1,720,979 research outputs found
Introduction
No full textMany everyday products are manufactured using particulate materials whose behavior and performances depend upon starting particle chemical and structural characteristics.
Since particle characteristics affect the properties of a material, particle selection is normally needed across a range of industries and laboratories. Separation techniques play therefore a prominent role in selecting components to characterize them and for finding their possible useful applications.
This book presents an overview of some common separation techniques used to select and isolate particulate materials in liquid suspension, for a size chracterization or to prepare homogenous samples for a more detailed and complete physico-chemical characterization. The goal is to provide the Reader with the basic elements of these techniques for their conscious selection
Particle characterization: parameters and selected methods
No full textMany studies conducted in research laboratories as well as many industrial processes are based on the use of particulate material. A good knowledge of the chemical and physical properties of the constituent particles is the starting point for optimizing their use and enhancing their performances.
Since the list of physicochemical parameters to be determined could be remarkably long, it is important to identify the most relevant properties required for a meaningful characterization. Numerous techniques are available today to determine the parameters of interest, but those selected must be the most suitable and appropriate, taking into account the nature of the sample, the sample preparation, and the measurement principle.
This chapter lists some physicochemical parameters commonly evaluated for the characterization of particulate materials, focusing on the determination of the particle size and particle size distribution, and on the most common techniques for obtaining this information
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
Curcumin containing monoolein aqueous dispersions: A preformulative study
No full textThe present study describes the production and characterization of monoolein aqueous dispersions (MAD) as
drug delivery systems for curcumin (CR).
MAD based on monoolein and different emulsifiers have been produced and characterized. Morphology and dimensional
distribution have been investigated by Cryogenic Transmission Electron Microscopy (cryo-TEM), Xray
and Photon Correlation Spectroscopy (PCS).
Monoolein in different mixtures with sodium cholate, sodium caseinate, bentonite and poloxamer resulted in
heterogeneous dispersions constituted of unilamellar vesicles, cubosomes and sponge type phases, depending
on the employed components, as found by cryo-TEM and X-ray studies. CR was encapsulated with entrapment
efficiencies depending on the MAD composition, particularly the highest was reached in the case of
monoolein/poloxamer/sodium cholate mixture. The same mixture was able to maintain CR stability also after
6 months.
CR release modalities were in vitro investigated in order to mimic a possible subcutaneous administration of
MAD. It was found that MAD constituted of monoolein/poloxamer and monoolein/poloxamer/sodium cholate
mixtures were able to sustain CR release.
MAD viscous vehicles were produced by xanthan gum.
CR percutaneous absorption has been studied in vitro using excised human skin membranes [stratum corneum
epidermis (SCE)] mounted into Franz cells. It was found that fluxes (Fn) of CR incorporated in MAD are influenced
by the presence of monoolein based nanosystems. In particular xanthan gumbased MAD better control CR diffusion
from MAD
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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