Une technique du vertige ?

À partir de la problématique des techniques du corps, nous proposons d’appréhender la via ferrata, pratique sportive ludique et aérienne, comme une technique du vertige. L’analyse du corps sportif comme moyen d’action permet d’étudier puis de relativiser l’importance de la technicité ascensionniste dans l’activité. Ayant mis en évidence que c’est dans le jeu vertigineux que se définit l’usage du corps ferratiste, nous pouvons essayer d’y voir un principe structurant.A technique of vertigo ? The uses of the body in a climbing technique : the via ferrataFrom the stand-point of the body techniques (Mauss’ « techniques du corps ») this paper presents via ferrata rock-climbing as a vertigo technique. The analysis of the body engaged in sports as a means of action enables to study  and to put into perspective the importance of technicality in the climbing process. Having shown that it is in this breathtaking game that is defined the use of the climber’s body, it is possible to identify in it a structuring principle.¿ Una técnica del vértigo ? Los usos del cuerpo en una práctica de escalada, la vía ferrata.A partir de la problemática de las técnicas del cuerpo, proponemos aprehender la via ferrata, práctica deportiva lúdica y aérea, en tanto que técnica del vértigo. El análisis del cuerpo que practica deporte como medio de acción permite estudiar, y más adelante relativizar, la importancia que posee la técnica de escalada en el conjunto de la actividad. Habiendo puesto en evidencia que el uso del cuerpo ferratista se define en el juego vertiginoso, podemos intentar detectar aquí un principio estructurante

Trace element composition of igneous and hydrothermal magnetite from porphyry deposits : relationship to deposit subtypes and magmatic affinity

Trace element compositions of igneous and hydrothermal magnetite from nineteen well-studied porphyry Cu ± Au ± Mo, Mo, and W-Mo deposits, combined with partial least squares-discriminant analysis (PLS-DA), were used to investigate the factors controlling magnetite chemistry during igneous and hydrothermal processes, as divided by magmatic affinity and porphyry deposit subtypes. Igneous magnetite can be discriminated by relatively high P, Ti, V, Mn, Zr, Nb, Hf, and Ta contents but low Mg, Si, Co, Ni, Ge, Sb, W, and Pb contents, in contrast to hydrothermal magnetite. Compositional differences between igneous and hydrothermal magnetite are mainly controlled by the temperature, oxygen fugacity, co-crystallized sulfides, and element solubility/mobility that significantly affect the partition coefficients between magnetite and melt/fluids. Binary diagrams based on Ti, V, and Cr contents are not enough to discriminate igneous and hydrothermal magnetite in porphyry deposits. Relatively high Si and Al contents discriminate porphyry W-Mo hydrothermal magnetite, probably reflecting the control by high Si, highly differentiated, granitic intrusions for this deposit type. Relatively high Mg, Mn, Zr, Nb, Sn, and Hf, but low Ti and V contents, discriminate porphyry Au-Cu hydrothermal magnetite, most likely resulting from a combination of mafic to intermediate intrusion composition, high chlorine in fluids, relatively high oxygen fugacity, and low temperature conditions. Igneous or hydrothermal magnetite from Cu-Mo, Cu-Au, and Cu-Mo-Au deposits cannot be discriminated from each other probably due to similar intermediate to felsic intrusion composition, melt/fluid composition, and conditions such as temperature and oxygen fugacity for the formation of these deposits. The magmatic affinity of porphyritic intrusions exerts some control on the chemical composition of igneous and hydrothermal magnetite in porphyry system. Igneous and hydrothermal magnetite related to alkaline magma is relatively rich in Mg, Mn, Co, Mo, Sn, and high field strength elements (HFSE), perhaps due to high concentrations of chlorine and fluorine in magma and exsolved fluids, whereas those related to calc-alkaline magma are relatively rich in Ca but depleted in HFSE, consistent with the high Ca but low HFSE magma composition. Igneous and hydrothermal magnetite related to high-K calc-alkaline magma is relatively rich in Al, Ti, Sc, and Ta, due to a higher temperature of formation or enrichment of these elements in melt/fluids. PLS-DA on hydrothermal magnetite compositions from worldwide porphyry Cu, iron oxide-copper-gold (IOCG), Kiruna-type iron oxide-apatite (IOA), and skarn deposits identify important discriminant elements for these deposit types. Magnetite from porphyry Cu deposits is characterized by relatively high Ti, V, Zn, and Al contents, whereas that from IOCG deposits can be discriminated from other types of magnetite by its relatively high V, Ni, Ti, and Al contents. IOA magnetite is discriminated by higher V, Ti, and Mg but lower Al contents, whereas skarn magnetite can be separated from magnetite from other deposit types by higher Mn, Mg, Ca, and Zn contents. Decreased Ti and V contents in hydrothermal magnetite from porphyry Cu and IOA, to IOCG, and to skarn deposits may be related to decreasing temperature and increasing oxygen fugacity. The relative depletion of Al in IOA magnetite is due to its low magnetite-silicate melt partition coefficient, immobility of Al in fluids, and earlier, higher-temperature magmatic or magmatic-hydrothermal formation of IOA deposits. The relative enrichment of Ni in IOCG magnetite reflects more mafic magmatic composition and less competition with sulfide, whereas elevated Mn, Mg, Ca, and Zn in skarn magnetite results from enrichment of these elements in fluids via more intensive fluid-carbonate rock interaction

