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Two Chinese pine (Pinus tabulaeformis) tree-ring width chronologies up to 375 years long were used to reconstruct rainfall from February to early July for the Wu Dangzhao region and from February to mid-July for the La Madong region, Inner Mongolia, China. The predictor variables account for 44.3% and 42.7% of the variance in precipitation, respectively. Both historical records and two other tree-ring based precipitation reconstructions from the environmentally sensitive zone (the northern Helan Mountain range and Baiyinaobao) confirm our results. After applying a 10-year moving average, the trends of four tree-ring based precipitation reconstructions vary synchronously. Periods with below-normal precipitation occurred during the 1720s–1730s, 1740s–1750s, 1790s, early 1810s, late 1830s–1860s, 1880s–1910s, late 1920s–1930s and after the late 1960s–early 1970s. Periods with above-normal precipitation occurred in the 1760s to early 1770s, 1820s to early 1830s, 1870s–1880s, early 1920s, 1940s to early 1960s, and 1990s. The late 1920s period was the most severe drought over a broad area in north China in the last 375 years. In contrast, the wettest period was in the late 1990s.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

<p>Hyperpolarized (HP) 129Xe MRI has emerged as a viable tool for evaluating lung function without ionizing radiation. HP 129Xe has already been used to image ventilation and quantify ventilation defects. However, this thesis aims to further develop imaging techniques that are capable of imaging, not just ventilation, but also gas transfer within the lung. This ability to image gas transfer directly is enabled by the solubility and chemical shifts of 129Xe that provide separate MR signatures in the airspaces, barrier tissue, and red blood cells (RBCs). </p><p>While 129Xe in the airspace (referred to as gas-phase 129Xe) can be readily imaged with standard vendor-provided imaging sequences, 129Xe in the barrier and RBC compartments (collectively referred to as dissolved-phase 129Xe) has such a rapid T2* (<2 msec at 2T) that even simple gradient recalled echo (GRE) sequences are ineffective at imaging the limited signal before it decays. To minimize these losses from T2* decay, the 3D radial sequence offers much shorter TEs that can image the dissolved-phase 129Xe. Despite their ability to image dissolved-phase signal, however, 3D radial sequences have not yet been widely adopted within the hyperpolarized gas community. In order to demonstrate the potential of the 3D radial pulse sequence, chapter 3 uses standard 129Xe ventilation imaging to compare 3D radial image quality and defect conspicuity with that of the conventional GRE. Since the 3D radial sequence offered comparable performance in ventilation imaging, and also provided the ability to image dissolved-phase 129Xe, chapter 3 establishes that the 3D radial sequence is well-suited for imaging 129Xe in humans.</p><p>Though 3D radial acquisition offers clear advantages for functional 129Xe lung imaging, its non-Cartesian sampling of k-space complicates image reconstruction. Chapter 4 carefully explains the process of gridding-based reconstruction, and describes how problems arising from non-selective RF pulses and undersampling, both of which are commonly employed in hyperpolarized 129Xe imaging, can be avoided by using appropriate reconstruction techniques. Furthermore, we detail a generalized procedure to optimize reconstruction parameters, then demonstrate the benefits of our improved reconstruction methods across both 1H anatomical imaging as well as functional imaging of 129Xe in the gas- and dissolved-phases. </p><p>These dissolved-phase images are particularly interesting because they consist of separate contributions from 129Xe in the RBCs and barrier tissue. Once these two resonances are disentangled from one another, they provide a noninvasive means to measure gas exchange regionally. However, such decomposition of these two resonances is predicated on prior knowledge of their spectroscopic properties. To that end, chapter 5 describes a non-linear spectroscopic curve fitting toolbox that we developed to more accurately characterize the 129Xe spectrum in vivo. Though previously, only two dissolved-phase resonances have ever been described within the lung, our fitting tools were able to identify a third dissolved-phase resonance in both healthy volunteers and healthy controls. Furthermore, we describe several spectroscopic features that differ statistically between our healthy volunteers and IPF subjects to demonstrate that this technique is sensitive to even subtle functional changes within the lung. These spectroscopic measurements provide the basis for imaging gas transfer. </p><p>Describing lung function regionally requires phase-sensitive imaging techniques that can decompose the dissolved-phase signal into images that represent the contribution from the RBC and barrier resonances. To date, only two implementations have been demonstrated, and both suffered from poor SNR and challenges in quantifying gas transfer. Chapter 6 adds quantitative processing techniques that improve phase sensitive imaging of 129Xe gas transfer. These methods 1) normalize both the RBC and barrier uptake images by gas-phase magnetization so that intensities can be compared across subjects, 2) compress the dynamic range of these functional images to enhance their perceived SNR, and 3) derive colormap thresholds from a healthy reference population to give intensities meaningful context.</p><p>To show the value of our quantitative gas transfer imaging, chapter 7 applies these techniques to a cohort of healthy volunteers and another of IPF patients. Since patients with IPF exhibit a progressive thickening and hardening of the pulmonary interstitium that severely restricts the transport of gases between the lungs and blood, they represent an ideal population to prove out our methods. This analysis identifies several patterns to the RBC and barrier distributions which could potentially represent different stages of disease. Furthermore, we demonstrate that our MRI-based findings correlate well with DLCO and FVC, and to a lesser extent with the structural cues seen in CT. This suggests that 129Xe imaging offers complimentary functional information that can’t be derived from CT, while also describing its spatial distribution unlike PFTs. </p><p>The work in this thesis has transitioned our HP 129Xe gas transfer studies from a proof of concept to an optimized and quantitative imaging protocol with robust processing pipelines. Using these MRI methods, we have shown that we can directly and quantitatively probe pulmonary ventilation and gas transfer within a single breath hold. In IPF, such noninvasive imaging methods are desperately needed to monitor the efficacy of these new treatments to ensure that the associated medical expense is justified with positive changes in outcomes. Finally, these new functional contrasts will be useful in studying other cardiopulmonary diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary arterial hypertension.</p> / Dissertation

