1,721,059 research outputs found
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
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
Gastrointestinal signals regulating appetite in humans
Get PDFObesity and its associated complications are a significant health problem in industrialized countries. This fact has generated great interest in the role of the gut in the regulation of food intake in the past three decades. Especially after the discoveries of gastrin, secretin and cholecystokinin (CCK), it was generally accepted that digestive processes are mainly regulated by hormones, but it has become apparent that there is a complex interplay between neural and hormonal pathways. Several systems seem to be involved in the regulation of bodyweight; one of them is primarily concerned with short-term regulation of food intake. The control circuits include central and peripheral signals. Much insight has been gained into physiological processes of satiety peptides like CCK, glucagon-like peptide-1 (GLP-1) and peptide tyrosine-tyrosine (PYY) in the past few years. The informations depicting their mechanism of action and potential interactions between different physiological signals involved in the short-term regulation of satiety are still limited in humans. The main interest of this thesis focuses on the further characterization of some of those signals, especially on the investigation in potential interactions between individual satiety factors.
The study set-up applied in the projects was standardized and is similar to experimental conditions used in prior studies. Here are some examples: nearly in every study, volunteers received an intraduodenal (ID) perfusion. To investigate a potential interaction between the stomach and the small intestine, a preload was given or the stomach was distended by a balloon for a short period of time before the test meal was offered. After the preload or the distension of the stomach, a standard meal was presented to the subjects, and they were invited to eat and drink as much as they wished for 60 min. During the study subjects scored their subjective feelings for hunger and fullness for the duration of each experiment using a visual analogue scale (VAS) and blood was drawn in regular intervals. The study was finished 60 min after meal start.
The stomach has an obvious role in the regulation of eating behavior, but until recently it was still unclear, if and to what extent pure mechanical distension of the fundus and the antrum can influence food intake. Therefore the first project was
designed to further understand the role of a) the gastric fundus and b) the gastric antrum in triggering satiation in healthy male volunteers. From previous study results it was anticipated that distension of the distal stomach could play a role in the generation of satiation.
In the first part of our study the fundus was distended by a balloon with increasing volumes. When the fundus was distended, no effect on food intake was observed, but a short-lasting effect on feelings of hunger and fullness. Gastric distension only seems to trigger satiety as long as mechanoreceptors in the stomach are stimulated; the short-lasting effect could indicate that the signals are transmitted via afferent nerves to the central nervous system (CNS).
The second part of this study was designed to examine the effect of antrum balloon distension on subsequent food intake; in addition, it was of interest to test whether ID fat could intensify the effect of distal gastric distension. Neither gastric distension alone nor in combination with ID fat reduced the subsequent calorie intake; also no effect was observed on feelings of hunger or fullness. ID fat does not seem to intensify gastric satiety signals induced by pure mechanical distension of the stomach.
Neither fundus nor antrum distension altered CCK and PYY plasma concentrations. This fact implies that signals induced by pure mechanical gastric distension are not mediated by circulating CCK or PYY. During ID fat perfusion, CCK and PYY plasma concentrations were significantly increased. The increase of CCK after ID fat confirmed previous study results. However, this study was one of the first which could show an increase of PYY after ID fat in humans.
Due to these study results pure mechanical gastric distension of the fundus or the antrum is presumably not a sufficient satiety signal to influence subsequent food intake.
An interaction effect on food intake resulting from an intestinal and a gastric satiety signal was already explored for CCK, but not for GLP-1. It was therefore of interest to find out whether an interaction exists between a preload and intravenous (i.v.) GLP-1. In the second project GLP-1 was given i.v. in a dose which mimics physiological GLP-1 plasma concentrations; the dose reduced calorie intake confirming previous study results. One major observation of this study was the demonstration that a protein-containing preload together with i.v. GLP-1 enhanced the satiety-inducing
effects of GLP-1 compared to a water preload plus infusion of GLP-1. This result provides strong evidence that GLP-1 interacts with gastric signals to modulate food intake and satiety in humans.
We inferred that GLP-1 is an important satiety factor which interacts with other satiety signals in order to control food intake and satiety. However, it still remains unclear whether the satiety effects of GLP-1 are directly mediated through peripheral or central receptors or indirectly by releasing other satiety peptides.
The following study was designed to further understand the potential interaction between protein and fat in regulating food intake in humans. It is known that ID lipid infusions and protein given as an oral preload reduce food intake in humans and from previous study results we inferred that ID fat interacts with gastric signals to regulate food intake. In the third project we were interested in exploring the potential interaction of the stomach and the small intestine; we also wanted to see whether GLP-1 and PYY are associated with this interaction.
ID fat perfusion alone reduced the amount of food eaten and the total calorie intake, but the reduction did not reach statistical significance. Although the design of the present study was similar to previous studies with respect to fat dose, experimental design and duration of fat perfusion, the variability of the individual responses to ID fat was greater than in previous studies and the reduction of food intake did not reach statistical significance. Due to these results it can be speculated that certain individuals have a reduced sensation to ID fat. The effects of ID fat on food intake do not seem to be mediated by changes in plasma GLP-1 or PYY levels, but they are largely dependent on CCK release, which is in agreement with previous findings.
