Atomistic Simulation of Crystal Change and Carbon Diffusion during Drawing of Pearlitic Steel Nano-sizedWire

Wire drawing is an efficient material processing technique for metals. Pearlitic steel is recognized as one of the most reliable and strong wire materials for industrial use. The microstructure of the pearlite phase, however, is quite complicated, with a lamellar structure containing alternating nanometer-thick layers of ferrite and cementite. In the present study, three-dimensional wire drawing models for pearlitic steel, in which a cementite layer occupies one half or one third of the wire cross section, are used in molecular dynamics simulations of the Fe-C system based on a pairwise potential. The results indicate that a body-centered cubic to face-centered cubic phase transition occurs in the ferrite layer during drawing. It is found that compressive hydrostatic stress is required to drive this phase transformation. The phase transition is followed by the formation of dislocations and grain boundaries. Cementite has an orthorhombic crystal structure and is more difficult to plastically deform than pure ferrite. During drawing of a pearlite wire, the large deformation of the ferrite layer compensates for the poor deformability of the cementite layer. The carbon content is important in pearlitic steel because carbon atoms can diffuse through all phases. As a indicator of the amount of carbon diffusion, the mean square displacement of carbon atoms is used. It is found that diffusion perpendicular to the ferrite/cementite interface tends to take place suddenly, but the total amount of diffusion is still less than that in the parallel direction

Canonical information flow decomposition among neural structure subsets

Partial directed coherence (PDC) and directed coherence (DC) which describe complementary aspects of the directed information flow between pairs of univariate components that belong to a vector of simultaneously observed time series have recently been generalized as bPDC/bDC respectively to portray the relationship between subsets of component vectors (Takahashi, 2009; Faes and Nollo, 2013). This generalization is specially important for neuroscience applications as one often wishes to address the link between the set of time series from an observed ROI (region of interest) with respect to series from some other physiologically relevant ROI. bPDC/bDC are limited, however, in that several time series within a given subset may be irrelevant or may even interact opposingly with respect to one another leading to interpretation difficulties. To address this, we propose an alternative measure, termed cPDC/cDC, employing canonical decomposition to reveal the main frequency domain modes of interaction between the vector subsets. We also show bPDC/bDC and cPDC/cDC are related and possess mutual information rate interpretations. Numerical examples and a real data set illustrate the concepts. The present contribution provides what is seemingly the first canonical decomposition of information flow in the frequency domain

Optical to Near-IR Spectrum of a Massive Evolved Galaxy at z = 1.26

We present the optical to near-infrared (IR) spectrum of the galaxy TSPS J1329-0957, a red and bright member of the class of extremely red objects (EROs) at z = 1.26. This galaxy was found in the course of the Tokyo-Stromlo Photometry Survey (TSPS) which we are conducting in the southern sky. The spectroscopic observations were carried out with the Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near Infra-Red Spectrograph (GNIRS) mounted on the Gemini-South telescope. The wide wavelength coverage of 0.6 - 2.3 um provides useful clues as to the nature of EROs while most published spectra are limited to a narrower spectral range which is dictated by the need for efficient redshift determination in a large survey. We compare our spectrum with several optical composite spectra obtained in recent large surveys, and with stellar population synthesis models. The effectiveness of using near-IR broad-band data, instead of the spectral data, in deriving the galaxy properties are also investigated. We find that TSPS J1329-0957 formed when the universe was 2 - 3 Gyr old, and subsequently evolved passively to become one of the most massive galaxies found in the z = 1 - 2 universe. Its early type and estimated stellar mass of M* = 10^{11.5} Msun clearly point to this galaxy being a direct ancestor of the brightest elliptical and spheroidal galaxies in the local universe.Comment: 18 pages, 4 figures. Accepted for publication in Ap

Diffuse galactic light in the field of the translucent high galactic latitude cloud MBM32

We have conducted B-, g-, V-, and R-band imaging in a 45′ × 40′ field containing part of the high Galactic latitude translucent cloud MBM32, and correlated the intensity of diffuse optical light S ν(λ) with that of 100 μm emission S ν(100 μm).

