1,086 research outputs found

    Statistical Gravitational Waveform Models: What to Simulate Next?

    Full text link
    Models of gravitational waveforms play a critical role in detecting and characterizing the gravitational waves (GWs) from compact binary coalescences. Waveforms from numerical relativity (NR), while highly accurate, are too computationally expensive to produce to be directly used with Bayesian parameter estimation tools like Markov-chain-Monte-Carlo and nested sampling. We propose a Gaussian process regression (GPR) method to generate accurate reduced-order-model waveforms based only on existing accurate (e.g. NR) simulations. Using a training set of simulated waveforms, our GPR approach produces interpolated waveforms along with uncertainties across the parameter space. As a proof of concept, we use a training set of IMRPhenomD waveforms to build a GPR model in the 2-d parameter space of mass ratio qq and equal-and-aligned spin χ1=χ2\chi_1=\chi_2. Using a regular, equally-spaced grid of 120 IMRPhenomD training waveforms in q[1,3]q\in[1,3] and χ1[0.5,0.5]\chi_1 \in [-0.5,0.5], the GPR mean approximates IMRPhenomD in this space to mismatches below 4.3×1054.3\times 10^{-5}. Our approach can alternatively use training waveforms directly from numerical relativity. Beyond interpolation of waveforms, we also present a greedy algorithm that utilizes the errors provided by our GPR model to optimize the placement of future simulations. In a fiducial test case we find that using the greedy algorithm to iteratively add simulations achieves GPR errors that are 1\sim 1 order of magnitude lower than the errors from using Latin-hypercube or square training grids

    Draft Genome Sequence of Kocuria sp. Strain UCD-OTCP (Phylum Actinobacteria).

    Get PDF
    Here, we present the draft genome of Kocuria sp. strain UCD-OTCP, a member of the phylum Actinobacteria, isolated from a restaurant chair cushion. The assembly contains 3,791,485 bp (G+C content of 73%) and is contained in 68 scaffolds

    Relationship Between Household Socio-Economic Status and under-five Mortality in Rufiji DSS, Tanzania.

    Get PDF
    Disparities in health outcomes between the poor and the better off are increasingly attracting attention from researchers and policy makers. However, policies aimed at reducing inequity need to be based on evidence of their nature, magnitude, and determinants. The study aims to investigate the relationship between household socio-economic status (SES) and under-five mortality, and to measure health inequality by comparing poorest/least poor quintile mortality rate ratio and the use of a mortality concentration index. It also aims to describe the risk factors associated with under-five mortality at Rufiji Demographic Surveillance Site (RDSS), Tanzania. This analytical cross sectional study included 11,189 children under-five residing in 7,298 households in RDSS in 2005. Principal component analysis was used to construct household SES. Kaplan-Meier survival incidence estimates were used for mortality rates. Health inequality was measured by calculating and comparing mortality rates between the poorest and least poor wealth quintile. We also computed a mortality concentration index. Risk factors of child mortality were assessed using Poisson regression taking into account potential confounders. Under-five mortality was 26.9 per 1,000 person-years [95% confidence interval (CI) (23.7-30.4)]. The poorest were 2.4 times more likely to die compared to the least poor. Our mortality concentration index [-0.16; 95% CI (-0.24, -0.08)] indicated considerable health inequality. Least poor households had a 52% reduced mortality risk [incidence rate ratio (IRR) = 0.48; 95% CI 0.30-0.80]. Furthermore, children with mothers who had attained secondary education had a 70% reduced risk of dying compared to mothers with no education [IRR = 0.30; 95% CI (0.22-0.88)]. Household socio-economic inequality and maternal education were associated with under-five mortality in the RDSS. Targeted interventions to address these factors may contribute towards accelerating the reduction of child mortality in rural Tanzania

    Harnessing the known and unknown impact of nanotechnology on enhancing food security and reducing postharvest losses : constraints and future prospects

    Get PDF
    Due to the deterioration of natural resources, low agricultural production, significant postharvest losses, no value addition, and a rapid increase in population, the enhancement of food security and safety in underdeveloped countries is becoming extremely tough. Efforts to incorporate the latest technology are now emanating from scientists globally in order to boost supply and subsequently reduce differences between the demand and the supply chain for food production. Nanotechnology is a unique technology that might increase agricultural output by developing nanofertilizers, employing active pesticides and herbicides, regulating soil features, managing wastewater and detecting pathogens. It is also suitable for processing food, as it boosts food production with high market value, improves its nutrient content and sensory properties, increases its safety, and improves its protection from pathogens. Nanotechnology can also be beneficial to farmers by assisting them in decreasing postharvest losses through the extension of the shelf life of food crops using nanoparticles. This review presents current data on the impact of nanotechnology in enhancing food security and reducing postharvest losses alongside the constraints confronting its application. More research is needed to resolve this technology’s health and safety issues

