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Israel Guerrero-Arguero,1 Siddiqur Rahman Khan,1 Brandon M Henry,1 Andreu Garcia-Vilanova,1 Kevin Chiem,1 Chengjin Ye,1 Sweta Shrestha,2 Deborah Knight,3 Mark Cristner,4 Shauna Hill,4 W James Waldman,3 Prabir K Dutta,2,5 Jordi B Torrelles,1 Luis Martinez-Sobrido,1 Amber M Nagy1,4 1Disease Intervention & Prevention and Population Health Programs, Texas Biomedical Research Institute, San Antonio, TX, USA; 2ZeoVation Inc., Columbus, OH, USA; 3Department of Pathology, The Ohio State University, Columbus, OH, USA; 4Chief Scientist’s Office of Science and Technology, 59th Medical Wing, Joint Base San Antonio-Lackland, San Antonio, TX, USA; 5Department of Chemistry, The Ohio State University, Columbus, OH, USACorrespondence: Prabir K Dutta; Amber M Nagy, Email dutta.1@osu.edu; AMallory@txbiomed.orgIntroduction: The coronavirus disease 2019 (COVID-19) pandemic has demonstrated the need for novel, affordable, and efficient reagents to help reduce viral transmission, especially in high-risk environments including medical treatment facilities, close quarters, and austere settings. We examined transition-metal nanozeolite suspensions and quaternary ammonium compounds as an antiviral surface coating for various textile materials.Methods: Zeolites are crystalline porous aluminosilicate materials, with the ability of ion-exchanging different cations. Nanozeolites (30 nm) were synthesized and then ion-exchanged with silver, zinc and copper ions. Benzalkonium nitrate (BZN) was examined as the quaternary ammonium ion (quat). Suspensions of these materials were tested for antiviral activity towards SARS-CoV-2 using plaque assay and immunostaining. Suspensions of the nanozeolite and quat were deposited on polyester and cotton fabrics and the ability of these textiles towards neutralizing SARS-CoV-2 was examined.Results: We hypothesized that transition metal ion containing zeolites, particularly silver and zinc (AM30) and silver and copper (AV30), would be effective in reducing the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Additionally, AM30 and AV30 antiviral potency was tested when combined with a quaternary ammonium carrier, BZN. Our results indicate that exposure of SARS-CoV-2 to AM30 and/or AV30 suspensions reduced viral loads with time and exhibited dose-dependence. Antiviral activities of the combination of zeolite and BZN compositions were significantly enhanced. When used in textiles, AM30 and AV30-coated cotton and polyester fabrics alone or in combination with BZN exhibited significant antiviral properties, which were maintained even after various stress tests, including washes, SARS-CoV-2-repeated exposures, or treatments with soil-like materials.Conclusion: This study shows the efficacy of transition metal nanozeolite formulations as novel antiviral agents and establishes that nanozeolite with silver and zinc ions (AM30) and nanozeolite with silver and copper ions (AV30) when combined with benzalkonium nitrate (BZN) quickly and continuously inactivate SARS-CoV-2 in suspension and on fabric materials.Keywords: SARS-CoV-2, disinfection, quats, zeolites, transition metals, coated fabrics

