Extreme Temperature Change of the Last 110 Years in Changchun,Northeast China

In China and East Asia,the long-term continuous observational data at daily resolution are insufficient,and thus there is a lack of good understanding of the extreme climate variation over the last 100 years plus.In this study,the extreme temperature indices defined by ETCCDI(Expert Team on Climate Change Detection and Indices)and local meteorological administrations were analyzed for Changchun City,Northeast China,by using the daily maximum temperature(Tmax)and daily minimum temperature(Tmin)over 1909?2018.The results showed that extreme cold events,such as cold days,cold nights,frost days,icing days,and low temperature days,decreased significantly at rates of?0.41 d(10 yr)^?1,?1.45 d(10 yr)^?1,?2.28 d(10 yr)^?1,?1.16 d(10 yr)?1 and?1.90 d(10 yr)^?1,respectively.Warm nights increased significantly at a rate of 1.71 d(10 yr)^?1,but warm days decreased slightly and the number of high temperature days decreased at a rate of?0.20 d(10 yr)?1.The frequency of cold surge events increased significantly at a rate of 0.25 d(10 yr)^?1,occurring mainly from the mid-1950s to late-1980s.The average Tmax,average Tmin and extreme Tmin increased at rates of 0.09℃(10 yr)^?1,0.36℃(10 yr)^?1 and 0.54℃(10 yr)^?1,respectively;and extreme Tmax decreased significantly at a rate of?0.17℃(10 yr)^?1.In 1909?2018,1951?2018 and 1979?2018,the indices related to cold events decreased,while the trends of the indices related to warm events were different for different periods.

Hexanuclear ring cobalt complex for photochemical CO_(2) to CO conversion

Photosynthesis in nature has been deemed as the most significant biochemical reaction,which maintains a relatively stable content of O_(2) and CO_(2) in the atmosphere.Herein,for a deeper comprehension of natural photosynthesis,an artificial photosynthesis model reaction of photochemical CO_(2) to CO conversion(CO_(2)+2 H^(+)+2e^(-)→CO+H_(2)O)catalyzed by a homogeneous hexanuclear ring cobalt complex{K_(2)[CoO_(3)PCH_(2)N(CH_(2)CO_(2))_(2)]}_(6)(Co6 complex)is developed.Using the[Ru(bpy)_(3)]^(2+)as a photosensitizer and TEOA as a sacrificial electron donor,an optimal turnover frequency of 503.3 h^(‒1) and an apparent quantum efficiency of 0.81%are obtained.The good photocatalytic CO_(2) reduction performance is attributed to the efficient electron transfer between Co6 complex and[Ru(bpy)_(3)]^(2+),which boosts the photogenerated carriers separation of the photosensitizer.It is confirmed by the j‐V curves,light‐assisted UV‐vis curves,steady‐state photoluminescence spectra and real‐time laser flash photolysis experiments.In addition,the proposed catalytic mechanism for CO_(2) reduction reaction catalyzed by the Co6 complex is explored by the potassium thiocyanate poison experiment,Pourbaix diagram and density functional theory calculations.

Analytical Modelling and Experiment of Novel Rotary Electro-Mechanical Converter with Negative Feedback Mechanism for 2D Valve

