Showing papers by "University of Paris published in 1987"
TL;DR: This work model the speckle according to the exact physical process of coherent image formation and accurately represents the higher order statistical properties of speckel that are important to the restoration procedure.
Abstract: Speckle is a granular noise that inherently exists in all types of coherent imaging systems. The presence of speckle in an image reduces the resolution of the image and the detectability of the target. Many speckle reduction algorithms assume speckle noise is multiplicative. We instead model the speckle according to the exact physical process of coherent image formation. Thus, the model includes signal-dependent effects and accurately represents the higher order statistical properties of speckle that are important to the restoration procedure. Various adaptive restoration filters for intensity speckle images are derived based on different model assumptions and a nonstationary image model. These filters respond adaptively to the signal-dependent speckle noise and the nonstationary statistics of the original image.
701 citations
TL;DR: In this paper, the authors report analyses of O, Sr, Nd and Pb isotope ratios in 52 fresh glasses of mid-ocean ridge basalt (MORB).
629 citations
TL;DR: In this paper, it was shown that bidentate acetates replace the OR groups and are directly bounded to the titanium, leading to Ti(OR) x (Ac) y. oligomers.
Abstract: Monolithic TiO 2 gels can be reproducibly obtained when the hydrolysis of titanium alkoxides is performed in the presence of acetic acid. This carboxilic acid does not act only as an acid catalyst, but also as a ligand and changes the alkoxide precursor at a molecular level therefore modifying the whole hydrolysis condensation process. Infra-red experiments show that bidentate acetates replace OR groups and are directly bounded to the titanium. Both, chelating and bridging acetates, are observed, leading to Ti(OR) x (Ac) y . oligomers. Hydrolysis of this new molecular precursor removes first (OR) groups and bridging acetates. Chelating acetates are still observed in the gel. They can only be removed upon heating above 200 °C.
593 citations
TL;DR: This new version of the GOR method increases the accuracy of prediction by 7%, bringing the amount of residues correctly predicted to 63% for three states and 68 proteins, each protein to be predicted being removed from the database and the parameters derived from the other proteins.
567 citations
TL;DR: In this article, a two-mode optical parametric oscillator operating above threshold was used to generate high-intensity twin beams which exhibit quantum correlations, and the noise power measured on the intensity difference between two such beams was reduced by 30% below the shot-noise limit.
Abstract: We have used a two-mode optical parametric oscillator operating above threshold to generate high-intensity twin beams which exhibit quantum correlations. The noise power measured on the intensity difference between two such beams is reduced by 30% below the shot-noise limit. Noise reduction is observed over a broad range of frequencies.
521 citations
TL;DR: In this paper, the authors give a characterization of rationalizability of decision rules in multiple dimensions, which is a generalization of the monotonicity condition of Spence-Mirrlees.
468 citations
430 citations
428 citations
TL;DR: In this article, the role of the Zeeman perturbation is considered in relation with the magnetic and EPR properties of the heterobimetallic complexes. And the authors propose a model for the isotropic interaction based on the concept of natural magnetic orbitals.
Abstract: The field of heteropolymetallic systems with magnetic metal centers occupies a crossing point between biology and physics. For instance the Cu(II)-Fe(III) interaction in cytochrome oxidase is of the same nature as the Cu(II)-Mn(II) interaction in a novel system which could be the first molecular ferromagnet. The mechanism of the interaction is discussed, both from a phenomenological view point using a spin Hamiltonian, and from an orbital view point. An orbital model for the isotropic interaction is presented. It is based on the concept of natural magnetic orbitals. The mechanism of the anisotropic and antisymmetric interactions is more briefly treated. The role of the Zeeman perturbation is then considered in relation with the magnetic and EPR properties of the heterobimetallic complexes. Several examples are presented to emphasize that the nature, ferro- or antiferromagnetic of the isotropic interaction is controlled by the symmetry of the magnetic orbitals. The concept of overlap density is introduced. It permits an estimation of the magnitude of the ferromagnetic stabilization in the case of orthogonality of the magnetic orbitals. The Cu(II)-Fe(III) interaction, in relation to the situation encountered in cytochrome oxidase, the Cu(II)-Ni(II) interaction and a few additional selected examples are discussed. A section deals with the case where one of the interacting ions has an orbital degeneracy. Afterwards, the heterotrinuclear complexes are studied. The important concept of regular and irregular spin state structure is developped and the Mn(II)Cu(II)Mn(II) triad is presented as a spectacular example of irregular spin state structure. A section is devoted to the ordered bimetallic chains. The theory is presented, both at a qualitative and quantitative levels and the already reported compounds of this kind are discussed. One of them may be considered as one of the first molecular ferromagnets. The last but one section concerns the systems with even more subtle spin orders. In conclusion, the vast perspectives of this area are outlined.
