What is the limit of improvement the structure obtained directly from the liquid state, with possible heat treatment (supersaturation and aging)? This question was posed by casting engineers who put arbitrary requirements on reducing the DAS (Dendrite Arm Spacing) length to less than a dozen microns. The results of tests related to modification of the surface microstructure of AlSi7Mg alloy casting treated by laser beam and the rapid remelting and solidification of the superficial casting zone, were presented in the paper. The local properties of the surface treated with a laser beam concerns only a thickness ranging from a fraction to a single mm. These local properties should be considered in the aspect of application on surfaces of non-machined castings. Then the excellent surface layer properties can be used. The tests were carried out on the surface of the casting, the surface layer obtained in contact with the metal mould, after the initial machining (several mm), was treated by the laser beam. It turned out that the refinement of the microstructure measured with the DAS value is not available in a different way, i.e. directly by casting. The experimental-simulation validation using the Calcosoft CAFE (Cellular Automaton Finite Element) code was applied.

[n the paper the cationic equilibrium in the leaves of aquatic plants Nymphaea alba L. and Nuphar lutea (L.) Sibith. & Sm. was studied according lo Czarnowski method. Plant material was collected in 25 sites from littoral of fourteen eutrophic lakes of Pojezierze Leszczyńskie in West Poland. After the leaves had been cleaned, dryed and pulverized, the concentrations of N, P, K, Ca, Mg, Na, S, Fe, Sr, V, Cu, Cr, Mn, Ni, Cd, Al, Co, Pb, Zn, and Ba in them were determined. Next, the relative concentrations of the examined elements (concentration of each element in relation to the sum of all elements) and their relationships were calculated. The values of weighed sums of square roots of the relative cation concentrations in Nymphaea alba L. and Nuphar lutea (L.) Sibith. & Sm. varied from 13.2 to 13.8 and from 13.5 to 14.0, respectively. These values were higher than 12.5 given by Czarnowski because of high calcium and sodium concentrations. Significant positive correlations between relative concentrations of potassium and nitrogen, magnesium and zinc, cadmium and lead, iron and copper, iron and aluminium, aluminium and manganese, cadmium and manganese, cadmium and nickel, cadmium and zinc, as well as nickel and zinc were found, which proves the evidence for existence of synergism between these ions. However, substantial negative correlation between potassium and calcium testified to antagonism between these cations.

A sensing system utilizing a standard optical fiber as a distributed sensor for the detection and localization of mechanical vibrations is presented. Vibrations can be caused by various external factors, like moving people, cars, trains, and other objects producing mechanical vibrations that are sensed by a fiber. In our laboratory we have designed a sensing system based on the Φ-OTDR (phase sensitive Optical Time Domain Reflectometry) using an extremely narrow laser and EDFAs.

The Author discusses the communist period of Polish history as it is pictured in selected products of contemporary popular culture. The present paper is based on textual analysis of comic books on the history of PRL (the first ones which appeared after 1989) and hip-hop songs.