| 1. |
- Asking, Lars, et al.
(författare)
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An electrostatic aerosol sampler
- 1988
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 19:7, s. 1023-1026
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Tidskriftsartikel (refereegranskat)
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Bower, K. N., et al.
(författare)
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Observations of the interaction of an urban plume with cloud
- 2000. - SUPPL. 1
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Ingår i: European Aerosol Conference 2000. - 0021-8502. ; 31, s. 66-67
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Konferensbidrag (refereegranskat)abstract
- Experiments were performed to examine the effects of the properties of the aerosol and trace gases in the airmassflowing into cloud on the microphysics and chemistry of the cloud and to investigate the role of the cloud in modifying the properties of the aerosol and trace gases emerging downwind of the cloud system. Measurements of the aerosol properties were made at out of the cloud sites both upwind and downwind of the cloud. Cloud microphysical measurements and bulk and size segregated cloud water chemical measurements were made along with measurements of the aerosol and gases interstitial to the cloud droplets.
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| 6. |
- Cederfelt, Sven Inge, et al.
(författare)
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On the charge limit for crystallizing particles
- 1990
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 21:SUPPL. 1, s. 127-130
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Tidskriftsartikel (refereegranskat)abstract
- The electrical charge limit of crystallizing sodium chloride droplets has been studied. Moderately charged sodium chloride solution droplets were dried to highly charged residual particles. The charge limit was found to be near the Rayleigh charge limit for saturated sodium chloride droplets of the same size as the residual particle. The charge loss was not found to affect the particle size to a detectable degree.
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| 7. |
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| 8. |
- Deppert, Knut, et al.
(författare)
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Size-selected nanocrystals of III-V semiconductor materials by the aerotaxy method
- 1998
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 29:5-6, s. 737-748
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a fabrication route to produce size-selected III-V semiconductor nanocrystals via a simple, reliable, and efficient aerosol route. Since this approach includes the reaction of aerosol particles and a self-organized growth of a new compound, all in the aerosol phase, we call this process aerotaxy. Size-selected nanocrystals of different III-V compounds in a diameter range below 20 nm were fabricated using this method. Through the reaction of arsine with gallium droplets or of phosphine with indium droplets, GaAs and InP clusters were formed. Our approach opens the possibility to produce contamination-free and size-selected nanocrystals of compound semiconductor materials with considerable freedom in composition and size.
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| 9. |
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| 10. |
- Frank, Göran, et al.
(författare)
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Characterisation of a unipolar charger for droplet aerosols of 0.1-20 mu m in diameter
- 2004
-
Ingår i: Journal of Aerosol Science. - 0021-8502. ; 35:1, s. 117-134
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Tidskriftsartikel (refereegranskat)abstract
- A charging unit for unipolar charging of cloud and fog droplets has been developed and calibrated regarding ion current, angular distribution of ions, mean droplet charge and droplet charge distribution. The charger is part of the droplet aerosol analyser, which is an instrument used for characterisation of droplets and interstitial particles in atmospheric clouds and fog. Three different calibration methods have been used for the charge calibration, whereof the third and newest method makes use of a differential mobility analyser, especially developed for large particles, up to at least 20 mum in diameter. The number of charges acquired is a strictly increasing function of the droplet diameter. Two charging models have been used for comparisons with the measurements and both models show good agreement with the data regarding the size dependency of the charge level. Both models can thus be used to describe the performance of the charger. (C) 2003 Elsevier Ltd. All rights reserved.
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| 11. |
- Gudmundsson, Anders, et al.
(författare)
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Characteristics of Mult-Nozzle Impactors with 50 µm Laser-Drilled Nozzles
- 1995
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 26:6, s. 915-931
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to provide data for the design of multi-nozzle impactors giving size-fractionated samples for X-ray emission analysis and for size-distribution determinations of the α-particle activity from aerosol-particle-attached radon progenies. Different multi-nozzle impactors with laser-drilled 50–60 μm diameter nozzles designed for a cut-off diameter of about 0.05 μm were experimentally characterised. The nozzles were placed in a spiral pattern within a circle of 8.0 mm diameter. The nozzle-plate porosities were 0.013 and 0.050 (porosity = total cross-sectional area of nozzles divided by nozzle-plate area). The results show that laser-drilled nozzles can be used for multi-nozzle impactors and that the maximum nozzle-plate porosity is limited by the cross flow. The collection characteristics of the multi-nozzle impactors studied here were found to be more dependent on the Reynolds number and the S/W ratio [the ratio of the distance (S) between nozzle plate and impaction plate to the nozzle diameter (W)], than what has been shown for single-nozzle impactors. The S/W ratio and the Reynolds number must be considered if high size resolution is to be achieved.
