Soft tissues are complex anisotropic composite systems comprising of multiple differently oriented layers of fiber embedded within a soft matrix. To date, soft tissues have been mainly characterized using simplified linear elastic material models, isotropic viscoelastic and hyperelastic models, and transversely isotropic models. In such models, the effect of fiber volume fraction (FVF), fiber orientation, and fiber-matrix interactions are missing, inhibiting accurate characterization of anisotropic tissue properties. The current work addresses this literature gap with the development of a novel soft composite based material framework to model tissue anisotropy. In this model, the fiber and matrix are considered as separate hyperelastic materials, and fiber-matrix interaction is modeled using multiplicative decomposition of the deformation gradient. The effect of the individual contribution of the fibers and matrix are introduced into the numerical framework for a single soft composite layer, and fiber orientation effects are incorporated into the strain energy functions. Also, strain energy formulations are developed for multiple soft composite layers with varying fiber orientations and contributions, describing the biomechanical behavior of an entire anisotropic tissue block. Stress-strain relationships were derived from the strain energy equations for a uniaxial mechanical test condition. To validate the model parameters, experimental models of soft composites tested under uniaxial tension were characterized using the novel anisotropic hyperelastic model (R2 = 0.983). To date, such a robust anisotropic hyperelastic composite framework has not been developed, which would be indispensable for experimental characterization of tissues and for improving the fidelity of computational biological models in future.
Background. Sedentary lifestyle and work from home schedules due to the ongoing COVID-19 pandemic in 2020 have caused a significant rise in obesity across adults. With limited visits to the doctors during this period to avoid possible infections, there is currently no way to measure or track obesity. Methods. We reviewed the literature on relationships between obesity and facial features, in white, black, hispanic-latino, and Korean populations and validated them against a cohort of Indian participants ( n = 106 ). The body mass index (BMI) and waist-to-hip ratio (WHR) were obtained using anthropometric measurements, and body fat mass (BFM), percentage body fat (PBF), and visceral fat area (VFA) were measured using body composition analysis. Facial pictures were also collected and processed to characterize facial geometry. Regression analysis was conducted to determine correlations between body fat parameters and facial model parameters. Results. Lower facial geometry was highly correlated with BMI ( R 2 = 0.77 ) followed by PBF ( R 2 = 0.72 ), VFA ( R 2 = 0.65 ), WHR ( R 2 = 0.60 ), BFM ( R 2 = 0.59 ), and weight ( R 2 = 0.54 ). Conclusions. The ability to predict obesity using facial images through mobile application or telemedicine can help with early diagnosis and timely medical intervention for people with obesity during the pandemic.
Slip and fall accidents are widespread in workplaces and on walkways. Slipping is generally initiated by a sudden change in the flooring properties or due to a low available traction at the shoe–floor interface. To measure shoe-floor traction, mechanical slip and fall risk estimation devices are typically employed. However, to date, such existing devices are lab-based, bulky, and are unable to simulate realistic slip biomechanics and measure whole footwear traction in realistic contaminated floorings at the same time. Moreover, these devices are expensive and not available in low- or lower-middle-income countries with limited awareness regarding slip testing. To overcome these challenges, in this work, a biofidelic, portable, and low-cost slip testing device was developed. A strategic three-part subassembly was designed for the application of normal load, slipping speed, and heel strike angle for its modularity. The developed slip tester was extensively tested and validated for its performance using 10 formal footwears and two floorings, under dry and wet conditions. The results indicated that the slip tester was accurate, repeatable, and reliable in differentiating traction measurements across varying combinations of shoes, contaminants, and floorings. The instrumentation performance of the slip tester was found to also capture the differences between different shoe tread patterns in the presence of fluid films. The developed device is anticipated to significantly impact the clinical, industrial, and commercial performance testing of footwear traction in realistic slippery flooring conditions, especially in the low- or middle-income countries.
Slippery flooring often leads to unintentional slips and falls, which results in traumatic injuries. To reduce slipping risks, adequate traction at the shoe and flooring contact is essential. In addition, viscous slippery contaminants like water or oil reduce a floor’s traction performance and increase slipping hazards. In this work, the effect of commonly available protective floor coatings on the traction performance of safety-labelled shoes was extensively studied. The study included three floor coatings, namely acid-based etchant coating, epoxy floor paint, and polyurethane, which were tested across five safety shoes. The coated floorings were tested using a robotic slip-testing device in dry and in the presence of water and machine oil—as separate contaminants. The application of floor coatings produced varying surface roughness for the flooring. Significant traction was generated by the etchant coating for the dry flooring, epoxy coating for the wet flooring, and polyurethane coating for all flooring conditions. A comparison of uncoated and coated floorings showed a high effectiveness of generating traction with epoxy coating on wet flooring and polyurethane coating on both wet and oily conditions. The study results are novel and are anticipated to provide valuable guidelines for the selection of slip-resistant coatings for different slippery floorings, and to reduce risks related to slips and falls.
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