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1
Ankers, Philippe. „Les strongles gastro-intestinaux chez le bétail en Gambia /“. [S.l : s.n.], 1995. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Fauvin, Aymeric. „Mécanismes moléculaires impliqués dans la résistance au lévamisole chez les strongles digestifs“. Thesis, Tours, 2011. http://www.theses.fr/2011TOUR4016/document.
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Actuellement, la lutte contre les strongles digestifs est essentiellement basée sur l’utilisation de traitements anthelminthiques. Cependant, leur utilisation massive a conduit à l’apparition d’isolats résistants. L’optimisation des stratégies de lutte nécessite une meilleure connaissance des mécanismes moléculaires impliqués dans l’acquisition de la résistance. Dans ce contexte, nous avons cherché à identifier le récepteur au lévamisole, une des molécules anthelminthiques les plus utilisée en élevage. Nous avons mis en évidence l’existence d’une forme tronquée d’une des sous-unités du récepteur au lévamisole chez certains isolats résistants des 3 principales espèces de strongles digestifs : Haemonchus contortus, Teladorsagia circumcincta et Trichostrongylus colubriformis. Le rôle de cette forme tronquée dans la fonctionnalité du récepteur a été testé en reconstituant le récepteur au lévamisole d’H. contortus en œufs de xénope. Ainsi, nous avons montré que la forme tronquée perturbe le fonctionnement normal du récepteur. Ce résultat constitue la première validation fonctionnelle d’un mécanisme moléculaire de résistance au lévamisole chez un nématode parasiteThe control of gastrointestinal strongyles is largely based on the use of anthelmintic treatments. However, the widespread use of these treatments has led to the emergence of resistant isolates. The optimization of control strategies requires a better understanding of the molecular mechanisms involved in the acquisition of resistance. In the present study, we have identified the receptor of levamisole, an anthelmintic molecule widely used in livestock. We demonstrated the existence of a truncated form of subunits in some resistant isolates in the 3 main species of gastrointestinal nematodes: Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis. The role of this truncated form in the receptor functionality was tested by reconstituting the receptor of levamisole of H. contortus in Xenopus oocytes. Thus, we showed that the truncated form disrupts the normal function of the receptor. Here we provide the first functional evidence for a molecular mechanism involved in levamisole resistance in a parasitic nematode
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Sallé, Guillaume. „Détection et validation fonctionnelle de régions du génome affectant la résistance aux strongles gastro-intestinaux chez le mouton“. Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0154/document.
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Les strongles gastro-intestinaux, dont Haemonchus contortus constituent un problème majeur pour l'élevage des ovins allaitants. Ils entrainent des pertes de production et le recours aux anthelminthiques est remis en question par l'apparition de souches de vers résistantes. La sélection d'ovins plus résistants fait partie des stratégies complémentaires de lutte les plus sérieuses. Cependant sa mise en oeuvre requiert une meilleure compréhension des mécanismes sous-jacents. Cette thèse vise à identifier les régions du génome ovin impliquées dans la résistance aux strongles gastro-intestinaux. Une analyse statistique d'association entre des marqueurs génétiques et des mesures de résistance d'un troupeau d'ovins croisés Martinik Black-belly x Romane a mis en évidence un nombre limité de régions d'intérêt. Parmi celles-ci, un segment du chromosome 12 a été choisi pour effectuer des accouplements raisonnés et valider son rôle dans la résistance à H. contortus. L'effet de cette région a été validé chez les descendants issus d'accouplements assistés par marqueurs génétiques. Cette région semble limiter fertilité des vers femelles tout en contribuant à une réponse immunitaire plus forte. Le rôle d'une région du chromosome 21 dans la variation de concentration plasmatique en pepsinogène, un marqueur de lésions abomasales, a également été confirmé. Un gène candidat sous-jacent est en cours de séquençage et l'analyse des polymorphismes devrait contribuer à la validation de son rôle. Deux autres gènes très proches pourraient également être impliqués et mériteraient une considération future. Ces travaux illustrent à la fois la variation génétique disponible pour les caractères de résistance à H. contortus et la complexité des mécanismes mis en jeu. Des études complémentaires de séquençage et d'étude d'expression par séquençage devrait contribuer à une meilleure compréhension des fonctions des gènes impliqués et de leurs interactionsGastro-intestinal nematodes, among which Haemonchus contortus are a major threat to the meat sheep industry. They are responsible for production losses and the apparition of worm populations resistant to drugs limits their use as worm control strategy. Breeding more resistant sheep is among the most practicable alternative strategy. However its implementation requires a deeper understanding of underlying mechanisms. This PhD aims at identifying regions of the ovine genome affecting resistance to gastro-intestinal nematodes. A statistical analysis of existing associations between genetic markers and resistance traits of a Martinik Black-belly x Romane cross-bred sheep flock unraveled a limited number of key players. Among these, a fragment of the chromosome 12 was chosen to perform marker-assisted matings and to validate its role in resistance to H. contortus. The effect of this region was validated in the progenies born from matings. It seems this chromosomic fragment limits female worms fertility and is associated to a stronger immune response. The putative role played by a fragment of the chromosome 21 in plasmatic pepsinogen concentration (a biomarker of abomasal lesions) was also confirmed in this work. A candidate gene underlying this region has been sequenced and the analysis of the detected polymorphisms should confirm its role. Further, two other genes in its vicinity could also play a role in this biological phenomenon and they should also deserve future considerations. This work illustrated both the existing genetic variation for resistance to H. contortus and the associated complexity of underlying mechanisms. Additional sequencing and gene expression sequencing studies should help understanding gene functions and interactions
4
Henzi, Martin. „Etude épidémiologique des strongles gastro-intestinaux chez les bovins de 1ère et 2ème saison de pâturage en Suisse /“. [S.l.] : [s.n.], 1992. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Laugier, Claire. „Contribution à l'étude des infestations par des petits strongles chez le cheval en Normandie : données épidemiologiques et aspects lésionnels“. Montpellier 2, 2002. http://www.theses.fr/2002MON20125.
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Selim, Suryahadi. „Effet de l'irrigation par submersion des pâturages sur l'écologie des strongles gastro-intestinaux et la localisation spatio-temporelle du risque“. Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb376012365.
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Laroche, Noémie. „Etude de l’effet de l’alimentation sur les helminthes, le microbiote intestinal et l’immunité du gros intestin du cheval“. Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK034.
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Face au développement accru de souches de strongles résistantes aux anthelminthiques chimiques et aux impacts négatifs de ces derniers sur la santé digestive des chevaux et sur l’environnement, la nécessité de trouver des alternatives de contrôle des infections aux strongles chez le cheval est aujourd’hui un enjeu majeur. L’étude des relations portées par le triptyque helminthes – microbiote – immunité du gros intestin de l’hôte en utilisant l’alimentation comme levier de son équilibre pourrait permettre de développer des solutions naturelles et durables. Cette thèse a étudié les effets directs et indirects (médiés par le microbiote et l’immunité du gros intestin équin) de la modulation de la composition du régime alimentaire du cheval ainsi que de l’inclusion de granulés déshydratés de Sainfoin (Onobrychis Viciifolia), une plante riche en polyphénols, connue pour exercer des propriétés anthelminthiques chez d’autres espèces herbivores. Les résultats ont montré que l’excrétion des œufs de strongles augmentait lorsque les chevaux étaient nourris avec un régime riche en amidon en comparaison d’un régime riche en fibres. En parallèle, une dysbiose du microbiote du gros intestin équin était constatée ce qui suggère un rôle de l’écosystème microbien sur la fertilité des strongles. Dans les différentes études in vivo menées, l’effet anthelminthique des granulés de sainfoin était variable et semblait être influencé par leur composition polyphénoliques. L’étude in vitro de l’effet anthelminthique de plusieurs granulés déshydratés de sainfoin, en parallèle de l’analyse métabolomique de leurs profils en polyphénols a permis de mettre en avnt un profil polyphénolique antiparasitaire d’intérêt. Globalement, les résultats de cette thèse montrent que les interventions nutritionnelles pourraient représenter une bonne alternative de contrôle des infections aux strongles équin, et que nourrir les chevaux avec une alimentation qui préserve l’équilibre du tryptique helminthes – microbiote – immunité pourrait être la première étape cléWith the increasing development of strongyle strains resistant to chemical anthelmintics and their negative impact on the digestive health of horses and the environment, the need to find alternative ways to control strongyle infections in horses is now a key research question. Nutritional adjustments resulting in the maintenance of a stable and healthy intestinal ecosystem, could be a natural and sustainable way to control helminth infections, by promoting host tolerance. This thesis aimed to investigate the direct and indirect effects of modulating the composition of the equine diet and including dehydrated granules of sainfoin (Onobrychis Viciifolia), a polyphenol-rich plant known to have anthelmintic properties in other herbivorous species. The results showed that strongyles egg excretion increased when horses were fed a high starch diet compared to ahigh fiber diet. At the same time, a dysbiosis of the equine colonic microbiota was observed, suggesting indirect effects mediated by the latter. The anthelmintic effect of sainfoin granules was variable and appeared to be influenced by their polyphenolic composition. The study of several dehydrated sainfoin granules in vitro, in parallel with the metabolomic analysis of their polyphenolic profiles, opened the possibility of an antiparasitic polyphenolic profile of interest. In conclusion, the results of this work show that nutritional interventions could be a good alternative for the control of strongyles infections in horses, and that providing horses with a diet that preserves the balance of the helminth-microbiota-immunity tryptic could be the first key step
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Selim, Suryahadi. „Effets de l'irrigation par submersion des pâturages sur l'écologie des strongles gastro-intestinaux et la localisation spatio-temporelle du risque d'infestation des Ovins“. Montpellier 2, 1986. http://www.theses.fr/1986MON20082.
