Chemical effects in different aqueous solutions induced by plasma with glow discharge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge char...Chemical effects in different aqueous solutions induced by plasma with glow discharge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..展开更多
Phosphorus-containing compounds are the promising halon alternatives for flame inhibitions. However, some literatures suggested that the phosphorus-related inhibitors may behave as the unfavorable ones that will incre...Phosphorus-containing compounds are the promising halon alternatives for flame inhibitions. However, some literatures suggested that the phosphorus-related inhibitors may behave as the unfavorable ones that will increase the burning velocity under lean-burn conditions, and this indeed posed potential threats to the fire prevention and fighting. To seek deeper insights into the reaction process, a numerical investigation was actualized to study the phosphorus-related effects on methane-air flames. By replacing a phosphorus-related inhibitor with the corresponding decomposed molecules, the detailed promoting and inhibiting effects of combustion were separated from the general chemical effect. A comparative study was carried out to identify the interaction between the two effects under different combustion conditions. It is observed that the promoting effect becomes the dominant factor during the reaction process when the equivalence ratio is smaller than 0.60. In this lean-burn condition, the exothermic reactions were faster than the others within the reaction chains due to the reduction of radical recombination in hydrocarbon oxidation. The results are believed to be useful for the further application and improvement of flame inhibitors.展开更多
We study chemical effect on the structural properties of Ti–Al melts, with the Al concentration systematically changed,via ab initio molecular dynamics simulations. By calculating the partial coordination numbers, we...We study chemical effect on the structural properties of Ti–Al melts, with the Al concentration systematically changed,via ab initio molecular dynamics simulations. By calculating the partial coordination numbers, we find a preferred connection between the nearest neighbors for Al–Ti pairs. This induces an excess Ti coordination in the cluster characterized by local five-fold symmetry in Voronoi tessellation. Structural entropy measured from the diversity of Voronoi polyhedrons shows an intriguing non-monotonic tendency with concentration: it first decreases to a minimum value at Ti_(40)Al_(60), and then increases beyond this concentration. This implies a more ordered local structure induced by the chemical interaction at the intermediate compositions. The spatial correlation among the crystalline-like or the icosahedral-like clusters also exhibits the highest intensity for Al–Ti pairs, verifying the important role played by the chemical interaction in the local structure connectivity.展开更多
With the progress of ULSI technology, materials with low dielectric constant are required to replace SiO2 film as the interlayer to scale down the interconnection delay. Fluorinated Si oxide thin films (SiOF) are a pr...With the progress of ULSI technology, materials with low dielectric constant are required to replace SiO2 film as the interlayer to scale down the interconnection delay. Fluorinated Si oxide thin films (SiOF) are a promising material for the low dielectric constant and the process compatibility in existing technology. However, SiOF films are liable to absorb moisture when exposed to air. By treating the SiOF films with O-2 plasma, it was found that the moisture resistibility of SiOF films was remarkably improved. The mechanism of the improvement in stability of dielectric constant was investigated. The results show that: 1) F atoms dissociated from the films and the bond angle of Si-O-Si decreased. 2) The plasma treatment enhanced the strength of Si-F bonds by removing unstable =SiF2 structures in the films. Resistibility of SiOF films in moisture was improved.展开更多
Sijunzi Decoction,as one of the classic Chinese traditional prescriptions,has been used clinically by major physicians since the Song Dynasty.This article reviewed and sorted out the literature on the effective chemis...Sijunzi Decoction,as one of the classic Chinese traditional prescriptions,has been used clinically by major physicians since the Song Dynasty.This article reviewed and sorted out the literature on the effective chemistry of Sijunzi Decoction and the mechanism of its prevention and treatment of digestive system diseases.At present,its effective chemical components are derived from the saponins and flavonoids in ginseng and licorice,and are effective for gastrointestinal mucosal injury diseases and malignant digestive system.Digestive system diseases such as tumors,functional gastrointestinal diseases,non-alcoholic fatty liver,acute liver injury,and liver failure show a multi-path,multi-target effect mechanism.This article reviews the effective chemical components and research of Sijunzi Decoction and the related mechanisms of prevention and treatment of digestive system diseases,and provides valuable clues for the follow-up research of Sijunzi Decoction.展开更多
