Optimization of a universal matchbox on an ultrasonic vibrating system

The main scope of the article is to investigate the effect of ferrite cores gap in a universal matchbox on an ultrasonic vibrating system. A gapped transformer mechanism in a universal matchbox has been thoroughly studied. Characteristics of an ultrasonic vibrating system have been recorded such as mechanical vibrations, inductance, resonant frequencies, current and voltage levels as the gap of ferrite cores gradually increases. In addition, the phase difference between the supplied voltage and the current is also computed and displayed in a Lissajous curve in order to determine the optimal gap between two ferrite cores in the universal matchbox. Explanations supplement the experiment results.     

New Fe(III)-mediated radical cascade reactions of cyclopropyl silyl ethers

[reaction: see text] Fe(III)-mediated ring opening of cyclopropyl ethers bearing a phenyl-substituted butenyl side chain leads to the generation of beta-keto radicals that undergo 5-exo cyclization followed by a novel cascade sequence resulting in the formation of tricyclic ethers.     

Considerations involved with the use of semipermeable membrane devices for monitoring environmental contaminants

Semipermeable membrane devices (SPMDs) are used with increasing frequency, and throughout the world as samplers of organic contaminants. The devices can be used to detect a variety of lipophilic chemicals in water, sediment/soil, and air. SPMDs are designed to sample nonpolar, hydrophobic chemicals. The maximum concentration factor achievable for a particular chemical is proportional to its octanol-water partition coefficient. Techniques used for cleanup of SPMD extracts for targeted analytes and for general screening by full-scan mass spectrometry do not differ greatly from techniques used for extracts of other matrices. However, SPMD extracts contain potential interferences that are specific to the membrane-lipid matrix. Procedures have been developed or modified to alleviate these potential interferences. The SPMD approach has been demonstrated to be applicable to sequestering and analyzing a wide array of environmental contaminants including organochlorine pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polychlorinated dioxins and dibenzofurans, selected organophosphate pesticides and pyrethroid insecticides, and other nonpolar organic chemicals. We present herein an overview of effective procedural steps for analyzing exposed SPMDs for trace to ultra-trace levels of contaminants sequestered from environmental matrices.     

Enhanced electrostatic modulation of ionic diffusion through carbon nanotube membranes by diazonium grafting chemistry

A membrane structure consisting of an aligned array of open ended carbon nanotubes (7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium-based electrochemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption–desorption and interfacial capacitance measurements indicate 5–6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1 M electrolyte solution consistent with the membrane pore geometry and increased functional density.     

Synthetic,Sodium-Ion-Conducting Tris(Macrocycle) Channels that Function in a Phospholipid Bilayer Membrane: An Overview

Abstract

A family of tris(macrocyclic) compounds of the form sidearm<N18N>C_n<N18N>C_n<N18N>sidearm, has been prepared, characterized chemically, and assayed by dynamic ²³Na-NMR for the ability to transport sodium cations in a mixed phosphatidylglycerol/phosphatidylcholine vesicle system. A number of control experiments have been conducted that reinforce the hypothesis that cation transport occurs by a channel mechanism. The tris(macrocycle) channels proved to be functional at a level of 25–50% of that found for the natural pentadecapeptide channel gramicidin. Fluorescence data confirm the expected position of the channel within the bilayer.     

Total synthesis of (±)-hibiscone C

A total synthesis of (±)-hibiscone C, one member of the furanosteroid family of natural products that also includes viridin and wortmannin, is reported. Two new pathways for formation of the key diacyl furan subunit are described.     

Charge regulation enables anionic hydroxypropyl guar-borate adsorption onto anionic and cationic polystyrene latex

Reported are adsorption isotherms for guar and hydroxypropyl guar (HPG), with and without the presence of borate ions, onto surfactant free anionic polystyrene latex. Guar and HPG formed adsorbed monolayers on the hydrophobic latex. The presence of borate ions converted the nonionic guar and HPG into an anionic polyelectrolyte. However, there was no measurable influence of bound borate ions on the adsorption of guar or HPG onto anionic, hydrophobic latex. To underscore the unusual behavior of HPG-borate, a sample of HPG was oxidized to introduce carboxyl groups, and the adsorption of the carboxylated HPG onto anionic polystyrene was measured. Unlike HPG-borate, oxidized HPG did not adsorb onto negative polystyrene latex at neutral pH because of electrostatic repulsion. To explain the adsorption of negative HPG-borate onto negative latex, we proposed that as HPG-borate segments approach the latex surface, the negative electrostatic potential near the latex surface induces the detachment of the labile borate groups from HPG.     

Does the Balanced Scorecard make a difference to the strategy development process?

A great number of strategy tools are being taught in strategic management modules. These tools are available to managers for use in facilitating strategic decision making and enhancing the strategy development process in their organisations. A number of studies have been published examining which are the most popular tools; however there is little empirical evidence on how their utilisation influences the strategy process. This paper is based on a large scale international survey on the strategy development process, and seeks to examine the impact of a particular strategy tool, the Balanced Scorecard (BSC), upon the strategy process. Recently, it has been suggested that as a strategy tool, the BSC can influence all elements of the strategy process. The results of this study indicate that although there are significant differences in some elements of the strategy process between the organisations that have implemented the BSC and those that have not, the impact is not comprehensive.     

Electrochemical mapping reveals direct correlation between heterogeneous electron-transfer kinetics and local density of states in diamond electrodes

Conducting carbon materials: a multi-microscopy approach shows that local heterogeneous electron-transfer rates at conducting diamond electrodes correlate with the local density of electronic states. This model of electroactivity is of considerable value for the rational design of conducting diamond electrochemical technologies, and also provides key general insights on electrode structure controls in electrochemical kinetics.