Radiation dosimetry is necessary for optimising radiation-based medical procedures for individual patients but in the field of nuclear medicine there are few widely available or widely used tools for performing this kind of analysis. Those tools that are available tend to focus on one particular component of the dosimetry problem and integrating tools to form a complete system is left to the end-user. A software system for performing individual, image-based dosimetry analysis of nuclear medicine studies has been developed and validated. The system consists of a suite of tools that use common file formats and data models. The tools can be integrated to form applications by means of a simple scripting system. One tool is a gamma camera simulator that can produce realistic images of dynamic activity distributions in planar or tomographic formats. Simulated imaging studies produced by this tool are used to validate the other tools in the system. In addition, the system implements a method of simulation assisted quantitation which is shown to achieve high accuracy in both software and physical phantom studies. The system is applied to the dosimetry of I-131 Lipiodol, a therapeutic agent used to treat primary and secondary cancers of the liver. Simulation studies are used to validate the analytic methods used. Studies of a series of patients, treated over a period 10 years, are retrospectively analysed using a selection of methods appropriate to the available data. The results of the analysis demonstrated a large range of lung doses from 1 to 10 Gy/GBq administered. The median absorbed dose in liver was 3 Gy (range 1 - 10 Gy) and the median absorbed dose in tumor was 19 Gy (range 5 - 84 Gy). The large individual variation reinforces the necessity of individualised dosimetry for treatment planning and follow up.

This thesis investigates the defects, charge states and spin properties of phosphorus doped silicon, and is motivated by a number of proposals for quantum information processing (QIP) that involve using the spin or charge of individual donors in silicon as qubits. The implantation of phosphorus into silicon is investigated; specifically the ability to remove damage and activate the implanted donors. The impact of implantation on the transport properties of silicon MOSFETs at cryogenic temperatures is used to investigate the damage. Implanting phosphorus into the MOSFET channel leads to reduced electron mobility. The defect density increases linearly with implant density (??ndefect = 0.08 ?? 0.01nimplant). Silicon implantation does not show this effect, suggesting that the additional defects are ionised P donors in the channel. Implant activation for low density donors was complete for an implant density of 2 x 1012 cm2. Similar studies were undertaken on devices with a variety of dielectrics. Thermally grown SiO2 was found to have the lowest defect density of those studied, although Al2O3 deposited via atomic layer deposition was found to have properties that may be useful for the fabrication of devices with low thermal processing budgets. The as-grown defect density of the thermal silicon dioxide was found to be 2.1 ?? 0.3 x 1011 cm2. Ion implantation of nanoscale devices allowed the spin properties of a small number of phosphorus donors in silicon to be probed via electrically detected magnetic resonance. This allowed the detection of the spin resonance of as few as 100 spins. This represents an improvement in number detection of 4 orders of magnitude over previous EDMR studies of donors in silicon. EDMR was used to investigate the properties of P donors in isotopically purified 28Si . The material had a background doping level too high to detect small numbers of spins, however, the narrow linewidth of the phosphorus resonance confirm that the isotopic purity is greater than 0.999. A proof-of-principle demonstration of pulsed EDMR of ion-implanted donors in silicon is presented. The spin dependent transient that results from manipulating the donor spins via pulsed ESR is sensitive to as few as 104 donors, and is a required component for observation of spin Rabi oscillations by this technique.

