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Characterization and night-time oxidation of pellet stove emissions
No full textA growing energy demand has shifted interest towards
alternative energy sources such as biomass combustion.
Wood has become an important fuel even in the
developed world, frequently used in households for
heating purposes mostly as logs but also as pellets.
During winter biomass burning is one of the most
important air pollution sources emitting both primary
organic aerosol (POA) and organic vapours that can be
oxidized producing secondary organic aerosol (SOA).
Pellet stoves are considered as low-emitting combustion
sources, but a growing influence of their emissions on
air quality is expected. For example, during 2018 global
wood pellet consumption increased by 130% compared
to its 2013 levels, reaching 53 million tons (EPC, 2019).
Half of this consumption took place in Europe (27
million tons; 60% increase in 5 years).
Recently, there has been increasing interest in
exploring the extent of night-time chemical processing
of biomass burning emissions. Hartikainen et al. (2018)
reported substantial SOA production in laboratory
experiments under dark conditions. Kodros et al. (2020)
suggested that dark oxidation of biomass burning
plumes by NO3 radicals may be an additional formation
pathway of oxygenated OA and may lead to secondary
inorganic and organic aerosol nitrate formation.
Environmental simulation chamber experiments
were performed in the Foundation of Research and
Technology-Hellas atmospheric simulation chamber
(FORTH-ASC), to characterize fresh and aged pellet
stove emissions. The fresh PM1 (particulate matter with
diameter less than 1 μm) emissions consisted mainly of
organics (93 ± 4 %), followed by black carbon (5 ± 3 %),
nitrates and sulfate (1 %). The emission rates of fresh
OA were in the range of 2.6 to 12 g kg-1 of pellets
depending on burning conditions, while the POA
oxygen-to-carbon ratio (O:C) was 0.58 ± 0.04. The pH for
the fresh emissions estimated to be 3.2 ± 0.3.
The oxidation of the pellet emissions was
investigated under dark conditions by injecting nitrogen
dioxide (NO2) and ozone (O3), at different relative
humidity (RH) levels. In all experiments SOA was formed
(1-32 μg m-3), increasing the OA levels by 2-28 % after a
few hours of exposure to NO3 radicals in the chamber (3
- 5 hours of equivalent atmospheric dark oxidation)
(Figure 1). An increase in the O:C ratio of the OA by 7-21
% was also observed.
Figure 1. SOA (red bars) and organic nitrate (black bars)
mass concentrations for the dark ageing experiments.
These results suggest that dark oxidation of pellet
emissions is an additional biomass burning SOA source
that should be considered in atmospheric models.
This work was supported by the European Research
Council PyroTRACH project (grant 726165) and the EU
Horizon-2020 project REMEDIA (grant 874753)
Characterization and dark oxidation of the emissions of a pellet stove
No full textPellet combustion in residential heating stoves has increased globally during the last decade. Despite their high combustion efficiency, the widespread use of pellet stoves is expected to adversely impact air quality. The atmospheric aging of pellet emissions has received even less attention, focusing mainly on daytime conditions, while the degree to which pellet emissions undergo night-time aging as well as the role of relative humidity remain poorly understood. In this study, environmental simulation chamber experiments were performed to characterize the fresh and aged organic aerosol (OA) emitted by a pellet stove. The fresh pellet stove PM1 (particulate matter with aerodynamic diameter less than 1 μm) emissions consisted mainly of OA (93 ± 4 %), and black carbon (5 ± 3 %). The primary OA (POA) oxygen-to-carbon ratio (O:C) was 0.58 ± 0.04, higher than fresh logwood emissions. The emitted OA at a concentration of 70 μg m-3 mainly consisted of semi-volatile (68%) and intermediate-volatility (16%) compounds. The oxidation of the pellet emissions under dark conditions was investigated by injecting nitrogen dioxide (NO2) and ozone (O3) in the chamber, at different (10-80%) relative humidity (RH) levels. In all dark aging experiments secondary organic aerosol (SOA) formation was observed, increasing the OA levels after a few hours of exposure to NO3 radicals. The change in the aerosol composition and the extent of oxidation depended on RH. For low RH, the SOA formed was up to 30% of the initial OA, accompanied by a moderate change in both O:C levels (7−8 % increase) and OA spectrum. Aging under higher RH conditions (60−80%) led to a more oxygenated aerosol (increase in O:C of 11−18 %), but only a minor (1−10%) increase in OA mass. The increase in O:C at high RH, indicates the importance of heterogeneous aqueous reactions in this system, that oxidize the original OA with a relatively small net change of the OA mass. These results show that the OA in pellet emissions can chemically evolve under low photochemical activity (e.g. wintertime period) with important enhancement in SOA mass under certain conditions
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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