Les systèmes biphasiques eau/huile stabilisés par des nanoparticules (NPs) amphiphiles et catalytiques sont à l'origine du concept "Pickering Interfacial Catalysis" (PIC). Favorisant la réaction à l'interface eau/huile grâce à une aire de contact fortement accrue, ces milieux réactionnels micro-dispersés constituent une alternative à l'utilisation de catalyseurs homogènes ou de transfert de phase, difficiles à recycler. La combinaison de NPs amphiphiles à base de polyoxométallates et de silices modifiées par greffages de chaînes aliphatiques et de sites acides a permis de transposer avec succès le concept PIC au clivage oxydant des oléfines pour la synthèse verte de diacides à fort intérêt industriel (e.g. l’acide adipique). En effet, l'association des deux types de NPs a révélé un fort effet synergique non seulement sur les propriétés des émulsions (taille des gouttelettes, stabilité) mais aussi vis-à-vis des performances catalytiques. En particulier, une sélectivité très élevée a été obtenue pour la synthèse de l'acide adipique mettant ainsi en avant la possibilité de réaliser des cascades catalytiques acide-redox à l’interface eau/huile. Au regard des résultats obtenus, nous avons dénommé cette nouvelle application du concept PIC "Pickering Interfacial Cascade Catalysis" (PICC). En associant deux types de NPs catalytiques à l’interface eau/huile, il s’avère ainsi possible de réaliser des cascades catalytiques en milieu biphasique tout en respectant les principes de chimie verte par rapport à l’économie d’atomes et à la séparation du produit de réaction et des NPs catalytiques. / Biphasic water/oil systems stabilized by catalytic amphiphilic nanoparticles (NPs) are the origin of the Pickering Interfacial Catalysis (PIC) concept. By favoring the reaction at the water/oil interface driven by an enhanced contact between the phases, these micro-dispersed systems provide an alternative to the use of homogeneous and phase-transfer catalysts, which are hardly recyclable. The combination of amphiphilic NPs based on polyoxometalates and silicas modifed by grafting alkyl chains and acid centers allowed the transposition of the PIC concept to the oxidative cleavage of olefins for the green synthesis of diacids with potential industrial value (e.g. adipic acid). Indeed, the combination of both NPs revealed a strong synergistic effect for Pickering emulsions (droplet size, stability) and the catalytic performance. In particular, very high selectivities were achieved for the synthesis of adipic acid, thus highlighting the possibility of carrying out acid-redox catalytic cascades at the water/oil interface. In light of the results, we termed this new application of the PIC concept as Pickering Interfacial Cascade Catalysis (PICC). By assembling two types of catalytic NPs at the water/oil interface, it is possible to design catalytic cascades in biphasic media while complying with the Green Chemistry principles with respect to atom economy and the separation of the reaction product and the catalytic NPs.

Ichtyofauna with emphasis on fish fry community was studied in cascade reservoir complex of the Vltava River. Fish spatial distribution and species composition was observed along longitudinal axis of Kamýk, Slapy, Štěchovice and Vrané reservoirs using hydroacoustic, trawling and beach seining.

abstract: DNA has recently emerged as an extremely promising material to organize molecules on nanoscale. The reliability of base recognition, self-assembling behavior, and attractive structural properties of DNA are of unparalleled value in systems of this size. DNA scaffolds have already been used to organize a variety of molecules including nanoparticles and proteins. New protein-DNA bio-conjugation chemistries make it possible to precisely position proteins and other biomolecules on underlying DNA scaffolds, generating multi-biomolecule pathways with the ability to modulate inter-molecular interactions and the local environment. This dissertation focuses on studying the application of using DNA nanostructure to direct the self-assembly of other biomolecular networks to translate biochemical pathways to non-cellular environments. Presented here are a series of studies toward this application. First, a novel strategy utilized DNA origami as a scaffold to arrange spherical virus capsids into one-dimensional arrays with precise nanoscale positioning. This hierarchical self-assembly allows us to position the virus particles with unprecedented control and allows the future construction of integrated multi-component systems from biological scaffolds using the power of rationally engineered DNA nanostructures. Next, discrete glucose oxidase (GOx)/ horseradish peroxidase (HRP) enzyme pairs were organized on DNA origami tiles with controlled interenzyme spacing and position. This study revealed two different distance-dependent kinetic processes associated with the assembled enzyme pairs. Finally, a tweezer-like DNA nanodevice was designed and constructed to actuate the activity of an enzyme/cofactor pair. Using this approach, several cycles of externally controlled enzyme inhibition and activation were successfully demonstrated. This principle of responsive enzyme nanodevices may be used to regulate other types of enzymes and to introduce feedback or feed-forward control loops. / Dissertation/Thesis / Ph.D. Biochemistry 2013

