• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 28
  • 10
  • 7
  • 4
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 69
  • 12
  • 12
  • 9
  • 8
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Validation of the WAM-model over the Baltic Sea

Berg, Caroline January 2008 (has links)
<p>In order to understand how waves influence the exchange of momentum, latent heat and other parameters, between the ocean surface and the atmosphere, one can use models. A coupling between a wave model and an atmospheric regional climate model, for the Baltic Sea, will be performed at the Meteorology Institute in Uppsala University. The wave model is a state of the art, third generation wave model called WAM.</p><p>The new version of the WAM model (cycle 4) needs to be validated. The aim of this thesis is to perform this validation and also to investigate what meteorological forcing one should use to achieve best results. Two different types of forcing are analyzed, ERA40 reanalysis and the RCA climate model. In order to do this, observations from six different buoys in the Baltic Sea will be compared with the model output from WAM. The parameters that will be compared in this study are significant wave height, direction and peak period.</p><p>A consistent phenomenon for all the buoys is a slightly overestimation by the model of what the rate of this increases with increasing wave height. If one compares the model output when WAM are forced with the RCA climate model and when it is forced with ERA40 reanalysis, the differences between them are notable but not large. ERA40 is slightly better.</p><p>Significant wave height is quite good and gives a reasonably result. Some buoys and periods are better and some are worse. There are some differences for the significant wave height between the east coast and the west coast of Sweden, when forcing the model with RCA. It is slightly better on the west coast. On the contrary, the results from ERA40 are very coherent. The quality of the hindcast for the direction and the peak period, in contrast to the significant wave height, is not that good. The results are not bad, but it only gives a rough picture of the sea state.</p>
42

Développement de procédés efficaces pour la construction et la production de vecteurs adénoviraux

