Prospects for NMR imaging in the study of biological morphogenesis

Summary Small objects can be visualised with a spatial resolution that approaches microscopic dimensions using the technique of high resolution nuclear magnetic resonance (NMR) imaging. Some important features of the method are described and the prospects for using the technique to study morphogenesis are discussed. It is concluded that NMR imaging, in conjunction with the related method of localised spectroscopy, is capable of producing novel structural information.     

A demonstration of the resolution of NMR imaging in biological systems.

A proton NMR imaging study of several fruit specimens demonstrates the integrity and resolution of this new imaging method.     

A demonstration of the resolution of NMR imaging in biological systems

Summary A proton NMR imaging study of several fruit specimens demonstrates the integrity and resolution of this new imaging method.Acknowledgment. We thank Professor E. R. Andrew, Dr W. S. Moore and Miss C. Simaroj for their contributions. The work was supported by MRC grant G975-102.     

基于压缩感知的多角度合成孔径雷达成像

多角度合成孔径雷达（syntheticapertureradar,SAR）成像是实现多SAR信息融合的重要方式．对提高成像分辨率．重构目标轮廓进而提高雷达目标检测或分类性能具有基础性价值．由于各传感器发射信号和测量位置的多样性,实现多角度SAR成像具有挑战性．如何在噪声干扰情况下快速实现多角度SAR成像是一个新问题．本文建立了基于压缩感知的多角度SAR测量模型．通过对测量矩阵的分析,证明多角度SAR测量角度范围、发射信号载频和空间采样位置是影响成像性能的关键因素,研究了目标空间离散间隔对成像质量和分辨率的影响．以上述分析为基础,本文对多角度SAR发射信号载频和测量位置进行设计,构建满足约束等距性的测量矩阵．针对测量矩阵阶次较高的问题,文章提出用分段正交匹配追踪（stagewiseorthogonalmatchingpursuit,STOMP）进行模型求解,在测量矩阵欠定严重的情况下,该算法可以迅速求得模型最优稀疏解．在实验环节．通过分析多角度SAR参数对成像性能的影响,进一步验证了本文结论．实验验证了模型和相应求解算法的有效性和鲁棒性．     

Magnetic resonance microscopy: in vivo sectioning of a developing insect

The utility of magnetic resonance imaging vis-a-vis insect morphology and development was investigated. MRI is a noninvasive technique that distinguishes between tissues based on proton content and proton 'environment'. At present a resolution of 100 micron is achievable. The technique avoids fixation artifacts and allows the detection of motion within the organism.     

基于光学衍射的纳米尺度深度重建

传统的离焦深度恢复方法（depth from defocus,DFD）在计算离焦图像的模糊程度时,均是基于几何光学成像原理,并没有考虑光波衍射对图像模糊的影响.然而,衍射现象是波的基本特性,以针孔成像为基础的光学成像系统中必然存在光波衍射.本文基于光学衍射和图像模糊机理,提出了一种精确的单目视觉全局景物3D深度信息获取方法.首先,详细分析了光学成像系统中的菲涅耳衍射机理,建立了衍射模糊与景物深度之间的关系曲线;然后,采用曲线拟合的方式建立了衍射模糊的模糊程度（点扩散函数扩散程度）与景物深度的数学关系模型,结合热辐射和图像相对模糊原理,构建了衍射模糊热辐射方程组,并把衍射模糊深度获取问题转换成一个深度信息动态优化问题.最后,使用标准的纳米栅格模板验证了衍射模糊深度重建算法在纳米尺度相对深度和绝对深度重建中的有效性和精确性.     

The application of the high-performance ion-exchange chromatography for the analysis of bovine milk proteins

A high-performance ion-exchange chromatographic (HPIEC) method for the analysis of milk proteins is described. The technique provides an alternative to other separation methods. The resolution obtained for both the proteins of the casein group and bovine lactoserum is comparable with that of electrophoretic analysis on polyacrylamide gels and low-pressure chromatography.     

The application of the high-performance ion-exchange chromatography for the analysis of bovine milk proteins

Summary A high-performance ion-exchange chromatographic (HPIEC) method for the analysis of milk proteins is described. The technique provides an alternative to other separation methods. The resolution obtained for both the proteins of the casein group and bovine lactoserum is comparable with that of electrophoretic analysis on polyacrylamide gels and low-pressure chromatography.     