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| 12. |
- Gudmundsson, Anders, et al.
(författare)
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Deposition of Airborne Particles onto the Human Eye - Wind Tunnel Studies of the Deposition Velocity onto the Eyes of a Mannequin
- 1997
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 28:6, s. 1085-1100
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Tidskriftsartikel (refereegranskat)abstract
- Abstract In the field of occupational hygiene much consideration is devoted to the uptake through the human airways, but there are also reports of irritations, complaints and hazards or potential hazards due to particle deposition onto the eyes. There is a need for data regarding the dependence of the deposition rate on particle size and environmental parameters in order to formulate sampling criteria and to find dose-response relations. The deposition of airborne particles onto the human eye was studied by making use of a dummy, the eyes of which were covered with pieces of transparent sticky foil. The dummy was exposed to airborne particles in a wind tunnel. The airborne particle concentration was simultaneously measured using an Aerodynamic Particle Sizer (APS, TSI Inc., U.S.A.). The deposited particles were counted using an optical microscope equipped with an image analyser. For the particle sizes (2–30 μm), wind velocities (0.5 and 1.0 m s−1), wind directions (0, 90 and 180°) and turbulence intensities (1.3 and 19%) employed in this study, deposition velocities onto the eyes were determined to be in the range of 0.001–1 cm s−1.
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| 13. |
- Gudmundsson, Anders, et al.
(författare)
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Determination of Particle Deposition Velocity onto the Human Eye
- 1992
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; Single Page Abstracts, s. 295-295
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Tidskriftsartikel (refereegranskat)abstract
- Studies have been performed on the deposition of airborne particles onto the human eye. A mannequin with sticky transparent foils covering its eyes is exposed to particles of fused alumina in a wind tunnel. The size distribution of the airborne particle is simultaneously measured with an Aerodynamic Particle Sizer. The particles on the foils are counted and measured with an optical microscope connected to an image analyzer. Deposition velocities have been determined for particles with aerodynamic diameters over the range 2 to 32 μm with different orientations of the mannequin to the wind direction at an air velocity of 1 m/s. The deposition velocity is in the order of 0.01 cm/s.
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| 14. |
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| 15. |
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| 16. |
- Gudmundsson, Anders, et al.
(författare)
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Particle Size Calibration between the Aerodynamic Particle Sizer and Optical Microscope for Wind Tunnel Studies with Particles of Fused Alumina
- 1991
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 22 S1, s. 347-350
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Tidskriftsartikel (refereegranskat)abstract
- Abstract When studying the deposition of particles in wind tunnel experiments, we measure theairborne particles with an Aerodynamic Particle Sizer (APS). The deposited particles are examined with an optical microscope connected to an image analyzer. Calibration between the APS and the optical microscope determinations of particle size has been performed for particles of fused alumina. The particle size calibration procedure is performed by comparing the 50% cutoff sizes, determined with APS and optical microscopy measurements, for different single-stage impactors.
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| 17. |
- Heintzenberg, J, et al.
(författare)
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Number and sulfur derived 3-parameter aerosol size distributions in the tropopause region from CARIBIC flights between Germany and the Indic
- 2002
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 33:4, s. 595-608
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol number concentrations in three size ranges (d(p) > 4, d(p) > 12, 18 less than or equal to, dp less than or equal to, 135 nm) and sulfur mass from impactor samples were collected over a total of about 120 sampling hours on 18 long-range commercial flights between the northern mid-latitudes and the equatorial region covering an altitude range between 8.8 and 11.2 km. The data were evaluated with a new random search algorithm to derive monomodal lognormal particle size distributions. Through tests of the algorithm using synthetic data and size distributions from mountain stations the retrieval capabilities of the fitting algorithm are established. The fitting of aerosol data yields three parameters of the submicrometer size distribution. Their latitudinal trends indicate the influence of tropical and mid-latitudinal source regions on the tropopause aerosol. Total particle numbers show maxima near tropical biomass burning, and over the European regions. Geometric mean diameters decrease north of 35degreesN while the width of the distribution increases, indicating a move towards more frequent recent nucleation events or more frequent bimodal size distributions. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 18. |
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| 19. |
- Johansson, Gerd, et al.
