5,222 research outputs found
Physical and morphological properties of z~3 LBGs: dependence on Lyalpha line emission
We investigate the physical and morphological properties of LBGs at z ~2.5 to
~3.5, to determine if and how they depend on the nature and strength of the
Lyalpha emission. We selected U-dropout galaxies from the z-detected GOODS
MUSIC catalog, by adapting the classical Lyman Break criteria on the GOODS
filter set. We kept only those galaxies with spectroscopic confirmation, mainly
from VIMOS and FORS public observations. Using the full multi-wavelength
14-bands photometry, we determined the physical properties of the galaxies,
through a standard spectral energy distribution fitting with the updated
Charlot & Bruzual (2009) templates. We also added other relevant observations,
i.e. the 24mu m observations from Spitzer/MIPS and the 2 MSec Chandra X-ray
observations. Finally, using non parametric diagnostics (Gini, Concentration,
Asymmetry, M_20 and ellipticity), we characterized the rest-frame UV morphology
of the galaxies. We then analyzed how these physical and morphological
properties correlate with the presence of the Lyalpha line in the optical
spectra. We find that, unlike at higher redshift, the dependence of physical
properties on the Lyalpha line is milder: galaxies without Lyalpha in emission
tend to be more massive and dustier than the rest of the sample, but all other
parameters, ages, SFRs, X-ray emission as well as UV morphology do not depend
strongly on the presence of the line emission. A simple scenario where all LBGs
have intrinsically high Lyalpha emission, but where dust and neutral hydrogen
content (which shape the final appearance of the Lyalpha) depend on the mass of
the galaxies, is able to reproduce the majority of the observed properties at
z~3. Some modification might be needed to account for the observed evolution of
these properties with cosmic epoch, which is also discussed.Comment: Accepted for publication on A&
UBR4 deficiency causes male sterility and testis abnormal in Drosophila
IntroductionIt has been established that UBR4 encodes E3 ubiquitin ligase, which determines the specificity of substrate binding during protein ubiquitination and has been associated with various functions of the nervous system but not the reproductive system. Herein, we explored the role of UBR4 on fertility with a Drosophila model.MethodsDifferent Ubr4 knockdown flies were established using the UAS/GAL4 activating sequence system. Fertility, hatchability, and testis morphology were studied, and bioinformatics analyses were conducted. Our results indicated that UBR4 deficiency could induce male sterility and influent egg hatchability in Drosophila.ResultsWe found that Ubr4 deficiency affected the testis during morphological analysis. Proteomics analysis indicated 188 upregulated proteins and 175 downregulated proteins in the testis of Ubr4 knockdown flies. Gene Ontology analysis revealed significant upregulation of CG11598 and Sfp65A, and downregulation of Pelota in Ubr4 knockdown flies. These proteins were involved in the biometabolic or reproductive process in Drosophila. These regulated proteins are important in testis generation and sperm storage promotion. Bioinformatics analysis verified that UBR4 was low expressed in cryptorchidism patients, which further supported the important role of UBR4 in male fertility.DiscussionOverall, our findings suggest that UBR4 deficiency could promote male infertility and may be involved in the protein modification of UBR4 by upregulating Sfp65A and CG11598, whereas downregulating Pelota protein expression
Measurements of psi(2S) decays to octet baryon-antibaryon pairs
With a sample of 14 million psi(2S) events collected by the BESII detector at
the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p
p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their
branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4,
(3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4,
respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter
alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure
3D Lyman-alpha radiation transfer. III. Constraints on gas and stellar properties of z~3 Lyman break galaxies (LBG) and implications for high-z LBGs and Lyman-alpha emitters(LAEs)
The Aim of our study is to understand the variety of observed Lyman-alpha
(Lya) line profiles and strengths in Lyman Break Galaxies (LBGs) and Lya
emitters (LAEs), the physical parameters governing them, and hence deriving
constraints on the gas and dust content and stellar populations of these
objects.
Using our 3D Lya radiation transfer code including gas and dust (Verhamme et
al. 2006), we fit 11 LBGs from the FORS Deep Field with redshifts between 2.8
and 5 observed by Tapken et al. (2007). A simple geometry of a spherically
expanding shell of HI is adopted.
RESULTS : The variety of observed Lya profiles is successfully reproduced.
