1,720,986 research outputs found
Effects of Lithium Niobate Polarization on Cell Adhesion and Morphology
No full textUnderstanding how the interfacial effects influence cell adhesion and morphology is of fundamental interest for controlling function, growth, and movement of cells in vitro and in vivo. In particular, the influence of surface charges is well-known but still controversial, especially when new functional materials and methods are introduced. Here, the influence of the spontaneous polarization of ferroelectric lithium niobate (LN) on the adhesion properties of fibroblast cells is investigated. The spontaneous polarization of LN has one of the largest known magnitudes at room temperature (similar to 78 mu C/cm(2)), and its orientation can be patterned easily by an external voltage, this motivating highly the investigation of its interaction with cells. Immunofluorescence and migration assays show strong evidence that the surface polarity regulates the adhesion functions, with enhanced spreading of the cytoskeleton on the negative face. The results suggest the potential of LN as a platform for investigating the role of charges on cellular processes, thus favoring new strategies in fabricating those biocompatible constructs used for tissue engineering. In fact, the orientation of the high-magnitude polarization can be patterned easily and, in combination with piezoelectric, pyroelectric, and photorefractive properties, may open the route to more sophisticated charge templates for modulating the cell response
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Simple and Rapid Bioink Jet Printing for Multiscale Cell Adhesion Islands
No full textA simple and rapid process for multiscale printing of bioinks with dot widths ranging from hundreds of microns down to 0.5 mu m is presented. The process makes use of spontaneous surface charges generated pyroelectrically that are able to draw little daughter droplets directly from the free meniscus of a mother drop through jetting ("p-jet"), thus avoiding time-consuming and expensive fabrication of microstructured nozzles. Multiscale can be easily achieved by modulating the parameters of the p-jet process. Here, it is shown that the p-jet allows us to print well-defined adhesion islands where NIH-3T3 fibroblasts are constrained to live into cluster configurations ranging from 20 down to single cell level. The proposed fabrication approach can be useful for high-throughput studies on cell adhesion, cytoskeleton organization, and stem cell differentiation
Graphene and carbon black nano-composite polymer absorbers for a pyro-electric solar energy harvesting device based on LiNbO3 crystals
No full textA novel scheme for solar energy harvesting based on the pyro-electric effect has been demonstrated. The proposed harvester is based on an optical system focusing solar radiation onto a ferroelectric crystal (i.e. lithium niobate). The face exposed to the heating source is coated with a nanocomposite material (i.e. carbon black and graphene particles) that greatly improves the adsorption of solar radiation. The solar energy focused onto the crystal through a simple optical system allows one to induce a thermal gradient able to generate electric charges. Experiments have been carried out indoor as well as outdoor (in Pozzuoli, Naples, Italy, on December). Results show that two configurations appear to be preferable: (a) pyro-electric element with carbon black-based coating and a Fresnel lens (surface of about 100 cm(2)); (b) pyro-electric element with graphene-based coating and a Fresnel lens (surface of about 600 cm(2)). In both experimental arrangements the maximum temperature variation reached locally onto the lithium niobate substrate is relatively high with peaks greater than 250 degrees C. The maximum electrical power peak is of about 90 mu W and about 50 mu W for (a) and (b) respectively. The results of this first investigation are encouraging for further development of more efficient harvesting devices. (C) 2014 Elsevier Ltd. All rights reserved
Bipolar Patterning of Polymer Membranes by Pyroelectrification
No full textPolymer freestanding membranes with permanent bipolar patterns are fabricated by "pyroelectrification". The thermal stimulation of periodically poled lithium niobate (PPLN) crystals simultaneously generates the pyroelectric effect, the glass transition of the polymer, and therefore the periodic electric poling of the polymer. The reliability of these membranes is demonstrated for applications under both dry and wet conditions, including cell patterning
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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