京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18855号 / 医博第3966号 / 新制||医||1007(附属図書館) / 31806 / 京都大学大学院医学研究科医学専攻 / (主査)教授 河野 憲二, 教授 黒田 知宏, 教授 富樫 かおり / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

Maintaining coherency in a distributed system can prove challenging, this is especially true for distributed shared memory systems. The problem with remote synchronization in the distributed shared memory software ArgoDSM occurs when a lock operation has to cross the boundaries of a node, this causes a large number of self-invalidations (SI) or self-downgrades (SD) which is costly. The performance of the coherency protocol can be improved if the SI/SD situations can be avoided by using a suitable alternative. This work explores if the use of selective coherence operations and non-synchronizing locking can help alleviate the issue of SI and SD in ArgoDSM in order to improve performance compared to the cache-wide coherence operations that are triggered by the default locking mechanism in ArgoDSM. An implementation of the concept is done by replacing the standard coherence protocol used in locking operations with selective operations which is then used to analyze the performance compared to the baseline software.  The selective coherence operations are more powerful than the default protocol when applied to synchronization-heavy benchmarks, while the baseline software performs better when there is a lower amount of parallel work being done.

With the increasing maturity of unmanned aerial vehicles (UAVs), also known as drones, wireless ecosystem is experiencing an unprecedented paradigm shift. These aerial platforms are specifically appealing for a variety of applications due to their rapid and flexible deployment, cost-effectiveness, and high chance of forming line-of-sight (LoS) links to the ground nodes. As with any new technology, the benefits of incorporating UAVs in existing cellular networks cannot be characterized without completely exploring the underlying trade space. This requires a detailed system-level analysis of drone cellular networks by taking the unique features of UAVs into account, which is the main objective of this dissertation. We first focus on a static setup and characterize the performance of a three-dimensional (3D) two-hop cellular network in which terrestrial base stations (BSs) coexist with UAVs to serve a set of ground user equipment (UE). In particular, a UE connects either directly to its serving terrestrial BS by an access link or connects first to its serving UAV which is then wirelessly backhauled to a terrestrial BS (joint access and backhaul). We consider realistic antenna radiation patterns for both BSs and UAVs using practical models developed by the third generation partnership project (3GPP). We assume a probabilistic channel model for the air-to-ground transmission, which incorporates both LoS and non-LoS links. Assuming the max-power association policy, we study the performance of the network in both amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols. Using tools from stochastic geometry, we analyze the joint distribution of distance and zenith angle of the closest (and serving) UAV to the origin in a 3D setting. Further, we identify and extensively study key mathematical constructs as the building blocks of characterizing the received signal-to-interference-plus-noise ratio (SINR) distribution. Using these results, we obtain exact mathematical expressions for the coverage probability in both AF and DF relaying protocols. Furthermore, considering the fact that backhaul links could be quite weak because of the downtilted antennas at the BSs, we propose and analyze the addition of a directional uptilted antenna at the BS that is solely used for backhaul purposes. The superiority of having directional antennas with wirelessly backhauled UAVs is further demonstrated via extensive simulations. Second, we turn our attention to a mobile setup and characterize the performance of several canonical mobility models in a drone cellular network in which UAV base stations serve UEs on the ground. In particular, we consider the following four mobility models: (i) straight line (SL), (ii) random stop (RS), (iii) random walk (RW), and (iv) random waypoint (RWP), among which the SL mobility model is inspired by the simulation models used by the 3GPP for the placement and trajectory of UAVs, while the other three are well-known canonical models (or their variants) that offer a useful balance between realism and tractability. Assuming the nearest-neighbor association policy, we consider two service models for the UEs: (i) UE independent model (UIM), and (ii) UE dependent model (UDM). While the serving UAV follows the same mobility model as the other UAVs in the UIM, it is assumed to fly towards the UE of interest in the UDM and hover above its location after reaching there. We then present a unified approach to characterize the point process of UAVs for all the mobility and service models. Using this, we provide exact mathematical expressions for the average received rate and the session rate as seen by the typical UE. Further, using tools from the calculus of variations, we concretely demonstrate that the simple SL mobility