元素化学教学中关于“无机物溶解性”的知识建构

无机物溶解性是元素化学教与学中的难点之一。本文选取教学中的代表性实例,通过分析、比较和归纳影响无机物溶解性的因素,对其进行本源性理解,建构一种便于学习者理解无机物溶解性的认识模型。基于“无机物溶解性”这一知识载体深入探讨“建构式”学习模式在元素化学教学中的应用。

Real-time and high-transmission middle-infrared optical imaging system based on a pixel-wise metasurface micro-polarization array

Real-time polarization medium-wave infrared(MIR)optical imaging systems enable the acquisition of infrared and polarization information for a target.At present,real-time polarization MIR devices face the following problems:poor real-time performance,low transmission and high requirements for fabrication and integration.Herein,we aim to improve the performance of real-time polarization imaging systems in the MIR waveband and solve the above-mentioned defects.Therefore,we propose a MIR polarization imaging system to achieve real-time polarization-modulated imaging with high transmission as well as improved performance based on a pixel-wise metasurface micro-polarization array(PMMPA).The PMMPA element comprises several linear polarization(LP)filters with different polarization angles.The optimization results demonstrate that the transmittance of the center field of view for the LP filters is up to 77%at a wavelength of4.0μm and an extinction ratio of 88 d B.In addition,a near-diffraction-limited real-time MIR imaging optical system is designed with a field of view of 5°and an F-number of 2.The simulation results show that an MIR polarization imaging system with excellent real-time performance and high transmission is achieved by using the optimized PMMPA element.Therefore,the method is compatible with the available optical system design technologies and provides a way to realize real-time polarization imaging in MIR wavebands.

UCHL5 inhibits U251 glioma cell proliferation and tumor growth via stabilizing and deubiquitinating PTEN

Glioma is the most common primary brain tumor.Exploration of new tumorigenesis mechanism of glioma is critical to determine more effective treatment targets as well as to develop effective prognosis methods that can enhance the treatment efficacy.We previously demonstrated that the deubiquitinase biquitin carboxyl-terminal hydrolase L5(UCHL5)was downregulated in human glioma.However,the effect and mechanism of UCHL5 on the proliferation of glioma cells remains unknown.Methods:Transfection of siRNA was used to knockdown the expression of UCHL5 in U251 cells.The 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide(MTT)assay,Edu assay,and colony formation assay were employed to identify the effect of UCHL5 on the proliferation of U251 glioma cells.Western blotting and quantitative real-time PCR were carried out to detect the interaction of UCHL5 and PTEN.The effect of UCHL5 on the growth of glioma in vivo was evaluated in nude mice.Then Immunohistochemistry(IHC)were performed to analysis the expression of UCHL5 and PTEN in human glioma tissues.Results:Here,we have reported that silencing of UCHL5 could promote the proliferation of U251 glioma cells through MTT assay,Edu assay,and colony formation assay.Mechanically,we revealed that UCHL5 stabilizes the phosphatase and tensin homolog(PTEN)expression by deubiquitination,thereby inhibiting cell proliferation in U251 cells.Tumor xenograft experiments further demonstrated that silencing the UCHL5 expression could accelerate U251 cell growth in vivo.Finally,in human glioma tissue microarray,the positive correlation between UCHL5 and PTEN expression was confirmed through IHC assay.Conclusion:UCHL5 restrains the proliferation of U251 glioma cells by stabilizing and deubiquitinating PTEN.Our findings provide ideas for developing enhanced targeted PTEN therapy for patients with glioma.

