Showing papers by "University of Montpellier published in 1982"
TL;DR: In this paper, the conditions of gel formation which determine the structure of the wet gel are first examined, and it is shown that, among the various methods of obtaining monolithic gels, that based on the hypercritical evacuation of the solvent is the most reliable.
Abstract: The synthesis of glasses from gels has recently aroused considerable interest both from the theoretical and practical standpoint. The conditions of gel formation which determine the structure of the wet gel are first examined. During the drying process, which is a decisive step in the obtention of monolithic gels, an essential role is played by capillary forces. It is shown that, among the various methods of obtaining monolithic gels, that based on the hypercritical evacuation of the solvent is the most reliable.
324 citations
TL;DR: In this article, the equilibria of small solid particles embedded in a solid matrix are considered, and three interface quantities are of significance; an interfacial free energy representing the work of creating the interface and two interfacial stresses.
205 citations
TL;DR: The age of the trans-Himalayan calkalk-alkaline magmatism has not been clearly established: on the basis of geological control, it is possible to infer a pre-late Cretaceous age for the plutonites at the southern edge of the batholith belt, and a late-Cretaceous or younger age for lava series on the top and/or to the north of the plutons as mentioned in this paper.
Abstract: The age of the trans-Himalayan calk-alkaline magmatism has not been clearly established: on the basis of geological control, it is possible to infer a pre-late Cretaceous age for the plutonites at the southern edge of the batholith belt, and a late Cretaceous or younger age for the lava series on the top and/or to the north of the plutons. K–Ar radiometric data previously obtained by Chinese groups agree with these geological ages. The 39Ar–40Ar method has been used to analyse more accurately some of the rocks which have been sampled during the joint French–Chinese field work in southern Tibet in the summer of 1980:the incremental degassing of argon gives generally more information about the thermal history of the sample. Using this method we now show that the earlier basic plutons of the southern edge of the trans-Himalayan belt have ages of 90–110 Myr (Albian to Cenomanian), whereas the lavas of the upper unconformable series are clearly younger (60 Myr, Palaeocene). The Ladakh and Kohistan magmatic belts further west are probable equivalents of the trans-Himalaya, north of the Indus suture. Their precise ages are also poorly known: Orbitolinas of middle Cretaceous (Aptian) age have been found in the Drosh–Yasin series which lie unconformably on dioritic plutons in the northern edge of the belt. The few radiometric data that are available give ages in fairly good agreement with those we have obtained in the trans-Himalaya. So we conclude that a subduction zone has been active during the Cretaceous between India and Asia. The only outstanding question is whether this active margin was, at that time, close to India, or to Asia, or somewhere in between.
100 citations
TL;DR: The European longtailed house mouse in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations.
Abstract: The European longtailed house mouse (M. m. brevirostris and domesticus) in the Rhaetian Alps and Lombardia presents a complex system of Robertsonian (Rb) variation and karyotype diversity, several adjoining populations homozygous for multiple Rb metacentric chromosomes, sites of coexistence of different Rb types, and zones of hybridization with non-Rb populations. The original "tobacco mouse" is just one of many local Rb variants, such as those from other Alpine areas (e.g., Orobian Alps) or from Central Lombardia, where a relatively large region within which the population is homogeneous for multi-Rb metacentrics is found. The present study is based strictly on material in which the chromosome arms were identified by G-banding, so that karyotypes within the areas under investigation could be compared. Altogether 111 mice were studied.
91 citations
TL;DR: The location in time and space of the terminal mitoses of type I and type II sensory hair cells of the developing crista ampullaris in rat lateral semicircular canal and macula utriculi was determined by radioautographs of specimens exposed to tritiated thymidine.
