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81.
Priscilla Avenier Xavier Solans-Monfort Laurent Veyre Filippo Renili Jean-Marie Basset Odile Eisenstein Mostafa Taoufik Elsje Alessandra Quadrelli 《Topics in Catalysis》2009,52(11):1482-1491
The silica-grafted Ta(V) imido amido complex [(≡SiO)2Ta(NH)(NH2)], 2, obtained from the reaction of either ammonia or dinitrogen plus hydrogen with the silica-grafted hydrides [(≡SiO)2Ta(III)H], 1a, and [(≡SiO)2Ta(V)H3], 1b, undergoes H/D exchange with D2. In situ IR spectroscopy shows that the fully labelled compound [(≡SiO)2Ta(ND)(ND2)], 2-d, can be obtained by moderate heating (60 °C, 3 h) under D2 atmosphere (550 torr, 300 eq. with respect to Ta), and that the exchange is reversible. The observed stretching and bending
frequencies of 2-d are in agreement with the expected isotopic shift upon H/D replacement with respect to literature values reported for 2 and have been corroborated by the independent synthesis of 2-d by reaction of deuterated 1a and 1b with N2 and D2. Density functional theory (DFT) calculations, performed using a periodic or a cluster model, explored the structures and
energetics of all minima involved in the reaction with H2 and showed that among the explored pathways the energetically preferred mechanisms for H2 reaction with [{(μ-O)[(HO)2SiO]2}Ta(V)(NH)(NH2)], 2q, is the heterolytic cleavage of either the imido Ta=N or the amido Ta-N bonds, to yield respectively [{(μ-O)[(HO)2SiO]2}TaH(NH2)2], 3q (ΔE = −9.5 kcal mol−1 and ΔG298K = +2.6 kcal mol−1 with respect to 2q) and [{(μ-O)[(HO)2SiO]2}Ta(NH)(NH3)], 4q (ΔE = −6.0 kcal mol−1 and ΔG298K = +7.9 kcal mol−1 with respect to 2q). All activation barriers are moderate (between 17.7 and 30.2 kcal mol−1) in agreement with the observed mild heating conditions necessary for the reaction to occur. 相似文献
82.
Odile Beaury Michèle Faucher Geneviève Teste de Sagey Paul Caro 《Materials Research Bulletin》1978,13(9):953-957
A new phase for the rare earth tungstate Y2WO6 was synthetized at high temperature. The parameters of the orthorhombic unit cell determined on small single crystals are , , and the space group is probably P212121.The fluorescence spectrum of the 2% Europium doped compound reveals the existence of four crystallographic sites for Yttrium, which is consistent with the X-Ray data. 相似文献
83.
Odile Paliès Michel Caillot Evelyne Cauzinille-Marmèche Jean-Louis Laurière Jacques Mathieu 《Computational Intelligence》1986,2(1):99-107
ELECTRE is a project to build an intelligent tutoring system for learning basic electricity. This paper describes a student model based on the student's cognitive processes. This model includes, for each student, his/her domain knowledge and the specific heuristics. Moreover, it uses meta-knowledge of problem solving. This model is simulated by a knowledge-based system that controls the solving processes by meta-rules. A case study is presented. 相似文献
84.
85.
Odile Macchi 《电信纪事》1981,36(11-12):615-625
The paper presents a detailed tutorial about an iterative learning algorithm that is intended to optimize the digital filtering of random observations with unknown statistics, in order to extract a useful signal correlated with the observation. It is the stochastic gradient algorithm that minimizes the mean square deviation between the output of an adaptative filter and the useful signal. In the communication context, this algorithm is used for applications such as equalization of high rate data transmission and echo cancellation. The paper recalls its foundations, summarizes the conditions under which it is used in data transmission, points out the difficulty of a convergence proof, states the first theorem suitable for practical applications, details the evaluation of the mean square deviation, for the case of a fixed step-size. 相似文献
86.
Franois Lelarge Batrice Dagens Jeremie Renaudier R. Brenot Alain Accard Frdric van Dijk Dalila Make Odile Le Gouezigou Jean-Guy Provost Francis Poingt Jean Landreau Olivier Drisse Estelle Derouin Benjamin Rousseau Frdric Pommereau Guang-Hua Duan 《IEEE journal of selected topics in quantum electronics》2007,13(1):111-124
This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm2 per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T0 larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time-jitter characteristics when QD lasers are actively mode-locked. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications 相似文献
87.
Lucio Martinelli Henri Benisty Olivier Drisse Estelle Derouin Frdric Pommereau Odile Legouezigou Guang-Hua Duan 《Photonics Technology Letters, IEEE》2007,19(5):282-284
The gridding irregularities of electron beam lithography may deterministically disorder photonic crystals (PhC). Their practical impact is addressed on a PhC wavelength selective device using a large grid size of 8 nm. The device operation, based on confined resonances and propagation mini-stopbands in a multimode waveguide, is deterministically blurred. Scattering length scales are correspondingly discussed. Strategies for higher throughput lithography are proposed accordingly 相似文献
88.
