VictorJuiz/thesis huggingface dataset:
Bose-Einstein Condensate Wavefunction Reconstruction Through Collisions with Optical Potentials
Keywords: Bose-Einstein Condensate
wavefunction

A new technique for the interferometric measurement of an atomic wavefunction is introduced theoretically, which is able to extract phase and amplitude information in a single measurement. I focus on the application of this technique to the single-particle wavefunction of a Bose condensed cloud of rubidium atoms. The technique differs from existing techniques mainly in its simplicity, as it requires only a single laser beam to be added to a typical Bose-Einstein condensation apparatus. A second novel aspect is the consideration of condensate collisions with an optical potential in the low-intensity limit where the potential barrier may be viewed as a phase mask. The technique is then demonstrated experimentally. A related effect, the transient enhancement of momentum during a collision, first predicted by JG Muga et al., has also been demonstrated. Finally, significant redesign and construction of an apparatus to produce condensates of 87Rb is documented. The main result of this work is the production of pure condensates of up to 150k atoms which can be repeated every 45s. A calibration technique is devised and demonstrated, whereby copies of the condensate are made, and the copies are used to reduce the centre-of-mass momentum uncertainty of the interacting cloud by a factor of five.
Passivity Methods for the Stabilization of Closed Sets in Nonlinear Control Systems
Keywords: Nonlinear Control Systems
Set Stabilization
Passive Systems

In this thesis we study the stabilization of closed sets for passive nonlinear control systems, developing necessary and sufficient conditions under which a passivity-based feedback stabilizes a given goal set. The development of this result takes us to a journey through the so-called reduction problem: given two nested invariant sets G1 subset of G2, and assuming that G1 enjoys certain stability properties relative to G2, under what conditions does G1 enjoy the same stability properties with respect to the whole state space? We develop reduction principles for stability, asymptotic stability, and attractivity which are applicable to arbitrary closed sets. When applied to the passivity-based set stabilization problem, the reduction theory suggests a new definition of detectability which is geometrically appealing and captures precisely the property that the control system must possess in order for the stabilization problem to be solvable. The reduction theory and set stabilization results developed in this thesis are used to solve a distributed coordination problem for a group of unicycles, whereby the vehicles are required to converge to a circular formation of desired radius, with a specific ordering and spacing on the circle.
Secondary School Students’ Misconceptions in Algebra
Keywords: Secondary mathematics
Curriculum and instruction
Measurement
Misconceptions
Algebra
Problem Solving

This study investigated secondary school students’ errors and misconceptions in algebra with a view to expose the nature and origin of those errors and to make suggestions for classroom teaching. The study used a mixed method research design. An algebra test which was pilot-tested for its validity and reliability was given to a sample of grade 11 students in an urban secondary school in Ontario. The test contained questions from four main areas of algebra: variables, algebraic expressions, equations, and word problems. A rubric containing the observed errors was prepared for each conceptual area. Two weeks after the test, six students were interviewed to identify their misconceptions and their reasoning. In the interview process, students were asked to explain their thinking while they were doing the same problems again. Some prompting questions were asked to facilitate this process and to clarify more about students’ claims. The results indicated a number of error categories under each area. Some errors emanated from misconceptions. Under variables, the main reason for misconceptions was the lack of understanding of the basic concept of the variable in different contexts. The abstract structure of algebraic expressions posed many problems to students such as understanding or manipulating them according to accepted rules, procedures, or algorithms. Inadequate understanding of the uses of the equal sign and its properties when it is used in an equation was a major problem that hindered solving equations correctly. The main difficulty in word problems was translating them from natural language to algebraic language. Students used guessing or trial and error methods extensively in solving word problems. Some other difficulties for students which are non-algebraic in nature were also found in this study. Some of these features were: unstable conceptual models, haphazard reasoning, lack of arithmetic skills, lack or non-use of metacognitive skills, and test anxiety. Having the correct conceptual (why), procedural (how), declarative (what), and conditional knowledge (when) based on the stage of the problem solving process will allow students to avoid many errors and misconceptions. Conducting individual interviews in classroom situations is important not only to identify errors and misconceptions but also to recognize individual differences.
Natural Health Products (NHPs) in Pregnancy and Lactation: A Review of the Landscape and Blueprint for Change
Keywords: pregnancy
natural health product
lactation
evidence based medicine
breatsfeeding
meta-analysis
systematic review
blue cohosh
NHP
MotherNature

