Gemini spectra of 12000K white dwarf stars

We report signal-to-noise ratio SNR ~ 100 optical spectra for four DA white dwarf stars acquired with the GMOS spectrograph of the 8m Gemini north telescope. These stars have 18<g<19 and are around Teff ~ 12000 K, were the hydrogen lines are close to maximum. Our purpose is to test if the effective temperatures and surface gravities derived from the relatively low signal-to-noise ratio ( ~ 21) optical spectra acquired by the Sloan Digital Sky Survey through model atmosphere fitting are trustworthy. Our spectra range from 3800A to 6000A, therefore including H beta to H9. The H8 line was only marginally present in the SDSS spectra, but is crucial to determine the gravity. When we compare the values published by Kleinman et al. (2004) and Eisenstein et al. (2006) with our line-profile (LPT) fits, the average differences are: Delta Teff ~ 320 K, systematically lower in SDSS, and Delta log g ~ 0.24 dex, systematically larger in SDSS. The correlation between gravity and effective temperature can only be broken at wavelengths bluer than 3800 A. The uncertainties in Teff are 60% larger, and in log g larger by a factor of 4, than the Kleinman et al. (2004) and Eisenstein et al. (2006) internal uncertainties.Comment: 11 pages and 8 figure

A technical note on the phase transformation in furnace container material after a periodic thermo-chemical treatment

The aim of this work is to investigate the metallurgical changes in the wall of cylindrical containers, fabricated by welding from AISI 310 steel, used in the thermal and chemical treatment of spindle chains for the automotive industry, for an in-service period of over 1000 h. In order to identify the phases originated during this in-service period, several etchants were used in the structural study, together with X-ray diffraction and 57Fe Mössbauer spectroscopy analysis. The metallographic technique demonstrates some limitations in the complete identification of the phases produced in the wall of the containers. The structure of the wall of the containers, after the referred to working period, is composed of an austenitic matrix, whose grain size is about 212 and 238 [mu]m, near the internal and external faces of the wall, respectively. These show numerous precipitates inside the grains and at the grain boundaries. The density of the precipitates decreases from the internal to the external surface. The precipitates are nitrides (Cr, Mo)12 (Fe,Ni)8-x N4-z near the internal surface, and carbides (Cr, Fe, Mo)23C6 on the other zones of the wall.http://www.sciencedirect.com/science/article/B6TGJ-4502Y49-G/1/4e6ae31d16e053b40c961bebbfda1e0

Debye temperature of disordered bcc-Fe-Cr alloys

Debye temperature, TD, of Fe100-xCrx disordered alloys with 0<x<99.9 was determined from the temperature dependence of the centre shift of 57Fe Mossbauer spectra recorded in the temperature range of 80-300K. Its compositional dependence shows an interesting non-monotonous behaviour. For 0<x<~45 as well as for ~75<x<~95 the Debye temperature is enhanced relative to its value of a metallic iron, and at x=~3 there is a local maximum having a relative height of ~12% compared to a pure iron. For ~45~95 the Debye temperature is smaller than the one for the metallic iron, with a local minimum at x=~55 at which the relative decrease of TD amounts to ~12%. The first maximum coincides quite well with that found for the spin-waves stiffness coefficient, D0, while the pretty steep decrease observed for x>~95 which is indicative of a decoupling of the probe Fe atoms from the underlying chromium matrix is likely related to the spin-density waves which constitute the magnetic structure of chromium in that interval of composition. The harmonic force constant calculated from the Debye temperature of the least Fe-concentrated alloy (x>99.9) amounts to only 23% of the one characteristic of a pure chromium.Comment: 15 pages, 7 figures, 26 reference

Study of Alpha-Sigma Phase Transformation in Mechanically Alloyed Fe-Cr-Sn Alloys

The solubility of tin is significantly extended by mechanical alloying in near equiatomic Fe-Cr alloys. The influences of Sn concentration and of grain size on the kinetics of formation of the sigma-phase have been studied using different techniques. The sigma-phase formation is much faster for as-milled alloys than it is for conventional alloys. The sigma-phase formation rate decreases with the increase of Sn concentration in alloys with nanometer-sized grains as it does in coarse-grained alloys. The mechanisms which are responsible for the slowing-down of the alpha-sigma transformation are different in both kinds of alloys

Sigma-phase in Fe-Cr and Fe-V alloy systems and its physical properties

A review is presented on physical properties of the sigma-phase in Fe-Cr and Fe-V alloy systems as revealed both with experimental -- mostly with the Mossbauer spectroscopy -- and theoretical methods. In particular, the following questions relevant to the issue have been addressed: identification of sigma and determination of its structural properties, kinetics of alpha-to-sigma and sigma-to-alpha phase transformations, Debye temperature and Fe-partial phonon density of states, Curie temperature and magnetization, hyperfine fields, isomer shifts and electric field gradients.Comment: 26 pages, 23 figures and 83 reference

SURGERY BY INFRARED VISION

This paper is about the development, uses and advantages of infrared thermography. Its principles had already been used by old civilizations as a manner of diseases diagnosis. The discovery of the infrared waves and its heating power happened on 1800, but its use in modern Medicine as a diagnosis method was only possible because of the scientific and technological development demanded by the Great Wars, in the 20th century. Here the authors present some news and promising surgery applications