1,720,989 research outputs found
The influence of C-ions and X-rays on human umbilical vein endothelial cells
Get PDFDamage to the endothelium of blood vessels, which may occur during radiotherapy, is discussed as a potential precursor to the development of cardiovascular disease. We thus chose human umbilical vein endothelial cells (HUVEC) as a model system to examine the effect of low and high linear energy transfer (LET) radiation. Cells were exposed to 250 kV X-rays or C-ions with the energies of either 9.8 MeV/u (LET=170 keV/µm) or 91 MeV/u (LET=28 keV/µm). Subculture of cells was performed regularly up to 49 days (~22 population doublings) post-irradiation. Immediately after exposure cells were seeded for the colony forming assay. Additionally, at regular intervals mitochondrial membrane potential (JC-1 staining) and cellular senescence (senescence associated β-galactosidase staining) were assessed. Cytogenetic damage was investigated by the micronucleus assay and the high-resolution mFISH technique. Analysis of radiation-induced damage shortly after exposure showed that C-ions are more effective than X-rays with respect to cell inactivation or the induction of cytogenetic damage (micronucleus assay) as observed in other cell systems. For 9.8 and 91 MeV/u C-ions relative biological effectiveness values of 2.4 and 1.5 were obtained for cell inactivation. At the subsequent time-points the number of micronucleated cells decreased to the control level. Analysis of chromosomal damage by mFISH technique revealed aberrations frequently involving chromosome 13 irrespective of dose or radiation quality. Disruption of the mitochondrial membrane potential was seen only a few days after exposure to X-rays or C-ions. Cellular senescence was not altered by radiation at any time-point investigated. Altogether our data indicate that C-ions were LET-dependently more effective in damaging endothelial cells shortly after exposure. Late damage to endothelial cells, however, was not found for the applied conditions and endpoints
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Chromosome aberrations in human lymphocytes irradiated with heavy ions
No full textBecause of the increasing use of heavy ions in cancer therapy and for the planning of manned space travels, a realistic estimate of the health risks associated with particle exposure is indispensable. The standard method to quantify the exposed dose and to assess the health risks of radiation is the analysis of chromosome aberrations in peripheral blood lymphocytes at the first post-irradiation mitosis at one fixed time, 48 h, after in vitro stimulation. Using this procedure very low RBE values for high LET particles are reported. However, evidence is accumulating that high LET induced cell cycle delays and apoptosis may influence the aberration yield observable in metaphase cells. To address these questions, lymphocytes obtained from a healthy donor were irradiated with X-rays, C-, Fe- and Fe-like particles with LETs ranging from 2-3160 keV/microm and chromosome aberrations were measured in first cycle metaphase cells at multiple 3 h collection intervals from 48 to 84 h post-irradiation. In parallel, aberrations were determined in G2-phase cells and cell cycle progression as well as radiation-induced apoptosis were examined. Analysis of the data sets shows that high LET-induced apoptosis does not affect the observable aberration yield. However, a relationship between high LET induced cell cycle delays and the number of aberrations carried by a cell was found: the delayed entry of heavily damaged cells into mitosis results from a prolonged arrest in G2 and the delay is dose- and LET-dependent. Detailed statistical analysis of the frequency distributions of aberrations among cells revealed a correlation between the selective delay of heavily damaged cells and the number of particle hits per cell nucleus. Altogether, the data demonstrate that the application of the standard metaphase assay 48 h post-irradiation results in an underestimation of the RBE of high LET particles. Application of alternative cytogenetic approaches (G2-PCC analysis, the integration analysis) confirmed this conclusion
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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