Search for Relationship

This involves the retrieval of physico-chemical and pharmacological properties with respect to a specific stmcture such as melting point, boiling point, log P, pAra, QSAR, QSPR etc. The logP (o/w) of the following stmcture is retrieved as (Fig. 1.41)  

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A variety of methods have been developed by mathematicians and computer scientists to address this task, which has become known as data mining (see Chapter 9, Section 9.8). Fayyad defined and described the term data mining as the nontrivial extraction of impHcit, previously unknown and potentially useful information from data, or the search for relationships and global patterns that exist in databases [16]. In order to extract information from huge quantities of data and to gain knowledge from this information, the analysis and exploration have to be performed by automatic or semi-automatic methods. Methods applicable for data analysis are presented in Chapter 9. 

Ozone and ozone precursor concentrations at nonurban locations in the eastern United States were studied extensively. The three parts of the study were field measurements, a quality assurance program, and an airborne monitoring program. The main objective of the study was to establish a data base for nonurban ozone and precursor concentrations. Simultaneous statistical summaries of the concentrations of nitrogen dioxide and nonmethane hydrocarbons were also provided. Another objective was to search for relationships between ozone concentrations and nitrogen dioxide and nonmethane hydrocarbon concentrations. 

The search for relationships among the dynamic and equilibrium properties of related series of compounds has been a paradigm of chemists for many years. The discovery of such unifying principles and predictive relationships has practical benefits. Numerous relationships exist among the structural characteristics, physicochemical properties, and/or biological qualities of classes of related compounds. Perhaps the best-known attribute relationships are the correlations between reaction rate constants and equilibrium constants for related reactions commonly known as linear tree-energy relationships (LFERs). The LFER concept led to the broader concepts of QSARs, which seek to predict the environmental fate of related compounds based on correlations between their bioactivity or physicochemical properties and structural features. For example, therapeutic response, environmental fate, and toxicity of organic compounds have been correlated with... 

Based on the experimental evidences discussed in sect. 3.6.4 of an effect of the ligand onto the lifetime, numerous publications have appeared that refer to the Forster s theory (De Sa et al., 1993 Beeby et al., 1999 Supkowski and Horrocks, 1999 An et al., 2000). However, this theory is not applied in order to derive the transfer rate constant or the mean interaction distance value but only to justify the search for relationships between the observed decay rate and the number of OH, CH or NH bonds of the ligand, plus a global parameter for the solvent. Thus, although based on a very different theoretical approach, one deals with equations similar to eq. (11), with more terms, as in the following example (Beeby et al., 1999) ... 

In the first comparative exercise, 44 compounds from different chemical classes were selected (Tennant et al., 1990). An analysis of the results of the comparative exercise is provided by (Benigni, 1997). Table 8.3 reports the main features of the participating approaches. Most of the systems that participated in the comparative exercise were SAR or QS AR approaches other approaches searched for relationships between carcinogenesis and shorter-term biological events (activity-activity relationships [AARs]). 

Group contribution methods search for relationships between structural properties and a physico-chemical or biological response based on the following models ... 

The quantitative property-activity models, commonly referred to as marking the beginning of QSAR/QSPR studies [Richet, 1893], have come from the search for relationships between the potency of local anesthetics and the oil/water partition coefficient [Meyer, 1899], between narcosis and chain length [Overton, 1901 Overton, 1991], and between narcosis and surface tension (Traube, 1904). 

The central concept in plant systematica (as in the systematics of other organisms animals, fungi, prokaryotes) is that of relationship, Different kinds of plant taxonomists, engaged in different kinds of research, will subscribe to the statement that searching for relationships is an essential part of their activities. Plant systematics can, therefore, rightly be defined as the science of relationships between plants - or rathert between plant populations. 

Look to see that there is enough information to solve the problem. Search for relationships between the data and what is wanted. Write down any chemical equations that relate to the problem. What are the assumptions and limitations that come with the problem What principle(s) was the problem designed to illustrate ... 

They constitute the most important class of experimental measurements and play a fundamental role as —> molecular descriptors both for their availability as well as for their interpret-ability [Exner, 1966 Lyman, Reehl et al., 1982 Reid, Prausnitz et al, 1988 Horvath, 1992 Abraham, 1993c Baum, 1997 Lide, 1999 Reinhard and Drefahl, 1999]. Physico-chemical properties are used both as the molecular properties to be correlated with molecular structure in QSPR modeling and as the molecular descriptors when searching for relationships with biological activities. Physico-chemical properties are constitutive parts of volume descriptors, —> electric polarization descriptors, spectra descriptors, chromatographic descriptors, and so on. Combinations of physico-chemical properties are largely used in the definition of environmental indices. Other important physico-chemical properties are the so-called technological properties useful to characterize materials. 

The limitations of modem experimental physico-chemical methods in the direct and detailed study of the monomer insertion in the polymer chain on the one hand, and the large amount of information about the dependence of the macromolecules primary structure on the reaction conditions on the other hand should be taken into account. Consequently, it seems that the only real path of the search for relationships between the electronic aspects of the reaction and the observed microstructural statistics of polymers is the heuristic method of formulation of definite rules. It is most suitable for carrying out an adequate formulation of these imaginary discoveries in the framework of an axiomatic approach. 

We have considered the fundamental principles of thermodynamics and reaction kinetics. Now we would like to search for relationships between stability, as defined by thermodynamics, and reactivity, which is described by kinetics. Reaction potential energy diagrams are key tools in making these connections. 

There is a rational belief about the logical inferences, which are not numerical but linguistically changeable as new knowledge and information enter the discussion domain of the problem. However, the fuzzy nature of logical thinking and search for relationship between causative and consequent elements do not cease... 

The search for relationships between molecular structure and chemical reactivity, presented in Chapter 7, was instrumental for the development of chemical kinetics in the beginning of the twentieth century. One of the early successes in this area was the relationship suggested by Brbnsted and Pedersen for the acid catalysis. 

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