The storage of pressure liquefied gas in vessels is subject to various regulations and codes of practice. For example, Liquefied Petroleum Gas (LPG), a commercially relevant product, is subject to Health and Safety Executive Guidelines regarding cylinder/tank arrangements and spacing. In the event of an incident involving fire, the internal pressure and shell temperature of an LPG vessel will rise, and the weakening of steel at elevated temperatures can result in the structural failure of the shell. This can be avoided by the fitting of pressure relief valves, which vent material at a pre-set pressure. However, an ignited release can create a high velocity jet flame which, because of significant radiative and convective components, can generate intense, localised heat loads on neighbouring vessels or pipe-work. However, existing codes of practice have no special provision for the possibility of jet fire incidents. Owing to a lack of detailed information on the thermal response of a LPG vessel exposed to jet flame impingement, a series of laboratory scale tests with simulated, localised jet fire impingement on the exterior shell of a pressure vessel was required. The thermal response and the effects of key parameters, Le. fill level, magnitude of heated zone (Le. size and intensity) and position of simulated impingement, could then be examined for the part-validation of a suitable computer model. In addition, these studies could be used to interpret the results from concurrent full scale jet fire impingement trials. An appropriate pressure vessel was constructed to standard design codes, which incorporated a vent line and dump tank. A suitable LPG substitute was selected. Results from the studies indicated that mixing, and therefore thermal stratification, was highly dependent on the size of the heated zone and its position in relation to the liquid/vapour interface. High Speed Micro-Cinematography was successfully employed to film individual bubble streams within the vessel and to measure individual bubble sizes and velocities for various experimental configurations. Studies were also made on the venting characteristics. Sudden pressure relief caused severe agitation of the liquid phase and the breakdown of thermal stratification. In addition, swelling and aerosol generation through homogenous boiling within the liquid phase was observed. Comparisons with the nodal computer model revealed that the use of only single vapour and liquid nodes was a poor approximation to the detail observed in the small scale studies, where the incident heat flux was relatively low and the simulated region of impingement was highly localised. However, the bulk liquid and vapour temperatures and the pressure response up to the time of venting was generally well predicted. As the degree of engulfment increased the model became a better approximation. Although the full scale trials employed an almost fully engulfing jet flame rather than point source impingement, comparisons have allowed understanding of the liquid and vapour thermal gradients, and the subsequent breakdown of these during venting.

No description available.

The motivation of this study lies in the necessity for a microfocal therapy to specifically target diseased areas in vascular pathologies such as age-related macular degeneration (AMD). AMD is the most common cause of legal blindness among people over the age of 60 in developed countries. This degenerative condition affects the macula, the central region of the retina, severely impairing detailed vision and hindering everyday activities. Worldwide, 25-30 million people live with some form of AMD. Among them, ~10% suffer from the more advanced and damaging form, wet-AMD, which causes rapid and severe loss of central vision. To date, there is no cure or long-term alternative for this degenerative disease despite intensive research efforts. With recent developments in biophysical tools and experimental procedures, in this study, we demonstrate a highly-localized therapeutic option: two-photon (2-photon) photodynamic therapy (PDT) that could be advantageous for the cure of wet-AMD, either alone or in combination with recently discovered anti-angiogenic therapies. This new approach offers selective targeting of the diseased area, thus minimizing damage to the surrounding sensitive healthy eye tissues, which is a major concern with the clinically-used, standard wide-beam, one-photon (1-photon) PDT. The objective of the research was to test the feasibility of microfocal 1-photon and the inherently localized 2-photon PDT, their optimization and also to evaluate the efficacy of existing 1-photon and novel 2-photon photosensitizers. In this thesis, I illustrated the in vitro (endothelial cell monolayer) and in vivo (window chamber mouse (WCM)) models that can be used to quantitatively compare the 2-photon efficiency of photosensitizers. Using the in vitro model, I compared the 2-photon efficacy of clinically used 1-photon PDT drugs Photofrin and Visudyne, and showed that the Visudyne is an order of magnitude better 2-photon photosensitizer than Photofrin. With the WCM model, I demonstrated a novel designer 2-photon photosensitizer is 20 times more efficient than Visudyne for single vessel occlusion. I also generated the drug and light dose reciprocity curve for localized single-vessel microfocal PDT. This is a necessary step towards applying the method to the relevant ocular models of AMD, which is the next phase for this research.

