Pole normalisation

The radius of the pole, r controls both the amplitude and the bandwidth of the resonance. As the value of oi decreases, its pole moves towards along the real axis towards the origin, and hence the frequency response has a lower amplitude at fi) = 0. From the difference equations, we know that a first order HR filter with oi < 1 is simply a decaying exponential. Small values of ai correspond to slow decay and narrow bandwidth, large values (still < 1) a steeper decay and wider bandwidth. This is exactly what we would e q)ect from the Fourier transform scaling property The standard measure of bandwidth is the 3db down point which is the width of the resonance at 1/ /2 down from the peak. For larger values of r = a, two useful approximations of the bandwidth (in normalised frequency) are ... 

Formant Frequency (Hz) Bandwidth (Hz) r 0 (normalised angular frequency) pole... 

Fig. 4A-H Comparison of two different variants of FRAP strip-FRAP and FLIP-FRAP (see also Fig. 3B, C). The combined use of the two protocols may allow to discriminate between transient binding and slow diffusion. The curves are based on computer simulated FRAP experiments (see the text) A, B schematic drawings of the strip-FRAP (see also Fig. 1C) and FLIP-FRAP methods. The FLIP-FRAP method differs from the strip-FRAP in that two areas are monitored after bleaching. Briefly, a strip at one pole of the nucleus is bleached for a relatively long period at a moderate excitation intensity. Subsequently the fluorescence is monitored in that region (FRAP), but also in the area at the other side of the nucleus (FLIP). Subsequently the difference between the two (normalised) fluorescence levels is plotted against time C schematic drawing of two scenarios where molecules are either free, but relatively slow (D=4 pmVs, top panel), or relatively fast (D=7 pm /s), but transiently immobilised such that 30% is immobile in steady state and individual molecules are immobilised for 45 s (bottom panel) D, E strip-FRAP and FLIP-FRAP curves of the scenarios depicted in C. In this case strip-FRAP can discriminate between the two cases, whereas the FLIP-FRAP curves are nearly identical F schematic drawing of a situation where freely mobile molecules are slower (D=l pmVs, top panel) than in C G,H strip-FRAP curves are identical whereas the FLIP-FRAP method can now discriminate between the two scenarios...

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