Nonequilibrium Thermodynamics of Porous Electrodes

We reformulate and extend porous electrode theory for non-ideal active materials, including those capable of phase transformations. Using principles of non-equilibrium thermodynamics, we relate the cell voltage, ionic fluxes, and Faradaic charge-transfer kinetics to the variational electrochemical potentials of ions and electrons. The Butler-Volmer exchange current is consistently expressed in terms of the activities of the reduced, oxidized and transition states, and the activation overpotential is defined relative to the local Nernst potential. We also apply mathematical bounds on effective diffusivity to estimate porosity and tortuosity corrections. The theory is illustrated for a Li-ion battery with active solid particles described by a Cahn-Hilliard phase-field model. Depending on the applied current and porous electrode properties, the dynamics can be limited by electrolyte transport, solid diffusion and phase separation, or intercalation kinetics. In phase-separating porous electrodes, the model predicts narrow reaction fronts, mosaic instabilities and voltage fluctuations at low current, consistent with recent experiments, which could not be described by existing porous electrode models

Phase Transformation Dynamics in Porous Battery Electrodes

Porous electrodes composed of multiphase active materials are widely used in Li-ion batteries, but their dynamics are poorly understood. Two-phase models are largely empirical, and no models exist for three or more phases. Using a modified porous electrode theory based on non-equilibrium thermodynamics, we show that experimental phase behavior can be accurately predicted from free energy models, without artificially placing phase boundaries or fitting the open circuit voltage. First, we simulate lithium intercalation in porous iron phosphate, a popular two-phase cathode, and show that the zero-current voltage gap, sloping voltage plateau and under-estimated exchange currents all result from size-dependent nucleation and mosaic instability. Next, we simulate porous graphite, the standard anode with three stable phases, and reproduce experimentally observed fronts of color-changing phase transformations. These results provide a framework for physics-based design and control for electrochemical systems with complex thermodynamics

Particle-Level Modeling of the Charge-Discharge Behavior of Nanoparticulate Phase-Separating Li-Ion Battery Electrodes

In nanoparticulate phase-separating electrodes, phase separation inside the particles can be hindered during their charge/discharge cycles even when a thermodynamic driving force for phase separation exists. In such cases, particles may (de)lithiate discretely in a process referred to as mosaic instability. This instability could be the key to elucidating the complex charge/discharge dynamics in nanoparticulate phase-separating electrodes. In this paper, the dynamics of the mosaic instability is studied using Smoothed Boundary Method simulations at the particle level, where the concentration and electrostatic potential fields are spatially resolved around individual particles. Two sets of configurations consisting of spherical particles with an identical radius are employed to study the instability in detail. The effect of an activity-dependent exchange current density on the mosaic instability, which leads to asymmetric charge/discharge, is also studied. While we show that our model reproduces the results of a porous-electrode model for the simple setup studied here, it is a powerful framework with the capability to predict the detailed dynamics in three-dimensional complex electrodes and provides further insights into the complex dynamics that result from the coupling of electrochemistry, thermodynamics, and transport kinetics

Identifying ILI Cases from Chief Complaints: Comparing the Accuracy of Keyword and Support Vector Machine Methods

We compared the accuracy of two methods of identifying ILI cases from chief complaints. We found that a support vector machine method was more accurate than a keyword method

Wellness Review 2020, Part 2

Introduction: This article comprises Part 2 of the Journal of Wellness review of 2020 wellness literature (July – December). In this review, JWellness editors continue the goal of offering a cohesive summary of recent publications within the wellness domain. We summarize new science and resilience initiatives published outside of JWellness that seek understanding of either burnout and its prevention or thriving in the medical community. Methods: From the interval of 01 July – 31 Dec 2020, PubMed was queried for empirical research studies, review articles, and editorials in accordance with the following algorithm: an article was required to have two delineating keywords, each from a separate grouping. The first identified medical professionals in either the title or the abstract: (“clinical professionals,” “physicians,” or “caregivers”), and the other identified a wellness-related keyword in the title: (“wellness,” “burnout,” “resilience,” or “resiliency”). Literature in Review: A total of 234 articles resulted. The list for inclusion was then narrowed to sixty-three articles plus one that was hand-picked. Recent literature into physician wellness, burnout and resilience continues to focus heavily on COVID-19. Well-researched topics include burnout surveillance, proposals for and small investigations into resilience, multiple studies attempting to differentiate characteristics that predispose to burnout, and the impact of the pandemic. Less has been written on leadership, financial wellness, and sustainable resilience-building initiatives. We note relatively few control-measured interventional studies—the majority of which remain small in endeavor and short in duration, limiting generalizability. Conclusion: Recent literature into physician wellness, burnout and resilience focuses heavily on COVID-19. Many workplace / organizational factors negatively influence wellness: cumbersome EHRs, cultures not focused on socialization and self-compassion, and high physician task load. We express optimism regarding future interventional studies of burnout mitigation and resilience enhancement

