Mie理论在生物组织散射特性分析中的应用

根据等效颗粒散射模型，运用经典的Mie理论，对生物组织的散射相函数、各向异性因子及散射系数进行了数值计算.计算结果表明：可见光照射生物组织时，各向异性因子、散射系数随等效颗粒直径增大而增大；等效颗粒直径较小时，各向异性因子、散射系数随入射光波长增大而单调减小；随着等效颗粒直径增大，各向异性因子、散射系数随入射光波长变化不再具有单调性.上述计算结果可合理解释公布的实验结果. 关键词： 生物组织 散射 Mie理论 等效颗粒     

Application of the T-matrix method to determine the structure of spheroidal cell nuclei with angle-resolved light scattering

We demonstrate an inverse light-scattering analysis procedure based on using the T-matrix method as a light-scattering model. We measure light scattered by in vitro cell monolayers using angle-resolved low-coherence interferometry (a/LCI) and compare the data to predictions of the T-matrix theory. The comparison yields measurements of the equal volume diameter and aspect ratio of the spheroid cell nuclei with accuracy comparable to quantitative image analysis of fixed and stained samples. These improvements represent a significant upgrade for the a/LCI technique, expanding both the range of tissue in which it is applicable and potentially increasing its value as a diagnostic tool.     

Application of the pattern equation method in spheroidal coordinates to solving diffraction problems with highly prolate scatterers

Acoustical Physics - The equations of the diagram equation method are formulated in terms of prolate spheroidal coordinates. Examples of the convergence and stability of numerical algorithms based...     

Application limitedness of the model of spheroidal scatterers for describing scattering properties of titanium dioxide

The results of measurements of the scattering matrix of an aqueous suspension of titanium dioxide at a wavelength of 0.63 μm in the scattering angle range of 10°–150° are presented. The results of the measurements are compared with calculation data for scatterers having the shape of prolate ellipsoids. It is shown that, even when the size parameter equals 4, the experimental and calculated values of the matrix elements f ₂₂ and f ₁₂ significantly differ, which is caused by a complex form of TiO₂ particles, and that the determination of the parameters of the distribution of TiO₂ suspension particles in the interpretation of the measurement data in the context of the considered model is possible with an error of 27% in the effective size and 16% in the distribution width.     

On the applicability of a spherical basis for spheroidal layered scatterers

The applicability of an analog of the extended boundary condition method, which is popular in light-scattering theory, is studied in combination with the standard spherical basis for the solution of an electrostatic problem appearing for spheroidal layered scatterers the sizes of which are small as compared to the incident radiation wavelength. In the case of two or more layers, polarizability and other optical characteristics of particles in the far zone are shown to be undeterminable if the condition under which the appearing systems of linear equations for expansion coefficients of unknown fields are Fredholm systems solvable by the reduction method is broken. For two-layer spheroids with confocal boundaries, this condition is transformed into a simple restriction on the ratio of particle semiaxes a/b< $\sqrt 2 $ + 1. In the case of homogeneous particles, the solvability condition is that the radius of convergence of the internal-field expansion must exceed that of the expansion of an analog of the scattering field. Since homogeneous spheroids (ellipsoids) are unique particles inside which the electrostatic field is homogeneous, it is shown that the solution can be always found in this case. The obtained results make it possible to match in principle the results of theoretical and numerical determinations of the domain of applicability for the extended boundary condition method with a spherical basis for spheroidal scatterers.     

Explanation of the patterns in Mie theory

The far-field scattered light intensity, or the related phase function, for a spherical particle is known to display an overall power-law structure when formulated in terms of the scattering wave vector. Empirically determined patterns in the intensity relating to the particle size and refractive index are known. The cause of the patterns, however, has not been satisfactorily explained. This work applies an exact microphysical model to explain most of the patterns, and specifically, to reveal the physical cause of crossovers from one power-law to another. A unique aspect of this microphysical approach is phasor analysis, which provides a visually based way to examine the angle-dependent wavelet superposition involved in the model. A simple color coding scheme connects the phasors to the interior of the particle, and it is this connection that reveals the meaning of the crossovers.     

