Color and structure

Most of the qualitative relationships between color and structure of methine dyes based on the resonance theory were established independently during the 1940 s by Brooker and coworkers (16, 72-74) and by Kiprianov (75-78), and specific application to thiazolo dyes appeared later with the studies of Knott (79) and Rout (80-84). In this approach, the absorptions of dyes belonging to amidinium ionic system are conveyed by a group of contributing structures resulting from the different ways of localization of the 2n rr electrons on the 2n l atoms of the chromophoric cationic chain, rather than by a single formula ... 

Evergreens are the classic choice for clipped hedges, giving a solid backdrop of color and structure year-round. Yew (Taxus baccata) and boxwood (Buxus) make traditional hedges with a smooth finish boxwood is ideal for low hedges as it grows more slowly than yew. 

Absorption spectra have also been used in the reexamination of pH-dependent color and structural transformations in aqueous solutions of some nonacylated anthocyanins and synthetic flavylium salts." ° In a recent study, the UV-Vis spectra of flower extracts of Hibiscus rosasinensis have been measured between 240 and 748 nm at pH values ranging from 1.1 to 13.0." Deconvolution of these spectra using the parallel factor analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species (Figure 2.21). The model allowed identification of seven anthocyanin equilibrium forms, namely the flavylium cation, carbinol, quinoidal base, and E- and Z-chalcone and their ionized forms, as well as their relative concentrations as a function of pH. The spectral profiles recovered were in agreement with previous models of equilibrium forms reported in literature, based on studies of pure pigments. 

This coevolution between plants and animals for their mutual benefit has not only resulted in the complex and individual fragrances that they produce but in the wonderful color and structure of flowers themselves. We do not know whether insects such as bees can smell precisely the same range of materials as ourselves or whether their olfactory world differs from ours in the same way as does their vision. Bees are able to "see" ultraviolet, and the patterns of flowers that guide the bee toward the source of food appear quite different to the bee than they do to us. But, since we are able to smell most constituents of essential oils, it is probably fair to assume that our range of smell is quite similar. Perhaps bees have a much clearer idea of the smell of benzyl alcohol, which occurs in many flowers, than do most perfumers. How it would actually smell to them we cannot imagine any more than we can imagine the color of ultraviolet. 

Table 1. Colors and structural data of tetracyanoplatinate(II) single crystals...

The Swedish system of Post and Granlund (1926) is based on a 10-grade scale of humification determined by the turbidity, color, and structure of the wet peat material when squeezed. 

According to Wilhelm Ostwald, acid-base indicators are weak acids or bases which, when undissociated, exhibit a color different from that of their ionic forms. Hantzsch and others have shown that the color change is not due to ionization, but rather results from a structural change. The explanation of Ostwald, however, is most suitable for purposes of elucidating the behavior of indicators at various hydrogen ion concentrations. We shall return in Chapter Seven to a comparison of the views of Ostwald and Hantzsch. It will then be found advisable to revise the definition of Ostwald as follows Indicators are weak acids and bases of which the ionogenic form possesses a color and constitution different from the color and structure of the pseudo or normal form. 

Indicators are (apparent) weak acids or bases of which the iono genic (a< - or baso- respectively) form possesses a color and constitution different from the color and structure of the pseudo- or normal compound. 

Figure 1.1 Kava plants of two different cultivats from the Fiji Islands. The plants are (A) six-months and (B) two-years old. Note the differences in the color and structural characteristics of the leaves and stems. (B) Reprinted from Singh (1992), Kava, an overview,of Ethno-pharmacology, 37, 13 5, with permission from Elsevier Science.

The quinones are colored substances. It is thought that the color is the result of the peculiar molecular structure which these compounds possess. The constitution of many colored substances is best explained by the hypothesis that they contain the so-called quinoid configuration. The relation between color and structure will be discussed in the chapter on dyes. 

Humus is an amorphous, hydrophillic, acidic, partly aromatic, generally dark colored, and structurally complex material, resulting from the microbial degradation of plant detritus. Humus can be further classified as follows (a) humic acids a fraction that is soluble in alkali but precipitates on acidification of the solution, (b) fulvic acids a fraction that remains in solution after the extraction is acidified, and (c) humin a fraction that cannot be extracted by either alkali or acid (see Chapter 5 for details). 

Fig. 4.31 The colors and structures of different anthocyanidins depending on the pH of the medium (the base decomposition of chalcone is not shown). The dyes in roses are derivatives of cyanidin, peonidin and pelargonidin in which the carbohydrate units are connected to positions 3...

The sample remains unaltered in color and structure. Absence of volatile compounds such as mercury and ammonium salts carbonates that lose carbon dioxide. Absence of organic matter or organometallic compounds. Absence of compounds containing water of crystallization or much adsorbed water (gels of oxyhydrates). Absence of compounds that, when heated alone or in mixture with suitable partners, are changed because of the occurrence of redox reactions. 

Yet it was told to create the butterfly car some natural solution principles from the perspective of biomimicry, bringing the alternatives the study of shapes, colors and structures of natural elements like the butterfly is an animal that possesses beauty, lightness and idea of freedom. 

We know from skin cancer research that a unique feature is not sufficient to diagnose precisely skin cancer, and that the combination of different criteria is the key to the early detection of malignant melanoma and other types of skin cancer. Combining color and structure features for classification, as done in this research, show that measuring these features can be a good guide for a diagnostic system to classify skin lesions. 

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