model provides a lower bound on the performance of other general mobility models (including the ones in which UAVs follow curved trajectories) as long as the movement of each UAV in these models is independent and identically distributed (i.i.d.). Continuing our analysis on mobile setups, we analyze the handover probability in a drone cellular network, where the initial positions of the UAVs serving the ground UEs are modeled by a homogeneous Poisson point process (PPP). Inspired by the mobility model considered in the 3GPP studies, we assume that all the UAVs follow the SL mobility model, i.e., move along straight lines in random directions. We further consider two different scenarios for the UAV speeds: (i) same speed model (SSM), and (ii) different speed model (DSM). Assuming nearest-neighbor association policy, we characterize the handover probability of this network for both mobility scenarios. For the SSM, we compute the exact handover probability by establishing equivalence with a single-tier terrestrial cellular network, in which the BSs are static while the UEs are mobile. We then derive a lower bound for the handover probability in the DSM by characterizing the evolution of the spatial distribution of the UAVs over time. After performing these system-level analyses on UAV networks, we focus our attention on the air-to-ground wireless channel and attempt to understand its unique features. For that, we first study the impact of UAV wobbling on the coherence time of the wireless channel between UAVs and a ground UE, using a Rician multi-path channel model. We consider two different scenarios for the number of UAVs: (i) single UAV scenario (SUS), and (ii) multiple UAV scenario (MUS). For each scenario, we model UAV wobbling by two random processes, i.e., the Wiener and sinusoidal processes, and characterize the channel autocorrelation function (ACF) which is then used to derive the coherence time of the channel. For the MUS, we further show that the UAV-UE channels for different UAVs are uncorrelated from each other. One key observation that is revealed from our analysis is that even for small UAV wobbling, the coherence time of the channel may degrade quickly, which may make it difficult to track the channel and establish a reliable communication link. Finally, we develop an impairments-aware air-to-ground unified channel model that incorporates the effect of both wobbling and hardware impairments, where the former is caused by random physical fluctuations of UAVs, and the latter by intrinsic radio frequency (RF) nonidealities at both the transmitter and receiver, such as phase noise, in-phase/quadrature (I/Q) imbalance, and power amplifier (PA) nonlinearity. The impact of UAV wobbling is modeled by two stochastic processes, i.e., the canonical Wiener process and the more realistic sinusoidal process. On the other hand, the aggregate impact of all hardware impairments is modeled as two multiplicative and additive distortion noise processes, which is a well-accepted model. For the sake of generality, we consider both wide-sense stationary (WSS) and nonstationary processes for the distortion noises. We then rigorously characterize the ACF of the wireless channel, using which we provide a comprehensive analysis of four key channel-related metrics: (i) power delay profile (PDP), (ii) coherence time, (iii) coherence bandwidth, and (iv) power spectral density (PSD) of the distortion-plus-noise process. Furthermore, we evaluate these metrics with reasonable UAV wobbling and hardware impairment models to obtain useful insights. Similar to our observation above, this work again demonstrates that the coherence time severely degrades at high frequencies even for small UAV wobbling, which renders air-to-ground channel estimation very difficult at these frequencies. / Doctor of Philosophy / With the increasing maturity of unmanned aerial vehicles (UAVs), also known as drones, wireless ecosystem is changing dramatically. Owing to their ease of deployment and high chance of forming direct line-of-sight (LoS) links with the other UAVs and ground users, they are very appealing for numerous wireless applications. As with any new technology, exploring the full extent of the benefits of UAVs requires careful exploration of the underlying trade space. Therefore, in this dissertation, our main focus is on the analysis of such aerial networks, their interplay with the current terrestrial networks, and the unique features of UAVs that make them different from conventional ground nodes. One important aspect of aerial communication systems is their integration into our current cellular networks. Clearly, the addition of these new aerial components has the potential of benefiting both the ground users (such as mobile users watching a concert who need cellular connectivity to share the moments) and the cellular base station (BS). Therefore, careful analysis of these ``aerial-terrestrial" networks is of utmost importance. In the first phase of this dissertation, we perform this analysis by interpreting the network as a combination of one-hop (from the BS to the user) and two-hop (from the BS to the UAV and then from the UAV to the UE) links. Since the locations of BSs, UAVs, and