Sepsis is life-threatening organ dysfunction produced by a dysregulated host response to infection in which neutrophils release neutrophil extracellular traps (NETs). NETs consist of DNA, histones, and antimicrobial peptides which kill pathogens. However, DNA and histones also exert damage by activating the intrinsic pathway of coagulation and inducing endothelial cell death, respectively. AADH, a 15kDa non-anticoagulant unfractionated heparin (UFH), prevents histone-mediated cytotoxicity in vitro and improves survival in septic mice. We explored the effectiveness of Vasoflux, a 5.5kDa low-molecular-weight-heparin as an anti-sepsis treatment as compared to enoxaparin and UFH. Vasoflux has reduced anticoagulant functions and hence reduces the risk of bleeding as compared to enoxaparin or UFH. We showed that UFH, enoxaparin, or Vasoflux at concentrations of up to 13.3uM, 40uM, or 40uM, neutralize histone-mediated cytotoxicity. These results suggest that these glycosaminoglycans (GAGs) are able to neutralize histone-mediated cytotoxicity independent of the AT-binding pentasaccharide. To quantitate the binding affinity between GAGs and histones, surface plasmon resonance was conducted. UFH is a more potent inhibitor of histone-mediated cytotoxicity compared to Vasoflux as UFH has a 10-fold greater binding affinity to histones compared to Vasoflux. To translate our in vitro findings to in vivo, Vasoflux, enoxaparin, and UFH were administered in a murine model of sepsis. Vasoflux at 8mg/kg - 50mg/kg reduced survival and exhibited damage in the lung, liver, and kidney in septic mice compared to 10 mg/kg of UFH or 8mg/kg of enoxaparin. This may be due to Vasoflux and UFH disrupting the DNA-histone complex, thereby releasing free procoagulant DNA. This is evident by our gel electrophoresis experiments, where addition of 1uM Vasoflux or 3.3uM UFH to DNA-histone complexes lead to histone dissociation from DNA. UFH bound to histones may be able to inhibit DNA-mediated thrombin generation, as it retains its anticoagulant properties, demonstrated by UFH-histone complexes attenuating DNA and TF-mediated thrombin generation. In contrast, Vasoflux may not neutralize the procoagulant DNA leading to a hypercoagulable state in the mice. Our study may have important clinical implications as there is an ongoing trial, HALO, which will administer intravenous UFH to patients suspected to have septic shock to reduce mortality. Based on our results, future clinical trials should consider the antithrombin-dependent anticoagulant activity of UFH being used as a sepsis treatment. / Thesis / Master of Science (MSc) / Sepsis is a life threatening condition caused by the body’s extreme response to microbial infection of the blood, whereby neutrophils release traps composed of cell-free DNA (cfDNA), histones, and antimicrobial proteins. In addition to fighting off infections, these traps also exert harmful effects like triggering clotting and killing host cells. Currently, no specific anti-septic drugs exist. Studies have shown that DNase1 (a recombinant protein that digests double stranded cfDNA) or a modified form of heparin (neutralizes histones) improves survival in septic mice. Our goal was to explore the protective effects of Vasoflux, (a non-anticoagulant heparin) and DNase1 in a mouse model of sepsis. We hypothesize that the combined therapy of DNase1 and Vasoflux will improve survival. We found that Vasoflux has minimal blood thinning activity and can prevent histones from killing cells. However, Vasoflux administered into septic mice worsened organ damage and decreased survival. We hypothesize that this damage may be due to Vasoflux’s ability to displace histones from histone-DNA complexes, thereby releasing free DNA, which promotes excessive blood clotting in sepsis.

