Showing papers by "University of Rennes published in 1996"
TL;DR: Although there is consensus about the importance of polyamine uptake inhibitors in the treatment of neoplastic disorders, a practically useful uptake inhibitor is still missing, the attempts to target tumours, and to increase the selectivity of cytotoxic agents by combining them with the polyamine structure, are promising.
342 citations
TL;DR: The Bixiling mafic-ultramafic complex is a tectonic block within biotite gneisses in the eastern part of the Dabie ultra-high-pressure metamorphic (UHPM) terrane as discussed by the authors.
295 citations
TL;DR: In this paper, the authors used 3D laboratory experiments to simulate a retreating subduction process in a compressional regime oriented perpendicularly to the direction of subduction, in which they also tested the influence of the gravitational collapse of the overriding plate.
Abstract: The E-W-opening Tyrrhenian Sea developed after the Cretaceous-Palaeogene Alpine collision, nearly perpendicular to the motion of the African plate, as a back-arc of the Adria-Ionian westward subduction. Three driving mechanisms have been proposed to explain the dynamic evolution of the Tyrrhenian-Apennine system: (1) the northward indentation of the African plate; (2) the retreating subduction of the Adria-Ionian lithosphere; and (3) the gravitational collapse of the Alpine post-collisional wedge. In order to define the relative contribution of each of these mechanisms in the Neogene dynamic of the Tyrrhenian-Apennine system, we performed 3-D laboratory experiments, in which we simulated a retreating subduction process in a compressional regime oriented perpendicularly to the direction of subduction; in this framework we also tested the influence of the gravitational collapse of the overriding plate. Experiments were constructed using dry sand and silicone putties to simulate brittle upper crust and ductile lower crust/upper mantle, respectively; these layers floated on a high-density, low-viscosity glucose syrup which simulated the asthenosphere. The main conclusion of our experiments is that large-scale continental extension, similar to that observed in the Tyrrhenian area, could be reproduced perpendicular to the shortening direction induced by the indentation of the African plate; in this framework, extensional processes are indeed possible if the trench retreat velocity is higher than the rate of shortening induced by the advancing African plate. Our experimental results indicate that this high trench retreat velocity could be explained by the coexistence of the gravitational collapse of the post-Alpine wedge with a slab-pull process, linked to the retreating subduction of the Adria-Ionian plate. While the first mechanism is predominant in the Northern Tyrrhenian area, the second one seems to be important in the latest stage of extension and oceanic accretion of the Southern Tyrrhenian area.
259 citations
Journal Article•
TL;DR: It is demonstrated that eRF3 is a GTP-binding protein endowed with a negligible, if any, intrinsic GTPase activity that is profoundly stimulated by the joint action of eRF1 and the ribosome, and that in ribosomes both hydrolytic reactions are mediated by the formation of the ternary eRF-eRF3-GTP complex.
Abstract: Termination of translation in eukaryotes is governed by two polypeptide chain release factors, eRF1 and eRF3 on the ribosome. eRF1 promotes stop-codon-dependent hydrolysis of peptidyl-tRNA, and eRF3 interacts with eRF1 and stimulates eRF1 activity in the presence of GTP. Here, we have demonstrated that eRF3 is a GTP-binding protein endowed with a negligible, if any, intrinsic GTPase activity that is profoundly stimulated by the joint action of eRF1 and the ribosome. Separately, neither eRF1 nor the ribosome display this effect. Thus, eRF3 functions as a GTPase in the quaternary complex with ribosome, eRF1, and GTP. From the in vitro uncoupling of the peptidyl-tRNA and GTP hydrolyses achieved in this work, we conclude that in ribosomes both hydrolytic reactions are mediated by the formation of the ternary eRF1-eRF3-GTP complex. eRF1 and the ribosome form a composite GTPase-activating protein (GAP) as described for other G proteins. A dual role for the revealed GTPase complex is proposed: in " GTP state," it controls the positioning of eRF1 toward stop codon and peptidyl-tRNA, whereas in "GDP state," it promotes release of eRFs from the ribosome. The initiation, elongation, and termination steps of protein synthesis seem to be similar with respect to GTPase cycles.
