Ray tracing is an attractive rendering option because it can produce high quality images that faithfully represent physically-based phenomena. Its embarrassingly parallel nature makes it a natural choice for rendering large-scale scene data, especially on machines that lack specialized graphics hardware. Unfortunately, the traditional recursive ray tracing algorithm is exceptionally memory inefficient for large scenes, especially when using a shading model that generates incoherent secondary rays. Queueing ray tracers have been shown to control scene state under these conditions, but they allow ray state to grow unchecked. Instead, we propose a ray tracing framework that controls both ray and scene state by dynamically adjusting the rendering algorithm to meet memory requirements. Our dynamic scheduling framework generalizes recursive and queueing tracers into a spectrum of ray schedules that can vary the active amount of ray and scene data in order to match the characteristics of the hardware’s memory system. This dissertation describes our dynamic ray scheduling approach that operates on memory-bound work units, which consist of both rays and scene data. It builds these work units by tracing rays iteratively and queueing them in spatial regions along with nearby data. By dynamically scheduling these work units, our approach can reduce data loads and improve total runtime by 2x to 30x . In addition, we show that our algorithm scales across more than 1000 distributed processors, which is an order of magnitude larger than previously published results. Our approach enables the use of complex lighting models on large data, particularly scientific data, which improves image quality and thereby improves the scientific insights possible. / text

Ray tracing based on geometric optics can be utilized for generating propagation models for arbitrary and complex environments. These methods can be employed to determine important wireless channel characteristics such as path gain and the channel impulse response which in turn can be used to deduce channel capacity. In this thesis, a fully vectorial 3-D ray-tracer is developed. The simulator is applied to study novel wireless systems such as ultra-wideband pulse propagation in complex railway tunnels and MIMO systems employing closely spaced low mutual coupling meta-material antennas. The computational complexity of the ray-tracing algorithm is reduced using optimizations and via the development of a novel hybrid method that combines the efficiency and accuracy of waveguide models with the flexibility of a ray-tracer. The resulting simulator is validated against measured results and demonstrated to show good agreement. Convergence of the solution using the ray-tracing method is also discussed.

Ray tracing based on geometric optics can be utilized for generating propagation models for arbitrary and complex environments. These methods can be employed to determine important wireless channel characteristics such as path gain and the channel impulse response which in turn can be used to deduce channel capacity. In this thesis, a fully vectorial 3-D ray-tracer is developed. The simulator is applied to study novel wireless systems such as ultra-wideband pulse propagation in complex railway tunnels and MIMO systems employing closely spaced low mutual coupling meta-material antennas. The computational complexity of the ray-tracing algorithm is reduced using optimizations and via the development of a novel hybrid method that combines the efficiency and accuracy of waveguide models with the flexibility of a ray-tracer. The resulting simulator is validated against measured results and demonstrated to show good agreement. Convergence of the solution using the ray-tracing method is also discussed.

