Manipulating Na occupation and constructing protective film of P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2) as long-term cycle stability cathode for sodium-ion batteries

P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2)(NNMO)is promising cathode material for sodium-ion batteries(SIBs)due to its high specific capacity and fast Na+diffusion rate.Nonetheless,the irreversible P2-O_(2)phase transformation,Na+/vacancy ordering,and transition metal(TM)dissolution seriously damage its cycling stability and restrict its commercialization process.Herein,Na occupation manipulation and interface stabilization are proposed to strengthen the phase structure of NNMO by synergistic Zn/Ti co-doping and introducing lithium difluorophosp(LiPO_(2)F_(2))film-forming electrolyte additive.The Zn/Ti co-doping regulates the occupancy ratio of Nae/Nafat Na sites and disorganizes the Na+/vacancy ordering,resulting in a faster Na+diffusion kinetics and reversible P2-Z phase transition for P2-Na_(0.67)Ni_(0.28)Zn_(0.05)Mn_(0.62)Ti_(0.05)O_(2)(NNZMTO).Meanwhile,the LiPO_(2)F_(2)additive can form homogeneous and ultrathin cathode-electrolyte interphase(CEI)on NNZMTO surface,which can stabilize the NNZMTO-electrolyte interface to prevent TM dissolution,surface structure transformation,and micro-crack generation.Combination studies of in situ and ex situ characterizations and theoretical calculations were used to elucidate the storage mechanism of NNZMTO with Li PO_(2)F_(2)additive.As a result,the NNZMTO displays outstanding capacity retention of 94.44%after 500 cycles at 1C with 0.3 wt%Li PO_(2)F_(2),excellent rate performance of 92.5 mA h g^(-1)at 8C with 0.1 wt%Li PO_(2)F_(2),and remarkable full cell capability.This work highlights the important role of manipulating Na occupation and constructing protective film in the design of layered materials,which provides a promising direction for developing high-performance cathodes for SIBs.

Four-to Six-Year Periodic Variation of Arctic Sea-Ice Extent and Its Three Main Driving Factors

Besides the rapid retreating trend of Arctic sea-ice extent(SIE),this study found the most outstanding low-frequency variation of SIE to be a 4-6-year periodic variation.Using a clustering analysis algorithm,the SIE in most ice-covered regions was clustered into two special regions:Region-1 around the Barents Sea and Region-2 around the Canadian Basin,which were located on either side of the Arctic Transpolar Drift.Clear 4-6-year periodic variation in these two regions was identified using a novel method called“running linear fitting algorithm”.The rate of temporal variation of the Arctic SIE was related to three driving factors:the regional air temperature,the sea-ice areal flux across the Arctic Transpolar Drift,and the divergence of sea-ice drift.The 4-6-year periodic variation was found to have always been present since 1979,but the SIE responded to different factors under heavy and light ice conditions divided by the year 2005.The joint contribution of the three factors to SIE variation exceeded 83%and 59%in the two regions,respectively,remarkably reflecting their dynamic mechanism.It is proven that the process of El Niño-Southern Oscillation(ENSO)is closely associated with the three factors,being the fundamental source of the 4-6-year periodic variations of Arctic SIE.

Export of Greenland Sea water across the Mohn Ridge induced by summer storms

The Mohn Ridge separates the Greenland Sea and the Lofoten Basin.Previous studies identified the export across the Mohn Ridge(EMR)from the Greenland Basin into the Lofoten Basin using water mass analysis and the tracer diffusion method,but there is still lack of direct current measurements.A surface mooring with four current meters was deployed on the Mohn Ridge from June 5 to June 18 in 2015,when three cyclones passed in the adjacent area.In the absence of cyclones,the flow on the Mohn Ridge was northeastward,parallel to the ridge.When cyclones appeared,the EMR occurred to transport Greenland Sea water into the Lofoten Basin.The probable mechanism is the sea level height variation caused by the perturbation of the low pressure of cyclones,which yields an outward pressure gradient force to drive the outflow.Our results suggest that the outflow is intermittent and only happens during cyclone activities.The annual mean volume flux of EMR was roughly estimated by the limited data,which is about 3.8×10^(6)m^(3)/s,a little bit smaller than the estimation based on volume conservation.The results indicate that the contribution of the cyclonic storms to EMR is a greatly important mechanism that potentially influences the global thermohaline circulation through the Greenland-Scotland Ridge overflow.

