Research Progress for the Development of Li-Air Batteries: Addressing Parasitic Reactions Arising from Air Composition

Li-air batteries are an extremely attractive technology for electrical energy storage,especially in long-range electric vehicles,owing to their high theoretical specific energy.However,many issues still exist before their practical realization.Herein,the sole complexity of electrode reaction in Li-air batteries is presented.And the critical components that influence the electrochemical performance of aprotic Li-air batteries operating in ambient air are discussed.These include the mechanisms and pathways of CO_(2)/Li_(2)CO_(3) and H_(2)O/LiOH,catalysts of CO_(2) reduction/evolution reactions,and reactions between the Li anode and air constituents.If these challenges can be solved,Li-air batteries will soon be realized for practical application.Some hot topics in field of Li-air batteries should be focused,such as the fundamental mechanism research referring to interfacial reactions of atmosphere components on porous electrode and Li metal anode,high-efficiency solid catalyst design,and discovery of suitable soluble redox mediators.

Design and Initial Testing of An Integrated Switched Reluctance Starter/Generator System for Unmanned Aerial Vehicle

According to specific performance requirements,an integrated switched reluctance starter/generator system,which can start the engine and supply electrical energy to the loads,is designed and manufactured for the unmanned aerial vehicle.Considering the required starting torque and speed range,the geometrical dimensions of the switched reluctance machine are calculated based on the output equation and further optimized with finite element analysis,and the flux-linkage,inductance and static torque characteristics are illustrated.To verify the performances of the designed system,detailed simulation with the model considering piston engine and experiment using the test bench are carried out.

Prevalence and Risk Factors of Postoperative Pressure Ulcers:A Systematic Review and Meta-analysis of Diagnostic Test

[Objectives]The paper was to analyze the total prevalence of postoperative pressure ulcers in patients and to reveal the epidemic law.[Methods]By searching English databases such as PubMed,Google Academics,Scopus,Science Direct and Web of Science(WOS),a total of 2018 English articles on pressure ulcers published from January 2015 to December 2020 were selected.According to the inclusion criteria,19 high-quality literatures were selected for the study,and the extended function of meta-analysis software of Review Manager 5.1 diagnostic test was used for data statistics and meta analysis of the results.[Results]There were 19 literatures with a total of 9400 patients included in the meta-analysis.The results showed that the total prevalence estimate of postoperative pressure ulcers was 20.00%(CI 95%:15.3-24.1).The total prevalence estimate of postoperative pressure ulcers in males was 10.1%(CI 95%:7.2-13.02),and that in females was 12.8%(CI 95%:8.1-17.3).The total prevalence estimates of stage I to IV postoperative pressure ulcers were 17.02%(CI 95%:11.06-22.09),6.7%(CI 95%:3.76-9.69),0.9%(CI 95%:0.21-1.26)and 0.4%(CI 95%:-0.05-0.8),respectively.[Conclusions]The prevalence of postoperative pressure ulcers is generally high.The prevalence of postoperative pressure ulcers in females is higher than that in males,and the prevalence of stage I pressure ulcers is higher than that of other stages,which is related to age,gender and other related risk factors.

Colon cancer-associated transcript 1(CCAT1):A potential novel target in cancer therapy

To the Editor:Long non-coding RNAs(lncRNAs)are a class of RNA molecules comprising more than 200 nucleotides in length,which possess negligible ability to encode functional proteins.LncRNAs are involved in several cell events,and their dysregulation has been reported to mediate tumor development and progression.Colon cancer-associated transcript 1(CCAT1)is consistently overexpressed in a range of cancer cells and tissues.Cancer treatment strategies that target CCAT1 have great potential.

静坐和运动时间与视网膜血管管径的相关性

目的：探讨静坐和运动时间与视网膜血管管径的相关性。方法：横断面研究。收集2008年3月至2017年7月在广州市第十一人民医院体检的40岁及以上、未发生过全身重大心脑血管事件的公务员6560名，对该群体静坐时间、高强度运动（指使呼吸比平常明显急促的运动，如快跑、游泳、打篮球等）、中等强度运动（指使呼吸比较急促的运动，如打太极拳、踢毽子、正常速度骑单车等）和走路时间等生活习惯进行问卷调查，通过眼底照相和有效的眼底血管分析方法测量视网膜动静脉管径。利用单变量线性回归进行混杂因素的筛选，在校正年龄、性别、血压（包括收缩压和舒张压）、吸烟、饮酒等因素后，采用多重线性回归模型分析静坐和运动时间与视网膜血管管径的相关性。结果：共纳入5857名参与者，在校正了年龄、性别、血压等传统心血管疾病危险因素之后，结果显示静坐时间与视网膜中央动脉管径相关且为视网膜中央动脉管径狭窄的危险因素（β=-0．29，P=0．032），高强度运动、中等强度运动和行走时间对视网膜血管并无保护作用。结论：静坐时间是视网膜动脉管径狭窄的危险因素，运动对视网膜动静脉管径并无明显影响。

