功能反应函数为x~(1/2)的食饵-捕食系统的定性分析

本文运用Liapunov第二方法,论证了功能反应函数为x～(1/x)的食饵-捕食系统x=x-ax-2~3-x~(1/x)y,βy=-sy βx~(1/x)y-εy~2唯一正平衡点的稳定性．其次将该系统化为二次微分系统Ⅲ类方程的标准形式,进而研究了极限环的存在唯一性问题．     

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.     

一类具功能反应的食饵-捕食者两种群模型的定性分析

对具功能反应的食饵-捕食者两种群模型x=xg(x)-y( )(x),y=y(-d+e( )(x)).在g(x)=α-baα,( )(x)=cxα(a,b,c＞0,1/2≤α＜1)且α使函数f(x)=x1/a在(-∞,+∞)上为偶函数时进行了研究,讨论了该系统平衡点的稳定性态,系统无环的充分条件以及在正平衡点外围存在惟一稳定极限环的条件.     

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．     

捕食者厌食的Predator-prey系统极限环存在性与唯一性

一、引言捕食系统的捕食者具有Ⅱ类功能反应时,功能函数为Φ(x)=αx/1+ωx,其中α,ω均为正常数,当x→+∞时,Φ(x)→α/ω>0,呈捕食饱和状态。而有些捕食生物种群,由于食饵过多而逐渐形成不爱捕食的习惯,这时用功能函数Φ(x)=αx/1+ωx+βx~2描述捕食状态,其中β>0,当x→+∞时,Φ(x)→0。系统为     

一类含单奇点的极限环的三次系统

证明具体三次系统x=y-εy~3,y=x(1-x~2)+(α-x~2)y,当α≥1或0<α≤1/3时,在区域|y|<1/ε~(1/2)内无含单奇点的极限环,这里ε>0.     

贵州两种黄脊蝗核型和C-带的比较研究

本文研究了贵州日本黄脊蝗 Patanga japonica Bolivar和印度黄脊蝗 P.Succincta Johansson的核型和c-带。结果表明：两种黄脊蝗的染色体数目均为2n(♂)=22+x.=23,全部为端着丝粒染色体;核型公式2n(♂)=2X=231,NF=23. 但日本黄脊蝗的染色体绝对长度总和(79.75±2.22μm)比印度黄脊蝗的(71.4 7±0.63μm)长;异染色质总量(35.65±0.14μm)比印度黄脊蝗的(10.76±0.11μm多;日本黄脊蝗的核型属“1B”核型,印度黄脊蜱的核型属“lc”核型。     

种群生态系统的持续生存

一、引言许多描述种群生态的数学模型都可以由一常微分方程组 x＇=f(x) (x＇=dx/dt) (1.1)来描述。这里, x=(x_1,x_2,…,x_1)~T∈R_+~n,t∈R_+,R_+~n={x|x≥0,i=1,2,…,n},R_+={t|t≥0},f(x)=〔f_1(x),f_2(x),…,f_2(x)〕~T,x_i表示种群的数量或密度。记intR_+~n为R_+~n的内部,bdR_+~n为RR_+~n的边界。对于一个生态系统,我们通常最关心的是生态平衡问题,这就需要研究系统(1.1)的动力学行为。对于系统(1.1)而言,若存在正平衡位置,且它相对于intR_+~n是全局渐近稳定     

响应曲面法优化灵芝廉价型深层发酵培养基的研究

为了获得生产用廉价型灵芝发酵培养基,采用中心组合旋转设计法和响应曲面法对低成本培养基组分进行了优化。优化的四个组分为玉米粉(x1)、麸皮粉(x2)、豆饼粉(x3)和蔗糖(x4)。结果表明,灵芝菌体发酵和多糖发酵的培养基预测模型分别为:Y1=15.1–0.31x1–0.34x2+0.36x3–0.44x4–1.26x12–1.98x22–0.85x32–1.15x42–0.59x2x3和Y2=2.0–0.08x1–0.08x2+0.04x3–0.09x4–1.13x12–0.33x22–0.08x32–0.16x42–0.16x2x3–0.10x1x4。从中获得菌体发酵的最优配方为:玉米粉19.7g/L,麸皮粉11.3g/L,豆饼粉6.3g/L,蔗糖19.5g/L;多糖发酵的最优配方为:玉米粉19.6g/L,麸皮粉11.0g/L,豆饼粉6.7g/L,蔗糖19.1g/L。150L发酵罐中试放大结果表明,灵芝菌体的产量为16.92g/L,多糖产量为1.86g/L。所得培养基为灵芝产品的高效低成本生产提供了基础。     