Title: Vessel segmentation Author: Ján Dupej Department / Institute: Department of Software and Computer Science Education Supervisor of the master thesis: RNDr. Josef Pelikán, KSVI Abstract: In this thesis we researched some of the blood vessed segmentation and visualization techniques currently available for angiography on CT data. We then designed, implemented and tested a system that allows both semi-automatic and automatic vessel segmentation and visualization. For vessel segmantation and tracking we used a region-growing algorithm that we overhauled with several heuristics and combined with centerline detection. We then automated this algorithm by automatic seed generation. The visualization part is accomplished with an adaptation of the well-known straightened CPR method that we enhanced so that it visualizes the whole cross-section of the blood vessel, instead of just one line of it. Furthermore, we used the Bishop frame to maintain minimal twist of the curve-local coordinate system along the whole vessel. Keywords: vessel segmentation, medical data analysis, volume data

Cerebral small vessel disease (SVD) is a leading cause of stroke and vascular dementia. The majority of cases are sporadic, occurring in the elderly hypertensive population. However, there also exist patients with familial disease. The most common form is Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), caused by mutations in the NOTCH3 gene. In recent years, other genes have also been found to cause familial SVD, such as COL4A1/A2, HTRA1, FOXC1 and TREX1. Genome wide association studies (GWAS) have also revealed loci associated with sporadic SVD strokes and its related features. This thesis explores the genetic basis of SVD primarily from the angle of the 'one gene, one disease' hypothesis. We explore the phenotype of familial SVD using CADASIL as a prototype. We next adopt a candidate gene approach to rare variant discovery using high throughput sequencing (HTS) techniques in two forms: 1) a multi-gene sequencing panel to examine the presence of rare variants in a cohort of 993 presumed-sporadic, early-onset SVD stroke patients, and 2) whole genome sequencing in 118 pedigrees with suspected familial SVD. We also evaluate the prevalence of known disease-causing mutations in the general population using a cohort of whole genome sequenced non-SVD patients, and other control databases. We demonstrate that a few presumed-sporadic SVD stroke patients may in fact have familial disease that was not previously diagnosed. We show that known and novel rare variants in candidate genes are found in our cohort of familial SVD patients, and suggest a possible role for rare variants in genes associated with related phenotypes and sporadic disease in this cohort. Finally, we identify known disease-causing variants in relatively high frequencies in the population, and show that conclusions on the pathogenicity of variants based on allele frequency and functional analyses may sometimes be misguided, thus highlighting the current limitations we face in the clinical interpretation of variants identified on HTS. In recent years genetic studies have revealed that pathways in different familial diseases are likely to converge in the pathogenesis of sporadic disease. Further uncovering the genetic basis of undiagnosed cases of familial SVD may shed light on the mechanisms underlying the sporadic form of disease, and may in turn drive the identification of potential therapeutic targets.

