Showing papers by "University of Nice Sophia Antipolis published in 1981"
TL;DR: In this article, the authors discuss the effects of atmospheric turbulence in optical astronomy, summarizes the present state of the theory, reviews the experimental checks that have been made, and discusses the implications in the domain of astronomical observations.
Abstract: Publisher Summary This chapter discusses the effects of atmospheric turbulence in optical astronomy, summarizes the present state of the theory, reviews the experimental checks that have been made, and discusses the implications in the domain of astronomical observations. Diffraction limited resolution has been obtained with large telescopes up to magnitude 13 by means of speckle interferometry. A Michelson interferometer is already working in the visible on a 20 m baseline up to magnitude 4, and many projects are nearing completion. However, such technological progress can be useful only if accurate quantitative measurements prove to be feasible through atmospheric turbulence. In addition, much work remains to be done before achieving a full understanding of atmospheric effects. The relationship between isoplanicity or speckle boiling and the structure of the atmosphere is still not clear.
932 citations
TL;DR: In this article, a new method of inversion of the Laplace transform based on its recently discovered eigenvalues and eigenfunctions is applied to the problem of inverting light scattering data from a polydisperse molecular suspension.
Abstract: A powerful new method of inversion of the Laplace transform, based on its recently discovered eigenvalues and eigenfunctions, is applied to the problem of inverting light scattering data from a polydisperse molecular suspension.
295 citations
TL;DR: In this paper, the authors define a class of three-dimensional differential equations which might present strange attractors of a new kind, which is illustrated by numerical observations on an explicit example.
Abstract: We define a class of three-dimensional differential equations which might present strange attractors of a new kind. This is illustrated by numerical observations on an explicit example.
285 citations
TL;DR: In this paper, a Lagrangian representation of the vortex sheet analogous to the Birkhoff equation in two dimensions is presented, and the global existence of a weak solution to the Euler equation with such initial conditions is established.
Abstract: The well-posed property for the finite time vortex sheet problem with analytic initial data was first conjectured by Birkhoff in two dimensions and is shown here to hold both in two and three dimensions. Incompressible, inviscid and irrotational flow with a velocity jump across an interface is assumed. In two dimensions, global existence of a weak solution to the Euler equation with such initial conditions is established. In three dimensions, a Lagrangian representation of the vortex sheet analogous to the Birkhoff equation in two dimensions is presented.
154 citations
TL;DR: In this paper, a cascade of stable homoclinic orbits is proposed to represent the transition from chaotic behavior to chaotic behavior with strange attractors via a cascade involving bifurcations of stable stable homometrics.
114 citations
TL;DR: This work has developed an assay which does not require purified protein and is based on the specific elution of the large-T ATPase activity from calf thymus DNA cellulose by recombinant DNA molecules including known sequences of the viral DNA.
Abstract: In order to map the high affinity binding site for the viral large-T protein on polyoma virus DNA, we have developed an assay which does not require purified protein. It is based on the specific elution of the large-T ATPase activity from calf thymus DNA cellulose by recombinant DNA molecules including known sequences of the viral DNA. Using this assay, a high affinity binding site has been mapped on the early region side of the ori region. Binding requires the integrity of a sequence /AGAGGC/TTCC/AGAGGC/ (nucleotides 49 to 64 in the DNA sequence of the A2 strain). Similar repeats of a PuGPuGGC sequence within less than 20 bases are not found within the viral coding regions, but are strikingly common in the control regions of papovaviruses and other eukaryotic DNAs.
73 citations
73 citations
TL;DR: Data indicate that at 37 C, the low affinity site is no longer present (or detectable), and/ or there is a marked decrease in cooperative interactions at this temperature.
