One-dimensional plasmons in ultrathin metallic silicide wires of finite width

The acoustic dispersion of plasmons (PLs) in narrow (4 nm) and ultrathin (one unit cell) metallic DySi2 wires, grown by self-assembly on vicinal Si(100)-[011] 4° turns out to be unidirectional. We observed the lowest intersubband PL as well as the acoustic PL. These PLs are specific for narrow metallic strips of finite width. Our experimental and theoretical analysis suggests that only one of two electron pockets in the surface Brillouin zone makes a substantial contribution to the PLs because the other pocket has a much smaller conductive character due to a strong admixture of electronic states with d character. © 2010 The American Physical Society

グァテマラにおけるテメホス剤を用いた広域でのブユ防除法の検討

金沢大学留学生センターグァテマラのオンコセルカ症流行地域における媒介ブユ幼虫の防除方法を改良する目的で, テメホスの各種剤型を用いて, 雨季にグアチピリン水系で広範囲にわたる野外実験を行った。その結果, 0.2∿2.0ppm/10minの範囲では有効距離に薬剤濃度は無関係で, 流水量が関係していた。テメホスの固型剤, 水和剤, 乳剤, 油剤の間, および瞬時投入と10分間投入との間には顕著な差は認められなかった。したがって, グァテマラにおけるオンコセルカ症媒介ブユ対策の作業は, テメホス水和剤1.0∿1.5g入りの袋を流水量とは無関係に, 50∿100mおきに瞬時投入するのが適切と考えられた。 In order to investigate an effective control method of blackfly larvae in an onchocerciasis endemic area of Guatemala, large scale stream tests were done in the rainy season using various formulations of temephos. The concentration of temephos had no relationship with its carry within a range of 0.2-2.0ppm/10min. There existed a clear tendency in that the larger the water discharge, the longer was the carry of the insecticide. No distinct difference was observed in efficacy among the four formulations, i.e. solid, water dispersible powders (wdp), emulsifiable concentrates (EC) and oil solution, as also between the two application methods, instantaneous pouring and pouring during a 10min period. It is recommended that in future vector control operations of Guatemalan onchocerciasis temephos wdp packed in a bag containing 1.0-1.5g of the active ingredient should be poured into a stream immediately after mixing it with stream water, regardless of the water discharge of stream. With this mode of application, 50-100m carry would be expected in streams infested with Simulium ochraceum, the principal vector of onchocerciasis

Electronic Structure of Small Spherical Metal Shells

The ground-state electronic structure of small spherical metal shells is examined on the basis of a model system which consists of valence electrons and a spherical jellium shell (JS). The electron density distribution and the effective one-particle potential are calculated by means of the density functional theory involving the local density approximation (LDA) and the self-interaction correction (SIC). By varying the electron number and the inner radius of the JS under the charge-neutrality condition of the whole system, we closely examine how the electronic structure evolves from a jellium-sphere system to an electron system sharply localized around a spherical surface. By comparing the results in the SIC-LDA scheme with those in the ordinary LDA scheme, we evaluate effects of the SIC especially on energy levels of occupied electron shells

Electronic Structure of the Carrier System in Small Semiconductor Particles

We clarify characteristics of the electronic structure of the carrier system in small semiconductor particles, and investigate the size dependence of this electronic structure with the doping level fixed. We assume spherical doped semiconductor particles in an insulating medium or in the vacuum, and calculate the carrier density distribution and the effective one-particle potential self-consistently. Irrespective of the particle size, a prominent peak appears right inside the carrier-deficient surface layer in the carrier density profile. With increase of the size, the density oscillation inside the prominent peak becomes less and less conspicuous, which reduced to nearly constant density to tend toward charge neutrality. The remarkable variation of the potential bending with increasing size depends on where the probability density of newly occupied carrier states is concentrated. This potential variation often entails the intersection of two close energy levels with different concentration features in their probability density distribution

Carrier Plasmon-Polar Phonon Coupling at Semiconductor Surfaces

We investigate the carrier plasmon-polar phonon coupling at semiconductor surfaces by taking account of the dielectric response of a semi-infinite carrier-electron gas and the polar-phonon polarization. The dynamical response of carriers is treated with the random-phase approximation, and the phonon polarization is described by the Lorentzian oscillator model. The coupling character of each coupled surface mode can be clarified by decomposing the induced charge-density distribution into a carrier component due to carrier density fluctuation, a phonon component originating from longitudinal polar-phonon polarization, and two on-surface components arising from termination of the phonon and the background polarization at the surface. The spatial structure of each surface mode can be visualized in the contour map showing the induced charge-density distribution and in the electric-field profile. We examine the coupling character and the spatial structure of each coupled surface mode, the evolution of the character and the structure of each mode with change of carrier concentration, and the origin of three coupled surface modes