Decoding Input Signals in Time Domain—A Model Approach

From an observation of efferent interspike intervals of a neuron, we consider how to decode the input temporal information. It is found that the integrate-and-fire model is blind in the temporal domain due to the fact that its efferent firing rate is independent of the input temporal frequency. The conclusion is then confirmed for the integrate-and-fire model with correlated inputs, with reversal potentials, with a nonlinear leakage and with a subthreshold oscillation. For the Hodgkin-Huxley model, however, in terms of efferent firing rates alone, it is possible to read out the input temporal information.     

贡嘎山暗针叶林生态系统基于KDW运动-弥散波模型的优先流研究

利用自制的土柱装置,开展室内土柱实验,并与野外实地示踪影像分析相结合,针对研究区域土壤包气带根系层中水分快速运动的优先流展开研究,其目的在于系统分析优先流对径流过程的影响,为长江上游暗针叶林生态系统土壤水分运动规律研究及有效流域管理提供理论支持。研究采用雷诺数计算及野外示踪映像分析方法,判定证明在所研究地区,有优先流现象发生,优先流是处于层流及紊流之间的过渡流。同时针对成熟林坡积物土壤的水分运移状况分析表明研究区域的壤中流过程主要表现为优先流,而土壤中的基质部分,则表现为不动区域。研究在以往优先流模型构建的基础上,综合考虑了研究区域的实地情况,应用融入弥散波的运动波模型(KDW优先流模型),利用交叉模拟方法和统计分析方法将此模型与实地实验检验分析,认定KDW优先流模型实用性强、可靠程度较高,可较好地模拟贡嘎山暗针叶林生态系统实地。     

海马记忆功能的神经网络模型

综合神经心理学,神经生理学、解剖学与神经网络研究的成果,提出一个海马记忆功能的神经网络模型。模型由三个神经网络所组成;海马的ＣＡ１和ＣＡ３网络和大脑皮层联合区,ＣＡ３的功能是将不同感觉输入联合起来,而ＣＡ１的作用是将它们结成一个单一的记忆。而大脑皮层则是长期记忆的部位。在ＶＡＸ１１／７５０上进行计算机仿真,仿真证明模型有近期及长期记忆功能,破坏模拟海马的部分,模型显示出与顺行性遗忘症相似的特性。在     

Coevolution of compositional protocells and their environment

The coevolution of environment and living organisms is well known in nature. Here, it is suggested that similar processes can take place before the onset of life, where protocellular entities, rather than full-fledged living systems, coevolve along with their surroundings. Specifically, it is suggested that the chemical composition of the environment may have governed the chemical repertoire generated within molecular assemblies, compositional protocells, while compounds generated within these protocells altered the chemical composition of the environment. We present an extension of the graded autocatalysis replication domain (GARD) model--the environment exchange polymer GARD (EE-GARD) model. In the new model, molecules, which are formed in a protocellular assembly, may be exported to the environment that surrounds the protocell. Computer simulations of the model using an infinite-sized environment showed that EE-GARD assemblies may assume several distinct quasi-stationary compositions (composomes), similar to the observations in previous variants of the GARD model. A statistical analysis suggested that the repertoire of composomes manifested by the assemblies is independent of time. In simulations with a finite environment, this was not the case. Composomes, which were frequent in the early stages of the simulation disappeared, while others emerged. The change in the frequencies of composomes was found to be correlated with changes induced on the environment by the assembly. The EE-GARD model is the first GARD model to portray a possible time evolution of the composomes repertoire.     

Prediction of protein local structures and folding fragments based on building-block library

In recent years, protein structure prediction using local structure information has made great progress. In this study, a novel and effective method is developed to predict the local structure and the folding fragments of proteins. First, the proteins with known structures are split into fragments. Second, these fragments, represented by dihedrals, are clustered to produce the building blocks (BBs). Third, an efficient machine learning method is used to predict the local structures of proteins from sequence profiles. Finally, a bi-gram model, trained by an iterated algorithm, is introduced to simulate the interactions of these BBs. For test proteins, the building-block lattice is constructed, which contains all the folding fragments of the proteins. The local structures and the optimal fragments are then obtained by the dynamic programming algorithm. The experiment is performed on a subset of the PDB database with sequence identity less than 25%. The results show that the performance of the method is better than the method that uses only sequence information. When multiple paths are returned, the average classification accuracy of local structures is 72.27% and the average prediction accuracy of local structures is 67.72%, which is a significant improvement in comparison with previous studies. The method can predict not only the local structures but also the folding fragments of proteins. This work is helpful for the ab initio protein structure prediction and especially, the understanding of the folding process of proteins.     

