On the evolution of anomalous X-ray pulsars and soft gamma ray repeaters with fallback disks

We show that the period clustering of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), their X-ray luminosities, ages and statistics can be explained with fallback disks with large initial specific angular momentum. The disk evolution models are developed by comparison to self-similar analytical models. The initial disk mass and angular momentum set the viscous timescale. An efficient torque, with (1 - w^2) dependence on the fastness parameter w leads to period clustering in the observed AXP-SGR period range under a wide range of initial conditions. The timescale t_0 for the early evolution of the fallback disk, and the final stages of fallback disk evolution, when the disk becomes passive, are the crucial determinants of the evolution. The disk becomes passive at temperatures around 100 K, which provides a natural cutoff for the X-ray luminosity and defines the end of evolution in the observable AXP and SGR phase. This low value for the minimum temperature for active disk turbulence indicates that the fallback disks are active up to a large radius greater than ~10^{12} cm. We find that transient AXPs and SGRs are likely to be older than their persistent cousins. A fallback disk with mass transfer rates corresponding to the low quiescent X-ray luminosities of the transient sources in early evolutionary phases would have a relatively lower initial mass, such that the mass-flow rate in the disk is not sufficient for the inner disk to penetrate into the light cylinder of the young neutron star, making mass accretion onto the neutron star impossible. The transient AXP phase therefore must start later. The model results imply that the transient AXP/SGRs, although older, are likely to be similar in number to persistent sources (abridged).Comment: 42 pages, 22 figures. Accepted for publication in the Astrophysical Journa

Millimeter interferometer observations of the magnetar 4U 0142+61

The Anomalous X‐ray Pulsar 4U 0142+61 is the only neutron star where it is believed that one of the long searched‐for ‘fallback’ disks has been detected in the mid‐IR by Wang et al. [1] using Spitzer. Such a disk originates from material falling back to the NS after the supernova. We search for cold circumstellar material in the 90 GHz continuum using the Plateau de Bure Interferometer. No millimeter flux is detected at the position of 4U 0142+61, the upper flux limit is 150 μJy corresponding to the 3σ noise rms level. The re‐processed Spitzer MIPS 24μm data presented previously by Wang et al. [2] show some indication of flux enhancement at the position of the neutron star, albeit below the 3σ statistical significance limit. At far infrared wavelengths the source flux densities are probably below the Herschel confusion limits

Credit information sharing and loan loss recognition

Does enhancing banks’ information sets and understanding of credit risks improve loan loss recognition? We study this question using a global dataset of staggered initiations and coverage increases of public credit registries (PCRs). Mandated by national regulators, PCRs collect borrower and loan information from lenders and share it with the banks in the financial system. This setting represents a significant improvement in banks’ assessment of loss events. We find that PCR initiations and coverage reforms enhance the timeliness of banks’ loan loss recognition—the extent to which loan loss provisions capture subsequent nonperforming loans. The effects are greater when PCRs distribute more information and are not driven by changes in borrower quality or supervisory stringency. Overall, these inferences are consistent with improvements in banks’ information sets leading to better provisioning decisions

The Anomalous X-Ray Pulsar 4U 0142+61: A Neutron Star with a Gaseous Fallback Disk

The recent detection of the anomalous X-ray pulsar (AXP) 4U 0142+61 in the mid-infrared with the {\it Spitzer} observatory by Z.Wang and coworkers constitutes the first instance of a disk around an AXP. We show, by analyzing earlier optical and near-IR data together with the recent data, that the overall broadband data set can be reproduced by a single model of an irradiated and viscously heated disk.Comment: 22 pages, 3 figures, minor revisons, appeared in Ap

Simultaneous use of linear and nonlinear gradients for B1 + inhomogeneity correction

The simultaneous use of linear spatial encoding magnetic fields (L-SEMs) and nonlinear spatial encoding magnetic fields (N-SEMs) in B1 + inhomogeneity problems is formulated and demonstrated with both simulations and experiments. Independent excitation k-space variables for N-SEMs are formulated for the simultaneous use of L-SEMs and N-SEMs by assuming a small tip angle. The formulation shows that, when N-SEMs are considered as an independent excitation k-space variable, numerous different k-space trajectories and frequency weightings differing in dimension, length, and energy can be designed for a given target transverse magnetization distribution. The advantage of simultaneous use of L-SEMs and N-SEMs is demonstrated by B1 + inhomogeneity correction with spoke excitation. To fully utilize the independent k-space formulations, global optimizations are performed for 1D, 2D RF power limited, and 2D RF power unlimited simulations and experiments. Three different cases are compared: L-SEMs alone, N-SEMs alone, and both used simultaneously. In all cases, the simultaneous use of L-SEMs and N-SEMs leads to a decreased standard deviation in the ROI compared with using only L-SEMs or N-SEMs. The simultaneous use of L-SEMs and N-SEMs results in better B1 + inhomogeneity correction than using only L-SEMs or N-SEMs due to the increased number of degrees of freedom. Copyright © 2017 John Wiley & Sons, Ltd

