371 research outputs found
Detailed Bathymetric Surveys in the Central Indian Basin
Over 420,000 line kilometers of echo-sounding data was collected in the Central Indian Basin. This data was digitized, merged with navigation data and a detailed bathymetric map of the Basin was prepared. The Basin can be broadly classified into three regions as high relief area, medium relief area and plain area represented by western, eastern and central portions of the Basin, respectively. The bathymetric map prepared from this survey is the first of its kind for this region and will in the future be used as a base by navigators and researchers
Probing the Parsec-scale Accretion Flow of 3C 84 with Millimeter Polarimetry
We report the discovery of Faraday rotation toward radio source 3C 84, the
active galactic nucleus in NGC1275 at the core of the Perseus Cluster. The
rotation measure (RM), determined from polarization observations at wavelengths
of 1.3 and 0.9 mm, is (8.7 +/- 2.3) x 10^5 radians/m^2, among the largest ever
measured. The RM remained relatively constant over a 2 year period even as the
intrinsic polarization position angle wrapped through a span of 300 degrees.
The Faraday rotation is likely to originate either in the boundary layer of the
radio jet from the nucleus, or in the accretion flow onto the central black
hole. The accretion flow probably is disk-like rather than spherical on scales
of less than a parsec, otherwise the RM would be even larger.Comment: 7 pages, 3 figures, accepted for publication in Ap
Interferometric Mapping of Magnetic Fields in Star-forming Regions I. W51 e1/e2 Molecular Cores
We present the first interferometric polarization map of the W51 e1/e2
molecular cores obtained with the BIMA array at 1.3 mm wavelength with
approximately 3 arcsecond resolution. The polarization angle varies smoothly
across the double cores with an average position angle of 23+-5 degrees for W51
e1 and 15+-7 degrees for W51 e2. The inferred magnetic field direction is
parallel to the minor axis of the double cores, which is consistent with the
theoretical picture that clouds collapse along the field lines. However, the
magnetic field may not determine the axis of angular momentum of these two
cores as the field directions of the two cores significantly differ with the
previously measured directions of rotational axes. The polarization percentage
decreases toward regions with high intensity, suggesting that the dust
alignment efficiency decreases toward high density regions. The field
directions are highly ordered, and the small dispersion of the polarization
angles implies that magnetic fields are strong ( 1 mG) and perhaps
dominate turbulence in W51 e1/e2.Comment: 9 pages, 3 figures. Accepted for publication in the Astrophysical
Journal, Nov 10, 2001 issu
BMP-SMAD Signaling Regulates Lineage Priming, but Is Dispensable for Self-Renewal in Mouse Embryonic Stem Cells
Naive mouse embryonic stem cells (mESCs) are in a metastable state and fluctuate between inner cell mass- and epiblast-like phenotypes. Here, we show transient activation of the BMP-SMAD signaling pathway in mESCs containing a BMP-SMAD responsive reporter transgene. Activation of the BMP-SMAD reporter transgene in naive mESCs correlated with lower levels of genomic DNA methylation, high expression of 5-methylcytosine hydroxylases Tet1/2 and low levels of DNA methyltransferases Dnmt3a/b. Moreover, naive mESCs, in which the BMP-SMAD reporter transgene was activated, showed higher resistance to differentiation. Using double Smad1;Smad5 knockout mESCs, we showed that BMP-SMAD signaling is dispensable for self-renewal in both naive and ground state. These mutant mESCs were still pluripotent, but they exhibited higher levels of DNA methylation than their wild-type counterparts and had a higher propensity to differentiate. We showed that BMP-SMAD signaling modulates lineage priming in mESCs, by transiently regulating the enzymatic machinery responsible for DNA methylation
Cross-National Differences in Victimization : Disentangling the Impact of Composition and Context
Varying rates of criminal victimization across countries are assumed to be the outcome of countrylevel structural constraints that determine the supply ofmotivated o¡enders, as well as the differential composition within countries of suitable targets and capable guardianship. However, previous empirical tests of these ‘compositional’ and ‘contextual’ explanations of cross-national di¡erences
have been performed upon macro-level crime data due to the unavailability of comparable individual-level data across countries. This limitation has had two important consequences for cross-national crime research. First, micro-/meso-level mechanisms underlying cross-national differences cannot be truly inferred from macro-level data. Secondly, the e¡ects of contextual measures (e.g. income inequality) on crime are uncontrolled for compositional heterogeneity. In this
paper, these limitations are overcome by analysing individual-level victimization data across 18 countries from the International CrimeVictims Survey. Results from multi-level analyses on theft and violent victimization indicate that the national level of income inequality is positively related to risk, independent of compositional (i.e. micro- and meso-level) di¡erences. Furthermore, crossnational variation in victimization rates is not only shaped by di¡erences in national context, but
also by varying composition. More speci¢cally, countries had higher crime rates the more they consisted of urban residents and regions with lowaverage social cohesion.
Stability of cellular patterns in directional solidification
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