1,720,958 research outputs found
Electronic and vibronic excitations of a quarter-filled periodic octamer
No full textLinear optical conductivity spectra of 1-D quarter-filled charge transfer crystals are interpreted on the basis of a periodic octamer and a Holstein-Hubbard model. It is shown how the low frequency spectral features are due to combined effects of electron correlations and of the dimerization of the system. Fermion-phonon interactions introduce other spectral features which produce strong changes in the spectra
A Possible Route for the Release of Fatty Acid from Fatty Acid-Binding Protein
Full text linkA simulation of the release of fatty acid from intestinal fatty acid-binding protein was attempted, starting with the crystallographic model and using molecular-dynamic processes at different temperatures. The release of the ligand was observed only at high temperature, which perhaps makes the process unreliable in detail. Nevertheless, the overall behaviour of the protein, also confirmed by the simulation performed at room temperature, strongly supports the idea that the fatty acid leaves the protein through an opening formed by alpha-helix II and turns beta C-beta D and beta E-beta F. Additionally, it suggests a role for the lack of hydrogen bonds between the main chains of beta-strands D and E: this feature, observed in all the protein structures of this family which have currently been determined, seems to provide the structure with great flexibility, allowing the barrel to open and close without disruption of the hydrogen-bond network
Optical excitations in quarter-filled Ni(dmit)2 based compound described by a dimerized octamer model
No full textThe reflectance spectra of [SMe3][Ni(dmit)(2) (dmit=1,3-dithiole-2 thione-4,5-dithiolato), quarter-filled organic conductor with strongly dimerized structure, will be discussed in the framework of the new Raman results for this compound. The spectra are interpreted on the basis of a dimerized Hubbard octamer model, which accounts for the low energy electronic transitions and for the coupling of the electronic excitations with the intramolecular vibrations
Numerical prediction of twisting power for chiral dopants
No full textWe have implemented a theoretical model for the numerical evaluation of the helical twisting power of chiral dopants in liquid crystal phases, on the basis of their shape and of solvent macroscopic properties. After summarizing the fundamentals of the method, the numerical procedure is briefly illustrated and the application to the case of biphenyl derivatives is presented
Simulated time resolved fluorescence in ordered phases
No full textAn interpretation of time resolved fluorescence emission experiments, performed on probes in isotropic and ordered polar phases, is developed. The system under scrutiny is provided by a dipolar molecule undergoing rotational diffusion, whose dipole moment is coupled to a stochastic reaction field generated by the ordered polar medium. Under quite general conditions, the fluorescence emission is defined as an integral over all possible orientations of the ground and excited states. Since the model allows to reproduce experimental results at a semi-quantitative level and a negligible computational cost, a user-friendly package with graphics utilities has been created, which can be of help to investigate interactively the dependence of the simulated spectra upon several macroscopical parameters such as the dielectric constants and the viscosity of the medium
Indagini spettroscopiche su proprieta' stutturali ed lettroniche di film molecolari conduttori li Langmuir-Blodgett
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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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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