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  1. Article: A Holstein–Peierls Approach to Excimer Spectra: The Evolution from Vibronically Structured to Unstructured Emission

    Bialas, April L. / Spano, Frank C.

    Journal of physical chemistry. 2022 Feb. 16, v. 126, no. 8

    2022  

    Abstract: The presence of excimers, as revealed by broad, structureless, and red-shifted emission, is quite common in a great many organic solution- and solid-phase systems. A fundamental theoretical account of excimer creation and relaxation has generated ... ...

    Abstract The presence of excimers, as revealed by broad, structureless, and red-shifted emission, is quite common in a great many organic solution- and solid-phase systems. A fundamental theoretical account of excimer creation and relaxation has generated enormous interest over the years. Here, a model based on a Holstein–Peierls Hamiltonian is presented to account for absorption and photoluminescence in molecular dimers. The model extends the Frenkel-charge transfer (CT)-Holstein model in order to account for both local and nonlocal coupling to a slow intermolecular vibrational mode. The model shows that excimer emission can be induced either through (1) local intermolecular coupling to the dimer CT states or through (2) the nonlocal Frenkel-CT coupling terms. Finally, by incorporating both the local and nonlocal intermolecular coupling, the measured absorption and excimer emission spectra for a set of two different bis(perylene diimide) covalently linked dimers are successfully reproduced. The evolution from structured to unstructured excimer emission likely occurs via an increase in the nonlocal coupling, but it can also be induced by the stabilization of the diabatic CT state.
    Keywords absorption ; chemical bonding ; models ; photoluminescence
    Language English
    Dates of publication 2022-0216
    Size p. 4067-4081.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.1c10255
    Database NAL-Catalogue (AGRICOLA)

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  2. Article ; Online: Mechano-Chemical Coupling in Hydra Regeneration and Patterning.

    Wang, Rui / Bialas, April L / Goel, Tapan / Collins, Eva-Maria S

    Integrative and comparative biology

    2023  Volume 63, Issue 6, Page(s) 1422–1441

    Abstract: The freshwater cnidarian Hydra can regenerate from wounds, small tissue fragments and even from aggregated cells. This process requires the de novo development of a body axis and oral-aboral polarity, a fundamental developmental process that involves ... ...

    Abstract The freshwater cnidarian Hydra can regenerate from wounds, small tissue fragments and even from aggregated cells. This process requires the de novo development of a body axis and oral-aboral polarity, a fundamental developmental process that involves chemical patterning and mechanical shape changes. Gierer and Meinhardt recognized that Hydra's simple body plan and amenability to in vivo experiments make it an experimentally and mathematically tractable model to study developmental patterning and symmetry breaking. They developed a reaction-diffusion model, involving a short-range activator and a long-range inhibitor, which successfully explained patterning in the adult animal. In 2011, HyWnt3 was identified as a candidate for the activator. However, despite the continued efforts of both physicists and biologists, the predicted inhibitor remains elusive. Furthermore, the Gierer-Meinhardt model cannot explain de novo axis formation in cellular aggregates that lack inherited tissue polarity. The aim of this review is to synthesize the current knowledge on Hydra symmetry breaking and patterning. We summarize the history of patterning studies and insights from recent biomechanical and molecular studies, and highlight the need for continued validation of theoretical assumptions and collaboration across disciplinary boundaries. We conclude by proposing new experiments to test current mechano-chemical coupling models and suggest ideas for expanding the Gierer-Meinhardt model to explain de novo patterning, as observed in Hydra aggregates. The availability of a fully sequenced genome, transgenic fluorescent reporter strains, and modern imaging techniques, that enable unprecedented observation of cellular events in vivo, promise to allow the community to crack Hydra's secret to patterning.
    MeSH term(s) Animals ; Hydra ; Models, Biological ; Body Patterning
    Language English
    Publishing date 2023-06-20
    Publishing country England
    Document type Review ; Journal Article
    ZDB-ID 2159110-6
    ISSN 1557-7023 ; 1540-7063
    ISSN (online) 1557-7023
    ISSN 1540-7063
    DOI 10.1093/icb/icad070
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Nonlinear elasticity and short-range mechanical coupling govern the rate and symmetry of mouth opening in

    Goel, Tapan / Adams, Ellen M / Bialas, April L / Tran, Cassidy M / Rowe, Trevor / Martin, Sara / Chandler, Maia / Schubert, Johanna / Diamond, Patrick H / Collins, Eva-Maria S

    Proceedings. Biological sciences

    2024  Volume 291, Issue 2017, Page(s) 20232123

    Abstract: ... ...

    Abstract Hydra
    MeSH term(s) Animals ; Hydra/physiology ; Mouth/physiology ; Epithelium ; Biomechanical Phenomena ; Neurons
    Language English
    Publishing date 2024-02-21
    Publishing country England
    Document type Journal Article
    ZDB-ID 209242-6
    ISSN 1471-2954 ; 0080-4649 ; 0962-8452 ; 0950-1193
    ISSN (online) 1471-2954
    ISSN 0080-4649 ; 0962-8452 ; 0950-1193
    DOI 10.1098/rspb.2023.2123
    Database MEDical Literature Analysis and Retrieval System OnLINE

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