非线性递归差分方程的全局渐近稳定性

得到下列非线性差分方程xn 1=xnxn-1 xn-2 axn-1 xnxn-2 a,n=0,1,2,…，其中a∈[0,∞),初值x-2,x-1,x0∈（0,∞)，全局渐近稳定性的一个充分条件，并且证明了一个猜测。     

具振动内禀增长率的单种群增长模型的振动性

研究离散的单种群增长模型x_(n+1)=x_nexp(rn (1-x_(n-k))/(1-cx_(n-k))),n=0,1,2,…,(*)的解的振动性,其中{r_n)_(n=1)~∞是任意实序列,k是正整数,0<相似文献   

火电厂生态工业园的能值评估

提出了反映火电厂生态工业园特点的能值评价指标：能值产出率PEYR和能值投资率PEIR考虑了园区各成员的共同贡献,即PEYR=6∑（i=1)(Fi+Ri+Ni)／6∑（i=1)Fi和PEIR=6∑（i=1)Fi／6∑（i=1)(Ni+Ri);环境负荷率PELR和能值可持续指标PESI考虑了火电厂生态工业园节省的不可再生能源、可再生能源、投入能值和减少的环境负荷,即PELR=6∑（i=1)Fi／F’和PESI=PEYR／PELR．以朔州火电厂生态工业园为案例进行了能值分析,结果表明,该能值评价指标能全面度量火电厂生态工业园及其可持续性．     

一阶泛函差分方程解振动的充分和必要条件

得到具有多个时滞的差分方程：An l-An m^∑i=1piAn-ki=0解振动的充分和必要条件,这里pi全是正数,ki是正整数,i=1,2,3,…,m,(或pi是负数,ki是负整数)。     

三种群合作系统的全局渐近性态

考虑三种群合作系统:dχi/dt=χi(b-∑j3=1αijχj),χi(0)>0,b>0,αij<0,i≠j,i,j=1,2,3,完整地分析了其全局渐近性态:证明了该系统不存在闭轨,给出了正平衡点存在且全局渐近稳定的充要条件,证明了若系统不存在正平衡点,则所有解均趋于无穷.     

论负二项分布的参数K值与平均数m之关系

负二项分布的参数k值与平均数m之相依关系可表达为如下3种形式: (1) 1/K=α/m+(β-1) (2) 1/K=+α/m+γm+(β′-1) (3) 1/K=αm~(h-2) 1/m 式中,α、β为m-m回归(Iwao 1968)的参数α、β值;α′、β′和γ为改进的m-m回归模式(徐汝悔等 1984)中的参数α′、β′和γ值;a、b为Taylor's(1965)指数法则中的a、b值。本文引用7种生物种群的资料论证了上述三种关系的存在,并对3个模型的优劣进行了比较。依据Taylor's指数法则中参数b的大小,又可将k与m的关系归纳为5种基本类型,表明了k值与m的关系是极其复杂的,用k值来测定生物种群的聚集强弱及建立耻论抽样数模型均是不恰当的。     

时滞偏LOGISTIC方程组的振动性

我们得到了时滞偏LOGISTIC方程组аNi（x,t）/аt=Ni（x,t）[αi-^m∑j=1 bijNj（x,t-τj）],i=1,2...,m.的所有解关于它的平衡点振动的充分条件。     

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’,”…     

分布时滞双向神经网络的周期解的渐近稳定性

利用重合度连续定理和适当的李亚普诺夫泛函,研究了分布时滞双向神经网络xi^.(t)=-ai(t)xi(t) ∑j=1^m pj,(t)∫-∞^t hji(t-s)fj(yj(s))ds Ii(t),i=1,2……,n,yj^.(t)=-bj(t)yj(t) ∑i=1^n qij(t)∫-∞^t kij(t-s)gi(xi(s))ds Jj(t),j=1,2,…,m的周期解的存在性和渐近稳定性。     

种群增长的矩阵计算模型

一、基本模型 首先简单地假设种群中雌性和雄性比例相等,在达到生育年龄时都能找到配偶,并且各个年龄的死亡率与性别无关。考虑在离散时刻t=0,1,2,…的种群大小N_t,时间单位可以任选,为方便以年计。在时间区间(i—1,i]出生的个体,在年度(i,i 1]内为0岁(i以前夭亡者不计),在(i 1,i 2]内为1岁,以此类推,这相当于实足年龄。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.