| fluctuation | 1. A motion like that of waves; a moving in this and that direction; as, the fluctuations of the sea. 2. A wavering; unsteadiness; as, fluctuations of opinion; fluctuations of prices. 3. <medicine> The motion or undulation of a fluid collected in a natural or artifical cavity, which is felt when it is subjected to pressure or percussion. Origin: L. Fluctuatio; cf. F. Fluctuation. Source: Websters Dictionary (01 Mar 1998) |
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| fluctuation analysis | Method used to determine (for example) how many ion channels contribute to the transmembrane current. On the assumption that each channel is either open or shut, the noise in the recorded current can be considered to arise from the statistical fluctuation in the number of channels open and the magnitude of the fluctuation gives an estimate of the conductance of a single channel. (18 Nov 1997) |
| fluctuation test | <investigation> Test devised by Luria and Delbruck to determine whether genetic variation in a bacterial population arises spontaneously or adaptively. In the original version the statistical variance in the number of bacteriophage resistant cells in separate cultures of bacteriophage sensitive cells was compared with variance in replicate samples from bulk culture. The greater variance in the isolated populations indicates that mutation occurs spontaneously before challenge with phage. (The proportion of resistant cells depends upon when after isolation the mutation arises which will be very different in separate populations). (18 Nov 1997) |