the aromatic ring is discussed. The stereochemical distribution for dialkylbenzene and trialkylbenzene is addressed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010321830186
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  • 79
    Digitale Medien
    Digitale Medien
    Determination of Equilibrium Dispersion of Pt on Al2O3 Support in Sintering Process (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 295-300 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Sintering ; kinetics ; Pt/Al2O3
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The variation of dispersion of Pt on Al2O3 support with sintering time is measured and the value of equilibrium dispersion of Pt is obtained directly. It is found that a General Power Law Expression can fit the experimental data well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010327210246
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  • 80
    Digitale Medien
    Digitale Medien
    c-Fos Expression by Dopaminergic Receptor Activation in Rat Hippocampal Neurons (2000)
    Springer
    Molecules and cells 10 (2000), S. 546-551 
    Details
    ISSN: 0219-1032
    Schlagwort(e): c-Fos ; Dopamine ; D1 ; Hippocampus ; Rat ; Synaptic Plasticity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract While dopamine is likely to modulate hippocampal synaptic plasticity, there has been little information about how dopamine affects synaptic transmission in the hippocampus. The expression of IEGs including c-fos has been associated with late phase LTP in the CA1 region of the hippocampus. The induction of c-fos by dopaminergic receptor activation in the rat hippocampus was investigated by using semiquantitative RT-PCR and immuno-cytochemistry. The hippocampal slices which were not treated with dopamine showed little expression of c-fos mRNA. However, the induction of c-fos mRNA was detected as early as 5 min after dopamine treatment, peaked at 60 min, and remained elevated 5 h after treatment. Temporal profiles of increases in c-fos mRNA by R(+)-SKF-38393 (50 μM) and forskolin (50 μM) were similar to that of dopamine. An increase in [cAMP] was observed in dopamine-, SKF-, or forskolin-treated hippocampal slices. By immunocytochemical studies, control hippocampal cells showed little expression of c-Fos immunoreactivity. However, when cells were treated with dopamine, an increase in the expression of c-Fos immunoreactivity was observed after treatment for 2 h. The treatment of hippocampal neurons with R(+)-SKF38393 (50 μM) or forskolin (50 μM) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependant pathway is associated with the expression of c-Fos in the hippocampal neurons. These data are consistent with the possible role of endogenous dopamine on synaptic plasticity via the regulation of gene expression. Furthermore, these results imply that dopamine might control the process of memory storage in the hippocampus through gene expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10059-000-0546-y
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  • 81
    Digitale Medien
    Digitale Medien
    A weighing method to identify the microbial growth phases in solid-state fermentation tests (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 601-605 
    Details
    ISSN: 1573-0972
    Schlagwort(e): Growth phases identification ; kinetics ; Rhizopus oryzae ; solid-state fermentation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A general equation correlating the variation rate of the fermenting medium weight (dry matter) and the cell biomass growth rate in solid-state fermentation tests is proposed with the main purpose of identifying the microbial growth phases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008970720794
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  • 82
    Digitale Medien
    Digitale Medien
    Electrochemical and Adsorption Studies on the Formation of Poly-8-Hydroxyquinaldine Thin Films at Glassy Carbon/Electrolyte Interface (2000)
    Springer
    Interface science 8 (2000), S. 111-121 
    Details
    ISSN: 1573-2746
    Schlagwort(e): 8-hydroxyquinaldine ; electropolymerization ; adsorption ; glassy carbon ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract The kinetics and thermodynamics of the electropolymerization of the chelating agent 8-hydroxyquinaldine on GCE's (Glassy Carbon Electrodes') surface from aqueous phosphate buffers are reported. Thermodynamic functions related to the adsorption of the monomer on the GCE's surfaces were determinated. No contribution from GCE surface's functional group to the electropolymerization reactions was reported. The effects of monomer concentration, pH, and temperature on the electrochemical growth of poly 8-hydroxyquinaldine were investigated. The results suggest that the propagation of the electropolymerization process takes place via a free radical chain reactions. Furthermore, the results indicate that the electrochemical growth of the polymeric films is dictated by pre-polymerization adsorption on the electrode surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008799724511
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  • 83
    Digitale Medien
    Digitale Medien
    Kinetic investigation of the alkylation of salts of 2,5-dimercapto-1,3,4-thiadiazole (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 857-861 
    Details
    ISSN: 1573-8353
    Schlagwort(e): salts of 2,5-dimercapto-1,3,4-thiadiazole ; alkylation ; kinetics ; electronic absorption spectra
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A kinetic investigation has been carried out, using electronic absorption spectra, of the alkylation with benzyl chloride of the dihydrazine, monohydrazine, and the disodium salts of 2,5-dimercapto-1,3,4-thiadiazole, and also of the hydrazine and sodium salts of 5-benzylthio-2-mercapto-1,3,4-thiadiazole. The rates orders and constants were established for the benzylation reaction and it was noted that the reaction rate depends on the cation of these salts and the degree of substitution of the 2,5-dimercapto-1,3,4-thiadiazole.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02256923
