Scholarly Work - Mechanical & Industrial Engineering
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Item Heat conduction simulation of chondrocyte-embedded agarose gels suggests negligible impact of viscoelastic dissipation on temperature change(Elsevier BV, 2024-09) Myers, Erik; Piazza, Molly; Owkes, Mark; June, Ronald K.Agarose is commonly used for 3D cell culture and to mimic the stiffness of the pericellular matrix of articular chondrocytes. Although it is known that both temperature and mechanical stimulation affect the metabolism of chondrocytes, little is known about the thermal properties of agarose hydrogels. Thermal properties of agarose are needed to analyze potential heat production by chondrocytes induced by various experimental stimuli (carbon source, cyclical compression, etc). Utilizing ASTM C177, a custom-built thermal conductivity measuring device was constructed and used to calculate the thermal conductivity of 4.5 % low gelling temperature agarose hydrogels. Additionally, Differential Scanning Calorimetry was used to calculate the specific heat capacity of the agarose hydrogels. Testing of chondrocyte-embedded agarose hydrogels commonly occurs in Phosphate-Buffered Saline (PBS), and thermal analysis requires the free convection coefficient of PBS. This was calculated using a 2D heat conduction simulation within MATLAB in tandem with experimental data collected for known boundary and initial conditions. The specific heat capacity and thermal conductivity of 4.5 % agarose hydrogels was calculated to be 2.85 J/g°C and 0.121 W/mK, respectively. The free convection coefficient of PBS was calculated to be 1000.1 W/m2K. The values of specific heat capacity and thermal conductivity for agarose are similar to the reported values for articular cartilage, which are 3.20 J/g°C and 0.21 W/mK (Moghadam, et al. 2014). These data show that cyclical loading of hydrogel samples with these thermal properties will result in negligible temperature increases. This suggests that in addition to 4.5 % agarose hydrogels mimicking the physiological stiffness of the cartilage PCM, they can also mimic the thermal properties of articular cartilage for in vitro studies.Item Aging decreases osteocyte peri-lacunar-canalicular system turnover in female C57BL/6JN mice(Elsevier BV, 2024-09) Vahidi, Ghazal; Boone, C.; Hoffman, F. O.; Heveran, Chelsea M.Osteocytes engage in bone resorption and mineralization surrounding their expansive lacunar-canalicular system (LCS) through peri-LCS turnover. However, fundamental questions persist about where, when, and how often osteocytes engage in peri-LCS turnover and how these processes change with aging. Furthermore, whether peri-LCS turnover is associated with natural variation in cortical tissue strain remains unexplored. To address these questions, we utilized confocal scanning microscopy, immunohistochemistry, and scanning electron microscopy to characterize osteocyte peri-LCS turnover in the cortical (mid-diaphysis) and cancellous (metaphysis) regions of femurs from young adult (5 mo) and early-old-age (22 mo) female C57BL/6JN mice. LCS bone mineralization was measured by the presence of perilacunar fluorochrome labels. LCS bone resorption was measured by immunohistochemical marker of bone resorption. The dynamics of peri-LCS turnover were estimated from serial fluorochrome labeling, where each mouse was administered two labels between 2 and 16 days before euthanasia. Osteocyte participation in mineralizing their surroundings is highly abundant in both cortical and cancellous bone of young adult mice but significantly decreases with aging. LCS bone resorption also decreases with aging. Aging has a greater impact on peri-LCS turnover dynamics in cancellous bone than in cortical bone. Lacunae with recent peri-LCS turnover are larger in both age groups. While peri-LCS turnover is associated with variation in tissue strain between cortical quadrants and intracortical location for 22 mo mice, these associations were not seen for 5 mo mice. The impact of aging on decreasing peri-LCS turnover may have significant implications for bone quality and mechanosensation.Item Cooperative Adsorption and Diffusion of Small Alcohols in Metal–Organic Framework ZIF-8 and Intrinsically Microporous Polymer PTMSP(American Chemical Society, 2024-08) Rutherford, Steven W.Fundamental understanding of molecular interactions and