VictorJuiz/thesis huggingface dataset:
MR-compatible modular tele-robotic system for MRI-guided neurosurgery

The basic premise of Magnetic Resonance Imaging (MRI)--guided neurosurgery is that the location of a surgical instrument can be shown on an image display monitor relative to a detailed depiction of the internal cranium. Precision and potential for tele-surgery are the prime motivations for applying robots in the MRI environments. Typically neurosurgeries are performed in open-bore MRI scanners. This results in the use of preoperative MRI images during the procedures. Use of closed-bore scanners would eliminate this concern; however there is no space for the neurosurgeon to perform operations. Therefore remote-control surgery would be the appropriate method to be used in closed-bore MRI-based surgery. In this dissertation the design and control paradigms of a novel modular tele-robotic system for closed-bore MRI-guided neurosurgery are presented. Candidate neurosurgical procedures enabled by this system would include thermal ablation, radiofrequency ablation, deep brain stimulators, and targeted drug delivery. A new infrastructure for MRI-guided intervention is also developed to address clinical requirements in a typical closed-bore MRI environment. The design paradigm is fundamentally based on a modular design configuration for the slave manipulator performing the required task inside MR scanner. Navigation and operating modules were designed to undertake the alignment and advancement of the surgical needle respectively. The control paradigm was developed based on two novel control methods including fiducials tracking and semi-autonomous motion. In the former, the surgeon could manipulate the needle inside the MRI scanner while relative position of the needle and the target are visualized on a display. In the latter, the needle is manipulated autonomously based on feedback from MR images to the controller. Two MR-compatible actuation systems that include ultrasonic motors and hydraulic/pneumatic cylinders were developed. A series of the experimental tests were conducted to evaluate MR-compatibility of an ultrasonic motor. The results show that the actuation of the motor only slightly deteriorated the MR image, and no image shift and significant degradation of signal-to-noise ratio was observed. This research provides a first complete surgical system for closed-bore MRI-based neurosurgery. The main contributions are the system MR-compatibility and the modular design and control paradigms.
Unpacking the garment district's innovation system: how the New York City women's wear industry stays in fashion

How do mature manufacturing sectors in a high wage context remain competitive? This dissertation addresses this question by examining the case of New York City women's wear. Drawing on seventy-five in-depth interviews and a comprehensive survey, the study finds that women's wear manufacturers have remained innovative by drawing on an extensive institutional and organizational infrastructure that has emerged in the midtown Manhattan Garment District. This infrastructure (or ‘innovation system’)—which consists of design schools, buying offices, forecasting services, trade associations, competing and complementary firms, and the institutions (habits, rules, norms) that shape their inter-relations—supports the manufacturers' innovation process by providing market-sensitive information and the capacity to utilize the information in the design and marketing of products. The spatial concentration of institutions and organizations helps to promote the development of shared understandings and conventions, which facilitate the exchange of information between District actors. The agglomeration of activities also benefits manufacturers in indirect ways, by enabling them to monitor the performance and solutions of rival firms as well as rival production systems. While most theories on industrial agglomerations cite the economic significance of consensus and system coherence, this dissertation argues that it is a balance between stability and an openness to novelty that underlies the Garment District's innovative capability. It concludes with a discussion of the theory and policy implications that this case suggests for promoting industrial agglomerations.
Browsing archived meeting audio and time-synchronized data

In a majority of meetings, speech and audio plays the most important role and therefore most of the meeting archives contain audio and some other data types, synchronized with it. Despite the importance of audio, its inherently sequential nature makes it difficult to be used as the guiding channel for browsing archives. In this thesis we describe the design and implementation of a prototype system for browsing archived meeting audio and other time-synchronized data using partially correct transcript for visualizing audio. We present a transcript based simultaneous-spatial audio browsing technique. This technique has been evaluated and found to be more efficient than the conventional interface for search tasks. It also allows an audio-data guided browsing of the archive. Furthermore, we present techniques for annotation and personalization of slide, audio and transcript data.
Dynamic compression measurements on selected granitic rocks using Split Hopkinson Pressure Bar test

