2,324,431 research outputs found

    Laser geodynamic satellite thermal/optical/vibrational analyses and testing. Volume 1: Executive summary

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    The results of the LAGEOS Thermal/Optical/Vibrational Analyses and test program conducted for the National Aeronautics and Space Administration are presented. The purpose of this study is to verify, through analysis and test, that the MSFC LAGEOS design inherently provides a retroreflector thermal environment which maintains acceptable retroreflector internal thermal gradients. Acceptable thermal gradients are those which result in less than 50% degradation of optical performance from isothermal optical performance. This volume provides an executive summary of the study program. It summarizes the study objectives, the study approach, the principal assumptions, the type of basic data generated and the significant results

    The M4 Core Project with HST --- I. Overview and First-Epoch

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    We present an overview of the ongoing Hubble Space Telescope large program GO-12911. The program is focused on the core of M4, the nearest Galactic globular cluster, and the observations are designed to constrain the number of binaries with massive companions (black holes, neutron stars, or white dwarfs) by measuring the ``wobble'' of the luminous (main-sequence) companion around the center of mass of the pair, with an astrometric precision of ~50 micro-arcseconds. The high spatial resolution and stable medium-band PSFs of WFC3/UVIS will make these measurements possible. In this work we describe: (i) the motivation behind this study, (ii) our observing strategy, (iii) the many other investigations enabled by this unique data set, and which of those our team is conducting, and (iv) a preliminary reduction of the first-epoch data-set collected on October 10, 2012.Comment: 25 pages, 14 figures (9 at low resolution), 3 tables. Published in: Astronomische Nachrichten, Volume 334, Issue 10, pages 1062-1085, December 2013. http://onlinelibrary.wiley.com/doi/10.1002/asna.201311911/abstrac

    Physical activity counselling during pulmonary rehabilitation in patients with COPD : a randomised controlled trial

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    Background Pulmonary rehabilitation programs only modestly enhance daily physical activity levels in patients with chronic obstructive pulmonary disease (COPD). This randomised controlled trial investigates the additional effect of an individual activity counselling program during pulmonary rehabilitation on physical activity levels in patients with moderate to very severe COPD. Methods Eighty patients (66 +/- 7 years, 81% male, forced expiratory volume in 1 second 45 +/- 16% of predicted) referred for a six-month multidisciplinary pulmonary rehabilitation program were randomised. The intervention group was offered an additional eight-session activity counselling program. The primary outcomes were daily walking time and time spent in at least moderate intense activities. Results Baseline daily walking time was similar in the intervention and control group (median 33 [interquartile range 16-47] vs 29 [17-44]) whereas daily time spent in at least moderate intensity was somewhat higher in the intervention group (17[4-50] vs 12[2-26] min). No significant intervention*time interaction effects were observed in daily physical activity levels. In the whole group, daily walking time and time spent in at least moderate intense activities did not significantly change over time. Conclusions The present study identified no additional effect of eight individual activity counselling sessions during pulmonary rehabilitation to enhance physical activity levels in patients with COPD

    Description of Liquid Nitrogen Experimental Test Facility

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    The Liquid Nitrogen Test Facility is a unique test facility for ground-based liquid nitrogen experimentation. The test rig consists of an insulated tank of approximately 12.5 cubic ft in volume, which is supplied with liquid nitrogen from a 300 gal dewar via a vacuum jacketed piping system. The test tank is fitted with pressure and temperature measuring instrumentation, and with two view ports which allow visual observation of test conditions. To demonstrate the capabilities of the facility, the initial test program is briefly described. The objective of the test program is to measure the condensation rate by injecting liquid nitrogen as a subcooled spray into the ullage of a tank 50 percent full of liquid nitrogen at saturated conditions. The condensation rate of the nitrogen vapor on the subcooled spray can be analytically modeled, and results validated and corrected by experimentally measuring the vapor condensation on liquid sprays

    Physician Executive Leadership: Assessing a Student-Led Approach to Healthcare Leadership Education in Medical School

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    Poster presented at: 14th Annual AMA Research Symposium in Orlando, Fl Objective: To investigate the effectiveness of Physican Leadership, an open access, student-led healthcare leadership program at Sidney Kimmel Medical College, in preparing to face five key emerging topics in medical practice: healthcare economics, health policy, care and quality and safety, law and medicine, and patient experience. The Problem: Gaps in Medical Education Healthcare in the US continues to evolve, and topics such as health policy, health finance, and patient experience are not central to the practice of medicine. However, the sheer volume of material students are required to learn in the preclinical years makes it challenging to introduce new subjects into traditional medical school curricula. As a result, these topics in healthcare leadership are often left out. Indeed, only 40-50% of medical student report appropriate training in the practice of medicine, including subjects as medical economics, healthcare systems, and managed care.https://jdc.jefferson.edu/pel/1002/thumbnail.jp

    Restoration of Fricitonal Characteristics on Older Portland Cement Concrete Pavement:Final Report for Iowa Highway Research Board Project HR-224, June 1986

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    Safety i s a very important aspect o f the highway program. The Iowa DOT initiated an inventory o f the friction values of all paved primary roadways i n 1969. This inventory, with an ASTM E-274 test unit, has continued to the present time. The t e s t i n g frequency varies based upon traffic volume and the previous friction value. Historically , the state o f Iowa constructed a substantial amount o f pcc pavement during the 1928-30 period t o "get Iowa out o f the mud". Some of that pavement has never been resurfaced and has been subjected to more than 50 years o f wear. The textured surface has been worn away and has subsequently polished. Even though some pavements from 15 t o 50 years old continue t o function structurally , because of the loss of friction , they do not provide the desired level o f safety to the driver. As a temporary measure, "Sl ippery -When -Wet " signs have been posted on many older pcc roads due to friction numbers below t h e desirable level. These signs warn the motorist of the current conditions. An economical method of restoring the high quality frictional properties i s needed

    The liquid Argon TPC: a powerful detector for future neutrino experiments and proton decay searches

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    We discuss the possibility of new generation neutrino and astroparticle physics experiments exploiting the liquid Argon Time Projection Chamber (LAr TPC) technique, following a graded strategy that envisions applications with increasing detector masses (from 100 ton to 100 kton). The ICARUS R&D program has already demonstrated that the technology is mature with the test of the T600 detector at surface. Since 2003 we have been working with the conceptual design of a very large LAr TPC with a mass of 50-100 kton to be built by employing a monolithic technology based on the use of industrial, large volume, cryogenic tankers developed by the petro-chemical industry. Such a detector, if realized, would be an ideal match for a Super Beam, Beta Beam or Neutrino Factory, covering a broad physics program that includes the detection of atmospheric, solar and supernova neutrinos, and searches for proton decay, in addition to the rich accelerator neutrino physics program. A "test module" with a mass of the order of 10 kton operated underground or at shallow depth would represent a necessary milestone towards the realization of the 100 kton detector, with an interesting physics program on its own. In parallel, physics is calling for a shorter scale application of the LAr TPC technique at the level of 100 ton mass, for low energy neutrino physics and for use as a near station setup in future long baseline neutrino facilities. We outline here the main physics objectives and the design of such a detector for operation in the upcoming T2K neutrino beam. We finally present the result of a series of R&D studies conducted with the aim of validating the design of the proposed detectors.Comment: 16 pages, 18 figures, Invited talk at High Intensity Physics HIF05, La Biodola, Isola d'Elba (Italy), June 200

    Stress-driven crystallization via shear-diffusion transformations in a metallic glass at very low temperatures

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    At elevated temperatures, glasses crystallize via thermally activated diffusion. However, metallic glasses can also undergo deformation-induced crystallization at very low temperatures. Here we demonstrate the crystallization of Al[subscript 50]Fe[subscript 50] metallic glasses under cyclic deformation at 50 K using molecular dynamics simulations and reveal the underlying atomic-scale processes. We demonstrate that stress-driven nonaffine atomic rearrangements, or shear diffusion transformation (SDT) events, lead to successive metabasin-to-metabasin transitions and long-range ordering. We also illustrate that the nucleation and growth of the crystal proceed via collective attachment of ordered clusters, advancing the amorphous/crystal interface in an intermittent manner. The cooperative nature of the steplike crystallization is attributed to the large activation volume of Eshelby transformations which generate as a by-product nonaffine diffusive atomic displacements that accumulate over loading cycles. The dual nature of shear (affine) and diffusion (nonaffine) in low-temperature stress-driven SDT events thus unifies inelasticity with crystallization.National Basic Research Program of China (973 Program) (Grant 2012CB619402)National Basic Research Program of China (111 Program) (Grant B06025)National Science Foundation (U.S.) (Grant DMR-1120901)National Science Foundation (U.S.) (Grant DMR-1410636

    "State of the Art” in Liver Resection and Living Donor Liver Transplantation: A Worldwide Survey of 100 Liver Centers

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    Background: New strategies have been developed to expand indications for liver surgery. The objective was to evaluate the current practice worldwide regarding critical liver mass and manipulation of the liver volume. Methods: A survey was sent to 133 liver centers worldwide, which focused on (a) critical liver volume, (b) preoperative manipulation of the liver mass, and (c) use of liver biopsy and metabolic tests. Results: The overall response rate to the survey was 75%. Half of the centers performed more than 100 resections per year; 86% had an associated liver transplant program. The minimal remnant liver volume for resection was 25% (15-40%) in cases of normal liver parenchyma and 50% (25-90%) in the presence of underlying cirrhosis. The minimal remnant liver volume for living donors was 40% (30-50%), whereas the accepted graft body weight ratio was 0.8 (0.6-1.2). Portal vein occlusion to manipulate the liver volume before resection was performed in 89% of the centers. Conclusions: Limits of liver volume and the current practice of liver manipulation before resection were comparable among different centers and continents. The minimal remnant liver volume in normal liver was 25%, and more than 80% of the centers performed portal vein occlusio
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