Variable equalisers

It is shown that the well known Bode variable equaliser is one member of a family of four networks having broadly similar properties. Two of these members, one of which appears to be new, have particular advantages for meeting requirements that are specified in the time domain.     

Simplifying the reaction system for the preparation of polyaniline nanofibers: Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media

In this study, several polyaniline samples were prepared by oxidative chemical polymerization using only aniline, (NH₄)₂S₂O₈ and HCl in aqueous media at room temperature for morphological studies by SEM (scanning electron microscopy). The results show that polyaniline nanofibers can be obtained by template-free oxidative chemical polymerization in a conventional low-pH acidic aqueous medium (pH ～ 0) at room temperature. The study indicates that it is crucial to employ a mild post-polymerization processing procedure, such as dialysis, to preserve the as-formed morphology of polyaniline nanofibers. Our study also suggests that polyaniline could adopt the nanofiber structure as its intrinsic morphology when it is synthesized in a simple oxidative chemical polymerization system consisting of only aniline, (NH₄)₂S₂O₈ and HCl in an aqueous medium at room temperature.     

Salmonella in uncooked retail meats in New Zealand

A national quantitative survey of Salmonella in five types of uncooked retail meats in New Zealand was undertaken from August 2003 to May 2005 to establish baseline proportionality data. The overall prevalence of Salmonella in 1,108 meat samples was 1.1% (95% confidence interval, 0.6 to 1.9). Low prevalences of Salmonella in each meat type were observed, with 3% (1.2 to 6.1) in chicken, 1.3% (0.3 to 3.8) in lamb and mutton, 0.5% (0 to 3.0) in unweaned veal, 0.4% (0 to 2.4) in beef, and 0% (0 to 1.6) in pork. The Salmonella serotypes isolated were Salmonella Infantis from beef; Salmonella Typhimurium PT1 from unweaned veal and chicken; Salmonella sp. 6,7:k:-, Salmonella Enteritidis PT9a, Salmonella sp. 4,5,12:-:-, Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT160 from chicken; and Salmonella sp. 4:-:2 and Salmonella Brandenburg from lamb. Four of the isolates from chicken, Salmonella sp. 4,5,12:-:- (two isolates), Salmonella sp. 4,12:-:-, and Salmonella Typhimurium PT1, were very similar phenotypically and serologically to the attenuated Salmonella vaccine strain used in MeganVacl for poultry. One lamb sample yielded a count of Salmonella Brandenburg of 4.24 most probable number (MPN)/g, while all other positive samples were <1.0 MPN/g. The results provide baseline proportionality data for Salmonella in retail uncooked meats that will contribute invaluably toward future risk assessment in light of other information, such as consumption data that can be used for risk characterization.     

Photoelectron spectroscopy of [CH(AsF5)0.1]x

We have studied pure and various stages of AsF₅-doped polyacetylenes by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), as well as X-ray-induced Auger electron spectroscopy (XAES). Spectra on the doped polymers are analyzed by comparison with corresponding spectra on the model molecules AsF₃ and AsF₅ in both the gaseous and condensed phases. The chemical composition of the dopant species can be addressed by interpretation of spectra on the basis of escape depths of the photoelectrons. The degree charge transfer from the host polymer to the dopant molecules results from an analysis of the chemical shifts of the C(1s) spectra of the doped polymers.     

Digital n-tuple Hamming comparator for weightless systems

A digital Hamming value comparator is presented which accepts two weightless tuples A and B. Combinatorial logic is used to determine three outputs: H_AB, H_A=H_B and H_A>H_B, where H_A and H_B are the Hamming values of tuples A and B, respectively     

Organic metals and semiconductors: The chemistry of polyacetylene, (CH)x,and its derivatives

Polyacetylene, (CH)_x, is the simplest organic polymer. Both the cis- and trans-forms may be prepared as silvery, flexible, polycrystalline, semiconducting films. The cis-films can be stretched to over three times their original length with partial alignment of the (CH)_x fibrils. Through chemical or electrochemical doping, the electrical conductivity of the films can be increased over twelve orders of magnitude with properties ranging from insulator (σ < 10^?10 ohm^?1 cm^?1) to semiconductor, to metal (σ > 10³ ohm^?1 cm^?1). By the use of donors or acceptors, n-type or p-type polymer, respectively, is produced. When doped, the partly aligned (CH)_x film shows marked anisotropic electrical and optical properties. The more chemically oriented aspects of (CH)_x and its derivatives and those physical studies which are most illustrative of the effects of doping will be discussed.