Cryogenic electron microscopy (cryo-EM) is an evolving field allowing molecular visu- alizations with picometer resolutions. Images are acquired by shooting electrons through molecular samples and detecting the scattered electrons. From such data, 3D shapes of the molecules can be inversely reconstructed. Currently, describing and simulating the cryo-EM image formation is based either on naive transmittance models or complicated wave-function formalisms. In this thesis, we explore the possibility of simulating cryo-EM image formation via Monte Carlo electron tracing. We combine a delta-tracking algorithm with an elec- tron elastic differential cross-section function and Rutherford formulae to derive two Monte Carlo estimators. The derived models are implemented in a high-performance C++/CUDA environment and compared with other common models. Our particle-based simulated images show considerable similarity to the wave-based state-of-the-art multi- slice model. We also evaluate our models on class averages of real measurements. Both of our proposed models have significantly higher normalized cross-correlation scores with the measured class averages when compared to the most commonly used transmittance model. The thesis proves the viability of a particle-based Monte Carlo simulation of elec- tron microscope...

This essay aims to find a link between NATO policy in Europe from 2014-2022 to Russia’sdecision to invade Ukraine in February 2022. A process tracing methodology is used in conjunction with an offensive realist framework to demonstrate NATO’s role in influencing Russian defense policy. The investigation finds US global hegemony dictates NATOambitions, leading the Alliance to adopt aggressive policy in Eastern Europe. In turn, Russia identifies NATO as a threat in its military doctrine and proceeds to strengthen its defensive capabilities. Putin outlines Russia’s need for a buffer zone between it and NATO, a prime target for such a place being Ukraine. A failure by both parties to accommodate each others interests leaves Russia with a convincing rationale to seek military force in securing a more favorable defensive position.

The topic of this essay is how countries can successfully democratize in different ways. The aim is to demonstrate how two vastly different countries as Chile and Mozambique were capable of democratizing through what at first glance looks like dissimilar ways, while at the same time trying the robustness of a known democratization theory. In this case study, I use a combination of qualitative, historical and process-tracing methods to get an in-depth understanding as I compare my two cases and measure them against Larry Diamond's theory. His theory is based upon internal- and external factors that play essential parts in democratization. My overall inference is that Chile meets essentially all theoretical expectations while Mozambique barely has more than half of the examined theoretical factors with at least somewhat favorable conditions. I also discovered that they share at least one important factor where they have plenty in common, democracy assistance. In addition to this, I also gained a new insight. Diamond's theory doesn't account for whether a country has a previous history of democracy. This appears to have played at least a significant part in many of his theoretical factors, and it's absolutely something that should be considered for the future. / <p>2022-05-25</p>

