Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (170)
  • Online Resource
  • 2000-2004  (79)
  • 1985-1989  (91)
  • kinetics
  • 1
    Electronic Resource
    Electronic Resource
    Why Does the Linear Driving Force Model for Adsorption Kinetics Work? (2000)
    Springer
    Adsorption 6 (2000), S. 137-147 
    Details
    ISSN: 1572-8757
    Keywords: adsorption ; kinetics ; linear driving force model ; process design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008965317983
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Effect of K, Cs and Ba on the kinetics of NH3 synthesis over carbon-based ruthenium catalysts (2000)
    Springer
    Catalysis letters 68 (2000), S. 163-168 
    Details
    ISSN: 1572-879X
    Keywords: ammonia synthesis ; kinetics ; ruthenium catalysts ; promotional effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019024629261
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Mechanism of the hydrodenitrogenation of o-toluidine and methylcyclohexylamine over NiMo/γ-Al2O3 (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 327-333 
    Details
    ISSN: 1572-9028
    Keywords: hydrodenitrogenation ; toluidine ; methylcyclohexylamine ; kinetics ; nickel-promoted molybdenum sulphide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al2O3 catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1027208200169
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Static and Kinetic Studies on the Adsorption Behavior of Sulfadiazene (2000)
    Springer
    Adsorption 6 (2000), S. 349-357 
    Details
    ISSN: 1572-8757
    Keywords: sulfadiazene ; adsorption ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026517117239
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    NO reduction over La2O3 using methanol (2000)
    Springer
    Catalysis letters 64 (2000), S. 65-75 
    Details
    ISSN: 1572-879X
    Keywords: NO reduction ; CH3OH ; La2O3 ; methyl nitrite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nitric oxide (NO) reduction by methanol was studied over La2O3 in the presence and absence of oxygen. In the absence of O2, CH3OH reduced NO to both N2O and N2, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O2 in the feed, rates were 4–8 times higher, but the selectivity to N2 dropped from 50% at 623 K to 10% at 723 K. The specific activities with La2O3 for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 μmol NO/s m2 was obtained whereas that for methanol was 600 μmol NO/s m2. The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH3OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH3OH and a near‐first order in H2. In the absence of O2, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH3OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O2 a homogeneous gas‐phase reaction between O2, NO, and CH3OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O2 present were significantly complicated by this homogeneous reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019036431195
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and p-benzoquinone in the presence of inorganic acid (2000)
    Springer
    Catalysis letters 69 (2000), S. 103-107 
    Details
    ISSN: 1572-879X
    Keywords: dicyclopentadiene ; Wacker oxidation ; Pd(AcO)2 ; benzoquinone ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and benzoquinone in the presence of perchloric acid was studied. Tricyclodecenone in high selectivity (85–98%) at a conversion of dicyclopentadiene up to 76% was obtained. The kinetic model assumed the significant inhibition complexation between dicyclopentadiene and tricyclodecenone with the catalytic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019053402854
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The oxygen uptake threshold during incremental exercise test (2000)
    Springer
    Pflügers Archiv 440 (2000), S. r200 
    Details
    ISSN: 1432-2013
    Keywords: Key words oxygen uptake ; kinetics ; threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The linear relationship between oxygen consumption (Vo2) and exercise intensity is a well established phenomenon observed during incremental exercise. Recently, a non-linear increase in Vo2 has been reported by Zoladz et al., who used a relatively complicated method to describe the phenomenon. In this study, we tried to ascertain whether the same phenomenon, which we named the oxygen uptake threshold (OUT), could be described by a simple method, using the two best fitting lines adopted for the less and more steep parts of the Vo2 increase. Our hypothesis was that the non-linear Vo2 increase was the result of a continuous Vo2 increase (oxygen drift) occurring during the more intense steps only. Therefore, we analysed the Vo2 time course during each step. Six cyclists performed an incremental exercise test on a cyclo - ergometer. The lactate threshold (LT) was calculated by using the intersection point of the two best fitting lines in the diagram of log LA (lactate concentration) dependence on log P (Power). The time course of Vo2 during each step was analysed by an exponential rise to the maximum model. The results showed that OUT could be determined in five of the six subjects, whereas LT could be determined in all six subjects. The power output determined by OUT (168 ± 13 W) was similar to that determined by LT (180 ± 25 W). The Vo2 time course during each step showed steady values during low intensity exercise. At intensities above LT and OUT, however, Vo2 increased continuously, showing oxygen drift. It may be concluded that OUT is a realistic phenomenon, which is based on oxygen drift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240000064
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Kinetic Analysis of the Decomposition of Chelates of Di-alkyldithiocarbamate of Cd(II) (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
    Details
    ISSN: 1572-8943
    Keywords: cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010120813517
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Kinetic and Thermodynamic Studies of Facial and Meridional uns-cis-[Co(eddp)gly] Complexes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
    Details
    ISSN: 1572-8943
    Keywords: facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010157821694
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Thermal Decomposition Kinetics of Some Metal Complexes of N,N-diethyl-n '-benzoylthiourea (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; metal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010171230450
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 11
    Electronic Resource
    Electronic Resource
    Fast Gas Adsorption Measurements For Complicated Adsorption Mechanisms (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
    Details
    ISSN: 1572-8943
    Keywords: adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010190131304
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Study of Thermal Decomposition Kinetics of Low-temperature Reaction of Ammonium Perchlorate by Isothermal TG (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
    Details
    ISSN: 1572-8943
    Keywords: activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010136308310
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Theoretical and Experimental Investigations of The Decomposition of 10-methylacridinium Halides (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010160132175
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Thermal Decomposition of Triazine Herbicides. I. 1,2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropionitrile (cyanazine) (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 103-110 
    Details
    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010132820788
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Influence of Gas Atmosphere on Removal of Sulphate Groups From Titanium Oxide (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
    Details
    ISSN: 1572-8943
    Keywords: desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010178130783
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Solid State Coordination Chemistry. The quantitative thermoanalytical study of thermal dissociation reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
    Details
    ISSN: 1572-8943
    Keywords: coordination compounds ; kinetics ; thermal dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010148028796
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    The Effect of Cross-linked Polyethylene As a Surface Modifier on Crystallization of Polypropylene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
    Details
    ISSN: 1572-8943
    Keywords: cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010129106561
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Formation of Cr(II) Species in the H2/CrO3 System. Parameter control (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
    Details
    ISSN: 1572-8943
    Keywords: Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010142904261
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Kinetic Modeling of Advanced Inorganic Glass-ceramics Formation by Crystal Growth From Pre-existing Nuclei (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
    Details
    ISSN: 1572-8943
    Keywords: accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010123805594
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Temperature Modulated DSC. Theoretical interpretation (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    Details
    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010148200201
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 21
    Electronic Resource
    Electronic Resource
    Practical Thermogravimetry (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
    Details
    ISSN: 1572-8943
    Keywords: decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010187019979
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 22
    Electronic Resource
    Electronic Resource
    The Thermodynamic Driving Force in the Kinetic Evaluation of Thermoanalytical Curves (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
    Details
    ISSN: 1572-8943
    Keywords: driving force ; kinetics ; rate equation ; reversible reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010159708593
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 23
    Electronic Resource
    Electronic Resource
    Kinetic Analysis of the Thermal Decomposition of Synthetic Malachite by CRTA (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
    Details
    ISSN: 1572-8943
    Keywords: CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010172111319
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 24
    Electronic Resource
    Electronic Resource
    Thermal Studies on Some Lanthanide Complexes (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
    Details
    ISSN: 1572-8943
    Keywords: complexes ; kinetics ; TG-DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010172926826
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 25
    Electronic Resource
    Electronic Resource
    Non-isothermal Kinetic Study of the Heterogeneous Thermal Decomposition of a Mannich Compound (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; Mannich compounds ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010197632277
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 26
    Electronic Resource
    Electronic Resource
    Polypropylene Crystallization in an Ethylene-propylene-diene Rubber Matrix (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    Details
    ISSN: 1572-8943
    Keywords: crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010165317028
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 27
    Electronic Resource
    Electronic Resource
    TG and DTA Study of the Thermal Dehydration of Metal-exchanged Zeolite-4A Samples (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; metal exchange ; thermaldehydration ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026725509732
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 28
    Electronic Resource
    Electronic Resource
    Kinetic Equations for Thermal Dissociation Processes. Part I. KEKAM equation (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
    Details
    ISSN: 1572-8943
    Keywords: KEKAM equation ; kinetics ; thermal dissociation of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010184224240
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 29
    Electronic Resource
    Electronic Resource
