Thesis (M.S.)--George Mason University, 2009. / Vita: p. 29. Thesis director: Zoran Durić. Submitted in partial fulfillment of the requirements for the degree of Master of Science in Computer Science. Title from PDF t.p. (viewed Oct. 11, 2009). Includes bibliographical references (p. 27-28). Also issued in print.

Fast-starts are high powered events of short duration, used by fish for prey capture and escape from predation. Here, the energetic cost of fast-starts in escape and prey capture for a fast-start specialist, the northern pike, Esox lucius, are determined and physiological and behavioural constraints assessed. This is done by comparing costs with literature values for physiological limits set my muscle mechanics and biochemistry, and comparing costs with other components of the energy budget. The combination of high speed film analysis (200-250Hz) and hydrodynamic models are used to determine the mechanical costs, hydrodynamic efficiencies and power output of fast-starts in prey capture (S-starts) and escape behaviour (C-starts). Excess post-exercise oxygen consumption (EPOC) is used to estimate the metabolic cost of fast-starts. A comparison of model predictions with required (acceleration) force estimates shows results are within 22% and similar to previous findings at lower film speeds. The caudal region including the caudal, dorsal and anal fins contribute the most to thrust (>90%) and the dorsal and anal fins contribute 28%. Due to the necessity for deceleration of fin sections during each tail beat, kinematics are not always optimal as predicted by the Weihs model. Mechanical power output, hydrodynamic efficiency and kinematic parameters (maximum velocities and maximum angle of attack of the caudal fin) are determined for fast-starts during prey capture and escape. Hydrodynamic efficiency averages 0.37 (range: 0.34 to 0.39) for C-starts and 0.27 (range: 0.16 to 0.37) for S-starts. The acceleration of added mass contributes the most to power output at 39%. Power output and efficiency for S-starts are more variable than C-starts and hydromechanical efficiency increases with number of tail beats for S-starts. Maximum muscle power output and maximum muscle stress during fast-starts in comparison to literature values for muscle function shows muscle power output during fast-starts is at its physiological limit but muscle stress is not. Metabolic efficiency is higher at 0.094 for C-starts than S-starts at 0.047. However, muscle efficiency estimates are similar averaging 0.252 for both fast-start types. Mean energetic cost of fast-starts is determined to be 26.5 J/kg for C-starts and 18.6 J/kg for S-starts. Based on the observation that pike can repeatedly fast-start up to 170 times before becoming exhausted and on estimates of available energy reserves from literature values for ATP and CrP concentrations in white muscle, the duration of fast-starts is concluded to not be limited by muscle physiology. Average power output is found to be similar for C and S-starts at 406 to 412 W/kg. Only hydrolysis of ATP and CrP can supply energy at this rate. Therefore, based on fish white muscle biochemistry and mechanics, power output during fast-starts appears to be limited by muscle physiology. The cost of fast-starts represents 0.03 to 2% of maintenance costs for pike and therefore only 5 to 30 fast-starts per day would be required to increase the daily energy budget by 10%. In addition, the cost of fast-starts represents 0.52 to 27.4% of surplus energy available from assimilated prey. Therefore, the cost of fast-starts can be significant and reducing fast-start duration is a probable strategy for minimising activity costs and thus increasing the energy available for growth or reproduction. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Muscle and joint force during locomotion is estimated according to available formulations consistent with available methods of solving the indeterminate problem. In the case of the knee joint direct comparisons of results between several optimization methods proposed in the literature presents difficulties due to largely varying model formulation, input data, algorithms and other issues. The application presented here introduces a new optimization program which includes linear and non-linear techniques allowing greater flexibility in problem formulation. It also increases the variety of cost functions under a unified solution which allows for direct evaluation of factors such as optimization criteria and constraints. The method demonstrates that nonlinear solutions lead to more synergistic activity and in contrast to linear formulations, allows antagonistic activity. Nonlinearity also improves concurrence of EMG activity and predicted forces. Higher joint force predictions are resulting as expected from improved predictions of synergistic-antagonistic activity. The formulation allows for relaxation of the requirement that muscles resolve the entire intersegmental moment which in turn maintains muscle synergism in the nonlinear formulation while relieving muscle antagonism and reducing the predicted joint contact force. These methods allow for more possibilities for exploring new optimization formulations and in comparing the solutions to previously reported formulation. The present study based its input data on healthy subjects volunteering for a variety of walking tasks involving normal walking and turning during walking. Muscle and joint contact forces agree with other published results and the lateral: medial bony contact force distribution is calculated as 1: 2.5.

Thèse : Sciences naturelles : Paris, Faculté des sciences : 1872. / Titre provenant de l'écran-titre.

Reproduction de : Thèse de doctorat : Psychologie : Lille 3 : 2007. / Résumés en français et en anglais. Titre provenant de l'écran- titre. Bibliographie p. 168-194.

Steroid hormones alter the excitability of neural circuits for motor behavior in vertebrates and invertebrates. The insect Manduca sexta, with its well-characterized developmental and endocrinological history, is a useful model system to study these effects. The wandering behavior is a stage-specific locomotor behavior triggered by the steroid hormone 20-hydroxyecdysone (20E) and consists of crawling and burrowing movements as the animal searches for a pupation site.The results of this dissertation show that 20E acts on the isolated larval nervous system to induce wandering activity. The mechanisms underlying the generation of this activity share features similar to other invertebrate systems, including the presence of segmental central pattern generating circuits. The time course for the nervous system response to 20E is long, suggestive of a genomic mechanism of action, and there are no earlier rapid effects of 20E on the intrinsic membrane properties of the abdominal motoneurons. The site of 20E action in inducing wandering locomotion is unlikely to be the abdominal motoneurons, but interneurons presynaptic to these motoneurons. One possible site of 20E action is the brain, which shows stage-dependent expression of ecdysteroid receptors in certain populations of neurons.Descending regulation by the brain and subesophageal ganglion (SEG) is exerted over the segmental motor circuits for crawling and burrowing and reflects stage-dependent differences. Prior to wandering, the brain exerts inhibition over the segmental motor circuits for crawling, but this inhibition is not present during wandering. Removal of the brain, SEG, and thoracic ganglia during on-going fictive locomotion alters the phase relationships between abdominal segments. Further alterations of fictive crawling motor output are observed in more reduced preparations, indicating the importance of intact connections between abdominal ganglia in the production of a reliable motor program. The SEG drives the fictive burrowing motor program. The burrowing motor program is more robustly expressed in nerve cords from wandering larvae, suggesting a stage-dependent difference due to 20E exposure. Subsequent future experiments will use electrophysiological methods and genetic manipulations in Manduca sexta and Drosophila melanogaster, respectively, to explore target sites for hormone action in the brain and the characterization of brain neurons that drive wandering behavior.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Thesis (Ph. D.)--Ohio State University, 1991. / Includes vita. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 104-107).