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  • Articles  (82)
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  • Springer  (82)
  • American Chemical Society
  • Cell Press
  • International Union of Crystallography
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  • 2000-2004
  • 1995-1999  (82)
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  • 1
    Electronic Resource
    Electronic Resource
    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
    Keywords: cyclic redox reaction ; dissolution ; kinetics ; manganese dioxide ; mechanism ; pyrite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003490810114
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  • 2
    Electronic Resource
    Electronic Resource
    Sensitivity of PSA process performance to input variables (1995)
    Springer
    Adsorption 1 (1995), S. 133-151 
    Details
    ISSN: 1572-8757
    Keywords: PSA process ; sensitivity ; equilibria ; kinetics ; heats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Mathematical models for pressure swing adsorption (PSA) processes essentially require the simultaneous solutions of mass, heat and momentum balance equations for each step of the process using appropriate boundary conditions for the steps. The key model input variables needed for estimating the separation performance of the process are the multicomponent adsorption equilibria, kinetics and heats of adsorption for the system of interest. A very detailed model of an adiabatic Skarstrom PSA cycle for production of high purity methane from a ethylene-methane bulk mixture is developed to study the sensitivity of the process performance to the input variables. The adsorption equilibria are described by the heterogeneous Toth model which accounts for variations of isosteric heats of adsorption of the components with adsorbate loading. A linear driving force model is used to describe the kinetics. The study shows that small errors in the heats of adsorption of the components can severely alter the overall performance of the process (methane recovery and productivity). The adsorptive mass transfer coefficients of the components also must be known fairly accurately in order to obtain precise separation performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705001
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  • 3
    Electronic Resource
    Electronic Resource
    Factors affecting bioleaching kinetics of sulfide ores using acidophilic micro-organisms (1999)
    Springer
    BioMetals 12 (1999), S. 1-10 
    Details
    ISSN: 1572-8773
    Keywords: acidophilic ; strain ; oxidation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: 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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009228210654
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  • 4
    Electronic Resource
    Electronic Resource
    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
    Keywords: Cellulose ; alkaline degradation ; peeling off ; degree of polymerization ; kinetics ; (gluco)isosaccharinic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021894102937
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Keywords: micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 6
    Electronic Resource
    Electronic Resource
    Furfural hydrogenation over carbon‐supported copper (1999)
    Springer
    Catalysis letters 60 (1999), S. 51-57 
    Details
    ISSN: 1572-879X
    Keywords: furfural hydrogenation ; Cu/carbon catalysts ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019090520407
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  • 7
    Electronic Resource
    Electronic Resource
    Study of the ammonia decomposition over iron catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 167-171 
    Details
    ISSN: 1572-879X
    Keywords: ammonia decomposition ; iron catalyst ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019007024041
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  • 8
    Electronic Resource
    Electronic Resource
    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
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 9
    Electronic Resource
    Electronic Resource
    Partial hydrogenation of benzene to cyclohexene in a continuously operated slurry reactor (1995)
    Springer
    Catalysis letters 31 (1995), S. 431-438 
    Details
    ISSN: 1572-879X
    Keywords: partial hydrogenation of benzene ; production of cyclohexene ; kinetics ; reaction mechanism ; ruthenium catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A method has been developed for direct measurement of reaction rates in a continuously operated slurry (CST-) reactor. In contrast to the usual procedure in a two-liquid-phase system the reactor contains only one liquid phase, an aqueous zinc chloride solution in which a ruthenium lanthanoxide catalyst is suspended. The selectivity of benzene hydrogenation with respect to cyclohexene is higher when the new one-liquid-phase procedure is applied. With decreasing degree of benzene conversion the selectivity with respect to cyclohexene approaches 100%. The conclusion is that cyclohexane is formed only by consecutive hydrogenation of cyclohexene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808607
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  • 10
    Electronic Resource
    Electronic Resource
    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
    Keywords: hydrogen ; desorption ; copper ; activation energy ; kinetics ; order of desorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019080823616
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  • 11
    Electronic Resource
    Electronic Resource
    Thermal Analysis Studies on Isopropylnitrate (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 9-19 
    Details
    ISSN: 1572-8943
    Keywords: ARC ; DSC ; HFC ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010190829563
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  • 12
    Electronic Resource
    Electronic Resource
    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
    Keywords: cadmium(II) atom ; kinetics ; non-isothermal decomposition ; Schiff-base compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010117113150
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  • 13
    Electronic Resource
    Electronic Resource
    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
    Keywords: dehydroxylation ; goethite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010181416785
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  • 14
    Electronic Resource
    Electronic Resource
    Thermogravimetric Analysis of Cobalt(II)-dothiepin Complexes (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 841-849 
    Details
    ISSN: 1572-8943
    Keywords: cobalt(II)-dothiepin ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010181716727
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  • 15
    Electronic Resource
    Electronic Resource
    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
    Keywords: β-zeolite ; coke ; cumene ; kinetics ; regeneration ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010178029977
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  • 16
    Electronic Resource
    Electronic Resource
    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
    Keywords: differential scanning calorimeter ; kinetics ; oil shale ; pyrolysis ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010107701483
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  • 17
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    Electronic Resource
    Pre-Eutectic Densification of Calcium Carbonate Doped with Lithium Carbonate (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1461-1473 
    Details
    ISSN: 1572-8943
    Keywords: CaCO3 ; densification ; kinetics ; Li2CO3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pressureless sintering of CaCO3 was carried out, with Li2CO3 (from 0.5 to 8 wt%) as an additive, under different pressures of CO2. Densification occurs between 600 and 700°C. Sintering above the eutectic temperature (T〉662°C) leads to the decomposition of calcium carbonate and the materials become expanded. At 620° under 1 kPa of CO2, a relative density of 96% is reached. Li2CO3 enhances the densification process and grain growth of calcium carbonate. CO2 pressure slows down densification and grain growth kinetics. These results are explained by the influence of carbonate and calcium ion vacancies on the sintering mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010191414628
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  • 18
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    Thermal Behaviour and Decomposition Kinetics for Two Palladium(II) Complexes with 1-aminopyrene and its Derivative (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 383-391 
    Details
    ISSN: 1572-8943
    Keywords: 1-aminopyrene (apyr) ; N-(2-pyridylmethylene)-1-pyrenylamine (pmpa) ; kinetics ; palladium(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition studies for two palladium(II) complexes Pd(apyr)2Cl2 and Pd(pmpa)Cl2 (apyr=1−aminopyrene and pmpa=N−(2−pyridylmethylene)−1−pyrenylamine) were carried out in pure nitrogen using TG-DTG techniques. The non-isothermal kinetic parameters for the two complexes were evaluated employing the method suggested by Málek, Šesták, Koga et al. Based on the above results, thermal behaviour of the complexes were carefully discussed, which showed that not only the parameters value, but also the decomposition pattern and mechanism for complex 1 are different from complex 2.
