(e, 3e) test on e-e correlations in helium

The angular variations of the five-fold differential cross section obtained by using different wave functions of helium are compared with experimental data. It is found that in the coplanar geometry two kinematical arrangements, (i) equal energy sharing between the two ejected electrons with one of them ejected along the momentum transfer direction and the other along varying direction and (ii) the Bethe ridge condition with fixed sum of ejected electron energies and varying angle between them, are very sensitive to e-e correlations contained in the target wave function. This comparison has been used to show that open-shell class of wave functions better incorporate e-e correlations than the closed-shell class.     

Development and Validation of a LC Method for the Analysis of Phenolic Acids in Turkish Salvia Species

An accurate, simple, reproducible, and sensitive method for determination of rosmarinic, caffeic, chlorogenic, and gallic acids in 12 Salvia species growing naturally in Anatolia, has been developed and validated. The phenolic acids were separated using a μBondapack C₁₈ column by gradient elution with a flow rate of 1.0 mL min⁻¹, which was adjusted to deliver firstly o-phosphoric acid 0.085% in water, 0.085% in methanol, and 0.085% in 2-propanol (80:10:10, v/v/v), then decreased gradually (60:20:20, v/v/v) during 20 min with a flow rate of 1.0 mL min⁻¹. The samples were monitored at 220 nm for gallic acid and 330 nm for rosmarinic, caffeic, and chlorogenic acids using photo-diode array detection. The linear range of detection for gallic, chlorogenic, caffeic, and rosmarinic acids were between 0.051–101.4, 0.207–103.6, 0.100–100, and 0.201–100.5 μg mL⁻¹, respectively. The linearity, range, peak purity, selectivity, system performance parameters, precision, accuracy, and robustness had also acceptable values. The developed method was applied to the flower, leaf, stem, and root parts of the Salvia species.

     

On-line preconcentration and determination of Au(III) in various environmental/industrial samples by flame atomic absorption spectrometry

A rapid and simple on-line method is described for the determination of Au(III) in various samples. The method is based on the sorption of gold(III) on Lewatit MonoPlus TP207 chelating resin including the iminodiacetate group, which is used as sorbent material and packed in a minicolumn. The chemical variables such as the pH of the sample solution, eluent type, interfering ions and concentrations of reagents, and instrumental variables such as sample loading volume, reagents flow rates, and tubing length, which affect the efficiency of the method were studied and optimised. Au(III) was sorbed on the chelating resin, from which it could be eluted with 3 mol L^?1 HCl, and then introduced directly to the nebuliser-burner system of FAAS. The limit of detection of the method was 0.2 µg L^?1 while the relative standard deviation was <4.0% for 20 µg L^?1 Au(III) concentration. The preconcentration factor was found to be 106 while the optimised sample volume was 15.3 mL. The accuracy of the method was verified by analysing the certified reference material. The developed method was applied successfully for the determination of gold in different samples with satisfactory results.     

Synthesis and Characterization of New Chelating Resin: Adsorption Study of Copper(II) and Chromium (III) Ions

Acrylamide based monomer, 5-methyl-2-thiozyl methacrylamide (MTMAAm) was synthesized by the reaction of 2-Amino-5-methyl thiazole with methacryloyl chloride in the presence of triethylamine(NR₃) at 0–5°C. The monomer MTMAAm was characterized by FT-IR and ¹H-and ¹³C-NMR spectral studies. A new chelating resin, poly(5-methyl-2-thiozyl methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinylbenzene) [MTMAAm/AMPS/DVB] was synthesized. This resin was characterized by FT-IR. In order to determine the adsorption behavior of chelating resin, the adsorption isotherm of Cr(III) and Cu(II) were studied. It was found that the adsorption isotherm of the ions fitted with Langmuir-type isotherms. From the Langmuir equation, the adsorption capacity of chelating resin for Cr(III) and Cu(II) was found to be 7.77 mg g^{? 1} and 4.27 mg g^{? 1}, respectively. Binding equilibrium constant was calculated to be 0.155 L mg^{? 1} and 0.106 L mg^{? 1} for Cu(II) and Cr(III), respectively.     

Lipase biosensor for tributyrin and pesticide detection

Potentiometric biosensors based on Candida rugosa lipase was described for the detection of organophosphorus pesticide; methyl-parathion and tributyrin. Lipase was immobilized on the glass electrode by means of a gelatin membrane, which is then cross-linked with glutaraldehyde. The principle of the biosensor is based on the measurement of pH variation which was recorded in millivolts due to the enzymatic hydrolysis of tributyrin to butyric acid. For the inhibitor detection, biosensor responses were measured after pesticide treatment, which caused a drop in enzyme activity because of the irreversible inhibition. Reactivation conditions of the reused enzyme electrodes were also investigated by pyridine-2-aldoxime methiodide (2-PAM). The limit of detection for tributyrin was estimated as 93?µM for lipase sensor within the linear range of 65–455?µM.     

