The three-dimensional(3D)morphology,anatomy,and in-situ chemical composition analysis of fossils are crucial for systematic paleontology and determining their phylogenetic positions.Scanning electron microscopy(SEM)co...The three-dimensional(3D)morphology,anatomy,and in-situ chemical composition analysis of fossils are crucial for systematic paleontology and determining their phylogenetic positions.Scanning electron microscopy(SEM)coupled with energy-dispersive X-ray spectroscopy(EDS),offers valuable structural and chemical information for the analysis of fossils.However,its primary limitation is the restriction to two-dimensional surface data,which limits the exploration of fossils’3D complexities.Conversely,3D X-ray microscopy(3D-XRM),also known as a novel form of micro-computed tomography(micro-CT)facilitates the non-destructive 3D reconstruction of fossil specimens.Nevertheless,it lacks the capability to provide in-situ compositional data.Acknowledging the constraints inherent in these individual techniques,and in response to the evolving requirements of paleontological research,this study introduces an integrated approach that combines 3D-XRM with EDS-coupled focused ion beam scanning electron microscopy(FIB-SEM).This innovative strategy is designed to synergize the advantages of both techniques,thereby addressing challenges that conventional methods cannot.It enables the rapid identification of regions of interest(ROI)within fossil specimens at micrometer resolution.Subsequently,this method collects detailed data on both 3D structures and chemical compositions at the nanometer scale for the identified ROI.This integrated approach represents a significant advancement in paleontological and geological research methodologies,promising to meet the increasing demands of these fields.展开更多
Agrochemicals,especially plant growth regulators(PGRs),are extensively used to modulate endogenous phytohormone signals in small quantities,significantly infiuencing plant growth and development.Plant hormones typical...Agrochemicals,especially plant growth regulators(PGRs),are extensively used to modulate endogenous phytohormone signals in small quantities,significantly infiuencing plant growth and development.Plant hormones typically exhibit diverse chemical structures,with common examples including indole rings,terpenoid frameworks,adenine motifs,cyclic lactones,cyclopentanones,and steroidal compounds,which are extensively employed in pesticides.This article explores the interactions and biological activities of small molecules on proteins,enzymes,and other reactive sites involved in the biosynthesis,metabolism,transport,and signal transduction pathways of various plant hormones.Additionally,it analyzes the structure-activity relationships(SARs)of pesticides incorporating these structural motifs to elucidate the relationship between active fragments,pharmacophores,and targets,highlighting the characteristics of potent small molecules and their derivatives.This comprehensive review aims to provide novel perspectives for the development and design of pesticides,offering valuable insights for researchers in the field.展开更多
This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix wi...This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.展开更多
Polycyclic polyprenylated acylphloroglucinols(PPAPs)represent a distinct subclass of specialized metabolites predominantly found in the plant kingdom,particularly within the Guttiferae(Clusiaceae)family.These compound...Polycyclic polyprenylated acylphloroglucinols(PPAPs)represent a distinct subclass of specialized metabolites predominantly found in the plant kingdom,particularly within the Guttiferae(Clusiaceae)family.These compounds exhibit remarkable structural diversity and a wide range of biological activities.Seco-and nor-PPAPs,two unique variants of PPAPs with diverse skeletal structures,have been extensively investigated.As of June 2023,200 compounds have been isolated from four genera,with Hypericum being the primary source.Notably,115 of these compounds were identified in the past four years,indicating a significant increase in research activity.Seco-and nor-PPAPs can be categorized into six main subgroups based on the original PPAP scaffolds.Biological studies have revealed their potential in various therapeutic applications,including anti-cancer,anti-inflammatory,hepatoprotective,anti-Alzheimer’s disease(anti-AD),multidrug resistance(MDR)reversal,anti-depressant,neuroprotective,and immunosuppressive effects.This review provides a comprehensive overview of the occurrence,structures,and bioactivities of natural seco-and nor-PPAPs,offering valuable insights for the further development of PPAPs.展开更多
