Liesegang Rings, Spirals and Helices

Dietrich, Sabine

doi:10.1007/978-3-030-05798-5_6

Cited by 2 publications

(2 citation statements)

References 24 publications

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“…For these structures, it has been suggested that episodically changing silica availability or varying calcite dissolution account for the formation of Liesegang-like concentric siliceous rings ( Hodges, 1932 ; Holdaway & Clayton, 1982 ). This similarity hints at genetic parallels, that is, reaction-diffusion processes ( Dietrich, 2019 ), which are likely linked with a gel-like state during early diagenesis.…”

Section: Discussionmentioning

confidence: 84%

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites

Klug

Silvestro²,

Hoffmann

et al. 2021

PeerJ

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Because of physiology of coleoids, their fossils preserve soft-tissue-remains more often than other cephalopods. Sometimes, the phosphatized soft-tissues, particularly parts of the muscular mantle, display dark circular patterns. Here, we showcase that these patterns, here documented for fossil coleoids from the Jurassic of Germany and the Cretaceous of Lebanon, superficially resemble chromatophores (which enable living coleoids to alter their coloration). We examined and chemically analyzed the circular structures in these specimens, describe them, and discuss their genesis. Based on their structure and color, we visually differentiate between three types of circles. By comparison with similar structures, we suggest that these structures are not biogenic but Liesegang rings, which formed due to reaction-diffusion processes very soon after death.

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Section: Discussionmentioning

confidence: 84%

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites

Klug

Silvestro²,

Hoffmann

et al. 2021

PeerJ

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“…Liesegang structures as radial concentric rings or tangential periodic bands ( n th zones), formed as a result of some ion-exchange precipitation reactions of chemical compounds in the absence of convection and mixing, are one of the examples of self-organization of molecular systems. − Such reactions are most often carried out inside a polymer hydrogel medium with a three-dimensional macromolecular network filled with a large amount of water (50–75% or higher), less often in a xerogel, airgel, or capillary. To date, periodic precipitation reactions have been studied for a wide range of chemical substances, a classification of their resulting periodic structures is given, and significant progress has been made in the theoretical understanding of this phenomenon; namely, main physicochemical mechanisms responsible for the formation of the structures observed are considered, theoretical approaches to their explanation are discussed, and phenomenological models are proposed to describe the formation of not only simple one-dimensional (1D) and two-dimensional Liesegang structures but also much more sophisticated, nontrivial ones (dislocations, helices, etc.…”

Section: Introductionmentioning

confidence: 99%

Formation of Liesegang Structures under the Conditions of the Spatiotemporal Reaction of Polymer-Analogous Transformation (Salt → Base) of Chitosan

et al. 2020

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This paper presents the results of our study of the diffusion front progression of OH − ions in the bulk of a flat layer of the salt chitosan form during the course of the chemical reaction of the polymer-analogous salt → base transformation, accompanied by the formation of a water-insoluble polymeric phase as a gel film with its structure of concentric rings or tangential bands. Using scanning electron microscopy and polarization microscopy, structural and morphological features of these periodic formations were visualized. Physicochemical parameters and spatiotemporal mass transfer characteristics were obtained. The process under study is shown to obey the classical laws of ion-exchange reactions, and the formation kinetics and the ratio of the positions of periodic structures are described by the laws characteristic of the Liesegang phenomenon. The average diffusion coefficients of hydroxide ions in the periodic formations calculated, considering the protonation degree of amino groups, were found to be no more than a decimal order of magnitude lower than those in an aqueous solution. This confirms the fact of swelling of the formed chitosan base and the existence of a gel film, in whose liquid phase diffusion occurs.

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Liesegang Rings, Spirals and Helices

Cited by 2 publications

References 24 publications

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites

Taphonomic patterns mimic biologic structures: diagenetic Liesegang rings in Mesozoic coleoids and coprolites

Formation of Liesegang Structures under the Conditions of the Spatiotemporal Reaction of Polymer-Analogous Transformation (Salt → Base) of Chitosan

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