1,721,014 research outputs found
Acetylene and oxygen as inhibitors of nitrous oxide production in Nitrosomonas europaea and Nitrosospira briensis: a cautionary tale
No full textAutotrophic ammonia-oxidizing bacteria produce nitrous oxide (N2O) as a by-product of nitrification or as an intermediate of nitrifier denitrification. In soil incubations, acetylene (C2H2) and large partial pressures of oxygen (O2) are used to distinguish between these sources. C2H2 inhibits ammonia oxidation and should therefore inhibit N2O production by both nitrification and nitrifier denitrification. O2 suppresses the reduction pathway of nitrifier denitrification. However, doubts concerning the reliability of C2H2 and O2 as inhibitors have arisen recently. Therefore, in this study we tested the influence of C2H2 and large partial pressures of O2 alone and in combination on N2O production in pure cultures of the ammonia oxidizers Nitrosomonas europaea and Nitrosospira briensis. C2H2 largely inhibited nitrite production in both ammonia oxidizers and N2O production by N. europaea. Surprisingly, it did not affect the N2O production in N. briensis. The variable response of ammonia oxidizers to C2H2 might have consequences for the use of C2H2 as an inhibitor of nitrification in soils. Different partial pressures of O2 ranging from less than 10 kPa O2 to 100 kPa O2 were tested for their effectiveness in inhibiting N2O production via nitrifier denitrification. The partial pressure of 100 kPa O2 yielded minimal N2O production by both ammonia-oxidizing species and seemed to inhibit N2O emission from nitrifier denitrification to a large extent. However, a negative effect of 100 kPa O2 on ammonia oxidation itself could not be excluded. The applicability of both inhibitors in determining N2O production pathways in soils is discussed. [KEYWORDS: Nitrous oxide; Acetylene; Oxygen; Ammonia oxidizer; Nitrifier denitrification]
Trends in global nitrous oxide emissions from animal production systems
No full textWastes from animal production systems contribute as much as 30-50% to the global N2O emissions from agriculture, but relatively little attention has been given on improving the accuracy of the estimates and on developing mitigation options. This paper discusses trends and uncertainties in global N2O emission from animal waste and discusses possible mitigation strategies, on the basis of literature data and results of simple calculations. Total N2O emissions from animal production systems are estimated at 1.5 Tg. Dung and urine from grazing animals deposited in pastures (41%), indirect sources (27%), animal wastes in stables and storages (19%), application of animal wastes to land (10%) and burning of dung (3%) are the five sources distinguished. Most sensitive factors are N excretion per animal head, the emission factor for grazing animals and that for indirect emissions. Total N2O emissions are related to type and number of animals, N excretion per animal, and the management of animal wastes. Projections by FAO suggest that animal numbers will increase by 40% between 2000 and 2030. Mean N excretion per animal head will probably also increase. These trends combined suggest a strong increase in total N2O emission from animal production systems in the near future, which is opposite to the objectives of the Kyoto Protocol. Improving N use efficiency, combined with anaerobic digestion of animal wastes for bio fuel generation are the most feasible options for mitigation, but these options seem insufficient to reverse the trend of increasing N2O emission. In conclusion, animal production systems are a major and increasing source of N2O in agriculture. The uncertainties in the emission estimates are large, due to the many complexities involved and the lack of accurate data, especially about N excretion and the management of animal wastes in practice. Suggestions are made how to increase the accuracy of the emission estimates and to mitigate N2O emission from animal production systems
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
Pilot‐scale investigations on phosphorus recovery from municipal wastewater
No full textAs a result of the implementation of the Urban Waste Water Treatment Directive, more stringent tertiary wastewater treatment is being implemented in more and more catchments throughout Europe. Limited supplies of naturally occurring phosphorus resources and their decreasing purity, coupled with legislative pressure on water‐service companies to remove phosphorus from both their effluent and waste streams, have focused considerable attention on recycling phosphorus recovered from domestic wastewater in existing phosphorus markets. Microalgae have proven efficient in recovering nutrients from different effluents such as municipal waste, agricultural waste, and industrial wastewater, avoiding nutrient runoff and eutrophication. Cultivation of extremophilic microorganisms has gained interest due to the ability of these microorganisms to accumulate and produce valuable compounds such as metabolites, enzymes, and surfactants. Chlamydomonas acidophila has been shown to be a promising agent for the removal of nutrients from different wastewaters, as it has high phosphorus and nitrogen uptake rates
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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