The overall aim of my PhD research work is to design, develop, and evaluate a new practical environment to generate separated representations of arterial and venous trees in non-contrast pulmonary CT imaging of human subjects and to extract quantitative measures at different tree-levels. Artery/vein (A/V) separation is of substantial importance contributing to our understanding of pulmonary structure and function, and immediate clinical applications exist, e.g., for assessment of pulmonary emboli. Separated A/V trees may also significantly boost performance of airway segmentation methods for higher tree generations. Although, non-contrast pulmonary CT imaging successfully captures higher tree generations of vasculature, A/V are indistinguishable by their intensity values, and often, there is no trace of intensity variation at locations of fused arteries and veins. Patient-specific structural abnormalities of vascular trees further complicate the task. We developed a novel multi-scale topo-morphologic opening algorithm to separate A/V trees in non-contrast CT images. The algorithm combines fuzzy distance transform, a morphologic feature, with a topologic connectivity and a new morphological reconstruction step to iteratively open multi-scale fusions starting at large scales and progressing towards smaller scales. The algorithm has been successfully applied on fuzzy vessel segmentation results using interactive seed selection via an efficient graphical user interface developed as a part of my PhD project. Accuracy, reproducibility and efficiency of the system are quantitatively evaluated using computer-generated and physical phantoms along with in vivo animal and human data sets and the experimental results formed are quite encouraging. Also, we developed an arc-skeleton based volumetric tree generation algorithm to generate multi-level volumetric tree representation of isolated arterial/venous tree and to extract vascular measurements at different tree levels. The method has been applied on several computer generated phantoms and CT images of pulmonary vessel cast and in vivo pulmonary CT images of a pig at different airway pressure. Experimental results have shown that the method is quite accurate and reproducible. Finally, we developed a new pulmonary vessel segmentation algorithm, i.e., a new anisotropic constrained region growing method that encourages axial region growing while arresting cross-structure leaking. The region growing is locally controlled by tensor scale and structure scale and anisotropy. The method has been successfully applied on several non-contrast pulmonary CT images of human subjects. The accuracy of the new method has been evaluated using manually selection of vascular and non-vascular voxels and the results found are very promising.

Les traumatismes infantiles (TI) sont un facteur de vulnérabilité majeur à la schizophrénie. Nous avons ici choisi d'étudier l’impact des TI sur le cerveau dans la schizophrénie.Dans notre première étude, en voxel-based morphometry (VBM) et portant sur 21 schizophrènes et 30 contrôles, la négligence émotionnelle était associée à une diminution du volume total de matière grise dans les deux groupes. Cette association était plus marquée chez les schizophrènes. Chez les patients, la négligence émotionnelle était prédictive de la densité de matière grise du cortex préfrontal dorso-latéral, elle-même prédictive de la sévérité de la désorganisation.Dans notre seconde étude, nous avons utilisé une tâche émotionnelle en IRMf pour explorer les liens entre TI et connectivité fonctionnelle PPI (psychophysiological interaction) de l’amygdale chez 21 schizophrènes et 25 contrôles. Au cours de la tâche, chez les patients, la sévérité des abus sexuels et négligences physiques été associée à une diminution de connectivité entre l’amygdale et la région du cortex cingulaire postérieur/précunéus.Enfin le résultat le plus répliqué de notre revue de la littérature (15 articles d'imagerie) est l’association forte entre TI et diminution du volume total de matière grise. Chez les schizophrènes les TI étaient associés à des diminutions de matière grise au niveau du cortex préfrontal, à des altérations de l’intégrité de la matière blanche et à des altérations de connectivité fonctionnelle.Ainsi nos résultats suggèrent que les TI, interagissant avec d'autres facteurs de vulnérabilité, pourraient modeler la psychopathologie schizophrénique via des effets cérébraux neurodéveloppementaux. / Childhood trauma (CT) is a major risk afctir for schizophrenia. The aim of this work was to question the possible impact of CT on the brain of schizophrenia patients.In our first study, using voxel-based morphometry (VBM) in 21 patients with schizophrenia and 30 controls, childhood emotional neglect was associated with decreased total grey matter volume in both groups, with a stronger association in the patients group. In schizophrenia, emotional neglect predicted grey matter decrease in dorsolateral prefrontal cortex, which in turn predicted the severity of disorganization.In our second study, we used an fMRI emotional task with PPI (psychophysiological interaction) in 21 schizophrenia patients and 25 controls. During the emotional task, in schizophrenia group, sexual abuse and physical neglect during childhood were associated with decreased connectivity between the amygdala and the precuneus/posterior cingulate region.Finaly, the most replicated result in our review is the strong association between CT and decreased total grey matter volume. In addition, CT in schizophrenia patients is related to decreased prefrontal cortex grey matter, widespread alterations of white matter integrity and alterations of functional connectivity in a network including the amygdala, the anterior cingular cortex, the precuneus/posterior cingulate region and the temporo-parietal junction.Our findings suggest that CT, in interaction with other factors, could shape the psychopathology of schizophrenia through developmental effects on the brain, with predominent alterations in the prefrontal cortex, or in stress-related circuits affecting self-consciousness and social cognition.

