为改进现有基于核磁共振(nuclear magnetic resonance,NMR)的饱和土渗透系数预测模型,提高NMR技术预测饱和土渗透系数的精度,在NMR弛豫时间T_(2)谱曲线及毛细管理论基础上,考虑毛细管迂曲度对渗透系数的影响,建立适用于饱和土体的渗透...为改进现有基于核磁共振(nuclear magnetic resonance,NMR)的饱和土渗透系数预测模型,提高NMR技术预测饱和土渗透系数的精度,在NMR弛豫时间T_(2)谱曲线及毛细管理论基础上,考虑毛细管迂曲度对渗透系数的影响,建立适用于饱和土体的渗透系数新模型。为验证该模型的准确性,对取自济南地铁裴家营站的粉质黏土试样进行固结渗透试验和核磁共振试验,分析固结过程中试样孔隙和渗透系数的变化规律,测定不同孔隙比状态下试样的渗透系数及T_(2)谱曲线,利用新模型对试样不同T_(2)谱曲线的饱和渗透系数进行预测,并与已有的4个核磁渗透系数模型预测结果进行比较。结果表明:本次试样的孔隙以小孔隙和中孔隙为主,固结中总孔隙的减小主要源自中孔隙的压缩;试样渗透系数随孔隙比降低而降低,两者间呈幂函数关系;在核磁T_(2)谱曲线和毛细管模型的基础上引入平均迂曲度可有效提高饱和土渗透系数预测精度,较已有模型,本研究新模型的预测值与实测值间的均方根误差降低43.1%~67.0%。展开更多
目的建立一种识别道地产区金银花、非道地产区金银花及山银花的方案。方法将核磁共振氢谱(proton nuclear magnetic resonance,1H-NMR)数据与一站式分析软件ChemPattern 2020相结合,对金银花进行模式识别,同时对金银花及山银花中的主要...目的建立一种识别道地产区金银花、非道地产区金银花及山银花的方案。方法将核磁共振氢谱(proton nuclear magnetic resonance,1H-NMR)数据与一站式分析软件ChemPattern 2020相结合,对金银花进行模式识别,同时对金银花及山银花中的主要有效成分绿原酸进行定量。结果建立了60批次金银花及山银花样品的指纹图谱,主成分分析结果显示前3个主成分的累积方差贡献率为96.79%,60批次样品聚为2组,金银花与山银花呈现一定的差异;正交偏最小二乘法的检验参数均接近于1,60批次样品聚为3组,确认了道地产区金银花、非道地产区金银花以及山银花的可识别性。进一步建立了基于支持向量机识别模型。核函数类型为径向基函数,10折交叉验证,数据预处理采用均一化的条件下,建立的支持向量机模型识别率为100%;同时,基于1H-NMR测定了来自13个不同产地的金银花和山银花中绿原酸的含量。结论1H-NMR结合模式识别能够有效区分道地产区金银花、非道地产区金银花及山银花。展开更多
为了精确表征压实石英的孔径分布,文章联合核磁共振(Nuclear Magnetic Resonance,NMR)技术和X射线计算机断层扫描(Computed Tomography,CT)技术对3种干密度压实石英的孔径分布进行了定量分析,同时对比了两种方法表征石英孔径分布的优缺...为了精确表征压实石英的孔径分布,文章联合核磁共振(Nuclear Magnetic Resonance,NMR)技术和X射线计算机断层扫描(Computed Tomography,CT)技术对3种干密度压实石英的孔径分布进行了定量分析,同时对比了两种方法表征石英孔径分布的优缺点。结果表明:基于T_(1)和T_(2)曲线的NMR法分析石英孔径分布范围基本重合;基于T_(2)曲线的NMR法与CT法所测得的石英孔径分布范围存在差异,但总体趋势相同,NMR法测得的石英的最大孔径、平均孔径均大于CT法测得的数据。NMR法测得的孔径分布包括小孔,难以体现孔隙的复杂程度,CT法能捕捉复杂孔隙,但孔径分布缺少小孔。结合两种方法可以比较全面地分析石英的孔径分布。展开更多
Nuclear magnetic resonance(NMR)spectroscopy is an indispensable tool to probe weak protein-ligand interactions,which are key to the hit identification and hit-to-lead evolution in fragment-based drug discovery(FBDD).T...Nuclear magnetic resonance(NMR)spectroscopy is an indispensable tool to probe weak protein-ligand interactions,which are key to the hit identification and hit-to-lead evolution in fragment-based drug discovery(FBDD).The integration of NMR technology in FBDD has facilitated the development of a diverse array of candidate compounds and FDAapproved drugs.Here,we summarized the rapid advancement and application of NMR techniques in contemporary China,which serves as a catalyst for the ongoing prosperousness of fragment-derived inhibitors against various targets.展开更多