Abstract: The location in time and space of the terminal mitoses of type I and type II sensory hair cells (HCI and HCII) of the developing crista ampullaris in rat lateral semicircular canal and macula utriculi was determined by radioautographs of specimens exposed to tritiated thymidine from the 13th to the 20th day of gestation. Qualitative analysis and statistical treatment of the percentages of labeled HCI and HCII show that the terminal mitoses occur first in the macula utriculi with a maximum percentage of the 14th day of gestation, for the HCI, and on the 15th day of gestation, for the HCII. In the lateral crista, the maximum percentage of labeled HCI occurs on the 17th and 18th day of gestation and on the 19th day of gestation for the HCII. A spatial distribution of this labeling activity is also described: the older cells are located at the top of the crista and at the level of the striola of the macula utriculi while the younger cells are found at the bottom of the crista and on the sides of the utricle. A study of the vestibular receptors in the fetuses shows that synaptic contacts already exist on the 18th day of gestation in the macula utriculi at the level of the striola and on the 19th day at the top of the crista; the cells situated on the periphery are still immature. The first hair cells to undergo their terminal mitoses are, therefore, connected first. These results also suggest that the two types of cells are genetically programmed and that the HCI start functioning first during the development of the labyrinth.
91 citations
TL;DR: In this article, it was shown that the crystallization was strongly influenced by the amount of alkali oxides present in the gel and the effect of additives such as boric anhydride.
Abstract: Silica gels were prepared by two different methods: (1) destabilization of a silica hydrosol (gel 1); (2) hydrolysis and polycondensation of a tetra-methoxysilane (gel 2). The crystallization of the gels was then studied as a function of the temperature by means of X-ray diffraction. It was evident that the crystallization was strongly influenced by the amount of alkali oxides present in the gel. It is effectively the concentration of akali impurities which could explain the lower temperature of crystallization necessary for gel 1 compared with that of gel 2. During the crystallization of the gel containing Na2O the crystalline phase of silica which appears first is the cristobalite; with Li2O it is quartz. The effect of additives such as boric anhydride was studied. This oxide was found to reduce the tendency of the gels to crystallize. The glasses of the system SiO2B2O3 obtained by the hot-pressing of the gels confirmed this phenomenon. Above 10 mol% B2O3 it was impossible to crystallize the gels and the glasses of this system under two hours.
90 citations
TL;DR: Evidence for a nervous connection between the brain and the pineal organ in the guinea-pig is shown and light-induced damage to photopic and scotopic mechanisms in the rat depends on rearing conditions.
Abstract: 75 G.A. Groos and D. van der Kooy, Functional absence of brain photoreceptors mediating entrainment of circadian rhythms in the adult rat. Experientia 37, 71-72 (1981). 76 B. Rusak and I. Zucker, Neural regulation of circadian rhythms. Physiol. Rev. 59, 449-526 (1979). 77 D.C. Klein and R.Y. Moore, Pineal N-acetyltransferase and hydroxyindole-O-methyltransferase: Control by the retinohypothalamic tract and the suprachiasmatic nucleus. Brain Res. 174, 245-262 (1979). 78 W.B. Quay, Pineal homeostatic regulation of shifts in the circadian activity rhythm during maturation and aging, Trans. N.Y. Acad. Sci. 34, 239-254 (1972). 79 F.A. Kincl, C.C. Chang and V. Zbuzkova, Observations on the influence of changing photoperiod on spontaneous wheel-running activity of neonatally pinealectomized rats. Endocrinology 87, 38-42 (1970). 80 J.S. Finkelstein, F.R. Baum and C.S. Campbell, Entrainment of the female hamster to reversed photoperiod: Role of the pineal. Physiol. Behav. 21, 105-111 (1978). 81 N. Dafny, Electrophysiological evidence of photic, acoustic and central input to the pineal body and hypothalamus. Exp. Neurol. 55, 449-457 (1977). 82 N. Dafny, Photic input to rat pineal gland conveyed by both sympathetic and central afferents. J. neural Transmission 48, 203-208 (1980). 83 H.-W. Korf and U. Wagner, Evidence for a nervous connection between the brain and the pineal organ in the guinea-pig. Cell Tissue Res. 209, 505-510 (1980). 84 D. Birch and G.H. Jacobs, Effects of constant illumination on vision in the albino rat. Physiol. Behav. 