Spectral properties, generation order parameters and luminosities for spin-powered X-ray pulsars

We show the spectral properties of 15 spin-powered X-ray pulsars, and the correlation between the average power-law photon index and spin-down rate. Generation order parameters (GOPs) based on polar-cap models are introduced to characterize the X-ray pulsars. We calculate three definitions of generation order parameters due to the different effects of magnetic and electric fields on photon absorption during cascade processes, and study the relations between the GOPs and spectral properties of X-ray pulsars. There exists a possible correlation between the photon index and GOP in our pulsar sample. Furthermore, we present a method due to the concept of GOPs to estimate the non-thermal X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated in the context of our polar-cap accelerator model which is well consistent with the most observed X-ray pulsar data. The ratio between X-ray luminosity estimated by our method and the pulsar's spin-down power is well consistent with the $L_{\rm X}\sim 10^{-3}L_{\rm sd}$ feature.Comment: 20 pages, 8 figures, 1 table, revised version for the publication in Ap

Effect of Native Defects on Optical Properties of InxGa1-xN Alloys

The energy position of the optical absorption edge and the free carrier populations in InxGa1-xN ternary alloys can be controlled using high energy 4He+ irradiation. The blue shift of the absorption edge after irradiation in In-rich material (x > 0.34) is attributed to the band-filling effect (Burstein-Moss shift) due to the native donors introduced by the irradiation. In Ga-rich material, optical absorption measurements show that the irradiation-introduced native defects are inside the bandgap, where they are incorporated as acceptors. The observed irradiation-produced changes in the optical absorption edge and the carrier populations in InxGa1-xN are in excellent agreement with the predictions of the amphoteric defect model

Extrinsic Curvature Embedding Diagrams

Embedding diagrams have been used extensively to visualize the properties of curved space in Relativity. We introduce a new kind of embedding diagram based on the {\it extrinsic} curvature (instead of the intrinsic curvature). Such an extrinsic curvature embedding diagram, when used together with the usual kind of intrinsic curvature embedding diagram, carries the information of how a surface is {\it embedded} in the higher dimensional curved space. Simple examples are given to illustrate the idea.Comment: 22 pages, 4 figure

The Low-level Spectrum of the W3W_3 String

We investigate the spectrum of physical states in the $W_3$ string theory, up to level 2 for a multi-scalar string, and up to level 4 for the two-scalar string. The (open) $W_3$ string has a photon as its only massless state. By using screening charges to study the null physical states in the two-scalar $W_3$ string, we are able to learn about the gauge symmetries of the states in the multi-scalar $W_3$ string.Comment: 31 pages, Plain Tex, CTP TAMU-70/92, Goteborg ITP 92-43, Imperial/TP/91-92/22, KCL-TH-92-

Analysis of the spectral function of Nd1.85Ce0.15CuO4, obtained by angle resolved photoemission spectroscopy

Samples of Nd(2-x)Ce(x)CuO(4), an electron-doped high temperature superconducting cuprate (HTSC), near optimal doping at x = 0.155 were measured via angle resolved photoemission (ARPES). We report a renormalization feature in the self energy ("kink") in the band dispersion at 50 - 60 meV present in nodal and antinodal cuts across the Fermi surface. Specifically, while the kink had previously only been seen in the antinodal region, it is now observed also in the nodal region, reminiscent of what has been observed in hole-doped cuprates.Comment: 4 pages, 4 figure

Human-Organization-Technology Fit Model for BIM Adoption in Construction Project Organizations: Impact Factor Analysis Using SNA and Comparative Case Study

