岩石的核磁共振弛豫时间加权微成像

根据自旋回波成像脉冲序列中像点信号强度与重复时间TR及回波时间TE的关系，结合岩石孔隙流体核磁共振她豫的多指数特性，利用T1加权和T2加权微成像提取岩样扎隙结构的信息，以此区分大孔和微孔．1实验方法自旋回波单片核磁共振成像脉冲序列如图1所示问．图中，GX为X方向的梯度场，用于信号的频率编码，实现X方向的空间定位；GY为Y方向的梯度场，用于信号的相位编码，实现Y方向的空间定位；GZ为Z方向的梯度场，结合形状脉冲，用于确定选片的位置及片厚，实现Z方向的空间定位．RF是射频脉冲发射通道，由90°宽带脉冲和180℃窄带形状…     

用23Na和27Al固体核磁共振研究Na+在γ-Al2O3上的吸附状态

The adsorption of Na~+ on γ-alumina surface at four coverages of Na_2CO_3 (5%, 10%, 15%, and 20% wt/wt) was characterized by solid-state ~(23)Na and ~(27)Al NMR spectroscopy. The experimental results suggest that two distinct adsorbed species are present on alumina surface: surface species and surface salts. At lower coverages of Na_2CO_3 (5% and 10%), a surface species is predominant, in which the Na~+ cations are associated with the oxygen atoms of γ-alumina. With increasing the loading level to 15%, a second adsorbed species begins to appear which is attributed to the surface salt, Na_2CO_3, deposited on the solid surface. Further adsorption of Na_2CO_3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. ~1H-~(27)Al CP/MAS experiments give the evidence that some Na~+ cations in the form of surface species are coordinated with the Br~(‥)onsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of Na_2CO_3/γ-Al_2O_3 catalyst.     

吸附在活性炭上的二氧六环类固相和类液相性质的NMR研究

In this paper a study of the spin lattice relaxation times of dioxane(DO) adsorbed on various charcoals is presented. Results show that the magnetziation of DO decays biexponentially (Table 1) as observed in the case of adsorbed hydrocarbons~[6]. The fast relaxing molecules are considered to be those adsorbed in micropores with radii less than 1.0 nm whose motion is restricted and slowed down, thus they form a solid like phase. However, the slow relaxing ones are those condensed in the micropores, they are free to move and form the liquid like phase. Molecules condensed in the interior of the micropores exchange rapidly with those situated in the vicinity of the pore wall according to Eq.(2).Comparison of data in Table 1 may lead to a conclusion that charcoal with greater density of surface acidic groups and greater percentage of pore capacity with radius<1.0 nm (V_(10)/V_(30)) has a greater percentage of solid like phase (P_f). Although V_(10)/V_(30) of density of surface acidic groups. It is apparent that surface acidic groups in micropores play an important role in the formation of solid like phase of DO on charcoals. It seems that DO form hydrogen bond with the surface acidic groups. It is this hydrogen bond and the hinderance effect of pores restrict the DO from moving freely, which results in the formation of the so called solid like phase. It can be found from small (0.10 ml/gC). This implies that DO vapour may first condense in the micropores having more acidic groups and higher activation energy, and then fill in other pores step by step as the adsorption process proceeds.     

用固体核磁共振研究Al/P>1的磷酸铝分子筛AlPO4-5

用固体高分辩核磁共振（ＮＭＲ）方法对一系列Ａｌ／Ｐ＞１的新型磷酸铝分子筛ＡｌＰＯ４－５中磷和铝的结构状态及联结方式进行了研究，＾２７Ａｌ和＾３１Ｐ ＮＭＲ都给出了在分子筛骨架中存在有Ａｌ－Ｏ－Ａｌ联结方式的实验证据，寓示着在该体系中Ｐ和Ａｌ的排布不再遵循Ｌｏｅｗｅｎｓｔｅｉｎ规则。     

改性VOx/Al2O3催化剂催化氧化甲醇的固体核磁共振研究

采用固体核磁共振研究了NaOH 和HNO₃改性的VO_x/Al₂O₃上甲醇选择性催化氧化反应. 实验结果表明: 在甲醇的氧化反应中, 酸位对二甲氧基甲烷的生成起了重要作用. 与VO_x/Al₂O₃催化剂相比, 酸改性的VO_x/Al₂O₃上的强的Bronsted酸位对二甲氧基甲烷的选择性较高, 没有Bronsted酸位的碱改性的VO_x/Al₂O₃上生成的不是二甲氧基甲烷而是甲酸盐.     