Urogenital chlamydia infection, caused by the bacterium Chlamydia trachomatis (CT), is the most common sexually transmitted bacterial infection in Sweden. In 2008 it was estimated by WHO that there were 105.7 million new cases of CT worldwide, an increase by 4.2 million cases (4.1%) compared to 2005. If untreated, CT infections can progress to serious reproductive health problems, especially in women. These complications include subfertility/infertility, ectopic pregnancy and chronic pain. The CT infection is often asymptomatic and reliable diagnostic methods and contact tracing are important tools for identifying infected individuals. CT infection is classified in the Swedish Communicable Diseases Act as a serious disease; consequently, written reporting and contact tracing are compulsory. Previous or ongoing CT infection is not uncommon in infertile couples, especially in women with tubal factor infertility (TFI). We have tested 244 infertile couples for CT antibodies, and CT IgG positive couples were tested for CT DNA in urine. The prevalence of CT antibodies was higher in infertile men and women, and ongoing CT infection was common. Our results support a role of CT in infertility and underscore the importance of prevention of CT infection. Contact tracing was studied during using questionnaires. A total of 544 questionnaires was sent to tracers in a Swedish county and 534 (98%) were completed. Centralized contact tracing performed by experienced tracers is effective; on average 65% of sexual contacts found by contact tracing are CT-infected. Our data show that it is worthwhile to extend the tracing period beyond 6 months as 30% of reported sexual contacts between months 7-12 were CT-infected. Contact tracing may be performed face-to-face at the clinic or by telephone. Because of the severe consequences of CT infection there is a need for useful methods for both primary and secondary prevention of CT and other sexually transmitted infections (STIs). An important sub-population for CT/STI-prevention is the “core group”, i.e. a subpopulation with high incidence of STIs combined with risky sexual behaviours. This subpopulation contributes particularly to the spread of STIs in the population. Therefore, we have developed and evaluated a brief standardised but flexible manual-based single-session intervention based on motivational interviewing (MI) for the reduction of high risk sexual behaviour. Women (n=105) and men (n=119) at high risk of contracting CT infection were randomly eighter offered brief MI counselling or standard care. Our findings support the effectiveness of brief MI-based counselling in reducing high-risk sexual behaviour and incident CT infection in women (p<0.01) but not in men. Our results suggest that gender aspects need to be considered and that men and women should be treated differently for achieving maximal risk-reduction. Whereas it might be sufficient to include information and motivation when performing risk-reducing counselling on women, counsellors may also add other components, such as behavioural skills and booster sessions, when counselling is performed on men. / Klamydiainfektion orsakas av Chlamydia trachomatis och är den vanligaste sexuellt överförda bakterieinfektionen. WHO har uppskattat att det år 2008 var 105,7 miljoner nya fall av klamydia i världen, en ökning med 4,2 miljoner fall (4,1 %) jämfört med år 2005. Klamydiainfektion är ett folkhälsoproblem och klassificeras i den svenska smittskyddslagen som en allmänfarlig sjukdom varför det är obligatoriskt att smittspåra och göra en skriftlig anmälan till smittskyddsläkaren och Smittskyddsinstitutet. Klamydiainfektionen ger oftast inga symtom och tillförlitliga diagnostiska metoder och smittspårning är viktiga ”redskap” för att hitta smittade personer. Om klamydiainfektionen inte behandlas kan den leda till allvarliga hälsoproblem, speciellt hos kvinnor. Bland komplikationer efter klamydiainfektion ingår ofrivillig barnlöshet, utomkvedshavandeskap och kronisk buksmärta. Tecken på tidigare eller pågående klamydiainfektion är vanliga hos ofrivilligt barnlösa par, speciellt hos kvinnor med skadade äggledare som orsak till barnlösheten. Våra resultat ger stöd för betydelsen av klamydia vid ofrivillig barnlöshet och understryker vikten av förebyggande åtgärder mot klamydia samt klamydiaprovtagning av både män och kvinnor vid utredning av ofrivillig barnlöshet. Centraliserad klamydiasmittspårning utförd av erfarna smittspårare är effektiv och i genomsnitt är 65 % av spårade sexuella kontakter klamydiasmittade. Våra data visar att det lönar sig att förlänga smittspårningsperioden från 6 till 12 månader eftersom betydligt fler klamydiasmittade kontakter då hittas. Den så kallade ”Västerbottensmodellen” med en smittspårningsperiod på 12 månader rekommenderas nu av Socialstyrelsen. Kontaktspårning kan utföras antingen på mottagningen eller per telefon. På grund av risk för allvarliga konsekvenser av klamydia finns det behov av metoder för att förebygga klamydiasmitta. En viktig grupp för prevention är den så kallade ”kärngruppen", alltså de personer som har en hög förekomst av klamydia och andra sexuellt överförda infektioner i kombination med sexuellt riskbeteende. Denna grupp bidrar särskilt till spridningen av sexuellt överförda infektioner bland befolkningen. Därför har vi utvecklat och utvärderat en kort samtalsmetod som bygger på metoden motiverande samtal (MI, motivational interviewing) för att minska sexuellt risktagande. Våra fynd visar att kort MI-baserad rådgivning för att minska sexuellt riskbeteende och klamydiainfektion fungerar bra på kvinnor men inte lika bra på män. Resultaten tyder på att genusaspekter måste beaktas och att kvinnor och män ska behandlas på olika sätt för att uppnå maximal riskminskning. Det kan vara tillräckligt att fokusera på information och motivation vid rådgivning av kvinnor men för rådgivning av män kan man behöva komplettera med beteendemässiga färdigheter och/eller upprepad MI-baserad rådgivning för att nå god effekt.

Ideas are formed in a process of idea generation that includes creation, development, and communication of new ideas. Drawing has been used as a support for ideation for centuries. Today, computerized tools are commonly used for drawing. Such tools form a user interface between the human and the resulting drawing presented on the screen. The interface may come between the user and the drawing in a disruptive way also affecting the ideation process. Using controlled laboratory studies, this thesis investigates the consequences of drawing with different user interfaces in two types of tasks: creative drawing tasks (based on a standardized test of creativity) and non-creative drawing tasks (i.e. shape-tracing tasks where no new idea is created). The goal was to identify and evaluate the consequences of the several issues originating from the use of different input devices, the functionality of the graphical user interfaces, the formulation of the drawing task, and the user’s previous experience. The results showed that drawing tasks are oriented toward quality of outcomes and that higher input accuracy led to higher quality of outcomes of both creative and non-creative drawing tasks. This came with a trade-off between the quantity and quality. In ideation, less accurate input devices facilitated significantly more ideas but these were of lower quality. In non-creative tracing, higher speeds caused lower quality of outcomes. The users subjectively preferred higher accuracy, also when an inaccurate user interface offered an eraser function. However, using the eraser allowed avoiding reinterpretations of ideas and led to ideation strategies characterized by laborious drawing that negatively affected the quality and quantity of the ideas produced. For non-creative drawing, the more difficult the shapes were, the lower the tracing accuracy. In the thesis a new framework for interaction analysis is introduced that improves the theoretical and practical understanding of computerized drawing tasks and the phenomena resulting from different aspects of the user interface design of computerized drawing tools. This thesis demonstrates that the inaccuracy of computerized tools cannot only make our drawings less aesthetically pleasing but also negatively affect ideas that are created in the process.

