Recent Submissions

  • Microbes and sulfur in a cave and karst system

    Robinson, Sasha R.; Slayback, Paul
    Shoshone Canyon Conduit Cave lies five miles west of Cody, Wyoming, and was found during the building of an irrigation tunnel through Cedar Mountain by the Bureau of Reclamation (BoR). As the cave lies within the tunnel, it can only be accessed with permission during the non-irrigation time of year. What makes this cave special is the high number of sulfides and sulfur deposits, alongside the many unique speleothems. To get a better understanding of the ecosystem and development of this karst system, a geobiological survey was completed of the microbiology and mineralogy of this sulfur cave on its speleothems, mineral deposits, and water. An analysis of the microbial population was done through small subunit ribosomal 16S rRNA gene analysis, prepared using a polymerase chain reaction (PCR) to amplify Bacteria and Archea. Within the low biomass we found more Bacteria over Archea, with a prevalence of sulfur metabolizers. Three especially interesting taxa present were Acidithiobacillus, Anaerolinacaea, and Ferroplasma. Petrography done on the mineral and speleothem samples showed diverse crystal growth, while X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) showed a variety of mineral morphotypes. With the amount of elemental sulfur in the cave, the taxa present, and the speleothems present, it is likely that this cave contains a semi-isolated complete sulfur cycle. Findings from this research can help to develop a greater understanding of the geobiology of sulfur karst systems, not just in the Rocky Mountains and the Greater Yellowstone Ecosystem.
  • Ray tracing ocean surface waves with rust

    Irving, Bryce A.; Castelão, Guilherme; Bôas, Bia Villas
    Ray-tracing is a powerful technique used in computer graphics and scientific simulations to model the propagation of waves. When it comes to ocean surface gravity waves, ray-tracing can provide valuable insights into wave propagation, including their interaction with ocean currents and the seafloor. Such insights are crucial for better understanding ocean wave physics and their role in climate, as waves are a major player in heat transfer and the exchange of gases between the ocean and the atmosphere. In the present work, we introduce a novel package to calculate the path of a wave propagating through the ocean. We developed the code in Rust for memory safety, high performance, robustness, and simple testing. The ray tracing uses the Runge-Kutta 4th order and bilinear interpolation methods to reduce integration error. The package includes supporting Python files to visualize the results. The components are tested individually, and the overall output is checked against known idealized cases. With these methods, our Rust crate can trace the propagation of a wave through a variable depth represented in cartesian coordinates and plot the results. These results are significant because accurately tracing the propagation of ocean waves with an efficient language will increase performance making it seamless to run large simulation ensembles. There are many reasonable opportunities for improvement in the future. The accuracy and realism of the program will improve by tracing bundles of multiple rays and accounting for the interactions with ocean currents. Additionally, the computational performance will improve by parallelizing the ray tracing.
  • Nucleophilic substitution reactions in hydrothermal degradation of per- and polyfluoroalkyl substances

    Brooks, Sean E.; Hao, Shilai; Strathmann, Timothy J.
    Per- and polyfluoroalkyl substances (PFAS) are a class of fluorinated surfactants used in aqueous film forming foam, plastics production, and semiconductor manufacturing, among other industrial applications. PFAS are highly recalcitrant and have been demonstrated to toxicologically affect wild organisms and humans. Hydrothermal alkaline treatment (HALT), which involves the rection of PFAS in a subcritical aqueous environment with the addition of a strong base, has been demonstrated to destroy two major categories of PFAS, perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), in highly-concentrated aqueous matrices. This research investigates the reaction mechanisms underpinning HALT by comparing the reactivity of different nucleophiles. Solutions (1M) of four nucleophiles – sodium bromide (nucleophilicity [n] =3.89), sodium hydroxide (n=4.20), potassium iodide (n=5.04), and sodium hydrosulfide (n=5.10 ) – were combined with a concentrated sample of ultrashort chain PFAS trifluoromethane sulfonate (TFMS) and reacted at 350°C for times ranging from 30 minutes to 180 minutes. Defluorination rates were determined by measuring fluoride in the post-treatment samples with a fluoride ion selective electrode (FISE). For each reaction time, sodium hydroxide promoted the greatest defluorination, which was nearly an order of magnitude higher than the next-best performing nucleophile, sodium hydrosulfide, for the 180 minute reaction. The findings from this study extend prior research into long chain PFSAs by experimentally determining the hydroxide amendment as the most effective nucleophile for defluorination of ultrashort chain PFSAs. This study provides further evidence to support the hypothesis that nucleophilic substitution reactions form the mechanism through which defluorination of PFAS occurs in HALT.
  • Quantifying flow regimes in pipelines using rock-flow cell