Most objects show outflow velocities of 150-200 km/s; two objects are most
likely quasi-static. The radial HI column density ranges from NH=2.10^{19} to
7.10^{20} cm^{-2}. Our Lya profile fits yield values of E(B-V)~0.05-0.2 for the
gas extinction. We find indications for a dust-to-gas ratio higher than the
Galactic value, and for a substantial scatter. The escape fraction of Lya
photons is found to be determined primarily by the extinction, and a simple fit
formula is proposed. Intrinsic EW(Lya)~50-100 Angstroms are found for 8/11
objects, as expected for stellar populations forming constantly over long
periods (> 10-100 Myr). In three cases we found indications for younger
populations. Correlations between the observed EW(Lya) and other observables
such as FWHM(Lya), E(B-V),SFR(UV) etc, are reproduced. We also show that there
is a clear overlap between LBGs and LAEs. Radiation transfer and dust effects
explain the increase of the LAE/LBG ratio, and a higher percentage of LBGs with
strong Lya emission with increasing redshift. [shortened]Comment: 26 pages, accepted for publication in A&
Structure of p300 bound to MEF2 on DNA reveals a mechanism of enhanceosome assembly
Transcription co-activators CBP and p300 are recruited by sequence-specific transcription factors to specific genomic loci to control gene expression. A highly conserved domain in CBP/p300, the TAZ2 domain, mediates direct interaction with a variety of transcription factors including the myocyte enhancer factor 2 (MEF2). Here we report the crystal structure of a ternary complex of the p300 TAZ2 domain bound to MEF2 on DNA at 2.2Å resolution. The structure reveals three MEF2:DNA complexes binding to different sites of the TAZ2 domain. Using structure-guided mutations and a mammalian two-hybrid assay, we show that all three interfaces contribute to the binding of MEF2 to p300, suggesting that p300 may use one of the three interfaces to interact with MEF2 in different cellular contexts and that one p300 can bind three MEF2:DNA complexes simultaneously. These studies, together with previously characterized TAZ2 complexes bound to different transcription factors, demonstrate the potency and versatility of TAZ2 in protein–protein interactions. Our results also support a model wherein p300 promotes the assembly of a higher-order enhanceosome by simultaneous interactions with multiple DNA-bound transcription factors
Observation of the decay \psip\rar\kstark
Using 14 million events collected with the BESII detector,
branching fractions of \psip\rar\kstarkpm and \kstarknn are determined to
be: \calB(\psip\rar\kstarkpm)=(2.9^{+1.3}_{-1.7}\pm0.4)\times 10^{-5} and
\calB(\psip\rar\kstarknn)=(13.3^{+2.4}_{-2.7}\pm1.9)\times 10^{-5}. The
results confirm the violation of the "12%" rule for these two decay channels
with higher precision. A large isospin violation between the charged and
neutral modes is observed.Comment: 5 pages, 3 figure
Improved W boson mass measurement with the D0 detector
We have measured the W boson mass using the D0 detector and a data sample of
82 pb^-1 from the Tevatron collider. This measurement used W -> e nu decays,
where the electron is close to a boundary of a central electromagnetic
calorimeter module. Such 'edge' electrons have not been used in any previous D0
analysis, and represent a 14% increase in the W boson sample size. For these
electrons, new response and resolution parameters are determined, and revised
backgrounds and underlying event energy flow measurements are made. When the
current measurement is combined with previous D0 W boson mass measurements, we
obtain M_W = 80.483 +/- 0.084 GeV. The 8% improvement from the previous D0
measurement is primarily due to the improved determination of the response
parameters for non-edge electrons using the sample of Z bosons with non-edge
and edge electrons.Comment: submitted to Phys. Rev. D; 20 pages, 18 figures, 9 table
Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm
The PHENIX experiement has measured the electron-positron pair mass spectrum
from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions
from light meson decays to e^+e^- pairs have been determined based on
measurements of hadron production cross sections by PHENIX. They account for
nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair
yield remaining after subtracting these contributions is dominated by
semileptonic decays of charmed hadrons correlated through flavor conservation.
Using the spectral shape predicted by PYTHIA, we estimate the charm production
cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which
is consistent with QCD calculations and measurements of single leptons by
PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables.
Submitted to Physics Letters B. v2 fixes technical errors in matching authors
to institutions. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV
The momentum distribution of electrons from semi-leptonic decays of charm and
bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is
measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC)
over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of
electrons from bottom to that from charm is presented. The ratio is determined
using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It
is found that the yield of electrons from bottom becomes significant above 4
GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative
quantum chromodynamics (pQCD) calculation agrees with the data within the
theoretical and experimental uncertainties. The extracted total bottom
production cross section at this energy is \sigma_{b\b^bar}= 3.2
^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Measurement of the Boson Mass
A measurement of the mass of the boson is presented based on a sample of
5982 decays observed in collisions at
= 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a
fit to the transverse mass spectrum, combined with measurements of the
boson mass, the boson mass is measured to be .Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures
(submitted to PRL
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