时间分辨荧光光谱测量结果的一种数据处理改进方法

在综合矩方法和拉普拉斯变换方法原理的基础上,本文报道一种时间相关单光子计数测出的荧光衰变动力学曲线的数据处理的改进方法.此方法使我们能在花费时间较少的条件下得出和用最小二乘法拟合相比拟的准确分析结果.这一方法的优点已被用于分析香豆素102+DCM和香豆素102+PBBO激光染料乙醇溶液的双指数荧光衰变过程的结果所证实,此外,本文也讨论了仪器时间漂移校正及拉普拉斯变换的数据截取问题.     

时间分辨荧光光谱测量结果的一种数据处理改进方法

在综合矩方法和拉普拉斯变换方法原理的基础上,本文报道一种时间相关单光子计数测出的荧光衰变动力学曲线的数据处理的改进方法.此方法使我们能在花费时间较少的条件下得出和用最小二乘法拟合相比拟的准确分析结果.这一方法的优点已被用于分析香豆素102+DCM和香豆素102+PBBO激光染料乙醇溶液的双指数荧光衰变过程的结果所证实,此外,本文也讨论了仪器时间漂移校正及拉普拉斯变换的数据截取问题.     

傅立叶变换红外光谱在生命科学中的应用

主要综述了傅立叶变换红外光谱在生命科学中的广泛应用.阐述了傅立叶变换红外光谱在生物大分子中的吸收峰位置、振动方式以及谱带归属,介绍了傅立叶变换红外光谱目前在肿瘤方面的研究,为从分子的角度研究癌变机理,提供了重要依据.     

心音信号的分析方法及其应用

心音信号包含了关于人体丰富的病理信息,其分析与研究为心血管疾病的诊断提供了很重要的临床依据.本文探讨了心音信号分析的研究现状,及其短时傅立叶变换(STFT),小波变换(WT),Hilbert-Huang变换在心音信号分析中的应用以及需要解决的理论问题,并运用PhysioBank数据库中的ECG数据,将Hilbert变换运用于ECG信号的分析中,结合MATLAB软件,做出了较为理想的瞬时频率图.     

使用Radon变换进行二维MRI图像配准

使用了一种基于Radon变换的技术来进行二维的MRI图像配准。MRI的图像配准一般使用灰度配准,而Radon变换一般用于CT图像的重建,虽然现已经存在使用Radon变换进行图像配准,但是比较繁琐,我们对这一配准算法进行了简化。     

初级视觉的小波表征及其图象压缩效果

初级视觉的Ｇａｂｏｒ函数模型和变换尺度为３是初级视觉处理外界信息的主要特征。在此基础上,由于小波所具有的多分辨特性与视觉处理由粗到细的过程相一致,因而,希望存在一类能够表征这两个初级视觉特征的小波变换。从这点出发,本文先给出了具有变换尺度为３的正交Ｈａａｒ基,而后给出了具有以上两个特征的小波基和小波滤波器。我们将其应用到图象信息的压缩上,着重与传统二进的小波变换图象压缩的效果进行了比较,结果说明具有视觉特征的小波变换能够提供良好的图象压缩效果和主观视觉效果     

基于小波变换心电信号消噪方法研究

小波变换是近年来兴起的热门信号处理技术,是一种非常有用的信号处理工具。本文阐述了连续小波去噪和离散小波去噪的原理,分析了基于小波去噪的几种不同方法（其中包括小波分解与重构,小波变换阈值法,小波变换模极大值法,以及它与独立分量分析相结合去除噪声的方法等）。通过检测和验证,表明该方法能较好的实现心电信号的消噪,都取得了较好的效果;同时,比较了每种方法的不足和缺陷。基于小波变换心电信号消噪的研究进展较快,通过多种方法结合运用进行消噪并取得了很好的效果,展望了利用基于小波变换心电信号消噪的前景。     

小波变换与生物医学信号处理

作为数字信号处理领域的一个重要分支,生物医学信号处理理论与技术的研究一直受到国内外科技工作者的高度重视。小波变换是近年来发展起来的一种新的信号分析工具。本文结合生物医学信号与小波变换的特点,探讨了小波变换在生物医学信号处理领域的应用前景。     

心音信号噪声消除的小波变换方法

心音信号幅值小,干扰多,采用常规的时、频域滤波方法往往不能收到良好的效果,本文根据信号和干扰在小波变换下的不同变化特性,利用二进小波变换的模极大值识别出心音信号中的干扰噪声的位置,剔除其相应的小波变换系数后,再通过小波逆变换重构出心音信号,并根据心音信号的特点选取了适当的母小波和分解尺度,给出了利用小波方法去噪前后的实际结果,结果表明,小波变换方法可有效地消除心音信号中的噪声干扰。     

