Non-equilibrium processes in poly(vinyl chloride) glasses vitrified at elevated pressures

The conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below T_g. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation. processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process while the exotherms are associated with the release of the frozen in stresses.     

Orientation in poly(N-vinyl carbazole) by melt extrusion

The use of poly(N-vinyl carbazole) (PVK) in photoconductive devices and the potential correlation of its unusual electrical properties with structure have resulted in several investigations concerning its morphology. Recent work with annealed solvent cast and stretched PVK films suggests that the high temperatures and stresses present during the melt extrusion of high molecular weight PVK could produce highly ordered structures. In the present work, calorimetry, thermogravimetry, infra-red dichroism, X-ray diffraction, optical microscopy, densitometry and small-angle laser light scattering measurements are used to evaluate the ordering produced by the high temperature melt extrusion of thin PVK films. The results indicate the high stress fields present during extrusion produce a highly ordered one-dimensional structure composed of closely packed, oriented chains.     

A simple optode based method for imaging O2 distribution and dynamics in tap water biofilms

A ratiometric luminescence intensity imaging approach is presented, which enables spatial O₂ measurements in biofilm reactors with transparent planar O₂ optodes. Optodes consist of an O₂ sensitive luminescent dye immobilized in a 1-10 μm thick polymeric layer on a transparent carrier, e.g. a glass window. The method is based on sequential imaging of the O₂ dependent luminescence intensity, which are subsequently normalized with luminescent intensity images recorded under anoxic conditions. We present 2-dimensional O₂ distribution images at the base of a tap water biofilm measured with the new ratiometric method and compare the results with O₂ distribution images obtained in the same biofilm reactor with luminescence lifetime imaging. Using conventional digital cameras, such simple normalized luminescence intensity imaging can yield images of 2-dimensional O₂ distributions with a high signal-to-noise ratio and spatial resolution comparable or even surpassing those obtained with expensive and complex luminescence lifetime imaging systems. The method can be applied to biofilm growth incubators allowing intermittent experimental shifts to anoxic conditions or in systems, in which the O₂ concentration is depleted during incubation.     

Using GIS to evaluate the impact of exclusion zones on the connection cost of wave energy to the electricity grid

An increase in the planning and environmental restrictions associated with wind energy has led to a growth in interest towards wave energy. However, as the connection cost of a wave energy development is a driving factor in the development's feasibility, existing wind farm cable-routing techniques used by renewable energy developers may not be satisfactory. A Geographical Information System (GIS) method is presented which optimises the cable route between a wave farm and the electricity network, while taking a range of exclusion zones, such as native vegetation, into account. The optimisation is presented for a South Australian study area, which subsequently showed that exclusion zones reduce the number of suitable locations for wave energy by almost 40%. The method presented also assesses the effect that each exclusion zone applied has upon the number of suitable locations within the study area. The analysis undertaken showed that National Parks and cliffs pose a significant limitation to the potential of a wave energy industry within South Australia. Allowing the transmission route to travel through a National Park, or traverse a cliff, resulted in an increase in the number of locations from which a connection could be made to the electricity grid for less than $10 million of 33% and 50%, respectively. Conservation Parks, Wilderness Areas and native vegetation also have an effect upon the number of suitable locations for wave energy within South Australia. The GIS methods developed may be of assistance to governments in setting appropriate marine renewable energy policy, and also in identifying existing policy which may require amending if the government wishes to pursue and support the development of wave energy.     

Chemical Evidence for Remnant cis Bonds in ‘trans’-Polyacetylene

Residual 740 cm^?1 absorption, a signature of the cis isomer, is always observed to the extent of ± 5% in ‘trans’-polyacetylene prepared thermally from the Shirawaka cis isomer, regardless of the temperature or duration of treatment. The view that a significant fraction of the ‘remnant cis bonds’ is in the form of or can be converted to cisoid single bonds is supported by the results of a Diels-Alder trapping experiment with maleic anhydride. The presence of the remnant cis linkages leads to simple rationalisation of free radical (soliton) generation and diffusion, conjugation lengths determined by Raman spectroscopy, x-ray structural evolution and electrical conductivity.     

Non-Newtonian flow and the steady-state shear compliance

A survey of viscoelastic data on amorphous polymer melts indicates that the steady-state shear compliance, J_e, of many systems can be approximated from a knowledge of their flow response. For systems with monomodel molecular weight distributions, the absolute value of the reduced complex viscosity, η^*/η₀, is found to equal 0.67 ± 0.03 at the frequency ω, where ωη₀J_e = 1. This result applies to a variety of polymer systems and to a wide range of molecular weights and distributions as long as the highest molecular weight dispersion of the distribution constitutes more than 20 weight per cent of the sample. This relationship determines J_e from non-Newtonian flow data and thus provides a consistent way to relate differently shaped reduced variable curves and to calculate compliances from characteristic times reported in the literature. The connection between some commonly used times and J_e is given. The method of calculating J_e is successfully applied to capillary measurements of melt viscosities and to characteristic times determined from steady-state shear measurements of concentrated polymer solutions.     

Volume reflection observations in bent crystals with 13 GeV/c particles

The article presents the results on the investigation of the channeling and volume reflection effects in a bent silicon crystal with 13 GeV/c positive and negative hadrons (mainly π+, p and π−) at the CERN PS T9 line. In particular, this is the first study carried out on volume reflection at this energy providing a deflection angle of 69.4 ± 4.7 μrad and an efficiency of 92.7 ± 3.3%, with positive particles.The measurements have been carried out on a bent silicon strip crystal, using a high precision tracking system based on microstrip silicon detectors; this setup is allowed to trigger on the desired beam portion and to select the incoming particle angular range. The article presents a brief introduction on the bent crystal phenomena, the experimental setup and the results of the measurements.     

Non-equilibrium processes in poly(vinyl chloride) glasses vitrified at elevated pressures

The conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below T_g. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process white the exotherms are associated withh the release of the frozen in stresses.     

Task planning and energy expended: Exploration of how goals influence performance.

[Correction Notice: An erratum for this article was reported in Vol 72(3) of Journal of Applied Psychology (see record 2008-10684-001). Table 1 on page 109 appeared with reversed labels for the high and low conditions. The corrected Table 1 is provided in the erratum.] Although many studies demonstrate the effectiveness of goal setting in organizations, it is unclear how goals actually influence performance. The present studies examined the effect of assigned goals and task information on performance, energy expended, and task planning or organizing. In Study 1, a 2&×&2 (Information&×&Goal) design was used. Subjects were 72 undergraduates working on a business simulation. In Study 2, 129 male and female workers from a service organization and a moving company responded to a survey assessing an individual's goal setting, job training, energy expended during a typical task performance, and task planning undertaken prior to performance. The results of both studies demonstrated that goal setting and task training influenced the dependent variables. In addition to influencing an individual's energy expended (effort and persistence), a specific goal led an individual to plan and organize more than did an individual given a general goal (i.e., "do your best"). The results of both studies suggest that goal setting and task-relevant information influence performance, in part, through their influence on energy expended and planning. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)