CS-MRI 中评价随机欠采样矩阵的新方法

在压缩感知-磁共振成像(CS-MRI)中,随机欠采样矩阵与重建图像质量密切相关．而选取随机欠采样矩阵一般是通过计算点扩散函数(PSF),以可能产生的伪影的最大值为评价参数,评估欠采样对图像重建的影响,然而最大值只反应了伪影的最坏情况．该文引入了两种新的统计学评价参数平均值(MV)和标准差(SD),其中平均值评估了伪影的平均大小,标准差可以反映伪影的波动情况．该文分别使用这3种参数对小鼠和人体脑部MRI数据以不同的采样比率进行CS图像重建,实验结果表明,当采样比率不低于4倍稀疏度时,使用平均值获得了质量更优的重建图像．因此,通过稀疏度先验知识指导合理选取采样比率,并以平均值为评价参数选取随机欠采样矩阵,能够获得更优的CS-MRI重建图像．
     

化学位移张量的测量

对于刚性晶格中的分子,化学位移是与外加磁场空间取向相关的张量,这个张量有6个独立的分量. 化学位移张量也可以利用其主轴分量及主轴与晶体坐标系的方向余弦来表示. 很显然,知道了固体分子中各不等价位置处的化学位移张量,就可以推测出分子中电子分布的图象,具有重要意义. 本文首先描述了化学位移张量测量的理论,对测量化学位移 各 向异性的各种方法作了介绍和比较,并详细论述了一些常用的方法,如二维魔角跳旋转(M a gic Angle Hopping, MAH)、二维魔角慢旋转(Magic Angle Turning, MAT)和二维变相旋转边带分离（2D phase-adjusted spinning sidebands, 2D-PASS）技术等. 最后,还介绍了单晶化学位移张量的常规测量方法.     

硅胶键合杯[4]芳烃固定相的合成和核磁共振表征

杯芳烃（Ｃａｌｉｘａｒｅｎｅｓ）［１］是由苯酚单体通过亚甲基单元连接起来的一类性质稳定的环状低聚物．由于它的独特结构特点以及由此表现出来的特有性能,使之已成为继冠醚和环糊精之后的第三代超分子［２］．近年来,杯芳烃在色谱中的应用已经引起人们的关注,有关...     

RESEARCH ON VIBRATION MODES OF THE CHINESE CHIME STONE

Nearfield acoustical holography is a powerful tool for imaging of acoustic sources. In this article, the basic theory treating steady-state acoustic radiation with generalized holography has been discussed. By holographic imaging, the vibration characteristics of irregular objects, the Chinese ancient musical instrument, the one-tone chime stone and the two-tone chime stone provided by the Institute of Archaeology, the Museum of Hubei Province, have been researched. The results show that the ancient chime stone has two main vibration modes, which make up the base of sound produced by the instrument. As for the two-tone chime stone, it is not so long and wide as the single-tone chime stone, but thicker and smoother than the single-tone chime stone. When it is excited at different positions, although it radiates sounds of different frequencies, its vibration modes are similar. This may be related to its dimensions and shape. The research is helpful for studying the sound producing system and the radiated field characteristics of the chime stone.     

Spiral MRI和图像处理

介绍了在Bruker Biospec 47/30 超导核磁共振成象仪(4.7 T)上实现Spiral快速成像及图像处理系统. 图像处理系统基于PC技术构建而成,主要功能包括：1） 将以Spiral形式采集到的时域磁共振信号转化为适用于快速傅立叶变换的笛卡尔网格(Cartesian)形式（网格化处理）;2）二维快速傅立叶变换(2D-FFT,图像重建);3）由化学位移偏置或磁场不均匀引起得偏共振效应(off-resonance effect)的校正;4）图像分析. 该软件适用于包括以多片多回波在内的各种采样方式得到的Spiral图像的重建和分析,也适用于常规成像数据的重建和分析. 所得到的图像可以以数据方式保存以供再次读入,也能够以TIF、GIF、JPG、BM等格式辅出为图像文件.