Showing papers by "University of Rennes published in 1990"
TL;DR: The concerted transition into mitosis involves both a reduction in the rate of p34cdc2 phosphorylation on tyrosine and an increase in its rate of dephosphorylation.
607 citations
TL;DR: In this paper, the authors used isotopic and geochemical data from Mesozoic and younger granitoids and sediments to place constraints on the tectonic evolution of Southeastern China and evaluate whether the young Phanerozoic foldbelts are representative of old rejuvenated landmass, whether they characterize crustal accretion through successive subduction processes, or whether they represent some intermediate situation.
382 citations
TL;DR: In artificially varied the coupling between ultrathin layers, the transition width increases and shows evidence of 2D fluctuations, and the influence of a magnetic field parallel to the layers is markedly reduced.
Abstract: We have artificially varied the coupling between ultrathin ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ layers by interposing insulating planes of ${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ in multilayers and studied the consequences of decoupling 12-A\r{} ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ unit cells on the superconducting properties. We find that the ${\mathrm{T}}_{\mathrm{c}}$ (midpoint) of a 12-A\r{}/12-A\r{} multilayer is 55 K, twice that of the corresponding alloy. ${\mathrm{T}}_{\mathrm{c}}$ decreases linearly with further separation of the ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ unit cells, the transition width increases and shows evidence of 2D fluctuations, and the influence of a magnetic field parallel to the layers is markedly reduced.
327 citations
TL;DR: In this paper, a formal biozonation for the Ordovician chitinozoans of the Northern Gondwana Domain is proposed based on the study of several thousand assemblages recovered from closely spaced samples (both outcrop and subsurface material).
207 citations
TL;DR: The authors showed that the existence of large undeformed regions might instead arise naturally from a fractal style of continental deformation, and they also showed that if continental faulting is fractal in nature, this will limit the validity of homogenization approaches to the modelling of continental Deformation, in which the rheology of the lithosphere is assumed to be homogeneous at scales larger than a threshold value.
Abstract: A KEY question in the study of continental deformation concerns the preservation of undeformed regions, sometimes quite large, in the midst of otherwise penetrative deformation. Some authors1 have interpreted such regions as being relatively strong, but we argue here that the existence of large undeformed regions might instead arise naturally from a fractal style of continental faulting. A scaling analysis derived from laboratory simulations of the India–Asia collision2–5 yields a predicted distribution of undeformed regions, which can be tested in the field. We also show that, if continental faulting is fractal in nature, this will limit the validity of 'homogenization' approaches to the modelling of continental deformation, in which the rheology of the lithosphere is assumed to be homogeneous at scales larger than a threshold value.
164 citations
TL;DR: In this article, the evolution of faunal assemblages and climatic characteristics from the Cambrian up to the end of the Devonian, demonstrates that Baltica and North Gondwana represent two major and independent palaeogeographic entities separated by a mid-European Rheic Ocean which opened as early as the Cambric and closed progressively from the devonian.
155 citations
TL;DR: Up to the midblastula stage, cell division in Xenopus is directed by maternal mRNAs and proteins that are inherited by the fertilized egg, and changes in polysomal localization coincide with this poly(A) metabolism.
145 citations
TL;DR: In this article, a study of the dynamics of a landscape at four periods of time (1952, 1961, 1972, 1985) done on 26 contiguous 16 ha quadrats is presented.
Abstract: Changes in agricultural systems since the 50's led to considerable changes in rural hedgerow network landscapes. In these landscapes, ecological processes depend on the spatial structure of the network (length of hedgerows, connectedness, grain size). This paper reports on a study of the dynamics of such a landscape at four periods of time (1952, 1961, 1972, 1985) done on 26 contiguous 16 ha quadrats. A correspondence analysis of the data matrix yields a gradient of change from dense highly connected networks to heterogeneous landscapes with few hedgerows. The study of individual trajectories of the quadrats allowed them to be regrouped in various types of changes. It is possible for a quadrat to go through several pathways. Rates of change varied through time, the 1961–1972 period had most changes. The use of supplementary elements in correspondence analysis proves to be a useful way to approach spatial hierarchy and allows a better understanding of the differentiation of landscape units.
