Éditeur(s) : HAL CCSD International Federation of Sports Medicine
Résumé : International audience
To study the exercise-induced arterial hypoxaemia (EIAH) kinetics in a world class Ironman triathlete at ventilatory threshold (TH vent), the authors simulated the cycle-run succession (CR, 20 min + 20 min) and a 20-min isolated run (R). Although 'moderate EIAH' was noted during CR, the SpO 2 kinetics of the isolated R reflected 'severe EIAH' from minutes 7 to 15 with a nadir of 85 % SpO 2 that stabilised at 90 % SpO 2 from minute 15 on. The physiological processes involved in these responses are discussed. These data indicate a systematic 'moderate EIAH' in a world class Ironman champion during CR and R at TH vent and a temporary 'severe EIAH' during R, which was attenuated when running was successive to cycling. The physiological significance of this phenomenon remains unclear, however, and further experiments are needed.
ISSN: 1528-3356

hal-01152346
https://hal.univ-antilles.fr/hal-01152346

Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
Abstract View references (60)Here we show the long term performance at high temperatures of a multi-tube module containing 8 membranes in 4 parallel lines with a total of 545 cm 2 area. The membranes were prepared via thin film dip coating of cobalt oxide silica (CoO xSi) sol-gel on tubular alumina supports. A preliminary study found that the sol-gel containing 20 mol% cobalt oxide formed the best microporous structure with the highest surface area and pore volume. All resulting membranes delivered permeances of ∼1 × 10 -7 mol m -2 s -1 Pa -1 at 500 °C, indicating a high repeatability for the membrane fabrication process. The permselectivities of helium (He) and hydrogen (H 2) over carbon dioxide (CO 2) and nitrogen (N 2) increased from 10-20 at 100 °C to values close to 1000 at 500 °C. Additionally, the apparent energies of activation (E act) for the smaller kinetic diameter gases He and H 2 at 12.2 and 19.5 kJ mol -1 were high and contrary to the negative values for larger gases N 2 and CO 2 at -1.8 and -7.4 kJ mol -1. These remarkable results were attributed to the molecular sieving mechanism of the microporous silica which was enhanced by the embedding of cobalt oxide into the matrix, delivering structural control with an average pore size of 3 Å. The E act for H 2 permeance was higher than that of He, indicating that the cobalt oxide played an important role in H 2 transport. Two membrane lines performed exceptionally well for binary gas mixture processing with H 2 purity reaching values close to 100% in the permeate stream for argon (Ar) concentrations of up to 80% in the retentate stream. A major finding here is that the binary gas selectivity was independent of temperature, contrary to the permselectivity observed for single gas permeance. Further, the H 2 flow rate was greatly affected by the concentration of Ar in the mixture, while the temperature dependency played only a marginal role. In particular, competitive adsorption in the percolative pathways containing pore constrictions or bottlenecks of the anisotropic CoO xSi matrix allowed Ar to impede H 2 diffusion. Finally, the CoO xSi membranes proved thermally stable and robust for 2000 h of testing for various thermal cycles up to 500 °C. © The Royal Society of Chemistry 2012.
Energy & Environmental Science

