Showing papers by "University of Nice Sophia Antipolis published in 1990"
TL;DR: In this paper, it was shown that the magmatic crust is very thin and locally discontinuous in large areas of the central Atlantic Ocean and that these peculiar aspects of the present-day structure of a slow-spreading major ocean are found in the ophiolites of the western Alps as well as in the Ligurian ophilia of the Apennines.
Abstract: Recent developments in knowledge of the structure of the central Atlantic clearly indicate that the magmatic crust is very thin and locally discontinuous in large areas of this ocean. Specifically, extensive outcrops of serpentinized mantle peridotites have been discovered along the present-day spreading axis away from fracture-zone scarps. These peculiar aspects of the present-day structure of a slow-spreading major ocean are found in the ophiolites of the western Alps as well as in the Ligurian ophiolites of the Apennines. This indicates that recent interpretations of the Alpine-Apennine ophiolites as remnants of poorly evolved "abnormal" ocean basins must be reconsidered.
268 citations
TL;DR: The obtaining of a well-differentiated epidermis grown in vitro on inert filters in a chemically defined medium should be useful as a standard system for studying epidermal differentiation, re-epidermization, cytotoxicity, epidersmal permeation, and transepidermal drug delivery.
257 citations
TL;DR: It is shown that when Bloch walls become chiral, they move with a velocity simply related to their chirality, which is a straightforward consequence of nonvariational effects, which are typical of nonequilibrium systems.
Abstract: At equilibrium, Bloch walls are chiral interfaces between domains with different magnetization. Far from equilibrium, a set of forced oscillators can exhibit walls between states with different phases. In this Letter, we show that when these walls become chiral, they move with a velocity simply related to their chirality. This surprising behavior is a straightforward consequence of nonvariational effects, which are typical of nonequilibrium systems.
239 citations
TL;DR: In this article, a characterization of Zr{sub 2}(O{sup i}Pr), sub 8}(sup i)PrOH, sub 2} by {sup 1}H and {sup 13}C NMR spectroscopy, ir spectroscopic, and single-crystal x-ray diffraction is reported.
Abstract: Characterization of Zr{sub 2}(O{sup i}Pr){sub 8}({sup i}PrOH){sub 2} by {sup 1}H and {sup 13}C NMR spectroscopy, ir spectroscopy, and single-crystal x-ray diffraction ({minus}100{degree}C) is reported. The unit cell contains four half-dimers in the asymmetric unit, all of which differ only in the rotational conformation about Zr-O and O-C bonds. In each dimer, the edge-shared bioctahedron has two {mu}-O{sup i}Pr groups. On opposite sides of this Zr{sub 2}({mu}-OR){sub 2} plane, each dimer forms two hydrogen bonds, one each between a coordinated alcohol and a terminal alkoxide. The NMR spectra at 25{degree}C are so simple as to be structurally uninformative, a result of rapid fluxionality which includes, as one component, proton migration among all O{sup i}Pr units. At {minus}80{degree}C in toluene, the NMR spectra are now too complex to be accounted for by a single edge-shared bioctahedral structure. The hafnium analogue is isomorphous with the zirconium compound. Although Ce{sub 2}(O{sup i}Pr){sub 8}({sup i}PrOH){sub 2} is not isomorphous, it exhibits an analogous hydrogen-bonded structure in which the O{hor ellipsis}O distance is as short as it is in the Zr analogue, in spite of a metal-metal separation which is longer by 0.28 {angstrom}. The generality of hydrogen bonding between M-OR and M-O(H)R groups whenmore » they are aligned parallel in a metal cluster is reviewed. 44 refs., 2 figs., 4 tabs.« less
173 citations
TL;DR: Cette revue considere les donnees recentes concernant l'activite mitogenique de la serotonine and le role of ce neurotransmetteur en tant que facteur de croissance.
170 citations
TL;DR: In this article, the authors focus on a simple theory of electroseismic activity based on mechano-electrical transduction effects such as the piezoelectric or the pressure-induced polarization effect.
