Conversion of Gyrotron Output into a Gaussian Beam Using the Far-Field

A compact system to convert gyrotron output into an intense gaussian beam has been designed by introducing an intermediate focusing element into the quasi-optical system. The design is significantly simplified by applying gaussian optics and confirmed by application of the Huygens equation. The beam quality is improved by truncating the sidelobes of the far-field. In spite of the beam truncation, only a small fraction (11 %) of the beam power is sacrificed.     

Mixture diffusion of sulfonated dyes into cellulose membrane. III. Application of parallel diffusion model to binary system of direct dyes with different affinity

Mixture diffusion of two dyes (C.I. Direct Blue 15 (DB15) and C.I. Direct Yellow 12 (DY12)) with different affinity onto the substrate into cellulose membrane from the binary solution was studied at 55°C. Uptake curves and concentration–distance profiles were measured experimentally in the ratios (DB15:DY12) 1:0.5, 1:1 and 1:2. It was examined whether the diffusion of the dyes could be analyzed based on the parallel diffusion theory of surface and pore diffusion. It was revealed that the diffusion of DB15 with higher affinity could be analyzed based on the model in the ratios 1:0.5 and 1:1, although the theoretical value deviated slightly from the data in the concentration–distance profile in the ratio 1:1. On the other hand, the diffusion of DY12 with smaller affinity could not be described by the model, because the diffusivity of the dye changed during the adsorption process against the assumption of the model.     

Generalization of Faraday's Law to include nonconservative spin forces

The usual Faraday's Law E=-dPhi/dt determines an electromotive force E which accounts only for forces resulting from the charge of electrons. In ferromagnetic materials, in general, there exist nonconservative spin forces which also contribute to E. These might be included in Faraday's Law if the magnetic flux Phi is replaced by [Planck's constant/(-e)]gamma, where gamma is a Berry phase suitably averaged over the electron spin direction. These contributions to E represent the requirements of energy conservation in itinerant ferromagnets with time dependent order parameters.     

Synthesis of Extended π‐Systems through C–H Activation

Activation of aromatic C? H bonds by a transition metal catalyst has received significant attention in the synthetic chemistry community. In recent years, rapid and site‐selective extension of π‐electron systems by C–H activation has emerged as an ideal methodology for preparing organic materials with extended π‐systems. This Review focuses on recently reported π‐extending C–H activation reactions directed toward new optoelectronic conjugated materials.     

Pyrimidine-pyrimidine base pairs stabilized by silver(I) ions

In the presence of Ag(I) ions, the C-T and m(5)iC (5-methylisocytosine)-T base pairs showed comparable stability to the C-Ag(I)-C base pair, and the m(5)iC-C base pair was highly stabilized by the synergetic effect of Ag(I) coordination and possible hydrogen bonding.     

Halichonines A, B, and C, novel sesquiterpene alkaloids from the marine sponge Halichondria okadai Kadota

Novel sesquiterpene alkaloids, halichonines A (1), B (2), and C (3), were identified from the marine sponge Halichondria okadai Kadota. By spectroscopic analyses and synthesis, their structures were revealed to include a 6,6-bicyclic ring system and two prenylated amine moieties. In addition, 2 induced apoptosis in HL60 human leukemia cells.     

Spectral Properties of the Linearization at the Burgers Vortex in the High Rotation Limit

We study a linearized operator of the equation for the axisymmetric Burgers vortex which gives a stationary solution to the three dimensional Navier–Stokes equations with an axisymmetric background straining flow. It is numerically known that the Burgers vortex obtains better stabilities as the circulation number (or the vortex Reynolds number) is increasing. Although the global stability of the axisymmetric Burgers vortex is already proved rigorously, mathematical understanding of this numerical observation has been lacking. In this paper we study a linearized operator that includes the circulation number as a parameter, and prove that if the operator is restricted on a suitable invariant subspace, then its spectrum moves to the left as the circulation number goes to infinity. As an application, we show that the axisymmetric Burgers vortex with a high rotation has a better stability, in the sense that the non-radially symmetric part of solutions to the associated evolution equation decays faster in time if the circulation number is sufficiently large.     

Electronic structures around the local defects in all-trans-polyacetylene: An analysis by the cluster-series model

A new approach to analyze the electronic structure around the local defects in a polymer chain is developed based on the cluster-series model. In this approach, by extending the cluster molecule to both sides of the defect, the size effect on electronic structure can be estimated systematically and efficiently. Moreover, through the extension process, the periodicity of electronic structure can be extracted in the form of the periodic pattern of stationary orbitals, which are molecular orbitals unaltered by the extension of the cluster. Such periodic orbitals characterize the bulk states of periodic polymer and the energy band structure can be reconstructed from them. Illustrative analyses of some kinds of local defects in all-trans-polyacetylene are presented at the ab initio STO -3G level. The effects of local defects can be detected by the deviation from periodic bulk states. © 1993 John Wiley & Sons, Inc.     

Iridium-catalyzed enantioselective Pauson-Khand-type reaction of 1,6-enynes

Iridium-chiral diphosphine complex catalyzes an enantioselective intramolecular Pauson-Khand-type reaction to give various chiral bicyclic cyclopentenones. The enantioselective reaction proceeds more smoothly and enantioselectively under a lower partial pressure of carbon monoxide. Moreover, aldehyde can be used as a CO source in the enantioselective carbonylative coupling.