The effect of different kinds of comonomers with or without flexible chain on properties of copolyesters, such as transition temperature, crystallization velocity, crystallinity and size Of crystallites, is studied. T...The effect of different kinds of comonomers with or without flexible chain on properties of copolyesters, such as transition temperature, crystallization velocity, crystallinity and size Of crystallites, is studied. The experimental results indicate the obvious difference in properties between comonomers with iso-and ortho-structure of phenyl ring and comonomers with flexible chain. The influence of chemical structure of comonomers on properties of copolyesters is discussed.展开更多
The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film ...The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF2 film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the asdeposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.展开更多
Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-c...Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-char and M-char)and two pulverized coals(H-PCI and P-PCI)were analyzed herein using thermogravimetric analysis–mass spectrometry.The apparent activation energy(Ea)of the sample under non-isothermal combustion conditions was obtained using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods,and the reaction mechanism for the fuels was established using the Malek method.Additionally,changes in the microscopic pore structure and carbon chemical structure of the fuels at different stages of combustion were characterized using N2 adsorption and X-ray diffraction to analyze the relationship between microstructural evolution and Ea.The results suggested that Ea of the sample first rapidly decreased and then became stabilized during combustion.Compared with pulverized coals,the two chars presented more developed micro-scopic pore structure,less-ordered carbon chemical structure and lower Ea during reaction.During combustion,the stacking height of the aromatic layer first decreased and then increased,whereas the specific surface area first increased and then decreased.The volatile content significantly influenced Ea only during the initial stage of combustion.During the middle stage,Ea was controlled more by the microscopic pore structure and the carbon chemical structure,and those influences disappeared in the later stage.The transition point of the structures affecting Ea occurred at a combustion rate between 52.9%and 72.0%.In general,the microscopic pore structure and the carbon chemical structure influenced kinetic parameters more than the volatile content.展开更多
The critical issue in developing mature Oxy-Coal Combustion Steam System technology could be the reactivity of deminer-alized coal which,is closely related to its chemical structure.The chemical structures of Liupansh...The critical issue in developing mature Oxy-Coal Combustion Steam System technology could be the reactivity of deminer-alized coal which,is closely related to its chemical structure.The chemical structures of Liupanshui raw coal(LPS-R)and Liupanshui demineralized coal(LPS-D)were analyzed by FTIR and solid-state 13C-NMR.The pyrolysis experiments were carried out by TG,and the pyrolysis kinetics was analyzed by three iso-conversional methods.FTIR and 13C-NMR results suggested that the carbon structure of LPS coal was not altered greatly,while demineralization promoted the maturity of coal and the condensation degree of the aromatic ring,making the chemical structure of coal more stable.The oxygen-containing functional groups with low bond energy were reduced,and the ratio of aromatic carbon with high bond energy was increased,decreasing the pyrolysis reactivity.DTG curve-fitting results revealed that the thermal weight loss of LPS coal mainly came from the cleavage of aliphatic covalent bonds.By pyrolysis kinetics analysis of LPS-R and LPS-D,the apparent activation energies were 76±4 to 463±5 kJ/mol and 84±2 to 758±12 kJ/mol,respectively,under different conversion rates.The reactivity of the demineralized coal was inhibited to some extent,as the apparent activation energy of pyrolysis for LPS-D increased by acid treatment.展开更多
Two new Components, spiramine N (1) and spiraminol (2) were isolated from Spiraea japonica var. aecuminata Franch. Their structureswere elucidated bychemical and spectxal means.
