VictorJuiz/thesis huggingface dataset:
A 3.8-6.4GHz Local Oscillator System Using an Injection-Locked Frequency Doubling and Phase Tuning Technique

This thesis studies the design of a novel local oscillator system based on low-voltage and low-power regenerative (injection locking) techniques. The LO system converts an input signal of frequeney 'fLO'/2 into a quadrature pair of LO signals at a frequency of 'fLO', intended to drive a pair of I and Q down-converting mixers. A new IC compatible technique for regenerative frequency doubling is presented. Regenerative frequency doublers are cascaded on-chip to provide a net multiply-by-4 function, generating frequencies in excess of <math> <f> <fr><nu>f<inf>T</inf></nu><de>2</de></fr></f> </math> without the need for interstage filtering. A new technique is also presented for frequency-independent phase control of the quadrature LO signals of a regenerative divider (I-Q generator), achieving a precision on the order of 0.01°. Results are presented in the context of a fabricated 5-6GHz image reject receiver.
The filmmaker as artist-educator, an inquiry into teaching and learning in film arts curriculum

Structured as a collection of essays that examine various aspects of film arts education through the different lenses of my experience as a filmmaker-educator, the six chapters in this dissertation articulate my vision and my efforts in developing a more holistic film arts learning experience. While there are common thematic concerns that link the various chapters, each chapter is written as an independent essay, incorporating qualitative personal narrative inquiries with conceptual framework and teaching practices in both formal curriculum and informal learning contexts. Ranging from a general overview of using films as resource materials in a film arts curriculum, to the role of the filmmaker-educator in inspiring creative learning in non-school settings, such as at film festivals, the six chapters of this dissertation detail some of the pedagogical methodology that I have developed for teaching and learning using my own films, and using films by other filmmakers. This dissertation will be of interest to those filmmaker-educators who share my vision for a holistic film arts curriculum and for a comprehensive creative learning experience for their students, for they may find some of my personal inquiries relevant as a springboard to launch their own creative explorations in developing other unique and innovative teaching and learning strategies to challenge themselves and their students.
Cytokine-mediated pathways of mdr1 gene regulation in cultured rat hepatocytes

P-Glycoprotein (PGP/mdr1) plays an important role in the distribution and elimination of many chemotherapeutic agents. Altered drug disposition in disease states and cancer may be due to changes in PGP/ mdr1 transporter expression. Previous results from our laboratory demonstrated a down-regulation in hepatic PGP expression and activity during acute inflammation in rats. We therefore examined the effect of various inflammatory cytokines on PGP/mdr1 regulation in cultured rat hepatocytes. Interleukin (IL-) 6 was found to decrease mdr1 mRNA expression via decreased mdr1 gene transcription, but not altered mRNA stability. Experiments in turpentine-treated rats confirmed that inflammation also caused decreased mdr1 mRNA levels and mdr1 transcription. IL-1β, on the other hand, decreased PGP protein expression, without affecting RNA levels, suggesting its action on protein stability or synthesis. We conclude that these cytokines may play roles in the regulation of PGP during acute inflammation, with IL 6 most responsible for the transcriptional effects on the mdr1 genes.
Encounters with Northern development workers, reflections from the "field"

This thesis is an exploration of how Northern development workers conceptualise relations between Northern and Southern countries, articulate the role of Northern development worker and understand identity issues. The focus of this research is participants' reflections of their work as Northern development workers and the meaning they make of these experiences to illuminate professional roles and practices. Through the lens of an interlocking theory of oppression, this inquiry of Northern development worker identity, experiences and practices is situated within a systemic analysis of power and privilege. This theory of interlocking oppression illuminates the workings of class, race, gender and Northern status, facilitating an exploration of the complexity of Northern development worker identity. The detailed accounts of participants' narrations of their experiences are significant as they reveal interpretive frameworks of identity, culture and power. This work considers the possibilities of consciousness-raising of Northern development workers through informal and self-reflective learning processes.
Characterization of dystrophin protein complexes in the retina