Abstract: Insulin and glucagon binding was studied in isolated rat hepatocytes, and the receptor occupancy was compared to the hormonal stimulation of amino acid transport. Binding was measured at 20 and 37 C in steady state conditions using 125I-labeled iodohormone and varying concentrations of unlabeled hormone. When measured at 20 C, insulin binding was compatible with either a two-site model: a high affinity (Kd ≅ 0.6 nM) and a low affinity (Kd ≅ 12 nM) site or one class of binding sites with negatively cooperative interactions. At 20 C, the rate of dissociation of bound [125I]iodoinsulin was enhanced in the presence of unlabeled insulin, suggesting negatively cooperative interactions among insulin receptors at this temperature. At 37 C, in contrast, insulin bound predominantly to a high affinity site (Kd ≅ 0.6 nM). These data indicate that at 37 C, the low affinity site is no longer present (or detectable), and/ or there is a marked decrease in cooperative interactions at this temperature. When insulin-stimula...
71 citations
01 Jan 1981
TL;DR: The results show that ob17 cell line should be an useful tool to study the role of thyroid hormones in the regulation of fatty acid synthesis and esterification in adipose cells.
Abstract: Cells of a preadipocyte clonal line (ob 17) isolated from epididymal fat pad of ob/ob mouse possess high-affinity binding sites for triiodothyronine. A single class of sites was found on growing and early confluent cells (KD 0.14 ± 0.025 nM; 5 000 ± 600 sites per cell). A two-fold increase in the number of T3 binding sites occurs during adipose conversion, with no significant change in KD values. The order of potency of structural analogs to compete with 125I-T3 is in favor of nuclear binding sites. A correlation was obtained between this order of potency and the ability of the analogs, included on a long-term basis to confluent cells, to increase 14C-acetate incorporation into lipids, suggesting an enhancement of de novo fatty acid synthesis. This hypothesis was supported by increased activity levels of fatty acid synthetase after chronic exposure to 1.5 nM triiodothyronine. Under these conditions activity levels of acid:CoA ligase and glycerol-3-phosphate dehydroge-nase were also increased signi...
62 citations
TL;DR: On the reef complex of Moorea, the Chaetodontidae were counted along a transect from the shore to 30 m depth, using SCUBA diving, and their quantitative distribution across the reef established.
45 citations
TL;DR: The effects of hypolipidemic drugs such as clofenapate observed on a long-term basis in vitro are consistent with the results of studies on adipose tissue in vivo.
TL;DR: The fact that none of the tumors analyzed (more than 20) were found to have retained the high serum dependence of CC139 cells strongly suggests that the partial loss of serum growth factor requirement acquired in vivo is an essential malignant character for bypassing the hormonal growth restraints imposed by the host upon CC 139 cells.
Abstract: The Chinese hamster lung fibroblast cell line (CC139) has high anchorage dependence for growth and has retained the high serum dependence of secondary cultures of adult fibroblasts. This cell line is tumorigenic in nude mice; however, the resulting tumor cells have different properties than those of the cell line injected. The tumor-derived cells had strongly reduced or even lost both the high anchorage and the high serum dependence of CC139 cells. This finding suggests that an in vivo selection is necessary for CC139 cells to acquire the malignant phenotype. After mutagenesis, which increases the frequency of CC139 colony formation in agarose up to 8-fold, we selected and analyzed 15 anchorage-independent colonies. No correlation between the colony-forming ability in agarose and serum-growth factor requirement for DNA synthesis was observed. Each of these clones were injected into nude mice and the growth factor dependence of the ensuing tumor cells was compared to that of corresponding injected cells. All of the anchorage-independent colonies with the exception of one (A71), had acquired in vivo a stable phenotype allowing for partial or total escape of growth factor requirement. A71, the only clone which maintained the same growth factor requirement after two passages in vivo (A71 T1 and A71 T2) had already gained, in vitro, the minimal growth factor "relaxation" compatible with in vivo growth. A71 and A71 T1 tumor cells arrested in G0/G1 can reinitiate DNA synthesis in the presence of mouse plasma, low concentrations of serum, or thrombin. The fact that none of the tumors analyzed (more than 20) were found to have retained the high serum dependence of CC139 cells strongly suggests that the partial loss of serum growth factor requirement acquired in vivo is an essential malignant character for bypassing the hormonal growth restraints imposed by the host upon CC139 cells.
