Open Theses and Dissertations

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    Theoretical and experimental studies in electron paramagnetic resonance I: an investigation of the 290K angular spectra of gadolinium (Gd3+, 8s) in Lanthanum Ethyl Sulphate at 5, 10 and 35 GHz using Conventional and generalized Spin-Hamiltonians
    (1969) Shing, Yuh Han; Buckmaster, Harvey A.
    The phenomenon of electron paramagnetic resonance is described microscopically using the rotating.codrdinate methodand macroscopically using the Bloch formalism. Two major nonradiative physical processes, the spin-lattice and spin-spin interactions, whereby a paramagnetic system can loose energy to its environment are briefly discussed. A qualitative description of the crystal-field theory is given. The spin-C Hamiltonian formalism developed by Abragam and Pryce (1951) for interpreting paramagnetic resonance experimental results is described. The conventional (Bleaney, etal., 1951) and generalized spin-Hamiltonian (Grant and Strandberg, 1964) for gadolinium, in lanthanum ethyl sulphate, arederived. The proposed mechanisms for interpreting:the splittingof the ground 8S state of Gd 3+ are reviewed. The EPR spectra of 0.1 per cent Gd 3 as a paramagnetic impurity in lanthanum ethyl' -sulphate were measured at'290°K using 5,10 and 35GHz. spectrometers which, are described. ,The parameters in the conventional:, and genèralizedspin-,Hamiltohian for,' Gin Ianthanum.ethyl, sü1hate were determined at directions parallel and perpendicuThr to lhe cry.sta1 :y 'metry axis using the 5, lQ and35GHz EPR spectra of AM = ± 1 transitions. 'A'convergent, least-mean-square.on1pUter method was utilized for the •àalculation. The eperi.mental and calculated-angular spectra of M = ± 1 and AM =± 2 transitions,are presehted. The experimental results and calculation methods are discussed.
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    Theoretical and experimental studies in electron paramagnetic resonance II : an investigation of the ground state splitting of the Gd3+[4f7, 8S7/2] ion in lanthanide ethylsulphates and the design of l-8GHz coaxial electron paramagnetic resonance spectrome
    (1972) Shing, Yuh Han; Buckmaster, Harvey A.
    Consistently normalized tensor operators T(J) expressed in terms of the angular momentum i are introduced to facilitate the analysis of EPR spectra. The various mathematical relationships involving these tensor operators necessary for their application in EPR spectral analyses are derived and tabulated. The tensor operator techniques of Racah (1942) were also employed to calculate the matrix elements of various interactions including the spin-orbit coupling in a crystalline electric field. These matrix element calculations facilitate theoretical investigations of the ground state splitting of Gd 3 in crystalline electric fields. An iterative, convergent computing procedure has been developed for determining from experimental EPR spectra the best-fit parameters in a generalized spin-Hamiltonian of arbitrary complexity. This procedure requires a high-speed digital computer and employs a least-square fit criterion and exact diagonalization of the spin-Hamiltonian secular matrix. The 1-8GHz, 10GHz and 35GHz EPR spectrometers employed to perform the measurements reported in this thesis are described. The 1-2GHz and 2-4GHz coaxial EPR spectrometers were designed for the direct determination of the ground state splitting of Gd 3+ in the ethylsulphate lattice and involved unique features. The ground state splitting of the Gd 3 {4f 7,8S712 } ion in the ethyl sulphate lattice has been investigated systematically using both conventional and weak magnetic field-sweep variable-frequency EPR spectroscopy. This splitting has also been calculated theoretically using various mechanisms based on the ionic model. The results of these studies showed that all these perturbation mechanisms are inadequate to explain this splitting. The generalized spin-Hamiltonian parameters of Gd 3 in lanthanum ethyisulphate (LaES) were determined from 290K, 35GHz EPR spectra. The parameters associated with a third- or higher-rank spin tensor operator are found to be six orders of magnitude smaller than the g-factor. Precision measurements and analyses have been made of 290.5K, 10GHz EPR spectra of the Gd 3 ion dilutely substituted ( 5:l0) into the C 3 site symmetry of the lanthanide host lattices Ln(C 2H5SO 4 )3.9H 20 where Ln La, Ce, Pr, Nd, Sm, Eu, Tb, Ho, Er, Tm, Yb and Lu as well as Y which is chemically lanthanide-like. It is found that empirical linear relationships exist between the spin-Hamiltonian parameter B1320 of Gd 3+ . and (i) the ionic radius of the lanthanide host; (ii) the unit cell dimensions of the host lattice; (iii) the molar volume of the host lattice; and (iv) the estimated crystal field parameter AGd . A similar linear relationship is found between the ionic radius of the lanthanide host and the spin-Hamiltonian parameter B60 , but not B40 . The 8s71.2 ground state splittings of Gd 3 in LaES have been determined directly using weak magnetic field-sweep variable-frequency EPR spectroscopy. These directly determined splittings were measured in single crystals of LaES doped with 0.5 and l.0(at)% Gd 3 impurity at 290.5 and 77K to a high accuracy of ± 0.1MHz. It is discovered that the J± ½> doublet of the 8S 7 /2 state of Gd 3+ in LaES sp lits anomialously n zero external magnetic fields. This anomalous splitting is found to be (16.60 ± l.0)MHz at 290.5K and (11.15 ± l.0)MHz at 77K. It is shown that spin-spin interaction can produce this type of splitting.