Natural products provide an important original source of structural diversity for finding new compounds as anti-peptic ulcer drugs. The present review highlights some recent advances on gastro-protective flavonoids, t...Natural products provide an important original source of structural diversity for finding new compounds as anti-peptic ulcer drugs. The present review highlights some recent advances on gastro-protective flavonoids, terpenes, alkaloids, steroids, phenylpropanoids,glycosides and chromenes from natural herbs or traditional medicinal plants, and helps us analyze the structure-activity relationship(SAR) of natural products in healing of peptic ulcer for further drug development.展开更多
The chemical structures of bagasse EMAL （enzymatic hydrolysis/mild acidolysis lignin） were revealed quantitatively with ^31p-NMR, DFRC （derivatization followed by reductive cleavage）. The thermochemical characteri...The chemical structures of bagasse EMAL （enzymatic hydrolysis/mild acidolysis lignin） were revealed quantitatively with ^31p-NMR, DFRC （derivatization followed by reductive cleavage）. The thermochemical characteristics of bagasse and bagasse EMAL were evaluated with thermogravimetry. The results show that bagasse EMAL is mainly formed by the phenolic hydroxyl group of guaiacyl and syringyl units. The DBDO content in bagasse EMAL was found to be 0.180 mmol.g^-1. The decomposition characteristics of bagasse EMAL under elevated temperature were much different from that of bagasse.展开更多
Rational architecture design has turned out to be an effective strategy in improving the electrochemical performance of electrode materials for batteries.However,an elaborate structure that could simultaneously endow ...Rational architecture design has turned out to be an effective strategy in improving the electrochemical performance of electrode materials for batteries.However,an elaborate structure that could simultaneously endow active materials with promoted reaction reversibility,accelerated kinetic and restricted volume change still remains a huge challenge.Herein,a novel chemical interaction motivated structure design strategy has been proposed,and a chemically bonded Co(CO_(3))_(0.5)OH·0.11 H_(2)O@MXene(CoCH@MXene)layered-composite was fabricated for the first time.In such a composite,the chemical interaction between Co^(2+)and MXene drives the growth of smaller-sized CoCH crystals and the subsequent formation of interwoven CoCH wires sandwiched in-between MXene nanosheets.This unique layered structure not only encourages charge transfer for faster reaction dynamics,but buffers the volume change of CoCH during lithiation-delithiation process,owing to the confined crystal growth between conductive MXene layers with the help of chemical bonding.Besides,the sandwiched interwoven CoCH wires also prevent the stacking of MXene layers,further conducive to the electrochemical performance of the composite.As a result,the as-prepared CoCH@MXene anode demonstrates a high reversible capacity(903.1 mAh g^(-1)at 100 mA g^(-1))and excellent cycling stability(maintains 733.6 mAh g^(-1)at1000 mA g^(-1)after 500 cycles)for lithium ion batteries.This work highlights a novel concept of layerby-layer chemical interaction motivated architecture design for futuristic high performance electrode materials in energy storage systems.展开更多
For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during...For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.展开更多
The chemical structure of an exopolysaccharide (EPS) produced by Sorangium cellulosum NUST06 was investigated. The EPS was found to have molecular masses greater than 2?106 Da, and consisted of D-glucose, D-mannose an...The chemical structure of an exopolysaccharide (EPS) produced by Sorangium cellulosum NUST06 was investigated. The EPS was found to have molecular masses greater than 2?106 Da, and consisted of D-glucose, D-mannose and D-glucuronic acid in a ratio of 5:4:1. The analytical results of methylation and nuclear magnetic resonance spectra suggested the EPS consist of following tetrasaccharide repeating units: 4) -b-D-Glup (1 4)- b-D-Glup (1 4) -b-D-Glup (1 a-D-GluAp (1 6) a-D-manp (1 6)-a-D-manp (1 6) (6) (4) (4) ↑ ↑ ↑ Me Ac Ac展开更多
The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, e...The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, especially, Cu-Sb-No three center conjugated π bonds and No-St-No conjugated π bonds were accounted for.展开更多
A new polysaccharide,GBW was obtained homogeneous as determined by HPLC from the roots of Glycyrrhizia uralensis Fisch. The molecular weight was estimated to be 4000. The component sugar was identified as glucose only...A new polysaccharide,GBW was obtained homogeneous as determined by HPLC from the roots of Glycyrrhizia uralensis Fisch. The molecular weight was estimated to be 4000. The component sugar was identified as glucose only. The specific rotation [α]^(28)_D (C=0.1,H_2O) was +1200. The α-configuration was established by IR and ^(13)C NMR. Methylation analysis, periodate oxidation, Smith degradation, partial hydrolysis, KI-I_2 reaction and ^(13)C NMR showed that GBW is a new (1→4)linked linear α-D-glucan. The structure is shown as 1.展开更多
