1,720,987 research outputs found
Mutual and intradiffusion coefficients for the binary system n-decyl dimethyl phosphine oxide + water at 25 °C
No full textDiffusion coefficients for the binary system n-decyl dimethyl phosphine oxide + water have been studied at 25 °C, with the aim to quantitatively describe the surfactant micellization process in aqueous medium. Accurate mutual diffusion coefficients have been measured by the Taylor dispersion technique. Intradiffusion coefficients of both components have been measured by the pulsed gradient spin echo (PGSE)-FT NMR technique. The data have been compared and interpreted in the framework of the equilibrium model of surfactant self-aggregation. Interpolation of the mutual diffusion coefficients has allowed us to estimate reliable values of the average number of surfactant molecules involved in the formation of a micellar aggregate and the constant of the equilibrium between these aggregates and surfactant unimers. Interpolation of water intradiffusion coefficients has allowed us to estimate the number of water molecules involved in the hydration of surfactants in unimeric and micellized form
Limiting partial molar volume of sodium chloride in 2-methyl-2,4-pentandiol-water mixed solvents at 25 °C
No full textAbstract Herein we report density measurements for the binary system 2-methyl-2,4-pentanediol(MPD,1)-water(0), and for the ternary system MPD(1)-NaCl(2)-water(0), at several fixed MPD/water ratios and at varying NaCl concentrations. The partial molar volume of MPD in the binary system has been discussed according to the McMillan-Meyer theory. At low MPD concentrations, the non-bonding MPD-MPD interactions are related to the overlapping of the hydrophobic parts of the hydration cospheres, whereas at higher concentrations the hydrophilic moieties are also involved in the solute-solute interactions. The ternary density data allowed us to determine the salt partial molar volume at infinite dilution. The trend of this quantity as a function of the MPD content in the MPD-water “mixed solvent” has been interpreted on the basis of the water partial molar volume in the binary MPD-water system
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
PHASE DIAGRAM OF THE AQUEOUS POLY(PROPYLENE OXIDE)-POLY(ETHYLENE OXIDE)-POLY(PROPYLENE OXIDE) TRIBLOCK COPOLYMER SYSTEM: A STRUCTURAL CHARACTERIZATION
No full textRUTHENIUM-BASED ANTICANCER ACTIVITY: A RAMAN-ASSISTED X-RAY CRYSTALLOGRAPHY APPROACH
No full textRaman microspectroscopy proved to be a valuable support to protein crystallography in all the steps of 3D structure determination. Authors have been using this approach to study changes in chemical composition [1, 2, 3], in secondary [3,4] and tertiary structure [5], and to follow chemical mechanisms [3, 6, 7].
The binding properties of AziRu (Fig. 1), a Ru(III) complex with high antiproliferative activity, toward hen egg white lysozyme [7], RNase A and human serum albumin have been investigated by X-ray crystallography and Raman microspectroscopy. The data provide clues on the mechanism of AziRu-protein adduct formation and clear evidences of ligand exchange in the crystal state (Figs. 2). The combined use of Raman and X-ray crystallography has provided complementary information that a single technique alone would not produce. For instance, in the case of hen egg white lysozyme [7], Raman spectra show not only the ligand exchange that is apparent in the X-ray structures but also the presence of Ru−O−Ru bonds (Fig. 3), which are not revealed by crystallography.
References
[1] Vergara, et al., Acta Cryst. Sect D: Biol Crystallogr. 64, 167-171 (2008).
[2] Caterino et al., A. Vergara , J. Sol. Chem., in press.
[3] Merlino, et al. Vergara, A., Acta Cryst. Sect D: Biol Crystallogr , 69, 137-40 (2013).
[4] Merlino, et al. A. Vergara, Biophys. Chem. 137, 24-27 (2008).
[5] Vergara, et al., J. Biol. Chem. 285, 32568-32575 (2010) .
[6] Vitagliano, L., Vergara, et al.., J Am Chem Soc. 130, 10527-10535 (2008).
[7] Vergara, et al, Inorg Chem 52, 4157-9 (2013)
Diffusion Coefficient Matrix in Nonionic Polymer-Solvent Mixtures.
No full textRecent predictive equations for evaluating the value of diffusion coefficients, developed for two hard sphere-solvent systems, have been extended to n-hard-sphere-solvent systems. This model has been used to predict the diffusion behavior of nonionic polymer-solvent mixtures as a first-order function of volume fraction from the knowledge of the distribution function. Hence, the entire diffusion matrix for polydisperse systems, which include both main- and cross-term diffusion coefficients, has been built up for the first time. The main-terms diffusion coefficients D ii. are mostly affected by the variation in viscosity. The magnitude of the cross-term diffusion coefficients D ij is strictly related to the abundance and diffusivity of solute i and to the molecular volume corresponding to solute j. The predicted diffusion coefficients have been used to calculate the apparent, average diffusion coefficients, which are compared with the experimental values measured by the Gouy interferometry method in the case of the poly(ethylene glycol) homologous series. The agreement between the calculated and experimental Gouy parameters is good. The cross-term diffusion coefficients are found to be significant in the calculation of the apparent diffusion coefficient for a polydisperse solute. Some comments on the study of ternary systems containing a polydisperse solute are done
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