Cellulose is an extraordinarily abundant polymer that can be harvested and purified from trees and other renewable sources. Cellulose derivatives have been widely used as coatings, optical films, fibers, molded objects, and matrices for controlled release. The properties of cellulose derivatives are not only affected by the degree of substitution, but also by the position of substitution. In order to establish the structure-property relationships of cellulose derivatives, it is of great importance to impart regioselectivity into functionalized cellulose. However, regioselective substitution of cellulose is extremely challenging, especially in the synthesis of regioselectively functionalized cellulose esters due to the unstable ester bond under aqueous alkaline or acid conditions. In this dissertation, the main objective is to search for new tools to synthesize regioselectively substituted cellulose esters, to understand how structural changes impact properties and performance, and thus to design cellulose derivatives delivering high performance. Several strategies for regioselective preparation of cellulose esters are discussed in detail. The obtained regioselective cellulose esters were fully characterized analytically. / Ph. D.

Variable Geometry Trusses (VGT’s) can be used as the fundamental building blocks in constructing long-chain, high degree-of-freedom manipulators. This thesis focuses on the kinematics of two such manipulators. It also illustrates how the concept of shape control can be applied to simplify the computational aspects of controlling these devices. To serve as examples, algorithms are developed for the control of both a thirty degree of freedom planar manipulator and a sixty degree-of-freedom spatial manipulator. Based on a review of the literature, this work appears to be the first attempt to develop real-time, position control strategies for such highly-dexterous manipulators. / Master of Science / incomplete_metadata

The normative foundation (axioms) of Bayesian belief updating has long been established in the literature of decision science. However, psychology and experiments suggest that while rational decision making is ideal, it is rarely achievable for ordinary people. Therefore, it is important to explore the foundations and consequences of rational decision making within the field of economics. This thesis involves three papers on this. In the first paper, I explore the consequences of wishful thinking on mechanism design. It suggests that wishful thinking bias could be profit-generating for mechanism designers. In the second paper, I investigate conservative updating and provide a foundation for it. The main behavioral axiom, ``conservative consistency," suggests that decision-makers may partially incorporate information, particularly when it requires them to revise their previous preferences (the preferences order according to their prior belief). In the third paper, I reframe the model selection problem as a rational decision-making problem. The decision-maker is restricted to choosing an advisor to delegate their choices. I explore the conditions under which a rational decision-maker selects models (or advisors) according to Bayes factor criteria. / Doctor of Philosophy / Most of us do not always make decisions completely rational. This thesis digs into how irrational decision-making fits into economics, with three papers to break it down. The first paper looks at wishful thinking and how it affects our decisions. It suggests that if we understand our biases, we can design better mechanism to generate profit. The second paper talks about conservative updating, which is all about how we pick and choose what information matters, especially when it clashes with our existing belief. Lastly, the third paper explores how we choose advisors to help us make decisions. It looks at when it is smart to pick based on Bayes factor criteria. Through these papers, this thesis helps us understand how rational decision-making plays out in real-life economics.

Yes / The archetypal prodrug of the imidazotetrazine class is the anticancer agent temozolomide (TMZ). The prodrug activation kinetics of TMZ show an unusual pH dependence: it is stable in acid and rapidly hydrolyses in alkali (Denny, B.J., et al. Biochemistry 1994, 33, 9045–9051). The incipient drug MTIC has the opposite properties—relatively stable in alkali but unstable in acid. In this study, the mechanism of prodrug activation was probed in greater detail to determine whether the reactions are specific or general acid or base catalysed. Three prodrugs and drugs were investigated, TMZ, MTIC and the novel dimeric imidazotetrazine EA27. Hydrolysis in a range of citrate-phosphate buffers (pH 8.0, 7.4, 4.0) was measured by UV spectrophotometry. Reaction of TMZ and MTIC obeyed single-phase, pseudo-first order kinetics (Figure 1). EA27 was more complex, showing biphasic but approximately pseudo-first order kinetics, Figure. General acid or base catalysis indicates that protonation or deprotonation is the rate-limiting step (rls). In biological milieu, the nature and concentration of other acidic or basic solutes may affect the prodrug activation reaction. In contrast, specific acid or base catalysis indicates that protonation or deprotonation occurs before the rls, so catalysis depends only on the local concentration of hydroxide or hydronium ion (i.e., pH) so the reaction kinetics are not expected to change appreciably in a biological medium.

