Showing papers by "University of Paris published in 1995"

EIT: Extreme-UltraViolet Imaging Telescope for the SOHO Mission

Abstract: The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 A), Fe XII (195 A), Fe XV (284 A), and He II (304 A) to provide sensitive temperature diagnostics in the range from 6 × 104 K to 3 × 10 6 K. The telescope has a 45×45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes.

Wavelet Shrinkage: Asymptopia?

Abstract: Much recent effort has sought asymptotically minimax methods for recovering infinite dimensional objects-curves, densities, spectral densities, images-from noisy data A now rich and complex body of work develops nearly or exactly minimax estimators for an array of interesting problems Unfortunately, the results have rarely moved into practice, for a variety of reasons-among them being similarity to known methods, computational intractability and lack of spatial adaptivity We discuss a method for curve estimation based on n noisy data: translate the empirical wavelet coefficients towards the origin by an amount √(2 log n) /√n The proposal differs from those in current use, is computationally practical and is spatially adaptive; it thus avoids several of the previous objections Further, the method is nearly minimax both for a wide variety of loss functions-pointwise error, global error measured in L p -norms, pointwise and global error in estimation of derivatives-and for a wide range of smoothness classes, including standard Holder and Sobolev classes, and bounded variation This is a much broader near optimality than anything previously proposed: we draw loose parallels with near optimality in robustness and also with the broad near eigenfunction properties of wavelets themselves Finally, the theory underlying the method is interesting, as it exploits a correspondence between statistical questions and questions of optimal recovery and information-based complexity

Medication use and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis

Abstract: Background Toxic epidermal necrolysis and Stevens–Johnson syndrome are rare, life-threatening, drug-induced cutaneous reactions. We conducted a case–control study to quantify the risks associated with the use of specific drugs. Methods Data were obtained through surveillance networks in France, Germany, Italy, and Portugal. Drug use before the onset of disease was compared in 245 people who were hospitalized because of toxic epidermal necrolysis or Stevens–Johnson syndrome and 1147 patients hospitalized for other reasons (controls). Crude relative risks were calculated and adjusted for confounding by multivariate methods when numbers were large enough. Results Among drugs usually used for short periods, the risks were increased for trimethoprim–sulfamethoxazole and other sulfonamide antibiotics (crude relative risk, 172; 95 percent confidence interval, 75 to 396), chlormezanone (crude relative risk, 62; 21 to 188), aminopenicillins (multivariate relative risk, 6.7; 2.5 to 18), quinolones (multivariate rel...

Defective myosin VIIA gene responsible for Usher syndrome type 1B

Abstract: USHER syndrome represents the association of a hearing impairment with retinitis pigmentosa1 and is the most frequent cause of deaf–blindness in humans. It is inherited as an autosomal recessive trait which is clinically and genetically heterogeneous2,3. Some patients show abnormal organization of microtubules in the axoneme of their photoreceptors cells (connecting cilium)4–6, nasal ciliar cells7 and sperm cells5, as well as widespread degeneration of the organ of Corti8. Usher syndrome type 1 (USH1) is characterized by a profound congenital sensorineural hearing loss, constant vestibular dysfunction and prepubertal onset of retinitis pigmentosa. Of three different genes responsible for USH19–11,USH1B maps to 11q13.5 (ref. 10) and accounts for about 75% of USH1 patients2,3. The mouse deafness shaker-1 (shl) mutation has been localized to the homologous murine region12,13. Taking into account the cytoskeletal abnormalities in USH patients, the identification of a gene encoding an unconventional myosin as a candidate for shaker-1(ref. 14) led us to consider the human homo-logue as a good candidate for the gene that is defective in USH1B. Here we present evidence that a gene encoding myosin VIIA is responsible for USH1B. Two different premature stop codons, a six-base-pair deletion and two different missense mutations were detected in five unrelated families. In one of these families, the mutations were identified in both alleles. These mutations, which are located at the amino-terminal end of the motor domain of the protein, are likely to result in the absence of a functional protein. Thus USH IB appears as a primary cytoskeletal protein defect. These results implicate the genes encoding other unconventional myosins and their interacting proteins as candidates for other genetic forms of Usher syndrome.