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    URL: http://dx.doi.org/10.1023/A:1010159322866
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  • 19
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    Studies on the Kinetics of the First Order Autocatalytic Decomposition Reaction of Highly Nitrated Nitrocellulose (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 403-411 
    Details
    ISSN: 1572-8943
    Keywords: first order autocatalytic reaction ; HNNC ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the first order autocatalytic decomposition reaction of highly nitrated nitrocellulose (HNNC, 14.14%N) was studied by using thermogravimetry (TG). The results show that the TG curve for the initial 50% of mass-loss of HNNC can be described by the first order autocatalytic equation $$\frac{{{\text{d}}y}} {{dt}} = - 10^{16.4} \exp \left( { - \frac{{210380}} {{RT}}} \right)y - 10^{16.7} \exp \left( { - \frac{{171205}} {{RT}}} \right)y(1 - y)$$ and that for the latter 50% mass-loss of HNNC described by the reaction equations $$\frac{{dy}} {{dy}} = - 10^{16.3} \exp \left( { - \frac{{169483}} {{RT}}} \right)y\quad (n = 1)$$ and $$\frac{{dy}} {{dt}} = - 10^{16.8} \exp \left( { - \frac{{165597}} {{RT}}} \right)y^{2.61} \quad (n \ne 1)$$
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010163423775
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  • 20
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    Spectroscopic and Thermal Studies on 2,4,6-trinitro Toluene (TNT) (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 173-185 
    Details
    ISSN: 1572-8943
    Keywords: IRS ; kinetics ; mechanism ; nitro aromatic ; TA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics and mechanism of the initial stage of thermal decomposition of 2,4,6-trinitro toluene (TNT), a widely used high explosive, have been studied, together with its morphology and evolved gaseous products using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR) and hot-stage microscopy. The kinetics of the thermolysis has been followed by IR after suppressing volatilisation by matrixing and by isothermal TG without suppressing volatilisation to simulate actual user conditions. The best linearity was obtained for Avrami-Erofeev equation for n=1 in isothermal IR and also in isothermal TG. The activation energy was found to be 135 kJ mol−1, with logA (in s−1) 12.5 by IR. The effect of additives on the initial thermolysis of TNT has also been studied. Evolved gas analysis by IR showed that CO2, NO2, NO and H2O are more dominant than N2O, HCN and CO. The decomposition involves the initial rupture of the C-NO2 bond, weakened by hydrogen bonding with the labile hydrogen atom of the adjacent CH3 group, followed by the abstraction of the hydrogen atom of the methyl group by NO2, generated in the initial step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010152626354
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  • 21
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    Thermal Decompositions of (RE)Ba2Cu3O6 (RE=Y, Nd, Er) (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 691-698 
    Details
    ISSN: 1572-8943
    Keywords: activation energy ; kinetics ; solid-state reactions ; superconductors ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetric in situ measurements of oxygen loss from (RE)Ba2Cu3O6 samples (RE=Y, Nd, Er) heated isothermally in a relatively high dynamic vacuum were made with a Cahn RG electrobalance. Single-phase orthorhombic samples of composition (RE)Ba2Cu3O7-x (highest oxygen content) were synthesized from stoichiometric (1:2:3) mixtures of high-purity (RE)2O3, BaCO3 and CuO. The original 1:2:3 mixture was prepared by the two-stage procedure described earlier. The crystal structure of the sample in the original orthorhombic phase was controlled by the X-ray powder method (CuKα radiation) using a Stadi P Stoe diffractometer with a position-sensitive detector. The decomposition curves are described by the sum of exponential terms corresponding to rapid and slow first-order processes in which differently sized grains of the powder samples are involved. The activation energies are estimated from appropriate Arrhenius plots.
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    Thermal Decompositions of the Molybdotellurates of Nickel(II) and Cobalt(II) (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 779-788 
    Details
    ISSN: 1572-8943
    Keywords: cobalt ; dynamic and isothermal methods ; kinetics ; molybdotellurates ; nickel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molybdotellurates [M(H2O)6]3·[TeMo6O24], with M=Ni(II) and Co(II), were synthesized and characterized by single-crystal X-ray diffraction for compound 1 and X-ray powder diffraction for compound 2, EDAX, IR, electronic spectra in the solid phase and in solution, and magnetic properties. Thermogravimetry and differential scanning calorimetry of both compounds revealed a loss of 11 water molecules through an endothermal process with ΔH=800 kJ mol−1 for the nickel compound and ΔH=833 kJ mol−1 for the cobalt compound. The residual compounds were characterized by chemical analysis, IR and XPS spectroscopy
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    Physicochemical Studies and Thermal Decomposition Kinetics of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Citronellal Anthranilic Acid (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 817-831 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; Schiff-bases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of two new Schiff-bases, citronellal anthranilic acid and citronellal-5-bromoanthranilic acid have been synthesized. On the basis of spectral, magnetic and thermal data, octahedral structure was assigned to all complexes [ML2(H2O)2]. Thermal decomposition of these complexes was studied by TG. Kinetic parameters, viz activation energy, E, pre-exponential factor, A, and order of reaction, n, were calculated from the TG curves using mechanistic and non-mechanistic integral equations.
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    RCTA Techniques Used in Studies of Solid State Reactions in Inorganic Compounds (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 17-26 
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    ISSN: 1572-8943
    Keywords: kinetics ; reaction controlled thermal analysis ; stepwise isothermal analysis ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Reaction Controlled Thermal Analysis techniques, RCTA, are very useful both in thermogravimetric and dilatometric studies. In the present paper this big family of techniques is divided into three main classes: Quasi-Isothermal techniques (QIA); Controlled Reaction Rate Thermal Analysis (CRTA) and Reaction (Event) Controlled Heating Rate Adaption. After a short presentation of these techniques and the general advantages of RCTA, two examples of kinetic studies on thermal decomposition of Ba- and Ce oxalates by using Stepwise Isothermal Analysis, SIA, introduced by the author is presented and discussed.
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    Isothermal and Non-Isothermal Kinetics When Mechanistic Information Available (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 783-792 
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    ISSN: 1572-8943
    Keywords: complex process ; DSC ; isoconversional methods ; kinetics ; model-free kinetics ; peak maximum evolution methods ; simulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In the case of a complex mechanism of two parallel independent reactions, peak maximum evolution methods and model-fitting methods give only a mean value of the kinetic parameters, while isoconversional methods are useful to describe the complexity of the mechanism. Isothermal and non-isothermal isoconversional methods can be used to elucidate the kinetics of the process. Nevertheless, isothermal isoconversional methods can be limited by restrictions on the temperature regions experimentally available because of duration times or detection limits.
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    Kinetic Study of Thermal Decomposition of the DMIT Complex of Cobalt (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 805-810 
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    ISSN: 1572-8943
    Keywords: cobalt ; dmit ligand ; kinetics ; non-linear method ; Zsakó method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work, a cobalt complex with dmit (1,3-dithiol-2-thione-4,5-dithiolate) as ligand was prepared and its thermal stability was studied by thermogravimetric analysis and kinetics by means of the Zsakó method and a non-linear method. For both methods, numerical binomial and polynomial filters were used, where points in the central interval were utilized.
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    DSC Analysis of the Induction Period in the Vulcanisation of Rubber Compounds (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1107-1113 
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    ISSN: 1572-8943
    Keywords: differential scanning calorimetry ; induction period ; kinetics ; vulcanisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Vulcanisation of rubber compounds was studied by DSC under isothermal and non-isothermal conditions. The parameters of an Arrhenius-like equation describing the temperature dependence of induction period have been obtained both from isothermal and non-isothermal measurements. A new method for obtaining the kinetic parameters from non-isothermal measurements, based on the dependence of onset temperature of vulcanisation peak on heating rate, is presented. Also, a procedure for the evaluation of temperature difference between the furnace and sample is proposed. It has been shown that the treatment of non-isothermal DSC measurements gives the kinetic parameters free of systematic errors. The new method can also be used for studying other reactions exhibiting the induction period.
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    Investigation of Kinetics of Solid-Phase Synthesis of Lithium Orthosilicate (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 699-705 
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    ISSN: 1572-8943
    Keywords: interaction in solid phase ; lithium carbonate ; lithium orthosilicate ; kinetics ; solid electrolytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the interaction between lithium carbonate and silica with various degrees of dispersion was investigated by TG and DTA methods. It was found that the utilization of pyrogenic silica with a specific surface area of about 300 m2g-1 instead of aerosil with one of 175 m2g-1 leads to an increase of the reaction rate between lithium carbonate and silica, which depends on the formation and growth of lithium orthosilicate crystals in the first stage, and is conditioned by the diffusion of lithium and oxygen ions through the lithium orthosilicate layer formed at temperatures above 800 K. This supposition is supported by the kinetic analysis results obtained with the use of the different models. The optimal regime of heating is recommended.
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    Crystallization Kinetics of Lithium Diborate Glass by DTA (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 755-761 
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    ISSN: 1572-8943
    Keywords: crystallization ; DTA ; kinetics ; Kissinger plot ; lithium diborate glass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystallization process of Li2B4O7 in the glass of stoichiometric composition, characterized by the crystal growth of pre-existing nuclei, was analyzed kinetically by means of DTA. Because the number of pre-existing nuclei for the subsequent growth varies depending on the cooling rate of the glass-forming melt and heating rate of the as-prepared glass, a modified Kissinger plot was applied for evaluating the apparent activation energy to the crystal growth in the glass samples with three different thermal histories, i.e., the pre-annealed, slowly quenched and quickly quenched glasses. The process was characterized by the three dimensional growth of pre-existing nuclei with the apparent activation energy of ca 340 kJ mol−1.
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    A Dilatometric Investigation of the Thermal Compaction of Ferrite Powders Prepared by Coprecipitation (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 603-610 
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    ISSN: 1572-8943
    Keywords: coprecipitation ; ferrite ; kinetics ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors report on a non-isothermal kinetic investigation (at constant heating rate) of the sintering of manganese and nickel-zinc ferrite powders prepared by coprecipitation. The kinetic results point to the thermal compaction of the powders, which occurs mainly in the intermediate stage of sintering. A comparative study was performed in order to determine the influence of the sample characteristics (such as chemical nature, density and shape) and the heating rate on the kinetics and mechanism of the compaction.
