1,720,992 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
VIBRATION-BASED STIMULATION OF CELLS ENHANCES POLYETHYLENIMINE-MEDIATED GENE DELIVERY
No full textIntroduction
Gene therapy is a promising strategy for the treatment of genetic disorders. In this context, a safe and efficient transfer of genetic material into target cells (i.e. transfection), i.e. the successful introduction of exogenous nucleic acids (DNA or RNA) through the cell membrane, is required [1-2]. Over the past two decades, considerable progress has been made in gene transfer technologies, and thus far, different delivery strategies have been developed. Chemical gene delivery vectors utilize specialized non-viral carriers, such as cationic polymers, to overcome the cellular barriers and ease the transfer of exogenously delivered nucleic acids into cells [3-4]. In this light, gene transfer mediated by cationic polymer/DNA complexes (polyplexes) exhibit high transfection efficiencies both in vitro and in vivo [5]. As an alternative to vector-mediated gene delivery, physical methods (e.g. electroporation, sonoporation, magnetofection) relies on the use of different kinds of mechanical forces to induce the relatively quick and transient destabilization of the plasma membrane barrier, hence enabling the nucleic acids to enter the cell [6].
Herein, we propose a novel in vitro transfection strategy relying on the combined use of a physical method and a chemical vector. Specifically, mechanical stimulation in the form of vibrations was used to induce a transient cell membrane poration in order to promote linear polyethylenimine (lPEI)/pDNA polyplex uptake by cells, and enhance transfection efficiency.
Results and Discussion
In this work a novel, inexpensive, easy-to-use mechanical stimulation device (Fig. 1-A), modified ad-hoc because not meant to stimulate cells, was used for cell culture experiments to induce transient cell membrane poration. We thus evaluated the role of different stimulation frequencies (i.e. 10, 50, 100, 500 and 1,000 Hz for 5 min) on the morphology of HeLa (human epithelial ovarian carcinoma cells) and MG-63 (human fibroblast osteosarcoma) cells by means of a Scanning Electron Microscopy (SEM) inspection. As shown in Fig. 1-B, unstimulated, 10 Hz- and 50 Hz-stimulated cells shared very similar morphologies and a marked smooth surface. Notably, when stimulated at 100, 500 and 1,000 Hz, SEM analysis revealed the presence of pores and blisters covering the whole cell surface (Fig. 1-B). Such protrusions found on the cell surface as the consequence of the high frequency-stimulation (i.e. from 100 Hz onward), may be related to the blebbing phenomenon, that is a defensive mechanism exploited by cells once subjected to some stressors [7].
We also examined the kinetics of cell membrane recovery after poration and we found that cells were able to restore membrane integrity and recover their original morphology within 1 hour when stimulation was released. Taken together, these observations pointed out that the application of mechanical stimulation was not detrimental to cells and proved that the vibration-based cell stimulation from 100 Hz onward led to a transient cell membrane destabilization, and ultimately to the formation of membrane pores.
Dynamic in vitro transfection experiments were performed as well. Cells were challenged with lPEI/pGL3 complexes (DH = 113±4 nm; surface charge (Zp) = +17±5 mV), then stimulated at different frequencies (10, 50, 100, 500 and 1,000 Hz for 5 min) and for different times (500 Hz for 5, 30 and 60 min). Transfection efficiency (TE) in stimulated cells was evaluated 24 hr-post transfection and compared to statically transfected cells. As reported in Fig. 1-C and 1-D, high-frequencies vibrational stimulation (from 100 Hz onward) dramatically enhanced TE of lPEI/DNA complexes, leading to a ≈50- and ≈100- fold increase in transgene expression in MG-63 and HeLa cells, respectively, irrespective of the duration of the stimulation. Besides, low-to-negligible cytotoxic effects were found in both cells lines.
These findings mirrored SEM results, since from 100 Hz onward, a change in cell morphology was observed, which ultimately resulted in enhanced cell uptake of polyplexes. We can speculate that cell blebbing induced through mechanical stimulation, together with the consequent cell repair mechanism, accounts for increased polyplex internalization, and for the consequent increase in TE. It is worthy of note that the same behavior was found in both HeLa and MG-63 cell lines, demonstrating that such stimulation effects were cell-type independent.
Conclusion
We herein demonstrated that the application of a vibration-based stimulation to cells at suitable frequencies (i.e. 100 Hz onward) dramatically enhanced the TE of lPEI-based DNA delivery, as compared to standard static transfection conditions, coupled with low-to-negligible cytotoxicity. Additional investigation on the precise mechanism(s) and pattern(s) involved in cell membrane perturbation and recovery are required to shed light on how mechanical vibrations enhance polyplex internalization
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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