(författare)
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A Study of Indoor Aerosol Size Distribution and Attachment of Radon Daughters
- 1983
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 14:3, s. 455-458
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Konferensbidrag (refereegranskat)abstract
- The particle size distribution in 11 different dwellings was studied during 5-7 days, samples being taken every 15 min. Large variation in the aerosol concentration has been found. Also the size distribution of the aerosol varies depending on the level of activity in the home, e.g. smoking and cooking. The average area median diameter found in the dwellings was 0.2 ,am. A technique for the measurement of radon daughter distribution on different airborne matter was developed and tested. The method is based on the use of an electrical mobility analyzer and alpha-spectrometry of the radon daughters collected on a fluoropore filter. Some results are presented and discussed.
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| 20. |
- Karlsson, Martin, et al.
(författare)
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Methods to measure and predict the transfer function size dependence of individual DMAs
- 2003
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 34:5, s. 603-625
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Tidskriftsartikel (refereegranskat)abstract
- In this study of the transfer function of copies of the Vienna-type differential mobility analyser (DMA) it was found that three, supposedly identical, DMAs exhibited distinct differences with respect to the width of the transfer function. This means that the transfer function of a DMA needs to be determined on an individual basis in order to obtain accurate results from DMA measurements. The size dependence of the transfer function width and the penetration of three DMAs were investigated experimentally in a broad range of Peclet numbers (400-400000). Two of the three DMAs exhibited transfer function widths in excess of the broadening induced by diffusion. The size dependence of the width of all three DMAs could be explained within a few percents by assuming an instrument-specific, size-independent broadening in addition to diffusion broadening. The penetration was evaluated by relating to deposition in a circular tube. Excellent agreement between the experimental data and the simple model was obtained. The penetration study was extended to include literature data, showing that the simple model could be applied and that there are distinct differences between different DMA types. The results of this study indicate that the size dependence of the width of the transfer function and the penetration can be estimated by measuring the transfer function for a single particle size, thus greatly reducing the amount of work required by DMA users to characterise their instruments. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 21. |
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| 22. |
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| 23. |
- Krinke, TJ, et al.
(författare)
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Microscopic aspects of the deposition of nanoparticles from the gas phase
- 2002
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 33:10, s. 1341-1359
-
Tidskriftsartikel (refereegranskat)abstract
- The deposition process in a homogeneous electric field, and the subsequent microscopic arrangement of charged, metallic nanoparticles in the size range below 100 nm on flat substrate surfaces is described. The main aspect of the investigation is the transfer of the particles from a three-dimensional distribution in the gas phase into their arrangement on the substrate surface, in dependence on particle-particle interactions and on Brownian motion. For this purpose, a trajectory model has been developed, which takes into account the flow field above the substrate surface, the electric field, the interactions of incoming particles with the substrate surface and with already deposited particles, as well as Brownian motion. The results from the trajectory calculations are compared with experimental results, obtained by scanning electron microscopy investigations of deposition patterns, created by deposition of indium and gold nanoparticles in an electrostatic precipitator. The particle diameter, the particle charge, the substrate material, the electric field strength and the number of particles deposited per unit area have been varied. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 24. |
- Malmqvist, Klas, et al.
(författare)
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Performance of a Personal Low-Weight Aerosol Sampler with Particle Size Fractionation and Time Resolution
- 1983
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 14:3, s. 409-413
-
Konferensbidrag (refereegranskat)abstract
- A low-weight aerosol sampler has been developed and tested. Internal losses for both sub-micron and large particles ( < 10 tam) are of the order of 5 %. The size fractionation patterns indicate that the sampler may be used to collect a separate respirable fraction in good agreement with the BMRC standard and a coarse fraction deternuned by the inlet design.
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| 25. |
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| 26. |
- Martinsson, Bengt G.
(författare)
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Physical basis for a droplet aerosol analysing method
- 1996
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 27:7, s. 997-1013
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Tidskriftsartikel (refereegranskat)abstract
- A technique for the characterisation of droplet aerosols is presented and theoretically evaluated. The system, which finds applications for example in the experimental study of cloud formation and cloud water chemistry, relies on a four-step process. The droplet aerosol is electrically charged in a unipolar charging unit, followed by diffusion drying of the droplets, resulting in charged particles consisting of non-volatile matter (droplet residues). In the third step, the residual particles are classified by electrostatic spectrometry, and in the final step the residual particles are detected, collected or further characterised. The basic function in respect of the charging process and the particle interaction with water vapour is demonstrated by model calculations, which show that droplets which are activated in a thermodynamical sense can be separated from unactivated droplets. Different strategies for the application of the system are briefly outlined. By measuring two parameters, associated droplet size and residual particle size can be determined. Results from the first field measurement campaign of the resulting instrument are also briefly presented.
