Study of properties of complexes of SNAZOXS and Naphthylazoxine 6S with copper(II), zinc(II) and lead(II) ions in solution by non-linear regression of spectrophotometric data

1979 ◽  
Vol 44 (7) ◽  
pp. 2032-2063 ◽  
Author(s):  
Milan Meloun ◽  
Jan Pancl
Keyword(s):  
Linear Regression ◽  
Sulphonic Acid ◽  
Matrix Analysis ◽  
Computer Assisted ◽  
Conditional Stability ◽  
Molar Ratios ◽  
Spectrophotometric Methods ◽  
Non Linear ◽  
Spectrophotometric Data ◽  
Conditional Stability Constants

Complexation equilibria of two metallochromic indicators viz. 7-(4-sulpho-1-naphthylazo)-8-hydroxyquinoline-5-sulphonic acid (SNAZOXS) and 7-(6-sulpho-2-naphthylazo)-8-hydroxyquinoline-5-sulphonic acid (Naphthylazoxine 6S) with copper(II), zinc(II), and lead(II) ions have been studied by various spectrophotometric methods in 0.1M-NaClO4 medium at 25 °C. Number of the coloured complexes in solution, their stoichiometry, and their overall and conditional stability constants have been determined by computer-assisted non-linear regression of the curves of continuous variations, the curves of molar ratios, the absorbance-pH curves, the curves of corresponding solutions, and by regression matrix analysis of the spectra. Besides the yellow complexes ML and ML2 the orange protonated forms MLH and M(LH)2 have also been determined.

Complex-formation reactions of 7-(o-carboxyphenylazo)-8-hydroxyquinoline-5-sulphonic acid with copper(II) ions: An application in EDTA photometric microtitrations

1982 ◽  
Vol 47 (8) ◽  
pp. 2110-2120 ◽  
Author(s):  
Jaromíra Chýlková ◽  
Václav Říha ◽  
Stanislav Kotrlý
Keyword(s):  
Sulphonic Acid ◽  
Matrix Analysis ◽  
Molar Ratio ◽  
Ratio Method ◽  
Computer Assisted ◽  
Conditional Stability ◽  
Molar Ratio Method ◽  
Wide Ph Range ◽  
Ph Range ◽  
Conditional Stability Constants

Colour reactions of 7-(o-carboxyphenylazo)-8-hydroxyquinoline-5-sulphonic acid (OKFAZOX) with various metal ions are described. The formation of copper(II) complexes has been studied spectrophotometrically within a wide pH range by molar ratio method using computer-assisted regression matrix analysis of the absorbance sets. The following complexes have been identified, in agreement with the results of non-linear regression of continuous variation plots, as predominating species: CuLH2 within pH 1.3-2.9; CuLH within pH 3-7. Then, between pH 7 and 10, the complexes CuL and CuL2 take part in a stepwise equilibrium. Relevant conditional stability constants have been determined. A new photometric EDTA microtitration of copper(II) using OKFAZOX as indicator is proposed with the following optimum arrangement: pH about 5 (acetate buffer) and ionic strength 0.01; indicator concentration approx. 5 μmol l-1 or slightly higher; absorbance followed at 510 nm. End-point extrapolation gives precise results even within micromolar range:e.g. 2 μmol l-1 Cu2+ can be determined with a relative error less than 2%.

Determination of dissociation constants of 7-(carboxyphenylazo)-8-hydroxyquinoline-5-sulphonic acids by nonlinear regression of spectrophotometric data

1979 ◽  
Vol 44 (9) ◽  
pp. 2815-2827 ◽  
Author(s):  
Milan Meloun ◽  
Jaromíra Chýlková
Keyword(s):  
Linear Regression ◽  
Nonlinear Regression ◽  
Dissociation Constants ◽  
Matrix Analysis ◽  
Absorption Coefficients ◽  
Non Linear ◽  
Spectrophotometric Data

Dissociation constants of three metallochromic indicators 7-(o-, m-, p-carboxyphenylazo)-8-hydroxyquinoline-5-sulphonic acids and values of molar absorption coefficients of the forms L3-, HL2-, H2L-, H3L have been determined in 0.1M-NaClO4 medium by non-linear regression of pH-absorbance curves by the program DCLET and by regression matrix analysis of the spectra by the program FA608 + EY608, respectively. All the three derivatives have been synthesized, purified, and their purity checked by chromatography.

