生物医学核磁共振中的模式识别方法

模式识别(PR)是把具体事物进行正确归类的科学,它能解决许多对复杂体系的认识问题. 生物医学核磁共振波谱(NMR)的理解和分析便是其中一种. 在受到病理或者其他刺激后,生物体内的代谢物水平会发生变化,这种变化可以通过液体高分辨核磁共振的手段来观察. 模式识别把这种认识进一步深化,不仅可以将正常状态与病理状态区分开,还能找到是哪些生化指纹导致两种状态的差异,为生理、病理和药理等研究,以及临床诊断提供依据. 模式识别与生物核磁共振波谱的结合,已经发展成为代谢组学研究的关键技术,甚至被称为基于核磁共振的代谢组学. 主要讨论适用于生物医学核磁共振中的模式识别方法及其最新进展.     

基于NMR的代谢组学方法最新进展及应用

代谢组学的定义“对病理/生理刺激以及基因改变时生物体系动态的代谢响应进行多参数的定量测量”已被广泛接受. 本文对代谢组学研究的最新进展及其在系统生物学中所发挥的作用进行了综述. 在代谢组学方法研究方面,着重讨论了现代NMR技术的进展及其对代谢组学所产生的影响,同时也包括用于分离的HPLC及其与质谱的连用技术. 对代谢组学广泛应用的概述,主要包括：对正常生理变化的新认识;药物和其他外源性化学物质的副作用;外源性物质对环境污染的影响以及逐渐增多的代谢组学方法在疾病检测中应用.     

热纤梭菌中心代谢产物的归属及初步代谢组分析

热纤梭菌(Clostridium thermocellum)是一种能够高效利用木质纤维素的嗜热厌氧革兰氏阳性菌,是目前利用整合生物加工技术生产纤维素乙醇的最重要的候选菌株之一.代谢物组可以反映细胞和环境因子相互作用,是系统生物学的重要组成部分.目前,尚无使用核磁共振(NMR)方法对热纤梭菌的代谢组进行研究的报道,而对热纤梭菌代谢物的归属是进行代谢组研究的基础.该文通过1H NMR和2D NMR技术,对热纤梭菌的中心代谢产物进行了归属.在归属过程中,发现了若干特殊的重要代谢产物,包括纤维糊精、磷酸烯醇式丙酮酸、赤藓糖-4-磷酸等.这些代谢物对热纤梭菌的胞内代谢具有特殊的意义.利用已归属的代谢物,对热纤梭菌的野生型和乙醇耐受菌株进行初步的代谢组分析表明,热纤梭菌乙醇耐受性的获得,可能与纤维二糖主动合成纤维糊精途径、非氧化磷酸戊糖途径的增强及糖酵解路径的抑制密切相关.     

代谢组学数据分析方法及在糖尿病研究中的应用

对NMR波谱数据的统计分析是基于NMR代谢组学研究的关键问题之一. 鉴于NMR波谱信号可以近似为样品中各种成分谱信号的线性叠加,本文将非负矩阵分解(NMF)方法引入基于NMR代谢组学的数据处理中,并与代谢组学中常用的统计方法--主成分分析(PCA)进行比较. 通过NMF和PCA两种方法对健康志愿者与2型糖尿患者血液和尿液的NMR谱图的统计分析,对所获取的特征代谢物进行比较和验证,并探讨了PCA方法可能存在的不足之处及其原因;阐明了NMF方法是基于NMR的代谢组学研究中较理想的数据分析方法. 最后,讨论了基于NMR代谢组学在糖尿病研究中的前景.     

L 1 范数支持向量机在代谢组学中的应用

代谢组学是关于生物体内源性代谢物质的整体及其变化规律的科学,也是一个数据密集型的研究领域,由此使得模式识别在代谢数据处理中有重要作用．L₁ 范数支持向量机(L₁-Norm Support Vector Machines, L₁-norm SVMs)作为在模式识别领域中准确、稳健的方法,在代谢组学中的应用较少．该文应用L₁-norm SVM 方法对小鼠感染血吸虫后的代谢数据进行了分析,分析结果显示L1-norm SVM 在聚类与特征选择方面具有优势,并表明它在代谢组学领域的应用有着潜力和前景．     

莽草酸途径中26种代谢物的NMR谱归属

莽草酸代谢途径广泛存在于植物、微生物与某些寄生虫中,是芳香氨基酸、植物激素与多种重要活性次生代谢物的主要合成通路.这些代谢物的系统核磁共振（NMR）研究尚不完备,且5-羟基吲哚乙酸与吲哚乳酸等代谢物的NMR数据归属尚不完整.本文对莽草酸代谢途径介导的26种代谢物（包括2种非芳香羧酸、2种植物激素、3种芳香类氨基酸、19种植物次生代谢物）结构进行了较为系统的NMR分析,对这些代谢物的¹H和¹³C NMR信号进行了归属,为植物化学及代谢组学研究提供了基础数据.     