    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. II. The activation energy obtained from isothermal data corresponding to two successive reactions (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 465-469 
    Details
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010100712853
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 30
    Electronic Resource
    Electronic Resource
    Kinetics of Thermal Decomposition of Plumbo-jarosite (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
    Details
    ISSN: 1572-8943
    Keywords: decomposition ; kinetics ; plumbo-jarosite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010122308490
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 31
    Electronic Resource
    Electronic Resource
    Thermal Characterization of Passivated Nanometer Size Aluminium Powders (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    Details
    ISSN: 1572-8943
    Keywords: aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010197115003
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 32
    Electronic Resource
    Electronic Resource
    Thermal and Spectroscopic Studies on the Decomposition of Some Aminoguanidine Nitrates (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    Details
    ISSN: 1572-8943
    Keywords: DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010113707251
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 33
    Electronic Resource
    Electronic Resource
    Fractal Approach in the Kinetics of Solid-Gas Decompositions. Part II (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
    Details
    ISSN: 1572-8943
    Keywords: kinetics ; nucleation-growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010175415429
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 34
    Electronic Resource
    Electronic Resource
    Study of The Mechanism and Kinetic Parameters of The Thermal Decomposition of Cobalt Sulphate Hexahydrate (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    Details
    ISSN: 1572-8943
    Keywords: CoSO46H2O ; kinetics ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010186628054
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 35
    Electronic Resource
    Electronic Resource
    Kinetic Study of the Accelerating Effect of Coal-burning Additives on the Combustion of Graphite (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
    Details
    ISSN: 1572-8943
    Keywords: coal-burning additive ; combustion ; graphite ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026769323844
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 36
    Electronic Resource
    Electronic Resource
    Critical Analysis of the Isoconversional Methods for Evaluating the Activation Energy. I. Theoretical background (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
    Details
    ISSN: 1572-8943
    Keywords: isoconversional methods ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010148611036
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 37
    Electronic Resource
    Electronic Resource
    Modeling of the Phase Transformation Induced by Ball Milling in Anatase TiO2 (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    Details
    ISSN: 1573-4870
    Keywords: TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011351807629
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 38
    Electronic Resource
    Electronic Resource
    Relating Single-Impact Events to Macrokinetic Features in Mechanical Alloying Processes (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 271-277 
    Details
    ISSN: 1573-4870
    Keywords: Comminution ; kinetics ; mechanical alloying ; phase transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011382008963
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 39
    Electronic Resource
    Electronic Resource
    High-Temperature Oxidation Behavior of the Co-Base Superalloy DZ40M in Air (2000)
    Springer
    Oxidation of metals 53 (2000), S. 351-360 
    Details
    ISSN: 1573-4889
    Keywords: Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004597405809
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 40
    Electronic Resource
    Electronic Resource
    Analysis of Aluminum—Yeast Hexokinase Interaction: Modifications on Protein Structure and Functionality (2000)
    Springer
    The protein journal 19 (2000), S. 199-208 
    Details
    ISSN: 1573-4943
    Keywords: Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007055719926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 41
    Electronic Resource
    Electronic Resource
    A Comparative Study of Human Muscle and Brain Creatine Kinases Expressed in Escherichia coli (2000)
    Springer
    The protein journal 19 (2000), S. 59-66 
    Details
    ISSN: 1573-4943
    Keywords: Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007047026691
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 42
    Electronic Resource
    Electronic Resource
    Stabilization of ammonium dinitramide in the liquid phase (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1974-1976 
    Details
    ISSN: 1573-9171
    Keywords: ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009555405171
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 43
    Electronic Resource
    Electronic Resource
    The kinetics and mechanism of cyclodimerization of alkylthiopropenals (2000)
    Springer
    Russian chemical bulletin 49 (2000), S. 1977-1980 
    Details
    ISSN: 1573-9171
    Keywords: 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009507522009
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 44
    Electronic Resource
    Electronic Resource
    Cooperative Interactions in Photosensitized Modification of DNA with Oligonucleotide-derived Binary Reagents (2000)
    Springer
    Molecular biology 34 (2000), S. 814-822 
    Details
    ISSN: 1608-3245
    Keywords: DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026619607955
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 45
    Electronic Resource
    Electronic Resource
    Functional Properties of Lactate Dehydrogenase from Dunaliella salina and Its Role in Glycerol Synthesis (2000)
    Springer
    Russian journal of plant physiology 47 (2000), S. 761-771 
    Details
    ISSN: 1608-3407
    Keywords: Dunaliella salina ; lactate dehydrogenase ; kinetics ; glycerol synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dependence of the catalytic properties of lactate dehydrogenase (LDH, EC 1.1.1.27) from a halophilic alga Dunaliella salina, a glycophilic alga Chlamydomonas reinhardtii, and from porcine muscle on glycerol concentration, medium pH, and temperature was investigated. Several chemical properties of the enzyme from D. salina differentiated it from the LDH preparation obtained from C. reinhardtii and any homologous enzymes of plant, animal, and bacterial origin. (1) V max of pyruvate reduction manifested low sensitivity to the major intracellular osmolyte, glycerol. (2) The affinity of LDH for its coenzyme NADH dropped in the physiological pH region of 6–8. Above pH 8, NADH virtually did not bind to LDH, while the enzyme affinity for pyruvate did not change considerably. (3) The enzyme thermostability was extremely low: LDH was completely inactivated at room temperature within 30 min. The optimum temperature for pyruvate reduction (32°C) was considerably lower than with the enzyme preparations from C. reinhardtii (52°C) and porcine muscle (61°C). (4) NADH greatly stabilized LDH: the ratio of LDH inactivation constants in the absence of the coenzyme and after NADH addition at the optimum temperature in the preparation from D. salina exceeded the corresponding indices of LDH preparations from C. reinhardtii twelve times and from porcine muscle eight times. The authors believe that these LDH properties match the specific metabolism of D. salina which is set at rapid glycerol synthesis under hyperosmotic stress conditions. The increase of cytoplasmic pH value produced in D. salina by the hyperosmotic shock can switch off the terminal reaction of the glycolytic pathway and thus provide for the most efficient utilization of NADH in the cycle of glycerol synthesis. As LDH is destabilized in the absence of NADH, this reaction is also switched off. In the course of alga adaptation to the hyperosmotic shock, glycerol accumulation and the neutralization of intracellular pH stabilize LDH, thus creating the conditions for restoring the complete glycolytic cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026607211936
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 46
    Electronic Resource
    Electronic Resource
    Kinetic study of a thermostable β-glycosidase of Thermus thermophilus. Effects of temperature and glucose on hydrolysis and transglycosylation reactions (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 377-383 
    Details
    ISSN: 1573-4986
    Keywords: β-glycosidase ; temperature dependence ; kinetics ; glucose ; transglycosylation ; (Thermus thermophilus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A β-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttβgly) has a broad substrate specificity towards β-D-glucoside, β-D-galactoside and β-D-fucoside derivatives. The thermostability of Ttβgly was exploited to study its kinetic properties within the range 25–80[emsp4 ]°C. Whatever the temperature, except around 60[emsp4 ]°C, the enzyme displayed non-Michaelian kinetic behavior. Ttβgly was inhibited by high concentrations of substrate below 60[emsp4 ]°C and was activated by high concentrations of substrate above 60[emsp4 ]°C. The apparent kinetic parameters (k cat and K m ) were calculated at different temperatures. Both k cat and K m increased with an increase in temperature, but up to 75[emsp4 ]°C the values of k cat increased much more rapidly than the values of K m . The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttβgly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007104030314
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 47
    Electronic Resource
    Electronic Resource
    Statistical Properties of Stimulated Raman Scattering in a Nonlinear Regime (2000)
    Springer
    Journal of applied spectroscopy 67 (2000), S. 981-989 
    Details
    ISSN: 1573-8647
    Keywords: nonlinear regime of stimulated Raman scattering ; fluctuation ; Stokes radiation ; kinetics ; spectrum ; distribution function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Statistical properties of the Raman scattering of an intense step pulse are investigated by numerical solution of the equations of a semi-classical theory with assignment of a random Gaussian distribution of the initial polarization over the sample. The probability density functions of the intensity, energy, delay time, and width of a Stokes pulse and also of the position, height, and width of the spectral peaks of the first incidental Stokes component with the preservation of the phase memory of scattering centers are calculated. The influence of collisional dephasing on the fluctuation of these characteristics is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004120404710
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 48
    Electronic Resource
    Electronic Resource
    Effect of Compaction Scheme on Property Distribution for Cumulative Charge Facings Formed from a Heterogeneous Powder Composite (2000)
    Springer
    Powder metallurgy and metal ceramics 39 (2000), S. 540-544 
    Details
    ISSN: 1573-9066
    Keywords: compaction ; facing ; cumulative charge ; powder ; composite ; heterogeneous structure ; particle ; kinetics ; surface ; die ; model ; xeroradiogram
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An experimental and numerical (finite element method) study is carried out for the effect of forming scheme on property distribution for cumulative charge facings made from composite heterogeneous powder material. An experimental procedure is developed for studying powder particle flow kinetics. It is shown that use of composite punches and partition of the moulded material into a number of sub-divisions with their successive compaction achieves a more uniform density distribution for an article. It is demonstrated how the direction of the force of friction on the die walls during compaction affects the compaction of articles with faces that are not perpendicular to the direction of the pressing. The results obtained make it possible to select the optimum compaction regime taking account of production features connected with powder material composition as well as service characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011359626701
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 49
