arXiv subjects

Emma Hunt

Publications and source records attributed to Emma Hunt.

3 recordsLinked to original sources

arXiv2025

Back-Focal-Plane Imaging and Linear Density Measurements Of Sub-Diffraction Sized Biological Filaments and Particles

Optical tweezers equipped with position detection allow for application of piconewton-scale forces and high-temporal-resolution measurements of nanometer-scale motion. While typically used for trapping microscopic objects, the optical tweezer detection pathway can also be used for a microscopy technique sensitive to nanometer-sized structures. Optical tweezers most commonly use back-focal-plane detection to determine the position of the trapped object. This technique involves analyzing the interference pattern between scattered and unscattered light. Despite the reliance on interference, we show that an image of an extended object can be understood as a sum of the images of individual point-like particles that make up the object. This allows for optical tweezers with back-focal-plane detection to be used as an imaging tool capable of determining the mass distribution of scanned structures. Furthermore, the sample-orientation-dependent detector response allows for a unique method of background subtraction. We demonstrate the quantitative imaging capabilities of optical tweezer microscopy by determining the size distributions multiple nearby particles and measuring the changing diameter of collagen fibrils. The background subtraction technique is demonstrated by imaging surface-bound microtubules with a strong background from protein aggregate co-adsorption. Optical tweezer microscopy allows for quantitative imaging of objects far from the coverslip surface. This makes it an excellent tool for studying the link between the structure and mechanics of microscopic systems.

physics.optics↗

arXiv2023

Group Dynamics in Inquiry-based Labs: Gender Inequities and the Efficacy of Partner Agreements

Recent studies provide evidence that social constructivist pedagogical methods such as active learning, interactive engagement, and inquiry-based learning, while pedagogically more effective, can enable inequities in the classroom. By conducting a quantitative empirical examination of gender-inequitable group dynamics in two inquiry-based physics labs, we extend results of previous work. Using a survey on group work preferences and video recordings of lab sessions, we find similar patterns of gendered role-taking noted in prior studies. These results are not reducible to differences in students' preferences. We find that an intervention which employed partner agreement forms, with the goal of reducing inequities, had a positive impact on students' engagement with equipment during a first-semester lab course. Our work will inform implementation of more effective interventions in the future and emphasizes challenges faced by instructors who are dedicated to both research-based pedagogical practices and efforts to promote diversity, equity, and inclusion in their classrooms.

physics.ed-ph↗

arXiv2019

A window into NV center kinetics via repeated annealing and spatial tracking of thousands of individual NV centers

Knowledge of the nitrogen-vacancy center formation kinetics in diamond is critical to engineering sensors and quantum information devices based on this defect. Here we utilize the longitudinal tracking of single NV centers to elucidate NV defect kinetics during high-temperature annealing from 800-1100 $^\circ$C in high-purity chemical-vapor-deposition diamond. We observe three phenomena which can coexist: NV formation, NV quenching, and NV orientation changes. Of relevance to NV-based applications, a 6 to 24-fold enhancement in the NV density, in the absence of sample irradiation, is observed by annealing at 980 $^\circ$C, and NV orientation changes are observed at 1050 $^\circ$C. With respect to the fundamental understanding of defect kinetics in ultra-pure diamond, our results indicate a significant vacancy source can be activated for NV creation between 950-980 $^\circ$C and suggests that native hydrogen from NVH$_y$ complexes plays a dominant role in NV quenching, in agreement with recent {\it ab initio} calculations. Finally, the direct observation of orientation changes allows us to estimate an NV diffusion barrier of 5.1~eV.

cond-mat.mtrl-sci↗