A novel alkaloid named Hypodemapyrazine was isolated from the whole plantof a fern, Hypodematium sinense Iwatsuki. Its chemical structure has been elucidated to be a novel skeleton containing a hydro-pyrazine by means...A novel alkaloid named Hypodemapyrazine was isolated from the whole plantof a fern, Hypodematium sinense Iwatsuki. Its chemical structure has been elucidated to be a novel skeleton containing a hydro-pyrazine by means of UV, IR, ~1H-NMR, ^(13)C-NMR and HRMS spectroscopy.展开更多
MAX phase ceramics is a large family of nanolaminate carbides and nitrides,which integrates the advantages of both metals and ceramics,in general,the distinct chemical inertness of ceramics and excellent physical prop...MAX phase ceramics is a large family of nanolaminate carbides and nitrides,which integrates the advantages of both metals and ceramics,in general,the distinct chemical inertness of ceramics and excellent physical properties like metals.Meanwhile,the rich chemical and structural diversity of the MAXs endows them with broad space for property regulation.Especially,a much higher self-lubricity,as well as wear resistance,than that of traditional alloys and ceramics,has been observed in MAXs at elevated temperatures in recent decades,which manifests a great application potential and sparks tremendous research interest.Aiming at establishing a correlation among structure,chemical composition,working conditions,and the tribological behaviors of MAXs,this work overviews the recent progress in their high-temperature(HT)tribological properties,accompanied by advances in synthesis and structure analysis.HT tribological-specific behaviors,including the stress responses and damage mechanism,oxidation mechanism,and wear mechanism,are discussed.Whereafter,the tribological behaviors along with factors related to the tribological working conditions are discussed.Accordingly,outlooks of MAX phase ceramics for future HT solid lubricants are given based on the optimization of present mechanical properties and processing technologies.展开更多
Viburnum dilatatum(jiami in Chinese),belonging to the Caprifollaceae family,is widely distributed in Japan and China.Phytochemical investigations of Viburnum dilatatum(V.dilatatum)have resulted in the isolation of tri...Viburnum dilatatum(jiami in Chinese),belonging to the Caprifollaceae family,is widely distributed in Japan and China.Phytochemical investigations of Viburnum dilatatum(V.dilatatum)have resulted in the isolation of triterpenoids,phenolic glycosides essential oil,norisoprenoids,etc.Research results have shown that the chemical constituents of V.dilatatum possess various pharmacological activities,including antihyperglycemic,antioxidant activity and antiulcer effects.This study reviewed the chemical constituents and pharmacological activities of V.dilatatum to provide practical and useful information for further research and development of this plant.展开更多
The program system described in this paper is a microcomputer analytic system for X-ray crystal structure used in chemical laboratories.The abbreviated name is NOMCSDP.NOMCSDP has been developed on the basis of NRCVAX...The program system described in this paper is a microcomputer analytic system for X-ray crystal structure used in chemical laboratories.The abbreviated name is NOMCSDP.NOMCSDP has been developed on the basis of NRCVAX and SHELXS-86.It is a software for X- ray crystal structure analysis of organic molecules,especially natural organic molecules(1-7).展开更多
基金founded by the National Natural Science Foundation of China(No.42022010)the National Key Research and Development Program of China(No.2022YFF0800100)the CAS Interdisciplinary Innovation Team(No.JCTD-2020-18)and the Youth Innovation Promotion Association.
文摘The three-dimensional(3D)morphology,anatomy,and in-situ chemical composition analysis of fossils are crucial for systematic paleontology and determining their phylogenetic positions.Scanning electron microscopy(SEM)coupled with energy-dispersive X-ray spectroscopy(EDS),offers valuable structural and chemical information for the analysis of fossils.However,its primary limitation is the restriction to two-dimensional surface data,which limits the exploration of fossils’3D complexities.Conversely,3D X-ray microscopy(3D-XRM),also known as a novel form of micro-computed tomography(micro-CT)facilitates the non-destructive 3D reconstruction of fossil specimens.Nevertheless,it lacks the capability to provide in-situ compositional data.Acknowledging the constraints inherent in these individual techniques,and in response to the evolving requirements of paleontological research,this study introduces an integrated approach that combines 3D-XRM with EDS-coupled focused ion beam scanning electron microscopy(FIB-SEM).This innovative strategy is designed to synergize the advantages of both techniques,thereby addressing challenges that conventional methods cannot.It enables the rapid identification of regions of interest(ROI)within fossil specimens at micrometer resolution.Subsequently,this method collects detailed data on both 3D structures and chemical compositions at the nanometer scale for the identified ROI.This integrated approach represents a significant advancement in paleontological and geological research methodologies,promising to meet the increasing demands of these fields.