For development and application of proton exchange membrane fuel cell(PEMFC) energy transformation technology, the cost performance must be elevated for the catalyst. At present, compared with noble metal-based cataly...For development and application of proton exchange membrane fuel cell(PEMFC) energy transformation technology, the cost performance must be elevated for the catalyst. At present, compared with noble metal-based catalysts, such as Pt-based catalysts, atomically dispersed metal–nitrogen–carbon(M–N–C) catalysts are popularity and show great potential in maximizing active site density, high atom utilization and high activity,making them the first choice to replace Pt-based catalysts. In the preparation of atomically dispersed metal–nitrogen–carbon catalyst, it is difficult to ensure that all active sites are uniformly dispersed, and the structure system of the active sites is not optimal. Based on this, we focus on various approaches for preparing M–N–C catalysts that are conducive to atomic dispersion, and the influence of the chemical environmental regulation of atoms on the catalytic sites in different catalysts. Therefore, we discuss the chemical environmental regulation of the catalytic sites by bimetals, atom clusters, and heteroatoms(B, S, and P). The active sites of M–N–C catalysts are explored in depth from the synthesis and characterization, reaction mechanisms, and density functional theory(DFT)calculations. Finally, the existing problems and development prospects of the current atomic dispersion M–N–C catalyst are proposed in detail.展开更多
Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show ...Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction (COF) is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.展开更多
The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function...The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.展开更多
Spectra of KX-rays emitted from pure 3 dtransition metals and their oxide and sulfate compounds were measured using a single crystal wavelength dispersive X-ray spectroscopy(WDXRF).The measurements were performed usin...Spectra of KX-rays emitted from pure 3 dtransition metals and their oxide and sulfate compounds were measured using a single crystal wavelength dispersive X-ray spectroscopy(WDXRF).The measurements were performed using a ZSX-100 esequential spectrometer equipped with an RhX-ray tube operated.An accurate analytical representation of each line was obtained by a fit to a Lorentz function.The spectra were analyzed in order to examine the KX-ray peak parameters such as asymmetry index,peak energy and relative intensity ratios.The energy shifts and relative intensities weredetermined tobetter understand the chemical effect.展开更多
In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond d...In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.展开更多
In order to create effective combustion technologies and fuels with low or no carbon emissions,the research was conducted to assess the coupled interactive effects of NH_(3) and H_(2) additions on ethylene counterflow...In order to create effective combustion technologies and fuels with low or no carbon emissions,the research was conducted to assess the coupled interactive effects of NH_(3) and H_(2) additions on ethylene counterflow diffusion flames from a kinetic perspective.The effects of the NH_(3)/H_(2) combination on flame temperatures,major species,key radicals,important intermediate species,representative oxygenated species and NO_xwere examined.The results of the study utilizing fictitious inert NH_(3) and/or H_(2) revealed the chemical effects of the two components.It was found that the NH_(3)/H_(2) coupled effects had a more effective inhibitory effect on soot precursors than the effects of corresponding sum of single NH_(3) or H_(2) addition.The production of soot precursors was promoted by the coupled chemical effects of NH_(3) and H_(2),but the coupled dilution and thermal effects were observed to have a greater impact,resulting in a decrease of the mole fractions of soot precursors.As for the interaction of NH_(3) and H_(2) effects,the presence of H_(2) decreased the chemical effects of NH_(3) on the augmentation of C_(2)H_(2),A1,A2,and CH_(3)CHO mole fractions.The NH_(3) addition alleviated the H_(2) chemical effects on increasing C_(2)H_(2),C_(3)H_(3),A1 and A2 concentrations.Conversely,the NH_(3)chemical effects on C_(3)H_(3),OH and CH_(3)CHO were enhanced when H_(2) was added.The presence of NH_(3) augmented the chemical effects of H_(2) on the growth of OH mole fraction.Moreover,the H_(2) chemical effects hindered the production of NO and NO_(2) in the presence of NH_(3).展开更多
