205 research outputs found

    Quantum Number Density Asymmetries Within QCD Jets Correlated With Lambda Polarization

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    The observation of jets in a variety of hard-scattering processes has allowed the quantitative study of perturbative quantum chromodynamics (PQCD) by comparing detailed theoretical predictions with a wide range of experimental data. This paper examines how some important, nonperturbative, facets of QCD involving the internal dynamical structure of jets can be studied by measuring the spin orientation of Lambda particles produced in these jets. The measurement of the transverse polarization for an individual Lambda within a QCD jet permits the definition of spin-directed asymmetries in local quantum number densities in rapidity space (such as charge, strangeness and baryon number densities) involving neighboring hadrons in the jet. These asymmetries can only be generated by soft, nonperturbative dynamical mechanisms and such measurements can provide insight not otherwise accessible into the color rearrangement that occurs during the hadronization stage of the fragmentation process.Comment: The replacement manuscript contains a new abstract, five pages of additional material and a revised version of Fig.

    A Comparison of Survey Methods for Documenting Presence of Myotis leibii (Eastern Small-Footed Bats) at Roosting Areas in Western Virginia

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    Many aspects of foraging and roosting habitat of Myotis leibii (Eastern Small-Footed Bat), an emergent rock roosting-obligate, are poorly described. Previous comparisons of effectiveness of acoustic sampling and mist-net captures have not included Eastern Small-Footed Bat. Habitat requirements of this species differ from congeners in the region, and it is unclear whether survey protocols developed for other species are applicable. Using data from three overlapping studies at two sampling sites in western Virginia’s central Appalachian Mountains, detection probabilities were examined for three survey methods (acoustic surveys with automated identification of calls, visual searches of rock crevices, and mist-netting) for use in the development of “best practices” for future surveys and monitoring. Observer effects were investigated using an expanded version of visual search data. Results suggested that acoustic surveys with automated call identification are not effective for documenting presence of Eastern Small-Footed Bats on talus slopes (basal detection rate of 0%) even when the species is known to be present. The broadband, high frequency echolocation calls emitted by Eastern Small-Footed Bat may be prone to attenuation by virtue of their high frequencies, and these factors, along with signal reflection, lower echolocation rates or possible misidentification to other bat species over talus slopes may all have contributed to poor acoustic survey success. Visual searches and mist-netting of emergent rock had basal detection probabilities of 91% and 75%, respectively. Success of visual searches varied among observers, but detection probability improved with practice. Additionally, visual searches were considerably more economical than mist-netting

    Early stages of ramified growth in quasi-two-dimensional electrochemical deposition

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    I have measured the early stages of the growth of branched metal aggregates formed by electrochemical deposition in very thin layers. The growth rate of spatial Fourier modes is described qualitatively by the results of a linear stability analysis [D.P. Barkey, R.H. Muller, and C.W. Tobias, J. Electrochem. Soc. {\bf 136}, 2207 (1989)]. The maximum growth rate is proportional to (I/c)Ύ(I/c)^\delta where II is the current through the electrochemical cell, cc the electrolyte concentration, and Ύ=1.37±0.08\delta = 1.37 \pm 0.08. Differences between my results and the theoretical predictions suggest that electroconvection in the electrolyte has a large influence on the instability leading to ramified growth.Comment: REVTeX, four ps figure

    “Dogged” Search of Fresh Nakhla Surfaces Reveals New Alteration Textures

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    Special Issue: 74th Annual Meeting of the Meteoritical Society, August 8-12, 2011, London, U.K.International audienceCarbonaceous chondrites are considered as amongst the most primitive Solar System samples available. One of their primitive characteristics is their enrichment in volatile elements.This includes hydrogen, which is present in hydrated and hydroxylated minerals. More precisely, the mineralogy is expected to be dominated by phyllosilicates in the case of CM chondrites, and by Montmorillonite type clays in the case of CI. Here, in order to characterize and quantify the abundance of lowtemperature minerals in carbonaceous chondrites, we performed thermogravimetric analysis of matrix fragments of Tagish Lake, Murchison and Orgueil

    Association between the Interleukin-6 Promoter Polymorphism −174G/C and Serum Lipoprotein(a) Concentrations in Humans

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    Background: Lipoprotein(a) [Lp(a)] is an independent risk factor for cardiovascular disease. The interleukin-6 (IL-6) receptor antagonist tocilizumab has been shown to lower serum Lp(a) concentrations. We investigated whether the IL-6 single nucleotide polymorphism 2174G/C is associated with baseline serum Lp(a) concentrations. Methodology/Principal Findings: We divided 2321 subjects from the Lipid Analytic Cologne (LIANCO) cohort into 2 groups, the ones with substantially elevated Lp(a), defined as concentrations $60 mg/dl (n = 510), and the ones with Lp(a),60 mg/ dl (n = 1811). The association with the genotypes GG (33.7%), GC (50.75%) and CC (15.55%) was investigated. The GC and the CC genotype were associated with a significantly increased odds ratio of having substantially elevated Lp(a) concentrations (OR = 1.3, 95 % CI 1.04 to 1.63, P = 0.02 and OR = 1.44, 95 % CI 1.06 to 1.93, P = 0.018). These associations remained significant after adjusting for age, sex, smoking behavior, body mass index, serum lipoproteins, hypertension and diabetes. Of these covariates, only LDL cholesterol was significantly and independently associated with elevated Lp(a) concentrations. Conclusions/Significance: The IL-6 single nucleotide polymorphism 2174G/C is associated with increased odds of having elevated Lp(a). Whether this association plays a role in the Lp(a)-lowering effects of IL-6 receptor antagonists remains to b

