岩石的核磁共振自旋密度微成像

岩，心是油气储层的基本单元，其内部结构和渗流性质反映了油藏的基本特征．岩。心的精细描述是油藏描述、储层动态监测及设计强化采油方案的重要基础．本文利用核磁共振（NMR）自旋密度做成像，快速无损地观测到两类基本储油岩石——砂岩和灰岩的内部结构，提供了岩石渗透性、孔隙性及灰岩沉积环境等重要信息．1实验方法以自旋回波单片NMR成像脉冲序列为基础，设。P平面内样品的目施密度为P（。，v）．演化期t。，在。方向梯度场G。作用下，各处横向磁化矢量获得的相移为式中，7为共振核（在成像中一般为质子）的旋磁比，g为坐标位置·…     

应用~1HNMR谱直接检测生物样品中的微量药物毒物和代谢产物

本文报告了一种新的、有效的用于生物体液的１ＨＮＭＲ方法──选择自旋翻转回波法。在弛豫剂氨基磺酸铵的存在下，通过去偶道对水质子施加１８０°－△选择性脉冲序列，得到自旋回波图谱。在ｐＨ４．６～７．８的范围内，应用该法可有效地抑制水峰，并可准确地测得药物和毒物的信号。在此方法的基础上，测定了水性生物样品中的某些药物和毒物，例如二氢埃托啡、梭曼等。这一方法也已用来研究催醒安（ＣＸＡ）和甲胺磷（ＭＡＰ）在灌流大鼠肝脏中的代谢过程。实验结果表明，该法是一种简便、有效、不需进行样品预处理而可直接对生物样品中药物和毒物进行检测的方法。     

基于固体核磁共振方法的蛋白质组装体三维结构解析

蛋白质组装体广泛存在于生物体内,具有相关生物学功能或与人类的重要疾病密切相关。蛋白质组装体分子量大,通常难以溶解和结晶,限制了常用的结构研究手段如X射线晶体学和液体NMR等在其高分辨三维结构解析中的应用。固体核磁共振技术(ssNMR)在难溶、非结晶样品的三维结构解析中具有独特的优势,尤其随着固体NMR硬件包括高场磁体和高性能的探头、固体NMR多维脉冲实验技术和样品制备技术特别是同位素标记技术的快速发展,固体NMR已经成为了蛋白组装体三维结构解析的重要手段。在样品制备方法方面,强调了样品制备条件的优化对得到构象均一样品的重要性,以及丰富的同位素标记方法的使用对固体NMR谱图分辨率提高的重要作用。同时多种脉冲序列如质子驱动自旋扩散技术(PDSD),偶极辅助旋转共振技术(DARR),质子辅助重偶技术(PAR)或转移回波双共振技术(TEDOR)等的建立和发展为结构约束条件收集提供了基本的技术方法。此外,固体NMR与其它实验技术如扫描透射电镜(STEM),冷冻电镜(Cryo-EM)等和理论模拟方法的联用能显著地提高固体NMR的能力,从而能解析分子量更大、结构更复杂的蛋白质组装体的三维结构。本文以Aβ纤维和T3SS针状体的三维结构解析为例介绍固体NMR在蛋白质组装体结构研究的最新实验方法,重点介绍最新的距离约束条件获取的实验方法进展,以及固体NMR与其它实验和理论模拟研究手段的联用在蛋白质组装体结构解析上的最新进展,期望有助于读者对固体NMR技术在蛋白质组装体的三维结构解析方面的研究进展有所了解。     

