1,721,001 research outputs found
Practical strategy to realistically measure the swelling ratio of poly(dimethylsiloxane) without underestimation due to the solvent volatility
No full textWe present an experimental method for measuring “realistically” the swelling ratio in terms of weight (SRW) of PDMS, where “realistically” means without the underestimation involved by the standard protocol (weight-measurements in open environment with time-delay incompatible with fast solvent evaporation rate). Comparison with the literature demonstrates that misleading conclusions can result under application of the standard protocol to very volatile solvents. To discuss this point, we develop a mathematical expression of SRW including solvent properties and the effective amount of sorbed solvent determining a weight gain, consider two solvents with different volatility that severely swell PDMS (i.e., toluene and dichloromethane), check that the results of our measurements are consistent with theoretical predictions, demonstrate that our protocol rules out any dependence of SRW on the solvent volatility and its reliability to measure and compare SRW values of PDMS (or any swelling polymer/soft material) in the case of solvents with very different volatility
Protocol of thermal aging against the swelling of poly(dimethylsiloxane) and physical insight in swelling regimes
No full textIn this paper, an unprecedented inspection of the effects of thermal aging on swelling and wettability of PDMS as a function of the interplay between temperature (from 100 to 180 °C) and duration (from 20 min to 24 h) of the treatment is presented. Dichloromethane was used as sample swelling solvent and the swollen weight was measured by a method properly designed to avoid underestimation related to the volatility of the solvent. This study: i) provides practical guidelines for performing optimal thermal aging treatments of PDMS against swelling (for example, in microfluidic platforms to synthesize cancer tracers), and ii) contributes to the fundamental understanding of the swelling process of soft matter systems. An interpretative model has been developed of the observed swelling regimes based on heating-promoted crosslinking and chain reorganization (inter-chain mobility) at short-lasting heating timescales and conformational changes (intra-chains transitions) at long-lasting heating timescales
Gold nanoholes fabricated by colloidal lithography: Novel insights into nanofabrication, short-range correlation and optical properties
No full textColloidal lithography is widely used as a low cost and large-area deposition approach, alternative to the conventional small-area expensive lithographic techniques, for the fabrication of short-range ordered sub-wavelength metallic nanostructures. This paper contributes to the understanding of the impact of the fabrication protocol of a colloidal mask on the optical and sensing properties of short range-ordered nanohole (NH) distributions fabricated by colloidal lithography in optically thin (20 nm thick) gold films. We consider polystyrene nanospheres (PS-NSPs) with a nominal diameter of 80 nm, electrostatically adsorbed from a salt-free colloidal solution onto a polydiallyldimethylammonium (PDDA) countercharged monolayer. By avoiding the conventional polyelectrolyte multilayer and based on the interplay between the deposition times of both PDDA and PS-NSPs, we demonstrate effective simplification of the commonly applied deposition protocol and effective tuning of the NH-to-NH spacing (d NN ) with negligible agglomeration. Comparison with NH samples prepared by salt-containing colloidal solutions points out the negative impact of salt addition on the optical properties. The effective tuning of d NN obtained by our protocol demonstrates highly correlated disorder under unsaturated adsorption and allows a discussion on the analogies of the optical response between long- and short- range ordered NH systems, which is a still debated topic. By Fast Fourier Transform of autocorrelation images of scanning electron microscopy micrographs we demonstrate quantitatively, rather than in principle, the correspondence between an inherent ordering length-scale and d NN . As optical transducers for detecting refractive index changes, our samples exhibit significant bulk sensitivity (∼309 nm RIU -1 ) in the framework of short range ordered NH systems
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
XPS CHARACTERIZATION OF PDMS BASED MICROFLUIDIC CHANNELS OF CLINICAL APPLICATION TREATED WITH DIFFERENT SOLVENTS
No full textRiassunti / absract presentati al XXV Congresso della Divisione di Chimica Analitica della Società Chimica Italian
“Determination of optical parameters of colloidal TiO2 nanocrystals-based thin films by using surface plasmon resonance measurements for sensing applications”
No full textSurface plasmon resonance (SPR) study in angular modulation was used to optically characterize porous thin films based on TiO2 colloidal nanocrystals. Organic solutions of surfactant-capped TiO2 nanocrystals prepared by means of a colloidal chemistry route, were deposited as thin film by spin coating. Optical parameters of the obtained thin layers were calculated by using SPR measurements on both as deposited and annealed in dry-air thin layers. By using direct fitting of a set of the SPR resonant curves with Fresnel's theory, the thickness and refractive index of the prepared thin films were determined. The application of the prepared layers as optical sensing materials was evaluated by detecting the variation of the optical parameters in the presence of different saturated alcohol vapours. Morphological and structural characterization of the thin layers was carried out and related to the optical behaviour of the sensing material. Adsorption of alcohol vapours onto the surface of the sensing layer was found to induce a variation of both thickness and refractive index of TiO2-based nanocrystals films. The presence of the organic passivating layer at the nanocrystal surface was demonstrated to play an effective role in the interaction between alcohol molecules and the sensing material
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