To see the other types of publications on this topic, follow the link: 1. Plasmid.
Dissertations / Theses on the topic '1. Plasmid'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic '1. Plasmid.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Abai, Anna Maia. "Gene therapy for type 1 diabetes mellitus : insulin delivery using plasmid DNA." Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412398.
Full text
2
Harrison, Eleanor. "Evolution of a selfish genetic element : the 2 micron plasmid of saccharomyces spp." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6068.
Full textAbstract:
The 2 Micron plasmid is a multicopy DNA circle inhabiting the genome of the budding yeasts, Sacchormyces spp. The plasmid confers no known benefits to the host, but imposes a small fitness cost. However the plasmid is able to drive, i.e. to transmit to >50% of sexual offspring, which allows the element to spread through an outcrossing host population. Therefore we can consider the plasmid a selfish genetic element of yeast. Here we draw on a number of approaches to improve our understanding of this element. Firstly, we examined the relationship between the cost of plasmid carriage and copy number by experimentally manipulating the number of plasmids in the host. We find that host fitness decreases at a rate of ~0.09% per additional plasmid. Secondly we use experimentally evolving yeast populations to test the hypothesis that sexual reproduction, which is fundamental to the evolution of selfish genetic elements, will drive increasing virulence in the plasmid. We find that 2 Micron copy number increased in outcrossing populations but remained constant in asexual populations. We also find that sex allowed the invasion of non-functional mitochondria in to the populations, showing that sex has the capacity to generate a driving selfish genetic element from one of the most fundamental endosymbionts of the eukaryotic cell. In addition, we have investigated plasmid variation from global populations of Saccharromyces spp. in order to better understand the population biology and evolution of this plasmid. Here we find evidence that the plasmid is able to move between species, recombine with other plasmids within the cell, and exist at a surprisingly wide range of copy numbers in different host populations. Understanding the population structure and evolution of this element allows us to view the plasmid as an autonomous unit evolving in its own right in the genomes of its hosts.
3
Seco, Bruna Mara Silva. "Persistência de plasmídeos que codificam carbapenemases do tipo New-Delhi-Metalo-β-Lactamase." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-28042016-101448/.
Full textAbstract:
As metalo-β-lactamases (MBL) são capazes de hidrolisar os carbapenêmicos, a classe de antimicrobianos com maior potência para o tratamento de infecções graves e de maior uso clinico. Dentre as MBL, o grupo mais recentemente descrito e que apresentou rápida disseminação em todo o mundo é o da New-Delhi-Metalo- β-lactamases (NDM). Nas enterobactérias, os genes que codificam essas enzimas estão mais frequentemente localizados em plasmídeos. O estudo da estabilidade de plasmídeos que albergam o gene blaNDM-1 é importante para entender a predominância de espécies que carregam esses plasmídeos, desvendar mecanismos moleculares envolvidos na sua persistência e para desenvolver novas drogas que possam diminuir a sua persistência. Estudos recentes sobre estabilidade plasmidial evidenciaram que a maprotilina é capaz de induzir perda plasmidial de até 90% em E. coli K12. Neste trabalho, foi estudado o efeito da maprotilina na indução de cura de plasmídeos, que albergam o gene blaNDM-1, em diferentes espécies da família Enterobacteriaceae. Nove isolados pertencentes a diferentes espécies foram incluídas no estudo. Os plasmídeos foram caracterizados quanto ao seu tamanho por eletroforese e por sequenciamento de DNA no sistema Illumina. A persistência plasmidial foi determinada pelo método de contagem em placa em LB ágar com e sem tratamento com maprotilina em concentrações sub-inibitórias (50mg/L). O experimento foi conduzido por 10 dias, representando aproximadamente 100 gerações. Neste estudo evidenciou-se que o grupo das enterobactérias estão envolvidas na disseminação de plasmídeos com blaNDM-1, sendo que plasmídeos do grupo IncF estão mais relacionados a essa dispersão. A maprotilina teve efeito de cura plasmidial em todos os isolados exceto em E. hormaechei \"subsp. oharae\" e C. freundii. O isolado P. rettgeri apresentou maior taxa de perda plasmidial e a análise comparativa da sequência nucleotídica do plasmídeo indicou que a presença da IS5 pode estar relacionada com a diminuição da persistência plasmidial. Diferenças na persistência plasmidial, quando tratados com maprotilina, entre E. hormaechei \"subsp. steigerwaltii\" e E. hormaechei \"subsp. oharae\" sugerem que E. hormaechei \"subsp. oharae\" pode ser um possível disseminador de plasmídeos albergando blaNDM-1, devido a processos de adaptação co-evolutivos.<br>Metallo- β-lactamases (MBL) are able to hydrolase carbapenems, an antimicrobial class in clinical use with high potency in the treatment of severe infections. The most recently decribed group of MBL is the New-Delhi-Metallo-β-lactamases (NDM). This group is mostly correlated to the spread of resistance mediated by plasmid in Enterobacteriaceae. Understanding the plasmid persistence pattern is important in order to understand the predominance of a given species related to antimicrobial resistance plasmids spread, to unveil molecular mechanisms involved in the increase of plasmid persistence and to develop new drugs which could decrease its persistence. Recent studies have associated maprotiline to a decrease in 90% of plasmid persistence in E. coli K12. In this work, we evaluated the effect of maprotiline in curing plasmids carrying blaNDM-1 in different species of Enterobacteriaceae. Nine isolates belonging to different species were evaluated. Plasmids were characterized by agarose gel electrophoresis and by DNA sequencing with Illumina platform. The plate counting method was used to determine plasmid persistence, with and without sub-inhibitory (50 mg/L) concentration of maprotiline during 10 days, representing approximately 100 generations. We found that Enterobacteriaceae are involved in the spread of NDM-1 plasmid-mediate resistance and the IncF group is the plasmid incompatibility group more frequently involved in this dissemination. Maprotiline showed a plasmid-curing effect in all isolates, except against plasmids of E. hormaechei \"subsp. oharae\" and C. freundii. The P. rettgeri isolate had the highest plasmid-curing rate. Sequencing analysis revealed an IS5 in the plasmid, which could be associated to a decrease in plasmid persistence. The difference between plasmid persistence pattern of plasmids isolated from E. hormaechei \"subsp. steigerwaltii\" and E. hormaechei \"subsp. oharae\", when treated with maprotiline, suggest that E. hormaechei \"subsp. oharae\", could be associated to the spread of plasmids carrying blaNDM-1 due to co-evolution adaptation.
4
Shirley, Matt, and n/a. "Characterisation of an 84 kb linear plasmid that encodes DDE cometabolism in Terrabacter sp. strain DDE-1." University of Otago. Department of Microbiology & Immunology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20060804.094902.
Full textAbstract:
DDT, an extremely widely used organochlorine pesticide, was banned in most developed countries more than 30 years ago. However, DDT residues, including 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE), still persist in the environment and have been identified as priority pollutants due to their toxicity and their ability to bioaccumulate and biomagnify in the food chain. In particular, DDE was long believed to be "enon-biodegradable"e, however some microorganisms have now been isolated that are able to metabolise DDE in pure culture. Terrabacter sp. strain DDE-1 was enriched from a DDT-contaminated agricultural soil from the Canterbury plains and is able to metabolise DDE to 4-chlorobenzoic acid when induced with biphenyl. The primary objective of this study was to identify the gene(s) responsible for Terrabacter sp. strain DDE-1�s ability to metabolise DDE and, in particular, to investigate the hypothesis that DDE-1 degrades DDE cometabolically via a biphenyl degradation pathway. Catabolism of biphenyl by strain DDE-1 was demonstrated, and a biphenyl degradation (bph) gene cluster containing bphDA1A2A3A4BCST genes was identified. The bphDA1A2A3A4BC genes are predicted to encode a biphenyl degradation upper pathway for the degradation of biphenyl to benzoate and cis-2-hydroxypenta-2,4-dienoate and the bphST genes are predicted to encode a two-component signal transduction system involved in regulation of biphenyl catabolism. The bph gene cluster was found to be located on a linear plasmid, designated pBPH1. A plasmid-cured strain (MJ-2) was unable to catabolise both biphenyl and DDE, supporting the hypothesis that strain DDE-1 degrades DDE cometabolically via the biphenyl degradation pathway. Furthermore, preliminary evidence from DDE overlayer agar plate assays suggested that Pseudomonas aeruginosa carrying the strain DDE-1 bphA1A2A3A4BC genes is able to catabolise DDE when grown in the presence of biphenyl.
A second objective of this study was to characterise pBPH1. The complete 84,054-bp sequence of the plasmid was determined. Annotation of the DNA sequence data revealed seventy-six ORFs predicted to encode proteins, four pseudogenes, and ten gene fragments. Putative functions were assigned to forty-two of the ORF and pseudogenes. Besides biphenyl catabolism, the major functional classes of the predicted proteins were transposition, regulation, heavy metal transport/resistance, and plasmid maintenance and replication. It was shown that pBPH1 has the terminal structural features of an actinomycete invertron, including terminal proteins and terminal inverted repeats (TIRs). This is the first report detailing the nucleotide sequence and characterisation of a (linear) plasmid from the genus Terrabacter.
5
Kapoor, Priya. "Reconstitution of Epstein-Barr nuclear antigen 1 (EBNA1)-mediated plasmid segregation in budding yeast requires human EBP2." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63132.pdf.
Full text
6
McCray, Andrea Nicole. "Electrogenetherapy of established B16 murine melanoma by using an expression plasmid for HIV-1 viral protein R." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001758.
Full text
7
Maria, Adriana Del Monaco de. "Subclonagem, expressão e purificação da enzima hialuronidase-1, variante 8, humana." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/9/9136/tde-25032014-105024/.
Full textAbstract:
O Ácido Hialurônico, HA, é um dos principais componentes da matriz extracelular dos vertebrados. É um glicosaminoglicano hidrolisado pelas enzimas da família da Hialuronidase, envolvidas na regulação de importantes processos biológicos, como a permeabilidade vascular e a angiogênese. Conforme o interesse pelo desenvolvimento de uma rota de síntese para esta enzima, objetivamos a obtenção de um plasmídeo, contendo a sequência que codifica a variante 8 do gene Hyal-1. Para isto, planejou-se a inserção de dois sítios de restrição para a sub-clonagem, sítio dirigida, BamH-1 na região 5\' e Not-1 na 3\' na sequência do códon da Hyal-1. O inserto foi sub-clonado no plasmídeo, pET28-a, e transfectado para expressão em Escherichia coli Bl-21. A expressão foi induzida por IPTG no melhor tempo, de 4 horas, e a confirmação da expressão protéica foi realizada por Western blotting. Observou-se uma proteína de 45 kDa, confirmando a presença da Hyal-1. Realizou-se a expressão em 4 litros de cultura para obtenção de uma quantia suficiente para purificação em coluna de níquel-agarose. O rendimento neste experimento foi de 25µg por litro. A rota sintética sugerida neste estudo mostrou-se eficiente para obtenção da proteína Hyal-1 recombinante, justificando futuros investimentos na otimização deste processo<br>Hyaluronic Acid, HA is a major component of the extracellular matrix of vertebrates. It is a glycosaminoglycan hydrolyzed by enzymes of the hyaluronidase family, involved in the regulation of important biological processes such as angiogenesis and vascular permeability. As interest in the development of a synthesis route for this enzyme, we aim to obtain a plasmid containing the coding sequence of the gene variant 8 Hyal-1. To obtain the plasmid insert was planned and two restriction sites for sub-cloning site directed at the 5\' Bam H-1 and 3\' Not-1 in codon sequence of Hyal-1. The insert was sub-cloned into plasmid pET28-a, and transfected for expression in Escherichia coli Bl-21. The expression was induced by IPTG in the best time of 4 hours and confirmation of protein expression was performed by Western blotting. There was a 45 kDa protein, thus confirming the presence of Hyal-1. Purification was performed on nickel-agarose column to obtain a larger amount of the protein, approximately 25µg/L. The route suggested in this study was efficient attainment of Hyal-1 recombinant protein.
8
Marusich, Amanda. "Chromosome knock-in vs. plasmid complementation : tagging hydA to investigate Fe-only hydrogenase maturation and assembly in Shewanella oneidensis MR-1 /." May be available electronically:, 2006. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
9
PENIDO, Ana Flávia Batista. "Sequência completa e caracterização do plasmídeo crípico pVCM1 isolado de Salmonella enterica." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/1297.