256 citations
01 Jan 1996
TL;DR: This paper describes a general approach to run-time specialization that automatically produces source templates at compile time, and transforms them so that they can be processed by a standard compiler, and is efficient, as shown by the implementation for the C language.
Abstract: Specializing programs with respect to run-time invariants is an optimization technique that has shown to improve the performance of programs substantially. It allows a program to adapt to execution contexts that are valid for a limited time.Run-time specialization is being actively investigated in a variety of areas. For example, recently, major operating system research projects have been focusing on run-time specialization as a means to obtain efficiency from highly extensible and parameterized systems.This paper describes a general approach to run-time specialization. For a given program and a declaration of its run-time invariants, it automatically produces source templates at compile time, and transforms them so that they can be processed by a standard compiler. At run time, only minor operations need to be performed: selecting and copying templates, filling holes with run-time values, and relocating jump targets. As a consequence, run-time specialization is performed very efficiently and thus does not require the specialized code to be executed many times before its cost is amortized.Our approach improves on previous work in that: (1) templates are automatically produced from the source program and its invariants, (2) the approach is not machine dependent, (3) it is formally defined and proved correct, (4) it is efficient, as shown by our implementation for the C language.
254 citations
TL;DR: In this article, the future of hedgerows is studied and the role of land use and boundary management plays a major role in determining the floristic composition of hedgers.
Abstract: Hedgerows, rows of trees or shrubs enclosing or separating fields, are man made. They are part of rural landscapes and should not be studied without considering the farming systems and the rural society as a whole. Their species composition depends on the history of the countryside, as well as current farming practices. Land use and boundary management play a major role in determining the floristic composition of hedgerows, and are strongly related to the grain size of the field's mosaic. Hedgerow networks, due to their rectilinear shape, and with their high degree of connection, enhance or interrupt many fluxes in the landscape. Hedgerows act as a corridor of movement and dispersal for many forest species, such as carabids, small mammals, and plants. On the other hand, hedgerows interrupt or slow down air fluxes and the propagules they carry. In the heterogeneous mosaic of fields and wooded patches, hedgerows often increase the functional connectivity of rural landscapes. The future of hedgerows...
213 citations
TL;DR: In this paper, a theory of random walks on the mapping class group and its non-elementary subgroups is developed, based on an analysis of the asymptotic geometry of Teichmuller space and of the contraction properties of the action of the class group on the Thurston boundary.
Abstract: A theory of random walks on the mapping class group and its non-elementary subgroups is developed. We prove convergence of sample paths in the Thurston compactification and show that the space of projective measured foliations with the corresponding harmonic measure can be identified with the Poisson boundary of random walks. The methods are based on an analysis of the asymptotic geometry of Teichmuller space and of the contraction properties of the action of the mapping class group on the Thurston boundary. We prove, in particular, that Teichmuller space is roughly isometric to a graph with uniformly bounded vertex degrees. Using our analysis of the mapping class group action on the Thurston boundary we prove that no non-elementary subgroup of the mapping class group can be a lattice in a higher rank semi-simple Lie group.
206 citations
TL;DR: In this article, the diiron complex was synthesized by the oxidative coupling of Fe(η5-C5Me5)(dppe) and C⋮CC⌈⌉CH.
199 citations
TL;DR: Examination of the mechanisms involved in post-transcriptional regulation of ER mRNA showed that the setting up and maintenance of this regulation process implies that estrogen receptor and the general translational activity within the cells, suggesting that ER mRNA depends on the synthesis of an estrogen-dependent protein.
191 citations
TL;DR: It is concluded that darkening of the encapsulated eggs was due to cell necrosis rather than to extracellular melanin deposition, and that haemocytes other than lamellocytes were engaged in capsule formation, and the immunosuppressive factors did not target only the lamellocyte but also the plasmatocytes.