400 citations
TL;DR: Examination of the function of the pre-gait weight shifts in generating the dynamic forces needed to start walking at different speeds suggested that dynamic phenomena prior to stepping are essential to walking as far as they contribute to the creation of convenient conditions for progression.
Abstract: The aim of our research was to examine the function of the pre-gait weight shifts in generating the dynamic forces needed to start walking at different speedsFive subjects participated in the experiment, and a total of 105 gait initiation movements, executed on a large force plate, for three speed conditions (slow, normal, and fast), were examinedResults, which related to durations of the anticipation and of the step execution phases and to biomechanical parameters (progression velocity of the center of gravity, backward shift of the center of foot pressure, and magnitude of propulsive forces at heel-off time), suggested that dynamic phenomena prior to stepping are essential to walking as far as they contribute to the creation of convenient conditions for progression The configuration of the support basis prior to stepping limits the progression velocity reached at the end of the first step
TL;DR: Observations strongly support the existence of "neurosteroids," which have been posited on the basis of biochemical, physiological, and behavioral studies.
Abstract: The steroid hormones corticosterone and testosterone are supplied to the central nervous system by endocrine glands, the adrenals and gonads. In contrast, the 3 beta-hydroxy-delta 5-derivatives of cholesterol, pregnenolone and dehydroepiandrosterone, accumulate in the rat brain through mechanisms independent of peripheral sources. Immunohistochemical studies have been performed with specific antibodies to bovine adrenal cytochrome P-450scc, which is involved in cholesterol side-chain cleavage and pregnenolone formation. The enzyme was localized in the white matter throughout the brain. Scarce clusters of cell bodies were also stained in the entorhinal and cingulate cortex and in the olfactory bulb. These observations strongly support the existence of "neurosteroids," which have been posited on the basis of biochemical, physiological, and behavioral studies.
TL;DR: On demontre que la constante de l'equation fonctionnelle de la Fonction L associe a une representation l-adique d'un corps de fonctions est un produit de constantes locales as discussed by the authors.
Abstract: On demontre que la constante de l'equation fonctionnelle de la fonction L associe a une representation l-adique d'un corps de fonctions est un produit de constantes locales. On donne une autre demonstration du theoreme de Deligne sur les poids dans la cohomologie l-adique
TL;DR: In this article, a new derivation of Wigner's function based on the property of positivity of its integrals along straight lines in phase space is proposed, and the authors identify the values of these marginalizations with densities pertaining to invariant observables.
Abstract: We propose a new derivation of Wigner's function based on the property of positivity of its integrals along straight lines in phase space. Identifying the values of these marginalizations with densities pertaining to invariant observables, we are able to reconstruct Wigner's pseudo-distribution from its slices.
TL;DR: In this paper, the dependence of zeolite acidity on framework properties is studied by considering the parallelism existing between the proton acid strength and the strength of the lattice Al-O bond.
TL;DR: Experiments have been performed to investigate the use of coral skeletons as bone graft substitutes and found that both cortical and spongy bone defects were at least partially filled by new bone after 8 weeks while the implants underwent continuous resorption.
Abstract: Experiments have been performed to investigate the use of coral skeletons as bone graft substitutes. Skeletal fragments of different coral genera were implanted into cortical and spongy bone defects and used to bridge transcortical resections in the femur. The implant site was monitored for up to 18 months. Radiographically, both cortical and spongy bone defects were at least partially filled by new bone after 8 weeks while the implants underwent continuous resorption. Coral resorption and replacement by new tissue was also observed in the transcortical resections. The process of resorption was attributed to the enzymatic attack, especially carboanhydrase. This was confirmed by experiments in which dogs were implanted with coral in transcortical resections and treated daily with acetazolamide, a carboanhydrase inhibitor; the absorption appeared delayed and the resections failed to heal.
TL;DR: On donne la validite de la conjecture de Fernique (1974) sur l'existence de mesures de majoration pouvant caracteriser la limitation des processus gaussiens as mentioned in this paper.
Abstract: On donne la validite de la conjecture de Fernique (1974) sur l'existence de mesures de majoration pouvant caracteriser la limitation des processus gaussiens
TL;DR: In this article, the mineral/groundmass partition coefficients for U, Th, Zr, Hf, Ta, Rb, REE, Co and Sc have been systematically measured in olivine, clinopyroxene, amphibole, biotite, Ti-magnetites, titanite, zircon and feldspars, in basaltic to trachytic lavas from alkaline series.
