scholarly journals STUDY OF CARBON DIOXIDE ADSORPTION ON CHROMIUM OXIDE AND GALLIUM OXIDE CATALYSTS ON BASIS OF NON-LINEAR RELAXATION TIMES

2018 ◽  
Vol 61 (2) ◽  
pp. 46 ◽  
Author(s):  
Nikolay I. Kol'tsov
Keyword(s):  
Carbon Dioxide ◽  
Relaxation Time ◽  
Chromium Oxide ◽  
Rate Constants ◽  
Gallium Oxide ◽  
Relaxation Times ◽  
Oxide Catalysts ◽  
Linear Relaxation ◽  
Adsorption And Desorption ◽  
Non Linear

Recently the analysis of transient regimes of chemical reactions is paid much attention. This is due to the fact that the time-dependent relaxation modes prior to achieving steady states contain important information about the features of the reactions. During unsteady mode the changes in reactant concentrations and rate of the reaction in time are observed. These changes are due to their own relaxation processes, depending on the structure of the reaction mechanism. A complete study of the reaction mechanism involves the study of the relaxation characteristics both near and away from the stationary state. Linear relaxation time describes the local transient modes near the steady state and it is calculated as the time decrease deviations of reactant concentrations from steady-state values in the e-times. Non-linear relaxation time describes the overall behavior reactions and it can be evaluated through the reaction time from the initial state to a stationary. Depending on the structural features of reactions ratio to determine the non-linear relaxation time through of reactions parameters (rate constants stages and reactant concentrations) differ significantly. The establishment of such ratio for a particular reaction allows getting more information to identify the mechanism and the constituent rate constants of its stages. The mechanism of any catalytic reaction involves stages adsorption of one or more of the starting materials on the catalyst surface. As a rule these stages are initial remaining stages of chemical transformation of reactants adsorbed forms follow them. Therefore, it is necessary to have the data on these stages and rate constants of adsorption of reagents on the catalyst surface. Earlier by author the method for estimating the values of the rate constants of adsorption and desorption by linear relaxation times was described. This method was used for determine of mechanism and kinetic parameters of process of adsorption of carbon dioxide on the chromium oxide and gallium oxide catalysts. In this article the method for estimating the values of the rate constants of adsorption and desorption by non-linear relaxation times for this process is described. The previously found CO2 dissociative adsorption mechanism was proved by the obtained results. The intervals of values changes of the rate constants of adsorption and desorption of carbon dioxide on the gallium oxide and chromium oxide catalysts were defined.Forcitation:Kol’tsov N.I. Study of carbon dioxide adsorption on chromium oxide and gallium oxide catalysts on basis of non-linear relaxation times. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 46-52

Study of carbon dioxide adsorption on chromium oxide and gallium oxide catalysts on the basis of linear relaxation times

2016 ◽  
Vol 89 (5) ◽  
pp. 719-726
Author(s):  
V. Kh. Fedotov ◽  
N. I. Kol’tsov ◽  
N. A. Gaidai ◽  
Yu. A. Agafonov ◽  
M. A. Botavina ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Chromium Oxide ◽  
Gallium Oxide ◽  
Relaxation Times ◽  
Oxide Catalysts ◽  
Linear Relaxation ◽  
Carbon Dioxide Adsorption

KINETIC STUDIES OF PROTEIN–DYE AND ANTIBODY–HAPTEN INTERACTIONS WITH THE TEMPERATURE-JUMP METHOD

1962 ◽  
Vol 40 (9) ◽  
pp. 1786-1797 ◽  
Author(s):  
A. Froese ◽  
A. H. Sehon ◽  
M. Eigen
Keyword(s):  
Relaxation Time ◽  
Bovine Serum Albumin ◽  
Rate Constants ◽  
Temperature Jump ◽  
Relaxation Times ◽  
Kinetic Studies ◽  
Single Relaxation Time ◽  
Effects Of Temperature ◽  
Arsonic Acid ◽  
Kinetics Of

The kinetics of protein–dye and antibody–hapten reactions were studied with the temperature-jump method. The systems used consisted of (i) bovine serum albumin (BSA) and the dye 1-naphthol-4-[4-(4′-azobenzene azo)phenyl arsonic acid], referred to as N—R′, (ii) BSA and the dye 1-naphthol-2-sulphonic acid-4-[4-(4′-azobenzene azo)phenyl arsonic acid], referred to as NS—R′, and (iii) rabbit antibodies to phenyl arsonic acid [Ab] and the hapten N—R′.Each of the systems exhibited a single relaxation time. From the analysis of the concentration dependence of the relaxation times, it was concluded that each system could be represented by the reactions[Formula: see text]where P refers to BSA or Ab, and D to N—R′ or NS—R′. The following rate constants were calculated for the three systems at 25 °C:[Formula: see text]The effects of temperature and pH on the rate constants of the system BSA – N—R′ are discussed.

