害虫,天敌和食料的数学模型

本文从实际问题出发,结合已有的描述群落生态的数学模型,提出了一组描述马尾松毛虫(Dendrolimus pnnctalus,walker)、条毒蛾(Lymantria dissoluta,Swinhoe)、天敌和食料之间动态关系的数学模型: w(k+1=(a_1x(k+1)/(1+a_2x(k+1)/_z(k))+a_3w(k)/(1+a_4w(k)/y(k)) x(k+1)=b_1w(k)/(1+b_2w(k)/y(k))+b_3x(k)/(1+b_4x(k)/z(k))+ y(k+1)=c_1z(k)/[1+c_sz(k)+c_3y(k)][1+c_4w(k)+(k+1)] z(k+1)=d_1z(k)/[1+d_2z(k)][1+d_3x(k)+d_4w(k)] 对于这个模型的线性化形式,详细讨论了控制松毛虫的暴发所需的条件及其生态学机制。     

一类具有垂直传染的SIR传染病模型

讨论了一类具有垂直传染的SIR传染病模型：(dS)/(dt)=6(1-m)(S R) (1- m)pb′I-βSI,(dI)/(dt)=βSI qb′I-d′I-rI,(dR)/(dt)=rI mb(S R) mpb′I-dR获得了无病平衡点与地方病平衡点的全局稳定性．     

一阶线性差分微分方程振动的充要条件及应用

本文的目的是建立一阶线性差分微分方程 (dx)/(dt)=-sum from i=1 to n p_i(t)x(t-i_x(t)) (1)的所有解关于θ振动的等价条件,然后把所得结果应用于生物自身调节反馈滞后型方程(dN(t))/(dt)=rN(t)[1-(N(t-i))/p] (2)的更一般形式     

一类KOLMOGOROV系统的极限环

关于两种群互相作用的Kolmogorov模型 x=xF_1(x,y), y=yF_2(x,y),文〔1〕根据生态意义对F_1、F_2给出较多限制条件下作过研究,由于现实中总结出的模型归结到F_1、F_2为x和y的多项式的形式不少〔2,3〕,本文讨论一类Kolmogorov系统x=x(a_0+a_1x-a_3x~2+a_2y+a_4xy),y=y(x-1) (1)极限环的存在性和唯一性,其中x和y分别表示两种群的密度,参数a_0>o,a_3>o,a_1、a_2、a_4不定号,它们各表示一定的生态意义,随不同的取值范围而反映两种群的不同作用〔1〕。     

生化反应中一类三次系统的极限环

研究生化反应中一类三次系统：dx/dt=-x-Ф1（x）＋yФ2（x）,dy/dt=a0＋Ф1（x）-yФ2（x）其中Ф1（x）=Ax^3＋ax^2＋bx＋B,Ф2（x）=cx^2＋dx＋e．较完整地解决了该系统极限环的存在性,唯一性与不存在性等问题．     

短梗霉多糖发酵过程特征的研究

本文针对短梗霉多糖发酵过程,经研究建立了基于逻辑方程和Luedeking—Piret方程的动力学模型： dx／dt=肛x(1一x／xm) dP／dt=m1x十m2(dx/dt) ds／dt=-b1x-b2(dx／dt)-b3(dP／dt) 其流变特性由初始时的牛顿流体转变为典型的假塑性非牛顿流体并遵从指数方程,即：τ=Kγn随发酵过程进行,发酵液的表观粘度增大,体积氧传质系数减小。搅拌转速的增加有利于提高体积氧传质系数。流变指数n、稠度系数K、气液传质系数Kla。与菌体浓度x、多糖浓度P、搅拌转速N及表观粘度ηa间分别有如下经验方程; k=1．2×10-2X2.43 n=0．461(P／Pm)0.07(x／xm)0.216 KLaDi2=1．48×104(D:N2)0.71(ηW)0.15 Dg ηa     

