Single-Molecule Techniques for Studying Molecular Machines
Dr. Paul Pease,

Sr. Business Development Scientist
LUMICKS

Monday, April 15, 3:00-4:00pm, 221 South Engineering

Refreshments at 2:30

At the heart of biological processes are complex molecular machines that operate at some of the smallest scales of distance, force, and time. In this seminar I will discuss some of the challenges and limitations of traditional approaches to understanding these molecular machines and review some of the single-molecule techniques that have enabled an exciting array of discoveries. In particular, I will focus on optical tweezers and the mechanistic insights that can be gained from correlative measurements of forces and single-molecule imaging. Specific examples will include the role of DNA topology in CRSPR gene editing, direct measurements of cytoskeleton motor proteins under external loads, measurements of cellular membrane tension propagation, and the physical properties of biomolecular condensates.

INVESTIGATION OF 2D POLYMER THIN FILMS IN 3D STRUCTURES INVOLVING CRUMPLING, ORIGAMI, KIRIGAMI AND ADHESION

Wathsala M. A. Jayawardana

Candidate for Ph.D.
Department of Physics,
North Dakota State University

Wednesday, Mar. 27, 3:00-4:00pm, 221 South Engineering. <Zoom link available upon request>

This dissertation delves into the fascinating world of thin films and their ability to transform into three-dimensional (3D) structures. One can simply crush a sheet of paper into a ball to make a 3D object faster, yet complex structure or by following a more organized folding technique (Origami) to create 3D objects with predictable structures. This dissertation mainly focuses on such 3D structures and introduces cuts (Kirigami) and adhesion to those 3D structures to understand more of their mechanical behavior.

 The investigation of polymer crumple mechanics by introducing the Kirigami approach, exploring how the sheet's topology influences crumpling, is discussed in this dissertation, which employs confocal microscopy, force experiments, and molecular dynamics simulations to investigate the effects of cutting on the behavior of crumpled sheets. The findings reveal that cutting does not significantly alter the compressive behavior; force scales according to a power law regardless of cuts, with only minor reductions in magnitudes.

The second chapter of this dissertation studies Origami-inspired adhesive capable of securely holding objects on a wall yet easily removable without damage, which should withstand significant forces when attached, then swiftly transition to a low-adhesion state for removal. Bi-stability of the proposed Origami designs with different compliance to achieve noticeable switching ratios has been investigated. These devices demonstrate moderate switching ratios and scalability, offering potential for arrayed applications through repetition of the Origami pattern.

Crumples combined with adhesion create stable 3D structures made from elastic thin sheets. The last chapter discusses the impact mitigation of such crumpling systems by observing sticky crumpled matter subjected to simple ball drop tests. These findings highlight the potential utility of sticky crumples as replacements for intricate engineered structures in protective layers.

How does adhesion work?
Dr. Andrew B. Croll

Professor,
Department of Physics,
North Dakota State University

Monday, March 25, 3:00-4:00pm, 208 South Engineering

Refreshments at 2:30

In this talk I will attempt to show how non-specific atom-scale forces result in macroscopic-scale outcomes such as adhesion.  I will begin with a review of the basic continuum ideas of surface science which lead to simple results like spherical-cap droplets on surfaces.  Next, I will show how an understanding of mechanics (fracture, really) is necessary to connect the microscopic details of surfaces to the macroscopic world that might try to separate them.  Finally, I will show practical results from our recent work examining the adhesion of silicone elastomers.  Specifically, I will show how viscoelasticity is a critical issue for understanding the adhesion of elastomers, compare our results to some recent theoretical models and point some classical polymer physics along the way.

Applying Theoretical Frameworks from Cognitive Psychology to Assess Faculty Professional

Alistair McIrney

Candidate for Ph.D.
Department of Physics,
North Dakota State University

Monday, Mar. 25, 1:00-2:00pm, <ONLINE ONLY, SEE EMAIL FOR LINK>

Refreshments at 2:30

Understanding human behavior and reasoning is essential for developing successful instruction.  Discipline-based education researchers have examined how students learn, informing the development of successful instructional strategies.  Research has also identified barriers to the successful implementation of such strategies and the need for professional development.  This work utilizes two theoretical frameworks from psychology to examine: (1) efforts to enact instructional change and (2) instructional approaches designed to improve students' reasoning in physics.  The Theory of Planned Behavior (TPB) is used to assess professional development to support the successful implementation of evidence-based instructional strategies.  The Dual-Process Theories of Reasoning (DPToR) are used to model human reasoning and explain persistent inconsistencies in student responses.  Guided by the TPB, an assessment instrument was created, validated, and implemented to evaluate instructor’s beliefs and intentions about active-learning methodologies.  The inconsistencies in student reasoning are examined using the DPToR, which describes reasoning in terms of two processes. Process 1 is quick but frequently inaccurate.  Process 2 is analytical but time-consuming and effortful. Three different types of DPToR-informed instructional interventions are implemented to help students develop skills to navigate reasoning hazards. Data from introductory calculus-based physics classes will be presented and implications for instruction will be discussed.

Combining the Bethe-Salpeter Equation, Kadanoff-Baym-Keldysh Technique, and Redfield Theory for an Improved Description of Semiconductor Nanocrystal Observables

Hadassah Griffin

Candidate for Ph.D.
Department of Physics,
North Dakota State University

Monday, Mar. 18, 12:00-1:00pm, 120 South Engineering.

Refreshments at 2:30

Semiconductor nanocrystals (NCs) are used in devices such as solar cells. The physical behavior of NCs can be described by different ab initio methods. For my doctoral research, I am combining the Bethe-Salpeter Equation (BSE), Kadanoff-Baym-Keldysh (KBK) technique, and Redfield Theory to describe NCs. The BSE describes exciton effects which are necessary for an accurate description of NCs. The KBK technique can be used to construct the Boltzmann Transport equation for different relaxation channels in a photo-excited nonequilibrium systems including exciton effects. Redfield Theory describes quantum system dynamics for a system weakly coupled to an external thermal bath. By combining aspects of these methods, my goal is to improve descriptions of NC observables. In this work, I present a review of these methods, preliminary results for Si, Pb, and Janus quantum dot NCs which were calculated by combining BSE output with Redfield Theory, and future plans for my doctoral study.

Equitable Grading Research & Practice in Physics & other STEM Courses
Dr. Cassandra Paul

Associate Professor,
Physics & Astronomy/Science Education Program
San José State University

Tuesday, March 19th, 2:00-3:00pm, 116 South Engineering

In higher education, the role of grades is paramount. The grade that students receive in each course communicates to the institution the degree to which the student was successful. Passing grades indicate that students are able to continue on to more advanced courses in the same topical area. Enough poor grades can cause a student to fail a course and, as a function of the individual university, this can in turn affect the student’s time-to-degree, their retention in a major, or even in their retention in college itself. However, despite its importance, many faculty receive little to no instruction on how to assign grades. I will discuss four different grading strategies that have been shown to decrease equity gaps in physics and other STEM courses:revise/retake options; minimum grading/4.0 scale; ungrading; and course component weighting. I will review some research behind these options, their effect on different students, and some practical ideas for how to implement them in your classroom.

Archive of Past Seminars

o either subscribe to or unsubscribe from this listserve please send an email to Listserv@listserv.nodak.edu with an empty subject and containing a body of
SUB NDSU-PHYSICS-SEMINAR or SIGNOFF NDSU-PHYSICS-SEMINAR respectively.