Photopolymerization of liquid carbon disulfide produces nanoscale polythiene films.

Broad band solar or 300--400 nm irradiation (Hg--Xe arc source) of liquid-phase carbon disulfide produces a new carbon--sulfur polymer with the approximate (n = 1.04--1.05) stoichiometry (CS(n))(x). The polymer, from here on called (CS)(x), forms as a approximately 200 nm thick transparent golden membrane as measured by SEM and AFM techniques. IR spectra for this polymer show some similarities with those obtained for the gas-phase photopolymerized (CS(2))(x) and the high-pressure-phase polymer of CS(2), called Bridgman's Black. The observed FT-IR absorptions of (CS)(x) include prominent features at 1431 (s, br), 1298 (m), 1250 (ms), and 1070 cm(-1) (m). In contrast to previous proposals for (CS(2))(x), (13)C labeling and model compound studies of alpha-(C(3)S(5))R(2) and beta-(C(3)S(5))R(2) (R = methyl or benzoyl) suggest that the absorption at 1431 cm(-1) and those at 1298 and 1250 cm(-1) are indicative of carbon--carbon double bonds and carbon--carbon single bonds, respectively. The molecular structure of alpha-(C(3)S(5))(C(O)C(6)H(5))(2), determined at -84 degrees C, belongs to space group P1, with a = 7.486(5) A, b = 13.335(11) A, c = 17.830(13) A, alpha = 105.60(6) degrees, beta = 95.32(6) degrees, gamma = 90.46(6) degrees, Z = 4, V = 1706(2) A(3), R = 0.0785, and R(w) = 0.2323. With use of electron and chemical ionization mass spectrometry, C(4)S(6) and C(6)S(7) were identified as the dominant soluble molecular side-products derived from a putative ethylenedithione (S==C==C==S) precursor. Atomic force microscopy (AFM) provided surface topology information for the thin film (CS)(x) and revealed features that suggested the bulk material is formed from small polymer spheres 20--50 nm in size. Both (CS(2))(x) and (CS)(x) are extensively cross-linked through disulfide linkages and both materials show strong EPR resonances (g > 2.006) indicative of sulfur-centered radicals from incomplete cross-linking. A polymerization mechanism based on the intermediacy of S(2)C=CS(2) is proposed.     

Development of multianalyte sensor arrays composed of chemically derivatized polymeric microspheres localized in micromachined cavities.

The development of a chip-based sensor array composed of individually addressable polystyrene-poly(ethylene glycol) and agarose microspheres has been demonstrated. The microspheres are selectively arranged in micromachined cavities localized on silicon wafers. These cavities are created with an anisotropic etch and serve as miniaturized reaction vessels and analysis chambers. A single drop of fluid provides sufficient analysis media to complete approximately 100 assays in these microetch pits. The cavities possess pyramidal pit shapes with trans-wafer openings that allows for both fluid flow through the microreactors/analysis chambers and optical access to the chemically sensitive microspheres. Identification and quantitation of analytes occurs via colorimetric and fluorescence changes to receptor and indicator molecules that are covalently attached to termination sites on the polymeric microspheres. Spectral data are extracted from the array efficiently using a charge-coupled device allowing for the near-real-time digital analysis of complex fluids. The power and utility of this new microbead array detection methodology is demonstrated here for the analysis of complex fluids containing a variety of important classes of analytes including acids, bases, metal cations, metabolic cofactors, and antibody reagents.     

Impulsive noise filtering based on noise detection in corrupted digital color images

This paper is an enhancement to our earlier research with grey-scale images. In this paper, we propose two new detection-estimation based image filtering algorithms that effectively remove corrupted pixels with impulsive noise in digital color images. The existing methods for enhancing corrupted color images typically possess inherent problems in computation time and smoothing out edges because all pixels are filtered. Our proposed algorithms first classify corrupted pixels in each channel or in each pixel. Because marginal or vector median filtering is only performed for the classified pixels, the process is computationally efficient, and edges are preserved well. In addition, because there is no appropriate criterion to evaluate the performance of impulsive noise detectors for color images, the objective comparison of noise detectors is difficult. Thus, we introduce a new efficiency factor for comparing the performance of noise detectors in digital color images. Simulation results show that the proposed algorithms perform better than existing methods, in both objective and subjective evaluations.This work was supported by the Korea Science & Engineering Foundation (KOSEF) under grant no. 981-0912-057-2.     

Polymer-based multi-layer conductive electrode film for plastic LCD applications

Thin films of polymer-based multi-layer conductive electrode to be used as a substrate for a plastic liquid crystal display (LCD) have been prepared by a DC magnetron roll-to-roll sputtering method. The conductive layer is composed of three layers, ITO/Ag/ITO or ITO/APC/ITO, where APC is Ag-Pd-Cu alloy, on the polymer substrate (Arton?), which has been treated with hard-coat and gas-barrier layers. The properties of the conductive electrode for the plastic LCD were the following: (1) sheet resistance is 6 Ω/square; (2) transparency is 88% at 550 nm; (3) H₂O gas permeation through the plastics is 0.35 g/m² in 24 h; (4) durability against solvents is good for 5% NaOH solution, IPA, methanol, NMP, acetone, etc.; (5) the irreversible shrinkage and the compaction rate are both less than 3 ppm/h after annealing for 100 h at 150 °C. Received: 22 January 2001 / Accepted: 30 January 2001 / Published online: 26 April 2001     