19, 255-259 (1977). 85 D.G. Birch and G.H. Jacobs, Light-induced damage to photopic and scotopic mechanisms in the rat depends on rearing conditions. Exp. Neurol. 68, 269-283 (1980). 86 K.V. Anderson and W.K. O'Steen, Black-white and pattern discrimination in rats without photoreceptors. Exp. Neurol. 34, 446-454 (1972). 87 J. Dunn, R. Dyer and M. Bennett, Diurnal variation in plasma corticosterone following long-term exposure to continuous illumination. Endocrinology 90, 1660-1663 (1972). 88 C.R.S. Machado, A. B. M. Machado and L.E. Wragg, Circadian serotonin rhythm control: Sympathetic and nonsympathetic pathways in rat pineals of different ages. Endocrinology 85, 846-848 (1969). 89 C.R.S. Machado, L.E. Wragg and A.B.M. Machado, Circadian rhythm of serotonin in the pineal body of immunosympathectomized immature rats. Science 164, 442 443 (1969). 90 L. Wetterberg, E. Geller and A. Yuwiler, Harderian gland: An extraretinal photoreceptor influencing the pineal gland in neonatal rats? Science 167, 884-885 (1970). 1021
82 citations
TL;DR: In this paper, the structural analogy between the gels and the corresponding glasses was shown by X-ray diffraction and IR spectroscopy, following their structural evolution during ageing.
Abstract: The gels of the binary system Na2OSiO2 are difficult to prepare under reproducible conditions because of the catalytic effect of the OH− ions. The gels were prepared in the whole range of composition which corresponds to the vitrification range. The structural analogy between the gels and the corresponding glasses was shown by X-ray diffraction and IR spectroscopy. The problems related to the preparation of these gels were studied, following their structural evolution during ageing. The action of atmospheric agents. (CO2 and H2O) induces a crystallization of carbonate compounds. The crystalline phase which appears is Na3H(CO3)2 2H2O in the case of gels containing less than 25 mol% Na2O. For a higher sodium content the compound which crystallizes is Na2CO3H2O. The interaction between the atmosphere and the gel starts at the “surface” of the samples as observed by the IR reflection spectroscopy.
78 citations
TL;DR: In this article, the possibility of converting a gel into glass by sintering depends on a competition between the phenomena which lead to densification and those which promote crystallization, and it is shown that in the case of gels, a heterogeneous nucleation mechanism is active which explains the variations of behaviour observed for gels prepared by different techniques.
Abstract: The possibility of converting a gel into glass by sintering depends on a competition between the phenomena which lead to densification and those which promote crystallization. Sintering kinetics are presented for a close-pore texture and an open-pore texture and the influence of various parameters is discussed. The devitrification versus compaction problem is studied using TTT diagrams. It is shown that in the case of gels, a heterogeneous nucleation mechanism is active which explanins the variations of behaviour observed for gels prepared by different techniques.
53 citations
25 citations
TL;DR: In this article, the mechanism of controlled crystallization of the AsGe-Se system glass nucleated by single nucleant (ZrSe2) and mixed nucleants (Z rSe2 + SnSe) has been studied.
Abstract: The mechanism of controlled crystallization of the AsGeSe system glass nucleated by single nucleant (ZrSe2) and mixed nucleant (ZrSe2 + SnSe) has been studied. With both nucleants new glass-ceramics of high toughness and sag point were prepared, but the mechanism of catalysed crystallization was different. With ZrSe2 only heterogeneous nucleation occurred. This consists of a two-step process, first ZrSe2 substrates precipitate from the initial supersaturated glass and then GeSe2 crystal nucleation and growth occur on the ZrSe2 substrates. With mixed nucleants a phase separation into two amorphous phases (a SnSe-rich phase and a SnSe-poor phase) was observed as the first step which is followed by crystallization of the SnSe-rich phase. The major crystalline phases obtained during heat treatment were GeSe2 and SnSe. The effect of different nucleants on the microstructure and thermomechanical properties of glass-ceramics is also discussed.
TL;DR: In this paper, a reproducible method for obtaining monolithic gel samples of 33 mol% Na2O-67 mol% SiO2 (33N) was described based upon hydration and polycondensation reactions of SiO(CH3)4 and NaOCH3.
