Simulations of angular momentum evolution in wind-fed CV precursors

It is thought that the secondary stars in cataclysmic variables (CVs) may undergo a period of mass loss in the form of a wind during the evolution of the system (Mullan et al. 1992). This wind is thought to magnetically brake the secondary star with a time-scale ~ 10^8 yr (e.g. van Paradijs 1986). When the secondary’s spin has been brought close to synchronism with the orbit it is possible for tidal torques to lock the secondary in synchronous rotation.

Observation of an Antimatter Hypernucleus

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprising an antiproton, an antineutron, and an antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons (3/Lambda(H) over bar) and 157 +/- 30 hypertritons ((3)(Lambda)H). The measured yields of (3)(Lambda)H (3/Lambda(H) over bar) and (3)He ((3)(He) over bar) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and of nuclei containing strange quarks, have implications spanning nuclear and particle physics, astrophysics, and cosmology.

Condições de energia de hawking e ellis e a equação de raychaudhuri

In the Einstein s theory of General Relativity the field equations relate the geometry of space-time with the content of matter and energy, sources of the gravitational field. This content is described by a second order tensor, known as energy-momentum tensor. On the other hand, the energy-momentum tensors that have physical meaning are not specified by this theory. In the 700s, Hawking and Ellis set a couple of conditions, considered feasible from a physical point of view, in order to limit the arbitrariness of these tensors. These conditions, which became known as Hawking-Ellis energy conditions, play important roles in the gravitation scenario. They are widely used as powerful tools for analysis; from the demonstration of important theorems concerning to the behavior of gravitational fields and geometries associated, the gravity quantum behavior, to the analysis of cosmological models. In this dissertation we present a rigorous deduction of the several energy conditions currently in vogue in the scientific literature, such as: the Null Energy Condition (NEC), Weak Energy Condition (WEC), the Strong Energy Condition (SEC), the Dominant Energy Condition (DEC) and Null Dominant Energy Condition (NDEC). Bearing in mind the most trivial applications in Cosmology and Gravitation, the deductions were initially made for an energy-momentum tensor of a generalized perfect fluid and then extended to scalar fields with minimal and non-minimal coupling to the gravitational field. We also present a study about the possible violations of some of these energy conditions. Aiming the study of the single nature of some exact solutions of Einstein s General Relativity, in 1955 the Indian physicist Raychaudhuri derived an equation that is today considered fundamental to the study of the gravitational attraction of matter, which became known as the Raychaudhuri equation. This famous equation is fundamental for to understanding of gravitational attraction in Astrophysics and Cosmology and for the comprehension of the singularity theorems, such as, the Hawking and Penrose theorem about the singularity of the gravitational collapse. In this dissertation we derive the Raychaudhuri equation, the Frobenius theorem and the Focusing theorem for congruences time-like and null congruences of a pseudo-riemannian manifold. We discuss the geometric and physical meaning of this equation, its connections with the energy conditions, and some of its several aplications.

Cosmic acceleration from second order gauge gravity

We construct a phenomenological theory of gravitation based on a second order gauge formulation for the Lorentz group. The model presents a long-range modification for the gravitational field leading to a cosmological model provided with an accelerated expansion at recent times. We estimate the model parameters using observational data and verify that our estimative for the age of the Universe is of the same magnitude than the one predicted by the standard model. The transition from the decelerated expansion regime to the accelerated one occurs recently (at similar to 9.3 Gyr).

Progressive power lens measurement by low coherence speckle interferometry

This work proposes a method for dioptric power mapping of progressive lenses through dual wavelength, low-coherence digital speckle pattern interferometry. Lens characterization finds several applications and is extremely useful in the fields of ophthalmology and astronomy, among others. The optical setup employs two red diode lasers which are conveniently aligned and tuned in order to generate a synthetic wavelength. The resulting speckle image formed onto a diffusive glass plate positioned behind the test lens appears covered of contour interference fringes describing the deformation on the light wavefront due to the analyzed lens. By employing phase stepping and phase unwrapping methods the wavefront phase was retrieved and then expressed in terms of a Zernike series. From this series, expressions for the dioptric power and astigmatic power were derived as a function of the x- and y-coordinates of the lens aperture. One spherical and two progressive lenses were measured. The experimental results presented a good agreement with those obtained through a commercial lensometer, showing the potentialities of the method. © 2013 Elsevier Ltd.

