Search

A phenomenological study of peripheral reactions induced by strongly bound, weakly bound and exotic projectiles on different targets is presented. A large number of experimental elastic scattering differential cross sections at energies close to the Coulomb barrier is studied on the basis of a simple nuclear optical model potential that depends on a small number of parameters. The derived wave functions, together with the imaginary component of the optical potential, allow the analysis of the radial peripheral absorption density distributions for the different kind of projectiles. These distributions, when appropriately normalized, show a clear correlation with the type of projectile regardless of the involved target and indicate that projectiles more prone to break up show a more peripheral absorption density distribution. This manifests in their magnitude, location and width. The relationship of these variables in the strongly bound group and the weakly bound group are described with a simple exponential function, while the exotic projectiles show two distinct groups, namely the neutron-halo and the proton-halo. For the neutron-halo projectiles such as He 6 , Li 11 and Be 11 there is a notable increment of the radial peripheral absorption density peak and the total reaction cross section as the breakup separation energy decreases. The same relationship is established for the proton-halo projectiles B 8 and F 17 but their reduced effective dipole charge leads to a lower probability of dipole Coulomb breakup that results in a substantial reduction in the extent of their peripheral absorption. [ABSTRACT FROM AUTHOR]

Carbon fiber composites are promising candidates for orthopedic implant applications, which calls for a combination of high mechanical strength and outstanding biotribological properties. In this work, hydroxyapatite nanobelts-carbon nanotubes (HN) were designed and constructed into carbon fiber-anhydrous dicalcium phosphate (DCPA)-epoxy composites (CDE) for simultaneously optimizing the mechanical and biotribological properties via the combined methods of pulse electrochemical deposition and injected chemical vapor deposition. HN provides more nucleation sites for the growth of DCPA and favors the infiltration of epoxy. In addition, HN optimizes the fiber/matrix interface by generating strong interfacial mechanical interlocking. Owing to the synergism of a strongly bound HN, the mechanical and biotribological properties of CDE have demonstrated significant improvement. The tensile strength and elastic modulus of HN-modified CDE (HN-CDE) increase by 52 and 170% compared with CDE, respectively. The wear rate and average friction coefficient of HN-CDE are decreased by 42% and increased by 45% compared with those of CDE, respectively. HN-CDE, with superior mechanical strength and biotribological properties, has high potential as a bone substitute and orthopedic implant.

Abstract: Fallout 137Cs and stable Cs in soils were separated with two extractants (1M CH3COONH4 solution and 0.8M CH3COONH4 in 5% HNO3 solution after H2O2 oxidization). The residue remaining after removal of the oxidizable organic-bound fraction was separated into the particle-size fractions including clay, silt, fine sand and coarse sand with a sieving and sedimentation method. Then, the concentrations of 137Cs and stable Cs in the extracted fractions and the particle-size fractions were determined. The 137Cs contents in the exchangeable and organic-bound fractions in the soil were approximately 10 and 20%, respectively. The 137Cs content in the strongly bound fraction was about 70%, and the concentration of 137Cs in the clay was the richest among the particle-size fractions. The specific activity of 137Cs (concentration ratio of fallout 137Cs/stable Cs) decreased in the order exchangeable, organic-bound and strongly bound fractions. The data suggest that equilibrium between 137Cs and stable Cs was not reached among those fractions, even though most of the 137Cs that had been deposited on the soil was derived from fallout weapons tests that occurred several decades ago. The concentration of 137Cs among the particle-size fractions in each soil was different, whereas the specific activity of 137Cs in the particle-size fractions had a relatively similar value. [Copyright &y& Elsevier]