Purpose: The purpose of our work is to develop a system for automatic contact tracing with the goal of identifying individuals who are most likely infected, even if we do not have direct diagnostic information on their health status. Control of the spread of respiratory pathogens (e.g. novel influenza viruses) in the population using vaccination is a challenging problem that requires quick identification of the infectious agent followed by large-scale production and administration of a vaccine. This takes a significant amount of time. A complementary approach to control transmission is contact tracing and quarantining, which are currently applied to sexually transmitted diseases (STDs). For STDs, identifying the contacts that might have led to disease transmission is relatively easy; however, for respiratory pathogens, the contacts that can lead to transmission include a huge number of face-to-face daily social interactions that are impossible to trace manually. Method: We developed a Bayesian network model to process context awareness proximity sensor information together with (possibly incomplete) diagnosis information to track the spread of disease in a population. Our model tracks real-time proximity contacts and can provide public health agencies with the probability of infection for each individual in the model. For testing our algorithm, we used a real-world mobile sensor dataset of 80 individuals, and we simulated an outbreak. Result: We ran several experiments where different sub-populations were ???infected??? and ???diagnosed.??? By using the contact information, our model was able to automatically identify individuals in the population who were likely to be infected even though they were not directly ???diagnosed??? with an illness. Conclusion: Automatic contact tracing for respiratory pathogens is a powerful idea, however we have identified several implementation challenges. The first challenge is scalability: we note that a contact tracing system with a hundred thousand individuals requires a Bayesian model with a billion nodes. Bayesian inference on models of this scale is an open problem and an active area of research. The second challenge is privacy protection: although the test data were collected in an academic setting, deploying any system will require appropriate safeguards for user privacy. Nonetheless, our work illustrates the potential for broader use of contact tracing for modelling and controlling disease transmission.

It was hypothesized that superparamagnetic nanoparticles encapsulated in a silica shell with a fluorescent dye could be functionalized with axonal tracers and could be used for serial, non-invasive imaging with magnetic resonance imaging (MRI) for axon tract tracing. Nanoparticles functionalized with amine, octadecyl, silica, and biotinylated dextran amine were manufactured and characterized with MRI, scanning electron microscopy, and UV-visible, infrared, and fluorescence spectroscopy. Nanoparticle concentrations of 10 mM were not toxic to adult rat neural progenitor cells (NPCs) and labeled approximately 90% of cells. Nanoparticles were assessed for anterograde and retrograde tract tracing in adult rat models. With MRI and microscopy, the nanoparticles did not appear to trace axons but did provide an MRI signal for up to 3 weeks post implantation. While functionalized nanoparticles did not appear to trace axons, they are not toxic to NPCs and may be used as a MRI contrast agent in the neural axis.

The use of Unmanned Combat Aerial Vehicles (UCAV) or drones have in recent yearsbecome the modus operandi of US counterterrorism strategy to eliminate sought out terrorists.Since the initiation of systematic drone strikes in Pakistan 2004, their use has increased andalso expanded into other countries. In 2012 Yemen experienced equal levels of strikes asPakistan. Thirteen years have passed since the “war on terror” began and although Osama binLaden has been killed, al-Qaeda still prevails and might be expanding. This study examines apossible spread of al-Qaeda from Pakistan to Yemen, since the initiation of drone strikes, byprocess tracing. Building on the literature of al-Qaeda, counterterrorism and UCAV, the aimhas been to analyze drone strikes affect on terrorism by tracing al-Qaeda’s development.Findings suggest there are indications of a spread from al-Qaeda in Pakistan to Yemen,although further research is required to confirm uncertainties in the material.

The use of Unmanned Combat Aerial Vehicles (UCAV) or drones have in recent years become the modus operandi of US counterterrorism strategy to eliminate sought out terrorists.Since the initiation of systematic drone strikes in Pakistan 2004, their use has increased andalso expanded into other countries. In 2012 Yemen experienced equal levels of strikes asPakistan. Thirteen years have passed since the “war on terror” began and although Osama bin Laden has been killed, al-Qaeda still prevails and might be expanding. This study examines apossible spread of al-Qaeda from Pakistan to Yemen, since the initiation of drone strikes, byprocess tracing. Building on the literature of al-Qaeda, counterterrorism and UCAV, the aimhas been to analyze drone strikes affect on terrorism by tracing al-Qaeda’s development.Findings suggest there are indications of a spread from al-Qaeda in Pakistan to Yemen,although further research is required to confirm uncertainties in the material.

This study was undertaken to locate and characterise the neurons in the central nervous system that project to the kidney. In particular, the aim was to illustrate and characterise the neural link between regions in the hypothalamus known to influence renal function and fluid balance, and nerves known to innervate the kidney.