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Search Results: 1 - 10 of 8245 matches for " Michel Rochette "
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First Step in Theoretical Approach in Study of Mars and Titan Atmospheres with an Inductively Coupled Plasma Torch
Pascal Andre,Stéphane Clain,Michel Dudeck,Boujema Izrar,David Rochette,Rachid Touzani,Damien Vacher
Physics , 2009,
Abstract: To obtain the modelling of an ICP torch that can be used as a test case, we have to determine all the thermodynamic properties and transport coefficients. To calculate the data we have first to determine the composition and the collisions integrals for all the species in the purpose to calculate the transport coefficients. We apply the calculation to the Mars and to the Titan atmosphere compositions. The intensities of the spectral lines are determined versus temperature.
A biomechanical model of the face including muscles for the prediction of deformations during speech production
Julie Groleau,Matthieu Chabanas,Christophe Marecaux,Natacha Payrard,Brice Segaud,Michel Rochette,Pascal Perrier,Yohan Payan
Physics , 2008,
Abstract: A 3D biomechanical finite element model of the face is presented. Muscles are represented by piece-wise uniaxial tension cable elements linking the insertion points. Such insertion points are specific entities differing from nodes of the finite element mesh, which makes possible to change either the mesh or the muscle implementation totally independently of each other. Lip/teeth and upper lip/lower lip contacts are also modeled. Simulations of smiling and of an Orbicularis Oris activation are presented and interpreted. The importance of a proper account of contacts and of an accurate anatomical description is shown
Electrostatic Separation as a Characterizing Tool for the Insulation of Conductive Mineral Particles  [PDF]
Philippe Bébin, Dave Mavrovic, Annie Rochette
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2014, DOI: 10.4236/jmmce.2014.23025
Abstract: This work deals with a non-conventional use of a drum-type electrostatic separator. Indeed, the electrostatic separation process is used as a tool to evaluate the efficiency of different formulations of insulating coatings surrounding coarse and irregular conducting mineral particles. Our analysis is based on the change of the particle’s distribution in the conductive and the non-conductive pans after the electrostatic separation process. Different coating formulations were tested and we found that only hydrophobic components have to be used and that a composite formulation must be considered to sufficiently increase the coating thickness. Viscous hydrophobic oil combined with talc is a particularly relevant coating formulation for insulating hematite or ilmenite particles. The viscosity of the binder plays a crucial role as it guarantees the necessary cohesion of the coating itself. To evaluate the required thickness to obtain efficient insulating capabilities for the coating surrounding coarse and irregular mineral particles, we linked the experimental volume ratio between the coating and the particles and the theoretical ratio. The experimental volume ratio is calculated using the weights of all the materials used and their respective densities. Whereas, the theoretical one is calculated using the volume the mineral particles would have, considering them all identical, spherical, with a smooth surface and the volume of the coating being uniform with the same thickness on each mineral particle. We found that an efficient insulating coating for hematite particles means a thickness of 9.5% of the average mineral radius, ranging from 125 μm to 1250 μm, resulting in an equivalent insulating thickness of about 48 μm for particles of around 1 mm in diameter. Interestingly, all results originate from the analysis of the change occurring in the particle’s distribution in the different collecting pans of an electrostatic separator.
Forgotten Radicals in Biology
Rochette Luc,Catherine Vergely
International Journal of Biomedical Science , 2008,
Abstract: Redox reactions play key roles in intra- and inter-cellular signaling, and in adaptative processes of tissues towards stress. Among the major free radicals with essential functions in cells are reactive oxygen species (ROS) including superoxide anion (O2 -), hydroxyl radical ( OH) and reactive nitrogen species (RNS) such as nitric oxide ( NO). In this article, we review the forgotten and new radicals with potential relevance to cardiovascular pathophysiology. Approximately 0.3% of O2 - present in cytosol exists in its protonated form: hydroperoxyl radical (HO2 ). Water (H2O) can be split into two free radicals: OH and hydrogen radical (H ). Several free radicals, including thiyl radicals (RS ) and nitrogen dioxide (NO2 ) are known to isomerize double bonds. In the omega-6 series of poly-unsaturated fatty acids (PUFAs), cis-trans isomerization of γ-linolenate and arachidonate catalyzed by RS has been investigated. Evidence is emerging that hydrogen disulphide (H2S) is a signaling molecule in vivo which can be a source of free radicals. The Cu-Zn superoxide dismutase (SOD) enzyme can oxidize the ionized form of H2S to hydro-sulphide radical: HS . Recent studies suggest that H2S plays an important function in cardiovascular functions. Carbonate radical, which can be formed when OH reacts with carbonate or bicarbonate ions, is also involved in the activity of Cu-Zn-SOD. Recently, it has been reported that carbonate anion were potentially relevant oxidants of nucleic acids in physiological environments. In conclusion, there is solid evidence supporting the formation of many free radicals by cells leading which may play an important role in their homeostasis.
