In the UK, large quantities of intermediate level waste pose complex radiological remediation challenges. Chemical understanding of uranium in these Mg-rich sludges is vital. Previous studies have examined uranium uptake by calcium carbonate minerals (calcite and aragonite) under conditions pertinent to both natural and anthropogenically perturbed systems. However, research on uranyl uptake by magnesium-rich minerals such as magnesite [MgCO3], brucite [Mg(OH)2], nesquehonite [MgCO3·3H2O] and hydromagnesite-[Mg5(CO3)4(OH)2·4H2O] has not, to the best of our knowledge, been previously conducted. Such experiments will improve our understanding of the mobility of uranium and other actinides in natural lithologies such as dolomitic limestones or mafic igneous emplacements, as well as provide key information applicable to nuclear waste repository strategies involving Mg-rich phases. By two EXAFS techniques, we determined: (1) where uranyl (UO22+) is adsorbed, and (2) how uranyl is attached to the mineral surface. Therefore powder experiments of U(VI) were performed with magnesite, brucite, nesquehonite and hydromagnesite. The second experiment (GIXAFS) consisted of single crystals of magnesite (10.4) and brucite (0001). The powders were reacted in solution pH ~8.5 with U(VI)nitrate for 48 hrs. under ambient PCO2 = -3.5. The single crystals were reacted under ambient and reduced PCO2 ~ -4.5 for 48 hrs. with concentrations of U(VI)chlroride above (500; 50 ppm) and below (5 ppm) solubility of schoepite [UO2(OH)2·H2O]. The GIXAFS measurements were made at χ = 0˚ and χ = 90˚ relative to the synchrotron beam polarisation to uequivocally determine the adsorbate structures. Kd values for Mg-carbonate phases were comparable to or exceeded those published for calcium carbonates. GIXAFS results clearly showed polarisation for both ambient and reduced PCO2. XANES results showed uranyl is oriented with the axial oxygens perpendicular to the mineral surface. This implies, using also X-ray reflectivity and diffuse scatter, local hydrated bayleyite [Mg2(UO2)(CO3)3∙18H2O] and possible rutherfordine-like [UO2CO3] regions, which will be useful to predict uranium behaviour in various remediation processes.

This study explored the role of transient receptor potential melastatin 8 ion channels (TRPM8) in mechanisms of human glioblastoma (DBTRG) cell migration. Menthol stimulated influx of Ca2+, membrane current, and migration of DBTRG cells. Effects on Ca2+ and migration were enhanced by pre-treatment with hepatocyte growth factor/scatter factor (HGF/SF). Effects on Ca2+ also were greater in migrating cells compared with non-migrating cells. 2-Aminoethoxydiphenyl borate (2-APB) inhibited all menthol stimulations. RT-PCR and immunoblot analysis showed that DBTRG cells expressed both mRNA and protein for TRPM8 ion channels. Two proteins were evident: one (130-140 kDa) in a plasma membrane-enriched fraction, and a variant (95-100 kDa) in microsome- and plasma membrane-enriched fractions. Thus, TRPM8 plays a role in mechanisms that increase [Ca2+]i needed for DBTRG cell migration.

No description available.

No description available.

<p>As secondary colorectal liver cancer is the most widespread malignancy in patients with colorectal cancer, the main aim of this study is to identify and differentiate between benign and malignant secondary colorectal liver cancer tissue. Low energy X-ray interaction techniques were used. XRF and coherent scattering data were collected for all 24 normal and 24 tumour matched pair tissues. Measurements of these parameters were made using a laboratory experimental set-up comprising a Mo X-ray tube, Si Drift detector and Scintillation (NaI) detector.</p> <p>Twelve elements of interest were statistically explored for normal and tumour samples. Comparing normal and tumour tissues, statistically significant differences have been determined for K, Ca, Cr, Fe, Cu, Zn, Br and Rb. However, for P, S, As and Se, no statistically significant differences have been found.</p> <p>Coherent scatter profiles were collected and fitted for all the samples and three peaks were observed at momentum transfer values: adipose peak: 1.1 nm^-1, fibrous peak: 1.6 nm^-1 and water content peak: 2.2 nm^-1. The Amplitude, FWHM and area under these peaks were statistically analysed. These parameters were found to be significantly higher in secondary colorectal liver tumour compared to surrounding normal liver tissue for both fibrous and water content peaks. However, no significant differences were found for adipose peak parameters.</p> <p>Multivariate analysis was performed using the XRF, coherent scatter and elemental ratios data separately and the accuracy of classification results of 20 unknown samples was found. However when all the variables were combined together, the classification models were improved. This study has shown that the XRF and coherent scatter data of normal and secondary colorectal liver cancer are statistically different and the combination of these variables in multivariate analysis has the potential to be used as a method of distinguishing normal liver tissue from the malignant tumour tissue.</p> / Master of Science (MSc)

