1,721,053 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Effetti di miscele di contaminati alimentari su target putativi di esposizione a interferenti endocrini : un approccio biomarker-tossicogenomico
No full textThe Endocrine Disruptors (EDs) are a class of chemicals that may interfere
with the endocrine system that plays a crucial role in maintaining the
physiological homeostasis of the human body as well as in regulating body
growth, metabolism, reproduction and behavior (Faroon et al., 2001; Schell
and Gallo, 2010). The EDs can exert their effects through a number of
different mechanisms in particular interacting with nuclear (NRs) and
orphan receptors, enzymatic pathways involved in steroid biosynthesis and
detoxification metabolism (Diamanti-Kandarakis, 2009).
Polychlorinated biphenyls (PCBs) form a group of fat soluble and
environmentally persistent EDs able to bioaccumulate in lipid fraction of
animal tissue leading to biomagnification in the food chain. PCBs intake via
food of animal origin represents the main route of human exposure (EFSA,
2010).
PCBs can be divided into two groups according to their biochemical and
toxicological properties: Dioxin-like (DL) PCBs, mainly interacting with
the Aryl Hydrocarbon Receptor (AhR) and Non Dioxin-like (NDL) PCBs
whose mechanisms of action are not fully clarified. Actually, organisms are
exposed to several congeners at the same time and, accordingly, the
observed toxicological effects, such as on liver, thyroid, immune function,
reproduction and behavior as well as carcinogenicity (EFSA, 2005), are
exerted by mixtures. Therefore, new researches are required to study EDs
mixtures, in particular on possible additive/synergistic effects at “real-life”
dose levels.
In this study, 21 environmentally relevant PCB congeners were divided in
three groups according to the proposed classification of Wolff et al. (1997)
and Negri et al. (2003), based on structural and modes of action similarities:
Mix1 (PCB 44, 49, 52, 101, 174, 177, 187, 201), potentially estrogenic
NDL congeners, Mix2 (PCB 77, 81, 105, 114, 118, 126, 169) featuring DLPCB
and Mix3 (PCB 99, 153, 180, 183, 196, 203), NDL-PCBs highly
persistent in the organism and phenobarbital-like inducers of Cytochrome
P450 (CYP450).
The aim of the present project was to evaluate potential effects on liver and
on adipose tissue as target organs of PCBs, elicited by the mixtures, at
realistic human exposure levels, as derived from human exposure data
through the evaluation of biomarkers response.
Two in vitro models have been selected as representative of liver tissue and
corresponding to two different life stages: infant (HuH6) and pubertal
(HepG2) cells.
To evaluate synergic effect, biomarkers of effect were used as indicators to
measure PCB-induced variation in cellular or biochemical processes (NRs,
NRF2, CYP450 enzymes and markers of oxidative stress). Moreover gene
expression profiles of PCBs treated HepG2 cell line were evaluated by
microarray analysis.
Moreover, PCBs bioaccumulation and permanence in animal fat could
affect preadipocyte programming and differentiation and adipocytes
metabolism. Therefore, differentiation of mouse (3T3-L1) and human
preadipocytes (SGBS cells) was evaluated to determine the effect of PCBs
exposure. Moreover gene expression of biomarkers involved in adipocytes
differentiation and metabolism were analyzed in 3T3-L1.
Previous reports classified Mix1 as potentially antiandrogenic congeners
(Wolff et al., 1995), on the contrary, we observed in HepG2 cell line, that
Mix1 significantly up-regulated only AR suggesting a potential androgenic
effect. In HepG2 cells, we also observed an uncoupling in ROS-CYP1A1
regulation and in HuH6, GSH/GSSG ratio was significantly higher. As for
Gene Ontology enrichment analysis, Mix1-modulated gene list was
uniquely significant for terms related to Nuclear Transport and significantly
affected only one pathway, the Intestinal Immune Network for IgA
production, implying a stimulation of the immune response. Overall, these
molecular processes may be considered specific markers of Mix1 effect in
hepatic cells.
