Impact of Screw Type on Torque During Slipped Capital Femoral Epiphysis Screw Removal

Slipped Capital Femoral Epiphysis (SCFE) is a disorder that occurs in adolescents in which the femoral head slips with respect to the femoral neck. SCFE can lead to abnormal hip mechanics which may result in the need for realignment of the femoral head through surgery. Percutaneous in situ fixation is the most common treatment for SCFE, where the femoral head is realigned on the neck through screw insertion to prevent further deformity during adolescence. The topic of screw removal is quite controversial. If the screws are left in the patient, there is the potential that fractures may occur later in life due to stress risers, yet screw removal requires a second surgical operation. In addition, there is no standard screw that is used for the procedure. Different physicians prefer various types of screws including titanium vs. non-titanium, cannulated vs. non-cannulated and threaded vs. partially-threaded. Therefore, the purpose of this research project is to determine the amount of torque required to remove various types of orthopaedic screws after closure of the physis. This analysis will quantify how various screws perform during screw removal and provide insight into tissue damage that may occur due to screw removal. The ultimate goal of this study is to determine the optimal screw to use during the procedure that will cause the least amount of damage after bone growth has occurred around the screw.

Continue reading Keith Grega »

Effect of Self-Oxidation on Deposited Cigarette Smoke Composition and Third-Hand Smoke

While the implications of first-hand and second-hand tobacco smoke have been thoroughly studied, much less is known about the effects of so-called ‘third-hand smoke’ (THS) on the environment and human health. THS is a collection of chemicals from cigarette smoke that adhere to indoor surfaces (e.g., walls, flooring, furniture, clothing) and extend the exposure risks for bystanders. As THS chemicals stay on surfaces for long periods of time, we hypothesize that reactions between chemicals within the deposited THS film, with previously deposited materials, and with the surface itself may be occurring. In this study, the mechanisms and rates of the former two categories of reactions were probed. Cigarette smoke was collected on glass surfaces and incubated under fluorescent lighting for various periods of time, revealing changes in the chemical composition. The rates of chemical removal and product formation were determined. Notably, experimental data has indicated a decrease in nicotine concentrations and an increase in nicotine oxide concentrations over time, signifying that nicotine was removed by oxidation reactions occurring within THS films. Further experiments were conducted in which cigarette smoke was collected on glass surfaces that were pre-coated with chemical scavengers to help identify oxidant species that affect the composition of THS films. Future studies will look to include a variety of deposited films, different reactive substrate materials, and other environmental factors in order to obtain a better understanding about what goes on after the cigarette goes out.

Continue reading April Hurlock »

U-Pb Isotope Dating of Monazite from the Sierra Estrella Mountains of Arizona: Evidence for ca. 1.4 Billion Year Old Metamorphism and Deformation.

U-Pb isotope dating of monazite from the Sierra Estrella mountains near Phoenix, Arizona, yield metamorphic ages between about 1.42 and 1.40 billion years old (b.y.o.). These ages suggest that the high temperature and high pressure metamorphism (T = 800 °C, P = 9 kbar) experienced by these rocks was associated with the 1.50 to 1.35 b.y.o. Picuris Orogeny. About 20 samples were collected from the Sierra Estrella mountains. Four samples were selected for U-Pb analyses of monazite, a rare earth element phosphate mineral (REE(PO4)). Monazite gains were identified and imaged using the scanning electron microscope in the Department of Geology, Bucknell University. U-Pb analyses of monazite were conducted at the University of New Brunswick using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Two samples from the north end of the mountain range (CD20-03Ba and CD20-07Bb) yield concordia ages of 1.400 ± .005 b.y.o (n= 8, MSWD = 0.13) and 1.410 ± 0.004 b.y.o. (n = 8, MSWD = 0.25), respectively. Two samples from about 20 km to the south (CD20-09 and CD20-14b) yield concordia ages of 1.410 ± 0.01 b.y.o. (n=8, MSWD = 0.74) and 1.420 +/- 0.006 b.y.o. (n = 8, MSWD = 0.18), respectively. Our new U-Pb ages are similar to 1.420-1.380 b.y.o. monazite previously reported in New Mexico that are also attributed to the Picuris Orogeny.

