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Low-fidelity ice accretion and performance degradation modeling for rotating bodies and an experimental shedding analysis
No full textAs Advanced Air Mobility (AAM) and Urban Air Mobility (UAM) gain popularity in the aviation industry, electric rotorcraft designs are at the forefront of this emerging technology. With these novel designs, new icing challenges are becoming prevalent due to factors such as performance degradation due to ice accretion and damage caused by ice shedding from rotor blades. As the aerospace industry pushes for higher efficiency, it is becoming more essential to understand the effects of icing early in the design phase. High-fidelity models show promise for providing accurate results but require substantial computing power and processing time. Low-fidelity tools are known to work well in the stationary frame and can be used to evaluate the aerodynamics of rotating bodies without icing. This thesis demonstrates methods using well-established low-fidelity tools that can provide results with limited computing power and short computing times, allowing for the faster processing of large amounts of calculations in both stationary and rotating reference frames to identify problematic areas for further investigation. These methods are then used to analyze ice accretions and resulting performance degradation, and comparisons are made to experimental propeller icing tests performed in the NASA Icing Research Tunnel (IRT). Another safety concern for propeller aircraft is ice shedding. Ice shedding poses its own threats to the safety of UAM vehicles, as ice may be released at high velocities, causing impact damage to aircraft components and leading to vibrational damage due to imbalance after a shedding event. Due to these concerns, researchers have been investigating the causes, trajectories, and mitigation strategies to better understand the parameters that affect ice shedding. This thesis also develops a method for researchers to obtain highly accurate shedding location data from experimental high-speed video and validates this method using video data gathered in the NASA IRT during a recent propeller icing study
In-tube sensors for continuous monitoring of cell cultures
No full textThis work presents a low-cost in-tube sensor platform for continuous, real-time monitoring of cell density and dissolved oxygen (DO) in microbial cultures. The system integrates two optical measurement modalities into dye-doped polymer tubing that directly interfaces with bioreactors or shake flasks, enabling flow-through sensing without disturbing culture conditions. Dissolved oxygen is quantified using platinum(II) octaethylporphyrin (PtOEP), whose phosphorescence lifetime is strongly quenched by molecular oxygen through a dynamic collisional mechanism. As oxygen concentration increases, the PtOEP excited-state lifetime decreases according to the Stern-Volmer relationship, allowing highly sensitive, calibration-based quantification of DO. A triggered UV LED excites the dye, and the emitted phosphorescence is captured with compact, high-speed photodetector and time-resolved electronics to extract lifetime values with high precision. Simultaneously, cell growth is assessed through LED-modulated optical backscattering, where Fourier-domain analysis isolates the modulation frequency to suppress background noise and reliably quantify scattering intensity associated with cell density. The platform’s in-tube format simplifies deployment by combining sampling, sensing, and fluid transport in a single disposable component. Because the tubing can be inserted directly into incubators, connected inline with culture vessels, or operated with peristaltic pumping, it enables hands-off, contamination-free, and continuous monitoring without modifying reactor hardware or interrupting cultivation. We demonstrate the utility of this system by monitoring the growth of Saccharomyces cerevisiae and Yarrowia lipolytica, two yeast species with distinct oxygen consumption behaviors driven by the Crabtree effect. The sensor accurately captured real-time changes in biomass accumulation and oxygen availability, revealing strain-specific metabolic patterns. Compact, modular, and highly accessible, this in-tube sensor provides a practical solution for precision biomanufacturing, offering time-resolved feedback on cell growth kinetics and oxygen demand. Its scalable design supports seamless integration into automated bioprocess monitoring workflows and broader adoption of real-time sensing in small- and mid-scale culture development
Plant immune responses to elevated carbon dioxide and implications for crop health in a changing climate
No full textRising atmospheric CO2 continues to affect plant growth environments and is expected to influence disease pressure in agriculture. However, it remains challenging to predict how elevated CO2 (eCO2) alters interactions between crops and microbial pathogens. This dissertation examines how eCO2 affects immunity and disease outcomes in soybean and maize and introduces a virus-based approach that enables efficient gene function studies in plants.
