1,937 research outputs found

    Toward vicarious calibration of microwave remote-sensing satellites in arid environments

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    The Soil Moisture and Ocean Salinity (SMOS) satellite marks the commencement of dedicated global surface soil moisture missions, and the first mission to make passive microwave observations at L-band. On-orbit calibration is an essential part of the instrument calibration strategy, but on-board beam-filling targets are not practical for such large apertures. Therefore, areas to serve as vicarious calibration targets need to be identified. Such sites can only be identified through field experiments including both in situ and airborne measurements. For this purpose, two field experiments were performed in central Australia. Three areas are studied as follows: 1) Lake Eyre, a typically dry salt lake; 2) Wirrangula Hill, with sparse vegetation and a dense cover of surface rock; and 3) Simpson Desert, characterized by dry sand dunes. Of those sites, only Wirrangula Hill and the Simpson Desert are found to be potentially suitable targets, as they have a spatial variation in brightness temperatures of <4 K under normal conditions. However, some limitations are observed for the Simpson Desert, where a bias of 15 K in vertical and 20 K in horizontal polarization exists between model predictions and observations, suggesting a lack of understanding of the underlying physics in this environment. Subsequent comparison with model predictions indicates a SMOS bias of 5 K in vertical and 11 K in horizontal polarization, and an unbiased root mean square difference of 10 K in both polarizations for Wirrangula Hill. Most importantly, the SMOS observations show that the brightness temperature evolution is dominated by regular seasonal patterns and that precipitation events have only little impact

    Determining the Cosmic Distance Scale from Interferometric Measurements of the Sunyaev-Zel'dovich Effect

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    We determine the distances to 18 galaxy clusters with redshifts ranging from z~0.14 to z~0.78 from a maximum likelihood joint analysis of 30 GHz interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We model the intracluster medium (ICM) using a spherical isothermal beta model. We quantify the statistical and systematic uncertainties inherent to these direct distance measurements, and we determine constraints on the Hubble parameter for three different cosmologies. These distances imply a Hubble constant of 60 (+4, -4) (+13, -18) km s-1 Mpc-1 for an Omega_M = 0.3, Omega_Lambda = 0.7 cosmology, where the uncertainties correspond to statistical followed by systematic at 68% confidence. With a sample of 18 clusters, systematic uncertainties clearly dominate. The systematics are observationally approachable and will be addressed in the coming years through the current generation of X-ray satellites (Chandra & XMM-Newton) and radio observatories (OVRO, BIMA, & VLA). Analysis of high redshift clusters detected in future SZE and X-ray surveys will allow a determination of the geometry of the universe from SZE determined distances.Comment: ApJ Submitted; 40 pages, 9 figures (fig 3 B&W for size constraint), 13 tables, uses emulateapj5 styl

    Determining molecular orientation via single molecule SERS in a plasmonic nano-gap

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    In this work, plasmonic nano-gaps consisting of a silver nanoparticle coupled to an extended silver film have been fully optimized for single molecule Surface-Enhanced Raman Scattering (SERS) spectroscopy. The SERS signal was found to be strongly dependent on the particle size and the molecule orientation with respect to the field inside the nano-gap. Using Finite Difference Time Domain (FDTD) simulations to complement the experimental measurements, the complex interplay between the excitation enhancement and the emission enhancement of the system as a function of particle size were highlighted. Additionally, in conjunction with Density Functional Theory (DFT), the well-defined field direction in the nano-gap enables to recover the orientation of individual molecules

    Haptoglobin Phenotype, Preeclampsia Risk and the Efficacy of Vitamin C and E Supplementation to Prevent Preeclampsia in a Racially Diverse Population