基于甲胺客体调制的混价态甲酸铁框架的构筑与磁电行为研究

N-型亚铁磁体可以在场冷时呈现负磁化行为，但在1 T强场场冷时依然能够保持负磁化行为的化合物却很罕见.本工作以CH₃NH₃⁺为客体阳离子，成功构筑了一例红砷镍矿（4⁹.6⁶）（4¹².6³）结构的混价态甲酸铁化合物[CH₃NH₃]_n[Fe^IIIFe^II（HCO₂）₆]_n（1），在1 T强场下呈现负磁化行为.1中甲酸根采用反，反模式连接Fe^II和Fe^III形成三维阴离子框架，八面体配位构型的Fe^II和Fe^III分别处于（4⁹.6⁶）和（4¹².6³）节点，而CH₃NH₃⁺则填充在框架空隙中平衡电荷.量热、介电和单晶X-射线衍射测试结果表明，1中存在由CH₃NH₃⁺无序-有序转变诱导的结构相变并伴随介电弛豫.磁性研究表明Fe^II和Fe^III之间存在较强的反铁磁耦合，但在冷却过程中Fe^II和Fe^III构成的亚晶格磁有序程度存在较大差异，且具有较小自旋的Fe^II磁矩先于Fe^III磁矩有序且平行于外加磁场，导致温度进一步降低时1呈现出负磁化行为，这表明1是一例罕见的N-型亚铁磁体.此外，1在1 T外加冷却场中依然能保持负磁化行为，表明1中存在较强的磁各向异性.值得注意的是，在100 Oe外场下冷却到17 K后，1呈现出正场调制的磁极翻转行为.进一步研究表明，1的场冷磁滞回线呈现不对称形状，并向冷却场方向发生偏转，其有效矫顽力（H_C^eff=（H⁺-H^-）/2）和交换偏置场（H_EB=（H⁺+H^-）/2）分别为21716 Oe和3322 Oe.总之，本研究表明客体分子尺寸和形状能够有效调控红砷镍矿结构中Fe^II的磁各向异性，从而实现较高的磁极翻转场、矫顽力和交换偏置场.     

低剂量氯化钐对大鼠血清激素水平的影响

应用放射免疫法测定了经腹腔注射、灌胃入尾静脉注射等３种不同方式，隔日给预寺鼠低剂量氯化钐０．０５ｍｇ／ｋｇ，一个月后，测试血清中生长激素，甲状腺素Ｔ３、Ｔ３及胰岛素水平。结果显示各实验组动物血清中生长激素、胰岛素水平均明显增高，甲状腺素Ｔ４及腹腔注射增高，其余两组无明显变化。     

基于B样条自由形变三维医学图像非刚性配准研究

医学超声成像具有成本低、实时成像等优势,基于超声的多模态配准在临床诊断、病情监测、外科手术等应用上具有较大的意义。三维医学图像能够清晰地显示病变大小、形态,提供相对完整的人体组织的三维结构信息。本文采用基于B样条自由形变模型的非刚性配准方法对三维超声图像和计算机断层扫描图像（Computed Tomography,CT）进行配准,利用薄板样条能量约束项解决三维图像配准过程中的图像交叉与重叠问题。此外,使用仿体数据以及临床数据验证算法性能,通过感兴趣区域的相对重叠率,互信息值和程序运行时间这三个指标对算法精度和速度进行评价。其中Demons方法平均耗时1896 s,本文改进算法平均耗时195 s,运行效率提高8.7倍;算法改进前后的感兴趣区域重叠率分别是89.58%和91.35%,精度提高2.0%。实验结果表明此算法能够对超声和CT图像进行配准并获得较好的结果。     

Slow diffusion by singlet state NMR spectroscopy

Small diffusion coefficients can be measured by using populations of singlet states that have a relaxation time constant, T(s), which can be much longer than the longitudinal relaxation time, T1. Spatial information can be encoded with pulsed field gradients in the manner of stimulated echo sequences. Singlet states can be excited via double-quantum coherences to enhance the efficiency of phase encoding and decoding.     

Pulsed NMR analysis of ion-selective electrode membranes

A novel method for evaluation of ion-selective electrode membranes was reported with the proton spin-spin relaxation time T(2) by pulsed NMR. The proton spin-spin relaxation time T(2) measurements provided valuable information about properties of the whole membrane matrix. The softer potentiometric liquid membrane possessed a large fraction F(L) providing relatively longer T(2) value. Pulsed NMR method can quantify the degree of the plasticization of ion-selective electrode membranes.     

Generating long-lasting 1H and 13C hyperpolarization in small molecules with parahydrogen-induced polarization

Recently, Levitt and co-workers demonstrated that conserving the population of long-lasting nuclear singlet states in weak magnetic fields can lead to a preservation of nuclear spin information over times substantially longer than governed by the (high-field) spin-lattice relaxation time T1. Potential benefits of the prolonged spin information for magnetic resonance imaging and spectroscopy were pointed out, particularly when combined with the parahydrogen induced polarization (PHIP) methodology. In this contribution, we demonstrate that an increase of the effective relaxation time by a factor up to three is achieved experimentally, when molecules hyperpolarized by PHIP are kept in a weak magnetic field instead of the strong field of a typical NMR magnet. This increased lifetime of spin information makes the known PHIP phenomena more compatible with the time scales of biological processes and, thus, more attractive for future investigations.     

