Showing papers by "Aix-Marseille University published in 1992"
TL;DR: In this paper, the number of light neutrino species is found to be Nv=3.30% CL with the constraints of the standard electroweak model, which rules out the possibility of a fourth type of LN at 98% CL.
234 citations
TL;DR: The Mediterranean seagrass Posidonia oceanica shows a clear distinction in two subcompartments regarding turnover time: aboveground and belowground as mentioned in this paper, where aboveground parts (leaves) are highly dynamic and most of the leaf material is decomposed or exported in less than one year, representing a net loss of nutrients.
Abstract: . The ecosystem associated to the Mediterranean seagrass Posidonia oceanica shows a clear distinction in two subcompartments regarding turnover time: aboveground and belowground. Aboveground parts (leaves) are highly dynamic, and most of the leaf material is decomposed or exported in less than one year, representing a net loss of nutrients. In contrast, belowground biomass (roots and rhizomes) has a turnover time of the order of centuries, with a consequent accumulation of organic matter in the sediment. The accumulation rates for the single elements rank in the order C > N > P. This ecosystem may be considered as a sink for biogenic elements.
144 citations
TL;DR: Significant differences in the number of species, number of individuals, biomass, and trophic structure of the fish assemblage were observed between sampling methods, and particular attention should be paid to the biases induced by sampling techniques when interpreting data.
Abstract: Fishes associated with the seagrass Posidonia oceanica were censused both by skid trawl and visual counts around Ischia Island, Italy Both sampling procedures were performed during the day in summer and in winter at two sites Significant differences in the number of species, number of individuals, biomass, and trophic structure of the fish assemblage were observed between sampling methods Fewer fish species were recorded by visual counts than by trawling More individuals and a greater biomass, however, were recorded from visual counts The population of macrocarnivores (Scorpaenidae, Serranidae) were better estimated by trawling, as were canopy-dwellers (Syngnathidae; Symphodus rostratus) and benthic species (Gobiidae; Blenniidae; Bothidae) Conversely, good swimmers (Sparidae; Coris julis, Symphodus spp), and planktivorous fishes (Centracanthidae, Pomacentridae) mostly escaped the trawl and were better assessed by visual counts The importance of methodological biases differed from one season to the other and was higher in summer than in winter Particular attention should be paid to the biases induced by sampling techniques when interpreting data, and different sampling methods should be used to accurately study the fish assemblages of seagrass meadows
129 citations
TL;DR: Scanning electron microscopic evaluations showed that preparation with a laser beam is possible and results in an improvement in the cleanliness of the canal walls when compared with conventional techniques.
121 citations
TL;DR: Comparative analysis of the spindle proprioceptive activities recorded in response to either vibration or isometric contractions suggests that these motor after-effects may both result from the fact that theSpindle afferents from agonist and antagonist muscles are asymmetrically activated in these two particular situations.
77 citations
TL;DR: Phylogenetic analyses undertaken using different methods showed deep radiations of phyla such as Ctenophora, Cnidaria and Placozoa but also for groups of Porifera of low taxonomic rank and some unexpected relationships were revealed among PoriferA.
Abstract: Sequences from the 5' end terminal part of 28S ribosomal RNA were obtained and compared for 22 animals belonging to all diploblastic phyla and for a large number of representatives of triploblastic Metazoa and protists. Phylogenetic analyses undertaken using different methods showed deep radiations of phyla such as Ctenophora, Cnidaria and Placozoa but also for groups of Porifera of low taxonomic rank. Short internodes between these radiations suggested an early rapid diversification of diploblasts. A long internal branch preceding the diversification of all triploblasts analyzed could be explained either by a long period with a single ancestor or by the extinction of the earliest triploblastic radiations. Finally some unexpected relationships were revealed among Porifera.
70 citations
TL;DR: The multilayered pattern of the brain parenchyma corresponding to the cellular migrational process is demonstrated in the in vivo MR study of a 23-week-old fetus.
Abstract: The multilayered pattern of the brain parenchyma corresponding to the cellular migrational process is demonstrated in the in vivo MR study of a 23-weck-old fetus.
65 citations
TL;DR: In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer, and presents very encouraging blood tolerability properties.
Abstract: The left ventricular assist device is based on the principle of the Maillard-Wenkel rotative pump. The materials which make up the pump must present particular mechanical, tribological, thermal and chemical properties. Titanium nitride (TiN) because of its surface properties and graphite because of its bulk characteristics have been chosen. The present study evaluated the in vitro hemocompatibility of TiN coating deposited by the chemical vapor deposition process. Protein adsorption, platelet retention and hemolysis tests have been carried out. In spite of some disparities, the TiN behavior towards albumin and fibrinogen is interesting, compared with the one of a reference medical grade elastomer. The platelet retention test gives similar results as those achieved with the same elastomer. The hemolysis percentage is near to zero. TiN shows interesting characteristics, as far as mechanical and tribological problems are concerned, and presents very encouraging blood tolerability properties.
