265 research outputs found

    A 3D Voronoi+Gapper Galaxy Cluster Finder in Redshift Space to z∼ 0.2 I: an Algorithm Optimized for the 2dFGRS

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    This paper is the first in a series, presenting a new galaxy cluster finder based on a three-dimensional Voronoi Tesselation plus a maximum likelihood estimator, followed by gapping-filtering in radial velocity(VoML+G). The scientific aim of the series is a reassessment of the diversity of optical clusters in the local universe. A mock galaxy database mimicking the southern strip of the magnitude(blue)-limited 2dF Galaxy Redshift Survey (2dFGRS), for the redshift range 0.009 N g ≥ 5, and 14% with N g < 5. The ensemble of VoML+G clusters has a ~59% completeness and a ~66% purity, whereas the subsample with N g ≥ 10, to z ~ 0.14, has greatly improved mean rates of ~75% and ~90%, respectively. The VoML+G cluster velocity dispersions are found to be compatible with those corresponding to "Millennium clusters" over the 300–1000 km s−1 interval, i.e., for cluster halo masses in excess of ~3.0 × 1013 M ⊙ h −1

    A Double‐Blind Randomized Placebo‐Controlled Trial of Oral Naltrexone for Heavy‐Drinking Smokers Seeking Smoking Cessation Treatment

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137315/1/acer13396.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137315/2/acer13396_am.pd

    Daily College Student Drinking Patterns Across the First Year of College

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    Objective: Despite the long recognized importance and well-documented impact of drinking patterns on health and safety, college student drinking patterns are understudied. This study used a daily-level, academic-year-long, multisite sample to identify subpopulations of college student drinking patterns and to describe how these groups differ from one another before, during, and after their first year of college. Method: wo cohorts of first-year college students (n = 588; 59% female) reported daily drinking on a biweekly basis using web-based surveys and completed surveys before and after their first year of college. Results: Cluster analyses based on time series analysis estimates of within-person drinking differences (per weekday, semester, first 6 weeks) and other descriptors of day-to-day drinking identified five drinking patterns: two low (47% and 6%), two medium (24% and 15%), and one high (8%) drinking cluster. Multinomial logistic regression analyses examined cluster differences in pre-college characteristics (i.e., demographics, alcohol outcome expectancies, alcohol problems, depression, other substance use) and first-year college experiences (i.e., academic engagement, alcohol consequences, risky drinking practices, alcohol problems, drinking during academic breaks). Low-drinking students appeared to form a relatively homogeneous group, whereas two distinct patterns were found for medium-drinking students with different weekend and Thursday drinking rates. The Thursday drinking cluster showed lower academic engagement and greater participation in risky drinking practices. Conclusions: These findings highlight quantitative and qualitative differences in day-to-day drinking patterns and suggest a link between motivational differences and drinking patterns, which may be addressed in developing tailored interventional strategies

    Effects of antenatal betamethasone on preterm human and mouse ductus arteriosus: comparison with baboon data.

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    BackgroundAlthough studies involving preterm infants ≤34 weeks gestation report a decreased incidence of patent ductus arteriosus after antenatal betamethasone, studies involving younger gestation infants report conflicting results.MethodsWe used preterm baboons, mice, and humans (≤276/7 weeks gestation) to examine betamethasone's effects on ductus gene expression and constriction both in vitro and in vivo.ResultsIn mice, betamethasone increased the sensitivity of the premature ductus to the contractile effects of oxygen without altering the effects of other contractile or vasodilatory stimuli. Betamethasone's effects on oxygen sensitivity could be eliminated by inhibiting endogenous prostaglandin/nitric oxide signaling. In mice and baboons, betamethasone increased the expression of several developmentally regulated genes that mediate oxygen-induced constriction (K+ channels) and inhibit vasodilator signaling (phosphodiesterases). In human infants, betamethasone increased the rate of ductus constriction at all gestational ages. However, in infants born ≤256/7 weeks gestation, betamethasone's contractile effects were only apparent when prostaglandin signaling was inhibited, whereas at 26-27 weeks gestation, betamethasone's contractile effects were apparent even in the absence of prostaglandin inhibitors.ConclusionsWe speculate that betamethasone's contractile effects may be mediated through genes that are developmentally regulated. This could explain why betamethasone's effects vary according to the infant's developmental age at birth

    A 3D Voronoi+Gapper Galaxy Cluster Finder in Redshift Space to z ∼ 0.2. II. An Abundant Cluster Population Dominated by Late-type Galaxies Unveiled

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    We identify 1901 galaxy clusters (N g ≥ 2) with the VoML+G algorithm (Paper I) on the Two-Degree Field Galaxy Redshift Survey. We present the 341 clusters with at least 10 galaxies that are within 0.009 < z < 0.14 (the Catalog), of which 254 (~75%) have counterparts in the literature (NED), with the remainder (87) plausibly "new" because of incompleteness of previous searches or unusual galaxy contents. The 207 clusters within z = 0.04–0.09 are used to study the properties of the galaxy systems in the nearby universe, including their galaxy contents parameterized by the late-type galaxy fractions (f L ). For this nearly complete cluster subsample, we find the following: (i) 63% are dominated by early-type galaxies (i.e., the late-type-poor clusters, f L < 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 22 ± 1 and 12.91 ± 0.04, respectively; and (ii) 37% are dominated by late-type galaxies (i.e., the late-type-rich clusters, f L ≥ 0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M ⊙) of 15.7 ± 0.9 and 12.66 ± 0.07, respectively. The statistical analysis of the late-type fraction distribution supports, with a 3σ confidence level, the presence of two population components. It is suggested that the late-type-poor galaxy systems reflect and extend the class of Abell-APM-EDCC clusters and that the late-type-rich systems (~one-third of the total) belong to a new, previously unappreciated class. The late-type-rich clusters, on average high mass-to-light ratio systems, appear to be more clustered on large scales than the late-type-poor clusters. A class of late-type-rich clusters is not predicted by current theory
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