检索结果-南通市图书馆

Recent progress in carbene-catalyzed fluoroalkylation

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第8期67卷 2448-2460页

作者： Bei zhang xuan zhang Jian Wang Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control Collaborative Innovation Center of Atmospheric Environment and Equipment TechnologySchool of Environmental Science and EngineeringNanjing University of Information Science and TechnologyNanjing 210044China School of Pharmaceutical Sciences Tsinghua UniversityBeijing 100084China

The fluoroalkyl fragment plays a vital role in various fields such as pharmaceuticals and materials science, and has a significant impact on human life not only on the present but also in the future. The insertion of fluoroalkyl groups into the chemical skeletons can cause considerable alternations in the chemical, physical and biological properties of molecules, which has attracted numerous scientists from different fields. This review focuses on N-heterocyclic carbene(NHC)-catalyzed fluoroalkylation reactions, providing a detailed analysis and summary of the achievements in the past two decades. Many successful examples clearly indicate that NHCs can catalyze the tranformation of fluoroalkylation reagents with various electronic characteristics, whether electrophilic, nucleophilic, or radical precursors. Herein, the fluoroalkylation reactions are classified based on different catalytic modes of NHCs: Lewis base catalysis, Umploung catalysis, radical catalysis and others. Meanwhile, by refining and systematically studying the contribution of NHC catalysis in fluoroalkylation reactions, this review is expected to provide valuable insights and enlightenment for related fields.

关键词： N-heterocyclic carbene fluoroalkylation radical catalysis

Microbial self-healing of cracks in cement-based materials and its influencing factors

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2023年第11期17卷 1630-1642页

作者： Xiaoniu YU Qiyong zhang xuan zhang Mian LUO Jiangsu Key Laboratory of Construction Materials Southeast UniversityNanjing 211189China College of Engineering and Technology Southwest UniversityChongqing 400715China School of Civil Engineering and Architecture Jiangsu University of Science and TechnologyZhenjiang 212114China College of Civil Science and Engineering Yangzhou UniversityYangzhou 225127China

Cement-based materials are brittle and crack easily under natural *** can reduce service life because the transport of harmful substances can cause corrosion damage to the *** review discusses the feasibility of using microbial self-healing agents for crack *** and spherical carriers can be used to load microbial self-healing agents and protect microbes,which prolongs the self-healing *** area self-healing ratio,permeability,mechanical strength,precipitation depth method,numerical modeling,and ultrasonic method can be employed to identify the self-healing effect of ***,the self-healing mechanism is systematically *** results showed that microbial self-healing agents can repair cracks in cement-based materials in underground projects and dam *** difficulties and future development of self-healing cracks were analyzed.A microbial selfhealing agent was embedded in the cement-based material,which automatically repaired the developing *** the development of intelligent building materials,self-healing cracks have become the focus of attention.

关键词： cement-based materials cracks microbial self-healing agent mechanism intelligent building materials

Size and shape effects of MnFe_(2)O_(4)nanoparticles as catalysts for reductive degradation of dye pollutants

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2021年第5期15卷 351-359页

作者： Guowen Hu Zeqi zhang xuan zhang Tianrong Li State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical EngineeringLanzhou UniversityLanzhou730000China

The magnetic nanoparticles that are easy to recycle have tremendous potential as a suitable catalyst for environmental toxic dye pollutant *** engineering shapes and tailoring the size of nanocatalysts are regarded as an effective manner for enhancing ***,we successfully synthesized three kinds of MnFe_(2)O_(4)NPs with distinctive sizes and shapes as catalysts for reductive degradation of methylene blue,rhodamine 6G,rhodamine B,and methylene *** was found that the catalytic activities were dependent on the size and shape of the MnFe_(2)O_(4)NPs and highly related to the surface-to-volume ratio and atom ***,all these nanocatalysts exhibit selectivity to different organic dyes,which is beneficial for their practical application in dye pollutant ***,the MnFe_(2)O_(4)NPs could be readily recovered by a magnet and reused more than ten times without appreciable loss of *** size and shape effects of MnFe_(2)O_(4)nanoparticles demonstrated in this work not only accelerate further understanding the nature of nanocatalysts but also contribute to the precise design of nanoparticles catalyst for pollutant degradation.

