An extremely simple cloning template for a cellular neural network (CNN) is presented that is capable of detecting the number of connected components of a vector in (+1, -1)/sup N/. By exploiting this capability, an architecture for a handwritten character recognition system was obtained. A preliminary test result (100 handwritten numbers, 0-9) shows 94-100% correct recognition rates.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The behavior of thin liquid films is known to be dominated by surface tension forces. We show that the crystallization of thin liquid films requires that two wetting angle conditions be simultaneously satisfied: (i) relating to the liquid‐vapor interface, and (ii) relating to the crystal‐liquid interface. The balance between capillary pressure and thermal gradient forces shows that the equilibrium freezing point of thin films is actually depressed below the bulk freezing point. The magnitude of the effect is 1 K in an 800Å thick film. These observations suggest that small‐scale thickness fluctuations may be responsible for the initiation of subgrain boundaries in the growth of crystalline silicon films.

Abstract Brush‐type chiral stationary phases (CSP) have been prepared both from a silica monolith and, separately, from 10 μm porous silica beads via a process of in‐column modification including attachment of the chiral selector via copper‐catalyzed azide–alkyne cycloaddition. Azide functionalities were first introduced on the pore surface of each type of support by reaction with 3‐(azidopropyl)trimethoxysilane, followed by immobilization of a proline‐derived chiral selector containing an alkyne moiety. This functionalization reaction was carried out in dimethylformamide (DMF) in the presence of catalytic amounts of copper (I) iodide. The separation performance of these triazole linked stationary phases was demonstrated in enantioseparations of four model analytes, which afforded separation factors as high as 11.4.

Abstract A driven second‐order negative‐resistance oscillator circuit has been observed experimentally to exhibit infinitely many distinct chaotic states in addition to infinitely many subharmonic responses of all orders. Each chaotic state is found to be born out of a devil's staircase whose steps are spaced in accordance with a definite period‐adding law . Each devil's staircase emerges at some level of frequency‐tuning resolution, where each level is embedded within an outer level, ad infinitum . The global bifurcation structure is self‐similar in the sense that upon rescaling, the devil's staircases appear to be clones of each other.

Here we present our work on development of new solution processable small molecules for efficient organic photovoltaic cells (OPVs). Boron subphthalocyanine derivatives possess unique structural and photophysical properties, i.e. excellent solubility, low tendency to aggregate, and high extinction coefficients, that enable the formation of high quality thin films via solution processing for OPVs application. Both p type (donor) and n type (acceptor) boron subphthalocyanine derivatives have been investigated. Using a soluble 2-Allylphenol SubPc derivative as donor and fullerene as acceptor, we have demonstrated simple planar heterojunction OPVs with power conversion efficiencies of over 1.7%, which represents one of the highest efficiencies for devices with solution processable small molecules to date. The use of fluorinated subphthalocyanines as acceptor and typical poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1, 4-phenylene vinylene] (MDMO-PPV) as donor has led to fully solution processed OPVs with efficiencies over 0.1%. Our work shows that solution processing of light harvesting small molecules has great potential for application in low cost thin film photovoltaic cells and boron subphthalocyanine derivatives are promising new-generation OPV materials.

A thermodynamic limit of 4n/sup 2/approx. =50 exists for the maximum absorption increase in a randomly textured semiconductor, where n is the semiconductor index of refraction. Optically enhanced solar cells do not achieve this large absorption increase due to parasitic optical absorption by the electrode structure and, scattering properties of surface textures. In this article the authors present a model of absorption enhancement in solar cells which relates independent optical measurements of parasitic absorption and texture performance to measured collection efficiency spectra. Using this model they define limits for short circuit current increases produced by enhancement.

Abstract The method of averaging has been used for years to prove the existence of oscillations in non‐linear circuits. In the past the application of averaging has tended to be ad hoc rather than systematic. In addition the validity of the method was not well established. the purpose of this paper is to rigorize and systematize the analysis of weakly non‐linear oscillator circuits via the method of averaging. In particular this paper will put on a rigorous foundation the work of Kuramitsu et al. 1‐3 on the ‘averaged potential’ and the work of T. Endo and others on the oscillatory modes of coupled oscillator circuits. Furthermore we give a novel way of simplifying the calculation of averages when we have a potential function representation.