    Final Reports of the Stardust ISPE: Seven Probable Interstellar Dust Particles

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    The Stardust spacecraft carried the first spaceborne collector specifically designed to capture and return a sample of contemporary interstellar dust to terrestrial laboratories for analysis [1]. The collector was exposed to the interstellar dust stream in two periods in 2000 and 2002 with a total exposure of approximately 1.8 10(exp 6) square meters sec. Approximately 85% of the collector consisted of aerogel, and the remainder consisted of Al foils. The Stardust Interstellar Preliminary Examination (ISPE) was a consortiumbased effort to characterize the collection in sufficient detail to enable future investigators to make informed sample requests. Among the questions to be answered were these: How many impacts are consistent in their characteristics with interstellar dust, with interplanetary dust, and with secondary ejecta from impacts on the spacecraft? Are the materials amorphous or crystalline? Are organics detectable? An additional goal of the ISPE was to develop or refine the techniques for preparation, analysis, and curation of these tiny samples, expected to be approximately 1 picogram or smaller, roughly three orders of magnitude smaller in mass than the samples in other small particle collections in NASA's collections - the cometary samples returned by Stardust, and the collection of Interplanetary Dust Particles collected in the stratosphere

    Connectivity precedes function in the development of the visual word form area

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    What determines the cortical location at which a given functionally specific region will arise in development? We tested the hypothesis that functionally specific regions develop in their characteristic locations because of pre-existing differences in the extrinsic connectivity of that region to the rest of the brain. We exploited the visual word form area (VWFA) as a test case, scanning children with diffusion and functional imaging at age 5, before they learned to read, and at age 8, after they learned to read. We found the VWFA developed functionally in this interval and that its location in a particular child at age 8 could be predicted from that child's connectivity fingerprints (but not functional responses) at age 5. These results suggest that early connectivity instructs the functional development of the VWFA, possibly reflecting a general mechanism of cortical development.National Institutes of Health (U.S.) (Grant F32HD079169)Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.) (Grant F32HD079169)National Institutes of Health (U.S.) (Grant R01HD067312)Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.) (Grant R01HD067312

    Shaping a screening file for maximal lead discovery efficiency and effectiveness: elimination of molecular redundancy

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    High Throughput Screening (HTS) is a successful strategy for finding hits and leads that have the opportunity to be converted into drugs. In this paper we highlight novel computational methods used to select compounds to build a new screening file at Pfizer and the analytical methods we used to assess their quality. We also introduce the novel concept of molecular redundancy to help decide on the density of compounds required in any region of chemical space in order to be confident of running successful HTS campaigns

    Aboveground biomass density models for NASA's Global Ecosystem Dynamics Investigation (GEDI) lidar mission

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    NASA's Global Ecosystem Dynamics Investigation (GEDI) is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI's footprint-level (similar to 25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final model selection. The data used to fit our models are from a compilation of globally distributed spatially and temporally coincident field and airborne lidar datasets, whereby we simulated GEDI-like waveforms from airborne lidar to build a calibration database. We used this database to expand the geographic extent of past waveform lidar studies, and divided the globe into four broad strata by Plant Functional Type (PFT) and six geographic regions. GEDI's waveform-to-biomass models take the form of parametric Ordinary Least Squares (OLS) models with simulated Relative Height (RH) metrics as predictor variables. From an exhaustive set of candidate models, we selected the best input predictor variables, and data transformations for each geographic stratum in the GEDI domain to produce a set of comprehensive predictive footprint-level models. We found that model selection frequently favored combinations of RH metrics at the 98th, 90th, 50th, and 10th height above ground-level percentiles (RH98, RH90, RH50, and RH10, respectively), but that inclusion of lower RH metrics (e.g. RH10) did not markedly improve model performance. Second, forced inclusion of RH98 in all models was important and did not degrade model performance, and the best performing models were parsimonious, typically having only 1-3 predictors. Third, stratification by geographic domain (PFT, geographic region) improved model performance in comparison to global models without stratification. Fourth, for the vast majority of strata, the best performing models were fit using square root transformation of field AGBD and/or height metrics. There was considerable variability in model performance across geographic strata, and areas with sparse training data and/or high AGBD values had the poorest performance. These models are used to produce global predictions of AGBD, but will be improved in the future as more and better training data become available
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