O-Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed-Valence Complexes

Herein we report an efficient synthesis to prepare O-doped nanographenes derived from the π-extension of pyrene. The derivatives are highly fluorescent and feature low oxidation potentials. Using electrooxidation, crystals of cationic mixed-valence (MV) complexes were grown in which the organic salts organize into face-to-face π-stacks, a favorable solid-state arrangement for organic electronics. Variable-temperature electron paramagnetic resonance (EPR) measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar π-stacking architectures. Electric measurements of single crystals of the MV salts show a semiconducting behavior with a remarkably high conductivity at room temperature. These findings support the notion that π-extension of heteroatom-doped polycyclic aromatic hydrocarbons is an attractive approach to fabricate nanographenes with a broad spectrum of semiconducting properties and high charge mobilities.     

The exponential image of simple complex lie groups of exceptional type

Let G be a connected reductive complex Lie group. Let E _G be the image of the exponential map of G and E' _G its complement in G. We give a purely algebraic characterization of the set E _G and also describe an algorithm for finding all conjugacy classes of G in E' _G . We are mainly interested in the case when the Lie algebra of G is simple and exceptional. Full details are provided for groups G of type G ₂, F ₄, and E ₆. If G is of type G ₂ then there are only two such conjugacy classes.This work was supported by NSERC Grant A-5285.     

Turyn‐Type Sequences: Classification,Enumeration, and Construction

Turyn‐type sequences, , are quadruples of ‐sequences , with lengths , respectively, where the sum of the nonperiodic autocorrelation functions of and twice that of is a δ‐function (i.e., vanishes everywhere except at 0). Turyn‐type sequences are known to exist for all even n not larger than 36. We introduce a definition of equivalence to construct a canonical form for in general. By using this canonical form, we enumerate the equivalence classes of for . We also construct the first example of Turyn‐type sequences .     

Silicothermic reduction process in magnesium production

In this paper there are presented the results of the characterization and thermal analysis of the slag from the magnesium plant ‘Bela Stena’, Serbia. The results of X-ray fluorescence analysis, scanning electron microscopy (SEM), optical microscopy (LOM) and X-ray diffraction (XRD) were used for chemical and mineralogical analysis of the solidified slag samples. Differential thermal analysis (DTA), thermo-gravimetric (TG) analysis and thermal microscopy results were used for determination of characteristic phase transformations. The solidified slag shows dicalcium silicate based structure. Magnesium is mostly present in the form of the following minerals: periclase, merwinite and melilite.     

Computers in mathematical research: the study of three-point root-finding methods

Numerical Algorithms - This paper is motivated by results of extensive comparative study of three-point methods for solving nonlinear equations presented in the paper (C. Chun, B. Neta, Comparative...     

Critical behaviour of an amorphous ferromagnet close to the percolation threshold

A detailed study of the magnetisation, electrical resistivity and ac magnetic susceptibility of the amorphous Fe₃Ni₇₇B₁₈Si₂ alloy has been performed. This alloy is ferromagnetic with the Curie temperature T_c = 19,5 K. Critical exponents δ = 4,9 and α = ?0,51 were obtained from the experiment while γ = 1,66 and β = 0,43 were calculated from the scaling relations. However the effective critical exponent γ ¹ deduced from the initial magnetic susceptibility exhibits a non-monotonic variation with temperature reaching a maximum of about 1.8 around 43 K. The results are discussed in terms of recent theoretical predictions.     

Braided Clifford Algebras as Quantum Deformations

We present a general algebraic framework for the study of quantum/braided Clifford algebras. We allow that the quadratic form g on the base vector space takes values from a noncommutative algebra . Clifford algebra is understood as a Chevalley—Kähler deformation of the braided exterior algebra built from V, , and the initial braid operator : . The new product is canonically associated to g, , and , and it is constructed by applying Rota's and Stein Cliffordization.     

Determination of selected pesticides in environmental water by employing liquid-phase microextraction and liquid chromatography–tandem mass spectrometry

An optimised extraction and cleanup method for the analysis of pesticide in natural water samples is presented. Sixteen pesticides of different polarity and from the different chemical classes (organophosphates, triazines, benzimidazoles, carbamates, carbamides, neonicotinoides, methylureas, phenylureas and benzohydrazides), most frequently used in Serbia, were selected for the analysis. Liquid-phase microextraction in a single hollow fibre (HF-LPME) has been applied for sample preparation. The concentrations of pesticides were determined using HPLC-MS/MS method with electrospray ionisation. The extraction behaviour and selection of the experimental conditions was predicted based on log D and pK _a values of targeted pesticides, which were calculated applying the computer software ACD/Labs PhysChem Suite v12. The influence of the donor pH and concentration of pesticides, organic phase composition as well as the extraction time on the extraction efficiency was investigated. Optimum extraction conditions were evaluated with respect to the investigated parameters of the extraction. The extraction method was validated for 10 out of 16 studied pesticides. Linear range of the pesticides was 0.1–5 μg L⁻¹ with the correlation coefficient from 0.991 to 0.9998, and the relative standard deviation for three standard measurements was between 0.2 and 11.8%. The limits of detections ranged from 0.026 to 0.237 μg L⁻¹ and the limits of quantifications from 0.094 to 0.793 μg L⁻¹. The optimised two-phase HF-LPME method was successfully applied for determination of moderately polar as well low-polar pesticides in the environmental water samples.