Abstracts: Friday, February 17th


Merci Best | Neuroscience
BMP Regulation of Germline Development During Testis Stem Cell Niche Formation
Advisor: Matthew Wawersik
Stem cells are vital for organogenesis, tissue regeneration, and tissue homeostasis and it is important to understanding how these cells first form. To better understand mechanisms regulating stem cell development, we are examining testis stem cell niche formation in Drosophila melanogaster. In adult testes, the stem cell niche is comprised of a tightly clustered group of cells which act as a signaling center to regulate sperm-producing germline stem cells (GSCs) as well as somatic cyst stem cells (CySCs). Bone Morphogenetic Protein (BMP) signaling from CySCs to GSCs has also been shown to regulate GSC maintenance in adult and larval gonads (Leatherman & DiNardo, 2010; see also Chang et al, 2013). Here we explore the functional significance of BMP activation during these stages of gonad development. We hypothesize that the BMP signaling pathway functions to repress premature spermatogenetic differentiation and/or germ cell death during testis niche formation. 


Daniel Borrus | Interdisciplinary Studies
Noise sources in finite-channel current balance equations using markov chains
Advisor: Greg Smith
My research is aimed at understanding two possible noise sources in neuron current balance equations that use markov chain modeling to simulate a finite number of channels. The first noise source is the external noise created by adding a random input directly to the neuron's voltage ODE in our current balance equation. The second noise source is internal and is generated by the random opening and closing of the current's channels (depending on voltage) using markov chains. Our goal is to understand when each of these noise sources is overriding the other, in order to strengthen the use of these types of simulations in the future. 

Colin Weinshenker | Computer Science
Characterization of Machine Learning Applications on Chiplet-based Architectures
Advisor: Adwait Jog
Advances in parallel computing architectures (e.g., Graphics Processing Units) have had great success in helping meet the performance and energy-efficiency demands of many high-performance computing applications. DRAM bandwidth is generally a performance bottleneck for many of such applications. With advances in memory technology, the DRAM bandwidth bottleneck is shifting towards other parts of the system hierarchy. In this project, we will study machine learning applications and show that interconnect is one of the biggest performance bottlenecks. We will first characterize these applications on different interconnect topologies to understand their performance sensitivities and communication patterns. Based on this characterization, we will show that interconnect bottlenecks can be significantly alleviated if the computing cores and caching units are carefully tiled (popularly called as "chiplets") and organized on the interconnect fabric. Time permitting, we will explore other optimizations (e.g., locality-based) on the chipleted-architecture to further alleviate the interconnect bottlenecks.


Aaron Bayles | Chemistry
Photocontrol of pH via Doped Conjugated Polymer Nanoparticles
Advisor: Elizabeth Harbron
My Honors project is concerned with the utilization of doped conjugated polymer nanoparticles as a tool to reversibly and noninvasively change the pH of a water-based solution in the presence of a light stimulus. These nanoparticles are doped with a photoreactive molecule that releases acid upon irradiation with ultraviolet light, and reabsorbs that acid when the light source is removed. Additionally, the nanoparticles are naturally fluorescent and the change in their fluorescence upon irradiation can be correlated to the amount of acid released, creating the ability to monitor the pH change without other more invasive methods. The ability to control and monitor pH in this manner is highly desirable in many chemical, biological, and material science systems. 

Ben Zhang | Chemistry
Modeling Fluorescence Switching in a Conjugated Polymer Nanoparticle System
Advisor: Elizabeth Harbron
Conjugated polymer nanoparticles (CPNs) harvest energy from photons and transfer it efficiently to dye molecules in their proximity. My research focuses on a kind of photochromic dye that harnesses the transferred energy to perform its photochromic conversion, resulting in fluorescence switching of the CPN. Using spectroscopic methods that measure the changing fluorescence and visible light absorbance of the CPN-dye system through time, we may study the reaction kinetics of the photochemical reactions involved. Our particular system features switchable fluorescence of the CPN that can be activated and detected using single color visible light by virtue of the photochemical properties of the CPN-dye combination. Kinetic analysis and modeling explains the single-color controlled fluorescence switching in our system, producing new insights that will both contribute to structural understanding of such systems and lead to potential applications that harness similar effects.  

Sarah Stratton | Chemistry
Tuning the pKa of Fluorescent Rhodamine pH Probes via Substituent Effects
Advisor: Elizabeth Harbron
The ability to accurately and quickly identify pH levels is particularly important when observing acidic cellular processes, like the digestive system of cells, and in regards to particular diseases, like Alzheimers and cancer. Rhodamine based dyes are useful as pH probes but typically fluoresce at levels too acidic for most biological systems. Since the pH at which the dyes fluoresce is a function of the effects of different molecules, or substituents, attached to the dye, we attached different substituents to the base rhodamine in order to study the effects on the pH of fluorescence. Ultimately, we were able to tune the pH response in order to develop a rhodamine pH probe capable of responding at a high enough pH for biological applicability. In the process we developed a better understanding of the steric and electronic interactions which drive the pH-dependent fluorescence of rhodamine dyes.


Haoge Chang | Mathematics
Completion of TP and TN Border Patterns
Advisor: Charles Johnson
A new class of TP- and TN- completable patterns is identified: the border patterns, possibly with a block inside. This answers an unpublished question about TP-completable patterns that has been outstanding for some time, and is the first case of completable patterns with all entries on the border specified. In the process, a new tool is developed: TP line insertion in the second or penultimate line when the first and last entries of the line are specified. Prior results about single unspecified entries are used and generalized.

Gregory Taylor | Mathematics
Real Representations and Involutions of the Finite Orthogonal Groups
Advisor: Ryan Vinroot
Arising naturally in geometry and containing a class of finite simple groups, the finite orthogonal groups enjoy a prominent role in the theory and applications of finite groups. In this work, we study the real representations of the finite orthogonal groups, their subgroups, and their quotient groups through the lens of Frobenius-Schur indicators, a technique which links reality properties of a group to the number of involutions in it. We give explicit expressions and generating functions for the number of involutions in these groups. Using the generating functions, we obtain statements about the asymptotic behavior of the number of involutions. Finally, in pursuit of a conjectured bound on the character degree sum of certain finite reductive groups, we bound the number of involutions in the finite orthogonal and symplectic groups in even characteristic.


Georgia Dassler | Anthropology 
En Pointe: An Ethnography of Movement, Ballet Shoes, and the Development of a Dancer
Advisor: Brad Weiss
As material objects that interact intimately with human movement, pointe shoes act on and are acted on by the ballet dancers who wear them. In this process of interaction, pointe shoes appear to harbor a number of contradictions. They are perishable and they cause pain, yet they also help to create beauty and empowerment. These inconsistencies both exemplify and help shape the actions and thoughts of ballet dancers. Thinking seriously about pointe shoes involves questions of the body, of movement, and of objects. By merging theories including embodiment, semiotics, and prosthetics, studying ballet through the lens of pointe shoes focuses on the material aspects of a discipline often thought of as ethereal and temporary and can help give voice to dancers' own motivations. 

Colleen Truskey | Anthropology 
Food & Sovereignty on the White Earth Indian Reservation
Advisor: Brad Weiss
This project explores the ties between food and indigenous land claims, treaty rights, and issues of sovereignty, utilizing the White Earth Indian Reservation (located in north-central Minnesota) as a case study. Based off of fieldwork conducted during the summer of 2016, this research aims to draw a direct link between foodways and notions of Native American political sovereignty, both as they are conceptualized and actually practiced.