Showing papers by "University of Rennes published in 1988"
TL;DR: The main framework for crustal evolution of the late Archean Taishan Complex in the Shandong Province of China is constructed using data from field investigation, petrographic examination, geochemical analysis and isotopic age determination as discussed by the authors.
259 citations
TL;DR: The first is based on a generalisation of Thom's lemma to the case of several variables and gives, after a linear change of coordinates, a cylindric algebraic decomposition of a semi- algebraic set where the incidence relation between the cells is easily obtained.
134 citations
Book•
01 Feb 1988TL;DR: This book attempts to provide a clear, practical and up-to-date guide to distributed algoriths and protocols in the area of control and describes the algorithms to solve it.
Abstract: The use of distributed algorithms offers the prospect of great advances in computing speed. This book attempts to provide a clear, practical and up-to-date guide to distributed algoriths and protocols in the area of control. The first chapter lays the foundations; subsequent chapters, which can be studied independently of each other, consider different aspects of control. Each chapter consists of an analysis of the problem, followed by descriptions of the algorithms to solve it, with proofs of correctness. The book will be of use for undergraduate and graduate students in computer science, and also researchers and software engineers.
122 citations
TL;DR: A trial was carried out in which the protocols and prototype test objects developed under a European Economic Community concerted research project for the assessment of MR imaging equipment were tested in a series of commercial imaging systems situated throughout Europe.
104 citations
TL;DR: In this paper, X-ray photoelectron spectroscopy has been applied to phosphorus oxynitride glasses NaPO3 − xN2x3(O < x ⩽ 1), prepared by melting sodium metaphosphate (NaPO3n)n in flowing ammonia, in order to determine the mechanism of the nitrogen/oxygen substitution.
Abstract: X-ray photoelectron spectroscopy has been applied to phosphorus oxynitride glasses NaPO3 − xN2x3(O < x ⩽ 1), prepared by melting sodium metaphosphate (NaPO3)n in flowing ammonia, in order to determine the mechanism of the nitrogen/oxygen substitution. The formation of phosphorus-nitrogen bonds in place of phosphorus-oxygen bonds involves two kinds of nitrogen atoms N (N1) and N (N2) in mixed tetrahedra P(O, N)4. They substitute bridging oxygen O and non-bridging oxygen =0 according to rules which have been defined from obvious chemical considerations, while another part of oxygen atoms carries the negative charges required for the electronegativity with respect to Na+ ions. This study also brings information about the kinetical aspect of nitridation. N1 and N2 are simultaneously involved; the N2 content, which is first predominant, reaches a limiting value which corresponds to one atom per tetrahedron.
104 citations
TL;DR: Local morphologic and contraction abnormalities in the RV free wall were more sensitive and specific signs for diagnosis of ARVD; these were localized akinetic or dyskinetic bulges sometimes giving a true image of aneurysm and wide and deep fissuring of the apex or of the inferior wall.
101 citations
TL;DR: The present study describes the structure and the organization of warbling song in individuals from varied geographical origins, showing warbling to be an extremely complex song in which there is much contrast.
Abstract: Male starlings sing two very different categories of song: whistles and warbles. The present study describes the structure and the organization of warbling song in individuals from varied geographical origins. In all cases, warbling is shown to be an extremely complex song in which there is much contrast: very different notes follow each other and are even superimposed. Higher levels of organizations are present: notes are grouped in repeating units, the motifs, each of which is sung in bouts of 1 to 12 repetitions, and finally these bouts show a clear sequential organization. A certain amount of variability occurs at each of these levels: slight variations are seen from one rendition of a given motif to the next; the number of repetitions of each motif varies from one song sequence to another and the sequential organization of bouts seems to be able to vary seasonally. All these characteristics were found in all individuals. Nevertheless, warbling appears to be an essentially individual song. Beyond two or three species-specific motifs, the others in the repertoire are individually characteristic. The beginnings and endings of the songs are clearly defined commencing usually with an individual motif whilst ending with a species-specific motif. We observed marked differences between individuals in repertoire size, extending from about 20 to more than 35 different motifs. This is the only measure of the repertoire that we have been able to define for this continuous song.