Recently, new hardware capabilities in GPUs has opened the possibility of ray tracing in real-time at interactive framerates. These new capabilities can be used for a range of ray tracing techniques - the focus of this thesis is on ray traced ambient occlusion (RTAO). This thesis evaluates real-time ray RTAO by comparing it with ground- truth ambient occlusion (GTAO), a state-of-the-art screen space ambient occlusion (SSAO) method. A contribution by this thesis is that the evaluation is made in scenarios that includes animated objects, both rigid-body animations and skinning animations. This approach has some advantages: it can emphasise visual artefacts that arise due to objects moving and animating. Furthermore, it makes the performance tests better approximate real-world applications such as video games and interactive visualisations. This is particularly true for RTAO, which gets more expensive as the number of objects in a scene increases and have additional costs from managing the ray tracing acceleration structures. The ambient occlusion methods are evaluated in terms of image quality and performance. Image quality is assessed using structural similarity index (SSIM) and through visual inspection. The performance is assessed by measuring computation time, in milliseconds. This thesis shows that the image quality of RTAOis a substantial improvement over GTAO, being close to offline rendering quality. The primary visual issue with RTAO is visible noise - especially noticeable around the contours of moving objects. Nevertheless, GTAO is very competitive due to its performance, the computation time for all GTAO tests were below one ms per frame. At 1080p full-resolution GTAO was computed in 0.3883 ms on a RTX 3070 GPU. In contrast, the computation time of RTAO at 1080p and two samples per pixels were 2.253 ms. The cost of updating and rebuilding ray tracing acceleration structures were also noteworthy. Overall, the results indicate that hardware accelerated ray tracing can be used for significant improvements in image quality but adoption of this technique is not trivial due to performance concerns. / Med hårdvaruaccelererad strålspårning på grafikkort som introducerades nyligen möjliggjordes flera strålspårningsbaserade tekniker för rendering i realtid. Detta examensarbete undersöker en sådan teknik - strålspårad ambient ocklusion (engelska: ray traced ambient occlusion (RTAO)). RTAO undersöks och utvärderas för användning i realtidsapplikationer genom en jämförelse med en ambient-ocklusionsmetod som beräknas i bildrummet (screen space ambient occlusion (SSAO)) kallad ground-truth ambient occlusion (GTAO). Detta examensarbete bidrar genom att utvärdera metoderna i testscenarion som inkluderar animerade objekt. Detta medför ett antal fördelar: utvärderingen kan betona visuella artefakter som kan uppstå när objekt rör sig och animeras. Vidare gör det att prestandatesterna kan inkludera kostnader som tillkommer när scener innehåller animerade objekt - detta är särskilt betydande för RTAO som blir dyrare att beräkna när antalet objekt stiger samt har ytterligare kostnader för att uppdatera datastrukturer som används för att accelerera strålspårningen. På så vis närmar sig testscenarion en bred kategori av applikationer som använder rendering i realtid, exempelvis spel och interaktiva visualiseringar. Utvärderingen sker på uppnådd bildkvalité samt metodernas prestanda. Bildkvalitén utvärderas genom structural similarity index (SSIM) samt visuellinspektion. Prestandan utvärderas genom att mäta beräkningstiden i millisekunder. Resultaten visar att RTAOs bildkvalité är tydligt överlägsen GTAO och närmar sig de resultat som uppnås genom förrendering. Det primära problemet med RTAOs bildkvalité är förekomsten av visuellt brus. Detta är extra tydligt runt konturerna på de objekt som är animerade och förflyttar sig. Hursomhelst är GTAO attraktivt då denna metod kan beräknas betydligt snabbare än RTAO. Samtliga GTAOs prestandatester visade på beräkningstider under en millisekund. Vid en upplösning på 1080p med två prov per pixel (samples per pixel) var beräkningstiden för RTAO 2,253 ms. Kostnaden för att uppdatera datastrukturerna för strålspårningen visade sig också vara betydlig i många tester. Sammantaget indikerar resultaten att hårdvaruaccelererad strålspårning kan resultera i en signifikant förbättring av bildkvalité men att det kan innebära en kostnad som kräver betänklighet.

No description available.

Multi-antenna communication systems are attracting research interest as a means to increase the information capacity, reliability, and spectral efficiency of wireless information transfer. Ray-tracing methods predict the behavior of wireless channels using a model of the propagation environment and are a low-cost alternative to direct measurements. We use ray tracing simulations to validate the statistical time and angle of arrival characteristics of an indoor multipath channel and compare model parameter estimates with estimates derived from channel sounding measurements. Ray tracing predicts the time and angle clustering of multipaths observed in the measurements and provides model parameter estimates which are closely correlated with measured estimates. The ray tracing parameters relating to power characteristics show more deviation from measurements than the time and angle related parameters. Our results also indicate that the description of reflective scatterers in the propagation environment is more important to the quality of the predicted statistical behavior than the description of bulk materials. We use a ray synthesis model to investigate means of efficiently representing the channel for feedback information to the transmitter as a means to increase the information capacity. Several methods of selecting the ray-model feedback information are demonstrated with results from simulated and measured channels. These results indicate that an ESPRIT algorithm coupled with ad hoc transmit/receive pairing can yield better than 90% of the ideal waterfilling capacity when adequate training-based channel estimates are available. Additionally, we investigate a covariance feedback method for providing channel feedback for increased capacity. Both the ray-based and covariance-based feedback methods yield their highest capacity improvements when the signal to noise ratio is low. This results because of the larger benefit of focusing transmit power into the most advantageous eigenmodes of the channel when fewer eigenmodes have power allocated to them by the waterfilling capacity solution. In higher signal to noise ratio cases, more eigenmodes of the channel receive power when waterfilling, and the capacity improvement from feedback information decreases relative to a uniform power allocation. In general, ray model feedback methods are preferable because the covariance feedback quickly requires higher computational effort as the array sizes increase and typically results in lower capacity for a given amount of feedback information.