This study investigates the possibility of using a time-resolved Fluorescence and Diffuse Reflectance Spectroscopy (tr-FRS) system to define tumour surgical margins of invasive ducal carcinoma of breast. UV excitation light was used for the fluorescence component and data was collected from the 370-550 nm range. A broadband source was used for diffuse reflectance collection and the emitted response was in the 400-800 nm range. 40 matched pair cases were collected from patients undergoing breast conservation surgeries. Histological analysis was performed on each sample to determine the fat and tumour content within each normal and tumour sample respectively. Statistical analysis was performed on the optical data to reveal biochemical changes in the endogenous fluorophores collagen, reduced nicotinamide adenine dinucleotide (NADH), and flavin adenine dinucleotide (FAD) as well as changes in absorption and scattering properties attributed to variances in absorber concentrations and cell density respectively. Statistical significant differences in collagen, NADH, and FAD lifetimes, collagen, NADH, FAD and NADH/FAD intensity, diffuse reflectance and reduced scatter coefficient were observed between tumour and normal breast samples. These significant factors were used in Principle Component Analysis model construction and a binary classification scheme using Soft Independent Modeling of Class Analogy (SIMCA) was used as a classification tool to predict unknown breast samples as either normal or tumour with specificity of 60% and sensitivity slightly over 50%. / Thesis / Master of Science (MSc)

En radiothérapie, la tomodensitométrie (CT) fournit l’information anatomique du patient utile au calcul de dose durant la planification de traitement. Afin de considérer la composition hétérogène des tissus, des techniques de calcul telles que la méthode Monte Carlo sont nécessaires pour calculer la dose de manière exacte. L’importation des images CT dans un tel calcul exige que chaque voxel exprimé en unité Hounsfield (HU) soit converti en une valeur physique telle que la densité électronique (ED). Cette conversion est habituellement effectuée à l’aide d’une courbe d’étalonnage HU-ED. Une anomalie ou artefact qui apparaît dans une image CT avant l’étalonnage est susceptible d’assigner un mauvais tissu à un voxel. Ces erreurs peuvent causer une perte cruciale de fiabilité du calcul de dose. Ce travail vise à attribuer une valeur exacte aux voxels d’images CT afin d’assurer la fiabilité des calculs de dose durant la planification de traitement en radiothérapie. Pour y parvenir, une étude est réalisée sur les artefacts qui sont reproduits par simulation Monte Carlo. Pour réduire le temps de calcul, les simulations sont parallélisées et transposées sur un superordinateur. Une étude de sensibilité des nombres HU en présence d’artefacts est ensuite réalisée par une analyse statistique des histogrammes. À l’origine de nombreux artefacts, le durcissement de faisceau est étudié davantage. Une revue sur l’état de l’art en matière de correction du durcissement de faisceau est présentée suivi d’une démonstration explicite d’une correction empirique. / Computed tomography (CT) is widely used in radiotherapy to acquire patient-specific data for an accurate dose calculation in radiotherapy treatment planning. To consider the composition of heterogeneous tissues, calculation techniques such as Monte Carlo method are needed to compute an exact dose distribution. To use CT images with dose calculation algorithms, all voxel values, expressed in Hounsfield unit (HU), must be converted into relevant physical parameters such as the electron density (ED). This conversion is typically accomplished by means of a HU-ED calibration curve. Any discrepancy (or artifact) that appears in the reconstructed CT image prior to calibration is susceptible to yield wrongly-assigned tissues. Such tissue misassignment may crucially decrease the reliability of dose calculation. The aim of this work is to assign exact physical values to CT image voxels to insure the reliability of dose calculation in radiotherapy treatment planning. To achieve this, origins of CT artifacts are first studied using Monte Carlo simulations. Such simulations require a lot of computational time and were parallelized to run efficiently on a supercomputer. An sensitivity study on HU uncertainties due to CT artifacts is then performed using statistical analysis of the image histograms. Beam hardening effect appears to be the origin of several artifacts and is specifically addressed. Finally, a review on the state of the art in beam hardening correction is presented and an empirical correction is exposed in detail.

