检索结果-南通市图书馆

Science China Chemistry 2021年第5期64卷 761-769页

作者： jia-Le Xie Zheng Xu Han-qi Zhou Yi-Xue Nie jian cao Guan-Wu Yin Jean-Philippe Bouillon Li-Wen Xu Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education Key Laboratory of Organosilicon Material Technology of Zhejiang ProvinceHangzhou Normal UniversityHangzhou 311121China State Key Laboratory for Oxo Synthesis and Selective Oxidation Suzhou Research Institute(SRI)Lanzhou Institute of Chemical Physics(LICP)University of the Chinese Academy of Sciences(UCAS)Lanzhou 730000China Normandie University INSA RouenUNIROUENCNRSCOBRA(UMR 6014)Rouen 76000France

Hydrosilylation is one of the most important reactions in synthetic chemistry and ranks as a fundamental method to access organosilicon compounds in industrial and academic ***,the enantioselective construction of chiral-at-silicon compounds via catalytic asymmetric hydrosilylation remained limited and *** we report a highly enantioselective hydrosilylation of ynones,a type of carbonyl-activated alkynes,using a palladium catalyst with a chiral binaphthyl phosphoramidite *** stereospecific hydrosilylation of ynones affords a series of silicon-stereogenic silylenones with up to 94%yield,>20:1 regioselectivity and 98:2 *** density functional theory(DFT)calculations were conducted to elucidate the reaction mechanism and origin of high degree of stereoselectivity,in which the powerful potential of aromatic interaction in this reaction is highlighted by the multiple C–H-πinteraction and aromatic cavity-oriented enantioselectivitydetermining step during desymmetric functionalization of Si–H bond.

关键词： asymmetric catalysis DFT calculations hydrosilylation silicon-stereogenic vinylsilanes aromatic interaction

Graphene-wrapped multiloculated nickel ferrite:A highly efficient electromagnetic attenuation material for microwave absorbing and green shielding

在线全文

学校读者我要写书评

暂无评论

Nano Research 2022年第7期15卷 6751-6760页

作者： Yuchang Wang Lihua Yao qi Zheng Mao-Sheng cao School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China School of Mechatronical Engineering Shanxi Datong UniversityDatong 037003China

Dedicating to the exploration of efficient electromagnetic(EM)absorption and electromagnetic interference(EMI)shielding materials is the main strategy to solve the EM radiation *** development of multifunction EM attenuation materials that are compatible together EM absorption and EMI shielding properties is deserved our exploration and ***,the graphenewrapped multiloculated NiFe_(2)O_(4) composites are reported as multifunction EM absorbing and EMI shielding *** conductive networks configurated by the overlapping flexible graphene promote the riched polarization genes,as well as electron transmission paths,and thus optimize the dielectric constant of the ***,the introduction of magnetic NiFe_(2)O_(4) further establishes the magnetic-dielectric synergy *** abundant non-homogeneous interfaces not only generate effective interfacial polarization,also the deliberate multiloculated structure of NiFe_(2)O_(4) strengthens multi-scattering and multi-reflection sites to expand the transmission path of EM *** it turns out,the best impedance matching is matched at a lower filled concentration to achieve the strongest reflection loss value of−48.1 ***,green EMI shielding based on a predominantly EM absorption and dissipation is achieved by an enlargement of the filled concentration,which is helpful to reduce the secondary EM wave reflection pollution to the *** addition,the electrocatalytic properties are further *** graphene-wrapped multiloculated NiFe_(2)O_(4) shows the well electrocatalytic activity as electrocatalysts for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),which is mainly attributed to the interconnected structures formed by graphene and NiFe_(2)O_(4) *** structural advantages of multiloculated NiFe_(2)O_(4) expose more active sites,which plays an important role in optimizing catalytic *** work provides an excellent jumping-off point

关键词： electromagnetic absorbing green electromagnetic shielding multifunction electromagnetic attenuation material graphenewrapped multiloculated Fe_(2)O_(4) oxygen evolution reaction hydrogen evolution reaction

Visualization Investigation on Flowing Condensation in Horizontal Small Channels with Liquid Separator

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 Thermal Science 2018年第1期27卷 48-54页

作者： ZHANG Xuan jia Li DANG Chao PENG qi Institude of Thermal Engineering School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing key laboratory of flow and heat transfer of phase changing in micro and small scale Beijing 100044China

A simultaneous visualization and measurement experiment was carried out to investigate condensation flow pat- terns and condensing heat transfer characteristics of refrigerant R14 lb in parallel horizontal multi-channels with liquid-vapor separator. The hydraulic diameter of each channel was 1.5 mm and the channel length was 100 ram. The refrigerant vapor flowing in the small channels was cooled by cooling water. The parallel horizontal mul- ti-channels were covered with a transparent silica glass for visualization of flow patterns. Experiments were per- formed at different inlet superheat temperatures （ranging from 3~C to 7~C）. Mass velocity was in the range of 82.37 kg mZs1 to 35.56 kg m-2s1. It was found that there were three different flow patterns through the mul- ti-channels with the increase of mass velocity. The flow patterns in each channel pass almost tended to be same and all of them were annular flows.＇ The efficiency of the liquid-vapor separator with U-type was related to vapor mass velocity and the pressure in the small channels. It was also found that the heat transfer coefficient increased with the increase of the mass velocity while the cooling water mass flow rate increased. It increased to a top point and then decreased. It increased with the increase of superheat in the low superheat temperature region.

