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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.
101

A model of the free surface dynamics of shallow turbulent flows

Nichols, Andrew, Tait, Simon J., Horoshenkov, Kirill V., Shepherd, Simon J. 06 April 2016 (has links)
Yes / Understanding the dynamic free surface of geophysical flows has the potential to enable direct inference of the flow properties based on measurements of the free surface. An important step is to understand the inherent response of free surfaces in depth-limited flows. Here a model is presented to demonstrate that free surface oscillatory spatial correlation patterns result from individual surface features oscillating vertically as they advect over space and time. Comparison with laboratory observations shows that these oscillating surface features can be unambiguously explained by simple harmonic motion, whereby the oscillation frequency is controlled by the root-mean-square water surface fluctuation, and to a lesser extent the surface tension. This demonstrates that the observed “complex” wave pattern can be simply described as an ensemble of spatially and temporally distributed oscillons. Similarities between the oscillon frequency and estimated frequency of near-bed bursting events suggest that oscillon behaviour is linked with the creation of coherent flow structures.
102

Vacancy : Sculpture for solitary bees

Drvota, Ariana January 2024 (has links)
This is a project that focuses on building awareness for solitary bees and how we can use public sculptures/artifacts to help and to create a positive vision of the future through art, design,science and to promote bio diversity. A lot of modern techniques like 3D modeling, 3D printing, and CNC milling were used to bring this artifact to life. Public artworks are proven to have a positive effect on our mental health and create discussion, so with this project I wanted to create a public sculpture/artifact that benefits both humans and bees, make sure that people would take notice to it and start to investigate the creation, see all the life that lives around and inside it. This is a form with a function. The material used in this creation will be discarded wood and the wood will decompose with time.  Vacancy focuses on integrating nests for species, in this case solitary bees, within artistic public sculptures and artifacts. Through the creation of this sculpture/artifact, the project aims to engage and inspire the curiosity of the viewer to reflect on the ongoing crisis facing our pollinators. Furthermore, the project aims to promote biological diversity.
103

Propagation of solitary waves and undular bores over variable topography

Tiong, Wei K. January 2012 (has links)
Description of the interaction of a shallow-water wave with variable topography is a classical and fundamental problem of fluid mechanics. The behaviour of linear waves and isolated solitary waves propagating over an uneven bottom is well understood. Much less is known about the propagation of nonlinear wavetrains over obstacles. For shallow-water waves, the nonlinear wavetrains are often generated in the form of undular bores, connecting two different basic flow states and having the structure of a slowly modulated periodic wave with a solitary wave at the leading edge. In this thesis, we examine the propagation of shallow-water undular bores over a nonuniform environment, and also subject to the effect of weak dissipation (turbulent bottom friction or volume viscosity). The study is performed in the framework of the variable-coefficient Korteweg-de Vries (vKdV) and variable-coefficient perturbed Korteweg-de Vries (vpKdV) equations. The behaviour of undular bores is compared with that of isolated solitary waves subject to the same external effects. We show that the interaction of the undular bore with variable topography can result in a number of adiabatic and non-adiabatic effects observed in different combinations depending on the specific bottom profile. The effects include: (i) the generation of a sequence of isolated solitons -- an expanding large-amplitude modulated solitary wavetrain propagating ahead of the bore; (ii) the generation of an extended weakly nonlinear wavetrain behind the bore; (iii) the formation of a transient multi-phase region inside the bore; (iv) a nonlocal variation of the leading solitary wave amplitude; (v) the change of the characteristics wavelength in the bore; and (vi) occurrence of a ``modulation phase shift" due to the interaction. The non-adiabatic effects (i) -- (iii) are new and to the best of our knowledge, have not been reported in previous studies. We use a combination of nonlinear modulation theory and numerical simulations to analyse these effects. In our work, we consider four prototypical variable topography profiles in our study: a slowly decreasing depth, a slowly increasing depth , a smooth bump and a smooth hole, which leads to qualitatively different undular bore deformation depending on the geometry of the slope. Also, we consider (numerically) a rapidly varying depth topography, a counterpart of the ``soliton fission" configuration. We show that all the effects mentioned above can also be observed when the undular bore propagates over a rapidly changing bottom . We then consider the modification of the variable topography effects on the undular bore by considering weak dissipation due to turbulent bottom friction or volume viscosity. The dissipation is modelled by appropriate right-hand side terms in the vKdV equation. The developed methods and results of our work can be extended to other problems involving the propagation of undular bores (dispersive shock waves in general) in variable media.
104