小波变换及其在医学图像处理中的应用

医学图像的好坏直接影响着医生对病情的诊断和治疗,因此利用数字图像处理等技术对医学图像进行有效的处理,已成为医学图像处理研究和开发的一大热点。小波变换是对傅里叶变换的继承和发展,在医学影像领域有着广泛的应用前景。本文介绍了二维离散小渡变换的一般形式,在图像分解与重构的基础上．系统地阐述了利用小小组变换的时频域特性与多分辨分析对医学图像进行去噪、增强以及边缘提取等深层次的处理,有效的改善图像质量。     

Atomic force microscope,molecular imaging,and analysis

Image visibility is a central issue in analyzing all kinds of microscopic images. An increase of intensity contrast helps to raise the image visibility, thereby to reveal fine image features. Accordingly, a proper evaluation of results with current imaging parameters can be used for feedback on future imaging experiments. In this work, we have applied the Laplacian function of image intensity as either an additive component (Laplacian mask) or a multiplying factor (Laplacian weight) for enhancing image contrast of high‐resolution AFM images of two molecular systems, an unknown protein imaged in air, provided by AFM COST Action TD1002 ( http://www.afm4nanomedbio.eu /), and tobacco mosaic virus (TMV) particles imaged in liquid. Based on both visual inspection and quantitative representation of contrast measurements, we found that the Laplacian weight is more effective than the Laplacian mask for the unknown protein, whereas for the TMV system the strengthened Laplacian mask is superior to the Laplacian weight. The present results indicate that a mathematical function, as exemplified by the Laplacian function, may yield varied processing effects with different operations. To interpret the diversity of molecular structure and topology in images, an explicit expression for processing procedures should be included in scientific reports alongside instrumental setups. Copyright © 2015 John Wiley & Sons, Ltd.     

Improving spatial and temporal resolution in evoked EEG responses using surface Laplacians

Spline generated surface Laplacian temporal wave forms are presented as a method to improve both spatial and temporal resolution of evoked EEG responses. Middle latency and the N1 components of the auditory evoked response were used to compare potential-based methods with surface Laplacian methods in the time domain. Results indicate that surface Laplacians provide better estimates of underlying cortical activity than do potential wave forms. Spatial discrimination among electrode sites was markedly better with surface Laplacian than with potential wave forms. Differences in the number and latencies of peaks, and their topographic distributions, were observed for surface Laplacian, particularly during the time period encompassing the middle latency responses. Focal activities were observed in surface Laplacian wave forms and topographic maps which were in agreement with previous findings from auditory evoked response studies. Methodological issues surrounding the application of spline methods to the time domain are also discussed. Surface Laplacian methods in the time domain appear to provide an improved way for studying evoked EEG responses by increasing temporal and spatial resolution of component characteristics.     

In vitro assessment of the toxicity of metal compounds

A review of the activity of metal compounds in mammalian cell transformation assays has been completed. Results from these assays appear to correlate well with the known carcinogenic activity displayed by specific metal compounds in vivo. Studies of cell transformation in vitro may provide information pertaining to the mechanism of the induction of carcinogenesis by certain metals.     

An asymptotic estimate for the effective radius of a concentric bipolar electrode.

A concentric bipolar electrode (CBE) (consisting of a central disc and an outer annulus) has been proposed as an approximate method of measuring the surface Laplacian of the body surface electrical potential distribution. The derivation of the surface Laplacian approximation, in terms of the potential difference measured with the bipolar electrode, contained an unspecified parameter which has been dubbed the 'effective radius' of the concentric bipolar electrode. This paper presents an asymptotic analysis to derive an expression for the effective radius in terms of the physical dimensions of the electrode (the radius of the central disc and inner and outer radii of the annulus). Also studied is the way in which the value of the effective radius affects the behaviour of the relative error in the surface Laplacian measurement at various dipole source locations within a conducting medium.     

Natural incorporation of mercury in bone

Mercury (Hg) is a highly toxic element that causes bone defects and malformations. Structure and surface analyses using quantitative x-ray diffraction using the Rietveld method, High-Resolution Transmission Electron Microscopy and nanodiffraction analyses, and Fourier-Transformed Infrared spectroscopy showed that bone enriched naturally with Hg (≤ 2.3 %) contained Hg₃PO₄ [(Hg₂)₃(PO₄)₂] and HgO. Bone [mostly as apatite, verified as carboxyapatite Ca₁₀(PO₄)₄(CO₃)₃(OH)₂(s)] and cinnabar (HgS) dissolved releasing Hg⁺ (existing as dimer Hg₂²⁺) and PO₄³⁻, both of which became immobilized as (Hg₂)₃(PO₄)₂. Besides, released Hg²⁺ became oxidized to form HgO. The outcome of this work is novel, provided that only a handful of stable compounds of Hg₂²⁺ are found in nature.     