This paper quantifies the direct relationship between GDP per Capita and Connectivity variables such as mobile phone per 100 inhabitants, broadband per 100 inhabitants, and individual internet use percentage across Resource, Innovation, and Efficiency Driven countries. In order to complete this analysis, the study utilizes a fixed effect model, inspired by a previous indirect study by Shamim, published in 2007. The regression outputs find a statistically significant, positive relationship between all three connectivity variables and GDP per Capita in all types of countries. These results could have important policy implications regarding governmental infrastructure investment and future economic development.

Floodplains, and the sediment accumulating naturally on them, are important to maintain stream water quality and serve as sinks for organic and inorganic carbon. Newer theories contend that land use and hydrologic connectivity (water-mediated transport of matter, energy, and/or organisms within or between elements of the hydrologic cycle) play important roles in determining sediment accumulation on floodplains. This study hypothesizes that changes in hydrologic connectivity have a greater impact on floodplain sediment accumulation than changes in land use. Nine sediment cores from seven sub-basins were collected from the Savannah River Site (SRS), South Carolina, and processed for grain-size, radionuclide dating (7Be, 137Cs, 210Pb), particulate organic carbon (POC), and microscopy. Historical records, including aerial and satellite imagery, were used to identify anthropogenic disturbances in the sub-basins, as well as to calculate the percentages of natural vegetation land cover at the SRS in 1951, and 2014. LiDAR and field survey data identified 251 flow impediments, measured elevation, and recorded standard stream characteristics (e.g., bank height) that can affect hydrologic connectivity. Radionuclide dating was used to calculate sediment mass accumulation rates (MARs) and linear accumulation rates (LARs) for each core. Results indicate that sedimentation rates have increased across all SRS sub-basins over the past 40-50 years, shortly after site restoration and recovery efforts began. Findings show that hydrologic connectivity proxies (i.e., stream characteristics and impediments) have stronger relationships to MARs and LARs than the land use proxy (i.e., vegetation cover), confirming the hypothesis. As stream channel depth and the number of impediments increase, floodplain sedimentation rates also increase. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain stated goals, particularly in terms of floodplain sediment retention.