Introduction: Based on the perceived risk to newborns and pregnancy outcomes associated with certain drugs, women may be hesitant to prescribe and take drugs during pregnancy. In cases like these, pregnant women may seek treatment using natural health products (NHPs) as alternatives to drugs. Unfortunately, evidence of safety in pregnancy and lactation is unknown for many NHPs. Objectives: To review the present state of evidence on the safety of NHPs during pregnancy and lactation. To create a new system to validate evidence on NHPs during pregnancy and lactation designed to affect medical decision. Methodology: NHPs were systematically reviewed and in some cases, meta-analyzed for evidence of safety during pregnancy and lactation. Results: In total, 79 NHPs were systematically reviewed and 2 NHPs were meta-analyzed in order to determine the evidence of safety in pregnancy and lactation. Despite the presence of data (72/79 NHPs in pregnancy and 53/77 NHPs in lactation), the quality of the data was generally poor. Using evidence-based medicine principles, a new system of evaluating evidence was established for studies involving NHPs in pregnancy and lactation. A number of NHPs were identified as being of potential risk in pregnancy. A number of NHPs were identified as potentially being apparently safe in pregnancy and lactation. Blue cohosh is of potential concern for harm in pregnancy given an apparent dose-dependant relationship. Conclusion: There is a large knowledge gap on the safety of NHPs in pregnancy, even more so in lactation. The new system for evaluating NHP safety in pregnancy and lactation will require validation. In order to improve the knowledge gap, future studies are proposed on NHPs in pregnancy and lactation as part of the newly formed MotherNature research network.
Tradition and Innovation in Brazilian Popular Music: Keyboard Percussion Instruments in Choro
Keywords: choro
Brazilian popular music
brazilian instrumental music
keyboard percussion
marimba
xylophone
vibraphone

The use of keyboard percussion instruments in choro, one of the earliest forms of Brazilian popular music, is a relatively recent phenomenon and its expansion into university music programs and relocation from small clubs and private homes to concert halls has changed the way that choro is learned and performed. For many Brazilians, this kind of innovation in a “traditional” genre represents a challenge to their notion of a Brazilian cultural identity. This study examines the dynamic relationship that Brazilians have with representations of their culture, especially in the area of popular music, through an in depth discussion of the use of keyboard percussion instruments within the genre of choro. I discuss the implications of using keyboard percussion in choro with a detailed description of its contemporary practice and a critical examination of the sociological and academic issues that surround choro historically and as practiced today. This includes an historical overview of choro and organology of keyboard percussion instruments in Brazil. I discuss multiple perspectives on the genre including a consideration of choro as part of the “world music” movement and choro’s ambiguous relationship to jazz. Through an examination of the typical instrumentation and performance conventions used in choro, I address the meanings and implications of the adaptation of those practices and of the various instrumental roles found in choro to keyboard percussion instruments. Solutions to problems relating to instrumental adaptation are offered, with particular attention to issues of notation, improvisation, rhythmic approach and the role of the cavaquinho. I also discuss the significance of rhythmic feel and suingue (swing) in relation to the concept of brasilidade (brazilianness) as informed by and expressed through Brazilian popular music.
Microfluidic Synthesis of Macroporous Polymer Particles and Development of Multifunctional Porous Polymer Hybrids
Keywords: Polymer
Chemistry

This thesis presents a preparation of porous polymer materials. The first half of this thesis focuses on the microfluidic synthesis of macroporous copolymer microparticles. Macroporous copolymer microparticles have a broad range of applications such as ion exchange resins and sorbents, catalyst supports, and carriers of biologically active species. Many of these applications require precise control of the dimensions of microparticles in the range from 50 to 100 μm and predetermined size of pores. First, this thesis reports semicontinuous photoinitiated microfluidic synthesis of macroporous copolymer microparticles with the designated dimensions and a range of internal structures. A synthesis of macroporous polymer microparticles under certain conditions produces microparticles with a smooth nonporous “skin” layer. This effect limits the applications of porous microbeads by preventing solute molecules to permeate the dense particle surface and reach particle’s porous interior. Second, this thesis reports a straightforward method that was used to suppress the formation of the “skin” on the surface of macroporous copolymers. The second half of this thesis focuses on the synthesis and applications of porous polymer hybrid materials (PHM). PHMs carrying inorganic nanoparticles on the surface of pores have important applications in chemical and biological sensing, in chromatography and in heterogeneous catalysis. Particularly, this thesis describes the results of the experimental study of the preparation of PHM carrying gold nanorods (NRs) on the surface of pores. The material was prepared by utilizing two effects occurring concurrently: the photoinitiated polymerization induced phase separation in the polymer–solvent mixture and the migration of the NRs to the interface between the polymer and the porogen solvent. We show that the enrichment of the interface with the NRs is enhanced at high polymerization rates leading to rapid phase separation. By contrast, a more rapid increase in viscosity achieved at high polymerization rates does not have a significant effect on the segregation of NRs to the surface of the pores. Finally,the PHM coated with gold nanorods was utilized for the simultaneous detection of different analytes using surface enhanced Raman scattering (SERS) spectroscopy and fluorescence microscopy.
Quantifying the Likelihood of Human-mediated Movements of Species and Pathogens: The Baitfish Pathway in Ontario as a Model System
Keywords: fisheries
model
likelihood
species
gravity model
bycatch
vector
spatial
ecology