关键词： condensation visualization multi-channels liquid-vapor separation

Mobile CRISPR-Cas9 based anti-phage system in E. coli

在线全文

学校读者我要写书评

暂无评论

Frontiers of Chemical Science and Engineering 2022年第8期16卷 1281-1289页

作者： Zhou cao Yuxin Ma Bin jia Ying-Jin Yuan Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering(Ministry of Education) Tianjin UniversityTianjin 300072China Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

Escherichia coli is one of the most important microbial cell factories,but infection by bacteriophages in the environment may have a huge impact on its application in industrial ***,we developed a mobile CRISPR-Cas9 based anti-phage system for bacteriophages defense in *** conjugative plasmids pGM1(phosphoglucomutase 1)and pGM2 carrying one and two guide RNAs,respectively,were designed to defend against a filamentous *** results showed that the pGM1 and pGM2 could decrease the phage infection rate to 1.6%and 0.2%respectively in infected *** preventing phage infection in ***,the pGM2 decreased the phage infection rate to 0.1%,while pGM1 failed to block phage *** verification revealed that point mutations in protospacer or protospacer adjacent motif sequences of the phage genome caused loss of the defense *** results support the potential application of MCBAS in *** cell factories to defend against phage infections.

关键词： phage infections anti-phage CRISPR-Cas9,conjugative transfer synthetic biology

Candidate chiral nuclei in bromine isotopes based on triaxial relativistic mean field theory

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第1期62卷 56-62页

作者： Bin qi Hui jia Chen Liu ShouYu Wang Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and Physics Institute of Space Sciences Shandong University

Following the observation of candidate chiral doublet bands in ^(78,80)Br, triaxial deformations with corresponding configurations in odd-odd bromine isotopes have been investigated using adiabatic and configuration-fixed constrained triaxial relativistic-meanfield calculations with an aim of finding the boundary of chirality in the chain of Br isotopes. Several minima with triaxial deformation and the proper particle-hole configuration were obtained in ^(74,76,78,80,82)Br, where the chiral doublet bands have the possibility of occurrence. Furthermore, the possible existence of multiple chiral doublet(MχD) bands is demonstrated in ^(74,76,78,80,82)*** to explore the chirality and MχD properties of Br isotopes are conducted to verify the predictions.

关键词： chiral doublet bands relativistic mean field bromine isotopes

MicroRNAs in colorectal cancer as markers and targets:Recent advances

在线全文

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2014年第15期20卷 4288-4299页

作者： Jing-jia Ye jiang cao Clinical Research Center The Second Affiliated HospitalZhejiang University School of Medicine

MicroRNAs are evolutionarily conserved small noncoding RNA molecules encoded by eukaryotic genomic DNA,and function in post-transcriptional regulation of gene expression via base-pairing with complementary sequences in target mRNAs,resulting in translational repression or degradation of target *** represent one of the major types of epigenetic modification and play important roles in all aspects of cellular *** expression of microRNAs has been found in various human diseases including *** efforts have been made to discover the characteristic microRNA expression profiles,to understand the roles of aberrantly expressed microRNAs and underlying mechanisms in different *** the application of DNA microarray,real-time quantitative polymerase chain reaction and other molecular biology techniques,increasing evidence has been accumulated which reveal that aberrant microRNAs can be detected not only intracellularly within the cancer cells,but also extracellularly in plasma of patients,postulating the potential of aberrant microRNAs as promising diagnostic/prognostic markers and attracting therapeutic *** review is intended to provide the most recent advances in microRNA studies in one of the most common cancers,colorectal cancer,especially the identification of those specifically altered microRNAs in colorectal cancer,validation for their relevance to clinical pathological parameters of patients,functional analyses and potential applications of these microRNAs.