Conserver mieux pour consommer loin

Image d’ouverture Vivre isolé dans un milieu sauvage : un camp de base d’expédition himalayenne. À 4 500 mètres dans le massif des Annapurnas (Népal), le camp de base implique de conserver la nourriture et de se nourrir en autonomie dans un environnement extrême (isolement, altitude, froid, vent…). © Éric Boutroy L’itinérance sportive en espace naturel (expédition, trekking, randonnée) s’est fortement développée ces dernières décennies. Depuis les cimes himalayennes où des dizaines de millie..

Conserver mieux pour consommer loin

Cet article porte sur deux activités sportives qui partagent des contraintes fortes de conservation, de transport et d’allègement des rations alimentaires : les expéditions d’alpinisme en Himalaya et le mouvement de la Marche Ultra-Légère (MUL). Ces itinérances sportives en milieu naturel impliquent de vivre et se déplacer de quelques jours jusqu’à plusieurs semaines dans un environnement plus ou moins extrême. Dans des contraintes inusuelles (contamination et souillure, isolement, conditions hostiles, altitude…), le système culinaire, et de fait les procédés de conservation, recouvrent pour ces voyageurs sportifs des enjeux variés : transportabilité et allègement, durabilité et protection, diététique et nutrition, appétence culturellement spécifiée, rapports sociaux ou symboliques. Il est alors possible de décrire finement la chaîne des techniques conservatoires (matières, objets, conduites, savoirs) mise en œuvre par les sportifs itinérants. De l’approvisionnement à la consommation, ces procédés très riches font, selon les cas, l’objet d’apprentissage ou de délégation : choix d’itinéraire, technique du corps, sélection d’aliments, traitement de conservation (séchage, lyophilisation, conserve…), conditionnement, protection et transport, préparation, repas, gestion des déchets… Derrière la variété et la richesse des opérations, nous suggérons que les pratiques conservatoires supportent deux sous-cultures matérielles qui révèlent, parfois explicitement, des conceptions et des valeurs contrastées entre partisans du minimalisme et aventuriers plus consuméristes.This article focuses on two sports activities that share strong constraints on conservation, transport and lightening of food : mountaineering expeditions in the Himalayas and the movement of the ultralight backpacking (in French : Marche Ultra-Légère, alias MUL). These sports trips in natural areas involve living and traveling for few days to several weeks in a more or less extreme environment. Within unusual constraints (contamination, loneliness, hostile conditions, high altitude…), the “culinary system”, and consequently the preservation techniques, include a variety of issues : transportability and lightening, durability and protection, dietetics and nutrition, culturally specified relish, social relationships, symbols. It is then possible to describe finely the chain of preservation techniques (materials, objects, operational sequences, knowledge) implemented by these travellers. From supplying to consumption, these very rich processes are, depending on the case, the object of learning or delegation : choice of itineraries, body techniques, food selection, preservation treatment (drying, lyophilisation, canning…), reconditioning, protection and transport, preparation, meal, waste management… Behind the variety and profusion of operations, we suggest that preservation techniques support two material subcultures that reveal, sometimes explicitly, contrasted conceptions and values between proponents of minimalism and adventurers-consumers

