多配位水分子的焦磷酸锰用于电催化水氧化研究

自然界水氧化中心Mn_(4)CaO_(5)团簇中的配位水被认为在促进水氧化方面起着重要作用.许多报道模拟了Mn_(4)CaO_(5)结构并研究了其析氧反应(OER)过程,但配位水结构难以模拟,在OER过程中的具体功能尚不明确.目前,揭示配位水在OER中的具体作用存在以下挑战.首先,大多数锰基材料的配位结构,特别是表面结构是模糊的,导致结构-性能相关性难以确定.其次,在Mn位点上引入配位水时,往往不可避免地会改变Mn中心的核心结构,甚至改变Mn的化合价,这些干扰因素可能严重混淆配位水对OER的影响,不利于探究OER过程中配位水分子的作用.因此,构建一个理想的催化剂平台用于研究配位水分子在水氧化过程中的作用具有重要意义.本文提出了一种研究OER过程中配位水分子作用的有效方法,并阐明了OER过程中源于锰中心配位水分子结构-活性关系.采用水热法合成了一种结晶型焦磷酸锰(crystalline MnPi).在相同起始物料比、不同反应条件下,采用共沉淀法制备了分子式相同的非晶型焦磷酸锰(amorphous MnPi).通过X射线衍射、红外光谱、拉曼光谱、热重分析和理论模拟,确定了MnPi催化剂的晶体结构(Mn_(2)P_(2)O_(7)·3H_(2)O).在0.05 mol L^(-1)pH=7.0的磷酸盐缓冲溶液中,crystalline MnPi催化剂比amorphous MnPi催化剂表现出更好的OER活性.晶体结构研究结果表明,crystalline MnPi催化剂暴露的Mn位点上含有四个配位水分子,并且相邻Mn位点通过氢键相互连接形成连续的氢键网络结构.连续的氢键网络使氧原子的电荷中和水平更高,使得crystalline MnPi催化剂中Mn^(Ⅱ/Ⅲ)转换更容易,进一步揭示了配位水在水氧化机理中扮演的重要角色.详细的电化学动力学研究、原位/非原位表面表征和理论计算结果表明,crystalline MnPi催化剂的Mn^(Ⅱ/Ⅲ)氧化过程在动力学和热力学上都比amorphous MnPi催化剂容易发生.同时,crystalline MnPi催化剂中配位水分管子有效参与了Mn(Ⅱ)到Mn(Ⅲ)的质子耦合电子转移过程,此过程是锰基体系中水氧化反应中的起始关键步骤.pH动力学实验结果表明,amorphous MnPi催化剂的Mn^(Ⅱ/Ⅲ)氧化步骤为常见的2H^(+)/le单位点过程.然而,由于crystalline MnPi催化剂表面暴露的Mn位点上存在多个配位水分子,导致crystalline MnPi催化剂的Mn^(Ⅱ/Ⅲ)氧化步骤为3H^(+)/2e双位点过程.双位点上的三个配位水分子失去三个质子生成三个OH基团,OH基团通过彼此之间以及与周围配位水分子之间的氢键来有效稳定中间体电荷,进而促进水氧化的发生.综上所述,以精心设计的催化剂平台进行对比研究,直观地观察和理解了配位水分子对电催化水氧化的重要作用,为阐明锰基催化体系中配位水分子在水氧化过程中的重要作用提供了有价值的见解.

Efficient and rapid capture of uranium(Ⅵ) in wastewater via multiamine modified β-cyclodextrin porous polymer

