Showing papers by "Université Paris-Saclay published in 2001"

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

Indian Ocean Experiment: An integrated analysis of the climate forcing and effects of the great Indo-Asian haze

Abstract: Every year, from December to April, anthropogenic haze spreads over most of the North Indian Ocean, and South and Southeast Asia. The Indian Ocean Experiment (INDOEX) documented this Indo-Asian haze at scales ranging from individual particles to its contribution to the regional climate forcing. This study integrates the multiplatform observations (satellites, aircraft, ships, surface stations, and balloons) with one- and four-dimensional models to derive the regional aerosol forcing resulting from the direct, the semidirect and the two indirect effects. The haze particles consisted of several inorganic and carbonaceous species, including absorbing black carbon clusters, fly ash, and mineral dust. The most striking result was the large loading of aerosols over most of the South Asian region and the North Indian Ocean. The January to March 1999 visible optical depths were about 0.5 over most of the continent and reached values as large as 0.2 over the equatorial Indian ocean due to long-range transport. The aerosol layer extended as high as 3 km. Black carbon contributed about 14% to the fine particle mass and 11% to the visible optical depth. The single-scattering albedo estimated by several independent methods was consistently around 0.9 both inland and over the open ocean. Anthropogenic sources contributed as much as 80% (±10%) to the aerosol loading and the optical depth. The in situ data, which clearly support the existence of the first indirect effect (increased aerosol concentration producing more cloud drops with smaller effective radii), are used to develop a composite indirect effect scheme. The Indo-Asian aerosols impact the radiative forcing through a complex set of heating (positive forcing) and cooling (negative forcing) processes. Clouds and black carbon emerge as the major players. The dominant factor, however, is the large negative forcing (-20±4 W m^(−2)) at the surface and the comparably large atmospheric heating. Regionally, the absorbing haze decreased the surface solar radiation by an amount comparable to 50% of the total ocean heat flux and nearly doubled the lower tropospheric solar heating. We demonstrate with a general circulation model how this additional heating significantly perturbs the tropical rainfall patterns and the hydrological cycle with implications to global climate.

Ethanol catabolism in Aspergillus nidulans: a model system for studying gene regulation.

Abstract: This article reviews our knowledge of the ethanol utilization pathway (alc system) in the hyphal fungus Aspergillus nidulans. We discuss the progress made over the past decade in elucidating the two regulatory circuits controlling ethanol catabolism at the level of transcription, specific induction, and carbon catabolite repression, and show how their interplay modulates the utilization of nutrient carbon sources. The mechanisms featuring in this regulation are presented and their modes of action are discussed: First, AlcR, the transcriptional activator, which demonstrates quite remarkable structural features and an original mode of action; second, the physiological inducer acetaldehyde, whose intracellular accumulation induces the alc genes and thereby a catabolic flux while avoiding intoxification; third, CreA, the transcriptional repressor mediating carbon catabolite repression in A. nidulans, which acts in different ways on the various alc genes; Fourth, the promoters of the structural genes for alcohol dehydrogenase (alcA) and aldehyde dehydrogenase (aldA) and the regulatory alcR gene, which exhibit exceptional strength compared to other genes of the respective classes. alc gene expression depends on the number and localization of regulatory cis-acting elements and on the particular interaction between the two regulator proteins, AlcR and CreA, binding to them. All these characteristics make the ethanol regulon a suitable system for induced expression of heterologous protein in filamentous fungi.

Wyburn-Mason or Bonnet-Dechaume-Blanc as Cerebrofacial Arteriovenous Metameric Syndromes (CAMS): A New Concept and a New Classification

Abstract: The diagnosis of Bonnet-Dechaume-Blanc or Wyburn-Mason syndrome encompasses a spectrum of phenotypic expression Features of the syndrome as originally described, and common to all, include arteriovenous malformations of the brain and orbit (with retinal and/or retrobulbar lesions) A portion of these patients manifest the complete expression of the disease with additional high-flow arteriovenous malformations of the maxillofacial or mandibular regions These present the distinct and additional risks of life-threatening epistaxis or gingival haemorrhage We suggest new diagnostic criteria for the syndrome Applying insights from modern developmental biology to our series of 15 patients (the largest to date), together with a review of the literature`, we have recognised metameric patterns of involvement in what we believe to be a disease of the neural crest or adjacent cephalic mesoderm This allows us to propose a new rational classification reflecting the putative, underlying disorder and to suggest a new name: Cerebrofacial Arteriovenous Metameric Syndrome (CAMS)

Trans-ethnic fine mapping of a quantitative trait locus for circulating angiotensin I-converting enzyme (ACE).

