The synthesis and application of novel profluorescent nitroxides as probes for polymer degradation

This PhD project has expanded the knowledge in the area of profluorescent nitroxides with regard to the synthesis and characterisations of novel profluorescent nitroxide probes as well as physical characterisation of the probe molecules in various polymer/physical environments. The synthesis of the first example of an azaphenalene-based fused aromatic nitroxide TMAO, [1,1,3,3-tetramethyl-2,3-dihydro-2-azaphenalen-2-yloxyl, was described. This novel nitroxide possesses some of the structural rigidity of the isoindoline class of nitroxides, as well as some properties akin to TEMPO nitroxides. Additionally, the integral aromatic ring imparts fluorescence that is switched on by radical scavenging reactions of the nitroxide, which makes it a sensitive probe for polymer degradation. In addition to the parent TMAO, 5 other azaphenalene derivatives were successfully synthesised. This new class of nitroxide was expected to have interesting redox properties when the structure was investigated by high-level ab initio molecular orbitals theory. This was expected to have implications with biological relevance as the calculated redox potentials for the azaphenalene ring class would make them potent antioxidant compounds. The redox potentials of 25 cyclic nitroxides from four different structural classes (pyrroline, piperidine, isoindoline and azaphenalene) were determined by cyclic voltammetry in acetonitrile. It was shown that potentials related to the one electron processes of the nitroxide were influenced by the type of ring system, ring substituents or groups surrounding the moiety. Favourable comparisons were found between theoretical and experimental potentials for pyrroline, piperidine and isoindoline ring classes. Substitution of these ring classes, were correctly calculated to have a small yet predictable effect on the potentials. The redox potentials of the azaphenalene ring class were underestimated by the calculations in all cases by at least a factor of two. This is believed to be due to another process influencing the redox potentials of the azaphenalene ring class which is not taken into account by the theoretical model. It was also possible to demonstrate the use of both azaphenalene and isoindoline nitroxides as additives for monitoring radical mediated damage that occurs in polypropylene as well as in more commercially relevant polyester resins. Polymer sample doped with nitroxide were exposed to both thermo-and photo-oxidative conditions with all nitroxides showing a protective effect. It was found that isoindoline nitroxides were able to indicate radical formation in polypropylene aged at elevated temperatures via fluorescence build-up. The azaphenalene nitroxide TMAO showed no such build-up of fluorescence. This was believed to be due to the more labile bond between the nitroxide and macromolecule and the protection may occur through a classical Denisov cycle, as is expected for commercially available HAS units. Finally, A new profluorescent dinitroxide, BTMIOA (9,10-bis(1,1,3,3- tetramethylisoindolin-2-yloxyl-5-yl)anthracene), was synthesised and shown to be a powerful probe for detecting changes during the initial stages of thermo-oxidative degradation of polypropylene. This probe, which contains a 9,10-diphenylanthracene core linked to two nitroxides, possesses strongly suppressed fluorescence due to quenching by the two nitroxide groups. This molecule also showed the greatest protective effect on thermo-oxidativly aged polypropylene. Most importantly, BTMIOA was found to be a valuable tool for imaging and mapping free-radical generation in polypropylene using fluorescence microscopy.

An inverse time admittance relay for fault detection in distribution networks containing DGs

Isolation of a faulted segment, from either side of a fault, in a radial feeder that has several converter interfaced DGs is a challenging task when current sensing protective devices are employed. The protective device, even if it senses a downstream fault, may not operate if fault current level is low due to the current limiting operation of converters. In this paper, a new inverse type relay is introduced based on line admittance measurement to protect a distribution network, which has several converter interfaced DGs. The basic operation of this relay, its grading and reach settings are explained. Moreover a method is proposed to compensate the fault resistance such that the relay operation under this condition is reliable. Then designed relay performances are evaluated in a radial distribution network. The results are validated through PSCAD/EMTDC simulation and MATLAB calculations.