transport within microporous materials displaying cooperative Type V adsorption is challenged by the unique features of this isotherm type. In order to capture a broad understanding of this uncommon, yet industrially relevant, behavior in microporous materials, this investigation examines the adsorption equilibria and kinetics of methanol and ethanol in both a metal–organic framework (MOF) material, ZIF-8, and a high free volume polymer of intrinsic microporosity, poly[1-(trimethylsilyl)-1-propyne] (PTMSP). A novel formulation that can capture the cooperative effects of small alcohols in its description of adsorption equilibria and kinetics is proposed. It is subsequently applied to successfully capture some previously uncharacterized or semiempirically characterized data for equilibria and the loading dependence of the diffusivity in both ZIF-8 and PTMSP, which are materials chosen for their industrial relevance. Finally, it is anticipated that the results of this study can fill the current void that exists in meaningful mechanistic and analytical descriptions of cooperative equilibrium and diffusion phenomena in microporous materials.Item Ising model-modified kelvin analysis (IMMKA) for the prediction of water adsorption equilibrium and assessment of contact angle in carbon micropores(Elsevier BV, 2024-09) Rutherford, Steven W.The unpredictable nature of the interaction of water molecules with carbon surfaces is evident in the wide-ranging behavior observed in simple macroscopic observations such as contact angle. Complex fluid–solid and fluid–fluid interactions can convolute the observed behavior and when coupled with confinement at the nanoscale, large deviations might be expected in predictions via macroscopic properties. However, by delivering a quantitative description of water adsorption in microporous carbon, this study demonstrates that macroscopic features can predict nanoscale behavior of confined water. Furthermore, through introduction of nanocapillarity and nanowetting, an Ising-Model-Modified-Kelvin Analysis (IMMKA) for water adsorption is proposed, interpreted and validated.Item Hydromulches suppress weeds and maintain fruit production in organically managed strawberry systems(Frontiers Media SA, 2024-05) Ahmad, Waqas; DeVetter, Lisa W.; McFadden, Dakota; Maupin, Brian; Bajwa, Dilpreet S.; Durado, Andrew; Weyers, Sharon; Galinato, Suzette P.; Weiss, Ben; Gramig, GretaPolyethylene (PE) mulches are widely used in strawberry (Fragaria × ananassa Duch) production for weed suppression and crop growth optimization. However, PE mulches are not biodegradable and contribute to plastic pollution. Our objective was to develop and test biodegradable liquid-applied ‘hydromulches’ (HMs) as a sustainable alternative to PE mulch. HM weed suppression efficacy, strawberry plant growth, and yield were evaluated. HM formulations consisted of shredded newsprint paper (NP), water, and a tackifier, either guar gum (GG) or psyllium husk (PH) added at 2 or 6%. Experiments were conducted at two environmentally distinct locations: northwest Washington (WA) and eastern North Dakota (ND). Five HM formulations were compared to black PE mulch within a randomized complete block design with four replications. PE mulch suppressed weeds completely at peak weed emergence and peak weed vegetative growth at both locations. Formulations of HM containing GG provided superior weed suppression compared to other HM formulations at peak weed emergence (4–6 vs. 18–22 plants m-2, respectively). At peak vegetative growth, HM formulations containing GG had the lowest weed density compared to other HMs in ND (1 vs. 9–12 plants m-2), whereas these differences were not observed in WA. Total weed biomass did not differ among HMs across both locations. GG HM formulations deteriorated similarly to PE mulch (3–5% vs. 2%, respectively) in ND, whereas other HMs deteriorated more substantially. In WA, all HMs deteriorated more than PE mulch (6–12% vs. 1%, respectively). Fruit yield did not differ among treatments in weedy and weed-free subplots (194–254 g plant-1) in WA. In ND, yield was greater in all HM treatments compared to PE mulch in both weedy and weed-free subplots. Across both locations, strawberry canopy cover was greater in PE mulch (56.1% canopy cover) compared to 2%GG and NP (42.4 and 39.8% canopy cover). Strawberry plant biomass was similar among mulch