174 research outputs found

    Homotopy groups of the moduli space of metrics of positive scalar curvature

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    We show by explicit examples that in many degrees in a stable range the homotopy groups of the moduli spaces of Riemannian metrics of positive scalar curvature on closed smooth manifolds can be non-trivial. This is achieved by further developing and then applying a family version of the surgery construction of Gromov–Lawson to certain nonlinear smooth sphere bundles constructed by Hatcher

    Restoration of critically endangered elkhorn coral (Acropora palmata) populations using larvae reared from wild-caught gametes

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    AbstractElkhorn coral (Acropora palmata) populations provide important ecological functions on shallow Caribbean reefs, many of which were lost when a disease reduced their abundance by more than 95% beginning in the mid-1970s. Since then, a lack of significant recovery has prompted rehabilitation initiatives throughout the Caribbean. Here, we report the first successful outplanting and long-term survival of A. palmata settlers reared from gametes collected in the field. A. palmata larvae were settled on clay substrates (substrate units) and either outplanted on the reef two weeks after settlement or kept in a land-based nursery. After 2.5 years, the survival rate of A. palmata settlers outplanted two weeks after settlement was 6.8 times higher (3.4%) than that of settlers kept in a land-based nursery (0.5%). Furthermore, 32% of the substrate units on the reef still harbored one or more well-developed recruit compared to 3% for substrate units kept in the nursery. In addition to increasing survival, outplanting A. palmata settlers shortly after settlement reduced the costs to produce at least one 2.5-year-old A. palmata individual from 325to325 to 13 USD. Thus, this study not only highlights the first successful long-term rearing of this critically endangered coral species, but also shows that early outplanting of sexually reared coral settlers can be more cost-effective than the traditional approach of nursery rearing for restoration efforts aimed at rehabilitating coral populations

    Wide-Field Infrared Survey Explorer Science Payload Update

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    The Wide Field Infrared Survey Explorer is a NASA Medium Class Explorer mission to perform a high-sensitivity, high resolution, all-sky survey in four infrared wavelength bands. The science payload is a 40 cm aperture cryogenically cooled infrared telescope with four 10242 infrared focal plane arrays covering from 2.8 to 26 μm. Mercury cadmium telluride (MCT) detectors are used for the 3.3 μm and 4.6 μm channels, and Si:As detectors are used for the 12 μm and 23 μm wavelength channels. A cryogenic scan mirror freezes the field of view on the sky over the 9.9-second frame integration time. A two-stage solid hydrogen cryostat provides cooling to temperatures less than 17 K and 8.3 K at the telescope and Si:As focal planes, respectively. The science payload collects continuous data on orbit for the seven-month baseline mission with a goal to support a year-long mission, if possible. As of the writing of this paper, the payload subassemblies are complete, and the payload has begun integration and test. This paper provides a payload overview and discusses instrument status and performance

    The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance

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    The all sky surveys done by the Palomar Observatory Schmidt, the European Southern Observatory Schmidt, and the United Kingdom Schmidt, the InfraRed Astronomical Satellite and the 2 Micron All Sky Survey have proven to be extremely useful tools for astronomy with value that lasts for decades. The Wide-field Infrared Survey Explorer is mapping the whole sky following its launch on 14 December 2009. WISE began surveying the sky on 14 Jan 2010 and completed its first full coverage of the sky on July 17. The survey will continue to cover the sky a second time until the cryogen is exhausted (anticipated in November 2010). WISE is achieving 5 sigma point source sensitivities better than 0.08, 0.11, 1 and 6 mJy in unconfused regions on the ecliptic in bands centered at wavelengths of 3.4, 4.6, 12 and 22 microns. Sensitivity improves toward the ecliptic poles due to denser coverage and lower zodiacal background. The angular resolution is 6.1, 6.4, 6.5 and 12.0 arc-seconds at 3.4, 4.6, 12 and 22 microns, and the astrometric precision for high SNR sources is better than 0.15 arc-seconds.Comment: 22 pages with 19 included figures. Updated to better match the accepted version in the A

    Striking the right balance in right whale conservation

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    Author Posting. © The Authors, 2009. This article is posted here by permission of NRC Research Press for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences 66 (2009): 1399-1403, doi:10.1139/F09-115.Despite many years of study and protection, the North Atlantic right whale (Eubalaena glacialis) remains on the brink of extinction. There is a crucial gap in our understanding of their habitat use in the migratory corridor along the eastern seaboard of the United States. Here, we characterize habitat suitability in migrating right whales in relation to depth, distance to shore, and the recently enacted ship speed regulations near major ports. We find that the range of suitable habitat exceeds previous estimates and that, as compared with the enacted 20 nautical mile buffer, the originally proposed 30 nautical mile buffer would protect more habitat for this critically endangered species.This work was supported in part by SERDP/DoD grant W912HQ-04-C-0011 to A.J. Read and P.N. Halpin as well as a James B. Duke Fellowship and a Harvey L. Smith Dissertation Year Fellowship to R.S. Schick

    Spatial patterns of scour and fill in dryland sand bed streams

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    Reproduced with permission of the publisher. © 2006 American Geophysical UnionSpatial patterns of scour and fill in two dryland ephemeral stream channels with sandy bed material have been measured with dense arrays of scour chains. Although the depth and areal extent of bed activity increased with discharge, active bed reworking at particular locations within the reaches resulted in downstream patterns of alternate shallower and deeper areas of scour. The variation was such that mean scour depths for individual cross sections varied about the mean for the reach by a factor of 2–4 while the locus of maximum scour traced a sinuous path about the channel centerline. The wavelength of the pattern of scour was about seven times the channel width. During each event, compensating fill returned the streambeds to preflow elevations, indicating that the streams were in approximate steady state over the period of study. Although the patterns of periodically enhanced scour along alternate sides of the channels are consistent with models of periodically reversing helical flow, further work is required to identify the causal relationships between patterns of flow and sediment transport in dryland sand bed channels