users are irregular in general, we use tools from stochastic geometry to carry out our analysis, which is a field of mathematics that studies random shapes and patterns. Also, because existing terrestrial BSs are primarily designed to serve the ``ground", we propose the addition of a separate set of antennas at the BS site that is solely used to serve the ``air", i.e., to communicate with the UAVs, and demonstrate the benefits of this additional infrastructure in detail. One of our assumptions in the first phase of this dissertation was that the considered network was static, i.e., the UAVs were hovering in the air and the BSs/users were also not moving. In the second phase, on the other hand, we explore the benefits and challenges of a mobile network of UAVs and characterize the performance of several canonical mobility models in a drone cellular network. In particular, one of the models that we studied extensively is the so-called straight line (SL) mobility model, which was inspired by the simulation models used by the third generation partnership project (3GPP) for the placement and trajectory of UAVs. Since the locations of UAVs could be assumed random in general, we use tools from stochastic geometry and present a unified approach to characterize the point process of UAVs, using which we obtained exact mathematical expressions for the average received rate (i.e., throughput) as seen by the users. Continuing our analysis on mobile setups and using the SL mobility model, we also analyze the handover probability in a drone cellular network, which is defined as the event when the serving UAV of a user changes. By establishing equivalence between our aerial setup with a terrestrial cellular network, we compute the exact handover probability in drone cellular networks. In the final phase of this dissertation, we focus our attention on the air-to-ground wireless channel and attempt to understand its unique features. For that, we propose an impairments-aware unified channel model for an air-to-ground wireless communication system and extensively analyze the link between a hovering UAV in the air and a static user on the ground. In particular, we consider two different types of impairments: (i) UAV wobbling, and (ii) hardware impairments, where the former is caused by random physical fluctuations, and the latter by intrinsic radio frequency (RF) nonidealities at both the transmitter and receiver. Using appropriate models for each type of impairment, we rigorously characterize the autocorrelation function (ACF) of the wireless channel, using which we provide a comprehensive analysis of key channel-related metrics, such as coherence time and coherence bandwidth. One key observation that is revealed from our analysis is that even for small UAV wobbling and low hardware impairment levels, the coherence time of the channel may degrade quickly at high frequencies, which could make it difficult to track the channel and establish a reliable communication link at these frequencies.

Background: The relevance of drusen-like deposits (DLD) in patients with systemic lupus erythematosus (SLE) is to a large extent uncertain. Their genesis is proposed to be correlated to immune-complex and complement depositions in the framework of SLE. The intention of this study was to determine potential morphological differences in the choroid and retina as well as potential microvascular changes comparing two cohorts of SLE patients divergent in the presence or absence of DLD using multimodal imaging. Methods: Both eyes of 16 SLE patients with DLD were compared to an age- and sex-matched control-group consisting of 16 SLE patients without detectable DLD. Both cohorts were treated with hydroxychloroquine (HCQ) and did not differ in the treatment duration or dosage. Using spectral-domain optical coherence tomography (SD-OCT) choroidal volume measures, choroidal vascularity indices (CVI) and retinal layer segmentation was performed and compared. In addition, by the exploitation of optical coherence tomography angiography vascular density, perfusion density of superficial and deep retinal capillary plexuses and the choriocapillaris were analyzed. For the choroidal OCT-scans, a subset of 51 healthy individuals served as a reference-group. Results: CVI measures revealed a significant reduction in eyes with DLD compared to healthy controls (0.56 (0.54−0.59) versus 0.58 (0.57−0.59) (p = 0.018) and 0.56 (0.54−0.58) versus 0.58 (0.57−0.60) (p < 0.001)). The photoreceptor cell layer presented significant thinning in both eyes of subjects with DLD compared to control subjects without DLD (68.8 ± 7.7 µm vs. 77.1 ± 7.3 µm for right eyes, p = 0.008, and 66.5 ± 10.5 µm vs. 76.1 ± 6.3 µm for left eyes, p = 0.011). OCTA scans revealed no significant changes, yet there could be observed numerically lower values in the capillary plexuses of the retina in eyes with DLD than in eyes without DLD. Conclusions: Our results illustrated significant alterations in the choroidal and retinal analyzes, suggesting a correlation between DLD and the progression of inflammatory processes in the course of SLE leading to retinal degeneration. For this reason, DLD could serve as a biomarker for a more active state of disease.

