Systems with strong spin-orbit coupling are of particular interest in solid state physics as an avenue for observing and manipulating spin physics using standard electrical techniques. This dissertation focuses on the characteristics of elemental bismuth (Bi), which exhibits some of the strongest intrinsic spin-orbit coupling of all elements, and InSb, which exhibits some of the strongest intrinsic spin-orbit coupling of all compound semiconductors. The experiments performed study the quantum transport signatures of nano- and micron-scale lithographically defined devices as well as spin-orbit coupled material/ferromagnet interfaces. All Bi structures are fabricated from Bi thin "films, and hence a detailed analysis of<br />the characteristics of Bi "film growth by thermal evaporation is provided. Morphologically and electrically high quality "films are grown using a two stage deposition procedure. The phase and spin coherence of Bi geometries constrained in one, two, and three dimensions are systematically studied by analysis of the weak antilocalization transport signature, a quantum interference phenomenon sensitive to spin-orbit coupling. The "findings indicate that the phase coherence scales proportionally to the limiting dimension of the structure for sizes less than 500 nm. Specifically, in Bi wires, the phase coherence length is approximately as long as the wire width. Dephasing due to quantum confinement e"ffects limit the phase coherence in small Bi structures, impairing the observation of controlled interference phenomena in nano-scale Bi rings. The spin coherence length is independent of dimensional constraint by the film thickness, but increases significantly as the lateral dimensions, such as wire width, are constrained. This is a consequence of the quantum transport contribution from the strongly spin-orbit coupled Bi(001) surface state. To probe the Bi surface state further, Bi/CoFe junctions are fabricated. The anisotropic magnetoresistance of the CoFe is modifi"ed when carriers tunnel into the CoFe from Bi, possibly due to a spin dependent tunneling process or an interaction between the spin polarized density of states in CoFe and the anisotropic spin-orbit coupled density of states in Bi. InSb/CoFe junctions are studied as InSb "films are a simpler spin-orbit coupled system compared to Bi "films. For temperatures below 3.5 K, a large, symmetric, and abrupt negative magnetoresistance is observed. The low-"field high resistance state has similar temperature and magnetic "field dependences as the superconducting phase, but a superconducting component in the device measurements seems absent. A differential conductance measurement of the InSb/CoFe interface during spin injection indicates a quasiparticle gap present at the Fermi energy, coinciding with the large magnetoresistance. / Ph. D.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24433号 / 理博第4932号 / 新制||理||1705(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 谷村 吉隆, 教授 林 重彦, 教授 鈴木 俊法 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24498号 / 医博第4940号 / 新制||医||1064(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 中本 裕士, 教授 森本 尚樹, 教授 大森 孝一 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Multiple sclerosis (MS) is the most common neurological disorder of young adulthood and is often associated with cognitive impairment and emotional dysfunction. Due to the nature of the disease, the cognitive deficits in MS are often variable in their presentation, and consist of deficits in processing speed, attention, working memory, and executive functioning. The purpose of the present study was to explore common methods of documenting MS-related cognitive deficits, to elucidate the relationship between the cognitive deficits seen in MS and physiological markers of cognitive functioning (i.e., quantitative EEG), and to analyze the relationship between cognitive deficits and mood dysfunction in MS. There were 26 participants diagnosed with remitting-relapsing multiple sclerosis and 18 age, sex, and education matched controls. Results of cognitive testing indicated deficits in gross cognitive functioning, language, attention, processing speed, working memory, and executive functioning. A MANOVA encompassing group, task (PASAT and SPT) and load (light and heavy) showed significant group and load effects, but no main effect of task. The MS group performed worse than the controls and both groups performed better on the light load than the heavy load. Post hoc analysis indicated that performance on the PASAT 3 second trial was worse than on the PASAT 2 second trail compared to controls. Given that the PASAT 3 trial is theoretically easier than the PASAT 2 trial and that the PASAT 3 was administered first, the above results likely reflect learning effects. A Repeated Measures ANCOVA encompassing EEG and cognitive data (PASAT and SPT) indicated group-level differences on task performance, and suggested that at rest mean peak alpha frequency (PAF) is associated with performance on the PASAT, but not the SPT. EEG coherence during cognitive tasks was reduced between short-range connections in the theta, alpha, and beta frequency bins and enhanced in a limited number of long-range, anterior to posterior connections in the theta frequency bin in the MS group compared to controls. Finally, the MS participants had significantly more symptoms of depression and anxiety compared to normal controls. A hierarchical multiple regression analysis suggested that cognitive functioning is deleteriously affected by depression and anxiety. Overall, the results of this study substantiate the feasibility of utilizing QEEG as a physiological indicator of cognitive and cortical dysfunction in MS and show the importance of recognizing depression and anxiety and their contributions to cognitive deficits in individuals with MS.