TL;DR: The specificity of bthe Na+ channel for monovalent cations has been analyzed in three different ways using neutrotoxins and excitable cells in culture and indicates that the selectivity filter and the gating system may be coupled entities.
Abstract: The specificity of bthe Na+ channel for monovalent cations has been analyzed in three different ways using neutrotoxins and excitable cells in culture.
1
Influx experiments using radioactive monovalent cations have shown that all neurotoxins or combination of neurotoxins which change the gating system of the Na+ channel (veratridine, batrachotoxin, dihydrograyanotoxin, scorpion and sea-anemone toxins) induce a considerable alteration of the permeability of the channel for monovalent cations. Theer is a much decreased ionic selectivity of the channel. Toxin-induced changes in ionic selectivity are the same or very similar in neuroblastoma cells and in skeletal myotubes. Thefact that toxins which change the kinetics of the gating system also change channel selectivity indicates that the selectivity filter and the gating system may be coupled entities.
2
Efflux experiments using neuroblastoma cells preloaded with 22N+, 42K+ or 86Rb+ indicate that the toxin stimulated release of these monovalent cations through the Na+ channel is not seen in the presence of cholinium in the external medium. It is seen only if the external medium contains permeant monovalent cations. The ‘chemical’ activation of the Na+ channel by neurotoxins necessitates the saturation at the external face of the channel of sites specific for permeant monovalent cations. Dose-response curves for the effect of increasing external concentrations of Na+, K+, Rb+ or guanidinium on 22Na+ efflux indicate positive cooperativity in the stimulating effect of these cations. The best apparent affinity is observed for guanidinium, then for Na+, K+ and Rb+.
3
Competition experiments between monovalent cations and a radiolabelled tritiated derivative of tetrodotoxin for binding to the tetrodotoxin receptor of the Na+ channel in neuroblastoma cells indicatae that monovalent cations bind cooperatively to external sites for Na+. The Hill coefficients and the dissociation constants for Na+ and guanidinium binding to the Na+ channel measured with this approach compare well to values found from 22Na+efflux experiments.
TL;DR: In this paper, les F-alcynes and les Falkynyl esters constituent des intermediaires remarquables for the synthese d'heterocycles substitues par des chaines F-alkyles.
TL;DR: Prostaglandin synthesis is maximal during the growth phase and decreases dramatically after confluence at a time where adipose conversion occurs, suggesting a possible relationship between both events.
TL;DR: The Lyapunov characteristic numbers were used to continue the study of a larger sample of orbits in the three-body three-dimensional restricted problem than that previously studied by Froeschle as mentioned in this paper.
Abstract: The Lyapunov characteristic numbers are used to continue the study of a larger sample of orbits in the three-body three-dimensional restricted problem than that previously studied by Froeschle [6]. These numbers are found to be sensitive indicators of stochasticity and the results confirm those found by Froeschle.
TL;DR: Activation of the eggs by weak amine bases (5 mM NH 4 Cl) which bypasses the early cortical reaction produces only a depletion in the Na + content of the egg similar to that produced by fertilization, although no transient variations are noted.
01 Jan 1981
TL;DR: These studies indicate that lipoprotein lipase and monoacylglycerol lipase are integral part of the program of differentiation of adipose cells, in contrast to unspecific monoester hydrolase.
TL;DR: It is presented that the expression of a fully transformed phenotype in FR 3T3 rat fibroblast cells transformed with polyoma virus requires two viral gene products, one of which is the membrane-associated middle T protein, and a second necessary function is dependent on an N-terminal region of the large T protein.
TL;DR: The adipose conversion of ob 17 preadipose cells can be irreversibly blocked when prostaglandin F2alpha is included post-confluence for a minimum of 24 h in insulin-containing media, and results indicate that both events can be dissociated.
TL;DR: The spectral characterization included identification of the complete spin systems for several amino acid residues, nuclear Overhauser effect measurements, the use of chemically induced dynamic nuclear polarization and studies of the pH dependence of the NMR spectrum.
