Low temperature (down to 450° C) annealed TiAl contacts on N-type gallium nitride characterized by differential scanning calorimetry

International audienceThis work reports on Differential Scanning Calorimetry (DSC) measurements performed on Ti-Al metallic layers stacks deposited on n+-GaN. The aim is to get better understanding of the mechanisms leading to ohmic contact formation during the annealing stage. Two exothermic peaks were found, one below 500°C and the other one around 660°C. They can be respectively attributed to Al3Ti and Al2Ti compounds formation. The locations of these peaks provide clear evidence of solid-solid reac-tions. Lowest contact resistance is well correlated with the presence of Al3Ti compound, corresponding to Al(200nm)/Ti(50nm) stoichiometric ratio. Subsequently, Al(200 nm)Ti(50 nm) stacks on n+-GaN were annealed from 400°C to 650°C. Specific Contact Resistivity (SCR) values stay in the mid 10-5 Ω.cm² range for annealing temperatures between 450°C and 650°C. Such low-temperature annealed contacts on n+-GaN may open new device processing routes, simpler and cheaper, in which Ohmic and Schottky contacts are annealed together

Venous bullet embolism and subsequent endovascular retrieval – A case report and review of the literature

AbstractINTRODUCTIONVascular bullet embolism is a rare phenomenon with fewer than 200 cases reported in the literature.PRESENTATION OF CASEA 22 year-old male presented with a gunshot wound to the right lower quadrant. Imaging demonstrated a bullet lodged in his left lower quadrant. Upon operative exploration, a single hole was found in the right external iliac vein without injury into the left lower quadrant. The bullet was found to have migrated intravascularly from the right external to the left common iliac vein, and was subsequently removed endovascularly.DISCUSSIONBullet embolism occurs infrequently, with arterial more common than venous. Arterial embolization usually requires emergency operative intervention due to ischemia. While venous embolization is often asymptomatic, removal of the bullet is recommended to avoid delayed complications when possible.CONCLUSIONVenous bullet emboli should be removed endovascularly whenever technically possible

Tracer studies in the coffee plant (Coffea arabica L.)

Due to the great importance of coffee to the Brazilian economy, a good deal of the work carried out in the "Laboratório de Isótopos", E. E. A. "Luiz de Queiroz", Piracicaba, S. Paulo, Brazil, was dedicated to the study of some problems involving that plant. The first one was designed to verify a few aspects of the control of zinc deficiency which is common in many types of soils in Brazil. An experiment conducted in nutrient solution showed that the leaf absorption of the radiozinc was eight times as high as the root uptake; the lower surface of the leaves is particularly suited for this kind of absorption. Among the heavy metal micronutrients, only iron did not affect the absorption of the radiozinc; manganese, copper, and molybdenum brought about a decrease of fifty per cent in total uptake. In another pot experiment in which two soils typical of the coffee growing regions were used, namely, a sandy soil called "arenito de Bauru" and a heavy one, "terra roxa", only O.l and 0.2 per cent of the activity supplied to the roots was recovered", respectively. This indicates that under field conditions the farmer should not attempt to correct zinc deficiency by applying zinc salts to the soil: leaf sprays should be used wherever necessary. In order to find out the most suitable way to supply phosphatic fertilizers to the coffee plant, under normal farm conditions, an experiment with tagged superphosphate was carried out with the following methods of distribution of this material: (1) topdressed in a circular area around the trees; (2) placed in the bottom of a 15 cm deep furrow made around the plant; (3) placed in a semicircular furrow, as in the previous treatment; (4) sprayed directly to the leaves. It was verified that in the first case, circa 10 per cent of the phosphorus in the leaves came from the superphosphate; for the other treatments, the results ware, respectively: 2.4, 1.7, and 38.0 per cent. It is interesting to mention that the first and the last methods of distribution were those less used by the farmers; now they are being introduced in many coffee plantations. In a previous trial it was demonstrated that urea sprays were an adequate way to correct nitrogen deficiency under field conditions. An experiment was then set up in which urea-C14 was used to study the metabolism of this fertilizer in coffee leaves. In was verified that in a 9 hours period circa 95 per cent of the urea supplied to the leaves had been absorbed. The distribution of the nitrogen of the urea was followed by standard chemical procedures. On the other hand the fate of the carbonic moiety was studied with the aid of the radiochromatographic technique. Thus, the incorporation of C14 in aminoacids, sugars and organic acids was ascertained. Data obtained in this work gave a definite support to the idea that in coffee leaves, as in a few other higher plants, a mechanism similar to the urea cycle of animals does exist

Évaluation comparative de plates-formes reconfigurables et programmables pour les télécommunications de 3ème génération

