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221.
海筒螅中3种化学成分的分离鉴定 总被引:2,自引:0,他引:2
海筒螅(Tubuaria marina)的94%乙醇提取物,在水中混悬后,用石油醚萃取,石油醚相中的提取物经反复硅胶柱色谱分离和SephadexLH-20凝胶柱色谱分离,得到三个纯净的化合物。经^1HNMR,^13CNMR和DEPT谱鉴定,分别确定为二十一碳一烯,胆甾-5-烯-3β-醇和1-壬基-甘油醚。 相似文献
222.
The food consumption and ecological conversion efficiency of a species marine pelagic andsmall size fish, Hyporhamphus sajori, were determined by using in situ stomach content method presented by Eggers. The results showed that: (1) the fish was taken in food all day, so empty-stomach rate was very low, taking up about 4.5% of the total determined fish number. However, the fish still has significant daily feeding rhythm. A feeding peak was found 0:00 o'clock at night, but feeding level was always high in the daytime; (2) relationship between instantaneous food content in stomach and corresponding time could be described as S_t = a ·e ~(-b ·t). There was not significant difference of instantaneous gastric evacuation rate between two determinations, with average value being 0.13 × 10~(-2)g/ (g·d) (wet weight); (3) the daily food consumption tended to change in irregular waving form, with average value being (10.16×l0~(-2)±1.19×l0~(-2) g/ (g·d) (wet weight) or (55.56 × 10~(-2) ±6.51 × 10~(-2) kJ/ 相似文献
223.
渤海小型底栖生物的丰度和生物量 总被引:9,自引:1,他引:9
该文是渤海 1997年 6月、1998年 9月和 1999年 4月 3个航次小型底栖生物调查结果。结果表明 ,3个航次小型底栖生物的平均丰度分别为 :(2 30 0± 12 0 6 ) ind/ (10 cm2 )、(86 9± 5 10 ) ind/(10 cm2 )和 (6 32± 4 0 0 ) ind/ (10 cm2 )。平均生物量分别为 :(15 2 1± 6 34) μg(dwt) / (10 cm2 )、(72 5±35 4 )μg (dwt) / (10 cm2 )和 (5 17± 393)μg (dwt) / (10 cm2 )。共鉴定出 14个小型底栖生物类群 ,其中自由生活海洋线虫丰度占绝对优势 ,桡足类丰度居第 2位 ,这两个类群总和占小型底栖生物总丰度的 94 .8%~ 97.5 %。在生物量中所占比例列前 4位的类群依次为线虫、多毛类、桡足类、双壳类 ,加起来超过小型底栖生物总生物量的 80 %。小型底栖生物的 74 %分布于 2 cm以浅表层中。小型底栖生物的丰度和生物量在渤海海峡和渤海中东部较高 ,与环境因子的相关分析表明小型底栖生物的丰度与水深呈极显著的正相关 ,与沉积物的中值粒径呈显著的负相关 相似文献
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226.
I\rnooUcrIoxThe drpdric fish species cor-npositlon is an imPOrtant element 1n the study of fish ecologyand plays an important guiding role ln fishery preduction and roouLrces rnanagement. Lin(l988) and Zhang (1994 and l995) have studied the simi1drities of mpulation COtwsition ofame s1ngle species of different yea-rs including hairtail Trichuras haumee and yellDw cndertwinena cmi. But no rePOrt is available on the discridrination of the sidrildrities amongmuLlt1ple sPecies composition of… 相似文献
227.
AbstractBased on hydrological data obtained during the 7th to 9th Chinese National Arctic Research Expeditions in the summers of 2016–2018, the main water structure on the shelf of the northern Bering Sea and the volume and heat fluxes of the Bering Strait throughflow were analyzed. Distinct variability was identified in the three Pacific water masses feeding the strait - Anadyr Water (AW), Bering Shelf Water (BSW) and Alaskan coastal water (ACW). Overall, the temperature and salinity of the entire section increased each year, with 2018 showing significant anomalies, i.e., a temperature anomaly of up to 1?°C and a maximum salinity anomaly of 2. From 2016 to 2018, the extent of the ACW gradually narrowed in the eastern part of this section, while the AW expanded eastward each year. The net volume transport through each of the three sections increased poleward from 1.65?Sv to 2.76?Sv, with the AW increasing from 0?Sv to 1.03?Sv, the BSW varying between 0.52–1.65?Sv, and the ACW gradually decreasing from 1.04?Sv to disappearing completely. The net heat fluxes were also poleward, varying between 25.77 TW and 61.50 TW, and showing a significant increase. Significant variations in magnitude and extent were observed in each water mass of the Bering Strait throughflow, which could produce widespread effects in the Arctic Ocean and the global ocean beyond. 相似文献
228.
科考船定点作业时会受到海洋风、涌、浪、流等外界环境因素影响,导致工作效率降低,原位测量精度下降,甚至影响作业安全。动力定位系统 (DP) 具有自动定位功能,能够抵抗外界环境因素的影响,可实现科考船高精度定点控位。
单波束测深仪不仅可以测量水深,也可反映水下设备深度信息,可以起到辅助监控水下设备功能。本文在介绍定点作业施工现状与局限性的基础上,分析 DP 系统与单波束测深仪工作原理,以“向阳红 01”船为载体,在定点作业时开启 DP 系统与单波束测深仪,发现该方法可以提高科考船定点作业工作效率、原位测量精度并保障作业安全,可为其他科考船定点作业提供参考。 相似文献
229.
Tang Rongqing Wang Daoyan Zhang Xixian Egnineer Shanghai Jiao Tong University Shanghai Associate Professor Shanghai Jiao University Shanghai 《中国海洋工程》1993,(3)
- The authors have used a low-cost ROV of observation type for underice surveying of the Nen-Jiang Cross-river oil pipe line in the Da Qing oil field. The operation method, process and the safety measures for severe cold areas are presented. The fruitful tries and experience may be useful to ROV operators in severe cold areas. 相似文献
230.
Zhang Changkuan Wang Zhen Zhang Dongsheng
Associate Professor Dept. of Navigation Ocean Engineering Hohai University Nanjing
Lecturer Dept. of Navigation Ocean Engineering Hohai University Nanjing
Professor Dept. of Navigation Ocean Engineering Hohai University Nanjing 《中国海洋工程》1995,(2)
A numerical model of shoreline change of sand beaches based on long-term field wave data is proposed, the explicit and implicit finite difference forms of the model are described, and an application of the model is presented. Results of the application indicate that the model is sensitive to the order of the input wave data, and that the effects of long-term wave series and the effects of the mean annual wave conditions on the model are different. Instead of a single wave condition, the wave series will make the calibration and the verification of the model more practical and the results of the model more reasonable. 相似文献