2,803 research outputs found

    An increase in hookworm infection temporally associated with ecologic change.

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    This report describes a significant increase in the prevalence of hookworm infection in an area of Haiti where intestinal parasites are common, but hookworm has not been common. Changing environmental conditions, specifically deforestation and subsequent silting of a local river, have caused periodic flooding with deposition of a layer of sandy loam topsoil and increased soil moisture. We speculate that these conditions, conducive to transmission of the infection, have allowed hookworm to reemerge as an important human pathogen

    Electric-Field Tuning of Spin-Dependent Exciton-Exciton Interactions in Coupled Quantum Wells

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    We have shown experimentally that an electric field decreases the energy separation between the two components of a dense spin-polarized exciton gas in a coupled double quantum well, from a maximum splitting of 4\sim 4 meV to zero, at a field of \sim 35 kV/cm. This decrease, due to the field-induced deformation of the exciton wavefunction, is explained by an existing calculation of the change in the spin-dependent exciton-exciton interaction with the electron-hole separation. However, a new theory that considers the modification of screening with that separation is needed to account for the observed dependence on excitation power of the individual energies of the two exciton components.Comment: 5 pages, 4 eps figures, RevTeX, Physical Review Letters (in press

    Phase-Field Model of Silicon Carbide Growth During Isothermal Condition

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    Silicon carbide (SiC) emerges as a promising ceramic material for high-temperature structural applications, especially within the aerospace sector. The utilization of SiC-based ceramic matrix composites (CMCs) instead of superalloys in components like engine shrouds, combustors, and nozzles offers notable advantages, including a 25% improvement in fuel efficiency, over 10% enhanced thrust, and the capability to withstand up to 500^{\circ}C higher operating temperatures. Employing a CALPHAD-reinforced multi-phase-field model, our study delves into the evolution of the SiC layer under isothermal solidification conditions. By modeling the growth of SiC between liquid Si and solid C at 1450^{\circ}C, we compared results with experimental microstructures and quantitatively examined the evolution of SiC thickness over time. Efficient sampling across the entire model space mitigated uncertainty in high-temperature kinetic parameters, allowing us to predict a range of growth rates and morphologies for the SiC layer. The model accounts for parameter uncertainty stemming from limited experimental knowledge and successfully predicts relevant morphologies for the system. Experimental results validated the kinetic parameters of the simulations, offering valuable insights and potential constraints on the reaction kinetics. We further explored the significance of multi-phase-field model parameters on two key outputs, and found that the diffusion coefficient of liquid Si emerges as the most crucial parameter significantly impacting the SiC average layer thickness and grain count over time. This study provides valuable insights into the microstructure evolution of the Si-C binary system, offering pertinent information for the engineering of CMCs in industrial applications

    Plantmetabolomics.org: mass spectrometry-based Arabidopsis metabolomics—database and tools update

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    The PlantMetabolomics (PM) database (http://www.plantmetabolomics.org) contains comprehensive targeted and untargeted mass spectrum metabolomics data for Arabidopsis mutants across a variety of metabolomics platforms. The database allows users to generate hypotheses about the changes in metabolism for mutants with genes of unknown function. Version 2.0 of PlantMetabolomics.org currently contains data for 140 mutant lines along with the morphological data. A web-based data analysis wizard allows researchers to select preprocessing and data-mining procedures to discover differences between mutants. This community resource enables researchers to formulate models of the metabolic network of Arabidopsis and enhances the research community's ability to formulate testable hypotheses concerning gene functions. PM features new web-based tools for data-mining analysis, visualization tools and enhanced cross links to other databases. The database is publicly available. PM aims to provide a hypothesis building platform for the researchers interested in any of the mutant lines or metabolites

    “We lost a lot, but something good came out of it too:” Exploring the impact of the COVID-19 pandemic on the mental wellbeing of British Muslim Pakistani women with family responsibilities

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    YesBackground The COVID-19 pandemic and associated restrictions caused major disruption globally, shedding light on the unprecedented strain upon the mental health and wellbeing of individuals around the world. Poor mental health in the pandemic is reported to be greater in women, with mothers being at increased risk. It is unclear whether there are differences in the impact of mental wellbeing on some ethnic groups over others. The aim of this study was to explore the experiences of British Muslim Pakistani women with family responsibilities during the COVID-19 pandemic, two years on from the first lockdown. Methods Qualitative interviews with women were conducted via telephone using a semi-structured topic guide. The sample included 25 British Muslim Pakistani women with family responsibilities, both English and non-English speaking. Women lived in households that ranged in number and included extended family. Key themes were determined using thematic analysis. Results Results were grouped under three themes. These were (1) Community, cultural and religious contributors to poor mental wellbeing, (2) religious and cultural mediators of mental distress, and (3) perceived positive impact on lifestyle. British Muslim Pakistani women were psychologically distressed by the high rates of virus transmission and deaths in their communities and at the prospect of older members of their extended family developing the virus. The impact of restrictions on fundamental religious and cultural interactions further exacerbated poor mental wellbeing in this population. Religion, community social capital and larger household structures were all effective coping strategies for British Muslim Pakistani women. Positive impacts of the pandemic included becoming closer to family and faith, and increased work/life harmony. Conclusions An exploration of religious and cultural coping mechanisms should be used to inform future national pandemic preparedness plans, as well as effective strategies for building and maintaining social capital. This may increase adherence to physical distancing and other protective behaviours in populations.Department of Health, United Kingdom, NIHR20016

    The Arecibo Arp 220 Spectral Census I: Discovery of the Pre-Biotic Molecule Methanimine and New Cm-wavelength Transitions of Other Molecules

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    An on-going Arecibo line search between 1.1 and 10 GHz of the prototypical starburst/megamaser galaxy, Arp 220, has revealed a spectrum rich in molecular transitions. These include the ``pre-biotic'' molecules: methanimine (CH2_{2}NH) in emission, three v2=1v_{2}=1 direct l-type absorption lines of HCN, and an absorption feature likely to be from either 18^{18}OH or formic acid (HCOOH). In addition, we report the detection of two, possibly three, transitions of λ\lambda4-cm excited OH not previously detected in Arp~220 which are seen in absorption, and a possible absorption feature from the 6.668-GHz line of methanol. This marks the first distant extragalactic detection of methanimine, a pre-biotic molecule. Also, if confirmed, the possible methanol absorption line presented here would represent the first extragalactic detection of methanol at a distance further than 10 Mpc. In addition, the strong, previously undetected, cm-wave HCN v2=1v_{2}=1 direct l-type lines will aid the study of dense molecular gas and active star-forming regions in this starburst galaxy.Comment: 25 pages, 10 figures. Accepted for publication in A
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