Showing papers by "University of Montpellier published in 1984"
TL;DR: In this article, the thermodynamics of stressed crystals that can change phase and composition are examined with particular attention to hypotheses used and approximations made, and the effects of vacancies, and their equilibrium within a solid and near surfaces are critically examined and previous formulas are found to be first order approximation.
Abstract: The thermodynamics of stressed crystals that can change phase and composition is examined with particular attention to hypotheses used and approximations made. Bulk and surface conditions are obtained and for each of them practical expressions are given in terms of experimentally measurable quantities. The concept of open-system elastic constants leads to the reformulation of internal elastochemical equilibrium problems into purely elastic problems, whose solutions are then used to compute the composition distribution. The atmosphere around a dislocation in a cubic crystal is one of several examples that are completely worked out. The effects of vacancies, and their equilibrium within a solid and near surfaces are critically examined and previous formulas are found to be first order approximations. Consequences of the boundary equations that govern phase changes are studied with several examples. Finally, problems connected with diffusional kinetics and diffusional creep are discussed.
288 citations
TL;DR: In this paper, the authors explore the recent discoveries by Williams of unusual phase diagram features for coherent phase equilibrium and explore a model that leads to a simple formulation involving only the minimization of a polynomial free energy function that includes an elastic energy term.
238 citations
TL;DR: In this article, light scattering results obtained from Brillouin and Raman scattering experiments in a series of B 2 O 3 − x M 2 O glasses (M Li, Na, K, Rb, Cs and Tl) were extracted.
Abstract: We report light scattering results obtained from Brillouin and Raman scattering experiments in a series of B 2 O 3 − x M 2 O glasses (M Li, Na, K, Rb, Cs and Tl). Raman lines related to the internal vibrations of structural units give information on the composition and concentration dependence of the short range arrangement in the glasses. The “Boson peak” is analysed on the basis of the Martin-Brenig model. The short correlation range is lower than 10 A and increases with the cation radius. From these experiments the very low frequency light scattering (Light Scattering Excess) is extracted. The temperature dependence of the LSE intensity in pure B 2 O 3 glass as well as its variation with composition at room temperature are studied. The Theodorakopoulos-Jackle theory relates this intensity to the acoustic attenuation deduced here from Brillouin linewidth measurements. While a theoretical description of the relation between the temperature variation of both quantities agrees well with experimental results, disagreement is apparent in their composition dependence. Finally, the sound velocity plotted versus concentration gives evidence of the contradictory influence of the hardening due to the change of the boron atom coordination number and the softening related to the distortion of the network by large cations.
136 citations
TL;DR: In this article, a method of obtaining monolithic dry gels by hypercritical solvent evacuation is presented, and the influence of various parameters on the possibility of obtaining crack-free pieces is studied in some detail.
Abstract: The method of obtaining monolithic dry gels by hypercritical solvent evacuation is presented. The influence of various parameters on the possibility of obtaining crack-free pieces is studied in some detail. The influence of these parameters on the final properties of the gel is also discussed.
103 citations
88 citations
TL;DR: In this paper, the gelling times vary with the molar percentage of SiO 2, and the solvent was evacuated under hypercritical conditions in an autoclave in order to obtain aerogels free of cracks.
Abstract: The gels in the binary and ternary systems: SiO 2 B 2 O 3 , SiO 2 P 2 O 5 , SiO 2 B 2 O 3 P 2 O 5 ; were prepared by hydrolysis and polydensation of metalorganic compounds. The gelling times vary with the molar percentage of SiO 2 . The solvent was evacuated under hypercritical conditions in an autoclave in order to obtain aerogels free of cracks. The monolithicity of the aerogels is influenced by the method of preparation of the alcogels. The crystallization of BPO 4 was observed in the ternary system only. These materials can be converted into glasses by heat treatment. The structural evolution was followed by means of infrared spectroscopy and textural evolution by dilatometric measurements.