It is quite important to ensure the safety and sustainable development of nuclear energy for the treatment of radioactive wastewater. To treat radioactive wastewater efficiently and rapidly, two multi-amine β-cyclodextrin polymers(diethylenetriamine β-cyclodextrin polymer(DETA-TFCDP) and triethylenetetramine β-cyclodextrin polymer(TETA-TFCDP)) were prepared and applied to capture uranium. Results exhibited that DETA-TFCDP and TETA-TFCDP displayed the advantages of high adsorption amounts(612.2and 628.2 mg·g-1, respectively) and rapid adsorption rates, which can reach(88 ± 1)% of their equilibrium adsorption amounts in 10 min. Moreover, the adsorbent processes of DETA-TFCDP and TETATFCDP on uranium(Ⅵ) followed the Langmuir model and pseudo-second-order model, stating they were mainly chemisorption and self-endothermic. Besides, TETA-TFCDP also showed excellent selectivity in the presence of seven competing cations and could be effectively reused five times via Na2CO3as the desorption reagent. Meanwhile, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy illustrated that the enriched multi-amine groups and oxygen-containing functional groups on the surface of TETA-TFCDP were the main active sites for capturing uranium(Ⅵ). Hence, multi-amine β-cyclodextrin polymers are a highly efficient, rapid, and promising adsorbent for capturing uranium(Ⅵ)from radioactive wastewater.

Detection accuracy of target accelerations based on vortex electromagnetic wave in keyhole space

The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed.The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated.The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space.According to the research,the effects about spectrum spreads of higher OAM modes are more obvious.The error in detection is mainly affected by OAM spectrum spreading,which can be reduced by reasonably using different combinations of OAM modes in different practical situations.The above results provide a reference idea for investigating keyhole effect when vortex electromagnetic wave is used to detect accelerations.

Quantum Spin Exchange Interactions to Accelerate the Redox Kinetics in Li–S Batteries

Spin-engineering with electrocatalysts have been exploited to suppress the“shuttle effect”in Li–S batteries.Spin selec-tion,spin-dependent electron mobility and spin potentials in activation barriers can be optimized as quantum spin exchange interactions lead-ing to a significant reduction of the electronic repulsions in the orbitals of catalysts.Herein,we anchor the MgPc molecules on fluorinated carbon nanotubes(MgPc@FCNT),which exhibits the single active Mg sites with axial displacement.According to the density functional theory calculations,the electronic spin polarization in MgPc@FCNT not only increases the adsorption energy toward LiPSs intermediates but also facilitates the tunneling process of electron in Li–S batter-ies.As a result,the MgPc@FCNT provides an initial capacity of 6.1 mAh cm^(-2) even when the high sulfur loading is 4.5 mg cm^(-2),and still maintains 5.1 mAh cm^(-2) after 100 cycles.This work provides a new perspective to extend the main group single-atom catalysts enabling high-performance Li–S batteries.

A sustainable process to 100%bio-based nylons integrated chemical and biological conversion of lignocellulose

Considerable progress has been made in recent years to the development of sustainable polymers from bio-based feedstocks.In this study,100%bio-based nylons were prepared via an integrated chemical and biological process from lignocellulose.These novel nylons were obtained by the melt polymerization of 3-propyladipic acid derived from lignin and 1,5-pentenediamine/1,4-butanediamine derived from carbohydrate sugar.Central to the concept is a three-step noble metal free catalytic chemical funnelling sequence(Raney Ni mediated reductive catalytic fractionation-reductive funnelling-oxidative funnelling),which allowed for obtaining a single component 3-propyladipic acid from lignin with high efficiency.The structural and thermodynamic properties of the obtained nylons have been systematically investigated,and thus obtained transparent bio-based nylons exhibited higher Mw(>32,000)and excellent thermal stability(Td5%>265℃).Considering their moderate Tg and good melt strength,these transparent bio-based nylons could serve as promising functional additives or temperature-responsive materials.

Retraction Note:Hydralazine Promotes Central Nervous System Recovery after Spinal Cord Injury by Suppressing Oxidative Stress and Inflammation through Macrophage Regulation

The Editor-in-Chief has retracted this article on the corresponding authors'request.The corresponding authors on behalf of all the authors stated that the data presented in this article does not belong to the named authors,but belongs to Prof.Sheng-xi Wu and Prof.Wang Xi of the Department of Neurobiology of the Fourth Military Medical University,Xi'an,China.