利用体内19F NMR研究5-氟尿嘧啶在小鼠肝脏及肿瘤组织中的代谢过程

利用体内¹⁹F NMR研究了5-氟尿嘧啶在小鼠肝脏及植入肿瘤组织中的代谢过程.5-氟尿嘧啶在肝脏中的生物半衰期为15~20min,而在S180肿瘤中的生物半衰期为50-60min.除5-氟尿嘧啶的信号外.在肝脏中观测到了5-氟尿嘧啶的分解代谢产物FUPA和FBAL,而在肿瘤中则只有合成代谢产物氟代核苷酸的信号.实验结果表明,核磁共振是研究药物在体内代谢过程的有力方法.     

NMR方法在煤炭分析中的应用进展

简要介绍了核磁共振（NMR）方法在煤炭组成及热解过程分析中的应用. 目前用于煤炭分析的NMR方法主要包括固体NMR和液体NMR. 从检测手段来看,以¹³C NMR和¹H NMR方法较多,¹⁵N NMR, ¹⁹F NMR和³¹P NMR也在煤炭的分析中发挥了重要作用. 其中用于区分和选择性检测不同官能团的NMR谱编辑方法的发展, 进一步推进了NMR在煤炭化工中的应用.     

涡虫代谢物组成的核磁共振分析

作为扁形动物门的代表动物,涡虫因其特殊的演化地位和极强的再生能力,迅速成为实验动物学、细胞遗传学、发育生物学和再生生物学等研究中的理想模式生物. 众多与涡虫相关的研究都取得了突破性进展,而其在核磁共振和代谢组领域的相关科研报道却极为匮乏. 该研究使用甲醇水提取方法获得了涡虫身体提取物样品,同时利用高分辨的1 GHz NMR谱仪对该样品采集了¹H NMR谱图和5种2D NMR谱图（¹H-¹H COSY,¹H-¹H TOCSY,¹H-¹H J-RES,¹H-¹³C HSQC和¹H-¹³C HMBC）. 通过归属得到涡虫身体提取物里所含有的53种代谢物质,包括氨基酸、糖类、脂类、有机羧酸、酮体、胺类、胆碱类以及核苷酸等. 这些物质覆盖了多种代谢途径,为涡虫代谢组研究提供了基本的NMR相关信息.     

冷冻干燥对人类体液代谢组影响的NMR研究

样品前处理是代谢组分析的重要环节，而冷冻干燥是样品前处理过程中去除溶剂的重要方法，但冷冻干燥对代谢组分析结果的影响还有待进一步研究.本文以人类尿液和血清样本为研究对象，采用核磁共振（NMR）技术分析了冷冻干燥对这两种重要体液代谢组的影响，发现冷冻干燥会引起体液样本中部分有机羧酸和氨基酸含量的改变；而且，冷冻干燥对尿液和血清样品代谢组的影响不同，这可能与两种体液的生物基质差异有关.本研究结果表明，在代谢组学研究中要格外关注冷冻干燥对样品前处理及后续数据归一化所产生的影响.     

Fluorescence enhancement of Ln doped nanoparticles

Fluorescence emission of Ln³⁺ doped nanoparticles is influenced by many factors. Enhancement of fluorescence emission of Ln³⁺ doped nanoparticles can be achieved either through an external approach or an internal adjustment. The external approaches mainly include application of core/shell configuration and metal or semiconductor nanoparticles. Varying the crystal phase of the nanoparticle or introducing a codopant sensitizer are the internal approaches frequently used to obtain fluorescence enhancement, which are through inner adjustments to change the local structure, local symmetry and interaction with active ions. In the current work, efforts to obtain luminescence enhancement in Ln³⁺ doped nanoparticles through external or internal approaches are reviewed. The important roles of local symmetry and asymmetric interactions with optically active ions are extensively discussed.     

An extension of the plane-symmetric electrovac general solution to Einstein equations

We present the general solution to Einstein-Maxwell equations representing plane-symmetric metrics associated with electromagnetic fields that are not fully plane-symmetric. There are two classes in the general solution, the first approaches Taub's static metric or Kasner's spatially homogeneous one as the electromagnetic field goes to zero, while the second approaches the fiat metric.     

