In mid‐December 2019, a disease caused by infection with severe acute respiratory syndrome coronavirus‐2, which began in Wuhan, China, has spread throughout the country and many countries around the ...world. The number of children with coronavirus disease‐2019 (COVID‐19) has also increased significantly. Although information regarding the epidemiology of COVID‐19 in children has accumulated, relevant comprehensive reports are lacking. The present article reviews the epidemiological characteristics of COVID‐19 in children.
The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the world is still expanding. Thus, there is an urgent need to better understand this novel virus and find a way to ...control its spread. Like other coronaviruses, the nucleocapsid (N) protein is one of the most crucial structural components of SARS-CoV-2. This protein shares 90% homology with the severe acute respiratory syndrome coronavirus N protein, implying functional significance. Based on the evolutionary conservation of the N protein in coronavirus, we reviewed the currently available knowledge regarding the SARS-CoV-2 N protein in terms of structure, biological functions, and clinical application as a drug target or vaccine candidate.
In this paper we consider a quasilinear viscoelastic wave equation in canonical form with the homogeneous Dirichlet boundary condition. We prove that, for certain class of relaxation functions and ...certain initial data in the stable set, the decay rate of the solution energy is similar to that of the relaxation function. This result improves earlier ones obtained by Messaoudi and Tatar S.A. Messaoudi, N.-E. Tatar, Global existence and uniform stability of solutions for a quasilinear viscoelastic problem, Math. Methods Appl. Sci. 30 (2007) 665–680 in which only the exponential and polynomial decay rates are considered. Conversely, for certain initial data in the unstable set, there are solutions that blow up in finite time. The last result is new, since it allows a larger class of initial energy which may take positive values.
Transition metal dichalcogenides have recently been considered the candidates for saturable absorption materials due to their advantages in both electronic and optoelectronic. Compared with MoS 2 and ...WS 2 , MoTe 2 exhibits smaller bandgap. As a result, MoTe 2 owns inherent advantages in the near-infrared applications. In this paper, the MoTe 2 saturable absorber (SA) were prepared by the magnetron sputtering deposition method. Owing to the enhanced light-materials interaction between MoTe 2 and evanescent field from the microfiber, the modulation depth of the MoTe 2 SA was up to 26.97%. By assembling the MoTe 2 SA into the erbium-doped fiber laser, the mode-locked fiber laser at 1.5 μm was demonstrated. The pulse duration of 111.9 fs was proved to be the shortest in the fiber lasers based on transition metal dichalcogenides. Moreover, the mode-locked fiber laser maintains the long-term stability. Our results suggest that the proposed MoTe 2 SA is promising for the ultrashort pulse generation and stable system operation.
The utilization of solar energy for the conversion of CO2 into valuable organic products is one of the best solutions to solve the problems of global warming and energy shortage. The development of ...photocatalysts capable of reducing CO2 under visible light, especially those containing earth-abundant metals, is significant. Herein we report that a series of earth-abundant Fe-containing MOFs (MIL-101(Fe), MIL-53(Fe), MIL-88B(Fe)) show photocatalytic activity for CO2 reduction to give formate under visible light irradiation. The direct excitation of the Fe–O clusters in these MOFs induces the electron transfer from O2– to Fe3+ to form Fe2+, which is responsible for the photocatalytic CO2 reduction. Among the three investigated Fe-based MOFs, MIL-101(Fe) showed the best activity due to the existence of the coordination unsaturated Fe sites in its structure. All three amine-functionalized Fe-containing MOFs (NH2-MIL-101(Fe), NH2-MIL-53(Fe) and NH2-MIL-88B(Fe)) showed enhanced photocatalytic activity in comparison to the unfunctionalized MOF, due to the existence of dual excitation pathways: i.e., excitation of an NH2 functionality followed by an electron transfer to the Fe center in addition to the direct excitation of Fe–O clusters.