Prediction of Surface Roughness and Optimization of Cutting Parameters in CNC Turning of Rotational Features

2020 ◽  
Vol 38 (8A) ◽  
pp. 1143-1153
Author(s):  
Yousif K. Shounia ◽  
Tahseen F. Abbas ◽  
Raed R. Shwaish
Keyword(s):  
Surface Roughness ◽  
Linear Regression ◽  
Regression Model ◽  
Linear Regression Model ◽  
Feed Rate ◽  
Cutting Parameters ◽  
Spindle Speed ◽  
Depth Of Cut ◽  
Non Linear ◽  
Optimization Of Cutting Parameters

This research presents a model for prediction surface roughness in terms of process parameters in turning aluminum alloy 1200. The geometry to be machined has four rotational features: straight, taper, convex and concave, while a design of experiments was created through the Taguchi L25 orthogonal array experiments in minitab17 three factors with five Levels depth of cut (0.04, 0.06, 0.08, 0.10 and 0.12) mm, spindle speed (1200, 1400, 1600, 1800 and 2000) r.p.m and feed rate (60, 70, 80, 90 and 100) mm/min. A multiple non-linear regression model has been used which is a set of statistical extrapolation processes to estimate the relationships input variables and output which the surface roughness which prediction outside the range of the data. According to the non-linear regression model, the optimum surface roughness can be obtained at 1800 rpm of spindle speed, feed-rate of 80 mm/min and depth of cut 0.04 mm then the best surface roughness comes out to be 0.04 μm at tapper feature at depth of cut 0.01 mm and same spindle speed and feed rate pervious which gives the error of 3.23% at evolution equation.

Spectrophotometric study of the interaction of Chromazurol S and Eriochromazurol B with surface active substances - tensides

1981 ◽  
Vol 46 (5) ◽  
pp. 1090-1106 ◽  
Author(s):  
Irena Burešová ◽  
Vlastimil Kubáň ◽  
Lumír Sommer
Keyword(s):  
Critical Micellar Concentration ◽  
Spectrophotometric Study ◽  
Conditional Stability ◽  
Acid Base ◽  
Binary Complexes ◽  
Chromazurol S ◽  
Acid Base Equilibrium ◽  
Poorly Soluble ◽  
Conditional Stability Constants ◽  
Triton X

The acid-base and optical properties of Chromazurol S and Eriochromazurol B in the presence of 1 . 10-6 - 2 . 10-2M solutions of cetylpyridinium bromide, cetyltrimethylammonium bromide and 1-ethoxycarbonylpentadecyltrimethylammonium bromide (Septonex) and 0.001-1.0% w/v solutions of octylphenolpolyethylene glycol ether (Triton X-100), polyoxyethylenemonolauryl ether (Brij 35) and lauryl sulphate sodium salt were determined by graphical and numerical interpretation of absorbance curves. The poorly soluble ion associates, which can be extracted into chloroform and which have the defined composition [LH4-nn-.n T+] or [LH3-nn-.n T+] are formed at submicellar concentration of the tenside. In regions close to the critical micellar concentration of the tenside, soluble binary complexes of the acid-base forms of the reagent are formed with tenside micelles. The conditional stability constants of the reagent acid-base equilibrium depend on the type and concentration of the tenside, on the reagent concentration, on the concentration and type of inorganic acid anions and on the ionic strength of the solution. The mechanism of interaction of the reagent with the tenside and the probable structure of the binary species are discussed.

