Long-term sensor measurements of lung deposited surface area of particulate matter emitted from local vehicular and residential wood combustion sources

Abstract

Lung deposited surface area (LDSA) is a relatively new metric that has been argued to be more accurate at predicting health effects from aerosol exposure. For typical atmospheric aerosol, the LDSA concentration depends mainly on the concentration of ultrafine particles (e.g. vehicular exhaust emissions and residential wood combustion) and therefore optical methods cannot be used to measure and quantify it. The objective of this study was to investigate and describe typical characteristics of LDSA under different urban environments and evaluate how a diffusion charging-based Pegasor AQ Urban sensor (Pegasor Ltd., Finland) can be used as an alternative to optical sensors when assessing local combustion emissions and respective LDSA concentrations. Long-term (12?months) sensor measurements of LDSA were carried out at three distinctly different measurement sites (four sensor nodes) in the Helsinki metropolitan area, Finland. The sites were affected mainly by vehicular exhaust emission (street canyon and urban background stations) and by residential wood combustion (two detached housing area stations). The results showed that the accuracy of the AQ Urban was good (R² = 0.90) for the measurement of LDSA when compared to differential mobility particle sizer. The mean concentrations of LDSA were more than twice as high at the street canyon (mean 22 µm² cm^?3) site when compared to the urban background site (mean 9.4 µm² cm^?3). In the detached housing area, the mean concentrations were 12 µm² cm^?3, and wood combustion typically caused high LDSA peaks in the evenings. High correlations and similar diurnal cycles were observed for the LDSA and black carbon at street canyon and urban background stations. The utilization of a small-scale sensor network (four nodes) showed that the cross-station variability in hourly LDSA concentrations was significant in every site, even within the same detached housing area (distance between the two sites ～670?m).     

Quantum measurements on finite dimensional systems: relabeling and mixing

Quantum measurements are mathematically described by positive operator valued measures (POVMs). Concentrating on finite dimensional systems, we show that one can limit to extremal rank-1 POVMs if two simple procedures of mixing and relabeling are permitted. We demonstrate that any finite outcome POVM can be obtained from extremal rank-1 POVMs with these two procedures. In particular, extremal POVMs with higher rank are just relabelings of extremal rank-1 POVMs and their structure is therefore clarified.     

On-Line Characterization of Morphology and Water Adsorption on Fumed Silica Nanoparticles

The first wetting layer on solid nanoparticles has direct implications on the roles these particles play in industrial processes and technological applications as well as in the atmosphere. We present a technique for online measurements of the adsorption of the first few water layers onto insoluble aerosol nanoparticles. Atomized fumed silica nanoparticles were dispersed from aqueous suspension and their hygroscopic growth factors (HGF) and number of the adsorbed water layers at subsaturated conditions were measured using a nanometer hygroscopic tandem differential mobility analyzer (HTDMA). Particle morphology was characterized by electron microscopy and particle density was determined by mobility analysis. The HGFs of the size-selected particles at mobility diameters from 10 to 50 nm at 90% relative humidity (RH) varied from 1.05 to 1.24, corresponding to 2–6 layers of adsorbed water. The morphology of the generated fumed silica nanoparticles varied from spheres at 8–10 nm to agglomerates at larger diameters with effective density from 1.7 to 0.8 g/cm³ and fractal dimension of 2.6. The smallest spheres and agglomerates had the highest HGFs. The smallest particles with diameters of 8 and 10 nm adsorbed two to three water layers in subsaturated conditions, which agreed well with the Frenkel, Halsey, and Hill (FHH) isotherm fitting. In comparison to the small spheres or large agglomerates, the compact agglomerate structure containing a few primary particles increased the number of adsorbed water layers by a factor of ～1.5. This was probably caused by the capillary effect on the small cavities between the primary particles in the agglomerate.     

Comparison of flexibility options to improve the value of variable power generation

As the share of variable generation in power systems increases, there is increasing value in more flexible use and generation of electricity. The paper compares the economic value of several flexibility options in a large power system with a large amount of reservoir hydro power. Generation planning models are needed to consider the impact of flexibility options on other investments in a power system. However, generation planning models do not include all the relevant operational details. The approach in the paper combines a generation planning model with a unit commitment and dispatch model. The results demonstrate the value of coupling the heat and power sectors and the value of transmission. Low-cost electricity storage does not appear to be as decisive in the Northern European context with wind power as the main variable generation source. The paper also addresses methodological issues related to the inclusion of operational constraints in generation planning.     

Phase State and Deliquescence Hysteresis of Ammonium-Sulfate-Seeded Secondary Organic Aerosol

The phase state of secondary organic aerosol (SOA) has an impact on its lifetime, composition, and its interaction with water. To better understand the effect of phase state of SOA on climate interactions, we studied the SOA phase state and the effect of its history and report here the phase state and the humidity-induced phase hysteresis of multicomponent-seeded SOA particles produced in a large, continuously stirred tank reactor. We determined the phase state of the particles by their bounced fraction impacting on a smooth substrate in a low-pressure impactor. The particles were composed of ammonium sulfate ([NH₄]₂SO₄) seed and a secondary organic matter (SOM) shell formed from oxidized α-pinene or isoprene. The ammonium sulfate (AS) seed dominated the deliquescence of the α-pinene SOM multicomponent particles, whereas their efflorescence was strongly attenuated by the SOM coating. Particles coated with isoprene SOM showed continuous phase transitions with a lesser effect by the AS seed. The results agree with and independently corroborate contemporary research.