Nuclear spin relaxation due to chemical shift anisotropy of gas-phase 129Xe

Nuclear spin relaxation provides detailed dynamical information on molecular systems and materials. Here, first-principles modeling of the chemical shift anisotropy (CSA) relaxation time for the prototypic monoatomic (129)Xe gas is carried out, both complementing and predicting the results of NMR measurements. Our approach is based on molecular dynamics simulations combined with pre-parametrized ab initio binary nuclear shielding tensors, an "NMR force field". By using the Redfield relaxation formalism, the simulated CSA time correlation functions lead to spectral density functions that, for the first time, quantitatively determine the experimental spin-lattice relaxation times T(1). The quality requirements on both the Xe-Xe interaction potential and binary shielding tensor are investigated in the context of CSA T(1). Persistent dimers Xe(2) are found to be responsible for the CSA relaxation mechanism in the low-density limit of the gas, completely in line with the earlier experimental findings.     

DIGITAL IMAGE ANALYSIS OF PHASE STRUCTURE IN THE BLEND OF POLY(BUTYLENE TEREPHTHALATE-COCAPROLACTONE) WITH POLYCARBONATE

The digital image processing technique was used for the extraction of physical information from the temporal image of phase structure in the process of phase separation in the blend of poly (butylene terephthalate-co-caprolactone )with polycarbonate. The power spectrum images of the two-dimensional Fourier transformation (2DFT) of the temporal image of phase structure reflect the change of the phase size with time.     

Segment identification of a ligand binding with a protein receptor using multidimensional T1rho-, diffusion-filtered and diffusion-ordered NOESY experiments.

Multidimensional T1rho-, diffusion-filtered and diffusion-ordered NOESY techniques were applied to identify segments of a ligand binding with a protein receptor. These experiments can easily provide intermolecular NOEs of the complex, which are of great significance for characterizing the binding epitopes of a ligand. This information cannot be obtained by high-throughput 1D NMR experiments, used for determining the binding affinity, although multidimensional NMR experiments require more experiment time. The present results indicate that the current experiments using T1rho- and diffusion-edited techniques are very suitable for identifying segments of a ligand binding with a protein receptor in the drug discovery process.     

NMR spectroscopy of citrate in solids: cross-polarization kinetics in weakly coupled systems

Solid-state NMR spectroscopy is a potentially powerful method for obtaining molecular level structural information crucial for understanding the specific relationship between calcite crystals and occluded organic molecules that are important in biomineralization and biomimetic materials. In this work, a method is developed based on cross-polarization/magic angle spinning (CP/MAS) NMR to measure the heteronuclear distances and obtain structural information for large intracrystalline citrate defects in a synthetic calcite/citrate composite. Using compounds with well-characterized crystal structures, Mg(II) citrate and Sr(II) citrate, a correlation is established between T(IS), the CP time, and M(2) (IS), the van Vleck heteronuclear dipolar second moment, which contains distance and structural information. This correlation is supported by peak assignments obtained from calculations of the (13)C chemical shifts for crystalline Mg(II) citrate. On the basis of T(IS) (-1) versus M(2) (IS) correlation, measurement of T(IS) for carbonate ions associated with citrate defects in a calcite((13)C-enriched)/citrate coprecipitate yields an estimate for the distance between citrate and the nearest carbonate carbon that indicates close spatial proximity and provides useful constraints for future computational study. The applicability of T(IS) (-1) versus M(2) (IS) correlations to other weakly coupled spin-1/2 systems is discussed in terms of the effects of (1)H homonuclear dipolar coupling, using the CP kinetics of Zn(II) dihydroxybenzoate and kaolinite for comparison. The results suggest a limited range of correlation constants and indicate that quantitative information can be obtained from CP/MAS kinetics obtained under similar experimental conditions.     

SpaRef: a clustering algorithm for multispectral images

Multispectral images such as multispectral chemical images or multispectral satellite images provide detailed data with information in both the spatial and spectral domains. Many segmentation methods for multispectral images are based on a per-pixel classification, which uses only spectral information and ignores spatial information. A clustering algorithm based on both spectral and spatial information would produce better results.

In this work, spatial refinement clustering (SpaRef), a new clustering algorithm for multispectral images is presented. Spatial information is integrated with partitional and agglomeration clustering processes. The number of clusters is automatically identified. SpaRef is compared with a set of well-known clustering methods on compact airborne spectrographic imager (CASI) over an area in the Klompenwaard, The Netherlands. The clusters obtained show improved results. Applying SpaRef to multispectral chemical images would be a straight-forward step.