Depuis ces deux dernières décennies, une nouvelle technologie sans fil appelée Réseau de Capteur Sans Fil (RCSF) résultant d"une fusion entre les systèmes embarqués et les communications sans fil a vu le jour. Un RCSF ("WSN : Wireless Sensor Network" en Anglais) est un réseau Ad hoc composé d"un grand nombre de nœuds qui sont des micro-capteurs qui peuvent être déployés de façon aléatoire ou déterministe dans une zone d"intérêt donnée. Ces nœuds capteurs sont capables de récolter plusieurs paramètres physiques sur l"environnement qui les entoure, appelé généralement zone de captage (ou zone de surveillance). Ensuite, ils doivent si nécessaire traiter les données capturées et les transmettre à un (ou plusieurs) nœud de collecte appelé station de base, centre de traitement ("sink" en Anglais). Beaucoup de domaines d"applications tels que le contrôle et suivi environnemental, le contrôle de production dans l"industrie, la surveillance de zone, le monitoring de l"habitat, l"agriculture intelligente, etc. sont basés sur les RCSF. Toutefois, les RCSF ne sont pas parfaits. En effet, compte tenu de leur petite taille, leur faible coût et leurs déploiement dans des zones souvent hostiles ou difficiles d"accès, les nœuds capteurs présentent un certain nombre de faiblesses parmi lesquelles une durée de vie du réseau limitée, une bande passante faible, des capacités de capture et de communication réduites, etc. Afin de surmonter ces contraintes des RCSF, plusieurs problématiques de recherche sont nées ces dernières années, et les principales portent sur l"optimisation de la consommation énergétique en vue d"améliorer la durée de vie du réseau. D"autres recherches importantes menées dans le domaine de ces réseaux portent sur les stratégies de placement des nœuds, sur la couverture de zones et sur la connectivité du réseau. Cependant, la plupart des solutions proposées ces dernières années ne prennent pas en compte toutes ces problématiques dans leurs modèles de résolution ; alors que dans beaucoup d"applications des RCSF telles que la surveillance de zone critique, le monitoring de l"habitat, l"agriculture intelligente, il est nécessaire de garantir en même temps une couverture complète de la zone de surveillance, une bonne connectivité du réseau, tout en optimisant au mieux la durée de vie de celui-ci. Le but de cette thèse est donc de proposer de nouveaux mécanismes efficaces pour l"optimisation de la durée de vie dans les RCSF, tout en garantissant, à tout moment de cette durée de vie, une couverture totale de la zone de surveillance, ainsi qu"une bonne connectivité du réseau. Pour atteindre nos objectifs, nous avons étudié et fait des propositions dans deux axes qui sont le placement des nœuds et les mécanismes d"ordonnancement au niveau de la couche MAC. Pour ces derniers, nous avons mis en place un algorithme appelé DSMAC (Distributed Scheduling Medium Acces Control) qui est basé sur notre méthode de placement des nœuds. Par ailleurs, DSMAC permet de couvrir 100% de la zone de surveillance, assure une bonne connectivité du RCSF et permet également aux nœuds capteurs d"économiser jusqu"à 30% de leur énergie comparativement à d"autres protocoles MAC tels que TunableMAC. / Since the past two decades, a new technology called Wireless Sensor Network (WSN) which result in a fusion of embedded systems and wireless communications has emerged. A WSN is Ad hoc network composed of many sensors nodes communicating via wireless links and which can be deployed randomly or deterministically over a given interest region. Theses sensors can also collect data from the environment, do local processing and transmit the data to a sink node or Base Station (BS) via multipath routing. Thereby, a wide range of potential applications have been envisioned using WSN such as environmental conditions monitoring, wildlife habitat monitoring, industrial diagnostic, agricultural, improve health care, etc. Nevertheless,WSN are not perfect. Indeed, given their small size, their low cost and their deployment generally in hostile or difficult access areas, sensor nodes have some weaknesses such as: a limited energy, so a network lifetime limited, limited bandwidth, limited computations and communications capabilities, etc. To overcome these limitations, several research issues from were created in recent years, and the main issues focus on the optimization of energy consumption in order to improve the network lifetime. Other important researches focus on issues of coverage areas, placement strategies of sensor nodes and network connectivity. However, most solutions proposed in recent years to resolve these issues do not take into account all these issues that we cited above in resolutions models; while in many WSN applications such as monitoring critical region, wildlife habitat monitoring, agricultural application, a full coverage of the monitoring region and network connectivity are mandatory as well an energy-awareness network lifetime. The objective of this thesis is thus to propose new scheduling mechanisms for optimizing the network lifetime in WSN, while ensuring at any time of the network lifetime a full coverage of the monitored region and network connectivity. To achieve our goals, we have study and done proposal in two axes which are placement strategy of sensor nodes and scheduling mechanism in the MAC layer. For these, we have implemented a Distributed Scheduling Medium Access Control algorithm (DSMAC) based on our placement method. Furthermore, DSMAC enables to cover 100% of the monitored region, to ensure optimal network connectivity and also allows sensors node to save up to 30% of their energy compared to other MAC protocols such as TunableMAC.

