人口问题中一广义扩散模型初边值问题的动力性态

本文研究人口问题中的一广义扩散模型考虑它的初边值问题，证明了问题整体吸引子的存在性。     

Mathematical analysis of multisolute renal flow in a single nephron model of the kidney

A single nephron model, which includes the Bowman's space, Cortical interstitium, and Pelvis as well-stirred baths, is investigated. A boundary value problem, which allows for pelvic reflux, is established for the fluid-multisolute flow in the nephron. The implicit function theorem is used to establish the existence and uniqueness of a solution of the boundary value problem for the case of small permeability coefficients and transport rates.Dedicated to Professor Emertius L. P. Burton, Auburn University, for the research guidance he gave this author thirty years agoSupported in part by NIH Grant 7-ROl-DK 38817     

具势能衰减的非线性拟抛物方程整体解的不存在性

利用Laplace算子的特征函数法研究了一类具势能衰减的非线性拟抛物方程的初边值问题整体解的不存在性与有限时间爆破．     

生物数学中的反应扩散系统奇摄动问题

研究了一类具有非线性捕食-被捕食反应扩散系统奇摄动问题,利用微分不等式理论,讨论了问题解的渐近性态。     

A one locus, biased mutation model and its equivalence to an unbiased model

Experimental data suggests that for some continuously-varying characters under stabilising selection, mutation may cause a mean change in the value of the character. A one locus, mathematical model of a continuously-varying biological character with this property of biased mutation is investigated. Via a mathematical transformation, the equilibrium equation describing a large population of individuals is reduced to the equilibrium equation describing a mutationally unbiased problem. Knowledge of an unbiased problem is thus sufficient to determine all equilibrium properties of the corresponding biased problem. In the biased mutation problem, the dependence of the mean equilibrium value of the character, as a function of the mutational bias, is non-monotonic and remains small, for all levels of mutational bias. The analysis presented in this work sheds new light on Turelli's House of Cards Approximation.     

Meaning Matters: The Biosemiotic Basis of Bioethics

If the central problem in philosophical ethics is determining and defining the scope of moral value, our normative ethical theories must be able to explain on what basis and to what extent entities have value. The scientific foundation of contemporary biosemiotic theory grounds a theory of moral value capable of addressing this problem. Namely, it suggests that what is morally relevant is semiosis. Within this framework, semiosis is a morally relevant and natural property of all living things thereby offering us an ecological, as opposed to merely environmental, ethic. A consequence of this semiotic theory is that living things are accorded inherent moral value based on their natural relational properties—their ability to signify. This consequence establishes a hierarchy of inherent moral value based on the scope of signification: the larger the Umwelten, the greater the value. This paper argues that a robust semiotic moral theory can take into account a much wider scope of inherent value.. These consequences have positive ramifications for environmental ethics in their recognition of the natural ecological networks in which each organism is bound. This presentation of a biosemiotic model of value offers a justificatory strategy for our contemporary moral intuitions concerning our semiotic/moral relationships with living things while also productively pushing our normative ethical boundaries.     

基于HP模型的大麻素受体CB2折叠研究

Cannabinoid receptor Type 2(简称CB2)是大麻素受体的一种亚型,因为其无中枢神经副作用,不会产生成瘾性及耐受性,显示出了非常好的开发前景和潜在的应用价值。其作为免疫调节剂、神经保护剂和抗癌药等将具有巨大市场价值。目前,CB2蛋白的空间结构还未被测定出来,对于CB2的折叠问题研究也开展的较少,为了研究大麻素受体亚型蛋白CB2的折叠问题以及方便更多的研究人员对CB2空间结构和相关药理特性的研究,本文提出了一种基于HP模型的折叠求解方法。通过使用回溯机制和蒙特卡罗方法对此优化问题进行求解,算法可有效的在全局范围内进行寻找最优解,避免了掉入局部最优问题。实验结果表明,本文方法获取的CB2蛋白空间构象具有较低的能量值,折叠情况较好。     