Full textAbstract:
Made available in DSpace on 2014-07-29T15:16:38Z (GMT). No. of bitstreams: 1
Dissertacao Ana Flavia B Penido.pdf: 829056 bytes, checksum: 63d111404f5b1f9b2d136e54aad128a4 (MD5)
Previous issue date: 2009-03-26<br>Samonella spp are Gram negatives bactérias belonging to Enterobacteriaceae family. S. enterica comprise about 2.500 sorovars. These sorovars can infect a broad range, including poultry, cattle, swins and humans, and are agent causative of salmonellosis an important public health issue worldwide. Small multicopy plasmids are frequently isolated from Gram negatives and Gram positives bacterias. In Salmonella, low molecular weight plasmids are found on 10% of Salmonella strains and their biological functions are unknown. However, many plasmids in Salmonella control important properties, such as, virulence factors, heavy metals and antibiotics resistance, and utilizations of alternative carbon sources. The pVCM1 plasmid was extracted from one strain of Samonella enteretidis isolated from broilers carcass. The strains were grown in liquid or solid Luria-Bertani broth at 37 °C. The plasmid was purified, separated on 1% agarose electrophoresis and visualized by ethidium bromide staining for analysis. Plasmid was digested with EcoRI enzyme and subcloned in the pUC18 vector.The plasmidal stability was evaluated, inoculating E. coli cells transformated with pVCM1 plasmid (cloned in pUC18) in liquid Luria-bertani broth supplemented with ampicillin. The pVCM1 was stable after 240 generations. The total DNA sequence of plasmid pVCM1 has 1981 pb. Genbank search resulted that pVCM1 showed 99% of identity with pB and 92% with pJ, which were isolated from Salmonella enteretidis. Only one ORF founded in pVCM1 showed significative similarity with others proteins of GenBank. The protein encoded by this ORF showed homology to Rep proteins of plasmids that replicates by rolling-circle mechanism. The pVCM1 posses three impotents elements: rep gene, single strand origin (SSO) and inverted repeat sequences. Such elements are importants for the rolling circle replication, suggesting that pVCM1 use this mechanism. The rep gene was amplified and cloned in the pGEMT-easy vector, but the heterologous expression of Rep protein wasn t gotten successfully.<br>Salmonellas ssp são bactérias Gram negativas pertencente a família das enterobácterias. A S. entérica compreende cerca de 2.500 sorovares. Esses sorovares podem infectar vários hospedeiros incluindo aves, bovinos, suínos e humanos, e são os agentes causais das salmoneloses, um importante problema de saúde pública em todo mundo. Múltiplas cópias de pequenos plasmídeos são frequentemente isolados de bactérias Gram negativas e Gram positivas. Nas salmonelas, plasmídeos com baixa massa molecular são encontradas em 10% das linhagens e suas funções biológicas são desconhecidas. Entretanto, muitos plasmídeos de salmonela controlam propriedades importantes, tais como, fatores de virulência, resistência a antibióticos e metais pesados, e utilização de fontes alternativas de carbono. O plasmídeo pVCM1 foi extraído de uma linhagem S. Enteritidis, isoladas de carcaças de frango. Essa linhagem foi crescida em meio Lúria-Bertani líquido e sólido à 37°C. O plasmídeo foi purificado, separado em gel de agarose 1% e visualizado com coloração por brometo de etídio. O plasmídeo foi digerido com EcoRI e subclonado no vetor pUC18. A estabilidade plasmidial foi avaliada inoculando células de E. coli transformadas com plasmídeo pVCM1 (clonado em pUC18) em meio Lúria- bertani líquido suplementado com ampicilina. O pVCM1 foi estável por mais de 240 gerações A sequência nucleotídica total do plasmídeo possui 1981 pb. Pequisa por sequências no GenBank, mostrou que o pVCM1 apresenta similaridade de 99% com o plasmídeo pB e 92% com plasmídeo pJ, os quais foram isolados de S. Enteritidis.Das 11 possíveis ORFS apenas uma única ORF apresentou similaridade significativa com outras proteínas do GenBank. A proteína codificada por essa ORF apresentou homologia com as proteínas Rep de plasmídeos que replicam via círculo rolante. O pVCM1 apresenta três regiões importantes: gene rep, origem de fita simples (SSO) e regiões repetidas invertidas. Tais regiões são importantes para o mecanismo de replicação via círculo rolante, sugerindo que o pVCM1 utilize esse mecanismo. O gene rep foi amplificado e clonado no vetor pGEM T-easy, mas a expressão heteróloga da proteína Rep não foi obtida com sucesso.
10
Mercieca, Kayron. "Plasma spectroscopy in pinch plasmas." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7118.
Full textAbstract:
Magnetic fields play a very important role in the dynamics of plasmas. Through interactions with the ions and electrons within plasmas, their behaviour and evolution can be drastically influenced. It is the Zeeman effect that is responsible for the splitting of radiative lines observed. Zeeman spectroscopy is a tool used for the diagnosis of these magnetic fields within plasmas when the extent of this line splitting is observable. Aluminium is chosen as an element to model as it is easy to place within a pinch plasma. It is also relatively easy to ionise Aluminium into being Hydrogen-like within the conditions of pinch plasmas. The calculation of Lyman Alpha and Lyman Beta spectral lineshapes for a Hydrogen-like Aluminium plasma is presented from a fundamental standpoint. The Stark and Zeeman effects are explored and modelled. Modelling of the former is aided by an adapted version of the APEX code by R. Lee in order to calculate the probability distribution of electric fields around a radiator ion in the plasma. Both effects are calculated together as a quantum perturbation to the π = 1, 2, 3 atomic energy levels including fine structure. The lineshapes resulting from this calculation are compared with H-Line’s models (a code also by R. Lee) and shown to be significantly more detailed, including visible Zeeman splitting for test external magnetic fields of B = 100 T and B = 1000 T. Natural and Doppler broadening are also modelled. These extra broadening effects (in particular Doppler) are shown to be destructive to discernable lineshape detail, largely preventing magnetic field diagnosis through Zeeman spectroscopy. Lastly, Lyman Alpha and Lyman Beta are modelled for plasmas with Z-pinch and X-pinch conditions in order to determine the viability of visible Zeeman line splitting.
11
OLIVEIRA, Vera Lúcia Cardoso de. "Caracterização Molecular Do Plasmídeo pLK39 Extraído De Uma Bactéria Endofítica Isolada De Solanum Lycocarpum." Universidade Federal de Goiás, 2002. http://repositorio.bc.ufg.br/tede/handle/tde/1287.
Full textAbstract:
Made available in DSpace on 2014-07-29T15:16:36Z (GMT). No. of bitstreams: 1
vera.pdf: 2531477 bytes, checksum: 5a02810a0fd91027af8891fb7a147973 (MD5)
Previous issue date: 2002-02-28<br>The characterization of the plasmid pLK39.was the aim of work.pLK39 was isolated from a
endophytic Gram-negative, bactéria isolated from leaves form Solanum lycocarpum
(Lobeira). In order to obtain a selection marker which would characterization in Escherichia
coli the kanamycin, resistence gene from pUC4K. was subcloned into the PstIsite of pLK39.
The characterization of PLK39 was basedon studies of stability, incompatibility,
determination of the copy number and through DNA sequencing. The stability was carried out
in Escherichia coli XL10 cells. Cells transformed with pLK39 were inoculated in Lúria broth
containing Kanamycin (50μg/ml) during24 hours. After 24 hours of incubation one sample of
the culture was in medim with and without selective pressure, and inoculated in Lúria broth
without pressure médium, for 240 generations. After 240 generations 81,5% of cells
maintained the plasmid, showing that pLK39is highly stable in Escherichia coli to make the
incompatibility test, cells of Escherichia coli XL10 were co-transformed with pLK39/pUC18;
pBR322 and pLK39/pACYC184. After 240 generations, the plasmid pLK39 iof detected in
all systems used, showing the compatibility of pLK39 with the plasmids tested. The copý
number pLK39 was estimated by the intensity of plasmidial bands in agarose gel,
electrophoresis using a photodocumentation and analysis system (KODAK EDAS). The copý
number of pLK39 was estimated as 25 copies per cell. PLK39 was digested with Sau3AI
restriction and subcloned into the BamHI site of plasmid pUC18. The recombinant clones
were sequenced and 1637 pb reading fragment was obtained. This sequence showed high
homology with pSW200, pSW100, pEC3, pUCD5000 and pBERT, which were isolated from
Gram-negative bacteria. This sequence possesses two possible genes. The ORF I showed high
homology with mobB gene from plasmid pSW200 (96%), pSW100 (96%), pEC3 (94%),
pUCD5000 (94%) and pBERT (87%). The ORF II showed homology with mobD gene from
plasmids pSW200 (92%), pSW100 (90%), pEC3 (90%) and PUCD5000 (89%).<br>O objetivo deste trabalho foi caracterizar o plasmídeo pLK39. Este plasmídeo foi extraído de
uma bactéria endofítica Gram-negativa, isolada da folha de Solanum Lycocarpum (Lobeira).
Este plasmídeo apresenta um tamanho de aproximadamente 4,5 kb. Visando obter uma marca
de seleção para permitir sua caracterização em células de Escherichia coli, foi introduzido o
gene de resistência à Kanamicina, extraído do plasmídeo pUC4K. A caracterização do pLK39
foi realizada através de estudos de estabilidade, incompatibilidade, estimativa do número de
cópias e através de seqüenciamento de parte do plasmídeo. A estabilidade foi testada em
células de Escherichia coli XL10. Células transformadas com pLK39 foram cultivadas em
meio Lúria suplementado com Kanamicina (50 μg/mL) durante 24 horas uma amostra da
cultura era plaqueada em meio seletivo e em meio sem pressão seletiva parte dessa amostra
foi inoculada em meio Lúria sem pressão seletiva e incubado por 24 até atingir 240 gerações.
Após 240 gerações 81.5% das células mantiveram o plasmídeo, mostrando que o pLK39 é
bastante estável em células de Escherichia coli. Para realização do teste de incompatibilidade,
células de Escherichia coli XL10 foram co-transformadas com os plasmídeos pLK39/pUC18,
pLK39/pBR322 e pLK39/pACYC184. Após 240 gerações, foi detectada a presença do
plasmídeo pLK39 em todos os sistemas testados, demonstrando a compatibilidade do pLK39
com os plasmídeos testados. O número de cópias do pLK39 foi estimado através da
comparação da intensidade das bandas plasmidiais, obtidas através de eletroforese em gel de
agarose, realizada a partir de uma extração de plasmídeos de células de Escherichia coli XL10
transformadas com pUC18, pBR322 e pLK39. A quantificação de cada banda foi realizada
utilizando o sistema de fotodocumentação e analise (KODAK EDAS). O número de cópias do
pLK39 foi estimado em 25 cópias por células. O plasmídeo pLK39 foi digerido com enzima
de restrição Sau3AI e sub-clonado no sítio de BamHI do plasmídeo pUC18. Os clones
recombinantes foram seqüenciados. Foi obtido um fragmento com 1.637 pb. Essa seqüência
apresentou uma grande homologia com os plasmídeos pSW200, pSW100, pEC3, pUCD5000
e pBERT, os quais foram isolados de diferentes bactérias Gram-negativas. A seqüência
apresentou dois possíveis genes. A ORF I apresentou grande homologia com o gene mobB
dos plasmídeos pSW200 (96%), pSW100 (96%), pEC3 (94%), pUCD5000 (94%) e pBERT
(87%). A ORF II apresentou homologia com o gene mobD dos plasmídeos pSW200 (92%),
pSW100 (90%), pEC3 (90%) e PUCD5000 (89%).
12
CARNEIRO, Lílian Carla. "Caracterização do plasmídeo pVCM 04 extraídos de Salmonella enterica isolada de carcaçãs de frangos." Universidade Federal de Goiás, 2010. http://repositorio.bc.ufg.br/tede/handle/tde/1010.
