Toxicity of chlorine to different sizes of black tiger shrimp (Penaeus monodon) in low-salinity shrimp pond water

An experiment was conducted, in a dark room with controlled temperature (27.3–28.4 °C), to determine the acute toxicity of chlorine concentration to black tiger shrimp (Penaeus monodon fabicus) of sizes 0.02 g, 2.75 g, 8.47 g and 23.65 g. Toxicity tests on each of these shrimp sizes were run in triplicate in glass jars under static conditions without media renewal. The concentration of active chlorine that killed 50% of the shrimp of each size after 24‐h exposure (LC₅₀‐24 h) was used as an indicator of acute toxicity. Chlorine concentrations applied in the shrimp toxicity test ranged from 2.0 to 14.5 mg L^?1 in shrimp pond water. As the test water contained total suspended solids of 22.0–85.0 mg L^?1 and total ammonia nitrogen of 0.18–0.40 mg L^?1, the resultant concentrations of combined residual chlorine ranged from 0.6 to 3.5 mg L^?1, which were the effective doses causing shrimp mortality. The test results showed that 24‐h LC₅₀ for average shrimp size at 0.02, 2.75, 8.47 and 23.65 g occurred in water containing combined residual chlorine at a concentration of 0.91, 1.39, 1.74 and 1.98 mg L^?1, for which the original application doses were 6.96, 2.05 11.50 and 13.34 mg L^?1 respectively.     

The role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem

We evaluated the role of flatfishes in the organization and structure of the eastern Bering Sea ecosystem using the Ecopath/Ecosim approach. As basic input data for the Ecopath/Ecosim model, we used estimates of biomass from bottom trawl surveys and age-structured population models, production/biomass (P/B) ratio, consumption/biomass (Q/B) ratio, diet composition (DC), and fisheries harvests for each component of species or species groups. We estimated the trophic level of each component, niche overlaps among flatfishes, and the impacts of competition and predation on flatfish species in the eastern Bering Sea ecosystem. Based on those estimates, we developed the tropho-dynamic structure of the ecosystem, and the model was used to simulate ecological effects of fishery exploitation patterns. No single flatfish species appeared to have a profound and uniquely important role in the organization and structure of the ecosystem. Instead, the most important component among the guild of flatfish species appeared to be yellowfin sole Pleuronectes asper, which had greater biomass than other flatfish and a relatively diverse diet among the small flatfish species. Pacific halibut Hippoglossus stenolepis, Greenland turbot Reinhardtius hippoglossoides, and arrowtooth flounder Atheresthes stomias were important keystone predators in the eastern Bering Sea ecosystem together with some groups of marine mammals and sea birds. Intra flatfish complex cannibalism was not observed, however, substantial diet overlaps were common in the flatfish guild system.     

文蛤染色体核型及三倍体诱导的初步研究

文蛤染色体核型及三倍体诱导的初步研究ＡＰＲＥＬＩＭＩＮＡＲＹＳＴＵＤＹＯＮＴＨＥＫＡＲＹＯＴＹＰＥＡＮＤＴＲＩＰＬＯＩＤＩＮＤＵＣＴＩＯＮＩＮＭＥＲＥＴＲＩＸＭＥＲＥＴＲＩＸ常建波魏利平杨建敏宫向红孙逢贤（山东省海洋水产研究所，烟台２６４０００）Ｃｈ...     

高压旋芯喷嘴的雾化特性

对直射式喷嘴进行加旋芯改进,改进后喷嘴的喷雾情况符合不稳定性理论规律。利用三维激光多普勒粒子测速仪（3D—PDPA）,测量了单相流细水雾喷嘴在1m处截面的雾化特性参数;研究了喷嘴直径和喷射压力对雾化特性的影响。试验结果表明,喷雾压力大于2MPa后,1m处截面的喷雾锥角、雾滴索太尔平均直径（SMD）和轴向速度的变化不大。所测试的系列喷嘴的最佳压力范围为7～8MPa;所形成的细水雾雾滴SMD均小于100μm,属于超细水雾范畴。     

装载机发动机与液力变矩器功率匹配优化

装载机发动机与液力变矩器之间的匹配对各自性能的发挥及整机牵引特性均有重要的影响。在拟合装载机发动机与液力变矩器有关特性曲线的基础上,以装载机的动力性为目标,建立发动机与液力变矩器匹配的优化模型,优化装载机发动机与液力变矩器的功率匹配,给出了算例并分析了优化结果。     