Les systèmes de capture du glutamate dans le noyau du tractus solitaire. Relations astrocytes-synapses et localisation subcellulaire des transporteurs du glutamate / Synapse-Glia interaction and subcellular localization of glutamate transporters in the Nucleus Tractus Solitarius

Chounlamountry, Keodavanh 14 November 2011 (has links)
Le glutamate est le principal neurotransmetteur excitateur du noyau du tractus solitaire (NTS), une structure sensorielle qui reçoit des informations provenant des viscères. Nous avons utilisé l'immunocytochimie et la microscopie électronique pour étudier les systèmes de recapture du glutamate dans le NTS. Nous montrons que le transporteur exprimé par les astrocytes est de type GLT-1 et que la couverture des synapses glutamatergiques par les processus astrocytaires n'est pas complète ce qui autorise des phénomènes de transmission à distance par diffusion du glutamate. Nous montrons aussi que les dendrites des neurones du NTS expriment le transporteur de type EAAC1. Ce transporteur est essentiellement présent sous forme d'un pool intracellulaire. Son expression membranaire pourrait donc être régulée par l'activité. Enfin, dans une dernière partie, nous montrons qu'une inflammation des viscères induit une augmentation de la couverture gliale des synapses glutamatergiques du NTS. / Glutamate is the main excitatory transmitter in the nucleus tractus solitarii (NTS), a sensory nucleus involved in visceral information processing. Using electron microscope immunocytochemistry, we have investigated neuron to glia relationships and localization of glutamate transporters in the NTS. We show that NTS astrocytes express GLT-1 and that astrocytic wrapping of NTS glutamatergic synapses is incomplete, allowing glutamate to diffuse out of the synaptic cleft. In addition, we demonstrate that NTS neurons express the EAAC1 transporter. EAAC1 is exclusively present in dendrites and mostly located intracellularly. Finally, we show that visceral inflammation increases the glial wrapping of NTS glutamatergic synapses.
105

Percurso do orfão na literatura infantil / juvenil, da oralidade à era digital: a trajetória do herói solitário / The orphan\'s course in Literature for Children and Youths, from orality to digital age: the path of a solitary hero

Cardoso, Lais de Almeida 28 March 2006 (has links)
A orfandade é um tema bastante recorrente na literatura infantil e juvenil. Desde as antigas narrativas orais, como os contos de fadas, por exemplo, o arquétipo do órfão é revisitado regularmente na construção de diferentes personagens, sendo mantida, porém, uma estrutura básica predominante, principalmente no que concerne à sua trajetória. Investigar a recorrência dessa temática, partindo da análise de alguns contos populares até alcançar as mais recentes obras voltadas para o público jovem, foi um dos objetivos desta pesquisa. Uma outra meta foi estabelecer paralelos e divergências entre as figuras secundárias que compõem essas narrativas, como as madrinhas, as madrastas, os irmãos, os amigos, os seres mágicos, entre outros, e focalizar o papel que elas desempenham na trajetória do órfão, agindo ora como \"desvios\", ora como \"atalhos\" em seu caminho. Um terceiro propósito da dissertação foi estudar a circulação da personagem órfã contemporânea entre a literatura e outras mídias, como as histórias em quadrinhos (HQ) e o cinema. Para isso, tomamos três personagens da ficção criadas originalmente para três diferentes suportes - Harry Potter (literatura), Peter Parker (HQ) e Luke Skywalker (cinema) - e procuramos estabelecer similaridades e divergências em três momentos de seus percursos: partida, iniciação e retorno. Ao compararmos as trajetórias desses três heróis órfãos, podemos perceber as visíveis intersecções entre elas e somos levados a crer que, mesmo modificadas pelos estilos literários e pelas mídias que lhes servem de suporte, essas personagens solitárias conservam, contudo, a essência das características de seu remoto substrato popular, proveniente da oralidade. / Orphanhood is quite a common theme in Children\'s Literature. From the old oral stories, as the fairy tales, for instance, the orphan archetype is regularly used in order to build different characters, keeping, however, a predominant basic structure, chiefly with regard to his path. Investigating the frequency of such a theme starting from the analysis of some popular tales and finally reaching the most recent works, offered to young people, was one of the purposes of this research. Another aim was to establish parallels and divergences ocurring to secondary characters that take part in those narratives, as the godmothers, stepmothers, brothers and sisters, magic creatures, among others, and focusing the role they play in the development of the orphan course, acting sometimes as \"sidetracks\", sometimes as \"shortcuts\" in his way. A third goal of this work was to study the circulation of the contemporary orphan character both in literature and other mass media, as comics and movies. For this purpose we chose three fiction characters, created originally for three different supports - Harry Potter (literature), Peter Parker (comics) and Luke Skywlaker (movies) - and tried to show similarities and differences in three moments of their route: start, initiation and return. Comparing the footsteps of those three orphan heroes, we may note the visible intersections among them and take into account that, even changed by literary style and mass media which support them, those solitary characters keep, nevertheless, the essence of the characteristics of their ancient popular substractum, coming from orality.
106