87 citations
TL;DR: U-Pb dating of zircons from two separate charnockite-granite associations from S.W. Nigeria, previously considered to be of Kibaran or Archean age, yield PanAfrican emplacement ages of 631±18 Ma and 586±5 Ma respectively when all the data points of each association are regressed together.
Abstract: U-Pb dating of zircons from two separate charnockite granite associations from S.W. Nigeria, previously considered to be of Kibaran or Archean age, yield PanAfrican emplacement ages of 631±18 Ma and 586±5 Ma respectively when all the data points of each association are regressed together. These U-Pb data on zircons do not permit a confirmation of the field-established sequence of rock emplacement within each charnockite-granite association; thus synchronous ages of 620±20 Ma (charnockite NIG 4), 634±21 Ma (charnockite NIG 7) and 621±10 Ma (granite NIG 12) are obtained for the three analyzed rocks of the Akure-Ikerre-Ado Ekiti association while those of the Idanre association yield younger but synchronous ages of 580±10 Ma (charnockite NIG 2), 593±13 Ma (charnockite NIG 3) and 587±10 Ma (granite NIG 11). The ages obtained for the rocks of the Akure-Ikerre-Ado Ekiti association very well fit the existing data on the tectonic evolution of the basement complex of Nigeria, whereas those from the Idanre area are difficult to reconcile with the current interpretation of tectonic data in this area.
72 citations
TL;DR: The degradation kinetics of a 3- acetoxymethylcephalosporin , cefotaxime sodium salt, in aqueous solution investigated by HPLC under different conditions (pH, ionic strength, temperature) and using different buffers are found to increase the degradation rates, while acetate buffer decreases the degraded rates.
61 citations
TL;DR: Call parameters studied except noise components show developmental changes that can be related to the development of the vocal tract, auditory system, and motivational valuation of the releasing situations.
Abstract: The development of cells (quantified by a series of acoustiv parameters) of (a) normal, (b) socially isolated, and (c) deafened kittens that were released in four different situation has been studied from birth to 170 days of age. All call parameters studied except noise components show developmental changes that can be related to the development of (a) the vocal tract (fundamental frequency, harmonic with maximum intensity, uper-frequency limit and frequency range, occurrence of frequency, and intensity modulations), (b) feedback control through the auditory system sound-pressure level, harmonic with maximum intensity, call-variability, and (c) motivational valuation of the releasing situations (duration). Isolated and deafened kittens displayed quantitative differences in certain call parameters compared with normal animals. Calls of deafened animals are, on the average, louder, more tonal and uniform, and differentially pitched compared with those of normal, hearing animals.
51 citations
TL;DR: Electron microscopy of the toadfish vestibular labyrinth demonstrated the usual cytoarchitectural efferent-hair cell organization with type II hair cells having efferent synaptic terminals directly onto the hair cell bodies.
46 citations
TL;DR: The pharmacokinetics of sulpiride, over the dose range tested, was therefore linear and independent of dose; the two-compartment body model proposed was validated by digital computer simulation on a small digital computer (32K).
TL;DR: In this paper, the structural evolution of the gel-glass transformation as a function of temperature was studied by DTA, X-ray diffraction and infra-red spectroscopy.
Abstract: Xerogels in the CaOAl2O3SiO2 system were prepared by hydrolysis and polycondensation reactions of metal alkoxides. The parameters governing the homogeneous gelation in the whole range of compositions were determined. The structural evolution of the gels as a function of temperature was studied by DTA, X-ray diffraction and infra-red spectroscopy. For the gel-glass transformation, the densification was followed by hot-pressing of gels of a given composition. Bloating of partially densified samples was observed by dilatometry and scanning electron microscopy.
TL;DR: In this paper, the authors derived the expressions of ac and dc conductivities and of permittivity for compensated semiconductors in the case of a Gaussian distribution of fluctuations.
