International audienceStrongly adsorbed polyelectrolytes are central in the conditioning properties of many personal care products. Whereas the mechanism of polymer adsorption is rather well understood, less is known about the actual mechanism of polyelectrolyte lubrication. We investigated the adsorption on mica and the lubricant properties of a strong polyelectrolyte, poly- (diallyldimethylammonium chloride), polyDADMAC, in aqueous solutions of different salt concentrations. We found that the adsorption of the polymer was enhanced and the morphology of the adsorbed layer modified by increasing salt concentration. The lubricant properties of the adsorbed polyelectrolyte layer were good at low compressions but rapidly deteriorated at larger applied pressure. A complex velocity dependence of the friction was observed, with a maximum value at intermediate velocities and hysteresis in an acceleration/ deceleration cycle. A progressive increase in separation between the rubbing surfaces with velocity was also observed. We developed a model that describes the complex behavior of friction observed, taking into account the hysteretic elastic deformation of the polymer layer under shear and the dilatency due to the elastohydrodynamic effects resulting from its low elastic modulus. Our results can help to explain the significant lasting of the lubricating properties when polyDADMAC is used in conditioners, where polymer-lubricated hair-hair contacts exhibit low shear forces
Non-alcoholic fatty liver disease (NAFLD) is the most common liver pathology characterized by fat accumulation in a context of metabolic syndrome or insulin resistance. It can be associated with obesity, diabetes, hyperinsulinemia, dyslipidemia as well as hypertension. NAFLD consists of a large spectrum of hepatic lesions including benign steatosis, non-alcoholic steatohepatitis (NASH), cirrhosis or hepatocellular carcinoma. Upon chronic stress, NASH would occur via at least "two-hits" process involving modulation of a high number of genes and proteins. Firstly, the accumulation of fat, either due to the increased inflow of free fatty acids or de novo lipogenesis, leads to steatosis. Secondly, when adaptive mechanisms for stress tolerance are overwhelmed, lipotoxicity and chronic inflammation trigger major hepatic damages, mainly via oxidative and inflammatory stress, lipid peroxidation and cell death. As a consequence, all these processes concur to favor steatohepatitis, fibrosis and cancer. Recently, the elucidation of physiopathological signaling cascades controlling NAFLD and NASH benefited from large-scale studies, namely the omics, such as transcriptomics, genomics, proteomics, and lipidomics. The advent of lipidomics would allow shedding light upon the respective roles of triglyceride and fatty acid metabolites in the lipotoxic liver injury hypothesis for the pathogenesis of NASH. In this review, the contribution of the omics to the understanding of the molecular basis of NASH is discussed that could offer perspectives for novel biomarkers discovery.
Most direct vascular trauma occurring during hip surgery results from injury to pelvic vascular structures which are not visible during the procedures of reaming, drilling holes or the fixation of screws. In this study, 5 pelves of fresh cadavers were injected with a radiopaque mixture and were visualised with a scanner according to 5 predetermined sections. Bone depth of the acetabulum was measured in each section. A calculation was made describing the minimal distance separating the inner cortex from the principal pelvic vessels. After an anatomic dissection of each pelvis, the relationship between the vessels and screws of the fixation cup, implanted identically on the quadranted acetabulum, was observed. The screws placed in the anterior and inferior quadrants and the center of the acetabulum endangered the external iliac v. and a. and the obturator pedicle. The depth of the periacetabular bone was greater in the superior and posterior quadrants. The inferior gluteal, pudendal and superior gluteal aa. were more than ten mm from the posterior wall. Conversely, the external iliac and obturator pedicles came in contact with the osseous surface on which they lay. A projection of the vessels on the acetabulum was made, and the reproducible character of the acetabular-quadrant system was verified. The superior quadrant offers all the characteristics of a vascular safe zone. A knowledge of these anatomic relationships explain vascular trauma in pelvic fractures and helps to prevent vascular injury in hip surgery.
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