Showing papers by "University of Rennes published in 1989"

Shear structures within deformed granites: Mechanical and thermal indicators

Abstract: Granitic rocks are here described as mixtures of weak and more resistant fractions whose proportions vary with strain and temperature and control some macroscopic characteristics of shear structures produced during deformation. Three main structural fields are distinguished on a strain/temperature diagram: (1) discrete shear zones anastomosed around low-strain domains, (2) microscale associations of pervasive foliation and ductile shear bands (e.g., C-S structures), and (3) "steady state" homogeneous foliations. We outline the following: a sharp drop in bulk strength is expected to occur around 500 °C within wet granites; the widespread occurrence of pervasive ductile shear bands is diagnostic of retrograde deformation histories, especially as encountered within syntectonic plutons; and most prograde deformation histories, as expected during reworking of pretectonic basement, should produce heterogeneous strain patterns associated with discrete shear zones.

Convergence en loi des suites d'intégrales stochastiques sur l'espace $$\mathbb{D}$$1 de Skorokhod

Abstract: For sequences of stochastic Integrals K n .X n , functional limit Theorems are presented, these results hold under simple natural conditions.

Identification and Estrogen Induction of Two Estrogen Receptors (ER) Messenger Ribonucleic Acids in the Rainbow Trout Liver: Sequence Homology with other ERs

Abstract: The estrogen-binding region of the cDNA for chicken ER reveals a mRNA of 3.5 kilobases (kb) in rainbow trout liver. The level of this messenger, which is very low in the liver of naive male animals, can be increased by estrogen stimulation. With this chicken probe, we have isolated a clone from a λ gt10 trout liver cDNA library. The partial cDNA sequence, which encompasses most of the coding region, shows two domains of striking amino acid homology with human, avian, and Xenopus estrogen receptors (ERs) (DNA binding region: 90%, Hormone binding region: 60%). With this specific probe rainbow trout ER, we detected another messenger (4.5 kb) that is less expressed than the 3.5 kb messenger. The kinetics of stimulation of the two messengers is compared with the kinetics of accumulation of vitellogenin mRNA after E2 administration. This report constitutes the first identification of ER mRNA from a fish.

Organometallic Chemistry of Arene Ruthenium and Osmium Complexes

Abstract: Publisher Summary This chapter focuses on the organometallic chemistry and new aspects of arene ruthenium and osmium complexes. It explores that arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal (0) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. Recently, from classic organometallic arene ruthenium and osmium chemistry has grown an area making significant contributions to the chemistry of cyclophanes. These compounds are potential precursors of organometallic polymers, which show interesting electrical properties and conductivity. The possibility of coordination of a two-electron ligand, in addition to arene, to the ruthenium or osmium atom provides a route to mixed metal or cluster compounds. Cocondensation of arene with ruthenium or osmium vapors has recently allowed access to new types of arene metal complexes and clusters. It reviews that arene ruthenium and osmium appear to be useful and specific catalyst precursors, apart from classic hydrogenation, for carbon–hydrogen bond activation and activation of alkynes; such compounds may become valuable reagents for organic syntheses.

Landscape structure effects on carabid beetles spatial patterns in western France

Abstract: Analysis of carabids spatial distribution in a hedgerow network landscape in western France, pinpoints the role of the landscape among other levels of ecological organization. Dispersion of forest species differs among core forest species, peninsula forest species and corridor forest species. Abundance 04 forest carabid species in a particular hedgerow is related to the positive effect of a dense herbaceous layer and the presence of a tree layer which is enhanced by the presence of two parallel hedgerows, especially along lanes. At the landscape level distance from the largest forest determines abundance of forest species within the first kilometer out of it. Beyond that, abundance is independent of distance from the source forest and the discriminant ecological factors are: hedgerow structure, presence of lanes bordered by two hedgerows. Introduction Hedgerow network or ‘bocage’ landscapes are characteristic of many parts of western Europe. (Flatres 1959; Meynier 1970), and particularly of western France in Normandy and Brittany. Ecolog- ical functions of hedgerows in agricultural areas have been widely studied for biological processes as well as for flows of energy or matter (Pollard

