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Efficient electroabsorption in an InGaAsP/InGaAsP MQW optical waveguide modulator structure is reported. A 17 dB extinction ratio is obtained by applying a 3.5 V drive voltage to a 78 μm long waveguide operating at 1.54 μm under TE-polarisation mode. The on-state attenuation is only 2 dB.

A new optical waveguide TE-TM mode-splitter realised on X-cut, Z-propagating lithium niobate is reported. At 1.52 μm, the device exhibits extinction ratios better than 18 dB for applied voltages lower than 20 V, and can be used as a polarisation switch.

The rates of acidolysis of the Group II organometallic compounds are in the order: (C 2 H 5 ) 2 Mg > C 2 H 5 MgX > (C 2 H 5 ) 2 Zn > (C 2 H 5 ) 2 Cd. In reactions between alcohols R′OH and R 2 Cd in diethyl ether, anisole or benzene as solvent, the mechanism is S E 2 c . In more basic solvents (tetrahydrofuran, 1,2-dimethoxyethane, tetramethylethylenediamine) the reaction is faster and should proceed by an S E 2 o mechanism. The latter mechanism also occurs when metallic halides (which accelerate these reactions), or reagents more acidic than alcohols are used. In hexamethylphosphorotriamide the reaction is very fast even without metallic halide. Kinetic and NMR studies show that RCdOR′ is formed more rapidly than R′OCdOR′.

Resume Une population de 8 athletes de haut niveau specialistes de demi-fond fut etudiee a trois reprises au cours d'une saison annuelle de competition. Ces examens successifs realises en debut d'annee, pendant la phase de preparation et pendant la phase de competition ont permis de recueillir le comportement alimentaire par le biais d'une enquete de type semainier, et les parametres physiologiques et biologiques suivants: V˙O2 max, puissance maximale anaerobie, masse grasse, parametres hematologiques, calcium et magnesium sanguin. Les resultats mettent en evidence une relation entre la depense energetique estimee de l'entrainement et les apports caloriques alimentaires. Sur le plan de la repartition plastique des calories, il existe une part importante des calories lipidiques (36%) et une insuffisance des calories glucidiques (44%) en comparaison avec les normes admises. L'analyse des resultats par periode de recueil ne met pas en evidence d'effet lie a la saison ou au type d'entrainement. Les parametres physiologiques revelent une augmentation legere mais significative du V˙O2 max a la periode de competition. Seule une chute du magnesium plasmatique accompagne cette modification. En conclusion, cette etude montre une relation entre depense et apport energetique, un exces relatif des calories lipidiques et une stabilite tout au long de la saison sportive du comportement alimentaire.

Alkylmagnesium halides in HMPA react with aliphatic esters to form predominantly the less substituted ketonic enolates. The direction of these enolizations is more selective than that of intermediate ketones. Aliphatic esters are only slightly or not at all enolized under these conditions. Hydrolysis, deuterolysis and alkylation of the ketonic enolates give the corresponding ketones. Benzoic acid derivatives and α-β unsaturated aliphatic and aromatic esters give only low yields of ketonic enolates. The low enolization of the intermediate ketones by these alkylmagnesium halides can explain this result.

PMR studies show that CH 3 CdOC(CH 3 ) 3 is formed more rapidly than symmetrical alkoxide from (CH 3 ) 2 Cd and (CH 3 ) 3 COH. Spectra of CH 3 CdOC(CH 3 ) 3 in different solvents show that this product is less solvated that (CH 3 ) 2 Cd. An interpretation based on exchange of methyl groups in various cases is proposed.

The reagent (acetic anhydride and perchloric acid in ethylacetate) proposed by Edwards and Rao for the enolacetylation of ketones is particularly well suited to the preparation of the enolacetates of cis and trans 2-decalones, and to the study of their equilibrium.

Peroperative and postoperative complications of phacophagy differ only slightly between the limbic and pars-plana approaches. We therefore choose the route according to the ease of access and the adequate treatment of the posterior segment. We prefer the limbic route for congenital cataracts and the pars-plana route for traumatic cataracts with vitreous or retinal changes.

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Spontaneous luxation of lens is a rare ocular disease. There are three forms: hereditary, great myopia and senile cataract. The authors report on a senile cataract case: the posterior luxation in the second eye occurs three months after the first. After temporary intraocular pressure elevation, there are no complications 8 years later.

Die Protolyse der metallorganischen Verbindungen (I)-(IV) mit n-Hexin oder Isoamylalkohol wird untersucht.

About 20 patients chosen at random, and counting 40 over 6 diop. myopic eyes, had their ocular pressure systematically checked. The results were compared with the ocular pressure of 40 non myopic eyes, matched one by one. All the myopic eyes went through a tonography, a gonioscopy and their visual fields were checked through the Friedmann's central field analyser. When no glaucoma was found among the non myopic eyes, 25% of myopic eyes were affected by a significantly high ocular pressure, gonioscopic and perimetric changes. The familial investigations only showed few glaucomatous antecedents. The treatment is debated.

Eye drops containing antibiotics are more and more numerous, we prescribe them more and more frequently. We found it interesting first to gather in six lists all antibiotics used locally in ophthalmology and to study for everyone its bacterial spectrum. After that we see which bacteria are most frequently met by ophthalmologists and when (presurgery examination, conjunctivitis, blepharitis, chalazion, meibomianitis, sty, corneal ulcer, lens infection). All this helps the ophthalmologist to choose the antibiotic he prescribes before the bacteriological specimen, with high confidence. At last, we sum up the little that is presently known about penetration of antibiotics into the eye.