Concentration of measure and isoperimetric inequalities in product spaces

Abstract: The concentration of measure phenomenon in product spaces roughly states that, if a set A in a product ΩN of probability spaces has measure at least one half, “most” of the points of Ωn are “close” to A. We proceed to a systematic exploration of this phenomenon. The meaning of the word “most” is made rigorous by isoperimetrictype inequalities that bound the measure of the exceptional sets. The meaning of the work “close” is defined in three main ways, each of them giving rise to related, but different inequalities. The inequalities are all proved through a common scheme of proof. Remarkably, this simple approach not only yields qualitatively optimal results, but, in many cases, captures near optimal numerical constants. A large number of applications are given, in particular to Percolation, Geometric Probability, Probability in Banach Spaces, to demonstrate in concrete situations the extremely wide range of application of the abstract tools.

Peptides as weapons against microorganisms in the chemical defense system of vertebrates

Abstract: The innate immunity of vertebrates to microbial invasion is arbitrated by a network of host-defense mechanisms involving both the long-lasting highly specific responses of the cell-mediated immune system and a nonspecific chemical defense system based on a series of broad-spectrum antimicrobial peptides that are analogous to those found in insects. Vertebrate antibiotic peptides secreted by nonlymphoid cells of the mucosal surfaces of the respiratory and gastrointestinal tracts as well as by the granular glands of the skin reportedly cause the lysis of numerous pathogenic microorganisms, including viruses, gram-positive and gram-negative bacteria, protozoa, yeasts, and fungi, as well as of cancer cells. Antimicrobial peptides isolated from vertebrates have three characteristic properties: They are relatively small (20-46 amino acid residues), basic (lysine- or arginine-rich), and amphipathic. Although these peptides differ widely in length and amino acid sequences, they may be grouped in four broad families based on characteristic structural features. Although the precise mechanism of action of these peptides remains to be defined, their microbicidal effect very likely results from their capacity to form channels or pores within the microbial membrane in order to permeate the cell and impair its ability to carry out anabolic processes. This secondary, chemical immune system provides vertebrates with a repertoire of small peptides that are promptly synthesized upon induction, easily stored in large amounts, and readily available for antimicrobial warfare.

Cognition and artifacts: a contribution to the study of though in relation to instrumented activity

Abstract: This paper addresses from a theoretical point of view a once much debated issue which is brought back to the fore in psychology as a result of a growing attention to the effects of technology and of technological change on the way we live, learn and work. This issue concerns the relationships between cognition and the artifactual nature of many of the objects on which it is brought to bear in everyday, work and school situations. If cognition evolves, as genetic epistemology has shown, through interaction with the environment, then it can be expected, in the course of its genesis, to have to accomodate to the particular specific functional and structural features which characterize artifacts. Does this have an effect on cognitive development, on knowledge construction and processing, on the nature itself of the knowledge generated? If so, through what macro and microgenetic processes can this effect be thought to be actuated? These questions are of particular relevance in the fields of technology and vocational education, but, in theory, they concern all situations in which activity is instrumented by some sort of technology including technology not habitually considered as such: symbols, numbers, graphics, etc. They also constitute an important dimension in the study of situated cognition. Discussion focuses first on the way past and present models of human cognition have related to instrumented activity and, subsequently, a model and concepts are suggested. These points are then illustrated through observational data relating to situations in which children were confronted with tasks involving designing artifacts and utilizing unfamiliar machines, i.e. a lathe and a robot. Finally areas for future research within this problematic are sketched out.

Contróle Exact De Léquation De La Chaleur

Abstract: (1995). Controle Exact De Lequation De La Chaleur. Communications in Partial Differential Equations: Vol. 20, No. 1-2, pp. 335-356.

