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The aquaculture industry of small abalone Haliotis diversicolor in southern China is now close to collapse because of high mortality at the grow-out stage. To examine if survival and growth (shell length increase) could be improved by cross breeding among populations, a 3 × 3 complete diallel cross was conducted among three populations from Japan (A), Taiwan (B) and Vietnam (C). Performances in growth rate and survival at early juvenile, later juvenile and grow-out stages were compared among the six reciprocal cross lines and three parental lines. Magnitude of heterosis for survival and growth varied among cross lines in the three growing stages. As to mid-parent heterosis, H AB was significantly ( P <0.01) higher than H AC and H BC at all three growing stages for both growth and survival, and all mid-parent heterosis fell between the two corresponding single-parent heterosis. H AB was 6.84% for shell length and 69.09% for survival at Day 420. Our results of high survival heterosis in line AB and line BA show that crossbreeding between different populations can benefit the small abalone breeding programs and the industry.  相似文献   
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Epiploic foramen entrapment (EFE) is one of the most common causes of small intestinal strangulation in horses. Cribbing and previous episodes of colic are suggested as risk factors for its occurrence. The aim of this study was to correlate the height, weight, breed, gender and age to the epiploic foramen (EF) length. Forty-three horses were submitted to post-mortem measurement of epiploic foramen with abdominal and thoracic organs positioned in situ. After data collection, linear regression between EF length and the explanatory variables was performed. None of the post-mortem physical variables was associated with EF length, supporting the hypothesis that there is no association between EF length and age, and that increased intra-abdominal pressure is the most important factor predisposing to EFE recurrence.  相似文献   
4.
活塞与活塞环是柴油机中工作强度最大的组件之一,对柴油机的性能、使用寿命和工作可靠性等指标都有极大影响。通过BH160F小型柴油机活塞材料的选用及对压缩高度、火力岸布置、活塞顶部形状和活塞环匹配等方面进行改进设计,使柴油机获得了良好性能指标。  相似文献   
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ABSTRACT

The research has been conducted for four years in five phytocenoses affected by the processes of naturalization. Two of them are located in non-flooded, relatively abandoned meadows and the remaining - flooded meadows in different parts of the Nemunas delta (Western Lithuania). The aim of the research was to estimate the influence of ecological conditions (humidity regimes, soil agrochemical parameters) on semi-natural meadow productivity. Humidity regimes and nitrogen amount in the soil influenced dry matter (DM) yield of meadow phytocesosis. The biggest DM yield (8.64 ± 0.77 t ha-1) was found in flooded meadow in the central part of the Nemunas delta in Terric Histosol (HSs) soil, which had moderate acidity and was rich in nitrogen. The economic value depended on the prevailing plant species and was the highest in non-flooded meadows. Botanical composition and plant species number depended on agrochemical characteristics of the soil and management activities: the greatest plant species diversity and the best plant population stability were established in flooded meadow in the riverside part of the Nemunas delta behind a levee in soil rich in phosphorus and potassium and low acidity. A similar number of plant species and similar ecological stability parameters were found in non-flooded meadow, whose soil was low in nutrients, but there was intensified farming.  相似文献   
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The ecological engineering of rivers has been emphasized in recent years; however, scant attention has been focused on the ecological environments of paddy fields and irrigation canals. In this study, a paddy field in Yuanli Township, Miaoli County, Taiwan, was used as a test field. We improved the ecological corridor, ensuring the continuity of the irrigation canal and paddy field, thereby enabling a constant flow of water in the longitudinal section of the paddy field corridor to facilitate smooth upstream migration of fish. Fish could also migrate upstream in the lateral section of the paddy field. Subsequently, loach were used to assess the effect of an enhanced rock pile in a pool area of the simplified paddy fishway, and fish were allowed to migrate up and down the paddy field and irrigation canal. The results indicated that the difference in water levels (i.e. a bottleneck for creating an ecological corridor) was enhanced by the simplified paddy‐field fishway and enhanced rock pile. In addition, removing bottlenecks along the ecological corridor enabled fish and shrimp to migrate in the longitudinal and lateral directions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
7.
建设廉洁政治是马克思主义政党的本质要求,也是关系到党和国家生死存亡的重大问题。建设廉洁政治要深化机制改革和制度创新;进一步加强反腐倡廉建设;提高廉政制度建设的科学化水平;尽快完善并运行社会廉政评价机制;加强廉政文化建设。  相似文献   
8.
    
Forests are dynamic ecosystems, spatial mosaics of localized disturbances and regenerating vegetation. Following forest conversion to human land uses, expanding forest cover follows four different modes of reforestation: (a) spontaneous natural regeneration; (b) assisted natural regeneration; (c) agroforestry; and (d) commercial tree plantations. Natural regeneration fundamentally depends on the alignment of ecological and social factors at landscape scales. A deeper socioecological understanding of reforestation in the tropics will lead to the development of effective policies and governance structures that enhance forest cover and ecosystem services, protect biodiversity, and improve forest-dependent livelihoods.  相似文献   
9.
矿山竖井勘察是一项十分复杂的工程地质勘察,其中地质构造、围岩质量等级、地下水富水性是勘察的重要内容,在勘察时应抓住关键问题进行合理布置工作,准确的分析、计算和评价。  相似文献   
10.
中原崛起与绿色中原建设   总被引:3,自引:0,他引:3  
中原崛起对于中部地区崛起、全国区域经济协调发展具有全局意义。实现中原崛起,全面建设小康社会,必须全面贯彻落实科学发展观,加快环境友好型社会建设,发展林业,推进绿色中原建设。针对中原崛起中的生态环境问题,根据河南省经济发展态势、资源禀赋条件、林地利用状况,研究提出了绿色中原建设的目标任务、资源配置和保障措施。  相似文献   
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