Energy transfer between Er 3 + and Tm 3 + ions in a barium fluoride – thorium fluoride glass

Abstract: The up-conversion of infrared radiation into green, red, and 805-nm fluorescence has been studied for ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions in both ${\mathrm{Yb}}^{3+}$-doped and non-${\mathrm{Yb}}^{3+}$-doped ${\mathrm{BaF}}_{2}$-${\mathrm{ThF}}_{4}$ fluoride glass over a wide temperature range and several dopant concentrations. It has been found that the addition of ${\mathrm{Tm}}^{3+}$ preferentially quenches the up-conversion efficiency of the green emission corresponding to a transition from the $^{4}\mathrm{S}_{3/2}$ level of ${\mathrm{Er}}^{3+}$. The decrease in emission amounts to a factor of about 50 for a concentration of 0.5 mol % ${\mathrm{TmF}}_{3}$ at 300 K. The quenching effect is discussed in terms of energy transfer between ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions. A rate equation model and a Judd-Ofelt analysis used in conjunction with the appropriate optical data lead to an understanding of the up-conversion process. The absolute values of the energy transfer rates and the electron populations in the lower excited states of the excited ${\mathrm{Er}}^{3+}$ and ${\mathrm{Tm}}^{3+}$ ions can be determined. This information should enable researchers to tailor materials to improve the efficiency of the up-conversion and laser devices.

Cervical or thoracic anastomosis for esophagectomy for carcinoma.

Abstract: A prospective trial was conducted to compare intrathoracic and cervical anastomoses after esophagectomy for squamous cell carcinoma of the middle or lower one-third of the esophagus. One hundred and twenty-three patients were randomized to have either a cervical or thoracic anastomosis. Thirty-one patients were subsequently excluded either because esophagectomy was performed without thoracotomy or the tumor was unresectable or because the randomization protocol was not complied with. Transfusion requirements and operating time were similar for the 49 patients having esophagectomy by way of the laparotomy and right thoracotomy (TA) and the 43 patients who underwent laparotomy, right thoracotomy and cervicotomy (CA). Forty-three per cent of the CA and 49 per cent of the TA patients had involved lymph nodes. An esophagectomy incorporating a cervical anastomosis resulted in a significantly greater margin of macroscopically normal esophagus above the tumor (median of 4.0 versus 1.5 centimeters for TA). A leak was significantly more frequent after cervical anastomosis (26 per cent) than thoracic (4 per cent) (p less than 0.002). Respiratory complications were more frequent with a thoracic anastomosis, but this was not statistically significant. Thirty day mortality rates were similar for the two groups: 14.3 per cent, TA, and 9.3 per cent, CA (p = N.S.). Postoperative strictures occurred in 14 per cent of TA and 23 per cent of CA patients and were most common after an anastomotic leak. The survival patterns of the two groups were similar. The median survival time for CA patients was 23 months and for TA, 20 months. Excluding hospital mortality, 47 per cent of patients were alive at two years and 30 per cent at 40 months. Survival was related to extent of disease. The greater length of tumor-free esophagus removed with a cervical anastomosis did not result in an improved long term survival period, but was associated with a significantly higher incidence of anastomotic fistula.

Paleointensity of the Earth's magnetic field and K‐Ar dating of the Louchadiere volcanic flow (central France): New evidence for the Laschamp excursion

Abstract: We report paleointensity results of the Earth's magnetic field from a Late Pleistocene lava flow (Louchadiere, Central France), which recorded an intermediate geomagnetic field direction (5 sites, mean declination=114.1°, inclination=58.2°, k=130, α95=6.7°). New K-Ar age determinations confirm that this flow is contemporaneous with the Laschamp and Olby flows, and that this excursion occurred around 45ka ago. Using the Thellier double heating method, reliable paleointensities have been obtained for ten samples from three different sites, providing an average field strength of 12.9 µT (±3.3). This low value and previous results of the Laschamp excursion from France and Iceland confirm that the Earth's magnetic field was in an intermediate state during the Laschamp excursion.

