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1.
We carried out molecular dynamics simulations of a Lorentz gas, consisting of a lone hydrogen molecule moving in a sea of stationary argon atoms. A Lennard-Jones form was assumed for the H2-Ar potential. The calculations were performed at a reduced temperatureK
* =kT/H
2–Ar = 4.64 and at reduced densities
*=
Ar
Ar
3
in the range 0.074–0.414. The placement of Ar atoms was assumed to be random rather than dictated by equilibrium considerations. We followed the trajectories of many H2 molecules, each of which is assigned in turn a velocity given by the Maxwell-Boltzmann distribution at the temperature of the simulation. Solving the equations of motion classically, we obtained the translational part of the incoherent dynamic structure factor for the H2 molecule,S
tr(q, ). This was convoluted with the rotational structure factorS
rot(q, ) calculated assuming unhindered rotation to obtain the total structure factorS(q, ). Our results agree well with experimental data on this function obtained by Egelstaffet al. At the highest density (
*=0.414) we studied the dependence ofS(q, ) on system size (number of Ar atoms), number of H2 molecules for which trajectories are generated, and the length of time over which these trajectories are followed. 相似文献
2.
A recent suggestion by Lebowitz and Percus that the median intermolecular potential may serve as a simple temperature-independent effective central potential is tested against virial inversion data for the site-site Lennard-Jones potential obtained by Smith and Tindell. Excellent agreement is found even when the anisotropy in the potential is large. Second virial coefficients computed from the effective potential reproduce the true values to a high degree of accuracy. 相似文献
3.
We describe a simple, sensitive method for the determination of phenobarbital, diphenylhydantoin, carbamazepine and primidone in serum, by use of gas-liquid chromatography with temperature programming. The methylated derivatives of these anticonvulsants were well resolved, as was 5-(p-methylphenyl)-5-phenylhydantoin, the internal standard. In this procedure we used an ion-exchange resin for separation of the drug from the serum. The proposed procedure requires only 1.0 ml of serum and can be done in less than 1 h. The lower limit of detection for each of the drugs is 0.5 mg/1. Analytical recoveries of drug from serum were excellent and peak height and concentration were linearly related up to twice the toxic concentration for serum. 相似文献
4.
The oxidation mechanism at pH 14 for a number of 1-phenylpyrazolidin-3-ones substituted in the 4 position of the heterocyclic ring has been investigated with electrochemical techniques. A general oxidation mechanism, resulting in the formation of a radical species and short-lived pyrazolinone tautomers has been postulated. 相似文献
5.
Joslin EE McMullin CL Gunnoe TB Cundari TR Sabat M Myers WH 《Inorganic chemistry》2012,51(8):4791-4801
The complexes TpRu[P(OCH(2))(2)(OCCH(3)](PPh(3))Cl (2) [Tp = hydridotris(pyrazolyl)borate; P(OCH(2))(2)(OCCH(3)) (1) = (4-methyl-2,6,7-trioxa-1-phosphabicyclo[2,2,1]heptane] and TpRu(L)(PPh(3))Cl [L = P(OCH(2))(3)CEt (3), PMe(3) (4) or P(OMe)(3) (5)], (η(6)-C(6)H(6))Ru(L)Cl(2) [L = PPh(3) (6), P(OMe)(3) (7), PMe(3) (8), P(OCH(2))(3)CEt (9), CO (10) or P(OCH(2))(2)(OCCH(3)) (11)] and (η(6)-p-cymene)Ru(L)Cl(2) [L = P(OCH(2))(3)CEt (12), P(OCH(2))(2)(OCCH(3))P(OCH(2))(2)(OCCH(3)) (13), P(OMe)(3) (14) or PPh(3) (15)] have been synthesized, isolated, and characterized by NMR spectroscopy, cyclic voltammetry, mass spectrometry, and, for some complexes, single crystal X-ray diffraction. Data from cyclic voltammetry and solid-state structures have been used to compare the properties of (1) with other phosphorus-based ligands as well as carbon monoxide. Data from the solid-state structures of Ru(II) complexes show that P(OCH(2))(2)(OCCH(3)) has a cone angle of 104°. Cyclic voltammetry data reveal that the Ru(II) complexes bearing P(OCH(2))(2)(OCCH(3)) have more positive Ru(III/II) redox potentials than analogous complexes with the other phosphorus ligands; however, the Ru(III/II) potential for (η(6)-C(6)H(6))Ru[P(OCH(2))(2)(OCCH(3))]Cl(2) is more negative compared to the Ru(III/II) potential for the CO complex (η(6)-C(6)H(6))Ru(CO)Cl(2). For the Ru(II) complexes studied herein, these data are consistent with the overall donor ability of 1 being less than other common phosphines (e.g., PMe(3) or PPh(3)) or phosphites [e.g., P(OCH(2))(3)CEt or P(OMe)(3)] but greater than carbon monoxide. 相似文献
6.
7.
Large-eddy simulation (LES) results for laminar-to-turbulent transition in a spatially developing boundary layer are presented.
The disturbances are ingested into a laminar flow through an unsteady suction-and-blowing strip. The filtered, three-dimensional
time-dependent Navier–Stokes equations are integrated numerically using spectral, high-order finite-differences, and a three-stage
low-storage Runge–Kutta/Crank–Nicolson time-advancement method. The buffer-domain technique is used for the outflow boundary
condition. The localized dynamic model used to parametrize the subgrid-scale (SGS) stresses begins to have a significant impact
at the beginning of the nonlinear transition (or intermittency) region. The flow structures commonly found in experiments
are also observed in the present simulation; the computed linear instability modes and secondary instability $\Lambda$-vortex
structures are in agreement with the experiments, and the streak-like structures and turbulent statistics compare with both
the experiments and the theory. The physics captured in the present LES are consistent with the experiments and the full Navier–Stokes
simulation (DNS), at a significant fraction of the DNS cost. A comparison of the results obtained with several SGS models
shows that the localized model gives accurate results both in a statistical sense and in terms of predicting the dynamics
of the energy-carrying eddies, while requiring fewer ad hoc adjustments than the other models.
Received: 5 April 1996 and accepted 27 March 相似文献
8.
9.
C.G. Joslin 《Chemical physics letters》1982,91(6):452-455
We examine the suggestion that the very high dielectric constant of water is associated with the absence of a significant component of the quadrupole tensor along the direction of the dipole moment. We find that although ?zz ≈ 0, there is a large “effective axial” moment ?effzz. 相似文献
10.
C.G. Joslin 《Molecular physics》2013,111(4):771-783
We calculate the two body contributions to the pressure, dielectric constant, depolarized light scattering intensity, electro-optical birefringence (Kerr effect), and other properties, of a fluid whose molecules are hard ellipsoids with embedded central point dipoles. The results are presented for various molecular anisotropies and dipole strengths. The second dielectric and Kerr virial coefficients are found to be particularly sensitive to molecular shape. 相似文献