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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Petrology and Sedimentology of the Morrissey Formation (Kootenay Group), southeast British Columbia - Southwest Alberta

Hogg, John Richard 04 1900 (has links)
<p> The Morrissey Formation of the Kootenay Group was mapped and sampled in three outcrops in southwestern Alberta and southeastern British Columbia; Burnt Ridge and Sparwood Ridge in British Columbia and Adanac Mine sight in Alberta. </p> <p> The lowest unit mapped was within the upper Fernie Formation (Passage beds) and consists of interbeds of sandstone and siltstone that were deposited as shallow water marine sediments. </p> <p> The Morrissey Formation conformably overlies the Fernie Formation and contains two members; the Weary Ridge Member and the Moose Mountain Member. The Weary Ridge Member consists of fine to medium grain, parallel and trough crossbedded sandstone, that was deposited as a delta-front-sand facies produced by coalescing of delta-sands from three to four delta complexes. The overlying Moose Mountain Member consists of high angle trough crossbedded, coarse grain, "salt and pepper" sandstone representing a distributary mouth bar environment. The Moose Mountain Member is unconventional in that the upper portion contains two units not seen in other sections. A marine trace fossil unit and a beach unit are both found within the upper portion of the member. These two units represent a transgression caused by channel switching and a regression and reworking of sediments into a beach respectively. </p> <p> Above the Morrissey Formation are the continental coals and fluvial systems of the Mist Mountain Formation. </p> <p> Petrographic studies on twenty five thin sections show two sedimentary sources for the Formation. The first source being chert rich Upper Paleozoic carbonates and the second source is Lower Paleozoic clastics that have previously been derived from a metamorphic complex of the Canadian Shield. The sandstones are cemented by quartz syntaxial overgrowths implying that there was a moderate degree of pressure solution, indicating a fairly high overburden pressure during diagenesis. </p> / Thesis / Bachelor of Science (BSc)
292

Arguing In an Age of Unreason: Elias Boudinot, Cherokee Factionalism, and the Treaty Of New Echota

Filler, Jonathan 13 July 2010 (has links)
No description available.
293

Development of Multichannel Analysis of Surface Waves (MASW) for Characterising the Internal Structure of Active Fault Zones as a Predictive Method of Identifying the Distribution of Ground Deformation

Duffy, Brendan Gilbert January 2008 (has links)
Bulk rock strength is greatly dependent on fracture density, so that reductions in rock strength associated with faulting and fracturing should be reflected by reduced shear coupling and hence S-wave velocity. This study is carried out along the Canterbury rangefront and in Otago. Both lie within the broader plate boundary deformation zone in the South Island of New Zealand. Therefore built structures are often, , located in areas where there are undetected or poorly defined faults with associated rock strength reduction. Where structures are sited near to, or across, such faults or fault-zones, they may sustain both shaking and ground deformation damage during an earthquake. Within this zone, management of seismic hazards needs to be based on accurate identification of the potential fault damage zone including the likely width of off-plane deformation. Lateral S-wave velocity variability provides one method of imaging and locating damage zones and off-plane deformation. This research demonstrates the utility of Multi-Channel Analysis of Surface Waves (MASW) to aid land-use planning in such fault-prone settings. Fundamentally, MASW uses surface wave dispersive characteristics to model a near surface profile of S-wave velocity variability as a proxy for bulk rock strength. The technique can aid fault-zone planning not only by locating and defining the extent of fault-zones, but also by defining within-zone variability that is readily correlated with measurable rock properties applicable to both foundation design and the distribution of surface deformation. The calibration sites presented here have well defined field relationships and known fault-zone exposure close to potential MASW survey sites. They were selected to represent a range of progressively softer lithologies from intact and fractured Torlesse Group basement hard rock (Dalethorpe) through softer Tertiary cover sediments (Boby’s Creek) and Quaternary gravels. This facilitated initial calibration of fracture intensity at a high-velocity-contrast site followed by exploration of the limits of shear zone resolution at lower velocity contrasts. Site models were constructed in AutoCAD in order to demonstrate spatial correlations between S-wave velocity and fault zone features. Site geology was incorporated in the models, along with geomorphology, river profiles, scanline locations and crosshole velocity measurement locations. Spatial data were recorded using a total-station survey. The interpreted MASW survey results are presented as two dimensional snapshot cross-sections of the three dimensional calibration-site models. These show strong correlations between MASW survey velocities and site geology, geomorphology, fluvial profiles and geotechnical parameters and observations. Correlations are particularly pronounced where high velocity contrasts exist, whilst weaker correlations are demonstrated in softer lithologies. Geomorphic correlations suggest that off-plane deformation can be imaged and interpreted in the presence of suitable topographic survey data. A promising new approach to in situ and laboratory soft-rock material and mass characterisation is also presented using a Ramset nail gun. Geotechnical investigations typically involve outcrop and laboratory scale determination of rock mass and material properties such as fracture density and unconfined compressive strength (UCS). This multi-scale approach is espoused by this study, with geotechnical and S-wave velocity data presented at multiple scales, from survey scale sonic velocity measurements, through outcrop scale scanline and crosshole sonic velocity measurements to laboratory scale property determination and sonic velocity measurements. S-wave velocities invariably increased with decreasing scale. These scaling relationships and strategies for dealing with them are investigated and presented. Finally, the MASW technique is applied to a concealed fault on the Taieri Ridge in Macraes Flat, Central Otago. Here, high velocity Otago Schist is faulted against low velocity sheared Tertiary and Quaternary sediments. This site highlights the structural sensitivity of the technique by apparently constraining the location of the principal fault, which had been ambiguous after standard processing of the seismic reflection data. Processing of the Taieri Ridge dataset has further led to the proposal of a novel surface wave imaging technique termed Swept Frequency Imaging (SFI). This inchoate technique apparently images the detailed structure of the fault-zone, and is in agreement with the conventionally-determined fault location and an existing partial trench. Overall, the results are promising and are expected to be supported by further trenching in the near future.
294

