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Evaluation of the Interaction of an Insecticidal Peptide and Bt Proteins or a Baculovirus for Managing Helicoverpa zea in Bt Cotton
No full textThe cotton bollworm, Helicoverpa zea (Bobbie), is a major and damaging pest of cotton, corn, sorghum, and other crops. This pest has developed field-evolved resistance to the Cry1 and Cry2 Bt proteins, and there are early warning signs for resistance to Vip3Aa. Chlorantraniliprole is the primary insecticide used to manage H. zea in sorghum and Bt-resistant H. zea in cotton. There is concern that overutilization of chlorantraniliprole may lead to resistance. Utilizing IPM-friendly biopesticides may be an alternative means for managing H. zea in cotton and sorghum. Spear RC (HXTX) is a new biopesticide derived from spider venom, but because this product requires aid from Bt to penetrate the mid-gut, its utility is diminished. However, cotton expressing Bt proteins may be able to serve as facilitators although it is uncertain if they will function for Bt resistant H. zea. Alternatively, Heligen (HearHPV), a Heliothine-specific virus, may also act as a facilitator for HXTX.
Experiments were conducted to determine the interaction between Bt proteins and HXTX on Bt-susceptible, Cry-resistant, and Vip-resistant H. zea. In diet-based bioassays in the absence of any Bt proteins, HXTX alone exhibited marginal activity on susceptible, Cry-resistant, and Vip-resistant H. zea, but when combined with overlays of 10��g/cm�� of Cry1Ac, toxicity to Cry-resistant H. zea was higher. However, the addition of 5��g/cm�� of Vip3Aa39 did not enhance HXTX toxicity to Vip-resistant H. zea. This suggests that Vip3Aa resistance probably involves binding site resistance, while Cry-resistance probably allows binding and some pore formation. Thus, Cry1Ac Bt protein expressed in cotton will serve as an effective facilitator toward H. zea that are resistant to Cry1Ac.
Diet-based bioassays were used to determine if HearNPV may serve as a facilitator for HXTX targeting Bt-susceptible and Cry-resistant H. zea. Neither HXTX alone nor HearNPV alone at LC������ and LC������ dosages had great activity towards H. zea. Against Bt-susceptible H. zea, when HXTX was combined with HearNPV there was a significant interaction and synergistic effect, but this relationship was not as pronounced with the Cry-resistant H. zea strain. Thus, HearNPV may serve as facilitator for HXTX, but it appears to be less consistent than Bt proteins.
In 2022-2023, field tests were conducted to field validate laboratory findings demonstrating the potential of utilizing HXTX for H. zea management in non-Bt and Bt cotton. Despite laboratory assays suggesting that HXTX has activity on H. zea when used in conjunction with Bt proteins, we were unable to demonstrate significant activity in cotton in the field. This was mostly likely due to inadequate spray coverage, residual persistence, and the lack of translaminar activity for HXTX
Evaluating the Attentional Demand of Visual and Auditory Stimuli on Adolescents with ADHD Using a Dual Task Paradigm
No full textAttention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder defined by impaired levels of inattention and/or hyperactivity ��� characterized by being unable to stay focused in the face of distraction or think flexibly when presented more than one stimulus. This inability to remain focused may make it difficult to do two things at one time, or dual task.
Dual task is a paradigm used to quantify allocation of attention by asking subjects to perform two tasks consecutively and measuring the difference in their performance individually to completing them together. Usually done with walking and a cognitive task. The type of cognitive task may be important in ADHD because of poorer responses to visual vs auditory stimuli.
This study sought out to examine the difference in dual task cost (DTC) between auditory and visual stimuli-based tasks in older adolescents with ADHD tendencies. The hypothesis was people with ADHD tendencies would experience a higher DTC under visual than the auditory tasks.
