Responses of nitrogen and phosphorus resorption from leaves and branches to long-term nitrogen deposition in a Chinese fir plantation

为了解森林养分内循环对全球变化的响应, 基于长期模拟氮沉降试验, 研究了杉木(Cunninghamia lanceolata)人工林不同龄级(一年生、二年生和衰老)叶和枝的氮(N)、磷(P)养分分配及其再吸收特征, 并分析了不同模拟N沉降处理时间(7年和14年)杉木叶N、P养分再吸收差异。在12年生杉木中开展模拟N沉降试验, 以尿素(CO(NH₂)₂)为N源, 设N0、N1、N2和N3 4个处理水平, 施氮量分别为0、60、120和240 kg·hm ^-2·a ^-1, 每个处理重复3次。结果表明: (1)叶和枝在衰老过程中碳(C)、N和P含量逐渐降低, 且叶的C、N和P含量比枝高; N含量大小依次为一年生叶>二年生叶>衰老叶>一年生枝>二年生枝>衰老枝, 且N3 > N2 > N1 > N0, 而C:N则呈现相反的趋势; 衰老器官的C:N、C:P、N:P比新鲜器官高; N沉降增加了不同龄级叶和枝(除二年生叶外)的N、N:P和C:P, 但降低了P和C:N。(2)叶和枝的N、P养分再吸收率(RE_N、RE_P)随龄级的增加至衰老有规律地递减, 且RE_P > RE_N; 受长期N沉降的影响, RE_N叶(28.12%) <枝(30.00%), 而RE_P则为叶(45.82%) >枝(30.42%); 杉木叶和枝N:P与RE_N:RE_P之间存在极显著的线性相关关系。(3)随N沉降处理时间的增加, 叶RE_N呈降低态势, 各处理(N1、N2和N3)分别降低了9.85%、3.17%和11.71%; 而RE_P则明显上升, 分别增加了71.98%、42.25%和9.60%。研究结果表明: 不同器官、不同龄级的养分再吸收率随氮沉降处理的水平、处理时间而所有不同; RE_N:RE_P与N:P之间存在紧密关系。     

Implementation of reflex loops in a biomechanical finite element model

In the field of biomechanics, the offer of models which are more and more realistic requires to integrate a physiological response, in particular, the controlled muscle bracing and the reflexes. The following work aims to suggest a unique methodology which couples together a sensory and motor loop with a finite element model. Our method is applied to the study of the oscillation of the elbow in the case of a biceps brachial stretch reflex. The results obtained are promising in the purpose of the development of reactive human body models.     

On the Information Matrix of Exponential Mixture Models with Long-term Survivors

The aim of this paper is to study the properties of the asymptotic variances of the maximum likelihood estimators of the parameters of the exponential mixture model with long-term survivors for randomly censored data. In addition, we study the asymptotic relative efficiency of these estimators versus those which would be obtained with complete follow-up. It is shown that fixed censoring at time T produces higher precision as well as higher asymptotic relative efficiency than those obtainable under uniform and uniform-exponential censoring distributions over (0, T). The results are useful in planning the size and duration of survival experiments with long-term survivors under random censoring schemes.     

Biology and comparative predation efficacy of three heteropteran species recorded as predators ofBemisia tabaci in Maharashtra

Two mirids,Deraeocoris sp. andCampylomma nicolasi Reuter and one lygaeid,Geocoris ochropterus Fieber were found preying onB. tabaci (Gennadius) for the first time in Maharashtra State of India during 1987–88. Their biology and predation capacity onB. tabaci were studied in detail under laboratory conditions. The nymphal stage ofDeraeocoris sp. passed through 6 instars, whereas 5 instars in case of the remaining species.G. ochropterus, Deraeocoris sp. andC. nicolasi consumed on an average 482.5, 275.3 and 128.8 nymphs of 57.3, 25.5 and 20.6 days, respectively. On the basis of consumption rate per day,Deraeocoris sp. proved to be a superior predator. Part of Ph. D. Thesis submitted to Marathwada Agricultural University, Parbhani 431402, India.     

A Parameter-Elimination Method for Nonlinear Regression with Linear Parameters and Autocorrelated Errors

In this study, we are interested in the problem of estimating the parameters in a nonlinear regression model when the error terms are correlated. Throughout this work, we restrict ourselves to the special case when the error terms follow a pth order stationary autoregressive model (AR(p)). Following the idea of LAWTON and SYLVESTRE (1971) and GALLANT and GOEBEL (1976), a parameter-elimination method is proposed, which has the advantages that it is not sensitive to the initial values and convergence of the procedure may be more stable because of the reduced dimension of the problem. The parameter-elimination method is compared with the methods by GALLANT and GOEBEL (1976) and GLASBEY (1980) by Monte Carlo Simulation, and the results of applying the first two methods to the real data obtained from the Environmental Protection Administration of the Executive Yuan of the Republic of China are presented.     

Generalized Rank Transformations for Tests of Survival

The asymptotic equivalence of nonparametric tests and parametric tests based on rank-transformed data (CONOVER and IMAN , 1981) can be extended to the case of censoring. This paper presents generalized rank transformations for analyses of censored data, of interval-censored data and of survival data with uncertain causes of death. A Monte Carlo study and an analysis of leukemia remission times demonstrate excellent agreement of suggested procedures with GEHAN 'S (1965) and PRENTICE 'S (1978) tests.     

Modelling and analyzing density-dependent population processes: Comparison between wild and laboratory strains of the bean weevil,Callosobruchus chinensis (L.)

Three models were constructed for analyzing the population characteristics ofC. chinensis on stored beans; model A describing the whole reproductive process with a single equation, model B describing the three age-specific processes (oviposition, egg survival and larval survival) with separate equations, and model C which describes all these processes not for the whole habitat but for the individual beans comprizing it. The logit equation was employed here as a common basis to describe the density-response relationship involved. All three models showed very good fit to the experimental data obtained for both laboratory and wild strains of the weevil. The parameter values characterizing the population dynamics were, however, widely different between the two strains; the laboratory one which had been reared for some 500 generations showed significantly higher reproductive capacity, less sensitive and gentler response to crowding in both adult and egg stages, and more uniform egg distribution among individual beans, as compared with the wild strain newly introduced. Sensitivity analyses using these models suggested that these changes in population characteristics have been attained by the process of domestication or adaptation to stable laboratory conditions through a long period of time. This process seemed in effect to have optimized the population's performances in the laboratory environment. Evolutionary significance of such optimization was discussed with reference to the selection pressure which may have acted upon individuals.