Heavily Obscured AGN in High Redshift Luminous Infrared Galaxies

We take advantage of the rich multi-wavelength data available in the Chandra Deep Field South (CDF-S), including the 4 Msec Chandra observations (the deepest X-ray data to date), in order to search for heavily-obscured low-luminosity AGN among infrared-luminous galaxies. In particular, we obtained a stacked rest-frame X-ray spectrum for samples of galaxies binned in terms of their IR luminosity or stellar mass. We detect a significant signal at E~1 to 8 keV, which we interpret as originating from a combination of emission associated with star-formation processes at low energies combined with a heavily-obscured AGN at E>5 keV. We further find that the relative strength of this AGN signal decays with decreasing IR luminosity, indicating a higher AGN fraction for more luminous IR sources. Together, these results strongly suggest the presence of a large number of obscured AGN in IR-luminous galaxies. Using samples binned in terms of stellar mass in the host galaxy, we find a significant excess at E=6-7 keV for sources with M>10^{11} Msun, consistent with a large obscured AGN population in high mass galaxies. In contrast, no strong evidence of AGN activity was found for less-massive galaxies. The integrated intensity at high energies indicates that a significant fraction of the total black hole growth, ~22%, occurs in heavily-obscured systems that are not individually detected in even the deepest X-ray observations. There are also indications that the number of low-luminosity, heavily-obscured AGN does not evolve significantly with redshift, in contrast to the strong evolution seen in higher luminosity sources.Comment: 5 pages, 3 figures in emulateapj format. Accepted by Astrophysical Journal Letter

Intelligent system for spoken term detection using the belief combination

Spoken Term Detection (STD) can be considered as a sub-part of the automatic speech recognition which aims to extract the partial information from speech signals in the form of query utterances. A variety of STD techniques available in the literature employ a single source of evidence for the query utterance match/mismatch determination. In this manuscript, we develop an acoustic signal processing based approach for STD that incorporates a number of techniques for silence removal, dynamic noise filtration, and evidence combination using Dempster-Shafer Theory (DST). A ‘spectral-temporal features based voiced segment detection’ and ‘energy and zero cross rate based unvoiced segment detection’ are built to remove the silence segments in the speech signal. Comprehensive experiments have been performed on large speech datasets and consequently satisfactory results have been achieved with the proposed approach. Our approach improves the existing speaker dependent STD approaches, specifically the reliability of query utterance spotting by combining the evidences from multiple belief sources

A small source in Q2237+0305 ?

Microlensing in Q2237+0305 between 1985 and 1995 (eg. Irwin et al. 1989; Corrigan et al. 1991; Ostensen et al. 1996) has been interpreted in two different ways; as microlensing by stellar mass objects of a continuum source having dimensions significantly smaller than the microlens Einstein radius (ER) (eg. Wambsganss, Paczynski & Schneider 1990; Rauch & Blandford 1991), and as microlensing by very low mass objects of a source as large as 5 ER (Refsdal & Stabell 1993; Haugan 1996). In this paper we present evidence in favour of a small source. Limits on the source size (in units of ER) are obtained from the combination of limits on the number of microlens Einstein radii crossed by the source during the monitoring period with two separate light-curve features. Firstly, recently published monitoring data (Wozniak et al. 2000; OGLE web page) show large variations (~0.8-1.5 magnitudes) between image brightnesses over a period of 700 days or ~15% of the monitoring period. Secondly, the 1988 peak in the image A light-curve had a duration that is a small fraction (<0.02) of the monitoring period. Such rapid microlensing rises and short microlensing peaks only occur for small sources. We find that the observed large-rapid variation limits the source size to be <0.2 ER (95% confidence). The width of the light-curve peak provides a stronger constraint of <0.02 ER (99% confidence). The Einstein radius (projected into the source plane) of the average microlens mass (m) in Q2237+0305 is ER ~ 10^{17}\sqrt{m} cm. The interpretation that stars are responsible for microlensing in Q2237+0305 therefore results in limits on the continuum source size that are consistent with current accretion disc theory.Comment: 8 pages, 3 figures, accepted for publication in M.N.R.A.

Signals were broadly positive for months, but never definitive: the tocilizumab story

BACKGROUND: Most COVID-19 treatment guidelines currently recommend tocilizumab in combination with dexamethasone in critically ill patients who are exhibiting rapid respiratory decompensation. OBJECTIVES: To produce a critical review and summary of the pathway which led to the repurposing of tocilizumab for COVID-19 treatment, from in vitro observations to guidelines recommendations. SOURCES: All studies evaluating the effectiveness of tocilizumab to treat COVID-19 disease published over July 2020-July 2021. CONTENT: Two large methodologically well conducted observational studies, the TESEO and the STOP COVID cohorts, showed a reduction in the risk of invasive mechanical ventilation or death in patients treated with tocilizumab as compared to standard of care in 2020. Concomitantly and up to February 2021 a number of small sample size randomized trials (RCTs) were showing discrepant results. These RCTs had a number of issues: small sample size, various designs and inclusion criteria and different dosages of tocilizumab used. The confidence interval of the meta-analytic estimate for the RCT results was consistent with the hypothesis of no efficacy of tocilizumab. In our opinion, this was mainly because the meta-analysis included small and heterogeneous studies. These results led to a delay in the inclusion of tocilizumab in guidelines which occurred only in the summer of 2021. IMPLICATIONS: Although observational studies are unable to control for unmeasured confounding, they can be put together quickly during a pandemic and promptly provide important information. The large sample size allows us to investigate effect measure modifiers and better target interventions. It is key that the effect size is somewhat large (RR>2), all sources of bias are properly accounted for and the direct evidence is weighted against these factors. It appears to us that for tocilizumab, not having dismissed the results of carefully designed and analysed observational studies in 2020 could have prevented many deaths over those months

What Do We Know About Alternative Work Arrangements in the United States?