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Merlin, Aurélie. „Optimisation de l’usage des antiparasitaires chez la génisse d’élevage en vue de prévenir le risque d’émergence de populations de strongles digestifs résistants : développement d’une stratégie durable de traitement sélectif“. Thesis, Nantes, Ecole nationale vétérinaire, 2017. http://www.theses.fr/2017ONIR093F/document.
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Les traitements anthelminthiques (AH) visant à maîtriser l’impact des strongles gastro-intestinaux (SGI) sur la croissance des jeunes bovins doivent être rationnalisés afin de préserver durablement leur efficacité. L’objectif de cette thèse a été de développer et d’évaluer des stratégies de traitement ciblé sélectif (TCS) basées sur la croissance chez les génisses laitières de première saison de pâturage afin de préserver des populations refuges de SGI, non exposées aux AH, et ainsi de retarder l’apparition de résistance. La relation croissance/parasitisme en fin de saison a tout d’abord été étudiée dans des environnements variés ce qui a permis d’appréhender des lots plus infestés et, à l’intérieur de ces lots, des individus plus fortement infestés. Un arbre de décision de traitement de rentrée a été ensuite proposé en combinant des indicateurs de conduite au pâturage pour identifier les groupes à risque et plusieurs seuils de GMQ pour identifier les animaux souffrant le plus du parasitisme. Une stratégie de TCS basée sur le GMQ moyen réalisé à mi- saison a été évaluée sur le terrain par comparaison avec un traitement collectif. Aucune différence significative, en termes de croissance et de parasitisme, n’a été observée à la rentrée entre le groupe TCS et le groupe traité collectivement. Enfin, les attitudes et les perceptions des vétérinaires vis-à-vis du contrôle des parasitoses digestives en élevage bovin laitier et notamment d’une gestion plus raisonnée des anthelminthiques, ont été évaluées. Les vétérinaires reconnaissent la nécessité d’appréhender les traitements AH de manière raisonnée mais identifient de nombreux freins relatifs au développement du conseil et à la disponibilité d’outils simples, fiables et peu couteux. Les résultats de cette thèse montrent qu’il est possible de cibler l’utilisation des AH chez les génisses laitières de première saison de pâturage en se basant sur des indicateurs individuels et de groupe simples d’emploiIn first grazing season calves (FGSC), the anthelmintic (AH) treatments used to control the negative impact of gastrointestinal nematodes (GIN) on growth must be rationalized to preserve their long-term efficacy. The aim of this PhD thesis was to develop and assess targeted selective treatment (TST) strategies based on growth in FGSC, in order to preserve GIN populations in refugia i.e. not exposed to AH, and thus delay the emergence of AH resistance. Firstly, the relation growth/GIN infection at housing was demonstrated in different environments which allowed identifying groups, and within groups, the most infected animals. Then, a tree treatment decision at housing was proposed combing grazing management indicators to identify the groups at risk, and several average daily weight gain (ADWG) thresholds to identify, within groups, the animals suffering the most of infection. A TST strategy based on mid- season mean ADWG was assessed in field survey in comparison with whole group treatment (WGT). No significant difference, in terms of growth and GIN infection, was observed at housing between the TST and the WGT groups. Lastly, the veterinarians’ behaviors and perceptions about the control of GIN in dairy cattle farming, including a more rational AH management, were assessed. The veterinarians recognize the need to consider the sustainability of the AH treatment but identify serval obstacles as the development of advices and the availability of simple, reliable and cheap tools.The results of this thesis show that it is possible to target the use of AH in FGSC basing on individual and group indicators
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De, la Chevrotière Claudia. „Analyse de la variabilité génétique de la résistance aux strongles gastro-intestinaux chez les chèvres créoles à des fins de sélection et de compréhension des mécanismes“. Thesis, Antilles-Guyane, 2011. http://www.theses.fr/2011AGUY0407/document.
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Les deux principaux objectifs de ce travail sont de proposer des outils pour la selection d'animaux résistants aux strongles gastro-intestinaux, parasites du tube digestif, et de faire progresser la compréhension des mécanismes de résistance chez la chèvre créole. La variabilité génétique du caractère de résistance au parasitisme digestif a été étudiée afin de vérifier quels critères décrivant le mieux la résistance, peuvent être utilisés pour la sélection. L'ensemble des résultats obtenus suggèrent que le critère d'excrétion d'oeufs et le critère d'éosinophilie sont les plus adaptés pour un schéma de sélection puisqu'ils possèdent une héritabillté moyenne et représentent le mieux la résistance. De plus, ils ne semblent pas en opposition avec le poids, principal critère de production. Le déterminisme génétique de la résistance aux strongles gastro-intestinaux a été étudié et a permis de mettre en évidence l'existence d'un gène majeur pour la résistance chez la population de chèvre créole. De plus, la primo-détection de qtl a permis d'identifier 13 régions du génome ayant un effet sur les critères de résistance. Les mécanismes responsables de la résistance aux strongles gastro-intestinaux ont également été à l'étude. L'ensemble des résultats met en évidence le rôle des éosinophiles dans la mise en place de la résistance aux strongles gastro-intestinaux. L'activité des immunogobulines e semblent dirigés vers les larves l3 d'haemonchus contortus et suggère la mise en place d'une réaction protectrice. Chez la chèvre créole. Ces deux mécanismes semblent donc jouer un rôle important dans la mise en place de la résistance aux strongles gastro-intestinauxThe two main objectives of this work are to propose tools for the selection of resistant animals to gastrointestinal nematodes and advance knowledge on mechanisms of resistance of creole goats. this work has analysed the genetic variability of resistance to digestive parasitism in order to determine which criteria best describes the resistance and can be use for selection. the overall results suggest that the egg excretion and the eosinophilia are the criteria most suitable for a breeding scheme because they have moderate heritability estimates and best represent the resistance. moreover, they do not seem in conflict with the weight, the main criterion of production. the genetic determinism of resistance to gastrointestinal parasites has been studied and has highlighted the existence of a major gene for resistance in creole goats. in addition, the primodetection of qtl identified 13 genomic regions that affect the resistance. the mechanisms behind the resistance to gastrointestinal parasites were also studied and first hypothesis regarding the involvment of the immune response in resistance have been made in goats. the overall results highlighted the role of eosinophils in the development of resistance to gastrointestinal nematodes. the activity of immunoglobulin e seems directed toward l3 larvae of haemonchus contortus and may be imply in the establishment of a protective response agasint nematode parasites. in creole goats, these two mechanisms seem to play an important role in the development of resistance to gastrointestinal nematode infections
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Achi, Yaba Louise. „Le polyparasitisme gastro-intestinal des ruminants domestiques dans la région des savanes de la cote d'ivoire“. Toulouse, INPT, 2004. http://www.theses.fr/2004INPT007A.
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La région des savanes est le berceau de l'élevage des ruminants en Côte d'Ivoire. Elle renferme 65% du cheptel national bovin, 16% du cheptel ovin et 15% du cheptel caprin. En dépit de l'importance reconnue des strongles gastro-intestinaux, aucune étude épidémiologique n'y a été entreprise pour aboutir à des mesures de luttes judicieuses. La zone est régie par un climat soudanien dont la saison des pluies a une hauteur de précipitations moyennes de 1200 mm. La végétation est à majorité constituée de savanes arborée et arbustive. L'étude sur l'épidémiologie des strongles a été réalisée par des autopsies de 48 bovins, 144 moutons et 72 chèvres. Elle a permis l'inventaire des strongles présents dans la région ainsi que la connaissance de leurs évolutions saisonnières. La quasi-totalité des animaux sont porteurs de strongles avec une prévalence de 100ù pour les bovins et les chèvres et 95% chez les moutons. [. . . ]
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Mandonnet, Nathalie. „Analyse de la variabilite genetique de la resistance aux strongles gastro-intestinaux chez les petits ruminants. Elements pour la definition d'objectifs et de criteres de selection en milieu tempere ou tropical“. Paris 11, 1995. http://www.theses.fr/1995PA112219.