基金The financial support from the National Key Research and Development Program of China(No.2023YFD1700600)。
文摘Agrochemicals,especially plant growth regulators(PGRs),are extensively used to modulate endogenous phytohormone signals in small quantities,significantly infiuencing plant growth and development.Plant hormones typically exhibit diverse chemical structures,with common examples including indole rings,terpenoid frameworks,adenine motifs,cyclic lactones,cyclopentanones,and steroidal compounds,which are extensively employed in pesticides.This article explores the interactions and biological activities of small molecules on proteins,enzymes,and other reactive sites involved in the biosynthesis,metabolism,transport,and signal transduction pathways of various plant hormones.Additionally,it analyzes the structure-activity relationships(SARs)of pesticides incorporating these structural motifs to elucidate the relationship between active fragments,pharmacophores,and targets,highlighting the characteristics of potent small molecules and their derivatives.This comprehensive review aims to provide novel perspectives for the development and design of pesticides,offering valuable insights for researchers in the field.
基金supported by the National Magnetic Con-finement Fusion Energy Research Project from the Ministry of Science and Technology of China(No.2022YFE03030004 and 2019YFE03120003)the National Natural Science Foundation of China(No.12275010,12275176,12275001,12335017,11921006,U21B2082,U22B2064 and U20B2025)+3 种基金the Beijing Municipal Natural Science Foundation(No.1222023)the Shenzhen Science and Technology Program(No.RCYX20210609103904028)Engang Fu acknowledges the support from the Science Fund or Creative Research Groups of NSFC,the Ion Beam Materials Laboratory(IBML)and Electron Microscopy Laboratory(EML)the High-performance Computing Platform(HPC)at Peking University.Xing Liu acknowledges the discussion with Prof.Ning Gao and Dr.Yifan Zhang.
文摘This study reports the response of helium(He)ion irradiation on binary-phase structured alloy V_(34)Ti_(25)Cr_(10)Ni_(30)Pd1.The alloy consists of a VCr matrix with nano-sized TiNi precipitates and a B2 TiNi matrix with nano-sized VCr precipitates.VCr is chemical-disordered and TiNi has a B2-ordered structure.The alloy was subjected to 400 keV He ion irradiation with a fluence of 1×10^(17)ions cm^(−2)at 450℃.The results show He bubbles within the chemical-disordered VCr matrix exhibit a near-spherical shape with a smaller size and higher density compared to that in chemical-ordered TiNi phase with a larger size,lower density,and faceted shape.This indicates the chemical-disordered VCr phase effectively suppresses He accumulation compared to the B2-ordered TiNi phase,emphasizing the dominance of chemical struc-tures in He bubble formation.The calculation of density functional theory(DFT)shows that Ti and Ni have lower vacancy formation energy than that of V and Cr,respectively,which results in the increased vacancy production in TiNi.Consequently,He bubbles in TiNi have a larger bubble size consistent with experimental observations of radiation-induced Ni segregation.These findings elucidate the roles of or-dered and disordered chemical structures in He bubble evolution,offering insights for the development of gas ion irradiation-resistant materials.
基金supported by the National Natural Science Foundation for Distinguished Young Scholars(No.81725021)the National Natural Science Foundation of China(Nos.82003633,32100321,and 32300335)+1 种基金the National Natural Science Foundation of Hubei Province(Nos.2023AFB791 and 2023AFB530)the Knowledge Innovation Project of Wuhan Science and Technology Bureau(No.2023020201020534).
文摘Polycyclic polyprenylated acylphloroglucinols(PPAPs)represent a distinct subclass of specialized metabolites predominantly found in the plant kingdom,particularly within the Guttiferae(Clusiaceae)family.These compounds exhibit remarkable structural diversity and a wide range of biological activities.Seco-and nor-PPAPs,two unique variants of PPAPs with diverse skeletal structures,have been extensively investigated.As of June 2023,200 compounds have been isolated from four genera,with Hypericum being the primary source.Notably,115 of these compounds were identified in the past four years,indicating a significant increase in research activity.Seco-and nor-PPAPs can be categorized into six main subgroups based on the original PPAP scaffolds.Biological studies have revealed their potential in various therapeutic applications,including anti-cancer,anti-inflammatory,hepatoprotective,anti-Alzheimer’s disease(anti-AD),multidrug resistance(MDR)reversal,anti-depressant,neuroprotective,and immunosuppressive effects.This review provides a comprehensive overview of the occurrence,structures,and bioactivities of natural seco-and nor-PPAPs,offering valuable insights for the further development of PPAPs.