To Bee or Not to Be : Critical Floral Resources of Wild-Bees

Larsson, Magnus January 2006 (has links)
<p>In recent decades, the development of strategies to prevent or slow the loss of biodiversity has become an important task for ecologists. In most terrestrial ecosystems wild-bees play a key role as pollinators of herbs, shrubs and trees. The scope of this thesis was to study 1) pollinator effectiveness of specialist bees vs. generalist flower-visitors, 2) critical floral resources for wild-bees, and 3) methods to estimate the size of wild-bee populations. The wild-bee species <i>Andrena hattorfiana </i>and <i>A. marginata </i>were used as model species. These two species are specialized on pollen from the plant family Dipsacaceae.</p><p>The bee <i>A. hattorfiana </i>was found to be a frequent visitor but a poor pollinator of its preferred food-plant <i>Knautia arvensis</i>. The female bees exert such a strong preference for pollen-producing inflorescences that they likely have deleterious effects on the plant, harvesting valuable pollen that could have been transferred to conspecific stigmas by other flower-visitors. To explore the relationship between wild-bees and their food-plants, the concept of pollen budget was developed. We quantified pollen production in the food-plant population and pollen consumption of wild-bee nests. A survey of the visitation by all flower-visitor taxa indicated that the degree of utilization (the fraction of the total pollen amount that is harvested and utilized by <i>A. hattorfiana</i>) varied from 12% to 80% among <i>K. arvensis</i> populations (N=26). The bee <i>Andrena marginata</i> utilized 44% of the pollen production in a population of <i>Succisa pratensis</i>. The pollen budget suggests that with an average flower-visitor diversity and abundance, 330 individuals of the food-plant <i>K. arvensis </i>are required to sustain a population of 20 <i>A. hattorfiana </i>♀ (the approximate median natural population size). Based on a study of <i>A. hattorfiana</i>, considerable simplifications were proposed for the commonly used mark-recapture design for measuring wild-bee population size. For this species, population size estimated based on mark-recapture data was strongly correlated with the number of observations per survey-walk. The results suggest that large-scale surveys of solitary bee species can be simplified by performing survey-walks.</p><p>The pollen budget and the method proposed for estimating the size of bee populations have the potential to become valuable tools for monitoring and management of wild-bee populations.</p>
107