A new calculating method of aerodynamic heating for unsteady hypersonic aircrafts with complex configuration is presented.This method,which considers the effects of high temperature chemical non-equilibrium and the he...A new calculating method of aerodynamic heating for unsteady hypersonic aircrafts with complex configuration is presented.This method,which considers the effects of high temperature chemical non-equilibrium and the heat transfer process in thermal protection structure,is based on the combination of the inviscid outerflow solution and the engineering method,where the Euler solver provides the flow parameters on boundary layer edge for engineering method in aerodynamic heating calculation.A high efficient interpolation technique,which can be applied to the fast computation of longtime aerodynamic heating for hypersonic aircraft,is developed for flying trajectory.In this paper,three hypersonic test cases are calculated,and the heat flux and temperature distribution of thermo-protection system are shown.The numerical results show the high efficiency of the developed method and the validation of thermal characteristics analysis on hypersonic aerodynamic heating.展开更多
We report a simple method for preparing copper(II) molybdate(CuMoO_4) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing...We report a simple method for preparing copper(II) molybdate(CuMoO_4) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the(CuMo)-precursor gel was studied by thermogravimetry–differential thermal analysis(TG–DTA), Fourier transform infrared spectroscopy(FTIR), and X-ray diffraction(XRD). We observed that the crystallization of CuMoO_4 powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m^2/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO_4 crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO_4^(2-)] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.展开更多
Engelhardia Leschen. ex Blume (Juglandaceae) is native to southern and southeastern Asia and used to be traditional medicines and health tea. Hitherto, a large amount of chemical constituents had been iso- lated fro...Engelhardia Leschen. ex Blume (Juglandaceae) is native to southern and southeastern Asia and used to be traditional medicines and health tea. Hitherto, a large amount of chemical constituents had been iso- lated from genus Engelhardia and more pharmacological effects were found due to the presence of the second metabolites. There have been few comprehensive reports about Engelhardia plants especially the chemical constituents by now. The traditional usage of Engelhardia plants were for treating cold fever, detoxication, rheumatism, diarrhea, obesity, gastrointestinal problem and so on. While the modern pharmacological activities showed antioxidant activity, anti-ischemialreperfusion injury, anticancer activity, anti-inflammatory activity, immunosuppression activity, antidiabetic activity, antitubercular activity and so on. In this review, constituents of this genus would be introduced and classified by structures, the pharmacological effects of which would be described as well.展开更多
The recent discovery of high-temperature superconductivity in iron-based pnictides (chalcogenides) not only trig- gers tremendous enthusiasm in searching for new superconducting materials, but also opens a new avenu...The recent discovery of high-temperature superconductivity in iron-based pnictides (chalcogenides) not only trig- gers tremendous enthusiasm in searching for new superconducting materials, but also opens a new avenue to the study of the Kondo physics. CeFeAsO is a parent compound of the 1111-type iron-based superconductors. It shows 3d- antiferromagnetic (AFM) ordering below 139 K and 4f-AFM ordering below 4 K. On the other hand, the phosphide CeFePO is a ferromagnetically corelated heavy-fermion (HF) metal with Kondo scale TK 10 K. These properties set up a new platform for research of the interplay among magnetism, Kondo effect, and superconductivity (SC). In this review, we present the recent progress in the study of chemical pressure effect in CeFeAsOl_yFy (y = 0 and 0.05). This P/As-doping in CeFeAsO serves as an effective controlling parameter which leads to two magnetic critical points, Xcl -- 0.4 and Xc2 - 0.92, associated with suppression of 3d and 4f magnetism, respectively. We also observe a turning point of AFM-FM ordering of Ce3+ moment at Xc3 - 0.37. The SC is absent in the phase diagram, which is attributed to the destruction to Cooper pair by Ce-FM fluctuations in the vicinity of Xcl. We continue to investigate CeFeAsl-xPxO0.95Fo.os. With the separation of xcl and xc3, this chemical pressure results in a broad SC region 0〈 x 〈 0.53, while the original HF behavior is driven away by 5% F- doping. Different roles of P and F dopings are addressed, and the interplay between SC and Ce-4f magnetism is also discussed.展开更多
The theory of chemical shift effect of substituent was applied to the assignment of the 13 C NMR spectra of the ethylene/propylene and ethylene/octene 1 copolymers. Using the parameters derived above a...The theory of chemical shift effect of substituent was applied to the assignment of the 13 C NMR spectra of the ethylene/propylene and ethylene/octene 1 copolymers. Using the parameters derived above and the DEPT technique, we then entirely assigned the 13 C NMR spectra of the ethylene/propylene/octene 1 terpolymers synthesized in the presence of the same heterogeneous supported Ziegler Natta catalyst, TiCl 4/MgCl 2/ i Bu 3Al. The present paper also covers the terpolymer composition and the monomer sequence distributions of a series of ethylene/propylene/octene 1 terpolymers.展开更多