Full textAbstract:
Made available in DSpace on 2014-07-29T15:10:31Z (GMT). No. of bitstreams: 1
Lilian CARLA CARNEIRO Tese.pdf: 936824 bytes, checksum: e49c7ff122a0392ea9e5120fd05064ed (MD5)
Previous issue date: 2010-05-31<br>A small cryptic plasmid isolated from Salmonella enterica Enteritidis called pVCM04 was
sequenced and characterizated. pVCM04 is a 3583 pb circle molecule that showed no
homology with other plasmids deposited in the GenBank. 12 ORF with more than 50
aminoacids were predicted using the ORF finder program. ORF1 and ORF2 showed
homology with replication proteins of different plasmids. ORF 3-5 showed homology with
mobilization proteins present in several plasmids; the others seven ORF showed no
homology with genes deposited in GenBank. The pVCM04 possess a region with more
than 500 pb that is not associated with none of the predicted proteins. This region is
organizated in a G+C rich, A+T rich and two repeat direct sequences. The second repeat
direct sequence contains a region of DnaA box connection (TTTACAC). This region is
probably associated to the replication origin theta type. The phylogenetic relationship
among replicase and mobilization deduced protein showed highest similarity of replicase
proteins than mobilization proteins. Conjugation experiments showed that the
pVCM04/pUC18 fusion not have a good ability to transfer, the plasmid stability test
showed that the cells lost 60% of pVCM04/pUC18 on the first day of cultivation. The
characterization suggests that the pVCM04 probably would be a cryptic plasmid from
fusion of different ancestral plasmid.<br>Um pequeno plasmídeo críptico isolado de Salmonella enterica Enteretidis denominado
pVCM04 foi sequênciado e caracterizado. O pVCM04 é uma molécula circular com 3583
pb a qual não apresenta homologia com outros plasmídeos depositados no GenBank . 12
ORF ( Open Read Frame ) com mais de 50 aminoácidos foram preditas usando o
programa ORFinder. A ORF1 e a ORF2 apresentaram homologia com proteínas de
replicação de diferentes plasmídeos. As ORF 3, 4 e 5 apresentaram homologia com
proteínas de mobilização presente em vários plasmídeos; as outras sete ORF não
apresentaram homologia com genes depositados no GenBank . O pVCM04 possui uma
região, com mais de 500 pb, que não está associada a nenhuma das proteínas preditas. Esta
região está organizada em uma sequência rica em G+C, A+T e duas sequências repetidas
diretas. A segunda sequência repetida direta contém uma sequência de ligação para a
proteína DnaA (TTTACAC). Esta região está provavelmente associada com a origem de
replicação do tipo theta. As relações filogenéticas para as proteínas deduzidas replicase e de
mobilização mostraram maior similaridade para proteínas replicase do que para proteínas
de mobilização. Experimentos de conjugação evidenciaram que a fusão pVCM04⁄pUC18
não possui uma boa capacidade de transferência; o teste de estabilidade plasmidial
demonstrou que as células perdem 60% do pVCM04⁄pUC18 no primeiro dia de cultivo. A
caracterização do pVCM04 sugere que este plasmídeo provavelmente seja um plasmídeo
críptico oriundo de diferentes ancestrais.
13
Gonsales, Fernanda Fidelis. "Ocorrência de Chlamydophila felis e do plasmídeo críptico em gatis nas cidades de São Paulo e Osasco." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/10/10134/tde-09092014-153345/.
Full textAbstract:
A infecção de trato respiratório superior em gatos é uma afecção muito frequente em indivíduos que vivem em abrigos, com elevada morbidade e em alguns casos, fatal. O herpesvírus felino tipo1 (FHV-1) e a Chlamydophila felis estão entre os principais causadores. O FHV-1 ocasiona quadros de espirros, secreção nasal e alterações oculares como conjuntivite. A C. felis é responsável pelos piores casos de conjuntivite e apresenta um plasmídeo críptico como possível fator de virulência. A presença dos retrovírus da leucemia felina (FeLV) e/ou imunodeficiência dos felinos (FIV) debilita a função do sistema imunológico, causando imunossupressão e consequentemente aumento no índice de morbidade e mortalidade. Neste trabalho foram avaliados quatro abrigos, três gatis particulares não-comercias (um localizado em Osasco/SP e outros dois São Paulo/SP). Os gatis possuiam alta densidade populacional e a procedência dos gatos alojados era desconhecida. A detecção de FHV-1, como de C. felis e de três genes do plasmídeo criptico foram realizadas por PCR em amostras de mucosa oral e de conjuntiva ocular de ambos os olhos obtidas com swabs de algodão, secos e estéreis. Amostras de sangue foram coletadas para a detecção do FIV e FeLV por meio de teste imunoenzimático. O sintomas clínicos dos animais foram classificados de 1 a 4, sendo 4 atribuído àqueles que apresentavam pior sintomatologia. A ocorrência de FIV e FeLV no 1° gatil foi de 4,63% e 3,70%, no 2° gatil foi de 0% e 6,45%, enquanto que no 3° gatil foi 75% e 0% respectivamente, estes vírus não foram detectados no 4° gatil. FHV-1 foi observado em 61,11% dos gatos no 1° gatil; 90,32% no 2° gatil, 100% no 3° gatil e em 89,74% dos animais do 4° gatil. No 1° gatil, 7,41% das amostras apresentavam C. felis, no 2° gatil, 58,06%; no 4° gatil, 23,08%; enquanto que no 3° gatil o agente não foi detectado. Dentre as amostras positivas para C. felis, os genes do plasmídeo críptico foram detectados; no 1o gatil o gene 1 estava presente em 62,50% das amostras, o gene 2 e 3 em 75%, para o 2° gatil obteve-se 61,11% de positividade para os genes 1 e 2 e 55,56% para o gene 3; no 4° gatil o gene 1 e 3 estavam presentes em 77,78% das amostras, o gene 2 em 55,56%. Os óbitos relatados no período do estudo foram de animais classificados com sintomas 3 ou 4 e positivos para C. felis e para o plasmídeo críptico. No presente trabalho foi observada uma elevada ocorrência de C. felis e de seu plasmídeo críptico, apesar da baixa ocorrência de FIV e FeLV nos gatis.<br>The infection of upper respiratory disease in cats is very common in individuals that living in shelters, with high morbidity, and in some cases, fatal. The feline herpesvirus type 1 (FHV- 1) and Chlamydophila felis are agents the main causes. The FHV- 1 causes sneezing, nasal discharge and ocular abnormalities such as conjunctivitis. The C. felis is responsible for the worst cases of conjunctivitis and features a cryptic plasmid as a possible virulence factor. The presence of the feline leukemia virus (FeLV) and/or vírus of feline immunodeficiency (FIV) weaken the function of the immune system, causing immunosuppression and therefore increased morbidity and mortality. This study evaluated four shelters, three catteries private non-commercial (one located in Osasco/SP and two in São Paulo/SP). Catteries possessed high population density and cats housed origin was unknown. The detection of FHV- 1 as three genes of the C. felis and cryptic plasmid was performed by PCR in oral mucosa and the ocular conjunctiva of both eyes obtained with cotton swabs, dried and sterile. Blood samples were collected for the detection of FeLV and FIV by enzyme immunoassay. The clinical symptoms of animals were classified from 1 to 4 , with 4 assigned to worst symptoms. The presence of the FIV and FeLV was in the first cattery 4.63% and 3.70%, in the second cattery was 0% and 6.45%, while in the third cattery was 75% and 0%, respectively, these viruses do not were detected in the 4th cattery. FHV- 1 was observed in 61.11 % of the cats in the first cattery; 90.32 % in the second cattery 100 % in the third and 89.74% of the animals of the fourth cattery. In the first cattery, 7.41% of the samples had C. felis, the second cattery, 58.06 %, in the fourth cattery, 23.08%, while the third cattery the agent was not detected. Among the samples positive for C. felis genes were detected cryptic plasmid; in the first cattery, the first gene was present in 62.50%, gene 2 and 3 in 75% of the samples; for the second cattery was obtained 61.11 % positive for 1 and 2 genes and 55.56 % to the third gene; in fourth cattery the first and the third genes were present at 77.78% of the samples in the second gene was in 55.56%. The deaths reported during the study period were classified in animals with symptoms 3 or 4 and positive for C. felis and the cryptic plasmid. In this study we observed a high incidence of C. felis and the cryptic plasmid, despite the low occurrence of FIV and FeLV in catteries.
14
Almustafa, Mohamad. "Modélisation des micro-plasmas, conception des circuits micro-ondes, Coupleur Directionnel Hybride pour Mesures et des applications en Télécommunication." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/14170/1/almustafa.pdf.
Full textAbstract:
L'intégration des nouveaux éléments basés sur la physique des plasmas dans le domaine des circuits et des systèmes micro-ondes est l'objectif de ce travail. En profitant des caractéristiques électromagnétiques des plasmas et en jouant sur leur architecture, on développe des micro-commutateurs micro-ondes et d'autres circuits radio et hyperfréquences en technologies microrubans ou en guide d'onde… La simulation de la propagation des ondes électromagnétiques dans un plasma et les études de l'interaction entre un plasma et les ondes électromagnétiques nécessite la connaissance des paramètres fondamentaux du plasma comme la permittivité. C'est pour cela qu'on étudie aussi les mesures plasmas par différents techniques comme la transmission/réflexion des ondes électromagnétiques, la perturbation des cavités résonnantes, ... Un schéma électrique équivalent modélisant un micro-commutateur hyperfréquence en plasma, est obtenu grâce aux mesures des courants de décharge électrique, à la rétro-simulation et aux techniques de modélisation numérique. Un coupleur directif hybride compact est utilisé pour les mesures plasmas en assurant la protection du matériel et de l'équipement de mesure des signaux d'un plasma.
15
Dyson, Anthony Edmund. "Measurements on under-dense plasmas with intense lasers and experiments on the laser-plasma beat wave." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47418.
Full text
16
Michalčák, Jan. "Výroba součásti z plastu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228395.
Full textAbstract:
The project elaborated in the frame of engineering studies branch N2307-00 is submitting design of a product from plastic from material PP GF30. In the frame of literal study there are summarized technical knowledge from the area of plastic processing. On its base there is selected and specified technology of plastic injection and costruction of injection mold. Thesis is further dealing with the construction of injection mold, which is solved as a 1+1 multiple with the use of side sliding flank cores. During the course of the tool construction there were used standardized elements of Hasco company. The tool will be fixed by the use of Arburg ALLROUNDER 320C injection press. In the conclusion of the thesis there are verified necessary strenght of the mold and basic production cost analyses.
17
Supiot, Philippe. "Etude spectroscopique en volume et modélisation d'un plasma froid différé d'azote : diagnostic spatial et interaction avec le 1, 1, 3, 3-tétraméthyldisiloxane induisant une polymérisation." Lille 1, 1993. http://www.theses.fr/1993LIL10107.
Full textAbstract:
Ce travail a trait à la description spectroscopique, mécanistique et cinétique du milieu réactionnel constitué par un plasma froid différé d'azote généré par cavité microonde résonnante (f=433 mhz) et de son interaction avec le 1,1,3,3-tétraméthyldisiloxane (tmds) conduisant à la formation d'un dépôt polymérique. L'existence, hors du plasma de décharge, de particules chargées (ionisation secondaire, is), modifie considérablement la nature et les concentrations des espèces actives présentes à des distances importantes de la décharge (post-décharge lointaine, pdl). Une étude spatiale menée par spectroscopie optique en émission (soe) uv-visible du plasma en écoulement permet de dégager les caractéristiques principales des différentes zones constituant celui-ci au travers de l'évolution des intensités des émissions rencontrées. Les paramètres de cette étude sont la pression du gaz (2p#n#2(hpa)10) et la puissance transmise au plasma (100pu(w)300). A partir d'un modèle cinétique s'appuyant sur les résultats expérimentaux et de certaines hypothèses, la température cinétique des électrons et la densité de la molécule n#2(a#3#u#+) peuvent être estimées dans l'is<br>L'importance de l'énergie vibrationnelle transportée par les molécules d'azote dans l'état électronique fondamental couplée à la température cinétique du gaz est démontrée. La réaction de polymérisation induite en pdl en présence du tmds est analysée par les études conjointes de la phase gazeuse par soe et des dépôts résultants par spectrométries ir-tf et raman. Un modèle réactionnel est proposé, mettant en lumière le rôle essentiel de l'azote atomique et de n#2(a#3#u#+) dans la dissociation du tmds, ainsi que l'importance de l'ajout en pdl d'oxygène moléculaire pour l'orientation des processus radicalaires de polymérisation. Les principales caractéristiques spectroscopiques des deux phases sont expliquées de façon satisfaisante par ce modèle
18
Carlsson, Carolin. "Konstruktion av en mindre variant av plasmiden pQlacZ-1." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-16390.
