Effect of Sb doping on phase transition and relaxor behaviour of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics

The effect of antimony dopant on phase transition, dielectric response and relaxor behaviour of (Pb_0.75Ba_0.25)(Zr_0.70Ti_0.30)O₃ ceramics was studied. Ceramic samples, with various Sb concentration from the range 1 to 4 at.%, were prepared by a conventional mixed oxide method. The crystal structure of the investigated ceramics was determined by an X-ray diffraction at room temperature that allowed to determine the unit cell parameters. Dielectric relaxation typical for ferroelectric relaxors was observed in the vicinity of diffuse ferroelectric–paraelectric phase transition. All parameters describing the relaxor behaviour determined from the Vogel–Fulcher relationship depend on the concentration of Sb dopant. The strong influence of antimony on grain structure and on remanent polarisation was confirmed as well.     

Ion-selective electrode for measuring low Ca2+ concentrations in the presence of high K+, Na+ and Mg2+ background

In this work, ion-selective electrodes for calcium ion were investigated. Two ionophores were used in the membranes: ETH 1001 and ETH 129. An internal filling solution buffered for primary ion was used that allowed the lower detection limit to be decreased down to 10^−8.8 M. Theoretical and experimental electrode characteristics pertaining to both primary and interfering ions are discussed. Better behavior was obtained with the electrode prepared with ETH 129 in the membrane. This electrode would be the most likely candidate for obtaining a low Ca²⁺ detection limit in measurements performed with high K⁺, Na⁺, Mg²⁺ background, which is found inside the cells of living organisms, for example. The potentiometric response of the electrode in solutions containing main and interfering ions is in good agreement with simulated curves obtained using the Nernst–Planck–Poisson (NPP) model.     

Watched guards in art galleries

The art gallery problem asks how many guards are sufficient to see every point of the interior of a polygon. A set of guards is called watched if each guard itself is seen by at least one of its colleagues. In 1994, Hernández-Pe?alver wrote that watched guards always suffice to guard any polygon with n vertices. However in 2001, Michael and Pinciu, and independently Żyliński, presented a class of polygons that required more than watched guards – which disproved the Hernández-Pe?alver’s result – and they established a new tight bound for watched guards: . Combinatorial bounds for watched guards in orthogonal polygons were independently given by Hernández-Pe?alver , and by Michael and Pinciu, who proved the -bound to be tight. In this paper, tight bounds for polygons of miscellaneous shapes are presented: watched guards for monotone and spiral polygons, and vertex watched guards for star-shaped polygons.     

Bernstein sets and κ ‐coverings

In this paper we study a notion of a κ ‐covering set in connection with Bernstein sets and other types of non‐measurability. Our results correspond to those obtained by Muthuvel in [7] and Nowik in [8]. We consider also other types of coverings (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Reactions of γ- ferrocenylallyl cations

The formation of γ-stable ferrocenylallyl cations which react with nucleophilic reagents yielding unrearranged products, was observed.     

Alpha decay of 114Ba

We measured for the first time the α decay of ¹¹⁴Ba. The results are discussed in comparison with theoretical predictions.