Nineteen subjects completed five randomized, one-minute collections of single task (ST) walking, ST visual, ST auditory, dual task (DT) visual (walking while performing the test), and DT auditory. The cognitive DTC was calculated using the percent correct answer difference. The gait DTC was calculated for step width and gait speed. Both the signed and absolute DTC values were analyzed to examine both the direction of the cost as well as the magnitude of the change. Comparisons were made between visual and auditory DTC for percent correct, gait speed, and step width. The absolute value of the cognitive DTC was found to have significance (p<0.001), with the auditory having a higher magnitude of DTC than the visual. Other comparisons were not significant.
Little to no evidence was found to support the hypothesis. This was likely due to the use of preferred gait speed, which may not have challenged attentional resources. Further, it is feasible that there is a cognitive benefit of walking on working memory. Future studies should investigate or control for subtypes or comorbidities of ADHD, the mechanisms of auditory processing in those with ADHD, and the cognitive benefits associated with walking
Characteristics of Atomic Mirrors in Waveguide QED
No full textThis thesis presents a detailed study of photon-atom interactions in one-dimensional waveguide systems, exploring the dynamics of photon decay in atomic cavities and the emission characteristics of single photons from two-level emitters. The study focuses on the decay dynamics of single-photon pulses in cavities formed by atomic mirrors coupled to waveguides and reveals strategies to increase photon storage times by optimizing system parameters such as coupling strength, cavity length, and atomic separation. In addition, the emission of single photons from two-level emitters in atomic cavities is investigated, demonstrating the potential for frequency combing and spectral narrowing through appropriate control of atomic separations. The results of this work contribute to the understanding of light-matter interactions in waveguide quantum electrodynamics and provide insight into the design of novel photonic devices for quantum information processing and communication
Analyzing the Effects of Groundwater Flow Rates on the Recovery Efficiency of Aquifer Thermal Energy Storage Systems Using Numerical Modelling
No full textThis study looks at the effects of groundwater flow velocity on the recovery efficiency of Aquifer Thermal Energy Storage (ATES) systems and how modifying the pumping rate and storage time can optimize the efficiency of an ATES system located in an aquifer with low to high regional flow rates. By examining the processes that control the efficiency of these energy storage systems, we hope to improve their effectiveness and contribute to their use as an energy conservation technology.
The ATES investigation was done by applying principles of heat and solute transport to a numerical model that represents a low-temperature doublet ATES system installed in a shallow confined aquifer. The finite difference method modeling suite MODFLOW was used as the primary modeling software, with MT3DMS serving as the solute transport engine. The model includes six regional groundwater flow rates ranging from 0-50 m/yr, two pumping regimes of 200-400 m3 /d (injection and extraction), and two storage times of 0-3 months. The ATES wells operated on annual cycles, with injection temperatures ranging from 5-30��C.
We found that groundwater velocity is a primary control in the recovery efficiency of ATES systems, with an average drop of 27% from no groundwater flow to 50 m/yr. Additionally, we found that at groundwater flow velocities higher than 30 m/yr, the injection rate is the most important secondary parameter, with lower pumping and injection rates associated with lower recovery efficiencies. Inversely, at groundwater flow velocities lower than 20 m/yr, storage time is the most important secondary parameter, with longer storage times associated with lower recovery efficiencies
Essays in Behavioral and Experimental Economics
No full textMy dissertation consists of three independent essays on the topics of behavioral economics, experimental economics, and information economics.
In Chapter 1, we investigate how rule enforcers leverage the options to hide or reveal their privately-informed detection ability and how agents respond utilizing a disclosure game of verifiable information with either transparent or opaque enforcement objectives. When governing entities levy financial penalties for rule violation, they may aim to maximize compliance or revenues. Agents may be uncertain of these objectives; further they may also not know enforcers��� detection ability for rule violation. Our model derives multiple equilibria. To examine the selection among those equilibria, we conduct laboratory experiments where the enforcer���s objective is known to the agent in transparent treatments, but unknown to the agent in the opaque treatment. In transparent treatments, unraveling occurs. However, under the opaque treatment, only compliance-maximizing enforcers with strong detection ability reveal their detection ability, and agents violate the rule when enforcers hide. Our results outline that when the enforcement objective is opaque to agents, strategic withholding information related to the detection ability benefits revenue-maximizing enforcers.
