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Povaha toku modelových suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The main object of the present investigation is to test the settling abilities of mixtures of solid particles in liquids. The key quantity here is the magnitude of the viscosity, both of the carrying liquid (water-glycerol solutions) and the effective viscosity of the two-phase mixture. Few model systems were used (glass and polystyrene pellets), to study the settling process. The sedimentation were recorded by a video camera and the resulting deposit structure was photographed. Besides, also a real suspension was tested, of geological materials (calcite, quartz, mixed geological powder, etc.). Immersion rotary viscometer Brookfield with special spindles (RVT and V spindles) was used to measure the effective viscosity of the dispersion.
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Viskozitní charakteristiky geologických suspenzí
Kulaviak, Lukáš ; Večeř, Marek ; Růžička, Marek ; Drahoš, Jiří ; Hladil, Jindřich
The system under study was real geological suspension – ground sedimentary rocks of different chemical composition (calcite, quartz, etc.) dispersed in water-glycerol solutions. The reference one-phase system was a Newtonian liquid (glycerine with water). It is problematic to measure the rheology of settling suspensions, so some specific tools must be used. We used the rotating vane rheometry, with the immersion viscometer Brookfield and two spindles V-71 and V-72. The basic rheological data of solid-liquid system are displayed as flow and effective viscosity curves. The obtained results on rheology were related to the settling behaviour of the geological mixtures, namely to the certain kind of the lateral instability.
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The earliest growth stages of amphiporids and archaeocyaths - a comparison
Hladil, Jindřich
The initial growth stages of amphiporids and archaeocyaths are mutually similar to identical. They both consist of (1) rudimentary bottom disc (covered by small tubercles or septum-like bulges), (2) first chamber, (3) smooth first tube and (4) an interval with relatively rapid metamorphosis to complex adult morphologies. Probably no sponges can produce such an earliest skeletal formation that consists of the first chamber and tube, both resembling an external wall, because the typical sponge gemmules usually produce a number of cells that expand laterally very fast, forming a soft network, and it is a very different process. The great degree of similarity between the earliest growth stages of amphiporids and archaeocyaths suggests that there was a sharply separated group of "archaeocyathid-amphiporid" organisms (working name "Amphicyathida"), which was different from other corals, sponges or stromatoporoids.
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Report on research in the San Salvador Island, Bahamas
Bosák, Pavel ; Hladil, Jindřich ; Slavík, Ladislav ; Melka, Karel ; Venhodová, Daniela ; Chadima, Martin ; Hercman, H. ; Nowicki, T.
Contact of two cycles at shallow carbonate platform shows traces of karstification, formation of soils and important changes of geochemistry (U, Th, K, Fe) and magnetic susceptibility.
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