As mobile phone connections approach two billion worldwide and become steadily more available and affordable, demands for scientific studies on the effect of such EMFs on human functioning similarly increase. The current thesis systematically investigated the effects of acute mobile phone exposure on human brain activity and performance using an in-vivo approach. The research question comprised the following parts: First, is human neural function sensitive to acute mobile phone exposure? Second, if so, what processes are affected? Third, if so, do these neural changes affect gross measures of performance or behaviour? A review of the previous literature found that there was some, but not conclusive evidence that mobile phone exposure affects neural function and some aspects of human performance, and that the studies in question required replication with reliable and realistic dosimetry, double-blinding and additional technical tests to ensure that the experimental set-up was free of artefact contamination. A pilot study was conducted to provide an indication of possible future results, assist in the formation of hypotheses for the main study, and highlight what technical issues required attention before the main study could begin. Results of the pilot study indicated that EMFs emitted by GSM900 mobile phones may alter human brain activity during an auditory task, particularly in proximity to the phone. Both early sensory and later more cognitive ERP components were significantly altered during active compared to sham exposure. Results also suggested that mobile phone exposure may hinder human performance, with longer RTs during the active exposure relative to the sham exposure. However, due to the small sample size of the pilot investigation and questions remaining as to possible technical limitations of the study, these results were treated with caution and used primarily in the formation of future hypotheses for the larger experimental study. Subsequent technical tests provided improvement and validation of the experimental set-up and exposure delivery system, and ensured that future research would be free from such technical limitations. These tests included the characterisation of spectral emissions by the test phone; ensuring that EMFs emitted by the test phones would not interfere with, nor distort, data from the response pad or that processed by the electrode leads; determining whether electrode leads cause an increase or decrease in SAR; and examining the issue of experimenter interference. These tests enabled the conclusion that a positive finding from the large experimental trial would be due to the active exposure of the mobile phone, or in the case of a null finding, would not be due to insufficient or unreliable exposure. Applying the knowledge gained from these technical tests, the main study aimed to provide results of a definitive nature by employing a sample size of 120 sufficient statistical power to detect relatively subtle effects, and a stringent methodological design to account for past limitations. The main study also increased the scope of investigation beyond that achieved in previous research by including endpoints related to sensory processing (auditory and visual tasks), higher cognitive processing (cardsorting task), performance (reaction time and accuracy) and cortical activation (EEG alpha power). To increase this scope even further, within these tasks, the study used data from each scalp electrode and offered insights into the effect of laterality (ipsi- versus contralateral in relation to the exposure source), psychological arousal, perception of transmission, and between-subject factors such as age, gender, previous mobile phone use and hemisphere exposed (right versus left hemisphere exposure). The results of the main study suggested that acute exposure to GSM900 mobile phone significantly reduced levels of psychological arousal, particularly in relation to selfratings of Energy. Results also indicated that only minutes of active exposure can lead to enhanced alpha EEG activity during active exposure relative to sham exposure. Interestingly, this effect was found to be transient, decreasing below sham levels after ten minutes of active exposure and up until ten minutes after exposure cessation. These exposure-induced changes in EEG alpha power were here interpreted as representing an overall reduction in integrative brain function, possibly caused by the physiological response to neural interference or altered synaptic transmission. Acute exposure did not alter human brain activity in the form of the early sensory or later cognitive ERP responses during an auditory or visual task, or EEG synchronisation during a higher cognitive task. The findings also suggested that resultant behaviour, as indexed by RT and accuracy, is unaffected by exposure. Conversely, exploration into specific groups within the sample resulted in some interesting interactions, which raised the possibility that active mobile phone exposure may affect individuals differently as a function of age, gender and which hemisphere is exposed. Specifically, the auditory processing of older individuals was particularly vulnerable to the detrimental effects of mobile phone exposure compared to their younger counterparts. Results of the visual task suggested that the performance of females may also be particularly vulnerable to the detrimental effects of active exposure, compared to males. Overall, the present study has confirmed that there are mobile phone-related bioeffects at the low levels that mobile phones are permitted to operate at. Although various effects have been observed, there is no indication from the present results that cumulative effects or any health consequences exist as this was not the focus of the research. It is argued that future investigation into mobile phone-related bioeffects should apply more sophisticated methodologies to the investigation of acute exposure on EEG alpha power and higher cognitive functioning, as well as larger sample sizes and fewer carefully planned comparisons in order to detect small effects. Further investigation into exposure-induced effects on different groups according to age, gender and which hemisphere is exposed should also be a priority.