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La resistance genetique des petits ruminants aux strongles gastro-intestinaux est un caractere d'adaptation au milieu dont la variabilite genetique a ete mise en evidence pour divers modeles ovin/strongles. Notre demarche visait de plus a apprecier la variabilite genetique disponible et, a terme, a proposer des outils d'evaluation et de selection operationnels pour l'amelioration genetique des races rustiques ou d'herbage. Nous parvenons aux resultats suivants. La mesure d'hematocrite apparait comme un bon indicateur de la taille d'une population vermineuse hematophage (h. Contortus). Cet indicateur est tres repetable, mais aucune variabilite genetique n'a ete mise en evidence dans nos conditions experimentales. Les techniques de dosage du pepsinogene, de l'albumine et des globulines seriques sont a ameliorer, la recherche de proteines plus specifiques sont necessaires. La coproscopie, indicateur classique de la resistance, a ete un reflet variable de la taille de la population vermineuse, en fonction du mode d'infestation, du temps et de l'espece vermineuse. Nos resultats vont dans le sens d'une influence de l'alimentation sur l'expression des genes de resistance. Des parametres genetiques ont ete estimes. La repetabilite de la mesure de coproscopie est plus elevee en infestation naturelle qu'en infestation artificielle et intra-infestation qu'entre infestations. L'heritabilite de la mesure ponctuelle de coproscopie est estimee a 0,34 en infestation par t. Circumcincta sur paturage et a 0,20 en infestation artificielle. La correlation genetique entre la resistance acquise suite a une infestation sur paturage et la resistance acquise suite a une serie d'infestation artificielle est proche de l'unite. Ainsi, la selection d'ovins pour leur resistance a une infestation au paturage par t. Circumcincta, est possible en utilisant comme critere leur reponse a une serie d'infestations artificielles
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Barbeito, Jessica Sofia Gonçalves. „The efficacy of moxidectin in equine strongyles and the effect of management practices in strongyle egg reappearance period and faecal worm egg counts in yards across the UK“. Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2016. http://hdl.handle.net/10400.5/12925.
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Dissertação de Mestrado Integrado em Medicina VeterináriaThe present study was designed to evaluate the efficacy of an oral anthelminic treatment, in particular a combination of moxidectin (MOX) and praziquantel (PRZ) against gastrointestinal strongyles in naturally infected horses. A total of eight yards in the UK were selected to participate in this study: Day 0, the horses were treated with an oral paste containing MOX and PRZ. Faecal samples for faecal egg counts (FECs) analysis were collected at the following time-points: day 0 (treatment day), 14 days post-treatment, 6, 10 and 12 weeks post-treatment (wpt). Faecal egg count reduction tests (FECRTs) were used to determine the product’s efficacy. Mean FECR and 95% confidence intervals were calculated using bootstrap analysis. Additional samples were collected at 6, 10 and 12 wpt, to determine the strongyle egg reappearance period (ERP). The ERP was evaluated using two different methods. Faecal cultures were performed to determine the prevalence of the nematode species present in the sample population. The influence of yard management (faecal removal [FR] from the pasture versus no faecal removal [NFR]) was analysed using a repeated measures analysis of variance (rANOVA), with the R program. Difference between factors (Group and Time) and their interaction was assessed with a significance level of 0.05. FECRT on day 14 indicated a 100% efficacy in 7 yards and 99.88% in the remaining yard. Using Method 1, the ERP was 6 weeks for all populations examined. Using Method 2, the ERP ranged from 6 weeks to >12 weeks. Only cyathostomin L3 larvae were detected in the faecal cultures throughout the study. Mean FECs of the two groups (FR and NFR) were compared at four time-points: 2 wpt (14 days post-treatment), 6 wpt, 10 wpt and 12 wpt, with significant difference in mean FEC observed between the groups (p = 0.003), since the FR showed lower EPGs. As major conclusions, our results still show an overall excellent efficacy for moxidectin regarding horse strongyle control, although it should not rely only on chemical compounds. Hence, and according to our data, it would appear that this aspect of yard management plays an important role in the levels of strongyle egg excretion after anthelmintic treatment.
RESUMO - O presente estudo tem como objectivo avaliar a eficácia de um tratamento anti-helmíntico oral usando uma combinação de moxidectina (MOX) e praziquantel (PRZ) contra estrongilídeos gastrointestinais em cavalos infetados naturalmente. Um total de 8 estabelecimentos equestres no Reino Unido foram selecionados para participar neste estudo. No Dia 0, os cavalos foram tratados com um anti-helmíntico oral contendo MOX e PRZ. As recolhas de amostras fecais para as contagens de ovos fecais foram realizadas nos seguintes tempos: dia 0 (dia do tratamento), 14 dias após tratamento, 6, 10 e 12 semanas após tratamento. Os Testes de Redução de Contagem de Ovos Fecais (TRCOF) foram usados para determinar a eficácia do produto. A média das RCOFs e os intervalos de confiança de 95% foram calculados usando a análise “bootstrap”. As amostras foram recolhidas às 6, 10 e 12 semanas após tratamento para determinar o Período de Reaparecimento de Ovos (PRO). O PRO foi calculado usando dois métodos diferentes. Adicionalmente, foram realizadas culturas fecais para determinar a prevalência das espécies de nematodes presentes nas amostras. A influência do maneio (remoção de fezes [RF] versus não remoção de fezes [NRF]) foi analisada usando uma análise de variância com medidas repetidas (rANOVA) através do programa R. A diferença entre dois fatores (grupo e tempo) e a sua interação foram avaliadas com um nível de significância de 0.05. O TRCOF indicou uma eficácia de 100% para 7 quintas equestres e 99.88% na restante. Usando o método 1, o PRO foi de 6 semanas para todas as populações estudadas. Usando o método 2, o PRO variou entre 6 a >12 semanas. Nas culturas fecais foram detetados apenas larvas L3 de ciatostomíneos. As médias das contagens de ovos fecais dos dois grupos (RF e NRF) foram comparadas em 4 pontos no tempo: 2 semanas após tratamento (14 dias após tratamento), 6, 10 e 12 semanas após tratamento, com uma diferença de médias significativa entre os grupos (p=0.003), visto que o grupo RF obteve menores contagens de ovos. Conclui-se que os resultados demonstram que a moxidectina apresenta uma eficácia muito boa no que toca ao controlo de estrongilídeos. Apesar disso, o seu controlo não deveria ser inteiramente químico. Portanto, e de acordo com o nosso estudo, é provável que este aspeto do maneio tem um papel importante nos níveis de excreção de ovos de estrôngilos após tratamento com anti-helmínticos.
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Sadeghi, Esfahani Hossein. „Strongly correlated ultracold plasma“. Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59478.
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Ultracold molecular plasmas represent a new frontier of plasma physics. They offer an easy and accessible laboratory for the study of strongly coupled Coulomb systems. Strong Coulomb coupling can give rise to exotic materials such as Wigner crystals and liquid like plasmas. In this thesis, I present a set of experiments and theoretical models that explore the properties of ultracold plasma in great detail. A supersonic beam of nitric oxide in helium creates a cold ensemble of ground state molecules. Upon two-color excitation, a Rydberg gas of nitric oxide evolves on a time scale of nanoseconds to form an ultracold plasma. The excited volume is imaged using a multichannel plate detector mounted on a movable grid. By moving the detector back and forth, we can observe the expansion dynamics of the plasma and its decay. Selective field ionization captures the relaxation of the Rydberg states to a plasma. We use a very reliable coupled-rate-equation model to understand the decay dynamics and evolution of Rydberg gas to a plasma by accounting for all the major processes that happen during the avalanche process. We find that a plasma evolved from an ultracold Rydberg gas expands very slowly, exhibits long relaxation time, and shows evidence suggesting the development of spatial order.Science, Faculty of
Chemistry, Department of
Graduate
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Kellermann, David Conrad Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. „Strongly orthotropic continuum mechanics“. Publisher:University of New South Wales. Mechanical & Manufacturing Engineering, 2008. http://handle.unsw.edu.au/1959.4/41454.
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The principal contribution of this dissertation is a theory of Strongly Orthotropic Continuum Mechanics that is derived entirely from an assertion of geometric strain indeterminacy. Implementable into the finite element method, it can resolve widespread kinematic misrepresentations and offer unique and purportedly exact strain-induced energies by removing the assumptions of strain tensor symmetry. This continuum theory births the proposal of a new class of physical tensors described as the Intrinsic Field Tensors capable of generalising the response of most classical mechanical metrics, a number of specialised formulations and the solutions shown to be kinematically intermediate. A series of numerical examples demonstrate Euclidean objectivity, material frame-indifference, patch test satisfaction, and agreement between the subsequent Material Principal Co-rotation and P??I??C decomposition methods that produce the intermediary stress/strain fields. The encompassing theory has wide applicability owing to its fundamental divergence from conventional mechanics, it offers non-trivial outcomes when applied to even very simple problems and its use of not the Eulerian, Lagrangian but the Intrinsic Frame generates previously unreported results in strongly orthotropic continua.
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Peidaee, Pantea, und pantea peidaee@rmit edu au. „Strongly Perturbed Harmonic Oscillator“. RMIT University. SECE, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080804.094824.
