1,720,974 research outputs found
TOF-SIMS PCA ANALYSIS OF Myrtus communis L.
No full textNowadays there is a growing interest of researchers for the application of sophisticated analytical
techniques in conjunction with statistical data analysis methods to the characterization of natural
products to assure their authenticity and quality, and for the possibility of direct analysis of food to
obtain maximum information. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS)
in conjunction with principal components analysis (PCA) are applied to study the chemical composition
and variability of Sardinian myrtle (Myrtus communis L.) through the analysis of both berries alcoholic
extracts and berries epicarp. ToF-SIMS spectra of berries epicarp show that the epicuticular waxes
consistmainly of carboxylic acids with chain length ranging from C20 to C30, or identical species formed
from fragmentation of long-chain esters. PCA of ToF-SIMS data from myrtle berries epicarp distinguishes
two groups characterized by a different surface concentration of triacontanoic acid. Variability in
antocyanins, flavonols, a-tocopherol, and myrtucommulone contents is showed by ToF-SIMS PCA
analysis of myrtle berries alcoholic extracts
HEMOCOMPATIBLE MATERIALS
No full textThe complexity of the interactions between materials
and blood makes the development of hemocompatible
surfaces very difficult. Biomaterials research is focused
on developing materials that have fewer risks and
greater benefits. Stents that ‘‘actively’’ prevent restenosis
are a great example of how surface modification of
metals can result in a dramatic clinical effect. Inert
materials are protein and platelet resistant, but they
do not prevent thromboembolic phenomena in vivo.
On the other hand, incorporating anticoagulants in to
surfaces reduces thrombin production, but this may
not be sufficient to prevent platelet adhesion and activation.
Thus, which approach will ultimately be successful is impossible to predict. Perhaps, the failure to produce
an ideal blood-compatible surface merely reflects our
limited understanding of the complex blood-materials
interaction.
Progresses in design hemocompatible materials will
be then determined by a deeper understanding of
both the surface properties of materials and the interfacial
phenomena originating at the blood–material
interface
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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