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| 27. |
- Nakaso, K, et al.
(författare)
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Evaluation of the change in the morphology of gold nanoparticles during sintering
- 2002
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 33:7, s. 1061-1074
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Tidskriftsartikel (refereegranskat)abstract
- Morphological changes of agglomerates consisting of nanometer primary gold particles were studied experimentally and theoretically. Gold aerosol nanoparticles were produced using the evaporation/condensation method, and the change in agglomerate size by reheating was examined experimentally using a tandem DMA setup. Numerical calculations, based on two extreme mechanisms to reshape agglomerates, i.e., subsequent coalescence of primary particles and subsequent rearrangement of primary particles, were carried out. By comparison with the experimental results, the sintering time and the rate constant of restructuring were obtained. Using these values, the change in particle size for different generation conditions could be calculated. The change in morphology of agglomerates can be explained from the comparison of the experimental results with the theoretical calculations: agglomerates with smaller primary particles will compact mainly by the subsequent coalescence of primary particles, while agglomerates with larger primary particles will compact mainly by a rearrangement of primary particles.
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| 28. |
- Pagels, Joakim, et al.
(författare)
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Characteristics of aerosol particles formed during grate combustion of moist forest residue
- 2003
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 34:8, s. 1043-1059
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of aerosol particles formed during combustion of moist forest residue were studied as a function of load in a I MW moving grate boiler and at almost full load in a similar larger 6 MW boiler. The coarse (1 mum < d(ae) < 10 mum) particle number and mass concentration increased by more than one order of magnitude and the fine particle mean diameter, total volume and mass decreased when the load was increased from 50% to 75%. The combined effects led to an increase in PM10 with increasing load. The number and mass concentration and the size distribution were similar in the two boilers when operated at high load. The dominant elements (Z > 12) were K, S and Cl in the fine mode and Ca, K and S in the coarse mode. The dominant ions in the fine mode were K+, SO42- and CO32-. The fine mode particles had hygroscopic growth factors of around 1.65 at RH=90%, with a deliquescence point at a relative humidity between 30% and 60%. It was assessed that K2CO3 is responsible for the low deliquescence point. Fine mode particles of a given dry diameter had similar chemical composition. (C) 2003 Elsevier Ltd. All rights reserved.
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| 29. |
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| 30. |
- Singh, Y, et al.
(författare)
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Approaches to increasing yield in evaporation/condensation nanoparticle generation
- 2002
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Ingår i: Journal of Aerosol Science. - 0021-8502. ; 33:9, s. 1309-1325
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Tidskriftsartikel (refereegranskat)abstract
- With the recent interest in the chemical, electronic and optical properties of nanometer scale metal particles, there is now interest in manufacturing these materials in larger quantities. Since both small particle size and high particle number concentrations are sought, there is a need for improved. particle generation reactors that can realize both goals. Here, results are presented for the synthesis of indium metal nanoparticles in an evaporation/condensation aerosol generator. Size distributions were measured for metal nanoparticles formed using a standard flow configuration, as well as using several variations on the standard configuration. The aim of the modifications is to increase the cooling rate and thus, to increase the nucleation rate of the nanoparticles. An increase in the number concentration of particles and, in some cases, a significant decrease in average particle size was observed when the modified reactor configurations were used. These results can be explained by the changes in the time-temperature history of the nanoparticles resulting from the modifications to the aerosol generator. A monodisperse model of nanoparticle formation and growth, accounting for nucleation, condensation and coagulation, was used to describe particle formation in the standard flow configuration, to guide the modifications, and to describe particle formation in one of the modified configurations, with qualitative agreement seen between measured and predicted particle sizes. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Wiedensohler, A., et al.