Riskanalyskartor i GIS över tsunamidrabbade områden vid ett skredscenario av vulkanen Cumbre Vieja på La Palma, Kanarieöarna / Vulnerability Maps in GIS of Tsunami Affected Areas for a Landslide Scenario of the Cumbre Vieja Volcano on La Palma, Canary Islands

Hagerfors, Erika, Lagrosen, Emelie January 2016 (has links)
På Kanarieön La Palma finns sprickzonen och vulkanen Cumbre Vieja. Under ett vulkanutbrott år 1949 bildades ett förkastningssystem längs vulkanens västra sida som skulle kunna vara ett förstadium till en framtida kollaps av vulkanen. Denna kollaps skulle kunna leda till bildandet av en tsunami när kollapsmaterial rasar ner i havet likt ett jordskred. Tsunamin kan komma att spridas över stora delar av Atlanten och i olika grad påverka de omkringliggande kontinenterna. Det finns olika teorier om hur stort jordskredet kommer att bli och om det kommer att ske successivt eller kollapsa som en enda enhet. I detta arbete studeras fyra kollapsscenarier med volymer av 20 km3, 40 km3, 80 km3 och 450 km3 närmare. Utifrån dessa volymer skapas riskanalyskartor i GIS över ön Teneriffa och New Yorks storstadsområde som visar hur långt över land tsunamin når vid de olika kollapsscenarierna. Dessa kartor jämförs sedan med markanvändningskartor över Teneriffa och New Yorks storstadsområde. Trots att tsunamivågen kan bli mycket hög vid Teneriffas kust kommer stora delar av ön att undkomma tsunamin, vilket bl.a. beror på öns höga höjd över havet. Då de flesta byggnader är belägna vid kusten innebär det att många människor ändå riskerar att drabbas. New Yorks storstadsområde är istället lågt beläget, vilket bidrar till att många kustnära områden kommer att drabbas trots att våghöjden har avtagit väsentligt. Då detta område är mycket tätbefolkat kan en tsunami därför leda till en stor påverkan. / On the Canary Island La Palma there is a volcanic ridge called Cumbre Vieja. During an eruption in 1949 a fault system was formed along the western flank of the volcano that can be an early stage of a future flank collapse of Cumbre Vieja. During this collapse a large volume of rock material will fall into the ocean like a landslide, which could lead to the formation of a tsunami. The tsunami could spread over large parts of the Atlantic Ocean and to varying extent affect the surrounding continents. There are different theories of how big the landslide will be and if it will collapse gradually or as a coherent block. In this study four collapse scenarios with different volumes, 20 km3, 40 km3, 80 km3 and 450 km3, are studied more closely. Based on these volumes, vulnerability maps are created in GIS covering the island Tenerife and the New York metropolitan area. The maps show the land reach of the tsunami for each of the collapse scenarios. These maps are thereafter compared with land use maps over Tenerife and the New York metropolitan area. Despite the high amplitude of the tsunami wave at the coast of Tenerife, large parts of the island will remain unaffected by the tsunami. This is due to, among other things, the high altitude of the island. However, most buildings are located along the coast, which means that many people are at risk. The New York metropolitan area has, on the other hand, low altitude which is one explanation why many coastal areas will be affected despite the significant decrease in tsunami wave height. A tsunami would have a major impact due to these areas being densely populated.
295