Full textAbstract:
Syftet med detta projekt var att konstruera en mindre variant av pQlacZ-1 för att senare kunna använda den som reportervektor i Ideonella dechloratans. pQlacZ-1 är en plasmid som är 17,1 kbp stor, som skulle kunna användas som reportervektor i Ideonella dechloratans för att kunna undersöka olika promotorsekvenser. Detta är möjligt eftersom pQlacZ-1 är en broad host range plasmid och saknar promotorsekvensen för lacZ genen. Ett problem med pQlacZ-1 är dess storlek vilket gör den svår att transformera, och då speciellt i Ideonella dechloratans som är svår att transformera överhuvudtaget. En stor del av projektet har lagts på att ta reda på hur pQlacZ-1 ser ut i detalj, då detta inte finns väl beskrivet. Även efter denna studie saknas information om ett fragment för att få en helt klar bild över hur plasmiden är uppbyggd. Efter att ha ställt upp en hypotes om hur plasmiden ser ut så identifierades ett område som kunde klyvas bort och det var fragmentet med lacA och lacY. Detta gjordes genom en dubbelklyvning med SalI och BstBI. Den nya mindre varianten av plasmiden har jag valt att kalla pQlacZ-1cc och den ska teoretiskt sett vara ca 13427 bp stor, vilket bör göra den lättare att jobba med. Ytterligare arbete behövs för att verifiera konstruktionen i pQlacZ-1cc.<br>The aim with this project was to design a smaller version of pQlacZ-1 in order to later use it as a reporter vector in Ideonella dechloratans. pQlacZ-1 is a plasmid that is 17,1 kbp big, which might be used as a reporter vector in Ideonella dechloratans to investigate different promoter sequences. This is possible because pQlacZ-1 is a broad host range plasmid and lacks the promoter sequence of the lacZ gene. A problem with pQlacZ-1 is its size which makes it difficult to transform, and especially in Ideonella dechloratans which is difficult to transform at all. A large part of the project has been about finding out how pQlacZ-1 looks like in detail, as this is not well described. Even after this study information about one fragment is missing to get a completely clear picture of how the plasmid is constructed. After formulation of a hypothesis about how the plasmid is constructed, a section that could be removed was identified. The part of pQlacZ-1 that was removed was the lacA and lacY. This was done by a double digestion with SalI and BstBI. The new smaller version of the plasmid, is called pQlacZ-1cc. Theoretically it should be about 13427 bp, which should make it easier to work with. Additional work is required to verify the design of pQlacZ-1cc.
19
Lomas, David Arthur. "The molecular pathophysiology of alphaâ†1-antitrypsin." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308299.
Full text
20
Santos, Giovanni Rocha dos. "Caracterização e avaliação do comportamento tribológico do aço DIN X100CrMoV8-1-1 com tratamento dúplex." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/131059.
Full textAbstract:
As vantagens relacionadas à utilização de revestimentos duros depositados via processos PAPVD (Plasma Assisted Physical Vapor Deposition) são bem conhecidas e dadas por suas propriedades. As principais propriedades destes filmes são a capacidade de não incrementar significativamente a rugosidade dos substratos em que são depositados, sua alta dureza conferindo alta resistência ao desgaste, baixa reatividade quando se trata de revestimentos de compostos cerâmicos e capacidade de reduzir o coeficiente de atrito de pares tribológicos inseridos em diversos meios. A nitretação a plasma de substratos antes da aplicação de um revestimento faz com que outros benefícios possam ser encontrados, dentre eles destacam-se o aumento da capacidade de sustentação de carga do substrato e a criação de uma região que propicia um gradiente de propriedades entre o substrato e o revestimento. Desta forma é caracterizado o tratamento dúplex, o qual consiste em um substrato nitretado seguido da aplicação de um revestimento. Através do processo de nitretação a plasma, camadas de difusão foram formadas em amostras de geometria cilíndrica do aço DIN X100CrMoV8-1-1, industrialmente utilizado para construção de ferramentas para operações de corte e estampagem. Duas profundidades distintas de camada de difusão foram formadas. O revestimento escolhido para este estudo foi o TiCN (carbonitreto de titânio), produzido industrialmente e disponível no mercado brasileiro. As técnicas de caracterização foram utilizadas para medir a rugosidade, a dureza, os perfis de composição química, as fases formadas, as tensões residuais e a adesão dos revestimentos. Após esta caracterização inicial, foram feitos ensaios utilizando a técnica de esfera-sobre-disco em amostras e de DST (Dobramento sob Tensão) em pinos com geometria específica com o objetivo de se avaliar o comportamento tribológico dos tratamentos dúplex desenvolvidos.<br>The advantages related to the utilization of hard thin films deposited on tools and components via PAPVD (Plasma Assisted Physical Vapor Deposition) are well known and given by their properties. The main properties of these coatings are their capacity to avoid significant roughness increase of the coated substrates, high hardness which provides high wear resistance, low reactivity in the case of ceramic coatings and the possibility to provide very low friction coefficient. The thin films associated with plasma nitriding (the so called duplex treatments) applied to the substrates can bring much more benefits. The coating load bearing capacity can be increased by the presence of the diffusion zone on the substrate that allows a gradient of mechanical properties from the coating to the core of the material. In this work, by plasma nitriding process, two distinct depths of diffusion layer were developed in samples and pins manufactured out of the DIN X100CrMoV8-1-1 steel. This steel grade is commonly used to manufacture tools for cutting and stamping operations. Following a previous work the chosen coating for this study was a graded TiCN (titanium carbonitride). The samples were characterized by several different techniques in order to access surface roughness, chemical composition profiles, present phases, residual stresses, hardness and adhesion of the obtained nitrided layer and coatings. After this initial characterization, tests were performed using a pin-on-disc apparatus and BUT (Bending under tension test) with the aim to evaluate the tribological behavior of the developed duplex treatment for for sheet metal forming application.
21
Lupi, Antonio. "Electrical detection of surface plasmon polaritons via the plasmon drag effect." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24769.
Full textAbstract:
This thesis concerns the measurement and characterization of the Surface Plasmon Drag Effect (SPDE) in metallic structures and its application to the electrical detection of surface plasmon polaritons (SPPs). We demonstrate that SPPs absorbed in a metallic structure generate an electric current, which polarity depends on the propagation direction of the absorbed SPP, without the need of any applied voltage. We investigate the effect in gold and silver thin films of different thickness and on various metallic bilayers, which are deposited on right angle prisms and hemispheres to allow coupling of light to SPP through the Kretschmann-Raether configuration. We then simultaneously measure the angular spectrum of the reflected light and the electric current generated by the effect. The accuracy of the experiment allow us to determine the effect efficiency and thus to quantitatively compare different samples. In an attempt to clarify the mechanism giving rise to the current generation, we compare our experiments with existing models of the Photon Drag Effect (PDE). This is a similar phenomenon mediated by photon absorption where the current is the result of momentum transfer from the photon to conduction electrons. We find that the model qualitatively predicts our results and thus SPDE can be interpreted as the result of quasimomentum transfer from SPPs to the electrons, but care must be taken for considering the prediction of the model quantitatively. In addiction, we discovered that the effect shows local efficiency enhancement and even change of the current polarity in the presence of films with defects. Those results suggest a different interpretation to previous literature results and overall deepen the understanding of the phenomenon. A clear comprehension of the mechanisms leading to current generation is crucial for designing future applications in sensing and photonic circuitry. Despite the low efficiency in the visible range, in fact, this effect can be attractive since it promises to have an ultrafast response, to retain its sensitivity at longer wavelengths and has the peculiar ability of sensing the propagation direction of the SPP.
22
Cameron, Richard. "Dust-plasma interactions in the plasma edge region." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/46194.
Full textAbstract:
This thesis concerns the interaction of small, particulate, solid matter - 'dust' - with plasmas, in the plasma edge region where such dust is commonly found. Dust in this region can have a significant impact on a variety of industrial plasma applications, and it is low-temperature industrial plasmas that form the focus of this work. A novel model for the sheath region at the edge of a plasma is proposed, to account for the loss of electrons at the plasma boundary. This is then compared to an existing Boltzmann electron model; significant differences are noted in the sheath structure, and consequently the charging and dynamics of dust in the plasma sheath. The effect of sparse ion collisions in the vicinity of a dust grain near the plasma edge is also investigated. The strong plasma flow in the edge region is found to significantly increase collisional charging of dust grains. Somewhat counter-intuitively, it is found that even sparse collisions can play a significant (and in fact dominant) role in the charging and shielding of dust grains at the edge of a plasma. The length-scale over which the charge on such grains is shielded by the plasma is found to be significantly less than the Debye length. Together, the altered grain charging and shielding behaviour have the potential to fundamentally alter how dust grains interact with edge-plasmas.
23
Rossi, Alberto. "Développement d'outils d'optimisation dédiés aux circuits magnétiques des propulseurs à effet Hall." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19234/1/ROSSI_Alberto_public.pdf.
Full textAbstract:
Aujourd’hui les propulseurs à effet Hall ont gagné une position dominante dans le marché des propulseurs électriques spatiales. Ce grand succès est du surtout à leur simplicité de réalisation (par rapport aux autres typologies des propulseurs) et à leur efficacité (par rapport aux propulseurs chimiques traditionnels). Les propulseurs à effet Hall sont aujourd’hui utilisés sur un très grand nombre des plateformes satellitaires (surtout pour les télécommunications). Les composants principales d’un propulseur à effet Hall sont : le circuit magnétique, le canal plasma, l’anode (placé au fond du canal plasma avec injecteur du gaz) et la cathode (placée à l’extérieur du canal plasma). Le fonctionnement d’un propulseur à effet Hall est basé sur la génération d’un champ électrique axial (généré entre l’anode et la cathode) et d’un champ magnétique radial (perpendiculaires entre eux). Le champ magnétique a le rôle de former une zone de très forte concentration électronique (il emprisonne les électrons générés par la cathode) pour permettre aux atomes neutres du gaz de se ioniser. Le champ électrique a le rôle d’accélérer les ions vers l’extérieur du canal. Cette accélération génère la poussée. Le champ magnétique joue un rôle crucial dans le fonctionnement d’un propulseur à effet Hall. La forme du champ magnétique impacte sur les performances propulsifs et sur l’érosion du propulseurs. La topologie magnétique classique des propulseurs à effet Hall n’a subi presque pas des changements depuis les années de développement de cette technologie parce qu’elle garanti des performances propulsifs assez satisfaisantes. Aujourd’hui, avec les nouvelles exigences propulsifs, il y a une très forte nécessité des moteurs avec une durée de vie plus longue. Des nouvelles topologie magnétique innovante sont proposés aujourd’hui comme par exemple le "Magnetique-Shielding" ou le "Wall-Less" . Ces topologies magnétique bouleverse complètement la topologie magnétique classique (en gardant des performances propulsif satisfaisantes) pour protéger le moteur de l’érosion du plasma. Dans cette thèse une autre approche a été adopté. Nous avons pensé d’utiliser une topologie magnétique classique et de déplacer les parties du circuit magnétique attaquées par l’érosion vers des zones moins dangereuses. Nous avons agit sur la forme du circuit magnétique et pas sur la forme de la topologie magnétique pour garder les même performances propulsifs de la topologie magnétique classique. L’objectif de la thèse était de créer des outils pour le design et l’optimisation des circuits magnétiques des propulseurs à effet Hall. Un algorithme nommé ATOP a été créé dans l’équipe de recherche GREM3 du laboratoire LAPLACE de Toulouse. Cette thèse a contribué à la création de la section d’optimisation paramétrique (ATOPPO) et d’une section d’optimisation topologique basée sur les algorithmes génétiques (ATOPTOga) de l’algorithme ATOP. Les algorithme conçues dans cette thèse permettent d’optimiser des propulseurs existants (en terme de forme, masse et courant) ou de concevoir des nouveaux propulseurs (nécessité de concevoir un nouveau propulseur capable de reproduire une topologie magnétique précise). Les algorithmes développées ont démontrés leur efficacité à travers leur application sur un propulseur réel, le PPS-1350-E® de SAFRAN. Ce propulseur a été optimisé en terme de masse et de courant bobines (minimisation de la masse et du courant bobines). Les algorithmes développés ont démontré donc leur efficacité comme instrument d’optimisation et de design. Ces deux algorithmes ont été utilisé pour le design d’un circuit magnétique innovant qui a comme objectif de réduire l’érosion du moteur. Les résultats de ce processus de design ont amené à la réalisation et à la construction d’un prototype qui possède la même topologie magnétique du propulseur PPS- 1350-E® commercialisé par SAFRAN mais avec une circuit magnétique de forme différente.
24
Fonseca, Júlio César David da. "Modelos de mapas simpléticos para o movimento de deriva elétrica com efeitos de raio de Larmor finito." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06062016-120807/.
