2,635 research outputs found

    A combinatorial approach to gene expression analysis: DNA microarrays.

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    The microarray technology is based on analytical tools that parallelize the quantitative and qualitative analysis of nucleic acids, proteins and tissue sections one of its more recent evolutions-. By miniaturizing the size of the reaction and sensing area, microarrays allow to assess at the activity of thousands of genes in a given tissue or cell line at once in a rapid and quantitative way, and to carry out serial comparative tests in multiple samples. These tools, that stem from the innovations resulting from the technological improvements and knowledge arising from the genome sequencing projects, can be considered as a combinatorial technique that can rapidly provide significant information about complex cellular pathways and processes within one or few ‘‘mass scale’’ and comprehensive testing of a biological sample’s composition

    Correlation functions at small quark masses with overlap fermions

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    We report on recent work on the determination of low-energy constants describing Delta{S}=1 weak transitions, in order to investigate the origins of the Delta{I}=1/2 rule. We focus on numerical techniques designed to enhance the statistical signal in three-point correlation functions computed with overlap fermions near the chiral limit.Comment: Talk presented at Lattice2004(weak), Fermilab, 21-26 June 2004, 3 pages, 2 figure

    Lattice Spacing Dependence of the First Order Phase Transition for Dynamical Twisted Mass Fermions

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    Lattice QCD with Wilson fermions generically shows the phenomenon of a first order phase transition. We study the phase structure of lattice QCD using Wilson twisted mass fermions and the Wilson plaquette gauge action are used in a range of beta values where such a first order phase transition is observed. In particular, we investigate the dependence of the first order phase transition on the value of the lattice spacing. Using only data in one phase and neglecting possible problems arising from the phase transition we are able to perform a first scaling test for physical quantities using this action.Comment: 15 pages, 7 figures, typo corrected, web-list of authors correcte

    A Dramatic Decrease in Carbon Star Formation in M31

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    We analyze resolved stellar near-infrared photometry of 21 HST fields in M31 to constrain the impact of metallicity on the formation of carbon stars. Observations of nearby galaxies show that the carbon stars are increasingly rare at higher metallicity. Models indicate that carbon star formation efficiency drops due to the decrease in dredge-up efficiency in metal-rich thermally-pulsing Asymptotic Giant Branch (TP-AGB) stars, coupled to a higher initial abundance of oxygen. However, while models predict a metallicity ceiling above which carbon stars cannot form, previous observations have not yet pinpointed this limit. Our new observations reliably separate carbon stars from M-type TP-AGB stars across 2.6-13.7 kpc of M31's metal-rich disk using HST WFC3/IR medium-band filters. We find that the ratio of C to M stars (C/M) decreases more rapidly than extrapolations of observations in more metal-poor galaxies, resulting in a C/M that is too low by more than a factor of 10 in the innermost fields and indicating a dramatic decline in C star formation efficiency at metallicities higher than [M/H] ≈\approx -0.1 dex. The metallicity ceiling remains undetected, but must occur at metallicities higher than what is measured in M31's inner disk ([M/H] ≳\gtrsim +0.06 dex).Comment: 16 pages, 13 Figures; text clarifications in response to the referee. Results are unchanged; accepted for publication in Ap

    The ACS Nearby Galaxy Survey Treasury. X. Quantifying the Star Cluster Formation Efficiency of Nearby Dwarf Galaxies

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    We study the relationship between the field star formation and cluster formation properties in a large sample of nearby dwarf galaxies. We use optical data from the Hubble Space Telescope and from ground-based telescopes to derive the ages and masses of the young (t_age < 100Myr) cluster sample. Our data provides the first constraints on two proposed relationships between the star formation rate of galaxies and the properties of their cluster systems in the low star formation rate regime. The data show broad agreement with these relationships, but significant galaxy-to-galaxy scatter exists. In part, this scatter can be accounted for by simulating the small number of clusters detected from stochastically sampling the cluster mass function. However, this stochasticity does not fully account for the observed scatter in our data suggesting there may be true variations in the fraction of stars formed in clusters in dwarf galaxies. Comparison of the cluster formation and the brightest cluster in our sample galaxies also provide constraints on cluster destruction models.Comment: 16 pages, 9 figures, Accepted to Ap

    Perturbative renormalization factors in domain-wall QCD with improved gauge actions

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    We evaluate renormalization factors of the domain-wall fermion system with various improved gauge actions at one loop level. The renormalization factors are calculated for quark wave function, quark mass, bilinear quark operators, three- and four-quark operators in modified minimal subtraction (MS-bar) scheme with the dimensional reduction(DRED) as well as the naive dimensional regularization(NDR). We also present detailed results in the mean field improved perturbation theory.Comment: 44 page

    Parental Compliance: Its Role in Termination of Parental Rights Cases

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    This article examines the current state of termination of parental rights (TPR) law, along with the results of an appellate case review, an exploratory project, and an empirical investigation of decision-making related to these cases. Section I begins with an overview of termination of parental rights law. The focus of this section is recent statutory changes in the area, highlighting some key differences between the former and the current law. In Section II, the focus shifts to a review of the foundations for the empirical study. Section III more specifically addresses the main areas that are explored in the empirical study, including descriptions of case plans, parental compliance with case plans, and the mental status of parents. Section IV describes the empirical study, which addressed whether certain factors contribute to TPRs. Finally, sections V and VI discuss the conclusions that can be drawn from the empirical study

    The Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE): The Dust Extinction Curve from Red Clump Stars

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    We use Hubble Space Telescope (HST) observations of red clump stars taken as part of the Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE) program to measure the average dust extinction curve in a ~ 200 pc x 100 pc region in the southwest bar of the Small Magellanic Cloud (SMC). The rich information provided by our 8-band ultra-violet through near-infrared photometry allows us to model the color-magnitude diagram of the red clump accounting for the extinction curve shape, a log-normal distribution of AVA_{V}, and the depth of the stellar distribution along the line of sight. We measure an extinction curve with R475=A475/(A475−A814)R_{475} = A_{475}/(A_{475}-A_{814}) = 2.65 ±\pm 0.11. This measurement is significantly larger than the equivalent values of published Milky Way RVR_{V} = 3.1 (R475=1.83R_{475} = 1.83) and SMC Bar RVR_{V} = 2.74 (R475=1.86R_{475} = 1.86) extinction curves. Similar extinction curve offsets in the Large Magellanic Cloud (LMC) have been interpreted as the effect of large dust grains. We demonstrate that the line-of-sight depth of the SMC (and LMC) introduces an apparent "gray" contribution to the extinction curve inferred from the morphology of the red clump. We show that no gray dust component is needed to explain extinction curve measurements when a full-width half-max depth of 10 ±\pm 2 kpc in the stellar distribution of the SMC (5 ±\pm 1 kpc for the LMC) is considered, which agrees with recent studies of Magellanic Cloud stellar structure. The results of our work demonstrate the power of broad-band HST imaging for simultaneously constraining dust and galactic structure outside the Milky Way.Comment: 16 pages, 12 figures, 5 tables. Accepted for publication in Ap
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