hal-01683199
https://hal.univ-antilles.fr/hal-01683199
DOI : 10.1039/c2ee03247c

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
BACKGROUND: Evidence of human sexual transmission during Zika virus emergence is a matter of concern, particularly in procreation, but to date, kinetics of seminal shedding and the effects of infection on human reproductive function have not been described. To investigate the effects of Zika virus infection on semen and clearance of Zika virus from semen and body fluids, we aimed to study a cohort of Zika virus-infected men. METHODS: This prospective observational study recruited men presenting with acute Zika virus infection at Pointe-à-Pitre University Hospital in Guadeloupe, French Caribbean, where a Zika virus outbreak occurred between April and November, 2016. Blood, urine, and semen were collected at days 7, 11, 20, 30, 60, 90, and 120 after symptom onset, and semen characteristics, such as total sperm count, sperm motility, vitality, and morphology, and reproductive hormone concentrations, such as testosterone, inhibin, follicle-stimulating hormone, and luteinising hormone, were assessed. At days 7, 11, and 20, semen was processed to isolate motile spermatozoa. Zika virus RNA was detected by RT-PCR using whole blood, serum, urine, seminal plasma, semen cells, and motile spermatozoa fractions. Zika virus was isolated from different sperm fractions on Vero E6 cultures. FINDINGS: 15 male volunteers (mean age 35 years [SD 5; range 25-44) with acute Zika virus infection and positive Zika virus RNA detection in blood or urine were enrolled. Total sperm count was decreased from median 119 × 10(6) spermatozoa (IQR 22-234) at day 7 to 45·2 × 10(6) (16·5-89·6) at day 30 and 70 × 10(6) (28·5-81·4) at day 60, respectively, after Zika virus infection. Inhibin values increased from 93·5 pg/mL (IQR 55-162) at day 7 to 150 pg/mL (78-209) at day 120 when total sperm count recovered. In motile spermatozoa obtained after density gradient separation, Zika virus RNA was found in three of 14 patients at day 7, four of 15 at day 11, and four of 15 at day 20, and replication-competent virus was found in the tested patient. Seminal shedding kinetics seemed heterogeneous among patients. Whole blood was the fluid most frequently positive for Zika virus RNA (62 of 92 samples) and three patients remained positive at day 120. INTERPRETATION: Semen alterations early after acute Zika virus infection might affect fertility and could be explained by virus effects on the testis and epididymis. Frequency of shedding and high viral load in semen, together with the presence of replicative virus in a motile spermatozoa fraction, can lead to Zika virus transmission during sexual contact and assisted reproduction procedures. Whole blood seems to be the best specimen for Zika virus RNA detection, diagnosis, and follow-up. FUNDING: Agence de la Biomédecine/Agence Régionale de Santé de la Guadeloupe/Inserm-REACTing.
ISSN: 0140-6736

hal-01647078
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01647078
DOI : 10.1016/S1473-3099(17)30444-9
PUBMED : 28838639

Éditeur(s) : HAL CCSD Elsevier
Résumé : Among the radionuclides that can migrate from radioactive wastes buried within consolidated argillaceous rocks, I-129 poses a particular problem due to its high mobility in geomedia and its very long half-life of 1.6 10(7) years. Previous studies carried out on such rocks showed the existence of a low iodide retardation regarding the other anion species. The purpose of the present study was two-fold. It was hoped (1) to confirm this retardation by means of radial diffusion experiments and (2) to estimate the influence of the initial iodide concentrations towards the iodide uptake. The results obtained from in-diffusion stage show that (1) no iodide uptake occurs at high initial concentrations and (2) an uptake at low initial concentrations cannot be clearly evidenced. Finally. the most singular behaviour of iodide was highlighted for all the initial iodide concentrations, from the out-diffusion stage. during which some amount of iodide, available for out-diffusion, were not involved in the diffusion process. Although the origin of such phenomenon remains unclear, a kinetic effect for the iodide uptake was proposed, assuming that the period of 55days (corresponding to the in-diffusion stage duration) would be necessary for inducing the iodide uptake. This kinetic effect, already shown elsewhere by (Descostes. M., Blin, V., Bazer-Bachi, F., Meier, P., Grenut, B., Radwan. J., Schlegel, M.L., Buschaert, S.. Coelho, D, Tevissen, E. Diffusion of anionic species in Callovo-Oxfordian argillites and Oxfordian limestones. In press for Appl. Geochem.) on similar materials, needs to be deepened.
ISSN: 0079-1946

hal-00412393
https://hal.archives-ouvertes.fr/hal-00412393
DOI : 10.1016/j.pce.2008.05.020