Magnetic resonance microscopy: in vivo sectioning of a developing insect

Summary The utility of magnetic resonance imaging vis-a-vis insect morphology and development was investigated. MRI is a noninvasive technique that distinguishes between tissues based on proton content and proton environment. At present a resolution of 100 m is achievable. The technique avoids fixation artifacts and allows the detection of motion within the organism.     

Sur une nouvelle méthode chromatographique pour la séparation de composés polycycliques aromatiques ou hétérocycliques

Summary A new chromatographic technique is described, which makes use of the affinity of anhydrides and imides of tetrahalogenophthalic acids towards aromatic and heterocyclic polycyclic compounds. This method has been successfully applied to the resolution of some problems of analytical organic chemistry.     

Protein NMR in biomedical research

Nuclear magnetic resonance (NMR) spectroscopy is a versatile biophysical technique with wide applicability in drug discovery research, particularly for the detection and characterization of molecular interactions. This review highlights in a comprehensive manner the aspects of biomolecular NMR which are most beneficial for pharmaceutical research and presents them as contributions to the different stages of a drug discovery program: target selection, assay development, lead generation and lead optimization. Emphasis is put on the concept of the particular NMR application, rather than on technical details, and on recent examples. Finally, an appendix of frequently asked questions is given.Received 7 October 2003; received after revision 11 November 2003; accepted 27 November 2003This revised version was published online in September 2004. In the previous version, the authors were listet in reverse order.     

A periodization of research technologies and of the emergency of genericity

According to the historian and sociologist of science Terry Shinn, the creator of the concept of ‘research technologies’: “Research technologies may sometimes generate promising packets of instrumentation for yet undefined ends. They may offer technological answers to questions that have hardly been raised. Research technologists׳s instruments are then generic in the sense that they are base-line apparatus which can subsequently be transformed by experimenters into products tailored to specific economic ends or adapted by experimenters to further cognitive ends in academic research.”¹ Genericity thus manifests one of three fundamental characteristics of research technologies. At the same time, however, each research technology emerges out of the specific disciplinary context in which it is initially developed with entirely concrete aims. Consequently, genericity does not exist from the outset but first has to form, along a path that remains to be clarified. It is produced or constructed by the actors on two levels: as an instrument in the laboratory and as a way of speaking at the representational level. This issue yields the structure of this paper. Three options for the transition of a specific technique into a generic research technology are compared. One of them proves to be the most frequent pattern of this dynamic. This is explored further, taking as paradigmatic examples ‘computed tomography’ (CT), ‘nuclear magnetic resonance׳ (NMR) and its application known as ‘magnetic resonance imaging’ (MRI), together with several additional examples.     

短基线前向散射雷达系统运动目标分辨率分析

针对短基线前向散射雷达系统特性,基于阴影逆合成孔径原理和模糊函数,分别推导了系统沿基线方向和垂直基线方向运动目标的分辨率,解析得到了系统分辨率计算公式;发现垂直基线方向分辨率正比于波长,并首次验证了前向散射雷达沿基线方向分辨目标的可能性;最后利用实测数据验证了沿基线方向和垂直基线方向分辨率分析的正确性.     

Understanding paternal genome demethylation through live-cell imaging and siRNA

Identification of a DNA demethylase responsible for zygotic paternal DNA demethylation has been one of the most challenging goals in the field of epigenetics. Several candidate molecules have been proposed, but their involvement in the demethylation remains controversial, partly due to the difficulty of preparing a sufficient quantity of materials for biochemical analysis. In this review, we utilize a recently developed method for live-cell imaging of mouse zygotes combined with RNA interference (RNAi) to search for factors that affect zygotic paternal DNA demethylation. The combined use of various fluorescent probes and RNAi is a useful approach for the study of not only DNA demethylation but also the spatiotemporal dynamics of histone depositions in zygotes, although it is not appropriate for large-scale screening or knockdown of genes that are abundantly expressed before fertilization. This new technique enables us to understand the epigenetic hierarchy during cellular response and differentiation in preimplantation embryos.     

