The measurement of nuclear magnetic resonance(NMR)porosity is affected by temperature.Without considering the impact of NMR logging tools,this phenomenon is mainly caused by variations in magnetization intensity of th...The measurement of nuclear magnetic resonance(NMR)porosity is affected by temperature.Without considering the impact of NMR logging tools,this phenomenon is mainly caused by variations in magnetization intensity of the measured system due to temperature fluctuations and difference between the temperature of the porous medium and calibration sample.In this study,the effect of temperature was explained based on the thermodynamic theory,and the rules of NMR porosity responses to temperature changes were identified through core physics experiments.In addition,a method for correcting the influence of temperature on NMR porosity measurement was proposed,and the possible factors that may affect its application were also discussed.展开更多
Extracts of plant origin,particularly tannins,are attracting growing interest for the sustainable development of materials in the industrial sector.The discovery of new tannins is therefore necessary.The aim of this w...Extracts of plant origin,particularly tannins,are attracting growing interest for the sustainable development of materials in the industrial sector.The discovery of new tannins is therefore necessary.The aim of this work was to contribute to the understanding of the properties of Paraberlinia bifoliolata tannin by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectroscopy MALDI-TOF/MS and Carbon 13 Nuclear Magnetic Resonance(13C NMR).The chemical composition of tannin extracted from Paraberlinia bifoliolata bark was determined,as was the mechanical strength of the resin hardened with Acacia nilotica extracts.Yield by successive water extraction was 35%.MALDI-TOF/MS analysis revealed the presence of three new compounds in this tannin,previously unknown in this family of extracts.These are 3-hydroxyproline acid,N-methyl-4-hydroxypipecolic acid and N-methyl-5-dihydroxypipecolic acid.The identification of the above molecules means that this tannin can be used for industrial applications,as a resin in the manufacture of particleboard and in the formulation of green corrosion inhibitors.This information is reinforced by 13C NMR spectrometry,which indicates the presence of several polyflavonoid units,confirming the condensed nature of the tannin.Thermomechanical analysis of the resin formed by the purified tannin of Paraberlinia bifoliolata to which a vegetal biohardener has been added provided a Modulus of Elasticity(MOE)value of 4840 MPa at 150°C,confirming its possible use as a binder resin in the manufacture of wood panels as well as for the formulation of a corrosion inhibitor.展开更多
Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the ...Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.展开更多
粮仓是一个复杂的生态系统,其内部生物、非生物以及环境的耦合关系复杂,且只能对温度等少数参数进行探测,粮仓生态近乎“黑箱”。为了便于研究粮仓复杂的耦合关系、核实其中的基本规律,研究提出了一种基于核磁共振(Nuclear Magnetic Res...粮仓是一个复杂的生态系统,其内部生物、非生物以及环境的耦合关系复杂,且只能对温度等少数参数进行探测,粮仓生态近乎“黑箱”。为了便于研究粮仓复杂的耦合关系、核实其中的基本规律,研究提出了一种基于核磁共振(Nuclear Magnetic Resonance,NMR)的粮仓多场耦合图形化探测系统。该系统由核磁共振成像分析仪、粮仓模拟装置和数据采集处理系统三部分组成,可同时实现粮堆温度、湿度和水分三参数的真实精准探测,并能通过配套云图生成软件直观、形象地呈现粮堆温度场、湿度场和水分场分布云图。该系统首次将低场核磁共振成像技术应用于粮堆多场耦合作用研究领域,为探明粮仓生态复杂的耦合关系,进一步证实相关理论研究结论提供了一种新的技术手段。该系统的提出有助于深化行业正在致力发展的粮堆多场耦合及生物场理论。展开更多
本研究通过使用灵敏度增强的带梯度形状脉冲进行异核单量子相干(HSQC)实验检测保健食品中违法添加的西地那非类物质。待测样品以甲醇溶解超声辅助提取,减压浓缩后以氘代DMSO溶解上机测试;利用Assure-NMR软件将得到的未知样品异核单量子...本研究通过使用灵敏度增强的带梯度形状脉冲进行异核单量子相干(HSQC)实验检测保健食品中违法添加的西地那非类物质。待测样品以甲醇溶解超声辅助提取,减压浓缩后以氘代DMSO溶解上机测试;利用Assure-NMR软件将得到的未知样品异核单量子相干(Heteronculear Single Quantum Coherence)谱图与已知西地那非类物质谱图进行模拟匹配。本方法检出限可以达到200μg·kg-1,能快速有效的对保健食品中西地那非类物质的违法添加侦察识别。该方法简便快捷,可以为食品安全监管部门提供一种新颖便捷的那非类物质监管稽查参考办法。展开更多
NMR relaxation analysis provides a unique and non-invasive probe of fluid dynamics within porous materials,and may be applied to the interpretation of a wide variety of material and interfacial characteristics.Here,we...NMR relaxation analysis provides a unique and non-invasive probe of fluid dynamics within porous materials,and may be applied to the interpretation of a wide variety of material and interfacial characteristics.Here,we report two-dimensional^(1)H T_(1)-T_(2)relaxation correlation measurements of a range of three-carbon adsorbates(1-propanol,2-propanol and propanoic acid)imbibed within the mesoporous metal oxide gamma-alumina.Our data,acquired across field strengths of 2 MHz,12.7 MHz and 43 MHz,clearly reveal two populations in each measurement,identified as the alkyl and hydroxyl moieties of each adsorbate.These results expand the range of materials in which such functional group resolved relaxation is known to occur,and demonstrate the clear persistence of such phenomena using a range of typical benchtop NMR systems employed to study fluid-saturated porous media.展开更多