Para melhorar a visualização das pequenas estruturas anatômicas importantes para o diagnóstico do câncer de mama e otimizar o processamento das mamografias pelos sistemas computadorizados de auxílio ao diagnóstico (CAD), foi desenvolvido um dispositivo, baseado na tecnologia slit, que melhora a aquisição dos mamogramas. Este dispositivo reduz a radiação espalhada e o tamanho do foco e foi projetado a partir de um modelo computacional. O modelo adotado permite quantificar o valor desses parâmetros para qualquer sistema radiológico, qualquer espessura de tecidos moles radiografada e qualquer tensão aplicada ao tubo de raios-X. O dispositivo foi implementado e testado, quantificando as melhorias obtidas. As imagens geradas foram comparadas com as fornecidas pelos sistemas mamográficos convencionais. O modelo serviu para estudar também a interferência do espalhamento sobre o desempenho dos algoritmos usados nos sistemas de diagnóstico auxiliado por computador (CAD). / In order to improve the visualization of the small and important anatomical structures for breast cancer diagnosis and to optimize the image processing of mammograms by the computer aided diagnosis systems (CAD), a device that comes from slit technology was developed to improve the acquisition of mammograms. This device reduces the amount of scattered radiation and the focus size and it can be projected from a computational model. This model allows quantifying the value of those parameters, scattered radiation and the focus size, for any radiological system, any X-rayed soft tissue thickness and any tension applied to the X-ray tube. The device was implemented and tested quantifying the obtained improvements. The generated images were compared to the supplied for conventional mammography systems. The model was also good for studying interference on the algorithms used in the computer aided diagnosis systems (CAD).

