Challenges in Li-ion battery high-voltage technology and recent advances in high-voltage electrolytes

The electrolyte directly contacts the essential parts of a lithium-ion battery,and as a result,the electrochemical properties of the electrolyte have a significant impact on the voltage platform,charge discharge capacity,energy density,service life,and rate discharge performance.By raising the voltage at the charge/discharge plateau,the energy density of the battery is increased.However,this causes transition metal dissolution,irreversible phase changes of the cathode active material,and parasitic electrolyte oxidation reactions.This article presents an overview of these concerns to provide a clear explanation of the issues involved in the development of electrolytes for high-voltage lithium-ion batteries.Additionally,solidstate electrolytes enable various applications and will likely have an impact on the development of batteries with high energy densities.It is necessary to improve the high-voltage performance of electrolytes by creating solvents with high thermal stabilities and high voltage resistance and additives with superior film forming performance,multifunctional capabilities,and stable lithium salts.To offer suggestions for the future development of high-energy lithium-ion batteries,we conclude by offering our own opinions and insights on the current development of lithium-ion batteries.

Nitrogen,phosphorus,and sulfur co-doped carbon nanotubes/melamine foam composite electrode for high-performance vanadium redox flow battery

The high cost and complex modification process of carbon felt electrodes limits its further popularization in vanadium redox flow batteries(VFBs).By introducing low-cost melamine foam,nitrogen,phosphorus,and sulfur co-doped carbon nanotubes/melamine foam composite electrode(NPS-CNTs-CMF)is designed and fabricated via immersing melamine foam in a solution containing N,P,and S co-doped CNTs.The integration of modified CNTs significantly enhances the conductivity and hydrophilicity of the electrode.Moreover,the composite electrode also demonstrates outstanding electrocatalytic activity owing to the heteroatom doping that further inspired the electrocatalytic activity of CNTs.Density function theory cal-culations further uncover that introducing heteroatoms on CNTs not only promotes the adsorption of vanadium ions but also facilitates the electron transfer between vanadium ions and MF substrate.As a result,the battery loading with NPS-CNTs-CMF exhibits excellent battery performance,achieving energy efficiency of 80.12%at 300 mA cm^(-2).Additionally,the long-term cycling stability is attained over 200 consecutive charge-discharge cycles at 300 mA cm^(−2).This study provides a novel melamine foam mate-rial with low cost and simple modification,and this new composite structure stimulates the development of high-performance electrodes in VFBs.

Local tetragonal distortion of Pt alloy catalysts for enhanced oxygen reduction reaction efficiency

Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and catalytic performance is still lacking.Herein,we present a synthetic strategy that uses transition-metal oxide-assisted thermal diffusion.PtCo/C catalysts with localized tetragonal distortion were obtained by controlling the thermal diffusion process of transition-metal elements.This localized structural distortion induced a significant strain effect on the nanoparticle surface,which further shortened the length of the Pt-Pt bond,improved the electronic state of the Pt surface,and enhanced the performance of the catalyst.PtCo/C catalysts with special short-range structures achieved excellent mass activity(2.27 Amg_(Pt)^(-1))and specific activity(3.34 A cm^(-2)).In addition,the localized tetragonal distortion-induced surface compression of the Pt skin improved the stability of the catalyst.The mass activity decreased by only 13% after 30,000 cycles.Enhanced catalyst activity and excellent durability have also been demonstrated in the proton exchange membrane fuel cell configuration.This study provides valuable insights into the development of advanced Pt-based nanocatalysts and paves the way for reducing noble-metal loading and increasing the catalytic activity and catalyst stability.

Distribution and influencing factors of acoustic characteristics of seafloor sediment in the Sunda Shelf

To understand the acoustic and physical properties of piston core samples collected from the Sunda continental shelf and analyze their distribution patterns,the samples were analyzed in laboratory,from which three provinces were divided in sound speed,sound speed ratio,porosity,wet bulk density,and maximum shear strength.ProvinceⅠhad lower sound speed and sound speed ratio(<1.04),high porosity,and low wet bulk density.ProvinceⅡhad higher sound speed and sound speed ratio(>1.04),low porosity,and high wet bulk density.ProvinceⅢhad the lowest sound speed and sound speed ratio(0.99),highest porosity(81%),and lowest wet bulk density(1.34 g/cm^(3)).The distribution pattern indicates that sediment movement,sediment source,topography,and hydrodynamic conditions influenced the distribution of acoustic and physical properties.Furthermore,we investigated the relationship of the maximum shear strength to the porosity and wet bulk density,and found that the maximum shear strength was proportional to both the porosity and wet bulk density.This finding has significant implications for ocean engineering applications.