Millimeter-wave (mmWave) is widely investigated for indoor communication scenarios thanks to the available rich spectrum. However, the shortened antenna size and the high frequency make mmWave extra sensitive to blockages. Indoor dense space (IDS) is a specific type of indoor environment, where the compact geometry together with a high number of blocking objects and users make it hard to fulfill the data rate required by all of the users in the mmWave network. With the capability of redirecting signals, the reconfigurable intelligent surface (RIS) has the potential to overcome the attenuation brought by the blockage. Aside from the promising improvement in data rate brought by the RIS, the power supply for RIS is also a major concern in IDS due to the cabling and the batteries. Dynamic RIS has the capability of reconfiguring its phase-shifts to offer a higher gain in data rate with the price of consuming power. In comparison, by sacrificing the reconfigurability, static RIS does not require any power, cabling, or batteries but is expected to provide lower data rates. To find the balance between the performance and cost trade-off, the concept of self-sustainable RIS in IDS is proposed. This approach involves the utilization of specific RIS elements to harvest energy, thereby providing support for the power requirements of the RIS operation, consequently reducing the reliance on traditional cabling infrastructure. In this work, we compare the coverage extension effect brought by deploying static, dynamic, and self-sustainable RISs in the aircraft cabin which is a typical example of an IDS. To capture the propagation characteristics of a RIS in IDS, we first provide guidelines for modeling the RIS in the ray tracing (RT) simulator, and then we select the best locations to deploy RISs among three candidates. For each type of RIS deployment, we propose an optimization algorithm, which jointly configures the RIS phase-shifts and the time resources to provide the maximum equal achievable data rate for all of the users. Additionally, for the self-sustainable RIS, the working mode of each RIS element is also jointly configured such that each element is used either to reflect the incoming signal or to use the signal for energy harvesting. Based on the results, the signal propagation of a single base station (BS) can be extended from 3 rows to 11 rows by deploying static or dynamic RISs. The minimal achievable data rate is 35.4 Mbps with the static RISs and 45.3 Mbps with the dynamic RISs. The results indicate that due to the limitation of self-sustainable constraints, RISs with 16 elements are hard to cover the whole 11 rows in the considered cabin. Nevertheless, with self-sustainable RIS, 10 more UEs are covered compared to the case where no RIS is deployed. The minimal data rate with the help of the self-sustainable RISs within the coverage is 0.75 Mbps. The feasibility study shows that this energy requirement has a greater likelihood of being fulfilled as the number of elements in RIS increases. / Millimetervåg (mmWave) är allmänt undersökt för inomhuskommunikationsscenarier tack vare det tillgängliga rika spektrumet. Den förkortade antennstorleken och den höga frekvensen gör dock mmWave extra känslig för blockeringar. Indoor dense space (IDS) är en specifik typ av inomhusmiljö, där den kompakta geometrin tillsammans med ett stort antal blockerande objekt och användare gör det svårt att uppfylla den datahastighet som krävs av alla användare i mmWave-nätverket. Med förmågan att omdirigera signaler har reconfigurable intelligent surface (RIS) potentialen att övervinna dämpningen av blockeringen. Bortsett från den lovande förbättringen av datahastigheten som RIS ger, är strömförsörjningen för RIS också ett stort problem inom IDS på grund av kablarna och batterierna. Dynamic RIS har förmågan att omkonfigurera sina fasförskjutningar för att erbjuda en högre förstärkning i datahastighet med priset för att förbruka energi. I jämförelse, genom att offra omkonfigurerbarheten, kräver statisk RIS ingen ström, kablar eller batterier utan förväntas ge lägre datahastigheter. För att hitta balansen mellan prestanda och kostnadsavvägning föreslås konceptet med självförsörjande RIS i IDS. Detta tillvägagångssätt involverar användningen av specifika RIS-element för att skörda energi, vilket ger stöd för strömkraven för RIS-driften, vilket minskar beroendet av traditionell kabelinfrastruktur. I det här arbetet jämför vi den täckningsförlängningseffekt som uppstår genom att installera statiska, dynamiska och självförsörjande RIS i flygplanskabinen, vilket är ett typiskt exempel på en IDS. För att fånga utbredningsegenskaperna för en RIS i IDS ger vi först riktlinjer för modellering av RIS i ray tracing (RT)-simulatorn, och sedan väljer vi de bästa platserna för att distribuera RIS bland tre kandidater. För varje typ av RIS-distribution föreslår vi en optimeringsalgoritm, som gemensamt konfigurerar RIS-fasförskjutningarna och tidsresurserna för att tillhandahålla den maximalt lika möjliga datahastigheten för alla användare. Dessutom, för den självförsörjande RIS, är arbetsläget för varje RIS-element också gemensamt konfigurerat så att varje element används antingen för att reflektera den inkommande signalen eller för att använda signalen för energiskörd. Baserat på resultaten kan signalutbredningen av en enda base station (BS) utökas från 3 rader till 11 rader genom att distribuera statiska eller dynamiska RIS:er. Den minsta möjliga datahastigheten är 35,4 Mbps med statiska RIS och 45,3 Mbps med dynamiska RIS. Resultaten indikerar att på grund av begränsningen av självförsörjande begränsningar är RIS med 16 element svåra att täcka hela 11 rader i den övervägda kabinen. Ändå, med självförsörjande RIS, täcks 10 fler UE jämfört med fallet där ingen RIS är utplacerad. Den minimala datahastigheten med hjälp av de självförsörjande RIS:erna inom täckningen är 0,75 Mbps. Förstudien visar att detta energibehov har större sannolikhet att uppfyllas i takt med att antalet element i RIS ökar.

