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Journal of Aerosol Science
Pergamon Press
Journal of Aerosol Science

Pergamon Press

0021-8502

Journal of Aerosol Science/Journal Journal of Aerosol ScienceSCIISTPEI
正式出版
收录年代

    Effect of breathing profiles on nebuliser drug delivery targeting the paranasal sinuses in a post-operative nasal cavity

    Shrestha K.Van Strien J.Shang Y.Petersen P....
    19页
    查看更多>>摘要：? 2021 Elsevier LtdChronic rhinosinusitis (CRS) is a common sinonasal condition that debilitates quality of life. Nasal sprays are inefficient for targeting the sinuses because of the highly inertial atomised droplets. This study evaluated sinus drug delivery via a nebuliser in a human nasal cavity using Computational Fluid Dynamics (CFD) simulations of different breathing conditions. The nebuliser was quantified through high-speed imaging of the spray plume and average velocity, while laser diffraction was used for droplet size distributions. A CT scan was acquired of a 75-year-old male with a confirmed diagnosis of CRS, and airway segmentation was performed to extract the nasal cavity and sinuses. Virtual surgery was then performed on the computational model. Two nozzle designs for the nebuliser under normal breathing, slow exhalation, and breath hold were investigated. The results demonstrated that drug delivery with a fully blocked nostril with a breath hold notably improved deposition targeting the maxillary sinuses and ethmoid sinuses, while using a nozzle that allowed co-flow of air was recommended for targeting the frontal and sphenoid sinuses.
      原文链接:
    • NSTL
    • Elsevier

    High-yield microplasma synthesis of monodisperse sub-3 nm diameter metal nanoparticles explained by a charge-mediated formation mechanism

    Sawyer W.J.Hart A.J.
    18页
    查看更多>>摘要：? 2021The size and composition of nanoparticles are instrumental to many catalytic processes; for example, their controlled synthesis is key to achieving high yield and quality in aerosol chemical vapor deposition (CVD) of carbon nanotubes (CNTs). Using a custom-built atmospheric pressure DC microplasma reactor, we synthesize sub-3 nm iron nanoparticle aerosols at high number concentration (>109 #/cm3) with narrow size distribution (σg<1.3) from a ferrocene vapor precursor. We demonstrate precise diameter control down to 1.1 nm and maximum yield near unity. We invoke a charge-mediated formation mechanism to show that the ～ 10 μs plasma residence time is sufficient to dissociate the precursor and partially ionize the resulting iron vapor, yet too short for the aggregation of clusters beyond 10 atoms. Thus, particle growth occurs primarily downstream of the plasma domain through aggregation of neutral and ionized vapor and clusters. This model closely reproduces the observed particle size distributions with the selection of an appropriate fractional ionization, yet is insufficient to entirely explain the rapid growth rate observed experimentally. This mechanism is different from that of existing microplasma processes, which have a longer residence time allowing particle formation to occur within the plasma, and may explain the demonstrated capability to co-optimize nanoparticle yield, throughput, and diameter control at a level exceeding the performance of previously published thermal and microplasma methods.
      原文链接:
    • NSTL
    • Elsevier

    Cluster activation studies with a diffusive condensation particle counter: Effect of chemical composition

    Kuldinow D.Przybylak A.Perez Lorenzo L.J.de la Mora J.F....
    9页
    查看更多>>摘要：? 2021We use KanomaxFMT's Fast Condensation Particle Counter (CPC) to study the growth (activation) of purified singly charged cluster ions of several salts by condensation of n-butanol vapor. Salts investigated include 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (EMI-FAP), and four tetra-alkylammonium bromides (CpH2p+1)4N+-Br-, with p = 4, 6, 7, 12. The clusters studied contained up to 20 salt molecules, which were formed via a bipolar electrospray source, and were size-selected with a differential mobility analyzer. The CPC is operated at variable condenser and fixed saturator temperatures, Tc, Ts. It uses 75% sheath gas, such that most aerosol-containing fluid streamlines are near the channel center, and experience very similar maximal saturation ratios. This results in a steep initial dependence of the activation probability on Ts for selected particles. Therefore, a well-defined activation onset temperature Ts? is determined as a function of cluster composition, polarity (±), and mobility diameter (dp). Notwithstanding a modest material dependence found for the inferred Tc?(dp) curves (±0.25 nm), the steepness of the activation curves measured permits determining particle size distributions for aerosols of known composition. There is some ambiguity in the precise temperature profile in the CPC channel. Nevertheless, using our best estimate, the onset condition for all but one of the seed particles studied agrees well with predictions from classical heterogeneous nucleation theory (Fletcher, 1962) when the pre-exponential term K in the nucleation rate is chosen appropriately. This enables the incorporation of materials properties into the sizing process in terms of only this single parameter K. This finding also provides a method to determine K experimentally, suggesting that the material dependence of the activation probability is due to the different interaction potentials between the clusters and the vapor. Tetraheptylammonium bromide is peculiar in that its cluster anions fit classical theory very much as all other materials studied, but its cluster cations do not.
      原文链接:
    • NSTL
    • Elsevier

