1,720,982 research outputs found
Relevant organic components in ambient particulate matter collected at Svalbard Islands (Norway)
No full textFractional factorial experiments using a test atmosphere to assess the accuracy and precision of a new passive sampler for the determination of formaldehyde in the atmosphere
No full textA new analytical method was developed for the determination of formaldehyde in ambient
air based on the use of a modified configuration of the Analyst® passive sampler. It consists of a
polyethylene cylinder filled with appropriate reactive adsorbent and a special anti-turbulence net
which works as an ozone scrubber.
The performance of a diffusive sampler depends critically on the selection and use of a suitable
adsorbent and on environmental factors, such as temperature, humidity and the interference of
oxidant species. In this study two adsorbent types were investigated: 2,4-dinitrophenylhydrazine (2,4-
DNPH) coated silica gel and Florisil® particles. Interference of ozone was removed by using a silver net
upstream as an anti-turbulence device. The performance of this net was then compared with that of
stainless steel. Furthermore, the aim of the work was the optimization of the adsorbent type and the
study of the interference of ozone with particular attention placed on the effect of relative humidity
and temperature.
A dynamic system for generating a known concentration of the test gas (formaldehyde) in an
appropriate exposure chamber was used to evaluate the performance of the passive sampler and to
allow the calibration of the methodology. Inter-comparisons with a reference method, active sampling
using 2,4-DNPH silica gel coated cartridges, were also carried out. Results were in accordance with
each other.
Tests were planned using a statistical method based on Design of Experiment methodology. The
operating conditions were chosen in order to obtain the best configuration of the passive device by
evaluating the statistical significance of the different factors and their interactions by analysis of
variance.
Results showed that the best configuration was achieved using 2,4-DNPH Florisil® coated particles as
an adsorbent and a silver anti-turbulence net as an ozone scrubber.
With the aim of achieving further results in realistic conditions, some field experiments were also
carried out
Uncertainties of polynuclear aromatic hydrocarbon and carbonyl measurements in heavy-duty diesel emission
No full textIn this note we describe the speciated particle-phase PM2.5 polynuclear aromatic hydrocarbon (PAH) and gas-phase carbonyl emissions as collected from a heavy-duty diesel bus outfitted with an oxidation catalyst for exhaust after-treatment. The vehicle was run on a chassis dynamometer during a transient cycle test reproducing a typical city bus route (Azienda Tramviaria Municipalizzata cycle). The diluted tail-pipe emissions were sampled for PAH using a 2.5 mu m cut size cyclone glass fiber filter assembly, while carbonyls were absorbed onto dinitrophenyl hydrazine-coated silica cartridges. The former compounds were analysed by CGC-MS, the latter by HPLC-UV. Combining the two sets of speciation data resulting from 15 identical dynamometer tests provided a profile of both unregulated organic emissions. PAH emission rates decreased with the number of benzene fused rings. Fluoranthene and pyrene amounted to 90% of total PAHs quantified; six-ring PAHs accounted only for 0.5%. Similarly, formaldehyde and acetaldehyde accounted for similar to 80% of the total carbonyl emissions. Uncertainties of the method in the determination of individual emission factors were calculated. Statistical data processing revealed that all the measurements were quite unaffected by systematic errors and repeatability percentages did not exceed 50% for the majority of components of both groups
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
Polycyclic Aromatic Hydrocarbon Emission Profiles and Removal Efficiency by Electrostatic Precipitator and Wetfine Scrubber in an Iron Ore Sintering Plant
