262 research outputs found
The Stellar Mass Density at z~6 from Spitzer Imaging of i-drop Galaxies
We measure the ages, stellar masses, and star formation histories of z~6
galaxies, observed within 1Gyr of the Big Bang. We use imaging from HST and
Spitzer from the public "Great Observatories Origins Deep Survey", coupled with
ground-based near-infrared imaging, to measure the spectral energy
distributions from 0.8-5microns, spanning the rest-frame UV and optical. From
our sample of ~50 i-drop Lyman-break star-forming galaxies in GOODS-South with
z'(AB)<27mag, we focus on ~30 with reliable photometric or spectroscopic
redshifts. Half of these are confused with foreground sources at Spitzer
resolution, but from the 16 with clean photometry we find that a surprisingly
large fraction (40%) have evidence for substantial Balmer-breaks. This
indicates the presence of old underlying stellar populations that dominate the
stellar masses. For these objects, we find ages of 200-700Myr, implying
formation redshifts of 7<z<14, and large stellar masses in the range
1-3x10^10M_sun. Analysis of 7 i-drops that are undetected at 3.6microns
indicates that these are younger, considerably less massive systems. We
calculate that line contamination should not severely affect our photometry or
derived results. Using data out to 8microns, we find little evidence for
substantial intrinsic dust reddening. Correcting for incompleteness in our
sample, we find a lower limit on the comoving stellar mass density at z~6 to be
2.5x10^6M_sun/Mpc^3. We are able to explore the star formation histories of our
selected galaxies, and we infer that the past global star formation rate may
have been much higher than that observed at z~6. The associated UV flux we
infer at z>7 could have played a major role in reionizing the universe.Comment: Accepted for publication in MNRAS. Minor changes in response to
referee repor
MoKCa database - mutations of kinases in cancer
Members of the protein kinase family are amongst the most commonly mutated genes in human cancer, and both mutated and activated protein kinases have proved to be tractable targets for the development of new anticancer therapies The MoKCa database (Mutations of Kinases in Cancer, http://strubiol.icr.ac.uk/extra/mokca) has been developed to structurally and functionally annotate, and where possible predict, the phenotypic consequences of mutations in protein kinases implicated in cancer. Somatic mutation data from tumours and tumour cell lines have been mapped onto the crystal structures of the affected protein domains. Positions of the mutated amino-acids are highlighted on a sequence-based domain pictogram, as well as a 3D-image of the protein structure, and in a molecular graphics package, integrated for interactive viewing. The data associated with each mutation is presented in the Web interface, along with expert annotation of the detailed molecular functional implications of the mutation. Proteins are linked to functional annotation resources and are annotated with structural and functional features such as domains and phosphorylation sites. MoKCa aims to provide assessments available from multiple sources and algorithms for each potential cancer-associated mutation, and present these together in a consistent and coherent fashion to facilitate authoritative annotation by cancer biologists and structural biologists, directly involved in the generation and analysis of new mutational data
Bridging Alone: Religious Conservatism, Marital Homogamy, and Voluntary Association Membership
This study characterizes social insularity of religiously conservative American married couples by examining patterns of voluntary associationmembership. Constructing a dataset of 3938 marital dyads from the second wave of the National Survey of Families and Households, the author investigates whether conservative religious homogamy encourages membership in religious voluntary groups and discourages membership in secular voluntary groups. Results indicate that couples’ shared affiliation with conservative denominations, paired with beliefs in biblical authority and inerrancy, increases the likelihood of religious group membership for husbands and wives and reduces the likelihood of secular group membership for wives, but not for husbands. The social insularity of conservative religious groups appears to be reinforced by homogamy—particularly by wives who share faith with husbands
5-hydroxymethylcytosine marks promoters in colon that resist DNA hypermethylation in cancer
The authors would like to acknowledge the support of The University of Cambridge, Cancer Research UK (CRUK SEB-Institute Group Award A ref10182; CRUK Senior fellowship C10112/A11388 to AEKI) and Hutchison Whampoa Limited. The Human Research Tissue Bank is supported by the NIHR Cambridge Biomedical Research Centre. FF is a ULB Professor funded by grants from the F.N.R.S. and Télévie, the IUAP P7/03 programme, the ARC (AUWB-2010-2015 ULB-No 7), the WB Health program and the Fonds Gaston Ithier. Data access: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=jpwzvsowiyuamzs&acc=GSE47592Background : The discovery of cytosine hydroxymethylation (5hmC) as a mechanism that potentially controls DNA methylation changes typical of neoplasia prompted us to investigate its behaviour in colon cancer. 5hmC is globally reduced in proliferating cells such as colon tumours and the gut crypt progenitors, from which tumours can arise. Results : Here, we show that colorectal tumours and cancer cells express Ten-Eleven-Translocation (TET) transcripts at levels similar to normal tissues. Genome-wide analyses show that promoters marked by 5hmC in normal tissue, and those identified as TET2 targets in colorectal cancer cells, are resistant to methylation gain in cancer. In vitro studies of TET2 in cancer cells confirm that these promoters are resistant to methylation gain independently of sustained TET2 expression. We also find that a considerable number of the methylation gain-resistant promoters marked by 5hmC in normal colon overlap with those that are marked with poised bivalent histone modifications in embryonic stem cells. Conclusions : Together our results indicate that promoters that acquire 5hmC upon normal colon differentiation are innately resistant to neoplastic hypermethylation by mechanisms that do not require high levels of 5hmC in tumours. Our study highlights the potential of cytosine modifications as biomarkers of cancerous cell proliferation.Publisher PDFPeer reviewe
Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2
We present the first observations of foreground Lyman- forest
absorption from high-redshift galaxies, targeting 24 star-forming galaxies
(SFGs) with within a region of the COSMOS
field. The transverse sightline separation is
comoving, allowing us to create a tomographic reconstruction of the 3D
Ly forest absorption field over the redshift range . The resulting map covers in the transverse plane and
along the line-of-sight with a spatial resolution of , and is the first high-fidelity map of large-scale
structure on scales at . Our map reveals significant
structures with extent, including several
spanning the entire transverse breadth, providing qualitative evidence for the
filamentary structures predicted to exist in the high-redshift cosmic web.
Simulated reconstructions with the same sightline sampling, spectral
resolution, and signal-to-noise ratio recover the salient structures present in
the underlying 3D absorption fields. Using data from other surveys, we
identified 18 galaxies with known redshifts coeval with our map volume enabling
a direct comparison to our tomographic map. This shows that galaxies
preferentially occupy high-density regions, in qualitative agreement with the
same comparison applied to simulations. Our results establishes the feasibility
of the CLAMATO survey, which aims to obtain Ly forest spectra for SFGs over of the COSMOS field, in order to map
out IGM large-scale structure at over a large
volume .Comment: Accepted for publication in Astrophysical Journal Letters; 8 pages
and 5 figure
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