Thick AlGaN layers and AlGaN/GaN superlattices have been grown on GaN using metalorganic chemical vapor deposition. Cross-sectional transmission electron microscopy has been used to show that V-shaped surface pits on these samples differ from similar features observed in the InGaN system. Inversion domains and segregated Al are found in the middle of each V pit, and superlattice layers are observed to follow the pit sidewalls.

When the stoichiometric TiN was deposited directly on GaN, we obtained columnar TiN grains of 5-20 nm section which cross the whole film thickness and are rotated mostly around the [111] axis. The conventional epitaxial relationship is obtained and no amorphous patches are observed at the interface. The deposition of TiN on Si doped GaN layers lead to the formation of an ohmic contact, whereas we obtain a rectifying contact on p type layers.

We report the results of photoluminescence (PL), transmission and photoconductance (PC) studies of InxGa1-xN alloys grown by metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). First, we demonstrate that PC measurements allow to determine the gap energy and give the same value as transmission experiments in the case of thin InGaN layers. Second, we have performed PL and PC measurements in thin InGaN films. The comparison between the PL peak and PC measurements gives the Stokes shift. We study the Stokes shift as a function of temperature, and explained it in terms of localization and Burstein - Moss effect. Finally, we show that our measurements can be extended to the case of InGaN/GaN quantum dots. (C) 2001 Elsevier Science B.V. All rights reserved.

Li-ion secondary batteries are currently the preferred solution to store energy since a decade for stationary applications or electrical traction. However, because of their safety issues, Li-ion batteries are still considered as a critical part. Thermal runaway has been identified as a major concern with Li-ion battery safety. In this context, IFPEN, INERIS and LISE launched a collaboration to promote a PhD thesis so called « understanding and modeling of thermal runaway events pertaining to new and aged Li-ion batteries ». To achieve this goal, a double approach with modeling and experimental investigation is used. A 3D thermal runaway model is developed at cell level, coupling thermal and chemical phenomena, and taking into account the growth of the SEI layer as main ageing mechanism on negative electrode. Advanced knowledge of cells thermal behavior in over-heated conditions is obtained particularly for commercial LFP / C cylindrical cells: A123s (2,3Ah), LifeBatt (15Ah), and NMC / C pouch cells: PurePower (30 Ah). The model was calibrated for LFP / C cells, and then it was validated with thermal abuse tests on A123s and LifeBatt cells. This model is helpful to study the influence of cell geometry, external conditions, and even ageing on the thermal runaway initiation and propagation. This study opens up new possibilities for improving the prediction of various events taking place during Li-ion batteries thermal runaway, at various scales for further practical applications for safety management of LIBs.; Les batteries lithium-ion s'affichent comme de bons candidats pour assurer le stockage réversible de l'énergie électrique sous forme électrochimique. Toutefois, elles sont à l'origine d'un certain nombre d'incidents aux conséquences plus ou moins dramatiques. Ces incidents sont souvent liés au phénomène d'emballement thermique. La sécurité des batteries Li-ion représente par conséquent un enjeu technique et sociétal très important. C'est dans ce contexte que vient s'inscrire ce travail de thèse dans le cadre d'une collaboration entre IFPEN, l'INERIS et le LISE. Une double approche de modélisation et expérimentation a été retenue. Un modèle 3D du comportement thermique a été développé à l'échelle de la cellule, couplant les phénomènes thermiques et chimiques, et prenant en compte le vieillissement par croissance de la SEI sur l'électrode négative. Le modèle a été calibré pour la chimie LFP/C sur deux technologies A123s (2,3 Ah) et LifeBatt (15 Ah), puis validé expérimentalement. Le modèle permet d'identifier les paramètres critiques d'emballement de cellules, il permet également de discuter l'effet du vieillissement sur l'emballement thermique. Grâce à l'expérimentation, les connaissances en termes d'amorçage et de déroulement d'un emballement thermique d'une batterie Li-ion, ont pu être enrichies, en particulier pour les cellules commerciales LFP/C cylindriques A123s, LifeBatt, et pour les cellules NMC/C prismatiques en sachet souple PurePower (30 Ah). Cette étude ouvre de nouvelles possibilités pour améliorer la prédiction des différents événements qui ont lieu lors de l'emballement thermique des batteries Li-ion, à différentes échelles.

Oral-facial-digital type I syndrome (OFDI) is characterised by an X-linked dominant mode of inheritance with lethality in males. Clinical features include facial dysmorphism with oral, dental and distal abnormalities, polycystic kidney disease and central nervous system malformations. Considerable allelic heterogeneity has been reported within the OFD1 gene, but DNA bi-directional sequencing of the exons and intron-exon boundaries of the OFD1 gene remains negative in more than 20% of cases. We hypothesized that genomic rearrangements could account for the majority of the remaining undiagnosed cases. Thus, we took advantage of two independent available series of patients with OFDI syndrome and negative DNA bi-directional sequencing of the exons and intron-exon boundaries of the OFD1 gene from two different European labs: 13/36 cases from the French lab; 13/95 from the Italian lab. All patients were screened by a semiquantitative fluorescent multiplex method (QFMPSF) and relative quantification by real-time PCR (qPCR). Six OFD1 genomic deletions (exon 5, exons 1-8, exons 1-14, exons 10-11, exons 13-23 and exon 17) were identified, accounting for 5% of OFDI patients and for 23% of patients with negative mutation screening by DNA sequencing. The association of DNA direct sequencing, QFMPSF and qPCR detects OFD1 alteration in up to 85% of patients with a phenotype suggestive of OFDI syndrome. Given the average percentage of large genomic rearrangements (5%), we suggest that dosage methods should be performed in addition to DNA direct sequencing analysis to exclude the involvement of the OFD1 transcript when there are genetic counselling issues.