The effects of ionising radiation (IR) present in aquatic environments have been observed principally in vertebrate species but the potential biological impacts for aquatic invertebrate species are less clear. It is important to determine the influence of IR as a pollutant causing DNA damage in invertebrates at the molecular level since this may serve as an early warning of future population level repercussions. In this study, the biological effects of the IR as an environemntal contaminant at the molecular level was investigated by studying the induction of DNA damage, measured as mRNA expression of DNA repair genes and comet damage, in experimentally- and environmentally-exposed mussels, M. edulis. The experimental exposure consisted of different IR doses (1, 2, 10 and 50 Gy) and sampling at different post-exposure time points (1hr, 4 and 7 days). The environmental exposure was investigated using mussels collected from a contaminated site (Ravenglass Estuary) and a reference site (Brighton Marina). Two new molecular biomarkers were developed and employed. The first involves Rad51, a key protein in resynthesis, catalyzing and transferring of strands between broken sequences and its homologues in double strand break (DSBs) damage. The second biomarker involved a cell cycle checkpoint protein, check point kinase 1 (Chk1). To explore the activation of Rad51 and Chk1 mRNA activity as a result of exposure to IR, Rad51 and Chk1 mRNA in M. edulis were partially isolated and characterized and a quantitative assay developed to measure their expression using real-time PCR. Experimental exposure of M. edulis to IR (1, 2, 10 and 50 Gy) resulted in a statistically significant increase in the levels of Rad51 transcripts. Chk1 mRNA expression levels, initially investigated in the experimental group, were altered following exposure to IR. In the samples collected from the environment, Rad51 mRNA expression levels were increased in Ravenglass M. edulis gonad samples compared with the reference samples from Brighton Marina. In contrast, Chk1 transcripts decreased in Ravenglass M. edulis gonad samples compared to Brighton samples. The observed effects, and the potential role of both Rad51 and Chk1 in the IR DNA damage response of mussels are discussed.

<p>Recent results at RHIC seem to confirm T.D.Lee's hypothesis that a new form of matter, the quark-gluon plasma (QGP), could be formed in heavy-ion collisions at high energies. Heavy quarks, being formed in the early stages of heavy-ion collisions, form a good probe for the properties of the QGP. The energy loss of heavy quarks as they traverse the medium is predicted to be less than that of the lighter quarks. However; previous measurements of the nuclear modification factor at RIHC indicate that the energy loss of heavy and light quarks is comparable. Thus measurements of the in-medium energy loss of heavy-quarks are of particular interest. In this thesis, a measurement of the differential production cross-section of electrons from the semi-leptonic decay of heavy-flavor quarks in [special characters omitted] = 2.76 TeV <i>pp</i> is presented. This provides a stringent test of perturbative QCD in a new energy regime, and forms a crucial baseline for Pb-Pb collisions where the in-medium energy loss mechanism can be studied. </p>

<p> The electric (<i>G_E</i>) and magnetic (<i> G_M</i>) form factors of the proton are fundamental observables which characterize its charge and magnetization distributions. There are two methods to measure the proton form factors: the Rosenbluth separation method and the polarization transfer technique. However, the ratio of the electric and magnetic form factors measured by those methods significantly disagree at momentum transfer <i>Q</i>² > 1 GeV². The most likely explanation of this discrepancy is the inclusion of two-photon exchange (TPE) amplitude contributions to the elastic electron-proton cross section which significantly changes the extraction of <i>G_E</i> from the Rosenbluth separation measurement. The Jefferson Lab CLAS TPE experiment determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections. The primary electron beam was used to create an