1,720,997 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
Untersuchung des Einflusses veränderter Schwerkraftbedingungen und unterschiedlichen Schwimmverhaltens auf die Genexpression bei Euglena gracilis
Get PDFEuglena gracilis is a photosynthetic unicellular flagellate, which actively uses the gravitational field for the orientation in turbid water columns by means of gravitaxis. This and other unique biological features and the robustness, which allows to withstand harsh environmental conditions have made Euglena a preferred component in space flight related studies and life support systems. While other model organisms have been studied thoroughly, investigation of the impact of acceleration changes on gene expression in Euglena was limited to a few mRNA molecules. However, based on recent sequencing advances, expression analysis of over 22.000 protein-coding transcripts was conducted by means of microarrays in the course of this thesis. The impact of microgravity, sub-1 x g accelerations and hypergravity was investigated in parabolic flights, MAXUS-9 sounding rocket, and centrifugation at 1.8 x g, respectively. Additionally, gene expression was examined in dependence of culture age and different gravitactic behavior.
In summary, altered accelerations induced commonly known effects in the protist, which have also been seen in other organisms. Signal transduction mechanisms, especially cAMP specific processes, were the most affected functional group. This indicates that acceleration changes in Euglena lead to diverse responses, which rely on signal transduction mechanisms so far of mostly unknown origin and outcome. Especially in hypergravity, upregulations for adenylyl cyclases were very pronounced and indicate an adaptation to a prolonged steady stimulus. The cytoskeleton is most likely affected by rearrangements rather than by changes in the absolute number of mRNA molecules, as no changes in actin or tubulin mRNA abundance were found but different associated molecules such as myosin kinase and microtubule-binding proteins were altered in their expression. Glycolysis and gluconeogenesis were engaged during altered accelerations by upregulation of sequences potentially coding for fructose 1,6-bisphosphate aldolase and enolase. This higher metabolic activity is associated with an increased demand for amino acids and energy due to adaptation processes. Stress and defense responses are a general finding under altered accelerations. In this regard, the generation of reactive oxygen species (ROS) is indicated by the up-regulation of detoxifying enzymes such as ascorbate peroxidase and glutathione S-transferase. Interestingly, when investigating different cell culture ages somewhat similar effects were seen in older negatively gravitactic cell cultures, which were compared to younger randomly moving cells. Abundance of mRNAs coding for adenylyl cyclases was also greatly increased, indicating differential reactions in older cells. In contrast, actin mRNA was reduced which is most likely a result of the reduction in cell size found in older cells. Decreased mRNA content for fructose 1,6-bisphosphate aldolase and enolase indicate a lower metabolic activity in older cells probably due to stationary growth phase, reduced cytokinesis and also due to depletion of nutrients in the medium. The generation of ROS is probably different for the various compartments in older cell cultures as different ascorbate peroxidases showed up- or down-regulations.
In conclusion, this thesis provides the groundwork for general effects induced by altered acceleration and cell age, which can be used as a resource for further experiments. In addition, it also defines a baseline for the time necessary for gene expression changes, as it was shown that 20 s during parabolic flights are sufficient to induce changes in mRNA levels, while more extensive changes were found after 10 to 30 min of hypergravity exposure by centrifugation. Furthermore, cells cultivated under identical conditions and subjected to the same stimuli showed reproducible changes with respect to their transcriptome. This highlights the fact that Euglena gracilis is a valuable model organism for applications in the field of molecular biology
