1,336 research outputs found
Joint constraints on galaxy bias and through the N-pdf of the galaxy number density
We present a full description of the N-probability density function of the
galaxy number density fluctuations. This N-pdf is given in terms, on the one
hand, of the cold dark matter correlations and, on the other hand, of the
galaxy bias parameter. The method relies on the assumption commonly adopted
that the dark matter density fluctuations follow a local non-linear
transformation of the initial energy density perturbations. The N-pdf of the
galaxy number density fluctuations allows for an optimal estimation of the bias
parameter (e.g., via maximum-likelihood estimation, or Bayesian inference if
there exists any a priori information on the bias parameter), and of those
parameters defining the dark matter correlations, in particular its amplitude
(). It also provides the proper framework to perform model selection
between two competitive hypotheses. The parameters estimation capabilities of
the N-pdf are proved by SDSS-like simulations (both ideal log-normal
simulations and mocks obtained from Las Damas simulations), showing that our
estimator is unbiased. We apply our formalism to the 7th release of the SDSS
main sample (for a volume-limited subset with absolute magnitudes ). We obtain and , for galaxy number density fluctuations in cells of a size of
Mpc. Different model selection criteria show that galaxy biasing is
clearly favoured.Comment: 25 pages, 9 figures, 2 tables. v2: Substantial revision, adding the
joint constraints with \sigma_8 and testing with Las Damas mocks. Matches
version accepted for publication in JCA
Evaluation of firefighters' functional movement
According to previous research, firefighters have a higher rate of being overweight, or obese, than the general population. these higher risk predict mortality, morbidity, short and long medical costs. Various programs in conjunction with acute care will allow for athletic trainers to utilize a variety of skills and improve the quality of health care provided for firefighters while reducing the fiscal bottom line.Firefighters who exercise regularly on-duty were found to have nearly half the odds of suffering a non-exercise- related injury compared with those who do not regularly on duty. One-third of the injuries reported among firefighters was the result of physical training or exercise, which are the most common sprains and strains
Shell-like structures in our cosmic neighbourhood
Signatures of the processes in the early Universe are imprinted in the cosmic
web. Some of them may define shell-like structures characterised by typical
scales. We search for shell-like structures in the distribution of nearby rich
clusters of galaxies drawn from the SDSS DR8. We calculate the distance
distributions between rich clusters of galaxies, and groups and clusters of
various richness, look for the maxima in the distance distributions, and select
candidates of shell-like structures. We analyse the space distribution of
groups and clusters forming shell walls. We find six possible candidates of
shell-like structures, in which galaxy clusters have maxima in the distance
distribution to other galaxy groups and clusters at the distance of about 120
Mpc/h. The rich galaxy cluster A1795, the central cluster of the Bootes
supercluster, has the highest maximum in the distance distribution of other
groups and clusters around them at the distance of about 120 Mpc/h among our
rich cluster sample, and another maximum at the distance of about 240 Mpc/h.
The structures of galaxy systems causing the maxima at 120 Mpc/h form an almost
complete shell of galaxy groups, clusters and superclusters. The richest
systems in the nearby universe, the Sloan Great Wall, the Corona Borealis
supercluster and the Ursa Major supercluster are among them. The probability
that we obtain maxima like this from random distributions is lower than 0.001.
Our results confirm that shell-like structures can be found in the distribution
of nearby galaxies and their systems. The radii of the possible shells are
larger than expected for a BAO shell (approximately 109 Mpc/h versus
approximately 120 Mpc/h), and they are determined by very rich galaxy clusters
and superclusters with high density contrast while BAO shells are barely seen
in the galaxy distribution. We discuss possible consequences of these
differences.Comment: Comments: 9 pages, 10 figures, Astronomy and Astrophysics, in pres
Implanted muon spin spectroscopy on 2-O-adamantane: a model system that mimics the liquid
The transition taking place between two metastable phases in 2-O-adamantane, namely the [Formula: see text] cubic, rotator phase and the lower temperature P21/c, Z  =  4 substitutionally disordered crystal is studied by means of muon spin rotation and relaxation techniques. Measurements carried out under zero, weak transverse and longitudinal fields reveal a temperature dependence of the relaxation parameters strikingly similar to those exhibited by structural glass[Formula: see text]liquid transitions (Bermejo et al 2004 Phys. Rev. B 70 214202; Cabrillo et al 2003 Phys. Rev. B 67 184201). The observed behaviour manifests itself as a square root singularity in the relaxation rates pointing towards some critical temperature which for amorphous systems is located some tens of degrees above that shown as the characteristic transition temperature if studied by thermodynamic means. The implications of such findings in the context of current theoretical approaches concerning the canonical liquid-glass transition are discussed.Postprint (author's final draft
Spherical model of the Stark effect in external scalar and vector fields
The Bohr-Sommerfeld quantization rule and the Gamow formula for the width of
quasistationary level are generalized by taking into account the relativistic
effects, spin and Lorentz structure of interaction potentials. The relativistic
quasi-classical theory of ionization of the Coulomb system (V_{Coul}=-\xi/r) by
radial-constant long-range scalar (S_{l.r.}=(1-\lambda)(\sigma r+V_0)) and
vector (V_{l.r.}=\lambda(\sigma r+V_0)) fields is constructed. In the limiting
cases the approximated analytical expressions for the position E_r and width
\Gamma of below-barrier resonances are obtained. The strong dependence of the
width \Gamma of below-barrier resonances on both the bound level energy and the
mixing constant \lambda is detected. The simple analytical formulae for
asymptotic coefficients of the Dirac radial wave functions at zero and infinity
are also obtained.Comment: 25 pages, 4 figures. Submitted to Int. J. Mod. Phys.
