基于最小生成树模型的树状灌溉管网的优化设计

针对灌溉管网优化中的管网布置和管径选择问题,以追求管网投资最小为目标,采用结合设计者工程经验的Kruskal算法生成符合工程要求的灌溉管网最小生成树。将管网中的线路根据节点之间的距离进行边权赋值,参与最小生成树求解,保证算法的可用性,并与相关生成树算法进行比较。实例研究表明,该方法能克服局部最优解的缺陷,能快速求解符合工程实际的树状管网布置和管径。     

Characterization of rosemary essential oil for biodegradable emulsions

The characterization of rosemary essential oil (EO) for its formulation in biodegradable emulsions has been carried out. Firstly, the required HLB (hydrophile-lipophile balance) value of the oil was determined to be 15 based on droplet size analysis and the stability of emulsions with synthetic surfactants. Moreover the emulsion resulted to be stable after 50 days of storage in ambient conditions. Secondly, four biodegradable and non-toxic surfactants derived from starch were tested. The effect of these surfactants was analyzed by measuring interfacial tension between the oil and the aqueous phase.     

Temperature‐dependent feed requirements in farmed blue mussels (Mytilus edulis L.) estimated from soft tissue growth and oxygen consumption and ammonia‐N excretion

Feed requirements were estimated from specific growth rates in standardized soft tissue dry weight (SGR_DW’) and atomic O:N ratios for mussels fed seven rations of microalgae (5–735 μg C h^?1 ind^?1) at 7 and 14°C respectively. The mean oxygen consumption and ammonia‐N excretion rates were significantly higher at 14°C (0.29 μg O² and 27.3 μg N ind^?1 h¹) compared with those at 7°C (0.16 μg O² and 11.4 μg N ind^?1 h^?1) (P < 0.05), resulting in O:N ratios between 3 and 45 at 7°C and 7 and 28 at 14°C. Low O:N ratios indicate protein catabolism and an unfavourable condition, whereas high ratios indicate that carbohydrate is the primary energy source. The measured SGR_DW’ suggests minimum feed requirements of ~240 and ~570 μg C ind^?1 h^?1 for weight maintenance at 7 and 14°C, with corresponding O:N ratios of 24 and 16, respectively, indicating a more stressed condition at 14°C. A 0.5% SGR_DW’ day^?1 was obtained by ~565 (O:N = 29) and ~680 (O:N = 23) μg C ind^?1 h^?1 at 7 and 14°C respectively. A positive and significantly higher SGR_DW’, with the lowest feed ration at 7°C compared with a negative SGR_DW’ at 14°C (P < 0.05), indicated that storage time can also possibly be prolonged at low temperatures if the mussels are not fed.     

广东省常用香草植物的应用价值及栽培

香草又称芳香植物、芳香药草,是会散发出独特香味的植物。介绍适应广东地区生长及常用香草植物种类,分析其应用价植,阐述香草植物从繁殖到田管理等方面栽培要点。     

天津市滨海新区小区园林绿化的设计构思

针对天津地区土质为盐碱性土壤这一特点,选择合理树种,合理配置,从绿化作用出发,使居住环境更好的适应现代化建筑,创造清新宜人的生活、休息场所。     

关于我国新一轮农业部重点实验室建设的思考

农业领域重点实验室是国家农业科技创新体系的重要组成部分。文章分析了我国农业领域重点实验室建设现状,阐述了新一轮农业部重点实验室建设的必要性,并就加强农业部重点实验室的运行与管理提出了应加强统筹管理,提高运行效率;加强经费支持,稳定研究方向;加强考核评估,适当动态调整;加强科研合作,实现资源共享等建议。     

RT-PCR法克隆广谱抗病基因TGA2及其蛋白表达载体构建

本试验采用Trizol Reagent提取拟南芥总RNA,设计相关引物,采用反转录PCR方法克隆TGA2转录因子;利用酶切连接方法,将该基因正向导入蛋白表达载体.经过相关检验,TGA2转录因子连接到pMXB10载体内含肽(Intein)的N端,成功构建包含TGA2转录因子的pMXB10-TGA2蛋白表达载体.     

循环农业的发展模式与关键措施——以北京市为例

以北京市为例分析了发展循环农业的必要性,在此基础上,研究了循环农业的4种基本模式,即农牧循环、农用循环、农菌循环和生态观光模式,并进一步分析了发展循环农业中的4个关键措施。     

花脸香蘑发酵物的体外抗氧化及抗肿瘤活性研究

[目的]测定花脸香蘑[Lepista sordida（Schumach.Fr.）Singer]发酵产物的体外抗氧化及抗肿瘤活性。[方法]利用不同溶剂对花脸香蘑发酵次生代谢物质进行了分级分离提取,用二苯基苦味酰基苯肼（DPPH）法检测各级分离物的抗氧化活性;用噻唑兰（MTT）法检测其体外抗肿瘤活性。[结果]固体发酵花脸香蘑乙酸乙酯相抗氧化活性最高,其次为发酵液乙酸乙酯相;花脸香蘑发酵液乙酸乙酯相抗肿瘤活性最高,对人宫颈癌细胞Hela的IC50值为50μg/ml;菌丝提取物也表现出较强的抗氧化、抗肿瘤活性。[结论]该结果为进一步研究和开发利用花脸香蘑提供了新的科学依据。     

秸秆生物反应堆技术及其在污染防治中的研究——以天津市宁河县设施农业为例

选取天津市宁河县设施农业黄瓜为示范工程,采用秸秆生物反应堆技术进行种植,同时取附近普通对照区用传统方法种植做对比试验。结果表明,示范区在CO2效应与热量效应、土壤改良、作物生长及品质改善等方面均优于对照区。经济效益、环境效益分析得出,示范区的化肥施用量节约50%以上,产量增加45%,经济收益提高39%。同时,削减农田径流面源污染负荷TN 1.07 kg/hm2、TP0.11 kg/hm2,综合效益明显优于对照区。