Variable fluorescence parameters in the filamentous Patagonian rhodophytes, Callithamnion gaudichaudii and Ceramium sp. under solar radiation
Get PDFThe filamentous rhodophytes Callithamnion gaudichaudi Agardh and Ceramium sp. were utilized to study the effects of solar radiation (PAR, 400–700 nm, UV-B, 280–315 nm and UV-A, 315–400 nm) on the photosynthetic performance in situ in Patagonia waters (Argentina). A pulse amplitude modulated (PAM) fluorometer was used to determine the fluorescence parameters. The two species grew in different habitats in the eulittoral: Ceramium sp. was found only in rock pools while C. gaudichaudii grew on exposed rocks and fell dry during low tide. Both species differed in their fluorescence parameters and their sensitivity to solar radiation exposure. The photosynthetic quantum yield had its lowest values at noon, but it recovered in the afternoon/evening hours, when irradiances were lower. PAR (irradiance of about 400 W m 2 at noon) was responsible for most of the decrease in the yield on clear days, especially in Ceramium sp., but UVR (280–400 nm) also accounted for a significant decrease. Fluence rate response curves indicated that both species were adapted to low fluence rates and showed a pronounced non-photochemical quenching at intermediate and higher irradiances. Both species showed a rapid adaptation during measurement of fast induction kinetics but differed significantly in their fluorescence components. All photosynthetic pigments were bleached after 8 h exposure to solar radiation over a full day. Strong absorption in the UV-A range, most likely due to mycosporine-like amino acids, was detected in both strains. The pronounced sensitivity to solar radiation in situ and the recovery capacity of these two filamentous Rhodophyte species, as well as the presence of protective compounds, suggests that these algae have the ability to adapt to the relatively high radiation levels and changes in irradiance found in the Patagonia waters.Fil: Häder, Donat P.. Friedrich Alexander Universität Erlangen Nurnberg; AlemaniaFil: Lebert, Michael. Friedrich Alexander Universität Erlangen Nurnberg; AlemaniaFil: Helbling, Eduardo Walter. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Playa Unión. Estación de Fotobiología Playa Unión; Argentin
Ökotoxikologische Bewertung von anthropologisch produzierten häufigen Schadstoffen in aquatischen Ökosystemen
Get PDFAbout 3% of the total water on earth is freshwater and only a small percentage (0.01%) of this freshwater is available for human use. This small proportion of freshwater is under immense stress due to various anthropogenic activities which cause problems of water pollution. The major causes of water pollution are indiscriminate disposal of industrial, municipal and domestic wastes. Other sources of water pollution are the extensive use of different chemicals in agriculture as well as household chemicals. In this study some common pollutants of aquatic environments like fertilizers, pesticides, detergents and wastewaters were evaluated for their ecotoxicological effects. Different parameters of Euglena gracilis like motility, gravitactic orientation, cell shape, photosynthesis, light-harvesting pigments and cell growth were used as end points. The effects of the tested substances were evaluated during short- (0 – 72 h) and long-term (7 days) experiments. Two commonly used fertilizers, urea and DAP (diammonium phosphate) were tested. Immediately upon exposure (0 h) DAP affected the motility parameters of E. gracilis with EC50 values 1.91, 3.46, 7.54, 5.486 and 6.896 g L-1 for velocity, motility, r-value, upward swimming, and compactness, respectively. With increasing exposure time only velocity and motility were affected in a dose-dependent way. The EC50 value for motility dropped from 3.46 g L-1 (0 h) to 1.295 g L-1 after 72 h. The quantum yield of photosystem II (Fv/Fm) was inhibited by DAP with EC50 values of 13.43, 3.26, 1.55 and 1.65 g L-1 after 0, 1, 24 and 72 h, respectively. Chl a and total carotenoids were decreased above 