Bi2Se3, as a three-dimensional topological insulator, has attracted worldwide attention for its unique surface states which are protected by time-reversal symmetry. Here we report the synthesis and characterization of...Bi2Se3, as a three-dimensional topological insulator, has attracted worldwide attention for its unique surface states which are protected by time-reversal symmetry. Here we report the synthesis and characterization of high-quality singlecrystalline Bi2Se3 nanowires. Bi2Se3 nanowires were synthesized by chemical vapor deposition(CVD) method via goldcatalyzed vapor-liquid-solid(VLS) mechanism. The structure and morphology were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), x-ray photoelectron spectroscopy(XPS), and Raman spectroscopy. In magnetotransport measurements, the Aharonov–Bohm(AB) effect was observed in a nanowire-based nanodevice, suggesting the existence of surface states in Bi2Se3 nanowires.展开更多
This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on asses...This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on assessing the coupled chemical effects of NH_(3) and CO_(2) on C2H4 combustion chemistry.The chemical effects could be evaluated by comparing fictitious inert NH_(3) or CO_(2) with normal active NH_(3) or CO_(2).The results revealed that the addition of NH_(3) decreased the mole fractions and production rates of key soot precursors,such as acetylene,propynyl,and benzene.When CO_(2) was used as the dilution gas,the coupled chemical effects of NH_(3) and CO_(2) were affected by the chemical effects of CO_(2) to varying degrees.With the oxidizer-side CO_(2) addition,the coupled chemical effects of NH_(3) and CO_(2) reduced the mole fractions of H,O,OH radicals,acetylene,propynyl,and benzene,while the effects differed from the fuel-side CO_(2) addition.The coupled chemical effects of NH_(3) and CO_(2) also promoted the formation of aldehyde contaminants,such as acetaldehyde,to some extent,particularly with CO_(2) addition on the oxidizer side.展开更多
Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene der...Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene derivatives and 2,7-dibromo-9,9-dioctylfluorene under six various catalytic conditions to investigate the substituent effects. The substituent can affect the electron cloud density of the active C―H bond, which can be monitored by the NMR chemical shift. The experimental results show that the reactivity decreases with increasing the chemical shift of active C―H bonds in the four thiophene derivatives, and thus can promote the direct arylation polycondensation. This phenomenon is explained by the electrophilic aromatic substitution(SEAr) mechanism. UV-Visible absorption and photoluminescence were studied to investigate the substituent effect on optical properties of the four copolymers. The results show that these alternating fluorene-thiophene copolymers with different substituents are good fluorescent materials and promising in PLED applications.展开更多
This article compared the pyrolysis characteristics of butene isomer fuels(n-butene,trans-2-butene,isobutene)under CO_(2) atmosphere.The focus of the study was on the impacts of fuels isomerization and CO_(2) chemistr...This article compared the pyrolysis characteristics of butene isomer fuels(n-butene,trans-2-butene,isobutene)under CO_(2) atmosphere.The focus of the study was on the impacts of fuels isomerization and CO_(2) chemistry on the formation of important pyrolysis intermediate products under two temperature conditions(at 1273 K and 1573 K).The results demonstrated that at 1273 K,the concentrations of all products in isobutene pyrolysis were significantly lower than those of the corresponding products formed by the pyrolysis of n-butene and trans-2-butene in the process of fuels pyrolysis.The generation or consumption rate of each species was arranged from high to low as n-butene>trans-2-butene>isobutene.At 1573 K,the chemical effect of CO_(2) could inhibit the consumption of ethylene(C_(2)H_(4)),promote the formation of diacetylene(C_(4)H_(2)),and inhibit the formation of acetylene(C_(2)H_(2))and benzene(A_(1)).During the pyrolysis of n-butene at 1573 K,the chemical effect of CO_(2) was mainly reflected in changes of the consumption paths of C_(2)H_(2) and benzyl(A_(1)CH_(2)).For trans-2-butene pyrolysis at 1573 K,CO_(2) addition could change the main consumption paths of methyl(CH_(3)),which then inhibited C_(2)H_(2) formation.In addition,CO_(2) chemical action significantly changed the consumption paths of C_(4)H_(2) and A_(1) in trans-2-butene pyrolysis at 1573 K.As for isobutene pyrolysis at 1573 K,the chemical effect of CO_(2) significantly inhibited the production of A_(1) by changing the main consumption paths of C_(2)H_(2) and propargyl(C_(3)H_(3)).展开更多
文摘Chemical effects in different aqueous solutions induced by plasma with glow discharge electrolysis (GDE) and contact glow discharge electrolysis (CGDE) are described in this paper. The experimental and discharge characteristics are also reviewed. These are followed by a discussion of their mechanisms of both anodic and cathodic CGDE..