Polymeric carriers designed to encapsulate protein antigens have great potential for improving the efficacy of vaccines and immunotherapeutics for diseases such as cancer. We recently developed a carrier system based on polyacrylamide hydrogel microparticles cross-linked with acid-labile moieties. After being phagocytosed by antigen-presenting cells, the protein encapsulated within the carrier is released and processed for subsequent presentation of antigenic epitopes. To understand the impact of particle size on the activation of T-cells following uptake by antigen-presenting cells, particles with mean diameters of 3.5 microm and 35 nm encapsulating a model protein antigen were synthesized by emulsion and microemulsion based polymerization techniques, respectively. In vivo tests demonstrated that both sizes of particles were effective at stimulating the proliferation of T-cells and were capable of generating an antigen-specific cytotoxic T-cell response when coadministered with immunostimulatory DNA. Contrary to previous reports in the literature, our results suggest that there is no significant difference in the magnitude of T-cell activation for the two sizes of particles used in these experiments. This disparity in findings may be related to fundamental differences in material properties of the carriers used in these studies, such as the hydrophilicity of the polyacrylamide particles described here versus the hydrophobic nature of carriers investigated by other groups.

Abstract A closed‐form solution of the variational equation associated with a piecewise‐linear differential equation is derived. This closed‐form solution is used to develop an efficient method for calculating the solution of the variational equation. The method relies on the matrix exponential and requires no integration beyond the calculation of the trajectory along which the variational equation is being solved. Numerical results for the three‐dimensional case show an increase in efficiency of one to two orders of magnitude over the traditional method.

An integrated software toolkit for the analysis of nonlinear dynamical systems is introduced. This user-friendly, graphically oriented collection of interactive programs includes software that calculates and displays trajectories, bifurcation diagrams, and two-dimensional phase portraits. Also included are programs that locate periodic solutions, calculate and display invariant manifolds of two-dimensional Poincaré maps, as well as compute Lyapunov exponents, Lyapunov dimension, fractal dimension, information dimension, and correlation dimension. The toolkit runs under both the UNIX and PC-DOS operating systems.

We describe the first application of optical enhancement to thin-film (∼0.75 μm thick) amorphous silicon solar cells and define cell geometries which maximize enhancement effects. We observed that due to the improved infrared absorption the external AM1 short circuit current increases by 3.0 mA/cm2 in cells constructed in accordance with the principles of optical enhancement.

An extremely efficient breakpoint-hopping algorithm is presented for tracing the driving-point and transfer characteristics of any nonlinear circuit made of linear (possibly multi-terminal) resistors, dc independent sources, linear controlled sources (all 4 types) and 2-terminal nonlinear resistors described by piecewise-linear <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\upsilon - i</tex> characteristics. Most resistive nonlinear electronic circuits can be realistically modeled by such circuits. The algorithm can trace not only violently nonlinear (with sharp turning points) and multivalued characteristics, but also characteristics composed of several disconnected branches, provided one point in each branch is given. The remarkable computational efficiency of the breakpoint-hopping algorithm is due to two key properties built into the algorithm: 1) the circuit equation is formulated into a special form; namely, a canonical piecewise-linear equation with a lattice structure. 2) the algorithm finds only the breakpoints and possibly one point on each end (unbounded) segment via explicit formulas (hence no convergence problem). These data points represent the minimal amount of information needed to specify a piecewise-linear characteristic uniquely.

In einem anderen Stern: Sternpolymere können sonst nicht kompatible Säure- und Base-Katalysatoren wie para-Toluolsulfonsäure- oder 4-(Dialkylamino)pyridin-Einheiten in ihrem sterisch abgeschirmten Inneren tragen (siehe Schema). Die Sternpolymere vermitteln homogen katalysierte Reaktionskaskaden in Eintopfverfahren, beispielsweise eine Sequenz aus säurekatalysierter Entschützung und durch ein nucleophiles Amin katalysierter Baylis-Hillman-Reaktion.