    Electronic Resource
    Electronic Resource
    Simultaneous Determination of the Heat and the Quantity of Vapor Sorption Using a Novel Microcalorimetric Method (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 701-706 
    Details
    ISSN: 1573-904X
    Keywords: vapor sorption ; molar heat of adsorption ; kinetics ; isothermal microcalorimetry ; recrystallization ; hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. In this study, instrumentation for measuring vapor sorptionenthalpies and sorption uptakes simultaneously with an isothermalmicrocalorimeter is introduced. Various pharmaceutical modelsubstances undergoing phase transitions when exposed to humid conditions(25°C), were employed to evaluate the usefulness and sensitivity ofthe constructed experimental method. Methods. The sample is placed in the sample vessel of a RH cell andthe moisture content of the air flow is controlled. From the RH cellthe air flow is conducted into a subsequent perfusion cell in which asaturated salt solution has been loaded. The RH cell and perfusioncells are positioned in the sample sides of two twin calorimetric units.Depending on the moisture content in the outlet flow leaving thepreceding RH cell, the heat flow signal from the subsequent perfusioncell will vary. By means of blank measurement with identical settings,the rate of water sorption can be calculated and, by integration, theamount of sorbed water is obtained. Results. Amorphous lactose and cefadroxil undergo recrystallizationwhen the moisture level in the surroundings exceeds the thresholdvalues specific to each compound. During the sorption phase, heat isevolved fairly linearly as a function of consumed moisture, and alsoafter the recrystallization, the heats indicate linear behavior. The heatvalues for the desorption phase of amorphous lactose and the adsorptionof crystalline lactose coincide. With the different anhydrous forms oftheophylline, the hydration takes place more rapidly in the metastableform I, and generally, the process is more energetic in form I. In allcases, the gravimetric results agree with the water sorption uptakescalculated from the calorimetric data. Conclusions. The technique introduced offers a rapid and sensitivemethod to gain new insights into the transitions in which vapors areinvolved. In addition, different kinds of surfaces with various energeticscan now be studied more closely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007530315652
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 50
    Electronic Resource
    Electronic Resource
    Mercury speciation in natural waters: Measurement of dissolved gaseous mercury with a field analyzer (2000)
    Springer
    Biogeochemistry 48 (2000), S. 237-259 
    Details
    ISSN: 1573-515X
    Keywords: gaseous ; kinetics ; mercury ; methods ; speciation ; waters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Mercury evasion from water is commonly modeled using measurements of dissolved gaseous mercury (DGM). We developed a method using a recently available automated field-ready mercury vapor analyzer to rapidly measure the concentrations of DGM in surface waters. We summarize here results of laboratory tests of the method, field intercomparisons with a manual method, and selected data from recent sampling campaigns in Florida and Michigan. The method uses the 1.5 lpm flow of a Tekran® Model 2537A mercury analyzer to purge and analyze discrete water samples, generating near real time (5-min) data on DGM in samples and blanks. Application of the Tekran allowed for detailed analysis of DGM removal kinetics and short-term diel studies characterizing the influence of sunlight and precipitation on DGM production in surface waters. Gas removal kinetics for dozens of samples indicates a first-order rate constant, and supports a 20-min. purge time for surface water samples from Florida (40-min for Michigan samples). Blanks are measured during a second such purge. Our results indicate that DGMs determined by both automated and manual methods are generally comparable, and that DGM in Florida samples is unstable during storage (loss rate constant ∼0.1--0.2 h-1), probably due to oxidation. This suggests that rapid in-field analysis is preferred to storage with delayed analysis. Our data indicate that DGM at the Florida site is influenced by inputs of reactive Hg in rainwater, and by production of surface DGM during photoreduction of oxidized Hg in the water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006228612872
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 51
    Electronic Resource
    Electronic Resource
    The Kinetics of Transposable Element Autoregulation (2000)
    Springer
    Genetica 108 (2000), S. 229-237 
    Details
    ISSN: 1573-6857
    Keywords: autoregulation ; dimerization ; kinetics ; post-transcriptional regulation ; transposable elements (TEs)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kinetic modeling of the self-regulatory mechanisms of transposable elements (TEs) involving interactions of one or a few gene products makes predictions that are often at odds with observed results. In particular, explanations of TE autorepression at high copy number that invoke a decrease in number of active monomers through dimerization, amyloidization, and protein-mRNA binding to create an inactive state are not supported by analysis of the corresponding kinetic models. This is also true for similar mRNA–mRNA binding models. Self-repression in marineras well as other TEs can, however, be explained by a host-independent model in which inactive dimers compete with monomers for TE binding sites at the ends of the element. This model would also allow heterodimer poisoning to down-regulate transposition in the presence of divergent nonautonomous elements, since nondivergent monomers would be required at both TE ends for transposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004172703790
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 52
    Electronic Resource
    Electronic Resource
    Control of the Mitochondrial Permeability Transition Pore by High-Affinity ADP Binding at the ADP/ATP Translocase in Permeabilized Mitochondria (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 91-96 
    Details
    ISSN: 1573-6881
    Keywords: Permeability transition ; ADP/ATP translocase ; kinetics ; adenosine diphosphate ; carboxya tractyloside ; bongkekic acid ; mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Low levels of ADP binding at the ADP/ATP translocase caused inhibition of the Ca2+-inducedpermeability transition of the mitochondrial inner membrane, when measured using the shrinkage assay on mitochondria, which have already undergone a transition. Inhibition was preventedby carboxyatractyloside, but potentiated by bongkrekic acid, which increased the affinity forinhibition by ADP. This suggests that inhibition was related to the conformation of thetranslocase. Ca2+ addition was calculated to remove most of the free ADP. Ca2+ added after ADPinduced a slow decay of the inhibition, which probably reflected the dissociation of ADP fromthe translocator. We conclude that the probability of forming a permeability transition pore(PTP) is much greater when the translocase is in the CAT conformation than in the BKAconformation, and, in the absence of CAT and BKA, the translocator is shifted between theBKA and CAT conformations by ADP binding and removal, even in deenergized mitochondria with no nucleotide gradients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005568630151
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 53
    Electronic Resource
    Electronic Resource
    The Relationship Between Rate of Administration of an Intubating Dose of Rocuronium and Time to 50% and 90% Block at the Adductor Pollicis Muscle (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 219-222 
    Details
    ISSN: 1573-2614
    Keywords: Neuromuscular relaxants ; rocuronium ; kinetics ; distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective.To determine the relationship between the rate ofrocuronium injection and the onset time of neuromuscular block. Methods.After intravenous induction, 60 female patients (ASA I–II) wereassigned randomly into 3 groups for rocuronium administration within1–15, 15–30 or 30–60 seconds. Acceleromyography of the thumbwas performed using train-of-four (TOF) stimulation. Times to 50% and 90%twitch depression of the first twitch of the TOF stimulation (T1) wererecorded. Results.Injection time significantly influences time to 50%relaxation, but not time to 90% relaxation. Body mass index is negativelycorrelated with time to 50% and 90% relaxation. Conclusions.Weconclude that rate of injection influences only the initial phase ofdevelopment of the block and that slower injection times do not significantlyaffect time to 90% relaxation at the adductor pollicis muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009964305762
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 54
    Electronic Resource
    Electronic Resource
    Non-Steady State Monitoring by Respiratory Gas Exchange (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 351-360 
    Details
    ISSN: 1573-2614
    Keywords: carbon dioxide ; oxygen ; kinetics ; non-steady state ; cardiac output ; PEEP ; pulmonary embolism ; pulmonary gas exchange monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Traditionally, the study of CO2 and O2 kinetics in the body has been mostly confined to equilibrium conditions. However, the peri-anesthesia period and the critical care arena often involve conditions of non-steady state. The detection and explanation of CO2 kinetics during non-steady state pathophysiology have required the development of new methodologies, including the CO2 expirogram, average alveolar expired PCO2, and CO2 volume exhaled per breath. Several clinically relevant examples of non-steady state CO2 kinetics perturbations are examined, including abrupt decrease in cardiac output, application of positive end-expiratory pressure during mechanical ventilation, and occurrence of pulmonary embolism. The lesser known area of non-steady state O2 kinetics is introduced, including the measurement of pulmonary O2 uptake per breath. Future directions include the study of the respiratory quotient per breath, where the anaerobic threshold during anesthesia is identified by increasing respiratory quotient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011447500984
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 55
    Electronic Resource
    Electronic Resource
    Interpretation of Simultaneous Measurements of Hepatic Extraction Fractions of Indocyanine Green and Sorbitol (2000)
    Springer
    Digestive diseases and sciences 45 (2000), S. 359-365 
    Details
    ISSN: 1573-2568
    Keywords: functional liver blood flow ; splanchnic hemodynamics ; intrahepatic shunts ; kinetics ; kinetic models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Sorbitol and indocyanine green (ICG) have high hepatic extraction fractions (E sorb and E ICG) in normal subjects. A curved relationship has been observed between E sorb and E ICG in liver disease. According to one interpretation, the decrease of E sorb is a result of intrahepatic shunting and 1 − E sorb is the fraction of shunted flow (the shunt hypothesis). Under the further assumption that capillarization of functioning sinusoids prevents hepatic uptake of plasma protein-bound ICG and allows uptake of water-soluble sorbitol, the difference Esorb − EICG has been suggested as a measure of capillarization. We propose an alternative hypothesis: that the sinusoidal permeability–surface area products for sorbitol and ICG are reduced in proportion by liver disease (proportional reduction hypothesis). Based on the sinusoidal perfusion model, predictions were produced from both hypotheses for the relation between E sorb and E ICG and the additional effects of capillarization were described. By use of liver vein catheterization, E sorb and E ICG were simultaneously measured during continuous infusions in 53 human subjects with varying degrees of liver disease. The data were in better agreement with the predictions of the proportional reduction hypothesis than with the shunt hypothesis. Even though both intrahepatic portosystemic shunts and sinusoidal capillarization are known to occur in cirrhosis and also may have influenced our data, they appeared to be of minor importance from a kinetic point of view. These findings favor the proportional reduction hypothesis and do not support the use of systemic nonrenal clearance of sorbitol as a measure of “functional liver blood flow.”
