1,721,015 research outputs found
Variable regions of PI4P 5-kinases direct PtdIns(4,5)P2 towards alternative regulatory functions in tobacco pollen tubes
No full textThe apical plasma membrane of pollen tubes contains different PI4P 5-kinases that all produce phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) but exert distinct cellular effects. In the present example, overexpression of Arabidopsis AtPIP5K5 or tobacco NtPIP5K6-1 caused growth defects previously attributed to increased pectin secretion. In contrast, overexpression of Arabidopsis AtPIP5K2 caused apical tip swelling implicated in altering actin fine structure in the pollen tube apex. AtPIP5K5, NtPIP5K6-1 and AtPIP5K2 share identical domain structures. Domains required for correct membrane association of the enzymes were identified by systematic deletion of N-terminal domains and subsequent expression of fluorescence-tagged enzyme truncations in tobacco pollen tubes. A variable linker region (Lin) contained in all PI4P 5-kinase isoforms of subfamily B, but not conserved in sequence, was recognized to be necessary for correct subcellular localization of AtPIP5K5, NtPIP5K6-1 and AtPIP5K2. Deletion of N-terminal domains including the Lin domain did not impair catalytic activity of recombinant AtPIP5K5, NtPIP5K6-1 or AtPIP5K2 in vitro; however, the presence of the Lin domain was necessary for in vivo effects on pollen tube growth upon overexpression of truncated enzymes. Overexpression of catalytically inactive variants of AtPIP5K5, NtPIP5K6-1 or AtPIP5K2 did not influence pollen tube growth, indicating that PtdIns(4,5)P2 production rather than structural properties of PI4P 5-kinases was relevant for the manifestation of growth phenotypes. When Lin domains were swapped between NtPIP5K6-1 and AtPIP5K2 and the chimaeric enzymes overexpressed in pollen tubes, the chimaeras reciprocally gained the capabilities to invoke tip swelling or secretion phenotypes, respectively. The data indicate that the Lin domain directed the enzymes into different regulatory contexts, possibly contributing to channeling of PtdIns(4,5)P2 at the interface of secretion and actin cytoskeleton
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
Oilseed rape in high-intensity crop rotations
Full text linkIn der Arbeit wurde der Einfluss einer Selbstfolge von Winterraps auf den Ertrag, ertragsbildende Parameter sowie die Wurzelhals- und Stängelfäule (Leptosphaeria maculans) untersucht. Die Untersuchungen wurden am Standort Etzdorf im Winterrapskonzentrationsversuch durchgeführt. Dieser wurde im Jahr 2002 angelegt und basierte auf der Fruchtfolge Winterweizen (WW)-WW-WW-Winterraps (WRa)-WRa-WRa und einer langjährigen Winterraps-Monokultur. Die Ergebnisse zeigen, dass der Ertrag des Winterrapses in einer zunehmenden Selbstfolge abnimmt, und die niedrigsten Erträge wurden für die Winterraps-Monokultur ermittelt. Weiterhin nehmen die Befallsintensität und die Befallsschwere der Wurzelhals- und Stängelfäule in Selbstfolge zu. Darüber hinaus wurden in dieser Arbeit internationale Fruchtfolgestudien ausgewertet. Hierbei wurde aufgezeigt, dass Raps weltweit vor allem nach dem Anbau von Leguminosen sowie nach zwei- bzw. dreijährigen Anbaupausen höhere Erträge erreicht.The impact of oilseed rape grown in succeeding years on yield, yield parameters and blackleg disease (Leptosphaeria maculans) was investigated in this thesis. The investigations were carried out in a crop rotation field trial at the experimental farm Etzdorf. The field trial was established in 2002 and was based on the crop rotation winter wheat (WW)-WW-WWoilseed rape (OSR)-OSR-OSR and a long-term OSR monoculture. The results demonstrated that yield of oilseed rape declines when the crop is following itself and were lowest when oilseed rape was grown in monoculture. Furthermore, it was shown that blackleg disease intensity and severity increased when oilseed rape was grown successively. In addition, global crop rotation experiments were analyzed. Here it was shown that oilseed rape especially benefits from legume pre-crops and from two- or three-year cropping breaks with higher yields
A molecular mechanism for root thermomorphogenesis in Arabidopsis thaliana seedlings
Full text linkGlobal warming effect has received increasing attention worldwide. To cope with elevated ambient temperature, plants undergo thermomorphogenesis, with above ground adjustments mainly involving temperature sensitive cell elongation. However, temperature influence on root growth remains unclear. Below the heat stress threshold Arabidopsis thaliana seedlings respond to elevated temperature by promoting primary root elongation , possibly enabling them to reach deeper soil layers with better water saturation . In this study, I propose that: 1. Roots possess an autonomous system that can sense and respond to temperature cues independently of the shoot. 2. An unidentified root thermosensor uses auxin as a messenger to convey temperature information, stimulating cell division in the root apical meristem through local auxin biosynthesis and temperature sensitive polar auxin transport. 3. The effects of thermotropism differ between Arabidopsis and maize. A positive thermotropi c effect could only be observed in maize.Die globale Erwärmung hat weltweit zunehmend Aufmerksamkeit erlangt. Daher gilt es, die morphologische Anpassung von Pflanzen auf erhöhte Umgebungstemperaturen zu erforschen, welche als Thermomorphogenese bezeichnet wird . Arabidopsis thaliana Sämlinge reagieren auf erhöhte Temperaturen mit einer Hypokotyl und Primärwurzelverlängerung. Im Spross wird das hauptsächlich durch Zellverlängerung erreicht und in der Wurzel ist es unbekannt. Die Verlängerung der Primärwurzeln führt möglicherweise dazu, tiefere Bodenschichten mit besserer Wassersättigung zu erreichen. Die folgende Studie zeigt: 1. Wurzeln verfügen über ein autonomes System, welches unabhängig vom Spross Temperatursignale wahrnimmt und darauf reagiert. 2. Ein nicht identifizierter Wurzeltemperatursensor nutzt Auxin als Botenstoff zur Übermittlung von Informationen. Dabei wird die Zellteilung im Wurzelapikalmeristem durch lokale Auxinbiosynthese und deren polaren Transport stimuliert. 3. Zusätzlich konnte ein positiver thermotroper Wurzeleffekt bei Mais beobachtet werden, welcher bei Arabidopsis nicht eintrat
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
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