单种群生长的广义Logistic模型中参数的一种估值方法

本文提出种群生长的实测数据与广义Logistic模型的相容性条件,给出估计环境容纳量K的数学方法,利用常微分方程反问题的处理方法与麦夸特方法,对模型中参数进行近似估计与优化估计,其方法简便、通用性强．     

Hormone-Autonomous Suspension Culture from Leaf Explants of Sugar Beets in Liquid Medium

Hormone autonomous callus was institutioniated reproduciblyon MS agar medium with 0.25 mg/liter of BA as the sole planthormone (AI medium) from young leaf explants of sugar beets.When leaf explants were inoculated into AI medium and culturedon a reciprocal shaker, single cells began to be released fromthe cut surfaces of the leaf pieces after 6 days, followed byactive release. When the single cells which had been releasedwere transferred to fresh liquid MS medium without any planthormones, they could divide and grow autonomously, giving riseto hormone-autonomous suspension cultures. The effects of BAon induction of hormone-autonomous cells are discussed. (Received March 12, 1987; Accepted October 13, 1987)     

生长曲线参数估计的一种新方法-优化回归组合法

在现有文献研究的基础上,对生长曲线参数估计问题又作了进一步研究,给出了生长曲线参数估计的一种新方法优化回归组合法,该方法创造性地将最优化方法与回归方法结合在一起,利用最优化理论中的区间搜索和一维搜索,可以得到一系列c^＊值,利用回归方法可求得与其相对应的一系列a和b的值．当c取最优值c时,a和b便得到最优值a^＊和b^＊经示例计算表明,这种参数估计法具有较高的精度,     

Equivariant Estimation for the Parameters of an Exponential Model Based on Censored Sampling

Lehmann (1983) provides a detailed discussion on equivariant estimation of the parameters of location, scale and location-scale models. Edwin Prabakaran and Chandrasekar (1994) developed simultaneous equivariant estimation approach and illustrated the method with examples. In this paper, we consider exponential models and obtain minimum risk equivariant estimators of the parameters based on Type II censored samples. The equivariant method of estimation is illustrated with biological and reliability applications.     

Influence of Population Densities of Heterodera schachtii on Sugar Beets Grown in Microplots

High initial population densities of Heterodera schachtii larvae (36 and 108/gm of soil) greatly retarded the seedling emergence of sugar beet ''Monogerm CSF 1971'' in Vineland fine sandy loam. In comparison with controls, initial population densities (P_i''s) of 1.7, 3.0, 6.2, and 14.4 larvae/gm of soil respectively reduced the weight of storage roots by 38, 56, 64, and 92%. Weights of tops also decreased with increases in P_i; weights of tap and small feeder roots tended to be higher at all P_i''s except the highest. Sucrose percentage was not affected by any initial nematode density. The populations were lower at midseason than at seeding, and at harvest had increased greatly, with respective populations of 339, 402, 222, and 140 larvae/gm of soil. At harvest, cysts/gm of soil and cysts/gm of root were respectively 4.4 and 72, 6.1 and 99, 6.1 and 191, and 5.8 and 140. The maximum rate of multiplication was 150-200. and maximum density was 400 larvae/gm of soil. The high pathogenicity and multiplication rate of the nematode was attributed to optimum temperature conditions and soil type.     

Comparing Stochastically Restricted Linear Estimators in a Regression Model

Conditions for superiority of the minimum dispersion estimator over another with respect to the covariance matrix are derived when the vector parameter of a regression model is subject to competing stochastic restrictions. The restrictions may also consist both of a deterministic part and a stochastic part.     

灌溉水稻生长发育和潜力产量的模拟模型

本文提出的HDRICE模型是灌溉水稻生长的生理生态模型,它由相互衍接的水稻形态发育、干物质积累和叶面积发育三模块组成。形态发育模块用以模拟逐日温度和日长对水稻发育的影响,其参数可反映水稻品种的基本营养性、感温性和感光性;干物质积累模块用以模拟冠层CO_2同化、作物的维持呼吸和生长呼吸及干物质分配等过程;叶面积发育模块用以模拟叶面积指数的动态。本文还讨论了模型的输入参数和模型检验。模型可应用于模拟水稻的生长发育,预测水稻品种潜在产量及为取得潜在产量所必需的群体数量指标。     

An Explanation for the Difference in Photosynthetic Capabilities of Healthy and Beet Yellows Virus-infected Sugar Beets (Beta vulgaris L.)

Sugar beets (Beta vulgaris L.) infected with the Beet Yellows Virus exhibit lower rates of net photosynthesis at light saturation than do healthy plants. These Pn reductions were correlated with increases in leaf resistance to water vapor loss. Theoretical analyses demonstrated that, although the leaf resistance to water vapor loss increases could account for a major part of the net photosynthesis decreases, some other aspect of leaf functioning also was debilitated by infection. Both the levels and the activities of ribulose-1, 5-diP carboxylase were less on a leaf area basis in extracts from infected leaves than from healthy ones. Soluble carbohydrates accumulate in Beet Yellows Virus-infected leaves, but inhibiting translocation in several ways provided no evidence in support of the hypothesis that the accumulation of photosynthates in leaves has a direct, short term, feed-back effect upon the photosynthetic rate.     

