Friction properties of in vivo human skin from visualized friction testing.

Investigations on mechanical behaviors of intravital human skin are of significance in various fields. However, due to the great complexity and the individual variation of human skin, traditional experimental mechanics often fails to work in such research objects. In this study, the friction property considering the skin-uplift effect of human skin was in vivo studied experimentally and theoretically. An in situ and noninvasive friction experiment was performed in vivo on human skin, where the projected contact morphology was captured through a novel specially developed optical system. According to the contact morphology, a model taking uplift resistance into account is proposed based on Greenwood model, in which the contact area was depicted as a combination of two ellipses to better characterize the skin deformation. Moreover, since the model degrades into Greenwood model in small deformation, it can be considered as an extension from the perspective of small deformation to large deformation. Based on the model, the adhesion friction and deformation friction have been separated according to the ratio of indentation depth to probe radius. The results show that the friction property of skin varies with the indentation depth changing, and the deformation friction is positively correlated with the ratio of indentation depth to probe radius.

The relationship between the levels and function of endothelial progenitor cells and factor V Leiden and protein C deficiency in patients with primary Budd-Chiari syndrome.

OBJECTIVE: Budd-Chiari syndrome (BCS) is a life-threatening hepatic disease characterized by hepatic venous obstruction at the level of hepatic vein, hepatic venules, or inferior vena cava. No evidence reported the relationship between the endothelial progenitor cells and the deficiency of factor V Leiden and protein C in patients with primary Budd-Chiari syndrome. PATIENTS AND METHODS: We recruited participants between June 2014 and July 2015. For primary BCS group, 28 patients were collected. 20 patients were included in the NAFLD group. Another 73 healthy participants were recruited into the control group. None of the patients and participants had received interventional therapy or had undergone surgery prior to being recruited. Levels and functions of endothelial progenitor cells (EPCs) were examined. The factor V Leiden mutation, protein C deficiency and protein S deficiency were evaluated. Finally, the relationship between the levels and function of endothelial progenitor cells and factor V Leiden and protein C deficiency in patients with primary Budd-Chiari syndrome was analyzed. RESULTS: The results showed that no significant differences were found between the BCS (and NAFLD) and control group considering age, sex, BMI, smoking (p>0.05 for variables). However, significant differences were observed in TG, TC, HDL-C, white blood cells, hemoglobin, ALT, AST, ALP, γ-GT, total bilirubin, and albumin (p<0.05 for variables). Compared with the healthy participants, significant downregulation was found in BCS and NAFLD patients regarding CD34+/CD45-, late outgrowth endothelial cells (OECs) colonies, OECs proliferation, and OECs tubulogenesis (p<0.001 for variables). Among the 28 BCS patients, factor V Leiden mutation (n=10, 35.71%, OR 12.67, 95% CI 5.24-27.93) and hereditary protein C deficiency (n=4, 14.29%, OR 7.48, 95% CI 2.02-21.43) were more prevalent than those in the control group. These results suggested that factor V Leiden mutation and protein C deficiency were major risk factors for BCS. Finally, we demonstrated that factor V Leiden and protein C deficiency may negatively regulate the OECs levels and functions in BCS patients. CONCLUSIONS: It's important to improve the OECs levels and functions, and to prevent the deficiency of factor V Leiden and protein C in the treatment of BCS.