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  • 84
    Digitale Medien
    Digitale Medien
    Detection and analysis of gastrointestinal sounds in normal and small bowel obstructed rats (2000)
    Springer
    Medical & biological engineering & computing 38 (2000), S. 42-48 
    Details
    ISSN: 1741-0444
    Schlagwort(e): Bowel sounds ; Rat ; Motility ; Body acoustics ; Signal detection ; Signal characterisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract This study is aimed at detecting gastrointestinal sounds (GIS) and correlating their characteristics with gastrointestinal (GI) conditions. The central hypotheses are that GIS generation depends on the motility patterns and the mechanical properties of the gut, and that changes in those result in measurable differences in GIS. An animal model which included both healthy rats and those with small bowel obstruction (SBO) was developed. The acoustic bursts, of GIS were detected by amplitude thresholding the signal envelope. Three methods of envelope estimation were proposed and evaluated. Envelope estimation using a Hilbert transform was found to produce the best results in the current application. The duration and dominant frequency of each detected GIS event was estimated and clear differences between healthy and diseased rats were discovered. In the control state, GIS events were found to consistently be of relatively short duration (3–65ms). Although the majority of events in the SBO state had similar short duration, infrequent longer events were also detected and appeared to be pathognomonic. Long duration events (〉100 ms) occurred in each of seven obstructed, but in none of 14 non-obstructed, cases (p〈0.001). It is concluded that GIS analysis may prove useful in the non-invasive, rapid, and accurate diagnosis of SBO.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02344687
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  • 85
    Digitale Medien
    Digitale Medien
    Kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 191-200 
    Details
    ISSN: 1572-8838
    Schlagwort(e): cyclic redox reaction ; dissolution ; kinetics ; manganese dioxide ; mechanism ; pyrite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract This paper describes a study of the kinetics and mechanism of MnO2 dissolution in H2SO4 in the presence of pyrite through leaching and electrochemical parameters. Manganese(iv) was found to dissolve mainly through reduction by the ferrous ion generated during oxidation of pyrite by the ferric ion. The oxidation which is slower and rate controlling may proceed through two different reactions, one producing S0 and the other SO42−. Manganese dissolution runs at the same rate as that of pyrite oxidation by maintaining ferrous ion concentration at a much lower level than that of ferric. Kinetic equations based on corrosion coupling principles are developed to explain the observed leaching behaviour.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003490810114
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  • 86
    Digitale Medien
    Digitale Medien
    Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)
    Springer
    BioMetals 12 (1999), S. 1-10 
    Details
    ISSN: 1572-8773
    Schlagwort(e): acidophilic ; strain ; oxidation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Recovery of metal values from sulfide ores by use of acidophilic microorganisms is gaining importance. A number of commercial/pilot plants are setup to find out the techno-economic feasibility of the overall process. The main drawback in the process is the slow kinetics of dissolution of metal values from the sulfide ores. To make the technology e attractive the kinetics should be improved considerably. There are various factors which determine the overall kinetics such as bacterial activity and concentration, iron and sulfur oxidation, oxygen consumption, reactor design and nature of ore. A brief review has been made dealing with the above parameters
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009228210654
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  • 87
    Digitale Medien
    Digitale Medien
    Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics (1999)
    Springer
    Journal of polymers and the environment 7 (1999), S. 41-51 
    Details
    ISSN: 1572-8900
    Schlagwort(e): Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are α- and β-(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021894102937
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  • 88
    Digitale Medien
    Digitale Medien
    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Schlagwort(e): micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 89
    Digitale Medien
    Digitale Medien
    Furfural hydrogenation over carbon‐supported copper (1999)
    Springer
    Catalysis letters 60 (1999), S. 51-57 
    Details
    ISSN: 1572-879X
    Schlagwort(e): furfural hydrogenation ; Cu/carbon catalysts ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Furfural hydrogenation over copper dispersed on three forms of carbon – activated carbon, diamond and graphitized fibers – were studied. Only hydrogenation of the C=O bond to form either furfuryl alcohol or 2‐methyl furan occurred at temperatures from 473 to 573 K. Reduction at 573 K gave the most active catalysts, all three catalysts had activation energies of 16 kcal/mol, and turnover frequencies were 0.018–0.032 s-1 based on the number of Cu0 + Cu+ sites, which were counted by N2O adsorption at 363 K and CO adsorption at 300 K, respectively. The Cu/activated carbon catalyst showed no deactivation during 10 h on stream, in contrast to the other two catalysts. A simple Langmuir–Hinshelwood model invoking two types of sites was able to fit all kinetic data quite satisfactorily, thus it was consistent with the presence of both Cu0 and Cu+ sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019090520407
