Recent development in the modification of ceria-based catalysts for exhaust gas treatment was reviewed with the dependence of redox properties on structural characters of materials. The doping of ceria with different ...Recent development in the modification of ceria-based catalysts for exhaust gas treatment was reviewed with the dependence of redox properties on structural characters of materials. The doping of ceria with different cations such as rare earth or transition metal oxides results in improvement of structural stability, catalytic function and resistance to sintering at high temperatures. Aging and reduction treatment at high temperatures promote ceria reduction and is beneficial for oxygen storage capacity of the three-way catalysts. Chemical filing technique is very effective in modifying the redox property in the low temperature regions.展开更多
Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures （commonly reffered to as, laser induced periodic surfac...Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures （commonly reffered to as, laser induced periodic surface structures, LIPSS）. The purpose of the present investigations is to explore the effect of fsec laser fluence and ambient environments （Vacuum ＆ 02） on the formation of LIPSS and conical structures on the Ti surface. The surface morphology was investigated by scanning electron microscope （SEM）. The ablation threshold with single and multiple （N = 100） shots and the existence of an incubation effect was demonstrated by SEM investigations for both the vacuum and the 02 environment. The phase analysis and chemical composition of the exposed targets were performed by x-ray diffraction （XRD） and energy dispersive x-ray spectroscopy （EDS）, respectively. SEM investigations reveal the formation of LIPSS （nano ＆ micro）. FFT d-spacing calculations illustrate the dependence of periodicity on the fluence and ambient environment. The periodicity of nano-scale LIPSS is higher in the case of irradiation under vacuum conditions as compared to 02. Furthermore, the 02 environment reduces the ablation threshold. XRD data reveal that for the 02 environment, new phases （oxides of Ti） are formed. EDS analysis exhibits that after irradiation under vacuum conditions, the percentage of impurity element （A1） is reduced. The irradiation in the 02 environment results in 15% atomic diffusion of oxygen.展开更多
Natural steroids have been showing notable cytotoxic activities, which are quite interesting lead compounds for the development of anticancer drug including estramustine and prednimustine. Considering that these semi-...Natural steroids have been showing notable cytotoxic activities, which are quite interesting lead compounds for the development of anticancer drug including estramustine and prednimustine. Considering that these semi-synthetic molecules are nitrogen mustard functionalized steroidal derivatives, the present review is focused on the methodologies of introducing nitrogen atom or nitrogen-containing heterocycles on A^D rings or side chains of steroids, and analysis of the structure-activity relationship（SAR） for these man-made cytotoxic steroids.展开更多
Sensitivity analysis and structural modification techniques are used to investigate the structural modifications of a machine gun tripod which suffers from severe vibration during firing due to the resonance. The fini...Sensitivity analysis and structural modification techniques are used to investigate the structural modifications of a machine gun tripod which suffers from severe vibration during firing due to the resonance. The finite element analysis and modal test techniques are used to determine the natural frequencies of the machine gun. The sensitivities of natural frequencies with respect to the structural parameters of the tripod are obtained by the method of sensitivity analysis, and they can be used as an indication for the structural modification of the tripod so as to shift the natural frequencies effectively. By the structural modification techniques, finally, the optimal structural modifications of the tripod for desired natural frequencies are made to avoid the resonance, and this optimal structural modification is verified by re-analysis of the modified structure and the vibration contrast between original structure and modified structure. The research resulted in a successful structural modification for desired natural frequencies, which can avoid the resonance and thereby greatly improve the shooting precision of the machine gun during firing.展开更多
Work-hardening behaviour of type 316 austenitic stainless steel having difFerent initial dislocation structures introduced by swaging to various levels is analysed by a simplified Kock's model which takes into acc...Work-hardening behaviour of type 316 austenitic stainless steel having difFerent initial dislocation structures introduced by swaging to various levels is analysed by a simplified Kock's model which takes into account the structural changes through the dislocation accumulation and annihilation process during deformation. The dislocation accumulation and annihilation factors show a temperature and structure dependence. The dislocation annihilation factor shows a plateau or decreasing tendency in the dynamic strain ageing (DSA) temperature range. This is attributed as either due to dislocation accumulation being more pronounced than dislocation annihilation or as due to precipitates being formed at DSA temperatures acting as obstacles to dislocation motion in the DSA temperature range.展开更多
This paper reviews recent progress in the structural modification and activities on Panax notoginseng saponins(PNS).PNS can not only improve the function of cardio-cerebral system,central nervous system and immune sys...This paper reviews recent progress in the structural modification and activities on Panax notoginseng saponins(PNS).PNS can not only improve the function of cardio-cerebral system,central nervous system and immune system,but also reveal anticancer,anti-aging and anti-oxidation activities.In order to solve the problem of low bioavailability and poor absorbability of PNS in vivo,usually,the researchers modified the structure of PNS with three methods:glycoside cleavage(including acid hydrolysis,sulfation,etc.),biotransformation method(including enzyme hydrolysis,microbial transformation)and combinatorial chemical method.It was found that the structural modification sites of PNS were single,mainly aimed at C-3,C-6 and C-20,which provided a new perspective for the structural modification of PNS.Therefore,structural modification on PNS with high yield and ready availability are significant in the discovery of new active ingredients and industrialization.Derivatives of PNS are applied to research of structure-activity relationship,which is beneficial to the development of new medicines.展开更多