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    Bonus bidding for petroleum leases in West Pembina
    (1980) Kirkby, Robert; McRae, Robert N.
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    Aspects of Taoism in the poetry of Walt Whitman
    (1984) Clark, Roger Y. (Roger Young), 1960-; Kher, Inder N.
    This thesis draws numerous parallels between Lao Tzu's Tao Te Ching, The Writings of Chuang Tze, and the poetry of Walt Whitman. Although Taoism is not one of the influences on Whitman or Leaves of Grass, the Chinese philosophy elucidates through comparison three of Whitman's major poetic themes or concepts. First, the ineffable, infinite, and transcendent nature of Tao helps one to understand Whitman's conception of Being. Second, though different degrees of transcendental awareness are attained by Whitman and the Taoists, they experience Being or Tao simultaneously with worldly experiences. Standing both 'in and out' of the world gives all of them a sense of security and objectivity, and helps them to understand both both the illusion and truth that the world presents. The third major parallel examined in this thesis is that of the paths taken, or methods employed, to arrive at the experience of Being. Throughout the application of Taoism to Whitman's poetry, other literary and religious expressions are employed. Yet the focus of the present study is always on the juxtaposition and comparison of quotations taken directly from Whitman and the Taoists.
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    Energy-Efficient Cooperative Routing in Wireless Networks
    (2010) Dehghan Shirehpaz, Mostafa; Ghaderi, Majid; Wang, Mea; Fapojuwo, Abraham Olatunji
    In this thesis, we explore physical layer cooperative communication in order to design network layer routing algorithms that are energy efficient. We assume each node in the network is equipped with a single omnidirectional antenna and that multiple nodes are able to coordinate their transmissions in order to take advantage of spatial diversity to save energy. Specifically, we consider cooperative diversity at physical layer and multi-hop routing at network layer, and formulate minimum energy routing as a joint optimization of the transmission power at the physical layer and the link selection at the network layer. We study wireless networks with both static and time-varying channels. Based on the optimal algorithms described throughout the thesis, we develop heuristic cooperative routing algorithms that find suboptimal routes, which are computationally simpler. Simulation results are also presented, which investigate the performance of optimal and heuristic routing algorithms in terms of energy efficiency and throughput.