The Duchenne Muscular Dystrophy gene, dystrophin, gives rise to a diverse family of protein isoforms that differ in structure, localization and function. Alternative splicing and internal promoter usage form the basis for this diversity and provide a framework for the creation of distinct dystrophin complexes. The retina is an excellent model and example of dystrophin's complexity as it allows for an in depth examination of the various functions of distinctive dystrophin protein complexes. Three dystrophin isoforms, Dp427, Dp260 and Dp71, are expressed in the retina and have non-overlapping patterns of localization at synaptic and non-synaptic layers. We hypothesize that these isoforms each interact with specialized sets of proteins that serve to tailor their individual functions. This thesis is focused on characterizing both novel and known dystrophin-associated proteins in order to understand the diverse functions of these extended dystrophin complexes. I have identified Ã-catulin as a novel dystrophin-associated protein that interacts with a unique C-terminus of dystrophin and is localized to the Mûller cell endfeet of the retina. I have also shown that isoforms of the dystrophin-associated protein dystrobrevin are differentially localized in the retina providing evidence for the existence of additional dystrophin complexes. My data indicate that the localization of each of these dystrophin-associated proteins is dependent upon the presence of its specific dystrophin partner. These findings provide new insight into the function of dystrophin in the retina and outline how the absence of specific isoforms and their extended protein complexes contributes to the disturbances in retinal neurotransmission observed in most Duchenne Muscular Dystrophy patients.
A Newton-Krylov solver for the Euler equations on unstructured grids

A Newton-Krylov solver for the Euler equations that govern the flow of a compressible inviscid flow, with application to flows over aerodynamic configurations, is presented. The Euler equations and a nonlinear artificial dissipation scheme are discretised in space using a node-based finite-volume formulation on arbitrary polygonal unstructured grids. The resulting system of nonlinear algebraic equations is solved using an inexact Newton strategy in which the linear problem arising at each Newton iteration is solved iteratively using the matrix-free GMRES algorithm preconditioned by an approximate Jacobian matrix subjected to an incomplete factorisation and reordering. Implicit Euler local time stepping is applied when solving transonic flows. The solver is tested with single and multi-element airfoils in the subsonic and transonic flow regimes. Various GMRES tolerances, preconditioner fill-in levels, and pre-conditioned tolerances are investigated. Sets of optimum base parameters are determined. Results show the solver to be competitive with other solvers. Recommendations are made for aspects of the solver that are worthy of further study.
Novel nonlinear finite element analysis of dynamic contact problems using variational inequalities

Dynamic contact problems play an important role in dictating the integrity, performance and safety of many engineering systems/components involved in vehicle design, armament and ballistics, metal forming/cutting, and surface treatments, just to name a few. Despite their importance to the mechanical integrity of the systems examined, dynamic contact effects are frequently treated using oversimplifying assumptions, which neglect the main feature of the problem. This is because of the complexity of the governing system of equations. In this work, dynamic frictional contact problems are formulated using the more reliable and consistent variational inequalities (VI) approach. Three aspects of the problem are accordingly examined. The first is concerned with the development of the appropriate variational inequality formulations and solution strategies for dynamic frictional contact problems involving material and geometrical nonlinearity. Two models of surfaces are taken into account: (i) perfectly smooth surfaces, and (ii) more realistic surfaces, which take into account the change in compliance due to surface roughness. A new technique for representing the kinematic contact conditions is developed. Two newly devised numerical procedures are devised to solve the general dynamic frictional contact problem for elastic and elasto-plastic media. The first solution strategy, which regularises friction, is based upon the iterative use of mathematical programming and Lagrange multipliers. The second approach is accomplished using a nondifferentiable optimisation algorithm, through a sequence of mathematical programming sub-problems. The second aspect of the work is concerned with the selection of a suitable time integration scheme for contact problems. The values of the time integration parameters are so chosen to ensure that the solution is second order accurate, unconditionally stable, preserves energy and momentum during rigid impact, thus minimising numerical oscillations and ensuring optimal numerical dissipation. Finally, the developed algorithms are validated and applied to the analysis of several interesting engineering problems. The numerical predictions are compared to existing experiments as well as a commercial finite element code. The results reveal that the new dynamic friction contact formulations are more accurate than the traditional variational methods. These newly developed algorithms should provide designers with a powerful tool for treating dynamic elasto-plastic problems involving frictional contact.
Design and implementation of a flexible control system for the power supplies of the vortek arc lamp

The goal of this thesis is to design a flexible control scheme for four power supplies to ignite, sustain and pulse a VORTEK--water-wall-high-pressure-argon-arc lamp. The control system includes the operation of the auxiliary system of the lamp. The power supplies and auxiliary components were provided, the task was to design some of the gating control and the central, microprocessor based, controller for the automatic coordinated control of all the required auxiliary functions and power supplies. The control requirements for the auxiliaries and power supplies are specified in this thesis. Based on these specifications the hardware and software is designed, tested and built. The different options for the power supply controls are discussed and the operation is optimized based on the operation of the lamp with an initial design. Using the flexibility of the designed control system, the lamp is operated in different ways and the observations provide new insight in the operation of such an arc-lamp. This will in turn lead to new strategies to design and build power supplies for arc-lamps.
Investigation of genes that are regulated during erythroid differentiation

