2,324 research outputs found
2-Point Moments in Cosmological Large Scale Structure: I. Theory and Comparison with Simulations
We present new perturbation theory (PT) predictions in the Spherical Collapse
(SC) model for the 2-point moments of the large-scale distribution of dark
matter density in the universe. We assume that these fluctuations grow under
gravity from small Gaussian initial conditions. These predictions are compared
with numerical simulations and with previous PT results to assess their domain
of validity. We find that the SC model provides in practice a more accurate
description of 2-point moments than previous tree-level PT calculations. The
agreement with simulations is excellent for a wide range of scales (5-50 Mpc/h)
and fluctuations amplitudes (0.02-2 variance). When normalized to unit variance
these results are independent of the cosmological parameters and of the initial
amplitude of fluctuations. The 2-point moments provide a convenient tool to
study the statistical properties of gravitational clustering for fairly
non-linear scales and complicated survey geometries, such as those probing the
clustering of the Ly-alpha forest. In this context, the perturbative SC
predictions presented here, provide a simple and novel way to test the
gravitational instability paradigm.Comment: 10 LaTeX pages, 9 figs, submitted to MNRA
Loss of heterozygosity at the 5,10-methylenetetrahydrofolate reductase locus in human ovarian carcinomas.
The high-affinity folate-binding protein (FBP) is primarily involved in the uptake of the 5-methyltetrahydrofolate, and its expression may be physiologically regulated by the intracellular folate content. The overexpression of FBP on the cell surface of ovarian carcinoma cells may be responsible for an increased folate uptake. We tested the hypothesis of the existence of a defect in the 5, 10-methylenetetrahydrofolate reductase (MTHFR) in ovarian tumours that could cause reduced intracellular regeneration of the 5-methyltetrahydrofolate and induce increased FBP expression. No sequence mutations were found in the MTHFR gene, but allelic deletions of this gene were frequently detected in ovarian tumours (59%). Chromosomal losses appeared to be confined to the 1p36.3 region to which the MTHFR gene maps. Although it cannot be stated that MTHFR is the target gene of the chromosomal loss involving the 1p36.3 region, a correlation between loss of heterozygosity at this locus and decrease in MTHFR activity was shown, suggesting a role of these allelic deletions in generating a biochemical defect in folate metabolism. Further studies are needed to assess further the relationship between MTHFR and FBP overexpression, but the demonstration of the alteration of a key metabolic enzyme of the folate cycle in a subset of human ovarian tumours is in accordance with the hypothesis of an altered folate metabolism in these neoplasias and might be exploited for therapeutic purposes
From Espresso to Codex
CODEX and ESPRESSO are concepts for ultra-stable, high-resolution
spectrographs at the E-ELT and VLT, respectively. Both instruments are well
motivated by distinct sets of science drivers. However, ESPRESSO will also be a
stepping stone towards CODEX both in a scientific as well as in a technical
sense. Here we discuss this role of ESPRESSO with respect to one of the most
exciting CODEX science cases, i.e. the dynamical determination of the cosmic
expansion history.Comment: To appear in the Proceedings of the Workshop "Science with the VLT in
the ELT era", 8-12 October 2007, Garching, A. Moorwood, e
Constraining Primordial Non-Gaussianity with High-Redshift Probes
We present an analysis of the constraints on the amplitude of primordial
non-Gaussianity of local type described by the dimensionless parameter . These constraints are set by the auto-correlation functions (ACFs) of two
large scale structure probes, the radio sources from NRAO VLA Sky Survey (NVSS)
and the quasar catalogue of Sloan Digital Sky Survey Release Six (SDSS DR6
QSOs), as well as by their cross-correlation functions (CCFs) with the cosmic
microwave background (CMB) temperature map (Integrated Sachs-Wolfe effect).
