Estimate of Hydrofluorocarbon Emissions for 2012–16 in the Yangtze River Delta, China

Hydrofluorocarbons(HFCs)have been widely used in China as substitutes for ozone-depleting substances,the production and use of which are being phased out under the Montreal Protocol.China is a major consumer of HFCs around the world,with its HFC emissions in CO2-equivalent contributing to about 18%of the global emissions for the period2012-16.Three methods are widely used to estimate the emissions of HFCs-namely,the bottom-up method,top-down method and tracer ratio method.In this study,the tracer ratio method was adopted to estimate HFC emissions in the Yangtze River Delta(YRD),using CO as a tracer.The YRD region might make a significant contribution to Chinese totals owing to its rapid economic growth.Weekly flask measurements for ten HFCs(HFC-23,HFC-32,HFC-125,HFC-134 a,HFC-143 a,HFC-152 a,HFC-227 ea,HFC-236 fa,HFC-245 fa and HFC-365 mfc)were conducted at Lin’an Regional Background Station in the YRD over the period 2012-16,and the HFC emissions were 2.4±1.4 Gg yr-1 for HFC-23,2.8±1.2 Gg yr-1 for HFC-32,2.2±1.2 Gg yr-1 for HFC-125,4.8±4.8 Gg yr-1 for HFC-134 a,0.9±0.6 Gg yr-1 for HFC-152 a,0.3±0.3 Gg yr-1 for HFC-227 ea and 0.3±0.2 Gg yr-1 for HFC-245 fa.The YRD total HFC emissions reached 53 Gg CO2-e yr-1,contributing 34%of the national total.The per capita HFC CO2-equivalent emissions rate was 240 kg yr-1,while the values of per unit area emissions and per million GDP emissions reached 150 Mg km-2yr-1 and 3500 kg yr-1(million CNY GDP)-1,which were much higher than national or global levels.

Erratum to:Estimate of Hydrofluorocarbon Emissions for 2012-16 in the Yangtze River Delta,China

In the original version of this article,the unit of the YRD total HFC emissions“Gg CO2-e yr^−1”in the abstract should be Tg CO2-e yr^−1.On Page 581,in the fifth line from the left bottom,the unit of the total CO2-equivalent emissions of HFCs“Gg yr^−1”should be Tg yr^−1.

Pressureless all-solid-state Na/S batteries with self-supporting Na_(5)YSi_(4)O_(12) scaffolds

The development of reliable and affordable all-solid-state sodium metal batteries(ASS-SMBs)requires suitable solid-state electrolytes with cost-efficient processing and stabilized electrode/electrolyte interfaces.Here,an integrated porous/dense/porous Na_(5)YSi_(4)O_(12)(NYS)trilayered scaffold is designed and fabricated by tape casting using aqueous slurries.In this template-based NYS scaffold,the dense layer in the middle serves as a separator and the porous layers on both sides accommodate the active materials with their volume changes during the charge/discharge processes,increasing the contact area and thus enhancing the utilization rate and homogenizing the current distribution.The Na/NYS/Na symmetric cells with the Pb-coated NYS scaffold exhibit significantly reduced interfacial impedance and superior critical current density of up to 3.0 mA cm^(-2)against Na metal owing to enhanced wettability.Furthermore,the assembled Na/NYS/S full cells operated without external pressure at room temperature showed a high initial discharge capacity of 970 mAh g^(-1)and good cycling stability with a capacity of 600 mAh g^(-1)after 150 cycles(based on the mass of sulfur).This approach paves the way for the realization of economical and practical ASS-SMBs from the perspective of ceramic manufacturing.

