尖头塘鳢(Eleotris oxycephala Temmiuck et Schlegel)的年龄、生长和生活史类型的研究

本文采用胸鳍第二支鳍骨为研究东江尖头塘鳢的年龄鉴定材料。胸鳍第二支鳍骨(远侧部)长的骨(R)与体长(L)的关系L=10.6565 54.3848R。用von Bertalanffy生长方程可表达体长、体重与年龄的关系:L=298.6(1-e~(-0.2313(t 0.3028))];W_t=577.4(1-e~(-0.2313(t 0.3028))]~3。根据r-选择和K-选择的典型特征以及渐近体长(L_∞)、渐近体重(W_∞)、生长系数(K)、瞬时自然死亡率(M)、初次生殖年龄(T_m)、最大年龄(T_(max))和性腺指数(GI)等7个生态学参数值,可以判断尖头塘鳢偏向r-选择。应用平衡产量模式计算改变瞬时捕捞死亡率(F)和渔业补充年龄(t_c)时的产量变化,同样证实尖头塘鳢生活史偏向r-选择。作为渔业管理对策,尖头塘鳢的捕捞年龄可定为2—3龄,以2龄为主,这样既能保护资源,又能获得较好的经济效益。     

四川裂腹鱼耳石碳、氧稳定同位素特征

为探讨耳石碳(δ¹³C)、氧(δ¹⁸O)稳定同位素在淡水鱼类群体识别中的作用,本研究以养殖条件下不同年龄组四川裂腹鱼为对象,采用稳定同位素质谱仪进行碳、氧同位素测定,揭示耳石中碳、氧稳定同位素特征,探讨其与环境间的关系. 结果表明:1⁺龄四川裂腹鱼δ¹³C和δ¹⁸O值均与耳石质量无显著相关关系,但在微耳石和星耳石之间存在显著差异;不同年龄四川裂腹鱼微耳石δ¹³C和δ¹⁸O平均值分别为(-9.58±0.06)‰、(-8.33±0.17)‰,其在雌雄个体之间均无显著性差异,但在不同年龄组间存在显著差异. 耳石δ¹⁸O和δ¹³C的关联分析能有效区分四川裂腹鱼不同养殖年龄群体,可作为一种识别淡水鱼类养殖群体的手段.     

作物磷素养分的动态模拟

基于养分平衡原理,分别建立了土壤有机磷与有机肥分解磷的释放、土壤有效磷吸附的动态模型,用Langmuir方程描述土壤吸附磷量与土壤溶液磷浓度的关系,建立了植株临界磷浓度与生理发育时间的关系模型,以及基于生长潜在需要和土壤水溶性磷浓度限制的作物磷素吸收动态模型.检验结果表明,模型对小麦植株含磷率的动态变化有较好的预测效果.     

土壤有机碳含量与同位素特征

根据长江口崇明东滩典型高程部位柱状样与鼎湖山不同海拔土壤剖面土壤有机碳(SOC)含量与SOC同位素资料(δ13C、Δ14C),研究了土壤有机质更新的元素与同位素特征。结果表明,土壤剖面δ13C最大值(δ13Cmax)深度以上土层的SOC含量与δ13C值呈负相关,该深度以下呈正相关。土壤SOC含量与δ13C呈负相关,说明有机质分解程度低,有机质中快循环组分的比例较高,为土壤表层新鲜有机质,有机质14C表观年龄不足200年;二者呈正相关指示有机质分解程度较高,为中、下部土层较稳定的有机质组分,成土年龄在300年以上。土壤SOC含量随时间下降的速率与成土时间呈负相关,δ13Cmax深度以下土层的下降速率明显低于该深度以上土层,且年代越老,SOC含量下降速率越慢,表明其有机质主要为慢循环组分。不同土壤剖面δ13C的时间趋势基本一致,在δ13Cmax深度以上土层,δ13C随时间延长而增大,该深度以下δ13C随时间延长而降低。土壤有机碳δ13C与SOC含量随时间的变化具有明显对应关系,表明二者的变化机制存在内在关联。     