基金Project supported by the National Natural Science Foundation of China(Grant No.51576183)the Fundamental Research Funds for the Central Universities,China(Grant Nos.WK2320000035 and WK2320000041)
文摘Phosphorus-containing compounds are the promising halon alternatives for flame inhibitions. However, some literatures suggested that the phosphorus-related inhibitors may behave as the unfavorable ones that will increase the burning velocity under lean-burn conditions, and this indeed posed potential threats to the fire prevention and fighting. To seek deeper insights into the reaction process, a numerical investigation was actualized to study the phosphorus-related effects on methane-air flames. By replacing a phosphorus-related inhibitor with the corresponding decomposed molecules, the detailed promoting and inhibiting effects of combustion were separated from the general chemical effect. A comparative study was carried out to identify the interaction between the two effects under different combustion conditions. It is observed that the promoting effect becomes the dominant factor during the reaction process when the equivalence ratio is smaller than 0.60. In this lean-burn condition, the exothermic reactions were faster than the others within the reaction chains due to the reduction of radical recombination in hydrocarbon oxidation. The results are believed to be useful for the further application and improvement of flame inhibitors.
基金Project supported by the Open Research Fund of Songshan Lake Materials Laboratory, China (Grant No. 2022SLABFN14)the Natural Science Foundation of Hunan Province, China (Grant No. 2021JJ30833)。
文摘We study chemical effect on the structural properties of Ti–Al melts, with the Al concentration systematically changed,via ab initio molecular dynamics simulations. By calculating the partial coordination numbers, we find a preferred connection between the nearest neighbors for Al–Ti pairs. This induces an excess Ti coordination in the cluster characterized by local five-fold symmetry in Voronoi tessellation. Structural entropy measured from the diversity of Voronoi polyhedrons shows an intriguing non-monotonic tendency with concentration: it first decreases to a minimum value at Ti_(40)Al_(60), and then increases beyond this concentration. This implies a more ordered local structure induced by the chemical interaction at the intermediate compositions. The spatial correlation among the crystalline-like or the icosahedral-like clusters also exhibits the highest intensity for Al–Ti pairs, verifying the important role played by the chemical interaction in the local structure connectivity.
基金The work was supported by the National Natural Science Foundation of China(No.69776026)the Foundation for University Key Teacher by the Ministry of Education.
文摘With the progress of ULSI technology, materials with low dielectric constant are required to replace SiO2 film as the interlayer to scale down the interconnection delay. Fluorinated Si oxide thin films (SiOF) are a promising material for the low dielectric constant and the process compatibility in existing technology. However, SiOF films are liable to absorb moisture when exposed to air. By treating the SiOF films with O-2 plasma, it was found that the moisture resistibility of SiOF films was remarkably improved. The mechanism of the improvement in stability of dielectric constant was investigated. The results show that: 1) F atoms dissociated from the films and the bond angle of Si-O-Si decreased. 2) The plasma treatment enhanced the strength of Si-F bonds by removing unstable =SiF2 structures in the films. Resistibility of SiOF films in moisture was improved.
文摘Sijunzi Decoction,as one of the classic Chinese traditional prescriptions,has been used clinically by major physicians since the Song Dynasty.This article reviewed and sorted out the literature on the effective chemistry of Sijunzi Decoction and the mechanism of its prevention and treatment of digestive system diseases.At present,its effective chemical components are derived from the saponins and flavonoids in ginseng and licorice,and are effective for gastrointestinal mucosal injury diseases and malignant digestive system.Digestive system diseases such as tumors,functional gastrointestinal diseases,non-alcoholic fatty liver,acute liver injury,and liver failure show a multi-path,multi-target effect mechanism.This article reviews the effective chemical components and research of Sijunzi Decoction and the related mechanisms of prevention and treatment of digestive system diseases,and provides valuable clues for the follow-up research of Sijunzi Decoction.
基金financial support from the National Natural Science Foundation of China (Nos. 21875221, 21571157, U1604123, and 21773016)the Youth Talent Support Program of HighLevel Talents Special Support Plan in Henan Province (ZYQR201810148)+1 种基金Creative talents in the Education Department of Henan Province (19HASTIT039)the project supported by State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology) (2019-KF-13)
文摘For development and application of proton exchange membrane fuel cell(PEMFC) energy transformation technology, the cost performance must be elevated for the catalyst. At present, compared with noble metal-based catalysts, such as Pt-based catalysts, atomically dispersed metal–nitrogen–carbon(M–N–C) catalysts are popularity and show great potential in maximizing active site density, high atom utilization and high activity,making them the first choice to replace Pt-based catalysts. In the preparation of atomically dispersed metal–nitrogen–carbon catalyst, it is difficult to ensure that all active sites are uniformly dispersed, and the structure system of the active sites is not optimal. Based on this, we focus on various approaches for preparing M–N–C catalysts that are conducive to atomic dispersion, and the influence of the chemical environmental regulation of atoms on the catalytic sites in different catalysts. Therefore, we discuss the chemical environmental regulation of the catalytic sites by bimetals, atom clusters, and heteroatoms(B, S, and P). The active sites of M–N–C catalysts are explored in depth from the synthesis and characterization, reaction mechanisms, and density functional theory(DFT)calculations. Finally, the existing problems and development prospects of the current atomic dispersion M–N–C catalyst are proposed in detail.
