VictorJuiz/thesis huggingface dataset:
Early Versus Delayed Cholecystectomy for Acute Calculous Cholecystitis
Keywords: acute cholecystitis
cholecystectomy

Introduction: Despite evidence in favour of cholecystectomy early during first presenting admission for most patients with acute calculous cholecystitis, variation in the timing of cholecystectomy remains evident worldwide. This dissertation characterizes the extent of variation within a large regional healthcare system, as well as addresses gaps in our current understanding of the clinical consequences and costs associated with early versus delayed cholecystectomy for acute cholecystitis. Methods: A population-based retrospective cohort of patients admitted emergently with acute cholecystitis was identified from administrative databases for the province of Ontario, Canada. First, the extent of variation across hospitals in the performance of early cholecystectomy (within 7 days of emergency department presentation) was characterized. Second, among patients discharged without cholecystectomy following index admission, the risk of recurrent gallstone symptoms over time was quantified. Third, operative outcomes of early cholecystectomy were compared to those of delayed cholecystectomy. Finally, a cost-utility analysis compared healthcare costs and quality-adjusted life-year gains associated with three management strategies for acute cholecystitis: early cholecystectomy, delayed cholecystectomy and watchful waiting, where cholecystectomy is performed urgently if recurrent gallstone symptoms arise. Results: The rate of early cholecystectomy varied widely across hospitals in Ontario (median rate 51%, interquartile range 25-71%), even after adjusting for patient characteristics (median odds ratio 3.7). Among patients discharged without cholecystectomy following an index cholecystitis admission, the probability of a gallstone-related emergency department visit or hospital admission was 19% by 12 weeks following discharge. Early cholecystectomy was associated with a lower risk of major bile duct injury (0.28%vs.0.53%, RR=0.53, 95%CI 0.31–0.90, p=0.025). No significant differences were observed in terms of open cholecystectomy (15%vs.14%, RR=1.07, 95%CI 0.99–1.16, p=0.10) or in conversion among laparoscopic cases (11%vs.10%, RR=1.02, 95%CI 0.93–1.13, p=0.68). Early cholecystectomy was on average less costly ($6,905 per person) and more effective (4.20 QALYs per person) than delayed cholecystectomy ($8,511; 4.18 QALYs per person) or watchful waiting ($7,274; 3.99 QALYs per person). Conclusions: Early cholecystectomy offers a benefit over delayed cholecystectomy in terms of major bile duct injury, mitigates the risk of recurrent symptoms, and is associated with the greatest QALY gains at the least cost.
Structural, Genetic and Physiological Analysis of the Juxtamembrane Region of Drosophila neuronal-Synaptobrevin
Keywords: neuronal-Synaptobrevin
SNARE protein
Juxtamembrane region
Synaptic transmission

Synaptic transmission requires the fusion of neurotransmitter containing vesicles with the neuron's plasma membrane in a temporally restrictive manner. In Drosophila, this challenge is accomplished in part by the SNARE protein neuronal-Synaptobrevin (n-Syb). The juxtamembrane region of this molecule, linking the cytosolic SNARE motif and transmembrane region, is hypothesized to play a functional role in facilitating membrane fusion. This short, 10 amino acid, segment contains numerous charged residues and one conserved tryptophan residue. Its short rigid structure may be important in transducing force during SNARE complex assembly. Tryptophan residues, common in membrane proteins, are often observed at the membrane-water interface. It was hypothesized that this conserved tryptophan residue was important for anchoring and positioning n-Syb in the membrane. Proteins produced with tryptophan mutated were tested for anchoring and stability in a membrane model using NMR spectroscopy. Experiments testing depth of insertion using exposure to oxygen, a paramagnetic species, and exchange with deuterium demonstrated that tryptophan anchored n-Syb in the membrane. To test a potential functional role for the juxtamembrane region of n-Syb in synaptic transmission, a reverse genetic approach was employed. Wild-type and mutant P-element clones were made using the genomic sequence of n-syb including the endogenous promoter. n-Syb was found to be expressed, integrate and orient correctly in the membrane of Drosophila S2 cells. Transgenic Drosophila, produced via P-element transformation, were also found to produce transgenic protein. Transgenic expression of wild-type n-syb was found to restore an n-syb hypomorphic mutant from severe motor impairment and limited lifespan to wild-type levels. Synaptic transmission was assessed in 3rd instar larval preparations of mutant and wild-type transgenics. Mutation of the tryptophan residue and insertion of a short flexible linker were both found to inhibit synaptic transmission, while insertion of a long flexible linker was not.
Planetary Dynamo Models: Generation Mechanisms and the Influence of Boundary Conditions
Keywords: Planetary Dynamo
Numerical Model
Boundary Conditions
Inner Core Conductivity
Scaling Laws
Generation Mechanism

