Master of Science / Department of Kinesiology / Thomas J. Barstow / Background and Aim: The power-duration relationship accurately predicts exercise tolerance for constant power exercise performed in the severe intensity domain. At intensities above critical power (CP), the power-duration relationship establishes a hyperbolic curve. However, the prediction of exercise tolerance is currently unclear for work rates within the extreme intensity domain (durations <2min). We hypothesized that the power-duration relationship deviates from a linear 1/time relationship for WRs within the extreme intensity domain. Methods: Six men completed nine bilateral knee-extension tests on non-consecutive days and then performed 3 exercise tests in the severe intensity domain (S1-S3; T[subscript lim]>2–15min) and 4 in the extreme domain at 60%, 70%, 80%, and 90%1RM (T[subscript lim]<2min), in random order. Twitch force (Q[subscript tw]), maximal voluntary contraction (MVC), and voluntary activation (VA) were measured on the right vastus lateralis before and after <80s) each test; EMG was measured on the right vastus lateralis throughout each test. T[subscript lim] were plotted as a function of 1/Time. T[subscript lim] for the extreme intensities were compared to the predicted T[subscript lim] of the slope of the S1-S3 regression. Results: The r² for the severe domain 1/time model was 0.99 ± 0.007. T[subscript lim] for exercise at 60%1RM was not different than the predicted T¬lim, however, T¬lim for exercise at 70–90%1RM was shorter than the predicted T[subscript lim] (p<0.05). Post hoc analysis of the extreme domain (70–90%1RM) revealed a significant linear relationship, suggesting a W’ within the extreme domain (W’ext). T[subscript lim] of exercise at 60% 1RM was not different from the predicted value of the 1/Time relationship of the extreme domain. Q[subscript tw] and MVC were significantly decreased following exercise at S1-S3 and 60% 1RM, while no changes existed in Q[subscript tw] or MVC following exercise at 80 and 90%1RM. Further, no changes were found in VA following any exercise intensity. Conclusion: These data suggest that exercise tolerance in the extreme domain is limited by different factors than in the severe domain. However, there is a separate but measurable W’ext. Further, the factors limiting exercise in the extreme domain must be those from can be recovered by the time post-exercise measurements were made.

Made available in DSpace on 2014-10-09T12:28:52Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:06Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia) / IPEN/D-MPLO / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP; Faculdade de Odontologia, Universidade de Sao Paulo, Sao Paulo

This study represents an attempt to model the disaggregation of daily rainfall at a point into individual storms for the summer rainy season in southeast Arizona. The purpose of the model is to simulate the number of storms per day and the amount, duration and time of occurrence of each event while maintaining daily statistics. Various storm ratios are introduced to describe the disaggregation of a daily amount into individual storm amounts. Marginal distributions are fit to the storm ratios and event starting times. On multiple-event days, starting times are obtained through the use of order statistics. Conditional distributions are fit to the number of storms per day, given a daily amount, and the duration of each event, given a storm amount. The simulated data compare favorably with the observed data. Statistical tests indicate that the model adequately transforms daily rainfall into a sequence of individual storms.

