Introductory Physics In Biological Context: An Approach To Improve Introductory Physics For Life Science Students

We describe restructuring the introductory physics for life science students (IPLS) course to better support these students in using physics to understand their chosen fields. Our courses teach physics using biologically rich contexts. Specifically, we use examples in which fundamental physics contributes significantly to understanding a biological system to make explicit the value of physics to the life sciences. This requires selecting the course content to reflect the topics most relevant to biology while maintaining the fundamental disciplinary structure of physics. In addition to stressing the importance of the fundamental principles of physics, an important goal is developing students\u27 quantitative and problem solving skills. Our guiding pedagogical framework is the cognitive apprenticeship model, in which learning occurs most effectively when students can articulate why what they are learning matters to them. In this article, we describe our courses, summarize initial assessment data, and identify needs for future research. (C) 2014 American Association of Physics Teachers

Sources Of Student Engagement In Introductory Physics For Life Sciences

We explore the sources of student engagement with curricular content in an Introductory Physics for Life Science (IPLS) course at Swarthmore College. Do IPLS students find some life-science contexts more interesting than others, and, if so, what are the sources of these differences? We draw on three sources of student data to answer this question: (1) quantitative survey data illustrating how interested students were in particular contexts from the curriculum, (2) qualitative survey data in which students describe the source of their interest in these particular contexts, and (3) interview data in which students reflect on the contexts that were and were not of interest to them. We find that examples that make interdisciplinary connections with students’ other coursework in biology and chemistry, and examples that make connections to what students perceive to be the “real world,” are particularly effective at fostering interest. More generally, students describe being deeply engaged with contexts that foster a sense of coherence or have personal meaning to them. We identify various “engagement pathways” by which different life-science students engage with IPLS content, and suggest that a curriculum needs to be flexible enough to facilitate these different pathways

Reducing The Gender Gap In The Physics Classroom

We investigate if the gender gap in conceptual understanding in an introductory university physics course can be reduced by using interactive engagement methods that promote in-class interaction, reduce competition, foster collaboration, and emphasize conceptual understanding. To this end we analyzed data from the introductory calculus-based physics course for non-majors at Harvard University taught traditionally or using different degrees of interactive engagement. Our results show that teaching with certain interactive strategies not only yields significantly increased understanding for both males and females, but also reduces the gender gap. In the most interactively taught courses, the pre-instruction gender gap was gone by the end of the semester. (c) 2006 American Association of Physics Teachers

Initial Interest, Goals, And Changes In CLASS Scores In Introductory Physics For Life Sciences

To examine the effect of extensive life science applications on student attitudes to learning physics, we analyzed CLASS data from life science students in introductory physics. We compare the same students\u27 responses from the first semester, taught with a standard syllabus, to the second semester, taught with extensive life science applications (IPLS). Although first semester responses become less favorable (pre to post), IPLS responses show an increase in favorable and a decrease in unfavorable responses. This is noteworthy because improvement is rarely observed without direct attention to attitudes/beliefs, and suggests IPLS courses are one possible approach to improving attitudes. Finally, we analyzed CLASS responses by gender, major, students\u27 stated goals in taking physics, and initial interest in physics; initial interest was determined from CLASS items chosen based on the Four-Phase Model of Interest Development. Most notably, we find that in the IPLS course, students identified as having low interest initially had the greatest gains

Life Science Students’ Attitudes, Interest, And Performance In Introductory Physics For Life Sciences: An Exploratory Study

In response to national calls for improved physical sciences education for students pursuing careers in the life sciences and medicine, reformed introductory physics for life sciences (IPLS) courses are being developed. This exploratory study is among the first to assess the effect of an IPLS course on students’ attitudes, interest, and performance. The IPLS course studied was the second semester of introductory physics, following a standard first semester course, allowing the outcomes of the same students in a standard course and in an IPLS course to be compared. In the IPLS course, each physics topic was introduced and elaborated in the context of a life science example, and developing students’ skills in applying physics to life science situations was an explicitly stated course goal. Items from the Colorado Learning about Science Survey were used to assess change in students’ attitudes toward and their interest in physics. Whereas the same students’ attitudes declined during the standard first semester course, we found that students’ attitudes toward physics hold steady or improve in the IPLS course. In particular, students with low initial interest in physics displayed greater increases in both attitudes and interest during the IPLS course than in the preceding standard course. We also find that in the IPLS course, students’ interest in the life science examples is a better predictor of their performance than their pre-IPLS interest in physics. Our work suggests that the life science examples in the IPLS course can support the development of student interest in physics and positively influence their performance

