Impact of internal bremsstrahlung on the detection of gamma-rays from neutralinos

We present a detailed study of the effect of internal bremsstrahlung photons in the context of the minimal supersymmetric standard models and their impact on gamma-ray dark matter annihilation searches. We find that although this effect has to be included for the correct evaluation of fluxes of high energy photons from neutralino annihilation, its contribution is relevant only in models and at energies where the lines contribution is dominant over the secondary photons. Therefore, we find that the most optimistic supersymmetric scenarios for dark matter detection do not change significantly when including the internal bremsstrahlung. As an example, we review the gamma-ray dark matter detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC stereoscopic system and the CTA project. Though the flux of high energy photons is enhanced by an order of magnitude in some regions of the parameter space, the expected fluxes are still much below the sensitivity of the instruments.Comment: 5 pages, twocolumn format, 3 figures:3 references added, accepted as Brief Report in PR

CVD of CrO2 Thin Films: Influence of the Deposition Parameters on their Structural and Magnetic Properties

This work reports on the synthesis of CrO2 thin films by atmospheric pressure CVD using chromium trioxide (CrO3) and oxygen. Highly oriented (100) CrO2 films containing highly oriented (0001) Cr2O3 were grown onto Al2O3(0001) substrates. Films display a sharp magnetic transition at 375 K and a saturation magnetization of 1.92 Bohr magnetons per f.u., close to the bulk value of 2 Bohr magnetons per f.u. for the CrO2. Keywords: Chromium dioxide (CrO2), Atmospheric pressure CVD, Spintronics.Comment: 5 pages, 6 figure

RIQUEZA E DIVERSIDADE DE PEQUENOS MAMÍFEROS NÃO VOADORES NA MATA DE TABULEIRO CAPIXABA

Pequenos mamíferos não voadores têm apresentado diferentes respostas diante de modificações ambientais, seja pelos ambientes afetados pela agricultura ou pelos agroecossistemas. Esta situação pode levar ao desequilíbrio entre as espécies oportunistas e as espécies sensíveis às alterações ambientais, podendo acarretar uma substituição ou sobreposição de espécies. Em sua maioria, as espécies de pequenos mamíferos têm uma relação de dependência com a floresta, pois, desempenham um papel importante nesses ambientes como predadores de sementes e de insetos, como dispersores de sementes e como a base da cadeia alimentar para outros vertebrados, motivos pelos quais, diversas espécies desta fauna são consideradas boas indicadoras de mudanças dos habitats e da paisagem quando uma floresta contínua sofrer perda de área. Os fragmentos remanescentes se tornam isolados, e com isso o número de espécies mudará de seu equilíbrio original, principalmente por causa dos efeitos da redução de área e distância da floresta contínua entre os seus fragmentos florestais. Com o tempo, a diversidade tende a diminuir, eventualmente, poderá atingir um novo estado de equilíbrio, porém este será menos diversificado. No estado do Espírito Santo a mastofauna de pequenos mamíferos não voadores ainda é pouco estudada, principalmente no que diz respeito à sua distribuição. Frente a redução da Mata de Tabuleiros em fragmentos isolados, o risco de defaunação e a ausência de estudos sobre a fauna de pequenos mamíferos no norte do ES, este trabalho teve os objetivos de (i) verificar a composição de espécies de pequenos mamíferos não voadores em três Unidades de Conservação no norte do Espírito Santo; (ii) examinar a composição faunística destas três e, (iii) avaliar se os resultados encontrados variam de acordo com a categoria de conservação

CVD of CrO2: towards a lower temperature deposition process

We report on the synthesis of highly oriented a-axis CrO2 films onto (0001) sapphire by atmospheric pressure CVD from CrO3 precursor, at growth temperatures down to 330 degree Celsius, i.e. close to 70 degrees lower than in published data for the same chemical system. The films keep the high quality magnetic behaviour as those deposited at higher temperature, which can be looked as a promising result in view of their use with thermally sensitive materials, e.g. narrow band gap semiconductors.Comment: 13 pages, 4 figure

KrP laser CVD of chromium oxide by photodissociation of Cr(CO)(6)

This work reports on the synthesis of chromium oxide thin films prepared by photodissociation of Cr(CO)(6) in an oxidizing atmosphere, using a pulsed UV laser (KrF, lambda = 248 nm). The experimental conditions, which should enable the synthesis of CrO2, are discussed and results on the deposition of CrxOy films on Al2O3 (0001) substrates are presented

The structure and photoluminescence of erbium-doped nanocrystalline silicon thin films produced by reactive magnetron sputtering

We have produced and studied undoped and erbium-doped nanocrystalline silicon thin films in order to evaluate the erbium influence on the film microstructure and how this correlates with the photoluminescence properties. Films were grown by reactive RF sputtering. For the doped films metallic erbium was added to the c-Si target. The structural parameters and the chemical composition of the different samples were investigated by X-ray in the grazing incidence geometry, Raman spectroscopy, ellipsometry and Rutherford Back Scattering. The effect of the nc-Si/SiOx matrix ,i.e., nc-Si volume fraction and the presence of SiO and/or SiO2 phases, on the erbium photoluminescence efficiency is discussed.(undefined

KrF pulsed laser deposition of chromium oxide thin films from Cr8O21 targets

Chromium oxides, CrxOy, are of great interest due to the wide variety of their technological applications. Among them, CrO2 has been extensively investigated in recent years because it is an attractive compound for use in spintronic heterostructures. However, its synthesis at low temperatures has been a difficult task due to the metastable nature of this oxide. This is indeed essential to ensure interface quality and the ability to coat thermal-sensitive materials such as those envisaged in spintronic devices. Pulsed Laser Deposition (PLD) is a technique that has the potential to meet the requirements stated above. In this work, we describe our efforts to grow chromium oxide thin films by PLD from Cr8O21 targets, using a KrF excimer laser. The as-deposited films were investigated by X-ray diffraction and Rutherford backscattering spectrometry. Structural and chemical composition studies showed that the films consist of a mixture of amorphous chromium oxides exhibiting different stoichiometries depending on the processing parameters, where nanocrystals of mainly Cr2O3 are dispersed. The analyses do not exclude the possibility of co-deposition of Cr2O3 and a low fraction of CrO2