No description available.

The sister city concept has now been around for several decades and yet there remains to be a paucity of literature dealing with the subject. Despite this unfortunate fact, there has been some literature written trying to deal with the progression of what sparked cities to try to establish sister city relationships with one another. However, this is still not enough. Diasporas have been neglected as a potential cause, which I try to remedy by employing the method of explaining outcome process tracing in a case study of the sister city relationship that began to be explored between the cities of Governador Valadares, Brazil and Framingham, United States.Information was collected using materials such as news articles from such sources as the Metrowest Daily News and official websites such as Governador Valadares’ official city webpage, and various histories, ethnographies, and other sources were also considered especially focusing on Framingham and the Greater Boston Area, allowing for the collection of materials of both primary and secondary nature and thus an in-depth analysis.What was found was that indeed, it is true that diaspora had a hand in influencing the negotiation of a sister city relationship between the two cities; First, the context of the Brazilian Diaspora in the United States was explained and analysed and it was found that it could be termed a termed a proletarian labour diaspora.Explaining outcome process tracing was then employed to inductively explain how the spark can be created, which suggested that the causal mechanism between the diaspora and the negotiations for the SCR to begin were that of an enclave forming due to the diaspora which then allowed social capital to be accumulated, allowing for Governador Valadares to grow despite Brazil’s bad economic conditions due to remittances, leading to the mayor of Governador Valadares initiating the talks.