    Skeletal Light-Scattering Accelerates Bleaching Response in Reef-Building Corals

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    Background At the forefront of ecosystems adversely affected by climate change, coral reefs are sensitive to anomalously high temperatures which disassociate (bleaching) photosynthetic symbionts (Symbiodinium) from coral hosts and cause increasingly frequent and severe mass mortality events. Susceptibility to bleaching and mortality is variable among corals, and is determined by unknown proportions of environmental history and the synergy of Symbiodinium- and coral-specific properties. Symbiodinium live within host tissues overlaying the coral skeleton, which increases light availability through multiple light-scattering, forming one of the most efficient biological collectors of solar radiation. Light-transport in the upper ~200 μm layer of corals skeletons (measured as ‘microscopic’ reduced-scattering coefficient, μ′S,m), has been identified as a determinant of excess light increase during bleaching and is therefore a potential determinant of the differential rate and severity of bleaching response among coral species. Results Here we experimentally demonstrate (in ten coral species) that, under thermal stress alone or combined thermal and light stress, low-μ′S,m corals bleach at higher rate and severity than high-μ′S,m corals and the Symbiodinium associated with low-μ′S,m corals experience twice the decrease in photochemical efficiency. We further modelled the light absorbed by Symbiodinium due to skeletal-scattering and show that the estimated skeleton-dependent light absorbed by Symbiodinium (per unit of photosynthetic pigment) and the temporal rate of increase in absorbed light during bleaching are several fold higher in low-μ′S,m corals. Conclusions While symbionts associated with low-μ′S,m corals receive less total light from the skeleton, they experience a higher rate of light increase once bleaching is initiated and absorbing bodies are lost; further precipitating the bleaching response. Because microscopic skeletal light-scattering is a robust predictor of light-dependent bleaching among the corals assessed here, this work establishes μ′S,m as one of the key determinants of differential bleaching response

    Transdiagnostic Ecological Momentary Intervention for Improving Self-Esteem in Youth Exposed to Childhood Adversity:The SELFIE Randomized Clinical Trial

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    Importance: Targeting low self-esteem in youth exposed to childhood adversity is a promising strategy for preventing adult mental disorders. Ecological momentary interventions (EMIs) allow for the delivery of youth-friendly, adaptive interventions for improving self-esteem, but robust trial-based evidence is pending.Objective: To examine the efficacy of SELFIE, a novel transdiagnostic, blended EMI for improving self-esteem plus care as usual (CAU) compared with CAU only.Design, Setting, and Participants: This was a 2-arm, parallel-group, assessor-blinded, randomized clinical trial conducted from December 2018 to December 2022. The study took place at Dutch secondary mental health services and within the general population and included youth (aged 12-26 years) with low self-esteem (Rosenberg Self-Esteem Scale [RSES] <26) exposed to childhood adversity.Interventions: A novel blended EMI (3 face-to-face sessions, email contacts, app-based, adaptive EMI) plus CAU or CAU only.Main Outcomes and Measures: The primary outcome was RSES self-esteem at postintervention and 6-month follow-up. Secondary outcomes included positive and negative self-esteem, schematic self-beliefs, momentary self-esteem and affect, general psychopathology, quality of life, observer-rated symptoms, and functioning.Results: A total of 174 participants (mean [SD] age, 20.7 [3.1] years; 154 female [89%]) were included in the intention-to-treat sample, who were primarily exposed to childhood emotional abuse or neglect, verbal or indirect bullying, and/or parental conflict. At postintervention, 153 participants (87.9%) and, at follow-up, 140 participants (80.5%), provided primary outcome data. RSES self-esteem was, on average, higher in the experimental condition (blended EMI + CAU) than in the control condition (CAU) across both postintervention and follow-up as a primary outcome (B = 2.32; 95% CI, 1.14-3.50; P < .001; Cohen d-type effect size [hereafter, Cohen d] = 0.54). Small to moderate effect sizes were observed suggestive of beneficial effects on positive (B = 3.85; 95% CI, 1.83-5.88; P < .001; Cohen d = 0.53) and negative (B = −3.78; 95% CI, −6.59 to −0.98; P = .008; Cohen d = −0.38) self-esteem, positive (B = 1.58; 95% CI, 0.41-2.75; P = .008; Cohen d = 0.38) and negative (B = −1.71; 95% CI, −2.93 to −0.48; P = .006; Cohen d = −0.39) schematic self-beliefs, momentary self-esteem (B = 0.29; 95% CI, 0.01-0.57; P = .04; Cohen d = 0.24), momentary positive affect (B = 0.23; 95% CI, 0.01-0.45; P = .04; Cohen d = 0.20), momentary negative affect (B = −0.33; 95% CI, −0.59 to −0.03, P = .01, Cohen d = −0.27), general psychopathology (B = −17.62; 95% CI, −33.03 to −2.21; P = .03; Cohen d = −0.34), and quality of life (B = 1.16; 95% CI, 0.18-2.13; P = .02; Cohen d = 0.33) across postintervention and follow-up. No beneficial effects on symptoms and functioning were observed.Conclusions and Relevance: A transdiagnostic, blended EMI demonstrated efficacy on the primary outcome of self-esteem and signaled beneficial effects on several secondary outcomes. Further work should focus on implementing this novel EMI in routine public mental health provision.Trial Registration Dutch Trial Register Identifier: NL7129(NTR7475
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