Comparative growth and diet of tench Tinca tinca (L.) larvae and juveniles from river floodplain biotopes in France and England

The growth and diet of larvae and 0 + juveniles of riverine tench Tinca tinca (L.) were compared in two stagnant floodplain biotopes from the upper River Rhône, France, and the River Great Ouse, England. The diet of tench was generally similar at the French and English sites, with Cladocera being the predominant prey of young larvae (English site only). Cladocera and Copepoda were the principal prey of older larvae and 0 + juveniles, though the latter took a variety of other, larger prey items. Ontogenetic changes in diet at both sites probably reflect prey availability. Protracted spawning at the French site contrasted a single spawning effort in the English backwater. Fluctuations in growth rate and condition were observed to coincide with shifts in diet, suggesting that tench developing in riverine biotopes may be vulnerable to competition at particular transitional intervals in their early ontogeny.     

缺省值问题中一种新的比较补充方法的方法

讨论了当缺省值问题中有多种补充方法时,从补充完整样本的损失的角度,并引进了统计决策理论来比较这些补充方法.当补充风险r(X ,X)=∫∫f(X (x)-x)dPXmisθxmis)dPθ(xobs)在决策空间是最小时,相应的补充方法就是容许决策法则.     

半线性抛物方程时间离散间断伽辽金方法的误差估计

本文讨论一类半线性方程间断伽辽金方法的时间离散格式，对ｑ＝０给出了先验误差估计，并将结果应用于一个抛物变分不等式。     

用多项式辅助估计动物的生长模型参数

本文尝试用多基工辅助估计生物学基础模型参数，并根据辅助对象划分为辅助微分模型和直接辅助参数估计法，拟合试验表明，辅助拟合法简便易懂，拟合精度高，尤其是直接辅助参数估计法的拟合效果接近Ｍａｒｑｕａｒｄｔ法。     

泵装置最佳转速理论探讨

根据泵装置运行特性,采用系统工程方法探讨其效率与转速之间的关系,建立了确定最佳转速的数学模型,并给出了具体的算例。     

火三含蜡原油管道初凝现象分析

通过对火三含蜡原油管道初凝现象以及对其处理过程中的运行参数进行分析，认为连续运行的管道，其下游的进站温度应控制在输送介质的凝点＋3℃温度以上；间歇运行的管道，末站进站温度应达到安全停输时间的要求，以保证管道在冬季安全运行。对于含蜡原油管道的初凝现象象，三个过程主导着压力，排量的变化和管道恢复正常的速度，第一是管内空隙的充装过程，第二是使末段部分温原油屈服的过程，第三是冲刷，剥落管壁凝油层，恢复管道正常排量的过程。     

热水加温处理病死木防治松材线虫、媒介昆虫效果的研究

松材线虫(Bursaphelenchus xylophilus)病在我国江苏南京、镇江、安徽马鞍山、和县和广东深圳等地普遍发生。江苏发生的面积达30余万亩,被害树种有黑松(Pinus thunbergii)、马尾松(P.massoniana)、湿地松(P.elliottii)、海岸松(P.pinaster)、黄松(P.thunbergiixp.massoniana)、千头赤松(P.densifloraxp.umbraculifera)、白皮松     

Observations on the natural history of the Gulf of Mexico sturgeon (Acipenser oxyrinchus de sotoi Vladykov 1955) in the Suwannee River, southeastern United States

From 1986 to 1994, we collected 3,098 Gulf of Mexico sturgeon (Acipenser oxyrinchus de sotoi) during their spring migration from the Gulf of Mexico to the Suwannee River, Florida. We estimated population size and described migratory and seasonal growth patterns of sturgeon in the Suwannee River, using data from tag returns, movement of ultrasonic-lagged fish and weight records. Population size estimates for 3.0- to 81.0-kg Gulf of Mexico sturgeon in the Suwannee River ranged from 1,504 to 3,066 fish. Sturgeon migrated from the Gulf of Mexico into the Suwannee River from mid-February to early May. Fish moved upstream and remained within a 2-km upstreamdownstream “home” area. These sites were closely associated with undenvater springs that discharge into the river. Sturgeon migrated downstream and into the Gulf of Mexico in October and November. In the Gulf of Mexico, ultrasonic-tagged fish were located in the Suwannee Sound area just north of Cedar Key, Florida. On an annual basis, fish gained an average of 20% of their body weight while in the Gulf of Mexico and lost about 12% of their weight during their stay in the Suwannee River. We observed movement of tagged sturgeon between the Suwannee and Apalachicola Rivers.     

一类三种群第Ⅲ类功能性反应系统的稳定性

本文对一类三种群第Ⅲ类功能性反应系统(1)进行了稳定性分析,研究了各平衡点的局部稳定性,讨论了该系统在 R_3~+={(x_1,x_2,x_3,)I_(x_i)>o~(i=1,2,3)} 中的一切解的有界性,利用 Liapurov 函数方法,得出了平衡点 E_4的全局渐近稳定性的充分条件,并阐明了其生态意义.     

Involvement of a sodium channel mutation in pyrethroid resistance in Cydia pomonella L, and development of a diagnostic test

Populations of the codling moth, Cydia pomonella L (Lepidoptera, Tortricidae) have developed resistance to several classes of insecticide such as benzoylureas, juvenile hormone analogues, ecdysone agonists and pyrethroids, but the corresponding resistance mechanisms have not been extensively studied. Knockdown resistance (kdr) to pyrethroid insecticides has been associated with point mutations in the para sodium channel gene in a great variety of insect pest species. We have studied two susceptible strains (S and Sv) and two resistant strains (Rt and Rv) of C pomonella that exhibited 4- and 80-fold resistance ratios to deltamethrin, respectively. The region of the voltage-dependent sodium channel gene which includes the position where kdr and super-kdr mutations have been found in Musca domestica L was amplified. The kdr mutation, a leucine-to-phenylalanine replacement at position 1014, was found only in the Rv strain. In contrast, the super-kdr mutation, a methionine-to-threonine replacement at position 918, was not detected in any C pomonella strain. These data allowed us to develop a PCR-based diagnostic test (PASA) to monitor the frequency of the kdr mutation in natural populations of C pomonella in order to define appropriate insecticide treatments in orchards.