153 citations
TL;DR: In this article, the problem of estimating the parameters in linear continuous differential equation models from sampled data is treated using a linear integral filter, and the identification model that is parametrized directly in the continuous-time model parameters is obtained.
141 citations
TL;DR: A number of results presented allow us to interpret recent observations in hydrodynamical-flow and directional-solidification and -fingering experiments.
Abstract: Symmetry arguments are used to classify the various modes of instabilities of one-dimensional periodic patterns. An important feature of this theory is to point out the coupling between these modes and the phase of the cellular structure. A number of results presented allow to interpret recent observations in hydrodynamical flows, directional solidification, and fingering experiments.
116 citations
TL;DR: Brain endothelin‐l and endotheli‐3 have different target cells in the brain and may have different functions.
Abstract: Endothelin-I, endothelin-3, and the snake venom toxin sarafotoxin 56b stimulate the hydrolysis of phosphatidylinositol by phospholipase C with similar potencies in primary cultures of astrocytes prepared from rat brain cortex In indo I-loaded cells, endoth elin-I, endothelin-2, endothelin-3, and sarafotoxin induce the rapid mobilization of intracellular Ca2+ stores and promote a more slowly developing influx of Ca2*+ These responses were insensitive to pertussis toxin and to inhibitors of cyclooxygenase and lipoxygenase Similar actions of endothelins and sarafotoxin were observed using astrocytes from the cerebellum and glioma cells from the C6 and NN cell lines The endthelin receptor of astrocytes differs from the receptor previously characterized in endothelial cells from brain microvessels in that it has a high affnity for endothelin-3 Thus, brain endothelin-l and endothelin-3 have different target cells in the brain and may have different functions
110 citations
TL;DR: It is concluded that nucleosomes are designed to open up transiently to allow the passage of a replication fork without histone displacement.
Abstract: A well-characterized set of proteins encoded by bacteriophage T4 replicates DNA in vitro and generates replication forks that can pass nucleosomes. The histone octamers remain associated with newly replicated DNA even in the presence of excess DNA competitor, and intact nucleosomes re-form on the two daughter DNA helices. It is concluded that nucleosomes are designed to open up transiently to allow the passage of a replication fork without histone displacement.
106 citations
TL;DR: In this article, a numerical simulation of the cast film process is performed using a finite element method, where the process is assumed to be isothermal between the die exit and the quick cooling on the chill roll.
Abstract: The cast film process is studied and a numerical simulation is performed using a finite element method. Two dimensional equations involving the thickness and a mean velocity are used by considering the film as a thin layer. The process is assumed to be isothermal between the die exit and the quick cooling on the chill roll. The width of the film is computed iteratively as a free surface problem by means of a finite element method. The thickness distribution of the film is obtained by a finite volume method. This approach allows modeling of the well known “dog-bone” or “edge bead” defect with a reasonable computation time.
TL;DR: Water stress was responsible for a decrease of the cytosolic protein content of the nodule and more specifically of leghemoglobin, and the alteration of the bacteroid environment appears to contribute to the decline in N(2) fixation under water restricted conditions.
Abstract: Water potentials of leaves and nodules of broad bean (Vicia faba L.) cultivated on a sandy mixture were linearly and highly (r(2) = 0.99) correlated throughout a water deprivation of plants. A decrease of 0.2 megapascal of the nodule water potential (Psi(nod)) induced an immediate 25% inhibition of the highest level of acetylene reduction of broad bean nodules attached to roots. This activity continued to be depressed when water stress increased, but the effect was less pronounced. Partial recovery of optimal C(2)H(2) reduction capacity of mildly water stressed nodules (Psi(nod) = -1.2 megapascals) was possible by increasing the external O(2) partial pressure up to 60 kilopascals. The dense packing of the cortical cells of nodules may be responsible for the limitation of O(2) diffusion to the central tissue. Bacteroids isolated from broad bean nodules exhibited higher N(2) fixation activity with glucose than with succinate as an energy-yielding substrate. Bacteroids from stressed nodules appeared more sensitive to O(2), and their optimal activity declined with increasing nodule water deprivation. This effect could be partly due to decreased bacteroid respiration capacity with water stress. Water stress was also responsible for a decrease of the cytosolic protein content of the nodule and more specifically of leghemoglobin. The alteration of the bacteroid environment appears to contribute to the decline in N(2) fixation under water restricted conditions.