Several systematic effects that may affect the observational estimates of the
ACFs and of the CCFs are investigated and conservatively accounted for. Our
approach exploits the large-scale scale-dependence of the non-Gaussian halo
bias. The derived constraints on {} coming from the NVSS CCF and
from the QSO ACF and CCF are weaker than those previously obtained from the
NVSS ACF, but still consistent with them. Finally, we obtain the constraints on
() and () from
NVSS data and SDSS DR6 QSO data, respectively.Comment: 16 pages, 8 figures, 1 table, Accepted for publication on JCA
Neutrino masses and cosmic radiation density: Combined analysis
We determine the range of neutrino masses and cosmic radiation content
allowed by the most recent CMB and large-scale structure data. In contrast to
other recent works, we vary these parameters simultaneously and provide
likelihood contours in the two-dimensional parameter space of N_eff}, the usual
effective number of neutrino species measuring the radiation density, and \sum
m_nu. The allowed range of \sum m_nu and N_eff has shrunk significantly
compared to previous studies. The previous degeneracy between these parameters
has disappeared, largely thanks to the baryon acoustic oscillation data. The
likelihood contours differ significantly if \sum m_nu resides in a single
species instead of the standard case of being equally distributed among all
flavors. For \sum m_nu=0 we find 2.7 < N_eff < 4.6 at 95% CL while \sum m_nu <
0.62 eV at 95% CL for the standard radiation content.Comment: 8 pages, 2 figure
ESPRESSO: The next European exoplanet hunter
The acronym ESPRESSO stems for Echelle SPectrograph for Rocky Exoplanets and
Stable Spectroscopic Observations; this instrument will be the next VLT high
resolution spectrograph. The spectrograph will be installed at the
Combined-Coud\'e Laboratory of the VLT and linked to the four 8.2 m Unit
Telescopes (UT) through four optical Coud\'e trains. ESPRESSO will combine
efficiency and extreme spectroscopic precision. ESPRESSO is foreseen to achieve
a gain of two magnitudes with respect to its predecessor HARPS, and to improve
the instrumental radial-velocity precision to reach the 10 cm/s level. It can
be operated either with a single UT or with up to four UTs, enabling an
additional gain in the latter mode. The incoherent combination of four
telescopes and the extreme precision requirements called for many innovative
design solutions while ensuring the technical heritage of the successful HARPS
experience. ESPRESSO will allow to explore new frontiers in most domains of
astrophysics that require precision and sensitivity. The main scientific
drivers are the search and characterization of rocky exoplanets in the
habitable zone of quiet, nearby G to M-dwarfs and the analysis of the
variability of fundamental physical constants. The project passed the final
design review in May 2013 and entered the manufacturing phase. ESPRESSO will be
installed at the Paranal Observatory in 2016 and its operation is planned to
start by the end of the same year.Comment: 12 pages, figures included, accepted for publication in Astron. Nach
The importance of sex as a risk factor for hospital readmissions due to pulmonary diseases
BACKGROUND: Pulmonary diseases are a common and costly cause of 30-day readmissions. Few studies have focused on the difference in risk for rehospitalization between men and women in older patients. In this study we analyzed the association between sex and the risk of readmission in a cohort of patients admitted to the hospital for chronic obstructive pulmonary disease (COPD) exacerbation and other major pulmonary diseases. METHODS: This was a retrospective cohort study based on administrative data collected in the Veneto Region in 2016. We included 14,869 hospital admissions among residents aged 6565\u2009years for diagnosis related groups (DRGs) of the most common disorders of the respiratory system: bronchitis and asthma, pneumonia, pulmonary edema, respiratory failure, and COPD. Multilevel logistic regressions were performed to test the association between 30-day hospital readmission and sex, adjusting for confounding factors. RESULTS: For bronchitis and asthma, male patients had significantly higher odds of 30-day readmission than female patients (adjusted odds ratio (aOR), 2.07; 95% confidence interval (CI), 1.11-3.87). The odds of readmission for men were also significantly higher for pneumonia (aOR, 1.40; 95% CI, 1.13-1.72), for pulmonary edema and respiratory failure (aOR, 1.28; 95% CI, 1.05-1.55), and for COPD (aOR, 1.34; 95% CI, 1.00-1.81). CONCLUSIONS: This study found that male sex is a major risk factors for readmission in patients aged more than 65\u2009years with a primary pulmonary diagnosis. More studies are needed to understand the underlying determinants of this phenomena and to provide targets for future interventions
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