Showing papers by "University of Paris published in 1991"
TL;DR: In this paper, it was shown that for every vector-valued function u Lp(X, p; Rd) there is a unique polar factorization u = V$.s, where $ is a convex function defined on R and s is a measure-preserving mapping from (x, p) into (Q, I. I), provided that u is nondegenerate.
Abstract: Given a probability space (X, p) and a bounded domain R in Rd equipped with the Lebesgue measure 1 . I (normalized so that 10 I = I ), it is shown (under additional technical assumptions on X and Q) that for every vector-valued function u E Lp(X, p; Rd) there is a unique “polar factorization” u = V$.s, where $ is a convex function defined on R and s is a measure-preserving mapping from (X, p) into (Q, I . I), provided that u is nondegenerate, in the sense that p(u-’(E)) = 0 for each Lebesgue negligible subset E of Rd. Through this result, the concepts of polar factorization of real matrices, Helmholtz decomposition of vector fields, and nondecreasing rearrangements of real-valued functions are unified. The Monge-Amgre equation is involved in the polar factorization and the proof relies on the study of an appropriate “Monge-Kantorovich” problem.
1,780 citations
TL;DR: The main features of real-world problems for which the outranking approach is appropriate and the concept of outranking relations are described and the definition of such out ranking relations is given for the main ELECTRE methods.
Abstract: In the first part of this paper, we describe the main features of real-world problems for which the outranking approach is appropriate and we present the concept of outranking relations. The second part is devoted to basic ideas and concepts used for building outranking relations. The definition of such outranking relations is given for the main ELECTRE methods in Part 3. The final part of the paper is devoted to some practical considerations.
1,751 citations
TL;DR: In APL, the t(15;17) translocation generates an RAR mutant that could contribute to leukemogenesis through interference with promyelocytic differentiation, and this gene product contains a novel zinc finger motif common to several DNA-binding proteins.
1,321 citations
TL;DR: The convergence of a wide class of approximation schemes to the viscosity solution of fully nonlinear second-order elliptic or parabolic, possibly degenerate, partial differential equations is studied in this paper.
Abstract: The convergence of a wide class of approximation schemes to the viscosity solution of fully nonlinear second-order elliptic or parabolic, possibly degenerate, partial differential equations is studied. It is proved that any monotone, stable, and consistent scheme converges (to the correct solution), provided that there exists a comparison principle for the limiting equation. Several examples are given where the result applies. >
1,063 citations
TL;DR: A retrospective survey of 7 European centers involving 20 surgeons who undertook 1,236 laparoscopic cholecystectomies was performed, and the total postoperative complication rate was 20 of 1,203 (1.6%), with 9 being serious complications requiring laparotomy.
Abstract: A retrospective survey of 7 European centers involving 20 surgeons who undertook 1,236 laparoscopic cholecystectomies was performed. The procedure was completed in 1,191 patients. Conversion to open cholecystectomy was necessary in 45 patients (3.6%) either because of technical difficulty (n = 33), the onset of complications (n = 11), or instrument failure (n = 1). There were no deaths reported, and the total postoperative complication rate was 20 of 1,203 (1.6%), with 9 being serious complications requiring laparotomy. The total incidence of bile duct damage was 4 of 1,203. The median hospital stay was 3 days (range: 1 to 27 days) and the median time to return to full activity after discharge was 11 days (range: 7 to 42 days).
903 citations
TL;DR: In this paper, a comparison of three widely used time propagation algorithms for the time dependent Schrodinger equation is described, and a new method is introduced which is based upon a low-order Lanczos technique.
860 citations
TL;DR: The expression of the Ruderman-Kittel-Kasuya-Yosida coupling between two ferromagnetic layers separated by a nonmagnetic spacer is derived and quantitative predictions of the interlayer coupling for Cu, Ag, and Au spacers are given.
Abstract: We have derived the expression of the Ruderman-Kittel-Kasuya-Yosida coupling between two ferromagnetic layers separated by a nonmagnetic spacer, for arbitrary crystal structure and Fermi surface. For the first time, quantitative predictions of the interlayer coupling for Cu, Ag, and Au spacers are given. The results are in good agreement with recent experimental data for fcc Co/Cu and Fe/Cu systems.
