The Mixed State of Charge-Density-Wave in a Ring-Shaped Single Crystals

Charge-density-wave (CDW) phase transition in a ring-shaped crystals, recently synthesized by Tanda et al. [Nature, 417, 397 (2002)], is studied based on a mean-field-approximation of Ginzburg-Landau free energy. It is shown that in a ring-shaped crystals CDW undergoes frustration due to the curvature (bending) of the ring (geometrical frustration) and, thus, forms a mixed state analogous to what a type-II superconductor forms under a magnetic field. We discuss the nature of the phase transition in the ring-CDW in relation to recent experiments.Comment: 6 pages, 4 figure

An Eco-Morphological Examination of Tiller and Stolon Dynamics in a \u3cem\u3eZoysia japonica\u3c/em\u3e Sward

Japanese lawn grass (Zoysia japonica), which dominates in grazed semi-natural grasslands in Japan, is being reconsidered recently, because of its high adaptability to poorer conditions and its aggressive creeping habit in open fields. Zoysia has a unique potential for indeterminate multiple-node generation in the stolon tip and differential tiller formation at two tillering sites of every multiple-node (Ta in the bottom node and Tb in the mid-part), so that it displays contrasting behaviour in stolon extension and aerial tiller production in various situations (Ito et al., 2003). In this study, we examined the population structure of various tillering modules of Zoysia clones in a dense sward

The Infocus Hard X-ray Telescope: Pixellated CZT Detector/Shield Performance and Flight Results

The CZT detector on the Infocus hard X-ray telescope is a pixellated solid-state device capable of imaging spectroscopy by measuring the position and energy of each incoming photon. The detector sits at the focal point of an 8m focal length multilayered grazing incidence X-ray mirror which has significant effective area between 20--40 keV. The detector has an energy resolution of 4.0keV at 32keV, and the Infocus telescope has an angular resolution of 2.2 arcminute and a field of view of about 10 arcminutes. Infocus flew on a balloon mission in July 2001 and observed Cygnus X-1. We present results from laboratory testing of the detector to measure the uniformity of response across the detector, to determine the spectral resolution, and to perform a simple noise decomposition. We also present a hard X-ray spectrum and image of Cygnus X-1, and measurements of the hard X-ray CZT background obtained with the SWIN detector on Infocus.Comment: To appear in the proceedings of the SPIE conference "Astronomical Telescopes and Instrumentation", #4851-116, Kona, Hawaii, Aug. 22-28, 2002. 12 pages, 9 figure

Infinite Layer LaNiO(2): Ni(1+)is not Cu(2+)

The Ni ion in LaNiO$_2$ has the same formal ionic configuration $3d^9$ as does Cu in isostructural CaCuO$_2$, but it is reported to be nonmagnetic and probably metallic whereas CaCuO$_2$ is a magnetic insulator. From ab initio calculations we trace its individualistic behavior to (1) reduced $3d-2p$ mixing due to an increase of the separation of site energies ($\epsilon_d - \epsilon_p$) of at least 2 eV, and (2) important Ni $3d(3z^2-r^2)$ mixing with La $5d(3z^2-r^2)$ states that leads to Fermi surface pockets of La $5d$ character that hole-dope the Ni 3d band.Correlation effects do not appear to be large in LaNiO$_2$. However, ad hoc increase of the intraatomic repulsion on the Ni site (using the LDA+U method) is found to lead to a novel correlated state: (i) the transition metal $d(x^2-y^2)$ and $d(3z^2-r^2)$ states undergo consecutive Mott transitions, (ii) their moments are antialigned leading (ideally) to a "singlet" ion in which there are two polarized orbitals, and (iii) mixing of the upper Hubbard $3d(3z^2-r^2)$ band with the La $5d(xy)$ states leaves considerable transition metal 3d character in a band pinned to the Fermi level. The magnetic configuration is more indicative of a Ni$^{2+}$ ion in this limit, although the actual charge changes little with U.Comment: 7 pages, 8 figure