不同安放角度对污水搅拌器水力特性的影响

为深入对比污水处理池中搅拌器不同安放角度对其水力特性的影响,文中基于Fluent对搅拌器在不同安放角度下的水力特性进行数值模拟,得出适合搅拌器工作的较优工况.利用标准k-ε湍流模型及 SIMPLEC 算法对不同工况进行模拟,对比相应的流速分布和搅拌器中心所在平面的速度分量.结果表明:当搅拌器安放角度为-15°时,处理池内平均流速较高该工况下处理池内平均流速较高且搅拌器消耗的功率较小.通过分析搅拌器安放位置中心横断面的速度分量发现,经过搅拌器的水体呈现螺旋状向流向方向发展;在直角坐标系中3个方向速度分量各不相同.在搅拌器安放角度为-15°时,水体流速在轴y,z分量较大且不与墙体冲突.因此,在实际应用中适当改变搅拌器的安放角度,可以有效改善水体循环流动,优化搅拌器的搅拌效果,研究结果可为潜水搅拌器的实际工程提供参考.     

影响负压反馈射流喷头水力性能的重要参数正交试验

为了探究影响负压反馈射流喷头水力性能的重要参数对水力性能的影响程度,并选出综合水力性能最优下的重要参数组合,首先设计了4因素3水平正交试验,并根据试验要求分别加工出3种长度(4.2,5.6,7.0 cm)的喷管、3种直径(3,4,5 mm)的喷嘴,以及射流进口宽×深为4 mm×8 mm、位差1.80 mm、侧壁夹角20°、劈距28.0 mm、3种喷射仰角(20°,30°,40°)的射流机构,用于水力性能测试.采用综合评分法和极差分析法对正交试验结果进行处理,并引入了射程和喷灌均匀系数对试验结果进行评价.结果表明:影响喷头综合水力性能的重要参数,影响程度由大到小依次为喷射仰角、主副喷嘴直径、工作压力、主副喷管长度.得到了在此射流机构下的最优重要参数组合为工作压力0.35 MPa、主×副喷嘴直径5 mm×4 mm、喷射仰角30°、主×副喷管长度4.2 cm×4.2 cm.试验结果可为该型国产喷头的产品化和未来工程应用提供理论数据支撑.     

高效节能水锤泵技术研究进展

为了厘清水锤泵的技术发展动态和目前的技术应用现状,文中回顾了水锤泵技术发展历史,并简要介绍了水锤泵的基本结构,在此基础上,阐述了水锤泵的效率计算方法,并对水锤泵的理论设计方法发展进行了梳理.随后对水锤泵的国内外研发现状进行了大致概括,提出了中国水锤泵发展受限的根本原因,并指出简化制造和装配工艺、发展大型化水锤泵制造技术以及研发轻型化和分体式水锤泵是未来发展的重点.接着总结出水锤泵系统参数和结构参数是影响水锤泵的主要因素.最后对国内外水锤泵的实际应用现状进行了对比分析,提出发展应用水锤泵应在考虑泄水阀和输水阀动态启闭过程的水锤泵运行全过程理论模型的基础上发展适用于不同群体或目标的水锤泵制造技术.研究成果对扩大水锤泵的应用范围,提升中国水锤泵的制造技术提供了一定的参考.     

草鱼呼肠孤病毒VP6蛋白在毕赤酵母中表达的初步研究

根据GeneBank中草鱼呼肠孤病毒(grass carp reovirus,GCRV)104株VP6蛋白的全基因序列(HM234682)设计一对特异引物,以提取的GCRV-104核酸为模板,采用RT-PCR技术扩增VP6蛋白编码基因,并将其克隆到含强启动子AOXⅠ的毕赤酵母(Pichia pastoris)表达载体pPICZB上。重组酵母质粒pPICZB-VP6经SacⅠ线性化,电击转化到毕赤酵母KM71菌株中,Zeocin抗性平板上筛选高拷贝转化子。阳性转化子在30℃,0.5%(V/V)的甲醇添加量的条件下,连续诱导3 d,表达产物经SDS-PAGE和Western-Blotting检测,结果表明成功实现了GCRV-104 VP6蛋白在毕赤酵母中的胞内表达,重组VP6蛋白相对分子质量约46 000,与天然VP6蛋白相对分子质量接近,并且可与鼠抗草鱼GCRV-104 VP6蛋白的多克隆抗体特异性结合。     

异精雌核发育草鱼F1与普通草鱼的SCAR标记鉴别初报

以赤眼鳟生理失活精子诱导的雌核发育草鱼F1群体(CC)和与之母本同源的普通草鱼群体(PC)为材料,采用RAPD和SCAR分子标记相结合的技术,在100条RAPD随机引物扩增的16条有效引物中扩增筛选出7条群体差异条带,其中1条为异精雌核发育草鱼群体中特有,其余均表现为异精雌核发育草鱼群体缺失;对7条RAPD特异条带的回收中仅得到S32和S336的特异条带。经回收、克隆、测序后根据序列信息设计了4对SCAR引物,其中S336的2对SCAR引物在两群体间扩增出的条带一致,特异性消失;S32的2对SCAR引物能扩增出两群体间的特异条带;对S32-Scar1F/S32-Scar1R扩增出的SCAR标记S321643进行大样本检测结果表明:该标记在异精雌核发育草鱼群体中的出现频率为0(0/55),在普通草鱼群体中出现频率为76.7%(46/60)。     

Effects of lysine and methionine supplementation on growth,body composition and digestive function of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal

A 76‐day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal (CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal (FM) diet was formulated as the normal control with 40 g kg^?1 FM and 300 g kg^?1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg^?1) without Lys or Met supplementation; CM supplement (CMS) diet was similar to CM diet but was supplemented with essential amino acids (EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar (P > 0.05), but higher than those of the grass carp fed CM diet (P < 0.05). The hepatosomatic index, relative gut length, intestosomatic index and intestinal folds height were significantly improved in fish fed FM and CMS diets as compared to CM diet (P < 0.05). Lower activities of trypsin, lipase and amylase in hepatopancreas were observed in fish fed CM diet (P < 0.05). Three hundred and forty gram per kilogram CM without Lys or Met supplementation significantly decreased trypsin, lipase and amylase mRNA levels in hepatopancreas (P < 0.05). These results indicated that the high supply of CM (340 g kg^?1) in plant protein (200 g kg^?1 soybean meal and 100 g kg^?1 cottonseed meal) diets decreased digestive ability through decreasing digestive enzyme activities and enzyme gene's expressions of grass carp, and these side effects can be reversed by supplementing Lys and Met. Therefore, CM could be high level used in a plant protein blend‐based extruded diet for grass carp as long as EAA were supplemented.     

草鱼出血病的电镜观察

草鱼出血病是由呼肠孤病毒感染所致的急性传染病，由于病鱼小血管受损引起全身性出血，并造成内脏器官和体壁肌肉组织局灶性病变。电镜观察表明病变细胞内各种细胞器的数量较正常细胞显著减少，形态结构也遭损坏。质膜的三层结构模糊不清，及至解体消失。与机体代谢密切相关的粗面内质网、滑面内质网、线粒体和高尔基复合体的数量减少及结构受损，使蛋白质、糖类和脂质合成及分解等一系列细胞代谢活动不能正常进行，加速了病鱼死亡。     

不同饲料原料对草鱼生长和肌肉品质的影响

分别以专用配合饲料、浸泡蚕豆、浸泡豌豆喂养体质量为(1540.9±57.5)g的草鱼(Cteno-pharyngodon idellus)90d,以考察不同原料对草鱼生长和肌肉品质的影响。结果表明,配合饲料组、浸泡蚕豆组和浸泡豌豆组草鱼的增重率分别为17.3%、13.7%和12.2%,饵料系数分别为5.00、4.09和5.08,三种原料对草鱼的脏体比、肝体比没有显著影响;与普通草鱼相比,三种原料组草鱼肌肉粗脂肪含量和肌肉失水率显著降低(P0.05),胶原蛋白含量和肌原纤维长度显著增加(P0.05)。上述结果表明,三种原料均可显著改善草鱼肌肉品质;与浸泡蚕豆组相比,专用配合饲料组显著提高了草鱼的生长性能。     

Generation and characterization of aptamers against grass carp reovirus infection for the development of rapid detection assay

Grass carp reovirus (GCRV) causes devastating viral haemorrhagic disease in farmed grass carp (Ctenopharyngon idellus). As novel molecular probes, aptamers have been widely applied in rapid diagnosis and efficient therapies against virus or diseases. In this study, three single‐stranded DNA (ssDNA) aptamers were selected against GCRV‐infected CIK cells via SELEX (systematic evolution of ligands by exponential enrichment technology). Secondary structures predicted by MFOLD indicated that aptamers formed stem‐loop structures, and GVI‐11 had the lowest ΔG value of ?30.84 KJ/mol. Three aptamers could specifically recognize GCRV‐infected CIK cells, with calculated dissociation constants (Kd) of 220.86, 176.63 and 278.66 nM for aptamers GVI‐1, GVI‐7 and GVI‐11, respectively, which indicated that they could serve as specific delivery system for antiviral therapies. The targets of aptamers GVI‐1, GVI‐7 and GVI‐11 on the surface of GCRV‐infected cells could be membrane proteins, which were trypsin‐sensitive. Furthermore, FAM‐labelled aptamer GVI‐7 could be applied to detect GCRV infection in vivo. It is the first time to generate and characterize aptamers against GCRV‐infected cells. These aptamers have great potentials in development of rapid diagnosis technology and antiviral agents against GCRV infection in aquaculture.     

Dietary Moringa oleferia leaf meal induce growth,innate immunity and cytokine expression in grass carp,Ctenopharyngodon idella

The present research was designed to investigate the growth promoting and immunostimulating properties of Moringa oleferia leaf meal (MLM) in grass carp. Juvenile grass carp (22.03 g ± 1.164) were fed with diets supplemented with 0, 50, 100 and 150 g/kg MLM for 48 days. At the end of feeding trial, skin mucus was used for analysis of lysozyme, protease, antiprotease and peroxidase activity. Head kidney was used for expression analysis of tumour necrosis factor‐alpha, interleukin‐8 and interferon‐γ. The obtained results showed that fish fed with 100 and 150 g/kg MLM had significant increase in weight gain and specific growth rate (p < .05). However, condition factor was not altered. The MLM (50 and 100 g/kg) inclusion resulted in higher mucus lysozyme and protease activity (p < .05), while peroxidase activity increased only in fish fed with 100 g/kg MLM and antiprotease activity was not altered. Expression of tnf‐α increased in a dose‐dependent manner, and significant (p < .05) increase was recorded in fish fed with 150 g/kg MLM. The expression of il‐8 and ifn‐γ increased in fish fed with 50 and 150 g/kg MLM; however, the increase was not significant (p > .05). In conclusion, supplementing juvenile grass carp feed with MLM up to 150 g/kg has growth promoting and immunostimulating effects.