关键词： Dye degradation MnFe_(2)O_(4)nanoparticles Size and shape-control

Adsorption equilibrium and the effect of honeycomb heat exchanging device on charge/discharge characteristic of methane on MIL-101(Cr)and activated carbon

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2020年第7期28卷 1964-1972页

作者： Guobin Zhao Qingrong Zheng xuan zhang Weidong zhang Provincial Key Laboratory of Naval Architecture&Ocean Engineering Institute of Marine EngineeringJimei UniversityXiamen 361021China

Experiments were conducted for developing suitable ANG adsorbents for vehicular ***-101 and activated carbon samples were respectively prepared by hydrothermal and chemical activation *** samples were undergone structure analysis on adsorption data of nitrogen at 77.15 K,and adsorption data of methane were then volumetrically measured within temperature-pressure range 293.15 K-313.15 K and 0-8 MPa.A conformable vessel in volume 2.5 L was employed for charge/discharge tests under the flow rate 10-30 L·min^-*** shows that limit isostreic heat of methane adsorption is respectively about 25.15 k J·mol^-1 and22.94 k J·mol^-1 on the activated carbon and the MIL-101,and isosteric heat within the experimental condition is 14-19.5 k J·mol^-1;employing a smaller charge/discharge flow rate can weaken the temperature fluctuation of the adsorbent bed and increase the charge/discharge amount;employing honeycomb heat exchanging device enhance the thermal conductivity of the adsorbent bed by consuming a negligible part of volume of the *** suggests that a smaller flow rate for charge/discharge should be employed,and MOFs together with the honeycomb heat exchanging device are promising for practical applications.

关键词： Natural gas MOFs Activated carbon Adsorption

Joint Spectrum Partition and Performance Analysis of Full-Duplex D2D Communications in Multi-Tier Wireless Networks

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2019年第7期61卷 171-184页

作者： Yueping Wang xuan zhang Yixuan zhang Nanjing University of Aeronautics and Astronautics NanjingChina Huawei Corporation NanjingChina Huawei Research Center Singapore

Full-duplex(FD)has been recognized as a promising technology for future 5G networks to improve the spectrum ***,the biggest practical impediments of realizing full-duplex communications are the presence of self-interference,especially in complex cellular *** the current development of self-interference cancellation techniques,full-duplex has been considered to be more suitable for device-to-device(D2D)and small cell communications which have small transmission range and low transmit *** this paper,we consider the full-duplex D2D communications in multi-tier wireless networks and present an analytical model which jointly considers mode selection,resource allocation,and power ***,we consider a distance based mode selection *** performance analysis of different D2D communications modes are performed based on stochastic geometry,and tractable analytical solutions are *** we investigate the optimal resource partitions between dedicated D2D mode and cellular *** results validate the theoretical anlaysis and indicate that with appropriate proportions of users operated in different transmission modes and optimal partitioning of spectrum,the performance gain of FD-D2D communication can be achieved.

关键词： Full-duplex device-to-device communications HetNets power control spectrum partition

Symbionts, a promising source of bioactive natural products

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2015年第7期58卷 1097-1109页

作者： xuan zhang Wei Wei Renxiang Tan State Key Laboratory of Pharmaceutical Biotechnology College of Life Science Nanjing University

Symbionts are microorganisms residing in multicellular hosts(e.g., plants and animals), and they have been witnessed to be a rich source of diverse functional molecules. This review describes structures and biological activities of symbiont-derived secondary metabolites commonly referred to as "natural products", and highlights that symbiotic microbes represent an underexplored reservoir of natural products with unique scaffolds and promising significance in managing human healthcare and agricultural production.

