3,758 research outputs found
The largest virialized dark halo in the universe
Using semi-analytic approach, we present an estimate of the properties of the
largest virialized dark halos in the present universe for three different
scenarios of structure formation: SCDM, LCDM and OCDM models. The resulting
virial mass and temperature increase from the lowest values of and 9.8 keV in OCDM, the mid-range values of and 31 keV in LCDM, to the highest values of
, 65 keV in SCDM. As compared with the
largest virialized object seen in the universe, the richest clusters of
galaxies, we can safely rule out the OCDM model. In addition, the SCDM model is
very unlikely because of the unreasonably high virial mass and temperature. Our
computation favors the prevailing LCDM model in which superclusters may be
marginally regarded as dynamically-virialized systems.Comment: 5 pages, Accepted by Int. J. Mod. Phys.
Experimental Investigation of Longitudinal Space-Time Correlations of the Velocity Field in Turbulent Rayleigh-B\'{e}nard Convection
We report an experimental investigation of the longitudinal space-time
cross-correlation function of the velocity field, , in a cylindrical
turbulent Rayleigh-B\'{e}nard convection cell using the particle image
velocimetry (PIV) technique. We show that while the Taylor's frozen-flow
hypothesis does not hold in turbulent thermal convection, the recent elliptic
model advanced for turbulent shear flows [He & Zhang, \emph{Phys. Rev. E}
\textbf{73}, 055303(R) (2006)] is valid for the present velocity field for all
over the cell, i.e., the isocorrelation contours of the measured
have a shape of elliptical curves and hence can be related to
via with and
being two characteristic velocities. We further show that the fitted is
proportional to the mean velocity of the flow, but the values of are
larger than the theoretical predictions. Specifically, we focus on two
representative regions in the cell: the region near the cell sidewall and the
cell's central region. It is found that and are approximately
the same near the sidewall, while at cell center.Comment: 16 pages, 15 figures, submitted to J. Fluid Mec
(Z)-3-(4-Chlorophenyl)-1-(2,4-difluorophenyl)-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-one
The asymmetric unit of the title compound, C17H10ClF2N3O, contains three independent molecules. In each molecule, the C=C bond has a cis conformation with respect to the triazole and chlorophenyl groups. The dihedral angles formed by the triazole ring with the diflurophenyl and chlorophenyl benzene rings, respectively, are 20.10 (14) and 73.22 (15), 25.31 (15) and 84.44 (15), and 16.44 (13) and 61.72 (14)° in the three molecules while the dihedral angles between the benzene rings are 66.54 (13), 85.82 (12) and 58.37 (12)°
Molecular Characterization of Three Novel Phospholipase A2 Proteins from the Venom of Atheris chlorechis, Atheris nitschei and Atheris squamigera
Secretory phospholipase A2 (sPLA2) is known as a major component of snake venoms and displays higher-order catalytic hydrolysis functions as well as a wide range of pathological effects. Atheris is not a notoriously dangerous genus of snakes although there are some reports of fatal cases after envenomation due to the effects of coagulation disturbances and hemorrhaging. Molecular characterization of Atheris venom enzymes is incomplete and there are only a few reports in the literature. Here, we report, for the first time, the cloning and characterization of three novel cDNAs encoding phospholipase A2 precursors (one each) from the venoms of the Western bush viper (Atheris chlorechis), the Great Lakes bush viper (Atheris nitschei) and the Variable bush viper (Atheris squamigera), using a “shotgun cloning” strategy. Open-reading frames of respective cloned cDNAs contained putative 16 residue signal peptides and mature proteins composed of 121 to 123 amino acid residues. Alignment of mature protein sequences revealed high degrees of structural conservation and identity with Group II venom PLA2 proteins from other taxa within the Viperidae. Reverse-phase High Performance Liquid Chromatography (HPLC) profiles of these three snake venoms were obtained separately and chromatographic fractions were assessed for phospholipase activity using an egg yolk suspension assay. The molecular masses of mature proteins were all identified as approximately 14 kDa. Mass spectrometric analyses of the fractionated oligopeptides arising from tryptic digestion of intact venom proteins, was performed for further structural characterization
(Z)-1-[4-Fluoro-2-(pyrrolidin-1-yl)phenyl]-3-phenyl-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-one
In the title molecule, C21H19FN4O, the triazole ring forms dihedral angles of 67.0 (1) and 59.6 (1)° with the phenyl and fluoro-substituted benzene rings, respectively. The dihedral angle between the phenyl ring and the fluoro-substituted benzene ring is 79.1 (1)°. The pyrrolidine ring is in a half-chair conformation. In the crystal, weak C—H⋯O and C—H⋯N hydrogen bonds connect molecules into layers parallel to (001)
Frequent mutation of hypoxia-related genes in persistent pulmonary hypertension of the newborn
AIMS: Persistent pulmonary hypertension of the newborn (PPHN) is characterized by sustained high levels of pulmonary vascular resistance after birth with etiology unclear; Arterial blood oxygen saturation of Tibetan newborns at high latitudes is higher than that of Han newborns at low latitudes, suggesting that genetic adaptation may allow sufficient oxygen to confer Tibetan populations with resistance to pulmonary hypertension; We have previously identified genetic factors related to PPHN through candidate gene sequencing; In this study, we first performed whole exome sequencing in PPHN patients to screen for genetic-related factors.
METHODS AND RESULTS: In this two-phase genetic study, we first sequenced the whole exome of 20 Tibetan PPHN patients and compared it with the published genome sequences of 50 healthy high-altitude Tibetanshypoxia-related genes, a total of 166 PPHN-related variants were found, of which 49% were from 43 hypoxia-related genes; considering many studies have shown that the differences in the genetic background between Tibet and Han are characterized by hypoxia-related genetic polymorphisms, so it is necessary to further verify whether the association between hypoxia-related variants and PPHN is independent of high-altitude life. During the validation phase, 237 hypoxia-related genes were sequenced in another 80 Han PPHN patients living in low altitude areas, including genes at the discovery stage and known hypoxia tolerance, of which 413 variants from 127 of these genes were shown to be significantly associated with PPHN.hypoxia-related genes.
CONCLUSIONS: Our results indicates that the association of hypoxia-related genes with PPHN does not depend on high-altitude life, at the same time, 21 rare mutations associated with PPHN were also found, including three rare variants of the tubulin tyrosine ligase-like family member 3 gene (TTLL3:p.E317K, TTLL3:p.P777S) and the integrin subunit alpha M gene (ITGAM:p.E1071D). These novel findings provide important information on the genetic basis of PPHN
N′2,N′5-Bis[(E)-2-hydroxybenzylidene]-3,4-dimethylthiophene-2,5-dicarbohydrazide
In the title molecule, C22H20N4O4S, both C=N bonds are in an E conformation. The benzene rings form dihedral angles of 12.10 (13) and 25.17 (12)° with the thiophene ring. The dihedral angle between the two benzene rings is 17.59 (14)°. There are two intramolecular O—H⋯N hydrogen bonds. In the crystal, N—H⋯O hydrogen bonds connect molecules into chains along [010]
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