TL;DR: In this article, a modified tensile tester in contact with bovine sublingual mucus, and the force-elongation behavior was measured up to the breakpoint was calculated and related to bioadhesive characteristics of the tablets.
TL;DR: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not, for teaching and research institutions in France or abroad, or from public or private research centers.
Abstract: HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Mammalian oocyte maturation C. Thibault, D. Szöllösi, Micheline Gérard
TL;DR: In this article, the authors define flasque tori and flasques resolutions of tori over an arbitrary base scheme (Sect. 1) and establish the basic cohomological properties of Flasque Tori over a regular scheme.
TL;DR: It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux, which leads to increases in mantle convection and true polar wander.
Abstract: True polar wander, the shifting of the entire mantle relative to the earth's spin axis, has been reanalyzed. Over the last 200 million years, true polar wander has been fast (approximately 5 centimeters per year) most of the time, except for a remarkable standstill from 170 to 110 million years ago. This standstill correlates with a decrease in the reversal frequency of the geomagnetic field and episodes of continental breakup. Conversely, true polar wander is high when reversal frequency increases. It is proposed that intermittent convection modulates the thickness of a thermal boundary layer at the base of the mantle and consequently the core-to-mantle heat flux. Emission of hot thermals from the boundary layer leads to increases in mantle convection and true polar wander. In conjunction, cold thermals released from a boundary layer at the top of the liquid core eventually lead to reversals. Changes in the locations of subduction zones may also affect true polar wander. Exceptional volcanism and mass extinctions at the Cretaceous-Tertiary and Permo-Triassic boundaries may be related to thermals released after two unusually long periods with no magnetic reversals. These environmental catastrophes may therefore be a consequence of thermal and chemical couplings in the earth's multilayer heat engine rather than have an extraterrestrial cause.
TL;DR: In this paper, it was shown that for a self adjoint quantic hamiltonian, the classical flow on a compact energy shell {p=λ} is ergodic and almost all the eigenfunctions of P(h) whose energy is near of λ are distributed according to the Liouville measure on {p =λ}.
Abstract: Consider a self adjoint quantic hamiltonian:P(h)=p(x, hDx) whereh>0 is the Planck's constant andp some smooth classical observable on the phase space R2n. When the classical flow on a compact energy shell {p=λ} is ergodic we prove that in the limith ↓ 0 almost all the eigenfunctions ofP(h) whose energy is near of λ are distributed according to the Liouville measure on {p=λ}.
TL;DR: From the data, it is concluded that the three distantly separated exonic sequences of the ps1A1 gene constitute a functional gene which probably operates by a trans‐splicing mechanism.
Abstract: The two homologous genes for the P700 chlorophyll a-apoproteins (ps1A1 and ps1A2) are encoded by the plastom in the green alga Chlamydomonas reinhardii. The structure and organization of the two genes were determined by comparison with the homologous genes from maize using data from heterologous hybridizations as well as from DNA and RNA sequencing. While the ps1A2 (736 codons) gene shows a continuous gene organization, the ps1A1 (754 codons) gene possesses some unusual features. The discontinuous gene is split into three separate exons which are scattered around the circular chloroplast genome. Exon 1 (86 bp) is separated by approximately 50 kb from exon 2 (198 bp), which is located approximately 90 kb apart from exon 3 (1984 bp). All exons are flanked by intronic sequences of group II. Transcription analysis reveals that the ps1A2 gene hybridizes with a 2.8-kb transcript, while all exon regions of the ps1A1 gene are homologous to a mature mRNA of 2.7 kb. From our data we conclude that the three distantly separated exonic sequences of the ps1A1 gene constitute a functional gene which probably operates by a trans-splicing mechanism.
TL;DR: It is proposed that cyclic‐GMP‐stimulation of a cyclic nucleotide phosphodiesterase may be one of several mechanisms by which acetylcholine regulates ICa.