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    Signaling Mechanisms to Physiological Function: Electrical and Second Messenger Communication in Resistance Arteries
    (2012-06-13) Tran, Cam Ha T.; Welsh, Donald
    The goal of this thesis was to develop a deeper understanding of electrical and second messenger communication in small resistance arteries, and how these key biological processes influence vascular contractility and blood flow control. To achieve this goal, we pursued three defined objectives. First, we determined why electrical responses initiated in smooth muscle fail to spread to neighboring cells like their endothelial counterparts. A functional assessment complemented by computational modeling revealed that the structural and connectivity properties of vascular cells play a key role in determining how charge moves asymmetrically among vascular cells. As such, certain cell-specific responses will conduct robustly from cell-to-cell while others will not. Second, we examined the nature of electrical communication in arterial networks and how this key biological process impacts on blood flow control. Once again, using a combination of functional experimentation and computational modeling, we observed that vessel length and branching play a role in determining how electrical phenomenon conduct within a network and influence blood flow control. Further, this work re-emphasizes the essential role of the endothelium in electrical communication and how a modest change in this layer’s coupling, due to disease, can compromise network perfusion. Lastly, using an integrated experimental approach, we explored whether second messengers could cross myoendothelial gap junctions and elicit a feedback response that limits constriction. This pathway begins with agonists inducing smooth muscle cell depolarization and a rise in second messenger concentration. Next, IP3 fluxes across myoendothelial gap junctions and elicits inducible Ca2+ wavelets, an event that in turn activates endothelial IK channels. The resulting hyperpolarization then moderates iv the initial depolarization of smooth muscle. Overall, the findings arising from the three objectives shed new light onto the basis of vasomotor and blood flow control in the resistance vasculature.
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    A traffic accident risk mapping framework
    (2012-06-20) WANG, JING; Wang, Xin
    Identifying traffic accident concentration area is important for road safety improvements. Previous spatial concentration detection methods did not consider the severity levels of accidents, and the final traffic accident risk map for the whole study area ignores the different users’ requirements. This thesis proposes an ontology-based traffic accident risk mapping framework. In the framework, the ontology represents the domain knowledge related to the traffic accidents and supports the data retrieval based on users' requirements. A new spatial clustering method, called DBCTAR (Density-based Clustering for Traffic Accident Risk), takes into account the numbers and severity levels of accidents is proposed for risk mapping. To demonstrate the framework and the new algorithm, the Ontology-based Traffic Accident Risk Mapping (ONTO_TARM) system and a web-based clustering service GeoClustering have been developed. Four case studies in the city of Calgary with final risk maps are presented and discussed.
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    Nonlinear elasticity, fluid flow and remodelling in biological tissues
    (2012-06-26) Tomic, Aleksandar; Federico, Salvatore
    Articular cartilage is a soft tissue with depth-dependent structure and composition that covers the ends of bones in diarthrodial joints. It transmits loads between bones and minimizes joint wear. The purpose of this work was to implement a large deformation nonlinear model for biological tissues with statistically oriented reinforcing fibres, using a biphasic formulation to model global articular cartilage behaviour. The implemented model takes into account the effect of the depth-dependent variation in the collagen fibre orientation and the influence of the collagen fibres on the overall permeability of the tissue. This model was implemented using Finite Element software to determine the depth-dependent deformation of articular cartilage. In addition, a separate investigation was conducted to determine the remodelling of the fibres in statistically oriented fibre reinforced materials as a response to an externally applied loading, using an arterial sample.
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    Total Knee Replacements: Component Design, Pain Prevention and Research Techniques
    (2012-06-26) Saevarsson, Stefan Karl; Anglin, Carolyn
    Total knee arthroplasty is a surgical procedure in which the knee is resurfaced with implants to relieve pain. This thesis presents computed tomography and radiography methods to determine the relative position (kinematics) for the patellofemoral and tibiofemoral joints in vivo for a full range of motion, as well as parameters related to surgical technique. These methods were used to compare: (1) subjects with gender-specific (GS) versus traditional implant designs, (2) symptomatic versus asymptomatic subjects, and (3) static versus dynamic kinematics. Quality of life (QOL) was also measured. GS implants only had a small but significant difference in patellofemoral translation in early flexion; no other differences were found for the kinematics or QOL. For all symptomatic subjects, differences in kinematics or surgical parameters were found, suggesting the cause for the subject’s postoperative pain. Static and dynamic kinematics were comparable in all but one case, where internal/external tibial rotation differed.
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    Gender and the Division of Household Labour: An Analysis of the Implications for Mental and Physical Health
    (2012-06-26) Polachek, Alicia Joyelle; Wallace, Jean E.
    This thesis examines the relationships between the division of household labour and mental and physical health using survey data from 1,193 male and female lawyers in Canada. Household labour is examined in terms of time spent in housework on work days and non-work days, relative contribution to housework, and perceptions of fairness about the division of household tasks. The results indicate that housework time and relative contributions are not particularly detrimental to mental and physical health. Rather, time spent in housework only appears to be harmful when it interferes with weekends or when individuals feel that the division of housework is unfair, particularly if it is unfair to one’s spouse. Interestingly, these relationships do not differ for men and women. The results also suggest that work demands mediate the relationships between gender and health, as well as housework and health. Several avenues for further research are discussed.