Oleanolic acid(OA),a pentacyclic triterpenoid,exhibits a broad spectrum of biological activities,including antitumor,antiviral,antibacterial,anti-inflammatory,hepatoprotective,hypoglycemic,and hypolipidemic effects.Si...Oleanolic acid(OA),a pentacyclic triterpenoid,exhibits a broad spectrum of biological activities,including antitumor,antiviral,antibacterial,anti-inflammatory,hepatoprotective,hypoglycemic,and hypolipidemic effects.Since its initial isolation and identification,numerous studies have reported on the structural modifications and pharmacological activities of OA and its derivatives.Despite this,there has been a dearth of comprehensive reviews in the past two decades,leading to challenges in subsequent research on OA.Based on the main biological activities of OA,this paper comprehensively summarized the modification strategies and structureactivity relationships(SARs)of OA and its derivatives to provide valuable reference for future investigations into OA.展开更多
To date,extensively high demand for hydrogen peroxide(H_(2)O_(2))has been predominantly supplied by the anthraquinone process for several worldwide applications,encompassing wastewater treatment,environmental remediat...To date,extensively high demand for hydrogen peroxide(H_(2)O_(2))has been predominantly supplied by the anthraquinone process for several worldwide applications,encompassing wastewater treatment,environmental remediation,and chemical synthesis.However,the compacted manufacturing,massive energy input and the release of tremendous wastes have restricted commercialization feasibility.Regards to mitigate such issues,the photocatalytic H_(2)O_(2)production by utilizing g-C_(3)N_(4)catalysts has endowed a greener,sustainable and promising alternative,considering that it involves water and oxygen as reactants in the present of sunlight as energy input.Herein,we have manifested a comprehensive overview of the research progress for g-C_(3)N_(4)-based semiconductors for photocatalytic H_(2)O_(2)generation.This review has systematically elucidated state-of-the-art development of different modifications on g-C_(3)N_(4)to unravel the fundamental mechanism of H_(2)O_(2)evolution via oxygen reduction reaction(ORR)and water oxidation reaction(WOR).In addition,the contribution made by vacancy introduction,doping,heterogenization,and co-catalyst passivation with respect to photoefficiency enhancement have been clarified.Furthermore,the current challenges and perspective of future development directions on photocatalytic H_(2)O_(2)production have also been highlighted.As such,g-C_(3)N_(4)stands as the next step toward advancement in the configuration and modulation of high-efficiency photocatalysts.展开更多
Parthenolide(PTL)is a sesquiterpene lactone derived from medicinal plant feverfew(Tanacetum parthenium).Recent studies have demonstrated that it has multiple pharmacological activities,especially in the treatment of v...Parthenolide(PTL)is a sesquiterpene lactone derived from medicinal plant feverfew(Tanacetum parthenium).Recent studies have demonstrated that it has multiple pharmacological activities,especially in the treatment of various hematological and solid cancers.The superior anticancer activity of PTL suggests that it has the potential to be a first-line drug.However,due to the limited physical and chemical properties,as well as bioavailability,structural modification strategies are strongly recommended to improve the anticancer activity.This review describes representative PTL derivatives obtained by different modification strategies,which are reported to exert antiproliferative activities superior to the parent compound PTL.Furthermore,we also summarize their basic mechanisms on cancer-related signaling pathways,so as to explain the potential and characteristics of PTL and its derivatives in cancer therapy.展开更多
The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of...The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions,it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn^(3+).Herein,the selective substitution of Cr by Zr in Na_(4)MnCr(PO_(4))_(3)was explored to enhance the structural stability,due to the pinning effect of Zr ions and the≈2.9-electron reactions,as-prepared Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C delivers a high capacity retention of 85.94%over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g^(-1)at 0.1 C,enabling the stable energy output as high as 555.2 Wh kg^(-1).Moreover,during the whole charge/discharge process,a small volume change of only 6.7%was verified by in situ X-ray diffraction,and the reversible reactions of Cr^(3+)/Cr^(4+),Mn^(3+)/Mn^(4+),and Mn^(2+)/Mn^(3+)redox couples were identified via ex situ X-ray photoelectron spectroscopy analyses.Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C electrode.This work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.展开更多
Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors ...Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors on the epoxidation of three unsaturated natural products were investigated by orthogonal design.Results The experimental results show that three unsaturated natural products are oxidized to the corresponding epoxides with hydrogen peroxide in the presence of 10%(mol/mol) of iodine at room temperature in high yields.Conclusion Iodine was found to be an efficient catalyst for the epoxidation of carbon-carbon double bonds in some unsaturated natural products with hydrogen peroxide at room temperature.展开更多
