Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 163-166).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Washington State University, May 2007. / Includes bibliographical references.

Th. doct.-ing.--Génie électrique--Toulouse--I.N.P., 1984. N°: 302.

Th.--Sci. phys.--Toulouse--I.N.P., 1981. N°: 51.

No description available.

Temporal features in the vocalizations of animals and insects play an important role in a diverse range of species-specific activities such as mate selection, territoriality, and hunting. The neural mechanisms underlying the response to such stimuli remain largely unknown. Two species of anuran amphibian provide a starting point for the investigation of the neurological response to species-specific advertisement calls. Neurons in the anuran midbrain of Rana pipiens and Hyla regilla exhibit an atypical response when presented with a fixed number of advertisement calls. The general response to these calls is mostly inhibitory; only when the correct number of calls is presented at the correct repetition rate will this inhibition be overcome and the neurons reach a spiking threshold. In addition to rate-dependent call-counting, these neurons are sensitive to missed calls: a pause of sufficient duration—the equivalent of two missed calls—effectively resets a neuron to its initial condition. These neurons thus provide a model system for investigating the neural mechanisms underlying call-counting and interval specificity in audition. We present a minimal computational model in which competition between finely-tuned excitatory and inhibitory synaptic currents, combined with a small propagation delay between the two, broadly explains the three key features observed: rate dependence, call counting, and resetting. While limitations in the available data prevent the determination of a single set of parameters, a detailed analysis indicates that these parameters should fall within a certain range of values. Furthermore, while network effects are counter-indicated by the data, the model suggests that recruitment of neurons plays a necessary role in facilitating the excitatory response of counting neurons—although this hypothesis remains untested. Despite these limitations, the model sheds light on the mechanisms underlying the biophysics of counting, and thus provides insight into the neuroethology of amphibians in general.

This dissertation presents the modeling, design, fabrication, and experimental testing of a polyimide based micro mirror for applications in MEMS logic devices based on its static behavior and in MEMS resonators using mixed frequency excitation. First, a universal MEMS logic device that can perform all the logic operations, such as INVERTER, AND, NAND, NOR, and OR gates using one physical structure, within an operating range of 0-10 volts. It can also perform XOR and XNOR with one access inverter using the same structure with different electrical interconnects. We discuss the fabrication, simulations and experimental results demonstrating these logic operations on a polyimide micro mirror. The device is capable of performing the switching operation with a frequency of 1 kHz, a switching time of 8.2 μs, and an electrical lifetime of 8000 cycles. Second, this study presents an experimental and theoretical investigation of a micro mirror under a mixed frequency signal composed of two harmonic AC sources. The experimental and theoretical dynamics are explored via frequency sweeps in the desired neighborhoods. One frequency is fixed while the other frequency is swept through a wide 5 range to study the dynamic responses of the micro mirror. These responses are studied under different frequencies and different input voltages. The results show interesting dynamics, where the system exhibits primary resonance, and combination resonances of additive and subtractive type. The mixed excitation is demonstrated as a way to increase the bandwidth of the resonator near primary resonance, which can be promising for resonant sensing applications in the effort to increase the signal-noise ratio over extended frequency range. It can be promising for energy harvesting as well; since it provides the system with resonances of very high amplitudes at very low frequencies regardless of what is the natural frequency of the system, however this still needs further investigation.

<p> The combined capabilities of alpha-particle emitting isotopic excitation sources and modern semiconductor detectors are investigated with a view to extending the light-element range of radioisotope-based X-ray emission analysis.</p> <p> The construction and performance of a windowless low-energy X-ray spectrometer designed around a lithium-drifted silicon detector and a 210Po source are discussed. It is shown that under the conditions used low-energy X-ray emission and detection are greatly favoured.</p> <p> Measurements of relative cross-sections for the production of X-rays by ~5.2 MeV alpha-particles in elements from oxygen to iron are reported. The results for elements of Z>16 are in good agreement with those predicted from the scaling of equal velocity proton values but show large positive deviations for elements of Z<16.</p> <p> Investigative applications of the spectrometer to quantitative analyses of blast-furnace slags, iron ores and silicate rocks for oxygen, silicon, sulpher, calcium and iron are described.</p> <p> The future prospects of radioisotopic alpha-particle X-ray excitation methods are surveyed.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The prevailing theory of Migdal for predicting the excitation probabilities of an atom from α-decay of the nucleus, considers the α-particle, after it has been emitted by the nucleus, as following a classical trajectory and interacting with the atom quantum mechanically. Recently an attempt was made to properly model this quantum mechanical phenomenon, in one dimension, with a quantum wavefunction treatment of the decaying α-particle, but a discrepancy was found between the new predictions and that of the traditional method. In light of this discrepancy, we have studied the various approximations made in that work. Our results concur with recent follow up work suggesting that agreement should be found between a fully quantum mechanical model and with the classical model of α-particle propagation where the α-particle is treated as a point particle.</p> / Thesis / Master of Science (MSc)