60 citations
TL;DR: Results indicate that NPY may be involved in regulating the activity of nigral dopaminergic and cortical glutamatergic afferent pathways and that of intrinsic GABA neurons in the rat striatum.
57 citations
TL;DR: The inhibition of positive and negative selection in double‐transgenic mice expressing the full‐length CD4 molecule was associated with a decreased interaction between the protein tyrosine kinase p56lck and CD8, which strongly implicate p 56lck in T cell repertoire selection.
Abstract: The CD4 and CD8 coreceptor molecules on immature thymocytes participate in T cell repertoire selection. To examine more definitively the role of CD4 and CD8 in the negative and positive selection of immature thymocytes, we generated transgenic mice with elevated surface CD4 expression and mated them with mice expressing a transgenic T cell receptor. Augmented CD4 expression was found to markedly alter CD8-dependent negative and positive selection of T cells specific for the male (H-Y) antigen presented by H-2Db major histocompatibility complex class I molecules. Moreover, the cytoplasmic tail of CD4 was essential for effecting these alterations, since the overexpression of tailless CD4 molecules failed to influence the outcome of CD8-dependent selection. The inhibition of positive and negative selection in double-transgenic mice expressing the full-length CD4 molecule was associated with a decreased interaction between the protein tyrosine kinase p56lck and CD8. These results strongly implicate p56lck in T cell repertoire selection.
55 citations
TL;DR: The superimposed weathering layers in equatorial rain forest lateritic mantles from Gabon, AtXca, function as interactive compartments forming a dynamic semipermeable geomembrane filter as mentioned in this paper.
Abstract: The superimposed weathering layers in equatorial rain forest lateritic mantles from Gabon, AtXca, function as interactive compartments forming a dynamic semipermeable geomembrane filter. Selectivity of the filter is controlled by a progressive downward disappearance Of Connected macropore pathways created by bioturbation and dissolution. The natural balance of root activity, translocation, dissolution, deformation, and pore evolution leads to the development of porous and permeable, mature, open geochemical weathering systems at the expense of the lithosphere. These conclusions can be useful in modeling the fate of lateritic soils, which cover one-third of the emerged area of the world and which are economically important both as metal deposits and agricultural soils.
TL;DR: In this paper, the authors used the geology of the Bougainville guyot and the outer arc slope in the DEZ-arc collision zone, and to decipher the mechanisms of scamount subduction.
TL;DR: In this article, a theoretical analysis of the linear burning response of an homogeneous solid propellant to pressure fluctuations is presented, which takes into account the non-steady effects of the gas phase in a systematic way.
Abstract: This paper presents a theoretical analysis of the linear burning response of an homogeneous solid propellant to pressure fluctuations. The major contribution of this work is to take into account the non-steady effects of the gas phase in a systematic way and thus, eliminate the strong limitation of previous analysis in which the gas-phase is assumed to respond in a quasi-steady manner. Two different response mechanisms are exhibited depending on the frequency range. In agreement with the well known quasi-steady theory, the low frequency response is mainly controlled by the thermal relaxation in the solid phase and is triggered through the pressure dependence of the prefactors in the pyrolysis and burning laws. At high frequencies, the gas temperature fluctuations associated with pressure oscillations, are shown to introduce a new response mechanism of the burning rate independent of the pressure exponents. This response mechanism involves the structure of the gaseous flame. The resulting vibrator...
TL;DR: In this paper, seven unambiguous events out of a sample of 270 000 Z0 decays, contain in the same jet a Ds meson and a muon at large transverse momentum relative to the jet axis.
TL;DR: A marked asymmetry is observed in the dispersion of the different contributions of the eigenstates associated with k-resolved inverse-photoemission spectroscopy and -${\mathbf{k}}_{\mathrm{\ensuremath{\parallel}}}$ to the KRIPES cross sections.
Abstract: The chemically prepared H/Si(111)-(1\ifmmode\times\else\texttimes\fi{}1) surface has been studied by k-resolved inverse-photoemission spectroscopy (KRIPES) along the two main directions (\ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} K\ifmmode\bar\else\textasciimacron\fi{} and \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} M\ifmmode\bar\else\textasciimacron\fi{}) of the surface Brillouin zone. Two conduction bands are evident at 2.6 and 4.0 eV at \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} and display some dispersion. A marked asymmetry is observed in their dispersion along the M\ifmmode\bar\else\textasciimacron\fi{} '\ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} M\ifmmode\bar\else\textasciimacron\fi{} direction. This asymmetry is a manifestation of the different contributions of the eigenstates associated with ${\mathbf{k}}_{\mathrm{\ensuremath{\parallel}}}$ and -${\mathbf{k}}_{\mathrm{\ensuremath{\parallel}}}$ to the KRIPES cross sections.
