Topological carbon allotropes: paradigm shift for materials innovation

Topology is a central concept of mathematics, which allows us to distinguish two isolated rings with linked ones. In material science, researchers discovered topologically different carbon allotropes in a form of a cage, a tube, and a sheet, which have unique translational and rotational symmetries, described by a crystallographic group theory, and the atoms are arranged at specific rigid positions in 3-dimensional ($D$) space. However, topological orders must be robust against deformations, so that we can make completely different families of topological materials. Here we propose various topological structures such as knots and links using covalent $\sigma$ bonds of carbon atoms, while allowing various topologically equivalent arrangements using weak $\pi$ bonds. By extending this idea, we invented a new 3D carbon allotrope, Hopfene, which has periodic arrays of Hopf-links to knit horizontal Graphene sheets into vertical ones without connecting by $\sigma$ bonds.Comment: 19 pages, 14 figure

パイオニア街の文化景観の変容とリトルインディアの形成--ロサンゼルスのエスノバーブ,アルテジア・セリトスの事例

アルテジアとセリトスはカリフォルニア州ロサンゼルス郡の南東端にある。近郊農業地域として始まったが，酪農家が1930年頃から本地域に集まり，酪農保護区に変わった。1950年代末に市政を布いた結果，酪農家はより外側に追われ，酪農保護区は細分され，住宅地等に変わった。1960・70年代にフィリピン系，韓国系，中国系などの多くの人びとが本地域に集中し，エスノバーブとなった。1923年のサンボーンマップによると，パイオニア街に面し立地した学校，病院，教会，郵便局，役場，商店が周囲の近郊農業地域から人を集めていた。1962年の電話帳と空中写真によると，パイオニア街の支配的な文化景観は病院と公共施設であった。1980年前後から多くのショッピングプラザが交差点や病院跡地に建設された。各ショッピングプラザはエスノバーブを反映し，民族系の商店とその組み合わせを特色とする。最も大きな文化景観の変化は商業中心地区が1995年頃からリトルインディアに変わったことである。最初のインド人の店は1979年に立地し，サリー店，レストラン，宝石店，食料品店が集積するようになった。Artesia and Cerritos are located in the southeastern edge of Los Angles County, California. Suburban gardening in these areas changed to the dairy reserve from 1930to 1960. Dutch and Portuguese dairy farmers were pushed out due to the urban development of Los Angeles and became concentrated in Artesia and Dairy Valley（now Cerritos）. Artesia and Cerritos were incorporated as indepenent cities just before 1960, and the dairy reserve was divided into small lots for the residential and commercial use. Many people, especially Pilipinos, Koreans and Chinese became concentrated there in the 1960s and 1970s. These ethnic groups formed one of the Ethnoburbs of Los Angeles. According to the Sanborn Map surveyed in 1923, public buildings such as school, hospital, churches, post office and town hall on Pioneer Street were focal points of people of the surrounding market gardening areas. Based on air photos and telephone directory of 1962, outstanding cultural landscape was hospitals on Pioneer Street, most of the public facilities and private shops were remained. Around 1980 many shopping plazas were constructed on the site formerly occupied by hospitals and at the crossroad. Each shopping plaza has ethnic features of banks, restaurants, clinic and grocery stores. One of the greatest changes of cultural landscape on Pioneer Street was the shift from central shopping district to "Little India." The first Indian shop opened in 1979, and sari shops, jewelry stores and restaurants increased. Around 1995 Indian shops accounted for the majority of the shopping district, suggeting the formation of "Little India.

Stimulated Raman amplification in Ga As/Al As intermixed superlattices

The enhancement of stimulated Raman scattering (SRS) with a Ga As / Al As intermixed superlattice that works as a χ ( 3 ) -quasi-phase-matched structure is studied, where such Kerr-induced effects as four-wave mixing (FWM), self-phase-modulation (SPM), cross-phase-modulation (XPM), and two-photon absorption (TPA) are included. In particular, the efficiency of anti-Stokes generation is enhanced here; anti-Stokes generation inherently has an extremely small efficiency due to a phase mismatch in the interaction of the pump, Stokes, and anti-Stokes waves (while the efficiency of Stokes generation is sufficiently large because of no such phase mismatch). The superlattice enhances the anti-Stokes efficiency up to the order of 10 3 when compared with that without the superlattice, particularly at a small pump intensity. In this enhancement, it is seen that there is an efficiency boost via simultaneous FWM. In this situation, it is shown how much SPM and XPM degrade the efficiency enhancement. Furthermore, an optimal superlattice length is identified that provides the highest efficiency. The degradation of the efficiency at the optimized length due to TPA is also analyzed. Finally, to gain more anti-Stokes efficiency (or control the sizes of the Stokes and anti-Stokes efficiencies), a photonic-band-gap cavity structure is proposed

On the weights of end-pairs in n-end catenoids of genus zero

First principles calculations are carried out to analyze adsorption of CO and H2 molecules on a Pt (111) surface and the effect of surface strain on the adsorption energy. A CO molecule is more adsorptive on the Pt (111) surface than a H2 molecule under an ordinary condition. Surface expansion enhances CO poisoning on a Pt (111) surface. On the contrary, a compressive strain reduces adsorptive strength of a CO molecule. Similar tendency is also found in adsorption of a H2 molecule on the bridge, fcc-hollow, and hcp-hollow sites. However, H2 adsorption on the top site is less affected by the strain. As a consequence, the difference of adsorption energies between CO and H2 molecules becomes smaller when compressive strain is introduced into the Pt (111) surface. Based on thermodynamics, surface coverage ratio is quantitatively evaluated with taking into account the effect of surface strain and partial pressure of gas phase. It is revealed that compressive strain improves probability of H2 adsorption on Pt surface