解析单颗粒电化学分步电子转移步骤用于识别电催化剂本征活性

揭示电催化剂本征活性对于量化其构-效关系至关重要.传统的整体表征方法只能提供大量纳米颗粒(NP)的平均性能,并且通常难以排除添加剂的贡献.单颗粒碰撞电化学(SNCE)技术能够有效地在单NP水平上揭示电催化剂活性.尽管SNCE领域已取得了很大的研究进展,但目前人们对其反应中的电子转移过程认识尚不充分,难以提供NPs结构与活性之间的定量关系.本文以铂纳米颗粒(PtNPs)氧还原反应(ORR)作为SNCE过程的模型体系,通过构建功能化锥形碳微米电极(CNE)界面,有效地调控了ORR电催化过程,揭示了SNCE分步电子转移在调节单个PtNP表观ORR活性中的重要作用.分别采用化学刻蚀和元素功能化技术调控CNE界面的表面粗糙度和氮元素掺杂组成,构筑了光滑碳电极(s-CNE)、粗糙碳电极(r-CNE)、光滑氮掺杂碳电极(sN-CNE)和粗糙氮掺杂碳电极(rN-CNE)四种功能化电极界面.实验表明,单个PtNP在s-CNE、r-CNE、sN-CNE和rN-CNE这四种功能化CNE界面上产生的ORR电流强度依次增大(即s-CNE<r-CNE<sN-CNE<rN-CNE),且在rN-CNE表面达到了扩散控制的极限电流.这一发现证明了,通过对电极界面进行功能化处理可以显著提升PtNPs的ORR性能,这是由于单个PtNP的ORR总反应速率受决速步控制.密度泛函理论计算和表征结果表明,对电极界面进行表面粗糙化处理或氮元素掺杂可以分别调控SNCE电催化中的单步电子转移过程,即增强NP与电极间的电子传递速率或NP的异相动力学速率.为深入解析这一复杂过程,构建了一个多物理场理论模型.该模型将NP与电极间的电子转移、NP表面的异相电子转移以及溶液中的物质传递作为SNCE过程中的连续步骤.通过将理论模拟与高分辨电化学测量相结合,成功量化了SNCE分步电子转移步骤的相应参数,包括NP与电极间的接触电阻、NP的异相动力学常数以及NP与电极间的吸附概率,从而明确了提高电催化剂本征活性的决速步.综上所述,本文通过单颗粒电化学测量和多物理场理论模拟,深入探究了SNCE分步电子转移过程,在单NP水平上识别了电催化剂的本征活性.同时,利用分步电子转移模型量化了电催化剂构-效关系,从而为合理设计和开发高效纳米催化剂提供启示.

第37届中国化学奥林匹克(初赛)有机试题解析

从学生解题角度出发,对第37届中国化学奥林匹克(初赛)试题中的有机化学第9和10题进行了全面详尽的分析,这可以培养学生的逻辑思维能力,进而提高学生解决有机化学问题的效率。同时,通过深入学习反应机理,帮助学生体会题目背后的科学思维,感受有机化学的魅力与乐趣。

Sustainable production of high-energy-density jet fuel via cycloaddition reactions

Developing an energy supply-chain based on renewable biomass holds great potential to build a low carbon society.High-energy-density(HED)jet fuel,featuring unique fused/strained cycloalkanes,is of great significance for volume-limited military aircrafts,as their high density and combustion heat can extend flight duration and increase the payload.Therefore,the exploration of biomass-based routes towards HED fuel has drawn much attention over the past decade.Cycloaddition reaction features rapid construction of various carbocycles in an atom-and step-economical fashion.This elegant strategy has been widely applied in the manufacture of sustainable HED fuel.Here we carefully summarize the progress achieved in this fascinating area and the review is categorized by the cycloaddition patterns including[4+2],[2+2],[4+4],and[2+1]cycloadditions.Besides,the energy densities of the as-prepared biofuels and petroleumbased fuels(conventional Jet-A and advanced JP-10)are also compared.This review will provide important insights into rational design of new HED fuel with different ring-types/sizes and inspire the chemists to turn those literature studies into practical applications in military field.