Éditeur(s) : Elsevier Sci Ltd
Résumé : The aim of this study is to establish a baseline for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) lifetime prediction in a marine environment, by means of mechanical and physico-chemical characterization of specimens immersed in continuously renewed and filtered natural seawater in the laboratory at different temperatures (4, 25 and 40°C). Samples were also aged at sea in Lorient harbour in order to compare laboratory and natural degradation mechanisms and kinetics. Due to its morphology, hydrolysis of PHBV in natural seawater is quite slow, and samples were observed to undergo preferentially an enzymatic surface degradation. Increasing the aging temperature in the laboratory promotes the water uptake and causes hydrolysis. As two degradation mechanisms occur in parallel, the choice of test conditions is critical, and the lifetime of PHBV in a marine environment is difficult to predict accurately.
Polymer Degradation And Stability (0141-3910) (Elsevier Sci Ltd), 2014-07 , Vol. 105 , P. 237-247

Droits : 2014 Elsevier Ltd. All rights reserved.
http://archimer.ifremer.fr/doc/00188/29972/28425.pdf
DOI:10.1016/j.polymdegradstab.2014.04.026
http://archimer.ifremer.fr/doc/00188/29972/

Éditeur(s) : HAL CCSD Elsevier
Résumé : We studied the evolution of the microstructure of ice-Ih during static recrystallization by stepwise annealing experiments. We alternated thermal annealing and electron backscatter diffraction (EBSD) analyses on polycrystalline columnar ice pre-deformed in uniaxial compression at temperature of −7 °C to macroscopic strains of 3.0–5.2. Annealing experiments were carried out at −5 °C and −2 °C up to a maximum of 3.25 days, typically in 5–6 steps. EBSD crystal orientation maps obtained after each annealing step permit the description of microstructural changes. Decrease in average intragranular misorientation at the sample scale and modification of the misorientation across subgrain boundaries provide evidence for recovery from the earliest stages of annealing. This initial evolution is similar for all studied samples irrespective of their initial strain or annealing temperature. After an incubation period ≥1.5 h, recovery is accompanied by recrystallization (nucleation and grain boundary migration). Grain growth proceeds at the expense of domains with high intragranular misorientations, consuming first the most misorientated parts of primary grains. Grain growth kinetics fits the parabolic growth law with grain growth exponents in the range of 2.4–4.0. Deformation-induced tilt boundaries and kink bands may slow down grain boundary migration. They are stable features during early stages of static recrystallization, only erased by normal growth, which starts after >24 h of annealing.
ISSN: 0191-8141

hal-01685644
https://hal.archives-ouvertes.fr/hal-01685644
DOI : 10.1016/j.jsg.2017.05.001

Éditeur(s) : HAL CCSD EDP Sciences
Résumé : We propose and we justify a Monte-Carlo algorithm which solves a spatially homogeneous kinetic equation of Boltzmann type that models the fusion reaction between a deuterium ion and a tritium ion, and giving an α particle and a neutron. The proposed algorithm is validated with the use of explicit solutions of the kinetic model obtained by replacing the fusion cross-section by a Maxwellian cross section.
ISSN: 1270-900X

hal-00689821
https://hal.archives-ouvertes.fr/hal-00689821
https://hal.archives-ouvertes.fr/hal-00689821/document
https://hal.archives-ouvertes.fr/hal-00689821/file/proc_versionHAL.pdf

Éditeur(s) : HAL CCSD Springer Verlag (Germany)
Résumé : International audience
The Michaelis-Menten enzymatic reaction is sufficient to perceive many subtleties of network modeling, including the concentration and time scales separations, the formal equivalence between bulk phase and single-molecule approaches, or the relationships between single-cycle transient probabilities and steady state rates. Twelve methods proposed by different authors and yielding the same famous Michaelis-Menten equation, are selected here to illustrate the kinetic and probabilistic use of rate constants and to review basic techniques for handling them. Finally, the general rate of an ordered multistep reaction, of which the Michaelis-Menten reaction is a particular case, is deduced from a Markovian approach.
ISSN: 0259-9791

hal-00920806
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00920806
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00920806v2/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-00920806/file/12MM.pdf
ARXIV : 1312.5468