In Chapter 2, we provide the means to have the largest comprehensive standardized test of all such elicitation mechanisms that are strategically-equivalent but cognitively-simpler than the Becker-Degroot-Marschak (BDM) mechanism. The dominant-strategy BDM mechanism is the prevailing mechanism for eliciting individuals��� valuations within economic research. However, recent research has highlighted systematic bidding mistakes under the BDM mechanism. We examine a BDM design for induced-value sellers in a controlled, laboratory environment. Treatments vary across three additional formats of elicitation mechanisms: (1) a descending price clock mechanism that satisfies refinements of dominant strategy, namely obviousness; (2) a BDM mechanism with additional contingent protocols that improves subjects��� understanding of the payoff function; and (3) a dynamic multiple price list with descending prices that simplifies the structure of the game. Our experimental results show that (3) appears to improve the game form misconceptions of the BDM mechanism but cannot improve overall accuracy of bids. Meanwhile, contrary to previous theoretical findings and online experiments, neither (1) nor (2) provides more accurate elicited values than the BDM mechanism in the laboratory.
In Chapter 3, we experimentally examine of two distinct channels influencing market behavior in a post-price mechanism of experienced goods: (1) whether there is a mandatory return option that the buyer can utilize or not, and (2) the degree to which buyers share different perceptions for the range of the random distribution that draws the experienced good���s true value. Previous literature has documented that a mandatory return option increases seller���s uniform price and buyer���s purchasing tendency in online sales platforms. However, limited attention has been given to its effect on experience goods���where the good���s true value is drawn from a random distribution, and only the buyer can learn it after purchase. Our results show that a mandatory return option decreases the seller���s uniform price for the experienced good. Conversely, for experienced goods with more heterogeneous perceptions, such heterogeneity benefits the buyer but hurts the seller. Our findings provide insights regarding the potential negative impacts of a mandatory return option on market behavior, particularly when buyer���s perception about the experienced good���s value varies in terms of its possible range
Customer Visitation Pattern: A Robust Heterogenous Network Model of Human Mobility
No full textStudying human mobility across time and space has significant implications for urban planning, business management, and disaster studies. However, previous research in this area has identified several gaps, including a lack of detailed understanding of the connection between location characteristics and visit frequencies, a lack of suitable spatial-temporal network models, and limitations in applying existing models to various scenarios. To address these gaps, this doctoral dissertation research aims to provide a general framework from a network perspective to model customer visit patterns, particularly before and after natural disasters. This research will develop a Geospatial Artificial Intelligence (GeoAI) based framework to derive the visitation pattern from heterogeneous data sources, such as mobile phone trajectories, online reviews, and official census data. The proposed research will address the following research questions: How to quantitatively delineate customer visitation patterns based on mobility data and deep learning? What is the typical visitation pattern, and how does it change after a natural disaster? What would the visitation pattern be if the business changed some strategies? The proposed research will model heterogenous data in a network and use deep learning methods to validate and derive knowledge from it. This knowledge can guide business management and support spatial decision-making. Overall, this research will contribute to the development of a network perspective framework for modeling customer visit patterns, which can be applied to various scenarios and guide urban planning and business management decisions
Hydro-Mechanical Study of Two Shrink-Swell Soils Under Hydrating and Shearing