Abstract: It is difficult to prepare gels of the binary Na2OSiO2 system because the presence of OH− ions promotes quick and controlled gellation. A reproducible method for obtaining monolithic gel samples of 33 mol% Na2O-67 mol% SiO2 (33N) is described based upon hydration and polycondensation reactions of SiO(CH3)4 and NaOCH3. Conversion of the dried gels to glasses and glass-ceramics is followed by the evolution of physicochemical properties and by comparing infrared reflection structural features of the gel-derived glasses with conventional melt-derived glasses. Densification in gel-glass transformation in the range from 490–520°C produces non-porous glass monoliths with density and structure equivalent to melt-derived 33N glasses. At higher temperatures (520°C) uncontrolled crystallization occurs.
TL;DR: In this paper, the appearance of lignin is closely correlated with variations of covalently bound peroxidases and especially with one isoenzyme which is specific for lignifying tissues.
TL;DR: The mean firing rate of regularly firing units was always higher than the two other categories of unit throughout all the stages of development in the cat and was compared with similar work performed in the rat.
Abstract: The spontaneous activity of primary vestibular neurons was studied during postnatal development in the cat. Activities were categorized as regular, intermediate and irregular on the basis of the coefficient of variation. At birth, few regularly firing units were found while the percentage of intermediate and irregular units was high. During development, the percentage of units meeting the criterion of regularity increased steadily with age. At the same time the number of intermediate and irregular units decreased. The average resting rate of all categories of unit showed an increase in firing from birth up to the adult stage, i. e., around the second postnatal month. The mean firing rate of regularly firing units was always higher than the two other categories throughout all the stages of development. These results were compared with similar work performed in the rat.
TL;DR: The effect of the differently charged cations Na+, Mg2+, spermidine and spermine on the acetylation of histones in vitro in soluble chromatin and in core particles was investigated and the role chromatin structure plays in determining the specificity of histone acetylations is discussed.
Abstract: The effect of the differently charged cations Na+, Mg2+, spermidine and spermine on the acetylation of histones in vitro in soluble chromatin and in core particles was investigated. Up to a given concentration, which depends on the charge of the cation, all four cations activate the acetylation of these fractions. Above this critical concentration a gradual inhibition of the acetyltransferase activity occurs.
Spermine, spermidine and Mg2+, but not Na+, affect the relative accessibilities of the acetyltransferase to the individual histones. As the concentration of these three polyvalent cations increases there is a gradual increase in the relative acetyl incorporation in histone H3 accompanied by a corresponding decrease in H4.
Kinetic aspects of the system were also studied. A minor fraction of the soluble chromatin (mononucleosomes and dinucleosomes) which is preferentially digested by micrococcal nuclease is also acetylated preferentially. The role chromatin structure plays in determining the specificity of histone acetylation is discussed.
TL;DR: The effects of neonatal hypothyroidism on the development of cytoplasmic oestradiol-binding sites were studied in the hypothalamus, pituitary and uterus of the rat and thyroid hormones appear to stimulate oest radiol binding-site levels directly rather than indirectly via plasma oestrogen titres.
01 Jan 1982
TL;DR: Although most pituitary hormones are producedin pulsatile sequences of varying frequencies, a fairly stable circadian secretory pattern usually emerges from this episodic background, which raises the first basic question applying to all circadian rhythms, as to whether neuroendocrine circadian rhythms are primarily driven by an endogenous, environmentally entrained oscillator or circadian pacemaker.
Abstract: Although most pituitary hormones are producedin pulsatile sequences of varying frequencies, a fairly stable circadian secretory pattern usually emerges from this episodic background. This raises the first basic question applying to all circadian rhythms, as to whether neuroendocrine circadian rhythms are primarily driven by an endogenous, environmentally entrained oscillator or circadian pacemaker. So far, the existence of such a pacemaker generating an overt neuroendocrine rhythm has only been clearly demonstrated in the pineal (Moore and Klein 1974) and in the adrenocorticotropic system. For the latter, the period of freerunning Cortisol rhythm was thus estimated at 24.8 h in blind men (Wever 1979), and for freerunning ACTH and corticosterone rhythms, it ranged from 24.2 h to 24.4 h in blind or dark-housed (DD) rats (Szafarczyk et al. 1980a, 1981b).
