1,720,966 research outputs found
A new maximum entropy conformational analysis of biphenyl in liquid crystal solution
No full textWe use the maximum entropy internal order (MEIO) method to reanalyze published (1)HNMR dipolar couplings for biphenyl dissolved in nematic solvents allowing for geometry variations with dihedral angle phi. We find that all present experimental data are consistent with similar conformational distributions with a maximum at phi = 34 - 35 degrees. Little rotational-conformational coupling has been found
The rotational-conformational distribution of 2,2'-bithienyl in liquid crystals
No full textWe have investigated the distribution of conformations and orientations for a simple internal rotor molecule, 2,2'-bithienyl dissolved in liquid crystal solvents. by re-analysing published proton dipolar coupling data with the maximum entropy internal order method (MEIO). We show that detailed, model independent, conformational information can be obtained when data of sufficiently high quality are available. We also propose a novel and convenient representation method for the orientational-conformational coupling
A Multi Technique Maximum Entropy approach to the determination of the orientation and conformation of flexible molecules in solution
Full text linkWe present a maximum entropy method that allows the simultaneous analysis of different types of experimental data in order to obtain conformational information on flexible molecules in solution. We consider various NMR observables (dipolar, quadrupolar, J-couplings, nuclear Overhauser enhancements), and dielectric and neutron scattering techniques, and we express them using a common formalism in terms of orientational-conformational order parameters. We then show how these observables can be inverted in structural information allowing for continuous or discrete internal degrees of freedom and for any available prior information. We demonstrate the potentialities of the method on simulated (HNMR)-H-1, (HNMR)-H-2 and dielectric data for some terminally halogenated alkyl chains and show the improvement in conformational analysis obtained by simultaneously analyzing different and complementary data sets. (C) 1998 American Institute of Physics
Maximum entropy internal order approach to the study of intramolecular rotations in liquid crystals
No full textThe conformations of alkyl chains in fluids. A maximum entropy approach
Full text linkWe present a maximum entropy internal order method for analyzing chain conformations in liquid crystalline solutions. We show how prior knowledge of the conformational distribution can be taken into account and apply the method to the determination of the conformation of n-alkanes in liquid crystals without invoking molecular field or other approximate theoretical models
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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