101 citations
TL;DR: In this article, a review and a discussion of the clast-bearing formations (diamicts) which occur in the uppermost part of the Ordovician succession of numerous regions in Southwestern Europe is presented.
96 citations
TL;DR: It is concluded that germ cell control over Sertoli cell function in vitro may be of important physiological significance during SERToli cell maturation in mammals.
Abstract: Indirect (hypotonically treated culture) and direct (coculture) approaches were used to study the influence of germ cells on androgen-binding protein (ABP) and 17β-estradiol secretion by Sertoli cells prepared from 10-, 15-, 20-, and 45- day-old rats. Using these approaches, the mechanisms that govern Sertoli cell-germ cell membrane recognition were shown to be unaltered by the hypotonic treatment, to vary with the age of the Sertoli cell donors, and to be FSH/(Bu)2cAMP dependent in the younger animals (10–20 days old). Hypotonic treatment had no effect on estradiol levels at all ages studied, but resulted in a marked fall of ABP production by Sertoli cells from 20 days onward. However, the relative stimulation of ABP induced by FSH/(Bu)2cAMP (ABP levels in FSH/(Bu)2cAMP/hypotonically treated Sertoli cell cultures us. ABP in hypotonically treated cultures) was markedly increased at 20 and 45 days, indicating that germ cells influence Sertoli cell responsiveness to FSH/(Bu)2cAMP. The addition of crude germ...
96 citations
TL;DR: In this paper, optical absorption and emission spectra for Dy3+ ions in fluorozirconate (ZBLA) glass are presented, and measured oscillator strengths and radiative rates for several transitions are compared with calculated values.
94 citations
TL;DR: It is concluded that germ cells normally located within the adluminal compartment of the seminiferous tubules may be capable of controlling their own supply of iron via their influence upon transferrin secretion by the Sertoli cells.
Abstract: Indirect approach (hypotonic treatment) and direct approaches (co-cultures and conditioned media) were used in order to investigate the effects of germ cells from adult rats upon transferrin secretion by Sertoli cell cultures prepared from 20-day-old rats. Removal of germ cells contaminating the Sertoli cell cultures resulted in a significant decrease in transferrin secretion whereas the addition of crude germ cell preparations or of enriched preparations of pachytene spermatocytes, early spermatids and of liver epithelial cells (LEC) markedly stimulated this parameter. Furthermore, spent media of pachytene spermatocytes and of early spermatids, but not of LEC, also stimulated transferrin production. It is concluded that germ cells normally located within the adluminal compartment of the seminiferous tubules may be capable of controlling their own supply of iron via their influence upon transferrin secretion by the Sertoli cells.
TL;DR: In this article, a series of scale-experiments were conducted to generate listric normal faults by extending models composed of colored sand layers deposited at regular time intervals throughout deformation during syntectonic sedimentation.
TL;DR: It is shown that polyadenylation of specific RNA species occurs after fertilization in Xenopus and that, in the absence of transcription, adenylation and deadenylations can occur simultaneously in the fertilized egg.
TL;DR: In this article, the authors studied the optical properties of Tm 3+ ions in indium-based heavy metal fluoride glasses and presented absorption and emission spectra as a function of temperature.
TL;DR: In this paper, the authors reported a Pb-Pb isochron age for a relatively young carbonate sequence in Taiwan and demonstrate that the long-lived U-pb decay scheme can be used to determine events as young as Mesozoic age.
Abstract: Direct determination of the depositional age of a sedimentary sequence usually relies on isotopic analyses of authigenic minerals such as glauconite1 and fine-grained clay minerals2–4. Moorbath et al.5 recently reported the first direct dating of sedimentary carbonates using the whole-rock Pb–Pb method. The success of this method depends on the chemical fractionation of U from Pb and the consequent variation in 206Pb/204Pb and 207Pb/204Pb ratios. The high values and large variation of U/Pb ratios in sedimentary carbonates, long known to marine geochemists, have, however, not been exploited by geochronologists until recently5,6. Here I report a Pb–Pb isochron age for a relatively young carbonate sequence in Taiwan and demonstrate that the long-lived U–Pb decay scheme can be used to determine events as young as Mesozoic age. The new results also lead to the identification of an early Jurassic (∼170 Myr BP) thermal event, which has never before been recognized in the polymetamorphic schist belt (the Tananao Schist) of Taiwan, but is widespread in southeastern continental China and other parts of eastern Asia7–10.