Insights into the enhanced structure stability and electrochemical performance of Ti^(4+)/F^(-) co-doped P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2) cathodes for sodium ion batteries at high voltage

P2-Na_(0.67)N_(i0.33)Mn_(0.67)O_(2)is considered as a promising cathode material for sodium-ion battery (SIBs)because of its high capacity and discharge potential.However,its practical use is limited by Na^(+)/vacancy ordering and P2-O2 phase transition.Herein,a Ti^(4+)/F^(-) co-doping strategy is developed to address these issues.The optimal P2-Na_(0.67)Ni_(0.33)Mn_(0.37)Ti_(0.3)O_(1.9)F_(0.1) exhibits much enhanced sodium storage performance in the high voltage range of 2.0–4.4 V,including a cycling stability of 77.2%over 300cycles at a rate of 2 C and a high-rate capability of 87.7 m Ah g^(-1) at 6 C.Moreover,the P2-Na_(0.67)Ni_(0.33)Mn_(0.37)Ti_(0.3)O_(1.9)F_(0.1) delivers reversible capacities of 82.7 and 128.1 m Ah g^(-1) at-10 and 50℃ at a rate of 2 C,respectively.The capacity retentions over 200 cycles at-10℃ is 94.2%,implying more opportunity for practical application.In-situ X-ray diffraction analysis reveals that both P2-O2 phase transitions and Na^(+)/vacancy ordering is suppressed by Ti^(4+)/F^(-) co-doping,which resulting in fast Na^(+) diffusion and stable phase structure.The hard carbon//P2-Na_(0.67)Ni_(0.33)Mn_(0.37)Ti_(0.3)O_(1.9)F_(0.1) full cell exhibits a high energy density of 310.2 Wh kg^(-1) and remarkable cyclability with 82.1%retention after 300 cycles at 1 C in the voltage range of 1.5–4.2 V.These results demonstrate that the co-doping Ti^(4+)/F^(-) is a promising strategy to improve the electrochemical properties of P2-Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2),providing a facile tactic to develop high performance cathode materials for SIBs.

Impacts of Changes in Sea Ice and Heat Flux on Arctic Warming

The reduction of Arctic sea ice has enhanced the sea-ice-air interaction in the Arctic atmospheric boundary layer, especially the increase in sea-air heat flux in autumn. Changes in radiation and heat flux and the role of sea-ice-air interactions in climate change in the central Arctic were analyzed and evaluated on the basis of the observation data of ice stations during the six Chinese Arctic Research Expeditions. The albedo is high in the Arctic sea-ice surface except the melting process. Overall, the Arctic sea-ice surface can absorb radiation energy, which is much lower than that absorbed by mid-latitude surfaces. Consequently, a relatively weak turbulence exchange occurred between the sea-ice surface and the atmosphere. Further estimates of the surface heat budget in the Arctic are obtained using eddy correlation and flux-profile method. The results are representative of the heat balance and ice-air interactions in the central Arctic Ocean. In the Arctic, changes in heat flux displayed notable interdecadal characteristics, similar to the change of sea-ice extent. The heat flux in September of each year in 2001-2014 was considerably higher compared with that in 1979-2000, particularly at the edges of the central Arctic Ocean. In September of each year in 1979-2014, the sea-ice extent was remarkably negatively correlated to the heat flux (sensible heat flux + latent heat flux), and the heat flux was considerably positively correlated to the atmospheric temperature at 2 m above sea level. This result demonstrates that a reduction of Arctic sea ice will lead to changes in heat flux, thereby warming the atmosphere and increasing the temperature of the atmospheric boundary layer over the Arctic. In addition, this impact is long-lasting.