Regulation of optical properties and electronic structure of graphitic carbon nitride （g-C3N4 ） via external strain has attracted much attention due to its potential in photocatalyst and electronic devices. However,...Regulation of optical properties and electronic structure of graphitic carbon nitride （g-C3N4 ） via external strain has attracted much attention due to its potential in photocatalyst and electronic devices. However, the identifi- cation of g-C3N4 structure transformation induced by strain is greatly lacking. In this work, the Raman spectra of g-C3N4 with external strain are determined theoretically based on the density function theory. Deformation induced by external strain not only regulates the Raman mode positions but also leads to a I^aman mode split- ting, which can be ascribed to crystal symmetry destruction by strain engineering. Our results suggest the use of Raman scattering in structural identification in deformed 9-C3N4 structure.展开更多
Objective To study mechanism of various effects of HLA antigen camouflaged by differentmPEGs. Methods Effects of the modification of HLA antigen camouflaged by various mPEGs were detected by microlymphocytotoxicity te...Objective To study mechanism of various effects of HLA antigen camouflaged by differentmPEGs. Methods Effects of the modification of HLA antigen camouflaged by various mPEGs were detected by microlymphocytotoxicity test. The ability of modification was detected by SDS-PAGE. The mechanism of the modification was depicted by the three-dimensional structure of HLA antigen. Results The specific reaction between HLA-A2 antigen and its antibody were completely blocked by mPEG-BTC and mPEG-SPA. mPEG-MAL did not camouflage HLA antigen. The diversity of the modification of HLA antigen camouflaged by varied mPEGs was closely associated with the amides displayed on the surface of HLA antigen. Conclusion Only the amides which were exposed to the surface of HLA antigen can be camouflaged by mPEG. The amides on the surface of three-dimensional structure of HLA-A2 antigen determine the effect of the modification by various mPEGs.展开更多
High-temperature proton exchange membranes(HT-PEMs) possess excellent thermal and outstanding electrochemical stability, providing an avenue to realize high-temperature proton exchange membranes fuel cells(HT-PEMFCs) ...High-temperature proton exchange membranes(HT-PEMs) possess excellent thermal and outstanding electrochemical stability, providing an avenue to realize high-temperature proton exchange membranes fuel cells(HT-PEMFCs) with both superior power density and long-term durability. Unfortunately, polybenzimidazole(PBI), a typical material for conventional HT-PEMs, fails to compromise the high nonaqueous proton conductivity and high mechanical properties, thus hindering their practical applications.Achieving efficient nonaqueous proton conduction is crucial for HT-PEMFC, and many insightful research works have been done in this area. However, there still lacks a report that integrates the host-guest interactions of phosphoric acid doping and the structural stability of polymers to systematically illustrate modification strategies. Here, we summarize recent advancements in enhancing the nonaqueous proton conduction of HT-PEMs. Various polymer structure modification strategies, including main chain and side group modification, cross-linking, blocking, and branching, are reviewed. Composite approaches of polymer, including compounding with organic porous polymers, filling the inorganic components and modifying with ionic liquids, etc., are also covered in this work. These strategies endow the HT-PEMs with more free volume, nanophase-separated structure, and multi-stage proton transfer channels, which can facilitate the proton transportation and improve their performance. Finally, current challenges and future directions for further enhancements are also outlined.展开更多
The relationships between the structure of oxime compounds(R^(1)R^(2)C=NOH,R^(1)/R^(2)=alkyl groups) with different substituents and their corresponding flotation performances were studied. The analyses of density fun...The relationships between the structure of oxime compounds(R^(1)R^(2)C=NOH,R^(1)/R^(2)=alkyl groups) with different substituents and their corresponding flotation performances were studied. The analyses of density functional theory(DFT) calculations illustrated that the introduced phenyl group at the R^(1) position could enhance the acidity,while the heptyl group could effectively increase the hydrophobicity and benefit van der Waals interactions. Meanwhile,the introduced amino group at the R^(2) position could provide cationic sites to interact with negatively charged surfaces of minerals, while the introduced hydroxyl group could provide additional action sites to form stable chelates with metal ions. Based on the structure-activity relationships, structural optimization was carried out to obtain three efficient collectors, which possessed superior flotation separation performances, proving the effectiveness of the structural modification to oxime compounds in this work.展开更多
This study is one of the first to focus on the unexpected drug leakage from discoidal recombinant high-density lipoproteins(d-rHDLs)as a consequence of remodeling process,mainly associated with lecithin-cholesterol ac...This study is one of the first to focus on the unexpected drug leakage from discoidal recombinant high-density lipoproteins(d-rHDLs)as a consequence of remodeling process,mainly associated with lecithin-cholesterol acyltransferase(LCAT)during their metabolic process.Here,a newly monocholesterylsuccinate(CHS)modified paclitaxel-loaded drHDLs(cP-d-rHDLs)were constructed successfully through structural modification,thus aiming to improve the performance of d-rHDLs.And next their in vitro physiochemical properties and pharmacokinetics in SpragueeDawley rats were elaborately investigated.Collectively our studies demonstrated that cP-d-rHDLs,whose remodeling behaviors were restrained effectively after structural modification,exhibited more excellent and promising properties as novel delivery vehicles for anti-cancer agents.展开更多