The Earth's magnetic field is generated in its fluid outer core through dynamo action. In this process, convection and differential rotation of an electrically conducting fluid maintain the magnetic field against its ohmic decay. Using numerical models, we can investigate planetary dynamo processes and the importance of various core properties on the dynamo. In this thesis, I use numerical dynamo models in Earth-like geometry in order to understand the influence of inner core electrical conductivity and the choice of thermal and velocity boundary conditions on the resulting magnetic field. I demonstrate how an electrically conducting inner core can reduce the frequency of reversals and produce axial-dipolar dominated fields in our models. I also demonstrate that a strong planetary magnetic field intensity does not imply that the dynamo operates in the strong field regime as is usually presumed. Through a scaling law analysis, I find that irrespective of the choice of thermal or velocity boundary conditions, the available power determines the magnetic and velocity field characteristics like the field strength, polarity and morphology. Also, whether a dynamo model is in a dipolar, transitional or multipolar regime is dependent on the force balance in the model. I demonstrate that the Lorentz force is balanced by the Coriolis force in the dipolar dynamo regime models resulting in magnetostrophically balanced dynamos whereas the Lorentz force is balanced by the Inertial force (and not the Coriolis force) in the multipolar dynamo regime models resulting in a non-magnetostrophically balanced dynamo. The generation mechanism differs between the regimes and depends on the velocity boundary conditions. The zonal flows of the stress-free models are stronger than in the no-slip models, and bistability is more prominent when stress-free boundary conditions are used. A single scaling law may be feasible for all the models, but there does appear to be some variation for models with different thermal and velocity boundary conditions. The results presented in this thesis are not only applicable to the geodynamo, but will also aid in understanding the dynamos of other planets and exoplanets.
Exotic Phases In Geometrically Frustrated Quantum Magnets
Keywords: Physics
Condensed Matter
Quantum Magnetism
Spin Liquids
Valence Bond Solid

Quantum magnetic materials provide pathways to exotic spin-disordered phases. We study two broad classes of quantum spin systems and their ground states. The first class is that of spin-dimer systems, which form valence-bond-solid states. In such systems, competition between interactions among the dimers can lead to interesting magnetization behaviour. We explain the magnetization of Ba3Cr2O8 as a Bose-Einstein condensate of spin-carrying excitations. Furthermore, we investigate possible dimerized and nearby magnetically ordered states in the Shastry-Sutherland compound (CuCl)LaNb2O7. The second class of spin systems feature geometric frustration, which may stabilize spin-liquid states without any order or particular dimerization. We argue the proximity of the face-centred-cubic double perovskite La2LiMoO6 to such a phase, to explain its lack of long-range order. We argue for the coexistence of such a state, along with spiral magnetic order, to explain the anomalous thermodynamic measurements in the spin-density-wave phase of powder samples of Volborthite, a distorted kagome-lattice spin system. Finally, we study spin liquid phases that have spin correlations consistent with those found from inelastic neutron scattering of the disordered kagome-lattice material Herbertsmithite. We predict electron spin resonance absorption lineshapes associated with these phases.
The (Co)isoperimetric Problem in (Random) Polyhedra
Keywords: Geometry
Combinatorics