Fabrication of Pd-based metal-acid-alkali multifunctional catalysts for one-pot synthesis of MIBK

The one-pot synthesis of methyl isobutyl ketone（MIBK） from acetone using multifunctional catalysts is an important sustainable organic synthesis method with high atom and energy efficiency.Herein. we report a series of Pd supported on mixed metal oxide（MMO） catalysts with controllable acidic/basic/metallic sites on the surface. We study the relationship between the nature, synergy,and proximity of active sites and the catalytic performance of the multifunctional catalyst in the tandem reaction, in detail. In the existence of Lewis acid and base sites, the catalysts with medium-strength acidic/basic sites show preferred activity and/or MIBK selectivity. For multifunctional catalysts, the catalytic properties are more than just a collection of active sites, and the Pd/Mg_3Al-MMO catalyst possessing 0.1% Pd loading and ~0.4 acid/base molar ratio exhibits the optimal 42.1% acetone conversion and 37.2% MIBK yield, which is among the best reported so far for this tandem reaction under similar conditions. Moreover, the proximity test indicates that the intimate distance between acidic/basic/metallic sites can greatly shorten the diffusion time of the intermediate species from each active site, leading to an enhancement in the catalytic performance.

Test on dynamic characteristics of subgrade of heavy-haul railway in cold regions

Dynamic characteristics of heavy-haul railway subgrade under vibratory loading in cold regions are investigated via low-temperature dynamie triaxial tests with multi-stage eyelic loading process. The relationship between dynamic shear stress and dynamic shear strain of frozen soil of subgrade under train loading and the influence of freezing temperatures on dynamic constitutive relation, dynamic shear modulus and damping ratio are observed in this study. Test results show that the dynamic constitutive relations of the frozen soils with different freezing temperatures comply with the hyperbolic model, in which model parameters a and b decrease with increasing freezing temperature. The dynamic shear modulus of the frozen soils decreases with increasing dynamic shear strains initially, followed by a relatively smooth attenuation tendency, whereas increases with decreasing freezing temperatures. The damping ratios decrease with decreasing freezing temperatures. Two linear functions are defined to express the linear relationships between dynamic shear modulus （damping ratio） and freezing temperature, respectively, in which corresponding linear coefficients are obtained through multiple regression analysis of test data.

Hydrogenase as the basis for green hydrogen production and utilization

Hydrogenase is a paradigm of highly efficient biocatalyst for H_(2) production and utilization evolved in nature. A dilemma is that despite the high activity and efficiency expected for hydrogenases as promising catalysts for the hydrogen economy, the poor oxygen tolerance and low yield of hydrogenases largely hinder their practical application. In these years, the enigmas surrounding hydrogenases regarding their structures, oxygen tolerance, mechanisms for catalysis, redox intermediates, and proton-coupled electron transfer schemes have been gradually elucidated;the schemes, which can well couple hydrogenases with other highly efficient(in)organic and biological catalysts to build novel reactors and drive valuable reactions, make it possible for hydrogenases to find their niches. To see how scientists put efforts to tackle this issue and design novel reactors in the fields where hydrogenases play crucial roles, in this review,recent advances were summarized, including different strategies for protecting enzyme molecules from oxygen, enzyme-based assembling systems for H_(2) evolution in the photoelectronic catalysis, enzymatic biofuel cells for H_(2) utilization and storage and the efficient electricity-hydrogen-carbohydrate cycle for high-purity hydrogen and biofuel automobiles. Limitations and future perspectives of hydrogenasebased applications in H_(2) production and utilization with great impact are discussed. In addition, this review also provides a new perspective on the use of biohydrogen in healthcare beyond energy.

Numerical simulation of vibrational response characteristics of railway subgrades with insulation boards

This study presents a numerical method based on the surface temperature data and the ground temperature increase in Daqing for predicting temperature field distribution in the Binzhou Railway subgrade and analyzing the temporal and spatial distribution of freeze−thaw status of railway subgrade.The calibrated numerical method is applied to simulate the temperature field distribution and roadbed vibrational response of the railway subgrade with a thermal insulation layer at different seasons.The results show the following:(1)The thermal insulation layer can remarkably increase the soil temperature below it and maximum frost depth in the subgrade.(2)Thermal insulation can effectively reduce the subgrade vibration and protect it from frost damage.(3)Given that the strength requirements are met,the insulation layer should be buried as shallow as possible to effectively reduce the subgrade vibration response.The research findings provide theoretical support for the frost damage prevention of railway subgrades in seasonally frozen regions.

