Dissecting the drivers of population cycles: Interactions between parasites and mountain hare demography

There is a growing awareness that cyclic population dynamics in vertebrate species are driven by a complex set of interactions rather than a single causal factor. While theory suggests that direct host-parasite interactions may destabilise population dynamics, the interaction between host and parasite may also influence population dynamics through indirect effects that result in delayed responses to either density or to life-history traits. Using empirical data on mountain hares (Lepus timidus) infected with a nematode parasite (Trichostrongylus retortaeformis), we developed an individual-based model (IBM) that incorporated direct effects and delayed life-history effects (DLHEs) of a macroparasite, alternative transmission mechanisms and seasonality in host population dynamics. The full model describes mean characteristics of observed mountain hare time series and parasite abundance, but by systematically removing model structure we dissect out dynamic influences of DLHEs. The DLHEs were weakly destabilising, increasing the propensity for cyclic dynamics and suggesting DLHEs could be important processes in host-parasite systems. Further, by modifying model structure we identify a strong influence of parasite transmission mechanism on host population stability, and discuss the implications for parasite aggregation mechanisms, host movement and natural geographical variation in host population dynamics. The effect of T. retortaeformis on mountain hares likely forms part of a complex set of interactions that lead to population cycles.     

Complex dynamics of the population with a simple age structure

The effects of the following modes of density-dependent control of population growth: density-dependent birth rate, adult survival rate, juvenile survival rate are compared based on the mathematical model of population dynamics. It is shown that the most efficient mechanisms limiting population size are decreasing with the growth of the adult population birth rate and/or the decreasing survival rate of the offspring with the increase in their number. However, these same mechanisms are responsible for oscillations of the population size and its chaotic change. The density-dependence of the adult survival rate is not efficient in constraining the population growth, but it can substantially limit the magnitude of oscillations of the population size.     

Study on mechanics and domino effect of large-scale goaf cave-in

A large area of continuous solid shallow-buried goaf group created by open-stope method, under the influence of space-time effects exerted by slow creep of the pillar-roof system, will wholly collapse driven by partly instability of pillar and roof collapse until the whole mine collapses, showing a domino effect. The dynamic process is ignored in the traditional analysis of mechanical stability. Based on analysis for the domino effect and disaster-relief mechanism in the mining goaf, the mechanical method combined with Voronoi graph method has been adopted to establish the dynamic analysis on the pillar-roof system stability. It seems more in line with the actual situations, and can help to more accurately predict the time and location of disaster. The conclusion is of great value on study of rock mechanics and mining companies’ safety production.     

复杂地基重力坝深层抗滑稳定非线性有限元分析

重力坝的深层抗滑稳定是保证大坝安全的一个重要条件。针对《混凝土重力坝设计规范》(DL5 10 8—1999)中关于复杂地基重力坝的稳定性需进行有限元分析的新规定,笔者结合某重力坝稳定问题实例,用非线性有限元方法进行了分析计算,并与刚体极限平衡法及结构可靠度分析方法的成果进行了对比。对有限元法的适用性,岩体侧面阻滑力的影响及抗滑稳定安全度的表达方法等问题进行了探讨     

CODCr测定中硫酸亚铁铵溶液稳定性的探讨

根据氧化－还原反应原理和电化学反应机理，对ＣＯＤｃｒ测定中所使用的硫酸亚铁铵溶液浓度稳定性进行探讨并提出使其稳定的方法。     

氰化物分析的条件优选及相关问题探讨

用正交试验法优选氰化物分析的主要测试条件，试验、讨论影响测定结果精确度的关键因素及其作用规律，并对存在的各种技术问题提出探讨意见。     

试论循环水浓缩倍数与节水

本文以该厂循环水实际运行情况，简述了影响循环水浓缩倍数提高的一些因素及对策，实现节约用水。     

石崆山Ⅱ号段岩质高边坡稳定性的有限单元法(FEM)分析评价

岩质高边坡是常见的自然地质环境问题和重要的岩土工程问题之一,涉及工程地质学、岩体力学问题。针对漳州—龙岩高速公路石崆Ⅱ号段岩质高边坡稳定性问题,采用有限单元法(FEM)进行计算分析。计算分析结果表明石崆山Ⅱ号段岩质高边坡是稳定安全的。有限单元法在岩质高边坡稳定性的计算分析中的应用,正处在完善和发展之中。它的计算分析正确与否或精确程度,很大程度上取决于对边坡岩体工程地质条件的正确理解和归纳概化,取决于计算参数的合理客观选取。     

Photocatalytic performance and dispersion stability of nanodispersed TiO2 hydrosol in electrolyte solutions with different cations

The existence of electrolytes in aquatic environment on the photocatalytic performance and coagulation of nanodispersed TiO₂ hydrosol and the corresponding photocatalytic alteration were investigated by studying cations (Na⁺, K⁺, Ca ²⁺, Mg²⁺, and Al³⁺). The photocatalysis reactions of nano TiO₂ with different dosages of electrolytes were measured by monitoring the degradation of Rhodamine B (RhB) under ultraviolet A (UV-A) irradiation over time. The results showed that the photocatalytic performance of TiO₂ was improved by the presence of Al³⁺, while the performance was impaired by the other tested cations. The negative influences of divalent ions on the photocatalytic performance of TiO₂ were more significant than monovalent ions. The TiO₂ sol dispersed stable at nano scale at low concentration of electrolyte (< 0.01?mol/L) with slight change of pH, and coagulated into micro sizes at high concentration of electrolytes (> 0.1?mol/L) with larger increase or decrease of pH. The positive effects of Al³⁺ on the photodegradation rate of RhB might relate to the strong hydrolytic action of Al³⁺ in aquatic solutions. The photocatalytic processes of TiO₂ in the presence of all ions followed the Langmuir-Hinshelwood model, and the reaction kinetic constant was increased with the decrease of pH caused by different cations. These work suggested a new perspective about the relationship between coagulation and photocatalytic performance of TiO₂ hydrosols in electrolyte with hydrolysable cations, which demonstrated that TiO₂ hydrosols may be suitable as photocatalysts in aquatic environments.     

序列式活性污泥法稳定性研究

本文报道了对序列式活性污泥法稳定性的研究结果,研究表明,对于周期间的变浓度恒负荷、变浓度变负荷以及周期内变浓度变负荷冲击,该工艺均表现出良好的稳定性。