intense bremsstrahlung photon beam. Some of the photons were then converted to a mixed <i>e</i>⁺/<i> e</i>^- beam which then interacted with a liquid hydrogen target. The <i>e</i>⁺<i>p</i> and <i> e</i>^-<i>p</i> events were detected by the CLAS (CEBAF Large Acceptance Spectrometer). The elastic cross section ratios ((&sigma;(<i> e</i>⁺<i>p</i>)/(&sigma;(<i>e</i>^-<i>p</i>)) were measured over a wide range of virtual photon polarization <i>&epsiv;</i> and <i>Q</i>². The cross section ratios displayed a strong <i>&epsiv;</i> dependence at <i>Q</i>² = 1.45 GeV². There is no significant <i>Q</i>² dependence observed at <i> &epsiv;</i> = 0.45. The results are consistent with a recent measurement at the VEPP-3 lepton storage ring in Novosibirsk and with the hadronic calculation by Blunders, Melnitchouk and Tjon. The hadronic calculation resolves the disagreement between the Rosenbluth separation and polarization transfer extractions of <i> G_E/G_M</i> at <i>Q</i>² up to 2 &ndash; 3 GeV². Applying the GLAS TPE correction to the Rosenbluth cross section measurements significantly decreases the extracted value of <i>G_E</i> and brings it into good agreement with the polarization transfer measurement at <i>Q</i>²&sim;1.75 GeV². Thus, these measurements appear to resolve the proton electric form factor discrepancy for <i>Q</i>² &lt; 2 GeV².</p>

This Project is aimed at developing and fabricating mid-infrared (MIR) transmitting germanium-antimony-selenium (Ge-Sb-Se) chalcogenide glass fibres for passive transmission in MIR sensing and as new high-purity low-loss optical fibres for active MIR supercontinuum generation (SCG). The work reported in this Thesis can be divided into three main categories: (i) a study of four Ge-Sb-Se glass compositions (atomic %): (Ge19Sb15Se66), (Ge20Sb10Se70), (Ge24Sb4Se72) and (Ge22Sb8Se70), in terms of their thermal properties, optical properties and cytotoxicity to match potential glass pairs for small-core step-index MIR SCG fibres; (ii) to develop and optimise methods of achieving high-purity chalcogenide glasses and (iii) a preliminary study of the structure of Ge-Sb-Se glasses along the stoichiometric tie-line x(GeSe2)-(1x)( Sb2Se3), to guide future selection of candidate glass pairs to draw to step-index fibre. The MIR spectral region covers the wavelengths 3-50 μm and characteristic vibrational absorption spectra unique to each molecular type. Vibrational spectroscopy can detect subtle changes in the specific spectral response within this region. Molecular vibrations are indicative of changes within biological cells relative to normal biological cells, signifying the presence or absence of a disease. This Project contributes to the collaborative MINERVA Project which is developing a remote skin cancer detection system using MIR absorption spectroscopy aiming to carry out disease diagnosis in vivo. Providing broadband photons at MIR wavelengths has previously presented difficulties. Conventional MIR blackbody light sources are weak and optical fibres for transmitting MIR light to/from tissue in vivo can be limited by strong material absorption such as silica glass > 2.4 μm and tellurite, and heavy metal fluoride, > 4.75μm. In contrast, chalcogenide glasses have been shown to transmit MIR light out to 25 μm and MIR SCG from ~ 2 – 15.1 µm has recently been demonstrated in chalcogenide glass fibre. This Thesis reports on the characterisation of four Ge-Sb-Se glass compositions to match potential glass pairs for fabrication of step-index fibres based on particular thermal properties and desired fibre numerical aperture (NA). Three glass pairs are drawn to fibre: Pair I (Ge22Sb8Se70) and (Ge24Sb4Se72), Pair II (Ge19Sb15Se66) and (Ge20Sb10Se70), and Pair III (Ge20Sb10Se70) and (Ge24Sb4Se72). Difficulties emerged and are examined in the extrusion and fibre drawing processes arising from a mismatch in the glass pair’s physical properties. Thus, a hierarchy of the order of selection of physical properties is suggested, with matching the glass transition temperature (Tg) deemed to be the top priority. The optical properties of the fabricated fibres are characterised in terms of predicted NA, near-field