Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates

The present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion, is naturally isolated from diabatic cross-contour motions. Therefore, Lagrangian particle motions in the transformed coordinate obey a transformed zeroth-order stochastic (i.e., random walk) model with the diffusivity replaced by the effective diffusivity. Such a stochastic model becomes the theoretical foundation on which both diffusivities are exactly unified. In the absence of small-scale diffusion, particles do not disperse at all in the transformed contour coordinate. Besides, the corresponding Lagrangian autocorrelation becomes a delta function and is thus free from pronounced overshoot and negative lobe at short time lags that may be induced by either Rossby waves or mesoscale eddies; that is, particles decorrelate immediately and Lagrangian diffusivity is already asymptotic nomatter how small the time lag is. The resulting instantaneous Lagrangian spreading rate is thus conceptually identical to the effective diffusivity that only measures the instantaneous irreversible mixing. In these regards, the present study provides a new look at particle dispersion in contour-based coordinates

Pattern and associated factors of cognitive failures in the general chinese population during the early stages of the COVID-19 pandemic: A cross-sectional study

Background: The coronavirus disease-2019 (COVID-19) pandemic worldwide has caused a high burden of mental problems, which may be associated with subjective cognitive impairment in the general population. Objectives: This cross-sectional survey aimed to investigate the level and pattern of cognitive failure (CF) and its negative changes during the COVID-19 pandemic among the general population in China. Methods: The participants completed an online questionnaire between April 18 and May 4, 2020, and those aged between 18 and 70 were included in this study. CF was measured using the 14-item CF Questionnaire (CFQ-14). Factors associated with CF and negative changes in CF were evaluated using multiple linear and logistic regression models. A total of 30,879 eligible participants were recruited; most were female (59.10%) and aged 31–45 (61.51%). Results: The mean CFQ-14 score was 15.62 (standard deviation = 11.55), and 4,619 (14.96%) participants reported negative changes in CF during the pandemic. Multiple regression analyses showed that participants with female gender, history of physical and mental disease, the self-perceived influence of COVID-19, altered appetite and taste preference, worse interpersonal relationships, long sleep duration, poor sleep quality, depressive, anxiety and posttraumatic stress disorder symptoms had a higher level of CF and negative CF changes, while regular exercise was associated with a lower risk of both outcomes. Conclusions: This study indicates that CF symptoms should be monitored in the general population during pandemics. A healthy lifestyle and reduction in psychological stress could help promote normal cognitive function during pandemics