Anisotropic damage model for collagenous tissues and its application to model fracture and needle insertion mechanics

Biomechanics and Modeling in Mechanobiology - The analysis of tissue mechanics in biomedical applications demands nonlinear constitutive models able to capture the energy dissipation mechanisms,...     

Growing skin: tissue expansion in pediatric forehead reconstruction

Tissue expansion is a common surgical procedure to grow extra skin through controlled mechanical over-stretch. It creates skin that matches the color, texture, and thickness of the surrounding tissue, while minimizing scars and risk of rejection. Despite intense research in tissue expansion and skin growth, there is a clear knowledge gap between heuristic observation and mechanistic understanding of the key phenomena that drive the growth process. Here, we show that a continuum mechanics approach, embedded in a custom-designed finite element model, informed by medical imaging, provides valuable insight into the biomechanics of skin growth. In particular, we model skin growth using the concept of an incompatible growth configuration. We characterize its evolution in time using a second-order growth tensor parameterized in terms of a scalar-valued internal variable, the in-plane area growth. When stretched beyond the physiological level, new skin is created, and the in-plane area growth increases. For the first time, we simulate tissue expansion on a patient-specific geometric model, and predict stress, strain, and area gain at three expanded locations in a pediatric skull: in the scalp, in the forehead, and in the cheek. Our results may help the surgeon to prevent tissue over-stretch and make informed decisions about expander geometry, size, placement, and inflation. We anticipate our study to open new avenues in reconstructive surgery and enhance treatment for patients with birth defects, burn injuries, or breast tumor removal.     

Biodegradation of the Water‐Soluble Gasoline Components in a Novel Hybrid Bioreactor

A novel hybrid bioreactor was designed to remove volatile organic compounds from water contaminated with water‐soluble gasoline components, and the performance of this new bioreactor was investigated. It was composed of two biotrickling filter sections and one biofilter section. The liquid phase pollutants were removed by a mixed culture in the biotrickling filter sections and the gas phase pollutants stripped by air injection in the biofilter section. The specific rates of chemical oxygen demand (COD) removal obtained in the reactor were directly proportional to the pollutant‐loading rate. A stable operation of the hybrid bioreactor was attained for long periods of time. The bioreactor had the potential to simultaneously treat a complex mixture of volatile organic compounds, e.g., those present in the water‐soluble fraction of gasoline, as well as the capacity to readily adapt to changing operational conditions, such as an increased contaminant loading, and variations in the airflow rate.     

Computational modeling of chemo-bio-mechanical coupling: a systems-biology approach toward wound healing

Wound healing is a synchronized cascade of chemical, biological, and mechanical phenomena, which act in concert to restore the damaged tissue. An imbalance between these events can induce painful scarring. Despite intense efforts to decipher the mechanisms of wound healing, the role of mechanics remains poorly understood. Here, we establish a computational systems biology model to identify the chemical, biological, and mechanical mechanisms of scar formation. First, we introduce the generic problem of coupled chemo-bio-mechanics. Then, we introduce the model problem of wound healing in terms of a particular chemical signal, inflammation, a particular biological cell type, fibroblasts, and a particular mechanical model, isotropic hyperelasticity. We explore the cross-talk between chemical, biological, and mechanical signals and show that all three fields have a significant impact on scar formation. Our model is the first step toward rigorous multiscale, multifield modeling in wound healing. Our formulation has the potential to improve effective wound management and optimize treatment on an individualized patient-specific basis.     

Linking microvascular collapse to tissue hypoxia in a multiscale model of pressure ulcer initiation

Biomechanics and Modeling in Mechanobiology - Pressure ulcers are devastating injuries that disproportionately affect the older adult population. The initiating factor of pressure ulcers is local...     

Effect of propanil,linuron, and dicamba on the degradation kinetics of 2,4‐dichlorophenoxyacetic acid by Burkholderia sp. A study by differential analysis of 2,4‐dichlorophenoxyacetic acid degradation data

The successive application of distinct pesticides, or mixtures of them, is a frequent practice that could adversely affect the microbial species inhabiting soil and aquatic ecosystems. The ability of soil or aquatic microbiota to degrade a pesticide could be affected by the presence of another. If the degradation rate of the first compound is inhibited, its dissipation half‐life in the environment could be hazardously enlarged. Few studies have been made to quantify the impact on the biodegradation rate of pesticides in soils or water by the presence of other pesticides. In this work, a method for assessing the effect of a pesticide on the biodegradation rate of another, measuring its effect on the biodegradation kinetics of a single bacterial strain is presented. The mathematical analysis is a powerful tool to study the stoichiometry and kinetics of microbial processes, which was used to evaluate independently, in detail, the effect of three pesticides (propanil, linuron, and dicamba) on the biodegradation kinetics of 2,4‐dichlorophenoxyacetic acid by a strain of Burkholderia sp. It was evidenced that linuron and dicamba caused a decay of more than 40% in the top instantaneous degradation rate of 2,4‐dichlorophenoxyacetic acid, while propanil showed a minimal effect.