Background: Authentic assessment and two-stage exams have recently received attention; however, they are rarely used together. We reimagine assessment by integrating an authentic, computer-based assessment into the structure of a two-stage exam in a large engineering class. Purpose: We seek to identify ways that such assessment extends classroom testing to better align with engineering practice by examining the ways teams negotiate uncertainty to make engineering decisions. We also identify differing students' reactions to increased uncertainty during tests.Design/Method: Using the methodical framework of design-based research, we analyze performance and reflection data for 117 student teams through two design iterations to explore four design and theoretical conjectures. Results: Teams chose multiple solution paths to this authentic task, an aspect that aligns with the characteristics of engineering practice that we seek to assess. In addition, the technology tool allows the evaluation of procedural accuracy for many of the teams' chosen paths. The teams' decision-making performances correlate; however, decision-making and traditional assessments do not correlate, suggesting they measure different competencies. The computerbased second stage provides a holistic assessment that shifts the messages that students implicitly receive about valued practices in the classroom. However, not all students took up the authentic group assessment in desired ways.Conclusions: Technology-based two-stage exams with authentic assessment show promise to shift testing practices in large engineering classes to include decision-making. Such assessments better align with engineering practices that are valued in the profession, but more work is needed to develop systems for widespread implementation.

The surface coatings applied to engineered nanomaterials (ENMs) during their manufacture have been shown to affect their aggregation behavior in aquatic media. This phenomenon has important implications on the environmental...

There is a critical need to generate environmentally relevant microplastics (MPs) and nanoplastics (NPs) to better investigate their behavior in laboratory settings. Environmental MPs are heterogenous in size and shape, unlike monodisperse and uniform microspheres commonly used as surrogates. Cryogenic grinding, or cryomilling, was successfully utilized to transform polystyrene (PS) bulk material into heterogenous micro and nano fragments. Fourier-Transform Infrared (FTIR) spectroscopy confirmed that this approach did not alter polymer surface chemistry. The number of milling cycles (time of milling) and frequency of grinding (intensity of milling) were varied to investigate the role cryomilling parameters had on generated MP characteristics. The resulting particle size distributions of cryomilled samples were measured and compared. Coulter Counter and Nanoparticle Tracking Analysis (NTA) were used to measure the particle size distributions at the micro and nanoparticle size ranges, respectively. Microspheres were used to determine what camera settings yielded more accurate sizing and to reduce bias in the NTA analysis. Increasing milling cycles generally increased the number of smaller particles. The evolution of the measured size distributions indicated that small nanosized fragments broke off from larger MPs during cryomilling, steadily eroding larger MP fragments. The number of milling cycles was observed to more consistently impact the size distributions of fragments compared to the frequency of milling. This study offers both analysis of the cryomilling process and recommendations for generating more realistic MP/NPs for examining environmental fate and effects.