Advances in the detec

Human health is threatened by foodborne illness and Staphylococcus aureus is a common foodborne pathogenic bacteria.It can cause food poisoning when we are infected,therefore,it is necessary to detect pathogenic bacteria.The virulence genes and detection methods of S.aureus are summarized from literatures.Traditional detection methods are simple but need bacteria enrichment and to prolong detection time.Immunological technology has high specificity,but false positive results are easy to occur in its detection.In recent years,molecular biology methods have developed rapidly,and various PCR techniques have been applied to detect foodborne pathogens.Real-time fluorescent quantitative PCR is more effective than ordinary PCR,while price is expensive when use it,the scope of use is limited.LAMP is a flexible detection method,biosensor and flow cytometry are fast but the cost of detection is high and the price is relatively expensive.

Development Prospects of Osmanthus fragrans Mixed Wine Based on Liquor and Spirits

As a plant resource, Osmanthus fragrans has both medicinal and edible effects. This paper reviews the active components and health-care functions of O. fragrans, and introduces the current research situation of O. fragrans mixed wine. In addition, combined with the development of new products of plant-based flower wine, it analyzes the development prospects of O. fragrans mixed wine based on liquor and spirits.

Photocatalytic synthesis of small-molecule drugs by porous framework materials

Small-molecule drugs are widely used in daily life.There are still issues with the current industrial synthesis techniques for small-molecule drugs,such as the use of expensive metal catalysts,convoluted reaction processes,and non-recyclable catalysts.The benefits of photocatalytic organic synthesis over conventional techniques are mild conditions,environmental friendliness,and great selectivity.Porous framework materials can precisely modulate catalytic sites'electronic state and ligand structure to improve photocatalytic performance.In particular,MOFs,COFs and PCCs based photocatalysts have received extensive research interest due to their unique morphology,structural adjustability,high photocatalytic performance,unique recyclability,excellent chemical stability,easy synthesis and low cost.Therefore,a key area for future research is the development of porous framework materials as photocatalysts for the synthesis of small-molecule drugs or drug precursors.

Paleontology Knowledge Graph for Data-Driven Discovery

A knowledge graph(KG)is a knowledge base that integrates and represents data based on a graph-structured data model or topology.Geoscientists have made efforts to construct geosciencerelated KGs to overcome semantic heterogeneity and facilitate knowledge representation,data integration,and text analysis.However,there is currently no comprehensive paleontology KG or data-driven discovery based on it.In this study,we constructed a two-layer model to represent the ordinal hierarchical structure of the paleontology KG following a top-down construction process.An ontology containing 19365 concepts has been defined up to 2023.On this basis,we derived the synonymy list based on the paleontology KG and designed corresponding online functions in the OneStratigraphy database to showcase the use of the KG in paleontological research.

KMT2D deficiency leads to cellular developmental disorders and enhancer dysregulation in neural-crest-containing brain organoids

KMT2D,a H3K4me1 methyltransferase primarily regulating enhancers,is a leading cause of KABUKI syndrome.This multisystem disorder leads to craniofacial and cognitive abnormalities,possibly through neural crest and neuronal lineages.However,the impacted cell-of-origin and molecular mechanism of KMT2D during the development of KABUKI disease remains unknown.Here we have optimized a brain organoid model to investigate neural crest and neuronal differentiation.To pinpoint KMT2D's enhancer target,we developed a genome-wide cis-regulatory element explorer(GREE)based on single-cell multiomic integration.Single cell RNA-seq revealed that KMT2D-knockout(KO)and patient-derived organoids exhibited neural crest deformities and GABAergic overproduction.Mechanistically,GREE identified that KMT2D targets a roof-plate-like niche cell and activates the niche cell-specific WNT3A enhancer,providing the microenvironment for neural crest and neuronal development.Interestingly,KMT2D-mutated mice displayed decreased WNT3A expression in the diencephalon roof plate,indicating impaired niche cell function.Deleting the WNT3A enhancer in the organoids presented phenotypic similarities to KMT2D-depletion,emphasizing the WNT3A enhancer as the predominant target of KMT2D.Conversely,reactivating WNT signaling in KMT2D-KO rescued the lineage defects by restoring the microenvironment.Overall,our discovery of KMT2D's primary target provides insights for reconciling complex phenotypes of KABUKI syndrome and establishes a new paradigm for dissecting the mechanisms of genetic disorders from genotype to phenotype.

