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Optical polarimetry results are presented for four spiral galaxies: NGC 5194 (M51), NGC 1068, NGC 4565 and NGC 4594 (Ml04). M51 and NGC 1068 show spiral polar isation patterns which are interpreted as indicating a spiral magnetic field in each case. NGC 4565 and M104 show polar isations in their dust lanes which are parallel to their galactic planes, and which are interpreted in terms of a magnetic field in the plane of each. It is hypothesised that the observed magnetic fields may be linked to galactic shocks. A discussion of the origin of galactic magnetic fields concludes that there is no evidence which necessitates a primordial magnetic field.

This thesis is concerned with the effect of static and oscillatory magnetic fields on the yield of radical recombination reactions and the proposal that such effects may constitute a possible mechanism for the interaction of environmental electromagnetic fields with biological systems. A brief overview of research pertaining to the biological effects of environmental electromagnetic fields is presented. Next, the concept of the radical pair is introduced and the theory of its behaviour in solution is examined in order to illustrate the mechanism by which magnetic fields can affect its probability of separation. Three different experimental systems involving the attack of free-radicals on DNA are presented. The extent of DNA damage is assayed in the presence and absence of a static magnetic field. These systems involve the killing of yeast cells as observed by the growth of subsequent colonies, direct observation of strand breaks to DNA, in vitro, by gel electrophoresis and the direct observation of intra- nuclear DNA damage by microgel analysis. In all systems, magnetic field effects are observed but are difficult to reproduce consistently. The design of novel apparatus for the observation of resonant radiofrequency effects is described. The application of a 30-40 MHz oscillating magnetic field is found to alter the yield of exciplex fluorescence in the photoreaction of anthracene-d₁₀ and 1,3-dicyanobenzene. The effect is interpreted in terms of a change in the efficiency of singlet andleftrightarrow; triplet interconversion in the {anthracene cation - DCB anion} radical pair when the oscillating field is in resonance with hyperfine splittings in the DCB anion radical.

There is increasing public concern over the possible harmful effects of extra-low-frequency (ELF) electromagnetic (em) fields. A variety of harmful effects have been linked with em field exposure, for example depression and suicide, carcinogenesis, birth defects, and spontaneous abortion. The epidemiological evidence, especially the more recent studies, suggests that there may be a small increased risk of childhood cancers in those living near overhead power lines. However laboratory evidence to date does not support this link. An epidemiological correlation does not necessarily imply a causal relationship: to confirm such a relationship, biological and laboratory evidence is required. This work studies the magnitude of human exposure to ELF magnetic fields from overhead power lines and visual display units (VDUs) and also investigates possible health effects at the microscopic level through cell culture experiments. From the epidemiological evidence, an effect threshold of approximately 300 nT was estimated. Detailed magnetic field distributions were measured round a variety of visual display units and only a very few emitted magnetic fields even close to the 300 nT threshold. Following an in-depth case study of a VDU operator who suffered from a combination of symptoms including eyestrain and headaches, a study of the health of nearly 200 office workers and VDU users was set up. The aims of the study were to investigate the range and severity of symptoms suffered by VDU users, to investigate possible causes and to study response to VDU work at an individual level. It was found that those working between 10 and 30 hours per week at a VDU were more likely to suffer symptoms of ill health. In contrast, those working more than 30 hours per week at a VDU were not more likely to suffer symptoms when compared with a control group of those working less than 10 hours per week at a VDU. In particular, increased reporting of eye problems and fatigue were most strongly associated with VDU work.

A thesis submitted to the faculty of science, University of the Witwatersrand, Johannesburg, In fulfilment of the requirements for the Degree of Doctor of Philosophy Johannesburg 1990 / The processing of near-earth satellite magnetometer data towards extracting an improved lithosphere anomaly map is addressed. The two aspects of the data reduction route where data quality has been compromised most by contemporary methods is researched, namely;[Abbreviated Abstract. Open document to view full version] / GR2017