Connectivity indices optimal

On the basis of data obtained the possibility of substrates distribution and their D-values prediction using the regressions which consider the hydrophobicity and stmcture of amines was investigated. The hydrophobicity of amines was estimated by the distribution coefficient value in the water-octanole system (Ig P). The molecular structure of aromatic amines was characterized by the first-order molecular connectivity indexes ( x)- H was shown the independent and cooperative influence of the Ig P and parameters of amines on their distribution. Evidently, this fact demonstrates the host-guest phenomenon which is inherent to the organized media. The obtained in the research data were used for optimization of the conditions of micellar-extraction preconcentrating of metal ions with amines into the NS-rich phase with the following determination by atomic-absorption method. 

D denotes the degrees of the atoms i and j of a molecular graph, and the sum goes over all adjacent atoms. The exponent was originally chosen by Randic to be -1/2 however, it has been used to optimize the correlation between the descriptor and particular classes of organic compounds. The connectivity index was later extended by Kier and Hall to applications with connected subgraphs [22],... 

Kier and Hall Index is a special form of the connectivity index that allows optimizing the correlation between the descriptor and particular classes of organic compounds. 

In combining QSPR with nonlinear optimization to perform the reverse engineering design of polymers with optimal balances of properties, Camarda and Maranas [14] adopted an approach based on the work described in this book and combined group contributions with connectivity index contributions to predict the properties. 

Accordingly to a study published in one of the classical papers [10], application of X = +0.25 and y = —0.95 in calculation of the optimal connectivity index ir(x,y) for correlation with normal boiling points of 21 sulfides gives considerable decrease of standard error, in comparison with the inflexible (0,0). 

In 1991 Randic introduced the variable vertex connectivity index [31] as an alternative approach to Kier and Hall s index for characterization of heterosystems in QSPR-QSAR studies. The main difference between both molecular descriptors is that the former index uses optimized vertex weights (degf) and the latter uses fixed vertex weights (deg,) ... 

The Optimal Variable Connectivity Index, Experimental and Calculated Boiling Points and Their Difference... 

The optimal variables found were the following for carbon, the optimal weight was 1.27 for chlorine, the optimal weight -0.235 for bromine, the optimal weight -0.653 and for iodine, the optimal weight was -0.8005. It is known from the early calculations with the variable connectivity index that small positive values for optimal weights have little influence on affecting bond contributions to the overall... 

Let revisit one illustration [33] involving the search for the optimal variable connectivity index for a set of 80 halo-alkanes, including only chlorine, bromine, and iodine compounds. In addition to differentiating between chlorine, bromine, and iodine in this particular work were discriminated also aliphatic carbon atoms (CJ, carbons forming cycles (C ), and carbons forming C=C bonds (C ), in all six variable parameters. The following optimal parameters were found ... 

A method to solve the problem is to determine in the Fourier space the connection between the logarithm of refractive index values and the amplitude reflection and transmission coefficients, represented as complex wavelength-dependent functions. The global minimum of thus obtained dependence is then determined. The solution is an inhomogeneous layer, further transformed into a two-material system and subsequently subjected to a new procedure of fine optimization. 

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