Pangea B: an artifact of incorrect paleomagnetic assumptions?
P. Rochette,D. Vandamme
Annals of Geophysics , 2001, DOI: 10.4401/ag-3582
Abstract: The detailed plate reconstruction within Pangea megacontinent has been an ongoing debate among the paleomagnetic community for decades. The Pangea B hypothesis, implying a 3500 km Triassic dextral megashear on the Gondwana-Laurussia limit, has been recently reinforced by new data, excluding Southern Alps sites. This configuration, at odds with geological evidence, does improve the coherency of paleomagnetic poles from Gondwana and Laurussia. However, the corresponding apparent latitudinal difference between the two supercontinents can be easily accounted for, without invoking this megashear, considering the effect of inclination error (or equivalent non-dipole field) on the site distribution used in the paleomagnetic study. Once northern hemisphere Southern Alps data are considered, Pangea B no longer holds. Large inclination errors (10°-30°) are to be expected in the Permo-Triassic continental sediments as demonstrated in the Esterel and possibly Argentina Permo-Triassic studies or in Neogene analogues such as the Siwalik or Catalan basin sequences. An overall discussion of the inclination error problem is given. Analysis of the database also suggests an age bias between the Gondwana and Laurussia reference poles at the Permo-Triassic boundary, partly responsible also for the latitudinal shift. Finally, Moroccan data are demonstrated to be irrelevant for computing a Gondwana early Triassic pole.
Photosensitivity at 1550 nm and Bragg grating inscription in As2Se3 microwires
Raja Ahmad,Martin Rochette
Physics , 2011, DOI: 10.1063/1.3625942
Abstract: We report the first experimental observation of photosensitivity in As2Se3 glass at a wavelength of 1550 nm. We utilize this photosensitivity to induce the first Bragg gratings using a laser source at a wavelength of 1550 nm. We quantify the photosensitivity thresholds related to exposition intensity and exposition time. Finally, we demonstrate that As2Se3 Bragg gratings are widely tunable in wavelength as the microwire can withstand an applied longitudinal strain of 4 \times 104 \mu{\epsilon}.
Chalcogenide optical parametric oscillator
Raja Ahmad,Martin Rochette
Physics , 2012, DOI: 10.1364/OE.20.010095
Abstract: We demonstrate the first optical parametric oscillator (OPO) based on chalcogenide glass. The parametric gain medium is an As2Se3 chalcogenide microwire coated with a layer of polymer. The doubly-resonant OPO oscillates simultaneously at a Stokes and an anti Stokes wavelength shift of >50 nm from the pump wavelength that lies at {\lambda}P = 1552 nm. The oscillator has a peak power threshold of 21.6 dBm and a conversion efficiency of >19 %. This OPO experiment provides an additional application of the chalcogenide microwire technology; and considering the transparency of As2Se3 glass extending far in the mid-infrared (mid-IR) wavelengths, the device holds promise for realizing mid IR OPOs utilizing existing optical sources in the telecommunications wavelength region.