No full textShrink-swell soils are a type of soil that expands and contracts in response to changes in moisture content. The soil is widely spread across the world and has become a prevalent geotechnical practice problem. The uneven shrink and swell behavior of shrink-swell soil causes damage to infrastructure and cost millions to repair. Most mechanical tests on shrink-swell soils have been conducted under oedometer conditions which restrict lateral movement. A limitation of such approach is that lateral soil strains are possible in practical problems. Triaxial tests, under controlled shear and confinement conditions, can represent better actual soil conditions. Very limited research has been conducted involving soil shearing and soaking behaviors under triaxial conditions, and they were related to low to intermediate expansive soils. Our research is pioneering in this area, exploring this feature of soil behavior of high to very high expansive clays under triaxial conditions. This study focuses on examining the behavior of unsaturated shrink-swell soils during shearing and soaking, aiming to offer reference soil data for civil structures like foundations and retaining walls built on these soils. It specifically investigates two types of shrink-swell soils, Texas natural soil and MX-80 bentonite, using an updated triaxial test protocol in the laboratory. The triaxial test results for Texas natural soil are utilized to validate the Barcelona Basic Model (BBM) in numerical modeling. Additionally, this dissertation includes a numerical study exploring the effect of horizontal swelling pressure on retaining wall structures in shrink-swell soil environments. The goal is to apply theoretical understanding of shrink-swell soils to address real-world geotechnical challenges. The behaviors of two shrink-swell soils under shearing and soaking are discussed and compared. The effects of stress level (particular deviatoric stress) on unsaturated shrink-swell soil volume change and final shear strength when subjected to soaking are investigated. The study also concludes how varying swelling properties of soils affect their behavior under shearing and soaking in different triaxial test conditions. BBM successfully replicates the behavior of Texas natural soil in terms of deviator stress and volume change under triaxial conditions. These insights contribute to setting benchmarks for shearing and soaking shear strength of shrink-swell soils in triaxial conditions and expanding the database available for the Texas region, aiding in foundation design. Moreover, the BBM helps to understand the distribution of horizontal swelling pressure on retaining walls, leading to simplified methods for inclusion in retaining wall design standards
Ultrasonic Spot Welding of FFF Printed Samples as a Means of Improving Interlayer Adhesion
No full textAdditive manufacturing (AM) is a technology that has improved manufacturing capabilities in a huge variety of industries, as well as increasing rapid prototyping capabilities. Fused filament fabrication (FFF) is one of these technologies, that has seen use in both industry and hobbyist settings to print thermoplastics and polymer matrix composites that have a thermoplastic matrix. However, it suffers from a major flaw in that the strength of printed parts is anisotropic and uneven, with tensile strength in the direction perpendicular to the printed layers, the interlayer adhesion, being anywhere from 50-75% lower than in the other orthogonal directions for fully dense parts made from standard glassy thermoplastics. This study attempts to improve this weakness by introducing an ultrasonic welding process to the normal FFF 3D printing method. Two welding treatments are attempted following different patterns, one where there are overlapping welds to cover as much surface area as possible, and another with no overlapping welds to prevent the risk of damaging or over-welding the part. The samples, as tested by a modified version of ASTM D5528, showed drastically increased maximum fracture load, suggesting a much stronger level of layer adhesion. Nylon samples showed a change from an average of 85.94 N for the control samples and 191.2 N for the best performing welding group average. ABS samples showed an average of 68.3 N for the control group and 102.58 N for the best performing welding group average. More testing will be required to produce a procedure that can be reliably applied to printed parts, but the procedure used in this study proved effective for both ABS and Nylon double cantilever beam samples
Quantifying Tradeoffs Among Water Use, Energy Use, Yield and Environmental Impact for Various Levels of Irrigation and Nitrogen Fertilization of Grain Sorghum
