1,720,966 research outputs found
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
Structural differences of ovalbumin and S-ovalbumin revealed by denaturing conditions
No full textWe found, by circular dichroism and Raman spectroscopy measurements. that the secondary structure of the native ovalbumin and of its heat-stable form, called S-ovalbumin, is a probe of the structural differences between the two proteins. Small angle X-ray scattering and circular dichroism measurements performed on the two proteins under denaturing conditions, with different concentrations of guanidine hydrochloride, show the changes of the tertiary and secondary structure and a different pathway in the unfolding process. These experimental data confirm that the conversion of native ovalbumin into S-ovalbumin is irreversible and reveal that the response of the two proteins to the same chemical environment is different
Spin-resolved X-ray absorption near edge structure (XANES) simulation of metmyoglobin
No full textSpin resolved multiple scattering (MS) calculations of Fe K-edge X-ray Absorption Near Edge Structure (XANES) of myoglobin are reported for the first time. The observed differences of the Fe K-edge XANES spectra of sperm whale metmyoglobin under spin transition as a function of temperature have been studied. The method allows one to compute separately spin effects and local structural effects. The results show that spin effects are confined in the absorption rising edge in the range 7111-7130 eV, while purely structural effects are dominant in the range 7130-7170 eV. Symmetry changes of the Fe coordination sphere mainly related to its movement towards the heme plane, coupled to an increase of axial asymmetry, can explain the XANES changes observed above 7130 eV without an appreciable change of the Fe-Np distance
Light induced states in MbCO denatured with guanidine hydrochloride
No full textWe present the results of a comparative study of the binding of carbon monoxide to myoglobin in glycerol/buffer solution with different concentrations of guanidine hydrochloride, under extended illumination over the temperature range 30-80 K. The changes in the Sorer band indicate that the folding state of the protein is a key parameter in determining the photodissociation process and the relaxation rate of the protein
The dinuclear copper site structure of Agaricus bisporus tyrosinase in solution probed by X-ray absorption spectroscopy
No full textWe have measured the x-ray absorption near edge structure (XANES) spectra of the enzyme tyrosinase from the mushroom Agaricus bisporus in solution in the oxy and deoxy forms, The spectra, obtained under the same conditions as the analogous forms of mollusc hemocyanin (Hc), show that the oxidation state of copper changes from Cu(II) (oxy form) to Cu(I) (deoxy form), and the copper active site(s) of A. bisporus tyrosinase in solution undergoes the same main conformational changes as Hc. We have applied the multiple scattering theory to simulate the XANES spectra of various alternative geometries of the copper site, accounting for the residual differences between Hc and tyrosinase. While oxy-Hc is reasonably fitted only by the pseudo-square-pyramidal geometry reported by its crystallographic data, oxytyrosinase can be fitted, starting from the Hc coordinates, either by distortions toward a pseudo-tetrahedral geometry, with inequivalent copper sites, or by an apically distorted square-pyramidal geometry (with an elongation of the apical distance of no more than 0.2 Angstrom)
LACK OF DELOCALIZED CU P-STATES AT THE FERMI LEVEL IN THE HIGH-TC SUPERCONDUCTOR YBA2CU3O-APPROXIMATELY 7 BY XANES SPECTROSCOPY
No full textConformational changes involved in the switch from ovalbumin to S-ovalbumin
No full textFor the first time a comparative study on conformational differences between native ovalbumin and its heat-stable form, called S-ovalbumin, using small angle x-ray scattering, is reported. To detect a different pathway in the folding mechanism of the two proteins, scattering measurements have been performed on ovalbumin and S-ovalbumin denatured with different concentrations of guanidine hydrochloride, and by heating the proteins at acid pH. The intensity scattering curves provide evidence that the intermediate states in the unfolding process are globular for both proteins while their compactness changes. The reported experimental results suggest that the ovalbumin to S-ovalbumin transformation can be considered a protein-switch triggered by changes in the chemical conditions of the protein environment. Because the conformational changes are likely to be of functional importance, we infer that the occurrence in vivo of S-ovalbumin is thus determined by the transformation of ovalbumin, with a functional role for embryonic development, into a new protein with a different function
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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