Efficient and broadband optical parametric four wave mixing in chalcogenide-PMMA hybrid microwires
Raja Ahmad,Martin Rochette
Physics , 2012, DOI: 10.1364/OE.20.009572
Abstract: The recent development of devices based on novel nonlinear materials like chalcogenides (ChGs), silicon (Si) and other semi-conductors has revolutionized the field of nonlinear photonics [1,2,3]. Among the nonlinear effects observed in these materials, four-wave mixing (FWM) is the process that finds the most applications including wavelength conversion [4], optical regeneration [5,6], optical delay [7], time-domain demultiplexing[8], temporal cloaking[9] and negative refraction[10]. Although FWM has been observed in several media including chalcogenides [11,12,13,14], silicon[15, 16], bismuth [17] and silica [18,19], there is a continued quest for devices that realize efficient and broadband FWM while offering compactness, low-power consumption and compatibility with optical fibers. Here, we demonstrate the fabrication of 10 cm long polymer cladded chalcogenide (As2Se3) microwires to realize FWM-led sub watt threshold (70-370 mW) wavelength conversion with a 12 dB bandwidth as broad as 190 nm, and conversion efficiency as high as 21 dB. This represents a 3-30 \times increase in bandwidth and 30-50 dB improvement in conversion efficiency over previous demonstrations in tapered and microstructured chalcogenide fibers [11,13,14]. These properties, combined with low loss (< 4 dB), ease of fabrication, and the transparency of As2Se3 from near to mid infrared regions (1 15 \mum) [20] make this device a promising building block for lasers, optical instrumentation and optical communication devices.
All chalcogenide Raman parametric Laser, Wavelength Converter and Amplifier in a Single Microwire
Raja Ahmad,Martin Rochette
Physics , 2013,
Abstract: Compact, power efficient and fiber compatible lasers, wavelength converters and amplifiers are vital ingredients for the future fiber optic systems and networks. Nonlinear optical effects, like Raman scattering and parametric four wave mixing, offer a way to realize such devices. Here we use a single chalcogenide microwire to realize a device that provides the functions of a Stokes Raman parametric laser, a four wave mixing anti Stokes wavelength converter, and an ultra broadband Stokes/anti Stokes Raman amplifier or supercontinuum generator. The device operation relies on ultrahigh Raman and Kerr gain (upto five orders of magnitude larger than in silica fibers), precisely engineered chromatic dispersion and high photosensitivity of the chalcogenide microwire. The Raman parametric laser operates at a record low threshold average (peak) pump power of 52 \muW (207 mW) and a slope efficiency of >2%. A powerful anti Stokes signal is generated via the nonlinear four wave mixing process. As amplifier or the broadband source, the device covers a wavelength (frequency) range of >330 nm (47 THz) when pumped at a wavelength of 1550 nm. Owing to the underlying principle of operation of the device being the nonlinear optical processes, the device is anticipated to operate over the entire transmission window of the chalcogenide glass ({\lambda}~1 10 \mum).
Genome-wide gene expression profiling analysis of Leishmania major and Leishmania infantum developmental stages reveals substantial differences between the two species
Annie Rochette, Frédéric Raymond, Jean-Michel Ubeda, Martin Smith, Nadine Messier, Sébastien Boisvert, Philippe Rigault, Jacques Corbeil, Marc Ouellette, Barbara Papadopoulou
BMC Genomics , 2008, DOI: 10.1186/1471-2164-9-255
Abstract: We used a multispecies DNA oligonucleotide microarray to compare whole-genome expression patterns of promastigote (sandfly vector) and amastigote (mammalian macrophages) developmental stages between L. major and L. infantum. Seven per cent of the total L. infantum genome and 9.3% of the L. major genome were differentially expressed at the RNA level throughout development. The main variations were found in genes involved in metabolism, cellular organization and biogenesis, transport and genes encoding unknown function. Remarkably, this comparative global interspecies analysis demonstrated that only 10–12% of the differentially expressed genes were common to L. major and L. infantum. Differentially expressed genes are randomly distributed across chromosomes further supporting a posttranscriptional control, which is likely to involve a variety of 3'UTR elements.This study highlighted substantial differences in gene expression patterns between L. major and L. infantum. These important species-specific differences in stage-regulated gene expression may contribute to the disease tropism that distinguishes L. major from L. infantum.Leishmania are protozoan parasites that cause a wide spectrum of clinical manifestations in humans, collectively referred to as leishmaniasis, ranging from self-resolving skin lesions (L. major and L. mexicana) to life-threatening visceral diseases (L. donovani and L. infantum) [1]. Leishmaniasis is endemic in 88 countries and the World Health Organization has estimated that more than 12 million people are currently infected with Leishmania and 350 million people are at risk of infection in tropical and subtropical regions of the world [1,2]. Leishmania parasites exist in two major developmental stages. In the alimentary tract of the sandfly vector, the parasites grow as extracellular flagellated promastigotes that are exposed to neutral pH and fluctuating temperatures averaging 25°C. Following the sand fly bite, the infective forms (metacyclic
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