Model Uncertainty and Aggregated Default Probabilities: New Evidence from Austria

Hofmarcher, Paul, Kerbl, Stefan, Grün, Bettina, Sigmund, Michael, Hornik, Kurt 01 1900 (has links) (PDF)
Understanding the determinants of aggregated default probabilities (PDs) has attracted substantial research over the past decades. This study addresses two major difficulties in understanding the determinants of aggregate PDs: Model uncertainty and multicollinearity among the regressors. We present Bayesian Model Averaging (BMA) as a powerful tool that overcomes model uncertainty. Furthermore, we supplement BMA with ridge regression to mitigate multicollinearity. We apply our approach to an Austrian dataset. Our findings suggest that factor prices like short term interest rates and energy prices constitute major drivers of default rates, while firms' profits reduce the expected number of failures. Finally, we show that the results of our baseline model are fairly robust to the choice of the prior model size. / Series: Research Report Series / Department of Statistics and Mathematics
296

Utredning av Valboåsens grundvattenmagasins förbindelse med Gavleån : En analys av halten löst syre genom mätningar

Östblom, John January 2015 (has links)
Gävle kommuns VA-huvudman Gästrike Vatten AB ansvarar för dricksvattenproduktionen i Gävle. För Gävles tätort tas vatten från Valboåsen som sträcker sig från öster om staden, genom staden och vidare norrut. Denna rapports syfte är att genom mätning av halten löst syre undersöka Valboåsens förbindelse till Gavleån. Detta kommer ge en ökad förståelse för åsens komplexitet. Resultatet kommer också att användas för att verifiera och utveckla den konceptuella modellen över flödena i åsens grundvattenmagasin som tagits fram av Midvatten AB. För att kunna mäta halten löst syre har en provtagning skett på grundvattenrör. I provtagningen ingick även så kallade slugtest där rörens kapacitet och anslutning till grundvattenmagasinet säkerställdes. Efter mätningen sammanställdes resultatet för att kunna jämföra halten löst syre i grundvattenrören mot den konceptuella modellen. Resultatet visade att halten löst syre i vattnet i de olika grundvattenrören stöder den konceptuella modellen till stora delar och gav även mer information om områden längs åsen där kunskap om flödesförhållandena tidigare var osäkra. Metoden i den utförda studien har visat stor användbarhet för att påvisa flödesförhållanden och ytvattenpåverkan i Valboåsen vilket visar att mätning av syrehalt kan vara mycket användbart i grundvattenutredningar angående ytvattenpåverkan. För att utöka studien av Valboåsen i framtiden behövs mer provtagning i grundvattenmagasinet på områden som inte ingick i denna studie. / Gävle municipality's water company is Gästrike Vatten AB. They manages the drinking water production for the City of Gävle. The production starts in the ridge of Valbo which extends between Överhärde (located in the south part of Valbo) and Strömsbro (located in the north part of Gavle). Purpose of this report is to measure the dissolved oxygen content in the aquifer throughout the whole area to investigate where the infiltration from the nearby Gavle River occurs. The aim of the study is to get a better understanding of the complexity of the Valbo ridge. The measurements will help to verify or modify the conceptual model of the directions of water flow in the Valbo ridge, developed by Midvatten AB. Dissolved oxygen content was measured through ground water pipes. To assess the pipes’ capacity and connection to the aquifer, slug tests were performed. The dissolved oxygen data were analyzed and compared with the conceptual model. The results showed that the dissolved oxygen content in the water supported the conceptual model to a large extent and also gave previously unknown information on some stretches of the ridge. The method shows great potential for additional future studies in Valbo ridge and elsewhere. To expand the study further, a need for more sampling of the aquifer throughout the areas that were not included in this study.
297

