9,966 research outputs found
Cell-type phylogenetics and the origin of endometrial stromal cells
SummaryA challenge of genome annotation is the identification of genes performing specific biological functions. Here, we propose a phylogenetic approach that utilizes RNA-seq data to infer the historical relationships among cell types and to trace the pattern of gene-expression changes on the tree. The hypothesis is that gene-expression changes coincidental with the origin of a cell type will be important for the function of the derived cell type. We apply this approach to the endometrial stromal cells (ESCs), which are critical for the initiation and maintenance of pregnancy. Our approach identified well-known regulators of ESCs, PGR and FOXO1, as well as genes not yet implicated in female fertility, including GATA2 and TFAP2C. Knockdown analysis confirmed that they are essential for ESC differentiation. We conclude that phylogenetic analysis of cell transcriptomes is a powerful tool for discovery of genes performing cell-type-specific functions
Gravitational anomalies: a recipe for Hawking radiation
We explore the method of Robinson and Wilczek for deriving the Hawking
temperature of a black hole. In this method, the Hawking radiation restores
general covariance in an effective theory of near-horizon physics which
otherwise exhibits a gravitational anomaly at the quantum level. The method has
been shown to work for broad classes of black holes in arbitrary spacetime
dimensions. These include static black holes, accreting or evaporating black
holes, charged black holes, rotating black holes, and even black rings. In the
case of charged and rotating black holes, the expected super-radiant current is
also reproduced.Comment: 7 pages; This essay received an "Honorable Mention" in the 2007 Essay
Competition of the Gravity Research Foundation; (v2) Short comments and
references added; (v3) Minor revisions and updated references to agree with
published versio
Norbert Eliasâs extended theory of community: from established/outsider relations to the gendered weâI balance
Density functional investigations of defect induced mid-gap states in graphane
We have carried out ab initio electronic structure calculations on graphane
(hydrogenated graphene) with single and double vacancy defects. Our analysis of
the density of states reveal that such vacancies induce the mid gap states and
modify the band gap. The induced states are due to the unpaired electrons on
carbon atoms. Interestingly the placement and the number of such states is
found to be sensitive to the distance between the vacancies. Furthermore we
also found that in most of the cases the vacancies induce a local magnetic
moment.Comment: 15 page
Physical and Spectral Characteristics of the T8 and Later-Type Dwarfs
We use new and published near-IR spectra, with synthetic spectra, to derive
physical properties of three of the latest-type T dwarfs. A new R~1700 spectrum
of the T7.5 dwarf HD 3651B, with existing data, allows a detailed comparison to
the well-studied and very similar dwarf, Gl 570D. We find that HD 3651B has
both higher gravity and metallicity than Gl 570D, with Teff=820-830K, log g=
5.4-5.5, [m/H]= +0.2 and Kzz=10^4cm^2/s. Its age is 8-12 Gyr and its implied
mass is 60-70 M_Jup. We perform a similar analyis of the T8 and T7.5 dwarfs
2MASS J09393548-2448279 and 2MASS J11145133-2618235 using published data,
comparing them to the well-studied T8, 2MASS J04151954-0935066. We find that
the two dwarfs have the same Teff as the reference dwarf, and similar
gravities, but lower metallicities. The parameters are Teff=725-775K and [m/H]=
-0.3; log g=5.3-5.45 for 2MASS J09393548-2448279 and log g=5.0-5.3 for 2MASS
J11145133- 261823. The age and mass are ~10Gyr and 60M_Jup for 2MASS
J09393548-2448279, and ~5 Gyr and 40M_Jup for 2MASS J11145133-261823. A serious
limitation is the incompleteness of the line lists of CH4 and NH3 at lambda
<1.7um. Spectra of Saturn and Jupiter, and of laboratory CH4 and NH3 gas,
suggest that NH3 features in the Y- and J-bands may be useful as indicators of
the next cooler spectral type, and not features in the H- and K-bands as
previously thought. However large uncertainties remain, as the abundance of NH3
is likely to be significantly below the chemical equilibrium value, and
inclusion of laboratory NH3 opacities predicts band shapes that are discrepant
with existing data. It is possible that the T spectral class will have to be
extended to low temperatures around 400K, when water clouds condense in the
atmosphere [abridged].Comment: 34 pages including 10 figures and two tables; accepted for
publication in the Astrophysical Journa
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