Abstract: Circulating angiotensin I-converting enzyme (ACE) levels are influenced by a major quantitative trait locus (QTL) that maps to the ACE gene. Phylogenetic and measured haplotype analyses have suggested that the ACE-linked QTL lies downstream of a putative ancestral breakpoint located near to position 6435. However, strong linkage disequilibrium between markers in the 3' portion of the gene has prevented further resolution of the QTL in Caucasian subjects. We have examined 10 ACE gene polymorphisms in Afro-Caribbean families recruited in JAMAICA: Variance components analyses showed strong evidence of linkage and association to circulating ACE levels. When the linkage results were contrasted with those from a set of British Caucasian families, there was no evidence for heterogeneity between the samples. However, patterns of allelic association between the markers and circulating ACE levels differed significantly in the two data sets. In the British families, three markers [G2215A, Alu insertion/deletion and G2350A] were in complete disequilibrium with the ACE-linked QTL. In the Jamaican families, only marker G2350A showed strong but incomplete disequilibrium with the ACE-linked QTL. These results suggest that additional unobserved polymorphisms have an effect on circulating ACE levels in Jamaican families. Furthermore, our results show that a variance components approach combined with structured, quantitative comparisons between families from different ethnic groups may be a useful strategy for helping to determine which, if any, variants in a small genomic region directly influence a quantitative trait.

Mutagenesis and heterologous expression in yeast of a plant Δ6‐fatty acid desaturase

Abstract: Membrane-bound microsomal fatty acid desaturases are known to have three conserved histidine boxes, comprising a total of up to eight histidine residues. Recently, a number of deviations from this consensus have been reported, with the substitution of a glutamine for the first histidine residue of the third histidine box being present in the so called 'front end' desaturases. These enzymes are also characterized by the presence of a cytochrome b 5 domain at the protein N-terminus. Site-directed mutagenesis has been used to probe the functional importance of a number of amino acid residues which comprise the third histidine box of a 'front end' desaturase, the borage Δ 6 -fatty acid desaturase. This showed that the variant glutamine in the third histidine box is essential for enzyme activity and that histidine is not able to substitute for this residue.

Aquaporins in Saccharomyces: Characterization of a second functional water channel protein

Abstract: The Saccharomyces cerevisiae genome database contains two ORFs with homology to aquaporins, AQY1 and AQY2. Aqy1p has been shown to be a functional aquaporin in some strains, such as Sigma1278b. AQY2 is disrupted by a stop codon in most strains; however, Sigma1278b has an intact ORF. Because Sigma1278b Aqy2p has an intracellular localization in Xenopus oocytes and in yeast, other strains of yeast were examined. Aqy2p from Saccharomyces chevalieri has a single amino acid in the third transmembrane domain (Ser-141) that differs from Sigma1278b Aqy2p (Pro-141). S. chevalieri Aqy2p is a functional water channel in oocytes and traffics to the plasma membrane of yeast. The Sigma1278b parental strain, the aqy1-aqy2 double null yeast, and null yeast expressing S. chevalieri Aqy2p were examined under various conditions. Comparison of these strains revealed that the aquaporin null cells were more aggregated and their surface was more hydrophobic. As a result, the aquaporin null cells were more flocculent and more efficient at haploid invasive growth. Despite its primary intracellular localization, Sigma1278b Aqy2p plays a role in yeast similar to Aqy1p and S. chevalieri Aqy2p. In addition, Aqy1p and Aqy2p can affect cell surface properties and may provide an advantage by dispersing the cells during starvation or during sexual reproduction.

Exploring polar stratospheric cloud and ozone minihole formation: The primary importance of synoptic-scale flow perturbations