1 g L-1 of DAP after 24 and 72 h. However, a decrease in chl b was observed only after 72 h at a concentration of 25 g L-1 or above. At 0 h exposure urea gave EC50 values of 13.361, 14.973, 16.327, 16.517 and 18.514 g L-1 for velocity, motility, r-value, upward swimming and cell shape, respectively. With increasing exposure time a decrease in the inhibitory effect of urea was observed. The maximum inhibition of Fv/Fm by urea was caused after 1 h and thereafter a recovery was shown. Urea caused a decrease in chl a and total carotenoids at all incubation times at doses above 50 or 25 g L-1; however, a decrease in chl b was caused only after 72 h. In long-term tests, EC50 values of DAP varied from 3.14 to 5.96 g L-1 for different parameters. EC50 values for urea ranged from 28 to 44.05 g L-1 for various parameters. Application of DAP resulted in an increased concentration of ammonia in culture and a slight increase of the pH but urea did not. A section of this study discusses effects of the pesticides carbofuran and malathion on E. gracilis. In short-term exposure carbofuran affected motility, orientation and cell shape but malathion inhibited only the cell velocity. No significant effect was observed on Fv/Fm except by the highest concentration of carbofuran (50 mg L-1) after 72 h. Both pesticides did not affect any pigment. In long-term experiments, cell growth, r-value and total carotenoids were significantly reduced by carbofuran but malathion had no effect on any parameter except a slight positive effect on cells orientation. Two commercially available detergents, Ariel (laundry detergent) and Green Care (dishwasher), were evaluated. In short-term tests with Ariel, velocity of the cells was the most sensitive parameter with a 72 h EC50 of 34 mg L-1. Chl a and carotenoids were sensitive to Ariel and after 72 h exposure both were significantly decreased at 50 mg L-1 or above while chl b was decreased at doses above 750 mg L-1. The maximum inhibition of photosynthesis by Ariel was caused after 24 h. In long-term experiments with Ariel, cell growth was inhibited at concentration of 1 mg L-1 or above. All other parameters, excluding gravitaxis, cell shape, and chlorophyll b, were inhibited at 5 mg L-1 or above. The Green Care also adversely affected all the tested parameters in E. gracilis, and the effects were more severe in long-term than in short-term tests. Industrial and municipal wastewater is among the major sources of water pollution. In this study wastewaters from different industries in Pakistan were tested. Most of the physicochemical properties of the tested samples were within the acceptable range of national environmental quality standards (NEQS). However, they impaired motility, orientation and shape of E. gracilis. This shows that different toxic substances present in wastewater, even at low concentrations, can be a possible threat to water quality. Short-term exposure to wastewater did not inhibit photosynthesis in E. gracilis but rather had a stimulatory effect. In long-term exposure, only 40% of the tested samples negatively affected photosynthesis. From the overall effects of wastewaters on various parameters of E. gracilis, it can be concluded that gravitactic orientation is its most sensitive parameter towards wastewater toxicity.Ungefähr 3 % des gesamten Wassers auf der Erde liegen als Frischwasser vor, von welchem wiederum nur ein geringer Anteil (0,01 %) für den Menschen verfügbar ist. Diese relativ geringe Wassermenge steht auf Grund verschiedenster menschlicher Aktivitäten unter starkem Druck, wie z. B. Wasserverschmutzung durch ungeregelte Einleitung von industriellem und kommunalem Abwasser, sowie aus Haushalten und der Landwirtschaft. In dieser Studie wurden typische Schadstoffe aquatischer Lebensräume, wie Dünger, Pestizide, Reinigungsmittel und Abwässer auf ihre ökotoxikologischen Eigenschaften hin untersucht. Verschiedene Parameter des Flagellaten Euglena gracilis, wie Beweglichkeit, gravitaktische Orientierung, Zellform, Photosynthese, photosynthetische Pigmente und Zellvermehrung wurden als Endpunkte verwendet. Der Effekt dieser Substanzen wurde im Rahmen von