Multicolinearidade em modelos de regressão logística / Multicollinearity in logistic regression models

Nakamura, Karina Gernhardt 21 March 2013 (has links)
Neste trabalho estudamos os efeitos da multicolinearidade em modelos de regressão logística e apresentamos estimadores viesados para que tais efeitos fossem minimizados. Primeiramente, o modelo de regressão logística e o processo para a estimação dos parâmetros foram apresentados. Foram feitos, também, alguns testes para avaliar a significância dos mesmos, bem como técnicas para analisar a qualidade do ajuste do modelo. Em seguida, os efeitos da multicolinearidade na estimação dos parâmetros e na sua inferência foram avaliados, bem como técnicas para o seu diagnóstico. Para amenizar o efeito deste problema, apresentamos dois estimadores alternativos ao de máxima verossimilhança: estimador em cristas e estimador em componentes principais. Comparamos, então, o desempenho dos três estimadores na forma de um estudo de simulação e de uma aplicação em um conjunto de dados reais. O principal resultado obtido foi que, na presença de multicolinearidade, os estimadores alternativos conseguiram um melhor ajuste em comparação ao de máxima verossimilhança, além de minimizar os seus efeitos. / This work proposes the use of some biased estimators to investigate whether is possible minimize the multicollinearity effects in logistic regression models. Initially, the latter model was presented, as well as its fitting process (therefore obtaining the maximum likelihood estimator), some tests to evaluate the significance of the parameters and techniques to analyze goodness of fit were also considered. Furthermore, the effects of multicollinearity in the fitting process and in the parameters inference were discussed, as well as techniques to identify the presence of multicollinearity. In order to diminish the effect of this problem, two alternative estimators were presented: ridge estimator and principal component estimator. Therefore, these three estimators performances were compared using a simulation study and applied in a real data set. The manly conclusion was that, in the presence of multicollinearity, the alternative estimators performed better than the maximum likelihood estimator, besides reducing its effects.
298

Significado morfotectônico dos planaltos isolados da Bocaina / Morphotectonics of the isolated plateaus of Bocaina

