Morphology and Nanomechanics of Sensory Neurons Growth Cones following Peripheral Nerve Injury

A prior peripheral nerve injury in vivo, promotes a rapid elongated mode of sensory neurons neurite regrowth in vitro. This in vitro model of conditioned axotomy allows analysis of the cellular and molecular mechanisms leading to an improved neurite re-growth. Our differential interference contrast microscopy and immunocytochemistry results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons from mice dorsal root ganglia sensory neurons but promoted the appearance of larger neurites and growth cones. Using atomic force microscopy on live neurons, we investigated whether membrane mechanical properties of growth cones of axotomized neurons were modified following sciatic nerve injury. Our data revealed that neurons having a regenerative growth were characterized by softer growth cones, compared to control neurons. The increase of the growth cone membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins

Elaboration par MOVPE des materiaux semiconducteurs II-VI a grand gap ZnSe et ZnTe: application a la croissance des superreseaux ZnSe-ZnTe

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 82559 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Epitaxial growth of ZnSiN2 single-crystalline films on sapphire substrates

International audienceA new family of wide band gap nitride semiconductors expressed as II-IV-N-2 have recently attracted attention due to their expected properties such as optical non-linearity. In addition, among these compounds, ZnGeN2 and ZnSiN2 have lattice parameters close to GaN and SiC respectively. Up to now, there is very little work reported on this class of materials and no systematic thin film growth study has been reported to date. In this paper we present the first study on the growth of ZnSiN2 on c-sapphire and (100) silicon substrates using low pressure MOVPE technique. Triethylamine:dimethylzinc adduct, silane diluted in H-2 and ammonia were used as source materials. Single crystalline epitaxial ZnSiN2 layers were obtained on nitridated c-sapphire substrates in the temperature range 873-973 K by using an adapted II/IV molar ratio ranging from 1.2 to 12. Assuming an orthorhombic unit cell, the lattice parameters calculated from the X-ray diffraction data are a = 0.534 nm, b = 0.617 nm and c = 0.504 nm

Towards the understanding of peptide/inorganic semiconductor complex interaction using molecular dynamics simulations

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Thermal and Mechanical Properties of Silicon Tetrachloride (SiCl4) and Germanium Tetrachloride (GeCl4) in Their Vapor and Liquid Phases

International audienceThe two chemical species SiCl4 and GeCl4 are used, to a large extent, as starting materials in the optical fiber and semiconductor industry. The knowledge of selected physical properties of these materials (e.g. vapor pressure, viscosity, thermal conductivity, heat of vaporization, and heat capacity among others) is required for the prediction of their evaporation and deposition processes. While some of the aforementioned properties are well documented in the literature, others are seldom found or incomplete and only available for fixed temperatures. The aim of this paper is to gather the most common physical and mechanical properties for both SiCl4 and GeCl4 in their liquid and vapor phases

Theoretical investigation of new MgS-ZnSe structures

International audienceheoretical studies of the excitonic properties for different designs of MgS-ZnSe structures are presented. Excitonic binding energies are calculated for single quantum wells. For MgS-ZnSe superlattices, the energy of electron-hole transitions are evaluated and compared with the experimental photoluminescence spectra

Growth of 3C-SiC on si by low temperature CVD

International audienceWe report on the growth of 3C-SiC/Si using propane and silane as precursor gases. All layers were deposited on exactly oriented Si substrates. The growth temperature ranged from 1200 degreesC to 1350 degreesC and the carbonization temperature from 1150 degreesC to 1350 degreesC. We focused our study on the optimization of the surface morphology and the suppression of interfacial voids at low growth temperature. All layers were characterized by X-ray diffraction (both single diffraction and omega -scan), micro-Raman on cleaved edges, AFM, optical microscopy,2K photoluminescence and IR reflectivity. We have developed a 1150 degreesC carbonization step which, combined with a growth temperature of 1250 degreesC results in good quality material

APPLICATION OF A NEW THEORETICAL TRANSPORT STUDY TO THE ASSESSMENT OF THE PURITY OF ZNSE

International audienceZinc selenide has been studied for a long time, mainly as a candidate for blue light electroluminescence. The main problem is to achieve a good control of the conductivity. Surprisingly, up to now, there have been few attempts to study the electrical properties of the material, in order to find the ultimate limits of the transport parameters and to determine the purity of the layers accurately. We have made a detailed analysis of the transport properties: the scattering mechanisms are discussed and the relevant ones are included in the Boltzmann transport equation, which is solved using two methods (variational and Rode's iterative method). The drift and Hall mobilities, as well as the Hall ratio are plotted against Hall factor at 300 K and 77 K, the compensation ratio (defined as N(a)-/N(d)+) being used as a parameter. These results can be used as a tool for assessing the material quality, by deducing the compensation ratio at 300 K and 77 K from Hall measurements. We apply this to our growth results as well as to other results reported in the literature and we discuss the purity of the material obtained in MBE and MOVPE. The nature of the impurities is discussed from the influence of the growth parameters and it is assumed that group VII elements are the dominant donor species while group la elements are the main acceptors

LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY GROWTH OF ZNTE USING TRIETHYLAMINE DIMETHYL ZINC ADDUCT

International audienceWe present for the first time a detailed investigation of the growth of ZnTe layers deposited on GaAs substrates by low pressure metalorganic vapour-phase epitaxy using the new triethylamine dimethyl zinc adduct in combination with diisopropyl telluride as zinc and tellurium precursors respectively. The influence of the growth temperature (T(g)), the VI/II molar ratio, and the overall growth pressure (P) are studied. The successful growth of ZnTe is demonstrated at temperatures as low as 300-degrees-C. For growth temperatures ranging between 300 and 450-degrees-C, the growth rate is limited by the kinetics at the growing interface, and we measure an activation energy of 28 kcal/mol. At T(g) = 375-degrees-C, we found a linear variation of the growth rate with the overall growth pressure on the one hand, and with both zinc and telluride molar flows on the other hand. Low temperature reflectance and photoluminescence measurements were performed to characterize all the samples and are used to determine the optimal growth conditions: T(g) = 350-degrees-C, VI/II = 2, with P = 40 Torr. The stress experienced by the epilayers is investigated using the reflectance measurements. The relative intensity of the arsenic related bound exciton emission at 2.367 eV decreases as T(g) decreases. On the other hand, the I(b)1 unknown acceptor related bound exciton emission at 2.356 eV decreases linearly with the growth rate