1,720,976 research outputs found
A novel endogenous antimalarial : Fe(II)-protoporphyrin IXα (heme) inhibits hematin polymerization to β-hematin (malaria pigment) and kills malaria parasites
No full textThe polymerization of hemoglobin-derived ferric-protoporphyrin IX [Fe(III)PPIX] to inert hemozoin (malaria pigment) is a crucial and unique process for intraerythrocytic plasmodia to prevent heme toxicity and thus a good target for new antimalarials. Quinoline drugs, i.e., chloroquine, and non-iron porphyrins have been shown to block polymerization by forming electronic π-π interactions with heme monomers. Here, we report the identification of ferrous-protoporphyrin IX [Fe(II)PPIX] as a novel endogenous anti-malarial. Fe(II)PPIX molecules, released from the proteolysis of hemoglobin, are first oxidized and then polymerized to hemozoin. We obtained Fe(II)PPIX on preparative scale by electrochemical reduction of Fe(III)PPIX, and the reaction was monitored by cyclic voltammetry. Polymerization assays at acidic pH were conducted with the resulting Fe(II)PPIX using a spectrophotometric microassay of heme polymerization adapted to anaerobic conditions and the products characterized by infrared spectroscopy. Fe(II)PPIX (a) did not polymerize and (b) produced a dose- dependent inhibition of Fe(III)PPIX polymerization (IC50 = 0.4 molar equiv). Moreover, Fe(II)PPIX produced by chemical reduction with thiol- containing compounds gave similar results: a dose-dependent inhibition of heme polymerization was observed using either L-cysteine, N-acetylcysteine, or DL-homocysteine, but not with L-cystine. Cyclic voltammetry confirmed that the inhibition of heme polymerization was due to the Fe(II)PPIX molecules generated by the thiol-mediated reduction of Fe(III)PPIX. These results point to Fe(II)PPIX as a potential endogenous antimalarial and to Fe(III)PPIX reduction as a potential new pharmacological target
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
The Italian central institute for cataloguing and documentation standards.
No full textThe Central Institute for Cataloguing and Documentation (ICCD) is an important Institute under the Ministry for Cultural Heritage and Activities (MiBAC) which defines the standards and tools for the Cataloguing and Documentation of the Italian cultural heritage.
The ICCD assumes responsibility for the coordination of research activities to define cataloguing standards for various types of cultural heritage, in the archaeological, environmental-architectural, historical, art and ethno-anthropological spheres.
The cataloguing standards consist of regulations, specific standards and support tools (glossaries, lists of values) and a set of rules and methodological guidelines to be followed for acquisition of information on properties and for the production of the pertinent documentation, with the objective of recording the data according to consistent, nationally-shared criteria
I-MIBAC Voyager and I-MIBAC 40: the cultural heritage in the palm of your hand.
No full textAn initial recognition of the tools available for providing information on the EU-CHIC introduces us to some brief considerations on potential shortcomings, both with reference to the categories of information identified and to the format that this information must/could have.
In fact, increasingly advanced systems now enable us to have an essentially infinite amount of information in the palm of our hand, which is easy to consult and clear to use. It is absolutely essential to think of EU-CHIC as part of the new virtual specialities generated with the aid of “augmented reality” systems, developed for mobile devices like the latest generation smartphones (Apple, Windows or Android OS), necessarily equipped with GPS for positioning, magnetometer (compass), webcam for viewing a video stream in real time and, obviously, an Internet connection system for receiving and sending data online
Establishing criteria for selection of efficent MTTs for Eu-CHIC project.
No full textThe main research topic concerning task 3 of WP4 regarded the development and definition of choice criteria and indicators of the main methods, tools and techniques (MTTs) used for collecting information on European cultural heritage
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