(författare)
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A novel unipolar charger for ultrafine aerosol particles with minimal particle losses
- 1994
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 25:4, s. 639-649
-
Tidskriftsartikel (refereegranskat)abstract
- A unipolar diffusion charger with minimal particle losses in the ultrafine size range has been developed. This charger uses two radioactive α-sources to produce ions which are drawn into the charging region by an alternating electric field. The aerosol flow in the centre of the charging region is surrounded by a particle-free sheath air flow to prevent particle losses. Charged aerosol particles move in a "zigzag" manner in the charging channel under the influence of the alternating electric field. Positive gas ions, with higher electrical mobilities than ultrafine aerosol particles, homogeneously fill the entire charging region. Here, the aerosol becomes unipolarly charged. The charging efficiency is strongly dependent on the residence time of the particles in the ion cloud. The ion current was measured in the charging region to determine the ion concentration. The residence time of the particles in the ion cloud was calculated for each stream line of the aerosol flow. The losses of ultrafine particles in the charger were experimentally determined. The unipolar charge distribution was measured and calculated by integrating the theoretical charge distribution over all stream lines of the aerosol flow.
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Wiman, Bo, et al.
(författare)
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Perspectives on Aerosol Deposition to Natural Surfaces: interactions between aerosol residence times, removal processes, the biosphere and global environmental change
- 1990
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Ingår i: Journal of Aerosol Science. - 0021-8502 .- 1879-1964. ; 21:3, s. 313-338
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the state-of-the-art and the research needs in the areas of aerosol residence-time assessments, deposition modelling, and understanding of aerosols in biogeochemistry. Research needs are emphasized from a systems perspective of global environmental change. Although fundamental quantitative knowledge is lacking, some qualitative linkages between source strengths, residence times, removal processes and the biosphere can be identified. It turns out that not only are the respective areas as such challenged by new problems, superimposed on the fairly well established conventional ones, but these areas also face mutually operating sets of feedbacks between residence times and sink/source characteristics of ecological systems subject to stress. To evaluate the sensitivity of these feedback loops, and to assess whether they are negative (stabilizing interactions) or positive (destabilizing) are important and potentially urgent tasks. Such studies should focus on a common goal, such as developing empirical and theoretical understanding of aerosol resuspension, transport and deposition for application in large-scale circulation models. A basic link in such advancements is that structural change of vegetated surfaces of the biosphere caused by deposition itself, and by changing land-use and climate, be understood and assessed. This article was initiated in connection with the Workshop on Aerosol Deposition to Natural Surfaces, Lund, Sweden, 2 September, 1988; conducted during the European Aerosol Conference (see J. Aerosol Sci. 19, 775–776). The authors wish to express their thanks to the workshop participants (list available from the workshop coordinators).
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| 39. |
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| 40. |
- Aromaa, Mikko, et al.
(författare)
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Atmospheric synthesis of superhydrophobic TiO2 nanoparticle deposits in a single step using Liquid Flame Spray
- 2012
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 52, s. 57-68
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide nanoparticles are synthesised in aerosol phase using the Liquid Flame Spray method. The particles are deposited in-situ on paperboard, glass and metal surfaces. According to literature, titanium dioxide is supposed to be hydrophilic. However, hydrophobic behaviour is observed on paperboard substrates but not on metal or glass substrates. Here, the water contact angle behaviour of the deposits is studied along with XRD, XPS, BET and HR-TEM. The deposits are compared with silicon dioxide deposits having, as expected, hydrophilic properties synthesised with the same method. It seems probable that the deposition process combusts some substrate material from the paperboard substrate, which later on condenses on top of the deposit to form a carbonaceous layer causing the hydrophobic behaviour of the TiO2 deposit. The similar layer does not form when depositing the nanoparticles on a metal or glass surfaces. The observations are more than purely aerosol phenomena. However, they are quite essential in nanoparticle deposition from the aerosol phase onto a substrate which is commonly utilised. (C) 2012 Elsevier Ltd. All rights reserved.
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| 41. |
- Bergman, Fanny, et al.