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005476913311
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 56
    Electronic Resource
    Electronic Resource
    Removal of Sulfate, Phosphate and Colored Substances in Wastewater Effluents using Feldspar (2000)
    Springer
    Water resources management 14 (2000), S. 417-434 
    Details
    ISSN: 1573-1650
    Keywords: adsorption ; feldspar ; industrial effluent ; pollution control ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract Feldspar, among many natural substances such as termitemount-clay, saw-dust, kaolinite and dolomite, offers asignificant removal ability for sulfate, phosphate, and coloredsubstances. Optimization of experimental parameters such assolution pH and flow rate reveals, that the maximum efficiency forremoval of phosphate, sulfate, and colored substances is about42, 52, and 73% respectively. X-ray diffraction, adsorptionisotherm and recovery studies suggest, that the removal processof anions occurs via ion exchange in conjunction with surfaceadsorption. Furthermore, reaction rate studies indicate thatthe removal of the selected pollutants by feldspar follows first-order kinetics. Although the percent removal, under the optimized conditions, is higher for laboratory prepared solutions, efficiency is a little less for industrial effluentsdue to interferent effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011171330097
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 57
    Electronic Resource
    Electronic Resource
    Microbalance and Related Studies of High-temperature Superconductors (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 353-363 
    Details
    ISSN: 1572-8943
    Keywords: controlled environment ; high-T c superconductors ; kinetics ; microgravimetric investigations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Many properties of oxide superconductors depend on the oxygen concentration and its distribution in the samples. The microgravimetric method is very useful to study of oxide superconductors, as it allows investigations in vacuum and controlled environments in classical applications: thermogravimetric analysis for the study of solid-state reactions, determinations of oxygen contents in redox reactions and the combined measurement of mass and additional parameters, e.g. evolved gas analysis etc. Single-phase samples of high-temperature superconductors were synthesized from stoichiometric mixtures of high-purity oxides and carbonates. Appropriate amounts of the precursor powders were homogenized manually or by a mechanical ball mill and subsequently calcined at temperatures in the 800 to 950°C range with intermediate grinding to ensure homogenous reaction. The lattice parameters of all preparations were controlled, in both initial and final experiments, by the X-ray powder method (CuKα radiation), using a Stadi P (Stoe) diffractometer with a position-sensitive detector. It is well known that temperature and mass can be measured with an accuracy higher by orders of magnitude than it is still possible for the thermoanalyst to determine the transformation temperatures or the mass changes due to overlapping partial reactions. Applications of Cahn microbalance to study of high-temperature superconductors are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010192804471
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 58
    Electronic Resource
    Electronic Resource
    Studies on Non-isothermal Kinetics of the Thermal Decomposition of Eu2(BA)6(bipy)2 (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 747-755 
    Details
    ISSN: 1572-8943
    Keywords: benzoic acid ; europium complex ; kinetics ; non-isothermal ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of Eu2(BA)6(bipy)2 (BA=C2H5N– 2, benzoate; bipy=C10H8N2, 2,2'-bipyridine)and its kinetics were studied under the non-isothermal condition by TG-DTG, IR and SEM methods. The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method, the Madhusudanan-Krishnan-Ninan (MKN) method, the Ozawa method and the Kissinger method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as: dα/dt=Aexp(–E/RT)3(1–α)2/3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026785727479
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 59
    Electronic Resource
    Electronic Resource
    Dsc Evaluations in F.c.c. Solid Solutions of Short-range-order Kinetics As Influenced by Bound Vacancies (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 397-413 
    Details
    ISSN: 1572-8943
    Keywords: Cu–5 at%Zn ; DSC ; F.C.C. (Face Centered Cubic) ; kinetics ; short-range-order ; solute-vacancy complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A modified first order kinetic law, which describes the roles of bound and unbound vacancies, is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. The model has been applied to differential scanning calorimetry (DSC) curves of Cu–5 at%Zn quenched from different temperatures. Activation energy for migration of solute-vacancy complexes was also assessed from the kinetics of short-range-order using DSC traces. A value of 89.5±0.32 kJ mol–1 was obtained. The relative contribution of bound and unbound vacancies to the ordering process as influenced by quenching temperature was determined. In conjunction, a parametric study of the initial total defect concentration and effective energy for defect migration was performed in order to envisage their influence on the calculated DSC profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010140409219
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 60
    Electronic Resource
    Electronic Resource
    Influence of DSC Measurement Conditions on Kinetic Parameters of Thermal Decomposition of 2,4,6-trinitrotoluene (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 25-33 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; kinetics ; thermal decomposition ; 2,4,6-trinitrotoluene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An autocatalytic model involving the limited solubility of volatile catalytic products was applied to the thermal decomposition of 2,4,6-trinitrotoluene. The critical supersaturation of the thermal decomposition products with the catalytic properties was higher at a low heating rate. Decrease of the sample mass led to an increased critical supersaturation of the decomposition products. This is probably a result of the greater contribution of products adsorption on the aluminium pan surface. It is presumed that the differences observed in the rate constant are connected with the uncontrolled critical supersaturation of the volatile thermal decomposition products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010108115336
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 61
    Electronic Resource
    Electronic Resource
    Positronium Spin-Conversion Reactions Promoted by 3d Complexes in Highand Low-Spin States (2000)
    Springer
    Structural chemistry 11 (2000), S. 341-346 
    Details
    ISSN: 1572-9001
    Keywords: Positronium chemistry ; kinetics ; spin-exchange reactions ; high- and low-spin 3d complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Continuing in our work on the correlations between the rate constants, k CR, of the ortho into para-positronium conversion reactions, CR, promoted by complexes of various 3d ions and the metal electron delocalization β caused by the ligands, the relationship between the parameters of the correlation lines pertinent to highand low-spin complexes of CrII, MnII, and CoII ions was ascertained. Moreover, it was experimentally verified, for the first time, that the statistical probability of the CR promoted by paramagnetic compounds with S = 1/2 is three times larger than that of the CR caused by compounds with S 〉 1/2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026513904160
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 62
    Electronic Resource
    Electronic Resource
    Efficiency of the muon catalyzed fusion in triple H/D/T mixtures (2000)
    Springer
    Hyperfine interactions 128 (2000), S. 481-493 
    Details
    ISSN: 1572-9540
    Keywords: muon catalyzed fusion ; triple mixture ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, we solve numerically kinetic equations for the chain reactions of μCF in triple H/D/T mixture. Regarding the computational results, we show that μCF efficiency decreases by adding hydrogen H to D/T mixture. This is in contradiction to the usual belief which expects the increase of μCF efficiency in H/D/T mixture. Our results are confirmed by the first and recent experiment on μdt cycling rate in the triple mixture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1012676825377
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 63
    Electronic Resource
    Electronic Resource
    Kinetics of Acetic Acid Esterification with 2-Methoxyethanol Over a Pillared Clay Catalyst (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 169-176 
    Details
    ISSN: 1588-2837
    Keywords: Al3+-exchanged pillared clay catalyst ; 2-methoxyethanol ; esterification ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pillared clay catalyst, which was obtained by exposing activated clay powder to sulfuric acid and aluminium salts and calcining in air at 373 – 673 K, was found to be highly active for the title reaction. The activity is mainly attributed to the Lewis acid sites and also to a small number of Brönsted acid sites, whose number and strength increases with the extent of pillaring. The kinetic equation of surface esterification is y = 2.57x - 1.47.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005625800341
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 64
    Electronic Resource
    Electronic Resource
    The Kinetics of Tenoxicam Photodegradation in Solution (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 119-124 
    Details
    ISSN: 1588-2837
    Keywords: Tenoxicam ; photodegradation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Photodegradation of tenoxicam was investigated under different reaction conditions. After 60 min of exposure to UV light, the photodegradation was extensive, and the maximum and minimum in the UV-visible spectrum were shifted to shorter and longer wavelengths, respectively. Ethanol exerted a photostabilizing effect on tenoxicam. Tenoxicam is more stable in acidic and basic media than in neutral solution. Increasing light intensity or temperature causes an increase in the rate of photodegradation. The photodegradation of tenoxicam was found to follow first-order kinetics under all these conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010370901272
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 65
    Electronic Resource
    Electronic Resource
    Kinetics of the N-Monoalkylation of Aniline with Methanol Over Zn1−XCoXFe2O4 (X = 0, 0.2, 0.5, 0.8 and 1.0)-Type Systems (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Keywords: Ferrites ; aniline alkylation ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Kinetic parameters such as the activation energy (Ea) and Arrhenius frequency factor (A) for the N-methylation of aniline using methanol over Zn-Co ferrites have been calculated. The Ea value is found to be lower than the existing best alkylating systems such as γ-alumina and magnesium oxide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010387304906
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 66
    Electronic Resource
    Electronic Resource
    Kinetics and Mechanism of the Oxidative Regeneration of Carbonyl Compounds from Oximes by Pyridinium Fluorochromate (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 343-347 
    Details
    ISSN: 1588-2837
    Keywords: Deoximination ; chromium (VI) ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oxidative deoximination of aldoximes and ketoximes by pyridium fluorochromate proceeds by nucleophilic attack of the chromate oxygen on the oxime carbon to give a cyclic intermediate in the rate-determining step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010391529810
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 67
    Electronic Resource
    Electronic Resource
    Homogeneous Catalysis of C-H Bond Activation by a Novel Ruthenium(III)-Complex (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 147-151 
    Details
    ISSN: 1588-2837