imaging and optical loss measurements. The minimum loss achieved (2.42 dB/m at 6.66 µm wavelength) is for Pair I (Core: Ge22Sb8Se70 and cladding: Ge24Sb4Se72). The effect of heat-treating to purify the precursor elements Sb and Se on subsequent fibre loss is observed and it is established that glass purity was a critical factor affecting the intensity of hydride and oxide impurity absorption bands punctuating the 2.5 – 10 µm wavelength transmission region. Therefore, distillation methods are explored as a means of generating high-purity chalcogenide glasses and a new distillation rig is developed. Preliminary cytotoxicity tests on a fibre fabricated from Pair I are conducted to provide the foundations of a procedure for future chalcogenide glass fibre cytotoxicity testing. The initial data demonstrated the potential of etching the Ge-Sb-Se chalcogenide glass fibres in propylamine to reduce any cytotoxic response caused by the Ge-Sb-Se fibres. Neutron diffraction experiments are combined with Tg and density measurements along the stoichiometric tie-line x(GeSe2)-(1-x)( Sb2Se3), to aid in a greater understanding of the structure-property relationship of Ge-Sb-Se glasses for the future selection of candidate glass step-index fibre pairs. The preliminary work established that the stoichiometric glasses are predominantly made up of [GeSe4] and [SbSe3] units. From the neutron diffraction data, it is suggested that the average bond length of a Sb-Se bond was 2.62 ± 0.001 Å and the average bond length of a Ge-Se bond was 2.37 ± 0.001 Å. Extracting the coordination of the Ge and Sb elements is found to be difficult on account of an overlap of the Ge-Se and Sb-Se peaks. Therefore further analysis, using nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) is suggested. It is shown that, as the vitreous structure changes from higher levels of [SbSe3] units to incorporate more [GeSe4] (thus a reduction of Sb), the Tg of the glass increases and the density decreases. A close match in Tg (< 23 °C) is recommended as critical for the successful fabrication of a Ge-Sb-Se chalcogenide glass fibre. Thus, knowledge of the trend in Tg, dependent on the ratio of [SbSe3] units to [GeSe4] units, is an initial step in selecting theoretical Ge-Sb-Se compositions with a closer match of thermal properties as candidate glass step-index fibre pairs. Having a more accurate guide to select theoretically Ge-Sb-Se glass compositions to match thermal properties is suggested to save time synthesising and characterising obsolete compositions. It is concluded that Ge-Sb-Se chalcogenide glass fibres, developed through this Project, are strong candidates towards achieving MIR SCG small-core fibres, with the potential application for the transmission of MIR to and from potentially cancerous skin tissue samples. Therefore, enabling in vivo mapping for an immediate diagnostic response.

Dosimetria usando Luminescência Opticamente Estimulada (OSL) é uma área em constante crescimento dentro da ciência e com excelentes perspectivas comerciais. O Óxido de Alumínio crescido na presença de uma atmosfera rica em Carbono (Al 2O3:C) tem fornecido bons resultados como detector luminescente. Esse material apresenta alta sensibilidade à radiação ionizante e boa resposta à estímulos ópticos. Estima-se que cerca de dois milhões de pessoas façam uso de dosímetros com detectores de Al 2O3:C em rotinas de dosimetria individual externa, que por apresentar varias vantagens experimentais acredita-se substituirá as outras duas técnicas dosimétricas mais adotadas: dosimetria fotográfica e termoluminescente. A certificação de uma técnica de dosimetria para uso comercial exige uma série de estudos. Neste trabalho apresentamos contribuições que complementam o entendimento e adoção da técnica de OSL em dosimetria pessoal. Nossa primeira contribuição consiste numa serie de testes de desempenho mostrando a eficácia da técnica para justificar nossa proposta de certificação de dosimetria individual externa usando OSL no Brasil. No intuito de relacionar centros paramagnéticos e o processo de luminescência, apresentamos resultados de espectros de EPR em detectores OSL. Detectamos e classificamos