Recent experiments have demonstrated that identical material samples can charge one another after being brought into symmetric contact. The mechanism for this charging is not known. In this article, we use a simplified one-dimensional lattice model to analyze charging in the context of agitated particles. We find that the electric field from a single weakly polarized grain can feed back on itself by polarizing its neighbors, leading to an exponential growth in polarization. We show that, by incorporating partial neutralization between neighboring polarized particles, either uniform alignment of dipoles or complex charge and polarization waves can be produced. We reproduce a polarized state experimentally using identical colliding particles and raise several issues for future study.

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Background The COVID-19 pandemic has uniquely affected the United States. We hypothesize that transplantation would be uniquely affected. Methods In this population-based cohort study, adult transplantation data were examined as time series data. Autoregressive-integrated-moving-average models of transplantation rates were developed using data from 1990 to 2019 to forecast the 2020 expected rates in a theoretical scenario if the pandemic did not occur to generate observed-to-expected (O/E) ratios. Results 32,594 transplants were expected in 2020, and only 30,566 occurred (O/E 0.94, CI 0.88–0.99). 58,152 waitlist registrations were expected and 50,241 occurred (O/E 0.86, CI 0.80–0.94). O/E ratios of transplants were kidney 0.92 (0.86–0.98), liver 0.96 (0.89–1.04), heart 1.05 (0.91–1.23), and lung 0.92 (0.82–1.04). O/E ratios of registrations were kidney 0.84 (0.77–0.93), liver 0.95 (0.86–1.06), heart 0.99 (0.85–1.18), and lung 0.80 (0.70–0.94). Conclusions The COVID-19 pandemic was associated with a significant deficit in transplantation. The impact was strongest in kidney transplantation and waitlist registration.

Background Lung transplantation is the mainstay of treatment for patients with end‐stage respiratory failure. This study sought to evaluate survival following transplantation compared to the general population and quantify standardized mortality ratios (SMRs) using a nested case‐control study design. Methods Control subjects were nonhospitalized inhabitants of the United States identified through the National Longitudinal Mortality Study. Case subjects were adults who underwent lung transplantation between 1990 and 2007 and identified through the Organ Procurement and Transplantation Network. Propensity‐matching (5:1, nearest neighbor, caliper = 0.1) was utilized to identify suitable control subjects based on age, sex, race, and location of residency. The primary study endpoint was 10‐year survival. Results About 14,977 lung transplant recipients were matched to 74,885 nonhospitalized US residents. The 10‐year survival rate of lung transplant recipients was 28% (95% confidence interval [CI] = 27%–29%). The population expected mortality rate was 19 deaths/100 person‐years while the observed ratio was 104 deaths/100 person‐years (SMR = 5.39, 95% CI = 5.35–5.43). The largest discrepancies between observed and expected mortality rates were in females (SMR = 5.97), Hispanic (SMR = 10.70), and single lung recipients (SMR = 5.92). SMRs declined over time (1990–1995 = 5.79, 1996–2000 = 5.64, and 2001–2007 = 5.10). Standardized mortality peaks in the first year after transplant and decreases steadily over time. Conclusions Lung transplant recipients experience a fivefold higher SMR compared to the nonhospitalized population. Long‐term mortality rates have experienced consistent decline over time.

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