The Contingent Worker Supplement (CWS) to the Current Population Survey (CPS), fielded six times between 1995 and 2017, was designed to measure jobs that were temporary in nature as well as work arrangements thought to be associated with less commitment between workers and employers. The latter includes independent contractor and platform work, temporary help and other intermediated contract work arrangements, and on-call work, which captures a certain type of unpredictable work schedule. While the CWS provides consistent measures of the work arrangements covered in the survey over a 22-year time span, it has shortcomings. Data from other household surveys, employer surveys, and administrative records provide important complementary and sometimes conflicting evidence on the alternative work arrangements measured by the CWS. Through a combination of new empirical analysis and a synthesis of existing research findings, we provide insights from these other data sources into the incidence and trends in alternative work arrangements, the characteristics of workers in these arrangements, and the implications of these arrangements for worker outcomes. Our analysis reveals large discrepancies between the CWS and alternate data sources in the size of the independent contractor workforce. In other cases, compared to the CWS, alternate data sources provide considerably broader measures of work arrangements, affecting our understanding of the number and characteristics of workers in them. We discuss lessons from our findings for improving the measurement of alternative work arrangements

The choice between hip prosthetic bearing surfaces in total hip replacement:a protocol for a systematic review and network meta-analysis

BACKGROUND: Prosthetic hip implants have many combinations of bearing surface materials, sizes, and fixation techniques, which can determine the quality of life of patients after primary total hip replacement (THR) and the likelihood of needing revision surgery. When an implant fails, patients require revision THR, which is distressing to the patient and expensive for the health care payer. Primary THR is one of the most common elective procedures performed worldwide, with over 300,000 performed annually in the USA and over 80,000 in England and Wales. It is important to review all available randomised controlled trial (RCT) evidence to determine which implant bearing surface materials, size, and fixation technique are most effective for patients. METHODS/DESIGN: This is a protocol for a systematic review and meta-analysis of RCTs comparing outcomes of hip implant bearing surfaces, size, and fixation techniques used in THR. Implant combinations compared in the literature include four bearing surface combinations (metal-on-polyethylene, metal-on-metal, ceramic-on-polyethylene, and ceramic-on-ceramic); two femoral head sizes (large vs small heads); and four fixation techniques (uncemented, cemented, hybrid, and reverse hybrids). The primary outcome will be revision surgery. We will also collect data on patient characteristics, mortality, quality of life, and other outcomes. In network meta-analysis, we will estimate the relative effectiveness of every implant bearing surface, head size (large vs small), and fixation permutation, using evidence where implants have been compared directly in an RCT and indirectly through common comparators in different RCTs. DISCUSSION: There has been much debate about materials used for prosthetic implants in THR. Different combinations of prosthetic materials, sizes, and fixation, can vary widely in cost and fail at different rates for different patient groups. Given the number of THRs performed yearly, and the increasing use of expensive implants, it is important to review evidence to inform surgeons, patients, and health care providers of optimal implant bearing combinations for given patient characteristics. This review will inform a cost-effectiveness model that will include evidence from other sources, to determine the most effective and cost-effective implant bearing combination for patients. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD4201501943

Unveiling hidden variability components in accreting X-ray binaries using both the Fourier power and cross-spectra

We present a novel method for measuring the lags of (weak) variability components in neutron-star and black-hole low-mass X-ray binaries (LMXBs). For this we assume that the power and cross-spectra of these sources consists of a number of components that are coherent in different energy bands, but are incoherent with one another. The technique is based on fitting simultaneously the power spectrum (PS) and the Real and Imaginary parts of the cross-spectrum (CS) with a combination of Lorentzian functions. We show that, because the PS of LMXBs is insensitive to signals with a large Imaginary part and a small Real part in the CS, this approach allows us to uncover new variability components that are only detected in the CS. We also demonstrate that, contrary to earlier claims, the frequency of the type-C quasi-periodic oscillation (QPO) in the black-hole binary GRS 1915+105 does not depend on energy. Rather, the apparent energy dependence of the QPO frequency can be explained by the presence of a separate QPO component with a slightly higher frequency than that of the QPO, whose rms amplitude increases faster with energy than the rms amplitude of the QPO. From all the above we conclude that, as in the case of the PS, the CS of black-hole and neutron-star binaries can be fitted by a combination of Lorentzian components. Our findings provide evidence that the frequency-dependent part of the transfer function of these systems can be described by a combination of responses, each of them acting over relatively well-defined time-scales. This conclusion challenges models that assume that the main contribution to the lags comes from a global, broadband, transfer function of the accreting system.</p