Evidence for two discrete sources of 2f1-f2 distortion-product otoacoustic emission in rabbit. II: Differential physiological vulnerability.

In a previous report, it was shown that, in normal rabbit ears, the amplitude and phase of 2f1-f2 distortion-product otoacoustic emissions (DPOAEs) elicited by low-level (< 60-70 dB SPL) stimuli display a differential dependence on stimulus parameters to those evoked by high-level (> 60-70 dB SPL) stimuli, indicating differences in the underlying generation mechanisms. In the present study, the physiological vulnerability of DPOAEs in each of the two 2f1-f2 DPOAE-response regions identified on the basis of differential parametric properties, was characterized. Thus emissions evoked using stimulus levels from 45-75 dB SPL were measured over time upon: (1) induction of lethal anoxia, (2) acute injection of ethacrynic acid, and (3) acute injection of ethacrynic acid 2 h after a single administration of gentamicin. The DPOAEs evoked by low-level stimuli (45 dB SPL) were abolished within 3-4 min of induction of anoxia, whereas DPOAEs evoked by high-level stimuli (75 dB SPL) were unchanged in this period. The high-level emissions decreased with a complex time course postmortem, and demonstrated behaviors, including evidence of susceptibility to fatigue, suggesting a dependence upon a cochlear energy supply. Low-level DPOAEs could be temporarily abolished, with complete recovery, by an acute administration of ethacrynic acid that had little effect on high-level DPOAEs. Treatment with the gentamicin and ethacrynic-acid combination, which would be expected to produce widespread hair-cell damage, eliminated low-level DPOAEs, and greatly reduced high-level emissions. In combination with previously published data, these findings strongly suggest that low- and high-level 2f1-f2 DPOAEs arise from discrete sources. The data are consistent with the proposal that the low-level DPOAE source is an active, micromechanical process, but suggest that the proposed origin of high-level DPOAEs exclusively in the passive macromechanics of the cochlear partition may be incorrect. The elimination of both low- and high-level DPOAEs revealed the presence of a third, residual 2f1-f2 DPOAE component, approximately 75-80 dB below the stimulus-tone levels, that may reflect the true passive-distortion response of the cochlea.     

Multiscale modeling of submonolayer growth for Fe/Mo (110)

We use a multiscale approach to study a lattice-gas model of submonolayer growth of Fe/Mo (110) by Molecular Beam Epitaxy. To begin with, we construct a two-dimensional lattice-gas model of the Fe/Mo (110) system based on our first-principles calculations of the monomer diffusion barrier and adatom-adatom interactions. The model is investigated by equilibrium Monte Carlo (MC) simulations to compute the diffusion coefficients of Fe islands of different sizes. These diffusion coefficients are used as input to the coarse-grained kinetic rate equation (KRE) approach. We also evaluate effects of the range of Fe-Fe interaction, restriction of interaction to third nearest neighbors allowed to develop feasible atomistic kinetic Monte Carlo (KMC) model. We calculate time evolution of the island size distributions by both KMC and KRE methods and find good agreement between the two methods.     

Magnetic circular dichroism of the first spin-forbidden transition in 2[Cr(en)3Cl3] . KCl . 6H2O

The longitudinal Zeeman effect of the ² E ←⁴ A ₂ transition of the Cr⁺³ ion in single crystals of 2[Cr(en)₃Cl₃] . KCl . 6H₂O has been measured using circularly polarized light as a function of magnetic field strength between 0 and 160 kgauss at ～80 K. The g factor for the ground state was determined to be g _‖(⁴ A ₂) = 2·01±0·05, in agreement with the E.S.R.-determined value. The ratio between the excited state g values and that of the ground state was determined; using the value g _‖(⁴ A ₂) = 1·99, the g factors g _‖(2) = 2·61±0·04 and g _‖() = 1·47±0·04 were obtained.     

Translation–rotation coupling in the self–diffusion of fluids: molecular dynamic investigation and a generalized exponential approach

Detailed molecular dynamics simulations are carried out to investigate the translation–rotation coupling in linear molecules. We calculated the moment of inertia ratio dependence of the self–diffusion coefficients D, the so–called dynamic isotope effect on the self–diffusion, in pure fluids. Our model systems consist of linear homonuclear pseudo–triatomic rigid molecules for three different molecular sizes over a wide range of density for a given temperature. For a compact representation of our results an exponential approach is employed, which demonstrates a strong translation–rotation coupling on the self–diffusion coefficient in a linear molecule. We find as a main result that in contrast to the low density behaviour at high densities the change of the rotation–translation coupling as a function of the moments of inertia is quite similar for all investigated molecules and we could explain this finding by a careful inspection of the corresponding velocity autocorrelation functions. Finally we present a comparison of experimental data for 20 neat molecular liquids and the corresponding theoretical predictions based on our findings for linear molecules. The good overall agreement indicates that our approach can be generalized and is therefore not only a compact representation of the calculated data but has also large predictive capabilities.     

Characterization of rapidly solidified powder of high-speed steel

Ionization and excitation cross sections as well as electron-energy spectra and stopping powers of the alkali metal atoms Li, Na, K, and Rb colliding with antiprotons were calculated using a time-dependent channel-coupling approach. An impact-energy range from 0.25 to 4000 keV was considered. The target atoms are treated as effective one-electron systems using a model potential. The results are compared with calculated cross sections for antiproton-hydrogen atom collisions.     

Lie algebroid morphisms, Poisson sigma models, and off-shell closed gauge symmetries

Chern–Simons (CS) gauge theories in three dimensions and the Poisson sigma model (PSM) in two dimensions are examples of the same theory, if their field equations are interpreted as morphisms of Lie algebroids and their symmetries (on-shell) as homotopies of such morphisms. We point out that the (off-shell) gauge symmetries of the PSM in the literature are not globally well defined for non-parallelizable Poisson manifolds and propose a covariant definition of the off-shell gauge symmetries as left action of some finite-dimensional Lie algebroid.

Our approach allows us to avoid complications arising in the infinite-dimensional super-geometry of the BV- and AKSZ-formalism. This preprint is a starting point in a series of papers meant to introduce Yang–Mills type gauge theories of Lie algebroids, which include the standard YM theory, gerbes, and the PSM.     

Optical properties of Zn0.5Cd0.5Se thin films grown on InP by molecular beam epitaxy

We report photoluminescence (PL) and reflectivity measurements of Zn_0.5Cd_0.5Se epilayers grown by molecular beam epitaxy on InP substrates. The low-temperature PL spectra are dominated by asymmetric lines, which can be deconvoluted into two Gaussian peaks with a separation of ∼8 meV. The behavior of these peaks is studied as a function of excitation intensity and temperature, revealing that these are free exciton (FE) and bound exciton emission lines. Two lower energy emission lines are also observed and assigned to the first and second longitudinal optical phonon replicas of the FE emission. The temperature dependence of the intensity, line width, and energy of the dominant emission lines are described by an Arrhenius plot, a Bose-Einstein type relationship, Varshni's and Bose-Einstein equations, respectively.