一类松籽、松鼠、幼苗的动态数学模型及讨论

本文给出一类红松林中松籽、松鼠及幼苗的动态数学模型x＝1 a_1x x~2-b_1yy=a_2x-yz＝a_3x b_2y-z利用三维的Hopf分支理论得到,对于充分小的δ＝a_2b_1-1-(√（a_2b_1-a_1）~2)-4,δ＜0时,系统（l）存在不稳定的周期解。同时讨论（1）存在通过原点的解平面的条件是b_2=0;并对（1）在解平面上轨线的走向进行了讨论。     

天花粉蛋白质晶体的旋转函数和平移函数计算以及晶胞中分子排布问题的探讨

本文采用大项计算程序,分别地从天花粉蛋白质母体及其铂[Pt(NO_2)4]~(-2)衍生物晶体所录的4(?) 分辨率的4334个反射中,挑选出约10%个具有大的结构振幅(F_p~2)_(max)或(F_p~2H)_(max)各458个反射,分壳层地计算旋转函数。两者均可得到晶胞不对称单元中非结晶学对称性为三个互相垂直的二次轴,用(x°,ψ°,(?)°)记号表示为:(180°,0°,0°),(180°,90°,0°)和(180°,90°,90°)。分别依据这三个非结晶学二次轴,计算天花粉母体晶体的平移函数。从平移函数剖面图上得到若干个有效的平移矢量⊿:旋转轴: 得到的平移矢量⊿:(180°,0°,0°) (1)/(5)b_0,(3)/(10)b_0(180°,90°,0°) (1)/(4)a_0,(3)/(4)a_0(180°,90°,90°) (2)/(5)c_0,(3)/(5)c_0最后,参考了一些天花粉重原子衍生物晶胞中的重原子坐标,进一步讨论了天花粉蛋白质分子在晶胞中的位置排布问题。     

可兴奋膜研究中的模型和系统辨识

在线性系统的研究工作中通常可从系统的输入、输出之间的关系中求得其动态特性。如图1a所示,当系统输入为x(t)时其输出为y(t),那末可用a_ny~(n)(t) a_(n-1)y~(n-1)(t) … a_1y′(t)十a_0y(t)=b_mx~(m)(t) b_(m-1)x~(m-1)(t) … b_1x′(t)十b_0x(t)(1)这样一个微分方程来表示该系统的动态特性。常用的脉冲反应函数、阶跃反应函数、传递函数、幅频-相频特性和实频-虚频特性等等实质上都是从输入、输出的关系中求得的系统动态特性。只要系统是线性的,那末,经过简单     

以x(m/n)为功能性反应函数的食饵-捕食系统的定性分析

研究了功能性反应函数ψ(x)为x(m/n)(0＜m/n＜1)的食饵-捕食系统dx/dt=ax-bψ(x)y-cx2,dy/dt=-dy+eψ(x)y-fy2.证明了此系统当1/2≤m/n＜1时至多存在唯一正平衡点;当0＜m/n＜1/2时必有出现三个正平衡点的可能.并讨论了此系统的拓扑结构,给出了数值例子.     

无人机近景摄影技术在崖壁植物多样性研究中的应用

崖壁植物具有不可及或不易及的特点,有关崖壁植物的调查一直面临着高成本、高风险和难鉴定的难题。本研究创新性地提出一种采用无人机近景摄影技术对崖壁植物拍照及专家鉴定的调查方法,通过分析崖壁植物群落的Margalef、Simpson与Pielou这3种多样性指数的变化,探究海拔、光照、立地条件与水汽条件这4种因子对崖壁植物多样性的影响。研究结果表明：本次调查共发现崖壁植物267种,分属于58科、140属;崖壁植物物种数目与海拔高度变化服从正态分布,物种数量在中海拔700-800m达到峰值,Simpson指数与Pielou指数在低海拔时达到最高,随海拔的升高而下降,但不表现出明显的变化规律;崖壁植物在不同的立地条件下,植物群落的物种组成、优势种类与出现频率均有所不同;崖壁植物的相关性分析显示,在光照条件出现差异或立地条件不同时,崖壁植物各指数之间存在着不同的显著性关系;近水崖壁植物与对照组的分析结果对比显示,崖壁植物的数量与物种组成受崖壁间水汽条件的影响,崖壁水汽条件越高的地区有着更丰富的植物种类。本研究表明崖壁植物的分布特征是受海拔、光照、立地条件以及水汽条件等多因素的综合作用而成。     

