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Accueil > Publications > Recherche par années > Années 1990 > 1999

1999

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Beagle 2 : A proposed exobiology lander for ESA’s 2003 Mars Express mission

The aim of the proposed Beagle 2 small lander for ESA’s 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X- ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies ; (C) 1999 COSPAR. Published by Elsevier Science Ltd.

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Behaviour of the bovine brain phosphatidylethanolamine binding protein at the air/water interface

The cytosolic bovine brain PEBP is a basic protein of 21 kDa devoid of disulfide bridges. It has been shown to form stable monomolecular protein films at the air/water interface. In the course of time, the PEBP films expanded nearly three times probably as the result of protein unfolding at the interface. The PEBP diffusion from a protein solution towards the interface is very low in account of its high content in polar residues and of its widely ß-sheet structure. The adsorption rate of PEBP at the air/water interface is dependent on the bulk concentration of the protein and the saturation of the surface occurs as early as the bulk concentration reaches 2.5 x 10(-6) M in amino acid. The surface concentration of PEBP at saturation is less than 2 x 10(18) amino acid/m(2) a value in a 10 lower range than observed for Ether proteins of the same size and devoid of disulfide bridges. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

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Cardiac performance and creatine kinase flux during inhibition of ATP synthesis in the perfused rat heart

To study the relation among mitochondrial energy supply, cardiac performance, and energy transfer through creatine kinase (CK), two acute models of inhibition of ATP synthesis were compared in the isovolumic acetate-perfused rat heart. Similar impairments of mechanical performance (rate-pressure product, RPP) were achieved by various stepwise decreases in O-2 ; supply (Po-2 down to 20% of control) or by infusing CN (0.15-0.25 mM). The forward CK flux measured by saturation-transfer P-31 NMR spectroscopy was 6.1 +/- 0.4 mM/s in control hearts. Only after severe hypoxia (Po-2

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Chemistry and biology of asparagine-linked glycosylation

The biosynthesis of glycoprotein conjugates is a complex process that involves the collective action of numerous enzymes. Recent research on the chemistry and biology of asparagine-linked glycosylation in our group has been focused on two specific areas. These are the development of potent inhibitors of oligosaccharyl transferase and the investigation of the conformational consequences of the glycosylation process. Since asparagine-linked glycosylation is an essential eukaryotic process, an understanding of the details of this complex transformation is of utmost importance both to fundamental biochemistry and to a consideration of the mechanisms of homeostatic control.

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Comparison of automated and visual texture analysis in MRI : characterization of normal and diseased skeletal muscle

Automated magnetic resonance imaging (MRI) texture analysis was compared with visual MRT analysis for the diagnosis of skeletal muscle dystrophy in 14 healthy and 17 diseased subjects. MRI texture analysis was performed on 8 muscle regions of interest (ROI) using four statistical methods (histogram, co-occurrence matrix, gradient matrix, runlength matrix) and one structural (mathematical morphology) method. Nine senior radiologists assessed full leg transverse slice images and proposed a diagnosis. The 59 extracted texture parameters for each ROI were statistically analyzed by Correspondence Factorial Analysis, Non-parametric tests,were used to compare diagnoses based on automated texture analysis and visual analysis. Texture analysis methods discriminated between healthy volunteers and patients with a sensitivity of 70%, and a specificity of 86%, Comparison with visual analysis of MR images suggests that texture analysis can provide useful information contributing to the diagnosis of skeletal muscle disease. (C) 1999 Elsevier Science Inc.

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