1,720,974 research outputs found
A theoretical model for folding/unfolding thermodynamics of single domain proteins based on the quasi-Gaussian entropy theory
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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
Multielectron excitations at the L edges of barium in aqueous solution
No full textAn extensive investigation of the x-ray-absorption spectra above the L edges of a Ba2+ water solution is presented. Anomalous features are clearly detected in the spectra and have been associated with the creation of 2p4d and 2s4d double-core hole states for the L3, L2, and L1 edges, respectively. A reliable determination of the double-electron edge parameters has been obtained by performing a combined L-edge analysis in the correct framework of the radial distribution function theory. Ba-O and Ba-H radial distribution functions have been calculated by means of molecular-dynamics simulations and have been used as relevant models in the calculation of the extended x-ray-absorption fine-structure (EXAFS) signals. The simultaneous analysis of the three edges allowed an unambiguous characterization of the multielectron transition affecting the L1 cross section. The experimental values of the energy onsets of the double-electron features are in good agreement with previous theoretical calculations. The influence of multielectron transitions in the EXAFS data analysis is discussed. The neglect of double-electron excitation effects results in systematic errors on the structural parameters and in particular in an underestimation of the coordination numbers. © 1996 The American Physical Society
An extended x-ray absorption fine structure study of aqueous solutions by employing molecular dynamics simulations
No full textBromine–oxygen radial distribution functions [g(r)] have been calculated by means of molecular dynamics simulations for aqueous solutions of rubidium bromide, 2‐bromopropane and bromoethane. X‐ray absorption spectra at the bromine K edge have been recorded for these solutions. The water contribution to the extended x‐ray absorption fine structure spectra has been calculated starting from the g Br,O(r) distribution function. Fits of the x‐ray absorption spectra have been performed directly on the raw experimental data, allowing the reliability of the g(r) distribution functions to be verified. The agreement between theoretical and experimental spectra is satisfactory. A procedure to improve model g(r) functions on the basis of the short‐range structural information provided by extended x‐ray absorption fine structure data is proposed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Beta-Hairpin conformation of fibrillogenic peptides: Structure and alpha-to-beta transition mechanism revealed by molecular dynamics simulations.
No full textUnderstanding the conformational transitions that trigger the aggregation and amyloidogenesis of otherwise soluble peptides at atomic resolution is of fundamental relevance for the design of effective therapeutic agents against amyloid-related disorders. In the present study the transition from ideal -helical to -hairpin conformations is revealed by long timescale molecular dynamics simulations in explicit water solvent, for two well-known amyloidogenic peptides: the H1 peptide from prion protein and the A(12-28) fragment from the A(1-42) peptide responsible for Alzheimer's disease. The simulations highlight the unfolding of -helices, followed by the formation of bent conformations and a final convergence to ordered in register -hairpin conformations. The -hairpins observed, despite different sequences, exhibit a common dynamic behavior and the presence of a peculiar pattern of the hydrophobic side-chains, in particular in the region of the turns. These observations hint at a possible common aggregation mechanism for the onset of different amyloid diseases and a common mechanism in the transition to the -hairpin structures. Furthermore the simulations presented herein evidence the stabilization of the -helical conformations induced by the presence of an organic fluorinated cosolvent. The results of MD simulation in 2,2,2-trifluoroethanol (TFE)/water mixture provide further evidence that the peptide coating effect of TFE molecules is responsible for the stabilization of the soluble helical conformatio
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