种群模型参数辨识的一种方法

1、M(。,m)模型的建立定理.对于微分方程 dnx,(t)dtn+口zd卜lx,(t) dtn一1+…+a。_:dx:(t) dt否,x,(‘)+box:(‘)+b3x;(‘)x:(‘)+…+”。·,x:(‘)‘二(‘)给定样本数据{x;(k)1,k二1,2,…,N,i=I,2,…,m,则该方程的参数向量a=〔a:aZ…a。一,ib:bZ…b二+:〕丁可通过〔(AIB)T(A{B)〕一’(A{B)TC辨识,其中,C=〔△,x;(2),△nx:(了),…,△。x,(N)〕T陈华豪等万卷s2/△,一‘x工(2)△“一‘x:(3)…△x:(2)△x:(3)A二一……△一’x,(N),△x,(、){,111\x,(z),x贯(1),x,(1)x:(1),…,x;(了).x二(I)B二‘1‘“’,‘飞‘”,‘1.:员.,‘2‘2’,”…     

Permanence of a stage-structured predator-prey system with a class of functional responses

A stage-structured predator-prey system incorporating a class of functional responses is presented in this article. By analyzing the system and using the standard comparison theorem, the sufficient conditions are derived for permanence of the system and non-permanence of predators.     

Optimal control mode of a biochemical feedback system

An optimal feedback system for constant-value control of biochemical reaction system was investigated by computer simulations. A feedback system containing a cyclic enzyme system where two enzyme types share a substrate in a cyclic manner, was found to be the most reliable one. This feedback system has a capability to keep the stationary value of the end product at a desired level against not only exogenous substrate supply but also endogenous parametric disturbances. The cyclic enzyme system installed as a control element of this feedback system played the role of comparator in this feedback system. The control mode of this feedback system was in good agreement with that of a system established by means of optimization technique based on the maximum principle. Also bang - bang control could be performed in this biochemical feedback system as well as in electrical one.     

Dynamic stability of a human standing on a balance board

The neuromuscular system used to stabilize upright posture in humans is a nonlinear dynamical system with time delays. The analysis of this system is important for improving balance and for early diagnosis of neuromuscular disease. In this work, we study the dynamic coupling between the neuromuscular system and a balance board—an unstable platform often used to improve balance in young athletes, and older or neurologically impaired patients. Using a simple inverted pendulum model of human posture on a balance board, we describe a surprisingly broad range of divergent and oscillatory CoP/CoM responses associated with instabilities of the upright equilibrium. The analysis predicts that a variety of sudden changes in the stability of upright postural equilibrium occurs with slow continuous deterioration in balance board stiffness, neuromuscular gain, and time delay associated with the changes in proprioceptive/vestibular/visual-neuromuscular feedback. The analysis also provides deeper insight into changes in the control of posture that enable stable upright posture on otherwise unstable platforms.     

Quantification of genetically modified soybeans using a combination of a capillary-type real-time PCR system and a plasmid reference standard

Because the labeling of grains and feed- and foodstuffs is mandatory if the genetically modified organism (GMO) content exceeds a certain level of approved genetically modified varieties in many countries, there is a need for a rapid and useful method of GMO quantification in food samples. In this study, a rapid detection system was developed for Roundup Ready Soybean (RRS) quantification using a combination of a capillary-type real-time PCR system, a LightCycler real-time PCR system, and plasmid DNA as the reference standard. In addition, we showed for the first time that the plasmid and genomic DNA should be similar in the established detection system because the PCR efficiencies of using plasmid DNA and using genomic DNA were not significantly different. The conversion factor (Cf) to calculate RRS content (%) was further determined from the average value analyzed in three laboratories. The accuracy and reproducibility of this system for RRS quantification at a level of 5.0% were within a range from 4.46 to 5.07% for RRS content and within a range from 2.0% to 7.0% for the relative standard deviation (RSD) value, respectively. This system rapidly monitored the labeling system and had allowable levels of accuracy and precision.     

