Evaluation of sorption of uranium onto metakaolin using X-ray photoelectron and Raman spectroscopies

Metakaolin prepared from a natural clay mineral ore of aluminium kaolinite is a promising low cost and high activity aluminosilicate material that has been investigated for studying the sorption behavior of uranium. Here, metakaolin was characterized using X-ray photoelectron spectroscopy (XPS) and the effects of pH, contact time and initial metal ion concentration on its sorption behavior were studied. The sorption process was found to initially be rapid (∼60% at time 0 min) but became slower with time; equilibrium was established within 24 h (∼80% sorption). The data were applied to study the kinetics of the sorption process. The Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms were used to describe partitioning behavior for the system at room temperature. The binding of metal ions was found to be pH dependent, with optimal sorption occurring at pH 5. The retained metal ions were eluted with 5 mL of 0.1 M HNO₃. Raman spectroscopy and XPS were used to evaluate the sorption mechanism of U(VI).     

Synthesis, structure and magnetic properties of chiral and nonchiral transition-metal malates

Carboxylate-bridged complexes of transition metals, M(II)=Mn(II), Fe(II), Co(II), Ni(II), Zn(II), were synthesised by reaction of M(II) salts with dl-malate and L-malate under hydrothermal conditions. These complexes form four series of compounds, which have been fully characterised structurally, thermally and magnetically. The crystal structures of the new chiral compounds, [Mn(L-mal)(H(2)O)] (1), [Fe(L-mal)(H(2)O)] (2), [Co(L-mal)(H(2)O)] (3) and [Zn(L-mal)(H(2)O)] (4) as well as those of the bimetallic analogues [Mn(0.63)Co(0.37)(L-mal)(H(2)O)] (5) and [Mn(0.79)Ni(0.21)(L-mal)(H(2)O)] (6) have been solved by single-crystal X-ray diffraction. The six L-malate monohydrates crystallise in the chiral space group P2(1)2(1)2(1) and consist in a three-dimensional network of metal(II) centres in octahedral sites formed by oxygen atoms. These structures were compared to those of the chiral trihydrate compounds [Co(L-mal)(H(2)O)]2 H(2)O (7), [Ni(L-mal)(H(2)O)]2 H(2)O (8) and [Co(0.52)Ni(0.48)(L-mal)(H(2)O)]2 H(2)O (9), which exhibit helical chains of M(II) centres, and those of dl-malate dihydrates [Co(dl-mal)(H(2)O)]H(2)O (10) and [Ni(dl-mal)(H(2)O)H(2)O (11) and trihydrate [Mn(L-mal)(H(2)O)]2 H(2)O (12) highlighting the great flexibility of the coordination by the malate ligand. UV/Vis spectroscopic results are consistent with octahedral coordination geometry of high-spin transition-metal centres. Extensive magnetic characterisation of each homologous series indicates rather weak coupling interaction between paramagnetic centres linked through carboxylate bridges. Curie-like paramagnetic, antiferromagnetic, ferromagnetic or weak ferromagnetic behaviour is observed and discussed on the basis of the structural features. The bimetallic compounds 5 and 6 represent new examples of chiral magnets.     

A validated spectrofluorometric assay for the determination of certain macrolide antibiotics in pharmaceutical formulations and spiked biological fluids

This paper describes a simple spectrofluorometric method for the analysis of 4 macrolide antibiotics. The method is based on the condensation of 10% (w/v) malonic acid and acetic acid anhydride under the catalytic effect of tertiary amine groups of the studied macrolides. The relative fluorescence intensity of the condensation product was measured at 397/452 nm (excitation/emission) for azithromycin dihydrate and at 392/445 nm (for clarithromycin, erythromycin ethylsuccinate, and roxithromycin. All variables affecting the reaction conditions were studied. The effects of potential interference due to common excipients, such as starch, lactose, sucrose, glucose, gum acacia, and magnesium stearate, as well as trimethoprim and sulfisoxazole acetyl formulated in primomycin capsules and pediazole oral suspension, respectively, were studied. A validation study for the proposed method was carried out according to U.S. Pharmacopeia 2002. The linearity ranges were 3-80 ng/mL for all of the cited macrolides. The limit of detection range was 0.74-1.20 ng/mL, while the limit of quantitation range was 2.47-4.02 ng/mL. The method was applied for the assay of the studied macrolides in pure pharmaceutical formulations and in spiked biological fluids. Results were compared with those obtained from the reported method, where calculated t- and F-values indicated high accuracy and good precision for the proposed method.     

Synthesis and X-ray crystal structure of pyrrolo[1,2-a]benzimidazoles

Reaction of nitrilimines 1 with 2-cyanomethylbenzimidazole 2 gave the 3-arylazo-2-methylpyrrolo[1,2-a]benzimidazole 4a rather than the reported 2-arylazo-3-methylpyrrolo[1,2-a]benzimidazole 3a. The correct structure of the product was determined using X-ray crystal structure analysis. The similar reaction of nitrilimines with 2-aminobenzimidazole 5 gave the acyclic nucleophilic addition product 6.     

