Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The complex electrical impedance of a garnet-biotite-sillimanite residual enclave in the Neogene dacite of El Hoyazo (SE Spain) has been determined up to 978 °C at 200-300 MPa. This well studied material represents a direct sampling of the Alborán Domain thinned lower crust undergoing partial melting. The paragenesis is garnet + biotite + sillimanite + plagioclase + graphite ± cordierite coexisting with widespread (~ 10 wt.%) rhyolitic melt occurring as inclusions and interstitial glass and developed during regional anatexis at 850 ± 50 °C and 500-700 MPa. The samples were used in cyclic measurements consisting in heating-cooling ramps at progressively higher maximum temperature to observe the effect of reactions on conductivity. In the first cycle up to 850 °C at 2-3 kbar, re-melting of the interstitial glass is achieved with no additional reactions and logarithmic conductivity (S/m) is up to − 1.5. At T > 950 °C new melt with orthopyroxene + ilmenite is produced from biotite partial breakdown and the logarithmic conductivity (S/m) is up to − 0.7. Application of mixing models as Hashin-Shtrikman bounds or Archie's Law, shows that once interconnected, melt controls the electrical conductivity of the enclave. The electrical conductivity of the rock can be simulated with the electrical conductivity data obtained on the starting Matrix glass of the enclave and with the new melt. Our experimental results obtained on a graphitic metasedimentary material evidence show that graphite does not contribute to the conductivity enhancement and that the electrical anomaly observed below the Betics can be explained as effect of partial melting of a residual crust. Comparison with previous works on mafic granulites shows that similar conductivity values can be achieved both by melting of a residual felsic crust or by melting of mafic materials and suggests that pelitic rocks can be more common at deep levels than expected.
ISSN: 0040-1951

hal-00823063
https://hal.archives-ouvertes.fr/hal-00823063
DOI : 10.1016/j.tecto.2012.11.003

Éditeur(s) : HAL CCSD Springer Verlag (Germany) Springer Verlag
Résumé : International audience
We have investigated the partitioning of Fe3+ between orthopyroxene (Opx) and garnet (Grt) in well-equilibrated mantle xenoliths using Mössbauer spectroscopy. The samples cover a wide range of P–T conditions (2.1–6.6 GPa, 690–1,412 °C) and geothermal gradients, and are thus representative for Earth’s upper mantle in both on-craton and off-craton continental settings. Garnet has Fe3+/Fetot ratios of 0.03–0.13 and Fe2O3 contents of 0.24–1.00 wt%. Orthopyroxene has, on average, lower Fe3+/Fetot ratios (0.01–0.09) and Fe2O3 contents (0.05–0.63 wt%). In low-pressure, high-temperature samples, however, Opx is systematically richer in Fe2O3 than the coexisting Grt. The Fe3+ Opx/Grt partition coefficient (DOpx/GrtFe3+) shows no obvious relationship with temperature, but increases with decreasing pressure and with increasing NaOpx. The observed Opx/Grt Fe3+ systematics imply that the Opx–Grt Fe–Mg exchange thermometer is not robust against redox changes if total Fe is treated as Fe2+. An approximate evaluation of errors on T estimates due to redox effects predicts negligible deviations for strongly reduced conditions (<65 °C), but potentially large deviations (> to ≫100 °C) for strongly oxidized conditions, especially at very high pressure and when both P and T are calculated by iteration.
ISSN: 0010-7999

hal-01121606
https://hal.archives-ouvertes.fr/hal-01121606
DOI : 10.1007/s00410-014-1101-8

Éditeur(s) : HAL CCSD Landes Bioscience
Résumé : International audience
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
Autophagy

hal-00735751
https://hal.archives-ouvertes.fr/hal-00735751
PUBMED : 22966490

Éditeur(s) : HAL CCSD Wiley-Blackwell
Résumé : International audience
Understanding the distribution of genetic diversity in the light of past demographic events linked with climatic shifts will help to forecast evolutionary trajectories of ecosystems within the current context of climate change. In this study, mitochondrial sequences and microsatellite loci were analysed using traditional population genetic approaches together with Bayesian dating and the more recent approximate Bayesian computation scenario testing. The genetic structure and demographic history of a commercial fish, the black scorpionfish, Scorpaena porcus, was investigated throughout the Mediterranean and Black Seas. The results suggest that the species recently underwent population expansions, in both seas, likely concomitant with the warming period following the Last Glacial Maximum, 20 000 years ago. A weak contemporaneous genetic differentiation was identified between the Black Sea and the Mediterranean Sea. However, the genetic diversity was similar for populations of the two seas, suggesting a high number of colonizers entered the Black Sea during the interglacial period and/or the presence of a refugial population in the Black Sea during the glacial period. Finally, within seas, an east/west genetic differentiation in the Adriatic seems to prevail, whereas the Black Sea does not show any structured spatial genetic pattern of its population. Overall, these results suggest that the Black Sea is not that isolated from the Mediterranean, and both seas revealed similar evolutionary patterns related to climate change and changes in sea level.
ISSN: 1471-8278

hal-01330323
https://hal-univ-perp.archives-ouvertes.fr/hal-01330323
DOI : 10.1111/mec.13616