This thesis is an attempt at studying quantum coherence effects coupled via plasmons. After introducing the quantum coherence in atomic systems in Chapter 1, we utilize it in Chapter 2 to demonstrate a new technique of detection of motion of single atoms or irons inside an optical cavity. By taking into account the interaction of coherences with surface plasmonic waves excited in metal nanoparticles, we provide a theoretical model along with experimental data in Chapter 3 to describe the modification of Raman spectra near metal nanoparticles. We show in chapter 4 that starting from two emitters, coupled via a plasmonic field, the symmetry breaking occurs, making detectable the simultaneous existence of the fast super-radiance and the slow sub-radiance emission of dye fluorescence near a plasmonic surface. In Chapter 5, we study the photon statistics of a group of emitters coupled via plasmons and by the use of quantum regression theorem, we provide a theoretical model to fully investigate the dependence of photon bunching and anti-bunching effects to the interaction between atoms, fields and surrounding mediums.

No description available.

This study was conducted in South Africa among a total of 86 South African adolescents. The aim of this study was to investigate self-perceived health among youths from two different socio-economic groups in South Africa, what they believe promote their health and what views they have on school health education. The study used a mixed method approach consisting of quantitative questionnaires and qualitative interviews. The study draws Aaron Antonovsky’s theory of health, the salutogenic perspective and the sense of coherence theory. In addition, Antonovsky’s 29-item orientation to life questionnaire formed the quantitative part of the study. The main findings of this study is that higher socio-economic status does not necessarily correlate with higher SOC. Family and supportive people had the greatest affect on the adolescents’ ability to cope with stressors and are therefore the main health promoting factors. Finally, health education and the subject Life Orientation, as well as the school as an institution, are health-promoting factors and have in different ways influenced the participants’ views on health.

Tomography in soft X-ray microscopy is an emerging technique for obtaining quantitative 3D structural information about cells. One of its strengths, compared with other techniques, is that it can image intact cells in their near-native state at a few 10 nm’s resolution, without staining. However, the methods for reconstructing 3D-data rely on algorithms that assume projection data, which the images are generally not due to the imaging systems’ limited depth of focus. To bring out the full potential of tomography in soft X-ray microscopy an improved understanding of the image formation is desired. This Thesis reviews zone plate-based X-ray microscopy for biological imaging and the theory necessary for a numerical implementation of a 3D image formation model. Furthermore, a novel reconstruction approach is proposed that improves the overall resolution in a reconstruction of a tomographically imaged object. This is demonstrated by simulations and experiments. Finally, this Thesis covers work on the Stockholm X-ray microscope, including an upgrade of the X-ray source yielding unprecedented brightness for a compact system. With this upgrade it was possible to do high-quality imaging of cells in their near-native state with only 10 second exposures. / Tomografi i mjukröntgenmikroskopi är en ny teknik för att få ut kvantitativ strukturell 3D information om celler. Dess styrka jämfört med andra tekniker är att den kan avbilda intakta celler i deras nära naturliga tillstånd med ett par 10 nm upplösning, utan omfattande preparering. Dock är metoderna för att rekonstruera 3D-data beroende av algoritmer som antar projektionsdata, vilket bilderna i allmänhet inte är på grund av avbildningsystemens begränsade skärpedjup. För att få ut den fulla potentialen av tomografi i röntgenmikroskopi behövs en ökad förståelse för avbildningsprocessen. Denna avhandling behandlar zonplatte-baserad röntgenmikroskopi för biologisk avbildning och den nödvändiga teorin för en numerisk implementering av en avbildningsmodell i 3D. En ny rekonstruktionsmetod föreslås som förbättrar upplösningen i rekonstruktionen för ett tomografiskt avbildat objekt. Detta visas i simuleringar och experiment. Slutligen omfattar denna avhandling arbete på Stockholms mjukröntgenmikroskop, inklusive en uppgradering av röntgenkällan som ger oöverträffad ljusstyrka för ett kompakt system. Denna uppgradering möjliggör högkvalitativ avbildning av celler i deras nästan naturliga tillstånd med endast 10 sekunders exponering. / <p>QC 20160324</p>

