2,170 research outputs found

    Rapid ascent and emplacement of basaltic lava during the 2005–06 eruption of the East Pacific Rise at ca. 9°51′N as inferred from CO2 contents

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    © The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Earth and Planetary Science Letters 453 (2016): 152-160, doi:10.1016/j.epsl.2016.08.007.Eruption rates at the mid–ocean ridges (MORs) are believed to strongly control the morphology and length of lava flows emplaced along the ridge axis, and thus the structure and porosity of the upper oceanic crust. Eruption rate also represents one of the few tools to gain insight into the driving pressures within sub-ridge magmatic systems. As eruption rate is inferred to vary systematically along the global mid-ocean ridge, understanding of how to assess eruption rate in submarine systems and how it maps to observable features of the ridge axis would provide a powerful tool to understand Earth's largest magmatic system. Eruption rates at MORs are poorly constrained, however, because of a lack of direct observations, preventing the duration of an eruption to be quantified. This study uses decompression experiments of MORB samples and numerical modeling of CO2 degassing to reconstruct the timescales for magma ascent and lava emplacement during the 2005–06 eruption of the East Pacific Rise at ca. 9°51’N. Samples collected from the lava flow are all supersaturated in dissolved CO2 contents, but CO2 decreases with distance from the vent, presumably as a consequence of progressive CO2 diffusion into growing bubbles. Samples collected at the vent contain ~105 vesicles per cm3. Pieces of these samples were experimentally heated to 1225°C at high pressure and then decompressed at controlled rates. Results, plus those from numerical modeling of diffusive bubble growth, indicate that magma rose from the axial magma chamber to the seafloor in ≤1 hour and at a rate of ≥2–3 km hr-1. Our modeling, as validated by experimental decompression of MORB samples with ~106 vesicles cm-3, also suggests that CO2 degassed from the melt within ~10–100 minutes as the vesicular lava traveled ~ 1.7 km along the seafloor, implying a volumetric flow rate on order of 103–4 m3 s-1. Given an ascent rate of ≥0.2 m s-1, the width of a rectangular dike feeding the lava would have been ~1–2 meters wide. MORB samples from the Pacific ridge are generally more supersaturated in dissolved CO2 than those from slower spreading Atlantic and Indian ridges. Our results suggest that Pacific MORBs ascend to the seafloor faster than Atlantic or Indian MORBsThis project was partially funded by a grant to J.E.G. from the U.S. National Science Foundation (OCE-1333882).2017-08-2

    Race affects SVR12 in a large and ethnically diverse hepatitis C-infected patient population following treatment with direct-acting antivirals: Analysis of a single-center Department of Veterans Affairs cohort.

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    Hepatitis C virus (HCV) infection is a major cause of chronic liver disease. HCV cure has been linked to improved patient outcomes. In the era of direct-acting antivirals (DAAs), HCV cure has become the goal, as defined by sustained virological response 12 weeks (SVR12) after completion of therapy. Historically, African-Americans have had lower SVR12 rates compared to White people in the interferon era, which had been attributed to the high prevalence of non-CC interleukin 28B (IL28B) type. Less is known about the association between race/ethnicity and SVR12 in DAA-treated era. The aim of the study is to evaluate the predictors of SVR12 in a diverse, single-center Veterans Affairs population. We conducted a retrospective study of patients undergoing HCV therapy with DAAs from 2014 to 2016 at the VA Greater Los Angeles Healthcare System. We performed a multivariable logistic regression analysis to determine predictors of SVR12, adjusting for age, HCV genotype, DAA regimen and duration, human immunodeficiency virus (HIV) status, fibrosis, nonalcoholic fatty liver disease (NAFLD) fibrosis score, homelessness, mental health, and adherence. Our cohort included 1068 patients, out of which 401 (37.5%) were White people and 400 (37.5%) were African-American. Genotype 1 was the most common genotype (83.9%, N = 896). In the adjusted models, race/ethnicity and the presence of fibrosis were statistically significant predictors of non-SVR. African-Americans had 57% lower odds for reaching SVR12 (adj.OR = 0.43, 95% CI = 1.5-4.1) compared to White people. Advanced fibrosis (adj.OR = 0.40, 95% CI = 0.26-0.68) was also a significant predictor of non-SVR. In a single-center VA population on DAAs, African-Americans were less likely than White people to reach SVR12 when adjusting for covariates

    2003 AAPP Monograph Series

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    It is significant that the African American Professors Program (AAPP) at the University of South Carolina is producing the third edition of its annual monograph series at this time-the fifth anniversary of AAPP. The program graciously accepts the challenge of putting into place a requirement for the scholars to produce quality research papers worthy of publication. This provides widespread visibility for them and enhances their curriculum vitae concurrently. Scholars who have contributed manuscripts for this monograph are to be commended for adding this additional responsibility to their academic workload. Writing across disciplines adds to the intellectual diversity of these papers. From neophytes, relatively speaking, to an array of very experienced individuals, the chapters have been researched and comprehensively written. Founded in 1997 through the Department of Educational Leadership and Policies in the College of Education, AAPP was designed to address the underrepresentation of African American professors on college and university campuses. Its mission is to expand the pool of these professors in critical academic and research areas. Sponsored by the University of South Carolina, the W. K. Kellogg Foundation, and the South Carolina General Assembly, the program recruits students with bachelor\u27s, master\u27s, and doctoral degrees for disciplines in which African Americans currently are underrepresented. An important component of the program is the mentoring experience that is provided. Each student is assigned to a mentor/professor who guides the student through a selected academic program and provides various learning experiences. When possible, the mentor serves as chair of the student\u27s doctoral committee. The mentor also provides opportunities for the student to team teach, conduct research, and co-author publications. Students have the advantage of attending committee, faculty, and professional meetings, as well as engaging in a range of activities that characterize professional life in academia. Scholars enrolled in the program also are involved in programmatic and institutional workshops, independent research, and program development. The continuation of this monograph series is seen as responding to a window of opportunity to be sensitive to an academic expectation of graduates as they pursue career placement and, at the same time, one that allows for the dissemination of AAPP products to a broader community. The importance of this monograph series has been voiced by one of our 2002 AAPP graduates, Dr. Shundelle LaTjuan Dogan, a recent Harvard Administrative Fellow at Harvard University and now Program Officer for the Southern Education Foundation, Atlanta, Georgia. Dr. Dogan wrote: One thing in particular that I want to thank you for is having the African American Professors Program scholars publish articles for the monograph. I have to admit that writing the articles seemed like extra work at the time. However, in my recent interview process, organizations have asked me for samples of my writing. Including an article from a published monograph helped to make my portfolio much more impressive. You were right on target in having us do the monograph series. We hope that you will read this monograph of the African American Professors Program with enthusiasm or enlightenment. John McFadden, Ph.D. The Benjamin Elijah Mays Professor Director, African American Professors Program University of South Carolinahttps://scholarcommons.sc.edu/mcfadden_monographs/1006/thumbnail.jp

    Electrospun amplified fiber optics

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    A lot of research is focused on all-optical signal processing, aiming to obtain effective alternatives to existing data transmission platforms. Amplification of light in fiber optics, such as in Erbium-doped fiber amplifiers, is especially important for an efficient signal transmission. However, the complex fabrication methods, involving high-temperature processes performed in highly pure environment, slow down the fabrication and make amplified components expensive with respect to an ideal, high-throughput and room temperature production. Here, we report on near infrared polymer fiber amplifiers, working over a band of about 20 nm. The fibers are cheap, spun with a process entirely carried out at room temperature, and show amplified spontaneous emission with good gain coefficients as well as low optical losses (a few cm^-1). The amplification process is favoured by the high fiber quality and low self-absorption. The found performance metrics promise to be suitable for short-distance operation, and the large variety of commercially-available doping dyes might allow for effective multi-wavelength operation by electrospun amplified fiber optics.Comment: 27 pages, 8 figure

    Transiting exoplanets from the CoRoT space mission IX. CoRoT-6b: a transiting `hot Jupiter' planet in an 8.9d orbit around a low-metallicity star

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    The CoRoT satellite exoplanetary team announces its sixth transiting planet in this paper. We describe and discuss the satellite observations as well as the complementary ground-based observations - photometric and spectroscopic - carried out to assess the planetary nature of the object and determine its specific physical parameters. The discovery reported here is a `hot Jupiter' planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The planet mass is close to 3 times that of Jupiter. The star has a metallicity of 0.2 dex lower than the Sun, and a relatively high 7^7Li abundance. While thelightcurveindicatesamuchhigherlevelof activity than, e.g., the Sun, there is no sign of activity spectroscopically in e.g., the [Ca ] H&K lines

