1,720,969 research outputs found
Airborne Dioxins, Furans, and Polycyclic Aromatic Hydrocarbons Exposure to Military Personnel in Iraq
Get PDFObjectives: The objective of this study was to use ambient polycyclic aromatic hydrocarbon (PAH), polychlorinated dibenzo-p-dioxins (PCDD), and polychlorinated dibenzofurans (PCDF) concentrations measured at Joint Base Balad in Iraq in 2007 to identify the sources of these species and their spatial patterns. Methods: The ratios of the measured species were compared with literature data for likely emission sources. Using the multiple site measurements on specific days, contour maps have been drawn using inverse distance weighting (IDW). Results: These analyses suggest multiple sources, including the burn pit (primarily a source of PCDD/PCDFs), the transportation field (primarily as source of PAHs), and other sources of PAHs that include aircraft, space heating, and diesel power generation. Conclusions: The nature and locations of the sources were identified. PCDD/PCDFs were emitted by the burn pit. Multiple PAH sources exist across the base
Source apportionment of airborne dioxins, furans, and polycyclic aromatic hydrocarbons at a United States forward operating Air Base during the Iraq War
No full textObjectives: The objective was to apportion the sources of the ambient polycyclic aromatic hydrocarbon (PAH), polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran concentrations measured at Joint Base Balad in Iraq. Methods: Positive matrix factorization (PMF) was applied to the data to obtain the chemical profiles and contribution time series of the PAHs, PCDDs, and PCDFs. Conditional probability function (CPF) analyses were performed to assess the source directionality relative to the monitoring sites. Results: Three source types were identified and apportioned. The sources were: the burn pit, diesel vehicles and generators, and aircraft emissions. The CPF plots were consistent with the assigned source types. Conclusions: The PCDDs and PCDFs originated primarily from the burn pit. Higher molecular weight PAHs were associated with vehicle emissions while the aircraft emissions were enriched in low molecular weight PAHs
Long-term trends in submicron particle concentrations in a metropolitan area of the northeastern United States
Get PDFSignificant changes in emission sources have occurred in the northeastern United States over the past decade, due in part to the implementation of emissions standards, the introduction and addition of abatement technologies for road transport, changes in fuel sulfur content for road and non-road transport, as well as economic impacts of a major recession and differential fuel prices. These changes in emission scenarios likely affected the concentrations of airborne submicron particles. This study investigated the characteristics of 11–500 nm particle number concentrations and their size spectra in Rochester, NY during the past 15 years (2002 to 2016). The modal structure, diurnal, weekly and monthly patterns of particle number concentrations are analyzed. Long-term trends are quantified using seasonal-trend decomposition procedures based on “Loess”, Mann-Kendall regression with Theil-Sen slope and piecewise regression. Particle concentrations underwent significant (p < 0.05) downward trends. An annual decrease of −323 particles/cm3/y (−4.6%/y) was estimated for the total particle number concentration using Theil-Sen analysis. The trends were driven mainly by the decrease in particles in the 11–50 nm range (−181 particles/cm3/y; −4.7%/y). Slope changes were investigated annually and seasonally. Piecewise regression found different slopes for different portions of the overall period with the strongest declines between 2005 and 2011/2013, followed by small upward trends between 2013 and 2016 for most size bins, possibly representing increased vehicular traffic after the recovery from the 2008 recession
Long-Term Changes of Source Apportioned Particle Number Concentrations in a Metropolitan Area of the Northeastern United States
