No description available.

No description available.

New federal regulations with regards to ammonia in wastewater effluent discharge will require over 1000 existing wastewater treatment facilities to be upgraded. Although biological treatment is the most common and economical means of wastewater ammonia removal, nitrification rates can be completely impeded at cold temperatures. Moving bed biofilm reactors (MBBR) have shown promise as an upgrade nitrifying unit at pilot-scale and full-scale applications with respect to low temperature nitrification. MBBR technologies offfer the advantages of less space requirement, utilizing the whole tank volume, no sludge recycling, and no backwashing, over other attached growth systems. Two laboratory MBBRs were used in this study to investigate MBBR nitrification rates at 20deg.C, after long-term exposure to 1deg.C, and at the kinetic threshold temperature of 5deg.C. Furthermore, the biologically produced solids from the MBBR system 20deg.C and after long-term exposure to 1deg.C, and the Arrhenius temperature correction models used to predict nitrification rates after long-term exposure to 1deg.C. The nitrification rates at 1deg.C over a four month exposure period as compared to the rate at 20deg.C were 18.7 + 5.5% and 15.7 + 4.7% for the two reactors. The nitrification rate at 5deg.C was 66.2 + 3.9% and 64.4 + 3.7% compared to the rate measured at 20deg.C for reactors 1 and 2, respectively, and as such was identified as the kinetic temperature threshold. The quantity of solids detached from the nitrifying MBBR biocarriers was low and did not vary significantly at 20deg.C and after long-term exposure to 1deg.C. Lastly, a temperature correction model based on exposure time to cold temperatures, developed by Delatolla et al. (2009) showed a strong correlation to the calculated ammonia removal rates relative to 20deg.C following a gradual acclimatization period to cold temperatures. Biofilm morphology along with biomass viability at various depths in the biofilm were investigated using variable pressure electron scanning microscope imaging (VPSEM) and confocal laser scanning microscope (CLSM) imaging in combination with viability live/dead staining. The biofilm thickness along with the number of viable cells showed significant increases after long-term exposure to 1deg.C while the dead cell coverage did not show significant increases after long-term exposure to 1deg.C while the dead cell coverage did not show significant changes. Hence, this study observed higher cell activities at warm temperatures and a slightly greater quantity of biomass with lower activities at cold temperatures in nitrifying MBBR biofilms. Using DNA sequencing analysis, 'Nitrosomonas' and 'Nitrosospira' (ammonia oxidizers)as well as 'Ntrospira' (nitrite oxidizer) were identified in which no population shift was observed during 20deg.C and after long-term exposure to 1deg.C. Furthermore, a number of non-nitrifiers were identified int he biofilm during warm and cold temperatures presenting the possibility that their presence may have provided some form of protection to the nitrifiers during long-term temperature exposure.

The performance of regenerative miniature refrigerators is governed by heat transfer and pressure drop losses, particularly in the regenerator. Steady flow experiments have been performed on various regenerator matrices at cryogenic temperatures and heat transfer from helium gas to the matrix, and pressure drop across the matrix have been determined. These data have been found to be in reasonable agreement with data obtained by other workers using transient flow techniques. In order to determine the applicability of such data to the performance of a cooling engine, experimental methods have been developed to measure the performance and losses in a working Stirling-cycle miniature refrigerator. These techniques have led to the analysis of pressure drop and shuttle heat transfer losses, regenerator efficiency, and to the measurement of other losses in the refrigerator. An energy balance is performed on the machine. These novel techniques, which allow the factors determining poor performance of a working refrigerator to be measured in situ, may be applied profitably to other cyclic machines.

Pepper (Capsicum annuum L.), which originates from tropical environments is particularly sensitive to low temperatures. The Canadian climate, with its risks of cool temperatures during spring time, greatly limits the production of this temperature-sensitive crop. This work dealt with pepper plant exposure to low temperatures (9 and 15$ sp circ$C), at two early growth stages. 'Lady Bell' pepper plants were grown from seed under controlled conditions of 21$ sp circ$C, 50 $ pm$ 10% R.H., 16/8 light/dark cycle and 300 $ mu$molm$ sp{-2} / rm s sp{-1}$ PAR at the canopy level. Once plants had reached either the cotyledonary or the three-true-leaf stage low temperatures were applied. Treatment conditions lasted until plants had produced three additional leaves after which they were returned to the pretreatment conditions. Evaluations were made at six recognized developmental stages and included destructive measurements for growth analysis, pigment content and leaf anatomical features as well as weekly non-destructive measurements. Results showed that plant responses to 9 and 15$ sp circ$C were not the same when applied at the cotyledonary or the three-true-leaf stage. Overall growth decreased with decreasing temperatures and plants exposed to 9$ sp circ$C at the cotyledonary stage died. Plants exposed to cold treatments underwent a whole complex of changes in morphology which included reduction in leaf size, stem diameter, internode length and on leaf, branch and developing fruit abnormalities. Dry matter accumulation and distribution, leaf area production and leaf pigment levels varied with treatments. The anatomical changes which included alterations in epidermal and mesophyll cell dimensions and arrangement were reminiscent of a general response to a wide range of stress conditions reported for several other plant species. Upon return to the control temperature recovery was clearly observed especially in those plants exposed to the 15$ sp circ$C treatments. Plants ex

This thesis explains low temperature operation of an InGaAs Avalanche Photo Diode (APD) cooled using thermoelectric coolers in order to utilize in the quantum cryptographic applications. A theoretical background for the equipment used in the experiment was provided. Circuitry and mechanics used for the low temperature operation were designed. Performance measures for APD were explained and experiment results were presented.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 70-73)

Thesis(M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 201-208). Also available on the Internet.

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009. / Committee Chair: M. R. Flannery; Committee Member: John Wood; Committee Member: Michael Schatz; Committee Member: Rigoberto Hernandez; Committee Member: Turgay Uzer. Part of the SMARTech Electronic Thesis and Dissertation Collection.