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.     

A comment on “cosmic censorship,black holes,and particle orbits”

A paper by Hiscock [1] implies that the cosmic censorship hypothesis is false. It is shown here that this result is not proven and, indeed, is probably wrong.     

Coupled bending and twisting of a timoshenko beam

Allowance is made for shear deflection and for rotary inertia of a non-uniform beam that executes coupled bending and twisting vibration. Principal modes are found, orthogonality conditions established and modal equations of forced motion derived.     

Electron-transfer reactions of the halogens and their compounds : Limiting conditions for the quantitative reaction of bromate with arsenic(iii) and antimony(iii)

The limits of hydrochloric acid concentration within which the titrimetric determination of antimony(III) and arsenic(III) with bromate is quantitative within the normal precision of careful volume measurement (0.04%), are defined for both visual indication with rosaniline hydrochloride and potentiometric indication, in media initially containing no or 0.l M bromide. These reactions are independent of the nature of the reductant, the rate-controlling step being the fourth-order reaction producing the active oxidising species. Rate constants and energy of activation were determined. The kinetic and potentiometric investigations were used to elucidate the origins of the errors arising under conditions outside the ranges of quantitative reaction.     

Enhanced eddy current loss due to domain displacement

Magnetization in materials with fine hard co-operative closure-domain structures involves not only the growth of field-favoured domains at the expense of those unfavourably oriented but also considerable displacement and distortion of the surrounding domain structure. Thus the volume swept by domain walls considerably exceeds the increased volume of favourably oriented domains. As micro-eddy currents are generated by all moving domain walls, this co-operative behaviour of complex fine domain structures constitutes an effective source of the enhanced eddy-current damping known to occur in alloys with fine structure in contradiction of the predictions of domain eddy-current models such as that of Pry and Bean. This paper seeks to quantify this phenomenon by calculating the eddy-current dissipation caused by pure displacement of six different characteristic model domain structures. In each case the calculated loss increases with refinement of the structure, the limiting loss per unit volume being (υΔJ)²/4?, where υ is the velocity of displacement, ? is the material resistivity and ΔJ is the change in polarization across an interior domain wall.     

CO2 laser-induced decomposition of propan-2-ol,butan-2-ol,pentan-2-ol,pentan-3-ol,and hexan-2-ol

The pulsed CO₂ laser-induced decompositions of propan-2-ol, butan-2-ol, pentan-2-ol, pentan-3-ol, and hexan-2-ol in the gas phase have been investigated. Like ethanol which we examined previously [1] the absorption cross section of propan-2-ol for pulsed 9R14 radiation increases with pressure at low pressures, an effect attributed to rotational hole-filling. In contrast the absorption cross section of butan-2-ol (10R24) has only a small pressure dependence and those of pentan-2-ol (9R26), pentan-3-ol (10R14), and hexan-2-ol (9P20) show little or no variation with pressure in the range 0.1–5.0 torr. Decomposition products have been investigated at low pressure where the excitation of the alkanols was essentially collision free. The observed products for all the alkanols can be rationalized on the basis of primary dehydration and C? C fission channels, with minor contributions from other molecular eliminations. © 1994 John Wiley & Sons, Inc.     

End‐to‐End Distances in Four‐Junction Polymers

The various end‐to‐end distances of four‐junction polymers are investigated. The sizes of the different kinds of equal length branches and the backbone of two different polymers, with either nine or eleven branches, are estimated by means of both renormalization‐group and MC calculations. The comparisons of first‐order ε = 4 − d predictions with the MC results are satisfactory. The same trends are present in both techniques. The excluded‐volume interactions from additional branches further expand the various parts of the chains so that internal branches are larger than external ones. The branch ratios in the eleven‐branch case are expanded even more than the corresponding ratios of the nine‐branch polymer.

     

Pinning frequencies of the collective modes in alpha-uranium

Uranium is the only known element that features a charge-density wave (CDW) and superconductivity. We report a comparison of the specific heat of single-crystal and polycrystalline alpha-uranium. In the single crystal we find excess contributions to the heat capacity at 41 K, 38 K, and 23 K, with a Debye temperature ThetaD = 265 K. In the polycrystalline sample the heat capacity curve is thermally broadened (ThetaD = 184 K), but no excess heat capacity was observed. The excess heat capacity Cphi (taken as the difference between the single-crystal and polycrystal heat capacities) is well described in terms of collective-mode excitations above their respective pinning frequencies. This attribution is represented by a modified Debye spectrum with two cutoff frequencies, a pinning frequency V0 for the pinned CDW (due to grain boundaries in the polycrystal), and a normal Debye acoustic frequency occurring in the single crystal.