1,720,963 research outputs found
Divergent functions of orthodenticle, empty spiracles and buttonhead in early head patterning of the beetle Tribolium castaneum (Coleoptera)
No full textAbstractThe head gap genes orthodenticle (otd), empty spiracles (ems) and buttonhead (btd) are required for metamerization and segment specification in Drosophila. We asked whether the function of their orthologs is conserved in the red flour beetle Tribolium castaneum which in contrast to Drosophila develops its larval head in a way typical for insects. We find that depending on dsRNA injection time, two functions of Tc-orthodenticle1 (Tc-otd1) can be identified. The early regionalization function affects all segments formed during the blastoderm stage while the later head patterning function is similar to Drosophila. In contrast, both expression and function of Tc-empty spiracles (Tc-ems) are restricted to the posterior part of the ocular and the anterior part of the antennal segment and Tc-buttonhead (Tc-btd) is not required for head cuticle formation at all. We conclude that the gap gene like roles of ems and btd are not conserved while at least the head patterning function of otd appears to be similar in fly and beetle. Hence, the ancestral mode of insect head segmentation remains to be discovered. With this work, we establish Tribolium as a model system for arthropod head development that does not suffer from the Drosophila specific problems like head involution and strongly reduced head structures
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
Molekulare Grundlagen der Entwicklung des Schwertes, eines sexuell selektierten Merkmales im Genus Xiphophorus
No full textThe sword, a colourful extension of the ventral caudal fin of male swordtails of the genus Xiphophorus was one of Darwin's chosen examples for his idea of sexual selection. Experiments in X. helleri have shown that (1) the total length of the sword is an important criterion during mate choice and (2) the females have a preference for a specific pattern of differently coloured stripes. Besides its role in the process of sexual selection the sword has an interesting evolutionary history. Only males of swordtail species develop a sword, whereas males of platyfish, another group within the genus Xiphophorus, are swordless. One scenario suggests a sworded common ancestor of all Xiphophorus species and a secondary loss of the sword in platyfish during evolution. It remains elusive which molecular events preceded the loss of the sword in platyfish, since the genetic network that controls sword development is poorly understood. Data from interspecies crosses suggests that multiple loci control sword development. In addition, testosterone was identified as sufficient factor to induce sword development in immature fish, which indicates that sword development is controlled by androgen signalling. Recent work also identified the homeobox transcription factor msxC as another potential candidate, since it was shown to be up-regulated in growing sword rays. Up-regulation of msxC has also been found in the developing gonopodium, the modified male anal fin that is also induced by exogenous testosterone. The gonopodium is evolutionary older than the sword and it was assumed that the genetic network controlling gonopodium development was partly co-opted for the sword.In chapter I we focussed on Fgf signalling that has been shown to regulate msxC expression during caudal fin regeneration. Both sword development and fin regeneration are characterized by elevated outgrowth of fin rays, which is likely controlled by a conserved genetic network. We showed that fgfr1 is specifically up-regulated in developing swords, which presents first evidence that fgfr1 is involved in sword development. A similar pattern was also observed in the developing gonopodium. fgfr1 is spatial-temporally co-expressed with msxC both in the sword and the gonopodium, which might indicate a putative interaction between both genes. Interestingly, in the ventral caudal fin rays of testosterone treated platyfish, fgfr1 and msxC are only up-regulated after prolonged hormone treatment. This points towards a disruption between the fgfr1/msxC network and its regulation by testosterone as a likely developmental cause for sword-loss in platyfish. Finally, we demonstrated that fgfr1 and msxC activation is correlated with fin ray growth rates by employing the X. maculatus brushtail mutant that exhibits excessive growth of the median caudal fin rays.Only a subset of the genes involved in sword development can be targeted by candidate gene approaches (e.g. as performed in chapter I), because prior knowledge about gene function is needed to select appropriate candidates. In chapter II we employed the suppression subtractive hybridisation (SSH) technique to bypass this limitation, because this method can be applied to isolate genes that are differentially expressed in swords and gonopodia compared to juvenile fins without ab initio knowledge of gene identity or function. In this study we identified 128 different sequences with significant similarity to known genes. We showed that four of these sequences with similarity to rack1, dusp1, klf2 and tmsb a-like are specifically up-regulated in induced swords and/or gonopodia. In parallel, we also showed that these genes are strongly expressed during fin regeneration. Therefore these four genes are interesting candidates to further analyse their role in both sword development and fin regeneration.The anal fin of male Xiphophorus fishes is modified into an intromittant organ, the gonopodium. The gonopodium is formed during sexual maturation by a subset of three anal fin rays, the 3-4-5 complex. These three rays are modified in terms of ray length, segment thickness and different distal structures like blades, claws, spines, hooks and serraes. Therefore, the mature gonopodium exhibits a strong proximo-distal polarity due to the smaller terminal segments and terminal structures. Gonopodium development is thought to proceed in two phases. During the first phase, low levels of testosterone promote ray outgrowth, whereas high levels of testosterone induce the formation of terminal structures during the second phase. Shh, androgen and probably Fgf signalling are involved in gonopodium development.In chapter 3 we tested the role of retinoic acid (RA) signalling during gonopodium development, for two reasons. RA signalling is essential for paired appendage development in vertebrates and it provides positional information along the proximodistal axis in developing and regenerating limbs. Therefore, RA signalling might either play a general role in gonopodium development or specific role in establishing the proximo-distal polarity within the gonopodium. RA, a small lipophilic, diffusible molecule is synthesised by retinaldehyde dehydrogenases (Aldh1as) and stimulates gene expression through binding to two types of receptors, retinoic acid receptors (RARs) and retinoic X receptors (RXRs). In this study we showed that aldh1a2, a RA synthesising enzyme, and two RA receptors, rarg-a and rarg-b, are expressed in developing gonopodia. Inhibiting RA synthesis with DEAB increases the length of newly formed terminal segments, whereas the segment length decreases when RA signalling is overactivated by exogenous all-trans RA. Both the expression and the functional data present first evidence that RA signalling is involved in gonopodium development. Finally, we showed that androgen receptors b (arb), a putative regulator up-stream of RA signalling is co-expressed with aldh1a2 in the distal mesenchyme of the gononopodial rays. Interestingly, developing swords lack the distal expression domain of both aldh1a2 and arb, whereas the two rars are similarly expressed in developing swords and gonopodia. This might point towards an interaction between these two genes.publishe
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