Research productivity levels of Chinese TEFL academics

Since China’s Economic Reform and its Open Door Policy, China has entered a new era of education (Adamson, 2002; Hu, 2005a). English has gained status as a language for international relations (Graddol, 1997) and international trade (Qu, 2007). Hence, in 2001, China’s Ministry of Education (MOE) required universities to offer 5-10% of their course units in English, particularly in the fields of information technology, biotechnology, finance and law (Jen, 2001; MOE, 2001). However, “the upgrading of national English proficiency, then, is predicted largely on the professional competence of the teaching force” (Hu, 2005b, p. 655). For TEFL academics, one component of this competence is the capacity to conduct research (Day, 1991; Shu, 2002). Indeed, research productivity has become essential for university success, and academics’ employment and promotional prospects. This study aims to investigate 182 Chinese TEFL academics’ research outputs across three Chinese higher education institutions through the research question: What are the research productivity levels of Chinese TEFL academics? A survey instrument was devised to gather TEFL academics’ calculations of research productivity and, in particular, the quality and quantity of research outputs over a five-year period (2004-2008). Descriptive statistics through SPSS were used to analyse data across research output fields (e.g., journal articles, conference papers). Academic status varied (n=182; teaching assistants 23.6%, lecturers 47.3%, associate professors 22.5%, and professors 6.6%) as did years of teaching (1-5 years 27.4%, 6-10 years 24.7%, 11-15 18.1%, 16-20 years 13.7%, > 21 years 15.9%). Results (n=182, male=27%, females=73%) indicated 18% had not produced any research in the five-year period. Indeed, more than 70% had produced no research in all categories except non-core journal articles and provincial projects. An overwhelming majority of TEFL academics had zero productivity in 10 of the 12 categories. Nevertheless, there were highly-productive TEFL academics, who had produced five or more pieces of research across the 12 categories. In addition, there was not much difference between sole and co-authored research outputs, except non-core journal articles where sole authored work was 20% higher than co-authored work. China’s desire for international competitiveness in education will require measures that facilitate higher levels of research productivity. These measures must include professional development, support and mentoring programs, and employment of personnel who can guide these processes. Research performance is an outcome, hence there is a need to understand Chinese TEFL academics’ perceptions about research, and experiences that may hinder and facilitate higher research productivity.

Synthesis of a heparan sulfate mimetic disaccharide with a conformationally locked residue from a common intermediate

A simple mimetic of a heparan sulfate disaccharide sequence that binds to the growth factors FGF-1 and FGF-2 was synthesized by coupling a 2-azido-2-deoxy-D-glucosyl trichloroacetimidate donor with a 1,6-anhydro-2-azido-2-deoxy--D-glucose acceptor. Both the donor and acceptor were obtained from a common intermediate readily obtained from D-glucal. Molecular docking calculations showed that the predicted locations of the disaccharide sulfo groups in the binding site of FGF-1 and FGF-2 are similar to the positions observed for co-crystallized heparin-derived oligosaccharides obtained from published crystal structures.

Calculation of habitable dwelling surfaces : an empirical analysis for the agglomerations of Munich and Sydney

In many countries the calculation of habitable dwelling surface is characterised by a chaotic variety of calculation variants hardly comprehensible for the end user - sometimes not even reproducible for the expert. Therefore dossiers were analysed on the basis of a random choice in order to determine the method according to which the habitable dwelling surface was measured and to find out wether customers can scrutinize the calculations. The paper compares Sydney and Munich, where in both cases property prices are situated at the high end of the market

End-winding effect on shalft voltage in AC generators

This paper presents effects of end-winding on shaft voltage in AC generators. A variety of design parameters have been considered to calculate the parasitic capacitive couplings in the machine structure with Finite Elements simulations and mathematical calculations. End-winding capacitances have also been calculated to have a precise estimation of shaft voltage and its relationship with design parameters in AC generators.