Polarimetry is one of the principal means of investigating the interaction of light with matter. Theoretical models and experimental techniques are presented in this dissertation for polarimetric characterization of random electromagnetic beams and of signatures of random media in different scattering regimes and configurations. The degree of polarization rather than the full description of the state of polarization is of interest in multiple scattering and free space propagation where the statistical nature and not the deterministic component of light bears the relevant information. A new interferometric technique for determining the degree of polarization by measuring the intensity fluctuations in a Mach-Zehnder interferometric setup is developed. For this type of investigations, one also needs a light source with a controllable degree of polarization. Therefore, also based on a Mach-Zehnder interferometer, we proposed a new method for generating complex random electromagnetic beams. As a direct application of the cross-spectral density matrix formalism, it is shown that the spectral and the polarimetric characteristics of light can be controlled by adjusting the correlations between parallel components of polarization propagating through the two arms of the interferometer. When optical beams are superposed in the previous applications it is desirable to understand how their coherence and polarimetric characteristics are combined. A generalization of the interference laws of Fresnel and Arago is introduced and as a direct application, a new imaging polarimeter based on a modified Sagnac interferometer is demonstrated. The system allows full polarimetric description of complex random electromagnetic beams. In applications such as active illumination sensing or imaging through turbid media, one can control the orientation of the incident state of polarization such that, in a given coordinate system, the intensities are equal along orthogonal directions. In this situation, our novel interferometric technique has a significant advantage over standard Stokes imaging polarimetry: one needs only one image to obtain both the degree of polarization and the retardance, as opposed to at least three required in classical Stokes polarimetry. The measurement of the state of polarization is required for analyzing the polarization transfer through systems that alter it. Two innovative Mueller matrix measurement techniques are developed for characterizing scattering media, either in quasi real-time, or by detection of low level signals. As a practical aspect of Mueller polarimetry, a procedure for selecting the input Stokes vectors is proposed. The polarimetric signatures of different particulate systems are related to their structural properties and to the size distribution, shape, orientation, birefringent or dichroic properties of the particles. Various scattering regimes and different geometries are discussed for applications relevant to the biomedical field, material science, and remote sensing. The analysis is intended to elucidate practical aspects of single and multiple scattering on polydisperse systems that were not investigated before. It seems to be generally accepted that depolarization effects can only be associated to multiple scattering. It is demonstrated in this dissertation that depolarization can also be regarded as an indication of polydispersity in single scattering. In order to quantify the polarizing behavior of partially oriented cylinders, the polarization transfer for systems consisting of individual layers of partially aligned fibers with different degrees of alignment and packing fractions is also analyzed in this dissertation. It is demonstrated that a certain degree of alignment has the effect of a partial polarizer and that the efficiency of this polarizer depends on the degree of alignment and on the packing fraction of the system. In specific applications such as long range target identification, it is important to know what type of polarization is better preserved during propagation. The experimental results demonstrate that for spherical particles smaller than the wavelength of light, linear polarization is better preserved than circular polarization when light propagates through turbulent media. For large particles, the situation is reversed; circular polarization is better preserved. It is also demonstrated here that this is not necessarily true for polyhedral or cylindrical particles, which behave differently. Optical activity manifests as either circular birefringence or circular dichroism. In this dissertation, a study is presented where both the effect of optical activity and that of multiple scattering are considered. This situation is relevant for medical applications and remote sensing of biological material. It is demonstrated here that the output state of polarization strongly depends on the optical density of the scattering medium, the optical rotatory power and the amount of circular dichroism associated to the scattering medium. This study shows that in the circular birefringence case, scattering and optical activity work together in depolarizing light, while in the dichroic case the two effects compete with each other and the result is a preservation of the degree of polarization. To characterize highly diffusive media, a very simple model is developed, in which the scattering is analyzed using the Mueller matrix formalism in terms of surface and volume contributions.

