Time delay can enhance spatio-temporal chaos in a prey–predator model

In this paper we explore how the time delay induced Hopf-bifurcation interacts with Turing instability to determine the resulting spatial patterns. For this study, we consider a delayed prey–predator model with Holling type-II functional response and intra-specific competition among the predators. Analytical criteria for the delay induced Hopf-bifurcation and for the delayed spatio-temporal model are provided with numerical example to validate the analytical results. Exhaustive numerical simulation reveals the appearance of three types of stationary patterns, cold spot, labyrinthine, mixture of stripe-spot and two non-stationary patterns, quasi-periodic and spatio-temporal chaotic patterns. The qualitative features of the patterns for the non-delayed and the delayed spatio-temporal model are the same but their occurrence is solely controlled by the temporal parameters, rate of diffusivity and magnitude of the time delay. It is evident that the magnitude of time delay parameter beyond the Hopf-bifurcation threshold mostly produces spatio-temporal chaotic patterns.     

人工养殖条件下东方蝾螈的繁殖生物学

通过室内饲养观察,重点研究了东方蝾螈的产卵行为、受精卵孵化、仔螈的变态发育等繁殖生物学.东方蝾螈雌螈产卵前有明显的筑巢行为,分批产卵,产卵时间不集中,产卵期持续46～98 d,平均产卵期为78 d±14 d,产卵高峰期在5月上中旬,平均产卵量为101±56枚;温度对受精卵孵化影响十分显著,3月份产的卵平均54.1 d孵出仔螈,6月份产的卵平均11 d孵出仔螈,在15～26℃的自然水温条件下,受精卵一般需要11～30 d孵出仔螈;仔螈的变态发育与温度、饲料等因素密切相关,在24～25℃的控温养殖条件下,仔螈40 d后外鳃开始萎缩,68～79 d完成变态发育,但在自然水温下,只有78%的仔螈当年能完成变态发育.     

Differential effects of egg albumen content on barn swallow nestlings in relation to hatch order

In diverse animal taxa, egg mass variation mediates maternal effects with long-term consequences for offspring ontogeny and fitness. Patterns of egg mass variation with laying order differ considerably among birds, but no study has experimentally investigated the function of variation in albumen or yolk egg content in the wild. In barn swallows (Hirundo rustica), absolute and relative albumen mass increased with egg laying order. Experimental albumen removal delayed hatching, had larger negative effects on growth of late-hatched nestlings, and reduced nestling survival. Laying order positively predicted hatch order. Because nestling competitive ability depends on size, and albumen egg content influences hatchling size, present results suggest that by increasing albumen content of late eggs mothers reduce hatching asynchrony and enhance growth particularly of late-hatched nestlings. Thus, variation in albumen mass with laying order may function to mitigate the negative phenotypic consequences of hatching late in species that adopt a 'brood-survival' strategy.     

柑桔爆皮虫幼期各虫态的形态学观察

采用田间观察和室内观察相结合的方法,使用Leica MZ 16A研究型体视解剖镜,对柑桔爆皮虫Agrilus auriventris Saunders幼期各虫态的形态进行了系统的观察。结果发现：卵初产时为乳白色,后变为浅褐色并开始皱缩,末期变为黄褐色,孵化前部分卵壳分离为白色蜡质外层和黄褐色内层两层;幼虫孵化的同时直接从卵壳贴近树皮的一侧蛀入韧皮部,同时将大量虫粪排入卵壳;幼虫随着虫龄的增加钳状突的阶数和口上片的宽度发生有规律的变化,末龄幼虫在木质部作一椭圆形蛹室化蛹,身体的头部和尾部以3∶7的比例对折; 化蛹前的幼虫经历一个身体缩短的预蛹状态;刚化的蛹为乳白色,复眼颜色与身体相似,化蛹后蛹的颜色逐渐变为淡黄色,复眼颜色变为浅红褐色,后期复眼变为红褐色,口器变黑,羽化前蛹的复眼、口器和体表全部变黑;羽化过程中,成虫体表的膨胀导致蛹表皮脱裂,前翅变黑和腹部背面变成碧蓝色后羽化成完整的成虫。本结果进一步支持将柑桔爆皮虫幼虫期分为5龄。     

具时滞n维Lotka-Volterra共存系统的全局稳定性

本文利用文献[1]中连续迭代和比较方法,借用Hofbauer,JandSigmual,K的文献[2],再结合自治系统吸引区域的论证方法,给出n维连续时滞Lotka-Volterra共存系统正平衡点的全局稳定性,将自治系统的结果推到了一般n维的时滞系统。     

具有时滞和反馈控制的非自治Schoner模型的持续生存与全局渐近稳定性

讨论了具有时滞和反馈控制的非自治Schoner模型,得到了系统一致持续生存和全局渐近稳定的充分条件．     

Incorporation of variability into the modeling of viral delays in HIV infection dynamics

We consider classes of functional differential equation models which arise in attempts to describe temporal delays in HIV pathogenesis. In particular, we develop methods for incorporating arbitrary variability (i.e., general probability distributions) for these delays into systems that cannot readily be reduced to a finite number of coupled ordinary differential equations (as is done in the method of stages). We discuss modeling from first principles, introduce several classes of non-linear models (including discrete and distributed delays) and present a discussion of theoretical and computational approaches. We then use the resulting methodology to carry out simulations and perform parameter estimation calculations, fitting the models to a set of experimental data. Results obtained confirm the statistical significance of the presence of delays and the importance of including delays in validating mathematical models with experimental data. We also show that the models are quite sensitive to the mean of the distribution which describes the delay in viral production, whereas the variance of this distribution has relatively little impact.     

一类具连续时滞的捕食-被捕食生态系统

本文讨论了一类具有强连续时滞的捕食-被捕食模型,分析了各非负平衡点的稳定性,利用区域连续收缩方法,得出非负平衡点全局稳定的充分条件,给出正平衡点全局稳定的充分条件,并给出系统出现Hopf的分支值．     

Mode of action of fosthiazate used for the control of the potato cyst nematode Globodera pallida

Fosthiazate (Nemathorin 10G Ishihara Sangyo Kaisha Ltd, Japan) is a new nematicide approved for use on potatoes Solanum tuberosum L. in die UK for die control of die potato cyst nematodes Globodera rostochiensis (Woll). Skarbilovich and G. pallida (Stone). Fosdiiazate delayed and suppressed hatch of die potato cyst nematode Globodera pallida in bom in vitro laboratory tests and a glasshouse pot experiment. In vitro hatch was temporarily inhibited by fosdiiazate concentrations above 0.09 μg ml^-1 and increasing me fosdiiazate concentration further prolonged the duration of hatch inhibition. Analysis of fosthiazate soil concentrations, using high-pressure liquid chromatography, during me glasshouse experiment showed mat hatch was suppressed in the soil at concentrations above 0.5 mg kg^-1. Other factors such as the paralysis of hatched nematodes in the soil solution are also involved.     

具有时滞的HBV病毒动力学模型稳定性分析

HBV（HePatitis B virus）是一种具有严重传染性的肝炎病毒,迄今为止,人们对它的免疫和慢性化的机制等方面还不甚了解。本文基于相关的病理知识,对应的建立了具有时滞的微分方程数学模型,系统地探讨了肝炎B病毒与宿主细胞之间的关系,利用Lyapunov函数方法研究了病毒动力学模型感染平衡点的局部稳定性和未感染平衡点全局稳定性,并利用数学模拟验证了理论分析。结果表明时滞的存在不会影响到感染平衡点的局部稳定性,但能影响平衡点到达的时间跨度,对于药物治疗的疗程和治疗时机的确定有参考意义。