The International Ultraviolet Association (IUVA) Task Force was formed to develop guidelines regarding testing and reporting on performance of UV LED water disinfection systems. The goal was to provide clarity in a guidance document on measuring system performance across the global UV LED water disinfection system market. A review of current performance measurement protocols for mercury lamp based systems shows that the common elements of UV LED system performance measurement protocols should be as follows: specified standard for the amount of pathogen reduction required, the requirement that the validation testing be conducted by a competent facility, and that the system be continually monitored by UV sensors while in use to verify system performance unless pathogen reduction is not claimed. UV LEDs have selectable peak wavelengths, as opposed to mercury lamps that have fixed emission wavelength values. As a result of this difference, the following changes to protocols used to test mercury lamp systems are recommended. First, the use of disinfection benchmarks other than 254 nm dose, such as direct inactivation values, dose benchmarks referenced to 254 nm, and/or dose benchmarks at the UV LED emission wavelength that give the same inactivation as the original 254 nm UV dose benchmark. Second, the use of 254 nm UV water transmittance values as a placeholder, rather than an assumed correct value, for systems under test with LED wavelengths >250 nm and water transmittance values ≥87%. More research is needed for lower wavelengths and UVTs. Third, the recommendation that germicidal response UV sensors be used in UV LED based systems to ensure that the validated disinfection is delivered. Finally, additional LED‐specific considerations were also noted. UV LEDs are also instant‐on devices, making them ideal light sources for systems operated intermittently. Performance testing of systems operated intermittently should include a test to insure that pathogens do not migrate past the UV LEDs while the LEDs are off. UV LED devices have recognized protocols for determining the lifetime of the devices, as well as for measuring other device properties. Caution should be exercised in using these lifetime values for devices in UV disinfection systems, since the thermal environment of the devices may be different for protocol testing and disinfection system operation. Practitioner Points: Validation of UVC LED fluid disinfection is necessary for point of use, point of entry, and municipal applications.The emission spectrum properties, considerations and measurements for output over lifetime, and unique system design considerations of UVC LEDs as light sources are factors that must be considered when evaluating fluid disinfection performance.The instant‐on operation, system geometry, validation benchmarks, system sensing, water transmittance, and fouling must also be considered for UVC LED devices when evaluating fluid disinfection performance. [ABSTRACT FROM AUTHOR]

The Threshold Concept Framework is used to initiate a dialogue on an empirically supported pedagogy that focuses on students' conceptual understanding required for solving application-based problems. The present paper uses a triangulation approach to identify the threshold concept in a third-year undergraduate civil engineering course on open channel hydraulics. Evidence from teachers, students, and assessment data point to "critical flow" as the threshold concept--a concept that is transformative, integrative, and troublesome. Identifying the threshold concept by engaging various course stakeholders in a dialogue about conceptual understanding and capabilities makes learning visible for all participants in the process. Implementing this approach can result in an empirically driven rationale for adjusting pedagogies and assessments to foster enhanced student learning outcomes.

The use of digital elevation models, which represent the surface of the earth by a matrix of heights, has proved an ideal introductory topic for developing both the matrix-handling and computational skills of undergraduate mathematicians. This article looks at the solving of an easily understandable, but not necessarily simple problem: given a particular date, time and terrain, and within the software skills available to first-year students via a computer algebra system, produce a map which can show those parts of the terrain which lie in shadow. (Contains 7 figures.)

This article illustrates how a computer algebra system, such as Maple[R], can assist in the study of theoretical fluid mechanics, for both Newtonian and non-Newtonian fluids. The continuity equation, the stress equations of motion, the Navier-Stokes equations, and various constitutive equations are treated, using a full, but straightforward, notation. Programs are presented that can produce these equations in various coordinate systems, as is the algebra system used to obtain solutions for specific examples in parallel and rotational flow.

The way in which computer algebra systems, such as Maple, have made the study of complex problems accessible to undergraduate mathematicians with modest computational skills is illustrated by some large matrix calculations, which arise from representing the Earth's surface by digital elevation models. Such problems are often considered to lie in the field of computer mapping and thus addressed by geographical information systems. The problems include simple identification of local maximum points, visualization by cross-sectional profiles, contour maps and three-dimensional views, consideration of the visual impact of the placement of large buildings and issues arising from reservoir creation. Motion through a virtual landscape can be simulated by an animation facility. This approach has been successful with first year students: the 'real world' problems considered are more accessible than many alternatives, and the attraction of using large matrices is retained.

If the point of suspension of a multiple pendulum is suitably oscillated then the pendulum can remain in motion in an upside-down position. Since such pendulums can model flexible materials, this inverted motion is sometimes referred to as an 'Indian rope trick'. Despite the complexity of the governing differential equations, this rope trick can be successfully demonstrated using a popular computer algebra system to formulate and solve the equations, and display an animation of the motion.

The way in which computer algebra systems, such as Maple, have made the study of physical problems of some considerable complexity accessible to mathematicians and scientists with modest computational skills is illustrated by solving the multiple pendulum problem. A solution is obtained for four pendulums with no restriction on the size of the angles through which they move, and for as many as a hundred pendulums if the angles remain sufficiently small. An attractive and informative graphical display of the motion in animated form can be obtained from the solution, and the effect of varying the initial conditions can be investigated visually. (Contains 8 figures.)