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．     

一类生化系统的极限环

本文研究了一类生化系统dx/dt=b-cx x^py,dy/dt=a-x^py,a,b,c,p均为正实数,得到了该系统不存在极限环,以及存在唯一稳定的极限环的充要条件。     

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.     

可逆两分子饱和反应动力系统的极限环

研究生化反应中一类可逆两分子饱和反应的数学模型dx/dt＝δ-xy cy^2,dy/dt=xy-cy^2-ay/b b,应用微分方程定性理论,完整地解决了该系统极限环的存在性,不存在性和唯一性。     

一类稀疏效应下食饵—捕食系统极限环的存在唯一性

本文研究如下一类具有稀疏效应的食饵－捕食模型dx/dt=bx^2(k-x)-bxy,dy/dt=-cy (βx-γy）y。应用常微分方程定性理论,对该系统的平衡点进行分析,得到了该系统极限环存在唯一的充分条件,并给出了生态解释。     

一类生化反应系统的定性分析

研究如下一类具米氏（Michalis）反应速度的化学反应模型dX/dt=A-BX-XY~2,dY/dt BX XY~2-υY/k Y'其中A,B,v及k为正常数,应用微分方程定性理论,在一定条件下研究了上述系统极限环的存在性,不存在性及唯一性问题．     

一类被开发的捕食系统的定性分析

讨论了一类食饵种群被开发的两种群捕食系统: dx/dt=x(a0+a1x-a2x2-a3y3)-h0, dy/dt=y(x-1)其中a0>0,a2>0,a3>0,h0>0,a1不定号.文中主要讨论了系统平衡点的行为以及系统的稳定性.用Pioncare切性曲线法及Dulac函数法讨论闭轨不存在的充分条件;用Hopf分支方法及张芷芬唯一性定理证明了极限环的存在性与唯一性.同时对相应结论的生态学意义给予了说明.     

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     

方程dx/dt=f(x(t-1))具有多个周期的周期解并蕴含浑沌的条件

本文给出了方程dx/dt=f(x(t-1))出现4/(2n 1),4/(2n-1),4/(2n-3),…,4/7,4/5,4/3,4一周期解并蕴含浑沌的一个条件。     

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.     

Morphology of the regiones ethmoidalis and orbitotemporalis in Galea musteloides Meyen 1832 and Kerodon rupestris (Wied-Neuwied 1820) (Rodentia: Caviidae) with comments on the phylogenetic systematics of the Caviidae

The present study describes the fetal regions ethmoidalis and orbitotemporalis of the cranium of Galea musteloides and Kerodon rupestris and compares them with Galea spixii and Cavia porcellus . The fetal crania of these representatives of the Caviinae were serially sectioned and 3D plate reconstructions were built. For a broader scope, serially sectioned heads of the caviomorph taxa Hydrochaeris hydrochaeris and Dasyprocta leporina were also examined. The ethmoidal and orbitotemporal regions of the cranium provides characters that are pertinent to the discussion of systematics of the Caviinae. Nine cranial characters were identified as being significant and discussed phylogenetically. Taking the monophyly of the Cavioidea as given, two characters are autapomorphic for the genus Galea: the reduction of the crista semicircularis and the lacrimale forming the 'arco antorbitario' (Kraglievich 1930). Cavia is the sister group of Galea; synapomorphic characters are the extent of the processus palatinus medialis of the praemaxillare and the presence lamina pterygoidea of the alisphenoid. There were no apomorphic characters of the structural complexes examined that could support the Caviinae. The reduced and nonperforated alisphenoid is an autapomorphic feature of the Caviidae. The division of the nasoturbinale is evidence for a sistergroup relationship of the Hydrochaeridae and the Caviidae. Autapomorphic characters for the Cavioidea include the ventrolateral opening of the organon vomeronasale and the lateral prolongation of the lacrimale.     

水稻胚与胚乳分化发育中的内源多胺

稻胚发育过程中,其内源多胺以腐胺、亚精胺为主。在幼胚分化期,腐胺和亚精胺的含量很高;幼胚分化完成时,其含量急剧下降;直至分化后期才趋稳定。在胚及胚乳发育时期,还出现一种未知多胺X_(22),其含量除在胚分化完成时较少外,在胚发育的其他各期中,含量则一直很高。DNA和蛋白质含量的变化,从分化期开始递增直至物质积累成熟期,其趋势均相同。多胺可能参与胚与胚乳中核酸和蛋白质合成的调节。     

