Distribution and Formation Causes of PM_(2.5) and O_(3) Double High Pollution Events in China during 2013–20

Fine particulate matter(PM_(2.5))and ozone(O_(3))double high pollution(DHP)events have occurred frequently over China in recent years,but their causes are not completely clear.In this study,the spatiotemporal distribution of DHP events in China during 2013–20 is analyzed.The synoptic types affecting DHP events are identified with the Lamb–Jenkinson circulation classification method.The meteorological and chemical causes of DHP events controlled by the main synoptic types are further investigated.Results show that DHP events(1655 in total for China during 2013–20)mainly occur over the North China Plain,Yangtze River Delta,Pearl River Delta,Sichuan Basin,and Central China.The occurrence frequency increases by 5.1%during 2013–15,and then decreases by 56.1%during 2015–20.The main circulation types of DHP events are“cyclone”and“anticyclone”,accounting for over 40%of all DHP events over five main polluted regions in China,followed by southerly or easterly flat airflow types,like“southeast”,“southwest”,and“east”.Compared with non-DHP events,DHP events are characterized by static or weak wind,high temperature(20.9℃ versus 23.1℃)and low humidity(70.0%versus 64.9%).The diurnal cycles of meteorological conditions cause PM_(2.5)(0300–1200 LST,Local Standard Time=UTC+8 hours)and O_(3)(1500–2100 LST)to exceed the national standards at different periods of the DHP day.Three pollutant conversion indices further indicate the rapid secondary conversions during DHP events,and thus the concentrations of NO_(2),SO_(2) and volatile organic compounds decrease by 13.1%,4.7%and 4.4%,respectively.The results of this study can be informative for future decisions on the management of DHP events.

Boosting polysulfide redox conversion of Li-S batteries by one-step-synthesized Co-Mo bimetallic nitride

Lithium-sulfur(Li-S)batteries are considered as one of the most promising next generation energy storage systems due to the high theoretical specific capacity,low cost,and environmental benignity.However,the notorious shuttle effect of polysulfides hinders the practical application of Li-S batteries.Herein,we have rationally designed and synthesized sea urchin-like Co-Mo bimetallic nitride(Co_(3) MO_(3) N)in the absence of additional nitrogen sources with only one step,which was applied as the sulfur host materials for Li-S batteries.The results indicate that Co_(3) Mo_(3) N can efficiently anchor and catalyze the conversion of polysulfides,thus accelerating the electrochemical reaction kinetics and enabling prominent electrochemical properties.As a consequence,the S@Co_(3) Mo_(3) N cathode exhibits a high rate performance of 705 mAh g^(-1) at 3 C rate and an excellent cycling stability with a low capacity fading rate of 0.08%per cycle at 1 C over 600 cycles.Even at a high sulfur loading of 5.4 cmg cm^(-2),it delivers a high initial areal capacity of 4.50 mAh cm^(-2) which is still retained at 3.64 mAh cm^(-2) after 120 cycles.Furthermore,the catalytic mechanism and structural stability of Co_(3) Mo_(3) N during cycling were elucidated by a combination of X-ray photoelectron spectroscopy and X-ray absorption fine structure.This work highlights the strategy of structure-catalysis engineering of bimetallic nitride,which is expected to have a wide application in Li-S batteries.

Carbon decorated Li_(3)V_(2)(PO_(4))_(3) for high-rate lithium-ion batteries:Electrochemical performance and charge compensation mechanism

Fast charging and high-power delivering batteries are highly demanded in mobile electronics,electric vehicles and grid energy storage,but there are full of challenges.The star-material Li_(3)V_(2)(PO_(4))_(3) is demonstrated as a promising high-rate cathode material meeting the above requirements.Herein,we report the carbon decorated Li_(3)V_(2)(PO_(4))_(3) (LVP/C) cathode prepared via a facile method,which displays a remarkable high-rate capability and long-term cycling performance.Briefly,the prepared LVP/C delivers a high discharge capacity of 122 mAh g^(-1)(-93% of the theoretical capacity) at a high rate up to 20 C and a superior capacity retention of 87.1% after 1000 cycles.Importantly,by applying a combination of X-ray absorption spectroscopy and full-range mapping of resonant inelastic X-ray scattering,we clearly elucidate the structural and chemical evolutions of LVP upon various potentials and cycle numbers.We show unambiguous spectroscopic evidences that the evolution of the hybridization strength between V and O in LVP/C as a consequence of lithiation/delithiation is highly reversible both in the bulk and on the surface during the discharge-charge processes even over extended cycles,which should be responsible for the remarkable electrochemical performance of LVP/C.Our present study provides not only an effective synthesis strategy but also deeper insights into the surface and bulk electrochemical reaction mechanism of LVP,which should be beneficial for the further design of high-performance LVP electrode materials.

An AIPE-active fluorinated cationic Pt(Ⅱ)complex for efficient detection of picric acid in aqueous media

A novel cationic Pt(Ⅱ)complex 2 with 2-(2,4-difluorophenyl)pyridine as the cyclometalating ligand and 1,10-phenanthroline as the auxiliary ligand has been synthesized and fully characterized.This complex exhibits much higher aggregation-induced phosphorescent emission activity than that of a nonfluorinated complex 1 in CH_(3)CN/H_(2)O.The complex 2 demonstrates efficient detection on picric acid(PA)in CH_(3)CN/H_(2)O,providing a high quenching constant(K_(SV)=2.3×10^(4) L/mol)and a low limit of detection(LOD=0.26μmol/L).In addition,complex 2 shows high selectivity for detection of PA in real water samples.Density functional theory calculations and proton nuclear magnetic resonance spectra suggest that the detection mechanism is attributed to the photo-induced electron transfer.

海洋考古在英国

水下考古在很多时候被理解为陆地考古向水下的延伸,然而从宏观上看水陆的界限并非如此死板,陆地考古的调查研究或多或少也与'水'有关。因此'与水有关的'考古可以被看作一个完全独立的、完整的学科。海洋考古(maritime archeology)这一门类的提出解决了相关领域对考古学分类的界定问题。英国海洋考古学先驱Sean McGrail对'maritime'一词进行了严格的分析与诠释,他认为maritime一词可以被看作是最全面最具综合性的一个术语,然而从某种程度上来说这项术语依旧有局限性,比如它无法涵盖对内陆的航道和水域的研究。

Versatile functions of RNA m6A machinery on chromatin

m6A,a conserved and abundant modification on RNA,regulates RNA processing and function.RNA m6A machinery,including writers,erasers,and readers of m6A,is indispensable for m6A installation and function.Intriguingly,recent studies have revealed that m6A machinery can be recruited to chromatin by pleiotropic factors,including nascent RNA,transcription factors,regulatory RNA,histone modifications,and epigenetic machinery.Consequently,recruitment of m6A machinery can directly regulate chromatin biology,such as transcription,DNA damage repair,and DNA recombination beyond installation of m6A on nascent mRNA.Here,we discuss recent evidence showing that m6A machinery is targeted to chromatin and the direct biological consequences along with the underlying mechanisms.