1,682 research outputs found

    Creep fatigue life prediction for engine hot section materials (isotropic)

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    A series of high temperature strain controlled fatigue tests have been completed to study the effects of thermomechanical fatigue, multiaxial loading, reactive environments, and imposed mean stresses. The baseline alloy used in these tests was cast B1900+Hf (with and without coatings); a small number of tests of wrought INCO 718 are also included. A strong path dependence was demonstrated during the thermomechanical fatigue testing, using in-phase, out-phase, and non-proportional (elliptical and 'dogleg') strain-temperature cycles. The multiaxial tests also demonstrated cycle path to be a significant variable, using both proportional and non-proportional tension-torsion loading. Environmental screening tests were conducted in moderate pressure oxygen and purified argon; the oxygen reduced the specimen lives by two, while the argon testing produced ambiguous data. Both NiCoCrAlY overlay and diffusion aluminide coatings were evaluated under isothermal and TMF conditions; in general, the lives of the coated specimens were higher that those of uncoated specimens. Controlled mean stress TMF tests showed that small mean stress changes could change initiation lives by orders of magnitude; these results are not conservatively predicted using traditional linear damage summation rules. Microstructures were evaluated using optical, SEM and TEM methods

    Virtual Supersymmetric Corrections in e^+e^- Annihilation

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    Depending on their masses, Supersymmetric particles can affect various measurements in Z decay. Among these are the total width (or consequent extracted value of αs\alpha_s), enhancement or suppression of various flavors, and left-right and forward-backward asymmetries. The latter depend on squark mass splittings and are, therefore, a possible test of the Supergravity related predictions. We calculate leading order corrections for these quantities considering in particular the case of light photino and gluino where the SUSY effects are enhanced. In this limit the effect on αs\alpha_s is appreciable, the effect on RbR_b is small, and the effect on the asymmetries is extremely small.Comment: 11 pages, LaTeX, 3 figures, revised, a reference adde

    Swift J1112.2-8238: A Candidate Relativistic Tidal Disruption Flare

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    We present observations of Swift J1112.2-8238, and identify it as a candidate relativistic tidal disruption flare (rTDF). The outburst was first detected by Swift/BAT in June 2011 as an unknown, long-lived (order of days) γ\gamma-ray transient source. We show that its position is consistent with the nucleus of a faint galaxy for which we establish a likely redshift of z=0.89z=0.89 based on a single emission line that we interpret as the blended [OII]λ3727\lambda3727 doublet. At this redshift, the peak X/γ\gamma-ray luminosity exceeded 104710^{47} ergs s1^{-1}, while a spatially coincident optical transient source had i22i^{\prime} \sim 22 (Mg21.4_g \sim -21.4 at z=0.89z=0.89) during early observations, 20\sim 20 days after the Swift trigger. These properties place Swift J1112.2-8238 in a very similar region of parameter space to the two previously identified members of this class, Swift J1644+57 and Swift J2058+0516. As with those events the high-energy emission shows evidence for variability over the first few days, while late time observations, almost 3 years post-outburst, demonstrate that it has now switched off. Swift J1112.2-8238 brings the total number of such events observed by Swift to three, interestingly all detected by Swift over a \sim3 month period (<3%<3\% of its total lifetime as of March 2015). While this suggests the possibility that further examples may be uncovered by detailed searches of the BAT archives, the lack of any prime candidates in the years since 2011 means these events are undoubtedly rare.Comment: 11 pages, 5 figures, accepted for publication by MNRA

