Critical Solvation Structures Arrested Active Molecules for Reversible Zn Electrochemistry

Aqueous Zn-ion batteries(AZIBs)have attracted increasing attention in next-generation energy storage systems due to their high safety and economic.Unfortunately,the side reactions,dendrites and hydrogen evolution effects at the zinc anode interface in aqueous electrolytes seriously hinder the application of aqueous zinc-ion batteries.Here,we report a critical solvation strategy to achieve reversible zinc electrochemistry by introducing a small polar molecule acetonitrile to form a“catcher”to arrest active molecules(bound water molecules).The stable solvation structure of[Zn(H_(2)O)_(6)]^(2+)is capable of maintaining and completely inhibiting free water molecules.When[Zn(H_(2)O)_(6)]^(2+)is partially desolvated in the Helmholtz outer layer,the separated active molecules will be arrested by the“catcher”formed by the strong hydrogen bond N-H bond,ensuring the stable desolvation of Zn^(2+).The Zn||Zn symmetric battery can stably cycle for 2250 h at 1 mAh cm^(-2),Zn||V_(6)O_(13) full battery achieved a capacity retention rate of 99.2%after 10,000 cycles at 10 A g^(-1).This paper proposes a novel critical solvation strategy that paves the route for the construction of high-performance AZIBs.

Biomineralization of soil with crude soybean urease using different calcium salts

Calcium salt is an important contributing factor for calcium-based biomineralization.To study the effect of calcium salt on soil biomineralization using crude soybean urease,the calcium salts,including the calcium chloride (CaCl_(2)),calcium acetate ((CH_(3)COO)_(2)Ca) and calcium nitrate (Ca(NO_(3))_(2)),were used to prepare the biotreatment solution to carry out the biomineralization tests in this paper.Two series of biomineralization tests in solution and sand column,respectively,were conducted.Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed to determine the microscopic characteristics of the precipitated calcium carbonate (CaCO_(3)) crystals.The experimental results indicate that the biomineralization effect is the best for the CaCl2 case,followed by (CH_(3)COO)_(2)Ca,and worst for Ca(NO_(3))_(2) under the test conditions of this study (i.e.1 mol/L of calcium salt-urea).The mechanism for the effect of the calcium salt on the biomineralization of crude soybean urease mainly involves: (1) inhibition of urease activity,and (2) influence on the crystal size and morphology of CaCO_(3).Besides Ca^(2+) ,the anions in solution can inhibit the activity of crude soybean urease,and NO_(3)− has a stronger inhibitory effect on the urease activity compared with both CH_(3)COO^(−) and Cl^(−) .The co-inhibition of Ca^(2+) and NO_(3)− on the activity of urease is the key reason for the worst biomineralization of the Ca(NO_(3))_(2) case in this study.The difference in biomineralization between the CaCl_(2) and (CH_(3)COO)_(2) Ca cases is strongly correlated with the crystal morphology of the precipitated CaCO_(3).

NH_(4)^(+)插层Mo掺杂MnO_(2)阴极实现强键合作用助力超稳定水系锌锰电池

水系可充电锌/二氧化锰电池因其成本低廉、能量密度高而引起了广泛关注.然而,缓慢的反应动力学和MnO_(2)阴极的歧化反应以及不可逆的相变现象对其发展造成了严重阻碍.在此,我们选用了Mo掺杂α-MnO_(2)(Mo–MnO_(2))作为阴极材料,通过铵根离子插层机制所形成的N–H···O强键合作用来稳定Mo–MnO_(2)的2×2隧道结构,并且有效抑制了Mn^(3+)溶解,在质子插入/脱出过程中不会引起晶格的畸变,进一步提高了其循环稳定性.获得的Mo–MnO_(2)正极在100 mA g^(−1)时表现出265.2 mA h g^(−1)的高比容量和364.3 W h kg^(−1)的能量密度.在2.0 A g^(−1)下1000次循环后,容量保持率达95.2%.这项工作有助于深入了解非金属阳离子在电极主体材料间的键合作用,为设计具有高能量密度和长期循环能力的水系锌离子电池提供了新思路.