The use of mobile phones is continually increasing throughout the world, with recent figures showing that there are currently more than 2 billion mobile phone users worldwide. However, despite the recognised benefits of the introduction and widespread use of mobile phone technologies, concerns regarding the potential health effects of exposure to the radiofrequency electromagnetic fields emitted by mobile phone handsets have similarly increased, leading to an increase in demand for scientific research to investigate the possibility of health effects related to the use of mobile phones. An increasing amount of radiofrequency bioeffects research related to mobile phone use has focussed on the possible effects of mobile phone exposure on human brain activity and function, particularly as the absorption of energy in the head and brain region is much higher than in other body regions, which is a direct result from the close proximity of the mobile phone to the head when in normal use. In particular, the use of sleep research has become a more widely used technique for assessing the possible effects of mobile phones on human health and wellbeing, and is particularly useful for providing important information in the establishment of possible radiofrequency bioeffects, especially in the investigation of potential changes in sleep architecture resulting from mobile phone use. A review of the previous literature showed that a number of studies have reported an increase in the electroencephalogram spectral power within the 8 � 14 Hz frequency range in both awake and sleep states following radiofrequency electromagnetic field exposure. In regards to sleep, the enhancements reported have not been entirely consistent, with some early studies failing to find an effect, while more recent studies have reported that the effect differs in terms of particular frequency range. However, in general the previous literature suggests that there is an effect of mobile phone emissions on the sleep electroencephalogram, particularly in the frequency range of sleep spindle activity. In addition to changes in spectral power, changes in other conventional sleep parameters and the production and secretion of melatonin have also been investigated, however, there has been little or no consistency in the findings of previous studies, with the majority of recent studies concluding that there is no influence of mobile phone radiofrequency fields on these parameters of sleep or melatonin. Following a detailed review of the previous research, the current study was developed with the aim to improve on previous methodological and statistical limitations, whilst also being the largest study to investigate mobile phone radiofrequency bioeffects on human sleep. The principle aims were thus to test for the immediate effects of mobile phone radiofrequency electromagnetic fields on human sleep architecture and the secretion of the pineal hormone, melatonin. The experiment included 50 participants who were randomly exposed to active and sham mobile phone exposure conditions (one week apart) for 30 minutes prior to a full night-time sleep episode. The experimental nights employed a randomised exposure schedule using a double-blind crossover design. Standard polysomnography was used to measure subsequent sleep, and in addition, participants were required to provide urine samples immediately following exposure and upon waking in the morning. A full dosimetric assessment of the exposure system was also performed in order to provide sufficient details of the exposure set-up used in the current thesis and to account for the lack of detailed dosimetric data provided in the majority of previous studies. The results of the current study suggest that acute exposure to a mobile phone prior to sleep significantly enhances electroencephalogram spectral power in the sleep spindle frequency range compared to the sham exposure condition. The current results also suggest that this mobile phone-induced enhancement in spectral power is largely transitory and does not linger throughout the night. Furthermore, a reduction in rapid eye movement sleep latency following mobile phone exposure was also found compared to the sham exposure, although interestingly, neither this change in rapid eye movement sleep latency or the enhancement in spectral power following mobile phone exposure, led to changes in the overall quality of sleep. Finally, the results regarding melatonin suggested that, overall, overnight melatonin secretion is unaffected by acute exposure to a mobile phone prior to sleep. In conclusion, the current study has confirmed that a short exposure to the radiofrequency electromagnetic fields emitted by a mobile phone handset immediately prior to sleep is sufficient to induce changes in brain activity in the initial part of sleep. The consequences or functional significance of this effect are currently unknown and it would be premature to draw conclusions about possible health consequences based on the findings of the current study.

R.B. Adler. / "May 27, 1949." / Bibliography: p. 137. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B Dept. of the Army Project No. 3-99-10-022