Hiruma, Silvio Takashi 29 October 2007 (has links)
O Planalto da Bocaina situa-se no flanco leste do Rift Continental do Sudeste do Brasil (RCSB), em uma das porções mais elevadas da Serra do Mar, com altitudes superiores a 2000 m, compondo, juntamente com o Planalto de Campos do Jordão, os altos blocos de planaltos cristalinos do sudeste do Brasil. A Bocaina apresenta uma sucessão de planaltos de relevo mais suavizado (planaltos isolados), separados por vales profundos, que perdem altura de NW para SE. A origem do desnivelamento desses planaltos tem sido associada ora à reativação de antigas zonas de cisalhamento por falhas com componente normal, ora à dissecação erosiva diferencial controlada por knickpoints, ou, ainda, à preservação de superfícies de erosão de idades diferentes. A presente pesquisa teve por finalidade analisar as diferentes hipóteses de modo a estabelecer a idade, estilo e magnitude dos eventos tectônicos e denudacionais, responsáveis pela atual distribuição dos planaltos isolados da Bocaina. A metodologia integra estudos geomorfológicos e estruturais, segundo uma abordagem morfotectônica, com apoio da análise de traços de fissão em apatita e determinações pelo método do radiocarbono. Esta análise constitui importante ferramenta para determinar histórias térmicas e idades de resfriamento, em escalas de tempo de 106 a 108 anos, e permite estimar taxas de denudação de blocos de embasamento. Modelos digitais de terreno e cartas morfométricas subsidiaram a análise morfotectônica. Os planaltos isolados são caracterizados por baixos valores de gradientes hidráulicos, declividade e amplitude do relevo. O condicionante tectônico no desnivelamento dos níveis topográficos e individualização desses planaltos é evidenciado pela estreita correlação entre estruturas rúpteis (falhas e fraturas), feições morfotectônicas (facetas triangulares, knickpoints, escarpas, capturas fluviais), distribuição dos principais alvéolos e padrão de drenagem. Diques registram fases distensivas desde a ruptura dos continentes no Eocretáceo até o Paleógeno. Regimes de esforços observados na Bocaina são compatíveis com o modelo tectônico proposto para o RCSB durante o Cenozóico. Os eventos tectono-magmáticos no sudeste do Brasil tiveram um importante papel nos processos denudacionais registrados pela análise de traços de fissão em apatitas no Planalto da Bocaina. As idades corrigidas de traços de fissão em apatitas para 15 amostras variam entre 326±30 e 54±5 Ma, incluindo um significativo conjunto de idades mais velhas do que 200 Ma - as mais antigas obtidas na região da Serra do Mar até o momento. As idades apresentam uma tendência de decréscimo de noroeste para sudeste, do interior do continente em direção à costa, padrão também reconhecido em outras margens continentais passivas. Esse padrão é perpendicular à direção estrutural principal do embasamento pré-cambriano, sugerindo um importante condicionante estrutural. Idades contrastantes em um mesmo planalto isolado, ou similares em altitudes diferentes, sugerem uma evolução tectonotermal regional complexa, possivelmente associada à evolução do RCSB. Um modelo simples de recuo de escarpa não explicaria a distribuição espacial das idades de traços de fissão em apatitas no Planalto da Bocaina; falhas devem ter sido responsáveis pela acentuação dos desníveis topográficos entre os planaltos isolados. As histórias térmicas registram importantes eventos de resfriamento relacionados à ruptura continental, ao magmatismo alcalino neocretáceo e à geração e deformação do RCSB. As idades mais antigas de traços de fissão da Serra do Mar foram obtidas nas porções mais elevadas da Bocaina, que guardam estreita semelhança com a paisagem dos altos campos no Planalto de Campos do Jordão, evidenciando que tais áreas provavelmente constituíram, por um longo período de tempo, importante área fonte de sedimentos para as bacias do Paraná, Bauru e Santos. / The Bocaina Plateau is situated on the eastern flank of the Continental Rift of Southeastern Brasil (CRSB), in the highest portions of the Serra do Mar, reaching more than 2000 meters in altitude. This and the Campos do Jordão Plateau comprise the high blocks of crystalline massifs of Southeastern Brasil. The Bocaina presents a succession of NW-SE topographically decreasing low-relief plateaus (isolated plateaus), separated by deep valleys. The origin of the differences in altitude among these plateaus has been associated with (1) tectonic reactivation of ancient shear zones by normal faulting, (2) differential erosional dissection controlled by knickpoints, and (3) preservation of erosional surfaces of different ages. This study examines these hypotheses in order to establish the age, style and magnitude of the tectonic and denudational events that resulted in the current distribution of the isolated plateaus of Bocaina. Structural and geomorphological analyses have been carried out using a morphotectonic approach, aided by apatite fission track analysis and radiocarbon dating. Apatite fission track analysis is an important tool to obtain thermal histories and cooling ages, on scales of 106 to 108 years, and is commonly used to estimate denudation rates in basement blocks. Morphotectonic analysis was supported by digital terrain models and morphometric maps. The isolated plateaus are characterized by low hydraulic gradient, slope and relief. Tectonic conditioning in the accentuation of differences in altitude and individualization of the plateaus is evinced by clear correlation between brittle structures (faults and fractures), morphotectonic features (triangular facets, knickpoints, scarps, fluvial captures), distribution of main alluvial plains and drainage pattern. Dikes indicate distensional phases since continental break-up in the Early Cretaceous till the Paleogene. Stress regimes observed in Bocaina are compatible with the tectonic model for the CRSB during the Cenozoic. Tectonic and magmatic events in Southeastern Brazil played an important role in denudational processes as recorded by apatite fission track analysis in the Bocaina plateau. Corrected fission track ages for 15 samples range from 326±30 to 54±5 Ma, including a significant set greater than 200 Ma, the oldest such ages yet registered in the Serra do Mar. Ages decrease NW-SE from the continent coastwards, a trend also recognized in other passive continental margins. This pattern is perpendicular to the main structural grain of the Precambrian basement, suggesting important structural control. Contrasting ages within a single plateau and similar ages at different altitudes indicate complex regional tectono-thermal evolution, possibly related to the evolution of the CRSB. Fission track age distribution in the Bocaina plateau cannot be explained by the simple scarp-retreat model; faults must have accentuated differences in altitude among the isolated plateaus. Thermal histories show important cooling events related to continental break-up, Early Cretaceous alkaline magmatism and origin of the CRSB. The oldest fission track ages obtained in the Serra do Mar region (> 200 Ma) were found in the highest portions of the Bocaina plateau, where the landscape system is very similar to that of the Campos do Jordão plateau. These areas have probably been an important, persistent source of sediments for the Paraná, Bauru and Santos basins, for a very long time.
299