776 citations
TL;DR: In this article, uniform estimates and blow-up behavior for solutions of −δ(u) = v(x)eu in two dimensions are presented, with a focus on partial differential equations.
Abstract: (1991). Uniform estimates and blow–up behavior for solutions of −δ(u)=v(x)eu in two dimensions. Communications in Partial Differential Equations: Vol. 16, No. 8-9, pp. 1223-1253.
679 citations
TL;DR: In this paper, the authors propose a method to solve the problem of image compression: https://www.spline.com/images/image-clips/imageclips.html
Abstract: Images
609 citations
TL;DR: In this paper, it was shown that if the initial data has moments inv higher than three, then the solution of Vlasov-Poisson has also moments inv high than three.
Abstract: We prove that, if the initial data has moments inv higher than three, then the solution of Vlasov-Poisson has also moments inv higher than three. We deduce from this different regularity results on the local density, the force field or the solution itself. Also we give a new uniqueness result, and new regularity results for solutions satisfying only the energy andL
∞ bounds. Our proofs are based on a new representation formula and logarithmic estimates for the force field.
590 citations
TL;DR: In this paper, the authors studied a class of Banach space operators patterned after the weighted backward shifts on Hilbert space, and showed that any non-scalar operator in the commutant of one of these generalized backward shifts has a dense, invariant linear manifold whose non-zero members are cyclic vectors.
TL;DR: In this article, a 13,000-yr record from Sumxi Co (western Tibet), constructed from both lake-core and shoreline studies, shows that conditions in the early-middle Holocene were warmer and wetter than at present.
Abstract: ALTHOUGH the Tibetan plateau is important in influencing the atmospheric circulation of the Northern Hemisphere1–3, there are only a few continuous palaeoclimate records available, and these are limited to the plateau's northeastern margin4–6. Here we present a 13,000-yr record from Sumxi Co (western Tibet), constructed from both lake-core and shoreline studies, which shows that conditions in the early–middle Holocene were warmer and wetter than at present. These results confirm model predictions of an intensified monsoon over the region at ∼9,000 yr BP, owing to an orbitally induced increase in summer insolation7,8. We also find evidence for warm, humid pulses at ∼12,500 and ∼10,000 yr BP, in phase with the steps of the last deglaciation, and for a return to cold, dry conditions at ∼11-10,000 yr BP, none of which can be explained by orbital variations. The existence of the cold episode confirms that the cooling associated with the Younger Dry as event occurred in continental China6,9, and provides further evidence of the global nature of this event10
TL;DR: An integrability criterion for discrete-time systems that is the equivalent of the Painlev\'e property for systems of a continuous variable is presented, based on the observation that for integrable mappings the singularities that may appear are confined, i.e., they do not propagate indefinitely when one iterates the mapping.
Abstract: We present an integrability criterion for discrete-time systems that is the equivalent of the Painlev\'e property for systems of a continuous variable. It is based on the observation that for integrable mappings the singularities that may appear are confined, i.e., they do not propagate indefinitely when one iterates the mapping. Using this novel criterion we show that there exists a family of nonautonomous integrable mappings which includes the discrete Painlev\'e equations by ${\mathit{P}}_{\mathrm{I}}$, recently derived in a model of two-dimensional quantum gravity, and ${\mathit{P}}_{\mathrm{II}}$, obtained as a similarity reduction of the integrable modified Korteweg--de Vries lattice. These systems possess Lax pairs, a well-known integrability feature.
TL;DR: In this paper, weak continuity of quadratic forms on spaces of L 2 solutions of systems of partial differential equations is studied. But defect measures on the space of positions and frequencies are not defined.
Abstract: In order to study weak continuity of quadratic forms on spaces of L2 solutions of systems of partial differential equations, we define defect measures on the space of positions and frequencies.A sy...
TL;DR: In this article, the incompressible Navier-Stokes equations were derived from a formal derivation in which limiting moments are carefully balanced rather than on a classical expansion such as those of Hilbert or Chapman-Enskog.
