In the past few years,efforts have been made to extend the sensitivity of surface nuclear magnetic resonance(SNMR)to short relaxation times,typical for strongly bound water,which,for example,occurs in partially satura...In the past few years,efforts have been made to extend the sensitivity of surface nuclear magnetic resonance(SNMR)to short relaxation times,typical for strongly bound water,which,for example,occurs in partially saturated soils.The two limiting factors for the sensitivity are the dead time after the excitation pulse and the duration of the pulse itself.To enable short pulses,while also achieving proper depths of investigation,high pulse amplitudes are needed.This makes it necessary to consider the Bloch-Siegert effect,i.e.the counter-rotating component and the parallel component of the excitation field have significant influence on the excitation.If an untuned transmitter circuit is used,the pulse shape will also be non-sinusoidal.In this paper,we demonstrate that this influences SNMR measurements with short pulses in two ways:On one hand,the pulse shape influences the phase of the fundamental frequency oscillation.On the other,at very high pulse amplitudes,other frequency components of the excitation field start to influence the excitation.The behavior of the macroscopic magnetizations in the subsurface during the pulse is simulated by solving the Bloch equations,using the pulse shape as an input.Since these calculations are computational expensive,we propose a lookup scheme that allows a time efficient modeling of the obtained SNMR data.展开更多
Nuclear magnetic resonance(NMR)spectroscopy is a powerful tool for analyzing molecular structure and composition.However,traditional NMR experiments suffer from long acquisition times,especially in multidimensional NM...Nuclear magnetic resonance(NMR)spectroscopy is a powerful tool for analyzing molecular structure and composition.However,traditional NMR experiments suffer from long acquisition times,especially in multidimensional NMR spectroscopy.This problem,to some extent,limits broader applications of NMR techniques.Various methods have been proposed to accelerate sampling,including non-uniform sampling(NUS),multi-FID acquisition(MFA),Hadamard encoding,Fourier encoding,spatial encoding Ultrafast 2D NMR(UF2DNMR),and so on.The review focuses on rapid sampling methods developed in contemporary China,introducing their fundamental principles and applications while discussing their respective advantages and disadvantages.展开更多
Coenzyme Q10 and vitamin E are among the most widely consumed nutritional supplements in China owing to their antioxidant and other health-promoting properties.This study aimed to establish an accurate and efficient a...Coenzyme Q10 and vitamin E are among the most widely consumed nutritional supplements in China owing to their antioxidant and other health-promoting properties.This study aimed to establish an accurate and efficient analytical method for the simultaneous determination of these two compounds in commercial softgel capsules,which is essential for rigorous quality control.Herein,a proton nuclear magnetic resonance(1H NMR)method was developed and validated using coumarin as an internal standard.Characteristic signals at 3.997 ppm for coenzyme Q10 and 2.621 ppm for vitamin E were selected for quantification.The method demonstrated excellent performance in terms of precision(relative standard deviation<2%),specificity(resolution>1.5),and stability(24-h variation<3%).The validation results complied with the China Food and Drug Administration guidelines,demonstrating high accuracy.Application to products from four different manufacturers showed compound contents ranging from 98.2%to 102.4%of label amounts.These findings support^(1)H NMR spectroscopy as a rapid,precise,and reliable approach for the simultaneous quality assessment of coenzyme Q10 and vitamin E formulations.展开更多
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
基金funded by the German Research Foundation(Deutsche Forschungsgemeinschaft-DFG)under grant MU 3318/8-1.
文摘In the past few years,efforts have been made to extend the sensitivity of surface nuclear magnetic resonance(SNMR)to short relaxation times,typical for strongly bound water,which,for example,occurs in partially saturated soils.The two limiting factors for the sensitivity are the dead time after the excitation pulse and the duration of the pulse itself.To enable short pulses,while also achieving proper depths of investigation,high pulse amplitudes are needed.This makes it necessary to consider the Bloch-Siegert effect,i.e.the counter-rotating component and the parallel component of the excitation field have significant influence on the excitation.If an untuned transmitter circuit is used,the pulse shape will also be non-sinusoidal.In this paper,we demonstrate that this influences SNMR measurements with short pulses in two ways:On one hand,the pulse shape influences the phase of the fundamental frequency oscillation.On the other,at very high pulse amplitudes,other frequency components of the excitation field start to influence the excitation.The behavior of the macroscopic magnetizations in the subsurface during the pulse is simulated by solving the Bloch equations,using the pulse shape as an input.Since these calculations are computational expensive,we propose a lookup scheme that allows a time efficient modeling of the obtained SNMR data.
基金financially supported by the National Natural Science Foundation of China(grant numbers 22174118,12411530077,and 22374124).
文摘Nuclear magnetic resonance(NMR)spectroscopy is a powerful tool for analyzing molecular structure and composition.However,traditional NMR experiments suffer from long acquisition times,especially in multidimensional NMR spectroscopy.This problem,to some extent,limits broader applications of NMR techniques.Various methods have been proposed to accelerate sampling,including non-uniform sampling(NUS),multi-FID acquisition(MFA),Hadamard encoding,Fourier encoding,spatial encoding Ultrafast 2D NMR(UF2DNMR),and so on.The review focuses on rapid sampling methods developed in contemporary China,introducing their fundamental principles and applications while discussing their respective advantages and disadvantages.
基金supported by the Open Research Fund Program of the Shandong Provincial Key Laboratory of Glycoscience and Glycotechnology(Ocean University of China)。
文摘Coenzyme Q10 and vitamin E are among the most widely consumed nutritional supplements in China owing to their antioxidant and other health-promoting properties.This study aimed to establish an accurate and efficient analytical method for the simultaneous determination of these two compounds in commercial softgel capsules,which is essential for rigorous quality control.Herein,a proton nuclear magnetic resonance(1H NMR)method was developed and validated using coumarin as an internal standard.Characteristic signals at 3.997 ppm for coenzyme Q10 and 2.621 ppm for vitamin E were selected for quantification.The method demonstrated excellent performance in terms of precision(relative standard deviation<2%),specificity(resolution>1.5),and stability(24-h variation<3%).The validation results complied with the China Food and Drug Administration guidelines,demonstrating high accuracy.Application to products from four different manufacturers showed compound contents ranging from 98.2%to 102.4%of label amounts.These findings support^(1)H NMR spectroscopy as a rapid,precise,and reliable approach for the simultaneous quality assessment of coenzyme Q10 and vitamin E formulations.
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。