Concentration-dependent energy-transfer processes in Er(3+)-and Tm(3+)-doped heavy-metal fluoride glass.

Abstract: The energy-transfer rate from the Er3+ 4I13/2 level to the Tm3+ 3H4 level (C11′NT) in BaF2/ThF4 fluoride glass is measured and calculated. The results can be used to determine whether rate equations can be used to predict energy-transfer rates.

Propriétés ergodiques, en mesure infinie, de certains systèmes dynamiques fibrés

Abstract: We study the ergodic properties of a class of dynamical systems with infinite invariant measure. This class contains skew-products of Anosov systems with ℝd. The results are applied to the K property of skew-products and also to the ergodicity of the geodesic flow on abelian coverings of compact manifolds with constant negative curvature.

Time-resolved study by X-ray powder diffraction with position-sensitive detector: rate of the β-Cs2Cdl4 transformation and the effect of preferred orientation

Abstract: A time-resolved X-ray powder diffraction of the transformation, at room temperature, of the metastable β-Cs2Cdl4 phase into α-Cs2Cdl4 is described. It is based on data collected by means of a conventional X-ray diffraction system combined to a curved position-sensitive detector. The transformation is governed by a nucleation and a three-dimensional growth process, and its rate depends on the particle size and crystal imperfections. When particle sizes are less than 40 μm, the rate of the transformation strongly decreases in the later stage of growth, due to the stresses produced by structural modifications. Particular attention is paid to the fact that the quantitative interpretation of experimental data in kinetic terms, can be influenced by the existence of a preferred orientation effect of the crystallites in the sample.

Spatial distribution of the cockroach, Blattella germanica, in a swimming‐bath facility

Abstract: A population of Blattella germanica L. was studied in a swimming-bath facility using a sampling method. A set of traps deposited weekly, over a period of 50 weeks, allowed us to follow the variations of the temporal and spatial distributions of the population inside the building. A Factorial Correspondance Analysis, performed on the data, led us to the conclusion that the population was stable in time. The spatial distribution of the insects was contiguous. Inside an aggregate, we were able to define a circular movement from the center towards the periphery and vice versa; this movement can be superimposed up on the biological development on the individuals. After birth in the middle of the aggregate, during development, larvae explore further a field as far as the border of the aggregate; this exploratory phase, related to foraging behavior or search for new shelters when these become limiting factors, could be considered as the spreading phase of the population. Then, with the imminence of the imaginai moult, old larvae tend to gather in high density areas in the middle of the aggregate. Newly molted adults look for a sexual partner. And finally females remain in the shelters during oothecae maturation. RESUME Distribution spatiale d'une population de Blattella germanica L. dans une piscine L'etude d'une population de Blattella germanica L. dans une piscine par des piegeages hebdomadaires pendant une periode de 50 semaines, nous a permis de suivre l'evolution spatiale et temporelle de cette population. Les resultats des piegeages etudies par Analyse Factorielle des Correspondances nous permettent de conclure a une certaine stabilite temporelle de la population. Elle se repartit en larges agregats dans lesquels s'inscrit un mouvement circulaire, allant du centre vers la peripherie et retour, qui se superpose au cycle de developpement des individus.

Transport and catabolism of proline betaine in salt-stressed Rhizobium meliloti

Abstract: Exogenous proline betaine (N,N-dimethylproline or stachydrine) highly stimulated the growth rate of Rhizobium meliloti, in media of inhibitory concentration of NaCl whereas proline was ineffective. High levels of proline betaine uptake occurred in cells grown in media of elevated osmotic strength; on the contrary, only low activity was found in cells grown in minimal medium. The apparent Km was 10 μM with a maximal transport rate of 25 nmol min-1 mg-1 of protein in 0.3 M NaCl-grown cells. The concentrative transport was totally abolished by KCN (2 mM), 2,4-dinitrophenol (2 mM), and carbonyl cyanide-m-chlorophenyl hydrazone (CCCP 10 μM) but was insensitive to arsenate (5 mM). Glycine betaine was a very potent inhibitor of proline betaine uptake while proline was not. Proline betaine transport was not reduced in osmotically shocked cells and no proline betaine binding activity was detected in the crude periplasmic shock fluid. In the absence of salt stress, Rhizobium meliloti actively catabolized proline betaine but this catabolism was blocked by increasing the osmotic strength of the medium. The osmolarity in the growth medium regulates the use of proline betaine either as a carbon and nitrogen source or as an osmoprotectant.