Multiple-Input Multiple-Output (MIMO) systems are viewed as the last available supply for the ever-growing demand on higher data rates in modern wireless communication systems. Smart exploitation of the traditional wireless resources (time-slots or bandwidth under the same transmit power level) has reached its saturation point. By making better use of the free space between the radio links, based on the multipath radio wave propagation, MIMO systems have shown significant capacity improvement with the same traditional wireless resources. In this multi-disciplinary research, we are exploring the link between the electromagnetic propagation and the information theory. Unlike the majority of recent research work, we model the propagation channel matrix between the transmit/receive elements in a deterministic manner under the Maxwellian framework. Having included the environment properties and the characteristics of the radiating elements, the deterministic approach provides a realistic assessment of the MIMO system performance in specific scenarios. The problem addressed in this research is the evaluation of the multi-antenna systems degrees of freedom (DOF) by employing all the available electromagnetic diversity resources (spatial, pattern and polarization). Based on a developed well-defined power independent dimensionality (PID) metric, we start by investigating the information-bearing potential of the collocated multi-polarization MIMO system. We study the hexapole system (exploiting both electric and magnetic fields in conveying independent information) and compare it to the tripole systems (exploiting the vectorial polarization diversity of one field only). We present numerical results for 3 deterministic scenarios: a canonical free-space (near and far field exact solution), a canonical perfect electric conductor (PEC) corridor using rigorous modal analysis, and a lossy-wall corridor using image ray tracing (IRT). Next, we provide deterministic results for the more interesting sampling problem of the electromagnetic vector fields: given a specific MIMO array size, what is the optimum number of packed multi-polarization antennas (i.e. multi-polarization 1D, 2D or 3D sampling) that yields the largest PID for a given environment and what is the estimate of this PID? Using a canonical case of multi-polarized arrays inside a multipath-rich PEC corridor, we show that the spatial frequency spectrum of the electromagnetic field governs the optimum PID of the site-specific scenario. The problem is analogous to the DOF determination of an essentially time-limited-band-limited 1D scalar function using the framework of the prolate spheroidal wave functions. We also present simulation results for the same sampling problem in a lossy-wall indoor environment using IRT.

Multiple-Input Multiple-Output (MIMO) systems are viewed as the last available supply for the ever-growing demand on higher data rates in modern wireless communication systems. Smart exploitation of the traditional wireless resources (time-slots or bandwidth under the same transmit power level) has reached its saturation point. By making better use of the free space between the radio links, based on the multipath radio wave propagation, MIMO systems have shown significant capacity improvement with the same traditional wireless resources. In this multi-disciplinary research, we are exploring the link between the electromagnetic propagation and the information theory. Unlike the majority of recent research work, we model the propagation channel matrix between the transmit/receive elements in a deterministic manner under the Maxwellian framework. Having included the environment properties and the characteristics of the radiating elements, the deterministic approach provides a realistic assessment of the MIMO system performance in specific scenarios. The problem addressed in this research is the evaluation of the multi-antenna systems degrees of freedom (DOF) by employing all the available electromagnetic diversity resources (spatial, pattern and polarization). Based on a developed well-defined power independent dimensionality (PID) metric, we start by investigating the information-bearing potential of the collocated multi-polarization MIMO system. We study the hexapole system (exploiting both electric and magnetic fields in conveying independent information) and compare it to the tripole systems (exploiting the vectorial polarization diversity of one field only). We present numerical results for 3 deterministic scenarios: a canonical free-space (near and far field exact solution), a canonical perfect electric conductor (PEC) corridor using rigorous modal analysis, and a lossy-wall corridor using image ray tracing (IRT). Next, we provide deterministic results for the more interesting sampling problem of the electromagnetic vector fields: given a specific MIMO array size, what is the optimum number of packed multi-polarization antennas (i.e. multi-polarization 1D, 2D or 3D sampling) that yields the largest PID for a given environment and what is the estimate of this PID? Using a canonical case of multi-polarized arrays inside a multipath-rich PEC corridor, we show that the spatial frequency spectrum of the electromagnetic field governs the optimum PID of the site-specific scenario. The problem is analogous to the DOF determination of an essentially time-limited-band-limited 1D scalar function using the framework of the prolate spheroidal wave functions. We also present simulation results for the same sampling problem in a lossy-wall indoor environment using IRT.

The purpose of the study is to better understand the factors that affect melt-wear in the armature-to-rail contact interface of an electromagnetic launcher (EML). In order to investigate the factors, the study uses finite element analysis (FEA) to vary parameters of a lab-scale EML at the Georgia Institute of Technology. FEA is used due to the complex nature of the system, which includes the geometry and various engineering aspects that the EML incorporates. The study focuses on an uncoupled analysis of the structural, electromagnetic (EMAG), thermal, and modal aspects. The reason for the uncoupled analysis was because the system was complex and there were computational limits. Also, by uncoupling the analysis fields, the way the parameters affected melt-wear could be viewed separately. The study varied the geometry of the armature, the stiffness of the rail system (compliance layer), and the material of the armature. The structural analysis was for the initial contact of the rail to the armature and found the von Mises stresses, contact area, and contact pressure. The EMAG analysis found the Lorentz forces in the system based on a current curve used in the lab-scale EML. The thermal analysis consisted of friction heating and Joule heating. The modal analysis was for the unstressed and pre-stressed armature. Based on the study conducted, it was found that aluminum would provide the best speeds due to its lighter mass, but lacked in the thermal resistance area. Tungsten provided the better thermal resistance, but lacked in the potential speed due to its heavier mass.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 126-136). Also available in print.