To Bee or Not to Be : Critical Floral Resources of Wild-Bees

Larsson, Magnus January 2006 (has links)
In recent decades, the development of strategies to prevent or slow the loss of biodiversity has become an important task for ecologists. In most terrestrial ecosystems wild-bees play a key role as pollinators of herbs, shrubs and trees. The scope of this thesis was to study 1) pollinator effectiveness of specialist bees vs. generalist flower-visitors, 2) critical floral resources for wild-bees, and 3) methods to estimate the size of wild-bee populations. The wild-bee species Andrena hattorfiana and A. marginata were used as model species. These two species are specialized on pollen from the plant family Dipsacaceae. The bee A. hattorfiana was found to be a frequent visitor but a poor pollinator of its preferred food-plant Knautia arvensis. The female bees exert such a strong preference for pollen-producing inflorescences that they likely have deleterious effects on the plant, harvesting valuable pollen that could have been transferred to conspecific stigmas by other flower-visitors. To explore the relationship between wild-bees and their food-plants, the concept of pollen budget was developed. We quantified pollen production in the food-plant population and pollen consumption of wild-bee nests. A survey of the visitation by all flower-visitor taxa indicated that the degree of utilization (the fraction of the total pollen amount that is harvested and utilized by A. hattorfiana) varied from 12% to 80% among K. arvensis populations (N=26). The bee Andrena marginata utilized 44% of the pollen production in a population of Succisa pratensis. The pollen budget suggests that with an average flower-visitor diversity and abundance, 330 individuals of the food-plant K. arvensis are required to sustain a population of 20 A. hattorfiana ♀ (the approximate median natural population size). Based on a study of A. hattorfiana, considerable simplifications were proposed for the commonly used mark-recapture design for measuring wild-bee population size. For this species, population size estimated based on mark-recapture data was strongly correlated with the number of observations per survey-walk. The results suggest that large-scale surveys of solitary bee species can be simplified by performing survey-walks. The pollen budget and the method proposed for estimating the size of bee populations have the potential to become valuable tools for monitoring and management of wild-bee populations.
108

Optical solitons in quadratic nonlinear media and applications to all-optical switching and routing devices

Santos Blanco, María Concepción 02 March 1998 (has links)
Esta tesis constituye un estudio detallado y exhaustivo de las propiedades de una variedad específica de ondas ópticas solitarias. Observadas experimentalmente por primera vez en 1995, estas ondas estan formadas por un haz óptico a frecuencia fundamental y su segundo armónico que están ligados entre sí y viajan juntos en el material cuadrático; y son debidas al equilibrio entre la difracción lineal que sufre el haz al propagarse y un término no lineal de segundo orden en la susceptibilidad del medio. Las llamamos por eso solitones ópticos en medios cuadráticos o simplemente 'solitones cuadráticos'. También se les conoce como 'Solitones Multicolor' aludiendo al hecho de que requieren de haces a diferentes frecuencias para formarse.Un medio no-lineal cuadrático tiene por fuerza que ser no-centrosimétrico, lo cual es una variedad de anisotropía. Una gran parte de los materiales no-lineales cuadráticos (los que tienen mayor interés para la industria) son uniaxiales lo que significa que presentan un eje de simetría que suele llamarse eje óptico. De la dirección de un haz relativa a ese eje óptico dependen las características de la propagación del haz en el medio cuadrático no-lineal. Una consecuencia de eso en configuraciones de interés es un desvío ('walk-off') sufrido por el haz respecto a su dirección de propagación inicial al entrar en el material no-lineal.Las propiedades de los solitones cuadráticos 'caminantes' son también estudiadas en la tesis, estableciendo que existe una relación entre la potencia inyectada en el medio y el ángulo de desvío (walking angle).Una parte importante de la tesis está dedicada al estudio a través de exhaustivos experimentos numéricos del potencial de estas ondas solitarias para constituir la base de dispositivos de conmutación y encaminamiento totalmente ópticos que puedan hacer realidad la promesa de la red transparente totalmente óptica. Los experimentos han permitido identificar varias configuraciones de interés con niveles de potencia y dimensiones que permiten plantearse el diseño y construcción de dispositivos comerciales de conmutación y encaminamiento totalmente ópticos basados en solitones ópticos cuadráticos. / This thesis is a comprehensive study of the fundamental properties of a specific kind of optical spatial solitary waves. First observed experimentally in 1995, these solitary waves are formed by an optical beam at a fundamental frequency and its second harmonic which propagate together and are mutually entangled; and are due to a balanced interplay between the beams' linear diffraction and a second-order nonlinear susceptibility of the medium. They are thereby referred as 'Optical Solitons in Quadratic Nonlinear Media' or simply 'Quadratic Solitons', They are also known as 'Multicolor Solitons' recalling that they are formed by beams at different frequencies.A quadratic nonlinear media needs to be non centrosymmetric which is a special kind of anisotropy. A great deal of quadratic nonlinear materials (the most used by industry such as lithim niobate, KTP, etc.) are uniaxial meaning that they feature a symmetry axis known as 'optical axis'. The direction of propagation of an optical beam relative to that axis determines the characteristics of the beam's propagation through the quadratic nonlinear material. A main result of that in some configurations of interest is a walk-off suffered by the beam as it enters the quadratic material.The properties of the families of quadratic solitons in the presence of a linear walk-off (quadratic walking solitons) are studied as well in the thesis stating that there is a relationship between the power injected into the medium and the walking angle, suitable to applications of all-optical switching and routing.An important last part of the thesis is devoted to the study from a practical viewpoint and through extensive numerical experiments of the potential of these solitary waves as the basis of practical all-optical switches and routers which could take the all-optical transparent network to a reality. The experiments have allowed to identify several configurations of interest with power level and dimensions suited to practical applications which could allow the production of commercial all-optical switching and routing devices based on quadratic solitons.
109