TL;DR: In this article, the structure of the BaTaO2N and BaNbO 2N perovskites has been refined by profile analysis of time-of-flight neutron diffraction data.
TL;DR: It is found that trout hepatocytes were more sensitive to estradiol than to other estrogens, and the rate of accumulation of vitellogenin mRNA in the secondary is a function of time of the first stimulation.
TL;DR: In this paper, a detailed study of garnet-chloritoid micaschists fom the Sesia zone (Western Alps) is used to constrain phase relations in high pressure metapelitic rocks.
Abstract: A detailed study of garnet–chloritoid micaschists fom the Sesia zone (Western Alps) is used to constrain phase relations in high pressure (HP) metapelitic rocks. In addition to quartz, phengite, paragonite and rutile, the micaschists display two distinct parageneses, namely garnet + chloritoid + chlorite and garnet + chloritoid + kyanite. Talc has never been observed. Garnet and chloritoid are more magnesian when chlorite is present instead of kyanite. The distinction of the two equilibria results from different bulk rock chemistries, not from P–T conditions or redox state. Estimated P–T conditions for the eclogitic metamorphism are 550–600°C, 15–18 kbar.
The presence of primary chlorite in association with garnet and chloritoid leads us to construct two possible AFM topologies for the Sesia metapelites. The paper describes a KFMASH multisystem for HP pelitic rocks, which extends the grid of Harte & Hudson (1979) towards higher pressures and adds the phase talc. Observed parageneses in HP metapelites are consistent with predicted phase relations. Critical associations are Gt–Ctd–Chl and Gt–Ctd–Ky at relatively low temperatures and Gl–Chl–Ky and Gt–Tc–Ky at relatively high temperatures.
TL;DR: It is demonstrated that modifications in the delta wave during exercise result from a balance between the relative effects of sympathetic stimulation on refractoriness of AP and normal AV conduction, and the limitations of the exercise test to predict the AERP of the AP.
Abstract: Modifications of the delta wave on the surface ECG during an exercise stress test were compared to electrophysiological variations in accessory pathway (AP) refractoriness and in AV node conduction, during intravenous isoproterenol infusion in ten patients with WPW syndrome. In one patient, the delta wave persisted unchanged at the end of exercise and, with isoproterenol, there was a greater reduction in the AP anterograde effective refractory period (AEHP) than in AV node conduction time. In three patients, the delta wave became less and less apparent but without completely disappearing; in these patients, the slight reduction of the AERP in the accessory pathway with isoproterenol was comparable to the reduction in AV node conduction time, explaining the progressive fusion between the two activation fronts. In the six other patients, the delta wave completely disappeared during exercise: in two cases, suddenly from one cycle to the next with strong concordance between the measured (isoproterenol) and the estimated (exercise test) AERP in the AP; in four cases, the disappearance was progressive with a significantly greater reduction in the AV node conduction time than in the measured AEHP of AP which was nonetheless very short, 190 to 225 ms, during isoproterenol infusion. These findings confirm the limitations of the exercise test to predict the AERP of the AP. In addition, they demonstrate that modifications in the delta wave during exercise result from a balance between the relative effects of sympathetic stimulation on refractoriness of AP and normal AV conduction.
TL;DR: In this article, pressure-temperature-time paths (P-T-t paths) were constructed from the Ca-Mg amphiboles in the River Vilaine area.
Abstract: Edenite/tremolite and edenite/magnesio-hornblende in equilibrium with plagioclase, chlorite, epidote, quartz and vapour involve several types of reactions for which KD can be related to T and P. Thermodynamic calculation of these equilibria leads to isopleth systems. Given knowledge of the progressive changes of end-member activities in zoned Ca–Mg amphiboles (based on microprobe analyses), it is possible to construct precise pressure–temperature–time paths (P–T–t paths) which have been followed by metabasites during polyphase metamorphism. When applied to basic rocks from the River Vilaine area, this method allows us to construct a P–T–t path that can be compared directly to the P–T–t path constructed from interbedded acid rocks (aluminous micaschists) in the same structural unit. Through time, both basic and acid rocks underwent the same complex deformation history that can be described conveniently in the L–S fabric system of Flinn. This allows us to construct a P–T–t deformation path for this structural unit.