We consider some aspects of the global geometry of cellular complexes. Motivated by techniques in graph theory, we develop combinatorial versions of isoperimetric and Poincare inequalities, and use them to derive various geometric and topological estimates. This has a progression of three major topics: 1. We define isoperimetric inequalities for normed chain complexes. In the graph case, these quantities boil down to various notions of graph expansion. We also develop some randomized algorithms which provide (in expectation) solutions to these isoperimetric problems. 2. We use these isoperimetric inequalities to derive topological and geometric estimates for certain models of random simplicial complexes. These models are generalizations of the well-known models of random graphs. 3. Using these random complexes as examples, we show that there are simplicial complexes which cannot be embedded into Euclidean space while faithfully preserving the areas of minimal surfaces.
Population Genetics and Speciation in Outcrossing Species in the Nematode Genus Caenorhabditis
Keywords: population genetics
Caenorhabditis
speciation
genetic variation

In Caenorhabditis nematodes, the androdioecious, self-fertilizing reproductive strategy has evolved relatively recently from gonochoristic, outcrossing ancestors. Transitions in mating system impact how genes are vertically transmitted between generations and horizontally between populations through gene flow. To date, species-wide studies have targeted selfing species, and we have limited understanding about how population genetic processes have shaped the genome structure and evolutionary history of outcrossing species of Caenorhabditis. To fill this gap, I investigate patterns of genetic variation and population genetic processes focusing on two outcrossing species in the genus, C. brenneri and C. remanei, using a survey of nucleotide polymorphisms in a multipopulation, multilocus context. I discover extensive genetic diversity in Caenorhabditis brenneri, termed hyperdiversity, giving this species the highest known levels of nucleotide polymorphism for any multicellular eukaryote. Genetic crosses between populations, extensive intra-locus recombination, and evidence of weak selection on codon usage all suggest that this is due to a large effective population size in the species and not an artifact of cryptic species divergence. I demonstrate that C. remanei also is characterised by high genetic variation globally, albeit not as extreme as in C. brenneri, and within each local population. Despite geographic barriers, considerable gene flow occurs between inter-continental locations. While exploring genetic diversity in C. remanei, I discovered C. sp. 23, a new, gonochoristic species reproductively isolated and highly divergent from it. Subsequently, taking advantage of this newly discovered species pair, I explore the patterns of postzygotic reproductive isolation between C. remanei and C. sp. 23. I find evidence of partial F1 hybrid inviability, strong F1 hybrid male sterility (Haldane’s rule) and strong F2 hybrid breakdown between the two. The findings from this thesis, especially the notion of hyperdiversity, can be taken advantage of to answer key questions on testing limits of natural selection, of evolution of genome complexity as well as identifying and characterising functional, non-coding regulatory elements. Discovery of a new species pair in Caenorhabditis helps establish an emerging age of speciation genetics in the worm.
Solving MAXSAT by Decoupling Optimization and Satisfaction
Keywords: Combinatorial optimization
Propositional logic
Maximum satisfiability
Weighted constraints
Integer programming
Satisfiability

