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《African Zoology》2013,48(2):318-325
It has been suggested that the invasive, omnivorous Clarias garipienus is capable of rapid invasions and long-term persistence in recently inhabited freshwater systems. To test this hypothesis, the life history of the established, extralimital Darlington Dam (33°10’31”S, 25°09’13”E) population was investigated. By counting post-fluorescent mark increments on otoliths from 21 chemically tagged wild fish recaptured 244–537 days later, the deposition of growth zones, comprising alternating opaque and translucent bands, was validated as annual. Examination of sectioned otoliths from 175 fish revealed that the oldest fish, two males of 840 and 1074 mm total length (TL), were 25 years old – 10 years older than previously described for any C. gariepinus population. The oldest female was 885 mm TL and 21 years old. Length-at-age was subsequently described using the von Bertalanffy growth model. Combined-sex growth was best described as Lt = 931.7(1– exp(–0.15(t+2.43))) mm TL. Total mortality (Z) was calculated using catch curve analysis and the Chapman & Robson estimator to be 0.35/yr. The presence of specimens 15 years and older indicates that these fish established quicklyand supports the finding that mortality rates are low, which, in turn, suggests likely long-term population persistence. 相似文献
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BACKGROUND: For an oil adjuvant to enhance uptake of a particulate active ingredient (AI), it is hypothesised that closer association between the two should result in higher uptake. Accordingly, factors important for the spray deposit size on grapevine leaves have been investigated for a series of model suspoemulsion formulations containing colloidal crystalline AI or fluorescent pigment particles and an emulsion of an oil adjuvant with different degrees of wetting and different spray volumes. RESULTS: Low spray volumes (<100 L ha(-1)) produced small deposits with high particle-adjuvant association. Complementary uptake studies showed increased uptake with decreasing deposit size, in agreement with the above hypothesis. Higher spray volumes produced larger deposits that consisted of annuli formed by pinning of the contact line by particles. Low surfactant concentrations favoured particles in the annulus and adjuvant separated in the centre. Intermediate surfactant concentrations produced annuli containing both particles and adjuvant, while with high surfactant concentrations the deposits were large with few annuli.CONCLUSIONS: Small deposits result in high AI-adjuvant association. With larger deposits, annulus structures allow for enhanced AI-adjuvant association (5-20 times greater). The formation of annuli appears to be important in enhancing the biodelivery of particulate AIs in adjuvant-containing suspoemulsion formulations at intermediate spray volumes. 相似文献
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Li Yourong 《保鲜与加工》1991,(5):64-68
A second law analysis is carried out on convective heat transfer through a horizontal annulus with constant heat flux. The entropy generation rate expression is obtained,and the influence of heat transfer across a finite temperature difference and fluid friction on the entropy generation rate is discussed. The optimum geometric parameters of a horfzontal annulus is found for which the entropy generated is minimum. The optimum fluid velocity which corresponds to the optimum geometric parameters is recommended. 相似文献