A new protein wood adhesive was studied with Camellia oleifera protein.Formaldehyde and N-(2)-L-Ala-L-Gln(LAG)were used as the model compounds of amino resins and Camellia oleifera protein,aiming to provide scientific...A new protein wood adhesive was studied with Camellia oleifera protein.Formaldehyde and N-(2)-L-Ala-L-Gln(LAG)were used as the model compounds of amino resins and Camellia oleifera protein,aiming to provide scientific foundations for the improvement and applications of Camellia oleifera protein adhesive by the reaction of model compounds.The experimental results demonstrate that,under alkaline conditions,formaldehyde is easier to react with Camellia oleifera protein by quicker reaction and lower curing temperature.Under acid conditions,amino hydroxymethylated structure of aliphatic series from LAG is difficult to form stable reactive intermediates and further polycondensation.Hydroxymethylation of end acylamino and peptide bond amino from LAG is relatively weak.Under alkaline conditions,the free aliphatic amino and acylamino of LAG both can make hydroxymethylation reaction with formaldehyde.In the polycondensation,hydroxymethyl amide is the initial structure and the reactive intermediate is produced by E1cb reaction of hydroxymethyl amide.Methylene bridge bonds and methylene ether bonds are structures of the polycondensation products,which are competing reactions.The former is mainly formed by the reaction between alkaline reactive intermediate and amino of aliphatic series,and the latter is produced by the reaction of reactive intermediate and amino of hydroxymethyl aliphatic series with hydroxymethyl amide.展开更多
基金This paper is supported by“National Natural Science Foundation of China(Grant No.42204106)”.
文摘The measurement of nuclear magnetic resonance(NMR)porosity is affected by temperature.Without considering the impact of NMR logging tools,this phenomenon is mainly caused by variations in magnetization intensity of the measured system due to temperature fluctuations and difference between the temperature of the porous medium and calibration sample.In this study,the effect of temperature was explained based on the thermodynamic theory,and the rules of NMR porosity responses to temperature changes were identified through core physics experiments.In addition,a method for correcting the influence of temperature on NMR porosity measurement was proposed,and the possible factors that may affect its application were also discussed.
基金supported by the Institut de la Francophonie pour le Developpement Durable(IFDD/Canada)/Projet de Deploiement des Technologies et Innovations Environnementales(PDTIE)funded by Organisation Internationale de la Francophonie(OIF)the Organisation of African,Caribbean and Pacific States and the European Union(EU)(FED/220/421-370)the Local Materials Promotion Authority(MIPROMALO)of the Ministry of Scientific Research and Innovation of Cameroon who made it possible for this scientific work to be carried out.
文摘Extracts of plant origin,particularly tannins,are attracting growing interest for the sustainable development of materials in the industrial sector.The discovery of new tannins is therefore necessary.The aim of this work was to contribute to the understanding of the properties of Paraberlinia bifoliolata tannin by Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectroscopy MALDI-TOF/MS and Carbon 13 Nuclear Magnetic Resonance(13C NMR).The chemical composition of tannin extracted from Paraberlinia bifoliolata bark was determined,as was the mechanical strength of the resin hardened with Acacia nilotica extracts.Yield by successive water extraction was 35%.MALDI-TOF/MS analysis revealed the presence of three new compounds in this tannin,previously unknown in this family of extracts.These are 3-hydroxyproline acid,N-methyl-4-hydroxypipecolic acid and N-methyl-5-dihydroxypipecolic acid.The identification of the above molecules means that this tannin can be used for industrial applications,as a resin in the manufacture of particleboard and in the formulation of green corrosion inhibitors.This information is reinforced by 13C NMR spectrometry,which indicates the presence of several polyflavonoid units,confirming the condensed nature of the tannin.Thermomechanical analysis of the resin formed by the purified tannin of Paraberlinia bifoliolata to which a vegetal biohardener has been added provided a Modulus of Elasticity(MOE)value of 4840 MPa at 150°C,confirming its possible use as a binder resin in the manufacture of wood panels as well as for the formulation of a corrosion inhibitor.
