Avoidant Learning Ability in Free Flying Housefly (Aldrichina grahami)by Electric Shock

下载PDF阅读器研究证实:蜜蜂和果蝇具有良好的学习记忆能力.利用自主改良的研究装置对另一种具有强大生存本能的双翅目昆虫--巨尾阿丽蝇(Aldrichina grahami)在自由状态下电击同避学习能力进行研究.结果表明,巨尾阿丽蝇具有良好的学习记忆能力,因为当刺激电压范围为5V到45V时,观察到巨尾阿丽蝇有显著的回避电刺激行为,而当电压达到60V时会受到明显伤害.由此推测,巨尾阿丽蝇适合作为神经系统研究的动物模型.该实验所采用的实验范例较以往有所改进,适合作为自由状态下研究昆虫的工具.

A preliminary study on fingerprinting approach in marine sediment dynamics with the rare earth elements

Locating the quantitized natural sediment fingerprints is an important work for marine sediment dynamics study. The total of 146 sediment samples were collected from the Shelf of the East China Sea and five rivers, including Huanghe (Yellow), Changjiang (Yangtze), Qiantang, Ou and Min River. The sediment grain size and the contents of rare earth elements (REEs) were measured with laser particle size analyzer and ICP-MS technology. The results show that absolute REE content (Sigma REE) and the concentration ratio of light REEs to heavy REEs (L/HREE) are different in the sediments among those rivers. There are higher REE contents in being less than 2 m and 2-31 mu m fractions in the Changjiang Estuary surface sediments. The REE contents of bulk sediment are dominated by the corresponding values of those leading size-fractions. Sigma REE of sediment is higher close to the estuaries and declines seaward on the inner shelf of the East China Sea (ECS). The L/HREE ratio has a tendency of increase southward from 28 degrees N. Hydrodynamic conditions plays a predominate role on spacial distributions of the surficial sediment's REE parameters. In some situations, the currents tend to remove the coarser light grains from initial populations, as well as the deposit of the finer heavy mineral grains. In other situations, the currents will change the ratio of sediment constituents, such as ratio between silts and clays in the sediments. As a result, the various values of Sigma REE or L/HREE ratio in different bulk sediments are more affected by the change of size-fractions than source location. Under the long-term stable hydrodynamic environment, i.e., the East China Sea Shelf, new sediment transport model based on the size and density gradation concept may help to understand the spatial distribution patterns of REE parameters.