Abstract: Eggs of an immune suppressive strain ( = virulent) of the parasitoid Leptopilina boulardi are encapsulated neither in resistant nor in susceptible strains of Drosophila melanogaster but are encapsulated in Drosophila yakuba. Eggs of a non-immune suppressive strain ( = avirulent) of the same parasitoid are encapsulated in a resistant strain of D. melanogaster and in D. yakuba but are not encapsulated in a susceptible strain of D. melanogaster. Egg chorion in the 2 parasitoid strains showed the same morphology and the same modifications after egg laying whatever the host strain. When a capsule is built, a small dotted dense layer was first spread on the chorion, followed by accumulation layers of cells (plasmatocytes and lamellocytes) and lastly necrosis of the inner haemocytes. The encapsulated eggs darken only at the time of necrosis of haemocytes. In susceptible hosts, neither the tiny dense layer nor haemocyte accumulation occured. We concluded that (1) this tiny dense layer was present before the deposition of the first haemocytes, (2) inhibition of deposition of this dense layer was the initial event of the induced immunosupression, (3) haemocytes other than lamellocytes were engaged in caspsule formation, (4) the immunosupressive factors did not target only the lamellocytes but also the plasmatocytes, (5) darkening of the encapsulated eggs was due to cell necrosis rather than to extracellular melanin deposition.
185 citations
TL;DR: Gorgona Island, Colombia is remarkable not only because it contains the only Phanerozoic komatiites, but also because it has mafic to ultramafic lavas with a wide range of compositions, from moderately enriched to extremely depleted (relative to Bulk Earth) as mentioned in this paper.
TL;DR: It was found that flavone, dl-aminoglutethimide, apigenin, quercetin, 7,4'- dihydroxyflavone, alpha-naphthoflavone and equol were potent inhibitors of the ovarian aromatase activity in rainbow trout.
TL;DR: Significant effects of drought stress, depending on its timing, were observed in the accumulation of secondary metabolites (i.e., phenolics and glucosinolates) which are of major importance for rapeseed meal quality.
TL;DR: In this article, the minimum age of protolith formation at ∼ 1.7 Ga, assuming their evolution from a depleted or a chondritic mantle, was calculated from geochemical analyses and isotopic age determinations.
TL;DR: In this article, the authors consider the dynamics of an ensemble of identical, inelastic, hard disks in a doubly periodic domain, where the total energy of the system is monotonically decreasing so that this idealized granular medium is cooling down.
Abstract: We consider the dynamics of an ensemble of identical, inelastic, hard disks in a doubly periodic domain. Because there is no external forcing the total energy of the system is monotonically decreasing so that this idealized granular medium is ``cooling down.'' There are three nondimensional control parameters: the coefficient of restitution r, the solid fraction \ensuremath{
u}, and the total number of disks in the domain N. Our goal is a comprehensive description of the phenomenology of granular cooling in the (r,\ensuremath{
u},N) parameter space. Previous studies have shown that granular cooling results in the formation of structures: both the mass and the momentum spontaneously become nonuniform. Four different regimes (kinetic, shearing, clustered, and collapsed) have been identified. Starting with the almost elastic case, in which r is just less than 1, the kinetic regime resembles a classical nondissipative gas in which there are no structures. When r is decreased (with fixed N and \ensuremath{
u}) the system evolves into the shearing regime in which most of the energy and momentum resides in the gravest hydrodynamic shear mode. At still smaller values of r the clustered regime appears as an extended transient. Large clusters of disks form, collide, breakup, and reform. From the clustered state the gas eventually either evolves into the shearing regime or, alternatively, collapses. The collapsed regime is characterized by a dynamical singularity in which a group of particles collides infinitely often in a finite time. While each individual collision is binary, the space and time scales decrease geometrically with the cumulative number of collisions so that a multiparticle interaction occurs. The regime boundaries (i.e., the critical values of r) in the (N,\ensuremath{
u}) plane have been delineated using event-driven numerical simulations. Analytic considerations show that the results of the simulations can be condensed by supposing that the critical values of r depend only on N and \ensuremath{
u} through the optical depth, \ensuremath{\lambda}\ensuremath{\equiv}d\ensuremath{\surd}N\ensuremath{\pi}\ensuremath{
u}/2 where d is the disk diameter. \textcopyright{} 1996 The American Physical Society.