The rapid evolution of portable devices and social media has enabled pervasive forms of distributed cooperation. A group could perform a task using a heterogeneous set of the devices (desktop, mobile), connections (wireless, wired, 3G) and software clients. We call this form of systems Distributed Dynamic Cooperative Environments (DDCEs). Content in DDCEs is created and shared by the users. The content could be static (e.g., video or audio), dynamic (e.g.,wikis), and/or Objects with behavior. Objects with behavior are programmed objects that take advantage of the available computational services (e.g., cloud-based services). Providing a desired Quality of Experience (QoE) in DDCEs is a challenge for cooperative systems designers. DDCEs are expected to provide groups with the utmost flexibility in conducting their cooperative activities. More flexibility at the user side means less control and predictability of the groups' behavior at the system side. Due to the lack of Quality of Service (QoS) guarantees in DDCEs, groups may experience changes in the system behavior that are usually manifested as delays and inconsistencies in the shared state. We question the extent to which cooperation among group members is sensitive to system changes in DDCEs. We argue that a QoE definition for groups should account for cooperation emergence and sustainability. An experiment was conducted, where fifteen groups performed a loosely-coupled task that simulates social traps in a 3D virtual world. The groups were exposed to two forms of system delays. Exo-content delays are exogenous to the provided content (e.g., network delay). Endo-content delays are endogenous to the provided content (e.g., delay in processing time for Objects with behavior). Groups' performance in the experiment and their verbal communication have been recorded and analyzed. The results demonstrate the nonlinearity of groups' behavior when dealing with endo-content delays. System interventions are needed to maintain QoE even though that may increase the cost or the required resources. Systems are designed to be used rather than understood by users. When the system behavior changes, designers have two choices. The first is to expect the users to understand the system behavior and adjust their interaction accordingly. That did not happen in our experiment. Understanding the system behavior informed groups' behavior. It partially influenced how the groups succeeded or failed in accomplishing its goal. The second choice is to understand the semantics of the application and provide guarantees based on these semantics. Based on our results, we introduce the following design guidelines for QoE provision in DDCEs. • If possible the system should keep track of information about group goals and add guarding constraints to protect these goals. • QoE guarantees should be provided based on the semantics of the user-generated content that constitutes the group activity. • Users should be given the option to define the content that is sensitive to system changes (e.g., Objects with behavior that are sensitive to delays or require intensive computations) to avoid the negative impacts of endo-content delays. • Users should define the Objects with behavior that contribute to the shared state in order for the system to maintain the consistency of the shared state. • Endo-content delays were proven to have significantly negative impacts on the groups in our experiment compared to exo-content delays. We argue that system designers, if they have the choice, should trade processing time needed for Objects with behavior for exo-content delay. / Ph. D.

Diese Arbeit beschäftigt sich mit der theoretischen Beschreibung eines Hybridsystems eines ultrakalten neutralen Atoms und eines einzelnen Ions. Diese Hybrid-Atom-Ion-Systeme verbinden die wichtigsten Vorteile von ultrakalten neutralen Atomen und Ionen. Neutrale Atome sind leicht skalierbar vor allem und können in großen Stückzahlen vorbereitet werden, wahrend gefangene Ionen über längere Zeiten gelagert werden können und leicht kontrollierbar sind. Einige der vorgeschlagenen Aussichten der hybriden Quantensysteme umfassen die sympathische Kühlung von eingefangenen Ionen, die ultrakalte Chemie, das Quantum Informationsverarbeitung, und Atom-Ionen-Quantensimulatoren. Diese Anwendungen erfordern eine äußerst präzise Steuerung und damit eine sehr genaue theoretische Modellierung. Eine neue Methode, die eine vollständige sechsdimensionale Behandlung von zwei Partikeln ermöglicht In räumlich getrennten dreidimensionalen Fangpotentialen wurde entwickelt. Indem man die raumliche Verschiebung zwischen den