A review on morphology, nanostructure, chemical composition, and number concentration of diesel particulate emissions.

Particulate matter (PM) emitted from compression ignition (CI) engines (diesel engines) has a detrimental effect on human health and the environment. The physical and chemical characteristics of PM emitted from CI-engines are influenced by engine operating conditions and fuel properties. The morphology, nanostructure, and chemical composition of PM affect its toxicity and interaction with the environment. From automotive industry perspective, these parameters influence the design of diesel particulate filters. This study presents a review of the physical and chemical characteristics of particulate emissions from the CI-engine. The present study commences with a brief description about the composition of PM emitted from CI-engine and the PM formation mechanism in CI-engine. Later on, the detailed review of PM's physical and chemical characteristics and the effect of engine operating parameters and alternative fuels on the particle number concentration, morphology, nano-structure, and oxidative reactivity of PM is presented. Online and offline methods of diesel particulate characterization and emerging chemical characterization techniques such as X-ray photoelectron spectroscopy and X-ray absorption fine structure (EXAFS) are also discussed briefly. Correlation between physical and chemical properties, and oxidative reactivity of PM is also discussed. It was found that engine operating parameters affect the physical and chemical properties of PM. Use of alternative fuels changes the diesel particulate morphology, nanostructure, and chemical composition which enhances the oxidative reactivity of PM.

Effect of compression ratio, nozzle opening pressure, engine load, and butanol addition on nanoparticle emissions from a non-road diesel engine.

Currently, diesel engines are more preferred over gasoline engines due to their higher torque output and fuel economy. However, diesel engines confront major challenge of meeting the future stringent emission norms (especially soot particle emissions) while maintaining the same fuel economy. In this study, nanosize range soot particle emission characteristics of a stationary (non-road) diesel engine have been experimentally investigated. Experiments are conducted at a constant speed of 1500 rpm for three compression ratios and nozzle opening pressures at different engine loads. In-cylinder pressure history for 2000 consecutive engine cycles is recorded and averaged data is used for analysis of combustion characteristics. An electrical mobility-based fast particle sizer is used for analyzing particle size and mass distributions of engine exhaust particles at different test conditions. Soot particle distribution from 5 to 1000 nm was recorded. Results show that total particle concentration decreases with an increase in engine operating loads. Moreover, the addition of butanol in the diesel fuel leads to the reduction in soot particle concentration. Regression analysis was also conducted to derive a correlation between combustion parameters and particle number emissions for different compression ratios. Regression analysis shows a strong correlation between cylinder pressure-based combustion parameters and particle number emission.

Salivary glands harbor more diverse microbial communities than gut in Anopheles culicifacies.

BACKGROUND: In recent years, it has been well documented that gut flora not only influence mosquito physiology, but also significantly alter vector competency. Although, salivary gland and gut constitute key partners of the digestive system, it is still believed that salivary glands may harbor less flora than gut (Parasit Vectors 6: 146, 2013). METHODS: Using a metagenomic approach, we have identified for the first time the diverse microbial community associated with these two physiologically different tissues of the digestive system in the mosquito Anopheles culicifacies. RESULTS: A total of 17 different phyla could be assigned to the whole metagenomic dataset, predominated by the phylum Proteobacteria, Firmicutes, Bacteriodetes, Tenericutes and Actinomycetes. Common bacteria included the members of Enhydrobacter, Agromonas, Serratia, Ralsonia, Lactobacillus, Pseudomonas, Streptococcus, Rubrobacter, Anaerococcus, Methylobacterium, Turicibacter, Elizabethkingia etc. in both the tissues representing 'core microbiota' of the mosquito digestive system. Salivary associated unique bacterial community included the members of Chloriflexi, Chlorobi, Cyanobacteria, Nitrospira, TM7, Armatimonadetes, Planctomycetes, Fibrobacteres etc. CONCLUSION: We find that the salivary gland microbial community structure is more diverse than gut of the mosquito, probably due to differential feeding associated engagements such as food acquisition, ingestion and digestion processes.