Ionized calcium (Ca2+) is a signaling messenger that controls numerous cellular processes essential for life. The fidelity of Ca2+ signaling depends on the mechanisms that dynamically regulate its cytosolic concentration and maintain it at a low level in a resting cell. Plasma Membrane Ca2+ ATPase (PMCA) is a high affinity Ca2+ extrusion pathway involved in Ca2+ homeostasis and signal transduction. PMCA are encoded by 4 genes (PMCA1-4), which are expressed in a tissue dependent manner. The diversity of PMCA isoforms is further increased by alternative splicing. Changes in PMCA activity occur in heart failure and hypertension. Specific inhibitors of other ion transporters such as thapsigargin and digoxin, have made their mark in cell biology, but the currently used inhibitors of PMCA (vanadate and eosin) are non-specific. Thus, selective inhibitors of PMCA are needed to discern its role in Ca2+ signaling in physiology and pathophysiology. We introduced the concept of caloxins - peptides that specifically inhibit the activity of PMCA by binding to one of its five extracellular domains (exdoms) 1 to 5. The earlier caloxins including 2a1 and 3a1 were obtained by screening a phage display random 12-amino acid peptide (Ph.D-12) library for binding to synthetic peptides based on the exdom sequences. However, they all had low affinity. The objective of this research was to develop caloxins with high affinity and PMCA4 isoform selectivity. A two-step screening method was developed to screen the Ph.D-12 library to first bind to the synthetic exdom of PMCA4, followed by affinity chromatography using PMCA protein purified from human erythrocyte ghosts (mainly PMCA4). This method was used to obtain caloxins 1b1 and 1b2 to bind to the N and C-terminal halves of the exdom 1 of PMCA4, respectively. Both caloxins 1b1 and 1b2 had a 10-fold higher affinity than the prototype caloxin 2a1 and showed slight PMCA4 isoform preference. To engineer inhibitors with greater affinity and PMCA4 isoform selectivity, Ph.D caloxin 1b1 like peptide library was constructed. Most of the peptides expressed in this library differed from caloxin 1b1 in 0, 1, 2 or 3 amino acid residues at random. The library was screened to obtain several peptides one of which was caloxin 1c2. Caloxin 1c2 had 200-fold higher affinity than caloxin 2a1 and was isoform selective, with greater than 10-fold affinity for PMCA4 than for PMCA isoforms 1, 2 or 3. Thus, caloxin 1c2 is the first high affinity PMCA inhibitor that also is selective for an individual PMCA isoform. The second aim of this research was to establish that caloxin 1c2 binds to PMCA protein in erythrocyte ghosts. Two photoreactive caloxin 1c2-derivatives containing the photoactivable residue benzoylphenylalanine (Bpa) and a C-terminal biotin tag were used. Bpa substituted tryptophan at position 3 (3Bpa1c2-biotin) and serine at position 16 (16Bpa1c2-biotin) in caloxin 1c2. Both the derivatives inhibited PMCA activity in the erythrocyte ghosts. The intensity of the biotin label in the photolabeled erythrocyte ghosts was much stronger with 3Bpa1c2-biotin, which was then used in the subsequent experiments. The photolabeled proteins in erythrocyte ghosts were detected as a 250-270 kDa doublet in Western blots using streptavidin and the PMCA specific antibody. The degree of photolabeling depended on the UV-crosslinking time, and on the concentrations of 3Bpa1c2-biotin and the ghost protein. The selectivity of the photolabeling site was confirmed by decreased photolabel incorporation at 250-270 kDa doublet in the presence of excess caloxin 1c2 and the synthetic exdom 1X peptide of PMCA4. The photolabeled erythrocyte ghosts were solubilized and analyzed by immunoprecipitation with the PMCA specific antibody. The immunoprecipitate showed a 250-270 kDa doublet in Western blots using streptavidin. This confirmed that PMCA protein was photolabeled by the photoreactive derivatives of caloxin 1c2. Thus, caloxin 1c2 inhibits PMCA activity by binding to the exdom 1X of PMCA4. My work in M.Sc. initiated the concept of caloxins in the literature. This research has taken it to the stage where we can obtain caloxins selective for individual PMCA isoforms. This contrasts with the relative paucity of inhibitors specific for individual isoforms of other ion pumps. The high affinity isoform selective caloxin 1c2 and previous caloxins are being used to study PMCA physiology in our lab and by other researchers. Since caloxins act when added extracellularly and it is possible to obtain PMCA isoform selective caloxins, it is anticipated that they will aid in understanding the role of PMCA in signal transduction and homeostasis in health and disease. / Thesis / Doctor of Philosophy (PhD)