No full textA monitoring campaign of polychlorinated dibenzo-p-dioxins and dibenzofurans, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyl was carried out in an Italian iron ore sintering plant by sampling the combustion gases at the electrostatic precipitator (ESP) outlet, at the Wetfine scrubber (WS) outlet, and by collecting the ESP dust. Few data are available on these micropollutants produced in iron ore sintering plants, particularly from Italian plants. This study investigates the PAH emission profiles and the removal efficiency of ESPs and WS. PAHs were determined at the stack, ESP outlet flue gases, and in ESP dust to characterize the emission profiles and the performance of the ESP and the WS for reducing PAH emission. The 11 PAHs monitored are listed in the Italian legislative decree 152/2006. The mean total PAH sum concentration in the stack flue gases is 3.96 mu g/N center dot m(3), in ESP outlet flue gases is 9.73 mu g/N center dot m(3), and in ESP dust is 0.53 mu g/g. Regarding the emission profiles, the most abundant compound is benzo(b)fluoranthene, which has a relative low BaP toxic equivalency factors (TEF) value, followed by dibenzo(a,l)pyrene, which has a very high BaP(TEF) value. The emission profiles in ESP dust and in the flue gases after the ESP show some changes, whereas the fingerprint in ESP and stack flue gases is very similar. The removal efficiency of the ESP and of WS on the total PAH concentration is 5.2 and 59.5%, respectively
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
Organic contaminants in the atmosphere of Ny-Ålesund
No full textIn-field measurements of atmospheric contaminants were undertaken in 1998 and 1999. Our concern was focused on organic chemicals, as important contributors to ambient toxicity, tracers of sources and indicators of meteo-climatic contour. As for gaseous chemicals, focus was on semi-volatile aldehydes; among particulate organics, n-alkanes, PAHs and Nitro-PAHs were investigated.
Carbonyls were collected on June 1998 on Zeppelin mount (ZM) and at CNR Scientific Base CSB). Samplings lasted 2 h, starting at 8:00 h, and contaminants were collected on silica gel cartridges loaded with pentafluorophenyl hydrazine (PFPH). Degradation of hydrazones was prevented by applying ozone scrubbers. Characterization of C3-C14 aldehydes was carried out through GC-MS analysis [Cecinato et al., Chromatographia 54 (2001), 263]. Formaldehyde, acetaldehyde and acetone were not determined due to interferences.
Suspended particulates (PM10 fraction) were collected at high-volume conditions on quartz filters, during summer 1998 and spring 1999. In 1998 a pair of 3-day sampling periods were undertaken in June (sunny hours); in 1999 (April-May) three sampling periods were selected, each day between last night and sunrise. Organic fraction was extracted in ultra-sonic bath, separated into three fractions through alumina column chromatography (non-polar aliphatics, polycyclic aromatics and polar organics), and analyzed for contents in n-alkanes, PAHs, Nitro-PAHs and fatty acids by means of GC-MSD.
About carbonyl during June 1998, the concentrations at the two locations investigated were different and showed important daily variability. Also their percent profiles and concentration ratios between the two stations changed widely. Total carbonyls ranged ~8-45 μg/m3 at ZM and ~2-7 μg/m3 at CSB.
The concentrations of n-alkanes in PM10 were different in 1998 and 1999 (~19 vs. 100 ng/m3 as period average), as well as percent distribution of <C24 homologues. According to that, in the summer bacteria and microorganisms provided important contribution to n-alkane occurrence, whilst in spring the petroleum exhausts were predominating. The emission of vegetation was scarce (CPI25≈1.4).
Total PAHs were, as average, more in Apr-May 1999 (~1.4 vs. 0.6 ng/m3) and distinct distributions were identified. It could depend in part on ambient temperature (semi-volatile compounds are enriched on particulate during winter). Nonetheless, a role was played also by the nature of emission sources (as suggested by changes in PAH concentration ratios), while reactivity of the atmosphere was unimportant (BaP/BeP ratio).
Though only nitrated fluoranthenes and pyrenes were investigated, Nitro-PAHs merited concern. Nitro-PAHs were more in the spring (~135 vs. 10 pg/m3) and, overall, the percent profiles were very different: 1-, 7-, 3-NFAs and 1-NPY, typical of direct emission, occurred in spring, 2-NFA and 2-NPY (generated by photochemical reactions) in the summer.
Fatty acids (ranging ~20-40 ng/m3 as total)were indicative of bacterial and small vegetation sources
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
- …
