Photostability of polyetherurethaneureas

Polyetherurethaneureas (PEUUs) were synthesised from polyethylene-glycols (PEGs) of molecular weight 400, 600 and 1000, 4,4′-diphenylmethanediisocyanate (MDI) and aliphatic diamine chain extenders, 1,3-propanediamine (PDA) and 1,6-hexanediamine (HDA). Polymer films were irradiated with 365 nm light at 293 K and the effects of polyether soft segment length and urea hard segment on photo-oxidative stability were studied by following the variation in weight-average molecular weight (M _w), gel formation and stress-strain properties. Changes in ultraviolet and infrared spectroscopy were monitored on photo-oxidation and hydroperoxide content determined. The soft segment length was increased by increasing the molecular weight of PEG from 400 to 1000 and hard segment structure was changed by variation of diamine. It was noted that the structure of urea and polyether soft segment length plays an important role in photostability of PEUUs. PDA chain extended PEUUs were more stable than HDA chain extended PEUUs.     

Sublethal effects of an organophosphate insecticide on the European eel, Anguilla anguilla

Recent research has found that family caregivers do not discuss their caregiving in terms of tasks but instead describe their care as shaped by concerns, commitments and goals. The purpose of this paper is to challenge the ways in which nurses approach the family caregiving process and to explore possibilities for evolving nursing knowledge by questioning existing practice in the light of developing insight into the ways in which being a family caregiver is meaningful. A critique of the philosophical orientations of rationalism and empiricism provides a platform to discuss the merits of a Heideggerian phenomenological approach in assisting nurses to better understand family caring experience. Such critique serves to support the notion of displacing the traditional scientific view as the prime means of disclosing truth, acknowledging alternative ways of knowing.     

Organizational computer security policy: the reality

Computer security issues are normally addressed from a technical perspective. Increasingly, however, organizations and computer specialists are coming to realise that applying more technology as the basis of an answer to a problem that derives from technology cannot, in the long term, be a viable solution. This paper shows how it is important that other considerations are taken into account, such as business and management requirements, and practical user issues. In order for this approach to make any progress, we must first establish the current situation in ordinary organizations. This paper describes key results from research carried out to determine the status of computer security in organizations today.     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed     

Physical and chemical characterization of thermosoftened bases for molten filled hard gelatin capsule formulations

Dynafill, Dynasan-114, Lutrol-F68, PEG-10000 and PEG-20000 have been examined as potential bases for the preparation of fusion formed solid dispersions for molten filling into hard gelatin capsules. Investigations included, an examination of thermal effects on crystal structure by DSC and XRD, a theological study to evaluate capsule filling characteristics, dissolution studies on drug/base formulations, chemical analysis for free fatty acid impurities in Dynafill and Dynasan-114, and detailed studies on selected drug/base formulations. PEG-20000 and Dynasan-114 were not examined in detail, after preliminary investigations had shown high viscosity and poor filling characteristics for PEG-20000 and poor dissolution characteristics for Dynasan-114. Dynafill provided good release profiles when formulated with a variety of model drugs (Acetohexamide, Ibuprofen, Indomethacin, Quinidine sulphate and Theophylline). Results from hot stage photomicrography supported by DSC and XRD were used to construct a phase diagram of the Ibuprofen/Lutrol-F68 system. The evidence from the phase diagram indicated the formulation of a simple eutectic system with no solid solubility and a eutectic composition at approximately 35% w/w Ibuprofen.     

Use of electric power in glass melting

The advantages and disadvantages of electric furnaces for melting frits and enamels and glasses for special applications were examined. It was shown that low-efficiency electric furnaces are more economical than furnaces heated by organic fuel. The main advantage of electric furnaces is the reduction in harmful emissions.Translated from Steklo i Keramika, Nos. 3–4, pp. 8–10, March–April, 1994.     

Effects of internal scattering on X-ray microtomography imagereconstruction

A computer simulation is used to study the problem of internal scattering for targets that are imaged using X-ray microtomography. A strategy is outlined for selecting X-ray energy and image resolution based on properties of the material being imaged. The X-ray scanning process is simulated by applying a Monte Carlo technique to a modeled target that emulates the material properties of a microelectronic device. The X-ray photons are subject to photoelectric absorption, Rayleigh scattering, and Compton scattering. The simulation applies a method of high-resolution image reconstruction based on discrete Fourier transforms. Examples of reconstructed images that have 0.5-μm spatial resolution are shown for images of simulated lead and aluminum targets