1,658 research outputs found

    Photometric analysis of a space shuttle water venting

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    Presented here is a preliminary interpretation of a recent experiment conducted on Space Shuttle Discovery (Mission STS 29) in which a stream of liquid supply water was vented into space at twilight. The data consist of video images of the sunlight-scattering water/ice particle cloud that formed, taken by visible light-sensitive intensified cameras both onboard the spacecraft and at the AMOS ground station near the trajectory's nadir. This experiment was undertaken to study the phenomenology of water columns injected into the low-Earth orbital environment, and to provide information about the lifetime of ice particles that may recontact Space Shuttle orbits later. The findings about the composition of the cloud have relevance to ionospheric plasma depletion experiments and to the dynamics of the interaction of orbiting spacecraft with the environment

    X-band operations metamaterial absorber with extended circular ring topology for size reduction

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    A metamaterial electromagnetic wave absorber consisting of a big circular ring patch with four smaller suppression circular rings is presented in this report. The metamaterial electromagnetic wave absorber introduces the concept of size reduction by suppressing the resonance frequency. An FR4 substrate was used and the incidental wave angles were varied from 00 to 600. Simulations results shows peak absorption of 100% was achieved at 10.7 GHz by the absorber for both TE and TM polarization incident waves. Minimum absorption for both TE and TM mode of 90.6% was achieved under TE mode. The metamaterial absorber was being tested with and Ultra-wide band antenna and the results were reported. © 2017, Institute of Advanced Engineering and Science. All rights reserved

    Challenges of providing healthcare worker education and training in protracted conflict: a focus on non-government controlled areas in north west Syria

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    Without healthcare workers (HCWs), health and humanitarian provision in Syria cannot be sustained either now or in the post-conflict phase. The protracted conflict has led to the exodus of more than 70% of the healthcare workforce. Those remaining work in dangerous conditions with insufficient resources and a healthcare system that has been decimated by protracted conflict. For many HCWs, particularly those in non-government-controlled areas (NGCAs) of Syria, undergraduate education and postgraduate training has been interrupted with few opportunities to continue. In this manuscript, we explore initiatives present in north west Syria at both undergraduate and postgraduate level for physician and non-physician HCWs. Conclusion: Challenges to HCW education in north west Syria can be broadly divided into 1. Organisational (local healthcare leadership and governance, coordination and collaboration between stakeholders, competition between stakeholders and insufficient funding.) 2. Programmatic (lack of accreditation or recognition of qualifications, insufficient physical space for teaching, exodus of faculty affecting teaching and training, prioritisation of physicians over non-physicians, informally trained healthcare workers.) 3. Healthcare system related (politicisation of healthcare system, changing healthcare needs of the population, ongoing attacks on healthcare.) Locally implementable strategies including dedicated funding are key to supporting retention of HCWs and return during post-conflict reconstruction

    Outcomes following in-hospital cardiopulmonary resuscitation in people receiving maintenance dialysis

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    RATIONALE & OBJECTIVE: Previous studies showing poor cardiopulmonary resuscitation (CPR) outcomes in the dialysis population have largely been derived from claims data and are somewhat limited by a lack of detailed characterization of CPR events. We aimed to analyze CPR-related outcomes in individuals receiving maintenance dialysis. STUDY DESIGN: Retrospective chart review. SETTING & PARTICIPANTS: Using electronic medical records from a single academic health care system, we identified all hospitalized adult patients receiving maintenance dialysis who had undergone in-hospital CPR between 2006 and 2014. EXPOSURE: Initial in-hospital CPR. OUTCOMES: Overall survival, predictors of unsuccessful CPR, predictors of death during the same hospitalization among initial survivors, predictors of discharge-to-home status. ANALYTICAL APPROACH: We provide descriptive statistics for the study variables and used RESULTS: A total of 184 patients received in-hospital CPR: 51 (28%) did not survive the initial CPR event, and 77 CPR survivors died (additional 42%) later during the same hospitalization (overall mortality 70%). Only 18 (10%) were discharged home, with the remaining 32 (17%) discharged to a rehabilitation facility or a nursing home. In the multivariable model, the only predictor of unsuccessful CPR was CPR duration (OR, 1.41; 95% CI, 1.24-1.61; LIMITATIONS: Retrospective study design, single-center study, no information on functional status. CONCLUSIONS: Patients receiving maintenance dialysis experience high mortality following in-hospital CPR and only 10% are discharged home. These data may help clinicians provide useful prognostic information while engaging in goals of care conversations

