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Reductive and Nucleophilic Cleavage of Peroxides and Synthesis of Tocotrienols as Radioprotective Targets
No full textI. SET CLEAVAGE OF PEROXIDES: INFLUENCE OF REDUCTANT AND PEROXIDE ON THE RATE AND MODE OF ALKOXY RADICAL FORMATION
The reductive cleavage of organic peroxides to generate alkoxy radicals is frequently accomplished via single-electron transfer (SET) from a reductant. Previous reports employ either symmetrical peroxides or peroxides with predictable cleavage behavior, such as peresters. We were interested in how the structure of the peroxide and the nature of the reducing system combine to impact the rate of reaction and the selectivity for alkoxy radical formation during cleavage of unsymmetric peroxides. In this dissertation, one will find the reactions of a family of peroxides (dialkyl peroxides, peroxyacetal, perester, alkyl/silyl peroxide, hydroperoxide) based upon a shared radical clock skeleton with a number of reductants, including three photoredox systems of varying potential. The observed outcomes demonstrate clear substrate- and reductant-dependent differences in the rate and selectivity of SET cleavage. These findings will allow researchers to selectively form desired alkoxy radicals by altering the reaction conditions.
II. INVESTIGATIONS OF A MODULAR SYNTHETIC ROUTE TO DT3 AND GT3 TOCOTRIENOLS AS RADIOPROTECTIVE TARGETS
With the increased risk of nuclear warfare attacks across the world, it is critical to have both a safe and potent radioprotective agent for nuclear emergencies. Both γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have been shown to act as effective radioprotectants. Isolation of GT3 and DT3 from natural sources can be achieved, but the resulting yield is very low due to a low natural abundance. Furthermore, the current synthetic approaches are lengthy, costly, and yield products with multiple stereoisomers. This dissertation chapter discusses the key features in the tocotrienol structure that are important for total synthesis and outlines previous synthetic approaches towards GT3 and DT3 tocotrienols.
III. INVESTIGATIONS INTO THE REDUCTIVE CLEAVAGE OF PEROXIDES WITH ORGANOCOPPER REAGENT
Ethers are important functional groups found widely in natural products and man-made materials. Approaches towards ether formation most commonly rely on the reaction of a nucleophilic oxygen with an electrophilic carbon. The polarity-reversed version of this transformation involves generation of ethers through the reaction of nucleophilic carbon with electrophilic oxygen. organomagnesium nucleophiles; the synthesis of tertiary ethers (containing a tertiary C-O bond) through reaction of Grignard reagents with tertiary peresters remains an important synthetic method. It was later discovered that ethers could be generated from reactions of dialkyl peroxides and organolithium compounds, but good yields were restricted to unhindered substrates. Our lab has explored the reactivity of peroxides towards organomagnesium and organolithium compounds and found that monoperoxyacetals exhibit enhanced reactivity compared to dialkyl and alkyl/silyl peroxides, efficiently transferring primary, secondary, and tertiary alkoxides to form ethers. However, these transformations rely upon strongly basic organolithium and organomagnesium nucleophiles. This dissertation work aims to expand this methodology to allow efficient ether formation using less basic organometallic nucleophiles, with an initial emphasis on organocopper reagents.