Utilizing Dynamic Data to Quickly Evaluate Advantageous Channels and Applications

In response to the high cost and difficulty of high-speed development and testing data in offshore oil fields, this paper proposes to use the most easily available production performance data as the basis and use the grey correlation method to calculate the correlation coefficient between oil and water wells to characterize the degree of development of advantageous channels. The consistency between the calculated results of this method and the tracer test results is over 80%. Based on the fitting results, the correlation coefficient exceeds 0.74 to determine the existence of an advantageous channel. According to the research results of grey correlation method, Bohai K oilfield has completed the combined profile control and flooding measures, and the daily oil production has increased by 20 m3/d. This method is simple, fast, and can achieve quantitative evaluation, which saves time and investment compared to offshore testing. It has strong application and reference value for the development of other offshore water injection oilfields.

Perceptions and Receipt of Cancer Screening among African Americans: A Community Networks Program Project

Objective: Minority groups constitute one of the nation’s highest cancer risk groups. Historically, these groups have not been adequately informed about cancer, its prevention and/or treatment. The purpose of this study was to examine participants’ receipt of cancer screening and to explore perceptions of barriers to and facilitators of cancer screening. Methods: A two-part study design consisting of a survey and focus group was conducted among African Americans residents of neighborhoods geographically defined as low-income areas of Chattanooga, Memphis, and Nashville in the state of Tennessee. The survey was administered to 1071 participants, and 12 focus groups were conducted with a total of 112 participants, with both sets of participants being residents of similarly defined underserved communities served by the community health centers. Results: Overall, 51% of surveyed respondents were females;the majority (75%) had a yearly income of less than $25,000;and 67% reported 12 years of education or less. Most surveyed respondents had a family history of cancer. More than 30% and 64% of male respondents over 50 years old did not receive prostate cancer and colorectal cancer screening, respectively;58% of women 50 years and older were not screened for colorectal cancer;28% of women over 40 years old did not receive breast cancer screening. Barriers to cancer screening included: lack of information about cancer screening and treatments, cost of cancer treatment and fear. The need for more information about cancer and cancer treatment, as well as the involvement of churches to increase cancer screening awareness was identified as facilitators. Conclusion: This study provides information into the structural and psychological barriers in cancer screening. It describes the self-reported prevalence/frequency of screening among men and women in our target population, and the associated facilitators to screening.

利用原子转移自由基反应在超大孔聚苯乙烯微球表面接枝含糖聚合物刷

超大孔聚苯乙烯微球具有力学强度高、化学稳定性好、传质速率快等优点,但其表面疏水性强,无法衍生,要想用作生物大分子分离介质必须对其亲水改性。文中利用原子转移自由基(ATRP)反应的方法在超大孔聚苯乙烯微球(PS)表面原位接枝含糖聚合物刷,得到亲水改性的超大孔聚苯乙烯微球。对溶剂、配体、催化剂及温度等反应条件进行了详细考察,优化了接枝反应条件。含糖聚合物刷最大接枝量达到490.8 mg/g干球,改性后微球表面接触角由124°下降到42°,对蛋白的吸附量也降低了10.2倍,亲水性和生物相容性明显提高,同时微球的超大孔未被堵塞,且柔性含糖聚合物刷在后期衍生过程中还起到了"间隔臂"的作用,将是一种非常优良的生物大分子分离介质,在快流速蛋白分离色谱领域有很大应用潜力。

临盘稠油木质素基自乳化驱油剂的研制及现场应用

随着国际原油价格的下降,前期研制的石油基自乳化驱油剂(NB-5034A)因为成本问题,难以继续在实际生产中应用。针对这一问题,开展了低成本木质素基自乳化驱油剂的研究。首先针对临盘稠油特点,优化得到了合适的木质素基自乳化驱油剂配方(NB-50PA);然后通过物模实验,研究了驱油剂浓度、实验温度、驱替速度与方式、岩心性质和稠油黏度等因素对采收率的影响,评估了NB-50PA的使用条件。现场试验表明,NB-50PA可使临盘稠油的平均采收率提高24.51%,并且成本仅为前期研制的石油基自乳化驱油剂的1/3。

Expert consensus on dental caries management

Dental Caries is a kind of chronic oral disease that greatly threaten human being’s health.Though dentists and researchers struggled for decades to combat this oral disease,the incidence and prevalence of dental caries remain quite high.Therefore,improving the disease management is a key issue for the whole population and life cycle management of dental caries.So clinical difficulty assessment system of caries prevention and management is established based on dental caries diagnosis and classification.Dentists should perform oral examination and establish dental records at each visit.When treatment plan is made on the base of caries risk assessment and carious lesion activity,we need to work out patient-centered and personalized treatment planning to regain oral microecological balance,to control caries progression and to restore the structure and function of the carious teeth.And the follow-up visits are made based on personalized caries management.This expert consensus mainly discusses caries risk assessment,caries treatment difficulty assessment and dental caries treatment plan,which are the most important parts of caries management in the whole life cycle.

