1,721,038 research outputs found
NMR spectroscopic applications to atmospheric organic aerosol analysis – Part 1: A critical review of data source and analysis, potentialities and limitations
Full text linkNMR techniques have been used for more than two decades in atmospheric aerosol research. Compared to aerosol mass spectrometric techniques, NMR applications remain limited but provide complementary information on the C–H structural properties of particulate organic compounds. Such information can be key for organic aerosol source apportionment, provided that a representative library of source-specific reference spectra is let available. In recent years, chemical shift data for a number of atmospheric organic tracers have been reported but significant gaps remain, as well as in the NMR characterization of several secondary organic aerosol systems. Although factor analysis and other multivariate techniques are gaining importance in NMR organic source apportionment, the bulk of the literature studies is based on functional group analysis. The creation of a community of research groups would be highly beneficial in setting standards, overcoming technical limitations and dealing with the complexity of the NMR spectra of atmospheric aerosol extracts
The power of communication: biogenic volatile organic compound-mediated interactions in land plants and marine phytoplankton
No full textIn this chapter, we summarize current knowledge on the diverse ecological functions of biogenic volatile organic compounds (BVOCs) in biotic interactions among living organisms of both terrestrial and marine habitats, at the individual and community levels. Research on the regulatory ecology of BVOCs in these systems shows how these compounds are crucial determinants of the “eco-active chemosphere” (i.e., the ecological environmental interface where multiorganisms interactions are chemically mediated) of both land plants and phytoplankton. Beyond the plant-insect communication mediated by BVOCs, it is becoming clear that volatiles act as fundamental chemical mediators in plant-microorganism interactions, particularly with fungi or bacteria. Moreover, research on the role of BVOCs in aquatic systems has been poorly explored, while the ecological function of BVOCs as crucial chemical cues is emerging also for this environment. These aspects are described in relation to exemplary multiorganism systems that are critical in terrestrial or marine habitats: (1) on land, the aboveground plant-phytopathogen and (2) the belowground plant-beneficial microbiome systems; (3) in water, the phytoplankton-marine communities’ system. We highlight how different mechanisms and processes driven by BVOCs are activated depending on the form of associations between organisms (detrimental vs beneficial). Indeed, BVOCs may have either beneficial or adverse effects on the receiver organism by playing a direct (antimicrobial activity and allelopathy) or indirect (induced resistance) defensive role, and in mutualistic associations by acting as growth-promoting effectors or stress mitigators. We conclude with novel perspectives based on the meta-organism concept that could contribute to better characterizing the complexity of the ecological roles of BVOCs at different organism-microorganism interfaces
Biogenic volatile organic compound emissions in response to climate change-induced environmental stresses
No full textIn the Anthropocene era, where environmental stresses are amplified and extremes occur more frequently, understanding the responses of biogenic volatile organic compound (BVOC) emissions has become a critical area of research. This chapter explores the complex relationship between BVOC emissions and environmental stressors, with a particular focus on how emissions will be affected by climate change. As global temperatures rise, BVOC emissions are projected to increase exponentially, up to a threshold that is intricately linked to specific plant functional types and other environmental stresses. Drought, while initially increasing emissions, can lead to a collapse in the plant's metabolic processes under conditions of prolonged water deficit. The co-occurrence of heat and drought is set to intensify BVOC emissions, leading to changes in both emission responses and composition. The impacts of ozone (O3), both increasing due to climate change, on the production and release of BVOC are also explored, revealing that they affect plant emissions in diverse ways, leading to species-specific responses and a diverse blend of BVOC emissions. The chapter then investigates the exceptional adaptive capacity of certain plants to extremely stressful environmental conditions, with 'resurrection plants' and other extremophiles providing a fascinating case study for stress responses. The impact of soil pollutants, particularly metals, on BVOC emissions and responses to environmental changes is also examined. The chapter concludes with a brief exploration of aquatic ecosystems, where algae, phytoplankton, and cyanobacteria contribute to BVOC emissions. The common thread running through all these diverse topics is the urgent need for a mechanistic understanding of BVOC emission responses to environmental stresses. As climate change intensifies, such understanding will be crucial in developing strategies to mitigate its impacts and protect our ecosystems
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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