Motivated by recent studies of the cluster Mott insulator candidate compound Nb_(3)Cl_(8),this study performs^(93)Nb and^(35)Cl nuclear magnetic resonance(NMR)measurements to investigate the electron correlations.Belo...Motivated by recent studies of the cluster Mott insulator candidate compound Nb_(3)Cl_(8),this study performs^(93)Nb and^(35)Cl nuclear magnetic resonance(NMR)measurements to investigate the electron correlations.Below the structural transition temperature T_(s)∼97 K,all satellites of the^(93)Nb NMR spectra split into three distinct peaks,which suggests symmetry lowering due to the structural transition and could be attributed to the change in the Nb-Nb bond-lengths of the Nb3 clusters.The spin-lattice relaxation rate 1/T_(1)divided by the temperature T,1/T_(1)T,increases upon cooling to T_(s)for all Cl sites,whereas only the Knight shift K of Cl located at the center of the Nb_(3) clusters exhibits a temperature dependence similar to that observed in magnetic susceptibility.These findings collectively demonstrate the existence of strong spin correlations between the Nb atoms in Nb_(3)Cl_(8),which are closely associated with Mottness.展开更多
WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphol...WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphological Division and Fractal Models”,Acta Geologica Sinica-English Edition(Accepted Article):https://doi.org/10.1111/1755-6724.15094.展开更多
Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the as...Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.展开更多
文摘为改进现有基于核磁共振(nuclear magnetic resonance,NMR)的饱和土渗透系数预测模型,提高NMR技术预测饱和土渗透系数的精度,在NMR弛豫时间T_(2)谱曲线及毛细管理论基础上,考虑毛细管迂曲度对渗透系数的影响,建立适用于饱和土体的渗透系数新模型。为验证该模型的准确性,对取自济南地铁裴家营站的粉质黏土试样进行固结渗透试验和核磁共振试验,分析固结过程中试样孔隙和渗透系数的变化规律,测定不同孔隙比状态下试样的渗透系数及T_(2)谱曲线,利用新模型对试样不同T_(2)谱曲线的饱和渗透系数进行预测,并与已有的4个核磁渗透系数模型预测结果进行比较。结果表明:本次试样的孔隙以小孔隙和中孔隙为主,固结中总孔隙的减小主要源自中孔隙的压缩;试样渗透系数随孔隙比降低而降低,两者间呈幂函数关系;在核磁T_(2)谱曲线和毛细管模型的基础上引入平均迂曲度可有效提高饱和土渗透系数预测精度,较已有模型,本研究新模型的预测值与实测值间的均方根误差降低43.1%~67.0%。
文摘目的建立一种识别道地产区金银花、非道地产区金银花及山银花的方案。方法将核磁共振氢谱(proton nuclear magnetic resonance,1H-NMR)数据与一站式分析软件ChemPattern 2020相结合,对金银花进行模式识别,同时对金银花及山银花中的主要有效成分绿原酸进行定量。结果建立了60批次金银花及山银花样品的指纹图谱,主成分分析结果显示前3个主成分的累积方差贡献率为96.79%,60批次样品聚为2组,金银花与山银花呈现一定的差异;正交偏最小二乘法的检验参数均接近于1,60批次样品聚为3组,确认了道地产区金银花、非道地产区金银花以及山银花的可识别性。进一步建立了基于支持向量机识别模型。核函数类型为径向基函数,10折交叉验证,数据预处理采用均一化的条件下,建立的支持向量机模型识别率为100%;同时,基于1H-NMR测定了来自13个不同产地的金银花和山银花中绿原酸的含量。结论1H-NMR结合模式识别能够有效区分道地产区金银花、非道地产区金银花及山银花。
文摘为了精确表征压实石英的孔径分布,文章联合核磁共振(Nuclear Magnetic Resonance,NMR)技术和X射线计算机断层扫描(Computed Tomography,CT)技术对3种干密度压实石英的孔径分布进行了定量分析,同时对比了两种方法表征石英孔径分布的优缺点。结果表明:基于T_(1)和T_(2)曲线的NMR法分析石英孔径分布范围基本重合;基于T_(2)曲线的NMR法与CT法所测得的石英孔径分布范围存在差异,但总体趋势相同,NMR法测得的石英的最大孔径、平均孔径均大于CT法测得的数据。NMR法测得的孔径分布包括小孔,难以体现孔隙的复杂程度,CT法能捕捉复杂孔隙,但孔径分布缺少小孔。结合两种方法可以比较全面地分析石英的孔径分布。
基金the National Key R&D Program of China(2024YFA1306200)National Natural Science Foundation of China(22377119)+2 种基金Anhui Provincial Natural Science Foundation(2208085MC50)USTC Research Funds of the Double First-Class Initiative(YD9100002028,YD9100002036)Research Funds of Center for Advanced Interdisciplinary Science and Biomedicine of IHM(QYPY20220008)for their financial support.