Stability improvement of the Nieuwland catalyst in the dimerization of acetylene to monovinylacetylene

In the process of dimerization of acetylene to produce monovinylacetylene （MVA）,the loss of active component CuCl in the Nieuwland catalyst due to the formation of a dark red precipitate was investigated.The formula of the precipitate was CuCl·2C2H2·1/5NH 3,and it was presumed to be formed by the combination of NH 3,C2H2 and [Cu]-acetylene π-complex,which was an intermediate in the dimerization reaction.The addition of hydrochloric acid into the catalyst can reduce the formation of precipitate,whereas excessive H＋ is unfavorable to the dimerization reaction of acetylene.To balance between high acetylene conversion and low loss rate of CuCl,the optimum mass percentage of HCl in the added hydrochloric acid was determined.The result showed the optimum mass percentage of HCl decreased from 5.0% to 3.2% when the space velocity of acetylene was from 140 h-1 to 360 h-1.The result in this work also indicated the pH of the Nieuwland catalyst should be kept in the range of 5.80-5.97 during the reaction process,which was good for both catalyst life and acetylene conversion.

Detection of heavy metals in water samples by laser-induced breakdown spectroscopy combined with annular groove graphite flakes

The use of laser-induced breakdown spectroscopy(LIBS) for the analysis of heavy metals in water samples is investigated. Some factors such as splashing, surface ripples, extinction of emitted intensity, and a shorter plasma lifetime will influence the results if the water sample is directly measured. In order to avoid these disadvantages and the ‘coffee-ring effect', hydrophilic graphite flakes with annular grooves were used for the first time to enrich and concentrate heavy metals in water samples before being analyzed by LIBS. The proposed method and procedure have been evaluated to concentrate and analyze cadmium, chromium, copper, nickel, lead,and zinc in a water sample. The correlation coefficients were all above 0.99. The detection limits of 0.029, 0.087, 0.012, 0.083, 0.125, and 0.049 mgl^(-1) for Cd, Cr, Cu, Ni, Pb, and Zn,respectively, were obtained in samples prepared in a laboratory. With this structure, the heavy metals homogeneously distribute in the annular groove and the relative standard deviations are all below 6%. This method is very convenient and suitable for online in situ analysis of heavy metals.

Ensemble Simulation of Land Evapotranspiration in China Based on a Multi-Forcing and Multi-Model Approach

In order to reduce the uncertainty of offline land surface model （LSM） simulations of land evapotranspiration （ET）, we used ensemble simulations based on three meteorological forcing datasets [Princeton, ITPCAS （Institute of Tibetan Plateau Research, Chinese Academy of Sciences）, Qian] and four LSMs （BATS, VIC, CLM3.0 and CLM3.5）, to explore the trends and spatiotemporal characteristics of ET, as well as the spatiotemporal pattern of ET in response to climate factors over China's Mainland during 1982-2007. The results showed that various simulations of each member and their arithmetic mean （EnsAVlean） could capture the spatial distribution and seasonal pattern of ET sufficiently well, where they exhibited more significant spatial and seasonal variation in the ET compared with observation-based ET estimates （Obs_MTE）. For the mean annual ET, we found that the BATS forced by Princeton forcing overestimated the annual mean ET compared with Obs_MTE for most of the basins in China, whereas the VIC forced by Princeton forcing showed underestimations. By contrast, the Ens_Mean was closer to Obs_MTE, although the results were underestimated over Southeast China. Furthermore, both the Obs_MTE and Ens_Mean exhibited a significant increasing trend during 1982-98; whereas after 1998, when the last big EI Nifio event occurred, the Ens_Mean tended to decrease significantly between 1999 and 2007, although the change was not significant for Obs_MTE. Changes in air temperature and shortwave radiation played key roles in the long-term variation in ET over the humid area of China, but precipitation mainly controlled the long-term variation in ET in arid and semi-arid areas of China.

