<p>The substantial advances of coronary CTA have resulted in a boost of use of this new technique in the last several years, which brings a big challenge to radiologists by the increasing number of exams and the large amount of data for each patient. The main goal of this study was to develop a computer tool to facilitate coronary CTA analysis by combining knowledge of medicine and image processing.Firstly, a competing fuzzy connectedness tree algorithm was developed to segment the coronary arteries and extract centerlines for each branch. The new algorithm, which is an extension of the “virtual contrast injection” method, preserves the low density soft tissue around the coronary, which reduces the possibility of introducing false positive stenoses during segmentation.Secondly, this algorithm was implemented in open source software in which multiple visualization techniques were integrated into an intuitive user interface to facilitate user interaction and provide good over¬views of the processing results. Considerable efforts were put on optimizing the computa¬tional speed of the algorithm to meet the clinical requirements.Thirdly, an automatic seeding method, that can automatically remove rib cage and recognize the aortic root, was introduced into the interactive segmentation workflow to further minimize the requirement of user interactivity during post-processing. The automatic procedure is carried out right after the images are received, which saves users time after they open the data. Vessel enhance¬ment and quantitative 2D vessel contour analysis are also included in this new version of the software. In our preliminary experience, visually accurate segmentation results of major branches have been achieved in 74 cases (42 cases reported in paper II and 32 cases in paper III) using our software with limited user interaction. On 128 branches of 32 patients, the average overlap between the centerline created in our software and the manually created reference standard was 96.0%. The average distance between them was 0.38 mm, lower than the mean voxel size. The automatic procedure ran for 3-5 min as a single-thread application in the background. Interactive processing took 3 min in average with the latest version of software. In conclusion, the presented software provides fast and automatic coron¬ary artery segmentation and visualization. The accuracy of the centerline tracking was found to be acceptable when compared to manually created centerlines.</p>

<p>Although the term maritime safety is widely used in the maritime domain, there is no exact definition of what is included in it. This thesis is an explorative study with focus on the Vessel Traffic Service domain. VTS operators were interviewed and observed to gain insights in how maritime safety is constructed from the perspective of an operator. Further, definitions of maritime safety by central organizations in the maritime domain have been studied through a literature study and several interviews.</p><p>The results of the study indicate that there is no common definition of the term maritime safety. The organizations generally identify maritime safety as an overall goal or an umbrella term for measures such as traffic separation schemes or fairway design etc. In contrast to this, the analysis of the data obtained indicates that VTS operators define maritime safety as a context-dependent condition which is shaped by their own action.</p><p>It is concluded that there is a gap between the central actors’ and the VTS operators’ understanding and definition of maritime safety. To increase the overall safety in the maritime domain, there is the need to overcome this gap through constructing common values, norms and identities. Instead of having several definitions of maritime safety, there should be one definition which can capture the fact of safety being a dynamic condition which is shaped by the enactment of reliability through, in this case, the VTS operators.</p><p>Finally, the VTS as service to the maritime community should be seen as the subject in the construction and promotion of maritime safety, not as just an object.</p>

