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Abstract  The behavior of pairs and clusters of vacancies in solid 4He crystals is studied with diffusion Monte Carlo method. We use a trial function suitable for describing solid 4He with long range order, arbitrary number of unoccupied sites and explicit Bose symmetry. It is found that vacancy clusters are unstable and collapse in all considered systems. We find no signature of stability of bound vacancy clusters of any size. Vacancies are found to exhibit weak attraction and a rough estimation of the binding energy is reported. [ABSTRACT FROM AUTHOR]

Abstract The ground state of the ionic solids LiD and LiH is theoretically studied using the Variational Monte Carlo (VMC) method. Our main focus has been the calculation of relevant properties of the H- and D- ions using a fully quantum approach. In particular, we report results on their kinetic energies, mean-squared displacements, Einstein frequencies, radial distribution functions, and density profiles around the sites. The microscopic results obtained for both isotopes show corrections beyond trivial isotopic effects due to their quantum behavior. Finally, the VMC results are compared with predictions from self consistent average phonon (SCAP) theory at T = 0 K. [ABSTRACT FROM AUTHOR]

Focuses on a study which determined the importance of motion analysis on evaluating a patient's gait and improving the adaptation of prosthetic materials or re-education schemes. Overview of gait analysis of transfemoral amputee; Protocol developed for studying kinematics of prosthetic and sound side joints, pelvis and truck in 3 planes; Discussion on common gait defaults; Impact of the choice of prosthetic materials on pelvis and hip motions.