1,721,036 research outputs found
PEG-epirubicin conjugates with high drug loading
No full textPEG is a polymer extensively studied in drug delivery and some of its conjugates with proteins are already on the market. Studies are also focusing on PEG as polymeric carrier for low molecular weight drugs, but limitations arise from the possibility to link the drug at the level of the only one or two hydroxyl residues of the polymer. The synthesis of dendrimeric structure at the level of these groups may be a convenient solution to increase the polymer drug payload. The present report deals with the preparation of dendrimers, based on amino adipic acid or beta-glutamic acid as branching molecule, built on a PEG diol of MW 10,000 Da.
The polycyclic large drug epirubicin was chosen as a model to investigate the influence of the branching moiety structure in avoiding the drug steric hindrance during the coupling reaction. Several derivatives with increasing number of drug molecules linked to each PEG chain were synthesized and their physical, chemical and biological properties were studied. The study demonstrated that the use of proper amino bicarboxylic acid (amino adipic acid or β-glutamic acid), as branching moiety for the dendrimer synthesis, allows the linking of hindered molecule as epirubicin to multibranched PEG. It was found that the most drug loaded conjugates dissolve in water only following a pre-dissolution in DMSO. This solubility problem could be solved by adding a hydrophilic peptide linker between drug and polymer. The conjugates, synthesized in good yield and purity, showed higher stability than free epirubicin in buffers at different pHs and in plasma and a much prolonged residence time in blood. Dynamic light scattering investigation showed the high tendency of these products to aggregate forming stable micelles
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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