Abstract: In compensated semiconductors, the occurrence of potential fluctuations which affect the local probability of ionization of deep levels cannot be ignored These fluctuations strongly change the frequency and temperature dependence of the conductivity due to carriers in the bands The expressions of ac and dc conductivity and of permittivity are derived in the case of a Gaussian distribution of fluctuations It is shown that, starting from the densities and energies of impurities in the sample, the theory leads to a very accurate description of the observed conductivity in quite different cases: semi-insulating GaAs (our data), crystalline silicon (data of Pollak and Geballe) It is demonstrated that the carriers in the band are solely responsible for the observed phenomena, provided that potential fluctuations are taken into account Band carrier conduction completely hides hopping conduction Similar conclusions are obtained from the interpretation of data of the literature as well as our data, on amorphous semiconductors It is inferred that the phenomena observed on a large variety of semiconductors merely reflect the same general effect of potential fluctuations on band carriers, rather than specific processes characteristic of the material
TL;DR: Somatostatin (SRIF) significantly inhibited the depolarization-induced release of immunoreactive thyrotropin-releasing hormone (IR-TRH) from superfused mediobasal hypothalami (MBH) containing mainly the median eminence (ME), without affecting the basal release of TRH.
TL;DR: A review of solar cell series resistance determinations from a theoretical point of view and from a confrontation with experimental results is discussed in this paper, where the cell diode model is considered to determine the limitation of each approximated method.
Abstract: A review of solar cell series resistance determinations is discussed from a theoretical point of view and from a confrontation with experimental results. The cell diode model is then considered to determine the limitation of each approximated method.
Les methodes experimentales conduisant a une determination approchee de la resistance serie d'une cellule solaire sont rapidement indiquees a travers une etude bibliographique. Lee descriptions theoriqrues sont comparees a des resultats experimentaux qui permettent de preciser les limites d'application de chaque methode.
TL;DR: In this paper, the effect of Na2O content on thermal processing variables includes evacuation of residual organic residues, decomposition of carbonates, beginning of densification (Tdb), and initiation of crystallization (Tci).
Abstract: SiO2 gels containing from 3.7 to 40 mol.% Na2O have been synthesized by the hydrolysis and polycondensation of metal organic precursors. The effect of Na2O content on thermal processing variables includes: evacuation of residual organic residues, decomposition of carbonates (Tce), beginning of densification (Tdb) and initiation of crystallization (Tci). Thermal control of the gel-glass conversion is shown to be a function of Na2O content and ΔTv = Tci − Tdb. At high Na2O content (> 33 mol.%) ΔTv is very small whereas at the Na2OSiO2 eutectic compositio it is nearly 200°C. By using this method Na2OSiO2 glasses are obtained in the range of 440–640°C.
TL;DR: The findings in two patients with ataxia, internuclear ophthalmoplegia, muscle weakness, atrophy, fasciculations, and bilateral Babinski's signs show that hyperparathyroidism may be associated with signs of severe central nervous system disease and that patients with unexplained neurological signs or symptoms should be checked for hyperparathroidism.
Abstract: Two patients, one with ataxia, internuclear ophthalmoplegia, muscle weakness, atrophy, fasciculations, and bilateral Babinski's signs, the other with dysarthria, dysphagia, muscle weakness, atrophy, fasciculations, and hyperreflexia, had elevated serum calcium and parathyroid hormone levels, establishing the diagnosis of primary hyperparathyroidism (HPT) Removal of a parathyroid adenoma in one patient and three hyperplastic parathyroid glands in the other resulted in remission of the hyperparathyroidism but left both patients with residual neurological damage Postmortem examination of the second patient showed typical features of amyotrophic lateral sclerosis The findings in these patients show that hyperparathyroidism may be associated with signs of severe central nervous system disease and that patients with unexplained neurological signs or symptoms should be checked for hyperparathyroidism
TL;DR: The noradrenergic innervation of the rat supraoptic nucleus (SON) was examined by high resolution radioautography after animals had been intracerebrally injected with [3H]noradrenaline (NA), and the possibility is discussed that at least some of the dendritic NA synapses detected in the ventral subdivision of the SON, which preferentially contains vasopressinergic perikarya, may affect the neurosecretory neurons located in the
TL;DR: Nakalimys possesses many primitive characters, but was not directly ancestral to fossil and extant Tachyoryctes of Africa, and points to interchange between eastern Africa and southern Asia earlier than 10 Ma, before a more recent period of strong faunal similarity at about the beginning of the Pliocene.
