Impact of gneissic layering and localized incipient melting upon melt flow during experimental deformation of migmatites

International audienceIn this study, we test experimentally the role of compositional layering as a key parameter for controlling melt flow in a natural migmatite during coaxial deformation. We performed in – situ pure-shear experiments on two natural gneisses. The first gneiss is weakly foliated with minerals homogenously distributed. The second gneiss shows a pronounced compositional layering of alternating quartz – feldspar – rich and biotite – muscovite – rich layers. Experimental conditions were selected to obtain homogeneous melt distribution in the homogeneous gneiss and heterogeneous melt distribution in the layered gneiss. Initial melt distribution is not modified by deformation in experiments on the homogeneous gneiss, implying that melting products did not migrate from their initiation sites. In contrast, melt flowed in shear zones or in inter-boudin positions during experimental deformation of the heterogeneous gneiss. These experiments attest to the strong influence of initial gneissic layering on melting pattern, melt segregation and flow during deformation of partially molten rocks

Absence of triadin, a protein of the calcium release complex, is responsible for cardiac arrhythmia with sudden death in human

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmogenic disease so far related to mutations in the cardiac ryanodine receptor (RYR2) or the cardiac calsequestrin (CASQ2) genes. Because mutations in RYR2 or in CASQ2 are not retrieved in all CPVT cases, we searched for mutations in the physiological protein partners of RyR2 and CSQ2 in a large cohort of CPVT patients with no detected mutation in these two genes. Based on a candidate gene approach, we focused our investigations on triadin and junctin, two proteins that link RyR2 and CSQ2. Mutations in the triadin (TRDN) and in the junctin (ASPH) genes were searched in a cohort of 97 CPVT patients. We identified three mutations in triadin which cosegregated with the disease on a recessive mode of transmission in two families, but no mutation was found in junctin. Two TRDN mutations, a 4 bp deletion and a nonsense mutation, resulted in premature stop codons; the third mutation, a p.T59R missense mutation, was further studied. Expression of the p.T59R mutant in COS-7 cells resulted in intracellular retention and degradation of the mutant protein. This was confirmed after in vivo expression of the mutant triadin in triadin knock-out mice by viral transduction. In this work, we identified TRDN as a new gene responsible for an autosomal recessive form of CPVT. The mutations identified in the two families lead to the absence of the protein, thereby demonstrating the importance of triadin for the normal function of the cardiac calcium release complex in humans

Anisotropie, fusion partielle et déformation de la croûte continentale : étude expérimentale et observations de terrain

Strain localization is a necessary feature of tectonic. To be able to localize deformation, rocks must undergo weakening. The main weakening process is weak phase interconnection. For continental crust, weak phases that are the most often responsible of strain localization are micas and melt. Although previous experimental studies exist about rheological properties of micas, none are about the effect of micas on the strain localization in the lower continental crust conditions. Previous experimental studies about the effect of partial melting were always done with isotropic starting material. But continental crust which undergo partial melting is very likely to be deformed before melting and therefore to be highly anisotropic. In the aim to bring new data about mechanical behavior and microstructures of anisotropic continental crust, as well as the effect of micas on strain localization, this thesis propose to conduct a series of experiments in a Griggs apparatus. This experimental approach is also coupled with field work on the Møre og Trøndelag Fault Zone (Norway). This crustal scale shear zone was partially synchronous with partial melting and therefore is well suited for studying relation ship between deformation and partial meltingLa localisation de la déformation est une caractéristique nécessaire de la tectonique. Pour localiser la déformation, une roche doit subir un affaiblissement. Le processus affaiblissant principal des roches est l'interconnexion de phases faibles. Dans le cas de la croûte continentale, les phases faibles étant le plus souvent responsables de la localisation sont les micas et les liquides silicatés résultant de la fusion partielle. Bien qu'il existe des études expérimentales sur la rhéologie des micas, il y a très peu d'études sur l'impact des micas sur la localisation dans les conditions de la croûte continentale inférieure. De même, les précédentes études expérimentales montrent l'effet de la fusion partielle sur la résistance des roches mais elles utilisent toutes un matériel de départ isotrope. Or la croûte subissant la fusion partielle dans les orogènes est susceptible d'être préalablement déformée et donc anisotrope. Dans le but d'apporter de nouvelles données sur le comportement mécanique et les microstructures de la croûte continentale anisotrope, ainsi que sur l'effet des micas sur la localisation de la déformation, cette thèse propose de réaliser une série d’expériences en presse de Griggs. Cette approche expérimentale est aussi couplée à un travail de terrain sur la zone de faille de Møre og Trøndelag (Norvège). Cette structure étant un zone de cisaillement d'échelle crustale dont la cinématique est partiellement synchrone de la fusion partielle, elle est adaptée à l'étude naturelle des relations entre fusion partielle et déformation

