Aberration corrections of doughnut beam by adaptive optics in the turbid medium

The doughnut beam is a spatially structured beam which has been widely used in super‐resolution microscopy, laser trapping and so on. However, when it passes through thick scattering medium, aberrations will seriously affect its performance. Currently, adaptive optics (AO) has become one of the most powerful tools to compensate aberrations. However, conventional AO always suffers from limited corrected field of view (FOV). Here, we propose a method with conjugate AO system based on coherent optical adaptive technique. The results show that the corrected FOV can be improved effectively. For a wide range of the optical applications with doughnut beam, our method has potentials in correcting aberrations with high speed in turbid media.(A) Mouse brain slice, (B) the distribution of r _PAO, (C) the distribution of r _CAO. The vortex beam focus of the blue point in (B) and (C) among a 137.5 × 137.5 μm FOV (D1) ideally, (D2) with scattering, (D3) in pupil AO system and (D4) in conjugate AO system.      

Monovision and the Misperception of Motion

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A Jackknife Variance Estimator for Unistage Stratified Samples with Unequal Probabilities

Existing jackknife variance estimators used with sample surveyscan seriously overestimate the true variance under unistagestratified sampling without replacement with unequal probabilities.A novel jackknife variance estimator is proposed which is asnumerically simple as existing jackknife variance estimators.Under certain regularity conditions, the proposed variance estimatoris consistent under stratified sampling without replacementwith unequal probabilities. The high entropy regularity conditionnecessary for consistency is shown to hold for the Rao–Sampforddesign. An empirical study of three unequal probability samplingdesigns supports our findings.     

Correction for light absorption in fluorescence studies of protein-ligand interactions

It is shown that absorption of the excitation light can lead to substantial systematic errors in fluorescence measurements of equilibrium constants for formation of protein-ligand complexes. The assumptions about the optical arrangement of the fluorescence spectrometer involved in the calculation of the correction of this absorption are discussed. A general semiempirical correction procedure which can be used for (calculated) absorbance values as high as 5 is described. The importance of choosing the excitation wavelength so as to minimize the necessity for these corrections is emphasized.     

一种估测土壤有机质含量的近红外光谱参数

通过系统分析我国中、东部地区5种不同类型土壤风干样本的有机质含量与近红外(1000～2500 nm)光谱反射率和一阶导数两波段构成的比值、差值及归一化指数之间的关系,构建了适合土壤有机质含量估测的光谱参数及定量反演模型.结果表明：用多元散射校正及Savitzky-Golay平滑方法对原始光谱反射率进行预处理后,其两波段组成的光谱参数与土壤有机质含量的相关性明显优于原始光谱反射率组成的光谱参数,而由上述预处理后的反射率一阶导数的两波段构成的光谱参数介于二者之间;不同类型光谱参数构成形式中,以差值指数的预测性最好,其次为比值和归一化指数;与土壤有机质含量相关程度最高的光谱参数,是以近红外合频区1883和2065 nm 2个波段的反射率经多元散射校正和Savitzky-Golay平滑后构建而成的差值指数DI(CR₁₈₈₃, CR₂₀₆₅),两者呈极显著的直线相关.经不同类型土壤的观测资料检验,模型的决定系数为0.837,均方根误差为4.06;与偏最小二乘法的全谱建模结果相比,尽管DI(CR₁₈₈₃, CR₂₀₆₅)的预测精度略低于后者,但该指数只使用了2个波段的反射率,且所建模型比较简单,能为便携式监测仪的研制提供更有效的信息,可作为一种良好的土壤有机质估测光谱参数.     

沱沱河地区紫花针茅群落种间联结性分析

基于方差比率(VR)、χ2检验和Jaccard指数对沱沱河地区紫花针茅群落12个主要种的种间联结性进行了分析。结果表明,紫花针茅群落优势种多物种间显著正关联,存在稳定共存的种间关系。建群种与其它物种间联结性不显著,在群落中能够稳定存在并占据优势生态位,群落处于植被演替过程的一个相对稳定的阶段。伴生种或次优势种之间联结显著,在群落中表现出很强的依赖性,分布易受其它物种的影响,在群落中不能稳定存在且只占据劣势生态位。根据种间联结性的分析结果,将紫花针茅群落分为2个不同的生态种组,但这2个生态种组并不具有明显的界限,它们之间存在着直接或间接的联系。     

点格局分析中边缘校正的一种新算法及其应用

在点格局分析中,通常选取一个矩形作为研究区域,而K(d)函数估计值的方差倾向于随着距离尺度的增加而增加.作为一种粗略的指导,距离尺度的最大值一般为矩形最小边长度的一半.在这种情况下,边缘校正的权重最小值为0.25.通过在校正圆上等弧长取点,用校正圆上落在研究区域之内的点数除以整个校正圆上的点数,作为边缘校正权重的近似值.点数越多,这种近似算法越接近传统的精确算法.这种近似算法不仅适用于计算研究区域为矩形的边缘校正权重,而且适用于计算研究区域为任意多边形的边缘校正权重.此外,当矩形研究区域中点事件的信息不足时,这种算法可以允许计算接近到距离尺度的上限(即矩形对角线长度的一半)对应的K(d)函数.