Skolkuratorers handlingsutrymme i en pedagogisk kontext : En kvalitativ studie

Esch-Ekström, Jasmine, Roovete, Isabella January 2013 (has links)
The aim of this study has been to highlight how school social workers experience their discretion, and furthermore how they feel about working in a context mainly dedicated to teachers. The study is executed with a qualitative research method where ten interviews with school social workers, in eight schools in the area of Stockholm have been conducted. The theoretical framework used to analyze the results was discretion, street-level bureaucracy and human service organizations.The main findings of this study imply that the most important ambition of the social work that was conducted in the schools was to help the students reach their knowledge goals. The assignment is, however, not clearly defined, which has lead to school social workers defining the mission and goals themselves. They all have wide discretion and great possibilities to decide how to execute their work, but how they use the freedom that was given seems to vary among them. An additional finding was that being a school social worker is often a solitary role in the organization, and therefore most of them highlight the importance of enjoying independent work and having a co-worker to discuss their work with.
110

Den samhällsfarlige filmjölkskastarn : En kritisk diskursanalys av synen på de placerade på Kriminalvårdens säkerhetsavdelningar

Hillblom, Jennifer, Darkland, Caroline January 2014 (has links)
Syftet med studien är att se hur Kriminalvårdens säkerhetsavdelningar kallade Fenixavdelningarna legitimeras, genom att göra en kritisk diskursanalys av synen på fångarna som placeras där. Vi gör det för att skapa en förståelse för de diskursiva processer som påverkar den kriminalpolitiska utvecklingen. Avsikten var att se till diskursen om de Fenixplacerade i ett dialektiskt förhållande till de institutioner som upprätthåller en särskiljning av fångarna inom fängelsesystemet. Studien är genomförd utifrån en kvalitativ ansats med Faircloughs metod av kritisk diskursanalys utifrån ett socialkonstruktivistiskt förhållningssätt. Den teoretiska ram som används är bland annat Foucaults teorier om den disciplinära makten, Goffmans om stigmatisering samt Maslows psykologiska teorier. Vi belyser även tidigare forskning inom de teoretiska fälten som komplement till teorierna. Resultatet påvisade att de diskursiva formationer som upprätthålls om de Fenixplacerade beskriver denna grupp fångar som särskilda eftersom de betraktas som ”psykiskt störda” och ”samhällsfarliga”. På så sätt legitimeras en disciplinerande isolering och avskildhet av dessa fångar för att kunna föra en nyliberal politik av ”hårdare tag” och strängare straff. Detta står i motsättning till det sociala arbetets mål om att skapa jämlika villkor i samhället. / The purpose of the study is to see how the “high security”-departments within the prison system in Sweden called “Fenixavdelningarna” are legitimized, by making a critical discourse analysis of the perception of the prisoners placed there. We do it to create an understanding of the discursive processes that affect criminal policy development. The intention was to look upon the discourse concerning this group of prisoners in a dialectical relationship with the institutions that maintains a separation of these prisoners within the prison system. The study was conducted based on a qualitative approach with Faircloughs critical discourse analysis approach based on the ideas of social construction. The theoretical framework used is among others Foucault's theories of disciplinary power, Goffman's theories of stigmatization and Maslow's psychological theories. To complement our theories we add earlier research within this field of knowledge. The results demonstrate that the discursive formations that are maintained on the prisoners placed in these “high security”-departments describes this as certain to other prisoners because they are considered to be "mentally disturbed" and "dangerous to society". Our conclusion is that this is legitimizing a disciplinary isolation and an exclusion of these prisoners in order pursue a neo-liberal policy of "hard on crime" and more severe punishments, and this development contradicts the objectives in social work.

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