Influence of mass ratio and calcination temperature on physical and photoelectrochemical properties of ZnFe-layered double oxide/cobalt oxide heterojunction semiconductor for dye degradation applications

A visible light-active photoelectrocatalyst,ZnFe-layered double oxide(LDO)/cobalt(II,III)oxide(Co_(3)O_(4))composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide(LDH)prepared by a hydrothermal and microwave hydrothermal method.The morphological studies revealed that the ZnFe-LDO/Co_(3)O_(4) composites exhibited a flower-like structure comprising Co_(3)O_(4) nanowires and ZnFe-LDO nanosheets.Further,when the mass ratio of Co(NO_(3))_(2)·6H_(2)O/LDH was 1:1.8 and the calcination temperature was 550℃,the ZnFe-LDO/Co_(3)O_(4) composite exhibited 93.3%degradation efficiency for methylene blue(MB)at the applied voltage of 1.0 V under visible light after 3 h.Furthermore,the Mott-Schottky model experiments showed that the formation of a p-n heterojunction between ZnFe-LDO and Co_(3)O_(4) could effectively inhibit the recombination of electrons and holes in the photoelectrocatalytic process.Meanwhile,free radical scavenging experiments showed that the active radicals of⋅OH played an important role in the degradation of MB.Therefore,the photoelectrocatalytic effect of ZnFe-LDO/Co_(3)O_(4) provides a simple and effective strategy for the removal of organic pollutants.

Numerical simulation and behavior prediction of a space net system throughout the capture process: Spread, contact, and close

In this paper,we develop an exhaustive numerical simulator for the dynamic visualization and behavior prediction of the tether-net system during the whole space debris capture phases,including spread,contact,and close.First of all,to perform its geometrically nonlinear deformation,discrete different geometry theory is applied to model the mechanical response of a flexible net.Based on the discretization of the whole structure into multiple vertexes and lines,the internal force and associated Hession are derived in a closed form to solve a series of nonlinear dynamic equations of motion.The spread and deployment of a packaged net can be realized using this well-established net solver.Next,a multidimensional incremental potential formulation is selected to achieve the intersection-free boundary nonlinear contact and collision between the deformable net and rigid debris.Finally,for the closing mechanism analysis,a log-like barrier functional is derived to achieve the nondeviation condition between the ring–rod linkage system.The C2 continuous log barrier functionals constructed for both the contact model and the linkage system are smooth and differentiable,and,therefore,the nonlinear net capture dynamic system can be efficiently solved through a fully implicit time integrator.Overall,as a demonstration,the whole capture process of a defunct satellite using a hexagon net is simulated through our well-established numerical framework.We believe that our comprehensive numerical methods could provide new insight into the optimal design of active debris removal systems and promote further development of the online control of tether tugging systems.

Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete(PC)box-girder bridge.The change of hydration heat temperature consists of four periods:temperature rising period,constant temperature period,rapid temperature fall period and stow temperature fall period.The peak value of hydration heat temperature increases with the increasing casting temperature of concrete;the relation between them is approximately linear.According to field tests,the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder.Furthermore,the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring.Such results show that the prevailing Chinese Code(2004)is insufficient since it does not take into account the temperature gradient of the bottom slab.Finally,some preventive measures against temperature cracks were proposed based on related studies.The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.

In-situ constructing visible light CdS/Cd-MOF photocatalyst with enhanced photodegradation of methylene blue

Based on high specific surface area,high porosity of metal-organic frameworks(MOFs)and excellent vis-ible light response of CdS,the CdS/Cd-MOF nanocomposites were constructed by in-situ sulfurization to form CdS using Cd-MOF as precursor and the CdS loading was controlled by the dose of thioac-etamide.Under the irradiation of simulated sunlight,the degradation rate of methylene blue(MB)by 10mg MOF/CdS-6(mass ratio of MOF to thioacetamide is 6:1)was 91.9%in 100min,which was higher than that of pure Cd-MOF(62.3%)and pure CdS(67.5%).This is attributed to the larger specific surface area of the composite catalysts,which provides more active sites.Meanwhile,the loading of CdS obvi-ously broadens the light response range of Cd-MOF and improves the utilization of visible light.The Mott-Schottky model experiment shows that the formed type-Ⅱheterojunction between Cd-MOF and CdS can effectively inhibit the recombination of photogenerated electrons and holes.Meanwhile,the photocurrent intensity of MOF/CdS-6 is 8 times and 2.5 times of that of pure Cd-MOF and CdS.In addi-tion,MOF/CdS-6 showed good photocatalytic performance after five cycles,showing excellent stability and reusability.