Gagnon, David 04 1900 (has links)
L’adénovirus possède plusieurs caractéristiques faisant de ce virus un candidat de choix pour la construction de vecteurs utiles dans les études de génomique fonctionnelle. Dans la majorité de ces applications, on a recours à un vecteur adénoviral de première génération délété de sa région E1. L’utilisation de vecteurs adénoviraux comprend deux maillons faibles : la construction du vecteur et la production subséquente de ce dernier. Le développement de méthodes alternatives est donc nécessaire pour renforcer ces deux maillons, permettant ainsi une utilisation étendue de ces vecteurs. Ce développement va s’articuler sur deux axes : l’ingénierie du vecteur de transfert pour la construction de l’adénovirus recombinant et l’ingénierie d’une lignée cellulaire pour la production du vecteur. En utilisant un vecteur de transfert adénoviral co-exprimant, à partir d’un promoteur régulable à la tétracycline, la protéase de l’adénovirus et une protéine de fluorescence verte (GFP) par l’intermédiaire d’un site d’entrée ribosomal interne (IRES), notre groupe a établi que la sélection positive, via l’expression ectopique de la protéase, est un processus efficace pour la création de librairie d’adénovirus recombinants. Par contre, la diversité atteinte dans ce premier système est relativement faible, environ 1 adénovirus recombinant par 1 000 cellules. Le travail effectué dans le cadre de cette thèse vise à construire un nouveau transfert de vecteur dans lequel l’expression de la protéase sera indépendante de celle du transgène permettant ainsi d’optimiser l’expression de la protéase. Ce travail d’optimisation a permis de réduire le phénomène de transcomplémentation du virus parental ce qui a fait grimper la diversité à 1 virus recombinant par 75 cellules. Ce système a été mis à l’épreuve en générerant une librairie adénovirale antisens dirigée contre la GFP. La diversité de cette librairie a été suffisante pour sélectionner un antisens réduisant de 75% l’expression de la GFP. L’amplification de ce vecteur adénoviral de première génération doit se faire dans une lignée cellulaire exprimant la région E1 telle que les cellules 293. Par contre, un adénovirus de première génération se répliquant dans les cellules 293 peut échanger, par recombinaison homologue, son transgène avec la région E1 de la cellule créant ainsi un adénovirus recombinant réplicatif (RCA), compromettant ainsi la pureté des stocks. Notre groupe a déjà breveté une lignée cellulaire A549 (BMAdE1) exprimant la région E1, mais qui ne peut pas recombiner avec le transgène du virus. Par contre, le niveau de réplication de l’adénovirus dans les BMAdE1 est sous-optimal, à peine 15-30% du niveau obtenu dans les cellules 293. Le travail fait dans le cadre de cette thèse a permis de mettre en évidence qu’une expression insuffisante d’E1B-55K était responsable de la mauvaise réplication du virus dans les BMAdE1. Nous avons produit de nouveaux clones à partir de la lignée parentale via une transduction avec un vecteur lentiviral exprimant E1B-55K. Nous avons confirmé que certains clones exprimaient une plus grande quantité d’E1B-55K et que ces clones amplifiaient de manière plus efficace un vecteur adénoviral de première génération. Ce clone a par la suite été adapté à la culture en suspension sans sérum. / The adenovirus has numerous interesting characteristics making this particular virus an ideal candidate for the construction of vector for conducting studies in functional genomics. The vast majority of those applications rely on a so-called “first-generation vector” in which the E1 region is replaced by a transgene. Despite all their advantages, there are 2 weak links associated with first-generation vector: the efficient construction of the actual vector and its production. Therefore, the development of alternative methods for construction and production is necessary to ensure their usefulness. The development will involve 2 axes: the reengineering of the transfer vector for the construction of recombinant adenovirus and the reengineering of the cell line capable of producing the vector. Using a transfer vector co-expressing the adenoviral protease (PS) gene and GFP by using an IRES under the control of a tetracycline-regulated promoter, our laboratory previously established the proof of concept that positive selection of recombinant adenovirus through ectopic expression of the PS gene was an efficient approach to generate adenoviral libraries. However, the diversity achieved was quite low, around 1 recombinant adenovirus per 1,000 cells. The goal of this thesis was to design a new transfer vector in which the PS expression was independent from the expression of the transgene in order to be able to optimize its expression independently. We also improved library diversity by lowering the amount of PS in order to reduce the the trans-complementation from the transfer vector. Using this method, at least 1 recombinant adenovirus per 75 cells was generated with 100% of the plaques being recombinant. This system was successfully used to generate an antisense library targeting GFP. The diversity of the library was high enough to allow the selection of an antisense that inhibited 75% of GFP expression. Amplification of those first-generation recombinant adenoviruses must take place in an E1-expressing cell such as 293 cells. However, when replicating in 293 cells, the recombinant adenovirus can exchange their transgene with the E1 region of the cell by homologous recombination, which results in the generation of a fully replicative adenovirus (RCA), a situation that compromises the purity of the viral preparation. Our laboratory has previously patented an A549 cell line expressing the E1 region and producing RCA-free recombinant adenovirus (BMAdE1). However, the replication of E1-deleted adenovirus in BMAdE1 cells was sub-optimal, in the range of 15-30% the level obtained in 293 cells. The work done in this thesis establishes that the low level of E1B-55K could be responsible for the lower productivity of BMAdE1 cells. Thus, we have derived new clones following lentiviral transduction in order to increase E1B-55K expression. Western blot confirmed that some clones expressed more E1B-55K than BMAdE1, and this correlated with a more robust replication of a recombinant adenovirus in those clones. This newly optimized BMAdE1 cell line was adapted to serum-free suspension culture.
43

Diferencias de los modelos de fiscalización ambiental de Proyectos con RCA y Proyectos sin RCA, análisis a partir de la fiscalización ambiental de faenas mineras de la Región de Antofagasta

