Decrypting magnetic fabrics (AMS, AARM, AIRM) through the analysis of mineral shape fabrics and distribution anisotropy

The fieldwork was supported by the DIPS project (grant no. 240467) and the MIMES project (grant no. 244155) funded by the Norwegian Research Council awarded to O.G. O.P.'s position was funded from Y-TEC.Anisotropy of magnetic susceptibility (AMS) and anisotropy of magnetic remanence (AARM and AIRM) are efficient and versatile techniques to indirectly determine rock fabrics. Yet, deciphering the source of a magnetic fabric remains a crucial and challenging step, notably in the presence of ferrimagnetic phases. Here we use X-ray micro-computed tomography to directly compare mineral shape-preferred orientation and spatial distribution fabrics to AMS, AARM and AIRM fabrics from five hypabyssal trachyandesite samples. Magnetite grains in the trachyandesite are euhedral with a mean aspect ratio of 1.44 (0.24 s.d., long/short axis), and > 50% of the magnetite grains occur in clusters, and they are therefore prone to interact magnetically. Amphibole grains are prolate with magnetite in breakdown rims. We identified three components of the petrofabric that influence the AMS of the analyzed samples: the magnetite and the amphibole shape fabrics and the magnetite spatial distribution. Depending on their relative strength, orientation and shape, these three components interfere either constructively or destructively to produce the AMS fabric. If the three components are coaxial, the result is a relatively strongly anisotropic AMS fabric (P’ = 1.079). If shape fabrics and/or magnetite distribution are non-coaxial, the resulting AMS is weakly anisotropic (P’ = 1.012). This study thus reports quantitative petrofabric data that show the effect of magnetite distribution anisotropy on magnetic fabrics in igneous rocks, which has so far only been predicted by experimental and theoretical models. Our results have first-order implications for the interpretation of petrofabrics using magnetic methods.Publisher PDFPeer reviewe

The alpine societies facing the death during the Late Antiquity in the mountain: in the heart of the civitas of Eturamina, the site of Saint-Pierre 2 at Thorame-Basse (Alpes-de-Haute-Provence, 04)

International audienceIn the heart of the upper Verdon valley (Alpes-de-Haute-Provence, 04), the civitas of Eturamina extended between the communes of Thorame-Haute and Thorame-Basse, in the Issole Valley. Mentioned as the diocese's chief town in the year 442, the name of this locality nevertheless disappears from the texts although we know of the existence of an ephemeral bishopric that existed for a short time during the 5th century. No remains relating to this ancient city have been identified in the valley. Indeed, the settlement dynamics over time in this vast sector was poorly understood until 2018. Since then, an interdisciplinary and diachronic research program has led to the discovery of an unpublished site located on the Plateau de Saint-Pierre, at an altitude of more than 1300 m. Since 2019, archaeological operations have revealed protohistoric and ancient built structures and have led to the discovery of a funerary space from the High Empire and a second one dating from late Antiquity. This project aims to maximise our understanding of the site through interdisciplinary research: paleoenvironmental approaches (anthracology, pedo-anthracology, geomorphology, geoarchaeology), as well as geophysical survey. This approach will elucidate our understanding of the forms and evolution of human settlement and the natural environment's management. The diachronic occupation suggests that this vast plateau may have been an essential settlement point for the valley due to its topographical configuration and dominant position during Antiquity. The final phase of the site, also the best documented period, corresponds to the late antique funerary zone, represented by about twenty burials dated between the end of the 4th century and the beginning of the 6th century (dated by 14C). The tombs are located in the partially dismantled ruins of an High Empire settlement. However, it remains difficult to understand the parameters implying a possible collective memory place for the funerary space of the Late Antiquity. Practices differ from those of the High Empire, which are represented, for the moment, only by cremations. The deceased (adults and perinatals) are buried in tegulae coffins or, sometimes, in flexible envelopes (shrouds). The elements discovered suggest clothed burials, with ornamental items (bracelet, earrings and glass beads), in particular a medallion with Sabazios, interpreted as a souvenir of an oriental pilgrimage. Beyond these strictly funerary considerations, this site's major contribution lies in the acquisition, for the first time, of data concerning the late Antiquity populations of a mountainous area. This may represent one of the first Christian communities' funerary spaces in the Alps, which underwent Christianization relatively late, i.e. during the 5th century

Identification of the functional states of human vitamin K epoxide reductase from molecular dynamics simulations

In mammalians, the enzymatic activity of vitamin K epoxide reductase (VKORC1) requires a protein conformational reorganisation that includes several transient enzymatic states involving a dynamic electron transfer. Regarding the structurally non-characterised human enzyme (hVKORC1), this process remains poorly explained and the different redox states of the enzyme generated by its biochemical transformation are unknown. Here, we report a 3D model of the fully reduced hVKORC1 at the atomistic level. By exploring this model through molecular dynamics (MD) simulations, we established the most probable intermediate states of the enzyme which were used for generation of the putative functionally related enzymatic states. Enzymatic functionality of each state was assigned by probing their recognition properties with respect to vitamin K in its quinone and hydroxyquinone forms. Two states were identified as contributing to the two-step vitamin K transformation. The state highly selective for native vitamin K was further validated through analyses of its free energy of binding with vitamin K agonists (VKAs) that showed a high correlation with the experimental inhibiting constants

Mourir au cœur de la civitas d’Eturamina : le site de Saint-Pierre 2 à Thorame-Basse (Alpes-de-Haute-Provence, France)

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Novel fine-grain back-bias assist techniques for 3D-monolithic 14 nm FDSOI top-tier SRAMs

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Back-bias impact on variability and BTI for 3D-monolithic 14nm FDSOI SRAMs applications

International audienceWe fabricated and characterized 14nm planar Fully-Depleted-Silicon-On-Insulator (FDSOI) 0.078µm² Static Random Access Memory (SRAM) cells. Temporal and spatial variability as well as sensibility to temperature, supply voltage (VDD) and back bias (Vwell) are extracted. These data evidence that the 14nm SRAM is read-limited, which could be improved by a smart back-bias management [1]. In this work we demonstrate a 50mV Static Noise Margin (SNM) variability improvement (at VDD=0.8V) by back-biasing, without additional Bias Temperature Instability (BTI) stress. Such an assist technique can be eventually leveraged at fine-grain by 3D monolithic integration, owing to local back-planes