3,201 research outputs found

    Diamagnetic repulsion of particles for multilaminar flow assays

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    © The Royal Society of Chemistry. We demonstrate diamagnetic repulsion forces for performing continuous multilaminar flow assays on particles based on their intrinsic properties and with a simple setup. The platform could be applied to sandwich assays on polystyrene particles, and to cell-based assays via their suspension in biologically benign magnetic media

    Theoretical approach to oxygen atom degradation of silver

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    Based on available Rutherford backscattering spectrometry (RBS), proton induced X-ray emission (PIXE) and ellipsometry data obtained on silver specimens subjected to atomic oxygen attack in low Earth orbit STS flight 41-G, a theory was developed to model the oxygen atom degradation of silver. The diffusion of atomic oxygen in a microscopically nonuniform medium is an essential constituent of the theory. The driving force for diffusion is the macroscopic electrochemical potential gradient developed between the specimen surface exposed to the ambient and the bulk of the silver specimen. The longitudinal electric effect developed parallel to the gradient is modified by space charge of the diffusing charged species. Lateral electric fields and concentration differences also exist due to the nonuniform nature of the medium. The lateral concentration differences are found to be more important than the lateral electric fields in modifying the diffusion rate. The model was evaluated numerically. Qualitative agreement exists between the kinetics predicted by the theory and kinetic data taken in ground-based experiments utilizing a plasma asher

    Characteristics of Duplicate Records in OCLC's Online Union Catalog

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    Duplicate records in the Online Union Catalog of the OCLC Online Computer Library Center, Inc., were analyzed. Bibliographic elements comprise information found in one or more fields of a bibliographic record; e.g., the author element comprises the main and added author entry fields. Bibliographic element mismatches in duplicate record pairs were considered relative to the number of records in which each element was present. When a single element differed in a duplicate record pair, that element was most often publication date. This finding shows that a difference in the date of publication is not a reliable indicator of bibliographic uniqueness. General cataloging and data entry patterns such as variations in title transcription and form of name, typographical errors, mistagged fields, misplaced subfield codes, omissions, and inconsistencies between fixed and variable fields often caused records that were duplicates to appear different. These factors can make it extremely difficult for catalogers to retrieve existing bibliographic records and thus avoid creating duplicate records. They also prevent duplicate detection algorithms used for tape-loading records from achieving desired results. An awareness of particularly problematic bibliographic elements and general factors contributing to the creation of duplicate records should help catalogers identify and accept existing records more often. This awareness should also help to direct system designers in their development of more sensitive algorithms to be used for tape loading. The resulting general reduction in the number of duplicate records in union catalogs will be a major step toward increased cataloger productivity, user satisfaction, and overall online database quality

    Preliminary Results from an Experimental Assessment of a Natural Laminar Flow Design Method

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    A 5.2% scale semispan model of the new Common Research Model with Natural Laminar Flow (CRM-NLF) was tested in the National Transonic Facility (NTF) at the NASA Langley Research Center. The model was tested at transonic cruise flight conditions with Reynolds numbers based on mean aerodynamic chord ranging from 10 to 30 million. The goal of the test was to experimentally validate a new design method, referred to as Crossflow Attenuated NLF (CATNLF), which shapes airfoils to have pressure distributions that delay transition on wings with high sweep and Reynolds numbers. Additionally, the test aimed to characterize the NTF laminar flow testing capabilities, as well as establish best practices for laminar flow wind tunnel testing. Preliminary results regarding the first goal of validating the new design method are presented in this paper. Experimental data analyzed in this assessment include surface pressure data and transition images. The surface pressure data acquired during the test agree well with computational fluid dynamics (CFD) results. Transition images at a variety of Reynolds numbers and angles of attack are presented and compared to computational transition predictions. The experimental data are used to assess transition due to a turbulent attachment line, as well as crossflow and Tollmien-Schlichting modal instabilities. Preliminary results suggest the CATNLF design method is successful at delaying transition on wings with high sweep. Initial analysis of the transition front images showed transition Reynolds numbers that exceed historic experimental values at similar sweep angles. , section lif