The manufacturing of spiral groove structure of two-dimensional valve(2D valve)feedback mechanism has shortcomings of both high cost and time-consuming.This paper presents a novel configuration of rotary electro-mechanical converter with negative feedback mechanism(REMC-NFM)in order to replace the feedback mechanism of spiral groove and thus reduce cost of valve manufacturing.In order to rapidly and quantitative evaluate the driving and feedback performance of the REMC-NFM,an analytical model taking leakage flux,edge effect and permeability nonlinearity into account is formulated based on the equivalent magnetic circuit approach.Then the model is properly simplified in order to obtain the optimal pitch angle.FEM simulation is used to study the influence of crucial parameters on the performance of REMC-NFM.A prototype of REMC-NFM is designed and machined,and an exclusive experimental platform is built.The torque-angle characteristics,torque-displacement characteristics,and magnetic flux density in the working air gap with different excitation currents are measured.The experimental results are in good agreement with the analytical and FEM simulated results,which verifies the correctness of the analytical model.For torque-angle characteristics,the overall torque increases with both current and rotation angle,which reaches about 0.48 N·m with 1.5 A and 1.5°.While for torque-displacement characteristics,the overall torque increases with current yet decrease with armature displacement due to the negative feedback mechanism,which is about 0.16 N·m with 1.5 A and 0.8 mm.Besides,experimental results of conventional torque motor are compared with counterparts of REMC-NFM in order to validate the simplified model.The research indicates that the REMC-NFM can be potentially used as the electro-mechanical converter for 2D valves in civil servo areas.

CCCH protein-PvCCCH69 acted as a repressor for leaf senescence through suppressing ABA-signaling pathway

CCCH is a subfamily of zinc finger proteins involved in plant growth,development,and stresses response.The function of CCCH in regulating leaf senescence,especially its roles in abscisic acid(ABA)-mediated leaf senescence is largely unknown.The objective of this study was to determine functions and mechanisms of CCCH gene in regulating leaf senescence in switchgrass(Panicum virgatum).A CCCH gene,PvCCCH69(PvC3H69),was cloned from switchgrass.Overexpressing PvC3H69 in rice suppressed both natural senescence with leaf aging and dark-induced leaf senescence.Endogenous ABA content,ABA biosynthesis genes(NCED3,NCED5,and AAO3),and ABA signaling-related genes(SnRKs,ABI5,and ABF2/3/4)exhibited significantly lower levels in senescencing leaves of PvC3H69-OE plants than those in WT plants.PvC3H69-suppression of leaf senescence was associated with transcriptional upregulation of genes mainly involved in the light-dependent process of photosynthesis,including light-harvesting complex proteins,PSI proteins,and PSII proteins and downregulation of ABA biosynthesis and signaling genes and senescence-associated genes.PvC3H69 could act as a repressor for leaf senescence via upregulating photosynthetic proteins and repressing ABA synthesis and ABA signaling pathways.

Design and in-situ construct BiOI/Bi/TiO_(2)photocatalysts with metal-mediated heterostructures employing oxygen vacancies in TiO_(2)nanosheets

The conventional p-n heterojunction photocatalysts suffer from the incompatibility between the interfacial charge transfer efficiency and the redox ability of charge carriers.To optimize the interfacial charge transfer of the conventional BiOI/TiO_(2) p-n photocatalyst,we synthesized the BiOI/Bi/TiO_(2) ternary photocatalyst with sandwiched metallic bismuth(Bi~0)by the oxygen-vacancy assisted method.The DFT calculation and structural characterizations confirmed the reaction of the electron-rich oxygen vacancies in the 2D-TiO_(2) nanosheets(TiO_(2)-NS)with the adsorbed BiO~+species.This reaction broke the Bi-O bonds to form Bi^(0) nanoparticles in-situ at the interface but still maintained the p-n heterojunction well.The NO-TPD and XRD analyses for samples correlated the Bi~0 formation with the oxygen vacancy concentrations well.The sandwiched Bi~0 functioned as an electronic transfer mediator like that in the Z-scheme heterostructure.Comparing with 0.20 BiOI/TiO_(2)-NP(NP,Nanoparticles),0.20 BiOI/Bi/TiO_(2)-NS-a(NS,Nanosheet)showed a much improved catalytic performance,i.e.,duplicated apparent quantum yield(AQY)and triplicated reaction rate constant(k).Also,the formation mechanism and the reaction mechanism were investigated in detail.This work provides a new strategy for the improving of the conventional p-n photocatalysts and new insights into the nature of the photocatalysis.

