The purpose of a newly developed foot prosthesis is to improve frontal plane foot adaptability for over 1 million adults living with lower extremity amputation in the US. On uneven ground, side slope, and turning corners, the anatomical foot can adapt but most prosthetic feet cannot. The innovative prosthesis mimics biomechanical aspects of anatomical joints that use ligaments in tension throughout the range of motion while the joint surface acts as a specialized load-bearing structure similar to that of a cross four-bar linkage. In the current prototype cam linkage, we found deviation between the instantaneous center of rotation (ICR) and the point of contact (POC) as it rotated through the frontal plane. The error in this distance could cause unexpected wear on the prosthesis. The goal of this project was to reduce the error caused by the difference in location of the ICR and POC during rotation and translation of the four-bar linkage. In a crossed four-bar linkage, the ICR is found at the intersection of the crossing links. To find the path of the ICR, we plotted a series of points by rotating the linkage about a fixed link in space. The continuous ICR path was estimated by smoothing the ICR points. The curved shape developed becomes the load-bearing surface of the linkage. To create the upper and the lower load-bearing surface, the upper and lower link must be fixed and the opposite rotated, respectively. Using the method described, we built linkage assemblies that showed an error of 0.96 mm per 20 degrees of rotation compared to 2.17 mm of error in the original prototype. The International Organization for Standardization (ISO) requires that foot prostheses undergo wear and fatigue testing. Reducing potential wear on the prosthesis is advantageous because engineers can design for optimal product durability for the foot.

Bacteria can inherit genes through two modes of transmission: vertical inheritance, in which a cell receives genes from its parent cell during division, or horizontal gene transfer, in which genes are passed laterally between two unrelated cells. Extrachromosomal DNA, called plasmids, can be transmitted from a bacterial cell to a neighboring cell of the same or different species through a form of horizontal gene transfer known as conjugation. These conjugative plasmids can encode for antibiotic resistance genes which allows a host cell to produce proteins that degrade antibiotics. In an environment with these drugs, a host cell with this plasmid would be more likely to survive, compared to a plasmid-free cell, due to the benefits of the antibiotic resistance gene. Additionally, these antibiotic resistance genes can often acquire mutations which increases the level of antibiotic resistance for the host cell. However, these acquired mutations may be more beneficial (i.e., higher resistance for the host cell) in one bacterial species than the same mutation in another species. In other words, the effect of mutation on the plasmid-encoded antibiotic resistance gene may be contingent upon the host species. Given that antibiotic resistance genes are often encoded on conjugative plasmids that are shared among species, my project is investigating how protein evolution may be affected due to plasmid genes existing in multiple bacterial hosts. I performed a series of competitions between three bacterial species containing plasmids with versions of an antibiotic resistance gene to determine which versions of the gene outcompete others in an environment containing antibiotics. In doing so, I can determine how this particular gene may evolve when various bacterial hosts exist in a microbial community. The results of this experiment will improve our understanding of plasmid biology and the evolution of antibiotic resistance genes in diverse communities of bacteria.

When massive stars die, they explode in violent spectacles known as supernovae, specifically core-collapse supernovae. These cataclysmic events produce and distribute a large fraction of the heavy elements in the universe, but the properties of the massive stars that produce them have historically been difficult to measure. I have made new measurements constraining the masses of stars that have produced core-collapse supernovae, also known as supernova progenitors. I have done this by measuring the ages of stars at the location of supernova remnants: the nebulae of excited and enriched gas left behind by supernovae that have occurred over the past 20,000 years. Assuming the progenitor was associated with these stars, I am able to estimate the age of the star that exploded. Using theoretical models, I am able to infer the mass from this age. I used images taken by the Hubble Space Telescope to investigate the stars responsible for producing hundreds of these remnants in the nearby galaxy NGC 6946. In addition to the remnants of supernovae, this galaxy has hosted ten observed core-collapse supernovae within the past hundred years, leading to it being referred to as the “Fireworks Galaxy”. I was able to constrain the progenitor mass distribution for 175 remnants, eight of the historically observed supernovae, as well as the progenitor of the first direct black hole formation candidate in NGC 6946. I found the distribution of progenitor masses was consistent with mass distributions measured for massive stars in other galaxies, including our own Milky Way. These new measurements allow NGC6946 to be included for the first time in statistical studies of the masses of stars that produce supernovae.

The historically racist relationship between Global South countries and the U.S. has led to misconstrued media representations of the Global South. This breeds ignorance about those countries when privileged U.S. travelers go to them, and a lack of critical consideration leading to limited perspectives of global citizenship and globalization. By intentionally exposing ourselves to proper representation of the Global South, U.S. travelers can begin to decolonize previous understandings of other countries and people. In my research, I analyze portrayals of globalization and global citizenship in the films Sleep Dealer (2008) by Alex Rivera and Ya No Estoy Aqui (2019) by Fernando Frias. I chose these films because they were created approximately a decade apart, which might indicate changes to portrayals of globalization and global citizenship. More importantly, they were created by Latino filmmakers who share the identities of the characters they portray. I explore how these films, when created by filmmakers from the Global South, can aid in efforts to decolonize globalization and global citizenship, and the discourses surrounding them. Such filmmakers push against boundaries set by Western media that offer simplistic, often voyeuristic representations of the Global South, by presenting complex, realistic portrayals that offer more nuance to Western audiences. The films also grapple with issues of immigration; by centering their narratives on undocumented people and their experiences with citizenship, these films challenge the legitimacy of dominant definitions of global citizenship. I found that films like the two I researched here can challenge commonly accepted definitions of globalization and global citizenship and may be successful in changing attitudes of travelers from the U.S. Moreover, these challenges to dominant discourses can breed inclusion for travelers of color who would typically be left out of travel or global citizenship.

