In this paper a new algorithm is presented for calculating the Green’s function of the Schrödinger equation in the presence of block layered potentials. Such Green’s functions have various and practical applications in quantum modelling of electron transport within nano-MOSFET transistors. The proposed method is based on expansions of the eigenfunctions of the subordinate Sturm–Liouville problems and a collocation matching procedure along possibly curved interfaces of the potential blocks. Accurate numerical results are provided to validate the proposed algorithm.
In developing countries, aerosol particles damage the health of hundreds of millions of people. Migration from the country side to megacities increases emissions and exposure to particles. Some countries have started to limit emissions based on particulate mass, but this may increase particle number concentrations. In this study we discuss some earlier measurements carried out in the developing world and compare results from one-week measurement campaigns concerning the particle number size distribution and PM10 mass concentrations in New Delhi, India and Beijing, China. Our results show that submicron particle concentrations are high in both places. The average PM10 concentration was 360 mu g/m(3) in New Delhi and 120 mu g/m(3) in Beijing. The corresponding total particle number concentrations in the size range 3-800 nm were 63 000 cm(-3) and 35 000 cm(-3). Number and mass concentrations and their characteristics showed significantly different behaviour between these two locations, which stresses the importance of long-term simultaneous measurements of both quantities in different types of megacities.
Sources of sulphate and oxidation pathways important to the formation of PM 2.5 during the Pacific 2001 field campaign in Canada, were studied in diurnal samples from an urban coastal and a rural inland site in the Fraser Valley, B.C. Ion and elemental characteristics of aerosols as well as the sulphur and oxygen isotopes in sulphate were compared and related using multiple linear regressions. Sources of sulphate in PM2.5 were distinguished at each site and included: 1. sulphate from DMS oxidation during the day-time in Vancouver that coincided with high sodium and oxalate concentrations inland, 2. well-mixed pollutant SO, from the Strait of Georgia that was oxidized to sulphate as it moved into the Vancouver area, 3. vehicle exhaust or a mixture of biomass burning and vehicle exhaust which has a larger fraction of primary sulphate than other sulphate sources and is possibly associated with Cu, and 4. isotopically light SO2 from a refinery in the US that was strongly associated with higher Zn concentrations in aerosols. Primary and secondary sulphate were quantified using an oxygen isotope apportionment model. On average 19-42% and 58-81% of the non-sea salt sulphate in PM2.5 was primary and secondary, respectively. More primary sulphate was present in Vancouver (0.21-0.47 mu gm(-3)) PM2.5 aerosols than at the site further inland (0.13-0.33 mu g m(-3)) but there was no difference between the amount of primary sulphate present during the day and night at each site. (c) 2006 Elsevier Ltd. All rights reserved.