Kurzzeit- (0 – 72 h) und Langzeitexperimenten (7 d) untersucht. Zwei häufig verwendete Düngemittel, Harnstoff und DAP (Diammoniumphosphat) wurden getestet. Sofort nach Exposition (0 h) beeinflusste DAP die Bewegungsparameter von E. gracilis mit EC50-Werten von 1,91, 3,46, 7,54 und 6,896 g L-1 für Geschwindigkeit, Beweglichkeit, r-Wert, Anteil nach oben schwimmender Zellen beziehungsweise Zellform. Bei längerer Expositionszeit wurden nur die Geschwindigkeit und Beweglichkeit dosisabhängig beeinträchtigt. Der EC50-Wert für die Beweglichkeit fiel von 3,46 g L-1 (0 h) auf 1,295 g L-1 nach 72 h. Die Quantenausbeute von Photosystem II (Fv/Fm) wurde durch DAP mit EC50-Werten von 13,43, 3,26, 1,55, 1,65 g L-1 nach 0, 1, 24 beziehungsweise 72 h gehemmt. Chl a und die Carotinoide verringerten sich in Gegenwart von mehr als 1 g L-1 DAP nach 24 und 72 h. Bei Chl b hingegen wurde eine Reduktion erst nach 72 h bei einer Konzentration von 25 g L-1 und darüber festgestellt. Bei 0 h Expositionszeit waren die EC50-Werte 13,361, 14,973, 16,327, 16,517 und 18,517 für Geschwindigkeit, Beweglichkeit, r-Wert, Anteil nach oben schwimmender Zellen beziehungsweise Zellform. Bei steigender Expositionszeit wurde eine Verringerung des hemmenden Effekts festgestellt. Die maximale Inhibition von Fv/Fm wurde nach 1 h beobachtet und danach eine Erholung festgestellt. Harnstoff führte zu einer Verringerung von Chl a und der Carotinoide bei allen Inkubationszeiten und Konzentrationen über 50 oder 25 g L-1. Die Verminderung der Chl b-Konzentration dagegen wurde erst nach 72 h beobachtet. Bei Langzeittests variierte der EC50-Wert von DAP zwischen 3,14 bis 5,96 g L-1. Die EC50-Werte bei Harnstoff reichten von 28 bis 44,05 g L-1 je nach Parameter. Nur DAP (nicht Harnstoff) erhöhte den Ammoniumgehalt und den pH. In einem anderen Teil der Studie wurde der Einfluss der Pestizide Carbofuran und Malathion auf E. gracilis untersucht. Bei Kurzzeitexposition beeinflusste Carbofuran die Beweglichkeit, Orientierung und Zellform, während Malathion nur die Geschwindigkeit inhibierte. Fv/Fm wurde nicht signifikant beeinträchtigt, außer nach 72-stündiger Exposition in der höchsten Konzentration von Carbofuran (50 mg L-1). Beide Pestizide hatten keinen Effekt auf die Pigmente. Bei Langzeitexposition wurde die Zellvermehrung, der r-Wert und die Menge an Carotinoiden durch Carbofuran deutlich beeinträchtigt, während Malathion keinen Effekt auf die gemessenen Parameter zeigte, außer eine leicht geförderte Gravitaxis. Das kommerziell erhältliche Waschmittel Ariel und das Geschirrspülmittel Green Care wurden ebenfalls getestet. Bei Kurzzeitexperimenten mit Ariel war die Geschwindigkeit mit einem EC50 von 34 mg L-1 nach 72 h Inkubation der sensitivste Parameter. Chl a und die Carotinoide wurden durch Ariel-Konzentration von 50 mg L-1 und darüber nach 72 h Inkubation deutlich reduziert, während Chl b erst ab Konzentrationen von über 750 mg L-1 beeinträchtigt wurde. Die Photosynthese wurde durch Ariel nach 24 h Inkubation am stärksten gehemmt. Bei Langzeitexperimenten mit Ariel wurde die Zellvermehrung bei Konzentrationen von 1 mg L-1 und darüber beeinträchtigt. Alle anderen Parameter, außer Gravitaxis, Zellform und Chl b, wurden bei Konzentrationen von 5 mg L-1 und darüber gehemmt. Auch Green Care beeinträchtigte die untersuchten Parameter. Die Effekte waren bei Langzeitexperimenten deutlicher ausgeprägt, als bei Kurzzeitexperimenten. Industrielle und kommunale Abwässer gehören zu den Hauptverursachern für Wasserverschmutzung in Pakistan. Im Rahmen dieser Studie wurden unterschiedliche Industrieabwässer in Pakistan untersucht. Die meisten physikalisch-chemischen Parameter waren im Rahmen des National Environmental Quality Standards (NEQS). Trotzdem beeinträchtigen sie Bewegungsparameter und Zellformparameter von E. gracilis. Bei kurzfristiger Exposition auf die Photosynthese zeigte sich ein leicht stimulierender Effekt. Bei Langzeitexposition beeinträchtigten nur 40 % der Proben die Photosynthese. Es hat sich gezeigt, dass für die Analyse von Abwasserproben die Gravitaxis der sensitivste Parameter ist
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