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    The Romantic View of Nature and the Conspiracy Theory in Environmental Documentaries
    (2012-07-11) Orda, Olga; Brent, Douglas Allan
    This project argues that environmental documentaries of the 2000s promote harmful Romantic views of nature and produce overly simplistic knowledge about the causes of global environmental degradation through the use of the conspiracy theory. By analyzing the rhetorical and ideological features of environmental documentaries through the tradition of scholars who write on the Romantic views of nature and the conspiracy theories, this project’s methodology will allow us to see how environmental documentaries frame nature and environmental problems in ways that are overly simplistic and even harmful to the advancement of the environmental movement itself. Ultimately, this project contributes a unique analysis not only of environmental films, but more importantly, the types of definitions of nature and environmental problems that circulate and that are perpetuated in popular culture and environmental movement circles.
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    Cardiovascular and renal effects of ANG II and NO in the newborn: roles of AT1Rs and /or AT2Rs
    (2012-07-12) Vinturache, Angela Elena; Smith, Francine Gabriel
    The vasoactive factors angiotensin II (ANG II) and nitric oxide (NO), and the balance between them play a major role in regulating cardiovascular and electrolyte homeostasis. During the perinatal period, both factors are elevated, yet their physiological roles have not been clearly defined. Furthermore, the temporal and spatial expression of the receptors for ANG II (AT1Rs and AT2Rs) is developmentally regulated, although their physiological roles are also unknown. The present study aimed to elucidate for the first time, the physiological effects of ANG II on the kidney during postnatal maturation, as well as the potential role of the ATRs in initiating these physiological effects. In addition, this study investigated for the first time the interaction between ANG II and NO in regulating cardiovascular and renal function during the period of adaptation of the newborn to life after birth. Two study protocols were carried out in conscious lambs at two stages of postnatal maturation - one and six weeks. The first protocol evaluated (a) the individual functions of ATRs and (b) any possible interaction between them in mediating haemodynamic and renal physiological responses of ANG II. The second protocol investigated the roles of ATRs in modulating physiological roles of endogenoulsy produced NO during development. Results from these experiments show for the first time, that there does not appear to be any interaction between AT1Rs and AT2Rs in mediating haemodynamic effects of endogenous ANG II early in life. In contrast, the renal effects of ANG II are mediated through AT1Rs in an age-dependent manner, whereas AT2Rs buffer these effects. My research also shows for the first time, that ANG II modulates the effects of NO on renal haemodynamics and function but not systemic haemodynamics in an age-dependent manner through activation of AT1Rs and AT2Rs. Furthermore, it appears that AT2Rs interact with AT1Rs in mediating the renal effects of NO in developing newborn animals. This is the first description of renal effects of ANG II and a new and important interaction between ANG II and NO under physiological conditions early in life.
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    Exploring the use of clickers to support active learning and knowledge building by pre-service teachers in large lectures
    (2012-07-12) Liu, Angyue; Jacobsen, Michele
    Educators in higher education are being challenged to engage every learner in their learning in large lectures. This case study explored the use of an Audience Response System (i.e., clickers) to engage pre-service teachers in active learning and collaborative knowledge building in a large lecture setting within a Bachelor of Education program. Qualitative and quantitative data was collected from classroom observations, student interviews, the instructor interview, and the student survey. This research found that with the opportunity to respond to clicker questions in lectures, especially to the open-ended text-entry questions, student teachers can be engaged in active learning, and also in the creation, sharing, and promising improvement of their ideas/knowledge as individuals and as a learning community in the large lecture setting. Findings from this study can enrich our understanding about effective strategies of using clickers to improve learning and teaching in large lectures in higher education.