    A comparative study on effective density, shape factor, and volatile mixing of non-spherical particles using tandem aerodynamic diameter, mobility diameter, and mass measurements

    Rahman M.M.Johnson T.J.Giannopoulos G.Boies A.M....
    20页
    查看更多>>摘要：? 2021 Elsevier LtdCombustion-generated particles are typically non-spherical (soot aggregates) and sometimes mixed with organic compounds (e.g. in vehicle emissions). The effective density, dynamic shape factor, and volatile mixing of particles are widely studied using aerosol instruments that measure the particle mobility diameter, aerodynamic diameter, and mass. In theory, any of these three physical properties can be obtained from a combination of the other two. In the present study, a tandem arrangement of aerodynamic aerosol classifier (AAC; measuring aerodynamic diameter), differential mobility analyzer (DMA; measuring mobility diameter), optional catalytic stripper (CS), and centrifugal particle mass analyzer (CPMA; measuring particle mass) was used to study the effective density, dynamic shape factor, and volatile mixing of non-spherical non-homogenous particles. In terms of mass, the vast majority of the particles were purely semi-volatile mixed with soot with and without semi-volatile coating. The effective density of polydisperse non-stripped particles was relatively constant (indicating nearly spherical particles), while that of polydisperse stripped particles decreased from ～1200 to ～800 kg/m3 as the particle size increased (indicating a compact structure). The effective density of monodisperse particles, measured by DMA-CPMA, AAC-DMA, and AAC-CPMA methods, was consistent within the measurement uncertainty; however, the latter method had larger discrepancy with the other two methods, particularly for non-spherical particles. The dynamic shape factor, measured by AAC-CPMA and DMA-CPMA methods, increased with the mobility diameter, a trend also supported by electron micrographs. The volatile mass fraction of particles decreased as their mobility diameter increased, with smaller particles having volatile mass fraction of ～20%. This result was further confirmed by chemical characterization of size-selected particles, proving the robustness of online aerosol measurements.
      原文链接:
    • NSTL
    • Elsevier

    Antibiotic resistance genes and antibiotic sensitivity in bacterial aerosols and their comparisons with known respiratory pathogens

    Wang M.Yao M.Zhu Y.-G.
    12页
    查看更多>>摘要：? 2021 Elsevier LtdAirborne transmission of antibiotic resistance genes (ARGs) has emerged as a global health threat, while their hosts’ resistance phenotype remains largely unknown. Here, culturable bacterial aerosol samples were collected from polluted air in Beijing using a portable high volume sampler (1000 L/min). Antimicrobial susceptibility testing was conducted to explore the antibiotic sensitivity of culturable bacterial aerosols to seven widely used antibiotics. As a comparison, ARG distribution and expression in two human respiratory pathogenic bacterial strains (Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus) and a non-pathogenic bacterial strain (Pseudomonas fluorescens) were also studied. Relative abundances of 39 ARG subtypes in three bacterial strains including Haemophilus influenzae were investigated by high throughput real-time qPCR platform. Surprisingly, 24.66% of the culturable bacterial aerosols in polluted air were resistant to vancomycin-the most powerful antibiotics to date, while 53.05% of airborne culturable bacteria were susceptible to ampicillin (β-lactams). Different bacteria demonstrated very different ARG distribution patterns of more or less skewed toward certain one ARG type. On the other hand, the vancomycin resistance gene vanB was detected both in H. influenza and P. fluorescens, however these bacteria did not exhibit anti-vancomycin phenotype. Furthermore, the resistance to ciprofloxacin (quinolones) was not observed in P. aeruginosa and P. fluorescens although these bacteria harbor abundant quinolone resistance gene qepA. Experimental data from this work show that air represents an important active reservoir of diverse ARGs, and some bacterial aerosols are harboring vancomycin resistance gene though not expressed. Results from human respiratory pathogens have further demonstrated similar findings. This work underscores the serious concern of airborne dissemination of ARBs including those resistant to vancomycin in polluted ambient environments, while revealing abundances and patterns of various ARGs in both pathogenic and non-pathogenic bacteria.
      原文链接:
    • NSTL
    • Elsevier

