113 research outputs found

    Compensation for Commuting in Imperfect Urban Markets

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    We develop an urban equilibrium job search model with employed and unemployed individuals where residential mobility of the unemployed is restricted. We assume a standard mono-centric model (firms are located in one location), but allow for imperfect labour markets. In contrast to models with perfect labour markets, the model predicts that the employed are only partially compensated for commuting costs in the form of wages. As a result, rent gradients are less steep than predicted by standard urban theories that assume perfectly competitive labour markets. © 2007 the author(s). Journal compilation © 2007 RSAI

    Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

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    We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--1.0M⊙1.0 M_\odot. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--1.0M⊙1.0 M_\odot, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

    Functional and self-rated health mediate the association between diabetes and depression

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    Depression is common among persons with diabetes and associated with adverse health outcomes. To date, little is known about the causal mechanisms that lead to depression in diabetes. The aim of the present study was to examine to which extent functional and self-rated health mediate the association between physical health and depressive symptoms in diabetes. Data of n = 3222 individuals with type 2 diabetes were analyzed cross-sectionally and longitudinally at three measurement occasions using path analysis. Indicators of physical health were glycemic control, number of comorbid somatic diseases, BMI, and insulin dependence. Furthermore, functional health, self-rated health and depressive symptoms were assessed. The effects of physical health on depressive symptoms were largely mediated by functional health and self-rated health. There was only a weak indirect effect of physical health on depressive symptoms. In contrast, self-rated health was a strong direct predictor of depressive symptoms. Self-rated health in turn depended strongly on patients’ functional health. The way individuals perceive their health appears to have a stronger effect on their depressive symptoms than objective physical indicators of diabetes. Therefore practitioners should be trained to pay more attention to their patients’ subjective health perceptions

    Self-perceived quality of life predicts mortality risk better than a multi-biomarker panel, but the combination of both does best

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    <p>Abstract</p> <p>Background</p> <p>Associations between measures of subjective health and mortality risk have previously been shown. We assessed the impact and comparative predictive performance of a multi-biomarker panel on this association.</p> <p>Methods</p> <p>Data from 4,261 individuals aged 20-79 years recruited for the population-based Study of Health in Pomerania was used. During an average 9.7 year follow-up, 456 deaths (10.7%) occurred. Subjective health was assessed by SF-12 derived physical (PCS-12) and mental component summaries (MCS-12), and a single-item self-rated health (SRH) question. We implemented Cox proportional-hazards regression models to investigate the association of subjective health with mortality and to assess the impact of a combination of 10 biomarkers on this association. Variable selection procedures were used to identify a parsimonious set of subjective health measures and biomarkers, whose predictive ability was compared using receiver operating characteristic (ROC) curves, C-statistics, and reclassification methods.</p> <p>Results</p> <p>In age- and gender-adjusted Cox models, poor SRH (hazard ratio (HR), 2.07; 95% CI, 1.34-3.20) and low PCS-12 scores (lowest vs. highest quartile: HR, 1.75; 95% CI, 1.31-2.33) were significantly associated with increased risk of all-cause mortality; an association independent of various covariates and biomarkers. Furthermore, selected subjective health measures yielded a significantly higher C-statistic (0.883) compared to the selected biomarker panel (0.872), whereas a combined assessment showed the highest C-statistic (0.887) with a highly significant integrated discrimination improvement of 1.5% (p < 0.01).</p> <p>Conclusion</p> <p>Adding biomarker information did not affect the association of subjective health measures with mortality, but significantly improved risk stratification. Thus, a combined assessment of self-reported subjective health and measured biomarkers may be useful to identify high-risk individuals for intensified monitoring.</p

    Declines in sexual activity and function predict incident health problems in older adults: prospective findings from the English Longitudinal Study of Ageing

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    The objective of this study was to investigate cross-sectional and longitudinal associations between declines in sexual activity and function and health outcomes in a large population-based sample of older adults. Data were from 2577 men and 3195 women aged ≄ 50 years participating in the English Longitudinal Study of Ageing. Past-year changes in sexual desire, frequency of sexual activity, and ability to have an erection (men)/become sexually aroused (women) were assessed at baseline by self-completion questionnaire. Health outcomes (self-rated health, limiting long-standing illness, doctor-diagnosed diseases of the vascular system, and cancer) were self-reported at baseline (2012/2013) and 4-year follow-up (2016/2017). Data were analyzed using logistic regression, adjusted for sociodemographics, health behaviors, and depressive symptoms. Prospectively, men who reported a decline in sexual desire had higher odds of incident limiting long-standing illness (OR 1.41, 95% CI 1.04–1.91) and incident cancer (OR 1.63, 95% CI 1.06–2.50) than those who maintained their sexual desire. Men who reported a decline in the frequency of sexual activities had higher odds of deterioration in self-rated health (OR 1.47, 95% CI 1.04–2.08) and incident limiting long-standing illness (OR 1.69, 95% CI 1.20–2.37). In women, a decline in frequency of sexual activities was associated with deterioration of self-rated health (OR 1.64, 95% CI 1.07–2.51). Erectile dysfunction was longitudinally associated with poorer health outcomes including incident cancer (OR 1.73, 95% CI 1.11–2.70), coronary heart disease (OR 2.29, 95% CI 1.29–4.07), and fair/poor self-rated health (OR 1.66, 95% CI 1.19–2.32). Practitioners should be mindful that a decline in sexual activity, desire, or function in older age may be an important indicator of future adverse health outcomes

    Localization and broadband follow-up of the gravitational-wave transient GW150914

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    A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams

    Multi-messenger observations of a binary neutron star merger

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    On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

    Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

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    We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society
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