The dynamic strength measurement on rocks has critical applications in areas ranging from blasting and fragmentation to design of underground structures. The present work on selected granitic rocks deals with measurements of compressive strength under dynamic loading conditions using the Split Hopkinson Pressure Bar apparatus. The tests involved two experimental setups with 19 mm and 25 mm diameter bar in order to study the strain-rate effects on dynamic compressive strength. Parametric studies have also been conducted to achieve dynamic stress equilibrium using pulse shapers. The ratio of dynamic compressive strength to static uniaxial compressive strength defined as dynamic increase factor (DIF) was found to be sim;1.7 at a strain rate of sim;550/s for Stanstead granite. Similar DIFs were obtained for the Laurentian and Barre granites. It was also noted that the use of pulse shapers can result in considerable reduction in strain rate without always achieving stress equilibrium.
Integration, testing, and operations of the CanX-1 picosatellite and the design of the CanX-2 attitude determination and control system

The availability of new miniaturized electronics and science instruments enables small, low cost spacecraft to perform what used to require much larger satellites. The Canadian Advanced Nanosatellite experiment (CanX) program was created at the University of Toronto Institute for Aerospace Studies Space Flight Laboratory to develop and launch small, low-cost satellites. This thesis aims to describe the integration and system level testing of the first satellite, CanX-1, launched in June 2003. Furthermore, satellite operations planning and results are presented along with a list of issues that were encountered and a summary of lessons learned by the CanX-1 team. An overview of the preliminary design of the follow-on satellite is presented as a background for a discussion of the design of the CanX-2 attitude determination and control system. This discussion outlines the control laws and attitude determination scheme used along with the design assumptions and pertinent simulation results.

Keywords: Nanosatellites
Nanosatellites, Attitude control systems
Nanosatellites, Control systems
Shear resistance of a polyurethane interface in concrete-steel composite beams

This thesis describes a series of pilot tests investigating the suitability of employing polyurethane to provide an adhesive shear connection between full depth precast concrete deck panels and steel girders in composite bridges. The study of an adhesive shear connection is the first step in developing a method of installing full depth precast concrete deck panels compatible with night closure concrete deck rehabilitation. The proposed connection detail also has the subsidiary benefit of increasing the structural strength and durability of precast concrete decks. Polyurethane, because of its rapid curing profile and comparatively low material cost, was used to construct push-out test specimens with varying shear connection configurations. Static testing of these specimens was performed to determine whether joint behaviour conformed to limit states requirements. Test results consistently showed polyurethane failure at low stresses indicating a need to refine the chemical formulation and method of polyurethane application.
The role of the immunoregulatory molecules T-bet and Cbl-b in the pathogenesis of autoimmune myocarditis

Idiopathic dilated cardiomyopathy (DCM) is a leading cause of heart failure and frequently results from postinfectious autoimmunity. Its pathophysiology is modeled by murine experimental autoimmune myocarditis (EAM). The goal of this thesis was to characterize the function of the immunoregulatory genes T-bet and Cbl-b in EAM pathogenesis using knockout mouse models. We first studied the role of the T-box transcription factor T-bet in EAM pathogenesis. T-bet is essential for Th1 cell differentiation and IFNgamma production. Surprisingly, we found that T-bet-/- mice develop severe EAM compared to T-bet +/+ controls. Genetic and cell transfer experiments demonstrated that EAM develops independently of Th1 or Th2 polarization. Further, T-bet-/- mice showed a marked increase in production of IL-17 by heart-infiltrating lymphocytes, and in vivo IL-17 depletion markedly reduced EAM severity in T-bet -/- mice. While heart-infiltrating T-bet +/+ CD8+ T cells secrete IFNgamma, a negative regulator of EAM and inhibitor of IL-17 production, T-bet-/- CD8+ lymphocytes lost their capacity to release IFNgamma within the heart. These data show that severe IL-17-mediated EAM develops in the absence of T-bet, and that T-bet can regulate autoimmunity via the control of CD8+ T cell bystander functions in the inflamed target organ. These studies characterized the role of two immunoregulatory genes in EAM pathogenesis, with perhaps surprising conclusions. In contrast to other autoimmune diseases, T-bet-/- mice develop highly severe EAM. Further, disease severity is not greatly increased in immunized Cbl-b-/- mice. This work therefore emphasizes the need for in vivo analysis in studying molecular pathogenesis. We then analysed the development of EAM in mice lacking Cbl-b, a negative regulator of T cell signaling. Cbl-b-/- mice did not develop EAM of increased severity when compared to Cbl-b +/+ controls. While stimulated and antigen-pulsed Cbl-b+/+ bone marrow dendritic cells (BMDCs) could transfer EAM to wildtype mice, Cbl-b-/- BMDCs could not. We observed no differences in the production of multiple inflammatory cytokines, or expression of activation markers, from stimulated Cbl-b+/+ and Cbl-b-/- BMDCs. Further, Cbl-b-/- BMDCs effectively presented peptide antigen to CD4+ T cells in vitro. We have therefore identified a requirement for Cbl-b in DC function in vivo that merits further research.
The mechanical characterization of a novel biodegradable interpenetrating phase composite

An interpenetrating phase composite (IPC) of porous calcium polyphosphate (CPP) and polyvinyl acid-carbonate copolymer (PVA-C), forming ionic bonds between phases, was produced as a potential material for forming a biodegradable osteosynthesis device. The effect of varying the porous CPP structure was investigated to optimize the IPC design in terms of initial stiffness and strength. Furthermore, a mechanism explaining the increase observed in bending strength has been proposed. Porous CPP having percentage theoretical densities of 65, 70, 77, and 82% were formed by gravity sintering amorphous CPP powders having particle size ranges of 75--106 mum, 106--150 mum, or 150--250 mum. The bending strength of IPC samples showed as much as a six-fold increase over that of CPP samples with elastic constants ranging from 15.4 to 39.8 GPa. Fracture toughness testing indicated a significant increase in KIC resulting from PVA-C infiltration of the porous CPP (K IC = 1.0 MPa· m1/2).
Dynamics of a semiconductor laser coupled to a dispersive external cavity

We present an investigation into various aspects of the dynamics of a laser consisting of a semiconductor diode coupled to a long external cavity, with particular emphasis on the role of the external cavity dispersion. We begin by developing a large-signal dynamical model for the diode itself. Employing a multiple scales analysis to simplify the familiar travelling wave phenomenological equations, we find the diode dynamics are accurately described by a time dependent reflection coefficient and one ordinary differential equation for the carrier density. We do not assume that the photon and carrier densities are uniform along the diode, nor need we calculate them explicitly at each point. Instead, we assume that the dynamical time scales of interest are longer than the round trip time within the diode. We apply this model first to the study of large-signal direct modulation of dispersive extended cavity semiconductor lasers, and find an expression for instantaneous frequency from which insight is gained into the role of dispersion. In cases where gain non-uniformity is important, we find significant differences between our results and those of previous models. We also apply our diode model to an investigation of laser stability. Surprisingly, instability had been observed experimentally for chirped fiber grating lasers, depending upon grating orientation. We reproduce this through a linear stability analysis, and find that the field equation resembles the nonlinear Schrödinger equation (NLSE). There is a range of dispersion parameter for which stable operation occurs, analogous to normal dispersion of the usual NLSE, but this range is finite due to non-instantaneous carrier dynamics. Lastly, we develop an alternate formalism for semiconductor diode—again without assuming uniformity or small signals—in order to describe etalon effects in non-dispersive external cavity lasers; we examine both laser stability and dynamics resulting from large-signal current modulation. All reflections are included with the introduction of a single additional feedback parameter, and one extra term in the field equation. In the limit of a single reflection, our field equation reduces to a form of the Lang-Kobayashi equation.
Interaction between Na/Ca² exchanger and Ca²⁺ current fluxes in cardiac excitation-contraction coupling

