1,720,956 research outputs found
Microbial use of maize cellulose and sugarcane sucrose monitored by changes in the C-13/C-12 ratio
No full textAn arable soil with organic matter formed from C3-vegetation was amended initially with maize cellulose (C-4-cellulose) and sugarcane sucrose (C-4-Sucrose) in a 67-day laboratory incubation experiment with microcosms at 25 degrees C. The amount and isotopic composition (C-13/C-12) Of Soil organic C, CO2 evolved, microbial biomass C, and microbial residue C were determined to prove whether the formation of microbial residues depends on the quality of the added C source adjusted with NH4NO3 to the same C/N ratio of 15. In a subsequent step, C-3-cellulosc (3 mg C g(-1) soil) was added without N to soil to determine whether the microbial residues formed initially from C-4-substrate are preferentially decomposed to maintain the N-demand of the soil microbial community. At the end of the experiment, 23% Of the two C-4-substrates added was left in the soil, while 3% and 4% of the added C-4-cellulose and C-4-sucrose, respectively, were found in the microbial biomass. The addition of the two C-4-substrates caused a significant 100% increase in C-3-derived CO, evolution during the 5-33 day incubation period. The addition of C-3-cellulose caused a significant 50% increase in C-4-derived CO2 evolution during the 38-67 day incubation period. The decrease in microbial biomass C-4-C accounted for roughly 60% of this increase. Cellulose addition promoted microorganisms strongly able to recycle N immediately from their own tissue by "cryptic growth" instead of incorporating NO3- from the soil solution. The differences in quality of the microbial residues produced by C-4-cellulose and C-4-Sucrose decomposing microorganisms are also reflected by the difference in the rates of CO2 evolution, but not in the rates of net N mineralization. (c) 2007 Elsevier Ltd. All rights reserved
Shifts in amino sugar and ergosterol contents after addition of sucrose and cellulose to soil
No full textAn incubation experiment with organic soil amendments was carried out with the aim to determine whether formation and use of microbial tissue (biomass and residues) could be monitored by measuring glucosamine and muramic acid. Living fungal tissue was additionally determined by the cell-membrane component ergosterol. The organic amendments were fibrous maize cellulose and sugarcane sucrose adjusted to the same C/N ratio of 15. In a subsequent step, spherical cellulose was added without N to determine whether the microbial residues formed initially were preferentially decomposed. In the non-amended control treatment, ergosterol remained constant at 0.44 mu g g(-1) soil throughout the 67-day incubation. It increased to a highest value of 1.9 mu g g(-1) soil at day 5 in the sucrose treatment and to 5.0 mu g g(-1) soil at day 33 in the fibrous cellulose treatment. Then, the ergosterol content declined again. The addition of spherical cellulose had no further significant effects on the ergosterol content in these two treatments. The non-amended control treatment contained 48 mu g muramic acid and 650 mu g glucosamine g(-1) soil at day 5. During incubation, these contents decreased by 17% and 19%, respectively. A 33% increase in muramic acid and an 8% increase in glucosamine were observed after adding sucrose. Consequently, the ratio of fungal C to bacterial C based on bacterial muramic acid and fungal glucosamine was lowered in comparison with the other two treatments. No effect on the two amino sugars was observed after adding cellulose initially or subsequently during the second incubation period. This indicates that the differences in quality between sucrose and cellulose had a strong impact on the formation of microbial residues. However, the amino sugars did not indicate a preferential decomposition of microbial residues as N sources. (C) 2007 Elsevier Ltd. All rights reserved
Formation and use of microbial residues after adding sugarcane sucrose to a heated soil devoid of soil organic matter
No full textA 67-day incubation experiment was carried out with a soil initially devoid of any organic matter due to heating, which was amended with sugarcane sucrose (C-4-sucrose with a delta C-13 value of -10.5 parts per thousand), inorganic N and an inoculum for recolonisation and subsequently at day 33 with C-3-cellulose (delta C-13 value of -23.4 parts per thousand). In this soil, all organic matter is in the microbial biomass or in freshly formed residues, which makes it possible to analyse more clearly the role of microbial residues for decomposition of N-poor substrates. The average delta C-13 value over the whole incubation period was -10.7 parts per thousand in soil total C in the treatments without C-3-cellulose addition. In the CO2 evolved, the delta C-13 values decreased from -13.4 parts per thousand to -15.4 parts per thousand during incubation. In the microbial biomass, the delta C-13 values increased from -11. 5 parts per thousand to -10. 1 parts per thousand at days 33 and 38. At day 67, 36% of the C-4-sucrose was left in the treatment without a second amendment. The addition of C-3-cellulose resulted in a further 7% decrease, but 4% of the C-3-cellulose was lost during the second incubation period. Total microbial biomass C declined from 200 mu g g(-1) soil at day 5 to 70 mu g g(-1) soil at day 67. Fungal ergosterol increased to 1.5 mu g g(-1) soil at day 12 and declined more or less linearly to 0.4 mu g g(-1) soil at day 67. Bacterial muramic acid declined from a maximum of 35 mu g g(-1) soil at day 5 to a constant level of around 16 mu g g(-1) soil. Glucosamine showed a peak value at day 12. Galactosamine remained constant throughout the incubation. The fungal C/bacterial C ratio increased more or less linearly from 0.38 at day 5 to 1.1 at day 67 indicating a shift in the microbial community from bacteria to fungi during the incubation. The addition Of C-3-cellulose led to a small increase in C-3-derived microbial biomass C, but to a strong increase in C-4-derived microbial biomass C. At days 45 and 67, the addition of N-free C-3-cellulose significantly decreased the C/N ratio of the microbial residues, suggesting that this fraction did not serve as an N-source, but as an energy source. (c) 2007 Elsevier Ltd. All rights reserved
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
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