Flocculated unclassified tailings settling efficiency improvement by particle collision optimization in the feedwell

Efficient thickening of tailings is a prerequisite for the metal mine tailings backfill and surface disposal operation.The effective collision of ultrafine tailings particles in suspension with flocculant molecules is essential for flocs aggregates formation and settling.Unreasonable feeding speed and flocculant adding method will lead to the failure of effective dispersion of flocculant and high particle content in thickener overflow.In this work,the effect of turbulence intensity and flocculant adding method on floc size,strength,and movement characteristics are analysed.Aiming to solve the turbidity increased,a pilot-scale continuous thickening test was carried out.Taking a single particle and multiple flocs of full tailings as the research object,the particle iterative settlement model of flocs was established.The influence of turbulence intensity on collision effect is studied by tracking and simulating particle trajectory.The results show that in the process of single particle settlement,chaos appears in the iterative process owing to particle adhesion which caused by micro action.When the turbulence intensity is 25.99%,the maximum particle size of tailings floc is 6.21 mm and the maximum sedimentation rate is 5.284 cm·s^(−1).The tailings floc presents a multi-scale structure of particle-force chain system when hindered settling,and the interweaving of strong and weak force chains constitutes the topological structure of particles.The results are applied to a thicker in plant,the flocculant addition mode and feed rate are optimized,and the flocs settling speed and overflow clarity are improved.

二维原子-分子异质结的制备及其类脑器件应用

类脑计算因模仿人脑高效且低能耗的信息处理特性,成为解决冯·诺依曼计算机架构在能源效率和处理速度方面瓶颈的有力方案.然而类脑计算器件中传统异质结构存在的性能单一、制作困难、结合力差等问题限制了技术的应用.新型二维原子-分子异质结(2DAMH)通过在二维材料表面共价修饰功能性分子提供的稳定性和功能可调性为类脑器件领域带来了新的机遇.本综述总结了2DAMH在电子特性、合成策略及类脑器件应用方面的最新进展,尤其是在定制界面特性及模拟生物突触功能上的潜力.尽管共价修饰在精确性、规模化生产和理论完善度等方面仍面临挑战,但不断涌现的创新研究正在积极探索解决方案,展现出在类脑计算智能系统中实现更高效、更节能计算模式的巨大潜力.

Polyoxometalates for continuous power generation by atmospheric humidity

Atmospheric humidity is a sustainable low-value energy widely existing in natural environment,which is a promising candidate to solve the noncontinuous and low efficiency of low-value energy power generation.Here the mono-substituted Dawson-type polyoxometalates are constructed to be highly dispersed organic ammonium-polyoxoanion clusters and are assembled into thin films power generators with micropores,working in atmospheric humidity.The optimal polyoxometalates generator with the thickness of 7.2μm and the area of 0.36 cm^(2) produces a voltage of 0.68 V and a current density of 19.5μA·cm^(-2) under simulated natural environment,and works continuously and stably under almost all-natural environments(humidity 10%–90%).The highly dispersed polyoxometalate nanoclusters can form microporous in polyoxometalate films to effectively absorb atmospheric humidity and spontaneously form distribution gradient of water,which is the structural basis of power generation.The continuous power generation may be maintained by the effective adsorption and utilization of H_(2)O,the huge electrostatic field of organic ammonium-polyoxoanion clusters,and the reasonably designed polyoxometalates containing inorganic small ions with high mobility.It is the first humidity generator designed with polyoxometalates,which may provide a new research direction for polyoxometalates in sustainable utilization of low-value energy.

Synergistic regulation of intermolecular interactions to control chiral structures for chiral recognition

Understanding the regulatory mechanism of self-assembly processes is a necessity to modulate nanostructures and their properties. Herein, we have studied the mechanism of self-assembly in the C3 symmetric 1,3,5-benzentricarboxylic amino acid methyl ester enantiomers(TPE) in a mixed solvent system consisting of methanol and water. The resultant chiral structure was used for chiral recognition. The formation of chiral structures from the synergistic effect of multiple noncovalent interaction forces was confirmed by various techniques. Molecular dynamics simulations were used to characterize the time evolution of TPE structure and properties in solution. The theoretical results were consistent with the experimental results. Furthermore, the chiral structure assembled by the building blocks of TPE molecules was highly stereoselective for diamine compounds.