    The Metabolism of Alcohol: Risk and Protective Factors

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    Purpose: Abstract for poster submission to VCU Poster Symposium for Undergraduate Research and Creativity Title: The Metabolism of Alcohol: Risk and Protective Factors Background: In 2002, it was reported by the National Institutes of Health that 60.3% of college aged students (18-22) drank alcohol in the past month of being asked, as compared to 51.9% of those not in college. They also found that 20% of college students met the criteria for at least one alcohol use disorder (AUDs)1. Many genes have been linked to an increased risk for AUDs and how individuals with various ethnic backgrounds respond to alcohol. Genes that metabolize alcohol are obvious candidate genes for alcohol-related phenotypes. The purpose of this presentation is to synthesize information about the key genes involved in alcohol metabolism, as documented in the literature. Methods: The information about each gene was found through a literature search using databases including PubMed, Google Scholar, and cited references from relevant papers. For database searches, the names of the genes were used as well as terms such as AUDs, alcohol metabolism, and alcohol and aldehyde dehydrogenase. The focus of the presentation will be relevant to college-aged students, but rely on research done in college and adult populations due to a lack of sufficient college- aged gene-based studies in this area. Results: Alcohol metabolism genes affect how individuals process and respond to alcohol. The main genes that have been studied are alcohol and aldehyde dehydrogenase genes. Alcohol dehydrogenase genes, like ADH1B and ADH1C, first metabolize ethanol (alcohol) into the by-product acetaldehyde and acetaldehyde is then metabolized by aldehyde dehydrogenase genes, like ALDH2, into the waste product acetate2. Many of the adverse effects associated with alcohol consumption are due to the build up of acetaldehyde. Some of these effects include facial blushing, nausea, headaches, and other similar alcohol sensitivity symptoms3,6. Acetaldehyde builds up in an individuals body after alcohol consumption if he or she has a super- active isoenzyme from the ADH1B and/or ADH1C genes and/or a slow ALDH2 enzyme. Individuals with the super-active alcohol dehydrogenase isoenzyme and slow aldehyde dehydrogenase enzyme are less likely to develop AUDs due to the negative effects from excess acetaldehyde in the body4,5,6. However, this also implies that individuals who do not exhibit the described protective phenotype are more likely to endorse increased drinking behaviors and AUDs. Spit for Science: the VCU Student Survey is currently investigating these genes and their association with alcohol consumption and alcohol use disorder symptoms. Due to the diverse nature of the sample, the researchers are able to explore ethnic differences in these alcohol metabolism genes and their effects. Implications: In general, the more public knowledge about these genes and research findings, the more at-risk individuals can get help and diagnosis. A better understanding of aggregate effects of alcohol metabolism genes, as well as more information regarding ethnic differences in the distribution of genetic variants which impact alcohol processing, will assist researchers and health professionals working with those at risk for AUDs.https://scholarscompass.vcu.edu/uresposters/1137/thumbnail.jp

    Exploring the Cosmic Evolution of Habitability with Galaxy Merger Trees

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    We combine inferred galaxy properties from a semi-analytic galaxy evolution model incorporating dark matter halo merger trees with new estimates of supernova and gamma ray burst rates as a function of metallicity from stellar population synthesis models incorporating binary interactions. We use these to explore the stellar mass fraction of galaxies irradiated by energetic astrophysical transients and its evolution over cosmic time, and thus the fraction which is potentially habitable by life like our own. We find that 18 per cent of the stellar mass in the Universe is likely to have been irradiated within the last 260 Myr, with GRBs dominating that fraction. We do not see a strong dependence of irradiated stellar mass fraction on stellar mass or richness of the galaxy environment. We consider a representative merger tree as a Local Group analogue, and find that there are galaxies at all masses which have retained a high habitable fraction (>40 per cent) over the last 6 Gyr, but also that there are galaxies at all masses where the merger history and associated star formation have rendered galaxies effectively uninhabitable. This illustrates the need to consider detailed merger trees when evaluating the cosmic evolution of habitability.Comment: 11 page, 10 figures. MNRAS accepted 13th Dec 2017. Updated to match accepted version, with additional discussion of metallicity effect

    Strong acceleration of glacier area loss in the Greater Caucasus between 2000 and 2020

