Catalyzed Gasoline Particulate Filters Reduce Secondary Organic Aerosol Production from Gasoline Direct Injection Vehicles

The effects of photochemical aging on exhaust emissions from two light-duty vehicles with gasoline direct injection (GDI) engines equipped with and without catalyzed gasoline particle filters (GPFs) were investigated using a mobile environmental chamber. Both vehicles with and without the GPFs were exercised over the LA92 drive cycle using a chassis dynamometer. Diluted exhaust emissions from the entire LA92 cycle were introduced to the mobile chamber and subsequently photochemically reacted. It was found that the addition of catalyzed GPFs will significantly reduce tailpipe particulate emissions and also provide benefits in gaseous emissions, including nonmethane hydrocarbons (NMHC). Tailpipe emissions composition showed important changes with the use of GPFs by practically eliminating black carbon and increasing the fractional contribution of organic mass. Production of secondary organic aerosol (SOA) was reduced with GPF addition, but was also dependent on engine design which determined the amount of SOA precursors at the tailpipe. Our findings indicate that SOA production from GDI vehicles will be reduced with the application of catalyzed GPFs through the mitigation of reactive hydrocarbon precursors

What do we know about transgender parenting?: Findings from a systematic review

Transgender issues are under‐explored and marginalised within mainstream social work and social care professional practice. The experience of gender transition has a profound impact on the individuals who have diverse gender identities and their family members. We present findings from a systematic review of studies concerning the experiences of transgender parenting conducted during January–September 2017. We took a life course approach, examining the research studies that investigated the experience of people identifying as transgender, who were already parents at the time of their transition or who wished to be parents following transition. The review evaluated existing findings from empirical research on transgender parenting and grandparenting to establish how trans people negotiate their relationships with children following transition, and sought to consider the implications for professional practice with trans people in relation to how best to support them with their family caring roles. We used the Preferred Reporting Items for Systematic Review and Meta‐Analyses (PRISMA) method. Empirical studies published from 1 January 1990 to 31 April 2017 in the English language, and which had transgender parenting as a significant focus, were included in the review. Twenty‐six studies met the criteria. Key themes reported are: how trans people negotiate their relationships with children following disclosure and transition; the impact of parental transitioning on children; relationships with wider families; trans people's desires to be parents; and the role of professional practice to support trans families. We discuss how the material from the review can inform social work education and practice, including to help identify future research, education and practice priorities in this area

Are sesquiterpenes a good source of secondary organic cloud condensation nuclei (CCN)? Revisiting β-caryophyllene CCN

Secondary organic aerosol (SOA) was formed in an environmental reaction chamber from the ozonolysis of β-caryophyllene (β-C) at low concentrations (5 ppb or 20 ppb). Experimental parameters were varied to characterize the effects of hydroxyl radicals, light and the presence of lower molecular weight terpene precursor (isoprene) for β-C SOA formation and cloud condensation nuclei (CCN) characteristics. Changes in β-C SOA chemicophysical properties (e.g., density, volatility, oxidation state) were explored with online techniques to improve our predictive understanding of β-C CCN activity. In the absence of OH scavenger, light intensity had negligible impacts on SOA oxidation state and CCN activity. In contrast, when OH reaction was effectively suppressed (> 11 ppm scavenger), SOA showed a much lower CCN activity and slightly less oxygenated state consistent with previously reported values. Though there is significant oxidized material present (O / C > 0.25), no linear correlation existed between the mass ratio ion fragment 44 in the bulk organic mass (<i>f</i><sub>44</sub>) and O / C for the β-C-O<sub>3</sub> system. No direct correlations were observed with other aerosol bulk ion fragment fraction (<i>f</i><sub><i>x</i></sub>) and κ as well. A mixture of β-C and lower molecular weight terpenes (isoprene) consumed more ozone and formed SOA with distinct characteristics dependent on isoprene amounts. The addition of isoprene also improved the CCN predictive capabilities with bulk aerosol chemical information. The β-C SOA CCN activity reported here is much higher than previous studies (κ < 0.1) that use higher precursor concentration in smaller environmental chambers; similar results were only achieved with significant use of OH scavenger. Results show that aerosol formed from a mixture of low and high molecular weight terpene ozonolysis can be hygroscopic and can contribute to the global biogenic SOA CCN budget

Cloud condensation nuclei (CCN) activity of aliphatic amine secondary aerosol

Aliphatic amines can form secondary aerosol via oxidation with atmospheric radicals (e.g., hydroxyl radical and nitrate radical). The particle can contain both secondary organic aerosol (SOA) and inorganic salts. The ratio of organic to inorganic materials in the particulate phase influences aerosol hygroscopicity and cloud condensation nuclei (CCN) activity. SOA formed from trimethylamine (TMA) and butylamine (BA) reactions with hydroxyl radical (OH) is composed of organic material of low hygroscopicity (single hygroscopicity parameter, κ, ≤ 0.25). Secondary aerosol formed from the tertiary aliphatic amine (TMA) with N_2O_5 (source of nitrate radical, NO_3) contains less volatile compounds than the primary aliphatic amine (BA) aerosol. As relative humidity (RH) increases, inorganic amine salts are formed as a result of acid–base reactions. The CCN activity of the humid TMA–N_2O_5 aerosol obeys Zdanovskii, Stokes, and Robinson (ZSR) ideal mixing rules. The humid BA + N_2O_5 aerosol products were found to be very sensitive to the temperature at which the measurements were made within the streamwise continuous-flow thermal gradient CCN counter; κ ranges from 0.4 to 0.7 dependent on the instrument supersaturation (ss) settings. The variance of the measured aerosol κ values indicates that simple ZSR rules cannot be applied to the CCN results from the primary aliphatic amine system. Overall, aliphatic amine aerosol systems' κ ranges within 0.2 < κ < 0.7. This work indicates that aerosols formed via nighttime reactions with amines are likely to produce hygroscopic and volatile aerosol, whereas photochemical reactions with OH produce secondary organic aerosol of lower CCN activity. The contributions of semivolatile secondary organic and inorganic material from aliphatic amines must be considered for accurate hygroscopicity and CCN predictions from aliphatic amine systems

Epoxy Cure Observed by Ultrasound, NMR and WAXS

The motivation behind this work was a requirement to optimise the cure cycles of adhesive used in the construction of automotive body shells and to establish the tolerance of the adhesive to uneven heating during cure, and to variation in the ratio of resin to hardener in the adhesive mixture. The rationale was that ultrasonic compression wave (CW) measurements on curing epoxy were relatively easy [1,2], and that increases in CW propagation velocity during cure corresponded to the development of mechanical moduli, given only small changes in the density of the adhesive during cure. Of interest was the way in which CW measurements relate to the evolving chemistry and structure in the adhesive, how they relate to the development of shear strength, and whether CW absorption measurements could be useful in tracking the cure cycle. In this work we have compared wide bandwidth measurements of absorption for both compression and shear (SW) waves. CW measurements were also compared to wide angle x-ray scattering (WAXS) measurements and to low resolution nuclear magnetic resonance (NMR) measurements in order to relate what was observable by ultrasound to the evolving structure in the adhesive and to the progress of the cure reaction. In a parallel study, not reported here, we have also made comparisons between CW and dielectric spectroscopy.</p