TL;DR: In this paper, the authors studied pluvial erosion of the Terres Noires (Jurassic marls) in badlands during the years 1986 to 1989 and found that the annual average rate of erosion, calculated during the study period, is of the order of 190 t ha−1 yr−1 for an average rainfall of 840 mm/yr.
TL;DR: Enhanced dispersion bandwidths are observed at room temperature for one C 60 monolayer, indicating stronger bonding at the interface, and k ∥-resolved inverse photoelectron spectroscopy reveals small dispersion effects in the conduction bands of epitaxial multilayers at 300 K.
Abstract: The natural one-dimensional corrugation of the (001) cleavage plane of GeS, together with favorable lattice matching, allow the successful growth of oriented ${\mathrm{C}}_{60}$(111) fullerite layers, as evidenced by sharp low-energy electron diffraction patterns. ${\mathit{k}}_{\mathrm{\ensuremath{\parallel}}}$-resolved inverse photoelectron spectroscopy reveals small dispersion effects in the conduction bands of epitaxial multilayers at 300 K. Enhanced dispersion bandwidths are observed at room temperature for one ${\mathrm{C}}_{60}$ monolayer, indicating stronger bonding at the interface.
TL;DR: In this paper, the strong coupling constant αs is derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions, based on second order perturbation theory and using two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model.
Abstract: Distributions of event shape variables obtained from 120600 hadronicZ decays measured with the DELPHI detector are compared to the predictions of QCD based event generators Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions The final result, αs(M
Z), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model
TL;DR: In this article, the search in DELPHI data for neutral Higgs bosons is described, and no candidate for the Standard Model Higgs is seen in Z0 decays to H 0 ν ν, H 0 μ + μ − or H 0τ+τ− after selections that proved efficient for finding simulated H0.
TL;DR: In this article, the title compounds are prepared from a dialkyl tartrate and PCl 3 and their use as chiral derivatizing agents for the determination of enantiomeric excess of primary, secondary and tertiary alcohols by 31 P NMR is described.
Abstract: The title compounds are prepared from a dialkyl tartrate and PCl 3 . Their use as chiral derivatizing agents for the determination of enantiomeric excess of primary, secondary and tertiary alcohols by 31 P NMR is described.
California Institute of Technology1, Cornell University2, Fermilab3, University of California, Santa Barbara4, Columbia University5, Stanford University6, University of Victoria7, CERN8, Aix-Marseille University9, University of California, Santa Cruz10, Karlsruhe Institute of Technology11, University of Illinois at Urbana–Champaign12, Ames Research Center13, Center for Naval Analyses14, University of Iowa15, University of Washington16, Indiana University17, University at Albany, SUNY18, Brookhaven National Laboratory19
TL;DR: In this article, a five-dimensional maximum likelihood technique was used to extract the relative fractions and phases of the amplitudes contributing to the [..., [...], [...], and [...] final states.
Abstract: We determine the resonant substructure of D -> [...] decays using a five-dimensional maximum likelihood technique to extract the relative fractions and phases of the amplitudes contributing to the [...], [...], and [...] final states. We find that two-body decay modes account for about 75% of these decays. We obtain branching ratios for [...], [...], [...], [...], and [...] decay modes, as well as several three and four-body decay modes. In the case of [...] and [...], we obtain the branching ratios for all three possible isospin combinations, enabling us to extract the isospin 1/2 and 3/2 amplitudes. This allows us to eliminate the ambiguity due to phase shifts between the isospin amplitudes when comparing our results with theoretical models. We find that the isospin 3/2 amplitudes are suppressed relative to the isospin 1/2 amplitudes, confirming that an understanding of the lifetime difference of the D0 and D+ depends on an understanding of two-body hadronic decays.
For the [...] decay modes, we obtain detailed information on the polarization of the [...] and [...]. This enables us to obtain information on form-factors for [...] and [...] transitions, within the context of the factorization hypothesis. Comparison of our results on [...] decays with recent results on semileptonic decays allows us to test the factorization hypothesis.
TL;DR: In this paper, a numerical model employing the vortex method was used to investigate the separated flow around a trip rod placed upstream of a resonator tube, and the acoustic power generated by the flow was calculated using Howe's theory of aerodynamic sound.
Abstract: A numerical model employing the vortex method is used to investigate the separated flow around a trip rod placed upstream of a resonator tube. The acoustic power generated by the flow is calculated using Howe's theory of aerodynamic sound.
TL;DR: Thoracic aorta to femoral artery bypass is a simple extra-anatomic technique which can be used in cases of failure of a previous aortA to lower limb reconstruction, and the haemodynamic results are good, and late results are better than axillo-femoral or bifemoral bypass.