Éditeur(s) : HAL CCSD Elsevier
Résumé : The correct characterization of the effective reactive transport dynamics is an important issue for modeling reactive transport on the Darcy scale, specifically in situations in which reactions are localized, that is when different reactions occur in different portions of the porous medium. Under such conditions the conventional approach of homogenizing only the porous medium chemistry is not appropriate. We consider here reactive transport in a porous medium that is characterized by mass transfer between a mobile and a distribution of immobile regions. Chemical and physical heterogeneities are reflected by distributions of kinetic reaction rate constants and residence times in the immobile zones. We derive an effective reactive transport equation for the mobile solute that is characterized by non-local physical mass transfer and reaction terms. Specifically, chemical heterogeneity is upscaled in terms of a reactive memory function that integrates both chemical and physical heterogeneity. Mass transfer limitations due to physical heterogeneity yield effective kinetic rate coefficients that can be much smaller than the volumetric average of the local scale coefficients. These results help to explain and quantify the often reported discrepancy between observed field reaction rate constants and the ones obtained under well mixed laboratory conditions. Furthermore, these results indicate that transport under physical and chemical heterogeneity cannot be upscaled separately.
ISSN: 0169-7722

hal-00617674
https://hal.archives-ouvertes.fr/hal-00617674
DOI : 10.1016/j.jconhyd.2010.06.002

Éditeur(s) : HAL CCSD BioMed Central
Résumé : International audience
Background: The filamentous fungus Trichoderma reesei is the main industrial cellulolytic enzyme producer. Several strains have been developed in the past using random mutagenesis, and despite impressive performance enhancements, the pressure for low-cost cellulases has stimulated continuous research in the field. In this context, comparative study of the lower and higher producer strains obtained through random mutagenesis using systems biology tools (genome and transcriptome sequencing) can shed light on the mechanisms of cellulase production and help identify genes linked to performance. Previously, our group published comparative genome sequencing of the lower and higher producer strains NG 14 and RUT C30. In this follow-up work, we examine how these mutations affect phenotype as regards the transcriptome and cultivation behaviour. Results: We performed kinetic transcriptome analysis of the NG 14 and RUT C30 strains of early enzyme production induced by lactose using bioreactor cultivations close to an industrial cultivation regime. RUT C30 exhibited both earlier onset of protein production (3 h) and higher steady-state productivity. A rather small number of genes compared to previous studies were regulated (568), most of them being specific to the NG 14 strain (319). Clustering analysis highlighted similar behaviour for some functional categories and allowed us to distinguish between induction-related genes and productivity-related genes. Cross-comparison of our transcriptome data with previously identified mutations revealed that most genes from our dataset have not been mutated. Interestingly, the few mutated genes belong to the same clusters, suggesting that these clusters contain genes playing a role in strain performance. Conclusions: This is the first kinetic analysis of a transcriptomic study carried out under conditions approaching industrial ones with two related strains of T. reesei showing distinctive cultivation behaviour. Our study sheds some light on some of the events occurring in these strains following induction by lactose. The fact that few regulated genes have been affected by mutagenesis suggests that the induction mechanism is essentially intact compared to that for the wild-type isolate QM6a and might be engineered for further improvement of T. reesei. Genes from two specific clusters might be potential targets for such genetic engineering.
ISSN: 1754-6834

Droits : http://creativecommons.org/licenses/by/
hal-01112360
http://hal.upmc.fr/hal-01112360
http://hal.upmc.fr/hal-01112360/document
http://hal.upmc.fr/hal-01112360/file/Poggi-Parodi_2014_Kinetic.pdf
DOI : 10.1186/s13068-014-0173-z