La synthèse dimensionnelle se focalise sur la détermination des dimensions des piècesconstituant le mécanisme et de leur placement. Cependant, malgré les nombreux travaux dansce domaine, les techniques actuelles de dimensionnement n’offrent des solutions satisfaisantesque pour des classes de mécanismes particulières.Dans nos travaux, nous décrivons une approche de résolution générique de problèmes desynthèse dimensionnelle de mécanismes. Une spécification déclarative par contraintes facilitela prise en compte de tout type de mécanismes (plans ou spatiaux, à topologie ouverteou fermée et comportant un nombre quelconque de pièces et de liaisons cinématiques). Lamodélisation des problèmes proposée rend possible la génération automatique d’équationstraduisant simultanément l’objectif à atteindre et les contraintes à respecter ainsi que laconstruction des différents mécanismes solution.Les équations résultantes étant non linéaires, fortement couplées et n’admettant pas nécessairementde solution exacte, nous proposons de les traiter par des méthodes d’optimisation.De plus, la stratégie développée se concentre sur la recherche de plusieurs minima locauxdu problème de synthèse et non sur la recherche d’un minimum global. En premier lieu, uneméthode d’optimisation globale par essaims particulaires explore le domaine de recherche etfournit plusieurs points approchant des minima. Plusieurs processus d’optimisation locale,basés sur la méthode de Nelder-Mead, exploitent ensuite de manière concurrente ces points.Cette stratégie permet d’améliorer considérablement la robustesse de chacune des méthodesprises indépendamment et surtout de proposer plusieurs configurations à l’utilisateur quipourra finalement sélectionner la meilleure solution d’après ses critères.Nous avons développé une maquette d’application de synthèse dimensionnelle de mécanismes,complètement intégrée dans un environnement de conception assistée par ordinateurindustriel qui nous permet de valider la démarche de conception que nous proposons sur unensemble de problèmes classiques. / Mechanism synthesis deals with design of mechanical devices capable of performing adesired task. Dimensional synthesis focuses on the determination of the parts’ dimensionsand locations in order to fulfill the requirements. Despite many works in this research field,current design techniques are lacking in generality and are only suitable for specific classesof mechanisms.This work proposes a generic approach to solve mechanism dimensional synthesis. Adeclarative specification based on constraints facilitates the design of almost any systemtopology such as planar and three-dimensional mechanisms with open and closed loop kinematicchains containing any number and type of joints. The modeling approach presentedallows automatic generation of systems of equations representing both the constraints tosatisfy and the target objectives to minimize, while enabling geometric construction of theobtained solutions.The resulting polynomial equations are nonlinear, highly coupled and do not necessarilyadmit an exact solution. Therefore, we propose to solve them by optimization methods. Thedeveloped strategy focuses on finding several local minima of synthesis problems instead offinding a global minimum. First, a particle swarm global optimization explores the searchdomain and provides points approximating these minima. Then, various Nelder-Mead basedlocal optimization processes handle these points concurrently. This strategy significantlyimproves the robustness of each optimization method taken independently. It also makes itpossible for the designer to choose the best solution among several configurations accordingto his criteria.A dimensional mechanism synthesis prototype, fully integrated with a commercial computeraided design software, has also been developed. It allows validating our design approachon a set of classical problems.

Main objective of this study is to design a compliant mechanism with high frequency and high mechanical amplification ratio to be used for amplifying the stroke of a piezostack actuator. In this thesis, first of all, related literature is investigated and then alternative conceptual designs are established utilizing the mechanisms found in literature survey. Once best conceptual design is selected, detailed design of this mechanism is done. For detailed design of the compliant mechanism, topology optimization method is used in this study. To design the mechanism, first a design domain is defined and then a finite element model of the design domain is prepared to be used in topology optimization runs. After running the topology optimization model by using TOSCA with ANSYS, results are imported to ANSYS, where final performance of the mechanism design is checked. After finalizing design of the mechanism, it is produced and its performance is tested through experiments.

