Type Ia supernovae from exploding oxygen-neon white dwarfs

Context. The progenitor problem of Type Ia supernovae (SNe Ia) is still unsolved. Most of these events are thought to be explosions of carbon-oxygen (CO) white dwarfs (WDs), but for many of the explosion scenarios, particularly those involving the externally triggered detonation of a sub-Chandrasekhar mass WD (sub-M-Ch, WD), there is also a possibility of having an oxygen-neon (ONe) WD as progenitor.

Aims. We simulate detonations of ONe WDs and calculate synthetic observables from these models. The results are compared with detonations in CO WDs of similar mass and observational data of SNe Ia.

Methods. We perform hydrodynamic explosion simulations of detonations in initially hydrostatic ONe WDs for a range of masses below the Chandrasekhar mass (M-Ch), followed by detailed nucleosynthetic postprocessing with a 384-isotope nuclear reaction network. The results are used to calculate synthetic spectra and light curves, which are then compared with observations of SNe Ia. We also perform binary evolution calculations to determine the number of SNe Ia involving ONe WDs relative to the number of other promising progenitor channels.

Results. The ejecta structures of our simulated detonations in sub-M-Ch, ONe WDs are similar to those from CO WDs. There are, however, small systematic deviations in the mass fractions and the ejecta velocities. These lead to spectral features that are systematically less blueshifted. Nevertheless, the synthetic observables of our ONe WD explosions are similar to those obtained from CO models.

Conclusions. Our binary evolution calculations show that a significant fraction (3-10%) of potential progenitor systems should contain an ONe WD. The comparison of our ONe models with our CO models of comparable mass (similar to 1.2 M-circle dot) shows that the less blueshifted spectral features fit the observations better, although they are too bright for normal SNe Ia.

The white dwarf's carbon fraction as a secondary parameter of Type Ia supernovae

Context. Binary stellar evolution calculations predict thatChandrasekhar-mass carbon/oxygen white dwarfs (WDs) show a radiallyvarying profile for the composition with a carbon depleted core. Manyrecent multi-dimensional simulations of Type Ia supernovae (SNe Ia),however, assume the progenitor WD has a homogeneous chemicalcomposition.
Aims: In this work, we explore the impact ofdifferent initial carbon profiles of the progenitor WD on the explosionphase and on synthetic observables in the Chandrasekhar-mass delayeddetonation model. Spectra and light curves are compared to observationsto judge the validity of the model.
Methods: The explosion phaseis simulated using the finite volume supernova code Leafs, which isextended to treat different compositions of the progenitor WD. Thesynthetic observables are computed with the Monte Carlo radiativetransfer code Artis. Results: Differences in binding energies ofcarbon and oxygen lead to a lower nuclear energy release for carbondepleted material; thus, the burning fronts that develop are weaker andthe total nuclear energy release is smaller. For otherwise identicalconditions, carbon depleted models produce less 56Ni.Comparing different models with similar 56Ni yields showslower kinetic energies in the ejecta for carbon depleted models, butonly small differences in velocity distributions and line velocities inspectra. The light curve width-luminosity relation (WLR) obtained formodels with differing carbon depletion is roughly perpendicular to theobserved WLR, hence the carbon mass fraction is probably only asecondary parameter in the family of SNe Ia.
Tables 3 and 4 are available in electronic form at http://www.aanda.org

Gamma-ray diagnostics of Type Ia supernovae. Predictions of observables from three-dimensional modeling