    The fear of bad smell: Health risk awareness related to using waste in agricultural production in Vietnam

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    Waste watersWater reuseAgricultural productionFish farmingIrrigation waterPublic healthRisksSkin diseasesOrganic fertilizersWomen

    Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design

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    A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5 angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for proper validation of the CFD

    Esterase Variants in Four Species of the Paramecium aurelia Complex 1

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    One hundred eighty-eight stocks of Paramecium primaurelia, P. biaurelia, P. tetraurelia , and P. octaurelia were grown axenically and tested for five esterases, visualized by starch gel electrophoresis, in a search for variant stocks. The five esterases can be distinguished on the bases of their substrate specificity, sensitivity to an inhibitor, and response to different growth conditions. This paper addresses the nature of the electrophoretic change in mobility of the variant stocks in order that species relationships can be more accurately assessed. Crosses carried out in all four species show that single genes determine the differences in mobility between variant and common subtypes. Extracts of variant stocks that gave similar patterns were run against each other, tested for their sensitivity to the inhibitor, and the pattern was compared to that found in extracts of stocks with variant and common subtypes in other species. The majority of the variants in P. primaurelia, P. tetraurelia , and P. octaurelia show an electrophoretic mobility characteristic of a common subtype, or a variant, in another species. The same proportion of variant subtypes as common subtypes have mobilities similar to esterase subtypes found in other species. Of the four species examined in this paper, P. tetraurelia and P. octaurelia appear to be most closely related on the basis of shared esterase subtypes. In P. biaurelia the mobilities of most of the variants are unique, as are the common esterase subtypes in this species. P. biaurelia stands out as having the greatest number of esterase subtypes, with very few of them homologous to subtypes found in other species. This observation supports the idea of greater diversification of stocks within P. biaurelia than for the other three species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75741/1/j.1550-7408.1982.tb01346.x.pd

    Aspirin Dosing for the Prevention and Treatment of Ischemic Stroke: An Indication-Specific Review of the Literature

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    OBJECTIVE: To evaluate the efficacy of aspirin for the treatment and prevention of ischemic stroke and identify the minimum dose proven to be effective for each indication. DATA SOURCES: PubMed and MEDLINE searches (January 2009–January 2010) were performed to identify primary literature, using search terms including aspirin, stroke prevention, acute ischemic stroke, acetylsalicylic acid, atrial fibrillation, myocardial infarction, and carotid endarterectomy. Additionally, reference citations from publications identified were reviewed. STUDY SELECTION AND DATA EXTRACTION: Articles published in English were evaluated and relevant primary literature evaluating the efficacy of aspirin in the prevention of stroke was included in this review. DATA SYNTHESIS: Antiplatelet therapy is the benchmark for the prevention of ischemic stroke. Aspirin has been proven to prevent ischemic stroke in a variety of settings. Despite the frequency at which aspirin continues to be prescribed in patients at risk of ischemic stroke, there remains confusion in clinical practice as to what minimum dose is required in various at-risk patients. A thorough review of the primary literature suggests that low-dose (50–81 mg daily) aspirin is insufficient for some indications. Acute ischemic stroke treatment requires 160–325 mg, while atrial fibrillation and carotid arterial disease require daily doses of 325 and 81–325 mg, respectively. CONCLUSIONS: Available evidence suggests that aspirin dosing must be individualized according to indication. Recommendations provided by national guidelines at times recommend lower doses of aspirin than have been proven effective. Higher doses are indicated for stroke prevention in atrial fibrillation (325mg) and acute ischemic stroke patients (160–325 mg). Aspirin has not yet been proven effective for primary prevention of strokes in men, and a minimum dose for these patients cannot be determined from the available data
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