一类带有阶段结构的比率依赖捕食系统周期解

考虑一类在周期环境中的比率依赖捕食系统．食饵种群分为幼年和成年两个阶段．该系统中捕食者的增长函数是成年食饵与捕食者的比率函数．幼年食饵按照一定比例转化成年食饵．通过运用拓扑度方法．获得了该系统至少存在一组易验证的严格正周期解的充分条件。     

一类具有时滞和收获的阶段结构的捕食系统

研究一类具有时滞和收获的非自治阶段结构的捕食与被捕食系统,其中食饵种群分两个阶段——幼年与成年．利用重合度理论中的延拓定理,当收获现象发生时,得到系统至少存在8个正周期解的充分条件．     

一类食饵具有阶段结构的时滞Predator-Prey系统的周期解

研究了一类时滞Predator-Prey系统,其中Prey种群是具有两个生命阶段的种群,即幼年阶段和成年阶段。Predator种群只能捕食Prey幼年种群。通过应用Gaines和Mawhin重合度理论的连续函数定理,给出了系统正周期解存在的充分条件。     

一个阶段结构种群的最优策略

研究了一个阶段结构鱼群的捕获模型,该模型具有幼年和成年两个生长阶段.当幼年和成年种群同时收获时,从控制论的观点出发对所研究模型的最优收获策略进行了研究.最优策略是bang-bang和奇异控制的结合.     

一类具有阶段结构和时滞的非自治捕食系统的持久性与周期性

研究一类具有阶段结构和时滞的捕食系统,考虑食饵种群具有幼年和成年两个生长阶段,食饵在从幼年到成年的转化过程中遭受一定的死亡风险,而捕食种群的增长受消化时滞的影响,利用比较定理探讨了该系统在一定条件下的持久性与周期性,最后利用数值模拟验证了结果的正确性.     

Snake成长阶段的分析方法

在传统的Ｓｎａｋｅ方法基础上,提出了Ｓｎａｋｅ成长阶段的分析方法,在Ｓｎａｋｅ成长过程中的不同阶段（即幼年期、成长期、定型期）采用针对性的处理方法,并引入一系列有效的生长机制,从而较好地缓和了传统Ｓｎａｋｅ方法中所存在的那些问题．通过实例说明,改进后的模型确实能更好地应用于比较复杂的目标图像的边缘检测     

具有年龄结构的单种群模型单一捕获的优化问题

研究了一个具有年龄结构(幼年和成年)的单种群模型，分别对其幼年种群和成年种群捕获的问题，给出以最大可持续均衡收获(MSY)为管理目标的最优捕获策略．同时，对经济学中的Gordon理论做了分析．     

具有时滞和阶段结构的捕食系统的持久性与周期性

研究一类具有阶段结构和时滞的捕食系统.在此系统中,考虑食饵种群具有幼年和成年两个生长阶段.幼年食饵由它们的父母喂养,不需外出觅食,从而捕食者对它们的攻击可以忽略不计.并且考虑捕食种群的增长受消化时滞的影响.利用一些引理和比较定理探讨了该系统在一定条件下的持久性和周期性.     

具有阶段结构的捕食-被捕食系统的全局渐近稳定性

研究了具有幼年和成年两阶段结构的捕食与被捕食系统.分析了非负平衡点的局部特性,得到了正平衡点全局渐近稳定的条件.     

一类具有阶段结构的自治捕食系统的持久生存

研究了食饵具有两个阶段即幼年和成年,并且捕食者只对成年食饵进行捕食,证明了在一定条件下系统是持续生存的.     

Immature crude oils in the salt lake depositional environment are related to organic matter precipitated at stage of carbonate in salt lake sedimentation sequences

The present paper studies the mineralogy and geochemistry of a geological section in Jianghan basin. Widely distributed immature oils in this basin have been shown to relate to the carbonate depositional stage of salt lake sedimentation cycle. It is concluded that only when the content of organic carbon in the rocks is taken into account, is it meaningful to calculate the immature oil in the source rocks.     