    Comparison of high- versus low-intensity community health worker intervention to promote newborn and child health in Northern Nigeria

    Get PDF
    In Northern Nigeria, infant mortality rates are two to three times higher than in the southern states, and, in 2008, a partnership program to improve maternal, newborn, and child health was established to reduce infant and child mortality in three Northern Nigeria states. The program intervention zones received government-supported health services plus integrated interventions at primary health care posts and development of community-based service delivery (CBSD) with a network of community volunteers and community health workers (CHWs), who focus on educating women about danger signs for themselves and their infants and promoting appropriate responses to the observation of those danger signs, consistent with the approach of the World Health Organization Integrated Management of Neonatal and Childhood Illness strategy. Before going to scale in the rest of the state, it is important to identify the relative effectiveness of the low-intensity volunteer approach versus the more intensive CBSD approach with CHWs. We conducted stratified cluster sample household surveys at baseline (2009) and follow-up (2011) to assess changes in newborn and sick child care practices among women with births in the five prior years (baseline: n = 6,906; follow-up: n = 2,310). The follow-up respondents were grouped by level of intensity of the CHW interventions in their community, with “low” including group activities led only by a trained community volunteer and “high” including the community volunteer activities plus CBSD from a CHW providing one-on-one advice and assistance. t-tests were used to test for significant differences from baseline to follow-up, and F-statistics, which adjust for the stratified cluster design, were used to test for significant differences between the control, low-intensity, and high-intensity intervention groups at follow-up. These analyses focused on changes in newborn and sick child care practices. Anti-tetanus vaccination coverage during pregnancy increased from 69.2% at baseline to 85.7% at follow-up in the intervention areas. Breastfeeding within 24 hours increased from 42.9% to 59.0% in the intervention areas, and more newborns were checked by health workers within 48 hours (from 16.8% at baseline to 26.8% at follow-up in the intervention areas). Newborns were more likely to be checked by trained health personnel, and they received more comprehensive newborn care. Compared to the control communities, more than twice as many women in intervention communities knew to watch for specific newborn danger signs. Compared to the control and low-intensity intervention communities, more mothers in the high-intensity communities learned about the care of sick children from CHWs, with a corresponding decline those seeking advice from family or friends or traditional birth attendants. Significantly fewer mothers did nothing when their child was sick. High-intensity intervention communities experienced the most decline. Those who did nothing for children with fever or cough declined from 35% to 30%, and with diarrhea from 40% to 31%. Use of medications, both traditional and modern, increased from baseline to follow-up, with no differentiation in use by intervention area. The community-based approach to promoting improved newborn and sick child care through community volunteers and CHWs resulted in improved newborn and sick child care. The low-intensity approach with community volunteers appears to have been as effective as the higher-intensity CBSD approach with CHWs for several of the key newborn and sick child care indicators, particularly in the provision of appropriate home care for children with fever or cough

    The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet

    Full text link
    We report the discovery of rising X-ray emission from the binary neutron star (BNS) merger event GW170817. This is the first detection of X-ray emission from a gravitational-wave source. Observations acquired with the Chandra X-ray Observatory (CXO) at t~2.3 days post merger reveal no significant emission, with L_x<=3.2x10^38 erg/s (isotropic-equivalent). Continued monitoring revealed the presence of an X-ray source that brightened with time, reaching L_x\sim 9x10^39 erg/s at ~15.1 days post merger. We interpret these findings in the context of isotropic and collimated relativistic outflows (both on- and off-axis). We find that the broad-band X-ray to radio observations are consistent with emission from a relativistic jet with kinetic energy E_k~10^49-10^50 erg, viewed off-axis with theta_obs~ 20-40 deg. Our models favor a circumbinary density n~ 0.0001-0.01 cm-3, depending on the value of the microphysical parameter epsilon_B=10^{-4}-10^{-2}. A central-engine origin of the X-ray emission is unlikely. Future X-ray observations at t100t\gtrsim 100 days, when the target will be observable again with the CXO, will provide additional constraints to solve the model degeneracies and test our predictions. Our inferences on theta_obs are testable with gravitational wave information on GW170817 from Advanced LIGO/Virgo on the binary inclination.Comment: 7 Pages, 4 Figures, ApJL, In Press. Keywords: GW170817, LV
    corecore