scholarly journals Thermodynamic protonation constants of vardenafil by the nonlinear regression of multiwavelength pH-spectrophotometric titration data

2013 ◽  
Vol 11 (2) ◽  
pp. 271-279 ◽  
Author(s):  
Milan Meloun ◽  
Zuzana Ferenčíková ◽  
Irena Niesnerová ◽  
Tomáš Pekárek
Keyword(s):  
Factor Analysis ◽  
Nonlinear Regression ◽  
Goodness Of Fit ◽  
Computational Prediction ◽  
Spectrophotometric Titration ◽  
Protonation Constants ◽  
Chemical Structures ◽  
Goodness Of Fit Tests ◽  
Error Ratio ◽  
Titration Data

AbstractpH-spectrophotometric titration data were used to determine protonation constants of vardenafil at different ionic strengths I and temperatures of 25°C and 37°C. The use of two different multiwavelength and the multivariate treatment of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis is presented. The reliability of the protonation constants of the drug was proven with goodness-of-fit tests of the pH-spectra. The thermodynamic protonation constants log K Ti were estimated by a nonlinear regression of (log K, I) data using the Debye-Hückel equation, yielding log K 4T = 3.59(1) and 3.26(1), log K 3T = 5.64(1) and 5.81(1), log K 2T = 9.41(1) and 8.59(2), log K 1T = 10.92(2) and 10.05(1) at 25°C and 37°C, where the figure in brackets is the standard deviation in last significant digit. Concurrently, the experimental determination of four thermodynamic protonation constants was combined with the computational prediction of the MARVIN program based on knowledge of the chemical structures of the drug and was in good agreement with its experimental value. The factor analysis of spectra in the INDICES program predicts the correct number of light-absorbing components when the instrument error is known and when the signal-to-error ratio SER is higher than 10.

scholarly journals The thermodynamic dissociation constants of methotrexate by the nonlinear regression and factor analysis of multiwavelength spectrophotometric pH-titration data

2010 ◽  
Vol 8 (3) ◽  
pp. 494-507 ◽  
Author(s):  
Milan Meloun ◽  
Zuzana Ferenčíková ◽  
Aleš Vrána
Keyword(s):  
Factor Analysis ◽  
Nonlinear Regression ◽  
Goodness Of Fit ◽  
Dissociation Constants ◽  
General Rule ◽  
Computational Prediction ◽  
Ph Titration ◽  
Chemical Structures ◽  
Goodness Of Fit Tests ◽  
Titration Data

AbstractThe mixed dissociation constants of methotrexate — chemically (2S)-2-[(4-{[(2,4-diamino-7,8-dihydropteridin-6-yl)methyl] (methyl)amino}phenyl)formamido]pentanedioic acid (the cas number 59-05-2) at various ionic strengths I of range 0.01–0.4, and at temperatures of 25°C and 37°C, were determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis according to a general rule of first, determining the number of components, and then calculating the spectral responses and concentrations of the components. Concurrently, the experimental determination of the thermodynamic dissociation constants was in agreement with its computational prediction of the PALLAS programme based on knowledge of the chemical structures of the drug. The factor analysis in the INDICES programme predicts the correct number of light-absorbing components when the data quality is high and the instrumental error is known. Three thermodynamic dissociation constants were estimated by nonlinear regression of {pK a , I} data: for methotrexate pK a1T= 2.895(13), pK a2T= 4.410(14), pK a3T= 5.726(15) at 25°C and pK a1T= 3.089(15), pK a2T= 4.392(12), pK a3T= 5.585(11) at 37°C, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of the drug were proven by conducting goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.

scholarly journals The thermodynamic dissociation constant of naphazoline by the regression analysis of potentiometric data

2011 ◽  
Vol 9 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Milan Meloun ◽  
Zuzana Ferenčíková ◽  
Lucie Netolická ◽  
Aleš Vrána
Keyword(s):  
Regression Analysis ◽  
Dissociation Constant ◽  
Goodness Of Fit ◽  
Protonation Constant ◽  
Parameter Estimates ◽  
Regression Diagnostics ◽  
Goodness Of Fit Tests ◽  
Constant Determination ◽  
Titration Data ◽  
Computational Strategy

AbstractThe mixed dissociation constant of naphazoline is determined at various ionic strengths I [mol dm−3] in the range of 0.01 to 0.26 and at temperatures of 25°C and 37°C using ESAB and HYPERQUAD regression analysis of the potentiometric titration data. A strategy of efficient experimentation is proposed in a protonation constant determination, followed by a computational strategy for the chemical model with a protonation constant determination. Two group parameters, L 0 and H T were ill-conditioned in the model and their determination is therefore uncertain. These group parameters, L 0 and H T, can significantly influence a systematic error in the estimated common parameter pKa and they always should be refined together with pK a. The thermodynamic dissociation constant pK aT was estimated by nonlinear regression of {pK a, I} data at 25°C and 37°C: for naphazoline pK alT = 10.41(1) and 10.13(2). Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates to be found.

scholarly journals Reliability of protonation constants of vildagliptin dimers by the regression analysis of pH-titration data

2013 ◽  
Vol 11 (7) ◽  
pp. 1101-1111 ◽  
Author(s):  
Milan Meloun ◽  
Zuzana Ferenčíková ◽  
Irena Niesnerová ◽  
Tomáš Pekárek
Keyword(s):  
Regression Analysis ◽  
Systematic Error ◽  
Temperature Variation ◽  
Goodness Of Fit ◽  
Formation Constants ◽  
Protonation Constants ◽  
Parameter Estimates ◽  
Regression Diagnostics ◽  
Ph Titration ◽  
Titration Data

