A dual-chamber method for quantifying the effects of atmospheric perturbations on secondary organic aerosol formation from biomass burning emissions

Biomass burning (BB) is a major source of atmospheric pollutants. Field and laboratory studies indicate that secondary organic aerosol (SOA) formation from BB emissions is highly variable. We investigated sources of this variability using a novel dual-smog-chamber method that directly compares the SOA formation from the same BB emissions under two different atmospheric conditions. During each experiment, we filled two identical Teflon smog chambers simultaneously with BB emissions from the same fire. We then perturbed the smoke with UV lights, UV lights plus nitrous acid (HONO), or dark ozone in one or both chambers. These perturbations caused SOA formation in nearly every experiment with an average organic aerosol (OA) mass enhancement ratio of 1.78 ± 0.91 (mean ± 1σ). However, the effects of the perturbations were highly variable ranging with OA mass enhancement ratios ranging from 0.7 (30% loss of OA mass) to 4.4 across the set of perturbation experiments. There was no apparent relationship between OA enhancement and perturbation type, fuel type, and modified combustion efficiency. To better isolate the effects of different perturbations, we report dual-chamber enhancement (DUCE), which is the quantity of the effects of a perturbation relative to a reference condition. DUCE values were also highly variable, even for the same perturbation and fuel type. Gas measurements indicate substantial burn-to-burn variability in the magnitude and composition of SOA precursor emissions, even in repeated burns of the same fuel under nominally identical conditions. Therefore, the effects of different atmospheric perturbations on SOA formation from BB emissions appear to be less important than burn-to-burn variability

Non-Native R1 Substitution in the S4 Domain Uniquely Alters Kv4.3 Channel Gating

The S4 transmembrane domain in Shaker (Kv1) voltage-sensitive potassium channels has four basic residues (R1–R4) that are responsible for carrying the majority of gating charge. In Kv4 channels, however, R1 is replaced by a neutral valine at position 287. Among other differences, Kv4 channels display prominent closed state inactivation, a mechanism which is minimal in Shaker. To determine if the absence of R1 is responsible for important variation in gating characteristics between the two channel types, we introduced the V287R mutant into Kv4.3 and analyzed its effects on several voltage sensitive gating transitions. We found that the mutant increased the voltage sensitivity of steady-state activation and altered the kinetics of activation and deactivation processes. Although the kinetics of macroscopic inactivation were minimally affected, the characteristics of closed-state inactivation and recovery from open and closed inactivated states were significantly altered. The absence of R1 can only partially account for differences in the effective voltage sensitivity of gating between Shaker and Kv4.3. These results suggest that the S4 domain serves an important functional role in Kv4 channel activation and deactivation processes, and also those of closed-state inactivation and recovery

The gender turnaround:Young women now travelling more than young men

AbstractDaily travel mobility is on a downward trend in several developed economies, including the UK. This paper examines how mobility trends are differentiated by gender and birth cohort. Over the last decade, young adult women in Britain have come to have greater weekly mobility than their male counterparts. Until recently, women have consistently had lower mobility than men - suggesting that this finding could be a significant break with the past. This gender turnaround is driven mainly by young men travelling substantially less today than previous generations of young men. We find that younger cohorts of women travel are travelling further as they age, whilst younger cohorts of men are no longer becoming more mobile as they approach early mid-life, traditionally a life course peak in travel mobility. Possible reasons for the greater mobility of young women than young men are discussed and areas for future research identified

Social Relationships and Mortality Risk: A Meta-analytic Review

In a meta-analysis, Julianne Holt-Lunstad and colleagues find that individuals' social relationships have as much influence on mortality risk as other well-established risk factors for mortality, such as smoking

An edition of two Old English Saints' Lives: The life of St. Giles and The life of St. Nicholas

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Polarimetric Decompositions of Temperate Wetlands at C-Band

C-band SAR is well established as a useful sensor for water resources applications. It is commonly accepted that the backscatter from wetlands that consist of many emergent stems over open water (swamps and marshes) is dominated by a double-bounce scattering mechanism. However, recent observations with fully polarimetric data from Radarsat-2 over the extensive wetlands of the Everglades and numerous small wetlands in Ontario appear to be inconsistent with this interpretation of the backscatter physics. In this paper, we use several forms of polarimetric analysis and decomposition. All of these indicate that the backscatter from small marshes and swamps in Ontario is dominated by polarimetric characteristics normally attributed to the odd-bounce mechanism. This anomalous result might be explained as a consequence of changes in the double-bounce reflectance properties of vegetation as a function of the incidence angle. However, detailed electromagnetic backscatter modeling will be needed to provide a more complete and reliable understanding of the details of backscattering from wetlands with emergent vegetation. Additional observational and theoretical work will be required to document and understand the unusual results we report here. If these results are substantiated, the SAR community must re-interpret the generally accepted meanings of the popular decomposition variables, and introduce new terminology to describe them. This would lead to an improved understanding of the backscatter physics and better use of polarimetric SAR for wetland management applications

Genetic Variation in Host Tolerance of an Invading Transposon in Drosophila melanogaster

Transposable Elements (TEs) are both important drivers of genome evolution and genetic parasites with potentially dramatic consequences for host fitness, including insertional inactivation of functional sequences and genomic instability (Reviewed in Hedges and Deininger 2007). Although host genomes minimize these deleterious eff¬ects by regulating the activity of resident TEs, they are often invaded by new TE families, which they are unable to control (Reviewed in Wallau et al. 2012). We are taking advantage of the historical invasion of the Drosophila melanogaster genome by P-elements (Reviewed in Engels 2003), a family of autonomous DNA transposons, to understand the impact that invading TEs have on their hosts, and the mechanisms through which TE regulation evolves. Using a panel of recombinant inbred lines (RILs), which were generated from naïve genotypes isolated from nature before P-element invasion (King et al. 2012), we have identified genetic variants that allow for tolerance or control of P-element activity. Such variants could have been beneficial after P-elements invaded D. melanogaster genomes ~1950, thereby contributing to the evolution of tolerance of the transposable element by its host.Biology and Biochemistry, Department ofHonors Colleg