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    Progress in Non-parametric Kinetics (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 843-849 
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    ISSN: 1572-8943
    Keywords: adiabatic calorimetry ; kinetics ; non-parametric kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The non-parametric kinetics (NPK) method has been recently developed for the kinetic treatment of thermoanalytical data. The most significant feature of this method is its ability to provide information about the reaction kinetics without any assumptions either about the functionality of the reaction rate with the degree of conversion or the temperature. This paper presents the results of the application of the method to adiabatic calorimetry. Some data have been obtained by numerical simulation, but also the thermal decomposition of DTBP, a well known first order reaction, has been studied, being the obtained results in good agreement with literature.
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    Kinetics of Thermal Decomposition of Dolomite (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 829-833 
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    ISSN: 1572-8943
    Keywords: dolomite ; kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition reactions of calcitic dolomite were investigated. Simultaneous TG/DTG/DTA were applied under non-isothermal conditions. From the recorded curves, the activation energies, pre-exponential factors and thermodynamic parameters of activation were calculated for the two thermal decomposition steps.
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    Determination of Activation Energies by Using Different Factors Φ in Adiabatic Calorimetry (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 215-223 
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    ISSN: 1572-8943
    Keywords: adiabatic calorimetry ; kinetics ; Kissinger method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Traditionally, the kinetic treatment of adiabatic calorimetry data has been based on the results of one or more experiments, but always with the assumption of the kinetic model that the reaction follows to calculate the kinetic parameters. In this paper a method for the determination of the activation energy that uses a set of adiabatic calorimetry data is developed. To check the method, the thermal decompositions of two peroxides were studied.
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    CRTA for the Thermoanalytical Screening of Volatile Compounds: 3. Study on thermal destruction process, taking place simultaneously with evaporation process (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 113-116 
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    ISSN: 1572-8943
    Keywords: coordinationcompounds ; CRTA ; kinetics ; polymerization ; pyrolysis ; quasi-equilibrium ; TG ; thermolysis ; volatility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Quasi-equilibrium thermogravimetry (variant of CRTA) is put to use as an express method of thermoanalytical screening for volatile compounds. During the experiments for P—T relationship calculations (running with several calibrated standard sample holders) the non-volatile (polymerized) residue is formed (and is decomposed with further temperature rising). Thermogravimetric data are used for the calculation of the kinetic parameters for the polymerization reaction, taking place (concurrently with the evaporation) in the melt of the studied volatile compound.
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    Study of the Kinetics of the Combustion Reaction on Shuangya Mountain Coal Dust by TG (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 447-453 
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    ISSN: 1572-8943
    Keywords: coal ; combustion reaction ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The combustion behavior of Shuangya Mountain (SYM) coal dust has been investigated by means of TG in this paper. The reaction fraction α can be obtained from isothermal TG data. The regressions of g(α), an integral function of α vs. t for different reaction mechanisms were performed. The mechanism of nucleation and nuclei growth is determined as the controlling step of the coal dust combustion reaction by the correlation coefficient of the regression, and the kinetic equation of the SYM coal dust combustion reaction has been established.
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    Electron Delocalization in 3d Complexes Caused by Dimethylurea Checked by Positron Annihilation (1999)
    Springer
    Structural chemistry 10 (1999), S. 433-437 
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    ISSN: 1572-9001
    Keywords: Positronium Chemistry ; kinetics ; spin exchange reactions ; paramagnetic 3d complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constants, k CR, of ortho- into para-positronium conversion reactions promoted by paramagnetic 3d complexes are linearly correlated with the electron delocalization, β, of unpaired metal electrons caused by ligands, β being the ratio between the inter-electronic repulsion parameters in complexes and in the free gaseous ions. By applying a procedure previously described the β values of MnII, CoII, NiII complexes with dimethylurea were deduced from the mentioned correlations and compared with those of complexes with urea obtained both by the method of Ps reactions here applied and that based on UV-Vis absorption spectroscopy.
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    Investigation of the Chemical Action of the Gliding and “Point” Arcs Between the Metallic Electrode and Aqueous Solution (1999)
    Springer
    Plasma chemistry and plasma processing 19 (1999), S. 53-67 
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    ISSN: 1572-8986
    Keywords: Arc ; gliding arc ; gas temperature ; electron temperature ; ion composition ; ion bombardment ; liquid electrode ; dye oxidation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The plasma–solution interaction processes for gliding and “point” arcs between the aqueous solution surface and the metal electrode in the gas phase are studied. The plasma, liquid, and surface zones are taken into consideration. The electric field strength is measured, and the gas and electron temperatures and ion composition are estimated for the plasma zone. The cathode fall, water vaporization rate, and active species current yield due to the radiation chemistry mechanism are determined for the surface zone. The efficiency of oxidation of iodine ions and organic dyes by different types of discharge in the liquid zone are investigated. The difference in action of the various discharge types may be connected with various influences of the plasma and surface zone on the oxidation processes.
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    A continuous and mechanistic representation of calcite reaction-controlled kinetics in dilute solutions at 25°C and 1 atm total pressure (1995)
    Springer
    Aquatic geochemistry 1 (1995), S. 105-130 
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    ISSN: 1573-1421
    Keywords: calcite ; precipitation ; dissolution ; kinetics ; reaction mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Calcite dissolution rates were measured using a free-drift technique at 25°C, 1 atm total pressure, and various $$P_{CO_2 } $$ in deionized water. The data were corrected for gas phase disequilibrium and fitted to a kinetic expression derived by coupling the mechanistic models of Plummeret al. (1987a) and Chouet al. (1989) to the surface complexation model of Van Cappellenet al. (1993). Corrected dissolution and precipitation rate measurements from previous investigations were combined to our data set and fitted to the same expression. The following reactions provide an adequate description of the calcite dissolution and precipitation mechanism in dilute solutions: for which the overall reaction rate is given by where 〉i are the densities of surface complexes (mol/m2),a i are the activities of dissolved species and,k i are the rate constants corresponding to the above reactions. This rate equation satisfies the principle of microscopic reversibility and applies to both dissolution and precipitation reactions over a wide range of $$P_{CO_2 } $$ , pH and saturation states. The rate constants obtained from fitting the data set to Equation (3) are compatible with values reported by Plummeret al. and Chouet al., as well as yielding a very good estimate of the thermodynamic solubility constant of calcite, K 0 sp .
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    Acetylcholinesterase from desert Cobra (Walterinnesia aegyptia) venom: Optimization and kinetics study (1995)
    Springer
    Molecular and cellular biochemistry 151 (1995), S. 21-26 
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    ISSN: 1573-4919
    Keywords: acetylcholinesterase ; optimization ; kinetics ; venom ; turnover number
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Acetylcholinesterase (AChE) was investigated inWalterinnesia aegyptia venom and characterized with respect to its kinetic properties. It was found that 4.0 ug of crude venom protein and an incubation time of 4.0 min were suitable conditions for linearity of AChE activity at 25°C. The optimum strength of the sodium phosphate buffer was 0.05 M, and the optimum pH was 7.75. The optimum temperature was 30°C. The activation energy and the heat of activation were observed to be 6510 and 5922 cal/mole. The AChE was specific for acetylthiocholine but it did not hydrolyse butyrylthiocholine. The optimum substrate concentration was 3.0 mM but at higher substrate concentrations, the AChE activity declined. The ASCh concentration ranges for different orders of the reactions were determined and kinetic parameters (Km, Vmax, kcat, and ksp) were established at each order of the reaction.