AbstractProtonation constants of protonated monomers and dimers of the vildagliptin are determined potentiometrically. For the low concentration c L = 3.3 mmol dm−3 the monomers L and LH dominate, while for a higher concentration c L = 6.3 mmol dm−3 the dimers L2H2, L2H3, L2H4 and L2H are mainly present. The algorithm used has little influence on the precision of the formation constants in comparison with the reproducibility of the titration. The mixed protonation constants of vildagliptin dimers Lq Hr at various temperatures are determined using FBSTAC4 and HYPERQUAD regression analysis of the potentiometric titration data. The accuracy of the protonation constants log10 βqr depends on the accuracy of the group parameters. As two group parameters L 0, H T are ill conditioned in a model, their determination is therefore uncertain; both can significantly cause a systematic error in the estimated common parameters log10 βqr . Using various regression diagnostics the goodness-of-fit proves the reliability of all parameter estimates. A rough estimation of thermodynamic enthalpies ΔH 0 (kJ mol−1) and entropies ΔS 0 (J K−1 mol−1) is determined from the temperature variation of protonation constants. The enthalpy shows the protonation process is exothermic, and the entropy indicates that it is spontaneous.

scholarly journals Translation and Validation of the Kaufman Domains of Creativity Scale on a Croatian Sample of Early Childhood and Preschool Education Students

2020 ◽  
Author(s):  
Marijana Županić Benić
Keyword(s):  
Factor Analysis ◽  
Early Childhood ◽  
Goodness Of Fit ◽  
Factor Model ◽  
Five Factor Model ◽  
Preschool Education ◽  
Education Students ◽  
Convenience Sample ◽  
Domain Specific ◽  
Goodness Of Fit Tests

The current literature describes creativity as a domain-specific phenomenon. According to Kaufman’s five-factor model, creativity can manifest in the following distinctive domains: Self/Everyday, Scholarly, Performance, Mechanical/Scientific and Artistic. The purpose of the present study was to validate the Croatian version of the Kaufman Domains of Creativity Scale. The scale was administered to a sample of early childhood and preschool education students (N = 222). The results of the exploratory factor analysis showed that certain Self/Everyday tasks did not load on any of the scales, whereas some music-related tasks separated from other Performance tasks into a separate factor. These results could be explained by the characteristics of the convenience sample recruited for the study. The confirmatory factor analysis of the five-factor model and goodness-of-fit tests yielded results that are as satisfactory and consistent as previous validations. The Kaufman Domains of Creativity Scale is therefore considered to be a potentially feasible scale for assessing creativity as a domain-specific phenomenon. Additional research is needed to confirm the validity of the Croatian version of the scale with a representative random sample.

Nonlinear regression approach to estimating Johnson SB parameters for diameter data

1999 ◽  
Vol 29 (3) ◽  
pp. 310-314 ◽  
Author(s):  
Kamziah Abd Kudus ◽  
M I Ahmad ◽  
Jaffirin Lapongan
Keyword(s):  
Maximum Likelihood ◽  
Nonlinear Regression ◽  
Goodness Of Fit ◽  
Estimation Method ◽  
Regression Method ◽  
Likelihood Method ◽  
Linear Regression Method ◽  
Goodness Of Fit Tests ◽  
Regression Approach ◽  
Nonlinear Regression Method

A nonlinear regression approach is proposed to estimate the parameters of the Johnson SB distribution. This method was compared to five other methods; these were the four percentile points method, the Knoebel-Burkhart method, the linear regression method, the maximum likelihood (Newton-Raphson) method, and the modified maximum likelihood method through simulation. The performance of the nonlinear regression method was also investigated by using the real diameter data collected from 20 even-aged sample plots of the Acacia mangium Willd. plantation in Sandakan, Sabah, measured annually from age 2 to 8 years. Goodness-of-fit tests based on empirical distribution function (namely the Kolmogorov-Smirnov statistic, Cramer - von Mises statistic, and the Anderson-Darling statistic) were used in selecting the most superior parameter estimation method. Results suggested that the nonlinear regression method was superior for estimating parameters of the Johnson SB distribution for diameter data in terms of bias, root mean square error, and goodness-of-fit tests.

Confirmatory Factor Analysis of the Long and Short Forms of the Worry Domains Questionnaire

2009 ◽  
Vol 25 (4) ◽  
pp. 239-243
Author(s):  
Roberto Nuevo ◽  
Andrés Losada ◽  
María Márquez-González ◽  
Cecilia Peñacoba
Keyword(s):  
Factor Analysis ◽  
Confirmatory Factor Analysis ◽  
Factor Structure ◽  
Goodness Of Fit ◽  
Factorial Validity ◽  
Fit Indices ◽  
Short Forms ◽  
Confirmatory Factor ◽  
Positive Correlations ◽  
Future Work

The Worry Domains Questionnaire was proposed as a measure of both pathological and nonpathological worry, and assesses the frequency of worrying about five different domains: relationships, lack of confidence, aimless future, work, and financial. The present study analyzed the factor structure of the long and short forms of the WDQ (WDQ and WDQ-SF, respectively) through confirmatory factor analysis in a sample of 262 students (M age = 21.8; SD = 2.6; 86.3% females). While the goodness-of-fit indices did not provide support for the WDQ, good fit indices were found for the WDQ-SF. Furthermore, no source of misspecification was identified, thus, supporting the factorial validity of the WDQ-SF scale. Significant positive correlations between the WDQ-SF and its subscales with worry (PSWQ), anxiety (STAI-T), and depression (BDI) were found. The internal consistency was good for the total scale and for the subscales. This work provides support for the use of the WDQ-SF, and potential uses for research and clinical purposes are discussed.

Sign in / Sign up

Export Citation Format

Share Document