Simulation experiments for evolution of fatty acids in immature source rocks

The anhydrous, hydrous and bitumen-extrac- ted simulations were carried out for the immature source rocks from the Liaohe sag. It has been shown from the result that with increasing temperature in simulation experiments, the fatty acids content decreased at first and then increased. The decrease of fatty acids in immature rocks is presumably related to alkanes generation in immature oils, whilst the increase may be related to the fact that some additional fatty acids are generated from kerogen and the tightly bound fatty acids in kerogen are released as bound fatty acids in kerogen and unbound fatty acids in bitumen. The fact that the bitumen generated from kerogen contains fatty acids has demonstrated that some bound and tightly bound fatty acids in kerogen can be transferred into bitumen. The preferential fatty acids in the immature source rocks are found to be mono-carboxylic acids with longer chains, whilst krogen contains relatively more di-carboxylic acids. It has been found that the fatty acids in immature source rocks can be changed from that with more longer chains to that with more shorter chains when evolution extent has been increased. Based on simulation results and the fact that the majority of fatty acids in immature oils are those with longer chains, it is inferred that the contribution of fatty acids to forming alkanes in immature oils mainly takes place at the evolution stage with R₀ <0.6%. The simulation experiments have also demonstrated that H₂O could promote the generation of fatty acids with more di-carboxylic acids and delay alkanes formation from fatty acids.     

具有阶段结构的SEI传染病模型的全局分析

建立和研究了一类具有幼年和成年两个阶段结构的SEI传染病模型,通过分析平衡点的特征方程,讨论了平衡点的局部稳定性.得到了基本再生数是传染病最终消除或成为地方病的阀值,当基本再生数小于1时,无病平衡点为全局稳定的,传染病最终消除,否则系统将一致持续生存.     

Structure of the immature retroviral capsid at 8 Å resolution by cryo-electron microscopy

The assembly of retroviruses such as HIV-1 is driven by oligomerization of their major structural protein, Gag. Gag is a multidomain polyprotein including three conserved folded domains: MA (matrix), CA (capsid) and NC (nucleocapsid). Assembly of an infectious virion proceeds in two stages. In the first stage, Gag oligomerization into a hexameric protein lattice leads to the formation of an incomplete, roughly spherical protein shell that buds through the plasma membrane of the infected cell to release an enveloped immature virus particle. In the second stage, cleavage of Gag by the viral protease leads to rearrangement of the particle interior, converting the non-infectious immature virus particle into a mature infectious virion. The immature Gag shell acts as the pivotal intermediate in assembly and is a potential target for anti-retroviral drugs both in inhibiting virus assembly and in disrupting virus maturation. However, detailed structural information on the immature Gag shell has not previously been available. For this reason it is unclear what protein conformations and interfaces mediate the interactions between domains and therefore the assembly of retrovirus particles, and what structural transitions are associated with retrovirus maturation. Here we solve the structure of the immature retroviral Gag shell from Mason-Pfizer monkey virus by combining cryo-electron microscopy and tomography. The 8-? resolution structure permits the derivation of a pseudo-atomic model of CA in the immature retrovirus, which defines the protein interfaces mediating retrovirus assembly. We show that transition of an immature retrovirus into its mature infectious form involves marked rotations and translations of CA domains, that the roles of the amino-terminal and carboxy-terminal domains of CA in assembling the immature and mature hexameric lattices are exchanged, and that the CA interactions that stabilize the immature and mature viruses are almost completely distinct.     

中华鳖红细胞发育过程的观察

通过骨髓、脾脏、肝脏、肾脏和外周血等器官涂片或印片观察来探讨中华鳖红细胞的产生器官、发育场所和发育各阶段的特征。结果表明骨髓是中华鳖红细胞的发源地，骨髓和脾脏是红细胞成熟的主要场所，在外周血和脾脏中亦可见少量未成熟或正在有丝分裂的红细胞，红细胞发育经过原始、幼稚和成熟等三个阶段，着重描述了红细胞发育各阶段的主要形态特征。     

小麦耐盐变异体的筛选——Ⅰ.小麦体细胞胚性无性系的建立

利用春小麦11个品种,通过幼穗和幼胚离体培养,研究了基因型,外植体和培养基成分对愈伤组织诱导率和分化率的影响.结果表明,不同基因型的愈伤组织诱导率和分化率差异明显.幼穗长度以10～14mm 时接种为宜,幼胚以开花后11～14d 接种效果最好.诱导培养基的效果以 MB>MS>N_6>LS,2,4-D 以2mg/L 较为合适,不宜加6BA 和 NAA,但加适量甘氨酸和谷氨酰胺有利于愈伤组织的诱导.分化培养基中加少量6BA 和 NAA 是必要的,而且 ZT 的作用优于 KT.通过以上研究,从中筛选出了3个能长期保持较高再生植株潜力的体细胞胚性无性系.     

具有父母照顾的捕食者捕食模型分析

分析了一个描述生态系统的反应扩散方程组.在此系统中,捕食者被分成不成熟和成熟两部分,不成熟的捕食者不能捕获猎物而是靠父母喂养;假设不成熟的捕食者的成熟率是食物的函数,研究了该系统的耗散性以及常数稳态解的局部稳定性.