Mobility and Saturation Velocity in Graphene on SiO2

We examine mobility and saturation velocity in graphene on SiO2 above room temperature (300-500 K) and at high fields (~1 V/um). Data are analyzed with practical models including gated carriers, thermal generation, "puddle" charge, and Joule heating. Both mobility and saturation velocity decrease with rising temperature above 300 K, and with rising carrier density above 2x10^12 cm^-2. Saturation velocity is >3x10^7 cm/s at low carrier density, and remains greater than in Si up to 1.2x10^13 cm^-2. Transport appears primarily limited by the SiO2 substrate, but results suggest intrinsic graphene saturation velocity could be more than twice that observed here

Investigating disease and radiotherapy response associations with rectal tumour expression of the DNA damage response proteins, ATM, MRE11, NBS1 and RAD50

Rectal cancers are thought to contribute approximately one third of all colorectal cancers worldwide, and are associated with considerable morbidity and mortality. Worryingly, the incidence of rectal cancer is increasing in developed economies, as genetics and environment converge to cause pathology in increasingly older populations. Despite current detailed knowledge of various molecular mechanisms responsible for oncogenesis, in general, the precise sequence of events causing disease, or influencing prognosis, in a particular patient is not completely understood. This is unsurprising given the multifactorial nature of disease and treatment responses in human populations with highly variable clinical histories. To overcome this knowledge gap, this thesis sought to further refine the understanding of the molecular mechanisms at work during rectal cancer development, and their effect on treatment responses and patient outcomes. Furthermore, by defining the molecular mechanisms of disease, biomarkers (single or multiple molecules whose expression levels serve to identify disease processes common to many patients with the same disease) can be developed and applied to clinical situations – helping to diagnose, prognosticate and determine treatment modalities, depending on the application in question. To this end, and given the large heritage literature concerning DNA damage response proteins and cancer pathophysiology, the expression of four central DNA repair proteins (ATM, MRE11, NBS1 and RAD50) in rectal cancers has been quantified by immunohistochemistry. This will enable correlation of expression levels in different regions of the tumour with available clinicohistopathological variables, such as overall and disease-free survival. Furthermore, although radiotherapy represents a first-line treatment for rectal cancer, highly variable treatment responses have been documented amongst patients. As not all patients stand to benefit from such treatments, the expression of the candidate proteins – central to repairing damaged DNA generated by radiotherapy – and the association with radiotherapy responses are investigated in rectal tumours. Firstly, in the case of ATM, it was found that reduced expression in the growing edge of the tumour (tumour periphery) was associated with better responses to radiotherapy and improved disease-free survival. ATM expression in the tumour centre was also associated with disease-free survival by uni- and multi-variate analyses. Secondly, MRE11 expression was found to be predictive of patient outcomes, when patients were also scored positive for high-grade disease, metastasis positive, and showed perineural invasion. In contrast, NBS1 expression levels in rectal tumours were only found to have a marginal association with patient overall survival, necessitating additional studies of NBS1 in rectal cancer. Low RAD50 expression was associated with worse disease-free survival. RAD50 levels also proved to be useful to delineate low- and high-grade disease subgroups. Together, the analysis of these four markers individually, led to several novel associations with regards to rectal cancer – highlighting their ‘biomarker’ potential in this clinical context. Furthermore, by combining expression of these proteins into combinatorial panels – made up of either ATM and MRE11, or MRE11, NBS1 and RAD50 – a greater predictive power of their expression levels with respect to patient outcomes was demonstrated, and support the use of multiple markers to better understand disease in different patient groups. Therefore, the utility of examining DDR proteins in the context of rectal cancer is demonstrated in this thesis, and the results provide evidence to support future studies investigating the roles of these proteins in larger rectal cancer patient cohorts and other cancers. Further studies and validation of the results of this thesis will help determine whether such proteins can serve as clinically-useful biomarkers for disease intervention

Current concepts in the management of hepatopulmonary syndrome

The hepatopulmonary syndrome is characterized as the triad of liver disease, pulmonary gas exchange abnormalities leading to arterial deoxygenation and evidence of intrapulmonary vascular dilatations. This review summarizes the pathological mechanisms leading to pulmonary vascular changes in hepatopulmonary syndrome. The role of the three currently used diagnostic imaging modalities of contrast-enhanced echocardiography, perfusion lung scanning and pulmonary arteriography that identify the presence of intrapulmonary vascular abnormalities are reviewed. Liver transplantation is considered to be the definitive treatment of hepatopulmonary syndrome with often successful reversal of hypoxemia, however other treatments have been trialed. This review further appraises the evidence for the use of pharmacological agents and the role of radiological interventions in hepatopulmonary syndrome

Descent methods for Nonnegative Matrix Factorization

In this paper, we present several descent methods that can be applied to nonnegative matrix factorization and we analyze a recently developped fast block coordinate method called Rank-one Residue Iteration (RRI). We also give a comparison of these different methods and show that the new block coordinate method has better properties in terms of approximation error and complexity. By interpreting this method as a rank-one approximation of the residue matrix, we prove that it \emph{converges} and also extend it to the nonnegative tensor factorization and introduce some variants of the method by imposing some additional controllable constraints such as: sparsity, discreteness and smoothness.Comment: 47 pages. New convergence proof using damped version of RRI. To appear in Numerical Linear Algebra in Signals, Systems and Control. Accepted. Illustrating Matlab code is included in the source bundl

WAN design with demand, hop limit and path diversity constraints

This thesis presents a challenging telecommunication network design problem, in which the network designer has to assure not only connectivity, but also some degree of performance guarantee and survivability to the solution. We introduce a topological and capacity design, with node-pair constraints of heterogeneous bounds. These constraints take into account the throughput, the number of node-disjoint paths, and the maximum number of hops. Moreover, the capacity to place on each link is chosen from a pool of available cable types, each with its maximum capacity and fixed cost, in other words the cost function is stepwise with respect to capacity usage. The solution space of the problem in study is composed by each one of the node-pair demands. An in-depth combinatorial study was done, leading to the development of a new coding for geneti

Hepatitis C Virus Associated Glomerulonephritis

Approximately 170 million persons worldwide are infected with the hepatitis C (HCV) virus. The incidence of glomerulonephritis in HCV-infected patients is unknown due to a lack of large-scale cross sectional surveys however subclinical renal involvement is believed to be highly prevalent among patients with HCV hepatitis. The most common HCVassociated glomerulonephritis is membranoproliferative glomerulonephritis (MPGN) type 1 with or without cryoglobulinaemia. MPGN typically presents several years, and often decades, after initial infection with HCV. Most patients have laboratory evidence of hypocomplementaemia, circulating rheumatoid factors, and cryoglobulinaemia. Other uncommon forms of glomerular disease that have been reported to be associated with HCV infection include membranous nephropathy, IgA nephropathy, focal segmental glomerulosclerosis, fibrillary glomerulonephritis/immunotactoid glomerulopathy, pauciimmune glomerulonephritis, and thrombotic microangiopathy