arXiv subjects

Catherine H. Crouch

Publications and source records attributed to Catherine H. Crouch.

3 recordsLinked to original sources

arXiv2022

The role of introductory physics for life sciences in supporting students to use physical models flexibly

A central goal of Introductory Physics for the Life Sciences (IPLS) is to prepare students to use physics to model and analyze biological situations, a skill of increasing importance for their future studies and careers. Here we report our findings on life science students' ability to carry out a sophisticated biological modeling task at the end of first-semester introductory physics. Some students were enrolled in a standard course (N = 34), and some in an IPLS course (N = 61); both courses were taught with active learning, used calculus, and included the same core physics concepts. Compared to those who took the standard course, we found that the IPLS students were significantly more successful at building a model that combined ideas in a manner they had not previously seen, and at making complex decisions about how to apply an equation to a particular physical situation, although both groups displayed similar success at solving simpler problems. Both groups identified and applied simple models that they had previously used in very similar contexts, and executed straightforward calculations, at statistically indistinguishable rates. We report both our findings and the rationale behind the development of the task, in the hopes that others may find this task either a valuable tool or a starting point to develop other such tasks. Further study is needed to determine the basis for the IPLS students' stronger performance--namely, what aspects of the IPLS course supports these students to be better prepared to do such modeling--as well as whether biological settings are important for IPLS students to succeed in flexible model building, and whether the ability to employ models flexibly persists over time.

physics.ed-ph↗

arXiv2021

The impact of introductory physics for the life sciences in a senior biology capstone course

A goal of Introductory Physics for Life Sciences (IPLS) curricula is to prepare students to effectively use physical models and quantitative reasoning in biological and medical settings. To assess whether this goal is being met, we conducted a longitudinal study of the impact of IPLS on student work in later biology and chemistry courses. We report here on one part of that study, a comparison of written responses by students with different physics backgrounds on a diffusion task administered in a senior biology capstone course. We observed differences in student reasoning that were associated with prior or concurrent enrollment in IPLS. In particular, we found that IPLS students were more likely than non-IPLS students to reason quantitatively and mechanistically about diffusive phenomena, and to successfully coordinate between multiple representations of diffusive processes, even up to two years after taking the IPLS course. Finally, we describe methodological challenges encountered in both this task and other tasks used in our longitudinal study.

physics.ed-ph↗

arXiv2006

Fluorescence blinking statistics from single CdSe nanorods

We report fluorescence blinking statistics measured from single CdSe nanorods (NRs) of seven different sizes with aspect ratio ranging from 3 to 11. This study included core/shell CdSe/ZnSe NRs and core NRs with two different surface ligands producing different degrees of surface passivation. We compare the findings for NRs to our measurements of blinking statistics from spherical CdSe core and CdSe/ZnS core/shell nanocrystals (NCs). We find that for both NRs and spherical NCs, the off-time probability distributions are well described by a power law, while the on-time probability distributions are best described by a truncated power law. The measured crossover time is indistinguishable within experimental uncertainty for core and core/shell NRs, and for core NRs with different ligands, indicating that surface passivation does not affect the blinking statistics significantly. We find that at fixed excitation intensity, the inverse crossover time increases approximately linearly with increasing NR aspect ratio; for a given sample, the inverse crossover time increases very gradually with increasing excitation intensity. The measured per-particle absorption cross section for all samples indicates that the change in NR absorption cross-section with sample size can account for some but not all of the differences in crossover time. This suggests that the degree of quantum confinement may be partially responsible for the aspect ratio dependence of the crossover time.

cond-mat.mtrl-sci↗