treatments. However, strawberry leaf and crown biomass were slightly lower in 2%PH compared to other mulch treatments. Results demonstrate HMs with GG tackifier are a promising alternative to PE mulch in organic strawberry systems based on ability to suppress weeds, enhance strawberry growth, and maintain yield.Item Molten salt biomass torrefaction - A sensitivity analysis of process conditions(Elsevier BV, 2024-07) Kohlin, Lee; Pritchard, Hayden; Gladen, Adam C.; Dehkordi, Behrooz; Bajwa, DilpreetBiomass is an abundant renewable resource that can be upgraded via torrefaction. Molten salts catalyze the torrefaction reaction, creating enhanced products for fuel and soil amendment purposes at lower temperatures than inert gas torrefaction. The objective of this study is to elucidate the main effects of molten salt torrefaction process conditions on ponderosa pine (Pinus ponderosa) and cave in rock switchgrass (Panicum virgatum) in a binary salt blend of lithium nitrate and potassium nitrate using a Plackett-Burman screening analysis. The investigated process conditions include sweep gas, temperature, salt to biomass ratio (S-B ratio), residence time, and lithium content. The metrics used to evaluate torrefaction severity include mass yields, chemical composition (lignin, cellulose, hemicellulose, extractives), higher heating value (HHV), carbon and nitrogen content, pH, and water sorption. The results show that switchgrass is more severely torrefied through molten salt torrefaction than pine at the same process conditions. For example, switchgrass mass yields are on average 23.3 % lower than pine mass yields across the test conditions. For both feedstocks, the most impactful process conditions are temperature, time, and lithium content in that order with some exceptions. For instance, the effect of temperature, time and lithium content on HHV are, respectively, 3.4×, 2.3×, and 1.7× larger than the next largest process condition for pine, whereas for switchgrass, these values are 3.6×, 2.7×, and 1×. Particle size, sweep gas, and S-B ratio have minor effects depending on the metric, but are overall not significant compared to temperature. The data suggests that an inert gaseous environment need not be maintained to facilitate molten salt torrefaction. Additionally, molten salt torrefaction can produce torrefied biomass with slightly different characteristics than inert gas torrefaction.Item Design, Fabrication, and Validation of a Portable Perturbation Treadmill for Balance Recovery Research(ASME International, 2024-06) Knutson, Robert G.; Whitten, Justin; Graham, David; Shankwitz, Craig; Pew, Corey A.Trips and falls are a major concern for older adults. The resulting injury and loss of mobility can have a significant impact on quality of life. An emerging field of study, known as Perturbation Training, has been shown to reduce injury rates associated with trips and falls in older adults. Treadmills traditionally used for Perturbation Training are large, expensive, and immobile, forcing users to travel long distances to receive care. A portable treadmill would serve a larger portion of the at-risk population than current methods. We developed a portable, low-cost, twin-belt perturbation treadmill capable of high-intensity Perturbation Training. Belt speeds are controlled by a custom mechanical and software interface, allowing operators with no programming experience to control the device. The treadmill can accommodate users up to 118 kg and provides a maximum acceleration and speed of 12 m/s2 and 3.3 m/s, respectively, under full load. The total weight is 180 kg, and the treadmill can be moved like a wheelbarrow, with handles in the back and wheels in the front. The prototype was validated with mechanical and human participant testing, showing it as a viable device for Perturbation Training. In this paper, we will go over the design, fabrication, and validation processes used to create the Portable Perturbation Treadmill.Item Unraveling sex-specific risks of knee osteoarthritis before menopause: Do sex differences start early in life?