Continue reading Valerie Justice »

Estimating the Pressure and Temperature of Metamorphism of ca. 1.4 Ga Metapelitic Rocks from the Sierra Estrella Range, Phoenix, Arizona USA

Meijer (2019) reported what is likely the first known occurrence of Mesoproterozoic granulite facies rocks in Arizona. However, the temperatures and pressures of metamorphism are unknown. To better constrain the conditions of metamorphism, metapelitic rocks were collected from the north end of the Sierra Estrella mountain range and are characterized by Grt-Bt-Pl-Qtz-Ky-Sil with significant retrograde Ms-Chl-Ep, and Grt-Bt-Pl-Qtz-Ky-Sil-Kfs with very little retrograde overprint.
Preliminary thermodynamic modeling of these two samples was performed with Theriak–Domino and the H&P ’98 data set. The Sil inclusions within Grt suggest Sil growth possibly during subsolidus St-breakdown or Ms-melting in both samples. The presence of Ky bearing melt textures in both samples may reflect prograde growth of Ky from Ms- or Bt-melting suggesting minimum P¬–T conditions > 7.5 kbar and > 700 °C. A significant amount of retrograde Ms in sample implies in-situ melt crystallization during retrograde cooling.
To further constrain pressures of metamorphism, Raman spectroscopy was employed to measure peak positions of quartz inclusions in garnet (QuiG). The results of this work show peak shifts ranging from 0 to -0.1 cm-1. This equates to metamorphic pressures of 8-9 kbar at about 750-800 °C.
Previously reported zircon ages for the area suggest partial melting near 1.4 Ga (Meijer, 2019). The timing and P-T conditions of metamorphism in the Sierra Estrella mountains are similar to high-grade metamorphic rocks in northern New Mexico and southern Colorado; these rocks likely represent the southwestern extension of the Picuris orogenic belt.

Continue reading Julian Cohen »

My Experiences Re-immersing into Introduction to Mathematical Thought

Throughout college, most students only have the opportunity to engage with course material once. As a senior, this past fall semester I had the opportunity to work with Dr. Lara Dick as a teacher assistant for the same elementary mathematics course I took my sophomore year. The ultimate goal was to re-immerse myself in both the math content and how children learn math concepts through the lens of a second-time learner, an observer, and a future elementary teacher. When attending classes, I learned both new and old concepts, formed new realizations about those concepts, and noted current preservice teachers’ struggles. In this poster, I share the methodology of conducting my self-study, the sub-categories that developed as a result of analyzing brain dumps I took after each class, and discuss how I will apply this experience to my future as an educator.

Continue reading Kaelyn Long »

Does Global Trade Help of Hinder Economic Equality?

The issue of globalization and its perceived winners and losers has recently come to the forefront of international conversation. In this project, we seek to answer the following question: has global trade helped decrease economic inequality? To address this problem, we created a tool that could be used to quantify the effect of global trade over time. Using a graph-theoretical approach, we adapt the Page Rank algorithm to account for a country’s importance in the trade network when considering financial flows that go in both directions, that is, both exports and imports. We then use the relative importance scores to quantify the economic inequality by computing the Gini coefficient of the world’s economy, as well as the associated Lorenz curve. By measuring the evolution of the Gini coefficient over time, we can estimate whether international trade helped or hindered addressing economic inequality among the participants in the global trade network.

Continue reading Ariel Kelly »

Visual Characterization of Aponeurosis Microstructure

Aponeurosis is a tendinous sheath-like tissue found in many muscle-tendon units, and the muscle-aponeurosis junction is poorly understood. We want to determine the structure of the transition from muscle to aponeurosis and how it may be similar or different from the myotendinous junction. Imaging and visually characterizing the muscle-aponeurosis junction using SEM imaging of tissue samples will show how the tendon and muscle fibers interact with one another in the transition zone. It has been observed that there is a non-uniform strain placed on the aponeurosis, and so imaging of the tissue will reveal how force affects the alignment of the collagen fibers found in aponeurosis tissue. Examining how the waviness of collagen fibers changes as the tissue is placed under force will allow for better understanding of the material and structural properties of aponeurosis tissue. Evaluating these characteristics will help us better understand how damages to the tissues occur, how those damages can be repaired and rehabilitated, and how to properly develop computer models of the musculoskeletal system. Sample images using the SEM have been taken to develop a general understanding of aponeurosis morphology.