The primary goal of this thesis is to improve the precision and efficiency of radiation therapy treatment. This goal is achieved by developing and implementing a direct aperture optimization (DAO) platform where the multileaf collimator (MLC) is rotated between each aperture. The approach is referred to as rotating aperture optimization (RAO). A series of tests is performed to evaluate how a final optimized plan depends on MLC parameters. Imposing constraints on the leaf sequence results in increased efficiency and a simplification of the treatment plan without compromising the quality of the dose distribution. It is also shown that an arrangement of equispaced collimator angles takes full advantage of the flexibility associated with collimator rotation. A study including ten recurring nasopharynx cancer patients is used to evaluate the capabilities of RAO compared to other optimization techniques. It is shown that RAO plans require significantly less linac radiation output (monitor units or MU) while maintaining equivalent dose distribution quality compared to plans generated with the conventional fluence based approach. Furthermore with an improved collimator rotation speed, the RAO plans should be executable in the same or less time than plans generated with the fluence-based approach. For the second part of the study it is shown that plans generated with RAO are as good as or better than plans generated with standard fixed collimator DAO. Film and ion chamber measurements indicate that RAO plans can be delivered more accurately than DAO plans. Additional applications of DAO were investigated through collaboration with two PhD students. First, Monte Carlo was used to generate pencil beam dose distributions for DAO inverse treatment planning (MC-DAO). The MC-DAO technique correctly models traditionally difficult treatment geometries such as small fields and tissue inhomogeneities. The MC-DAO also takes advantage of the improved MU efficiency associated with the DAO technique. Secondly DAO is proposed for adaptive radiation therapy. The results show that plan re-adaptation can be performed more quickly than complete plan regeneration thereby minimizing the time the patient has to spend in the treatment room and reducing the potential for geometric errors in treatment delivery. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The health, safety, comfort and productivity of a room’s occupants is greatly influenced by the sound field within it. An acoustical engineer is often consulted during the design of a room to prevent or alleviate unwanted acoustical problems. Prediction models are often used to find the most cost-effective solution to a given acoustical problem. The accuracy of sound-field prediction varies with the particular model, as do the parameters predicted. Most models only predict sound-pressure levels. Many only predict energetic quantities, ignoring wave phase and, therefore, interference and modal effects in rooms. A ray-tracing model, capable of predicting sound-pressure level, reverberation time and lateral energy fraction was translated into MATLAB code and modified to increase accuracy by including phase. Modifications included phase effects due to path length travelled and phase changes imparted by surface reflections as described by complex reflection coefficients. Further modifications included predicting steady-state and transient sound-intensity levels, providing information on the direction of sound-energy flow. The modifications were validated in comparison with free-field theory and theoretical predictions of sound fields in the presence of a single surface. The complex reflection coefficients of four common building materials were measured using two methods—an impedance tube and the spherical-decoupling method. Using these coefficients, the modified program was compared with experimental data measured in configurations involving one or more surfaces made of these materials, in an anechoic chamber, a scale-model room, and a full-scale office space. Prediction accuracy in the anechoic chamber, and in the presence of a single reflecting surface, greatly improved with the inclusion of phase. Further comparison with full-scale rooms is required before the accuracy of the model in such rooms can be evaluated definitively. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

PURPOSE: To compare the effects of recovery intensity on performance of a bicycle sprint task and blood La⁻ clearance. METHODS: On three separate days twelve trained male subjects (27.4 ± 3.9 yrs) performed three supramaximal exercise (SE) bouts at 120% of maximum aerobic power (MAP) for 60% of the time to exhaustion (TTE). Bouts were separated by 5 mm of passive recovery (PR), active recovery (AR) or combined active recovery (CAR). The third bout was followed by a 14 mm recovery. Recovery intensities were: PR (rest), AR at 50% of the workload difference between the individual anaerobic threshold (IAT) and the individual ventilatory threshold (IVT) below the IVT ( ₋50%ΔT), or CAR at the IAT workload for 5 mm and at the ₋50%ΔT workload for 9 mm. Five 10 s sprints were performed 2 mm post-recovery. Blood lactate (La⁻) concentration, power parameters (Peak Power (PP), Mean Power (MP), Fatigue Index (Fl), and Total Work (TW)), Heart Rate (HR), and Oxygen Uptake (VO₂ ) were compared using repeated-measures ANOVA. Pairwise comparisons and dependent T-tests were performed to analyze differences. RESULTS: Mean La⁻ values for AR and CAR were lower than PR (9.7 ± 3.5, 9.5 + 3.5, 11.7 + 3.6, respectively, p≤0.05). La⁻ was significantly lower with CAR versus PR at the 3rd, 6th, 9th, and 14th mm of recovery (p≤0.05). AR versus PR La⁻ was lower at the 3rd, 6th, 9th, and 14th min of recovery (p≤0.05). Mean MP was greater in the AR group compared to the PR group (800.1 ± 114.5 vs 782.2 ± 111.7 W, p≤0.05). TW during AR was greater than PR (p≤0.05) but not CAR (p≤0.05, 40003.3 ± 5110.2, 39108.3 ± 4852.9, 39335.8 ± 5022.6 J, respectively). CONCLUSIONS: AR and CAR both demonstrated improved La⁻ clearance when compared to PR, but differences in La⁻ clearance did not determine performance on the sprint task. AR resulted in more TW than PR and greater maintenance of power over the sprints. / Education, Faculty of / Kinesiology, School of / Graduate