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This dissertation explores the utility of using Complexity studies to improve our understanding of peacebuilding and the coherence dilemma, which is regarded as one of the most significant problems facing peacebuilding interventions. Peacebuilding is said to be complex, and this study investigates what this implies, and asks whether Complexity could be of use in improving our understanding of the assumed causal link between coherence, effectiveness and sustainability. Peacebuilding refers to all actions undertaken by the international community and local actors to consolidate the peace – to prevent a (re)lapse into violent conflict – in a given conflict-prone system. The nexus between development, governance, politics and security has become a central focus of the international effort to manage transitions, and peacebuilding is increasingly seen as the collective framework within which these diverse dimensions of conflict management can be brought together in one common framework. The coherence dilemma refers to the persistent gap between policy-level assumptions about the value and causal role of coherence in the effectiveness of peacebuilding and empirical evidence to the contrary from peacebuilding practice. The dissertation argues that the peacebuilding process is challenged by enduring and deep-rooted tensions and contradictions, and that there are thus inherent limits and constraints regarding the degree to which coherence can be achieved in any particular peacebuilding context. On the basis of the application of the general characteristics of Complexity to peacebuilding, the following three recommendations reflect the core findings of the study: (1) Peacebuilders need to concede that they cannot, from the outside, definitively analyse complex conflicts and design ‘solutions’ on behalf of a local society. Instead, they should facilitate inductive processes that assist knowledge to emerge from the local context, and such knowledge needs to be understood as provisional and subject to a continuous process of refinement and adaptation. (2) Peacebuilders have to recognise that self-sustainable peace is directly linked to, and influenced by, the extent to which a society has the capacity, and space, to selforganise. For peace consolidation to be self-sustainable, it has to be the result of a home-grown, bottom-up and context-specific process. (3) Peacebuilders need to acknowledge that they cannot defend the choices they make on the basis of pre-determined models or lessons learned elsewhere. The ethical implications of their choices have to be considered in the local context, and the effects of their interventions - intended and unintended - need to be continuously assessed against the lived-experience of the societies they are assisting. Peacebuilding should be guided by the principle that those who will have to live with the consequences should have the agency to make decisions about their own future. The art of peacebuilding lies in pursuing the appropriate balance between international support and home-grown solutions. The dissertation argues that the international community has, to date, failed to find this balance. As a result, peacebuilding has often contributed to the very societal weaknesses and fragilities that it was meant to resolve. On the basis of these insights, the dissertation concludes with a call for a significant re-balancing of the relationship between international influence and local agency, where the role of the external peacebuilder is limited to assisting, facilitating and stimulating the capacity of the local society to self-organise. The