1,721,901 research outputs found
The effect of avian predation on cryptic polymorphic prey
No full textThere is good experimental evidence that predators often remove more of common prey types. This apostatic selection could maintain colour polymorphism within prey species. Many colour pattern morphs of species in nature appear to match components of the background. My aims were to gather experimental evidence for background tracking and for apostatic selection on cryptic prey. All the experiments use wild passerine birds as predators and pastry, coloured with food dye, as prey. Selection was infered from the numbers of prey eaten from dimorphic populations. Three different designs of background were used: cylindrical prey closely resembled inedible wooden models (masquerade), disc shaped prey rested on flat boards (simple crypsis), and cylindrical prey rested on hessian sheets among coloured stones (crypsis). A field investigation into the polymorphism and crypsis of the meadow grasshopper, Chorthippus parallelus was also conducted. The masquerade experiment showed that selection by wild birds could be background colour composition dependent but background tracking seemed an unlikely outcome. The simple crypsis experiment was an unsuccessful attempt to develop a design to provide crypsis for artificial prey. The experiment with cylindrical prey and stones provided evidence for background colour composition dependent selection: the predators selected against the morph that resembled the uncommon background colour component. Further support for background tracking came from an experiment where predators generated morph frequency equilibria that were proportional to the background composition frequencies, after a series of 25 simulated generations. An experiment designed to test how distinctness of colour morphs is maintained provided evidence that predators effect a kind of disruptive selection such that a polymorphic population arrives at morph colour pattern optima determined by the colour composition of the background. In an experiment designed to test apostatic selection on prey that match the background predators were presented with a range prey frequencies and selection measured when prey matched the background was compared to two situations where they did not. Selection was apostatic in all three backgrounds but strongest in the matching one.The ecological conclusion is clear: apostatic selection for crypsis by predators would maintain colour polymorphisms in cryptic prey species and would give rise to parallelisms of colour morph frequency and corresponding background colour element frequency. The field investigation provided a possible example of the outcome of such selection on a cryptic polymorphic species. Assuming the selection observed happens in nature, the results may help to explain the widespread occurrence of polymorphism in cryptic prey.</p
Nanofabrication of electrode arrays by electron-beam and nanoimprint lithographies
No full textThe fabrication of ordered nanoelectrode arrays using both electron-beam lithography and nanoimprint lithography is described. Arrays of nanoelectrodes with varying individual electrode diameters were produced and characterised electrochemically. Whilst both methods are highly reproducibile, nanoimprint lithography has the potential to produce devices rapidly and at low-cost. To our knowledge, this is the first report where nanoimprint lithography is employed for the production of nanoelectrode arrays for electroanalytical sensors
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
Original X-Ray Diffraction Images For 5-Aminolevulinic Acid Dehydratase (Alad) From E. Coli Complexed With Porphobilinogen.
No full textThe diffraction images which allowed the original 2.1 Angstrom resolution structure determination of Escherichia coli ALAD co-crystallised with a non-covalently bound moiety of the product, porphobilinogen (PBG), are presented. </span
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
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