(författare)
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Physicochemical metamorphosis of re-aerosolized urban PM2.5
- 2024
-
Ingår i: Journal of Aerosol Science. - : Elsevier Ltd. - 0021-8502 .- 1879-1964. ; 181
-
Tidskriftsartikel (refereegranskat)abstract
- The toxicity of particulate matter (PM) is dependent on particle physical and chemical properties and is commonly studied using in vivo and in vitro approaches. PM to be used for in vivo and in vitro studies is often collected on filters and then extracted from the filter surface using a solvent. During extraction and further PM sample handling, particle properties change, but this is often neglected in toxicology studies, with possible implications for health effect assessment. To address the current lack of knowledge and investigate changes in particle properties further, ambient PM with diameter less than 2.5 μm (PM2.5) was collected on filters at an urban site and extracted using a standard methanol protocol. After extraction, the PM was dried, dispersed in water and subsequently nebulized. The resulting aerosol properties were then compared to those of the ambient PM2.5. The number size distribution for the nebulized aerosol resembled the ambient in terms of the main mode diameter, and >90 % of particle mass in the nebulized size distribution was still in the PM2.5 range. Black carbon made up a similar fraction of PM mass in nebulized as in ambient aerosol. The sulfate content in the nebulized aerosol seemed depleted and the chemical composition of the organic fraction was altered, but it remains unclear to what extent other non-refractory components were affected by the extraction process. Trace elements were not distributed equally across size fractions, neither in ambient nor nebulized PM. Change in chemical form was studied for zinc, copper and iron. The form did not appear to be different between the ambient and nebulized PM for iron and copper, but seemed altered for zinc. Although many of the studied properties were reasonably well preserved, it is clear that the PM2.5 collection and re-aerosolization process affects particles, and thus potentially also their health effects. Because of this, the effect of the particle collection and extraction process must be considered when evaluating cellular and physiological outcomes upon PM2.5 exposure. © 2024 The Authors
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| 42. |
- Bergman, Fanny, et al.
(författare)
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Physicochemical metamorphosis of re-aerosolized urban PM2.5
- 2024
-
Ingår i: Journal of Aerosol Science. - : Elsevier Ltd. - 0021-8502 .- 1879-1964. ; 181
-
Tidskriftsartikel (refereegranskat)abstract
- The toxicity of particulate matter (PM) is dependent on particle physical and chemical properties and is commonly studied using in vivo and in vitro approaches. PM to be used for in vivo and in vitro studies is often collected on filters and then extracted from the filter surface using a solvent. During extraction and further PM sample handling, particle properties change, but this is often neglected in toxicology studies, with possible implications for health effect assessment. To address the current lack of knowledge and investigate changes in particle properties further, ambient PM with diameter less than 2.5 μm (PM2.5) was collected on filters at an urban site and extracted using a standard methanol protocol. After extraction, the PM was dried, dispersed in water and subsequently nebulized. The resulting aerosol properties were then compared to those of the ambient PM2.5. The number size distribution for the nebulized aerosol resembled the ambient in terms of the main mode diameter, and >90 % of particle mass in the nebulized size distribution was still in the PM2.5 range. Black carbon made up a similar fraction of PM mass in nebulized as in ambient aerosol. The sulfate content in the nebulized aerosol seemed depleted and the chemical composition of the organic fraction was altered, but it remains unclear to what extent other non-refractory components were affected by the extraction process. Trace elements were not distributed equally across size fractions, neither in ambient nor nebulized PM. Change in chemical form was studied for zinc, copper and iron. The form did not appear to be different between the ambient and nebulized PM for iron and copper, but seemed altered for zinc. Although many of the studied properties were reasonably well preserved, it is clear that the PM2.5 collection and re-aerosolization process affects particles, and thus potentially also their health effects. Because of this, the effect of the particle collection and extraction process must be considered when evaluating cellular and physiological outcomes upon PM2.5 exposure.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Elihn, Karine, et al.
(författare)
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Correlation between airborne particle concentrations in seven industrial plants and estimated respiratory tract deposition by number, mass and elemental composition
- 2011
-
Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 42:2, s. 127-141
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Tidskriftsartikel (refereegranskat)abstract
- The number and mass distribution of airborne particles were recorded in several industrial plants. From the data obtained, particle deposition was estimated in three regions of the respiratory tract using the ICRP grand average deposition model based on Hinds' (1999) parameterization. The median diameter was 30-70 nm (number distributions), and >4 mu m (mass distributions) near most work activities, resulting in linear relationships between the deposited number/mass concentrations and the number/mass concentrations in the air. Welding and laser cutting produced particles in the 200-500-nm range; total deposition was small, not in accordance with the linear relationship observed for the other work activities. The elemental content varied between particle sizes in some workplaces, causing different elements to deposit in different respiratory regions. Iron was the most abundant element in the particles in many of the workplaces; in an iron foundry, however, Fe was most abundant only in the micron-sized particles whereas the nanoparticles mainly comprised Pb and Sb.
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| 47. |
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| 48. |
- Gren, Louise, et al.
