University of Waterloo

We present path integral Monte Carlo simulation results for the equation of state of solid parahydrogen between 0.024 and 0.1Å−3 at T = 4.2 K. The simulations are performed using non-additive isotropic ab initio two-body, three-body, and four-body potential energy surfaces (PESs). We apply corrections to account for both the finite size simulation errors and the Trotter factorization errors. Simulations that use only the two-body PES during sampling yield an equation of state similar to that of simulations that use both the two-body and three-body PESs during sampling. With the four-body interaction energy, we predict an equilibrium density of 0.02608Å−3, very close to the experimental result of 0.0261Å−3. The inclusion of the four-body interaction energy also brings the simulation results in excellent agreement with the experimental pressure–density data until around 0.065Å−3, beyond which the simulation results overestimate the pressure. These PESs overestimate the average kinetic energy per molecule at the equilibrium density by about 7% compared to the experimental result. Our findings suggest that, at higher densities, we require five-body and higher-order many-body interactions to quantitatively improve the agreement between the pressure-density curve produced by simulations and that of the experiment. Using the four-body PES during sampling at excessively high densities, where such higher-order many-body interactions are likely to be significant, causes an artificial symmetry breaking in the hcp lattice structure of the solid.

Identifying ultrathin and flexible solid‐state electrolytes with high ionic conductivity and low interfacial resistance is crucial for scale‐up production of solid‐state sodium (Na) metal batteries (SSMBs). However, the challenges of poor processing scalability, insufficient intrinsic mechanical strength, and limited ionic transport capacity remain unaddressed. Herein, an ultrathin 9.7 µm solid‐state electrolyte membrane featuring a dual‐polymer entangled network is meticulously engineered through an arrayed multi‐nozzle electrospinning technique with a swelling and hot pressing process using polyacrylonitrile and poly(ether‐block‐amide), which exhibits an exceptional voltage tolerance, enhanced tensile strength, and superior thermal stability. The soft ether oxygens segments in multiblock copolymers complex with Na⁺ to promote the rapid hopping transport of Na⁺. Meanwhile, interconnected electronegative channels based on carbonyl and cyanogen groups serve as Na⁺ conduits to smooth ion fluctuations and accelerate Na⁺ selective conduction simultaneously. The obtained inorganic‐organic composite solid electrolyte interface with the improved mechanical strength of ultrathin solid‐state electrolytes effectively suppresses Na dendrites with low overpotential over 500 h. The solid‐state cells paired with layered oxides deliver a capacity retention of over 91.1% between 25 °C and 65 °C, and assembled pouch cells exhibit impressive energy density over 100 cycles, showing great potential for large‐scale application of ultrathin structure in the SSMBs.

Analyzing diabetes‐related hormones such as insulin and glucagon using conventional enzyme‐linked immunosorbent assay (ELISA) has been the gold standard. However, ELISAs have a long sample processing time, including blood serum/plasma preparation which restricts the number of measurement time points, making it difficult to accurately track hormone dynamics in relation to each other and to blood glucose levels. Here, a multi‐module microfluidic platform, named quantum dot integrated real‐time (QIRT)‐ELISA system, that uses a bead‐based quantum dot‐mediated immunoassay (BQI) to continuously monitor insulin and glucagon in whole blood samples and in a multiplexed setting is demonstrated. The use of BQI simplifies the technical aspect of the system, removes the need for bulky and expensive equipment, and most importantly enhances the sensitivity, specificity, and temporal resolution. Validation experiments measuring levels of insulin and glucagon in rats during glucose tolerance tests demonstrate the accuracy of QIRT‐ELISA for simultaneously measuring endogenous hormones within the physiological range during an oral glucose load.

Background Detecting early changes in walking speed can allow older adults to seek preventative rehabilitation. Currently, there is a lack of consensus on which assessments to use to assess walking speed and how to continuously monitor walking speed outside of the clinic. Chirp is a privacy-preserving radar sensor developed to continuously monitor older adults’ safety and mobility without the need for cameras or wearable devices. Our study purpose was to evaluate the inter-sensor reliability, intrasession test-retest reliability, and concurrent validity of Chirp in a clinical setting. Methods We recruited 35 community-dwelling older adults (mean age 75.5 (standard deviation: 6.6) years, 86% female). All participants lived alone in an urban city in southwestern Ontario and had access to a smart device with wireless internet. Data were collected with a 4-meter ProtoKinetics ZenoTM Walkway (pressure sensors) with the Chirp sensor (radar positioning) at the end of the walkway. We assessed participants walking speed during normal and adaptive locomotion experimental conditions (walking-while-talking, obstacle, narrow walking, fast walking). We selected walking speed as a measure as it is a good predictor of functional mobility but also is associated with physical and cognitive functioning in older adults. Each of the experimental conditions was conducted twice in a randomized order, with fast walking trials performed last. For intra-session reliability testing, we conducted two blocks of walks within a participant session separated by approximately 30 minutes. Intraclass Correlation Coefficient(A,1) (ICC(A,1)) was used to assess the reliability and validity. Linear regression, adjusted for gender, was used to investigate the association between Chirp and cognition and health-related quality of life scores. Results Chirp walking speed inter-sensor reliability ICC(A,1) = 0.999[95% Confidence Interval [CI]: 0.997 to 0.999] and intrasession test-retest reliability [ICC(A,1) = 0.921, 95% CI: 0.725 to 0.969] were excellent across all experimental conditions. Chirp walking speed concurrent validity compared to the ProtoKinetics ZenoTM Walkway was excellent across experimental conditions [ICC(A,1) = 0.993, 95% CI: 0.985 to 0.997]. We found a weak association between walking speed and cognition scores using the Montreal Cognitive Assessment across experimental conditions (estimated β-value = 7.79, 95% CI: 2.79 to 12.80) and no association between walking speed and health-related quality of life using the 12-item Short Form Survey across experimental conditions (estimated β-value = 6.12, 95% CI: -7.12 to 19.36). Conclusion Our results demonstrate that Chirp is a reliable and valid measure to assess walking speed parameters in clinics among older adults.

The anode catalyst layer is composed of catalytically functional IrOx and protonic conducting ionomer and largely dictates catalytic performance of proton exchange membrane water electrolyzer (PEMWE). Here, we report a new type of anode nanocatalyst that possesses both IrOx’s catalytic function and high proton conductivity that traditional anode catalysts lack and demonstrate its ability to construct high‐performance, low‐ionomer‐dependent anode catalyst layer, the interior of which—about 85% of total catalyst layer—is free of ionomers. The proton‐conducting anode nanocatalyst is prepared via protonation of layered iridate K0.5(Na0.2Ir0.8)O2 and then exfoliation to produce cation vacancy‐rich, 1 nm‐thick iridium oxide nanosheets (labeled as □‐HxIrOy). Besides being a proton conductor, the □‐HxIrOy is found to have abundant catalytic active sites for the oxygen evolution reaction due to the optimization of both edge and in‐plane iridium sites by multiple cation vacancies. The dual functionality of □‐HxIrOy allows the fabrication of low‐iridium‐loading, low‐ionomer‐dependent anode catalyst layer with enhanced exposure of catalytic sites and reduced electronic contact resistance, in contrast to common fully mixed catalyst/ionomer layers in PEMWE. This work represents an example of realizing the structural innovation in anode catalyst layer through the bifunctionality of anode catalyst.