Visualizing Complex Anatomical Structure in Bamboo Nodes Based on X-ray Microtomography

In recent years,bamboo has been widely used in a broad range of applications,a thorough understanding of the structural characteristics of bamboo nodes is essential for better processing and manufacturing of biomimetic materials.This study investigated the complex anatomical structure for the nodes of two bamboo species,Indocalamus latifolius(Keng)McClure and Shibataea chinensis Nakai,using a high-resolution X-ray microtomography(μCT).The results show that the vascular bundle system in the nodal region of I.latifolius and S.chinensis is a net-like structure composed of horizontal and axial vascular bundles.Furthermore,the fiber sheath surrounding metaxylem vessels tended to be shorter in the tangential direction.This structure of bamboo nodes facilitates the tangential and axial transport of moisture and nutrients.The anatomical structure of I.latifolius and S.chinensis nodes has obvious differences,especially in the arrangement of vascular bundles.Vascular bundle frequency was significantly higher in S.chinensis nodes than in I.latifolius nodes.These findings indicate thatμCT is a nondestructive three-dimensional imaging method that can used to examine the anatomical structure of bamboo nodes.

Dramatic decline of observed atmospheric CO_(2) and CH_(4) during the COVID-19 lockdown over the Yangtze River Delta of China

The temporal variation of greenhouse gas concentrations in China during the COVID-19 lockdown in China is analyzed in this work using high resolution measurements of near surface ΔCO_(2),ΔCH_(4) andΔCO concentrations above the background conditions at Lin’an station(LAN),a regional background station in the Yangtze River Delta region.During the pre-lockdown observational period(IOP-1),bothΔCO_(2) andΔCH_(4) exhibited a significant increasing trend relative to the 2011-2019 climatological mean.The reduction ofΔCO_(2),ΔCH_(4) andΔCO during the lockdown observational period(IOP-2)(which also coincided with the Chinese New Year Holiday)reached up to 15.0 ppm,14.2 ppb and 146.8 ppb,respectively,and a reduction ofΔCO_(2)/ΔCO probably due to a dramatic reduction from industrial emissions.ΔCO_(2),ΔCH_(4) and ΔCO were observed to keep declining during the post-lockdown easing phase(IOP-3),which is the synthetic result of lower than normal CO_(2) emissions from rural regions around LAN coupled with strong uptake of the terrestrial ecosystem.Interestingly,the trend reversed to gradual increase for all species during the later easing phase(IOP-4),with ΔCO_(2)/ΔCO constantly increasing from IOP-2 to IOP-3 and finally IOP-4,consistent with recovery in industrial emissions associated with the staged resumption of economic activity.On average,ΔCO_(2) declined sharply throughout the days during IOP-2 but increased gradually throughout the days during IOP-4.The findings showcase the significant role of emission reduction in accounting for the dramatic changes in measured atmosphericΔCO_(2) and ΔCH_(4) associated with the COVID-19 lockdown and recovery.

Diketopyrrolopyrrole-derived organic small molecular dyes for tumor phototheranostics

Cancer is one of the leading causes of human death around the world. Phototherapy, including photodynamic therapy(PDT) and photothermal therapy(PTT), is an emerging light-triggered cancer treatment and shows the advantages of non-invasiveness and low side effects. The design and preparation of efficient phototherapeutic agents are of great significance for phototherapy. Diketopyrrolopyrrole(DPP) is a small molecular organic dye featuring outstanding photophysical properties, facile tuning of structures and properties, and excellent photostability;thus, phototherapeutic agents based on organic small molecular DPP derivatives have attracted significant research attention for not only phototherapy but also photodiagnosis of fluorescence imaging(FLI) and photoacoustic imaging(PAI). This review summarizes the recent progress of various DPP-based organic small molecules on phototheranostics during the last five years. The molecular structure design and their phototheranostics performances are discussed in detail,as will be of great help for further creation of DPP-based phototheranostics.