These paths are interpreted in terms of an under/overthrusting continental collision belt (the Hercynian belt), and represent an illustration of the time delay caused by stacking of more than two crustal units.
TL;DR: In this paper, unstabilized inines are synthetized in gram-scale by vacuum dehydrochlorination of N-chloroalkylamines and by vacuum de-cycled α-aminonitriles on solid base.
TL;DR: An efficient procedure for the preparation of 4,4′,4″-tri- tert -butylterpyridine (trpy*) which is formed together with 4, 4′-di- tert-butylbipyridine(bipy*) is described in this paper.
TL;DR: It is hypothesized that germ cells, in particular pachytene spermatocytes and early sper matids, may influence Sertoli cell function during sexual development in the rat.
TL;DR: The concept of a control of certain important aspects of Sertoli cell function by late spermatids in the adult rat is supported, in parallel to the drop in the number of these germ cell types, ABP production fell whereas FSH levels rose.
TL;DR: The mixed-valence oxynitride LaWO/sub 0.6/N/sub 2.4/ is a new example of a conductor with the perovskite structure as mentioned in this paper.
TL;DR: In this article, the reduced compound YBa 2 Cu 3 O 6 is found to order antiferromagneticnetically belowT N = 420 ± 10K, and the magnetic moment is about 0.6 ± 0.05 μ B on the Cu 2+ sites and aligned perpendicular to the tetragonal caxis.
Abstract: Neutron diffraction experiments have been performed on powder and single crystal (2×5×2×1.5 mm 3 ) samples of YBa 2 Cu 3 O 6+x compounds. The reduced compound YBa 2 Cu 3 O 6 is found to order antiferromagnetically belowT N = 420 ± 10K. The magnetic moment is about 0.6 ± 0.05 μ B on the Cu 2+ sites and aligned perpendicular to the tetragonal c-axis. The magnetic structure is characterized by an in-plane wave vector|1/2 1/2 0| and an antiferromagnetic coupling between the two CuO 2 planes of the unit cell. The addition of oxygen induces only a decrease of T N and the moment value (290 ± 10 K, 0.45 ± 0.05 μ B and 245 ± 10 K, 0.28± 0.05 μ B , for x = 0.25 ± 0.03 and 0.38 ± 0.03, respectively). The long range order disappears abruptly aroundx = 0.40.
TL;DR: The relationship between strain and anisotropy of magnetic susceptibility (AMS) has been investigated in the Carboniferous Flamanville granite in the Armorican Massif, NW France as mentioned in this paper.
TL;DR: In this paper, the authors investigated two important electrochemical reaction processes, hydrogen evolution and molecular oxygen reduction in acid medium, comparing the transition metal cluster compounds Mo 4 Ru 2 Se 8, Mo 2 Re 4 Se 8, Mo 6 Se 8 and Mo metal.
TL;DR: In this article, an uplift path of the aragonite-bearing rocks of the Western Vanoise is constructed using two independent methods: (1) temperature estimates using the Sr++ content of aragonitic veins and (2) the kinetics of the Aragonitecalcite solid-state transition.
Abstract: Aragonite occurrences from two areas of the Western Alps are described. It is shown that aragonite has been formed under blueschist metamorphic conditions in the Western Vanoise, while it has been precipitated under sub-surface conditions in the Queyras region. An uplift (P, T) path of the aragonite-bearing rocks of the Western Vanoise is constructed using two independent methods: (1) temperature estimates using the Sr++ content of aragonite in the successive veins and (2) the kinetics of the aragonitecalcite solid-state transition. The uplift (P, T) path has an unusual shape with an important temperature decrease (100° to 150° C for a pressure decrease of 0.2 GPa) following blueschists metamorphism (P=0.7 GPa, T=300° C). Thermal models show that this unusual (P, T) path of the Western Vanoise can be explained if one maintains a low temperature (between 125° and 175° C) at the base of the tectonic unit containing the aragonite-bearing rocks during part of its burial history, followed by the whole of its exhumation. A tectonic scenario is proposed to account for the observed and modelled (P, T) path.