文摘The effect of different kinds of comonomers with or without flexible chain on properties of copolyesters, such as transition temperature, crystallization velocity, crystallinity and size Of crystallites, is studied. The experimental results indicate the obvious difference in properties between comonomers with iso-and ortho-structure of phenyl ring and comonomers with flexible chain. The influence of chemical structure of comonomers on properties of copolyesters is discussed.
基金financially supported by the Research Fund of the State Key Laboratory of Solidification Processing,Northwestern Polytechnical University,China(Grant No.155-QP-2016)the Fundamental Research Funds for the Central Universities(No.3102014JCQ01032)the 111 Project(No.B08040)
文摘The chemical structures, optical properties and laser-induced damage thresholds of magnesium fluoride films annealed at different temperatures were investigated. The results showed that the stoichiometry of MgF2 film changed a little with the increase in annealing temperature. Analysis of the optical properties indicated that excellent antireflection behavior of the film in the range of 200-400 nm can be obtained by the samples coated with MgF2 film. The refractive index increased and the extinction coefficient decreased with increasing annealing temperature. Compared with the asdeposited films, the laser-induced damage threshold was improved after annealing process and decreased with the increase in annealing temperature, which was probably due to the denser film and more absorption centers under higher annealing temperature.
基金the National Natural Science Foundation of China(Nos.51704224 and 51574189)the Natural Science Foundation of Shaanxi,China(No.2016JQ5041)the Ministry of Education Services Local Scientific Research Program,Shaanxi,China(No.201刀F012),and Yulin Government of Science and Technology.
文摘Pyrolysis chars have potential as fuels for pulverized coal injection(PCI);however,their proper and efficient utilization requires evaluation of char combustion kinetics.The combustion characteristics of two chars(F-char and M-char)and two pulverized coals(H-PCI and P-PCI)were analyzed herein using thermogravimetric analysis–mass spectrometry.The apparent activation energy(Ea)of the sample under non-isothermal combustion conditions was obtained using the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods,and the reaction mechanism for the fuels was established using the Malek method.Additionally,changes in the microscopic pore structure and carbon chemical structure of the fuels at different stages of combustion were characterized using N2 adsorption and X-ray diffraction to analyze the relationship between microstructural evolution and Ea.The results suggested that Ea of the sample first rapidly decreased and then became stabilized during combustion.Compared with pulverized coals,the two chars presented more developed micro-scopic pore structure,less-ordered carbon chemical structure and lower Ea during reaction.During combustion,the stacking height of the aromatic layer first decreased and then increased,whereas the specific surface area first increased and then decreased.The volatile content significantly influenced Ea only during the initial stage of combustion.During the middle stage,Ea was controlled more by the microscopic pore structure and the carbon chemical structure,and those influences disappeared in the later stage.The transition point of the structures affecting Ea occurred at a combustion rate between 52.9%and 72.0%.In general,the microscopic pore structure and the carbon chemical structure influenced kinetic parameters more than the volatile content.
基金supported by the National Natural Science Foundation of China (51536002)the Fundamental Research Funds for the Central Universities (2015QNA12)the Open Sharing Fund for the Large-scale Instruments and Equipments of China University of Mining and Technology (CUMT).
