Structural analysis, combining methods

The crystallographic data explosion. A consequence of the development of the direct methods of crystal structure analysis combined with automation of the experimental measurements has been the dramatic increase in the number of crystal structure analyses reported, as illustrated in Fig. 1.6. Fortunately, this explosion in crystallographic data has been accompanied by the development of data bases where this vast amount of structural information at atomic resolution is stored. Equally important has been the computer software development, whereby this information can be retrieved in forms appropriate to the interests of the interrogators of the data bases [39, 40]. 

COMBINED APPLICATION OF COMPOSITION AND STRUCTURE ANALYSIS METHODS TO THE DETERMINATION OF MAGNESIUM CONCENTRATION AND LOCATION IN BONE... 

When required, combined with the use of computers, the finite element analysis (FEA) method can greatly enhanced the capability of the structural analyst to calculate displacement and stress-strain values in complicated structures subjected to arbitrary loading conditions. In its fundamental form, the FEA technique is limited to static, linear elastic analysis. However, there are advanced FEA computer programs that can treat highly nonlinear dynamic problems efficiently. 

Tables 6.3-6.5 record data developed to undertake structural analysis in systems possessing chromophores that are conjugated or otherwise interact with each other. Chromophores within a molecule interact when linked directly to each other or when they are forced into proximity owing to structural constraints. Certain combinations of functional groups comprise chromophoric systems that exhibit characteristic absorption bands. In the era when UV-VIS was one of the principal spectral methods available to the organic chemist, sets of empirical rules were developed to extract as much information as possible from the spectra. The correlations referred to as Woodward s rules or the Woodward-Fieser rules, enable the absorption maxima of dienes (Table 6.3) and enones and dienones (Table 6.4) to be predicted. When this method is applied, wavelength increments correlated to structural features are added to the respective base values (absorption wavelength of parent compound). The data refer to spectra determined in methanol or ethanol. When other solvents are used, a numerical correction must be applied. These corrections are recorded in Table 6.5.

Various separation methods have been used to isolate, fractionate, and characterize humic materials. Originally it was fractionation, based on solubility differences of humic components in diluted alkalis and acids, which laid the ground work for the first classifications of humic substances (HS) in the 19th century (Mulder, 1861 Sprengel, 1837) and provided for operational definition of HS (Kononova, 1966). And now, alkali extraction is the method of choice for isolating HS from solid humus-containing substrates like soil, peat, coal, and so on (Swift, 1996), while hydrophobic resins (e.g., Amberlite XAD resins) are typically used to extract HS dissolved in natural waters (Aiken, 1985). Initial research on HS began with the used simple separation methods to prove, examine, and define characteristics of components of humic matter (Oden, 1919).Today, however, advances in HS research require ever more sophisticated techniques of separation combined with structural analysis (Orlov, 1990 Stevenson, 1994). 

Clerk, J.T., Pretsch, E., and Seibl, J., Structural Analysis of Organic Compounds by Combined Application of Spectroscopic Methods, Elsevier, Amsterdam, 1981. 

Several analyses can be performed once the full simulation method has been completed. One of the most useful is secondary structure analysis using do dssp. This program, in combination with the xpm2ps program, uses the Dictionary... 

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