The expected extinction time of a population within a system of interacting biological populations

The quasi-stationary distribution of a population within a system of interacting populations is approximated by a stochastic logistic process. The parameters of this process can be expressed in the parameters of the full system. Using the diffusion approximation, an expression for the expected extinction time is derived from this logistic process. Since the expected extinction time is expressed in the parameters of the full system, the effect of these parameters on the extinction risk can be easily evaluated, which may be of use for studies in ecology, conservation biology and epidemiology. The outcome is compared with simulation results for the case of a prey-predator system.     

Co-expression of a prophage system and a plasmid system in Bacillus subtilis

A dual expression system for overexpressing two proteins by a single cell strain has been developed in Bacillus subtilis. This dual expression system combines the phi105MU331 prophage system and a plasmid system within a single cell. Protein expression by the prophage system is heat inducible, while that of the plasmid system is constitutive. Three candidate genes, BPN, BT, and amyE, all of Bacillus origin, were used as test models. Seven strains (BPN, BT, AMY, BS168K, MU331K, BPNK, and BTK) were constructed to investigate the influences of the prophage system and the plasmid system on each other, and to compare the efficiency of the individual expression systems with that of the dual expression system. Individually, the yield of the plasmid system is higher than that of the prophage system, which could be attributed to the constitutive nature of the expression of the plasmid system. Nonetheless, for the dual expression strains, the expression of two enzymes in a single fermentation run can reduce costs in facilities, manpower, and utilities. Fed-batch fermentation of BPNK strains confirmed the feasibility of applying this dual expression system in industrial-scale production.     

四环素诱导组织特异性表达系统的构建

如果获得一种可以特异调控基因表达的系统。对于研究某一基因在各个不同发育时期的功能会有很大的帮助。为了控制外源基因在特定的时间和组织内在转基因植物中表达。将四环素诱导元件和花药绒毡层特异表达启动子TA29结合。构建了一个新的系统。通过基因枪将该系统转入烟煤草（Nicotiana tabacumL.cv.Wisconsin38)组织,GUS瞬时表达结果表明,四环素诱导前,没有任何烟草组织染上蓝色,表明该系统不表达;而四环素诱导仅30min后,花药就染上明显蓝色,而且集中在花药绒毡层,其对照子房在四环素诱导前和诱导后均未染蓝色。这些结果表明。该系统既是四环素诱导又是花药绒毡层特异表达的。     

四环素诱导组织特异性表达系统的构建

如果获得一种可以特异调控基因表达的系统,对于研究某一基因在各个不同发育时期的功能会有很大的帮助.为了控制外源基因在特定的时间和组织内在转基因植物中表达,将四环素诱导元件和花药绒毡层特异表达启动子TA29结合,构建了一个新的系统.通过基因枪将该系统转入烟草(Nicotiana tabacum L. cv.Wisconsin 38)组织,GUS瞬时表达结果表明,四环素诱导前,没有任何烟草组织染上蓝色,表明该系统不表达;而四环素诱导仅30min后,花药就染上明显蓝色,而且集中在花药绒毡层.其对照子房在四环素诱导前和诱导后均未染上蓝色.这些结果表明,该系统既是四环素诱导又是花药绒毡层特异表达的.     

Development of a direct digital-controlled fermentor using a microminicomputer hierarchical system

A computerized fermentation system was developed for use in a research environment. Major goals in the design and construction of the system were flexibility and versatility. Direct digital control is employed for all low-level and high-level control loops. A microminicomputer hierarchical configuration is used to implement this control structure. The microcomputer is also utilized to simplify the interface with the fermentor, both at the hardware and minicomputer software levels. This computerized fermentation system provides accurate data acquisition, excellent control, and flexibility in the fermentation operation.     

Experimental modeling of a novel magnetic confinement system: Galathea with a myxine in the shape of a convex polyhedron

A new type of magnetic confinement system—a Galathea with a myxine in the shape of a convex polyhedron—is proposed. The system was modeled experimentally by passing an RF current through the myxine. On the one hand, the myxine acts as an inductor whose electric field ionizes the gas and, on the other, it acts as an RF magnetic confinement system. A steady-state plasma produced and confined in this system is almost spherical in shape. The electron density and specific (per unit volume) glow intensity of the plasma produced are found to be higher than those in conventional helical inductors.