我国学者在无标记远场超分辨领域取得突破

正超越"衍射极限",实现具有亚百纳米分辨率的显微成像已成为人类探索微观世界不可或缺的技术手段,是国际研究热点。2014年的诺贝尔奖得主发明了基于荧光标记的STED、STORM、和PALM,使人类的光学显微进入了超分辨时代。然而目前的超分辨技术面临着需要借助荧光标记、视场狭窄、样品选择性强、应用对象极为受限等瓶颈。普适性强、可快速成像的无标记的宽场远场超分辨显微方法成为显微领域亟待突破的关键。近来,浙江大学杨青、刘旭团队开创性地将发     

双光子共焦荧光显微系统成像分析及实验研究

双光子共焦荧光显微系统可以突破传统光学显微镜的成像分辨率极限,提高厚荧光物三维扫描的横向及轴向分辨力.基于共焦荧光显微原理和菲涅耳衍射公式,分析了反射式双光子共焦荧光显微系统的三维光学传递函数.讨论了在实验条件下,共焦模块参数对双光子共焦荧光读取分辨率的影响.双光子共焦荧光系统采用的共焦小孔半径为3.92 μm时,其层析能力比采用78.4 μm共焦小孔的系统提高了1.56倍.通过已知尺寸荧光物的双光子共焦荧光成像实验,验证了共焦小孔直径与系统横向及轴向分辨率的反比关系.     

荧光探针检测活性氧的研究进展

环境中很多途径都可以产生活性氧,过量的活性氧对有机体是非常不利的,将给细胞造成不可逆的伤害。用于检测活性氧的电子自旋共振及色谱技术受到诸多条件制约。荧光探针由于具有灵敏程度高,数据采集简化度好,显微成像分辨率高等优点,能够克服其他检测方法存在的不利因素。介绍了荧光探针在对过氧化氢,单线态氧,超氧阴离子,羟基自由基等活性氧检测方面的进展情况。     

突破极限,见所未见——2014年诺贝尔化学奖侧记

2014年诺贝尔化学奖给了三个物理学家：艾力克·贝齐格（Eric Betzig）、斯特凡·W·赫尔（Stefan W.Hell）和W·E·莫纳（W.E.Moerner）,以表彰他们对于发展超分辨率荧光显微镜做出的卓越贡献。他们的突破性工作使光学显微技术进入了纳米尺度,从而使科学家们能够观察到活细胞中不同分子在纳米尺度上的运动。这三位获奖科学家都是业内知名人士,很有知名度。     

微扫描超分辨率超声成像技术研究

针对提高超声成像的分辨率问题展开研究,提出了微扫描超分辨率超声成像的方法.通过将微扫描和超分辨率技术结合并应用于超声成像中,微扫描技术获取满足超分辨率技术的多幅低分辨率图像,然后应用超分辨率图像重建算法获取高分辨力图像,并对此过程进行了仿真.仿真结果表明:提出的基于微扫描的超分辨率超声成像方法在实际应用中有一定的可行性,对提高超声成像设备的分辨率具有参考价值.     

自适应光学在生物荧光显微成像技术中的应用

显微成像是开展微观生命科学研究的重要手段,其中荧光显微成像以其可特异性标记、暗场对比度高、动态示踪性能出色等优势在生物成像领域占据重要地位.由于活体生物组织通常是非透明、非均匀、各向异性的复杂三维结构,激发光和发射荧光在生物组织内传播时均会由于折射、散射、吸收等作用使得光波波前发生明显畸变,造成激发光点扩散函数以及荧光成像点扩散函数的性能显著降低.借助自适应光学技术可对上述经由生物组织传播产生的波前畸变进行实时探测和精确校正,从而提升激发光照明和发射荧光成像的空间分辨率和深度.本文归纳了生物荧光显微成像中的不同像差来源,介绍了自适应光学波前传感和校正的方法,概括了不同成像方式下波前校正的要求,重点讨论了自适应光学技术在不同类型荧光显微成像中的运用和实现方法,并对其今后的应用目标和发展方向提出展望.     

光学显微三维成像特性的实验研究

讨论了激光共焦扫描显微镜的三维超分辨率成像特性,通过实验论证了在理论分析上所具有的三维超分辨率成像特性.理论分析和实验结果表明这种新的显微系统可以成高分辨率的二维层析图像并重构成三维图像.     

基于结构先验的人脸图像超分辨率技术概述

人脸图像超分辨率技术,又名人脸幻觉,可根据给定的低分辨率人脸图像中恢复出对应的高分辨率人脸图像.该技术无论是在学术界还是在工业界都具有非常广泛的应用前景.人脸,作为一种具有高度结构先验的对象,其结构先验可以为网络提供结构信息,从而辅助人脸图像超分辨率任务的执行,改善人脸图像超分辨率性能.因而许多基于结构先验的人脸图像超分辨率方法被提出.为了了解和掌握基于结构先验的人脸图像超分辨率技术的发展状况,本文对其进行了系统的总结与归类,主要从先先验、并行先验、中间先验和后先验,四个方面对基于结构先验的人脸图像超分辨率技术进行概述.最后分析基于结构先验的人脸图像超分辨率技术存在的问题与挑战.     

