1,720,970 research outputs found
Acidity and sampling artifacts of PM2.5 in Hong Kong
No full textSulfate in atmospheric particles has been found to be correlated with excess mortality rate and it is well known that sulfate particles are acidic. This thesis investigates the aerosol acidity, which is likely a better causal agent of health effects, in PM2.5 in Hong Kong. The strong acidity and the concentrations of ammonium, sodium, sulfate, nitrate and chloride in PM2.5 in Hong Kong, using a Harvard honeycomb denuder/filter-pack system were measured at the different sites (HKUST, TST and Ho Man Tin) in Hong Kong. Overall, the strong acidity of PM2.5 in HK is higher than that reported elsewhere (maximum of about 180 nmol/m3 in this study). Using back trajectory and mixing height analysis, we estimated that 40% of the measured sulfate and ammonium of PM2.5 in Hong Kong is from non-local sources.The sampling of acidity and semi-volatile species such as ammonium, nitrate and chloride is complicated by artifacts. Various reactions between gas and particles and among the collected particles lead to sampling errors. We examined the role of aerosol composition in the sampling artifacts of aerosols. The results show that the analysis of the artifact formation can be categorized into two regimes; as ammonium rich (AR) with the molar ratio [NH4+]/[SO42-] ≥ 1.5 and as ammonium poor (AP) samples with the molar ratio [NH4+]/[SO42-] < 1.5. The AR samples were characterized by high nitrate concentrations and low in-situ free acid; the evaporation of HNO3 and HC1 with concomitant evaporation of NH3, was more important in the sampling artifact of nitrate and chloride. The AP samples were characterized by low nitrate concentrations and high in-situ free acid; the evaporation of HNO3 or HCl alone was the important parameter in controlling the extent of sampling loss.We have also developed a methodology to estimate the contribution of each artifact reaction in the sampling artifacts of nitrate, chloride, ammonium and acidity. We extended our analysis to a much larger database, that is the 24-hr Respirable Suspended Particles (RSP: PM10) data set from seven air-quality-monitoring sites run by the Hong Kong Environmental Protection Department in 2001, to estimate the aerosol acidity of PM2.5, which is not regularly monitored. In-situ free acid concentrations and pH of aerosols, which are more relevant to environmental impact of aerosols than their strong acidity, were estimated. Because of the small variation in ambient temperature in HK, the acidity characteristics of fine particles are a function of mainly the relative humidity and the ammonium to sulfate ratio. Overall, the fine mode particles are highly acidic with average molar [NH4+]/[SO42-] ratio of 1.25, strong acidity of 66.3 nmol/m3, in-situ acidity ([H+]free) of 21 nmol/m3, and in-situ pH of -0.05. Our findings suggest that even the more neutralized ([NH4+]/[SO42-] >1.5) particles, such as those found when HK is under the influence of continental air masses from the Chinese mainland, can have high in-situ acidity and low pH when the RH is low. This study calls for more investigations of the acidity of aerosols in HK.</p
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
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
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
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
Inter-particle and gas-particle interactions in sampling artifacts of PM<sub>2.5</sub> in filter-based samplers
No full textDespite the recent rapid development of real-time measurements of chemical compositions in atmospheric aerosols, filter-based aerosol sampling for an extended period of time with post-sampling chemical analysis is still very common. The collected particles interact with both the in-coming gas and each other. These interactions lead to sampling artifacts. This paper investigates the role of aerosol ionic composition, inter-particle and gas-particle interactions in the sampling artifacts of PM2.5 at high relative humidity. This is achieved by comparing PM2.5 samples collected with and without a denuder/filter pack system at urban and suburban sites in Hong Kong. The samples collected with a denuder/filter pack were used to estimate the artifact-free ambient gas and particulate concentrations. Because of the prevailing high relative humidity (>70%RH) in HK, the collected particles were expected to have deliquesced and form an internal mixture, according to thermodynamic predictions. It was found that an ambient molar particulate [NH4+]/[SO42-] ratio of 1.5 is a critical condition to the sampling artifact characteristics of PM2.5. The urban samples were all ammonium rich (AR; [NH4 +]/[SO42-] greater than 1.5) and were characterized by a high nitrate concentration and low strong-acidity. They had a significant strong acidity loss of 73%, roughly half of which was due to the neutralization of acidity by ammonia. The suburban samples were all ammonium poor (AP; [NH4+]/[SO42-] less than or equal to 1.5) and were characterized by a low nitrate concentration and high strong-acidity. Sampling artifacts of the acidity, ammonium and sulfate were not important in the AP samples. In both the AR and AP samples, the individual evaporation of HNO3 and HCl were the primary reactions for the artifacts of nitrate and chloride while the concomitant evaporation of HNO 3 and HCl with NH3 was insignificant. In general, the extents of the sampling artifacts of nitrate and chloride increased with increasing gas-to-particulate concentration ratio of these two species. A methodology to estimate the artifact-free ambient concentrations of nitrate and chloride from measurements of filter pack samplers (without any denuders) for deliquesced particles is proposed.</p
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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