Differential Phase-contrast Interior Tomography

Differential phase contrast interior tomography allows for reconstruction of a refractive index distribution over a region of interest (ROI) for visualization and analysis of internal structures inside a large biological specimen. In this imaging mode, x-ray beams target the ROI with a narrow beam aperture, offering more imaging flexibility at less ionizing radiation. Inspired by recently developed compressive sensing theory, in numerical analysis framework, we prove that exact interior reconstruction can be achieved on an ROI via the total variation minimization from truncated differential projection data through the ROI, assuming a piecewise constant distribution of the refractive index in the ROI. Then, we develop an iterative algorithm for the interior reconstruction and perform numerical simulation experiments to demonstrate the feasibility of our proposed approach

DsD_s Asymmetry in Photoproduction

By adopting two models of strange and antistrange quark distributions inside nucleon, the light-cone meson-baryon fluctuation model and the effective chiral quark model, we calculate the $D_s^+ - D_s^-$ asymmetry in photoproduction in the framework of heavy-quark recombination mechanism. We find that the effect of asymmetry of strange sea to the $D_s$ asymmetry is considerable and depending on the different models. Therefore, we expect that with the further study in electroproduction, e.g. at HERA and CEBAF, the experimental measurements on the $D_s^+ - D_s^-$ asymmetry may impose a strong restriction on the strange-antistrange distribution asymmetry models.Comment: 4 pages, talk presented by I. Caprini at the International Conference on QCD and Hadronic Physics, June 16-20 2005, Beijin

Tin-selenium compounds at ambient and high pressures

SnxSey crystalline compounds consisting of Sn and Se atoms of varying composition are systematically investigated at pressures from 0 to 100 GPa using the first-principles evolutionary crystal structure search method based on density functional theory (DFT). All known experimental phases of SnSe and SnSe2 are found without any prior input. A second order polymorphic phase transition from SnSe-Pnma phase to SnSe-Cmcm phase is predicted at 2.5 GPa. Initially being semiconducting, this phase becomes metallic at 7.3 GPa. Upon further increase of pressure up to 36.6 GPa, SnSe-Cmcm phase is transformed to CsCl-type SnSe-Pm3m phase, which remains stable at even higher pressures. A metallic compound with different stoichiometry, Sn3Se4-I43d, is found to be thermodynamically stable from 18 GPa to 70 GPa. Known semiconductor tin diselenide SnSe2-P3m1 phase is found to be thermodynamically stable from ambient pressure up to 18 GPa. Initially being semiconducting, it experiences metalization at pressures above 8 GPa

The Influence Of Light On The Electrochemical Characteristics Of Pure Aluminum

The objective of this work was to study the influence of light (wave length ~ 460 nm) on the electrochemical characteristics of pure aluminum. The open circuit potential (OCP) measurements, potentiostatic polarization, cyclic potentiodynamic polarization and Zero Resistance Ammetry (ZRA) were performed in 0.1 M NaCl solution. It was observed that the incident light shifted the OCP in the noble direction by 100 mV. Furthermore, ZRA was performed to measure the galvanic current between illuminated and non-illuminated aluminum electrodes. Cyclic potentiodynamic polarization tests revealed the influence of light on the pitting potential, passive current density, corrosion current density, and repassivation potential. This study indicated that the incident light modified electronic properties of the passive film, which influenced the corrosion behavior. Future research using Mott-Schottky analysis will develop further insight into the influence of light on the electronic properties of the passive film

Classification of Arbitrary Multipartite Entangled States under Local Unitary Equivalence

We propose a practical method for finding the canonical forms of arbitrary dimensional multipartite entangled states, either pure or mixed. By extending the technique developed in one of our recent works, the canonical forms for the mixed $N$-partite entangled states are constructed where they have inherited local unitary symmetries from their corresponding $N+1$ pure state counterparts. A systematic scheme to express the local symmetries of the canonical form is also presented, which provides a feasible way of verifying the local unitary equivalence for two multipartite entangled states.Comment: 22 pages; published in J. Phys. A: Math. Theo