Gaussian-like peak

Approximate Methods For certain conditions, symmetrical, Gaussian-like peaks are obtained experimentally. Such peaks may be empirically described by ... 

Gaussian-like peak A bell-shaped curve described by the equation Y = Aexp — (x /B). See Chapter 10 for more details. 

The electron diffraction determination of the u values is based upon the study of the natural damping of the various sine terms making up the electron diffraction intensity curve. This damping of the sine terms can be measured from the radial-distribution curve by studying the width of the corresponding Gaussian-like peak. As mentioned earlier, the u value may be obtained either directly from the intensity curve or from the radial-distribution curve using least-squares calculations. 

The output of modem instruments usually includes the DTG, namely the trace of weight loss rate, d/w/dt, v.v T (where T is the thermodynamic temperature), or v.v t (t stands for time). When several compounds are released within the same T (or t) range, DTG trace allows the relevant, To, and 7 e (mean, onset and end temperature, respectively) to be more easily determined for each of them. In this case the DTG trace appears as a multi-peak trend. It can be easily shown that the DTG trace can be deconvolved into a sum of gaussian or gaussian-like peaks, each related to a single compound. This is the start point to make a kinetic parameter of the weight loss (see Appendix A2). 

Care must be taken in the use and interpretation of literature efficiency values. Efficiency values are likely the most incorrectly calculated chromatographic figure of merit. The commonly used equations based on peak width at the base or at half the height of the peak are valid only for perfectly Gaussian shaped peaks. This problem has been realized by chromatographers for some time, but the popularity of these methods continues because until recently the only alternative was computer based moment calculations. Kirkland et al. addressed this problem and recommended that peak symmetry values be reported along with efficiency values (8 ). They further showed that the calculation... 

Each one contributes additively to the final Gaussian-like shape of a chromatographic peak because variances ([Pg.286]

In view of the data obtained when extracts from P. sylvestris and D. dolichopetala were purified by immunoaffinity chromatography and analysed by ion-suppression, reverse phase HPLC, it would have been very tempting to assume that the application of these procedures to the analysis of extracts from dwarf-1 Zea mays, and other tissues, would also provide accurate quantitative estimates of endogenous lAA. The HPLC trace illustrated in Fig. 8B, in which a Gaussian-shaped fluorescent lAA-like peak is a major component, would appear to support this belief. However, the data in Fig. 8C show that such an assumption would have been incorrect and led to an inaccurate overestimate of lAA. 

Fig. 3.9 (a) Calorimeter response to a Gaussian-like signal input by the calibration heater in simulation mode at a density of SCCO2 of 661.5 kg (b) Calorimeter response to a peak signal input by the calibration heater in simulation mode at a density of SCCO2 of 661.5 kg m . ... 

Chromatograms are usually obtained by the elution technique The sample is injected onto the column and is carried by a fluid through the column to the detector, so various compounds arrive to the same place at different times. Chromatographic peaks obtained by the elution technique ideally possess a Gaussian-like shape. In practice, peak shapes are often different, frequently indicating problems with the separation process. The two common problematic peak shapes are shown in Fig. 2. 

Odors may be detected for a very short exposure period, perhaps less than one second. It is thus necessary to determine the likely one-second peaks knowing the concentrations derived from the Gaussian equation. This is based on 10-minute average period. The equation to convert the time-averaging period is ... 

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