Avaliação da remodelação do rebordo alveolar após exodontia minimamente traumática e utilização de enxerto xenógeno para preservação alveolar / Dimensional changes of alveolar bone in extraction sockets, after minimally traumatic extraction and socket fill with xenogenic bone

Fiamengui Filho, Jorge Francisco 09 April 2015 (has links)
Introdução: Após a exodontia, a cicatrização natural do alvéolo provoca alterações dimensionais no rebordo alveolar, com diminuição dos tecidos moles e duros. Diferentes técnicas podem ser utilizadas para tentar diminuir essas alterações, com a intenção de facilitar a reabilitação estética e funcional com implantes, principalmente em áreas de dentes anteriores. Objetivos: Os objetivos deste estudo foram verificar a eficácia da utilização do material de origem xenógena Orthogen® na preservação do rebordo alveolar pós-exodontia e avaliar as características histológicas após 4 meses de reparo. Materiais e Métodos: 20 pacientes foram divididos aleatoriamente em 2 grupos, de acordo com a abordagem que iriam receber após a exodontia de uma raiz residual. No grupo teste, os alvéolos foram preenchidos com Orthogen® e selados com EGL (Enxerto Gengival Livre). No grupo controle, um coágulo foi preservado no alvéolo e o mesmo também foi selado com EGL, sem a utilização do Orthogen®. Em ambos os grupos as exodontias foram realizadas de maneira minimamente traumática, com o Kit de Extração Atraumática Neodent®. Modelos de gesso obtidos antes das exodontias (tempo 1) e após 4 meses (tempo 2), momentos antes da instalação dos implantes, foram utilizadas para as medidas dimensionais, através do escanemento dos modelos e medidas no programa Orthoanalyzer®. Amostras ósseas obtidas após 4 meses de reparo foram utilizadas para a análise histológica descritiva. Resultados: Os resultados demonstraram que, após 4 meses de reparo alveolar, os dois grupos apresentaram remodelação do rebordo alveolar e diminuição nas medidas realizadas. Porém, a remodelação do rebordo foi mais evidente no grupo controle (coágulo). Histologicamente foi possível observar formação de novo osso ao redor das partículas do Orthogen®. Conclusões: A utilização do Orthogen® para preenchimento dos alvéolos e preservação do rebordo alveolar foi eficaz na diminuição das alterações dimensionais nos tecidos duro e mole do rebordo alveolar pós-exodontia. / Introduction: After tooth extraction, the natural healing of the socket is followed by dimensional changes of ridge contour, with marked reduce of hard and soft tissues. Socket reservation techniques can be used to improve functional and esthetics of the dental implants in this areas, especially in anterior teeth areas. Objectives: The aims of this study are to verify the efficacy of use Orthogen® to ridge preservation and analysis the histological characteristics after 4 months repair of the sockets. Material and Methods: 20 patients were randomly distributed in 2 groups, according with the treatments. In test group, the sockets were filled with Orthogen® and closed with a gingival free graft. In control group, the clots were preserved into the socket and free gingival graft was sutured in the deepithelialized marginal tissue of the socket. Stone casts were used to analyze the ridge dimensional changes with the Orthoanalyzer® software. After 4 months, bone samples were obtained during the dental implant procedure and were used to describe the histological characteristics. Results: The results showed that, after 4 months of wound healing, both groups showed a decrease in the measurements. However, the remodeling of the ridge was most evident in the control group (clot). Histological images showed the formation of new bone around the Orthogen® particles. Conclusion: The use of Orthogen® to socket preservation can collaborate to reduce the dimensional changes of the hard and soft tissue in post-extraction alveolar ridge sites.
300

