Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 176-184). Also available on microfiche.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 123-131).

PhD. (Environmental Management) / This research investigates associations between El Niño Southern Oscillation (ENSO) phases and the occurrence of an unusual atmospheric transport patterns over southern Africa, observed during the SAFARI 2000 field campaign. This transport pattern manifested itself as a smoke and hazeladen flow, originating from the sub-equatorial tropical regions over northern Angola and western Zambia, and traversing the subcontinent with exit off the south-east coast over southern Mozambique and northern KwaZulu-Natal into the Indian Ocean. This pattern has been dubbed The River of Smoke. This pattern is distinctly different from the continental re-circulation pattern associated with continental high-pressure systems over the subtropical sub-region, which is the prevalent system according to current literature. The period during which the SAFARI 2000 campaign was conducted happened to be at the height of the strong 1999/2000 La Niña episode, associated with excessively wet conditions over the sub-continent. In contrast, during an earlier field campaign, SAFARI’92, the continental re-circulation transport mode, termed the gyre, was observed to prevail over the subtropical sub-region. SAFARI’92 coincided with the 1991/1992 El Niño episode that resulted in drought conditions over much of southern Africa. These observations triggered the current investigation of the causal associations and frequencies of the River of Smoke flow with phases of the ENSO. This study has employed conventional and modeled methods of meteorological analysis to investigate the influence of ENSO on atmospheric transport and synoptic coupling mechanisms, Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) forward trajectory computations supported by an enhanced method of cluster analysis were used to determine and characterize the mean atmospheric transport modes over the subcontinent. Trajectories were calculated originating at two source points, representative of the tropical and subtropical subregions respectively (Mongu, Zambia; and Tshane, Botswana). Three study years were selected, corresponding to three distinct phases of ENSO: an El Niño episode during 1991/1992, a neutral ENSO episode during 1996/1997, and a La Niña episode during 1999/2000. The National Center for Environmental Prediction (NCEP)/ National Center for Atmospheric Research (NCAR) Reanalysis model is employed to reproduce mean composite synoptic circulation fields over southern Africa during the three periods. Findings show that for airflows originating over tropical southern Africa, the Indian Ocean fast exit pathway is unique to the neutral ENSO phase, while the continental re-circulation transport mode exhibits zero occurrences during the neutral phase. A continental re-circulation transport mode in the lower troposphere was observed during the El Niño and La Niña extremes, but with low annual frequencies (less than 30%). The direct Atlantic Ocean, the north-west and the Indian Ocean slow exit pathways are common to all three ENSO phases. For airflows originating over the subtropical sub-region, the continental re-circulation transport mode has the highest vi frequencies during all three ENSO phases, more especially during the El Niño episode, with more than 50% annual frequency, as observed during SAFARI’92. The north-west, Indian Ocean slow and Indian Ocean fast pathways are observed during all the three ENSO phases, with lower overall frequencies. The anticyclonic circulation flows are driven by the strengthened high-pressure systems over southern Africa: the semi-permanent subtropical high-pressure systems over the adjacent oceans (Atlantic Ocean High and Indian Ocean High) and the transient cut-off continental high-pressure systems. Airflows exiting toward the Indian Ocean have been described previously. In this work, a novel distinction is made between the Indian Ocean fast and the Indian Ocean slow exit pathways. The Indian Ocean slow corresponds to the conventional off-coast flow, such as observed during SAFARI’92. The Indian Ocean fast exit pathway is a newly described transport mode, which results from strong coupling between the subtropical circulation systems and the mid-latitude westerly flows. This strong-coupling induced transport mechanism provides favourable conditions for transport of mass fluxes, such as fire emissions originating from the tropical sub-region, towards the Indian Ocean. The Indian Ocean fast exit transport mode is characterized by higher speeds while exiting off the south-east coast, and extends further into the temperate latitudes towards Australia. When coupled with tropical sub-region, this flow mode is responsible for the occurrence of the River of Smoke phenomenon identified during SAFARI 2000. This Indian Ocean fast transport mode is intermittent in nature, and couples to the tropical sub-region only during the neutral ENSO episode, during which it exhibits low monthly frequencies, mainly during the dry season July through October. The intermittent nature, dependent on ENSO phases, and the associated low frequencies, may explain why it was observed in SAFARI 2000, but escaped observation and comment during previous studies, such as SAFARI’92.

Recently-developed technologies for monitoring activity in populations of neurons make it possible for the first time, in principle, to ask many basic questions in neuroscience. However, computational tools for analyzing newly available data need to be developed. The goal of this thesis is to contribute to this effort by focusing on two specific problems. First, we used a point-process regression framework to provide a methodology for statistical assessment of the link between neural spike synchrony and network-wide oscillations. In simulations, we showed that our method can recover ground-truth relationships, and in two types of spike train data we illustrated the kinds of results the method can produce. The approach improves on methods in the literature and may be adapted to many different experimental settings. Second, we considered the problem of source extraction in calcium imaging data, i.e., the detection of neurons within a field of view and the extraction of each neuron’s activity. The data we mainly focus on are recorded with a microendoscope, which has the unique advantage of imaging deep brain regions in freely behaving animals. These data suffer from high levels of background fluorescence, as well as the potential for overlapping neuronal signals. Based on the existing constrained nonnegative matrix factorization (CNMF) framework, we developed an efficient method to process microendoscopic data. Our method utilizes a novel algorithm to initialize the spatial shapes and temporal activity of the neurons from the raw video data independently from the strong fluctuating background. This step ensures the efficiency and accuracy of solving a nonconvex CNMF problem. Our method also models the complicated background by including its low-spatial frequency structure and the locally-low-rank feature to avoid absorbing cellular signals into the background term. We developed a tractable solution to estimate the background activity using this new model. After subtracting the approximated background, we followed the CNMF framework to demix neural signals and recover denoised and deconvolved temporal activity. We optimized several algorithms in solving the CNMF problems to get accurate results. In practice, our method outperforms all existing methods and has been adopted by many experimental labs.

