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Stimulation-induced increases of astrocytic oxidative metabolism in rats and humans investigated with 1-11C-acetate
No full textThe purpose of this study was to investigate astrocytic oxidative metabolism using 1-(11)C-acetate. 1-(11)C-acetate kinetics were evaluated in the rat somatosensory cortex using a beta-scintillator during different manipulations (test-retest, infraorbital nerve stimulation, and administration of acetazolamide or dichloroacetate). In humans a visual activation paradigm was used and kinetics were measured with positron emission tomography. Data were analyzed using a one-tissue compartment model. The following features supported the hypothesis that washout of radiolabel (k(2)) is because of (11)C-CO(2) and therefore related to oxygen consumption (CMRO(2)): (1) the onset of (11)C washout was delayed; (2)k(2) was not affected by acetazolamide-induced blood flow increase; (3)k(2) demonstrated a significant increase during stimulation in rats (from 0.014+/-0.007 to 0.027+/-0.006 per minute) and humans (from 0.016+/-0.010 to 0.026+/-0.006 per minute); and (4) dichloroacetate led to a substantial decrease of k(2). In the test-retest experiments K(1) and k(2) were very stable. In summary, 1-(11)C-acetate seems a promising tracer to investigate astrocytic oxidative metabolism in vivo. If the washout rate indeed represents the production of (11)C-CO(2), then its increase during stimulation would point to a substantially higher astrocytic oxidative metabolism during brain activation. However, the quantitative relationship between k(2) and CMRO(2) needs to be determined in future experiments.LND
InAIN/GaN metal-oxide-semiconductor high electron mobility transistor with Al2O3 insulating films grown by metal organic chemical vapor deposition using Ar and NH3 carrier gases
No full textAl2O3 thin films were deposited by a metal organic chemical vapour deposition on InAIN/GaN heterostructures using Ar or NH3 as a carrier gas. Effects of NH3 and Ar carrier gases on the electrical and structural properties of Al2O3/InAIN/GaN HEMT devices were investigated by current voltage, current collapse, and Auger electron spectroscopy measurements. Al2O3 deposited using Ar as a carrier gas leads to a substantial gate leakage current reduction with no increase of the current collapse compare to Schottky gate based HEMT. On the other hand, HEMT electrical performance shows degradation if NH3 carrier gas is used. Similarly, Auger electron spectroscopy revealed presence of carbon on InAIN surface when NH3 carrier gas was applied. It is suggested that the formation of carbon-related traps on the InAIN surface takes place in the early stages of the Al2O3 deposition with NH3 carrier gas that strongly influences the HEMT performance. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3021034]LASP
Image registration with sparse approximations in parametric dictionaries
No full textWe examine in this paper the problem of image registration from the new perspective where images are given by sparse approximations in parametric dictionaries of geometric functions. We propose a registration algorithm that looks for an estimate of the global transformation between sparse images by examining the set of relative geometrical transformations between the respective features. We propose a theoretical analysis of our registration algorithm, and we derive performance guarantees based on two novel important properties of redundant dictionaries, namely the robust linear independence and the transformation inconsistency. We propose several illustrations and insights about the importance of these dictionary properties and show that common properties such as coherence or the restricted isometry property fail to provide sufficient information in registration problems. We finally show with illustrative experiments on simple visual objects and handwritten digit images that our algorithm outperforms baseline competing methods in terms of transformation-invariant distance computation and classification.LTS
Fast directed evolution of non-immunoglobulin proteins by somatic hypermutation in immune cells
No full textA review. New, improved phenotypes. Somatic hypermutation in immune cells can be used for the fast directed evolution of proteins other than Igs (e.g., autofluorescent proteins). The target gene is inserted into the genome of activated B lymphocytes where it is mutated. Cells expressing a desired phenotype are selected and subjected to further evolution cycles to accumulate beneficial mutations. [on SciFinder (R)]LPPTLI
Microelectronic, high-speed data processing calculators for power system analysis: Comparison
No full textThis paper highlights the increasing need for faster than real-time simulators of the electric power system and shows that microelectronic emulation is a very promising solution to overcoming speed problems of current numerical simulators. Research is focused on two different emulation approaches. Both of them are detailed in this paper and their electronic implementation is shown. Furthermore, the two approaches are compared and their final capabilities are depicted. By doing so, the paper shows that the two approaches are not competing; each one has its own advantages.GR-KADES
The Optimal MAC Layer for Low Power UWB Networks is With Independent Channels and No Power Control
