Showing papers by "University of Nice Sophia Antipolis published in 1983"
TL;DR: In this article, a numerical method for investigating the possibility of blow-up after a finite time is introduced for a large class of nonlinear evolution problems, including inviscid and viscous Burgers equations.
222 citations
TL;DR: In this article, the authors presented the latest results obtained from the analysis of the full-disk Doppler shift observations obtained at the geographic South Pole in 1981, and about 80 normal modes of oscillation (l = 0-3) have now been identified.
Abstract: This paper presents the latest results obtained from the analysis of the full-disk Doppler shift observations obtained at the geographic South Pole in 1981. About 80 normal modes of oscillation (l= 0–3) have now been identified. Their frequencies range from 1886 μHz (l = l, n = 12) to 5074.5 μHz (l = 2, n = 35), and their amplitudes are as low as 2.5 cm s−1. Amplitude modulation occurs with periods of 1–2 days, and the individual oscillations appear to be excited randomly and independently. In cases where other groups have observed some of the modes identified by us, the agreement in frequency is good.
167 citations
TL;DR: It is demonstrated the possibility of controlling, practically independently, the form and indices of proton-exchanged lithium niobate guides by means of guide annealing and proton exchange in lithium-rich solutions.
Abstract: We demonstrate the possibility of controlling, practically independently, the form and indices of proton-exchanged lithium niobate guides by means of guide annealing and proton exchange in lithium-rich solutions. Experimental results are presented that indicate how one can realize specific guide designs.
132 citations
TL;DR: In this article, a three-dimensional map is proposed to model the effects of periodic forcing on a system displaying a transition to chaos through a cascade of period-doubling bifurcations.
95 citations
TL;DR: In this article, experimental melting enthalpies and entropies of a great number of salt hydrates are reviewed and/or determined by differential scanning calorimetry (DSC).
64 citations
TL;DR: It is shown that the plasma membrane of unfertilized eggs contains a permanent and reversible Na+/H+ exchanger which contributes to the regulation of pHi, and the relationship between the permanent Na+, amiloride, and H+ exchange involved in pHi regulation and the transient Na-H+ exchange occurring at fertilization is discussed.
64 citations
TL;DR: An extension of the fundamental wavelength phase-matching range for second-harmonic generation based on titanium-indiffused proton-exchanged lithium niobate guides has been demonstrated.
Abstract: An extension of the fundamental wavelength phase-matching range for second-harmonic generation based on titanium-indiffused proton-exchanged lithium niobate guides has been demonstrated. Both the theoretical basis and experimental verification are presented.
62 citations
TL;DR: The usefulness of Rous sarcoma virus (RSV) in the establishment of a neuronal clone from quail embryo neuroretina, the first time that a neuronal cell clone of defined origin has been obtained from the CNS.
Abstract: Neuroretina (NR) is an evagination of the central nervous system (CNS) which is composed of photoreceptors, glial (Muller) cells and horizontal, bipolar, amacrine and ganglion neuronal cells We describe here the usefulness of Rous sarcoma virus (RSV) in the establishment of a neuronal clone from quail embryo neuroretina When primary cultures of chick and quail embryo neuroretina cells are transformed by RSV, neuronal markers such as ribbon synapses, choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD) specific activity are present These RSV-transformed primary cultures can be established into permanent cell lines from which neuronal clones have been isolated One of them, clone QNR/D, can generate tetrodotoxin(TTX)-inhibitable action potentials on electrical stimulation, has a high GAD activity and binds monoclonal antibodies raised against chick embryo neuroretina The presence of these neuronal markers suggests that the QNR/D clone is derived from cells of the amacrine or ganglionic lineage This is the first time that a neuronal cell clone of defined origin has been obtained from the CNS The neuronal markers of the QNR/D clone are expressed at both the permissive and the non-permissive temperatures for transformation
59 citations
TL;DR: In this paper, the shape design sensitivity of a typical integral functional is determined, and explicit and computable formulas for the derivative (first variation) of the structural response and the eigenvalues with respect to the shape of a membrane are presented.
Abstract: The dependence of the static response and the eigenvalues of a membrane on its shape is characterized. A transformation function is defined to determine the shape of the membrane. Differential operator properties and transformation techniques of integral calculus are employed to show that the static response and the eigenvalues of the system depend in a continuous and differentiable way on the shape of the membrane. Explicit and computable formulas are presented for the derivative (first variation) of the structural response and the eigenvalues with respect to the shape. A rigorous proof is provided, and the shape design sensitivity of a typical integral functional is determined.