    Quantitative assessment of coagulation of atmospheric particles onto airborne birch pollen grains

    Visez N.Blanchenet A.-M.Roose A.Choel M....
    9页
    查看更多>>摘要：? 2021 Elsevier LtdThe coagulation of airborne particles on the surface of allergenic pollen grains is poorly described in the literature. However, particles deposited on the surface of pollen grains could have an effect on allergy and its symptoms. Observations of pollen surface alterations reported in the literature are either qualitative or are tainted by sampling artifacts that overestimate surface particulate pollution. Birch pollen grains (BPGs) were sampled in the atmosphere during pollination to quantitatively assess the extent of particulate deposition on allergenic pollen surfaces. Airborne PGs were collected with a cascade impactor ensuring no sampling artifact unlike pollen samplers usually used in this type of study. Counting, sizing and elemental analysis of particles adhering on pollen surfaces were performed by SEM/EDX. 68% of PGs did not carry any particle on their visible surface while the remaining 32% had between 1 and 16 particles on their surface. On average, polluted BPGs carried 2 ± 1 particles, representing an average surface coverage of 0.95%. We hypothesized that the main coagulation process was particle deposition by gravitational settling. Collision velocity calculations indicate that coagulation due to gravitational settling is prevalent under typical pollination atmospheric conditions. However, the effects of electric charges carried by pollen are largely unknown and may significantly alter coagulation rates. The presence of particle-polluted allergenic pollens appears to be common in the urban atmosphere, even under low air pollution conditions. The impact of chemical pollution of BPGs due to the presence of particulate matter (including soot particles) remains relatively unknown, both on the allergy and on the reproductive capacity of the trees.
      原文链接:
    • NSTL
    • Elsevier

    Activation of sub-3 nm organic particles in the particle size magnifier using humid and dry conditions

    Rorup B.Dada L.Baalbaki R.Kangasluoma J....
    11页
    查看更多>>摘要：? 2022 The AuthorsThe accurate measurement of aerosol particles and clusters smaller than 3 nm in diameter is crucial for the understanding of new particle formation processes. The particle counters used for measuring these particles are typically calibrated with metal or salt particles under dry conditions, which does not always represent the field conditions where these instruments are later used. In this study, we calibrated the A11 nano Condensation Nucleus Counter (nCNC), consisting of the PSM (Particle Size Magnifier) and a laminar flow butanol based CPC (Condensational Particle Counter), with well-defined biogenic oxidation products from β-caryophyllene oxidation and compared it to a calibration with tungsten oxide under the same conditions. The organic particles were detected less efficiently than the inorganic ones. This resulted in a higher cut-off size for β-caryophyllene oxidation products than for tungsten oxide. At the same PSM settings, the cut-off size for tungsten oxide was 1.2 nm and for β-caryophyllene oxidation products 1.9 nm. However, repeating the calibration of the biogenic particles at 13% relative humidity at 31°C, increased their detection efficiency in the PSM, increasing the cut-off diameter to 1.6 nm. Additionally, we present a comparison of the ion concentrations measured with the PSM and the NAIS (Neutral Cluster and Air Ion Spectrometer) during new particle formation experiments in the CLOUD (Cosmics Leaving Outdoors Droplets) chamber. In these experiments, we produced particles from different organic precursors, such as α-pinene, β-caryophyllene and isoprene, as well as iodine. This way, we could determine the shift in cut-off diameter of the PSM for several different atmospherically relevant chemical compounds and compare it to the laboratory calibrations. We saw a diameter shift for the organic precursors of +0.3 nm in the PSM compared to the NAIS. These two approaches agreed well with each other and show that it is important to know the chemical composition of the measured particles to determine the exact size distribution using a supersaturation scanning method.
      原文链接:
    • NSTL
    • Elsevier