The American marten (Martes americana) is an endangered species in Vermont and a Regional Species of Greatest Conservation Need in the northeastern United States. Though historically widespread in northeastern forests, their range presumably contracted to northern Maine and the High Peaks region of the Adirondacks by the early 1900s. Regionally, populations appear to be in recovery. Natural recolonization is believed to have occurred in New Hampshire, northeastern Vermont and the western Adirondacks. A reintroduction effort in southern Vermont that was originally declared unsuccessful is now believed to be the source of a recently detected population in the area. However, our current knowledge of distribution, population history and population connectivity relies primarily on occurrence data from harvest records, which are limited in scope and resolution. In Vermont, where population size is estimated to be extremely low, more robust estimates of population status may be critical to continued recovery. I genotyped individuals from Maine, New York, New Hampshire, northeastern Vermont and southern Vermont at ten microsatellite loci and amplified a 320 base pair segment of the control region of mtDNA to estimate the source(s) of the two Vermont populations using statistical tests of genetic differentiation. I also used Bayesian and stochastic genetic clustering methods to estimate population genetic structure in the northeastern United States. Genetic structure exists at multiple scales in the region as a result of natural barriers to gene flow, human-mediated gene flow, and lineage sorting in relic populations. My results suggest that New Hampshire is a major source of colonization of northeastern Vermont and the population in southern Vermont is either a remnant of the reintroduction or a pre-reintroduction relic that has experienced introgression from the reintroduction stock. I identified three regions where relic populations perceived to be extirpated in the 1900s may have persisted. I also developed an occupancy model for American marten in the northeastern United States using mixed-effects logistic regression based on expert opinion data. Eighteen experts from Maine, New Hampshire, Vermont and New York with backgrounds in trapping, wildlife management, and wildlife science participated in the survey. Experts were asked to estimate the probability of marten occupancy at 30 sites in the northeastern United States. Three top models described the data. Habitat covariates in those models were 1) percent canopy cover, 2) percent spruce-fir forest cover, 3) winter temperature, 4) elevation, and 5) road density. An AIC-weighted average of these three models had significant predictive ability (area under an ROC curve = 0.88) with respect to occurrence records in the northeastern United States. In addition, the model predicted that high quality habitat existed patchily along the central and northern Green Mountain spine in Vermont – where no occurrence records exist for at least a century. Top-scoring movement corridors between southern Vermont and nearby populations in northeastern Vermont/New Hampshire and New York occurred in the northern and central Green Mountains and across high resistance movement barriers in the Champlain valley. Corridors to New York were considered strong movement barriers and are unlikely to facilitate gene flow.

Mountain headwater catchments in the semi-arid Intermountain West are important sources of surface water because these high elevations receive more precipitation than neighboring lowlands. The hydrology of these mountain catchments is especially important as the region faces water shortages and conflicts. Conifer encroachment on aspen stands has been observed across the western US and can result in a decline in water yield. The overall objective of this study was to further our understanding of hillslope-stream connectivity in a headwater catchment of Northern Utah and any observable differences in this connection between aspen and conifer hillslopes. Hillslopes are the fundamental unit of a watershed. Therefore understanding processes at the hillslope scale is pertinent to managing valuable water resources. However, hillslope hydrology is understudied in the snow-driven, semi-arid west, leaving a gap in our knowledge of how watersheds function. This thesis focuses on how and when hillslope water contributes to stream water: hillslope-stream connectivity. Its specific objectives are (1) to compare peak snow accumulation under aspen and conifer stands, (2) to determine if shallow soil moisture shows organized patterns, indicating hillslope-connectivity and compare these patterns between vegetation types, (3) to examine hillslope-stream connectivity within deep layers of the soil profile and compare times of connectivity between vegetation types and (4) to find any thresholds past which hillslope-stream connectivity begins.