    Carmosino, Catherine J.
    For multiphase system under flow, as in oil and gas production, flow regime in flow lines are of great importance to efficiently and safely transport fluids. In this research, the flow regime and mixing of the phases that occur in these flow lines are experimentally studied by using a novel device called rock-flow cell, which is a benchtop tool that simulates multiphase flow conditions by controlling temperate, pressure, liquid volume, and rocking conditions (rate and tilt angle). Through the manipulation of these conditions, every type of flow regime can be replicated and analyzed. This research aims to quantify and correlate the flow conditions in the rock-flow cell to those in flow lines by using video images with image analysis, coded in Python, to quantify the flow elements, which will later be used to match with other experiments and simulations of actual flow lines.
  • Enabling personalized medical implants through additively manufactured medical alloys

    Chase, Rachel; Hawkins, Clinton; Dahl, Scott; Lowe, Terry C.
    Additive manufacturing is enabling the expansion of the personalization of bone and joint replacements to match the exact needs of individuals. However, the success of 3-D printing of medical device alloys such as Ti-6Al-7Nb and Ti-6Al-4V depends upon non-isothermal deposition and cooling processes being able to produce acceptable microstructures defined by set standards. In this work, we develop and implement metallographic preparation and analysis techniques to show that desirable fine structured alpha+beta phase morphologies can be created by additive manufacturing. We further show how low-hazard etchants can effectively replace the use of hydrofluoric acid for revealing microstructures in additively manufactured alloys. 
  • "What goes around comes back around": analyzing the surfaces of medical metal devices during their multistage journey to the surgical operating room

    Hirsch, Daniela; Lowe, Terry C.
    Alloys of titanium and stainless steel are used to fabricate medical devices that temporarily or permanently augment the function of our musculoskeletal and other physiological systems. At every step of fabrication and packaging, careful attention is given to the conditions of the surfaces of these alloys since adsorption of compounds from the liquid or gaseous environments they are exposed to can affect downstream manufacturing processes and the ultimate medical function of the device. As Justin Timberlake put it “what goes around comes back around” and often not in a good way. In this work, we show how spatially resolved surface analysis techniques can detect surface-environment interactions on metallic medical devices at various stages of manufacturing. In selected case studies we show how Energy Dispersive Spectroscopy and other spectrographic methods can trace the evolution of surface conditions on trauma, orthopedic, and cardiovascular devices. In each case, we emphasize how surface science enables health science and the well-being of patients who require the use of medical metals.
  • Continuous and noninvasive microwave biosensor for lactate monitoring

    Koehler, Katie; Lee, T. Ann; Langdon, D.; Quach, C.; Elmiladi, L.; Kaylor, H.; Dang, E.; Street, S.; Dulitz, C.; Jones, R.; et al.
    This project proposes a microwave biosensor to noninvasively and continuously detect the concentration of lactate in athletes and healthcare patients. Lactate is a byproduct produced during aerobic and anaerobic metabolism when the body cannot produce sufficient oxygen to meet the body’s energy demands. In athletes, these levels are currently tracked by blood samples to determine the athlete’s fitness level. In healthcare patients, lactate production is measured to determine the oxygen supply to a patient’s tissues. By monitoring lactate levels, healthcare providers can provide appropriate treatment and improve patient outcomes, while athletes can adjust their training plans to improve performance and reduce the risk of injury. In the initial phase of our sensor development, we report on the initial design by testing the sensor’s sensitivity to detect salt concentration changes in deionized water in a well-controlled laboratory environment. The sensor consists of a microwave resonator and microfluidic chip assembly, and it allows us to detect small changes in the dielectric properties of the deionized water solution resulting from different salt concentration levels. The results of this study will be used to further refine the sensitivity of the sensor as we move towards developing the lactate sensor.
  • Analyzing the impacts of wildfires on solar photovoltaic generation

