1,720,957 research outputs found
Organic geochemical controls on the dermal absorption of polycyclic aromatic hydrocarbons from manufactured gasworks soils
Full text linkBrownfield sites, such as former manufactured gas plants (MGPs), hold potential for urban redevelopment. However, the soils in these areas are often contaminated with a variety of organic pollutants. Among these, polycyclic aromatic hydrocarbons (PAHs) are persistently found as mixtures in soil, with several PAHs being recognized as potentially carcinogenic. Human health risk assessments (HHRAs) establish estimates on the risks posed from individual PAHs, including the potential dermal bioavailability. However, the dermal bioavailability values of PAHs currently applied in HHRAs are based on a single study that does not comprehensively represent the complexities of PAH-soil interactions. The study's singular PAH spiking approach within a single soil type failed to account for the heterogeneous interplay between diverse PAHs, soil properties and environmental factors. Consequently, this previous study potentially overestimated the PAH availability in soil and creates uncertainty in any calculated dermal bioavailability. There is a shortage of research investigating the dermal bioavailability of a large diversity of PAHs from different soil types in real-world contaminated soils (not spiked), including no knowledge of the dermal absorption behaviour of alkylated PAHs (alkyl-PAHs) and a lack of research into the organic matter (OM) fractions influencing PAH dermal bioavailability.
To address these gaps this thesis focuses on assessing the relationships between both parent and alkylated PAHs and the characterised bulk OM of real-world contaminated MGP soils. The aim is to ascertain whether characterised bulk OM contribute to variations in PAH distributions across MGP sites and industrial processes, as well as to explore their influence on in vitro human dermal bioavailability.
In this work, quantification of PAHs was achieved through gas chromatography tandem mass spectroscopy (GC-MS/MS), while bulk OM is characterised using Rock-Eval(6) Pyrolysis (RE). Chapter 5 describes the employment of principal component analysis (PCA) to differentiate MGP processes based on PAH distributions, with the assistance of the RE parameters. The findings reveal distinctive signatures for MGP processes with oil associations and lower temperatures, from petrogenic signatures and contributions of heavier weight PAHs, whereas other processes were found challenging to identify. Varied quantities of alkyl-PAHs in MGP soils were identified, emphasising the need to investigate the dermal bioavailability of these compounds.
Chapter 6 reports the measured dermal absorption (quantified as dermal fluxes) of 27 parent and alkylated high molecular weight (HMW) PAHs from real-world soils. Fluxes of the receptor solution (RS) and synthetic membrane are quantified, revealing that real-world contaminated soils influenced by environmental factors, lead to lower dermal fluxes compared to previous investigations using spiked soils. The majority of available HMW PAHs were measured in the membrane, showing that the membrane acted as a sink for PAHs released from soils, resulting in delayed diffusion of HMW PAHs into the RS. Notably, fluxes decrease with increases in the PAH ring number, highlighting the potential risks associated with low ring number PAHs including one alkyl-PAH group at longer exposure timesteps, a factor currently overlooked in HHRAs.
Chapter 7 reports linear regression analysis relationships between RE parameters and RS fluxes of five MGP samples which indicated strong associations between HMW PAHs exhibiting high fluxes and specific RE parameters. However, it is important to acknowledge that these relationships were primarily driven by one sample exhibiting exceptionally high PAH concentrations and RE values. Nonetheless, RE demonstrates promise as a screening tool for characterising contaminated soil, particularly for PAHs with higher fluxes and stronger correlations estimated for the membrane fluxes. However, further investigations exploring a larger dataset of soils is recommended to verify assumptions and produce models capable of predicting the dermal bioavailability of HMW PAHs from soils.
