VictorJuiz/thesis huggingface dataset:
A study of the discharge coefficient of jets from angled slots and conical orifices

Non-ideal flows through angled orifices occur often in engineering applications such as mass flow meters, blast-wave simulators, gas propulsion devices and projectile launchers. For such flows, a correction factor in the form of a discharge coefficient is required to facilitate good design and efficient operation. The discharge coefficient depends on many parameters including atmospheric to stagnation pressure ratio, gas specific heat ratio, exit to channel area ratio, orifice shape, wall angle and orifice edge rounding. The dependence on these parameters (except edge rounding) was studied numerically by developing a two-dimensional finite-difference computer program that solves the subsonic flowfield in the hodograph plane by a relaxation method and the attached supersonic flowfield, if present, in the physical plane by a method of characteristics, joined together at the sonic surface by matching stream function values. The discharge coefficient was also studied experimentally by developing and testing an experimental facility using a new technique based on the partial blowdown of a pressurized vessel through a short pipe ending with conical orifices of different area ratios, wall angles and orifice edge roundings. Numerical and experimental data from these studies and also from the literature are compared and discussed. A software package called the "' Cd' Algorithm" was developed to reproduce quickly the combined numerical and experimental discharge coefficients for the entire set of parameters, and it outperforms previous algorithms in accuracy, efficiency and comprehensiveness. This 'Cd' Algorithm uses analytical, numerical and experimental results at the limits for incompressible, critical and choked flows, and other 'Cd' values between these limits are reproduced by using piecewise cubic polynomial splines.
Stimulation-evoked pain and temperature sensations in thalamus of pain and non-pain patients

This thesis examined the location and incidence of thalamic microstimulation-evoked painful/thermal sensations in pain and non-pain patients. Awake patients undergoing functional stereotactic surgery were asked to report any sensations evoked by microstimulation (300Hz, 0.2ms, 1 sec. trains) at 1-mm intervals along microelectrode trajectories through ventrocaudal nucleus (Vc) and ventroposterior (VPVc) region. In 49 movement-disorder and 37 pain patients microstimulation evoked painful/thermal sensations at 6.6% of the 5842 stimulation sites. The majority (77.3%) of these pain/temperature sites was located ventroposterior to Vc. The incidence of pain sites was higher in post-stroke pain patients (PSP, n = 11) compared to other patients (15.1% vs 1.6% in Vc; 9.5% vs 2.8% in VPVc). In contrast, thermal sites within VPVc were evoked less frequently in PSP patients (2.3%) than in other groups (7.4%). These data demonstrate that most pain/thermal sites were located in VPVc and suggest that alterations in thalamocortical sensory processing in PSP patients may mediate chronic pain.
Retroviral-mediated gene transfer and expression of the multidrug resistance-associated protein 1 for hematopoietic chemoprotection, preclinical trials in a canine model

Multidrug Resistance-Associated Protein 1('MRP1') is a member of the ABC superfamily of transporters that confers multidrug resistance. We hypothesized that the transfer and expression of the 'MRP1' gene to hematopoietic stem cells (HSCs) might provide protection from the myelosuppressive effects of chemotherapy. We developed a retroviral producer cell line, MRP1-PG13, and optimized conditions for transfer of the human ' MRP1' cDNA into HSCs. We demonstrated that MRP1-PG13 is able to transfer ' MRP1' to human cultured cells and that expression gives rise to drug resistance. We also established that 'MRP1' gene transfer into canine hematopoietic progenitors (CD34+) was feasible ' in vitro' at a level of ~13%. For 'in vivo' studies, ' MRP1' transduced autologous CD34+ cells were infused into two dogs. Dogs received multiple drug challenges. Despite the lack of hematopoietic chemoprotection, we demonstrated that vector-containing cells engrafted and proliferated, as 'MRP1' positive CFUs were detected in blood and marrow after drug challenges.
Implicit Navier-Stokes computations of unsteady flows using subiteration methods

A time-accurate, implicit numerical method for the two-dimensional compressible thin-layer Navier-Stokes equations is described. Subiteration techniques are used to solve the non-linear problem arising at each time step. The subiteration methods have been incorporated in the well-known implicit Navier-Stokes flow solver ARM, developed at the NASA Ames Research Center. Two different subiteration techniques are used. They employ similar methodologies used to solve steady-state problems such as approximate factorization, diagonalization, and local time-stepping. One scheme uses a single time-step value while the other uses a dual time-stepping approach where one time-step governs the temporal accuracy of the code and the second time-step is chosen to accelerate convergence at each iteration. Two modifications are made to the subiteration schemes to improve the efficiency of the code. The combined second and fourth-difference dissipation, which requires the inversion of a set of scalar pentadiagonal equations, is altered to use a modified second-difference dissipation scheme in the implicit operator, leading to a scalar tridiagonal form. The second modification consists of freezing the Jacobian matrices during the subiterations. Turbulent flow about an airfoil under buffet conditions is also considered. (Abstract shortened by UMI.)
The design of a photoregulated enzymatic system

