Returnability in complex directed networks (digraphs)

The concept of returnability is proposed for complex directed networks (digraphs). It can be seen as a generalization of the concept of reciprocity. Two measures of the returnability are introduced. We establish closed formulas for the calculation of the returnability measures, which are also related to the digraph spectrum. The two measures are calculated for simple examples of digraphs as well as for real-world complex directed networks and are compared with the reciprocity.     

The Bioassay-Guided Isolation of Growth Inhibitors of Adult T-Cell Leukemia (ATL), from the Jamaican Plant <em>Hyptis verticillata</em>, and NMR Characterization of Hyptoside

Through bioassay-guided isolation, five compounds with growth inhibitory activity on S1T, an adult T-cell leukemia (ATL) cell line, were isolated from the crude methanol extract of the aerial parts of Hyptis verticillata.     

Diphenyl N-halosulfilimines : Preparation,decomposition, and reactions with nucleophiles

Diphenyl N chloro (l)-N bromo (2) and N-iodo-sulfilimines (3) were prepared by halogenation of diphenyl free sulfilimine. Compound 1 decomposed in benzene at room temperature. The decomposition of 1 is a chain reaction since the reaction was induced by chlorine or t-butyl hypochlorite affording diphenyl(diphenylsulfilimino) sulfonium chloride(4a) while it was inhibited by styrene or stilbene. Compound 4a was also obtained by the reaction of 1 with diphenyl sulfide in benzene. Decomposition of 1 in acetic acid proceeded smoothly affording various products. Compound 1 reacted with sulfides sulfoxides triarylphosphines and triethylamine affording the N-substituted iminosulfonium salts. Compounds 1 and 2 were hydrolyzed with sodium hydroxide affording diphenyl sulfoximine. The reaction of 1 with sodium cyanide gave diphenyl N cyanosulfilimine(17). The reaction of 1 with Grignard reagent gave diphenyl free sulfilimine. Compounds 2 and 3 are more stable than 1. Decomposition of 2 in benzene or acetic acid gave diphenyl(diphenylsulfilimino)sulfonium perbromide(4c)     

Fabrication of χ{2) Grating in Poled Polymer Waveguide Based on Direct Laser Beam Writing

A simple method is described for fabricating high resolution χ⁽²⁾ grating in poled polymer waveguide. It is found that the second-order nonlinearity of corona-poled polymer thin film is erased after visible laser (450 nm) irradiation. The mechanism of the erasure of χ^{2) is discussed. High resolution χ⁽²⁾ grating structure in several poled polymer waveguides is demonstrated by direct writing with a cw He-Cd laser.On leave from the Department of Optical Instruments, Zhejiang University, Hangzhou, Zhejiang Province, 310027, P.R. of China.     

Frame-rate analysis of arterial blood flow in human and rat using laser speckle image sensing

In imaging of blood flow by means of a laser speckle technique, we have proposed so far an estimation parameter based on the spatial contrast of speckle patterns observed for the blood flow in skin tissue and a blood vessel. This parameter enable us to image a relative blood flow distribution from a single speckle pattern, thus, it analyzes the blood flow with a frame-rate of an imaging device used. In this study, we investigated availability of this parameter for detecting changes in arterial blood flow caused by medication and cold stimulation to the skin tissue. Experiments were conducted for an anesthetized rat and a human wrist to confirm the feasibility of the present parameter.     

Quantum interference effect of resonant transport in nano-scale systems

We propose a new method of analyzing the quantum interference effect of the resonant transport in ballistic open systems. The new method is to obtain the resonant eigenvalues by computing the norm of the retarded and advanced Green's functions. Using the method, we illustrate for a fullerene and an AB-ring the relation between each resonant state and each asymmetric conductance peak, namely the Fano peak. We show that the combination of resonant states determines the symmetry of a conductance peak and that the Fano peak is caused by the asymmetry of the numerator of the conductance around a resonance. The Fano peak appears not only due to the quantum interference effect as often claimed, but more generally due to the resonant transport.     

Quasibound states in the continuum in a two channel quantum wire with an adatom

We report the prediction of quasibound states (resonant states with very long lifetimes) that occur in the eigenvalue continuum of propagating states for certain systems in which the continuum is formed by two overlapping energy bands. We illustrate this effect using a quantum wire system with two channels and an attached adatom. When the energy bands of the two channels overlap, a would-be bound state that lays just below the upper energy band is slightly destabilized by the lower energy band and thereby becomes a resonant state with a very long lifetime (a second such state lays above the lower energy band). Unlike the bound states in continuum predicted by von Neumann and Wigner, these states occur for a wide region of parameter space.     

Improvement of the sensitivity in velocity sensing using dynamic speckles

Dynamic speckle patterns can be used for imaging of relative velocity of moving objects in fields of biomedical and mechanical measurements. In spite of the widespread use of this method, the effect of speckle size on velocity sensing has not fully been estimated so far. In addition, effects of speckle contrast and random noises on the sensitivity of velocity sensing have not been investigated yet. In the present study, we estimated condition of image processing of speckle patterns for reducing effects of random noises with relation to linearity and sensitivity in velocity sensing. We further introduced binarization of the speckle pattern to improve the sensitivity in velocity sensing. Experiments were conducted for sample models using a diffusive plate and fluid flows to confirm the feasibility of the proposed method.     

SYNTHESES AND SOME PROPERTIES OF SULFOXIDES,SULFILIMINES, AMINOSULFONIUM SALTS AND SULFOXIMINES CONTAINING PYRIDINE NUCLEI

Abstract

Several 2-pyridyl sulfides (1) (e.g., methyl (1a), ethyl (1b), isopropyl (1c), benzyl (1d), 1-phenylethyl (1e), l-menthyl (If) 2-pyridyl sulfides; and bis(2-pyridylthio)methane (1g), and methyl 2-(N-oxy-pyridyl) sulfide (1h) were prepared by the usual method. Sulfoxides (2) were prepared by oxidation of the corresponding sulfides with m-chloroperbenzoic acid in good yields. A few sulfoxides were found to work as phase-transfer catalysts for some typical nucleophilic reactions in nonpolar solvents such as benzene, and in two-phase systems such as benzene-water. S-2-Pyridyl-N-(p-toluenesulfonyl) sulfilimines (3) were prepared upon treatment of sulfides with Chloramine-T. Hydrolysis of N-(p-toluenesulfonyl)-2-pyridyl-o-tolylsulfilimine (3i) with conc. sulfuric acid gave the corresponding free sulfilimine in a moderate yield. S-2-Pyridyl sulfoximines (4) were not obtained by the general method from the sulfoxides and hydrazoic acid. Alkyl-2-pyridyl sulfoximines, however, were obtained by oxidation of the free sulfilimines derived from the corresponding aminosulfonium salts (5) prepared by reaction of the sulfides with mesitylene-sulfonylhydroxylamine (MSH). These free sulfilimines and sulfoximines thus prepared were found to give adducts with a few copper salts.