一种喉部疾病口语声诊断新方法

本文提出了声带的三质量块模型,并应用这模型模拟病噪产生的嘶哑语声,这些嘶声包括有声带闭合不全,声带小结,声带麻痹,喉炎,声带淀粉样变和声门癌等十六种典型情况。采用快速傅里叶变换,线性预测,倒谱技术和离荼余弦变换等分析各类喉病引起的嘶哑语声,实验结果表明声带模型分析法是喉病诊断的一种有效方法。     

藏波罗花补血效果的实验研究

为开发利用藏波罗花及明确其药用效果,选用昆明种小鼠建立急性失血性贫血和溶血性贫血模型,分为阳性对照组、贫血模型组、水提物组、80％乙醇组、无水乙醇组、乙酸乙酯组和乙醚组,以0．5g原药／只剂量经口灌服,测定实验鼠的体重、红细胞数、白细胞数、血红蛋白值、骨髓有核细胞数和骨髓血红蛋白值。结果表明水提物及醇提物组为主要有效组分,与模型组相比差异极显著,具有显著的补血效果。     

EQUALITY AND THE TREATMENT‐ENHANCEMENT DISTINCTION

In From Chance to Choice, Allen Buchanan, Dan Brock, Norman Daniels and Daniel Wikler propose a new way of defending the moral significance of the distinction between genetic treatments and enhancements. They develop what they call a ‘normal function model’ of equality of opportunity and argue that it offers a ‘limited’ defence of this distinction. In this article, I critically assess their model and the support it (allegedly) provides for the treatment‐enhancement distinction. First, I argue that there is a troubling tension in the normal function model. Secondly, I argue that neither of the rationales invoked by Buchanan et al. really serves to justify this model or the results they seek to derive from it with respect to the significance of the distinction between treatments and enhancements.     

A coalescent model of background selection with recombination,demography and variation in selection coefficients

There is increasing evidence that background selection, the effects of the elimination of recurring deleterious mutations by natural selection on variability at linked sites, may be a major factor shaping genome-wide patterns of genetic diversity. To accurately quantify the importance of background selection, it is vital to have computationally efficient models that include essential biological features. To this end, a structured coalescent procedure is used to construct a model of background selection that takes into account the effects of recombination, recent changes in population size and variation in selection coefficients against deleterious mutations across sites. Furthermore, this model allows a flexible organization of selected and neutral sites in the region concerned, and has the ability to generate sequence variability at both selected and neutral sites, allowing the correlation between these two types of sites to be studied. The accuracy of the model is verified by checking against the results of forward simulations. These simulations also reveal several patterns of diversity that are in qualitative agreement with observations reported in recent studies of DNA sequence polymorphisms. These results suggest that the model should be useful for data analysis.     

Dipalmitoylphosphatidylcholine membranes modified with carotenoid pigment lutein: Experiment versus Monte Carlo simulation study of the membrane organization

Organization of bilayer lipid membrane formed with dipalmitoylphosphatidylcholine and containing a xanthophyll pigment lutein was studied by both the Monte Carlo simulation and UV-Vis absorption spectroscopy. The simulations were based on ten-state Pink model. The proposed model consisted of two monolayers represented by a two-dimensional triangular lattice with vacancies. The orientation and aggregation state of lutein, obtained from the analysis of the spectroscopic measurements, were used to calibrate intermolecular interactions in the model. In accordance with the experimental data, the model allows two orientations of lutein molecules: one spanning the membrane and the other parallel to its plane. The influence of the intermolecular interactions on the main phase transition as well as on the aggregation of lutein molecules is discussed. The analysis of the model enables us to learn about molecular mechanisms that govern the effects of lutein on the membrane properties as well as the effects of the lipid matrix on lutein organization in the membrane. A concept is discussed according to which increasing domination of parallel lutein orientation, observed at high temperatures, can protect the membrane against penetration by water molecules and reactive oxygen species and against loss of the membrane compactness, especially in the regions of oxidized acyl chains.     

