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Recent Experimental Observations (recent + experimental_observation)
Selected AbstractsWelfare Economics with Intransitive Revealed Preferences: A Theory of the Endowment EffectJOURNAL OF PUBLIC ECONOMIC THEORY, Issue 2 2006H. LORNE CARMICHAEL Economists use the standard rational model to predict behavior after a policy change and to determine the policy's welfare implications. Recent experimental observations are casting doubt on the predictive accuracy of the standard model, but the more realistic behavioral alternatives often provide a poor basis for making normative evaluations. This paper suggests that we can still predict behavior and measure welfare within the same model. We show that optimizing agents with standard preferences will in some cases behave as if they are subject to an endowment effect. Even so, we may still be able to uncover information about their preferences. [source] Reaction pathways of propene pyrolysisJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2010Yena Qu Abstract The gas-phase reaction pathways in preparing pyrolytic carbon with propene pyrolysis have been investigated in detail with a total number of 110 transition states and 50 intermediates. The structure of the species was determined with density functional theory at B3PW91/6-311G(d,p) level. The transition states and their linked intermediates were confirmed with frequency and the intrinsic reaction coordinates analyses. The elementary reactions were explored in the pathways of both direct and the radical attacking decompositions. The energy barriers and the reaction energies were determined with accurate model chemistry method at G3(MP2) level after an examination of the nondynamic electronic correlations. The heat capacities and entropies were obtained with statistical thermodynamics. The Gibbs free energies at 298.15 K for all the reaction steps were reported. Those at any temperature can be developed with classical thermodynamics by using the fitted (as a function of temperature) heat capacities. It was found that the most favorable paths are mainly in the radical attacking chain reactions. The chain was proposed with 26 reaction steps including two steps of the initialization of the chain to produce H and CH3 radicals. For a typical temperature (1200 K) adopted in the experiments, the highest energy barriers were found in the production of C3 to be 203.4 and 193.7 kJ/mol. The highest energy barriers for the production of C2 and C were found 174.1 and 181.4 kJ/mol, respectively. These results are comparable with the most recent experimental observation of the apparent activation energy 201.9 ± 0.6 or 137 ± 25 kJ/mol. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] A theoretical study on the catalytic mechanism of Mus musculus adenosine deaminaseJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 12 2010Xian-Hui Wu Abstract The catalytic mechanism of Mus musculus adenosine deaminase (ADA) has been studied by quantum mechanics and two-layered ONIOM calculations. Our calculations show that the previously proposed mechanism, involving His238 as the general base to activate the Zn-bound water, has a high activation barrier of about 28 kcal/mol at the proposed rate-determining nucleophilic addition step, and the corresponding calculated kinetic isotope effects are significantly different from the recent experimental observations. We propose a revised mechanism based on calculations, in which Glu217 serves as the general base to abstract the proton of the Zn-bound water, and the protonated Glu217 then activates the substrate for the subsequent nucleophilic addition. The rate-determining step is the proton transfer from Zn-OH to 6-NH2 of the tetrahedral intermediate, in which His238 serves as a proton shuttle for the proton transfer. The calculated kinetic isotope effects agree well with the experimental data, and calculated activation energy is also consistent with the experimental reaction rate. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] A Theoretical Study on the Mechanism of C2H4 Oxidation over a Neutral V3O8 ClusterCHEMPHYSCHEM, Issue 8 2010Yan-Ping Ma Dr. Abstract Density functional theory (DFT) calculations are used to investigate the reaction mechanism of V3O8+C2H4. The reaction of V3O8 with C2H4 produces V3O7CH2+HCHO or V3O7+CH2OCH2 overall barrierlessly at room temperature, whereas formation of hydrogen-transfer products V3O7+CH3CHO is subject to a tiny overall free energy barrier (0.03 eV), although the formation of the last-named pair of products is thermodynamically more favorable than that of the first two. These DFT results are in agreement with recent experimental observations. The (Ob)2V(OtOt). (b=bridging, t=terminal) moiety containing the oxygen radical in V3O8 is the active site in the reaction with C2H4. Similarities and differences between the reactivities of (Ob)2V(OtOt). in V3O8 and the small VO3 cluster [(Ot)2VOt.] are discussed. Moreover, the effect of the support on the reactivity of the (Ob)2V(OtOt). active site is evaluated by investigating the reactivity of the cluster VX2O8, which is obtained by replacing the V atoms in the (Ob)3VOt support moieties of V3O8 with X atoms (X=P, As, Sb, Nb, Ta, Si, and Ti). Support X atoms with different electronegativities influence the oxidative reactivity of the (Ob)2V(OtOt). active site through changing the net charge of the active site. These theoretical predictions of the mechanism of V3O8+C2H4 and the effect of the support on the active site may be helpful for understanding the reactivity and selectivity of reactive O. species over condensed-phase catalysts. [source] | ||||||||||