    Keywords: Oxo-functionalization ; [RuIII(amp)(pic)(H2O)] ; t-BuOOH ; kinetics ; cyclohexane cyclohexene ; toluene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel mixed-ligand [RuIII(amp)(pic)(H2O)] complex (1) (H2amp = N-(hydroxyphenyl)salicyldimine; pic = picolinate) has been synthesized and characterized by physico-chemical methods. Complex 1has been found to be an effective catalyst in oxo-functionalization of C-H bond of organic substrates by using tert-butyl hydroperoxide (t-BuOOH) as a terminal oxidant. Formation of a high valent Ru(V)-oxo species as catalytic intermediate is proposed to be the source of oxygen atom in the oxidised product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010331219928
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 68
    Electronic Resource
    Electronic Resource
    Study of the Ligand Substitution Reaction [Fe(CN)5(4-tbupy)]3- + Pyrazine in Concentrated Aqueous Electrolyte Solutions: Estimation of the Activation Volume (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 389-394 
    Details
    ISSN: 1588-2837
    Keywords: Fe(CN)5(4-tbupy)3- ; kinetics ; electrolytes ; substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The ligand substitution reaction [Fe(CN)5(4-tbupy)]3- + pyrazine (4-tbupy=4-tertbutylpyridine) was studied in aqueous concentrated electrolyte solutions at 298 K. Plots of ln(k/kw) against (γ-γw), where the subscript w refers to pure water and γ is the surface tension of the appropriate salt solution, gave a common straight line for all the electrolytes studied and permits to estimate the activation volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010373823987
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 69
    Electronic Resource
    Electronic Resource
    Kinetics of Coke Formation for the Reactions of Light Olefins Ethene, Propene and 1-Butene Over Ushy Zeolite (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 39-46 
    Details
    ISSN: 1588-2837
    Keywords: Coke formation ; kinetics ; USHY zeolites ; ethene ; propene ; 1-butene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A simplified three-parameter model for the interpretation of the kinetic data of coke formation during transformation of light olefins is presented. This model has been applied to the transformation of ethene, propene and 1-butene over fresh and regenerated zeolite USHY at 623 K. The proposed model covers both the coverage of the acid sites and the autocatalytic growth of coke.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005684524023
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 70
    Electronic Resource
    Electronic Resource
    Regioselective Dichlorocyclopropanation of 4-Vinyl-1-Cyclohexene Using the New Diquat, DQ-Br, under Controlled Phase Transfer Catalysis Conditions (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 161-167 
    Details
    ISSN: 1588-2837
    Keywords: Dichlorocyclopropanation ; 4-vinyl-1-cyclohexene ; phase transfer catalysis ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of regioselective dichlorocyclopropanation of 4-vinyl-1-cyclohexene has been studied under controlled phase transfer catalysis conditions, using aqueous sodium hydroxide as the base and 2-benzylidine-N,N,N,N′,N′,N′-hexaethylpropane-1,3-diammonium dibromide (Dq-Br) as a new phase transfer reagent. The reaction was carried out at 40 °C under pseudo-first order conditions by employing aqueous sodium hydroxide and chloroform in excess and was monitored by gas chromatography. The effect of various experimental parameters on the rate of the reaction has been studied and based on the experimental results, a suitable mechanism is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005673716271
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 71
    Electronic Resource
    Electronic Resource
    Kinetics of Oxidation of Phosphinic, Phenylphosphinic and Phosphorous Acid by Benzyltrimethylammonium Chlorobromate (2000)
    Springer
    Reaction kinetics and catalysis letters 69 (2000), S. 247-252 
    Details
    ISSN: 1588-2837
    Keywords: Phosphorous acid ; oxidation ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The oxidation of lower phosphorus oxyacids by benzyltrimethylammonium chlorobromate (BTMACB) proceeds by a mechanism involving a hydride-ion transfer from oxyacids to the oxidant in the rate-determining step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005635529900
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 72
    Electronic Resource
    Electronic Resource
    Low-Temperature Catalytic Oxidation of Sulfide Ions in Aqueous Solutions on a Ni-Oxide System (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 139-145 
    Details
    ISSN: 1588-2837
    Keywords: Oxidation of sulfides ; kinetics ; Ni-oxide system ; reaction mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Catalytic oxidation of sulfide ions in aqueous solutions by air oxygen has been investigated using a Ni-oxide system as a catalyst. The kinetics and the selectivity of the oxidation process were studied by varying the pH, catalyst amount and reaction temperature. A reduction/oxidation mechanism of the reaction has been supposed comprising interaction between the surface active oxygen of the catalyst and HS− and reoxidizing of the reduced catalyst by the dissolved oxygen. The results obtained show that the Ni-oxide system is a promising catalyst for practical application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010379103089
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 73
    Electronic Resource
    Electronic Resource
    Coupling of Methanol and Isobutanol to Ethers over γ-Alumina Catalyst. Kinetic Studies (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 235-241 
    Details
    ISSN: 1588-2837
    Keywords: Methanol ; isobutanol ; ethers ; γ-Al2O3 ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic of methanol (MeOH) and isobutanol (iBuOH) coupling to ethers has been studied. Catalytic tests were carried out in the gas phase in a fixed-bed flow microreactor, in the temperature range of 463-533 K, under atmospheric pressure, using γ-Al2O3 as the catalyst. The quasi-homogeneous model for the process was assumed. The reaction rates were described by simple kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010320312175
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 74
    Electronic Resource
    Electronic Resource
    Rate Constant for the Reaction of the OH-Radical with CH2F2 (2000)
    Springer
    Reaction kinetics and catalysis letters 70 (2000), S. 319-324 
    Details
    ISSN: 1588-2837
    Keywords: Atmospheric chemistry ; kinetics ; OH-radical ; CH2F2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The rate constant value of k 1 = (6.05 ± 0.20)×109 cm3 mol−1 s−1 (with ± 1σ error) has been determined for the reaction OH + CH2F2 (1) by applying the discharge-flow/resonance-fluorescence method at 298 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010349118536
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 75
    Electronic Resource
    Electronic Resource
    Kinetics and Stereoselectivity in Gas-Phase Hydrogenation of Alkylbenzenes Over Ni/Al2O3 (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 47-54 
    Details
    ISSN: 1588-2837
    Keywords: Alkylbenzenes ; hydrogenation ; nickel ; kinetics ; stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Experimental data on gas-phase hydrogenation of several alkylbenzenes (toluene, ethlylbenzene, o-, m-, p-xylenes, mesitylene) over nickel catalyst are summarized. Rate dependence as a function of the chemical nature of substituent and position in the aromatic ring is discussed. The stereochemical distribution for dialkylbenzene and trialkylbenzene is addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010321830186
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 76
    Electronic Resource
    Electronic Resource
    Determination of Equilibrium Dispersion of Pt on Al2O3 Support in Sintering Process (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 295-300 
    Details
    ISSN: 1588-2837
    Keywords: Sintering ; kinetics ; Pt/Al2O3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The variation of dispersion of Pt on Al2O3 support with sintering time is measured and the value of equilibrium dispersion of Pt is obtained directly. It is found that a General Power Law Expression can fit the experimental data well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010327210246
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 77
    Electronic Resource
    Electronic Resource
    A weighing method to identify the microbial growth phases in solid-state fermentation tests (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 601-605 
    Details
    ISSN: 1573-0972
    Keywords: Growth phases identification ; kinetics ; Rhizopus oryzae ; solid-state fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A general equation correlating the variation rate of the fermenting medium weight (dry matter) and the cell biomass growth rate in solid-state fermentation tests is proposed with the main purpose of identifying the microbial growth phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008970720794
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 78
    Electronic Resource
    Electronic Resource
    Electrochemical and Adsorption Studies on the Formation of Poly-8-Hydroxyquinaldine Thin Films at Glassy Carbon/Electrolyte Interface (2000)
    Springer
    Interface science 8 (2000), S. 111-121 
    Details
    ISSN: 1573-2746
    Keywords: 8-hydroxyquinaldine ; electropolymerization ; adsorption ; glassy carbon ; 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 , Physics
    Notes: Abstract The kinetics and thermodynamics of the electropolymerization of the chelating agent 8-hydroxyquinaldine on GCE's (Glassy Carbon Electrodes') surface from aqueous phosphate buffers are reported. Thermodynamic functions related to the adsorption of the monomer on the GCE's surfaces were determinated. No contribution from GCE surface's functional group to the electropolymerization reactions was reported. The effects of monomer concentration, pH, and temperature on the electrochemical growth of poly 8-hydroxyquinaldine were investigated. The results suggest that the propagation of the electropolymerization process takes place via a free radical chain reactions. Furthermore, the results indicate that the electrochemical growth of the polymeric films is dictated by pre-polymerization adsorption on the electrode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008799724511
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 79
    Electronic Resource
    Electronic Resource
    Kinetic investigation of the alkylation of salts of 2,5-dimercapto-1,3,4-thiadiazole (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 857-861 
    Details
    ISSN: 1573-8353
    Keywords: salts of 2,5-dimercapto-1,3,4-thiadiazole ; alkylation ; kinetics ; electronic absorption spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A kinetic investigation has been carried out, using electronic absorption spectra, of the alkylation with benzyl chloride of the dihydrazine, monohydrazine, and the disodium salts of 2,5-dimercapto-1,3,4-thiadiazole, and also of the hydrazine and sodium salts of 5-benzylthio-2-mercapto-1,3,4-thiadiazole. The rates orders and constants were established for the benzylation reaction and it was noted that the reaction rate depends on the cation of these salts and the degree of substitution of the 2,5-dimercapto-1,3,4-thiadiazole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02256923
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 80
    Electronic Resource
    Electronic Resource
    Plasma adrenaline kinetics in Type 1 (insulin-dependent) diabetic patients with and without autonomie neuropathy (1989)
    Springer
    Diabetologia 32 (1989), S. 810-813 
    Details
    ISSN: 1432-0428
