Comparison of different calibration methods for the determination by FT-NIR spectroscopy of the hydroxyl number in polyester resins

Different calibration methods have been applied for the determination of the Hydroxyl Number in polyester resins, namely Partial Least Squares (PLS), Principal Component Regression (PCR), Ordinary Least Squares with selection of the variables by genetic algorithm (OLS-GEN) and back-propagation Artificial Neural Networks (BP-ANN). The predictive ability of the regression models was estimated by splitting the dataset in training and test sets by application of the Kohonen self-organising maps. The linear methods (OLS-GEN, PLS and PCR) showed comparable results while artificial neural networks provided the best results both in fitting and prediction.     

Optimal location and design of a competitive facility

A single facility has to be located in competition with fixed existing facilities of similar type. Demand is supposed to be concentrated at a finite number of points, and consumers patronise the facility to which they are attracted most. Attraction is expressed by some function of the quality of the facility and its distance to demand. For existing facilities quality is fixed, while quality of the new facility may be freely chosen at known costs. The total demand captured by the new facility generates income. The question is to find that location and quality for the new facility which maximises the resulting profits.It is shown that this problem is well posed as soon as consumers are novelty oriented, i.e. attraction ties are resolved in favour of the new facility. Solution of the problem then may be reduced to a bicriterion maxcovering-minquantile problem for which solution methods are known. In the planar case with Euclidean distances and a variety of attraction functions this leads to a finite algorithm polynomial in the number of consumers, whereas, for more general instances, the search of a maximal profit solution is reduced to solving a series of small-scale nonlinear optimisation problems. Alternative tie-resolution rules are finally shown to result in problems in which optimal solutions might not exist.Mathematics Subject Classification (2000):90B85, 90C30, 90C29, 91B42Partially supported by Grant PB96-1416-C02-02 of the D.G.E.S. and Grant BFM2002-04525-C02-02 of Ministerio de Ciencia y Tecnología, Spain     

Observation of self-focusing of light mediated by cubic nonlinearities in potassium titanyl phosphate

We report our observations of the transient self-narrowing of light beams mediated by dominant Kerr nonlinearities and two-photon absorption in a bulk potassium titanyl phosphate crystal near conditions for second-harmonic generation. Drastic differences between upconversion and downconversion processes are highlighted.     

Signal analysis of behavioral and molecular cycles

Background  

Circadian clocks are biological oscillators that regulate molecular, physiological, and behavioral rhythms in a wide variety of organisms. While behavioral rhythms are typically monitored over many cycles, a similar approach to molecular rhythms was not possible until recently; the advent of real-time analysis using transgenic reporters now permits the observations of molecular rhythms over many cycles as well. This development suggests that new details about the relationship between molecular and behavioral rhythms may be revealed. Even so, behavioral and molecular rhythmicity have been analyzed using different methods, making such comparisons difficult to achieve. To address this shortcoming, among others, we developed a set of integrated analytical tools to unify the analysis of biological rhythms across modalities.     

Pyrene covalently anchored on a large external surface area zeolite as a selective heterogeneous sensor for iodide

Pyrene as a fluorophore has been covalently anchored on a delaminated ITQ-2 zeolite having a large external surface area (730 m2 g-1) and the resulting solid found to have a selective response as a heterogeneous sensor for I- in the presence of other halides.     

Oxidative coupling of platinum arylamides: temperature dependent C-H or C-F cleavage

The oxidation of an arylamido platinum complex leads to C-C coupling with selective C-H versus C-F bond cleavage depending on the reaction temperature.     

A synthetic receptor for choline and carnitine

A synthetic receptor is described with the appropriate shape and size for alkylated trimethylammonium ions such as choline and carnitine. The structure features a deep, concave binding site, lined with aromatic walls that provide cation-pi interactions between host and guest. Molecular mechanic calculations suggest that the host's shape is maintained through intermolecular hydrogen bonding with DMSO solvent molecules. The cavity is too small to accommodate larger ions. Choline and carnitine are recognized and bound with high affinity even though no complementary charges are involved in the process.     

A class of ABS algorithms for Diophantine linear systems

Summary. Systems of integer linear (Diophantine) equations arise from various applications. In this paper we present an approach, based upon the ABS methods, to solve a general system of linear Diophantine equations. This approach determines if the system has a solution, generalizing the classical fundamental theorem of the single linear Diophantine equation. If so, a solution is found along with an integer Abaffian (rank deficient) matrix such that the integer combinations of its rows span the integer null space of the cofficient matrix, implying that every integer solution is obtained by the sum of a single solution and an integer combination of the rows of the Abaffian. We show by a counterexample that, in general, it is not true that any set of linearly independent rows of the Abaffian forms an integer basis for the null space, contrary to a statement by Egervary. Finally we show how to compute the Hermite normal form for an integer matrix in the ABS framework. Received July 9, 1999 / Revised version received May 8, 2000 / Published online May 4, 2001