Europium-doped calcium pyrophosphates : allotropic forms and photoluminescent properties

In a search for new luminescent biological probes, we synthesized calcium pyrophosphates doped with europium up to an atomic Eu/(Eu+Ca) ratio of 2%. They were prepared by coprecipitating a mixture of calcium and europium salts with phosphate. After heating at 900°C in air, two phases coexisted, identified as the β calcium pyrophosphate form and EuPO4. Heating near 1250°C in air, during the β→ transformation, europium ions substitute for calcium ions in the * calcium pyrophosphate structure as demonstrated by the spectroscopic study. Europium ions with both valence states (divalent and trivalent) were observed in the samples. Following the synthesis procedure, partial reduction of Eu3+ took place even in an oxidizing atmosphere. The 0.5%-doped compound could serve as a sensitive probe in biological applications. Depending on the excitation wavelength, the luminescence occurs either in the red or in the blue regions, which discriminates it from parasitic signals arising from other dyes or organelles in live cells

Методи за двумерно пропорционално разпределение

Михаил Константинов, Костадин Янев, Галина Пелова, Юлиана Бонева - В работата се разглеждат двумерни пропорционални изборни системи, при които броят на партийните мандати се определя на национално ниво, а персонификацията на мандатите става чрез регионални партийни листи. При това, броят на мандатите във всеки район се определя пропорционално на населението. Предложени са нови подобрени методи за двумерно разпределение и са представени резултати от числени пресмятания с данните от парламентарните избори през 2009 г.The paper deals with 2D proportional (or bi-proportional) electoral systems in which the number of party mandates is determined at a nation wide level while the personification of mandates is done through regional party lists. In addition, the number of mandates in each region is preliminary determined proportionally to the population. Variants of such systems have been used in seven parliamentary elections in Bularia during the period 1990–2009. These systems as well as new improved 2D apportionment methods are considered. Results from numerical simulations with data rom the 2009 Bulgarian parliamentary elections are given. * 2000 Mathematics Subject Classification: Primary 91B12, Secondary 91B14

Application of "The Water Layer Model" to self-compacting mortar with different size distributions of fine aggregate

Self-Compacting Concrete is a relatively new type of concrete. Up to now only a few models have been developed to explain its physical behaviour, like the Water Layer Model and the Excess Paste Model. In this paper, the difference between the Water Layer Model and the Excess Paste Model is highlighted, and the validity of the Water Layer Model to Self-Compacting Mortar with different characteristics of the sand is investigated. The results of this investigation show that the Water Layer Model is effective for the determination of the quantity of water. Furthermore the function of water and superplasticizer is explained using this model.Design and ConstructionCivil Engineering and Geoscience