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Resolution enhancement sine-bell

Heteronuclear-shift-correlation spectra, which are usually presented in the absolute-value mode, normally contain long dispersive tails that are suppressed by applying a Gaussian or sine-bell function in the F domain. In the El dimension, the choice of a weighting function is less critical. If a better signal-to-noise ratio is wanted, then an exponential broadening multiplication may be employed. If better resolution is needed, then a resolution-enhancing function can be used. [Pg.170]

There are generally three types of peaks pure 2D absorption peaks, pure negative 2D dispersion peaks, and phase-twisted absorption-dispersion peaks. Since the prime purpose of apodization is to enhance resolution and optimize sensitivity, it is necessary to know the peak shape on which apodization is planned. For example, absorption-mode lines, which display protruding ridges from top to bottom, can be dealt with by applying Lorentz-Gauss window functions, while phase-twisted absorption-dispersion peaks will need some special apodization operations, such as muliplication by sine-bell or phase-shifted sine-bell functions. [Pg.180]

Use the same series of data and follow the same procedure as before to try out the Lorentz-Gauss convert window type. There is one single parameter LB available to adjust the window. Set the initial value to LB = 0, increment and decrement its value in small steps and inspect the shape of the window using the interactive mode. Note that for LB > 0 the shape of the window is similar to the exponential window (signal-to-noise improvement) whereas for LB < 0 the window shape is similar to the sine-bell squared window. Try out a few values to enhance the signal-to-noise ratio and to improve the resolution, store the results and compare the spectra using the multiple display. [Pg.179]

A very simple window function for resolution enhancement is the sine bell (Fig. 3.34), which is just the function sin(x) for x = 0 to 180°. This function grows for the first half of the FID and then brings the signal smoothly to zero during the second half. We saw examples of this window in Chapter 2 (Figs. 2.9 and 2.10). We will see that the sine-bell family of... [Pg.125]

Fig. 4. High-frequency shifted portions of the 500 MHz H NMR spectra of sperm whale metMbiCN ) at pH 9.2, 30 "C. (A) In 90 10 = H2O H2O. (B) In 49 51 = H2O H2O. The expanded plots show the three resolved heme methyl signals after resolution enhancement by sine-bell function the vertical scale is arbitrary, frequency scale magnified by a factor of 5. Asymmetry in the expanded peaks is due to overlapping lines of different width. (From ref. 79, 1987, with permission from the publishers.)... [Pg.198]

Figure 5.22. Contour plots of (a) the phase-twist lineshape, (b) the same following magnitude calculation, and (c) the same following resolution enhancement with an unshifted sine-bell window and magnitude calculation. Figure 5.22. Contour plots of (a) the phase-twist lineshape, (b) the same following magnitude calculation, and (c) the same following resolution enhancement with an unshifted sine-bell window and magnitude calculation.
Many other weighting functions have been used for sensitivity enhancement and resolution enhancement. Perhaps the most popular are the sine bell are variants on it, which are illustrated in Fig. 4.13. [Pg.60]

The basic sine bell is just the first part of a sin 9 for 9 = 0 to 6 = tv, this is illustrated in the top left-hand plot of Fig. 4.13. In this form the function will give resolution enhancement rather like the combination of a rising exponential and a Gaussian function (compare Fig. 4.11 (j)). The weighting function is chosen so that the sine bell fits exactly across the acquisition time mathematically the required function is ... [Pg.60]

The sine bell can be modified by shifting it the left, as is shown in Fig. 4.13. The further the shift to the left the smaller the resolution enhancement effect will be, and in the limit that the shift is by tt/2 or 90° the function is simply a decaying one and so will broaden the lines. The shift is usually expressed in terms of a phase (p (in radians) the resulting weighting function is ... [Pg.61]

Explain why use of a sine bell weighting function shifted by 45° may enhance the resolution but use of a sine bell shifted by 90° does not. [Pg.64]

Apodization is the process of multiplying the FID prior to Fourier transformation by a mathematical function. The type of mathematical or window function applied depends upon the enhancement required the signal-to-noise ratio in a spectrum can be improved by applying an exponential window function to a noisy FID whilst the resolution can be improved by reducing the signal linewidth using a Lorentz-Gauss function. ID WIN-NMR has a variety of window functions, abbreviated to wdw function, such as exponential (EM), shifted sine-bell (SINE) and sine-bell squared (QSINE). Each window function has its own particular parameters associated with it LB for EM function, SSB for sine functions etc. [Pg.76]

Figure 6a shows the aromatic part of the 360 MHz spectrum of bovine pancreatic rlbonuclease A (1.5 idH In D2O, pH 7.0, 38%). The spectral resolution was artificially enhanced by multiplication of the FID by a sine bell (HOthrlch et al., 1977). The spectrum of RNase S Is very similar. The doublet resonances of three of the six tyrosine residues Indicated by Yl, Y2, and Y3 have been Indentlfled by double resonance methodes (Lenstra et al., 1978). The photo-CIDNP difference spectra of RNase A and RNase S taken under the same conditions are shown In Figure 6b and 6c. Positively enhanced lines at 7.92 ppm and 6.71 ppm belong to the C-2 and C-4 protons of His 119. This active site residue Is also the most exposed of the four histidines as judged from the X-ray structure (Richards and Wyckoff, 1971) For RNase A (figure 6b)... [Pg.221]


See other pages where Resolution enhancement sine-bell is mentioned: [Pg.403]    [Pg.176]    [Pg.179]    [Pg.50]    [Pg.132]    [Pg.404]    [Pg.246]    [Pg.73]    [Pg.166]    [Pg.173]    [Pg.173]    [Pg.237]    [Pg.273]    [Pg.61]    [Pg.333]    [Pg.157]    [Pg.57]    [Pg.58]    [Pg.141]    [Pg.142]    [Pg.147]    [Pg.148]    [Pg.202]    [Pg.22]   
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