2 research outputs found
Evolution of In-Cylinder Diesel Engine Soot and Emission Characteristics Investigated with Online Aerosol Mass Spectrometry
To design diesel engines with low
environmental impact, it is important
to link health and climate-relevant soot (black carbon) emission characteristics
to specific combustion conditions. The in-cylinder evolution of soot
properties over the combustion cycle and as a function of exhaust
gas recirculation (EGR) was investigated in a modern heavy-duty diesel
engine. A novel combination of a fast gas-sampling valve and a soot
particle aerosol mass spectrometer (SP-AMS) enabled online measurements
of the in-cylinder soot chemistry. The results show that EGR reduced
the soot formation rate. However, the late cycle soot oxidation rate
(soot removal) was reduced even more, and the net effect was increased
soot emissions. EGR resulted in an accumulation of polycyclic aromatic
hydrocarbons (PAHs) during combustion, and led to increased PAH emissions.
We show that mass spectral and optical signatures of the in-cylinder
soot and associated low volatility organics change dramatically from
the soot formation dominated phase to the soot oxidation dominated
phase. These signatures include a class of fullerene carbon clusters
that we hypothesize represent less graphitized, C<sub>5</sub>-containing
fullerenic (high tortuosity or curved) soot nanostructures arising
from decreased combustion temperatures and increased premixing of
air and fuel with EGR. Altered soot properties are of key importance
when designing emission control strategies such as diesel particulate
filters and when introducing novel biofuels
Novel loci for adiponectin levels and their influence on type 2 diabetes and metabolic traits: a multi-ethnic meta-analysis of 45,891 individuals
Circulating levels of adiponectin, a hormone produced predominantly by adipocytes, are highly heritable and are inversely associated with type 2 diabetes mellitus (T2D) and other metabolic traits. We conducted a meta-analysis of genome-wide association studies in 39,883 individuals of European ancestry to identify genes associated with metabolic disease. We identified 8 novel loci associated with adiponectin levels and confirmed 2 previously reported loci (P = 4.5×10(-8)-1.2×10(-43)). Using a novel method to combine data across ethnicities (N = 4,232 African Americans, N = 1,776 Asians, and N = 29,347 Europeans), we identified two additional novel loci. Expression analyses of 436 human adipocyte samples revealed that mRNA levels of 18 genes at candidate regions were associated with adiponectin concentrations after accounting for multiple testing (p<3×10(-4)). We next developed a multi-SNP genotypic risk score to test the association of adiponectin decreasing risk alleles on metabolic traits and diseases using consortia-level meta-analytic data. This risk score was associated with increased risk of T2D (p = 4.3×10(-3), n = 22,044), increased triglycerides (p = 2.6×10(-14), n = 93,440), increased waist-to-hip ratio (p = 1.8×10(-5), n = 77,167), increased glucose two hours post oral glucose tolerance testing (p = 4.4×10(-3), n = 15,234), increased fasting insulin (p = 0.015, n = 48,238), but with lower in HDL-cholesterol concentrations (p = 4.5×10(-13), n = 96,748) and decreased BMI (p = 1.4×10(-4), n = 121,335). These findings identify novel genetic determinants of adiponectin levels, which, taken together, influence risk of T2D and markers of insulin resistance