Afferent connections of the medial frontal cortex of the rat. II. Cortical and subcortical afferents

Abstract: In order to compare the frontal cortex of rat and macaque monkey, cortical and subcortical afferents to subdivisions of the medial frontal cortex (MFC) in the rat were analyzed with fluorescent retrograde tracers. In addition to afferent inputs common to the whole MFC, each subdivision of the MFC has a specific pattern of afferent connections. The dorsally situated precentral medial area (PrCm) was the only area to receive inputs from the somatosensory cortex. The specific pattern of afferents common to the ventrally situated prelimbic (PL) and infralimbic (IL) areas included projections from the agranular insular cortex, the entorhinal and piriform cortices, the CA1-CA2 fields of the hippocampus, the subiculum, the endopiriform nucleus, the amygdalopiriform transition, the amygdalohippocampal area, the lateral tegmentum, and the parabrachial nucleus. In all these structures, the number of retrogradely labeled cells was larger when the injection site was located in area IL. The dorsal part of the anterior cingulate area (ACd) seemed to be connectionally intermediate between the adjacent areas PrCm and PL; it receives neither the somatosensory inputs characteristic of area PrCm nor the afferents characteristic of areas PL and IL, with the exception of the afferents from the caudal part of the retrosplenial cortex. A comparison of the pattern of afferent and efferent connections of the rat MFC with the pattern of macaque prefrontal cortex suggests that PrCm and ACd areas share some properties with the macaque premotor cortex, whereas PL and IL areas may have characteristics in common with the cingulate or with medial areas 24, 25, and 32 and with orbital areas 12, 13, and 14 of macaques.

The thermodynamics of fractals revisited with wavelets

Abstract: The multifractal formalism originally introduced to describe statistically the scaling properties of singular measures is revisited using the wavelet transform. This new approach is based on the definition of partition functions from the wavelet transform modulus maxima. We demonstrate that very much like thermodynamic functions, the generalized fractal dimensions D q and the f ( α ) singularity spectrum can be readily determined from the scaling behavior of these partition functions. We show that this method provides a natural generalization of the classical box-counting techniques to fractal signals, the wavelets playing the role of “generalized boxes”. We illustrate our theoretical considerations on pedagogical examples, e.g., devil's staircases and fractional Brownian motions. We also report the results of some recent application of the wavelet transform modulus maxima method to fully developed turbulence data. That we emphasize the wavelet transform as a mathematical microscope that can be further used to extract microscopic informations about the scaling properties of fractal objects. In particular, we show that a dynamical system which leaves invariant such an object can be uncovered form the space-scale arrangement of its wavelet transform modulus maxima. We elaborate on a wavelet based tree matching algorithm that provides a very promising tool for solving the inverse fractal problem. This step towards a statistical mechanics of fractals is illustrated on discrete period-doubling dynamical systems where the wavelet transform is shown to reveal the renormalization operation which is essential to the understanding of the universal properties of this transition to chaos. Finally, we apply our technique to analyze the fractal hierarchy of DLA azimuthal Cantor sets defined by intersecting the inner frozen region of large mass off-lattice diffusion-limited aggregates (DLA) wit a circle. This study clearly lets out the existence of an underlying multiplicative process that is likely to account for the Fibonacci structural ordering recently discovered in the apparently disordered arborescent DLA morphology.

SUMER — Solar Ultraviolet Measurements of Emitted Radiation

Abstract: The instrument SUMER — Solar Ultraviolet Measurements of Emitted Radiation is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere, from the chromosphere through the transition region to the inner corona, over a temperature range from 104 to 2 x 106 K and above. These observations will permit detailed spectroscopic diagnostics of plasma densities and temperatures in many solar features, and will support penetrating studies of underlying physical processes, including plasma flows, turbulence and wave motions, diffusion transport processes, events associated with solar magnetic activity, atmospheric heating, and solar wind acceleration in the inner corona. Specifically, SUMER will measure profiles and intensities of EUV lines; determine Doppler shifts and line broadenings with high accuracy; provide stigmatic images of the Sun in the EUV with high spatial, spectral, and temporal resolution; and obtain monochromatic maps of the full Sun and the inner corona or selected areas thereof. SUMER will be flown on the Solar and Heliospheric Observatory (SOHO), scheduled for launch in November, 1995. This paper has been written to familiarize solar physicists with SUMER and to demonstrate some command procedures for achieving certain scientific observations.

Robust acoustic time reversal with high-order multiple scattering

Abstract: We report the first experiments showing the reversibility of transient acoustic waves through high-order multiple scattering by means of an acoustic time-reversal mirror. A point source generates a pulse which scatters through 2000 steel rods immersed in water. The time-reversed waves are found to converge to their source and recover their original wave form, despite the high order of multiple scattering involved and the usual sensitivity to initial conditions of time-reversal processes. Surprisingly, the observed resolution was one-sixth of the theoretical limit for the mirror's aperture.