Einfangpotentialen erlaubt, ist es möglich, die gesteuerte Bewegung eines einzelnen Ions durch ein optisches Gitterpotential zu beschreiben, das mit neutralen Atomen gefüllt ist. Die Wechselwirkung zwischen dem neutralen Atom und dem geladenen Ion wird durch eine realistische Born-Oppenheimer Potentialkurve beschrieben. Eines der hier diskutierten Hybridsysteme ist 7Li2+ Isotop, das mit der neu entwickelten Methode untersucht wird, dabei wurden vermiedene Kreuzungen im Energiespektrum zwischen molekularen Zuständen und den Schwingungszuständen des Fallenpotentials als Funktion des Abstandes zwischen den beide Fallen beobachtet. Diese vermiedenen Kreuzungen bestatigen die bereits vorhergesagten falleninduzierten Resonanzen, die mithilfe der Quantendefekttheorie bestimmt wurden. Ebenfalls werden die erst kürzlich entdeckten inelastischen falleninduzierten Resonanzen in ultrakalten Atomen auch in den Atom-Ion Systemen beobachtet. / This thesis deals with the theoretical description of a hybrid system of an ultracold neutral atom and a single ion. These hybrid atom-ion systems combine the key advantages of ultracold neutral atoms and ions. In particular, neutral atoms are easily scalable and can be prepared in large numbers, while trapped ions can be stored for much longer times and are easy to control. Some of the proposed prospects of the hybrid quantum systems include sympathetic cooling of trapped ions, ultracold chemistry, quantum information processing, and atom-ion quantum simulators. These applications require extremely precise control and thus very accurate theoretical modeling. A new method that allows for a full 6-dimensional treatment of two particles in spatially separated 3-dimensional trapping potentials was developed. By allowing for the spatial displacement between the trapping potentials, it is possible to describe the controlled motion of a single ion through an optical-lattice potential filled with neutral atoms. The interaction between the neutral atom and the ion is modeled using realistic Born-Oppenheimer potential curves from ab initio quantum chemistry calculations. An application of the developed approach to the hybrid atom-ion system reveals avoided crossings between the molecular bound states and the unbound trap states as a function of the separation between the two traps. These avoided crossings correspond to trap-induced resonances. This finding confirms the trap-induced resonances predicted earlier based on quantum-defect-theory calculations. Also, the recently found inelastic confinement-induced resonances in ultracold neutral atoms are demonstrated to be present in atom-ion systems. These resonances arise due to the coupling between the center-of-mass and relative motions. The inelastic confinement-induced resonances could be used in coherent molecular ion formation and in the determination of atom-ion scattering properties like the scattering lengths.

Fine-grained sediment accumulation in the interstices of gravel beds is a key factor in degrading riverine habitats. However, interstitial deposits are highly dynamic and are not sufficiently understood. This work enhances the understanding of interstitial fine sediment deposition by investigating interstitial storage and ingress, flow, suspended sediment and gravel bed character. Furthermore, this work introduces a numerical suspended sediment deposition model with the power to predict patterns of interstitial ingress. The investigation of interstitial deposition were carried out on two levels. Both data orginating from flume experiments and from three locations of the River Culm, Devon, UK was collected. The experimental data showed the significant influence of small scale variations in flow and bed character and their influence on interstitial ingress. The field investigation showed clear differences in interstitial fine-grained sediment for the different river reaches and an overall higher interstitial ingress compared to recent published data. The numerical model development was realised in a two-step approach. First, the model was coded and calibrated for the flume scale processes and, second, an upscaled reach scale model was devolped for the field data. This reach scale suspended sediment deposition model included flow information, for which depthaveraged two dimensional hydrodynamic models were developed with the software Delft3D. The overall explanatory power of the model at this state is not satisfactory with regards to local deposition distribution. A separate chapter discusses the possible causes and implications of this short coming for further research from a data aquisition and modelling perspective.

