Representational insight

With better hardware and software, more exact methods can be used for the representation of chemical structures and reactions. More and more quantum mechanical calculations can be utilized for chemoinformatics tasks. The representation of chemical structures will have to correspond more and more to our insight into theoretical chemistry, chemical bonding, and energetics. On the other hand, chemoinformatics methods should be used in theoretical chemistry. Why do we not yet have databases storing the results of quantum mechanical calculations. We are certain that the analysis of the results of quantum mechanical calculations by chemoinformatics methods could vastly increase our chemical insight and knowledge. 

In this section we resume our examination of the equivalency of time and temperature in the determination of the mechanical properties of polymers. In the last chapter we had several occasions to mention this equivalency, but never developed it in detail. In examining this, we shall not only acquire some practical knowledge for the collection and representation of experimental data, but also shall gain additional insight into the free-volume aspect of the glass transition. 

The piezoelectric polymer investigations give new physical insight into the nature of the physical process in this class of ferroelectric polymers. The strong nonlinearities in polarization with stress are apparently more a representation of nonlinear compressibility than nonlinear electrical effects. Piezoelectric polarization appears to be linear with stress to volume compressions of tens of percent. The combination of past work on PVDF and future work on copolymers, that have quite different physical features promises to provide an unusually detailed study of such polymers under very large compression. 

T. Kohonen, K. Masisara, and T. Saramaki, Phonotopic Maps—Insightful Representation of Phonological Features for Speech Representation, Proceedings IEEE 7th International Conference, Montreal, Canada (1984). 

Sub-micro representations are used extensively in teaching the mole concept, stoichiometiy, solubihty and chemical equilibrium at UCT. Having students draw and annotate chemical diagrams representing chemical phenomena at the sub-micro level can provide some insight into their understanding of chemistiy at the macro level. The following examples are typical of the questions used to probe links between the sub-micro and symbohc levels of representations as part of the assessment practice for this course. For example, students were asked to balance the equation shown in Fig. 8.7. 

See, J.L. Leblanc, Insight into elastomer—filler interactions and their role in the processing behaviour of mbber compounds, Prog. Rubber Plast. TechnoL, 10/2, 110-129, 1994, for a pictorial representation of such a morphology. 

Molecular Graphics. The first contact many chemists have had with computer modeling is usually with computer graphic representations of chemicals. These pictures are providing much better insight as to the spatial relationships with and between molecules. CHEMLAB... 

Figure 3 (Plate 2). Representation of molecular structure in MD simulations. Shown here is the SOPC lipid, discussed in the text. The numbers at each atom indicate the partial charge on the atom. The space-filling picture on the left gives insight into the van der Waals radii of the various groups, and thus into the shape of the molecule. Reproduced from (58) with permission from the Biophysical Society...

The pairs of log and C that yielded quite acceptable representations of the data are shown by the symbols on Figure 7. The agreement between the symbols and the smooth curve in Figure 7 support the validity of the approach of Method II, and the insight that is gained from this approach. 

Richards s demand for an "explanation," not a representation, was a valid concern among chemists concerned with the practical implications in laboratory work of mathematical equations and theoretical speculations. Could one predict and plan chemical syntheses on the basis of knowing the reaction pathway, step by step and molecule by molecule And what triggered a chemical reaction What made a stable substance transform itself and assume a new identity Were there insights from experimental and theoretical physics which now could aid the chemistry of the late nineteenth century ... 

These solutions to the one-dimensional advection-diffusion model can be used to estimate reaction rate constants Ck) from the pore-water concentrations of S, if and s are known. More sophisticated approaches have been used to define the reaction rate term as the sum of multiple removals and additions whose functionalities are not necessarily first-order. Information on the reaction kinetics is empirically obtained by determining which algorithmic representation of the rate law best fits the vertical depth concentration data. The best-fit rate law can then be used to provide some insight into potential... 

A paper airplane and a plasticine car each represent models that might apply, say, in aerospace or automotive research and development. That each approximates the reality of actual aircraft and motor vehicles is intuitively obvious, yet it is immediately clear that neither suffices to explain the theory of their operation or to overcome production problems. Paper and plasticine and even fashion modehng provide types of media that appeal to visual appreciation but fail to provide deep understanding of fundamental issues. To overcome this lack, better media that allow for truer representation and insightful analyses are required. 

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