激光与生物组织相互作用：光子迁移与生物传热理论

激光热疗中,激光与生物组织相互作用研究主要包含两方面：光子在生物组织中的迁移规律,以及光生扫热在生物组织在的传导。对前者的描述主要为,基于传输理论的解析法和Ｍｏｎｔｅ￣Ｃａｒｌｏ模拟,生物组织中光子迁移规律的研究能定量描述组织中的光分布,并进一步获得生物组织中的热分布;考虑到了生物组织特性,所建立了生物组织中温度场分布及变化规律。光子迁移与生物传热理论是研究激光热序不可分割的传热模型,全面描述了生     

蛋白质中原子与基团的可及性的一种新计算方法及其应用

实现了一种新的蛋白质中原子层次可及面积的计算方法－Ｍｏｎｔｅ－Ｃａｒｌｏ模拟方法。计算了溶菌酶各个原子与功能基团的可及性,并应用于蛋白质结构和功能的研究中。使得对蛋白质性能的预测更准确,提供了一种对蛋白质结构和功能研究的新思路。     

生物组织的折射率对漫反射光分布的影响

采用杂合算法,讨论了折射率对不同吸收系数的生物组织漫反射光分布的影响。计算结果表明,在近源处生物组织的折射率越小,漫反射光模拟计算的相对误差越小;而在远离源处,其相对误差随折射率的增大而减小。同时也说明杂合模型不太适合模拟吸收生物组织的漫反射光分布。     

二组分荧光寿命成像显微术的研究

用ＭｏｎｔｅＣａｒｌｏ方法研究了激发光的调制频率、ＣＣＤ所记录到的光强度、荧光寿命的大小以及权值对二组分荧光寿命成像显微术的频域外差法测量及数据处理精度的影响,提出了改进测量精度的方法,如选择合适的调制频率和染料,使调制频率ω和荧光寿命τ满足（１４）和（１５）式;增大ＣＣＤ的积分时间等。     

激光照射血液疗法中的组织光学研究及其应用

本文从组织光学的角度 ,对激光照射血液疗法中的发展现状与存在问题进行分析 ,提出该领域应开展的若干研究内容。本文开展了激光照射血液疗法所涉及的若干组织光学研究。获得了中国人血液的吸收系数、散射系数、各项异性因子、全衰减系数等 ;研究获得了人血管的若干光学参数。通ＭｏｎｔｅＣａｒｌｏ模拟计算 ,以及实验测试结果 ,分别从理论与实际上分析对比了激光血管内照射时 ,光在人体血管、血液中的分布情况 ,以及不同的激光入射角 ,发散角 ,不同的血管直径等因素对激光血液照射的影响。根据对应的组织光学的研究结果 ,文中还讨论并提出…     

北京东灵山地区植物群落多样性的研究 Ⅲ.几种类型森林群落的种-多度关系研究

选用描述种－多度关系的二类共８个模型（对数级数分布ＬＳ、对数正态分布ＬＮ、负二项分布ＮＢ和几何分布ＧＯＭ以及“分割线段”模型ＢＳＭ、生态位优先占领模型ＮＰＭ、Ｚｉｐｆ模型ＺＭ和Ｚｉｐｆ－Ｍａｎｄｅｌｂｒｏｔ模型ＺＭＭ）对东灵山地区９个类型的森林群落进行了研究。结果表明,ＬＳ和ＮＢ对大多数群落可以很好地拟合,ＬＮ和ＧＯＭ对每一个群落都不能很好地拟合;ＺＭＭ可以很好地、ＮＰＭ也可以较好地拟合每一个群落,ＺＭ可以很好地拟合大多数群落,而ＢＳＭ则反之。ＬＳ中的参数α与４个丰富度指数呈极强的线性关系,与３个多样性指数也有较强的线性关系。因此,α可以作为群落的一个多样性指数使用,并且它更多地反映了群落的丰富度。本研究也表明,将包含多个参数的非线性方程组逐渐化为只含一个参数的非线性方程,再将ＭｏｎｔｅＣａｒｌｏ方法、区间二分法和迭代法相结合以求解该方程,从而实现参数估计,这种算法是可行的;在拟合三参数模型ＺＭＭ时,先固定参数β,再通过线性化求出另外２个参数,经过多次计算,求出一组参数值作为下一步非线性方程拟合的初值,这种算法也是成功的。在进行种重要性顺序－多度表模型的评价时,不能只考虑剩余标准差或相关指数,它们是基于误差平方和的两个指标,对真实的误差有某种夸张作用;应该尽可能地考虑平均绝对误差这个指标。     

