Jun Yamauchi

First-principles study on energetics of cBN(001) reconstructed surfaces

Total energies of various reconstructed configurations of cubic boron nitride (001) surfaces are studied systematically by the local density functional approach with ultrasoft pseudopotentials. Stable phases as a function of nitrogen chemical potential are predicted theoretically. Furthermore, we examine the validity of the electron counting rule, which plays an important role in the GaAs study, and obtain the supplemental factors to determine stable surface structures. The difference between cBN and GaAs surfaces is also discussed.

Theoretical study of dissociative adsorption of Cl2 on the Al surface

Abstract The dissociative adsorption of Cl 2 molecules onto the Al(001) surface is investigated through theoretical calculation of the local-density-functional approach with ab initio norm-conserving pseudopotential method. The reaction path of dissociative adsorption is revealed, and it is found that there is no activation barrier in this process. From an analysis of the electronic states, it is found that the dissociative adsorption of Cl 2 onto an Al surface proceeds spontaneously, with a charge transfer taking place from the Al surface to the antibonding state of the Cl 2 molecule (3pσ∗ orbital) and is followed by ionic bond formation between the Al surface and the Cl atom.

Ab initio study of Si(001)2 × 1C chemisorption surface

The optimized structure of Si(001)2 × 1C with monolayer coverage, is obtained by the first-principles molecular dynamics method with a plane-wave basis set. It is revealed that the symmetric dimer structure is stable, although the Si(001)2 × 1 surface prefers an asymmetric dimer structure, and that this surface shows a semiconducting feature with an indirect gap. Although the optimized dimer structure is rather flat, it is slightly raised from the substrate. The Cue5f8C dimer bond is much shorter than the diamond single bond. These features are mainly due to the strong interaction between the carbon atoms.

IDENTIFICATION OF INFLAMMATORY CELLS INFILTRATING RENAL ALLOGRAFTS

Eight nephrectomies and 13 biopsies of renal allografts (living 15, cadaveric 6) were investigated on the origin of inflammatory cells in the graft tissues by the use of an immunohistologic method (ABC method). Various monoclonal antibodies and heterosera were used to identify different leukocyte subsets. In all specimens the most predominant inflammatory cells were T cells. Other cells decreased in the following order; B cells, neutrophils and monocytes, and natural killer cells. In T cell subsets Leu 2a‐positive cells (suppressor/ cytotoxic T cells) predominated over Leu 3a‐positive cells (helper/inducer T cells) in 4 nephrectomies (living 1, cadaveric 3) and 12 biopsies (living 11, cadaveric 1). Among these 16 cases, 7 were undergoing acute rejection in various degrees, and 9 were without clinical rejection. In the former 7 cases only one was suffering from another disease. In contrast, Leu 3a‐positive cells predominated over Leu 2a‐positive cells in 1 biopsy (living) and 4 nephrectomies (living 2, cadaveric 2). Four of these 5 cases concurrently had other diseases in addition to acute rejection. Two cases underwent acute tubular necrosis (cadaveric graft nephrectomies) and 2 underwent chronic rejection and crescentic glomerulonephritis (living graft nephrectomies). The one remaining case was without clinical rejection.

Renal Allografts With Glomerulonephritic Change and Proteinuria

Eight cases of renal allografts with glomerulonephritic change and proteinuria were classified into three groups according to the morphological features of the glomerular lesions. Group I (3 cases): By light microscope, remarkable reduplication of glomerular basement membrane (GBM), widening of mesangial region, and slight increase in mesangial cells, were observed. Electron microscopy revealed thickening of subendothelial space by deposition of electron‐lucent material, mesangial interposition, and dense deposits in various regions (mainly in the subendothelial space). Group II (3 cases): By light microscope, crescent formation and reduplication of GBM were observed, while by electron microscope, changes of GBM similar to group I, but less remarkable, were seen. Group III (2 cases): Light microscope revealed spike formation in one case, but not in the other. With an electron microscope, subepithelial dense deposits were observed in both cases. Thickening of subendothelial space by deposition of electron‐lucent material was noted in one case, while thickening of lamina densa was observed in the other case. Morphological change caused by rejection was observed in all eight cases, with six cases showing massive proteinuria and the other two showing slight proteinuria.

Structure and electronic states of the Si(001) 2×1/C surface by first-principles molecular dynamics calculations

Abstract To obtain a theoretical basis for the initial formation process of carbon layers on silicon substrates, we calculated the electronic states and the detailed geometry of a carbon monolayer on a Si(001) surface. With use of the first-principles molecular dynamics method, we determined the optimized geometry of the Si(001)2 X 1/C surface. It is found that the symmetric dimer structure is the most stable, and the C-C bond length in the dimer is much shorter than the bond length of diamond and close to that of benze. The structure formed by the dimer bond and back-bonds is rather flat, but not a planar structure. Thus, the electronic configuration at the carbon site is intermediate between sp 3 and sp 2 .