Full textAbstract:
Mapas simpléticos têm sido amplamente utilizados para modelar o transporte caótico em plasmas e fluidos. Neste trabalho, propomos três tipos de mapas simpléticos que descrevem o movimento de deriva elétrica em plasmas magnetizados. Efeitos de raio de Larmor finito são incluídos em cada um dos mapas. No limite do raio de Larmor tendendo a zero, o mapa com frequência monotônica se reduz ao mapa de Chirikov-Taylor, e, nos casos com frequência não-monotônica, os mapas se reduzem ao mapa padrão não-twist. Mostramos como o raio de Larmor finito pode levar à supressão de caos, modificar a topologia do espaço de fases e a robustez de barreiras de transporte. Um método baseado na contagem dos tempos de recorrência é proposto para analisar a influência do raio de Larmor sobre os parâmetros críticos que definem a quebra de barreiras de transporte. Também estudamos um modelo para um sistema de partículas onde a deriva elétrica é descrita pelo mapa de frequência monotônica, e o raio de Larmor é uma variável aleatória que assume valores específicos para cada partícula do sistema. A função densidade de probabilidade para o raio de Larmor é obtida a partir da distribuição de Maxwell-Boltzmann, que caracteriza plasmas na condição de equilíbrio térmico. Um importante parâmetro neste modelo é a variável aleatória gama, definida pelo valor da função de Bessel de ordem zero avaliada no raio de Larmor da partícula. Resultados analíticos e numéricos descrevendo as principais propriedades estatísticas do parâmetro gama são apresentados. Tais resultados são então aplicados no estudo de duas medidas de transporte: a taxa de escape e a taxa de aprisionamento por ilhas de período um.<br>Area-preserving maps have been extensively used to model chaotic transport in plasmas and fluids. In this work we propose three types of maps describing electric drift motion in magnetized plasmas. Finite Larmor radius effects are included in all maps. In the limit of zero Larmor radius, the monotonic frequency map reduces to the Chirikov-Taylor map, and, in cases with non-monotonic frequencies, the maps reduce to the standard nontwist map. We show how the finite Larmor radius can lead to chaos suppression, modify the phase space topology and the robustness of transport barriers. A method based on counting the number of recurrence times is used to quantify the dependence on the Larmor radius of the threshold for the breakup of transport barriers. We also study a model for a system of particles where the electric drift is described by the monotonic frequency map, and the Larmor radius is a random variable that takes a specific value for each particle of the system. The Larmor radius\' probability density function is obtained from the Maxwell-Boltzmann distribution, which characterizes plasmas in thermal equilibrium. An important parameter in this model is the random variable gamma, defined by the zero-order Bessel function evaluated at the Larmor radius\'particle. We show analytical and numerical computations related to the statistics of gamma. The set of analytical results obtained here is then applied to the study of two numerical transport measures: the escape rate and the rate of trapping by period-one islands.
25
Kravitz, Steven. "Heme oxygenase-1 suppressor (HOS) activity in Alzheimer plasma." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80306.
Full textAbstract:
Heme oxygenase-1 is a 32 kDa protein that catalyzes the degradation of heme to biliverdin in brain and other tissues. Our laboratory had previously reported significantly decreased HO-1 protein levels in AD plasma and CSF and HO-1 mRNA in AD mononuclear cells (which may be chemically unstable relative to the levels seen in normal elderly control (NEC) subjects). We hypothesized that there exists a heme oxygenase-1 suppressor (HOS) factor in the plasma of AD patients. Using a novel, glial-based bioassay, we showed that plasma HOS activity was detected in 23/24 AD patients, 3/8 mild cognitive impairment (MCI) patients and in 0/21 NEC patients (HOS activity signifying HO-1 suppression of >50% compared to positive controls). Antioxidant exposure and hypercortisolemia did not account for the HOS activity in AD plasma. We investigated the specificity and selectivity of the HOS factor by analyzing plasma derived from patients with non-Alzheimer's dementia's and non-dementing neurological disorders. We conclude that a HOS factor exists in the plasma of sporadic AD and some MCI patients but is undetectable in NEC plasma. The presence of a circulating HOS factor may further signify systemic redox derangements in early sporadic AD and provide a possible biological marker for this condition.
26
Cooksley, Susan. "The ectoenzyme PC-1 in lymphocyte function." Thesis, Open University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244376.
Full text
27
Cruz, Barrón Magali de la. "Compartmentalization of class 1 integrons and IncP-1 plasmids in the Orne river (France), an aquatic ecosystem impacted by urban and industrial anthropogenic pressures." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0212/document.
Full textAbstract:
Les éléments génétiques mobiles (EGM) sont des structures génétiques fréquemment associées à la dissémination de gènes de résistance aux antibiotiques (GRA). Dans ce travail, nous avons utilisé deux EGM comme « proxies », les intégrons de classe 1 et les plasmides IncP-1, afin de mieux comprendre (i) le devenir possible des GRA une fois relargués dans un écosystème fluvial (l’Orne, France), ainsi que (ii) l’effet des pressions anthropiques sur leur persistance. À partir d'analyses de l'eau des rivières, nous avons pu montrer que les deux EGM ne se comportaient pas de la même manière. L'entrée des intégrons de classe 1 dans le système fluvial semblait être diffuse plutôt que ponctuelle, tandis que l'abondance du plasmide IncP-1 est relativement stable le long de la section de la rivière étudiée (23 km), indiquant ainsi une origine plutôt indigène. Les intrants anthropiques tels que les stations d’épuration des eaux usées ne semblent pas affecter l’abondance des EGM en raison d’un niveau trop élevé de dilution des effluents. Par ailleurs, il est intéressant de noter que les bactéries porteuses d’EGM semblaient être enrichies sur les matières en suspension, susceptibles de servir de véhicule pour amener des communautés de bactéries plus riches en EGM vers les sédiments. L'analyse de deux carottes de sédiment indique clairement que seules les couches supérieures présentent un niveau élevé de bactéries porteuses d’EGM. Ces abondances diminuent dans les couches plus profondes où seules des zones ponctuelles présentent des microréservoirs avec des abondances d’EGM plus élevées. Pour une carotte sédimentaire au moins, nous avons pu montrer que l'abondance relative d’EGM corrèle négativement la présence de polluants tel que le plomb ou certains HAP<br>Mobile genetic elements (MGEs) are genetic structures frequently associated to the dissemination of antibiotic resistance genes (ARGs). In this work, we used two of them as proxies, class 1 integrons and IncP-1 plasmids, to better understand (i) the possible fate of ARGs once released in a river ecosystem (Orne, France), as well as (ii) the effect of anthropogenic pressures on their persistence. From river water analyses, we could show that the two MGEs do not behave the same way. The entry of class 1 integrons in the river system appeared to be diffuse rather than punctual, while the abundance of IncP-1 plasmid is relatively stable along the river section studied (23 km) thus indicating a rather indigenous origin. Anthropic inputs such as wastewater treatment plant did not seem to affect the abundance of MGEs because a too high level of effluent dilution. Interestingly, MGE-bearing bacteria appeared to be enriched on suspended material, which is likely to serve as a vehicle to drive MGE-richer communities of bacteria toward the sediments. The analysis of two sediment cores clearly indicates that only the top layers displayed an elevated level of MGE-bearing bacteria. These abundances decrease in deeper layers where only localized zones display micro-reservoirs of elevated MGE abundances. For one sediment core at least, we could show that the relative abundance of MGE negatively correlates with pollutants such as lead or certain PAHs
28
Droppa, Junior Roosevelt. "Interferometria com laser de CO2 no TC-1 da UNICAMP." [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278495.
Full textAbstract:
Orientador: Munemasa Machida<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin<br>Made available in DSpace on 2018-07-23T15:45:24Z (GMT). No. of bitstreams: 1
DroppaJunior_Roosevelt_M.pdf: 2488983 bytes, checksum: 9e4fdd0d5495c29cdcbb1714907d1843 (MD5)
Previous issue date: 1998<br>Resumo: Foram executadas, no toroide compacto TC-1 da UNICAMP, um thetapinch que permite a geração e o confinamento magnético de plasmas, tres técnicas de medição da densidade eletrônica integrada do plasma baseadas em interferometria, utilizando-se como fonte de radiação eletromagnética um laser de CO2( l = 10.6 mm). Na primeira delas, utiliza-se apenas um detetor de infravermelho para contagem de franjas de interferência. O número de franjas deslocadas quando ocorre a implosão do plasma é diretamente proporcional à variação da densidade eletrônica integrada ao longo do caminho percorrido pelo feixe de laser no interior do plasma. Com isso, pode-se acompanhar a evolução da densidade do plasma formado no interior do toroide. A segunda técnica faz uso de um único detetor assim como a primeira, porém o sinal que se obtem é modulado por um espelho móvel colocado no caminho de um dos feixes de laser com o intuito de se adicionar um "ruido controlado" ao sinal e, com isso, facilitar a contagem das franjas de interferência. O maior problema das técnicas em que se utilizam apenas um detector é a falta de informação sobre a direção de deslocamento das franjas quando o sinal do detector atinge um ponto de valor máximo ou mínimo. Para eliminar isso, emprega-se uma nova técnica em que são usados dois detectores posicionados de modo que os sinais fiquem defasados de 90 graus um em relação ao outro. Isso faz com que possamos obterr a informação que nos faltava e portanto acompanhar no tempo a evolução da densidade do plasma de maneira mais confiável. Foram feitas medidas com o laser atravessando o plasma ao longo de seu diâmetro e ao longo de seu eixo. Além disso, foi observada a evolução da densidade para quatro pressões de trabalho diferentes de H 2 no caso em que se utilizam dois detectores. Os resultados foram, então, comparados com aqueles obtidos pela técnica de espalhamento Thomson implantada simultaneamente no TC-1<br>Abstract: Three techniques for line integrated electron density measurement based on CO2 laser interferometry have been carried out on the compact toroid TC-1 UNICAMP, a theta-pinch that allows the generation and magnetic confinement of hidrogen plasma. In the first technique, it is used only one infrared detector for the counting of the interference fringes. The number of fringes displaced, when occurs the plasma implosion, is directly proportional to the variation of the electron density integrated along the laser beam path travelling through the plasma. The second technique makes use of one detector, like the first one, but the signal is now modulated by a moving mirror placed on the path of the reference laser beam, in order to add a "controlled noise" to this signal, thereby making the fringe counting easier. The main difficulty of the techniques above is the lack of information about the direction of the fringe displacement, when the signal from the detector reaches one of its extreme values. In order to eliminate this difficulty, a new technique is employed. There, two detectors are placed in a way that their signals have a phase difference of 90 degrees. This allows us to obtain the lacking information and, therefore, to observe the evolution of the plasma density in a more reliable way. It has been made measurements with the laser beam going through the plasma along its diameter and its axis. Using the third technique, it was also observed the density evolution for four word pressures. Finally, the results have beem compared with those obtained by Thomson scattering measurements<br>Mestrado<br>Física<br>Mestre em Física
29
McKee, Erik Scott. "Neutron Production from Z-pinch Plasmas at the 1 MA Zebra Generator." Thesis, University of Nevada, Reno, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10247687.
Full textAbstract:
<p> Neutrons produced deuterium Z-pinch plasmas are widely acknowledged to be a consequence of highly accelerated deuterons undergoing nuclear fusion with relatively stationary deuterons. The acceleration is thought to occur in intense fields created in the MHD instabilities that punctuate the plasma column. Interestingly, the energies of the accelerated ions exceed the applied voltage across the electrode gap. We use the 1 MA Zebra pulsed-power generator at the Nevada Terawatt Facility (NTF) to explore this poorly understood fast neutron production mechanism by creating deuterium Z-pinches in three distinct types of target loads. The loads are a cylindrical shell of deuterium gas, the far less explored deuterided palladium wire arrays, and a deuterium-carbon ablated laser plume target, which is unique to the NTF. </p><p> The pinch dynamics vary considerably in these three targets and provide the opportunity to explore the ion acceleration mechanism. We infer the characteristics of the accelerating fields from a wide range of diagnostic data including the neutron yield, energy spectrum and angular distribution, and the properties of the matching electron beams that are accelerated in the same field, and the energetic X-rays they produce on stopping. The plasma and the instabilities were recorded on several high-speed imaging diagnostics along with time-integrated soft (<10 keV) X-ray pinhole images. The three load types produced total neutron yields in the 10<sup>8</sup>–10<sup>10</sup> n/pulse range. The synchronization we observe between the ion and electron beams and the development of instabilities leads us to conrm the acceleration hypothesis. We also present the characteristics of the fields and ion beams in these varied pinches.</p>
30
Neto, Ibrahim El Chamaa. "Estudo do Funcionamento do Tokamak TBR-1 sob a Influência de Perturbações Elétricas e Magnéticas." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-27022014-144055/.
