Wpływ swobodnej energii powierzchniowej na właściwości tribologiczne warstw tlenkowych wytwarzanych na stopie aluminium EN AW-5251

This paper presents the influence of the parameters of the formation of oxide layers on the surface free energy and the tribological properties of these layers. The layers were formed electrochemically on aluminium alloy EN AW-5251, with variable values of electrolyte temperature and current density. A three-component electrolyte was used to produce oxide layers. The surface free energy was determined by the droplet deposition method by measuring the wetting angles, while the van Oss-Chaunhury-Good method was used for the calculations. Tribological tests were performed on a T-17 tribological tester under conditions of technically dry friction for reciprocating motion. T7W composite was used as a specimen in tribological tests.W artykule przedstawiono wpływ parametrów wytwarzania warstw tlenkowych na swobodną energię powierzchniową oraz właściwości tribologiczne tych warstw. Warstwy zostały wytworzone na stopie aluminium EN AW-5251 metodą elektrochemiczną, przy zmiennych wartościach temperatury elektrolitu oraz gęstości prądowej. Do wytwarzania warstw tlenkowych zastosowano elektrolit trójskładnikowy. Swobodna energia powierzchniowa wyznaczona została metodą osadzonej kropli poprzez pomiar kątów zwilżania, natomiast do obliczeń zastosowano metodę van Ossa-Chaunhury’ego-Gooda. Testy tribologiczne przeprowadzono na testerze tribologicznym T-17 w warunkach tarcia technicznie suchego dla ruchu posuwisto-zwrotnego. W testach tribologicznych jako próbki użyto kompozytu T7W

Efficiency of a 252Cf source in normal or in B-10 enriched lymphocytes evaluated by SCGE assay, classical cytogenetics and FISH technique

Biological effectiveness of a californium-252 source was evaluated after irradiations in vitro of normal or pretreated cells with compound enriched in the B-10 ion (Na210B12H11SH also known as BSH) in order to check the possibility of any enhancement effect due to the process of boron neutron capture. Peripheral blood lymphocytes were used as a model for human cells. Human blood samples or isolated lymphocytes were irradiated with the isotopic source of 252Cf, at the Faculty of Physics and Nuclear Techniques at the University of Mining and Metallurgy, Kraków, (both the neutron source and the samples were placed in an "infinite" polyethylene block). DNA and chromosomal damage were studied to compare the biological effectiveness of irradiation. Single cell gel electrophoresis also known as the Comet assay was done to investigate the DNA damage. Classical cytogenetic analysis was applied to assess the frequencies of unstable aberrations (dicentrics, rings and acentric fragments). To evaluate the frequencies of stable aberrations the fluorescence in situ hybridisation (FISH) with probes for chromosomes 1, 4 (14,3% of the whole genome) was performed. Linear (or close to linear) increases with radiation doses were observed for the DNA damage and aberration frequencies in lymphocytes both untreated or pretreated with BSH. Levels of translocations evaluated for the whole genome were comparable with the frequencies of dicentrics and rings. No significant differences were detected due to radiation dose in the frequencies of sister chromatid exchanges (SCE) detected in the second mitosis. Statistically no significant differences were observed in various biological end-points between normal or boron pre-treated cells

Variability of high rainfalls and related synoptic situations causing heavy floods at the northern foothills of the Tatra Mountains

This contribution provides the basics of the climatology of the Polish Tatra Mountains in a nutshell, with particular reference to intense precipitation and its relation to atmospheric circulation. Variability of various precipitation characteristics, including selected indices of intense precipitation in Zakopane and at Kasprowy Wierch, is illustrated in this paper. None of the trends in these characteristics and indices calculated for the entire time interval exhibit a statistical significance, but short-time fluctuations are evident. The occurrence of intense precipitation in the Tatra Mountains is strongly related to three circulation types. These situations (Nc, NEc, Bc) are associated with cyclones following track Vb after van Bebber. In addition to changing frequencies of circulation, this study also reveals an increase in the frequency of the circulation types associated with extreme precipitation

Decadal variability of floods in the northern foreland of the Tatra Mountains

Floods in the northern foreland of the Tatra Mountains considerably contribute to the total flood damage in Poland. Therefore, the question whether the magnitude and frequency of floods have changed in this region is of high interest. This study aims at investigating the inter-decadal variability of magnitude, frequency and seasonality of floods since the mid-twentieth century, to better understand regional changes. The analysis was accomplished in a multi-temporal approach whereby trends are fitted to every possible combination of start and end years in a record. Detected trends were explained by estimating correlations between the investigated flood parameters and different large-scale climate indices for the northern hemisphere, and by trends found in intense precipitation indices, number of days with snow cover, cyclonic circulation types, temperature and moisture conditions. Catchment and channel changes that occurred in the region over the past decades were also considered. Results show that rivers in the area exhibit considerable inter-decadal variability of flows. The magnitude and direction of short-term trends are heavily influenced by this inter-decadal variability; however, certain patterns are apparent. More extreme, although perhaps less frequent floods are now likely to occur, with a shift in the seasonality, decreasing flood magnitudes in winter and increasing during autumn and spring. The identification of the factors contributing to the occurrence of flood events and their potential changes is valuable to enhance the flood management in the region and to improve the resilience of the population in this mountainous area

Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project

The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness

Changes of flood risk on the northern foothills of the Tatra Mountains

The present paper reviews selected outcomes of the FLORIST project devoted to flood risk in the region of the northern foothills of the Tatra Mountains in Poland and summarizes novel results. The project encompassed theoretical, field, and modeling work. It was focused around observation-based hydroclimatology; projections for the future; dendrogeomorphology; as well as influence of transport of large wood on fluvial processes. The project improved understanding and interpreting changes in highflow frequency and magnitude as well as changes in flood risk in the region, related to the presence of large wood in mountain streams. A unique database on past episodes of intense precipitation and flooding was created, harnessing multiple sources. The project showed that the analysis of tree rings and wood logs can offer useful information, complementing and considerably enriching the knowledge of river floods in the region of northern foothills of the Tatra Mountains. Retrospective and scenario-defined modeling of selected past fluvial events in the region was also performed