3,477 research outputs found
Regulation of expression of two LY-6 family genes by intron retention and transcription induced chimerism.
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.BACKGROUND: Regulation of the expression of particular genes can rely on mechanisms that are different from classical transcriptional and translational control. The LY6G5B and LY6G6D genes encode LY-6 domain proteins, whose expression seems to be regulated in an original fashion, consisting of an intron retention event which generates, through an early premature stop codon, a non-coding transcript, preventing expression in most cell lines and tissues. RESULTS: The MHC LY-6 non-coding transcripts have shown to be stable and very abundant in the cell, and not subject to Nonsense Mediated Decay (NMD). This retention event appears not to be solely dependent on intron features, because in the case of LY6G5B, when the intron is inserted in the artificial context of a luciferase expression plasmid, it is fully spliced but strongly stabilises the resulting luciferase transcript. In addition, by quantitative PCR we found that the retained and spliced forms are differentially expressed in tissues indicating an active regulation of the non-coding transcript. EST database analysis revealed that these genes have an alternative expression pathway with the formation of Transcription Induced Chimeras (TIC). This data was confirmed by RT-PCR, revealing the presence of different transcripts that would encode the chimeric proteins CSNKbeta-LY6G5B and G6F-LY6G6D, in which the LY-6 domain would join to a kinase domain and an Ig-like domain, respectively. CONCLUSION: In conclusion, the LY6G5B and LY6G6D intron-retained transcripts are not subjected to NMD and are more abundant than the properly spliced forms. In addition, these genes form chimeric transcripts with their neighbouring same orientation 5' genes. Of interest is the fact that the 5' genes (CSNKbeta or G6F) undergo differential splicing only in the context of the chimera (CSNKbeta-LY6G5B or G6F-LY6G6C) and not on their own
Brightest galaxies as halo centre tracers in SDSS DR7
Determining the positions of halo centres in large-scale structure surveys is
crucial for many cosmological studies. A common assumption is that halo centres
correspond to the location of their brightest member galaxies. In this paper,
we study the dynamics of brightest galaxies with respect to other halo members
in the Sloan Digital Sky Survey DR7. Specifically, we look at the line-of-sight
velocity and spatial offsets between brightest galaxies and their neighbours.
We compare those to detailed mock catalogues, constructed from high-resolution,
dark-matter-only -body simulations, in which it is assumed that satellite
galaxies trace dark matter subhaloes. This allows us to place constraints on
the fraction of haloes in which the brightest galaxy is not the
central. Compared to previous studies we explicitly take into account the
unrelaxed state of the host haloes, velocity offsets of halo cores and
correlations between and the satellite occupation. We find that
strongly decreases with the luminosity of the brightest galaxy
and increases with the mass of the host halo. Overall, in the halo mass range
we find , in good
agreement with a previous study by Skibba et al. We discuss the implications of
these findings for studies inferring the galaxy--halo connection from satellite
kinematics, models of the conditional luminosity function and galaxy formation
in general.Comment: 24 pages, 15 figures. Accepted for publication in MNRA
The Galaxy Clustering Crisis in Abundance Matching
Galaxy clustering on small scales is significantly under-predicted by
sub-halo abundance matching (SHAM) models that populate (sub-)haloes with
galaxies based on peak halo mass, . SHAM models based on the peak
maximum circular velocity, , have had much better success. The
primary reason based models fail is the relatively low abundance
of satellite galaxies produced in these models compared to those based on
. Despite success in predicting clustering, a simple based SHAM model results in predictions for galaxy growth that are at
odds with observations. We evaluate three possible remedies that could "save"
mass-based SHAM: (1) SHAM models require a significant population of "orphan"
galaxies as a result of artificial disruption/merging of sub-haloes in modern
high resolution dark matter simulations; (2) satellites must grow significantly
after their accretion; and (3) stellar mass is significantly affected by halo
assembly history. No solution is entirely satisfactory. However, regardless of
the particulars, we show that popular SHAM models based on
cannot be complete physical models as presented. Either truly is
a better predictor of stellar mass at and it remains to be seen how
the correlation between stellar mass and comes about, or SHAM
models are missing vital component(s) that significantly affect galaxy
clustering.Comment: 25 pages, 22 figures, submitted to MNRAS, comments welcom
The Immitigable Nature of Assembly Bias: The Impact of Halo Definition on Assembly Bias
Dark matter halo clustering depends not only on halo mass, but also on other