Anisotropy, partial melting and deformation of the continental crust : experimental study and field observations

La localisation de la déformation est une caractéristique nécessaire de la tectonique. Pour localiser la déformation, une roche doit subir un affaiblissement. Le processus affaiblissant principal des roches est l'interconnexion de phases faibles. Dans le cas de la croûte continentale, les phases faibles étant le plus souvent responsables de la localisation sont les micas et les liquides silicatés résultant de la fusion partielle. Bien qu'il existe des études expérimentales sur la rhéologie des micas, il y a très peu d'études sur l'impact des micas sur la localisation dans les conditions de la croûte continentale inférieure. De même, les précédentes études expérimentales montrent l'effet de la fusion partielle sur la résistance des roches mais elles utilisent toutes un matériel de départ isotrope. Or la croûte subissant la fusion partielle dans les orogènes est susceptible d'être préalablement déformée et donc anisotrope. Dans le but d'apporter de nouvelles données sur le comportement mécanique et les microstructures de la croûte continentale anisotrope, ainsi que sur l'effet des micas sur la localisation de la déformation, cette thèse propose de réaliser une série d’expériences en presse de Griggs. Cette approche expérimentale est aussi couplée à un travail de terrain sur la zone de faille de Møre og Trøndelag (Norvège). Cette structure étant un zone de cisaillement d'échelle crustale dont la cinématique est partiellement synchrone de la fusion partielle, elle est adaptée à l'étude naturelle des relations entre fusion partielle et déformation.Strain localization is a necessary feature of tectonic. To be able to localize deformation, rocks must undergo weakening. The main weakening process is weak phase interconnection. For continental crust, weak phases that are the most often responsible of strain localization are micas and melt. Although previous experimental studies exist about rheological properties of micas, none are about the effect of micas on the strain localization in the lower continental crust conditions. Previous experimental studies about the effect of partial melting were always done with isotropic starting material. But continental crust which undergo partial melting is very likely to be deformed before melting and therefore to be highly anisotropic. In the aim to bring new data about mechanical behavior and microstructures of anisotropic continental crust, as well as the effect of micas on strain localization, this thesis propose to conduct a series of experiments in a Griggs apparatus. This experimental approach is also coupled with field work on the Møre og Trøndelag Fault Zone (Norway). This crustal scale shear zone was partially synchronous with partial melting and therefore is well suited for studying relation ship between deformation and partial meltin