Mission d'étude technique et économique sur la production fruitière en Colombie

\u3cp\u3eRisk for premature osteoporosis is a major health concern in astronauts and cosmonauts; the reversibility of the bone lost at the weight-bearing bone sites is not established, although it is suspected to take longer than the mission length. The bone three-dimensional structure and strength that could be uniquely affected by weightlessness is currently unknown. Our objective is to evaluate bone mass, microarchitecture, and strength of weight-bearing and non-weight-bearing bone in 13 cosmonauts before and for 12 months after a 4-month to 6-month sojourn in the International Space Station (ISS). Standard and advanced evaluations of trabecular and cortical parameters were performed using high-resolution peripheral quantitative computed tomography. In particular, cortical analyses involved determination of the largest common volume of each successive individual scan to improve the precision of cortical porosity and density measurements. Bone resorption and formation serum markers, and markers reflecting osteocyte activity or periosteal metabolism (sclerostin, periostin) were evaluated. At the tibia, in addition to decreased bone mineral densities at cortical and trabecular compartments, a 4% decrease in cortical thickness and a 15% increase in cortical porosity were observed at landing. Cortical size and density subsequently recovered and serum periostin changes were associated with cortical recovery during the year after landing. However, tibial cortical porosity or trabecular bone failed to recover, resulting in compromised strength. The radius, preserved at landing, unexpectedly developed postflight fragility, from 3 months post-landing onward, particularly in its cortical structure. Remodeling markers, uncoupled in favor of bone resorption at landing, returned to preflight values within 6 months, then declined farther to lower than preflight values. Our findings highlight the need for specific protective measures not only during, but also after spaceflight, because of continuing uncertainties regarding skeletal recovery long after landing.\u3c/p\u3

Trace element composition of iron oxides from IOCG and IOA deposits : relationship to hydrothermal alteration and deposit subtypes

Trace element compositions of magnetite and hematite from 16 well-studied iron oxide–copper–gold (IOCG) and iron oxide apatite (IOA) deposits, combined with partial least squares-discriminant analysis (PLS-DA), were used to investigate the factors controlling the iron oxide chemistry and the links between the chemical composition of iron oxides and hydrothermal processes, as divided by alteration types and IOCG and IOA deposit subtypes. Chemical compositions of iron oxides are controlled by oxygen fugacity, temperature, co-precipitating sulfides, and host rocks. Iron oxides from hematite IOCG deposits show relatively high Nb, Cu, Mo, W, and Sn contents, and can be discriminated from those from magnetite + hematite and magnetite IOA deposits. Magnetite IOCG deposits show a compositional diversity and overlap with the three other types, which may be due to the incremental development of high-temperature Ca–Fe and K–Fe alteration. Iron oxides from the high-temperature Ca–Fe alteration can be discriminated from those from high- and low-temperature K–Fe alteration by higher Mg and V contents. Iron oxides from low-temperature K–Fe alteration can be discriminated from those from high-temperature K–Fe alteration by higher Si, Ca, Zr, W, Nb, and Mo contents. Iron oxides from IOA deposits can be discriminated from those from IOCG deposits by higher Mg, Ti, V, Pb, and Sc contents. The composition of IOCG and IOA iron oxides can be discriminated from those from porphyry Cu, Ni–Cu, and volcanogenic massive sulfide deposits

Effects of strontium ranelate and alendronate on bone microstructure in women with osteoporosis: Results of a 2-year study