sinais de EPR relacionados a impurezas nas amostras, porem, sinais dos centros luminescentes não foram detectados. Finalmente, apresentamos um estudo preliminar sobre a resposta de luminescência do Al2O3:C quando exposto a diferentes comprimentos de onda de radiação UV. A inexistência de dosimetria de nêutrons por técnicas de OSL motivou o estudo de vários óxidos dopados com Térbio como possíveis candidatos a material dosimétrico. Alguns resultados preliminares do espectro de EPR desses óxidos quando irradiados em campo beta de 90Sr/90Y e da resposta de luminescência em função da luz de excitação para análise dos tipos de armadilhas criadas pela presença do Tb+3 são apresentados. / Dosimetry using Optically Stimulated Luminescence (OSL) is an expanding scientific research area which also shows excellent commercial potential. Aluminum oxide grown in an atmosphere in the presence of Carbon, Al 2O3:C, presented excellent results as a luminescent detector. This material has high sensitivity when exposed to ionizing radiation and good responses to optical stimulation. Over two million people use dosimeters with Al 2O3:C detectors in personal dosimetry procedures. The experimental advantages of using OSL are believed to replace the two other usual techniques: photographic and thermoluminescent dosimetry. To validate the commercial use of a dosimetry technique it is necessary to evaluate a number of studies. In this work we present results which increase our understanding of OSL dosimetry. First we present a number of behavior tests to show the efficiency of the technique for the purpose of justifying the use of OSL in personal dosimetry in Brazil. In an attempt to correlate paramagnetic centers and the luminescence process we present EPR results in OSL detectors. We could detect and classify impurities centers in our samples; however we could not find conclusive results about paramagnetic centers generated by exposition to ionizing radiation. We present a preliminary study about the luminescence behavior from Al 2O3:C when exposed to different UV wavelengths. The nonexistence of a neutron dosimetry using OSL suggested a study of three types of oxides doped with Terbium which are strong candidates as OSL detectors due to their sensitivity to neutron expositions. We present preliminary results of EPR spectroscopy from these oxides when exposed in a beta field of 90Sr/90Y and the luminescent response when the excitation light is used to analyze traps generated by the presence of Tb+3.

In the European XFEL, electrons bunches are accelerated up to 20 GeV and thenenter undulators where coherent X-rays are produced which can be used for imaging atva molecular level. Electrons may stray from the path and hit the permanent magnets inthe undulators. It is well known that ionizing radiation can affect the magnetic characteristics of permanent magnets. The undulators are therefore equipped with a type of semiconductor dosimeters, RADFETs, so that the potential damage from ionizing radiation to the magnets can be measured and corrected for. It is also known that heat will be generated from air-coils in the accelerator which can change the ambient temperature around the dosimeters up to 25 K. All semiconductor technology is highly susceptible totemperature. This report investigates the fading characteristics of the RADFET under different temperatures and times after irradiation. It also investigates the dose responseunder dierent temperatures and estimates the magnitude of errors in measured dose which can be expected if temperatures are not accounted for. It is seen that a delta T of a few K can have a large impact on RADFETs' ability to both record and retain dose. A strong time dependence is also seen. The fading is the largest during irradiation andthen slows down exponentially, stabilizing after 1 to 2 months. An increase from 20 deg C to 26 deg C will increase the fading by 2 Gy/h during irradiation, and 0.015 Gy/h weeks afterirradiation. It is estimated that dose measurements at XFEL can have errors of up to 14% if long-term fading is not accounted for. A model for estimating long-term fading as a function of temperature is proposed.