文摘The critical issue in developing mature Oxy-Coal Combustion Steam System technology could be the reactivity of deminer-alized coal which,is closely related to its chemical structure.The chemical structures of Liupanshui raw coal(LPS-R)and Liupanshui demineralized coal(LPS-D)were analyzed by FTIR and solid-state 13C-NMR.The pyrolysis experiments were carried out by TG,and the pyrolysis kinetics was analyzed by three iso-conversional methods.FTIR and 13C-NMR results suggested that the carbon structure of LPS coal was not altered greatly,while demineralization promoted the maturity of coal and the condensation degree of the aromatic ring,making the chemical structure of coal more stable.The oxygen-containing functional groups with low bond energy were reduced,and the ratio of aromatic carbon with high bond energy was increased,decreasing the pyrolysis reactivity.DTG curve-fitting results revealed that the thermal weight loss of LPS coal mainly came from the cleavage of aliphatic covalent bonds.By pyrolysis kinetics analysis of LPS-R and LPS-D,the apparent activation energies were 76±4 to 463±5 kJ/mol and 84±2 to 758±12 kJ/mol,respectively,under different conversion rates.The reactivity of the demineralized coal was inhibited to some extent,as the apparent activation energy of pyrolysis for LPS-D increased by acid treatment.
文摘Two new Components, spiramine N (1) and spiraminol (2) were isolated from Spiraea japonica var. aecuminata Franch. Their structureswere elucidated bychemical and spectxal means.
基金supported by the National Natural Science Foundation of China(No.21272136)Youth Talent Development Foundation of China Three Gorges University
文摘Natural products provide an important original source of structural diversity for finding new compounds as anti-peptic ulcer drugs. The present review highlights some recent advances on gastro-protective flavonoids, terpenes, alkaloids, steroids, phenylpropanoids,glycosides and chromenes from natural herbs or traditional medicinal plants, and helps us analyze the structure-activity relationship(SAR) of natural products in healing of peptic ulcer for further drug development.
基金The authors are grateful for the financial support of this research from the National Natural Science Foundation of China(No.30371138 and 20576043)the Visiting Scholarship Grant from the Key Laboratory of Lignocellulosics Chemistry,Chinese Academy of Sciences(No.109).
文摘The chemical structures of bagasse EMAL （enzymatic hydrolysis/mild acidolysis lignin） were revealed quantitatively with ^31p-NMR, DFRC （derivatization followed by reductive cleavage）. The thermochemical characteristics of bagasse and bagasse EMAL were evaluated with thermogravimetry. The results show that bagasse EMAL is mainly formed by the phenolic hydroxyl group of guaiacyl and syringyl units. The DBDO content in bagasse EMAL was found to be 0.180 mmol.g^-1. The decomposition characteristics of bagasse EMAL under elevated temperature were much different from that of bagasse.
基金financially supported by the National Natural Science Foundation of China(No.51933007,No.51673123 and No.22005346)the National Key R&D Program of China(No.2017YFE0111500)+1 种基金the State Key Laboratory of Polymer Materials Engineering(Grant No.:sklpme2020-1-02)Financial support provided by the Fundamental Research Funds for the Central Universities(No.YJ202118)。
文摘Rational architecture design has turned out to be an effective strategy in improving the electrochemical performance of electrode materials for batteries.However,an elaborate structure that could simultaneously endow active materials with promoted reaction reversibility,accelerated kinetic and restricted volume change still remains a huge challenge.Herein,a novel chemical interaction motivated structure design strategy has been proposed,and a chemically bonded Co(CO_(3))_(0.5)OH·0.11 H_(2)O@MXene(CoCH@MXene)layered-composite was fabricated for the first time.In such a composite,the chemical interaction between Co^(2+)and MXene drives the growth of smaller-sized CoCH crystals and the subsequent formation of interwoven CoCH wires sandwiched in-between MXene nanosheets.This unique layered structure not only encourages charge transfer for faster reaction dynamics,but buffers the volume change of CoCH during lithiation-delithiation process,owing to the confined crystal growth between conductive MXene layers with the help of chemical bonding.Besides,the sandwiched interwoven CoCH wires also prevent the stacking of MXene layers,further conducive to the electrochemical performance of the composite.As a result,the as-prepared CoCH@MXene anode demonstrates a high reversible capacity(903.1 mAh g^(-1)at 100 mA g^(-1))and excellent cycling stability(maintains 733.6 mAh g^(-1)at1000 mA g^(-1)after 500 cycles)for lithium ion batteries.This work highlights a novel concept of layerby-layer chemical interaction motivated architecture design for futuristic high performance electrode materials in energy storage systems.
基金This project is supported by National Natural Science Foundation of China(No. 50544025)Natural Science Foundation of High Education of Jiangsu Province, China (No. 05KJB460030)
文摘For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.