As relações entre a Matemática e a Astronomia no século XVI: tradução e comentários da obra Ouranographia de Adriaan van Roomen

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A relação cartográfica e geometria diferencial de Mercator a Gauss

Pós-graduação em Educação Matemática - IGCE

Memórias da educação em astronomia no Brasil: recortes a partir das falas de pesquisadores entrevistados sobre o tema

This paper presents a historical retrospective concerning data from a research in Astronomy Education in Brazil, after 1973. It was organized on the basis of the speech analysis of national researchers considered references in this field by their peers. Furthermore, it was elaborated on the basis of other studies from the areas of Science Education, Physics and Astronomy. This historical overview was developed in order to facilitate understanding of the contexts in which the interviewed researchers have developed professionally. Moreover, we attempted to recover the memory of the growing field of research in Astronomy Education in the country. We believe that the history presented can help those trying to understand the past in an attempt to resolve current and future demands.

Ensino de física com histórias em quadrinhos: o astronauta em magnetar

This monograph has the inspiring theme using Comic Books in physics education. The Comic Books are objects, which are part of our current daily life, in newspaper, magazines, comics and electronic media, and providing entertainment to the readers. Beyond this property, the ludic nature and linguistics become an interesting material when applied on Education. Our goal was to research an analyze a Comic Book that could be used in a Physics class. The chosen material was Astronauta Magnetar from Danilo Beyruth. With this Comic Book, we perform a short course with students from three High School grade, where the themes of labor were Astrophysics and Electromagnetism. From the results of this short course, we prepared a lot of comments and discussions about the role of Comic Books in a classroom, as an significant instrument for Physics Education

Comparison of crystalline thin poly(vinylidene (70%)–trifluoroethylene (30%)) copolymer films with short chain poly(vinylidene fluoride) films

We compare the photoemission and electron energy loss spectra of crystalline poly(vinylidene-fluoride with trifluoroethylene: 70%: 30%), P(VDF–TrFE), films, fabricated by the Langmuir–Blodgett technique and annealed in vacuum, with in situ thermally evaporated films of poly(vinylidene-fluoride) (PVDF) in vacuum. The electronic structure and vibrational modes of the short chain PVDF films compare well with the crystalline P(VDF–TrFE) films indicating that vacuum annealed films prepared ex situ are free of significant surface contamination once vacuum annealed. The electronic structure for the short chain PVDF films exhibits, however, different temperature dependence than the crystalline P(VDF–TrFE) films. PACS: 68.47.Mn; 71.20.Rv; 63.22.+m; 73.22.-f

Radiation doses along selected flight profiles during two extreme solar cosmic ray events

The radiation dose rates at flight altitudes may be hazardously increased during solar cosmic ray events. Within the scope of this paper we investigate the total accumulated radiation doses, i.e. the contribution of galactic and solar cosmic rays, during the two extreme solar cosmic ray events on 29 September 1989 and on 20 January 2005 along selected flight profiles. In addition, the paper discusses the consequences of possible solar cosmic ray flux approximations on the results of the radiation dose computations.