138 citations
TL;DR: Evidence is provided for the involvement of germ cells, in particular of early spermatids, in the local testicular regulation of inhibin gene expression and production in the rat and for the activity of this cell line is not mediated via a diffusible factor.
120 citations
TL;DR: The principal structural characteristics of the complete coding sequence of the rtER are: first a remarkable homology of the DNA binding (C) and hormone binding (E) domains with those of other species, and second the lack of an A region, the function of which is not yet known but which is well conserved in other species.
120 citations
TL;DR: In this article, Probleme Mixte Hyperbolique Quasi-Lineaire Caracteristique was used for partial differential equations in Partial Differential Equations (PDE).
Abstract: (1990). Probleme Mixte Hyperbolique Quasi-Lineaire Caracteristique. Communications in Partial Differential Equations: Vol. 15, No. 5, pp. 595-654.
TL;DR: Immunoprecipitation of the in vivo labelled proteins showed that ornithine decarboxylase accumulated less rapidly in stage IV oocytes than in previtellogenic stage I + II oocytes, indicating that during the growth phase of oogenesis, ornithin decar boxylase expression is regulated at a translational level.
Abstract: The level at which ornithine decarboxylase expression is regulated in growing oocytes has been investigated. Immunoprecipitation of the in vivo labelled proteins showed that ornithine decarboxylase accumulated less rapidly in stage IV oocytes than in previtellogenic stage I + II oocytes. Quantitative Northern analysis showed that ornithine decarboxylase mRNA is abundant in oocytes (about 8 x 10(8) transcripts/cell) and this number does not significantly change during oogenesis. Polysome analysis showed that this mRNA is present in polysomes in stage I + II oocytes but has passed into puromycin-insensitive mRNP particles by stage IV of oogenesis. Therefore, during the growth phase of oogenesis, ornithine decarboxylase expression is regulated at a translational level. These results are discussed relative to the temporal expression of ornithine decarboxylase and of other proteins whose expression also decreases during oogenesis. In order to perform these experiments, the cDNA (XLODC1) corresponding to Xenopus laevis ornithine decarboxylase mRNA was cloned and sequenced.
TL;DR: In this article, the effects of tillage due to modern agriculture are reviewed and the results from four experiments in "prehistoric cultivation" are presented, based on a study of soils from various archaeological sites in north-west Europe.
Abstract: The study of early agricultural soils using micromorphology is outlined. The effects of tillage due to modern agriculture are reviewed and the results from four experiments in ‘prehistoric cultivation’ are presented. These are used in the interpretation of prehistoric agricultural practices, based on a study of soils from various archaeological sites in north‐west Europe. It is suggested that microfabric features, varying according to soil texture, can be diagnostic of tillage. Microfabric type, textural features (e.g. coatings) and structure are, taken together, better indicators of ancient tillage than single features.
TL;DR: A kinematic formulation of the mechanical problem is proposed which suggests an analogy with previously studied fractal-growth problems, and complex fractal patterns of faults are formed with fractal dimension 1.70±0.05 independent of the fault densities associated with different brittle-ductile coupling.
Abstract: Experiments on the formation of faults in a laboratory model of the Earth's crust are presented; they respect its vertical rheological stratification, a brittle layer on top of ductile layers. As a result of the competition between the different nature of the brittle and ductile-layer deformations, complex fractal patterns of faults are formed with fractal dimension 1.70\ifmmode\pm\else\textpm\fi{}0.05 independent of the fault densities associated with different brittle-ductile coupling. We propose a kinematic formulation of the mechanical problem which suggests an analogy with previously studied fractal-growth problems.
TL;DR: The 250 km long, deep Seismic reflection survey across the Pyrenees from one foreland (Ebro Basin) to the other (Aquitaine Basin) was designed to study the structure of the deformed Mesozoic boundary between the Iberian and European Plates.
TL;DR: In this paper, an isotopic and REE analysis of metakomatiitic amphibolites from the Sino-Korean craton northeast of Bohai Bay in southern Jilin/eastern Liaoning Provinces is presented.
TL;DR: In this article, the authors proposed a petrogenetic model for the Ntem complex in south Cameroon and showed that the TTG suite was not emplaced during the granulite-facies metamorphism, but this occurred later, affecting only some parts of the basement.