基于字典学习的超分辨率显微CT图像重建

为提高显微CT重建图像的空间分辨率,提出了一种基于字典学习的超分辨率图像重建算法.首先,将重建图像进行网格细化,并使用面积权值模型实现对投影过程的精确建模.然后,选择高质量的图像作为训练样本,采用K-SVD算法构建图像字典.基于该图像字典,利用正交匹配追踪算法实现对重建图像的稀疏表达,并以此作为稀疏项约束引入到重建算法的目标函数中.最后,使用梯度下降法求解目标函数.实验结果表明:与传统的基于插值的超分辨率重建算法相比,所提算法的超分辨率结果在图像对比度、边缘保持方面具有优势,并且保留了更多的图像高频信息,从而有效提高了重建图像的空间分辨率.     

超分辨率采样模式中的高模式和超模式对比研究

超分辨率技术用于提高卫星遥感影像分辨率已经在国际上得到了越来越多的关注和认可,高模式(hipermode)和超模式(supermode)是超分辨率技术中非常重要的两种采样模式.本文对高模式和超模式进行了对比研究.通过两种模式的采样原理、采样效果、采样数据分析等几个方面的对比,得出两种模式的优缺点并分析了在当前的技术环境下采用哪种模式具有更多的优势和性价比.     

Tunable nanowire nonlinear optical probe

One crucial challenge for subwavelength optics has been the development of a tunable source of coherent laser radiation for use in the physical, information and biological sciences that is stable at room temperature and physiological conditions. Current advanced near-field imaging techniques using fibre-optic scattering probes have already achieved spatial resolution down to the 20-nm range. Recently reported far-field approaches for optical microscopy, including stimulated emission depletion, structured illumination, and photoactivated localization microscopy, have enabled impressive, theoretically unlimited spatial resolution of fluorescent biomolecular complexes. Previous work with laser tweezers has suggested that optical traps could be used to create novel spatial probes and sensors. Inorganic nanowires have diameters substantially below the wavelength of visible light and have electronic and optical properties that make them ideal for subwavelength laser and imaging technology. Here we report the development of an electrode-free, continuously tunable coherent visible light source compatible with physiological environments, from individual potassium niobate (KNbO3) nanowires. These wires exhibit efficient second harmonic generation, and act as frequency converters, allowing the local synthesis of a wide range of colours via sum and difference frequency generation. We use this tunable nanometric light source to implement a novel form of subwavelength microscopy, in which an infrared laser is used to optically trap and scan a nanowire over a sample, suggesting a wide range of potential applications in physics, chemistry, materials science and biology.     

Structured illumination microscopy for super-resolution and optical sectioning

Optical microscopy plays an essential role in biological studies due to its capability and compatibility of non-contact, minimally invasive observation and mea- surement of live specimens. However, the conventional optical microscopy only has a spatial resolution about 200 nm due to the Abbe diffraction limit, and also lacks the ability of three-dimensional imaging. Super-resolution far- field optical microscopy based on special illumination schemes has been dramatically developed over the last decade. Among them, only the structured illumination microscopy （SIM） is of wide-field geometry that enables it easily compatible with the conventional optical microscope. In this article, the principle of SIM was introduced in terms of point spread function （PSF） and optical transform function （OTF） of the optical system. The SIM for super-resolution （SIM-SR） proposed by Gustafsson et al. and the SIM for optical sectioning （SIM-OS） pro- posed by Neil et al. are the most popular ones in the research community of microscopy. They have the same optical configuration, but with different data post- processing algorithms. We mathematically described the basic theories for both of the SIMs, respectively, and pre- sented some numerical simulations to show the effects of super-resolution and optical sectioning. Various approaches to generation of structured illumination patterns were reviewed. As an example, a SIM system based on DMD- modulation and LED-illumination was demonstrated. A lateral resolution of 90 nm was achieved with gold nanoparticles. The optical sectioning capability of the microscope was demonstrated with Golgi-stained mouse brain neurons, and the sectioning strength of 930 nm was obtained.     

核级石墨氧化后孔隙结构表征

 高温气冷堆是第4代先进核能系统的候选堆型之一,核级石墨作为高温气冷堆重要的中子慢化剂、反射层和结构材料,对于保证反应堆的安全运行和完整性至关重要。核级石墨的氧化会引起其内部孔隙结构的变化,从而对其力学、热学、辐照等性能产生影响。本文介绍了定量描述核级石墨氧化后孔隙结构特征的参量,包括孔隙率、失重率、孔径及BET面积等。系统地总结了国内外用于核级石墨氧化后微观结构表征的常用方法和应用现状,包括直接测量方法和间接测量方法两大类,前者主要有质量-体积法、压汞法、气体吸附法等,后者主要有光学显微成像、X射线成像、显微CT技术、超声波法等;讨论了各种方法和技术的工作原理、应用范围和优缺点,并对核级石墨氧化后的性能研究进行了展望。     