方差组分估计方法MIVQUE和REML的模拟比较

利用ＭｏｎｔｅＣａｒｌｏ方法,对４种数据结构进行了ＭＩＶＱＵＥ和ＲＥＭＬ两种方差组分估计方法的模拟比较。方差组分估计所用的模型为奶牛育种中常用的公畜模型,它包括场年季固定效应、公牛组固定效应和公牛随机效应。４种数据结构中最大的有１２８４７个观察值,场年季效应和公牛效应水平数分别为７７８和４７,它与北京市目前可利用的奶牛头胎产奶量记录资料相当。最小的数据结构只有２００个观察值,１４８个场年季和２０头公牛。比较指标为估计值的偏差和方差（理论的或根据１０００次重复模拟所得的经验值）。结果表明,对于较大样本的数据结构,两种方法差异很小,它们间的估计值的相关接近于１,偏差小于真值的１％,方差近似相等。对于较小样本的数据结构,ＭＩＶＱＵＥ则明显优于ＲＥＭＬ。本研究还表明,对于ＲＥＭＬ来说,类似数据结构１的样本已能满足其渐近无偏性和有效性的大样本特性。     

应用复合单标记分析进行QTL检测和参数估计的研究

随着现代分子生物技术的进展,在整个基因组范围内系统地搜索影响数量性状的基因座(ＱＴＬ)已成为可能,这便是利用分子遗传标记,通过标记ＱＴＬ连锁分析来对ＱＴＬ进行检测和参数估计。目前对标记基因进行连锁分析的原理与方法相对成熟,而在标记ＱＴＬ连锁分析方面,仍然有许多值得研究的问题。根据简单的性质,本研究提出了一种新的基于单标记分析的ＱＴＬ定位方法———复合单标记分析(ＣＳＭ),并通过Ｍｏｎｔｅ-Ｃａｒｌｏ模拟,研究了在近交系设计(ＢＣ1)当中,不同因素(如标记密度、ＱＴＬ效应等)对ＱＴＬ检测效率及参数估计精度的影响,同时…     

北美CHIUHUAHUAN荒漠啮齿动物群落动态：Ⅳ.群落变量的模拟

利用ＭｏｎｔｅＣａｒｌｏ方法模拟了北美ＣＨＩＨＵＡＨＵＡＮ荒漠啮动物群落变量的总和,月间和年间变动情况及统计学特征,这些变量是：物种数,生物量,物种多样性和均匀性。模拟产生的１００００个样本显示这４个变量的平均值是８．９１,１．５４４ｋｇ／ｈｍ＾２,１．５８和０．７３。真实群落４个变量的所有值均在模拟群落变量的９５％置信区间内。模拟群落物种数,生物量和物种多样性有相同的年间变动规律。物种数和生物量     

北美CHIHUAHUAN荒漠啮齿动物群落动态 IV.群落变量的模拟(英文)

利用ＭｏｎｔｅＣａｒｌｏ方法模拟了北美ＣＨＩＨＵＡＨＵＡＮ荒漠啮齿动物群落变量的总和、月间和年间变动情况及统计学特征,这些变量是：物种数、生物量、物种多样性和均匀性。模拟产生的１００００个样本显示这４个变量的平均值是８９１,１５４４ｋｇ／ｈｍ２,１５８和０７３。真实群落４个变量的所有值均在模拟群落变量的９５％置信区间内。模拟群落物种数、生物量和物种多样性有相同的年间变动规律。物种数和生物量有相同的季节变动规律。当零假设为这些变量均服从正态分布时,Ｘ２检验及偏度和峭度说明,在９５％的显著性水平上,物种数有９６２个样本,生物量有１０９个样本,物种多样性有５５２９个样本,均匀性有６６５４个样本服从正态分布,即在９５％的显著性水平上,没有一个变量是服从正态分布的。结果说明,当样本含量较小时,我们不能用（平均数＋１９６×标准误）的公式来计算     

Comparaison de deux modèles hybrides simulant la propagation de la lumière dans les tissus biologiques

In this paper, two numerical hybrid methods to model photon transport phenomena in biological tissues are compared. The coupled radiative transfer–diffusion model is based on the finite element solution of the radiative transfer equation and its approximation. The hybrid Monte-Carlo–diffusion consists in modeling the propagation of laser light in turbid media with the pure statistical Monte-Carlo method in the vicinity of the source and the boundaries and the diffusion approximation elsewhere in the domain. We apply these codes to calculate the spatially resolved reflectance amplitude and phase resulting from an intensity modulated laser beam. The results show that the hybrid methods can be used to simulate light propagation with good accuracy and speed.     