Some environments hinder microbes from gaining the nutrients they need for a chemical reaction. Species in this circumstance collaborate to produce energy by clearing toxic substrates or providing nutrients. This is mutualism, where two species benefit from each other’s fitness. Previously, Desulfovibrio vulgaris and Methanococcus maripaludis were forced to rely on mutualism for survival over time. D. vulgaris catabolizes lactate, producing hydrogen as a byproduct. Hydrogen is inhibiting at high concentrations. M. maripuladis consumes this hydrogen and uses it for energy, producing methane as a byproduct. To learn how these microbes adapted to mutualism over time, 22 communities were propagated for 5000 generations. Each species was also propagated alone in environments that were as similar as possible to the mutualistic evolution environment. The whole genomes of the entire population of D. vulgaris or M. maripaludis were sequenced for the first 1000 generations using Illumina sequencing. This was done from 8 mutualism-evolved and 8 solitary-evolved cultures. Our research goal is to identify alleles that were substituted because they had a beneficial effect on mutualism fitness instead of other generic features of the environment. We can rule out generic adaptations in the population data by comparing mutations in community versus solitary-evolved clones. Clones were collected from each population that had been stored at –80 °C by streaking them on plates. Plates were also used to test if the clones could grow on sulfate. The DNA of these clones will be sequenced to confirm the presence and determine linkage of alleles that are beneficial to mutualism. It is anticipated that the mutation frequency of catabolic proteins will increase within D. vulgaris solitary clones in comparison with community D. vulgaris clones. This experiment has greater implications for mutualistic interactions between microbes, specifically in terms of the methane greenhouse gas that microbes produce.

Δ⁹-tetrahydrocannabinol (THC) is the primary psychoactive compound found in Cannabis sativa. The psychoactive and cannabimimetic behaviors associated with THC have been well described as being dependent on the partial agonist activity of THC at the endogenous cannabinoid 1 receptor (CB₁R). We are investigating the direct action of THC on the medial prefrontal cortex (mPFC, a brain region primarily responsible for executive function), and the effects of adolescent THC exposure on µ-opioid receptor (MOR) expression in adult periaqueductal grey (PAG, a brain region involved in opioid-mediated pain inhibition). To increase our understanding of the cannabimimetic behavioral effects of THC, and its direct pharmacological action in the brain, it is important to map the neuro-anatomical expression of target proteins. We examined expression patterns of CB₁R and MOR in the mPFC and the PAG, respectively. To do this, we utilized a form of in situ hybridization, RNAscope. We leveraged RNAscope by preparing tissue samples from brain regions of interest for treatment with mRNA-specific probes, allowing us to target CB₁R and MOR mRNA. After a series of washes and incubations, these fluorescent probes hybridize to our target mRNAs and allow us to visualize their expression under a confocal microscope. Analysis of mRNA expression informs us on the localization of the CB1R/MOR and known neuron types within our brain regions of interest. After imaging, we are able to utilize HALO software to analyze the levels of expression and co-localization of CB₁R/MORs with neuronal markers for glutamatergic and GABAergic neuron types. By creating and optimizing a workflow for extraction, preparation, hybridization, and analysis, we determined CB₁R mRNA is primarily co-localized with glutamatergic neurons in the mPFC. Moving forward, we are utilizing this RNAscope technique to investigate differential CB₁R expression GABA interneuron subpopulations in the mPFC. (Funded by DA051558)

With growing concerns surrounding global warming, both pollution and alternative sources of energy have become the focus of intense research. These research efforts have addressed the need to power pollution sensors by alternative means. Harvesting energy from trees is both minimally invasive to the environment and eliminates harmful waste produced by non-green energy solutions like batteries. The intent of this research is to verify the possibility of developing an unconventional thermoelectric generator (TEG) in order to increase the energy obtained from trees. We believe that a comprehensive understanding of the temperature characteristics of trees improves the current thermoelectric harvester design. A more robust TEG produces the voltages necessary to power these IoT devices. The primary concerns in selecting materials for a specialized TEG are the thermal impedance, the dimensions and arrangement of semiconducting material, and the overall geometric composition of the TEG itself. The selection of these materials and the overall physical characteristics of the TEG depend on the analysis of the internal temperature of trees. We have developed and will soon deploy a system that captures this valuable data over time. Furthermore, we have established a theoretical TEG design tailored specifically to harvest energy from trees more effectively than previous implementations. The new harvester will be utilized to power LoRa wireless sensor networks capable of monitoring pollution and other environmental hazards. If successful, future research should be devoted to optimizing the TEG to minimize thermal resistances and parasitic heat losses, as well as efforts to maximize temperature differentials with the use of smart heat exchangers on the TEG’s ambient side. Electrical matching of the TEG and sensor node could be desirable too. Finally, integration of the TEG into other sensor applications such as wildfire monitoring is more than reasonable.