Abstract: The formation of polar stratospheric clouds (PSCs) is sometimes attributed to cooling induced by mountain waves. Some examples of PSCs explained by this mechanism are found in the literature. Other studies show that the cooling producing PSCs is of synoptic scale. In this paper we use data from Polar Ozone Aerosol Measurement (POAM) II and from TIROS Operational Vertical Sounder (TOVS) showing coincident occurrences of PSCs and ozone miniholes over the sea and land. Using European Centre for Medium-Range Weather Forecasts (ECMWF) analyses, we show that when both PSCs and localized ozone minima appear, they are associated primarily with anticyclonic potential vorticity anomalies near the tropopause. The flow anomaly penetrates upward and downward, inducing an upward displacement of isentropic surfaces above and a downward displacement below, the upward and downward penetration being consistent with the deformation scale. These flow anomalies result in synoptic-scale quasi-adiabatic uplift through the lower stratosphere. The adiabatic cooling of the air masses creates the conditions for PSC formation. Coincidentally, the ozone partial pressure decreases, and the localized ozone minimum appears. Our purpose in this paper is to show that the primary PSC formation mechanism in the Arctic is the same as for minihole formation: synoptic-scale dynamics. We show three multiday sequences of PSCs and localized ozone minima. We reveal the robustness of the PSC/dynamics link by showing multiyear, monthly statistics of POAM II PSC sighting fraction compared with PSC formation temperature and isentropic geopotential.

Measurement of the B → J/ψK*(892) decay amplitudes

Abstract: We present a measurement of the decay amplitudes in B-->J/psi K^*(892) channels using 20.7 fb-1 of data collected at the Upsilon(4S) resonance with the BABAR detector at PEP-II. We measure a P-wave fraction R_perp = (16.0+/-3.2+/-1.4)% and a longitudinal polarization fraction (59.7+/-2.8+/-2.4)%. The measurement of a relative phase that is neither 0 nor pi, phi_ll = 2.50+/-0.20+/-0.08 radians, favors a departure from the factorization hypothesis. Although the decay B-->J/psi Kpi proceeds mainly via K^*(892), there is also evidence for K^*_2(1430) and Kpi S-wave contributions.

HiHCoHP-Toward a realistic communication model for hierarchical hyperclusters of heterogeneous processors

Abstract: A parameterized model of hyperclusters of processors-clusters of clusters of... of clusters of processors-is formulated under which a hypercluster enjoys generality along three orthogonal axes: (1) Its processors are heterogeneous: they may have different computational powers (speed of computation and memory access). (2) Its constituent clusters are interconnected via a hierarchy of networks of possibly differing bandwidths and speeds. (3) Its clusters at each level of the hierarchy are heterogeneous: they may differ in size. The model accounts for architectural details such as the bandwidths and transit costs of both networks and their ports. The algorithmic tractability of the model is demonstrated via broadcast and reduction algorithms, which are predictably efficient in general and actually optimal in special circumstances.

Clustered DNA Damages as Dosemeters for Ionising Radiation Exposure and Biological Responses

Abstract: Clustered DNA damages-two or more lesions (oxidised bases, abasic sites, or strand breaks) within a few DNA helical turns on opposing strands-are induced in DNA in solution and in vivo in human cells by ionising radiation. They have been postulated to be difficult to repair, and thus of potentially high biological significance. Since the total of clustered damages produced by ionising radiation is at about 3 to 4 times higher levels than double-strand breaks and are apparently absent in unirradiated cells, levels of clustered damages present immediately after radiation exposure could serve as sensitive dosemeters of radiation exposure. Since some clusters may not be repairable and may accumulate in cells, they might also be useful as integrating dosemeters of biological effects of radiation damage.

Measurement of the decays B → φK and B → φK*

Abstract: We have observed the decays B--> phiK and phiK(*) in a sample of over 45 million B mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are B(B+--> phiK+) = (7.7(+1.6)(-1.4)+/-0.8)x10(-6), B(B0--> phiK0) = (8.1(+3.1)(-2.5)+/-0.8)x10(-6), B(B+--> phiK(*+)) = (9.7(+4.2)(-3.4)+/-1.7)x10(-6), and B(B0--> phiK(*0)) = (8.7(+2.5)(-2.1)+/-1.1)x10(-6). We also report the upper limit B(B+--> phipi(+))<1.4x10(-6) ( 90% C.L.).

Linear polarization measurement of interband transitions in superdeformed 190Hg: Model-independent evidence for octupole vibrational structures

Abstract: The linear polarization of $\ensuremath{\gamma}$ rays between excited and yrast superdeformed (SD) states in ${}^{190}\mathrm{Hg}$ was measured using the four-element CLOVER detectors of the EUROBALL IV $\ensuremath{\gamma}$-ray spectrometer. This measurement shows in a model-independent way that the interband transitions which compete with the highly collective in-band quadrupole transitions are largely enhanced electric dipoles. Not only do these results represent the first measurement of the multipolarity of transitions between different SD states, but they also provide strong evidence for the interpretation of the structures in the SD minimum of the $A\ensuremath{\sim}190$ region in terms of octupole excitations.