Loeser Edwards, Francisco Javier January 2018 (has links)
Memoria (licenciado en ciencias jurídicas y sociales) / Este trabajo realiza una comparación de los dos modelos de fiscalización ambiental que conviven actualmente en Chile, en base a criterios cualitativos y cuantitativos, se pretende comparar la fiscalización ambiental de proyectos que cuentan con RCA favorable, con la fiscalización de proyectos que no cuentan con dicho instrumento de gestión. Este contraste, en primer lugar, se centra en el diseño formal de ambos modelos de fiscalización, en segundo lugar, se busca realizar un análisis práctico, por un lado, basándose en el estudio del estado actual de la fiscalización ambiental de faenas mineras dentro de la región de Antofagasta, por otro lado, dando cuenta de las principales críticas que han tenido ambos sistemas.
44

Maintenir la paix, mais laquelle ? : Interdépendances, zones d’action et conjoncture de maintien de la paix dans le secteur de la sécurité collective / Keep the peace, but which peace ? : Interdependance, areas of action and conjuncture of peacekeeping in the collective security sector

Godefroy, Maxime 05 April 2016 (has links)
A travers l’exemple des opérations de maintien de la paix (OMP) conjointes entre les Nations Unies et l’Union européenne au Tchad et en République centrafricaine (Eufor Tchad-RCA et Minurcat) entre 2008 et 2010, cette thèse questionne les mécanismes qui mènent au déclenchement d’une opération de sécurité collective dite de maintien de la paix ainsi que son déroulement. Alors que les analyses anglo-saxonnes du maintien de la paix dans le champ des Relations internationales questionnent peu le processus qui mène à leur déploiement, faisant de celui-ci une réponse quasi rationnelle à l’émergence ou la reprise d’une « crise », cette thèse analyse finement le processus non linéaire qui mène au déploiement des opérations Eufor Tchad-RCA et Minurcat. Cela permet d’interroger de manière originale les disfonctionnements du maintien de la paix en ne s’intéressant pas uniquement à l’appropriation locale d’une OMP comme dans la littérature sur la paix libérale mais en analysant les continuités entre les phases dites de décision et celles de mise en oeuvre. La thèse défendue ici est que le déclenchement d’une OMP se comprend comme le produit de l’activité sociale ayant lieu autour d’un enjeu sécuritaire qui mène à la structuration d’une zone d’action conjoncturelle dans le secteur de la sécurité collective. On parle de conjoncture de maintien de la paix. Le déroulement de l’OMP s’analyse alors comme la poursuite de l’activité au sein de cette zone d’action qui intègre de nouveaux acteurs durant la phase de conduite des opérations. La reconfiguration de la zone d’action peut mener à la poursuite de l’OMP ou à sa fin suivant la dynamique sociale qui se met en place. / Through the example of joint peackeeping operations (PKO) between the United Nations and the European union in Chad and Central african Republic (known by their French acronyms as Eufor Tchad-RCA and Minurcat) between 2008 and 2010, the purpose of this research is to question the social process that lead to the launching and the implementation of a collective security operation knwon as a peacekeeping operation.Though the Anglo-Saxon analyses of peacekeeping inspired by the International Relations theory not often question the decisionnal process, considering the deployment as a rational mean to treat a crisis, this thesis is an analysis of the non-linear social process that led to the deployment of Eufor Tchad-RCA and Minurcat. This analysis allows us to question in an orignal way the dysfunction of peacekeeping by shifting the focus from the local appropriation of the PKO as suggested by the Libera Peace approach to the continuity between decisionnal stages and implementation stages of the PKO. The thesis proposed here is that the launching of a PKO must be understood as the output of the social activity that takes place around a security issue that lead to the structuration of an area of action in the collective security sector. We named that periode a conjuncture of peacekeeping. The conduct of the operation is then analysed as the continuity of the activity in this area of action which includes new actors during its implementation stage. The re setup of the area of action can lead to the pursuit of the PKO or to its end, regarding the social dynamic that is set up.
45

