Pentagonal-Dodecahedral La2 Charge Density in [80-Ih]Fullerene: La2@C80

No Abstract     

Multiple Coulomb excitation of a 70Ge beam and the interpretation of the 02 + state as a deformed intruder

Electromagnetic properties of the low-lying states in a ⁷⁰Ge nucleus were studied through the multiple Coulomb excitation of a ⁷⁰Ge beam with a ^natPb target. Relative γ-ray intensities were measured as a function of emission angle relative to the scattered projectile. Sixteen E2 matrix elements, including diagonal ones, for 6 low-lying states have been determined using the least-squares search code GOSIA. The expectation values 〈Q ²〉 of 0₁ ⁺ and 0₂ ⁺ states in ⁷⁰Ge are compared with those in ^{72, 74, 76}Ge. Simple mixing calculations indicate that the 0₂ ⁺ states in ⁷⁰Ge and ⁷²Se can be treated as deformed intruder states. It is shown that the deformed intruder becomes the ground state in ⁷⁴Kr. These interpretations of the 0₂ ⁺ states in this region are compared with the potential-energy surface calculations by the Nilsson-Strutinsky model, which allow to interpret the experimental results in a qualitative way from the theoretical point of view. Received: 2 September 2002 / Accepted: 5 November 2002 / Published online: 25 February 2003 RID="a" ID="a"e-mail: sugawara@pf.it-chiba.ac.jp Communicated by D. Schwalm     

Laser-induced forward transfer technique for maskless patterning of amorphous V2O5 thin film

A laser-induced forward transfer technique has been applied for the maskless patterning of amorphous V₂O₅ thin films. A sheet beam of a frequency doubled (SHG) Q-switched Nd:YAG laser was irradiated on a transparent glass substrate (donor), the rear surface of which was pre-coated with a vacuum-deposited V₂O₅ 180 nm thick film was either in direct contact with a second glass substrate (receiver) or a 0.14 mm air-gap was maintained between the donor film and the receiving substrate. Clear, regular stripe pattern of the laser-induced transferred film was obtained on the receiver. The pattern was characterized using X-ray diffraction (XRD), optical absorption spectroscopy, scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), atomic force microscopy (AFM), etc.     

Theoretical analysis on the limitations of the open-circuit voltage of a hydrogenated amorphous silicon p-i-n solar cell

We have made theoretical studies on the limitation of the open-circuit voltageV _oc of a hydrogenated amorphous silicon (a-Si:H) p-i-n type solar cell. The effects of the tail states in the a-Si:H i layer and of the interface recombination are discussed in detail. The opencircuit voltage increases when the distribution of the tail states is sharp and/or the capture cross sections of these states are small. This is because the recombination rate of photogenerated carriers and/or the density of space charge due to trapped carriers in these states become low in these conditions. These effects of the tail states on the value ofV _oc become pronounced when the built-in potential of the p-i-n junction is high. The decrease in the effective recombination velocity of carriers at the p/i and n/i interfaces results in an increase ofV _oc. This increase becomes remarkable when the effects of the tail states on the value ofV _oc are small. Both the sharp distribution of tail states and the small value of the interface recombination velocity are necessary to increase considerably the value ofV _oc. We show the conditions of the material parameters necessary to obtain an open-circuit voltage of 1.0 V.     

Stereoselective synthesis of trans olefins by the reaction of Wittig reagents with selenium. Formation of selenocarbonyl compounds.

Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction.     

High-Pressure Synthesis of Fully Occupied Tetragonal and Cubic Tungsten Bronze Oxides

A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K₃W₅O₁₅ (K_0.6WO₃). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of R_W=3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice. The asymmetric nature of the tetragonal tungsten bronze K_xWO₃-K_0.6−yBa_yWO₃ phase diagram implies that superconductivity for x≤0.45 originates from the lattice instability because of potassium deficiency. A cubic perovskite KWO₃ phase was also identified as a line phase—in marked contrast to Na_xWO₃ and Li_xWO₃ with varying quantities of x (<1). This study presents a versatile method by which the solubility limit of tungsten bronze oxides can be extended.     

Catalytic activity and regeneration property of a Pd nanoparticle encapsulated in a hollow porous carbon sphere for aerobic alcohol oxidation

A core-shell composite consisting of a palladium (Pd) nanoparticle and a hollow carbon shell (Pd@hmC) was employed as a catalyst for aerobic oxidation of various alcohols. The core-shell structure was synthesized by consecutive coatings of Pd nanoparticles with siliceous and carbon layers followed by removal of the intermediate siliceous layer. Structural characterizations using TEM and N(2) adsorption-desorption measurements revealed that Pd@hmC thus-obtained was composed of a Pd nanoparticle core of 3-6 nm in diameter and a hollow carbon shell with well-developed mesopore (ca. 2.5 nm in diameter) and micropore (ca. 0.4-0.8 nm in diameter) systems. When compared to some Pd-supported carbons, Pd@hmC showed a high level of catalytic activity for oxidation of benzyl alcohol into benzaldehyde using atmospheric pressure of O(2) as an oxidant. The Pd@hmC composite also exhibited a high level of catalytic activity for aerobic oxidations of other primary benzylic and allylic alcohols into corresponding aldehydes. The presence of a well-developed pore system in the lateral carbon shell enabled efficient diffusion of both substrates and products to reach the central Pd nanoparticles, leading to such high catalytic activities. This core-shell structure also provided high thermal stability of Pd nanoparticles toward coalescence and/or aggregation due to the physical isolation of each Pd nanoparticle from neighboring particles by the carbon shell: this specific property of Pd@hmC resulted in possible regeneration of catalytic activity for these aerobic oxidations by a high-temperature heat treatment of the sample recovered after catalytic reactions.     

Biobased myo-inositol as nucleator and stabilizer for poly(lactic acid)

myo-Inositol made from a biomass feedstock was used as an additive for poly (l-lactic acid) (PLLA) which was also made from biomass feedstock. The crystallization and stabilization of PLLA by the addition of myo-inositol were evaluated by the melt injection molding process. While the isothermal crystallization of PLLA at 100 °C had finished over 14 min after melting, that of PLLA with 5 wt% myo-inositol finished within 2 min. The crystal growth of PLLA started when the myo-Inositol crystal was added, and the crystallization was promoted. Furthermore, the molecular weight of PLLA with myo-inositol did not decrease during the melt-mixed at 200 °C, different from that of PLLA without the myo-inositol. myo-Inositol prevented the degradation of PLLA during the thermal melting process. The biomass carbon ratio measured by the accelerator mass spectroscopy method showed that the PLLA with 5 wt% myo-inositol was a fully biobased material. It was demonstrated that myo-inositol was a multi-functional biobased additive for the modification of PLLA without decreasing its mechanical properties.