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Showing papers by "Pierre-and-Marie-Curie University published in 1981"


Journal ArticleDOI
TL;DR: In this article, the results of work on the preparation of aqueous magnetic liquids without using organic stabilizing agents are presented, and the results are compared to those of the same authors.
Abstract: The results of work on the preparation of aqueous magnetic liquids without using organic stabilizing agents is presented.

2,527 citations


Journal ArticleDOI
TL;DR: A few principles relative to the presentation and use of nitrogen stable isotopic data are briefly reviewed in this article, where some classical relationships between the isotope composition of a substrate undergoing a single-step unidirectional reaction, are introduced.
Abstract: A few principles relative to the presentation and use of nitrogen stable isotopic data are briefly reviewed. Some classical relationships between the isotope composition of a substrate undergoing a single-step unidirectional reaction, are introduced.

1,514 citations


Journal ArticleDOI
TL;DR: In this paper, the spectral dependence law of absorption appears to vary within a restricted range, and an average law can be considered representative of rapid measurements at one selected wavelength, and the concentration appears influenced predominantly by natural and industrial land discharges.
Abstract: Spectral values of absorption of light by dissolved organic matter were measured in samples originating from diverse parts of the ocean, quite different with respect to pigment and particle content. The use of llO-cm cells and then of lo-cm cells, with a highly sensitive spectrophotometer, allowed measurement throughout the UV-visible range (200-700 nm) even for the low concentrations of yellow substance encountered in the open sea. The concentration appears influenced predominantly by natural and industrial land discharges. In oceanic waters, it remains low and seems to be related to the biological activity averaged over a long period rather than to the local and temporary phytoplankton content. However, even at such low concentrations, yellow substance in the open sea may have an effect on absorption and hence on ocean color similar to that of low or moderate algal biomass. The spectral dependence law of absorption appears to vary within a restricted range, and an average law can be considered representative of rapid measurements at one selected wavelength.

1,491 citations


Journal ArticleDOI
01 Nov 1981
TL;DR: In this article, the effect of discreteness on absorption properties of a medium containing an absorbing substance as particles is examined theoretically, under the assumption concerning the complex refractive index that is reasonable in case of algal cells (index close to that of water and weakly absorbing substance).
Abstract: The radiation absorption within a medium supposedly non-absorbing in itself but containing an absorbing substance as particles is examined theoretically. Absorption by such particles can be treated independently of (Mie) scattering under an assumption concerning the complex refractive index that is reasonable in case of algal cells (index close to that of water and weakly absorbing substance). The effect of discreteness on absorption properties is ruled by a function of the dimensionless parameter that combines through their product the size (d) and the absorption coefficient of the cell material (acm). The limiting value of this function (d → 0) describes the case of a true solution of the same material, whereas its variations with d and acm imply that the specific absorption coefficient, for a given substance, is variable in magnitude and in spectral behaviour. Consequently, Beer's law, which rests on the existence of a constant specific coefficient, generally cannot apply when canopy changes intervene in an algal population. Various cases of such changes are studied along with their consequences on absorptive properties. The theoretical conclusions are exemplified by some experimental results concerning algal cultures. The absorption properties of the cell material for each species can be extrapolated from the actual absorption spectra of intact cells. Problems that originate from the non-constancy of the specific absorption coefficient (spectral values or mean value) are examined in view of two kinds of applications: the photosynthetic (quantum) yield evaluation and the algal biomass assessment by remote sensing, for which the constancy is generally postulated.