一种单种群收获模型的稳定性分析

建立了一种按年龄分组的单种群收获模型,详细分析了该模型的稳定性,并得到了该模型临界稳定充分必要条件,还得到了在临界稳定平衡中的极限状态解及界稳定的生物学意义。     

一个带白噪声的可变时滞Lotka-Volterra人口模型(英文)

因为人口模型经常遭遇环境噪音的影响,本文将如下Lotka-Volterra模型(t)=diag(x(t))[b+Ax(t)+Bx(t-δ(t))]随机扰动为It型随机微分方程dx(t)=diag(x(t))[(b+Ax(t)+Bx(t-δ(t)))dt+(Qx(t)+Rx(t-δ(t))dw(t)].在这个随机模型中对系数b,A,B不需任何限制,我们证明了环境噪音不仅会压制人口的爆炸还会使得方程的解随机一致有界.     

具有年龄结构的接种流行病模型正平衡解的全局稳定性

研究一个具有年龄结构的接种SIS流行病模型正平衡解的稳定性,先利用等价积分方程给出了正平衡解存在的充分条件,再利用迭代方法及函数的单调性,得到了零平衡解与正平衡解全局稳定的充分条件。     

青海湖裸鲤生活史类型的研究

用模糊聚类法定量研究了青海湖裸鲤的生活史类型,以平衡产量模式进行了验证,并用世代生物量法探讨了其合理捕捞强度与捕捞年龄.结果表明：青海湖裸鲤属比较典型的k-选择类型鱼类;青海湖裸鲤平衡产量曲线与达氏鳇的平衡产量曲线非常相似;青海湖裸鲤的临界年龄为15.67龄,整个世代生物量在11～16龄达到最大;建议对青海湖裸鲤进行捕捞的最小捕捞年龄为12龄,捕捞强度不超过0.1.     

营养液强度对AM真菌生长发育的影响

研究了在贫营养基质中不同强度 Hoagland 营养液对丛枝菌根(Arbuscular mycorrhizae,M) 真菌 Glomus versiforme 生长发育的影响。结果表明：本试验条件下,菌根侵染率、菌丝量、孢子数间呈显著正相关。在施加5％～50％强度。Hoagland 营养液时,菌根真菌的生长与宿主植物高粱根中磷浓度、可溶性糖浓度密切相关,而与氮浓度无显著相关。由此认为：在盆栽生产菌根菌剂时,基质中存在一个临界磷浓度,在这个临界浓度之下,菌根真菌的生长发育随磷浓度的提高而增长,超过该临界浓度则会随磷浓度的提高而下降。施用20％、50％强度 Hoagland 营养液对菌根真菌生长最为有利,其菌根侵染率、菌丝量、孢子数均高于其它处理,因此认为：宿主植物一菌根真菌之间共生关系的基础是营养条件,基质中养分的高低会影响互惠共生关系的建立和发展。在高质量菌剂生产中,菌根共生体双方的生长发育完全可以由人工控制。施加营养液是一种有效的调控手段,有可能使共生平衡向有利于菌根真菌生长发育的方向倾斜,使真菌得到最大程度的生长。     

