1,720,982 research outputs found
Modelling the survival of bacteria in drylands: the advantage of being dormant
No full textWe introduce a simple mathematical model for the description of
`dormancy', a survival strategy used by some bacterial populations that
are intermittently exposed to external stress. We focus on the case of
the cyanobacterial crust in drylands, exposed to severe water shortage,
and compare the fate of ideal populations that are, respectively,
capable or incapable of becoming dormant. The results of the simple
model introduced here indicate that under a constant, even though low,
supply of water the dormant strategy does not provide any benefit and it
can, instead, decrease the chances of survival of the population. The
situation is reversed for highly intermittent external stress, due to
the presence of prolonged periods of dry conditions intermingled with
short periods of intense precipitation. In this case, dormancy allows
for the survival of the population during the dry periods. In contrast,
bacteria that are incapable of turning into a dormant state cannot
overcome the difficult times. The model also rationalizes why dormant
bacteria, such as those composing the cyanobacterial crust in the
desert, are extremely sensitive to other disturbances, such as trampling
cattle
Diversity of vegetation patterns and desertification
No full textA new model for vegetation patterns is introduced. The model reproduces
a wide range of patterns observed in water-limited regions, including
drifting bands, spots, and labyrinths. It predicts transitions from bare
soil at low precipitation to homogeneous vegetation at high
precipitation, through intermediate states of spot, stripe, and hole
patterns. It also predicts wide precipitation ranges where different
stable states coexist. Using these predictions we propose a novel
explanation of desertification phenomena and a new approach to
classifying aridity
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
A mathematical model of plants as ecosystem engineers
No full textUnderstanding the structure and dynamics of plant communities in
water-limited systems often calls for the identification of ecosystem
engineers-key species that modify the landscape, redistribute resources
and facilitate the growth of other species. Shrubs are excellent
examples; they self-organize to form patterns of mesic patches which
provide habitats for herbaceous species. In this paper we present a
mathematical model for studying ecosystem engineering by woody plant
species in drylands. The model captures various feedbacks between
biomass and water including water uptake by plants' roots and increased
water infiltration at vegetation patches. Both the uptake and the
infiltration feedbacks act as mechanisms for vegetation pattern
formation, but have opposite effects on the water resource; the former
depletes the soil-water content under a vegetation patch, whereas the
latter acts to increase it. Varying the relative strength of the two
feedbacks we find a trade-off between the engineering capacity of a
plant species and its resilience to disturbances. We further identify
two basic soil-water distributions associated with engineering at the
single patch level, hump-shaped and ring-shaped, and discuss the niches
they form for herbaceous species. Finally, we study how pattern
transitions at the landscape level feedback to the single patch level by
affecting engineering strength. (c) 2006 Elsevier Ltd. All rights
reserved
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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