Firstly discovered in 1980s, human immunodeficiency virus （HIV） continues to affect more and more people. However, there is no effective drug available for the therapy of HIV infection. Betulinic acid existing in va...Firstly discovered in 1980s, human immunodeficiency virus （HIV） continues to affect more and more people. However, there is no effective drug available for the therapy of HIV infection. Betulinic acid existing in various medicinal herbs and fruits exhibits multiple biological effects, especially its outstanding anti-HIV activity, which has drawn the attentions of many pharmacists. Among the derivatives of betulinic acid, some compounds exhibited inhibitory activities at the nanomolar concentration, and have entered phase II clinical trials. This paper summarizes the current investigations on the anti-HIV activity of betulinic acid analogues, and provides valuable data for subsequent researches.展开更多
CC chemokine receptor 4(CCR4)is a kind of G-protein-coupled receptor,which plays a pivotal role in allergic inflammation.The interaction between 2-(2-(4-chloro-phenyl)-5-{[(naphthalen-1-ylmethyl)-carbamlyl]-methyl-4-o...CC chemokine receptor 4(CCR4)is a kind of G-protein-coupled receptor,which plays a pivotal role in allergic inflammation.The interaction between 2-(2-(4-chloro-phenyl)-5-{[(naphthalen-1-ylmethyl)-carbamlyl]-methyl-4-oxo-thiazolidin-3-yl)-N-(3-morpholin-4-yl-propyi)-acetamide(S009)and the N-terminal extracellular tail(ML40)of CCR4 has been validated to be high affinity by capillary zone electrophoresis(CZE).The S009 is a known CCR4 antagonist.Now,a series of new thiourea derivatives have been synthesized.Compared with positive control S009,they were screened using ML40 as target by CZE to find some new drugs for allergic inflammation diseases.The synthesized compounds XJH-5,XJH-4,XJH-17 and XJH-1 displayed the interaction with ML40,but XJH-9,XJH-10,XJH-I 1,XJH-12,XJH-13,XJH-14,XJH-3,XJH-8,XJH-6,XJH-7,XJH-15,XJH-16 and XJH-2 did not bind to ML40.Both qualification and quantification characterizations of the binding were determined.The affinity of the four compounds was valued by the binding constant,which was similar with the results of chemotactic experiments.The established CEZ method is capable of sensitive and fast screening for a series of lactam analogs in the drug discovery for allergic inflammation diseases.展开更多
The hydrocarbon accumulation modes and differences in the Tethyan realm serve as a hot research topic in the petroleum geology community at home and abroad.Both the Persian Gulf Basin in the Middle East and the Sichua...The hydrocarbon accumulation modes and differences in the Tethyan realm serve as a hot research topic in the petroleum geology community at home and abroad.Both the Persian Gulf Basin in the Middle East and the Sichuan Basin in China,situated on the southern and northern sides of the Tethyan realm,respectively,record the whole geological process of the opening and closure of the Prototethys,the Paleotethys,and the Neotethys sequentially,exhibiting anomalous hydrocarbon enrichment.Based on the analysis of the plate tectonic evolution in the Tethyan realm,this study dissects the structures and hydrocarbon accumulation conditions of both basins.Followed by a systematic comparative analysis of the factors controlling hydrocarbon enrichment in the process of plate breakup and convergence in the Tethyan realm,this study proposes petroleum exploration targets in the realm.The results are as follows:(1)Since the Meso-Neoproterozoic,the Persian Gulf Basin and the Sichuan Basin have undergone similar tectonic evolution in the early stage but different in the late stage.Under the influence of the formation and evolution of the Prototethys,Paleotethys,and Neotethys oceans,both basins experienced multi-stage development and modification,forming two major extension-convergence cycles.Consequently,both basins are characterized by the vertical orderly superimposition of various basin prototypes in the order of rift-intracratonic basin(passive continental margin)-foreland.(2)The fact that the Tethyan realm was long located at medium-low latitudes and the local anoxic environment formed in the process of plate breakup and convergence played a vital role in the formation of extensive source rocks.The source rocks are predominantly distributed in underfilled rifts and deep depressions that were connected to the ocean in the unidirectional continental breakup process;basin-slopes and intra-shelf basins on passive continental margins;basinal lows within intracratonic basins,and underfilled foredeeps in foreland basins.The favorable areas for the formation of carbonate reservoirs include platform margins,submarine highs and paleo-uplifts within platforms,and fault zones.The evaporite cap rocks,intimately associated with the basin evolutionary stages and global dry-hot events,are critical for large-scale hydrocarbon preservation.(3)Under the influence of Tethyan evolution,the Persian Gulf Basin and the Sichuan Basin share similar primary factors controlling hydrocarbon enrichment.The moderate tectono-sedimentary differentiation and structural modification in the process of prototype basin superimposition,as well as the spatio-temporal matching of elements critical for hydrocarbon accumulation,are beneficial for the development of large oil and gas fields.The macroscopic hydrocarbon distribution is dictated by source rock-cap rock assemblages,while the local hydrocarbon distribution is governed by trap-reservoir assemblages.The critical factors determining the differential hydrocarbon enrichment in the Persian Gulf Basin and the Sichuan Basin include plate size and position,basement stability,eustatic movement,paleoclimate,and tectonic transformation.Besides,different tectonic modification intensities are closely related to the type,enrichment degree,and distribution of hydrocarbon reservoirs.展开更多
文摘Recent development in the modification of ceria-based catalysts for exhaust gas treatment was reviewed with the dependence of redox properties on structural characters of materials. The doping of ceria with different cations such as rare earth or transition metal oxides results in improvement of structural stability, catalytic function and resistance to sintering at high temperatures. Aging and reduction treatment at high temperatures promote ceria reduction and is beneficial for oxygen storage capacity of the three-way catalysts. Chemical filing technique is very effective in modifying the redox property in the low temperature regions.