Abstract: The membrane toxin VII2 from the venom of Naja mossambica mossambica was investigated in aqueous solution by one-dimensional and two-dimensional high-resolution nuclear magnetic resonance (NMR) techniques at 360 MHz. The spectral characterization included identification of the complete spin systems for several amino acid residues, nuclear Overhauser effect measurements, the use of chemically induced dynamic nuclear polarization and studies of the pH dependence of the NMR spectrum. Data from homologous toxins, in particular direct lytic factor 12B from Haemachatus haemachatus, were used to establish assignments of aromatic and methyl proton resonances. From these experiments a short, triple-stranded fragment of antiparallel beta structure could be determined, which includes the residues 23-27, 43-46 and 60-62. Furthermore, the nuclear Overhauser effect measurements indicate close proximity in the protein conformation of the aromatic rings of Trp-14, Tyr-25 and Tyr-59, and the side chain of Ile-46.
TL;DR: The most spectacular morphological changes were observed with axonal membranes treated with cardiotoxin containing traces of venom phospholipase A2, and are interpreted as being due to the removal of intrinsic membrane proteins from the membrane by the combined action of cardiot toxin and phospholipses A2.
TL;DR: Calculations clearly indicate a conformational change with the hexanucleosome and the results suggest that, at low ionic strength, the chromatin adopts a loosely helical structure of 28-nm diameter and 22-nm pitch.
Abstract: Quasielastic laser light scattering measurements have been made on chromatin oligomers to obtain information on the transition in their electrooptical properties, previously observed for the hexameric structures [Marion, C. and Roux, B. (1978) Nucleic Acids Res. 5, 4431-4449]. Translational diffusion coefficients were determined for mononucleosomes to octanucleosomes containing histone H1 over a range of ionic strength. At high ionic strength, oligomers show a linear dependence of the logarithm of diffusion coefficient upon the logarithm of number of nucleosomes. At low ionic strength a change occurs between hexamer and heptamer. Our results agree well with the recent sedimentation data of Osipova et al. [Eur. J. Biochem. (1980) 113, 183-188] and of Butler and Thomas [J. Mol. Biol. (1980) 140, 505-529] showing a change in stability with hexamer. Various models for the arrangements of nucleosomes in the superstructure of chromatin are discussed. All calculations clearly indicate a conformational change with the hexanucleosome and the results suggest that, at low ionic strength, the chromatin adopts a loosely helical structure of 28-nm diameter and 22-nm pitch. These results are also consistent with a discontinuity every sixth nucleosome, corresponding to a turn of the helix. This discontinuity may explain the recent electric dichroism data of Lee et al. [Biochemistry (1981) 20, 1438-1445]. The hexanucleosome structure which we have previously suggested, with the faces of nucleosomes arranged radially to the helical axis has been recently confirmed by Mc Ghee et al. [Cell (1980) 22, 87-96]. With an increase of ionic strength, the helix becomes more regular and compact with a slightly reduced outer diameter and a decreased pitch, the dimensions resembling those proposed for solenoid models.
TL;DR: In this paper, the initial results of round-the-clock observations of solar oscillations at the South Pole are summarized by describing the Figures 1 to 4 of the Figure 1.
Abstract: Initial results of round-the-clock observations of solar oscillations at the South Pole are briefly summarized by describing the Figures 1 to 4.
TL;DR: In this article, the Darzens glycidic esters were synthesized under very mild conditions with pyridinium-poly-hydrogen fluoride to give corresponding 3-fluoro 3-phenyllactates with high regio and stereoselectivity.
TL;DR: In this article, the influence of the telescope diameter on solar observations is shown graphically, and predictions for the observed contrast in solar granulation are made as a function of wavelength.
Abstract: Fried's seeing parameter r
0 can be determined from the observed r.m.s. contrast of solar granulation. The computation is based on results obtained from solar speckle interferometry. The influence of the telescope diameter on solar observations is shown graphically, and predictions for the observed contrast in solar granulation are made as a function of wavelength. The importance of seeing conditions is discussed, and a conclusion is made on the optimum telescope size to be used for given turbulence conditions