Abstract: A new genus and species, Nakalimys lavocati, is described from the Nakali locality, Kenya, of about 10 Ma. This muroid rodent is assigned to the Rhizomyidae and is most similar to Kanisamys indicus from the Miocene of Pakistan, with which it was originally considered congeneric. Nakalimys, with other rodents and vertebrates, points to interchange between eastern Africa and southern Asia earlier than 10 Ma, before a more recent period of strong faunal similarity at about the beginning of the Pliocene. Nakalimys possesses many primitive characters, but was not directly ancestral to fossil and extant Tachyoryctes of Africa.
TL;DR: This work studies here the particular class of dags having an induced partial order of width 2, and gives a characterization of such graphs with σ( G )= i, which yields immediately a polynomial algorithm to compute the jump number in this particular class.
TL;DR: Regional patterns of hibernation, body weight, plasma testosterone and thyroxine were measured in two groups of edible dormice exposed to a constant photoperiod and to either environmental temperature and irregular infradian fluctuations were observed.
TL;DR: In this article, the authors report on polarized infra-red absorption spectra of polyacetylene and deuterated polyacetylacetylene, oriented by rolling, which allows for a complete description of the optically active normal modes, and evidence of some defect modes.
TL;DR: It is concluded that organoph phosphate resistance in S54 was due to detoxification by carboxylesterase wherease organophosphate and carbamate resistance in MAURIN had a strong non-metabolic component, possibly an insensitive acetylcholinesterase.
Abstract: Three French strains of Culex pipiens L. were compared at the fourth larval instar for tolerance to organophosphate and carbamate insecticides, with and without the addition of synergists (the oxidase inhibitors piperonyl butoxide and CGA 84708) (a propynyl compound) and the carboxylesterase inhibitors triphenyl phosphate (TPP) and S,S,S -tributyl phosphorotrithioate (TBPT). The S54 strain was resistant to all the organophosphates tested (chlorpyrifos, malathion, monocrotophos and profenofos) compared to the susceptible LA VIS strain but only slightly tolerant to the two carbamates (carbaryl and naphthyl phenylcarbamate). The MAURIN strain was resistant to all the insecticides, including the carbamates, at a higher level. The action of chlorpyrifos and malathion on S54 was very strongly synergised by TBPT, less strongly by TPP and not at all by piperonyl butoxide. In fact, resistance was enhanced by piperonyl butoxide, as was resistance to monocrotophos and profenofos by CGA 84708. No synergist had much effect on the MAURIN strain, although TPP slightly increased the toxicity of malathion, and piperonyl butoxide and CGA 84708 slightly increased the toxicity of carbaryl. The toxic effect of carbaryl was also increased by the addition of extra acetone. Electrophoretic studies showed that the carboxylesterase enzyme coded by gene Est-2 0.64 (which is in linkage disequilibrium with Est-3 A and acts as a marker for it) was absent from LA VIS but present in the resistant strains; but, whereas S54 was monomorphic for the gene, MAURIN was polymorphic (frequency 0·5). It is concluded that organophosphate resistance in S54 was due to detoxification by carboxylesterase wherease organophosphate and carbamate resistance in MAURIN had a strong non-metabolic component, possibly an insensitive acetylcholinesterase.
01 Jan 1984
TL;DR: In this article, the use of two manipulators, working together in assembly tasks, is discussed, and the significance of their cooperation is discussed in terms of kinematic problems.
