6,626 research outputs found
PHLDA1 (pleckstrin homology-like domain, family A, member 1)
Short communication on PHLDA1, with data on DNA/RNA, on the protein encoded and where the gene is implicated
Response of dark matter halos to condensation of baryons: cosmological simulations and improved adiabatic contraction model
The cooling of gas in the centers of dark matter halos is expected to lead to
a more concentrated dark matter distribution. The response of dark matter to
the condensation of baryons is usually calculated using the model of adiabatic
contraction, which assumes spherical symmetry and circular orbits. In contrast,
halos in the hierarchical structure formation scenarios grow via multiple
violent mergers and accretion along filaments, and particle orbits in the halos
are highly eccentric. We study the effects of the cooling of gas in the inner
regions of halos using high-resolution cosmological simulations which include
gas dynamics, radiative cooling, and star formation. We find that the
dissipation of gas indeed increases the density of dark matter and steepens its
radial profile in the inner regions of halos compared to the case without
cooling. For the first time, we test the adiabatic contraction model in
cosmological simulations and find that the standard model systematically
overpredicts the increase of dark matter density in the inner 5% of the virial
radius. We show that the model can be improved by a simple modification of the
assumed invariant from M(r)r to M(r_av)r, where r and r_av are the current and
orbit-averaged particle positions. This modification approximately accounts for
orbital eccentricities of particles and reproduces simulation profiles to
within 10-20%. We present analytical fitting functions that accurately describe
the transformation of the dark matter profile in the modified model and can be
used for interpretation of observations.Comment: 12 page
A new method of measuring the cluster peculiar velocity power spectrum
We propose to use spatial correlations of the kinetic Sunyaev-Zeldovich (KSZ)
flux as an estimator of the peculiar velocity power spectrum. In contrast with
conventional techniques, our new method does not require measurements of the
thermal SZ signal or the X-ray temperature. Moreover, this method has the
special advantage that the expected systematic errors are always sub-dominant
to statistical errors on all scales and redshifts of interest. We show that
future large sky coverage KSZ surveys may allow a peculiar velocity power
spectrum estimates of an accuracy reaching ~10%.Comment: 5 pages, 2 figures, MNRAS in Press (doi:
10.1111/j.1365-2966.2008.13454.x
Association between monosodium glutamate intake and sleep-disordered breathing among Chinese adults with normal body weight
ObjectiveTo assess whether monosodium glutamate (MSG) intake is associated with sleep-disordered breathing (SDB).MethodsData from 1227 Chinese subjects who participated in the Jiangsu Nutrition Study were analyzed. All the participants were examined at two time points (baseline in 2002 and follow-up in 2007). The MSG intake was assessed quantitatively in 2002 and a sleep questionnaire was used to assess snoring and to construct an SDB probability score in 2007. Those within the fifth quintile of the score (highest) were defined as having a high probability of SDB.ResultsThe MSG intake was positively associated with snoring and a high probability of SDB in participants who had a normal body weight but in those who were overweight. A comparison of the extreme quartiles of MSG intake in subjects with a body mass index lower than 23 kg/m² showed an odds ratio of 2.02 (95% confidence interval 1.02-4.00) for snoring and an odds ratio of 3.11 (95% confidence interval 1.10-8.84) for a high probability of SDB. There was a joint effect between MSG and overweight in relation to SDB.ConclusionThe intake of MSG may increase the risk of SDB in Chinese adults with a normal body weight.Zumin Shi, Gary A. Wittert, Baojun Yuan, Yue Dai, Tiffany K. Gill, Gang Hu, Robert Adams, Hui Zuo, Anne W. Taylo
The Large Scale Bias of Dark Matter Halos: Numerical Calibration and Model Tests
We measure the clustering of dark matter halos in a large set of
collisionless cosmological simulations of the flat LCDM cosmology. Halos are
identified using the spherical overdensity algorithm, which finds the mass
around isolated peaks in the density field such that the mean density is Delta
times the background. We calibrate fitting functions for the large scale bias
that are adaptable to any value of Delta we examine. We find a ~6% scatter
about our best fit bias relation. Our fitting functions couple to the halo mass
functions of Tinker et. al. (2008) such that bias of all dark matter is
normalized to unity. We demonstrate that the bias of massive, rare halos is
higher than that predicted in the modified ellipsoidal collapse model of Sheth,
Mo, & Tormen (2001), and approaches the predictions of the spherical collapse
model for the rarest halos. Halo bias results based on friends-of-friends halos
identified with linking length 0.2 are systematically lower than for halos with
the canonical Delta=200 overdensity by ~10%. In contrast to our previous
results on the mass function, we find that the universal bias function evolves
very weakly with redshift, if at all. We use our numerical results, both for
the mass function and the bias relation, to test the peak-background split
model for halo bias. We find that the peak-background split achieves a
reasonable agreement with the numerical results, but ~20% residuals remain,
both at high and low masses.Comment: 11 pages, submitted to ApJ, revised to include referee's coment
Galaxy clustering and projected density profiles as traced by satellites in photometric surveys: Methodology and luminosity dependence
We develop a new method which measures the projected density distribution
w_p(r_p)n of photometric galaxies surrounding a set of
spectroscopically-identified galaxies, and simultaneously the projected
correlation function w_p(r_p) between the two populations. In this method we
are able to divide the photometric galaxies into subsamples in luminosity
intervals when redshift information is unavailable, enabling us to measure
w_p(r_p)n and w_p(r_p) as a function of not only the luminosity of the
spectroscopic galaxy, but also that of the photometric galaxy. Extensive tests
show that our method can measure w_p(r_p) in a statistically unbiased way. The
accuracy of the measurement depends on the validity of the assumption in the