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    Effects of phosphatidylinositol 4,5-bisphosphate and neomycin on phospholipase D: Kinetic studies (1999)
    Springer
    Molecular and cellular biochemistry 197 (1999), S. 195-201 
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    ISSN: 1573-4919
    Keywords: phospholipase D ; phosphatidylinositol 4,5-bisphosphate ; neomycin ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The kinetics of phosphatidylcholine-specific phospholipase D activated by phosphatidylinositol 4,5-bisphosphate (PIP2) and inhibition by neomycin were studied in an enzyme preparation partially purified from human hepatocarcinoma cell line. It was found that phospholipase D was marginally activated by phosphatidyl-4-phosphate (PIP) and phosphatidylethanolamine (PE). In contrast, it was considerably activated by PIP2 in different concentration of phosphatidylcholine (PC). Sphingomyelin (SM), lysophosphatidylcholine (LPC) and phosphatidylserine (PS) were neither substrates nor inhibitors of the phospholipase D. PIP2 induced an allosteric effect on phospholipase D and a negative cooperative effect with respect to phosphatidylcholine as indicated in the Lineweaver-Burk plot. In the absence of PIP2, a straight line was obtained, whereas a downward concave curve was observed in the presence of 25 μM of PIP2. The Hill coefficient and the apparent Km of phosphatidylcholine in the presence of 25 μM PIP2 were calculated to be 0.631 and 10.79 mM, respectively. PIP2 also increased the maximal velocity (Vmax) of the phospholipase D reaction, suggesting that the affinity of substrate to enzyme was decreased, and the turnover number of the enzyme (kcat) was increased by PIP2. The activation of phospholipase D by PIP2 was dose dependent up to 50 μM of PIP2. The Ka of PIP2 was 15.8 mM. Neomycin, a polycationic glycoside, was shown to be an uncompetitive inhibitor of phospholipase D, and revealed the formation of a neomycin-PIP2 complex. The Ki of neomycin was estimated to be 8.7 mM.
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    Regulatory mechanisms of poly(ADP-ribose) polymerase (1999)
    Springer
    Molecular and cellular biochemistry 193 (1999), S. 19-22 
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    ISSN: 1573-4919
    Keywords: poly(ADP-ribose)polymerase ; kinetics ; allosterism ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Here, we describe the latest developments on the mechanistic characterization of poly(ADP-ribose) polymerase (PARP) [EC 2.4.2.30], a DNA-dependent enzyme that catalyzes the synthesis of protein-bound ADP-ribose polymers in eucaryotic chromatin. A detailed kinetic analysis of the automodification reaction of PARP in the presence of nicked dsDNA indicates that protein-poly(ADP-ribosyl)ation probably occurs via a sequential mechanism since enzyme-bound ADP-ribose chains are not reaction intermediates. The multiple enzymatic activities catalyzed by PARP (initiation, elongation, branching and self-modification) are the subject of a very complex regulatory mechanism that may involve allosterism. For instance, while the NAD+ concentration determines the average ADP-ribose polymer size (polymerization reaction), the frequency of DNA strand breaks determines the total number of ADP-ribose chains synthesized (initiation reaction). A general discussion of some of the mechanisms that regulate these multiple catalytic activities of PARP is presented below.
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    Kinetics of Inhibition of Green Crab (Scylla Serrata) Alkaline Phosphatase by Sodium (2,2′-bipyridine) Oxodiperoxovanadate (1999)
    Springer
    The protein journal 18 (1999), S. 735-740 
    Details
    ISSN: 1573-4943
    Keywords: Alkaline phosphatase ; sodium (2, 2′-bipyridine) oxodiperoxovanadate ; inhibition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Green crab (Scylla serrata) alkaline phosphatase (EC 3.1.3.1) is a metalloenzyme, which catalyzes the nonspecific hydrolysis of phosphate monoesters. The kinetics of inhibition of the enzyme by sodium (2, 2′-bipyridine) oxodiperoxovanadate, pV(bipy), has been studied. The time course of the hydrolysis of p-nitrophenyl-phosphate catalyzed by the enzyme in the presence of different pV(bipy) concentrations showed that at each pV(bipy) concentration, the rate decreased with increasing time until a straight line was approached, the straight line slopes are the same for all concentrations. The results suggest that the inhibition of the enzyme by pV(bipy) is a slow, reversible reaction with fractional remaining activity. The microscopic rate constants are determined for the reaction of inhibitor with the enzyme.
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    Structure-property relationships in thin films and membranes (1995)
    Springer
    Journal of sol gel science and technology 4 (1995), S. 117-133 
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    ISSN: 1573-4846
    Keywords: kinetics ; precursor chemistry ; silica ; permeability ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The molecular-scale species distributions and intermediate-scale structure of silicate sols influence the microstructures of the corresponding thin films prepared by dip-coating. Using multi-step hydrolysis procedures, we find that, depending on the sequence and timing of the successive steps, the species distributions (determined by 29Si NMR) and intermediate scale structure (determined by SAXS) can change remarkably for sols prepared with the same nominal composition. During film formation, these kinetic effects cause differences in the efficiency of packing of the silicate species, leading to thin film structures with different porosities.
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    3D Monte Carlo Simulations of Diffusion Limited Cluster Aggregation up to the Sol-Gel Transition: Structure and Kinetics (1999)
    Springer
    Journal of sol gel science and technology 15 (1999), S. 129-136 
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    ISSN: 1573-4846
    Keywords: simulation ; percolation ; aggregation ; structure ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three-dimensional (3D) Monte Carlo simulations of diffusion limited cluster aggregation at different concentrations (φ) show a crossover from a flocculation regime at short times to a percolation regime close to the gel time (tg). Contrary to suggestions in the literature tg is independent of the system size (L) for large L. The structural and temporal crossovers between flocculation and percolation take place at characteristic values of the cluster mass (mc) and the time (tc) which depend on φ. After normalisation by these characteristic values the crossovers are independent of φ except for very small clusters and at short times. The concentration dependence of mc and tc indicates that the crossover takes place at a given cumulated volume fraction of the clusters independent of φ. At low concentrations the φ-dependence of tg is determined by the cluster growth in the flocculation regime.
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    URL: http://dx.doi.org/10.1023/A:1008735404991
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    Probing a functional role of Glu87 and Trp89 in the lid ofHumicola lanuginosa lipase through transesterification reactions in organic solvent (1995)
    Springer
    The protein journal 14 (1995), S. 217-224 
    Details
    ISSN: 1573-4943
    Keywords: Hydrolase ; site-directed mutagenesis ; kinetics ; cyclohexane ; butanoic acid esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract To reveal the functional role of Glu87 and Trp89 in the lid ofHumicola lanuginosa lipase, site-directed mutagenesis at Glu87 and Trp89 was carried out. The catalytic performance of wild-type and mutated lipases was studied in transesterification reactions in cyclohexane at a controlled water activity. Two different acyl donors were used in the investigation: tributyrin, a natural substrate for a lipase, and vinyl butyrate, an activated ester suitable for fast and efficient lipase-catalyzed transformations in preparative organic synthesis. As acyl acceptor 1-heptanol was used. The Glu87Ala mutation decreased theV max,app value with tributyrin and vinyl butyrate by a factor of 1.5 and 2, respectively. TheK m,app for tributyrin was not affected by the Glu87Ala mutation, but theK m,app for vinyl butyrate increased twofold compared to the wild-type lipase. Changing Trp89 into a Phe residue afforded an enzyme with a 2.7- and 2-fold decreasedV max,app with the substrates tributyrin and vinyl butyrate, respectively, compared to the wild-type lipase. No significant effects on theK m,app values for tributyrin or vinyl butyrate were seen as a result of the Trp89Phe mutation. However, the introduction of a Glu residue at position 89 in the lid increased theK m,app for tributyrin and vinyl butyrate by a factor of 〉5 and 2, respectively. The Trp89Glu mutated lipase could not be saturated with tributyrin within the experimental conditions (0–680 mM) studied here. With vinyl butyrate as a substrate theV max,app was only 6% of that obtained with wild-type enzyme.
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    URL: http://dx.doi.org/10.1007/BF01886762
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    Kinetics of Inhibition of Green Crab (Scylla serrata) Alkaline Phosphatase by L-Cysteine (1999)
    Springer
    The protein journal 18 (1999), S. 603-607 
    Details
    ISSN: 1573-4943
    Keywords: Alkaline phosphatase ; green crab ; inhibition ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The inhibition of alkaline phosphatase from green crab (Scylla serrata) by L-cysteine has been studied. The results show that L-cysteine gives a mixed-type inhibition. The progress-of-substrate-reaction method previously described by Tsou [(1988), Adv. Enzymol. Related Areas Mol. Biol. 61, 391–436] was used to study the inactivation kinetics of the enzyme by L-cysteine. The microscopic rate constants were determined for reaction of the inhibitor with the free enzyme and the enzyme–substrate complex (ES) The results show that inactivation of the enzyme by L-cysteine is a slow, reversible reaction. Comparison of the inactivation rate constants of free enzyme and ES suggests that the presence of the substrate offers marked protection of this enzyme against inactivation by L-cysteine.