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Experiments were carried out to investigate the effect of ambient air temperatures on the heat pump performance using a variable speed compressor. Ambient air temperatures were varied from 40 to 60 °F to simulate different seasons. The compressor frequencies of 45 Hz, 50 Hz, 55 Hz, and 60 Hz were studied to determine the optimal frequency under various heating loads. The investigation was carried out by showing the compressor power input, heating output, and coefficient of performance for each case. Thermal cycle analysis along with the heat exchanger theory was used to analyze the system energy balance, heat transfer rates, p-h diagrams, and coefficient of performance. The overall heat transfer coefficients were also determined for both the evaporator and the condenser. Only the capillary tube was used to regulate the refrigerant flow rate. The variable speed compressor system used in this study will help save energy when compared with the traditional steady speed system. The variable speed compressor system will hopefully provide a more comfortable and steady indoor temperature than the traditional system, which is controlled by only an on-off switch. The speed controlled compressor system proposed we believe will help saving more energy than traditional steady speed system. The variable speed compressor system will hopefully provide a more comfort and steady indoor temperature than the traditional system which is controlled by one switch. It is believed that the variable speed compressor system may allow the indoor temperature air to be steady-going and prevent the switch working frequently. / Mechanical Engineering

Two novel pump/probe techniques have been developed for measuring the recombination lifetime in crystalline silicon wafers. The first technique, single-beam pump/probe, uses one laser as both pump and probe. The second technique, quasi-steady state free-carrier absorption, measures lifetime under quasi-steady state conditions. These techniques are supported by a general mathematical model that predicts the experimental signal accounting for the 3D charge-carrier transport and recombination within the semiconductor. The predictions of the model are validated experimentally, and quantitative agreement is found between the model and experimental results for both techniques. The recombination lifetime measured by these techniques is verified independently using a standard pump/probe method, and the results are in agreement with this work. Single-beam pump/probe is a first-time demonstration of a technique capable of measuring lifetime in silicon using a single laser beam. It dramatically simplifies traditional pump/probe measurements by completely eliminating the second laser beam. QSS-FCA is the first quasi-steady state technique that can be calibrated in situ without the requirement of a calibrated reference wafer. The calibration constant is the free-carrier absorption cross section of silicon, which is a material constant. QSS-FCA is able to measure this cross section to a higher precision than what has been reported in the literature. Precise measurement of this constant opens up the possibility of studying more fundamental physics of silicon using QSS-FCA. / Thesis / Doctor of Philosophy (PhD)

At the moment, when energy and environmental issues are of concerned in our society, photovoltaic technology has received tremendous development and demand. Because carrier lifetime and diffusion coefficient are the important indicators to determine the recombination level, which influences the efficiency of solar cells to a large extent, they are regarded as key in choosing solar cell materials. A technique for effective lifetime measurement, modulated free-carrier absorption (FCA), can extract lifetime and diffusion coefficient simultaneously, which is supported by a general mathematical model that predicts the experimental signal accounting for the 3-dimensional (3D) charge-carrier transport and recombination within the semiconductor. A single mode 1064 nm laser modulated by an EO modulator is used as the pump and a 2050 nm modulated LED is used as probe in this experiment as the pump/probe parts. An IR camera detects the frequency-domain diffusion image from the tested silicon sample at the tested frequency range between 1 kHz to 200 kHz and the lifetime can be extracted by frequency-domain free-carrier concentration equation, which is a Lorentzian model. By simulating the diffusion data from the camera with the 3D free-carrier absorption model, we can extract lifetime and diffusion coefficient simultaneously. The fitted lifetime from frequency-domain free-carrier absorption equation is 33.5 ± 1.3 μs, and the fitted lifetime from this 3D FCA model is 32.8 ± 1.5 μs, which match to within the error bars. The fitted diffusion coefficient from this 3D FCA model is 15.6 ± 0.7 cm2/s, which agrees with the theoretical value of 16 cm2/s for silicon. Good quantitative agreement is found among the model, experimental data, and theory. / Thesis / Master of Applied Science (MASc)

This thesis provides a comprehensive look at water hammer with an emphasis on home plumbing systems. The mathematics of water hammer are explained, including the momentum and continuity equations for conduits, system construction, and the four-point implicit finite difference scheme to numerically solve the problem. This paper also shows how the unsteady momentum and continuity equations can be used to solve water distribution problems instead of the steady-state energy and continuity equations, along with the examples problems which show that an unsteady approach is more suitable than the standard Hardy-Cross method. Residential plumbing systems are examined in this paper, household fixtures are modeled for their hydraulic functions, and several water hammer simulations are run using the Water Hammer and Mass Oscillation program (WHAMO). It is determined from these simulations that the amount of air volume in the system is a key factor in controlling water hammer. Abnormal pump operation is clearly explained including a description of the four quadrants and eight zones of operation as well as the mathematics and a numerical scheme for computation. Low pressures caused by transients can lead to intrusion and contamination of the drinking water supply. Several scenarios are simulated using the WHAMO program and cases are provided in which intrusion occurs. From the intrusion scenarios, key factors for intrusion to occur during transients include the starting energy in the system, the magnitude of the transient, the hydraulics of the intrusion opening, and the external energy on the pipe (the level of the groundwater table). A primer for using WHAMO is provided as an appendix as well. / Master of Science