Photoregulated enzymes could be used to study cellular processes, create in vitro enzymatic cascade systems, or to modify the substrate specificity of an enzyme catalyst. In this work a photoregulated enzyme system has been designed by incorporating a photoswitchable amino acid into the primary sequence of RNase S. In part 1, the development of a novel fluorescent substrate for RNase is described. The 5'Fl-AAAArUAAAA-3' Rh substrate was designed to provide information on changes occurring in the enzyme binding cleft of RNase S. Fluorescence resonance energy transfer (FRET) was used to monitor substrate cleavage by ribonuclease. The kinetic characterization of the fluorescent substrate, with RNase A, is carried out in part II. Kinetic measurements were performed and the kcat and KM constants were determined. RNase S contains two polypeptide sequences, the S-peptide and the S-protein. In part III, S-peptide analogues were synthesized with the photoswitchable amino acid phenylazophenylalanine (PAP) replacing one of the native residues. Non-covalent reassociation of the S-peptide and S-protein forms an active enzyme complex in solution under physiological conditions. S-peptide analogues were designed with a PAP residue in positions 4, 7, 10, or 11 of the peptide sequence. PAP modified RNase S enzymes were formed; peptide/protein interactions, and maximum initial rates were measured using the fluorescent substrate. A nitrogen laser (337nm) was used to switch the PAP molecule in the enzyme complex, between cis and trans conformations and photoregulation was observed in the PAP 4 and PAP 7 RNase S complexes.
Treatment outcomes with osseointegrated Brånemark implants in diabetic patients, a retrospective study

All diabetic patients treated with Brånemark osseointegrated implants in the Implant Prosthodontic Unit of the Faculty of Dentistry, University of Toronto were identified by way of a retrospective chart survey. Each of these patients was matched to two control subjects by age, sex, location of implants (jaw and zone), type of prosthetic restoration, opposing arch and duration of edentulism. Additional factors including the presence of other medical conditions, smoking habits, medication use, and bone quality and quantity of the jaw treated with implants were controlled for by utilising logistic and linear regression. Diabetic patients had no increased risk of implant failure, lost more bone in year one of loading, had less soft tissue complications, had a similar numbers of prosthodontic complications and reported more paresthesia and less post operative pain compared to matched non-diabetic controls. These results suggest that non-brittle diabetic patients should be considered for treatment with implant supported prostheses.
Geographic variability in components of the male advertisement call among populations of the northern spring peeper, Pseudacris crucifer crucifer

I studied variation in three parameters of the male advertisement call across nine populations of the spring peeper, 'Pseudacris crucifer '. I discovered significant inter-populational variability in two of those components: the midpoint of the dominant frequency and call duration. Frogs from the southwestern Unites States, living in open habitats, have a lower MDF and a longer call than their northeastern brethren living in forested habitats; possibly due to different transmission parameters in open versus forested habitats. There was also a significant difference in body size among populations in the northeast, although the reason for such size variation awaits further investigation. Based upon my results, I believe that it is important for researchers investigating the effects of female preferences on the evolution of male advertisement call to also consider the effects of environmental selection in shaping the structure of the call.
Electromagnetic levitation of a solid metallic torus

The electromagnetic levitation of a solid metallic torus has been investigated using both experiments and analysis. The investigation was primarily focused on bulk stability and the magnetic pressure distribution on the toroidal surface. Three different induction coil designs were studied: a two-loop design, a reverse-loop design, and a basket design. The two-loop design did not exhibit bulk stability. The reverse-loop design was shown to exhibit bulk stability, however the magnetic pressure distribution on the surface of the torus is inadequate for levitating large amounts of molten metal. Stable levitation could not be achieved during experiments with the basket design, due to output voltage limitations of the available power supply. The analysis of the basket design showed that it should exhibit bulk stability if properly energized, and that the magnetic pressure distribution is adequate for levitating large amounts of molten metal.
Design and control of a novel actuator based on human muscle characteristics, the Muscle Actuator