In summary, this research advances the knowledge of dermal bioavailability by investigating the largest number of different PAHs, including previously unstudied alkyl-PAHs, and demonstrating their potential risk for dermal absorption. Additionally, certain RE parameters offer promise for estimating PAH bioavailability in soil. By elucidating the complexities of PAH-soil interactions and assessing their influence on dermal absorption, this study enriches our understanding of PAHs' dermal bioavailability from real-world contaminated soils. This knowledge can contribute to the refinement of accurate HHRAs, particularly regarding the potential risks posed by a diverse set of PAHs in varied contaminated soil contexts
Organic geochemical controls on the dermal absorption of polycyclic aromatic hydrocarbons from manufactured gasworks soils
Full text linkBrownfield sites, such as former manufactured gas plants (MGPs), hold potential for urban redevelopment. However, the soils in these areas are often contaminated with a variety of organic pollutants. Among these, polycyclic aromatic hydrocarbons (PAHs) are persistently found as mixtures in soil, with several PAHs being recognized as potentially carcinogenic. Human health risk assessments (HHRAs) establish estimates on the risks posed from individual PAHs, including the potential dermal bioavailability. However, the dermal bioavailability values of PAHs currently applied in HHRAs are based on a single study that does not comprehensively represent the complexities of PAH-soil interactions. The study's singular PAH spiking approach within a single soil type failed to account for the heterogeneous interplay between diverse PAHs, soil properties and environmental factors. Consequently, this previous study potentially overestimated the PAH availability in soil and creates uncertainty in any calculated dermal bioavailability. There is a shortage of research investigating the dermal bioavailability of a large diversity of PAHs from different soil types in real-world contaminated soils (not spiked), including no knowledge of the dermal absorption behaviour of alkylated PAHs (alkyl-PAHs) and a lack of research into the organic matter (OM) fractions influencing PAH dermal bioavailability.
To address these gaps this thesis focuses on assessing the relationships between both parent and alkylated PAHs and the characterised bulk OM of real-world contaminated MGP soils. The aim is to ascertain whether characterised bulk OM contribute to variations in PAH distributions across MGP sites and industrial processes, as well as to explore their influence on in vitro human dermal bioavailability.
In this work, quantification of PAHs was achieved through gas chromatography tandem mass spectroscopy (GC-MS/MS), while bulk OM is characterised using Rock-Eval(6) Pyrolysis (RE). Chapter 5 describes the employment of principal component analysis (PCA) to differentiate MGP processes based on PAH distributions, with the assistance of the RE parameters. The findings reveal distinctive signatures for MGP processes with oil associations and lower temperatures, from petrogenic signatures and contributions of heavier weight PAHs, whereas other processes were found challenging to identify. Varied quantities of alkyl-PAHs in MGP soils were identified, emphasising the need to investigate the dermal bioavailability of these compounds.
Chapter 6 reports the measured dermal absorption (quantified as dermal fluxes) of 27 parent and alkylated high molecular weight (HMW) PAHs from real-world soils. Fluxes of the receptor solution (RS) and synthetic membrane are quantified, revealing that real-world contaminated soils influenced by environmental factors, lead to lower dermal fluxes compared to previous investigations using spiked soils. The majority of available HMW PAHs were measured in the membrane, showing that the membrane acted as a sink for PAHs released from soils, resulting in delayed diffusion of HMW PAHs into the RS. Notably, fluxes decrease with increases in the PAH ring number, highlighting the potential risks associated with low ring number PAHs including one alkyl-PAH group at longer exposure timesteps, a factor currently overlooked in HHRAs.
Chapter 7 reports linear regression analysis relationships between RE parameters and RS fluxes of five MGP samples which indicated strong associations between HMW PAHs exhibiting high fluxes and specific RE parameters. However, it is important to acknowledge that these relationships were primarily driven by one sample exhibiting exceptionally high PAH concentrations and RE values. Nonetheless, RE demonstrates promise as a screening tool for characterising contaminated soil, particularly for PAHs with higher fluxes and stronger correlations estimated for the membrane fluxes. However, further investigations exploring a larger dataset of soils is recommended to verify assumptions and produce models capable of predicting the dermal bioavailability of HMW PAHs from soils.
In summary, this research advances the knowledge of dermal bioavailability by investigating the largest number of different PAHs, including previously unstudied alkyl-PAHs, and demonstrating their potential risk for dermal absorption. Additionally, certain RE parameters offer promise for estimating PAH bioavailability in soil. By elucidating the complexities of PAH-soil interactions and assessing their influence on dermal absorption, this study enriches our understanding of PAHs' dermal bioavailability from real-world contaminated soils. This knowledge can contribute to the refinement of accurate HHRAs, particularly regarding the potential risks posed by a diverse set of PAHs in varied contaminated soil contexts
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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