Extraction and determination of hexavalent chromium in soil samples

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l⁻¹ was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO₄. The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.     

Tb3Sc2Al3O12-TbScO3 eutectic self-organized microstructure for metamaterials and photonic crystals application

Eutectics are the materials with foreseen application in the field of photonic crystals and metamaterials. In this paper, the dependence on chemical composition of the microstructures of terbium-scandium-aluminium gamet and terbium-scandium perovskite (Tb₃Sc₂Al₃O₁₂-TbScO₃) eutectics has been studied. The growth of the eutectic rods by the micro-pulling down method is presented, using compositions with several different volume fractions of the garnet and the perovskite phases, V_TSAG:V_TSP = 4, 3, 2, 1, 1/2. The phases have been characterized by powder X-ray diffraction and energy dispersive spectrometry. The relationship between the lattice constant of individual phases and the chemical composition is presented. The unidirectional growth of microrods has been also investigated by electron backscattering diffraction.     

The formyl fluoride photochemical laser: photochemistry and energy content of the HF photoelemination product

Photolysis (λ > 1650 Å) of formyl fluoride (HFCO) leads to HF infrared laser emission. The energy content of the HF photoelemination primary product is only a small fraction (≈ 7%) of the available excess energy. Fluorine atoms may also be produced as primary photochemical products.     

Ψ-density topology

We study the notion of ψ-density point and ψ-density topologies for non-decreasing continuous functions ψ. Also basic properties of ψ-approximately continuous functions are considered.     

Synthesis and reactivity of bis(cycloamidinium-2-yl)alkane bromide tribromides,brominating agents and tectons for molecular engineering

Bis(cycloamidine-2-yl)alkanes easily form bromide tribromide salts in the reduction-oxidation processes with bromine. Bis(tetrahydroimidazolium-2-yl)ethane and bis(hexahydropyrimidinium-2-yl)-ethane bromide tribromides are such new convenient brominating agents for aromatic amides in chemo- and regioselective electrophilic substitutions and α-bromination reactions. Correspondence: Katarzyna Ostrowska, Department of Organic Chemistry, Jagiellonian University, R. Ingardena 3, PL-30060 Kraków, Poland.     

Interval methods of Adams-Bashforth type with variable step sizes

Numerical Algorithms - In a number of our previous papers, we have proposed interval versions of multistep methods (explicit and implicit), including interval predictor-corrector methods, in which...     

RBF–DQ algorithms for elliptic problems in axisymmetric domains

Numerical Algorithms - A radialbasis function (RBF)–differentialquadrature (DQ) method is applied for the numerical solution of elliptic boundary value problems (BVPs) in three-dimensional...     

A Parallel Algorithm for Multiple Objective Linear Programs

This paper presents an ADBASE-based parallel algorithm forsolving multiple objective linear programs (MOLPs). Job balance,speedup and scalability are of primary interest in evaluatingefficiency of the new algorithm. The scalability of a parallelalgorithm is a measure of its capacity to increase performance withrespect to the number of processors used. Implementation results onIntel iPSC/2 and Paragon multiprocessors show that the algorithmsignificantly speeds up the process of solving MOLPs, which isunderstood as generating all or some efficient extreme points andunbounded efficient edges. The algorithm is shown to be scalable andgives better results for large problems. Motivation andjustification for solving large MOLPs are also included.     

In situ Raman imaging of astaxanthin in a single microalgal cell

Raman imaging is shown to be a highly selective and sensitive method of studying in situ and in vivo astaxanthin distribution, concentration and molecular structure in the cyst form of the unicellular microalgae Haematococcus pluvialis.