营养液强度对AM真菌生长发育的影响*

研究了在贫营养基质中不同强度Hoagland营养液对丛枝菌根(Arbuscular mycorrhizae, M)真菌Glomus versiforme生长发育的影响。结果表明:本试验条件下,菌根侵染率、菌丝量、孢子数间呈显著正相关。在施加5%~50%强度Hoagland营养液时, 菌根真菌的生长与宿主植物高粱根中磷浓度、可溶性糖浓度密切相关,而与氮浓度无显著相关。由此认为:在盆栽生产菌根菌剂时,基质中存在一个临界磷浓度,在这个临界浓度之下,菌根真菌的生长发育随磷浓度的提高而增长,超过该临界浓度则会随磷浓度的提高而下降。施用20%、50%强度Hoagland营养液对菌根真菌生长最为有利,其菌根侵染率、菌丝量、孢子数均高于其它处理,因此认为:宿主植物—菌根真菌之间共生关系的基础是营养条件,基质中养分的高低会影响互惠共生关系的建立和发展。在高质量菌剂生产中, 菌根共生体双方的生长发育完全可以由人工控制。施加营养液是一种有效的调控手段,有可能使共生平衡向有利于菌根真菌生长发育的方向倾斜,使真菌得到最大程度的生长。     

Multiallelic selection polymorphism

The existence and stability of an internal (i.e., completely polymorphic) equilibrium for viability selection at a single multiallelic locus is investigated. Generations are discrete and nonoverlapping; the population is panmictic, monoecious, and diploid. Various necessary and sufficient conditions for the existence of an internal equilibrium are established and applied to the loss of alleles. Some necessary conditions for the existence of an asymptotically stable internal equilibrium are also established. All these conditions are simpler and yield general biological conclusions more easily than the classical necessary and sufficient conditions.     

Marginal production technologies for life cycle inventories

Marginal technologies are defined as the technologies actually affected by the small changes in demand typically studied in prospective, comparative life cycle assessments. Using data on marginal technologies thus give the best reflection of the actual consequences of a decision. Furthermore, data on marginal technologies are easier to collect, more precise, and more stable in time than data on average technologies. A 5-step procedure is suggested to identify the marginal technologies. The step-wise procedure first clarifies the situation in which the marginal should apply, and then identifies what specific technology is marginal in this situation. The procedure is illustrated in two examples: European electricity production and pulp and paper production.     

Isolated cytoskeletons of human blood platelets: dark-field imaging of coiled and uncoiled microtubules

Detergent extraction of human blood platelets pre-treated with Taxol to stabilize microtubules allows isolation of marginal band (MB) cytoskeletons. We studied MB cytoskeleton structure using dark-field light microscopy and negative stain electron microscopy (EM). Dark-field illumination clearly demonstrated the "hoop" shape of MB cytoskeletons in unfixed suspensions where the microtubule coils had a mean diameter of 2.87 microns (+/- 0.18 micron, SD). Microtubules were uncoiled by brief exposure to trypsin (2 ng/micrograms protein) or by NaCl (154-600 mM) but not by DNase I, which removed approximately 40% of total actin, but had no effect on dark-field images of microtubule coils. As microtubules uncoiled, a single fiber emerged from the hoop and gradually lengthened as the brightness of the hoop diminished; these fibers correspond to the single microtubules seen by EM. Polypeptides of coiled and uncoiled MB cytoskeletons were analyzed by SDS-PAGE. When microtubules became uncoiled, no changes in the major components (alpha- and beta-tubulin, IEF-51K, or actin) were found. However, a number (greater than 10) of minor polypeptides, each less than 5% of total cytoskeletal protein and with an Mr ranging from 80,000- greater than 260,000, were decreased in "uncoiled" MB cytoskeletons. These results implicate one or more of these minor polypeptides in maintenance of hoop integrity. Dark-field light microscopy thus provides an approach toward investigating the mechanism(s) involved in maintaining the microtubule coil of the platelet marginal band.     

Consequences of Future Data Center Deployment in Canada on Electricity Generation and Environmental Impacts: A 2015–2030 Prospective Study