properties such as concentration and shape. This phenomenon is known broadly as
assembly bias. We explore the dependence of assembly bias on halo definition,
parametrized by spherical overdensity parameter, . We summarize the
strength of concentration-, shape-, and spin-dependent halo clustering as a
function of halo mass and halo definition. Concentration-dependent clustering
depends strongly on mass at all . For conventional halo definitions
(), concentration-dependent clustering
at low mass is driven by a population of haloes that is altered through
interactions with neighbouring haloes. Concentration-dependent clustering can
be greatly reduced through a mass-dependent halo definition with for haloes with . Smaller implies larger radii and
mitigates assembly bias at low mass by subsuming altered, so-called backsplash
haloes into now larger host haloes. At higher masses () larger overdensities, , are necessary. Shape- and spin-dependent clustering are
significant for all halo definitions that we explore and exhibit a relatively
weaker mass dependence. Generally, both the strength and the sense of assembly
bias depend on halo definition, varying significantly even among common
definitions. We identify no halo definition that mitigates all manifestations
of assembly bias. A halo definition that mitigates assembly bias based on one
halo property (e.g., concentration) must be mass dependent. The halo
definitions that best mitigate concentration-dependent halo clustering do not
coincide with the expected average splashback radii at fixed halo mass.Comment: 19 pages, 13 figures. Updated to published version. Main result
summarized in Figure 1
How to Optimally Constrain Galaxy Assembly Bias: Supplement Projected Correlation Functions with Count-in-cells Statistics
Most models for the connection between galaxies and their haloes ignore the
possibility that galaxy properties may be correlated with halo properties other
than mass, a phenomenon known as galaxy assembly bias. Yet, it is known that
such correlations can lead to systematic errors in the interpretation of survey
data. At present, the degree to which galaxy assembly bias may be present in
the real Universe, and the best strategies for constraining it remain
uncertain. We study the ability of several observables to constrain galaxy
assembly bias from redshift survey data using the decorated halo occupation
distribution (dHOD), an empirical model of the galaxy--halo connection that
incorporates assembly bias. We cover an expansive set of observables, including
the projected two-point correlation function ,
the galaxy--galaxy lensing signal , the void
probability function , the distributions of
counts-in-cylinders , and counts-in-annuli
, and the distribution of the ratio of counts in cylinders
of different sizes . We find that despite the frequent use of the
combination in
interpreting galaxy data, the count statistics, and
, are generally more efficient in constraining galaxy
assembly bias when combined with . Constraints
based upon and
share common degeneracy directions in the parameter space, while combinations
of with the count statistics are more
complementary. Therefore, we strongly suggest that count statistics should be
used to complement the canonical observables in future studies of the
galaxy--halo connection.Comment: Figures 3 and 4 show the main results. Published in Monthly Notices
of the Royal Astronomical Societ
SUSY-QCD Effect on Top-Charm Associated Production at Linear Collider
We evaluate the contribution of SUSY-QCD to top-charm associated production
at next generation linear colliders. Our results show that the production cross
section of the process could be as large as 0.1
fb, which is larger than the prediction of the SM by a factor of .Comment: version to appear in PR
The Scots at the Battle of Neville's Cross, 17 October 1346
This is an analysis of the loyalties and political rivalries of the army of David II of Scotland at the battle of Neville's Cross in 1346 where that king was apparently deserted by some of his subjects and led off to eleven years' captivity in England
T-Violation in Decay And Supersymmetry
Measurement of the transverse muon polarization in the decay will be attempted for the first time at the
ongoing KEK E246 experiment and also at a proposed BNL experiment. We provide a
general analysis of how is sensitive to the physical
-violating phases in new physics induced four-Fermi interactions, and then
we calculate the dominant contributions to from squark family
mixings in generic supersymmetric models. Estimates of the upper bounds on
are also given. It is found that a supersymmetry-induced
right-handed quark current from boson exchange gives an upper limit on
as large as a few per cent, whereas with
charged-Higgs-exchange induced pseudoscalar interaction, is no
larger than a few tenths of a per cent. Possible correlations between the muon
polarization measurements in and decays are discussed, and distinctive patterns of
this correlation from squark family-mixings and from the three-Higgs-doublet
model are noted.Comment: Revtex, 29 pages including 4 epsf figure
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