Interface roughness effect on friction map under fretting contact conditions

In many industrial applications where fretting damage is observed in the contact (e.g. rotor/blade, electrical contacts, assembly joint, axe/wheel, clutch) the external loadings or geometry design cannot be changed. Therefore, the surface preparation and finishing process become essential to control and reduce the damage caused by fretting. In this paper, the authors present the experimental study of the initial surface roughness and machining process influence on fretting conditions in both partial and full sliding regimes. Surfaces prepared by milling and smooth abrasive polishing processes have been analysed. The influence of roughness on sliding behaviour and analysis of friction have been reported. Also, the contact pressure influence and qualitative analysis of fretting wear scar have been presented

Influence of argon pollution on the weld surface morphology

In this paper the surfaces of butt welded joints in steel tubes were analyzed using an optical 3D measurement system to determine the morphology and topographic parameters. It was established that pollution of the argon shield gas with oxygen did not influence the width of the heat-affected zone. However, the composition of the shield gas significantly influenced the surface asymmetry, Ssk, and its inclination Sku. The measurement of these parameters enabled the selection of a higher quality surface, which was visually proven by the reduction in discoloration of the surface of the weld joint. High quality surfaces eliminate a potential habitat for bacteria and a future source of corrosion as well as providing less resistance to fluid flow

Sclero-topometry metrology in valorisation of waste oil for micro-machining of ductile cast iron

During the time, the specific characteristics and the efficient life time of oil progressively decrease, due to complex pollution, ultimately making the oil unsuitable for the initial applications. The strategy to regenerate and to valorise waste oils is investigated using improved combinations of sclerometric and topometric tests on ductile nodular cast iron. Tribo-abrasive tests are performed in critical conditions, with base oil, waste oil and regenerated oil, of similar viscosities in order to discriminate their interfacial performances. The forms of the scratch traces indicate wear resistance and tendency to elasto-plastic deformation. The mechanisms of deformation and frictional behaviours were evaluated using optical and Scanning Electron Microscopy and measured for various tribological conditions with tactile and optical profilometry. The Energy Dispersive X ray Spectroscopy completes the chemical superficial distribution of pertinent elements. The surface topography metrology is used to characterize the scratch profiles and to determine the volume of the displaced and removed material, as well as maximum pit height. The originality of this paper is that it is a unique approach specifically devoted to transformer oil concerning tribological conditions

Odd-Skipped Related Genes Regulate Differentiation of Embryonic Limb Mesenchyme and Bone Marrow Mesenchymal Stromal Cells

The regulation of progenitor cell differentiation to a specific tissue type is one of the fundamental questions of biology. Here, we identify Osr1 and Osr2, 2 closely related genes encoding zinc finger transcription factors, as being strongly expressed in irregular connective tissue (ICT) fibroblasts in the chicken embryo, suitable as a developmental marker. We provide evidence that both Osr1 and Osr2 regulate mesenchymal cell-type differentiation. Both Osr1 and Osr2 can promote the formation of ICT, a cell type of so far unknown molecular specification, while suppressing differentiation of other tissues such as cartilage and tendon from uncommitted progenitors. Conversely, knockdown of either Osr gene alone or in combination reverses this effect, thereby leading to decreased differentiation of ICT fibroblasts and increased chondrogenesis in vitro. This indicates that Osr genes play a pivotal role in ICT fibroblast differentiation. Undifferentiated mesenchymal cells reside in the adult body in the form of mesenchymal stem cells in the bone marrow cavity. Using bone marrow stromal cells (BMSCs) isolated from chicken fetal long bones, we show that Osr1 and Osr2 have an intrinsic role in BMSC differentiation similar to their role in early embryonic development, that is, the enforcement of CT fibroblast differentiation and the repression of other cell types as exemplified here by osteoblast differentiation

Scléro-topométrie sur fonte sphéroïdale en régime de lubrification limite appliquée à l’étude de la valorisation des huiles usagées

La scléro-topométrie permet de mieux cerner les mécanismes de la déformation plastique en régime de lubrification limite, et par conséquent mieux cerner l’abrasion des matériaux, sous l’angle de la déformation et de l’usinage. Cette combinaison métrologique associe les efforts s’exerçant sur une particule abrasive modèle, à la morphologie de la trace générée en présence d’un fluide. L’interface tri-phasique ainsi réalisée permet la métrologie des interactions abrasives, qui sont fonction des propriétés physico-chimiques, rhéologiques et morphologiques de la surface dans des conditions cinématiques définies. Dans cette étude des hydrocarbures neufs, usagés (pollués par les Polychlorobiphényls) et régénérés, ayant des propriétés physico-chimiques et rhéologiques proches, sont comparés sur une fonte à graphite sphéroïdal, matériau de frottement largement employé dans l’industrie du transport. Nous montrons que les paramètres classiquement pris en compte (largeur et profondeur du sillon) ne permettent pas d’approfondir la connaissance des mécanismes d’abrasion. Une séquence de techniques d’analyse de surface (Microscopie électronique à balayage, microscopie optique et numérique, interférométrie 3D) est développée et combinée aux mesures des forces tangentielles et normales des essais. Cette séquence analytique permet la détermination du taux de déformation de la fonte, par la mesure des volumes de matière déplacée. Cette étude a mis en évidence une potentielle nouvelle voie de quantification de l’action des fluides lubrifiants, et par conséquent une revalorisation des huiles usagées dans l’usinage des métaux

Genome Res.

Animal genomes possess highly conserved cis-regulatory sequences that are often found near genes that regulate transcription and development. Researchers have proposed that the strong conservation of these sequences may affect the evolution of the surrounding genome, both by repressing rearrangement, and possibly by promoting duplicate gene retention. Conflicting data, however, have made the validity of these propositions unclear. Here, we use a new computational method to identify phylogenetically conserved noncoding elements (PCNEs) in a manner that is not biased by rearrangement and duplication. This method is powerful enough to identify more than a thousand PCNEs that have been conserved between vertebrates and the basal chordate amphioxus. We test 42 of our PCNEs in transgenic zebrafish assays—including examples from vertebrates and amphioxus—and find that the majority are functional enhancers. We find that PCNEs are enriched around genes with ancient synteny conservation, and that this association is strongest for extragenic PCNEs, suggesting that cis-regulatory interdigitation plays a key role in repressing genome rearrangement. Next, we classify mouse and zebrafish genes according to association with PCNEs, synteny conservation, duplication history, and presence in bidirectional promoter pairs, and use these data to cluster gene functions into a series of distinct evolutionary patterns. These results demonstrate that subfunctionalization of conserved cis-regulation has not been the primary determinate of gene duplicate retention in vertebrates. Instead, the data support the gene balance hypothesis, which proposes that duplicate retention has been driven by selection against dosage imbalances in genes with many protein connections