Water Stability Improvement of Acid Fine Aggregate-Based Asphalt Concrete

In general,acid aggregates are not used in combination with asphalt concrete because of their poor compatibility with the asphalt binder,which typically results in a scarce water stability of the concrete.In the present study,the feasibility of a new approach based on the combination of acid granite fine aggregate with alkaline limestone coarse aggregate and Portland cement filler has been assessed.The mineral and chemical compositions of these three materials have first been analyzed and compared.Then,the effect of different amounts of Portland cement(0%,25%,50%,75%and 100%of the total filler by weight)on the mechanical performance and water stability of the asphalt concrete has been considered.Asphalt concrete has been designed by using the Marshall method,and the mechanical performance indexes of this material,including the Marshall stability and indirect tensile strength(ITS),have been measured together with the related water stability indexes(namely the Marshall stability(RMS)and tensile strength ratio(TSR)).The results indicate that the alkaline limestone coarse aggregate and Portland cement filler can balance the drawback caused by the acid granite fine aggregate.The asphalt concrete has good mechanical performances and water stability when the amount of common limestone powder filler replaced by cement is not less than 75%.

Churning loss characteristics of a wet three-phase high-speed reluctance motor

With the increasing requirements of electro-hydrostatic actuators(EHAs)for power,volume,and pressure,there is a growing tendency in the industry to combine the motor and pump to form a so-called'motor pump'to improve the integration.In this paper,a novel structure for a wet three-phase high-speed reluctance motor pump is proposed,which can further improve integration by removing the dynamic seal on the pump shaft,thereby avoiding the problems of dynamic seal wear and oil leakage and improving heat dissipation under high-speed working conditions.However,after the motor is wetted,the churning loss caused by immersion of the rotor in the oil causes additional fluid resistance torque.Based on fundamental fluid mechanics,an analytical model of the churning torque of a wet motor was established.To verify the accuracy of the analytical model,a simulation model of churning loss was established based on computational fluid dynamics(CFD),and the churning torque and flow field state were analyzed.Finally,an experimental prototype was designed and manufactured,and a test bench for churning loss was built.The oil churning torque was measured at different speeds and temperatures.The results from the analytical,simulation,and experimental models agreed well.The experimental results validated the analytical model and CFD simulation.This research provides a practical method for calculating the churning loss and serves as guidance for future optimization of churning loss reduction.

Dual-curvilinear beam enabled tunable manipulation of high-and low-refractive-index particles

We present an innovative approach for the simultaneous agile manipulation of high-refractive-index(HRI) and low-refractive-index(LRI) particles. Our method involves introducing a dual-curvilinear optical vortex beam(DC-OVB) generated by superimposing a pair of curved beams: HRI and LRI particles are controlled by the bright curve and the dark channel between the two curves, respectively. The proposed DC-OVB provides customizable motion paths and velocities for both LRI and HRI particles. Each curve of the DC-OVB can support a distinct orbital flow density(OFD), enabling the application of torques to HRI and LRI particles, guiding them to orbit along specified trajectories and prompting them to execute various curvilinear motions simultaneously,including curvilinear movement, revolution, and rotation.

HtrA1丝氨酸蛋白酶在息肉状脉络膜血管病变发病机制中作用的研究进展

息肉状脉络膜血管病变(PCV)是一种以视网膜下橙红色结节样病灶、视网膜色素上皮层下出血性或浆液性脱离为特征的脉络膜新生血管性病变,好发于亚洲人群。关于PCV的确切发病机制尚不明确,通过以往的研究发现HtrA1丝氨酸蛋白酶在PCV的发病过程中起到重要作用。对HtrA1在PCV发病过程中所起作用的探索结果,有助于指导相应的临床治疗。现对相关研究进展进行综述。

轻质储氢材料改性与热力学调控进展

为解决环境与能源问题,氢能作为一种理想的二次能源,受到国内外研究者的关注。众多储氢方式中,固态储氢能量密度高、安全性好,被认为是最具有发展前景的储氢方式之一。由轻质元素组成的储氢材料(包含金属氢化物、硼氢化物、铝氢化物、氨基氢化物、氨硼烷)因其具有高的储能密度成为储氢领域的研究热点。本文从热力学角度出发,对几种轻质储氢材料的研究进展,尤其是材料的改性进行了总结,并对轻质储氢材料的发展趋势进行了展望。