    Glaister, Jade; Garcia, E.; Tabares-Velasco, Paulo Cesar
    As the intensity and frequency of wildfires increase, understanding the effects of wildfires on solar energy sources is critical to illuminating future trends in energy. Previous studies show that concentrations of ~75 ug/m3 of PM2.5 decrease photovoltaic generation by ~20%. The purpose of this research study is to verify previous studies and analyze the impact of wildfires on photovoltaic generation in Golden, Colorado by interpreting particulate matter and photovoltaic data. This is done through a MATLAB framework code that imports and organizes 2020 datasets from PurpleAir and NREL to create plots that display data relationships. These plots demonstrate how photovoltaic generation changes under different concentrations of particulate matter, including the impact of cloud cover on the data. An understanding of this relationship will provide insight on adjusting energy sources to compensate for changes in photovoltaic generation due to increasing wildfires.
  • Optical microstructural characterization of highly deformed and etch resistant materials

    Hawkins, C. J.; Lowe, Terry C.
    In academia [sic] settings access to advanced characterization methods are often readily available and used without a second thought. While these methods are beneficial to all, their limited availability can be problematic for others trying to reproduce or develop discoveries made in research without access to the same characterization methods. To support collaborators in developing new materials our team has been researching alternatives to advanced characterization methods using more readily available digital optical microscopes. This project specifically focuses on using chemical etching and optical microscopy to reveal the microstructure of highly deformed Inconel 625 wires to evaluate their potential uses for a wide range of neurovascular devices and other medical applications.
  • Hydrologic impacts of the Slumgullion landslide on Lake Delta formation

    Tuminello, Morgan A.; Dugan, Brandon
    The Slumgullion landslide, located in southwestern Colorado near Lake City, has been an area of interest for many scientists for 300 years. Data on the movement of the slide indicates that the younger, active part of the landslide moves over the older, inactive part of the landslide. To further our understanding of the landslide dynamics, we integrated data previously collected from easy-to-access outcrops with our analyses of satellite imagery and hydrologic data. We see that on average the shallow area of the landslide moves 0.755 m/yr (+/- 0.078 m/yr) with faster movement to the south. Aerial data combined with precipitation and lake level data was used to determine if the amount of rainfall and the lake level have any effect on the average rate of movement determined. Based on our analyses of the annual precipitation data, we interpret that precipitation does impact the migration rate. This work demonstrates the necessity for more process-based linkages between surface and subsurface hydrology and mobility of the Slumgullion slide. We recommend future, priority measurements to further our understanding of the slide dynamics include water table levels along the slide, strength of materials in the slide, and higher resolution characterization of the hydrology and deformation.
  • Development of calcium and oxygen nanosensors for in-vivo diagnostics

    Isbell, Sydney; Mendonsa, Adrian; Cash, Kevin J.
    Diagnostic tests to determine analyte concentration can be repetitive and require extensive training for proper analysis. To address these limitations, we developed two ratiometric nanosensors (calcium (Ca2+) and oxygen (O2)) which could be implemented in-vivo to give insight into biological functions such as nerve signaling and cellular respiration. The Ca2+ nanosensors’ optical properties (fluorescence and absorbance) vary to reflect the surrounding Ca2+ concentration. These sensors are selective to Ca2+ over other biologically relevant cations (Mg2+, Na+, K+) and show a sensitivity to Ca2+ at concentrations as low as 100 µM. The O2 nanosensor is composed of two dyes encapsulated in a hydrophobic PVC matrix. The O2 sensitive dye, platinum octaethylporphyrin (PtOEP), shows a decrease in luminescence with increasing oxygen concentrations. Whereas, the reference dye, DiA, has no O2 sensitivity. These O2 sensors are reversible and have a detection range that spans from anoxic (0% O2) to atmospheric conditions (21% O2). While the Ca2+ and O2 sensors showed functionality in in-vitro studies, testing these sensors in-vivo will determine their effectiveness as a long-term diagnostic aid.
  • Harnessing geomicrobial respiration in engineered wetlands for pre-treatment of brackish waters