Copyright 2015 American Association for Aerosol Research     

Optimization of large-area OLED current distribution grids with self-aligned passivation

The luminance homogeneity of large-area organic light emitting diodes (OLEDs) is limited by the sheet resistance of the transparent electrode. A large lateral voltage drop inside the electrode and thus brightness inhomogeneity result from the high sheet resistance of transparent conductors. To improve sheet resistance, a low-resistance metal grid is often included. To prevent shorting, the grid needs to be passivated. However, since passivation further decreases the device active area, accurate alignment of the passivation layer is crucial. We report simulations of a Joule-heating-based self-alignment method for the passivation layer. The Joule heating model was divided into two sub-models: a current model to study current distribution on grid scale during Joule heating, and thermoelectric model to study heat transfer in the system. Grid design rules – minimum line pitch and the geometry of the grid – necessary for a successful Joule heating process were studied. The line group design was found to be the best option for a current distribution grid. The minimum line pitch limited by heat transfer was 0.8 mm on an indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrate. With the line group design, maximum luminance output was achieved with a pitch of 4 mm, when the sheet resistance of the metal lines was 0.01 Ω/□$\mathrm{\Omega }/\square$. This fulfils the demands placed by the Joule heating process.     

Biocompatibility of cellulose sponge with bone

The purpose of this study was to investigate the biocompatibility of viscose cellulose sponge (VCS) with bone. Twenty-five Sprague-Dawley rats were used for the study. After curettage of the bone marrow from both femoral cavities, VCS (15 x 1 x 1 mm) was implanted into one femur, leaving the contralateral side empty as a control. The rats were killed 1-6 weeks after curettage, and bone formation inside the sponge was assessed by light-microscopic examination and histomorphometric assessment. Whereas normal bone formation in rat femoral cavity took place in 2 weeks after curettage, 4 weeks were needed for bone formation in the cellulose sponge. VCS is a compatible matrix for osseous tissue ingrowth and it may be useful as a scaffold for bone tissue engineering in experiments and possibly also in clinical practice.     

Ion mobility distributions during the initial stages of new particle formation by the ozonolysis of α-pinene

An ion mobility spectrometer (IMS) was used to study gas phase compounds during nucleation and growth of secondary organic aerosols (SOA). In this study SOA particles were generated by oxidizing α-pinene with O(3) and OH in a 6 m(3) reaction chamber. Positive ion peaks with reduced mobilities of 1.59 cm(2)(Vs)(-1) and 1.05 cm(2)(Vs)(-1) were observed 7 min after α-pinene and ozone were added to the chamber. The detected compounds can be associated with low volatility oxidation products of α-pinene, which have been suggested to participate in new particle formation. This is the first time that IMS has been applied to laboratory studies of SOA formation. IMS was found suitable for continuous online monitoring of the SOA formation process, allowing for highly sensitive detection of gas phase species that are thought to initiate new particle formation.     

Metallic Contact between MoS2 and Ni via Au Nanoglue

A critical factor for electronics based on inorganic layered crystals stems from the electrical contact mode between the semiconducting crystals and the metal counterparts in the electric circuit. Here, a materials tailoring strategy via nanocomposite decoration is carried out to reach metallic contact between MoS₂ matrix and transition metal nanoparticles. Nickel nanoparticles (NiNPs) are successfully joined to the sides of a layered MoS₂ crystal through gold nanobuffers, forming semiconducting and magnetic NiNPs@MoS₂ complexes. The intrinsic semiconducting property of MoS₂ remains unchanged, and it can be lowered to only few layers. Chemical bonding of the Ni to the MoS₂ host is verified by synchrotron radiation based photoemission electron microscopy, and further proved by first‐principles calculations. Following the system's band alignment, new electron migration channels between metal and the semiconducting side contribute to the metallic contact mechanism, while semiconductor–metal heterojunctions enhance the photocatalytic ability.     

Gas-Sensing Properties of Nanocrystalline WO3 Films Made by Advanced Reactive Gas Deposition

Nanocrystalline WO₃ films were produced by advanced reactive gas deposition onto alumina substrates. The as-deposited films had a tetragonal crystal structure and a mean grain size of around 6 nm, as found by X-ray diffraction and electron microscopy. Sintering at a temperature τ_s > 770 K yielded monoclinic films. We investigated the gas-sensing properties of films sintered up to 870 K. After an initial "activation" at τ_s= 750 K, the nanocrystalline WO₃ films showed excellent gas-sensing properties, even at room temperature, on exposure to low concentrations of H₂S in air. As little as 10 ppm of H₂S made the conductance increase by a factor of about 10³ within 10 min. The initial properties could be restored by heating the films to 530 K for 1 min.