Melatonin inhibits ESCC tumor growth by mitigating the HDAC7/β-catenin/c-Myc positive feedback loop and suppressing the USP10-maintained HDAC7 protein stability

Background:Melatonin,a natural hormone secreted by the pineal gland,has been reported to exhibit antitumor properties through diverse mechanisms of action.However,the oncostatic function of melatonin on esophageal squamous cell carcinoma(ESCC) remains elusive.This study was conducted to investigate the potential effect and underlying molecular mechanism of melatonin as single anticancer agent against ESCC cells.Methods:ESCC cell lines treated with or without melatonin were used in this study.In vitro colony formation and 5-Ethynyl-2’-deoxyuridine(EdU) incorporation assays,and nude mice tumor xenograft model were used to confirm the proliferative capacities of ESCC cells.RNA-seq,qPCR,Western blotting,recombinant lentivirus-mediated target gene overexpression or knockdown,plasmids transfection and co-IP were applied to investigate the underlying molecular mechanism by which melatonin inhibited ESCC cell growth.IHC staining on ESCC tissue microarray and further survival analyses were performed to explore the relationship between target genes’ expression and prognosis of ESCC.Results:Melatonin treatment dose-dependently inhibited the proliferative ability and the expression of histone deacetylase 7(HDAC7),c-Myc and ubiquitin-specific peptidase 10(USP10) in ESCC cells(P<0.05).The expressions of HDAC7,c-Myc and USP10 in tumors were significantly higher than the paired normal tissues from 148 ESCC patients(P<0.001).Then,the Kaplan-Meier survival analysis suggested that ESCC patients with high HDAC7,c-Myc or USP10levels predicted worse overall survival(log-rank P<0.001).Co-IP and Western blotting further revealed that HDAC7physically deacetylated and activated β-catenin thus promoting downstream target c-Myc gene transcription.Notably,our mechanistic study validated that HDAC7/β-catenin/c-Myc could form the positive feedback loop to enhance ESCC cell growth,and USP10 could deubiquitinate and stabilize HDAC7 protein in the ESCC cells.Additionally,we verified that inhibition of the HDAC7/β-catenin/c-Myc axis and USP10/HDAC7 pathway mediated the anti-proliferative action of melatonin on ESCC cells.Conclusions:Our findings elucidate that melatonin mitigates the HDAC7/β-catenin/c-Myc positive feedback loop and inhibits the USP10-maintained HDAC7 protein stability thus suppressing ESCC cell growth,and provides the reference for identifying biomarkers and therapeutic targets for ESCC.

Microfluidic field strategy for enhancement and scale up of liquid-liquid homogeneous chemical processes by optimization of 3D spiral baffle structure

Due to the scale effect, the uniform distribution of reagents in continuous flow reactor becomes bad when the channel is enlarged to tens of millimeters. Microfluidic field strategy was proposed to produce high mixing efficiency in large-scale channel. A 3D spiral baffle structure(3SBS) was designed and optimized to form microfluidic field disturbed by continuous secondary flow in millimeter scale Y-shaped tube mixer(YSTM). Enhancement effect of the 3SBS in liquid-liquid homogeneous chemical processes was verified and evaluated through the combination of simulation and experiment. Compared with 1 mm YSTM, 10 mm YSTM with 3SBS increased the treatment capacity by 100 times, shortened the basic complete mixing time by 0.85 times, which proves the potential of microfluidic field strategy in enhancement and scale-up of liquid-liquid homogeneous chemical process.

