Automated NanoSIMS Measurements of Spinel Stardust from the Murray Meteorite

We report new O isotopic data on 41 presolar oxide grains, 38 MgAl2O4 (spinel) and 3 Al2O3 from the CM2 meteorite Murray, identified with a recently developed automated measurement system for the NanoSIMS. We have also obtained Mg-Al isotopic results on 29 of the same grains (26 spinel and 3 Al2O3). The majority of the grains have O isotopic compositions typical of most presolar oxides, fall well into the four previously defined groups, and are most likely condensates from either red giant branch or asymptotic giant branch stars. We have also discovered several grains with more unusual O and Mg compositions suggesting formation in extreme astrophysical environments, such as novae and supernovae. One of these grains has massive enrichments in 17O, 25Mg, and 26Mg, which are isotopic signatures indicative of condensation from nova ejecta. Two grains of supernova origin were also discovered: one has a large 18O/16O ratio typical of Group 4 presolar oxides; another grain is substantially enriched in 16O, and also contains radiogenic 44Ca from the decay of 44Ti, a likely condensate from material originating in the O-rich inner zones of a Type II supernova. In addition, several Group 2 presolar spinel grains also have large 25Mg and 26Mg isotopic anomalies that are difficult to explain by standard nucleosynthesis in low-mass stars. Auger elemental spectral analyses were performed on the grains and qualitatively suggest that presolar spinel may not have higher-than- stoichiometric Al/Mg ratios, in contrast to SIMS results obtained here and reported previously.Comment: 58 pages, 10 figures, 1 table, published in Ap

Force Concept Inventory: More than just conceptual understanding

The Force Concept Inventory (FCI) can serve as a summative assessment of students’ conceptual knowledge at the end of introductory physics, but previous work has suggested that the knowledge measured by this instrument is not a unitary construct. In this article, we consider the idea that FCI performance may reflect a number of student attributes including relational knowledge structures of physics concepts, expertlike attitudes, and problem-solving skills. Using a large calculus-based introductory physics course, we show that knowledge of conceptual relationships (i.e., knowledge structures), attitudinal measures, and problem-solving ability are all measures that uniquely contribute to a postinstruction FCI score. While these associations do not reveal the nature of their relation to the FCI (it could be that good students perform well on all these measures), they do provide evidence that improving any one of these aspects may improve a student’s overall FCI score

Understanding the relationship between student attitudes and student learning

Student attitudes, defined as the extent to which one holds expertlike beliefs about and approaches to physics, are a major research topic in physics education research. An implicit but rarely tested assumption underlying much of this research is that student attitudes play a significant part in student learning and performance. The current study directly tested this attitude-learning link by measuring the association between incoming attitudes (Colorado Learning Attitudes about Science Survey) and student learning during the semester after statistically controlling for the effects of prior knowledge [early-semester Force Concept Inventory (FCI) or Brief Electricity and Magnetism Assessment (BEMA)]. This study spanned four different courses and included two complementary measures of student knowledge: late-semester concept inventory scores (FCI or BEMA) and exam averages. In three of the four courses, after controlling for prior knowledge, attitudes significantly predicted both late-semester concept inventory scores and exam averages, but in all cases these attitudes explained only a small amount of variance in concept-inventory and exam scores. Results indicate that after accounting for students’ incoming knowledge, attitudes may uniquely but modestly relate to how much students learn and how well they perform in the course

Dissociative conceptual and quantitative problem solving outcomes across interactive engagement and traditional format introductory physics

The existing literature indicates that interactive-engagement (IE) based general physics classes improve conceptual learning relative to more traditional lecture-oriented classrooms. Very little research, however, has examined quantitative problem-solving outcomes from IE based relative to traditional lecture-based physics classes. The present study included both pre- and post-course conceptual-learning assessments and a new quantitative physics problem-solving assessment that included three representative conservation of energy problems from a first-semester calculus-based college physics course. Scores for problem translation, plan coherence, solution execution, and evaluation of solution plausibility were extracted for each problem. Over 450 students in three IE-based sections and two traditional lecture sections taught at the same university during the same semester participated. As expected, the IE-based course produced more robust gains on a Force Concept Inventory than did the lecture course. By contrast, when the full sample was considered, gains in quantitative problem solving were significantly greater for lecture than IE-based physics; when students were matched on pre-test scores, there was still no advantage for IE-based physics on gains in quantitative problem solving. Further, the association between performance on the concept inventory and quantitative problem solving was minimal. These results highlight that improved conceptual understanding does not necessarily support improved quantitative physics problem solving, and that the instructional method appears to have less bearing on gains in quantitative problem solving than does the kinds of problems emphasized in the courses and homework and the overlap of these problems to those on the assessment

Multiyear, multi-instructor evaluation of a large-class interactive-engagement curriculum

Interactive-engagement (IE) techniques consistently enhance conceptual learning gains relative to traditional-lecture courses, but attitudinal gains typically emerge only in small, inquiry-based curricula. The current study evaluated whether a “scalable IE” curriculum—a curriculum used in a large course (∼130 students per section) and likely adoptable by a wide range of physics departments—could produce significant attitudinal benefits relative to a traditional-lecture curriculum. This study included data across three years, 10 instructors, over 30 sections, and over 1100 students, and our analytic strategy allowed us to isolate the effects that were due to the curriculum itself rather than other potential factors such as instructor differences or preexisting differences among students. Results revealed that our Active-Physics curriculum, which is based on Moore’s Six Ideas That Shaped Physics, produced significant attitudinal and conceptual-learning benefits relative to our traditional-lecture physics curriculum. Further, the Active-Physics curriculum, for the most part, benefitted males and females equally, and relative to the Fall semester alone, the benefits of Active Physics became more robust when viewed across the entire two-semester sequence of introductory physics. Our data highlight that some (though not all) of the attitudinal benefits of small, inquiry-based courses may be achievable in larger course with scalable IE curricula that can potentially reach a large proportion of introductory physics students