Distributional study of the Zion Snail, Physa zionis, Zion National Park, Utah

The major hanging gardens and associated water seeps in Zion National Park were surveyed for the presence of the Zion Snail ( Physa zionis ). Environmental parameters, including water depth, water velocity, substrate slope, and algal cover, were measured to determine their effect on the local distribution of the snail. Large populations (densities 125 to 250/m 2 ) were found in the Virgin River Narrows area of the park and at a hanging garden and seep located 1.0 km north of Scout Lookout. Densities in other localities were low in comparison. Snails were not found in all hanging gardens or seeps. The major factor controlling within seep distribution was determined to be water velocity. Experiments were conducted to test the ability of the snail to remain attached during differing water flows. The snail showed an ability to remain attached during high flows, but few snails were found in areas of high flow.     

豚鼠耳蜗基底膜的振动特性

为探讨豚鼠耳蜗基底膜的听觉机制,利用多普勒激光测振技术进行了声音在28只成年健康豚鼠耳中传递的测试实验.将豚鼠麻醉后切断头取出听泡,采用电钻暴露其耳蜗基底膜,利用多普勒激光测振仪在给定的声压级、频率的纯音激励条件下测量豚鼠外耳道耳蜗基底膜的振动速度,并测量了中耳镫骨的振动速度.结果表明,豚鼠外耳道基底膜具有频率选择特性,而且其基底膜的振动具有行波特性.     

On-demand single-electron transfer between distant quantum dots

Single-electron circuits of the future, consisting of a network of quantum dots, will require a mechanism to transport electrons from one functional part of the circuit to another. For example, in a quantum computer decoherence and circuit complexity can be reduced by separating quantum bit (qubit) manipulation from measurement and by providing a means of transporting electrons between the corresponding parts of the circuit. Highly controlled tunnelling between neighbouring dots has been demonstrated, and our ability to manipulate electrons in single- and double-dot systems is improving rapidly. For distances greater than a few hundred nanometres, neither free propagation nor tunnelling is viable while maintaining confinement of single electrons. Here we show how a single electron may be captured in a surface acoustic wave minimum and transferred from one quantum dot to a second, unoccupied, dot along a long, empty channel. The transfer direction may be reversed and the same electron moved back and forth more than sixty times-a cumulative distance of 0.25 mm-without error. Such on-chip transfer extends communication between quantum dots to a range that may allow the integration of discrete quantum information processing components and devices.