12 research outputs found
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Complex refractive index, single scattering albedo, and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors
Refractive index and optical properties of biogenic and anthropogenic secondary organic aerosol (SOA) particles were investigated. Aerosol precursors, namely longifolene, α-pinene, 1-methylnaphthalene, phenol, and toluene were oxidized in a Teflon chamber to produce SOA particles under different initial hydrocarbon concentrations and hydroxyl radical sources, reflecting exposures to different levels of nitrogen oxides (NOx). The real and imaginary components (n and k, respectively) of the refractive index at 375 nm and 632 nm were determined by Mie theory calculations through an iterative process, using the χ2 function to evaluate the fitness of the predicted optical parameters with the measured scattering, absorption, and extinction coefficients from a Photoacoustic Extinctiometer and Cavity Attenuated Phase Shift Spectrometer. Single scattering albedo (SSA) and bulk mass absorption coefficient (MAC) at 375 nm were calculated. SSA values of SOA particles from biogenic precursors (longifolene and α-pinene) were ∼0.98–0.99 (∼6.3% uncertainty), reflecting purely scattering aerosols regardless of the NOx regime. However, SOA particles from aromatic precursors were more absorbing and displayed NOx-dependent SSA values. For 1-methylnaphthalene SOA particles, SSA values of 0.92–0.95 and ∼0.75–0.90 (∼6.1% uncertainty) were observed under intermediate- and high-NOx conditions, respectively, reflecting the absorbing effects of SOA particles and NOx chemistry for this aromatic system. In mixtures of longifolene and phenol or longifolene and toluene SOA under intermediate- and high-NOx conditions, k values of the aromatic-related component of the SOA mixture were higher than that of 1-methylnaphthalene SOA particles. With the increase in OH exposure, kphenol decreased from 0.10 to 0.02 and 0.22 to 0.05 for intermediate- and high-NOx conditions, respectively. A simple relative radiative forcing calculation for urban environments at λ = 375 nm suggests the influence of absorbing SOA particles on relative radiative forcing at this wavelength is most significant for aerosol sizes greater than 0.4 µm. Copyright © 2019 American Association for Aerosol Research</p
The pre-history of health psychology in the UK: From natural science and psychoanalysis to social science, social cognition and beyond
Health psychology formally came of age in the United Kingdom in the 1980s, but it was prefigured by much discussion about challenges to the dominance of biomedicine in healthcare and debates. This articles focuses on what could be termed the pre-history of health psychology in the UK. This was the period in the earlier 20th century when psychological approaches were dominated by psychoanalysis which was followed by behaviourism and then cognitivism. Review of this pre-history provides the backdrop for the rise of health psychology in the UK and also reveals the tensions between the different theoretical perspectives
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Complex refractive index, single scattering albedo, and mass absorption coefficient of secondary organic aerosols generated from oxidation of biogenic and anthropogenic precursors
The Effect of a Receding Saline Lake (The Salton Sea) on Airborne Particulate Matter Composition
The composition of ambient particulate
matter (PM) and its sources were investigated at the Salton Sea, a
shrinking saline lake in California. To investigate the influence
of playa exposure on PM composition, PM samples were collected during
two seasons and at two sites around the Salton Sea. To characterize
source composition, soil samples were collected from local playa and
desert surfaces. PM and soil samples were analyzed for 15 elements
using mass spectrometry and X-ray diffraction. The contribution of
sources to PM mass and composition was investigated using Al-referenced
enrichment factors (EFs) and source factors resolved from positive
matrix factorization (PMF). Playa soils were found to be significantly
enriched in Ca, Na, and Se relative to desert soils. PMF analysis
resolved the PM<sub>10</sub> data with four source factors, identified
as Playa-like, Desert-like, Ca-rich, and Se. Playa-like and desert-like
sources were estimated to contribute to a daily average of 8.9% and
45% of PM<sub>10</sub> mass, respectively. Additionally, playa sources
were estimated to contribute to 38–68% of PM<sub>10</sub> Na.
PM<sub>10</sub> Se concentrations showed strong seasonal variations,
suggesting a seasonal cycle of Se volatilization and recondensation.
These results support the importance of playas as a source of PM mass
and a controlling factor of PM composition
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Exposure to Dimethyl Selenide (DMSe)-Derived Secondary Organic Aerosol Alters Transcriptomic Profiles in Human Airway Epithelial Cells
Dimethyl selenide (DMSe) is one of the major volatile organoselenium compounds released from aquatic and terrestrial environments through microbial transformation and plant metabolism. The detailed processes of DMSe leading to secondary organic aerosol (SOA) formation and the pulmonary health effects induced by inhalation of DMSe-derived SOA remain largely unknown. In this study, we characterized the chemical composition and formation yields of SOA produced from the oxidation of DMSe with OH radicals and O3 in controlled chamber experiments. Further, we profiled the transcriptome-wide gene expression changes in human airway epithelial cells (BEAS-2B) after exposure to DMSe-derived SOA. Our analyses indicated a significantly higher SOA yield resulting from the OH-initiated oxidation of DMSe. The oxidative potential of DMSe-derived SOA, as measured by the dithiothreitol (DTT) assay, suggested the presence of oxidizing moieties in DMSe-derived SOA at levels higher than typical ambient aerosols. Utilizing RNA sequencing (RNA-Seq) techniques, gene expression profiling followed by pathway enrichment analysis revealed several major biological pathways perturbed by DMSe-derived SOA, including elevated genotoxicity, DNA damage, and p53-mediated stress responses, as well as downregulated cholesterol biosynthesis, glycolysis, and interleukin IL-4/IL-13 signaling. This study highlights the significance of DMSe-derived SOA as a stressor in human airway epithelial cells
Discovery of a Potent and Selective ROMK Inhibitor with Pharmacokinetic Properties Suitable for Preclinical Evaluation
A new subseries of ROMK inhibitors
exemplified by <b>28</b> has been developed from the initial
screening hit <b>1</b>. The excellent selectivity for ROMK inhibition
over related ion channels and pharmacokinetic properties across preclinical
species support further preclinical evaluation of <b>28</b> as
a new mechanism diuretic. Robust pharmacodynamic effects in both SD
rats and dogs have been demonstrated