D. González-Arjona

Authentication and differentiation of irish whiskeys by higher-alcohol congener analysis

Abstract Four higher alcohols, namely, 1-propanol, 2-methyl-1-propanol, 3-methyl-1-butanol and 2-methyl-1-butanol, selected as chemical descriptors, were determined by head space gas chromatography. Fifty eight samples of commercialized whiskeys consisting of 12 samples of irish whiskey, 20 samples of bourbon whiskey and 26 samples of single malt scotch whiskey were analyzed for their content in higher alcohols. The use of straightforward chemometric procedures showed that irish whiskeys are well characterized by the four higher alcohols and can be easily differentiated from other whiskeys.

Non-linear QSAR modeling by using multilayer perceptron feedforward neural networks trained by back-propagation

The use of multilayer perceptrons (MLP) feedforward neural networks trained by back-propagation (BP) for non-linear QSAR model building is presented and explained in detail through a case study. This method was compared with others often used in this field, such as multiple linear regression (MLR), partial least squares (PLS) and quadratic PLS (QPLS). The case study deals with a series of 18 alpha adrenoreceptors agonists belonging to three different classes (alpha-1, alpha-2 and alpha-1,2) according to their different pharmacological effects. Each of them is described by 15 chemical features (the X block). Six pharmacological responses were also measured for each one to build the matrix of biological responses (the Y block). The results obtained indicated a slightly better performance of MLP against the other procedures, when using the correlation coefficient of the observed versus predicted response plots as an indicator of the goodness of the fit.

Performing procrustes discriminant analysis with HOLMES.

Program HOLMES devised by target factor analysis has been updated for performing procrustes discriminant analysis (PDA). Computational details are outlined. The equivalence between PDA and partial least squares-discriminant analysis (PLS-DA) is established. Application of the PDA is illustrated by two case studies taken from literature.

Programmable microcomputer-controlled ramp generator for use in electrochemical experiments

Abstract In this article a microcomputer-controlled circuit for generation of linear analog waveforms for use in electrochemical experiments is proposed. The circuit permits the generation of complex waveforms, uses an inexpensive 8-bit D/A converter, and is adaptable to microcomputers with parallel I/O interface.

Holmes, a program for performing Procrustes Transformations

Abstract The program Holmes 2000, intended for performing Procrustes Transformations, like in Target Factor Analysis (TFA) and Procrustes Discriminant Analysis (PDA), is presented and described in terms of quality and performance for chemometric purposes.

Adaptation of linear discriminant analysis to second level-pattern recognition classification

Abstract Linear Discriminant Analysis (LDA) may be easily adapted to second level-pattern recognition by building hyperspherical boundaries around the class centroid in the discriminant space. Thus, a given test object may belong to one of the studied classes, to more than one class (when situated within overlapped class envelopes) or may be an outlier. In order to evaluate the performance of the adapted LDA, three reference data sets were processed and the results compared with other class-modelling techniques such as SIMCA and UNEQ.

Computational program for evaluating and optimizing response–surface curves based on uniform shell designs

A program for optimizing uniform shell designs, called DOEHLOPT, is proposed. The scope and features of DOEHLOPT are discussed and compared with those of a general purpose program (GOSSET). DOEHLOPT was applied to a worked example for the sake of illustration.

holmes: a program for target factor analysis

Abstract A computer program called holmes , written in QuickBasic for performing target factor analysis, is outlined. Chemical data taken from the literature were processed with holmes and the results were compared with the data obtained when using well-known programs like target90 .

Estimation of activity coefficients at different temperatures by using the mean spherical approximation

A method of estimating activity coefficients for a variety of electrolytes at different temperatures is presented. The MSA approximation is used to calculate the activity coefficients from experimental data available in the literature. This strategy provides suitable results within a wide range of temperatures, electrolyte stoichiometries and concentrations of investigated solutions.

Advantages of target factor analysis against multiple linear regression methods for testing model equations in linear free energy relationships

The advantages of target factor analysis for checking model equations in linear free energy relationships are discussed. These are illustrated with several worked examples taken from the literature and processed with the HOLMES program.