Bipolar membrane electrodialysis integrated with in-situ CO_(2)absorption for simulated seawater concentrate utilization,carbon storage and production of sodium carbonate

In the context of carbon capture,utilization,and storage,the high-value utilization of carbon storage presents a significant challenge.To address this challenge,this study employed the bipolar membrane electrodialysis integrated with carbon utilization technology to prepare Na_(2)CO_(3)products using simulated seawater concentrate,achieving simultaneous saline wastewater utilization,carbon storage and high-value production of Na_(2)CO_(3).The effects of various factors,including concentration of simulated seawater concentrate,current density,CO_(2)aeration rate,and circulating flow rate of alkali chamber,on the quality of Na_(2)CO_(3)product,carbon sequestration rate,and energy consumption were investigated.Under the optimal condition,the CO_(3)^(2-)concentration in the alkaline chamber reached a maximum of 0.817 mol/L with 98 mol%purity.The resulting carbon fixation rate was 70.50%,with energy consumption for carbon sequestration and product production of 5.7 k Whr/m^(3)CO_(2)and1237.8 k Whr/ton Na_(2)CO_(3),respectively.This coupling design provides a triple-win outcome promoting waste reduction and efficient utilization of resources.

Efficient and selective photocatalytic nitrite reduction to N_(2)through CO_(2)anion radical by eco-friendly tartaric acid activation

In this study,the environmentally friendly precursor,tartaric acid(TA),was employed for the generation of CO_(2)anion radical(CO_(2)^(·-))in an advanced UV/TA/Fe^(3+)system to reduce the hazardous NO_(2)^(-)-N in wastewater.To optimize this process,various factors,including the dosage of Fe^(3+),TA,and p H,were systematically investigated for their impact on the reduction process.Under the conditions of 3 mmol/L Fe^(3+)dosage,10 mmol/L TA dosage,and a pH of 2.5,NO_(2)^(-)-N was effectively removed from the water within 60 min,selectively transformed into N_(2),with a remarkable N_(2)selectivity of 91.2%.In the optimal conditions,the NO_(2)^(-)-N reduction mechanism in the UV/TA/Fe^(3+)system and the critical role of CO_(2)^(·-)were illustrated.Finally,this study explored the reduction of real nitrified seawater using the UV/TA/Fe^(3+)system.The results demonstrated that the UV/TA/Fe^(3+)system could completely eliminate NO_(2)^(-)-N and achieve a N_(2)selectivity of up to 90%,with minimal interference from coexisting ions.This work holds promising implications for the environmentally benign treatment of nitrite-polluted wastewater.

Pulmonary Bacterial Infection and Liver Cirrhosis: Current Status and Treatment

Liver cirrhosis has a higher incidence rate and mortality when complicated with bacterial infections.Concomitant bacterial infections,especially bacterial pneumonia,increase the susceptibility of cirrhotic patients to decompensation,with a higher likelihood of mortality.Bacterial pneu-monia is often overlooked in patients with liver cirrhosis,although it can impact the clinical progress and outcomes.Untimely diagnosis and inappropriate antibiotic treatments are associated with poor prognosis and increased mortality.Current understanding of mechanisms and appropriate antibiotic treatments for cirrhosis-related bacterial pneumonia remain inadequate.Herein,we reviewed the epidemiology,clinical characteristics and treatment of pulmonary bacterial infections in cirrhotic patients to provide suggestions for clinical practice.

本征导热聚合物研究:机理、结构与性能及应用

散热已成为制约超高频、大功率微电子器件和高电压电气绝缘设备日益微型化的技术瓶颈和发展面临的重要挑战,急需高性能的导热材料实现快速散热。相比导热高分子复合材料,本征结构的导热高分子材料因同步的高导热及高绝缘强度、优异柔韧性、轻质高强等优异的综合性能及优势受到了国内外学者的广泛研究和关注。本文首先讨论了聚合物的本征导热机理,系统深入地分析和评述了单体及分子链结构、结晶、取向、分子链间作用、交联、缺陷等结构因素,以及温度、压力、环境等因素对声子热传递及聚合物导热的影响机理,进一步归纳了本征导热聚合物的制备策略和途径。最后总结了当前本征导热聚合物研究面临的主要问题和挑战,展望了未来发展方向及其在众多领域的重要潜在应用。