56 citations
TL;DR: In this paper, the authors reported a 45 dB amplification gain of a laser diode signal emitting at 1.24?m, in a single-mode fiber, with low pump power, using the stimulated Raman scattering effect.
Abstract: The letter reports, for the first time, a 45 dB amplification gain of a laser diode signal emitting at 1.24 ?m, in a single-mode fibre, with low pump power, using the stimulated Raman scattering effect.
54 citations
TL;DR: It is concluded that Na+ channels in muscle surface and T-tubular membranes have different toxin-binding properties, which must reflect a difference in molecular structure.
Abstract: The effect of ethylenediamine derivatives of tetrodotoxin (en TTXI and en TTXII) on frog skeletal muscle was studied both electrophysiologically and biochemically. Electrophysiological experiments with one of these molecules (enTTXI) showed that the concentrations needed to block the early phase of the inward sodium current (K
0.5=7 nM) are much lower than those needed to block the late phase of inward current or muscle contraction (K
0.5=40 mM). Conversely, tubular Na+ channels are more sensitive to enTTXII than are surface Na+ channels. Toxin binding to isolated muscle membranes was studied using3H-enTTXI and3H-enTTXII. The first derivative (3H-enTTXI) has a higher affinity (K
d=8 nM) for Na+ channels in the surface membrane than for Na+ channels in the T-tubular membrane (K
d> 20 nM). In contrast,3H-enTTXII has a higher affinity for the tubular Na+ channel (K
d=0.2 nM) than for the receptor in surface membranes (K
d=4 nM). We conclude that Na+ channels in muscle surface and T-tubular membranes have different toxin-binding properties, which must reflect a difference in molecular structure.
TL;DR: Calcium depletion in either medium seems to increase the calcium permeability, and no correlation was found between Ca-ATPase activity in the gill tissue and calcium uptake in freshwater-adapted fish.
Abstract: Extraintestinal calcium influxes were measured in the killifish, Fundulus heteroclitus, in solutions with different calcium concentrations, from distilled water level (near 0) to seawater level (approximately 12 mM). The extraintestinal influx is modified by the concentration of calcium in the medium during the adaptive period. In freshwater-adapted fish, calcium depletion resulted in an increase in calcium uptake. Such an adaptation was not observed in calcium-depleted fish in artificial calcium-deficient seawater. Calcium depletion in either medium seems to increase the calcium permeability. No correlation was found between Ca-ATPase activity in the gill tissue and calcium uptake.
University of Maryland, College Park1, University of Southampton2, Ateneo de Manila University3, University of Oxford4, Rutgers University5, University of Bremen6, University of Nice Sophia Antipolis7, University of California, Davis8, Darmstadt University of Applied Sciences9, Université libre de Bruxelles10, State University of New York System11, Claremont Graduate University12, Royal Institute of Technology13, Clemson University14, Rensselaer Polytechnic Institute15, Oklahoma State University–Stillwater16
TL;DR: Since 1970, the number of U.S. college and university students choosing to major in mathematics has declined sharply as discussed by the authors, and many conjectures about the causes of this decline have been made.
Abstract: Since 1970 the number of U.S. college and university students choosing to major in mathematics has declined sharply. There are several sources of data describing this decline and many conjectures about the causes. The situation is summarized in two sections of the paper below.
TL;DR: Data obtained on 88 patients with refractory anemia or preleukemia, without previous cytotoxic treatment, showed medullar chromosomal abnormalities in 32% and a high frequency of acute transformation was observed in patients with abnormal clones.
TL;DR: Results indicate that Chinese hamster lung fibroblasts possess at least two types of IGF receptors, an insulin-insensitive IGF receptor with high affinity for MSA which apparently mediates its biological effect, and an IGF-I receptor which appears to exert its mitogen-potentiating activity in CC139 fibroblast by interacting with the IGF- I receptor.
TL;DR: The data demonstrate that long-term effects of insulin on lipid synthesis can be dissociated from its effect on cell growth, and the Ob17 cell line should be a useful model to study the role of insulin in the regulation of lipid synthesis in adipose cells.
TL;DR: In this paper, a large class of mean-field spin-glass models is solved by two methods: ergodicity hypothesis for the random variables which enter in the definition of the coupling constants and the well-known $n$-replicas trick.
Abstract: A large class of mean-field spin-glass models is solved by two methods. The first one uses an ergodicity hypothesis for the random variables which enter in the definition of the coupling constants. The second method is the well-known $n$-replicas trick. The comparison of these two methods when applied to a limit Hamiltonian of the class gives new insights on the Sherrington-Kirkpatrick model and on the breaking of the replicas' symmetry.
