1,721,001 research outputs found
Probing self-assembly of silane molecules in monolayers at active solid-liquid interfaces
No full textSelf-assembly is a particularly appealing phenomenon for bottom-up approaches to nanotechnology involving spontaneous ordering of molecules. When self-assembly of molecules occurs at active solid-liquid interfaces, the superficial chemistry of substrates can be altered.
In the present study, self-assembly of trimethoxysilanes solely differing for their head group chemistry is investigated. In particular, glass substrates were pre-activated by hydroxylation and then silane anchoring was achieved by means of a wet chemistry-based route. Synergistic investigation in terms of morphology and chemistry turned out to be an appropriate evaluation tool for the quality attributes of the silane layering on glass. Preliminary assessment of effective functionalization was carried out in terms of contact angle and surface zeta potential analyses. Then, chemistry of functionalized glass was probed by means of X-Ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS). Lastly, Atomic Force Microscopy was adopted for the characterization of surface topography.
Keeping the same optimized synthesis protocol for all the samples, we were able to highlight the effect of varying head group chemistries of silanizing agents on the final functionalization features, such as spatial homogeneity and number of layers. High-quality monolayers carrying thiol, methacrylate and glycidyloxy exposed groups were successfully synthesized. Surface roughness resulted to be around 1 nm and presence of characteristic elements confirmed effective functionalization. Conversely, as regards amino-terminated silanes, a multi-layered structure was obtained. Surface roughness dramatically increased and correlation between ideal and experimental elemental ratios characterizing the monolayer was lost.
We conclude that the polarity of the functionalizing agent turned out to have a pivotal role in directing self-assembly at active interfaces and leading to the effective formation of monolayers on amorphous substrates. High-quality and reproducibility make such surfaces ideal candidates to be used as heteronucleants for pharmaceutical crystallization studies
Role of self-assembled surface functionalization on nucleation kinetics and oriented crystallization of a small-molecule drug: batch and thin-film growth of aspirin as a case study
Full text linkThe present paper assesses the heterogeneous nucleation of a small-molecule drug and its relationship with the surface chemistry of engineered heteronucleants. The nucleation of aspirin (ASA) was tuned by different functional groups exposed by self-assembled monolayers (SAMs) immobilized on glass surfaces. Smooth topographies and defect-free surface modification allowed the deconvolution of chemical and topographical effects on nucleation. The nucleation induction time of ASA in batch crystallization was mostly enhanced by methacrylate and amino groups, whereas it was repressed by thiol groups. In this perspective, we also present a novel strategy for the evaluation of surface-drug interactions by confining drug crystallization to thin films and studying the preferential growth of crystal planes on different surfaces. Crystallization by spin coating improved the study of oriented crystallization, enabling reproducible sample preparation, minimal amounts of drug required, and short processing time. Overall, the acid surface tension of SAMs dictated the nucleation kinetics and the extent of relative growth of the ASA crystal planes. Moreover, the face-selective action of monolayers was investigated by force spectroscopy and attributed to the preferential interaction of exposed groups with the (100) crystal plane of ASA
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
Water resistant ethylene/acrylic acid plasma-deposited coatings
No full textThin films were deposited from a mixture of ethylene and acrylic acid in RF (13.56 MHz, parallel plate) glow discharges in different experimental conditions to obtain substrate-adherent coatings stable in water, surface-functionalized with tunable density of carboxyl groups. The surface composition of the coatings as well as their stability in water was investigated by X-ray Photoelectron Spectroscopy measurements and Toluidine Blue-O derivatization of the carboxylic acid functionalities. Coatings stable in water media were obtained, with tunable surface density of -COOH groups, of possible interest in biomedical applications. Such coatings were used in cell culture experiments with Saos-2 osteoblast cell lines
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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