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    Haptoglobin's (Hp) antioxidant and pro-angiogenic properties differ between the 1-1, 2-1, and 2-2 phenotypes. Hp phenotype affects cardiovascular disease risk and treatment response to antioxidant vitamins in some non-pregnant populations. We previously demonstrated that preeclampsia risk was doubled in white Hp 2-1 women, compared to Hp 1-1 women. Our objectives were to determine whether we could reproduce this finding in a larger cohort, and to determine whether Hp phenotype influences lack of efficacy of antioxidant vitamins in preventing preeclampsia and serious complications of pregnancy-associated hypertension (PAH). This is a secondary analysis of a randomized controlled trial in which 10,154 low-risk women received daily vitamin C and E, or placebo, from 9-16 weeks gestation until delivery. Hp phenotype was determined in the study prediction cohort (n = 2,393) and a case-control cohort (703 cases, 1,406 controls). The primary outcome was severe PAH, or mild or severe PAH with elevated liver enzymes, elevated serum creatinine, thrombocytopenia, eclampsia, fetal growth restriction, medically indicated preterm birth or perinatal death. Preeclampsia was a secondary outcome. Odds ratios were estimated by logistic regression. Sampling weights were used to reduce bias from an overrepresentation of women with preeclampsia or the primary outcome. There was no relationship between Hp phenotype and the primary outcome or preeclampsia in Hispanic, white/other or black women. Vitamin supplementation did not reduce the risk of the primary outcome or preeclampsia in women of any phenotype. Supplementation increased preeclampsia risk (odds ratio 3.30; 95% confidence interval 1.61-6.82, p<0.01) in Hispanic Hp 2-2 women. Hp phenotype does not influence preeclampsia risk, or identify a subset of women who may benefit from vitamin C and E supplementation to prevent preeclampsia

    Moderate to severe gambling problems and traumatic brain injury: A population-based study

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    Traumatic brain injury (TBI) is a common injury characterized by a change in brain function after an external blow to the head and is associated with substance abuse, psychological distress, risk-taking, and impulsivity. Convenience and clinical samples have also linked TBI to problem gambling, but have not ruled out confounding variables such as hazardous drinking and psychological distress. This study examines the relationship between TBI and moderate to severe problem gambling in a general population probability sample controlling for hazardous drinking and psychological distress. The data were obtained from a 2015–2016 cross-sectional general population telephone survey of adults ages 18+from Ontario, Canada (N = 3809). Logistic regression was used to estimate the association as adjusted odds ratios (AOR). Moderate to severe problem gambling was independently associated with a history of TBI after adjusting for potential confounders (AOR: 2.80), and had a statistically significant relationship with psychological distress (AOR = 2.74), hazardous drinking (AOR = 2.69), and lower educational levels (AOR = 0.37). This study provides further data to suggest a link between TBI and moderate to severe problem gambling; however, more research is needed to determine if there is a causal relationship or the potential implications for prevention and treatment

    Moderate to severe gambling problems and traumatic brain injury: A population-based study

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    Traumatic brain injury (TBI) is a common injury characterized by a change in brain function after an external blow to the head and is associated with substance abuse, psychological distress, risk-taking, and impulsivity. Convenience and clinical samples have also linked TBI to problem gambling, but have not ruled out confounding variables such as hazardous drinking and psychological distress. This study examines the relationship between TBI and moderate to severe problem gambling in a general population probability sample controlling for hazardous drinking and psychological distress. The data were obtained from a 2015–2016 cross-sectional general population telephone survey of adults ages 18+from Ontario, Canada (N = 3809). Logistic regression was used to estimate the association as adjusted odds ratios (AOR). Moderate to severe problem gambling was independently associated with a history of TBI after adjusting for potential confounders (AOR: 2.80), and had a statistically significant relationship with psychological distress (AOR = 2.74), hazardous drinking (AOR = 2.69), and lower educational levels (AOR = 0.37). This study provides further data to suggest a link between TBI and moderate to severe problem gambling; however, more research is needed to determine if there is a causal relationship or the potential implications for prevention and treatment

    Clinical leadership through commissioning: Does it work in practice?

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    In tune with much international practice, the English National Health Service has been striving to transform health care provision to make it more affordable in the face of rising demand. At the heart of a set of recent radical reforms has been the launch of ‘clinical commissioning’ using the vehicle of local groups of General Practitioners (GPs). This devolves a large portion of the total healthcare budget to these groups. National government policy statements make clear that the expectation is that the groups will ‘transform’ the organization and provision of health services. In this article we draw upon interviews, observations and analysis of internal documents to make an assessment of the extent to which clinical leaders have seized the opportunity presented by the creation of these groups to attempt transformative service redesign
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