Full textAbstract:
Neste trabalho foram realizados estudos experimentais de operação do tokamak TBR-I sob condições extremas de densidade e de campo magnético toroidal e, também, sob a influência de perturbações elétricas radiais e magnéticas helicoidais aplicadas na região periférica da coluna de plasma. Realizou-se, também, uma análise preliminar das características das descargas na região da corrente de plasma com predominância de elétrons fugitivos. Para isso foi utilizada a maioria dos diagnósticos já construídos no Laboratório de Física de Plasmas da USP, que são: diagnóstico por sondas eletrostáticas, bobinas de Mirnov, espectroscopia óptica, interferômetro de micro ondas, detector de raios-X duros, detector de H, bobinas de Rogowski, bobinas de posição, espiras das tensões de enlace e medição da pressão com \"ion-gauges\" e analisador de gás residual. Os resultados permitiram obter uma lei de escala para as descargas do TBR-1 associando a densidade média de partículas com a densidade média de corrente de plasma. Foram observados efeitos muito interessantes nas oscilações magnéticas do plasma sob ação dos campos perturbativos. Em particular, para os campos elétricos radiais com polarização negativa, observou-se uma diminuição considerável das frequências dessas oscilações e uma atenuação nas amplitudes das mesmas, segundo uma análise de Fourier. Ao contrário, para polarizações positivas, foi observado um plasma mais turbulento. Este resultado repetiu-se (porém não tão acentuado como descrito no caso anterior) quando foi aplicada uma perturbação magnética helicoidal simultaneamente com o campo elétrico radial. Finalmente, as descargas do TBR-1 são caracterizadas pela baixa densidade de elétrons n IND.e 10 POT.12 cm POT.-3 e alta corrente de elétrons fugitivos (I I IND.P). O parâmetro de Shafranov foi calculado a partir das medidas do campo magnético vertical e do deslocamento do centro da coluna de plasma. A diferença de A nos cálculos é explicada pelo deslocamento da órbita do feixe de elétrons fugitivos.<br>In this work, experimental studies of operation limits of the TBR-l tokamak were accomplished under extreme conditions of density and toroidal magnetic field, a1so, under the influences of helical magnetic field and radial electric field perturbations, applied in the border zone of the plasma column. Also, a preliminary analysis of the charactetistics of the runaway discharges was performed. For measurements of the plasma charactetistics most of the diagnostics built in the USP Laboratório de Física de Plasmas, were used: electrostatic probes, Mirnov coils, optical spectroscopy, micro wave interferometer, hard X-rays detector, H detector, Rogowski coils, position sensors, loop voltage, pressure measurements with ion-gauges and a residual gas analyzer. From the result, the scaling law for the discharges of the TBR-l were obtained, associating the average densities of particles with average plasma current densities. Very interesting effects were observed in the magnetic oscillations of the plasma under the action of the perturbation fields. In particular, for the radial electric fields with negative polarization a considerable decrease in the frequency and an attenuation in the amplitude of the MHD oscillations were observed, according to a Fourier analysis. On the contrary, for positive polarization a more turbulent plasma was observed. Similar results, but not so strong, were obtained when a helical magnetic perturbation was applied simultaneously with the radial electric field. Finally, runaway discharges in the TBR-l were investigated and the current was found to be predominantly dominated by e1ectron beams. The Shafranov parameter A was calculated from the vertical field as well as from the plasma center displacement and found to be different, which can he explained by the orbit shifted runaway beams.
31
Gräns, Samuelsson Linnéa. "Conservation laws in kinetic theory for spin-1/2 particles." Thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110967.
Full textAbstract:
In this thesis a kinetic theory for spin-1/2 particles is given a brief overview, focusing on the derivation of an evolution equation for the quasiprobability distribution function used in the theory to describe certain types of quantum plasma. The current theory is expanded upon by exploring conservation laws. A local conservation law for momentum is derived using two different expressions for electromagnetic momentum, given by Abraham and Minkowski respectively. There has been some controversy over which of these expressions should be used; in the case considered here the expression given by Minkowski seems to be more suitable. Based on the conservation law for momentum, a conservation law for angular momentum is also derived.
32
Bråve, Andreas. "Prime-boost immunization strategies against HIV-1 /." Stockholm : Karolinska institutet, 2007. http://diss.kib.ki.se/2007/978-91-7357-327-6/.
Full text
33
Roy, Kirsty. "Spray deposition for plastic electronics." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45287.
Full textAbstract:
Spray deposition is a promising technique for the solution processing of plastic electronic devices due to its potential for high-speed, large-scale device fabrication using low capital cost equipment. Most recent reports of spray-deposited electronic devices have used ultrasonic systems for film deposition to minimise surface roughness, but such systems suffer from low materials throughput, and are consequently ill-suited to industrial manufacturing. Gas-driven spray-heads enable higher throughput materials delivery but can result in an unacceptably rough film due to the large, broadly distributed droplet sizes that are often generated and the hard-impact nature of the deposition process. This thesis describes a new automated gas-driven spray coater for the controlled deposition of a broad variety of solution processed electronic materials. It is specifically suited to the deposition of polymer films such as poly(3-hexylthiophene) (P3HT), overcoming many of the usual disadvantages of conventional gas-driven spray coaters. Key features of the system include: a novel, high performance 3D-printed spray-head for the generation of ultrafine sprays; full three-dimensional position and velocity control of the spray head; integrated temperature control; and independent control of solution and gas flow rates. To determine the optimum solution composition for spray-deposition of P3HT films, the aggregation and gelation dynamics of various P3HT/o-xylene solutions were first investigated by static light scattering. On the basis of these measurements, we conclude that dilute solutions (with polymer concentration < 5 mg/ml) of low (< 20 kg/mol ) molecular weight polymer containing a small amount of a secondary solvent. are optimal for avoiding gelation and clogging of the spay-head. For higher weight material, heating of the solution is necessary to avoid gelation. The thesis also describes the development of an optical profiling technique for the characterisation of polymer films, which provides a fast method for quantitatively characterising the uniformity of large-area, thin polymer films. Using this technique, we were able to confirm that the spray-deposition system yields high quality, thin semiconducting polymer films, allowing for the controlled fabrication of active layers in organic photovoltaic devices from non-chlorinated solvents. The influence of solution composition and deposition variables such as gas pressure, solvent composition and substrate temperature were investigated, and optimised conditions for the deposition of high quality (device-grade) thin P3HT films were thereby identified. A maximum device efficiency of 4.0 % was achieved for the spray-deposited bulk heterojunction P3HT:fullerene films processed from xylene. The results indicate that, providing the active layer is continuous, high device efficiency may be achieved even with relatively rough films, spray-coated from non-chlorinated processing solvents.
34
Berri, Fatma. "Rôle de l'hémostase dans l'inflammation induite par les virus influenza A." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10351/document.
Full textAbstract:
La grippe est une maladie respiratoire aigüe, due à une infection par des virus influenza et qui représente un problème important de santé publique. Une meilleure compréhension des interactions entre le virus influenza et son hôte nous permettra de mieux comprendre la physiopathologie de l'infection grippale, et donc, à terme, de mieux se protéger contre la maladie. La morbidité et la mortalité, causées par les infections grippales sévères, sont associées à une dérégulation de la réponse immunitaire, au niveau pulmonaire. Cette inflammation délétère serait à l'origine de dommages collatéraux du poumon, entrainant une diminution de la capacité respiratoire du patient. Bien que les mécanismes impliqués ne soient pas totalement élucidés, de récents travaux mettent en évidence un rôle central des cellules endothéliales dans la dérégulation de la réponse de l'hôte face à l'infection grippale. Lors d'une agression de l'endothélium, le processus physiologique de l'hémostase (activation plaquettaire, coagulation et fibrinolyse) s'active afin de permettre la cicatrisation de la plaie et de maintenir l'intégrité des vaisseaux sanguins. Dans de nombreuses maladies inflammatoires, la seule dérégulation de l'hémostase est directement liée à une réponse inflammatoire délétère. Lors de ma thèse, nous avons émis l'hypothèse que l'hémostase pouvait être à l'origine de la dérégulation inflammatoire durant les infections grippales. Nos données montrent le rôle de deux facteurs fortement impliqués dans l'hémostase : le récepteur activé par la thrombine, PAR-1 (Protease Activated Receptor J) ainsi que le plasminogène, dans l'inflammation délétère des poumons et dans la pathogénicité des virus influenza. Outre le rôle de l'hémostase, nous avons également pu mettre en évidence que le virus influenza incorpore des protéines cellulaires dans l'enveloppe virale, lui permettant d'échapper au système immunitaire, ce qui pourrait aussi contribuer à la dérégulation de la réponse de l'hôte. L'ensemble des résultats obtenus ont permis de mieux comprendre les mécanismes à l'origine d'une réponse immunitaire dérégulée dans les infections grippales et de proposer de nouvelles cibles thérapeutiques pour lutter contre la maladie<br>Influenza is an acute respiratory disease caused by infection with influenza virus and is a major public health problem. A better understanding of the interaction between influenza virus and host allow us to better understand the pathophysiology of influenza infection, and thus, ultimately, to better protect themselves against the disease. Morbidity and mortality caused by severe influenza infections are associated with dysregulation of the immune response in the lung. This deleterious inflammation is the cause of lung collateral damage, causing a decrease in the patient's breathing capacity. Although the mechanisms involved are not fully understood, recent studies point to a central role of endothelial cells in the deregulation of the host response to influenza infection. During endothelium aggression, the physiological process of hemostasis (platelet activation, coagulation and fibrinolysis) is activated in order to allow wound healing and to maintain the integrity of blood vessels. In many inflammatory diseases, the only dysregulation of hemostasis is directly linked to a deleterious inflammatory response. During my thesis, we hypothesized that hemostasis could be the cause of the inflammatory dysregulation during influenza infections. Our data show the role of two factors strongly involved in hemostasis: the thrombin activated receptor, PAR-1 (protease activated receptor 1) and plasminogen, in the deleterious lung inflammation and in the pathogenicity of influenza virus. Besides the role of hemostasis, we have also been able to show that the influenza virus incorporates cellular proteins in the viral envelope, allowing it to evade the immune system, which could also contribute to the deregulation of the host response. All the results obtained allowed to better understand the mechanisms involved in immune response dysregulation during influenza infection and suggest new therapeutic targets to fight against the disease
35
Bricogne, C. C. "Plasma membrane dynamics regulating the PD-1/PD-L1 Pathway." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1473199/.
Full textAbstract:
The PD-1/PD-L1 pathway in T lymphocytes is emerging as one of the most promising targets for cancer immunotherapy but few details are yet known about how its inhibitory influence is achieved. This work set out to investigate the role of plasma membrane dynamics, on both T cells and tumour cells, in modulating the pathway. In eukaryotic cells, calcium influx leads to rapid changes in the plasma membrane. Exocytosis, phospholipid scrambling, membrane shedding and massive endocytosis can all occur. The calcium sensors for these processes, their inter-dependence and their effects on transmembrane protein expression remain largely unknown. Here we show that the ion channel TMEM16F is the calcium sensor for large exocytosis and that phospholipid scrambling and microvesicle shedding are coupled to exocytosis. The absence of TMEM16F not only abrogates exocytosis but also results in massive endocytosis in response to calcium. Intracellular polyamines regulate these phenotypes, switching cell responses from massive exo- to endocytosis by blocking the TMEM16F conductance. This massive endocytosis also occurs during apoptosis via a calcium-independent mechanism. In lymphocytes, PD-1 participates selectively in both shedding and massive endocytosis, targeting that depends on the PD-1 transmembrane region, independent of actin and classical protein adaptors. We also found that PD-L1 on tumour cells can be transferred to lymphocytes, and be maintained in stable complex with PD-1 on in vitro and in vivo. This may modulate the PD-L1/PD-1 pathway in tumours. Together, these results provide new insights into the plasma membrane reorganization that occurs following calcium transients, establishes a mechanism of PD-1 regulation dependent solely on protein-membrane interaction, and also introduces a new modality by which PD-L1:PD-1 interactions can be sustained beyond cell-cell contact in tumours.
36
Drews, Christian [Verfasser]. "Interstellar Pickup Ions at 1 AU with STEREO/PLASTIC / Christian Drews." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1035405539/34.
Full text
37
Elizondo, Juan Iraburu. "Medição de Densidade no Tokamak TBR-1 por Rotação de Faraday." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-02072013-115509/.
