Surface Concentration Of Particles Research Articles

Creating High Yield Stress Particle-Laden Oil/Water Interfaces Using Charge Bidispersity.

Interfacial engineering has been increasingly used to stabilize Pickering emulsions in commercial products and biomedical applications. Pickering emulsion stabilization is aided by interfacial viscoelasticity; however, typically the primary means of stabilization are steric hindrances between high surface concentration shells of particles around the drops. In this work, the concept of creating large interfacial viscoelastic yield stresses with low particle surface concentrations (<50%) using bidisperse charged particle systems is tested to evaluate their potential efficacy in emulsion stabilization. To explore this hypothesis, interfacial rheology and visualization experiments are conducted at o/w interfaces using positively charged amidine, negatively charged carboxylate, and negatively charged sulfate-coated latex spheres and compared to a model based on interparticle forces. Bidisperse particle systems have been observed to create more networked structures than monodisperse systems. For surface concentrations of <50%, bidisperse interfaces created measurable viscoelastic moduli ∼1 order of magnitude larger than monodisperse interfaces. Furthermore, these interfaces have measurable yield stresses on the order of 10-4 Pa·m when monodisperse systems have none. Bidispersity impacts surface viscoelasticity primarily by increasing the overall magnitude of attraction between particles at the interface and not due to changes in the microstructure. The developed model predicts the relative surface fraction that creates the largest moduli and shows good agreement with the experimental data. The results demonstrate the ability to create large viscoelastic moduli for small surface fractions of particles, which may enable stabilization using fewer particles in future applications.

Development, characterization and validation of a novel physics-informed equivalent circuit model for silicon–graphite battery cells

The widespread deployment of electric vehicles (EVs), as well as the growing requirements both from manufacturers and consumers, necessitate an increase in energy density with regard to current lithium-ion batteries (LIBs). In this regard, one of the most promising alternatives is the addition of silicon to conventional graphite anodes, thus giving rise to energy-dense LIBs. However, this entails a significant increment in modeling, parameterization and computational complexities due to the interactions between both negative electrode materials. In this article, we present a novel physics-informed equivalent circuit model for cells with blended electrodes, which is able to provide accurate results with respect to a state-of-the-art electrochemical model, not only for the output voltage (≤25 mV RMS), but also internal states, namely active material particle surface concentrations (≤1.2 %) and current distribution (≤2.6 %) at a much lower computational cost. Furthermore, this formulation also allows for a notable simplification of model parameterization. Hence, we describe thorough static and dynamic parameterization processes from half-cell experimental data and impedance measurements. Finally, we validate the proposed model in constant-current as well as dynamic operation, highlighting the influence that the choice of hysteresis model has on the latter. We understand that the presented model is an interesting alternative for the modeling of cells with blended electrodes, and is also suitable for its implementation in Battery Management Systems (BMSs) in EVs.

Electrical and Optical Switching in Vanadium Dioxide Nanostructures Decorated with Gold Nanoparticles

The electrical parameters of the semiconductor-metal phase transition in vanadium dioxide nanostructures synthesized by chemical vapor deposition on a silicon substrate (100) and decorated with gold nanoparticles with a surface concentration from 3∙109 to 3∙1010 cm–2 are studied. X-ray phase analysis revealed that the synthesized nanostructures of vanadium dioxide contain a monoclinic M1 phase undergoing a phase transition at a temperature of about 68 °C. The morphology of the surface of vanadium dioxide nanostructures coated with gold nanoparticles was studied using a scanning electron microscope and an atomic force microscope. The characteristics of the temperature phase transition of the initial nanostructures and nanostructures decorated with gold nanoparticles are determined. The temperature dependence of the resistance near the phase transition point of the initial nanostructures showed that the resistance jump is about four orders of magnitude, which confirms their high quality. It is shown that an increase in the surface concentration of gold particles to a value of 3∙1010 cm–2 increases the conductivity of vanadium dioxide at room temperature by about two times, and shifts the phase transition temperature by 5 °C: from 68 °C to 63 °C. Optical switching in vanadium dioxide with an array of gold particles with a size of 9 nm is considered by numerical modeling methods. It is established that the response of the electromagnetic wave from the VO2 material during the phase transition is enhanced due to the excitation of localized plasmon resonance in gold nanoparticles and reaches a local maximum in the region of 600 nm. Additionally, this effect is enhanced at angles of incidence near the pseudo-Brewster angle for vanadium dioxide. The considered hybrid VO2–Au nanostructures are promising as basic nanoelements for next-generation computers, as well as for ultrafast and highly sensitive sensors.