Abstract: 1. The effect of intracellular perfusion with cyclic AMP and cyclic GMP on Ca2+ current (ICa) was studied in single cells isolated from frog ventricle using the whole-cell patch-clamp technique and a perfused pipette. 2. Intracellular perfusion with cyclic GMP (0.1-20 microM) had no effect on the basal ICa. However, when ICa was increased by isoprenaline or by intracellular perfusion with cyclic AMP, perfusion with cyclic GMP (20 microM) reduced ICa by an average of 67%. The effect of cyclic GMP on ICa elevated by cyclic AMP was reversible. A half-maximal effect of cyclic GMP was observed at 0.6 microM. Cyclic GMP had no significant effect on the shape of the ICa current-voltage relationship. 3. The effect of cyclic GMP was specific to the 3',5' form; 2',3'-cyclic GMP had no effect. 4. The effect of cyclic GMP was apparently not mediated by stimulation of cyclic-GMP-dependent protein kinase because 8-bromo-cyclic GMP, a very potent activator of the protein kinase, was without effect. 5. Cyclic GMP had no effect on ICa elevated by the non-hydrolysable 8-bromo-cyclic AMP. The effect of cyclic GMP on cyclic-AMP-elevated ICa was partially blocked by the phosphodiesterase inhibitor, methylisobutylxanthine. Thus, it was hypothesized that the effect of cyclic GMP was mediated by hydrolysis of cyclic AMP as a result of a stimulation of a cyclic nucleotide phosphodiesterase by cyclic GMP. 6. The dose-response curve for cyclic AMP on ICa was well fitted by the Michaelis equation with a K50 (i.e. concentration of cyclic AMP at which response is 50% of the maximum) of 0.7 microM and a maximal 11-fold stimulation of ICa. Cyclic GMP shifted the curve one log unit to the right and decreased the maximal stimulation to 8.6-fold. Thus, the effect of cyclic GMP appeared uncompetitive. 7. The products of cyclic AMP and cyclic GMP hydrolysis, 5'-AMP and 5'-GMP, had no effect on ICa. Furthermore, strong buffering of intracellular pH did not reduce the effect of cyclic GMP. 8. It is proposed that cyclic-GMP-stimulation of a cyclic nucleotide phosphodiesterase may be one of several mechanisms by which acetylcholine regulates ICa.
TL;DR: It is shown that the many-body final states arise from the characteristic properties of these materials: the presence of localized 4f level above the oxygen 2p band separated by a gap and the mixing of 4f localized states with ligand valence orbitals such that the hybridization energy V is of the same order of magnitude as the energy separation \ensuremath{\Delta}E.
Abstract: The intermediate valence of formally tetravalent compounds has been detected by ${L}_{3}$ x-ray-absorption near-edge structure (XANES) in ${\mathrm{CeO}}_{2}$ and in ${\mathrm{PrO}}_{2}$ but not in ${\mathrm{UO}}_{2}$, which have the same ${\mathrm{CaF}}_{2}$ structure and large f and ligand mixing. The intermediate valence has been found both in ${\mathrm{CeO}}_{2}$ and in Ce(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O, which have similar local structure but different crystal structure. We show that ${L}_{3}$ XANES final states are a direct probe of configuration interaction between 4${f}^{n}$ and 4${f}^{n+1}$L configurations in the ground state and that the weight of the 4${f}^{n+1}$L in the ground state can be deduced. The many-body final states arise from the characteristic properties of these materials: (i) the presence of localized 4f level above the oxygen 2p band separated by a gap \ensuremath{\delta}\ensuremath{\varepsilon} with relevant correlation energy ${U}_{\mathrm{ff}}$ (${U}_{\mathrm{ff}}$\ensuremath{\ge}\ensuremath{\delta}\ensuremath{\varepsilon}) and (ii) mixing of 4f localized states with ligand valence orbitals such that the hybridization energy V is of the same order of magnitude as the energy separation \ensuremath{\Delta}E between the many-body configuration 4${f}^{n}$ and 4${f}^{n+1}$L (V\ensuremath{\ge}\ensuremath{\Delta}E). These insulating materials, which cannot be classified as standard mixed-valence systems, are called here interatomic intermediate-valence systems.
TL;DR: In this article, the authors derived from the solution of premixed laminar flames in a stagnation point flow are important in the determination of chemically controlled extinction limits and in the ability to characterize the combustion processes occurring in turbulent reacting flows.
Abstract: Conclusions derived from the solution of premixed laminar flames in a stagnation point flow are important in the determination of chemically controlled extinction limits and in the ability to characterize the combustion processes occurring in turbulent reacting flows. In the neighborhood of the stagnation point produced in these flames, a chemically reacting boundary layer is established. For a given equivalence ratio, the input flow velocity can be varied and solutions can be determined for increasing values of the strain rate. As the strain rate increases, the flame nears extinction. Recent experimental, computational and theoretical work has shown that extinction of these flames can be achieved by either flame stretch or by a combination of flame stretch and incomplete chemical reaction. Extinction by flame stretch is possible when the Lewis number of the deficient reactant is greater than a critical value and extinction resulting from both flame stretch and incomplete chemical reaction is pos...
TL;DR: A new, computerized, thermodilution method that determines right ventricular ejection fraction (RVEF) seems particularly appropriate for serial monitoring of RV performance.
Abstract: In 34 patients, we assessed the reproducibility and accuracy of a new, computerized, thermodilution method that determines right ventricular ejection fraction (RVEF). We compared the results from this new algorithm with simultaneous results from the conventional plateau thermodilution method and fro