1,721,024 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
Transport of the anti-diabetic VO2+ complexes formed by pyrone derivatives in the blood serum
No full textThe biotransformation in the blood serum of the two anti-diabetic agents [VO(ema)2] – or BEOV – and [VO(koj)2] formed by ethylmaltol (Hema) and kojic acid (Hkoj) was studied with EPR spectroscopy, pH-potentiometry and DFT calculations. For comparison, the behavior of the systems with tropolone (Htrop) was also analyzed. The interaction of [VO(ema)2] and [VO(koj)2] with the most important bioligands of the serum, lactic (Hlact) and citric acid (H3citr), human serum transferrin (hTf), human serum albumin (HSA) and immunoglobulin G (IgG) was examined and discussed. Among the several mixed species observed, cis-VO(carrier)2(hTf), cis-VO(carrier)2(HSA) and cis-VO(carrier)2(IgG), where carrier is ethylmaltolate or kojate, with a His-N of the protein coordinated in the equatorial position, are plausible candidates for the transport processes of the drug toward the target organs. The values of the logβ are in the range 19.6–19.8 for the species formed by ethylmaltol and 17.4–17.6 for those formed by kojic acid. The formation of such species was confirmed through pH-titrations of the model systems VO2 +/carrier/1-MeIm and VO2 +/carrier/Ac-his, where 1-MeIm and Ac-his are 1-methylimidazole and N-acetylhistamine, and DFT calculations of 51V Az of the model species cis-[VO(carrier)2(1-MeIm)] and cis-[VO(carrier)2(Ac-his)]. The values of the stability constants for the mixed species observed were used to predict the biodistribution of VO2 + ion between the blood serum components for concentrations of 1, 10 and 50 μM
Equilibrium between Different Coordination Geometries in Oxidovanadium(IV) Complexes
No full textIn this laboratory activity, the equilibrium between square pyramidal and octahedral V(IV)O2+ complexes is described. We propose a set of experiments to synthesize and characterize two types of V(IV)O2+ complexes. The experiment allows great flexibility and may be effectively used at a variety of levels and the activity can be lengthened or shortened depending on the available time. The laboratory practice can combine various experiments: (i) synthesis of solid transition metal complexes, (ii) analysis of the solid complexes to hypothesize their coordination geometry, (iii) measurement of room temperature and frozen solution EPR (Electron Paramagnetic Resonance) spectra obtained when dissolving the solid complexes in different solvents, (iv) software simulation of room temperature and frozen solution EPR spectra, (v) measurement of UV?vis spectra of solutions obtained when dissolving the solid complexes in different solvents, (vi) optimization of the coordination geometry of V(IV)O2+ complexes with DFT calculations, (vii) calculation of the EPR parameters of V(IV)O2+ complexes with DFT methods, and (viii) influence of the temperature on the equilibrium calculated using DFT methods. The activity is organized to guide the students towards to a plausible explanation of the experimental evidence
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
Uptake of potential anti-diabetic VIVO compounds of picolinate ligands by red blood cells
No full textThe interaction of three potential anti-diabetic (VO)-O-IV compounds formed by picolinate (pic), 3-methylpicolinate (3-mepic) and 6-methylpicolinate (6-mepic) with hemoglobin (Hb) and red blood cells was studied with the combined application of spectroscopic (EPR), spectrophotometric (UV-Vis) and computational (DFT methods) techniques. In the ternary systems with hemoglobin, pic and 3-mepic (L) form mixed species cis-VOL2(Hb), with the equatorial binding of an accessible His residue, whereas 6-mepic forms VO(6-mepic)(OH)(Hb). The experiments about the uptake of (VO)-O-IV complexes by red blood cells indicate that only [VO(pic)(2)(H2O)] penetrates the erythrocyte membrane in a significant amount, whereas for [VO(3-mepic)(2)] and [VO(6-mepic)(2)] the hydrolytic reactions at physiological pH hinder the diffusion in the intracellular medium. Inside the red blood cells, the biotransformations depend mainly on the strength of the ligand. Pic and 3-mepic form cis-VOL2(Hb) and cis-VOL2(Cys-S ) with the equatorial coordination of a thiolate-S stemming from GSH or a membrane protein. Instead, the less thermodynamically stable compound, [VO(6-mepic)(2)], loses the two ligands after the interaction with the membrane or inside the erythrocytes to give the same species formed by free (VO2+)-O-IV ion: (VO) Hb(beta) and (VO)Hbc gamma, with (VO2+)-O-IV coordinated to the sites beta and gamma of hemoglobin, and VO(L-1, L-2) and VO(L-3, L-4), where L-1, L-2, L-3 and L-4 are generic red blood cell bioligands, such as proteins (for example, Hb) or low molecular mass (l.m.m.) components. The distribution of an insulin-enhancing V compound between the serum and the red blood cells may influence the mechanism of action and the activity of a V drug and explain the different effectiveness observed in the literature
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
The Equilibrium Between the Octahedral and Square Pyramidal Form and the Influence of an Axial Ligand on the Molecular Properties of V<sup>IV</sup>O Complexes: A Spectroscopic and DFT Study
No full textThe previously unreported equilibrium in aqueous solution between the (VO)-O-IV square pyramidal and trans octahedral form with an axial water molecule for a number of bidentate ligands with (N,O) and (O,O) donor sets (6-methylpicolinic (6-mepicH) and 6-methyl-2,3-pyridinedicarboxylic (6-me-2,3-pdcH(2)) acids, dipyridin-2-ylmethanol (Hdpmo) and 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone (Hdhp)) has been demonstrated by the combined application of EPR spectroscopy and DFT methods. The EPR spectra suggest that, with increasing ionic strength, the equilibrium is shifted towards the formation of the penta-coordinated species and values of K approximate to 4.0 and 7.0 for the systems containing 6-methyl-2,3-pyridinedicarboxylic acid and dipyridin-2-ylmethanol were measured. DFT calculations performed with Gaussian 03 and ORCA software predict the V-51 anisotropic hyperfine coupling constant along the z axis (A(z)), which can be used to demonstrate the presence of an axially bound ligand trans to the V=O bond. The results suggest that an axial donor (charged or not) can lower vertical bar A(z)vertical bar, in contrast to what was previously believed on the basis of the "additivity rule", and this explains the anomalous behaviour of the (VO)-O-IV complexes formed by N-{2- [(2-pyridylmethylene)amino]phenyl}-pyridine-2-carboxamide (Hcapca) and several amidrazone derivatives. The decrease in vertical bar A(z)vertical bar for the axial binding of a solvent molecule is mainly a result of the reduction of vertical bar A(iso)vertical bar and this was also observed when the solid [VO(6-methylpicolinato)(2)] was dissolved in DMSO or DMF. The variations in the structural (V=O, V-O and V-N distances, O-V-O and N-V-N angles, and the trigonality index tau) and spectroscopic (vertical bar A(z)vertical bar, vertical bar A(iso)vertical bar and v(V=O)) properties as a function of the axial V-OH2 distance (R) are also presented. Finally, the electronic structures of the penta-and hexacoordinated complexes are discussed
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
- …