    2005 AAPP Monograph Series

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    The African American Professors Program (AAPP) at the University of South Carolina is proud to publish the fifth edition of its annual monograph series. The program recognizes the significance of offering its scholars avenue to engage actively in research and publish papers related thereto. Parallel with the publication of their refereed manuscripts is the opportunity to gain visibility among scholars throughout institutions worldwide. Scholars who have contributed manuscripts for this monograph are to be commended for adding this additional responsibility to their academic workload. Writing across disciplines adds to the intellectual diversity of these papers. From neophytes, relatively speaking, to an array of very experienced individuals, the chapters have been researched and comprehensively written. Founded in 1997 through the Department of Educational Leadership and Policies in the College of Education, AAPP was designed to address the underrepresentation of African American professors on college and university campuses. Its mission is to expand the pool of these professors in critical academic and research areas. Sponsored by the University of South Carolina, the W. K. Kellogg Foundation, and the South Carolina General Assembly, the program recruits doctoral students for disciplines in which African Americans currently are underrepresented among faculty in higher education. The continuation of this monograph series is seen as responding to a window of opportunity to be sensitive to an academic expectation of graduates as they pursue career placement and, at the same time, one that allows for the dissemination of AAPP products to a broader community. The importance of this monograph series has been voiced by one of our 2002 AAPP graduates, Dr. Shundele LaTjuan Dogan, a recent Administrative Fellow at Harvard University and now a Program Officer for the Southern Education Foundation, Atlanta, Georgia. Dr. Dogan wrote: One thing in particular that I want to thank you for is having the African American Professors Program scholars publish articles for the monograph. I have to admit that writing the articles seemed like extra work at the time. However, in my recent interview process, organizations have asked me for samples of my writing. Including an article from a published monograph helped to make my portfolio much more impressive. You were \u27right on target\u27 in having us do the monograph series. (MPP 2003 Monograph, p. xi) The African American Professors Program offers this 2005 publication as a contribution to its readership and hopes that you will be inspired by this select group of manuscripts. John McFadden, Ph.D. The Benjamin Elijah Mays Professor Director, African American Professors Program University of South Carolinahttps://scholarcommons.sc.edu/mcfadden_monographs/1007/thumbnail.jp

    Shark depredation: future directions in research and management

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    Shark depredation is a complex social-ecological issue that affects a range of fisheries worldwide. Increasing concern about the impacts of shark depredation, and how it intersects with the broader context of fisheries management, has driven recent research in this area, especially in Australia and the United States. This review synthesises these recent advances and provides strategic guidance for researchers aiming to characterise the occurrence of depredation, identify the shark species responsible, and test deterrent and management approaches to reduce its impacts. Specifically, the review covers the application of social science approaches, as well as advances in video camera and genetic methods for identifying depredating species. The practicalities and considerations for testing magnetic, electrical, and acoustic deterrent devices are discussed in light of recent research. Key concepts for the management of shark depredation are reviewed, with recommendations made to guide future research and policy development. Specific management responses to address shark depredation are lacking, and this review emphasizes that a “silver bullet” approach for mitigating depredation does not yet exist. Rather, future efforts to manage shark depredation must rely on a diverse range of integrated approaches involving those in the fishery (fishers, scientists and fishery managers), social scientists, educators, and other stakeholders

    Caesium incorporation and retention in illite interlayers

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    Radioactive caesium (chiefly 137Cs) is a major environmental pollutant. The mobility of Cs in temperate soils is primarily controlled by sorption onto clay minerals, particularly the frayed edges of illite interlayers. This paper investigates the adsorption of Cs to illite at the molecular scale, over both the short and long term. Transmission electron microscopy (TEM) images showed that after initial absorption into the frayed edges, Cs migrated into the illite interlayer becoming incorporated within the mineral structure. Caesium initially exchanged with hydrated Ca at the frayed edges, causing them to collapse. This process was irreversible as Cs held in the collapsed interlayers was not exchangeable with Ca. Over the long term Cs did not remain at the edge of the illite crystals, but diffused into the interlayers by exchange with K. Results from extended X-ray absorption fine structure spectroscopy (EXAFS) and density functional theory modelling confirmed that Cs was incorporated into the illite interlayer and revealed its bonding environment

    A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)

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    We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data sample consists of 29.7 fb1{\rm fb}^{-1} recorded at the Υ(4S)\Upsilon(4S) resonance and 3.9 fb1{\rm fb}^{-1} off-resonance. One of the neutral B mesons, which are produced in pairs at the Υ(4S)\Upsilon(4S), is fully reconstructed in the CP decay modes J/ψKS0J/\psi K^0_S, ψ(2S)KS0\psi(2S) K^0_S, χc1KS0\chi_{c1} K^0_S, J/ψK0J/\psi K^{*0} (K0KS0π0K^{*0}\to K^0_S\pi^0) and J/ψKL0J/\psi K^0_L, or in flavor-eigenstate modes involving D()π/ρ/a1D^{(*)}\pi/\rho/a_1 and J/ψK0J/\psi K^{*0} (K0K+πK^{*0}\to K^+\pi^-). The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample finds Δmd=0.516±0.016(stat)±0.010(syst)ps1\Delta m_d = 0.516\pm 0.016 {\rm (stat)} \pm 0.010 {\rm (syst)} {\rm ps}^{-1}. The value of the asymmetry amplitude sin2β\sin2\beta is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged B0B^0 decays in the CP-eigenstate modes. We find sin2β=0.59±0.14(stat)±0.05(syst)\sin2\beta=0.59\pm 0.14 {\rm (stat)} \pm 0.05 {\rm (syst)}, demonstrating that CP violation exists in the neutral B meson system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
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