Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) is a newly emerging human contagious coronavirus that causes Coronavirus Disease 2019(COVID-19).In this article,we illustrate the physical characteristics of SARS-CoV-2 and review the pathogenesis,symptoms and immune responses of COVID-19.We discuss the current treatment options and potential new therapies for COVID-19.We provide the prospects for the development of the effective COVID-19 vaccines.This review aims to gain a comprehensive understanding of SARS-CoV-2 and COVID-19 and help to develop successful strategies for curbing the COVID-19 pandemic.
Based on the Landsat ETM + remote sensing images as well as the field investigation data,evolvement of spatial pattern of land use degree in the study area was analyzed during2000- 2013 by means of spatial autocorrelation and semi-variance analysis. The results showed that: the land use degree showed an obvious scale effect,as the scale increases the spatial autocorrelation gradually weakened; In 2000 and 2005,the Hot-spots were mainly distributed in the radiation range of township administrative Center in a granular pattern,the Cold-spots were sporadically distributed around the Island. While in 2009 and 2013,the spatial agglomeration of Hot-spots and Cold-spots were significantly enhanced,the Hot-spots were mainly distributed in Tancheng Town and Beicuo Town in a granular pattern,as well as along the 162 County Road. While the Cold-spots were mainly distributed in Scenic Area such as Junshan,as well as in fish farming area and beach of Lunan Region. There was a significant spatial heterogeneity of land use degree during the researchperiod,its spatial variability was dramatically enhanced,The directional structure of land use in Haitan Island was prominent,the dominant land use patterns showed east-west direction in 2000 and2005,but showed north-south direction since 2009. Land use degree was mainly at the level of relatively high and moderate,it showed a totally rising trend due to the combined effect of administrative center and the main road.
The severely eroded land,four artificial forest( 2,7,13,30 years) and native forest were chosen for the research subjects in the area of Changting county of Fujian province.The vegetation community diversity at different recovery period were studied based on the richness index,diversity index,evenness index and dominance index.The results show: With the increase of vegetation management period,Plant species shows an overall increasing trend.Native forest plot reaches the maximum,which holds 31 families,55 genera and 60 species.But the restoration and succession of plant is a long process.In the process of vegetation restoration and succession,The Patrick richness index,Shannon-wiener diversity index,Sheldon evenness index and Simpson dominance index in the tree layer,shrub layer and herb layer change are not the same.Patrick richness index and Shannon-wiener diversity index vary spatially in the following order: shrub layer tree layer,herb layer,while Sheldon evenness index and Simpson dominance index show the opposite trend.
The problem of designing a guaranteed cost controller for a class of linear discretetime systems with saturation nonlinearities is considered. Together with a given quadratic performance index,a sufficient condition for the existence of state feedback guaranteed cost controller is derived on basis of Lyapunov stability theory and linear matrix inequalities. Furthermore,we give an approach for getting guaranteed cost controller law via linear matrix inequalities method. Finally,an example is given to demonstrate the efficiency of the proposed approach.
According to the basic principle and calculation model of water resources ecological footprint,Water resources ecological footprints and ecological carrying capacity of Fujian province is analyzed from 2004 to 2012. The results shown that: Fujian water resources ecological footprint change periodically and between 0. 86 ~ 0. 92 hm2,mainly in the production,especially in the agricultural water,consumption accounts for 50% ~ 60%. On water resources ecological carrying capacity,interannual variation is distinctness,affected by annual precipitation was significant,and are mainly composed of surface water. In view of the space,the water resources ecological footprint and surplus are obviously different. The per capita water resources ecological footprint is higher in the west of Fujian,lower in the East of Fujian. Water resources ecological footprint is surplus around the city,higher in the west of Fujian,lower in the East of Fujian. On the convergence and divergence,the three districts in the west of Fujian overall for the upward divergence condition,The ecological footprint of water resources per capita upward deviation on the average value. East of Fujian is basically upward convergence,southern Xiamen,Zhangzhou two city is downward divergence. In the Time series evolution,Fujian province and the Ten thousand yuan GDP water resources ecological footprint is a trend of decline,relative value of declining in Fuzhou is 20%,other all maintained at more than 60%.
According to the problem of reservoired in Jiulong River basin,the judgment standard of reservoired river was determined,and the concept of integrate hydropower station was presented. Then,the parameter value of degradation coefficient K was calibrated with water quality model based on a large number of measured data of water quality. On this basis,calculation method of water environmental capacity for reservoired river was proposed. Finally,research was carried on water environmental capacity accounting of reservoired river in Jiulong River basin. The results show the effect of reservoired on water environmental capacity calculation,and the water environmental capacity of reservoired river,which provided scientific basis for the total emission control,management and decision-making of water environmental capacity in Jiulong River basin.
