Masculinization under combined administration of an androgen and an aromatase inhibitor in the Ussuri catfish,Pelteobagrus ussuriensis (Dybowski, 1872)

In this study, we used the central composite experimental design and response surface methodology to investigate the masculinization as well as larval growth, survival under combined administration of an androgen (17α‐methyltestosterone, MT) and an aromatase inhibitor (letrozole, AI) in the Ussuri catfish, Pelteobagrus ussuriensis. The results showed that the masculinization was significantly promoted by MT and AI. The nonsignificant MT × AI interaction indicated that MT acted on masculinization independently of AI and vice versa, suggesting that they may function through different molecular pathways. The impact of MT was greater than that of AI, indicating that masculinization via the direct action of MT was more important than that of AI during masculinization. The optimal MT/AI dosage was obtained by simultaneously optimizing three reliable models in consideration of the growth and survival. A verification trial under the commercial setting showed that this optimal MT/AI combination had greater potential for application to culture production, albeit not complete sex reversal. Our results suggest that using a combined administration of MT and AI to masculinize the Ussuri catfish be preferred.     

Optimum arginine requirement of juvenile black sea bream,Sparus macrocephalus

An 8‐week feeding trial was conducted to determine the dietary arginine requirement of juvenile black sea bream Sparus macrocephalus in 18 350 L indoors flow‐through circular fibreglass tanks. Six isonitrogenous and isoenergetic diets were formulated to contain graded levels of l ‐arginine (1.85%, 2.23%, 2.51%, 2.86%, 3.20% and 3.46% dry diet) from dietary ingredients and crystalline arginine. Each diet was randomly assigned to triplicate groups of 25 juvenile fish (10.51±0.15 g) twice daily (08:00 and 16:00 hours) to apparent satiation. Results showed that the specific growth rate (SGR) increased with increasing dietary arginine levels up to 2.51% and remained nearly the same thereafter. Feed efficiency ratio, protein efficiency ratio (PER) and protein productive value all showed an increasing tendency and then levelled off. Apparent digestibility coefficients of dry matter, crude protein and gross energy significantly improved up to 2.86% arginine diet and decreased at different extents thereafter. Fish fed 1.85% arginine diet had significantly lower protein content in the whole body and dorsal muscle than those fed diets supplemented with or >2.86% of arginine. Lipid content decreased and lower value occurred at 3.46% of dietary arginine. The dietary essential amino acid composition in the whole body of the black sea bream was significantly influenced by dietary arginine. Arginine retention increased with an increasing dietary arginine level from 1.85% to 3.20%, then declined slightly at 3.46% arginine diet. Serum biochemical parameters were significantly affected by the dietary arginine level except for the cholesterol content. Broken‐line regression based on SGR and second‐order polynomial regression based on PER indicated that the optimum dietary arginine requirements for juvenile black sea bream were 2.79% and 3.09% diet, corresponding to 7.74% and 8.13% of the dietary protein respectively.     

一类四阶两点边值问题解的存在性

应用Leray Schauder原理,研究四阶两点边值问题{u(4)(t)=f(t,u(t),u"(t)),t∈(0,1) u'(0)=u'(1)=u"'(0)=u"'(1)=0 解的存在性,在两参数非共振条件以及非线性项f满足至多线性增长性条件下给出了此类问题有解存在的最优充分条件,最后举例说明了所获结果.     

狗牙根ISSR-PCR反应体系的优化

利用正交设计试验,对影响ISSR-PCR的Mg~(2+)、dNTPs、引物、Taq DNA聚合酶和模板DNA 5个因素进行优化试验.结果表明:25μL ISSR-PCR反应体系中各因素的最佳条件为Mg~(2+)2.5 mmol/L、dNTPs 0.25 mmol/L、引物0.2μmol/L、Taq DNA聚合酶1.0 U,模板DNA 40 ng.通过对狗牙根ISSR-PCR最佳反应体系进行梯度退火试验,得到引物UBC881的最佳退火温度为50.5℃.该体系在24个狗牙根种质中获得较好的扩增结果,该优化体系为今后利用ISSR技术进行狗牙根属种质资源的遗传多样性分析奠定了技术基础.     

施肥对连作蔬菜地蔬菜产量和土壤氮素含量的影响

为了研究施肥对连作蔬菜地蔬菜产量、肥料效应以及土壤养分铵态氮与硝态氮含量的影响,笔者等人进行了连续四茬蔬菜的田间试验。结果表明,在试验设计范围内,随着施氮量的增加,四茬蔬菜鲜样可食部分产量随着施氮量的增加而增加,芹菜的最佳施氮量为537.4kg/hm2,白菜的最佳施氮量为473.88kg/hm2。同时,与对照相比,用于每茬蔬菜生长所施用的肥料明显增加了土壤中铵态氮含量,且随着施用量的增加而显著增加。土壤硝态氮含量随施肥量的增加而增加,随蔬菜种植时间的延长而上升。试验同时表明,经过了四茬蔬菜收获后,土壤剖面硝态氮含量已经发生了变化,除了未施肥对照区的土壤剖面硝态氮含量下降外,其余施肥处理土壤剖面硝态氮含量均呈上升趋势。研究结果给连作蔬菜地的合理施肥提供了参考依据。     

考虑大陆引水的海岛地区复杂水工程群多目标优化配置研究

考虑海岛地区大陆引水的必要性以及水工程群组合运行以完成供水过程的复杂性,提出一种新的适用于海岛地区的水资源优化配置方法.基于"分区-分级"的优化配置理念,分析海岛地区复杂系统下水力联系并进行系统概化,完成"分区",结合水厂特性进行"分级";在多水源多用户下以水厂供水保证率最大、供水成本和水厂余蓄量最小为目标函数构建优化...     

沈阳市浑北灌区水资源实时预报优化调度的研究

采用实时预报方法对沈阳浑北灌区水资源的优化调度进行了研究,实时预报优化调度以系统分析理论为基础,以短期天气预报较高可信度为前提,根据运行费用和缺水造成的减产损失之和为最小的原则建立目标函数。以灌水过程中的实际情况作为约束条件,用Ｃ语言编制了以线性规划中的单纯形法为主的实时优化调度程度。这种预报方法可以克服常规灌溉方法的一些缺点,达到充分利用降雨,节约灌溉水资源的效果。     

Grey Optimal Options of Design Plans for Deep Cutting Slope

The selection of the design plans for deep cutting slope of high-level highway in mountain area,in general speaking,only depends on the designer's experience and intuitive determination at the present time,which results in unreasonable,even error,decision or plan.It unavoidably causes enormous damage.This paper proposes to adopt correlation degree analysis method of grey system theory for choosing the optimal design plan.It will give a definite and real meaning about choosing design plan and avoiding or reducing errors in design work.     

喷灌系统田间管网的优化设计及其投资比较

本文通过多种田间管网的布置形式方案的比较,研究和探讨了适合湛江市区情的喷灌方式。