Studies in Radiation Chemistry: Application to Ozonation and Other Advanced Oxidation Processes

Advanced oxidation/reduction processes (AORPs) are an alternative water treatment that is becoming more widely utilized. Our radiation-chemistry based studies are being used to develop a fundamental understanding of AOP treatment options, and are divided into three complementary types of contaminants; disinfection by-products (DBPs), emerging pollutants of concern (EPoCs), and natural organic matter (NOM). More than 600 DBPs have been identified, and one class that appears to have severe potential adverse health effects is the halonitromethanes (HNMs). Of the nine HNMs, trichloronitromethane (chloropicrin) is the most common, with levels up to 180 nM in US drinking waters. EPoCs are of interest because of their biological activity at low concentrations in water and while the initial focus was on endocrine disruptor chemicals (EDCs) this class has now been expanded to include many other recalcitrant chemicals such as hormones, antibiotics, industrial contaminants, and health care products. Natural organic matter is one of the most common radical scavengers in natural waters and therefore may adversely affect AOPs. Our approach is to study NOM both directly and using model compounds thought to be representative of structural components of this complex material.     

The Design and Characterisation of an Optical VLSI Processor for Real Time Centroid Detection

The integration of photo-detectors onto a standard CMOS integrated circuit is presented. This device provides the optical front end for a real time centroid detection system to be used as part of a larger system for implementing a Shack-Hartmann wavefront sensor. A hardware emulation system containing a Field Programmable Gate Array is used to prototype suitable algorithms prior to IC fabrication. Data is presented on the performance of photodetectors and the ability to extract in real time a centroid coordinate.     

Anionic synthesis of poly(urethane-g-acrylonitrile)

High molecular weight poly(ester-urethane) based on diphenyl methane-4,4′-diisocyanate (MDI), PU1, and also on toluene diisocyanate (TD1), PU2, have been metallated using sodium hydride in N,N-dimethylformamide, (DMF). Metallation was confirmed by coupling samples of metallated PU1 and PU2 with methyl iodide and the use of infra-red, and n.m.r. G.p.c. studies indicated that an increase in the percentage of metallation at about 0°C in DMF caused a decrease in the stability of the soluble metallated backbone polymer and was accompanied by degradation. An increase in temperature from 0° to 100°C of a 15% metallated polyurethane sample in DMF increased the extent of degradation. At 0°C, polymers with a degree of metallation of less than 50% were relatively stable. At about 0°C in DMF, acrylonitrile was successfully grafted by anionic polymerization following metallation of PU1 and the graft copolymers were readily separated by fractionation from small amounts of the homopolymer, polyacrylonitrile. The graft copolymers were characterized by micro-analysis, solubility measurements, infra-red spectroscopy and viscometry. The vinyl monomers styrene, methyl methacrylate and vinyl acetate, and the cyclic monomers ethylene oxide, propylene oxide, N-methyl-2-pyrrolidone and hexamethylcyclotrisiloxane, could not be grafted anionically to the metallated polyurethane based on MDI.     

Novel method for amplitude measurement of signals up to microwave frequencies

The method gives very good input/output linearity down to input amplitudes of 100 mV; by using germainum diodes, this could probably be extended down to 10 mV even lower.     

Circuits for the precise synthesis of the sine function

Bipolar circuits are described for generating the sine function with high accuracy from an analogue angle input. The teachnique offers operation over any number of quadrants without switching high bandwidth and circuit simplicity. The identity of the sine to a summation of tanh terms is utilised, a proof of which is provided.     

Corrosion behaviour of a 2219 aluminium alloy treated with a chromate conversion coating exposed to a 3.5% NaCl solution

This study investigates the formation of a chromate conversion coating at Al–Cu–Fe–Mn intermetallic sites of an Al2219 alloy and the corrosion initiation at these sites in a 3.5% NaCl solution, using SEM, AES and EDX. Changes in the surface chemistry were monitored after progressive exposures to the solution up to 42 h. The coating was found to be thinner and more defective on the intermetallic. Initially, Al is dissolved and Al(OH)₃ deposited on and around the intermetallic. After 42 h of exposure, Al(OH)₃, Fe and Mn oxides and small particles of elemental Cu are deposited as corrosion products.     

Changes in fatty acid composition of sunflower (Helianthus annuus) seeds in response to time of nitrogen application,supply rates and defoliation

The fatty acid composition of sunflower (Helianthus annuus L ) seed oil was shown to respond to N supply rates and the time of N application in four glasshouse and two field experiments using five cultivars. Changes in individual fatty acids % total were smaller than those caused by differences in minimum temperatures during seed development but they were statistically significant. N supply rates before floret initiation affected the % fatty acid composition of mature seeds; the percentage of palmitic (16:0) and linoleic (18:2) acids responded positively to increases in N supply whereas % stearic (18:0) and oleic (18:1) acids responded negatively. The only fatty acid to respond to N supply rates between floret initiation and anthesis was 18:0 acid. The percentage of 18:1 responded positively and that of 18:2 acid negatively to high N supply rates after anthesis Responses to single N applications at different stages of plant development in the field confirmed these findings but results were more variable than in the glasshouse. Partial or complete defoliation at anthesis in the field caused the same changes in fatty acid composition as did a low N supply after anthesis. The results are difficult to interpret in terms of our current knowledge of lipid biosynthesis. N supply rates may affect the rate of hydrolysis of fatty acid complexes or their transport from the proplastid to the cytosolic compartment. There was no compelling support for the hypothesis that N supply rates bejore floret initiation were affecting fatty acid composition through their effects on other plant characters such as leaf mass, seed number or single seed weight.     

The spectrum of Trp- mutants isolated as 5-fluoroanthranilate-resistant clones in Saccharomyces bayanus, S. mikatae and S. paradoxus

5-Fluoroanthranilic acid (FAA)-resistant mutants were selected in homothallic diploids of three Saccharomyces species, taking care to isolate mutants of independent origin. Mutations were assigned to complementation groups by interspecific complementation with S. cerevisiae tester strains. In all three species, trp3, trp4 and trp5 mutants were recovered. trp1 mutants were also recovered if the selection was imposed on a haploid strain. Thus, FAA selection may be more generally applicable than was previously described.