Context. Although the question of progenitor systems and detailed explosion mechanisms still remains a matter of discussion, it is commonly believed that Type Ia supernovae (SNe Ia) are production sites of large amounts of radioactive nuclei. Even though the gamma-ray emission due to radioactive decays is responsible for powering the light curves of SNe Ia, gamma rays themselves are of particular interest as a diagnostic tool because they directly lead to deeper insight into the nucleosynthesis and the kinematics of these explosion events. Aims: We study the evolution of gamma-ray line and continuum emission of SNe Ia with the objective of analyzing the relevance of observations in this energy range. We seek to investigate the chances for the success of future MeV missions regarding their capabilities for constraining the intrinsic properties and the physical processes of SNe Ia. Methods: Focusing on two of the most broadly discussed SN Ia progenitor scenarios - a delayed detonation in a Chandrasekhar-mass white dwarf (WD) and a violent merger of two WDs - we used three-dimensional explosion models and performed radiative transfer simulations to obtain synthetic gamma-ray spectra. Both chosen models produce the same mass of 56Ni and have similar optical properties that are in reasonable agreement with the recently observed supernova SN 2011fe. We examine the gamma-ray spectra with respect to their distinct features and draw connections to certain characteristics of the explosion models. Applying diagnostics, such as line and hardness ratios, the detection prospects for future gamma-ray missions with higher sensitivities in the MeV energy range are discussed. Results: In contrast to the optical regime, the gamma-ray emission of our two chosen models proves to be quite different. The almost direct connection of the emission of gamma rays to fundamental physical processes occurring in SNe Ia permits additional constraints concerning several explosion model properties that are not easily accessible within other wavelength ranges. Proposed future MeV missions such as GRIPS will resolve all spectral details only for nearby SNe Ia, but hardness ratio and light curve measurements still allow for a distinction of the two different models at 10 Mpc and 16 Mpc for an exposure time of 106 s. The possibility of detecting the strongest line features up to the Virgo distance will offer the opportunity to build up a first sample of SN Ia detections in the gamma-ray energy range and underlines the importance of future space observatories for MeV gamma rays.

Dinámicas de externalización entre las ONG locales y las ONG extranjeras (terceros actores) presentes en Egipto: 2004-2009 (TERCEROS ACTORES) PRESENTES EN EGIPTO: 2004-2009

El propósito de la presente monografía es evaluar el papel de las ONG internacionales en la apertura de espacios de participación política para la sociedad civil en Egipto. En ese sentido, se analiza el contexto de oportunidades políticas locales y transnacionales del país, así como los procesos de articulación entre la política local e internacional a través de los niveles de integración entre sus actores. Mediante una investigación de tipo cualitativa basada en los desarrollos sobre teorías de la acción colectiva planteados por Sidney Tarrow, Charles Tilly, Robert Benford y David Snow, y las teorías sobre redes transnacionales de defensa desarrolladas por Margaret Keck y Kathryn Sikkink, se avanza hacia la identificación del desarrollo de procesos de externalización como medio para el fortalecimiento de organizaciones locales como alternativa de oposición política.

Caracterización de las principales cadenas agroalimentarias en Argentina y Brasil

Cada día es mayor la demanda de alimentos a nivel mundial y menor su oferta debido a múltiples razones, por eso que es de gran importancia encontrar las mejores prácticas para que la cadena de suministro de productos alimenticios sea más eficiente y productiva, no sólo con el fin de llegar a la mayor población posible, sino también de mejorar los rendimientos de cada uno de los participantes de la misma. Este proyecto busca analizar las tres principales cadenas agroalimentarias de Argentina y Brasil, con el fin de determinar su desempeño actual, su grado de madurez y su productividad; para lograr esto, primero se va a levantar la información pertinente al tema, luego se identificarán las mejores prácticas en la cadena de suministro para los tres productos más importantes de la canasta básica de ambos países, posteriormente se analizará el desempeño de las agrocadenas y por último se determinará la madurez y productividad de las mismas. La metodología utilizada en este documento se basa principalmente en la búsqueda de información en fuentes gubernamentales y oficiales de cada país para obtener información verídica, confiable y actualizada. Estas fuentes nos aportarán la información que junto con un análisis propio permitirá cumplir los objetivos del proyecto. El resultado de estos datos es de gran importancia, ya que con la investigación realizada se podrán identificar las buenas prácticas para enriquecer el análisis o identificar las malas prácticas y así, proponer modelos que permitan el manejo eficiente de las agrocadenas buscando su desarrollo y perdurabilidad.

Las empresas sociales del estado y el derecho fundamental a la salud. Estudio de caso hospital simón bolívar E.S.E (2002-2014)

El presente trabajo busca hacer un análisis sobre los arreglos institucionales introducidos con la ley 100 de 1993 a las Empresas Sociales del Estado (ESE), y cómo estos han afectado la prestación del servicio de salud y la garantía del derecho; para lo cual se escoge como ejemplo el Hospital Simón Bolívar E.S.E de Bogotá durante los años 2002 a 2014. Se explica como con la implementación de la descentralización, el modelo de aseguramiento y la autonomía financiera se afectó la prestación del servicio de salud, teniendo en cuenta la introducción de un eslabón dentro del sistema de salud: las Empresas Promotoras de Salud (EPS).