Main objective of this study is to design a compliant mechanism with high frequency and high mechanical amplification ratio to be used for amplifying the stroke of a piezostack actuator. In this thesis, first of all, related literature is investigated and then alternative conceptual designs are established utilizing the mechanisms found in literature survey. Once best conceptual design is selected, detailed design of this mechanism is done. For detailed design of the compliant mechanism, topology optimization method is used in this study. To design the mechanism, first a design domain is defined and then a finite element model of the design domain is prepared to be used in topology optimization runs. After running the topology optimization model by using TOSCA with ANSYS, results are imported to ANSYS, where final performance of the mechanism design is checked. After finalizing design of the mechanism, it is produced and its performance is tested through experiments.

Choline oxidase (E.C. 1.1.3.17) from Arthrobacter globiformis catalyzes the four-electron oxidation of choline to glycine betaine (N,N,N-trimethylglycine) via two sequential, FAD-dependent reactions in which betaine aldehyde is formed as an enzyme-bound intermediate. In each oxidative half-reaction, molecular oxygen acts as electron acceptor and is converted into hydrogen peroxide. Biochemical, structural, and mechanistic studies on the wild-type and a number of mutant variants of choline oxidase have recently been carried out, allowing for the depiction of the mechanism of alcohol oxidation catalyzed by the enzyme. Catalysis by choline oxidase is initiated by the removal of the hydroxyl proton of alcohol substrate by a catalytic base in the enzyme-substrate complex, yielding the formation of the alkoxide species. In this dissertation, the roles of His351 and conserved His466 were investigated. The results presented demonstrate that His351 is involved in the stabilization of the transition state for the hydride transfer reaction and contributes to substrate binding. His466 is likely to be a catalytic base in choline oxidase due to its dramatic effect on enzymatic activity. Comparison of choline oxidase and other enzymes within its superfamily reveals the presence of a conserved His-Asn pair within the active site of enzymes. Therefore, the role of the conserved Asn510 in choline oxidase was examined in this study. The results presented here establish the importance of Asn510 in both the reductive and oxidative half-reactions. The lost of ability to form a hydrogen bond interaction between the side chain at position 510 with neighboring residues such as His466 resulted in a change from stepwise to concerted mechanism for the cleavages of OH and CH bonds of choline, as seen in the Asn510Ala mutant. Finally, the steady-state kinetic mechanism of pyranose 2-oxidase in the pH range from 5.5 to 8.5 was investigated. It was found that pH exerts significant effects on enzyme mechanism. This study has established the involvement of the residues in the initiation of enzyme catalysis and the stabilization of the alkoxide intermediate in choline oxidase. In addition, this work demonstrates the first instance in which the kinetic mechanism of a flavin-dependent oxidase is governed by pH.

This research is to carry out an experimental study to examine and verify the effectiveness of the control algorithms and strategies developed at the Advanced Engineering Design Laboratory (AEDL). For this purpose, two objectives are set to be achieved in this research. The first objective is to develop a generic experiment environment (test bed) such that different control approaches and algorithms can be implemented on it. The second objective is to conduct an experimental study on the examined control algorithms, as applied to the above test bed. <p>To achieve the first objective, two main test beds, namely, the real-time controllable (RTC) mechanism and the hybrid machine, have been developed based on a two degree of freedom (DOF) closed-loop five-bar linkage. The 2-DOF closed-loop mechanism is employed in this study as it is the simplest of multi-DOF closed-loop mechanisms, and control approaches and conclusions based on a 2-DOF mechanism are generic and can be applied to a closed-loop mechanism with a higher number of degrees of freedom. The RTC mechanism test bed is driven by two servomotors and the hybrid machine is driven by one servomotor and a traditional CV motor. To achieve the second objective, an experimental study on different control algorithms has been conducted. The Proportional Derivative (PD) based control laws, i.e., traditional iii PD control, Nonlinear-PD (NPD) control, Evolutionary PD (EPD) control, non-linear PD learning control (NPD-LC) and Adaptive Evolutionary Switching-PD (AES-PD) are applied to the RTC mechanism; and as applied to the Hybrid Actuation System (HAS), the traditional PD control and the SMC control techniques are examined and compared. <p> In the case of the RTC mechanism, the experiments on the five PD-based control algorithms, i.e., PD control, NPD control, EPD, NPD-LC, and AES-PD, show that the NPD controller has better performance than the PD controller in terms of the reduction in position tracking errors. It is also illustrated by the experiments that iteration learning control (ILC) techniques can be used to improve the trajectory tracking performance. <p>However, AES-PD showed to have a faster convergence rate than the other ILC control laws. Experimental results also show that feedback ILC is more effective than the feedforward ILC and has a faster convergence rate. In addition, the results of the comparative study of the traditional PD and the Computed Torque Control (CTC) technique at both low and high speeds show that at lower speeds, both of these controllers provide similar results. However, with an increase in speed, the position tracking errors using the CTC control approach become larger than that of the traditional PD control. In the case of the hybrid machine, PD control and SMC control are applied to the mechanism. The results show that for the control of the hybrid machine and the range of speed used in this experimental study, PD control can result in satisfactory performance. However, SMC proved to be more effective than PD control.