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    An updated glacier inventory is important for understanding glacier behaviour given the accelerating glacier retreat observed around the world. Here, we present data from a new glacier inventory for two points in time (2000, 2020) covering the entire Greater Caucasus (Georgia, Russia, and Azerbaijan). Satellite imagery (Landsat, Sentinel, SPOT) was used to conduct a remote-sensing survey of glacier change. The 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine aspect, slope, and elevations, for all glaciers. Glacier margins were mapped manually and reveal that in 2000 the mountain range contained 2186 glaciers with a total glacier area of 1381.5 ± 58.2 km2. By 2020, the area had decreased to 1060.9 ± 33.6 km2 a reduction of 23.2 ± 3.8 % (320.6 ± 45.9 km2) or −1.16 % yr−1 over the last 20 years in the Greater Caucasus. Of the 2223 glaciers, 14 have an area > 10 km2, resulting in the 221.9 km2 or 20.9 % of total glacier area in 2020. The Bezengi Glacier with an area of 39.4 ± 0.9 km2 was the largest glacier mapped in the 2020 database. Glaciers between 1.0 and 5.0 km2 accounted for 478.1 km2 or 34.6 % in total area in 2000, while they accounted for 354.0 km2 or 33.4 % in total area in 2020. The rates of area shrinkage and mean elevation vary between the northern and southern and between the western, central, and eastern Greater Caucasus. Area shrinkage is significantly stronger in the eastern Greater Caucasus (−1.82 % yr−1), where most glaciers are very small. The observed increased summer temperatures and decreased winter precipitation along with increased Saharan dust deposition might be responsible for the predominantly negative mass balances of Djankuat and Garabashi glaciers with long-term measurements. Both glacier inventories are available from the Global Land Ice Measurements from Space (GLIMS) database and can be used for future studies

    The obscured hyper-energetic GRB 120624B hosted by a luminous compact galaxy at z = 2.20

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    Gamma-ray bursts are the most luminous explosions that we can witness in the Universe. Studying the most extreme cases of these phenomena allows us to constrain the limits for the progenitor models. In this Letter, we study the prompt emission, afterglow, and host galaxy of GRB 120624B, one of the brightest GRBs detected by Fermi, to derive the energetics of the event and characterise the host galaxy in which it was produced. Following the high-energy detection we conducted a multi-wavelength follow-up campaign, including near-infrared imaging from HAWKI/VLT, optical from OSIRIS/GTC, X-ray observations from the Chandra X-ray Observatory and at sub-millimetre/millimetre wavelengths from SMA. Optical/nIR spectroscopy was performed with X-shooter/VLT. We detect the X-ray and nIR afterglow of the burst and determine a redshift of z = 2.1974 +/- 0.0002 through the identification of emission lines of [OII], [OIII] and H-alpha from the host galaxy of the GRB. This implies an energy release of Eiso = (3.0+/-0.2)x10^54 erg, amongst the most luminous ever detected. The observations of the afterglow indicate high obscuration with AV > 1.5. The host galaxy is compact, with R1/2 < 1.6 kpc, but luminous, at L ~ 1.5 L* and has a star formation rate of 91 +/- 6 Msol/yr as derived from H-alpha. As other highly obscured GRBs, GRB 120624B is hosted by a luminous galaxy, which we also proof to be compact, with a very intense star formation. It is one of the most luminous host galaxies associated with a GRB, showing that the host galaxies of long GRBs are not always blue dwarf galaxies, as previously thought.Comment: 6 pages, 4 figures, 4 tables; accepted for publication in A&

    Understanding of the role of surveillance in Health Promotion for NCDs among Georgians

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    Background: Recognizing the need to build local capacity for non-communicable diseases (NCDs) and having a skilled workforce is an important strategy to implement the policy changes necessary to reduce the burden of NCDs. Indicators of tobacco smoking, alcohol consump on and drug abuse are s ll very high among Georgians. Nine out of ten deaths are a ributed to cardio-vascular diseases (CVD), cancer and injuries, the majority of which are caused by unhealthy behaviors. There is a very unclear understanding of health promo on (HP) approaches as a best opportunity to impact on NCDs and their risk factors even among Georgian professionals and more at the popula on level. The present study is the first effort to iden fy gaps, requirements and opportuni es in the health- promo on communica on system in Georgia, in order to iden fy the needs of capacity building for NCDs and their risk factors. Purpose: The Health Promo on Capacity Assessment aimed to evaluate the current health promo on system in Georgia. It covers the following issues: quality of health promo on/communica on and disease  preven on services, access to services, resources, health-promo on informa on/ communica on system and health-promo on financing. Its specific aims were (1) To iden fy the shor alls, requirements and opportuni es in health-promo on communica on through quan ta ve and qualita ve research; and (2) To define and analyze healthcare workers' knowledge, a tude and prac ce (KAP) related to health promo on/communica on aspects, the level of the professional development and requirements for their future training/retraining