In this thesis we attempted to identify novel genes that may play a role in erythroid proliferation and differentiation using the unique erythroleukemia cell line HB60-5. By utilizing the approach of subtractive hybridization, I have isolated clone 5, a gene whose expression is regulated during erythroid differentiation. Expression of clone 5 is high in HB60-5 cells and decreases as cells are induced to undergo terminal differentiation. Clone 5 appears to be widely expressed in murine and human hematopoietic and non-hematopoietic cell lines. However expression of clone 5 appears to be minimal in normal murine tissue with the exception of brain. A decrease in clone 5 expression was also observed during terminal differentiation of various hematopoietic precursors. Therefore clone 5 may represent a novel gene that plays a role in the transition from cellular proliferation to différentiation. Characterization of this gene may provide further insights into the mechanisms of hematopoiesis and malignant transformation.
Transformation of formaldehyde aminals into diaminocarbenes and carbenium salts

The reactivities of the two stable diaminocarbenes 1,3-di-'tert '-butyl-imidazole-2-ylidene 1 and 1,3-di-'tert '-butyl-imidazolidine-2-ylidene 2 toward hydrogen, oxygen, water and carbon monoxide and SO2 were investigated. Contrary to common belief the deterioration of 1 and 2 is not due to oxidation by triplet oxygen, but is the result of hydrolysis. The hydrolysis rate at room temperature is very low for the aromatically stabilized 1 but very rapid for the non-aromatic 2. The reactions are not acid or base catalyzed. Computational data show that the reaction with triplet oxygen is only kinetically hindered and that the oxidation of 1 and 2 to the respective ureas is in fact strongly exothermic. Both carbenes insert into dihydrogen only in the presence of hydrogenation catalysts. Carbene 2 forms a 1:1 adduct with SO2 that is best described as a Lewis adduct. The aromatic ring protons in 1 undergo rapid deuterium - hydrogen exchange in DMSO-'d'6, CD3OD and D2O. The oxidation of animals by oxidizing agents like NBS, NCS, CCl4, CBr4, I2 or CuCl2 leads to diaminocarbeniurn salts in high yields. These oxidations can be extended to 1,3,5-triazacyclohexane R3TAC systems, to give the monocationic salts [R 3TAC][X]. The carbene, 1,3,5-tri-'tert'-butyl-1,3,5-triazacyclohexane-2-ylidene 9, derived through deprotonation of the [R3TAC][Br] has been observed in benzene-'d'6 solutions. Reaction of R3TAC with CuCl2 leads to metal-1,3,5-triazacyclohexane complexes.
Teaching and learning high school physics through analogies, case study of Kenyan classrooms

Analogy is a widely used instructional tool in science. Because of the in physics education. Analogies differ in character depending on who constructs them, the context in which they are used and the grade level being taught. This study describes the analogies that physics teachers use in teaching form two (grade 10) physics in Kenya. The study extended over 14 weeks of classroom observation in three form two physics classes, supplemented by teacher and student interviews. A total of 20 analogies were identified and analysed in terms of Nashon's (2000) Working With Analogies (WWA) model. Findings showed that the analogies were largely 'environmental ' (cultural), 'anthropomorphic' and spontaneously generated. There was no evidence to indicate teachers' use of a theoretical model, such as Zeitoun's (1984) General Model for Analogical Teaching (GMAT), Glynn's (1991) Teaching With Analogies (TWA) or Nashon's (2000) Working With Analogies (WWA) model. It was found that alternative frameworks for some concepts still existed among the students despite the analogical teaching. Some of the frameworks appeared to persist even in the presence of correct information, while others were a consequence of literal interpretation of scientific terms or phrases. The few analogies that students generated for themselves reflected their understanding of analogically taught concepts (Pittman, 1999) and could therefore, to some extent be judged successful. However, some misconceptions were still noticeable. Findings of this study may have an impact on the way teachers teach science, and, more so, physics--in particular, on the analogies they use, the concepts they teach and the methods they chose to use in teaching the concepts (in general), all of which depend on the context.
Cognitive performance of children with an arithmetic disability with and without attention-deficit hyperactivity disorder

Using a selection of cognitive, memory, and academic tasks, this study examined the performance of children with a Specific Arithmetic Disability (SAD; no reading disability), investigating whether difficulties were exacerbated by Attention-Deficit/Hyperactivity Disorder (ADHD). Comparisons were made between children with SAD, normal achievement, ADHD, and combined SAD and ADHD. ADHD was found to diminish the already-impaired visual-motor, reading comprehension, and spelling abilities of children with SAD. At younger ages, children with ADHD had more difficulty with phonological processing tasks than those without, possibly because of the memory requirements necessary for these skills. The presence of either or both ADHD and SAD had a negative impact on memory for numbers. Additional difficulties coinciding with the presence of either disability separately were apparent in certain areas. Support was found for the hypothesis that ADHD further impairs the performance of children with an arithmetic disability.
Tripping over patents, AIDS, access to treatment and the manufacturing of scarcity

