We perform 31p nuclear magnetic resonance （NMR） measurements on a single crystal of RuP. The anomalies in resistivity at about TA = 270 K and TB = 330 K indicate that two phase transitions occur. The line shape of a...We perform 31p nuclear magnetic resonance （NMR） measurements on a single crystal of RuP. The anomalies in resistivity at about TA = 270 K and TB = 330 K indicate that two phase transitions occur. The line shape of alp NMR spectra in different temperature ranges is attributed to the charge density distribution. The Knight shift and spin-lattice relaxation rate 1/T1T are measured from 1OK to 30OK. At about TA = 270K, they both decrease abruptly with the temperature reduction, which reveals the gap-opening behavior. Well below TA, they act like the case of normal metal. Charge-density-wave phase transition is proposed to interpret the transition occurring at about TA.展开更多
Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance pr...Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance proportional coefficient. The NMR spectrometer used this investigation was a Bruker AM-500 spectrometer operating at 202.4 MHz for ^(31)P chemical shifts are relative to 85% phosphoric acid. TIC was carried out by silica gel H plate developed in chloroform-methanol-glacial acetic acid-ethanol-water(25:4:6:2:0.5),with Vaskovsky reagent as colour -developing agent of phospholipids.展开更多
Proton nuclear(^(1)H)is the observed nucleus on which most magnetic resonance imaging(MRI)applications depend.Most traditional^(1)H MRI can provide structural and functional information about organisms,while various n...Proton nuclear(^(1)H)is the observed nucleus on which most magnetic resonance imaging(MRI)applications depend.Most traditional^(1)H MRI can provide structural and functional information about organisms,while various non-proton nuclei(X-nuclei)MRI can provide more metabolic information.However,due to the relatively poor signal-to-noise ratio(SNR)of X-nuclei MRI,their applications are quite rare compared to^(1)H.Benefit from the rapid developments of MRI hardware and software technologies,X-nuclei MRI has recently attracted increasing interests in biomedical research.This review firstly introduces some current methods to improve the SNR of X-nuclei MRI.Secondly,this review describes biomedical applications of X-nuclei MRI,especially focusing on the current use of X-nuclei(^(13)C,^(17)O,^(19)F,^(23)Na and^(31)P)MRI to study related diseases in different organs,including the brain,liver,kidney,heart and bone.Finally,perspectives studies on X-nuclei imaging and its potential applications are described in biomedical research.展开更多
土壤有机磷(P_(o))是土壤中重要的磷库,其形态、含量与生物有效性随成土过程而发生变化,进而影响土壤磷素供应、养分平衡及生态系统生产力。然而,与土壤无机磷(P_(i))相比,以往的研究对P_(o)的重视不够,这主要是由于土壤中P_(o)的提取...土壤有机磷(P_(o))是土壤中重要的磷库,其形态、含量与生物有效性随成土过程而发生变化,进而影响土壤磷素供应、养分平衡及生态系统生产力。然而,与土壤无机磷(P_(i))相比,以往的研究对P_(o)的重视不够,这主要是由于土壤中P_(o)的提取、分析和鉴定方法难于P_(i)。近年来,随着液相^(31)P核磁共振(^(31) P NMR)波谱技术在土壤学领域的应用,为定量分析土壤P_(o)组分及含量提供了新的技术手段,同时为更好地理解生态系统演化过程中不同形态P_(o)的转化特征奠定了基础。本文主要总结了土壤P_(o)的种类和性质,介绍了液相^(31)P NMR分析土壤P_(o)的原理和方法,在此基础上综述了自然成土过程中不同形态P_(o)的转化特征及其影响因素,并指出了需进一步研究的方向和关键科学问题:包括量化成土过程中不同形态P_(o)转化速率、途径与环境阈值,阐明不同发育阶段土壤P_(o)与C、N等养分之间的耦合关系及其固释机理,构建不同类型土壤P_(o)演化模型。回答上述问题有助于更好地理解地球关键带磷素生物地球化学循环,为不同发育阶段土壤养分管理与调控及土壤资源可持续利用提供理论依据。展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11025422the National Basic Research Program of China under Grant Nos 2011CB921700 and 2015CB921300the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB07020200
文摘We perform 31p nuclear magnetic resonance （NMR） measurements on a single crystal of RuP. The anomalies in resistivity at about TA = 270 K and TB = 330 K indicate that two phase transitions occur. The line shape of alp NMR spectra in different temperature ranges is attributed to the charge density distribution. The Knight shift and spin-lattice relaxation rate 1/T1T are measured from 1OK to 30OK. At about TA = 270K, they both decrease abruptly with the temperature reduction, which reveals the gap-opening behavior. Well below TA, they act like the case of normal metal. Charge-density-wave phase transition is proposed to interpret the transition occurring at about TA.