The sluggish adoption of building information modeling (BIM) is attributable to various technical, managerial, personnel, procedural, and institutional issues encountered by an organization in which such adoption takes place. However, these issues are under researched from a holistic perspective. Based on a proposed human-organization-technology (HOT) fit model, this paper aims to study the impacting factors of HOT fit in BIM adoption within construction project organizations (CPOs). The HOT fit indexes of 14 BIM case projects were operationalized using social network analysis (SNA) method and how different factors impact the HOT fit and its three subdimensions [i.e., human-technology (HT) fit, organization-technology (OT) fit, and human-organization (HO) fit] was investigated using a comparative case study. It was found that the project size has significantly negative relations with HOT fit, HT fit, and OT fit; while hierarchy steepness has positive correlations with HT fit, OT fit, and HO fit. OT fit was also found to have a weakly negative relationship with BIM level of details (LODs). A joint factor analysis further disclosed that the flatter the hierarchy, the larger the project size, and the higher the BIM LOD, the more difficult to achieve a high HOT fit, HT fit, or OT fit. Thus, CPOs should use steeper hierarchical structure and take a progressive BIM adoption strategy by adopting from smaller projects and/or lower LODs. This research empirically examined how project organizational and technological factors can impact BIM adoption. The HOT fit model can help CPOs evaluate their general HOT fit status, redesign optimal HOT configuration, diagnose the problems when the HOT fit is not ideal, and make strategic directions to better harvest the benefits of BIM. Limitations and future research directions are also identified

Non-Thermal X-ray Properties of Rotation Powered Pulsars and Their Wind Nebulae

We present a statistical study of the non-thermal X-ray emission of 27 young rotation powered pulsars (RPPs) and 24 pulsar wind nebulae (PWNe) by using the Chandra and the XMM-Newton observations, which with the high spatial resolutions enable us to spatially resolve pulsars from their surrounding PWNe. We obtain the X-ray luminosities and spectra separately for RPPs and PWNe, and then investigate their distribution and relation to each other as well as the relation with the pulsar rotational parameters. In the pair-correlation analysis we find that: (1) the X-ray (2-10 keV) luminosities of both pulsar and PWN (L_{psr} and L_{pwn}) display a strong correlation with pulsar spin down power Edot and characteristic age, and the scalings resulting from a simple linear fit to the data are L_{psr} \propto Edot^{0.92 \pm 0.04} and L_{pwn} \propto Edot^{1.45 \pm 0.08} (68% confidence level), respectively, however, both the fits are not statistically acceptable; (2) L_{psr} also shows a possible weak correlation with pulsar period P and period derivative Pdot, whereas L_{pwn} manifests a similar weak correlation with Pdot only; (3) The PWN photon index Gamma_{pwn} is positively correlated with L_{pwn} and L_{pwn}/Edot. We also found that the PWN X-ray luminosity is typically 1 to 10 times larger than that from the underlying pulsar, and the PWN photon indices span a range of ~1.5 to ~2. The statistic study of PWN spectral properties supports the particle wind model in which the X-ray emitting electrons are accelerated by the termination shock of the wind.Comment: 15 pages, 9 figures, 3 Tables, ApJ accepted version. Substantial revision, especially luminosity uncertainty taken into accounted and one fig added. Main conclusions unchange

Sex-Specific Modulation of Gene Expression Networks in Murine Hypothalamus

The hypothalamus contains nuclei and cell populations that are critical in reproduction and that differ significantly between the sexes in structure and function. To examine the molecular and genetic basis for these differences, we quantified gene expression in the hypothalamus of 39 pairs of adult male and female mice belonging to the BXD strains. This experimental design enabled us to define hypothalamic gene coexpression networks and provided robust estimates of absolute expression differences. As expected, sex has the strongest effect on the expression of genes on the X and Y chromosomes (e.g., Uty, Xist, Kdm6a). Transcripts associated with the endocrine system and neuropeptide signaling also differ significantly. Sex-differentiated transcripts often have well delimited expression within specific hypothalamic nuclei that have roles in reproduction. For instance, the estrogen receptor (Esr1) and neurokinin B (Tac2) genes have intense expression in the medial preoptic and arcuate nuclei and comparatively high expression in females. Despite the strong effect of sex on single transcripts, the global pattern of covariance among transcripts is well preserved, and consequently, males and females have well matched coexpression modules. However, there are sex-specific hub genes in functionally equivalent modules. For example, only in males is the Y-linked gene, Uty, a highly connected transcript in a network that regulates chromatin modification and gene transcription. In females, the X chromosome paralog, Kdm6a, takes the place of Uty in the same network. We also find significant effect of sex on genetic regulation and the same network in males and females can be associated with markedly different regulatory loci. With the exception of a few sex-specific modules, our analysis reveals a system in which sets of functionally related transcripts are organized into stable sex-independent networks that are controlled at a higher level by sex-specific modulators