TL;DR: In this paper, a simple faceting model is proposed, which explains why and how an initially clean disordered surface becomes gradually transformed into a hill-and-valley structure which is correlated with a transformation of some disordered faces into ordered faces.
TL;DR: In this paper, three features have been combined to raise the efficiency of solar cells made on industrial multicrystalline silicon wafers: reduction of bulk recombination by a special gettering process, reduction of back recombination using a p/p + junction, and reduction of front recombinations by emitter back-etching and passivation.
Abstract: Three features have been combined to raise the efficiency of solar cells made on industrial multicrystalline silicon wafers: 1) reduction of bulk recombination by a special gettering process, 2) reduction of back recombination by using a p/p + junction, 3) reduction of front recombination by emitter back-etching and passivation. A conversion efficiency of 15.6% has been achieved on 2 × 2 cm2 solar cells. Spectral response measurements are used to identify the role of each processing parameter.
01 Jan 1992
TL;DR: Anti-peptide antibodies directed against epitopes of human (h) c-erbA, specific for the alpha or beta form of thyroid hormone receptors, were prepared and used to immunolocalize the different forms ofc-erb A proteins in adult and fetal rat liver, by a sensitive immunohistochemical technique.
Abstract: The cell-specific expression and tissue distribution of c-erbA proteins alpha and beta is still unknown. To address this problem, we prepared anti-peptide antibodies directed against epitopes of human (h) c-erbA, specific for the alpha or beta form of thyroid hormone receptors. The cDNAs coding for h c-erbA beta 1, alpha 1 and alpha 2 were transcribed and the mRNAs were translated in vitro in the presence of 35S-methionine, and then their reactivity with the antisera was evaluated. The antiserum anti-beta 62-81 immunoprecipitated only the beta 1 receptor. The antiserum anti-alpha 144-162 determined precipitation of both alpha 1 and alpha 2 proteins but not of the beta 1 receptor. Anti-alpha 2 431-451 produced a selective precipitation of alpha 2, and had no effect on alpha 1 or beta 1 receptor. In order to study the interaction of the antibodies with native T3 receptor we evaluated the binding of antibodies to rat liver T3 receptors by Sephacryl S300 chromatography: both antisera anti-beta 62-81 and anti-alpha 144-162 caused a partial shift of the labeled T3-receptor complex to a higher molecular form, while the antibody directed against c-erbA alpha 2 did not produce any significant shift. The anti-peptide antibodies were then immunopurified by affinity chromatography and used to immunolocalize the different forms of c-erb A proteins in adult and fetal rat liver, by a sensitive immunohistochemical technique. All 3 antibodies stained mainly the nuclei of the majority of adult liver cells. No staining was detectable when the original antiserum was deprived of anti-peptide antibodies by running through the affinity columns or when the antibodies were pre-absorbed with the homologous peptide. No significant staining was present in the liver from rat fetus.
TL;DR: In this paper, a theoretical study of momentum, heat and mass transfer in the laminar boundary layer which develops over an inclined flat plate by either free or forced convection when a constant wall heat flux is specified is presented.
TL;DR: Algal colonization seemed linked with turbid waters and access by the epibionts to the nutritive and oxygenated flows created by the rhythmical beat of the thoracic legs of the branchiopods.
Abstract: Epizootic algae and Protozoa occur on the exoskeleton of fresh water branchiopods in temporary ponds in Morocco. Algal colonization seemed linked with turbid waters and access by the epibionts to the nutritive and oxygenated flows created by the rhythmical beat of the thoracic legs of the branchiopods. It also seemed linked to the mode of life (planktonic or benthic) of the host, and to their exposition to light. Appendages of anostracans, which swim ventral side up, bear a rich community of Chlorophytes, while in conchostracans, where body and appendages are protected by a bivalve carapace, and which swim ventral side down, epibionts colonize the valves, particularly near the hinge and umbo. The lack of algae on notostracans may result from their habit of living in the deeper part of ponds. Protozoans fixed on notostracan shields and on conchostracan valves or appendages, seem to benefit principally from the flow of nutrient- and oxygen-rich water created by the host.
Journal Article•
TL;DR: New acridinonic derivatives, which are hydroxy- and methoxy-substituted in positions 1, 4, and 1,4 were prepared with a view to obtain antiparasitic drugs and their capability of interacalation into DNA was determined.
Abstract: New acridinonic derivatives, which are hydroxy- and methoxy-substituted in positions 1, 4, and 1,4 were prepared with a view to obtain antiparasitic drugs. These compounds were tested against Trypanosoma cruzi strains and their capability of interacalation into DNA was determined. Nucleus substitutions, DNA binding, and trypanocidal activities have been correlated.