Neste trabalho, avaliou-se a quantidade de informação diagnóstica contida na distribuição da radiação espalhada em mamografia, através de simulações Monte Carlo (MC). Para isto, este trabalho consistiu de dois objetivos: o primeiro diz respeito ao desenvolvimento de um código MC para o transporte de fótons em radiodiagnóstico, com ênfase em mamografia. O segundo diz respeito ao estudo da distribuição da radiação espalhada pela mama, e seu potencial diagnóstico. O modelo geométrico adotado nas simulações consistiu de uma mama comprimida semi-infinita, com um nódulo esférico inserido, simulando um nódulo maligno. Um receptor plano ideal foi posicionado abaixo da mama, a uma distância h. A distribuição angular da radiação espalhada pela mama, e sua distribuição espacial sobre o receptor, foram obtidas para um feixe estreito incidindo perpendicularmente sobre a superfície da mama. Estas distribuições foram utilizadas para calcular valores de contraste (CS) e razão contraste-ruído (CNRS) dos fótons espalhados, comparando as distribuições provenientes de regiões da mama sem e com o nódulo. Valores de CS e CNRS foram estudados para diferentes energias do feixe incidente, tamanho e posição do nódulo, e espessura e composição da mama. A influência de feixes polienergéticos nos valores de CS e CNRS também foi investigada. Para a distribuição espacial da radiação espalhada, valores de CS e CNRS também foram estudados como função da distância do receptor à mama. Os resultados mostram que a distribuição da radiação espalhada apresenta picos de espalhamento, que são produzidos pelos fótons elasticamente espalhados, e estão relacionados com a composição da mama. As distribuições angulares de CS e CNRS mostraram que valores máximos destas distribuições ocorrem próximos ao primeiro pico de espalhamento. Valores de CS maiores que o contrate primário foram obtidos em todas situações analisadas, embora o CNRS tenha se mostrado consideravelmente mais baixo que o CNR primário. As distribuições espaciais de CS e CNRS no receptor indicam que o uso de um receptor plano não reduz os valores de CS, comparados com os obtidos para a distribuição angular, embora o CNRS decresça a medida que h aumenta. Imagens planares, obtidas utilizando o feixe espalhado, mostram que, além de fornecer valores de contraste maiores que o contraste primário, a técnica permite realçar um determinado tipo de tecido na imagem, a partir da seleção de um determinado valor de momentum transferido x. Os resultados obtidos neste trabalho indicam que a radiação espalhada contém informação diagnóstica a respeito da presença de um nódulo na mama. Estudos futuros a respeito da otimização das condições de irradiação da mama e detecção da radiação espalhada devem ser realizados, a fim de se aumentar os valores de CNRS, sem comprometer os valores de CS. / In this work, the potential of forward x-ray scattering for contrast enhancement of malignant nodules in mammography was studied through MC simulations. This work consisted of two objectives: the ¯rst one refers to the development of a Monte Carlo (MC) code for simulation of photon transport in radiodiagnostic, focusing on mammography. The second objective refers to the study of the distribution of scattered photons by the breast, and its diagnostic potential. The geometric model adopted in the simulations consisted of a semi-in¯nite compressed breast, with a spherical nodule inserted within it, simulating a nodule. A planar ideal receptor was positioned under the breast, at a distance h from it. The angular distribution of scattered photons exiting the breast, and its spatial distribution on the receptor, were obtained for a pencil beam impinging normally on the breast surface. These distributions were used to compute values of scatter contrast (CS) and contrast-to-noise ratio (CNRS), by comparing the signal from regions of the breast without and with the nodule. Values of CS and CNRS were studied for di®erent beam energies, nodule size and position, and breast thickness and composition. In°uence of polienergetic spectra on CS and CNRS were also investigated. For the spatial distribution of scattered photons on the receptor, values of CS and CNRS were also studied as a function of the distance of the receptor to the breast. Results show that the distributions of scattered photons present scattering peaks, which are yielded by the elastic scattered photons, and are related to the breast composition. The angular distributions of CS and CNRS showed that maximum values occur close to the adipose scattering peak. Values of CS greater than primary contrast were obtained in all situations analyzed, although the CNRS was considerably lower than primary CNR. The spatial distributions of CS and CNRS indicate that the use of a planar receptor does not reduce the values of CS, compared with those from the angular distribution, although the CNRS decreases as h increases. Planar images, obtained for the scattered beam, showed that, in addiction to contrast enhancement, this technique allows the accentuation of a given tissue in image, by selecting a given value of transfer momentum x. The results obtained in this work indicate that scattered radiation contains diagnostic information about the presence of a nodule within the breast. Further studies, regarding optimization of conditions of breast irradiation and radiation detection, should be performed, in order to increase values of CNRS, without reducing values of CS.

Made available in DSpace on 2015-03-05T14:01:22Z (GMT). No. of bitstreams: 0 Previous issue date: 12 / Bolsa para curso e programa de Pós Graduação / Este trabalho aborda o uso de uma metaheurística populacional para a solução do problema de otimização conhecido, na Pesquisa Operacional, como Programação de Horário de Cursos Baseada em Currículos. O problema de Programação de Horário de Cursos Baseada em Currículos consiste na construção das grades de horário de cursos em instituição de ensino que indicam em quais períodos semanais cada disciplina destes cursos deverá ocorrer, alocando professores e salas e respeitando um conjunto de requisitos organizacionais, pedagógicos e pessoais. Este trabalho apresenta uma formulação matemática para o problema e especifica um algoritmo de solução baseado na técnica metaheurística Busca Dispersa, combinada com o método de Reconexão por Caminhos. Além disso, é apresentado o registro de testes realizados com instâncias de problemas utilizadas na International Timetabling Competition e também em um problema real de uma instituição local de esino superior. / This paper discusses the use of a populational metaheuristic to solve the optimization problem known in Operational Research, as Curriculum Based Timetabling. The Curriculum Based Timetabling problem is the construction of schedule of courses in educational institutions that indicate which weekly times each subject of these courses should occur, allocating rooms and teachers and a respecting a set of organizational, pedagogical and personal requirements. This paper presents a mathematical formulation for the problem and specify a solution algorithm based on the Scatter Search metaheuristic technique, combined with the method Path Relinking. Furthermore, it is present the record of tests with instances of problems used in the International Timetabling Competition and also a real problem of a local institution.