There is evidence that athermal radiofrequency radiation can alter Heat Shock Protein (HSP) expression or protein phosphorylation, or alter MAP kinase signalling. Effects of long-term exposure in brain tissue due to repeated HSP perturbation (eg an inhibition of apoptosis) have been hypothesised (French et al, 2001). This study aimed to investigate the RNA expression profile (12,000 genes) and HSP family protein expression levels after either acute 1-hour or chronic 4-day intermittent exposures to simulated GSM radiation in a human primary fibroblast model. The results found minimal or no effects of GSM. Flasks were exposed to 900 MHz (217 Hz modulation) at 0.18 W/kg SAR within a Transverse Electromagnetic Mode chamber (TEM cell). Cultures rested for 2 hours before exposures. Affymetrix U95A microarray analysis of a single pilot set of experiments showed that about 40 genes were reported as upregulated &gt=2.5 fold in each condition. There was no evidence of altered expression of any MAPK-associated genes. Target genes reported in both conditions (CBFA2T1, ZNF148, ITGA1), and genes altered in one condition (CCS, PLEC1, BIRC5), and marginally altered HSP72 were selected for PCR analysis. No other members of the HSP family were altered. In three replicate experiments assayed by real-time PCR, six genes were either unchanged or showed randomly variable expression. However HSP72 RNA showed possible consistent slight upregulation of 1.37 +/- 0.21 in the chronic condition. Western immunoblots of HSP-60, -70, -72 and -V90 proteins showed no significant changes 5 hours after exposure. In preliminary studies using a serum starvation protocol, ERK-1 phosphorylation was unaltered after 5 or 30 minutes GSM (single experiments). When flasks were transiently cooled, ERK-1 phosphorylation was increased 20 minutes later, indicating a source of artefact in some protocols. An inflammatory challenge experiment with a low-dose of the cytokine IL-1???? found that acute GSM exposure post-challenge inhibited NF????B-mediated GRO???? induction by 1.5 fold (2 experiments). Preconditioning with mild heat induces transient inhibition of both NF????B signalling and apoptosis. Other studies indicate that EMF exposures similarly evoke cytoprotection. It is suggested that GSM evoked cytoprotective signalling in this inflammatory model.

This thesis is concerned with the role the rich cluster environment plays in the evolution of its galaxy population. We approach this issue from two angles, first we use deep wide-field imaging to investigate the effect of the cluster environment on the spatial and luminosity distribution of galaxies. Secondly, we focus on one particularly interesting class of galaxy, the enigmatic E+A galaxies, using a combination of state-of-the-art telescopes and novel instrumentation to elucidate the physical mechanisms and environmental influences causing the rapid change in star-formation activity in these galaxies. We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z=0.18) based on Hubble Space Telescope images. These have been used to derive the cluster luminosity function to extremely faint limits. We find the faint-end slope of the luminosity function to vary with environment within the cluster - in the sense that the ratio of `dwarf' galaxies to `giant' galaxies increases in the lower-density outskirt regions. Using imaging obtained with the Isaac Newton Telescope (INT) we confirm the presence of luminosity segregation in Abell 2218. However, luminosity segregation in clusters does not appear to be ubiquitous, with two other clusters studied with the INT (A119 at z=0.04 and A2443 at z=0.11) showing no sign of luminosity segregation of their galaxy populations. We use integral field spectroscopy of a sample of E+A galaxies in intermediate redshift clusters, obtained with the FLAMES system on the European Southern Observatory's VLT and the GMOS instrument on Gemini-North, to determine the radial variation in the strength of Hdelta absorption in these galaxies, and hence map out the distribution of the recently formed stellar population. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: with gradients that are either negative, flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies.

