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    Entropy-driven formation of a chiral liquid-crystalline phase of helical filaments (2006)
    American Physical Society
    Details
    Publication Date: 2022-05-25
    Description: 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.
    Description: 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.
    Description: M. S. and R. O. are supported by NIH Grant No. EB002583.
    Keywords: Entropy ; Molecular biophysics ; Liquid crystal phase transformations ; Symmetry ; Chirality
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 765344 bytes
    Format: application/pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Construction and applications of symmetrized valence bond wave functions (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 66 (1998), S. 1-7 
    Details
    ISSN: 0020-7608
    Keywords: Symmetry ; projection operator ; VB wave function ; transition energy ; chemical bonds ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method constructing symmetry-adapted bonded Young tableau bases is proposed, based on the symmetry properties of bonded tableaus and the projection operator associated with a point group. Several examples including the ground states and π excited states of O3-, O3, O3+, and C3- are shown for instruction to construct the symmetrized valence bond (VB) wave function. Excitation energies of transitions from the ground states to π excited states of O3-, C3H5, and C3- are calculated with an optimized symmetrized valence bond wave function in the σ-π separation approximation. Good agreement between the VB and experimental excitation energies is observed. The bonding features of the ground state and the first π excited singlet and triplet states for S3 are discussed according to bonding populations from VB calculations. Both the singlet-biradical and the dipole structures have significant contributions to the ground state X 1A1 of S3, while the excited state 1 1B2 is essentially composed of the dipole structures, and the 1 3B2 excited state is comprised from a triplet-biradical structure.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 66: 1-7, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Molecular symmetry and shielding tensor properties - some illustrative examples (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 679-690 
    Details
    ISSN: 0749-1581
    Keywords: High-resolution solid-state NMR ; Shielding tensor ; Symmetry ; 29Si, 119Sn, 207Pb CP/MAS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C, 29Si, 119Sn and 207Pb cross-polarization magic angle spinning (CP/MAS) spectra for a series of closely related compounds R4-nM(C≡CR′)n, (n = 1-4; M = Si, Sn, Pb; R = alkyl; R′ = alkyl, SiMe3) are reported. Shielding tensor components for 29Si, 119Sn and 207Pb as obtained from CP/MAS spectra are discussed in relation to the respective highest possible molecular symmetry group as a function of the degree of substitution n = 1-4. For this class of compounds the orientation of the shielding tensor of M within the molecular frame can sometimes be derived from symmetry considerations. The limitations of such considerations, based on shielding tensor components obtained from polycrystalline powder samples under CP/MAS conditions, are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260321108
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