Thesis (MEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Sedimentation and the effects it has on turbine blades was the primary problem identified in run-of-river (RoR) hydropower schemes. Sedimentation in RoR hydropower schemes also increases trash rack blockage and reduces energy output in the long-term. Damage occurs to all underwater parts that come into contact with sediment. The main concern is sediment passing through the hydropower intake and causing turbine damage. The reason for the abrasion and cavitation of turbine blades is increased sediment loads in river channels. This problem can be overcome in two ways. The first is the use of existing lakes or reservoir storage upstream as natural sand traps, and the second is by investigating the three features associated with river bend diversion, which are: the optimum diversion location in a river bend to minimise the abstraction of sediment, the optimum diversion structure angle to limit coarse sediment diversion, and the sediment load diverted through the intake. The first objective of the research was investigated by construction of a physical model of a curved river channel to determine the location of the deepest scour forming on the outside of the bend. The second objective was to test the diversion orientation to maximize the local scour and thereby limiting sediment diversion at the intake. A third objective was to compare mathematical 2D model simulated scour results with the findings of the laboratory tests to evaluate the reliability of the numerical model predictions. Finally different diverted discharge ratios were tested with different intake setups in the physical model, to evaluate the sediment load diverted. . The first experiment in the curved laboratory channel was to predict where the deepest scour takes place without a diversion structure. This was then followed by placing a diversion structure at the maximum scour position, retrieved from experiment one, and by angling the structure with reference to the flow direction. The flow direction vector was placed as a tangent to the bend and orientated at angles of 0⁰, 30⁰, 45⁰ and 60⁰ into the bend direction. The optimum diversion location was found to be positioned on the outside of the bend, approximately 60⁰ into the channel bend. The final position of maximum scour in a 90⁰ bend corresponds with the Sediment Committee and the Chinese Hydraulic Engineering Societies (1992) prediction of 60⁰ into the bend. The optimal diversion had a 30⁰ angle to the flow direction, as this presented the most efficient and effective scouring in front of the model intake. Numerical simulations were performed with the CCHE 2D (hydrodynamics and sediment dynamics) modelling program. The numerical results were compared to the physical results to validate CCHE as a beneficial simulation tool. It was found that the numerical model predicted the scour depths at the intakes tested with an accuracy of 43.8%, which is within the accuracy range of the sediment transport equation used by the numerical model. The final experiment was the diversion of sediment with different intake level heights and discharges. It was evident from the results that low sediment diversion ratios were achieved with a diverted discharge ratio of 50% or less. The intake elevation highest above the channel bed diverted the least sediment. The interrelationship between Diverted Discharge Ratio (DDR), Diverted Froude number Ratio (DFrR) and Diverted Sediment load Ratio (SDR) was established in the study. It is recommended that RoR schemes have sand traps downstream of the diversion structures and that turbines are coated with HVOF to overcome the power loss arising due to the excessive erosion of hydro turbines. / AFRIKAANSE OPSOMMING: Sedimentasie en die invloed wat dit het op turbines was die primêre probleem geïdentifiseer in “run-of-river” (RoR) hidrokrag-skemas. Die sediment wat saam met die water uit ‟n rivier uitgekeer word beskadig die inlaatrooster en verlaag kragopwekking in die langtermyn. Skade word aangerig aan alle onderwatertoerusting en masjinerie wat aan sediment blootgestel word. Die grootste probleem tydens die uitkering van water is die growwe sediment wat daarmee deur die onttrekking inlaat gaan en turbineskade veroorsaak. Soos wat die sedimentlading in die rivier drasties toeneem, sal afslyting en kavitasie van turbinelemme meer gereeld voorkom. Dié probleem kan op twee maniere beperk word. Die een is die gebruik van bestaande opgaardamme stroomop, en die tweede is deur die ondersoek van drie kenmerke van rivierdraaie en uitkeringstrukture, bv. die optimale uitskurings posisie in 'n rivierdraai (sonder ʼn struktuur) om die diepste uitskuringposisie op die buitekant van die draai te bepaal, die optimale uitkeringsstruktuuroriëntasie wat maksimum uitskuring verseker en die sediment uitkering beperk, en die lading van sedimentonttrekking deur die inlaat. Die eerste doelwit van die navorsing is ondersoek deur ʼn fisiese model te bou van ʼn kronkelkanaal en te bepaal waar die diepste uitskring plaasvind op die buitekant van die draai. Die tweede doelwit van die studie was om die optimale uitkeringshoek te bepaal vir 'n uitkeringstruktuur