method that the foreground/background galaxies are randomly distributed and
thus uncorrelated with those galaxies of interest. Therefore, our method can be
applied to the cases where foreground/background galaxies are distributed in
large volumes, which is usually valid in real observations. We applied our
method to data from SDSS including a sample of 10^5 LRGs at z~0.4 and a sample
of about half a million galaxies at z~0.1, both of which are cross-correlated
with a deep photometric sample drawn from the SDSS. On large scales, the
relative bias factor of galaxies measured from w_p(r_p) at z~0.4 depends on
luminosity in a manner similar to what is found at z~0.1, which are usually
probed by autocorrelations of spectroscopic samples. On scales smaller than a
few Mpc and at both z~0.4 and z~0.1, the photometric galaxies of different
luminosities exhibit similar density profiles around spectroscopic galaxies at
fixed luminosity and redshift. This provides clear support for the assumption
commonly-adopted in HOD models that satellite galaxies of different
luminosities are distributed in a similar way, following the dark matter
distribution within their host halos.Comment: 38 pages, 12 figures, published in Ap
The Halo Occupation Distribution of Active Galactic Nuclei
Using a fully cosmological hydrodynamic simulation that self-consistently
incorporates the growth and feedback of supermassive black holes and the
physics of galaxy formation, we examine the effects of environmental factors
(e.g., local gas density, black hole feedback) on the halo occupation
distribution of low luminosity active galactic nuclei (AGN). We decompose the
mean occupation function into central and satellite contribution and compute
the conditional luminosity functions (CLF). The CLF of the central AGN follows
a log-normal distribution with the mean increasing and scatter decreasing with
increasing redshifts. We analyze the light curves of individual AGN and show
that the peak luminosity of the AGN has a tighter correlation with halo mass
compared to instantaneous luminosity. We also compute the CLF of satellite AGN
at a given central AGN luminosity. We do not see any significant correlation
between the number of satellites with the luminosity of the central AGN at a
fixed halo mass. We also show that for a sample of AGN with luminosity above
10^42 ergs/s the mean occupation function can be modeled as a softened step
function for central AGN and a power law for the satellite population. The
radial distribution of AGN inside halos follows a power law at all redshifts
with a mean index of -2.33 +/- 0.08. Incorporating the environmental dependence
of supermassive black hole accretion and feedback, our formalism provides a
theoretical tool for interpreting current and future measurements of AGN
clustering.Comment: 14 pages, 11 figures, 2 Tables (Matches the MNRAS accepted version
Detecting Sunyaev-Zel'dovich clusters with PLANCK: I. Construction of all-sky thermal and kinetic SZ-maps
All-sky thermal and kinetic Sunyaev-Zel'dovich (SZ) maps are presented for
assessing how well the PLANCK-mission can find and characterise clusters of
galaxies, especially in the presence of primary anisotropies of the cosmic
microwave background (CMB) and various galactic and ecliptic foregrounds. The
maps have been constructed from numerical simulations of structure formation in
a standard LCDM cosmology and contain all clusters out to redshifts of z = 1.46
with masses exceeding 5e13 M_solar/h. By construction, the maps properly
account for the evolution of cosmic structure, the halo-halo correlation
function, the evolving mass function, halo substructure and adiabatic gas
physics. The velocities in the kinetic map correspond to the actual density
environment at the cluster positions. We characterise the SZ-cluster sample by
measuring the distribution of angular sizes, the integrated thermal and kinetic
Comptonisations, the source counts in the three relevant PLANCK-channels, and
give the angular power-spectra of the SZ-sky. While our results are broadly
consistent with simple estimates based on scaling relations and spherically
symmetric cluster models, some significant differences are seen which may
affect the number of cluster detectable by PLANCK.Comment: 14 pages, 16 figures, 3 tables, submitted to MNRAS, 05.Jul.200
Some Secrets of Fluorescent Proteins: Distinct Bleaching in Various Mounting Fluids and Photoactivation of cyan fluorescent proteins at YFP-Excitation
Background
The use of spectrally distinct variants of green fluorescent protein (GFP) such as cyan or yellow mutants (CFP and YFP, respectively) is very common in all different fields of life sciences, e.g. for marking specific proteins or cells or to determine protein interactions. In the latter case, the quantum physical phenomenon of fluorescence resonance energy transfer (FRET) is exploited by specific microscopy techniques to visualize proximity of proteins.

Methodology/Principal Findings
When we applied a commonly used FRET microscopy technique - the increase in donor (CFP)-fluorescence after bleaching of acceptor fluorophores (YFP), we obtained good signals in live cells, but very weak signals for the same samples after fixation and mounting in commercial microscopy mounting fluids. This observation could be traced back to much faster bleaching of CFP in these mounting media. Strikingly, the opposite effect of the mounting fluid was observed for YFP and also for other proteins such as Cerulean, TFP or Venus. The changes in photostability of CFP and YFP were not caused by the fixation but directly dependent on the mounting fluid. Furthermore we made the interesting observation that the CFP-fluorescence intensity increases by about 10 - 15% after illumination at the YFP-excitation wavelength – a phenomenon, which was also observed for Cerulean. This photoactivation of cyan fluorescent proteins at the YFP-excitation can cause false-positive signals in the FRET-microscopy technique that is based on bleaching of a yellow FRET acceptor.

Conclusions/Significance
Our results show that photostability of fluorescent proteins differs significantly for various media and that CFP bleaches significantly faster in commercial mounting fluids, while the opposite is observed for YFP and some other proteins. Moreover, we show that the FRET microscopy technique that is based on bleaching of the YFP is prone to artifacts due to photoactivation of cyan fluorescent proteins under these conditions
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