纳米材料和技术在可再生能源方面的应用

纳米光子学,产生于纳米技术和光子学的交界处,处理光和物质在纳米尺度的相互作用,可以被用来产生新的效果和发展纳米尺度的器件。世界在迎接未来能源需求方面正面临巨大挑战。纳米光子学为太阳能转换提供了新的进展。在太阳能转换领域,我们正加速开展新的基于纳米光子学让太阳光子在整个光谱范围从紫外到红外有效率地被吸收和转换,并且有效率地转换为电能方面的研究（比如直接或者电化学的转换）。纳米技术也为热电和能量储存方面的研究提供了新的途径,我们正追求把它们和太阳能获取整合在一起从而提供广泛的能源解决方案。     

A unified view of imaging the elastic properties of tissue

A number of different approaches have been developed to estimate and image the elastic properties of tissue. The biomechanical properties of tissues are vitally linked to function and pathology, but cannot be directly assessed by conventional ultrasound, MRI, CT, or nuclear imaging. Research developments have introduced new approaches, using either MRI or ultrasound to image the tissue response to some stimulus. A wide range of stimuli has been evaluated, including heat, water jets, vibration shear waves, compression, and quasistatic compression, using single or multiple steps or low-frequency (<10 Hz) cyclic excitation. These may seem to be greatly dissimilar, and appear to produce distinctly different types of information and images. However, our purpose in this tutorial is to review the major classes of excitation stimuli, and then to demonstrate that they produce responses that fall within a common spectrum of elastic behavior. Within this spectrum, the major classes of excitation include step compression, cyclic quasistatic compression, harmonic shear wave excitation, and transient shear wave excitation. The information they reveal about the unknown elastic distribution within an imaging region of interest are shown to be fundamentally related because the tissue responses are governed by the same equation. Examples use simple geometry to emphasize the common nature of the approaches.     

Alternative calculations of initial value problem for electromagnetic field in dielectric waveguide

Two ways of solving an initial value problem in a dielectric waveguide is presented. Each way describes one of two complementary approaches: a progressive or Brillouin waves approach and an oscillatory or eigenfrequency approach. The evolution of a transient electromagnetic field in the waveguide after an instant change of its permittivity is considered and calculated. The results of the approaches coincide completely, however, the Brillouin approach is more intuitive, visual, and less demanding computationally.     

Possible Approach to Improve Sensitivity of a Michelson Interferometer

We propose a possible approach to achieve a 1/N sensitivity of Michelson interferometer by using a properly designed random phase modulation. Different from other approaches, the sensitivity improvement does not depend on increasing optical powers or utilizing the quantum properties of light. Moreover the requirements for optical losses and the quantum efficiencies of photodetection systems may be lower than the quantum approaches and the sensitivity improvement is independent of frequency in all the detection bands.     

Equivalence of kinetic-theory and random-matrix approaches to Lyapunov spectra of hard-sphere systems

In the study of chaotic behaviour of systems of many hard spheres, Lyapunov exponents of small absolute values exhibit interesting characteristics leading to speculations about connections to non-equilibrium statistical mechanics. Analytical approaches to these exponents so far can be divided into two groups, macroscopically oriented approaches, using kinetic theory or hydrodynamics, and more microscopically oriented random-matrix approaches in quasi-one-dimensional systems. In this paper, I present an approach using random matrices and weak-disorder expansion in an arbitrary number of dimensions. Correlations between subsequent collisions of a particle are taken into account. It is shown that the results are identical to those of a previous approach based on an extended Enskog equation. I conclude that each approach has its merits, and provides different insights into the approximations made, which include the Stoßzahlansatz, the continuum limit, and the long wavelength approximation. The comparison also gives insight into possible connections between Lyapunov exponents and fluctuations.     

Physical Modeling of Aqueous Solvation

We consider the free energies of solvating molecules in water. Computational modeling usually involves either detailed explicit-solvent simulations, or faster computations, which are based on implicit continuum approximations or additivity assumptions. These simpler approaches often miss microscopic physical details and non-additivities present in experimental data. We review explicit-solvent modeling that identifies the physical bases for the errors in the simpler approaches. One problem is that water molecules that are shared between two substituent groups often behave differently than waters around each substituent individually. One manifestation of non-additivities is that solvation free energies in water can depend not only on surface area or volume, but on other properties, such as the surface curvature. We also describe a new computational approach, called Semi-Explicit Assembly, that aims to repair these flaws and capture more of the physics of explicit water models, but with computational efficiencies approaching those of implicit-solvent models.     

光学技术在运动人体科学中的应用

研究了光学技术在人体运动研究中潜在应用．光生物调节作用可以抑制细胞凋亡．色光疗法、低强度激光针灸和鼻腔内低强度激光照射可以调节植物神经功能和昼夜节律，它们具有防治运动性疲劳的潜在价值．蛋白质分子构型变化可以用园二色谱表征，组织和大脑血氧饱和度的变化可以用近红外光谱表征，尿液可以用傅里叶红外光谱进行代谢组学研究，它们都可以作为运动训练的有效表征工具．