Modeling of Particle Size Distribution in the Presence of Flocculant

This study presents a mathematical description of the solid fraction aggregation process in the presence of a flocculant and its result. The basis is a population balance equation. The model is realized in Python language. Verification was carried out using red mud from the investigated enterprise; Flomin AL P 99 VHM was used as a flocculant. The mean square deviation for the parameter “mean aggregate diameter” is equal to 19.88 μm. The time required for the model calculation is about 3 min. The time spent on modeling depends on the number of calculation channels. In this study, 40 channels (20 with PSD source data, and 20 with empty values required for the calculation) were used for the calculation. The time spent on the model calculation is much shorter than the inertia via each of the communication channels for the studied symmetric radial type thickener. A user interface is developed, where the input parameters are the initial pulp particle size distribution, viscosity and density of pulp in the thickener, particle surface area, concentration and flow rate of flocculant, concentration of solid particles, inner diameter and height of the feed well, and simulation time. The result of the simulation is particle size distribution in the feed well of the washer and the mean flocculus diameter.

The Aerosol Optical Characteristics in Different Dust Events Based on a 532 nm and 355 nm Polarization Lidar in Beijing

Extreme weather events are happening more frequently as a result of global climate change. Dust storms broke out in the spring of 2017 in China and drastically impacted the local air quality. In this study, a variety of data, including aerosol vertical profiles, surface particle concentration, meteorological parameters, and MODIS–derived aerosol optical depth, as well as backward trajectory analysis, were employed to analyze two dust events from April to May in Beijing. The dust plumes were mainly concentrated below 0.8 km, with peak PM10 values of 1000 μg·m−3 and 300 μg·m−3 in the two cases. The aerosols showed different vertical distribution characteristics. The pure dust in case 1 from 4 to 5 May 2017 had a longer duration (2 days) and presented a larger aerosol extinction coefficient (2.27 km−1 at 355 nm and 1.25 km−1 at 532 nm) than that of the mixed dust in case 2 on 17 April 2017 (2.01 km−1 at 355 nm and 1.33 km−1 at 532 nm). The particle depolarization ratio (PDR) remained constant (0.24 ± 0.03 in case 1) from the surface to 0.8 km in height. In contrast, the PDR profile in the mixed dust (case 2) layer was split into two regions—large values exceeding 0.15 above 0.6 km and small values of 0.11 ± 0.03 below 0.6 km. The influence of meteorological information on aerosol distribution was also investigated, and wind was predominant through the observing period. The pure dust in case 1 was mainly from Mongolia, with strong northwest winds, while the near-surface mixed pollution was caused by the combination of long-transported sand and local emission. Furthermore, lidar-derived profiles of dust mass concentrations in the two cases were presented. This study reveals the vertical characteristics of dust aerosols in the production and dissipation of localized dust events and confirms the efficacy of thorough observations with multiple approaches from the ground to space to monitor dust events in real time.

Construction of a geoecological map of dust particles transfer from the surface of the Shymkent lead (plumbum) factory dump

The study of horizontal migration of heavy metals is relevant for Shymkent city. In 1934, lead processing began, and sludge waste was stored on the territory of the lead factory. Ameliorative or other structures capable of reducing dust emissions have not been built around the lead dump, allowing lead dust to freely spread over long distances from the SPZ (sanitary protection zone). In this article, the horizontal migration of lead dust was studied based on climatic and calculated data by building a physical model; in addition, a geoecological map was built. This work has practical significance for further ecological and geochemical assessment of soils for the content of heavy metal concentrations, since it visually characterizes the spread of lead dust along the wind rose. To build a geoecological map of the transfer of impurities, we are faced with the task of determining the rate of settling of hovering particles and their distributions depending on the masses of particles and wind speed. To determine the rate of deposition of lead particles in the atmosphere, we need to study the shape of lead, background meteorological situation, particle diameter, solid particle density, medium density and dynamic viscosity of the medium. The removal of dust particles from the surfaces of ash and slag dumps of industrial facilities into the atmosphere under the influence of wind erosion, followed by their deposition on the soil, is one of the most common ways of polluting the territories of industrial facilities. As a result of the calculations, the surface concentration of dust particles was derived and a geoecological map was compiled. Keywords: geoecological map, lead dumps, assessment of dust emissions, horizontal migration of heavy metals, physical model of transport and scattering.