Full textAbstract:
Neste trabalho, são apresentados os resultados experimentais de medições de densidade eletrônica no tokamak TBR-l, obtidas por meio de rotação de Faraday num feixe de micro-ondas. O feixe (65 GHz, 500 m W) é gerado por uma klystron e atravessa o plasma no plano médio horizontal. Os valores obtidos para a densidade concordam bem com as medições feitas com um interferômetro de micro-onda o; convencional. A partir das simulações numéricas e das medições, conclui-se ser recomendável o uso de comprimentos de onda menores, para minimizar a refração do feixe no plasma, Os resultados obtidos demonstram a viabilidade do método de medição de densidade por rotação de Faraday. em experiência feita pela primeira vez em tokamak, para a geometria considerada.<br>In this work, the experimental results of electronic density measurements in the TBR-l tokamak, obtained by Faraday rotation of a microwave beam, are presented. The beam (65 GHz, 500 mW) is generated by a klystron and crosses the plasma in the horizontal plane. The density values obtained are in agreement with the measurements of a conventional microwave interferometer. As a result of numerical simulations and measurements, it can be concluded that it would be advisable the use of lower wavelengths, to minimize the beam refraction when it crosses the plasma. The results show the feasability of the Faraday rotation method for density measurement, in the first experiment performed in a tokamak for the geometry considered.
38
LE, CHATELIER EMMANUELLE. "Initiation et controle de la replication du plasmide pam-beta-1 chez bacillus subtilis." Paris 11, 1994. http://www.theses.fr/1994PA112141.
Full textAbstract:
Pam-beta-1 est un grand plasmide isole d'enterococcus faecalis qui se replique par un mecanisme theta dans un grand nombre de bacteries a gram positif incluant bacillus subtilis. Deux aspects de sa replication ont ete abordes dans ce travail. Le premier concerne le mecanisme d'initiation. Les observations suivantes ont conduit a la proposition que pam-beta-1 se replique par un mecanisme original: (i) sa replication depend de l'adn polymerase i de l'hote et de deux elements plasmidiques, une proteine d'initiation (repe) et un fragment origine, et (ii) aucune homologie n'est trouvee entre pam-beta-1 et les replicons des bacteries a gram negatif. Le deuxieme aspect concerne la regulation de la replication. Celle-ci est realisee essentiellement en modulant la transcription du gene repe. Deux niveaux de controle independants et additifs ont ete detectes: un systeme d'attenuation transcriptionnelle regule par un arn antisens qui provoque une terminaison prematuree de 90% des transcrits, et un represseur proteique qui diminue d'un facteur 10 la transcription initiee au niveau de ce promoteur
39
Ramdayal, Kavisha. "Evolution of HIV-1 subtype C gp120 envelope sequences in the female genital tract and blood plasma during acute and chronic infection." University of the Western Cape, 2014. http://hdl.handle.net/11394/4355.
Full textAbstract:
Philosophiae Doctor - PhD<br>Heterosexual transmission of HIV-1 via the female genital tract is the leading route of HIV infection in sub-Saharan Africa. Viruses then traffic between the cervical compartment and blood ensuring pervasive infection. Previous studies have however reported the existence of genetically diverse viral populations in various tissue types, each evolving under separate selective pressures within a single individual, though it is still unclear how compartmentalization dynamics change over acute and chronic infection in the absence of ARVs. To better characterize intrahost evolution and the movement of viruses between different anatomical tissue types, statistical and phylogenetic methods were used to reconstruct temporal dynamics between blood plasma and cervico-vaginal lavage (CVL) derived HIV-1 subtype C gp120 envelope sequences. A total of 206 cervical and 253 blood plasma sequences obtained from four treatment naïve women enrolled in the CAPRISA Acute Infection study cohort in South Africa were evaluated for evidence of genotypic and phenotypic differences between viral populations from each tissue type up to 3.6 years post-infection. Evidence for tissue-specific differences in genetic diversity, V-loop length variation, codon-based selection, co-receptor usage, hypermutation, recombination and potential N-linked glycosylation (PNLG) site accumulation were investigated. Of the four participants studied, two anonymously identified as CAP270 and CAP217 showed evidence of infection with a single HIV-1 variant, whereas CAP177 and CAP261 showed evidence of infection by more than one variant. As a result, genetic diversity, PNLGs accumulation and the number of detectable recombination events along the gp120 env region were lowest in the former patients and highest in the latter. Overall, genetic diversity increased over the course of infection in all participants and correlated significantly with viral load measurements from the blood plasma in one of the four participants tested (i.e. CAP177). Employing a structured coalescent model approach, rates of viral migration between anatomical tissue types on time-measured genealogies were also estimated. No persistent evidence for the existence of separate viral populations in the cervix and blood plasma was found in any of the participants and instead, sequences generally clustered together by time point on Bayesian Maximum Clade Credibility (MCC) trees. Clades that were monophyletic by tissue type comprised mostly of low diversity or monotypic sequences from the same time point, consistent with bursts of viral replication. Tissue-specific monophyletic clades also generally contained few sequences and were interspersed among sequences from both tissue-types. Tree and distance-based statistical tests were employed to further evaluate the degree to which cervical and blood plasma viruses clustered together on Bayesian MCC trees using the Slatkin-Maddison (S-M), Simmonds Association index (AI), Monophyletic Clade (MC), Wright’s measure of population subdivision (FST) and Hudson’s Nearest Neighbour (Snn) statistics, in the presence and absence of monotypic and low diversity sequences. Statistical evidence for the presence of tissue-specific population structure disappeared or was greatly reduced after the removal of monotypic and low diversity sequences, except in CAP177 and CAP217, in 3/5 of longitudinal tree and distance-based tests. Analysis of phenotypic differences between viral populations from the blood plasma and cervix revealed inconsistent tissue-specific patterns in genetic diversity, codon-based selection, co-receptor usage, hypermutation, recombination, V-loop length variation and PNLG site accumulation during acute and chronic infection among all participants. There is therefore no evidence to support the existence of distinct viral populations within the blood plasma and cervical compartments longitudinally, however slightly constrained populations may exist within the female genital tract at isolated time points, based on the statistical findings presented in this study.
40
Chruszez, Olivier. "Caractérisation de matériaux plasmas pour la conception de fonctions hyperfréquences." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/15662/1/CHRUSZEZ.pdf.
Full textAbstract:
Afin de mettre à profit les propriétés des plasmas pour développer des fonctions hyperfréquences originales, le milieu plasma doit d’abord être caractérisé dans cette gamme de fréquence car son expansion et sa densité, supposée homogène, sont des paramètres mal maîtrisés. Une méthode de mesure de la constante diélectrique du plasma a donc été développée pour déterminer une permittivité relative complexe moyenne dans les conditions d’utilisation et d’excitation. A partir d’un modèle basé sur une méthode modale, et de la mesure de fréquence de résonance d’un résonateur, on caractérise un milieu plasma (permittivité, fréquence de coupure plasma) généré au sein d’une ligne microruban multicouches. Cette thèse, à l’intersection entre deux disciplines, plasmas et micro-ondes, valide l’utilisation de plasma localisé au sein d’une technologie planaire multicouches pour dimensionner des lignes d’impédance et/ou longueur de ligne variables. Elle met également en avant les difficultés rencontrées en termes de réalisation, pour générer des plasmas reproductibles et stables.
41
Saavedra, García Paula. "FABP4: interactions with endothelial cell plasma membrane and effects on vascular smooth muscle cells." Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/348560.
Full textAbstract:
Fatty acid-binding protein 4 (FABP4) és una adipoquina secretada pel teixit adipós implicada en la regulació del metabolisme energètic i la inflamació. S'han detectat nivells elevats de FABP4 circulant en persones amb factors de risc cardiovascular i aterosclerosi, encara que no hi ha moltes dades sobre FABP4 i l'aterosclerosi en humans. Alguns estudis han demostrat que FABP4 té un efecte directe sobre els teixits perifèrics, concretament promovent la disfunció endotelial. La disfunció endotelial juga un paper clau en el desenvolupament de lesions ateroscleròtiques, així com la migració i proliferació de cèl·lules de múscul llis vascular. No obstant això, el mecanisme d'acció i funcions de FABP4 circulant són poc conegudes. La hipòtesi d'aquest treball és que FABP4 interacciona amb teixits perifèrics contribuint a la disfunció endotelial i remodelació vascular a partir de la interacció amb proteïnes de membrana plasmàtica, que actuarien com a elements d'ancoratge i/o receptors mitjançant rutes de senyalització intracel·lular, i/o internalització.
Els nostres resultats indiquen que FABP4 exògena interactua específicament amb citoqueratina 1 (CK1) en les membranes cel·lulars endotelials i la seva inhibició farmacològica per BMS309403 disminueix lleugerament la formació d'aquests complexos. A més, FABP4 exògena travessa la membrana plasmàtica per entrar al citoplasma i nucli de cèl·lules endotelials (HUVECs). També hem demostrat que FABP4 exògena forma un complex amb CK1 en les cèl·lules del múscul llis vascular (HCASMCs) i que té un efecte directe induint la migració i proliferació de les HCASMCs a través de l'activació de la via de senyalització MAPK per la fosforilació de ERK1/2 i activació dels factors de transcripció nuclears c-myc i c-jun. Aquests resultats suggereixen que FABP4 circulant podria tenir un paper en el remodelat vascular i progressió de l'aterosclerosi. Aquestes dades contribueixen al nostre coneixement actual sobre el mecanisme d'acció de FABP4 circulant.<br>Fatty acid-binding protein 4 (FABP4) es una adipoquina secretada por el tejido adiposo implicada en la regulación del metabolismo energético y la inflamación. Se han detectado niveles elevados de FABP4 circulante en personas con factores de riesgo cardiovascular y aterosclerosis, aunque no hay muchos datos sobre FABP4 y aterosclerosis en humanos. Algunos estudios han demostrado que FABP4 tiene un efecto directo sobre los tejidos periféricos, concretamente promoviendo la disfunción endotelial. La disfunción endotelial juega un papel crucial en el desarrollo de lesiones ateroscleróticas, así como la migración y proliferación de células de músculo liso vascular. Sin embargo, el mecanismo de acción y las funciones de FABP4 circulante son desconocidos. La hipótesis de este trabajo es que FABP4 interacciona con tejidos periféricos contribuyendo a la disfunción endotelial y remodelación vascular a partir de la interacción con proteínas de membrana plasmática, que actuarían como elementos de anclaje y/o receptores mediando rutas de señalización intracelular, y/o internalización.
Nuestros resultados indican que FABP4 exógena interactúa específicamente con citoqueratina 1 (CK1) en las membranas celulares endoteliales y su inhibición farmacológica por BMS309403 disminuye ligeramente la formación de estos complejos. Además, FABP4 exógena atraviesa la membrana plasmática para entrar en el citoplasma y núcleo de células endoteliales (HUVECs). También hemos demostrado que FABP4 exógena también forma un complejo con CK1 en las células del músculo liso vascular (HCASMCs) y que tiene un efecto directo sobre la migración y proliferación de HCASMCs a través de la activación de la vía de señalización MAPK por la fosforilación de ERK1/2 y activación los factores de transcripción nucleares c-myc y c-jun. Estos resultados sugieren que FABP4 circulante podría tener un papel en el remodelado vascular y en la progresión de la aterosclerosis. Estos datos contribuyen a nuestro conocimiento actual sobre el mecanismo de acción de FABP4 circulante.<br>Fatty acid-binding protein 4 (FABP4) is an adipose tissue-secreted adipokine that is involved in the regulation of energetic metabolism and inflammation. Increased levels of circulating FABP4 have been detected in individuals with cardiovascular risk factors and atherosclerosis, although there is not much data on FABP4 in human atherosclerosis. Some studies have demonstrated that FABP4 has a direct effect on peripheral tissues, specifically promoting endothelial dysfunction. Endothelial dysfunction plays crucial roles in the development of atherosclerotic lesions as well as migration and proliferation of vascular smooth muscle cells. However, the mechanism of action and functions of circulating FABP4 are unknown. The hypothesis of this study is that circulating FABP4 has a direct effect on peripheral tissues. In particular at vessel wall level, FABP4 contributes to endothelial dysfunction and artery wall remodelling through interaction with endothelial plasma membrane proteins that act as anchoring elements and/or receptors mediating intracellular signalling, and/or FABP4 internalization. FABP4 acts on smooth muscle cells influencing cell migration and proliferation as well.