TL;DR: It is demonstrated that degenerative changes are extensively present in membranes that rupture prematurely, particularly before the onset of premature labour, and a role for plasminogen in membrane rupture is suggested.
TL;DR: The results reveal that fluctuations in the lengths of mature leaves arise from variations in the speed of growth and in the length of the growth period during the course of a year, and could be connected with a drop in photosynthesis and absorption induced by physical environmental conditions.
Abstract: The growth of leaves and roots of Posidonia oceanica (L.) Delile was studied in order to explain seasonal variations observed in the mean length of the leaves. From July 1977 to November 1978 a colony of P. oceanica off the coast of Cape Croisette, in Cannes, France, was sampled and tagged at regular intervals. The collection area was about 1 ha. The results reveal that fluctuations (20 to 70 cm) in the lengths of mature leaves arise from variations in the speed of growth and in the length of the growth period during the course of a year. New leaves in autumn attain a maximum length of 70 cm in July, with a total life-span of 9 mo; however, new leaves at the end of spring reach a maximum length of only 20 cm in October with a shorter life-span of 3 to 4 mo. The roots also display seasonal differences in growth and development. The causes of the seasonal variations are discussed. The slower growth of the leaves during the warm season could be connected with a drop in photosynthesis and absorption induced by physical environmental conditions and in particular the abundance of epiphytes on the leaves during summer.
TL;DR: The HGFu cell line seems to be a useful model for the study on a long term basis of the mechanisms of action both of insulin and triiodothyronine and will make it possible to realize comparative studies between clonal lines established from the lean adult mouse (HGFu line) and from the genetically obese adult mice (Ob17 line).
Abstract: A clonal cell line has been established from the epididymal fat pad of the C57 BL/6J +/? mouse. This line, designated HGFu, is aneuploid and exhibits both morphological and biochemical properties characteristic of mature adipocytes. Adipose conversion begins after confluence and is accompanied by (a) an early emergence of lipoprotein lipase, (b) an increase in the incorporation of [14C]acetate into lipids and in the activities of acid:CoA ligase and glycerol-3-phosphate dehydrogenase, (c) a 27- to 35-fold increase in the average triglyceride content per cell. In the presence of a β-agonist (isoproterenol) a full lipolytic response (measured by fatty acid release) is observed with differentiated cells, whereas the responsiveness examined by cyclic AMP (cAMP) production is present both in undifferentiated and differentiated cells. Adipose conversion, estimated by activities of enzyme markers, is accelerated by the continuous presence in the culture medium of insulin and triiodothyronine both within their physiological range of concentrations, whereas insulin at supraphysiological concentrations shows a growth promoting activity. The concentrations of insulin and triiodothyronine required for half-maximal lipogenic effects are in agreement with the Kd values of their respective high affinity binding sites present in HGFu cells. The HGFu cell line seems to be a useful model for the study on a long term basis of the mechanisms of action both of insulin and triiodothyronine. Moreover it will make it possible to realize comparative studies between clonal lines established from the lean adult mouse (HGFu line) and from the genetically obese adult mouse (Ob17 line).
TL;DR: It is found that under standard conditions of serum or growth factor removal (30 hr), A71 cells maintain a metabolically elevated growth‐arrested state, different from that of their nontumoral counterparts, and much lower concentrations of growth factors are needed to induce a proliferative response in these tumoral cells.
Abstract: The Chinese hamster lung fibroblast line, CCl39, displays the properties characteristic of normal secondary cultures of Chinese hamster fibroblasts including: reversible G0 growth arrest (less than 2% labeled nuclei), anchorage dependence, and high serum-growth factor dependence. Injection of CCl39 cells, or anchorage-independent variants, in nude mice leads to tumor formation; however, as we have previously shown (Perez-Rodriguez et al., 1981b), the resulting tumor clones no longer possess the high serum dependence of injected CCl39 cells. Hormonal growth restraints imposed by the host create an in vivo selection for diminished, or "relaxed," growth factor requirement. To characterize this growth factor "relaxation" further, we have analyzed the mitogenic response of parental CCl39 cells, anchorage-independent clones, and selected tumoral derivatives, to purified growth factors. Two highly purified growth factors, thrombin and insulin, together fulfill the growth factor requirements of CCl39 cells; thrombin (1 U/ml) stimulates the reinitiation of DNA synthesis in G0-arrested CCl39 cells, and insulin (10 micrograms/ml) maximally potentiates this stimulation to the level obtained with 10% fetal calf serum. First, we found no correlation between loss of anchorage dependence and growth factor relaxation. Second, we found that A71 (anchorage independent), a tumoral variant of CCl39 capable of growth arrest, and tumor-derived cells all display an increased sensitivity to thrombin and a diminished requirement for the potentiating action of insulin. Examination of thrombin binding to CCl39, A51 (nontumoral, anchorage independent), and A71 cells revealed that the increased sensitivity to thrombin of A71 cells is not attributable to an alteration in thrombin cell surface receptor number or affinity for thrombin. Rather, under standard conditions of serum or growth factor removal (30 hr), A71 cells maintain a metabolically elevated growth-arrested state, different from that of their nontumoral counterparts. Consequently, much lower concentrations of growth factors are needed to induce a proliferative response in these tumoral cells.