关键词： MicroRNA Epigenetic modification Colorectal cancer Marker Therapy

A physically based methodology for predicting anisotropic creep properties of Ni-based superalloys

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

Rare Metals 2016年第8期35卷 606-614页

作者： jia Huang Duo-qi Shi Xiao-Guang Yang School of Energy and Power Engineering Beihang University

This paper is focused on developing suitable methodology for predicting creep characteristics （i.e., the minimum creep strain rate, stress rupture life and time to a specified creep strain） of typical Ni-based directionally solidified （DS） and single-crystal （SC） superalloys. A modem method with high accuracy on simulating wide ranging creep properties was fully validated by a sufficient amount of experimental data, which was then developed to model anisotropic creep characteristics by introducing a simple orientation factor defined by the ultimate tensile strength （UTS）. Physical confidence on this methodology is provided by the well-predicted transitions of creep defor- mation mechanisms. Meanwhile, this method was further adopted to innovatively evaluate the creep properties of different materials from a relative perspective.

关键词： Wilshire equations Anisotropic creepproperties Ni-based superalloy Prediction methodologyCreep mechanism

Whole petroleum system and ordered distribution pattern of conventional and unconventional oil and gas reservoirs

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2023年第1期20卷 1-19页

作者： Cheng-Zao jia Xiong-qi Pang Yan Song PetroChina Research Institute of Petroleum Exploration&Development Beijing100083China State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China China University of Petroleum Beijing102249China

The classical source-to-trap petroleum system concept only considers the migration and accumulation of conventional oil and gas in traps driven dominantly by buoyance in a basin,although revised and improved,even some new concepts as composite petroleum system,total petroleum system,total composite petroleum system,were proposed,but they do not account for the vast unconventional oil and gas reservoirs within the system,which is not formed and distributed in traps dominantly by ***,the petroleum system concept is no longer adequate in dealing with all the oil and gas accumulations in a basin where significant amount of the unconventional oil and gas resources are present in addition to the conventional oil and gas *** paper looked into and analyzed the distribution characteristics of conventional and unconventional oil/gas reservoirs and their differences and correlations in petroliferous basins in China and North America,and then proposed whole petroleum system(WPS)concept,the WPS is defined as a natural system that encompasses all the conventional and unconventional oil and gas,reservoirs and resources originated from organic matter in source rocks,the geological elements and processes involving the formation,evolution,and distribution of these oil and gas,reservoirs and *** is found in the WPS that there are three kinds of hydrocarbons dynamic fields,three kinds of original hydrocarbons,three kinds of reservoir rocks,and the coupling of these three essential elements lead to the basic ordered distribution model of shale oil/gas reservoirs contacting or interbeded with tight oil/gas reservoirs and separated conventional oil/gas reservoirs from source rocks upward,which is expressed as“S\T-C”.Abnormal conditions lead to other three special ordered distribution models:The first is that with shale oil/gas reservoirs separated from tight oil/gas *** second is that with two direction ordered distributions from sou

关键词： Conventional and unconventional oil and gas Petroleum system Whole petroleum system Hydrocarbon reservoirs ordered distribution model Fossil energy

The Effect of Heating Direction on Flow Boiling Heat Transfer of R134a in Microchannels

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2017年第2期26卷 166-174页

作者： XU Mingchen jia Li DANG Chao PENG qi Institute of Thermal Engineering School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing Key Laboratory of Flow and Heat Transfer of Phase Changing in Micro and Small Scale Beijing 100044China

This paper presents effects of heating directions on heat transfer performance of R134 a flow boiling in micro-channel heat sink. The heat sink has 30 parallel rectangular channels with cross-sectional dimensions of 500mm width 500mm depth and 30 mm length. The experimental operation condition ranges of the heat flux and the mass flux were 13.48 to 82.25 W/cm^2 and 373.3 to 1244.4 kg/m^2 s respectively. The vapor quality ranged from 0.07 to 0.93. The heat transfer coefficients of top heating and bottom heating both were up to 25 k W/m^2 K. Two dominate transfer mechanisms of nucleate boiling and convection boiling were observed according to boiling curves. The experimental results indicated that the heat transfer coefficient of bottom heating was 13.9% higher than top heating in low heat flux, while in high heat flux, the heat transfer coefficient of bottom heating was 9.9%.higher than the top heating, because bubbles were harder to divorce the heating wall. And a modified correlation was provided to predict heat transfer of top heating.

关键词： top heating bottom heating flow boiling micro-channels R134a correlation

Effective exposure of nitrogen heteroatoms in 3D porous graphene framework for oxygen reduction reaction and lithium–sulfur batteries

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2018年第1期27卷 167-175页

作者： jia-Le Shi Cheng Tang jia-qi Huang Wancheng Zhu qiang Zhang Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Advanced Research Institute for Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Department of Chemical Engineering Qufu Normal UniversityQufu 273165ShandongChina Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education) Nankai UniversityTianjin 300071China CAS Key Laboratory of Carbon Materials.Institute of Coal Chemistry Chinese Academy of SciencesTaiyuan 030001ShanxiChina

The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.

关键词： Nitrogen-doped graphene Chemical vapor deposition Oxygen reduction reaction Lithium-sulfur battery Porous carbon materials Exposure of active sites