TL;DR: Biochemical analysis of polychaete annelids from the English Channel and the Atlantic Coast has shown that they represent two genetically isolated species, Ophelia bicomis and O. radiata, characterized by different alleles at four loci and a mean number of 15 and 14 pairs of gills, respectively.
TL;DR: An analog of PAF-acether which contains a short spin-labeled acyl chain at position 2 is described which exchanges freely between serum albumin, model membranes and micelles and mixes as easily with rigid or fluid membrane regions.
Abstract: The paper describes the synthesis of an analog of PAF-acether which contains a short spin-labeled acyl chain at position 2. This product exchanges freely between serum albumin, model membranes and micelles (CMC <0.3 μM). It mixes as easily with rigid or fluid membrane regions. The probe is localized near the interface between lipid or protein and water.
TL;DR: The allozyme polymorphism at 28 loci was examined in four Indonesian species of Rattus and in two French species (R. rattus and R. norvegicus), and genetic relationships between the six species were established using two different methods.
TL;DR: Using spectroscopic data (I.R., Raman), the authors built a dynamical model for an infinite cis polyacetylene chain, which allows an assignement of Raman frequencies and discussion of experimental results.
Abstract: Using spectroscopic data (I.R., Raman), we have built a dynamical model for an infinite cis polyacetylene chain. This model allows an assignement of Raman frequencies and discussion of experimental results.
TL;DR: There is a widespread need for a common international notation in biological wastewater treatment as discussed by the authors, and the efforts of a working group set up by the IAWPR and IUPAC are described.
TL;DR: The Bodian method showed in the remaining cortical neuronic population, the existence of voluminous intracytoplasmic aggregates and the hypertrophy of the dendritic apparatus.
Abstract: The neuropathologic study of an alcoholic cirrhotic encephalopathy was made after the fixation of the brain by immersion in a solution specially prepared for the electronic microscopy. The histological technics were used then, the Golgi-Cox method among others, confirmed the classic notions of neuronal rarefaction and of the proliferation of the glia cells, particularly in the cerebral cortex. The Bodian method for its part showed in the remaining cortical neuronic population, the existence of voluminous intracytoplasmic aggregates and the hypertrophy of the dendritic apparatus.
TL;DR: From the aerial parts of Artemisia mesatlantica, a new highly methoxylated flavone was isolated and its structure was determined by spectroscopic methods as 5,4′-dihydroxy-6,7,3′,5′-tetramethoxyflavone as mentioned in this paper.
TL;DR: Six loci were investigated in five populations of four species of sand-flies belonging to genus Sergentomyia from the Peoples Republic of Congo, and the derived dendogram is in good agreement with the ecology of these species.
TL;DR: In this article, the authors studied the crystallization of various gels of composition K 0-Al20c.-6Si02, Na20-Al2C>3-6Si2, LigOAl 0, 6si02, Li20, KNO3 and Li20.
Abstract: The gels of composition K 0-Al20c.-6Si02, Na20-Al2C>3-6Si02, LigOAl„0,-6si02 w e r e prepared following two different techniques, destabilization of a colloidal solution of silica and hydrolysis and polycondensation of S^OCHo)^. AI2O3, Ha 0, K£0, Li20 were added in the form of nitrates in aqueous solution. The crystallization of these gels was studied as a function of temperature by X-Ray diffraction. At low temperature all these gels show characteristic X Ray peaks and also I.R. bands due to the presence of different nitrates. These nitrates however decompose at higher temperatures ; consequently, the structure becomes amorphous. At more elevated temperature the gel containing KNO3 shows a weaker tendency to crystallize. The contraction of the gel was found to be important at low temperatures as observed by dilatometry measurements.
TL;DR: In this article, the authors used the sol destabilization method to obtain the ranges of gel formation in the binary systems Al2O3-SiO2 and CaO- SiO2.
