Effect of thermal hysteresis on the gas permeation properties of 6FDA‐based polyimides

The effect of thermal hysteresis on the polymer chain packing and permeation properties of two 6FDA‐based polyimide isomers was investigated. Thermal quenching resulted in a small increase in the fractional free volume of the polyimides with respect to the samples that had been annealed. Quenching from above the glass‐transition temperature also resulted in larger increases in the permeabilities for both 6FDA–6FmDA and 6FDA–6FpDA with respect to annealed samples. Meta‐connected 6FDA–6FmDA exhibited a larger increase in the permeability after quenching than the para‐connected isomer, 6FDA–6FpDA. This larger increase in the permeability for 6FDA–6FmDA may have been due to differences in the effects of the increases in the free volume on the intersegmental resistance to chain motions. Although physical aging over a 3‐month period resulted in a reduction in the permeability of quenched samples of 6FDA–6FpDA, the quenched samples maintained higher permeabilities than the annealed samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1174–1182, 2004     

Autoxidation of fatty materials in emulsion. II. Factors affecting the histidine-catalyzed autoxidation of emulsified methyl linoleate

Several factors which affect autoxidation of methyl linoleate in emulsion have been examined. Data are presented which indicate: 1) In the presence of histidine, the ionic (anionic) emulsifiers examined promote autoxidation of emulsified methyl linoleate, but nonionic emulsifiers do not. 2) The concentration of an emulsifier affects the rate of oxygen absorption. 3) Inorganic salts (0.1 M or less) such as sodium chloride, sodium acetate and sodium sulfate affect oxygen absorption of emulsified methyl linoleate prepared with either ionic or nonionic emulsifiers. In histidine-catalyzed autoxidation there is a suppressing effect in the case of the ionic and a promotional effect in the case of the nonionic. In uncatalyzed autoxidation, these salts have a promotional effect in ionic emulsions and none in nonionic emulsions. 4) Sodium phosphate buffers completely suppress autoxidation due to histidine catalysis, but do not suppress the normal uncatalyzed autoxidation of emulsified methyl linoleate. 5) The pro-oxidative effects of histidine and histidine-metal ion complexes on emulsified unsaturated materials is not limited to polyolefins but also includes mono-olefinic compounds. Presented at the AOCS meeting in Toronto, October, 1962. E. Utiliz. Res. and Dev. Div., ARS, USDA.     

Metalloorganic solution deposition of ferroelectric PZT films

The metallo-organic solution deposition (MOSD or sol-gel) technique can be used for preparing lead zirconate titanate (PZT) ceramics with a wide range of compositions and crystal structures for electrooptical applications. Film morphology is affected by the stoichiometry of the film, hydrolysis and polymerization of the sol-gel solution, and thermal treatment of the deposited material. The lattice parameter decreases with the amount of titanium in the PZT, in agreement with ceramic data. A slight initial excess of lead in the coating solution is found to improve film morphology. Unlike traditional powder ceramic processing techniques, MOSD permits the growth of small uniform grains that are conducive to achieving consistent electronic and optical properties. Results show that the properties of films prepared by the MOSD process can be tailored to meet the needs of device applications.     

Packing products for customers: an ergonomics evaluation of three supermarket checkouts

The introduction of laser scanners at supermarket checkout areas has resulted in previous ergonomics studies focusing specifically on the scanning process and associated cumulative trauma disorders in the hands and arms. Few studies have evaluated the increased musculoskeletal load and exertion of checkout staff when they are also expected to pack the products into bags for the customers. This paper describes an ergonomics evaluation of three different designs of checkout workstation, which require the operator to stand when they scan the products, pack them into plastic bags and transfer the packed bags to the customer. Musculoskeletal load and exertion associated with the different checkouts were measured using OWAS, heart rate recordings and ratings of perceived exertion. In addition, subjective rankings of the workstations were obtained and the productivity associated with each design examined as part of the evaluation. Some of the variables measured showed significant differences in postural load between the workstations. The results of the evaluation formed the basis of recommendations for an improved workstation design. Some of the suggestions made to reduce postural load and increase productivity include positioning the weigh scale to the side and the bag frame beneath the scanner.     

A demographic overview of the ageing of First World populations

The ageing of the UK population, and other similar populations, is now well advanced. The process is probably irreversible and may well be repeated across the globe. It is reasonable to assume that 40-50% of the UK adult population will be over 50 for the foreseeable future, and that the number of people in their 80s and 90s will continue to increase for some decades. Growing awareness of this may well lead to a reinterpretation of the life course with consequent changes in lifestyle and activity. In the past, the main focus of design, both of products and environments, has been the working population. There is clearly an urgent need to direct attention to older sectors of the population, including: fit and active people in retirement; affluent groups in old age; single households; women, who form a majority of the over 50s; and other groups which have been neglected in many work studies.     

Development and use of a two-dimensional interferometer to measure mass flow from a multi-shell Z-pinch gas puff

For gas puff Z-pinches, the K-shell x-ray yield is maximized with the use of a multi-shell nozzle. Optimization of the yield, verification of hydrodynamic models of the nozzle flows, and plausible MHD code modeling of the implosions require data on the radial and axial (R,Z) distribution of mass in the nozzle's flow field. Interferometry is a well-established technique for acquiring such data. We describe the development and use of a two-dimensional interferometer with emphasis on the required data reduction methods. We also show that the instrument can derive the flow from each individual nozzle in a multi-shell system.     

The Role of Σ9 Boundaries in Grain Boundary Engineering

In a grain-boundary-engineered (GBE) microstructure, Σ9 boundaries are the second most abundant boundary type. This article presents data showing that, in GBE copper, most Σ9s were special. Σ9 boundaries are also a geometrically necessary component of a GBE microstructure. It is suggested that there are competing requirements for Σ9s; during iterative GBE processing, they are required to be mobile, whereas afterward, it is desirable that they are special boundaries.