近视性屈光参差儿童青少年配戴角膜塑形镜的临床效果

目的:观察青少年近视性屈光参差配戴角膜塑形镜的临床效果。方法:回顾性自身对照研究。收集浙江大学医学院附属第二医院眼科中心从2015年12月至2017年6月之间开始配戴角膜塑形镜的患者32例,年龄8~16(11.2±2.2)岁,随访时间2年。双眼等效球镜度(SE)差值≥1.00 D,滴用睫状肌麻痹剂后的SE范围为-0.75^-6.00 D。分为高屈光度眼组(两眼中屈光度较高眼)和低屈光度眼组(两眼中屈光度较低眼),均配戴角膜塑形镜。观察双眼戴镜前以及戴镜后半年、1年、1.5年,2年的眼轴变化。数据采用配对t检验进行比较。结果:双眼眼轴差值由戴镜前的(0.46±0.24)mm下降到戴镜2年后的(0.33±0.28)mm,差异有统计学意义(t=5.038,P<0.001),高屈光度眼组戴镜2年后眼轴变化量[(0.38±0.21)mm]小于低屈光度眼组眼轴变化量[(0.51±0.26)mm],差异有统计学意义(t=6.52,P<0.001)。结论:青少年长期配戴角膜塑形镜可以减小近视性屈光参差双眼之间的眼轴差值,减少屈光参差量,可以更有效减缓近视屈光度较高眼的眼轴增长,配戴角膜塑形镜是改善屈光参差的一种有效方式。

角膜塑形镜控制近视进展的研究现状

近年来, 近视呈现高发、低龄的趋势。近视不仅影响视力, 还可引起玻璃体及眼底的退行性病变, 高度近视相关并发症更是导致低视力和盲的重要病因。角膜塑形镜作为目前控制近视进展的重要方法也成为了一大热点。如今国内外关于角膜塑形镜控制近视进展的研究较多, 现笔者针对近视流行及角膜塑形镜控制近视的有效性和安全性等方面作一综述。

Vascular protection and regenerative effects of intranasal DL-3-N butylphthalide treatment after ischaemic stroke in mice

Objective To investigate the effects of DL-3-N butylphthalide(NBP)via intranasal delivery after ischaemic stroke in mice.Methods C57BL/6 mice were divided into three groups:sham,stroke with vehicle and stroke with NBP treatment.Ischaemic stroke was induced by permanent ligation of right middle cerebral artery with 7 min common carotid artery occlusion.NBP(100 mg/kg)or vehicle was intranasally administered at 1 hour after stroke and repeated once a day until sacrifice.Bromodeoxyuridine(BrdU)(50 mg/kg/day)was given from the third day until sacrifice.Sensorimotor function was tested during 1-21 days after stroke.Local cerebral blood flow in the ischaemic and peri-infarct regions was measured using laser Doppler flowmetry before,during and 3 days after ischaemia.Expressions of vascular endothelial growth factor(VEGF)and endothelial nitric oxide synthase as well as regenerative marker BrdU in the peri-infarct region were analysed by western blotting and immunohistochemical methods.Results Compared with the vehicle group,NBP treatment significantly increased the VEGF expression in the poststroke brain.Stroke mice that received NBP showed significantly less vascular damage after stroke and more new neurons and blood vessels in the peri-infarct region at 21 days after stroke.In the adhesive removal test,the sensorimotor function of stroke mice treated with NBP performed significantly better at 1,3 and 7 days after stroke compared with vehicle controls.Conclusion Daily intranasal NBP treatment provides protective and neurogenic/angiogenic effects in the poststroke brain,accompanied with functional improvements after a focal ischaemic stroke in mice.

SNObase,a database for S-nitrosation modification

S-Nitros(yl)ation is a ubiquitous redox-based post-translational modification of protein cysteine thiols by nitric oxide or its derivatives,which transduces the bioactivity of nitric oxide(NO)by regulation of protein conformation,activity,stability,localization and pro-tein-protein interactions.These years,more and more S-nitrosated proteins were identified in physiological and pathological processes and the number is still growing.Here we developed a database named SNO-base(http://www.nitrosation.org),which collected S-nitrosation targets extracted from literatures up to June 1st,2012.SNObase contained 2561 instances,and provided information about S-nitrosation targets,sites,biological model,related diseases,trends of S-nitrosation level and effects of S-nitrosation on protein function.With SNObase,we did functional analysis for all the SNO targets:In the gene ontology(GO)biological process category,some processes were discovered to be related to S-nitrosation(“response to drug”,“regulation of cell motion”)besides the previously reported related processes.In the GO cellular component category,cytosol and mitochondrion were both enriched.From the KEGG pathway enrichment results,we found SNO targets were enriched in different diseases,which suggests possible significant roles of S-nitrosation in the progress of these diseases.This SNObase means to be a database with precise,comprehensive and easily accessible information,an environment to help researchers integrate data with comparison and relevancy analysis between different groups or works,and also an SNO knowledgebase offering feasibility for systemic and global analysis of S-nitrosation in interdisciplinary studies.