The role of temperature and frequency on fretting wear of a like-on-like stainless steel contact

The influences of environmental temperature and fretting frequency on the mechanisms and rates of wear in a like-on-like 304 stainless steel contact were examined, and mainly attributed to changes in the mechanical response of the bulk material and to changes in the behaviour of the oxide debris formed in the fretting process. At low temperatures, wear proceeds by continual oxide formation and egress from the contact, whilst at high temperatures, the rate of wear is much reduced, associated with the development of oxide formed into a protective bed within the contact. The temperature at which the change between these two behaviours took place was dependent upon the fretting frequency, with evidence that, at this transition temperature, changes in behaviour can occur as the fretting test proceeds under a fixed set of conditions. An interaction diagram has been developed which provides a coherent framework by which the complex effects of these two parameters can be rationalised in terms of widely accepted physical principles

Développement et tests de rotors soudés de turbo-alternateurs pour les centrales nucléaires

La conception standard actuelle des rotors de turbo-alternateurs utilise des pièces forgées en un seul bloc pour toutes les tailles (rotor monobloc). Du fait de la fiabilité des méthodes d’assurance de la qualité et des contrôles, même les plus grands rotors à quatre pôles des turbo-alternateurs utilisés pour les applications nucléaires sont fabriqués à partir de pièces forgées en un seul bloc. Au début des années 2000, on a considéré que la renaissance de la production nucléaire pouvait créer une croissance rapide de la demande de turbo-alternateurs et engendrer ainsi de longs délais de livraison en raison d’une situation d’approvisionnement unique des très grosses pièces forgées de rotor. Pour éviter un goulot d’étranglement et sur la base de la technologie éprouvée, largement expérimentée dans le domaine des turbines, il a été suggéré de fabriquer l’arbre des rotors à quatre pôles des turbo-alternateurs par soudage de pièces cylindriques forgées alignées. Les rotors soudés présentent plusieurs avantages : des pièces forgées de petite taille plus faciles et plus fiables à fabriquer et à contrôler, et une plus grande sécurité des délais d’approvisionnement auprès de plusieurs fournisseurs. Cet article a été présenté au Symposium Fontevraud 8 en septembre 2014

Increased metabolic fluxes in tomato stems infected by Botrytis cinerea

International audienc

Increased metabolic fluxes in tomato stems infected by Botrytis cinerea

International audienc

Increased metabolic fluxes in tomato stems infected by Botrytis cinerea

International audienc

Feature and duration of metre-scale sequences in a storm-dominated carbonate ramp setting (Kimmeridgian, northeastern Spain)

Metre-scale sequences may result from the combined effects of allocyclic and autocyclic processes which are closely inter-related. The carbonate ramp that developed northwest of the Iberian Basin during the late Kimmeridgian was affected by northwestward migrating cyclones. Marl–limestone alternations that settled in mid-ramp environments contain abundant mm to cm thick coarse-grained accumulations that have been related to these events. The aim of this paper is to determine the impact of storm-induced processes on the metre-scale sequence features. Four sections (R3, R4, R6, and R7), which are 5 to 7 m in thickness, were studied bed-by-bed along a 4 km-long outcrop, which shows the transition between the shallow and the relatively deep realms of the middle ramp. Metre-scale sequences were defined and correlated along this outcrop according to the detailed microfacies analysis of host, fine-grained deposits, palynofacies and sequence-stratigraphic analyses, and carbon- and oxygen-isotope measurements. The evolution through time of sedimentary features such as the size of quartz grains and the relative abundance of grains other than quartz (i.e., muscovite, bivalve, ooid, and intraclast) does not correlate from one section to the other, suggesting that the finest as well as the coarsest sediment was reworked in these storm-dominated environments. Small- and medium-scale sequences are defined according to changes in alternation, marly interbed, and limestone bed thickness, and correlated from one section to the other. Because of the effects of storms on sediment distribution and preservation, sequence boundaries coincide with thin alternations and marly interbeds in the most proximal sections (i.e., R3, R4), while they correspond to thin alternations and limestone beds in the most distal sections (i.e., R6, R7). Field observations and palynofacies analyses confirm this sequence-stratigraphic analysis. The excursions in carbon- and oxygen-isotope values are consistent with the lithological correlations, but in themselves are not conclusive. Marl–limestone alternations, and small-, and medium-scale sequences are hierarchically stacked, suggesting an orbital control on sedimentation with alternations lasting 20 kyr, small-scale sequences, 100 kyr, and medium-scale sequences, 400 kyr. As biostratigraphic analyses and spectral analysis are not the most appropriate tools to validate this time calibration in such a short interval and highly dynamic system, an alternative approach is developed, which is based on the quantification of the rates of sediment accumulation, preservation, and sea-level rise

Modelling metabolic fluxes of tomato stems reveals that nitrogen shapes central metabolism for defence against Botrytis cinerea

Among plant pathogens, the necrotrophic fungus Botrytis cinerea is one of the most prevalent, leading to severe crop damage. Studies related to its colonization of different plant species have reported variable host metabolic responses to infection. In tomato, high N availability leads to decreased susceptibility. Metabolic flux analysis can be used as an integrated method to better understand which metabolic adaptations lead to effective host defence and resistance. Here, we investigated the metabolic response of tomato infected by B. cinerea in symptomless stem tissues proximal to the lesions, with a reconstructed metabolic model constrained with a large and consistent metabolic dataset acquired under four different N supplies, throughout 7 days post inoculation (dpi). An overall comparison of 48 flux solution vectors of Botrytis- and mock-inoculated plants showed that fluxes were higher in Botrytis-inoculated plants, and the difference increased with a reduction in available N, accompanying an unexpected increase in radial growth. Despite higher fluxes, such as those involved in cell wall synthesis and other pathways, fluxes related to glycolysis, the TCA cycle, amino acids and protein synthesis were limited under very low N, which might explain the enhanced susceptibility. Limiting starch synthesis and enhancing fluxes towards redox and specialized metabolism also contributed to defence independent of N supply