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  • Author or Editor: Ł. Głowacki x
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The biodiversity and species richness of benthic macroinvertebrate assemblages are under the strong pressure of environmental variables compounded with geographical and historical processes. Numerous studies that have investigated biodiversity and assemblage stability have shown the importance of choosing proper methodologies and paradigms. Consequently, the use of diversity measures and the partitioning of biodiversity at different spatial and temporal scales are of particular significance. Within habitats, only those species whose preferences remain within a tolerable range of the variability of abiotic factors are able to survive. The structure of biocoenosis at the local scale is determined mainly by current velocity/discharge, granulometry of the inorganic bottom substrate, quantity and quality of particulate organic matter, as well as water quality variables. Dispersion plays a key role in shaping regional diversity gradients, which supports the permanent inflow of individuals and their exchange between riverine basins. However, dispersion is also one of the basic aspects of the saturation/non-saturation of local communities with species from the regional species pool; a respective concept tries to determine how, why and to what degree local species richness is dependent on regional species richness.

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Abstract

The pyrolysis of Y(CF3COO)3·nH2O at temperatures up to 1,000 °C, under flowing pure Ar, O2 and O2 saturated with water vapour, was extensively analysed. The formation of HF is observed directly and the existence of a :CF2 diradical is inferred during a trifluoroacetic acid salt decomposition. High resolution thermogravimetry, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy indicated that the exothermic one-stage decomposition of the anhydrate salt occurs at 267 °C, forming YF3. Fourier transform infrared spectroscopy identified (CF3CO)2O, CF3COF, COF2, CO2 and CO as the principal volatile species; and revealed the influence of water on the reactions liberating gaseous CF3COOH, CHF3, HF, and SiF4 (from reactions with glass or quartz components). NO2 and N2O evolution suggested that traces of CH3NO2 were present in the starting material. Thermogravimetry and X-ray diffractometry indicated that the slow hydrolysis of the fluoride occurs between 630 and 655 °C, forming a mixture of Y2O3, YOF, Y7O6F9, and YF3. The decomposition and hydrolysis temperatures are significantly lower than previously reported, which has implications for sol–gel processing.

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