The work described in this thesis tested the feasibility of using a towed array of hydrophones to: 1. localise sources of underwater acoustic noise radiated by the towvessel, 2. determine the absolute amplitudes of these sources, and 3. determine the resulting far-field acoustic signature of the tow-vessel. The concept was for the towvessel to carry out a U-turn manoeuvre so as to bring the acoustic section of the array into a location suitable for beamforming along the length of the tow-vessel. All three of the above were shown to be feasible using both simulated and field data, although no independent field measurements were available to fully evaluate the accuracy of the far-field acoustic signature determinations. A computer program was written to simulate the acoustic signals received by moving hydrophones. This program had the ability to model a variety of acoustic sources and to deal with realistic acoustic propagation conditions, including shallow water propagation with significant bottom interactions. The latter was accomplished using both ray and wave methods and it was found that, for simple fluid half-space seabeds, a modified ray method gave results that were virtually identical to those obtained with a full wave method, even at very low frequencies, and with a substantial saving in execution time. A field experiment was carried out during which a tug towing a 60-hydrophone array carried out a series of U-turn manoeuvres. The signals received by the array included noise radiated by the tow-vessel, signals from acoustic tracking beacons mounted on the tow-vessel, and transient signals generated by imploding sources deployed from a second vessel. / Algorithms were developed to obtain snapshots of the vertical plane and horizontal plane shapes of the array from the transient data and to use range data derived from the tracking beacon signals to track the hydrophones in the horizontal plane. The latter was complicated by a high proportion of dropouts and outliers in the range data caused by the directionality of the hydrophones at the high frequencies emitted by the beacons. Despite this, excellent tracking performance was obtained. Matched field inversion was used to determine the vertical plane array shapes at times when no transient signals were available, and to provide information about the geoacoustic properties of the seabed. There was very good agreement between the inversion results and array shapes determined using transient signals. During trial manoeuvres the array was moving rapidly relative to the vessel and changing shape. A number of different array-processing algorithms were developed to provide source localisation and amplitude estimates in this situation: a timedomain beamformer; two frequency-domain, data independent beamformers; an adaptive frequency-domain beamformer; and an array processor based on a regularised least-squares inversion. The relative performance of each of these algorithms was assessed using simulated and field data. Data from three different manoeuvres were processed and in each case a calibrated source was localised to within 1 m of its known position at the source's fundamental frequency of 112 Hz. / Localisation was also successful in most instances at 336 Hz, 560 Hz and 784 Hz, although with somewhat reduced accuracy due to lower signal to noise ratios. Localisation results for vessel noise sources were also consistent with the positions of the corresponding items of machinery. The estimated levels of the calibrated source obtained during the three manoeuvres were all within 4.1 dB of the calibrated value, and varied by only 1.3 dB between manoeuvres. Results at the higher frequencies had larger errors, with a maximum variation of 3.8 dB between serials, and a maximum deviation from the calibrated value of 6.8 dB. An algorithm was also developed to predict the far-field signature of the tow-vessel from the measured data and results were produced. This algorithm performed well with simulated data but no independent measurements were available to compare with the field results.

Although lymphatic vessel behavior is analogous to hearts (e.g. systole and diastole) and blood vessels (e.g. basal tone), hearts and blood vessels have fundamentally different contractile properties. While summation during contraction is minimized in the heart, summation is necessary for tonic contraction in blood vessels. Because lymphatic vessel behavior mimics cardiac and vascular behavior, we hypothesized that above a critical contraction frequency there is significant summation, evidenced by significantly increased diastolic active tension (i.e. basal tone). We used an isovolumic, controlled-flow preparation to examine the interaction of contraction cycle-time with contraction frequency. Using segments of isolated lymphatic vessels (~1 cm in length and 3-4 mm in diameter) from bovine mesentery, we measured transmural pressure and diameter for end-diastole and end-systole during spontaneous contractions for 10 volume steps. We found time between contractions (beat-to-beat period) decreases with increasing diameter, and total contraction time (vessel twitch length, 11.08 ± 1.54 s) slightly increases with increasing diameter. At the intersection of these relationships, there is a critical period, below which the vessel does not have time to fully relax. Above the diameter at the critical period, diastolic active tension (end-diastolic minus passive vessel tension) significantly increases with increases in diameter (309 to 562% change in slope, p<0.0001), and, below the critical period, diastolic active tension increases with decreases in beat-to-beat period (712 to 2208% change in slope, p<0.0014). Because this transition occurs within a physiological range, it suggests summation may be crucial for lymphatic vessel function as a pump and a conduit.

The ocean, especially the deep ocean, dominates this world; it is the largest single habitat on the planet, a habitat whose inhabitants constitute the most common forms of life on this planet. By its immense influence on the global climate systems, this vast realm continually shapes life on the land. It is the least understood realm on the planet, home to a system of life that we did not know existed ? nor was it one we could even have imagined - only found by accident in the late twentieth century. We are tampering blindly with this vast realm, destroying segments of the intricate and complex systems of life within it. We plunder its riches and only return our waste. We need to know the ocean; it just may control our fate. <br /><br /> Presently, there is a gap in our ability to study this realm: we can no longer only sit on the surface, peering in from time to time; we need to look beneath the ocean's obscuring surface, at any point, for extended periods. Small research submersibles and self-contained diving gear only become available in the later half of the twentieth century, allowing us to venture beneath the ocean's surface. However, these have severe limitations, in their endurance (usually measured in hours) and operational conditions. The heyday for underwater research was the late nineteen-sixties; at that time there were, around the world, over fifty fixed undersea habitats operated by half a dozen countries. Their complexity, and their large on- and off- shore support requirements, eventually lead their sponsors to abandon of most of these habitats. There are only two left operating today, both of which are just off the coast of Florida, with one converted to a dive-access hotel in a coastal lagoon and the other anchored well offshore, the last remaining active undersea research habitat in the world. <br /><br /> We need a new type of ocean-going research vessel that will operate as an observation post on the deep ocean. Scientists need to collect a variety of data, over scales ranging from millimetres to kilometres and time spans ranging from seconds to days, years, and even decades; do this through a continuous, comprehensive, long-term, manned presence on and in the ocean, down to the seafloor, instead of trying to piece together processes by taking intermittent snapshots of a relatively few places and events; and keep this whole endeavour open and accessible to the entire world. A vessel that bridges the surface that isolates the two separate but intricately linked worlds, above and below, would enable researchers to be in both places at once. What such a vessel would be like, how it would function, and what challenges it would deal with; such a vessel is the focus of this thesis.