Mie光散射理论的数值计算方法

Mie散射级数的计算速度和精度对颗粒测量结果有着重要的影响。针对不同颗粒直径和相对折射率，一般采用前向递推，后向递推，连分式法等计算Mie散射级数。在这3种方法的基础上提出一种改进算法，即首先通过连分式法计算Mie散射级数的初始值，然后后向递推其余各值。该算法在Matlab中实现时，数据以数组的数据类型存储和调用，程序采用递归算法。通过比较计算结果发现，该算法耗时短且结果不易溢出，具有快速、稳定、不受颗粒直径和折射率范围影响等优点。     

Application of the Mie effect to the holographic electron microscope

Using Mie's theory, we reduce the spherical aberration of the system. We then calculate the resolution limit of the holographic electron microscope and improve the usual theoretical resolution limit.     

Large-scale electronic structure calculation theory and applications to nanostructure materials

We review our recently developed methods in large-scale electronic structure calculations. The calculation is based on the tight-binding formalism of the Hamiltonian. First, the mathematical foundation of Krylov subspace method is focused. The density matrix can be calculated exactly and the numerical accuracy can be monitored during the iterative calculation. The key technique of the shifted-COCG (conjugate orthogonal conjugate gradient) method, collinear residual and seed switching, is explained in details. Second, several applications to nanostructure of semiconductors and metals, fracture propagation and surface reconstruction and formation process of gold nanowire, are explained.     

Mie theory 1908, on the mobile phone 2008

Hundred years ago Gustav Mie published his famous paper on the theory of light scattering by spherical particles. It has been programmed in many programming languages since invention of the computer. Nowadays with the mobile phone becoming an educational tool it would be of interest to port a Mie scattering application to a Java enabled hand set. The objective of this paper is to investigate the feasibility of porting existing Mie software to a hand held device. We will show that the mobile phone can be an advanced programming environment for the Mie theory and we will present some exemplary computational results.     

Improving the accuracy of laser particle sizer with Mie scattering theory

Using the classical Mie scattering theory and Fraunhofer diffraction theory,adetailed analysis of the differences of the light energy distribution falling on the multi-elementconcentric photo-detector of a diffraction based laser particle sizer is given.Numerical calcula-tions and computer simulation are carried out. Experimental studies are also made with latexspheres as Standard Reference Material.Our research shows that when the classical Mie scat-tering theory is used,the accuracy of the particle sizer can be essentially improved not only inthe small size range,but also for large paticles.At the same time the time needed for data re-duction in both cases is almost the same.     

Mie theory interpretations of light scattering from intact cells

We present a Mie theory-based analysis of angularly resolved light scattering from intact cells that involves the product of a particle size distribution rho and the scattering cross section sigma. The analysis shows that the ability to size intracellular organelles depends strongly upon the assumed functional form of the particle size distribution; however, the product sigma rho extracts the dominant light scatterers regardless of this choice. We examine goniometer measurements from our own and another laboratory and find that this analysis reconciles seemingly conflicting results and confirms that mitochondrial-sized organelles dominate scattering from intact cells in the angular range 50 degrees - 90 degrees.     

金纳米球壳光学吸收的Mie理论分析

基于Mie散射理论研究了金壳厚度变化、内核尺寸变化及内核介质变化下金纳米球壳的吸收光谱.研究发现,随着金壳厚度的增加,颗粒光学吸收增加到最大值后逐渐降低;随着内核尺寸逐渐增加,金壳颗粒的光学吸收最大值逐渐减小.此外,还发现随着内核介电常数的增大,颗粒的光学吸收逐渐减弱,当内核为空心时,吸收最强.利用等离激元杂化理论及自由电子和振荡电子变化的竞争机制对上述现象进行了理论分析. 关键词： 金纳米球壳 等离激元共振 吸收光谱     

Application of spheroidal functions in theory of light scattering by nonspherical particles: Separation of variables method

The separation of variables method (SVM), which uses a spheroidal basis, is proposed. According to this method, fields are presented in the form of expansion in terms of spheroidal functions. The previously conducted analysis of various methods using a spherical basis showed that the SVM is applicable in a broader area for numerical calculations, while the proposed approach using a spheroidal basis yields reliable results in the case of spheroids with a high degree of asphericity where other methods and approaches cannot be used. Importantly, the method includes an SVM that uses a spherical basis as the limiting case. Thus, the proposed method has all chances of being highly efficient for calculation of optical characteristics of various nonspherical particles in a wide range of parameters of the formulated problem.     

Determination of structure of weak scatterers from holographic images

For a weak scatterer a three dimensional Fourier transform of the image formed by a generalized hologram is shown to yield directly the Fourier transform of the scattering potential evaluated on the Ewald sphere. The entire scattering potential can be approximately determined if the object is illuminated from all directions in a series of experiments and if the scattering potential is essentially bandlimited to within a sphere of radius 4π/λ.