Summary: Strontium ranelate appears to influence more than alendronate distal tibia bone microstructure as assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), and biomechanically relevant parameters as assessed by micro-finite element analysis (μFEA), over 2years, in postmenopausal osteoporotic women. Introduction: Bone microstructure changes are a target in osteoporosis treatment to increase bone strength and reduce fracture risk. Methods: Using HR-pQCT, we investigated the effects on distal tibia and radius microstructure of strontium ranelate (SrRan; 2g/day) or alendronate (70mg/week) for 2years in postmenopausal osteoporotic women. This exploratory randomized, double-blind trial evaluated HR-pQCT and FEA parameters, areal bone mineral density (BMD), and bone turnover markers. Results: In the intention-to-treat population (n = 83, age: 64 ± 8years; lumbar T-score: −2.8 ± 0.8 [DXA]), distal tibia Cortical Thickness (CTh) and Density (DCort), and cancellous BV/TV increased by 6.3%, 1.4%, and 2.5%, respectively (all P < 0.005), with SrRan, but not with alendronate (0.9%, 0.4%, and 0.8%, NS) (P < 0.05 for all above between-group differences). Difference for CTh evaluated with a distance transformation method was close to significance (P = 0.06). The estimated failure load increased with SrRan (+2.1%, P < 0.005), not with alendronate (−0.6%, NS) (between-group difference, P < 0.01). Cortical stress was lower with SrRan (P < 0.05); both treatments decreased trabecular stress. At distal radius, there was no between-group difference other than DCort (P < 0.05). Bone turnover markers decreased with alendronate; bALP increased (+21%) and serum-CTX-I decreased (−1%) after 2years of SrRan (between-group difference at each time point for both markers, P < 0.0001). Both treatments were well tolerated. Conclusions: Within the constraints of HR-pQCT method, and while a possible artefactual contribution of strontium cannot be quantified, SrRan appeared to influence distal tibia bone microstructure and FEA-determined biomechanical parameters more than alendronate. However, the magnitude of the differences is unclear and requires confirmation with another metho

A Longitudinal HR-pQCT Study of Alendronate Treatment in Postmenopausal Women With Low Bone Density: Relations Among Density, Cortical and Trabecular Microarchitecture, Biomechanics, and Bone Turnover

The goal of this study was to characterize longitudinal changes in bone microarchitecture and function in women treated with an established antifracture therapeutic. In this double-blind, placebo-controlled pilot study, 53 early postmenopausal women with low bone density (age = 56 ± 4 years; femoral neck T-score = −1.5 ± 0.6) were monitored by high-resolution peripheral quantitative computed tomography (HR-pQCT) for 24 months following randomization to alendronate (ALN) or placebo (PBO) treatment groups. Subjects underwent annual HR-pQCT imaging of the distal radius and tibia, dual-energy X-ray absorptiometry (DXA), and determination of biochemical markers of bone turnover (BSAP and uNTx). In addition to bone density and microarchitecture assessment, regional analysis, cortical porosity quantification, and micro-finite-element analysis were performed. After 24 months of treatment, at the distal tibia but not the radius, HR-pQCT measures showed significant improvements over baseline in the ALN group, particularly densitometric measures in the cortical and trabecular compartments and endocortical geometry (cortical thickness and area, medullary area) (p < .05). Cortical volumetric bone mineral density (vBMD) in the tibia alone showed a significant difference between treatment groups after 24 months (p < .05); however, regionally, significant differences in Tb.vBMD, Tb.N, and Ct.Th were found for the lateral quadrant of the radius (p < .05). Spearman correlation analysis revealed that the biomechanical response to ALN in the radius and tibia was specifically associated with changes in trabecular microarchitecture (|ρ| = 0.51 to 0.80, p < .05), whereas PBO progression of bone loss was associated with a broad range of changes in density, geometry, and microarchitecture (|ρ| = 0.56 to 0.89, p < .05). Baseline cortical geometry and porosity measures best predicted ALN-induced change in biomechanics at both sites (ρ > 0.48, p < .05). These findings suggest a more pronounced response to ALN in the tibia than in the radius, driven by trabecular and endocortical changes. © 2010 American Society for Bone and Mineral Research