Microstructure and strengthening mechanism of hot-extruded ultralight Mg-Li-Al-Sn alloys with high strength

Duplex-structured Mg-7Li-2Al-1.5Sn alloys with high strength were fabricated and their strengthening mechanism was investigated.The Mg-7Li-2Al-1.5Sn alloys were prepared by casting and extruded at the temperature of 533 K with an extrusion ratio of 25:1.The microstructure and mechanical properties of Mg-7Li-2Al-1.5Sn alloys were systematically investigated by OM,XRD,SEM,TEM,and tensile tests.The results show that Mg-7Li-2Al-1.5Sn alloys are mainly composed ofα-Mg,β-Li,LiMgAl_(2),Mg_(2)Sn and Li_(2)MgSn phases.The yield strength(YS),ultimate tensile strength(UTS)and elongation(EL)of the extruded alloy at room temperature reach 250 MPa,324 MPa and 11.9%,respectively.A lot of Sn-rich precipitates(Mg_(2)Sn and Li_(2)MgSn)are precipitated during extrusion with an average size of∼14 nm,which is beneficial to the grain refinement.Dynamic recrystallization occurs during hot deformation and the nanoprecipitates effectively refine the dynamic recrystallized(DRXed)grains.Besides,the residual dislocations existed in DRXed and un-DRXed grains result in the dislocation strengthening in the extruded alloy.Mg7Li-2Al-1.5Sn alloys possess excellent high-temperature mechanical properties with the YS,UTS and EL of 200 MPa,237 MPa and 26.7%at 423 K,respectively.Sn-rich precipitates with good thermal stability can effectively prevent grain growth,which is good for the improvement of the high-temperature performance of Mg-Li-Al-Sn alloy.

A high efficiency electrolyte enables robust inorganic–organic solid electrolyte interfaces for fast Li metal anode

Developing a high-rate Li metal anode with superior reversibility is a prerequisite for fast-charging Li metal batteries.However,the build-up of large concentration gradients under high current density leads to inhomogeneous Li deposition and unstable passivation layers of Li metal,resulting in lower Coulombic efficiency.Here we report a concentrated dual-salts LiFSI-LiNO_(3)/DOL electrolyte to improve the high-rate performance of Li metal anode.Sufficient Li salts help passivate the fresh Li deposition quickly.Further,DOL contributes to the formation of flexible organic layers that can accommodate the rapid volume change of Li metal upon cycling.Li metal in the electrolyte remains stable over 240 cycles with the average Coulombic efficiency of 99.14%under a high current density of 8.0 mA cm^(-2).

Lignin-derived Zn single atom/N-codoped porous carbon forα-alkylation of aromatic ketones with alcohols via borrowing hydrogen strategy

A green and scalable strategy has been developed for the synthesis of lignin-derived Zn single atom/N-codoped porous carbon(LCN@Zn-SAC)containing similar ZnNx sites with carbonic anhydrases.This catalyst exhibits superior activity on theα-alkylation of ketones with alcohols via borrowing hydrogen strategy(TON up to 15 h^(−1))than most of previously reported works.The dehydrogenation of benzyl alcohol is the rate-determining step based on kinetic experiment results.According to experimental and theoretical calculation results,Zn electron density is inversely proportional to reaction energy barriers,because Zn sites with less positive charge(ZnN_(4) and ZnN_(3)C)in Zn-SACs display better borrowing hydrogen ability than other Zn sites.Furthermore,this catalyst can be recycled by simple centrifugation,which can be reused at least 8 runs with no obvious lose in activity.To the best of our knowledge,this is the first example of non-noble metal-SAC-catalyzedα-alkylation via borrowing hydrogen strategy.