<p>Fledermaus is software where different kind of analysis with spatial data can be done. The main area where to use Fledermaus is related to hydrographical surveys. This study is aimed to test and analyse the way Swedish Maritime Administration (Sjöfartsverket) uses Fledermaus. Through step by step explaining how to do when measuring sea bed conditions from a vessel, this text is possible to use as a manual for the applications that are mentioned in this report.</p><p>Another thing that is treated is the squat effect that belongs to vessel dynamic motions. Test of visualization that concerning squat in Fledermaus is done, but with a negative result when squat in a perspective to show motions in height that can be up to about a metre is very hard in a terrain model of thousands of metres. By further tests by arranging the input data, several interesting diagrams have been created through Microsoft Excel where graphs show that the depths are affecting the squat effect. This is showed in same diagram but with two different scales to show the relationship between how a point at the vessel moves in height compared to the depth under the vessel when the vessel is navigating in the sea.</p> / <p>Fledermaus är en programvara där olika analyser med rumsliga data kan genomföras. Största användningsområdet är att använda Fledermaus till mätningar som är relaterade till sjömätning. Den här studien är inriktad till att testa och analysera applikationer som Sjöfartsverket använder sig av i Fledermaus. Genom att steg för steg förklara hur Fledermaus ska användas när bottenförhållanden ska mätas sett från ett fartyg, så blir texten även möjlig att använda som en manual till de applikationer i Fledermaus som är nämnda i denna rapport.</p><p>Det andra som behandlas är squateffekten som tillhör ett fartygs dynamiska rörelser. Test av visualisering som behandlar squat i Fledermaus är genomförd, dock med negativt resultat då squat i ett perspektiv med att visa rörelser i höjd som kan uppgå till runt en meter är väldigt svårt i en terrängmodell som sträcker sig tusentals meter. Dock genom vidare tester genom behandling av indata, har flertalet intressanta diagram skapats genom Microsoft Excel där kurvor visar att djupet inverkar på squateffekten. Detta visas genom att i samma diagram fast med två olika skalor visa förhållandet mellan hur en punkt på båten rör sig i höjd jämfört med att djupet under fartyget ändras då fartyget gör fart genom vattnet.</p>

Xylem vessels have long been proposed as a key innovation for the ecological diversification of angiosperms by providing a breakthrough in hydraulic efficiency to support high rates of photosynthesis and growth. However, recent studies demonstrated that angiosperm woods with structurally ‘primitive’ vessels did not have greater whole stem hydraulic capacities as compared to vesselless angiosperms. As an alternative to the hydraulic superiority hypothesis, the heteroxylly hypothesis proposes that subtle hydraulic efficiencies of primitive vessels over tracheids enabled new directions of functional specialization in the wood. However, the functional properties of early heteroxyllous wood remain unknown. We selected the two species of Canellales from Madagascar to test the heteroxylly hypothesis because Canellaceae (represented by Cinnamosma madagascariensis) produces wood with vessels of an ancestral form, while Winteraceae, the sister-clade (represented by Takhtajania perrieri) is vesselless. We found that heteroxylly correlated with increased wood functional diversity related mostly to biomechanical specialization. However, vessels were not associated with greater stem hydraulic efficiency or increased shoot hydraulic capacity. Our results support the heteroxylly hypothesis and highlight the importance integrating a broader ecological context to understand the evolution of vessels.

Submerged arc welding (SAW) is often the method of choice in pressure vessel fabrication. This process features high production rates, welding energy and/or welding speed and requires minimal operator skill. The selection of appropriate parameters in SAW is essential, not only to optimize the welding process in order to maintain the highest level of productivity, but also to obtain the most desirable mechanical properties of the weld.<p> The focus of this study was to investigate the effect of welding speed on the properties of SA516 Grade 70. Plates of SA516 Gr. 70 steel 17 mm x 915 mm x 122 mm were submerged arc welded with a welding current of 700 A and welding speeds of 15.3, 12.3 and 9.3 mm/s. Following the welding; strength, microstructure, hardness and impact toughness of the specimens were examined. Charpy impact testing was performed according to ASTM E 23 on specimens notched in the weld metal (WM) and in the heat-affected zone (HAZ), to measure the impact toughness. Fractography was performed on broken specimens using optical and scanning electron microscopy in order to correlate the mechanisms of fracture with the impact toughness values.<p> The highest hardness values were in the coarse-grained HAZ followed by the WM with the lowest hardness in the parent metal (PM). The HAZ had higher impact toughness than the WM and PM for all welding speeds. The slowest welding speed (9.3 mm/s) obtained complete penetration and therefore produced the most visually sound weld. The fastest welding speed (15.3 mm/s) had the narrowest HAZ and showed good ductile-to-brittle transition behaviour for both the WM and HAZ specimens, but produced incomplete penetration defects. Welding speed had little affect on the notch toughness of the HAZ with only a 9 J rise in upper shelf energy and an 8 °C drop in the impact transition temperature (ITT) with increased welding speed from 9.3 to 15.3 mm/s. However, for the WM, there was a 63 J drop in the upper shelf energy but also a 41 °C improvement of the ITT between the 9.3 and 15.3 mm/s welding speeds.