Continue reading Olivia Dyer »

Noise-driven aggregation of swimmers in the Kolmogorov flow

We investigate theoretically the dynamics of ellipsoidal microswimmers in an externally imposed, laminar Kolmogorov flow. Through a phase-space analysis of the dynamics without noise, we find that swimmers favor either cross-stream or rotational drift, depending on their swimming speed and aspect ratio. When including noise, i.e. rotational diffusion, Langevin simulations of our model show a transition from swimmer aggregation in low-shear regions of the flow to aggregation in high-shear regions as the parameters are varied. We find that rotational diffusion tends to drive swimmers into certain parts of phase space. We characterize the dependence of this noise-driven phase-space aggregation on a swimmer’s speed, aspect ratio, and rotational diffusivity. The properties of the swimmer trajectories with noise explain the transition from high-shear to low-shear aggregation.

*Support from NSF Grants: DMR- 1806355 and CMMI-1825379.

Continue reading Kyle Ferguson »

The Mechanical Properties of Ramming Animal Horn Shapes

One of the most common, yet very dangerous injuries in the world of sports are concussions, which are caused by brain cavity accelerations. Concussions can lead to serious health conditions such as Chronic Traumatic Encephalopathy or CTE, which is a degenerative brain disease that can be fatal. Unlike humans, male Bighorn Sheep are capable of, and frequently do, ram heads at high velocities repeatedly without exhibiting clear signs of CTE. It is apparent that the biomechanical structure and function of their skull and horns play an important role in ramming and possible prevention of CTE. It has been shown in previous studies that after impact, oscillations of the horns could dissipate kinetic energy and reduce brain cavity accelerations. As a result, it is hypothesized that the unique shape of the horns could be a contributing factor to this energy dissipation. In order to test this hypothesis, a drop test will be conducted with a loaded container. On it will be attached ram horn shapes as well as miscellaneous shapes. It is expected that when the horn models are attached to the cylinder, the max acceleration on the container will be less than when the other shapes are attached. Based on the findings, the efficacy of bighorn sheep-like horn shapes as a possible energy dissipating structure will be determined. If it is seen to be effective, such structures could lead to designs that will reduce accelerations due to impact in many cases, such as automotives, sports, and construction.

Continue reading Jake Schaefer »

Dissociating Socioeconomic Influences on Maternal Language Input and Child Language Outcomes

Early language development is associated with children’s socioeconomic status (SES). Specifically, children from lower SES backgrounds, on average, exhibit slower language development compared to their peers from higher-SES backgrounds. Even though SES is a multidimensional construct, research often relies on a single dimension or a composite measure when studying child language development. In this article, I investigate four dimensions of SES, including maternal education, income-to-needs ratio, financial security, and neighborhood SES. Specifically, I examine whether the quantity and quality of maternal linguistic input mediates the relationships between dimensions of SES and child receptive language skills. Mothers and their 36-40 months old children (n=276 dyads) were video recorded during a 15-minute free play session. Three measures of maternal linguistic input were derived from verbatim transcripts, including one quantitative measure (number of words spoken) and two qualitative measures (lexical diversity and syntactic complexity). Children’s concurrent receptive language skills were measured by a standardized measure of children’s ability to receive, process, and execute oral instructions of increasing syntactic complexity. Results revealed that maternal education was the strongest predictor of both maternal linguistic input and child receptive language outcomes. Syntactic complexity of input was the only measure that mediated the relationship between maternal education and child receptive language skills. These findings critically identify which early environmental factors are mechanistically related to SES disparities in children’s language development and provide implications for interventions to reduce these disparities.

Continue reading Klaudia Kulawska »