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根据分别采集于贵州清水江和都柳江的316例瓣结鱼标本,观察了瓣结鱼鳞片、主鳃盖骨、背鳍条、脊椎骨和匙骨等5种材料的年轮特征并进行了瓣结鱼的年龄鉴定。结果表明,瓣结鱼这5种年龄鉴定材料的年轮特征各不相同。其中瓣结鱼鳞片和主鳃盖骨的年轮最为清晰,而匙骨的年轮则较为模糊。分别采用鳞片、主鳃盖骨、背鳍条和脊椎骨等4种材料对瓣结鱼年龄鉴定的结果表明,鳞片和主鳃盖骨年龄鉴定的吻合率最高,达92.1%,瓣结鱼鳞片的年轮形成期主要在每年的5月、8月和10月。鳞片为瓣结鱼年龄鉴定的主要依据材料,而主鳃盖骨和背鳍条则为瓣结鱼年龄鉴定的重要佐证。 相似文献
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Jihye Choi Hyunwook Kim Junghee Yoon 《Journal of veterinary science (Suw?n-si, Korea)》2013,14(1):85-90
This study evaluated pulsed TDI variables including the isovolumic time interval and duration of the major wave in a population of large healthy dogs. Longitudinal myocardial motion at the septal mitral annulus was evaluated with pulsed TDI in 45 healthy adult dogs. Maximal myocardial velocities, isovolumic time intervals, and duration of the myocardial waves were measured. The correlation between time intervals and velocity variables was also investigated. The mean maximal systolic velocity was 6.92 ± 1.78 cm/sec, the mean early diastolic velocity (Em) was 6.58 ± 1.81 cm/sec, the mean late diastolic velocity (Am) was 5.10 ± 2.00 cm/sec, the mean isovolumic contraction time (IVCT) was 53.61 ± 95.13 msec, and the mean isovolumic relaxation time (IVRT) was 26.74 ± 57.24 msec. The early diastolic mitral inflow velocity (E)/Em ratio was 10.94 ± 3.27 while the Em/Am ratio was 1.40 ± 0.40. There was a negative correlation between Am duration and Am amplitude, and a positive correlation between the IVRT and Em/Am ratio (p < 0.05). The normal LV parameter using pulsed TDI method could be used as the reference range for identifying myocardial dysfunction in dogs. 相似文献
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为深入探讨筒装料管道水力输送过程中同种型号双车运行时所产生的动边界条件下有压管道内部断面压力分布以及压降特性问题,对型号100 mm×60 mm、荷载750 g的管道双车在30,40,50,60,70 m3/h等不同流量作用下两车车身环隙断面、车间断面的压力分布以及车组沿程压降特性进行试验研究和分析,两车运行时车间距离条件为10 cm.研究表明:当流量增大时各测试断面压力值增大;双车车体沿程压力呈现先减小后增大的趋势;沿水流方向,后车引起的压降值明显高于前车;后车环隙断面内,自固定边壁向动边界压力值呈现“降-升-降”趋势,前车环隙内则为总体下降趋势,且后车环隙压力梯度高于前车;不同流量条件下,车间断面内压力分布基本为管道边壁附近值较大,内部值较小,且分布不均匀,压力梯度随流量增大而增大. 相似文献
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水培生菜自动纵向包装装置设计与试验 总被引：2，自引：0，他引：2
为提升设施园艺中水培生菜生产全程机械化水平,设计了收获后生菜自动纵向包装装置,包括导向装盒机构、切膜与封膜机构等。利用聚拢气缸和压菜气缸执行生菜纵向装盒,同时利用导向环保证装盒过程中生菜偏移、翻转等位姿要求;通过柔性毛刷对薄膜的梳刷作用及薄膜自粘性使其贴于包装盒,完成包装盒封膜。根据生菜挤压试验、力学分析、理论计算,分别确定了包装盒尺寸、导向装盒机构参数、切膜与封膜机构参数。基于高速摄像,提出了生菜水平偏移、姿态角量化方法;通过生菜装盒位姿特性试验,研究了导向环对装盒过程生菜位姿特性的影响。研制了自动包装样机,利用正交试验优化了切膜作业参数并进行了试验验证。生菜装盒位姿特性试验结果显示:生菜入盒时有导向环水平偏移平均值、姿态角平均值分别为5. 8 mm、17. 9°,相较无导向环时分别减小75. 0%、74. 2%,导向环保证了生菜纵向装盒成功率。正交试验结果显示:切膜作业参数最优组合为薄膜纵向切刀与薄膜夹角30°、拉膜辊拉膜速度300 mm/s、薄膜横向切刀速度500 mm/s。最优参数组合下,包装成功率为96%,样机单次包装用时10. 5 s,比人工缩短58%。 相似文献
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为进一步探讨不同因素对动边界环隙流场水力特性的影响,采用试验和理论分析相结合的方法,对环隙宽度条件分别为25,20,15,10 mm的动边界环隙流场水力特性进行研究,试验采用筒装料管道水力输送管道车模型在管路系统平直段部分完成,流量条件为60 m3/h,管道车模型质量为750 g．研究结果表明:平直管段动边界环隙内部水流为紊流形态;环隙断面内各测点压力值随环隙宽度增大趋于集中,且同一断面内动边界管道车壁附近压力值较小,固定管道边壁处压力值较大;同一宽度条件下,轴向速度在车中断面内分布较车前、车后断面更为均匀,且呈现动边界附近速度值较大,固定边界附近值较小的环绕车体层状分布;环隙宽度为20 mm时,断面内轴向速度分布均匀性最好;各环隙宽度条件下,车身沿程各测试断面内周向速度均呈现不均匀分布． 相似文献
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