Maximal velocity of photons in non-relativistic QED

We consider the problem of propagation of photons in the quantum theory of non-relativistic matter coupled to electromagnetic radiation, which is, presently, the only consistent quantum theory of matter and radiation. Assuming that the matter system is in a localized state (i.e for energies below the ionization threshold), we show that the probability to find photons at time t at the distance greater than ct, where c is the speed of light, vanishes as t goes to infinity as an inverse power of t.Comment: 21 page

Star formation in the giant HII regions of M101

The molecular components of three giant HII regions (NGC 5461, NGC 5462, NGC 5471) in the galaxy M101 are investigated with new observations from the James Clerk Maxwell Telescope, the NRAO 12-meter, and the Owens Valley millimeter array. Of the three HII regions, only NGC 5461 had previously been detected in CO emission. We calculate preliminary values for the molecular mass of the GMCs in NGC 5461 by assuming a CO-to-H_2 factor (X factor) and then compare these values with the virial masses. We conclude that the data in this paper demonstrate for the first time that the value of X may decrease in regions with intense star formation. The molecular mass for the association of clouds in NGC 5461 is approximately 3x10^7 Mo and is accompanied by 1-2 times as much atomic mass. The observed CO emission in NGC 5461 is an order of magnitude stronger than in NGC 5462, while it was not possible to detect molecular gas toward NGC 5471 with the JCMT. An even larger ratio of atomic to molecular gas in NGC 5471 was observed, which might be attributed to efficient conversion of molecular to atomic gas. The masses of the individual clouds in NGC 5461, which are gravitationally bound, cover a range of (2-8) x 10^5 Mo, comparable with the masses of Galactic giant molecular clouds (GMCs). Higher star forming efficiencies, and not massive clouds, appear to be the prerequisite for the formation of the large number of stars whose radiation is required to produce the giant HII regions in M101.Comment: 32 pages, 5 figures, accepted for publication in the Astrophysical Journa

Incorporation of oxygen and nitrogen in ultrathin films of SiO/sub 2 annealed in NO

The areal densities of oxygen and nitrogen incorporated into ultrathin films of silicon dioxide during rapid thermal processing in nitric oxide, as well as the regions where these incorporations took place, were determined by combining nuclear reaction analysis and narrow nuclear resonance depth profiling with isotopic enrichment of the processing gas. Oxygen is seen to incorporate in the near-surface and near-interface regions of the oxynitride films, whereas nitrogen is incorporated only in the near-interface regions. The growth of the oxynitride film is very moderate as compared to that of a SiO2 film in dry O2 . The thermal oxynitridation of ultrathin SiO2 films takes place by two mechanisms in parallel: the major part of the NO molecules, which react with the silica, decompose in the near-surface region, the O atoms being exchanged for O atoms preexistent in this region of the SiO2 films; a minor portion of the NO molecules diffuse through the silica film in interstitial sites, without reacting with it, to react at the oxynitride/Si interface

A two-mass expanding exact space-time solution

In order to understand how locally static configurations around gravitationally bound bodies can be embedded in an expanding universe, we investigate the solutions of general relativity describing a space-time whose spatial sections have the topology of a 3-sphere with two identical masses at the poles. We show that Israel junction conditions imply that two spherically symmetric static regions around the masses cannot be glued together. If one is interested in an exterior solution, this prevents the geometry around the masses to be of the Schwarzschild type and leads to the introduction of a cosmological constant. The study of the extension of the Kottler space-time shows that there exists a non-static solution consisting of two static regions surrounding the masses that match a Kantowski-Sachs expanding region on the cosmological horizon. The comparison with a Swiss-Cheese construction is also discussed.Comment: 15 pages, 5 figures. Replaced to match the published versio

Dynamics of Relativistic Interacting Gases : from a Kinetic to a Fluid Description

Starting from a microscopic approach, we develop a covariant formalism to describe a set of interacting gases. For that purpose, we model the collision term entering the Boltzmann equation for a class of interactions and then integrate this equation to obtain an effective macroscopic description. This formalism will be useful to study the cosmic microwave background non-perturbatively in inhomogeneous cosmologies. It should also be useful for the study of the dynamics of the early universe and can be applied, if one considers fluids of galaxies, to the study of structure formation.Comment: Latex file, 28 pages, accepted for publication in Class. Quant. Gra

Colliding Branes in Heterotic M-theory

We study the collision of two flat, parallel end-of-the-world branes in heterotic M-theory. By insisting that there is no divergence in the Riemann curvature as the collision approaches, we are able to single out a unique solution possessing the local geometry of (2d compactified Milne)/Z_2 x R_3, times a finite-volume Calabi-Yau manifold in the vicinity of the collision. At a finite time before and after the collision, a second type of singularity appears momentarily on the negative-tension brane, representing its bouncing off a zero of the bulk warp factor. We find this singularity to be remarkably mild and easily regularised. The various different cosmological solutions to heterotic M-theory previously found by other authors are shown to merely represent different portions of a unique flat cosmological solution to heterotic M-theory.Comment: 29 pp, 4 figs; Appendix B revised to include junction condition for scala