Abstract: The connection between kinetic theory and the macroscopic equations of fluid dynamics is described. In particular, our results concerning the incompressible Navier-Stokes equations are based on a formal derivation in which limiting moments are carefully balanced rather than on a classical expansion such as those of Hilbert or Chapman-Enskog. The moment formalism shows that the limit leading to the incompressible Navier-Stokes equations, like that leading to the compressible Euler equations, is a natural one in kinetic theory and is contrasted with the systematics leading to the compressible Navier-Stokes equations. Some indications of the validity of these limits are given. More specifically, the connection between the DiPerna-Lions renormalized solution of the classical Boltzmann equation and the Leray solution of the Navier-Stokes equations is discussed.
TL;DR: In this article, the magnetic and magneto-transport properties of Co/Cu multilayers prepared by sputtering were studied and a giant magnetoresistance was observed in the half-periods with antiferromagnetic interlayer coupling.
TL;DR: In this article, the evolution from the first transtensional phase of extension to the passive margin stage is analyzed and four main rifting events are recognized in the Tethyan realm.
TL;DR: A calcium atomic beam excited in an optical Ramsey geometry was rotated about an axis perpendicular to the plane defined by the laser beams and the atomic beam and a frequency shift of the Ramsey fringes of several kHz has been measured.
Abstract: A calcium atomic beam excited in an optical Ramsey geometry was rotated about an axis perpendicular to the plane defined by the laser beams and the atomic beam. A frequency shift of the Ramsey fringes of several kHz has been measured which is proportional to the rotation frequency of the apparatus and to the distance between the laser beams. The results can be interpreted in three equivalent ways as the Sagnac effect in a calcium-atomic-beam interferometer: in the rotating frame of the laser beams either along straight paths or along the curved trajectories of the atoms, or in the inertial atomic frame.
TL;DR: This paper presents discrete forms of the Painlev\'e transcendental equations that complement the list of the already known and shows that the discrete Painleve mappings satisfy the same reduction relations as the continuous Painlevese transcendents.
Abstract: We present discrete forms of the Painlev\'e transcendental equations ${\mathit{P}}_{\mathrm{III}}$,${\mathit{P}}_{\mathrm{IV}}$, and ${\mathit{P}}_{\mathrm{V}}$ that complement the list of the already known ${\mathit{P}}_{\mathrm{I}}$ and ${\mathit{P}}_{\mathrm{II}}$. These, most likely integrable, nonautonomous mappings go over to the usual Painlev\'e equations in the continuous limit, while in the autonomous limit we recover discrete system that belong to the integrable family of Quispel et al. Finally, we show that the discrete Painlev\'e mappings satisfy the same reduction relations as the continuous Painlev\'e transcendents, namely, ${\mathit{P}}_{\mathrm{V}}$\ensuremath{\rightarrow}{${\mathit{P}}_{\mathrm{III}}$, ${\mathit{P}}_{\mathrm{IV}}$}\ensuremath{\rightarrow}${\mathit{P}}_{\mathrm{II}}$\ensuremath{\rightarrow}${\mathit{P}}_{\mathrm{I}}$.
TL;DR: In this paper, the authors measured cyanide concentrations in blood samples obtained at the scene of residential fires from 109 fire victims before they received any treatment, and compared the results with those in 114 persons with drug intoxication (40 subjects), carbon monoxide intoxication (29 subjects), or trauma (45 subjects).
Abstract: Background The nature of the toxic gases that cause death from smoke inhalation is not known. In addition to carbon monoxide, hydrogen cyanide may be responsible, but its role is uncertain, because blood cyanide concentrations are often measured only long after exposure. Methods We measured cyanide concentrations in blood samples obtained at the scene of residential fires from 109 fire victims before they received any treatment. We compared the results with those in 114 persons with drug intoxication (40 subjects), carbon monoxide intoxication (29 subjects), or trauma (45 subjects). The metabolic effect of smoke inhalation was assessed by measuring plasma lactate at the time of admission to the hospital in 39 patients who did not have severe burns. Results. The mean (±SD) blood cyanide concentrations in the 66 surviving fire victims (21.6±36.4 μmol per liter, P<0.001) and the 43 victims who died (116.4±89.6 μmol per liter, P<0.001) were significantly higher than those in the 114 control subjects (5.0±5.5 ...
TL;DR: It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress, to stomatal closure which leads to a decrease in leaf internal CO2 concentration.
Abstract: Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter ΔF/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87-92; ΔF = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using (18)O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, ΔF/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.