Obtaining accurate measurements of the sea surface height from a GPS buoy

A dedicated GPS buoy is designed for calibration and validation(Cal/Val)of satellite altimeters since 2014.In order to evaluate the accuracy of the sea surface height(SSH)measured by the GPS buoy,twelve campaigns have been done within China sea area between 2014 and 2021.In six of these campaigns,two static Global Navigation Satellite System stations were installed at distances of<1 km and 19 km from the buoy to assess how the baseline length influenced the derived SSH from the buoy solutions.The GPS buoy data was processed using the GAMIT/GLOBK software+TRACK module and CSRS-PPP tool to achieve the SSH.The SSH was compared with conventionally tide gauge(TG)data to evaluate the accuracy of the buoy with the standard deviation of the height element.The results showed that the difference in the standard deviation of the SSH from the buoy and the TG was less than 16 mm.The SSHs processed with different ephemeris(Ultra-Rapid,Rapid,Final)were not significantly different.When the baseline length was 19 km,the SSH solution of the GPS buoy performed well,with standard bias of less than 26 mm between the heights measured by the buoy and TG,meaning that the buoy could be used for Cal/Val of altimeters.The bias between the Canadian Spatial Reference System-precise point positioning tool and the TRACK varied a lot,and some of them were over 130 mm.This deemed too high to be useful for Cal/Val of satellite altimeters.Moreover,the GPS buoy solutions processed by GAMIT/GLOBK software+TRACK module were used for in-orbit Cal/Val of HY-2B/C satellites in ten campaigns.The SSH and significant wave height of the altimeters showed good agreements with the GPS buoy solutions.

Cs-Induced Phase Transformation of Vanadium Oxide for High-Performance Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries are promising candidate for gridscale energy storage.However,the development of zinc-ion batteries has been plagued by the lack of cathode materials with high specific capacity and superior lifespan.Herein,hexagonal Cs_(0.3)V_(2)O_(5)cathode is fabricated and investigated in zinc-ion batteries.Compared with the traditional vanadium oxides,the introduction of Cs changes the periodic atomic arrangements,which not only stabilizes the open framework structure but also facilitates the Zn^(2+)diffusion with a lower migration energy barrier.Consequently,high specific capacity of 543.8 mA h g^(-1)at 0.1 A g^(-1)is achieved,which surpasses most of reported cathode materials in zinc-ion batteries.The excellent cycle life is achieved over 1000 cycles with about 87.8%capacity retention at 2 A g^(-1).Furthermore,the morphological evolution and energy storage mechanisms are also revealed via a series of techniques.This work opens up a phase engineering strategy to fabricate the hexagonal vanadium oxide and elucidate the application of phase-dependent cathodes in zinc-ion batteries.

Quantum cascade lasers grown by MOCVD

Sharing the advantages of high optical power,high efficiency and design flexibility in a compact size,quantum cascade lasers(QCLs)are excellent mid-to-far infrared laser sources for gas sensing,infrared spectroscopic,medical diagnosis,and defense applications.Metalorganic chemical vapor deposition(MOCVD)is an important technology for growing high quality semiconductor materials,and has achieved great success in the semiconductor industry due to its advantages of high efficiency,short maintenance cycles,and high stability and repeatability.The utilization of MOCVD for the growth of QCL materials holds a significant meaning for promoting the large batch production and industrial application of QCL devices.This review summarizes the recent progress of QCLs grown by MOCVD.Material quality and the structure design together determine the device performance.Research progress on the performance improvement of MOCVD-grown QCLs based on the optimization of material quality and active region structure are mainly reviewed.

Hydralazine Promotes Central Nervous System Recovery after Spinal Cord Injury by Suppressing Oxidative Stress and Inflammation through Macrophage Regulation

