ABSTRACT A common distinction in engineering problems is classifying them as well-structured or ill-structured. It is assumed that classroom problems are well-structured while workplace problems are ill-structured. However, we cannot find empirical data to confirm or deny the claim that the bulk of classroom problems are well-structured. This research characterised 3,387 end-of-chapter problems presented in two engineering statics textbooks. Our data revealed that 99% of all problems were algorithmic, requiring a solution that was either numeric or an expression 92% of the time. Additionally, our analysis of pictorial representations (useful for cognitive scaffolding) revealed mixed results: while modeling was frequently used and beneficial, affordances were inconsistently applied, and embodiments were rarely employed. Even in foundational statics courses, students could benefit from exposure to a greater variety of problem types and cognitive scaffolding, providing students with opportunities to become more familiar with and better prepared for the nature of workforce problems.

Industrial munition facilities are increasingly manufacturing insensitive high explosives (IHEs) to improve safety. The explosive residues in wastewater from these facilities are treated to meet regulatory standards. However, the resulting effluent contains elevated levels of mineralized nitrogen species. This study evaluated the potential of vetiver grass (Chrysopogon zizanioides), a non-invasive perennial species, to remove high concentrations of nitrate, nitrite, and ammonium from munition plant wastewater. Vetiver was grown hydroponically in synthetic wastewater containing high levels of nitrogen compounds simulating munitions plant effluents. Vetiver plants were treated with one nitrogen species at a time, with concentrations ranging from 165 to 24,700 mg N/L of nitrate, 100 to 4000 mg N/L of nitrite, and 260 to 39,000 mg N/L of ammonium. Nitrogen concentrations in the media and plant responses were monitored over time. The results showed significant nitrogen removal at lower concentration ranges. When concentrations exceeded 3800 mg N/L of nitrate, 800 mg N/L of nitrite, and 2600 mg N/L of ammonium, the removal rates declined after 7 days. At higher nitrogen levels, vetiver exhibited stress symptoms such as chlorosis and elevated antioxidant enzyme activity. Our study demonstrates the potential of vetiver grass in treating nitrogen-rich wastewater from the munition industry and provides a baseline for future large-scale studies to optimize the technology.

Background/Objective: Oligodeoxynucleotides (ODNs) containing base-labile modifications such as N4-acetyldeoxycytidine (4acC), N6-acetyladenosine (6acA), N2-acetylguanosine (2acG), and N4-methyoxycarbonyldeoxycytidine (4mcC) are highly challenging to synthesize because standard ODN synthesis methods require deprotection and cleavage under strongly basic and nucleophilic conditions, and there is a lack of ideal alternative methods to solve the problem. The objective of this work is to explore the capability of the recently developed 1,3-dithian-2-yl-methoxycarbonyl (Dmoc) method for the incorporation of multiple 4acC modifications into a single ODN molecule and the feasibility of using the method for the incorporation of the 6acA, 2acG and 4mcC modifications into ODNs. Methods: The sensitive ODNs were synthesized on an automated solid phase synthesizer using the Dmoc group as the linker and the methyl Dmoc (meDmoc) group for the protection of the exo-amino groups of nucleobases. Deprotection and cleavage were achieved under non-nucleophilic and weakly basic conditions. Results: The 4acC, 6acA, 2acG, and 4mcC were all found to be stable under the mild ODN deprotection and cleavage conditions. Up to four 4acC modifications were able to be incorporated into a single 19-mer ODN molecule. ODNs containing the 6acA, 2acG, and 4mcC modifications were also successfully synthesized. The ODNs were characterized using RP HPLC, capillary electrophoresis, gel electrophoresis and MALDI MS. Conclusions: Among the modified nucleotides, 4acC has been found in nature and proven beneficial to DNA duplex stability. A method for the synthesis of ODNs containing multiple 4acC modifications is expected to find applications in biological studies involving 4acC. Although 6acA, 2acG, and 4mcC have not been found in nature, a synthetic route to ODNs containing them is expected to facilitate projects aimed at studying their biophysical properties as well as their potential for antisense, RNAi, CRISPR, and mRNA therapeutic applications.