scholarly journals Is There a Relationship between the Elasticity of Brain Tumors, Changes in Diffusion Tensor Imaging, and Histological Findings? A Pilot Study Using Intraoperative Ultrasound Elastography

2021 ◽  
Vol 11 (2) ◽  
pp. 271
Author(s):  
Santiago Cepeda ◽  
Sergio García-García ◽  
María Velasco-Casares ◽  
Gabriel Fernández-Pérez ◽  
Tomás Zamora ◽  
...  
Keyword(s):  
Brain Tumor ◽  
Diffusion Tensor Imaging ◽  
Linear Regression ◽  
Brain Tumors ◽  
Diffusion Tensor ◽  
Intraoperative Ultrasound ◽  
Ultrasound Elastography ◽  
Proliferation Index ◽  
Strong Positive Correlation ◽  
Non Linear

Intraoperative ultrasound elastography (IOUS-E) is a novel image modality applied in brain tumor assessment. However, the potential links between elastographic findings and other histological and neuroimaging features are unknown. This study aims to find associations between brain tumor elasticity, diffusion tensor imaging (DTI) metrics, and cell proliferation. A retrospective study was conducted to analyze consecutively admitted patients who underwent craniotomy for supratentorial brain tumors between March 2018 and February 2020. Patients evaluated by IOUS-E and preoperative DTI were included. A semi-quantitative analysis was performed to calculate the mean tissue elasticity (MTE). Diffusion coefficients and the tumor proliferation index by Ki-67 were registered. Relationships between the continuous variables were determined using the Spearman ρ test. A predictive model was developed based on non-linear regression using the MTE as the dependent variable. Forty patients were evaluated. The pathologic diagnoses were as follows: 21 high-grade gliomas (HGG); 9 low-grade gliomas (LGG); and 10 meningiomas. Cases with a proliferation index of less than 10% had significantly higher medians of MTE (110.34 vs. 79.99, p < 0.001) and fractional anisotropy (FA) (0.24 vs. 0.19, p = 0.020). We found a strong positive correlation between MTE and FA (rs (38) = 0.91, p < 0.001). A cubic spline non-linear regression model was obtained to predict tumoral MTE from FA (R2 = 0.78, p < 0.001). According to our results, tumor elasticity is associated with histopathological and DTI-derived metrics. These findings support the usefulness of IOUS-E as a complementary tool in brain tumor surgery.

scholarly journals Non-Parametric Generalized Additive Models as a Tool for Evaluating Policy Interventions

Mathematics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 299
Author(s):  
Jaime Pinilla ◽  
Miguel Negrín
Keyword(s):  
Linear Regression ◽  
Regression Models ◽  
Linear Trend ◽  
Generalized Additive Models ◽  
Additive Models ◽  
Linear Regression Models ◽  
Non Linear ◽  
Nonlinear Trends ◽  
The Impact ◽  
Non Parametric

The interrupted time series analysis is a quasi-experimental design used to evaluate the effectiveness of an intervention. Segmented linear regression models have been the most used models to carry out this analysis. However, they assume a linear trend that may not be appropriate in many situations. In this paper, we show how generalized additive models (GAMs), a non-parametric regression-based method, can be useful to accommodate nonlinear trends. An analysis with simulated data is carried out to assess the performance of both models. Data were simulated from linear and non-linear (quadratic and cubic) functions. The results of this analysis show how GAMs improve on segmented linear regression models when the trend is non-linear, but they also show a good performance when the trend is linear. A real-life application where the impact of the 2012 Spanish cost-sharing reforms on pharmaceutical prescription is also analyzed. Seasonality and an indicator variable for the stockpiling effect are included as explanatory variables. The segmented linear regression model shows good fit of the data. However, the GAM concludes that the hypothesis of linear trend is rejected. The estimated level shift is similar for both models but the cumulative absolute effect on the number of prescriptions is lower in GAM.

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