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991.
The behavior of arsenite, methylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, dimethyl-R-arsine oxides, and trimethyl-R-arsonium compounds (R = carboxymethyl, 2-carboxyethyl, 2-hydroxyethyl) toward sodium borohydride and hot aqueous sodium hydroxide was investigated. The arsines obtained by sodium borohydride reduction of the undigested and digested solutions were collected in a liquid-nitrogen cooled trap, separated with a gas chromatograph, and detected with a mass spectrometer in the selected-ion-monitoring mode. The investigated arsenic compounds were stable in hot 2 mol dm?3 sodium hydroxide except arsenobetaine [trimethyl(carboxymethyl)arsonium zwitterion] that was converted to trimethylarsine oxide, and dimethyl(ribosyl)arsine oxides that were decomposed to dimethylarsinic acid. Hydride generation before and after digestion of extracts from marine organisms allowed inorganic arsenic, methylated arsenic, arsenobetaine, and ribosyl arsenic compounds to be identified and quantified. This method was applied to extracts from shellfish, fish, crustaceans, and seaweeds. 相似文献
992.
团簇结构测量是团簇科学研究中的一个重要课题。文章对近几年发展的注入离子漂移管技术进行了详细介绍与分析,该技术是上前测量团簇结构近似程度最高的技术,已在C,Si,Ge及Al等原子团簇的结构研究中获得广泛应用,并取得了许多重要结果。 相似文献
993.
994.
We study numerically the nature of the diffusion process on a honeycomb and a quasi-lattice, where a point particle, moving along the bonds of the lattice, scatters from randomly placed scatterers on the lattice sites according to strictly deterministic rules. For the honeycomb lattice fully occupied by fixed rotators two (symmetric) isolated critical points appear to be present, with the same hyperscaling relation as for the square and the triangular lattices. No such points appear to exist for the quasi-lattice. A comprehensive comparison is made with the behavior on the previously studied square and triangular lattices. A great variety of diffusive behavior is found, ranging from propagation, superdiffusion, normal, quasi-normal, and anomalous, to absence of diffusion. The influence of the scattering rules as well as of the lattice structure on the diffusive behavior of a point particle moving on the all lattices studied so far is summarized. 相似文献
995.
Thermal Aqueous Liquid Chromatography (TALC) using pure water as a mobile phase should be a very attractive technique promoting the use of liquid chromatography in routine analysis, either in the laboratory or in future on-line process control. This simple form of chromatography, the selectivity of which depends on the fixed phase only, would allow the use of flame ionization as an almost universal, low-cost detector in liquid chromatography. The potential of the TALC technique is illustrated by selected examples. 相似文献
996.
Summary The effect of experimental conditions such as gas flow rates, detector and column temperatures on sulphur response are discussed. It is concluded that the response of the flame photometric detector is affected by the O/H ratio and the total gas flow. Column temperature has an important influence upon S2 emission. It is shown that the sulphur response of the FPD is dependent on the compound containing the sulphur. 相似文献
997.
The partition of the canonical entropy (invariant of motion) into a thermodynamic part 5th and a nonthermodynamic oneS
nonth, respectively increasing and decreasing functions of time for a system approaching equilibrium, was proposed by Prigogine and co-workers. This viewpoint is critically examined in the special case of an initially uncorrelated gas of hard disks. BothSth and the leading term ofS
nonth are evaluated for finite assemblies of 400,1600, and 6400 disks, by the method of molecular dynamics. There is good evidence that, in the limit of an infinite system, the Prigogine scheme is verified.On leave of absence from the University of Brussels, Belgium. 相似文献
998.
Water-like lattice gases on the triangular and body-centered cubic lattices are investigated. Molecules may reside on the lattice sites in either of two possible orientations, a hydrogen bond being formed between molecules on neighboring sites if they have the proper orientation with respect to one another. For a range of chemical potential at sufficiently low temperatures, the models are shown to have an ordered phase consisting of an open, hydrogen-bonded, icelike structure. The models are shown to be transitionfree at sufficiently high temperature, indicating the existence of a critical point.Research supported in part by the U.S. National Science Foundation, Grant CHE-7726177, and by The Robert A. Welch Foundation, Grant P-446. 相似文献
999.
LI Zhihui ZHANG Hanxin & FU Song ⒈ National Laboratory for CFD Hypervelocity Aerodynamics Institute China Aerodynamics Research Development Center Mianyang China .Department of Engineering Mechanics Tsinghua University Beijing China 《中国科学G辑(英文版)》2005,48(4):496-512
~~Gas kinetic algorithm for flows in Poiseuille-like microchannels using Boltzmann model equation1. Feynman, R., There's plenty of room at the bottom, Journal of Microelectromechanical Systems, 1992, 1: 60 -66.
2. Piekos, E. S., Breuer, K. S., Numerical modeling of micromechanical devices using the direct simulation Monte Carlo method, Transactions of the ASME, Journal of Fluids Engineering, 1996, 118: 464-469.
3. Beskok, A., Karniadakis, G. E., Trimmer, W., Rarefaction and … 相似文献
1000.
A. V. Latyshev V. N. Popov A. A. Yushkanov 《Journal of Applied Mechanics and Technical Physics》2004,45(1):17-22
The slip velocity of a rarefied gas with inhomogeneous temperature and mass velocity on a solid spherical surface is calculated with the use of a twomoment boundary condition in the linear approximation in terms of the Knudsen number. The dependence of the slip velocity on accommodation coefficients of the two first moments of the distribution function is studied. 相似文献