Optical Coherence Tomography (OCT) is a novel optical imaging technique that has assumed significant importance in bio-medical imaging in the last two decades because it is non-invasive and provides accurate, high resolution images of three dimensional cross-sections of body tissue, exceeding the capabilities of the current predominant imaging technique –ultrasound. In this thesis, high resolution OCT is investigated for in vivo detection of abnormal skin pathology for the early diagnosis of cancer. The technology presented is based on a dynamic focusing microscopic imaging probe conceived for skin imaging and the detection of abnormalities in the epithelium. A novel method for dynamic focusing in the biological sample using liquid crystal (LC) lens technology to obtain three dimensional images with invariant resolution throughout the cross-section and depth of the sample is presented and discussed. Two different skin probe configurations that incorporate dynamic focusing with LC lenses, one involving a reflective microscope objective sub-system, and the other involving an all-refractive immersion microscope objective sub-system are investigated. In order to ensure high resolution imaging, a low coherence broadband source, namely a femtosecond mode-locked Ti: sapphire laser centered at a wavelength of approximately 800nm is used to illuminate the sample. An in-depth description and analysis of the optical design and predicted performance of the two microscope objectives designed for dynamic three dimensional imaging at 5ìm resolution for the chosen broadband spectrum is presented.

Microvasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and potentially skin cancer. However, the capillary network is typically only one cell in wall thickness with 5 to 10 microns in diameter and located in the dermis region of skin. Therefore, a non-invasive flow imaging technique that is capable of depth sectioning at high resolution and high speed is demanded. Optical coherence tomography (OCT), particularly after its advancement in frequency domain OCT (FD-OCT), is a promising tool for non-invasive high speed, high resolution, and high sensitivity depth-resolved imaging of biological tissues. Over the last ten years, numerous efforts have been paid to develop OCTbased flow imaging techniques. An important effort is the development of phase-resolved Doppler OCT (PR-DOCT). Phase-resolved Doppler imaging using FD-OCT is particularly of interest because of the direct access to the phase information of the depth profile signal. Furthermore, the high speed capability of FD-OCT is promising for real time flow monitoring as well as 3D flow segmentation applications. However, several challenges need to be addressed; 1) Flow in biological samples exhibits a wide dynamic range of flow velocity caused by, for example, the iv variation in the flow angles, flow diameters, and functionalities. However, the improvement in imaging speed of FD-OCT comes at the expense of a reduction in sensitivity to slow flow information and hence a reduction in detectable velocity range; 2) A structural ambiguity socalled 'mirror image' in FD-OCT prohibits the use of maximum sensitivity and imaging depth range; 3) The requirement of high lateral resolution to resolve capillary vessels requires the use of an imaging optics with high numerical aperture (NA) that leads to a reduction in depth of focus (DOF) and hence the imaging depth range (i.e. less than 100 microns) unless dynamic focusing is performed. Nevertheless, intrinsic to the mechanism of FD-OCT, dynamic focusing is not possible. In this dissertation, the implementation of PR-DOCT in a high speed swept-source based FD-OCT is investigated and optimized. An acquisition scheme as well as a processing algorithm that effectively extends the detectable velocity dynamic range of the PR-DOCT is presented. The proposed technique increased the overall detectable velocity dynamic range of PR-DOCT by about five times of that achieved by the conventional method. Furthermore, a novel technique of mirror image removal called ‘Dual-Detection FD-OCT’ (DD-FD-OCT) is presented. One of the advantages of DD-FD-OCT to Doppler imaging is that the full-range signal is achieved without manipulation of the phase relation between consecutive axial lines. Hence the full-range DD-FDOCT is fully applicable to phase-resolved Doppler detection without a reduction in detectable velocity dynamic range as normally encountered in other full-range techniques. In addition, PRDOCT can utilize the maximum SNR provided by the full-range capability. This capability is particularly useful for imaging of blood flow that locates deep below the sample surface, such as v blood flow at deep posterior human eye and blood vessels network in the dermis region of human skin. Beside high speed and functional