Modeling Electrochemical Oxidation of Hydrogen on Ni–YSZ Pattern Anodes

A computational model is developed to represent the coupled behavior of elementary chemistry, electrochemistry, and transport in the vicinity of solid-oxide fuel cell three-phase boundaries. The model is applied to assist the development and evaluation of H_2 charge-transfer reaction mechanisms for Ni–yttria-stabilized zirconia (YSZ) anodes. Elementary chemistry and surface transport for the Ni and YSZ surfaces are derived from prior literature. Previously published patterned-anode experiments [J. Mizusaki et al., Solid State Ionics, 70/71, 52 (1994)] are used to evaluate alternative electrochemical charge-transfer mechanisms. The results show that a hydrogen-spillover mechanism can explain the Mizusaki polarization measurements over wide ranges of gas-phase composition with both anodic and cathodic biases

Rhinitis in the geriatric population

The current geriatric population in the United States accounts for approximately 12% of the total population and is projected to reach nearly 20% (71.5 million people) by 2030[1]. With this expansion of the number of older adults, physicians will face the common complaint of rhinitis with increasing frequency. Nasal symptoms pose a significant burden on the health of older people and require attention to improve quality of life. Several mechanisms likely underlie the pathogenesis of rhinitis in these patients, including inflammatory conditions and the influence of aging on nasal physiology, with the potential for interaction between the two. Various treatments have been proposed to manage this condition; however, more work is needed to enhance our understanding of the pathophysiology of the various forms of geriatric rhinitis and to develop more effective therapies for this important patient population

The incorporation of solid electrolyte interphase (SEI) chemistry into Li-ion battery models

During lithium-ion battery operation and storage, the active electrode particles react with the electrolyte solution to form passivating surface films. These surface films prevent the continuous oxidation/reduction of the electrolyte solution, which can lead to large irreversible losses and electrode structural failure. Surface films form on both anode (graphite) and cathode (transition metal oxide) particles. However, the electrolyte solution is thermodynamically unstable at the operating potentials of graphite. Thus, the surface film, also referred to as the solid electrolyte interphase (SEI) film, that is formed on graphite particles is more critical to battery performance and lifetime. Aurbach and colleagues have used various spectroscopic and electrochemical measurements to study the SEI films formed on carbon particles Christensen and Newman developed a physically based model for SEI growth on a single graphite-particle surface The SEI-formation chemistry is modeled with a reaction mechanism that describes the two-electron reduction of ethylene carbonate (C 3 H 4 O 3 ) to form lithium carbonate (Li 2 CO 3 ) as single species that represents the SEI film The particle model is used to study film growth during cycling. Models often use an empirical expression to represent SEI film resistance as R SEI = kt 1/ 2 , where t is time and k is a proportionality constant. The film resistance depends on film thickness l and resistivity ρ as R SEI = ρl . During a single cycle, film thickness is not proportional to the square root of time (se

Model for the role of macromolecular crowding in regulation of cellular volume.

A simple model is proposed to account for large increases in transporter-mediated ion flux across cell membranes that are elicited by small fractional changes of cell volume. The model is based upon the concept that, as a result of large excluded volume effects in cytoplasm (macromolecular crowding), the tendency of soluble macromolecules to associate with membrane proteins is much more sensitive to changes in cell water content than expected on the basis of simple considerations of mass action. The model postulates that an ion transporter may exist in either an active dephosphorylated state or an inactive phosphorylated state and that the steady-state activity of the transporter reflects a balance between the rates of phosphatase-catalyzed activation and kinase-catalyzed inactivation. Cell swelling results in the inhibition of kinase relative to phosphatase activity, thereby increasing the steady-state concentration of the active form of the transporter. Calculated volume-dependent stimulation of ion flux is comparable to that observed experimentally

The Effects of a Modeling and Computational Thinking Professional Development Program on STEM Educators’ Perceptions toward Teaching Science and Engineering Practices

Teachers’ integration of the Next Generation Science Standards and corresponding Science and Engineering Practices (SEPs) illustrate current science education reform in the United States. Effective teacher professional development (PD) on SEPs is essential for reform success. In this study, we evaluated the Nebraska STEM Education Conference, a PD program for middle school, high school, and first- and second-year post-secondary STEM teachers. This SEP-oriented PD program focused predominantly on the SEPs ‘developing and using models’ and ‘using mathematics and computational thinking.’ An electronic survey was used to measure participants’ (n = 45) prior integration of SEPs, influential factors and barriers to using SEPs, and changes to interest and confidence in using SEPs as a result of attending the PD program. Our results showed that teachers had limited prior use of SEPs in their teaching. Student interest and learning outcomes were the factors found to be most influential to teachers’ use of SEPs, while limited knowledge, confidence, and resources were the most commonly identified barriers. As a result of attending the PD program, participants significantly improved their confidence and interest to incorporate SEPs. We recommend continued SEP-oriented PD to foster successful NGSS integration and to advance reforms in science education

Voltage-Based Strategies for Preventing Battery Degradation under Diverse Fast-Charging Conditions

Maintaining safe operating conditions is a key challenge for high-performance lithium-ion battery applications. The lithium-plating reaction remains a risk during charging, but limited studies consider the highly variable charging conditions possible in commercial cells. Here we combine pseudo-2D electrochemical modeling with data visualization methods to reveal important relationships between the measurable cell voltage and difficult-to-predict Li-plating onset criteria. An extensively validated model is used to compute Li plating for thousands of multistep charging conditions spanning diverse rates, temperatures, states-of-charge, and cell aging. We observe an empirical cell operating voltage limit below which plating does not occur across all conditions, and this limit varies with the battery state-of-charge and aging. A model sensitivity analysis also indicates that, when comparing two charging voltage profiles, the capacity difference at 4.0 V correlates well with the difference in the plating onset capacity. These results encourage simple strategies for Li-plating prevention that are complementary to existing battery controls