锯缘青蟹胚胎复眼发生的形态观察

采用光镜和电镜技术。观察了锯缘青蟹胚胎复眼发生的过程，并将之划分为4个阶段：复眼色素带出现期，复眼色素带斑状期，复眼色素带条状期和复眼色素带核仁期．刚孵出幼体的复眼呈黑色半球形，着生在粗短的眼柄原基上。小眼表面观呈六边形．复眼发生和胚胎颜色变化密切相关，复眼可作为评判锯缘青蟹胚胎发育阶段的重要指标，为其科学人工育苗提供指导．     

荧光共焦显微镜相干面光源相位滤波器

光源尺寸是荧光共焦显微镜的一个重要参数,增大面光源的尺寸使荧光共焦显微镜分辨率变差,为了克服这个缺点,提出了使用相位滤波器改变相干面光源不同环区的相位．作为一个例子,采用一个两区相位滤波器,数值计算结果表明系统的分辨率能得到改善,同时光源孔径可以增大．     

Optical microscopy using a single-molecule light source

Rapid progress in science on nanoscopic scales has promoted increasing interest in techniques of ultrahigh-resolution optical microscopy. The diffraction limit can be surpassed by illuminating an object in the near field through a sub-wavelength aperture at the end of a sharp metallic probe. Proposed modifications of this technique involve replacing the physical aperture by a nanoscopic active light source. Advances in the spatial and spectral detection of individual fluorescent molecules, using near-field and far-field methods, suggest the possibility of using a single molecule as the illumination source. Here we present optical images taken with a single molecule as a point-like source of illumination, by combining fluorescence excitation spectroscopy with shear-force microscopy. Our single-molecule probe has potential for achieving molecular resolution in optical microscopy; it should also facilitate controlled studies of nanometre-scale phenomena (such as resonant energy transfer) with improved lateral and axial spatial resolution.     

阴极真空电弧沉积MgO薄膜的椭偏光谱研究

采用阴极真空电弧离子沉积技术在硅基片上制备出了MgO薄膜。利用椭圆偏振光谱、原子力显微镜及扫描电子显微镜分别对不同氧流量下制备的MgO薄膜的厚度,光学常数,表面粗糙度及表面形貌进行了分析,并对椭圆偏振光谱的光学粗糙度结果和原子力显微镜的均方根粗糙度结果进行了对比和分析。结果表明,不同氧流量下制备出的MgO薄膜,表面粗糙度及薄膜颗粒随着氧流量的增加而增大。椭偏光谱与AFM得到的表面粗糙度存在线性一致关系,表明椭偏光谱可作为一种很好的无损分析手段。     

Hacking the optical diffraction limit: Review on recent developments of fluorescence nanoscopy

Subject to the diffraction limit, the resolution of conventional optical microscopy is constrained to about 200 and 500 nm in the lateral and axial planes, respectively. The advantage of optical microscopy in the life sciences over electronic microscopy, especially fluorescence microscopy, drives scientists to develop novel "hacks" to reach nanoscale resolutions by optical means. In this review, three aspects of the techniques are discussed: (1) lateral super-resolution; (2) axial super-resolution; (3) super-resolution in three dimensions. The principles of how the methods achieve the cross-barrier resolution are discussed, and recent advances in current techniques are described. With these methods, the use of fluorescence microscopy is growing quickly toward a new era: fluorescence nanoscopy that will reveal 2 orders of magnitude more information on cellular structure and dynamics.     

Three-dimensional chromatin distribution in neuroblastoma nuclei shown by confocal scanning laser microscopy

The relationship between cell shape and function has long been of interest. However, although the behaviour of the cytoskeleton during the cell cycle has been studied extensively variations in the shape and three-dimensional substructure of the nucleus are less well documented. The spatial distribution of chromatin has previously been studied by a mathematical analysis of the optical densities of stained nuclei, allowing an indirect derivation of the three-dimensional distribution of chromatin. More direct information on chromatin organization can be obtained from electron-microscopic serial sections, although this is very laborious. Using an iterative deconvolution algorithm, Agard and Sedat achieved a degree of optical sectioning in conventional fluorescence microscopy and reconstructed the three-dimensional arrangement of polytene chromosomes. We report here on the three-dimensional structure of cultured mammalian cells as visualized by confocal scanning laser microscopy (CSLM). The exceptionally short depth of field of this imaging technique provides direct optical sectioning which, together with its higher resolution, makes CSLM extremely useful for studying the three-dimensional morphology of biological structures.     

多光子近场共焦光学扫描显微镜表面非传播光场的特性研究

对多光子近场共焦光学扫描显微镜非传播光场的特性进行了系统的理论分析。导出了多光子近场共焦光学扫描显微镜表面非传播光场的频率宽与相差的测不准关系表达式及二维的点扩散函数光学传递函数和能量分布表达式。研究结果表明：多光子近场共焦光学扫描显微镜比单光子共焦显微镜具有更高的横向分辨率和纵向分辨率。而多光子近场共焦光学扫描显微镜比双光子共焦显微镜具有更高的空间分辨率。样品置于其表面的非传播光场内,能得最佳的超分辨效果。