生态学中一类具时滞反应扩散方程组解的性质

本文讨论一类具时滞反应扩散方程组初边值问题,得到该问题解的存在唯一性并讨论解的渐近性态．     

Predictive potential of wildlife value orientations for acceptability of management interventions

Wildlife value orientations are patterns of basic beliefs that give direction and meaning to fundamental values in the context of wildlife. Wildlife value orientations can help managers estimate public evaluations to management interventions. Their usefulness, both practically and scientifically, depends on their predictive potential. This article examined the predictive value of wildlife value orientations on the acceptability of wildlife management interventions in different situations. The situations varied in (a) severity of the human wildlife problem and (b) severity of the interventions for wildlife. Two wildlife value orientations were measured: domination (human needs have priority over wildlife well-being, 10 items) and mutualism (rights are assigned to wildlife, 9 items). Acceptability was measured as a dichotomous variable for management interventions across 5 different situations. The predictive value of wildlife value orientations was largest for acceptability of the most severe interventions (hunting, 35–42% of variance explained), followed by the least severe interventions (doing nothing, 5–17%) and the intermediate interventions (shaking eggs or applying contraceptives, 1–9%) in the scenarios that include a problem for humans. Value priorities appear to be an integral feature of value orientations. Intermediate interventions do not harm wildlife, but might solve the problem caused by wildlife. Such interventions also create minimal small internal value conflicts. Orientations that prioritize values and offer a template for conflict resolution are likely to have less predictive potential for these interventions.     

The value of information in reserve site selection

The reserve site selection problem is to select sites for the establishment of biological reserves with the goal to maximize the number of species contained in the reserves. When species distributions are known, this corresponds to the maximal coverage problem. In practice, knowledge of species distributions may be incomplete and only incidence probabilities are available. In this case, the goal is to maximize the expected number of species contained in the reserves. This is called the maximal expected coverage problem. This paper describes and illustrates a formal approach to assess the value of information, such as site surveys or species surveys, in this problem.     

生态学中一类n维反应扩散方程组解的性质

本文讨论一类不满足所谓的拟单调条件的反应扩散方程组的初边值问题．应用谱论和单调性方法证明了问题解的存在唯一性和平衡解的渐近稳定性．并进一步讨论了生态学中n种群单食物链模型的第二初值问题,得到了问题的非负平衡解的存在性和渐近性以及相应的吸引区域．     

具潜伏期的无免疫型传染病动力学模型解的适定性

考虑一类无免疫型传染病动力学的一阶双曲型方程组的非线性非局部的初边值问题,给出经典解的整体存在唯一性,并同时得到解关于初值条件的连续依赖性.     

二阶脉冲微分方程边值问题解的存在性

利用Leray-Schauder不动点理论研究了一类二阶脉冲微分方程三点边值问题,将以往所研究的方程的边界条件和脉冲项做了推广,得到了其解的存在性的新结果,最后通过实例说明了结论的应用.     

A parameter identification problem arising from a model of canalicular bile formation

We develop a simple mathematical model for bile formation and analyze some features of the model that suggest the design for future physiological experiments. The mathematical model results in a boundary value problem for a system of functional differential equations depending on several physical parameters. From the observability of the boundary values we can identify, both qualitatively and quantitatively, some of these physical parameters. This identification then suggests physical experiments from which one could infer some of the bile transport phenomena that are not, at present, directly observable. The mathematical parameter identification problem is solved by converting the boundary value problem to a transition time problem for a quadratic system of ordinary differential equations on the plane where we are able to employ some special properties of quadratic systems in order to obtain a solution.The author was supported by the Air Force Office of Scientific Research and the National Science Foundation under the grants AF-AFOSR-89-0078 and DMS-9022621The author was supported by National Institutes of Health under grant number R37 DK-27623     

Propagation of excitation in a model of neural system

The study of the characteristic statistical properties of neural systems, which was started in a previous paper, is continued here. The initial value problem for the kinetic equations describing the systems is solved in the one-dimensional case under particular conditions. To handle this problem use is made of certain techniques previously introduced by Landau and later improved by Backus and Turski in the context of the study of oscillations in a linearized plasma. The result is used for the discussion of a very simple neural system.     