民族主义视角下泰国王室对北部山地少数民族的整合研究

王室民族主义是泰国现代民族国家建构的重要来源,泰国现代民族国家的建构进程始终与王权政治影响下王室民族主义的兴衰紧密相关。泰国王室对泰北山地少数民族的整合大致分为五个主要阶段,由此反映出王室民族主义“重构—复兴—巩固—衰落”的发展脉络。建立以王权为国家政治核心的现代民族国家体系是泰国王室民族主义的重要特征,但也因此引发了相应的族群身份政治问题,对泰国现代民族国家的建构带来不利影响。

A strategy for highly dispersed Mo2C/MoN hybrid nitrogen- doped graphene via ion-exchange resin synthesis for efficient electrocatalytic hydrogen reduction

Molybdenum carbide/molybdenum nitride hybrid N-doped graphene （abbreviated as Mo2C/MoN/NG）, as an efficient electrocatalyst for the hydrogen evolution reaction （HER）, was synthesized via simple ion-exchange resin synthesis followed by a two-step annealing process, which increased the dispersion degree of the electrocatalyst＇s active sites on the support skeleton and simplified the synthetic conditions. Additionally, N-doped graphene （NG） enhanced the electron transfer and reduced the inner resistance. The material has a graphene-like morphology and highly dispersed Mo2C/MoN nanoparticles about 2 nm in diameter on the NG. X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy revealed that Mo2C/MoN/NG consisted of Mo2C and MoN composited together. Finally, Mo2C/MoN/NG exhibited remarkable performance as an electrocatalyst for the HER with a small overpotential of 78.82 mV and a small Tafel slope of 39.3 mV.dec^-1 in a 0.5 mol.L-1 H2SO4 solution. Its activity was approximately 30% lower than that of 20% Pt/C and 60% higher than that of NG. Also, it exhibited a low onset overpotential of 24.82 mV, which is similar to the theoretical HER potential. Our work provides a foundation for advanced HER applications of molybdenum compounds.

MEF2C promotes M1 macrophage polarization and Th1 responses

The polarization of macrophages to the M1 or M2 phenotype has a pivotal role in inflammation and host defense;however,the underlying molecular mechanism remains unclear.Here,we show that myocyte enhancer factor 2 C(MEF2C)is essential for regulating M1 macrophage polarization in response to infection and inflammation.Global gene expression analysis demonstrated that MEF2C deficiency in macrophages downregulated the expression of M1 phenotypic markers and upregulated the expression of M2 phenotypic markers.MEF2C significantly promoted the expression of interleukin-12 p35 subunit(Il12a)and interleukin-12 p40 subunit(Il12b).Myeloid-specific Mef2c-knockout mice showed reduced IL-12 production and impaired Th1 responses,which led to susceptibility to Listeria monocytogenes infection and protected against DSS-induced IBD in vivo.Mechanistically,we showed that MEF2C directly activated the transcription of Il12a and Il12b.These findings reveal a new function of MEF2C in macrophage polarization and Th1 responses and identify MEF2C as a potential target for therapeutic intervention in inflammatory and autoimmune diseases.

Regulating interfacial morphology and charge-carrier utilization of Ti_(3)C_(2)modified all-sulfide CdS/ZnIn_(2)S_(4)S-scheme heterojunctions for effective photocatalytic H_(2) evolution

The separation efficiency of electrons and holes and the enhancement of the surface reductive reaction in the metal sulfide semiconductor photocatalysts are important factors in boosting photocatalytic H_(2)evolution from water.The control of both interface morphology and the charge-carrier utilization of metal sulfide-based photocatalysts can effectively improve the separation efficiency of electrons and holes and increase the surface reaction active sites,which are considered to be effective methods to improve the photocatalytic activity of semiconductors.Here,the Ti_(3)C_(2)(Mxene)modified all-sulfide 2D/2D Sscheme heterojunction Ti_(3)C_(2)/Zn In_(2)S_(4)(ZIS)/CdS composite material was firstly synthesized by a two-step solvothermal method.The formation of all-sulfide S-scheme heterojunction improves the efficiency of electron-hole separation.The intimate 2D/2D van der Waals structure provides a strong interaction force and a large contact area to enhance charge transfer.The addition of 2D Ti_(3)C_(2)forms the accumulation layer,reducing the recombination of electrons and holes.Under the synergistic promotion,the highest hydrogen production of the prepared Ti_(3)C_(2)/ZIS/CdS composite photocatalyst could reach 8.93 mmol/h/g.This work not only enriches the photocatalytic systems through integrating the ohmic junction and the 2D/2D all-sulfide S-scheme heterojunction,but also provides a satisfactory design strategy for engineering interfacial morphology and charge-carrier utilization.