779 citations


Journal ArticleDOI
01 Jun 1981
TL;DR: In this article, the authors proposed a new 1-atm equation of state for seawater that has been suggested for use by the United Nations Educational, Scientific and Cultural Organization (UNESCO) joint panel on oceanographic tables and standards.
Abstract: The density measurements by Millero, Gonzalez and Ward (1976, Journal of Marine Research,34, 61–93) and Poisson, Brunet and Brun-Cottan (1980, Deep-Sea Research, 27, 1013–1028), from 0 to 40°C and 0.5 to 43 salinity, have been used to determine a new 1-atm equation of state for seawater. The equation is of the form (t°C; S; ϱ kg m−3) ρ=ρ 0 +AS+BS 3 2 +CS , where A=8.24493×10 −1 −4.0899×10 −3 t+7.6438×10 −5 t 2 −8.2467×10 −7 t 3 +5.3875×10 −9 t 4 B=−5.72466×10 −3 +1.0227×10 −4 t−1.6546×10 −6 t 2 C=4.8314×10 −4 and ϱ0 is the density of water ( Bigg , 1967, British Journal of Applied Physics, 8, 521–537). ρ 0 =999.842594+6.793952×10 −2 t−9.095290× −3 t 2 +1.001685×10 −4 t 3 −1.120083×10 −6 t 4 +6.536336×10 −9 t 5 . The standard error of the equation is 3.6 × 10−3 kg m−3. This equation will become the new 1-atm equation of state of seawater that has been suggested for use by the UNESCO (United Nations Educational, Scientific and Cultural Organization) joint panel on oceanographic tables and standards.

599 citations


Journal ArticleDOI
TL;DR: In this paper, a parametrization of the deuteron wave function calculated with the Paris potential is presented, in both configuration and momentum spaces, for the case where the wave function is assumed to have the same momentum.

431 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of the Aegean Sea by extensional tectonics is related to the subduction of the Mediterranean floor below the Hellenic arc, and it is shown that the outer arc was built since the beginning of this episode of subduction by vertical uplift.
Abstract: We summarize briefly the main features of a kinematic model of evolution of the Aegean area since 13 Ma. The formation of the Aegean Sea by extensional tectonics is related to the subduction of the Mediterranean floor below the Hellenic arc. We then make a quantitative estimate of vertical movements in the Aegean area, on the basis of geological data, and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift. The easiest way to explain the uplift is by underplating. Finally, we discuss briefly the dynamics of the subduction - marginal sea formation processes in this continental collision framework.

427 citations


Journal ArticleDOI
TL;DR: In this article, the existence and uniqueness of a natural isomorphism ojα of Kj(A) with Kj+1(A ⋊α R ), j ϵ Z /2 where (A, R, α) is a C∗ dynamical R -system, K is the functor of topological K theory and A is the crossed product of A by the action of R.

358 citations


Journal ArticleDOI
TL;DR: In this article, a general method of approximation of nonsingular solutions and simple limit points of nonlinear equations in a Banach space has been studied, and general approximation results of the branches of solutions in the neighborhood of a simple bifurcation point have been derived.
Abstract: In the first two papers of this series [4, 5], we have studied a general method of approximation of nonsingular solutions and simple limit points of nonlinear equations in a Banach space. We derive here general approximation results of the branches of solutions in the neighborhood of a simple bifurcation point. The abstract theory is applied to the Galerkin approximation of nonlinear variational problems and to a mixed finite element approximation of the von Karman equations.

276 citations


Journal ArticleDOI
TL;DR: In this article, the major and seventeen trace element distribution coefficients between main phenocrysts (olivine, clinopyroxene, amphibole, mica, feldspars and Fe-Ti oxides) and groundmass have been measured in the alkali basalt suite of Chaine des Puys (Massif Central, France).

272 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the quotienting of the space of connections by the group of gauge transformations in Yang-Mills theory is aC fixme∞ principal fibration, and that the underlying quotient space, the gauge orbit space, is explicitly aC¯¯¯¯∞ manifold modelled on a Hilbert space.
Abstract: In an appropriate mathematical framework we supply a simple proof that the quotienting of the space of connections by the group of gauge transformations (in Yang-Mills theory) is aC ∞ principal fibration. The underlying quotient space, the gauge orbit space, is seen explicitly to be aC ∞ manifold modelled on a Hilbert space.

Journal ArticleDOI
TL;DR: In this article, the exact number of solutions for semi-linear elliptic problems is computed for concave and convex nonlinear problems, based on simple eigenvalue comparison arguments.