TL;DR: Efficient operation of a channel waveguide laser and aChannel waveguide amplifier in Nd:MgO:LiNbO(3) is reported, and a slope efficiency of 13% was achieved.
Abstract: We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.6 mW of absorbed pump power. The absorbed pump power at threshold was 1.5 mW, and a slope efficiency of 13% was achieved. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power.
TL;DR: Dormancy appears to be dependent on ABA synthesis but not concomitant with its accumulation; it must therefore be induced by ABA during maturation.
Abstract: Mature seeds of Helianthus annuus L. exhibit dormancy that is eliminated during storage in dry conditions. In vitro culture of immature embryos isolated at different times after anthesis showed that the youngest embryos are able to germinate, but within the third week after pollination, dormancy progressively affected most of the embryos. A radioimmunoassay showed that the endogenous abscisic acid (ABA) level, which increased sharply in the first half of the development period, fell at precisely the moment when embryo dormancy became established. An application of fluridone, before the increase of ABA level, prevented both ABA synthesis and development of embryo dormancy. Applied later, after the rise of the ABA level, fluridone could not prevent embryo dormancy development. Dormancy thus appears to be dependent on ABA synthesis but not concomitant with its accumulation; it must therefore be induced by ABA during maturation. Furthermore, a preincubation in water allowed dormant embryos to germinate. This acquisition of germinability could not be directly related to a leaching of free ABA. Possible effects of this treatment are discussed.
TL;DR: In this article, the Quillen-Suslin Theorem has been shown to have no common zero in the algebraic closure of any polynomials of maximal degree.
Abstract: Let k be an arbitrary field, X1,….,Xn indeterminates over k and F1…, F3 e ∈ k[X1…,Xn] polynomials of maximal degree (Fi). We give an elementary proof of the following effective Nullstellensatz: Assume that F1,…,F have no common zero in the algebraic closure of k. Then there exist polynomials P1…, P3 e ∈ k[X1…,Xn] such that PiFi and
This result has many applications in Computer Algebra. To exemplify this, we give an effective quantitative and algorithmic version of the Quillen-Suslin Theorem baaed on our effective Nullstellensatz.
TL;DR: Results suggest activation of the immune system during the course of proliferative vitreoretinopathy, and class II antigen expression could play a crucial role in this immune reaction, which resulted in immunoglobulin deposition and activation of complement.
TL;DR: It is proposed that lipoprotein particles have two separate effects, i.e. a ligand- induced effect leading to cholesterol translocation from intracellular stores to the cell surface and a bilayer-induced effect allowing cholesterol efflux from the cellsurface to the acceptor.
TL;DR: In this paper, two different tau-Chebyshev methods based on the vorticity-streamfunction formulation and using multistep time schemes are considered to assess the validity of the solutions.
Abstract: SUMMARY Pseudospectral methods are used for the computation of the time-dependent convective flows which arise in shallow cavities filled with low-Prandtl-number liquids when submitted to a horizontal temperature gradient. In similar situations several former numerical results have been shown to disagree about the determination of the threshold of oscillations and about the subsequent supercritical regimes. Two different tau-Chebyshev methods based on the vorticity-streamfunction formulation and using multistep time schemes are considered. Their results are discussed to assess the validity of the solutions. The physical problems concern rectangular cavities which involve either a rigid or a stress-free top wall and either conducting or insulating horizontal walls. Aside from the prediction of the onset of oscillations, which is discussed in the various situations with respect to the results of linear and non-linear analyses and to other computational results, the present study exhibits some bifurcation sequences and a hysteresis cycle at moderate Grashof numbers which are associated to the occurrence of multiple solutions.