Estimating the risk associated with species and pathogen movements involves considerable uncertainty. One key uncertainty concerns the extent and frequency of human-mediated species and pathogen movements relative to the distribution of recipient ecosystems. Baitfish use in Ontario, Canada is one of many pathways with the potential to introduce and spread biota to beyond their current geographic range. To determine the biological risk associated with baitfish use, models were used to estimate the probability of species occurrences throughout pathway levels, from the commercial harvest level, to retail tank and angler purchases, to movement and release by the end-user (i.e., the angler). Vector activity, as the primary contributor of species movements and introductions associated with this pathway, was modeled within a spatial interaction framework that incorporated landscape structure (e.g., the distribution of angling populations, lake size and sportfish richness, and their physical separation via least-cost routing of transportation networks) to predict the extent of movement. Agent-based models of vector activity were used to relate vector movements to region-specific probability thresholds of risk activity. Model outputs were used to estimate the movement and introduction of species and pathogens to lake ecosystems resulting from a variety of infection scenarios. Species results identified a pronounced reduction in the probability of non-target species occurrences throughout pathway levels. However, the occurrence of biological invaders and other non-target fishes at retail levels implied incidental bycatch throughout the pathway. Relatively short, frequent vector movements associated with incidentally purchased species were very likely, yet would not contribute to species range expansions due to the homogeneity of biological communities at those levels. However, rarer, yet considerably lengthier, vector movements associated with key species and pathogens implied the potential for low-probability, long-distance species and pathogen movements resulting from human activities.
Three Essays on Macroeconomics
Keywords: macroeconomics
economics of climate change
energy efficiency
fiscal policy with sovereign default

This dissertation consists of three independent essays in macroeconomics. The first essay studies the transition to a low carbon economy using an extension of the neoclassical growth model featuring endogenous energy efficiency, exhaustible energy and explicit climate-economy interaction. I derive the properties of the laissez faire equilibrium and compare them to the optimal allocations of a social planner who internalizes the climate change externality. Three main results emerge. First, the exhaustibility of energy generates strong market based incentives to improve energy efficiency and reduce CO2 emissions without any government intervention. Second, the market and optimal allocations are substantially different suggesting a role for the government. Third, high and persistent taxes are required to implement the optimal allocations as a competitive equilibrium with taxes. The second essay focuses on coal fired power plants (CFPP) - one of the largest sources of CO2 emissions globally - and their generation efficiency using a macroeconomic model with an embedded CFPP sector. A key feature of the model is the endogenous choice of production technologies which differ in their energy efficiency. After establishing four empirical facts about the CFPP sector, I analyze the long run quantitative effects of energy taxes. Using the calibrated model, I find that sector-specific coal taxes have large effects on generation efficiency by inducing the use of more efficient technologies. Moreover, such taxes achieve large CO2 emissions reductions with relatively small effects on consumption and output. The final essay studies the procyclicality of fiscal policy in developing countries, which is a well-documented empirical observation seemingly at odds with Neoclassical and Keynesian policy prescriptions. I examine this issue by solving the optimal fiscal policy problem of a small open economy government when the interest rates on external debt are endogenous. Given an incomplete asset market, endogeneity is achieved by removing the government's ability to commit to repaying its external obligations. When calibrated to Argentina, the model generates procyclical government spending and countercyclical labor income tax rates. Simultaneously, the model's implications for key business cycle moments align well with the data.
Impact of Neisseria gonorrhoeae on HIV-1 Replication and Immune Cell Activity in Co-infected Peripheral Blood Mononuclear Cells
Keywords: Sexually transmitted infection
Neisseria gonorrhoeae
HIV
co-infection