S/Se-embedded acenaphthylene-imide-containing polycyclic heteroaromatic hydrocarbon

Acenapththylene-imide(An I),similar to naphthalene diimide(NDI),is an outstanding building block for organic functional materials and has gained a lot of research attention.Herein,Sulphur and Selenium-embedded AnI-containing polycyclic aromatic hydrocarbon molecules,AnI-SQ and AnI-SeQ,with[1,2,5]thiadiazolo[3,4-g]quinoxaline(SQ)and[1,2,5]selenadiazolo[3,4-g]quinoxaline(Se Q)are designed and synthesized with low-lying LUMO energy levels.The absorption and emission of AnI-SQ and An I-Se Q displayed a bathochromic shift upon protonation of the C=N bond.Besides,theoretical calculation indicates remarkable rigid planar backbones for both An I-SQ and An I-Se Q.Through self-assembly with polymeric Pluronic?F-127,corresponding hydrophilic nanoparticles(NPs)were prepared with low cytotoxicity.And AnI-SQ NPs could be applied for in vitro two-photon fluorescence imaging.

Eu^(3+)ions grafted polyacrylonitrile nanofibers possessing enhanced fluorescence performance by introducing benzoic acid as assistant ligand

Eu^(3+) ions were grafted onto the surface of electrospun polyacrylonitrile(PAN)nanofibers through coordination effect between C≡N groups on PAN nanofibers and Eu^(3+) ions,and benzoic acid(BA)was introduced as an assistant ligand.The impacts of concentrations of Eu^(3+) ions and BA,and reaction time on the properties of final products were investigated.The results reveal that Eu^(3+) ions can be successfully grafted onto PAN nanofibers,but the fluorescence intensity of the obtained PAN@Eu^(3+) nanofibers is very weak.After BA is introduced as the assistant ligand,the fluorescence intensity of the obtained PAN@(Eu^(3+)/BA)nanofibers is greatly stronger than that of PAN@Eu^(3+)nanofibers,and meanwhile,concentration quenching effect of Eu^(3+) ions can be effectively restrained.Furthermore,the superior structure of PAN@(Eu^(3+)/BA)nanofibers not only brings the effective utilization of precious elemental europium,but also guarantees high mechanical strength.

Coverage of 13-Valent Pneumococcal Conjugate Vaccine Among Children 0–15 Months of Age—9 Provinces,China,2019–2021

Summary What is already known on this topic?Limited data exist regarding the coverage of the 13-valent pneumococcal conjugate vaccine(PCV13)in China.A lack of official statistics,coupled with an insufficient body of published literature,hinders the accurate depiction of the current situation.What is added by this report?This study investigated the utilization of PCV13 and estimated its coverage in nine provinces across eastern,central,and western China between 2019 and 2021.Despite an annual increase in PCV13 usage during this period,the overall coverage remained suboptimal.

Acidic oxygen evolution reaction:Mechanism,catalyst classification,and enhancement strategies

As the most desirable hydrogen production device,the highly efficient acidic proton exchange membrane water electrolyzers(PEMWE)are severely limited by the sluggish kinetics of oxygen evolution reaction(OER)at the anode.Rutile IrO2 is a commercial acid-stable OER catalyst with poor activity and high cost,which has motivated the development of alternatives.However,hitherto most of the designed acidic OER catalysts have disadvantages of low activity or stability,which cannot meet the requirement of industrial applications.Thus,exploring suitable strategies to enhance the activity and stability of cost-effective acidic OER catalysts is crucial for developing the PEMWE technique.In this review,the main OER mechanisms,different types of catalysts,and their activity and stability characteristics are summarized and discussed,and then possible strategies to improve activity and stability are proposed.Finally,the problems and prospects of such catalysts are generalized to shed some light on the future research of advanced catalysts for acidic OER.

Enhanced room-temperature Na^(+) ionic conductivity in Na_(4.92)Y_(0.92)Zr_(0.08)Si_(4)O_(12)

Developing cost-effective and reliable solid-state sodium batteries with superior performance is crucial for stationary energy storage.A key component in facilitating their application is a solid-state electrolyte with high conductivity and stability.Herein,we employed aliovalent cation substitution to enhance ionic conductivity while preserving the crystal structure.Optimized substitution of Y^(3+)with Zr^(4+)in Na_(5)YSi_(4)O_(12) introduced Naþion vacancies,resulting in high bulk and total conductivities of up to 6.5 and 3.3 mS cm^(-1),respectively,at room temperature with the composition Na_(4.92)Y_(0.92)Zr_(0.08)Si_(4)O_(12)(NYZS).NYZS shows exceptional electrochemical stability(up to 10 V vs.Naþ/Na),favorable interfacial compatibility with Na,and an excellent critical current density of 2.4 mA cm^(-2).The enhanced conductivity of Naþions in NYZS was elucidated using solid-state nuclear magnetic resonance techniques and theoretical simulations,revealing two migration routes facilitated by the synergistic effect of increased Naþion vacancies and improved chemical environment due to Zr^(4+)substitution.NYZS extends the list of suitable solid-state electrolytes and enables the facile synthesis of stable,low-cost Naþion silicate electrolytes.

我国大气本底观测站创新发展的思考和建议

大气本底监测是指在远离人类活动影响的地方对经过充分混合的、不受局地污染影响的大气成分进行长期定点的观测.由于大气本底监测能在全球或区域尺度上反映出人类活动所造成的大气成分的长期变化,因此对社会经济建设和科学研究等都具有非常重要的作用[1~3].自20世纪50年代开始,国外的一些观测台站进行了二氧化碳、臭氧及大气重金属等主要大气成分的本底观测[4~8].

A survey on ensemble learning

Despite significant successes achieved in knowledge discovery,traditional machine learning methods may fail to obtain satisfactory performances when dealing with complex data,such as imbalanced,high-dimensional,noisy data,etc.The reason behind is that it is difficult for these methods to capture multiple characteristics and underlying structure of data.In this context,it becomes an important topic in the data mining field that how to effectively construct an efficient knowledge discovery and mining model.Ensemble learning,as one research hot spot,aims to integrate data fusion,data modeling,and data mining into a unified framework.Specifically,ensemble learning firstly extracts a set of features with a variety of transformations.Based on these learned features,multiple learning algorithms are utilized to produce weak predictive results.Finally,ensemble learning fuses the informative knowledge from the above results obtained to achieve knowledge discovery and better predictive performance via voting schemes in an adaptive way.In this paper,we review the research progress of the mainstream approaches of ensemble learning and classify them based on different characteristics.In addition,we present challenges and possible research directions for each mainstream approach of ensemble learning,and we also give an extra introduction for the combination of ensemble learning with other machine learning hot spots such as deep learning,reinforcement learning,etc.

高稳定可逆的混合导电金属钠基负极助力高性能钠金属电池

钠金属二次电池由于丰富的地壳钠资源储备、金属钠负极高的理论容量等优势受到广泛的关注,已成为后锂离子电池时代的重要技术之一.然而,金属钠负极在充放电循环过程中存在枝晶生长、体积变化等严重问题,严重制约了钠金属电池技术的发展.基于以上问题,本文提出在金属钠负极体相内引入NaSICON型固态钠离子导体,构建具有离子/电子混合传输能力的金属钠基复合负极.一方面,通过钠离子传导相和金属电子导电相之间的紧密接触构建了快速的离子/电子通道和丰富的电化学反应界面,有利于实现稳定可逆的钠沉积/剥离;另一方面,紧密堆积的复合结构保护了金属钠免受液态有机电解质的腐蚀和副反应的发生.得益于上述独特的结构设计,复合负极表现出高度可逆和稳定的钠的沉积/剥离行为.在碳酸酯类电解液中,对称电池在1 m A cm^(-2)的电流密度、5 m Ah cm^(-2)的高充放电容量下实现了高于700 h的超长寿命,以及高达8 m A cm^(-2)电流密度的出色倍率性能.在搭配Na_(3)V_(2)(PO_(4))_(3)/C正极时,全电池展现出优异的循环稳定性(容量衰减单次平均仅0.012%)以及低的充放电极化.

