Persistence of endogenous SARS-CoV-2 and pepper mild mottle virus RNA in wastewater settled solids

Limited information is available on the decay rate of endogenous SARS-CoV-2 and pepper mild mottle virus (PMMoV) RNA in wastewater and primary settled solids, potentially limiting an understanding of how transit or holding times within wastewater infrastructure might impact RNA measurements and their relationship to community COVID-19 infections. In this study, primary settled solids samples were collected from two wastewater treatment plants in the San Francisco Bay Area. Samples were thoroughly mixed, aliquoted into subsamples, and stored at 4°C, 22°C, and 37°C for 10 days. The concentration of SARS-CoV-2 (N1 and N2 targets) and PMMoV RNA was measured using an RT-ddPCR. Limited decay (< 1 log10 reduction) was observed in the detection of viral RNA targets at all temperature conditions, suggesting that SARS-CoV-2 and PMMoV RNA can be highly persistent in solids. First-order decay rate constants ranged from 0.011 - 0.098 day-1 for SARS-CoV-2 RNA and 0.010 - 0.091 day-1 for PMMoV RNA, depending on temperature conditions. Slower decay was observed for SARS-CoV-2 RNA in primary settled solids compared to previously reported decay in wastewater influent. Further research is needed to understand if solid content and wastewater characteristics might influence the persistence of viral RNA targets.

Resilience of countries to COVID-19 correlated with trust

We characterized > 150 countries’ resilience to COVID-19 as the nationwide decay rate of daily cases or deaths from peak levels. Resilience to COVID-19 varies by a factor of ~ 40 between countries for cases/capita and ~ 25 for deaths/capita. Trust within society is positively correlated with country-level resilience to COVID-19, as is the adaptive increase in stringency of government interventions when epidemic waves occur. By contrast, countries where governments maintain greater background stringency tend to have lower trust within society and tend to be less resilient. All countries where > 40% agree “most people can be trusted” achieve a near complete reduction of new cases and deaths, but so do several less-trusting societies. As the pandemic progressed, resilience tended to decline, as adaptive increases in stringency also declined. These results add to evidence that trust can improve resilience to epidemics and other unexpected disruptions, of which COVID-19 is unlikely to be the last.

Mean square stability with general decay rate of nonlinear neutral stochastic function differential equations in the $ G $-framework

<abstract><p>Few results seem to be known about the stability with general decay rate of nonlinear neutral stochastic function differential equations driven by $ G $-Brownain motion ($ G $-NSFDEs in short). This paper focuses on the $ G $-NSFDEs, and the coefficients of these considered $ G $-NSFDEs can be allowed to be nonlinear. It is first proved the existence and uniqueness of the global solution of a $ G $-NSFDE. It is then obtained the trivial solution of the $ G $-NSFDE is mean square stable with general decay rate (including the trivial solution of the $ G $-NSFDE is mean square exponentially stable and the trivial solution of the $ G $-NSFDE is mean square polynomially stable) by $ G $-Lyapunov functions technique. In this paper, auxiliary functions are used to dominate the Lyapunov function and the diffusion operator. Finally, an example is presented to illustrate the obtained theory.</p></abstract>

On the optimality of optical pumping for a closed Λ-system with large decay rates of the intermediate excited state

We use optimal control theory to show that for a closed Λ-system where the excited intermediate level decays to the lower levels with a common large rate, the optimal scheme for population transfer between the lower levels is actually optical pumping. In order to obtain this result we exploit the large decay rate to eliminate adiabatically the weakly coupled excited state, then perform a transformation to the basis comprised of the dark and bright states, and finally apply optimal control to this transformed system. Subsequently, we confirm the optimality of the optical pumping scheme for the original closed Λ-system using numerical optimal control. We also demonstrate numerically that optical pumping remains optimal when the decay rate to the target state is larger than that to the initial state or the two rates are not very different from each other. The present work is expected to find application in various tasks of quantum information processing, where such systems are encountered

Persistence of fecal indicator bacteria and associated genetic markers from wastewater treatment plant effluents in freshwater microcosms

Limited information exists on the environmental persistence of genetic markers for fecal indicator bacteria (FIB) in treated wastewaters. Here, the decay rate constants of culturable cells and genetic markers for four diverse groups of FIBs, such as enterococci, Clostridium, Escherichia coli, and Bacteroides, were investigated in freshwater microcosms seeded with disinfected and non-disinfected secondary-treated wastewaters. Decay rate constants of genetic markers and culturable cells varied significantly among the different FIB groups. Water temperatures (winter vs. fall/spring/summer) significantly affected the decay of all genetic marker and cell types; however, genetic marker decay were not found to be significantly different in disinfected (chlorination/ultraviolet) and non-disinfected wastewater-seeded microcosms or, for example, lake- and river-receiving waters. No evidence was seen that decay rate constants of FIB genetic markers from treated wastewater were substantially different from those observed in similar, previously reported microcosm studies using raw sewage. Unexpected relationships between decay rate constants of genetic markers and culturable cells of Bacteroides were observed. Results suggest that decay rate constants of FIB genetic markers determined from other studies may be applicable to treated wastewaters. Results of this study should be informative for ongoing efforts to determine the persistence of FIB genetic markers relative to surviving pathogens after wastewater treatment.

Decay of weak solutions to Vlasov equation coupled with a shear thickening fluid

We show that the energy norm of weak solutions to Vlasov equation coupled with a shear thickening fluid on the whole space has a decay rate the energy norm $E(t) \leq {C}/{(1+t)^{\alpha }}, \forall t \geq 0$ for $\alpha \in (0,3/2)$ .

Pseudo-bounces vs. new instantons

Some false vacua do not decay via bounces. This usually happens when a flat direction of the tunneling action due to scale invariance is lifted to a sloping valley by a scale breaking perturbation, pushing the bounce off to infinity. We compare two types of alternative decay configurations that have been proposed recently to describe decay in such cases: pseudo-bounces and new instantons. Although both field configurations are quite similar, we find that the pseudo-bounce action is lower than the new instanton one and describes more faithfully the bottom of the action valley. In addition, pseudo-bounces cover a range of field space wider than new instantons and, as a result, lead to a decay rate that can be lower than the one via new instantons by orders of magnitude.