鳗鲡模式游动的鱼体变形曲率波的传播特性研究

将鳗鲡模式游动的七鳃鳗简化成材料性质均匀的变截面黏 弹性梁,通过数值方法求解鱼体在主动弯矩波(作为激励的驱动波)的驱动下匀速游动时身体变形曲率波的传播特性. 结果表明,当主动弯矩 的驱动频率高于鱼体结构基频时,可以观察到曲率波相对于驱动波存在相位滞后,且越靠近尾部滞后现象越明显,这意味着曲率波的波速 小于驱动波的波速,也间接地验证了前人的实验结果. 通过参数研究发现,鱼体变形曲率波与驱动波的波速比与表征流体黏性作用的雷诺数无关,而与表征驱动波和鱼体材料属性的 无量纲激励频率、激励波长及鱼体黏性系数有关. 对于鳗鲡模式游动的鱼类,曲率波与驱动波的波速比随着无量纲激励频率和波长的增大而降低,随着鱼体黏性系数的增大而增大. 进一步研究发现,通过小扰动分析得到的组合相似性参数$\varPi$可以统一描述波速比与激励参数、材料参数之间的关系.      

Monitoring sea lamprey pheromones and their degradation using rapid stream‐side extraction coupled with UPLC‐MS/MS

Pheromones guide adult sea lamprey (Petromyzon marinus) to suitable spawning streams and mates, and therefore, when quantified, can be used to assess population size and guide management. Here, we present an efficient sample preparation method where 100 mL of river water was spiked with deuterated pheromone as an internal standard and underwent rapid field‐based SPE and elution in the field. The combination of field extraction with laboratory UPLC‐MS/MS reduced the sample consumption from 1 to 0.1 L, decreased the sample process time from more than 1 h to 10 min, and increased the precision and accuracy. The sensitivity was improved more than one order of magnitude compared with the previous method. The influences of experimental conditions were assessed to optimize the separation and peak shapes. The analytical method has been validated by studies of stability, selectivity, precision, and linearity and by the determination of the limits of detection and quantification. The method was used to quantify pheromone concentration from five streams tributary to Lake Ontario and to estimate that the environmental half‐life of 3kPZS is about 26 h.