文摘Nuclear magnetic resonance(NMR)spectroscopy is an indispensable tool to probe weak protein-ligand interactions,which are key to the hit identification and hit-to-lead evolution in fragment-based drug discovery(FBDD).The integration of NMR technology in FBDD has facilitated the development of a diverse array of candidate compounds and FDAapproved drugs.Here,we summarized the rapid advancement and application of NMR techniques in contemporary China,which serves as a catalyst for the ongoing prosperousness of fragment-derived inhibitors against various targets.
基金supported by the National Key Research and Development Projects of China(Grant Nos.2022YFA1403402,2023YFA1406103,2024YFA1409200,2024YFA1611302,and 2023YFF0718400)the National Natural Science Foundation of China(Grant Nos.12374142,12304170,W2411004,and 12374197)+3 种基金the Beijing Natural Science Foundation(Grant No.JQ23001)the Beijing National Laboratory for Condensed Matter Physics(Grant No.2024BNLCMPKF005)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2023B151520013)supported by the Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘Motivated by recent studies of the cluster Mott insulator candidate compound Nb_(3)Cl_(8),this study performs^(93)Nb and^(35)Cl nuclear magnetic resonance(NMR)measurements to investigate the electron correlations.Below the structural transition temperature T_(s)∼97 K,all satellites of the^(93)Nb NMR spectra split into three distinct peaks,which suggests symmetry lowering due to the structural transition and could be attributed to the change in the Nb-Nb bond-lengths of the Nb3 clusters.The spin-lattice relaxation rate 1/T_(1)divided by the temperature T,1/T_(1)T,increases upon cooling to T_(s)for all Cl sites,whereas only the Knight shift K of Cl located at the center of the Nb_(3) clusters exhibits a temperature dependence similar to that observed in magnetic susceptibility.These findings collectively demonstrate the existence of strong spin correlations between the Nb atoms in Nb_(3)Cl_(8),which are closely associated with Mottness.
文摘WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphological Division and Fractal Models”,Acta Geologica Sinica-English Edition(Accepted Article):https://doi.org/10.1111/1755-6724.15094.
基金supported by the National Energy R&D Center of Petroleum Refining Technology(RIPP,SINOPEC),the National Natural Science Foundation of China(Grants 22161132028,22172177,22225205,22372191 and 22372178)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0540000)+2 种基金the International Partnership Program of the Chinese Academy of Sciences(314GJH2022022FN)Natural Science Foundation of Hubei Province(2021CFA021)Hubei International Scientific and Technological Cooperation Program(2024EHA043)and Base(SH2303).
文摘Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.