Journal ArticleDOI
01 Sep 1981-Nature
TL;DR: It is reported here that PMA, but not its weakly or non-promoting derivatives, induced chromosomal aberrations with high efficiency in phytohaemagglutinin (PHA)-stimulated human lymphocytes, but was only a weak producer of SCE.
Abstract: The mouse skin tumour promoter phorbol-12-myristate-13-acetate (PMA) does not form covalent adducts with cellular DNA and its mutagenic potency in several systems is low or absent1–6. There have been conflicting reports of the capacity of PMA to produce sister chromatid exchanges (SCEs)3,6–8. As PMA induces the formation of superoxide radicals in polymorphonuclear leukocytes and mitogen-stimulated lymphocytes9–11, we suggested that it might produce DNA damage via indirect action by the formation of intermediate active oxygen species12,13. As is typical for other DNA-damaging agents which mainly act indirectly, for example, ionizing radiation, PMA would be expected to have low mutagenicity but high clastogenic (chromosome-breaking) activity14. In agreement with this, we report here that PMA, but not its weakly or non-promoting derivatives, induced chromosomal aberrations with high efficiency in phytohaemagglutinin (PHA)-stimulated human lymphocytes, but was only a weak producer of SCE. This activity was suppressed by superoxide dismutase, which catalyses the breakdown of superoxide radicals.

Journal ArticleDOI
TL;DR: Results from this study are consistent with the hypothesis that GABA is the inhibitory transmitter of the nigrotectal projection of the rat.

Journal ArticleDOI
TL;DR: The fate of the multiple innervation of Purkinje cells by climbing fibers was studied as a function of age in immature rats rendered agranular by X-irradiation, in immature hypothyroid rats, and compared to that in controls by examining in each group the intracellular activities of PCs mediated via CFs throughout maturation.

Journal ArticleDOI
TL;DR: Experimental autoimmune uveoretinitis was induced in rats after one injection of purified retinal S antigen mixed with adjuvants, giving a hyperacute Arthus-type inflammation, even with low doses of antigen.
Abstract: Experimental autoimmune uveoretinitis was induced in rats after one injection of purified retinal S antigen mixed with adjuvants. Lewis and PVG/c rat strains were highly sensitive. S antigens isola...

Journal ArticleDOI
TL;DR: In this paper, a model of a fully ionized strongly coupled hydrogen plasma is described by hypernetted chain theory and the ion- and electron-velocity autocorrelation functions are computed.
Abstract: Results of "molecular dynamics" simulations are reported for a model of a fully ionized strongly coupled hydrogen plasma. Quantum effects are taken into account through the use of effective pair potentials; at short distances, these differ significantly from the bare Coulomb potential. Static properties of the plasma are shown to be well described by hypernetted chain theory. The ion- and electron-velocity autocorrelation functions have been computed and the electrical conductivity turns out to be roughly twice that expected on the basis of the electron self-diffusion coefficient. The predictions of Vlasov theory for the damping and dispersion of the plasmon mode are found to be in generally poor agreement with the results of the computer "experiments", but the collective dynamical properties are successfully described by a memory-function scheme in which explicit account is taken of ion-electron correlations. Prospects for future work are briefly reviewed.

Journal ArticleDOI
TL;DR: The Acapulco meteorite as discussed by the authors is a unique object with chondritic composition but achondritic texture, and it is formed under redox conditions intermediate between those of H- and E-chondrites at ~ 1100°C, from which it cooled at a rate > 10°C/Myr.

Journal ArticleDOI
23 Apr 1981-Nature
TL;DR: Polyoma mutants that will grow in EC F9 cells are described, and the sequence changes in two of them can be folded into a putative tRNA-like secondary structure which may be involved in the regulation of viral early transcription with respect to the state of differentiation of the host cell.
Abstract: Polyoma virus can develop lytically in differentiated mouse cells, but is unable to express either early or late functions in undifferentiated early embryonic cells1 or in embryonal carcinoma (EC) cells of the mouse. However, the EC cells become susceptible during differentiation and then behave as do mouse somatic cells2. We have recently described the isolation of a new class of polyoma virus mutant (Py EC) able to develop normally in an EC cell line (PCC4-Aza) that is capable of trigerminal differentiation in vivo3 but exhibits a very limited differentiation in vitro4. The mutants do not grow in another EC cell line (F9) that is ‘blocked’—‘nullipotent’ in vivo, but able to differentiate in vitro when grown in the presence of chemical inducers. Compared with their parental strain, all Py EC genomes analysed so far have an extra 20–50 bases in their HpaII-3 restriction fragment5. We now describe polyoma mutants that will grow in EC F9 cells, and the sequence changes in two of them. The region involved in the mutations can be folded into a putative tRNA-like secondary structure which may be involved in the regulation of viral early transcription with respect to the state of differentiation of the host cell.