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    International development partnerships and diffusion of renewable energy technologies in developing countries: cases in Latin America
    (2012-07-12) Platonova, Inna; Muller, Larissa
    Access to energy is vital for sustainable development and poverty alleviation, yet billions of people in developing countries continue to suffer from constant exposure to open fires and dangerous fuels, such as kerosene. Renewable energy technologies are being acknowledged as suitable solutions for remote rural communities in much of the developing world and international development non-governmental organizations (NGOs) increasingly play important roles in the diffusion of these technologies via development partnerships. While these partnerships are widely promoted, many questions related to their functioning and effectiveness remain open. To advance the theory and practice, this interdisciplinary exploratory research provides in-depth insights into the nature of international NGO-driven development partnerships in rural renewable energy and their effectiveness based on the case studies in Talamanca, Costa Rica and Cajamarca, Peru. The analysis of the nature of development partnerships shows that partnerships in the case studies differ in structure, size and diversity of actors due to differentiation in the implementation strategies, technological complexities, institutional and contextual factors. A multi-theoretical approach is presented to explain the multiple drivers of the studied development partnerships. The research highlights partnership constraints related to the provision of rural renewable energy, the organizational type and institutional environments. Based on the case studies this research puts forward theoretical propositions regarding the factors that affect the effectiveness of the partnerships. In terms of the partnership dynamics dimension, several key factors of success are confirmed from the existing literature, namely shared values and goals, complementary expertise and capacities, confidence and trust, clear roles and responsibilities, effective communication. Additional factors identified are personality match and continuity of staff. In terms of the partnership outcomes dimension, a previously under-researched aspect of partnerships, this study found that success was associated with a local champion who is trusted by the community, has the resources and skills to educate and engage the community and build capacities for sustainable provision of energy services, and institutionalizes its learning processes. Providing affordable technological solutions that meet people’s needs and are developed in a participatory way are other important factors found to be positively associated with the effectiveness of the studied partnerships.
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    An augmented reality system for the BPM based on the museum circle
    (2012-07-12) Mor, Liraz; Levy, Richard M.; Boyd, Jeffrey E.
    Museums enrich our lives. By presenting knowledge, culture, history and more, the museum experience can add interest and fun to our day. But how do people experience museum visits? Moreover, how can museums stimulate people to return? Augmented reality (AR) can intensify a museum experience and contribute to learning, education and the training process. People can learn more easily when they are active and involved with their environment. Traditionally, most visual arts do not require the visitorsʼ active engagement, aside from looking and thinking about the artworks presented. As a result, there is a limit to the artworks ability to transfer only a fraction of the information that can be transferred. When people are actively engaged in an educational experience, there is potential for them to develop an emotional experience. AR can be a new way to enrich a museum experience and encourage visitors to return. This Thesis research explores the design of an interactive educational installation using AR. A is a growing field, AR enables the user to simultaneously explore their physical surroundings while accessing computer-generated visual data. This research was done in collaboration with the Banff Park Museum (BPM) National Historic Site of Canada. The museum has been in existence for over 100 years, and it mainly holds preserved taxidermy specimens as well as some geological artifacts and historical documentations. Although the museum holds historical significance, it struggles to keep its relevance to some modern day audiences. Furthermore, the taxidermy elicits a negative emotional response for a number of visitors, as values and traditions change over time. This research suggests a set of guidelines for creating a system based on AR for a handheld device for easy use in the museum. The AR system would give the visitors additional computer-graphic information about the specimens presented in the museum. By building a museum theory, and by using guidelines to create the AR system, this research hopes to increase in the future the visitorsʼ interest in the museum content. Furthermore, as a result of increasing the visitorsʼ interests, it is hoped that those visitors who previously recoiled from the taxidermy would now have a more positive emotional response, or at the very least - acceptance.
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    Effect of combined oligofructose and sitagliptin treatment on pre-pregnancy weight loss and gut microbiota in diet-induced obese rats
    (2012-07-12) Eslinger, Amanda; Reimer, Raylene
    The purpose of this study was to evaluate a combined dietary (oligofructose) and pharmacological (sitagliptin) anti-obesity therapy in diet-induced obese female Sprague-Dawley rats and determine if the effects persist throughout pregnancy and lactation. Body weight, glucose tolerance, satiety hormones, and gut microbiota were measured following obesity induction, treatment, and lactation phases of the study. During the treatment period, rats were randomized to seven experimental groups (n=13): (1) High Fat/High Sucrose (Obese Control); (2) Lean Control (Never Obese); (3) AIN-93M (Control-Treated Obese); (4) Oligofructose (Fiber-Treated Obese); (5) Sitagliptin (Drug-Treated Obese); (6) Oligofructose and Sitagliptin (Combination-Treated Obese); and (7) Caloric Restriction (Weight-Matched to Group 6). The combination of oligofructose and sitagliptin resulted in enhanced weight loss, improved glucose tolerance, and gut hormone and microbiota profiles associated with a lean phenotype. Some, but not all, benefits persisted to the end of lactation. The combined therapy may represent a novel anti-obesity treatment.