    Particle deposition characteristics in the formation of Hard Grey Scale (HGS) on cold surfaces exposed to aluminium production off-gas

    Perez Clos D.Zedel H.Johnsen S.G.Aune R.E....
    16页
    查看更多>>摘要：? 2022 The AuthorsHard Grey Scale (HGS) is a hard and strongly adhering fouling material that forms on solid surfaces impinged by the off-gas generated in the pot cells of aluminium production plants. Different theories on HGS formation mechanisms have been suggested, involving particle re-crystallization or formation of a binder phase between the deposited particles. However, no conclusive proofs have yet been presented. This study focuses on statistical quantification of HGS growth rates and particle deposition characteristics from analysis of fouling experiments in a primary aluminium production plant. The experiments were performed with a cylindrical cold-finger inserted in a duct upstream of the Gas Treatment Center (GTC) with durations ranging from a few hours to several months. Detailed characterization of cold-finger deposits and off-gas particle size distributions was performed using image analysis (IA) and a Particle Diffraction Sizer (PDS) to investigate particle capture efficiencies on both sides of the cold-finger. In addition, an old HGS sample from a secondary alumina transport pipe, with different appearance than cold-finger HGS, was analyzed. Results show that HGS particles have a log-normal size distribution centered at 1.2 μm with 35% of the particles below 1 μm. A similar granular structure and size distribution was found for the HGS sample from the secondary alumina transport pipe, suggesting that a similar formation mechanism exists for the two types of HGS. Particle capture efficiency results for cold-finger HGS at low Stokes numbers are in good agreement with numerical studies considering inertial impaction efficiencies. At larger Stokes numbers, i.e. larger particle sizes, rebounding and re-entrainment effects result in lower capture efficiencies than those predicted by the impaction models. The present results suggest that HGS formation is due to inertial deposition of small particles, with the submicron-sized fraction generating a closely packed structure responsible for the HGS bulk properties.
      原文链接:
    • NSTL
    • Elsevier

    The role of the driving dynamics beyond RDE limits and DPF regeneration events on pollutant emissions of a Euro 6d-temp passenger vehicle

    Toumasatos Z.Raptopoulos-Chatzistefanou A.Kolokotronis D.Pistikopoulos P....
    16页
    查看更多>>摘要：? 2021 Elsevier LtdThe current study investigates gaseous and particulate emissions of a diesel passenger car (Euro 6d-temp), under specific operation events, including diesel particulate filter (DPF) active regeneration. The contribution of DPF active regeneration to sub-23nm volatile and solid particle emissions was investigated in a dedicated measurement campaign. A novel exhaust gas sampling and dilution system was employed for the determination of solid particle number (SPN) emissions down to 23 nm, 10 nm, and 2.5 nm. Total particle number (TPN) emissions, including semi-volatiles, down to 10 nm and down to 5.6 nm were also measured. A DPF active regeneration was triggered during real driving emissions (RDE) testing. DPF regeneration increased NOx and SPN down to 23 nm (SPN23) by 1.7 times and 3 orders of magnitude, respectively, compared to non-regenerating conditions. A second DPF regeneration was triggered during steady-state conditions in the laboratory. Once again, SPN23 emissions were at least 3 orders of magnitude higher compared to normal operation. Under regeneration conditions, SPN down to 2.5 nm (SPN2.5) was 2.3 times higher than SPN23, which suggests that a significant number of particles reside below the regulated limit of 23 nm during DPF regeneration. Moreover, TPN emissions were at least 7 times higher than SPN ones. Both these observations suggest that a significant number of particles during DPF regeneration evades current SPN23 regulation. Based on the DPF active regeneration findings in RDE and lab conditions, the current study introduces an enhanced particulate emission factor that includes the impact of active DPF regenerations.
      原文链接:
    • NSTL
    • Elsevier

    Announcement of the 2021 Journal of Aerosol Science Excellence in Research Award Recipients

    Hogan C.
    2页
      原文链接:
    • NSTL
    • Elsevier