The temperature dependence of passivity breakdown on a titanium alloy determined by cyclic noise thermammetry

A new sensitive electrochemical technique is presented which is designed to measure the temperature dependence of the breakdown of passivity of metal surfaces. The method, termed “cyclic noise thermammetry”, consists of scanning the temperature of an electrochemical cell linearly and cyclically between two predefined limits, whilst simultaneously measuring the current flowing from a potentiostatically maintained microelectrode. An example of the new technique is presented, which describes the effect of temperature on the nucleation of corrosion pits on the titanium-based alloy, Ti-6Al-4V, in acidic chloride solution far below the pitting potential. Results are presented over the temperature range 20-50 °C. Events due to breakdown of passivity were detected throughout the entire temperature range. These events are the nucleation of corrosion pits, although they do not propagate into stable pits under the applied experimental conditions. Results show that passivity breaks down over the entire range of temperature, at a frequency that increases with increase in temperature.     

A semantic Web services architecture

The semantic Web services initiative architecture (SWSA) committee has created a set of architectural and protocol abstractions that serve as a foundation for semantic Web service technologies. This article summarizes the committee's findings, emphasizing its review of requirements gathered from several different environments. We also identify the scope and potential requirements for a semantic Web services architecture.     

Parent psychopathology, parenting, and child internalizing problems in substance-abusing families.

A structural model accounting for child internalizing problems in substance-abusing families was tested. Parents receiving substance abuse treatment (N = 242) completed forms about children between the ages of 6 and 18 who resided in their home. The effects of parent gender, child gender, and child age were controlled. Negative parenting was examined as a mediator between parent internalizing and externalizing problems and child anxiety and affective problems using path analysis. Negative parenting mediated relations only between parent internalizing problems and child affective problems. High-positive involvement moderated relations between parent externalizing problems and child internalizing problems. Relations between parent externalizing problems and child anxiety and affective problems were significant only among families in which high-positive involvement was present. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auger spectral analysis of oxide films on brass—a quantitative method

Auger spectral analysis of the black tarnish films formed on 64/36 brass after immersion in Mattsson's solution in the pH range 7.17–7.35 gives a composition Cu₂O containing 4–5 at.%Zn(II).A method of quantitative analysis of the differential Auger spectra without the use of spectral standards is proposed. The method is tested for a spectrum of pure Cu₂O.     

Correlation between gas molecular weight, heating value and sonic speed under variable compositions of natural gas

A simulation study of likely uncertainties in molecular weight and heating value of the gas mixture as predicted from measured or calculated sonic speed. The sonic speed, molecular weight and heating value of natural gas were studied as a function of random fluctuation of the gas fractions. A method of sonic speed prediction was developed and used for over 50,000 computer-simulated variants of component concentrations in four- and five-component mixtures. Comparison of the obtained and the reference data on binary (methane–ethane) and multicomponent (Gulf Coast) gas mixtures under standard pressure and moderate temperatures indicates predictability of sonic speed on the basis of the binary virial coefficients, sonic speeds and heat capacities of the pure components. The results for two natural gas mixtures — with and without nonflammable components — are reported. Bivariate distribution and covariance elliptic zone plots are presented for three pairs of dependences of practical interest: molecular weight–sonic speed, heating value–sonic speed and heating value–molecular weight. The correlation coefficients, covariance, and regression equations are given for each pair of variance and mixture.     

Study of polymer electrolytes with grafted Au–γ-Fe2O3 nanoparticles

The work is aimed at enhancing the Li⁺ ion-conduction properties of polymer electrolytes (PE) for thin-film solid-state batteries. The research exploits novel ideas of structuring ionically conducting polymers or molecular polyether building blocks with grafted magnetic nanoparticles with the use of magnetic field, in order to enhance ionic conductivity along oriented helical PE chains. The experimental route being tested is based on the chemisorption of thiolated PEO on core–shell gold-coated maghemite. It was found that casting, under a gradient magnetic field (GMF), of concentrated PEs containing very small concentration – 0.5%(w/w) dithiol-connected Fe₂O₃/Fe₃O₄–Au nanoparticles results in enhancement of the total ionic conductivity by more than an order of magnitude.     

Constitutive activation of the m5 muscarinic receptor by a series of mutations at the extracellular end of transmembrane 6

The m5 muscarinic acetylcholine receptor was constitutively activated by a wide range of amino acid substitutions at a residue (serine 465) that is positioned at the junction of the sixth transmembrane domain and the extracellular loop. Of 13 substitutions tested, 11 produced significant increases in constitutive activity. Replacement of serine 465 with large (phenylalanine and valine) or basic residues (arginine and lysine) increased the constitutive activity of the receptor to between 55 and 110% of the maximum response of the wild-type receptor to the agonist carbachol. Other substitutions (e.g., cysteine and leucine) increased the constitutive activity to an intermediate level (30%), while small and acidic residues (glycine, aspartate, and glutamate) caused small or insignificant increases. The increase in the constitutive activity of each mutant receptor correlated with an increase in the potency of carbachol in both binding and functional assays, with the most constitutively activated receptors showing a 40-fold decrease in the EC50 of carbachol. The negative antagonist atropine bound to and reversed the constitutive activity of all mutant receptors with equal potency. These data were fitted to a two-state model of receptor function. The data are consistent with the primary effect of substitutions to serine 465 being to selectively destabilize the inactive state of the receptor, thus favoring formation of the active state in the absence of agonists. Our data strongly support this two-state model of receptor function and identify a critical role of this domain in the activation of muscarinic receptors.     

Vector potential of houseflies (Musca domestica) for Helicobacter pylori

The mode of transmission of Helicobacter pylori is unknown. Since viable bacteria have been shown to be excreted in feces from infected individuals and houseflies habitually develop and feed on excrement, we hypothesized that flies ingest and harbor H. pylori and, in turn, contaminate the human environment. This study examined the possible vector potential of houseflies (Musca domestica) for H. pylori. Caged houseflies were exposed to freshly grown H. pylori on agar plates. After a 6-h feeding period, the plates were removed and were replaced with sterile petri dishes containing a droplet of sterile brucella broth. At regular intervals, small numbers of houseflies were removed for microbiological and histological analysis, and the petri dishes were replaced with fresh sterile plates with fresh drops of brucella broth. The flies' bodies, the flies' dissected alimentary tracts, and excreta on the petri dishes were cultured for H. pylori, whose identity was confirmed by the urease, catalase, and oxidase reactions and Gram staining. In contrast to control flies, viable H. pylori could be isolated from external surfaces for up to 12 h and from gut and excreta for as long as 30 h after the initial feeding period. After 30 h other gram-negative bacteria overgrew the cultures of samples from all locations tested, rendering the selective culture of H. pylori colonies impossible. Histological analysis revealed Helicobacter-like organisms in the gut lumen and attached to intestinal epithelial cells. We conclude that houseflies can harbor viable H. pylori on their bodies and in their intestinal tracts. They are also able to disseminate viable H. pylori in excreta, and they may therefore present a significant reservoir and be a vector in the transmission of H. pylori.