Propane Dehydrogenation on Chromium Oxide and Gallium Oxide Catalysts in the Presence of CO2

2018 ◽  
Vol 59 (6) ◽  
pp. 744-753 ◽  
Author(s):  
Yu. A. Agafonov ◽  
N. A. Gaidai ◽  
A. L. Lapidus
Keyword(s):  
Chromium Oxide ◽  
Gallium Oxide ◽  
Oxide Catalysts ◽  
Propane Dehydrogenation

Dehydrogenation of ethane with carbon dioxide over supported chromium oxide catalysts

2000 ◽  
Vol 196 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Shaobin Wang ◽  
K Murata ◽  
T Hayakawa ◽  
S Hamakawa ◽  
K Suzuki
Keyword(s):  
Carbon Dioxide ◽  
Chromium Oxide ◽  
Oxide Catalysts ◽  
Chromium Oxide Catalysts

scholarly journals T2 mapping of the peritumoral infiltration zone of glioblastoma and anaplastic astrocytoma

2021 ◽  
pp. 197140092198932
Author(s):  
Timo Alexander Auer ◽  
Maike Kern ◽  
Uli Fehrenbach ◽  
Yasemin Tanyldizi ◽  
Martin Misch ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Isocitrate Dehydrogenase ◽  
Anaplastic Astrocytoma ◽  
T2 Mapping ◽  
Relaxation Times ◽  
Region Of Interest ◽  
World Health ◽  
High Grade ◽  
High Grade Gliomas ◽  
Health Organization

Purpose To characterise peritumoral zones in glioblastoma and anaplastic astrocytoma evaluating T2 values using T2 mapping sequences. Materials and methods In this study, 41 patients with histopathologically confirmed World Health Organization high grade gliomas and preoperative magnetic resonance imaging examinations were retrospectively identified and enrolled. High grade gliomas were differentiated: (a) by grade, glioblastoma versus anaplastic astrocytoma; and (b) by isocitrate dehydrogenase mutational state, mutated versus wildtype. T2 map relaxation times were assessed from the tumour centre to peritumoral zones by means of a region of interest and calculated pixelwise by using a fit model. Results Significant differences between T2 values evaluated from the tumour centre to the peritumoral zone were found between glioblastoma and anaplastic astrocytoma, showing a higher decrease in signal intensity (T2 value) from tumour centre to periphery for glioblastoma ( P = 0.0049 – fit-model: glioblastoma –25.02± 19.89 (–54–10); anaplastic astrocytoma –5.57±22.94 (–51–47)). Similar results were found when the cohort was subdivided by their isocitrate dehydrogenase profile, showing an increased drawdown from tumour centre to periphery for wildtype in comparison to mutated isocitrate dehydrogenase ( P = 0.0430 – fit model: isocitrate dehydrogenase wildtype –10.35±16.20 (–51) – 0; isocitrate dehydrogenase mutated 12.14±21.24 (–15–47)). A strong statistical proof for both subgroup analyses ( P = 0.9987 – glioblastoma R2 0.93±0.08; anaplastic astrocytoma R2 0.94±0.15) was found. Conclusion Peritumoral T2 mapping relaxation time tissue behaviour of glioblastoma differs from anaplastic astrocytoma. Significant differences in T2 values, using T2 mapping relaxation time, were found between glioblastoma and anaplastic astrocytoma, capturing the tumour centre to the peritumoral zone. A similar curve progression from tumour centre to peritumoral zone was found for isocitrate dehydrogenase wildtype high grade gliomas in comparison to isocitrate dehydrogenase mutated high grade gliomas. This finding is in accordance with the biologically more aggressive behaviour of isocitrate dehydrogenase wildtype in comparison to isocitrate dehydrogenase mutated high grade gliomas. These results emphasize the potential of mapping techniques to reflect the tissue composition of high grade gliomas.

scholarly journals Theoretical Effect of Temperature on Threshold in the Hodgkin-Huxley Nerve Model

1966 ◽  
Vol 49 (5) ◽  
pp. 989-1005 ◽  
Author(s):  
Richard Fitzhugh
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Giant Axon ◽  
Temperature Curve ◽  
Effect Of Temperature ◽  
Threshold Temperature ◽  
Ionic Conductances ◽  
And Shifts ◽  
The Right ◽  
Increasing Temperature

In the squid giant axon, Sjodin and Mullins (1958), using 1 msec duration pulses, found a decrease of threshold with increasing temperature, while Guttman (1962), using 100 msec pulses, found an increase. Both results are qualitatively predicted by the Hodgkin-Huxley model. The threshold vs. temperature curve varies so much with the assumptions made regarding the temperature-dependence of the membrane ionic conductances that quantitative comparison between theory and experiment is not yet possible. For very short pulses, increasing temperature has two effects. (1) At lower temperatures the decrease of relaxation time of Na activation (m) relative to the electrical (RC) relaxation time favors excitation and decreases threshold. (2) For higher temperatures, effect (1) saturates, but the decreasing relaxation times of Na inactivation (h) and K activation (n) factor accommodation and increased threshold. The result is a U-shaped threshold temperature curve. R. Guttman has obtained such U-shaped curves for 50 µsec pulses. Assuming higher ionic conductances decreases the electrical relaxation time and shifts the curve to the right along the temperature axis. Making the conductances increase with temperature flattens the curve. Using very long pulses favors effect (2) over (1) and makes threshold increase monotonically with temperature.

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