472 research outputs found
Role of Protein Kinase Network in Excitation-Contraction Coupling in Smooth Muscle Cell
The aim of this chapter is to present a review of the main protein kinases involved in the signalling pathways between the stimulation of smooth muscle cell and the resulting dynamic contraction. As in striated muscle cells, contraction in smooth muscle cells (SMC) is primarily triggere
Light Emission in Silicon from Carbon Nanotubes
The use of optics in microelectronic circuits to overcome the limitation of
metallic interconnects is more and more considered as a viable solution. Among
future silicon compatible materials, carbon nanotubes are promising candidates
thanks to their ability to emit, modulate and detect light in the wavelength
range of silicon transparency. We report the first integration of carbon
nanotubes with silicon waveguides, successfully coupling their emission and
absorption properties. A complete study of this coupling between carbon
nanotubes and silicon waveguides was carried out, which led to the
demonstration of the temperature-independent emission from carbon nanotubes in
silicon at a wavelength of 1.3 {\mu}m. This represents the first milestone in
the development of photonics based on carbon nanotubes on silicon
Optical Gain in Carbon Nanotubes
Semiconducting single-wall carbon nanotubes (s-SWNTs) have proved to be
promising material for nanophotonics and optoelectronics. Due to the
possibility of tuning their direct band gap and controlling excitonic
recombinations in the near-infrared wavelength range, s-SWNT can be used as
efficient light emitters. We report the first experimental demonstration of
room temperature intrinsic optical gain as high as 190 cm-1 at a wavelength of
1.3 {\mu}m in a thin film doped with s-SWNT. These results constitute a
significant milestone toward the development of laser sources based on carbon
nanotubes for future high performance integrated circuits.Comment: 4 figure
Amélioration des propriétés des huiles pyrolytiques : par hydrotraitement de la biomasse
La nĂ©cessitĂ© de trouver une alternative aux ressources fossiles dans les domaines Ă©nergĂ©tique et chimique oriente une partie de la recherche vers la valorisation de la biomasse. Le procĂ©dĂ© thermochimique de pyrolyse rapide suscite beaucoup dâintĂ©rĂȘts depuis quelques annĂ©es car il permet de produire majoritairement une phase liquide, appelĂ©e biohuile Ă partir dâune biomasse. Celle-ci possĂšde le potentiel de devenir un biocombustible ou un biocarburant mais un certain nombre de caractĂ©ristiques physico-chimiques freine son application. Les hĂ©micelluloses et les cendres Ă travers leurs produits de dĂ©gradation ou leur rĂŽle catalytique sont Ă lâorigine de lâaciditĂ©, de lâinstabilitĂ© et du faible pouvoir calorifique de lâhuile pyrolytique. Dans cette thĂšse, pour amĂ©liorer la qualitĂ© de la biohuile, la biomasse a Ă©tĂ© hydrotraitĂ©e avant dâĂȘtre pyrolysĂ©e. Les biomasses Ă©tudiĂ©es sont des billes de faible diamĂštre de peuplier faux tremble (Populus tremuloides) et dâĂ©pinette blanche (Picea glauca), deux essences rĂ©pandues dans la rĂ©gion du Bas Saint Laurent au QuĂ©bec. Elles ont Ă©tĂ© mises sous forme de copeaux avant de subir lâhydrotraitement. Ce prĂ©traitement a permis dâĂ©liminer une partie des hĂ©micelluloses et des cendres du peuplier et de lâĂ©pinette. Une partie des lignines du peuplier se retrouve Ă©galement solubilisĂ©e par le traitement appliquĂ© Ă haute sĂ©vĂ©ritĂ©. Lâinfluence des modifications chimiques occasionnĂ©es par lâhydrotraitement sur le comportement pyrolytique