Mechanistic studies of electrochemical proton coupled electron transfer (PCET) have attracted attention for many decades due to their importance in many fields ranging from electrocatalysis to biology. However, mechanistic research is confined to only a few groups, and challenges in this field can be found in both theory and experiment. The contributions to mechanistic studies of electrochemical PCET reaction in this thesis can be categorized under the following two headings: 1) mechanistic studies of an aminobenzoquinone modified monolayer system with multiple electron/proton transfer reaction; 2) studies that attempt to develop the relationship between thermochemical data and electrochemical PCET mechanism. An aminobenzoquinone modified monolayer showing nearly ideal electrochemical behavior and high stability was successfully prepared and used as a model system for the mechanistic study of electrochemical multiple electron/proton transfer. This model system has been proposed to undergo a 2e3H transfer at low pH electrolyte and a 2e2H transfer at high pH electrolyte. Two non-destructive electrochemical techniques (cyclic voltammetry and chronocoulmetry) have been applied for the measurement of apparent standard rate constant as a function of pH. Both pH dependent apparent formal potential and pH dependent apparent standard rate constant have been used to determine the charge transfer mechanism of this monolayer system. Under the assumption of an operative PCET mechanism (i.e. electron transfer step is the rate determining step), a theoretical description of this system has been developed based on the refinement and extension of previous models. By combining this extended theoretical model with pH dependent apparent formal potential and apparent standard rate constant, charge transfer pathways have been determined and shown to be consistent with the observed pH dependent electrochemical response, in addition, the determined pathways in this aminobenzoquinone modified monolayer are similar to previous reported pathways for benzoquinone freely dissolved in aqueous buffered electrolyte. A series of analytical expressions built in this thesis demonstrate that the parameters that differentiate stepwise mechanisms from concerted mechanisms can be classified into two aspects: thermodynamic parameters, namely acid dissociation constants, standard formal potentials; and kinetic parameters, namely standard rate constants, standard transfer coefficients. Although attempts to understand the relation between controlling parameters and electrochemical PCET mechanism (stepwise versus concerted) has been reported previously by some groups, there are still lots of unresolved aspects requiring further investigation. In this thesis, an important conclusion has been drawn which is that for the stepwise mechanism, an apparent experimentally observable kinetic isotope effect (KIE) can be induced by solvent isotope induced variation of acid dissociation constants, which contradicts previous understanding. Additionally, for the first time, values of apparent KIE, which were measured for the aminobenzoquinone modified monolayer system with stepwise PCET mechanism, were successfully explained by variation in acid dissociation constants, not by variation in standard rate constants. Based on theoretical prediction, a nitroxyl radical modified bilayer showing one electron one proton transfer reaction has been prepared in an effort to afford experimental verification. After applying similar analytical procedures as those for the aminobenzoquinone modified monolayer system, this bilayer system has been shown to follow the concerted 1e1H transfer pathway in high pH electrolytes. These latter contributions provide evidence that further development in this field will eventually lead to a comprehensive theory that can use known thermochemical variables to fully predict PCET mechanism.