TL;DR: The effects of different forms of GnRHa on the stimulation of gonadotropin secretion and the rate of ovulation were investigated in the rainbow trout, Oncorhynchus mykiss and a comparison of variability of egg quality with treatments is discussed.
TL;DR: It was demonstrated that haemoglobin, platelets, and bone marrow-blasts are the best factors to predict survival or leukaemic transformation (LT), and monocytes are not good parameters to predict the type of leukemic transformation.
TL;DR: In the Late Ordovician, both SW Europe and Africa were situated in high latitudes as discussed by the authors and biogeography suggests that these regions were separated by the Rheic (mid-European) Ocean from Baltica, with the suture lying between the Armorican Massif and the Ardennes.
Abstract: In the Late Ordovician, both SW Europe and Africa were situated in high latitudes. Sedimentary fades and biogeography suggest that these regions were separated by the Rheic (Mid-European) Ocean from Baltica, with the suture lying between the Armorican Massif and the Ardennes. During the Silurian and the Devonian, palaeobiogeographic affinities persisted between S Europe and N Africa. It is concluded that S Europe consisted of several discrete blocks or microplates prior to the Hercynian Orogeny.
TL;DR: In this paper, the attenuation spectra of TeX glasses have been investigated and it has been shown that these glasses exhibit low optical losses in the 8-12 μm atmospheric window.
Abstract: The reaction of tellurium with the halogens Cl, Br and I leads to a new family of halide glasses which are structurally related to Se. These chain-like materials are characterized by a broad optical window lying from 1 to 13 μm or 1 to 20 μm, depending on the weight of the halogen. When combined with S or specially Se, many of these new IR glasses exhibit a strong resistance towards devitrification and water corrosion. Infrared optical fibers have been prepared from these so-called TeX glasses. The position and the dependence of the multiphonon edge as well as the bandgap have been investigated by measuring the attenuation spectra. It has been shown that these glasses exhibit low optical losses in the 8–12 μm atmospheric window. Thin layers of TeX glasses have been deposited by sputtering on silica or fluoride glass substrates, and antireflection coatings deposited on bulk TeX glasses allow the reduction of optical losses by reflection.
TL;DR: An isotopic and geochemical study on the Miocene to late Paleozoic sediments and metasediments of Taiwan has been conducted in order to decipher the crustal evolution of SE China.
TL;DR: The regime of diffusion among the Tm-doped and (Tm,Ho)-doped indium-based fluoride glasses ions is clearly established and the cross-relaxation of the lowest excited states has been proved and its efficiency calculated.
Abstract: The ${\mathrm{Tm}}^{3+}$\ensuremath{\rightarrow}${\mathrm{Tm}}^{3+}$ and ${\mathrm{Tm}}^{3+}$\ensuremath{\rightleftarrows}${\mathrm{Ho}}^{3+}$ energy transfers have been studied in both Tm-doped and (Tm,Ho)-doped indium-based fluoride glasses over a wide temperature range for several dopant concentrations. The regime of diffusion among the ${\mathrm{Tm}}^{3+}$ ions is clearly established and the cross-relaxation $^{3}$${\mathit{H}}_{4}$, $^{3}$${\mathit{H}}_{6}$${\ensuremath{\rightarrow}}^{3}$${\mathrm{F}}_{4}$${,}^{3}$${\mathit{F}}_{4}$ has been proved and its efficiency calculated. The temperature dependence of the thermal equilibrium observed between the lowest excited states $^{3}$${\mathit{F}}_{4}$ of ${\mathrm{Tm}}^{3+}$ and $^{5}$${\mathit{I}}_{7}$ of ${\mathrm{Ho}}^{3+}$ ions in codoped glasses is explained in terms of the Boltzmann distribution of the state populations governed by efficient forward and backward energy transfers. When ${\mathrm{Tm}}^{3+}$ ions are excited in the $^{3}$${\mathit{H}}_{4}$ level near 0.8 \ensuremath{\mu}m, it is shown that two cross-relaxation processes compete: one between ${\mathrm{Tm}}^{3+}$ ions and the other between ${\mathrm{Tm}}^{3+}$ and ${\mathrm{Ho}}^{3+}$ ions. Their efficiencies are shown to strongly depend on the relative Tm and Ho concentrations.