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  • 90
    Digitale Medien
    Digitale Medien
    Study of the ammonia decomposition over iron catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 167-171 
    Details
    ISSN: 1572-879X
    Schlagwort(e): ammonia decomposition ; iron catalyst ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The decomposition of ammonia is a reaction associated with the process of the nitriding of metals. The kinetics of the ammonia decomposition on iron catalysts has been studied using a differential reactor with internal mixing. The balance between the inlet and outlet ammonia quantity has been used to determine the degree of conversion. The rate of ammonia decomposition could be described by the following expression: r = k0 exp (Ea/RT)pNH3. The activation energy of the ammonia decomposition process has been found for samples with potassium as E a= 96 kJ/mol, for samples without potassium as E a= 87 kJ/mol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019007024041
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  • 91
    Digitale Medien
    Digitale Medien
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Schlagwort(e): kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 92
    Digitale Medien
    Digitale Medien
    The detailed kinetics of the desorption of hydrogen from polycrystalline copper catalysts (1999)
    Springer
    Catalysis letters 59 (1999), S. 143-149 
    Details
    ISSN: 1572-879X
    Schlagwort(e): hydrogen ; desorption ; copper ; activation energy ; kinetics ; order of desorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of desorption of hydrogen from the copper component of an alumina-supported polycrystalline copper catalyst has been studied in detail by temperature-programmed desorption (TPD). Line-shape analysis of the hydrogen TPD spectra shows: (i) that the desorption is second order, (ii) that the desorption activation energy is in the range 64–68 kJ mol−1 in the coverage range 7–44% of a monolayer, and (iii) that the desorption pre-exponential term has a value ∼10−5 cm2 s−1 atom−1 consistent with the desorption being second order, involving mobile adsorbates and a mobile desorption transition state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019080823616
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  • 93
    Digitale Medien
    Digitale Medien
    Growth of Ordered Domains in a Computer Model Alloy with Lattice Misfit (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 23-43 
    Details
    ISSN: 1572-9613
    Schlagwort(e): model alloy ; Monte Carlo ; elastic interactions ; phase separation ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study via Monte Carlo simulations the influence of elastic interactions on the ordering and decomposition of a two-dimensional model binary alloy with antiferromagnetic nearest and ferromagnetic next nearest neighbor type interactions following a quench into the coexistence region. The elastic interaction leads to the development of a platelet morphology for the segregated ordered and disordered regions. A length scale characterizing the coarsening process follows a law of the type R=a+bt 1/3 with the growth b decreasing with the amount of ordered phase; this appears to be due to the presence of anti-phase boundaries between neighboring domains ordered on different sublattices which are difficult to eliminate. The application of uniaxial external stress results in “rafting” of the domains. Many of the simulation results are in agreement with experimentally observed effects in nickel-base superalloys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004569209618
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  • 94
    Digitale Medien
    Digitale Medien
    Nucleotide sequences of three distinct complementary DNA clones encoding rat class II major histocompatibility complex RT1.D β-chain proteins (1999)
    Springer
    Immunogenetics 49 (1999), S. 735-737 
    Details
    ISSN: 1432-1211
    Schlagwort(e): Key words Class II MHC sequence ; Rat ; Cloning ; RT-PCR ; Polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002510050676
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  • 95
    Digitale Medien
    Digitale Medien
    Thermal Analysis Studies on Isopropylnitrate (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 9-19 
    Details
    ISSN: 1572-8943
    Schlagwort(e): ARC ; DSC ; HFC ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Isopropylnitrate (IPN) is described as a detonable material used in propellants and explosives. While there is considerable information available on its sensitivity and compatibility with other materials, very little is known about its thermochemical properties. This paper will describe the results obtained from some DSC, heat flux calorimetry (HFC) and accelerating rate calorimetry (ARC) measurements. The ASTM DSC method using a hermetic aluminum pan having a lid with a laser-produced pin hole was used to determine the vapour pressure of IPN1. Results calculated from an Antoine equation are in substantial agreement with those determined from DSC measurements. From the latter measurements, the enthalpy of vaporization was determined to be 35.32±0.62 kJ mol−1. Attempts to determine vapour pressures above about 0.8 MPa resulted in significant decomposition of IPNg. The enthalpy change for decomposition in sealed glass systems was found to be -3.43±0.09 kJ g−1 and -3.85±0.03 kJ g−1, respectively from DSC and HFC measurements on IPN1 samples loaded in air. Slightly larger exotherms were observed for the HFC results in air than those in inert gas, suggesting some oxidation occurs. In contrast, no significant difference in the observed onset temperature of about 150°C was observed for both the HFC and ARC results. From DSC measurements, an Arrhenius activation energy for decomposition of 126±4 kJ mol−1 was found. These measurements were also conducted in sealed glass systems and decomposition appeared to proceed primarily from the liquid phase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010190829563
