Section efficace de la réaction 16O(t, n) 18F application au dosage de l'oxygène

Des échantillons de tantale oxydés anodiquement ont été irradiés avec des tritons de 1,6 à 3,7 MeV. La section efficace a été déterminée par mesure de la radioactivité du 18F. La valeur trouvée à 2 MeV est de 220 mb. Nos résultats sont en désaccord avec les valeurs publiées par Jarmie jusqu'à 2,2 MeV et avec la forme de la courbe obtenue par Barrandon et Albert entre 2 et 3 MeV. La réaction 16O(t, n) 18F a été utilisée pour doser l'oxygène à la surface d'échantillons d'acier inoxydable. Une limite de détection de 0,004 μg.cm-2 a été obtenue à 2 MeV, après 10 min. d'irradiation avec un faisceau de 0,2 μA de tritons. Les possibilités d'application aux dosages dans la masse sont discutées

In vitro and in vivo ocular biocompatibility of electrospun poly(ɛ-caprolactone) nanofibers.

Biocompatibility is a requirement for the development of nanofibers for ophthalmic applications. In this study, nanofibers were elaborated using poly(ε-caprolactone) via electrospinning. The ocular biocompatibility of this material was investigated. MIO-M1 and ARPE-19 cell cultures were incubated with nanofibers and cellular responses were monitored by viability and morphology. The in vitro biocompatibility revealed that the nanofibers were not cytotoxic to the ocular cells. These cells exposed to the nanofibers proliferated and formed an organized monolayer. ARPE-19 and MIO-M1 cells were capable of expressing GFAP, respectively, demonstrating their functionality. Nanofibers were inserted into the vitreous cavity of the rat's eye for 10days and the in vivo biocompatibility was investigated using Optical Coherence Tomography (OCT), histology and measuring the expression of pro-inflammatory genes (IL-1β, TNF-α, VEGF and iNOS) (real-time PCR). The OCT and the histological analyzes exhibited the preserved architecture of the tissues of the eye. The biomaterial did not elicit an inflammatory reaction and pro-inflammatory cytokines were not expressed by the retinal cells, and the other posterior tissues of the eye. Results from the biocompatibility studies indicated that the nanofibers exhibited a high degree of cellular biocompatibility and short-term intraocular tolerance, indicating that they might be applied as drug carrier for ophthalmic use

Análise não linear de chapas através de uma formulação do método dos elementos de contorno com convergência quadrática

No presente trabalho foi desenvolvida a formulação não-linear do método dos elementos de contorno para a análise estrutural de chapas escrita em termos de deslocamentos e forças nas direções normal e tangencial ao contorno da sua superfície. A equação integral do deslocamento é deduzida a partir do Teorema de Reciprocidade de Betti, considerando-se espessura constante na chapa. Para calcular a integral de domínio envolvendo o campo de esforços iniciais (ou inelásticos) deve-se discretizar o domínio em células. A solução não linear se obtém por uma formulação implícita, na qual as correções das deformações são feitas através do operador tangente consistente que se atualiza a cada nova iteração, tendo como referência os valores das variáveis internas referentes ao incremento convergido, o que leva a uma convergência quadrática do processo iterativo. Utilizou-se como critério de ruptura o de von Misses e exemplos foram analisados a fim de mostrar a convergência quadrática no processo iterativo e também a convergência dos resultados numéricos a medida que se refinava a discretização do contorno em elementos e do domínio em células

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc