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Microbial and hydrolase activity after release of low molecular weight organic compounds by a model root surface in a clayey and a sandy soil
No full textThe stimulatory effects of low molecular weight organic compounds (LMWOC) such as glucose, citrate, oxalate, glutamate, on microbial and hydrolase activity, in the rhizosphere and bulk soil layers of a clayey and a sandy soil were studied. Incubation units reproducing the rhizosphere environment were used, allowing additions and precise sampling of soil. All LMWOC stimulated respiration in both soils although the degree of LMWOC mineralization was different in the two soils. The double-stranded DNA (dsDNA) content increased significantly in the rhizosphere layer of the clayey soil treated with glucose or glutamate, but not with citrate or oxalate. In the sandy soil, a significant increase in the dsDNA content was only observed in the rhizosphere layer upon release of oxalate, whereas differences of the other treatments over the control were not significant. Hydrolase activity in the rhizosphere soil layer was generally stimulated. The alkaline phosphatase activity was significantly stimulated by glucose, glutamate and citrate in both the clayey and sandy soils, whereas the acid phosphatase activity was significantly stimulated by citrate in the clayey soil and by glutamate, citrate and oxalate in the sandy soil. Phosphodiesterase activity was significantly stimulated by glutamate and citrate in the clayey soil and by citrate only in the sandy soil. Urease activity was significantly stimulated by glucose and citrate in the clayey soil, whereas, the stimulation of urease activity in the sandy soil upon release of glucose, citrate and oxalate was not significant. No response to LMWOC release was observed for proatease activity in the rizosphere or bulk soil layer of both soils. It was concluded that in the rhizosphere, different LMWOC commonly released in the root exudates stimulate soil microbial activity and hydrolase activity differently depending on the compound released and soil type
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Microbial diversity and microbial activity in the rhizosphere
Get PDFIt is well established that microbial life only occupies a minor volume of soil being localised in hot spots such as the rhizosphere soil (Nannipieri et al., 2003), where microflora has a continuous access to a flow of low and high molecular weight organic substrates derived from roots. This flow, together with specific physical, chemical and biological factors, can markedly affect microbial activity and community structure of the rhizosphere soil
Root exudate effects on the bacterial communities, CO2 evolution, nitrogen transformations and ATP content of rhizosphere and bulk soils
No full textThe ATP content, soil respiration, bacterial community composition, and gross N mineralization and immobilization rates were monitored under laboratory condition at 25°C for 28 d in a model system where low molecular weight root exudates (glucose and oxalic acid) were released by a filter placed on the surface of a forest soil also treated with 15N, so as to simulate rhizosphere conditions. Periodically, the soil was sampled from two layers, 0-2 and 6-14 mm below the filter's surface, which were indicated as rhizosphere and bulk soils, respectively. The isotope dilution technique was used to determine the effect of these low molecular weight organic compounds (LMWOCs) on gross N mineralization and immobilization rates. From 0 to 3 d both glucose and oxalic acid amended soils showed a rapid evolution of CO2, more pronunced in the latter treatment together with a decrease in the amount of mineral N of the rhizosphere soil, probably due to N immobilization. Nevertheless, these changes were accompanied by a very small increase in the net ATP content probably because the low C application rate stimulated microbial activity but microbial growth only slightly. A positive 'priming effect' probably developed in the oxalic acid amended soil but not in the glucose amended soil. Gross N mineralization and immobilization rates were only observed in the rhizosphere soil, probably due to the greater C and N concentrations and microbial activity, and were a little higher in both amended soils than in the control soil, only between 1 and 7 d. Both glucose and oxalic acid influenced the bacterial communities of the rhizosphere soil, as new bands in the DGGE profiles appeared at 3 and 7 d. Glucose induced lower changes in the bacterial community than oxalic acid, presumably because the former stimulated a larger proportion of soil microorganisms whereas the latter was decomposed by specialized microorganisms. Peaks of net daily soil respiration and net ATP content and the appearence of new dominant bacterial populations were shifted in time, probably because there was less ATP synthesis and DGGE patterns changed after complete substrate mineralization
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