文摘Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures （commonly reffered to as, laser induced periodic surface structures, LIPSS）. The purpose of the present investigations is to explore the effect of fsec laser fluence and ambient environments （Vacuum ＆ 02） on the formation of LIPSS and conical structures on the Ti surface. The surface morphology was investigated by scanning electron microscope （SEM）. The ablation threshold with single and multiple （N = 100） shots and the existence of an incubation effect was demonstrated by SEM investigations for both the vacuum and the 02 environment. The phase analysis and chemical composition of the exposed targets were performed by x-ray diffraction （XRD） and energy dispersive x-ray spectroscopy （EDS）, respectively. SEM investigations reveal the formation of LIPSS （nano ＆ micro）. FFT d-spacing calculations illustrate the dependence of periodicity on the fluence and ambient environment. The periodicity of nano-scale LIPSS is higher in the case of irradiation under vacuum conditions as compared to 02. Furthermore, the 02 environment reduces the ablation threshold. XRD data reveal that for the 02 environment, new phases （oxides of Ti） are formed. EDS analysis exhibits that after irradiation under vacuum conditions, the percentage of impurity element （A1） is reduced. The irradiation in the 02 environment results in 15% atomic diffusion of oxygen.
基金Financial support from the National Natural Science Foundation of China(No.21272136)Youth Talent Development Foundation of China Three Gorges University
文摘Natural steroids have been showing notable cytotoxic activities, which are quite interesting lead compounds for the development of anticancer drug including estramustine and prednimustine. Considering that these semi-synthetic molecules are nitrogen mustard functionalized steroidal derivatives, the present review is focused on the methodologies of introducing nitrogen atom or nitrogen-containing heterocycles on A^D rings or side chains of steroids, and analysis of the structure-activity relationship（SAR） for these man-made cytotoxic steroids.
文摘Sensitivity analysis and structural modification techniques are used to investigate the structural modifications of a machine gun tripod which suffers from severe vibration during firing due to the resonance. The finite element analysis and modal test techniques are used to determine the natural frequencies of the machine gun. The sensitivities of natural frequencies with respect to the structural parameters of the tripod are obtained by the method of sensitivity analysis, and they can be used as an indication for the structural modification of the tripod so as to shift the natural frequencies effectively. By the structural modification techniques, finally, the optimal structural modifications of the tripod for desired natural frequencies are made to avoid the resonance, and this optimal structural modification is verified by re-analysis of the modified structure and the vibration contrast between original structure and modified structure. The research resulted in a successful structural modification for desired natural frequencies, which can avoid the resonance and thereby greatly improve the shooting precision of the machine gun during firing.
文摘Work-hardening behaviour of type 316 austenitic stainless steel having difFerent initial dislocation structures introduced by swaging to various levels is analysed by a simplified Kock's model which takes into account the structural changes through the dislocation accumulation and annihilation process during deformation. The dislocation accumulation and annihilation factors show a temperature and structure dependence. The dislocation annihilation factor shows a plateau or decreasing tendency in the dynamic strain ageing (DSA) temperature range. This is attributed as either due to dislocation accumulation being more pronounced than dislocation annihilation or as due to precipitates being formed at DSA temperatures acting as obstacles to dislocation motion in the DSA temperature range.
基金Supported by High-level Talent Training Program for Graduate Students of Tibet University(2020-GSP-B014)National Natural Science Foundation of China(81560589)Yunnan Provincial Department of Science and Technology-Kunming Medical University Applied Basic Research Joint Special Fund(2017FE468-001)。
文摘This paper reviews recent progress in the structural modification and activities on Panax notoginseng saponins(PNS).PNS can not only improve the function of cardio-cerebral system,central nervous system and immune system,but also reveal anticancer,anti-aging and anti-oxidation activities.In order to solve the problem of low bioavailability and poor absorbability of PNS in vivo,usually,the researchers modified the structure of PNS with three methods:glycoside cleavage(including acid hydrolysis,sulfation,etc.),biotransformation method(including enzyme hydrolysis,microbial transformation)and combinatorial chemical method.It was found that the structural modification sites of PNS were single,mainly aimed at C-3,C-6 and C-20,which provided a new perspective for the structural modification of PNS.Therefore,structural modification on PNS with high yield and ready availability are significant in the discovery of new active ingredients and industrialization.Derivatives of PNS are applied to research of structure-activity relationship,which is beneficial to the development of new medicines.
基金supported by the Lianyungang Postdoctoral Research Funding Program(No.LYG20210018).
文摘Oleanolic acid(OA),a pentacyclic triterpenoid,exhibits a broad spectrum of biological activities,including antitumor,antiviral,antibacterial,anti-inflammatory,hepatoprotective,hypoglycemic,and hypolipidemic effects.Since its initial isolation and identification,numerous studies have reported on the structural modifications and pharmacological activities of OA and its derivatives.Despite this,there has been a dearth of comprehensive reviews in the past two decades,leading to challenges in subsequent research on OA.Based on the main biological activities of OA,this paper comprehensively summarized the modification strategies and structureactivity relationships(SARs)of OA and its derivatives to provide valuable reference for future investigations into OA.
基金the Ministry of Higher Education(MOHE)Malaysia under the Fundamental Research Grant Scheme(FRGS)(Ref no:FRGS/1/2020/TK0/XMU/02/1)the Ministry of Science,Technology and Innovation(MOSTI)Malaysia under the Strategic Research Fund(SRF-APP)(S.22015)+4 种基金the National Natural Science Foundation of China(Ref no:22202168)Guangdong Basic and Applied Basic Research Foundation(Ref no:2021A1515111019)Xiamen University Malaysia Investigatorship Grant(Grant no:IENG/0038)Xiamen University Malaysia Research Fund(ICOE/0001,XMUMRF/2021-C8/IENG/0041 and XMUMRF/2019-C3/IENG/0013)Hengyuan International Sdn.Bhd.(Grant no:EENG/0003).
