Contour levels

FIG. 20-78 Reaction in compacts of magnesium carbonate when pressed (P = 671 kg/cnr ). (a) Stress contour levels in kilograms per square centimeter, (h) Density contours in percent solids, (c) Reaction force developed at wedge responsible for stress and density patterns. [Tf ain, Trans. Inst. Cbem. Eng. (London), 35, 258 (1957).]... 

For molecular systems with up to thirty valence electrons, an amplitude of =t0.1 a.u. was chosen for the contour level. For systems with more than thirty valence electrons it was necessary to reduce this value to 0.08 a.u. to maintain the orbital size at a comfortable visual level. The molecular orbitals were normalized to an occupancy... 

Figure 3.12 Two-dimensional NMR plots recorded at different contour levels, (a) Two-dimensional spectra recorded at low contour level usually have noise lines across the plot, (b) With a higher contour level, many of the noise peaks are eliminated and the peaks become clearer.

Fig. 1. MEP contour maps calculated for the CO molecule using the SCF (la), MP2 (lb) and LCGTO-DF (Ic) methods. The contour levels and MEP minima are given in kcal/mol.

Figure 2. L-alanine. Dynamic deformation density in the COO plane, (a) Model dynamic deformation density A Modei. (b) MaxEnt dynamic deformation density (Agj, (x)) map obtained with a non-uniform prior of spherical-valence shells. Map size 6.0A x 6.0A Contour levels from -1.0 to 1.0 eA 3, step 0.075 e A-f...

Figure 6. l-Alanine. Fit to noisy data. Calculation A. MaxEnt deformation density and error map in the COO- plane Map size, orientation and contouring levels as in Figure 2. (a) MaxEnt dynamic deformation density A uP. (b) Error map qME - Model. 

Figure 3. Differences among water dimer densities p, as obtained with the theoretical models explored in this work. Same symmetry plane, geometry, basis set and contour levels as that of Figure 2. 

Comparison of the model maps (Figure 1(c) and (d)) again shows qualitative agreement. All regions agree to within one contour level (0.05 e A 3) except for the lone pair regions for 0(2) and 0(3) which are significantly sharpened compared to those obtained with the SC data. 

Figure 25 shows a comparison between an H2BC (left) and an HMBC (right) spectrum of cyclosporine recorded under identical conditions and using the same contour levels. The spectra are quite complementary, as... 

Figure 34 Excerpts of two-dimensional HMBC spectra of cholesteryl acetate recorded on a Bruker Avancell 400 MHz spectrometer (A) with the standard HMBC pulse sequence (Figure 1), and (B) with the IMPACT-HMBC experiment depicted in Figure 30. The same contour levels are used for all spectra. In (A), F, ridges are still visible (indicated by a vertical arrow), while they are very efficiently suppressed in (B). The proposed sequence results in signals with no coupling structure, as a result of the incorporation of a constant-time period. The improved peak dispersion is shown for the correlation between C-3 and H-2 (expanded in the small boxes). Asterix and the dashed box indicate residual Vch signals. The measurement duration was 22 min for both experiments.

Fig. 13. Stereo drawing of one contour level in the electron density map at 2 A resolution for the residue 54-68 helix in staphylococcal nuclease. Carbonyl groups point up, in the C-terminal direction of the chain the asterisk denotes a solvent peak bound to a carbonyl oxygen in the last turn. Side chains on the left (including a phenylalanine and a methionine) are in the hydrophobic interior, while those on the right (including an ordered lysine) are exposed to solvent.

Fig. 14.5 Computation of VolSurf descriptors [155, 156] derived from GRID molecular interaction fields. Interactions of the example molecule with a water and dry probe at different contour levels are used to compute a vector of 72 volume-, size- and surface-based descriptors.

FIG. 11.11 Electron-density difference maps on Li2BeF4 calculated with all reflections < sin 6/1 = 0.9 A"1 (81 K). (a) Based on the neutral atom procrystal model, (b) based on the ionic model. Contour levels are drawn at intervals of 0.045 eA"3.1 Full lines for positive density, dashed lines for negative and zero density. The standard deviation, estimated from [2Lff2(F0)]1/2N, is 0.015 eA-3. Source Seiler and Dunitz (1986). 

DEFINE SPECTRUM PLOT (SPECTRAL LIMITS, PEAK INTENSITIES, CONTOUR LEVELS, PLOT SIZE, SCALES, COLORS, TITLE)... 

This section describes the function of the most important buttons in the button panel (Fig. 4.21). Further options available within the Display pull-down menu of 2D WIN-NMR will be discussed in section 4.8.3. Two procedures to set contour levels for a 2D spectrum displayed as a contour plot are discussed in section 4.8.2. 

Contour mode The currently selected 2D spectrum is displayed as a contour plot, the usual mode of display. At the same time corresponding local mode buttons appear in the button panel (Fig. 4.21) which allow to set contour levels. See section 4.8.2 or use the Help tool for more information concerning these options. 

With a 2D spectrum displayed in the Contour mode, the number, intensitiy and color of contour levels have to be defined. Two procedures to set contours exist ... 

As an alternative contour levels may be defined using suitable rows or columns of a 2D spectrum. This is especially useful if very weak cross peaks with intensities close to the noise level should be detected. To set levels in this way the Scan mode i.s activated and the option to freeze a suitable row or column is exploited. 

Note that for plotting 2D spectra up to 14 contour levels may be used. They can be defined with the Page Layout option in the Output pull-down menu (see 4.10.2). 

Colors... Allows you to set the screen colors (contour levels, background). 

Choose the Page Setup... option in the Output pull-down menu and select the plotting parameters and projections to be included in the plot. Adjust the sizes of all windows (title, parameter, spectrum) to the size of the paper sheet. Set up a title and select the parameters to be plotted. Load the defined levels with the Load button, choose different colors for the levels if you have a multicolor output device. Click the Preview button to inspect the final layout in the Preview window. Repeat these steps, load the defined levels with the Load button as before, but add additional contour levels with the Fill button. 

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