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Over the course of four years, we have researched and transformed a key course in the career of an undergraduate physics major--junior-level electricity and magnetism. With the aim of educating our majors based on a more complete understanding of the cognitive and conceptual challenges of upper-division courses, we used principles of active engagement and learning theory to develop course materials and conceptual assessments. Our research results from student and faculty interviews and observations also informed our approach.We present several measures of the outcomes of this work at the University of Colorado at Boulder and external institutions. Students in the transformed courses achieved higher learning gains compared to those in the traditionally taught courses, particularly in the areas of conceptual understanding and ability to articulate their reasoning about a problem. The course transformations appear to close a gender gap, improving female students' scores on conceptual and traditional assessments so that they are more similar to those of male students. Students enthusiastically support the transformations, and indicate that several course elements provide useful scaffolding in conceptual understanding, as well as physicists' "habits of mind" such as problem-solving approaches and work habits. Despite these positive outcomes, student conceptual learning gains do not fully meet faculty expectations, suggesting that it is valuable to further investigate how the content and skills indicative of "thinking like a physicist" can be most usefully taught at the upper division. (Contains 1 table and 2 figures.)

As part of an effort to systematically improve our junior-level E&M I course, we have developed a tool to assess student conceptual learning of electrostatics at the upper division. Together with a group of physics faculty, we established a list of learning goals for the course that, with results from student observations and interviews, served as a guide in creating the Colorado Upper-Division Electrostatics (CUE) assessment. The result is a 17-question open-ended post-test diagnostic (with an optional 7-question pretest) and an accompanying grading rubric. We present measures of the validation and reliability of the instrument and grading rubric, plus results from 535 students in both standard and interactive-engagement courses across seven institutions as a baseline for the instrument. Overall, we find that the CUE is a valid and reliable measure, and the data herein are intended to be of use to researchers and faculty interested in using the CUE to measure student learning. (Contains 1 table and 7 figures.)

We discuss common difficulties in upper-division electricity and magnetism (E&M) in the areas of Gauss's law, vector calculus, and electric potential using both quantitative and qualitative evidence. We also show that many of these topical difficulties may be tied to student difficulties with mathematics. At the junior level, some students struggle to combine mathematical calculations and physics ideas, to account for the underlying spatial situation when doing a mathematical calculation, and to access appropriate mathematical tools. We discuss the implications of our findings for E&M instruction at the junior level. (Contains 6 figures.)

The fine-scale temporal patterns of water velocities, accelerations, and velocity gradients encountered by individual zooplankters carried in ambient flow can affect their dispersal, behavior, and interaction with other organisms, but have not yet been measured in realistic flow environments. We focused on zooplankton in wavy turbulent boundary layer flow near benthic communities because such flow affects important processes, including larval settlement and prey capture by benthic zooplanktivores. Flow across fouling communities measured in the field was mimicked in a wave flume, where time-varying velocity fields over biofouled surfaces were quantified using particle image velocimetry (PIV). Trajectories of simulated zooplankters seeded into these flow fields were followed to quantify temporal patterns of velocity gradients and accelerations that individuals encountered. We found that such zooplankters are not subjected to steady velocities or velocity gradients, but rather encounter rapidly fluctuating accelerations and velocity gradients with peaks reaching several orders of magnitude above mean values and lasting fractions of a second, much shorter than the wave period. We calculated the proportion of time zooplankters spent affected (e.g., being damaged, changing behavior) by accelerations or velocity gradients and found that a small increase in mean velocity can cause a much larger increase in time affected. Animal reaction threshold and reaction time also changed the fraction of time they were affected by the flow. Using different PIV spatial resolutions showed that inter-vector spacing should be ≤0.5 Kolmogorov length (smallest eddy scale) to accurately capture velocity gradients along trajectories, but coarser resolutions (≤2-6 × Kolmogorov length) are sufficient for velocities, accelerations, and zooplankton trajectories. Electronic supplementary material The online version of this article (doi:10.1007/s00227-015-2713-x) contains supplementary material, which is available to authorized users., Author(s): Rachel E. Pepper[sup.1] , Jules S. Jaffe[sup.2] , Evan Variano[sup.3] , M. A. R. Koehl[sup.4] Author Affiliations: (1) Department of Physics, University of Puget Sound, Tacoma, WA, USA (2) [...]

Alternative UO2 nuclear fuels, incorporating Cr as a dopant, are currently in use in light–water reactors. Dissolution experiments using Cr-doped UO2, performed as a function of Cr content in a simplified groundwater solution and under oxic conditions, established that the addition of Cr to the UO2 matrix systematically reduced the normalised dissolution rate of U at 25 and 40 °C. This effect was most notable under dilute solution conditions, and is the result of galvanic coupling between Cr and U, resulting from the presence of Cr2+ in the UO2 matrix, as corroborated by activation energy determination. Under conditions of solution saturation, where schoepite ((UO2)8O2(OH)12·(H2O)12) and Na2U2O7·6H2O were identified as secondary phases, the rate of U dissolution was invariant with Cr content. Moreover, at 60 °C, the trend was reversed and the rate of U dissolution increased with increasing Cr content. Under these conditions, other factors, including U solubility or bicarbonate-surface interactions, exert a stronger influence on the U dissolution kinetics than Cr. Increased grain size, a feature of Cr-doped UO2 fuel, was also found to reduce the normalised dissolution rate of U. In establishing the mechanisms by which Cr dopants influence UO2 fuel dissolution, it can be concluded that, overall, Cr-doped UO2 nuclear fuel possesses similar dissolution kinetics to undoped UO2 fuel, giving confidence for its eventual disposal in a geological facility. [ABSTRACT FROM AUTHOR]