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The limits of current micro-scale technology is approaching rapidly. As the technology is going toward nano-scale devices, physical phenomena involved are fundamentally different from micro-scale ones [1], [2]. Principles in classical physics are no longer powerful enough to explicate the phenomena involved in nano-scale devices. At this stage, quantum mechanic sheds some light on those topics which cannot be described by classical physics. The primary focus of this research work is the development of an analysis technique for understanding the behavior of strongly perturbed harmonic oscillators. Developing ``auxiliary'' boundary value problems we solve monomially perturbed harmonic oscillators. Thereby, we assume monomial terms of arbitrary degree and any finite coefficient desired. The corresponding eigenvalues and eigenvectors can be utilized to solve more complex anharmonic oscillators with non polynomial anharmonicity or numerically defined anharmonicity. A large number of numerical calculations demonstrate the robustness and feasibility of our technique. Particular attention has been paid to the details as have implemented the underlying formula. We have developed iterative expressions for the involved integrals and the introduced ``Universal Functions.'' The latter are applications and adaptations of a concept which was developed in 1990's to accelerate computations in the Boundary Element Method.
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Kennedy, Claire Julia. „Strongly typed evolutionary programming“. Thesis, University of Bristol, 2000. http://hdl.handle.net/1983/dd67df3a-62d4-4b54-93c9-449cb4f56522.
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As the potential of applying machine learning techniques to perplexing problems is realised, increasingly complex problems are being tackled, requiring intricate explanations to be induced. Escher is a func tional logic language whose higher-order constructs allow arbitrarily complex observations to be captured and highly expressive generalisations to be conveyed. The work presented in this thesis alleviates the challenging problem of identifying an underlying structure normally required to search the resulting hypothesis space efficiently. This is achieved through STEPS, an evolutionary based system that allows the vast space of highly expressive Escher programs to be explored. STEPS provides a natural upgrade of the evolution of concept descriptions to the higher-order level. In particular STEPS uses the individual-as-terms approach to knowledge representation where all the information provided by an example is localised as a single closed term so that examples of arbitrary complexity can be treated in a uniform manner. STEPS also supports ?-abstractions as arguments to higher-order functions thus enabling the invention of new functions not contained in the original alphabet. Finally, STEPS provides a number of specialised genetic operators for the design of specific concept learning strategies. STEPS has been successfully applied to a number of complex real world problems, including the international PTE2 challenge. This problem involves the prediction of the Carcinogenic activity of a test set of 30 chemical compounds. The results produced by STEPS rank joint second if the hypothesis must be interpretable and joint first if interpretability is sacrificed for increased accuracy.
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Liu, Tianhan. „Strongly Correlated Topological Phases“. Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066403.
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Cette thèse porte principalement sur l'étude de modèles de fermions en interactions contenant un couplage spin-orbite. Ces modèles (i) peuvent décrire une classe de matériaux composés d'iridates sur le réseau en nid d'abeille ou (ii) pourraient être réalisés artificiellement dans des systèmes d’atomes froids. Nous avons étudié, dans un premier temps, le système à demi-remplissage avec l'interaction de Hubbard et un couplage spin-orbite anisotrope. Nous avons trouvé plusieurs phases: la phase isolant topologique pour de faibles corrélations, et deux phases avec des ordres magnétiques frustrés, l'ordre de Néel et l'ordre spiral, dans la limite de très fortes corrélations. La transition entre les régimes de faibles et de fortes corrélations est une transition de Mott dans laquelle les excitations électroniques se fractionnent en excitations de charge et de spin. Les charges sont localisées par l'interaction. Le secteur de spin présente de fortes fluctuations qui sont modélisées par un gaz d’instantons. Nous avons ensuite exploré la physique d'un système régi au demi-remplissage par le modèle de Kitaev-Heisenberg, qui présente une phase magnétique de type zig-zag. En dopant le système, autour du quart remplissage, la structure de bande présente de nouveaux centres de symétrie en plus de la symétrie d'inversion. Le couplage de spin de Kitaev-Heisenberg favorise alors la formation de paires de Cooper dans un état triplet autour de ces centres de symétrie. La condensation de ces paires de Cooper autour de ces vecteurs d'onde non triviaux se manifeste par une modulation spatiale du paramètre d'ordre supraconducteur, comme dans la supraconductivité de Fulde–Ferrell–Larkin–Ovchinnikov (FFLO). La dernière partie de la thèse propose et étudie une implémentation des phases topologiques dite de Haldane et de Kane-Mele dans un système avec deux espèces de fermions sur le réseau en nid d'abeille, stabilisée grâce à l’interaction RKKY médiée par l’espèce rapide et qui agit sur l’espèce lenteThis thesis is dedicated largely to the study of theoretical models describing interacting fermions with a spin-orbit coupling. These models (i) can describe a class of 2D iridate materials on the honeycomb lattice or (ii) could be realized artificially in ultra-cold gases in optical lattices. We have studied, in the first part, the half-filled honeycomb lattice model with on-site Hubbard interaction and anisotropic spin-orbit coupling. We find several different phases: the topological insulator phase at weak coupling, and two frustrated magnetic phases, the Néel order and spiral order, in the limit of strong correlations. The transition between the weak and strong correlation regimes is a Mott transition, through which electrons are fractionalized into spins and charges. Charges are localized by the interactions. The spin sector exhibits strong fluctuations which are modeled by an instanton gas. Then, we have explored a system described by the Kitaev-Heisenberg spin Hamiltonian at half-filling, which exhibits a zig-zag magnetic order. While doping the system around the quarter filling, the band structure presents novel symmetry centers apart from the inversion symmetry point. The Kitaev-Heisenberg coupling favors the formation of triplet Cooper pairs around these new symmetry centers. The condensation of these pairs around these non-trivial wave vectors is manifested by the spatial modulation of the superconducting order parameter, by analogy to the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superconductivity. The last part of the thesis is dedicated to an implementation of the Haldane and Kane-Mele topological phases in a system composed of two fermionic species on the honeycomb lattice. The driving mechanism is the RKKY interaction induced by the fast fermion species on the slower one
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Goyal, Vipul. „Stronger notions of secure computation“. Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=2025452011&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Ahnert, Karsten. „Compactons in strongly nonlinear lattices“. Phd thesis, Universität Potsdam, 2010. http://opus.kobv.de/ubp/volltexte/2010/4853/.
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In the present work, we study wave phenomena in strongly nonlinear lattices. Such lattices are characterized by the absence of classical linear waves. We demonstrate that compactons – strongly localized solitary waves with tails decaying faster than exponential – exist and that they play a major role in the dynamics of the system under consideration. We investigate compactons in different physical setups. One part deals with lattices of dispersively coupled limit cycle oscillators which find various applications in natural sciences such as Josephson junction arrays or coupled Ginzburg-Landau equations. Another part deals with Hamiltonian lattices. Here, a prominent example in which compactons can be found is the granular chain. In the third part, we study systems which are related to the discrete nonlinear Schrödinger equation describing, for example, coupled optical wave-guides or the dynamics of Bose-Einstein condensates in optical lattices.
Our investigations are based on a numerical method to solve the traveling wave equation. This results in a quasi-exact solution (up to numerical errors) which is the compacton. Another ansatz which is employed throughout this work is the quasi-continuous approximation where the lattice is described by a continuous medium. Here, compactons are found analytically, but they are defined on a truly compact support. Remarkably, both ways give similar qualitative and quantitative results.
Additionally, we study the dynamical properties of compactons by means of numerical simulation of the lattice equations. Especially, we concentrate on their emergence from physically realizable initial conditions as well as on their stability due to collisions. We show that the collisions are not exactly elastic but that a small part of the energy remains at the location of the collision. In finite lattices, this remaining part will then trigger a multiple scattering process resulting in a chaotic state.In der hier vorliegenden Arbeit werden Wellenphänomene in stark nichtlinearen Gittern untersucht. Diese Gitter zeichnen sich vor allem durch die Abwesenheit von klassischen linearen Wellen aus. Es wird gezeigt, dass Kompaktonen – stark lokalisierte solitäre Wellen, mit Ausläufern welche schneller als exponentiell abfallen – existieren, und dass sie eine entscheidende Rolle in der Dynamik dieser Gitter spielen. Kompaktonen treten in verschiedenen diskreten physikalischen Systemen auf. Ein Teil der Arbeit behandelt dabei Gitter von dispersiv gekoppelten Oszillatoren, welche beispielsweise Anwendung in gekoppelten Josephsonkontakten oder gekoppelten Ginzburg-Landau-Gleichungen finden. Ein weiterer Teil beschäftigt sich mit Hamiltongittern, wobei die granulare Kette das bekannteste Beispiel ist, in dem Kompaktonen beobachtet werden können. Im dritten Teil werden Systeme, welche im Zusammenhang mit der Diskreten Nichtlinearen Schrödingergleichung stehen, studiert. Diese Gleichung beschreibt beispielsweise Arrays von optischen Wellenleitern oder die Dynamik von Bose-Einstein-Kondensaten in optischen Gittern. Das Studium der Kompaktonen basiert hier hauptsächlich auf dem numerischen Lösen der dazugehörigen Wellengleichung. Dies mündet in einer quasi-exakten Lösung, dem Kompakton, welches bis auf numerische Fehler genau bestimmt werden kann. Ein anderer Ansatz, der in dieser Arbeit mehrfach verwendet wird, ist die Approximation des Gitters durch ein kontinuierliches Medium. Die daraus resultierenden Kompaktonen besitzen einen im mathematischen Sinne kompakten Definitionsbereich. Beide Methoden liefern qualitativ und quantitativ gut übereinstimmende Ergebnisse. Zusätzlich werden die dynamischen Eigenschaften von Kompaktonen mit Hilfe von direkten numerischen Simulationen der Gittergleichungen untersucht. Dabei wird ein Hauptaugenmerk auf die Entstehung von Kompaktonen unter physikalisch realisierbaren Anfangsbedingungen und ihre Kollisionen gelegt. Es wird gezeigt, dass die Wechselwirkung nicht exakt elastisch ist, sondern dass ein Teil ihrer Energie an der Position der Kollision verharrt. In endlichen Gittern führt dies zu einem multiplen Streuprozess, welcher in einem chaotischen Zustand endet.