Abstract: This paper deals with the use of two manipulators, working together in assembly tasks, and tries to show the significance of their cooperation. It surveys some different examples of such a cooperation: kinematic problems are examined. The paper then presents experiments that have been carried out with two compliant arms; the solutions used are also developed. At the end of the paper, problems set by using two manipulators are briefly described.
01 Jan 1984
TL;DR: The particular aspect of the neuronal ER results from its highly regionalized organization: whereas the RER and Golgi complexes are rigorously confined to the perikarya and the proximal part of the dendrites, the SER is present in all neuronal sections, especially all along the d endoplasmic reticulum processes, which may extend over distances thousands of times greater than the cell body diameter.
Abstract: The concept of endoplasmic reticulum (ER) was introduced by electron mi-croscopists to designate a well-developed system of reticular membrane occurring in the internal regions of most cells. This specific intracellular membranous system is particularly important in neurons, where it forms a complex network of intraneuronal channels isolated from the surrounding neuroplasm. Three main components have generally been attributed to this intracellular membranous compartment: the rough endoplasmic reticulum (RER), the Golgi apparatus, and the smooth endoplasmic reticulum (SER). The particular aspect of the neuronal ER results from its highly regionalized organization: whereas the RER and Golgi complexes are rigorously confined to the perikarya and the proximal part of the dendrites, the SER is present in all neuronal sections, especially all along the dendritic and axonal processes, which may extend over distances thousands of times greater than the cell body diameter.
TL;DR: In order to investigate the pharmacokinetics of heptaminol in dogs, a high-performance liquid chromatographic assay of the drug was devised and it was evaluated in a general purpose validation design through analysis of variance.
01 Sep 1984
TL;DR: In this paper, a systeme de mesures automatiques commande par ordinateur nous a permis de realiser l'acquisition des donnees I-V for des conditions experimentales variables en intensite lumineuse and en temperature.
Abstract: Le fonctionnement d'une photopile en tant que generateur de puissance est equivalent a celui d'un circuit electrique comportant un generateur de courant, une combinaison de resistances, et une ou deux diodes qui figurent les exponentielles des modeles. Le modele a une exponentielle est le plus courant et est utilise par de nombreux auteurs pour obtenir les valeurs de certains elements par des methodes d'approximation. Les resultats ainsi obtenus sont confrontes ici avec ceux obtenus par des methodes d'analyse numeriques precises. Un systeme de mesures automatiques commande par ordinateur nous a permis de realiser l'acquisition des donnees I-V pour des conditions experimentales variables en intensite lumineuse et en temperature. L'evaluation de l'efficacite des modeles a une ou a deux exponentielles permet de selectionner celui qui est le plus approprie et d'envisager une simulation precise de la photopile en situation reelle.
TL;DR: Both cold and restraint stresses elicited sustained adrenocortical activation and no thyroid response to cold appeared after complete or partial neural deafferentation of the hypothalamus, indicating that cold signals were conveyed to the thyrotropic centers from peripheral and/or deep thermoreceptors through neural posterior-lateral afferents to the hypothalamic.
01 Jan 1984
TL;DR: This paper presents work currently in progress at LAMM and Dassault-Systemes in the area of computer-aided design of robots and of their environments, as well as to program trajectories and to control a process with the simulation results.
Abstract: This paper presents work currently in progress at LAMM and Dassault-Systemes in the area of computer-aided design (CAD) of robots and of their environments. Several results of previous work concerning mathematical modelling of complex mechanisms have been implemented in CATIA* (computer aided design with a three-dimensional interactive system). So far, it is possible to build robot models and to visualize their motions on a graphic display, as well as to program trajectories and to control a process with the simulation results.
TL;DR: A series of new homologous B-norbenzomorphans, the 3,5methano-2,3,4,5-tetrahydro-lH-l and 2-benzazepines inculding 7- and 8-intro or amino derivatives have been synthesized as potential CNS drugs as discussed by the authors.