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In this work, the elastic and thermodynamic properties of Pt3Al under high pressure are investigated using density functional theory within the generalized gradient approximation. The results of bulk modulus and elastic constants at zero pressure are in good agreement with the available theoretical and experimental values. Under high pressure, all the elastic constants meet the corresponding mechanical stability criteria, meaning that Pt3Al possesses mechanical stability. In addition, the elastic constants and elastic modulus increase linearly with the applied pressure. According to the Poisson's ratio v and elastic modulus ratio (B/G), Pt3Al alloy is found to be ductile, and higher pressure can significantly enhance the ductility. Those indicate that the elastic properties of Pt3Al will be improved under high pressure. Through the quasi-harmonic Debye model, we first successfully report the variations of the Debye temperature ΘD, specific heats CP, thermal expansion coeWcient α, and Grüneisen parameter γ under pressure range from 0 to fi00 GPa and temperature range from 0 to 1000 K. [ABSTRACT FROM AUTHOR]

We estimated the influence of plasmids with DNA carrying the neurotrophin-3 (NT-3) gene on apoptosis in the gastrocnemius muscle and content of Ca-ATPase in the latter after sciatic nerve injury. Sixty adult Wistar rats were randomly divided into the saline (control) and NT-3 groups. The related indices, such as expression of caspase-3 protein, the rate of apoptosis in the muscle evaluated using a TUNEL technique, and the level of Ca-ATPase estimated using Western blot, were observed. Expression of caspase-3 protein was elevated at different post-operative times after peripheral nerve injury; NT-3 expression and the rate of muscle cell apoptosis decreased, whereas the level of Ca-ATPase in the sarcoplasmic reticulum increased; significant differences were observed compared with the saline group ( P < 0.05). The mitigation mechanism of NT-3 on muscle atrophy after peripheral nerve injury is expressed as inhibition of caspase-3 gene expression, increase in the Ca-ATPase level, and reduction in the rate of muscle apoptosis. [ABSTRACT FROM AUTHOR]

Hypersingular integral equations for two intersecting three-dimensional cracks are derived by using Somigliana formula, in which the unknown functions are the displacement discontinuities on the crack-surfaces. The singularity of the unknowns at the crack-front is analyzed by the analytical asymptotic method, and the analytical solutions of the singular stresses near the crack-front are given. Numerical solutions of the stress intensity factors for some examples are presented and discussed. [ABSTRACT FROM AUTHOR]

For the purpose of design and optimization of functionally graded piezoelectric material (FGPM) transducers, wave propagation in FGPM structures has received much attention in the past twenty years. But previous research efforts have been focused essentially on semi-infinite structures and one-dimensional structures, i.e., structures with a finite dimension in only one direction, such as horizontally infinite flat plates and axially infinite hollow cylinders. This paper proposes a double orthogonal polynomial series approach to solving the wave propagation problem in a two-dimensional FGPM structure, namely an FGPM ring with a rectangular cross-section. By numerical comparison with the available reference results for a purely elastic homogeneous rectangular rod, the validity of the extended polynomial approach is illustrated. The dispersion curves and the electric potential distributions of various FGPM rectangular rings with different material gradient directions, different polarization directions, different radius to thickness ratios, and different width to thickness ratios are calculated to reveal the guided wave characteristics. [ABSTRACT FROM AUTHOR]