Keggin and Dawson polyoxometalates as electrodes for flexible and transparent piezoelectric nanogenerators to efficiently utilize mechanical energy in the environment

In recent years,piezoelectric nanogenerators(PENGs)have been developed as a promising energyharvesting electronic device.However,the electrodes of most PENGs devices are precious metals,thus increasing the production cost.Here,we propose a flexible transparent PENGs with polyoxometalates(POMs)as the electrodes;it can effectively utilize ambient mechanical energy to generate electricity.Five types of polyoxometalates with different structures and compositions are selected as the electrode materials for PENGs for the first time,and the output performance of different PENGs electrode devices is tested.The PENG device with(NH4)6 P2 Mo18 O62 as the electrode can steadily provide a high electric output with an open-circuit voltage of 2.8 m V and a short-circuit current of 8.5 mA at the bending degree of90°.At the same time,the transmission spectrum shows that the average visible transmittance(AVT)of PENG can reach 31%,thus outperforming the benchmark for window applications.Finally,the working mechanism,force analysis,repeatability,and stability of PENG are systematically evaluated.All the studies show that this flexible transparent device has potential application prospect in wearable electronic devices.

Highly doped NaErF_(4)-based nanocrystals for multi-tasking application

How to engineer single nanocrystal to achieve multiple functions is still a huge challenge.In this work,a novel highly doped rare earth nanocrystal NaErF_(4)@NaGdF_(4)@NaDyF_(4)(Er@Gd@Dy)was designed and fabricated,which exhibits various performances by itself,including the longitudinal(T1)and transverse relaxation time(T2)double-mode magnetic resonance imaging(MRI),upconversion luminescence and down-shifting luminescence.Upon irradiation of 808 nm near-infrared(NIR)light,the upconverted red light can indirectly activate the photo sensitizer Ce6 conjugated on the surface of nanocrystals for photodynamic therapy(PDT).In vivo experiments demonstrate that the nano materials can eradicate notably primary tumors without obvious systematic toxicity.In addition,the longitudinal and transverse relaxation rates of Er@Gd@Dy are 24.83 and 319.86(mmol/L)^(-1)/s,respectively,which are superior to those of the nanocrystals reported previously.Simultaneously,the nanocrystals have the ability to generate NIR-Ⅱlight located at 1530 nm,favorable in bioimaging in deeper tissues.As a consequence,this new nanoplatform will advance the improvement of multimodal imaging guided tumor diagnosis and treatment.

Using a Hidden Markov Model to Analyze the Flood-Season Rainfall Pattern and Its Temporal Variation over East China

The homogeneous hidden Markov model(HMM), a statistical pattern recognition method, is introduced in this paper. Based on the HMM, a 53-yr record of daily precipitation during the flood season(April-September) at 389 stations in East China during 1961-2013 is classified into six patterns: the South China(SC) pattern, the southern Yangtze River(SY) pattern, the Yangtze-Huai River(YH) pattern, the North China(NC) pattern, the overall wetter(OW) pattern, and the overall drier(OD) pattern. Features of the transition probability matrix of the first four patterns reveal that 1) the NC pattern is the most persistent, followed by the YH, and the SY is the least one; and 2) there exists a SY-SC-SY-YH-NC propagation process for the rain belt over East China during the flood season. The intraseasonal variability in the occurrence frequency of each pattern determines its start and end time. Furthermore,analysis of interdecadal variability in the occurrence frequency of each pattern in recent six decades has identified three obvious interdecadal variations for the SC, YH, and NC patterns in the mid-late 1970 s, the early 1990 s, and the late 1990 s. After 2000, the patterns concentrated in the southern region play a dominant role, and thus there maintains a "flooding in the south and drought in the north" rainfall distribution in eastern China. In summary, the HMM provides a unique approach for us to obtain both spatial distribution and temporal variation features of flood-season rainfall.