1,720,984 research outputs found
XAS characterization of the Zn site of non-structural protein 3 (NS3) from hepatitis C virus
No full textXANES spectra of non structural protein 3 (NS3) have been calculated using 4 Zn coordination models from three crystallographic structures in the Protein Data Base (PDB): 1DY9, subunit B, 1CU1 subunit A and B, and 1JXP subunit B. Results indicate that XANES is an appropriate tool to distinguish among them. Experimental XANES spectra have been simulated refining crystallographic data. The model obtained by XAS is compared with the PDB models. © 2007 American Institute of Physics
XAS STUDY OF SOLUBILIZATION LOCI OF BROMINATED MOLECULES IN AQUEOUS MICELLAR SOLUTIONS
No full textX-ray absorption measurements performed on various systems containing brominated hydrocarbons showed
remarkable differences in the bromine K-edge spectra recorded in polar or nonpolar media. For this reason,
the brominated hydrocarbons can be used to monitor the polarity of the medium in which they are buried. By
determining the coordination of the bromine atom, information on the interactions between the probe molecule
and several systems such as micelles, macromolecules, membranes, solvent molecules, and host molecules in
inclusion compounds can be obtained. Brominated hydrocarbons in aqueous micellar solutions of sodium and
rubidium deoxycholate and sodium dodecyl sulfate have been investigated by means of the XAS technique.
Experimental and calculated EXAFS spectra and Fourier transform functions are presented. The results are
supported by the XANES experimental spectra. As already found for 2-bromopropane, the polarity of the
solubilization loci of bromoethane in sodium and rubidium deoxycholate micellar solutions decreases by increasing
the solute concentration. On the contrary, in micellar solutions of sodium dodecyl sulfate, these molecules are
embedded in a more apolar environment. The polarity of the spectra of 2-bromopropane changes with the probe
concentration, while bromoethane presents a marked apolar coordination which seems to be independent from
the probehost ratio. The bromine intermolecular coordination in 1-bromobutane has been found to be apolar
in both classes of surfactants. Functionalized surfactants with -ene, -yne, or bromo as the terminal group of
the alkyl chain were used by different researchers to investigate micellar structures. In fact, for a micellar
aggregate with a hydrocarbon core and an outer region containing the polar heads, the chain terminal group
may be buried in the micelle core or placed in the head group region of the micelle, in contact with water. In
the latter case, the alkyl chain flexibility may give rise to a chain folded conformation which increases the
probability of finding the terminal group at the micelle-water interface. EXAFS data analysis of aqueous
micellar solutions of sodium and rubidium 12-bromo dodecyl sulfate and sodium 1 I-bromoundecanoate at the
Br K-edge has been accomplished. The chemical constitution of the locus of solubilization of the terminal
bromine has been determined, and it has been found to be apolar for the dodecyl sulfate salts and polar in the
case of sodium 1 1-bromoundecanoate
Isolation, Characterization and Structural Investigation by EXAFS/XANES of High-valent Manganese Porphyrin Complexes as Active Species in the NaOCl/ Mn(Porphyrin)X Oxygenation System
No full textAbstrac
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
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
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