4,581 research outputs found
Lasercooled RaF as a promising candidate to measure molecular parity violation
The parameter , which characterizes nuclear spin-dependent
parity violation effects within the effective molecular spin-rotational
Hamiltonian, was computed for the electronic ground state of radium fluoride
(RaF) and found to be one of the largest absolute values predicted so far.
These calculations were performed with the complex generalised Hartree-Fock
method within a two-component (quasi-relativistic) zeroth-order regular
approximation framework. Peculiarities of the molecular electronic structure of
RaF lead to highly diagonal Franck-Condon matrices between vibrational states
of the electronic ground and first excited states, which renders the molecule
in principle suitable for direct laser cooling. As a trapped gas of cold
molecules offers a superior coherence time, RaF can be considered a promising
candidate for high-precision spectroscopic experiments aimed at the search of
molecular parity-violation effects.Comment: 4.5 pages, 1 figure, 2 tables. Supplementary material can be
requested from the authors. Minor changes to version
Propagating Residual Biases in Cosmic Shear Power Spectra
In this paper we derive a full expression for the propagation of
multiplicative and additive shape measurement biases into the cosmic shear
power spectrum. In doing so we identify several new terms that are associated
with selection effects, as well as cross-correlation terms between the
multiplicative and additive biases and the shear field. The computation of the
resulting bias in the shear power spectrum scales as the fifth power of the
maximum multipole considered. Consequently the calculation is unfeasible for
large l-modes, and the only tractable way to assess the full impact of shape
measurement biases on cosmic shear power spectrum is through forward modelling
of the effects. To linear order in bias parameters the shear power spectrum is
only affected by the mean of the multiplicative bias field over a survey and
the cross correlation between the additive bias field and the shear field. If
the mean multiplicative bias is zero then second order convolutive terms are
expected to be orders of magnitude smaller.Comment: 10 pages, accepted to the Open Journal of Astrophysic
Association between consumption of black tea and iron status in adult Africans in the North West Province: The THUSA study
The association between black tea consumption and iron status was investigated in a sample of African adults participating in the cross-sectional THUSA (Transition and Health during Urbanization of South Africans) study in the North West Province, South Africa. Data were analysed from 1605 apparently healthy adults aged 15-65 years by demographic and FFQ, anthropometric measurements and biochemical analyses. The main outcome measures were Hb and serum ferritin concentrations. No associations were seen between black tea consumption and concentrations of serum ferritin (men P=0.059; women P=0.49) or Hb (men P=0.33; women P=0.49). Logistic regression showed that tea consumption did not significantly increase risk for iron deficiency (men: OR 1.36; 95 % CI 0.99, 1.87; women: OR 0.98; 95 % CI 0.84, 1.13) nor for iron deficiency anaemia (men: OR 1.28: 95 % Cl 0.84, 1.96; women: OR 0.93; 95 % Cl 0.78, 1.11). Prevalence of iron deficiency and iron deficiency anaemia was especially high in women: 21.6 and 14.6 %, respectively. However, the likelihood of iron deficiency and iron deficiency anaemia was not significantly explained by tea consumption in sub-populations which were assumed to be at risk for iron deficiency. Regression of serum ferritin levels on tea consumption in women : 40 years, adults with a daily iron intak
Gravitational Lensing in the metric theory proposed by Sobouti
Recently, Y. Sobouti (2007) has provided a metric theory f(R) that can
account for certain dynamical anomalies observed in spiral galaxies. Mendoza &
Rosas-Guevara (2007) have shown that in this theory there is an extra-bending
as compared to standard general relativity. In the present work we have
developed in more specific detail this additional lensing effect and we have
made evaluations of the alpha parameter used in the model adjusting the theory
to observations in X-rays of 13 clusters of galaxies with gravitational lensing
(Hoekstra (2007)).Comment: 7 pages, 2 figure
Scaling relations for galaxy clusters: properties and evolution
Well-calibrated scaling relations between the observable properties and the
total masses of clusters of galaxies are important for understanding the
physical processes that give rise to these relations. They are also a critical
ingredient for studies that aim to constrain cosmological parameters using
galaxy clusters. For this reason much effort has been spent during the last
decade to better understand and interpret relations of the properties of the
intra-cluster medium. Improved X-ray data have expanded the mass range down to
galaxy groups, whereas SZ surveys have openened a new observational window on
the intracluster medium. In addition,continued progress in the performance of
cosmological simulations has allowed a better understanding of the physical
processes and selection effects affecting the observed scaling relations. Here
we review the recent literature on various scaling relations, focussing on the
latest observational measurements and the progress in our understanding of the
deviations from self similarity.Comment: 38 pages. Review paper. Accepted for publication in Space Science
Reviews (eds: S. Ettori, M. Meneghetti). This is a product of the work done
by an international team at the International Space Science Institute (ISSI)
in Bern on "Astrophysics and Cosmology with Galaxy Clusters: the X-ray and
Lensing View
Joint Analysis of Cluster Observations: II. Chandra/XMM-Newton X-ray and Weak Lensing Scaling Relations for a Sample of 50 Rich Clusters of Galaxies
We present a study of multiwavelength X-ray and weak lensing scaling
relations for a sample of 50 clusters of galaxies. Our analysis combines
Chandra and XMM-Newton data using an energy-dependent cross-calibration. After
considering a number of scaling relations, we find that gas mass is the most
robust estimator of weak lensing mass, yielding 15 +/- 6% intrinsic scatter at
r500 (the pseudo-pressure YX has a consistent scatter of 22%+/-5%). The scatter
does not change when measured within a fixed physical radius of 1 Mpc. Clusters
with small BCG to X-ray peak offsets constitute a very regular population whose
members have the same gas mass fractions and whose even smaller <10% deviations
from regularity can be ascribed to line of sight geometrical effects alone.
