紫外線オゾン処理によるハイドロキシアパタイトの高機能ナノバイオ界面制御

広島大学(Hiroshima University)博士(歯学)Doctor of Philosophy in Dental Sciencedoctora

Acute osteomyelitis of the acetabulum induced by Staphylococcus capitis in a young athlete

Acute hematogenous osteomyelitis (AHOM) of the acetabulum is a rare condition in children and usually caused by Staphylococcus aureus. We present an 11-year-old soccer athlete who suffered from acute osteomyelitis involving the acetabulum caused by S. capitis, a normal flora of the human skin but never reported in this condition. The disease was associated with repetitive skin injuries of the knee and potential osseous microtrauma of the hip joint by frequent rigorous exercise. This unusual case suggests that osseous microtrauma of the acetabulum, in addition to repetitive skin injuries, allowed normal skin flora to colonize to the ipsilateral acetabulum, which served as a favorable niche and subsequently led to AHOM

Numerical and Experimental Studies on Choked Underexpanded Jets

Axisymmetric underexpanded supersonic jets are investigated numerically and experimentally. A time-dependent technique of solution is applied to solve the Euler equations for a compressible ideal gas. The characteristics of the Mach disk obtained by the numerical calculations are compared with the experiments, and a good agreement is obtained. It is shown that the numerical results are very sensitive to the choice of the boundary conditions imposed on the artificially introduced numerical boundaries. The boundary condition giving the best results is found to be the ambient gas condition. It is shown that the global jet structure with a nearly regular shock pattern, wich is stable and steady itself, is destabilized by the vortex rings (Kelvin-Helmholtz roll-up) on the jet boundary. These vortices produce shocks inside the jet, which are convected downstream with the eddies. This strongly suggests that a time-independent or a time-converged solution cannot be expected without making a suitable time-averaging of the time-dependent solutions

Improving the tensile properties of additively manufactured β-containing tial alloys via microstructure control focusing on cellular precipitation reaction

The effect of a two-step heat treatment on the microstructure and high-temperature tensile properties of β-containing Ti-44Al-4Cr (at%) alloys fabricated by electron beam powder bed fusion were examined by focusing on the morphology of α2/γ lamellar grains and β/γ cells precipitated at the lamellar grain boundaries by a cellular precipitation reaction. The alloys subjected to the first heat treatment step at 1573 K in the α + β two-phase region exhibit a non-equilibrium microstructure consisting of the α2/γ lamellar grains with a fine lamellar spacing and a β/γ duplex structure located at the grain boundaries. In the second step of heat treatment, i.e., aging at 1273 K in the β + γ two-phase region, the β/γ cells are discontinuously precipitated from the lamellar grain boundaries due to excess Cr supersaturation in the lamellae. The volume fraction of the cells and lamellar spacing increase with increasing aging time and affect the tensile properties of the alloys. The aged alloys exhibit higher strength and comparable elongation at 1023 K when compared to the as-built alloys. The strength of these alloys is strongly dependent on the volume fraction and lamellar spacing of the α2/γ lamellae. In addition, the morphology of the β/γ cells is also an important factor controlling the fracture mode and ductility of these alloys.Cho K., Odo H., Okamoto K., et al. Improving the tensile properties of additively manufactured β-containing tial alloys via microstructure control focusing on cellular precipitation reaction. Crystals, 11, 7, 809. https://doi.org/10.3390/cryst11070809