Sixteen alkyl three methyl ammol/Lonium salt modified bentonite(DK1) was used for preparation of supported nano zero valent iron(n ZVI/DK1),combined with Fenton method for removal of 2,4-DCP in aqueous solution. The different influences such as the initial p H value,H2O2 concentration,n ZVI/DK1 dosage,2,4-DCP initial concentration on 2,4-DCP removal were observed. The results showed that the 2,4-DCP removal efficiency were 29. 0%,45. 7%,20. 2%,71. 1% by DK1,n ZVI/DK1,n ZVI/H2O2,n ZVI/DK1 /H2O2,respectively. And the hydrophobic clay support n ZVI enhanced the removal efficiency of 2,4-DCP. The p H value of solution,H2O2 concentration were in control of Fe0 activity in Fenton and catalysis,which significantly influenced the degradation of 2,4-DCP. At the condition of p H 3,H2O2 concentration 10 mmol·L- 1,n ZVI/DK1 dosage 0. 5 g·L- 1,2,4-DCP initial concentration 50 mg·L- 1,2,4-DCP removal efficiency reached 93. 4%. While the COD removal efficiency can reach as high as 78. 6%,it is further proved that n ZVI/DK1 has the function of adsorption and degradation in Fenton method.
A vertical flat-bed discontinuous polyacrylamide gel electrophoresis technique was used to compare the phenotypes of four isozymes(i. e. Malate dehydrogenase, Superoxide dismutase, Esterase and α-Amylase) among three amphioxus species, Branchiostoma belcheri,B. japonicum and B. floridae. It was found that there were significant differences in the number,staining intensity and relative mobility of enzymic spectrum among three species,and the differences of isozymic pattern can be used to distinguish the species. It can be also confirmed that B. belcheri and B. japoncum are two separated species in Xiamen waters in virtue of the difference of isozymic phenotypes between both species. For the same species,the electrophoretic patterns between female and male or between individuals with mature and immature gonad were slightly differences. It needs to be careful when the isozymic pattern was used to distinguish the sex.
The aspects of denitrifying bacteria species,the theory of denitrification,the impact factors on denitrification and denitrifying bacterial application progress in environmental remediation were reviewed. In addition,combined with the current research situation,and put forward the future research direction.
Consider the first eigenvalue λ0 of transient birth-death processes on Z+∶ = { 0,1,2,…} with Dirichlet boundary at 0 and ∞. By adopting the proper h-transformation and making full use of existing results for ergodic birth-death processes with Dirichlet boundary at 0,obtain explicit estimates for λ0. Furthermore,the h-transformation applies to study the associated Poincare-type inequalities.
It proposes a progressive iterative approximation( PIA) algorithm for B-spline curve approximation with tangent constraint.On the one hand the discrete data points of the tangent vector,curvature and other geometric characteristics are fully applied to the approximation problem of discrete data points,using tangent constraint can avoid unnecessary fluctuations,and obtain better approximation effect.On the other hand,the number of selecting feature points is less than the number of data points,so the PIA algorithm can be used for the approximation of the mass of discrete data points.The steps in the process of each iteration of the algorithm are independent,which is easy to be applied to the parallel computing,which greatly improve the computational efficiency.Some examples are given to show the validity of the algorithm.
Let F be a field whose characteristic is not equal to 2,L a Lie algebra over F.A map φ on L is called a nonlinear strongly commuting map,if for any x,y ∈ L,[φ( x),y] = [x,φ( y) ].If P is a parabolic subalgebra of a general linear Lie algebra gl( n,F)( n ≥2),it is shown that any nonlinear strongly commuting map on P is a sum of a scalar multiplication map and a central quasiderivation.And if P is a parabolic subalgebra of a finite dimensional simple Lie algebra L over F,it is shown that any nonlinear strongly commuting map is a scalar multiplication map.
Let G be a group,an automorphism φ: G → G is called a commuting automorphism,if for all x ∈ G,φ(x) x = xφ(x). Let n be a positive integer larger than 3 and F a field. Denote by Tnthe multiplicative group consisting of all n × n invertible upper triangular matrices over F.Prove that a map φ: Tn→ Tnis a commuting automorphism on Tnif and only if there exist group honmomorphisms σi: F*→ F*,1 ≤ i ≤ n,such that φ(A) =(∏ni=1σi(aii)) A,for A =(aij)n × n∈Tn,and for any k = 1,2,…,n and any a ∈ Imσk,the equation xσ1(x) σ2(x) …σn(x) = a has a unique solution in F*.
