Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 1: Ejecta production and orbital dynamics in cislunar space

Particulate matter possessing lunar escape velocity sufficient to enhance the cislunar meteroid flux was investigated. While the interplanetary flux was extensively studied, lunar ejecta created by the impact of this material on the lunar surface is only now being studied. Two recently reported flux models are employed to calculate the total mass impacting the lunar surface due to sporadic meteor flux. There is ample evidence to support the contention that the sporadic interplanetary meteoroid flux enhances the meteroid flux of cislunar space through the creation of micron and submicron lunar ejecta with lunar escape velocity

Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 2: Ejecta dynamics and enhanced lifetimes in the Earth's magnetosphere

Extensive studies were conducted concerning the indivdual mass, temporal and positional distribution of micron and submicron lunar ejecta existing in the Earth-Moon gravitational sphere of influence. Initial results show a direct correlation between the position of the Moon, relative to the Earth, and the percentage of lunar ejecta leaving the Moon and intercepting the magnetosphere of the Earth at the magnetopause surface. It is seen that the Lorentz Force dominates all other forces, thus suggesting that submicron dust particles might possibly be magnetically trapped in the well known radiation zones

On the Form Factor for the Unitary Group

We study the combinatorics of the contributions to the form factor of the group U(N) in the large $N$ limit. This relates to questions about semiclassical contributions to the form factor of quantum systems described by the unitary ensemble.Comment: 35 page

Simulation of truncated normal variables

We provide in this paper simulation algorithms for one-sided and two-sided truncated normal distributions. These algorithms are then used to simulate multivariate normal variables with restricted parameter space for any covariance structure.Comment: This 1992 paper appeared in 1995 in Statistics and Computing and the gist of it is contained in Monte Carlo Statistical Methods (2004), but I receive weekly requests for reprints so here it is

Effect of anisotropy on universal transport in unconventional superconductors

We investigate the universal electronic transport for a mixed $d_{x^2-y^2}$+s-wave superconductor in the presence of an anisotropic elliptical Fermi surface. Similar to the universal low-temperature transport predicted in a $d_{x^2-y^2}$-wave superconductor with a circular Fermi surface, anisotropic universal features are found in the low-temperature microwave conductivity, and thermal conductivity in the anisotropic system. The effects of anisotropy on the penetration depth, impurity induced $T_c$ suppression, and the zero-frequency density of states are also considered. While a small amount of anisotropy can lead to a strong suppression of the effective scattering rate and hence the density of states at zero frequency, experimental data suggests that large effects are restored by a negative $s$-component gap admixture.Comment: 8 page

Kaon decay interferometry as meson dynamics probes

We discuss the time dependent interferences between $K_L$ and $K_S$ in the decays in $3\pi$ and $\pi\pi\gamma$, to be studied at interferometry machines such as the $\phi$-factory and LEAR. We emphasize the possibilities and the advantages of using interferences, in comparison with width measurements, to obtain information both on $CP$ conserving and $CP$ violating amplitudes. Comparison with present data and suggestions for future experiments are made.Comment: 15 pages, in RevTex, Report INFNNA-IV-93-31, UTS-DFT-93-2

Tweed in Martensites: A Potential New Spin Glass

We've been studying the ``tweed'' precursors above the martensitic transition in shape--memory alloys. These characteristic cross--hatched modulations occur for hundreds of degrees above the first--order shape--changing transition. Our two--dimensional model for this transition, in the limit of infinite elastic anisotropy, can be mapped onto a spin--glass Hamiltonian in a random field. We suggest that the tweed precursors are a direct analogy of the spin--glass phase. The tweed is intermediate between the high--temperature cubic phase and the low--temperature martensitic phase in the same way as the spin--glass phase can be intermediate between ferromagnet and antiferromagnet.Comment: 18 pages and four figures (included

The a-axis optical conductivity of detwinned ortho-II YBa_2Cu_3O_6.50

The a-axis optical properties of a detwinned single crystal of YBa_2Cu_3O_6.50 in the ortho II phase (Ortho II Y123, T_c= 59 K) were determined from reflectance data over a wide frequency range (70 - 42 000 cm^-1) for nine temperature values between 28 and 295 K. Above 200 K the spectra are dominated by a broad background of scattering that extends to 1 eV. Below 200 K a shoulder in the reflectance appears and signals the onset of scattering at 400 cm^-1. In this temperature range we also observe a peak in the optical conductivity at 177 cm^-1. Below 59 K, the superconducting transition temperature, the spectra change dramatically with the appearance of the superconducting condensate. Its spectral weight is consistent, to within experimental error, with the Ferrell-Glover-Tinkham (FGT) sum rule. We also compare our data with magnetic neutron scattering on samples from the same source that show a strong resonance at 31 meV. We find that the scattering rates can be modeled as the combined effect of the neutron resonance and a bosonic background in the presence of a density of states with a pseudogap. The model shows that the decreasing amplitude of the neutron resonance with temperature is compensated for by an increasing of the bosonic background yielding a net temperature independent scattering rate at high frequencies. This is in agreement with the experiments.Comment: 13 pages 16 figure

Measuring surface-area-to-volume ratios in soft porous materials using laser-polarized xenon interphase exchange NMR

We demonstrate a minimally invasive nuclear magnetic resonance (NMR) technique that enables determination of the surface-area-to-volume ratio (S/V) of soft porous materials from measurements of the diffusive exchange of laser-polarized 129Xe between gas in the pore space and 129Xe dissolved in the solid phase. We apply this NMR technique to porous polymer samples and find approximate agreement with destructive stereological measurements of S/V obtained with optical confocal microscopy. Potential applications of laser-polarized xenon interphase exchange NMR include measurements of in vivo lung function in humans and characterization of gas chromatography columns.Comment: 14 pages of text, 4 figure

Infrared response of ordered polarons in layered perovskites

We report on the infrared absorption spectra of three oxides where charged superlattices have been recently observed in diffraction experiments. In La$_{1.67}$Sr$_{0.33}$NiO$_4$, polaron localization is found to suppress the low-energy conductivity through the opening of a gap and to split the $E_{2u}$-$A_{2u}$ vibrational manifold of the oxygen octahedra. Similar effects are detected in Sr$_{1.5}$La$_{0.5}$MnO$_4$ and in La$_2$NiO$_{4+y}$, with peculiar differences related to the type of charge ordering.Comment: File latex, 11 p. + 3 Figures, to appear on Phys. Rev. B (Rapid Commun.), 1 Oct. 1996. The figures will be faxed upon request. E-mail:[email protected] Fax: +39-6-446315