Fully submerged composite cryogenic testing

New methods for marine salvage and decommissioning of structures in the open sea are continually being sought in order to improve control and lower operational costs [1]. The concept design of a lightweight, cryogenic, marine, heavy lift, buoyancy system has been investigated [2]. The objective is to be able to raise or lower high mass objects controlled solely from a surface support vessel. The overall design concept and associated system development issues have been discussed previously. A number of the sub-systems in one complete buoyancy system involve considerable design and development, these include: structural design of the buoyancy chamber, mechanical systems to control and connection to the lift device, the cryogenic system itself and overall process control systems. The main area of concern in the design process is the composite cryogenic Dewar. This is required to operate not only at temperatures as low as -196oC but also to withstand pressure differences exceeding 35bar. As such the composite materials have to perform in a very aggressive environment. This work details a method for fully submersed composite cryogenic testing in order to qualify the materials for use in the Dewar of the buoyancy system

Learning together: Lessons from a collaborative curriculum design project

Based on an action research project implemented at two South African universities, we argue that content and language integration (ICL) collaborative partnerships benefit not only from collaboration between language and content specialists, but in addition, from collaboration between language specialists, general education specialists and content specialists from a variety of disciplines. However, as we illustrate below, these benefits may be accompanied by substantial challenges. We make a further claim, for the value of a transformative approach towards collaboration for content and language integration, in which the teacher/researchers engage in their practice in a critical and reflexive manner, and by so doing, foster their own deep learning, as well as the deep learning of the students

Role of the heat shock transcription factor, Hsf1, in a major fungal pathogen that is obligately associated with warm-blooded animals

Peer reviewedPublisher PD

Modulation of cytochrome oxidase kinetics by indirect antibody action

AbstractPolyclonal antibodies raised against isolated subunit V from beef heart cytochrome oxidase or against the intact enzyme increase its apparent affinity for the substrate cytochrome c at the high-affinity site while diminishing the turnover at that site. At the low-affinity site the major action of both types of antibody is to reduce the apparent affinity for cytochrome c. At high ionic strengths the kinetic effect of anti-subunit V is very small although it still binds to the enzyme. The results are interpreted in terms of a model for the enzyme in which antibodies can modulate cytochrome oxidase kinetics by affecting the binding of cytochrome c, even if the antibody-binding site is on a subunit not directly involved in substrate binding

A mechanism for NADPH inhibition of catalase compound II formation

AbstractCatalase-bound NADPH both prevents and reverses the accumulation of inactive bovine liver catalase peroxide compound II generated by ‘endogenous’ donors under conditions of steady H2O2 formation without reacting rapidly with either compound I or compound II. It thus differs both from classical 2-electron donors of the ethanol type, and from 1-electron donors of the ferrocyanide/phenol type. NADPH also inhibits compound II formation induced by the exogenous one-electron donor ferrocyanide. A catalase reaction scheme is proposed in which the initial formation of compound II from compound I involves production of a neighbouring radical species. NADPH blocks the final formation of stable compound II by reacting as a 2-electron donor to compound II and to this free radical. The proposed behaviour resembles that of labile free radicals formed in cytochrome c peroxidase and myoglobin. Such radical migration patterns within haem enzymes are increasingly common motifs

Microwaves enable activated plasma figuring for ultra-precision fabrication of optics

Activated plasma figuring using microwaves aims at providing highly efficient activated energy beams for rapid fabrication of optics. The chemical nature of this type of energy beam leads to targeting silicon-based materials. Furthermore this technology is proposed to address the needs of ultra-precision optical components. In this paper, we present a novel ADTEC microwavegenerated plasma torch design which is operated at atmospheric pressure. In this study, the plasma torch is fed with either argon or helium carrier gas. However this novel design for Plasma Figuring is targeted at local surface correction of crystal quartz which is a material of great interest for optical systems, such as acousto-optic devices. Also this novel design is targeted at reducing midspatial frequency errors such as waviness, ripple errors and residual sub-aperture tool footprints. These are responsible for the scattering of light at small angles, resulting in optical hazing effects, photonic energy loss and pixel cross-talk. Also the results of a preliminary investigation using Optical Emission Spectroscopy (OES) are reported and discussed. These results show the operat ing range when the main processing parameters are changed: microwave forward power values, gas flow rates and the types of gasses

Two phase detonation studies

An experimental study of the passage of a shock wave over a burning fuel drop is described. This includes high speed framing photographs of the interaction taken at 500,000 frames per second. A theoretical prediction of the ignition of a fuel drop by a shock wave is presented and the results compared with earlier experimental work. Experimental attempts to generate a detonation in a liquid fuel drop (kerosene)-liquid oxidizer drop (hydrogen peroxide)-inert gas-environment are described. An appendix is included which gives the analytical prediction of power requirements for the drop generator to produce certain size drops at a certain mass rate. A bibliography is also included which lists all of the publications resulting from this research grant