Reversal of Fe-Mg partitioning between garnet and staurolite in eclogite-facies metapelites from the Champtoceaux nappe (Brittany, France)

Abstract: This paper concentrates on the petrology of eclogite-facies metapelites and, particularly, the significance of staurolite in these rocks. A natural example of staurolite-bearing eclogitic micaschists from the Champtoceaux nappe (Brittany, France) is first described. The Champtoceaux metapelites present, in addition to quartz, phengite, and rutile, two successive parageneses: (1) chloritoid + staurolite-I-garnet cores, and (2) garnet rims-hkyanite± chloritoid. Detailed microprobe analyses show that garnet and chloritoid evolve towards more magnesian compositions and that staurolite is more Fe-rich than coexisting garnet. A comparison of the studied rocks with other known occurrences of eclogitic metapelites shows that whereas staurolite is always more Fe-rich than garnet in high-pressure eclogites, the reverse is true in low-to medium-pressure micaschists. Phase relations between garnet, staurolite, chloritoid, biotite, and chlorite are analysed in the KFMASH system (with excess quartz, phengite, rutile, and H20). The topology of univariant reactions is depicted for a normal and a reverse Fe-M g partitioning between garnet and staurolite. Mineral compositional changes are also predicted for varying bulk-rock chemistries. In the studied micaschists, the zonal arrangement of garnet inclusions and the progressive compositional changes of ferromagnesian phases record part of the prograde P-T path, before the attainment o f 'peak' metamorphic conditions (at about 650-700 °C, 18-20 kb). The retrograde path, which records the uplift of the Champtoceaux nappe, occurs under decreasing temperatures.

Assessment of Testicular Function after Acute and Chronic Irradiation: Further Evidence for an Influence of Late Spermatids on Sertoli Cell Function in the Adult Rat*

Abstract: To study cell to cell communications within the testis of adult Sprague-Dawley rats, we used acute whole body neutron plus gamma-irradiation (0.99 Gray of neutron and 0.24 Gray of gamma-rays, 3 min; Exp A) over 7-121 days postirradiation and chronic whole body gamma-irradiation (7 cGy/day 60Co gamma-rays; Exp B) over 14-84 days of irradiation and 7-86 days postirradiation. Neither irradiation protocol had an effect on the body weight of the animals. Neutron plus gamma-rays induced dramatic damages to spermatogonia, preleptotene spermatocytes, spermatozoa, and, to a lesser extent, pachytene spermatocytes. In contrast, gamma-rays induced a selective destruction of spermatogonia. Subsequently, in both experiments a maturation-depletion process led to a marked decrease in all germ cell types. A complete or near complete recovery of the different germ cell types and spermatozoa took place during the two postirradiation periods. Under both irradiation protocols Sertoli cells number was unchanged. Androgen-binding protein and FSH levels were normal in spite of the disappearance of most germ cells from spermatogonia to early spermatids. However, the decline of androgen-binding protein as well as the rise of FSH and their subsequent recovery were highly correlated to the number of late spermatids and spermatozoa. Moreover, it appeared that spermatocytes may also interfere with the production of inhibin (Exp B). With neither irradiation was Leydig cell function altered, except in Exp B in which elevated LH levels were temporarily observed. Correlation analysis suggested a relationship between preleptotene spermatocytes and Leydig cell function. In conclusion, this study establishes that chronic gamma-irradiation is particularly useful in the study of intratesticular paracrine regulation in vivo and provides further support to the concept that late spermatids play a major role in controlling some aspects of Sertoli cell function in the adult rat.