Advisor: Patrick H. Dussaul
Rapid Fabrication of Liquid Metal Patterns for Stretchable Electronic Circuits
No full textStretchable circuits are crucial for the development of large-area electronics that can be used in wearable computing, soft robotics, and physical human-machine interaction. Gallium-based room temperature liquid metals (LMs) have emerged as a promising option for use as electrical conductors in soft and stretchable electronics. However, the lack of efficient and robust fabrication techniques has hindered the widespread use of LM electronics. Current methods typically require specialized equipment and cleanroom fabrication, which can be labor-intensive. To address this challenge, I have developed a facile and digital fabrication approach for creating LM-based circuit assemblies that can be interfaced with a broad range of substrate materials, from hyperelastic elastomers to spandex-blend fabrics. This method involves bonding a readily available and cost-effective copper (Cu) metal leaf to the substrate, which is then coated with LM. UV laser micromachining is used to pattern the biphasic Cu-LM film, a method commonly utilized in creating conventional printed circuit boards, by taking advantage of photophysical ablation. Off-the-shelf microelectronic components can then be directly interfaced with the Cu-LM biphasic film to create fully untethered circuits. The circuit connections between the Cu-LM biphasic film and microelectronic components are improved by a bulk HCl vapor treatment, which is only possible due to the Cu adhesion layer. I have demonstrated the versatility of this method with several implementations on a variety of substrate materials. The maskless, digital fabrication approach will enable rapid prototyping and fabrication of LM-based circuit assemblies, allowing for the creation of untethered on-skin electronics and biosensing devices without the need for cleanroom fabrication. This approach offers a low-cost, scalable, and efficient alternative to current fabrication methods, which could pave the way for more widespread use of LM electronics in soft and stretchable applications
Modeling the Survival of \u3cem\u3eSalmonella\u3c/em\u3e in Beef Jerky: Influence of Product Thickness and Temperature on Dehydration Rate and Microbial Inactivation
No full textThe production of safe, shelf-stable beef jerky requires validated thermal processes capable of consistent pathogen reduction, particularly against Salmonella. This study evaluated the effects of beef portion thickness, drying temperature, and contamination route on Salmonella survival kinetics during dehydration and storage. The objective was to inform HACCP strategies and support compliance with USDA-FSIS lethality guidelines.
Beef eye of round slices were cut into three thicknesses (0.38, 0.64, 0.95 cm), inoculated with a five-serovar Salmonella cocktail via direct immersion or spice mix marinade, and dried at 154 °F (68 °C) or 160 °F (71 °C) using a home-style dehydrator. Water activity (aw) was monitored hourly. Salmonella counts were measured over a 6-hour drying period and at Days 7 and 14 post-dehydration. A factorial design assessed the impact of treatment combinations on lethality and shelf-stability.
Product thickness significantly influenced time to reach aw ≤ 0.85 (p = 0.0144), with thicker slices requiring longer drying times. Thickness and drying time significantly affected microbial log reductions, while temperature and inoculation method did not independently impact lethality. After 6 hours, all treatments achieved \u3e 6-log CFU/g reductions, surpassing the USDA-FSIS benchmark for ready-to-eat jerky. However, Salmonella was still detectable (up to 3 log CFU/g) after 14 days of ambient storage, indicating its desiccation tolerance and potential for long-term survival.
To model microbial survival kinetics, several non-linear inactivation models were evaluated. The Weibull model with residual population (Albert & Mafart, 2005) best described the data, capturing both shoulder and tail phases of microbial death curves. It achieved an average Acceptable Prediction Zone (APZ) of 94.05%, adjusted R2 of 0.96, and low RMSE of 0.26, indicating high predictive accuracy.
In summary, drying alone can provide sufficient lethality when properly controlled, but slice thickness, real-time aw monitoring, and predictive modeling are crucial for effective process validation. The results support improved process control and the potential need for post-lethality interventions to ensure jerky safety, particularly for small and very small processors striving for USDA-FSIS regulatory compliance.