文摘Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.
文摘粮仓是一个复杂的生态系统,其内部生物、非生物以及环境的耦合关系复杂,且只能对温度等少数参数进行探测,粮仓生态近乎“黑箱”。为了便于研究粮仓复杂的耦合关系、核实其中的基本规律,研究提出了一种基于核磁共振(Nuclear Magnetic Resonance,NMR)的粮仓多场耦合图形化探测系统。该系统由核磁共振成像分析仪、粮仓模拟装置和数据采集处理系统三部分组成,可同时实现粮堆温度、湿度和水分三参数的真实精准探测,并能通过配套云图生成软件直观、形象地呈现粮堆温度场、湿度场和水分场分布云图。该系统首次将低场核磁共振成像技术应用于粮堆多场耦合作用研究领域,为探明粮仓生态复杂的耦合关系,进一步证实相关理论研究结论提供了一种新的技术手段。该系统的提出有助于深化行业正在致力发展的粮堆多场耦合及生物场理论。
文摘本研究通过使用灵敏度增强的带梯度形状脉冲进行异核单量子相干(HSQC)实验检测保健食品中违法添加的西地那非类物质。待测样品以甲醇溶解超声辅助提取,减压浓缩后以氘代DMSO溶解上机测试;利用Assure-NMR软件将得到的未知样品异核单量子相干(Heteronculear Single Quantum Coherence)谱图与已知西地那非类物质谱图进行模拟匹配。本方法检出限可以达到200μg·kg-1,能快速有效的对保健食品中西地那非类物质的违法添加侦察识别。该方法简便快捷,可以为食品安全监管部门提供一种新颖便捷的那非类物质监管稽查参考办法。
基金the Forrest Research Foundation.Carmine D’Agostino would like to acknowledge the EPSRC for grant no.EP/S019138/1.
文摘NMR relaxation analysis provides a unique and non-invasive probe of fluid dynamics within porous materials,and may be applied to the interpretation of a wide variety of material and interfacial characteristics.Here,we report two-dimensional^(1)H T_(1)-T_(2)relaxation correlation measurements of a range of three-carbon adsorbates(1-propanol,2-propanol and propanoic acid)imbibed within the mesoporous metal oxide gamma-alumina.Our data,acquired across field strengths of 2 MHz,12.7 MHz and 43 MHz,clearly reveal two populations in each measurement,identified as the alkyl and hydroxyl moieties of each adsorbate.These results expand the range of materials in which such functional group resolved relaxation is known to occur,and demonstrate the clear persistence of such phenomena using a range of typical benchtop NMR systems employed to study fluid-saturated porous media.
基金Funded by the National Natural Science Foundation of China (32160348)the Department Program of Guizhou Province (ZK[2021]162 and[2019]2325)+1 种基金the Special Project of“Doctor Professor Service Group of Kaili University (BJFWT201906)the Cultivation Project of Guizhou University of China ([2019]37)。
文摘A new protein wood adhesive was studied with Camellia oleifera protein.Formaldehyde and N-(2)-L-Ala-L-Gln(LAG)were used as the model compounds of amino resins and Camellia oleifera protein,aiming to provide scientific foundations for the improvement and applications of Camellia oleifera protein adhesive by the reaction of model compounds.The experimental results demonstrate that,under alkaline conditions,formaldehyde is easier to react with Camellia oleifera protein by quicker reaction and lower curing temperature.Under acid conditions,amino hydroxymethylated structure of aliphatic series from LAG is difficult to form stable reactive intermediates and further polycondensation.Hydroxymethylation of end acylamino and peptide bond amino from LAG is relatively weak.Under alkaline conditions,the free aliphatic amino and acylamino of LAG both can make hydroxymethylation reaction with formaldehyde.In the polycondensation,hydroxymethyl amide is the initial structure and the reactive intermediate is produced by E1cb reaction of hydroxymethyl amide.Methylene bridge bonds and methylene ether bonds are structures of the polycondensation products,which are competing reactions.The former is mainly formed by the reaction between alkaline reactive intermediate and amino of aliphatic series,and the latter is produced by the reaction of reactive intermediate and amino of hydroxymethyl aliphatic series with hydroxymethyl amide.
