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    The structural and functional effects of electromagnetic fields on the plasma membrane of Vicia faba, the broad bean : a thesis dissertation presented in partial fulfilment of the requirements for the degree of Master of Science, Plant Biology at Massey University
    (Massey University, 1995) Stange, Bernadette Cathy
    Vicia faba (broad bean) root-tip cells were exposed to electromagnetic fields at 50 and 60 Hz, square and sine waveforms and 0.1, 1, and 10 gauss. Levels of [³H]-alanine uptake and ion efflux were measured at these parameters and compared to unexposed control seedlings. The ultrastructure of cortical cells from the zone of elongation exposed to a 1 gauss, 50 hertz, squarewave field was studied under the electron microscope. In the first uptake trials alanine uptake via ATP dependant membrane carriers was stimulated by square waveform fields, but inhibited by 50 Hz fields. In the replicate trials alanine uptake was inhibited by both 50 and 60 hertz, square and sine waveform fields. The different response between trials was attributed to aging of the seeds used, owing to a six month chemical supply delay. This apparent aging of the seeds appeared to increase seedling susceptibility to modification by electromagnetic fields. The ion efflux trials saw no significant change in the pattern of ion efflux (as measured by conductivity) from exposed cells, although there was a significant decrease in hydrogen ion efflux at 0.1 and 1 gauss. A secondary inhibition effect on hydrogen ion efflux occurred with exposure to sine and square waveforms, but only in the presence of 0.1 and 1 gauss field amplitudes. The reduction in hydrogen efflux was most probably due to the inhibition of an active ATP dependent membrane carrier responsible for maintaining the transmembrane electrochemical gradient. Under the electron microscope exposed cortex cells from the zone of elongation had significantly more pinocytotic vesicles than the controls. These vesicles were believed to be involved in bulk uptake of extracellular media, which may permit exposed cells to expand more rapidly than the controls. Thus the functioning of three separate membrane transport systems were shown to be susceptible to functional modification, at least in the short term, by extremely low frequency electromagnetic fields. This introduces the potential for an enormous array of downstream effects to echo through-out the organism via signal transduction pathways.
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    Effects of 50 Hz intermittent magnetic field exposure on human performance and cardiovascular response : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Psychology at Massey University
    (Massey University, 1995) Whittington, Craig J
    One hundred subjects (aged 18-48 years) were exposed and sham exposed to a 100 μT intermittent magnetic field, modulated sinusoidally at 50 Hz. To examine the effect of field exposure on performance, a two alternative forced-choice duration discrimination task with 3 levels of difficulty was used. Cardiovascular response was also assessed using measures of blood pressure and pulse rate. A number of factors were incorporated into the experiment with the aim of increasing sensitivity above that of past research. In particular, the experiment's statistical power was increased using several techniques (e.g., large sample size and a repeated measures design). Also, intermittent exposure was used instead of continuous, and the conditions of exposure were optimised using field parameters specified by parametric resonance theory. To measure performance during exposure, the subjects' task on each of 150 trials was to decide which of two sequentially presented light flashes had the longer duration. The base duration was 50 ms and the alternative durations were 65, 100, or 125 ms. Both reaction time and percentage of correct responses were recorded for each subject. Total exposure time lasted approximately 9 minutes. Blood pressure and pulse were measured for a minimum of 5 minutes, both before and after exposure and sham exposure. The results showed that compared to sham exposure, real exposure decreased reaction time on the hardest level of the performance task. No reliable field-related effects were observed with percentage of correct decisions or the measures of cardiovascular response. The difficulty of making comparisons with similar studies was discussed along with the need for future magnetic field research to be designed with maximum experimental sensitivity in mind given that small effects are likely.
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    Characterization of extremely low-frequency electromagnetic sources in conducting media : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University
    (Massey University, 2001) Rumball, Edward Ian
    Physical fields whose sources exist within maritime vessels are of concern to ship-designers and military planners. Among the fields of most significance which have been studied intensively, are those of magnetic, acoustic and pressure sources. New technological developments now require analyses of the underwater electric and magnetic fields of onboard, extremely low-frequency electromagnetic sources. This study investigated methods by which the electromagnetic sources of maritime vessels may be characterised during normal operations in typical coastal environments. It focused on situations where both the sources and field measurement points were located in a common seawater volume. At the electromagnetic frequencies of interest such a medium acts as a thin conducting layer with significant levels of wave reflection and refraction at the media boundaries. To enhance propagation models of the electromagnetic fields over short ranges, the initial investigations aimed to characterise key parameters of the conducting media in shallow-water conditions Conductivity values of seawater can be readily established by conventional methods. However, in the case of the seabed media, direct conductivity measurements are usually highly variable along horizontal and vertical sections due to aeons of land erosion, and the long-term effects of inshore waves and currents. Procedures are described which show how electromagnetic theory and indirect measurement techniques may be used to infer the characteristic values of key seabed parameters in shallow-water areas. This element of the study utilised both analytical and numerical electromagnetic models, and the efficacy of each in this context was examined. Subsequent phases of the study analysed the nature of the electromagnetic sources. In some situations the sources were regarded as point dipoles, and in others they were assumed to have a finite length. Techniques were developed to characterise the dipole moment, length and the location of a typical ship-like source, when each is treated as an electric current dipole. This information was used in turn to demonstrate the likely accuracy in ranging operations on extremely low-frequency, electromagnetic sources over short ranges, and in shallow-water conditions.