铋系含氧酸盐改性镁水解制氢的动/热力学研究

Mg基制氢材料具有来源广泛、反应温和、工艺简单、安全可控、理论产氢量高等优势,是当今的研究热点.本文提出采用高能球磨方法制备Mg-Bi系含氧酸盐Bi_(x)M_(y)O_(z)(M=Ti,V,Cr,Mo,W)复合材料以改善Mg水解制氢性能.本工作研究发现,掺杂Bi_(2)Mo O_(6)的Mg基复合制氢材料具有较好的性能,Mg-7 wt%Bi_(2)Mo O_(6)在298.15 K的最大产氢速率为756.1 m L g^(-1)min(-1).通过引入多壁碳纳米管(CNTs)可以进一步改善Mg-Bi_(2)Mo O_(6)的产氢性能,Mg-7 wt%Bi_(2)Mo O_(6)/CNTs的最大产氢速率达2172.4 m L g^(-1)min(-1),产氢活化能下降至23.6 k J mol^(-1).X光电子能谱(XPS)分析表明Bi_(2)Mo O_(6)/CNTs与Mg在球磨过程中发生固相反应生成Bi单质.密度泛函理论(DFT)计算揭示Bi原子掺杂可改变Mg的局域电荷分布,增强Mg对H_(2)O的吸附能,并降低H_(2)O解离后H原子的吸附能,促进水解反应进行.

微重力环境引起宇航员眼部改变及其机制的研究进展

宇航员进入微重力环境后可出现一系列眼部改变,这些改变若得不到及时干预或治疗,将导致宇航员出现长期或永久的视力损害,不仅影响飞行任务的执行,还威胁宇航员的人身安全。尽管目前宇航员出现这些眼部改变的确切机制尚不明确,但相关研究已发现,宇航员进入微重力环境后会出现颅内压升高、神经系统改变、生化改变及淋巴、静脉系统循环障碍,这些可能都参与了疾病的发生与发展。现归纳国内外近50年来关于宇航员进入微重力环境后出现的眼部改变及其可能的发生机制,以期寻找针对这些眼部改变的预防和治疗措施,为宇航员筛查、训练及防治工作提供相关理论支持。

Damage on lining concrete in highway tunnels under combined sulfate and chloride attack

The combined effect from sulfate and chloride is one of the important reasons to cause the damage of lining concrete in highway tunnels. To investigate the effect of chloride ions on the corrosion of lining concretes under sulfate attack, ultrasonic detecting, compression test and X-ray Diffraction （XRD） were performed on the concretes to obtain the ultrasonic velocity, corrosion thickness, compression strength and corrosion products. The ultrasonic results, compression strength and XRD patterns confirmed that the existence of chloride certainly depressed the corrosion damage on the lining concretes under sulfate attack, and the depressing effect increased with the content of chloride in the composite solution. The corrosion damage on the concretes experienced three stages independent of the composition of corrosive solution： initial slower enhancement on the strength, stabilization period and linear degradation period. The existence of chloride mainly affected the final degradation stage and obviously decreased the corrosion thickness.

Synthesis, structure and photocatalysis properties of two 3D Isostructural Ln (Ⅲ)-MOFs based 2,6-Pyridinedicarboxylic acid