Much of our understanding of the fascinating complexity of neuronal circuits comes from anatomical tracing studies that use dyes or fluorescent markers to highlight pathways that run through the brain and spinal cord. Viral vectors have been utilized by many previous groups as tools to highlight pathways or deliver transgenes to neuronal populations to stimulate growth after injury. In a series of studies, we explore anterograde and retrograde tracing with viral vectors to trace spinal pathways and explore their contribution to behavior in a rodent model. In a separate study, we explore the effect of stimulating intrinsic growth programs on regrowth of corticospinal tract (CST) axons after contusive injury. In the first study, we use self-complimentary adeno associated viral (scAAV) vectors to trace long descending tracts in the spinal cord. We demonstrate clear and bright labeling of cortico-, rubro- and reticulospinal pathways without the need for IH, and show that scAAV vectors transduce more efficiently than single stranded AAV (ssAAV) in neurons of both injured and uninjured animals. This study demonstrates the usefulness of these tracers in highlighting pathways descending from the brain. Retrograde tracing is also a key facet of neuroanatomical studies involving long distance projection neurons. In the next study, we highlight a lentivirus that permits highly efficient retrograde transport (HiRet) from synaptic terminals within the cervical and lumbar enlargements of the spinal cord. By injecting HiRet, we can clearly identify supraspinal and propriospinal circuits innervating MN pools relating to forelimb and hindlimb function. We observed robust labeling of propriospinal neurons, including high fidelity details of dendritic arbors and axon terminals seldom seen with chemical tracers. In addition, we examine changes in interneuronal circuits occurring after a thoracic contusion, highlighting populations that potentially contribute to spontaneous behavioral recovery in this lesion model. In a related study, we use a modified version of HiRet as part of a multi-vector system that synaptically silences neurons to explore the contribution of the rubrospinal tract (RST) and CST to forelimb motor behavior in an intact rat. This system employs Tetanus toxin at the neuronal synapse to prevent release of neurotransmitter via cleavage of vesicle docking proteins, effectively preventing the propagation of action potentials in those neurons. We find that shutdown of the RST has no effect on gross forelimb motor function in the intact state, and that shutdown of a small population of CST neurons in the FMC has a modest effect on grip strength. These studies demonstrate that the HiRet lentivirus is a unique tool for examining neuronal circuitry and its contribution to function. In the final study, we explore stimulation of the Phosphoinositide 3-kinase/Rac-alpha serine/threonine Protein Kinase (PI3K/AKT) growth pathway by antagonizing phosphatase and tensin homolog (PTEN), a major inhibitor, to encourage growth of CST axons after a contusive injury. We use systemic infusions of four distinct PTEN antagonist peptides (PAPs) targeted at different sites of the PTEN protein. We find robust axonal growth and sprouting caudal to a contusion in a subset of animals infused with PAPs targeted to the PTEN enzymatic pocket, including typical morphology of growing axons. Serotonergic fiber growth was unaffected by peptide infusion and did not correlate with CST fiber density. Though some variability was seen in the amount of growth within our animal groups, we find these PTEN antagonist peptides a promising and clinically relevant tool to encourage CST sprouting, and a potentially useful addition to therapies using combinatory strategies to enhance growth. These studies demonstrate that viral tracing is a powerful tool for mapping spinal pathways and elucidating their ability to reform spinal circuits after injury. Viral vectors can be used in both anterograde and retrograde tracing studies to highlight intricacies of neuronal cell bodies, axons and dendritic arbors with a high degree of fidelity. In the injured state, these tools can help identify pathways that contribute to spontaneous recovery of function by highlighting those that reform circuits past an injury site. In the uninjured state, these vectors can contain neuronal silencing methods that help define the contribution of specific pathways to behavior. / Neuroscience