文摘To date,extensively high demand for hydrogen peroxide(H_(2)O_(2))has been predominantly supplied by the anthraquinone process for several worldwide applications,encompassing wastewater treatment,environmental remediation,and chemical synthesis.However,the compacted manufacturing,massive energy input and the release of tremendous wastes have restricted commercialization feasibility.Regards to mitigate such issues,the photocatalytic H_(2)O_(2)production by utilizing g-C_(3)N_(4)catalysts has endowed a greener,sustainable and promising alternative,considering that it involves water and oxygen as reactants in the present of sunlight as energy input.Herein,we have manifested a comprehensive overview of the research progress for g-C_(3)N_(4)-based semiconductors for photocatalytic H_(2)O_(2)generation.This review has systematically elucidated state-of-the-art development of different modifications on g-C_(3)N_(4)to unravel the fundamental mechanism of H_(2)O_(2)evolution via oxygen reduction reaction(ORR)and water oxidation reaction(WOR).In addition,the contribution made by vacancy introduction,doping,heterogenization,and co-catalyst passivation with respect to photoefficiency enhancement have been clarified.Furthermore,the current challenges and perspective of future development directions on photocatalytic H_(2)O_(2)production have also been highlighted.As such,g-C_(3)N_(4)stands as the next step toward advancement in the configuration and modulation of high-efficiency photocatalysts.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK20201332)the“Double First-Class”University Project(No.CPU2018GF03)+1 种基金the Six Talent Peaks Project of Jiangsu Province(No.SWYY-107)Jiangsu Province‘333’Project,111 Center from Ministry of Education of China and the State Administration of Foreign Experts Affairs of China(No.B18056).
文摘Parthenolide(PTL)is a sesquiterpene lactone derived from medicinal plant feverfew(Tanacetum parthenium).Recent studies have demonstrated that it has multiple pharmacological activities,especially in the treatment of various hematological and solid cancers.The superior anticancer activity of PTL suggests that it has the potential to be a first-line drug.However,due to the limited physical and chemical properties,as well as bioavailability,structural modification strategies are strongly recommended to improve the anticancer activity.This review describes representative PTL derivatives obtained by different modification strategies,which are reported to exert antiproliferative activities superior to the parent compound PTL.Furthermore,we also summarize their basic mechanisms on cancer-related signaling pathways,so as to explain the potential and characteristics of PTL and its derivatives in cancer therapy.
基金Financial support from the National Natural Science Foundation of China(22075016 and 22103057)Fundamental Research Funds for the Central Universities(FRF-TP-20-020A3 and QNXM20220060)+1 种基金Interdisciplinary Research Project for Young Teachers of USTB(FRF-IDRY-21-011)111 Project(B170003 and B12015)
文摘The development of high-energy and long-lifespan NASICON-type cathode materials for sodium-ion batteries has always been a research hotspot but a daunting challenge.Although Na_(4)MnCr(PO_(4))_(3)has emerged as one of the most promising high-energy-density cathode materials owing to its three-electron reactions,it still suffers from serious structural distortion upon repetitive charge/discharge processes caused by the Jahn-Teller active Mn^(3+).Herein,the selective substitution of Cr by Zr in Na_(4)MnCr(PO_(4))_(3)was explored to enhance the structural stability,due to the pinning effect of Zr ions and the≈2.9-electron reactions,as-prepared Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C delivers a high capacity retention of 85.94%over 500 cycles at 5 C and an ultrahigh capacity of 156.4 mAh g^(-1)at 0.1 C,enabling the stable energy output as high as 555.2 Wh kg^(-1).Moreover,during the whole charge/discharge process,a small volume change of only 6.7%was verified by in situ X-ray diffraction,and the reversible reactions of Cr^(3+)/Cr^(4+),Mn^(3+)/Mn^(4+),and Mn^(2+)/Mn^(3+)redox couples were identified via ex situ X-ray photoelectron spectroscopy analyses.Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrated the fast reaction kinetics of the Na_(3.9)MnCr_(0.9)Zr_(0.1)(PO_(4))_(3)/C electrode.This work offers new opportunities for designing high-energy and high-stability NASICON cathodes by ion doping.
文摘Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of different factors on the epoxidation of three unsaturated natural products were investigated by orthogonal design.Results The experimental results show that three unsaturated natural products are oxidized to the corresponding epoxides with hydrogen peroxide in the presence of 10%(mol/mol) of iodine at room temperature in high yields.Conclusion Iodine was found to be an efficient catalyst for the epoxidation of carbon-carbon double bonds in some unsaturated natural products with hydrogen peroxide at room temperature.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61264008 and 61274121the Natural Science Foundation of Jiangsu Province under Grant No BK2012829
文摘Regulation of optical properties and electronic structure of graphitic carbon nitride （g-C3N4 ） via external strain has attracted much attention due to its potential in photocatalyst and electronic devices. However, the identifi- cation of g-C3N4 structure transformation induced by strain is greatly lacking. In this work, the Raman spectra of g-C3N4 with external strain are determined theoretically based on the density function theory. Deformation induced by external strain not only regulates the Raman mode positions but also leads to a I^aman mode split- ting, which can be ascribed to crystal symmetry destruction by strain engineering. Our results suggest the use of Raman scattering in structural identification in deformed 9-C3N4 structure.