Effect of solvent on catalytic performance of anhydrous catalyst in acetylene dimerization to monovinylacetylene

The production of monovinylacetylene （MVA） through Cu（I）-catalyzed acetylene dimerization reaction was performed in different reaction media. Based on the analyses of crystals precipitated from the catalyst solution and UV-Vis spectra of the catalysts, the reaction mechanism and solvent dependence were studied. The highest yield of MVA can be obtained when dimethylformamide is used as solvent because of its strong coordination ability to Cu（I）. The activation of C=C bond is presumed to be improved when the catalytic metal ion is coordinated by a solvent with less steric hindrance and electron-rich coordination atom. The results of the present study provide a possible way to accelerate the metal-catalyzed homogeneous reaction of alkyne substrates through careful selection of a solvent.

Natural Host–Environmental Media–Human: A New Potential Pathway of COVID-19 Outbreak

传统上,识别第一个感染病例(零号病人)是追溯病毒来源的关键,但是,常常很难找到零号病人。特别是如果零号病人无症状或症状非常轻微,无看医生或相关病情记录,可能永远也无法找到。因此,是否可以跳过零号病人追溯到病毒的来源?针对上述问题,研究中分析了人类历史上的病毒暴发以及病毒在环境中的存活时间等。发现很大比例的疫情事件都是由人类直接接触带有传染性病毒的环境介质而引起的,同时病毒可以在环境介质中长期保持活性。另一方面,随着人类活动能力不断增强,与动物等生存空间的逐渐重叠,人类与带病毒环境介质(我们称之为"环境准宿主")之间的接触大大增加。因此,研究中提出了跳过零号病人在环境中追溯病毒来源的可能路径,即以携带SARS-CoV-2或RaTG3相关冠状病毒的环境介质为目标,基于自然宿主-环境介质(环境准宿主)-人的传播路径,进行新冠病毒溯源。

Rapid synthesis of highly active Pt/C catalysts with various metal loadings from single batch platinum colloid

A series of Pt/C catalysts for proton exchange membrane fuel cells(PEMFCs) with various metal loadings is synthesized by a microwave-assisted polyol process via mixing an extremely stable platinum colloid(> 3 months’ shelf life) from single batch preparation with activated carbon ethylene glycol suspension.21 wt%, 42 wt% and 61 wt% Pt loadings are employed to showcase the advantages of the improved polyol process. The ultraviolet(UV)–visible spectra and ζ-potential measurements are conducted to monitor the wet chemistry process during catalyst preparation. The powder X-ray diffraction(XRD), transmission electron microscopy(TEM) and thermogravimetric analysis(TGA) characterizations are carried out on catalysts. The catalyst activities are investigated using electrochemical and single cell tests. The stability of Pt nanoparticle colloid is explored by ORR, cyclic voltammetry(CV) and ζ-potential measurements. The TEM results show the Pt particle sizes of the colloid, and the sizes of the 21 wt%, 42 wt% and 61 wt%Pt/C samples are 2.1–3.9 nm. Because of the high Pt dispersion, the Pt/C catalysts exhibit superior electroactivity toward ORR. In addition, four 61 wt% Pt/C catalysts made from the Pt colloid with 0–3 months’ shelf life show almost the same performance, which exhibits superior stability of the Pt colloid system without surfactant protection.

Telecoupled land-use changes in distant countries

International food trade has become a key driving force of agricultural land-use changes in trading countries, which has influenced food production and the global environment. Researchers have studied agricultural land-use changes and related environmental issues across multi-trading countries together, but most studies rely on statistic data without spatial attributes. However, agricultural land-use changes are spatially heterogeneous. Uncovering spatial attributes can reveal more critical information that is of scientific significance and has policy implications for enhancing food security and protecting the environment. Based on an integrated framework of telecoupling （socioeconomic and environmental interactions over distances）, we studied spatial attributes of soybean land changes within and among trading countries at the same time. Three distant countries -- Brazil, China, and the United States -- constitute an excellent example of telecoupled systems through the process of soybean trade. Our results presented the spatial distribution of soybean land changes-- highlighting the hotspots of soybean gain and soybean loss, and indicated these changes were spatially clustered, different across multi-spatial scales, and varied among the trading countries. Assisted by the results, global challenges like food security and biodiversity loss within and among trading countries can be targeted and managed efficiently. Our work provides simul- taneously spatial information for understanding agricultural land-use changes caused by international food trade globally, highlights the needs of coordination among trading countries, and promotes global sustainability.