Optimal Rehabilitation Strategy In Water Distribution Systems Considering Reduction In Greenhouse Gas Emissions

Most of water distribution systems (WDS) need rehabilitation due to aging infrastructure leading to decreasing capacity, increasing leakage and consequently low performance of the WDS. However an appropriate strategy including location and time of pipeline rehabilitation in a WDS with respect to a limited budget is the main challenge which has been addressed frequently by researchers and practitioners. On the other hand, selection of appropriate rehabilitation technique and material types is another main issue which has yet to address properly. The latter can affect the environmental impacts of a rehabilitation strategy meeting the challenges of global warming mitigation and consequent climate change. This paper presents a multi-objective optimization model for rehabilitation strategy in WDS addressing the abovementioned criteria mainly focused on greenhouse gas (GHG) emissions either directly from fossil fuel and electricity or indirectly from embodied energy of materials. Thus, the objective functions are to minimise: (1) the total cost of rehabilitation including capital and operational costs; (2) the leakage amount; (3) GHG emissions. The Pareto optimal front containing optimal solutions is determined using Non-dominated Sorting Genetic Algorithm NSGA-II. Decision variables in this optimisation problem are classified into a number of groups as: (1) percentage proportion of each rehabilitation technique each year; (2) material types of new pipeline for rehabilitation each year. Rehabilitation techniques used here includes replacement, rehabilitation and lining, cleaning, pipe duplication. The developed model is demonstrated through its application to a Mahalat WDS located in central part of Iran. The rehabilitation strategy is analysed for a 40 year planning horizon. A number of conventional techniques for selecting pipes for rehabilitation are analysed in this study. The results show that the optimal rehabilitation strategy considering GHG emissions is able to successfully save the total expenses, efficiently decrease the leakage amount from the WDS whilst meeting environmental criteria.

Simetria na dança: vestígios matemáticos na prática da dança esportiva em cadeira de rodas

To investigate in practice of the Wheelchair Dancesport (WDS), the mathematics of the characteristic isometric movements of the dance of ChaChaCha was the generating subject of this study. The subjects and the locus of the research were the athletes dancers of the Associação Baiana de Dança em Cadeira de Rodas (ABDCR). Referred him study aimed at to describe reflections concerning the athletes' practicing dancers of the technical acting Wheelchair Dancesport, using the inherent mathematical knowledge to the isometric movements executed in the ChaChaCha. For that, I stimulated in the athlete dancer the need to be investigating of his/her own practice, motivating him/it to be searching of information that they collaborate with his/her technical refinement, proposing like this roads to make possible his/her growth, while dancer and, also, promoting of their own movements. To reach my objectives I dialogued with some specialists to understand, to the light of their theories as, Espaçonumerática, Sociology of the mathematics, Etnomathematical, Dance and Symmetry, as those spaces they interact with the atmosphere of the Wheelchair Dancesport and that contributions could supply to the study. However, two authors of the Dancesport for walking , Ried e Laird, they brought contributions that aided in the creation of a prototype for the study of isometric movements in practice of the modality promoting the interface between the theory and the practice. The study showed to be possible to navigate still with the Mathematical Education in an universe little known as the one of the Wheelchair Dancesport. And it is in this adapts that propose a more attentive glance to the illustrations executed by the athlete dancer wheelchair and walking , in the dance of the ChaChaCha, verifying and proposing an analysis with focus investigate, looking for mathematical tracks concerning the symmetry that you/they characterize some of their illustrations

Efeito do processamento da soja integral sobre a energia metabolizável e a digestibilidade dos aminoácidos para aves

Essa pesquisa foi desenvolvida para se avaliar o valor nutricional da soja integral submetida a diferentes processamentos. Quatro ensaios de metabolismo foram conduzidos para determinar os coeficientes de digestibilidade da matéria seca (CDMS), do extrato etéreo (CDEE) e dos aminoácidos e os valores de energia metabolizável aparente e verdadeira da soja integral desativada (SID) e extrusada (SIE) e das misturas de farelo de soja com óleo degomado de soja (FSO) ou com óleo ácido de soja (FSOA). Nos ensaios um e dois, utilizou-se a metodologia tradicional de coleta total de excretas com pintos e galos, respectivamente. A metodologia da alimentação forçada com galos adultos intactos foi utilizada no ensaio três, e com galos cecotomizados, no ensaio quatro. Os CDMS e CDEE e a energia metabolizável determinados com galos foram superiores aos determinados com pintos. Os maiores valores de CDMS, CDEE e de energia metabolizável foram obtidos para FSO, seguidos pelos da SIE e FSOA, e os menores, para a SID. O processo de extrusão proporcionou melhores resultados no aproveitamento da gordura do grão de soja e, conseqüentemente, da energia. Entretanto, a digestibilidade dos aminoácidos não foi influenciada pelos processamentos. Os diferentes processamentos conferiram à soja integral características nutricionais que se distinguiram, principalmente quanto ao valor de energia metabolizável, que também variou com a idade das aves.