Over the past two decades considerable progress has been made in developing conventional actuator technologies for robotics. Nevertheless, new actuation technologies are required for the emergence of high performance robots. While sophisticated control algorithms can be used to improve actuator performance, limitations are imposed by the mechanical and electrical hardware of such systems. Given the shortcomings, a radically different approach was pursued that consisted of developing a new linear electromagnetic actuator (linear motion), called the 'Muscle Actuator'. Extensive simulation studies revealed that the global characteristics of the human muscle (' force'/'length and force'/'velocity') are key to high performance applications. The human muscle is capable of an abrupt stop without oscillation, even after high speed movements which are characteristic of high performance drive applications. Following the simulation studies, the global characteristics of the human muscle were adapted and emulated in a linear electromagnetic actuator. Based on the proposed design, extensive simulations and experiments were carried out to measure the force/length and force/velocity characteristics of the muscle actuator, and study the behavior of the actuator when parameters such as activation level (input current) and applied load vary. The experimental results are in good agreement with the results obtained from mathematical models. The non-linear damping characteristic of the designed actuator was analyzed in detail because it is the most important characteristic in the context of high speed/high precision motion. Despite the open-loop stability of the muscle actuator, the stability of the muscle actuator in the closed loop was also investigated. Closed-loop control is useful in compensating for uncertainty in parameters, which is due either to the nonlinear values not being exactly known, or because they vary during operations. A controller was designed using the 'feedback linearization' technique, and it was proved that the closed-loop is stable under certain conditions. Moreover, a pair of muscle actuators was used to make a one-degree-of-freedom joint, and the complete interfaces for the one-degree-of-freedom joint setup were designed and built. This setup was used to study the performance of the designed controller and the joint stiffness modulation capability in an antagonistic configuration. The modulation allows the mechanism to have a variable, depending on task, stiffness when contact between the joint-link and the surroundings occur. Finally, as a starting point for future work, an optimized design of the linear muscle actuator and two possible configurations for the rotary muscle actuator were presented.
Olfactory plasticity in Caenorhabditis elegans, a separation of adaptation and habituation

Continuous presentation of an olfactory stimulus causes a chemotaxis response decrement in the nematode 'Caenorhabditis elegans', but the differences between the learning process of habituation (a reversible decrease in behavioural response) and other olfactory plasticity such as adaptation (a decrement in response due to sensory/motor fatigue, which cannot be dishabituated) have not been addressed. Using the volatile odorant diacetyl (DA) I assessed the distinct processes of olfactory adaptation and habituation. Pre-exposing and testing worms to 100% DA caused a chemotaxis decrement which was not reversible despite the presentation of potentially dishabituating stimuli. This DA adaptation is abolished in 'odr-10' mutants but remains intact in ' odr-1' mutants. Although DA pre-exposure to intermediate concentrations of DA (0.01% and 25%) produced no chemotaxic response decrement, pre-exposure to low DA concentrations (0.001%) produced either a dishabituable response decrement (habituation) or sensitization. The distinct behavioural effects observed after DA pre-exposure highlight a concentration-dependent dissociation between adaptation and habituation.
Environmental education in pre-service teacher training programs in Canadian tertiary institutions

Continually identified as one of the key agents of change, teachers play an important part in promoting and improving the capacity of individuals to address environmental and development issues and problems. The preparation of pre-service teachers is especially critical in achieving environmental and ethical awareness, as well as in developing the values, attitudes, skills and behaviours conducive to a sustainable future. However, despite being recognized as a major priority for research and action in many major international conferences on environmental education, environmental education research in pre-service programs has been given little attention in Canada. The only systematic national evaluation of environmental education at the teacher preparation level in Canada was conducted by John Towler (1980-81), nearly 20 years ago. Since Towler's (1980-81) survey, there have been few investigations examining the status of environmental education in Canadian pre-service teacher preparation programs. Towler surveyed pre-service teacher education programs across Canada and reported that many of the respondents at that time did not indicate a high level of commitment to implementing environmental education in teacher programs, despite the call for increased environmental education at all levels of education. This present study was an attempt to assess the status of environmental education at the teacher preparation level since Towler's study. A national survey using a modified version of Towler's questionnaire was distributed to all pre-service teacher training institutions across the Canadian provinces to determine the present level of environmental education which pre-service teachers receive in teacher preparation programs. In addition, two case studies examining the design, content, and methods of two pre-service teacher education courses with specialization in environmental education were conducted to understand and describe the nature of environmental education currently found in pre-service teaching programs. (Abstract shortened by UMI.)
Pretreatment motivational enhancement therapy for eating disorders, a pilot study

Eating disorder patients are notoriously ambivalent about treatment and often lack motivation to change. These characteristics may decrease the number of patients entering treatment and increase the number of patients dropping out of treatment prematurely. The aim of this pilot study was to develop and evaluate a motivational enhancement therapy (MET) group program for eating disorder patients. The goal of the MET intervention was to increase participants' motivation to change which might be expected to increase the success of future treatment of the eating disorder and reduce the rate of treatment drop-out. Nineteen individuals who were referred for specialized treatment took part in the study. The intervention was based on existing literature in the field of addictions and modified for eating disorders. The motivational measures suggested that the participants' motivation to change increased following the intervention A decrease in depressive symptoms and an increase in self-esteem were also detected. The results of this study provide a rationale to conduct further investigations into the effectiveness of MET for eating disorder patients.
Monitoring stable carbon isotopes during biodegradation of toluene, implications for contaminated site assessment

