7,284 research outputs found
Mid-infrared sources in the ELAIS Deep X-ray Survey
We present a crossâcorrelation of the European Large Area Infrared Space Observatory (ISO) survey (ELAIS) with the ELAIS Deep Xâray Survey of the N1 and N2 fields. There are seven Chandra point sources with matches in the ELAIS Final Analysis 15âÎŒm catalogue, out of a total of 28 extragalactic ISO sources present in the Chandra fields. Five of these are consistent with active galactic nuclei (AGN) giving an AGN fraction of âŒ19 per cent in the 15âÎŒm flux range 0.8â6âmJy. We have coâadded the hard Xâray fluxes of the individually undetected ISO sources and find a low significance detection consistent with star formation in the remaining population. We combine our point source crossâcorrelation fraction with the XMMâNewton observations of the Lockman Hole and Chandra observations of the Hubble Deep Field North to constrain source count models of the midâinfrared galaxy population. The low dustâenshrouded AGN fraction in ELAIS implied by the number of crossâidentifications between the ELAIS midâinfrared sample and the Chandra point sources is encouraging for the use of midâinfrared surveys to constrain the cosmic star formation history, provided there are not further large undetected populations of Comptonâthick AGN
The ELAIS deep X-ray survey - I. Chandra source catalogue and first results
We present an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources
Clustering of galaxies at 3.6 microns in the Spitzer Wide-area Infrared Extragalactic legacy survey
We investigate the clustering of galaxies selected in the 3.6 micron band of
the Spitzer Wide-area Infrared Extragalactic (SWIRE) legacy survey. The angular
two-point correlation function is calculated for eleven samples with flux
limits of S_3.6 > 4-400 mujy, over an 8 square degree field. The angular
clustering strength is measured at >5-sigma significance at all flux limits,
with amplitudes of A=(0.49-29)\times10^{-3} at one degree, for a power-law
model, A\theta^{-0.8}. We estimate the redshift distributions of the samples
using phenomological models, simulations and photometric redshifts, and so
derive the spatial correlation lengths. We compare our results with the GalICS
(Galaxies In Cosmological Simulations) models of galaxy evolution and with
parameterized models of clustering evolution. The GalICS simulations are
consistent with our angular correlation functions, but fail to match the
spatial clustering inferred from the phenomological models or the photometric
redshifts. We find that the uncertainties in the redshift distributions of our
samples dominate the statistical errors in our estimates of the spatial
clustering. At low redshifts (median z<0.5) the comoving correlation length is
approximately constant, r_0=6.1\pm0.5h^{-1} Mpc, and then decreases with
increasing redshift to a value of 2.9\pm0.3h^{-1} Mpc for the faintest sample,
for which the median redshift is z=1. We suggest that this trend can be
attributed to a decrease in the average galaxy and halo mass in the fainter
flux-limited samples, corresponding to changes in the relative numbers of
early- and late-type galaxies. However, we cannot rule out strong evolution of
the correlation length over 0.5<z<1.Comment: 14 pages, 9 (colour) figures. Published in MNRA
Individual Variation in Fathersâ Testosterone Reactivity to Infant Distress Predicts Parenting Behaviors with their 1-Year-Old Infants
Positive father involvement is associated with positive child outcomes. There is great variation in fathersâ involvement and fathering behaviors, and menâs testosterone (T) has been proposed as a potential biological contributor to paternal involvement. Previous studies investigating testosterone changes in response to father-infant interactions or exposure to infant cues are unclear as to whether individual variation in T is predictive of fathering behavior. We show that individual variation in fathersâ T reactivity to their infants during a challenging laboratory paradigm (Strange Situation) uniquely predicted fathersâ positive parenting behaviors during a subsequent father-infant interaction, in addition to other psychosocial determinants of paternal involvement, such as dispositional empathy and marital quality. The findings have implications for understanding fathering behaviors and how fathers can contribute to their childrenâs socioemotional development
The ELAIS Deep X-ray Survey
We present initial follow-up results of the ELAIS Deep X-ray Survey which is
being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray
sources are detected in our two 75 ks ACIS-I observations in the well-studied
ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to
R=26 with a median magnitude of R=24. We show that objects which are unresolved
optically (i.e. quasars) follow a correlation between their optical and X-ray
fluxes, whereas galaxies do not. We also find that the quasars with fainter
optical counterparts have harder X-ray spectra, consistent with absorption at
both wavebands. Initial spectroscopic follow-up has revealed a large fraction
of high-luminosity Type 2 quasars. The prospects for studying the evolution of
the host galaxies of X-ray selected Type 2 AGN are considered.Comment: 9 pages, 5 figures, To appear in Proceedings of XXI Moriond
Conference: "Galaxy Clusters and the High Redshift Universe Observed in
X-rays", edited by D. Neumann, F.Durret, & J. Tran Thanh Va
Automated Glaucoma Detection Using Hybrid Feature Extraction in Retinal Fundus Images
Glaucoma is one of the most common causes of blindness. Robust mass screening may help to extend the symptom-free life for affected patients. To realize mass screening requires a cost-effective glaucoma detection method which integrates well with digital medical and administrative processes. To address these requirements, we propose a novel low cost automated glaucoma diagnosis system based on hybrid feature extraction from digital fundus images. The paper discusses a system for the automated identification of normal and glaucoma classes using higher order spectra (HOS), trace transform (TT), and discrete wavelet transform (DWT) features. The extracted features are fed to a support vector machine (SVM) classifier with linear, polynomial order 1, 2, 3 and radial basis function (RBF) in order to select the best kernel for automated decision making. In this work, the SVM classifier, with a polynomial order 2 kernel function, was able to identify glaucoma and normal images with an accuracy of 91.67%, and sensitivity and specificity of 90% and 93.33%, respectively. Furthermore, we propose a novel integrated index called Glaucoma Risk Index (GRI) which is composed from HOS, TT, and DWT features, to diagnose the unknown class using a single feature. We hope that this GRI will aid clinicians to make a faster glaucoma diagnosis during the mass screening of normal/glaucoma images
Development and clinical performance of high throughput loop-mediated isothermal amplification for detection of malaria.