The Coronal Diagnostic Spectrometer for the solar and heliospheric observatory

Abstract: The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150–800 A. By observing the intensities of selected lines and line profiles we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Furthermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere.

Magnetism of Heterobimetallics: Toward Molecular-Based Magnets

Abstract: Publisher Summary The field of heterobimetallic systems has developed tremendously over the past several years particularly in relation to the synthesis of molecular-based magnets This chapter reviews the advancements in the field of bimetallic magnets The chapter also discusses some key concepts in molecular magnetism—as spin delocalization, spin polarization—and the interaction between two spin carriers Several compounds are presented in order of increasing nuclearity and dimensionality The chapter focuses on the bridges that have allowed the design of molecular-based magnets These bridges are oxamato, oxamido, oxalato, dithiooxalato, oximato, and cyano Molecular magnetism has emerged as a novel field of research over the past several years This field concerns the chemistry and the physics of open-shell molecules and molecular assemblies containing open-shell units Among all molecules and molecular assemblies relevant to molecular magnetism, those containing two (or possibly more) kinds of metal ions have played a particularly important role

Relationship between Hepatitis C Virus Genotypes and Sources of Infection in Patients with Chronic Hepatitis C

Abstract: This study examined the relationships between hepatitis C virus (HCV) genotypes and the routes of HCV transmission in 101 patients with chronic hepatitis C. Patients who received blood transfusions (43%) and those with chronic hepatitis C of unknown cause (37%) had similar mean ages, age distribution, and HCV genotype distribution (1a, 19% vs. 14% ; 16, 52% vs. 54% ; 3a, 10% vs. 9% ; other, 19% vs. 23%). Intravenous drug users (IVDUs) were significantly younger and had a different genotype distribution (1a, 33% ; 16, 0 ; 3a, 63% ; other, 5% ; P < .001). Transmission of HCV 3a has been observed only over the past 20 years ; other genotypes were transmitted up to 40 years ago. These results suggest that for 20 years there have been two independent ongoing hepatitis C epidemics. One affects persons who received blood transfusions or whose source of infection is unknown. These persons are older and are mainly infected by HCV 1b. The second type of infection occurs in IVDUs and infects younger persons, mainly with HCV 3a.

NPI1, an essential yeast gene involved in induced degradation of Gap1 and Fur4 permeases, encodes the Rsp5 ubiquitin-protein ligase

Abstract: When yeast cells growing on a poor nitrogen source are supplied with NH4+ ions, several nitrogen permeases including the general amino acid permease (Gap1p) are rapidly and completely inactivated. This report shows that inactivation by NH4+ of the Gap1 permease is accompanied by its degradation. A functional NPl1 gene product is required for both inactivation and degradation of Gap1p. Molecular analysis of the NPl1 gene showed that it is identical to RSP5. The RSP5 product is a ubiquitin-protein ligase (E3 enzyme) whose physiological function was, however, unknown. Its C-terminal region is very similar to that of other members of the E6-AP-like family of ubiquitin-protein ligases. Its N-terminal region contains a single C2 domain that may be a Ca(2+)-dependent phospholipid interaction motif, followed by several copies of a recently identified domain called WW(P). The Npi1/Rsp5 protein has a homologue both in humans and in mice, the latter being involved in brain development. Stress-induced degradation of the uracil permease (Fur4p), a process in which ubiquitin is probably involved, was also found to require a functional NPl1/RSP5 product. Chromosomal deletion of NPl1/RSP5 showed that this gene is essential for cell viability. In the viable npi1/rsp5 strain, expression of NPl1/RSP5 is reduced as a result of insertion of a Ty1 element in its 5' region. Our results show that the Npi1/Rsp5 ubiquitin-protein ligase participates in induced degradation of at least two permeases, Gap1p and Fur4p, and probably also other proteins.