Oxygen vacancy promising highly reversible phase transition in layered cathodes for sodium-ion batteries

Phase transition is common during (de)-intercalating layered sodium oxides, which directly affects the structural stability and electrochemical performance. However, the artificial control of phase transition to achieve advanced sodium-ion batteries is lacking, since the remarkably little is known about the influencing factor relative to the sliding process of transition-metal slabs upon sodium release and uptake of layered oxides. Herein, we for the first time demonstrate the manipulation of oxygen vacancy concentrations in multinary metallic oxides has a significant impact on the reversibility of phase transition, thereby determining the sodium storage performance of cathode materials. Results show that abundant oxygen vacancies intrigue the return of the already slide transition-metal slabs between O_(3) and P_(3) phase transition, in contrast to the few oxygen vacancies and resulted irreversibility. Additionally, the abundant oxygen vacancies enhance the electronic and ionic conductivity of the Na0.9Ni0.3Co0.15Mn0.05Ti0.5O2 electrode, delivering the high initial Coulombic efficiency of 97.1%, large reversible capacity of 112.7 mAh·g−1, superior rate capability upon 100 C and splendid cycling performance over 1,000 cycles. Our findings open up new horizons for artificially manipulating the structural evolution and electrochemical process of layered cathodes, and pave a way in designing advanced sodium-ion batteries.

Recent advances in synthesis of organosilicons via radical strategies

Organosilicon compounds play an important role in the fields of materials science,pharmacy,and organic synthesis.The development of effective approaches for the preparation of these compounds have also become a research focus in organic synthesis.In recent years,free radical synthesis of organosilicons has been vigorously developed,which generally has the advantages of milder synthesis conditions,higher yields and selectivity,and free of precious metal catalysts compared with traditional strategies.This article reviews research progresses in the synthesis of organosilico n compounds by free radical pathways since 2016.In most cases,the radical silylation is achieved based on the reaction of silyl radicals,which are triggered by four routes including peroxide,transition-metal-induced peroxide decomposition,alkali,photocatalysis.The alkyl radicals can also initiate the radical silylation for the generation of C(sp^(3))—Si bonds.

Sonochemical synthesis and characterization of magnetic separable Fe_(3)O_(4)-TiO_(2)nanocomposites and their catalytic properties

A novel sonochemical method is described for the preparation of Fe_(3)O_(4)–TiO_(2)photocatalysts in which nanocrystalline titanium dioxide particles are directly coated onto a magnetic core.The Fe_(3)O_(4)nanoparticles were partially embedded in TiO_(2)agglomerates.TiO_(2)nanocrystallites were obtained by hydrolysis and condensation of titanium tetraisopropyl in the presence of ethanol and water under high-intensity ultrasound irradiation.This method is attractive since it eliminated the high-temperature heat treatment required in the conventional sol–gel method,which is important in transforming amorphous titanium dioxide into a photoactive crystalline phase.In comparison to other methods,the developed method is simple,mild,green and efficient.The magnetization hysteresis loop for Fe_(3)O_(4)–TiO_(2)nanocomposites indicates that the hybrid catalyst shows superparamagnetic characteristics at room temperature.Photocatalytic activity studies confirmed that the as-prepared nanocomposites have high photocatalytic ability toward the photodegradation of RhB solution.Furthermore,the photodecomposition rate decreases only slightly after six cycles of the photocatalysis experiment.Thus,these Fe_(3)O_(4)–TiO_(2)nanocomposites can be served as an effective and conveniently recyclable photocatalyst.

日常饮茶与视网膜血管管径的相关性

目的:探讨日常饮茶种类和饮茶量与视网膜血管管径的相关关系。方法:横断面研究。纳入年龄40岁及以上、无严重心脑血管疾患的广州市公务员4430人。通过问卷采集参与者日常主要饮茶种类(包括绿茶、乌龙茶、红茶或普洱茶3类)和平均饮茶量(分为从不饮茶、偶有饮茶、少于每天1杯、每天1~2杯、每天2杯以上5组)。通过IVAN眼底血管分析系统测定研究对象的眼底照片评估视网膜血管管径。多重线性回归模型分析日常饮茶与视网膜血管管径的相关关系。结果:本研究参与者年龄为(58.8±9.9)岁,其中男性占56.00%,从不饮茶为775人(17.49%),饮用绿茶、乌龙茶、红茶的人数分别是645人(14.56%)、1240人(27.99%)、1770人(39.95%)。在矫正了年龄、血压等传统心脑血管危险因素及日常生活习惯后,在3个不同的饮茶种类人群中,视网膜血管管径与饮茶量不相关(P>0.05)。结论:日常生活的饮茶量与视网膜血管管径并无相关关系。