Periodicity and boundedness of solutions of generalized differential equations of growth

Sufficient conditions are given for the existence of periodic solutions of differential equations, having as special cases the equations used to describe the competition between two species. The Poincaré bifurcation theory is used to secure one set of conditions, and another set of conditions is secured through a generalization of a method of V. Volterra. The question of boundedness is considered and conditions implying boundedness and conditions implying that populations are bounded away from zero are given. Several integrable classes of systems are discovered and a particular example having periodic solutions is examined in detail. This research was supported by the Air Force Office of Scientific Research under Grant 62-207.     

Interpretation of Tracer Data

The necessary and sufficient conditions for a particular compartment in an n-compartment system, under certain initial conditions, to be described by two exponential terms have been given by Mann and Gurpide (1969). These conditions are here derived in matrix-vector form, by an essentially algebraic process, under more general initial conditions. The existence of a certain constant is required by the Mann-Gurpide conditions. It is shown that that constant must be one of the real roots of a given matrix. Under certain restrictions, that constant is the unique largest real root of that matrix. Certain obvious sufficient conditions for the Mann-Gurpide conditions to hold are shown to be necessary in the case of symmetrizable systems.     

Biodegradability of chlorinated solvents and related chlorinated aliphatic compounds

The biodegradability of chlorinated methanes, chlorinated ethanes, chlorinated ethenes, chlorofluorocarbons (CFCs), chlorinated acetic acids, chlorinated propanoids and chlorinated butadienes was evaluated based on literature data. Evidence for the biodegradation of compounds in all of the compound categories evaluated has been reported. A broad range of chlorinated aliphatic structures are susceptible to biodegradation under a variety of physiological and redox conditions. Microbial biodegradation of a wide variety of chlorinated aliphatic compounds was shown to occur under five physiological conditions. However, any given physiological condition could only act upon a subset of the chlorinated compounds. Firstly, chlorinated compounds are used as an electron donor and carbon source under aerobic conditions. Secondly, chlorinated compounds are cometabolized under aerobic conditions while the microorganisms are growing (or otherwise already have grown) on another primary substrate. Thirdly, chlorinated compounds are also degraded under anaerobic conditions in which they are utilized as an electron donor and carbon source. Fourthly, chlorinated compounds can serve as an electron acceptor to support respiration of anaerobic microorganisms utilizing simple electron donating substrates. Lastly chlorinated compounds are subject to anaerobic cometabolism becoming biotransformed while the microorganisms grow on other primary substrate or electron acceptor. The literature survey demonstrates that, in many cases, chlorinated compounds are completely mineralised to benign end products. Additionally, biodegradation can occur rapidly. Growth rates exceeding 1 d^-1 were observed for many compounds. Most compound categories include chlorinated structures that are used to support microbial growth. Growth can be due to the use of the chlorinated compound as an electron donor or alternatively to the use of the chlorinated compound as an electron acceptor (halorespiration). Biodegradation linked to growth is important, since under such conditions, rates of degradation will increase as the microbial population (biocatalyst) increases. Combinations of redox conditions are favorable for the biodegradation of highly chlorinated structures that are recalcitrant to degradation under aerobic conditions. However, under anaerobic conditions, highly chlorinated structures are partially dehalogenated to lower chlorinated counterparts. The lower chlorinated compounds are subsequently more readily mineralized under aerobic conditions.     

Optimization of DNA blot hybridization conditions for various types of membranes]

A set of experiments has been conducted to choose the optimal conditions for DNA transfer and fixation on two types of the nitrocellulose, three types of nylon membranes and on capron filters. The buffer capillary transfer systems, electroblotting and gel hybridization are analyzed. Two techniques for DNA binding have been tested under different transfer conditions for all the membrane types: a vacuum fixation at 80 degrees C and a UV-exposure. The results indicate the critical dependence of the efficiency of blot-hybridization on the conditions of UV-treatment. The UV-exposure longer or shorter than the optimal one resulted in a loss of the hybridization efficiency. The optimal DNA-transfer and fixation conditions are recommended for all the membranes tested. The dependence of the optimal transfer and binding conditions on the specific characteristics of different membrane types was demonstrated for maximal sensitivity of the blot-hybridization.     