In soybean, which uses the C3 photosynthetic pathway, growth under eCO2 (550 ppm) resulted in physiological changes and enhanced activation of early immune signaling. When challenged with diverse pathogens, soybean grown in eCO2 showed reduced susceptibility to Pseudomonas syringae pv. glycinea, consistent with stronger pattern-triggered immune responses. In contrast, susceptibility increased to bean pod mottle virus, soybean mosaic virus, and Fusarium virguliforme. Susceptibility to Pythium sylvaticum remained similar under both CO2 conditions, although eCO2 led to greater biomass loss during infection. These findings indicate that eCO2 alters soybean immunity and that outcomes varied across the pathogens examined, with enhanced defense against a bacterial pathogen but reduced antiviral responses.
In maize, a C4 plant, growth under eCO2 also altered immune responses and interactions with some pathogens with similarities and differences when compared to soybean. Increased basal immune responses were observed under eCO2, together with reduced susceptibility to Clavibacter nebraskensis, Exserohilum turcicum, and Colletotrichum graminicola. Susceptibility increased to sugarcane mosaic virus and did not change for Puccinia sorghi or Pythium sylvaticum. Overall, these findings suggest that eCO2 influences immunity in both crops, although the direction and magnitude of effects differ among pathosystems.
To support rapid functional analysis of defense pathways, a turnip mosaic virus-based vector was engineered for CRISPR guide RNA delivery in Nicotiana benthamiana. The system enabled detectable somatic genome editing, including multiplex guide delivery and the use of a mobility element. Although editing efficiencies were modest, the results demonstrate that guide RNA delivery by a potyvirus is achievable and provide a starting point for further optimization.
Together, this dissertation provides new insight into how eCO2 alters immune processes in C3 and C4 crops and introduces a viral genome-editing system designed to accelerate the study of plant defense genes and gene modification for crop improvement. The results demonstrate that eCO2 reshapes disease outcomes in a pathogen- and host-dependent manner rather than producing a uniform shift in susceptibility. Understanding this variation and enabling faster functional analysis of immune pathways has important implications for predicting disease risks in future agricultural environments and for developing strategies to maintain crop productivity as atmospheric CO2 rises
Impacts of rotation, tillage, cover cropping, and drainage on soil health in soybean-based cropping systems: Evidence from 4–50-year trials across the US
No full textRecent studies highlight conservation management practices as an effective strategy to enhance soil health. However, results vary, particularly regarding which soil health parameters respond most sensitively to these practices. More studies covering a wide range of soil types and climatic conditions are needed to assist farmers in making management decisions on production practices related to soil health. In this study, we collected soil samples (0–15 cm) from 21 (4–50 years) soybean [Glycine max (L.) Merr.]-based cropping systems trials across the United States (US) to assess the impact of management practices on soil health indicators. Soil indicators included wet aggregate stability (WAS), permanganate oxidizable carbon (POXC), organic matter loss-on-ignition (OM-LOI), mineralizable carbon (Min-C), water extractable organic carbon (WEOC), total organic carbon (TOC), soil extractable protein (ACE-N), total nitrogen (TN), pH, soil test phosphorus (STP), and soil test potassium (STK). Our objectives were: (i) to assess the effects of crop rotation, tillage, cover cropping, and artificial drainage on soil health; (ii) to inform soybean farmers about the management practices that are associated with improvements on soil health; and (iii) to develop and share a unique and open soil health dataset with the research community for future global meta-studies. To assess the effects of management practices on soil health indicators, both meta-analysis approach and linear mixed-effect models were used. Two-crop rotations were associated with greater STP values compared to a single-crop. The inclusion of cover crops was associated with greater Min-C and WEOC compared to no cover crops. No-tillage showed more acidic pH than conventional tillage. The remaining soil health indicators tested did not change in response to the management practices assessed. There were no statistically significant differences in observed soil tests between tile-drained and undrained treatments. Overall results suggest that cover crops can play an important role in building soil health in soybean-based cropping systems. Our open-access dataset provides a valuable resource for future research and meta-studies, ultimately contributing to the development of more effective management strategies for promoting more sustainable soybean cropping systems.This article is published as Silva, Tatiane Severo, Lindsay Chamberlain Malone, Matthew D. Ruark, Chad D. Lee, David Jordan, Hanna J. Poffenbarger, Herman J. Kandel et al. "Impacts of rotation, tillage, cover cropping, and drainage on soil health in soybean-based cropping systems: Evidence from 4–50-year trials across the US." Agriculture, Ecosystems & Environment 395 (2026): 109950. https://doi.org/10.1016/j.agee.2025.109950This research was supported by the Agriculture and Food Research Initiative- project award No. 2023-67013-39817, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture and the Wisconsin Soybean Marketing Board
