The effects of rate sensitivity and plastic potential surface curvature on plastic flow localization in porous solids

Plastic flow localization in porous elastic-viscoplastic solids is analyzed with an emphasis on the effects of material rate sensitivity and plastic potential surface curvature. The effect of rate sensitivity is included in a material model that accounts for a change of yield surface curvature in a rate-insensitive porous ductile solid. Shear band formation under plane strain and axisymmetric tension, and localized necking in biaxially stretched sheets are analyzed by using the present material model. The results illustrate the interactions of the effects of void nucleation and growth, material rate sensitivity and plastic potential surface curvature on plastic flow localization. The effects of nonproportional straining paths on localized necking in thin sheets are also demonstrated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42772/1/10704_2004_Article_BF00015862.pd

Protein misfolding and dysregulated protein homeostasis in autoinflammatory diseases and beyond.

Cells have a number of mechanisms to maintain protein homeostasis, including proteasome-mediated degradation of ubiquitinated proteins and autophagy, a regulated process of ‘self-eating’ where the contents of entire organelles can be recycled for other uses. The unfolded protein response prevents protein overload in the secretory pathway. In the past decade, it has become clear that these fundamental cellular processes also help contain inflammation though degrading pro-inflammatory protein complexes such as the NLRP3 inflammasome. Signaling pathways such as the UPR can also be co-opted by toll-like receptor and mitochondrial reactive oxygen species signaling to induce inflammatory responses. Mutations that alter key inflammatory proteins, such as NLRP3 or TNFR1, can overcome normal protein homeostasis mechanisms, resulting in autoinflammatory diseases. Conversely, Mendelian defects in the proteasome cause protein accumulation, which can trigger interferon-dependent autoinflammatory disease. In non-Mendelian inflammatory diseases, polymorphisms in genes affecting the UPR or autophagy pathways can contribute to disease, and in diseases not formerly considered inflammatory such as neurodegenerative conditions and type 2 diabetes, there is increasing evidence that cell intrinsic or environmental alterations in protein homeostasis may contribute to pathogenesis

Recent advances in ankylosing spondylitis: understanding the disease and management

The term spondyloarthritis refers to a group of immune-mediated diseases characterised by inflammation of the axial skeleton, peripheral joints, and entheses. Ankylosing spondylitis (AS) is the most common and characteristic of these entities and even though it was first described over two centuries ago, the understanding of the underlying disease mechanism remains incomplete. It is known that around 40% of patients with AS have subclinical bowel inflammation, suggesting that the origin of the disease could be in the gut. Also, more genes and new molecules have demonstrated a role in the pathogenesis of AS. In this review, we analyse the latest therapies for spondyloarthritis and the most relevant discoveries over the last three years, together with their implications for different aspects of the disease

Fine-grained sediment spatial distribution on the basis of a geostatistical analysis: Example of the eastern Bay of the Seine (France)

The eastern Bay of the Seine (English Channel) was the subject in 1991 of a sampling survey of superficial sediments. Geostatistic tools were used to examine the complexity of the spatial distribution of the fine-grained fraction (o50 mm). A central depocentre of fine sediments (i.e. content up to 50%) oriented in a NW–SE direction in a muddy coastal strip, in a very high energy hydrodynamical situation due to storm swells and its megatidal setting, is for the first time recognised and discussed. Within this sedimentary unit, the distribution of the fine fraction is very heterogeneous, with mud patches of less than 4000m diameter; the boundary between these mud patches and their substratum is very sharp. The distribution of this fine fraction appears to be controlled by an anticyclonic eddy located off the Pays de Caux. Under the influence of this, the suspended material expelled from the Seine estuary moves along the coast and swings off Antifer harbour, towards the NW. It is trapped within this eddy because of the settling of suspended particulate matter. Both at a general scale and a local scale the morphology (whether inherited or due to modern processes) has a strong influence on the spatial distribution of the fine fraction. At the general scale, the basin-like shape of the area facilitates the silting, and the presence of the submarine dunes, called ''Ridins d'Antifer'', clearly determines the northern limit of the muddy zone. At a local scale, the same influence is obvious: paleovalleys trap the fine sediments, whereas isolated sand dunes and ripples limit the silting. This duality of role of the morphology is therefore one of the reasons why the muddy surface is extremely heterogeneous spatially. The presence of an important population of suspension feeding echinoderm, the brittle-star Ophiothrix fragilis Abildgaard, has led to a local increase in the silting, and to the modification of the physicochemical and sedimentological parameters. A complex relationship is shown to occur between the amount of fine fraction and the number of brittle-stars (ind.m2). Classical statistical methods are not appropriate to study the spatial distribution of the mud fraction, because the spatial component of the percentage of the distribution is not integrated in the analysis. On the other hand, this is the main property of the geostatistic concepts. The use of geostatistic tools within a strict and clearly identified procedure enables the proposal of an accurate cartography. Further application of the proposed protocol (based on a semivariographic study and a conditional simulation interpolation) for surficial sediments mapping will help explain spatial and temporal variations of fine-grained fraction. Then assessments of sedimentation and erosion stages allow highlighting signature of environmental processes

L'envasement sous l'influence des organismes benthiques : exemple des ophiures en baie de Seine