Cardiac Na+/Ca2+ exchanger (NCX) is central to [Ca2+] homeostasis by regulating Ca2+ efflux. Since NCX expression and activity are often altered in disease, recent studies suggest NCX inhibition as a possible therapeutic approach. However, the role of NCX Ca2+ influx in excitation-contraction (EC) coupling during an action potential (AP) remains uncertain. Contraction of cardiac myocytes is initiated primarily by L-type Ca 2+ current (ICa, L) which triggers intracellular Ca 2+ release from the sarcoplasmic reticulum (SR). SR release flux was measured by Ca2+ spikes in patch-clamped rat myocytes to isolate the contribution of NCX to Ca2+ release. In response to AP stimulation, normalized Ca2+ spike amplitudes (DeltaF/F 0) increased from 0.40+/-0.08 to 0.80+/-0.06 as [Na +], increased from 0 to 20 mmol/L (EC50=9.08+/-0.97 mmol/L). Enhancement of Ca2+ release was independent of I Na or SR Ca2+ load. However, NCX inhibition with KB-R7943 or inhibitory peptide XIP reduced DeltaF/F0 in myocytes containing 20 (but not 5) mmol/L [Na+]i. ICa, L inhibition with Cd2+ abolished spikes even when [Na+] i was elevated, demonstrating that Ca2+ influxes through NCX and ICa, L interact supra-additively to enhance triggered release. Initial AP repolarization rate is a key regulator of EC coupling. To test the hypothesis that NCX-ICa, L interaction is responsible for AP modulation of EC coupling, Ca2+ spikes were triggered by APs with varying repolarization rates. In myocytes containing 20 mmol/L [Na +]i, DeltaF/F0 displayed a biphasic relationship with AP duration at 50% repolarization (APD50), increasing initially then decreasing as APD50 increased from 4 to 52 ms. Maximal DeltaF/F 0 was achieved at 16 ms APD50 (DeltaF/F0=0.77+/-0.06). In the presence of XIP, APD enhancement of DeltaF/F0 was blunted (DeltaF/F0=0.60+/-0.06 when APD50=16ms). With only 5 mmol/L [Na+]i, APD enhancement of DeltaF/F 0 was also blunted and was unaffected by XIP. In myocytes with 20 mmol/L [Na+]i, and XIP, DeltaF/F0 was similar to that in myocytes containing 5 mmol/L [Na+] i with or without XIP. This thesis resolves the controversy regarding NCX in EC coupling, providing unequivocal evidence that NCX Ca2+ influx enhances Ca 2+ release during AP stimulation. NCX enhancement of release is achieved by supra-additive interaction between NCX and ICa, L and is sensitive to early AP repolarization rate.
Optimization of low-thrust spacecraft trajectories by direct shooting methods

The direct approach for trajectory optimization was found to be very robust. For most problems, solutions were obtained even with poor initial guesses for the controls. The direct approach was also found to be only slightly less accurate than the indirect methods found in the literature (within 0.7%). The present study investigates minimum-time and minimum-fuel low-thrust trajectory problems via a single shooting direct method. Various Earth-based and interplanetary case studies have been examined and have yielded good agreement with similar cases in the literature. Furthermore, new near-optimal trajectory problems have been successfully solved. A multiple-orbit thrust parameterization strategy was also developed to solve near-optimal very-low-thrust Earth-based transfers. Lastly, this thesis examines the use of the high-accuracy complex-step derivative approximation method for solving low-thrust transfer problems. For certain very nonlinear transfer problems, the complex-step derivative approximation was found to increase the robustness of the single shooting direct method.

Keywords: Space trajectories
Artificial satellites, Orbits
Signaling effects induced by pharmacological Tie2 receptor dimerization in lentivirally transduced cells

Engineering hematopoietic stem cells (HSCs) to express therapeutic transgenes provides the opportunity to treat various diseases. However, a critical number of transduced cells are required. One approach to increase transduced cell number is to activate modified receptor tyrosine kinases (RTKs) with chemical inducers of dimerization (CIDs), thereby promoting selective expansion. Tie2 is a RTK that modulates HSC function. For this project, a chimeric receptor was constructed with a CID-binding domain fused to the signaling domain of Tie2. Sequences encoding this receptor (termed LFT2) were cloned into a lentiviral vector. HUVEC cells transduced to express LFT2 showed an increase in phosphorylated Akt (p-Akt), which mediates cell survival, when treated with the CID AP20187. Similar increases in p-Akt were also observed in LFT2-expressing UKE-1 cells. Modest increases in proliferation were seen in HUVEC-LFT2 cells in response to AP20187. These results demonstrate the ability of the chimeric receptor system to cause Tie2-mediated signaling changes.
Induction of resistance to HIV-1 infection: Susceptibility is an inverse function of globotriaosylceramide (Gb(3)/P(k)) expression