Objective:This study aims to investigate the effects of hydralazine on inflammation induced by spinal cord injury(SCI)in the central nervous system(CNS)and its mechanism in promoting the structural and functional recovery of the injured CNS.Methods:A compressive SCI mouse model was utilized for this investigation.Immunofluorescence and quantitative real-time polymerase chain reaction were employed to examine the levels of acrolein,acrolein-induced inflammation-related factors,and macrophages at the injury site and within the CNS.Western blotting was used to evaluate the activity of the phosphoinositide 3-kinase(PI3K)/AKT pathway to study macrophage regulation.The neuropathic pain and motor function recovery were evaluated by glutamic acid decarboxylase 65/67(GAD65/67),vesicular glutamate transporter 1(VGLUT1),paw withdrawal response,and Basso Mouse Scale score.Nissl staining and Luxol Fast Blue(LFB)staining were performed to investigate the structural recovery of the injured CNS.Results:Hydralazine downregulated the levels of acrolein,IL-1β,and TNF-αin the spinal cord.The downregulation of acrolein induced by hydralazine promoted the activation of the PI3K/AKT pathway,leading to M2 macrophage polarization,which protected neurons against SCI-induced inflammation.Additionally,hydralazine promoted the structural recovery of the injured spinal cord area.Mitigating inflammation and oxidative stress by hydralazine in the animal model alleviated neuropathic pain and altered neurotransmitter expression.Furthermore,hydralazine facilitated motor function recovery following SCI.Nissl staining and LFB staining indicated that hydralazine promoted the structural recovery of the injured CNS.Conclusion:Hydralazine,an acrolein scavenger,significantly mitigated SCI-induced inflammation and oxidative stress in vivo,modulated macrophage activation,and consequently promoted the structural and functional recovery of the injured CNS.

Correction to:Molecular characterization and functional analysis of daf-8 in the pinewood nematode,Bursaphelenchus xylophilus

Correction to:J.For.Res.(2022)33:689–698 https://doi.org/10.1007/s11676-021-01335-7 In the Original Publication,the text“Acknowledgements sdfkjds”has been inadvertently appeared in the paper.The Original article has been corrected.

Diagnostic accuracy of apparent diffusion coefficient to differentiate intrapancreatic accessory spleen from pancreatic neuroendocrine tumors

BACKGROUND Intrapancreatic accessory spleen(IPAS)shares similar imaging findings with hypervascular pancreatic neuroendocrine tumors(PNETs),which may lead to unnecessary surgery.AIM To investigate and compare the diagnostic performance of absolute apparent diffusion coefficient(ADC)and normalized ADC(lesion-to-spleen ADC ratios)in the differential diagnosis of IPAS from PNETs.METHODS A retrospective study consisting of 29 patients(16 PNET patients vs 13 IPAS patients)who underwent preoperative contrast-enhanced magnetic resonance imaging together with diffusion-weighted imaging/ADC maps between January 2017 and July 2020 was performed.Two independent reviewers measured ADC on all lesions and spleens,and normalized ADC was calculated for further analysis.The receiver operating characteristics analysis was carried out for evaluating the diagnostic performance of both absolute ADC and normalized ADC values in the differential diagnosis between IPAS and PNETs by clarifying sensitivity,specificity,and accuracy.Inter-reader reliability for the two methods was evaluated.RESULTS IPAS had a significantly lower absolute ADC(0.931±0.773×10^(-3)mm^(2)/s vs 1.254±0.219×10^(-3)mm^(2)/s)and normalized ADC value(1.154±0.167 vs 1.591±0.364)compared to PNET.A cutoff value of 1.046×10^(-3)mm^(2)/s for absolute ADC was associated with 81.25%sensitivity,100%specificity,and 89.66%accuracy with an area under the curve of 0.94(95%confidence interval:0.8536-1.000)for the differential diagnosis of IPAS from PNET.Similarly,a cutoff value of 1.342 for normalized ADC was associated with 81.25%sensitivity,92.31%specificity,and 86.21%accuracy with an area under the curve of 0.91(95%confidence interval:0.8080-1.000)for the differential diagnosis of IPAS from PNET.Both methods showed excellent inter-reader reliability with intraclass correlation coefficients for absolute ADC and ADC ratio being 0.968 and 0.976,respectively.CONCLUSION Both absolute ADC and normalized ADC values can facilitate the differentiation between IPAS and PNET.