    Garza, Max; Gidley, Nicholas; Wang, Weishi; Yang, Zhaoxun; Vega, Michael A. P.; Vanzin, Gary; Sharp, Jonathan O.
    As arid regions become increasingly vulnerable to climate change, brackish groundwater offers the potential to supplement existing water resources, particularly for inland states such as Colorado. However, Brackish Water Reverse Osmosis (BWRO), presents a unique set of challenges that include membrane fouling due to elevated concentrations of inorganic precipitates and the production of substantial quantities of brine concentrate that often harbor heavy metal contamination. A possible mechanism for increasing BWRO efficacy is the use of shallow, unit process open water (UPOW) wetlands colonized by diatoms for biological pre-treatment. The photosynthetic diel (day/night) cycling in the wetlands, which passively increases pH during the day as carbonate is consumed, mimics traditional water treatment to create favorable, alkaline conditions needed for metal precipitation, but without chemical additions. Through various processes, the microbial mat (biomat) that naturally forms within UPOW wetlands can potentially reduce scalants (calcium, magnesium, and sulfates), as well as oxidize challenging constituents, such as arsenite, from the water prior to membrane treatment. Therefore, laboratory-scale UPOW wetlands were created using biomat harvested from an operational field-scale constructed wetland and challenged with synthetic brackish water. Preliminary results suggest that the reduction of scalant concentrations and oxidation of heavy metals can prevent excess membrane fouling and enhance RO rejection. This approach promotes environmental sustainability by eliminating the need for chemical additions, reducing brine concentrate volumes, and by decreasing energy and labor requirements. Findings may ultimately help address technoeconomic issues associated with BWRO and help guide further investigations into biological pre-treatment of brackish water.
  • Hip-belt load sharing reduces peak shoulder pressure across walking slopes during heavy load carriage

    Inge, Madeline M.; Rizeq, Hedaya N.; Slider, Amy; Sessoms, Pinata H.; Silverman, Anne K.; Sturdy, Jordan T.
    Musculoskeletal injury to the spine and lower back resulting from heavy load carriage (30–40 kg) is common among military service members. Static peak pressure is a reliable parameter for predicting discomfort. The effect of using a hip belt on shoulder pressure is not well understood. This study aimed to quantify the pressure under shoulder straps when carrying a backpack with and without a hip belt. Three military service members wore a helmet and body armor (~6.5kg) and carried a backpack in two attachment conditions: (1) entirely shoulder borne, and (2) with a hip-belt engaged, all totaling 40% body weight. Participants walked at three different slope conditions (10° downhill, level, and 10° uphill) at 1.15 m/s for each backpack condition. Peak pressure across both shoulders was extracted from each condition. Shoulder borne peak pressure (down: 36.33 kPa; level: 37.67 kPa; up: 36.67 kPa) was greater than the hip belt (down: 29.67 kPa; level: 24.67 kPa; up: 29.67 kPa). Walking with the hip belt engaged compared with the shoulder borne-only backpack resulted in ~9 kPa smaller peak shoulder pressure on average across all three slopes, indicating that peak pressure is reduced when using a hip belt, although greater participant numbers are needed to confirm these results.
  • Optimization of space nuclear reactor shielding through computational analysis

    Hoffmann, Madeline; King, Jeffrey C.
    Nuclear reactors emit ionizing radiation that can be harmful to people and electronic equipment. Shielding materials that attenuate this radiation can be a significant fraction of the mass of a space nuclear reactor power system. Optimizing space reactor shielding geometry and composition allows the design of shields that can reduce neutron and gamma-ray doses from the reactor to an acceptable using the minimum amount of shielding material. This project generated a Python 3.10 script that uses OpenMC to test arbitrary compositions of different materials in various layers and geometries to optimize a shield for space reactor applications. OpenMC is an open-source Monte Carlo-based neutron transport code that probabilistically models the movement of neutrons and photons as they interact with a user-specified environment. When finished, the program will analyze combinations of neutron absorbers (lithium hydride, enriched lithium hydride, and boron carbide) and photon absorbers (tungsten and depleted uranium) arranged in different layers and thicknesses to determine their ability to reduce dose from a hypothetical space reactor to 5 mrem/hr at a point 10 m from the surface of the payload-side of the shield. The shield will be modeled as two opposed truncated cones with a total thickness of 50 cm. The cones will be tested with in multiple configurations to determine the optimal geometry to minimize mass while meeting the target dose. Future investigations will expand the model to include total thickness optimizations and a more detailed dose analysis over a target area.
  • Backpack motion relative to the torso is affected by walking slope