Two new 3 D metal-organic frameworks（MOFs） named [Pr2（PDA）3-3 H2 O]-H2 O（1） and[Nd2（PDA）3-3 H2 O] H2 O（2） [2,6-Pyridinedicarboxylic acid（H2 PDA）] were synthesized by solvothermal method. They were characterized by elemental analyses（EA）, infrared spectroscopy（FT-IR）, thermogravimetric analysis（TG）, photocatalysis performance and single crystal X-ray diffraction studies（XRD）.The XRD analysis indicated that MOFs（1） and（2） both belong to the monoclinic system with space group P2（1）/C. The structural model were drawn by the diamond software, and the structure revel that MOFs（1） and（2） adopt three-dimensional（3 D） frameworks constructed by cross-linking of one-dimensional（1 D） infinite chain secondary building unit（SBU） by 2,6-Pyridinedicarboxylic acid and hydrogen bond as linker. These frameworks feature channels inside which coordinated H20 solvent molecules are located. Thermogravimetric analysis showed that both MOFs are thermally stable, the photocatalytic evaluation showed the materials have a good prospect in degration methylene blue. As for complex1, the decomposition efficiency of Methylene blue was about 91.08% after 130 min and the complex 2 reach 90.45% after 160 min under the sun light.

Small-molecule based thermally activated delayed fluorescence materials with dual-emission characteristics

Organic thermally activated delayed fluorescence(TADF)emitters have attracted increasing concerns,owing to their atypical photophysical features that can pave the way to the innovative engineering applications.As cutting-edge type of luminescent molecules,however,most of them only exert a single-wavelength emission from the lowest excited state,according to Kasha’s rule.To develop their potential applications in multicolor luminescence and multi-functional luminescent probes for biological imaging,researchers have begun to turn their attention to design organic TADF molecules with dual-emission characteristics,by employing an additional fluorescence,phosphorescence,or TADF signal within a single-component system.We herein summarized the design principles as well as the luminescence mechanism of organic donor-acceptor TADF compounds with dual-emission characteristics,the superiority of which can cover unique material applications in modern luminescencerelated fields.

Targeted metabolic analysis of nucleotides and identification of biomarkers associated with cancer in cultured cell models

Cancer,like other diseases accompanied by metabolic changes,shows characteristic DNA/RNA modifications and activities of modifying enzymes,resulting in fluctuations in nucleoside levels.In this study,we undertook targeted metabolomic analyses of nucleotides in different cancer cell culture models using a sensitive and reproducible ion-pair HPLC method.The experimental data were analyzed by principal component analysis(PCA)to identify potential biomarkers in cancer cells,and statistical significance was determined by one-way analysis of variance.As a result,a clear differentiation of normal and tumor cells into two clusters was shown,indicating abnormal metabolism of nucleotides in tumor cells.Six variables(AMP,UDP,CTP levels with a significance of Po0.05;ATP,UTP and GMP levels with a significance of Po0.01)were considered as potential biomarkers;the content of AMP,UTP,GMP and ATP was significantly higher in cancer cells.The receiver operating characteristic(ROC)curve analysis allowed us to discriminate normal cells from tumor cells based on area under the curve(AUC).The sequence of their AUC values were:ATP(0.979)4UTP(0.938)4CTP¼GMP(0.896)4AMP(0.812)4UDP(0.792),so we conclude that ATP and UTP are the best potential biomarkers in tumor cells.This study may provide a valuable tool for studying minute alterations of intracellular nucleotide pools induced by anticancer/antiviral drugs,diseases or environmental factors.

Modulating microenvironments to enhance CO_(2) electroreduction performance

Microenvironments of the catalytic center,which play a vital role in adjusting electrocatalytic CO_(2) reduction reaction(ECO_(2) RR)activity,have received increasing attention during the past few years.However,controllable microenvironment construction and the effects of multi-microenvironment variations for improving ECO_(2) RR performance remain unclear.Herein,we summarize the representative strategies for tuning the catalyst and local microenvironments to enhance ECO_(2) RR selectivity and activity.The multifactor synergetic effects of microen-vironment regulation for enhancing CO_(2) accessibility,stabilizing key intermediates,and improving the performance of ECO_(2) RR catalysts are discussed in detail,as well as perspectives on the challenges when investigating ECO_(2) RR microenvironments.We anticipate that the discussions in this review will inspire further research in microenvironment engineering to accelerate the development of the ECO 2 RR for practical application.