用蒙特卡罗方法模拟光在多层组织中的吸收特性

在讨论目前新颖的组织功能成像打骂能性（例如光声成像）时,光子在组织中的吸收和散射特性是一个很重要的问题,鉴于这一点,本文利用一个多层模型研究了光子在皮肤,脂肪和肌肉组织中的吸收和散射特性,得到了在组织中某一深度处光子在一个平面上的吸收分布,以及在不同吸收系数和散射系数的情况下,光子的反射,吸收和透射几率,结果表明在经过多次散射后,大部分的光子被吸收,在本文的模型中只有7.3%的光子从表面反射（包括镜面反射和漫反射）,还讨论了不同光学参灵敏对参流分布的影响。     

The role of polymer matrix structure and interparticle interactions in diffusion-limited drug release.

A lattice random-walk model is used to simulate diffusion in a porous polymer. This model may be useful for the practical design of drug-release systems. Both interacting and noninteracting particles (random walkers) were allowed to diffuse through a pore with a single exit hole. It was found that the specific interactions among the diffusing particles have little influence on the overall release rate. Diffusion through more complicated structures was investigated by simulating the diffusion of particles through two pores connected by a constricted channel whose length and width were varied. The overall rate of release was found to be proportional to the width of the constricted channel. When the length of the channel was greater than or equal to the length of the pore, the rate of release was also inversely proportional to the channel length. From a practical standpoint, release rates can be decreased (and times for release increased) by one or two orders of magnitude by decreasing the width and expanding the length of the interconnecting channels in the polymer matrix.     

Estimating diffuse irradiance on organisms: A comparison of results from isotropic and anisotropic sky radiance models

In calculating the diffuse irradiances of both solar and longwave radiation on geometric solids chosen to simulate organisms or parts of organisms, it is conventional to employ an isotropic sky model. This simplifies computations but may be unrealistic for radiative fluxes of atmospheric origin. The purpose of this investigation is to evaluate the significance of error brought about by the adoption of the isotropic assumption to compute the diffuse irradiance on the sphere, the vertical circular cylinder, the horizontal circular cylinder, the cone, the inclined plane, the parallelipiped, the vertical elliptical cylinder, the horizontal cylinder with hemispheric ends and the vertical cylinder with an upfacing hemispheric end. Theory is presented for the diffuse irradiance on an infinitessimal element, and for that on the solid forms. Results using the isotropic assumption are compared to those obtained using empirically-derived radiance distributions for atmospheric longwave irradiance and for solar diffuse irradiance under both overcast and cloud-free skies. These experiments suggest that, for the longwave irradiance, the isotropic sky model performs well. For solar diffuse radiation, however, errors are larger. Data are presented which permit estimation of the magnitude and direction of the error under a variety of conditions. Ultimately, the decision to employ an isotropic or anisotropic sky model will depend on the nature of the application. The methods described provide a means of evaluating the likely error resulting from the adoption of the more convenient isotropic sky model.     

时间分辨反射确定生物组织光学性质的方法研究

通过考虑吸收系数对漫射常数的影响,改进了时间分辨反射中两点测量生物组织光学性质的方法,对约化散射系数与吸收系数之比较小的生物组织进行了模型测量,结果表明此种不仅减小了测量的系统误差,而且扩展了两点测量法的应用范围。同时也较为详细地讨论了有效时间的选择和光源与探测点间的距离对测量结果的影响。     

Improving the accuracy of a solid spherical source radius and depth estimation using the diffusion equation in fluorescence reflectance mode

Background  

Non-invasive planar fluorescence reflectance imaging (FRI) is used for accessing physiological and molecular processes in biological tissue. This method is efficiently used to detect superficial fluorescent inclusions. FRI is based on recording the spatial radiance distribution (SRD) at the surface of a sample. SRD provides information for measuring structural parameters of a fluorescent source (such as radius and depth). The aim of this article is to estimate the depth and radius of the source distribution from SRD, measured at the sample surface. For this reason, a theoretical expression for the SRD at the surface of a turbid sample arising from a spherical light source embedded in the sample, was derived using a steady-state solution of the diffusion equation with an appropriate boundary condition.     

用于胃癌检测的漫反射光谱

胃癌正严重地威胁人类的健康,为了开发一种可以诊断早期胃癌的新型光学检测技术,建立了一套简便的组织体漫反射光谱检测装置.首先,根据组织体的光学特性,介绍光谱检测方法的基本原理.然后,利用组织癌变导致的组织体光学特性变化,建立漫反射光谱检测的实验装置.最后,利用该实验装置分别获取正常胃组织和胃癌组织的漫反射光谱.实验结果表明:癌变和正常胃组织的漫反射光谱在可见光区域有明显差别,特别是在波长为500 nm和630 nm处,但是漫反射光谱检测无法分辨来自组织不同层的光谱信息.这些结果说明漫反射光谱检测装置可用于胃癌的辅助检测.     

