Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Abstracted in Dissertation abstracts, v. 17 (1957) no. 8, p. 1727-1728. Vita. Description based on print version record. Includes bibliographical references (leaves 86-89).

Thesis--Catholic University of America. / "Footnotes and references": p. 51-55.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [142]-144).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 188-190).

An experimental investigation of the velocity of sound in liquid helium at temperatures near 1° K was abandoned (at an early stage)^when the results of Whitney and Chase(16) became available. The original investigation, which had been motivated by the idea that the peak in the attenuation-temperature curve near 1° K is related to a corresponding feature in the velocity-temperature curve, evolved into a search for mathematical relations connecting the temperature variations of velocity and attenuation. Classical dispersion theory is reviewed, with emphasis on its physical and mathematical foundations. Applications of the theory in the fields of electrical network design, dielectric dispersion and ultrasonics are described in order to illustrate the use and the limitations of the Kramers-Kronig relations. The possibility of extending the scope of the Kramers-Kronig relations, by using variables other than frequency, is discussed. A brief sketch of the quantum mechanical basis of linear response theory is given in support of a proposal to use reciprocal temperature as a variable in dispersion-type relations. An attempt was made to apply dispersion relations in reciprocal temperature to the problem of ultrasonic propagation in liquid helium and a comparison of the predicted and the experimentally observed attenuations at the λ point was found to give encouraging results. The interferometer, to have been used in the proposed experiment is described. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Bibliography: pages 113-114. / A wave-train-echo technique, with repeated forward-and-return travels of the signal, was used to study the propagation of ultrasonic waves in nickel wire. In particular, the origin of often observed anomalous waves in nickel wire was investigated. A possible explanation of an aspect of the phenomenon was devised. During continuing investigation of the phenomenon of anomalous waves, an unexpected effect of stress on the attenuation of ultrasonic waves in annealed nickel wire was observed. Attention was transferred to the new phenomenon, and extensive experimental work carried out to measure the effects of direct and flexural stress on the attenuation. The effect was found to occur with torsional stress also. Computer-aided determinations of attenuation were made from the experimental readings of signal strength for variations of stress and signal frequency. A detailed study and documentation of known processes of attenuation of acoustic vibrations in solids was made. Indications of the nature of the mechanism of stress-dependent attenuation have been sought, and a tentative conclusion arrived at.

No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 77-78.

Sonoporation, being an ultrasound-induced membrane perforation phenomenon, has received considerable interest in view of its therapeutic potential and is rapidly emerging as a promising approach to facilitate drug delivery. This event generally occurs when acoustic cavitation develops in the vicinity of living cells, as the mechanical interactions between ultrasound and microbubble would exert a force that is substantial enough to create pores on the cell membrane. The resulting increase in cell membrane permeability is transient in nature, and short-term survival of sonoporated cells is generally assumed. However, it remains unclear as to whether sonoporation would affect the cell fate in the long run. In particular, the contemporary mechanistic understanding of sonoporation has lacked account of the cellular response at a subcellular level. This inherently raises concerns on the general therapeutic applicability of sonoporation in mediating drug delivery. This thesis first addressed the question of whether cell fate may be affected on time-lapse basis as a result of sonopopration. As observed our analysis of DNA contents and cytoplasmic signaling proteins, some cells were found to commit apoptosis (programmed cell death) after sonoporation while the remaining viable cells may enter into cell-cycle arrest that disrupted normal cell proliferation. These findings should carry two major implications from a drug-delivery standpoint. First, cellular protection strategies should be developed when using sonoporation for drug delivery in cases where cell viability should be maintained. Second, for cancer therapy where cell death is required, the cytotoxic impact of sonoporation may represent a complementary factor that can be leveraged upon in facilitating the delivery of anti-cancer drugs. Further investigations were conducted to gain insight into the intermediate transduction mechanism in which sonoporation has entailed to bring about various cytoplasmic signaling changes that promote cell-cycle arrest and apoptosis. Our results reveal a transient enhancement of intracellular Ca2+ concentration in sonoporated cells. This bioelectrical disruption event is often recognized as a central messenger to instigate a series of cell-fate regulation pathways. In addition, observations on cell membrane repair revealed an exocytotic patching mechanism, accumulation of internal vesicles and increased activities in the Golgi apparatus. Given that the elevated Ca2+ level were observed in sonoporate cells, a follow-up study was conducted to investigate the potential role of endoplasmic reticulum (ER) and mitochondria in sonoporation-induced bioeffects. These two organelles were found to be activated in succession and in ways connected to the initiation of pro-apoptotic signaling. In particular, stress response was found to be active in the ER, and this in turn induced the dysfunction of mitochondria. Also, our time-lapse observations on the mitochondrial membrane potential have confirmed that this organelle is involved in facilitating sonoporation-induced apoptosis. In summary, investigations of time-lapse dynamics of cellular and subcellular responses mediated by sonoporation are so important in elucidating the fate of the sonoporated cells and understanding the mechanism in which sonoporation has entailed to instigate the sequential signaling pathways that bring cells into such conditions, thereby refining the therapeutic role of this biophysical phenomenon and making it more efficient in facilitating drug delivery. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy