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The formation of secondary organic aerosol (SOA) is inextricably linked to the photo‐oxidation of aromatic hydrocarbons. However, models still exhibit biases in representing SOA mass and chemical composition. We implemented a box model coupled with a near‐explicit photochemical mechanism, the Master Chemical Mechanism (MCMv3.3.1), to simulate a series of chamber studies and assess model biases in simulating SOA from representative monocyclic aromatic hydrocarbons, that is, toluene and three xylene isomers (TX SOA). The box model underpredicted SOA yields of toluene and xylenes by 4.7%–100%, which could be improved by adjusting the saturation vapor pressure (SVP) of their oxidation products. After updating the SVP values, the mass concentration of TX SOA in the Yangtze River Delta region during summer doubled, and there was also an approximate 3% enhancement in the total SOA. Compared to a lumped mechanism used for simulating TX SOA, MCM predicted comparable mass concentrations but exhibited different volatility distributions and oxidation states. Plain Language Summary: Saturation vapor pressure (SVP) is a key factor affecting the partitioning of condensable organic compounds and the formation of secondary organic aerosol (SOA). However, accurate determination of SVP remains challenging due to significant uncertainties associated with limited experimental data or theoretical calculations based on molecular structures. In this study, we assessed the parameterization of SVP for oxidation products of toluene and xylenes using a box model coupled with a near‐explicit photochemical mechanism, the Master Chemical Mechanism (MCMv3.3.1), against SOA chamber experiments. Subsequently, the refined SVP parameterization was incorporated into the regional CMAQ‐MCM‐SOA model, substantially enhancing modeled concentrations of toluene and xylene SOA during summer in the Yangtze River Delta region. This study underscores the significance of accurately representing SOA yields and chemical composition in models to evaluate its impacts comprehensively. Key Points: Adjusted saturation vapor pressure (SVP) significantly reduces secondary organic aerosol (SOA) yield errors from toluene and xylenesToluene and xylene SOA from gas‐particle partitioning doubles with the updated SVP parameterization in the Yangtze River Delta regionMCM and SAPRC07 predicte different volatility distributions and oxidation states for toluene and xylene SOA [ABSTRACT FROM AUTHOR]

Brown carbon (BrC) exhibits a highly complex chemical composition with diverse light‐absorbing properties, which complicates our understanding of its climate impacts. This study examined the impact of molecular characteristics (including molecular mass, unsaturation, oxidation state, and polarity) and heteroatoms on the light‐absorbing properties (absorptivity and wavelength dependence) of BrC from a molecular perspective, based on the ultraviolet‐visible spectra of over 40,000 light‐absorbing substances in aerosol from different sources and ambience. Our findings reveal that the light‐absorptivity of BrC molecules increases with decreasing polarity and O/C ratio, while it rises with higher molecular mass and unsaturation. We developed predictive models for molecular absorptivity based on its double bond equivalent and O/C ratio. In addition, we observed an inverse correlation between absorptivity and wavelength dependence at the molecular level, as determined through mathematical analysis. This molecular‐level understanding provides valuable insights into BrC absorbing mechanisms, facilitating more accurate characterization in atmospheric models. Plain Language Summary: Brown carbon (BrC) plays a crucial role in global climate and air quality. However, extremely complex chemical composition with diverse optical properties in organic aerosols leads to a great variety of BrC in different atmospheric environments, which brings challenges for accurate representation in atmospheric models. This study investigates factors influencing light‐absorbing properties of BrC from a molecular perspective. Our study indicates that the diversity in BrC properties across different environment is an integrated result of variations in molecular mass, unsaturation and oxidation state, all of which should be taken into account. Additionally, it's not accurate to simply label organic aerosol molecules as either absorbing or non‐absorbing. Instead, this study proposes a method to continuously predict the absorption capacity of BrC molecules. Furthermore, we also noticed that as the ability of molecules to absorb light increases, their dependency on wavelength decreases, a relationship we identified and explained using mathematical equations at the molecular level. Key Points: The rising absorptivity of brown carbon (BrC) is an integrated result of lower polarity or O/C ratio, and higher molecular mass or unsaturationThe absorptivity of molecules in BrC can be predicted with double bond equivalent and O/C ratioAn inverse correlation between absorptivity and wavelength dependence is observed and mathematically derived at the molecular level [ABSTRACT FROM AUTHOR]

Since the distinct thermostability difference of sulfate ammonium and nitrate ammonium aerosols, their distributions, evolutions and sources could be unpredictable on a long‐range transport condition. Here, we highlighted the 3‐D structures and sources of SO42−, NO3− and NH4+ (SNA) during two cold front episodes in east China. Cold fronts effectively uplift and transport PM2.5 and its precursors from upstream sources to the Yangtze River Delta (YRD). Specifically, in the YRD, surface SO42− is mostly imported from the upstreams, accounting for ∼48%, significantly higher than the contribution from the YRD itself (∼29%). In contrast, NH4NO3 is thermally unstable and more easily lost in the warmer and lower boundary layer (BL) ahead of cold front. Consequently, only 20% of the total NO3− originates from upstreams, while the YRD contributes 28%. In the upper BL, the contribution of SO42− from upstreams remain high (∼49%), with only 18% originating from the YRD. However, due to the intense thermostability of NH4NO3 in colder and wetter air, the YRD's contribution to NO3− is 27%, and upstreams contribute 20%. The physical processes exert relatively consistent effects on variations of PM2.5 and SNA concentrations. The aerosol chemical process (AERO) of (NH4)2SO4 consistently contributes positively throughout the entire BL. Conversely, the temperature‐sensitive NH4NO3 undergoes repeated dissociation/condensation and deposition, causing positive AERO contributions in upper BL and negative contributions in lower BL. Results indicate that one difference in physicochemical property of species could induce their distinct distributions and sources in large scale, and should be considered in regional air pollution control. Plain Language Summary: Long‐range transport of PM2.5 by cold frontal passage is an important haze formation mechanism. Previous field and modeling studies have revealed that the vertical distribution of particle sulfate and particle nitrate concentrations varied significantly. However, few studies have explored the 3‐D structures and sources of particle sulfate and nitrate under a long‐range transport conditions. In this study, we used combined observations and model simulations during cold front events to address the unrevealed inconsistent 3‐D structures and sources of sulfate and nitrate resulting from temperature stability differences. Cold front episodes redistribute SNA and precursors in three dimensions, driven by drastic meteorology changes and long range transport. Consequently, the distributions, variations and sources of SNA may exhibit complexity and unpredictablility during long‐range transport. Specificlly, (NH4)2SO4 is mostly imported from the upstream in the whole boundary layer (BL), but NH4NO3 is dominant by local source. Moreover, uplifting by cold front, temperature‐sensitive NH4NO3 form in the upper BL and dissociation in the lower BL, whereas (NH4)2SO4 forms uniformly across the whole BL. These findings suggest that one difference in physicochemical property of species can induce distinct distributions and sources in large scale, highlighting the importance of considering such differences in regional air pollution control. Key Points: Uplifted by cold fronts, the temperature‐sensitive NH4NO3 forms in the upper BL and dissociates in the lower BL(NH4)2SO4 forms in the whole BL because it is highly thermally stable and impervious to dissociationThe differences in thermostability and lifetime result in local sources being dominant for NH4NO3, while upstream sources dominate for (NH4)2SO4 [ABSTRACT FROM AUTHOR]

In 2021, the World Health Organization ranked Nigeria among the most polluted nations in the world, an indication of a deteriorating air quality, especially in the major urban areas of the country, which might pose adverse human health impacts. In this study, the Integrated Source Apportionment Method (ISAM) tool in the Community Multiscale Air Quality (CMAQ) model (CMAQ‐ISAM) was employed to quantify the contributions of eight emissions sectors to fine particulate matter (PM2.5) and its major components in Lagos during a prolonged severe atmospheric pollution episode (APE) in January 2021. The influence of meteorological conditions on the formation and dispersion of PM2.5 during the APE was also elucidated. Spatially, elevated PM2.5 concentrations were found in the northwestern region of Lagos, an urban area with larger anthropogenic emissions. Residential and industry were the two major sources of PM2.5. Residential contributed the most to total PM2.5 (∼40 μg/m3), followed by industry (∼20 μg/m3). High concentrations of secondary inorganic aerosols (SIA) at the northwest and upper northern areas of Lagos were majorly attributed to residential and industry sectors. In addition, sulfate accounted for the largest fraction of PM2.5, with residential, industry, and energy being its major sources. Residential, industry, and on‐road sectors dominated the contributions to nitrate, while residential and industry were the major contributors to ammonium. Furthermore, the elevated PM2.5 concentrations during the APE were greatly enhanced by unfavorable meteorological conditions. This study provides insights for designing effective emissions control strategies to mitigate future severe PM2.5 pollution episode in Lagos. Plain Language Summary: With a population of about 23.5 million as at 2018, Lagos is the largest metropolitan city in Africa, and also the most economically and industrially‐developed city in Nigeria. As a result, the city has been suffering from severe fine particulate matter (PM2.5) pollution for more than two decades. In January 2021, a prolonged severe atmospheric pollution episode (APE) occurred in the city. In this study, the contributions of eight emissions sectors to PM2.5 and its major components, as well as the meteorological influences on PM2.5 pollution during the APE were elucidated. The results provide insights into the emissions sectors dominating PM2.5 pollution in Lagos as well as the meteorological influences, and could be used to better understand the causal factors of PM2.5 pollution episode in other areas of the world that can then be applied to develop more effective control strategies that would reduce the magnitude of the episode and better protect public health. Key Points: Lagos experienced a prolonged severe PM2.5 pollution episode in January 2021PM2.5 pollution was enhanced by unfavorable meteorological conditionsEffective emissions control strategies to reduce PM2.5 concentrations are urgently required in Lagos [ABSTRACT FROM AUTHOR]

Previous studies on the impacts of severe haze episode on meteorology were generally focused on single episodes. This study aimed to obtain the common features of the influence of aerosol direct radiative effects on meteorology during severe particulate pollution events by composite analyses on model results from the Weather Research and Forecasting Model with online chemistry. Five heavily polluted events (15–17 January 2014, 13–15 January 2015, 8–10 December 2015, 21–23 December 2015, and 29–31 December 2016) in the North China Plain (NCP, 35.4–41.2°N, 113.3–119.3°E) were selected, which were representative of the most frequently observed weather patterns for severe haze. Model results showed that aerosols in the five heavily polluted events led to strong negative changes in radiative flux of 52.1–86.7 W m−2, reductions in the 2‐m temperature by 0.28–0.97°C, and the reductions in planetary boundary layer heights by 23.1–58.5 m, when averaged over the areas with PM2.5 concentrations >150 μg m−3. The magnitudes of aerosol induced changes in the 2‐m temperature were found to be influenced not only by aerosol concentration but also by wind speed, wind direction, and the convergence or divergence of winds. High wind speed diluted the aerosol‐induced cooling, the convergence of wind limited the temperature change to local area, and the intrusion of cold air mass near the surface enhanced the aerosol‐induced cooling. In all the cases, aerosols induced an anti‐cyclone at 500 hPa around NCP and anomalous northerlies or northeasterlies at the surface in the eastern NCP. Plain Language Summary: The impact of aerosol direct radiative effects (DRE) on meteorology are very important, but previous studies on such effects were generally focused on one pollution episode. In order to obtain the common features of the DRE of aerosols on meteorology, we applied the Weather Research and Forecasting‐Chemistry model to simulate five heavily polluted events belonging to the most frequently observed weather patterns for severe particulate pollution in the North China. We found that aerosols lead to the reductions in surface radiative flux, 2‐m temperature, and planetary boundary layer height. In addition, the magnitudes of aerosol‐induced decreases in 2‐m temperature are influenced by winds, including wind speed, wind direction, and the convergence or divergence of winds. High wind speed dilutes the aerosol‐induced cooling, the convergence of wind limits the temperature change to local area, and the intrusion of cold air mass near the surface enhances the aerosol‐induced cooling. Aerosols also can induce an anti‐cyclone at 500 hPa around North China Plain (NCP) and anomalous northerlies or northeasterlies at the surface in the eastern NCP. Key Points: Aerosols induced reductions in surface radiative flux, 2‐m temperature, and planetary boundary layer heightAerosol‐induced changes in surface air temperature were determined by aerosol concentrations and speed and direction of windsAerosols induced an anti‐cyclone at 500 hPa and anomalous northerlies or northeasterlies at the surface in the east of North China [ABSTRACT FROM AUTHOR]

Large emission reductions of anthropogenic nitrogen oxides (NOx) due to the coronavirus disease 2019 (COVID‐19) lockdown policies in China have been extensively reported since the outbreak, while assessments of sectoral emission changes during that period are still limited. In this study, a source‐oriented community multiscale air quality (CMAQ) model was applied to quantify NO2 concentrations from major emission sectors. A new optimization approach was employed to obtain the sectorial emission reductions using satellite and ground‐level observations as constraints. The optimized emissions significantly improved the model performance of NO2 during the lockdown period. February NOx emission changes varied with regions and sectors, with relatively larger reductions in transportation (286.6 kt) and industrial sources (260.1 kt). The maximum amount of NOx emission reduction occurred in the North China Plain (230.6 kt). Our work presents a quick and reliable technique for assessing sector‐specific emission changes due to short‐term emission control policies. Plain Language Summary: In China, the strict lockdown periods in February 2020 to slow the spread of coronavirus disease 2019 (COVID‐19) led to significant reductions in the emissions of nitrogen oxides (NOx). While the total amounts of emission reductions have been inferred from surface and satellite observations, studies on the changes from major emission sources such as transportation and industry sectors are still limited. In this study, we use an advanced air quality model to determine the contributions of different emission sectors to NO2 concentrations. A new optimization method is then applied to determine the emission reductions of each sector. The agreement between modeled and observed concentrations improved significantly with the adjusted emission estimations. February NOx emission changes vary with regions and sectors, with relatively larger reductions in transportation (286.6 kt) and industrial sources (260.1 kt). The maximum amount of NOx emission reduction happened in the North China Plain (230.6 kt). Our work presents a quick and reliable technique for assessing sector‐specific emission changes due to short‐term emission control policies. Key Points: A new optimization method coupled with a source‐oriented model was applied to estimate sector‐based NOx emission changesNOx emission changes vary with regions and sectors, with larger reductions in transportation (286.6 kt) and industrial sources (260.1 kt)Our work presents a quick and reliable technique for assessing the actual sectoral NOx emission changes due to short‐term control policies [ABSTRACT FROM AUTHOR]

A source‐ and age‐resolved algorithm (SARA) was developed in the CMAQ model and applied to study the sources and ages of primary fine particulate matter (PPM) and secondary inorganic aerosols (SNA) in China during January 2013. Residential and industry are the major contributors to PPM and sulfate, especially for fresh particles. The contributions of power increase with age, accounting for 25% and 51% of aged sulfate and nitrate (>48 hr), respectively. Local emissions and intra‐regional transport with younger age contribute to over 70% of PPM and SNA in Beijing, while long‐range transport from northern China with older age becomes more significant in Shanghai. On pollution days, the ages of PPM and SNA consistently increase, suggesting enhanced contributions from regional transport. This study highlights that the age‐specific particle source and region information produced by our SARA algorithm can help design cost‐effective emission control strategies to reduce extreme haze pollution. Plain Language Summary: Severe haze still exists in China, which is harmful to human health. Studying the source contributions of air pollutants can help policymakers design effective control measures. Previous studies mainly focus on the source sectors and locations of pollutants but neglect the temporal information. Atmospheric age, defined as the time that a certain species has remained in the atmosphere since emitted, provides an opportunity to investigate the temporal contributions of pollutants. Here, a source‐ and age‐resolved algorithm (SARA) was developed to assess the sources and ages of PM2.5 in China during a severe haze episode. Results showed that residential and industry are the major contributors of PPM and sulfate, mainly from local emissions. Power is an important source of sulfate and nitrate, while its contribution increases with age. Long‐range transport from northern China contributes a considerable fraction of particles in Shanghai, especially for aged sulfate. During haze episodes, the enhanced contribution of regional transport from upwind regions brings more aged particles to Beijing and Shanghai. This study highlights that the source type, location, and time information provided by SARA algorithm helps design precise emission control strategies to improve air quality, especially for large public events such as sports games and parades. Key Points: Fresh local emissions from residential and industry are the major contributors to primary fine particulate matter (PPM) and sulfateLong‐range transport from northern China with aged particles contributes to high aerosol loading in ShanghaiDuring haze episodes, regional transport becomes more significant and brings more aged PPM and secondary inorganic aerosols [ABSTRACT FROM AUTHOR]

This study employs the self‐organizing map classification to track wintertime PM2.5 pollutions in Delhi under four atmospheric circulation patterns during 2013–2020. We found that the most polluted circulation pattern was characterized by a northward shift in the subtropical jet stream and a northward intrusion of the subtropical high, leading to descending anomalies from the upper troposphere to the near surface. Together, the resultant reduced passage of cyclones, lower planetary boundary layer, weakened near‐surface winds and less precipitation contributed to wintertime PM2.5 pollution in Delhi. Compared with the 1981–2010 mean levels, Coupled Model Intercomparison Project 6 models project Delhi would experience two fewer days of severe pollution‐favorable circulation pattern and seven more days of clean‐favorable circulation pattern in 2070–2099 under the shared socioeconomic pathway 5–8.5. Future decrease in the severe pollution‐favorable circulation pattern may be attributed to the warming trends in sea surface temperature over the central Pacific and North Atlantic Ocean. Plain Language Summary: Delhi, the capital city of India, currently suffers severe fine particulate matter (PM2.5) pollution, which poses serious public health hazards. The root cause of this problem is excessive emissions from power plants, vehicles, manufactures, and domestic heating released into the atmosphere. During winter, severe air pollutions with high PM2.5 concentrations frequently occurred when coincided with bad weather conditions. Here, we show these unfavorable weather conditions were associated with a circulation pattern which can be captured by climate models. Global warming is projected to be a beneficial role throughout the whole 21st century, leading to decrease in pollution‐favorable weather days and increase in clean‐favorable weather days. Our findings have important implications for future air quality management in Delhi. Key Points: Circulation patterns inducing wintertime PM2.5 pollution in Delhi are identified using self‐organizing map classificationClimate models project decrease (increase) in frequency of pollution (clean)‐favorable circulation pattern throughout the 21st centuryWarming trends of sea surface temperature in the central Pacific and Atlantic Oceans lead to decrease in pollution‐favorable circulation [ABSTRACT FROM AUTHOR]

Studying the influence of electric field on the icing process of insulators with various dielectric surfaces is of great importance to the design of external insulation. This study established a finite element model to simulate the distribution of electric field around various insulator strings. Energised and non‐energised icing tests were conducted to obtain the influence rules of electric field on the insulator icing process. The results of water droplets freeze experiment provided microscopic explanation of icing tests. Research results indicate that electric field and surface dielectrics have influence on the appearance, density and mass of ice on insulators. In microcosmic view, water droplets on super‐hydrophobic surface correspond to longer freezing time and smaller average diameters, which leads to the better anti‐icing character of super‐hydrophobic insulator. Different types of ice branches appear in the water droplets freezing process on various dielectric surfaces. Owing to the polarisation effect, electric field can inhibit the formation and growth of ice branch, which contributes to different anti‐icing characters of various dielectric surfaces in electric field. The effect of dielectric surface on insulator icing process mainly act at the initial period, surface coatings of insulators are not suggested to be applied in heavily icing area. [ABSTRACT FROM AUTHOR]

It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH‐20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID‐19) outbreak, than in 2019 (NYH‐19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH‐19 and NYH‐20. Much higher secondary aerosol fraction in PM2.5 were observed during NYH‐20 (73%) than during NYH‐19 (59%). During NYH‐20, PM2.5 levels correlated significantly with the oxidation ratio of nitrogen (r2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH‐20, despite the overall low atmospheric NO2 levels. Plain Language Summary: In China, there are multiple cases (e.g., the 2008 Summer Olympics in Beijing and the 2010 World Expo in Shanghai) when combustion‐related emissions (e.g., NOx) were actively, and successfully, reduced to transiently improve air quality. During the extended Chinese Lunar New Year holiday in 2020 (between 24 January and 10 February), whole China was in an unprecedented state of shutdown, because most people were contained in their homes to reduce the spread of the novel coronavirus disease (COVID‐19). Mobility, energy demand, and industrial output remained far below their normal levels. Nevertheless, widespread haze pollution still occurred over Eastern China. To elucidate haze formation mechanisms, we performed comprehensive and continuous measurements of aerosol chemistry and physics in and out of Shanghai before, during, and after the Chinese New Year Holiday in 2019 and 2020, respectively. We argue that the synergistic effects of long‐range transport and atmospheric chemistry leading to the efficient conversion of NOx to particulate nitrate were the key of haze formation during the Chinese New Year Holiday of the COVID‐19 outbreak in Shanghai. Key Points: Higher concentrations and distinct compositions of aerosol particles were observed during the COVID‐19 shutdownFast formation of secondary inorganic aerosol contributed to high aerosol mass loadingLonger‐range, regional transport facilitated and enhanced particulate nitrate formation [ABSTRACT FROM AUTHOR]

Summary: Genome‐wide association studies (GWASs) combining high‐throughput genome resequencing and phenotyping can accelerate the dissection of genetic architecture and identification of genes for plant complex traits. In this study, we developed a rapeseed genomic variation map consisting of 4 542 011 SNPs and 628 666 INDELs. GWAS was performed for three seed‐quality traits, including erucic acid content (EAC), glucosinolate content (GSC) and seed oil content (SOC) using 3.82 million polymorphisms in an association panel. Six, 49 and 17 loci were detected to be associated with EAC, GSC and SOC in multiple environments, respectively. The mean total contribution of these loci in each environment was 94.1% for EAC and 87.9% for GSC, notably higher than that for SOC (40.1%). A high correlation was observed between phenotypic variance and number of favourable alleles for associated loci, which will contribute to breeding improvement by pyramiding these loci. Furthermore, candidate genes were detected underlying associated loci, based on functional polymorphisms in gene regions where sequence variation was found to correlate with phenotypic variation. Our approach was validated by detection of well‐characterized FAE1 genes at each of two major loci for EAC on chromosomes A8 and C3, along with MYB28 genes at each of three major loci for GSC on chromosomes A9, C2 and C9. Four novel candidate genes were detected by correlation between GSC and SOC and observed sequence variation, respectively. This study provides insights into the genetic architecture of three seed‐quality traits, which would be useful for genetic improvement of B. napus. [ABSTRACT FROM AUTHOR]

The possibility of insulator flashover would be higher with the increase in icing degree. Therefore, the method of monitoring the icing weight of the insulator is of vital importance. In this study, the estimation method of icing weight on composite insulator in rime icing was proposed. By quite a few experiments under different rime icing conditions, results showed good agreement between estimated value and measured icing weight. Therefore, the estimation method of icing weight proposed by this study was effective and may be used for predicting icing weight. Based on the estimation method, this study discusses the effect of key structural parameters of composite insulator under different rime conditions on icing weight. In order to better apply the composite insulator to electric transmission line in icing area, several suggestions on design optimisation of structural parameters are proposed. [ABSTRACT FROM AUTHOR]