Validation of the WAM-model over the Baltic Sea

Berg, Caroline January 2008 (has links)
In order to understand how waves influence the exchange of momentum, latent heat and other parameters, between the ocean surface and the atmosphere, one can use models. A coupling between a wave model and an atmospheric regional climate model, for the Baltic Sea, will be performed at the Meteorology Institute in Uppsala University. The wave model is a state of the art, third generation wave model called WAM. The new version of the WAM model (cycle 4) needs to be validated. The aim of this thesis is to perform this validation and also to investigate what meteorological forcing one should use to achieve best results. Two different types of forcing are analyzed, ERA40 reanalysis and the RCA climate model. In order to do this, observations from six different buoys in the Baltic Sea will be compared with the model output from WAM. The parameters that will be compared in this study are significant wave height, direction and peak period. A consistent phenomenon for all the buoys is a slightly overestimation by the model of what the rate of this increases with increasing wave height. If one compares the model output when WAM are forced with the RCA climate model and when it is forced with ERA40 reanalysis, the differences between them are notable but not large. ERA40 is slightly better. Significant wave height is quite good and gives a reasonably result. Some buoys and periods are better and some are worse. There are some differences for the significant wave height between the east coast and the west coast of Sweden, when forcing the model with RCA. It is slightly better on the west coast. On the contrary, the results from ERA40 are very coherent. The quality of the hindcast for the direction and the peak period, in contrast to the significant wave height, is not that good. The results are not bad, but it only gives a rough picture of the sea state.
46

Développement de procédés efficaces pour la construction et la production de vecteurs adénoviraux