- L'évolution des systèmes de radio-communications cellulaires se traduit par un accroissement important de la complexité des applications à implanter. En particulier, l'utilisation de la technologie WCDMA (Wideband Code-Division Multiple Access) dans les systèmes de troisième génération nécessite des capacités de calcul élevées. Dans cet article, les résultats de l'implantation d'un récepteur WCDMA au sein de différentes plates-formes programmables ou reconfigurables sont présentés. Les différentes solutions d'implantation sont comparées en termes de coût, de performances et d'efficacité énergétique. De plus, la méthodologie proposée pour obtenir la spécification en virgule fixe du récepteur est exposée

Genome wide analysis of fatty acid desaturation and its response to temperature

Plants modify the polyunsaturated fatty acid content of their membrane and storage lipids in order to adapt to changes in temperature. In developing seeds, this response is largely controlled by the activities of the microsomal ω-6 and ω-3 fatty acid desaturases, FAD2 and FAD3. Although temperature regulation of desaturation has been studied at the molecular and biochemical levels, the genetic control of this trait is poorly understood. Here, we have characterized the response of Arabidopsis (Arabidopsis thaliana) seed lipids to variation in ambient temperature and found that heat inhibits both ω-6 and ω-3 desaturation in phosphatidylcholine, leading to a proportional change in triacylglycerol composition. Analysis of the 19 parental accessions of the multiparent advanced generation intercross (MAGIC) population showed that significant natural variation exists in the temperature responsiveness of ω-6 desaturation. A combination of quantitative trait locus (QTL) analysis and genome-wide association studies (GWAS) using the MAGIC population suggests that ω-6 desaturation is largely controlled by cis-acting sequence variants in the FAD2 5′ untranslated region intron that determine the expression level of the gene. However, the temperature responsiveness of ω-6 desaturation is controlled by a separate QTL on chromosome 2. The identity of this locus is unknown, but genome-wide association studies identified potentially causal sequence variants within ∼40 genes in an ∼450-kb region of the QTL

Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane

During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113 ± 5% and 395 ± 82% (Baltic Sea, February and July 1992) and 126 ± 8% (south central North Sea, September 1992). On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a concept of regional gas transfer coefficients. Our estimates computed with two different air-sea exchange models lie in the range of 11-18 Tg CH4 yr-1. Despite the fact that shelf areas and estuaries only represent a small part of the world's ocean they contribute about 75% to the global oceanic emissions. We applied a simple, coupled, three-layer model to numerically simulate the time dependent variation of the oceanic flux to the atmosphere. The model calculations indicate that even with increasing tropospheric methane concentration, the ocean will remain a source of atmospheric methane

PIONIER: a visitor instrument for the VLTI

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used in scanning mode. It provides low spectral resolution in H and K band. PIONIER is designed for imaging with a specific emphasis on fast fringe recording to allow closure-phases and visibilities to be precisely measured. In this work we provide the detailed description of the instrument and present its updated status.Comment: Proceedings of SPIE conference Optical and Infrared Interferometry II (Conference 7734) San Diego 201

Strategies for Recruiting Women Living with Human Immunodeficiency Virus in Community-Based Research: Lessons from Canada

Objectives: This study sought to describe the recruitment of women living with HIV (WLWH) into the community-based Canadian HIV Women’s Sexual and Reproductive Health Cohort Study (CHIWOS), because women are underrepresented in HIV research. Methods: There were 1,424 WLWH were enrolled from British Columbia, Ontario, and Québec, who completed detailed questionnaires administered by peer research associates (PRAs; WLWH with research training). During screening, participants were asked: “How did you hear about the study?” We describe recruitment strategies by subpopulation and offer reflections on challenges and successes. Results: Of 1,131 participants with complete data, 40% identified as White, 33% African/Caribbean/Black, and 19% Indigenous. The median age was 45 years (interquartile range, 37–51) and 4% identified as trans women. Overall, 35% were recruited through PRAs/peers, 34% clinics, and 19% AIDS service organizations (ASOs). PRAs/peers were the predominant recruitment method in Ontario (49%), compared with clinics in British Columbia (40%), and Québec (43%). Nationally, PRAs/peers were more successful in recruiting WLWH commonly considered to be “harder to reach” (e.g., women identifying as trans, using drugs, not receiving HIV care). Clinics were more effective in recruiting younger women (16–29 years) and women not using ASOs. Recruitment challenges centered on engaging these harder to reach women. Successes included hiring PRAs who built participant trust, linking with clinics to reach women isolated from HIV communities, involving outreach workers to engage street-involved women, and disseminating study information to diverse stakeholders. Conclusions: Having multiple approaches, engaging a diverse team of PRAs, ensuring flexibility, and cultivating reciprocal relationships with community stakeholders were key to recruiting a diverse and representative sample of WLWH