1,721,061 research outputs found
Superhydrophobic surfaces fabricated from nano- and microstructured cellulose stearoyl esters
No full textRobust, superhydrophobic and self-cleaning films were fabricated using nano- or microstructured cellulose fatty acid esters, which were prepared via nanoprecipitation. The superhydrophobic films could be coated on diverse surfaces with non-uniform shapes by distinct coating techniques
Transparent Slippery Surfaces Made with Sustainable Porous Cellulose Lauroyl Ester Films
No full textIn recent years, liquid repellent surfaces have attracted considerable attention because of their wide array of potential applications. In the present study, slippery surfaces were fabricated using novel sustainable, nanoporous cellulose lauroyl ester (CLE) films and slippery lubrication fluid. The nanoporous CLE films were obtained after spray-coating target surfaces using a nanoparticle suspension of CLE that was prepared via nanoprecipitation. After the deposition of the slippery liquid within the porous network, the obtained slippery surfaces exhibit both excellent liquid repellency upon liquid impact and anti-icing properties (by significantly retarding the icing time). Three-dimensional droplet manipulation was also achieved on these surfaces by taking advantage of the materials’ low contact angle hysteresis and low adhesion property
Temperature-Responsive Thin Films from Cellulose Stearoyl Triester
No full textIn comparison to synthetic thermoresponsive polymers, thermoresponsive materials based on naturally occurring polysaccharides and in particular cellulose are scarce. In this study, thermoresponsive hairy-rod polymer, cellulose stearoyl triester (CSE) with a high degree of esterification of 2.95, was synthesized and used for the formation of temperature-responsive films. Transparent and hydrophobic thin films were fabricated by dip-coating hydrophilic and hydrophobic surfaces with CSE. The films had thicknesses between 8 and 360 nm, depending on the concentrations of CSE solutions. Static contact angles of water drops on the films were up to 120°. The thin films from CSE solutions in toluene with concentrations of at least 5 mg/mL were not permeable for water molecules, as shown via cyclic voltammetric analysis. Based on film properties and morphologies, different self-assembly mechanisms of CSE films on hydrophilic and hydrophobic surfaces were proposed. In addition, these films showed temperature-responsiveness, which was demonstrated by the temperature-controlled release of rhodamine B molecules from films
Lightweight Natural Fiber Insulation Boards Produced with Kapok Fiber ( Ceiba Pentandra ) and Polylactic Acid or Bicomponent Fiber as a Binder
No full textAbstract Traditionally, kapok fiber is employed as filling for soft pillows, bedding, and diverse elements. Due to its buoyancy and proportion between cell wall and lumen, it is also applied as buoyant material in life vests and insulation materials. This study examine slightweight insulation panels produced from kapok fibers. Lightweight insulation boards are produced by hot‐air using kapok fibers (95%) bonded with polylactic acid or bicomponent fiber (5%), achieving very low densities of 10,15, and 20 kg.m −3 . The technological attributes like density, porosity, water absorption, wettability, compression, and thermal conductivity, are evaluated against commercial glass wool. In terms of water absorption rates, there is a direct correlation with density. All the variables reach short‐term water absorption values less than 1 kg.m −2 , which are comparable to commercial standards. This can be attributed to the lower density, higher porosity of the samples, and the inherent hydrophobic wax layer in the cell wall surface of kapok fibers. This trend is also evident in wettability tests, where produced boards demonstrated water‐repellency when exposed to water. Regarding the mechanical property of compression, neither the binder nor the density significantly impacts compression strength. The thermal conductivity performance of kapok‐based boards is comparable with commercially available ones.Georg-August-Universität Göttingen https://doi.org/10.13039/501100003385Open-Access-Publikationsfonds 202
Evaporative cooling of sessile water microdrops measured with atomic force microscope cantilevers
No full textWe monitored the evaporation kinetics of drops from solid surfaces and the resulting cooling of the surfaces. To do this we deposited water drops with diameters smaller than 100 μm onto atomic force microscope (AFM) cantilevers. Due to the surface tension of the liquid, the Laplace pressure inside the drop, the change of the interfacial stress at the solid–liquid boundary and evaporative cooling, the cantilevers are deflected by typically some hundred nanometers. We used pure silicon and gold-coated silicon cantilevers in order to be able to separate and quantify the cooling effect from that due to the surface tension. We measured the bending of the cantilevers along their longitudinal axis versus time with an AFM-like setup, and monitored the contact angle and radius of the evaporating drops with video microscopy. We developed a FEM model for the bending of a cantilever as a result of surface forces and evaporative cooling. Experimental results are reproduced by FEM simulations
Investigation of electrokinetic forces on single particles
No full textThis work shows that in many aspects of colloidal systems there exists a coupling between hydrodynamic and electrostatic interactions. For charged particles immersed in a polar medium, there is a pronounced influence of the electric field upon the motion of the particle in the fluid. Experimentally, this leads to electrokinetic effects , which may influence the coagulation of colloid particles and their adsorption at surfaces. These effects can be
described by extending the equations of motion by an additional electrostatic term.
This work also gives evidence of the existence of the hydrodynamic phenomenon of slip between hydrophilic bodies in an aqueous medium. Recently, more general boundary conditions, differing from the no-slip boundary condition , have been proposed. Due to the experiments presented here, the more general boundary conditions have to be considered only for shear stresses, which the liquid experiences in the vicinity of the solid interfaces.
In order to carry out these measurements using the colloidal probe technique , new types of rectangular tipless cantilevers have been designed and fabricated. These have the advantage, with respect to commercial triangular cantilevers, of affecting less the hydrodynamics of the microsphere in vicinity of the flat surface. These home made cantilevers have also a higher sensitivity in the specific range of forces of our interest (0.1 ÷ 10 nN)
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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