Youth agricultural entrepreneurship in selected Sub-Saharan Africa countries: Assessing drivers of engagement, implementation modalities, and prevailing practices
No full textThe rising youth population in Sub-Saharan Africa (SSA) presents challenges such as unemployment, food insecurity and poverty. Agricultural entrepreneurship has been proposed as a long-term solution to addressing increasing youth unemployment and food insecurity in the region. This has led to a proliferation of youth agricultural entrepreneurship in the region; however, unemployment and food insecurity keep increasing. The purpose of this study which followed a three-article dissertation format was to explore the meaning of agricultural entrepreneurship, implementation practices, and the perspectives of youth who engage in it in selected SSA countries. Specifically, the study assessed factors influencing youth participation in agricultural entrepreneurship programs, explored how the concept of youth agricultural entrepreneurship is interpreted in selected SSA countries, and compared existing youth agricultural entrepreneurship program (YAEP) implementation strategies with the lived experience of youth who engaged in YAEP. The methods employed include an integrative literature review, mixed methods design, and a qualitative comparative analysis. The results of the first article, an integrative literature review of existing research and youth programs in selected countries, revealed that the concept of agricultural entrepreneurship is often associated with farming. Strategies such as creation of targeted programs, including school gardening, demonstration farming, the provision of inputs, and participation in agricultural shows were identified as among the commonly used implementation approaches. The second article, a mixed methods study, revealed institutional support, individual interest in agriculture, family, and peers’ recommendations as the main factors influencing youth participation in Iowa State University-Uganda Program (ISU-UP) YAEP. The third article, a comparative analysis of the first and second articles, indicated that there were no differences between the structure and implementation strategies of youth agricultural entrepreneurship programs documented in the literature and those experienced by youth in the ISU-UP YAEP. The analysis revealed that YAEP programs in selected SSA countries did not emphasize training the youth in some of the important principles of positive youth development (PYD), such as character and caring. Furthermore, little to no emphasis was placed on building an effective and efficient social support system to ensure sustainability of the programs. A sustainable youth agricultural entrepreneurship (agripreneurship) framework that integrates the microsystem and positive youth development principles was proposed to guide the implementation of youth agricultural entrepreneurship programs in selected SSA. The results indicated the need for youth-serving organizations focusing on agricultural programs in these selected SSA countries to adopt integrated approaches that strongly recognize and collaborate with the microsystem to educate, plan, implement, and evaluate youth agricultural entrepreneurship programs
Building Resilience Against Flash Floods: A Tale of Two Communities in Des Moines, Iowa, USA
No full textGlobal climate change is increasingly affecting weather patterns and putting communities through disaster shocks with which they have no previous experience. Many cities in the United States are operating on infrastructure and stormwater drainage systems that were not designed to handle increasingly turbulent weather patterns, including extreme flood events. They are adapting both green and gray infrastructures to build longer-term resilience in communities. There is a lack of systematic analysis on community choices, government priorities, and the effectiveness of different flood mitigation strategies, especially in small and medium-sized cities in the United States. Using the case study of the 2018 flash flood in Des Moines, Iowa, this paper compares nature-based solutions (NBS), green infrastructure investments, and property buyouts, examining how community members perceive these different methods of flood mitigation following a major flash flooding event. Fifteen inter-views with key informants and government officials, and secondary evidence are used. The results show a detectable resistance within communities towards funded gray infrastructures and relocations that fracture neighborhoods after disasters. The findings add a comparison of green infrastructure investments, property buyouts, and gray infrastructure improvements as methods of flash flood mitigation in Des Moines, Iowa, and their effectiveness in the contexts of affected communities. The study concludes that context-specific and community-focused approaches, combined with pre-disaster recovery planning, are more effective in building longer-term resilience to floods and other climate-induced disasters than following popular prescriptive approaches.This article is published as Kapayou, D.; Young, L.; Ghimire, J. Building Resilience Against Flash Floods: A Tale of Two Communities in Des Moines, Iowa, USA. Journal of Hazards, Risk and Resilience 2026, 1 (1), 6. https://www.sciltp.com/journals/jhrr/articles/2601002909Funding: Financial support for this study was provided in part by the Meskwaki Higher Education Program and the Iowa State University Dean’s Doctoral Support Scholarship Program. The views expressed herein are those of the authors and do not necessarily reflect the positions of the funding agencies
