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461.
The modified free-energy averaged potential for water vapour is extended to NH3 vapour. The resulting temperature-dependent parameters are used to compute the second virial coefficient of NH3 vapour which agrees with experimental results particularly at higher temperatures. 相似文献
462.
An expression for the width of the plasmon excitations in electron liquid has been obtained using the mode coupling approximation. It is shown that the exact weak coupling (rs → 0) results of the plasmon width in the long wavelength limit is obtained as a very special case in this approach. 相似文献
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465.
The expression for the fourth frequency moment of current correlation function in a two-component fluid is derived. This result is used to obtain certain exact sum rules, in the long-wavelength limit, for charge current correlations in fused salts. 相似文献
466.
Kedar Pathak 《Applied Surface Science》2007,253(15):6359-6365
The process of laser ablation of carbon in presence of background gas is simulated numerically. The plume dynamics in laser ablation is important to study for many reasons including temperature of plume particles and shielding of target by previously ablated plumes. Shielding leads directly to the change in energy deposition of incident laser pulse at the target surface and in turn influences the ablation dynamics and amount of material removed. Carbon ablation is studied for single and multiple laser hits typical for synthesis of nanotubes. Two models of correction of ablated velocity and pressure resulting from shielding effect are proposed and investigated. Numerical modeling of this plume dynamics and its integral effect of shielding is challenging due to inherent high nonlinearity of the problem. Some of available numerical techniques handles nonlinearity but are dissipative, e.g. Godunov type schemes. Other techniques are less dissipative but fail to account for strong nonlinearity typical for initial stages of ablation, e.g. the ENO-Roe. To effectively model this highly nonlinear plume dynamics a combination of two of above mentioned schemes is developed so as the numerical evaluation of fluxes is close to their physical values and the scheme has minimum dissipation. The non-monotonic behavior of ablated mass as a function of time duration between two laser pulses is studied. 相似文献
467.
The pyruvic acid molecule and its various isomers have been studied in aqueous solution in order to understand the mechanism of decarboxylation. The tautomeric equilibrium remains in favor of the keto form in aqueous solution, but the energy difference between the two tautomers decreases. The anion also exists in the keto form in aqueous solution. Good agreement between the calculated and observed gas phase protonation and basicity values is obtained, and the calculated pKa value is also in reasonable agreement with the literature value. The importance of the catalytic mechanism may be gauged from the fact that, in the absence of an enzymatic pathway, the reaction has high activation barrier and may not occur at all. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
468.
-H
,M,a
H
,b
. - — H
,M
H
. . , H
,–1/2, H
,H,a
H
,1/a
H
,M
H
. , . 相似文献
469.
Sun YP Meziani MJ Pathak P Qu L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(5):1366-1373
In this concept paper we highlight applications of supercritical fluid technology in particle formation and production, especially some recent advances in the rapid expansion of supercritical solutions (RESS) processing technique. We also highlight the simple but significant modification to the traditional RESS by using a liquid solvent or solution at the receiving end of the supercritical solution expansion, or the rapid expansion of a supercritical solution into a liquid solvent (RESOLV), and applications of the technique to the preparation of nanoparticles. In particular, successes and challenges in the use of RESOLV for nanoscale (<100 nm) polymeric particles and the subsequent protection of the suspended nanoparticles from agglomeration are discussed. 相似文献
470.
Nanosizing drug particles in supercritical fluid processing 总被引:7,自引:0,他引:7
Pathak P Meziani MJ Desai T Sun YP 《Journal of the American Chemical Society》2004,126(35):10842-10843
The supercritical fluid-processing technique, rapid expansion of a supercritical solution into a liquid solvent (RESOLV), was applied to the nanosizing of water-insoluble drug particles. Selected for demonstration were antiinflammatory drugs Ibuprofen and Naproxen, for which CO2 and CO2-cosolvent systems were used. The RESOLV process produces exclusively nanoscale (less than 100 nm) Ibuprofen and Naproxen particles suspended in aqueous solutions, and the aqueous suspensions of the drug nanoparticles are protected from particle agglomeration and precipitation by using common polymeric and oligomeric stabilization agents. 相似文献