235 research outputs found
Uniqueness of the Fock quantization of scalar fields under mode preserving canonical transformations varying in time
We study the Fock quantization of scalar fields of Klein-Gordon type in
nonstationary scenarios propagating in spacetimes with compact spatial
sections, allowing for different field descriptions that are related by means
of certain nonlocal linear canonical transformations that depend on time. More
specifically, we consider transformations that do not mix eigenmodes of the
Laplace-Beltrami operator, which are supposed to be dynamically decoupled. In
addition, we assume that the canonical transformations admit an asymptotic
expansion for large eigenvalues (in norm) of the Laplace-Beltrami operator in
the form of a series of half integer powers. Canonical transformations of this
kind are found in the study of scalar perturbations in inflationary
cosmologies, relating for instance the physical degrees of freedom of these
perturbations after gauge fixing with gauge invariant canonical pairs of
Bardeen quantities. We characterize all possible transformations of this type
and show that, independently of the initial field description, the combined
criterion of requiring (i) invariance of the vacuum under the spatial
symmetries and (ii) a unitary implementation of the dynamics, leads to a unique
equivalence class of Fock quantizations, all of them related by unitary
transformations. This conclusion provides even further robustness to the
validity of the proposed criterion, completing the results that have already
appeared in the literature about the uniqueness of the Fock quantization under
changes of field description when one permits exclusively local time dependent
canonical transformations that scale the field configuration.Comment: 12 pages, submitted to Phys. Rev.
HTself2: Combining p-values to Improve Classification of Differential Gene Expression in HTself
HTself is a web-based bioinformatics tool designed to deal with the classification of differential gene expression for low replication microarray studies. It is based on a statistical test that uses self-self experiments to derive intensity-dependent cutoffs. The method was previously described in Vêncio et al, (DNA Res. 12: 211- e 214, 2005). In this work we consider an extension of HTself by calculating p-values instead of using a fixed credibility level α. As before, the statistic used to compute single spots p-values is obtained from the gaussian Kernel Density Estimator method applied to self-self data. Different spots corresponding to the same biological gene (replicas) give rise to a set of independent p-values which can be combined by well known statistical methods. The combined p-value can be used to decide whether a gene can be considered differentially expressed or not. HTself2 is a new version of HTself that uses the idea of p-values combination. It was implemented as a user-friendly desktop application to help laboratories without a bioinformatics infrastructure
Massless scalar field in de Sitter spacetime: unitary quantum time evolution
We prove that, under the standard conformal scaling, a massless field in de
Sitter spacetime admits an O(4)-invariant Fock quantization such that time
evolution is unitarily implemented. This result disproves previous claims in
the literature. We discuss the relationship between this quantization with
unitary dynamics and the family of O(4)-invariant Hadamard states given by
Allen and Folacci, as well as with the Bunch-Davies vacuum.Comment: 23 pages. Typos corrected, matches published versio
Unitary evolution and uniqueness of the Fock quantization in flat cosmologies with compact spatial sections
We study the Fock quantization of scalar fields with a time dependent mass in
cosmological scenarios with flat compact spatial sections. This framework
describes physically interesting situations like, e.g., cosmological
perturbations in flat Friedmann-Robertson-Walker spacetimes, generally
including a suitable scaling of them by a background function. We prove that
the requirements of vacuum invariance under the spatial isometries and of a
unitary quantum dynamics select (a) a unique canonical pair of field variables
among all those related by time dependent canonical transformations which scale
the field configurations, and (b) a unique Fock representation for the
canonical commutation relations of this pair of variables. Though the proof is
generalizable to other compact spatial topologies in three or less dimensions,
we focus on the case of the three-torus owing to its relevance in cosmology,
paying a especial attention to the role played by the spatial isometries in the
determination of the representation.Comment: 23 pages. New section 4.2. Added references. Published in EJT
Uniqueness of the Fock quantization of scalar fields in spatially flat cosmological spacetimes
We study the Fock quantization of scalar fields in (generically) time
dependent scenarios, focusing on the case in which the field propagation occurs
in --either a background or effective-- spacetime with spatial sections of flat
compact topology. The discussion finds important applications in cosmology,
like e.g. in the description of test Klein-Gordon fields and scalar
perturbations in Friedmann-Robertson-Walker spacetime in the observationally
favored flat case. Two types of ambiguities in the quantization are analyzed.