This thesis deals with the dependence of the linear spatial growth rate of the cross-field ion acoustic instability on various plasma parameters. A kinetic theory model, with elastic and inelastic ion-neutral collisions included, is presented and used to conduct a numerical survey of the instability. The growth rate is computed as a function of distance into the plasma, taking into account the attenuation of the ion beam by charge exchange collisions. Further calculations show the variation in growth rate as a function of the following quantities: electron and ion beam temperature, electron density, beam velocity, background ion temperature, magnetic field, the angle between magnetic field direction and wave vector and the finite width of the plasma. The instability was observed in a double plasma device where an ion beam was passed through a background of stationary magnetized electrons. The magnetic field was sufficiently weak to allow approximately rectilinear ion motion. The growth rate of the wave was studied using interferometer techniques. It was identified by the dispersion relation as the cross-field ion acoustic wave propagating as the slow mode of the beam. It was found that the background ions play an important role in determining the phase velocity. Experimental data of the growth rate dependence on wave number, beam velocity and magnetic field strength were found to be well described by the theoretical model. The growth rate dependence of magnetic field direction on plasma width was furthermore found to be in qualitative agreement with the model. / Thesis (M.Sc.)-University of Natal, Durban, 1990.

This is an investigation into the association between ionospheric absorption caused by electron precipitation and ELF:3 Hz-3 kHz and VLF:3 kHz-30 kHz, chorus. Ionospheric absorption was measured using the chain of riometers in Finland and related to chorus events recorded simultaneously at SANAE (L=4.2), Antarctica. The displacement in longitude of the Finnish riometers from SANAE’s conjugate point made it impossible to establish a clear relationship between chorus and riometer absorption. The diurnal variation of chorus has been established for the years 2002, 2004 and 2005 and it is shown that chorus can occur at any Local Time(LT) but has a well defined maximum probability of occurring between 0800 LT to 0900 LT. To study the occurrence of chorus automatically we have developed an Index of ELF/VLF activity which enables us to identify chorus and distinguish it from other emissions such as hiss and whistlers. This index of VLF Activity was established by computing the standard deviation of the VLF signal amplitude and it has been observed that the index is larger for the chorus signature as opposed to the hiss which is low and does not vary widely due to the hiss’ steady signal. This index is called ASD index of “VLF Activity”. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

This study was designed to determine the potential biological effects of electric and magnetic fields (EMF), generated by 735 kV alternating current (AC) high tension lines upon the hormonal profile, some health-related parameters, stress response and productivity in dairy cattle. An EMF exposure chamber to house eight animals at one time was constructed. Forty-nine cows were divided according to their production stage; 8 pregnant non-lactating cows, 16 pregnant lactating cows, 16 non-pregnant lactating cows and 9 non-lactating non-pregnant heifers. They were exposed to an EMF of 10 kilovolts per meter (kV/m) and 30 micro-Tesla $( mu T)$ in two different fashions: (a) for three consecutive periods of 28 days in two sequences either with the EMF on/off/on or off/on/off, in a switch back design; (b) for three consecutive periods with the sequence OFF (5 days), ON (30 days) and OFF (5-12 days). The intensity of the EMF chosen for the experiments resembled a situation in which the cattle are standing continuously under a 735 kV AC high tension line when the line has a maximum load of current. In reality, these conditions are found only for a few days during the winter in the Province of Quebec. / Milk production and composition, feed consumption, blood hormonal profiles and cerebrospinal fluid (CSF) components were assessed during the different periods of exposure. Most of the variables assessed were not affected by EMF. However, there was a positive association between EMF and feed consumption, milk fat content, blood plasma progesterone during pregnancy and estrous cycle length. Also, there were changes in the mineral and neurotransmitter metabolite concentrations in the CSF that showed a relationship to the EMF. / In conclusion, it could be stated that EMF caused a biological response in dairy cattle. It is speculated that these changes do not represent a health hazard for exposed cattle, although they warrant further research.