BACKGROUND: Accurate and efficient detection of sub-microscopic malaria infections is crucial for enabling rapid treatment and interruption of transmission. Commercially available malaria LAMP kits have excellent diagnostic performance, though throughput is limited by the need to prepare samples individually. Here, we evaluate the clinical performance of a newly developed high throughput (HTP) sample processing system for use in conjunction with the Eiken malaria LAMP kit. METHODS: The HTP system utilised dried blood spots (DBS) and liquid whole blood (WB), with parallel sample processing of 94 samples per run. The system was evaluated using 699 samples of known infection status pre-determined by gold standard nested PCR. RESULTS: The sensitivity and specificity of WB-HTP-LAMP was 98.6% (95% CI, 95.7-100), and 99.7% (95% CI, 99.2-100); sensitivity of DBS-HTP-LAMP was 97.1% (95% CI, 93.1-100), and specificity 100% against PCR. At parasite densities greater or equal to 2 parasites/ÎŒL, WB and DBS HTP-LAMP showed 100% sensitivity and specificity against PCR. At densities less than 2 p/ÎŒL, WB-HTP-LAMP sensitivity was 88.9% (95% CI, 77.1-100) and specificity was 99.7% (95% CI, 99.2-100); sensitivity and specificity of DBS-HTP-LAMP was 77.8% (95% CI, 54.3-99.5) and 100% respectively. CONCLUSIONS: The HTP-LAMP system is a highly sensitive diagnostic test, with the potential to allow large scale population screening in malaria elimination campaigns
Disability and perceived stress in primary care patients with major depression
Background: Major depressive disorder (MDD) is highly prevalent in the Spanish primary care (PC) setting and the leading cause of disability in Spain. The aim of this study was to evaluate several key psychometric properties of the Sheehan Disability Scale (SDS) in patients with or without MDD and varying degrees of symptom severity using the Patient Health Questionnaire-9 (PHQ-9).
Method: A total of 1, 704 PC patients participating in the PsicAP clinical trial completed the SDS and PHQ-9. We evaluated the factor structure, measurement invariance across gender, internal consistency, and the discriminative and predictive validity.
Results: Confirmatory factor analyses revealed a unifactorial model of the SDS containing 4 items (SDS-4) with the best model fit (CFI: .99; GFI: .99; TLI: 96; RMSEA: .10). This model contained the three life domain items (work, family, and social life) plus perceived stress (PS) with significant loadings. The internal consistency of the SDS-4 was acceptable in patients with or without MDD, regardless of symptom severity. The SDS-4 also showed good discriminative capacity and acceptable predictive validity in all subsamples.
Conclusions: These findings support the use of the SDS-4 to assess depression-related disability in patients at Spanish primary care centres
Size and frequency of natural forest disturbances and Amazon carbon balance
Forest inventory studies in the Amazon indicate a large terrestrial carbon sink. However, field plots may fail to represent forest mortality processes at landscape-scales of tropical forests. Here we characterize the frequency distribution of disturbance events in natural forests from 0.01 ha to 2,651 ha size throughout Amazonia using a novel combination of forest inventory, airborne lidar and satellite remote sensing data. We find that small-scale mortality events are responsible for aboveground biomass losses of B1.28 Pg C y 1 over the entire Amazon region. We also find that intermediate-scale disturbances account for losses of B0.01 Pg C y 1 , and that the largest-scale disturbances as a result of blow-downs only account for losses of B0.003 Pg C y 1 . Simulation of growth and mortality indicates that even when all carbon losses from intermediate and large-scale disturbances are considered, these are outweighed by the net biomass accumulation by tree growth, supporting the inference of an Amazon carbon sink
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