602 research outputs found
Is There Enhanced Depletion of Gas-Phase Nitrogen in Moderately Reddened Lines of Sight?
We report on the abundance of interstellar neutral nitrogen (NI) for 30
sightlines, using data from the Far Ultraviolet Spectroscopic Explorer (FUSE)
and the Hubble Space Telescope (HST). NI column densities are derived by
measuring the equivalent widths of several ultraviolet absorption lines and
subsequently fitting those to a curve of growth. We find a mean interstellar
N/H of 51+/-4 ppm. This is below the mean found by Meyer et al. of 62(+4,-3)
ppm (adjusted for a difference in f-values). Our mean N/H is similar, however,
to the (f-value adjusted) mean of 51+/-3 ppm found by Knauth et al. for a
larger sample of sightlines with larger hydrogen column densities comparable to
those in this study. We discuss the question of whether or not nitrogen shows
increased gas-phase depletion in lines of sight with column densities
log(H_tot) >~ 21, as claimed by Knauth et al. The nitrogen abundance in the
line of sight toward HD 152236 is particularly interesting. We derive very
small N/H and N/O ratios for this line of sight that may support a previous
suggestion that members of the Sco OB1 association formed from an N-deficient
region.Comment: Accepted in The Astrophysical Journal, 9/2006 (expected pub. date:
1/2007) 38 pages, 5 figures (4 color
Heat-transfer distributions on biconics at incidence in hypersonic-hypervelocity He, N2, air, and CO2 flows
Laminar heat transfer rates were measured on spherically blunted, 13 deg/7 deg on axis and bent biconics (fore cone bent 7 deg upward relative to aft cone) at hypersonic hypervelocity flow conditions in the Langley Expansion Tube. Freestream velocities from 4.5 to 6.9 km/sec and Mach numbers from 6 to 9 were generated using helium, nitrogen, air, and carbon dioxide test gases, resulting in normal shock density ratios from 4 to 19. Angle of attack, referenced to the axis of the aft cone, was varied from 0 to 20 deg in 4 deg increments. The effect of nose bend, angle of attack, and real gas phenomena on heating distributions are presented along with comparisons of measurement to prediction from a code which solves the three dimensional parabolized Navier-Stokes equations
A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory
Compact elliptical galaxies are characterized by small sizes and high stellar
densities. They are thought to form through tidal stripping of massive
progenitors. However, only a handful of them were known, preventing us from
understanding the role played by this mechanism in galaxy evolution. We present
a population of 21 compact elliptical galaxies gathered with the Virtual
Observatory. Follow-up spectroscopy and data mining, using high-resolution
images and large databases, show that all the galaxies exhibit old metal-rich
stellar populations different from those of dwarf elliptical galaxies of
similar masses but similar to those of more massive early-type galaxies,
supporting the tidal stripping scenario. Their internal properties are
reproduced by numerical simulations, which result in compact dynamically hot
remnants resembling the galaxies in our sample.Comment: 26 pages, 5 figures, 2 tables. Science in press, published in Science
Express on 1/Oct/2009. Full resolution figures in the supplementary online
material are available from the Science Magazine web-sit
Serial Sexual Murderers and Prostitutes as their Victims: Difficulty Profiling Perpetrators and Victim Vulnerability as Illustrated by the Green River Case
Gary Ridgway, the Green River killer, is the most prolific serial killer in U.S. history, preying upon the most vulnerable of victims: prostitutes. This paper examines the difficulty experienced by law enforcement officials when trying to develop the profile of a serial sexual murderer, as illustrated by the Green River case. The lives and experiences of prostitutes are examined to establish their level of susceptibility to crime while also exploring the customers who frequent them. A summary of current research on criminal profiling is analyzed in conjunction to the Green River case with the goal of obtaining an understanding of the drives and motivations behind these crimes. In addition, the forensic and ethical implications of the case are discussed
Quantum BTZ black hole
We study a holographic construction of quantum rotating BTZ black holes that incorporates the exact backreaction from strongly coupled quantum conformal fields. It is based on an exact four-dimensional solution for a black hole localized on a brane in AdS4, first discussed some years ago but never fully investigated in this manner. Besides quantum CFT effects and their backreaction, we also investigate the role of higher-curvature corrections in the effective three-dimensional theory. We obtain the quantum-corrected geometry and the renormalized stress tensor. We show that the quantum black hole entropy, which includes the entanglement of the fields outside the horizon, satisfies the first law of thermodynamics exactly, even in the presence of backreaction and with higher-curvature corrections, while the Bekenstein-Hawking-Wald entropy does not. This result, which involves a rather non-trivial bulk calculation, shows the consistency of the holographic interpretation of braneworlds. We compare our renormalized stress tensor to results derived for free conformal fields, and for a previous holographic construction without backreaction effects, which is shown to be a limit of the solutions in this article
On the Finsler metrics obtained as limits of chessboard structures