Detection and Initial Response to a Type 2 Vaccine-Derived Poliovirus—Sichuan Province,China,2019

What is already known about this topic?After the type 2 strain of the live,attenuated poliovirus vaccine was withdrawn globally in 2016,any identification of a type 2 poliovirus is a Public Health Emergency of International Concern.A vaccinederived type 2 poliovirus(VDPV2)was identified in Sichuan,prompting an urgent,comprehensive investigation and response.What is added by this report?Type 2 monovalent,live,attenuated oral poliovirus vaccine(mOPV2)is being used to respond to the numerous VDPV2 outbreaks seen around the world.In contrast,the response in Sichuan used Sabin strain inactivated poliovirus(sIPV)to stop circulation of the VDPV2.In the 6 months following the vaccination response,there have been no VDPV2s detected in Sichuan,despite extensive search.What are the implications for public health practices?Further search for the VDPV2 must continue in order to determine whether transmission has been stopped.The ongoing investigation and response to the Sichuan VDPV2 is providing evidence to the Global Polio Eradication Initiative on managing VDPV2 outbreaks.

Influence of High Relative Humidity on Secondary Organic Carbon: Observations at a Background Site in East China

To investigate the impacts of relative humidity(RH) on secondary organic aerosol(SOA) concentrations and chemical reactions, the carbonaceous aerosol components [i.e., organic carbon(OC) and element carbon(EC)] were quantified in daily PM2.5 samples collected at a background site in East China during summer 2015. Based on the method of EC-tracer, the concentration of secondary organic carbon(SOC) demonstrated an obvious negative relationship with RH higher than 60%. Moreover, the ratio of SOC/EC also exhibited obvious decreasing trends with increasing RH, indicating negative effects for chemical production of SOA under high RH conditions. Due to high RH,photochemistry was weakened, gaseous oxidant concentrations was lowered(e.g., significantly decreased O3 levels),and the production rates of SOA were relatively low. On the other hand, because of more water uptake under higher RH conditions, the aerosol droplet acidity was reduced and enhancement of SOA formation by acidity was accordingly absent. In addition, high RH also plays an important role in changing viscosity of pre-existing aerosol coatings,which can affect reactive uptake yield of SOA. Overall, the results from this study imply that SOA production may be more associated with photochemical processes, while aqueous-phase chemistry is not very important for some SOA formation in a moist ambient environment. In the ambient atmosphere, oxidant concentrations, reaction rates,airborne species, etc., are highly variable. How do these factors affect SOA yields under given ambient environment warrants further detailed investigations.

Morphology,composition,and sources of individual aerosol particles at a regional background site of the YRD,China

Aerosol samples were collected at Lin'an, a background site of Yangtze River Delta(YRD).Morphology, size, composition, and mixing state of individual aerosol particles were characterized by transmission electron microscopy(TEM) coupled with energy dispersive X-ray spectroscopy(EDS), and the soluble ions of PM_(1.0) were studied by aerosol mass spectrometer(AMS). The daily average AMS mass concentrations of sulfate, nitrate, and ammonium were about 5.8, 8.6, and 5.6 μg/m^3, respectively. Individual aerosol particles were classified into seven types: S-rich, K-rich, organic matter(OM), soot, fly ash, metal, and mineral. S-rich particles were dominant in all size bins, and 51%(by number) of S-rich particles were internally mixed with other particles. The fraction of organic coating particles was 13.7% in morning, 25.2% in afternoon, and 11% in evening, suggesting that the strong photochemical process during afternoon produced more secondary organic aerosols(SOA) on the surface of inorganic particles. Fly ash and metal particles were abundant during the day, suggesting the influence of emissions from coal-fired power plants and steel plants. The results indicate that the intense industrial emissions in the YRD significantly transported to the background areas. PM_(2.5) concentration may be lower in background air than in urban air but complex mixing state of aerosol particles indicates that the long-range transported particles substantially influenced the background air quality.