Prevention, control, and treatment of digital dermatitis in dairy cattle
No full textAs one of the leading causes of lameness in dairy cattle (and, increasingly, in feedlot cattle), Bovine Digital Dermatitis (DD) has major economic and welfare implications for producers in these industries. Efforts to prevent, control, and treat this disease have generally met with poor or mixed results, and there is still much to learn about the pathophysiology, immune response, and efficacy of even the more popular interventions currently utilized by producers. The goal of this thesis was to better describe bovine immune response to the disease, as well as to determine the efficacy of interventions to prevent, control, or treat it that are commonly used or favored by producers. By utilizing an effective induction model to reinduce animals that had previously been induced with DD and subsequently healed, it was observed that 100% of naïve animals were induced while 63% of previously induced animals were successfully reinduced. Humoral and cellular proliferative responses did not differ between groups or between induction positive vs. negative individuals. These results suggest that following resolution of DD lesions, immunity provides partial protection (at best) against reinfection. Due to the polybacterial nature of DD, a polyvalent bacterin vaccine was tested using the same induction model to assess efficacy. The vaccine contained four bacterial pathogens associated with DD, isolated from naturally occurring lesions, and was administered; induction was performed 43 days later. Eighty-two percent of the vaccinated group had a least one lesion, while 91% of the placebo group did. Percentage of actual feet that developed a lesion (50% vaccinated, 71% placebo), while not statistically significant, showed a more profound difference than that of individuals, potentially hinting at partial immune protection. Two of the most common interventions intended to deal with DD lesions on farms are footbathing and topical tetracycline treatment. Footbathing was assessed as a means of reducing and/or resolving early lesions (1 or 2 according to the Iowa DD scoring system). A group of Holstein dairy cows was put through a 3% formalin footbath three times weekly for four weeks; another group was put through a tap water footbath. Results tentatively suggest that formalin footbathing causes greater regression of early lesions than tap water. Finally, cows with naturally occurring DD lesions were treated with either a single topical tetracycline wrap or three consecutive weekly wraps and assessed over the course of 127 days. There is evidence that three weekly treatments cause more significant regression at 127 days than a single treatment, although only 9% of lesions were completely resolved at that time. The results of these studies support the hypothesis that immune response to DD infection is partially protective at best, and while no single intervention acts as a panacea, vaccination warrants further investigation, as does the potentially complementary (or even synergistic) effect of incorporating formalin footbathing and topical tetracycline treatment into a farm’s DD control program
Exploring a Unique Class II Diterpene Cyclase: The Modified Catalytic Acid Motif Contributes to Ring Contraction in Premutilin Synthase
No full textThe class II diterpene cyclase from pleuromutilin biosynthesis contains a unique variant of the otherwise highly conserved DxDD motif (DxDM), which cooperatively serves as the catalytic acid, and uniquely produces an “A” ring contracted product, mutildienyl pyrophosphate (MPP). The correlation between these features was investigated here via substitution of aspartate for methionine, which largely blocks the production of MPP and leads to a novel hydroxylated product, syn-halima-13E-en-5β-ol-15-PP, providing insight into this unique reaction.This article is published as Helwig, Kristin, Jun Xie, Cody Lemke, Meimei Xu, Xinye Kang, Meirong Jia, and Reuben J. Peters. "Exploring a Unique Class II Diterpene Cyclase: The Modified Catalytic Acid Motif Contributes to Ring Contraction in Premutilin Synthase." Organic Letters (2026). https://doi.org/10.1021/acs.orglett.5c04898This work was supported in part by grants from the National Institutes of Health to R.J.P. (currently GM156300) for the work done in the United States and a grant from the National Natural Science Foundation of China to M.J. (22207129) for the work done in China
Effects of alternative harvest regulations on Smallmouth Bass angler harvest in Missouri River reservoirs
No full textObjective: Smallmouth Bass Micropterus dolomieu is an important sport fish in parts of the United States. Although voluntary angler catch and release is common in many Largemouth Bass Micropterus nigricans fisheries, Smallmouth Bass harvest may be higher in the northern Midwest. Our objectives were to evaluate temporal angler catch and harvest patterns and the potential effects of alternative bag and length limits for managing populations in Missouri River reservoirs, South Dakota.