Many problems that arise in the real world are difficult to solve partly because they present computational challenges. Many of these challenging problems are optimization problems. In the real world we are generally interested not just in solutions but in the cost or benefit of these solutions according to different metrics. Hence, finding optimal solutions is often highly desirable and sometimes even necessary. The most effective computational approach for solving such problems is to first model them in a mathematical or logical language, and then solve them by applying a suitable algorithm. This thesis is concerned with developing practical algorithms to solve optimization problems modeled in a particular logical language, MAXSAT. MAXSAT is a generalization of the famous Satisfiability (SAT) problem, that associates finite costs with falsifying various desired conditions where these conditions are expressed as propositional clauses. Optimization problems expressed in MAXSAT typically have two interacting components: the logical relationships between the variables expressed by the clauses, and the optimization component involving minimizing the falsified clauses. The interaction between these components greatly contributes to the difficulty of solving MAXSAT. The main contribution of the thesis is a new hybrid approach, MaxHS, for solving MAXSAT. Our hybrid approach attempts to decouple these two components so that each can be solved with a different technology. In particular, we develop a hybrid solver that exploits two sophisticated technologies with divergent strengths: SAT for solving the logical component, and Integer Programming (IP) solvers for solving the optimization component. MaxHS automatically and incrementally splits the MAXSAT problem into two parts that are given to the SAT and IP solvers, which work together in a complementary way to find a MAXSAT solution. The thesis investigates several improvements to the MaxHS approach and provides empirical analysis of its behaviour in practise. The result is a new solver, MaxHS, that is shown to be the most robust existing solver for MAXSAT.
Appliction-driven Memory System Design on FPGAs
Keywords: FPGA
Memory System
Muti-port Memory Controller
Switch Fabric
Cache Churn Rate
Flash
XML
Quality-of-Service
Bandwidth Guarantee
Crosspoint Queued Switch
Zipf's Law
Online Video

Moore's Law has helped Field Programmable Gate Arrays (FPGAs) scale continuously in speed, capacity and energy efficiency, allowing the integration of ever-larger systems into a single FPGA chip. This brings challenges to the productivity of developers in leveraging the sea of FPGA resources. Higher level of design abstractions and programming models are needed to improve the design productivity, which in turn require memory architectural supports on FPGAs. While previous efforts focus on computation-centric applications, we take a bandwidth-centric approach in designing memory systems. In particular, we investigate the scheduling, buffered switching and searching problems, which are common to a wide range of FPGA applications. Despite that the bandwidth problem has been extensively studied for general-purpose computing and application specific integrated circuit (ASIC) designs, the proposed techniques are often not applicable to FPGAs. In order to achieve optimized design implementations, designers need to take into consideration both the underlying FPGA physical characteristics as well as the requirements from applications. We therefore extract design requirements from four driving applications for the selected problems, and address them by exploiting the physical architectures and available resources of FPGAs. Towards solving the selected problems, we manage to advance state-of-the-art with a scheduling algorithm, a switch organization and a cache analytical model. These lead to performance improvements, resource savings and feasibilities of new approaches for well-known problems.
Making Meaning of von Hagens' Body Worlds: Towards an Interdisciplinary Approach to Science Exhibitions
Keywords: Body Worlds
museum
informal learning
science centre
controversial issues
interdisciplinary
science exhibitions

Body Worlds is a traveling exhibition of plastinated human cadavers that offers the general public an opportunity to experience the human body in a unique way. It has been met with controversy and awe; public reactions and responses have been mixed. This case study research explored visitor responses to this controversial science exhibition, and examined the meaning visitors made of their experience. Specifically, the following research questions directed this study: Within the context of the Body Worlds exhibition: (a) What meaning did visitors make and how did they respond to the exhibits? (b) What tensions and issues arose for visitors? and (c) What did this type of exhibition convey about the changing role of science centres and the nature of their exhibitions? The primary sources of data for this study were 46 semi-structured interviews with visitors to the exhibition, observation notes, and 10 comment books including approximately 20 000 comments. Data suggested that the personal, physical, and sociocultural contexts (Falk &amp; Dierking, 2000) contributed to visitor meaning meaning-making. The use of plastinated human cadavers within this exhibition raised ethical and moral questions and controversies about body procurement, use of human cadavers in display, representations of the bodies, and issues related to the sanctity of life. The tensions and issues identified by visitors demonstrated that messages (intended or unintended) located within Body Worlds were critically examined by visitors and called into question. Finally, data from this study suggested that an interdisciplinary approach to the presentation of science served to enhance accessibility for the viewer. This exhibition demonstrated that visitors responded positively and made personal connections when the arts, spirituality, edutainment, issues, and a combination of historical and contemporary museum practices were used to present science.
Concurrent Memory Load, Working Memory Span, and Morphological Processing in L1 and L2 English
Keywords: Psycholinguistics
Memory
Second Language Acquisition
Morphological Processing
Morphology
Transfer
Automaticity
Self-Paced Reading

