Mechanics of Webs Encountering Concave Rolls

Mechanical Engineerin

Nitrogen deficiency impacts on leaf cell and tissue structure with consequences for senescence associated processes in Brassica napus

International audienceImprovement of nutrient use efficiency is a major goal for several crop plants, especially Brassica napus. Indeed, the low nitrogen use efficiency (NUE) in this crop results in negative economic and ecological consequences. The low NUE of oilseed rape is mainly due to low remobilization of nitrogen from vegetative parts to growing organs. Remobilization of leaf nitrogen takes place during senescence, a process known to strongly modify cell and tissue structure. This study focused on the impact of moderate N depletion, expected to induce 30% reduction of seed yield, on these structural modifications. Two genotypes (Aviso and Express) were studied, with different tolerance of nitrogen depletion, evaluated through seed yield and dry mass production. Structural modifications of leaf cells and tissues were investigated through NMR relaxometry and light microscopy. Lower tolerance of N depletion was associated with higher impact on senescence associated structural modification pattern. The link between leaf structure modifications and nutrient remobilization is discussed. It is proposed that leaf structure monitoring during senescence through NMR device could be developed to select genotypes with high NUE

[Mortality rate of HIV-infected adults on long term combination antiretroviral therapy.]

International audienc

Definite Streptococcus bovis endocarditis: characteristics in 20 patients

ObjectiveTo determine the specific characteristics of Streptococcus bovis infective endocarditis (IE) by reviewing our own experience of S. bovis IE.MethodsTwenty episodes of definite S. bovis IE were reviewed in 20 patients hospitalized from 1980 to 1996.ResultsThe mean age was 62 ± 14 years, and 14 (70%) patients had no known predisposing cardiac condition. The principal antimicrobials used were penicillin G (N = 10) and amoxycillin (N = 8). Surgery was required in four (20%) patients. Neurologic complications occurred in eight (40%) patients, after initiation of therapy in six (75%) (mean time: 14 days). An unfavorable outcome was observed in four of 20 patients and tended to be more frequent in patients who had had neurologic complications (P – 0.10). Colonic tumors were present in 11 of 16 (69%) patients.ConclusionsAdvanced age, occurrence of IE on presumably normal valves, high rate of neurologic complications, associated gastrointestinal diseases and low mortality rate during initial follow-up are characteristic features of S. bovis IE observed in this study

A microfabricated sensor for thin dielectric layers

We describe a sensor for the measurement of thin dielectric layers capable of operation in a variety of environments. The sensor is obtained by microfabricating a capacitor with interleaved aluminum fingers, exposed to the dielectric to be measured. In particular, the device can measure thin layers of solid frozen from a liquid or gaseous medium. Sensitivity to single atomic layers is achievable in many configurations and, by utilizing fast, high sensitivity capacitance read out in a feedback system onto environmental parameters, coatings of few layers can be dynamically maintained. We discuss the design, read out and calibration of several versions of the device optimized in different ways. We specifically dwell on the case in which atomically thin solid xenon layers are grown and stabilized, in cryogenic conditions, from a liquid xenon bath