imaging capability, another key parameter that will open path for optical diagnostics using OCT technology is high resolution imaging (i.e. in a regime of a few microns or sub-micron). Even though the lateral resolution of OCT can be independently improved by opening the NA of the imaging optics, the high lateral resolution is maintained only over a short range as limited by the depth of focus that varies inversely and quadratically with NA. Recently developed by our group, ‘Gabor-Domain Optical Coherence Microscopy’ (GD-OCM) is a novel imaging technique capable for invariant resolution of about 2-3 m over a 2 mm cubic field-of-view. This dissertation details the imaging protocol as well as the automatic data fusion method of GD-OCM developed to render an in-focus high-resolution image throughout the imaging depth of the sample in real time. For the application of absolute flow measurement as an example, the precise information about flow angle is required. GDOCM provides more precise interpretation of the tissue structures over a large field-of-view, which is necessary for accurate mapping of the flow structure and hence is promising for diagnostic applications particularly when combined with Doppler imaging. Potentially, the ability to perform high resolution OCT imaging inside the human body is useful for many diagnostic applications, such as providing an accurate map for biopsy, guiding surgical and other treatments, monitoring the functional state and/or the post-operative recovery process of internal organs, plaque detection in arteries, and early detection of cancers in the gastrointestinal tract. Endoscopic OCT utilizes a special miniature probe in the sample arm to vi access tubular organs inside the human body, such as the cardiovascular system, the lung, the gastrointestinal tract, the urinary tract, and the breast duct. We present an optical design of a dynamic focus endoscopic probe that is capable of about 4 to 6 m lateral resolution over a large working distance (i.e. up to 5 mm from the distal end of the probe). The dynamic focus capability allows integration of the endoscopic probe to GD-OCM imaging to achieve high resolution endoscopic tomograms. We envision the future of this developing technology as a solution to high resolution, minimally invasive, depth-resolved imaging of not only structure but also the microvasculature of in vivo biological tissues that will be useful for many clinical applications, such as dermatology, ophthalmology, endoscopy, and cardiology. The technology is also useful for animal study applications, such as the monitoring of an embryo’s heart for the development of animal models and monitoring of changes in blood circulation in response to external stimulus in small animal brains.

Most of the physically realizable optical sources are radiating in a random manner given the random nature of the radiation of a large number of atoms that constitute the source. Besides, a lot of natural and synthetic materials are fluctuating randomly. Hence, the optical fields that one encounters, in most of the applications are fluctuating and must be treated using random or stochastic functions. Within the framework of the scalar-coherence theory, one can describe changes of the properties of any stochastic field such as the spectral density and the spectral degree of coherence on propagation in any linear medium, deterministic or random. One of the frequently encountered random media is the atmospheric turbulence, where the fluctuating refractive index of such medium severely degrades any signal propagating through it; especially it causes intensity fades of the signal. The usage of stochastic beams at the transmitter instead of deterministic ones has been suggested sometime ago to suppress the severe effects of intensity fluctuations caused by the atmospheric turbulence. In this dissertation, we study the usage of partially coherent beams in long path propagation schemes through turbulent atmosphere such as one frequently encounters in remote sensing, in the use of communication systems, and in guiding. Also the used detection scheme at the receiver is important to quantify the received signal efficiently, hence we compare the performance of incoherent (direct) detection versus coherent (heterodyne) detection upon the use of either one of them at the receiver of the communication system of beams propagating in turbulent atmosphere and namely we evaluate the signal-to-noise-ratio (SNR) for each case. The scalar-coherence theory ignored the vector nature of stochastic fields, which should be taken into account for some applications such as the ones that depend on the change of the polarization of the field. Recently generalization for the scalar-coherence theory including the vector aspects of the stochastic beams has been formulated and