Our results indicate that exogenous FABP4 interacts with specifically CK1 on endothelial cell membranes and the pharmacological FABP4 inhibition by BMS309403 decreases the formation of these complexes slightly. Furthermore, exogenous FABP4 crosses the plasma membrane to enter the cytoplasm and nucleus in HUVECs. In addition, we also demonstrated that exogenous FABP4 forms a complex with CK1 on vascular smooth muscle cells (HCASMCs) and has a direct effect of FABP4 on the migration and proliferation of HCASMCs through the activation of the ERK1/2 MAPK signalling pathway and activating the nuclear transcription factors c-myc and c-jun. Taking all these results together, it suggests that circulating FABP4 could have a role in vascular remodelling and atherosclerosis progression. These data contribute to our current knowledge regarding the mechanism of action of circulating FABP4.
42
Doléans-Jordheim, Anne. "Facteurs de virulence et d'endémicite chez legionella pneumophila sérogroupe 1." Lyon 1, 2006. http://www.theses.fr/2006LYO10087.
Full textAbstract:
Nos travaux ont porté sur l'étude de facteurs potentiellement impliqués dans la virulence et/ou l'endémicité de souches de légionelles. Notre première étude a confirmé la virulence accrue de Legionella pneumophila sérogroupe 1 (Lp1) en démontrant que la prédominance de Lp1 en clinique n'était pas le reflet d'une prédominance dans l'environnement. Par ailleurs, nous avons montré que les profils PFGE de l'espèce L. Anisa étaient très homogènes, contrairement à ceux des Lp1. Nous avons également démontré qu'un élément de type plasmide-like de 36 kb de la souche endémique Lp1 Paris, s'intègre au chromosome durant la phase exponentielle de croissance bactérienne par un phénomène de recombinaison au niveau de sites att spécifiques. L'expression de certains gènes de cet élément serait liée à la quantité de forme épisomique, et surviendrait en phase de latence. Nous avons enfin étudié une protéine spécifique de L. Pneumophila indispensable à la multiplication intra-amibienne
43
Jowhari, Moghadam Shirin. "Plastic buckling of columns and plates." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/29865.
Full textAbstract:
The theory of buckling strength of compression members in the plastic range has been extensively studied, and numerical methods already exist which deal with such behaviour. However, there is a significant research interest in developing analytical models for the plastic buckling, largely driven by the need for simplified mechanics based design tools, but also by the desire for enhanced understanding of this complex phenomenon. A thorough investigation into the inelastic buckling of columns and plates reveals the existence of two well-known inconsistencies recognised as the 'Column Paradox' and the 'Plate Plastic Buckling Paradox'. In the current research, addressing the conceptual issues related to the plastic buckling of columns and plates, including the two associated paradoxes, has been achieved by means of development and application of analytical models that are verified against nonlinear finite element analysis. These models are based on sound principles of structural mechanics and are intended to illustrate the mechanics of the plastic buckling response of stocky columns/plates by means of a simplified analytical approach, from the point of buckling initiation and considering the post-buckling response. In these models, the Rotational Spring Analogy is used for formulating the geometric stiffness matrix, whereas the material stiffness matrix is obtained with due consideration for the spread of material plasticity. It is shown that the buckling of stocky perfect columns starts at the Engesser load while the von Karman upper limit is typically not realised due to tensile yielding at the outer fibre of the column cross-section. Furthermore, it is established that beyond a threshold level of imperfection, as evaluated directly from the developed model, the plastic post-buckling response of columns is barely affected by a further increase in the out-of-straightness. Besides identifying previous misconceptions in the research literature, the proposed analytical models for the plastic buckling of plates have proven to offer valuable insight into factors that influence the plastic buckling of stocky plates, and hence succeeded in resolving the long-standing paradox. It is the major contention of this thesis, verified through extensive studies, that the 'Plate Plastic Buckling Paradox' is resolved with the correct application of plasticity theory, considering not only the influence of initial imperfections but also the interaction between flexural and planar actions.
44
Favaedi, Leila. "Image processing for plastic surgery planning." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6063.
Full textAbstract:
This thesis presents some image processing tools for plastic surgery planning. In particular, it presents a novel method that combines local and global context in a probabilistic relaxation framework to identify cephalometric landmarks used in Maxillofacial plastic surgery. It also uses a method that utilises global and local symmetry to identify abnormalities in CT frontal images of the human body. The proposed methodologies are evaluated with the help of several clinical data supplied by collaborating plastic surgeons.
45
Willis, Christopher Thomas Nigel. "Dust in stationary and flowing plasmas." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9329.
Full textAbstract:
This thesis contains work of a computational and theoretical nature. The floating potential of dust grains immersed in plasma is investigated via particle-in-cell simulation for a range of parameters. In particular, work is focused on the charging of grains large with respect to the electron Debye length. Numerical fits are given for the floating potential of large grains in stationary and flowing plasma. A modified version of the well known orbit-motion-limited (OML) theory is developed for large dust grains. The modified OML theory is shown to be in good agreement with simulation. This modified theory is then adapted for use with flowing plasmas. In the case of flowing plasma, for low ion temperatures and flow speeds upwards of Mach 1, interesting and unexpected effects are seen in the potential and density distribution around dust grains, these are investigated and discussed. Finally, the application of this work is outlined with particular focus on dust grains in a tokamak plasma environment.
46
Marinho, Fernando Antonio Medeiros. "Shrinkage behaviour of some plastic soils." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/11381.
Full text
47
Rahman, Joynur. "Magnetised transport in laser produced plasmas." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/11875.
Full text
48
Semple, James. "High-throughput large-area plastic nanoelectronics." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/39573.
Full textAbstract:
Large-area electronics (LAE) manufacturing has been a key focus of both academic and industrial research, especially within the last decade. The growing interest is born out of the possibility of adding attractive properties (flexibility, light weight or minimal thickness) at low cost to well-established technologies, such as photovoltaics, displays, sensors or enabling the realisation of emerging technologies such as wearable devices and the Internet of Things. As such there has been great progress in the development of materials specifically designed to be employed in solution processed (plastic) electronics, including organic, transparent metal oxide and nanoscale semiconductors, as well as progress in the deposition methods of these materials using low-cost high-throughput printing techniques, such as gravure printing, inkjet printing, and roll-to-roll vacuum deposition. Meanwhile, industry innovation driven by Moore's law has pushed conventional silicon-based electronic components to the nanoscale. The processes developed for LAE must strive to reach these dimensions. Given that the complex and expensive patterning techniques employed by the semiconductor industry so far are not compatible with LAE, there is clearly a need to develop large-area high throughput nanofabrication techniques. This thesis presents progress in adhesion lithography (a-Lith), a nanogap electrode fabrication process that can be applied over large areas on arbitrary substrates. A-Lith is a self-alignment process based on the alteration of surface energies of a starting metal electrode which allows the removal of any overlap of a secondary metal electrode. Importantly, it is an inexpensive, scalable and high throughput technique, and, especially if combined with low temperature deposition of the active material, it is fundamentally compatible with large-area fabrication of nanoscale electronic devices on flexible (plastic) substrates. Herein, I present routes towards process optimisation with a focus on gap size reduction and yield maximisation. Asymmetric gaps with sizes below 10 nm and yields of > 90 % for hundreds of electrode pairs generated on a single substrate are demonstrated. These large width electrode nanogaps represent the highest aspect ratio nanogaps (up to 108) fabricated to date. As a next step, arrays of Schottky nanodiodes are fabricated by deposition of a suitable semiconductor from solution into the nanogap structures. Of principal interest is the wide bandgap transparent semiconductor, zinc oxide (ZnO). Lateral ZnO Schottky diodes show outstanding characteristics, with on-off ratios of up to 106 and forward current values up to 10 mA for obtained upon combining a-Lith with low-temperature solution processing. These unique devices are further investigated for application in rectifier circuits, and in particular for potential use in radio frequency identification (RFID) tag technology. The ZnO diodes are found to surpass the 13.56 MHz frequency bernchmark used in commercial applications and approach the ultra-high frequency (UHF) band (hundreds of megahertz), outperforming current state of the art printed diodes. Solution processed fullerene (C60) is also shown to approach the UHF band in this co-planar device configuration, highlighting the viability of a-Lith for enabling large-area flexible radio frequency nanoelectronics. Finally, resistive switching memory device arrays based on a-Lith patterned nanogap aluminium symmetric electrodes are demonstrated for the first time. These devices are based either on empty aluminium nanogap electrodes, or with the gap filled with a solution-processed semiconductor, the latter being ZnO, the semiconducting polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) or carbon nanotube/polyfluorene blends. The switching mechanism, retention time and switching speed are investigated and compared with published data. The fabrication of arrays of these devices illustrates the potential of a-Lith as a simple technique for the realisation of large-area high-density memory applications.
49
Ng, Binghao. "Terahertz sensing with spoof plasmon surfaces." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24487.
Full textAbstract:
Terahertz (THz) radiation (≈ 0.1-10x10^12 Hz) is non-ionizing and its photon energies correspond to the rotational and vibrational modes of many complex molecules. Hence many substances of interest for biological and security applications can be detected using THz light; making THz spectroscopy an ideal tool for bio- and security sensing. However, a size mismatch between the photon wavelength and the size of many commonly sensed targets, and a lack of powerful sources hamper the progress of THz technology towards more widespread real-world applications. The focus of this thesis is to use novel concepts in the field of metamaterials to overcome or side step some of these challenges. In particular, the use of confined electromagnetic surface modes, such as lattice resonances and spoof plasmons, on metamaterial surfaces to conduct THz sensing is investigated. Different ways in which sensing information can be extracted from these specially structured metamaterial surfaces are explored so as to demonstrate the feasibility and versatility of metamaterial surfaces in THz sensing applications. The application of lattice resonances to detect refractive index changes caused by various fluids on an array of metallic rods is first reported in this thesis. This can be seen as a prelude to the work presented in later chapters where strongly confined spoof plasmons are employed for THz sensing. A metamaterial surface supporting spoof plasmons (simply termed as a Spoof Plasmon Surface (SPS)), consisting of a linear array of metallised sub-wavelength grooves, is filled with various fluids and shown to be capable of high performance refractive index sensing in an Otto prism setup. Sharp phase changes, readily available from THz time-domain spectroscopy (THz-TDS), associated with the coupling of THz radiation to spoof plasmons are used as the readout response in this case to indicate changes in the refractive indices of the fluids filling the grooves. Building upon the initial work on spoof plasmon sensing, further investigations demonstrate the feasibility of SPSs as a versatile platform on which various forms of sensing information can be extracted by using THz radiation that is coupled in and out of spoof plasmons via the scattering edge coupling scheme. The time-domain signal from the SPS is analysed using a short- time Fourier transform (STFT), enabling the extraction of the broadband spoof plasmon dispersion with a single measurement as well as the attenuation coefficient with a minimum of two measurements. Broadband sensing is demonstrated, again by filling the grooves with various fluids, which results in changes in the spoof plasmon dispersion and attenuation coefficients. In addition, the observation of the absorption peak of α-lactose monohydrate at 1.37 THz due to the enhanced light- matter interactions on an SPS is demonstrated and opens the door towards a more spectroscopic approach to THz sensing using SPSs.
50
Pike, Oliver. "Particle interactions in high temperature plasmas." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/28911.
Full textAbstract:
High temperature plasmas are ubiquitous in high energy astrophysics and are becoming increasingly accessible in the laboratory. This thesis is concerned with two interactions that are important in these systems. The first is the Coulomb interaction, which influences phenomena in systems ranging from controlled fusion experiments to catastrophic astrophysical events. In many of these cases, the motion of the electrons is relativistic. To account for this we extend Spitzer's famous work on dynamical friction in a plasma to relativistic interactions, deriving the Fokker-Planck coefficients and test particle relaxation rates in the same analytical form as Trubnikov's classical results. Following this, we present a self-consistent transport theory for a relativistic, magnetised plasma, including simple polynomial fits to the transport coefficients for various values of atomic number. This is the relativistic generalisation of the work of Braginskii and, within the confines of linear transport theory, is valid for all temperatures and field strengths of interest. These results are subsequently verified using Monte Carlo simulations, and the effects of non-Gaussian multiple scattering on transport in a plasma are shown to be small. Beyond relativistic corrections, high temperature plasmas are fundamentally different to their classical counterparts due to the possibility of pair production. One of the primary mechanisms for this and the second interaction we consider is the Breit-Wheeler process: the formation of an electron-positron pair in the collision of two photons. Despite being the simplest way in which light can be converted into matter, this process has never been directly observed in the laboratory. Here, we present a new design of photon-photon collider, in which a laser wakefield-driven gamma-ray beam is fired into the high temperature radiation field of a laser-heated hohlraum. On matching experimental parameters to current facilities, Monte Carlo simulations suggest this is capable of producing over 10^5 Breit-Wheeler pairs per shot.