With an estimated 4.7 million--or approximately one-in-nine--people living with HIV/AIDS, South Africa is in crisis. Understanding that its ability to turn the tide against the epidemic in large part hinges on whether the majority of people with HIV/AIDS will have access to treatment, this thesis explores the extent of regulatory flexibility permissible under the World Trade Organization's Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS). I argue that despite the international harmonization of intellectual property law, countries like South Africa are permitted by TRIPS to take certain regulatory steps to ensure the accessibility of essential treatments. When properly interpreted in accordance with recognized principles of international law and in the light of the 'Constitution of the Republic of South Africa, 1996', TRIPS does not prevent--but rather contemplates and permits--the taking of certain legal steps to ensure meaningful reductions in drug prices.
Rigid rod polymers in confined geometries

This thesis examines properties of rigid-rod polymers in confined geometries. Organization of polymers in self-assembled layers on a single surface, and thin polymer films confined between two solid substrates has been studied. Adsorption and self-assembly of rigid-rod polypeptides from dilute solution onto a single surface was studied by Atomic Force Microscopy supplemented by Dynamic Light Scattering. Various factors affecting organization of self-assembled layers were examined: the nature of the surface and solvents; polymer architecture, molecular weight, polydispersity, and concentration. It was shown that polypeptides assemble into fiber-like structures onto a hydrophilic mica surface via dipole-charge interactions, while on a hydrophobized surface adsorption is suppressed. Different types of substrates used for polypeptide self-assembly and Surface Force Balance (SFB) studies were obtained by modification of atomically smooth mica surfaces with octadecyltrichlorosilane (OTS) and mixed monolayers. An established protocol of mica silanization with OTS produced smooth and stable hydrophobic surfaces. Two approaches to the preparation of mixed monolayers involving (i) self-assembly of cationic surfactants and (ii) silanization were thoroughly examined. Properties of poly(ã-n-hexyl-L-glutamate) (PHLG) layers confined between two mica surfaces were studied using the SFB technique. Normal and shear forces in PHLG layers were examined for different types of confining surfaces as a function of polymer concentration in solution and for various shear parameters. The shear response of the confined PHLG layers was analyzed using rheological models developed in this work. PHLG layers confined between the bare mica surfaces exhibited strong hydrodynamic interactions characteristic of the rheological regime of friction. In contrast, polymer layers confined between the hydrophobically modified surfaces displayed moderate shear forces with the onset of shear interactions shifted to shorter intersurface separations. The shear response was dominated by slip and thus was formally characteristic of the tribological regime of friction. Finally, reversible liquification of the PHLG layers was observed and discussed. To analyze orientational transitions of rigid-rod polymers in constrained geometries, an analytical model based on analysis of birefringence in SFB was developed. This model was tested with low-molecular weight liquid crystals (LCs) under different experimental conditions. Good agreement between the model and the experimental data was found.
Pole-potential mapping and synthetic arrays in electrical exploration

Many interesting geological features can be characterized by the electrical resistivity Consequently, the resistivity and induced polarization methods are extensively applied to map subsurface electrical properties and often provide a suggestive outline of geological structure. Standard survey methods collect data using linear configurations and, in 1d or 2d environments, survey and interpretation methods are well developed. However, in the complex geological settings often encountered the responses of most linear array configurations suffer from an extreme sensitivity to near-surface structure which can obscure the more desirable response from deeper structure. Furthermore, linear profiles and sections can be ambiguous when coarse sampling intervals are used, a problem compounded by the lack of information from between survey lines. Improving the accuracy of electrical prospecting methods requires that a more complete map of field measurements be taken over a two dimensional set of source and receiver positions. I suggest a 3d mapping method using a 2d surface grid, a method I name pole-potential mapping. To interpret the data from such a survey, I suggest several approaches to defining apparent resistivity in terms of gridded potential maps about a distributed grid of current poles. This approach significantly improves our ability to resolve subsurface features. Sensitivity analysis, numerical and analytic model studies clearly show the sensitivity of circular arrays to be more localized in one region in the earth than traditional configurations and the location and depth extent of the high sensitivity region is easily controlled by varying the location and dimension of the synthetic arrays. Finally, to show that systematic pole-potential mapping could practically be carried out on a regular basis with an efficient field methodology, I designed and constructed suitable instrumentation. From practical tests in a scale modelling tank and in a small scale field experiment at Fort York, I show measurement error in synthetic data can be made low enough to exploit the improved signal of deep targets to surficial noise. A roll-along approach, analogous to that used in seismic surveying, is a very efficient field methodology. The results are consistent with predictions from the numerical studies indicating the utility of pole-potential mapping.