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Garnet growth in high-pressure, mafic garnet granulites formed by dehydration melting of hornblende-gabbronorite protoliths in the Jijal complex (Kohistan palaeo-island arc complex, north Pakistan) was investigated through a microstructural EBSD-SEM and HRTEM study. Composite samples preserve a sharp transition in which the low-pressure precursor is replaced by garnet through a millimetre-sized reaction front. A magmatic foliation in the gabbronorite is defined by mafic-rich layering, with an associated magmatic lineation defined by the shape-preferred orientation (SPO) of mafic clusters composed of orthopyroxene (Opx), clinopyroxene (Cpx), amphibole (Amp) and oxides. The shape of the reaction front is convoluted and oblique to the magmatic layering. Opx, Amp and, to a lesser extent, Cpx show a strong lattice-preferred orientation (LPO) characterized by an alignment of [001] axes parallel to the magmatic lineation in the precursor hornblende-gabbronorite. Product garnet (Grt) also displays a strong LPO. Two of the four < 111 > axes are within the magmatic foliation plane and the density maximum is subparallel to the precursor magmatic lineation. The crystallographic relationship < 111 >(Grt)//[001](Opx,Cpx,Amp) deduced from the LPO was confirmed by TEM observations. The sharp and discontinuous modal and compositional variations observed at the reaction front attest to the kinetic inhibition of prograde solid-state reactions predicted by equilibrium-phase diagrams. The P-T field for the equilibration of Jijal garnet granulites shows that the reaction affinities are 5-10 kJ mol.(-1) for the Grt-in reaction and 0-5 kJ mol.(-1) for the Opx-out reaction. Petrographic and textural observations indicate that garnet first nucleated on amphibole at the rims of mafic clusters; this topotactic replacement resulted in a strong LPO of garnet. Once the amphibole was consumed in the reaction, the parallelism of [001] axes of the mafic-phase reactants favoured the growth of garnet crystals with similar orientations over a pyroxene substrate. These aggregates eventually sintered into single-crystal garnet. In the absence of deformation, the orientation of mafic precursor phases conditioned the nucleation site and the crystallographic orientation of garnet because of topotaxial transformation reactions and homoepitaxial growth of garnet during the formation of high-pressure, mafic garnet-granulite after low-pressure mafic protoliths.
ISSN: 0263-4929

hal-00411323
https://hal.archives-ouvertes.fr/hal-00411323
DOI : 10.1111/J.1525-1314.2008.00789.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The kinetics of hydrogenation of dry iron-bearing olivine single crystals was determined by performing hydration experiments under hydrothermal conditions at high pressure. The experiments were performed in a multi-anvil press at 3 GPa, for a temperature range between 900 and 1200 °C and for various durations. The oxygen fugacity was buffered along Ni-NiO joint. Polarized Fourier transform infrared spectroscopy and recent empirical calibration were used to quantify the hydroxyl distributions in the samples along crystallographic axes after the experiments. The chemical diffusion coefficients are similar (barely slower) than in olivine hydrated at lower pressure (0.2 and 0.3 GPa) for the same diffusion mechanism. Under the given experimental conditions, the anisotropy of diffusion is the same as for proton-vacancy mechanism, with diffusion along the [0 0 1] axis faster than along the [1 0 0]. However, the anisotropy at 3 GPa is weaker compared to measurements at lower pressures and the analysis of concentration profiles using 3D models shows that an isotropic solution could also be relevant. Fits of the diffusion data to an Arrhenius law yield activation energies for the slightly faster [0 0 1] axis of the crystallographic axes around 198 ± 5 kJ mol−1, a value only slightly lower than the results from previous experimental studies for natural iron-bearing olivine hydrogenated at lower confining pressure. At 3 GPa, hydrogenation can be well approximated by a single mechanism controlled by coupled diffusion of protons and octahedral vacancies (di- and tri-valent ions). The diffusion rates are fast enough to alter hydrogen concentration within olivine in xenoliths ascending from the mantle or experiencing hydrogen-rich metasomatism events, but too slow to permit complete homogenization of hydrogen in olivine-rich rocks at kilometer scale in less than one My.
ISSN: 0031-9201

hal-01412663
https://hal.archives-ouvertes.fr/hal-01412663
DOI : 10.1016/j.pepi.2016.08.005

