Crystal growth and properties of Ln2Ag1−xGa10−y (Ln=La, Ce), a disordered variant of the Ce2NiGa10-structure type

We report the flux growth and characterization of Ln₂Ag_1−xGa_10−y (Ln=La, Ce), a disordered variant of the Ce₂NiGa₁₀ structure type. Single crystals of La₂Ag_1−xGa_10−y (x∼0.3; y∼0.6) and Ce₂Ag_1−xGa_10−y (x∼0.3; y∼0.9) were grown by the self-flux method and characterized using single-crystal X-ray diffraction. Transport measurements of Ce₂Ag_1−xGa_10−y (x∼0.3; y∼0.9) reveal metallic behavior with a transition at 3 K. Magnetic measurements indicate antiferromagnetic ordering at 3 K of localized Ce³⁺ moments for Ce₂Ag_1−xGa_10−y. Magnetoresistance is positive with a maximum value of 16% at 9 T. La₂Ag_1−xGa_10−y exhibits metallic behavior with magnetic susceptibility showing temperature independent paramagnetism. We will compare Ce₂Ag_1−xGa_10−y (x∼0.3; y∼0.9) to Ce₂NiGa₁₀ to examine the effects of transition metal substitution and to the related Ce(Ag,Ga)₄ phase to examine the effects of crystal structure on the physical properties.     

Hydrogen production in the radiolysis of bromide solutions

The radiolysis of water without a protecting agent is found to form a low steady-state concentration of molecular hydrogen. The addition of bromide anion leads to a linear response for molecular hydrogen production with doses up to 300 kGy. Bromide concentrations are found to remain constant over this dose range due to recycling of the oxidized species containing the bromine atom by hydrated electrons, H atoms or HO₂ (O₂⁻). This process appears to occur many times with little change in total bromide anion concentration. Efficient electron scavengers are found to have no effect on bromide anion concentration except possibly at extremely high concentrations. Nitrous oxide saturated solutions show a significant depletion of bromide anion concentration with a concurrent formation of BrO₃⁻ and a suppressed yield of molecular hydrogen.     

A grasp-knapsack hybrid for a nurse-scheduling problem

This paper is concerned with the application of a GRASP approach to a nurse-scheduling problem in which the objective is to optimise a set of preferences subject to a set of binding constraints. The balance between feasibility and optimality is a key issue. This is addressed by using a knapsack model to ensure that the solutions produced by the construction heuristic are easy to repair. Several construction heuristics and neighbourhoods are compared empirically. The best combination is further enhanced by a diversification strategy and a dynamic evaluation criterion. Tests show that it outperforms previously published approaches and finds optimal solutions quickly and consistently.     

Bounds for indecomposable torsion-free modules

Let M be a finitely generated torsion-free module over a one-dimensional reduced Noetherian ring R with finitely generated normalization. The rank of M is the tuple of vector-space dimensions of M_P over each field R_P (R localized at P), where P ranges over the minimal prime ideals of R. We assume that there exists a bound N_R on the ranks of all indecomposable finitely generated torsion-free R-modules. For such rings, what bounds and ranks occur? Partial answers to this question have been given by a plethora of authors over the past forty years. In this article we provide a final answer by giving a concise list of the ranks of indecomposable modules for R a local ring with no condition on the characteristic. We conclude that if the rank of an indecomposable module M is (r,r,…,r), then r∈{1,2,3,4,6}, even when R is not local.     

A comparative investigation of the presence of psychological conditions in high achieving eighth graders from TIMSS 2007 Mathematics

This study is a second analysis of Trends in International Mathematics and Science Study (TIMSS) 2007 background questionnaires to investigate high achieving eighth-grade students’ possession of three elements of Krutetskii’s (The Psychology of Mathematical Abilities in Schoolchildren, The University of Chicago, 1976) psychological conditions. Analyses were made between high achieving eighth graders and their lower achieving counterparts, and between Korean high achievers and their high achieving peers across ten high performing TIMSS participating countries. After reviewing 44,643 students across selected countries, we conclude that a larger percentage of students with mathematical talent demonstrate positive attitudes toward mathematics, value mathematics, and have self-confidence in their ability to learn mathematics than their peers without high achievement in mathematics. However, a larger portion of high achieving Korean students displayed low self-confidence and valued mathematics less than their peers from other high performing countries. Findings from this study will provide insight into some educational issues in science, technology, engineering and mathematics education.     

Synthesis of 7-alkoxy-4-trifluoromethylcoumarins via the von Pechmann reaction catalyzed by molecular iodine

The synthesis of a series of 7-alkoxy-4-trifluoromethylcoumarins via the von Pechmann reaction catalyzed by molecular iodine is described. The reaction protocol is simple, inexpensive and leads to the formation of the corresponding coumarin derivatives in good yield and high purity. A key intermediate as well as several iodo byproducts were isolated.     

A novel approach for concurrent quantitation of glutathione,glutathione disulfide,and 2‐hydroxyethylated glutathione in lungs of mice exposed to ethylene oxide,using liquid chromatography–positive electrospray tandem mass spectrometry

Glutathione (GSH), glutathione disulfide (GSSG) and 2‐hydroxyethylated glutathione (HESG) are important biomarkers for exploring the genotoxicity mechanism of ethylene oxide (EO) or ethylene in vivo. A liquid chromatography–tandem mass spectrometry method was developed for simultaneous determination of GSH, GSSG and HESG in mouse lung tissues after inhalation exposure to EO. The lower limit of quantitation for all these biomarkers was 0.002 µg/mL. The linearity of the calibration curves for all analytes was >0.998. The intra‐day assay precision relative standard deviation (RSD) values for quality control samples for all analytes were ≤12.8% with accuracy values ranging from 87.2 to 113%. The inter‐day assay precision (RSD) values for all analytes were ≤13.1% with accuracy values ranging from 86.9 to 103%. This method was applied to concurrently determine the levels of GSH, GSSG and HESG in lung samples isolated from mouse after 4‐week inhalation exposure to EO at 0, 10, 50, 100 and 200 ppm. Copyright © 2015 John Wiley & Sons, Ltd.