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    URL: http://dx.doi.org/10.1023/A:1020611602818
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    Kinetics of the course of reactivation of aminoacylase reconstituted using Mn2+ ions (1995)
    Springer
    The protein journal 14 (1995), S. 695-701 
    Details
    ISSN: 1573-4943
    Keywords: Aminoacylase ; metal ion ; reactivation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic theory of the substrate reaction during irreversible change of enzyme activity previously described by Tsou (Tsou (1988),Adv. Enzymol. Relat. Areas Mol. Biol.61, 381–436] has been applied to a study of the kinetics of the course of reactivation during reconstitution of apo-aminoacylase using Mn2+ or Zn2+. The kinetic parameters for Mn2+-and Zn2+-reconstituted enzymes and the microscopic rate constants for reactivation during reconstitution were determined. The kinetic analysis suggests the presence of a second Mn2+ binding site in Mn2+-reconstituted aminoacylase.
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    URL: http://dx.doi.org/10.1007/BF01886908
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    Complexes of rhodium carbonylchloride and phosphorus(iii) cyanides in mediated electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichlorocyclopropane (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 1890-1891 
    Details
    ISSN: 1573-9171
    Keywords: electrochemistry ; metal complexes ; dichlorocyclopropane ; kinetics ; reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrochemical reduction of the complexes Rh(CO)ClL2 [L = (EtO)2PCN (1), Ph2PCN (2)] and Rh2(CO)4L [L = P(CN)3 (3), $$Ph\begin{array}{*{20}c} P \\ | \\ {CN} \\ \end{array} ---\begin{array}{*{20}c} P \\ | \\ {CN} \\ \end{array} Ph$$ (4)] and their catalytic properties in electrochemical reduction of 2-carbomethoxy-2-methyl-1,1-dichloro-cyclopropane were studied. The catalytic electroreduction of a substrate at the reduction potentials of the central ion was developed for complexes2–4. This process is accelerated substantially for complexes2 and3 in the presence of anthracene.
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    URL: http://dx.doi.org/10.1007/BF00707219
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    Photochemical transformations of 1-arylcyanomethyl-9,10-anthraquinones (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 1907-1913 
    Details
    ISSN: 1573-9171
    Keywords: photochemical transformations ; 1-arylcyanomethyl-9 ; 10-anthraquinones ; nucleophilic addition ; oxidation ; kinetics ; quantum-chemical calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photochemical transformations of 1-arylcyanomethyl-9,10-anthraquinones were studied. It was established that under irradiation, the hydrogen atom of the substituted methyl group is transferred to aperi-quinoid oxygen atom to form the corresponding 9-hydroxy1, 10-anthraquinone-1-arylcyanomethides. Dark transformations of photoinduced quinonemethides result from three competing parallel processes: intramolecular transfer of the hydrogen atom, a reaction with a solvent (alcohol), and oxidation by dissolved oxygen. The kinetics of these reactions were studied.
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    URL: http://dx.doi.org/10.1007/BF00707225
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  • 50
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    Kinetics of the thermal decomposition of bis(2,2-dinitropropyl)-N-fluoroamine (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 847-850 
    Details
    ISSN: 1573-9171
    Keywords: fluoroamines, thermal decomposition ; nitrocompounds ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of bis(2,2-dinitropropyl)-N-fluoroamine are studied in the liquid phase. The reaction is autocatalytic in a melt. In dilute solution, the reaction rate is described by the first-order law. It is tens of times faster in polar sulfolan than in weakly polar dimethyl phthalate. A mechanism of the decomposition involving the formation of a cyclic transition state at the first, limiting stage of the process is suggested.
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    URL: http://dx.doi.org/10.1007/BF00696915
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    Salt effects and the mechanism of electrophilic mercuration of unsaturated compounds (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 336-344 
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    ISSN: 1573-9171
    Keywords: solvomercuration ; mechanism of reaction ; mercury acetate ; salt effect ; alkenes ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the addition of Hg(OAc)2 to strained and unstrained alkenes was studied in MeOH solution in the presence of NaOAc. Based on salt effects, the HgOAc ion was shown to be the actual reagent in the reaction of the unstrained alkenes, whereas Hg(OAc)2 was the reagent in the case of the strained alkenes. The mechanisms of the solvomercuration of alkenes of various structures were proposed.
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    URL: http://dx.doi.org/10.1007/BF00702148
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    Kinetic peculiarities of redox reactions sensitized by colloidal CdS under steady-state irradiation. The effect of adsorption-desorption processes on the reaction (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 236-246 
    Details
    ISSN: 1573-9171
    Keywords: photocatalyst ; adsorption ; surfactant ; kinetics ; colloid ; cadmium sulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photoreduction of Methyl Orange dye (MOr) by sodium sulfide was studied under steady-state photolysis (λ = 365 nm). The reaction was sensitized by the CdS colloid with the characteristic ∼5-nm particle size. The quantum yield of the reaction is independent of the light intensity when the latter is less than 5 mW cm−2. The form of the dependence of the initial quantum yield of the reaction on [MOr] coincides qualitatively with the adsorption isotherm of the dye on the CdS surface. The reaction kinetics under steady-state irradiation were analyzed. The kinetics in solution as a whole are shown to be adequate to those on a single colloidal particle. On the basis of the experimental data, two types of surfaces of the colloidal particles are suggested (“open” and “covered” with macromolecules of a colloid stabilizer), which significantly differ in the rate at which they establish an adsorption-desorption equilibrium with the solution.
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    Kinetic scheme of homogeneous acid-catalyzed transformation of isopentenols (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 840-843 
    Details
    ISSN: 1573-9171
    Keywords: isopentenols, reaction scheme ; Prins reaction ; acid catalysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reactions occurring in an equilibrium mixture of 3-methyl-1-buten-3-ol and 3-methyl-2-buten-1-ol in 24–49 % aqueous solutions of H2SO4 yield isoprene, 3-methyl-3-buten-1-ol, isobutylene, formaldehyde, 3-methylbutane-1,3-diol. Isobutylene is rapidly hydrated to give 2-methylpropan-2-ol. The presence of formaldehyde in the reaction mixture indicates that the transformations involve the reverse Prins reaction. On the basis of experimental and literature data, two most probable reaction schemes were suggested.
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    Sorption of rubidium chloride by crown-containing polymer (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 989-991 
    Details
    ISSN: 1573-9171
    Keywords: sorption ; kinetics ; mechanism ; polymer ; dibenzo-18-crown-6 ; RbCl ; equilibrium constant ; diffusion coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics and mechanism of the sorption of rubidium chloride from ethanol by granulated polymer containing immobilized dibenzo-18-crown-6 are studied. The sorption of RbCl is controlled by internal diffusion accompanied by complex formation in the polymer. The equilibrium constants of the sorption and diffusion coefficients of the electrolyte in the sorbent are calculated.
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    Kinetic measurements of binding of galectin 3 to a laminin substratum (1999)
    Springer
    Glycoconjugate journal 16 (1999), S. 365-373 
    Details
    ISSN: 1573-4986
    Keywords: galectin 3 ; laminin binding ; kinetics ; cooperativity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Galectin 3, a β-galactoside binding protein, contains a C-terminal carbohydrate recognition domain (CRD) and an N-terminal segment including multiple repeats of a proline/tyrosine/glycine-rich motif. Previous work has shown that galectin 3 but not the isolated CRD binds to laminin, a multivalent ligand, with positive cooperativity indicating the formation of multiple interactions although the lectin in solution is monomeric. Using surface plasmon resonance, we find that hamster galectin 3 at sub-µmolar concentrations or its isolated CRD at all concentrations binds to a laminin substratum with similar association (kass; 10 – 30 000 M−1 S−1) and dissociation (kdiss; 0.2 – 0.3 S 1 −1 ) rates and weak affinity (Ka; 1 - 3 X 105 M−1). At higher concentrations of galectin 3 the off rate decreases ten fold leading to increased affinity. Ligation of an N-terminal epitope of galectin 3 with a monoclonal Fab fragment increases association and dissociation rates ten fold. A recombinant protein obtained by deletion of the first 93 N-terminal residues binds to laminin with positive cooperativity and a slowly dissociating fraction (Kdiss; 0.002 S−1) accummulates on the substratum. The data suggest that homophilic interactions between CRD as well as N terminal domains are implicated in galectin 3 aggregation on the substratum leading to positive binding cooperativity.
