1,721,049 research outputs found
Copolymers with polyester-polycarbonate blocks containing poly(caprolactone) segments, and use thereof for the preparation of biodegradable matrixes
No full textThe invention relates to [OCO2AOCO2B]a, where a is an integer between 1 and 300 inclusive; A and B, which may be the same or different, are blocks which can be obtained by reaction between a bis(chloroformate) of oligomeric poly(caprolactone) and HO[R1CO2]x[R2CO2]yH, where R1 and R2, which may be the same or different, are each an aliph. hydrocarbon residue with a linear or branched chain having from 1 to 4 carbon atoms; x and y are integers from 1 to 50, in any possible ratio from 0 to 1; the groups R1CO2 and R2CO2 being randomly distributed in the polyester residue. These polymers are useful as matrixes for controlled release of drugs
A new chain extension reaction on poly(lactic-glycolic acid) (PLGA) thermal oligomers leading to high molecular weight PLGA-based polymeric products
No full textA novel and effective chain-extension procedure for obtaining high-molecular-weight PLGA-based bioerodible polymers is described. This procedure consists in a polycondensation reaction between PLGA thermal oligomers of average molecular weight 1000-3000 and bischlorofomates of either simple diols or α,ω-bis-hydroxylated oligomers, such as polyethyleneglycols or bis-hydroxy terminated poly-∈-caprolactones. In the latter case, multiblock copolymers are obtained. By varying the nature and the length of the starting diol, as well as the lactic/glycolic acid molar ratio in the starting PLGA oligomer, products with widely different physicochemical properties can be synthesized. In particular, dissolution times in aqueous media can be tuned within an ample range, from a few days to several months. This provides exceptional opportunities for designing products whose properties are tailored in view of specific applications in the biomedical field
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
Multiblock copolymers based on segments of poly(D-L-lactic-glyolic acid) and poly- (ethylene glycol) or poly(e-caprolactone): a comparison of their thermal properties and degratation behaviour
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