sodat die uitskuring by die inlaat ʼn maksimum is om die uitkering van sediment te beperk. ʼn Derde doelwit was om die akkuraatheid van ʼn wiskundige model se uitskuring voorspelling te toets teen die waargenome laboratorium resultate. Die finale doelwit was om vir verskillende inlaatontwerpe, rivier- en uitkeervloeie die sedimentladings wat uitgekeer word te ondersoek. Die eerste eksperiment in die kronkelende kanaal was voorberei om die optimale uitskuring in die draai te bepaal. Dit is gevolg deur toetse met uitkeerstrukture by die maksimum uitskurings posisie te plaas en die hoek van die struktuur dan te verander met verwysing na die vloeirigting. Die vloeirigting vektor was as 'n raaklyn geplaas op die kanaal draai en georiënteer met hoeke: 0⁰, 30⁰, 45⁰ en 60⁰, in die rigting van die draai. Die optimale uitskurings posisie was aan die buiterand van die kanaal draai gevind, ongeveer 60⁰ in die draai in. Die maksimum uitskuur posisie van 'n 90⁰ kanaal draai stem ooreen met SC en CHES (1992) se resultaat van 60⁰ in die draai in. Daar was ook genoegsame bewyse dat 'n optimale uitkeerwerke oriëntasie van 30⁰ die doeltreffendste en effektiefste uitskuring sal gee. Numeriese simulasies is deur middel van 'n twee dimensionele wiskundige model CCHE 2D (hidro- en sedimentdinamika) uitgevoer. Die numeriese resultate was vergelyk met die laboratoriumresultate om die CCHE program te verifieer as 'n voordelige simulasie program. Daar is gevind dat die wiskundige model die uitskuurdieptes by die inlate met ʼn akkuraatheid van 43.8 % voorspel, wat binne die akkuraatheid is van die sedimentvervoervergelyking wat deur die numeriese model gebruik word. Die finale eksperiment was die uitkering van sediment met verskillende inlaathoogtes en uitkerings sedimentladings. Uit die toetse was dit duidelik dat 'n lae sediment uitkeerverhouding behaal kan word met 'n uitkeerverhouding van 50% en minder. Verdere waarnemings het ook gewys dat die inlaathoogte van die uitkeerstruktuur met die optimale resultate die hoogste bokant die rivierbedding was. Die verwantskap tussen die uitgekeerde deurstromingverhouding, die uitgekeerde Froude getal verhouding en die uitgekeerde sedimentlading is bepaal in die navorsing. Dit word aanbeveel dat sandvangkanale stroomaf van uitkeerwerke geplaas word en dat turbines met HVOF as bedekkingsmateriaal beskerm word om kragverliese as gevolg van buitensporige erosie van die turbines te voorkom.

No description available.

No description available.

Coastal Indigenous Peoples worldwide have relied on fish and other marine resources for millennia, and continue to do so despite recent degradation of ocean systems. Their traditional ecological knowledge, comprised of experiences, observations, beliefs, and lifeways, is relevant for modern marine management and conservation. This thesis explores the utility of traditional and local ecological knowledge for extending an understanding of changes over time for places or periods in which scientific data are unavailable. This thesis had three goals: 1) undertake research that is collaborative and inclusive, and that addresses priorities established by participating First Nations; 2) contribute to fisheries management and conservation recommendations by focusing on a species of cultural importance and exploring the applications of traditional and local ecological knowledge to species-level understandings; and 3) contribute a marine social-ecological case study that investigates the use of traditional and local ecological knowledge to understand change over time and provides appropriate context. Two main objectives allowed me to accomplish my goals: 1) demonstrate the application of traditional and local ecological knowledge to establish historical baselines that extend farther back in time than scientific surveys, and investigate reasons for changes, and 2) investigate the utility of a social-ecological trap framework in assessing impacts to a social-ecological system and identifying ways to escape such a trap. My case study occurred in collaboration with four First Nations (as many Indigenous Peoples of Canada are called) on the Central Coast of British Columbia, Canada. My methods included semi-structured interviews with knowledge holders to examine traditional and local ecological knowledge of a culturally and economically important species, Yelloweye rockfish (Sebastes ruberrimus). In this study, I interviewed First Nations fishers and Elders (n=43), asking about: observed changes to the body sizes (length) and abundance of this species over the last ~60 years, the factors driving these changes, stewardship principles or traditional management strategies, concerns for marine resources, and perceived opportunities for cultural revitalization. I then quantified the interview participants’ current and historical estimates of size and abundance, compared interview data to current biological survey data, and qualitatively analyzed responses regarding stewardship, culture, perceived threats, and cultural solutions. I utilized the framework of a social-ecological trap to analyze responses about stewardship, traditional stories or management, and threats to culture, selecting illustrative