River barriers, such as dams, culverts and diversions are important for water conveyance, but disrupt river ecosystems and hydrologic processes. River barrier removal is increasingly used to restore and improve river habitat and connectivity. Most past barrier removal projects prioritized individual barriers using score-and-rank techniques, neglecting the spatial structure and cumulative change from multiple barrier removals. Similarly, most water demand models satisfy human water uses or, only prioritize aquatic habitat, failing to include both human and environmental water use benefits. In this study, a dual objective optimization model identified in-stream barriers that impede quality-weighted aquatic habitat connectivity for Bonneville cutthroat trout. Monthly streamflow, stream temperature, channel gradient and geomorphic condition were indicators of aquatic habitat suitability. Solutions to the dual objective problem quantify and graphically present tradeoffs between quality-weighted habitat connectivity and economic water demands. The optimization model is generalizable to other watersheds, but it was applied as a case study in Utah’s Weber Basin to prioritize removal of environmentally-harmful barriers, while maintaining human water uses. Modeled results suggest tradeoffs between economic costs of removing barriers and quality-weighted habitat gains. Removing 54 in-stream barriers increases quality-weighted habitat by about 160 km and costs approximately $10M, after which point the cost effectiveness of removing barriers to connect river habitat slows. In other words, there is decreasing benefit of removing barriers, so that after removing the first 54 barriers, it costs more to connect more high-quality habitat. Removing reservoirs or diversions that result in large economic losses did not substantially increase habitat. This suggests that removing numerous small barriers results in greater increases in habitat for the same removal costs, without significant water scarcity losses. The set of barriers prioritized for removal varied monthly depending on limiting habitat conditions for Bonneville cutthroat trout. The common barriers removed in the model were identified to communicate the most environmentally harmful barriers to local stakeholders and inform decision-making. Additionally, limiting the budget or number of barrier removal projects resulted in a different set of barriers removed. This research helps prioritize barrier removals and future restoration decisions in the Weber Basin although the model formulation is generalizable to other watersheds. Available data and a simplified approach limit the scope of this model. The modeling approach expands current barrier removal optimization methods by explicitly including economic and environmental water uses.

Four linked experiments were run in order to understand the relationship between frequency judgment and recognition discrimination tasks. The purpose of these studies was to contrast the common-path model and recursive reminding hypothesis as explanations for the underlying principles that drive these tasks. Item-attribute variables such as printed frequency, connectivity, and set size, and an episodic variable, study frequency were manipulated. Memory for recent episodes was evaluated using recognition and frequency judgment tasks. Although all of the variables, with the exception of set size, had significant effects in both tasks, an analysis of effect sizes revealed differences between the tasks in relation to the variables. Specifically, the item-attribute variables had larger effects in recognition than in JOF, and the effect size for study frequency was greater in the JOF task compared to recognition. The reliability of these differences was statistically established by a repeated measures analysis run on the correlations between each subject's mean and the variables. Although the effect size pattern is consistent with the reminding hypothesis, the effects of connectivity and printed frequency in the JOF task are not as they represent familiarity measures. Thus, this finding indicates that familiarity must be involved in making frequency judgments, making the reminding hypothesis inadequate as an explanation as it does not take into account the effect of item-attribute variables and their contribution to familiarity with its subsequent effect on frequency estimates. Therefore, it is proposed that a dual-process approach that takes into account both the reminding and recollection at test in the JOF task, as well as attempting to explain the influence of an underlying construct such as familiarity that effects both tasks may be the most appropriate explanation for frequency estimation results.

In 5G systems, two radio air interfaces, evolved LTE and New Radio (NR), will coexist. By using millimeter waves, NR will provide high throughputs, but the higher frequencies will also lead to increased losses and a worse coverage. Multi-connectivity is therefore envisioned as a way to tackle these effects by connecting to multiple base stations simultaneously, allowing users to benefit from both air interfaces’ advantages. In this thesis, we investigate how multi-connectivity can be used efficiently in ultra-dense networks, a new paradigm in which the number of access nodes exceeds the number of users within the network. A framework for secondary cell association is presented and an energy efficiency’s condition is proposed. Upper and lower bounds of the network’s energy efficiency are analytically expressed. Algorithms for secondary cell selection are designed and evaluated through simulations. Multi-connectivity showed an improvement of up to 50% in reliability and and an increase of up to 20% in energy efficiency.