The potential for using compound-specific isotope analysis (CSIA) as a tool for monitoring the biodegradation of toluene was evaluated in laboratory experiments under anaerobic and aerobic conditions and at a contaminated field site. Within the ±0.5&permil; accuracy and reproducibility associated with CSIA, there was no significant change in the isotopic composition of the residual toluene despite greater than 85% aerobic biodegradation using two populations of mixed consortia and two different strains of 'Pseudomonas putida'. The lack of a discernible isotopic fractionation signal produced during aerobic biodegradation in these laboratory experiments was also observed at the contaminated field site. In contrast, the anaerobic biodegradation of toluene, carried out under both methanogenic and sulfate-reducing conditions, produced a small (~2&permil;), yet resolvable 13C-enrichment in the residual toluene at advanced stages of degradation. This thesis demonstrates that relating carbon isotope fractionation effects to intrinsic bioremediation of BTEX compounds will pose a challenge.
Various aspects of latex film formation in the presence of additives

This thesis examines the interaction of small macromolecules, like surfactants and oligomers, with poly(butyl methacrylate) (PBMA) latex particles. In this work, we mostly concentrated on nonionic surfactants, with the general structure R-(EO)n, where, R represents the hydrophobic moiety, and (EO) n is the hydrophilic moiety consisting of n units of ethylene oxide. We also performed a number of experiments with other low molecular weight species, such as BMA oligomers and oligo(ethylene glycols) (PEG) as well as with a two ionic surfactants, sodium dodecyl sulfate (SDS) and dihexyl sulfosuccinate (C941). Binding isotherms for a series of nonylphenyl ether surfactants NP-(EO)n with PBMA latex reveal that the interactions between latex particles and nonionic surfactants decreases drastically with increasing EO chain length. We found that nonionic surfactants and PEG oligomers have very limited miscibility with PBMA at room temperature, but the miscibility increases with increasing temperature and decreasing EO chain length. The low molecular weight species which are not miscible with polymeric matrix phase separate to form domains in the latex films. The movement of surfactant to the surface (exudation) upon annealing is connected with the existence of micrometer-diameter channels leading to the film surface. From polymer diffusion and miscibility measurements, we learned that when surfactant or oligomer stays in the film as a separate domains, it retards polymer diffusion, but when it is fully miscible with the polymeric matrix, it can act as a traditional plasticizer, and promote polymer diffusion by introducing free volume into the system. In this case the Fujita-Doolitle free volume theory is able to describe the effect of additive on the polymer diffusion rate. The effect of NP-(E0)20 surfactant and BMA oligomers can be described in this way. To investigate the influence of soft filler domains on polymer diffusion in latex films, we developed a model system consisting of cross-linked soft PBA latex particles dispersed in PBMA latex films. These experiments, show that the overall effect of added soft particles on polymer diffusion (retardation or enhancement) depends on a combination of different contributions: obstacle effects, wetting phenomena and changes in the morphology of the film.
The role of plantar cutaneous mechanoreceptors in the control of compensatory stepping in the young and older adult

Inability to adequately control compensatory stepping reactions, as might occur with aging, is likely to lead to an increase in the risk of failing. My studies specifically focused on the role played by sensory information, from the mechanoreceptors of the soles of the feet, in the control of compensatory stepping. There is a well documented age-related loss in plantar-surface sensation of pressure, and the presumed role of such sensors in the control of balance could lead to effects on control of the compensatory stepping response which may lead to an increase in falling risk. To attempt to address this potentially important relationship between plantar surface sensitivity and the control of compensatory stepping, the study adopted three specific stages, to: (1) determine the role of mechanoreceptors in control of compensatory stepping (using hypothermia to attenuate the sensation of the plantar surface of the foot); (2) determine whether facilitation of this sensation would improve stepping performance (by placing a raised edge underneath the perimeter of the plantar foot surface, thus facilitating sensation from the stability boundaries of the base-of-support); and (3) establish if the natural age-related deterioration of this sensation can predict impaired stepping performance in older adults (by examining the relative ability of various sensory, neural and musculoskeletal measures to predict stepping performance). The results from the first study support the importance of sensory input from the sole of the feet in the control of the stepping response, particularly in controlling stability during prolonged swing phase and in controlling foot contact and the subsequent weight transfer and centre-of-mass deceleration. The facilitation study supported these conclusions and provided evidence that mechanical facilitation of sensation from the boundaries of the plantar surface of the foot can improve the efficacy of stabilizing stepping reactions. The results of the third study indicated that, although stepping performance appears to depend, in a complex manner, on interactions between age-related impairments in the different systems, cutaneous sensation appears to be among the more predominant factors affecting stepping performance. The results these studies indicate the critical role that sensation from the plantar surface of foot plays in postural control.