Ecological features of cenofloras of subarctic tundras of Siberia

The cenofloras of moss tundras, dryas tundras, and cryophytic grassy bogs of Subarctic Yamal, Taimyr, and Yakutia have been compared in such parameters as activity and species richness of their ecological groups. Comparison of the three cenofloras of subarctic tundras in conditions of heat and moisture has shown that the habitats of Yamal noticeably differ from the habitats of Taimyr and Yakutia. In Yamal, the conditions are warmer in all the habitats except grassy bogs in the zone of typical tundras. Most habitats in Yamal are drier. The hydrothermal conditions of Taimyr and Yakutia are similar. The differences arise as the climate becomes increasingly more continental from west to east.     

Adaptations of dragonflies (Odonata) under desert conditions

Different types of adaptations of dragonflies to climatic conditions of the desert zone are described. The main habitats of the dragonfly nymphs are lotic and semi-lotic artificial reservoirs. The life cycles are synchronous with seasonal climatic changes, reproduction being restricted to periods of the optimal hygrothermal conditions. Some species reveal vertical seasonal migrations. The labile daily activity rhythms allow the dragonflies to avoid the effects of unfavorable conditions. Adults of many species emerge at night.     

一类三次Kolmogorov系统极限环的存在性和唯一性

研究一类三次Ｋｏｌｍｏｇｏｒｏｖ系统,获得了系统存在极限环和存在唯一极限环以及不存在极限环的条件。     

Phenotypic plasticity of hermaphrodite sex allocation promotes the evolution of separate sexes: an experimental test of the sex-differential plasticity hypothesis using Sagittaria latifolia (Alismataceae)

Separate sexes can evolve under nuclear inheritance when unisexuals have more than twice the reproductive fitness of hermaphrodites through one sex function (e.g., when females have more than twice the seed fertility of hermaphrodites). Because separate sexes are thought to evolve most commonly via a gynodioecious intermediate (i.e., populations in which females and hermaphrodites cooccur), the conditions under which females can become established in populations of hermaphrodites are of considerable interest. It has been proposed that resource-poor conditions could promote the establishment of females if hermaphrodites are plastic in their sex allocation and allocate fewer resources to seed production under these conditions. If this occurs, the seed fertility of females could exceed the doubling required for the evolution of unisexuality under low-, but not high-resource conditions (the sex-differential plasticity hypothesis). We tested this hypothesis using replicate experimental arrays of the aquatic herb Sagittaria latifolia grown under two fertilizer treatments. The results supported the sex-differential plasticity hypothesis, with females having more than twice the seed fertility of hermaphrodites under low-, but not high-fertilizer conditions. Our findings are consistent with the idea that separate sexes are more likely to evolve under unfavorable conditions.     

Variable helper effects, ecological conditions, and the evolution of cooperative breeding in the acorn woodpecker

The ecological conditions leading to delayed dispersal and helping behavior are generally thought to follow one of two contrasting scenarios: that conditions are stable and predictable, resulting in young being ecologically forced to remain as helpers (extrinsic constraints and the habitat saturation hypothesis), or that conditions are highly variable and unpredictable, leading to the need for helpers to raise young, at least when conditions are poor (intrinsic constraints and the hard life hypothesis). We investigated how variability in ecological conditions influences the degree to which helpers augment breeder fitness in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus), a species in which the acorn crop, territory quality, and prior breeding experience all vary in ways that have important effects on fitness. We found that the relationship between ecological conditions and the probability that birds would remain as helpers was variable but that helpers generally yielded greater fitness benefits when ecological conditions were favorable, rather than unfavorable, for breeding. These results affirm the importance of extrinsic constraints to delayed dispersal and cooperative breeding in this species, despite its dependence on a highly variable and unpredictable acorn crop. Our findings also confirm that helpers can have very different fitness effects, depending on conditions, but that those effects are not necessarily greater when breeding conditions are unfavorable.