TL;DR: These studies indicate that the sulphonylureas tested do not have a direct effect on insulin receptors in hepatocytes; and that, in vitro, they do not alter the post-receptor events involved in the insulin-induced stimulation of amino acid transport in these cells.
Abstract: The effects of four sulphonylureas (gliclazide, glibenclamide, chlorpropamide and glipizide) on insulin binding and insulin action were studied in vitro using primary cultured rat hepatocytes. Cells were cultured for 20 h in the absence or presence of the sulphonylurea. The binding of insulin to rat hepatocyte monolayers was not altered in cells previously exposed to gliclazide at 0.7, 7.0 or 70 μg/ml; and to glibenclamide, chlorpropamide, or glipizide at 0.1, 1.0 and 10 μg/ ml. Insulin-induced down regulation was not affected by a simultaneous exposure of hepatocyte monolayers to any of the four agents. The stimulatory effect of insulin on α-aminoisobutyric acid uptake by the cells was not modified following exposure to the drugs. These studies indicate that the sulphonylureas tested do not have a direct effect on insulin receptors in hepatocytes; and that, in vitro, they do not alter the post-receptor events involved in the insulin-induced stimulation of amino acid transport in these cells.
TL;DR: In this article, the authors discuss the seismic stratigraphy and define the shallow geological structure of this complex area of the northern Ionian Sea, including the Taranto valley and the Apulian slope.
TL;DR: In this article, a simulation of a parametric pumped pendulum is presented in the framework of two-dimensional invertible mappings, where the scenario leading to chaos via a period-doubling bifurcations is sometimes interrupted by an odd-period Bifurcation.
TL;DR: In this article, the cholesteric pitch P of lyotropic mesophases of hydroxypropyl-cellulose is determined from optical measurements, i.e., angular dependence of the scattered light intensity and transmission spectra.
Abstract: The cholesteric pitch P of lyotropic mesophases of hydroxypropyl-cellulose are determined from optical measurements, i.e., angular dependence of the scattered light intensity and transmission spectra. The observed results are explained with help of Pincus’ theory for cholesteric liquid crystals. The variations of the twisting power with physical parameters such as polymer concentration C, nature of solvent, molecular weight, and ageing are investigated. The power law P = P oC−α is well satisfied for all polymer solvent combinations. It is proposed that the solvent could influence the cholesteric pitch not only through its intrinsic properties, but also through modifications of the macromolecular characteristics themselves.
TL;DR: Thrombin action in platelets and growth factor-induced mitogenesis, share common post-receptor molecular events, as well as a rapid 4- to 6-fold increased phosphorylation of a peptide with apparent Mr = 27,000 in SDS-PAGE.
TL;DR: It is shown that fresh amniotic epithelial cells which are negative by indirect immunofluorescence for HLA and Trf receptors become positive for both of these markers following prolonged culture and that markers of normal extra-embryonic epithelium in vivo are lost after the cells have been cultured in vitro.
TL;DR: In this paper, a systematic on-line cesium mass separation from A=122 to A=132 and subsequent gamma and electron decay spectroscopy at very low energy, new isomers have been precisely identified:122mCs (T1/2=0.36±0.02 s),124mCs(T 1/2 =6.3± 0.2 s), and130mCs
Abstract: By a systematic on-line cesium mass separation fromA=122 toA=132 and subsequent gamma and electron decay spectroscopy at very low energy, new isomers have been precisely identified:122mCs (T1/2=0.36±0.02 s),124mCs (T1/2=6.3±0.2 s) and130mCs (T1/2=3.46±0.06 min). Detailed level schemes are given for both124mCs and130mCs. Comparison of excited levels known in the odd-odd nuclei of the same region shows that more experimental informations are needed to propose a clear and realistic picture of the nuclear states structure.