it is well-known as the unified theory of coherence and polarization of stochastic beams. The use of the unified theory of coherence and polarization makes it possible to study both the coherence properties and the polarization properties of stochastic electromagnetic beams on propagation in any linear media. The central quantity in this theory is a 2 × 2 matrix that describes the statistical ensemble of any stochastic electromagnetic beam in the space-frequency domain or its Fourier transform in the space-time domain. In this dissertation we derive the conditions that the cross-spectral density matrix of a so-called planar, secondary, electromagnetic Gaussian Schell-model source has to satisfy in order to generate a beam propagating in vacuum. Also based on the unified-theory of coherence and polarization we investigate the subtle relationship between coherence and polarization under general circumstances. Besides we show the effects of turbulent atmosphere on the degree of polarization and the polarization state of a partially coherent electromagnetic beam, which propagates through it and we compare with the propagation in vacuum. The detection of the optical signals is important; hence it affects the fidelity of the communication system. In this dissertation we present a general analysis for the optical heterodyne detection of stochastic electromagnetic beams. We derive an expression for the SNR when two stochastic electromagnetic beams are mixed coherently on a detector surface in terms of the space-time domain representation of the beams, the beam coherence polarization matrices. We evaluate also the heterodyne efficiency of a heterodyne detection system for stochastic beams propagating in vacuum and we discuss the dependence of the heterodyne efficiency of the detection process on the changes in the beam parameters as the beam propagates in free space.

This thesis deals with the circumstances that lead to a fragmented implementation of post-conflict justice and security reforms and their negative impact on institutional capacity to provide justice and security for citizens. It strenghtens the existing critique of SSR by employing liberal peacebuilding critique to examine the development of the SSR agenda within the security-development nexus mainstream and the difficulties in learning from SSR experience. The main research question concerns the factors affecting the coherence and sequencing of justice and security system reforms, and is addressed through a case study of Mozambique. The analysis identifies power dynamics surrounding formal and informal interactions that impact institutional change, and showcase the vulnerability of justice and security system reforms to co-optation by powerful international and national players. Throughout, patterns of critical juncture and path dependence are identified that have influenced the adaptation of powerful local players to external and domestic pressures which resulted in political and institutional bricolage. The thesis also looks at how the sequencing of Mozambique’s triple transition, in which economic liberalisation prevailed over peacebuilding and democratisation, shaped the post-civil war direction and pace of the defence, police and justice reforms. The 1992 peace agreement and the public sector reform programme are investigated with regards to the failure of driving substantive SSR and of imparting it coherence and sequencing in the short, medium and longer term. Finally, lessons are proposed for future reform in Mozambique, and recommendations are drawn for improving the design of strategy and implementation of SSR in general. / Portuguese Foundation of Science and Technology

Välbefinnande är ett mångdimensionellt begrepp som rymmer flera olika förklaringsmodeller. Tidigare forskning har visat att välbefinnandet i relation till krig är komplicerat och grundar sig i individuella och kontextuella skillnader. Föreliggande studie syftade till att belysa vilka faktorer som haft en inverkan på välbefinnandet hos kvinnliga krigsflyktingar från Bosnien. Totalt ingick 6 kvinnor i undersökningen. Studien har kvalitativ karaktär och tematisk analys användes som analysmetod. Resultatet visade att både coping såväl som olika aspekter av KASAM var framträdande för gott välbefinnande. Både emotionellt fokuserad och problemfokuserad coping har använts i bearbetningsprocessen. Den förstnämnda användes i samtliga fall först och efter en viss tid, när nya strukturer börjat formas i deltagarnas liv, blev den sistnämnda mer framträdande. Slutsatsen visade att det finns en relation mellan copingstrategier, KASAM och välbefinnande samt att flera faktorer ligger bakom valet av strategi. Studien har kunnat fylla en kunskapslucka med tanke på att det enbart finns ett mindre antal genomförda undersökningar kring den valda målgruppen.