The ocean, especially the deep ocean, dominates this world; it is the largest single habitat on the planet, a habitat whose inhabitants constitute the most common forms of life on this planet. By its immense influence on the global climate systems, this vast realm continually shapes life on the land. It is the least understood realm on the planet, home to a system of life that we did not know existed ? nor was it one we could even have imagined - only found by accident in the late twentieth century. We are tampering blindly with this vast realm, destroying segments of the intricate and complex systems of life within it. We plunder its riches and only return our waste. We need to know the ocean; it just may control our fate. <br /><br /> Presently, there is a gap in our ability to study this realm: we can no longer only sit on the surface, peering in from time to time; we need to look beneath the ocean's obscuring surface, at any point, for extended periods. Small research submersibles and self-contained diving gear only become available in the later half of the twentieth century, allowing us to venture beneath the ocean's surface. However, these have severe limitations, in their endurance (usually measured in hours) and operational conditions. The heyday for underwater research was the late nineteen-sixties; at that time there were, around the world, over fifty fixed undersea habitats operated by half a dozen countries. Their complexity, and their large on- and off- shore support requirements, eventually lead their sponsors to abandon of most of these habitats. There are only two left operating today, both of which are just off the coast of Florida, with one converted to a dive-access hotel in a coastal lagoon and the other anchored well offshore, the last remaining active undersea research habitat in the world. <br /><br /> We need a new type of ocean-going research vessel that will operate as an observation post on the deep ocean. Scientists need to collect a variety of data, over scales ranging from millimetres to kilometres and time spans ranging from seconds to days, years, and even decades; do this through a continuous, comprehensive, long-term, manned presence on and in the ocean, down to the seafloor, instead of trying to piece together processes by taking intermittent snapshots of a relatively few places and events; and keep this whole endeavour open and accessible to the entire world. A vessel that bridges the surface that isolates the two separate but intricately linked worlds, above and below, would enable researchers to be in both places at once. What such a vessel would be like, how it would function, and what challenges it would deal with; such a vessel is the focus of this thesis.

In this dissertation, I investigated computing algorithms for automated retinal blood vessel detection. Changes in blood vessel structures are important indicators of many diseases such as diabetes, hypertension, etc. Blood vessel is also very useful in tracking of disease progression, and for biometric authentication. In this dissertation, I proposed two algorithms to detect blood vessel maps in retina. The first algorithm is based on integration of a Gaussian tracing scheme and a Gabor-variance filter. This algorithm traces the large blood vessel in retinal images enhanced with adaptive histogram equalization. Small vessels are traced on further enhanced images by a Gabor-variance filter. The second algorithm is called a radial contrast transform (RCT) algorithm, which converts the intensity information in spatial domain to a high dimensional radial contrast domain. Different feature descriptors are designed to improve the speed, sensitivity, and expandability of the vessel detection system. Performances comparison of the two algorithms with those in the literature shows favorable and robust results. Furthermore, a new performance measure based on central line of blood vessels is proposed as an alternative to more reliable assessment of detection schemes for small vessels, because the significant variations at the edges of small vessels need not be considered. The proposed algorithms were successfully tested in the field for early diabetic retinopathy (DR) screening. A highly modular code library to take advantage of the parallel processing power of multi-core computer architecture was tested in a clinical trial. Performance results showed that our scheme can achieve similar or even better performance than human expert readers for detection of micro-aneurysms on difficult images.