No full textCrop production systems are the most complex systems, which have many interlinkages among different sectors. Identifying and quantifying tradeoffs among those interlinkages is important to enhance the sustainability of crop production. This study aims to use water-energy-food (WEF) nexus approach to quantify tradeoffs among water use, energy use, food production, economic return and environmental impact to identify the optimum levels of irrigation and nitrogen (N) fertilization for grain sorghum production in the southeast region of Texas. The field experiment was conducted at the research farm of Prairie View A&M University in 2023. Four irrigation levels (rainfed and three levels of crop evapotranspiration including 75%, 100% and 125%) and four N fertilizer applications (recommended level, half recommended, double recommended and zero) were selected as treatments. Water use efficiency, yield, energy productivity, net income and carbon footprint were selected as indicators to represent interlinkages among different sectors and estimated for 16 different levels of irrigation and N fertilizer application combinations. WEF nexus index was developed using the above five selected indicators and the treatment with the highest WEF nexus index was selected as optimum combination. Among 16 treatments, in rainfed conditions and at 75% ET irrigation level, yield was low, and the cost of production was high with a negative net income. Highest yield, water use efficiency and carbon footprint were observed in the 100% ET with double recommended N fertilizer application while highest energy productivity and net income were observed at the 100% ET with half recommended N fertilizer application. Application of irrigation water at 100% of crop evapotranspiration and half recommended N fertilizer (90 kg of N/ha) resulted in the highest WEF nexus index value, which is 0.812 and was hence selected as optimum levels for grain sorghum to enhance the sustainable production. The findings of this study highlight the importance of quantifying tradeoffs among water-energy and food production and applying holistic tool such as WEF nexus index to make decisions on selecting appropriate crop management practices to ensure the sustainable use of water and energy in crop production while achieving optimum productivity
Addressing the Escalating Impact of Rice Kernel Smut: Insights into Genetic Diversity, Fungicide Resistance, Seed Endophytes, and Cultivar Resistance for Effective Management
No full textOnce considered a minor disease, rice kernel smut, caused by Tilletia horrida, has become one of the most economically important rice diseases in the US. With a lack of resistant rice cultivars, management heavily relies on the midseason preventive applications of propiconazole-based fungicides. However, the effectiveness of fungicide application seldom effective due to gaps in knowledge of the disease���s biology and epidemiology. We address, for the first time, the genetic diversity, fungicide resistance, seed endophytic microbiome, and host resistance, with the target to develop an effective kernel smut management program. We performed multi-locus sequence analysis to explore the genetic diversity of 63 T. horrida isolates collected from across the US. These isolates were grouped into five clades, with 59% of the isolates clustering together. The ITS region phylogeny grouped the 22 Tilletia spp. from eight different countries (Australia, China, India, Korea, Pakistan, Taiwan, The US, and Vietnam) together. Of the 63 US T. horrida isolates tested here, >80% were found to be tolerant at the baseline propiconazole concentration of 0.2 mg/L. While over 60% of the isolates displayed no inhibition at a concentration of 10 mg/L, 22% of the isolates tolerated at 25 mg/L, and one single isolate was not inhibited even at 50 mg/L. The T. horrida genomes sequenced, assembled, and annotated as part of this thesis revealed the presence of a single copy of Cyp51, a target gene for demethylation inhibitors (DMIs). In the cyp51 protein sequences of propiconazole-resistant isolates, five amino acid substitutions, G22A, R183K, V279A, L387I, and G494S, were observed. An efficient artificial inoculation method was established for T. horrida infection. Direct injection with pathogen spores onto developing panicles at the late-boot stage resulted in a higher level of disease infection compared to other inoculation methods evaluated. Field evaluation of 32 rice cultivars identified nine cultivars with partial resistance to kernel smut. An amplicon-based analyses of seed endophytic microbial diversity revealed differences between organic and conventional rice farming systems, with higher bacterial diversity in the latter and increased fungal diversity in the former. In parallel the cultivable endophytic bacteria isolated from rice seeds were identified based on the full-length 16S rRNA gene sequences. Among the 31 unique bacterial isolates tested in vitro, the strains Bacillus sp. ST24, Burkholderia sp. OR5, Pantoea sp. ST25, and Pseudomonas sp. OR4 exhibited antagonistic activities against T. horrida and, three seedling blight pathogens (Marasmius graminum, Rhizoctonia solani AG4, and R. solani AG11). The findings of this study provide insights into genetic diversity, fungicide resistance, and seed endophytes, and cultivar resistance for effective management of kernel smut in rice