A 200-amino acid ATPase module in search of a basic function

Abstract: A fast growing family of ATPases has recently been highlighted. It was named the AAA family, for ATPases Associated to a variety of cellular Activities. The key feature of the family is a highly conserved module of 230 amino acids present in one or two copies in each protein. Despite extensive sequence conservation, the members of the family fulfil a large diversity of cellular functions: cell cycle regulation, gene expression in yeast and HIV, vesicle-mediated transport, peroxisome assembly, 26S protease function etc. In addition, several members of this family can be found in the same organism (up to 17 in S. cerevisiae). The contrast between functional diversity and structural conservation of the module, from archaebacteria to mammals, suggests that it plays an essential, but as yet unknown, role at key points of the cellular machinery. Two (non-exclusive) such possibilities are: (1) ATP-dependent proteasome function and (2) ATP-dependent anchorage of proteins. Finally, the basic biochemical activity of the AAA module is still a matter of speculation, and we propose that it acts as an ATP-dependent protein clamp.

Characterizing long-range correlations in DNA sequences from wavelet analysis.

Abstract: The fractal scaling properties of DNA sequences are analyzed using the wavelet transform. Because the wavelet transform microscope can be made blind to the ``patchiness'' of genomic sequences, we demonstrate and quantify the existence of long-range correlations in genes containing introns and noncoding regions. Moreover, the fluctuations in the patchy landscapes of DNA walks are found to be homogeneous with Gaussian statistics.

Extrahepatic Immunologic Manifestations in Chronic Hepatitis C and Hepatitis C Virus Serotypes

Abstract: Objective: To determine, using a serotyping assay, whether the occurrence of extrahepatic immunologic disorders in patients with chronic hepatitis C is dependent on hepatitis C virus serotype. Desi...

Male pseudohermaphroditism due to a homozygous missense mutation of the luteinizing hormone receptor gene

Abstract: Leydig cell hypoplasia is a rare autosomal recessive condition that interferes with normal development of male external genitalia in 46,XY individuals. We have studied two Leydig cell hypoplasia patients (siblings born to consanguineous parents), and found them to be homozygous for a missense mutation (Ala593Pro) in the sixth transmembrane domain of the luteinizing hormone (LH) receptor gene. In vitro expression studies showed that this mutated receptor binds human choriogonadotropin with a normal KD, but the ligand binding does not result in increased production of cAMP. We conclude that a homozygous LH receptor gene mutation underlies the syndrome of autosomal recessive congenital Leydig cell hypoplasia in this family. These results have implications for the understanding of the development of the male genitalia.

Multicentre study of cancer pain and its treatment in France

Abstract: Objective: To describe the treatment of cancer pain in France and to evaluate the predictive factors for inadequate management. Design: Multicentre, representative cross sectional survey. Setting: 20 treatment centres, including cancer centres, university hospitals, state hospitals, private clinics, and one homecare setting (in which patients are supported at home). Subjects: 605 patients with cancer. Main measures: Patients rated prevalence and severity of pain and functional impairment related to pain. Doctors reported patients9 cancer characteristic, performance status, pain severity, and analgesic drugs ordered. Results: 57% (340/601) of patients with cancer reported pain due to their disease, and, of those with pain, 69% (224/325) rated their worst pain at a level that impaired their ability to function. 30% (84/279) were reported as receiving no drugs for their pain. Of the 270 patients in pain for whom information on treatment was available 51% (137/270) were not receiving adequate pain relief, according to an index based on the World Health Organisation9s guidelines. French doctors were found to underestimate the severity of their patients9 pain. Younger patients, patients without metastatic disease, patients with a better performance status, and patients who rated their pain as more severe than their doctors did were at greater risk for undertreatment of their pain. Conclusions: In the light of the high prevalence and the severity of pain among patients with cancer, the assessment and treatment of cancer pain in France remain inadequate, emphasising the need for changes in patient care. Key messages Key messages Data on prevalence, severity, and treatment of pain in patients with cancer are fragmentary This national French study shows that pain is present in over half of cancer patients, that more than two thirds rate their worst pain as impairing their ability to function, and that half of patients in pain do not receive adequate treatment Doctors underestimate the severity of their patients9 cancer pain and provide inadequate treatment These results are useful baseline data against which to evaluate future programmes for the control of cancer pain in France