    Keywords: Adrenaline ; autonomic neuropathy ; catecholamine ; kinetics ; Type 1 (insulin-dependent) diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Plasma adrenaline kinetics (clearance, extraction across the forearm, initial plasma disappearance rate, mean sojourn time, volume of distribution) were studied in sixteen Type 1 (insulin-dependent) diabetic patients during constant i.v. infusion of tritium labelled adrenaline. In patients with (n=8) and without (n=8) neuropathy forearm venous plasma noradrenaline and adrenaline concentrations as well as plasma clearance of adrenaline based on arterial sampling (1.7 vs 2.1 l/min) were not significantly different. The initial disappearance time (T1/2) after the infusion of the tritium labelled adrenaline had been stopped was significantly prolonged in Type 1 diabetic patients with neuropathy compared to those without (after 20 min infusion 2.7 vs 2.2 min, p〈0.02, after 75 min infusion 3.7 vs 2.9 min, p〈0.05). The corresponding values for the mean sojourn time of adrenaline in plasma were 6.5 vs 4.7 min (p〈0.05) after 20 min infusion and 18 vs 10 min (p〈0.05) after 75 min of infusion. The unchanged plasma clearance and the prolonged initial halftime and mean sojourn time of adrenaline in plasma suggest that adrenaline is distributed in a larger volume in Type 1 diabetic patients with neuropathy as compared to patients without neuropathy (estimated space of distribution 29 vs 201). Our results suggest that patients with diabetic neuropathy do not adjust the plasma adrenaline concentration to changes in adrenaline infusion rate as rapidly as those without neuropathy, i. e. the effect of an elevated adrenaline secretion rate may be prolonged in patients with diabetic autonomic neuropathy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264912
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 81
    Electronic Resource
    Electronic Resource
    Sodium channel opening as a precursor to inactivation (1989)
    Springer
    European biophysics journal 16 (1989), S. 321-325 
    Details
    ISSN: 1432-1017
    Keywords: Sodium currents ; inactivation ; kinetics ; channel gating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The time constant of the process producing the delay in Na inactivation development as determined by the two pulse method (τdelay) was extracted and compared to that of the slowest Na activation process τ3 for the I Na during the conditioning pulse of that same determination. τdelay and two pulse inactivation τc values were computer generated using a nonlinear least squares algorithm. τh and single pulse inactivation τh values were independently generated for each determination also with the aid of the computer using the same non-linear least squares algorithm. In one determination at 2 mV, τc was 4.68 and τdelay 0.494 ms while τh was 4.70 and τ3 0.491 ms for a τc/τh of 0.996 and a τdelay/τ3 of 1.006. Mean τdelay/τ3 from five determinations in four axons, both Cs and K perfused, and spanning a potential range of-27 to 2mV was 1.068. The precursor process to inactivation is channel opening. Some fraction of channels presumably inactivate via another route where prior channel opening is not required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257880
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 82
    Electronic Resource
    Electronic Resource
    Kinetics and thermodynamic transitions of N-acetyl-β-D-glucosaminidase A and B in free and bound forms: Role of cellulose ion-exchangers (1989)
    Springer
    Molecular and cellular biochemistry 86 (1989), S. 65-70 
    Details
    ISSN: 1573-4919
    Keywords: Hex A ; Hex B ; N-acetyl-glucosaminidases ; kinetics ; thermodynamic transitions ; ion-exchangers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetic and thermodynamic properties of N-acetyl-β-D-glucosaminidase A (Hex A) and N-acetyl-β-D-D-glucosaminidase β (Hex B) from goat testes were investigated in free and bound (after binding them on ion-exchangers such as DEAE- or CM-cellulose respectively) forms. The optimum pH of free Hex A and Hex B was at 4.2 and 5.4, whereas the bound forms showed the optimum pH at 4.0 and 5.2 respectively. While apparent Km of free and bound Hex A (0.8 and 1.0 mM respectively) did not differ, the Km of Hex B increased when bound on CM-cellulose (Km of free Hex B = 0.96 mM versus bound Hex B = 1.6 mM). Though the free Hex A was more thermo-labile than the free Hex B, both isozymes, on insoluble matrices decayed at faster rates on heating. Activation analysis revealed that the energy of activation (E infa supo ) for transition state of free Hex B (81 Kcal deg−1 mole−1) did not differ from E infa supo of bound Hex B. On the other hand, E infa supo of free Hex A declined from 77.2 to 71.1 Kcal deg−1 mole−1 when heat transitions were carried out in free and bound state respectively. Thermodynamic analysis suggested a change in entropy of activation (ΔS*) of free Hex A and Hex B as 200 and 211 eu respectively. While ΔS* of Hex B did not change after heat transitions, ΔS* of Hex A was 182.5 eu.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231690
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 83
    Electronic Resource
    Electronic Resource
    The regulatory kinetic properties of porcine hepatic glucokinase (1989)
    Springer
    Molecular and cellular biochemistry 86 (1989), S. 171-179 
    Details
    ISSN: 1573-4919
    Keywords: porcine glucokinase ; purification ; kinetics ; sulfhydryl-related states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Porcine hepatic glucokinase (ATP: D-hexose 6-phosphotransferase EC 2.7.1.1) has been purified by a modification of the procedure for its purification from rats. However, difficulties were encountered with endogenous proteases and the reliability of a source for porcine livers. The molecular weight has been determined to be 60 400 ± 1400 by sodium dodecyl sulfate, polyacrylamide gel electrophoresis. The enzyme has been characterized kinetically. The parameter values, S 0.5 (glucose) and Hill coefficient (nH) are 2.4 mM and 1.9 respectively under sulfhydryl-reducing conditions. The enzyme undergoes the two sulfhydryl-related decays of its activity previously observed in the enzyme isolated from rat (Tippett PS, Neet KE: Arch Biochem Biophys 222:285–298, 1983). The enzyme is inhibited by palmitoyl-CoA, K i (apparent) = 1.0 µM, nH = 1.8; this concentration of inhibitor is significantly below its critical micelle concentration. Physically and kinetically glucokinase isolated from pig is similar to the enzyme isolated from rat. The porcine system provides a second source for isolation and further characterization of this important and unusual enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222617
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 84
    Electronic Resource
    Electronic Resource
    Molten carbonate-induced hot corrosion of nickel (1989)
    Springer
    Oxidation of metals 32 (1989), S. 225-240 
    Details
    ISSN: 1573-4889
    Keywords: Hot corrosion ; nickel ; TGA ; kinetics ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The accelerated oxidation of pure nickel in the presence of a molten carbonate mixture has been studied in O2 and CO2-containing atmospheres. The oxidation rate of nickel with carbonate coatings was at least four orders of magnitude faster than that without salt coatings. The extent of oxidation, in terms of unit area weight gain, depended on both the amount of carbonate mixture coatings and the gas atmosphere. The unit area weight gain due to oxidation increased with increasing amounts of salt coatings up to a certain value. These observations suggest that the termination of nickel oxidation results from the exhaustion of either the salt coatings or metallic nickel. Porous and particulate oxide products were observed from scanning electron microscopic (SEM) examinations. The energy-dispersive analysis of x-rays (EDAX) shows that no salt remains on the specimen surface after the oxidation experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664800
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 85
    Electronic Resource
    Electronic Resource
    Effect of acidicpH on the protein carmin from safflower seed (Carthamus tinctorius) (1989)
    Springer
    The protein journal 8 (1989), S. 529-548 
    Details
    ISSN: 1573-4943
    Keywords: carmin ; association-dissociation ; denaturation ; reaggregation ; kinetics ; reversibility ; hydrophobic interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of a decrease inpH on the structural integrity of carmin has been monitored by a variety of biophysical techniques. The protein undergoes initial dissociation up topH 3.5–4.0 without any significant denaturation. Below thispH the process of dissociation and denaturation appears to be simultaneous. Further, in thepH range of 2.5–1.6 the protein reassociates to probably a different polymer resulting from possibly, an entropically driven hydrophobic interaction. The process of dissociation appears to be reversible to a large extent. The process of denaturation appears to be governed by the kinetic path that the denatured protein molecule follows either by a sudden decrease inpH or through a gradual decrease inpH. These results are interpreted while keeping in view the oligomeric and globular structure of carmin at neutralpH. The results would help in understanding of structure-function relationship of the protein and its role in hydrogen ion bindingin vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026437
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 86
    Electronic Resource
    Electronic Resource
    Characterization of sodium and pyruvate interactions of the two carrier systems specific of mono- and di- or tricarboxylic acids by renal brush-border membrane vesicles (1989)
    Springer
    The journal of membrane biology 108 (1989), S. 197-205 
    Details
    ISSN: 1432-1424
    Keywords: sodium ; pyruvate ; transport ; proximal tubule ; kinetics ; kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The experiments reported in this paper aim at characterizing the carboxylic acid transport, the interactions of pyruvate and citrate with their transport sites and specificity. The study of these carriers was performed using isotopic solutes for the influx measurements in brush-border membrane vesicles under zerotrans conditions where the membrane potential was abolished with KCl preloading with valinomycin or equilibrium exchange conditions and Δψ=0. Under zerotrans condition and Δψ=0, the influence of pyruvate concentrations on its initial rates of transport revealed the existence of two families of pyruvate transport sites, one with a high affinity for pyruvate (K t =88 μm) and a low affinity for sodium (K t =57.7mm) (site I), the second one with a low affinity for pyruvate (K t =6.1mm) and a high affinity for sodium (K t =23.9mm) (site II). The coupling factor [Na]/[pyruvate] stoichiometry were determined at 0.25mm and 8mm pyruvate and estimated at 1.8 for site I, and 3 when the first and the second sites transport simultaneously. Under chemical equilibrium (Δψ≅0) single isotopic labeling, transport kinetics of pyruvate carrier systems have shown a double interaction of pyruvate with the transporter; the sodium/pyruvate stoichiometry also expressed according to a Hill plot representation wasn=1.7. The direct method of measuring Na+/pyruvate stoichiometry from double labeling kinetics and isotopic exchange, for a time course, gives an=1.67. Studies of transport specificity, indicate that the absence of inhibition of lactate transport by citrate and the existence of competitive inhibition of lactate and citrate transports by pyruvate leads to the conclusion that the low pyruvate affinity site can be attributed to the citrate carrier (tricarboxylate) and the high pyruvate affinity site to the lactate carrier (monocarboxylate).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871734
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 87
    Electronic Resource
    Electronic Resource
    Kinetic response of H+-coupled transport to extracellular pH: Critical role of cytosolic pH as a regulator (1989)
    Springer
    The journal of membrane biology 108 (1989), S. 253-261 
    Details
    ISSN: 1432-1424