Open Access Influence on Argentinean Scientific Community's Publishing Patterns

Este estudio tiene como objetivo estimar la influencia del acceso abierto en los patrones de publicación de la comunidad científica argentina en diferentes campos temáticos (Medicina; Física y Astronomía; Agricultura y Ciencias biológicas y Ciencias sociales y Humanidades), a partir del análisis del modelo de acceso de las revistas elegidas para comunicar los resultados de investigación en el período 2008-2010. La producción fue recogida de la base de datos SCOPUS y los modelos de acceso de las revistas determinados a partir de la consulta a las fuentes DOAJ, e-revist@s, SCielo, Redalyc, PubMed, Romeo-Sherpa y Dulcinea. Se analizó la accesibilidad real y potencial de la producción científica nacional por las vías dorada y verde, respectivamente, así como también por suscripción a través de la Biblioteca Electrónica de Ciencia y Tecnología del Ministerio de Ciencia, Tecnología e Innovación Productiva de la Nación Argentina. Los resultados muestran que en promedio, y para el conjunto de las temáticas estudiadas, el 70 de la producción científica argentina visible en SCOPUS se publica en revistas que adhieren de una u otra forma al movimiento de acceso abierto, en una relación del 27 para la vía dorada y del 43 para las que permiten el autoarchivo por la vía verde. Entre el 16 y el 30 (según las áreas temáticas) de los artículos publicados en revistas que permiten el autoarchivo se accede vía suscripción. El porcentaje de revistas sin acceso es del orden del 30 en Ciencias Sociales y Humanidades, y alcanza cerca del 45 en el resto de las áreas. Se concluye que Argentina presenta condiciones muy favorables para liberar un alto porcentaje de la literatura científica generada en el país bajo la modalidad del acceso abierto a través de repositorios institucionales y de mandatos para el auto-archivo, contribuyendo además a incrementar la accesibilidad y la preservación a largo plazo de la producción científica y tecnológica nacional

Acceso abierto real y potencial a la producción científica de un país. El caso argentino

Se aporta una metodología para estimar la disponibilidad real y potencial de la producción científica de un país, según el modelo de acceso de las revistas elegidas por los investigadores para publicar sus artículos. Se estudia el caso de la producción científica argentina del período 2008-2010 en medicina, física y astronomía, agricultura y ciencias biológicas, y ciencias sociales y humanidades. La producción fue recogida de la base de datos Scopus y los modelos de acceso de las revistas, determinados a partir de la consulta a DOAJ, e-revist@s, SciELO, RedALyC, PubMed, Romeo-Sherpa y Dulcinea. Se concluye que Argentina presenta condiciones muy favorables para liberar un alto porcentaje de la literatura científica generada en el país bajo la modalidad de acceso abierto a través de repositorios; y que la metodología es reproducible para realizar comparaciones con otros países y campos temáticos. Los resultados aportan conocimiento útil a los gestores de repositorios de las instituciones académicas y de investigación de cara a promocionar su desarrollo y justificar su sostenimiento

Opiniones y hábitos de publicación en acceso abierto de los investigadores argentinos. Un estudio basado en los datos de la encuesta SOAP

El presente trabajo tiene como principal objetivo conocer las opiniones y hábitos de publicación en acceso abierto de los investigadores argentinos en cuatro áreas temáticas: Medicina, Física y Astronomía, Agricultura y Ciencias Biológicas y Ciencias Sociales y Humanidades. El estudio se basa en las respuestas de los investigadores que participaron de la encuesta mundial realizada en 2010 en el marco del proyecto SOAP (Study of Open Access Publishing). Los resultados obtenidos son comparados con los hallazgos de la encuesta SOAP a escala mundial, y con un estudio previo sobre prácticas de publicación de los investigadores argentinos según el modelo económico de las revistas donde publican. Las conclusiones y discusión advierten que si bien la publicación en acceso abierto es, desde las opiniones de los investigadores, considerado beneficioso, no es suficiente para que modifiquen sus hábitos de publicación

Acceso abierto real y potencial a la producción científica de un país. El caso argentino

Se aporta una metodología para estimar la disponibilidad real y potencial de la producción científica de un país, según el modelo de acceso de las revistas elegidas por los investigadores para publicar sus artículos. Se estudia el caso de la producción científica argentina del período 2008-2010 en medicina, física y astronomía, agricultura y ciencias biológicas, y ciencias sociales y humanidades. La producción fue recogida de la base de datos Scopus y los modelos de acceso de las revistas, determinados a partir de la consulta a DOAJ, e-revist@s, SciELO, RedALyC, PubMed, Romeo-Sherpa y Dulcinea. Se concluye que Argentina presenta condiciones muy favorables para liberar un alto porcentaje de la literatura científica generada en el país bajo la modalidad de acceso abierto a través de repositorios; y que la metodología es reproducible para realizar comparaciones con otros países y campos temáticos. Los resultados aportan conocimiento útil a los gestores de repositorios de las instituciones académicas y de investigación de cara a promocionar su desarrollo y justificar su sostenimiento