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    Three-dimensional topology and dynamical modelling of vortex shedding from finite surface-mounted bluff bodies
    (2012-07-12) Bourgeois, Jason; Martinuzzi, Robert
    While the dynamically rich behaviour of fully turbulent wakes is very high dimensional, the most energetic, large scale coherent structures generated through instability processes are typically low dimensional and are thereby conducive to reduced order modeling procedures. These large scale eddies associated with the flow instability have the most anisotropic and geometry dependent topology and act as a source of kinetic energy in the cascade process, making them the most important to characterize. Dissipative small scale structure can then be modelled with reasonable accuracy by traditional means. The present study experimentally educes the coherent structures in the complex three-dimensional wake of a wall-mounted finite square-cross-section cylinder of aspect ratio h/d=4 and 8 immersed in boundary layers of thickness delta/d=0.72 and 2.6 at a Reynolds number of 12,000. Coherent structure eduction is carried out using phase averaging and a novel generalized phase averaging technique that incorporates proper orthogonal decomposition (POD) modes that are most important in the nonlinear instability saturation process. Global flow estimation and mode construction is undertaken using linear pressure-POD coefficient correlations, applicable to experimental investigations where practicality demands that subdomains of the global field are measured asynchronously. The large-scale coherent structures of the wakes investigated are analyzed in terms of their topology, their turbulent kinetic energy (amounting to roughly half the total fluctuation energy), and their influence on turbulence production. The educed coherent vortical structures are found to have either full-loop or half-loop topological structure depending on the boundary layer thickness, showing vortical connector strands connecting alternately shed vortices from either side of the obstacle. The structure provides an explanation of the dipole and quadrupole distributions of streamwise vorticity that have previously been observed in these types of three-dimensional wakes. The reduced order nonlinear Galerkin models derived for the dynamics of the coherent structures using the generalized phase average are shown to successfully account for the slow base flow transients, the instability saturation mechanism, and the excitation of the second harmonic modes.
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    Cycloruthenated chromophores for the dye-sensitized solar cell
    (2012-07-13) Bomben, Paolo Giovanni; Berlinguette, Curtis Paul
    A series of bidentate cyclometalated Ru(II) complexes of general formula [Ru(N^N)(N^N)(C^N)]+, where N^N = polypyridyl ligand and C^N = cyclometalating ligand, have been synthesized, characterized and tested in dye-sensitized solar cells (DSSCs). Cyclometalated Ru(II) complexes, in general, exhibited broader absorption profiles and cathodically shifted electrochemical potentials compared to their polypyridyl analogues. The prototypical cycloruthenated compound, [Ru(bpy)2(ppy)]+ (bpy = 2,2'-bipyridine; Hppy = 2-phenylpyridine), displayed comparable UV-vis spectral coverage to the standard DSSC dye, N3. Molar extinction coefficients were enhanced and the absorption profile was red-shifted through substitution of the molecular periphery. Molecules from the [Ru(bpy)2(ppy)]+ family displayed HOMO and excited-state energy levels properly aligned for use in the DSSC. Anchoring –CO2H groups were ideally located on the bidentate polypyridyl ligands (e.g., H2dcbpy; H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) because this arrangement localized excited-state electron density proximate to TiO2. Increased molecular light absorption was accomplished by installing conjugated substituents (e.g., -NO2, -phenyl, -pyridyl, -2-thiophene-carbaldehyde) on the anionic ring of molecules with general formula [Ru(H2dcbpy)2(C^N)]+. Aromatic substituents were superior to –NO2 because of an ideally positioned lowest excited-state (i.e., localized to H2dcbpy instead of –NO2). Substitution of the anionic ring with 2-thiophene-5-carbaldehyde para to the Ru-C bond resulted in a superior absorption profile enabling a modest cell power conversion efficiency (PCE) of 3.3%. Replacement of one H2dcbpy ligand with bpy generated tris-heteroleptic cyclometalated Ru(II) dyes with general formula [Ru(H2dcbpy)(bpy)(C^N)]+. The use of electron-rich cyclometalating ligands, however, led to poor PCEs because of incompatible Ru electrochemical potentials for dye regeneration. Strong electron withdrawing groups (e.g., –CF3) were required on the C^N ligand to overcome this problem. The combination of electron-rich aromatic (e.g., thiophene, triarylamine) groups on the ancillary bpy and –CF3 groups on the C^N ligand enabled the best light-absorption properties of any dyes examined in this dissertation, while also maintaining properly aligned HOMO and excited-state energy levels for use in the DSSC. Power conversion efficiencies of 7.3% at 1 Sun were attained with these dyes, exceeding the 6.3% achieved by the paradigmatic N3 dye under the same conditions.
