Uniqueness of the Fock quantization of a free scalar field on S1S^1 with time dependent mass

We analyze the quantum description of a free scalar field on the circle in the presence of an explicitly time dependent potential, also interpretable as a time dependent mass. Classically, the field satisfies a linear wave equation of the form $\ddot{\xi}-\xi"+f(t)\xi=0$. We prove that the representation of the canonical commutation relations corresponding to the particular case of a massless free field ($f=0$) provides a unitary implementation of the dynamics for sufficiently general mass terms, $f(t)$. Furthermore, this representation is uniquely specified, among the class of representations determined by $S^1$-invariant complex structures, as the only one allowing a unitary dynamics. These conclusions can be extended in fact to fields on the two-sphere possessing axial symmetry. This generalizes a uniqueness result previously obtained in the context of the quantum field description of the Gowdy cosmologies, in the case of linear polarization and for any of the possible topologies of the spatial sections.Comment: 13 pages, typos corrected, version accepted for publication in Physical Review

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

Fock quantization of a scalar field with time dependent mass on the three-sphere: unitarity and uniqueness

We study the Fock description of a quantum free field on the three-sphere with a mass that depends explicitly on time, also interpretable as an explicitly time dependent quadratic potential. We show that, under quite mild restrictions on the time dependence of the mass, the specific Fock representation of the canonical commutation relations which is naturally associated with a massless free field provides a unitary dynamics even when the time varying mass is present. Moreover, we demonstrate that this Fock representation is the only acceptable one, up to unitary equivalence, if the vacuum has to be SO(4)-invariant (i.e., invariant under the symmetries of the field equation) and the dynamics is required to be unitary. In particular, the analysis and uniqueness of the quantization can be applied to the treatment of cosmological perturbations around Friedmann-Robertson-Walker spacetimes with the spatial topology of the three-sphere, like e.g. for gravitational waves (tensor perturbations). In addition, we analyze the extension of our results to free fields with a time dependent mass defined on other compact spatial manifolds. We prove the uniqueness of the Fock representation in the case of a two-sphere as well, and discuss the case of a three-torus.Comment: 30 page

Selection of trees for rubbing by red and roe deer in forest plantations

Antler rubbing is a form of behaviour by which deer may damage and ultimately induce mortality of trees. Understanding factors affecting selection of trees for rubbing may contribute to mitigation of negative effects of such behaviour in plantations or woodlands. We analysed characteristics of trees rubbed by red and roe deer along transects established in plantations of Pinus pinaster (Aiton), Pseudotsuga menziesii (Mirbel) Franco, Betula alba L. and Quercus robur L. in Northeast Portugal. Transects were walked during five sampling periods covering mating seasons of red and roe deer. Red deer preferentially rubbed trees adjacent to the edge of plantations and large clearings whilst roe deer selected those inside plantations within small clearings. There was seasonal segregation in the number of trees rubbed by each deer species with red deer rubbing trees mainly between September and February and roe deer mainly between December and June. Both red and roe deer selected trees with smaller diameter than those of available trees although trees selected by red deer had larger diameters than those selected by roe deer. Roe, but not red deer, tended to avoid trees protected by shrubs. Overall, the selection of trees for rubbing was site-dependent suggesting that generalizations across sites should be made with caution. Mitigating measures, such as deer control, tree protection or provision of alternative rubbing posts should target stands of particular tree species, location of trees in relation to stand clearings and tree size classes.http://www.sciencedirect.com/science/article/B6T6X-4HGM78R-2/1/29fe58190c40581f0716e977b7847d3

Coffee Diterpene Derivatives as Anti-angiogenesis Agent

Among the several compounds present in coffee, the coffee-specific diterpenes have been identified as important chemoprotective agents which possess anti-carcinogenic properties.info:eu-repo/semantics/publishedVersio

Quantum Gowdy T3T^3 model: A unitary description

The quantization of the family of linearly polarized Gowdy $T^3$ spacetimes is discussed in detail, starting with a canonical analysis in which the true degrees of freedom are described by a scalar field that satisfies a Klein-Gordon type equation in a fiducial time dependent background. A time dependent canonical transformation, which amounts to a change of the basic (scalar) field of the model, brings the system to a description in terms of a Klein-Gordon equation on a background that is now static, although subject to a time dependent potential. The system is quantized by means of a natural choice of annihilation and creation operators. The quantum time evolution is considered and shown to be unitary, allowing both the Schr\"odinger and Heisenberg pictures to be consistently constructed. This has to be contrasted with previous treatments for which time evolution failed to be implementable as a unitary transformation. Possible implications for both canonical quantum gravity and quantum field theory in curved spacetime are commented

