Investigating Formations on Titanium Surfaces for Enhanced Fluid-Surface Interactions

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US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference

Enhanced Zika virus susceptibility of globally invasive Aedes aegypti populations

The drivers and patterns of zoonotic virus emergence in the human population are poorly understood. The mosquito Aedes aegypti is a major arbovirus vector native to Africa that invaded most of the world’s tropical belt over the past four centuries, after the evolution of a “domestic” form that specialized in biting humans and breeding in water storage containers. Here, we show that human specialization and subsequent spread of A. aegypti out of Africa were accompanied by an increase in its intrinsic ability to acquire and transmit the emerging human pathogen Zika virus. Thus, the recent evolution and global expansion of A. aegypti promoted arbovirus emergence not solely through increased vector–host contact but also as a result of enhanced vector susceptibility

Student representational competence and self-assessment when solving physics problems

Student success in solving physics problems is related to the representational format of the problem. We study student representational competence in two large-lecture algebra-based introductory university physics courses with approximately 600 participants total. We examined student performance on homework problems given in four different representational formats (mathematical, pictorial, graphical, verbal), with problem statements as close to isomorphic as possible. In addition to the homeworks, we examine students’ assessment of representations by providing follow-up quizzes in which they chose between various problem formats. As a control, some parts of the classes were assigned a random-format follow-up quiz. We find that there are statistically significant performance differences between different representations of nearly isomorphic statements of quiz and homework problems. We also find that allowing students to choose which representational format they use improves student performance under some circumstances and degrades it in others. Notably, one of the two courses studied shows much greater performance differences between the groups that received a choice of format and those that did not, and we consider possible causes. Overall, we observe that student representational competence is tied to both micro- and macrolevel features of the task and environment

Effect of instructional environment on physics students’ representational skills

In a recent study we showed that physics students’ problem-solving performance can depend strongly on problem representation, and that giving students a choice of problem representation can have a significant impact on their performance [P. B. Kohl and N. D. Finklestein, Phys. Rev. ST. Phys. Educ. Res. 1, 010104 (2005)] In this paper, we continue that study in an attempt to separate the effect of instructional technique from the effect of content area. We determine that students in a reform-style introductory physics course are learning a broader set of representational skills than those in a more traditional course. We also analyze the representations used in each course studied and find that the reformed course makes use of a richer set of representations than the traditional course and also makes more frequent use of multiple representations. We infer that this difference in instruction is the source of the broader student skills. These results provide insight into how macrolevel features of a course can influence student skills, complementary to the microlevel picture provided by the first study

Patterns of multiple representation use by experts and novices during physics problem solving

It is generally believed that students should use multiple representations in solving certain physics problems, and earlier work in PER has begun to outline how experts and novices differ in their use of multiple representations. In this study, we build on this foundation by interviewing expert and novice physicists as they solve two types of multiple representation problems: those in which multiple representations are provided for them and those in which the students must construct their own representations. We analyze in detail the types of representations subjects use and the order and manner in which they are used. Expert and novice representation use is surprisingly similar in some ways, especially in that both experts and novices make significant use of multiple representations. Some significant differences also emerge. Experts are more flexible in terms of starting point and move between the available representations more quickly, and novices tend to move between more representations in total. In addition, we find that an examination of how often and when multiple representations are used is inadequate to fully characterize a problem-solving episode; one must also consider the purpose behind the use of the available representations. This analysis of how experts and novices use representations sharpens the differences between the two groups, demonstrates analysis techniques that may be useful in future work, and suggests possible paths for instruction

Effects of representation on students solving physics problems: A fine-grained characterization

Recent papers document that student problem-solving competence varies (often strongly) with representational format, and that there are significant differences between the effects that traditional and reform-based instructional environments have on these competences [Kohl and Finkelstein, Phys. Rev. ST Phys. Educ. Res. 1, 010104 (2005); Kohl and Finkelstein, Phys. Rev. ST Phys. Educ. Res. 2, 010102 (2006)]. These studies focused on large-lecture introductory physics courses, and included aggregate data on student performance on quizzes and homeworks. In this paper, we complement previous papers with finer-grained in-depth problem-solving interviews. In 16 interviews of students drawn from these classes, we investigate in more detail how and when student problem-solving performance varies with problem representation (verbal, mathematical, graphical, or pictorial). We find that student strategy often varies with representation, and that in this environment students who show more strategy variation tend to perform more poorly. We also verify that student performance depends sensitively on the particular combination of representation, topic, and student prior knowledge. Finally, we confirm that students have generally robust opinions of their representational skills, and that these opinions correlate poorly with their actual performances