关键词： symbionts natural products bioactivities

Size and strain rate effects in tensile strength of penta-twinned Ag nanowires

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2017年第4期33卷 792-800页

作者： xuan zhang Xiaoyan Li Huajian Gao Centre of Advanced Mechanics and Materials Department of Engineering Mechanics Tsinghua University School of Engineering Brown University

Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength（defined as the critical stress for dislocation nucleation） increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1–10b^3,where b is the magnitude of the Burgers vector for a full dislocation.

关键词： nucleation tensile dislocation modulus apparent diameters decreasing magnitude crystalline penta

Gastrointestinal involvement in systemic lupus erythematosus:Insight into pathogenesis, diagnosis and treatment

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2010年第24期16卷 2971-2977页

作者： Tian, Xin-Ping zhang, xuan Chinese Acad Med Sci Peking Union Med Coll Peking Union Med Coll Hosp Dept Rheumatol Beijing 100730 Peoples R China

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by the presence of a plethora of autoantibodies and immune complex formation. Virtually every system and organ can be affected by SLE. Gastrointestinal symptoms are com-mon in SLE patients, and more than half of them are caused by adverse reactions to medications and viral or bacterial infections. Though not as common as lu-pus nephritis, SLE-related gastrointestinal involvement is clinically important because most cases can be life-threatening if not treated promptly. Lupus mesenteric vasculitis is the most common cause, followed by pro-tein-losing enteropathy, intestinal pseudo-obstruction, acute pancreatitis and other rare complications such as celiac disease, inflammatory bowel diseases, etc. No specific autoantibody is identified as being associated with SLE-related gastroenteropathy. Imaging studies, particularly abdominal computed tomography scans, are helpful in diagnosing some SLE-related gastroen-teropathies. Most of these complications have good therapeutic responses to corticosteroids and immu-nosuppressive agents. Supportive measures such as bowel rest, nutritional support, antibiotics and proki-netic medications are helpful in facilitating functional recovery and improving the outcome.

关键词： Systemic lupus erythematosus Systemic Vasculitis Gastroenteropathy

Influence of ecological function protection zone on the water conservation in Gansu-Qinghai Contiguous Region of the upper Yellow River

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mountain Science 2024年第4期21卷 1345-1357页

作者： TONG Huali CHEN Qingbo zhang xuan College of Geography and Environmental Science Northwest Normal UniversityLanzhou 730070China Gansu Province Land Use and Comprehensive Improvement Engineering Research Center Lanzhou 730070China

The implementation of Ecological Function Protection Zone(EFPZ)policy is significant for the ecological restoration and conservation of soil and water in the territory *** manuscript analyzed and quantified the impact of EFPZ on the regional water conservation function,based on land use data from 2005,2008,2010,2015 and 2020,by conducting a counterfactual simulation along with the GeoSOS-FLUS model and the InVEST *** results demonstrate that the delineation of EFPZ can significantly influence the water conservation.(1)From 2010 to 2020,as the EFPZ was implemented,the water conservation in the study area was increasing year by year,with a growth rate of 0.03×10^(8) m^(3)∙a^(-1).On the other hand,the simulated water conservation capacity without the implementation of EFPZ decreased year by year,with a decrease rate of 0.01×10^(8) m^(3)∙a^(-1).(2)The EFPZ accounts for only 23%of the total area,but the contribution rate of water conservation reaches 80%.The actual values of water conservation and average water yield per unit pixel in the EFPZ show an increasing trend both internally and externally,while the counterfactual simulation values exhibit a decreasing trend.(3)The water conservation is much higher within the EFPZ than without *** implementation of EFPZ has a significant effect on the improvement of the water conservation capacity in Maqu EFPZ and Yellow River Source *** protection effectiveness should be enhanced in Qilian Mountain EFPZ and afforestation activities need to be carefully considered in Loess Plateau EFPZ.

关键词： Water conservation function Ecological Function Protection Zone Counterfactual simulation Geo SOS-FLUS model InVEST model