Boundary Effects in Local Inflation and Spectrum of Density Perturbations

We observe that when a local patch in a radiation filled Robertson-Walker universe inflates by some reason, outside perturbations can enter into the inflating region. Generally, the physical wavelengths of these perturbations become larger than the Hubble radius as they cross into the inflating space and their amplitudes freeze out immediately. It turns out that the corresponding power spectrum is not scale invariant. Although these perturbations cannot reach out to a distance inner observer shielded by a de Sitter horizon, they still indicate a curious boundary effect in local inflationary scenarios.Comment: 11 pages, 8 figures, revtex4, v4: minor typos corrected, twocolumn versio

Ultrasound mapping of pelvic endometriosis: does the location and number of lesions affect the diagnostic accuracy? a multicentre diagnostic accuracy study

BACKGROUND: Endometriosis is a common condition which causes pain and reduced fertility. Treatment can be difficult, especially for severe disease, and an accurate preoperative assessment would greatly help in the managment of these patients. The objective of this study is to assess the accuracy of pre-operative transvaginal ultrasound scanning (TVS) in identifying the specific features of pelvic endometriosis and pelvic adhesions in comparison with laparoscopy. METHODS: Consecutive women with clinically suspected or proven pelvic endometriosis, who were booked for laparoscopy, were invited to join the study. They all underwent a systematic transvaginal ultrasound examination in order to identify discrete endometriotic lesions and pelvic adhesions. The accuracy of ultrasound diagnosis was determined by comparing pre-operative ultrasound to laparoscopy findings. RESULTS: 198 women who underwent preoperative TVS and laparoscopy were included in the final analysis. At laparoscopy 126/198 (63.6%) women had evidence of pelvic endometriosis. 28/126 (22.8%) of them had endometriosis in a single location whilst the remaining 98/126 (77.2%) had endometriosis in two or more locations. Positive likelihood ratios (LR+) for the ultrasound diagnosis of ovarian endometriomas, moderate or severe ovarian adhesions, pouch of Douglas adhesions, and bladder deeply infiltrating endometriosis (DIE), recto-sigmoid colon DIE, rectovaginal DIE, uterovesical fold DIE and uterosacral ligament DIE were >10, whilst for pelvic side wall DIE and any ovarian adhesions the + LH was 8.421 and 9.81 respectively. The negative likelihood ratio (LR-) was: <0.1 for bladder DIE; 0.1-0.2 for ovarian endometriomas, moderate or severe ovarian adhesions, and pouch of Douglas adhesions; 0.5-1 for rectovaginal, uterovesical fold, pelvic side wall and uterosacral ligament DIE. The accuracy of TVS for the diagnosis of both total number of endometriotic lesions and DIE lesions significantly improved with increasing total number of lesions. CONCLUSIONS: Our study has shown that the TVS diagnosis of endometriotic lesion is very specific and false positive results are rare. Negative findings are less reliable and women with significant symptoms may still benefit from further investigation even if TVS findings are normal. The accuracy of ultrasound diagnosis is significantly affected by the location and number of endometriotic lesions

Non-LTE modeling of supernova-fallback disks

We present a first detailed spectrum synthesis calculation of a supernova-fallback disk composed of iron. We assume a geometrically thin disk with a radial structure described by the classical alpha-disk model. The disk is represented by concentric rings radiating as plane-parallel slabs. The vertical structure and emission spectrum of each ring is computed in a fully self-consistent manner by solving the structure equations simultaneously with the radiation transfer equations under non-LTE conditions. We describe the properties of a specific disk model and discuss various effects on the emergent UV/optical spectrum. We find that strong iron-line blanketing causes broad absorption features over the whole spectral range. Limb darkening changes the spectral distribution up to a factor of four depending on the inclination angle. Consequently, such differences also occur between a blackbody spectrum and our model. The overall spectral shape is independent of the exact chemical composition as long as iron is the dominant species. A pure iron composition cannot be distinguished from silicon-burning ash. Non-LTE effects are small and restricted to few spectral features.Comment: ApSS, accepted, Proceedings of Isolated Neutron Stars: from the Interior to the Surface, April 24-28, 2006, London, U

Somatostatin in human pancreatic and gastric juice

Considerable amounts of IRS are secreted after secretin injection in human pancreatic juice collected during endoscopic retrograde cholangiopancreatography. The mean IRS levels in the pancreatic juice of non-diabetic patients were 79+/-10 (SE) pg/ml. The IRS levels in NIDDM were considerably higher, the mean value being 1635+/-313 (SE) pg/ml. The mean IRS level in IDDM were 312+/-151 (SE) pg/ml. In IDDM, those patients whose blood glucose levels were well controlled by insulin showed low pancreatic juice IRS ranging from non-detectable to 46 pg/ml. On the other hand, those with uncontrolled hyperglycemia showed IRS levels ranging from 452 to 1047 pg/ml. Gel-filtration profiles of IRS in pancreatic juice extracts were not consistent in all cases. Some showed IRS peaks eluting with SS14 and SS28, while others contained IRS species that were eluted in more retarded fractions. The retarded IRS fraction exhibited biological activity indistinguishable from that of SS14 as indexed using a quantitative cytochemical method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24539/1/0000818.pd