1,720,982 research outputs found
Structural and Morphological Investigation of Ceria-promoted Al2O3 Support Under Severe Reducing/Oxydizing Conditions
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Raman imaging study on living tardigrades: origin, nature and function of pigments in Echiniscus blumi
No full textTardigrades exhibit a variety of pigmentations. Several species are translucent or whitish, but many others are markedly colored with red-orange, brown, green and yellow pigments. These pigments may be found in the body cavity, storage cells, epidermis, eye-spots and, according to literature, in cuticle. The genus Echiniscus is composed of many species. Despite occurrence of pigments is well documented for many of them, the chemical nature, source and function (especially in relation to their resistance to harsh physical and chemical conditions) of these pigments remain unknown. Some hypotheses were formulated about them, but to the best of our knowledge no direct and conclusive experimental proof has been reported to date. Therefore, we are taking this opportunity to attempt a resolution for these open questions using Raman spectroscopy on living individuals of Echiniscus blumi.
Raman spectroscopy is a non-destructive and (semi)-quantitative analytical technique based on scattering laser radiation by vibrating molecules, which proved to be an ideal tool for studying living cells and biological tissues. Moreover, by incorporating Raman micro-spectroscopy it is possible to obtain an image of the spatial distribution of the main biochemical constituents of a biological sample (i.e. Raman mapping or imaging).
In our analyses, pigments in E. blumi are identified as carotenoids. Their spectra well match those available in literature for β-carotene, zeaxanthin and β-cryptoxanthin, all having 11 conjugated C=C bonds, but not that of lutein, which has only 10. Previously reported chemical reactivity data of Echiniscus pigments suggest β-carotene as the most likely candidate pigment in the genus. Moreover, pigment distribution within the animal body cavity is imaged with Raman mapping. The dietary origin of the pigments (from the moss, Grimmia orbicularis) is demonstrated, as well as their presence in the eggs and in eye-spots, and their absence in the animal cuticle. Using in-vivo Raman imaging, a decrease in carotenoid content is detected after the induction of oxidative stress on animals, supporting the hypothesis of an antioxidant function of these pigments during anhydrobiosis.
Considering the lack of methods to directly study antioxidant function of carotenoids in vivo, pigmented tardigrades, investigated with Raman imaging, could be used as model organisms for this purpose opening new perspectives of research in living organisms
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
Raman imaging of erythrocytes infected with the malaria parasite Plasmodium falciparum
No full textRed blood cells infected with the malaria parasite Plasmodium falciparum have been investigated with Raman spectroscopy. Using a motorized stage and a Raman microscope, Raman spectra have been collected from a grid of points superimposed over the optical image of infected erythrocytes, with a step of 1 m. A preliminary data analysis evidenced the anomalous distribution of hemoglobin in infected cells compared to normal erythrocytes, indicating the position occupied by the parasite inside the cells. Such information, obtained without the use of any staining, has been confirmed by cluster analysis performed on the Raman data set. Spectroscopic data clearly evidenced the presence of hemozoin (or malaria pigment), the crystalline detoxification product of host hemoglobin. This indicates that Raman imaging can provide useful informations on the internal structure of parasites.
These preliminary data suggest that the imaging based on “point to point” Raman mapping could be exploited to study the malaria parasite and its interaction with the red blood cells, also upon exposure to anti-malarial drugs.
ANTIMAL EU018834 support is acknowledged
Sara Finaurini is training AntiMal International PhD Programm
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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