Abstract: Gels in the system CaO-Al2O3-SiO2 were prepared by the sol destabilization method. Aqueous solutions of calcium and aluminium nitrate were added to a colloidal silica solution. In order to avoid a selective precipitation of calcium and aluminium hydroxide, the gelation was done at definite pH. The ranges of gel formation in the binary systems Al2O3-SiO2 and CaO-SiO2 have been established. They lie from 100 to 75 mole % SiO2 and from 100 to 25 mole % SiO2 respectively. The range of formation in the ternary system CaOAl2O3-SiO2 was displaced towards the compositions rich in calcium and gels containing up to 75 mole % CaO were prepared. The gelation time was reduced by calcium ions while the aluminium ions increased it. The structural evolution of these gels were followed as a function of temperature by X-ray diffraction. Calcium nitrate crystals occured at low temperature and decomposed as the temperature increased. This decomposition was facilited in the composition domain rich in aluminium.
TL;DR: In this paper, Brillouin and low frequency Raman scattering experiments have been performed on series of B203 xM20 glasses where M = Li, Na, K, Rb, Cs, 11.
Abstract: Brillouin and low frequency Raman scattering experiments have been performed on series of B203 xM20 glasses where M = Li, Na, K, Rb, Cs, 11. The concentration and composition dependences of the velocity and attenuation of longitudinal and transversal acoustic waves have been measured, as well as those of the Raman "boson" peak. The composition and concentration dependence of the acoustic velocity seems to result from two competitive effects : the first one is related to the transition of boron atoms from three to four coordination with increasing x and the second one to the structural changes connected to the sterical hinderance of the M" cations. The maximum frequency of the boson peak has a behaviour similar to that of sound velocity. This similarity can be understood on the basis of the continuum theory of low-frequency Raman spectrum. Introduction. The binary borate glasses B203 x M20 are currently used as vitreous matrices for the elaboration of ionic conductors. In order to understand the conduction mechanisms in ternary systems (e.g. B203 xLi 20-y LiC£ or B203 x Li20yLi2S00 (7,2,3), it is necessary in a first step, to get structural informations on the binary matrix. For this purpose we have used the Brillouin and Raman scattering techniques. The identification of the structural units of the glass can be made qualitatively from the analysis of the "high frequency" part of the Raman spectra, while Brillouin experiments can give connection between the acoustical and structural properties. Brillouin results are also of first interest for the interpretation of the so-called Boson peak which dominates the low frequency part of the Raman spectra. Following the Martin and Brenig model (4) the structural correlation range, which reflects the average size of the boron oxygen edifices, can be deduced. High frequency Raman data. The amorphous B203 x M20 systems have already been widely studied by Raman spectroscopy 11,5,6). This spectrum is dominated by two lines at 806 cm and 780-765 cm respectively due to the breathing vibration of boroxol and of six-membered rings containing BO., units (di tri tetraborate groups). By a systematic study of all alcali borate glasses (and also T£20 containing glasses) we have found different laws for the progressive disappearance of the boroxol 806 cm line with increasing values of x : the larger the ionic radius of M, the earlier the 806 cm line disappears. This is compatible with an Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19829108 C9-542 JOURNAL DE PHYSIQUE increase of the dimensions of the borate edifices with increasing s izes of M+ and can be interpreted from stoechiometric reasons by the dominant formation of tribor a t e groups i n the case of B2O3-x Li20 , and tetraborate groups for B203 X Cs20 (0 0.2) 20 does not exceed the dimension of one six-membered ring (this is for instance the case of tr iborate groups). A s the mass of the M atom increases, 20. also increases ; t h i s agrees with the formation of borate groups containing more than one six-membered rings. A detailed analysis of these resul ts w i l l be published i n a subsequent forthcoming paper. Fig.2 Low frequency Raman s p e c t r a of Fig .3 S t r u c t u r a l c o r r e l a t i o n range B203-0 ,25 M20 g l a s s e s deduced from the Martin-Brenig t h e o r e t i c a l f i t s wi th Martinmodel.