TL;DR: In this article, the authors consider real C' functions F defined on a Banach space X and present a rather general deformation result for finding critical points of F. They use versions of Ekeland's Principle and deformation arguments.
Abstract: In the course of writing a chapter of a book we observed some simple facts dealing with the Palais SmaIe property and critical points of functions. Some of these facts turned out to be known, though not well-known, and we think it worthwhile to make them more available. In addition, we present some other recent results which we believe will prove to be useful-in particular, a result of Ghoussoub and Preiss; see [ 91, [ 81. There are two useful techniques used in obtaining critical points. One is Ekeland’s Principle (see below), the other is based on deformation arguments. We will use versions of both of them. In particular we present a rather general deformation result. Throughout this paper we consider real C’ functions F defined on a Banach space X. When looking for critical points of F it has become standard to assume the following “compactness condition”:
TL;DR: The paper presents the actual procedures used to mechanically produce such test sets, using Horn clause logic, embedded in an interactive system which, given some general hypotheses schemes and an algebraic specification, produces a test set and the corresponding hypotheses.
Abstract: This paper addresses the problem of constructing test data sets from formal specifications. Starting from a notion of an ideal exhaustive test data set which is derived from the notion of satisfaction of the formal specification, it is shown how to select by refinements a practicable test set, i.e. computable, not rejecting correct programs (unbiased), and accepting only correct programs (valid), assuming some hypotheses. The hypotheses play an important role: they formalize common test practices and they express the gap between the success of the test and correctness ; the size of the test set depends on the strength of the hypotheses. The paper shows an application of this theory in the case of algebraic specifications and presents the actual procedures used to mechanically produce such test sets, using Horn clause logic. These procedures are embedded in an interactive system which, given some general hypotheses schemes and an algebraic specification, produces a test set and the corresponding hypotheses.
TL;DR: Successful applications of two efficient algorithms which allow amino acid side chain conformations to be optimized rapidly for a given peptide backbone conformation to the prediction of known protein conformations are presented.
Abstract: Two efficient algorithms have been developed which allow amino acid side chain conformations to be optimized rapidly for a given peptide backbone conformation. Both these approaches are based on the assumption that each side chain can be represented by a small number of rotameric states. These states have been obtained by a dynamic cluster analysis of a large data base of known crystallographic structures. Successful applications of these algorithms to the prediction of known protein conformations are presented.
TL;DR: An electron-energy-loss-spectroscopy study of the characteristic oxygen K and iron edges in FeO, where the recorded changes of relative intensity are predominantly governed by strong Coulomb and exchange interactions on the excited cation.
Abstract: We report an electron-energy-loss-spectroscopy study of the characteristic oxygen K and iron ${\mathit{L}}_{2,3}$ edges in FeO, ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$, \ensuremath{\alpha}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$, and \ensuremath{\gamma}-${\mathrm{Fe}}_{2}$${\mathrm{O}}_{3}$ thin films. Data have been processed for quantitative elemental analysis and for detailed comparison of the different fine structures (energy position and width as well as relative intensities). Oxygen edge profiles are sensitive to the local bonding and symmetry properties on the excited anion. The features of the prepeak at the onset are governed by the 3d components in the hybridized unoccupied pd wave functions. They can be described in a molecular-orbital scheme and depend on the first coordination shell. Oscillations at higher energies are interpreted in terms of backscattering from the next coordination shells. The intense white lines on the iron ${\mathit{L}}_{2,3}$ edges are due to strong 2${\mathit{p}}^{6}$3${\mathit{d}}^{\mathit{n}}$\ensuremath{\rightarrow}2${\mathit{p}}^{5}$3${\mathit{d}}^{\mathit{n}+1}$ excitations, and the recorded changes of relative intensity (or branching ratio) are predominantly governed by strong Coulomb and exchange interactions on the excited cation.
TL;DR: In this article, the authors studied the critical points at infinity of the variational problem, in which the failure of the Palais-Smale condition is the main obstacle for solving equations of type (4).
TL;DR: The synthetic replicate was shown to be indistinguishable from natural dermaseptin with respect to chromatographic properties, amino acid sequence determination, and mass spectrometry analysis.