Éditeur(s) : Elsevier Science Inc
Résumé : The sex-determining system of Crassostrea gigas is still poorly known, especially regarding the potential influence of temperature. In order to address this question, mRNA expressions of actors of the molecular cascade (Cg-DMI, Cg-SoxE, Cg-beta-catenin, Cg-Foxl2/Cg-FoxI2os) and of Oyvlg, a germ cell marker, were investigated by real-time PCR in spat grown at different temperatures (18, 22, 25 and 28 degrees C). In parallel, gonadic differentiation, gametogenesis and sex ratios were assessed by histology at each of these temperatures. Whatever the temperature, Cg-DMI, Cg-SoxE, Cg-beta-catenin and Oyvlg expressions peaked at the same developmental stage, always after Cg-Foxl2/Cg-Foxl2os (around 40-44 dpf for spat grown at 18 degrees C). Temperatures increased the kinetics of first gonadic differentiation and gametogenesis. At 25 degrees C a significant switch occurred in sex ratio towards males and in the balance of expression between male and female genes, in favor of males. A slight gametogenesis disturbance was also observed. These results strengthen the hypotheses about the sex-determining time window and molecular cascade governing the development of C gigas, with notably the involvement of Cg-Foxl2/Cg-Foxl2os in the very early steps. They also suggest an influence of temperature on the oyster's sex determination which, associated to genetic control, would induce a mixed sex determination system (GSD +TSD). (C) 2013 Elsevier Inc. All rights reserved.
Comparative Biochemistry And Physiology A-molecular & Integrative Physiology (1095-6433) (Elsevier Science Inc), 2013-05 , Vol. 165 , N. 1 , P. 61-69

Droits : 2013 Elsevier Inc. All rights reserved
http://archimer.ifremer.fr/doc/00136/24767/22874.pdf
DOI:10.1016/j.cbpa.2013.02.007
http://archimer.ifremer.fr/doc/00136/24767/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The discerning behavior of living systems relies on accurate interactions selected from the lot of molecular collisions occurring in the cell. To ensure the reliability of interactions, binding partners are classically envisioned as finely preadapted molecules, selected on the basis of their affinity in one-step associations. But the counterselection of inappropriate interactions can in fact be much more efficiently obtained through difficult multi-step adjustment, whose final high energy state is locked by a fluctuation ratchet. The progressive addition of molecular bonds during stereo-adjustment can be modeled as a predominantly backward random walk whose first arrival is frozen by a micro-irreversible transition. A new criterion of ligand specificity is presented, that is based on the ratio rejection/incorporation. In addition to its role in the selectivity of interactions, this generic recipe can underlie other important biological phenomena such as the regular synthesis at low level of supramolecular complexes, monostable kinetic bimodality, substrate concentration thresholds or the preparation of rapidly depolymerizable structures with stored energy, like microtubules
ISSN: 0079-6107

hal-01274234
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01274234
DOI : 10.1016/j.pbiomolbio.2016.02.001
PUBMED : 26867859

Éditeur(s) : Academic Press Inc Elsevier Science
Résumé : Several Vibrio species are known to be pathogenic to the Pacific oyster Crassostrea gigas. Survival varies according to pathogen exposure and high mortality events usually occur in summer during gametogenesis. In order to study the effects of gametogenetic status and ploidy (a factor known to affect reproduction allocation in oysters) on vibriosis survival, we conducted two successive experiments. Our results demonstrate that a common bath challenge with pathogenic Vibrio splendidus and Vibrio aestuarianus on a mixture of mature, spawning and non-mature oysters can lead to significant mortality. Previous bath challenges, which were done using only non-mature oysters, had not produced mortality. Immunohisto-chemical analyses showed the affinity of Vibrio for gonadic tissues, highlighting the importance of sexual maturity for vibriosis infection processes in oysters. Mortality rate results showed poor repeatability between tanks, however, in this bath challenge. We then tested a standardized and repeatable injection protocol using two different doses of the same combination of two Vibrio species on related diploid and triploid oysters at four different times over a year. Statistical analyses of mortality kinetics over a 6-day period after injection revealed that active gametogenesis periods correspond to higher susceptibility to vibriosis and that there is a significant interaction of this seasonal effect with ploidy. However, no significant advantage of triploidy was observed. Triploid oysters even showed lower survival than diploid counterparts in winter. Results are discussed in relation to differing energy allocation patterns between diploid and triploid Pacific oysters. (C) 2010 Elsevier Inc. All rights reserved.
Journal Of Invertebrate Pathology (0022-2011) (Academic Press Inc Elsevier Science), 2011-02 , Vol. 106 , N. 2 , P. 179-191

