How vector feeding preference through an infectious host relates to the seasonal transmission rates in a mathematical vector‐host model

Vector‐borne diseases, such as leishmaniasis, dengue, malaria, and yellow fever, transmitted by microparasites show periodic fluctuations in their prevalence. The novelty of this research is to assess the relationship between the vector feeding preference for an infectious host and the annual seasonal transmission through a vector‐host mathematical model. For the first time, numerical simulations illustrate that by increasing the vector feeding preference value in the transmission dynamics, periodic fluctuations accentuate and the endemic equilibrium average increases in vector and host populations. Moreover, increasing the vector feeding preference value, the amplitude strengthens for the infectious host and vector populations. This periodic behavior shows a similar pattern with the Peruvian incidence data from 2000 to 2016 for Andean cutaneous leishmaniasis provided by the Ministry of Health of Peru (MINSA). In addition, using the Floquet theory, the time average method and the linear operator method provides for the first time that the basic reproduction number for a nonautonomous system depends explicitly on the vector feeding preference for the infectious host. The nonautonomous model system shows that is a threshold parameter for the local stability of the disease‐free periodic solution. Therefore, the vector feeding preference is an important factor that should be considered and attended to for future research. Public and veterinary health in Peru and other countries should consider the vector feeding preference for specific host to vector control.     

Development and analysis of a malaria transmission mathematical model with seasonal mosquito life-history traits

In this paper, we develop and analyze a malaria model with seasonality of mosquito life-history traits: periodic-mosquitoes per capita birth rate, -mosquitoes death rate, -probability of mosquito to human disease transmission, -probability of human to mosquito disease transmission, and -mosquitoes biting rate. All these parameters are assumed to be time dependent leading to a nonautonomous differential equation system. We provide a global analysis of the model depending on two threshold parameters and (with ). When , then the disease-free stationary state is locally asymptotically stable. In the presence of the human disease-induced mortality, the global stability of the disease-free stationary state is guarantied when . On the contrary, if , the disease persists in the host population in the long term and the model admits at least one positive periodic solution. Moreover, by a numerical simulation, we show that a sub-critical (backward) bifurcation is possible at . Finally, the simulation results are in accordance with the seasonal variation of the reported cases of a malaria-epidemic region in Mpumalanga province in South Africa.     

The Photodecomposition of 1,l-Dichloro-2,2-bis(5′-chloro-2′-methoxyphenyl)ethylene (MPE), an Analogue of DDE

The solution-phase photodecomposition of l, l-dichloro-2,2-bis(5′-chloro-2′-methoxy-phenyl)ethylene (MPE) has been studied at an excitation wavelength of 313 nm in the presence of O₂ as well as in vacuum-degassed solutions. Only two non-volatile compounds are produced: 2,5-dichloro-3-(5′-chloro-2′-methoxyphenyl)benzofuran (BFD) and a minor product which was not identified. The BFD represents approximately 90% of the total non-volatiles. The volatile products were identified as CH₃Cl, CH₄ and HC1, with CH₃C1 being approximately 99.9 % of the total volatiles. Photolyses were carried out in C₆H₁₂ and CCI₄ solvents, the same products being observed in both solvents. Variation of MPE concentration has little or no effect on the relative quantum yield of decomposition. The photodecomposition of MPE does not follow the same pathway as the photodecomposition of DDE.     

加权季节性指数法及其应用

预测医院季度出院人数季度变动趋势;加权季节性指数法;用加权季节性指数法进行季度变动趋势的定量预测与分析,对历史数据样本数量要求不多,并且计算简便;计算结果更具客观性、真实性.     

结合离群值对广东省进出口总额的预测分析

以国际贸易理论为基础,利用广东省若干宏观经济数据,对广东省进出口额进行实证分析.本文采用了季节性ARIMA模型并结合离群值分析的方法对进出口额进行研究.实证分析此方法具有良好的效果.     