基金Supported by the National Major Scientific and Technological Special Project during the Twelfth Five-year Plan Period under Grant No 2011ZX02704the National Natural Science Foundation of China under Grant No 51205387the Science and Technology Commission of Shanghai under Grant Nos llnm0500300 and 14XD1425300
文摘Effects of abrasive concentration on material removal rate CMRR) and surtace quality m the chemical mecnamcal polishing (CMP) of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction (COF) is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11004156 and 11547172the Science and Technology Star Project of Shaanxi Province under Grant No 2016KJXX-45
文摘The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.
基金the Scientific and Technological Research Council of Turkey (TUBITAK), under the project No. 10GT045
文摘Spectra of KX-rays emitted from pure 3 dtransition metals and their oxide and sulfate compounds were measured using a single crystal wavelength dispersive X-ray spectroscopy(WDXRF).The measurements were performed using a ZSX-100 esequential spectrometer equipped with an RhX-ray tube operated.An accurate analytical representation of each line was obtained by a fit to a Lorentz function.The spectra were analyzed in order to examine the KX-ray peak parameters such as asymmetry index,peak energy and relative intensity ratios.The energy shifts and relative intensities weredetermined tobetter understand the chemical effect.
文摘In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.
基金supported by the National Natural Science Foundation of China(Grant Nos. 52076110 and 52106160)Jiangsu Provincial Natural Science Foundation of China(Grant Nos. BK20200490 and BK20220955)the Fundamental Research Funds for the Central Universities(Grant No. 30920031103)。
文摘In order to create effective combustion technologies and fuels with low or no carbon emissions,the research was conducted to assess the coupled interactive effects of NH_(3) and H_(2) additions on ethylene counterflow diffusion flames from a kinetic perspective.The effects of the NH_(3)/H_(2) combination on flame temperatures,major species,key radicals,important intermediate species,representative oxygenated species and NO_xwere examined.The results of the study utilizing fictitious inert NH_(3) and/or H_(2) revealed the chemical effects of the two components.It was found that the NH_(3)/H_(2) coupled effects had a more effective inhibitory effect on soot precursors than the effects of corresponding sum of single NH_(3) or H_(2) addition.The production of soot precursors was promoted by the coupled chemical effects of NH_(3) and H_(2),but the coupled dilution and thermal effects were observed to have a greater impact,resulting in a decrease of the mole fractions of soot precursors.As for the interaction of NH_(3) and H_(2) effects,the presence of H_(2) decreased the chemical effects of NH_(3) on the augmentation of C_(2)H_(2),A1,A2,and CH_(3)CHO mole fractions.The NH_(3) addition alleviated the H_(2) chemical effects on increasing C_(2)H_(2),C_(3)H_(3),A1 and A2 concentrations.Conversely,the NH_(3)chemical effects on C_(3)H_(3),OH and CH_(3)CHO were enhanced when H_(2) was added.The presence of NH_(3) augmented the chemical effects of H_(2) on the growth of OH mole fraction.Moreover,the H_(2) chemical effects hindered the production of NO and NO_(2) in the presence of NH_(3).
文摘A new calculating method of aerodynamic heating for unsteady hypersonic aircrafts with complex configuration is presented.This method,which considers the effects of high temperature chemical non-equilibrium and the heat transfer process in thermal protection structure,is based on the combination of the inviscid outerflow solution and the engineering method,where the Euler solver provides the flow parameters on boundary layer edge for engineering method in aerodynamic heating calculation.A high efficient interpolation technique,which can be applied to the fast computation of longtime aerodynamic heating for hypersonic aircraft,is developed for flying trajectory.In this paper,three hypersonic test cases are calculated,and the heat flux and temperature distribution of thermo-protection system are shown.The numerical results show the high efficiency of the developed method and the validation of thermal characteristics analysis on hypersonic aerodynamic heating.
