[show abstract][hide abstract] ABSTRACT: We consider mature femoral cortical bone which is in contact with a hip implant having a rough coating. The bone is assumed to be separated from the implant by a thin layer of microscopic peaks and valleys formed on the surface of the coating. The size of the peaks and valleys is very small compared with the macrosize of the implant stem and bone. This makes the direct application of the FEM for the calculation of the bone- stem contact problem prohibitively costly. A method is developed that allows deriving a macrocontact condition on the bone-stem interface. The method involves an asymptotic homogenisation procedure that takes into account the microgeometry of the interface layer and the stiffnesses of the bone and the implant material. The macrocontact condition is then used in a FEM model for the bone-stem contact problem on the macrolevel. The averaged contact stiffness obtained allows the replacement of the interface layer in the macromodel by the macrocontact condition. An approximation to the microstresses is found by two-scale homogenization and can be used for the macrostrength estimation. Treatment for hip osteoarthritis focuses on decreasing pain and improving joint move- ment. When conservative methods of treatment fail, it is necessary to replace the affected joint with an artificial replacement called a joint prosthesis. Nowadays there are two types of hip prosthesis: cemented and cementless. The cementless hip prosthesis, the most re- cent type, represents approximately 35% of the European market and is regarded as more promising. The surface of the cementless implant is coated in such a way that the bone is in direct contact with this surface with the idea that the bone grows into the microvalleys and pores of the coating to provide enhanced stability and rapid osseointegration. The aim of the present paper is to investigate the dependence of the bone-implant con- tact condition on the microgeometry and mechanical properties of the coating. To achieve
[show abstract][hide abstract] ABSTRACT: Objective: To determine whether facial morphology is associated with fasting insulin, glucose and lipids independent of body mass index (BMI) in adolescents. three-dimensional facial laser scans, collected during a follow-up clinic at the age of 15, 2348 white British adolescents (1127 males and 1221 females) were selected on the basis of complete data on cardiometabolic parameters, BMI and Tanner's pubertal stage. Main outcome measures: Fasting insulin, glucose and lipids (triglycerides, high-density lipoprotein cholesterol (HDLc) and low-density lipoprotein cholesterol (LDLc)). Results: On the basis of the collection of 63 x, y and z coordinates of 21 anthropometric landmarks, 14 facial principal components (PCs) were identified. These components explained 82% of the variation in facial morphology and were used as exposure variables. With adjustment for age, gender and pubertal stage, seven PCs were associated with fasting insulin, none with glucose, three with triglycerides, three with HDLc and four with LDLc. After additional adjustment for BMI, four PCs remained associated with fasting insulin, one with triglycerides and two with LDLc. None of these associations withstood adjustment for multiple comparisons. Conclusions: These initial hypotheses generating analyses provide no evidence that facial morphology is importantly related to cardiometabolic outcomes. Further examination might be warranted. Facial morphology assessment may have value in identifying other areas of disease risk.
[show abstract][hide abstract] ABSTRACT: We have found a number exact of solutions to non-linear differential-difference equations of a viscous incompressible fluid with finite relaxation time. The results are used to solve a few hydrodynamic problems; in particular, we describe a one-dimensional flow arising from longitudinal periodic oscillations of a rigid plane and a two-dimensional periodic flow with pressure gradient near a fixed porous plate. We discuss issues of hydrodynamic instability of solutions as well as ways to enhance differential-difference fluid and related heat and diffusion models. The modified relaxation fluid model presented may theoretically explain one of the causes of the onset of turbulence. We also give a few exact solutions to the Racke–Saal non-linear hyperbolic fluid equations.
International Journal of Non-Linear Mechanics 01/2013; 57:116–122.