Urban Garden Survival

Urban gardens are community led plots designated for agricultural purposes in residential and urban areas. Greenville County has seen a recent growth in urban gardens with the assistance of non-profit groups like Gardening for Good. The current total in Greenville County stands at 79 with new gardens added every year. While the growth is encouraging, some gardens have failed. This study uses GIS to explore the social and ecological factors that correlate with urban garden survival in an effort to provide garden managers with information that will help them develop gardens that thrive and persist

The economics of vertical coordination in the organic wheat supply chain

The organic wheat supply chain in Canada operates in a relatively new sector for which there is very little public information to aid in price discovery. Organic wheat producers must use available information in order to decide when to sell their wheat and whom to sell to. The relatively low degree of market information, especially for producers, suggests a problem of information asymmetry, which may have ramifications for efficiency and the distribution of rents in the organic wheat supply chain. The literature on Transaction Cost Economics, Agency Theory and the Economics of Information is used in the thesis to theorize differences between methods of selling organic wheat that vary in terms of vertical coordination. The analysis involves a comparison of selling to large and small grain companies, selling through Producer-Owned Firms (POFs) and selling directly to processors. The theory predicts that producers gain from using a POF because of savings in transaction costs and higher prices. These theorized differences in transaction costs and price are due to increased sharing of information between the producer and the marketing agent, enhanced producer control over the marketer, and incentive for the marketer to provide producers with a high price. These benefits can also be realized by selling directly to a processor, but only if the producer can effectively and efficiently perform his or her own marketing functions. Average cost, price and profit margins are used as a metric for comparing each of the four governance structures. A survey of organic wheat producers in Saskatchewan was undertaken in order to collect data on organic Hard Red Spring Wheat (HRSW) transactions. The results indicate that governance structure has a statistically significant effect on organic HRSW prices and on producer transaction costs. The analysis concludes that the producer receives the greatest profit margin from selling through the vertically coordinated POF, while a marketer receives the greatest profit margin if it operates as a large grain company and purchases HRSW on the spot market. The results also suggest that organic producers that “eliminate the middleman” and sell directly to processors cannot market as efficiently and effectively compared with producers that use a POF. The results of this thesis emphasize that increased coordination between producer and marketer through a POF can be advantageous for the producer, but not necessarily for the marketer, due to the difference in the distribution of rents

Wellness Review 2023, Part 1

Introduction: The 2023 Part 1 summary reviews research on wellness in healthcare professionals published outside of JWellness from January 1, 2023 to June 30, 2023. Methods: Editors conducted a Boolean search of titles and abstracts in PubMed utilizing keyword identifiers pairing healthcare personnel (providers, nurses, and other staff) with a well-being metric. Of 416 relevant articles, an intriguing and innovative 30 were selected for inclusion, with two additional articles manually curated. Literature Review: This sample of the recent literature into healthcare professional wellness included multiple targeted interventions and studies of resilience. Main themes that emerged include: positive systematic healthcare changes spurned by COVID-19, strategies for retention of talent, optimistic outcomes from mindfulness interventions, work-life balance implications, bolstering of well-being through compassion, kindness and empathy, team resilience and cohesion, and well-being modifications recommended to medical training programs. Conclusion: JWellness editors highlight positive outcomes related to the strain of COVID-19. We continue to advocate for and summarize resilience building interventions and systemic workplace changes that facilitate comprehensive well-being. Healthcare professionals equipped with tools of emotional regulation can not only a endure strenuous work environment, but emerge stronger after encountering hardship