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  • 96
    Digitale Medien
    Digitale Medien
    Kinetics of Thermal Decomposition of Mixed Ligand Trinuclear Compound of Cadmium(II) (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 233-241 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cadmium(II) atom ; kinetics ; non-isothermal decomposition ; Schiff-base compound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal C81H78N12O6Cd3 was synthesized and its structure was determined by single crystal X-ray diffraction method. The complex crystallizes in the monoclinic system space group P21/n with cell parameters, a=15.959(4) Å, b=26.222(3) Å, c=25.907(6) Å, β=101.60(2)°. The non-isothermal kinetics of the crystal was studied by use of non-isothermal TG and DTG curves. The kinetic parameters were analyzed by means of integral and differential methods, and mechanism functions of the thermal decomposition reaction for its second step were proposed. The kinetic equation of thermal decomposition is expressed as: dα/dt=Aexp(-E/RT)1.5(1-α)4/3[1/(1-α)1/3-1]−1. The average values of E(kJ mol−1) and lnA/s−1 are 339.25, 43.95, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010117113150
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  • 97
    Digitale Medien
    Digitale Medien
    Re-examination of the Kinetics of the Thermal Dehydroxylation of Goethite (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 301-309 
    Details
    ISSN: 1572-8943
    Schlagwort(e): dehydroxylation ; goethite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of thermal dehydroxylation of aluminuous goethites [1] synthesised from a ferrous salt has been re-examined using the general reaction order kinetic law. The utilised data processing was based on the procedures employed by dissolution kinetics. Recalculation of the activation energies EA of the dehydroxylation yielded the values 130, 132, 128, and 123 kJ mol−1 for pure goethite, goethite with 10, 20, and 30 mol% Al substitution, respectively. The values of EA are in a good agreement with those given for goethite in literature. The EA values are linearly related with the chemically bound excess H2O/OH− in the crystal lattice that is apparently influenced by Al substitution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010181416785
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  • 98
    Digitale Medien
    Digitale Medien
    Thermogravimetric Analysis of Cobalt(II)-dothiepin Complexes (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 841-849 
    Details
    ISSN: 1572-8943
    Schlagwort(e): cobalt(II)-dothiepin ; kinetics ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The complexes of cobalt(II) with dothiepin (DOT) hydrochloride have been studied for kinetics of thermal degradation by thermogravimetric analysis (TG) and derivative thermogravimetric studies (DTG) in a static nitrogen atmosphere at a heating rate of 10° C min−1. A general mechanism of thermal decomposition is advanced involving dehydration and decomposition process for both organic and inorganic ligands. The thermal degradation reactions were found to proceed in three steps having an activation energy in the range 6.75–170 kJ mol−1. Thermal decomposition kinetics parameters were computed on the basis of thermal decomposition data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010181716727
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  • 99
    Digitale Medien
    Digitale Medien
    Gegeneration of Deactivated β-Zeolite by Coke Oxidation (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 297-303 
    Details
    ISSN: 1572-8943
    Schlagwort(e): β-zeolite ; coke ; cumene ; kinetics ; regeneration ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An accurate description of coke burn off is obtained from a catalyst based on β-zeolite and used for benzene alkylation with propylene giving cumene by using the thermogravimetric technique. A simple empirical kinetic model was successfully applied to interpolate the data of thermogravimetric analysis performed on samples after partial burn off. Different temperatures, partial pressures of oxygen and gas flow rates were the variables studied in order to calculate the apparent rates and the activation energy for the coke oxidation reaction and to outline the best conditions for the industrial regeneration procedure of our proprietary catalyst PBE-1 for cumene synthesis. Combining the unusually long lifetime per reaction cycle with the optimized regeneration procedure leads to an outstanding overall catalyst life.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010178029977
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  • 100
    Digitale Medien
    Digitale Medien
    Non-Isothermal Pyrolysis and Kinetics of Oil Shales (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 953-958 
    Details
    ISSN: 1572-8943
    Schlagwort(e): differential scanning calorimeter ; kinetics ; oil shale ; pyrolysis ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In this research, non-isothermal pyrolysis behavior and kinetics of three oil shales were studied by thermal analysis methods. All the thermal effects were endothermic and no exothermic region was observed in DSC curves. When oil shales are heated in nitrogen atmosphere in TG/DTG, two different mechanisms causing loss of mass were observed. The region between ambient temperature and 500 K was distillation. The second mechanism was visbreaking and cracking and it was observed between the region 500 and 800 K. Kinetic parameters of all the samples are determined by Coats and Redfern method and the results are discussed with regard to their accuracy and the ease of interpretation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010107701483
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