Gagnon, David 04 1900 (has links)
L’adénovirus possède plusieurs caractéristiques faisant de ce virus un candidat de choix pour la construction de vecteurs utiles dans les études de génomique fonctionnelle. Dans la majorité de ces applications, on a recours à un vecteur adénoviral de première génération délété de sa région E1. L’utilisation de vecteurs adénoviraux comprend deux maillons faibles : la construction du vecteur et la production subséquente de ce dernier. Le développement de méthodes alternatives est donc nécessaire pour renforcer ces deux maillons, permettant ainsi une utilisation étendue de ces vecteurs. Ce développement va s’articuler sur deux axes : l’ingénierie du vecteur de transfert pour la construction de l’adénovirus recombinant et l’ingénierie d’une lignée cellulaire pour la production du vecteur. En utilisant un vecteur de transfert adénoviral co-exprimant, à partir d’un promoteur régulable à la tétracycline, la protéase de l’adénovirus et une protéine de fluorescence verte (GFP) par l’intermédiaire d’un site d’entrée ribosomal interne (IRES), notre groupe a établi que la sélection positive, via l’expression ectopique de la protéase, est un processus efficace pour la création de librairie d’adénovirus recombinants. Par contre, la diversité atteinte dans ce premier système est relativement faible, environ 1 adénovirus recombinant par 1 000 cellules. Le travail effectué dans le cadre de cette thèse vise à construire un nouveau transfert de vecteur dans lequel l’expression de la protéase sera indépendante de celle du transgène permettant ainsi d’optimiser l’expression de la protéase. Ce travail d’optimisation a permis de réduire le phénomène de transcomplémentation du virus parental ce qui a fait grimper la diversité à 1 virus recombinant par 75 cellules. Ce système a été mis à l’épreuve en générerant une librairie adénovirale antisens dirigée contre la GFP. La diversité de cette librairie a été suffisante pour sélectionner un antisens réduisant de 75% l’expression de la GFP. L’amplification de ce vecteur adénoviral de première génération doit se faire dans une lignée cellulaire exprimant la région E1 telle que les cellules 293. Par contre, un adénovirus de première génération se répliquant dans les cellules 293 peut échanger, par recombinaison homologue, son transgène avec la région E1 de la cellule créant ainsi un adénovirus recombinant réplicatif (RCA), compromettant ainsi la pureté des stocks. Notre groupe a déjà breveté une lignée cellulaire A549 (BMAdE1) exprimant la région E1, mais qui ne peut pas recombiner avec le transgène du virus. Par contre, le niveau de réplication de l’adénovirus dans les BMAdE1 est sous-optimal, à peine 15-30% du niveau obtenu dans les cellules 293. Le travail fait dans le cadre de cette thèse a permis de mettre en évidence qu’une expression insuffisante d’E1B-55K était responsable de la mauvaise réplication du virus dans les BMAdE1. Nous avons produit de nouveaux clones à partir de la lignée parentale via une transduction avec un vecteur lentiviral exprimant E1B-55K. Nous avons confirmé que certains clones exprimaient une plus grande quantité d’E1B-55K et que ces clones amplifiaient de manière plus efficace un vecteur adénoviral de première génération. Ce clone a par la suite été adapté à la culture en suspension sans sérum. / The adenovirus has numerous interesting characteristics making this particular virus an ideal candidate for the construction of vector for conducting studies in functional genomics. The vast majority of those applications rely on a so-called “first-generation vector” in which the E1 region is replaced by a transgene. Despite all their advantages, there are 2 weak links associated with first-generation vector: the efficient construction of the actual vector and its production. Therefore, the development of alternative methods for construction and production is necessary to ensure their usefulness. The development will involve 2 axes: the reengineering of the transfer vector for the construction of recombinant adenovirus and the reengineering of the cell line capable of producing the vector. Using a transfer vector co-expressing the adenoviral protease (PS) gene and GFP by using an IRES under the control of a tetracycline-regulated promoter, our laboratory previously established the proof of concept that positive selection of recombinant adenovirus through ectopic expression of the PS gene was an efficient approach to generate adenoviral libraries. However, the diversity achieved was quite low, around 1 recombinant adenovirus per 1,000 cells. The goal of this thesis was to design a new transfer vector in which the PS expression was independent from the expression of the transgene in order to be able to optimize its expression independently. We also improved library diversity by lowering the amount of PS in order to reduce the the trans-complementation from the transfer vector. Using this method, at least 1 recombinant adenovirus per 75 cells was generated with 100% of the plaques being recombinant. This system was successfully used to generate an antisense library targeting GFP. The diversity of the library was high enough to allow the selection of an antisense that inhibited 75% of GFP expression. Amplification of those first-generation recombinant adenoviruses must take place in an E1-expressing cell such as 293 cells. However, when replicating in 293 cells, the recombinant adenovirus can exchange their transgene with the E1 region of the cell by homologous recombination, which results in the generation of a fully replicative adenovirus (RCA), a situation that compromises the purity of the viral preparation. Our laboratory has previously patented an A549 cell line expressing the E1 region and producing RCA-free recombinant adenovirus (BMAdE1). However, the replication of E1-deleted adenovirus in BMAdE1 cells was sub-optimal, in the range of 15-30% the level obtained in 293 cells. The work done in this thesis establishes that the low level of E1B-55K could be responsible for the lower productivity of BMAdE1 cells. Thus, we have derived new clones following lentiviral transduction in order to increase E1B-55K expression. Western blot confirmed that some clones expressed more E1B-55K than BMAdE1, and this correlated with a more robust replication of a recombinant adenovirus in those clones. This newly optimized BMAdE1 cell line was adapted to serum-free suspension culture.
47

天津外貿的比較利益與影響因素 / Comparative advantage and determinants of foreign trade in Tianjin, China

