Search results for "regression"
showing 10 items of 2619 documents
Application of molecular topology in the prediction of new compounds with anti-trypanosomal cytotoxic activity
2021
La enfermedad de Chagas es una antropozoonosis parasitaria de transmisión mayoritariamente vectorial. Si bien afecta principalmente a América, constituye una de las mayores enfermedades desatendidas a nivel mundial. Solamente dos fármacos con un alto grado de toxicidad se encuentran disponibles para su tratamiento, por lo que es preciso aunar esfuerzos en pos del desarrollo de nuevas drogas antitripanosomales eficaces y con escasos efectos adversos. En este estudio, se aplicó la topología molecular para el desarrollo de un modelo QSAR capaz de predecir la actividad citotóxica antitripanosomal de un grupo de 39 compuestos. El modelo desarrollado mediante análisis lineal discriminante permiti…
Is there an environmental Kuznets curve for Spain? Fresh evidence from old data
2012
Abstract The information content of the environmental Kuznets curve (EKC) is subject to change over time and all the empirical modeling work that does not take into account the possible variations and instabilities may fail to explain the variations in the per-capita CO2 and per-capita income relationship. In this paper we consider the possibility that a linear cointegrated regression model with multiple structural changes would provide a better empirical description of the Spanish EKC during the period 1857–2007. Our methodology is based on instability tests recently proposed in Kejriwal and Perron (2008, 2010) as well as on cointegration tests developed in Arai and Kurozumi (2007) and Kej…
Getting discriminant functions of antibacterial activity from physicochemical and topological parameters.
2001
Linear discriminant analysis has been demonstrated to be a very useful tool in the selection and design of new drugs. Up to now we have used it through the search of a topological pattern of activity. In this work our goal is to calculate a complete set of physicochemical parameters using semiempirical (quantum chemical) calculations as well as topological indices (TIs) and try to find out any discriminant function for antibacterial activity through the combined use of both types of descriptors. The physicochemical parameters, such as heat of formation, HOMO, LUMO, dipole moment, polarizability, hyperpolarizability, PM3 generated IR vibrational frequencies, etc., were calculated using PM3 H…
13C NMR study on the methoxy carbon chemical shifts in chloro-substituted anisoles and guaiacols
1983
The 13C NMR chemical shifts of methoxy carbons in chlorinated anisoles and guaiacols have been measured for acetone-d6 solutions. Multiple linear regression analysis, and also ‘simple sum rule’ calculations, have been used to estimate the effects of the chlorine atoms (the position and degree of substitution) on the chemical shifts. The most important effects have shown to be due to the chlorine atoms adjacent to the methoxy and hydroxy substituents. For chlorinated guaiacols, the greatest effect is due to the chlorine atom adjacent to the methoxy group. For chlorinated anisoles, the substituents adjacent to the methoxy group (2,6-disubstitution) cause large effects. For both groups of comp…
Using regression analysis method to model and optimize the quality of chip-removing processed metal surfaces
2017
The paper aim is to identify based on regression analysis, the quantitative relationship between the cutting process parameters (cutting speed, cutting depth and feed per tooth) and the arithmetic mean deviation of the surface profile, measured longitudinally and transversely on the cutting feed direction, which describe the system at any point in the chosen experimentally studied range. The equations coefficients means the influence of the variables on the pursued answer.
Prediction of acute toxicity of organophosphorus pesticides using topological indices
2007
Topological indices were used in the prediction of the acute toxicity (intraperitoneal and oral LD(50)) of organophosphorus pesticides on rats. Models with six variables for the prediction of LD(50)-i.p. (r = 0.849, Q(2) = 0.613) and eight variables for LD(50)-oral (r = 0.906, Q(2) = 0.701) were selected. External group and cross-validation by use of leave-n-out tests were also performed in order to assess the stability and the prediction performance of the selected topological models.
Analysis of the sensitivity to the systematic error in least-squares regression models
2004
An algorithm that calculates the sensitivity to the systematic error of the fitted parameters of a least-squares regression model, with respect to the known parameters, is developed. The algorithm can be applied to mechanistic and empirical models, obtained by linear and non-linear regression, including principal component and partial least-squares. It can be useful in identifying those parameters or calibration regions that can influence other parameters and the response mostly, and thus, whose accuracy should be particularly procured. Other applications are the weighing of experimental points and the comparison of different models and regression methods in terms of its ability of amplifyi…
A comparative study of the application of the method of least-squares in the potentiometric determination of protonation constants.
1982
Methods of simple and multiple linear regression applied to the potentiometric determination of protonation constants of diprotic and triprotic acids are studied critically. The best way of fitting the data, according to the order of magnitude of the constants, is established. The conclusions are checked by calculating the protonation constants of succinic and citric acids.
Direct determination of minerals in human diets by infrared spectroscopy and X-ray fluorescence
2014
The use of near and mid infrared spectroscopy and X-ray fluorescence (XRF) to determine the concentration of mineral elements in Spanish human diets was investigated. Thirty-five commercial baby foods, 6 children fast food menus and 13 university canteen menu samples were analysed by infrared and XRF spectroscopy and spectra evaluated by using reference data obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES). Models for calcium, potassium, iron, magnesium, sodium and zinc determination were built and validated. Spectra were pre-treated by using different pre-processing algorithms (multiplicative scatter correction, standard normal variation, first derivate, ortho…
Evaluation of infrared spectroscopy as a screening tool for serum analysis
2013
Abstract The application of attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy to the determination of clinical parameters in serum using partial least squares (PLS) has been evaluated as a point-of-care diagnostic tool. In this study the effect of using an increased size of the calibration set and the influence of the origin of samples and their interyear variation on the prediction capability of the method were considered. PLS-ATR-FT-IR provides a green, fast and cheap point-of-care tool for the determination of total protein. Albumin, glucose, urea, HDL, LDL and total cholesterol were predicted with relative errors between 15 and 32%. The analytical predicti…