京津冀地区城市化与生态环境交互耦合关系定量测度

城市化与生态环境之间客观上存在着极其复杂的交互耦合关系,如何实现城市化与生态环境协调发展将是世界经济社会发展的核心议题,也是近年来国内外研究的热点命题。首先构建了城市化和生态环境系统综合评价指标体系,然后借助物理学耦合模型,构建了城市化与生态环境动态耦合协调度模型,定量分析了1980—2011年京津冀地区城市化与生态环境的耦合过程与演进趋势。结果表明:人口城市化和生态压力分别对城市化子系统与生态环境子系统的贡献份额最大,明显高于其他因素;在耦合协调度测算模型中,城市化子系统与生态环境子系统3种不同贡献份额所得出的耦合协调度的变化趋势是一致的,表明耦合协调度模型受城市化与生态环境子系统贡献份额比例的影响很小;1980年以来京津冀地区的城市化与生态环境耦合协调度呈现出S型曲线变化,协调类型从严重不协调-城市化受阻发展到高级协调-生态环境滞后类型;正确认识城市化与生态环境交互胁迫的时空动态耦合规律,采取恰当的区域发展政策和适当的城市发展战略,对进一步加快区域城市化进程,改善生态环境,实现京津冀地区城市化与生态环境的协调和可持续发展具有重要的指导意义。     

Mortality of a heterogeneous cohort; description and implications

"A recent model for heterogeneous mortality by Vaupel et al....is shown to be based on incorrect definitions. An alternative formulation is presented. The results indicate that current methods for computing the survivorship and life expectation functions underestimate the true values. A method is given for determining the possible magnitude of this underestimation. The method is illustrated by a numerical example using U.S. data."     

生物量精确估算模型与参数辨识方法及应用

从生物量模型的构建与参数辨识方法的改进对生物量进行精确估算。用Chebyshev多项式系的组合构建了p维连续函数空间的一组乘积型基,进而建立了生物量估算统一模型,它具有如下特点:(1)可以克服常用生物量估算模型的经验性、不稳定性、不通用性及对生物量影响因素适应性差的特点,(2)它适合于影响生物量的任何因素,故适应范围非常广且很稳定,(3)可根据实际需要及估算精度确定影响生物量的因素及其阶数大小,(4)模型对生物量的估算相当于在区间[-1,1]上进行的数值插值,变量阶数越高,所插入的点就越多,估算结果越符合实际,整个估算的插值过程与树木的树干解析与树木生长原理是相一致的。对所建模型的参数辨识方法做了探讨,经典最小二乘算法是生物量估算的最常用参数辨识方法,由于它本身固有的一些缺陷使常用最小二乘的估算精度与使用范围受到很大的限制,现代多元统计分析的偏最小二乘算法可以克服常用最小二乘的缺陷,但在提取成分时仍具有不足,针对偏最小二乘的缺陷本文对它做了改进,改进算法即能克服偏最小二乘的不足还能使估算精度大大提高。用2个案例对3种生物量估算方法做了对比分析,结果表明生物量估算统一模型与偏最小二乘改进算法精度最高,其生物量估计误差在零附近排成一条直线。     

交通网络空间互动视角下生态足迹驱动机制

长江中游城市群是中部崛起战略的重要区域,同时依托长江黄金水道面临发展和保护的困境。交通网络空间互动视角下的生态足迹驱动机制研究对统筹长江中游城市群经济社会高质量发展和生态文明高水平建设以实现可持续发展具有重要意义。基于生态足迹模型测度了长江中游城市群县域尺度的可持续发展状况,并在STIRPAT模型框架下基于交通网络空间互动关系挖掘生态足迹的驱动机制和空间效应,为交通网络扩张背景下的跨区域生态治理与可持续发展提供参考。研究结果显示：(1)2010—2017年,长江中游城市群县域生态足迹均值有所下降;(2)道路交通网络和铁路交通网络规模均有所扩大,但连通性略有下降;(3)在基于交通网络构建的空间互动媒介下,城镇化率和人均GDP对生态足迹具有显著的促进作用,而第三产业增加值占比对生态足迹产生抑制影响,且生态足迹表现出积极的空间外溢效应。基于以上研究结果,建议在基于交通网络加强区域生态协同发展的同时,建设产业互促、资源互通、技术互享的区域联动可持续发展新格局。     

