Evaluation of Adaptive Bone Remodeling after Total Hip Arthroplasty Using Finite Element Analysis

We compared equivalent stress and strain energy density (SED) to bone mineral density (BMD) in the femur after total hip arthroplasty (THA) using subject-specific finite element analysis (FEA). Equivalent stress and BMD were maintained in the distal femur after THA, whereas both decreased in the proximal femur. A significant correlation was observed between the rates of changes in BMD and equivalent stress before and after THA. Therefore, FEA can predict adaptive bone remodeling after mechanical loading changes. Additionally, we evaluated the effects of two different types of stem geometries (Zweymüller-type stem and fit-and-fill-type stem) on load distribution and BMD using the same method. Equivalent stress and BMD in the medial side of the proximal femur were significantly lower with the Zweymüller-type stem than with the fit-and-fill-type stem. Therefore, FEA can assess the effects of stem geometry on bone remodeling after THA. Moreover, we evaluated the effects of bone geometry on load distribution and BMD after THA. Equivalent stress in the medial side of the proximal femur was significantly lower in the stovepipe model implanted with large tapered wedge-type stems than in the champagne flute and intermediate models, and there was a significant loss of BMD in the stovepipe model. Therefore, a large tapered wedge-type stem and stovepipe femur may be associated with significant proximal BMD loss

Analysis of Changes in Soil Water Content under Subsurface Drip Irrigation Using Ground Penetrating Radar

Abstract: In arid or semi-arid regions high-performance irrigation systems are necessary to minimize the amount of water used for agriculture purposes. Among common irrigation systems, subsurface irrigation is known to increase the water use efficiency by decreasing the water loss from the ground surface. For effective design and management of the subsurface irrigation systems, non-destructive methods to observe changes in water contents in soils are essential. Ground penetrating radar (GPR), one of the geophysical methods for subsurface measurement, has been used to observe subsurface water contents non-destructively. The main objective of this study was to investigate whether or not changes in soil water content distributions under subsurface irrigation can be observed using GPR. In this study, laboratory experiments were conducted using a soil lysimeter (120 cm × 75 cm × 60 cm) filled with river sands. An irrigation pipe was placed at a depth of 23 cm to supply water at a given head for 60 minutes. A GPR system with 1000 MHz central frequency was used in this study. GPR common offset (CO) data were collected during and after irrigation. CO profile data (radagram) show reflections from wetting fronts around the irrigation pipe. Vertical distributions of water contents at the center were then estimated from two-way travel time of EM waves. This study demonstrates that GPR can be used to observe changes in water contents due to subsurface irrigation

Structural Study of SiO_x Amorphous Thin Films by the Grazing Incidence X-ray Scattering (GIXS) Method

Atomic structures of SiO_x amorphous thin films of 200 nm thick were analyzed by the grazing incident x-ray scattering (GIXS) method. The radial distribution functions (RDFs) were experimentally determined in two SiO_x amorphous thin films grown in the atmosphere with and without N_2 gas. The SiO_x amorphous film grown with N_2 gas forms the network structure consisting of SiO_4 tetrahedra which are connected each other by oxygen atoms at their vertices. This network structure is similar to the one observed in SiO_2 glass. On the other hand, in the SiO_x amorphous film grown without N_2 gas, the atomic distance of Si-O pairs is a few percent longer and the coordination number of O-O pairs is smaller than the other. This suggests that some of oxygen atoms in a SiO_4 tetrahedron are not connected to a next neighboring tetrahedron. Namely, some part of the network structure is disconnected in the SiO_x amorphous film grown without N_2 gas. Due to this imperfection of the network structure, it is expected that the SiO_x film grown without N_2 gas would be inferior to the other one grown with N_2 gas in some electrical properties as an insulator