des biomasses a Ă©tĂ© Ă©tudiĂ©e par pyrolyse-chromatographie en phase gazeuse couplĂ©e Ă une spectromĂ©trie de masse menĂ©e sous des conditions simulant la pyrolyse Auger pour la production de lâhuile. Les composĂ©s phĂ©noliques, dĂ©rivĂ©s des lignines, sont les constituants majoritaires des huiles pyrolytiques. Une augmentation de la teneur en anhydrosucres, principalement du lĂ©voglucosane, a Ă©tĂ© observĂ©e pour les huiles issues de la pyrolyse de biomasse prĂ©traitĂ©e. Ce phĂ©nomĂšne est accentuĂ© si la vitesse de chauffe du procĂ©dĂ© de pyrolyse augmente. Lâinfluence de lâhydrotraitement sur la qualitĂ© de la biohuile a Ă©tĂ© Ă©valuĂ©e pour le peuplier faux-tremble. Le procĂ©dĂ© de pyrolyse a Ă©tĂ© effectuĂ© au moyen dâune unitĂ© laboratoire de pyrolyse Auger. MĂȘme si lâimpact sur le rendement ne semble pas Ă©vident, lâhydrotraitement a permis dâamĂ©liorer les propriĂ©tĂ©s physicochimiques de lâhuile pyrolytique tels que la teneur en eau, le pouvoir calorifique, et le point dâĂ©clair. En revanche, le pH acide de lâhuile pyrolytique est maintenu. Mots clĂ©s : biomasse forestiĂšre, peuplier faux tremble, Ă©pinette blanche, pyrolyse, biohuile ou huile pyrolytique, hydrotraitement, rĂ©acteur Auger, pyrolyse GC-MS.The need to find an alternative to fossil resources as source of energy and chemicals has directed the research towards the valorization of biomass. Nowadays there is a growing interest for the thermochemical process of fast pyrolysis because of its major product, liquid bio-oil. Currently, some of its physical and chemical properties impede the direct application of bio-oil as fuel. The thermal degradation of hemicelluloses generates oxygenated compounds which cause the acidity and the instability of the bio-oil. Ash constituents catalyze secondary pyrolysis reactions which decrease the quality of bio-oil. In order to improve the bio-oil quality, the biomass is subjected in this project to a hydrothermal pretreatment before pyrolysis. Two woody biomasses, which are widespread in the forest of Bas-Saint Laurent (Quebec, Canada), are studied: trembling aspen (Populus tremuloides) and white spruce (Picea glauca). The whole logs are converted into wood chips before the hydrotreatment. This pretreatment was determined to remove hemicelluloses and ash from woody biomass. Moreover a partial solubilisation of lignins is observed for aspen. The impact of the pretreatment on pyrolytic behavior of woody biomasses has been studied by an analytical pyroprobe with a gas chromatograph coupled with a mass spectrometer using a protocole simulating the pyrolysis process. The phenolic compounds, derived from the degradation of lignins, are the major constituents of the bio-oil. A substantial increase of anhydrosugars content is noticed in the case of the bio-oil produced from pretreated biomass. This phenomenon is enhanced if the pyrolysis is performed at a high heating rate. The influence of the pretreatment on the bio-oil quality has been evaluated only for the trembling aspen. The pyrolysis process has been performed in a mobile pyrolysis Auger reactor. Even if the hydrotreatment seemed to have no impact on the bio-oil yield, it appeared to improve bio-oil characteristics such as water content, heating value and flash point, Nevertheless, the acid pH of bio-oil remained unchanged. Key words: forest biomass, trembling aspen, white spruce, fast pyrolysis, bio-oil, Auger reactor, hydrothermal pretreatment
Bevacizumab in a treat-and-extend regimen for neovascular age related macular degeneration in a resource limited sector.