Uniqueness of the Fock representation of the Gowdy S1×S2S^1\times S^2 and S3S^3 models

After a suitable gauge fixing, the local gravitational degrees of freedom of the Gowdy $S^1\times S^2$ and $S^3$ cosmologies are encoded in an axisymmetric field on the sphere $S^2$. Recently, it has been shown that a standard field parametrization of these reduced models admits no Fock quantization with a unitary dynamics. This lack of unitarity is surpassed by a convenient redefinition of the field and the choice of an adequate complex structure. The result is a Fock quantization where both the dynamics and the SO(3)-symmetries of the field equations are unitarily implemented. The present work proves that this Fock representation is in fact unique inasmuch as, up to equivalence, there exists no other possible choice of SO(3)-invariant complex structure leading to a unitary implementation of the time evolution.Comment: 10 pages, minor changes, version accepted for publication in Classical and Quantum Gravit

Availability of timber housing construction techniques in Brazil

Se analiza la representatividad de las viviendas hechas en madera, en Brasil, indicando el porcentaje de cada técnica constructiva según la oferta de las empresas evaluadas. Los porcentajes que evidencian la frecuencia de utilización de las técnicas de construcción en madera fueron medidos por medio de dos metodologías aplicadas en las empresas: encuesta por entrevistas personales a sus propietarios y búsqueda de datos en sus sitios web. El método de encuestas por entrevistas evaluó 107 empresas brasileñas, y el de búsqueda en los sitios web alcanzó 207 empresas; se consiguió 50,95 y 98,57 %, respectivamente, de la población estimada. A pesar de esta diferencia, ambos métodos demostraron un escenario similar. Las entrevistas presentaron mayores costos de aplicación. Las técnicas contemporáneas están disponibles en más del 90 % de los productores brasileros. Las casas de tablas horizontales clavadas y las casas de tablas horizontales entre pilares fueron las que tuvieron mayores ofertas.This paper analyzes the representativeness of timber housing in Brazil, identifying the percentage of construction techniques offered by each evaluated company. Percentages that evidence the frequency of use of wooden building techniques were measured using two methods applied in the companies: survey through face-to-face interviews with owners and data search on their websites. The survey through interviews evaluated 107 Brazilian companies, while the data search included 207 companies, obtaining 50.95% and 98.57% of the estimated population, respectively. In spite of this difference, both methods showed a similar scenario. Interviews evidenced higher application costs. Contemporary techniques are available in more than 90% of Brazilian constructors. Houses with nailed horizontal boards and houses with horizontal wooden boards between columns were offered the most

Absence Seizures as a Feature of Juvenile Myoclonic Epilepsy in Rhodesian Ridgeback Dogs

Myoclonic epilepsy in Rhodesian Ridgeback (RR) dogs is characterized by myoclonic seizures occurring mainly during relaxation periods, a juvenile age of onset and generalized tonic-clonic seizures in one-third of patients. An 8-month-old female intact RR was presented for myoclonic seizures and staring episodes that both started at 10 weeks of age. Testing for the DIRAS1 variant indicated a homozygous mutant genotype. Unsedated wireless video-electroencephalography (EEG) identified frequent, bilaterally synchronous, generalized 4 Hz spike-and-wave complexes (SWC) during the staring episodes in addition to the characteristic myoclonic seizures with generalized 4-5 Hz SWC or 4-5 Hz slowing. Photic stimulation did not evoke a photoparoxysmal response. Repeat video-EEG 2 months after initiation of levetiracetam treatment disclosed a >95% decrease in frequency of myoclonic seizures, and absence seizures were no longer evident. Absence seizures represent another seizure type in juvenile myoclonic epilepsy (JME) in RR dogs, which reinforces its parallels to JME in humans.Peer reviewe

Electron and Hole Spin Splitting and Photogalvanic Effect in Quantum Wells

A theory of the circular photogalvanic effect caused by spin splitting in quantum wells is developed. Direct interband transitions between the hole and electron size-quantized subbands are considered. It is shown that the photocurrent value and direction depend strongly on the form of the spin-orbit interaction. The currents induced by structure-, bulk-, and interface-inversion asymmetry are investigated. The photocurrent excitation spectra caused by spin splittings in both conduction and valence bands are calculated.Comment: 7 pages, 3 figure