TL;DR: A detailed structural analysis indicates two strain fields associated with two deformational episodes: D1 and D2 as discussed by the authors, where the D1 episode produced dome-and-basin structures and affected merely the older greenstones and the gneisses.
TL;DR: The results in this article show that the earliest Amphbolite-facies metamorphism of the Isua belt for which pressure and temperature conditions can be obtained (P ≈ 5 kbar; T ≈ 500-600°C) is late Archaean, and not early Archaean as had been assumed earlier by some authors.
TL;DR: A variety of neutral ruthenium−carbene complexes have been prepared by reaction of [RuCl2(arene)]2 precursors with the enetetraamines as discussed by the authors.
01 Sep 1996
TL;DR: In this article, the authors propose alternative computational methods for dealing with the following three classical problems in the study of zero-dimensional systems, rephrased in the context of finite-dimensional algebras over a field k of characteristic zero.
Abstract: We want to propose alternative computational methods for dealing with the following three classical problems in the study of zero-dimensional systems, rephrased in the context of finite-dimensional algebras over a field k of characteristic zero. It is the main feature of our approach to adapt to the affine case the concept of the u-Chow form (or u-resultant) which was developed in the projective case (and has been used by several authors, e.g., [Ca] and [Re]).
12 Feb 1996
TL;DR: As partial evaluation gets more mature, it is now possible to use this program transformation technique to tackle realistic languages and real-size application programs.
Abstract: As partial evaluation gets more mature, it is now possible to use this program transformation technique to tackle realistic languages and real-size application programs. However, this evolution raises a number of critical issues that need to be addressed before the approach becomes truly practical.
TL;DR: In this article, Henyey and Pomphrey developed a differential self-consistent model that is shown to be a good approximation for porous/cracked rocks, but as it considers cracks with zero thickness, it can not account for fluid content effects.
Abstract: Although P- and S-wave dispersion is known to be important in porous/cracked rocks, theoretical predictions of such dispersions have never been given. The authors report such calculations and show that the predicted dispersions are high in the case of low aspect ratio cracks ({le}10{sup {minus}3}) or high crack density ({ge}10{sup {minus}1}). Their calculations are derived from first-principle computations of the high- and low-frequency elastic moduli of a rock permeated by an isotropic distribution of pores or cracks, dry or saturated, with idealized geometry (spheres or ellipsoids). Henyey and Pomphrey developed a differential self-consistent model that is shown to be a good approximation. This model is used here, but as it considers cracks with zero thickness, it can not account for fluid content effects. To remove this difficulty, one combines the differential self-consistent approach with a purely elastic calculation of moduli in two cases: that of spherical pores and that of oblate spheroidal cracks with a nonzero volume. This leads to what the authors call the extended differential, self-consistent model (EM). When combining these EM results with the Gassmann equation, it is possible to derive and compare the theoretical predictions for high- and low-frequency effective moduli in the case of amore » saturated rock. Since most laboratory data are ultrasonic measurements and in situ data are obtained at much lower frequencies, this comparison is useful for interpreting seismic data in terms of rock and fluid properties. The predicted dispersions are high, in agreement with previous experimental results. A second comparison is made with the semi-empirical model of Marion and Nur, which considers the effects of a mixed porosity (round pores and cracks together).« less
TL;DR: In this article, the optical properties of fluorophosphate glasses of composition were investigated in the 4.2-300 K temperature range by using optical absorption spectroscopy and time-resolved resonant laser-induced fluorescence line narrowing.