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    An agile framework for variability management in software product line engineering
    (2012-07-13) Ghanam, Yaser; Maurer, Frank
    During the past few years, research in agile product line engineering has been gaining more popularity, driven by the much needed ability to combine the flexibility and high responsiveness of agile methods with the economic advantages of reuse and mass customization offered by software product lines. This dissertation presents a novel framework to manage variability in software product lines in an agile context. By leveraging agile practices such as iterative and incremental development, test-driven development, and refactoring, this dissertation shows that a reactive approach to variability management is indeed feasible. The findings of this research demonstrate that acceptance tests can play an important role in variability elicitation; but they may not be sufficient to deduce implicit constraints from requirements. This issue is addressed by using executable acceptance tests alongside feature models in order to uncover implicit constraints and hidden dependencies. The dissertation also discusses the role of executable acceptance tests in supporting the evolution of variability by providing instantaneous feedback on the impact of adding or removing features or variants. For requirements that cannot be adequately described using acceptance tests such as usability and portability requirements, the dissertation demonstrates how such requirements can be treated using a lightweight and reactive approach. At the implementation level, the results of this research show that realizing variability can occur in a reactive manner provided that proper refactoring and testing practices are followed. The results also illustrate how the process can be made more systematic by using tests as a common starting point to inject variability on-demand. The efficiency of the process can be improved by providing automated tool support. Once variability has been realized in the system, the dissertation discusses how individual products can be built using the derivation technique or the instantiation technique. Finally, the dissertation presents important findings on the issues and challenges likely to arise when adopting a new software product line framework in an industrial context. The findings reveal a number of technical challenges, but also bring to surface non-technical issues related to the business needs, the organizational context, and a raft of human factors.
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    A study in the logic of institutions
    (2012-07-13) Payette, Gillman; Zach, Richard
    In my dissertation A Study in the Logic of Institutions I develop a logical system for reasoning about institutions and their consistency. Since my dissertation is a work in logic rather than one in socio-political philosophy, I don’t defend a particular theory of institutions. Instead, I did as Yogi Bera suggested and simply took the fork in the road. A well-developed account of institutions is given by John Searle in (1995); and (2010). His account bases all social reality on language, and I use his account to provide a logic for institutional norms. Briefly, social reality is constructed via language by making our intentions clear to one another. And we do this via speech acts. There is one particular type of speech act that is important to institutions: declarations. Declarations bring about new social objects and create social states of affairs. It is via declarations that social institutions are created. In so far as groups recognize an institution sustaining/making authority, that authority has the ability to generate new institutional rules via declarations. According to Vanderveken (1990, 1991); see also Searle and Vanderveken (1985), speech acts have a logic. That is, performing one speech act can satisfy the conditions of having performed another speech act. A priest declaring a baby baptized will also make it so that the priest has asserted that the baby is baptized, for instance. More importantly, certain declarations will result in the declarations of some of the logical consequences of the initial declarations. I characterize the set of speech acts that stand in that relationship and develop a logical system around that characterization. The formal framework incorporates action and permits representations of complex institution-dependent relations, e.g., rights and duties. I further develop this formalism to investigate the notion of normative consistency. I show how to represent at least a minimal conception of normative inconsistency within the formal framework, and characterize its properties. I conclude by comparing my work to that of others.