Signal-levelling agents for eliminating the interferences of iron,aluminium, barium and calcium in the determination of lead by flame atomic absorption spectrometry

The interferences of iron, aluminium, barium and calcium on the determination of lead by flame atomic absorption spectrometry are discussed; a titration procedure was used. Ascorbic acid, citric acid, EDTA and nitric acid were used successfully for levelling the interfering effects from the cations.     

Spectrophotometric microdetermination of copper(II), silver(I), and gold(III) using azastyrene Schiff bases

A new method for the spectrophotometric microdetermination of Cu(II), Ag(I), and Au(III) using β-2-hydroxybenzyl-5-bromo- (I_a), 5-chloro- (I_b), and 3-methoxy-2-hydroxyazastyrene (I_c) is given. The optimum conditions favoring the formation of the colored complexes are extensively studied. The molecular structure was found to be (1:1) and (1:2) (M:L). Beer's law is obeyed up to 5.00, 8.64, and 11.82 ppm for Cu(II), Ag(I), and Au(III), respectively, while the optimum concentration ranges using the Ringbom method are 0.6–5.00, 1.00–8.60, and 2.00–11.80 ppm for the same metal ions, respectively.     

Export Performance and Export Policy: Evidence from the U.K. Clothing Industry

This paper examines the relationship between a number of export policy measures and the export sales performance of a sample of companies in the U.K. clothing industry. Policy measures are used first in a discriminant analysis of above- and below-average exporters and, second, to explain a multi-dimensional measure of export performance using canonical correlation. The "jack-knife" technique is used to test the stability of these analyses.     

Fireworks algorithm framework for Big Data optimization

This paper presents a novel optimization framework based on the Fireworks Algorithm for Big Data Optimization problems. Indeed, the proposed framework is composed of two optimization algorithms. A single objective Fireworks Algorithm and a multi-objective Fireworks Algorithm are proposed for solving the Big Optimization of Signals problem “Big-OPT” which belongs to the Big Data Optimization problems class. The single objective Fireworks Algorithm adopts a modified search mechanism to ensure rapidity and preserve the explorative capacities of the basic Fireworks Algorithm. Afterward, the algorithm is extended to handle multi-objective optimization of Big-OPT with a supplementary special sparks phase and a novel strategy for next generation selection. To validate the performance of the framework, extensive tests on six EEG datasets are performed. The framework is also compared with several approaches from recent state of the art. The study concludes the competitive performance of the proposed framework in comparison with the other techniques reported in this paper.     

The new one‐dimensional coordination polymer catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐[diaquairon(III)]‐μ‐oxalato]

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one‐, two‐ or three‐dimensional extended structures. Yellow single crystals of a new mixed‐metal oxalate, namely catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′‐[diaquairon(III)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′], [NaFe(C₂O₄)₂(H₂O)₄]_n, have been synthesized and the crystal structure elucidated by X‐ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space group I4₁ (Z = 4). The asymmetric unit contains one Na^I and one Fe^III atom lying on a fourfold symmetry axis, one μ₂‐bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one‐dimensional chains of alternating FeO₄(H₂OW1)₂ and NaO₄(H₂OW2)₂ octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of the cis configuration and the μ₂‐coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H₂O and oxalate ligands, leading to a two‐dimensional framework. The structure of this new one‐dimensional coordination polymer is shown to be unique among the A^IM^III(C₂O₄)₂(H₂O)_n series. In addition, the absorption bands in the IR and UV–Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well‐known ternary oxide NaFeO₂.     

Influence of Discretization Step on Asymptotic Stability of a Certain Class of Two-dimensional Continuous-discrete Fractional Linear Systems

The effectiveness of this paper lies in the influence of the discretization step on the asymptotic stability of the positive two-dimensional fractional linear systems. It aims at investigating whether, how and when this step affects the asymptotically stable two-dimensional positive fractional linear continuous-discrete systems. To accomplish this study, a new test was outlined and used so that the asymptotic stability of the system was measured both before and after being exposed to the samplin...     

Minimality of invariant submanifolds in metric contact pair geometry

Annali di Matematica Pura ed Applicata (1923 -) - We study invariant submanifolds of manifolds endowed with a normal or complex metric contact pair with decomposable structure tensor $$\phi $$ ....