    Giltinan, Kagan P.; Rizeq, Hedaya N.; Slider, Amy; Sessoms, Pinata H.; Silverman, Anne K.; Sturdy, Jordan T.
    Military backpacks are equipped with hip belts, which have been shown to support 30% of the vertical force from the backpack. These belts do not offload enough force to prevent tissue strain on the shoulders, which can lead to discomfort and injury. Stiffness and damping in a backpack’s straps and connections can affect backpack movement, which may be related to tissue strain, when walking. However, the effects of using a hip belt on relative motion between the backpack and the wearer are unclear. Four active duty military participants walked at 1.15 m/s on uphill (+10¬∞), downhill (‚àí10¬∞), and level (0¬∞) slopes. They wore body armor with helmet and backpack using only the shoulder straps (Shoulder) or with the hip belt secured (Hip Belt), carrying 40% body weight total. 3D motion of the backpack and torso was obtained with optical motion capture. Maxima and minima of backpack-torso displacement were calculated in each walking condition. The difference between sequential maxima and minima were used to obtain ranges of vertical backpack-torso displacement during each walking condition for each participant. The hip-belt did not influence relative vertical motion of the backpack. The pack and slope did affect the horizontal relative displacement (p = .086). The greatest relative displacement for anterior/posterior direction was 7.7mm, and vertical direction was 19.9mm. Horizontal displacement was not affected by slope alone during Hip Belt, but was affected during Shoulder (p = .056). The vertical relative displacement was affected by slope, p = .007.
  • Low-cost modular and flexible laser source

    Spoor, Henry; Adams, Daniel
    This project investigates the feasibility of producing high-quality, high-reliability laser beams from traditional handheld laser pointers. The goals of this project included understanding the fundamental principles and functionality of a handheld laser pointer as well as conversion of said laser pointer to a setup that could be used in a research-level capacity. To achieve these goals, handheld lasers were disassembled to their component parts, and extensive testing was performed on the maximum capabilities of the laser pointers. Data was collected on the maximum supplied current the laser diode could withstand, the viability of creating a tunable intensity laser and the potential for making a reproducible product. In the testing process, the converted laser pointers were found to be reliable if constrained to a limited current. Additionally, the laser beam was successfully made to have a tunable intensity by varying the supplied current. Additional testing will be performed to determine the lifespan of the converted laser pointer as well as the reproducibility of the project for use in a research setting.
  • Relationship between hand grip strength and mediolateral torso movement in five times sit-to-stand, The

    Beebe, Claire A.; Silverman, Anne K.; Miller, Michael F.
    Balance regulation during daily activities is a key component of movement performance and fall risk as we age. There is a well-defined correlation between lower limb muscle strength and hand grip strength (HGS) and lower limb muscle strength is critical for balance regulation. The Five Times Sit-To-Stand test (5xSTS) is an evaluation of muscle strength and mobility during transitions that helps identify individuals at risk of fall. Thus, we aimed to determine if mediolateral movement biomechanics during the 5xSTS test, which are important for balance performance, were correlated with HGS. Ten young and healthy participants completed a 5xSTS trial where they rose from the seat to a standing position and returned to the seat five consecutive times as quickly as possible. We performed a Pearson correlation analysis (α ± < 0.05) between range of mediolateral torso center of mass (COM) displacement, dominant HGS and time to completion of 5xSTS. There was not a significant correlation between time to completion and HGS (rho (ρ) = -0.515, p = 0.127). A moderate negative correlation that approached significance (0.05 < p < 0.10) was found between mediolateral torso COM displacement and HGS (rho (ρ) = -0.558, p = 0.094). There was no correlation between mediolateral torso COM displacement and time to completion (rho (ρ) = 0.143, p = 0.693). HGS could help indicate mediolateral balance performance during 5xSTS and improve the lower limb strength assessment due to its correlation with torso motion. Recording dominant HGS alongside 5xSTS completion time may provide insight into mediolateral dynamic balance performance.
  • Changes in extracellular matrix stiffness affect pancreatic islet function

