84 research outputs found
Testing the dark energy with gravitational lensing statistics
We study the redshift distribution of two samples of early-type gravitational
lenses, extracted from a larger collection of 122 systems, to constrain the
cosmological constant in the LCDM model and the parameters of a set of
alternative dark energy models (XCDM, Dvali-Gabadadze-Porrati and Ricci dark
energy models), under a spatially flat universe. The likelihood is maximized
for when considering the sample excluding the
SLACS systems (known to be biased towards large image-separation lenses) and
no-evolution, and when limiting to gravitational
lenses with image separation larger than 2" and no-evolution. In both cases,
results accounting for galaxy evolution are consistent within 1. The
present test supports the accelerated expansion, by excluding the
null-hypothesis (i.e., ) at more than 4,
regardless of the chosen sample and assumptions on the galaxy evolution. A
comparison between competitive world models is performed by means of the
Bayesian information criterion. This shows that the simplest cosmological
constant model - that has only one free parameter - is still preferred by the
available data on the redshift distribution of gravitational lenses. We perform
an analysis of the possible systematic effects, finding that the systematic
errors due to sample incompleteness, galaxy evolution and model uncertainties
approximately equal the statistical errors, with present-day data. We find that
the largest sources of systemic errors are the dynamical normalization and the
high-velocity cut-off factor, followed by the faint-end slope of the velocity
dispersion function.Comment: 14 pages, 10 figures, accepted for publication in The Astrophysical
Journal. Updated to match print versio
Evolution of the Early-Type Galaxy Fraction in Clusters since z = 0.8
We study the morphological content of a large sample of high-redshift
clusters to determine its dependence on cluster mass and redshift. Quantitative
morphologies are based on bulge+disk decompositions of cluster and field
galaxies on deep VLT/FORS2 images of 18 optically-selected clusters at 0.45 < z
< 0.80 from the ESO Distant Cluster Survey (EDisCS). Morphological content is
given by the early-type galaxy fraction f_et, and early-type galaxies are
selected based on their bulge fraction and image smoothness. A set of 158 SDSS
clusters is analyzed exactly as the EDisCS sample to provide a robust local
comparison. Our main results are: (1) f_et values for the SDSS and EDisCS
clusters exhibit no clear trend as a function of sigma. (2) Mid-z EDisCS
clusters around sigma = 500 km/s have f_et ~= 0.5 whereas high-z EDisCS
clusters have f_et ~= 0.4 (~25% increase over 2 Gyrs). (3) There is a marked
difference in the morphological content of EDisCS and SDSS clusters. None of
the EDisCS clusters have f_et greater than 0.6 whereas half of the SDSS
clusters lie above this value. This difference is seen in clusters of all
velocity dispersions. (4) There is a strong correlation between morphology and
star formation in SDSS and EDisCS clusters. This correlation holds independent
of sigma and z even though the fraction of [OII] emitters decreases from z~0.8
to z~0.06 in all environments. Our results pose an interesting challenge to
structural transformation and star formation quenching processes that strongly
depend on the global cluster environment and suggest that cluster membership
may be of lesser importance than other variables in determining galaxy
properties. (ABRIDGED)Comment: 22 pages, 10 figures, accepted for publication in A&
Recommendations for reporting results of diagnostic genetic testing (biochemical, cytogenetic and molecular genetic)
Genetic test results can have considerable importance for patients, their parents and more remote family members. Clinical therapy and surveillance, reproductive decisions and genetic diagnostics in family members, including prenatal diagnosis, are based on these results. The genetic test report should therefore provide a clear, concise, accurate, fully interpretative and authoritative answer to the clinical question. The need for harmonizing reporting practice of genetic tests has been recognised by the External Quality Assessment (EQA), providers and laboratories. The ESHG Genetic Services Quality Committee has produced reporting guidelines for the genetic disciplines (biochemical, cytogenetic and molecular genetic). These guidelines give assistance on report content, including the interpretation of results. Selected examples of genetic test reports for all three disciplines are provided in an annexe.</p
Physical activity and risk of colon adenoma: A meta-analysis
BACKGROUND: Little evidence is available on the relation of physical activity with colon adenomas, a colon cancer precursor. METHODS: We conducted a systematic literature review and meta-analysis of published studies (in English) through April 2010, examining physical activity or exercise and risk or prevalence of colon adenoma or polyp. Random effects models were used to estimate relative risks (RRs) and corresponding confidence intervals (CIs). A total of 20 studies were identified that examined the association and provided RRs and corresponding 95% CIs. RESULTS: A significant inverse association between physical activity and colon adenomas was found with an overall RR of 0.84 (CI: 0.77–0.92). The association was similar in men (RR=0.81, CI: 0.67–0.98) and women (RR=0.87, CI: 0.74–1.02). The association appeared slightly stronger in large/advanced polyps (RR=0.70, CI: 0.56–0.88). CONCLUSION: This study confirms previous reports of a significant inverse association of physical activity and colon adenoma, and suggests that physical activity can have an important role in colon cancer prevention
Role of IKK/NF-κB Signaling in Extinction of Conditioned Place Aversion Memory in Rats
The inhibitor κB protein kinase/nuclear factor κB (IKK/NF-κB) signaling pathway is critical for synaptic plasticity. However, the role of IKK/NF-κB in drug withdrawal-associated conditioned place aversion (CPA) memory is unknown. Here, we showed that inhibition of IKK/NF-κB by sulphasalazine (SSZ; 10 mM, i.c.v.) selectively blocked the extinction but not acquisition or expression of morphine-induced CPA in rats. The blockade of CPA extinction induced by SSZ was abolished by sodium butyrate, an inhibitor of histone deacetylase. Thus, the IKK/NF-κB signaling pathway might play a critical role in the extinction of morphine-induced CPA in rats and might be a potential pharmacotherapy target for opiate addiction
The redshift distribution of gravitational lenses revisited: Constraints on galaxy mass evolution
The redshifts of lens galaxies in known gravitational lens systems probe the
volume distribution of lensing mass. Following earlier work by Kochanek, we
re-derive the lens redshift probability distribution, allowing for mass and
number density evolution of the lensing galaxies, and apply this test to a much
enlarged sample of lens systems. From a literature survey of all known lenses,
we have selected an unbiased sample of 15 lenses with complete redshift
information. For a flat Universe and no lens evolution, we can only put an
upper limit on the cosmological constant of Omega_lambda<0.89 at the 95% CL.
Omega_lambda~0.7 and no evolution is consistent with the data. Allowing for
evolution in an Omega_m=0.3, Omega_lambda=0.7 cosmology, we find that the
best-fit evolution in sigma* (i.e., the characteristic velocity dispersion in a
Schechter-like function) of early-type galaxies, in the redshift range z~0 to
1, is d[log sigma*(z)]/dz=-0.10+/-0.06. This is consistent with no evolution
and implies that, at 95% CL, sigma* of early-type galaxies at z~1 was at least
63% of its current value. Alternatively, if there is no mass evolution, a
present-day value of sigma*>175 km/s for elliptical galaxies is required (95%
CL).Comment: 15 pages, MNRAS, in pres
Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK): Explanation and Elaboration
The REMARK “elaboration and explanation” guideline, by Doug Altman and colleagues, provides a detailed reference for authors on important issues to consider when designing, conducting, and analyzing tumor marker prognostic studies
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