No full textWe are interested in the design of a MAC layer for systems that use ultra-wide band (UWB) communication and transmit very little power. We first explore the design space and find, that, for such networks, the optimal MAC should allow concurrent transmissions on as many channels as there are destinations; this is in sharp contrast to the established way of designing MAC protocols. Further, power control is not optimal: sources should always send at full power when they have something to transmit. Sources should constantly adapt their rate, either at the physical layer (which is difficult for the UWB channel) or at the MAC layer, using an increase/decrease protocol and incremental redundancy. Second, we explore the implications of a MAC layer with concurrent transmissions. We find that, in practice, because of nodes that can do only one thing at a time, there is a need for a ``private MAC" protocol. Also, broadcasting to destinations that can listen to many channels is highly non deterministic. This makes network coding an attractive alternative to flooding for protocols, such as the address resolution protocol (ARP) and routing, that need broadcasting.LCALCA
Transformation of Glucose to 5-Hydroxymethylfurfural Over Regenerated Cellulose Supported Nb2O5 center dot nH(2)O in Aqueous Solution
No full textNiobic acid (Nb2O5 center dot nH(2)O) was immobilized on regenerated cellulose (Re-Cellulose) to afford a heterogeneous catalyst, termed Nb2O5 center dot nH(2)O@Re-Cellulose, that was characterized by powder X-ray diffraction, microscopy (SEM and TEM) and spectroscopic (Raman and FTIR) techniques. The surface acidity of the catalyst was determined using FTIR spectroscopy employing pyridine as a molecular probe. The Nb2O5 center dot nH(2)O@Re-Cellulose catalyst was investigated in the conversion of glucose into 5-hydroxymethylfurfural (HMF) in aqueous media. The catalyst can be reused several times without undergoing a significant loss in activity.LCOMGM
Molecular Detection of Tetrachloroethene-Dechlorinating Bacteria in Environmental Samples
No full textLBEPoster Abstract: Gordon Research Conference on Applied and environmental Microbiology, New London, Connecticut, USA, July 22-27, 200
Towards a kinetic model of the phospholipids biosynthesis of the yeast Saccharomyces cerevisiae
No full textLipids, as vital eukaryotic cellular components, play a major role in cell, tissue and organ physiology. Alterations of lipid enzymes and metabolic pathways are related to many human diseases, such as cancer, diabetes and neurodegenerative diseases. In this study, we focus on phospholipids, the major components of all cell membranes, which not only act as structural membrane constituents but also play a vital role in cellular energy storage and in signaling pathways. The yeast, Saccharomyces cerevisiae, has been chosen as a cell model, due to its strong homology of proteins and pathways with higher eukaryotes. The benefits of studying the glycerophospholipid metabolism of S. cerevisiae will provide critical insight into phospholipid homeostasis of this model organism in various cellular states. The reconstructed model of phospholipid metabolism consists of 118 reactions and 80 metabolites. Beyond combining knowledge of all published yeast genome-scale models, it incorporates missing reactions reported in the literature along with the current state of the art concerning the participating enzymes. Pathways regarding compounds from the glycolysis pathway and synthesis of acyl-CoAs, required for phospholipid biosynthesis, have also been included. A steady state flux analysis was performed with the growth capacity of the cell being able to vary between maintenance and a maximum experimentally observed growth rate, in aerobic carbon-limiting conditions, with mass balance constraints calculated based on experimental data reported in the most recent yeast genome scale model. A thermodynamic curation of all the reactions of the pathway followed, which constrains the allowed space of the concentration ranges of metabolites of the pathway and also provides information about the directionality of all the reactions. Finally, we applied the ORACLE methodology in order to identify enzymes that determine the lipid composition in the various steady states of the cell. Generating a comprehensive kinetic model will be a useful tool for predictive analysis, drug designing or further biomedical research.LCS
Capteur CentoNewton-Bd' - ajustement
No full textCe document décrit l'ajustement de la version Bd' du capteur de force CentoNewton. Malgré les corrections déjà introduites, l'itération Bd a toujours un problème d'ajustement de l'offset, en raison du mauvais appariement des résistances d'ajustement grossier discret de l'offset (1±, 2±, et 3±), et de l'impossibilité de mesurer des offsets négatifs inhérente au signal amplifié. De ce fait, une révision mineure (Bd') a été faite, avec 1) un meilleur appariement des coupes et 2) un plus grand décalage positif intentionnel des valeurs d'offset du circuit combiné avec un faible gain initial, pour éviter / minimiser la saturation de l'offset initial. This document describes the trimming of version Bd' of the CentoNewton force sensor. In spite of previously-introduced corrections adjustment of the offset of version Bd still turned out to be problematic, due to the poor matching of the digital rough offset trimming resistors. combined with the impossibility to measure negative offset, which is inherent to the trimming of the amplified signal. Therefore, a minor revision (Bd') was made, with 1) better matching of the digital cuts and 2) an larger intentional positive offset shift of the circuit, combined with a low initial gain, in order to avoid / minimise the saturation of the initial offset.LPMPrésenté / publié en partie à IMAPS-PL Rzeszów-Czarna, Infoscience #20510