TL;DR: In this article, two areas in the Qianxi region (Qianan County) have been investigated for U-Pb age study: (1) the Caozhuang area in the south, and (2) the Shuichang-Yangyashan region in the north.
TL;DR: In this paper, the authors used the vast extent of sedimentation deposits making up the Gres Armoricain and its equivalents over the north Gondwanan domain to test the hypothesis of continuity between the Armorica and Gondwana plates during the Early Ordovician.
Abstract: The vast extent of sedimentation deposits making up the Gres Armoricain and its equivalents over the north Gondwanan domain is used in this study to test the hypothesis of continuity between the Armorica and Gondwana plates during the Early Ordovician. The distribution of continental and marine environments, the large volume of transported elastic material, and the consistent current directions all indicate that the source of sediment supply on the north Gondwanan margin was to the south of the Sahara. Although there were local signs of incipient rifting between the two plates, Armorica was not yet detached from Gondwana by Arenigian time.
TL;DR: An indirect fluorescent-antibody (IFA) technique, which employed adsorbed Behring polyvalent I O antiserum, was used to detect Salmonella spp.
Abstract: An indirect fluorescent-antibody (IFA) technique, which employed adsorbed Behring polyvalent I O antiserum, was used to detect Salmonella spp. in environmental water systems. The IFA method used in this study detected 95% of Salmonella serotypes encountered in human infections in France, with a sensitivity threshold of 7.5 x 10(3) bacteria per ml of wastewater. Specificity was assessed by testing IFA against Salmonella-free seawater and a variety of bacteria other than Salmonella spp. When used to examine raw and chlorinated wastewater over a 2-month period, the IFA method was successful in detecting Salmonella spp. in all 12 of the samples examined, with total numbers determined to be 4.5 x 10(5) to 3.3 x 10(7) salmonellae per 100 ml. In comparison, for the same samples, enumeration by culture, using the most-probable-number technique, was effective in detecting Salmonella spp. in only four of eight raw-water samples and one of four chlorinated water samples tested. Three samples were further tested by using the direct viable count procedure combined with IFA and results showed that 5 to 31.5% of the Salmonella spp. enumerated by this method in chlorinated water were substrate responsive.
TL;DR: In this article, the authors measured the isotopic compositions of komatiites from the 3450 Ma old Barberton greenstone belt, southern Africa, and found that the initial ϵHf values close to zero were at variance with the strongly negative or positive values that should be observed if these rocks came from old garnetdepleted or garnet-enriched layers, such as may have formed during the solidification of an ancient terrestrial magma ocean.
TL;DR: The fact that E. coli grew better in the sediments than in seawater is attributed somewhat to the high content of organic matter in the sediment but mainly to the accumulation of glycine betaine.
Abstract: Escherichia coli grew faster in autoclaved marine sediment than in seawater alone. When E. coli was cultivated in sediment diluted with minimal medium M63 at 0.6 M NaCl, supplemented or not supplemented with glucose or with seawater, the osmoprotector glycine betaine was accumulated in the cells. The best growth occurred on glucose. Accumulation of glycine betaine was not observed with E. coli was grown in sterile seawater alone. The fact that E. coli grew better in the sediments than in seawater is attributed somewhat to the high content of organic matter in the sediment but mainly to the accumulation of glycine betaine. Thus, osmoprotection should be considered to be an additional factor in bacterial survival in estuarine sediments.
TL;DR: Magnetic measurements performed on PbMo6S8 single crystals show that this classic isotropic superconductor (Tc = 14.5 K) presents surprisingly similar irreversibility and relaxation properties as those generally attributed to layered high-Tc superconductors as discussed by the authors.
Abstract: Magnetic measurements performed on PbMo6S8 single crystals show that this classic isotropic superconductor (Tc = 14.5 K) presents surprisingly similar irreversibility and relaxation properties as those generally attributed to layered high-Tc superconductors. An irreversibility line H ∗ = H ∗ 0 (1-t) m with m∼ 3 2 is observed for H ⪅ 1 kOe. From the magnetic relaxation rates measured below this irreversibility line, activation energies U0 around 15 meV are derived within the flux creep picture. The similarity with the high-Tc oxides is explained by the very short coherence length ξ ≈ 25 A of PbMo6S8 which also makes this compound sensitive to disorder and local defects.