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    URL: http://dx.doi.org/10.1023/A:1007004330048
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    Isothermal and Nonisothermal Decomposition of Famotidine in Aqueous Solution (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 599-604 
    Details
    ISSN: 1573-904X
    Keywords: famotidine ; degradation ; isothermal ; nonisothermal ; kinetics ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of hydrolysis of famotidine in aqueous solution was studied by isothermal and nonisothermal method over the pH range of 1.71 to 10.0. Nonisothermal kinetics was studied with the purpose of determining its use in the establishment of the expiration date of pharmaceutical preparations, particularly drugs in solutions and for assessment of stability characteristics of pharmaceutical formulations during the development stage. A comparison of isothermal (55, 70 and 85°C) and nonisothermal kinetics was performed. Aqueous solutions of famotidine were buffered at pH 1.71, 2.24, 2.66, 4.0, 8.5, 9.0 and 10.0 were used. In the nonisothermal studies, the temperature rate of the reaction was continuously varied throughout the experiment. The energies of activation were found to be in close agreement for isothermal and nonisothermal studies, indicating that nonisothermal studies may save considerable amount of time in the early stages of drug development and stability testing. Logk-pH profiles were constructed for 55, 70 and 85°C from the first-order rate constants obtained from isothermal studies at pH values ranging from 1.71 to 10.00. The pH-rate profile indicated that famotidine undergoes specific acid catalysis in the acidic region and general base catalysis in the alkaline region. Hydrolysis in the acidic and alkaline media resulted in the formation of four and five degradation products, respectively. A possible degradation pathway for the acidic and alkaline hydrolysis was discussed.
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    A Novel Oligodeoxynucleotide Inhibitor of Thrombin. I. In VitroMetabolic Stability in Plasma and Serum (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 1937-1942 
    Details
    ISSN: 1573-904X
    Keywords: oligodeoxynucleotides ; nuclease degradation ; plasma stability ; kinetics ; in vitrometabolism ; thrombin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine the degradation rates and pathways of GS-522, a potent oligodeoxynucleotide (GGTTGGTGTGGTTGG) inhibitor of thrombin, in serum and plasma. Methods. A stability-indicating, anion-exchange HPLC method was developed and used to determine concentrations of GS-522 and metabolites. Results. In monkey plasma at 2 µM or below, the degradation of GS-522 can be fit to a first-order exponential with a kp obs ~ 0.01 min−1. At 3 µM and above the degradation process deviates from a monoexponential decay profile. An initial fast degradation process is followed by a slower phase with an observed rate constant equal to that observed at 2 µM and below. In monkey serum, the KMand Vmaxare 8.4 µM and 0.87 µM min−1, respectively. Conclusions. The kinetics are consistent with an equilibrium binding of GS-522 to prothrombin in plasma (Kd = 50 nM) which saturates at GS-522 concentrations 〉2 µM. Compared to a scrambled sequence (GGTGGTGGTTGTGGT), with no defined tertiary structure, GS-522 is 4-fold more stable in serum. The metabolic profile in plasma is consistent with a 3′-exonuclease catalyzed hydrolysis of GS-522.
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    Dielectric method for detection of phase separation and its kinetics in TMPC/PS blends (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 524-532 
    Details
    ISSN: 1435-1536
    Keywords: Blends ; tetramethyl polycarbonate ; polystyrene ; LCST ; phase separation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new method for the detection of phase separation and its kinetics through real-time measurements is presented using the dielectric technique. The kinetics of phase separation were determined for a blend of tetramethyl bisphenol-A polycarbonate TMPC and polystyrene PS at different temperatures. The temperature dependence of the rate constant of phase separation was determined. The activation energy of phase separation process is found to be equal to 46 kcal/mole. In addition, it was possible to determine the variation in the composition of the TMPC-rich phase with time. The results obtained were compared with the literature data and were found to be in good agreement.
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    Electron transfer from cytochromeb 5 to cytochromec (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 331-340 
    Details
    ISSN: 1573-6881
    Keywords: Cytochromeb 5 ; cytochromec ; electron transfer ; kinetics ; ruthenium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The reaction of cytochromeb 5 with cytochromec has become a very prominent system for investigating fundamental questions regarding interprotein electron transfer. One of the first computer modeling studies of electron transfer and protein/protein interaction was reported using this system. Subsequently, numerous studies focused on the experimental determination of the features which control protein/protein interactions. Kinetic measurements of the intracomplex electron transfer reaction have only appeared in the last 10 years. The current review will provide a summary of the kinetic measurements and a critical assessment of the interpretation of these experiments.
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    URL: http://dx.doi.org/10.1007/BF02110102
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    Control of mitochondrial and cellular respiration by oxygen (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 583-596 
    Details
    ISSN: 1573-6881
    Keywords: Oxygen limitation ; p 50 ; critical oxygen pressure ; respirometry ; polarographic oxygen sensor ; human endothelial cells ; rat liver mitochondria ; intracellular $$p_{O_2 } $$ ; oxygen gradients ; kinetics ; nonequilibrium thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Control and regulation of mitochondrial and cellular respiration by oxygen is discussed with three aims: (1) A review of intracellular oxygen levels and gradients, particularly in heart, emphasizes the dominance of extracellular oxygen gradients. Intracellular oxygen pressure, $$p_{O_2 } $$ , is low, typically one to two orders of magnitude below incubation conditions used routinely for the study of respiratory control in isolated mitochondria. The $$p_{O_2 } $$ range of respiratory control by oxygen overlaps with cellular oxygen profiles, indicating the significance of $$p_{O_2 } $$ in actual metabolic regulation. (2) A methodologically detailed discussion of high-resolution respirometry is necessary for the controversial topic of respiratory control by oxygen, since the risk of methodological artefact is closely connected with far-reaching theoretical implications. Instrumental and analytical errors may mask effects of energetic state and partially explain the divergent views on the regulatory role of intracellular $$p_{O_2 } $$ . Oxygen pressure for half-maximum respiration,p 50, in isolated mitochondria at state 4 was 0.025 kPa (0.2 Torr; 0.3 ΜM O2), whereasp 50 in endothelial cells was 0.06–0.08 kPa (0.5 Torr). (3) A model derived from the thermodynamics of irreversible processes was developed which quantitatively accounts for near-hyperbolic flux/ $$p_{O_2 } $$ relations in isolated mitochondria. The apparentp 50 is a function of redox potential and protonmotive force. The protonmotive force collapses after uncoupling and consequently causes a decrease inp 50. Whereas it is becoming accepted that flux control is shared by several enzymes, insufficient attention is paid to the notion of complementary kinetic and thermodynamic flux control mechanisms.
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    Kinetic and regulatory aspects of the function of the alternative oxidase in plant respiration (1995)
    Springer
    Journal of bioenergetics and biomembranes 27 (1995), S. 387-396 
    Details
    ISSN: 1573-6881
    Keywords: Plant mitochondria ; alternative oxidase ; kinetics ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The kinetic modelling of the respiratory network in plant mitochondria is discussed, with emphasis on the importance of the choice of boundary conditions, and of modelling of both quinol-oxidising and quinone-reducing pathways. This allows quantitative understanding of the interplay between the different pathways, and of the functioning of the plant respiratory network in terms of the kinetic properties of its component parts. The effects of activation of especially succinate dehydrogenase and the cyanide-insensitive alternative oxidase are discussed. Phenomena, such as respiratory control ratios depending on the substrate, shortcomings of the Bahr and Bonner model for electron distribution between the oxidases and reversed respiratory control, are explained. The relation to metabolic control analysis of the respiratory network is discussed in terms of top-down analysis.
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    Dynamic measurements of adsorption of hydrolyzed polyacrylamide (HPAM) onto hematite (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1028-1032 
    Details
    ISSN: 1435-1536
    Keywords: Hydrolyzed polyacrylamide ; hematite ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption measurements of hydrolyzed polyacrylamide (HPAM) onto hematite suspension are carried out to study the dynamics of the polymer adsorption onto the suspension particles and to investigate the mode of the polymer adsorption. The polymer is found to show much affinity for the adsorption because of the opposite charges possessed by the polymeric flocculant and the suspension particles. Various adsorption parameters such as adsorption coefficient, the rate constants for the adsorption and desorption, are evaluated with the help of a recently proposed kinetic scheme. It is found that the extent of adsorption and the adsorption rate are adequately affected by increasing the pH of the suspension while, unexpectedly, the adsorption is found to show only a marginal increase on addition of Na2SO4. Both the amount of the adsorbed polymer and the adsorption rate are also found to increase with the degree of hydrolysis of the polyelectrolyte.