Resistance of large caisson in floating transport considering the influence of air

This paper deals with the floating resistance of super large caisson by numerical simulation,and the influence of air resistance on the caisson,which is often ignored by previous researchers,is considered.The floating caisson of Taizhou Highway Bridge’s middle tower pier is investigated,and the software package FLUENT is used to simulate the floating process of largescale rounded rectangular steel caisson.This simulation adopts the volume of fluid(VOF)model with water-air two-phase flow,which can take both the hydraulic resistance and air resistance into account.Subsequently,the analyses on hydraulic resistance and air resistance under different working conditions,such as different flow velocities and different draughts of water are performed,and the results are compared with those calculated by related empirical formula.The comparison shows that the air resistance takes up notable portion in the total resistance on the floating caisson,and the effect of air resistance on the safety of caisson should be paid sufficient attention to rather than be ignored.

Experimental study on concrete box culverts in trenches

Concrete box culverts are widely used in expressways in mountain areas.Many problems frequently take place due to improperly estimated vertical earth pressures on culverts.The prevailing Chinese General Code for Design of Highway Bridges and Culverts(CGCDHBC)stipulates the computation of the design load on culverts primarily based on the linear earth pressure theory,which cannot accurately describe the variation of the vertical load on culverts in trenches.In this paper,a full-scale experiment and numerical simulation were conducted to evaluate the variation of vertical earth pressures on culvert and soil arching in backfill.The variations of foundation pressure and settlement were also analyzed.The result revealed that the soil arch forms when the backfill on the culvert reaches a certain height.The soil arching effect reduces the stress concentration on the crown of the culvert but it is unstable.The vertical earth pressure on top of the culvert is significantly different from that recommended by the CGCDHBC.

Risk Factors for Severity and Mortality in Adult Patients Confirmed with COVID-19 in Sierra Leone: A Retrospective Study

Background:The coronavirus disease 2019(COVID-19)is a highly infectious respiratory disease.There is no recommended antiviral treatment approved for COVID-19 in Sierra Leone,and supportive care and protection of vital organ function are performed for the patients.This study summarized the clinical characteristics,drug treatments,and risk factors for the severity and prognosis of COVID-19 in Sierra Leone to provide evidence for the treatment of COVID-19.Methods:Data of 180 adult COVID-19 patients from the 34th Military Hospital in Freetown Sierra Leone between March 31,2020 and August 11,2020 were retrospectively collected.Patients with severe and critically ill are classified in the severe group,while patients that presented asymptomatic,mild,and moderate disease were grouped in the non-severe group.The clinical and laboratory information was retrospectively collected to assess the risk factors and treatment strategies for severe COVID-19.Demographic information,travel history,clinical symptoms and signs,laboratory detection results,chest examination findings,therapeutics,and clinical outcomes were collected from each case file.Multivariate logistic analysis was adopted to identify the risk factors for deaths.Additionally,the clinical efficacy of dexamethasone treatment was investigated.Results:Seventy-six(42.22%)cases were confirmed with severe COVID-19,while 104 patients(57.78%)were divided into the non-severe group.Fever(56.67%,102/180)and cough(50.00%,90/180)were the common symptoms of COVID-19.The death rate was 18.89%(34/180),and severe pneumonia(44.12%,15/34)and septic shock(23.53%,8/34)represented the leading reasons for deaths.The older age population,a combination of hypertension and diabetes,the presence of pneumonia,and high levels of inflammatory markers were significantly associated with severity of COVID-19 development(P<0.05 for all).Altered level of consciousness[odds ratio(OR)=56.574,95%confidence interval(CI)5.645–566.940,P=0.001],high levels of neutrophils(OR=1.341,95%CI 1.109–1.621,P=0.002)and C-reactive protein(CRP)(OR=1.014,95%CI 1.003–1.025,P=0.016)might be indicators for COVID-19 deaths.Dexamethasone treatment could reduce mortality[30.36%(17/56)vs.50.00%(10/20)]among severe COVID-19 cases,but the results were not statistically significant(P>0.05).Conclusions:The development and prognosis of COVID-19 may be significantly correlated with consciousness status,and the levels of neutrophils and CRP.