An Optimization Model for Reliability Improvement and Cost Reduction Through EV Smart Charging

There is a general concern that the increasing penetration of electric vehicles(EVs)will result in higher aging failure probability of equipment and reduced network reliability.The electricity costs may also increase,due to the exacerbation of peak load led by uncontrolled EV charging.This paper proposes a linear optimization model for the assessment of the benefits of EV smart charging on both network reliability improvement and electricity cost reduction.The objective of the proposed model is the cost minimization,including the loss of load,repair costs due to aging failures,and EV charging expenses.The proposed model incorporates a piecewise linear model representation for the failure probability distributions and utilizes a machine learning approach to represent the EV charging load.Considering two different test systems(a 5-bus network and the IEEE 33-bus network),this paper compares aging failure probabilities,service unavailability,expected energy not supplied,and total costs in various scenarios with and without the implementation of EV smart charging.

Pollution characteristics of organic and elemental carbon in PM_(2.5) in Xiamen,China

Xiamen, located on the southeastern coastal line of China, is undergoing rapid urbanization and industrialization, so its air quality has a trend of degradation. However, studies on level, temporal and spatial changes of fine particles （PM2.5） and their carbonaceous fractions are scarce. In this article, abundance, sources, seasonal and spatial variations, distribution of organic carbon （OC） and elemental carbon （EC） in PM2.5, were studied at suburban, urban and industrial sites in Xiamen during four season-representative months in 2009-2010. PM2.5 samples were collected with middle volume sampler and were analyzed for OC and EC with thermal optical transmittance （TOT） method. Results showed that the annual average PM2.5 concentrations were 63.88-74.80 Ixg/m3 at three sites. While OC and EC concentrations were in the range of 15.81-19.73 [xg/m3 and 2.74-3.49 ~tg/m3, respectively, and clearly presented the summer minima and winter maxima in this study. The carbonaceous aerosol accounted for 42.8%-47.3% of the mass of PMzs. The annual average of secondary organic carbon （SOC） concentrations in Xiamen were 9.23-11.36 ~g/m3, accounting for approximately 56% of OC. Strong correlations between OC and EC was found in spring （R2 = 0.50） and autumn （R2 = 0.73）, suggesting that there were similar emission and transport processes for carbonaceous aerosols in these two seasons, while weak correlations were found in summer （R2 = 0.33） and winter （R2 = 0.41）. The OCI＇EC ratios in PM2.5 varied from 2.1 to 8.7 with an annual average of 5.7, indicating that vehicle exhaust, coal smoke and biomass burning were main source apportionments of carbonaceous fractions in Xiamen.

Efficient Synthesis of Graphene Nanoribbons Sonochemically Cut from Graphene Sheets

We report a facile approach to synthesize narrow and long graphene nanoribbons (GNRs) by sonochemically cutting chemically derived graphene sheets (GSs). The yield of GNRs can reach ~5 wt% of the starting GSs. The resulting GNRs are several micrometers in length, with ~75% being single-layer, and ~40% being narrower than 20 nm in width. A chemical tailoring mechanism involving oxygen-unzipping of GSs under sonochemical conditions is proposed on the basis of experimental observations and previously reported theoretical calculations;it is suggested that the formation and distribution of line faults on graphite oxide and GSs play crucial roles in the formation of GNRs. These results open up the possibilities of the large-scale synthesis and various technological applications of GNRs.