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    Absolute Rate Coefficients for the Gas-Phase Reactions of NO3 Radical with a Series of Monoterpenes at T = 298 to 433 K (1999)
    Springer
    Journal of atmospheric chemistry 33 (1999), S. 265-282 
    Details
    ISSN: 1573-0662
    Keywords: atmosphere ; kinetics ; nitrate radical ; monoterpenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The aim of this work is to study the reactivity of some naturally emitted terpenes, 2-carene, sabinene, myrcene, α-phellandrene, d-limonene, terpinolene and γ-terpinene, towards NO3 radical to evaluate the importance of these reactions in the atmosphere and their atmospheric impact. The experiments with these monoterpenes have been carried out under second-order kinetic conditions over the range of temperature 298–433 K, using a discharge flow system and monitoring the NO3 radical by Laser Induced Fluorescence (LIF). This work is the first temperature dependence study for the reactions of the nitrate radical with the above-mentioned monoterpenes. The measured rate constants at 298 K for the reaction of NO3 with such terpenes are as follows: 2-carene, 16.6 ± 1.8, sabinene 10.7 ± 1.6, myrcene 12.8 ± 1.1, α-phellandrene 42 ± 10, d-limonene 9.4 ± 0.9, terpinolene 52 ± 9 and γ-terpinene 24 ± 7, in units of 10-12 cm3 molecule-1 s-1. The proposed Arrhenius expressions, for the reactions of NO3 with 2-carene, sabinene, myrcene and α-phellandrene are, respectively k1 = (1.4 ± 0.7) × 10-12 exp[(741 ± 190/T)] (cm3 molecule-1 s-1), k2=(2.3 ± 1.3) × 10-10 exp[−(940 ± 200/T)] (cm3 molecule-1 s-1), k3 = (2.2 ± 0.2) × 10-12 exp[(523 ± 35/T)] (cm3 molecule1 s-1) and k4 = (1.9 ± 1.3) × 10-9 exp[−(1158 ± 270/T)] (cm3 molecule-1 s-1). A decrease in the rate constants when raising the temperature has also been found for the reaction of d-limonene with NO3 while an increase in the rate constant with temperature has been observed for the reactions of terpinolene and γ-terpinene with NO3. Tropospheric half-lives for these terpenes have been calculated at night and during the day for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important, if not dominant, loss process for these naturally emitted organics and for NO3 radicals.
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    Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone (1999)
    Springer
    Journal of atmospheric chemistry 34 (1999), S. 163-170 
    Details
    ISSN: 1573-0662
    Keywords: δ3-carene ; chlorine atoms ; isoprene ; kinetics ; methacrolein and methyl vinyl ketone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10-10, (2.1 ± 0.5) × 10-10, (3.2 ± 0.5) × 10-10, and (4.9 ± 0.5) × 10-10 cm3 molecule-1 s-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and δ3-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.
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    URL: http://dx.doi.org/10.1023/A:1006214423298
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    Non-isothermal Decomposition Kinetics of Complex of Co(III), Ni(II) with O,O'-dialkyldithiophosphates and Adducts of Ni-complex with Pyridines (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 197-203 
    Details
    ISSN: 1572-8943
    Keywords: adducts ; cobalt complex ; DSC ; kinetics ; nickel complex ; O,O'-dialkyldithiophosphate ; pyridine ; TG-DTG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)3 and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)2 and its adducts with pyridine, Ni(detp)2(py)2 or 4-methylpyridine, Ni(detp)(mpy)2 in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type.
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    Kinetics of Dehydration of Lanthanide(III) 2-Amino-4-Chlorobenzoates (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 653-659 
    Details
    ISSN: 1572-8943
    Keywords: dehydration ; kinetics ; lanthanide complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The 2-amino-4-chlorobenzoates of Y(III), La(III), Pr(III), Sm(III), Gd(III), Dy(III), Tm(III) and Lu(III) were prepared. Their general formula is Ln(C6H3NH2ClCOO)3·H2O. X-ray analysis demonstrated that all the prepared complexes are isostructural. This indicates the same mode of coordination of water and organic ligands throughout the whole series of lanthanide(III) 2-amino-4-chlorobenzoates. The dehydrations of the complexes were studied under non-isothermal conditions in air. From the thermogravimetric data on the dehydrations, the kinetic models best fitting the experimental TG curves were selected. These models suggest that the dehydration is governed by diffusion processes. Kinetic parameters such as the activation energy and pre-exponential factor were calculated by means of the differential and integral methods.
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    URL: http://dx.doi.org/10.1023/A:1010174725871
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    Dehydration Reaction of Manganese(II) Oxalate Dihydrate in the Solid State New Method in the Study of Non-isothermal Kinetics (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 877-884 
    Details
    ISSN: 1572-8943
    Keywords: dehydration ; kinetics ; manganese(II) oxalate dihydrate ; mechanism ; non-isothermal ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method was proposed for determining the most probable mechanism function of a solid phase reaction. According to Coats-Redfern's integral equation Eβ→0 was calculated by extrapolating β to zero using a series of TG curves with different heating rates. Similarly, Eα→0 was calculated according to Ozawa's equation. The most probable mechanism function of the solid phase dehydration of manganese(II) oxalate dihydrate was confirmed to be G(α)=(1-α)1/2 by comparing Eα→0 with Eβ→0.
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    URL: http://dx.doi.org/10.1023/A:1010189918544
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    Thermal Analysis and Kinetics of Solid-State Reactions Its Application to Education in Chemistry (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 855-861 
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    ISSN: 1572-8943
    Keywords: education ; kinetics ; microscopy ; solid-state reactions ; teaching materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In an attempt to show the importance of preparing extensively teaching materials for comprehensive education in thermal analysis at an undergraduate level, the significance of the teaching materials concerning the thermal analysis and kinetics of the solid-state reactions is discussed by reviewing our teaching activities at Hiroshima University. Application of the thermoanalytical techniques to thermal decomposition of basic copper(II) salts is appropriate for an introductory experiment to thermal analysis. Microscopic observations of the textural change during the thermal dehydration of inorganic salt hydrates are suitable for introducing the kinetics of solid-state reactions. A computer practice of drawing the experimental master plot enables students to understand the kinetic theory.
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    Characterization of Oil Shales by High Pressure DSC (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 939-946 
    Details
    ISSN: 1572-8943
    Keywords: combustion ; high pressure DSC ; kinetics ; oil shale ; pyrolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Pressurised differential scanning calorimeter (PDSC) has been used to obtain information on the pyrolysis and combustion characteristics of oil shales. Two distinct exothermic peaks were identified in combustion experiments known as low temperature oxidation (LTO) and high temperature oxidation (HTO) reaction regions. The pyrolysis process of all studied oil shale samples showed one exothermic effect at each total pressure studied. Kinetic data were analysed by Roger & Morris and Arrhenius methods and the results are discussed.
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    Thermoanalytical Study of the Dehydration of Cyclodextrin Inclusion Complexes of Clofibric Acid (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1329-1334 
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    ISSN: 1572-8943
    Keywords: cyclodextrin complexes ; dehydration ; kinetics ; TG-DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrated inclusion complexes of the hosts β-CD (CD=cyclodextrin), γ-CD and permethylated β-CD with the guest clofibric acid were analysed by TG and DSC methods to characterise their dehydration behaviours. Activation energies for dehydration of the β- and γ-CD clofibric acid complexes, determined by isothermal thermogravimetry, are significantly lower (∼20-25%) than those for the corresponding uncomplexed hydrated CDs. These data can be reconciled with X-ray structural data which show that H2O molecules in the complexes occupy different crystal sites from those occupied in the parent CDs.
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    Kinetics of Solute Flow to Partial Dislocation in Cu–3.4 At.% Sb (1999)
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 607-622 
    Details
    ISSN: 1572-8943
    Keywords: Cu–3.4 At.% Sb alloy ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of solute segregation to partial dislocations in a Cu–3.4 At.% Sb alloy was studied by using a phenomenological approach with differential scanning calorimetry and isothermal calorimetry. The material, severely deformed by repeated bending, presented an excess of dissociated edge dislocations with a dislocation density amounting to about 8.5·1014 m−2, calculated using a prior model of the authors, together with calorimetric recrystallization trace analysis. The kinetics was found to be ruled by two overlapping mechanisms: diffusion of solute atoms mostly through dislocation pipes in the initial and middle stages of the reaction process, acting together with bulk solute diffusion in these stages and later. Bulk solute diffusion increases as the reaction proceeds, as shown by the increasing values of apparent activation energy in the reaction. The exponent of the Mehl-Johnson-Avrami equation used in the phenomenological description was successfully fitted to a time—temperature-dependent function, increasing in agreement with the apparent activation energy behaviour, as may be expected.