The impact of diffuse sunlight on canopy light-use efficiency, gross photosynthetic product and net ecosystem exchange in three forest biomes

For three forest canopies (a sparse, boreal needleleaf; a temperate broadleaf; and a dense, tropical, broadleaf stand) light‐use efficiency (LUE) is found to be 6–33% higher when sky radiance is dominated by diffuse rather than direct sunlight. This enhancement is much less than that reported previously for both crops (110%; Choudbury, 2001 ) and moderately dense temperate woodland (50–180%). We use the land‐surface scheme JULES to interpret the observed canopy response. Once sunflecks and leaf orientation are incorporated explicitly into the scheme, our simulations reproduce convincingly the overall level of canopy gross photosynthetic product (GPP), its enhancement with respect to diffuse sunlight and the mean 15% reduction in productivity observed during the afternoon due to stomatal closure. The LUE enhancement under diffuse sunlight can be explained by sharing of the canopy radiation‐load, which is reduced under direct sky radiance. Once sunflecks are accounted for the advantage of implementing more sophisticated calculations of stomatal conductance (e.g. Ball–Berry and SPA submodels) is less obvious even for afternoon assimilation. Empirical relations are developed between observed carbon flux and the environmental variables total downwelling shortwave radiation (SW), canopy temperature (T) and the fraction of diffuse sky radiance (fDIF). These relations allow us to gauge the impact of increased/reduced insolation on GPP and net ecosystem exchange (NEE). Overall the three stands appear to be fairly stable within global trends and typical interannual variability (SW changing by <15%). Greatest sensitivity is exhibited by the boreal site, Zotino, where NEE falls by 9±4% for a 15% reduction in SW.     

Improved model for myocardial diffuse reflectance spectra by including mitochondrial cytochrome aa3, methemoglobin,and inhomogenously distributed RBC

The aim of this study was to compare a previously used light transport model (I) comprising the chromophores hemo‐ and myoglobin, fat, and water, with two extended models, where the chromophores of cytochrome aa3, methemo‐ and metmyoglobin are added (model II), and in addition, accounting for an inhomogenous hemoglobin distribution (model III). The models were evaluated using calibrated diffuse reflectance spectroscopy measurements on the human myocardium. Model II proved a significantly better spectral fitting, especially in the wavelength ranges corresponding to prominent absorption characteristics for the added chromophores. Model III was significantly better than model II and displayed a markedly higher tissue fraction and saturation of hemo‐ and myoglobin. The estimated tissue chromophore fractions, saturation and oxidation levels, were in agreement with other studies, demonstrating the potential of diffuse reflectance spectroscopy measurements for evaluating open heart surgery. However, the choice of chromophores and vessel packaging effects in the light transport model has a major effect on the results. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simulation of photosynthetic plasticity in response to highly fluctuating light: an empirical model integrating dynamic photosynthetic induction and capacity

An empirical model was developed to simulate photosynthetic responses of leaves to highly fluctuating light, with a special focus on the functional role of photosynthetic induction and capacity. Based on diurnal courses of light as input data, which were recorded at natural plant sites, we applied this model to simulate the corresponding course of net photosynthesis (output data) for leaves of two neotropical tree species. All six model input parameters (leaf-specific) were obtained via measurements of leaf gas exchange. The model was tested for leaves in their natural environments, characterized by frequent light-flecks. We compared measured carbon gains with computed ones, using a standard steady-state and our induction model. Simulation runs with the steady-state model can result in an immense overestimation of the true situation, by 13.4% at open sites [pioneer species Heliocarpus appendiculatus (Turczaninow)] and by 86.5% at low light environments of the understorey [mid to late successional species Billia colombiana (Planchon and Lindley)]. These significant overestimations, particularly in the understorey, are mainly the consequence of neglecting a dynamic photosynthetic induction under fluctuating light conditions. The model presented here resulted in clearly improved predictions; in open and understorey sites the true carbon gain of leaves was computed with a mean error of less than 7%. As most leaves at natural plant sites are exposed to light environments allowing for dynamic rather than steady-state CO₂ assimilation, the significance of such induction models is evident and is discussed in relation to scaling-up from leaf to canopy and to the whole plant indicating a large potential for errors. Received: 3 May 1999 / Accepted: 9 July 1999