525 research outputs found

    Simulation of the low earth orbital atomic oxygen interaction with materials by means of an oxygen ion beam

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    Atomic oxygen is the predominant species in low-Earth orbit between the altitudes of 180 and 650 km. These highly reactive atoms are a result of photodissociation of diatomic oxygen molecules from solar photons having a wavelength less than or equal to 2430A. Spacecraft in low-Earth orbit collide with atomic oxygen in the 3P ground state at impact energies of approximately 4.2 to 4.5 eV. As a consequence, organic materials previously used for high altitude geosynchronous spacecraft are severely oxidized in the low-Earth orbital environment. The evaluation of materials durability to atomic oxygen requires ground simulation of this environment to cost effectively screen materials for durability. Directed broad beam oxygen sources are necessary to evaluate potential spacecraft materials performance before and after exposure to the simulated low-Earth orbital environment. This paper presents a description of a low energy, broad oxygen ion beam source used to simulate the low-Earth orbital atomic oxygen environment. The results of materials interaction with this beam and comparison with actual in-space tests of the same meterials will be discussed. Resulting surface morphologies appear to closely replicate those observed in space tests

    Effects of rotation on coolant passage heat transfer. Volume 1: Coolant passages with smooth walls

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    An experimental program was conducted to investigate heat transfer and pressure loss characteristics of rotating multipass passages, for configurations and dimensions typical of modern turbine blades. The immediate objective was the generation of a data base of heat transfer and pressure loss data required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. Experiments were conducted in a smooth wall large scale heat transfer model

    GLP-1 Agonists in Type 1 Diabetes Mellitus: A Review of the Literature

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    Objective: To review the use of GLP-1 agonists in patients with type 1 diabetes mellitus (T1DM). Data Sources: A search using the MEDLINE database, EMBASE, and Cochrane Database was performed through March 2016 using the search terms glucagon-like peptide 1 (GLP-1) agonists, incretin, liraglutide, exenatide, albiglutide, dulaglutide, type 1 diabetes mellitus. Study Selection and Data Extraction: All English-language trials that examined glycemic end points using GLP- 1 agonists in humans with T1DM were included. Data Synthesis: A total of 9 clinical trials examining the use of GLP-1 agonists in T1DM were identified. On average, hemoglobin A1C (A1C) was lower than baseline, with a maximal lowering of 0.6%. This effect was not significant when tested against a control group, with a relative decrease in A1C of 0.1% to 0.2%. In all trials examined, reported hypoglycemia was low, demonstrating no difference when compared with insulin monotherapy. Weight loss was seen in all trials, with a maximum weight loss of 6.4 kg over 24 weeks. Gastrointestinal adverse effects are potentially limiting, with a significant number of patients in trials reporting nausea. Conclusion: The use of GLP-1 agonists should be considered in T1DM patients who are overweight or obese and not at glycemic goals despite aggressive insulin therapy; however, tolerability of these agents is a potential concern. Liraglutide has the strongest evidence for use and would be the agent of choice for use in overweight or obese adult patients with uncontrolled T1DM

    Strategies for the Management of Postoperative Anemia in Elective Orthopedic Surgery

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    Objective: To assess the use of oral iron, intravenous (IV) iron, and erythropoiesis-stimulating agents (ESAs) for the prevention and management of perioperative anemia in elective orthopedic surgery patients, and to provide a clinical algorithm for use. Data Sources: A PubMed and MEDLINE search was conducted from 1964 through March 2016 using the following search terms alone or in combination: orthopedic, surgery, elective, anemia, blood transfusion, iron, erythropoiesisstimulating agents, and erythropoietin. Study Selection and Data Extraction: All English-language prospective and retrospective human studies and meta-analyses evaluating oral iron, IV iron, or ESA alone or in combination in elective orthopedic surgery patients were evaluated, provided they reported blood transfusion outcomes. Data Synthesis: A total of 9 prospective and retrospective studies and 1 meta-analysis were identified and included. In the preoperative setting, administration of oral iron, IV iron, or ESA alone or in combination to correct underlying anemia led to significantly reduced transfusion rates. Transfusion requirements were generally less with combination therapy (ESA + oral or IV iron). In the short-term perioperative or postoperative period, use of oral or IV iron led to conflicting results, with some reporting a statistically significant reduction in blood transfusions, whereas others reported none. Conclusions: In elective orthopedic surgery, IV or oral iron with or without an ESA may provide benefit in prevention of postoperative anemia and results in blood transfusion reduction without significantly increasing the risk of adverse events. These agents should be considered at the lowest effective dose with emphasis on administration prior to planned surgery

    Non-specific LTD at parallel fibre - Purkinje cell synapses in cerebellar cortex provides robustness against local spatial noise during pattern recognition

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    © 2011 Safaryan et al; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedPoster presented at CNS 2011Peer reviewe

    How well can machine-generated texts be identified and can language models be trained to avoid identification?