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Shelton, David G. „Low dimensional strongly correlated systems“. Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320594.
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Gomes, Cipriano Nabais Conde Teresa. „On certain strongly quasihereditary algebras“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:29052b1b-bce1-4406-a360-b8ead0309e1b.
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Given a finite-dimensional algebra A we may associate to it a special endomorphism algebra, RA, introduced by Auslander. The algebra RA is a "Schur-like" algebra for A: it contains A as an idempotent subalgebra (up to Morita equivalence) and it is quasihereditary with respect to a particular heredity chain. The main purpose of this thesis is to describe the quasihereditary structure of RA which arises from such heredity chain, and to investigate the corresponding Ringel dual of RA. It turns out that RA belongs to a certain class of strongly quasihereditary algebras defined axiomatically, which we call ultra strongly quasihereditary algebras. We derive the key properties of ultra strongly quasihereditary algebras, and give examples of other algebras which fit into this setting.
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Sadofyev, Andrey V. „Probes of strongly interacting plasma“. Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112072.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-138).
In this thesis we discuss recent results on the medium/probe interaction in the strongly coupled plasma produced in heavy-ion collisions. Such processes involve physics at multiple energy scales making a consistent theoretical description challenging. We show how insights from various regimes can be combined to extend our understanding of the underlying physics. As a first example, we start with the novel contributions to the drag force acting on a heavy quark moving through the strongly coupled holographic plasma. The new terms are proportional to the coefficient of the axial anomaly and to the chiral asymmetry in the medium. These chiral contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid. We show that the chiral drag force vanishes for heavy quarks that are at rest in a suitably chosen frame in the weak field limit. In this frame, the heavy quark at rest sees counter propagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport. Then, we extend this result introducing a concept of an "anomalous wind" felt by probes at rest. This phenomenon modifies previous results on the medium/probe interaction. We demonstrate that by deriving the anomalous correction to the screening length of the heavy quarkonium color potential. Finally, we discuss the strong magnetic field limit to the leading order in the weak medium/probe coupling. It is shown that the drag force is suppressed along the magnetic field and in the exact chiral limit tends to zero. This anisotropy in the drag force is present in the system even at zero chiral asymmetry and may lead to strong observable effects. Then, we turn to the main available probes of the plasma produced in experiments - jets. We supplement the holographic description corresponding to the infinite medium/probe coupling limit with an initial parameter distribution for an ensemble of jets motivated by the weakly coupled dynamics and similar to the case of proton-proton collisions. The model constructed in this way, combining insights from both weakly and strongly coupled regimes, is used to analyze the evolution of an ensemble, as it propagates through an expanding cooling droplet of strongly coupled plasma as in heavy ion collisions. Each jet in the ensemble is represented holographically by a string in the dual 4 + 1-dimensional gravitational theory. Firstly, the full string dynamics is approximated by assuming that the string moves at the speed of light. We study the evolution of the jet opening angle distribution upon propagating the droplet and study the medium effect on the mean opening angle within a simple two parametric phenomenological model. Then, we extend this result analyzing the full string dynamics for a range of possible initial conditions. That gives access to the dynamics of holographic jets just after their creation. We analyze the full jet shape modification and find the result that the jet shape scales with the opening angle at any particular energy. Further, we construct an ensemble of dijets with energies and energy asymmetry distributions taken from events in proton-proton collisions and jet shape taken from proton-proton collisions and scaled according to our result. We study how these observables are modified after the ensemble of dijets is propagated through the strongly-coupled plasma. The results of this simple model is in qualitative agreement with the experimental data.
by Andrey V. Sadofyev.
Ph. D.
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Iqbal, Nabil. „Holography and strongly correlated systems“. Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68873.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 221-231).
In this thesis we apply techniques arising from string theory - gauge-gravity/duality, or holography - to problems associated with strongly coupled quantum field theories under extreme conditions such as finite temperature or density. We first study a strongly coupled field theory at finite temperature. We demonstrate that its low frequency limit is determined by the horizon geometry of its gravity dual, i.e. by the "membrane paradigm" fluid of classical black hole mechanics. Thus generic boundary theory transport coefficients can be expressed in terms of geometric quantities evaluated at the horizon, providing a simple understanding of results such as the universality of the shear viscosity in theories with gravity duals. Away from the low frequency limit we find a nontrivial radial flow from the black hole horizon to the boundary of the spacetime; we derive equations governing this flow and demonstrate their use in the simple examples of charge and momentum diffusion. Next, we turn to the study of strongly coupled theories with a finite density of a U(1) charge. The near-horizon geometry of the gravity dual of such a state has an AdS 2 factor, indicating the existence of a nontrivial emergent conformal symmetry in the infrared with nontrivial scaling only in the time direction. We review earlier work indicating that fermionic perturbations of such a state reveal non-Fermi-liquid behavior, i.e. gapless fermionic excitations that are not those of Fermi liquid theory. We perform a one-loop calculation in the bulk to compute the contribution from these Fermi surfaces to the conductivity of the full system. Interestingly, within this class of non-Fermi liquids we find examples whose single-particle spectral function and transport behavior both resemble those of strange metals, i.e. the anomalous metallic state existing in the real-life high Tc cuprates above their superconducting transition temperature. In particular, for these examples the contribution to the conductivity is inversely proportional to temperature. In our treatment these properties can be understood as being controlled by the scaling dimension of the fermion operator in the emergent IR fixed point. We then turn to models of symmetry breaking in holographic models at finite density. We observe that the presence of the AdS₂ factor can result in the condensation of a neutral scalar operator. This can be used to model an "antiferromagnetic" phase in which a global SU(2) symmetry is broken down to U(1). We study the collective modes of the ordered phase and recover the expected spin waves from a gravitational treatment. We then note that the phase transition can be driven to zero temperature by tuning various bulk couplings, resulting in a quantum phase transition of the Berezinskii-Kosterlitz-Thouless type. We study this transition in detail, revealing novel critical behavior, including locally quantum critical dynamics and the existence of an infinite tower of excited states related by a discrete subgroup of the original emergent conformal symmetry. Throughout this thesis we focus on how the novel viewpoint provided by holography can help us gain new insights into the physics of strongly correlated systems.
by Nabil Iqbal.
Ph.D.
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Johnson, Tomi Harry. „Non-equilibrium strongly-correlated dynamics“. Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:55d438cc-d9a1-4898-ac05-49299bad6806.
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We study non-equilibrium and strongly-correlated dynamics in two contexts. We begin by analysing quantum many-body systems out of equilibrium through the lens of cold atomic impurities in Bose gases. Such highly-imbalanced mixtures provide a controlled arena for the study of interactions, dissipation, decoherence and transport in a many-body quantum environment. Specifically we investigate the oscillatory dynamics of a trapped and initially highly-localised impurity interacting with a weakly-interacting trapped quasi low-dimensional Bose gas. This relates to and goes beyond a recent experiment by the Inguscio group in Florence. We witness a delicate interplay between the self-trapping of the impurity and the inhomogeneity of the Bose gas, and describe the dissipation of the energy of the impurity through phononic excitations of the Bose gas. We then study the transport of a driven, periodically-trapped impurity through a quasi one-dimensional Bose gas. We show that placing the weakly-interacting Bose gas in a separate periodic potential leads to a phononic excitation spectrum that closely mimics those in solid state systems. As a result we show that the impurity-Bose gas system exhibits phonon-induced resonances in the impurity current that were predicted to occur in solids decades ago but never clearly observed. Following this, allowing the bosons to interact strongly, we predict the effect of different strongly-correlated phases of the Bose gas on the motion of the impurity. We show that, by observing the impurity, properties of the excitation spectrum of the Bose gas, e.g., gap and bandwidth, may be inferred along with the filling of the bosonic lattice. In other words the impurity acts as a probe of its environment. To describe the dynamics of such a strongly-correlated system we use the powerful and near-exact time-evolving block decimation (TEBD) method, which we describe in detail. The second part of this thesis then analyses, for the first time, the performance of this method when applied to simulate non-equilibrium classical stochastic processes. We study its efficacy for a well-understood model of transport, the totally-asymmetric exclusion process, and find it to be accurate. Next, motivated by the inefficiency of sampling-based numerical methods for high variance observables we adapt and apply TEBD to simulate a path-dependent observable whose variance increases exponentially with system size. Specifically we calculate the expected value of the exponential of the work done by a varying magnetic field on a one-dimensional Ising model undergoing Glauber dynamics. We confirm using Jarzynski's equality that the TEBD method remains accurate and efficient. Therefore TEBD and related methods complement and challenge the usual Monte Carlo-based simulators of non-equilibrium stochastic processes.