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How individuals process different affective cues, as well as how intensely they experience different emotions, may influence how efficient they are at engaging inhibitory control. To date, it is unclear if these influences differ among young adults with and without ADHD. The current study tested the variation in young adults’ inhibitory control to three affective cues (i.e., fear, happy, and neutral) in an Emotion Go/Nogo task. Results suggest better inhibitory control in response to more distinct cues (i.e., fear Nogo/happy Go). The order in which cues were presented also mattered, such that participants displayed enhanced inhibitory control when first presented with expressions that had similar valence. This task order was particularly helpful for inhibitory control engagement among young adults with ADHD. Furthermore, self-report measures suggest that young adults with ADHD were associated with higher levels of affect intensity. However, no additional relations were found in the processing of affective cues, affect intensity, and inhibitory control between young adults with and without ADHD. Results provide evidence for how affective cues and contexts differentially influence behavioral responses in young adults. Individuals with and without ADHD also appear to differ in the intensity with which they experience different emotions. Overall, the current study provides a framework for how to further explore how emotional cues and affect intensity influence inhibitory control.

Includes bibliographical references (leaves 32-34). / According to the Competition Act of South Africa, proposed mergers, if rejected on the grounds of anti-competitive effects as well as the efficiency considerations, may be passed on certain public interest grounds. The fourth public interest clause potentially allows mergers to be passed should the merged firm become more able to compete in international markets. This paper interprets the clause to refer to a relationship between firm size and exports, and investigates this supposed relationship and, in so doing, the validity of the clause. It is found that firm size is positively related to export propensity, the likelihood of exporting any output. However, firm size is found to be unrelated to the intensity of exporting, the proportion of output that is exported by the firm. This paper covers new areas of research, and its conclusions call into question the inclusion of the relevant public interest clause in the Competition Act.

The deposition of ultrasonic energy in tissue can cause tissue damage due to local heating. For pressures above a critical threshold, cavitation will occur in tissue and bubbles will be created. These oscillating bubbles can induce a much larger thermal energy deposition in the local region. Traditionally, clinicians and researchers have not exploited this bubble-enhanced heating since cavitation behavior is erratic and very difficult to control. The present work is an attempt to control and utilize this bubble-enhanced heating. First, by applying appropriate bubble dynamic models, limits on the asymptotic bubble size distribution are obtained for different driving pressures at 1 MHz. The size distributions are bounded by two thresholds: the bubble shape instability threshold and the rectified diffusion threshold. The growth rate of bubbles in this region is also given, and the resulting time evolution of the heating in a given insonation scenario is modeled. In addition, some experimental results have been obtained to investigate the bubble-enhanced heating in an agar and graphite based tissue- mimicking material. Heating as a function of dissolved gas concentrations in the tissue phantom is investigated. Bubble-based contrast agents are introduced to investigate the effect on the bubble-enhanced heating, and to control the initial bubble size distribution. The mechanisms of cavitation-related bubble heating are investigated, and a heating model is established using our understanding of the bubble dynamics. By fitting appropriate bubble densities in the ultrasound field, the peak temperature changes are simulated. The results for required bubble density are given. Finally, a simple bubbly liquid model is presented to estimate the shielding effects which may be important even for low void fraction during high intensity focused ultrasound (HIFU) treatment.