1,720,995 research outputs found
Microbial community structure and resource availability drive the catalytic efficiency of soil enzymes under land-use change conditions
No full textThe turnover of nutrients bound to organic matter is largely mediated by extracellular hydrolytic enzymes (EHEs) produced by soil microorganisms. However, little is known about the environmental drivers (e.g., soil pH, C content, C:N ratio) of the catalytic properties of EHEs and their functional link to the structure of soil microbial communities. We linked catalytic properties, K-m and V-max, determined by Michaelis-Menten kinetics, to a set of environmental and microbial properties in the soils of a land-use sequence ranging from undisturbed natural forest to pastures of different ages and to secondary succession in the Andes of southern Ecuador. The sensitivity of the substrate affinity constant (K-m) and the maximum rate (V-max) of six EHEs (beta-cellobiohydrolase (CBH), beta-glucosidase (BG), N-acetylglucosaminidase (NAG), alpha-glucosidase (AG), xylanase (XYL), acid phosphomonoesterase (AP)) to changing environmental conditions was tested by fluorogenic substrates. We used the V-max-to-K-m ratio (K-a) as a proxy for the catalytic efficiency and the signature membrane phospholipid fatty acids as a proxy of microbial community structure. Microbial communities adapted to environmental changes, selected for enzymes with higher substrate affinity (K-m) and catalytic efficiency (K-a) compared with pure cultures. Along the land-use sequence, catalytic efficiency increased from natural forest to young pasture, while it decreased during long-term pasture use and secondary succession. This is consistent with three to five times faster turnover of tested substrates (estimated based on Michaelis-Menten kinetic parameters) at the young pasture compared with the long-term pasture and secondary succession. Environmental drivers of the K-m were enzyme-specific (e.g., the pH for XYL, the C:N ratio for AP, and the C availability for NAG) and differed from those for V-max. A decoupled response of V-max and K-m to land-use changes observed for AG, BG, CBH, XYL, and AP, implies divers consequences for ecosystem processes mediated by these enzymes. A high abundance of Gram(-) bacteria triggered the catalytic properties (K-m and/or K-a) of enzymes decomposing cellulose, hemicellulose, starch, and monophosphoesters. The importance of climatic factors for catalytic properties of EHEs was emphasized by the K-a values extracted from the literature and demonstrated good correspondence of K-a between soils from geographically distinct experimental plots. (C) 2015 Elsevier Ltd. All rights reserved
Drought tolerance of emerging European silver fir seedlings (Abies alba Mill.) does not follow geographic gradients
Full text linkAbstract One of silviculture's primary objectives is converting monospecific into diverse forest stands comprising climate-tolerant species, aiming to mitigate global change. In practice, this is often achieved by enrichment planting or seeding of species, currently not occurring in the specific area. Silver fir ( Abies alba ) is considered one of the European native species regarded as climate tolerant. The species, therefore recently received increasing attention in research and forestry in the context of climate change adaptation. The intra-specific variation in drought tolerance has been intensively studied in Abies alba adult trees, but not in seedlings. Here, we explore the potential of Abies alba seedlings to withstand simulated summer droughts in central Europe. A climate chamber experiment was conducted, examining the resistance to and recovery from drought of silver fir seedlings of four provenances representing a geographic West–East gradient in Europe. Seedlings were exposed to two 30-day drought scenarios of differing severity under controlled conditions. We measured biomass partitioning patterns and individual photosynthetic efficiency. Growth and maximum photosynthetic efficiency were unaffected by intermediate drought. Intense drought significantly reduced the maximum photosynthetic efficiency of all provenances. Seedlings of the easternmost provenance showed the greatest biomass across all treatments; however, they failed to recover from drought. Our findings show that differences in drought susceptibility of emerging Abies alba seedlings do not follow geographic gradients
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
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