文摘Five phospholipids in human placenta were determined by phosphorus 31 nuclear magnetic resonance(^(31)P NMR)spectroscopy and thin-layer chromatography(TLC) scanning combined with the corrective method of absorbance proportional coefficient. The NMR spectrometer used this investigation was a Bruker AM-500 spectrometer operating at 202.4 MHz for ^(31)P chemical shifts are relative to 85% phosphoric acid. TIC was carried out by silica gel H plate developed in chloroform-methanol-glacial acetic acid-ethanol-water(25:4:6:2:0.5),with Vaskovsky reagent as colour -developing agent of phospholipids.
基金supported by Chinese Academy of Sciences MRI Technology Alliance under Grant 2020GZ1003.
文摘Proton nuclear(^(1)H)is the observed nucleus on which most magnetic resonance imaging(MRI)applications depend.Most traditional^(1)H MRI can provide structural and functional information about organisms,while various non-proton nuclei(X-nuclei)MRI can provide more metabolic information.However,due to the relatively poor signal-to-noise ratio(SNR)of X-nuclei MRI,their applications are quite rare compared to^(1)H.Benefit from the rapid developments of MRI hardware and software technologies,X-nuclei MRI has recently attracted increasing interests in biomedical research.This review firstly introduces some current methods to improve the SNR of X-nuclei MRI.Secondly,this review describes biomedical applications of X-nuclei MRI,especially focusing on the current use of X-nuclei(^(13)C,^(17)O,^(19)F,^(23)Na and^(31)P)MRI to study related diseases in different organs,including the brain,liver,kidney,heart and bone.Finally,perspectives studies on X-nuclei imaging and its potential applications are described in biomedical research.
文摘农田生态系统中土壤磷形态转化,影响土壤磷对作物的有效供应。土壤磷分为无机磷和有机磷两大部分。化学连续提取法(chemical sequential fractionation,CSF)研究土壤磷形态分级,采用不同的化学提取剂,分级提取土壤中组成或分解能力接近的有机无机含磷化合物,是目前表征土壤磷素形态的重要方法。但该方法虽历经改进,仍难以确切反映土壤磷的实际组成,提取的不同磷形态间存在重叠,有机磷和无机磷组分分级存在一定的误差;不同分级磷组分对作物的有效性,需谨慎评估。核磁共振波谱技术(nuclear magnetic resonance,NMR)根据核磁共振波谱图上共振峰的位置、强度和精细结构来研究土壤中含磷化合物的分子结构。液相31PNMR可以同吋检测出土壤中多种磷组分,如正磷酸盐、磷酸单酯、磷酸二酯、膦酸脂、焦磷酸盐和多聚磷酸盐,识别土壤提取物磷形态,可将有机磷与无机磷分开。本文综述了应用31P-NMR技术研究土壤磷形态组分的一些进展,总结了样品制备过程、NMR测试参数及在土壤磷形态转化研究中的应用。二维31P-NMR技术发展为鉴定分析土壤中更多种类的含磷化合物提供了契机。
文摘土壤有机磷(P_(o))是土壤中重要的磷库,其形态、含量与生物有效性随成土过程而发生变化,进而影响土壤磷素供应、养分平衡及生态系统生产力。然而,与土壤无机磷(P_(i))相比,以往的研究对P_(o)的重视不够,这主要是由于土壤中P_(o)的提取、分析和鉴定方法难于P_(i)。近年来,随着液相^(31)P核磁共振(^(31) P NMR)波谱技术在土壤学领域的应用,为定量分析土壤P_(o)组分及含量提供了新的技术手段,同时为更好地理解生态系统演化过程中不同形态P_(o)的转化特征奠定了基础。本文主要总结了土壤P_(o)的种类和性质,介绍了液相^(31)P NMR分析土壤P_(o)的原理和方法,在此基础上综述了自然成土过程中不同形态P_(o)的转化特征及其影响因素,并指出了需进一步研究的方向和关键科学问题:包括量化成土过程中不同形态P_(o)转化速率、途径与环境阈值,阐明不同发育阶段土壤P_(o)与C、N等养分之间的耦合关系及其固释机理,构建不同类型土壤P_(o)演化模型。回答上述问题有助于更好地理解地球关键带磷素生物地球化学循环,为不同发育阶段土壤养分管理与调控及土壤资源可持续利用提供理论依据。
