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Abstract

This paper gives a description of the head shield of Alona protzi, a rare species of Cladocera (water fleas) whose separated head shield has not yet been described in detail. Subfossil head shields of A. protzi were found in sediment cores taken from lakes in Denmark, Sweden, Finland, Estonia and Poland. Despite the rarity of the species this suggests a wide distribution of A. protzi in northern Europe. The ecology of A. protzi is poorly known. The environmental spectrum of the finding sites was wide and ranged from relatively nutrient poor clear water lakes to eutrophic turbid water lakes, indicating that A. protzi is not narrowly restricted. Most of the lakes were, however, meso-eutrophic with neutral to high pH, and with a relatively low abundance of submerged macrophytes. However, we cannot exclude the possibility that A. protzi mainly lives in groundwater and is only occasionally transported into lakes.

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Authors and Affiliations

Rikke Bjerring
Mirva Nykänen
Kaarina Sarmaja-Korjonen
Artem Sinev
Karina Jensen
Liisa Nevalainen
Krystyna Szeroczyńska
Edyta Zawisza
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Abstract

Climate deterioration of the Little Ice Age was manifested in the most spectacular way in the glaciated high mountains, but it should also be analysed in term of a climatic concept. Spatial variation in LIA climate is illustrated also in non-glaciated areas of the Northern Hemisphere in a broader contex. Extreme climatic events were forcing factors for mountain slope deformation by geomorphic processes in the High Tatra Mountains. The old chronicles, lichenometric dating of landforms and lacustrine sediments are used to determine the beginning of "Little Ice Age - type events" (about AD 1400) and its end (about AD 1920). During this time span the set of climatic conditions responsible for triggering high-energy geomorphic processes was recognised. The catastrophic hydrometeorological events were concentrated in certain periods. Clustering of weather anomalies and natural disasters resulting from them are discussed in the paper.
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Authors and Affiliations

Adam Kotarba
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Abstract

This paper extends knowledge about flow in an agitated batch with pitched blade multi-stage impellers. Effects of various geometrical parameters (blade number, distance between impellers) of pitched blade multi-stage impellers on pumping ability have been investigated. Axial velocity profiles were measured by LDA (Laser Doppler Anemometry). Axial pumping capacities were obtained by integration of measured axial velocity profiles in outflow from impellers. Main attention was focused on the effect of the distance between impellers in multi-stage configurations, on their pumping capacity and flow in the mixing bath in comparison with an independently operating pitched blade impeller with the same geometry. In case of a relatively close distance between impellers H3/d = 0.5 - 0.75, the multi-stage impeller creates only one circulation loop and the impellers itself behave identically as pumps in series. However for relative higher distance of impellers than H3/d = 1.25, the multi-stage impeller creates two separated circulation loops.

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Authors and Affiliations

Tomáš Jirout

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