光催化分解水制备氢气和过氧化氢（英文）

过氧化氢不仅是一种广泛应用于化学合成、消毒、废水处理及纸浆漂白等领域的高价值化学品,还是一种具有潜力的能源载体.此外,过氧化氢燃料电池因其结构简单而受到广泛关注.蒽醌法是工业生产过氧化氢的传统方法,但是这种方法不仅能耗高,而且生产过程会造成严重的环境问题.因此,通过环保并且低成本的工艺直接合成过氧化氢具有重要研究意义.以太阳能为动力的光催化法生产过氧化氢被认为是最有前景的方法之一.目前,光催化已在制氢、二氧化碳还原和水处理等诸多领域取得了重要进展.但是,利用光催化分解水制备过氧化氢的研究还非常少.尽管通过光催化还原氧气可以制备过氧化氢,但是通过分解水同时制备高价值过氧化氢和氢气更具有吸引力.在本项工作中,我们利用Pt/TiO_2(锐钛矿)光催化剂在没有牺牲剂的条件下实现了高效产氢和过氧化氢,氢气和过氧化氢的生成速率分别达到7410和5096μmol g^(–1) h^(–1) (第一小时),远高于市售的Pt/TiO_2 (锐钛矿)体系和文献报道数值.本文采用X射线光电子能谱(XPS)、电子自旋共振(ESR)和荧光标记法等表征手段研究了Pt/TiO_2上同时生成氢气和过氧化氢的催化机理.XPS测试结果表明, Pt/TiO_2在光照射1 h后, XPS信号发生明显变化.与其他样品相比,物理吸附水和羟基的峰明显增加.因此,我们推测羟基和物理吸附水对过氧化氢的生成具有重要影响.进一步采用电子自旋共振(ESR)和荧光标记法对羟基进行了测量.ESR结果显示,紫外光照60 s即可检测到羟基捕获剂与羟基的结合物5,5-dimethyl-1-pyrroline-N-oxide-OH(DMPO-OH)的特征峰.此外,在体系中加入荧光标记分子对苯二甲酸(TANa)后也可以迅速检测到2-羟基对苯二甲酸(TAOH)在422 nm处明显的荧光信号.因此, ESR和荧光结果均表明所产生的羟基自由基在过氧化氢形成中起着重要作用.上述结果表明,在本体系中氢气和过氧化氢的生成遵循两电子转移过程.与传统全分解水体系生成氢气和氧气相比,两电子转移过程比四电子过程更容易发生.因此,光催化水氧化制过氧化氢是实现大规模生产氢气和过氧化氢的一种很有前景的方法.

碱金属阳离子对铁卟啉电催化CO_(2)还原的影响

电催化CO_(2)还原反应(CO_(2)RR)可以有效地将温室气体转化为燃料或高附加值的化学品,从而缓解目前人类所面临的环境问题和能源危机,其中开发高效的电催化剂是至关重要的环节.近年来,研究者设计了多种高效的过渡金属配合物(包括Mn,Fe,Co,Ni和Cu)用作CO_(2)RR分子电催化剂,并研究了其中的构效关系,例如,在分子内修饰质子给体取代基或电荷取代基可以显著提高CO_(2)RR的催化效率.而电催化CO_(2)RR的实际应用要在含有碱金属阳离子(例如,Na^(+)和K^(+))的电解质水溶液中进行,但在已有报道中,很少有关于碱金属阳离子对CO_(2)RR的影响.在众多的分子催化剂中,铁卟啉可以以较高的催化活性和选择性实现CO_(2)到CO的转化.重要的是,卟啉环的刚性结构、稳定的配位环境及其骨架上官能团的易于修饰性成为研究CO_(2)RR的构效关系的理想分子模型.基于以上考虑,本文以铁卟啉配合物为分子模型,研究了碱金属阳离子Na^(+)和K^(+)对电催化CO_(2)RR的影响.首先,本文合成了简单的A4型铁卟啉化合物四-(3,4,5-三甲氧基苯基)-铁卟啉(FeP).并采用核磁共振、质谱分析、单晶衍射等表征手段对化合物进行了表征,在含有电解质的DMF溶液中测试其电催化CO_(2)还原性能.实验结果表明,FeP可以实现高效的电催化CO_(2)还原,催化电流随FeP的浓度呈线性增加,说明催化反应速率与催化剂浓度呈一级反应速率关系.较长时间的恒电压电解实验以及电解前后化合物的紫外-可见光谱证实了FeP的稳定性.通过气相色谱对产物进行分析,CO为主要产物,法拉第效率为95%.以上结果均表明,FeP是一个优良的分子催化剂.在此基础上,本文还发现加入Na^(+)和K^(+)均可以显著提升催化活性,而K^(+)的加入使催化电流的提升更加显著,这可能是由于K^(+)在溶液中的迁移速度比Na^(+)更快.基于此实验现象,本文通过在FeP的第二配位层修饰1-氨-18-冠-6-醚官能团(^(N)18C6),合成了^(N)18C6-FeP化合物.结果表明,由于^(N)18C6与Na^(+)/K^(+)之间的配位作用,使得^(N)18C6-FeP比FeP具有更好的电催化CO_(2)RR活性.研究表明,催化活性的提升归因于碱金属阳离子能够通过静电相互作用稳定Fe-CO_(2)中间体.1H NMR谱证实了^(N)18C6基团的确能够螯合碱金属阳离子.本文研究证明了碱金属阳离子对改善电催化CO_(2)RR的积极作用,对于进一步深入了解CO_(2)RR催化反应机理和未来合理的设计高效催化剂也都具有重要意义.