Journal ArticleDOI
TL;DR: In this paper, a riemannian calculus for the configuration space of pure Yang-Mills theory has been developed, and it has been shown that the Gribov ambiguity is more than an artefact of the choice of a gauge condition, and is related to the existence of conjugate points on the geodesics.
Abstract: We state some new results about the configuration space of pure Yang-Mills theory. These results come from the study of the kinetic energy term of the Lagrangian of the theory. This term defines a riemannian metric on the space of non-equivalent gauge potentials. We develop a riemannian calculus on the configuration space, compute the riemannian connection, the curvature tensor, and solve for the geodesics, etc. We show that the Gribov ambiguity is more than an artefact of the choice of a gauge condition, and is related to the existence of conjugate points on the geodesics, and is thus an intrinsic feature of the theory.

Journal ArticleDOI
TL;DR: In normal animals, SN stimulation induced both inhibitory and excitatory responses in SC cells, and this observation clearly demonstrates that the nigro-tectal pathway is inhibitory.

Journal ArticleDOI
TL;DR: In this paper, the authors calculate the difference in the surface potentials between the free surface of a liquid metal and the same metal in an ideally polarizable interface at the point of zero charge, due to the deformation of the electronic cloud of the metal by the solvent molecules.

Journal ArticleDOI
TL;DR: A detailed field analysis of Neogene and Quaternary faults in Baja California has enabled us to reconstruct the stress pattern and the tectonic evolution of the central and southern parts of the peninsula.

Journal ArticleDOI
TL;DR: Thylakoid membranes of higher plants and green algae can be resolved by SDS-polyacrylamide gel electrophoresis into at least 2 different chlorophyll-protein complexes and -30 polypeptides, and little is known about their lipid composition other than pigments.

Journal ArticleDOI
TL;DR: Evidence for such a 4-step scheme--fall in cAMP levels, then in C sub-unit levels, dephosphorylation of Mp leading to the synthesis of MPF and finally MPF-triggered GVBD--is presented and discussed.

Journal ArticleDOI
TL;DR: In this article, the eigenvalues and eigenfunctions corresponding to the three-dimensional equations for the linear elastic equilibrium of a clamped plate of thickness 2 ϵ, are shown to converge (in a specific sense) to the 2-dimensional biharmonic operator of plate theory, as ϵ approaches zero.

Journal ArticleDOI
01 Jan 1981
TL;DR: A new class of hypergraphs (partitive hyper graphs) is defined which generalizes both, the set of all externally related subsets of a graph and theset of all committees of an hypergraph.
Abstract: We define a new class of hypergraphs (partitive hypergraphs) which generalizes both, the set of all externally related subsets of a graph and the set of all committees of an hypergraph. We give a characterization of the partitive hypergraphs and moreover of those which are associated with hypergraphs or graphs.

Journal ArticleDOI
TL;DR: In this paper, the quantum inverse scattering method was applied to a discretization of the generalized Toda field theory and a family of solutions of the factorization equations were obtained.

Journal ArticleDOI
TL;DR: In this paper, it was shown that (I) has an infinite number of solutions for a residual set of ƒ in H − 1 (Ω), such that for many n ∈ R N there exists an open and dense subset of ǫ in H−1 (ǫ) such that (i) has n distinct solutions for such anǫ.

Journal ArticleDOI
TL;DR: Results indicate the stereospecificity of platelet activation induced by PAF, and the intermediates in synthesis are easier to purify, with better yields.