Rheotaxis

Based on the discussed example parameters that influence the turbulent mixing process, it is clear that plume structure can be described in general terms, but the specific characteristics are likely to be case dependent. Nevertheless, certain characteristics, such as those employed by the odor-gated rheotaxis with bilateral comparison strategy, may be similar enough to allow animals and engineered systems to track chemical plumes for a wide range of flow conditions. 

A different aspect of preparation of an organized nanoparticles on a fluid is called as the rheotaxy technique. It is a well-established one to fabricate a well-crystallized film. Mobility of the atoms on the surface of the liquid substrate favors the aggregation of atoms in the growing films (41). In order to avoid a drawback of the rheotaxy, i.e., the negative effect of high surface tension of the substrate, a modification has been made by Romeo et al. (42,43), where they used substrates of elevated temperature close to but below their melting points. They prepared, e.g., ZnS Mn thin films on some low-melting metals such as Pb, Bi or Bi-Sb alloy. 

Hodes et al. suggested that this was due to quasi-rheotaxy type of crystalhne growth. The films annealed at the higher temperatures also showed higher photoactivity. 

Diagram of the MGS 1100 sensor from Motorola. Micromachined sensor element is illustrated on the left, and the sensor housing on the right. The sensitive films were obtained by rheotaxial growth and thermal oxidation of tin layers (RGTO) deposited on the silicon oxide-nitride membrane. From Simon etal. (2001). 

In experiments to study the movements of coho salmon under each of these two conditions, imprinting odor distributions were established in two experimental channels which simulated these two configurations. The movements of individual fish which had been imprinted to these and other synthetic compounds were recorded in relation to controlled distributions of the stimuli (Johnsen and Hasler, 1980). When imprinting odors were distributed across the full width of the stream, fish imprinted to that compound exhibited straight, positive rheotaxis. If the homestream (imprinting) compound was absent, fish exhibited negative rheotaxis and actively moved downstream until they again detected the home scent. 

The two major patterns of upstream movement include straight positive rheotaxis in water scented from bank to bank and zig-zag swimming along the interface of the scented plume at the confluence of two tributaries. 

An additional feature includes negative rheotaxis in the absence of the homestream odor. I believe that these simple behaviors, positive and negative rheotaxis and zig-zagging at the confluence of two streams, are sufficient to guide fish to the homestream. 

Stabell, 0. B., 1982, Detection of natural odorants by Atlantic salmon parr using positive rheotaxis olfactometry, n "Salmon and Trout Migratory Behavior Symposium," E. L. Brannon, and E. 0. Salo, eds.. School of Fisheries, University of Washington, Seattle. 

Rheotaxial growth with following thermal oxidation (RGTO)... 

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