Spin-Polarized Positronium Time-of-Flight Spectroscopy for Probing Spin-Polarized Surface Electronic States.

The energy spectrum of positronium atoms generated at a solid surface reflects the electron density of states (DOS) associated solely with the first surface layer. Using spin-polarized positrons, the spin-dependent surface DOS can be studied. For this purpose, we have developed a spin-polarized positronium time-of-flight spectroscopy apparatus based on a ^{22}Na positron source and an electrostatic beam transportation system, which enables the sampling of topmost surface electrons around the Γ point and near the Fermi level. We applied this technique to nonmagnetic Pt(111) and W(001), ferromagnetic Ni(111), Co(0001) and graphene on them, Co_{2}FeGa_{0.5}Ge_{0.5} (CFGG) and Co_{2}MnSi (CMS). The results showed that the electrons of Ni(111) and Co(0001) surfaces have characteristic negative spin polarizations, while these spin polarizations vanished upon graphene deposition, suggesting that the spin polarizations of graphene on Ni(111) and Co(0001) were mainly induced at the Dirac points that were out of range in the present measurement. The CFGG and CMS surfaces also exhibited only weak spin polarizations suggesting that the half-metallicity expected for these bulk states was not maintained at the surfaces.

The electronic structure and spin states of 2D graphene/VX2 (X = S, Se) heterostructures.

The structural, magnetic and electronic properties of 2D VX2 (X = S, Se) monolayers and graphene/VX2 heterostructures were studied using a DFT+U approach. It was found that the stability of the 1T phases of VX2 monolayers is linked to strong electron correlation effects. The study of vertical junctions comprising of graphene and VX2 monolayers demonstrated that interlayer interactions lead to the formation of strong spin polarization of both graphene and VX2 fragments while preserving the linear dispersion of graphene-originated bands. It was found that the insertion of Mo atoms between the layers leads to n-doping of graphene with a selective transformation of graphene bands keeping the spin-down Dirac cone intact.

Optic tract syndrome with relative afferent pupillary defect.

Two cases are reported of optic tract lesions with complete homonymous hemianopia, characteristic optic atrophy and retinal nerve fiber bundle defect, and relative afferent pupillary defect (RAPD). RAPD was 0.6 log units in both cases. Infrared pupillography revealed pupillary light response of the ipsilateral side to be 1.2 or 1.3 times higher than that of the contralateral side. We confirmed that the detection of RAPD is helpful in differentiating optic tract lesions from suprageniculate lesions in cases of complete homonymous hemianopia.

Metabolism of glycoproteins in cultured retinal pigment epithelium.

The turnover and migration of synthesized glycoproteins in the cultured retinal pigment epithelium have been studied. Quantitative study indicated that half-time of 3H-fucosylglycoproteins was 11.6 days. Autoradiography was performed several times after incubation of 3H-fucose. Retinal pigment epithelium constantly synthesized glycoproteins and released them into the basal extracellular material. Possible functions of the glycoproteins are discussed.

Reduced protein synthesis in diabetic retina and secondary reduction of slow axonal transport.

Protein synthesis in the retina in diabetic rabbits decreased as the severity of the diabetes increased, but protein degradation and replacement were not affected. The reduction in the amount of orthograde slow axonal transport in diabetic rabbits closely paralleled the reduction in the amount of fast axonal transport and protein synthesis in the retina. The reduction in slow flow is most probably a simple reflection of reduced protein synthesis in the retinal ganglion cells. The relationships among reduction in axon diameter, volume of perikaryon, slow axonal transport and diabetic neuropathy are discussed.

Recovery of fast axonal transport and retinal protein synthesis in the rabbits after intraocular administration of vinblastine.

Orthograde fast axonal transport was almost completely blocked one day after the intraocular injection of 10-100 micrograms of vinblastine (VLB), then recovered gradually for up to 2 months. Recovery was not complete, however; there was a definite relationship between the dose of VLB administered and the degree of recovery of fast axonal transport. Retinal protein synthesis was reduced by intraocular VLB, but there was no relationship between the dose administered and the amount of reduction of protein synthesis. Cytotoxicity of VLB to the retina is less probable. The participation of retrograde axonal transport in the metabolism of cell bodies is discussed.