Relationships between the anisotropy of longitudinal wave velocity and hydroxyapatite crystallite orientation in bovine cortical bone

Quantitative ultrasound (QUS) is now widely used for evaluating bone in vivo, because obtained ultrasonic wave properties directly reflect the visco-elasticity. Bone tissue is composed of minerals like hydroxyapatite (HAp) and a collagen matrix. HAp crystallites orientation is thus one parameter of bone elasticity. In this study, we experimentally investigated the anisotropy of ultrasonic wave velocity and the HAp crystallites orientation in the axial-radial and axial-tangential planes in detail, using cylindrical specimens obtained from the cortical bone of three bovine femurs. Longitudinal bulk wave propagation was investigated by using a conventional ultrasonic pulse system. We used the one cycle of sinusoidal pulse which was emitted from wide band transmitter. The nominal frequency of the pulse was 1 MHz. First, we investigated the anisotropy of longitudinal wave velocity, measuring the anisotropy of velocity in two planes using cylindrical specimens obtained from identical bone areas. The wave velocity changed due to the rotation angle, showing the maximum value in the direction a little off the bone axis. Moreover, X-ray pole figure measurements also indicated that there were small tilts in the HAp crystallites orientation from the bone axis. The tilt angles were similar to those of the highest velocity direction. There were good correlations between velocity and HAp crystallites orientation obtained in different directions. However, a comparatively low correlation was found in posterior bone areas, which shows the stronger effects of bone microstructure. In the radial-tangential plane, where the HAp crystallites hardly ever align, weak anisotropy of velocity was found which seemed to depend on the bone microstructure.     

Novel electron transfer mediators based on dichloroindophenol derivatives for lactate oxidase

Novel indophenol derivatives were synthesized and characterized electrochemically with respect to their abilities to act as electron-transfer mediators for lactate oxidase. These compounds showed suitable redox potentials and high second-order rate constants, k_med, in solution for electron-transfer from the reduced enzyme. A lactate sensor using these derivatives demonstrated high sensitivity and good substrate selectivity. This sensor could also achieve excellent durability which retained more than 70% residual activity and good linearity in the range from 0 to 16 mM lactate concentration even after 10 days.     

Appearance of anisotropic non s-wave superconductivity above the critical pressure of antiferromagnetic CeRhIn5

We have carried out ¹¹⁵In nuclear quadrupole resonance (NQR) measurements in CeRhIn₅. At ambient pressure, CeRhIn₅ undergoes an antiferromagnetic AF phase transition at K. The ¹¹⁵In NQR spectrum has shown the appearance of a small internal field in the direction perpendicular to the tetragonal c-axis. With application of a hydrostatic pressure, the AF state is suppressed and the superconductivity appears just above the critical pressure (P = 17 kbar). The nuclear spin lattice relaxation rate 1/T₁ of ¹¹⁵In measured at P = 27 kbar indicates the occurrence of the superconductivity in the nearly AF region. In the superconducting state, 1/T₁ has no Hebel-Slichter coherence peak just below of 2 K and has a power law T-dependence (T³) down to 300 mK. This is consistent with anisotropic superconductivity, with line nodes in the superconducting energy gap: non-s-wave superconductivity occurs in CeRhIn₅. Received 5 July 2000     

The core of an economy with a common pool resource: A partition function form approach

In this paper we consider a model of an economy with a common pool resource. Under decreasing returns to scale, it is well-known that no Nash equilibrium attains Pareto efficiency. We examine whether it is possible to achieve Pareto efficiency and avoid the tragedy of the commons through cooperation among players. For that purpose, we use the notion of a game in partition function form. Whether or not the core exists depends crucially on the expectations of each coalition regarding the coalition formation of the outsiders. If each coalition has pessimistic expectations, then the core always exists, while if it has optimistic expectations, the core may be empty. Received: January 1998/Final version: November 1998     

Cell sheet engineering: intelligent polymer patterned surfaces for tissue engineered liver

We describe a new culture system utilizing the temperature-responsive polymer grafted surface for designing of cell position and layered tissue reconstruction. Organizing of the hepatic tissue structure by controlling the culture system, that is patterned co-culture and layered cell sheet co-culture achieved by moving the cultured cells from the culture surface, resulted in regulation of the hepatocyte function. The technique for cell sheet manipulation would promote the liver tissue engineering in quality.