Contribution to the study of alliinase, the active principle of garlic

Alliinase is a crucial enzyme in the Allium genus. The conversion of its substrates, cysteine sulfoxides, into volatile thiosulfinates is an important mechanism in the defence of the plant. It also provides the typical pungent flavour of garlic. As a matter of fact, the thiosulfinates decompose in a range of organosulfur compounds (OSC) known for their biological activities (antioxidant, anticancer, anti-diabetes properties, etc.). The environment of the decomposition of the thiosulfinates determines the type and amount of products released. A deeper knowledge of the conditions that form each OSC could help us in the preparation of garlic-based nutraceutics in the perspective of healthier food consumption. This study aims to improve the extraction and purification the enzyme alliinase in order to perform the reaction between the enzyme and its substrates and assess the potentialities of garlic preparations. Three methods have been applied to evaluate the efficiency of the extractions and purifications of the enzyme. A first idea of the purity of the enzyme is given by an electrophoresis separation of each sample on a polyacrylamide gel (SDS-PAGE). The protein content is then measured by UV-vis spectrometry with Lowry-Folin reagent for the coloration and BSA as an external standard. Finally, the specific activity is assessed by an indirect measure of the pyruvate (released as a co-product): the addition of NADH and lactate dehydrogenase turns the pyruvate in lactate, and the disappearance of NADH is measured by UV-vis spectrometry at 340 nm. The extraction of the enzyme from garlic was performed either by PEG 8000 precipitation or by ammonium sulphate precipitation. Two purifications were tested: affinity chromatography (on ConA) and size-exclusion chromatography. The combination of the ammonium sulphate process with the ConA chromatography provided the purest enzyme, with the best activity but a lower yield than the size-exclusion process. Finally the stability of the enzyme has been assessed at 4, -20 and -80 °C, showing that the enzyme could be kept at -80 °C for over 4 months without deterioration, while activity loss was observed at higher temperature

A new generation Griggs apparatus with active acoustic monitoring

International audienceHigh pressure and temperature experiments are necessary to understand geological processes at deep earth conditions. Here, we present a new generation Griggs-type apparatus, designed to perform deformation experiments at P-T conditions of the lower crust and upper mantle, i.e. up to 5 GPa and 1000 • C. We first detail the experimental design, setup and procedure, as well as the calibration protocol of the apparatus. The main innovation of this new setup is the development of an active acoustic monitoring pulse-transmission technique, which enables us to monitor the evolution of P-wave elastic velocities, at 5 MHz, contemporaneously with deformation. This may provide information on the evolution of the microstructure, in particular when mineralogical (metamorphic) reactions are taking place. For instance, P-wave velocity variations across the α → β quartz transition are recorded for the first time within a Griggs apparatus, at 0.5 and 0.8 GPa. This new setup opens up important perspectives for the study of the complex couplings that may take place between mineral reactions and deformation under in lithospheric stress and temperature conditions

Mechanical and microstructural effect of partial melting of continental crust

International audienceWe present a set of experiments done in order to investigate the effect of melt on the strength and the microstructures of crustal rocks. Experiments were conducted in a Griggs-type apparatus with a mixture of 90 vol. % quartz and 10 vol. % biotite at 1 GPa confining pressure and a temperature between 700 and 900 °C. In some experiments, 5 vol. % or 10 vol. % of haplogranitic glass (HPG) powder was added to generate melt in the sample. Above the glass temperature transition (GTT), which occurs at 780 °C, HPG viscosity is 4 orders of magnitude lower than that of quartz and thus the sample strength and microstructures should be similar to those of partially molten sample. We performed a comparative study, in which samples were deformed without melt and without HPG, with HPG, but below the GTT, with HPG above the GTT, and finally with melt generated from biotite breakdown reactions. Samples with HPG above GTT and melt from biotite breakdown have the same microstructures and strength. Our data show that melt has two major consequences on the deformation of quartz-biotite aggregates : (1) while deformation is localized through a network of shear bands in experiments without melt and quartz is deformed by dislocation creep, there is no localization of the deformation with HPG or melt and the sample deformed by melt enhanced grain boundary sliding (2) melt reduces the strength of the sample but this weakening is lower than previously suggested if the long term resistance of the samples ( γ > 2.5 ) instead of peak resistance is taken into account