When subjects consumed an oral protein preload, calorie intake was significantly reduced. The increase of premeal plasma concentrations of GLP-1 and PYY did not differ compared to placebo. Therefore the inhibitory effect of oral protein on eating behavior is not mediated by changes in circulating plasma hormone levels.
The simultaneous administration of an oral protein preload and ID fat did not show a synergistic reduction in calorie consumption, rejecting the hypothesis that oral protein and ID fat exert a positive synergistic effect.
The fourth project examined the physiological and the pharmacological role of PYY in regulating eating behavior. Due to human study results it was supposed that
PYY (3-36) is a potent physiological regulator of satiety with a potential for therapeutic application. Because the physiological role of PYY in humans has not been investigated in detail, we first wanted to define a range of physiological PYY plasma levels after two meals differing in their calorie content. The results showed that only large meals are able to stimulate the release of larger amounts of PYY, whereas a low-calorie meal has minimal effects on postprandial hormone plasma levels.
In the second part of the study we wanted to examine the effects of graded doses of i.v. PYY (3-36) on eating behavior in healthy human subjects. We found a dose-dependent satiety effect of i.v. applied PYY (3-36). These results support the hypothesis that exogenously administrated PYY (3-36) is able to suppress food intake in humans. However, when the postprandial physiological levels of PYY after the high calorie meal are compared to those obtained after peripheral administration, it can be suggested that the significant satiety effect of PYY (3-36) is only seen at plasma concentrations higher than those after a large meal. The smallest administered dose of PYY (3-36) did not significantly reduce food intake and showed PYY plasma levels about in the same range as the physiological ones. Due to these results we infer that the PYY satiety effect seen with the middle and the highest dose of exogenous PYY (3-36) was rather a pharmacological than a physiological effect. It seems to be unlikely that PYY is a major physiological satiety factor, but still more information is necessary.
Dose-dependent side effects of PYY (3-36) like nausea and vomiting could be observed. PYY (3-36) seems to have a narrow therapeutic window, which could limit its therapeutic potential.
In summary it was shown in the present thesis that 1) pure gastric balloon distension of the fundus and the antrum is not a sufficient satiety signal to influence subsequent food intake; 2) the effect of gastric distension on eating behavior is not amplified by ID fat; 3) GLP-1 is an important satiety factor and seems to interact with gastric signals to modulate food intake and satiety in humans; 4) the satiating effect of protein as an oral preload cannot be amplified by ID fat; 5) the release of physiological PYY is dependent on the calorie content of a meal; 6) exogenous PYY (3-36) reduces food intake in a dose-dependent manner; 7) the effect of exogenous PYY (3-36) on food intake seems to be a pharmacological rather than a physiological effect; 8) PYY (3-36) has a narrow therapeutic window
Influence of natural substances on mediators of intestinal inflammation "in vitro"
Get PDFNatural plant extracts and their isolated phenolic substances have been shown to exhibit several functions including the anti-inflammatory activity in various tissues. EGCG, curcumin and resveratrol have been identified as possible anti-inflammatory agents while little is known about extracts of Boswellia serrata (BS) and Rosmarinus officinalis (RO). In this thesis project, several methods were applied in order to identify the anti-inflammatory effects of aforementioned substances and extracts in “inflamed” intestinal epithelial cells. The colon cancer cell lines, HT29 and T84, were stimulated with TNF-α in the presence of various concentrations of EGCG, BS, RO, curcumin and resveratrol. Their effects were analyzed at different levels: (1) on the expression of multiple genes involved in inflammatory responses; (2) on the generation of metabolites such as PGE2, and production of chemokines (e.g., IL-8 and MIP-3α); (3) and on the protein expression. The expression of genes was determined by quantitative RT-PCR and microarray technology. The production of IL-8, MIP-3α and PGE2 were measured by ELISA. The expression of proteins belonging to the NF-κB pathway was analyzed by immunoblots. In addition, NF-κB DNA binding was carried out using EMSA. Treatment of activated cells with EGCG, BS, RO, curcumin and resveratrol reduced the expression of most genes related to the inflammatory response of HT29 and T84 cells. Furthermore, EGCG, curcumin and resveratrol diminished the generation of PGE2 in HT29 cells. In addition, the secretion of IL-8 and MIP-3α were dose-dependently inhibited by candidate compounds in HT29 cells. EGCG reduced the production of these chemokines also in T84 cells while curcumin and resveratrol only diminished MIP-3α synthesis. Moreover, the expression of IκBα and NF-κB p65 were analyzed in HT29 cells. BS was not able to prevent IκBα degradation and subsequent NF-κB translocation whereas RO interfered with IκBα degradation, however, it did not impede the activation of NF-κB. Additionally, RO reduced NF-κB DNA binding tested by EMSA. Collectively, the presented data show that phenolic substances or whole plant extracts have the capacity to attenuate inflammatory features by modulating genes involved in inflammatory responses; by reducing the chemoattraction of immunocytes through the inhibition of IL-8 and MIP-3α; and by affecting specific pathways involved in inflammation such as the NF-κB. Furthermore, phenolic compounds might have a preventive and/or therapeutic utility in chronic inflammation such as IBD, and therefore, they should be further analyzed in in vivo studies to consolidate these findings
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