    ESTIMA, a tool for EST management in a multi-project environment

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    BACKGROUND: Single-pass, partial sequencing of complementary DNA (cDNA) libraries generates thousands of chromatograms that are processed into high quality expressed sequence tags (ESTs), and then assembled into contigs representative of putative genes. Usually, to be of value, ESTs and contigs must be associated with meaningful annotations, and made available to end-users. RESULTS: A web application, Expressed Sequence Tag Information Management and Annotation (ESTIMA), has been created to meet the EST annotation and data management requirements of multiple high-throughput EST sequencing projects. It is anchored on individual ESTs and organized around different properties of ESTs including chromatograms, base-calling quality scores, structure of assembled transcripts, and multiple sources of comparison to infer functional annotation, Gene Ontology associations, and cDNA library information. ESTIMA consists of a relational database schema and a set of interactive query interfaces. These are integrated with a suite of web-based tools that allow a user to query and retrieve information. Further, query results are interconnected among the various EST properties. ESTIMA has several unique features. Users may run their own EST processing pipeline, search against preferred reference genomes, and use any clustering and assembly algorithm. The ESTIMA database schema is very flexible and accepts output from any EST processing and assembly pipeline. ESTIMA has been used for the management of EST projects of many species, including honeybee (Apis mellifera), cattle (Bos taurus), songbird (Taeniopygia guttata), corn rootworm (Diabrotica vergifera), catfish (Ictalurus punctatus, Ictalurus furcatus), and apple (Malus x domestica). The entire resource may be downloaded and used as is, or readily adapted to fit the unique needs of other cDNA sequencing projects. CONCLUSIONS: The scripts used to create the ESTIMA interface are freely available to academic users in an archived format from . The entity-relationship (E-R) diagrams and the programs used to generate the Oracle database tables are also available. We have also provided detailed installation instructions and a tutorial at the same website. Presently the chromatograms, EST databases and their annotations have been made available for cattle and honeybee brain EST projects. Non-academic users need to contact the W.M. Keck Center for Functional and Comparative Genomics, University of Illinois at Urbana-Champaign, Urbana, IL, for licensing information

    The Broad Absorption Line Tidal Disruption Event iPTF15af: Optical and Ultraviolet Evolution

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    We present multi-wavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by the intermediate Palomar Transient Factory (iPTF) survey at redshift z=0.07897z=0.07897. The optical and ultraviolet (UV) light curves of the transient show a slow decay over five months, in agreement with previous optically discovered TDEs. It also has a comparable black-body peak luminosity of Lpeak1.5×1044L_{\rm{peak}} \approx 1.5 \times 10^{44} erg/s. The inferred temperature from the optical and UV data shows a value of (3-5) ×104\times 10^4 K. The transient is not detected in X-rays up to LX<3×1042L_X < 3 \times 10^{42}erg/s within the first five months after discovery. The optical spectra exhibit two distinct broad emission lines in the He II region, and at later times also Hα\alpha emission. Additionally, emission from [N III] and [O III] is detected, likely produced by the Bowen fluorescence effect. UV spectra reveal broad emission and absorption lines associated with high-ionization states of N V, C IV, Si IV, and possibly P V. These features, analogous to those of broad absorption line quasars (BAL QSOs), require an absorber with column densities NH>1023N_{\rm{H}} > 10^{23} cm2^{-2}. This optically thick gas would also explain the non-detection in soft X-rays. The profile of the absorption lines with the highest column density material at the largest velocity is opposite that of BAL QSOs. We suggest that radiation pressure generated by the TDE flare at early times could have provided the initial acceleration mechanism for this gas. Spectral UV line monitoring of future TDEs could test this proposal.Comment: 20 pages, 12 figures, published in Ap
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