Effect of a net on the limiting current distribution in a parallel plate electrochemical reactor. Part II: combined effects

In Part I, we used computational fluid dynamics (CFD) to solve the Navier-Stokes equations surrounding the inert net in a parallel plate channel and presented the individual effects of the transverse and longitudinal ribs on the limiting current density distribution. The type, location, spacing, and number of the ribs of the net were shown to affect the local and average current density distributions on each of the two electrodes. In Part II, we present the combined effects of the longitudinal and transverse ribs on the limiting current distribution. We calculated the enhancement factors for both the combined and individual effects and compared. The longitudinal ribs decreased the average current density whereas the transverse ribs increased the average current density relative to the no-net parallel plate reactor system. A maximum enhancement of 250% in the average current density for a spacing of 0.94 × 10⁻³ m was obtained with 16 transverse ribs. For the same spacing, a negative 70% enhancement was obtained with 14 longitudinal ribs and no transverse ribs. A maximum enhancement of 180% was observed for the entire net (14 longitudinal and 29 transverse ribs). The enhancements at each electrode are different for a given geometry.     

A single amino acid in the PB2 gene of influenza A virus is a determinant of host range

The single gene reassortant virus that derives its PB2 gene from the avian influenza A/Mallard/NY/78 virus and remaining genes from the human influenza A/Los Angeles/2/87 virus exhibits a host range restriction (hr) phenotype characterized by efficient replication in avian tissue and failure to produce plaques in mammalian Madin-Darby canine kidney cells. The hr phenotype is associated with restriction of viral replication in the respiratory tract of squirrel monkeys and humans. To identify the genetic basis of the hr phenotype, we isolated four phenotypic hr mutant viruses that acquired the ability to replicate efficiently in mammalian tissue. Segregational analysis indicated that the loss of the hr phenotype was due to a mutation in the PB2 gene itself. The nucleotide sequences of the PB2 gene of each of the four hr mutants revealed that a single amino acid substitution at position 627 (Glu-->Lys) was responsible for the restoration of the ability of the PB2 single gene reassortant to replicate in Madin-Darby canine kidney cells. Interestingly, the amino acid at position 627 in every avian influenza A virus PB2 protein analyzed to date is glutamic acid, and in every human influenza A virus PB2 protein, it is lysine. Thus, the amino acid at residue 627 of PB2 is an important determinant of host range of influenza A viruses.     

Brush electrodeposited CdS films on low temperature substrates

Cadmium sulphide films were deposited by the brush plating technique on titanium and conducting glass substrates using a current density of 80 mA cm^− 2. X-ray diffraction studies indicated the polycrystalline nature of the films with hexagonal structure. As the deposition temperature decreased, the peaks were broad indicating the formation of nanocrystallites. Optical absorption measurements yielded band gap values in the range of 2.39-3.10 eV as the deposition temperature decreases. XPS studies confirmed the formation of CdS. Atomic force microscope studies indicated the roughness of the films decreases with the decrease of deposition temperature. The as deposited films were photoactive.     

Synthesis and dielectric properties of MXTi<Subscript>7</Subscript>O<Subscript>16</Subscript> (M = Ba and Sr; X = Mg and Zn) hollandite ceramics

MXTi₇O₁₆ (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (ε_r), loss tangent (tan δ) and temperature variation of dielectric constant (τ_εr) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.     

Efficacy of Novel Electroless Plating Process for Dense Pd/Cr2O3/PSS Membrane Fabrication

This work addresses the role of chromia diffusion barrier on the combinatorial plating characteristics of Pd plating baths during fabrication of dense Pd/Cr₂O₃/porous stainless steel (PSS) composite membranes and is compared with those obtained during fabrication of Pd/PSS membranes. Cr₂O₃ was deposited by electroplating technique followed with oxidation at 700°C and Pd films were deposited using a novel Pd electroless plating process that provides optimal performance. Apart from providing similar process characteristics, the Pd/Cr₂O₃/PSS membrane provided 15.2% lower Pd film thickness in comparison with Pd/PSS membrane for similar pore densification values.     

BER performance analysis of compound chaotic sequence (CCS)-based NR-DCSK system under multipath fading channel

This paper presents the performance analysis of compound chaotic sequence (CCS)-based noise reduction differential chaos shift keying (NR-DCSK) system under multipath Rayleigh fading channel conditions. The special characteristics of chaotic sequences are their deterministic randomness behaviour that adds security and multipath immunity to the data when used as a carrier in communication systems. In this paper, the chaotic sequences are generated by combining the outputs of chaotic maps, such as logistic map, Chebyshev map, Bernoulli shift map, tent map, etc., leading to new complex sequences known as CCSs. This sequence possesses more randomness, overcomes severe interference levels encountered during transmission and provides higher multipath immunity compared with those of pseudo-noise (PN) codes. Since NR-DCSK is a spread spectrum technique, its performance in wireless multipath fading channels has important considerations. The CCS is used as a carrier in NR-DCSK systems, which leads to improved bit error rate (BER) performance. Comparisons of simulation results to theoretical BER expressions of additive white Gaussian noise (AWGN) and Rayleigh fading channels have been carried out to test the efficiency of the proposed CCS-based NR-DCSK system.     

Non-linear viscoelastic model based ranking of modified binders for their rutting performance

Rutting is one of the most common distresses observed in bituminous pavements. A number of test procedures, associated parameters, and correlations have been developed for the binder and the mixture to evaluate their rutting performance. In this investigation, the rutting performance of an unmodified, and three modified binders (Elastomer, Plastomer and Crumb rubber) was evaluated separately for the binders and mixtures. Creep-recovery and stress relaxation experiments were carried out on binders in the temperature range of 46–70 \({^{\circ }}\)C. The mixtures were subjected to dry rut wheel testing at 50 and 60 \({^{\circ }}\)C. A nonlinear viscoelastic fluid model was used to capture the response of the binder. Using the material parameters identified separately for creep-recovery and stress relaxation experiments, the apparent viscosity was computed for each binder at different stress levels. It was seen that the ranking of mixtures evaluated from rut wheel testing was captured by the apparent viscosity predicted using the non-linear viscoelastic model.     

Ageing studies of discontinuous copper and silver thin films

The results of experiments carried out on the post-deposition resistance changes in discontinuous films of copper and silver with and without overlayers of SiO and Al₂O₃ are presented. The changes in the sheet resistance of the films with time and pressure were studied for the above combinations. Mobility coalescence is assumed to be responsible for the resistance increase of an uncovered copper film of initial resistance 1.9 M/. On exposure to the atmosphere, it was found that an Ag/SiO combination of initial resistance of 0.1 M/ achieved stability in the sheet resistance much quicker than a Cu/Al₂O₃ combination of initial resistance 20 M/. The fall in resistance of the Cu/Al₂O₃ composite is attributed to the formation of Al₂(OH)₆ due to the interaction of Al₂O₃ with the water vapour in atmosphere. Copper films with and without overlayers of Al₂O₃ show an abrupt increase in the sheet resistance as a function of pressure at a pressure of about 5 × 10^–2 torr with the maximum rate of change of resistance occurring at higher pressure for the higher resistance film. This indicates that the overlayer of Al₂O₃ is very porous in nature. Field effect studies were carried out on an uncovered copper film of initial resistance 10 M/ and the behaviour was found to be ohmic up to a field of 800 V cm^–1.