文摘The chemical structure of an exopolysaccharide (EPS) produced by Sorangium cellulosum NUST06 was investigated. The EPS was found to have molecular masses greater than 2?106 Da, and consisted of D-glucose, D-mannose and D-glucuronic acid in a ratio of 5:4:1. The analytical results of methylation and nuclear magnetic resonance spectra suggested the EPS consist of following tetrasaccharide repeating units: 4) -b-D-Glup (1 4)- b-D-Glup (1 4) -b-D-Glup (1 a-D-GluAp (1 6) a-D-manp (1 6)-a-D-manp (1 6) (6) (4) (4) ↑ ↑ ↑ Me Ac Ac
文摘The canonical and locatized molecutar orbiters of [NCCuS_2NoS_2]^(2-) cluster were calculated by means of CNDO quantum chemistry method. Then the energy and properties of corresponding chemicat bonds were discussed, especially, Cu-Sb-No three center conjugated π bonds and No-St-No conjugated π bonds were accounted for.
文摘A new polysaccharide,GBW was obtained homogeneous as determined by HPLC from the roots of Glycyrrhizia uralensis Fisch. The molecular weight was estimated to be 4000. The component sugar was identified as glucose only. The specific rotation [α]^(28)_D (C=0.1,H_2O) was +1200. The α-configuration was established by IR and ^(13)C NMR. Methylation analysis, periodate oxidation, Smith degradation, partial hydrolysis, KI-I_2 reaction and ^(13)C NMR showed that GBW is a new (1→4)linked linear α-D-glucan. The structure is shown as 1.
文摘A novel alkaloid named Hypodemapyrazine was isolated from the whole plantof a fern, Hypodematium sinense Iwatsuki. Its chemical structure has been elucidated to be a novel skeleton containing a hydro-pyrazine by means of UV, IR, ~1H-NMR, ^(13)C-NMR and HRMS spectroscopy.
基金National Natural Science Foundation ofChina,Grant/Award Number:52275212Fundamental Research Funds for theCentral Universities,Grant/Award Number:D5000230047the"Special Lubrication and Sealing forAerospace"Shaanxi Provincial Scienceand Technology Innovation Team,Grant/Award Number:2024RS-CXTD-63。
文摘MAX phase ceramics is a large family of nanolaminate carbides and nitrides,which integrates the advantages of both metals and ceramics,in general,the distinct chemical inertness of ceramics and excellent physical properties like metals.Meanwhile,the rich chemical and structural diversity of the MAXs endows them with broad space for property regulation.Especially,a much higher self-lubricity,as well as wear resistance,than that of traditional alloys and ceramics,has been observed in MAXs at elevated temperatures in recent decades,which manifests a great application potential and sparks tremendous research interest.Aiming at establishing a correlation among structure,chemical composition,working conditions,and the tribological behaviors of MAXs,this work overviews the recent progress in their high-temperature(HT)tribological properties,accompanied by advances in synthesis and structure analysis.HT tribological-specific behaviors,including the stress responses and damage mechanism,oxidation mechanism,and wear mechanism,are discussed.Whereafter,the tribological behaviors along with factors related to the tribological working conditions are discussed.Accordingly,outlooks of MAX phase ceramics for future HT solid lubricants are given based on the optimization of present mechanical properties and processing technologies.
文摘Viburnum dilatatum(jiami in Chinese),belonging to the Caprifollaceae family,is widely distributed in Japan and China.Phytochemical investigations of Viburnum dilatatum(V.dilatatum)have resulted in the isolation of triterpenoids,phenolic glycosides essential oil,norisoprenoids,etc.Research results have shown that the chemical constituents of V.dilatatum possess various pharmacological activities,including antihyperglycemic,antioxidant activity and antiulcer effects.This study reviewed the chemical constituents and pharmacological activities of V.dilatatum to provide practical and useful information for further research and development of this plant.
文摘The program system described in this paper is a microcomputer analytic system for X-ray crystal structure used in chemical laboratories.The abbreviated name is NOMCSDP.NOMCSDP has been developed on the basis of NRCVAX and SHELXS-86.It is a software for X- ray crystal structure analysis of organic molecules,especially natural organic molecules(1-7).
