1,721,096 research outputs found
Retro-favorskii reaction employing fluoride sources and its use as immobilization strategy
No full textIn this study, we developed a novel and simple approach to perform retro-Favorskii type reactions comprising the use of a readily available fluoride source. Compared to the methods usually employed – which rely on the use of strong basic systems, such as KOH in toluene, at high temperatures and a reaction time of several hours – the one we propose employs milder conditions, shorter reaction times, is compatible with more solvents, and produces no appreciable amount of byproducts, thus allowing simple workup procedures. The reaction we describe is enabled by the strong basic character of the fluoride ion in absence of water. However, we observed that the reaction is remarkably tolerant to humidity and no anhydrous conditions are needed, making the reaction extremely straightforward to perform. The possibility of performing such reactions in a fast and reliable manner, without the appreciable formation of byproducts, can offer new interesting opportunities to efficiently employ propargyl alcohols derivatives as a masking group for carbonyls. The latter approach can be particularly interesting for the synthesis and derivatization of carbonyl-rich compounds – such as large, conjugated, electron-deficient systems or quinoid-based pigments – for which the limited solubility often precludes the synthesis of certain derivatives or their application in functional devices
Conformable on-skin devices for thermo-electro-tactile stimulation: Materials, design, and fabrication
No full textConformable electronics is an emerging and innovative research field investigating functional materials and electronic devices capable of adhering and conforming to non-planar surfaces such as human skin. Conformable devices find applications of high economical and scientific interest in healthcare, human-machine interfaces, wearable electronics, robotics, and the internet of things. Compared to the more widely used rigid and bulky electrodes often employed in wearable platforms, the former offers multiple advantages such as imperceptibility, low cost, and the possibility of continuous use, being able to follow the multiple deformations of curvilinear living tissues. In recent years, much attention has been paid to the development of soft and skin-wearable sensors, but an additional area of great interest is certainly that of conformable electrodes capable of providing some kind of stimulation. This review provides an overview of the most attractive and innovative conformable devices developed to stimulate the human body through thermal, electrical, mechanical, and optical stimuli. In particular, it focuses on the functional materials employed, the fabrication techniques involved, and the design solutions proposed to improve the performance of conformable stimulation devices
Novel, High-Resolution, Subtractive Photoresist Formulations for 3D Direct Laser Writing Based on Cyclic Ketene Acetals
No full textDirect laser writing (DLW) is an innovative technology based on two-photon polymerization processes which allow the 3D printing of architectures with arbitrary complexity at the (sub)micrometer scale. While most of the research interest in this field relies on additive manufacturing, subtractive approaches can be extremely helpful in nano/microfabrication, allowing the preparation of expendable scaffolds, replaceable parts, and for the protection of fragile structures. In this study, we show that the simple addition of 2-methylene-1,3-dioxepane, a cyclic ketene acetal compound, to a series of different acrylate-based photoresists results in functional formulations that allow the 3D-printing of degradable poly(ester-co-acrylate) microstructures via DLW. These latter could be degraded reliably under mild conditions compatible with other photoresists and materials of common use in the fabrication of MEMS, thus opening new opportunities to design novel fabrication procedures. In addition, the possibility of using different acrylate mixtures without affecting the degradability, allows the users to choose between a broad range of properties for the printed structures to fit their needs, without affecting the degradability. Finally, the authors show the potential of these photoresists in the fabrication of shadowing masks on 3D objects and their selective degradation employing a photobase
Functional Materials for Two‐Photon Polymerization in Microfabrication
No full textDirect laser writing methods based on two-photon polymerization (2PP) are powerful tools for the on-demand printing of precise and complex 3D architectures at the micro and nanometer scale. While much progress was made to increase the resolution and the feature size throughout the years, by carefully designing a material, one can confer specific functional properties to the printed structures thus making them appealing for peculiar and novel applications. This Review summarizes the state-of-the-art of functional resins and photoresists used in 2PP, discussing both the range of material functions available and the methods used to prepare them, highlighting advantages and disadvantages of different classes of materials in achieving certain properties
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
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