Water-retaining properties of NCZ composite dust suppressant and its wetting ability to hydrophobic coal dust

Coal dust is a primary threat to underground coal miners.The most common approach to control coal dust is hydraulic methods,such as water spray and coal seam water injection.To improve the dust suppressant efficiency of hydraulic methods,a novel chemical composite dust suppressant,called NCZ,was prepared in this study using calcium chloride(CaCl_(2)),magnesium chloride(MgCl_(2)),and nonionic surfactants using a thermal synthesis method.The water-retaining properties of NCZ powder and its solutions were characterized using the water absorption rate(WAR)and evaporation rate(ER),respectively,and the wetting abilities of the NCZ solutions on coal dust were tested using the initial contact angle(ICA)and sink rate(SR).The results indicate that the NCZ solutions have anti-evaporation effects,and the ER of the solution with a 20.0 wt%NCZ is reduced by 11.7%compared with that of clean water.Furthermore,NCZ solutions have remarkable enhancement effects on the wettability of coal dust.The ICA and SR of clean water and the NCZ solution at 20.0 wt%are 141.9°and 0 mg/s,and 29.3°and 1.46 mg/s,respectively.Finally,quantitative relationships between the solution surface tension and the ICA and IR were established using the least squares method.This study provides a new product for dust suppression in underground mines,which is significant for the optimum applied con-centration of dust suppressant in mining operations.

Recent Progress in Atmospheric Chemistry Research in China: Establishing a Theoretical Framework for the “Air Pollution Complex”

Atmospheric chemistry research has been growing rapidly in China in the last 25 years since the concept of the“air pollution complex”was first proposed by Professor Xiaoyan TANG in 1997.For papers published in 2021 on air pollution(only papers included in the Web of Science Core Collection database were considered),more than 24000 papers were authored or co-authored by scientists working in China.In this paper,we review a limited number of representative and significant studies on atmospheric chemistry in China in the last few years,including studies on(1)sources and emission inventories,(2)atmospheric chemical processes,(3)interactions of air pollution with meteorology,weather and climate,(4)interactions between the biosphere and atmosphere,and(5)data assimilation.The intention was not to provide a complete review of all progress made in the last few years,but rather to serve as a starting point for learning more about atmospheric chemistry research in China.The advances reviewed in this paper have enabled a theoretical framework for the air pollution complex to be established,provided robust scientific support to highly successful air pollution control policies in China,and created great opportunities in education,training,and career development for many graduate students and young scientists.This paper further highlights that developing and low-income countries that are heavily affected by air pollution can benefit from these research advances,whilst at the same time acknowledging that many challenges and opportunities still remain in atmospheric chemistry research in China,to hopefully be addressed over the next few decades.

Highly dispersed NiMo@rGO nanocomposite catalysts fabricated by a two-step hydrothermal method for hydrogen evolution

Exploring and designing a high-performance non-noble metal catalyst for hydrogen evolution reaction(HER)are crucial for the large-scale application of H2 by water electrolysis.Here,novel catalysts with NiMo nanoparticles decorated on reduced graphene oxide(NiMo@r GO)synthesized by a two-step hydrothermal method were reported.Physical characterization results showed that the prepared NiMo@r GO-1 had an irregular lamellar structure,and the NiMo nanoparticles were uniformly dispersed on the rGO.NiMo@rGO-1 exhibited outstanding HER performance in an alkaline environment and required only 93 and 180 mV overpotential for HER in 1.0 M KOH solution to obtain current densities of-10 and-50 mA·cm^(-2),respectively.Stability tests showed that NiMo@rGO-1 had a certain operating stability for32 h.Under the same condition,the performance of NiMo@rGO-1 can be comparable with that of commercial Pt/C catalysts at high current density.The synergistic effect between NiMo particles and lamellate graphene can remarkably promote charge transfer in electrocatalytic reactions.As a result,NiMo@rGO-1 presented the advantages of high intrinsic activity,large specific surface area,and small electrical impedance.The lamellar graphene played a role in dispersion to prevent the aggregation of nanoparticles.The prepared NiMo@rGO-1 can be used in anion exchange membrane water electrolysis to produce hydrogen.This study provides a simple preparation method for efficient and low-cost water electrolysis to produce hydrogen in the future.

Polarization sensitive photodetector based on quasi-1D ZrSe_(3)

The in-plane anisotropy of transition metal trichalcogenides(MX_(3))has a significant impact on the molding of materi-als and MX_(3) is a perfect choice for polarized photodetectors.In this study,the crystal structure,optical and optoelectronic aniso-tropy of one kind of quasi-one-dimensional(1D)semiconductors,ZrSe_(3),are systematically investigated through experiments and theoretical studies.The ZrSe_(3)-based photodetector shows impressive wide spectral response from ultraviolet(UV)to near in-frared(NIR)and exhibits great optoelectrical properties with photoresponsivity of 11.9 mA·W^(-1) and detectivity of~106 at 532 nm.Moreover,the dichroic ratio of ZrSe_(3)-based polarized photodetector is around 1.1 at 808 nm.This study suggests that ZrSe_(3) has potential in optoelectronic applications and polarization detectors.