Freeze-drying and hot-pressing strategy to embed two-dimensional Ti_(0.87)O_(2) monolayers in commercial polypropylene films with enhanced dielectric properties

The dielectric capacitor has been widely used in advanced electronic and electrical power systems due to its capability of ultrafast charging–discharging and ultrahigh power density.Nevertheless,its energy density is still limited by the low dielectric constant(≈2.2)of the commercial dielectric polypropylene(PP).The conventional enhancement strategy by embedding inorganic fillers in PP matrix is still difficult and challenging due to that PP hardly dissolves in any inorganic/organic solvent.In this work,we develop a new strategy including freeze-drying,surface functionalization,and hot-pressing to incorporate Ti_(0.87)O_(2) monolayers in PP film.A series of uniform composited Ti_(0.87)O_(2)@PP film has been successfully fabricated with Ti0.87O2 content range of 0–15 wt%.The maximum dielectric constant of the as-prepared Ti_(0.87)O_(2)@PP film is 3.27 when the Ti_(0.87)O_(2) content is 9 wt%,which is about 1.5 times higher than that of pure PP.Our study provides a feasible strategy to embed two-dimensional material into commercial PP thin-film with superior dielectric performance for practical application.

Theoretical and experimental investigation on the efficiency of a novel roller piston pump

This study presents a novel roller piston pump,in which a cam guide-roller type rolling support is adopted to replace the sliding pair support of the swash plate-slipper pair to achieve the oil suction and discharge of the piston cavity.In addition,the shaft distribution is used to replace the original valve plate distribution and the driving shaft is used as the distribution shaft to remove the valve plate structure,which greatly simplifies the design of the axial piston pump.Such a configuration largely reduces the number of sliding friction pairs of the pump,and avoids the influence of the sliding friction pair on it under high-speed and variable-speed conditions.Firstly,mathematical models of the mechanical and volumetric efficiencies of the roller pump are deduced respectively through force analysis and the compressibility equation.Based on the numerical simulation of MATLAB and AMESim,the effects of load pressure and rotational speed on mechanical and volumetric efficiencies are studied respectively,and it is verified that the roller pump has no structural flow pulsation.The prototype pump is then designed and built,along with a special test rig.The outlet pressure,outlet flow,and torque of the pump under different load pressures and rotational speeds are measured,and the mechanical and volumetric efficiencies of the prototype pump under various load pressures and rotational speeds are obtained.The experimental results are in good agreement with the simulated analysis.When the load pressure is 8 MPa and the speed is 5000 r/min,the mechanical and the volumetric efficiencies are 85.5% and 96.8%,respectively.When the speed is increased to 10000 r/min,the mechanical and the volumetric efficiencies are 66.7% and 95.6%,respectively.The experimental results show that the proposed roller piston pump has excellent efficiency under wide-speed and high-speed conditions and can be a potential solution as a fuel pump in aerospace fuel systems.

Molecular confined synthesis of magnetic CoO_(x)/Co/C hybrid catalyst for photocatalytic water oxidation and CO_(2)reduction

Photosynthesis[6CO_(2)+12H_(2)O→(CH_(2)O)+6O_(2)+6H_(2)O]in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide(CO_(2))reduction to carbohydrates,which is of great significance for the survival of living matter.Therefore,for simulating photosynthesis,it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO_(2)reduction performances.Herein,a molecular confined synthesis strategy is reasonably proposed and applied,that is the bifunctional CoO_(x)/Co/C-T(T=700,800 and 900℃)photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N_(2) and air atmosphere in turn.Among the prepared photocatalysts,the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%.In addition,for CO_(2)reduction reaction,the CO evolution rate of 12.6μmol/h and selectivity of 75%can be achieved over this catalyst.The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst,which is strongly supported by the current densityvoltage G-V,steady-state and time-resolved photoluminescence spectra(PL).Overall,this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO_(2)reduction reactions.