1,721,214 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
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
Seladin-1 as a new marker for oxidative stress and degeneration in central neurons and astroglia
No full textSeladin-1 (Sel-1) stands for Selective Alzheimer’s Disease Indicator-1. By sequence similarity, it was identified as DHCR24, a broadly expressed enzyme highly expressed in brain, that converts desmosterol to cholesterol, and conserved from plants to mammals. Its inactivating mutations are the genetic basis of desmosterolosis, a disease characterisedd by several neurologic defects. Relative to Alzheimer’s disease (AD), Seladin-1 mRNA is downregulated in the brain regions more susceptible to the AD pathology. Moreover, a relative Seladin-1 transcription fluctuation during aging in a transgenic mouse model of AD has been reported;. In brief, seladin’s role appears to be implicated with protection of cells against b amyloid (Abeta) induced toxicity and oxidative stress, suggesting a role in cell survival.
Aim: This study set off to investigate the intracellular distribution of sel-1 gene product under normal conditions, or after overexpression, as well as its expression under toxic insults, using neuronal and astroglial models.
Materials and Methods: Immortalised neuronal cell lines, GN11 (mouse immature,migrating neurons), GT1-7 (mouse mature hypothalamic neurons), were used; moreover primary cultures of purified mouse astrocyte type-1 cells were prepared. A custom made anti-sel-1 primary polyclonal Ab was used, along with cholesterol (filipin), ER, Golgi and mitochondrial markers. A sel-1_GFP-tagged vector was used to overexpress the protein in neurons. We used different agents to mediate toxic insults, simulating cellular oxidative stress conditions (BSO, DEM, H2O2), and the AD defects (Abeta and INFg) in neurons and astroglia.
Results-Conclusion
Using RT-PCR we confirmed the expression of the sel-1 gene in neurons and astroglia. Using immunofluorescence we observed a partial colocalisation of sel-1 with the Golgi and the ER, and a vesicular distribution only in the mature neurons, with the vesicles budding out of the Golgi and accumulating near the axon terminals. Overexpression of the protein in the immature GN11 neurons by transfection with Sel-1_GFP resulted in their morphological differentiation and induced a vesicular distribution similar to that of the mature neurons.
Sel-1 mRNA levels quantified by Real Time PCR appear to be 100 fold higher in the mature GT1-7 neurons and astroglia, compared to the immature GN11 neurons. Moreover, sublethal toxic insults and oxidative stress significantly downregulated sel-1 mRNA in neurons and astroglial cultures; however this downregulation is accompanied with the appearance of an alternative longer splicing variant of Sel-1. Thus, we suggest this longer form to be a “stress marker” considering it became prominent upon stress induction. Moreover, this “stress marker” reached the expression levels of the normal transcript present in control samples. On the basis of sequence analysis of mouse, rat and human sel-1, we found a TATA-less CpG island that probably regulates the expression of the protein with the enzymatic activity and the cholesterol production from its precursor. The second transcript, given its apparition under cell stress, may encode a protein that plays a role in the cell response to stress. We have been working on a region that could correspond to the second promoter, and we have yet to experimentally verify all its trans acting elements.
In conclusion, we hereby report a different mRNA expression of sel-1 between mature and immature neurons, and a differential protein distribution in the two cell types. Moreover we report a modification of this gene at the transcriptional level upon stress induction, both in neurons and astroglia. Thus, sel-1 is a not only a indicator of neurodegeneration due to AD pathology, but a critical cell stress marker whose precise role in cell survival is yet to be characterized. (Grants: MIUR PRIN 2003060512_001; Fondazione CARIPLO
Differential expression of Selective Alzheimer Disease Indicator (Seladin-1)/DHCR24 gene in immortalized GnRH neurons
No full textMembrane cholesterol-enriched lipid domains (lipid-rafts) are essential for the structural and functional integrity of neuronal membranes; they have been involved in a variety of different functions (e.g., signal transduction, lipid transport and metabolism, cell growth and migration) and can be modified by aging and certain neurodegenerative diseases. Recently, a new gene termed "selective Alzheimer’s disease indicator 1" (Sel-1) was shown to confer resistance to Alzheimer’s disease-associated neurodegeneration acting as a antiapoptotic agent; Sel-1 was found to be identical to the human gene which encodes for a cholesterol-biosynthetic enzyme 3beta-hydroxysterol delta24-reductase (DHCR24), found to be mutated in the patients affected by desmosterolosis. In the present study we used immortalized neurons derived from mature (GT1-7 cell line) and from immature (GN11 cell line) GnRH neurons to investigate the role of Sel-1/DHCR24 on neuronal functions. By real time-PCR technique, we found that GT1-7 cells present 10-100 times higher levels of Sel-1 mRNA compared to GN11 cells. The immunoreactivity of endogenous Sel-1 appears mainly distributed around the nucleus associated by endoplasmic reticulum; transfection of a fluorescent construct of Sel-1 (Sel-1GFP) showed a similar distribution of the protein. The staining of the two cell lines with filipin, a fluorescent polyene antibiotic that detects unesterified cholesterol, revealed a significant accumulation of free cholesterol in vesicular structures. Finally, we report the differential modification of the expression of Sel-1 under several toxic insults (oxidative stress, cholesterol depletion, beta-amyloid). In conclusion, these data indicate that mature and immature GnRH neurons differentially express Sel-1, providing a good cell model to investigate the role of this protein and of cholesterol in neuronal physiopathology. (Grants: MIUR COFIN2003-2005, 2003060512 and Fondazione CARIPLO)
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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