quotes to contextualize the lived experiences of participants. Overwhelmingly, respondents had observed a decrease in Yelloweye rockfish body sizes since the 1980s. Median historical length observed by participants was nearly twice the modern length. Participants reported substantial decrease in Yelloweye rockfish abundance since the 1980s, and most stated that this change was evident in the early 2000s. Sizes of modern Yelloweye rockfish estimated by participants resembled measurements from ecological data recorded concurrently at the study region. Thus, my study extends baseline historical data of Yelloweye rockfish reliably by about 50 years. Questions about traditional stories and culture revealed the presence of a social-ecological trap created and reinforced by the interplay between species decline and colonization (e.g. the residential schooling system). When asked about traditional management or stewardship practices, only one participant could remember specific traditional stories about Yelloweye rockfish, though all participants expressed adherence to the stewardship principles of taking only what is needed and respecting all life. Though participants expressed concern about the muting of traditional ecological knowledge, culture, and language, they also highlighted key ways towards revitalization and Indigenous resurgence. The ubiquitous presence of stewardship principles suggests there are ways beyond the social trap: participants described on-going cultural revitalization efforts, recovery of depleted species and ecosystems, and the reassertion of Indigenous management rights as ways to overcome problems inherent to the social-ecological trap. My research adds to a growing body of literature that supports the use of traditional and local ecological knowledge in marine management and conservation science. Adding to this literature, my work suggests the significant value of traditional and local ecological knowledge for filling gaps in historical scientific data or in data-poor regions, and highlights the importance of appropriately contextualizing Indigenous knowledge. To overcome the social-ecological trap of knowledge loss and to achieve informed marine management, reassertion of Indigenous management rights and application of traditional management strategies to modern fisheries management is vital. / Graduate / 0326 / 0768 / 0416 / eckertleckert@gmail.com

Nos connaissances et notre compréhension de la dynamique sédimentaire des plages macrotidales sont encore limitées de nos jours en raison d'un manque de données lié à la plus faible proportion de ces plages à l'échelle mondiale. Trois plages macrotidales à barres et à bâches du littoral de la Côte d'Opale dans le Nord de la France ont été choisies pour mener cette étude. Elle se base sur trois approches différentes visant à caractériser (1) le régime tidal et les conditions hydrodynamiques, (2) la morphologie de la zone intertidale et (3) les flux sédimentaires longitudinaux (FL) et transversaux (FC) dans diverses conditions tidales et énergétiques. Le transport a été mesuré dans la zone proche du déferlement à l’aide de pièges à sédiment de type Kraus (1987) permettant de caractériser le débit solide à plusieurs niveaux au dessus du fond au cours de conditions d'agitation faibles à modérées (Hs < 1 m). Malgré une uniformité des flux le long de la plage, les phénomènes de vidange des bâches par l’intermédiaire de chenaux perpendiculaires au trait de côte permettent l’introduction de volumes de sédiment significatifs, augmentant localement le FL. La distribution des flux à travers l’estran présente, quant à elle, une décroissance nette du bas de plage vers le haut de plage. Les mesures simultanées de FL et de FC ont démontré que le FC dirigé vers le haut de plage et la résultante du FC sont dans la plupart des cas supérieurs aux FL en raison de la plus forte intensité des vitesses de courant oscillatoire. Ces résultats mettent en évidence des mouvements significatifs de volume de sable à travers la zone intertidale à l’échelle de la mesure, ce qui influence fortement la morphodynamique de la plage. L’ensemble de la zone intertidale est toutefois apparue relativement stable, avec des changements plus significatifs à court terme qu'à plus long terme. Les mesures de transport ont permis de mettre en lumière le rôle fondamental des bâches dans la dynamique des plages macrotidales. Ces dépressions inter-barres sont en effet responsables de la canalisation du sédiment le long du rivage, limitant ainsi les transports sédimentaires transversaux et par conséquent la migration des barres intertidales. Il est vraisemblable que le temps de résidence et l'intensité des processus hydro-sédimentaires jouent un rôle prépondérant dans la dynamique des barres intertidales. Les mesures ont également été comparées avec plusieurs estimations du transport sédimentaire issues de modèles numériques et morphodynamiques. Bien que les flux calculés surestiment en général le transport mesuré, certaines formules semblent plus adaptées pour déterminer le FL dans la zone de levée. / Our knowledge and understanding of the sediment dynamics of sandy macrotidal beaches is still limited by