(Elsevier BV, 2024-05) Hernandez, Paula A.; Churchill Bradford, John; Brahmachary, Priyanka; Ulman, Sophia; Robinson, Jennifer L.; June, Ronald K.; Cucchiarini, MagaliObjective. Sufficient evidence within the past two decades have shown that osteoarthritis (OA) has a sex-specific component. However, efforts to reveal the biological causes of this disparity have emerged more gradually. In this narrative review, we discuss anatomical differences within the knee, incidence of injuries in youth sports, and metabolic factors that present early in life (childhood and early adulthood) that can contribute to a higher risk of OA in females. Design. We compiled clinical data from multiple tissues within the knee joint—since OA is a whole joint disorder—aiming to reveal relevant factors behind the sex differences from different perspectives. Results. The data gathered in this review indicate that sex differences in articular cartilage, meniscus, and anterior cruciate ligament are detected as early as childhood and are not only explained by sex hormones. Aiming to unveil the biological causes of the uneven sex-specific risks for knee OA, we review the current knowledge of sex differences mostly in young, but also including old populations, from the perspective of (i) human anatomy in both healthy and pathological conditions, (ii) physical activity and response to injury, and (iii) metabolic signatures. Conclusions. We propose that to close the gap in health disparities, and specifically regarding OA, we should address sex-specific anatomic, biologic, and metabolic factors at early stages in life, as a way to prevent the higher severity and incidence of OA in women later in life.Item Role of sodium sulfate in electrical conductivity and structure of lignin-derived carbons(Elsevier BV, 2024-08) Kane, Seth; Hodge, David B.; Saulnier, Brian; Bécsy-Jakab, Villő Enikő; Dülger, Dilara N.; Ryan, CecilyLignin is a promising renewable alternative to fossil fuels for producing carbon materials such as carbon fibers, activated carbons, or carbon black. Despite extensive research, lignin-derived carbon materials show limited graphitization relative to comparable petroleum-derived carbons. Further, lignin-derived carbons show high variation in graphitization and electrical conductivity depending on the source of the lignin. Herein, nine lignins, derived from various feedstocks and isolation procedures, are pyrolyzed to produce biochar at 1100∘C. These lignins have a range of chemical compositions, carbon structures, and particle sizes. As a result, the pyrolysis behavior of these lignins varies, with powdered, clumped powder, and “foam” biochar morphologies resulting from finely powdered lignin. The produced biochars vary widely in both electrical conductivity, from 0.19 to 19 S/cm, and in-plane graphitic crystallite size, from 3.4 to 41.2Å. A significant decrease in electrical conductivity is identified when Na2SO4 is removed from lignin, accompanied by an increase in graphitic crystallite size. Based on this finding, a quadratic relationship between biochar graphitic crystallite aspect ratio and electrical conductivity is proposed that builds on established quasi-percolation models for biochar electrical conductivity.Item Investigating atomization characteristics in an electrostatic rotary bell atomizer(Elsevier BV, 2024-05) Krisshna, Venkata; Owkes, MarkElectrostatic rotary bell atomizers are commonly used in several engineering applications, including the automobile industry. A high-speed rotating nozzle operating in a strong background electric field atomizes paint into charged droplets that range from a few micrometers to tens of micrometers in diameter. The atomization process directly determines the droplet size and droplet charge distributions which subsequently control the transfer efficiency and the surface finish quality. We have previously developed a tool to perform high fidelity simulations of near-bell atomization with electrohydrodynamic effects. In this work, we perform simulations employed with a droplet ancestry extraction tool to analyze previously inaccessible information and understand the physical processes driving atomization. We find that the electric field accelerates breakup processes and enhances secondary atomization. The total number of droplets, the ratio of secondary to primary droplets, and the ratio of coalescence to breakup activity are all much higher when operating in an electric field. We analyze the droplet velocity, local Weber number and charge density statistics to understand the complex physics in electrically assisted breakup. The results of the study have helped us gain insights into the physics of atomization in electrostatic rotary sprays.