一类具有非线性控制和基层具有饱和吸收率的恒化器藻类模型

本文通过对藻类的增长率和基层的吸收率提出有生物意义的表达式,研究了一类具有非线性控制藻类恒花器模型．用定性理论证明了非线性控制可以使变产量的恒化器模型有一个全局渐进稳定的正平衡点．     

Model for Branch Initiation in Aspergillus nidulans Based on Measurements of Growth Parameters

The rate of hyphal elongation and the number of branches per hypha were measured on short sporelings of Aspergillus nidulans growing at different rates. The rate of elongation was proportional to total length in unbranched and branched hyphae. At each growth rate, the number of branches per hypha increased with increasing length and gave approximately straight-line graphs when plotted against length. The average number of branches per unit of hyphal length was quite different for the various growth rates and increased in direct proportion to the growth rate. The results are interpreted to mean that (i) growing tips have a maximum rate at which they can elongate and which is reached at hyphal lengths characteristic of the particular growth rate and (ii) a new branch is formed when the capacity of the hypha to elongate exceeds that of the existing tips.     

删失数据下非线性半参数回归模型中参数的经验似然推断

考察了响应变量在随机删失情形下的非线性半参数回归模型,构造了未知参数的经验对数似然比统计量和调整经验对数似然比统计量,证明在一定条件下,所构造的经验似然比统计量渐近于X~2分布,并由此构造出未知参数的置信域.此外,又构造了未知参数的最小二乘估计量,证明了它的渐近性质.通过模拟研究表明,经验似然方法在置信域的覆盖概率以及精度方面要优于最小二乘法.     

Effect of Plant Age and Transplanting Damage on Sugar Beets infected by Heterodera schachtii

Sugar beet (Beta vulgaris L. cv. Monogerm C.S.F. 1971) seeds sown into Vineland fine sandy loam, infested with 15,500 H. schachtii juveniles/pot, showed little growth during an 11-week test in the greenhouse. Seedlings transplanted at 2, 4, and 6 weeks of age had 32, 30, and 31% less top weight and 71, 68, and 59% less root weight, respectively, compared to controls grown in nematode-free soil. Nematode reproduction in both direct-seeded and transplanted sugar beets was limited and related to root weight. Shoot/root ratios were increased by the nematodes in all nematode-infected beets compared to those grown in soil without nematodes. In contrast to seeding or transplanting sugar beets into nematode-infested Vineland fine sandy loam, an inoculation of Beverly fine sandy loam supporting 0 (seeds), 2-, 4-, and 6-week-old sugar beet seedlings with 7,400 juveniles/pot, followed by 11 weeks of growth in the growth-room, resulted in top weight losses of only 13, 3, 18, and 15% and losses in root weight of 44, 38, 36, and 38%, respectively. Nematode reproduction was high and all shoot/root ratios were increased by the nematode compared to the noninoculated controls. These experiments have shown that sugar beets sown into nematode-infested soil are damaged much more heavily by H. schachtii juveniles than seeds inoculated with the nematode immediately following sowing. Results indicate that an increase in tolerance of sugar beets to attack by H. schachtii does not occur beyond the first 2 weeks of growth and that transplanting damage lowers the tolerance of seedlings to nematode attack.     

一类单种群增长模型正解的振动性

利用一种新的方法研究了一类单种群增长模型—时滞微分方程N(t)=的解关于其正平衡点N=1的振动性,所获结果改进了已有文献中的相关结论。     

种群增长的分段指数模型及其参数估计

本文给出了种群增长的分段指数模型其中N（t）是在时刻t种群的密度,No=N（t0）,r0和rl是群群的内禀增长率,t0是转变点,H（t-t0）=1,t≥t0,H（t-t0）=0,t＜t0．利用非线性模型的正割法（DUD,Doesn’tusederivatives）,可同时确定模型的所有参数（包括交点t0在内）．并用于描述长爪沙鼠种群动态．     

Nonlinear control for algae growth models in the chemostat

This paper deals with output feedback control of phytoplanktonic algae growth models in the chemostat. The considered class of model is of variable yield type, meaning that the ratio between the environmental nutrient absorption rate and the cells’ growth rate varies, which is different from classical bioprocesses assumptions. On the basis of weak qualitative hypotheses on the analytical expressions of the involved biological phenomena (which guarantee robustness of the procedure toward modeling uncertainties) we propose a nonlinear controller and prove its ability to globally stabilize such processes. Finally, we illustrate our approach with numerical simulations and show its benefits for biological laboratory experiments, especially for ensuring persistence of the culture facing classical experimental problems.     

Improved solution for solitary waves in arteries

 Nonlinear waves are investigated numerically by a direct analysis of the field equations, thereby establishing the magnitude of the errors inherent in the commonly used reductive perturbation technique. The method is also applied beyond the long-wave approximation and a comparative assessment of the results obtained is presented. Received: 11 March 1998 / Revised version: 19 May 1998     

Respiration Modelling and Hypothesis Testing with a Dynamic Model of Sugar Beet Growth

Respiration was predicted quantitatively during sugar-beet growthsimulations by assuming an intimate coupling to growth and maintenanceprocesses. Changes in the growth and maintenance respiratorycoefficients for successive simulations expressed alternativehypotheses regarding the nature of that coupling. Large differencesin yield, partitioning patterns, and the relative importanceof the growth and maintenance components were predicted in responseto changes in respiratory coefficients within the range consideredphysiologically realistic. Beta vulgaris L, sugar beet, respiration, growth yield, mathematical modelling