abstract: In contemporary society, sustainability and public well-being have been pressing challenges. Some of the important questions are:how can sustainable practices, such as reducing carbon emission, be encouraged? , How can a healthy lifestyle be maintained?Even though individuals are interested, they are unable to adopt these behaviors due to resource constraints. Developing a framework to enable cooperative behavior adoption and to sustain it for a long period of time is a major challenge. As a part of developing this framework, I am focusing on methods to understand behavior diffusion over time. Facilitating behavior diffusion with resource constraints in a large population is qualitatively different from promoting cooperation in small groups. Previous work in social sciences has derived conditions for sustainable cooperative behavior in small homogeneous groups. However, how groups of individuals having resource constraint co-operate over extended periods of time is not well understood, and is the focus of my thesis. I develop models to analyze behavior diffusion over time through the lens of epidemic models with the condition that individuals have resource constraint. I introduce an epidemic model SVRS ( Susceptible-Volatile-Recovered-Susceptible) to accommodate multiple behavior adoption. I investigate the longitudinal effects of behavior diffusion by varying different properties of an individual such as resources,threshold and cost of behavior adoption. I also consider how behavior adoption of an individual varies with her knowledge of global adoption. I evaluate my models on several synthetic topologies like complete regular graph, preferential attachment and small-world and make some interesting observations. Periodic injection of early adopters can help in boosting the spread of behaviors and sustain it for a longer period of time. Also, behavior propagation for the classical epidemic model SIRS (Susceptible-Infected-Recovered-Susceptible) does not continue for an infinite period of time as per conventional wisdom. One interesting future direction is to investigate how behavior adoption is affected when number of individuals in a network changes. The affects on behavior adoption when availability of behavior changes with time can also be examined. / Dissertation/Thesis / M.S. Computer Science 2013

abstract: Signaling cascades transduce signals received on the cell membrane to the nucleus. While noise filtering, ultra-sensitive switches, and signal amplification have all been shown to be features of such signaling cascades, it is not understood why cascades typically show three or four layers. Using singular perturbation theory, Michaelis-Menten type equations are derived for open enzymatic systems. When these equations are organized into a cascade, it is demonstrated that the output signal as a function of time becomes sigmoidal with the addition of more layers. Furthermore, it is shown that the activation time will speed up to a point, after which more layers become superfluous. It is shown that three layers create a reliable sigmoidal response progress curve from a wide variety of time-dependent signaling inputs arriving at the cell membrane, suggesting that natural selection may have favored signaling cascades as a parsimonious solution to the problem of generating switch-like behavior in a noisy environment. / Dissertation/Thesis / Ph.D. Applied Mathematics 2013

Marine ecosystems contain both highly abundant and diverse communities of vertebrates and invertebrates; however anthropogenic activity has drastically altered the species composition and diversity of these ecosystems. Specifically, human activity has targeted high trophic level species and degraded much of the biogenic habitat that faunal communities rely upon. These alterations have resulted in the loss of many marine predators and overall declines of marine biodiversity. To investigate the consequences of marine predator loss and community level species decline, I use a combination of large-scale data synthesis and in situ field observations of marine fish communities. I first use a meta-analysis approach to synthesize the consequences of marine predator loss in benthic marine ecosystems worldwide. From this synthesis, I was able to determine some of the biotic and abiotic factors that regulate the response of marine herbivores and primary producers to predator loss. Specifically, I show that marine predators have the strongest effect on populations of marine herbivores when predators and herbivores were similar in size and when larger herbivores were involved. Conversely the factors that best explained the response of the primary producer populations were related to the abiotic environment. The results show that primary producers respond the most positively to the presence of predators in high nutrient environments. While I found no link between the magnitude of change in the herbivore population and the magnitude of change in the producer population, I was able to demonstrate that primary producers are under the strongest top-down controls when nutrient concentrations are high, sea surface temperatures are low, and when the predator is larger in size than the herbivore. Finally, I use the data related to marine reserves to show that reserves are an effective tool to help reverse the trophic consequences of marine predator loss and that they are most effective when they are older in age. The third chapter examines the links between community diversity and community biomass within fish communities in eelgrass ecosystems in Northern British Columbia. After controlling for environmental variation, I found that it was the dominance of certain species within a community that resulted in the highest ecosystem function. This finding was demonstrated by both the taxonomic and functional metrics of diversity used. While previous work on this topic has shown that richness is positively correlated to function, my results are to the contrary, and suggest that further investigation into which aspects of community diversity drive ecosystem function is required. In conclusion, my results provide a new synthesis of the consequences of marine predator loss across the world and show how species diversity is linked to ecosystem function in local eelgrass fish communities. / Graduate / 2018-12-17

Abstract The Generalized Predictive Controller in transfer function representation is proposed for the cascade control task. The recommended cascade GPC (CGPC) applies one predictor and one cost function that results in several advantageous features: The disturbance regulations of the inner and the outer loops can be totally decoupled; The inner disturbance regulation is well damped, the typical overshoot of the traditional cascade control structure is avoided; The robustness properties of the inner and the outer loops can be designed separately; The anti-windup properties of the CGPC are exactly as perfect as in the case of the simple SISO GPC. The typical problem of the saturation in the inner loop, resulting in modeling error for the outer loop, is prevented. The CGPC was applied as the oxygen controller of a pilot fluidized bed boiler. The investigation is based on simulation experiments and on experiments on a pilot scale boiler. In another simulation experiment, the CGPC was applied as the temperature controller of at a steam superheater stage. The results of the experiments well illustrated the power of the proposed cascade control algorithm.