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Nailana, Kwena Rufus. „(Strongly) zero-dimensional ordered spaces“. Master's thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/17403.
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Includes bibliographical references.The relationship between transitive uniform spaces and zero-dimensional topological spaces was first established by Banaschewski [1957], and was later investigated by Levine [1969]. The theory of transitive quasi-uniform spaces is treated in [Fletcher and Lindgren 1972], [Brummer 1984] and [Kiinzi 1990, 1992a, 1992b,1993]; a convenient presentation for our purpose is to be found in [Fletcher and Lindgren 1982]. After Reilly [1972] introduced the notion of zero-dimensionality in bitopological spaces, Birsan [1974] and Halpin [1974] studied the relationship between transitive quasi-uniform spaces and zero-dimensional bitopological spaces. In this thesis we define a notion of zero-dimensionality in ordered topological spaces and examine the relationship between transitive quasi-uniform spaces and zero-dimensional ordered topological spaces. To a large extent, our presentation is influenced by the situation in bitopological spaces (cf. [Halpin 1974] and [Birsan 1974]), and uses the commutative diagrams which occur in [Schauerte 1988] and [Brummer 1977, 1982]. We also study strongly zero-dimensional ordered topological spaces and their relation with functorial quasi-uniformities. In this respect, our results are influenced by those of [Fora 1984], [Banaschewski and Brummer 1990] and [Kiinzi 1990] for strongly zero-dimensional bitopological spaces.
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Verney, Lucas. „Strongly driven quantum Josephson circuits“. Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE008/document.
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Dans cette thèse, nous étudions le comportement de circuits Josephson sous l'action de champs microondes forts. Les circuits Josephson dans le régime quantique sont une brique pour émuler une variété d'hamiltoniens, utiles pour traiter l'information quantique. Nous étudions ici le transmon, constitué d'une jonction Josephson et d'un condensateur en parallèle. À travers des simulations numériques et en comparant aux résultats expérimentaux, nous montrons que ces champs conduisent à une instabilité qui envoie le circuit sur des états qui ne sont plus confinés par le potentiel Josephson en cosinus. Quand le transmon occupe de tels états, le circuit se comporte comme si la jonction avait été remplacée par un interrupteur ouvert et toute non-linéarité est perdue, ce qui se traduit par des limitations sur les amplitudes maximales des hamiltoniens émulés. Dans une deuxième partie, nous proposons et étudions un circuit alternatif basé sur un transmon avec une inductance en parallèle, qui fournit un confinement harmonique. La dynamique de ce circuit est stable et bien capturée par un modèle moyennisé qui fournit alors un outil pratique pour l'analyse analytique ou les simulations rapides. Nous avons développé un nouvel outil de simulations modulaire et basé sur la théorie de FloquetMarkov pour permettre de simuler facilement d'autres circuits Josephson en évitant les limitations des analyses perturbatives. Enfin, nous étudions les propriétés d'une version asymétrique du Josephson Ring Modulator, un circuit actuellement utilisé pour l'amplification et la conversion, comme source de non-linéarité pour émuler les hamiltoniens d'interaction à deux et quatre photons requis pour l'encodage de l'information quantique sur des états de chats de SchrödingerIn this thesis, we investigate the behavior of Josephson circuits under the action of strong microwave drives. Josephson circuits in the quantum regime are a building block to emulate a variety of Hamiltonians, useful to process quantum information. We are here considering a transmon device, made of a Josephson junction and a capacitor in parallel. Through numerical simulations and comparison with experimental results, we show that these drives lead to an instability which results in the escape of the circuit state into states which are no longer confined by the Josephson cosine potential. When the transmon occupies such states, the circuit behaves as if the junction had been removed and all non-linearities are lost, which translates into limitations on the emulated Hamiltonian strengths. In a second part, we propose and study an alternative circuit consisting of a transmon device with an extra inductive shunt, providing a harmonic confinement. This circuit is found to be stable for all pump powers. The dynamics of this circuit is also well captured by a time-averaged model, providing a useful tool for analytical investigation and fast numerical simulations. We developed a novel numerical approach that avoids the built-in limitations of perturbative analysis to investigate the dynamical behavior of both of these circuits. This approach, based on the Floquet-Markov theory, resulted in a modular simulation framework which can be used to study other Josephson-based circuits. Last, we study the properties of an asymmetric version of the Josephson Ring Modulator, a circuit currently used for amplification and conversion, as a more robust source of non-linearity to engineer two-photon and four-photon interaction Hamiltonians required for the catstate encoding of quantum information
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Clark, Hannah Jane. „The molecular mechanisms of benzimidazole resistance in equine small strongyles“. Thesis, University of Liverpool, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441739.
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Gleiss, Petra M., Josef Leydold und Peter F. Stadler. „Circuit Bases of Strongly Connected Digraphs“. Department of Statistics and Mathematics, Abt. f. Angewandte Statistik u. Datenverarbeitung, WU Vienna University of Economics and Business, 2001. http://epub.wu.ac.at/178/1/document.pdf.
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The cycle space of a strongly connected graph has a basis consisting of directed circuits. The concept of relevant circuits is introduced as a generalization of the relevant cycles in undirected graphs. A polynomial time algorithm for the computation of a minimum weight directed circuit basis is outlined. (author's abstract)Series: Preprint Series / Department of Applied Statistics and Data Processing
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Janmark, Jonatan. „Quantum Search on Strongly Regular Graphs“. Thesis, KTH, Teoretisk fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-126266.
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Nossek, Elisabeth [Verfasser]. „Dual strongly perfect lattices / Elisabeth Nossek“. Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/103793539X/34.
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Coles, David. „Polaritions in strongly-coupled organic microcavities“. Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548467.
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Sung, Kyung-Sub. „Turbulent dispersion in strongly stratified turbulence“. Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582577.
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The first part is the derivation of one-particle vertical diffusion for stably stratified turbulence with or without rapid rotation. Nicolleau & Vassilicos (2000) have analytically calculated vertical one-particle diffusion in stably stratified turbulence without rotation. One-particle vertical diffusion for turbulence with stable stratification and with or without rapid rotation has been derived here analytically using the solutions of the linearized equations of motions. The second part is an attempt to explain the depletion of horizontal pair diffusion in strongly stratified turbulence. "Recently, Nicolleau et al. (2005) have shown that in their Kinematic Simulations (KS) of vertically stably and strongly stratified homogeneous turbulence (Froude number smaller than 1). horizontal pair diffusion is significantly depleted by comparison to unstratified isotropic and homogeneous two- and three-dimensional turbulence. We have seeked to explain this depletion of horizontal pair diffusion by vertical stratification in terms of the probability density function of the horizontal divergence of the velocity field and the statistics of stagnation points following the recent approach to Richardson pair diffusion by Davila & Vassilicos (2003), Goto & Vassilicos (2004), Goto et al. (2005) and Osborne et al. (2005). We measure the number density of stagnation points in the KS of three-dimensional strongly stratified turbulence and find that it is virtually identical to what it is in KS of three-dimensional isotropic turbulence The third part is a study of the vertical motions of small, spherical inertial particles in strongly stratified turbulence.
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Moore, Dennis. „HILBERT POLYNOMIALS AND STRONGLY STABLE IDEALS“. UKnowledge, 2012. http://uknowledge.uky.edu/math_etds/2.
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Strongly stable ideals are important in algebraic geometry, commutative algebra, and combinatorics. Prompted, for example, by combinatorial approaches for studying Hilbert schemes and the existence of maximal total Betti numbers among saturated ideals with a given Hilbert polynomial, three algorithms are presented. Each of these algorithms produces all strongly stable ideals with some prescribed property: the saturated strongly stable ideals with a given Hilbert polynomial, the almost lexsegment ideals with a given Hilbert polynomial, and the saturated strongly stable ideals with a given Hilbert function. Bounds for the complexity of our algorithms are included. Also included are some applications for these algorithms and some estimates for counting strongly stable ideals with a fixed Hilbert polynomial.
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Steinbrenner, Todd James. „Citius, Altius, Fortius: faster, higher, stronger“. Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/34747.
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Approved for public release; distribution is unlimitedChinese elite female athletes have experienced extraordinary success in international athletic competitions. Since 1992, elite women athletes have been more represented and successful in the Olympics and National Championships then men; while accounting for less than 50 percent of the elite athletes in China, and competing in less Olympic events, in the Olympics, women were represented in less than 50 percent of the events until 2012. Concisely, the rise of Chinese female athletic participation and success in international competitions has become the backbone for Chinas rise to sports relevance, and has been unlike historical Western nation-states experience in athletics. This historical examination chronologically documents the rise of Chinese elite female athletes and the policies affecting athletes from 1949 to the present, and reveals a connection between female athletic success and state enforced gender equality policies that targeted culture, education, and labor. Through gender equality policies, men and women were uniformly exposed to a national sports system that invested in research, training, equipment, recruitment, and incentivizing athletes to win honors for the country. Moreover, this examination evaluates various hypotheses on what Chinese policies, if any, have produced these extraordinary results, and proposes the sports system, although exceptionally successful, is ultimately imbalanced and plateauing, while the Chinese Communist Party desires participation, power, and control at the expense of possible broad athletic victory.
