Effective Modeling Of Agricultural Practices Within Large-Scale Hydrologic And Water Quality Simulations

The previously developed watershed hydrological and water quality model for St. Louis Bay watershed by Kieffer (2002) was refined and calibrated. The aspects of model development refinement included development of fertilization-related nutrient input parameters, evaluation of nutrient input methods, development of plant uptake-related nutrient input parameters, non-cropland simulation using PQUAL module, and recalibration of hydrology in Jourdan River. The related information of typical cropland management practice based on consultation from Mississippi State University Extention Service personnel was integrated into the watershed model. In addition, the Mississippi Department of Environmental Quality (MDEQ) observed water quality data were analyzed to evaluate the appropriateness of current watershed delineation and assess the health of the stream based on the MDEQ proposed numerical water quality target. The refined watershed model was calibrated in Wolf Rover and Jourdan River using both USGS and MDEQ observed water quality data. The concentrations of water quality constituents calculated from the developed watershed model will be provided as boundary conditions for the developed Bay hydrodynamic and water quality model for Total Maximum Daily Load studies

A Microfabrication Approach to Multicellular Mechanics

To address the question of how cell-generated forces regulate the organization and function of endothelial cells, I investigated the mechanical forces in a simple model of cell-cell contact: paired cells contacting each other via a single cell-cell junction. To study the responsiveness of AJs to force, I adapted a system of microfabricated force sensors to quantitatively report both the cell-cell tugging force and the size of adherens junctions (AJ). I observed that AJ size was modulated by tugging force: AJs and tugging force grew or decayed with myosin activation or inhibition, respectively. This myosin-dependent regulation operated in concert with a Rac1, force-independent control of AJ size, and was illustrated by showing that effects of vascular permeability agents (S1P, thrombin) on junctional stability are reversed by changing the extent to which these agents coupled to the Rac and myosin-dependent pathways. Furthermore, I showed that direct application of mechanical tugging force, rather than myosin activity per se, is sufficient to trigger AJ growth. Inspired by the study of mechanical force on the junctions between two cells, I further extended our tools to measure mechanical force in a more complicated multicellular system involving more cells and more than one type of cells. I investigated the role of mechanical force in a model system of monocytes transmigrating across an endothelial monolayer. Using our force measurement system, I first found that the average traction force in the whole endothelial monolayer increased during monocyte firm adhesion and transmigration. By specifically look at traction forces at the cellular level, I found that the endothelial cell with the monocyte firmly adhered on it showed a much larger traction forces, with the direction of the traction force aligned more centripetally toward the monocyte. Moreover, the sub-cellular and pan-cellular analysis of the traction forces in the monolayer revealed an increase of traction force in local zones vicinity to the monocyte. Finally, engagement of endothelial adhesion molecules could increase traction forces in the endothelial cells. Taken together, this study implicates mechanical forces in firm adhesion and transmigration

Experimental Evaluation of Surfactant Application to Improve Oil Recovery

The objective of this research was to identify high performance surfactant formulations and design efficient core floods for a limestone reservoir with high salinity formation brine. Microemulsion phase behavior experiments were conducted to identify best chemicals formulation (including surfactants, alcohol, alkali, polymer and electrolyte) for core flood test. A successful formulation should be one clear stable phase at reservoir conditions, fluid microemulsion phase, fast equilibration and high solubilization ratio. Formulations with glycol ether alcohols were easier to achieve one clear stable phase than formulations with sec-butanol. Primary surfactant-to-cosurfactant ratio and alcohol concentration were fine tuned to obtain fluid microemulsion phase and sufficiently high solubilization ratio. Core floods with optimized formulation validated its high oil recovery efficiency (95-99%) in Berea sandstone cores with synthetic formation brine. The effect of surfactant slug size, surfactant slug/polymer drive viscosity and formation brine composition was discussed to design more efficient core flood. The properties of the aqueous phase from chemical flood, e.g. total dissolved solids, viscosity and pH were measured to help understand oil displacement process in the core during the chemical flood. Core floods in Indiana limestone cores yielded low oil recovery (27-41%) suffering from large dispersion of the core. Recommendations were made to improve oil recovery on future limestone core floods and field application

The MLE of the Parameters of a Discrete Competitive System Subject to Environmental Noise

A randomized discrete competitive system is investigated and the maximum likelihood estimation (MLE) of the parameters of the system is obtained. Also, a corresponding numerical simulation is offered to support our theoretical results

The Predicament of Specialized Villages and Its Solutions: A Case Study of Zhe-Village

Due to high competition in the same trade, residents in a specialized village become “homogeneous without shared interest”. Based on a case study of Zhe-Village, this paper describes the competition and conflicts inside specialized villages, as well as attempts at reconciliation. We find traditional measures of reconciliation, e.g. through personal relationship, community elites or their local government, to be fundamentally divergent from the economic aim of specialized villages, hence the limited effectiveness. Establishing a trade association is a possible solution to the predicament of Zhe-Village, but the lack of shared interests and inaction of the local government, combined with the attitude and distorted knowledge of villagers, hamper the founding of a trade association. To overcome these obstacles, specialized villages need rules of market competition, government support and updated knowledge. In this process, social integration may reappear in specialized village