Dosimetria usando Luminescência Opticamente Estimulada (OSL) é uma área em constante crescimento dentro da ciência e com excelentes perspectivas comerciais. O Óxido de Alumínio crescido na presença de uma atmosfera rica em Carbono (Al 2O3:C) tem fornecido bons resultados como detector luminescente. Esse material apresenta alta sensibilidade à radiação ionizante e boa resposta à estímulos ópticos. Estima-se que cerca de dois milhões de pessoas façam uso de dosímetros com detectores de Al 2O3:C em rotinas de dosimetria individual externa, que por apresentar varias vantagens experimentais acredita-se substituirá as outras duas técnicas dosimétricas mais adotadas: dosimetria fotográfica e termoluminescente. A certificação de uma técnica de dosimetria para uso comercial exige uma série de estudos. Neste trabalho apresentamos contribuições que complementam o entendimento e adoção da técnica de OSL em dosimetria pessoal. Nossa primeira contribuição consiste numa serie de testes de desempenho mostrando a eficácia da técnica para justificar nossa proposta de certificação de dosimetria individual externa usando OSL no Brasil. No intuito de relacionar centros paramagnéticos e o processo de luminescência, apresentamos resultados de espectros de EPR em detectores OSL. Detectamos e classificamos sinais de EPR relacionados a impurezas nas amostras, porem, sinais dos centros luminescentes não foram detectados. Finalmente, apresentamos um estudo preliminar sobre a resposta de luminescência do Al2O3:C quando exposto a diferentes comprimentos de onda de radiação UV. A inexistência de dosimetria de nêutrons por técnicas de OSL motivou o estudo de vários óxidos dopados com Térbio como possíveis candidatos a material dosimétrico. Alguns resultados preliminares do espectro de EPR desses óxidos quando irradiados em campo beta de 90Sr/90Y e da resposta de luminescência em função da luz de excitação para análise dos tipos de armadilhas criadas pela presença do Tb+3 são apresentados. / Dosimetry using Optically Stimulated Luminescence (OSL) is an expanding scientific research area which also shows excellent commercial potential. Aluminum oxide grown in an atmosphere in the presence of Carbon, Al 2O3:C, presented excellent results as a luminescent detector. This material has high sensitivity when exposed to ionizing radiation and good responses to optical stimulation. Over two million people use dosimeters with Al 2O3:C detectors in personal dosimetry procedures. The experimental advantages of using OSL are believed to replace the two other usual techniques: photographic and thermoluminescent dosimetry. To validate the commercial use of a dosimetry technique it is necessary to evaluate a number of studies. In this work we present results which increase our understanding of OSL dosimetry. First we present a number of behavior tests to show the efficiency of the technique for the purpose of justifying the use of OSL in personal dosimetry in Brazil. In an attempt to correlate paramagnetic centers and the luminescence process we present EPR results in OSL detectors. We could detect and classify impurities centers in our samples; however we could not find conclusive results about paramagnetic centers generated by exposition to ionizing radiation. We present a preliminary study about the luminescence behavior from Al 2O3:C when exposed to different UV wavelengths. The nonexistence of a neutron dosimetry using OSL suggested a study of three types of oxides doped with Terbium which are strong candidates as OSL detectors due to their sensitivity to neutron expositions. We present preliminary results of EPR spectroscopy from these oxides when exposed in a beta field of 90Sr/90Y and the luminescent response when the excitation light is used to analyze traps generated by the presence of Tb+3.