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    Preparation and Study of Epoxidized Natural Rubber (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 293-299 
    Details
    ISSN: 1572-8943
    Keywords: ENR ; kinetics ; thermal degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Epoxidized natural rubbers (ENRs) with different extents of epoxidation (B) were prepared under various reaction conditions. The effects of the amount of H2O2 and the reaction time on B are discussed. The glass transition temperature Tg, the thermal degradation temperature and the activation energy of thermal degradation of the ENRs increase with B. The results indicate that the thermal stability of the ENRs increases with B.
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    Kinetics of Direct Reduction of Chrome Iron Ore (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 317-322 
    Details
    ISSN: 1572-8943
    Keywords: chrome iron ore ; kinetics ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of direct reduction of artificial chrome iron ore was studied by isothermal and non-isothermal methods. In the initial, middle and final periods, the reaction is controlled by nucleation and growth, a phase boundary reaction, and diffusion, respectively. In the main reaction region, the kinetic equation is 1−(1−α)1/3=kt and the apparent activation energy is 270 kJ mol−1. The kinetic mechanisms found with the isothermal and non-isothermal methods do not differ, and the activation energy values are approximately the same. However, the non-isothermal method can demonstrate the kinetic process completely.
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    Modeling of oxygen adsorption on silver (1999)
    Springer
    Reaction kinetics and catalysis letters 66 (1999), S. 265-272 
    Details
    ISSN: 1588-2837
    Keywords: Oxygen ; surface ; silver ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different adsorption forms of oxygen on silver are discussed. Four main types of oxygen forming at different temperatures and oxygen pressures have been distinguished. A kinetic model describing the formation and transformations of the oxygen forms and taking into account the surface amorphization has been proposed. Numerical modeling of stationary concentrations using this model gives evidence for a temperature window ΔT=500–800 K, where a quasimolecular oxygen state (E=530.5 eV, Tdes=800–900 K) can exist at high oxygen pressures.
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    Photocatalytic water purification: Destruction of resorcinol by irradiated titania (1999)
    Springer
    Reaction kinetics and catalysis letters 66 (1999), S. 289-295 
    Details
    ISSN: 1588-2837
    Keywords: Resorcinol photooxidation ; kinetics ; intermediates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ethanedial, butanoic acid anhydride and trihydroxybenzenes have been determined as intermediates of resorcinol photocatalytic oxidation. The photoreaction rate shows a 1st order dependence on resorcinol concentration. The calculated reaction rate constant is 2.1×10−8 mol dm−3 s−1, which is similar to the rate constant of phenol photocatalytic oxidation on TiO2 reported beore.
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    Low-temperature heterogeneous oxidation of sulfide ions on a higher Co oxide system in aqueous medium (1999)
    Springer
    Reaction kinetics and catalysis letters 66 (1999), S. 55-62 
    Details
    ISSN: 1588-2837
    Keywords: Oxidation of sulfides ; kinetics ; higher Co oxide IR ; XPS ; reaction mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Low-temperature heterogenous oxidation of sulfide ions on a higher Co oxide system in aqueous medium has been studied. The effects of pH, temperature and catalyst amount on the kinetic parameters as well as on the selectivity of the oxidation process were investigated. An oxidation mechanism has been proposed based on the results of kinetic investigations and on the data obtained by IR and XPS spectroscopic studies of Co oxide before and after sulfide ion oxidation.
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    Kinetics of supramolecular crystallization of concentrated suspensions of monodisperse spherical silica particles (1999)
    Springer
    Reaction kinetics and catalysis letters 68 (1999), S. 387-391 
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    ISSN: 1588-2837
    Keywords: Silica ; monodisperse particles ; supramolecular crystallization ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of supramolecular crystallization of concentrated suspensions is three-dimensional and follows the Avrami-Erofeev equation: A=1-exp[-(kt)m], where m=4. The rate constant k is proportional to the probability of the appearance of a crystallization center in unit volume in unit time and the linear crystal growth rate, which is determined experimentally.
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    Kinetics of oxidation of diols by ozone in aqueous solution (1999)
    Springer
    Reaction kinetics and catalysis letters 68 (1999), S. 237-242 
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    ISSN: 1588-2837
    Keywords: Diols ; oxidation ; ozone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the oxidation of diols by ozone was investigated by a spectrophotometric method in the temperature interval of 277–304 K. The activation parameters of the reaction were determined.
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    Kinetics of oxidation of aliphatic alcohols by ozone in aqueous solutions (1999)
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    Reaction kinetics and catalysis letters 68 (1999), S. 257-263 
    Details
    ISSN: 1588-2837
    Keywords: Alphatic alcohols ; oxidation ; ozone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of oxidation of aliphatic alcohols by ozone in aqueous solutions was investigated in the temperature interval of 292–317 K. The activation parameters of the reaction were determined. The dissociation energies of CH-bonds of the studied substrates were calculated with the use of the AM1 semiempirical method.
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    Isothermal and Non-Isothermal Techniques in Kinetic Studies of Reactions in a Photoactive Molecular Material (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 35 (1999), S. 139-146 
    Details
    ISSN: 1573-1111
    Keywords: dihydropyridine ; photochromism ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of thermally driven reactions in a crystalline photochromic solid, 1-methyl-2,4,4,6-tetraphenyl-1,4-dihydropyridine (DHP), has been studied. The processes have been monitored by measuring the isothermal bleaching of coloured species produced upon UV irradiation of DHP, and by measuring the heat flow in non-isothermal differential scanning calorimetry experiments. Signatures of two processes were detected; a combination of quantum-chemical calculations and spectroscopic measurements allowed us to attribute them to reactions occurring in the photochromic system.
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    Manganese cycling in a eutrophic lake — Rates and pathways (1995)
    Springer
    Aquatic geochemistry 1 (1995), S. 399-426 
    Details
    ISSN: 1573-1421
    Keywords: manganese reduction ; manganese oxidation ; organic matter oxidation ; kinetics ; bacteria ; alkalinity ; lake chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The redox processes regulating transport of Mn in the water column of a eutrophic, dimictic lake (Lake Norrviken, Sweden) are interpreted based on a one-dimensional diffusion-reaction model for Mn(II). It is found that rates and rate constants for oxidation and reduction vary greatly with depth and also with time during the season of stratification. Calculated rates show that Mn(II) oxidation and reduction generally occur in narrow depth intervals (25–50 cm). This is in good agreement with measured profiles of particulate Mn (MnO x ). Maximum oxidation rate constants (assuming first order kinetics) at each date are in the first half of the season 〈1 d−1, but then increases to a rather constant value of about 25 d−1. These high rate constants are indicative of microbiological involvement in the Mn(II) oxidation. This is further evidenced by SEM-EDS analysis showing Mn enriched particles morphologically similar toMetallogenium. Reductive dissolution of Mn oxides occurs mainly in the zone just below the zone of maximum oxidation rate. The release of Mn(II) is accompanied by production of alkalinity and ΣCO2. The relation between production rates of Mn(II) and alkalinity indicates that Mn oxides act as terminal electron acceptors in the bacterially mediated oxidation of organic matter. However, the ΔMn2+/ΔΣCO2 ratio is significantly lower than what is expected from this process. It is suggested that the Mn reduction is coupled to fermentation. Close coexistence of Mn reduction and oxidation at high rates, such as found in the water column of this lake, facilitates rapid and continuous regeneration of reducible Mn oxides. This gives rise to a quantitatively important mechanism of organic matter oxidation in the water column.
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    Kinetics and mechanism of azidomercuration of alkenes, cycloalkenes, and their derivatives with a mercuric acetate-sodium azide system (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2375-2381 
    Details
    ISSN: 1573-9171
    Keywords: azidomercuration ; alkenes ; cycloalkenes ; strained double bond ; kinetics ; reaction mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of azidomercuration of alkenes, cycioalkenes, and their derivatives with a Hg(OAc)2-NaN3 system (1 ∶ 1, 1 ∶ 2, and 1 ∶ 3) was studied. Based on the data on the product structure and kinetic results, it was concluded that HgOAcN3 and Hg(N3)2 play the role of azidomercuration reagents. The reactions with alkenes having a strained double bond occur by a concerted scheme. With nonstrained alkenes, a multistep mechanism is realized, its first reversible step involving the formation of a mercurinium intermediate with an ion pair structure.
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    URL: http://dx.doi.org/10.1007/BF00713611
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