In this thesis, we study the effects of doping in two-dimensional quantum antiferromagnets. We consider cases where the undoped parent compound is a Mott insulator with long-range antiferromagnetic order and focus on the low-doping situations. The limit of localized impurities is studied in a system consisting of a host magnet and two additional weakly coupled spins. We derive the effective Hamiltonian describing the interaction between these impurities as a function of their distance and show that it exhibits xyz anisotropy, leading to NMR and EPR line broadening. We calculate the magnetization disturbance in the host magnet induced by a single impurity and find that it always enhances Neel order. Relaxing the localization constraint, we investigate the single-hole dynamics of the t-J model on the honeycomb lattice. Using exact diagonalizations, series expansion and the self-consistent Born approximation, we calculate the quasi-particle dispersion, bandwidth and residues and compare our findings with the well-established results for the square lattice. Similar to the latter case, we find an almost flat band along the edges of the magnetic Brillouin zone and well-defined hole pockets around the corners. The most important part of this thesis is devoted to the magnetic properties of lightly doped La2-xSrxCuO4, the simplest and by far most studied cuprate superconductor. Starting from the undoped parent compound, we calculate the spin-wave spectrum and the spin-flop transitions in a uniform magnetic field at zero temperature. We then consider the low-doping regime and derive the effective field theory describing the spin dynamics in insulating La2-xSrxCuO4, x ≤ 0.055, at low temperature. The spin structure resulting from the spiral solution of the extended t-J model, obtained by taking into account the Coulomb trapping of holes by Sr ions, is confined in the copper-oxide planes. Our solution explains why the incommensurate structure is directed along the orthorhombic b axis and allows us to calculate the positions and shapes of the neutron scattering peaks numerically. These results are in perfect agreement with experimental data. We also show that topological defects (spin vortex-antivortex pairs) are an intrinsic property of the spin-glass ground state.

Radiation dosimetry is necessary for optimising radiation-based medical procedures for individual patients but in the field of nuclear medicine there are few widely available or widely used tools for performing this kind of analysis. Those tools that are available tend to focus on one particular component of the dosimetry problem and integrating tools to form a complete system is left to the end-user. A software system for performing individual, image-based dosimetry analysis of nuclear medicine studies has been developed and validated. The system consists of a suite of tools that use common file formats and data models. The tools can be integrated to form applications by means of a simple scripting system. One tool is a gamma camera simulator that can produce realistic images of dynamic activity distributions in planar or tomographic formats. Simulated imaging studies produced by this tool are used to validate the other tools in the system. In addition, the system implements a method of simulation assisted quantitation which is shown to achieve high accuracy in both software and physical phantom studies. The system is applied to the dosimetry of I-131 Lipiodol, a therapeutic agent used to treat primary and secondary cancers of the liver. Simulation studies are used to validate the analytic methods used. Studies of a series of patients, treated over a period 10 years, are retrospectively analysed using a selection of methods appropriate to the available data. The results of the analysis demonstrated a large range of lung doses from 1 to 10 Gy/GBq administered. The median absorbed dose in liver was 3 Gy (range 1 - 10 Gy) and the median absorbed dose in tumor was 19 Gy (range 5 - 84 Gy). The large individual variation reinforces the necessity of individualised dosimetry for treatment planning and follow up.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

Radiation dosimetry is necessary for optimising radiation-based medical procedures for individual patients but in the field of nuclear medicine there are few widely available or widely used tools for performing this kind of analysis. Those tools that are available tend to focus on one particular component of the dosimetry problem and integrating tools to form a complete system is left to the end-user. A software system for performing individual, image-based dosimetry analysis of nuclear medicine studies has been developed and validated. The system consists of a suite of tools that use common file formats and data models. The tools can be integrated to form applications by means of a simple scripting system. One tool is a gamma camera simulator that can produce realistic images of dynamic activity distributions in planar or tomographic formats. Simulated imaging studies produced by this tool are used to validate the other tools in the system. In addition, the system implements a method of simulation assisted quantitation which is shown to achieve high accuracy in both software and physical phantom studies. The system is applied to the dosimetry of I-131 Lipiodol, a therapeutic agent used to treat primary and secondary cancers of the liver. Simulation studies are used to validate the analytic methods used. Studies of a series of patients, treated over a period 10 years, are retrospectively analysed using a selection of methods appropriate to the available data. The results of the analysis demonstrated a large range of lung doses from 1 to 10 Gy/GBq administered. The median absorbed dose in liver was 3 Gy (range 1 - 10 Gy) and the median absorbed dose in tumor was 19 Gy (range 5 - 84 Gy). The large individual variation reinforces the necessity of individualised dosimetry for treatment planning and follow up.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.