    Keywords: Chara ; Cl− ; cotransport ; reaction kinetic model ; pH ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary H+-coupled transport in plant and fungal cells is relatively insensitive to external pH (pH o ). H+-coupled Cl− transport at the plasma membrane ofChara corallina was studied to explore the phenomena responsible for this insensitivity. Raising pH o from a control value of 7.5 to 9.0 results in a modest (2.5-fold) decline inJ max and increase inK m . Further increase in pH o results in a selective increase inJ max, in accordance with predictions from a reaction kinetic model of the transport system (Sanders, D., Hansen, U.-P., 1981.J. Membrane Biol. 58:139–153). Increase in cytosolic Cl− concentration ([Cl−] c ) also results in a selective decrease inJ max at pH o =7.5. Quantitative kinetic modeling of the results is not possible if it is assumed that the sole effect of pH o isvia mass action on the binding of external H+ to a transport site. If, instead, the dependence of cytosolic pH (pH c ) on pH o (Smith, F.A., 1984,J. Exp. Bot. 35:1525–1536) is taken into account along with the dependence of Cl− influx on pH c (Sanders, D., 1980,J. Membrane Biol. 53:129–141), then the observed modest changes in Michaelis parameters can be accommodated by a reaction kinetic model. The quantitative parameters of the model yield respective pK a s of the internal and external H+-binding sites=7.85 and 7.2, respective dissociation constants of the internal and external Cl−-binding sites=160 and 40 μm, and an additional, kinetically transparent, H+-binding site with a pK a 〉8.0. The quantitative model independently predicts the response ofJ max andK m to acidic conditions. The results are discussed in terms of the general physiological requirement that fluxes through H+-coupled transport systems are relatively insensitive to environmental variation in pH o . It is proposed that (i) the weak (but finite) dependence of pH c on pH o , coupled with (ii) the strong dependence of H+-coupled transport on pH c are instrumental in endowing H+-coupled transport systems with a relative insensitivity to variation in pH o . This hypothesis might also explain why pH c in plants and fungi is not acutely controlled with respect to variation of pH o .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871740
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 88
    Electronic Resource
    Electronic Resource
    Pre-steady-state analysis of the turn-on and turn-off of water permeability in the kidney collecting tubule (1989)
    Springer
    The journal of membrane biology 110 (1989), S. 57-65 
    Details
    ISSN: 1432-1424
    Keywords: fluorescence ; water transport ; vasopressin ; kidney collecting tubule ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Water transport across the mammalian collecting tubule is regulated by vasopressin-dependent water channel insertion into and retrieval from the cell apical membrane. The time course of osmotic water permeability (P f ) following addition and removal of vasopressin (VP) and 8-Br-cAMP was measured continuously by quantitative fluorescence microscopy using an impermeant fluorophore perfused in the lumen. Cortical collecting tubules were subjected to a 120 mOsm bath-to-lumen osmotic gradient at 37°C with 10–15 nl/min lumen perfusion and 10–20 ml/min bath exchange rate. With addition of VP (250 μU/ml), there was a 23±3 sec (sem,n=16) lag in whichP f did not change, followed by a rise inP f (initial rate 1.4±0.2×10−4 cm/sec2) to a maximum of 265±10×10−4 cm/sec. With addition of 8-Br-cAMP (0.01–1mm) there was an 11±2 sec lag. For [8-Br-cAMP]=0.01, 0.1 and 1mm, the initial rate ofP f increase following the lag was (units 10−4 cm/sec2): 1.1±0.1, 1.2±0.1 and 1.7±0.3. MaximumP f was (units 10−4 cm/sec): 64±4, 199±9 and 285±11. With removal of VP,P f decreased to baseline (12×10−4 cm/sec) with aT 1/2 of 18 min; removal of 0.1 and 1mm 8-Br-cAMP gaveT 1/2 of 4 and 8.5 min. These results demonstrate (i) a brief lag in theP f response, longer for stimulation by VP than by 8-Br-cAMP, representing the transient build-up of biochemical intermediates proximal to the water channel insertion step, (ii) similar initialdP f /dt (water channel insertion) over a wide range of [8-Br-cAMP] and steady-stateP f values, and (iii) more rapidP f decrease with removal of 8-Br-cAMP than with VP. These pre-steady-state results define the detailed kinetics of the turn-on and turn-off of tubuleP f and provide kinetic evidence that the rate-limiting step for turn-on ofP f is not the step at which VP regulates steady-stateP f . If water channel insertion is assumed to be the rate-limiting step in the turn-on ofP f , these results raise the possibility that water channels must be activated following insertion into the apical membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870993
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 89
    Electronic Resource
    Electronic Resource
    Analysis of the blocking activity of charybdotoxin homologs and iodinated derivatives against Ca2+-Activated K+ channels (1989)
    Springer
    The journal of membrane biology 109 (1989), S. 269-281 
    Details
    ISSN: 1432-1424
    Keywords: charybdotoxin ; erythrocytes ; iodination ; kinetics ; peptides ; potassium channels ; scorpions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Two charybdotoxin peptides were purified from venom of the Israeli scorpion,Leiurus quinquestriatus hebraeus. Microsequencing of the most abundant toxin, ChTX-Lq1, revealed identity with the 37-residue peptide previously sequenced by Gimenez-Gallego et al. [Gimenez-Gallego, G., et al.,Proc. Natl. Acad. Sci. USA 85:3329–3333 (1988)]. Sequence data on the minor peptide, ChTX-Lq2, showed substantial homology to ChTX-Lq1 with differences observed at eight positions. These two charybdotoxin sequences, along with that of noxiustoxin, define a distinct family of scorpion peptide toxins with activity against K+ channels. Both charybdotoxin homologs inhibited Ca2+-dependent K+ efflux from human erythrocytes with similar potency,K 0.5∼-40nm. In planar bilayer assays of single K(Ca) channels from rat muscle, ChTX-Lq1 and ChTX-Lq2 blocked with intrinsicK d's of 1.3 and 43nm, respectively, in the presence of 50mm external KCl. A new application of dwell-time histogram analysis of single-channel blocking events was used to characterize the kinetic homogeneity of toxin samples and the blocking kinetics of ChTX derivatives. The lower blocking affinity of ChTX-Lq2 was the combined result of a faster dissociation rate and a slower association rate as compared to ChTX-Lq1. The blocking activity of two mono-iodinated derivatives of ChTX-Lq1 was also analyzed. Blocked dwell-time histograms of the iodinated peptides were characterized by predominately brief (0.2–2 sec) blocking events in comparison to the native toxin (20 sec). Histogram analysis revealed that mono-iodination of ChTX-Lq1 impairs blocking activity by adverse effects on both dissociation and association rate constants. Frequency density histograms of single channel blocking events provide a sensitive assay of toxin purity suitable for quantitating structure-activity relationships of charybdotoxin derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870284
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 90
    Electronic Resource
    Electronic Resource
    Folinic acid modulation of fluorouracil: tissue kinetics of bolus administration (1989)
    Springer
    Investigational new drugs 7 (1989), S. 27-36 
    Details
    ISSN: 1573-0646
    Keywords: kinetics ; fluorouracil ; bolics ; administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Thymidylate synthase (TS) is the enzyme target of 5-fluorouracil (FUra) that recent laboratory and clinical studies with folinic acid (calcium leucovorin) suggest may mediate important antitumor cytotoxicity. Measurement in carcinoma tissue of parameters related to TS inhibition by 5-fluorodeoxyuridylate (FdUMP), by analogy to hormone receptor analysis, should be useful to determine which patients should receive fluoropyrimidine drug therapy and to evaluate folinic acid requirements. Folinic acid is metabolized to 5,10-methylenetetrahydropteroylglutamine (CH2FH4), which must be present in large excess to effect desired levels of maximal inhibition of TS, by promoting formation and stabilization of TS-FdUMP-CH2FH4 ternary complexes. In patients with metastatic disease, serial biopsies of tumor and normal tissues for studies of pharmacodynamic responses to test-dose FUra or folinic acid are shown to be easily added to routine intraoperative management. A suitable methodologic approach is described and examples given of assays of free TS, FdUMP, dUMP, and CH2FH4 levels after FUra or folinic acid, that may be useful in future studies aimed at improving the cost-effectiveness of FUra-folinic acid combinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178189
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 91
    Electronic Resource
    Electronic Resource
    Heterogeneous survival and cell kinetics responses of human astrocytoma clones to α-difluoromethylornithine in vitro (1989)
    Springer
    Investigational new drugs 7 (1989), S. 155-161 
    Details
    ISSN: 1573-0646
    Keywords: heterogeneity ; polyamines ; cell killing ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of α-difluoromethylornithine (DFMO) on survival, cell kinetics and polyamine levels were studied on two clones of human astrocytoma in vitro. The survival responses were dose and time dependent; and treatments with DFMO which lasted for 72 h resulted in heterogeneous responses with one clone being up to 6 times more sensitive than the other. Shorter treatments produced more uniform killing in the clones. A continuous exposure of the cells to 5 mM DFMO resulted in a rapid decrease in putrescine values in both clones, followed by decreases in the spermidine levels. These effects were closely followed by 148% to 170% increases in cell population doubling times, and a lowering of saturation densities. No clear correlations could be established among baseline polyamine levels and cell kinetics or survival responses to DFMO treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170852
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 92
    Electronic Resource
    Electronic Resource
    The population pharmacokinetics of theophylline in neonates and young infants (1989)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 17 (1989), S. 47-66 
    Details
    ISSN: 1573-8744
    Keywords: theophyliine ; population analysis ; methylxanthines ; neonatal apnea ; kinetics ; NONMEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The population pharmacokinetics of theophylline were evaluated using 391 theophylline serum concentration measurements from 108 neonates and young infants (postnatal age 0–26 weeks), who received theophylline for the treatment of neonatal apnea. A one-compartment pharmacokinetic model with first-order elimination was used, with intravenous aminophylline and oral theophylline administration modeled as zero-order infusions. The effect of a variety of developmental and demographic factors on clearance (CL) and volume (V) were investigated. Hypothesis testing to evaluate potentially significant factors produced a final model in which clearance was based on weight (kg) raised to an exponential power and postnatal age (weeks), with CL (ml/hr)=17.5 (weight)1.28 + 1.17 (postnatal age). Clearance was reduced by 12% for patients receiving parenteral nutrition. Volume of distribution in this population was adequately described using only weight, with V (L)=0.858 L/kg. Bioavailability of orally administered drug was not significantly less than unity. Interindividual variability in clearance was modest, with a coefficient of variation for clearance of 16%. An estimate of interindividual variability in volume could not be obtained. As a measure of residual variability in theophylline serum concentrations, the coefficients of variation for theophylline serum concentrations of 5.0, 10.0, and 13.0 mg/L were found to be approximately, 25, 12, and 9%, respectively. The identification of influential patient factors and the quantification of their influence on theophylline disposition allow for a priori estimates of theophylline pharmacokinetic parameters in these patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059087
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 93
    Electronic Resource
    Electronic Resource
    The influence of Trypanosoma congolense infection on the disposition kinetics of diminazene aceturate in the dog (1989)
    Springer
    Veterinary research communications 13 (1989), S. 231-236 
    Details
    ISSN: 1573-7446
    Keywords: diminazene aceturate ; dog ; kinetics ; Trypanosoma congolense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Diminazene aceturate was administered intravenously at 3.5 mg/kg body weight to mongrel dogs before and after infection with Trypanosoma congolense. Plasma and urine were collected at varying intervals thereafter and analysed for the compound. The mean are under the concentration-time curve (AUC) of diminazene in healthy dogs was 25.8 h.μg/ml but was significantly increased (p〈0.05) to 35.7 h.μg/ml after infection with T. congolense. The distribution half-life was significantly reduced (p〈0.05) in dogs after infection, being 0.12 h compared to 0.17 h in the same dogs before infection. The mean proportion of the diminazene recovered in the urine of infected dogs (25.1%) was not significantly different from that recovered in the urine of healthy dogs (26.8%). These results indicate that infection with T. congolense increases the rate at which diminazene is distributed in the body but that the infection has no marked influence on the urinary excretion of the drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00142049