dissertation thus argues for reframing peacebuilding as something that must be essentially local. / AFRIKAANSE OPSOMMING: Hierdie proefskrif ondersoek die toepaslikheid van Kompleksiteitstudies om ons begrip van vredesbou en die dilemma van koherensie te verbeter, wat as een van die gewigtigste probleme vir die toetrede tot vredesbou beskou kan word. Vredesbou word as kompleks beskou en die implikasies van hierdie siening word in hierdie proefskrif ondersoek. Dienooreenkomstig word die vraag na die nut van Kompleksiteitstudies vir die verbetering van ons begrip van die veronderstelde kousale verband tussen koherensie, doeltreffendheid en volhoubaarheid aangespreek. Vredesbou verwys na alle handelinge wat deur die internasionale gemeenskap en plaaslike belanghebbendes onderneem word om vrede binne ʼn gegewe sisteem, wat neig na konflik, te konsolideer om sodoende ’n (her)verval in gewelddadige konflik te voorkom. Die aanknopingspunt tussen ontwikkeling, staatsbestuur, staatkunde en sekuriteit is tans die sentrale fokus van die internasionale poging om sodanige oorgange te beheer, en vredesbou word toenemend as ’n kollektiewe raamwerk beskou, waarbinne hierdie onderskeie dimensies van konflikbestuur in een gemeenskaplike raamwerk saamgebring kan word. Die koherensiedilemma verwys na die voortdurende gaping tussen beleidsvlakaannames ten opsigte van die waarde en kousale rol van koherensie vir die doeltreffendheid van vredesboupogings en empiriese data vanuit die vredesboupraktyk wat hierdie aanvaarde kousale verband weerspreek. Die proefskrif toon dat vredesboupogings uitgedaag word deur voortdurende en diepgewortelde spanninge en teenstrydighede, en dat daar dus inherente beperkings en stremmings is ten opsigte van die mate waartoe koherensie binne enige spesifieke vredesboukonteks moontlik is. Op grond van die toepassing van die algemene kenmerke van Kompleksiteitstudies op die vredesbouproses, weerspieël die volgende drie aanbevelings die kernbevindings van die studie: (1) Vredesbouers moet toegee dat hulle nie daartoe in staat is om komplekse konflikte van buite af bepalend te analiseer en ‘oplossings’ namens ’n plaaslike gemeenskap te ontwerp nie. Hulle behoort eerder induktiewe prosesse te fasiliteer om ondersteuning te bied sodat kennis uit die plaaslike konteks na vore kom, en sodanige kennis moet as voorlopig en onderhewig aan ’n voortdurende proses tot verfyning en aanpassing, verstaan word. (2) Vredesbouers moet besef dat die selfvolhoubaarheid van vrede direk verband hou met, en beïnvloed word deur, die mate waartoe ’n gemeenskap oor die vermoë tot en ruimte vir selforganisering beskik. Vir vredeskonsolidering om selfvolhoubaar te wees, moet die proses wat daartoe aanleiding gee inheems, van ‘onder-na-bo’ en konteks-spesifiek wees. (3) Vredesbouers moet aanvaar dat hulle nie die besluite wat hulle neem op grond van voorafbestaande modelle of lesse wat elders geleer is kan regverdig nie. Die etiese implikasies van hulle besluite moet in terme van die plaaslike konteks beoordeel word, en die effekte van hulle ingrepe – bepland en onbepland – moet voortdurend opgeweeg word teen die daaglikse ervaring van die samelewings wat bygestaan word. Vredesbehoupogings behoort gelei te word deur die beginsel dat diegene wat met die gevolge van die proses sal moet saamleef, die agentskap behoort te hê om besluite oor hulle eie toekoms te neem. Die kuns van vredesbou lê in die vasstel van ’n toepaslike balans tussen internasionale ondersteuning en inheemse oplossings. Die proefskrif se argument is dat die internasionale gemeenskap tot dusver daarin gefaal het om hierdie balans te vind. As gevolg hiervan het pogings tot vredesbou dikwels bygedra tot die presiese swakhede en broosheid in die gemeenskap wat dit veronderstel was om aan te spreek. Op grond van hierdie insigte sluit die proefskrif af met ’n beroep tot ’n betekenisvolle herbalansering van die verhouding tussen internasionale invloed en plaaslike agentskap, waarin die rol van die eksterne vredesbouer beperk moet word tot die ondersteuning, fasilitering en stimulering van die plaaslike gemeenskap se vermoë tot selforganisering. Die proefskrif bepleit dus dat vredesbou herontwerp word binne ’n essensieel plaaslike raamwerk.