influence of piston shape and injector geometry on combustion and emission characteristics of syngas in direct injection spark ignition engine

Abstract This paper presents a numerical study of the influence of piston shape and injector geometry on combustion and emissions characteristics of a direct-injection spark-ignition engine fueled by syngas (50% by volume of hydrogen, 50% by volume of carbon monoxide) under low/medium load conditions. Three different piston cup geometries namely: High-clearance Combustion Cup (HCC), Low-clearance Combustion Cup (LCC) and Omega Combustion Cup (OCC) have been considered with a compression ratio of 14. An axial full-cone gas jet injector has been considered together with a hollow-cone gas jet injector with several included half-angles, i.e. 30°, 45°, 52.5° and 60°. Computational fluid dynamics modelling has been performed to simulate the combustion process. The results indicate that, in terms of performance, OCC shape is favorable, even if OCC generates relatively higher NOx than the other two configurations. A further analysis has been performed by simulating an engine with OCC piston shape and an included half-angle of injection of 30°, by varying the Start Of Injection (SOI). The results show that the flame propagation velocity reduces as the SOI advances, since the fuel distribution becomes more homogeneous approaching to a premixed case. However, the flame speed reduction is partially balanced by the disappearance of very lean regions thanks to fuel convection and diffusion

Passive Sampling of Organic Contaminants as a Novel Approach to Monitor Seawater Quality in Aquarium Ocean Tanks

The determination of trace pollutants in seawater is challenging, and sampling is a crucial step in the entire analytical process. Passive samplers combine in situ sampling and preconcentration, thus limiting the tedious treatment steps of the conventional sampling methods. Their use to monitor water quality in confined marine environment could bring several advantages. In this work, the presence of organic contaminants at trace and ultra-trace levels was assessed in the Genoa Aquarium supply-and-treated water using Polar Organic Integrative Samplers (POCIS). Both untargeted gas chromatography-mass spectrometry and targeted liquid chromatography-tandem mass spectrometry were employed. The untargeted approach showed the presence of hydrocarbons, diphenyl sulfone and 2,4-di-tert-butyl-phenol. Only hydrocarbons were detected in all the samples. Nineteen emerging contaminants, belonging to different classes (pharmaceuticals, UV-filters, hormones and perfluorinated compounds), were selected for the target analysis. Thirteen analytes were detected, mainly in supply water, even though the majority of them were below the quantitation limit. It is worthy to note that two of the detected UV-filters had never been reported in seawater using the POCIS samplers. The comparison of the analytes detected in supply and treated water indicated a good performance of the Aquarium water treatment system in the abatement of seawater contaminants

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

Multivariate optimization of an extraction procedure based on magnetic molecular imprinted polymer for the determination of polycyclic aromatic hydrocarbons in sea water

The present work deals with the optimization of a magnetic solid phase extraction of polycyclic aromatic hydrocarbons (PAHs) from sea water, based on molecular imprinted microparticles, for subsequent GC–MS analysis. The extraction efficiency of the magnetic molecular imprinted polymer (MIP) was compared with that of the corresponding non-imprinted polymer; only small differences in the recovery of the extraction procedure were shown, but higher repeatability was observed using MIP. An experimental design (Plackett-Burman) allowed a fast optimization identifying the only significant factor influencing the extraction recovery, namely the ratio between the amount of microparticles and the sample volume. Two optimal ratios, based on the PAHs molecular weight, were selected for 20 mL of sea water samples: 5 mg or 20 mg of microparticles for compounds ranging from 128 to 228 and from 252 to 278 Da, respectively. The recoveries ranges were 76–104% for the low molecular weight PAHs and 95–101% for the high molecular weight PAHs. The analytical method showed satisfactory figures of merit, with detection limits ranging from 30 to 375 ng L−1 and relative standard deviations on replicate extractions from 3.7 to 12.2%. The developed method, which is fast, easy and requires very small volumes of organic solvent, was applied for the determination of PAHs in selected sea water samples. © 2018 Elsevier B.V