基金supported by two French-Moroccan projects: Volubilis Partenariat Hubert Curien (PHC No.MA 09 205)Projet de Recherches Convention Internationale du CNRS (CNRS-CNRST No.w22572)
文摘We report a simple method for preparing copper(II) molybdate(CuMoO_4) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the(CuMo)-precursor gel was studied by thermogravimetry–differential thermal analysis(TG–DTA), Fourier transform infrared spectroscopy(FTIR), and X-ray diffraction(XRD). We observed that the crystallization of CuMoO_4 powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m^2/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO_4 crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO_4^(2-)] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.
基金supported by grants from National Major Scientific and Technological Specialized Project for “New Drugs Development” (No.2017ZX09301062)
文摘Engelhardia Leschen. ex Blume (Juglandaceae) is native to southern and southeastern Asia and used to be traditional medicines and health tea. Hitherto, a large amount of chemical constituents had been iso- lated from genus Engelhardia and more pharmacological effects were found due to the presence of the second metabolites. There have been few comprehensive reports about Engelhardia plants especially the chemical constituents by now. The traditional usage of Engelhardia plants were for treating cold fever, detoxication, rheumatism, diarrhea, obesity, gastrointestinal problem and so on. While the modern pharmacological activities showed antioxidant activity, anti-ischemialreperfusion injury, anticancer activity, anti-inflammatory activity, immunosuppression activity, antidiabetic activity, antitubercular activity and so on. In this review, constituents of this genus would be introduced and classified by structures, the pharmacological effects of which would be described as well.
基金supported by the National Basic Research Program of China(Grant Nos.2011CBA00103 and 2010CB923003)the National Natural Science Foundation of China
文摘The recent discovery of high-temperature superconductivity in iron-based pnictides (chalcogenides) not only trig- gers tremendous enthusiasm in searching for new superconducting materials, but also opens a new avenue to the study of the Kondo physics. CeFeAsO is a parent compound of the 1111-type iron-based superconductors. It shows 3d- antiferromagnetic (AFM) ordering below 139 K and 4f-AFM ordering below 4 K. On the other hand, the phosphide CeFePO is a ferromagnetically corelated heavy-fermion (HF) metal with Kondo scale TK 10 K. These properties set up a new platform for research of the interplay among magnetism, Kondo effect, and superconductivity (SC). In this review, we present the recent progress in the study of chemical pressure effect in CeFeAsOl_yFy (y = 0 and 0.05). This P/As-doping in CeFeAsO serves as an effective controlling parameter which leads to two magnetic critical points, Xcl -- 0.4 and Xc2 - 0.92, associated with suppression of 3d and 4f magnetism, respectively. We also observe a turning point of AFM-FM ordering of Ce3+ moment at Xc3 - 0.37. The SC is absent in the phase diagram, which is attributed to the destruction to Cooper pair by Ce-FM fluctuations in the vicinity of Xcl. We continue to investigate CeFeAsl-xPxO0.95Fo.os. With the separation of xcl and xc3, this chemical pressure results in a broad SC region 0〈 x 〈 0.53, while the original HF behavior is driven away by 5% F- doping. Different roles of P and F dopings are addressed, and the interplay between SC and Ce-4f magnetism is also discussed.
基金Supported by the Foundation of Educational Ministry of China.
文摘The theory of chemical shift effect of substituent was applied to the assignment of the 13 C NMR spectra of the ethylene/propylene and ethylene/octene 1 copolymers. Using the parameters derived above and the DEPT technique, we then entirely assigned the 13 C NMR spectra of the ethylene/propylene/octene 1 terpolymers synthesized in the presence of the same heterogeneous supported Ziegler Natta catalyst, TiCl 4/MgCl 2/ i Bu 3Al. The present paper also covers the terpolymer composition and the monomer sequence distributions of a series of ethylene/propylene/octene 1 terpolymers.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2014CB921103 and 2013CB921103)the National Natural Science Foundation of China(Grant Nos.11274003 and 91421109)Collaborative Innovation Center of Solid-State Lighting and Energy-Saving Electronics,China
文摘Bi2Se3, as a three-dimensional topological insulator, has attracted worldwide attention for its unique surface states which are protected by time-reversal symmetry. Here we report the synthesis and characterization of high-quality singlecrystalline Bi2Se3 nanowires. Bi2Se3 nanowires were synthesized by chemical vapor deposition(CVD) method via goldcatalyzed vapor-liquid-solid(VLS) mechanism. The structure and morphology were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), x-ray photoelectron spectroscopy(XPS), and Raman spectroscopy. In magnetotransport measurements, the Aharonov–Bohm(AB) effect was observed in a nanowire-based nanodevice, suggesting the existence of surface states in Bi2Se3 nanowires.