Throughout human history man has utilized the environment to varying degrees, depending on technology and population. These ¨ecosystem services¨ have suffered sustained degradation over the centuries, resulting in large investments having to be made to prevent and reverse further changes to the environment. Few studies have attempted to quantitatively compare how these changes, occurring long before modern environmental monitoring programs started, affected important ecosystem services such as species diversity, water quality, carbon burial and soil stability. The aims of this study were to i) assess whether human impact on ecosystem services have varied over time in perspective of relative change, and ii) to assess the individual (per capita) contributions. I used multiple sediment proxies from a 6 m C¹⁴-dated core collected from lake Ekoln, South-Central Sweden, to reconstruct environmental changes while tracking the population growth in the city of Uppsala during the last ten centuries. Through the use of pollen and diatom assemblages I reconstructed the changing terrestrial and aquatic diversities over time, while sediment accumulation rates and the X-ray fluorescence spectroscopy of the sediment was used to reconstruct soil stability, carbon burial and water quality, respectively. In the latter case, sediment phosphorus concentrations were used as a proxy for freshwater eutrophication while metals (mercury and lead) were used to infer inputs of toxic pollutants. Finally, I normalized (z) all data to create meta-data. The z-values and reconstructed population for Uppsala made it possible to differentiate 5 unique time periods based on anthropogenic induced change, which were not previously visible in the data, and all of which have been linked to the most likely historical causes, including the Black Death. The results show that the most significant anthropogenic impacts in terms of pollution volume occurred in the 1960s, while the period from 1200-1500 AD saw the most significant environmental change in terms per head of capita, most likely caused by the shift from woodland to open landscape through twiddening, a process of burning forest to create agricultural land, prior to 1500 AD. Moreover, rapid recovery is visible after the implementation of environmental policies from the 1970s onwards. / <p>Full surname: Kilpatrick van Houte</p>

This thesis develops and describes methods for real-time tracking, segmentation and 3-dimensional (3D) model acquisition, in the context of developing games for stroke patients that are rehabilitating at home. Real-time tracking and reconstruction of a stroke patient's feet, hands and the control objects that they are touching can enable not only the graphical visualization of the virtual avatar in the rehabilitation games, but also permits measurement of the patient's performs. Depth or combined colour and depth imagery from a Kinect sensor is used as input data. The 3D signed distance function (SDF) is used as implicit shape representation, and a series of probabilistic graphical models are developed for the problem of model-based 3D tracking, simultaneous 3D tracking and reconstruction and 3D tracking of multiple objects with identical appearance. The work is based on the assumption that the observed imagery is generated jointly by the pose(s) and the shape(s). The depth of each pixel is randomly and independently sampled from the likelihood of the pose(s) and the shape(s). The pose(s) tracking and 3D shape reconstruction problems are then cast as the maximum likelihood (ML) or maximum a posterior (MAP) estimate of the pose(s) or 3D shape. This methodology first leads to a novel probabilistic model for tracking rigid 3D objects with only depth data. For a known 3D shape, optimization aims to find the optimal pose that back projects all object region pixels onto the zero level set of the 3D shape, thus effectively maximising the likelihood of the pose. The method is extended to consider colour information for more robust tracking in the presence of outliers and occlusions. Initialised with a coarse 3D model, the extended method is also able to simultaneously reconstruct and track an unknown 3D object in real time. Finally, the concept of `shape union' is introduced to solve the problem of tracking multiple 3D objects with identical appearance. This is formulated as the minimum value of all SDFs in camera coordinates, which (i) leads to a per-pixel soft membership weight for each object thus providing an elegant solution for the data association in multi-target tracking and (ii) it allows for probabilistic physical constraints that avoid collisions between objects to be naturally enforced. The thesis also explore the possibility of using implicit shape representation for online shape learning. We use the harmonics of 2D discrete cosine transform (DCT) to represent 2D shapes. High frequency harmonics are decoupled from low ones to represent the coarse information and the details of the 2D shape. A regression model is learnt online to model the relationship between the high and low frequency harmonics using Locally Weighted Projection Regression (LWPR). We have demonstrated that the learned regression model is able to detect occlusion and recover them to the complete shape.

One of the most far reaching failures of Radical reconstruction in the South was the inability of the southern Republican parties to evolve into stable political organizations in the accepted American tradition. The standard interpretation of this problem emphasizes the role of unyielding white opposition in undermining the southern Republican regimes. This thesis approaches the subject from a different angle. Focusing upon Louisiana during the administration of that state's first reconstruction Governor, Henry Clay Warmoth, party factionalism is examined as a source of Republican weakness.

This thesis covers the history of education in Reconstruction Period Texas.

This thesis discusses the Reconstruction period in the southern United States, including the events leading up to Reconstruction, the socioeconomic factors of Reconstruction itself, and the effect it had on both black and white societies.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.