1,551 research outputs found

    Maxent Estimation of Aquatic Escherichia Coli Stream Impairment

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    Background.The leading cause of surface water impairment in United States’ rivers and streams is pathogen contamination. Although use of fecal indicators has reduced human health risk, current approaches to identify and reduce exposure can be improved. One important knowledge gap within exposure assessment is characterization of complex fate and transport processes of fecal pollution. Novel modeling processes can inform watershed decision-making to improve exposure assessment

    Metabolomic Shifts Associated with Heat Stress in Coral Holobionts

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    Understanding the response of the coral holobiont to environmental change is crucial to inform conservation efforts. The most pressing problem is “coral bleaching,” usually precipitated by prolonged thermal stress. We used untargeted, polar metabolite profiling to investigate the physiological response of the coral species Montipora capitata and Pocillopora acuta to heat stress. Our goal was to identify diagnostic markers present early in the bleaching response. From the untargeted UHPLC-MS data, a variety of co-regulated dipeptides were found that have the highest differential accumulation in both species. The structures of four dipeptides were determined and showed differential accumulation in symbiotic and aposymbiotic (alga-free) populations of the sea anemone Aiptasia (Exaiptasia pallida), suggesting the deep evolutionary origins of these dipeptides and their involvement in symbiosis. These and other metabolites may be used as diagnostic markers for thermal stress in wild coral

    A Lower Limit on the Mass of Our Galaxy from the H3 Survey

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    The timing argument provides a lower limit on the mass of the Milky Way. We find, using a sample of 32 stars at R>60R > 60 kpc drawn from the H3 Spectroscopic Survey and mock catalogs created from published numerical simulations, that M200>0.91×1012_{200} > 0.91\times 10^{12} M_\odot with 90% confidence. We recommend using this limit to refine the allowed prior mass range in more complex and sophisticated statistical treatments of Milky Way dynamics. The use of such a prior would have significantly reduced many previously published uncertainty ranges. Our analysis suggests that the most likely value of M200_{200} is 1.4×1012\sim 1.4 \times 10^{12} M_\odot, but establishing this as the Milky Way mass requires a larger sample of outer halo stars and a more complete analysis of the inner halo stars in H3. The imminent growth in the sample of outer halo stars due to ongoing and planned surveys will make this possible.Comment: 8 pages, submitted for publicatio

    Automated Low-Gravitation Facility Would Make Optical Fibers

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    A report describes a proposed automated facility that would be operated in outer space to produce high-quality optical fibers from fluoride-based glasses, free of light-scattering crystallites that form during production in normal Earth gravitation. Before launch, glass preforms would be loaded into a mechanism that would later dispense them. A dispensed preform would be melted, cooled to its glass-transition temperature rapidly enough to prevent crystallization, cooled to ambient temperature, then pushed into a preform tip heater, wherein it would be reheated to the softening temperature. A robotic manipulator would touch a fused silica rod to the softened glass to initiate pulling of a fiber. The robot would pull the fiber to an attachment on a take-up spool, which would thereafter be turned to pull the fiber. The diameter of the fiber would depend on the pulling speed and the viscosity of the glass at the preform tip. Upon depletion of a preform, the robot would place the filled spool in storage and position an empty spool to pull a fiber from a new preform. Pulling would be remotely monitored by a video camera and restarted by remote command if a break in the fiber were observed

    Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure

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    In the Λ\LambdaCDM paradigm the Galactic stellar halo is predicted to harbor the accreted debris of smaller systems. To identify these systems, the H3 Spectroscopic Survey, combined with GaiaGaia, is gathering 6D phase-space and chemical information in the distant Galaxy. Here we present a comprehensive inventory of structure within 50 kpc from the Galactic center using a sample of 5684 giants at b>40|b|>40^{\circ} and Z>2|Z|>2 kpc. We identify known structures including the high-α\alpha disk, the in-situ halo (disk stars heated to eccentric orbits), Sagittarius (Sgr), GaiaGaia-Sausage-Enceladus (GSE), the Helmi Streams, Sequoia, and Thamnos. Additionally, we identify the following new structures: (i) Aleph ([Fe/H]=0.5=-0.5), a low eccentricity structure that rises a surprising 10 kpc off the plane, (ii, iii) Arjuna ([Fe/H]=1.2=-1.2) and I'itoi ([Fe/H]<2<-2), which comprise the high-energy retrograde halo along with Sequoia, and (iv) Wukong ([Fe/H]=1.6=-1.6), a prograde phase-space overdensity chemically distinct from GSE. For each structure we provide [Fe/H], [α\alpha/Fe], and orbital parameters. Stars born within the Galaxy are a major component at Z|Z|\sim2 kpc (\approx60%\%), but their relative fraction declines sharply to \lesssim5%\% past 15 kpc. Beyond 15 kpc, >>80%\% of the halo is built by two massive (M108109MM_{\star}\sim10^{8}-10^{9}M_{\odot}) accreted dwarfs: GSE ([Fe/H]=1.2=-1.2) within 25 kpc, and Sgr ([Fe/H]=1.0=-1.0) beyond 25 kpc. This explains the relatively high overall metallicity of the halo ([Fe/H]1.2\approx-1.2). We attribute \gtrsim95%\% of the sample to one of the listed structures, pointing to a halo built entirely from accreted dwarfs and heating of the disk.Comment: Submitted to ApJ. Key results in Figures 18-21. Summary of individual structures in Sec. 3.3 and Table 1. Comments very welcome