Research on contaminant sources identification of uncertainty water demand using genetic algorithm

Urban water supply network is easily affected by intentional or occasional chemical and biological pollution, which threatens the health of consumers. In recent years, drinking water contamination happens occasionally, which seriously harms social stabilization and safety. Placing sensors in water supply pipes can monitor water quality in real time, which may prevent contamination accidents. However, how to reversely locate pollution sources through the detecting information from water quality sensors is a challengeable issue. Its difficulties lie in that limited sensors, massive pipe network nodes and dynamic water demand of users lead to the uncertainty, large-scale and dynamism of this optimization problem. This paper mainly studies the uncertainty problem in contaminant sources identification (CSI). The previous study of CSI supposes that hydraulic output (e.g., water demand) is known. Whereas, the inherent variability of urban water consumption brings an uncertain problem that water demand presents volatility. In this paper, the water demand of water supply network nodes simulated by Gaussian model is stochastic, and then being used to solve the problem of CSI, simulation–optimization method finds the minimum target of CSI and concentration which meet the simulation value and detected value of sensors. This paper proposes an improved genetic algorithm to solve the CSI problem under uncertainty water demand and comparative experiments are placed on two water distribution networks of different sizes.     

Solution of the time-dependent ionic diffusion equation

The ionic diffusion problem here solved is that of the voltage clamp experiment. In this, the total voltage across the membrane and double layers is held constant. Since the diffusion of the ions would normally result in a change in the membrane voltage with time, a part of the complexity of the solution of the problem is in the correction procedure required to so modify the electric field as to hold the voltage at a fixed value. The program could, however, be readily modified to conform to other requirements: e.g., current clamp, linearly rising voltages, etc.A significant improvement in speed of convergence is obtained by using the membrane parameters existing at the midpoint of the time step (Crank-Nicolson method), rather than, as has been more customarily done, at the end of the step (“implicit” method).Convergence is further speeded by estimating the new value of the electric field at each station by extrapolation; and convergence of iterations at each time level is aided by a backward-averaging of the computed electric field. So far as the author is aware, these procedures have not previously been described for use in this type of problem.     

Joint distribution of first exit times of a two dimensional Wiener process with jumps with application to a pair of coupled neurons

Motivated by a neuronal modeling problem, a bivariate Wiener process with two independent components is considered. Each component evolves independently until one of them reaches a threshold value. If the first component crosses the threshold value, it is reset while the dynamics of the other component remains unchanged. But, if this happens to the second component, the first one has a jump of constant amplitude; the second component is then reset to its starting value and its evolution restarts. Both processes evolve once again until one of them reaches again its boundary. In this work, the coupling of the first exit times of the two connected processes is studied.     

基于多目标的杨树速生丰产林主伐决策分析

经济效益综合评价是产业决策研究的重要内容.从系统工程观点来看,经济效益综合评价本质上是一个有限方案多目标决策问题.因此,本文采用多目标决策法对杨树速生丰产林的主伐决策进行研究,以年均净现值、内部收益率、土地期望价、效益成本比、成本利润率为指标,提出用熵技术法确定评价指标权重,结合"理想点"法、TOPSIS法和线性加权和法三种方法对决策方案进行排序择优,得到不同排序结果,最后用平均值法得到最终综合评价结果.结果表明,对所研究的密度为10×10m~2、8×8m~2、6×8m~2、5×6m~2的杨速生丰产林进行分析得到综合评价结果,其最优主伐龄分别为:13年、10年、9年、9年.随着密度的增大,经济成熟龄提前.本研究表明该方法对杨树速生丰产林的主伐决策研究是有效可行的.     

Malignant mesothelioma of the pericardium--diagnostic problems]

A case of the malignant mesothelioma of pericardium is presented as this is rare primary neoplasm of pericardium. Diagnosis of the malignant mesothelioma of pericardium is a difficult clinical problem. The authors discuss the value of various diagnostic techniques used in diagnosis of the malignant mesothelioma of pericardium.