基于高通量测序技术挖掘分子遗传标记及其在蛋鸡生产中的精准应用

高通量测序技术是研究物种复杂生物性状遗传机制的基础,随着高通量测序技术的不断优化提升,一些与生物表型性状密切相关的基因组变异被精准地挖掘出来,其中包括单核苷酸多态位点(SNP)、小片段的插入或缺失(Indel)、拷贝数变异(CNV)以及结构变异(SV)为代表的分子标记。与传统遗传标记相比较,分子遗传标记具有多态性高、遍布整个基因组、检测手段简单快捷以及成本低廉的特点。通过检测覆盖全基因组范围内的分子标记,利用基因组水平的遗传信息对个体或群体遗传资源进行评估,能够缩短世代间隔、提高选种的准确性,进而在短期内取得较大的遗传进展。作者从高通量测序技术挖掘分子遗传标记角度入手,综述了三代测序技术发展历程和应用领域以及三代分子遗传标记检测技术在蛋鸡种业创新中的应用,并详细阐述了高通量测序技术与分子遗传标记相结合在蛋鸡群体遗传多样性及进化分类、群体遗传图谱的构建和功能基因定位、数量性状形成的遗传机制解析和质量性状形成的遗传机制解析等4个方面的精准应用,以期为蛋鸡基因组选择进入实质应用阶段提供科学依据和指导。     

不同施肥量对旱作沟垄集雨种植农田土壤水分及玉米产量的影响

[目的]沟垄集雨种植是西北旱作农田广泛运用的高效节水栽培模式.研究不同施肥处理对旱作沟垄集雨种植农田土壤水分及玉米产量的影响,为优化施肥配置,进一步提升其增产效能提供科学依据.[方法]以玉米为供试作物,在宁夏回族自治区固原市进行了连续5年的田间定位施肥试验.试验玉米栽培采用集雨沟垄栽培技术,设置4个施肥水平处理:无肥对...     

基于离子液体与超声波辅助提取普洱茶茶多酚的工艺优化

本试验利用新型绿色环保溶剂离子液体(1-丁基-3-甲基咪唑溴盐,[BMIM]Br)为提取溶剂,采用超声波辅助提取普洱茶中茶多酚.在以[BMIM]Br浓度、提取时间、提取率及料液比为单因素的试验基础上,进行响应面法优化普洱茶茶多酚的提取工艺.确定最佳提取工艺为:[BMIM]Br浓度0.3 mol/L,料液比1:30,提取...     

我国农村生活污水治理的现状分析和对策探究

随着我国“乡村振兴”“厕所革命”等国家战略的实施,我国农村生活污水的治理也越来越受到重视,但是农村生活污水不同于城市生活污水,它的治理在标准、模式、技术、运维等方面存在诸多问题。本文详细介绍了我国农村污水治理现状,针对全国不同地区农村生活污水处理工艺和典型案例,从处理技术、排放标准以及运维管理等方面进行了系统分析,重点论述了处理技术的优缺点,并结合农村自然的自净能力和面源污染的根本原因,提出了建立排放标准的合理前提,同时也介绍了智慧运维在农村生活污水处理中的积极作用。另外,根据农村居住分散、地势差异大的特点,强调了分散式处理的重要性,旨在从根本上解决农村生活污水收集难、处理复杂的难题,以生态处理模式实现美丽乡村建设。     

四川盆地丘陵区土壤水分垂直变异特征研究

根据四川盆地丘陵区重庆市璧山县青杠墒情站点土壤水分每天的动态监测资料,用小波分析的谱相分析方法研究了土壤水分的垂直异质性。结果表明:土壤水分变化是个随机平稳的波动序列;就时间变异来看,其变异有一定的隐周期,大致可分为3~5月的次波动期、7~9月的剧烈波动期、10~2月的相对稳定期。就土壤的垂向变化来看,站点的0~10 cm的变异高于10~20、20~40 cm层变异;各层变异之间存在一定的因果关系,可用互谱密度系数表示,但受降水、蒸发、作物利用等多种因素的制约,并未表现出完全的同步响应关系。