Advisor: Byron D. Chave
Examination of cooperative extension as a bridging organization to enhance cross boundary collaborative water management
No full textRethinking Assessment in Asynchronous Learning: A Benchmark Portfolio for MNGT 301
No full textThis teaching portfolio evaluates the instructional redesign of MNGT 301 Introduction to Management at the University of Nebraska–Lincoln, focusing on improving student learning outcomes, addressing performance disparities across demographic groups, and enhancing assessment alignment with course goals. The redesign primarily involved modifying assessment types and implementing clearer structure and grading expectations. The analysis compares student performance data from Fall 2024 and Spring 2025, disaggregated by demographic indicators including gender, race/ethnicity, parent education, neighborhood opportunity index, and rural/urban background. In addition, student perceptions were assessed through a midsemester Keep-Stop-Start survey. Findings suggest that redesign elements enhanced student engagement and equity by reducing performance gaps, particularly through the use of application assignments. Applications showed strong performance metrics and positive student feedback, confirming their effectiveness. However, other assessments, such as discussion boards and the semester project, revealed opportunities for further refinement due to mixed feedback and remaining performance disparities. Planned changes include replacing discussion boards with a simulation, increasing scaffolding within the semester project, and leveraging applications as formative learning tools
Veterinary Drug Residue Regulations in Major U.S. Export Markets
No full textTrade agreements shape the global agricultural trade landscape, encompassing both tariff and non-tariff measures. Among the latter, sanitary and phytosanitary (SPS) measures such as maximum residue limits (MRLs) are gaining attention. As trade tensions escalate, there is growing concern that countries could use SPS measures as a tool of retaliation in international agricultural markets, as they are often a focal point in trade negotiations (Disdier and Marette, 2010; Disdier and van Tongeren 2010; Grant et al., 2015)
Upland Switchgrass Cultivars have Similar Bioethanol Production Profile under Separate Hydrolysis and Fermentation: A Course Based Undergraduate Research Experience (CURE) in Biofuel Production
No full textThe modified Course-Based Undergraduate Research Experience (CURE) in bioenergy research evaluated four upland switchgrass cultivars namely Carthage, NE2010, RC Sundance, and Sunburst for bioethanol production using a separate hydrolysis and fermentation (SHF) process. The cultivars were not different in their biomass composition, sugar and ethanol yields. Carthage produced the highest ethanol yield (10 g/L), followed by Sunburst (9 g/L). A strong correlation was observed between glucose concentration at 48 hours (maximum glucose release) and ethanol yield at 72 hours. Ethanol production increased after 48 hours, and by 72 hours, residual glucose levels in the fermentation medium were negligible. The fermentation efficiency was approximately 85%, with a theoretical ethanol yield of 0.51 g per gram of glucose
Comparative Performance of Reciprocal Cross Hybrid Striped Bass in Three Intensive Production Systems
No full textObjective: The objective of these two studies was to quantify the comparative performances of yearling and 2- year- old reciprocal cross hybrid Striped Bass (White Bass Morone chrysops ♀ × Striped Bass M. saxatilis ♂), also called sunshine bass, and water quality in traditional and split ponds and an outdoor mixotrophic biofloc technology production system. Methods: In study 1, two- year- old fish (247.9 g/fish) were stocked at 7,410 fish/ha (0.86 fish/m3) in ponds and 6.3 fish/m2 (7.1 fish/m3) in biofloc system tanks and grown for 151–153 d. In study 2, yearling fish (147.0 g/fish) were stocked at 7,904 fish/ha (0.91 fish/m3) in ponds and 5.4 fish/m2 (6.1 fish/m3) in the biofloc system and grown for 153–157 d. All fish were fed a commercially formulated 40% protein, 12% lipid floating extruded feed to apparent satiation 6 d/week. Water samples were collected weekly from all production units and analyzed. Results: The metrics for hybrid Striped Bass performance in traditional and split ponds did not differ significantly (P \u3e 0.05) in either study. However, the biofloc system yield (kg/m3) was significantly greater than that in traditional ponds in both studies. However, fish in the biofloc system were significantly smaller (P ≤ 0.05) and skewed toward the smaller market size- classes. The elevated concentration of total suspended solids in the study 1 biofloc system appeared to negatively affect weight gain and yield. Mean total ammonia- nitrogen concentration was significantly lower (P ≤ 0.05) in split ponds (0.54–0.85 mg/L NH3- N) than in traditional ponds (0.97–1.26 mg/L NH3- N). The measured water quality variables in the biofloc system differed significantly (P ≤ 0.05) from that in the traditional ponds. Conclusions: Hybrid Striped Bass can be grown in split ponds, and baseline performance of yearling and 2- year- old fish was established for the split- pond system at traditional pond stocking rates for this species. However, stocking rate in split ponds must be optimized to increase the yield of market size fish, followed by an economic analysis to determine the feasibility of using the split- pond system to produce market size hybrid Striped Bass. Yearling and 2- year- old hybrid Striped Bass can be grown in the biofloc system, but the results suggest that they are not a viable candidate species for grow out in the outdoor biofloc system
Timber Talk, Vol. 63, No. 3, July 2025 (Special)
No full textTimber Talk, Vol. 63, No. 3, July 2025 (Special