基金Supported by the National High Technology Research and Development Program(2001AA261161) of China(863 Program).
文摘Objective To study mechanism of various effects of HLA antigen camouflaged by differentmPEGs. Methods Effects of the modification of HLA antigen camouflaged by various mPEGs were detected by microlymphocytotoxicity test. The ability of modification was detected by SDS-PAGE. The mechanism of the modification was depicted by the three-dimensional structure of HLA antigen. Results The specific reaction between HLA-A2 antigen and its antibody were completely blocked by mPEG-BTC and mPEG-SPA. mPEG-MAL did not camouflage HLA antigen. The diversity of the modification of HLA antigen camouflaged by varied mPEGs was closely associated with the amides displayed on the surface of HLA antigen. Conclusion Only the amides which were exposed to the surface of HLA antigen can be camouflaged by mPEG. The amides on the surface of three-dimensional structure of HLA-A2 antigen determine the effect of the modification by various mPEGs.
基金supported by the Science Foundation of National Key Laboratory of Science and Technology on Advanced Composites in Special Environmentsthe National Natural Science Foundation of China (No.12002109)+1 种基金sponsored by Natural Science Foundation of Chongqing, China (Nos.CSTC2021jcyj-msxm X10305, CSTB2022NSCQMSX0246, CSTB2022NSCQ-MSX0242, CSTB2022NSCQMSX1244, CSTB2022NSCQ-MSX0441, CSTB2022NSCQMSX1356, CSTB2022NSCQ-MSX1572, CSTB2022NSCQ-MSX1583, CSTB2022NSCQ-MSX0487, CSTB2022TFII-OFX0034)Chongqing Technology Innovation and Application Development Special Key Project (No.CSTB2023TIAD-KPX0010)。
文摘High-temperature proton exchange membranes(HT-PEMs) possess excellent thermal and outstanding electrochemical stability, providing an avenue to realize high-temperature proton exchange membranes fuel cells(HT-PEMFCs) with both superior power density and long-term durability. Unfortunately, polybenzimidazole(PBI), a typical material for conventional HT-PEMs, fails to compromise the high nonaqueous proton conductivity and high mechanical properties, thus hindering their practical applications.Achieving efficient nonaqueous proton conduction is crucial for HT-PEMFC, and many insightful research works have been done in this area. However, there still lacks a report that integrates the host-guest interactions of phosphoric acid doping and the structural stability of polymers to systematically illustrate modification strategies. Here, we summarize recent advancements in enhancing the nonaqueous proton conduction of HT-PEMs. Various polymer structure modification strategies, including main chain and side group modification, cross-linking, blocking, and branching, are reviewed. Composite approaches of polymer, including compounding with organic porous polymers, filling the inorganic components and modifying with ionic liquids, etc., are also covered in this work. These strategies endow the HT-PEMs with more free volume, nanophase-separated structure, and multi-stage proton transfer channels, which can facilitate the proton transportation and improve their performance. Finally, current challenges and future directions for further enhancements are also outlined.
基金the support of the National Natural Science Foundation of China(Nos.51774329 and 51904337)the High Performance Computing Center of Central South University,China。
文摘The relationships between the structure of oxime compounds(R^(1)R^(2)C=NOH,R^(1)/R^(2)=alkyl groups) with different substituents and their corresponding flotation performances were studied. The analyses of density functional theory(DFT) calculations illustrated that the introduced phenyl group at the R^(1) position could enhance the acidity,while the heptyl group could effectively increase the hydrophobicity and benefit van der Waals interactions. Meanwhile,the introduced amino group at the R^(2) position could provide cationic sites to interact with negatively charged surfaces of minerals, while the introduced hydroxyl group could provide additional action sites to form stable chelates with metal ions. Based on the structure-activity relationships, structural optimization was carried out to obtain three efficient collectors, which possessed superior flotation separation performances, proving the effectiveness of the structural modification to oxime compounds in this work.
基金This study is financially supported by National Science Foundation Grant of China(No.81072587)Jiangsu Province Ordinary College and University Innovative Research Programs(No.CXZZ110805)+1 种基金the Major Project of National Science and Technology of China for New Drugs Development(No.2009ZX09310-004)the Special Found Project of Universities’Basic Scientific Research of Central Authorities(No.ZJ11253).
文摘This study is one of the first to focus on the unexpected drug leakage from discoidal recombinant high-density lipoproteins(d-rHDLs)as a consequence of remodeling process,mainly associated with lecithin-cholesterol acyltransferase(LCAT)during their metabolic process.Here,a newly monocholesterylsuccinate(CHS)modified paclitaxel-loaded drHDLs(cP-d-rHDLs)were constructed successfully through structural modification,thus aiming to improve the performance of d-rHDLs.And next their in vitro physiochemical properties and pharmacokinetics in SpragueeDawley rats were elaborately investigated.Collectively our studies demonstrated that cP-d-rHDLs,whose remodeling behaviors were restrained effectively after structural modification,exhibited more excellent and promising properties as novel delivery vehicles for anti-cancer agents.
基金This research was supported by the National Natural Science Foundation of China （No. 81273537）, Scientific Research Fund of Education Department of Hunan Province （No. 17A190）, the Key Project of Science and Technology Department of Hunan Province （No. 2016DK2001）, and the Key Disciplines of Hunan Province and the Zhengxing Scholar Program of the University of South China.