A fictitious-gas based statistical narrow-band model for ir long-range sensing of h2o at high temperature

Abstract: An original approximate model, similar to Ludwig's multigroup statistical narrow-band model, and to the fictitious gas CK model (CKFG) has been developed and validated to treat IR long-range sensing applications involving H2O as emitting and absorbing species. The main idea is to split the lines of a gas into N classes depending on the values of E″, the energies of the lower levels of the transitions. The statistical narrow-band (SNB) model and the Curtis–Godson approximation are applied separately to each class. Parameters of the model have been extracted from an adjustment of the curves of growth obtained from line-by-line calculations. Relative errors of the model in typical conditions of atmospheric long-range sensing are about a few per cent by reference to line-by-line calculations, much smaller than errors due to a classical SNB approach in the same conditions.

Synthesis and Metal Ion Extraction of Calix[4]crown-6-azacrown-5

Abstract: have received much attention because of theirstructural peculiarities. They present two binding siteslocated on both sides of the calixarene and are linked to eachother by a π-basic aromatic tunnel. Previously, we reported the synthesis of calix[4]azacrownethers in which an oxygen atom is replaced by a nitrogenatom and their selective metal or ammonium ion complex-ation.

Measurement of the branching fractions for ψ(2s)→e+e- and ψ(2s)→μ+μ-

Abstract: We measure the branching fractions of the psi(2S) meson to the leptonic final states e+e- and mu+mu- relative to that for psi(2S)-->J/psi pi+pi-. The method uses psi(2S) mesons produced in the decay of B mesons at the Upsilon(4S) resonance in a data sample collected with the BABAR detector at the Stanford Linear Accelerator Center. Using previous measurements for the psi(2S)-->J/psi pi+pi- branching fraction, we determine the e+e- and mu+mu- branching fractions to be 0.0078+/-0.0009+/-0.0008 and 0.0067+/-0.0008+/-0.0007 respectively.

U-Curved Relation Between Total Fasting Serum Cholesterol and Hostility: A Population-Based Study

Abstract: Some researchers have found higher cholesterol levels linearly related to hostility, whereas others have found no relation. Even so, it remains unclear whether research should seek to find a linear relation between hostility and cholesterol levels. We hypothesized that a U-curved association was the proper test of the relation between hostility and cholesterol. Total fasting and low-density lipoprotein (LDL) cholesterol levels were collected from a population-based sample of 2,306 Canadians. Barefoot’s (1989) scoring of the Cook-Medley Hostility Scale was used to assess hostility levels. Both a linear and a U-curved relation among hostility scores, fasting total, and LDL cholesterol levels were significant. Participants with low and high cholesterol levels had significantly higher hostility scores than the normal cholesterol group. A U-curved relation between hostility and serum cholesterol levels may be a more appropriate function to consider given the all-cause mortality findings we seek to explain.

Sensitivity of temperature and concentration measurements in hot gases from ftir emission spectroscopy

Abstract: The IR emission spectra of combustion gases in a quasi-two-dimensional burner have been measured and processed for temperature and concentration determinations. A Fourier transform spectrometer with a spectral resolution up to 0.02 cm −1 has been used in the spectral range 1700– 4300 cm −1 . An original data reduction procedure based on the adjustment of the measured spectra and calculated ones at low spectral resolution has been developed and is shown to be efficient for temperature, CO2 and H2O measurements. The temperature was also deduced from the ratio of the intensities of a suitable pair of CO lines and CO concentration was determined from individual CO line intensities. The sensitivity of the different data reduction procedures is discussed and FTIR results are also compared to probe measurements.

Fractional quantum Hall junctions and two-channel Kondo models

Abstract: A mapping between fractional quantum Hall (FQH) junctions and the two-channel Kondo model is presented. We discuss this relation in detail for the particular case of a junction of a FQH state at {nu}=1/3 and a normal metal. We show that in the strong coupling regime this junction has a non-Fermi-liquid fixed point. At this fixed point the electron Green{close_quote}s function has a branch cut and the impurity entropy is equal to S=1/2ln2. We construct the space of perturbations at the strong coupling fixed point and find that the dimension of the tunneling operator is 1/2. These properties are strongly reminiscent of the non-Fermi-liquid fixed points of a number of quantum impurity models, particularly the two-channel Kondo model. However we have found that, in spite of these similarities, the Hilbert spaces of these two systems are quite different. In particular, although in a special limit the Hamiltonians of both systems are the same, their Hilbert spaces are not since they are determined by physically distinct boundary conditions. As a consequence the spectrum of operators in the two problems is different.