Pitch material is an important precursor in the production of carbon bre, carbon composites and synthetic graphite. It has a complex transformation during pyrolysis which incorporates the separation of a liquid crystalline phase, known as mesophase. This thesis attempts to enhance the understanding of this change in composition, structure and its resultant behaviour. In this study, two pitches, a coal-tar pitch (MP110) and a (SASOL) Lurgi-gasi er pitch, are pyrolised to produce material at di erent stages of mesophase development. These pitches produce mesophase of di erent mosaic type and therefore also resultant coke. The MP110 was thermally treated up to a temperature of 437 and produced anisotropic pitch (which still contains signi cant particulate matter). The nucleated mesophase spheres did not coalesce to produce domains; this behaviour being attributed to the particulate material. The SASOL pitch produced a di erent type of mesophase material. The mesophase produced was of ne mosaic domains; a sample with continuous mesophase regions was also produced with a mesophase content of approximately 60% (by volume). The aromatic starting material of MP110 produced higher quinolone and toluene insoluble (QI and TI) compounds after pyrolysis. This was also observed in the increase of C/H (molar ratio of carbon to hydrogen). The more aliphatic SASOL starting pitch showed similar trends to its MP110 counterparts with respect to QI (quinoline insolubles), TI (toluene insolubles) and C/H. The glass transition and associated temperatures of the pitches were analysed via thermal mechanical analysis (TMA), dynamic scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The techniques showed consistency between instruments, with TMA providing the likeliest re ection of the true thermodynamic glass transition temperature. The loss of volatile components was accompanied by an increase in glass transition temperature (observed in conjunction with C/H and mesophase content). For anisotropic MP110 pitches, two relaxations were observed, one for the isotropic fraction, the other for the mesophase. No such behaviour was easily observed for the SASOL pitches. Rheological measurements were obtained to understand the behaviour of the pitches. Measurements were limited to a speci c viscosity range. The measurements of the samples were therefore made at di erent temperatures. The relation of the measurement temperature to the glass transition temperature is thus of extreme importance. The temperature governs the state of the structure; whether it be suspension, emulsion or gel. Oscillatory shear experiments were undertaken for the pitch material. Predominantly isotropic material showed transition from viscoelastic solid to viscoelastic liquid as previously observed in pitch material. The anisotropic MP110 pitches did not allow for the production of mastercurves due to non-linear viscoelastic e ects caused by the softening of mesophase. This being the transition from a suspension of hard spheres to an emulsion of deformable droplets (depending on temperature). For the higher mesophase content anisotropic SASOL pitches, mastercurves were produced; it had a similar shape to the isotropic pitches (at temperatures closer to the glass transition), but signi cantly increased elasticity was observed at higher temperatures. This phenomenon supported the hypothesis of a strong interaction between the components and phases of the pitch, and thus the possibility of gelled systems. Rotational shear-rheometry was also utilised and showed that isotropic pitch material behaves as a predominantly isoviscous uid. The anisotropic MP110 pitches of approximately 30% mesophase showed high- and low-shear viscosity plateau uid behaviour. This being caused by the breakup of agglomerated mesophase spheres. This was tested by the implementation of the Krieger- Dougherty suspension model. The possibility of droplet deformation was investigated for these samples by utilising a Krieger-Douherty based emulsion analogue, which con- rmed suspension like behaviour (at the measured temperatures). MP110 samples with more mesophase were measured at higher temperatures. Their behaviour is more akin to Power-law shear-thinning behaviour. Being further away from the continuous isotropic phase glass transition temperature, the behaviour observed is similar to that of emulsions. SASOL anisotropic pitches showed signi cant yielding upon shear, which is attributed to structure breakdown. This behaviour is appropriately described by a yield stress, shearthinning model such as Herschel-Bulkley. Measurements of viscosity for these samples were made at temperatures signi cantly further from the glass transition temperature as compared to that of the MP110 pitches. This corroborates strong interaction between its components. The observed shapes of the curve, at temperatures of measurement, support the notion of a gel structure. This behaviour is rst proposed via the complex structure observed (clusters of ne mosaic mesophase domains) and supported by strong interaction of the components inferred from obtained rheological properties. / Thesis (PhD)--University of Pretoria, 2015. / tm2015 / Chemical Engineering / PhD / Unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21948号 / 理博第4526号 / 新制||理||1650(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 WENDELL Roger, 教授 中家 剛, 教授 鶴 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22350号 / 医博第4591号 / 新制||医||1042(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 斎藤 通紀, 教授 浅野 雅秀, 教授 安達 泰治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22639号 / 医博第4622号 / 新制||医||1044(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 林 康紀, 教授 伊佐 正, 教授 斎藤 通紀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23001号 / 理博第4678号 / 新制||理||1671(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 中家 剛, 准教授 市川 温子, 准教授 成木 恵 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(医科学) / 甲第23424号 / 医科博第129号 / 新制||医科||9(附属図書館) / 京都大学大学院医学研究科医科学専攻 / (主査)教授 林 康紀, 教授 伊佐 正, 教授 高橋 淳 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM