Water volume in the shallow alluvial aquifer in the Mississippi Delta region is subject to seasonal declines and annual fluctuations caused by both climatological variability and crop water use variations from year-to-year. The most recently documented water volume decline in the aquifer is estimated at 500,000 acreeet. Available climate, crop acreage, irrigation water use, and groundwater decline data from Sunflower County, MS are used to evaluate the climate-groundwater interactions in the Mississippi Delta region. This research produced a model that simulates the effects of climatic variability, crop acreage changes, and specific irrigation methods on consequent variations in the water volume in the aquifer. Climatic variability is accounted for in the model by predicative equations that relate annual measured plant water use (irrigation) to growing season precipitation amounts. This derived relationship allows the application of a long-term climatological record to simulate the cumulative impact of climate on groundwater used for irrigation.

The purpose of the study was to determine students’ and faculty members’perceptions of the accelerated nursing programs at two colleges in the Mississippi Delta, Coahoma and Mississippi Delta Community College. The study centered on whether the age, race or gender of the students affected their perceptions of program support, key issues and challenges, and program limitations. The study explored differences in faculty and students’ perceptions of the accelerated nursing program in regards to local support, nursing faculty, most complicated areas of the program (which were clinical and exams), and barriers. A quantitative research design was used for this study. The survey was themethodological framework that was employed in this investigation to collect the data. The participants consisted of 13 faculty members and 33 students of the accelerated nursing program at two community colleges. The procedure to gather data for this study was two surveys developed by the researcher. The data in this study were obtained by using an Independent t-test, ANOVA and descriptive statistics. The following were findings of this study. No significant differences found in students’ perceptions of the accelerated nursing program by age or gender. Significant differences were found in students’ perceptions of the accelerated nursing program by race. The differences found were that Caucasians had a more positive perception than African Americans of salary attracting them to stay and work in the Mississippi Delta. Caucasians also had a more positive perception than African Americans that clinical is the most complicated area of the nursing program. In addition, Caucasians had a more positive perception than African Americans that transportation was a program barrier. Overall, faculty perceptions of the accelerated nursing program varied. Significant differences were found when students; and faculty perceptions were compared. The differences found were that students felt positive about the exams being the most complicated area of the program and the faculty disagreed. The other difference found was that faculty had a negative feeling toward their college lacking financial support from the local area, while students had a positive feeling.

The Mississippi Delta has been recognized for its poverty level and high rate of obesity. As an effort to combat the obesity issue while also considering the poverty issue of the population, a descriptive analysis was developed to understand what intervention might be beneficial. Focus groups were conducted to determine barriers to healthy eating behaviors for children, grades K-2. Focus groups (n=6) with parents or guardians of children from the six elementary schools in the Mississippi Delta were conducted in the Spring of 2007. The emergent themes included, perceived healthy foods, where diet information had been retrieved, and the efforts associated with meal preparation. Participants also voiced concern regarding the school policy on vending and coke machines that provide high-calorie non-nutritious foods.

The etiology of many gestational disorders is still unknown. However, insufficient trans-placental passage of nutrients and wastes due to poor placentation is characteristic of several pathologies and may be due, in part, to altered function of placental mitochondria. Mitochondrial activity is essential in pregnancy because it sustains the metabolic activity of the placenta throughout gestation. Exposure to stressors that perturb processes governing placentation, including maternal drug use, can negatively impact fetal development. Cannabis use is prevalent during pregnancy. The psychoactive constituent, delta-9-tetrahydrocannbinol (THC), can cross the placenta to affect placental and fetal physiology. Importantly, cannabinoid receptors have been reported on trophoblast cells, and on mitochondria which are abundant in placentae. It has been reported that THC may target the mitochondria in various tissue types, including placental tissue, and alter its function. However, few studies have addressed the physiological control of mitochondria within the placenta, an organ that is critical for fetal growth and pregnancy maintenance. I investigated the role of mitochondria in trophoblast differentiation and syncytialization using rotenone, a complex I inhibitor. Subsequently, I investigated the role of THC on two important aspects of placentation – invasion and syncytialization – using placental trophoblast cells HTR8/SVneo and BeWo, respectively. In response to rotenone and THC, there was increased ROS production, oxidative stress, and altered transcriptional markers favouring mitochondrial fragmentation. Treatment with 20µM THC for 48 hours led to reduced mitochondrial respiration, ATP production and loss of mitochondrial membrane polarity. Critically, these THC-induced mitochondrial changes occurred concomitant with evidence of reduced trophoblast invasion and syncytialization. Furthermore, THC exposure reduced levels of human chorionic gonadotropin, human placental lactogen and insulin-like growth factor 2, which are growth factors necessary for fetal development. Placental mitochondrial dysfunction, particularly when THC-induced, may be critical in a range of gestational disorders which have important implications for maternal and fetal/offspring health. / Dissertation / Doctor of Philosophy (Medical Science) / Cannabis is commonly used by pregnant women. Fetal exposure to cannabis and its components can impair fetal growth and neurological development. These negative fetal outcomes may be the result of poor placental formation, due to placental cell exposure to cannabis and its psychoactive component, delta-9-tetrahydrocannabinol (THC). Importantly, THC can also target intracellular organelles, like the mitochondria which are known as the “powerhouses” of the cell. Few studies have investigated the direct effects of THC on placental development. The purpose of this study was to determine how THC exposure to placental cells may alter their function. We found that THC impaired processes that allow placental attachment to the uterus and form a protective barrier, and compromised mitochondrial function, which are important for placental formation. These findings serve to inform scientists and doctors, thus stimulating the creation of new ideas and methods to further explore the impact of THC on pregnancy outcomes.

This dissertation presents the results of a research effort aimed at improving the current occupant injury criteria typically used to assess occupant injury risk in crashes involving roadside hardware such as guardrail. These metrics attempt to derive the risk of injury based solely on the response of the vehicle during a collision event. The primary purpose of this research effort was to determine if real-world crash injury prediction could be improved by augmenting the current vehicle-based metrics with vehicle-specific structure and occupant restraint performance measures. Based on an analysis of the responses of 60 crash test dummies in full-scale crash tests, vehicle-based occupant risk criteria were not found to be an accurate measure of occupant risk and were unable to predict the variation in occupant risk for unbelted, belted, airbag only, or belt and airbag restrained occupants. Through the use of Event Data Recorder (EDR) data coupled with occupant injury data for 214 real-world crashes, age-adjusted injury risk curves were developed relating vehicle-based metrics to occupant injury in real-world frontal collisions. A comparison of these risk curves based on model fit statistics and an ROC curve analysis indicated that the more computationally intensive metrics that require knowledge of the entire crash pulse offer no statistically significant advantage over the simpler delta-V crash severity metric in discriminating between serious and non-serious occupant injury. This finding underscores the importance of developing an improved vehicle-based injury metric. Based on an analysis of 619 full-scale frontal crash tests, adjustments to delta-V that reflect the vehicle structure performance and occupant restraint performance are found to predict 4 times the variation of resultant occupant chest acceleration than delta-V alone. The combination of delta-V, ridedown efficiency, and the kinetic energy factor was found to provide the best prediction of the occupant chest kinematics. Real-world crash data was used to evaluate the developed modified delta-V metrics based on their ability to predict injury in real-world collisions. Although no statistically significant improvement in injury prediction was found, the modified models did show evidence of improvement over the traditional delta-V metric. / Ph. D.

The growing demand of “System on a Chip” applications necessitates integration of multiple devices on the same chip. Analog to Digital conversion is essential to interfacing digital systems to external devices such as sensors. This presents a difficulty since high precision analog devices do not mix well with high speed digital circuits. The digital environment constraints put demand on the analog portion to be resource efficient and noise tolerant at the same time. Even more demanding, Analog to Digital converters must consume a small amount of power since “System on a Chip” circuits often target portable applications. Analog to digital conversion based on Delta Sigma modulation offers an optimal solution to the above problems. It is based on digital signal processing theory and offers benefits such as small footprint, high precision, noise de-sensitivity, and low power consumption. This thesis presents a methodology for designing low power Delta Sigma modulators using a combination of modern circuit design techniques. The developed techniques have resulted in several modulators that satisfy the initial design parameters. We applied this method to design three different modulators in the 0.35um digital CMOS technology with a 3.3V supply voltage. A first order Self-Referenced modulator has a resolution of 8 bits and the lowest power consumption at 75 uW. The most successful design is the second order Self Referenced modulator that produces 12 bits of resolution with a power consumption of 87 uW. A second order Floating Gate modulator possesses features for high noise rejection, and produces 10 bits of resolution while consuming 276 uW. It is concluded that self-referenced modulators dissipate less power and offer higher performance as compared more complicated circuits such as the floating gate modulator. / Master of Science

One of the most important data elements recorded in the National Automotive Sampling System / Crashworthiness Data System (NASS/CDS) is the vehicle change in velocity, or ?V. ?V is the vector change in velocity experienced by a vehicle during a collision, and is widely used as a measure of collision severity in crash safety research. The ?V information in NASS/CDS is used by the U.S. National Highway Traffic Safety Administration (NHTSA) to determine research needs, regulatory priorities, design crash test procedures (e.g., test speed), and to determine countermeasure effectiveness. The WinSMASH crash reconstruction code is used to compute the ?V estimates in the NASS/CDS. However, the reconstruction accuracy of the current WinSMASH version has not previously been examined for side impacts. Given the importance of side impact crash modes and the widespread use of NASS/CDS data, an assessment of the program's reconstruction accuracy is warranted. The goal of this thesis is to quantify the accuracy of WinSMASH ?V estimations for side impact crashes, and to suggest possible means of improving side impact reconstruction accuracy. Crash tests provide a wealth of controlled crash response data against which to evaluate WinSMASH. Knowing the accuracy of WinSMASH in reconstructing crash tests, we can infer WinSMASH accuracy in reconstructing real-world side crashes. In this study, WinSMASH was compared to 70 NHTSA Moving Deformable Barrier (MDB) - to - vehicle side crash tests. Tested vehicles were primarily cars (as opposed to Light Trucks and Vans, or LTVs) from model years 1997 - 2001. For each test, the actual ?V was determined from test instrumentation and this ?V was compared to the WinSMASH-reconstructed ?V of the same test. WinSMASH was found to systemically over-predict struck vehicle resultant ?V by 12% at time of vehicle separation, and by 22% at time of maximum crush. A similar pattern was observed for the MDB ?V; WinSMASH over-predicted resultant MDB ?V by 6.6% at separation, and by 23% at maximum crush. Error in user-estimated reconstruction parameters, namely Principal Direction Of Force (PDOF) error and damage offset, was controlled for in this analysis. Analysis of the results indicates that this over-prediction of ?V is caused by over-estimation of the energy absorbed by struck vehicle damage. In turn, this ultimately stems from the vehicle stiffness parameters used by WinSMASH for this purpose. When WinSMASH was forced to use the correct amount of absorbed energy to reconstruct the crash tests, systemic over-prediction of ?V disappeared. WinSMASH accuracy when reconstructing side crash tests may be improved in two ways. First, providing WinSMASH with side stiffness parameters that are correlated to the correct amount of absorbed energy will correct the systemic over-prediction of absorbed energy when reconstructing NHTSA side crash tests. Second, providing some treatment of restitution in the reconstruction process will correct the under-prediction of ?V due to WinSMASH's assumption of zero restitution. At present, this under-prediction partially masks the over-prediction of ?V caused by over-prediction of absorbed energy. If the over-prediction of absorbed energy is corrected, proper treatment of restitution will correct much of the remaining error observed in WinSMASH reconstructions of NHTSA side crash tests. / Master of Science

Wireless sensor nodes are emerging in a wide range of critical applications such as environmental monitoring, health applications, home automation and military surveillance and reconnaissance. The addition of low power wireless capability to such sensor nodes allows communication between a node and a base station or between nodes, resulting in the formation of wireless sensor networks. Sensor networks can use the information available from the distributed sensor nodes to determine the location and nature of a stimulus or environmental condition. The information collected by the base station can be used to determine the appropriate course of action for dealing with the stimulus. In chemical/biological defense or safety monitoring scenarios, wireless sensor networks can be used to identify and track harmful chemical or biological agents which might be present in a particular area. Due to the potentially remote areas that wireless sensor networks aim to cover, it is essential to minimize the power consumption of a sensor node so that it can operate over a long period of time without a connection to the power grid. Sensor nodes can contain multiple blocks, such as the readout circuit which interfaces with the sensor, an embedded processor, and the wireless transceiver circuits, all of which need to operate on a low power budget. This thesis specifically focuses on design of low power mixed signal readout circuits which interface with chemoresistive chemical sensors, i.e. sensors that demonstrate a variation of resistance (or impedance) in the presence of chemical agents. For this thesis, the sensor can be either a chemoresistive bead or a nanowire. By integrating multiple non-specific chemoresistive sensors together in arrays, a cross-reactive array can be realized, where the combined response of the arrayed sensors can be used to determine analytes present in a mixture even if their concentrations are low. In this thesis, a CMOS resistive readout circuit based on a sigma-delta ADC is presented. The design is used to measure the resistance of chemoresistive beads and nanowires with respect to time. The frequency of the ADC output varies as the resistance of a sensor changes and, based on the magnitude and duration of the variation, the type of chemical agent and its concentration can potentially be estimated. For future cross-reactive sensor applications, an array of 16x16 sites is also included in the readout circuit design. Individual sites in the sensor array can be accessed using addressing blocks which designed to select a particular row and column using an 8-bit addressing system. This thesis also covers the techniques used for integration of chemoresistive beads and nanowires into the array locations provided on the prefabricated CMOS IC. Measurement results that demonstrate the operation of the resistive readout circuitry are presented. Finally, a second readout circuit is proposed to measure complex impedance variations of a sensor device. Measurement of magnitude and phase changes of a sensor device can provide another degree of freedom in the analysis of chemical mixture. Simulation results demonstrating the functionality of the proposed impedance measurement system are also presented. / Master of Science

Several different approaches to determining second-order moments in plane frames were studied during this research. The focus of the research was to compare the moments predicted by four different commercially available computer analysis programs and the current design specification, the AISC LRFD moment magnification method. For this research, the second-order moments for ten commonly designed frames were compared. An overview of various second-order analysis procedures is presented first. The solution procedure utilized by each computer program and the AISC moment magnification method are explained. Also, the frames considered in the research are described. Next the frames are analyzed and the results between each of the computer programs and the current design specifications are compared. Finally, conclusions are drawn concerning the consistency of the second-order moments predicted by each of the solution procedures and recommendations for their use are discussed. In general, each of the four computer analysis programs evaluated and the AISC moment magnification method can consistently and adequately predict the second-order moments in plane frames. / Master of Science

published_or_final_version / Urban Planning / Master / Master of Science in Urban Planning