Droits : 2010 Elsevier Inc. All rights reserved.
http://archimer.ifremer.fr/doc/00030/14108/11368.pdf
DOI:10.1016/j.jip.2010.09.003
http://archimer.ifremer.fr/doc/00030/14108/

Éditeur(s) : HAL CCSD Trans Tech Publications Inc.
Résumé : Two, high purity, Al-0.1 and 0.3wt%Mn alloys have been cold deformed in plane strain compression to strains of order 1.8 and the kinetics of subsequent recovery by sub-grain coarsening during annealing at 150-300°C measured by high resolution FEG-SEM EBSD. Accurate sub-grain size and misorientation distributions and their evolution with time and temperature have been determined. The average growth rates are then used to estimate the sub-grain boundary mobilities. Growth is analyzed by two well-known growth laws for the average sub-grain size δ (t): i) the standard relation for grain growth: where the exponent n takes values of 2-8 and ii) the relation proposed by Nes for dislocation climb in sub-grain walls: It is shown that the latter relation gives a better fit with the data in terms of the time and temperature dependence of the sub-grain sizes. In particular the activation energies for the logarithmic law are much closer to the values expected for solute-controlled movement of sub-boundaries.
Materials Science Forum

hal-00795441
https://hal.archives-ouvertes.fr/hal-00795441
DOI : 10.4028/www.scientific.net/MSF.715-716.725

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
To test the impact of fluid flow on the reactivity of porous (ultra-)mafic rocks, reactive percolation experiments were realized during which CO2-enriched water was injected at two different injection rates (Q = 0.1 and 1 mL h−1) through sintered analogues of olivine-accumulation zones in basaltic flows at temperature and fluid composition conditions (T = 180 °C; NaHCO3 buffered solution) favorable for CO2-mineralization (carbonation).All experiments resulted in silicate dissolution, carbonate precipitation upstream and (proto-)serpentine formation downstream indicating a decrease in the fluid reactivity along flow paths. The measured bulk carbonation rates ranged from 4 to 7 × 10−8 s−1; these values were significantly lower than previously published values of olivine carbonation rate obtained on powders in closed batch and flow-through reactors. Our study show complex couplings, at pore scale, between fluid flow, localization of reaction zones, and chemical reaction kinetics which in turn control hydrodynamic properties, carbonation rate and efficiency and fluid reactivity. This results in carbonation rates being higher when injection rates are high and permeability ultimately controlling carbonation reactions by limiting fluid input. During experiments, notable changes in permeability occurred for only minor changes in porosity indicating a control by the geometry of the porous network: heterogeneities in the distribution of flow paths favored the localization of precipitated minerals which in turn resulted in the closure of flow paths. This mechanism was particularly efficient at low injection rates. These results imply that controlling the injection rate could allow enhancing/limiting the efficiency of in situ carbonation.
ISSN: 0883-2927

hal-01115284
https://hal.archives-ouvertes.fr/hal-01115284
DOI : 10.1016/j.apgeochem.2014.11.024