Influence of annealing on X-ray diffraction of natural alexandrite

In this work we present results of X-ray diffraction using powder method, on natural alexandrite samples from Minas Gerais State (Brazil), as a function of a sequence of annealing. From these measurements we determine lattice parameters before (a = 9.405 Angstrom, b = 5.471 Angstrom, c = 4.409 Angstrom) and after annealing, and its structure is confirmed as orthorhombic. Measurements done after an annealing of 15 minutes at 700 degreesC and for 5 hours at 1000 degreesC indicate the migration of atoms present in the sample through different phases, which were also identified by Microprobe Analysis (WDS). However we have verified that such migration does not modify the structure. X-ray diffraction measurements have been carried out in conjunction with optical absorption in the UV-Vis as a function of annealing. (C) 2002 International Centre for Diffraction Data.

Study of electrical, chemical and structural characteristics of superconductor thin film obtained by polymeric precursors method

Superconductor films of the BSCCO system have been grown by dip coating technique with good success. The chemical method allows us to grow high temperature superconductor thin films to get better control of stoichiometry, large areas and is cheaper than other methods. There is a great technological interest in growth oriented superconductor films due anisotropic characteristics of superconductor materials of high critical temperature, specifically the cuprates, as we know that the orientation may increase the electrical transport properties. Based on this, the polymeric precursor method has been used to obtain thin films of the BSCCO system. In this work we have applied that method together with the deposition technique known as dip coating to obtain Bi-based superconductor thin films, specifically, Bi1.6Pb0.4Sr2.0C2.0Cu3.0Ox+8, also known as 2223 phase with a critical temperature around 110 K. The films with multilayers have been grown on crystalline substrates of LaAlO3 and orientated (100) after being heat treated around 790 degrees C - 820 degrees C in lapse time of 1 hour in a controlled atmosphere. XRD measurements have shown the presence of a crystalline phase 2212 with a critical temperature around 85 K with (001) orientation, as well as a small fraction of 2223 phase. SEM has shown a low uniformity and some cracks that maybe related to the applied heat treatment. WDS has also been used to study the films composition. Different heat treatments have been used with the aim to increase the percentage of 2223 phase. Measurements of resistivity confirmed the presence of at least two crystalline phases, 2212 and 2223, with T-c around 85 K and 110 K, respectively.

Nanosized precipitates in H13 tool steel low temperature plasma nitriding

A comprehensive study of pulsed nitriding in AISI H13 tool steel at low temperature (400 degrees C) is reported for several durations. X-ray diffraction results reveal that a nitrogen enriched compound (epsilon-Fe2-3N, iron nitride) builds up on the surface within the first process hour despite the low process temperature. Beneath the surface, X-ray Wavelength Dispersive Spectroscopy (WDS) in a Scanning Electron Microscope (SEM) indicates relatively higher nitrogen concentrations (up to 12 at.%) within the diffusion layer while microscopic nitrides are not formed and existing carbides are not dissolved. Moreover, in the diffusion layer, nitrogen is found to be dispersed in the matrix and forming nanosized precipitates. The small coherent precipitates are observed by High-Resolution Transmission Electron Microscopy (HR-TEM) while the presence of nitrogen is confirmed by electron energy loss spectroscopy (EELS). Hardness tests show that the material hardness increases linearly with the nitrogen concentration, reaching up to 14.5 GPa in the surface while the Young Modulus remains essentially unaffected. Indeed, the original steel microstructure is well preserved even in the nitrogen diffusion layer. Nitrogen profiles show a case depth of about similar to 43 mu m after nine hours of nitriding process. These results indicate that pulsed plasma nitriding is highly efficient even at such low temperatures and that at this process temperature it is possible to form thick and hard nitrided layers with satisfactory mechanical properties. This process can be particularly interesting to enhance the surface hardness of tool steels without exposing the workpiece to high temperatures and altering its bulk microstructure. (c) 2012 Elsevier B.V. All rights reserved.