陳瑀彤, Chen, Yu Tung Unknown Date (has links)
2009年中國大陸正式超越德國,成為全球最大出口國,顯示中國大陸在國際貿易市場的重要地位,而天津市以16.4%經濟成長速度成為2011 年中國大陸各省區中,經濟增長最快速的城市。同時,也為英國《經濟學人智庫》2012年公布全球最具經濟競爭力城市。中國大陸傳統產業升級,天津市經濟轉型成功,以及天津市具有沿海的外貿地緣及資源優勢,外貿帶動經濟發展前景不容小覷。 本研究針對天津市外貿及觀察各類出口產品結構變化,以SITC國際貿易標準分類,以顯著性比較利益法及波士頓矩陣分析,探討天津市各項出口產品的比較利益分析。 此外,本研究利用實證模型分析影響天津整體出口額之因素中,將各項自變數分類為要素因素、外部拉動因素以及金融因素之三大影響因素,研究方法先以進行單根檢定(unit-root test),確定變數資料成為定態(stationary),再以迴歸分析方式,藉此檢驗各項變數與天津外貿之間因果關係為何。 / China overtaken Germany as the world's top merchandise exporter in 2009 from WTO data, demonstrates trade status of China in the international trade market. Tianjin posted the fastest growth rates of 16.4 percent among the provinces in China in 2011 as well as ranked as top city in 2012 of economic strength in the global competitiveness by EIU. Trade transition from traditional industry in China transformed the impetus of foreign trade successfully bringing economy prospects in Tianjin with superiority of geography and resources. The research utilized RCA and BCG analysis to observe significance and comparative advantage of each kind of Tianjin’s export products classified by SITC international trade standard method. Moreover, the research selected several affects factors categorized as fundamental element、global propelling and financial factor to examine each variable would be influential and the relation on foreign trade in Tianjin by regression analysis.
48

Aplicación del Artículo 25 quinquies en el marco de la ejecución de proyectos mineros

Ibáñez Núñez, Rossy Andrea January 2016 (has links)
Tesis (magíster en derecho ambiental) / Actividad formativa equivalente a Tesis (AFET) / La siguiente Actividad Formativa Equivalente a Tesis (AFET) tiene por objetivo verificar cómo se han resuelto cinco solicitudes de revisión de Resoluciones de Calificación Ambiental (RCA) de proyectos de la industria minera que se encuentran en etapa de ejecución, en el marco de la aplicación del artículo 25 quinquies de la LBGMA, así como también busca determinar si los casos analizados realmente corresponden a una variación sustantiva de una variable del plan de seguimiento; comprobar si la autoridad ambiental (SEA) se ha comportado coherentemente y establecer el efecto de la participación ciudadana en estos procedimientos de revisión. Luego del análisis crítico de los cinco casos de solicitud de aplicación del artículo 25 quinquies en el marco de la ejecución de proyectos mineros, se pudo concluir, de manera general, que aún faltan mayores especificaciones respecto a lo que es y cómo se debe aplicar el artículo 25 quinquies, tanto por los titulares, como por la misma autoridad sectorial, ya que en dos de los casos estudiados, no se reunían las condiciones establecidas para la solicitud de dicho artículo, ya sea porque no correspondía a una variable que formara parte del plan de seguimiento o porque no se establecieron medidas de control y mitigación durante la evaluación ambiental para una de las variables identificadas. Además se pudo observar que de los cinco casos de revisión de RCA estudiados, en solo uno existió observación ciudadana, la cual no tuvo efecto alguno en el procedimiento de revisión.
49

Evaluation of Alkali-Silica Reaction (ASR)-Induced Damage Generation and Prolongation in Affected Recycle Concrete