Based on previous findings, we propose that Gb3 is a natural resistance factor against HIV infection. CD4+ HeLa cells were used to increase Gb3 expression via an adenoviral vector containing the Gb3 synthase gene. Cell surface and intracellular Gb3 expression was increased in cells infected with the vector, and after infection with HIV-1IIIB, these cells were substantially less infectable. This suggests that HIV infection is inversely proportional to Gb3 levels. We also pharmacologically mimicked genetic Gb3 polymorphisms in THP-1 and U87 cells by (a) inhibition of the alpha-galactosidase A responsible for Gb3 breakdown, using 1-deoxygalactonojirimycin (DGJ) and (b) inhibition of glucosylceramide synthase using P4 to deplete cellular Gb3. DGJ increased Gb3 in THP-1 and U87 cells and P4 reduced Gb3 over the same period. DGJ treated cells became resistant to HIV-1 infection, while P4 cells became more susceptible. We suggest that pharmacological induction of modest cellular accumulation of Gb3 represents a novel means for enhancing resistance to HIV infection.
Evaluation of two automated methods for determination of the air void system parameters of hardened concrete

Determination of air void parameters of hardened concrete is usually performed according to ASTM C 457 standard. This standard process is tedious and the results depend on the skill of the operator. Several researchers have proposed alternative automated methods for performing the test. Two of these new methods are Rapid Air 457 and the scanner method. Rapid Air 457 collects images from the surface of concrete samples using a digital microscope whereas in the scanner method, the surface is scanned by a flat-bed scanner. Then, the captured images are analyzed by different computer software. In this thesis, 22 concrete samples were examined by these two methods and the air void parameters were compared to those obtained from the standard method. Moreover, different parameters influencing the results of the test were examined and the precision of the results were compared to the recommendations of ASTM standard.
Phase transitions in liquid crystal + aerosil gels

Liquid Crystals (LCs) are found in many different phases, the most well-known, basic ones being Isotropic (I), Nematic (N), and Smectic-A (SmA). LCs show a rich variety of phase transitions between these phases. This makes them very interesting materials in which to study the basics of phase transitions and related topics. In the low symmetry phases, LCs show both positional and directional orders. X-ray scattering is an important tool to study these phase transitions as it probes the instantaneous positional correlations in these phases. Random forces have a nontrivial effect on ordering in nature, and the problem of phase transitions in the presence of a random field is a current and not well-understood topic. It has been found that aerosils posses a quenched randomness in the mixture of LC+aerosil samples, forming a gel random network which destroys long-range order (LRO) in the SmA phase. This can be modeled as a random field problem. The results of the studies of this thesis provide models for random filed systems. Particularly, the developed line-shape analysis can be used to analyze all random field problems in general. In the N to SmA phase transition in 4O.8 LC (butyloxybenzlidene octylaniline), orientational order (N) is modified by a 1-D density wave describing 2-D fluid layer spacing structure (SmA). Likewise the I to Sm A phase transition in 10CB LC (decylcyanobiphenyl), a transitional ordered phase develops without going through an orientational ordered phase. To study these phase transitions with aerosil dispersion carries the opportunity to probe the effect of induced quenched random disorder on phase transitions, which are 2nd order in the first case and 1st order in the second case. A two-component line-shape analysis is developed to define the phases in all temperature ranges. It consists of the thermal and the static structure factors. The reentered nematic (RN) phase of the [6:8]OCB+aerosil gels ([6:8]OCB is a mixture of hexyloxycyanobiphenyl and octyloxcyanobiphenyl) is another interesting case in which to study the quenched random disorder effects. The weak SmA phase of [6:8]OCB+aerosil gels is followed by a RN phase at low temperatures.