1,720,967 research outputs found
Novel co-axial electrohydrodynamic in-situ preparation of liquid-filled polymer-shell microspheres for biomedical applications.
No full textSuspensions consisting of polymer-shelled microspheres are finding increasing use in a diverse range of technologies or applications, e.g. in the medical field, such as diagnostic imaging, drug and gene delivery and tissue engineering. In this work, a solution of water-insoluble polymethylsilsesquioxane was perfused through the outer needle of a co-axial needle arrangement while air was passed simultaneously through the inner needle, with both needles placed in an electric field. The liquid and air flow rates were varied but at 5 microl s(-1) for each material stable microbubble formation was achieved at 5.7 kV. The microbubbles were collected in a vial of distilled water and they rapidly converted into polymer-shelled microspheres containing approximately 60 wt% liquid. Microscopic examination of the spheres within 300 s of preparation showed a large population of near-spherical polymer-shelled microspheres with a mean size of 6 +/- 2 microm diameter near the water surface. After 48 h, the microspheres had collected at the bottom of the vial. The fact that the microspheres absorbed and encapsulated the liquid in which they were collected and the fact that their size (< 10 microm) is suitable for vascular administration make this a new one-step preparation technology for microspheres used in biomedical applications
Microbubbling and microencapsulation by co-axial electrohydrodynamic atomization
No full textMicrobubbles coated with polymers or surfactants have been used in medical imaging
for several years as ultrasound contrast agent particles and are now being investigated
by researchers as drug and gene delivery vehicles and blood substitutes. Current
methods available for the preparation of microbubbles are insufficient as they result in
microbubbles with a wide size distribution and as such filtration is necessary before
their use. With a view to fill the above demand, a detailed investigation has been carried
out in this research to learn the viability of co-axial electrohydrodynamic atomization
(CEHDA) technique to prepare microbubbles. The research also focuses on the effects
of the process parameters such as flow rates, applied voltage and material parameters
such as electrical conductivity, surface tension and viscosity with the objective of
preparing polymer or surfactant coated stabilized microbubbles with diameters < 8 μm
and with a narrow size distribution. A model glycerol-air system was used so that the
CEHDA technique was modified to generate suspensions of microbubbles to a diameter
< 8 μm with a narrow size distribution and then to characterise the CEHDA
microbubbling process in terms of size and stability with varying process parameters
and material parameters. Construction of a parametric plot between the air flow rate and
the liquid flow rate was extremely useful in identifying the flow rate regime of air and
liquid or suspension or solution for the continuous microbubbling of the system used.
With further investigations into the CEHDA microbubbling technique, it was possible
to develop strategies, first, to prepare suspensions of stabilized phospholipids-coated
microbubbles with a mean diameter of ~ 5 μm and a polydispersivity index of 9%, and
second, polymeric microspheres with a mean diameter of 400 nm and a polydispersivity
index of 8% using a biocompatible polymer
Electrohydrodynamic forming of porous ceramic capsules from a preceramic polymer
No full textPorous polymeric near-spherical capsules, ~ 3.6 mm in diameter, were prepared using an electrodydrodynamic process. These capsules were pyrolysed to porous ceramics, ~ 3 mm in diameter. The ceramic capsules had interconnected pores of ~ 1.3 μm in size, and large cells with a mean size of 28 μm. The larger pores resemble the cells in a typical ceramic foam and were evenly distributed throughout the structure. A large proportion of the ceramic capsules contained 65-70% porosity, and their compressive strength was 0.2-0.4 MPa. © 2008 Elsevier B.V. All rights reserved
Generation of multi-layered structures for biomedical applications using a novel tri-needle co-axial device and electrohydrodynamic flow
Full text linkIn this short communication, we describe the scope and flexibility of using a novel device containing three coaxially arranged needles to form a variety of novel morphologies. Different combinations of materials are subjected to controlled flow through the device under the influence of an applied electric field. The resulting electrohydrodynamic flow allows us to prepare double-layered bubbles, porous encapsulated threads and nanocapsules containing three layers. The ability to process such multilayered structures is very significant for biomedical engineering applications, for example, generating capsules for drug delivery, which can provide multistage controlled release
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
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
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