Significant Temperature Dependence of the Isosteric Heats of Adsorption of Gases in Zeolites Demonstrated by Experiments and Molecular Simulations

2019 ◽  
Vol 123 (33) ◽  
pp. 20405-20412 ◽  
Author(s):  
Alexander S. Hyla ◽  
Hanjun Fang ◽  
Salah Eddine Boulfelfel ◽  
Giovanni Muraro ◽  
Charanjit Paur ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Molecular Simulations ◽  
Heats Of Adsorption ◽  
Significant Temperature ◽  
Adsorption Of Gases

scholarly journals The role of enzyme dynamics and tunnelling in catalysing hydride transfer: studies of distal mutants of dihydrofolate reductase

2006 ◽  
Vol 361 (1472) ◽  
pp. 1307-1315 ◽  
Author(s):  
Lin Wang ◽  
Nina M Goodey ◽  
Stephen J Benkovic ◽  
Amnon Kohen
Keyword(s):  
Temperature Dependence ◽  
Dihydrofolate Reductase ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Activation Parameters ◽  
Physical Nature ◽  
Enzyme Dynamics ◽  
Temperature Dependences ◽  
Donor Acceptor ◽  
Significant Temperature

Residues M42 and G121 of Escherichia coli dihydrofolate reductase ( ec DHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ec DHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), their temperature dependence and activation parameters were studied. The findings presented here are in accordance with the environmentally coupled hydrogen tunnelling. In contrast to the wild-type (WT), fluctuations of the donor–acceptor distance were required, leading to a significant temperature dependence of KIEs and deflated intercepts. A comparison of M42W and G121V to the WT enzyme revealed that the reduced rates, the inflated primary KIEs and their temperature dependences resulted from an imperfect potential surface pre-arrangement relative to the WT enzyme. Apparently, the coupling of the enzyme's dynamics to the reaction coordinate was altered by the mutation, supporting the models in which dynamics of the whole protein is coupled to its catalysed chemistry.

Thermotransport of Noble Metal Impurities in Lead

1972 ◽  
Vol 27 (1) ◽  
pp. 138-140 ◽  
Author(s):  
George A. Sullivan ◽  
Sune Larsson ◽  
Per T. Thernquist
Keyword(s):  
Steady State ◽  
Temperature Dependence ◽  
Noble Metal ◽  
Temperature Gradients ◽  
Electronic Contribution ◽  
Kcal Mole ◽  
Cold Side ◽  
Heat Of Transport ◽  
Metal Impurities ◽  
Significant Temperature

Abstract Steady-state distributions of Au, Ag and Cu tracers in Pb wafers subjected to temperature gradients have been determined. The effective heats of transport were + 5.8 ± 1.1 for Ag, - 0.5 ± 0.3 for Au, and of the order of + 35 for Cu (all in kcal/mole, positive values denoting the impurity migrating to the cold side of the Pb wafer). No significant temperature dependence of the heats of transport could be detected. The results are difficult to reconcile with existing theories of the intrinsic and electronic contribution to the heat of transport.

Isosteric Heats of Adsorption of Gases and Vapors on a Microporous Carbonaceous Material

2018 ◽  
Vol 63 (8) ◽  
pp. 3107-3116 ◽  
Author(s):  
S. Hadi Madani ◽  
Francisco Rodríguez-Reinoso ◽  
Mark J. Biggs ◽  
Phillip Pendleton
Keyword(s):  
Carbonaceous Material ◽  
Heats Of Adsorption ◽  
Adsorption Of Gases

scholarly journals DEPENDENCE OF THE COSMIC MUON FLUX ON ATMOSPHERIC PRESSURE AND TEMPERATURE

2007 ◽  
Vol 14 (1) ◽  
pp. 56
Author(s):  
PHAM NGOC DIEP ◽  
PHAM THI TUYET NHUNG ◽  
PHAM NGOC DINH ◽  
NGUYEN HAI DUONG ◽  
PIERRE DARRIULAT ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Atmospheric Pressure ◽  
Muon Flux ◽  
Ground Temperature ◽  
Cosmic Muon ◽  
Significant Temperature ◽  
Temperature And Pressure

The dependence upon atmospheric pressure of the cosmic muon flux in Hanoi has been measured to be -1.47± 0.50 permil per mbar in agreement with expectation from a naive estimate. The dependence over ground temperature is observed to largely reflect the correlation existing between temperature and pressure. Once the effect of this correlation is removed a smaller, barely significant temperature dependence of -0.57± 0.34 permil per °C subsists.

Temperature dependence of charge carrier ranges in stabilized a-Se photoconductors

2014 ◽  
Vol 92 (7/8) ◽  
pp. 634-640 ◽  
Author(s):  
Bud Fogal ◽  
Safa Kasap
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
Collection Efficiency ◽  
Activation Energies ◽  
Charge Collection Efficiency ◽  
X Ray ◽  
Thermally Activated ◽  
Deep Traps ◽  
Significant Temperature ◽  
Experimental Errors

Using time-of-flight (TOF) and interrupted-field TOF we have measured the electron and hole drift mobilities, μe and μh, lifetimes, τe and τh, and hence carrier ranges, μeτe and μhτh, in stabilized a-Se as a function of temperature from −25 to 45 °C. Above room temperature, μeτe and μhτh show a slight increase with temperature and peak around 31 and 35 °C, respectively. The μeτe at 35 °C and μhτh at 40 °C are approximately the same as room temperature values. Below room temperature, down to −25 °C, both μe and μh decrease with decreasing temperature with activation energies Eμe and Eμh that are 0.38 and 0.21 eV. The electron and hole lifetimes, τe and τh, are also thermally activated but they increase with decreasing temperature with activation energies Eτe and Eτh that are 0.31 and 0.18 eV. These are quite close to corresponding activation energies for the drift mobilities within experimental errors. The electron and hole ranges, μeτe and μhτh, therefore exhibit only a weak temperature dependence, both increase slightly with temperature. These observations are consistent with shallow trap controlled transport in the presence of a set of deep traps. The X-ray sensitivity of a photoconductor, among other factors, depends on the charge collection efficiency, which depends on electron and hole ranges, μeτe and μhτh. Because these carrier ranges do not show any significant temperature dependence, one can conclude that the X-ray sensitivity of stabilized a-Se over the temperature range from −25 to 40 °C should not be affected by changes in the collection efficiency.

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