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 94
    Electronic Resource
    Electronic Resource
    On Tanaka-Fillmore's kinetics swelling of gels (1989)
    Springer
    Colloid & polymer science 267 (1989), S. 179-183 
    Details
    ISSN: 1435-1536
    Keywords: Gel ; swelling ; kinetics ; diffusion
    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 Tanaka and Fillmore treated the swelling of a gel as a process where a crosslinked polymer network having been initially under uniform stress is expanded by osmotic pressure, sucking up the surrounding fluid medium. We point out that their physical reasoning is unnatural and leads to an unacceptable conclusion; we propose a more sound approach to the same problem. Our treatment assumes that the gel network is extended not by the osmotic pressure of the gel, but rather by the swelling pressure which is generated by the excess fluid penetrating in against the real nature of a polymer network that tends to shrink. The diffusion equation of the fluid, hence, plays a dominant role and gives the distribution of fluid concentration in contrast to Tanaka-Fillmore's scheme. The expression for the distribution of local strain in a spherical gel is deduced from the relation of mechanical balance between two forces, the one is due to the elasticity of the network and the other due to the gradient in the chemical potential of the fluid. The results obtained have forms analytically similar to Tanaka-Fillmore's, but are differ in the physical meanings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410357
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 95
    Electronic Resource
    Electronic Resource
    Diffusion of protons in silica hydrogel (1989)
    Springer
    Colloid & polymer science 267 (1989), S. 460-464 
    Details
    ISSN: 1435-1536
    Keywords: Diffusion ; silica gel ; kinetics ; surface area ; proton
    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 effect of preparation pH of silica hydrogel on the effective diffusion coefficient of protons in silica hydrogel (D e , m2/s), on surface area of silica gel (S, m2/s) and on particle size of silica gel (D p , mm) was studied. Silica hydrosols were obtained by adding water glass to sulfuric acid. The effective diffusion coefficient of proton in silica hydrogel was determined by the method of diffusion from silica hydrogel plane sheet to a stirred solution of a limited volume. A numerical solution was obtained for the diffusion equation using the Regula Falsi method. Regression analyses of experimental data were conducted. Diffusion of protons in silica hydrogel is a complicated process due to a decelerating effect of the porous structure of silica hydrogel and to the accelerating effects of slow ions such as Na+ and surface diffusion. The effective diffusion coefficient increased with surface area of silica gel, indicating the diffusion of protons on the surface of the silica particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410194
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 96
    Electronic Resource
    Electronic Resource
    How rapid are the internal reactions of the ubiquinol:cytochrome c 2 oxidoreductase? (1989)
    Springer
    Photosynthesis research 22 (1989), S. 69-87 
    Details
    ISSN: 1573-5079
    Keywords: electron transport ; kinetics ; Q-cycle ; Rb. sphaeroides ; thermodynamics ; ubiquinol:cytochrome c 2 oxidoreductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temperature dependence of the partial reactions leading to turn-over of the UQH2:cyt c 2 oxidoreductase of Rhodobacter sphaeroides have been studied. The redox properties of the cytochrome components show a weak temperature dependence over the range 280–330 K, with coefficients of about 1 m V per degree; our results suggest that the other components show similar dependencies, so that no significant change in the gradient of standard free-energy between components occurs over this temperature range. The rates of the reactions of the high potential chain (the Rieske iron sulfur center, cytochromes c 1 and c 2, reaction center primary donor) show a weak temperature dependence, indicating an activation energy 〈 8 kJ per mole for electron transfer in this chain. The oxidation of ubiquinol at the Qz-site of the complex showed a strong temperature dependence, with an activation energy of about 32 kJ mole−1. The electron transfer from cytochrome b-566 to cytochrome b-561 was not rate determining at any temperature, and did not contribute to the energy barrier. The activation energy of 32 kJ mole−1 for quinol oxidation was the same for all states of the quinone pool (fully oxidized, partially reduced, or fully reduced before the flash). We suggest that the activation barrier is in the reaction by which ubiquinol at the catalytic site is oxidized to semiquinone. The most economical scheme for this reaction would have the semiquinone intermediate at the energy level indicated by the activation barrier. We discuss the plausibility of this simple model, and the values for rate constants, stability constant, the redox potentials of the intermediate couples, and the binding constant for the semiquinone, which are pertinent to the mechanism of the ubiquinol oxidizing site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00114768
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 97
    Electronic Resource
    Electronic Resource
    Aspects of the phosphorus cycle in Hartbeespoort Dam (South Africa) (1989)
    Springer
    Hydrobiologia 183 (1989), S. 87-95 
    Details
    ISSN: 1573-5117
    Keywords: phosphorus ; Hartbeespoort Dam ; algal uptake ; abiotic effects ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of biotic processes in a warm, monomictic, hypertrophic African impoundment (Hartbeespoort Dam) is examined using 32P radiobioassays. Phosphorus demand is assessed by phosphorus turnover times, alkaline phosphatase activity, cellular phosphorus status and the phosphorus deficiency index. Long turnover times indicative of an enriched system were recorded, ranging from 9 h to 1992 h, with no evidence of phosphorus stress being present. These turnover times support the hypothesis that the phosphorus cycle in Hartbeespoort Dam is dominated by the algal community which is shown to play an important role in phosphorus cycling within the water column. However, hydrological processes remain the driving force in phosphorus seasonality in the lake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018714
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 98
    Electronic Resource
    Electronic Resource
    Cytochromec oxidase ofEuglena gracilis: Purification, characterization, and identification of mitochondrially synthesized subunits (1989)
    Springer
    Journal of bioenergetics and biomembranes 21 (1989), S. 359-373 
    Details
    ISSN: 1573-6881
    Keywords: Cyrochromec oxidase ; kinetics ; subunit composition ; mitochondrially synthesized polypeptides ; Euglena gracilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Cytochromec oxidase was purified from mitochondria ofEuglena gracilis and separated into 15 different polypeptide subunits by polyacrylamide gel electrophoresis. All 15 subunits copurify through various purification procedures, and the subunit composition of the isolated enzyme is identical to that of the immunoprecipitated one. Therefore, the 15 protein subunits represent integral components of theEuglena oxidase. In anin vitro protein-synthesizing system using isolated mitochondria, polypeptides 1–3 were radioactive labeled in the presence of [35S]methionine. This further identifies these polypeptides with the three largest subunits of cytochromec oxidse encoded by mitochondrial DNA in other eukaryotic organisms. By subtraction, the other 12 subunits can be assigned to nuclear genes. The isolatedEuglena oxidase was highly active withEuglena cytochromec 558 and has monophasic kinetics. Using horse cytochromec 550 as a substrate, activity of the isolated oxidase was rather low. These findings correlate with the oxidase activity of mitochondrial membranes. Again, reactivity was low with cytochromec 550 and 35-fold higher with theEuglena cytochromec 558. The data show that the cytochromec oxidase of the protistEuglena is different from other eukaryotic cytochromec oxidases in number and size of subunits, and also with regard to kinetic properties and substrate specificity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00762727
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 99
    Electronic Resource
    Electronic Resource
    Rate of opening of a population of Na channels in frog skeletal muscle fibers (1989)
    Springer
    Journal of biological physics 17 (1989), S. 75-94 
    Details
    ISSN: 1573-0689
    Keywords: Na channels ; skeletal muscle ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Linear Systems convolution analysis of muscle sodium currents was used to predict the opening rate of sodium channels as a function of time during voltage clamp pulses. If open sodium channel lifetimes are exponentially distributed, the channel opening rate corresponding to a sodium current obtained at any particular voltage, can be analytically obtained using a simple equation, given single channel information about the mean open-channel lifetime and current. Predictions of channel opening rate during voltage clamp pulses show that sodium channel inactivation arises coincident with a decline in channel opening rate. Sodium currents pharmacologically modified with Chloramine-T treatment so that they do not inactivate, show a predicted sustained channel opening rate. Large depolarizing voltage clamp pulses produce channel opening rate functions that resemble gating currents. The predicted channel opening rate functions are best described by kinetic models for Na channels which confer most of the charge movement to transitions between closed states. Comparisons of channel opening rate functions with gating currents suggests that there may be subtypes of Na channel with some contributing more charge movement per channel opening than others. Na channels open on average, only once during the transient period of Na activation and inactivation. After transiently opening during the activation period and then closing by entering the inactivated state, Na channels reopen if the voltage pulse is long enough and contribute to steady-state currents. The convolution model overestimates the opening rate of channels contributing to the steady-state currents that remain after the transient early Na current has subsided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417749
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 100
    Electronic Resource
    Electronic Resource
    2-Chloro adenosine triphosphate as substrate for sea urchin axonemal movement (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 13 (1989), S. 239-244 
    Details
    ISSN: 0886-1544
    Keywords: sperm ; nucleotide analog ; kinetics ; Stronglyocentrotus purpuratus ; reactivation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The 2-substituted ATP analog 2-Chloro ATP was tested for its capacity to support axonemal movement. The movement of sea urchin axonemes reactivated with 2-CI ATP appeared very similar to that with ATP. Detailed waveform analysis indicated that bend angle and shear amplitude were not significantly different for ATP and 2-CI ATP. Although wavelength differs at particular nucleotide concentrations, if normalized to the beat frequency, it is similar for ATP and 2-CI ATP. The main difference in the movement with the two analogs was seen in beat frequency and sliding velocity. The Vmax for beat frequency and mean sliding velocity was lower for 2-CI ATP. The apparent Km for beat frequency and sliding velocity was much lower for 2-CI ATP. The ratio of these two effects, that is, (Vmax/Km) is higher for 2-CI ATP. Thus 2-CI ATP is a good substrate for axonemal movement. The significantly lower Km of 2-CI ATP was also demonstrated by its ability to support oscillatory motion at concentrations below that for ATP. The observations identify the structures and conformation of substrate necessary to support axonemal movement.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970130403
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...