(författare)
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Effects of renewable fuel and exhaust aftertreatment on primary and secondary emissions from a modern heavy-duty diesel engine
- 2021
-
Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 156
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Tidskriftsartikel (refereegranskat)abstract
- Compared to petroleum diesel, renewable diesel fuels and exhaust aftertreatment systems can reduce primary exhaust emissions that are hazardous to human health and the environment. Secondary aerosol emissions which form upon atmospheric processing have, however, been less studied. This study aimed to quantify the impacts of replacing petroleum diesel with renewable fuels (hydrotreated vegetable oil [HVO] and rapeseed methyl ester [RME]) on primary and secondary aerosol emissions from a heavy-duty diesel engine at different stages of an exhaust aftertreatment system. Emission characterization was obtained by combining a battery of physical characterization techniques with chemical characterization using aerosol mass spectrometry. At engine-out measurements, RME and HVO reduced primary particulate matter (PM) emissions (for example equivalent black carbon [eBC]) and secondary aerosol production (studied with an oxidation flow reactor [OFR]) by mass compared to petroleum diesel. The diesel oxidation catalyst (DOC) reduced primary nucleation mode emissions, reduced the effective density of soot mode emissions, and reduced secondary particle production by mass. The DOC + a diesel particulate filter removed >99% of the particle number and eBC emissions. Volatile PM emissions (for example organic aerosol) were found to be distributed between the nucleation mode and soot mode for both primary and secondary emissions, to a degree that depends on both fuel type and aftertreatment. A high mass concentration of condensable species and a low condensation sink in the soot mode led to increased fractions of condensable species present in the nucleation mode. Aging in the OFR led to increases in particle effective density. Motoring the engine (running without combustion) showed that the nucleation mode originated primarily from lubricating oil, and nonvolatile nanoparticle emissions were identified down to 1.2 nm in particle size. In conclusion, replacing petroleum diesel with HVO and RME changes emission characteristics and can help reduce key aerosol emissions of relevance for adverse health and climate impact, especially for diesel engines with no or limited exhaust aftertreatment.
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| 49. |
- Hazeri, Mohammad, et al.
(författare)
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Regional deposition of the allergens and micro-aerosols in the healthy human nasal airways
- 2021
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 152
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Tidskriftsartikel (refereegranskat)abstract
- The nasal cavity is the inlet to the human respiratory system and is responsible for the olfactory sensation, filtering pollutant particulate matter, and humidifying the air. Many research studies have been performed to numerically predict allergens, contaminants, and/or drug particle deposition in the human nasal cavity; however, the majority of these investigations studied only one or a small number of nasal passages. In the present study, a series of Computed Tomography (CT) scan images of the nasal cavities from ten healthy subjects were collected and used to reconstruct accurate 3D models. All models were divided into twelve anatomical regions in order to study the transport and deposition features of different regions of the nasal cavity with specific functions. The flow field and micro-particle transport equations were solved, and the total and regional particle deposition fractions were evaluated for the rest and low activity breathing conditions. The results show that there are large variations among different subjects. The standard deviation of the total deposition fraction in the nasal cavities was the highest for 5 x 10(4) impaction parameter (IP)<1.125 x 10(5) with a maximum of 20%. The achieved results highlighted the nasal cavity sections that are more involved in the particle deposition. Particles with IP = 30,000 deposit more in the middle turbinate and nasopharynx areas, while for particles with IP = 300,000, deposition is mainly in the anterior parts (kiesselbach and vestibule regions). For small IP values, the amounts of deposition fractions in different regions of the nasal cavity are more uniform.
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| 50. |
- Holmgren, Helene, 1981, et al.
(författare)
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Size Distribution of Exhaled Particles in the Range from 0.01 to 2.0 µm
- 2010
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 41:5, s. 439-446
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the number size distribution of endogenously produced exhaled particles during tidal breathing and breathing with airway closure. This is the first time that the region below 0.4 µm has been investigated. The particle concentration was generally lower for tidal breathing than for airway closure, although the inter-individual variation was large. During tidal breathing, the size distribution peaks at around 0.07 µm. This peak is still present during the airway closure manoeuvre, but an additional broad and strong peak is found between 0.2 and 0.5 µm. This suggests that different mechanisms govern the generation of particles in the two cases. The particles produced from airway closure may be attributed to formation of film droplets in the distal bronchioles during inhalation. It is speculated that the very small particles are film droplets originating from the alveolar region.
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