Master of Medical Science in Ophthalmology. University of KwaZulu-Natal. Durban, 2016.Abstract available in PDF file
Optical microcavity with semiconducting single-wall carbon nanotubes
We report studies of optical Fabry-Perot microcavities based on
semiconducting single-wall carbon nanotubes with a quality factor of 160. We
experimentally demonstrate a huge photoluminescence signal enhancement by a
factor of 30 in comparison with the identical film and by a factor of 180 if
compared with a thin film containing non-purified (8,7) nanotubes. Futhermore,
the spectral full-width at half-maximum of the photo-induced emission is
reduced down to 8 nm with very good directivity at a wavelength of about 1.3
m. Such results prove the great potential of carbon nanotubes for photonic
applications
Multimedia data mining for automatic diabetic retinopathy screening
International audienceâ This paper presents TeleOphta, an automatic sys-tem for screening diabetic retinopathy in teleophthalmology networks. Its goal is to reduce the burden on ophthalmologists by automatically detecting non referable examination records, i.e. examination records presenting no image quality problems and no pathological signs related to diabetic retinopathy or any other retinal pathology. TeleOphta is an attempt to put into practice years of algorithmic developments from our groups. It combines image quality metrics, specific lesion detectors and a generic pathological pattern miner to process the visual content of eye fundus photographs. This visual information is further combined with contextual data in order to compute an abnormality risk for each examination record. The TeleOphta system was trained and tested on a large dataset of 25,702 examination records from the OPHDIAT screening network in Paris. It was able to automatically detect 68% of the non referable examination records while achieving the same sensitivity as a second ophthalmologist. This suggests that it could safely reduce the burden on ophthalmologists by 56%
PECAM-1 engagement counteracts ICAM-1-induced signaling in brain vascular endothelial cells
Interactions between leukocytes and vascular endothelial cells are mediated by a complex set of membrane adhesion molecules which transduce bi-directional signals in both cell types. Endothelium of the cerebral blood vessels, which constitute the bloodâbrain barrier, strictly controls adhesion and trafficking of leukocytes into the brain. Investigating signaling pathways triggered by the engagement of adhesion molecules expressed on brain endothelial cells, we previously documented the role of ICAM-1 in activation of the tyrosine phosphorylation of several actin-binding proteins and subsequent rearrangements of the actin cytoskeleton. In the present study, we show that, whereas PECAM-1 is known to control positively the trans-endothelial migration of leukocytes via homophilic interactions between leukocytes and endothelial cells, PECAM-1 engagement on brain endothelial surface unexpectedly counteracts the ICAM-1-induced tyrosine phosphorylation of cortactin and rearrangements of the actin cytoskeleton. We present evidence that the PECAM-1-associated tyrosine phosphatase SHP-2 is required for ICAM-1 signaling, suggesting that its activity might crucially contribute to the regulation of ICAM-1 signaling by PECAM-1. Our findings reveal a novel activity for PECAM-1 which, by counteracting ICAM-1-induced activation, could directly contribute to limit activation and maintain integrity of brain vascular endothelium
Piégeage d'une fissure interfaciale par structuration d'un empilement multicouche magnétron
Pour renforcer l'interface faible d'un empilement multicouches, on peut utiliser un mĂ©canisme de piĂ©geage en modifiant localement la tĂ©nacitĂ© de cette interface. Ce renforcement est la consĂ©quence de l'existence d'un rĂ©gime de piĂ©geage dĂ» Ă un changement local de tĂ©nacitĂ©. Dans cette Ă©tude, nous avons Ă©tudiĂ© le piĂ©geage d'une fissure lors d'un test de clivage pour des dĂ©fauts macroscopiques simples. Les dĂ©fauts ont Ă©tĂ© obtenus par rayage superficiel de façon Ă supprimer localement l'interface faible de l'empilement. Ainsi, lors de l'assemblage de l'Ă©prouvette de clivage, on gĂ©nĂšre localement des zones de forte adhĂ©sion dans le sillon des rayures. Pour diffĂ©rents types de dĂ©fauts, nous avons montrĂ© que la morphologie du front de fissure pouvait ĂȘtre dĂ©crite par une approche perturbative du premier ordre initialement dĂ©veloppĂ©e par Gao et Rice. Cette description nous a aussi permis de dĂ©terminer les tĂ©nacitĂ©s locales dans les zones de piĂ©geage
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