a lack of data from these macrotidal environments. This limitation is due to the relatively small proportion of macrotidal coasts in the world. Three sandy beaches on the coast of Northern France were chosen to conduct this study. Three scientific approaches were used: 1) characterization of tidal and waves energy conditions using wave and current meters deployed on the foreshore; 2) beach morphology survey and 3) estimation of longshore (FL) and cross-shore (FC) sediment transport using streamer traps similar to those designed by Kraus (1987). Sand transport was measured about 1 m water, next to the breaker zone and either in the shoaling zone or in the surf zone; under low to moderate waves energy conditions (Hs < 1 m). In spite of a low longshore variability in sediment transport due to a high degree of hydrodynamic uniformity along the shore, runnel drainage can locally increase sediment transport rates. Cross-shore distribution appeared to be more variable as sediment transport decreased from the lower to the upper part of the beach. Onshore, offshore and longshore sediment transport measured simultaneously showed that under various energetic conditions, FC appeared to be generally higher than FL. Although net littoral drift is directed towards the Belgian coast, these results suggest that significant volumes of sand move across the intertidal zone. These significant volumes of sand most likely have a strong influence on the morphodynamics of the beach. Daily topographical survey has shown little morphological variations while sediment transport rates appeared very variable and very significant, especially during the highest wave energy conditions. Sediment transport measurements across the foreshore highlight the important role played by inter-bar troughs in the morphodynamics of macrotidal beaches. Higher bed roughness in these depressions is responsible for an increase in sediment resuspension through the water column. Suspended transport is therefore favoured in troughs and hinders the cross-shore sediment transport, which is responsible for the bar migration across the intertidal zone. Morphological changes are dependent of the time residence of the hydrodynamic zones, but the morphodynamics of the intertidal bars appear to be strongly controlled by the amplitude of the incident waves. FL were also compared with calculated data computed using from numerical and morphodynamic model. Although computed transport rates are generally higher than in situ measurements, it appears that some formulae provide better estimate of FL, especially in the shoaling zone

Neste trabalho descrevemos a produção e estudo de excitações topológicas em um condensado de Bose-Einstein em átomos de Rubídio-87. O condensado é produzido através de resfriamento evaporativo forçado por rádio-freqüência em uma armadilha puramente magnética do tipo QUIC. A armadilha magnética é carregada por um sistema de duplo-MOT. A temperatura de transição é de cerca de 150nK. Condensados puros com 1 - 2 × 10^5 átomos de Rb-87 são observados. Realizamos uma caracterização da amostra em relação às suas características fundamentais. Fração condensada, expansão anisotrópica, distribuição espacial e efeitos de temperatura finita são descritos. Com o objetivo de observar excitações coerentes do condensado entre os estados da armadilha, adicionamos um campo magnético do tipo quadrupolo esférico oscilante no tempo. Observamos, no entanto, a transferência de momento angular para a amostra com a formação de vórtices e arranjos de vórtices. Definimos regiões de amplitude que geram números de vórtices crescentes. Observamos a formação de estruturas de três vórtices não convencionais donde supusemos a possibilidade de excitação conjunta de vórtices e anti-vórtices. Observamos evidência de turbulência quântica, um estado onde os arranjos dos vórtices não são regulares nem as linhas de vórtices têm um eixo de rotação comum. / In this work we describe the production and investigation of topological excitations in a Bose-Einstein condensate in Rubidium-87 atoms. The condensate is produced through forced evaporative cooling by radio-frequency in a QUIC-type purely magnetic trap. The magnetic trap is loaded from a double-MOT system. Transition temperature is about 150nK. Pure condensates containing 1-2×105 87Rb atoms are observed. We performed the characterization of the sample in relation to its fundamental aspects. Condensed fraction, anisotropic expansion, spacial distribution and finite temperature effects are described. Aiming to observe coherent topological excitations of the condensate between two states of the trap, we added a spherical quadrupole magnetic fields oscillating in time. We observe, instead, angular momentum tranference to the sample and the formation of vortices and arrays of vortices. We define amplitude regions where an increasing number of vortices are observed. We observe the formation of non-usual three-vortex structures from which we infer the existence of vortices and anti-vortices together in the sample. We observe evidence of quantum turbulence, a state where non-regular vortex arrays appear as well as vortex lines have no preferred direction to form.