Characterization of polycyclic aromatic hydrocarbons and gas/particle partitioning in a coastal city, Xiamen, Southeast China

An intensive sampling program had been undertaken in autumn （October, 2008） and winter （December, 2008 and January, 2009） at urban （Xiamen University and Xianyue residential area）, suburban （Institute of Urban Environment）, industrial area （Lulian Hotel） and background （Tingxi Reservoir） in Xiamen, Fujian Province, to characterize the atmospheric concentration and gas-particle phase partitioning of PAHs. The average concentration of total PAHs in winter was almost 1.7 times higher than those in autumn. The log scale plot of Kp versus sub-cooled liquid vapor pressure （PL^0） for all the data of autumn and winter season samples gave significantly different slopes. The slope for the winter samples （-0.72） was steeper than that for the autumn samples （-0.58）. The partitioning results indicated that slope values varied depending on characteristics of specific site, source region and meteorological conditions which play important roles in the partitioning of PAHs. In addition, local emission sources had a stronger effect on partitioning results than long-transported polluted plume. The sources of PAHs in five sampling sites in Xiamen also have been discussed initially. Diagnostic ratios showed that the primary source of PAHs in urban, suburban and industrial area was from vehicle exhausts. While emission from petrochemical factory and power plant was another main contributor to industrial area.

5 nm NiCoP nanoparticles coupled with g-C3N4 as high-performance photocatalyst for hydrogen evolution

Graphitic carbon nitride(g-C3N4) coupled with NiCoP nanoparticles with sizes around 5 nm have been fabricated via a controllable alcohothermal process. NiCoP is an excellent electron conductor and cocatalyst in photocatalytic reactions. The coupling between tiny NiCoP nanoparticles and g-C3N4 through in-situ fabrication strategy could be a promising way to eliminate the light screening effect, hinder the recombination of photo-induced charge carriers, and improve the charge transfer. The NiCoP/g-C3N4 nanohybrids exhibit an excellent photocatalytic activity in the hydrogen generation, with a significantly improved performance compared with original g-C3N4, CoP/g-C3N4 and Ni2P/g-C3N4, respectively. This study paves a new way to design transition metal phosphides-based photocatalysts for hydrogen production.

PBS3 Protects EDS1 from Proteasome-Mediated Degradation in Plant Immunity

Plant immunity is controlled by both positive regulators such as PBS3 and EDS1 and negative regulators such as NPR3 and NPR4.However,the relationships among these important immune regulators remain elusive.In this study,we found that PBS3 interacts with EDS1 in both the cytoplasm and the nucleus,and is required for EDS1 protein accumulation?NPR3 and NPR4,which function as salicylic acid receptors and adaptors of Cullin3-based E3 ligase,interact with and mediate the degradation of EDS1 via the 26S proteasome.We further discovered that PBS3 inhibits the polyubiquitination and subsequent degradation of EDS1 by reducing the association of EDS1 with the Cullin3 adaptors NPR3 and NPR4.Furthermore,we showed that PBS3 and EDS1 also contribute to PAMP-triggered immunity in addition to effector-triggered immunity.Collectively,our study reveals a novel mechanism by which plants fine-tune defense resporises by inhibiting the degradation of a positive player in plant immunity.

Chemical characteristics of PM_(2.5) during haze episodes in the urban of Fuzhou,China

Atmospheric fine particles （PM2.5） were collected in this study with middle volume samplers in Fuzhou, China, during both normal days and haze days in summer （September 2007） and winter （january 2008）. The concentrations, distributions, and sources of polycyclic aromatic hydrocarbons （PAHs）, organic carbon （OC）, elemental carbon （EC）, and water soluble inorganic ions （WSIls） were determinated. The results showed that the concentrations of PM2.s, PAHs, OC, EC, and WSIIs were in the orders of haze 〉 normal and winter〉 summer. The dominant PAHs of PM2.s in Fuzhou were Fluo, Pyr, Chr, BbF, BkF, BaP, BghiP, and IcdP, which represented about 80.0% of the total PAHs during different sampling periods. The BaPeq concentrations of ^-~PAHs were 0.78, 0.99, 1.22, and 2.43 ng/m3 in summer normal, summer haze, winter normal, and winter haze, respectively. Secondary pollutants （SO42 , NO3 , NH4＊, and OC） were the major chemical compositions of PM2.5, accounting for 69.0%, 55.1%, 63.4%, and 64.9% of PM2.s mass in summer normal, summer haze, winter normal, and winter haze, respectively. Correspondingly, secondary organic carbon （SOC） in Fuzhou accounted for 20.1%, 48.6%, 24.5%, and 50.5% of OC. The average values of nitrogen oxidation ratio （NOR） and sulfur oxidation ratio （SOR） were higher in haze days （0.08 and 0.27） than in normal days （0.05 and 0.22）. Higher OC/EC ratios were also found in haze days （5.0） than in normal days （3.3）. Correlation analysis demonstrated that visibility had positive correlations with wind speed, and neg- ative correlations with relative humidity and major air pollutants. Overall, the enrichments of PM2.5, OC, EC, SO42 ,andNO3 promoted haze formation. Furthermore, the diagnostic ratios of IcdP/（IcdP ＋ BghiP）, lcdP/BghiP, OC/EC, and NO3 /SO42 indicated that vehicle exhaust and coal consumption were the main sources of pollutants in Fuzhou.