TL;DR: In this paper, the analysis of sediments in and around the large and deep burrows made by the callianassid shrimp Callichirus laurae, Jordan Gulf of Aqaba (Red Sea), showed that organic carbon, humic matter (HM), humic (HA), and fulvic acids (FA) are redistributed both quantitatively and qualitatively by sediment reworking activities.
Abstract: Analysis of sediments in and around the large and deep burrows made by the callianassid shrimp Callichirus laurae, Jordan Gulf of Aqaba (Red Sea), showed that organic carbon (OC), humic matter (HM), humic (HA) and fulvic acids (FA) are redistributed both quantitatively and qualitatively by sediment reworking activities:
TL;DR: The algorithms are optimal from the point of view of the overall complexities in parallel and in sequential (number of processors) and the new outcomes concern parallelism where the number of processors is controlled by the intrinsic sequential complexity of quantifiers.
TL;DR: In this article, a detailed field mapping together with structural and biostratigraphic analysis have been conducted in the Ilocos Foothills, on the western flank of the Central Cordillera Cenozoic magmatic arc.
TL;DR: A technique is proposed allowing estimation of the spatial coherence outer scale, from simultaneous measurements of Fried's parameter ro and of the variance of angle-of-arrival fluctuations.
Abstract: A technique is proposed allowing estimation of the spatial coherence outer scale, from simultaneous measurements of Fried's parameter ro and of the variance of angle-of-arrival fluctuations. This optical parameter must be differentiated from the classical geophysical parameter called the outer scale of turbulence; its knowledge is important for long baseline interferometry and imaging in optical astronomy.
TL;DR: The results show that there is no primary dormancy in Z. noltii and that unfavourable environmental conditions and tegument impermeability are the factors which prevent rapid germination.
Journal Article•
TL;DR: Cell sensitization to MVMp appears to be oncogene-specific and cannot be taken as an absolute correlative with neoplastic transformation, and the failure of BPV-1 transformation to sensitize murine cells to parvoviral attack may be ascribed to the tumor virus rather than to the cells undergoing transformation.
Abstract: The rat cell line FR3T3 was transformed with the retroviral oncogenes v-myc or v-src, with the DNA tumor viruses SV40 or bovine papilloma virus strain 1 (BPV-1) or with the 69% transforming region of BPV-1. The transformants were compared with the uncloned parental line for their susceptibility to the lytic effect and to the replication of MVMp, an autonomous parvovirus. Expression of v-myc and v-src proteins and of SV40 large T antigen correlated with a greater cell susceptibility to MVMp-induced killing. Thus, the expression of both cytoplasmic and nuclear oncogene products may sensitize rat fibroblasts to MVMp. In contrast, cell lines transformed by BPV-1, including highly tumorigenic and tumor-derived clones, were on the average as resistant as the parental cell line to MVMp infection. A similar resistance to MVMp-induced killing was displayed by BPV-1-transformed NIH3T3 cells. However, supertransformation of one of the BPV-1-transformants by the human EJ-Harvey ras-1 oncogene, known to sensitize FR3T3 and NIH3T3 cells, correlated with an increase in susceptibility to MVMp. Therefore, the failure of BPV-1 transformation to sensitize murine cells to parvoviral attack may be ascribed to the tumor virus rather than to the cells undergoing transformation. Hence, cell sensitization to MVMp appears to be oncogene-specific and cannot be taken as an absolute correlative with neoplastic transformation.
TL;DR: The data show that these cell lines constitute homogeneous cell material that has retained the main differentiative, functional, and growth properties of normal astrocytes, and should be useful for further molecular studies, addressing terminal differentiation of glial cells, glioneuronal interactions, and astroglial expression of receptors for neurotransmitters.