Échinodermes de l'Ordovicien supérieur (Ashgill) de Sardaigne et d'Algérie

Research on the influence of sea level variations on the benthic faunas have been carried out in the Upper Ordovician of Sardinia. Study of the depositional facies and sequence analysis of the upper part (Lower Ashgill) of the Portixeddu Formation led to the identification of the sedimentary environments. Cystoids and crinoids are associated to bryozoans and brachiopods in most levels. The numerical analysis of associations and megaguilds shows that crinoids and cystoids have a higher frequency in the proximal and median facies of the upper offshore. The columnal association characterized by Conspectocrinus celticus and the coronoid Mespilocystites tregarvanicus has been discovered in the upper part of the formation. This material and complementary samples from Upper Ordovician of Sardinia and Kabylia (Algeria) bring additional data on the systematic and show the wide distribution of this fauna outside of the Ibero-armorican domain. The distribution of this echinoderm association supports a palaeogeographical position of the Ibero-armorican domain and Sardinia within the north gondwanan margin during the Lower Palaeozoic.     

The impact of European Directives on estuarine and coastal science and management

Many recent developments in European marine and estuarine science have been against the demands of European Union legislation. The implementation of certain statutes, the role of scientists and the nature of the data required are discussed using examples from the UK, the Netherlands and Portugal. This includes the implementation of the EU Directives on Urban Waste-water Treatment, the control of Nitrates, the designation of Species and Habitats, the control of Dangerous Substances, the statutory requirement for Environmental Impact Assessments and the recently proposed Water Framework Directive. For these, the integration of physical, chemical and biological monitoring and investigation is discussed in relation to the science dictated by the legislative and administrative requirements. Each of these Directives requires the development of generic guidelines and protocols for implementation and the use of national enabling legislation. This indicates that, in several cases, the science should concentrate on monitoring and assessment in a well-structured and quality-controlled manner. The paper concludes by summarising developments based on similarities in the implementation of present and proposed Directives across Europe.     

Genetic analysis as a tool to investigate the molecular mechanisms underlying seed development in maize

BACKGROUND: In angiosperms the seed is the outcome of double fertilization, a process leading to the formation of the embryo and the endosperm. The development of the two seed compartments goes through three main phases: polarization, differentiation of the main tissues and organs and maturation. SCOPE: This review focuses on the maize kernel as a model system for developmental and genetic studies of seed development in angiosperms. An overview of what is known about the genetic and molecular aspects underlying embryo and endosperm formation and maturation is presented. The role played by embryonic meristems in laying down the plant architecture is discussed. The acquisition of the different endosperm domains are presented together with the use of molecular markers available for the detection of these domains. Finally the role of programmed cell death in embryo and endosperm development is considered. CONCLUSIONS: The sequence of events occurring in the developing maize seed appears to be strictly regulated. Proper seed development requires the co-ordinated expression of embryo and endosperm genes and relies on the interaction between the two seed components and between the seed and the maternal tissues. Mutant analysis is instrumental in unravelling the genetic control underlying the formation of each compartment as well as the molecular signals interplaying between the two compartments.     

Comparison of mineral contents between the arteries in upper and lower limbs of japanese monkeys

To examine whether the calcium accumulation in aged arteries is related to the way of walking, the mineral contents were determined in the arteries of Japanese monkeys of quadrupedal walk by inductively coupled plasma-atomic emission spectrometry. Sixteen Japanese monkeys consisting of 7 males and 9 females ranging in age from 2 to 33 yr were studied. The accumulation of calcium, phosphorus, and magnesium occurred progressively in most, but not all, of the arteries with aging. It was found that independent of the upper and lower limbs, a higher accumulation of calcium, phosphorus, and magnesium occurred in the arteries of the proximal regions with aging, compared with the arteries of the distal regions. In a comparison between the arteries of anatomically corresponding regions of the upper and lower limbs, the accumulation of calcium and magnesium was 20–60% higher in the external iliac and femoral arteries of the lower limb than in the axillary and brachial arteries of the upper limb. Regarding phosphorus, the accumulation was 20–120% higher in the external iliac and femoral arteries than in the axillary and brachial arteries. It was known that in humans, the accumulation of calcium, phosphorus, and magnesium was three to seven times higher in the arteries of the lower limb than in the arteries of the upper limb. It is clear that there is a very significant difference in the accumulation of calcium and magnesium in the arteries of the lower limbs between Japanese monkeys and humans. The present study suggests that the accumulation of calcium and magnesium in the arteries of the lower limb with aging is affected by the way of walking.     

