160,974 research outputs found
Airborne organophosphate pesticides drift in Mediterranean climate: The importance of secondary drift
No full textPesticide application is a short-term air-pollution episode with near and far field effects due to atmospheric drift. In order to better evaluate resulting air concentrations in nearby communities following pesticide application, measurements of airborne pesticides were conducted at ~70 m from field edge. This was done following three different application events of the organophosphate pesticide Chlorpyrifos in a persimmon orchard. Complementary information on larger spatial scale was obtained using CALPUFF modeling in which application and meteorological data was used to better evaluate dispersion patterns.Measurements indicated high airborne concentrations during application hours (few μg m-3 for 8 h average), which dropped to tens of ng m-3 in the following days. Measured atmospheric concentrations show that secondary drift (i.e., post-application drift) involves significant loads of pesticides and hence should not be ignored in exposure considerations. Furthermore, CALPUFF modeling revealed the complex dispersion pattern when weak winds prevailed, and showed that during the 24 h after application air concentrations reached levels above the hourly Texas effect screening level (0.1 μg m-3). Interestingly, weak winds on the night after application resulted in a secondary peak in measured and modeled air concentrations.Long exposure time (when secondary drift is considered) and concentrations measured following such common air-assisted orchard application, suggest pesticide drift may have health repercussions that are currently unknown, and emphasize the need for further epidemiological studies
Evaluation of low-cost gas sensors to quantify intra-urban variability of atmospheric pollutants
No full textLow-cost air quality monitoring units were tested within the context of the European research project TRAFAIR. This study aims to quantify the intra-urban variability of atmospheric pollutants by means of a low-cost sensor network, which was deployed across the urban area of Modena, in the Po Valley (Italy) for the assessment of air quality in the city. Each sensor unit featured a set of electrochemical cells responding to NO, NO 2 and O 3 delivering a current/voltage proportional to the mixing ratio of the target atmospheric pollutant. Each unit was calibrated using field colocation next to an urban regulatory air quality monitoring station in the city. A machine learning Random Forest algorithm was used as a calibration model and different configurations of the model were applied. The results from these configurations were compared in terms of their prediction performance and consistency of the explanatory variable role within the model. A significant variability in all pollutants across town was revealed by the units, highlighting areas impacted by local sources
Assessing the Influence of Polymer-Based Anti-Drift Adjuvants on the Photolysis, Volatilization, and Secondary Drift of Pesticides after Application
No full textOne practice to reduce spray drift during pesticide application is the addition of certain chemical adjuvants to spraying solutions, which change their physicochemical properties and result in larger droplets. The environmental impact of these agrochemicals continues however also after application, depending on surface processes occurring upon treated surfaces. While the impact of anti-drift adjuvants has been studied regarding spray drift, their impact on the fate of deposited pesticides has received little attention. Here, the effect of a polymer-based adjuvant (polyacrylamide) on the photolysis and evaporation rates of pyrimethanil (common fungicide) from dry films were investigated under controlled laboratory conditions and during two field studies. The laboratory results indicate that the adjuvant enhances the volatilization and photolysis rate both on hydrophobic lemon leaves and hydrophilic glass substrates. These results can be attributed to an increase in the geometrical area of residual film and a widening of its circumference rim, where solutes are likely to concentrate, when generated from adjuvant-containing droplets. Such morphological differences may enhance the exposure of deposited pesticides to interact with the overlaying atmosphere and incident radiation. The field data was less conclusive, suggesting a small impact of the anti-drift adjuvant on the fungicide’s secondary drift from crops and an even lower effect on volatilization from bare soil
Key environmental processes affecting the fate of the insecticide chloropyrifos applied to leaves
No full textChlorpyrifos (CP) is still a commonly employed organophosphorus insecticide worldwide. In semi-arid and Mediterranean climates, applied CP is expected to remain on leaves surfaces for relatively long time due to the lack of summer rains and common use of drip irrigation. The present work examines the loss rate of CP from leaves via different surface processes: evaporation, direct photolysis and reactions with ozone and [rad]OH radicals. Laboratory experiments showed that evaporation rate constant of CP increased from 0.109 to 0.492 h−1with the increase in wind speed up to 4 m/s. First-order rate constant of direct photolysis, measured using a solar simulator, was k’UV = 1.15 (±0.01) x 10−20 cm2photon−1. Second-order rate constants for the reaction of CP with ozone and [rad]OH were measured as 6 × 10−20and 6 × 10−12 cm3 molecule−1 s−1, respectively. The above rate constants were applied successfully in an outdoor experiment to predict the disappearance of chloropyrifos under specific environmental conditions. Further modeling showed that the insecticide half-life time on exposed surfaces under typical Mediterranean environment will be in the range of 0.9–6.9 h. Evaporation is expected to be the dominant removal path under most environmental conditions, followed by direct photolysis and reaction with [rad]OH
Treewidth Parameterized by Feedback Vertex Number
No full textWe provide the first algorithm for computing an optimal tree decomposition for a given graph G that runs in single exponential time in the feedback vertex number of G, that is, in time 2^{(fvn(G))}⋅ n^{(1)}, where fvn(G) is the feedback vertex number of G and n is the number of vertices of G. On a classification level, this improves the previously known results by Chapelle et al. [Discrete Applied Mathematics '17] and Fomin et al. [Algorithmica '18], who independently showed that an optimal tree decomposition can be computed in single exponential time in the vertex cover number of G.
One of the biggest open problems in the area of parameterized complexity is whether we can compute an optimal tree decomposition in single exponential time in the treewidth of the input graph. The currently best known algorithm by Korhonen and Lokshtanov [STOC '23] runs in 2^{(tw(G)²)}⋅ n⁴ time, where tw(G) is the treewidth of G. Our algorithm improves upon this result on graphs G where fvn(G) ∈ o(tw(G)²). On a different note, since fvn(G) is an upper bound on tw(G), our algorithm can also be seen either as an important step towards a positive resolution of the above-mentioned open problem, or, if its answer is negative, then a mark of the tractability border of single exponential time algorithms for the computation of treewidth
Variations on the Author
No full text“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
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Larry O. Spencer, Conference Author Presentation
No full textGen. Larry O. Spencer, USAF (Ret.), author of Dark Horse: A Journey from the Horseshoe to the Pentago
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Author Under Sail The Imagination of Jack London, 1902-1907
No full textIn this second volume of Author Under Sail Jay Williams investigates the life of Jack London as a professional writer at the turn of the 1900s, as his publications spanned The Call of the Wild to The Iron Heel and The Road. While documenting key life events, especially his rising fame, this biography explores London's necessity to illustrate the inner workings of his own vast imagination through his socialist essays and fiction.Cover -- Title Page -- Copyright Page -- Contents -- Acknowledgments -- Introduction -- 1. Howl, O Heav'nly Muse! -- 2. Jesus in the Theater of Socialism -- 3. Jack London's Place in American Literature -- 4. Theater of War, Theater at Home -- 5. Revolution, Evolution, and the Scene of Writing -- 6. The Jack London Show Goes on the Road -- 7. Red Atavisms and Revolution -- 8. Earthquake Apocalypse and Building the City, Boat, and House Beautiful -- 9. The Future of Socialism and the Death of the Individual -- 10. The Road Never Ends -- Notes -- Bibliography -- IndexIn this second volume of Author Under Sail Jay Williams investigates the life of Jack London as a professional writer at the turn of the 1900s, as his publications spanned The Call of the Wild to The Iron Heel and The Road. While documenting key life events, especially his rising fame, this biography explores London's necessity to illustrate the inner workings of his own vast imagination through his socialist essays and fiction.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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