The electrical characteristics of ice‐covered insulators in coexisting conditions of high altitude, icing and pollution are a basis for external insulation selection of transmission lines in icing regions. Ice accretion on insulators has been studied for decades, while few studies focus on the flashover performance of ice‐covered insulators polluted by two types of contamination, that is the solid layer method and icing water conductivity method, simultaneously. On the basis of the investigations on DC flashover performance of ice‐covered insulators in the artificial climate chamber, the influence of different parameters, such as insulator string length, icing water conductivity, salt deposit density as well as atmospheric pressure on DC icing flashover voltage of insulator strings is studied. According to the experimental results, the relationships between the flashover voltage and each of such factors are determined and analysed. Moreover, the correction formula for DC flashover voltage of ice‐covered insulators in complex ambient conditions is proposed. [ABSTRACT FROM AUTHOR]

Icing experiments on three units of XP4‐160 insulator string are conducted to reveal the influence of the crystallisation effect of conductive ions during phase transition on melting water conductivity and ice flashover voltage, and to analyse the motion of conductive ions and its spatial distribution. The influence of different parameters, such as freezing water conductivity, electric field and pollution, on crystallisation effect is examined and analysed. Results of the tests indicate that the melting water conductivity of the ice layer and icicles is considerably greater than that of freezing water, particularly for a polluted insulator, because of the crystallisation effect. The electric field has a significant influence on the crystallisation effect, that is, the melting water conductivity under a non‐energised condition is higher than that under an energised condition. Finally, through 35 kV insulator flashover tests, the reason for the propagation of partial arcs over icicles is determined, and the flashover process is illustrated. The crystallisation effect during phase transition changes the ion distribution in a solid ice layer, thereby increasing water film conductivity, and is also a critical reason for the decline of ice flashover voltage. [ABSTRACT FROM AUTHOR]

To prevent atmospheric ice on optical fibre composite overhead ground wire (OPGW) from affecting the safe and stable operation of power system, applying the direct current (DC) ice‐melting technology to remove ice from OPGW is a feasible option. If the selection of DC ice‐melting current is unreasonable, the temperature of optical fibre can be extremely high which may shorten its operating life or even cause it to burn. Therefore, based on the finite element method, the ice‐melting process of OPGW under glaze icing condition is simulated by COMSOL and MATLAB. The ice‐melting time and temperature variations of optical fibre for ice‐covered OPGW under different environmental conditions are obtained. Then, a series of ice‐melting tests are carried out in an artificial climate chamber to verify the calculation results. Results show that the ice‐melting and temperature increase of optical fibre gradually slow down during the entire DC ice‐melting process. When ice sheds from the OPGW, the temperature of optical fibre reaches its maximum value. The ice‐melting time is closely related to the ice‐melting current, ambient temperature, wind speed, ice thickness and type of OPGW. The maximum temperature of optical fibre is significantly influenced by ice thickness and ice‐melting current. [ABSTRACT FROM AUTHOR]

The ac pollution flashover performance and flashover process of LXHY3‐I6O insulators was investigated at a high altitude site (altitude of 1400m) in this paper. The solid layer method was used, and even‐rising voltage method was adopted. According to the test results, the average pollution flashover voltage (Uav) decreased with the increase of pollution, and there was no obvious relationship between the exponent characterising the influence of pollution and the length of the insulator strings. The relationship between Uav and the length of the insulator strings was nearly linear. Subsequently, the effect of the pollution and the length of insulator strings on the critical flashover arc trajectory were analysed. It concluded that the critical flashover distance (lc) decreased with the increase of pollution, and it was shorter than the leakage distance (L0), whereas there was no significant relationship between lc/L0 and the length of insulator strings. The arc appearance at the high altitude site was very irregular with obvious bending and rocking; the local arcs deviated from the surface of the polluted insulators even more seriously and the diameter was thicker than those obtained in the normal environment. Moreover, the brightness and diameter of local arcs was related to pollution. [ABSTRACT FROM AUTHOR]

Direct labelling: 5‐Formylcytosine in DNA can be selectively labelled by fluorescent dyes containing an active amino group. The labelled DNA shows strong fluorescence and can be detected by polyacrylamide gel electrophoresis (PAGE) and fluorescence measurements (see scheme). This method can distinguish 5‐formylcytosine from other methylation forms of cytosine in DNA. [ABSTRACT FROM AUTHOR]