archives@tulane.edu / Louisiana's deltaic wetlands are threatened in the 21st century by rapid sediment subsidence that compounds climate-driven rising sea levels. Much of the coastal wetlands that fringe the Mississippi Delta are underlain by 1-2 m of an organic-rich and highly compressible surficial marsh mat substrate, where shallow subsidence is controlled by the interrelated factors of mineral and organic loading-induced compaction and the vertical accretion rate, as well as subsidence occurring deeper in the sediment column through a variety of drivers. The supply of organic and mineral sediment varies dependent on local elevation, marsh type, and hydrologic connectivity with riverine and turbid estuarine water bodies that supply mineral sediment. Shallow subsidence is thought to be a major factor driving coastal wetland land loss in the Mississippi Delta compounding other factors such as disconnection with riverine sediment sources, prolonged inundation resulting in marsh drowning, and marsh fragmentation through canal dredging. An analysis of delta-wide Coastwide Reference Monitoring Systems (CRMS), rod- surface elevation table (R-SET) data illustrates that there is also a relationship between mineral and organic loading to subsidence. Continuously recording surface elevation tables (CR-SET) were deployed at four different marsh ecotypes within Barataria Basin, Louisiana to examine mechanisms that influence marsh surface elevation change. The CR-SET’s are located adjacent to long-term CRMS stations that record vertical accretion and surface elevation change. This study examines (1) the impact of seasonal and daily meteorological changes on water levels and marsh surface elevation, aims to (2) directly measure subsidence in the wetland layer over a water year, and (3) examine the interrelationship of these factors with marsh stratigraphy. Results show that marsh elevation fluctuations are correlated with subsurface groundwater levels controlled by water level in nearby canals. The most organic-rich site showed a higher correlation with water levels and larger fluctuations of the surface elevation on diel and monthly timescales. Surface fluctuations are a direct response to lateral draining and filling of the marsh vadose zone, with frequency and degree of water exchange and surface elevation variation controlled by distance from the nearest canal edge and subsurface stratigraphy. Shallow subsidence rates calculated by previous studies from CRMS vertical accretion and total elevation change measurements, are revised for the fresh, intermediate, brackish, and saline marsh study sites using a normalization for a mean water level—the revised subsidence rates are not greatly influenced by the marsh expansion-contraction process. Marsh fragmentation through canal cutting and interior ponding increases linear extent of marsh edge, creating increased vadose spatial extent and frequency of exposure to air-filled pores in a given marsh. A hypothesis is explored herein that suggest that this increase in marsh edge in Barataria and other degrading Mississippi Delta sub-basins can result in increased peat oxidation that may have increased compactional subsidence in recent decades. / 1 / Autumn Skye Murray

Akademisk afhandling--Lund. / "Förteckning öfver otryckta källor": p. 31-34.

Inaug.-diss.--Berlin. / Vita. "Libri ... ": p. [6].

Thesis (Ph. D.)--University of Chicago, 1916. / "A Private edition distributed by the University of Chicago Libraries." "Reprinted from the Physical review, N.S., Vol. VIII, No. 6, December, 1916." Includes bibliographical references.

Inaug.-diss.--Berlin. / Vita. "Libri ... ": p. [6].

Thesis (Ph. D.)--University of Chicago, 1916. / "A Private edition distributed by the University of Chicago Libraries." "Reprinted from the Physical review, N.S., Vol. VIII, No. 6, December, 1916." Includes bibliographical references. Also available on the Internet.

Après beaucoup de travail, de nombreuses heures de réflexion, d'idées à améliorer et, des fois, à rejeter, une quantité innombrable d'échantillons et d'heures passés sur les différentes installations, nous voilà au point de présenter les résultats de tous ces efforts. Tout au début, nous avions décidé de se lancer dans la recherche et le développement de dispositifs à ondes acoustiques de surface pouvant servir en tant que filtres électriques passe-bande pour les nouvelles technologies de télécommunication et en tant que capteurs de liquide. Nous avons commencé à faire l'inventaire des tous les domaines que nous allions aborder lors de nos travaux de recherche, en nous en avons présenté ce qui nous semblait important. Même si la science est le pilier principal de cette thèse, nous nous sommes assurés que nos efforts ne seraient pas vains dès le départ en analysant les besoins industriels, et donc indirectement les retombées économiques possibles, en dispositifs à ondes acoustiques de surface. Nous nous sommes donc dotés de tous les outils nécessaires pour pouvoir avancer : Nous avons étudié l'évolution des dispositifs à ondes acoustiques de surface afin de reconnaître, avec un peu de chance, des tendances et de nouvelles ouvertures. Nous avons élucidé la partie théorique correspondante, au niveau de la piézoélectricité et des ondes acoustiques de surface. Nous avons fait le tour des matériaux piézoélectriques utilisées pour se faire une idée des leurs propriétés pour pouvoir faire, le moment venu, une sélection judicieuse selon les besoins de l'application. En partant de la théorie générale des ondes acoustiques de surface, nous avons étudié les différents types d'ondes existants dans la même optique : Disposer d'une multitude intéressante de choix possibles pour trouver la bonne solution à la fin. [...] / After a lot of hard work, countless hours of brainstorming, ideas to still improve or simply to drop, an amazing number of processed samples and a remarkable amount of time spent on all of those different machines have finally brought us to the point where we are able to present our results. Right at the beginning of this work, we had decided to get into the development of surface acoustic wave devices that could possibly serve as well as electric band pass filters as as liquid sensors. We have started out by making an inventory in all domains that we would possibly be confronted with and we proposed a selection of the most valuable information that could be found. Even if science is at the heart of this thesis, we wanted to be sure that our efforts would not be opposed to real world economic and industrial needs. We have thus arranged all necessary tools to our side: From historical evolution of surface acoustic wave devices through acoustic wave theory in solids, from general piezo-electricity to surface acoustic waves. We went through commonly used piezoelectric materials in order to get an idea of their properties and differences to be able to make the right decision at the right time, similarly to the study of the different types of acoustic surface waves with always the same goal in mind: Rely on the vastest number of possibilities in order to make the right decision when required. [...]