Synthesis and Characterization of New Light Emitter Symmetrical Phenoxazinium Salt and Its Potential Application as Sensor for Assessment of Hg2+

The sensitization of the excited triplet state of a novel symmetrical Bis(dialkylamino)phenoxazinium salt was developed in the presence of Hg²⁺. This effect was used to determine the concentration of Hg²⁺ in different water samples. The phenoxazinium salt sensor was characterized by different spectroscopic tools such as: UV, FTIR, NMR and fluorescence spectra. The sensor has an emission band at 347 nm in DMSO. Hg²⁺ in DMSO at pH 5.6 can remarkably quench the fluorescence intensity of the sensor at 347 nm and a new band was appeared at 436 nm due to the strong complex formation between Hg²⁺ and sensor. The quenching of the band intensity at 347 and the enhancement of the intensity of the new band at 436 were used to determine the Hg²⁺ in different waste water samples. The dynamic range found for the determination of Hg²⁺ concentration is 8.7?×?10^-10 – 1.4?×?10^-6 mol L^?1 with a detection limit of 5.8?×?10^?10 mol L^?1 and quantification detection limit of 1.8?×?10^-9 mol L^-1.     

Hausdorff and Packing Spectra,Large Deviations,and Free Energy for Branching Random Walks in {\mathbb{R}^d}

Consider an \({\mathbb{R}^d}\) -valued branching random walk (BRW) on a supercritical Galton Watson tree. Without any assumption on the distribution of this BRW we compute, almost surely and simultaneously, the Hausdorff and packing dimensions of the level sets E(K) of infinite branches in the boundary of the tree (endowed with its standard metric) along which the averages of the BRW have a given closed connected set of limit points K. This goes beyond multifractal analysis, which only considers those level sets when K ranges in the set of singletons \({\{\alpha\}, \alpha \in \mathbb{R}^d}\) . We also give a 0–∞ law for the Hausdorff and packing measures of the level sets E({α}), and compute the free energy of the associated logarithmically correlated random energy model in full generality. Moreover, our results complete the previous works on multifractal analysis by including the levels α which do not belong to the range of the gradient of the free energy. This covers in particular a situation that was until now badly understood, namely the case where a first order phase transition occurs. As a consequence of our study, we can also describe the whole singularity spectrum of Mandelbrot measures, as well as the associated free energy function (or L ^q -spectrum), when a first order phase transition occurs.     

Total domination in inflated graphs

The inflation $G_I$ of a graph $G$ is obtained from $G$ by replacing every vertex $x$ of degree $d\left(x\right)$ by a clique $X=K_{d\left(x\right)}$ and each edge $xy$ by an edge between two vertices of the corresponding cliques $X$ and $Y$ of $G_I$ in such a way that the edges of $G_I$ which come from the edges of $G$ form a matching of $G_I$. A set $S$ of vertices in a graph $G$ is a total dominating set, abbreviated TDS, of $G$ if every vertex of $G$ is adjacent to a vertex in $S$. The minimum cardinality of a TDS of $G$ is the total domination number ${\gamma }_t\left(G\right)$ of $G$. In this paper, we investigate total domination in inflated graphs. We provide an upper bound on the total domination number of an inflated graph in terms of its order and matching number. We show that if $G$ is a connected graph of order $n\ge 2$, then ${\gamma }_t\left(G_I\right)\ge 2n/3$, and we characterize the graphs achieving equality in this bound. Further, if we restrict the minimum degree of $G$ to be at least $2$, then we show that ${\gamma }_t\left(G_I\right)\ge n$, with equality if and only if $G$ has a perfect matching. If we increase the minimum degree requirement of $G$ to be at least $3$, then we show ${\gamma }_t\left(G_I\right)\ge n$, with equality if and only if every minimum TDS of $G_I$ is a perfect total dominating set of $G_I$, where a perfect total dominating set is a TDS with the property that every vertex is adjacent to precisely one vertex of the set.     

General and multiplicative non-parametric corporate performance models with interval ratio data

The increasing intensity of global competition has led organizations to utilize various types of performance measurement tools for improving the quality of their products and services. Data envelopment analysis (DEA) is a methodology for evaluating and measuring the relative efficiencies of a set of decision making units (DMUs) that use multiple inputs to produce multiple outputs. All the data in the conventional DEA with input and/or output ratios assumes the form of crisp numbers. However, the observed values of data in real-world problems are sometimes expressed as interval ratios. In this paper, we propose two new models: general and multiplicative non-parametric ratio models for DEA problems with interval data. The contributions of this paper are fourfold: (1) we consider input and output data expressed as interval ratios in DEA; (2) we address the gap in DEA literature for problems not suitable or difficult to model with crisp values; (3) we propose two new DEA models for evaluating the relative efficiencies of DMUs with interval ratios, and (4) we present a case study involving 20 banks with three interval ratios to demonstrate the applicability and efficacy of the proposed models where the traditional indicators are mostly financial ratios.