Effet de l’endommagement transverse sur la résistance en compression sens fibre d’un composite carbone/époxy

National audienceL'étude expérimentale proposée analyse l'influence de l'endommagement transverse sur la résistance en compression sens fibre pour des composites tissés carbone/époxy. Afin d'explorer plusieurs méthodes expérimentales, l'étude porte d'abord sur des essais de flexion pure où le comportement dans la zone comprimée est exploré pour des éprouvettes saines. Ensuite un essai de compression pure sur des tubes préalablement endommagés en torsion est proposée. Les essais sont suivis par corrélation d'image afin de déterminer les effets de structure nuisant à la caractérisation du matériau. On montrera finalement que l'endommagement transverse influence la tenue mécanique en compression

Neurofilaments form flexible bundles during neuritogenesis in culture and in mature axons in situ

Neurofilaments (NFs) undergo cation-dependent phospho-mediated associations with each other and other cytoskeletal elements that support axonal outgrowth. Progressive NF-NF associations generate a resident, bundled population that undergoes exchange with transporting NFs. We examined the properties of bundled NFs. Bundles did not always display a fully linear profile but curved and twisted at various points along the neurite length. Bundles retracted faster than neurites and retracted bundles did not expand following extraction with Triton, indicating that they coiled passively rather than due to pressure from the cell. Bundles consisted of helically wound NFs, which may provide flexibility necessary for turning of growing axons during pathfinding. Interactions between NFs and other cytoskeletal elements may be disrupted en masse during neurite retraction or regionally during remodeling. It is suggested that bundles within long axons that cannot be fully retracted into the soma could provide maintain proximal support yet still allow more distal flexibility for remodeling and changing direction during pathfinding

Infecção pelo HIV e AIDS em um pequeno município no Sudeste brasileiro

OBJECTIVE: Studies on the aspects of HIV infection in small Brazilian municipalities are invaluable to appropriately design control strategies, better allocate resources, and improve health care services. The objective of the study was to assess the clinical and epidemiological aspects of HIV infection in a small municipality. METHODS: A descriptive study was carried out in Miracema, a small municipality in the northwestern area of the state of Rio de Janeiro, Brazil, between July 1999 and December 2003. All HIV-infected adult patients followed up at the local HIV/AIDS Program were included. Clinical and epidemiologic characteristics were prospectively assessed through standardized questionnaires. RESULTS: A total of 65 adult patients who attended the local HIV/AIDS Program were analyzed. Most (34) were women (male to female ratio: 0.9). An absolute predominance of patients who were born in Miracema or neighboring municipalities (94%), lived in Miracema (90.7%), were single (70.8%), attributed the acquisition of HIV infection to unprotected heterosexual intercourse (72.3%) and had a past history of snorting cocaine (27.7) was found Central nervous system disorders (including five cases of cryptococcal meningitis) and acute pulmonary pneumocystosis-like respiratory failure were major causes of morbidity. Most patients (56.9%) were at presented in advanced stages of HIV infection. CONCLUSIONS: The predominance of patients on advanced stages of HIV infection suggest the existence of a large pool of undiagnosed cases in the community. A major feature of the cohort was an inverted male to female ratio. Further investigations over a broader geographic area are urgently needed for better understanding the clinical and epidemiological characteristics of HIV infection in small Brazilian municipalities and rural areas.OBJETIVO: Estudos sobre as características da infecção pelo HIV em pequenos municípios brasileiros são de grande importância para o desenho de estratégias de intervenção, para a alocação apropriada de recursos e melhoria da assistência. O objetivo foi investigar as características clínicas e epidemiológicas da infecção pelo HIV em um pequeno município. MÉTODOS: Foi realizado estudo descritivo em Miracema, município do noroeste do Estado do Rio de Janeiro, entre julho de 1999 e dezembro de 2003. Foram analisados todos os pacientes adultos com diagnóstico de infecção pelo HIV atendidos no Programa Municipal de HIV/Aids. Dados clínicos e epidemiológicos foram coletados prospectivamente por meio de questionário padronizado. RESULTADOS: Foram analisados no total 65 pacientes adultos que receberam atendimento no Programa Municipal de HIV/Aids. A maioria (34) eram mulheres (razão de sexos homem-mulher de 0,9). Encontrou-se preponderância absoluta de pacientes que nasceram em Miracema ou municípios vizinhos (94%), moravam em Miracema (90,7%), eram solteiros (70,8%), atribuíam a aquisição da infecção ao contato heterossexual desprotegido (72,3%) e tinham antecedentes de uso de cocaína inalada (27,7%). Desordens do sistema nervoso central (incluindo cinco casos de neurocriptococose) e insuficiência respiratória aguda semelhante à pneumocistose pulmonar foram as principais causas de morbidade. A maioria dos pacientes (56,9%) iniciou acompanhamento em estágios avançados de infecção pelo HIV. CONCLUSÕES: A preponderância de pacientes em estágios avançados de infecção pelo HIV sugere a existência de um grande reservatório de casos não diagnosticados na comunidade. Uma característica marcante da casuística foi a inversão da razão de sexos homem-mulher. Investigações adicionais cobrindo áreas geográficas maiores são urgentemente necessárias para o melhor entendimento do espectro clínico e epidemiológico da infecção pelo HIV em pequenos municípios brasileiros e áreas rurais