Current research and development of robotic arms aims to increase both functionality and versatility. In the agriculture industry autonomous harvesting machines have the potential to be cost effective tools that efficiently pick crops, and robotic arms are a key component of that process. The agricultural robotics market was valued at $7.4 billion in 2020. Robotic arms available are typically designed to pick up one specific object. The market lacks solutions that can harvest a wide variety of crops quickly and carefully. The goal of this research is to develop an adaptable and robust grasping mechanism to attach to robotic arms for harvesting crops from a prototype developed for prostheses. This design adapts in position in response to the object geometry to reduce pressure on the object and requires less time to position the arm. Reducing pressure is a key metric in this study because of the fragile nature of many crops. Utilization of this mechanism reduces articulation time because it can adapt to the shape of the object being grasped at any orientation. My work in the lab has been to develop testing methods to prove these theories, both in simulation and through printing my own prototypes and performing physical tests. Preliminary virtual models and prototype tests consist of repeated grasp tests on a standard set of different grasp test objects including plastic fruits, cleaning supplies, and children’s toys. The objects are grasped repeatedly with and without the linkage mechanism attached. Results show that the mechanisms are adaptable and provide more contact area with the grasped object, reducing point pressure and requiring less articulation of the robotic arm. Further testing will apply the mechanisms in an agriculture setting and include prototyping with different materials and improved design.

 Cannabis sativa is one of the most widely used drugs in the world. In humans, Cannabis sativa is commonly used to alleviate anxiety and pain, among other things, in medical and recreational contexts. In mice, intraperitoneal (i.p.) injections of its primary psychoactive compound, Δ9-tetrahydrocannabinol (THC) produce a characteristic triad of behavioral responses consisting of hypolocomotion, hypothermia, and analgesia. However, injections of THC do not accurately represent how humans typically administer THC, which primarily consists of inhalation and oral consumption. To better model a typical route of administration used by humans, we developed a voluntary oral consumption paradigm in mice whereby THC is formulated in gelatin. Following habituation, mice were given ad libitum access to THC gelatin for 2 hours. We measured the triad behaviors immediately following consumption to determine whether voluntary oral consumption of THC-gelatin using this paradigm induces acute cannabimimetic behaviors. Due to the slow pharmacokinetic activity of orally consumed THC, we measured triad responses immediately, 1 hour, and 2 hours after consumption. To compare our relative THC-gelatin-induced cannabimimetic behaviors to published data, we replicated the triad experiment and demonstrated our ability to obtain dose-dependent triad responses by using i.p. injections. At high concentrations (4mg/15mL) of THC-gelatin, cannabimimetic behavioral responses matched those of mice treated with low-dose (3 mg/kg) of THC i.p. injections. From these initial studies we conclude that development of THC-gelatin formulation triggers characteristic cannabimimetic behavioral effects in mice. These results suggests that classical THC and cannabinoid-dependent behaviors in mice can feasibly be studied with a more translational model (Funded by DA051558). Optimizing an oral administration model of cannabinoids in mice will enable future research on the pharmacology of oral cannabinoid therapeutics. 

The Seattle COVID-19 Oral History Project (SCOHP), sponsored by the Harry Bridges Center for Labor Studies, was started in the spring of 2020 as an initiative to document the experiences and stories of workers and unemployed individuals in Western Washington during the COVID-19 pandemic. Focusing especially on communities of color, the project aims to create an oral history archive for students, researchers, and the general public housed in the Labor Archives of Washington (LAW). Although educational institutions such as Columbia University have started oral history projects to document the effect of COVID-19 on their local communities, many of these are not geared specifically toward frontline workers, whose daily lives have collectively been changed the most by the pandemic. I have developed the idea and structure for SCOHP as a project utilizing oral history to obtain an in-depth, on-the-ground perspective for studying workers and marginalized communities specifically. I collaborate with the local chapter of the Asian and Pacific American Labor Alliance (APALA Seattle), UNITE HERE Local 8, and Service Employees International Union (SEIU) 1199NW to set intentions for the project, co-develop interview questions, and recruit interviewees. Collaborating with LAW, I have helped create and implement oral history trainings for a team of 12 student interns who will assist in preparation, interviewing, and processing. Our goal is to collect and process at least 20 interviews over the course of Winter and Spring of 2021, focusing on the topics of worker health and safety, race and intersectionality, childcare, the Black Lives Matter movement, labor unions, and differences across industries. This work is important for both documenting the experiences of occupational and other communities who have often been underrepresented in media coverage and popular discourse on COVID-19, and highlighting the intersections between occupation, race, ethnicity, immigration, and public health in a global pandemic.