幼儿体力活动水平:基于幼儿身体活动观察记录系统的评估

中高强度的体力活动与幼儿身体素质相关显著,幼儿园应保障幼儿每天有足够的中高强度体力活动。本研究运用幼儿身体活动观察记录系统,在广东省54所幼儿园开展幼儿体力活动水平调查。结果发现,幼儿的体力活动水平整体较低,久坐行为频率高,中高强度活动频率低。不同活动类型和不同等级幼儿园在体力活动水平上差异显著,具体表现为:在平均体力活动水平方面,自由游戏与早操显著高于体育游戏,省一级、办园级显著高于市一级;在久坐行为频率方面,自由游戏显著低于早操和体育游戏,省一级显著低于市一级;在中高强度活动频率上,自由游戏显著高于体育游戏和早操,省一级显著高于市一级。幼师比偏高,生均活动面积和生均器材数量偏少,教师对户外活动中的运动安全和常规格外关注,专注于游戏情境创设,对运动量和强度关注太少,编制的早操活动结构不合理、基本体操不科学,是幼儿体力活动水平整体不高、幼儿在教师组织实施的体育游戏与早操中的体力活动水平反不如户外自由游戏的重要原因。为提高幼儿在园体力活动水平,幼儿园应合理分配户外活动类型比例,增加户外自由游戏时间;相关部门应提升教师体育素养,加强对幼儿园户外活动的专业评价与监督。