This study utilized the moving-window self-paced reading paradigm to investigate the processing of English morphemes by native speakers of English, Chinese, and Korean. The morphemes belonged to three distinct theoretical types: Stratum 1 derivation ({-ALADJ}, {-ITY}, and {-OUSADJ}), Stratum 2 derivation ({-NESS}, {-FULADJ}, and {-ERAGENT}), and inflection ({-SPL}, {-EDPAST}, and {-S3RDSGPRES}). Participants were presented with either (1) fully grammatical sentences which contained words featuring these morphemes or (2) ungrammatical sentences in which one word form lacked one of the morphemes when it was obligatory (e.g., Canada is one of the most *prosper and developed countries in the world). Half the sentences were presented with a concurrent working memory load, which consisted of remembering the result of a simple calculation (e.g., subtracting 3 from 95) while processing a sentence and reporting the number immediately thereafter. Reading times for the target word and the three words immediately following it were used as the main dependent variable. The background measures included a C-Test of English proficiency, a reading span task, a digits-forward task, a digits-backward task, and a detailed background questionnaire. In agreement with previous research, it was found that morphological violations tended to cause slowdowns in processing. Conversely, the presence of a concurrent memory load tended to cause speedups. Native speakers differed from non-native speakers by: (1) showing an early sensitivity to violations of Stratum 2 derivational morphology; (2) exhibiting a delayed response to violations of Stratum 1 derivation; and (3) not slowing down after violations of inflectional morphology. In addition, native speakers were the only group exhibiting no relationship between morphological processing on one side and short term-memory, working memory, and C-Test scores on the other. Overall, the similarity between native and non-native speakers was the greatest in the processing of Stratum 1 derivation. Crucially, the temporal pattern of the Korean participants&rsquo; responses to morphological violations in English placed them in an intermediate position between the English and Chinese native speakers, which was interpreted as evidence of L1 &ndash; L2 transfer in morphological processing. Notably, this transfer occurred between an agglutinative L1 and an unrelated mixed-type L2.
Regina: A Chamber Opera in One Act
Keywords: Opera
Chamber Music
Rabbi
Jewish
Regina Jonas

Regina is a one-act opera based on the true story of Regina Jonas, the first woman to be ordained as a rabbi in the Jewish faith, in 1935. Jonas struggled to gain this recognition and subsequently perished in the concentration camp at Auschwitz. It was only in 1991 that another woman uncovered the papers that proved Jonas' legacy. This opera follows Regina, waiting to be uncovered in the piles of paper records locked away in East Berlin, and through vignettes of her past. This is paralleled with the story of Anna, who is desperately fighting against her Nazi father's legacy. Anna believes that, if she can uncover stories like Regina's, she will free herself of her father's torment. Regina is similarly haunted by her mother's ghost, whose discouraging words have shaped Regina's lifelong self-doubt. Both Regina and Anna need to be set free. This opera uses leitmotifs to differentiate the two main characters, but these themes are also often used as signifiers of the common struggles that both characters embody and represent. As well, they employ rhythmic and melodic styles that pervade both the vocal and instrumental parts throughout the opera, thus unifying the characters' goals. Because of the fact that the opera takes place in multiple time periods (sometimes simultaneously) the various choices of instrumentation and harmonic material often reflect these temporal shifts (for example, the accordion is often associated with Regina's path to ordination, her relationship with her rabbi, and a time of joy and calm before the war.) In addition, melodic and rhythmic motifs are used to represent specific as well as general events, such as the three-note 'ordination' theme and the two-chord repeated motif in the piano. The overall extended tonal style contributes to a largely lyrical setting of Maya Rabinovitch's libretto.