Abstract: Permanent untransformed cell lines have been established from the cerebral cortex of transgenic mice that carry the polyoma virus large T gene. The immortalized cells described here synthesize laminin and neural cell adhesion molecules and induce primary neurons to develop neuritic processes. As shown by immunofluorescence and immunoblotting assays, they begin to synthesize the glial fibrillary acidic protein (GFAP) after confluence. Double labelling experiments indicated that GFAP expression is reversibly correlated with the arrest of cell division. The present cells also display adrenergic, serotoninergic, and high levels of muscarinic receptors coupled to the phosphatidylinositol signalling pathway. Taken together, our data show that these cell lines constitute homogeneous cell material that has retained the main differentiative, functional, and growth properties of normal astrocytes. Therefore, such clonal untransformed cell lines should be useful for further molecular studies, addressing terminal differentiation of glial cells, glioneuronal interactions, and astroglial expression of receptors for neurotransmitters. Furthermore, we suggest that this approach of cell immortalization by the use of transgenic mice carrying a non-transforming oncogene might be extended to a variety of cell types.
01 Jan 1990
TL;DR: New, well-defined surfactants and cosurfactants were synthesized with the objective of enhancing the stability of fluorocarbon emulsions destined to serve as oxygen carriers for biomedical applications, and display strong surface activity and produce a remarkable synergistic stabilization of a fluorOCarbon/Pluronic F-68 type emulsion.
Abstract: New, well-defined surfactants and cosurfactants were synthesized with the objective of enhancing the stability of fluorocarbon emulsions destined to serve as oxygen carriers for biomedical applications. Monoperfluoroalkylated ethers of xylitol were achieved by addition of perfluoroalkyl iodide on the double bond of a protected xylitol allyl ether in a one-step addition-elimination reaction. Monoesters were obtained specifically on position 5 by treating 1,2:3,4-di-O-isopropylidenexylitol with perfluoroalkylated acid chlorides of various chain lengths in pyridine at room temperature. The products display strong surface activity and produce a remarkable synergistic stabilization of a fluorocarbon/Pluronic F-68 type emulsion. Biocompatibility data are reported, which include in vitro toxicity tests on Namalva cell cultures and hemolysis tests on human blood cells; the latter was found to decrease as the length of the F-alkyl chain increased. IV injection in mice (n = 10) showed that these products were innocuous at 400-1000 mg/kg of body weight. Preliminary exchange-perfusion experiments on rats with an emulsion containing the F-octyl xylitol ether were encouraging.
TL;DR: In this article, the concentrations of Pb, Cu, Zn and Cd were measured using flameless atomic absorption spectrophotometry, which allowed the two contributions to be separated, and then, to be estimated.
TL;DR: Glycine betaine transport showed considerable structural specificity: choline, proline betaine, gamma-butyrobetaine and trigonelline did not competitively inhibit the system, although choline and prolinebetaine were transported by bacteroids, which might have a significant role in the maintenance of nitrogenase activity in bacteroids subjected to salt stress.
Abstract: SUMMARY: Bacteroids isolated from alfalfa nodules induced by Rhizobium meliloti 102F34 transported glycine betaine at a constant rate for up to 30 min. Addition of sodium salts greatly increased the uptake activity, whereas other salts or non-electrolytes had less effect. The apparent K
m for glycine betaine uptake was 8.3 μM and V was about 0.84 nmol min-1 (mg protein)-1 in the presence of 200 mM-NaCl which gave maximum stimulation of the transport. Supplementing bacteroid suspensions with various energy-yielding substrates, or ATP, did not increase glycine betaine uptake rates. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP), and the respiratory inhibitor potassium cyanide strongly inhibited glycine betaine uptake, but arsenate was totally inactive. Glycine betaine transport showed considerable structural specificity: choline, proline betaine, γ-butyrobetaine and trigonelline did not competitively inhibit the system, although choline and proline betaine were transported by bacteroids. Both a high-affinity activity and a low-affinity activity were found for choline uptake. These osmoprotective compounds might have a significant role in the maintenance of nitrogenase activity in bacteroids subjected to salt stress.