Style v dans le bassin du Douro: Tradition et changement dans les graphies des chasseurs du Paléolithique Supérieur européen

The documentation of some figures of hoofed in Siega Verde on panels of palaeolithic style and its stylistic references in the whole south of Europe, constitutes the starting point of the reflection on the presence of style v in the outdoors sites of the peninsular occident. In the Douro's region exists a richer documentation than the habitual in Europe: the outdoors panels of Côa and Siega Verde, the engravings on palaeolithic figures of La Griega, the paintings with direct chronologies of Ojo Guareña, the decorated plaquettes of the level 4 of Fariseu and the pebbles and plaquettes of Estebanvela. Painting in the caverns, outdoors and cave engravings and mobile art, with good references of absolute chronology between 11,500 BP and 9000 BP that confirm the continuity of the Palaeolithic art. If we compare the data of the peninsular occident with those of the north, those of Levant and those that begin to be known in Andalusia, the coincidence of dates is astonishing. In the same way if we compare these ones with the dates of the South of France and Italy. The external art of the western facade of the Iberian Peninsula possesses not only a unite palaeolithic contrasted sequence but rather it also puts in evidence the reality of the recurrent and continued locations in the whole sector during 30,000 years.Above the 11,000 BP, the transformations of the hunter groups begin to be evident in the whole south of Europe and the graphics demonstrate these changes, with a progressive transformation of contents and style that leads to a bigger schematization. The interesting cohabitation among naturalism and schematism that demonstrate the direct dates of C¹⁴, apparent a progressive transformation that discards radical ruptures between the social and graphic world of the palaeolithic hunters and their heirs.     

Areography of the Gymnosperms of China (1) Distribution of the Pinaceae of China

Nine of 10 genera and 119 of approximately 240 species of the Pinaceae occur in China, including 67 endemic species and two endemic genera. In this paper, the distributional maps of all the genera of the Pinaceae are presented (fig. 1-8). The horizontal and vertical distributions of species in each genus are discussed. The analysis of the distribution patterns of the genera indicates that some genera, such as Keteleeria, Tsuga, Pseudotsuga, Cathaya and Pseudolarix, are restricted to the area south of the Qinling Mountains and the Huaihe River, and the others, i. e. Picea, Abies, Larix and Pinus, extend northward to northeastern China. However, all of the genera except Keteleeria and Pinus are not found in very dry areas and tropical mountainous regions of China. The monotypic genera, Cathaya and Pseudolarix, are distributed in eastern and central China. The genus Keteleeria consists of 10 species, 7 of which are concentrated in southern Guizhou, northern Guangxi, southwestern Hunan and easternmost Yunnan. The distribution of the remaining 6 genera shows the maximum concentration in western Sichuan and northwestern Yunnan. (Figs. 2-8). Furthermore, more than third of species of the Pinaceae (37.8%) are also concentrated in western Sichuan and northwestern Yunnan. where a great variety of habitats and different topographic features occur. It is apparent that to conduct our systematic and evolutionary studies on this family in these region is especially needed. The relations between the areal size and the tolerance of species are discussed. The distributions of macrofossils and microfossils of the genera of the Pinaceae ia China are given, and it has been proved that areas of most genera of the family were considerably larger in the past. than at present.     

Cdc42 protein acts upstream of IQGAP1 and regulates cytokinesis in mouse oocytes and embryos

Cdc42 and Rac1 Rho family GTPases, and their interacting protein IQGAP1 are the key regulators of cell polarity. We examined the role of Cdc42 and IQGAP1 in establishing the polarity of mouse oocyte and regulation of meiotic and mitotic divisions. We showed that Cdc42 was localized on the microtubules of meiotic and mitotic spindle and in the cortex of mouse oocytes and cleaving embryos. IQGAP1 was present in the cytoplasm and cortex of growing and fully-grown oocytes. During maturation it disappeared from the cortex and during meiotic and mitotic cytokinesis it concentrated in the contractile ring. Toxin B inhibition of the binding activity of Cdc42 changed the localization of IQGAP1, inhibited emission of the first polar body, and caused disappearance of the cortical actin without affecting the migration of meiotic spindle. This indicates, that in maturing oocytes accumulation of cortical actin is not indispensable for spindle migration. In zygotes treated with toxin B actin cytoskeleton was rearranged and the first and/or subsequent cytokinesis were inhibited. Our results indicate that Cdc42 acts upstream of IQGAP1 and is involved in regulation of cytokinesis in mouse oocytes and cleaving embryos, rather than in establishing the polarity of the oocyte.