36
Linkins, Jonathan Matthew. „Global instability in strongly nonhomogeneous systems“. Thesis, University College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428711.
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37
Hart, Ian. „Magnetostriction in strongly correlated electron systems“. Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259584.
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38
Snape, Michael. „Homological invariants of strongly invertible knots“. Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/39015/.
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This thesis explores the relationship between Khovanov homology and strongly invertible knots through the use of a geometric construction due to Sakuma. On the one hand, new homological and polynomial invariants of strongly invertible knots are extracted from Sakuma's construction, all of which are related to Khovanov homology. Conversely, these invariants are used to study the two-component links and annular knots obtained from Sakuma's construction, the latter of which are almost entirely disjoint from the class of braid closures. Applications include the problem of unknot detection in the strongly invertible setting, the efficiency of an invariant when compared with the η-polynomial of Kojima and Yamasaki, and the use of polynomial invariants to bound the size of the intrinsic symmetry group of a two-component Sakuma link. We also define a new quantity, κA, and conjecture that it is an invariant of strongly invertible knots.
39
Kurs, André. „Power transfer through strongly coupled resonances“. Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/45429.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (leaves 41-42).
Using self-resonant coils in a strongly coupled regime, we experimentally demonstrate efficient non-radiative power transfer over distances of up to eight times the radius of the coils. We use this system to transfer 60W with approximately 45% efficiency over distances in excess of two meters. We present a quantitative model describing the power transfer which matches the experimental results to within 5%, and perform a finite element analysis of the objects used. We finally discuss the robustness of the mechanism proposed and consider safety and interference concerns.
by André Kurs.
S.M.
40
Loh, Yen Lee. „Studies of strongly correlated electron systems“. Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615109.
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41
Hofmann, Johannes Benedict. „Exact relations for strongly interacting fermions“. Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648470.
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42
Dimopoulos, Stamatis. „New aspects of strongly compact cardinals“. Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752815.
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43
Franosch, Thomas. „Complex transport in strongly disordered materials“. Diffusion fundamentals 16 (2011) 17, S. 1, 2011. https://ul.qucosa.de/id/qucosa%3A12695.
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44
Dordevic, Sasa V. „Electrodynamics of strongly correlated electron systems /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3044790.
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45
Youssef, Abdelsallam Ebrahim Abdelsallam. „Physical aging in strongly interacting blends“. Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2885.
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Physical aging is the general term used to describe changes in the properties of glassy materials as a function of storage time, at a temperature below the glass transition, Tg. Extensive studies have been carried out on homopolymers and copolymers but fewer investigations have dealt with aging in polymer blends. This Thesis reports a detailed study of physical aging in polymer-polymer mixtures where strong intermolecular interactions are active between components. Miscible blends incorporating poly(4-hydroxystyrene) (P4HS) or styrene-co-4- hydroxystyrene (SHS) and poly(ethyl methacrylate) , poly(ethylene oxide) , poly(4- vinylpyridine) and poly(methyl methacrylate) were prepared. Fourier transform infrared spectroscopy was used to extract qualitative and quantitative information on the strength and number of hydrogen bonds. The effect of temperature and dilution of the hydrogen bonding sites is discussed and a comparison made between different systems. Enthalpic relaxation data for a series of homopolymers and copolymers, including poly(methyl methacrylate-co-ethyl methacrylate), and blends incorporating P4HS and SHS were collected and analysed using Cowie-Ferguson relaxation model. It is found that the enthalpic relaxation for all P4HS and SHS blends increases upon increasing hydrogen bonding strength between the components. The relaxation rate also increases with increasing strength of interaction as well as chain rigidity. Average activation energies were calculated of all homopolymers, copolymers and blends under study. This parameter is shown to be correlated to polymer structure and polymer-polymer interactions and it is therefore useful to compare the aging behaviour of different systems.
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Franosch, Thomas. „Complex transport in strongly disordered materials“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184699.
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Ramos, Igor Rochaid Oliveira. „Study of strongly correlated colloidal systems“. reponame:Repositório Institucional da UFC, 2014. http://www.repositorio.ufc.br/handle/riufc/11286.
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RAMOS, Igor Rochaid Oliveira. Study of strongly correlated colloidal systems. 2014. 113 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2014.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-04-09T20:37:08Z No. of bitstreams: 1 2014_tese_iroramos.pdf: 4160505 bytes, checksum: 1c5b95406b1be080fece98a7bc0bf05a (MD5)
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This thesis presents the study of the structural and dynamical properties, as well as, melting of colloidal systems. Initially, we study the structure and phonon spectrum of a system of charged magnetic dipoles, organized in a bilayer structure and oriented perpendicular to the plane of the layers. This system can be tuned through six different crystalline phases by changing parameters such as the interlayer separation and/or the charge and/or dipole moment of the particles. The presence of the electric charge on the dipole particles is responsible for the nucleation of five staggered phases and a disordered phase which are not found in the magnetic dipole bilayer system previously presented in the literature. These extra phases are a consequence of the competition between the repulsive Coulomb and the attractive dipole interlayer interaction. The minimum energy structures are summarized in a phase diagram associated to the separation between the layers and to the relative importance between the magnetic and electric interactions. We determine the order of the structural phase transitions. The phonon spectrum of the system was calculated within the harmonic approximation. A non-monotonic behavior of the phonon spectrum is found as a function of the effective strength of the inter-particle interaction. The thermodynamic stability of the different phases is determined. Then, we study the bilayer system of charged magnetic dipoles for nonzero temperatures, investigating the melting behavior of the system through the modified Lindemann criterion, as a function of the parameters: (i) the distance between the layers η and (ii) the relative intensity of the magnetic interaction with respect to the electric interaction λ. For large enough λ, one of the phases (the matching hexagonal phase) exhibits a re-entrant melting behavior as a function of η. Since the charges and the magnetic dipole moment of the colloidal particles can be altered, for example, by changing the pH of the solution in which they are immersed or an external magnetic field, respectively, this system can be in principle verified experimentally. Last, a two-dimensional (2D) binary colloidal system consisting of interacting dipoles is investigated. Within the harmonic approximation, we obtained the phonon spectrum of the system as a function of the composition, dipole moment ratio and mass ratio between the small and big particles. Through a systematic analysis of the phonon spectra, we are able to determine the stability region of the different lattice structures of colloidal alloys. The gaps in the phonon frequency spectrum, the optical frequencies in the long-wavelength limit and the sound velocity are discussed as well. Using the modified Lindemann criterion and within the harmonic approximation, we estimated the melting temperature of the sub-lattice generated by the big particles.
Nesta tese, estudamos as propriedades estruturais e dinâmicas, bem como, a fusão de sistemas coloidais. Inicialmente, abordamos o problema de determinar as estruturas de mínima energia e o espectro de fônons de um sistema de dipolos magnéticos carregados, organizados em uma estrutura de bicamadas e orientados perpendicularmente ao plano das camadas. Este sistema pode ser sintonizado através de seis diferentes fases cristalinas, através da variação de parâmetros tais como a separação entre as camadas e/ou a carga e/ou o momento de dipolo das partículas. A presença de carga elétrica nas partículas dipolares é responsável pela nucleação de cinco fases onde as camadas não estão alinhadas verticalmente e uma fase desordenada, que não são encontradas no sistema em bicamadas de dipolos magnéticos previamente apresentado na literatura. Estas fases extras são uma consequência da competição entre a repulsão coulombiana e a interação atrativa entre os dipolos em diferentes camadas. As estruturas de mínima energia são sumarizadas em um diagrama de fases associado à separação entre camadas e a importância relativa entre as interações elétrica e magnética. Determinamos, ainda, a ordem das transições estruturais entre as várias configurações de mínima energia. O espectro de fônons do sistema foi calculado usando a aproximação harmônica. Um comportamento não-monotônico do espectro de fônons é encontrado como função da interação efetiva entre as partículas. A estabilidade termodinâmica das diferentes fases é determinada. Em seguida, estudamos o sistema de bicamadas de dipolos magnéticos carregados para temperaturas diferentes de zero, investigando a fusão do sistema através do critério de Lindemann modificado, em função dos parâmetros: (i) a distância entre as camadas η e (ii) a intensidade relativa da interação magnética com respeito à interação elétrica λ. Para λ suficientemente grande, uma das fases (a fase hexagonal com alinhamento vertical) exibe um comportamento reentrante na temperatura de fusão em função de η. Uma vez que a carga e o momento de dipolo magnético das partículas coloidais pode ser alterado, por exemplo, pela variação do pH da solução na qual estão imersos e por um campo magnético externo, respectivamente, este sistema pode ser em princípio verificado experimentalmente. Por último, um sistema bidimensional (2D) coloidal binário consistindo de dipolos interagentes é investigado. Dentro da aproximação harmônica, calculamos o espectro de fônons do sistema em função da composição, da razão entre os momentos de dipolo e da razão entre as massas das partículas pequenas e grandes. Através de uma análise sistemática dos espectros de fônons, determinamos a região de estabilidade das diferentes estruturas das ligas coloidais. As lacunas no espectro de frequência dos fônons, as frequências óticas no limite de longos comprimentos de onda e a velocidade do som são também discutidos. Usando o critério de Lindemann modificado e dentro da aproximação harmônica, estimamos a temperatura de fusão da sub-rede gerada pelas partículas grandes.
