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Electrophysiological response of endothelial cells to fluid-imposed shear stress
(1985) De Souza, Peter Andre; Levesque, Murina J.; Nerem, Robert M.; Kleis, Stanley J.; VanArsdale, William E.; Hwang, Neddy H. C.
The purpose of this investigation was (i) to develop a technique for recording intracellular potentials of cultured monolayers of bovine endothelial cells using an impalement method and (ii) to apply the technique to record the intracellular potentials of endothelial cell samples that were exposed, for specific durations of time, to various levels of shear stress. Endothelial cell samples were exposed to six levels of shear stress (15, 30, 45, 60, 75 and 90 dynes/cm^2) using a parallel plate flow chamber, for periods of 5 hours and 25 hours. During exposure to shear stress, the cell samples were viewed continuously and their morphometric changes were recorded on a time-lapse video recorder. A morphometric analysis was performed using a Videoplan image analyser. It was found that endothelial cells aligned with the flow field at all levels of shear stress, and the cells became more elongated with increased shear stress. The intracellular potential recordings were obtained from two regions of the cells (cytoplasm and nucleus) using glass microelectrodes. It was found that after exposure to shear stress, the magnitude of the intracellular potentials increased with the level of shear stress and duration of exposure.
Forced convection from finite inclined plane surfaces in laminar flow
(1985) Loh, Yvette Shukhoon; Kleis, Stanley J.; Bannerot, Richard B.; Witte, Larry C.; Kareem, Ahsan; Nerem, Robert M.
Forced convection heat transfer for air flow over a wedge with a finite length in the flow direction was investigated. Wind-tunnel heat transfer experiments were performed for five approach velocities ranging from 3.3 m/s to 11.1 m/s. The wedge angle was kept constant at 60 degrees and the heated surface was isothermal. The surface temperature was about 11[degrees]C above the ambient temperature in the wind-tunnel. Average heat transfer coefficients were obtained. The resulting heat transfer coefficient versus approach velocity followed the same trend as the infinite wedge solution but was about 28% higher. Flow experiments were also performed in the wind-tunnel, to obtain the variation of freestream velocity over the finite wedge. The measured freestream velocities were used to predict the local heat transfer coefficients by an integral method based on Falkner-Skan wedge flow. Results for the predicted heat transfer coefficients were very close to the infinite wedge solution near the leading edge, but became higher than the infinite wedge solution as the trailing edge was approached. The measured velocity variation was found to deviate significantly from the infinite wedge velocity variation, especially near the trailing edge. Hence using this method to predict the heat transfer coefficients is expected to lead to under-prediction.
Chromate ion-exchange study for cooling water
(1984) SenGupta, Arup K.; Clifford, Dennis A.; Matson, Jack V.; Vestal, Marvin L.; Pollard, Richard
In spite of high chromate selectivity, the ion-exchange process for Cr(VI) recovery from cooling tower blowdown is yet to be commercially popular. Possible degradation of the ion-exchange resin by the oxidative action of Cr(VI) during ion exchange has, for long, been considered as the prime obstacle. In recent years, resins have been manufactured with fairly acceptable properties to withstand both physical attrition and chemical oxidation. Another conspicuous shortcoming which has been observed by all the previous investigators and demonstrated during the course of this research is early, gradual Cr(VI) breakthrough during fixed- bed column runs at acidic pH in the presence of competing sulfate and chloride anions. The advantage of high chromate selectivity is essentially lost due to the early Cr(VI) breakthrough because the column runs are always terminated after a pre-determined level of Cr(VI) has appeared in the treated water. Experimental results provide sufficient evidence that such early, gradual breakthrough is not due to poor column kinetics or electrolyte penetration. Furthermore, chromate/chloride and chromate/sulfate isotherms at acidic pH show positive curvature (unfavorable type) which is again unusual for a preferred component. The chromate ion-exchange mechanism has been investigated in order to explain the foregoing anomalies for the chromate-exchange process. Chromate may exist in different ionic forms in the aqueous phase and their relative predominance is governed by pH, total Cr(VI) concentration and the ionic strength of the aqueous phase. [...]
Computer-based design synthesis : an approach to problem solving
(1984) Kuppuraju, Nagesh; Mistree, Farrokh; Eichhorn, Roger; Law, J. S.; Muster, Douglas F.; Nerem, Robert M.
The primary goal of this thesis is to devise strategies in order to improve the effectiveness of designers working in a computer assisted environment. A secondary goal is to transfer strategies so developed from a research-oriented environment to an academic, teaching-oriented environment. Therefore, this thesis is presented as five self-contained units to facilitate independent study. This work could not have been accomplished but for the expert guidance and motivation offered by many people. In particular, I wish to thank the following persons: I express my sincere gratitude to Dr. Farrokh Mistree, my thesis advisor, and his wife Dr. Janet Allen but for whose encouragement and support, intellectual and moral, this thesis would have never seen the light of day. My sincere thanks are due to Dr. Roger Eichhorn who took time to read through patiently every line of this thesis and offer very valuable advice on improving its quality. Dr. Douglas Muster's philosophical and intellectual pointers in the earlier portion of this thesis helped place the work in an appropriate context and draw attention to the essential components of the design strategies presented. My thanks are due to the committee members of my defense for taking time to read and appreciate my efforts. The effort put in by Harshavardhan Karandikar in offering helpful suggestions for improvements in Unit 4 of this thesis is very much appreciated. The constant support and camaraderie of the design group (Prawit Ittimakin, Azim Jivan, Jon Shupe and Marsha Shupe) has been a source of inspiration throughout the writing of this thesis.
Single crystal x-ray diffraction study of the molecular structures of six cobalt and rhodium compounds : an investigation of spontaneous resolution in coordination compounds
(1988) Cetrullo, James; Bernal, Ivan; Geanangel, Russell A.; Wendlandt, Wesley W.; Cox, James R.; Widger, William R.
The crystal and molecular structures of six compounds named hereafter were determined by single crystal x-ray diffraction methods using an Enraf- Nonius CAD-4 automated diffractometer. These determinations were made as a study of the phenomenon of conglomerate crystallization and, more specifically, to examine the process of spontaneous resolution in coordination compounds. This is a process by which a substance will crystallize from solution in an enantiomorphic form without the aid of a resolving agent. Some clues as to the mechanism of conglomerate crystallization are provided by these studies of the hydrogen bonding interactions between complex cations and their neighboring anions and cations and intramolecular hydrogen bonding between ligands of an individual cation. [...]