Note:

Avaliou-se “in vitro" o selamento apical em canais curvos que sofreram desvio apical de instrumentação (ZIP), utilizando quatro técnicas obturadoras: Condensação Lateral, Condensação Lateral com moldagem térmica direta do cone principal, Thermafil e System B e dois tipos de cimentos: Óxido de zinco e eugenol e AH Plus acrescido de 5% de Hidróxido de Cálcio. Foram empregadas 80 raízes mésio-vestibulares de dentes molares superiores humanos extraídos. Foi realizada a instrumentação pela Técnica Escalonada Regressiva, tendo como instrumento memória a lima do tipo Kerr n.º30, realizando-se o recuo até a n.º45. As raízes tiveram suas superfícies externas impermeabilizadas e os canais foram obturados segundo as técnicas citadas. Imediatamente após a obturação, as raízes foram impermeabilizadas no terço cervical com cera rosa derretida e imersas em solução corante de Rhodamine B a 0,2% por 72 horas a 37ºC. Para avaliação da infiltração as raízes foram desgastadas no sentido longitudinal em uma das faces proximais até expor-se a obturação. As infiltrações foram medidas com auxilio de uma ocular micrometrada pela técnica linear da planimetria em microscópio óptico comum. Após análise estatística constatou-se que a Técnica do System B, bem como, o cimento AH plus acrescido de 5% de hidróxido de Cálcio apresentaram melhores resultados quando comparados às demais técnicas estudadas e ao cimento de Óxido de Zinco e Eugenol. / The main purpose of this in vitro study is to test the sealing properties (leakage) of two cements (zinc oxide-eugenol and AH Plus with 5% calcium hydroxide) using four different apical sealing techniques: lateral condensation only, lateral condensation with direct gutta percha cone thermal molding, Thermafil and System B. Eighty (N=80) mesial- vestibular human upper molar roots had instrumentation induced apical ZIP and were treated by stepback instrumentation technique (Reamer: Kerr nº. 30-45) followed by apical isolation and root filling. All ten (N=10) specimens of each experimental group (N=8) were sectioned at cervical level and immersed in 0,2% Rhodamine B solution for 72 hours at 37°C. Longitudinal cuts were made to verifying leakage using an optical microscope and the linear technique. Statistical analysis showed statistically significant results for the group using cement AH Plus wíth 5% calcium hydroxide and System B Technique.

Dans un avenir proche, l'utilisation des bandes libres à 60 GHz permettra des débits de plusieurs Gb/s sur de courtes distances. Cependant, la conception de ces systèmes de communication sans fil dépendra fortement des caractéristiques du canal de propagation. L'objectif de cette thèse porte sur la caractérisation spatiotemporelle du canal de propagation afin de quantifier l'apport des techniques multi antennes (MIMO) sur les performances de la communication. Un sondeur de canal adapté à cette bande passante est développé afin d'effectuer des mesures intensives de caractérisation à l'intérieur des bâtiments. Pour la caractérisation théorique du canal, le modèle déterministe de tracé de rayons fut complété pour prendre en compte i) la diffraction sur les arêtes horizontales d'un obstacle rectangulaire, une nouvelle méthode hybride basée sur la théorie uniforme de la diffraction et de l'optique physique a été proposée et validée, ii) les caractéristiques de diffusion pour des matériaux typiquement rencontrés dans les constructions, ces caractéristiques ayant été estimées à partir de la caractérisation expérimentale. Ces résultats ont montré que l'introduction des coefficients de diffusion pour chaque matériau améliore la précision du modèle contrairement à ce qui peut être trouvé dans la littérature où un paramètre moyen de diffusion est proposé pour un environnement donné. Enfin, à partir des mesures de sondage de canal, les simulations des performances du standard IEEE 802.15c MIMO-OFDM montrent que l'utilisation des techniques multi antennes peut à la fois augmenter le débit d' un facteur de 3,7 et la distance de communication d'un mètre. / The use of the license-free 60-GHz frequency band will allow multi-Gb/s data transmission over short distances. The design of these wireless communication systems strongly depends on the propagation channel. The objective of the thesis focuses on the multidimensionnal channel characterization to quantify at the end the contribution of multi-antenna techniques (MIMO) on the performance of communication. A wideband mm-W frequency channel sounder was developed and has allowed extensive indoor channel measurements. In order to compare experimental results with theoretical value, the ray tracing tool was improved. Taking into account the diffraction that takes place at the top of a rectangular obstacle, a new method based on a hybrid uniform theory of diffraction-physical optics has been proposed and validated. Experimental results had also allowed to quantify the diffuse parameters for materials usually found in indoor environments. It was shown that introducing the contribution of diffuse scattering improves the accuracy of the RT tool unlike what it can be found in the literature where an average diffuse scattering parameter is proposed for a given environment. Finally, based on the channel measurements, the performance of IEEE 802.15.3c MIMO-OFDM systems was performed and the results show that the use of antennas array at both the transmitter and receiver side could increase both the throughput by a factor of 3.7 and the communication distance by 1 meter.