An official website of the United States government
Abstract In this paper, we discuss our experience in collaborating with mathematicians to increase their use of active learning pedagogy in a proof-based linear algebra course. The mathematicians we worked with valued using active learning pedagogy to increase student engagement but were reluctant to use active learning pedagogy due to time constraints. Our mathematicians perceived obligations in their teaching that increased the time it would take to implement some of the active learning pedagogy that we suggested, leading them to view this pedagogy as inviable. By attending to mathematicians’ obligations, we were able to design active learning strategies that met the interests and needs of the mathematics educators and mathematicians collaborating on this project.
more »
« less
Spatiotemporal control of structure and dynamics in a polar active fluid
We apply optimal control theory to drive a polar active fluid into new behaviors: relocating asters, reorienting waves, and on-demand switching between states. This study reveals general principles to program active matter for useful functions.
more »
« less
- PAR ID:
- 10589906
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Soft Matter
- Volume:
- 20
- Issue:
- 35
- ISSN:
- 1744-683X
- Page Range / eLocation ID:
- 7059 to 7071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Topological defects play a central role in the physics of many materials, including magnets, superconductors, and liquid crystals. In active fluids, defects become autonomous particles that spontaneously propel from internal active stresses and drive chaotic flows stirring the fluid. The intimate connection between defect textures and active flow suggests that properties of active materials can be engineered by controlling defects, but design principles for their spatiotemporal control remain elusive. Here, we propose a symmetry-based additive strategy for using elementary activity patterns, as active topological tweezers, to create, move, and braid such defects. By combining theory and simulations, we demonstrate how, at the collective level, spatial activity gradients act like electric fields which, when strong enough, induce an inverted topological polarization of defects, akin to a negative susceptibility dielectric. We harness this feature in a dynamic setting to collectively pattern and transport interacting active defects. Our work establishes an additive framework to sculpt flows and manipulate active defects in both space and time, paving the way to design programmable active and living materials for transport, memory, and logic.more » « less
-
Abstract BackgroundThe University of California system has a novel tenure-track education-focused faculty position called Lecturer with Security of Employment (working titles: Teaching Professor or Professor of Teaching). We focus on the potential difference in implementation of active-learning strategies by faculty type, including tenure-track education-focused faculty, tenure-track research-focused faculty, and non-tenure-track lecturers. In addition, we consider other instructor characteristics (faculty rank, years of teaching, and gender) and classroom characteristics (campus, discipline, and class size). We use a robust clustering algorithm to determine the number of clusters, identify instructors using active learning, and to understand the instructor and classroom characteristics in relation to the adoption of active-learning strategies. ResultsWe observed 125 science, technology, engineering, and mathematics (STEM) undergraduate courses at three University of California campuses using the Classroom Observation Protocol for Undergraduate STEM to examine active-learning strategies implemented in the classroom. Tenure-track education-focused faculty are more likely to teach with active-learning strategies compared to tenure-track research-focused faculty. Instructor and classroom characteristics that are also related to active learning include campus, discipline, and class size. The campus with initiatives and programs to support undergraduate STEM education is more likely to have instructors who adopt active-learning strategies. There is no difference in instructors in the Biological Sciences, Engineering, or Information and Computer Sciences disciplines who teach actively. However, instructors in the Physical Sciences are less likely to teach actively. Smaller class sizes also tend to have instructors who teach more actively. ConclusionsThe novel tenure-track education-focused faculty position within the University of California system represents a formal structure that results in higher adoption of active-learning strategies in undergraduate STEM education. Campus context and evolving expectations of the position (faculty rank) contribute to the symbols related to learning and teaching that correlate with differential implementation of active learning.more » « less
-
Abstract Active restoration often aims to accelerate ecosystem recovery. However, active restoration may not be worthwhile if its effects are overwhelmed by changes that occur passively. Moreover, it can be challenging to separate the effects of passive processes, such as dispersal and natural succession, from active restoration efforts.We assess the 24‐year impact of actively restoring a Minnesota old‐field grassland via seed addition of native tallgrass prairie species. We compared the abundance of four functional plant groups in actively restored plots against abundances in three reference classes: (1) unrestored plots undergoing passive recovery within the same old field, (2) passively recovering plots in two nearby old fields of similar age and (3) a chronosequence of 21 old fields within the same landscape.Active restoration led to a higher abundance of native grasses and forbs in the 36 m2treatment plots. Seed addition was more effective if the original vegetation was first removed using herbicide, burning and tilling. However, long‐term conclusions about the efficacy of active restoration varied widely depending on the choice of reference class.In our small‐scale restoration experiment, native abundance was similarly high in both the actively restored and reference plots after 24 years, suggesting either (1) passive recovery or (2) local dispersal of native species from nearby treatment plots (i.e. cross‐contamination). In contrast, a comparison with two nearby reference fields suggested active restoration resulted in much higher native abundance relative to passive recovery. A smaller, positive effect was detected when we compared actively restored plots to the chronosequence of old fields. In the chronosequence, many passively recovering old fields had transitioned to native grass dominance naturally, although active restoration appeared to increase native forb abundance.Synthesis and applications: Our findings highlight the importance of using scale‐appropriate references for assessing the efficacy and need for active restoration. Comparing actively restored plots with the surrounding landscape, we found that active restoration and passive recovery led to similar plant communities after 24 years. Because local dispersal from actively restored sites can nearby references, caution should be exercised when evaluating long‐term restoration projects using only small‐scale experiments.more » « less
-
PurposeAn MRI scanner is equipped with global shim systems for shimming one region of interest (ROI) only. However, it often fails to reach state‐of‐the‐art when shimming two isolated regions of interest simultaneously, even though the two‐area shimming can be essential in scan scenarios, such as bilateral breasts or dyadic brains. To address these challenges, a hybrid active and passive local shimming technique is proposed to simultaneously shim two isolated region‐of‐interest areas within the whole FOV. MethodsA local passive shimming system is constructed by optimized bilateral ferromagnetic chip arrays to compensate for the magnet's significant high‐order B0inhomogeneities at the boundary of the manufacturer's specified homogeneous volume, thus locally improving the available FOV. The local active shimming consists of 40‐channel DC loops powered by 64‐channel current amplifiers. With the optimized current distribution, active shimming can correct the residual low‐order B0inhomogeneities and subject‐specific field inhomogeneities. In addition, active shimming is used to homogenize the center frequencies of the two regions. ResultsWith the implementation of the hybrid active and passive local shimming, the 95% peak‐to‐peak was reduced from 1.92 to 1.12 ppm by 41.7%, and RMS decreased from 0.473 to 0.255 ppm by 46.1% in a two‐phantom experiment. The volume ratio containing MR voxels within a 0.5‐ppm frequency span increased from 64.3% to 81.3% by 26.3%. ConclusionThe proposed hybrid active and passive local shimming technique uses both passive and active local shimming, and it can efficiently shim two areas simultaneously, which is an unmet need for a commercial MRI scanner.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d4sm00547c