The environmental impacts of data centers that provide information and communication technologies (ICTs) services are strongly related to electricity generation. With the increasing use of ICT, many data centers are expected to be built, causing more absolute impacts on the environment. Given that electricity distribution networks are very complex and dynamic systems, an environmental evaluation of future data centers is uncertain. This study proposes a new approach to investigate the consequences of future data center deployment in Canada and optimize this deployment based on the Energy 2020 technoeconomic model in combination with life cycle assessment methodology. The method determines specific electricity sources that will power the future Canadian data centers and computes related environmental impacts based on several indicators. In case‐study scenarios, the largest deployment of data centers leads to the smallest impact per megawatt of data centers for all of the environmental indicators. It is found that an increase in power demand by data centers would lead to a reduction in electricity exports to the United States, driving the United States to generate more electricity to meet its energy demand. Given that electricity generation in the United States is more polluting than in Canada, the deployment of data centers in Canada is indirectly linked to an increase in overall environmental impacts. However, though an optimal solution should be found to mitigate global greenhouse gas emissions, it is not clear whether the environmental burden related to U.S. electricity generation should be attributed to the Canadian data centers.     

一类具常数接触率传染病模型的稳定性分析

本文研究了一类具常数接触率的传染病模型,用上下解方法和Liapnuov泛函讨论了地方病平衡点及无病平衡点的渐近行为,得到了各自全局稳定的充分条件.     

Marginal tests with sliced average variance estimation

We present a new computationally feasible test for the dimensionof the central subspace in a regression problem based on slicedaverage variance estimation. We also provide a marginal coordinatetest. Under the null hypothesis, both the test of dimensionand the marginal coordinate test involve test statistics thatasymptotically have chi-squared distributions given normallydistributed predictors, and have a distribution that is a linearcombination of chi-squared distributions in general.     

Transhumance with cows as a rational land use option in the Gredos Mountains (Central Spain)

Existing transhumance practices in the Gredos Mountains are studied and the origin, destination, number of livestock, livestock raiser characteristics, and environmental variables of winter and summer pasture areas and drovers roads are analyzed. The important ecological, economic, and cultural role of transhumance is emphasized and attention is drawn to the need for its support and conservation.     

两个基因座位的遗传平衡原理

由于许多教科书中关于连锁平衡的介绍,多是引用结论或是推导不太严谨,使学生在学习群体遗传学时对理解连锁平衡的原理感到困难。本文从遗传平衡的基本条件出发,通过较严谨的数学推导,介绍了两个基因座的连锁平衡条件、平衡过程等原理,供教师和学生在群体遗传学教学中参考。Abstract: Because linkage equilibrium is introduced by directly quoting the conclusions or imprecise mathematical reasoning in most of textbooks, many students are puzzled with the problem of linkage equilibrium when they learn population genetics. Based on the radical conditions of genetic equilibrium, the principle of linkage equilibrium condition and process, for two gene loci is introduced by precise mathematical reasoning. The article may provide reference to teachers and students in the teaching and learning of population genetics.     

Hide-and-seek strategies and post-contact immobility

To understand why an animal might gain by playing dead, or more precisely, exhibit post-contact immobility (PCI), we consider the context in which this behaviour occurs. Is it, for example, a method by which a potential victim encourages a predator to direct its attention elsewhere? We investigate this possibility by using the marginal value theorem to analyse predator behaviour in the context of this defence strategy by potential prey. We consider two models. In the first, (random revisiting) the predator may return to sites it has already depleted within the patch. In the second, (systematic search) the predator goes only to new sites within the patch. The results of the two models are qualitatively extremely similar. We show that when prey occur in patches, PCI favours prey survival. Indeed, certain antlion larvae have PCI durations characterized by very long half-lives. These appear to be of such long durations that further increases would convey no substantial benefits in redirecting potential predators to other antlions within the patch and subsequently to other patches.     

边缘幸存空间──一个新概念的提出

通过对物种及其生存空间的研究,提出了边缘幸存空间这一新的概念─—物种生存空间之外,居群不能稳定地延续,而生物个体可以存在的空间。还讨论了边缘幸存空间的存在特点及明确了几种在地层中识别边缘幸存空间的方法。最后,以这一概念为基础,讨论了西藏白垩纪赛诺曼期Ｂｉｓｃｕｔｕｍｅｌｌｉｐｔｉｃｕｍ的发现及其意义。