First, the infinite ambiguity existing in the choice of a Fock representation
for the canonical commutation relations, understandable as the freedom in the
choice of inequivalent vacua for a given field. Besides, in cosmological
situations, it is customary to scale the fields by time dependent functions,
which absorb part of the evolution arising from the spacetime, which is treated
classically. This leads to an additional ambiguity, this time in the choice of
a canonical pair of field variables. We show that both types of ambiguities are
removed by the requirements of (a) invariance of the vacuum under the
symmetries of the three-torus, and (b) unitary implementation of the dynamics
in the quantum theory. In this way, one arrives at a unique class of unitarily
equivalent Fock quantizations for the system. This result provides considerable
robustness to the quantum predictions and renders meaningful the confrontation
with observation.Comment: 15 pages, version accepted for publication in JCA
Incidencia de la aplicación de un protocolo de educación, evaluación y entrenamiento mediante nuevas tecnologías (plataforma vibratoria) sobre la condición física en el personal no docente de la UMaza. (Parte II)
Esta investigación corresponde a la etapa II del trabajo realizado durante en
2012 titulado “Diseño prueba y ajuste de un protocolo de evaluación de la
condición física”. En esta segunda etapa, procederemos a la aplicación del
mismo como instrumento de evaluación y de educación anexando el entrenamiento
con nuevas tecnologías, específicamente una plataforma vibratoria. Las
intervenciones se realizarán sobre el personal administrativo no docente de la
UMAZA a través de una convocatoria voluntaria de los mismos.
Este trabajo se realizará con el objetivo de detectar la incidencia de la
aplicación de un protocolo de educación, evaluación y entrenamiento mediante
plataforma vibratoria sobre la condición física en el personal no docente de
UMaza. Al grupo de estudio se le realizarán tres evaluaciones, antes, durante
y después de las intervenciones con la plataforma vibratoria y en forma simultánea
en cada evaluación se educará de manera personalizada sobre la relación
entre los resultados de los parámetros evaluados y conductas saludables,
mientras que el grupo control solamente será evaluado en las tres oportunidades, pero sin ningún tipo de intervención
Fluoxetine can make marine organisms unhappy: a study on the sub-lethal effects on marine invertebrates
The environmental effects caused by selective serotonin reuptake inhibitor drugs have been investigated for marine organisms and coastal ecosystems but are scarce in neotropical organisms. This investigation aimed to evaluate the sublethal effects of fluoxetine on the embryonic development of the sea urchin Echinometra lucunter and the survival and swimming behavior of the brine shrimp Artemia sp. The organisms were exposed to four different concentrations of fluoxetine (30, 300, 3000 and 30000 ng L-1) and to a negative control (filtered seawater), following the respective standard testing protocols. We verified a significant reduction of the embryos development to pluteus larvae, starting from 3000 ng L-1 (54.0±10.9% normal larvae), in comparison with the controls (83.5±3.1%). The non-observed effect concentration (NOEC) was estimated at 300 ng L-1, and the lowest observed effect concentration (LOEC) was 3000 ng L-1. In the behavior tests with Artemia sp, no significant adverse effects were reported for mobility, swimming speed and inactivity time. These results show that Fluoxetine can interfere on the development of species like the sea urchin E. lucunter, but short term exposure did not affected the swimming behavior of the brine shrimp Artemia sp. Fluoxetine presents thus a potential to affect marine biota and disrupt the equilibrium of the coastal ecosystems
The Mre11-Rad50-Nbs1 complex mediates activation of TopBP1 by ATM
The activation of ATR-ATRIP in response to double-stranded DNA breaks (DSBs) depends upon ATM in human cells and Xenopus egg extracts. One important aspect of this dependency involves regulation of TopBP1 by ATM. In Xenopus egg extracts, ATM associates with TopBP1 and thereupon phosphorylates it on S1131. This phosphorylation enhances the capacity of TopBP1 to activate the ATR-ATRIP complex. We show that TopBP1 also interacts with the Mre11-Rad50-Nbs1 (MRN) complex in egg extracts in a checkpoint-regulated manner. This interaction involves the Nbs1 subunit of the complex. ATM can no longer interact with TopBP1 in Nbs1-depleted egg extracts, which suggests that the MRN complex helps to bridge ATM and TopBP1 together. The association between TopBP1 and Nbs1 involves the first pair of BRCT repeats in TopBP1. In addition, the two tandem BRCT repeats of Nbs1 are required for this binding. Functional studies with mutated forms of TopBP1 and Nbs1 suggested that the BRCT-dependent association of these proteins is critical for a normal checkpoint response to DSBs. These findings suggest that the MRN complex is a crucial mediator in the process whereby ATM promotes the TopBP1-dependent activation of ATR-ATRIP in response to DSBs
Cost and burden of hypercholesterolemia In Portugal
Copyright © 2014 Published by Elsevier Inc.Hypercholesterolemia is a risk factor for ciculatory diseases. This study estimates the impact of hypercholesterolemia on populations’ health levels and its economic impact in Portugal.info:eu-repo/semantics/publishedVersio
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