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New results of 40Ar/39Ar dating constrain the timing of transition from fissure-type to central volcanism at Mount Etna (Italy) (2008)

De Beni, E. ; Wijbrans, J. R. ; Branca, S. ; [weitere]

Blackwell Publishing Ltd

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Publikationsdatum: 2017-04-04

Beschreibung: Recent geological studies performed at Etna allow reassessing the stratigraphic frame of the volcano where distinct evolutionary phases are defined. This stratigraphic reconstruction was chronologically constrained on the basis of a limited number of U–Th and K–Ar age determinations whose uncertainty margins are sometimes too wide. For this reason, we successfully adopted at Etna the 40Ar/39Ar technique that allowed obtaining more precise age determinations. The incremental heating technique also gives information on sample homogeneity, and potential problems of trapped argon. Five samples were collected from stratigraphically well-controlled volcanic units in order to chronologically define the transition between the fissure-type volcanism of the Timpe phase to the central volcanism of the Valle del Bove Centers. Isotopic ages with an uncertainty margin of 2–4% have been obtained emphasizing that this transition occurred (130– 126 ka) without significant temporal hiatus.

Beschreibung: University of Catania grants (COFIN- 2002, resp. F. Lentini); CNR-IDPA and INGV-Sezione di Catania grants.

Beschreibung: Published

Beschreibung: 292-298

Beschreibung: 3.5. Geologia e storia dei sistemi vulcanici

Beschreibung: JCR Journal

Beschreibung: reserved

Schlagwort(e): 40Ar/39Ar dating ; Etna ; 04. Solid Earth::04.04. Geology::04.04.99. General or miscellaneous

Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)

Materialart: article

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Entropy-driven formation of a chiral liquid-crystalline phase of helical filaments (2006)

Barry, Edward ; Hensel, Zach ; Dogic, Zvonimir ; [weitere]

American Physical Society

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Publikationsdatum: 2022-05-25

Beschreibung: Author Posting. © The Authors, 2006. This article is posted here by permission of American Physical Society for personal use, not for redistribution. The definitive version was published in Physical Review Letters 96 (2006): 018305, doi:10.1103/PhysRevLett.96.018305.

Beschreibung: We study the liquid-crystalline phase behavior of a concentrated suspension of helical flagella isolated from Salmonella typhimurium. Flagella are prepared with different polymorphic states, some of which have a pronounced helical character while others assume a rodlike shape. We show that the static phase behavior and dynamics of chiral helices are very different when compared to simpler achiral hard rods. With increasing concentration, helical flagella undergo an entropy-driven first order phase transition to a liquid-crystalline state having a novel chiral symmetry.

Beschreibung: M. S. and R. O. are supported by NIH Grant No. EB002583.

Schlagwort(e): Entropy ; Molecular biophysics ; Liquid crystal phase transformations ; Symmetry ; Chirality

Repository-Name: Woods Hole Open Access Server

Materialart: Article

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