No description available.

In this thesis we have used temperature and high pressure to investigate the loss mechanisms present in visible, near infrared and infrared strained and unstrained semiconductor lasers. We find that tensile strained lasers show pressure dependent loss mechanisms similar in magnitude to those of unstrained and compressively strained devices. We present for the first time measurements of the temperature sensitivity of long wavelength lasers as a function of high pressure. Unstrained lasers show a pressure dependent temperature sensitivity whilst tensile strained lasers do not, over the range 150K to 300K. This leads us to conclude that phonon assisted Auger may be more significant than band to band Auger in tensile strained devices. We also demonstrate a possible mechanism for the decrease of Auger for these quantum well structures by estimating the effect of pressure on the gain - carrier density relation. High pressure measurements on 800nm GaAs quantum well lasers with superlattice barriers show the effect of changing the relative positions of the superlattice barrier IF and X minima. We find that the threshold current increases rapidly when the barrier is made indirect and conclude that this effect is due to repopulation of the barrier X minima with electrons from the active quantum well. For visible lasers we find that above lOkbar the effect of pressure on the threshold current is an increase which is attributable to losses from the active region to the X minima in the barrier. For a Philips bulk visible laser the threshold current remains relatively constant with pressure below lOkbar, whereas a Philips compressively strained device shows a decrease in Iý of about 25% up to 6kbar, a behaviour never seen before in short wavelength lasers. For the Philips 1% compressively strained laser the increase in Ith above 6kbar is also attributed to losses to the X minima. Measurements of a 1% compressively strained IBM laser showed immediate increases of threshold current with pressure, which is again attributed to the X minima in the barriers.

No description available.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Kalmia Kniel, Dept. of Animal & Food Sciences. Includes bibliographical references.

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

No description available.

No description available.

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

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 196-198). Also available via the Internet.

Adaption to environmental stresses is vital for the survival of all organisms living in any environment. Two of the major environmental factors in the deep sea environment are high hydrostatic pressure and high salt concentration. Hydrostatic pressure and osmotic pressure share similarities in their effects on organisms living in the deep sea but this overlap has been little explored. Major studies from Japan and California over the last 40 years have shown the effects of hydrostatic pressure on bacteria from the deep sea (see [1] for a review). These are complemented by work by Yancey et al. [2] showing that specific solutes accumulated in response to osmotic pressure in fish have the ability to enhance resistance to hydrostatic pressure. However, this work has been done in vitro or with larger organisms and not much is known about the overlap of osmotic and hydrostatic pressure in bacteria. In this study I investigated the effects of osmotic and hydrostatic pressure on two model organisms: Photobacterium profundum and Escherichia coli. In order to accomplish this task I developed novel imaging equipment which allows for high resolution imaging of bacteria at pressure. I also developed a new method of growing bacteria in 96-well plates at high pressure, which lead to the identification of a hierarchy of genes essential for the growth of E. coli at pressure. I used the same 96-well plate technique to monitor the growth of P. profundum at differing osmotic and hydrostatic pressures. Furthermore I also attempted to analyse the solutes accumulated by different strains of P. profundum in response to osmotic and hydrostatic pressures.