Dispersion Study of the Infrared Transmission Resonances of Freestanding Ni Microarrays

Nickel films (several-micrometer thickness, with 5.2-μm square holes in a square lattice array with 12.7-μm hole-to-hole spacing) exhibit Ebbesen's extraordinary transmission effect in the infrared; that is, they transmit a higher fraction of incident infrared light than the fractional open area of the holes. The role of surface plasmons (SPs) in this phenomenon is much debated, so we have obtained a data set whereby this idea and others can be tested against empirically determined dispersion curves. Unpolarized, zero-order transmission spectra have been recorded by rotating the mesh (from −2° to 60° in 1° steps) relative to the spectrometer's incident beam about an axis along the mesh's nearest hole-to-hole spacing in order to create the dispersion diagram. The data are numerically analyzed for peak centers that are then projected outside of the light line (by SP momentum matching equations) to two SP dispersion curves that are spaced in frequency by a splitting. With this caveat, all of the observed structure is accounted for by a simple SP model.     

THE ENFORCEMENT OF COOPERATION BY POLICING

Policing is regarded as an important mechanism for maintaining cooperation in human and animal social groups. A simple model providing a theoretical overview of the coevolution of policing and cooperation has been analyzed by Frank (1995, 1996b, 2003, 2009) , and this suggests that policing will evolve to fully suppress cheating within social groups when relatedness is low. Here, we relax some of the assumptions made by Frank, and investigate the consequences for policing and cooperation. First, we address the implicit assumption that the individual cost of investment into policing is reduced when selfishness dominates. We find that relaxing this assumption leads to policing being favored only at intermediate relatedness. Second, we address the assumption that policing fully recovers the loss of fitness incurred by the group owing to selfishness. We find that relaxing this assumption prohibits the evolution of full policing. Finally, we consider the impact of demography on the coevolution of policing and cooperation, in particular the role for kin competition to disfavor the evolution of policing, using both a heuristic “open” model and a “closed” island model. We find that large groups and increased kin competition disfavor policing, and that policing is maintained more readily than it invades. Policing may be harder to evolve than previously thought.     

The evolution of trans-generational altruism: kin selection meets niche construction

A cornerstone result of sociobiology states that limited dispersal can induce kin competition to offset the kin selected benefits of altruism. Several mechanisms have been proposed to circumvent this dilemma but all assume that actors and recipients of altruism interact during the same time period. Here, this assumption is relaxed and a model is developed where individuals express an altruistic act, which results in posthumously helping relatives living in the future. The analysis of this model suggests that kin selected benefits can then feedback on the evolution of the trait in a way that promotes altruistic helping at high rates under limited dispersal. The decoupling of kin competition and kin selected benefits results from the fact that by helping relatives living in the future, an actor is helping individuals that are not in direct competition with itself. A direct consequence is that behaviours which actors gain by reducing the common good of present and future generations can be opposed by kin selection. The present model integrates niche-constructing traits with kin selection theory and delineates demographic and ecological conditions under which altruism can be selected for; and conditions where the 'tragedy of the commons' can be reduced.     

杭州西湖引水后生态系统中磷循环模型

报道了杭州西湖截污和引灌钱塘江水后的一个富营养化模型。它按照年度描述西湖生态系统中的磷循环。状态变量有浮游植物磷、正磷酸盐、碎屑磷和沉积物磷。模型校准和检验结果表明,对于系统给定的强制函数（引水量和水温等）的改变,模型作出的状态变量的描述是合理的。并且利用该模型模拟在不同引水量及挖泥量下西湖水质变化。模型对引水及挖泥的效益所作出的评估可供综合治理时参考。