As regards effects on adipocytes, Mix1 increased SGBS differentiation at
3x concentration and in 3T3-L1 affected only C/EBP involved in adipose
tissue development.
Mix2, featuring DL-PCB congeners, exerted the up-regulation of AR and
AhR in HepG2 cells. Moreover, Mix2 increased ROS levels as well as
CYP1A1 mRNA expression both mediated by AhR (Kopf et al., 2010).
However Mix2 significantly decreased the CYP1A1 enzyme activity,
indicating a different effect possibly due to the low concentrations used.
In HuH6, Mix2 induced a down regulation of CAR mRNA expression that
may explain the reduction of CYP1A1 and CYP3A4 activity. Therefore,
CAR gene expression and CYP1A1 and CYP3A4 activities may be
assumed as target of DL-PCBs disruption on this hepatic cell line.
Microarray results evidenced Mix2 affected genes involved in RNA
processing and splicing, protein localization and catabolism and
macromolecules degradation. Noteworthy, main and characteristic effects of
Mix2 relied a) on enrichment of genes related several cancer pathways as
p53, activator of genes involved also in cell cycle arrest (Lanni and Jacks,
1998), apoptosis and in communication in adjacent cells, and b) on cell
cycle progression, inducing of G1 phase and inhibiting S phase. So we may
hypothesize that a sum of contrasting mode of action exerted by PCB
congeners in Mix2 occurred.
As regards effects on adipocytes, Mix2 significantly induced SGBS
differentiation only at 3x concentration, probably due to the mixture effect
and/or the lower concentration levels used in this study.
Mix3 treatment affected the wider number of NRs expression (ER , ER ,
AR, PXR, RAR , THR ) as well as NRF2, in particular, in HuH6. To our
knowledge, it is the first study that showed AR mRNA expression due to
PCB congeners included in Mix3, whereas the observed ER and ER
induction confirmed the estrogenic effect of PCB 99 and 153 (Warner et al,
2012).The decrease in the CYP3A4 enzyme activity in HuH6 cells was in
agreement with NRF2 gene expression down-regulation (Itoh et al, 1997).
Microarray analysis showed that Mix3 modulated the higher number of
genes (5979 genes) with 1501 shared with Mix2-affected genes. Apart some
GO enriched terms related to cell organization, Mix3 did not share other
effects with Mix1, the other NDL mixture.
One of the most interesting evidence is the enrichment of genes involved in
the Wnt signaling pathway by only Mix3, suggesting an unbalance toward
pluripotency promotion (Takemarua and Moona, 2000).
Mix3 also affected some cancer pathways as well as the adherens junction
pathway as Mix2 but modulating a different panel of involved genes.
Moreover Mix3 exerted the higher magnitude of effect on pre-adipocytes
differentiation in both murine and human cell lines. Gene expression
evaluation analysis outlined that Mix3 down regulated Hes1, a DNA
binding protein whose expression blocks adipogenesis (Ross et al., 2006).
Overall results confirmed that the adopted grouping of PCBs in three
mixtures served to highlight different modes of action as well as biomarkers
responses, also among mixtures featuring NDL congeners. Moreover, the
two hepatic cell lines and the two pre-adipocytes cell lines appear to be
differently reactive to PCBs, indicating the need to use different in vitro
models and a panel of biomarkers in order to characterize the EDs effects.
These represented new results since there are no studies on PCB mixtures
summarizing effects on oxidative stress, metabolism, nuclear receptors gene
expression and adipocytes differentiation responses following treatment at
human real exposure concentrations.
As prompted by EFSA (2005), it is necessary to provide evidences
concerning comprehensive toxicological end-points of NDL effects.
Therefore, these data may serve as a basis for developing relative
toxicological factors for the NDL congeners risk assessment
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