Spectral decomposition for the search and analysis of RNA secondary structure.

Scales in RNA, based on geometrical considerations, can be exploited for the analysis and prediction of RNA structures. By using spectral decomposition, geometric information that relates to a given RNA fold can be reduced to a single positive scalar number, the second eigenvalue of the Laplacian matrix corresponding to the tree-graph representation of the RNA secondary structure. Along with the free energy of the structure, being the most important scalar number in the prediction of RNA folding by energy minimization methods, the second eigenvalue of the Laplacian matrix can be used as an effective signature for locating a target folded structure given a set of RNA folds. Furthermore, the second eigenvector of the Laplacian matrix can be used to partition large RNA structures into smaller fragments. An illustrative example is given for the use of the second eigenvalue to predict mutations that may cause structural rearrangements, thereby disrupting stable motifs.     

Local estimate of surface Laplacian derivation on a realistically shaped scalp surface and its performance on noisy data

A new implementation of the surface Laplacian derivation (SLD) method is desribed which reconstructs a realistically shaped, local scalp surface geometry using measured electrode positions, generates a local spectral-interpolated potential distribution function, and estimates the surface Laplacian values through a local planar parametric space using a stable numerical method combining Taylor expansions with the least-squares technique. The implementation is modified for efficient repeated SLD operations on a time series. Examples are shown of applications to evoked potential data. The resolving power of the SLD is examined as a function of the spatial signal-to-noise (SNR) ratio. The analysis suggests that the Laplacian is effective when the spatial SNR is greater than 3. It is shown that spatial low-pass filtering with a Gaussian filter can be used to reduce the effect of noise and recover useful signal if the noise is spatially incoherent.     

基于Fiedler向量的基因表达谱数据分类方法

尝试将一种基于图的Fiedler向量的聚类算法引入到基因表达谱数据的肿瘤分类中来。该方法将分属不同类的所有样本通过高斯权构造Laplace完全图,经SVD分解后获得Fiedler向量,利用各样本所对应的Fiedler向量分量的符号差异来进行基因表达谱数据的分类。通过模拟数据仿真实验和对白血病两个亚型(ALL与AML)及结肠癌真实数据实验,证明了这一方法的有效性。     

Characteristics of beryllium bonds; a QTAIM study

The nature of beryllium bonds formed between BeX2 (X is H, F and Cl) and some Lewis bases have been investigated. The distribution of the Laplacian of electron density shows that there is a region of charge depletion around the Be atom, which, according to Laplacian complementary principal, can interact with a region of charge concentration of an atom in the base and form a beryllium bond. The molecular graphs of the investigated complexes indicate that beryllium in BeH2 and BeF2 can form “beryllium bonds” with O, N and P atoms but not with halogens. In addition, eight criteria based on QTAIM properties, including the values of electron density and its Laplacian at the BCP, penetration of beryllium and acceptor atom, charge, energy, volume and first atomic moment of beryllium atom, have been considered and compared with the corresponding ones in conventional hydrogen bonds. These bonds share many common features with very strong hydrogen bonds, however,some differences have also been observed.     

Determining skeletal muscle architecture with Laplacian simulations: a comparison with diffusion tensor imaging

Determination of skeletal muscle architecture is important for accurately modeling muscle behavior. Current methods for 3D muscle architecture determination can be costly and time-consuming, making them prohibitive for clinical or modeling applications. Computational approaches such as Laplacian flow simulations can estimate muscle fascicle orientation based on muscle shape and aponeurosis location. The accuracy of this approach is unknown, however, since it has not been validated against other standards for muscle architecture determination. In this study, muscle architectures from the Laplacian approach were compared to those determined from diffusion tensor imaging in eight adult medial gastrocnemius muscles. The datasets were subdivided into training and validation sets, and computational fluid dynamics software was used to conduct Laplacian simulations. In training sets, inputs of muscle geometry, aponeurosis location, and geometric flow guides resulted in good agreement between methods. Application of the method to validation sets showed no significant differences in pennation angle (mean difference \(0.5{^{\circ }})\) or fascicle length (mean difference 0.9 mm). Laplacian simulation was thus effective at predicting gastrocnemius muscle architectures in healthy volunteers using imaging-derived muscle shape and aponeurosis locations. This method may serve as a tool for determining muscle architecture in silico and as a complement to other approaches.