Mo的引入方式对CeO_(2)脱硝性能的影响

固定源排放的氮氧化物(NOx)导致了严重的环境污染问题,NH_(3)选择性催化还原(NH_(3)-SCR)被认为是目前控制NOx排放的最有效技术,已广泛应用于电力行业的烟气排放治理.然而,我国非电行业的NOx减排仍然面临着重大挑战,因为其排放的废气温度通常低于300℃,且含有一定量的SO_(2),传统的钒基SCR催化剂因活性温度(300~400℃)较高而无法有效发挥作用.因此,亟待开发新型的高效低温SCR催化剂.铈基催化剂由于氧化铈(CeO_(2))的优异储氧能力(OSC)和良好的氧化还原能力而显示出较好的低温(80~300℃)脱硝性能,如Mn-Ce,W-Ce,Ta-Ce,Cu-Ce和Nb-Ce等.但这些铈基催化剂易被烟气中的SO_(2)毒化而导致催化活性降低.因此,提高铈基SCR催化剂抗硫中毒能力是其产业化应用的关键.已有研究发现,通过构筑结构保护层或添加另一种金属来保护活性组分是提高SCR催化剂抗硫性能的一种可行策略.氧化钼(MoO3)通常被用做传统V_(2)O_(5)/TiO_(2)催化剂的促进剂以提高其水热稳定性和表面酸性.研究表明,在V/Ti催化剂中引入钼物种不仅可以提高其SCR活性,而且提高了V/Ti催化剂的抗SO_(2)性能,这是由于VMo/Ti表面较少的V‒O‒V键削弱了对SO_(2)的氧化作用.Tang等开发了一种Fe_(2)O_(3)/MoO3纳米片催化剂,显示出比纯Fe_(2)O_(3)更好的抗SO_(2)能力,主要是由于层状结构的MoO3能阻止NH4+在硫酸氢铵中的沉积.目前关于Mo的引入方式即催化剂的制备方法对铈基催化剂物化性能和NH_(3)-SCR催化性能(特别是抗SO_(2)能力)的影响的研究还比较少.本文分别采用浸渍法和沉淀法在CeO_(2)中引入钼物种,制备了Mo-CeO_(2)和MoCe-cp催化剂来探究制备方法对MoCe催化剂的脱硝性能及抗SO_(2)中毒能力的影响.结果表明,引入Mo可以显著地提高CeO_(2)的低温脱硝性能,其中Mo-CeO_(2)催化剂在150℃即可达到80%以上的脱硝效率,同时抗SO_(2)中毒性能也得到了显著提高.对催化剂结构、氧化还原能力、表面酸度和反应物分子的吸附脱附性质进行了表征,并与MoCe催化剂脱硝性能和抗硫性能相关联.结果表明,Mo-CeO_(2)和MoCe-cp催化剂的物理化学性质和脱硝性能有明显区别.首先,Mo-CeO_(2)中的钼物种主要存在于CeO_(2)表面,而MoCe-cp中的钼物种主要存在于CeO_(2)体相,其为Mo-CeO_(2)表面带来大量的Brönsted酸位并抑制了硝酸盐的吸附,促使NH_(3)-SCR反应按照Eley-Rideal机理进行,进而表现出优于MoCe-cp的低温活性.其次,Mo-CeO_(2)表面更多的Mo物种抑制了SO_(2)的吸附,从而使Mo-CeO_(2)表现出更好的抗SO_(2)性能.本文为具有实际应用前景的铈基NH_(3)-SCR催化剂的设计提供了参考.

Conceptual design of an extractive distillation process for the separation of azeotropic mixture of n-butanol-isobutanol-water

In many chemical processes, large amounts of wastewater containing butanol and isobutanol are produced.Given that n-butanol-isobutanol-water can form triple azeotrope, high-purity butanol cannot be recovered from the wastewater by ordinary distillation. To economically and effectively recover butanol from this kind of wastewater, 1,4-butanediol is selected as an extractant to break the formation of the azeotropes, and a doubleeffect extractive distillation process is proposed. The conceptual design of the proposed process is accomplished based on process simulation. With the proposed process, the purity of recovered butanol and water is greater than 99.99 wt%. In comparison with the conventional azeotropic distillation process, economic analysis shows that the operating cost of the proposed process is lower: when the capacity of wastewater treatment is 100 t·h^(-1), the total operating cost decreases by 5.385 ×10~6 USD per year, and the total annual cost of the new process decreases by 5.249 ×10~6 USD per year. In addition, in the extractive distillation system, variable effects on separation purities and cost are more complex than those in the ordinary distillation system. The method and steps to optimize the key variables of the extractive distillation system are also discussed in this paper and can provide reference for similar studies.

High powerλ~8.5μm quantum cascade laser grown by MOCVD operating continuous-wave up to 408 K

Robust quantum cascade laser(QCL)enduring high temperature continuous-wave(CW)operation is of critical importance for some applications.We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition(MOCVD).High interface quality structures designed for light emission at 8.5μm are achieved by optimizing and precise controlling of growth conditions.A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10μm-wide coated laser.Corresponding maximum wall-plug efficiency and threshold current density were 7.1%and 1.18 kA/cm2,respectively.The device can operate in CW mode up to 408 K with an output power of 160 mW.