Selective back-extraction and preconcentration of zinc(II) from metal-1,3,5-triketone extracts prior to its determination by flame atomic absorption spectrometry

A simple back-extraction method was developed for the separation and preconcentration of trace levels of zinc from different matrices. Ethyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (EMPC) was used as a new complexing agent for the extraction of zinc(II) from the aqueous sample phase to the methyl isobutyl ketone (MIBK) phase as Zn(EMPC)₂ complexes. The Zn(II) can be selectively stripped with 1?mL of 0.5?mol?L^?1 HCl from Mⁿ⁺(EMPC)_n complexes [Ag(I), Al(III), Cd(II), Cr(III), Cu(II), Fe(II), Fe(III), Mn(II), Ni(II), Pb(II) and Pd(II)] which dissolved in MIBK phase. Some experimental parameters, which are important for the whole extraction process, including pH, sample volume, shaking time, amount of the EMPC reagent, amount of MIBK, ionic strength, and type of back-extractant were investigated. The recovery for Zn(II) was greater than 95%. The detection limit of the method was found to be 0.2?µg?L ^{? 1} and the relative standard deviation as 6.4%. The concentrations of Zn(II) in the certified reference materials (LGC6019 river water and NIST-1547 peach leaves) by the presented method were in good agreement with the certified values. The proposed method was succesfully applied to the determination of zinc in some natural waters, rice, hair, soil, and tea samples.     

Stability and bifurcations analysis of a competition model with piecewise constant arguments

In this paper, we investigate local and global asymptotic stability of a positive equilibrium point of system of differential equations where t ≥ 0, the parameters r₁, k₁, α₁, α₂, r₂, k₂, and d₁ are positive, and [t] denotes the integer part of t ∈ [0, ∞ ). x(t) and y(t) represent population density for related species. Sufficient conditions are obtained for the local and global stability of the positive equilibrium point of the corresponding difference system. We show through numerical simulations that periodic solutions arise through Neimark–Sacker bifurcation. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of some trace metal ions in various samples by FAAS after separation/preconcentration by copper(II)-BPHA coprecipitation method

A separation/preconcentration procedure based on the coprecipitation of Pb(II), Fe(III), Co(II), Cr(III) and Zn(II) ions with copper(II)-N-benzoyl-N-phenyl-hydroxylamine complex (Cu-BPHA) has been developed. The analytical variables including pH, amount of BPHA, amount of copper(II) as carrier element, and sample volume were investigated for the quantitative recoveries of the elements. No interfering effects were observed from the concomitant ions when present in real samples. The recoveries of the analyte ions were in the range of 95–100%. The detection limits (3 s) for Pb(II), Co(II), Fe(III), Cr(III) and Zn(II) ions were found to be 2.3, 0.7, 0.7, 0.3 and 0.4 µg L^?1, respectively. The validation of the procedure was performed by the analysis of CRM (SRM NIST-1547 peach leaves and LGC6019 river water) standard reference materials. The method was applied to the determination of the analytes in real samples including natural waters, hair, urine, soil, sediment and peritoneal fluids samples etc., and good results were obtained (relative standard deviations <4%, recoveries >95%).     

Efficient adaptive regression spline algorithms based on mapping approach with a case study on finance

Multivariate adaptive regression splines (MARS) has become a popular data mining (DM) tool due to its flexible model building strategy for high dimensional data. Compared to well-known others, it performs better in many areas such as finance, informatics, technology and science. Many studies have been conducted on improving its performance. For this purpose, an alternative backward stepwise algorithm is proposed through Conic-MARS (CMARS) method which uses a penalized residual sum of squares for MARS as a Tikhonov regularization problem. Additionally, by modifying the forward step of MARS via mapping approach, a time efficient procedure has been introduced by S-FMARS. Inspiring from the advantages of MARS, CMARS and S-FMARS, two hybrid methods are proposed in this study, aiming to produce time efficient DM tools without degrading their performances especially for large datasets. The resulting methods, called SMARS and SCMARS, are tested in terms of several performance criteria such as accuracy, complexity, stability and robustness via simulated and real life datasets. As a DM application, the hybrid methods are also applied to an important field of finance for predicting interest rates offered by a Turkish bank to its customers. The results show that the proposed hybrid methods, being the most time efficient with competing performances, can be considered as powerful choices particularly for large datasets.     

Spectrophotometric determination of selenium(IV) with 4-methyl-<Emphasis Type="Italic">o</Emphasis>-phenylenediamine based on piazselenol formation

A method has been developed for the spectrophotometric determination of selenium(IV) using 4-methyl-o-phenylenediamine (MOPDA) as a chromogenic reagent. In hydrochloric acid media at about pH 2, MOPDA forms a piazselenol complex with selenium(IV), which gives an absorption maximum at 332 nm. After transfer of the formed piazselenol complex into organic phase with n-hexane, the absorbance of the piazselenol complex was measured by a UV-Vis spectrophotometer. The effective parameters of the experimental conditions such as pH, formation time of the complex, amount of MOPDA, ionic strength, volume of sample and effects of diverse ions, were investigated. The detection limit of the proposed method was found to be 0.95 μg/L Se(IV) (n = 14, 3σ). The method was successfully applied to tap water, sea water and wastewater samples from washings of flue gases with satisfactory results.