Itinerant memory dynamics and global bifurcations in chaotic neural networks

We have considered itinerant memory dynamics in a chaotic neural network composed of four chaotic neurons with synaptic connections determined by two orthogonal stored patterns as a simple example of a chaotic itinerant phenomenon in dynamical associative memory. We have analyzed a mechanism of generating the itinerant memory dynamics with respect to intersection of a pair of alpha branches of periodic points and collapse of a periodic in-phase attracting set. The intersection of invariant sets is numerically verified by a novel method proposed in this paper.     

Synthesis of the P-cluster inorganic core of nitrogenases

The [8Fe-7S] core of the P-clusters in nitrogenases is unique among the known [Fe-S] clusters which are essential to electron-transfer processes in nature. The [8Fe-7S] cluster has been thought unstable and to exist only in protein environments. We found that this unusual [8Fe-7S] structure can be self-assembled from the reaction of Fe(II) bis-amide, tetramethylthiourea, 2,4,6-triisopropylbenzenethiol, and elemental sulfur in a specific mole ratio. The structure of the complex isolated therefrom closely resembles that of the reduced form (PN) of the P-clusters, while the 6Fe(II)2Fe(III) oxidation state was manifested by the M?ssbauer study.     

A convenient synthesis of the beraprost intermediate: a useful method for introducing a C3 unit at the benzyl position

[reaction: see text] The Heck reaction is a more efficient and reliable method than previous ones for introducing a C3 unit at the benzyl position for the synthesis of Beraprost. Especially, trialkylated long-chain amines such as (n-C(8)H(17))(3)N and (n-C(12)H(25))(3)N resulted in good yields. This development will be used for the industrial synthesis of Beraprost.     

Microscopically controlled oxidation of H/Si(1 0 0) by lateral surface electric field studied by emission electron microscopies

The ultrathin oxidation of a H/Si(1 0 0) surface with microfabricated pn-junctions was studied by photoemission electron microscopy (PEEM), mirror electron microscopy (MEM) and microscopic X-ray photoelectron spectroscopy (μ-XPS). The ultrathin oxidation inverts the contrast of the junctions in PEEM images. It is found by analyzing the intensity profiles of images that the potential distribution across the pn-junctions is also inverted by the oxidation. The charging of the oxide by ultraviolet irradiation from a light source of PEEM is attributed as the cause of the inversion of the contrast shown by μ-XPS and MEM.     

Influence of intramolecular vibrations in charge redistribution at the pentacene-graphite interface

We have investigated the relation between the intramolecular vibrational modes of pentacene and the charge redistribution at the pentacene-graphite interface by using high-resolution electron-energy-loss-spectroscopy. The three main vibrational peaks shift to lower energies as the pentacene film thickness decreases. In order to discuss this energy shift, we have calculated the vibrational energies of a free pentacene molecule by changing its charge state. We have also calculated the vibrational energies of a pentacene molecule adsorbed on a graphite sheet by changing the pentacene-graphite distance. Taking the experimental and calculation results into account, we conclude that the observed energy shifts result from an intramolecular charge redistribution. The present results indicate that the effect of an intramolecular charge redistribution is essential to discuss the origin of an energy shift observed in a vibrational study of an organic molecule/substrate interface.     

Stress distribution in poly‐p‐phenylenebenzobisoxazole (PBO) fiber estimated from vibrational spectroscopic measurement under tension. II. Analysis of inhomogeneous stress distribution in PBO fiber

Fourier transform Raman spectra were measured for poly‐p‐phenylenebenzobisoxazole (PBO) fiber subjected to a tensile stress, and the Raman shift factor (the frequency shift caused by 1 GPa tensile stress) depended strongly on the sample‐preparation condition. To clarify the reasons of this dependency, a mechanical series parallel model was adopted that could successfully and quantitatively explain the observed Raman shift factors and gave a concreate heterogeneous stress distribution in the PBO fibers. As a result, a mechanical series model was reasonable for PBO fiber. Broadening of Raman bands, which was observed when the PBO fiber was tensioned, could also be interpreted on the basis of an idea of heterogeneous stress distribution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1281–1287, 2002     

Reproduction of distance matrices and original time series from recurrence plots and their applications

We propose a method to reproduce distance matrices and original time series from recurrence plots. The procedure is to (i)convert a recurrence plot to a weighted graph and (ii)calculate a distance between each pair of nodes on this weighted graph. We demonstrate this method by reproducing the topological shape of original time series. We also propose two applications. The first application is to obtain the maximal Lyapunov exponent from a recurrence plot without reproducing the shapes of original time series. The second application is to reconstruct a common deterministic driving force from observations of forced systems. Thus, the method opens new fields in data analysis.     

Universal Schwinger cocycles of current algebras in (D+1)-dimensions: Geometry and physics

We discuss the universal version of the Schwinger terms of current algebra (we call it the universal Schwinger cocycle) forp=3 (herep denotes the class of the Schatten idealI _p , which is related to the (D+1) space-time dimensions byp=(D+1)/2) in detail, and give a conjecture of the general form of the cocycle for anyp. We also discuss the infinite charge renormalizations, the highest weight vector and state vectors forp=3. Last, we give brief comments on the problems caused by the difficulties to construct the measure of infinite-dimensional Grassmann manifolds.