文摘Firstly discovered in 1980s, human immunodeficiency virus （HIV） continues to affect more and more people. However, there is no effective drug available for the therapy of HIV infection. Betulinic acid existing in various medicinal herbs and fruits exhibits multiple biological effects, especially its outstanding anti-HIV activity, which has drawn the attentions of many pharmacists. Among the derivatives of betulinic acid, some compounds exhibited inhibitory activities at the nanomolar concentration, and have entered phase II clinical trials. This paper summarizes the current investigations on the anti-HIV activity of betulinic acid analogues, and provides valuable data for subsequent researches.
基金supported by the National Key New Drug Creation Program of China(2009ZX09103-724)the National Natural Science Foundation of China grants(30872292,90813025 and 81072612)+2 种基金the Natural Science Foundation of Beijing(7102107)the Open Foundation of State Key Laboratory of Natural and Biomimetic Drugs(K20090207)the National New Drug Research and Development Project of China(2009ZX09301-010)
文摘CC chemokine receptor 4(CCR4)is a kind of G-protein-coupled receptor,which plays a pivotal role in allergic inflammation.The interaction between 2-(2-(4-chloro-phenyl)-5-{[(naphthalen-1-ylmethyl)-carbamlyl]-methyl-4-oxo-thiazolidin-3-yl)-N-(3-morpholin-4-yl-propyi)-acetamide(S009)and the N-terminal extracellular tail(ML40)of CCR4 has been validated to be high affinity by capillary zone electrophoresis(CZE).The S009 is a known CCR4 antagonist.Now,a series of new thiourea derivatives have been synthesized.Compared with positive control S009,they were screened using ML40 as target by CZE to find some new drugs for allergic inflammation diseases.The synthesized compounds XJH-5,XJH-4,XJH-17 and XJH-1 displayed the interaction with ML40,but XJH-9,XJH-10,XJH-I 1,XJH-12,XJH-13,XJH-14,XJH-3,XJH-8,XJH-6,XJH-7,XJH-15,XJH-16 and XJH-2 did not bind to ML40.Both qualification and quantification characterizations of the binding were determined.The affinity of the four compounds was valued by the binding constant,which was similar with the results of chemotactic experiments.The established CEZ method is capable of sensitive and fast screening for a series of lactam analogs in the drug discovery for allergic inflammation diseases.
基金supported by the National Natural Science Foundation of China (Grant Nos.92255302,U19B6003 and 42002137)。
文摘The hydrocarbon accumulation modes and differences in the Tethyan realm serve as a hot research topic in the petroleum geology community at home and abroad.Both the Persian Gulf Basin in the Middle East and the Sichuan Basin in China,situated on the southern and northern sides of the Tethyan realm,respectively,record the whole geological process of the opening and closure of the Prototethys,the Paleotethys,and the Neotethys sequentially,exhibiting anomalous hydrocarbon enrichment.Based on the analysis of the plate tectonic evolution in the Tethyan realm,this study dissects the structures and hydrocarbon accumulation conditions of both basins.Followed by a systematic comparative analysis of the factors controlling hydrocarbon enrichment in the process of plate breakup and convergence in the Tethyan realm,this study proposes petroleum exploration targets in the realm.The results are as follows:(1)Since the Meso-Neoproterozoic,the Persian Gulf Basin and the Sichuan Basin have undergone similar tectonic evolution in the early stage but different in the late stage.Under the influence of the formation and evolution of the Prototethys,Paleotethys,and Neotethys oceans,both basins experienced multi-stage development and modification,forming two major extension-convergence cycles.Consequently,both basins are characterized by the vertical orderly superimposition of various basin prototypes in the order of rift-intracratonic basin(passive continental margin)-foreland.(2)The fact that the Tethyan realm was long located at medium-low latitudes and the local anoxic environment formed in the process of plate breakup and convergence played a vital role in the formation of extensive source rocks.The source rocks are predominantly distributed in underfilled rifts and deep depressions that were connected to the ocean in the unidirectional continental breakup process;basin-slopes and intra-shelf basins on passive continental margins;basinal lows within intracratonic basins,and underfilled foredeeps in foreland basins.The favorable areas for the formation of carbonate reservoirs include platform margins,submarine highs and paleo-uplifts within platforms,and fault zones.The evaporite cap rocks,intimately associated with the basin evolutionary stages and global dry-hot events,are critical for large-scale hydrocarbon preservation.(3)Under the influence of Tethyan evolution,the Persian Gulf Basin and the Sichuan Basin share similar primary factors controlling hydrocarbon enrichment.The moderate tectono-sedimentary differentiation and structural modification in the process of prototype basin superimposition,as well as the spatio-temporal matching of elements critical for hydrocarbon accumulation,are beneficial for the development of large oil and gas fields.The macroscopic hydrocarbon distribution is dictated by source rock-cap rock assemblages,while the local hydrocarbon distribution is governed by trap-reservoir assemblages.The critical factors determining the differential hydrocarbon enrichment in the Persian Gulf Basin and the Sichuan Basin include plate size and position,basement stability,eustatic movement,paleoclimate,and tectonic transformation.Besides,different tectonic modification intensities are closely related to the type,enrichment degree,and distribution of hydrocarbon reservoirs.