    Sela, Amit; Johansen, Chelsea; Farnsworth, Nikki
    In the pancreas, the islet is surrounded by a specialized protein scaffold known as the extracellular matrix (ECM) that regulates cell survival and insulin secretion. Little is known about how the properties of the pancreas microenvironment, like matrix stiffness, regulate islet function in health and disease. Previous studies have shown that tissue stiffness in muscle cells regulates phosphofructokinase (PFK) activity. The mechanisms underlying mechanotransduction regulation of insulin secretion have not been well studied in the β-cell and a connection between metabolism and mechanotransduction has never been studied in intact islets. We hypothesize that increasing matrix stiffness will increase islet glucose sensitivity by increasing PFK activity. Our lab has developed a 3D reverse thermal gel (RTG) system that allows us to mimic the islet microenvironment and to investigate how the environment affects islet function. To determine the effect of changes in ECM stiffness on islet function we encapsulated mouse islets in the RTG with increasing stiffness as determined by rheological analysis. Glucose-stimulated insulin secretion, PFK activity, and PFK expression was measured after 24 hours of culture. We found that increasing RTG wt% yielded increasing stiffness at 40°C. Insulin secretion increased as the matrix stiffness increased in basal and high glucose conditions. Insulin secretion at high glucose normalized to low glucose (stimulation index) decreases with matrix stiffness indicating dysfunction to insulin secretion. PFK activity increased in islets encapsulated in stiffer RTGs. Our results provide insight into how changes in ECM stiffness contribute to islet dysfunction.
  • Intelligent prediction of traffic conditions via integrated data-driven crowdsourcing and learning

    Seo, Hoon; Rippey, Caroline; Taylor, Ethan
    Intelligent Transportation Systems (ITS) are gaining popularity among governments, businesses, and individuals due to their potential to make travel safer and more efficient. Machine learning for traffic prediction has emerged as a promising subfield of ITS, with the potential to aid in routing planning, congestion management, and urban development. Traffic infrastructure and mobile devices collect large amounts of heterogeneous data that can be used to predict traffic conditions, including real-time traffic data such as traffic camera images, speed measurements, and volume counts, as well as long-term static data such as speed limits, road conditions, and surrounding geography and infrastructure. Despite the availability of traffic data, many current machine learning models struggle to handle the wide variety of data types and to address both temporal aspects of real-time data and spatial aspects of long-term static data. To address this, we propose a new enrichment learning model that integrates dynamic data containing varying numbers of instances with static data to create an enriched fixed-length vector which can be used with other machine learning methods to improve performance and identify regions important for prediction. Results show that this novel enrichment learning model can improve the performance of traditional machine learning methods in the task of predicting future traffic speeds.
  • Ankle muscle strength affects muscle forces during double leg hopping

    Vargas, Brooklyn L.; Miller, Michael F.; Daley, Monica A.; McNitt-Gray, Jill; Silverman, Anne K.
    Falls are a primary cause of morbidity and mortality in older adults, with dynamic balance decline often being the precursor to a fall. Declining lower limb strength has been linked to dynamic balance decline. Therefore, this study will evaluate the effect of ankle muscle weakness on muscle control and coordination of double leg hopping, a task that requires precise dynamic balance control. A healthy adult performed ten continuous double leg hops. Motion capture and ground reaction forces were collected. A model was developed in Visual3D (C-Motion, Inc.), and inverse kinematics (IK) of three hops were computed. The GRFs along with the IK solutions were exported to OpenSim v 4.4 and applied to a scaled musculoskeletal model. A Residual Reduction Algorithm (RRA) improved dynamic consistency. Computed Muscle Control (CMC) then determined the needed muscle excitation patterns. A weakened model was developed with reduced maximum isometric force of the MG, LG, and SOL to represent aging. Peak dynamic force from MG and SOL decreased by 16% and 3% respectively in the weakened model, while the LG increased by 16%, compensating for MG force deficits. Several agonist muscles in the weakened model increased their peak force output, suggesting they are compensating for the weakened MG, LG, and SOL. The ankle reserve actuator peak torque increased by 135% in the weakened model. These findings indicate ankle muscle weakness associated with aging affects hopping strategy and muscle recruitment. Strength should be preserved to maintain movement and prevent dynamic balance decline.

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