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Wyszukujesz frazę "Silica Formation" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Multi-snail infestation of Devonian crinoids and the nature of platyceratid-crinoid interactions
Autorzy:
Baumiller, T K
Powiązania:
https://bibliotekanauki.pl/articles/20265.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
USA
Silica Formation
Devonian
platyceratid-crinoid interaction
biotic interaction
crinoid
snail
Middle Devonian
paleontology
Ohio
Opis:
The well−known association of platyceratid snails and crinoids typically involves a single snail positioned on the tegmen of the crinoid host; this has led to the inference of coprophagy. Two specimens of the camerate crinoid Arthroacantha from the Middle Devonian Silica Formation of Ohio, USA, exhibit numerous snails on their tegmens. On one of these, 6 platyceratid juveniles of approximately equal size are found on the tegmen. On the second crinoid, the largest of 7 infesting platyceratids occupies the typical position over the anal vent while others are either superposed (tiered) upon it or are positioned elsewhere on the tegmen. These specimens illustrate that platyceratids (1) settled on crinoids as spat, (2) were not strictly coprophagous during life yet (3) benefited from a position over the anal vent.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of lithium nitrate on the reaction between opal aggregate and sodium and potassium hydroxides in concrete over a long period of time
Autorzy:
Zapała-Sławeta, J.
Owsiak, Z.
Powiązania:
https://bibliotekanauki.pl/articles/200662.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
alkali-silica reaction
lithium nitrate
ettringite formation
expansion
SEM/EDS
azotan litu
ekspansja
Opis:
Alkali-silica reaction (ASR) is a reaction between amorphous or poorly crystallized siliceous phase, present in aggregates, and sodium and potassium hydroxides in the pore solution of concrete. Chemical admixtures such as lithium compounds are known to have high potential of inhibiting ASR. The aim of this study was to determine the effect of lithium nitrate on ASR in mortars containing high reactive opal aggregate over a long period of time. Mortar bar expansion tests were performed and microstructures of mortar bars were observed by scanning electron microscopy coupled with an energy dispersive X-ray microanalyser. Results from this study showed that effectiveness of lithium nitrate in mitigating ASR was limited over a long period of time. A larger amount of ASR gel which was formed in the presence of lithium nitrate indicated that the deterioration processes intensify within longer periods of time, which so far has not been observed in literature. Microscopic observation confirmed the presence of alkali-silica gel and delayed ettringite in mortars with lithium nitrate.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2017, 65, 6; 773-778
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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