Research and development program on magnetic electrical conductor, electrical insulation, and bore seal materials - Electrical conductor and electrical insulation materials topical report

Electrical, mechanical, and thermo-physical properties of conductor and insulation materials for application to advanced space electric power system

Radio Emission Associated with Ultraluminous X-ray Sources in the Galaxy Merger NGC 3256

We present new 6, 3.6, and 2 cm VLA radio observations of the nearby merger system NGC 3256, with resolutions of ~100 pc, which reveal compact radio sources embedded in more diffuse emission at all three wavelengths. The two radio nuclei are partially resolved, but the two dominant compact sources that remain coincide with the two most powerful compact Ultraluminous X-ray sources (ULXs) recently reported by Lira et al. The radio/X-ray ratios for these two sources are too high by factors of >100-1000 to be normal X-ray binaries. However, their radio and X-ray powers and ratios are consistent with low-luminosity active galactic nuclei (LLAGNs), and optical emission lines suggest the presence of a nuclear disk around the northern nucleus. If the two nuclear ULXs are LLAGNs, their associated black holes are separated by only \~1kpc, about 6 times closer to one another than those found recently in the merger galaxy NGC 6240. A third ULX on the outskirts of the merger is also a radio source, and probably is a collection of supernova remnants. The remaining ULXs are not coincident with any source of compact radio emission, and are consistent with expectations for beamed X-ray binaries or intermediate-mass black holes.Comment: Accepted for ApJ (10 pages, 5 figures

A reassessment of Antarctic plateau reactive nitrogen based on ANTCI 2003 airborne and ground based measurements

The first airborne measurements of nitric oxide (NO) on the Antarctic plateau have demonstrated that the previously reported elevated levels of this species extend well beyond the immediate vicinity of South Pole. Although the current database is still relatively weak and critical laboratory experiments are still needed, the findings here suggest that the chemical uniqueness of the plateau may be substantially greater than first reported. For example, South Pole ground-based findings have provided new evidence showing that the dominant process driving the release of nitrogen from the snowpack during the spring/summer season (post-depositional loss) is photochemical in nature with evaporative processes playing a lesser role. There is also new evidence suggesting that nitrogen, in the form of nitrate, may undergo multiple recycling within a given photochemical season. Speculation here is that this may be a unique property of the plateau and much related to its having persistent cold temperatures even during summer. These conditions promote the efficient adsorption of molecules like HNO3 (and very likely HO2NO2) onto snow-pack surface ice where we have hypothesized enhanced photochemical processing can occur, leading to the efficient release of NOx to the atmosphere. In addition, to these process-oriented tentative conclusions, the findings from the airborne studies, in conjunction with modeling exercises suggest a new paradigm for the plateau atmosphere. The near-surface atmosphere over this massive region can be viewed as serving as much more than a temporary reservoir or holding tank for imported chemical species. It defines an immense atmospheric chemical reactor which is capable of modifying the chemical characteristics of select atmospheric constituents. This reactor has most likely been in place over geological time, and may have led to the chemical modulation of some trace species now found in ice cores. Reactive nitrogen has played a critical role in both establishing and in maintaining this reactor. © 2007 Elsevier Ltd. All rights reserved

Исследование влияния давления прессования на дефектное состояние ферритовой керамики

Объектом исследования настоящей работы является LiTiZn ферритовая керамика марки 3СЧ18, спрессованная при различных давлениях прессования. Целью работы являются исследования влияния давления прессования на физические и магнитные характеристики образцов LiTiZn ферритовой керамики, изготовленных и спеченных по классической керамической технологии в лабораторных условиях. В процессе исследования были проведены расчеты плотности и пористости ферритовой керамики, спрессованной при различных режимах давления. Был определен средний размер зерен образцов. Были проведены исследования температурных зависимостей начальной магнитной проницаемости исследуемых образцов.В результате исследования было показано, что выбранные режимы давления прессования оказывают незначительное влияние на микроструктуру.The object of the present study is LiTiZn ferrite ceramics of grade 3CH18, pressed at various pressing regimes. The aim of the work is investigation the effect of pressing regimes on the physical and magnetic characteristics of LiTiZn samples of ferrite ceramics, which was made and sintered using classical ceramic technology under laboratory conditions. In the course of the study, the density and porosity of ferrite ceramics, which was compacted at various pressure regimes, were calculated. The average grain size of the samples was determined. The temperature dependences of the initial permeability of the test samples were studied. As a result of the study, it was shown that the selected pressing regimes had little effect on the microstructure

A study of boundary layer behavior associated with high NO concentrations at the South Pole using a minisodar, tether balloon, and sonic anemometer, Atmos