The quasiclassical theory of the Dirac equation with a scalar-vector interaction and its applications in the theory of heavy-light mesons
We construct a relativistic potential quark model of , , , and
mesons in which the light quark motion is described by the Dirac equation
with a scalar-vector interaction and the heavy quark is considered a local
source of the gluon field. The effective interquark interaction is described by
a combination of the perturbative one-gluon exchange potential
and the long-range Lorentz-scalar and
Lorentz-vector linear potentials and , where
. Within the quasiclassical approximation, we obtain
simple asymptotic formulas for the energy and mass spectra and for the mean
radii of , , , and mesons, which ensure a high accuracy of
calculations even for states with the radial quantum number . We
show that the fine structure of P-wave states in heavy-light mesons is
primarily sensitive to the choice of two parameters: the strong-coupling
constant and the coefficient of mixing of the long-range
scalar and vector potentials and .
The quasiclassical formulas for asymptotic coefficients of wave function at
zero and infinity are obtained.Comment: 22 pages, 6 figure
La vida en un laboratorio de alta seguridad biológica
El trabajo e investigación con ciertos microorganismos puede suponer un gran riesgo tanto para el personal que trabaja con ellos, como para los animales y el medio ambiente. Ello hace necesaria la existencia de laboratorios de alta seguridad biológica que permitan su estudio sin riesgo. En este tipo de laboratorios las medidas de bioseguridad son muy estrictas y ello puede afectar al personal que trabaja a diario en estos centros. Conocer cómo les afectan, en qué medida y por qué ha sido el objetivo principal de nuestro trabajo. Para ello se realizó y diseñó una encuesta que ha permitido recoger la opinión de los trabajadores de tres importantes centros de alta seguridad biológica dedicados a Sanidad Animal y Salud Pública. Tras el análisis de las respuestas se observó que la mayorÃa de encuestados encuentra factores limitantes para su trabajo en este tipo de centros, si bien estos varÃan de un centro a otro y no impiden valorar la necesidad de estas medidas.To work and research with some kind of microorganism could suppose a high risk for humans, animals and environment. This fact makes necessary the existence of biosafety laboratories. In this type of centres, high security conditions are very strict and that could affect people who work daily inside it. Knowing how it affects them is the main objective of our study. For that reason we have done a survey to know the impressions of people who work in laboratories of Biosafety level 3 (BSL-3) . After analyzing the results of this survey, we could say that working inside BSL-3 implies certain limitations for people who work inside them, but they respect and value the importance of this security conditions
Coulomb focusing at above-threshold ionization in elliptically polarized mid-infrared strong laser fields
The role of Coulomb focusing in above-threshold ionization in an elliptically
polarized mid-infrared strong laser field is investigated within a
semiclassical model incorporating tunneling and Coulomb field effects. It is
shown that Coulomb focusing up to moderate ellipticity values is dominated by
multiple forward scattering of the ionized electron by the atomic core that
creates a characteristic low-energy structure in the photoelectron spectrum and
is responsible for the peculiar energy scaling of the ionization normalized
yield along the major polarization axis. At higher ellipticities, the electron
continuum dynamics is disturbed by the Coulomb field effect mostly at the exit
of the ionization tunnel. Due to the latter, the normalized yield is found to
be enhanced, with the enhancement factor being sharply pronounced at
intermediate ellipticities
The Investigation of Flowering Control in Late/Rare Flowering Lolium Perenne
Flowering in Lolium perenne (perennial ryegrass) results in reduced digestibility and its inhibition would enhance forage quality. Flowering regulation has been well studied in Arabidopsis thaliana (Simpson and Dean, 2002) and orthologs of Arabidopsis flowering genes underlying heading date Quantitative Trait Loci (QTL) have been identified in rice (Yano, M et al., 2000). However it is not clear yet how universally applicable such studies are to Lolium. The project goals are to characterise the gene expression profiles of late/rare flowering L. perenne plants to determine factors affecting flowering and to map the genes involved in the flowering process. Initial studies, reported here, have focussed on the ability of 6 plant lines from the Oak Park breeding programme, previously identified as rare or non-flowering under natural day length conditions, to flower in controlled environments
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