Extraction de fragments forestiers et caractérisation de leurs évolutions spatio-temporelles pour évaluer l'effet de l'histoire sur la biodiversité : une approche multi-sources / Forest fragments extraction and characterization of their spatiotemporal evolution to evaluate the effects of history on biodiversity : a multi-source approach

Herrault, Pierre-Alexis 19 June 2015 (has links)
La biodiversité dans les paysages dépend des caractéristiques de ce paysage mais peut aussi être influencée par son histoire. En effet, certaines espèces ne réagissent pas immédiatement à une perturbation mais peuvent montrer un temps de réponse plus ou moins long. De ce fait, la prise en compte de l'évolution de l'habitat des espèces est devenue un enjeu important en écologie depuis quelques années, pour mieux comprendre la présence ou la diversité biologique actuelle. L'objectif de cette thèse en géomatique s'inscrit dans ce contexte applicatif d'écologie historique. Le sujet que nous traitons porte sur l'extraction automatique d'îlots boisés et la caractérisation de leur évolution spatio-temporelle depuis le milieu du XIXe siècle pour modéliser l'effet de leur trajectoire historique sur la diversité actuelle en syrphes forestiers (Diptera : Syrphidae). Le site d'étude est un paysage agri-forestier des Coteaux de Gascogne. La démarche générale proposée se compose de trois étapes principales : (1) la constitution de la base de données spatiales des îlots boisés intégrant plusieurs sources de données hétérogènes, (2) l'appariement des îlots boisés aux différentes dates avec la caractérisation de leur évolution spatio-temporelle, (3) la modélisation statistique des relations espèces-habitats intégrant l'histoire comme un des facteurs explicatifs de la diversité en syrphes observée. Plusieurs contributions méthodologiques ont été apportées à cette démarche. Nous avons proposé une nouvelle méthode de correction géométrique fondée sur la régression ridge à noyau pour rendre compatible les données spatiales anciennes et actuelles mobilisées. Nous avons également développé une approche et un outil de vectorisation automatique des forêts dans les dessins-minutes de la carte d'Etat-Major du XIXe siècle. Enfin, une première évaluation de l'impact de l'incertitude spatiale sur la réponse des modèles espèces-habitats a également été initiée. D'un point de vue écologique, les résultats ont révélé un effet significatif de la continuité temporelle des habitats sur la diversité en syrphes forestiers. Nous avons montré que les forêts les plus isolées présentaient une dette d'extinction ou un crédit de colonisation selon le type d'évolutions apparues au cours de la dernière période étudiée (1979-2010). Il s'est avéré qu'une durée de 30 ans n'était pas suffisante aux syrphes forestiers pour qu'ils retrouvent un été d'équilibre à la suite d'une évolution spatiale de leur habitat isolé. / Biodiversity in landscapes depends on landscape spatial patterns but can also be influenced by landscape history. Indeed, some species are likely to respond in the longer term to habitat disturbances. Therefore, in recent years, landscape dynamics have become a possible factor to explain current biodiversity. The aim of this thesis in GIS is part of this historical ecology context. We are dealing with automatic extraction of forest patches and characterization of their spatiotemporal evolution. The objective is to evaluate forest dynamics effects on current diversity of forest hoverflies. (Diptera: Syrphidae) in the agri-forestry landscape of Coteaux de Gascogne. The proposed general approach consists of three main steps: (1) the forest spatial database production from heterogeneous sources, (2) forest patches matching and characterization of their spatiotemporal evolution, (3) species-habitat modeling while integrating history as one of the factors likely to explain hoverflies diversity. Several methodological contributions were made. We proposed a new geometric correction approach based on kernel ridge regression to make consistent past and present selected data sources. We also developed an automatic extraction approach of forest from Historical Map of France of the 19th century. Finally, spatial uncertainty effects on ecological models responses have been assessed. From an ecological viewpoint, a significant effect from historical continuity of patches on forest hoverflies diversity was revealed. The most isolated fragments presented an extinction debt or a colonization credit according to area dynamics occurred in the last time-period (1970-2010). As it turns out, 30 years was not sufficient for forest hoverflies to reach new equilibrium after isolated habitat changes.

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