Collective properties of polyatomic gases in a magnetic field: Effects on light scattering spectrum

The effect of magnetic fields on collective properties of polyatomic gases has been extended outside the hydrodynamic regime. The calculations are based on a linearized Waldmann-Snider equation. The Waldmann-Snider collision operator is truncated yielding a finite matrix equation. The resulting matrix equation is solved on a computer to yield the polarized and depolarized light scattering spectra. These spectra are calculated in the absence and presence of a magnetic field. For long wavelengths it is found that the magnetic effects are of the same order of magnitude as in the Senftleben-Beenakker effects. For shorter wavelengths the effects disappear due to Doppler effects.This work was supported by NSF GP22881.Alfred P. Sloan Foundation Fellow.NIH Predoctoral Fellow.     

Ionic association in aqueous solutions of strong electrolytes

A more accurate calculation of relaxation effects obtained with the standard Debye-Hückel-Onsager model has been presented recently and is here applied to several aqueous 1:1 electrolytes. The variation of the standard deviation between calculated and observed equivalent conductivities withK _A leads to an ill-defined minimum; but, where data over a wide concentration range are available, the minimum corresponds to values of the contact distancea which approximate to estimates from ionic dimensions. It is therefore proposed that, although preciseK _A values from conductance cannot be determined, the most probable values are those associated with realistic estimates ofa. When data cover a limited concentration range, minimum standard deviations are often indeterminate or vary greatly for duplicate runs. It is shown that reasonable values ofK _A can be obtained from such data if comparison is made at estimated values ofa.Notation The symbols not defined in the text are the following b e ²/kTa for 1:1 electrolytes - e electronic charge - k Boltzmann gas constant - T absolute temperature - dielectric constant of solvent - –(3/2y)(_e0/₀)     

The Boltzmann equation for a polyatomic gas

A formulation of the kinetic theory of dilute, classical polyatomic gases is given which parallels the Waldmann development for structureless molecules. In the first section the Boltzmann equation is written in terms of the specific rates of inelastic collision processes and then the properties of these rates and those of the corresponding collision cross sections are examined. The dependence of the distribution function on the dynamical variables is discussed and the equations of change for the gas are derived. Finally, a study is made of the properties of the linearized Boltzmann collision operation. In the second section the Boltzmann equation is deduced from a rigorous statistical-mechanical point of view and discussed in terms of the basic ideas of Bogoliubov. The computationally important special case of impulsive interactions is then considered.This research was supported in part by a grant from the National Science Foundation and in part by the Ames Laboratory of the U. S. Atomic Energy Commission. Contribution No. 2554.     

Activity coefficients for HCl+NiCl2+H2O at 298.15°K and effects of higher-order electrostatic terms

Activity coefficients for CHl in the system HCl+NiCl ₂ +H ₂ O at 298.15°K at constant total ionic strengths of 0.1, 0.5, 1.0, 2.0, and 3.0 moles-kg ^–1 have been determined by an emf method. A comparison was made between Scatchard's and Pitzer's interpretations of mixed-electrolyte solutions for this system and six related systems. Preference can be given to Pitzer's method provided cognizance is taken of the effects of higher-order electrostatic terms beyond the Debye-Hückel approximation on the thermodynamic properties of asymmetrical mixtures.     

Cosolvency effects on copolymer solutions at high pressure

Cloud-point data to 180°C and 2800 bar are presented for polyethylene, poly(methyl acrylate), and two poly(ethylene-co-methyl acrylate) copolymers (10 and 31 mol % methyl acrylate) in propane and chlorodifluoromethane with two cosolvents, acetone and ethanol. The addition of small amounts of either cosolvent to the copolymer–solvent mixtures shifts the cloud-point curve to lower pressures and temperatures, as both cosolvents provide favorable polar interactions with the acrylate group in the backbone of the copolymer. Ethanol has a larger effect than acetone since ethanol hydrogen bonds to the acrylate group. However, if the concentration of ethanol is increased above ca. 10 wt %, it self-associates and reverts to antisolvent behavior, forcing the copolymer out of solution. For nonpolar polyethylene–propane mixtures, the polar cosolvents behave as traditional an-tisolvents. In poly(methyl acrylate)–chlorodifluoromethane mixtures, both polar cosolvents enlarge the single-phase region. The cloud-point curves for the (co)polymer–propane–acetone mixtures are modeled reasonably well using the Sanchez–Lacombe equation of state with two adjustable mixture parameters. No attempt is made to model the mixtures that exhibit hydrogen bonding. © 1993 John Wiley & Sons, Inc.     

Determination of intrinsic properties of immobilized enzymes

Staphylococcal nuclease has been insolubilized, directly through its amino groups, on CNBr-activated Sepharose 2B. For kinetic studies, a small substrate (thymidine 5′-(p-nitrophenyl phosphate) 3′-phosphate) has been used to measure the hydrolytic activity. With this system the absence of diffusional limitation has been proven. Eadie-Hofstee analysis of the data has been employed to determine the intrinsic kinetic constants of the insolubilized enzyme. Thek _cat-pH andK _M−pH profiles and the activation energies are similar for the soluble and for the insolubilized nuclease. At the same time conditions are established in which a stirred batch reactor containing particles of insolubilized nuclease behaves as an open system.     

Optical studies of local flow behaviour of a non-Newtonian fluid inside a porous medium

In this study the local flow of a polymeric solution inside a porous medium is studied visually. While the flow is quite uniform for low volume flow rates it shows pronounced nonuniformity for higher volume flow rates. That is to say, only certain preferred passages are taken and these passages change in time (they fluctuate). This flow irregularity is the reason for increased resistance. Received: 28 April 1997 Accepted: 30 December 1997     

导管架海洋平台自振特性的简化计算方法

本文提出一个方程中考虑剪切、弯曲、转动惯量效应,而其它如塔架形状变化,平台面转动惯量及台面集中质量变化等其它影响因素均以修正系数方法确定,给出平台基本频率的简化算法。     

Dusty effects on pulsating viscous flow of two immiscible fluids between two parallel plates

The flow of two immiscible incompressible dusty viscous fluids between two parallel plates generated by a pulsating pressure gradient is investigated. Velocity fields for the fluid-particle system along with the expressions for the skin friction drag at the plates are obtained and studied graphically. It is found that there is an immediate response to pressure fluctuations in the first stream at low frequency range 0<σ≤4 being maximum at σ=4. On the contrary, the second stream is more responsive to fluctuations at relatively higher frequencies. The maximum response in this case is shifted to σ=16.     

LiF插层对有机发光二极管磁场效应的调控

制备了有LiF插层的有机发光二极管,以八羟基喹啉铝（Alq₃）作为电子传输层,N, N′-二苯基-N, N′-二(1-萘基)-1,1′-联苯-4,4′-二胺（NPB）作为空穴传输层.通过改变Alq₃与NPB间LiF插层的厚度,研究了不同温度下器件的光电特性及电致发光的磁场效应.测量结果表明:LiF插层可以影响器件内部载流子的输运和激发态的形成.较厚的插层阻碍了空穴的传输,使器件的电流效率变低.但实验中发现, 关键词： LiF插层结构 磁场效应 三重态激子