Photodynamic therapy (PDT) is a form of local cancer treatment in which cell death is caused by photochemical reactions involving an exogenous photosensitizer. The photosensitizer, which is preferentially retained in malignant tissues, is photoactivated and cell death results from the generation of reactive products -most likely excited molecular (singlet) oxygen. The development of in vivo PDT dosimetry would be greatly aided by the ability to directly measure the local concentration of this product by non-invasive means. In condensed media singlet oxygen will, with some small probability, undergo a radiative transition to the ground state with emission at 1270 nm. This infrared phosphorescence may provide a means for monitoring the production of singlet oxygen in vivo. Unfortunately the background infrared fluorescence observed from tissue may be many times the expected magnitude of the 1270 nm phosphorescence, even within the bandwidth encompassing the peak. The principal aim of this project was the design of a system optimized for the in vivo detection of the singlet oxygen emission. The system makes use of the most sensitive commercially available detector and uses phase sensitive detection to discriminate against infrared fluorescence. The system's performance matched theoretical expectations for the photosensitizer Photofrin II in aqueous and methanol solutions. However, a discrepancy in the observed and theoretical values was noted for aluminum chlorosulphonated phthalocyanine suggesting a deviation from simple first order kinetics. Singlet oxygen phosphorescence was not observed during PDT of cell suspensions or mouse tumours even though considerable cell death and tumour necrosis were observed. The most likely explanation of this failure is that, due to quenching by biomolecules, the lifetime of singlet oxygen in cells or tissue is much lower than in solution so that the probability of emission is reduced accordingly. Quantitative calibration of the system yielded a lower limit of approximately 0.1 us on the singlet oxygen lifetime in tissue. This suggests that singlet oxygen is generated in a protein environment. / Thesis / Master of Science (MS)

As ubiquitous wireless communication becomes part of life, the demand on antenna miniaturization and interference reduction becomes more extreme. However, antenna size and performance are limited by radiation physics, not technology. In order to understand antenna radiation and energy storage mechanisms, classical and alternative viewpoints of radiation are discussed. Unlike the common sense of classical antenna radiation, it is shown that the entire antenna fields contribute to both radiation and energy storage with varying total energy velocity during the radiation process. These observations were obtained through investigating impedance, power, the Poynting vector, and energy velocity of a radiating antenna. Antenna transfer functions were investigated to understand the real-world challenges in antenna design and overall performance. An extended model, using both the singularity expansion method and spherical mode decomposition, is introduced to analyze the characteristics of various antenna types including resonant, frequency-independent, and ultra-wideband antennas. It is shown that the extended model is useful to understand real-world antennas. Observations from antenna radiation physics and transfer function modeling lead to both corrections and extension of the classical fundamental-limit theory on antenna size. Both field and circuit viewpoints of the corrected limit theory are presented. The corrected theory is extended for multi-mode excitation cases and also for ultra-wideband and frequency-independent antennas. Further investigation on the fundamental-limit theory provides new innovations, including a low-Q antenna design approach that reduces antenna interference issues and a generalized approach for designing an antenna close to the theoretical-size limit. Design examples applying these new approaches with simulations and measurements are presented. The extended limit theory and developed antenna design approaches will find many applications to optimize compact antenna solutions with reduced near-field interactions. / Ph. D.

The aim of this study is to optimise the acquisition and reconstruction for SPECT with 111In- pentetrotide with the iterative reconstruction software OSEMS. For 111In-pentetrotide SPECT, the uptake in the tumour is usually high compared to uptake in normal tissue. It may, however, be difficult to detect small tumours with the SPECT method because of high noise levels and the low spatial resolution. The liver is a common region for somatostatin-positive metastases, and to visually detect small tumours in the liver, as early as possible, is important for an effective treatment of the cancer disease. The study concentrates on the acquired number of projections, the subset size in the OSEM reconstruction and evaluates contrast as a function of noise for a range of OSEM iterations. The raw-data projections are produced using Monte Carlo simulations of an anthropomorphic phantom, including tumours in the liver. Two General Electric (GE) collimators are evaluated, the extended low-energy general-purpose (ELEGP) and the medium energy general-purpose (MEGP) collimator. Three main areas of reconstruction are investigated. First the reconstructions are performed for so called full time scans with the acquisition time used clinically. Also the effect of performing the examination in half-time or with half the injected activity is evaluated with the most optimal settings gained from the full time scans for both collimators. In addition images reconstructed without model-based compensation are also included for comparison. This study is a continuation of a previous study on 111In-pentetrotide SPECT where collimator choice and model-based compensation were evaluated for a cylindrical phantom representing small tumours in liver background. As in the previous study, ELEGP proved to be the better collimator. For ELEGP, the most optimal setting was 30 projection angles and a subset size of 6 projections in the OSEM reconstruction, and for MEGP optimal setting was 60 projections and 4 subsets. The difference between the different collimator settings were, however, rather small but proven significant. For both collimators the half-time scan including model-based compensation was better compared to the full-time reconstructions without model-based compensation.