Abstract This paper focuses on the use of an acoustic sounder, or sodar, during the 2003 Antarctic Tropospheric Chemistry Investigation (ANTCI), to document the behavior of very shallow (o50 m) stable boundary layers thought to be one of the critical factors for explaining the very high levels of nitric oxide (NO) found in past field experiments at the South Pole. The use of a tethered balloon, profiling wind, temperature, NO, and ozone provided for a detailed interpretation of sodar data for the period 12-30 December 2003. For the same period, sonic anemometer 2-m turbulence measurements, averaged to 0.5 h, linked surface processes to the evolution of the boundary layer in response to changing radiative balance and synoptic weather changes. A mixing-layer detection method was developed and applied to half-hour average sodar amplitude profiles for the period 23 November-30 December 2003. These data also allowed for testing of simple diagnostic equations for the mixing-layer depth as well as estimates of vertical diffusion rates under stable conditions, the latter being important for the effective depth of the mixing layer vis-a`-vis the nonlinear NO chemistry postulated from earlier analyses. With the extended sampling period, two sub-seasonal regimes were examined: (1) a late-December period, with the full suite of supporting measurements, where the earlier results that shallow mixing layers associated with light winds and strong surface stability can be among the dominant factors leading to high NO levels were repeated and (2) a late November period that revealed additional complexities with very high NO concentrations appearing at times in concert with higher winds, weaker surface stability, and deeper mixing layers. The latter results are only consistent with a more complicated picture of how NO can build to very high levels that involves invoking the previously expressed dependence of elevated NO levels on nonlinear NO x (NO x ¼ NO+NO 2 ) chemistry, greater fluxes of NO x from the snowpack than previously observed at the South Pole, and the potential for enhanced NO x accumulation effects involving air parcels draining off the high platea

Quasi-Homogeneous Thermodynamics and Black Holes

We propose a generalized thermodynamics in which quasi-homogeneity of the thermodynamic potentials plays a fundamental role. This thermodynamic formalism arises from a generalization of the approach presented in paper [1], and it is based on the requirement that quasi-homogeneity is a non-trivial symmetry for the Pfaffian form $\delta Q_{rev}$. It is shown that quasi-homogeneous thermodynamics fits the thermodynamic features of at least some self-gravitating systems. We analyze how quasi-homogeneous thermodynamics is suggested by black hole thermodynamics. Then, some existing results involving self-gravitating systems are also shortly discussed in the light of this thermodynamic framework. The consequences of the lack of extensivity are also recalled. We show that generalized Gibbs-Duhem equations arise as a consequence of quasi-homogeneity of the thermodynamic potentials. An heuristic link between this generalized thermodynamic formalism and the thermodynamic limit is also discussed.Comment: 39 pages, uses RevteX. Published version (minor changes w.r.t. the original one

Confirmation of Cylindrical Perfect Invisibility Cloak Using Fourier-Bessel Analysis

A cylindrical wave expansion method is developed to obtain the scattering field for an ideal two-dimensional cylindrical invisibility cloak. A near-ideal model of the invisibility cloak is set up to solve the boundary problem at the inner boundary of the cloak shell. We confirm that a cloak with the ideal material parameters is a perfect invisibility cloak by systematically studying the change of the scattering coefficients from the near-ideal case to the ideal one. However, due to the slow convergence of the zero$^{th}$ order scattering coefficients, a tiny perturbation on the cloak would induce a noticeable field scattering and penetration.Comment: 10 pages, 3 figure

Relative sound localisation abilities in human listeners

Spatial acuity varies with sound-source azimuth, signal-to-noise ratio, and the spectral characteristics of the sound source. Here, the spatial localisation abilities of listeners were assessed using a relative localisation task. This task tested localisation ability at fixed angular separations throughout space using a two-alternative forced-choice design across a variety of listening conditions. Subjects were required to determine whether a target sound originated to the left or right of a preceding reference in the presence of a multi-source noise background. Experiment 1 demonstrated that subjects' ability to determine the relative location of two sources declined with less favourable signal-to-noise ratios and at peripheral locations. Experiment 2 assessed performance with both broadband and spectrally restricted stimuli designed to limit localisation cues to predominantly interaural level differences or interaural timing differences (ITDs). Predictions generated from topographic, modified topographic, and two-channel models of sound localisation suggest that for low-pass stimuli, where ITD cues were dominant, the two-channel model provides an adequate description of the experimental data, whereas for broadband and high frequency bandpass stimuli none of the models was able to fully account for performance. Experiment 3 demonstrated that relative localisation performance was uninfluenced by shifts in gaze direction