The goal of this thesis was to produce an animal model that develops atherosclerotic plaque featuring plaque neovascularization leading to intraplaque hemorrhage and is suitable for noninvasive imaging studies. Several strategies were tested for their effectiveness in producing such plaques in the rabbit aorta, including: a high cholesterol diet, vascular endothelial growth factor injections, therapeutic contrast ultrasound, and balloon catheter injury. It was found that a combination of the high cholesterol diet and balloon injury was able to achieve plaque neovascularization in a manner dependent on circulating plasma cholesterol levels. In addition, a contrast-enhanced magnetic resonance imaging technique implemented in the animal model was able to detect plaque neovascularization and monitor its change over time in a single group of animals. In conclusion, an animal model was created where plaque neovascularization occurs in a predictable fashion and can be studied with non-invasive magnetic resonance imaging.

This thesis presents a high-resolution volumetric technique to measure the longitudinal relaxation time T1 in the vessel wall using MRI. The method of Variable Flip Angles (VFA) was applied using a new strategy for flip angle selection that allows measurement of T1 with high accuracy (< 10% mean error) and precision (T1-to-noise ratio > 10) over the wide range of anticipated values (300-3000ms) in the vessel wall. This strategy was validated in simulation, phantom and volunteer spinal cord experiments. Initial validation of vessel wall T1 measurements was performed in ex-vivo thoracic aorta samples from cholesterol-fed rabbits. For in-vivo vessel wall T1 mapping, the technique was augmented with spatial saturation bands for flow suppression and applied to the carotid arteries of three volunteers. Preliminary results from volunteers suggest that this approach may be useful in characterizing T1 changes associated with high-risk atherosclerotic disease.

Cerebral small vessel disease (SVD) is highly prevalent in older adults and is a predictor of stroke, dementia, and death. SVD is also associated with cognitive dysfunction, gait problems, and urinary incontinence. SVD is diagnosed based on white matter hyperintensities on T2 weighted scans. This thesis investigates the cardiac frequency component of resting state functional magnetic resonance imaging data in young healthy adults, older healthy adults, and older adults with pronounced SVD. A cardiac pulsatility metric is defined, and a tissue type contrast is observed between white matter, grey matter, and cerebrospinal fluid. Aging and disease effects are observed on cardiac pulsatility in white matter. The increased pulsatility may reflect the pathology of venous collagenosis and draining vein stenosis. Developing a better understanding of the etiology of SVD is an important step towards treating the disease.

The goal of this thesis was to produce an animal model that develops atherosclerotic plaque featuring plaque neovascularization leading to intraplaque hemorrhage and is suitable for noninvasive imaging studies. Several strategies were tested for their effectiveness in producing such plaques in the rabbit aorta, including: a high cholesterol diet, vascular endothelial growth factor injections, therapeutic contrast ultrasound, and balloon catheter injury. It was found that a combination of the high cholesterol diet and balloon injury was able to achieve plaque neovascularization in a manner dependent on circulating plasma cholesterol levels. In addition, a contrast-enhanced magnetic resonance imaging technique implemented in the animal model was able to detect plaque neovascularization and monitor its change over time in a single group of animals. In conclusion, an animal model was created where plaque neovascularization occurs in a predictable fashion and can be studied with non-invasive magnetic resonance imaging.

This thesis presents a high-resolution volumetric technique to measure the longitudinal relaxation time T1 in the vessel wall using MRI. The method of Variable Flip Angles (VFA) was applied using a new strategy for flip angle selection that allows measurement of T1 with high accuracy (< 10% mean error) and precision (T1-to-noise ratio > 10) over the wide range of anticipated values (300-3000ms) in the vessel wall. This strategy was validated in simulation, phantom and volunteer spinal cord experiments. Initial validation of vessel wall T1 measurements was performed in ex-vivo thoracic aorta samples from cholesterol-fed rabbits. For in-vivo vessel wall T1 mapping, the technique was augmented with spatial saturation bands for flow suppression and applied to the carotid arteries of three volunteers. Preliminary results from volunteers suggest that this approach may be useful in characterizing T1 changes associated with high-risk atherosclerotic disease.