Methods: We used angler use and harvest surveys and the fisheries analysis and modeling simulator (FAMS) to evaluate temporal angler catch and harvest patterns and the potential effects of alternative bag and length limits for managing populations in Missouri River reservoirs, South Dakota.
Results: The anglers that were targeting Smallmouth Bass had higher probabilities of catching, harvesting, and releasing Smallmouth Bass than the other anglers did. The probability of an angler catching and releasing a Smallmouth Bass increased from May 1 to September 1, whereas for anglers that caught a bass, angler catch, harvest, and release rates decreased with Julian day. Bag limits ≥3 fish/d resulted in small reductions in harvest, whereas bag limits
Conclusions: Unlike many southern Smallmouth Bass populations, we found that anglers in Missouri River reservoirs readily harvest Smallmouth Bass and that more conservative bag limits and length limits could reduce harvest and increase abundance, spawning potential ratio, and size structure.This article is published as Christian Slone, Kyle Olivencia, Mark J Fincel, Michael J Weber, Effects of alternative harvest regulations on Smallmouth Bass angler harvest in Missouri River reservoirs, North American Journal of Fisheries Management, 2026;, vqaf125, https://doi.org/10.1093/najfmt/vqaf125This research was supported by SDGFP through Contract 20SC06W008. Open access funding provided by Iowa State University Library
Dual genetic mechanisms of heterosis: population structure and gene action
No full textIntroduction: Heterosis refers to the superiority of a hybrid over its parents. Existing heterosis theory has not sufficiently addressed the contribution of inbreeding at both population level and the level of individual lines within populations. The objectives of the present paper were to formalize theoretical extensions of heterosis theory to address inbreeding at multiple levels, to empirically test the theory in maize, and to provide greater clarity in the quantitative genetic interpretation of heterosis as a function of independent genetic principles of population structure and gene action.Methods: Existing heterosis theory for biparental crosses was extended by adding terms for inbreeding within panmictic parent populations. The theory was tested with an experiment in maize with a diverse set of panmictic and inbred parents.Results: Extended theory demonstrated that both heterosis and inbreeding depression are linear functions of inbreeding, FST at the population level, and f at the individual level, under a model of directional dominance. The model demonstrates that heterosis is expected to be negatively related to both midparent value and inbreeding depression within parent populations, i.e., heterosis increases as midparent value decreases and as inbreeding depression within parent populations decreases. Consistent with theoretical predictions we found that that for maize grain yield midparent value predicted 86% of heterosis in a set of crosses and parental inbreeding depression predicted 70% of variation in heterosis among crosses.Discussion: Model extensions presented here illustrate the excess and transient nature of heterozygosity in the F1 generation that is partially responsible for the unique performance benefit of F1 hybrids. Mechanistically, the theory illustrates that heterosis is a function of two separate and independent mechanisms, population structure and gene action, both of which need to be considered in understanding the mechanisms of heterosis.This article is published as Aguilar FS, Lamkey KR and Edwards JW (2026) Dual genetic mechanisms of heterosis: population structure and gene action. Front. Plant Sci. 16:1715826. doi: 10.3389/fpls.2025.1715826The author(s) declared that financial support was received for this work and/or its publication. This research was supported in part by the US. Department of Agriculture, Agricultural Research Service (USDA ARS) Project No. 5030-21000-073-000D. FSA received a Fulbright Scholarship to study in the United States