Clinical and epidemiological studies have provided a large body of evidence supporting a link between HIV and other sexually transmitted co-infections. Co-infections have been associated with promoting HIV transmission and acquisition. One of the closest studied interactions is the co-infection with N. gonorrhoeae, the etiological agent of gonorrhea, yet a clear understanding of this relationship is still elusive. Studies aimed at deciphering how N. gonorrhoeae mediates these effects have provided mixed results with some suggesting co-infection promotes HIV replication, and others suggesting the opposite. The aim of this thesis is to uncover molecular mechanisms that explain these results through in vitro co-infection studies using a combination of mixed peripheral mononuclear blood cells (PBMCs) and isolated human cell types. The results presented here demonstrate that gonococcal co-infection profoundly inhibits HIV replication in co-infected PBMCs. This inhibition is due to both the release of anti-HIV IFN via TLR9-mediated activation of plasmacytoid dendritic cells (pDCs), and the activation of  T cells. In addition, I show that responses between CD4+ T cell lines, such as the Jurkat cell line, and primary CD4+ T cells can differ, which may explain some of the contrasting results seen in published literature. The results in this thesis have implications for understanding the relationship between gonococci and HIV, providing new insight into molecular and immunological interactions that influence viral transmission, and reveal new opportunities to combat HIV.
The Co-occurrence of Multisensory Facilitation and Competition in the Human Brain and its Impact on Aging
Keywords: multisensory integration
aging

Perceptual objects often comprise of a visual and auditory signature, which arrives simultaneously through distinct sensory channels, and multisensory features are linked by virtue of being attributed to a specific object. The binding of familiar auditory and visual signatures can be referred to as semantic audiovisual (AV) integration because it involves higher level representations of naturalistic multisensory objects. While integration of semantically related multisensory features is behaviorally advantageous, multisensory competition, or situations of sensory dominance of one modality at the expense of another, impairs performance. Multisensory facilitation and competition effects on performance are exacerbated with age. Older adults show a significantly larger performance gain from bimodal presentations compared to unimodal ones. In the present thesis project, magnetoencephalography (MEG) recordings of semantically related bimodal and unimodal stimuli captured the spatiotemporal patterns underlying both multisensory facilitation and competition in young and older adults. We first demonstrate that multisensory processes unfold in multiple stages: first, posterior parietal neurons respond preferentially to bimodal stimuli; secondly, regions in superior temporal and posterior cingulate cortices detect the semantic category of the stimuli; and finally, at later processing stages, orbitofrontal regions process crossmodal conflicts when complex sounds and pictures are semantically incongruent. Older adults, in contrast to young, are more efficient at integrating semantically congruent multisensory information across auditory and visual channels. Moreover, in these multisensory facilitation conditions, increased neural activity in medial fronto-parietal brain regions predicts faster motor performance in response to bimodal stimuli in older compared to younger adults. Finally, by examining the variability of the MEG signal, we also showed that an increase in local entropy with age is also behaviourally adaptive in the older group as it significantly correlates with more stable and more accurate performance in older compared to young adults.
Global CO2 Flux Inferred From Atmospheric Observations and Its Response to Climate Variabilities
Keywords: Carbon dioxide
Atmospheric inversion
Diurnal variations
Interannual variability
Sink and source
Terrestrial carbon cycle

Atmospheric inversion has recently become an important tool in estimating CO2 sinks and sources albeit that the existing inversion results are often uncertain and differ considerably in terms of the spatiotemporal variations of the inverted carbon flux. More measurements combined with terrestrial ecosystem information are expected to improve the estimates of global surface carbon fluxes which are used to understand the relationships between variabilities of the terrestrial carbon cycle and anomalies of climatic factors. Inversions using more observations have often been hampered by the intense diurnal variations of CO2 concentrations at continental sites. Diurnal variations of the surface flux are included with atmospheric boundary dynamics in order to improve the atmospheric inversion accuracy. Modeling experiments conducted in this study show that inverse estimates of the carbon flux are more sensitive to the variation of the atmospheric boundary layer dynamics than to the diurnal variation in the surface flux. It is however generally better to consider both diurnal variations in the inversion than to consider only either of them. Forest carbon dynamics is closely related to stand age. This useful terrestrial ecosystem information has been used as an additional constraint to the atmospheric inversion. The inverse estimates with this constraint over North America exhibit an improved correlation with carbon sink estimates derived from eddy-covariance measurements and remotely-sensed data, indicating that the use of age information can improve the accuracy of atmospheric inversions. Terrestrial carbon uptake is found mainly in northern land, and a strong flux density is revealed in southeastern North America in an improved multi-year inversion from 2002 to 2007. The global interannual variability of the flux is dominated by terrestrial ecosystems. The interannual variabilities of regional terrestrial carbon cycles could be mostly explained by monthly anomalies of climatic conditions or short-time extreme meteorological events. Monthly anomalies of the inverted fluxes have been further analyzed against the monthly anomalies of temperature and precipitation to quantitatively assess the responses of the global terrestrial carbon cycle to climatic variabilities and to determine the dominant mechanisms controlling the variations of terrestrial carbon exchange.