La partie orientale de la baie de Seine est une zone soumise à fort hydrodynamisme lié en particulier aux courants de marée (existence de ridins actifs) et paradoxalement existent des zones localisées par une vingtaine de m de profondeur sur des sables grossiers et graviers présentant un envasement, pouvant aboutir à des vases noires anoxiques qui sont fréquemment associées à des populations d'ophiures denses. Ce lien potentiel entre envasement et populations d'ophiures existe-t-il réellement et si oui, pourquoi ? Pour répondre à ces questions, nous avons utilisé les résultats de huit missions effectuées entre 1986 et 2009. Deux cartographies générales de la baie de Seine ont montré que les fortes densités d'ophiures (jusqu'à 7500 ind.m-2) sont concentrées au large du port d'Antifer. Cependant, la distribution apparaît spatialement très irrégulière. Les ophiures se concentrent dans des zones géographiquement limitées de diamètre kilométrique. Cette répartition se traduit par la juxtaposition de patches en ophiures et de zones sans aucune ophiure à quelques dizaines de m de distance. Trois séries de résultats, obtenus après une forte crue, une forte tempête ou une période de stabilité environnementale prolongée, ont permis de progresser dans notre compréhension du processus. En période de crue, le Taux de Fraction Fine (TF2) augmente linéairement avec le nombre d'ophiures par m2 (r2 = 0,91). Cet envasement pourrait être lié : (1) au mode d'alimentation des ophiures suspensivores qui collectent les particules en suspension ; (2) à l'impact physique de la population d'ophiures à l'interface eau-sédiment, à partir de 900 ind.m-2, les ophiures sont enchevêtrées voire superposées. Cette disposition semble favoriser le freinage de la couche limite de fond et par là même la sédimentation des particules fines. Dans les deux cas, l'envasement est proportionnel à la densité de la population. Une tempête provoque la dispersion des populations de faibles densités. Au delà de 1000 ind.m-2, la houle ne semble pas agir sur la densité de la population d'ophiures. On note cependant une diminution du taux maximal de fraction fine. Les fortes densités d'ophiures n'empêchent pas une érosion du sédiment sous-jacent mais la limite. En période de stabilité hydrodynamique, l'envasement est plus important qu'en période de crue pour une même densité d'ophiures. Cette comparaison permet donc de conclure que ce n'est pas la quantité de matière amenée sur le site qui est le facteur essentiel mais plutôt la durée de stabilité des populations d'ophiures. Les dépôts de type "vases noires " constituent l'évolution ultime de l'envasement et de l'enrichissement en matière organique à l'interface eau-sédiment en baie de Seine. Cette situation ne peut en définitive résulter que d'une stabilité temporelle importante des populations d'ophiure

Live under tidal regime: the role of the brittle-star Ophiothrix fragilis beds from the eastern Bay of Seine in the fine particle deposit-suspension mechanisms

In the English Channel, the brittle-star Ophiothrix fragilis is a common epifauna species mainly found in strong tidal current characterized by pebbles benthic habitats (Holme, 1984). In the Bay of Seine, O. fragilis is however living on gravel and coarse sandy sediments and more locally, it occurs in areas with unexpected amount of fine particles for such high hydrodynamic areas (Mear et al., 2006; Lozach et al., 2011). This species forms dense aggregation supporting high density populations (1,500 to 7,000 ind.m-2) and both ophiuroid aggregation morphology and behaviour of juveniles play an important role in formation of relatively large patches in term of surface area on the seafloor. Moreover, living in dense aggregations may reduce displacement by strong currents (Warner and Woodley, 1975). Adults, although mobile, are not highly active, but O. fragilis can be a crawling epibenthic species; individuals will crawl back and forth across water currents until a conspecific was found (Broom, 1975). Some migration of adults from nearby populations may be possible. Where dense Ophiothrix aggregations are found on bedrock surfaces they may monopolize the substratum, virtually to the exclusion of other epifauna. In contrasts, beds on soft bottom may contain a rich associated fauna, with a dominance of large suspension-feeders. In addition, O. fragilis plays a major role in pelago-benthic transfer of particles from the water column to the benthic habitats due to its suspension feeding activity (Davoult and Gounin, 1995)

Construction d’une base de données multi-utilisateurs pour améliorer la gestion des empreintes génétiques des variétés de pomme de terre produites en plants en France

National audienceA set of SSR markers is routinely used in 5 French labs for identification of potato cultivars by their genetic fingerprint. Information on molecular profiles has to be exchanged interactively. An internet platform named IdeAle was designed by FN3PT IT department. Login and password are needed to access the platform (https). Data are encrypted and hosted in a professional French data center. The database is now containing the profiles of 939 varieties and 342 hybrids. Information concerning 30 markers is available: 7 of the kit in use in the seed certification labs and 23 markers used in the molecular description of the Inra collection. 551 alleles are represented and 1483 profiles were published. 10 new alleles were added to the previously known pannel routinely in use thanks to the analyses of the Inra varieties collection. Transferability of the markers to various revelation systems was evaluated.Un kit de marqueurs SSR est utilisé en routine dans 5 laboratoires français pour identifier les variétés de pomme de terre par leur empreinte génétique. L’information sur les profils moléculaires doit être échangée entre les partenaires de façon interactive. Une plateforme internet (IdeAle) a été construite par le service informatique de la FN3PT. L’accès au site se fait en mode sécurisé (https) par identifiant et mot de passe. Les données sont cryptées et localisées chez un hébergeur professionnel français. La base de données contient les profils de 939 variétés et 342 hybrides. La base contient de l’information pour 30 marqueurs : 7 de la procédure FN3PT/EPR utilisée pour la certification des plants et 23 spécifiques d’un projet Inra d’analyse de diversité génétique. Ces marqueurs représentent 551 allèles. 1483 profils ont été publiés. 10 nouveaux allèles du kit d’identification variétale ont été identifiés grâce au travail réalisé sur une partie de la collection de variétés gérée par l’Inra. La portabilité des marqueurs de ce kit sur plusieurs systèmes de révélation a été évaluée