基金National Natural Science Foundation of China(52076110,52106160)Jiangsu Provincial Natural Science Foundation of China(BK20200490,BK20220955)Fundamental Research Funds for the Central Universities(30923010208 and 30920031103).
文摘This study aimed to investigate the effects of ammonia addition on ethylene counter-flow diffusion flames with different diluents on the fuel or oxidizer side,using kinetic analyses.A special emphasis was put on assessing the coupled chemical effects of NH_(3) and CO_(2) on C2H4 combustion chemistry.The chemical effects could be evaluated by comparing fictitious inert NH_(3) or CO_(2) with normal active NH_(3) or CO_(2).The results revealed that the addition of NH_(3) decreased the mole fractions and production rates of key soot precursors,such as acetylene,propynyl,and benzene.When CO_(2) was used as the dilution gas,the coupled chemical effects of NH_(3) and CO_(2) were affected by the chemical effects of CO_(2) to varying degrees.With the oxidizer-side CO_(2) addition,the coupled chemical effects of NH_(3) and CO_(2) reduced the mole fractions of H,O,OH radicals,acetylene,propynyl,and benzene,while the effects differed from the fuel-side CO_(2) addition.The coupled chemical effects of NH_(3) and CO_(2) also promoted the formation of aldehyde contaminants,such as acetaldehyde,to some extent,particularly with CO_(2) addition on the oxidizer side.
基金financially supported by the National Natural Science Foundation of China(Nos.60976019 and 61250016)Education Department Program(No.JA12069)and Program for Innovative Research Team in Science and Technology in Fujian Province
文摘Four thiophene derivatives were prepared by replacing the 3,4 positions of thiophene by―OCH3, ―CH3―COOCH3 and ―CN, respectively. The polycondensations via direct arylation took place between the four thiophene derivatives and 2,7-dibromo-9,9-dioctylfluorene under six various catalytic conditions to investigate the substituent effects. The substituent can affect the electron cloud density of the active C―H bond, which can be monitored by the NMR chemical shift. The experimental results show that the reactivity decreases with increasing the chemical shift of active C―H bonds in the four thiophene derivatives, and thus can promote the direct arylation polycondensation. This phenomenon is explained by the electrophilic aromatic substitution(SEAr) mechanism. UV-Visible absorption and photoluminescence were studied to investigate the substituent effect on optical properties of the four copolymers. The results show that these alternating fluorene-thiophene copolymers with different substituents are good fluorescent materials and promising in PLED applications.
基金supported by the National Key Research and Development Program of China(2018YFB0605200)National Natural Science Foundation of China(51822605)the Fundamental Research Funds for the Central Universities(30920031103,30919011284)。
文摘This article compared the pyrolysis characteristics of butene isomer fuels(n-butene,trans-2-butene,isobutene)under CO_(2) atmosphere.The focus of the study was on the impacts of fuels isomerization and CO_(2) chemistry on the formation of important pyrolysis intermediate products under two temperature conditions(at 1273 K and 1573 K).The results demonstrated that at 1273 K,the concentrations of all products in isobutene pyrolysis were significantly lower than those of the corresponding products formed by the pyrolysis of n-butene and trans-2-butene in the process of fuels pyrolysis.The generation or consumption rate of each species was arranged from high to low as n-butene>trans-2-butene>isobutene.At 1573 K,the chemical effect of CO_(2) could inhibit the consumption of ethylene(C_(2)H_(4)),promote the formation of diacetylene(C_(4)H_(2)),and inhibit the formation of acetylene(C_(2)H_(2))and benzene(A_(1)).During the pyrolysis of n-butene at 1573 K,the chemical effect of CO_(2) was mainly reflected in changes of the consumption paths of C_(2)H_(2) and benzyl(A_(1)CH_(2)).For trans-2-butene pyrolysis at 1573 K,CO_(2) addition could change the main consumption paths of methyl(CH_(3)),which then inhibited C_(2)H_(2) formation.In addition,CO_(2) chemical action significantly changed the consumption paths of C_(4)H_(2) and A_(1) in trans-2-butene pyrolysis at 1573 K.As for isobutene pyrolysis at 1573 K,the chemical effect of CO_(2) significantly inhibited the production of A_(1) by changing the main consumption paths of C_(2)H_(2) and propargyl(C_(3)H_(3)).