The objective of this study is to reconstruct the history of glaciation from the start of Fraser (Late Wisconsinan) Glaciation to the end of deglaciation, for three areas in the Cascade Mountains. The Cascade Mountains are located between the Coast Mountains and the Interior Plateau in southwestern British Columbia. The Coast Mountains were glaciated by mountain glaciation followed by frontal retreat, whereas the Interior Plateau underwent ice sheet glaciation followed by downwasting and stagnation. The Cascades were supposed to have undergone a style of glaciation transitional between these two. Terrain mapping on air photographs followed by field checking was used to locate surficial materials and landforms indicative of glaciation style and pattern. All three study areas were glaciated by mixed mountain and ice sheet glaciation. At the start of Fraser Glaciation, alpine and valley glaciers formed around higher summits as occurred in the Coast Mountains. At the glacial maximum the entire area was covered by the Cordilleran Ice Sheet. Deglaciation was largely by continuous downvalley retreat of active glaciers, contrasting with downwasting and stagnation in the Interior Plateau, and frontal retreat in the Coast Mountains. The scarcity of fresh moraines in the cirques suggests that, unlike in the Coast Mountains, most cirque glaciers were not active at the end of glaciation. Only the highest north facing cirques remained above the local snowline throughout deglaciation and, as a result, glaciers in these valleys remained active and retreated up valley. The pattern of glaciation in the Cascade Mountains was similar to that of other areas which underwent mixed mountain and ice sheet glaciation, such as the Presidential Range in New Hampshire, the Green Mountains in Vermont, mountain ranges in west central Maine and the Insular Mountains on Vancouver Island. However, deglaciation in al l areas was complex and depended strongly on local conditions. For this reason local patterns cannot be predicted easily on the basis of glaciation style. The value of an understanding of glaciation style to improve the accuracy of terrain mapping was also investigated. It was found that the model developed for the Cascade Mountains was of some use in predicting the presence of fine-textured material in valley bottoms and for the prediction of glaciofluvial material overlying till . However fine-textured sediments were not found in al l valleys which were predicted to contain them. The model appears to be most useful as an indicator of where to concentrate field checking in order to locate fine-textured sediments. / Arts, Faculty of / Geography, Department of / Graduate

Hydroamination stands as a desirable approach to nitrogen-containing molecules, which have important applications ranging from pharmaceuticals (fine chemicals) to paints, coatings, insecticides and agrochemicals (bulk chemicals). It features the use of alkene and alkyne starting materials, which are abundant and rarely used in the formation of C-N bonds. This work aims at building on the improved Cope-type reactivity developed in the Beauchemin group by expanding the reach of the reaction and understanding its mechanistic complexities. The first part of this thesis describes the development of cascade reactions to provide a thermodynamic driving force for the intermolecular Cope-type hydroamination of alkenes. The methodology serves as a proof of concept that the dipolar reaction intermediates can be engineered to further react irreversibly to more stable products, and has shown potential in improving the syntheses of natural alkaloids. The second part of the thesis describes the expansion of Cope-type hydrazide hydroaminations through a systematic investigation of hydrazine analogs as reactants. Optimized reagents are featured in the first reported intermolecular Cope-type hydrohydrazidation of alkenes. Mechanistic investigations and isolation of ammonium ylide intermediates support a 5-membered concerted and planar mechanistic pathway for hydrazide hydroaminations, similar to that observed with hydroxylamines. The final section presents mechanistic data disproving a previously assumed difficult proton transfer step in the hydroamination using hydroxylamines. From such findings, early results are presented towards a hydrogen-bond catalyzed hydroamination, which has potential applicability across the field of Cope-type hydroaminations and beyond.

Emissions of CO$_2$ largely contribute to global warming. Carbon dioxide can be captured and used to produce value-added chemicals. This thesis focuses on bioelectrocatalysis as a green and sustainable approach. Our aim was to perform conversion of CO$_2$ to methanol via a multi-enzymatic cascade. However, for reactions involving oxidoreductases, ß-NAD is required as a cofactor. Its use in stoichiometric amounts is unprofitable. We address the issue by employing electrochemical regeneration of the cofactor. For the cascade, we expressed and purified formate dehydrogenase, formaldehyde dehydrogenase and alcohol dehydrogenase. Enzymes activity was tested and found to be low for two enzymes. A reliable method to detect methanol via headspace gas chromatography with a flame ionization detector was developed. We tested the cascade with employed in situ electrochemical cofactor regeneration. After two and a half hours of the reaction 4 µmol methanol were detected. Further research is needed to optimize the setup.