Éditeur(s) : HAL CCSD
Résumé : International audience
A long standing debate in biochemistry is to determine whether the conformational changes observed during biomolecular interactions proceed through conformational selection (of preexisting isoforms) or induced fit (ligand-induced 3D reshaping). The latter mechanism had been invoked in certain circumstances, for example to explain the non-Michaelian activity of monomeric enzymes like glucokinase. But the relative importance of induced fit has been recently depreciated in favor of conformational selection, assumed to be always sufficient, predominant in general and in particular for glucokinase. The relative contributions of conformational selection and induced fit are reconsidered here in and out of equilibrium, in the light of earlier concepts such as the cyclic equilibrium rule and the turning wheel of Wyman, using single molecule state probability, one-way fluxes and net fluxes. The conditions for a switch from conformational selection to induced fit at a given ligand concentration are explicitly determined. Out of equilibrium, the inspection of the enzyme states circuit shows that conformational selection alone would give a Michaelian reaction rate but not the established nonlinear behaviour of glucokinase. Moreover, when induced fit and conformational selection coexist and allow kinetic cooperativity, the net flux emerging in the linkage cycle necessarily corresponds to the induced fit path. © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Molé
Biochimie

hal-01367150
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01367150
DOI : 10.1016/j.biochi.2016.06.012

Éditeur(s) : HAL CCSD Royal Society of Chemistry
Résumé : International audience
A full equilibrium treatment of molecular aggregation is presented for prototypes of 1D and 3D aggregates, with and without nucleation. By skipping complex kinetic parameters like aggregate size-dependent diffusion, the equilibrium treatment allows to predict directly time-independent quantities such as critical concentrations. The relationships between the macroscopic equilibrium constants for the different paths are first established by statistical corrections and so as to comply with the detailed balance constraints imposed by nucleation, and the composition of the mixture resulting from homogeneous aggregation is then analyzed using the polylogarithm function. Several critical concentrations are distinguished: the residual monomer concentation in equilibrium (RMC) and the critical nucleation concentration (CNC), that is the threshold concentration of total subunits necessary for initiating aggregation. When increasing the concentration of total subunits, the RMC converges more strongly to its asymptotic value, the equilibrium constant of depolymerization, for 3D aggregates and in case of nucleation. The CNC moderately depends on the number of subunits in the nucleus, but sharply increases with the difference between the equilibrium constants of polymerization and nucleation. As the RMC and CNC can be numerically but not analytically determined, ansatz equations connecting them to thermodynamic parameters are proposed
PCCP : Physical chemistry chemical physics

Droits : info:eu-repo/semantics/OpenAccess
hal-01565995
https://hal.archives-ouvertes.fr/hal-01565995
https://hal.archives-ouvertes.fr/hal-01565995/document
https://hal.archives-ouvertes.fr/hal-01565995/file/Aggregates_in_equilibrium.pdf
DOI : 10.1039/c6cp08369b

Éditeur(s) : Gauthier-Villars
Résumé : Moored current measurements carried out from 31 March 1990 to 15 September 1991 in two stages at a point (near 6 degrees N) located over the mid-continental slope off French Guiana are presented. Six current meters were positioned between 200 and 2700 m depth. Upper level mean current data showed a northwestward flowing North Brazil Current (NBC) with mean velocity values decreasing from 10 cm/s in the range 200-250 m to almost zero at 800 m depth, the level of the Antarctic Intermediate Waters. In the range 500-800 m, the current reversed in spring in the presence of the southeastward Western Boundary Under Current (WBUC); the mean velocity from February to June 1991 is around 2 cm/s. Deep currents over the continental rise show a strong southeastward Deep Western Boundary Current extending from around 1000 m depth to the bottom (3000 m depth in this case) with mean core speeds of 20 cm/s at 2000-2070 m depth. Transport estimates based on these data and a few Pegasus sections for the mean vertical and lateral extensions of the DWBC yield a value of 21 x 10(6) m(3)/s at that location. Low-frequency current fluctuations were dominated by a well-defined 50- to 70-day period oscillation with peak-to-peak northwestward velocity amplitude of around 90 cm/s at the upper level. The mean vertical eddy kinetic energy distribution showed an abrupt decrease of the energy down to 800 m depth and a slight decrease below and down to the bottom.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1994 , Vol. 17 , N. 4 , P. 345-354

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00098/20897/18510.pdf
http://archimer.ifremer.fr/doc/00098/20897/