Implications from the optical to UV flux ratio of FeII emission in quasars

We investigate FeII emission in Broad Line Region (BLR) of AGNs by analyzing the FeII(UV), FeII(4570) and MgII emission lines in 884 quasars in the Sloan Digital Sky Survey (SDSS) Quasar catalog in a redshift range of 0.727 < z < 0.804. FeII(4570)/FeII(UV) is used to infer the column density of FeII-emitting clouds and explore the excitation mechanism of FeII emission lines. As suggested before in various works, the classical photoionization models fail to account for FeII(4570)/FeII(UV) by a factor of 10, which may suggest anisotropy of UV FeII emission; otherwise, an alternative heating mechanism like shock is working. The column density distribution derived from FeII(4570)/FeII(UV) indicates that radiation pressure plays an important role in BLR gas dynamics. We find a positive correlation between FeII(4570)/FeII(UV) and the Eddington ratio. We also find that almost all FeII-emitting clouds are to be under super-Eddington conditions unless ionizing photon fraction is much smaller than that previously suggested. Finally we propose a physical interpretation of a striking set of correlations between various emission-line properties, known as ``Eigenvector 1''.Comment: 10 pages, 10 figures, accepted for publication in MNRA

Supernova dust for the extinction law in a young infrared galaxy at z = 1

We apply the supernova(SN) extinction curves to reproduce the observed properties of SST J1604+4304 which is a young infrared (IR) galaxy at z = 1. The SN extinction curves used in this work were obtained from models of unmixed ejecta of type II supernovae(SNe II) for the Salpeter initial mass function (IMF) with a mass range from 8 to 30 M_sun or 8 to 40 M_sun. The effect of dust distributions on the attenuation of starlight is investigated by performing the chi-square fitting method against various dust distributions. These are the commonly used uniform dust screen, the clumpy dust screen, and the internal dust geometry. We add to these geometries three scattering properties, namely, no-scattering, isotropic scattering, and forward-only scattering. Judging from the chi-square values, we find that the uniform screen models with any scattering property provide good approximations to the real dust geometry. Internal dust is inefficient to attenuate starlight and thus cannot be the dominant source of the extinction. We show that the SN extinction curves reproduce the data of SST J1604+4304 comparable to or better than the Calzetti extinction curve. The Milky Way extinction curve is not in satisfactory agreement with the data unless several dusty clumps are in the line of sight. This trend may be explained by the abundance of SN-origin dust in these galaxies; SN dust is the most abundant in the young IR galaxy at z = 1, abundant in local starbursts, and less abundant in the Galaxy. If dust in SST J1604+4304 is dominated by SN dust, the dust production rate is about 0.1 M_sun per SN.Comment: 12 pages, 8 figures, 1 tabl

AKARI near- and mid-infrared spectroscopy of APM 08279+5255 at z=3.91

We present rest-frame optical/near-infrared spectra of the gravitationally lense d quasar APM 08279+5255 at $z=3.91$ that has been taken using the Infrared Camera (IRC) onboard the AKARI infrared satellite. The observed continuum consists of two components; a power-law component dominating optical wavelengths which is the direct light from the central source and thermal emission dominating near-infrared wavelengths which is attributed to the emission from hot dust in the circumnuclear region. The thermal emission well represents optically thick emission by hot dust at T ~ 1300K with tau(2micron)> 2 and apparent mass, M(hot) >10 M_sun. Thus, our observations directly detected the optically thick region of hot dust in APM 08279+5255. HI recombination lines of H_alpha(0.656micron), Pa_alpha(1.875micron), and Pa_beta(1.282micron) are clearly detected at 3.2, 6.3, and 9.3 micron. Simulations with the photoionization models suggest that APM 08279+5255 has BLR(Broad Line Region) clouds characterized by log n_{H} ~ 12- 14 for the gas density, log U ~ -2 - -6$for the ionization parameter, and E(B-V) ~ 0.3-0.6$for the broad line region. Thus, optically thick emission of hot dust support an idea on non-spherical distribution of dust near the central source, consistent with the Active Galactic Nuclei model with the dust torus. The temperature of hot dust and flux ratios of these HI lines are similar to those observed in low-redshift quasars. There are significant time-variations in the HI lines, which are probably caused by variations in the brightness of the central source.Comment: ApJ, in pres