推广了Buhler定理.设C是预Abel的正合范畴,如果A→B1b1→Cd1→W1与Aa2→B2b2→C2d2→W2以及b:B1→B2,c:C1→C2使得（cb1,b2b）构成推出,且a2=ba1,d1=Coker（b1a1）,d2=Coker（b2a2）,则存在容许单态射h:W1→W2,使得hd1=d2c.并进一步给出该定理的一个应用.
This paper introduces marine radar digital signal processing background,principles and methods STC control. Put forward the index on STC gain control in the form of curve STC made exponential gain control curve,Using MATLAB to simulation the exponential curve STC algorithm,adjust the parameters so that the image is clear,Compared the image,the final image is very clear,meet the requirements of radar signal preprocessing. And presents considerations and preferences Radar STC design process.
For the parameter uncertainty and norm bounded Delta operator time-delay system,we designed the state feedback controller to ensure the closed-loop system is robust asymptotically stable for all allowable uncertainties,and the system specified output indicators meet the given constraints. In addition,it finds the smallest upper bound of performance index of the system. By using Lyapunov stability theory and linear matrix inequality( LMI) method,it finds out a sufficient condition of the existence of the optimal guaranteed cost state feedback controller,on the further,it puts forward the design method of the optimal guaranteed cost controller. Finally,a numerical example is verified the feasibility of method.
We analyzed the plants species and flora composition from the highway evaluation zone Putian to Yongding,based on the ways of field investigation,literature research and the list of vascular plants arrangement.Our result showed that: 1 914 species vascular plants( 831 genera,213 families) were recorded in the evaluation zone.It was abundant with plants species and diversity.Among the areal types of families,the Tropical element was the dominant which accounted to 62.5%,especially the Pantropic was abundant,and the Cosmopolitan( 48.7%) was less.The Temperate elements were abundant with the percent of 17.1%.Among the areal types of genera,the Tropical element also occupied the dominant status which accounted to 60.7%,but the Temperate elements( 12.3%) outnumbered the Cosmopolitan( 11.8%).The study indicated that geographical flora composition was complicated and closely associated with tropical flora,and the special ingredients occupied certain proportion,etc.
This paper used three kinds of flocculants including alum,ferric chloride and chitin to study the flocculating effect and the influence on three kinds of algal cells including Isochrysis galbana,Platymonas subcordiformis and Pyramimonas sp..The result determined the flocculating rate,the morphologic change of algae cells and the bait effect on Coelomactra antiquate.The result showed that alum and ferric chloride have faster flocculating rate to P.subcordiformis and P.sp.within 60min after the experiment beginning.But to I.galbana,they can be achieve substantially precipitation more than 120min.The flocculating effect of Chitin on I.galbana,P.subcordiformis and P.sp.were insignificant.The higher the initial flocculant concentration is,the easier for algal cells to form a large group,that is not good for the cultivation of algal cells.Considering about the time and concentration of flocculants and the damage effect on algal cells,the ideal effect concentration of alum should respectively be 160mg·L- 1and 120 mg·L- 1to P.subcordiformis and P.sp.and the ferric chloride both should be 40mg·L- 1.While to I.galbana,the concentration of alum is 200mg·L- 1and ferric chloride is 80mg·L- 1.The form of algae cells did not insignificant change and fracture after flocculation.There was no remarkable difference between the growth results of larvae and juvenile of C.antiquate feeded by algae before and after flocculation,which showed that I.galbana and P.sp.did not affect the growth of juveniles of C.antiquata after flocculation and could be applied to the artificial seedling of shellfish.
To investigate the formation of iron / manganese plaque on Phytolacca acinosa root surface under different conditions( i.e.Fe2 +,Mn2 +concentration,iron-manganese oxidizing bacteria MN1405 inoculation concentration,pH level) and also to analyze the optimal conditions of the formation of iron / manganese plaques.Whatever,hydroculture and atomic absorption spectrometer experiment methods were applied.The results showed that P.acinosa formed different contents of iron / manganese plaque on root surface under different culture conditions.That the culture conditions of pH 6,MN1405 inoculation concentration 10%,Fe2 +concentration 30mg·L- 1,Mn2 +concentration 700mg·L- 1is beneficial to the formation of iron / manganese plaque of P.acinosa,the amounts of the iron and manganese plaque reached up to( 835.5 ± 30.0)g·kg- 1and( 7 752.7 ±126.7) g·kg- 1,respectively.
The geometry of submanifolds in Kenmotsu manifolds is studied,and a necessary and sufficient condition under which certain operators on the submanifold is to be parallel is obtained. Using this result,sufficient conditions under which a submanifold of the Kenmotsu manifold is an invariant submanifold is obtained.
