基于自主研发的500 MHz NMR谱仪的紫杉醇结构解析

中国科学院武汉物理与数学研究所（WIPM）于2010年成功研制了500 MHz（WIPM-I 500）高分辨超导核磁共振（NMR）谱仪,并将其投入实际应用中.然而,关于其二维核磁共振（2D NMR）谱图的准确性及在此基础上对复杂物质的结构解析尚无系统完整的数据报道.该文利用WIPM-I 500型NMR谱仪,对紫杉醇样品进行了1D NMR及2D NMR（包括¹H-¹H COSY、¹H-¹H TOCSY、J-Res、¹H-¹³C HMQC和¹H-¹³C HMBC）实验,将谱图分析结果与进口仪器进行了对比.结果表明：利用WIPM-I 500型NMR谱仪能够采集准确的2D NMR谱图,为紫杉醇的正确归属提供了实验基础;而且该文也纠正了文献中对紫杉醇的错误归属.     

核磁共振谱仪超导磁体研究

对核磁共振谱仪超导磁体作了一些调研 ,并在理论的基础上对 4 0 0 MHz NMR谱仪超导磁体进行了方案设计计算     

没有磁场的核磁共振谱学

核磁共振谱学（NMR）可能是有机化学研究中最有用的技术.但是常规的NMR谱仪要求将样品放置在非常强的磁场中,这就需要使用液氦冷却的庞大而昂贵的超导磁铁.美国的一个从事交叉学科研究的小组研制成功没有磁铁的NMR谱仪.     

NMR波谱仪控制台系统的软件测试

作为保证软件质量的重要手段,软件测试多年来一直受到关注. 本文阐述了核磁共振（NMR）波谱仪研制中的软件测试方法,从软件测试的概念出发,结合波谱仪控制台系统的软件结构和核磁共振实验本身的特性,介绍了整个测试过程,分析了测试难点及其解决方法,并详细说明了软件测试的实现过程以及在提高波谱仪可靠性和稳定性上所起的积极作用.      

一体化核磁共振谱仪数据交换的实现机制

核磁共振（NMR）随着其应用领域的拓展和深入,核磁共振谱仪技术得到了不断的发展和完善^[1,2]_. 针对以往谱仪存在的一些问题,本文提出了一种一体化核磁共振谱仪数据交换的实现机制,同时提出了基于ARM（Advanced RISC Machines,先进精简指令计算机）微处理器的嵌入式操作系统软件设计方案,并给出了谱仪各功能模块的实际性能测试结果,对实验结果进行了总结和讨论.      

自主研制核磁共振波谱仪的性能评估

主要介绍自主研制500 MHz核磁共振谱仪的性能评估情况,旨在建立一台功能完整的核磁共振波谱仪. 首先利用系统调试使控制台各个硬件单元在用户软件控制下实现NMR实验中的基本功能,然后通过性能测试保障功率线性度、信号稳定性和场频联锁的可靠性,实验验证了谱仪溶剂峰压制的效果,并获得良好的探头线形指标（0.43/5.46/10.73 Hz）和¹H灵敏度指标（信噪比为728∶1）,表明自主研制500 MHz核磁共振波谱仪系统能够满足常规核磁共振实验需求.     

高聚物微观结构的固体NMR研究

核磁共振波谱是研究高聚物结构和动力学的有效手段,特别是固体高分辨NMR实验方法的不断发展及谱仪技术的进步,使这方面的研究不断深入. 文中简述了若干固体高分辨NMR技术在固态高聚物结构研究中的应用和重要进展. 部分实验工作在Varian UNITYplus 400MHz NMR谱仪的固体单元上完成.     

HC-4型固体多核宽线CW-NMR波谱仪

设计和研制了一台用于检测固体中NMR宽谱线、型号为HC-4的CW-NMR波谱仪.谱仪由APPLE-Ⅱ微型计算机控制扫描、信号累加和数据处理.配备了自制的交叉线圈型和魔T型NMR探头和高温(1300K)探头,使谱仪具有较高的检测灵敏度和较强的测量功能,适用于检测固体中多种非质子核的NMR宽谱线及动态NMR测量.本文简要介绍该谱仪的基本结构、系统各部分的技术性能和测量应用的具体实例.     

Bruker AC-80核磁共振谱仪故障判断与排除

就Bruker公司AC-80核磁共振谱仪的一些常见故障做了分析和总结,并给出排除方案. 一方面,谱仪故障的及时排除能给科研节省宝贵的时间;另一方面,了解谱仪容易出故障的地方及做好相应对策,对于研究者自行对商用谱仪所不能达到创新性实验研究所要求部件进行改造、设计有着重要的意义.     

布鲁克新一代NMR自动调谐探头

所有的分析仪器总是不断追求进一步提高自动化程度,例如在有机合成和药物化学方面,为了适应大量筛选工作的需要,组合化学应运而生,对仪器自动化的要求更高.在这个领域里,NMR是个关键的分析技术,首当其冲地面对这些要求.作为主要的分析仪器生产厂家,布鲁克公司的承诺是——永远不断创新.最近,布鲁克公司推出用计算机控制的自动调谐和匹配的新一代NMR探头,就是又一个明显的例子.这种新探头,不仅满足了用户对NMR谱仪不断提高的要求,同时,使分子结构的测定和验证接近于完全自动化.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.