Collective Fluorescence Enhancement In Nanoparticle Clusters

Many nanoscale systems are known to emit light intermittently under continuous illumination. In the fluorescence of single semiconductor nanoparticles, the distributions of bright and dark periods (\u27on\u27 and \u27off\u27 times) follow Levy statistics. Although fluorescence from single-quantum dots and from macroscopic quantum dot ensembles has been studied, there has been little study of fluorescence from small ensembles. Here we show that blinking nanorods (NRs) interact with each other in a cluster, and the interactions affect the blinking statistics. The on-times in the fluorescence of a NR cluster increase dramatically; in a cluster with N NRs, the maximum on-time increases by a factor of N or more compared with the combined signal from N well-separated NRs. Our study emphasizes the use of statistical properties in identifying the collective dynamics. The scaling of this interaction-induced increase of on-times with number of NRs reveals a novel collective effect at the nanoscale

Classroom Demonstrations: Learning Tools Or Entertainment?

We compared student learning from different modes of presenting classroom demonstrations to determine how much students learn from traditionally presented demonstrations, and whether learning can be enhanced by simply changing the mode of presentation to increase student engagement. We find that students who passively observe demonstrations understand the underlying concepts no better than students who do not see the demonstration at all, in agreement with previous studies. Learning is enhanced, however, by increasing student engagement; students who predict the demonstration outcome before seeing it, however, display significantly greater understanding

Femtosecond Laser-Induced Formation Of Submicrometer Spikes On Silicon In Water

We fabricate submicrometer silicon spikes by irradiating a siliconsurface that is submerged in water with 400 nm, 100 fs laser pulses. These spikes are less than a micrometer tall and about 200 nm wide—one to two orders of magnitude smaller than the microspikes formed by laser irradiation of silicon in gases or vacuum. Scanning electron micrographs of the surface show that the formation of the spikes involves a combination of capillary waves on the molten siliconsurface and laser-induced etching of silicon. Chemical analysis and scanning electron microscopy of the spikes show that they are composed of silicon with a 20-nm-thick surface oxide layer

Visible And Near-Infrared Responsivity Of Femtosecond Laser-Structured Photodiodes

We investigated the current-voltage characteristics and responsivity of photodiodes fabricated with silicon that was microstructured by use of femtosecond-laser pulses in a sulfur-containing atmosphere. The photodiodes that we fabricated have a broad spectral response ranging from the visible to the near infrared (400-1600 nm). The responsivity depends on substrate doping, microstructuring fluence, and annealing temperature. We obtained room-temperature responsivities as high as 100 A/W at 1064 nm, 2 orders of magnitude higher than for standard silicon photodiodes. For wavelengths below the bandgap we obtained responsivities as high as 50 mA/W at 1330 nm and 35 mA/W at 1550 nm

Fluorescence Blinking Statistics From CdSe Core And Core/Shell Nanorods

We report fluorescence blinking statistics measured from single CdSe nanorods (NRs) of seven different sizes with aspect ratios ranging from 3 to 11. This study also 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, P(tau(on)) similar to tau(-alpha)(on)e(on)(-tau)(/tau c). The measured crossover time, tau(c), is indistinguishable within experimental uncertainty for core and core/shell NRs, as well as for core NRs with different ligands, for the same core size, indicating that surface passivation does not affect the blinking statistics significantly. We find that, at fixed excitation intensity, 1/tau(c) increases approximately linearly with increasing NR aspect ratio; for a given sample, 1/tau(c) increases very gradually with increasing excitation intensity. Examining 1/tau(c) versus the single-particle photon absorption rate 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