季节因素对气候网络影响研究

气候网络在地球科学领域研究中是一个新的热点,对于分析和揭示气候场的特征及关联结构具有较强优势.已有气候网络的构建一般选取冬季月份的样本数据,而且在研究中忽略了其他季节月份对气候网络的影响.本文研究了季节因素对气候网络的影响,研究发现:气候网络在不同季节的整体特征参数基本保持稳定,但是网络社团结构以及局部节点拓扑连接随季节变化显著.可以利用这一结论来研究不同季节全球遥相关模态变化情况以及局部地区气候特征随季节变化情况.     

黄河三角洲盐生草甸白茅(Imperata cylindrica var. major)群落季节性动态的研究

采用定位研究的方法研究了生长季白茅(Imperata cylidrica var. major)群落的主要特征和动态。群落的种类组成较简单,其盖度一般在七月中旬达到100％。群落的高增长及地上生产量符合逻辑斯蒂增长模型(Logistic model),并主要受环境中水分和温度因子的影响。群落的最大高度为59cm,出现在八月中旬;地上生产量最大值为干重563g/m~2,出现在九月中旬。     

杭州市园林鸟类群落结构及其季节变化

园林鸟类是城市环境质量的重要指标,也是城市自然保护和生态建设的重要组成部分.1997年10月至1998年12月,通过选取杭州市区20个主要园林,根据季节每月一至两次调查园林鸟类的物种和数量,对杭州市园林鸟类的群落结构及其季节变化进行了分析探讨,结果显示:全部园林中共记录到鸟类82种,其中迁徙鸟类50种,占61%,留鸟32种,占39%;园林鸟类群落呈现出较强的季节性,从全部园林总体上看,物种数和总数量呈现春秋两个高峰,夏季最低;从单个园林来看,多数园林鸟类群落物种数的最高峰集中在冬季,而各园林鸟类总数量的季节变化呈现不同程度的波动性.     

Seasonality in estuarine sources of methylated arsenic

The effect of seasonal temperature change on the release of methylated arsenic from macroalgae, phytoplankton and sediment porewaters has been investigated by a series of controlled laboratory experiments. The appearance of dissolved arsenic species in the overlying waters was monitored using a coupled hydride generation/GC AA analytical technique. The liberation of dissolved arsenic species by the macroalgae Ascophyllum nodosum was examined under estuarine conditions at 5 °C and 15 °C. At the lower temperature the release rates were 0.2 μg kg^?1 h^?1 (wet weight of material) for monomethylarsenic (MMA) and 0.5 μg kg^?1 h^?1 for dimethylarsenic (DMA), whereas at 15 °C the rates were 0.4 μg kg^?1 h^?1 and 3.2 μg kg^?1h^?1, respectively. Incubation experiments were also carried out at 15 °C using the diatom Skeletonema costatum. During the log growth phase, when chlorophyll a concentrations were in the range 1-5 μg dm^?3, the rate of appearance of DMA in the water was ～3 ng dm^?3 h^?1. Sediment samples from the freshwater and seawater end-members of the Tamar Estuary, UK, were incubated under natural conditions at 5 °C and 15 °C. The freshwater sediments released DMA in preference to MMA; the concentrations of both species increased exponentially and reached a steady state in the overlying water after 250 h. Considerably more DMA was produced at 15 °C than at 5 °C, whilst the amount of MMA produced appeared to be insensitive to the temperature increase. In contrast, the seawater sediments always produced more MMA than DMA and the increase in temperature had little effect on the production of either MMA or DMA. The results of the laboratory experiments were compared with field observations in temperate estuaries, including the Tamar Estuary. The implications of changes of water temperature on the fate of arsenic in estuaries is discussed and modifications to the estuarine arsenic cycle are proposed.     

经济时间序列的X-11季节调整方法(Ⅰ)

本讲座以美国普查局的Ｘ－１１程序为背景，介绍程序中涉及的经济概念和统计方法，并结合实例介绍方法的应用．