Mechanical and microstructural effect of partial melting of continental crust

International audienceWe present a set of experiments done in order to investigate the effect of melt on the strength and the microstructures of crustal rocks. Experiments were conducted in a Griggs-type apparatus with a mixture of 90 vol. % quartz and 10 vol. % biotite at 1 GPa confining pressure and a temperature between 700 and 900 °C. In some experiments, 5 vol. % or 10 vol. % of haplogranitic glass (HPG) powder was added to generate melt in the sample. Above the glass temperature transition (GTT), which occurs at 780 °C, HPG viscosity is 4 orders of magnitude lower than that of quartz and thus the sample strength and microstructures should be similar to those of partially molten sample. We performed a comparative study, in which samples were deformed without melt and without HPG, with HPG, but below the GTT, with HPG above the GTT, and finally with melt generated from biotite breakdown reactions. Samples with HPG above GTT and melt from biotite breakdown have the same microstructures and strength. Our data show that melt has two major consequences on the deformation of quartz-biotite aggregates : (1) while deformation is localized through a network of shear bands in experiments without melt and quartz is deformed by dislocation creep, there is no localization of the deformation with HPG or melt and the sample deformed by melt enhanced grain boundary sliding (2) melt reduces the strength of the sample but this weakening is lower than previously suggested if the long term resistance of the samples ( γ > 2.5 ) instead of peak resistance is taken into account

Infertility management according to the Endometriosis Fertility Index in patients operated for endometriosis: What is the optimal time frame?

International audienceIntroduction The Endometriosis Fertility Index (EFI) is a validated score for predicting the postoperative spontaneous pregnancy rate in patients undergoing endometriosis surgery. However, the practical use of the EFI to advise patients about postoperative fertility management is unclear. Materials and methods All patients participating in the ENDOQUAL study–a prospective observational bi-center cohort study conducted between 01/2012 and 06/2018–who underwent surgery for infertility were asked to complete a questionnaire collecting time and mode of conception. Statistical analysis was performed with the Fine and Gray model of competing risks and analysis of fertility according to the EFI. Results Of the 234 patients analyzed, 104 (44.4%) conceived postoperatively including 58 (55.8%) spontaneous pregnancies. An EFI of 0–4 for spontaneous pregnancies was associated with a lower cumulative pregnancy incidence compared to an EFI of 5–10 (52 versus 34 pregnancies respectively, Subdistribution Hazard Ratio (SHR) = 0.47; 95% CI [0.2; 1.1]; p = 0.08). An EFI of 0–4 was associated with a higher cumulative pregnancy rate for pregnancies obtained by artificial reproduction technology (ART), compared to an EFI of 5–10 (12 versus 6 pregnancies respectively, SHR = 1.9; CI95% [0.96; 3.8]; p = 0.06). Fecundability decreased from 12 months for EFI 0–4 and from 24 months for EFI 5–10. Conclusion Our analysis suggests that patients with an unfavorable EFI (4) have more ART pregnancies than patients with a favorable EFI (5) and should be referred for ART shortly after surgery. Patients with a favorable EFI may attempt spontaneous pregnancy for 24 months before referral. Copyright

Deep Focus Earthquakes: From High Temperature Experiments to Cold Slabs

International audienceDeep Focus Earthquakes (DFEs) present an interesting scientific challenge in that they occur at depths where brittle failure should be impossible. The fact that their occurrence is confined to locations where subducting lithospheric slabs are crossing through the transition zone suggests that the olivine phase transformations may be involved in the production of these earthquakes. Experimental studies have shown that olivine can persist metastably in subducting slabs and that the olivine phase transformations can lead to faulting at high pressures. However, it has been argued that large DFEs are too large to be contained within a metastable olivine wedge (MOW) preserved in the interior of subducting slabs. Here, we demonstrate using experiments on olivine-analog materials that transformational faulting can continue to propagate via shear-enhanced melting into the stable high-pressure phase. We also show that transformational faulting is controlled by the ratio between strain rate and the kinetics of the olivineringwoodite transformation and extrapolate this relationship to the natural conditions of DFEs. Counterintuitively, these results imply that cold and fast-subducting slabs produce transformational faulting at higher temperatures, which results in more numerous DFEs