Ti-substituted NH2-Uio-66(Zr/Ti) prepared by using a post-synthetic exchange (PSE) method showed enhanced photocatalytic performance for both CO2 reduction and hydrogen evolution under visible light. ...Density functional theory (DFT) calculations and electron spin resonance (ESR) results reveal that the introduced Ti substituent acts as a mediator to facilitate electron transfer, which results in enhanced performance.
In this paper, we consider a system of two coupled quasilinear viscoelastic equations in canonical form with Dirichlet boundary condition. We use the perturbed energy method to show that the ...dissipations given by the viscoelastic terms are strong enough to ensure uniform decay (with exponential and polynomial rates) of the solutions energy, which extends some existing results for a single equation to the case of a coupled system.
This work focuses on chirped solitons in a higher-order nonlinear Schrödinger equation, including cubic-quintic-septic nonlinearity, weak nonlocal nonlinearity, self-frequency shift, and ...self-steepening effect. For the first time, analytical bright and kink solitons, as well as their corresponding chirping, are obtained. The influence of septic nonlinearity and weak nonlocality on the dynamical behaviors of those nonlinearly chirped solitons is thoroughly addressed. The findings of the study give an experimental basis for nonlinear-managed solitons in optical fibers.
Summary Background On March 30, 2013, a novel avian influenza A H7N9 virus that infects human beings was identified. This virus had been detected in six provinces and municipal cities in China as of ...April 18, 2013. We correlated genomic sequences from avian influenza viruses with ecological information and did phylogenetic and coalescent analyses to extrapolate the potential origins of the virus and possible routes of reassortment events. Methods We downloaded H7N9 virus genome sequences from the Global Initiative on Sharing Avian Influenza Data (GISAID) database and public sequences used from the Influenza Virus Resource. We constructed phylogenetic trees and did 1000 bootstrap replicates for each tree. Two rounds of phylogenetic analyses were done. We used at least 100 closely related sequences for each gene to infer the overall topology, removed suspicious sequences from the trees, and focused on the closest clades to the novel H7N9 viruses. We compared our tree topologies with those from a bayesian evolutionary analysis by sampling trees (BEAST) analysis. We used the bayesian Markov chain Monte Carlo method to jointly estimate phylogenies, divergence times, and other evolutionary parameters for all eight gene fragments. We used sequence alignment and homology-modelling methods to study specific mutations regarding phenotypes, specifically addressing the human receptor binding properties. Findings The novel avian influenza A H7N9 virus originated from multiple reassortment events. The HA gene might have originated from avian influenza viruses of duck origin, and the NA gene might have transferred from migratory birds infected with avian influenza viruses along the east Asian flyway. The six internal genes of this virus probably originated from two different groups of H9N2 avian influenza viruses, which were isolated from chickens. Detailed analyses also showed that ducks and chickens probably acted as the intermediate hosts leading to the emergence of this virulent H7N9 virus. Genotypic and potential phenotypic differences imply that the isolates causing this outbreak form two separate subclades. Interpretation The novel avian influenza A H7N9 virus might have evolved from at least four origins. Diversity among isolates implies that the H7N9 virus has evolved into at least two different lineages. Unknown intermediate hosts involved might be implicated, extensive global surveillance is needed, and domestic-poultry-to-person transmission should be closely watched in the future. Funding China Ministry of Science and Technology Project 973, National Natural Science Foundation of China, China Health and Family Planning Commission, Chinese Academy of Sciences.
Super-spreading occurs when a single patient infects a disproportionate number of contacts. The 2015 MERS-CoV, 2003 SARS-CoV, and to a lesser extent 2014–15 Ebola virus outbreaks were driven by ...super-spreaders. We summarize documented super-spreading in these outbreaks, explore contributing factors, and suggest studies to better understand super-spreading.
Super-spreading occurs when a single patient infects a disproportionate number of contacts. The 2015 MERS-CoV, 2003 SARS-CoV, and to a lesser extent 2014–15 Ebola virus outbreaks were driven by super-spreaders. We summarize documented super-spreading in these outbreaks, explore contributing factors, and suggest studies to better understand super-spreading.
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