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Liu, Daerhan. „Novel Strongly Coupled Magnetic Resonant Systems“. FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3717.
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Wireless power transfer (WPT) technologies have become important for our everyday life. The most commonly used near-field WPT method is inductive coupling, which suffers from low efficiency and small range. The Strongly Coupled Magnetic Resonance (SCMR) method was developed recently, and it can be used to wirelessly transfer power with higher efficiency over a longer distance than the inductive coupling method.
This dissertation develops new SCMR systems that have better performance compared to standard SCMR systems. Specifically, two new 3-D SCMR systems are designed to improve the angular misalignment sensitivity of WPT systems. Their power transfer efficiency for different angular misalignment positions are studied and analyzed. Prototypes are built for both systems and their performance is validated through measurement. Furthermore, new planar broadband conformal SCMR (CSCMR) systems are developed that maintain high efficiency while providing significantly larger bandwidth than standard CSCMR systems. Such broadband CSCMR systems are used here for the first time to simultaneously accomplish highly efficient wireless power transfer and high data rate communication through the same wireless link. These systems that combine wireless power and communication are expected to enable next-generation applications with battery-less and “power-hungry” sensors. Example applications include implantable and wearable sensors as well as embedded sensors for structural health monitoring.
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Vernon, Kristy C. „Strongly localised plasmons in metallic nanostructures“. Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/19318/2/Kristy_Vernon_Citation.pdf.
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Strongly localised plasmons in metallic nano-structures offer exciting characteristics for guiding and focusing light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved resolution of optical microscopy. The work presented in this thesis focuses on two major areas of plasmonics research - nano-focusing structures and nano-sized waveguides. Nano-focusing structures focus light to an area smaller than the wavelength and will find applications in sensing, efficiently coupling light to nano-scale devices, as well as improving the resolution of near field microscopy. In the past the majority of nano-focusing structures have been nano-scale cones or tips, which are capable of focusing light to a spot of nano-scale area whilst enhancing the light field. The alternatives are triangular nano-focusing structures which have received far less attention, and only one type of triangular nano-focusing structure is known – a sharp V-groove in a metal substrate. This structure focuses light to a strip of nano-scale width, which may lead to new applications in microscopy and sensing. The difficulty with implementing the V-groove is that the structure is not robust and is quite difficult to fabricate. This thesis aims to develop new triangular nano-focusing devices which will overcome these difficulties, whilst still producing an intense light source on the nano-scale. The two proposed structures presented in this thesis are a metallic wedge submerged in uniform dielectric and a tapered metal film lying on a dielectric substrate, the latter being the easier to fabricate and the more structurally sound and robust. The investigation is performed using the approximation of continuous electrodynamics, the geometrical optics approximation and the zero-plane method. The second aim of this thesis is to investigate plasmonic waveguides and couplers for the development of nano-optical circuitry, more compact photonic devices and sensors. The research will attempt to fill the gaps in the current knowledge of the V-groove waveguide, which consists of a sharp triangular groove in a metal substrate, and the gap plasmon waveguide, which consists of a rectangular slot in a thin metal film. The majority of this work will be performed using the author’s in house finite-difference time-domain algorithm and FEMLAB as well as the effective medium method and geometric optics approximation. The V-groove may be used as either a nano-focusing or waveguiding device. As a waveguide the V-groove is one of the most promising plasmonic waveguides in the optical regime. However, there exist quite a number of gaps in the current knowledge of V-groove waveguides which this thesis will attempt to fill. In particular, the effect of rounded groove tip on plasmon propagation has been assessed for the V-groove. The investigation of rounded groove tip is important, as due to modern fabrication processes it’s not possibly to produce an infinitely sharp groove, and the existing literature has not considered the impact of this problem. The thesis will also investigate the impacts of the inclusion of dielectric filling in the groove on plasmon propagation parameters. This research will be important for optimising the propagation characteristics of the mode for certain applications, but it may also lead to easier methods of fabricating the V-groove device and prevent oxidation of the metal film. The gap plasmon waveguide is easier to fabricate than the V-groove, and is a new type of sub-wavelength waveguide which displays many advantages over other types of plasmon waveguides, including ease of fabrication, almost 100% transmission around sharp bends, sub-wavelength localisation and long propagation distances of the guided mode, etc. This waveguide may prove invaluable in the development of compact photonic devices. In the past the modes supported by this structure were not thoroughly analysed and the possibility of using this structure to develop sub-wavelength couplers for sensing and nano-optical circuits was not considered in detail. This thesis aims to resolve these issues. In conclusion, the results of this thesis will lead to a better understanding of Vgroove and gap plasmon waveguide devices for the development of nano-optical circuits, compact photonic devices and sensors. This thesis also proposes two new nano-focusing structures which are easier to fabricate than the V-groove structure and will lead to applications in sensing, coupling light efficiently into nano-scale devices and improving the resolution of near-field microscopy.
50
Vernon, Kristy C. „Strongly localised plasmons in metallic nanostructures“. Queensland University of Technology, 2008. http://eprints.qut.edu.au/19318/.
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Strongly localised plasmons in metallic nano-structures offer exciting characteristics for guiding and focusing light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved resolution of optical microscopy. The work presented in this thesis focuses on two major areas of plasmonics research - nano-focusing structures and nano-sized waveguides. Nano-focusing structures focus light to an area smaller than the wavelength and will find applications in sensing, efficiently coupling light to nano-scale devices, as well as improving the resolution of near field microscopy. In the past the majority of nano-focusing structures have been nano-scale cones or tips, which are capable of focusing light to a spot of nano-scale area whilst enhancing the light field. The alternatives are triangular nano-focusing structures which have received far less attention, and only one type of triangular nano-focusing structure is known – a sharp V-groove in a metal substrate. This structure focuses light to a strip of nano-scale width, which may lead to new applications in microscopy and sensing. The difficulty with implementing the V-groove is that the structure is not robust and is quite difficult to fabricate. This thesis aims to develop new triangular nano-focusing devices which will overcome these difficulties, whilst still producing an intense light source on the nano-scale. The two proposed structures presented in this thesis are a metallic wedge submerged in uniform dielectric and a tapered metal film lying on a dielectric substrate, the latter being the easier to fabricate and the more structurally sound and robust. The investigation is performed using the approximation of continuous electrodynamics, the geometrical optics approximation and the zero-plane method. The second aim of this thesis is to investigate plasmonic waveguides and couplers for the development of nano-optical circuitry, more compact photonic devices and sensors. The research will attempt to fill the gaps in the current knowledge of the V-groove waveguide, which consists of a sharp triangular groove in a metal substrate, and the gap plasmon waveguide, which consists of a rectangular slot in a thin metal film. The majority of this work will be performed using the author’s in house finite-difference time-domain algorithm and FEMLAB as well as the effective medium method and geometric optics approximation. The V-groove may be used as either a nano-focusing or waveguiding device. As a waveguide the V-groove is one of the most promising plasmonic waveguides in the optical regime. However, there exist quite a number of gaps in the current knowledge of V-groove waveguides which this thesis will attempt to fill. In particular, the effect of rounded groove tip on plasmon propagation has been assessed for the V-groove. The investigation of rounded groove tip is important, as due to modern fabrication processes it’s not possibly to produce an infinitely sharp groove, and the existing literature has not considered the impact of this problem. The thesis will also investigate the impacts of the inclusion of dielectric filling in the groove on plasmon propagation parameters. This research will be important for optimising the propagation characteristics of the mode for certain applications, but it may also lead to easier methods of fabricating the V-groove device and prevent oxidation of the metal film. The gap plasmon waveguide is easier to fabricate than the V-groove, and is a new type of sub-wavelength waveguide which displays many advantages over other types of plasmon waveguides, including ease of fabrication, almost 100% transmission around sharp bends, sub-wavelength localisation and long propagation distances of the guided mode, etc. This waveguide may prove invaluable in the development of compact photonic devices. In the past the modes supported by this structure were not thoroughly analysed and the possibility of using this structure to develop sub-wavelength couplers for sensing and nano-optical circuits was not considered in detail. This thesis aims to resolve these issues. In conclusion, the results of this thesis will lead to a better understanding of Vgroove and gap plasmon waveguide devices for the development of nano-optical circuits, compact photonic devices and sensors. This thesis also proposes two new nano-focusing structures which are easier to fabricate than the V-groove structure and will lead to applications in sensing, coupling light efficiently into nano-scale devices and improving the resolution of near-field microscopy.