The Hard X-ray Emission of Cen A

The radio galaxy Cen A has been detected all the way up to the TeV energy range. This raises the question about the dominant emission mechanisms in the high-energy domain. Spectral analysis allows us to put constraints on the possible emission processes. Here we study the hard X-ray emission as measured by INTEGRAL in the 3-1000 keV energy range, in order to distinguish between a thermal and non-thermal inverse Compton process. The hard X-ray spectrum of Cen A shows a significant cut-off at energies Ec = 434 (+106 -73) keV with an underlying power law of photon index 1.73 +- 0.02. A more physical model of thermal Comptonisation (compPS) gives a plasma temperature of kT = 206+-62 keV within the optically thin corona with Compton parameter y = 0.42 (+0.09 -0.06). The reflection component is significant at the 1.9 sigma level with R = 0.12 (+0.09 -0.10), and a reflection strength R>0.3 can be excluded on a 3 sigma level. Time resolved spectral studies show that the flux, absorption, and spectral slope varied in the range f(3-30 keV) = (1.2 - 9.2)e-10 erg/cm**2/s, NH = (7 - 16)e22 1/cm**2, and photon index 1.75 - 1.87. Extending the cut-off power law or the Comptonisation model to the gamma-ray range shows that they cannot account for the high-energy emission. On the other hand, also a broken or curved power law model can represent the data, therefore a non-thermal origin of the X-ray to GeV emission cannot be ruled out. The analysis of the SPI data provides no sign of significant emission from the radio lobes and gives a 3 sigma upper limit of f(40-1000 keV) < 0.0011 ph/cm**2/s. While gamma-rays, as detected by CGRO and Fermi, are caused by non-thermal (jet) processes, the main process in the hard X-ray emission of Cen A is still not unambiguously determined, being either dominated by thermal inverse Compton emission, or by non-thermal emission from the base of the jet.Comment: 8 pages, 6 figures, accepted for publication in A&

QUALITY OF LIFE IN DEAF SIGN LANGUAGE USERS IN SOUTHERN BRAZIL PSYCHOLOGICAL DOMAIN

Introduction: Deaf users of Brazilian Sign Language (Libras) constitute part of a population who need to integrate and interact with other people in society. However, many Libras users are not able to communicate through spoken Portuguese and this may have an impact on their quality of life (QoL). Few studies have investigated factors that influence the quality of life of Libras users. Objective: To verify how a group of Libras users, who lives in the South of Brazil, perceive their QoL, especially in the psychological domain. Method: 60 deaf sign language users participated in this study by completing two questionnaires: 1) WHOOQL-BREF instrument in Portuguese written language and/or WHOOQL-Bref - Libras and 2) Identification questionnaire. The research was conducted between, July 2015 February 2016. Results: From the 60 deaf sign language users, 20% were male and 40% female. The mean age was 28 years old, with high school and college education. Overall mean score on WHOOQL-Bref was 43.3%. The Psychological domain have a score (61,26%) Conclusion: Deaf sign language users have low results in the Psychological Domain when compared to hearing people research results. There is association between the results in this domain scores with lack of accessibility and interaction, negative thoughts and depression.  Article visualizations

Análisis técnico - económico de recuperación secundaria en campo secoya

Los campos maduros aumentan cada vez más, ya que la presión del yacimiento decae de una manera considerable, debido a la producción del mismo por un tiempo considerable, lo que ocasiona que los índices de producción dejen de ser económicamente rentables, es ahí cuando entra en consideración la aplicación de la técnica de recuperación secundaria, en este caso por inyección de agua, con el objetivo de incrementar la cantidad de petróleo a producir aumentando la energía en el yacimiento. El uso de esta técnica puede llegar a producir hasta un 40% del petróleo original existente en el yacimiento, aumentando de manera significativa la recuperación de reservas y el factor de recobro del yacimiento. El presente proyecto se enfoca en el campo Secoya específicamente en su arena productora U Superior, para ello se llevó a cabo una revisión de las operaciones de producción en los pozos productores SCY-19, SCY-22, SCY-38, SCY-39, SCY-44, SCY-45 y SCY-50 que son beneficiados por los tres pozos inyectores SCY-26, SCY-27 y SCY-40 que cuentan con un total de inyección de 6200 BAPD. Lo cual sirvió para establecer la incidencia que tuvo la aplicación de recuperación secundaria en cada uno de los pozos ya mencionados, dando como resultado que la producción acumulada por producción primaria paso de 5,99 MMBbls a 7,43 MMBbls, lo cual representa un incremental de petróleo de aproximadamente 1,4 MMBbls, generando una utilidad total del proyecto de $21,63 MMUSD y un aumento de factor de recobro del 5% en el yacimiento, gracias a la aplicación de la técnica