The fast transient sky with Gaia

The ESA Gaia satellite scans the whole sky with a temporal sampling ranging from seconds and hours to months. Each time a source passes within the Gaia field of view, it moves over 10 CCDs in 45 s and a lightcurve with 4.5 s sampling (the crossing time per CCD) is registered. Given that the 4.5 s sampling represents a virtually unexplored parameter space in optical time domain astronomy, this data set potentially provides a unique opportunity to open up the fast transient sky. We present a method to start mining the wealth of information in the per CCD Gaia data. We perform extensive data filtering to eliminate known on-board and data processing artefacts, and present a statistical method to identify sources that show transient brightness variations on ~2 hours timescales. We illustrate that by using the Gaia photometric CCD measurements, we can detect transient brightness variations down to an amplitude of 0.3 mag on timescales ranging from 15 seconds to several hours. We search an area of ~23.5 square degrees on the sky, and find four strong candidate fast transients. Two candidates are tentatively classified as flares on M-dwarf stars, while one is probably a flare on a giant star and one potentially a flare on a solar type star. These classifications are based on archival data and the timescales involved. We argue that the method presented here can be added to the existing Gaia Science Alerts infrastructure for the near real-time public dissemination of fast transient events.Comment: 10 pages, 5 figures and 5 tables; MNRAS in pres

Gaia eclipsing binary and multiple systems. Two-Gaussian models applied to OGLE-III eclipsing binary light curves in the Large Magellanic Cloud

The advent of large scale multi-epoch surveys raises the need for automated light curve (LC) processing. This is particularly true for eclipsing binaries (EBs), which form one of the most populated types of variable objects. The Gaia mission, launched at the end of 2013, is expected to detect of the order of few million EBs over a 5-year mission. We present an automated procedure to characterize EBs based on the geometric morphology of their LCs with two aims: first to study an ensemble of EBs on a statistical ground without the need to model the binary system, and second to enable the automated identification of EBs that display atypical LCs. We model the folded LC geometry of EBs using up to two Gaussian functions for the eclipses and a cosine function for any ellipsoidal-like variability that may be present between the eclipses. The procedure is applied to the OGLE-III data set of EBs in the Large Magellanic Cloud (LMC) as a proof of concept. The bayesian information criterion is used to select the best model among models containing various combinations of those components, as well as to estimate the significance of the components. Based on the two-Gaussian models, EBs with atypical LC geometries are successfully identified in two diagrams, using the Abbe values of the original and residual folded LCs, and the reduced $\chi^2$. Cleaning the data set from the atypical cases and further filtering out LCs that contain non-significant eclipse candidates, the ensemble of EBs can be studied on a statistical ground using the two-Gaussian model parameters. For illustration purposes, we present the distribution of projected eccentricities as a function of orbital period for the OGLE-III set of EBs in the LMC, as well as the distribution of their primary versus secondary eclipse widths.Comment: 20 pages, 29 figures. Submitted to A&

The Optical Gravitational Lensing Experiment. Catalog of stellar proper motions in the OGLE-II Galactic bulge fields

We present a proper motion (\mu) catalogue of 5,080,236 stars in 49 Optical Gravitational Lensing Experiment II (OGLE-II) Galactic bulge (GB) fields, covering a range of -11 deg. <l< 11 deg. and -6 deg. <b<3 deg., the total area close to 11 square degrees. The proper motion measurements are based on 138 - 555 I-band images taken during four observing seasons: 1997-2000. The catalogue stars are in the magnitude range 11 < I < 18 mag. In particular, the catalogue includes Red Clump Giants (RCGs) and Red Giants in the GB, and main sequence stars in the Galactic disc. The proper motions up to \mu = 500 mas/yr were measured with the mean accuracy of 0.8-3.5 mas/yr, depending on the brightness of a star. This catalogue may be useful for studying the kinematic of stars in the GB and the Galactic disk.Comment: 13 pages, 16 figures, MNRAS in pres