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    With the rise of generative pre-trained transformer models such as GPT-3, GPT-NeoX, or OPT, distinguishing human-generated texts from machine-generated ones has become important. We refined five separate language models to generate synthetic tweets, uncovering that shallow learning classification algorithms, like Naive Bayes, achieve detection accuracy between 0.6 and 0.8. Shallow learning classifiers differ from human-based detection, especially when using higher temperature values during text generation, resulting in a lower detection rate. Humans prioritize linguistic acceptability, which tends to be higher at lower temperature values. In contrast, transformer-based classifiers have an accuracy of 0.9 and above. We found that using a reinforcement learning approach to refine our generative models can successfully evade BERT-based classifiers with a detection accuracy of 0.15 or less.Comment: This paper has been accepted for the upcoming 57th Hawaii International Conference on System Sciences (HICSS-57

    The Impact of an International Interprofessional Experience on Perceptions of Pharmacist-Physician Relationships

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    Objective. To assess the impact of this international interprofessional learning experience on perceptions of pharmacist-physician relationships and interprofessional teams. Methods. Medical and pharmacy students completed a one-week interprofessional medical mission experience in the Dominican Republic. Anonymous surveys were administered to 17 students before and after completion to measure perceptions of pharmacist-physician relationships and interprofessional teams. Responses were matched and changes in perceptions were analyzed using the Wilcoxon Signed Rank test. The SPICE-R2 instrument was administered after the experience to measure attitudes toward interprofessional teams. Results. Of the 17 participants, 100% responded to all surveys. Significant improvements were seen in the perception of pharmacists as an integral part of medical mission trips (P=0.035) and confidence in the ability to communicate with other healthcare disciplines (P=0.033). All students stated they would recommend this experience, and agreed that interprofessional experiences enhance their team work skills and should be incorporated into their education. Student comments supported that this was a meaningful and effective interprofessional experience. The results of the SPICE-R2 demonstrated positive attitudes about interprofessional teams, with all questions having a median score of “agree” or “strongly agree.” Conclusions. An international interprofessional experience improved the perception of pharmacist-physician relationships. The experience provided understanding of the other healthcare discipline, an appreciation for the importance of interprofessional teamwork, increased student confidence in communicating with the other discipline, and cultivated interest in future interprofessional collaboration

    Steady-State Vacuum Ultraviolet Exposure Facility With Automated Lamp Calibration and Sample Positioning Fabricated

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    The Next Generation Space Telescope (NGST) will be placed in an orbit that will subject it to constant solar radiation during its planned 10-year mission. A sunshield will be necessary to passively cool the telescope, protecting it from the Sun s energy and assuring proper operating temperatures for the telescope s instruments. This sunshield will be composed of metalized polymer multilayer insulation with an outer polymer membrane (12 to 25 mm in thickness) that will be metalized on the back to assure maximum reflectance of sunlight. The sunshield must maintain mechanical integrity and optical properties for the full 10 years. This durability requirement is most challenging for the outermost, constantly solar-facing polymer membrane of the sunshield. One of the potential threats to the membrane material s durability is from vacuum ultraviolet (VUV) radiation in wavelengths below 200 nm. Such radiation can be absorbed in the bulk of these thin polymer membrane materials and degrade the polymer s optical and mechanical properties. So that a suitable membrane material can be selected that demonstrates durability to solar VUV radiation, ground-based testing of candidate materials must be conducted to simulate the total 10- year VUV exposure expected during the Next Generation Space Telescope mission. The Steady State Vacuum Ultraviolet exposure facility was designed and fabricated at the NASA Glenn Research Center at Lewis Field to provide unattended 24-hr exposure of candidate materials to VUV radiation of 3 to 5 times the Sun s intensity in the wavelength range of 115 to 200 nm. The facility s chamber, which maintains a pressure of approximately 5 10(exp -6) torr, is divided into three individual exposure cells, each with a separate VUV source and sample-positioning mechanism. The three test cells are separated by a water-cooled copper shield plate assembly to minimize thermal effects from adjacent test cells. Part of the interior sample positioning mechanism of one test cell is shown in the illustration. Of primary concern in VUV exposure is the maintenance of constant measured radiation intensity so that the sample s total exposure can be determined in equivalent Sun hours. This is complicated by the fact that a VUV lamp s intensity degrades over time, necessitating a decrease in the distance between the test samples and the lamp. The facility overcomes this challenge by periodically measuring the lamp s intensity with a cesium-iodide phototube and adjusting the sample distance as required to maintain constant exposure intensity. Sample positioning and periodic phototube location under the lamp are both achieved by a single lead-screw assembly. The lamps can be isolated from the main vacuum chamber for cleaning or replacement so that samples are not exposed to the atmosphere during a test
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