Differentially Coherent Blind Adaptive Receiver for Rayleigh Fading CDMA Channels

Interest in code division multiple access (CDMA) has increased dramaticallyin boththe industry and academia. This is due to the potential increase in usercapacity andinterference, multipath fading, and jam-resistant capabilities. Differentapproaches ofmultiuser detection schemes have shown improvement over the conventionalreceiver.However, multiuser detectors require system parameters and adaptive multiuserreceivers require training sequences. These parameters are difficult toobtain inmultipath fading channels with a degradation in performance. A blind adaptivemultiuser receiver for flat fading and frequency-selective fading environments isstudied in this paper. This receiver alleviates the problem of multiuser detectors and adaptivemultiuser receivers by using a blind adaptive equalization method. The structure of the receiveris similar to that of the adaptive MMSE receiver which consists of an adaptive equalizer and an adaptivemechanism that uses a standard least mean-squared (LMS) algorithm, but uses a matched filterto generate a reference signal. The receiver is shown to be effective in different fadingchannels with perfect power control and a near-far effect. Furthermore, the simulationresults show that the blind MMSE receiver outperforms the conventional receiver and theRAKE receiver.     

The effect of Co incorporation on electrical characteristics of n+/p shallow junction formed by dopant implantation into CoSi2 and anneal

The impact of Co incorporation on the electrical characteristics has been investigated in n⁺/p junction formed by dopant implantation into CoSi₂ and drive-in anneal. The junctions were formed by As⁺ (30 or 40 keV, 1×10¹⁶ cm ^-2) implantation into 35 nm-thick CoSi₂ followed by drive-in annealing at 900°C for 30 s in an N₂ ambient. Deeper junction implanted by As⁺ at 40 keV was not influenced by the Co incorporation. However, for shallower junction implanted by As ⁺ at 30 keV, incorporation of Co atoms increased its leakage current, which were supposed to be dissociated from the CoSi₂ layer by silicide agglomeration during annealing. The mechanism of such a high leakage current was found to be Poole-Frenkel barrier lowering induced by high density of Co traps     

Impact and high strain rate delamination characteristics of carbon fibre epoxy composites

Delamination mechanisms and energy dissipation of carbon fibre epoxy composites under impact and high strain rate conditions are studies in terms of a new experimental set-up. The test set-up is designed to separate the Mode-I, -II and mixed mode delamination resistance so that relevant mechanisms can be studied in greater detail. The impact specimens consist of 18 × 18 mm laminated composite pieces bonded to steel bars to form the impact specimens with the normal Charpy and Izod specimen geometry. The impact energy dissipation is recorded and taken as a dynamic delamination toughness measurement, and the transition from the pure Mode-I to Mode-II through the mixed mode delamination is measured. Detailed delamination surface examinations by scanning electron microscopy (SEM) show that different failure mechanisms are involved in the dynamic and usual quasi-static delamination processes. The influence of chopped Kevlar fibres used as low cost interlaminar reinforcement on the energy dissipation is also studied.     

The maximal downstroke of epicardial potentials as an index of electrical activity in mouse hearts

The maximal upstroke of transmembrane voltage (dV(m)/dt(max)) has been used as an indirect measure of sodium current I(Na) upon activation in cardiac myocytes. However, sodium influx generates not only the upstroke of V(m), but also the downstroke of the extracellular potentials V(e) including epicardial surface potentials V(es). The purpose of this study was to evaluate the magnitude of the maximal downstroke of V(es) (|dV(es)/dt (min)|) as a global index of electrical activation, based on the relationship of dV(m)/dt(max) to I(Na). To fulfill this purpose, we examined |dV(es)/dt(min)| experimentally using isolated perfused mouse hearts and computationally using a 3-D cardiac tissue bidomain model. In experimental studies, a custom-made cylindrical "cage" array with 64 electrodes was slipped over mouse hearts to measure V(es) during hyperkalemia, ischemia, and hypoxia, which are conditions that decrease I(Na). Values of |dV(es)/dt(min)| from each electrode were normalized (|dV(es)/dt (min)|(n)) and averaged (|dV(es)/dt(min)|(na)). Results showed that |dV(es)/dt(min)|(na) decreased during hyperkalemia by 28, 59, and 79% at 8, 10, and 12?mM [K(+)](o), respectively. |dV(es)/dt(min)| also decreased by 54 and 84% 20 min after the onset of ischemia and hypoxia, respectively. In computational studies, |dV(es)/dt(min)| was compared to dV(m)/dt(max) at different levels of the maximum sodium conductance G(Na), extracellular potassium ion concentration [K(+)](o), and intracellular sodium ion concentration [Na(+)](i), which all influence levels of I(Na). Changes in |dV(es)/dt(min)|(n) were similar to dV(m)/dt (max) during alterations of G(Na), [K(+)](o), and [Na(+)](i). Our results demonstrate that |dV(es)/dt(min)|(na) is a robust global index of electrical activation for use in mouse hearts and, similar to dV(m)/dt(max), can be used to probe electrophysiological alterations reliably. The index can be readily measured and evaluated, which makes it attractive for characterization of, for instance, genetically modified mouse hearts and drug effects on cardiac tissue.