NMR structural studies of glutathione S-transferase

The use of nuclear magnetic resonance (NMR) spectroscopy for the structure determination of small proteins is now widely recognized; what is less frequently reported is the application of NMR techniques for high-resolution studies of large proteins (M _r larger than 30 kD). We demonstrate here how an integrated approach, using heteronuclear NMR and X-ray crystallography, can provide useful and biologically important information for large protein systems. The dynamic features of the human A1-1 glutathione S-tranferase and the role of the C-terminal region are being probed by NMR; in the X-ray crystal structure, the electron densities for this region of the protein are uninterpretable.     

In-vivo soft tissue NMR imaging of the rat thorax and abdomen

Summary An in vivo study of the anatomy of the thorax and abdomen of a rat by proton sensitive-line NMR imaging is presented and a contrast mechanism for soft tissue differentiation in images discussed.Acknowledgment. I thank E.R. Andrew, W.S. Hinshaw, G.N. Holland, W.S. Moore, and C. Simaroj for their valuable contributions, and the MRC for financial support.     

面向AFM的纳米目标快速重定位方法

原子力显微镜（atomic force microscope,AFM）具有极高的观测分辨率和作业精度,在纳米材料表征与纳米器件组装方面发挥了不可替代的作用.AFM工作区域的选取依赖于光学显微镜,受可见光波波长的限制,光学显微镜的分辨率一般不超过200 nm,这导致光学显微镜无法有效辨识AFM观测目标样本所在的区域.当样本被移动或者更换AFM扫描探针引起样本与探针针尖的相对位置发生变化时,如何重新将AFM探针精确定位到原观测/操作区域具有非常大的挑战性.本文研究提出了一种新的免标记探针重定位方法,综合考虑了样本角度旋转与位置偏移两个因素,首先利用光学显微镜选取样本基底上易于识别的自然特征作为参照点,基于坐标变换原理实现微米级精度的探针盲定位,进而通过AFM扫描图像的匹配获得X-Y水平方向的位置偏差,通过修改AFM的扫描参数实现纳米目标的原位快速精确重定位.该方法的优点在于不需要在纳米目标样本操作区域上制作特殊的标记,操作过程简单、定位快速、定位范围较广且具有极高的重定位精度.对纳米小球、单壁碳纳米管（single-walled carbon nanotubes,SWCNTs）、纳米划痕等样本的重定位实验验证了该方法的实用性和高效性.     

Magnetische Kernresonanz und Festkörperphysik

Summary Nuclear magnetic resonance (NMR) deals with isotopes possessing a nuclear magnetic dipole moment. The nuclei are used as probes to explore the internal magnetic fields in solids. Thus NMR has become a new tool in solid-state physics. Some typical examples of the application of NMR to solid-state problems are discussed.The location and orientation of water molecules in crystals are determined by NMR with relative ease. The second moment of an NMR line shape yields information on the structure as well as on the mobility of the atoms. The various types of resonance frequency shifts may be used for the understanding of the interactions and bonds in the solid and the dynamics of the crystal lattice.Very important are nuclei possessing both a magnetic dipole and an electric quadrupole moment. They serve as very sensitive detectors of the internal electric fields prevailing in solids. Apart from further structural information, NMR spectra influenced by electric quadrupole interaction may be used for studying such topics as aluminium-silicon ordering in feldspars or phase transitions in ferroelectrics.The utility of NMR in treating problems of the bonding is exemplified by showing that the covalent effects in the alkali halides are very small.Some investigations of ferromagnetism, antiferromagnetism and superconductivity are mentioned.     

Non-invasive monitoring of ionic current flow during development by SQUID magnetometry

Summary The ionic currents flowing in developing organisms produce weak magnetic fields that can be detected using SQUID magnetometers. The method is non-invasive and dc recording is possible. To date SQUID magnetometers have mainly been used in human studies. The features of the technique are described and the prospects of extending its use to developmental studies are discussed. Feasible instrumental specifications are indicated. A recent SQUID magnetometer investigation of ionic current flow in the developing chick in ovo is summarised as an illustration of the magnetometer method. The paper as a whole argues that magnetometry is a useful alternative or adjunct to electrode-based experiments on the electrophysiology of developing organisms.