Indices of Congested Areas and Contributions of Customers to Congestions in Radial Distribution Networks

Congestions are becoming a significant issue with an increasing number of occurrences in distribution networks due to the growing penetration of distributed generation and the expected development of electric mobility.Fair congestion management(CM)policies and prices require proper indices of congested areas and contributions of customer to congestions.This paper presents spatial and temporal indices for rapidly recognizing the seriousness of congestions from the perspectives of both magnitude violation and duration to prioritize the affected areas where CM procedures should be primarily activated.Besides,indices are presented which describe the contributions of customers to the congestions.Simulation tests on IEEE 123-bus and Australian 23-bus low-voltage distribution test feeders illustrate the calculation and capabilities of the proposed indices in balanced and unbalanced systems.

NLR immune receptor RB is differentially targeted by two homologous but functionally distinct effector proteins

Plant nucleotide-binding leucine-rich repeat(NLR)receptors mediate immune responses by directly or indirectly sensing pathogen-derived effectors.Despite significant advances in the understanding of NLR-mediated immunity,the mechanisms by which pathogens evolve to suppress NLR activation triggered by cognate effectors and gain virulence remain largely unknown.The agronomically important immune receptor RB recognizes the ubiquitous and highly conserved IPI-O RXLR family members(e.g.,IPI-O1)from Phytophthora infestans,and this process is suppressed by the rarely present and homologous effector IPIO4.Here,we report that self-association of RB via the coiled-coil(CC)domain is required for RB activation and is differentially affected by avirulence and virulence effectors.IPI-O1 moderately reduces the self-association of RB CC,potentially leading to changes in the conformation and equilibrium of RB,whereas IPIO4 dramatically impairs CC self-association to prevent RB activation.We also found that IPI-O1 associates with itself,whereas IPI-O4 does not.Notably,IPI-O4 interacts with IPI-O1 and disrupts its self-association,therefore probably blocking its avirulence function.Furthermore,IPI-O4 enhances the interaction between RB CC and IPI-O1,possibly sequestering RB and IPI-O1 and subsequently blocking their interactions with signaling components.Taken together,these findings considerably extend our understanding of the underlying mechanisms by which emerging virulent pathogens suppress the NLR-mediated recognition of cognate effectors.

Quantification,morphology and source of humic acid,kerogen and black carbon in offshore marine sediments from Xiamen Gulf,China

Three types of macromolecular organic matters （MOMs）, i.e. humic acid （HA）, kerogen＋black carbon （KB）, and black carbon （BC） were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry （EA/IRMS） and scanning electron microscope （SEM）. The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content （TOC）, while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ 13 C values of the three fractions suggested that materials from terrestrial C 3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ 13 C values of MOMs in the offshore marine sediments.

Arabidopsis EED1 encoding a plant-specific nuclear protein is essential for early embryogenesis

Embryogenesis is central to the life cycle of higher plants,which starts from division of the single-cell zygote and culminates in formation of the mature embryo with major cell precursors.Such a process generally involves tightly orchestrated cell division,differentiation,and pattern formation.