    Small-molecule antagonists of the oncogenic Tcf/β-catenin protein complex

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    AbstractKey molecular lesions in colorectal and other cancers cause β-catenin-dependent transactivation of T cell factor (Tcf)-dependent genes. Disruption of this signal represents an opportunity for rational cancer therapy. To identify compounds that inhibit association between Tcf4 and β-catenin, we screened libraries of natural compounds in a high-throughput assay for immunoenzymatic detection of the protein-protein interaction. Selected compounds disrupt Tcf/β-catenin complexes in several independent in vitro assays and potently antagonize cellular effects of β-catenin-dependent activities, including reporter gene activation, c-myc or cyclin D1 expression, cell proliferation, and duplication of the Xenopus embryonic dorsal axis. These compounds thus meet predicted criteria for disrupting Tcf/β-catenin complexes and define a general standard to establish mechanism-based activity of small molecule inhibitors of this pathogenic protein-protein interaction

    Immune Evasion by Murine Melanoma Mediated through CC Chemokine Receptor-10

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    Human melanoma cells frequently express CC chemokine receptor (CCR)10, a receptor whose ligand (CCL27) is constitutively produced by keratinocytes. Compared with B16 murine melanoma, cells rendered more immunogenic via overexpression of luciferase, B16 cells that overexpressed both luciferase and CCR10 resisted host immune responses and readily formed tumors. In vitro, exposure of tumor cells to CCL27 led to rapid activation of Akt, resistance to cell death induced by melanoma antigen-specific cytotoxic T cells, and phosphatidylinositol-3-kinase (PI3K)–dependent protection from apoptosis induced by Fas cross-linking. In vivo, cutaneous injection of neutralizing antibodies to endogenous CCL27 blocked growth of CCR10-expressing melanoma cells. We propose that CCR10 engagement by locally produced CCL27 allows melanoma cells to escape host immune antitumor killing mechanisms (possibly through activation of PI3K/Akt), thereby providing a means for tumor progression

    A Diffuse Metal-Poor Component of the Sagittarius Stream Revealed by the H3 Survey

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    The tidal disruption of the Sagittarius dwarf galaxy has generated a spectacular stream of stars wrapping around the entire Galaxy. We use data from GaiaGaia and the H3 Stellar Spectroscopic Survey to identify 823 high-quality Sagittarius members based on their angular momenta. The H3 Survey is largely unbiased in metallicity, and so our sample of Sagittarius members is similarly unbiased. Stream stars span a wide range in [Fe/H] from 0.2-0.2 to 3.0\approx -3.0, with a mean overall metallicity of \langle[Fe/H]=0.99\rangle=-0.99. We identify a strong metallicity-dependence to the kinematics of the stream members. At [Fe/H]>0.8\gt -0.8 nearly all members belong to the well-known cold (σv<20\sigma_v \lt 20 km/s) leading and trailing arms. At intermediate metallicities (1.9<-1.9 \lt[Fe/H]<0.8\lt -0.8) a significant population (24%\%) emerges of stars that are kinematically offset from the cold arms. These stars also appear to have hotter kinematics. At the lowest metallicities ([Fe/H]2\lesssim-2), the majority of stars (69%\%) belong to this kinematically-offset diffuse population. Comparison to simulations suggests that the diffuse component was stripped from the Sagittarius progenitor at earlier epochs, and therefore resided at larger radius on average, compared to the colder metal-rich component. We speculate that this kinematically diffuse, low metallicity, population is the stellar halo of the Sagittarius progenitor system.Comment: 18 pages, 12 figures, 1 table. Submitted to Ap
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