Crystalline and Electronic Structures of Molecular Solid C50_{50}Cl10% _{10}: First-Principles Calculation

A molecular solid C$_{50}$Cl$_{10}$ with possible crystalline structures, including the hexagonal-close-packed (hcp) phase, the face-centered cubic (fcc) phase, and a hexagonal monolayer, is predicted in terms of first-principles calculation within the density functional theory. The stable structures are determined from the total-energy calculations, where the hcp phase is uncovered more stable than the fcc phase and the hexagonal monolayer in energy per molecule. The energy bands and density of states for hcp and fcc C$_{50}$Cl$_{10}$ are presented. The results show that C$_{50}$Cl% $_{10}$ molecules can form either a hcp or fcc indirect-gap band insulator or an insulating hexagonal monolayer.Comment: 5 pages, 6 figure

Half-Metallic Silicon Nanowires: Multiple Surface Dangling Bonds and Nonmagnetic Doping

By means of first-principles density functional theory calculations, we find that hydrogen-passivated ultrathin silicon nanowires (SiNWs) along [100] direction with symmetrical multiple surface dangling bonds (SDBs) and boron doping can have a half-metallic ground state with 100% spin polarization, where the half-metallicity is shown quite robust against external electric fields. Under the circumstances with various SDBs, the H-passivated SiNWs can also be ferromagnetic or antiferromagnetic semiconductors. The present study not only offers a possible route to engineer half-metallic SiNWs without containing magnetic atoms but also sheds light on manipulating spin-dependent properties of nanowires through surface passivation.Comment: 4 pages, 5 figure

Relation between space-time inversion and particle-antiparticle symmetry and the microscopic essence of special relativity

After analyzing the implication of investigations on the C, P and T transformations since 1956, we propose that there is a basic symmetry in particle physics. The combined space-time inversion is equivalent to particle-antiparticle transformation, denoted by ${\cal PT=C}$. It is shown that the relativistic quantum mechanics and quantum field theory do contain this invariance explicitly or implicitly. In particular, (a) the appearance of negative energy or negative probability density in single particle theory -- corresponding to the fact of existence of antiparticle, (b) spin- statistics connection, (c) CPT theorem, (d) the Feynman propagator are linked together via this symmetry. Furthermore, we try to derive the main results of special relativity, especially, (e) the mass-energy relation, (f) the Lorentz transformation by this one ``relativistic'' postulate and some ``nonrelativistic'' knowledge.Comment: 29 pages, Latex, 1 figur

Protection of y-39983 preconditioning from retinal ischemia-reperfusion injury in rats

AIM: To investigate the neuroprotective effect of rho-associated coiled coil-forming protein kinase(ROCK)inhibitor y-39983 on retinal ischemia reperfusion(IR)injury in rats. <p>METHODS: Sixty adult SD rats were randomly assigned into normal group(<i>n</i>=15), IR group(<i>n</i>=15), saline group(<i>n</i>=15), y-39983 group(<i>n</i>=15), and the rats in later three groups were induced retinal IR by intra-anterior chamber infusion of saline solution. Rats in the saline and y-39983 groups were intravitreously injected with normal saline and y-39983 respectively, 5 minutes prior to the induction of ischemia. The protein expression of intercellular cell adhesion molecules-1(ICAM-1)was determined by immunohistochemical staining. Retrograde labeling of retinal ganalion cells(RGCs)with fluorogold was performed to assess the number of RGCs. Histologic studies and electroretinogram were carried out to evaluate retinal damage. <p>RESULTS: The preadminisration of y-39983 decreased ICAM-1 expression, elevated the survival rate of RGCs and the recoverage rate of amplitude of b wave and O₂ wave significantly, and attenuated the IR-induced the thinning of inner retina. <p>CONCLUSION: y-39983 can protect the rat retina from IR injury at least partially by inhibiting ICAM-1 abnormal expression, suggesting that y-39983 may have therapeutic potential for the retinal diseases associated with IR