1,720,961 research outputs found
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
Spray-dried chitosan/ethylcellulose microspheres for nasal drug delivery: swelling study and evaluation of in vitro drug release properties
No full textThe aim of this study was to develop spray-dried chitosan-based microspheres, suitable for nasal
delivery of loratadine, and to evaluate their potential of modifying loratadine release. The microspheres
were composed with ethylcellulose (EC) and chitosan (CM) in two different weight ratios, 1:2 and 1:3.
One-phase systems (dispersions) and two-phase systems (emulsions and suspensions) were subjected
to spray-drying, resulting in conventional and composed microspheres, respectively. The microspheres
were evaluated with respect to the yield, particle size, encapsulation efficiency, physical state of the
drug in the polymer matrix, swelling properties and in vitro drug release profile. It was shown that
particle size, swelling ability and loratadine release from spray-dried microspheres were significantly
affected by the polymeric composition and feed concentration in spray-drying process. Emulsifying
method to produce composed EC/CM microspheres resulted in improved loratadine entrapment
and moderate swelling, when compared to conventional chitosan microspheres. It seems like better
formation of EC cores and chitosan coating were obtained when higher feed concentration and
ultrasonic homogenization were employed in the preparation of emulsion systems and when EC to
CM weight ratio was 1:
Development and bioadhesive properties of chitosan-ethylcellulose microspheres for nasal delivery
No full textLoratadine-loaded microspheres were prepared by spray-drying of dispersions, emulsions and suspensions differing in polymeric
composition and solvents used. Conventional microspheres were obtained by spray-drying of dispersions composed of
chitosan (CM) as only polymer, while composed microspheres were obtained by spray-drying of two-phase systems composed
of chitosan and ethylcellulose (EC). Microspheres differed in EC/CM weight ratio (0:1, 1:2 and 1:3) and in loratadine/polymers
weight ratio (1:6 and 1:8).
The entrapment efficiencies were between 67.9 and 86.1%; less loratadine was entrapped as polymer/drug ratio decreased.
In comparison to one-phase systems composed of CM as only polymer, spray-drying of two-phase systems composed of both,
CM and EC resulted in improved loratadine entrapment (80.1–86.1%). All microspheres were positively charged, indicating the
presence of chitosan at the surface, regardless of the drug content and the type of spray-dried system. The highest zeta-potential
was measured for loratadine-free conventional microspheres, consisting of chitosan only (32.7±1.3 mV). Tensile studies showed
that both, EC/CM ratio and the type of spray-dried system influenced the bioadhesive properties of the microspheres in a way
that the microspheres with higher chitosan content were more bioadhesive and microspheres prepared from suspensions were
more bioadhesive than those prepared from emulsions, regardless of the same polymeric composition. The results suggested that
the spray-drying method is useful to produce bioadhesive loratadine-loaded microspheres.
© 2004 Elsevier B.V. All rights reserved
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
Encapsulation and release of gemfibrozil from biodegradabile polymer microspheres and macromolecular prodrugs
No full textThe purpose of this study was to evaluate and compare the ability of the macromolecular conjugates and microspheres to modify the
release rate of gemfibrozil (Gem). Gem was covalently linked to two similar polymers: poly[a,b-(N-2-hydroxyethyl-DL-aspartamide)]
(PHEA) and poly[a,b-(N-3-hydroxypropyl-DL-aspartamide)] (PHPA) by an ester linkage. The polymer–drug conjugates obtained
(PHEA–G(1–3) and PHPA–G) differ in weight-average molecular weight, length of spacer and Gem content. Microspheres, composed of
chitosans of different molecular weight alone or as a mixture with (2-hydroxypropyl)methylcellulose (HPMC), PHEA or PHPA and with
different theoretical polymer/drug ratio (2:1 and 3:1, w/w) were prepared by spray drying. The microparticulate systems were
morphologically characterised by scanning electron microscopy, particle size analysis and Gem content was determined. In vitro
dissolution tests were performed to evaluate the feasibility of conjugates and microspheres in modulating Gem release. The results
obtained show that microspheres are always suitable to modulate Gem release and that the best conditions are achieved by microspheres
composed of the low molecular weight chitosan (CL) combined with PHPA or HPMC with either 2:1 or 3:1 (w/w) polymer/drug ratio.
The PHEA–G conjugates exhibited rapid Gem release within less than 2 h, while the PHPA–G conjugate showed sustained Gem release
profiles over a 10-h period.
2002 Elsevier Science B.V. All rights reserved
Self-emulsifying pellets prepared by wet granulation in high-shear mixer: influence of formulation variables and preliminary study on the in vitro absorption
No full textA method of producing self-emulsifying pellets by wet granulation of powder mixture composed of microcrystalline cellulose, lactose and nimesulide as model drug with a mixture containing mono- and di-glycerides, polisorbate 80 and water, in a 10-l high shear mixer has been investigated. The effects of the formulation variables on pellets characteristics were evaluated by mixtures experimental design and by a polynomial model, in order to describe the phenomenon, to verify eventual interactions among components of the mixture and to investigate the feasibility of scaling-up. After determination of size distribution, the pellets were characterised by scanning electron microscopy, dissolution and disintegration tests, and by in vitro absorption test Such an approach, applied to the development of a self-emulsifying system for nimesulide as poorly water-soluble model drug, resulted in different formulations with improved drug solubility and permeability characteristics. The data demonstrate that pellets composed of oil to surfactant ratio of 1:4 (w/w) presented improvement in performance in permeation experiments
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