Get PDFThe northeastern United States has experienced significant emissions reductions in the last two decades leading to a decrease in PM2.5, major gaseous pollutants (SO2, CO, NOx) and ultrafine particles (UFPs) concentrations. Emissions controls were implemented for coal-fired power plants, and new heavy-duty diesel trucks were equipped with particle traps and NOx control systems, and ultralow sulfur content is mandatory for both road and non-road diesel as well as residual oil for space heating. At the same time, economic changes also influenced the trends in air pollutants. Investigating the influence of these changes on ultrafine particle sources is fundamental to determine the success of the mitigation strategies and to plan future actions. Particle size distributions have been measured in Rochester, NY since January 2002. The particle sources were investigated with positive matrix factorization (PMF) of the size distributions (11–470 nm) and measured criteria pollutants during five periods (2002–2003, 2004–2007, 2008–2010, 2011–2013, and 2014–2016) and three seasons (winter, summer, and transition). Monthly, weekly, and hourly source contributions patterns were evaluated
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
Changes in the Acute Response of Respiratory Diseases to PM2.5 in New York State from 2005 to 2016
Get PDFPrior studies reported that exposure to increased concentrations of fine particulate matter (PM2.5) were associated with increased rates of hospitalization and emergency department (ED) visits for asthma and chronic obstructive pulmonary disease (COPD). In this study, rates were examined from 2005 to 2016 using a case-crossover design to ascertain if there have been changes in the rates per unit mass exposure given substantial reductions in PM2.5 concentration and changes in its composition. PM2.5 concentrations were reduced through a combination of policies designed to improve air quality and economic drivers, including the 2008 economic recession and shifts in the relative costs of coal and natural gas. The study period was split into three periods reflecting that much of the emissions changes occurred between 2008 and 2013. Thus, the three periods were defined as: BEFORE (2005 to 2007), DURING (2008–2013), and AFTER (2014–2016). In general, the number of hospitalizations and ED visits declined with the decreased concentration of PM2.5. However, the rate of COPD hospitalizations and asthma ED visits associated with each interquartile range increase in ambient PM2.5 concentration was larger in the AFTER period than the DURING and BEFORE periods. For example, each 6.8 μg/m3 increase in PM2.5 on the same day was associated with 0.4% (0.0%, 0.8%), 0.3% (−0.2%, 0.7%), and 2.7% (1.9%, 3.5) increases in the rate of asthma emergency department visits in the BEFORE, DURING, and AFTER periods, respectively, suggesting the same mass concentration of PM2.5 was more toxic in the AFTER period
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
The Association between Respiratory Infection and Air Pollution in the Setting of Air Quality Policy and Economic Change
Get PDFRationale: Fine particulate air pollution (≤2.5μm; PM2.5) has been associated with an increased risk of respiratory disease, but assessments of specific respiratory infections in adults are lacking. Objective: To estimate the rate of respiratory infection healthcare encounters in adults associated with acute increases in PM2.5 concentrations. Methods: Using case-crossover methods, we studied 498,118 adult New York State residents with a primary diagnosis of influenza, bacterial pneumonia, or culture negative pneumonia upon hospitalization or emergency department (ED) visit (2005-2016). We estimated the rate of healthcare encounters associated with increases in PM2.5 in the previous 1-7 days and explored differences Before (2005 to 2007), During (2008-2013), and After (2014-2016) implementation of air quality policies and economic changes. Results: Interquartile range increases in PM2.5 over the previous 7 days were associated with increased excess rates of culture negative pneumonia hospitalizations (2.5%; 95% CI 1.7%, 3.2%) and ED visits (2.5%; 95% CI 1.4%, 3.6%), and increased excess rates of influenza ED visits (3.9%; 95% CI 2.1%, 5.6%). Bacterial pneumonia hospitalizations but not ED visits were associated with increases in PM2.5 and though imprecise, were of a similar magnitude to culture negative pneumonia (Lag day 6 ER 2.3%; 95% CI: 0.3, 4.3). Increased relative rates of influenza ED visits and culture negative pneumonia hospitalizations were generally larger in the After period (p< 0.025 for both outcomes), compared to the During period, despite reductions in overall PM2.5 concentrations. Conclusion: Increased rates of culture negative pneumonia and influenza were associated with increased PM2.5 concentrations during the previous week, which persisted despite reductions in PM2.5 from air quality policies and economic changes. Though unexplained, this temporal variation may reflect altered toxicity of different PM2.5 mixtures or increased pathogen virulence
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