Cool-core clusters, while a somewhat different population, also show the same
(<10%) scatter in the gas mass-lensing mass relation. There is a good
correlation and a hint of bimodality in the plane defined by BCG offset and
central entropy (or central cooling time). The pseudo-pressure YX does not
discriminate between the more relaxed and less relaxed populations, making it
perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic
masses underestimate weak lensing masses by 10% on the average at r500; but
cool-core clusters are consistent with no bias, while non-cool-core clusters
have a large and constant 15-20% bias between r2500 and r500, in agreement with
N-body simulations incorporating unthermalized gas. For non-cool-core clusters,
the bias correlates well with BCG ellipticity. We also examine centroid shift
variance and and power ratios to quantify substructure; these quantities do not
correlate with residuals in the scaling relations. Individual clusters have for
the most part forgotten the source of their departures from self-similarity.Comment: Corrects an error in the X-ray luminosities (erratum
submitted)---none of the other results are affected. Go to
http://sfstar.sfsu.edu/jaco for an electronic fitter and updated quick data
download link
Loading Stark-decelerated molecules into electrostatic quadrupole traps
Beams of neutral polar molecules in a low-field seeking quantum state can be
slowed down using a Stark decelerator, and can subsequently be loaded and
confined in electrostatic quadrupole traps. The efficiency of the trap loading
process is determined by the ability to couple the decelerated packet of
molecules into the trap without loss of molecules and without heating. We
discuss the inherent difficulties to obtain ideal trap loading, and describe
and compare different trap loading strategies. A new "split-endcap" quadrupole
trap design is presented that enables improved trap loading efficiencies. This
is experimentally verified by comparing the trapping of OH radicals using the
conventional and the new quadrupole trap designs
Status and capacity of Farmer Training Centers (FTCs) in the Improving Productivity and Market Success (IPMS) Pilot Learning Woredas (PLWs)
Grupos asociativos de turismo rural en Argentina : el caso de los grupos Cambio Rural del Centro Regional Buenos Aires sur del INTA
El Turismo Rural en la Argentina, surge acompañando los cambios en la demanda de los turistas que buscan formas de recreación en espacios abiertos. En esta actividad coexisten diferentes actores que llevan adelante la actividad. Si bien prevalecen los emprendimientos individuales y de baja escala de producción, existen grupos que trabajan en forma asociativa con la finalidad de facilitar la adaptación a los cambios y desafÃos que plantea el nuevo escenario nacional y mundial. Dentro de estos, se destacan aquellos nucleados en la región del CeRBAS (Centro Regional Buenos Aires Sur) perteneciente al INTA (Instituto Nacional de TecnologÃa Agropecuaria), por ser una región que logró mantener la cantidad de grupos asociativos; explicando en la actualidad el 20 por ciento del total a nivel paÃs. En este sentido, surge como objetivo de investigación dilucidar qué aspectos ha logrado resolver el trabajo asociativo en este grupo y cuáles aún se presentan como desafÃos a solucionar en pos del desarrollo sostenido de la actividad. Se utilizó como metodologÃa el estudio de caso simple a partir del desarrollo del caso CeRBAS. Se seleccionaron tres variables: la tecnológica, la comercial y la actitudinal, las cuales se midieron a partir de encuestas semi estructuradas a 45 productores del grupo. Los resultados de las encuestas se procesaron con herramientas estadÃsticas multivariadas (Componentes principales y Análisis de Clúster), utilizando el software PC-ORD. En dos ejes se logró explicar el 64,5 por ciento de la variación total de la muestra. Del análisis de las variables se observa que la mayor limitante corresponde a la dimensión comercial y dentro de esta, el indicador de mayor peso, fue la dificultad de acceso al mercado (64 por ciento). El trabajo del grupo logró posicionarlos por encima de la media tecnológica del sector de Turismo Rural. Estos resultados se acompañaron de una actitud positiva frente al trabajo grupal (98 por ciento de los productores). La limitante comercial se correlacionó positivamente con la percepción de la performance económica por parte del productor que manifestó tener falta de fondos para inversión (91 por ciento) y retiros mensuales insuficientes (49 por ciento). Se concluye que los productores nucleados en los grupos asociativos de Turismo Rural del caso estudiado lograron ventajas tecnológicas, actitudinales y mostraron predisposición al trabajo en grupo, sin embargo, no logran resolver aspectos comerciales representando una de las principales limitaciones que dificulta la sostenibilidad de la actividad de los mismos
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