    Formation of plasma around a small meteoroid: 1. Kinetic theory

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    This article is a companion to Dimant and Oppenheim [2017] https://doi.org/10.1002/2017JA023963.This paper calculates the spatial distribution of the plasma responsible for radar head echoes by applying the kinetic theory developed in the companion paper. This results in a set of analytic expressions for the plasma density as a function of distance from the meteoroid. It shows that at distances less than a collisional mean free path from the meteoroid surface, the plasma density drops in proportion to 1/R where R is the distance from the meteoroid center; and, at distances much longer than the mean‐free‐path behind the meteoroid, the density diminishes at a rate proportional to 1/R2. The results of this paper should be used for modeling and analysis of radar head echoes.This work was supported by NSF grant AGS-1244842. (AGS-1244842 - NSF

    Understanding Surface Processes on Mars Through Study of Iron Oxides/Oxyhydroxides: Clues to Surface Alteration and Aqueous Processes

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    We are performing oxidation and reduction reactions on hydrated ferric oxide minerals in order to investigate how these might alter under a variety of conditions on the surface of Mars. Preliminary experiments on ferrihydrite and goethite showed that heating these minerals in a dry oxidizing environment produces fine-grained hematite, while heating these minerals in a reducing environment produces fine-grained magnetite. Under Mars-like oxidation levels this magnetite then oxidizes to maghemite. These reactions are dependent on the presence of water and organic material that can act as a reductant. We are using reflectance and Mossbauer spectroscopy to characterize the reaction products and TEM to analyze the sample texture. Our preliminary results indicate that magnetite and maghemite could be formed in the soil on Mars from ferrihydrite and goethite if organics were present on early Mars

    Selecting and implementing overview methods: implications from five exemplar overviews

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    This is the final version of the article. Available from BioMed Central via the DOI in this record.Background Overviews of systematic reviews are an increasingly popular method of evidence synthesis; there is a lack of clear guidance for completing overviews and a number of methodological challenges. At the UK Cochrane Symposium 2016, methodological challenges of five overviews were explored. Using data from these five overviews, practical implications to support methodological decision making of authors writing protocols for future overviews are proposed. Methods Methods, and their justification, from the five exemplar overviews were tabulated and compared with areas of debate identified within current literature. Key methodological challenges and implications for development of overview protocols were generated and synthesised into a list, discussed and refined until there was consensus. Results Methodological features of three Cochrane overviews, one overview of diagnostic test accuracy and one mixed methods overview have been summarised. Methods of selection of reviews and data extraction were similar. Either the AMSTAR or ROBIS tool was used to assess quality of included reviews. The GRADE approach was most commonly used to assess quality of evidence within the reviews. Eight key methodological challenges were identified from the exemplar overviews. There was good agreement between our findings and emerging areas of debate within a recent published synthesis. Implications for development of protocols for future overviews were identified. Conclusions Overviews are a relatively new methodological innovation, and there are currently substantial variations in the methodological approaches used within different overviews. There are considerable methodological challenges for which optimal solutions are not necessarily yet known. Lessons learnt from five exemplar overviews highlight a number of methodological decisions which may be beneficial to consider during the development of an overview protocol.The overview conducted by Pollock [19] was supported by a project grant from the Chief Scientist Office of the Scottish Government. The overview conducted by McClurg [21] was supported by a project grant by the Physiotherapy Research Foundation. The overview by Hunt [22] was supported as part of doctoral programme funding by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care South West Peninsula (PenCLAHRC). The overview conducted by Estcourt [20] was supported by an NIHR Cochrane Programme Grant for the Safe and Appropriate Use of Blood Components. The overview conducted by Brunton [23] was commissioned by the Department of Health as part of an ongoing programme of work on health policy research synthesis. Alex Pollock is employed by the Nursing, Midwifery and Allied Health Professions (NMAHP) Research Unit, which is supported by the Chief Scientist Office of the Scottish Government. Pauline Campbell is supported by the Chief Nurses Office of the Scottish Government

    Large magnetic anisotropy in Ferrihydrite nanoparticles synthesized from reverse micelles

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    Six-line ferrihydrite(FH) nanoparticles have been synthesized in the core of reverse micelles, used as nanoreactors to obtain average particle sizes \approx 2 to 4 nm. The blocking temperatures TBmT_B^m extracted from magnetization data increased from 10\approx 10 to 20 K for increasing particle size. Low-temperature \MOS measurements allowed to observe the onset of differentiated contributions from particle core and surface as the particle size increases. The magnetic properties measured in the liquid state of the original emulsion showed that the \FH phase is not present in the liquid precursor, but precipitates in the micelle cores after the free water is freeze-dried. Systematic susceptibility \chi_{ac}(\emph{f},T) measurements showed the dependence of the effective magnetic anisotropy energies EaE_{a} with particle volume, and yielded an effective anisotropy value of Keff=312±10K_{eff} = 312\pm10 kJ/m3^3.Comment: 8 pages, 10 figures. Nanotechnology, v17 (Nov. 2006) In pres
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