Tresse O Shannon K Pinon A Malle P Vialette M Midelet-Bourdin G 《Journal of food protection》2007,70(7):1569-1578
One hundred one strains of Listeria monocytogenes isolated from seafood and cheese industry samples and from patients with listeriosis were assessed using a microtiter plate method for adhesion to polystyrene and stainless steel surfaces. The adhesion rate for these strains ranged from 3.10 to 35.29% with an inoculum of 8 x 10(8) cells per well. A strong correlation was found between adhesion to polystyrene and stainless steel microtiter plates, indicating that the intrinsic ability of L. monocytogenes to adhere to inert surfaces is stronger than the influence of the surface's physicochemical properties. The clinical strains were less adherent to inert surfaces than were the industrial strains. By integrating other factors such as location of the industrial strains, contamination type of the clinical strains, serotype, and pulsotype into the analysis, some weak but significant differences were noted. For the industrial isolates, the number of cells attached to both surfaces differed significantly depending on whether they were isolated from food or food-processing environments in the seafood and cheese industry. For clinical isolates, sporadic strains exhibited greater adhesion to polystyrene than did epidemic strains. Strains belonging to the pulsed-field gel electrophoretype clusters A and M (lineages II and I, respectively) were less able to adhere to polystyrene and stainless steel than were strains in the more common clusters. 相似文献
89.
Charles Nkoumbou Frdric Villieras Daniel Njopwouo Clment Yonta Ngoune Odile Barres Manuel Pelletier Angelina Razafitianamaharavo Jacques Yvon 《Applied Clay Science》2008,41(3-4):113-132
Three talc deposits were discovered at Ngoung, Lamal Pougue and Bibodi Lamal (Cameroon). They derived from ultramafic rocks and are enclosed in a Pan-African garnet and muscovite-bearing mica schist of the Yaoundé series. The physico-chemical properties of these talc deposits have been investigated by different techniques including Scanning Electron and Transmission Microscopy (SEM and TEM), chemical analyses, X-ray diffraction (XRD), infrared spectroscopy, particle size analysis by laser diffraction and low temperature gas absorption–desorption. The mineralogical composition deduced from XRD is wide (talc + chlorite + tremolite ± anthophyllite ± chromite ±serpentine ± brucite ± magnesite ± dolomite), but due to the high talc contents (≈ 90%) the samples are close to monomineralic. SEM studies reveal that all talc deposits comprise bundles of platy talc and a few prismatic crystals of amphiboles and other contaminating minerals. Laser diffraction confirms the coarse particle size of the talc crystals. Mode values are as high as 105–170 μm (except two samples displaying 76 and 42 μm) and d50 ranges from 107 to 25 μm. The values of specific surface area measured by BET and t-plot methods range from 1 to 6 m2/g and are correlated with external specific surface area measured by laser diffraction. Discrepancies from the trend are due to the semi-crystalline texture of the samples and mostly to intra-crystalline structural defects revealed by TEM observations. In infrared spectra, specific absorption bands are distinguished for talc, chlorite, tremolite, carbonates, serpentine, brucite and water. Occasional substitutions in minerals led to a shift in some absorption bands. The chemical composition criteria important for most of the industrial applications such as ceramics and pharmaceutics are closely complied with in untreated samples from these deposits. In summary, high talc proportions, chemical compositions, platy morphology and coarse grain size of its crystals lead to the conclusion that the studied deposits are economically attractive. The data set of the present work is an important tool for choosing the beneficiation methods for specific applications. 相似文献
90.
Christophe Cullin Agns Baudin-Baillieu Elisabeth Guillemet Odile Ozier-Kalogeropoulos 《Yeast (Chichester, England)》1996,12(15):1511-1518
We have analysed the function of the open reading frame (ORF) YCL09C. The deletion of this ORF from chromosome III does not affect the physiology of the corresponding yeast strain enough to give a distinct phenotype. Nevertheless a computational analysis reveals high homology between this ORF and the enterobacterial genes encoding the regulatory subunit of acetolactate synthase. We have therefore tested the possibility that ycl09cp is the regulatory subunit of yeast acetolactate synthase by in vitro enzymatic analysis. The acetolactate synthase was previously shown to be retroinhibited by its final product valine. In Escherichia coli this retro-control is assured by the regulatory subunit. Using a yeast strain carrying a complete deletion of YCL09C, we have observed the loss of such retro-inhibition. These results together with the computational predictions show that YCL09C encodes the regulatory subunit of yeast acetolactate synthase. 相似文献