Optical properties and radiative forcing of urban aerosols in Nanjing, China

AbstractContinuous measurements of atmospheric aerosols were made in Nanjing, a megacity in China, from 18 January to 18 April, 2011 (Phase 1) and from 22 April 2011 to 21 April 2012 (Phase 2). Aerosol characteristics, optical properties, and direct radiative forcing (DRF) were studied through interpretations of these measurements. We found that during Phase 1, mean PM2.5, black carbon (BC), and aerosol scattering coefficient (Bsp) in Nanjing were 76.1 ± 59.3 μg m−3, 4.1 ± 2.2 μg m−3, and 170.9 ± 105.8 M m−1, respectively. High pollution episodes occurred during Spring and Lantern Festivals when hourly PM2.5 concentrations reached 440 μg m−3, possibly due to significant discharge of fireworks. Temporal variations of PM2.5, BC, and Bsp were similar to each other. It is estimated that inorganic scattering aerosols account for about 49 ± 8.6% of total aerosols while BC only accounted for 6.6 ± 2.9%, and nitrate was larger than sulfate. In Phase 2, optical properties of aerosols show great seasonality. High relative humidity (RH) in summer (June, July, August) likely attributed to large optical depth (AOD) and small Angstrom exponent (AE) of aerosols. Due to dust storms, AE of total aerosols was the smallest in spring (March, April, May). Annual mean 550-nm AOD and 675/440-nm AE were 0.6 ± 0.3 and 1.25 ± 0.29 for total aerosols, 0.04 ± 0.02 and 1.44 ± 0.50 for absorbing aerosols, 0.48 ± 0.29 and 1.64 ± 0.29 for fine aerosols, respectively. Annual single scattering albedo of aerosols ranged from 0.90 to 0.92. Real time wavelength-dependent surface albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to assess aerosol DRFs. Both total and absorbing aerosol DRFs had significant seasonal variations in Nanjing and they were the strongest in summer. Annual mean clear sky TOA DRF (including daytime and nighttime) of total and absorbing aerosols was about −6.9 and +4.5 W m−2, respectively. Aerosol DRFs were found to be sensitive to surface albedo. Over brighter surfaces, solar radiation was more absorbed by absorbing aerosols and less scattered by scattering aerosols

ATHENA detector proposal — a totally hermetic electron nucleus apparatus proposed for IP6 at the Electron-Ion Collider

ATHENA has been designed as a general purpose detector capable of delivering the full scientific scope of the Electron-Ion Collider. Careful technology choices provide fine tracking and momentum resolution, high performance electromagnetic and hadronic calorimetry, hadron identification over a wide kinematic range, and near-complete hermeticity. This article describes the detector design and its expected performance in the most relevant physics channels. It includes an evaluation of detector technology choices, the technical challenges to realizing the detector and the R&D required to meet those challenges

Magneto-optical properties of one-dimensional conjugated magnetophotonic crystals heterojunctions

The 4 × 4 transfer matrix for the magneto-optical layer at oblique incidence is derived. With the help of the transfer matrix, the magneto-optical properties of one-dimensional conjugated magnetophotonic crystals (MPC) heterojunctions are studied. The results show that there exists a Tamm state localized at the interface between conjugated MPC. By coupling the Tamm states, high transmittance and large Faraday rotation angle can be obtained simultaneously in conjugated MPC multiple heterojunctions structure. It can be used to make novel mageto-optical device, promised to further application in optical information process

Formation mechanism of heterogeneous microstructures and shape memory effect in NiTi shape memory alloy fabricated via laser powder bed fusion

Additive manufacturing involves the process of track-by-track melt pools accompanied by the localized rapid melting/solidification, which can determine unique nonequilibrium microstructures. In this study, we report formation of heterogeneous nonequilibrium microstructures in near-equiatomic NiTi fabricated via laser powder bed fusion (LPBF) additive manufacturing, and further discuss their underlying formation mechanisms and influences on shape memory effect of the LPBF NiTi. Specifically, the heterogeneous microstructures include the core (HCP α-Ti)-shell (Ti2Ni) structural nano-sized precipitation phases in columnar grains, which were resulted from high undercooling and cooling rate during LPBF solidification, the intermediate R phase in cellular and columnar grains, which was stemmed from residual thermal stress during LPBF, the nano-sized cellular substructure in columnar grains with boundaries decorated with Ti2Ni precipitates, which was originated from enriched Ti atoms at the solidification front during directional and orderly solidification of melt pools, together with the abundant dislocations. Interestingly, the two-way shape memory strain of 0.8% in LPBF NiTi was obtained by cycle loading–unloading-heating–cooling training process. These findings achieved in this work enrich the knowledge on formation mechanism of heterogeneous microstructures in LPBF NiTi SMAs, and further pave the way for engineering applications of two-way shape memory effect of LPBF NiTi shape memory alloys

Carbon nitride thin films deposited by nitrogen-ion-assisted KRF excimer ablation of graphite

Applied Surface Science138-1391-4494-498ASUS

A Comparative Study of Modified Materials of Acetylcholinesterase Biosensor

International audienceIn this study, multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and Prussian Blue (PB) were used for modifying glassy carbon working electrode (GCE) to construct acetylcholinesterase (AChE) biosensor respectively. Chitosan membrane was used for immobilizing AChE through glutaraldehyde cross-linking attachment to recognize pesticides selectively. Before the detection, the enzyme membrane was quickly fixed on the surfaces of modified electrode with O-ring to prepare an ampero-metric acetylcholinesterase biosensor for organophosphate pesticides. The fabrication procedures were characterized by cyclic voltammetry and amperometric i-t curve. The electrochemical behaviours of three modified sensors were compared, and the results showed that AChE-PB/GCE possessed higher oxidation peak current at a lower potential. Based on the inhibition of organophosphorus pesticides to the enzymatic activity of AChE, using dichlorvos as model compound, the sensitivity of three modified biosensors were compared, the results showed that the detection limit of AChE-PB/ GCE was lowest