Abstract: A 34-residue antimicrobial peptide named dermaseptin was purified to homogeneity from amphibian skin by a 3-step protocol involving molecular sieve filtration, ion-exchange chromatography, and reversed-phase high-performance liquid chromatography. The complete amino acid sequence of dermaseptin, ALWKTMLKKLGTMALHAGKAALGAAADTISQGTQ, was determined by automated Edman degradation of the peptide and of fragments generated by trypsin. Fast atom bombardment mass spectra of dermaseptin gave a protonated molecular ion m/z 3455.4 which matched the theoretical molecular weight predicted from the amino acid sequence. Dermaseptin was synthesized by the solid-phase method. The synthetic replicate was shown to be indistinguishable from natural dermaseptin with respect to chromatographic properties, amino acid sequence determination, and mass spectrometry analysis. Dermaseptin is a water-soluble, thermostable, and nonhemolytic peptide endowed with highly potent antimicrobial activity against pathogenic fungi at micromolar concentration. Circular dichroism spectra of dermaseptin in hydrophobic media indicated 80% alpha-helical conformation, and predictions of secondary structure suggested that dermaseptin can be configured as an amphiphatic alpha-helix spanning over residues 1-27, a structure that perturbs membrane functions regulating water flux.
TL;DR: In this paper, the authors considered the scattering problem for the nonlinear Schrodinger equation in 1+1 dimensions and showed that modified wave operators for (*) exist on a dense set of a neighborhood of zero in the Lebesgue spaceL2(R) or in the Sobolev spaceH1(R).
Abstract: We consider the scattering problem for the nonlinear Schrodinger equation in 1+1 dimensions:
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where ∂ = ∂/∂x,λ∈R∖{0},μ∈R,p>3. We show that modified wave operators for (*) exist on a dense set of a neighborhood of zero in the Lebesgue spaceL2(R) or in the Sobolev spaceH1(R)., The modified wave operators are introduced in order to control the long range nonlinearity λ|u|2u.
TL;DR: In this article, the π0-form factor of the η-meson was determined from its decay modes π+π−π0, π +π−γ and the neutral decay mode γγ.
Abstract: We present measurement of the π0γ*γ, ηγ*γ and η′γ*γ form factors. The π0-form factor is for the first time observed in the space-like region. The transition form factor of the η-meson is determined from its decay modes π+π−π0, π+π−γ and the neutral decay mode γγ. The decay of the η′ is observed in the decay channels ργ, ηπ+π− with η→γγ and in the four charged prong final state stemming from ηπ+π− with the η decaying into π+π−(π0/γ). All form factors agree well with a simple ρ-pole predicted by the vector meson dominance model and also with the QCD inspired Brodsky-Lepage model.
TL;DR: These findings are similar to those reported in rats with non-insulin-dependent diabetes induced by neonatal streptozocin administration and support the concept that chronic elevation in plasma glucose may be responsible, at least in part, for the β-cell desensitization to glucose in this model.
Abstract: In early 1988, a colony of GK rats was started in Paris with progenitors issued from F 35 of the original colony reported by Goto and Kakisaki. When studied longitudinally up to 8 mo, GK rats showed as early as 1 mo (weaning) significantly higher basal plasma glucose (9 mM) and insulin levels (doubled), altered glucose tolerance (intravenous glucose), and a very poor insulin secretory response to glucose in vivo compared with Wistar controls. Males and females were similarly affected. Studies of in vitro pancreatic function were carried out with the isolated perfused pancreas preparation. Compared with nondiabetic Wistar rats, GK rats at 2 mo showed a significantly increased basal insulin release, no insulin response to 16 mM glucose, and hyperresponse to 19 mM arginine. Pancreatic insulin stores were only 50% of that in Wistar rats. Perfusion of GK pancreases for 50 or 90 min with buffer containing no glucose partially improved the insulin response to 16 mM glucose and markedly diminished the response to 19 mM arginine, whereas the responses by Wistar pancreases were unchanged. These findings are similar to those reported in rats with non-insulin-dependent diabetes induced by neonatal streptozocin administration and support the concept that chronic elevation in plasma glucose may be responsible, at least in part, for the β-cell desensitization to glucose in this model. The GK rat seems to be a valuable model for identifying the etiology of β-cell desensitization to glucose.