Magnetic Structure of Nano-Graphite Moebius Ribbon

We consider the electronic and magnetic properties of nanographite ribbon with zigzag edges under the periodic or Moebius boundary conditions. The zigzag nano-graphite ribbons possess edge localized states at the Fermi level which cause a ferrimagnetic spin polarization localized at the edge sites even in the very weak Coulomb interaction. The imposition of the Moebius boundary condition makes the system non-AB-bipartite lattice, and depress the spin polarization, resulting in the formation of a magnetic domain wall. The width of the magnetic domain depends on the Coulomb interaction and narrows with increasing U/t.Comment: 4 pages; 6 figures; published at J. Phys. Soc. Jpn. Vol. 72 No. 5 pp. 998-1001 (2003

Dimerization structures on the metallic and semiconducting fullerene tubules with half-filled electrons

Possible dimerization patterns and electronic structures in fullerene tubules as the one-dimensional pi-conjugated systems are studied with the extended Su-Schrieffer-Heeger model. We assume various lattice geometries, including helical and nonhelical tubules. The model is solved for the half-filling case of $\pi$-electrons. (1) When the undimerized systems do not have a gap, the Kekule structures prone to occur. The energy gap is of the order of the room temperatures at most and metallic properties would be expected. (2) If the undimerized systems have a large gap (about 1eV), the most stable structures are the chain-like distortions where the direction of the arranged trans-polyacetylene chains is along almost the tubular axis. The electronic structures are ofsemiconductors due to the large gap.Comment: submitted to Phys. Rev. B, pages 15, figures 1

Electronic States and Magnetic Propertis of Edge-sharing Cu-O Chains

The electronic states and magnetic properties for the copper oxides containing edge-sharing Cu-O chains such as Li$_2$CuO$_2$, La$_6$Ca$_8$Cu$_{24}$O$_{41}$ and CuGeO$_3$ are systematically studied. The optical conductivity $\sigma(\omega)$ and the temperature dependence of the magnetic susceptibility $\chi(T)$ for single crystalline samples Li$_2$CuO$_2$ are measured as a reference system and analyzed by using the exact diagonalization method for small Cu-O clusters. It is shown that the spectral distribution of $\sigma(\omega)$ is different between edge-sharing and corner-sharing Cu-O-Cu bonds. The charge transfer gap in edge-sharing chains is larger than that of high-$T_{c}$ cuprates. The exchange interaction between nearest-neighbor copper ions in edge-sharing chains $J_1$ depends sensitively on the Cu-O-Cu bond angles. In addition to $J_1$, the exchange interaction between next-nearest-neighbor copper ions $J_2$ has sufficient contribution to the magnetic properties. We calculate $J_1$ and $J_2$ for all the copper oxides containing edge-sharing Cu-O chains and discuss the magnetic properties.Comment: 10 pages,RevTeX,8 postscript figures. Accepted for publication in Phys. Rev.

Electronic states and quantum transport in double-wall carbon nanotubes

Electronic states and transport properties of double-wall carbon nanotubes without impurities are studied in a systematic manner. It is revealed that scattering in the bulk is negligible and the number of channels determines the average conductance. In the case of general incommensurate tubes, separation of degenerated energy levels due to intertube transfer is suppressed in the energy region higher than the Fermi energy but not in the energy region lower than that. Accordingly, in the former case, there are few effects of intertube transfer on the conductance, while in the latter case, separation of degenerated energy levels leads to large reduction of the conductance. It is also found that in some cases antiresonance with edge states in inner tubes causes an anomalous conductance quantization, $G=e^2/\pi\hbar$, near the Fermi energy.Comment: 24 pages, 13 figures, to be published in Physical Review

A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model

We upgrade a SU_6 quark-model description for the nucleon-nucleon and hyperon-nucleon interactions by improving the effective meson-exchange potentials acting between quarks. For the scalar- and vector-meson exchanges, the momentum-dependent higher-order term is incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the nucleon and Lambda, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region q_1=5 - 20 fm^-1. A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the rho-meson exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up to T_lab=350 MeV are greatly improved especially for the 3E states. The low-energy observables of the nucleon-nucleon and the hyperon-nucleon interactions are also reexamined. The isospin symmetry breaking and the Coulomb effect are properly incorporated in the particle basis. The essential feature of the Lambda N - Sigma N coupling is qualitatively similar to that obtained from the previous models. The nuclear saturation properties and the single-particle potentials of the nucleon, Lambda and Sigma are reexamined through the G-matrix calculation. The single-particle potential of the Sigma hyperon is weakly repulsive in symmetric nuclear matter. The single-particle spin-orbit strength for the Lambda particle is very small, in comparison with that of the nucleons, due to the strong antisymmetric spin-orbit force generated from the Fermi-Breit interaction.Comment: Revtex v2.09, 69 pages with 25 figure

Various Spatiotemporal Expression Profiles of Anther-Expressed Genes in Rice

The male gametophyte and tapetum play different roles during anther development although they are differentiated from the same cell lineage, the L2 layer. Until now, it has not been possible to delineate their transcriptomes due to technical difficulties in separating the two cell types. In the present study, we characterized the separated transcriptomes of the rice microspore/pollen and tapetum using laser microdissection (LM)-mediated microarray. Spatiotemporal expression patterns of 28,141 anther-expressed genes were classified into 20 clusters, which contained 3,468 (12.3%) anther-enriched genes. In some clusters, synchronous gene expression in the microspore and tapetum at the same developmental stage was observed as a novel characteristic of the anther transcriptome. Noteworthy expression patterns are discussed in connection with gene ontology (GO) categories and gene annotations, which are related to important biological events in anther development, such as pollen maturation, pollen germination, pollen tube elongation and pollen wall formation

Extra-Renal Elimination of Uric Acid via Intestinal Efflux Transporter BCRP/ABCG2

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats

Lack of association of genetic variation in chromosome region 15q14-22.1 with type 2 diabetes in a Japanese population

<p>Abstract</p> <p>Background</p> <p>Chromosome 15q14-22.1 has been linked to type 2 diabetes (T2D) and its related traits in Japanese and other populations. The presence of T2D disease susceptibility variant(s) was assessed in the 21.8 Mb region between <it>D15S118 </it>and <it>D15S117 </it>in a Japanese population using a region-wide case-control association test.</p> <p>Methods</p> <p>A two-stage association test was performed using Japanese subjects: The discovery panel (Stage 1) used 372 cases and 360 controls, while an independent replication panel (Stage 2) used 532 cases and 530 controls. A total of 1,317 evenly-spaced, common SNP markers with minor allele frequencies > 0.10 were typed for each stage. Captured genetic variation was examined in HapMap JPT SNPs, and a haplotype-based association test was performed.</p> <p>Results</p> <p>SNP2140 (rs2412747) (<it>C/T</it>) in intron 33 of the ubiquitin protein ligase E3 component n-recognin 1 (<it>UBR1</it>) gene was selected as a landmark SNP based on repeated significant associations in Stage 1 and Stage 2. However, the marginal <it>p </it>value (<it>p </it>= 0.0043 in the allelic test, OR = 1.26, 95% CI = 1.07–1.48 for combined samples) was weak in a single locus or haplotype-based association test. We failed to find any significant SNPs after correcting for multiple testing.</p> <p>Conclusion</p> <p>The two-stage association test did not reveal a strong association between T2D and any common variants on chromosome 15q14-22.1 in 1,794 Japanese subjects. A further association test with a larger sample size and denser SNP markers is required to confirm these observations.</p