Abstract: The optical properties of ${\mathrm{Eu}}^{3+}$-doped fluorophosphate glasses of composition (in mol %) 60 ${\mathrm{NaPO}}_{3}$-${15\mathrm{B}\mathrm{a}\mathrm{F}}_{2}$-(25-x)${\mathrm{YF}}_{3}$-x${\mathrm{EuF}}_{3}$ (x=0.5, 2, 5, 10, 15, 20, and 25) have been investigated in the 4.2--300 K temperature range by using optical absorption spectroscopy and time-resolved resonant laser-induced fluorescence line narrowing. From the room-temperature absorption spectra Judd-Ofelt parameters have been obtained and used to calculate the spontaneous emission probabilities from the $^{5}$${\mathit{D}}_{0}$ state. The spectral features of the time-resolved fluorescence line-narrowed $^{5}$${\mathit{D}}_{0}$${\ensuremath{\rightarrow}}^{7}$${\mathit{F}}_{0,1}$ emission spectra obtained under resonant excitation at different wavelengths along the $^{7}$${\mathit{F}}_{0}$${\ensuremath{\rightarrow}}^{5}$${\mathit{D}}_{0}$ transition as a function of concentration and temperature reveal the existence of energy migration between discrete regions of the inhomogeneous broadened spectral profile. From the concentration and time dependence of the average rate of excitation transfer, the electronic mechanism ruling the ion-ion interaction can be identified as a dipole-dipole energy transfer process. At low temperatures the average transfer rate parameter slightly depends on wavelength showing a temperature independent behavior. Above 77 K the weak dependence of the transfer rate on excitation wavelength (weak dependence on energy mismatch) together with its T${\mathrm{}}^{3}$ temperature dependence point to a transfer mechanism consistent with a two-site nonresonant two-phonon assisted process. The estimated average crystal field strength grows monotonically with the $^{7}$${\mathit{F}}_{0}$${\ensuremath{\rightarrow}}^{5}$${\mathit{D}}_{0}$ energy suggesting a large variation in the local environment of ${\mathrm{Eu}}^{3+}$ ions in these glasses. The slight increase with concentration of the $^{5}$${\mathit{D}}_{0}$ fluorescence decays together with their single exponential character suggest that the transfer process may be fast enough to drive the system of excited centers to thermal equilibrium. \textcopyright{} 1996 The American Physical Society.
TL;DR: In this article, the relativistic effects have been taken into account in the computations carried out with the help of two independent computer programs, SUPERSTRUCTURE (SST) and RELATIVISTIC HARTREE-FOCK (HFR).
Abstract: Radiative transition probabilities have been calculated for the magnetic dipole (M1) and electric quadrupole (E2) transitions connecting the 63 metastable levels in the 3d 6 4s, 3d 7 and 3d 5 4s 2 configurations in Fe II. The most important configuration interaction (CI) and relativistic effects have been taken into account in the computations carried out with the help of two independent computer programs, SUPERSTRUCTURE (SST) and RELATIVISTIC HARTREE-FOCK (HFR). The results obtained in the present work are compared with previous theoretical studies and with some astrophysical observations. The new data presented here are probably the most reliable to date.
TL;DR: Results clearly show that hepatocytes immobilized in calcium-alginate beads remain functional even after cryopreservation indicating that they represent a promising approach for xenobiotic metabolism and toxicity studies.
TL;DR: DFMO strongly inhibits root growth and arbuscular mycorrhizal infection of Pisum sativum and this inhibition is reversed when exogenous polyamine (putrescine) is included in the DFMO treatment, suggesting that ODC may have a role in root Growth and myCorrhizals infection.
TL;DR: This poster presents a probabilistic procedure to determine the carrier and removal status of canine coronavirus using a simple, straightforward, two-step procedure.
Abstract: Reference LSR-ARTICLE-1996-004doi:101145/227210227230View record in Web of Science Record created on 2005-05-20, modified on 2017-05-12
TL;DR: In this paper, several poly-ynes X-[C-C6H4-]nC≡C-SiiPr3 (X = H, SiMe3) with controlled length (n = 1, 2, 3, 4) have been prepared from the easily accessible 4-trimethylsilylethynyl iodobenzene by using iterative and convergent methods based on both Pd/Cu catalysed C-C cross-coupling and selective desilylation reactions.
TL;DR: In this paper, a comparison of marine, lacustrine, and terrestrial records from twenty-four sites suggests the existence of a Younger Dryas-type climate oscillation just prior to the Oxygen Isotope Stage 6/5e boundary.