Trottier, Cassandra 24 September 2020 (has links)
Recycled concrete is among the rising eco-friendly construction materials which helps to reduce waste and the need for new natural resources. However, such concrete may present previous deterioration due to, for instance, alkali-silica reaction (ASR), which is an ongoing distress mechanism that may keep being developed in the recycled material. This work aims to evaluate the potential of further distress and crack development (i.e. initiation and propagation) of AAR-affected RCA concrete in recycled mixtures displaying distinct past damage degrees and reactive aggregate types. Therefore, concrete specimens incorporating two highly reactive aggregates (Springhill coarse aggregate and Texas sand) were manufactured in the laboratory and stored in conditions enabling ASR development. The specimens were continuously monitored over time and once they reached marginal (0.05%) and very high (0.30%) expansion levels, they were crushed into RCA particles and re-used to fabricate RCA concrete. The RCA specimens were then placed in the same previous conditions and the “secondary” ASR-induced development monitored over time. Results show that the overall damage in ASR-affected RCA concrete is quite different from affected conventional concrete, especially with regards to the severely damaged RCA particles, where ASR is induced by a reactive coarse aggregate, as the RCA particle itself may present several levels of damage simultaneously caused by past/ongoing ASR and newly formed ASR. Moreover, the influence of the original damage extent in such RCA concrete was captured by the slightly damaged RCA mixture eventually reaching the same damage level as the severely damaged mixture. Furthermore, the original extent of deterioration influence the “secondary” induced expansion and damage of RCA concrete since the higher the original damage level, the higher the cracks numbers and lengths observed in the RCA concrete for the same expansion level whereas wider cracks are generated by RCA having previously been subjected to slight damage thus indicating the difference in the distress mechanism as a function of original extent of damage. In addition, it has been found that distress on RCA containing a reactive sand generates and propagates from the residual mortar (RM) into the new mortar (NM) as opposed to RCA containing a reactive coarse aggregate, being generated and propagated from the original coarse aggregate (i.e. original virgin aggregate – OVA) into the NM. Likewise, RCA containing a reactive sand caused longer and higher number of cracks for the same “secondary” induced expansion than the RCA made of reactive coarse aggregate. Finally, novel qualitative and descriptive models are proposed in this research to explain ASR-induced distress generation and propagation on RCA mixtures made of reactive fine and coarse aggregates.
50

Using aptamers to regulate rolling circle amplification

Bialy, Roger January 2021 (has links)
The work described in this dissertation focuses on developing simple yet effective assays integrating nucleic acid (NA) aptamers with rolling circle amplification (RCA) for the detection of non-NA biomarkers. The first project, a comprehensive literature review, highlights the current state of the art in functional NA-based RCA applications, and identifies shortcomings in the detection of non-NA targets with RCA. Biosensor design is critically evaluated from four key perspectives: regulation, efficiency, and detection of RCA, and the integration of all three components for point of care (POC) applications. The second project investigates how target-binding to a linear aptamer can be utilized to regulate RCA in a simple and inexpensive format. Phi29 DNA polymerase (DP) exhibits difficulty processing DNA strands that are bound to non-NA materials such as proteins. The work uses this restriction of phi29 DP as a feature by utilizing protein-binding aptamers as primer strands (aptaprimers) for RCA. The simplicity is showcased by adapting the method to a cellulose paper-based device for the real-time detection and quantification of PDGF or thrombin within minutes. As the second project is a turn-off sensor, the third project exploits the inherent 3’-exonuclease activity of phi29 DP to generate a simple turn-on assay instead. As target-bound aptamers were shown to be resistant to exonuclease activity, the phi29 DP preferentially digests target-free aptaprimers instead of target-bound aptaprimers. The target-bound aptaprimer could be liberated by a circular template (CT) by incorporating toehold-mediated strand displacement (TMSD), and used for RCA. Sensitivity was improved relative to project two, though the dynamic range was narrow owing to difficulty liberating target-bound aptaprimer at high target concentrations. Project four instead used RecJ, which has 5’-exonuclease activity, to modulate aptaprimer availability. Similarly to project three, target-binding conferred protection on the aptaprimer from 5’-exonuclease digestion by RecJ. By including a free 3’ terminus on the aptaprimer, inhibition of RCA due to target binding was avoided and CT-mediated TMSD was not needed, simplifying the assay. As well, this approach was generalizable as it was demonstrated using both a protein (thrombin) and a small molecule (ochratoxin A) target. This turn-on method further improved the assay compared to project three with a 100-fold enhancement in sensitivity and a restoration of the dynamic range. In sum, this work contributed multiple simple and sensitive approaches for the real-time fluorescent detection of proteins and small molecules with the RCA of linear aptamers. / Thesis / Doctor of Science (PhD)

Page generated in 0.0344 seconds