We study the geodesics in a planar chessboard structure with two values 1 and
. The results for a fixed structure allow us to infer the properties
of the Finsler metrics obtained, with an homogenization procedure, as limit of
oscillating chessboard structures.Comment: 31 pages, 15 figure
Paediatric Behcet's Disease: A Comprehensive Review with an Emphasis on Monogenic Mimics
Behçet’s disease (BD) is a polygenic condition with a complex immunopathogenetic background and challenging diagnostic and therapeutic concepts. Advances in genomic medicine have provided intriguing insights into disease pathogenesis over the last decade, especially into monogenic mimics of BD. Although a rare condition, paediatric BD should be considered an important differential diagnosis, especially in cases with similar phenotypes. Emerging reports of monogenic mimics have indicated the importance of genetic testing, particularly for those with early-onset, atypical features and familial aggregation. Treatment options ought to be evaluated in a multidisciplinary setting, given the complexity and diverse organ involvement. Owing to the rarity of the condition, there is a paucity of paediatric trials; thus, international collaboration is warranted to provide consensus recommendations for the management of children and young people. Herein, we summarise the current knowledge of the clinical presentation, immunopathogenetic associations and disease mechanisms in patients with paediatric BD and BD-related phenotypes, with particular emphasis on recently identified monogenic mimics
Collagens XII and XIV: Two collagen types both associated with bovine muscle and intramuscular lipid metabolism
In continental Europe, intramuscular fat (IMF) content in beef is low but plays a key role in determining flavor. IMF expands inside the extracellular matrix (ECM) of intramuscular connective tissue. This ECM contains among others, collagens XII and XIV, two minor collagens probably involved in muscle metabolism. So, our purpose was to determine if there was an association between the contents in collagens XII and XIV and muscle metabolism. Rectus abdominis (RA, oxidative) and Semitendinosus (ST, oxido-glycolytic) muscles were sampled from steers of two genotypes with high (Angus [Ang], n=10) or low (Limousine [Lim], n=10) intramuscular fat level. Collagens XII and XIV relative abundance was evaluated by Western blot analysis. The characteristic parameters of metabolism were previously measured. Ang muscles contained more collagen XIV than Lim muscles (p<0.001). RA muscle contained more collagen XII than ST muscle (p<0.01). Across the two breeds and muscles, collagen XII was positively correlated with A- and H-fatty acid binding protein (FABP) contents (+0.43 and +0.53, respectively, p<0.05) and activities of three oxidative enzymes (cytochrome-c oxidase: +0.41, isocitrate dehydrogenase [ICDH]: +0.40, citrate synthase [CS]: +0.32) (p<0.05) and collagen XIV was positively correlated with triacylglycerol content (+0.35, p<0.35), A- and H-FABP protein contents (+0.35 and +0.38, respectively, p<0.05) and ICDH (+0.34, p<0.05) and negatively with activities of two enzymes of glycolytic metabolism (phosphofructokinase: -0.31 and lactate dehydrogenase: -0.42, p<0.05). After removing the genotype and muscle effects, only collagen XII remained correlated with A- and H-FABP and CS activity (+0.30, +0.34 and +0.46, respectively, p<0.0505). H-FABP is expressed in various tissues but predominantly in cardiac and oxidative skeletal muscles, whereas A-FABP is exclusively expressed within adipocytes. From these results, we can conclude that collagen XII and XIV are both associated with bovine muscle fiber and intramuscular lipid metabolism, but probably by different mechanisms. As a matter of fact, collagens XII is associated with intramuscular fat differentiation (from its correlation with A-FABP content) and oxidative metabolism (from its correlation with H-FABP content and CS activities) regardless of breed and muscle, whereas type XIV collagen is associated with the same parameters plus enzymes of glycolytic metabolism that discriminate breeds
Analysis of the Arabidopsis venosa4-0 mutant supports the role of VENOSA4 in dNTP metabolism
Human Sterile alpha motif and histidine-aspartate domain containing protein 1 (SAMHD1) functions as a dNTPase to maintain dNTP pool balance. In eukaryotes, the limiting step in de novo dNTP biosynthesis is catalyzed by RIBONUCLEOTIDE REDUCTASE (RNR). In Arabidopsis, the RNR1 subunit of RNR is encoded by CRINKLED LEAVES 8 (CLS8), and RNR2 by three paralogous genes, including TSO MEANING 'UGLY' IN CHINESE 2 (TSO2). In plants, DIFFERENTIAL DEVELOPMENT OF VASCULAR ASSOCIATED CELLS 1 (DOV1) catalyzes the first step of the de novo biosynthesis of purines. Here, to explore the role of VENOSA4 (VEN4), the most likely Arabidopsis ortholog of human SAMHD1, we studied the ven4‐0 point mutation, whose leaf phenotype was stronger than those of its insertional alleles. Structural predictions suggested that the E249L substitution in the mutated VEN4-0 protein rigidifies its 3D structure. The morphological phenotypes of the ven4, cls8, and dov1 single mutants were similar, and those of the ven4 tso2 and ven4 dov1 double mutants were synergistic. The ven4‐0 mutant had reduced levels of four amino acids related to dNTP biosynthesis, including glutamine and glycine, which are precursors in the de novo purine biosynthesis. Our results reveal high functional conservation between VEN4 and SAMHD1 in dNTP metabolism
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