Logistic Curve with Offset on the Axis The logistic equation

Figure A4-16. Logistic curve with offset on they-axis. The curve follows equation A4-13 with a = 1, b = -2, c = 1 and d = -0.2.

This equation takes into account the value of the plateau maximum and minimum (coefficients a and d, respectively), the offset on the *-axis, and the Hill slope.

Gaussian Curve. The Gaussian or normal error curve (equation A4-14)

can be used to model UV-visible band shapes, usually in order to deconvolute a spectrum consisting of two or more overlapping bands. When used for deconvolution, a simplified form of the Gaussian formula can be used, for example

where A is absorbance, x is the independent variable, either wavelength (e.g., nm), or, more commonly, 1/wavelength (e.g., cm-1), and m is the value of * at Amax- The parameter s is related to the bandwidth at half-height.

Figure A4-17. Gaussian curve. The curve follows equation A4-15 with Amax = 10, m = 5 and s= 1.5.

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