309 research outputs found

    Does Pollution Increase School Absences?

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    We examine the effect of air pollution on school absences using unique administrative data for elementary and middle school children in the 39 largest school districts in Texas. These data are merged with information from monitors maintained by the Environmental Protection Agency. To control for potentially confounding factors, we adopt a difference-in-difference-in differences strategy, and control for persistent characteristics of schools, years, and attendance periods in order to focus on variations in pollution within school-year-attendance period cells. We find that high levels of carbon monoxide (CO) significantly increase absences, even when they are below federal air quality standards.

    Interplanting Floral Resource Plants with Vegetable Plants Enhances Beneficial Arthropod Abundance in a Home Garden

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    We examined whether interplanting vegetable and ornamental flowering plants reduces herbivory and enhances photosynthetic rate, plant growth, natural enemy abundance, and pollinator visitation relative to monoculture plantings. We found no evidence of physiological or growth costs due to growth in polyculture. Herbivore damage to plants did not differ with planting regime. Natural enemies occurred in greater abundance in polycultures compared to monocultures. Pollinator diversity was enhanced in some polyculture plots. We suggest that interplanting vegetable and flowering ornamental plants at small spatial scales may improve plant health and reproduction through natural pest control and a diversified pollinator pool

    Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on Massive YSOs

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    Massive young stellar objects (YSOs), like low-mass YSOs, appear to be surrounded by optically thick envelopes and/or disks and have regions, often bipolar, that are seen in polarized scattered light at near-infrared wavelengths. We are using the 0.2'' spatial resolution of NICMOS on Hubble Space Telescope to examine the structure of the disks and outflow regions of massive YSOs in star-forming regions within a few kpc of the Sun. Here we report on 2 micron polarimetry of NGC 6334 V and S255 IRS1. NGC 6334 V consists of a double-lobed bright reflection nebula seen against a dark region, probably an optically thick molecular cloud. Our polarization measurements show that the illuminating star lies ~ 2'' south of the line connecting the two lobes; we do not detect this star at 2 micron, but there are a small radio source and a mid-infrared source at this location. S255 IRS1 consists of two YSOs (NIRS1 and NIRS3) with overlapping scattered light lobes and luminosities corresponding to early B stars. Included in IRS1 is a cluster of stars from whose polarization we determine the local magnetic field direction. Neither YSO has its scattered light lobes aligned with this magnetic field. The line connecting the scattered light lobes of NIRS1 is twisted symmetrically around the star; the best explanation is that the star is part of a close binary and the outflow axis of NIRS1 is precessing as a result of non-coplanar disk and orbit. The star NIRS3 is also offset from the line connecting its two scattered light lobes. We suggest that all three YSOs show evidence of episodic ejection of material as they accrete from dense, optically thick envelopes.Comment: 39 pages, 7 figures, 4 tables To be published in The Astrophysical Journa

    Care-seeking during fatal childhood illness in rural South Africa: a qualitative study

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    Objectives: This study aimed to better understand reasons why children in South Africa die at home, including caregivers’ care-seeking experiences, decision-making, choice of treatment provider and barriers to accessing care during a child’s final illness. Design: This qualitative study included semi-structured in-depth interviews and focus group discussions with caregivers of children who died below the age of 5 years. Data were thematically analysed, and key findings compared with the Pathways to Survival Framework—a model frequently used in the study of child mortality. An adapted model was developed. Setting: Two rural health and demographic surveillance system (HDSS) sites in South Africa—the Agincourt HDSS and the Africa Health Research Institute. Participants: Thirty-eight caregivers of deceased children (29 participated in in-depth interviews and 9 were participants in two focus group discussions). Caregivers were purposively sampled to ensure maximum variation across place of death, child age at death, household socioeconomic status, maternal migration status and maternal HIV status. Findings: Although caregivers faced barriers in providing care to children (including insufficient knowledge and poor transport), almost all did seek care from the formal health system. Negative experiences in health facilities did not deter care-seeking, but most respondents still received poor quality care and were not given adequate safety-netting advice. Traditional healers were only consulted as a last resort when other approaches had failed. Conclusion: Barriers to accessing healthcare disrupt the workings of previously accepted care-seeking models. The adapted model presented in this paper more realistically reflects care-seeking experiences and decision-making during severe childhood illness in rural South Africa and helps explain both the persistence of home deaths despite seeking healthcare, and the impact of a child’s death on care-seeking in future childhood illness. This model can be used as the basis for developing interventions to reduce under-5 mortality

    Design and Implementation of the ABRACADABRA-10 cm Axion Dark Matter Search

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    The past few years have seen a renewed interest in the search for light particle dark matter. ABRACADABRA is a new experimental program to search for axion dark matter over a broad range of masses, 1012ma10610^{-12}\lesssim m_a\lesssim10^{-6} eV. ABRACADABRA-10 cm is a small-scale prototype for a future detector that could be sensitive to QCD axion couplings. In this paper, we present the details of the design, construction, and data analysis for the first axion dark matter search with the ABRACADABRA-10 cm detector. We include a detailed discussion of the statistical techniques used to extract the limit from the first result with an emphasis on creating a robust statistical footing for interpreting those limits.Comment: 12 pages, 8 figure
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