Thermochromic and temperature regulation properties of phase change materials derived from polymer composites loaded with VO2 particles

AbstractThis research work concerns the development of phase change materials based on poly(ethylene terephthalate) (PET) mixed with vanadium dioxide particles (VO2). Monoclinic VO2 particles were synthesized via a hydrothermal process followed by modification of the particle surface with a silane coupling agent, namely 3‐(aminopropyl) triethoxysilane (APTES). After that, the metal oxide particles were mixed with PET flakes, derived from used PET bottles, in an internal mixer. In this study, the effects of surface modification and concentrations of VO2 particles on thermomechanical and optical properties of the composites were investigated. From the DSC results, it was found that the percentage crystallinity of PET increased after loading with VO2. This indicates that VO2 can act as a nucleating agent inducing the crystallization of the PET chains. From the scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM–EDX) images, better dispersion of VO2 particles in the PET matrix was noticed when the surface‐modified VO2 particles were used as a replacement for the normal VO2 particles. This contributed to the greater percentage of visible light transmittance through the composite sheets. Thermogravimetric analysis (TGA) profiles of both PET and PET/VO2 specimens are similar, indicating that the VO2 did not accelerate the thermal decomposition of the PET. When the specimens were exposed to an IR lamp, it was found that the temperature behind the PET/VO2 sheets dropped when compared to that of the neat PET sheets. Some shrinkage and deformation of the PET/VO2 specimens were also noticed. The higher the VO2 loading, the greater the deformation. The effect was ascribed to the fact that the actual temperature was above the critical transition temperature of VO2. Consequently, the NIR transmittance was suppressed at the expense of the greater NIR absorbance by the VO2 phase in the composites. Finally, when the specimens were exposed to solar irradiation at ambient temperature, the temperature underneath the PET/VO2 specimens became greater than that of the control specimen (the neat PET). The result was discussed in the light of the emissivity of VO2 at ambient temperature, which is considerably low. Overall, this study demonstrates that PET/VO2 can exhibit both cooling and warming effects, depending on the ambient temperature in relation to the critical transition temperature (Tc) of VO2.

Data level and decision level fusion of satellite multi-sensor AOD retrievals for improving PM2.5 estimations, a study on Tehran

One of the techniques for estimating the surface particle concentration with a diameter of fewer than 2.5 micrometers (PM2.5) is using aerosol optical depth (AOD) products. Different AOD products are retrieved from various satellite sensors, like MODIS and VIIRS, by various algorithms, such as Deep Blue and Dark Target. Therefore, they do not have the same accuracy and spatial resolution. Additionally, the weakness of algorithms in AOD retrieval reduces the spatial coverage of products, particularly in cloudy or snowy areas. Consequently, for the first time, the present study investigated the possibility of fusing AOD products from observations of MODIS and VIIRS sensors retrieved by Deep Blue and Dark Target algorithms to estimate PM2.5 more accurately. For this purpose, AOD products were fused by machine learning algorithms using different fusion strategies at two levels: the data level and the decision level. First, the performance of various machine learning algorithms for estimating PM2.5 using AOD data was evaluated. After that, the XGBoost algorithm was selected as the base model for the proposed fusion strategies. Then, AOD products were fused. The fusion results showed that the estimated PM2.5 accuracy at the data level in all three metrics, RMSE, MAE, and R2, was improved (R2=0.64). Despite the simplicity and lower computational cost of the data level fusion method, the spatial coverage did not improve considerably due to eliminating poor quality data through the fusion process. Afterward, the fusion of products at the decision level was followed in eleven scenarios. In this way, the best result was obtained by fusing Deep Blue products of MODIS and VIIRS sensors (R2=0.81)

Microplastic Effects on Thrombin-Fibrinogen Clotting Dynamics Measured via Turbidity and Thromboelastography.

Micro/nanoplastics, whether manufactured or resulting from environmental degradation, can enter the body through ingestion, inhalation, or dermal pathways. Previous research has found that nanoplastics with diameters of ≤100 nm can translocate into the circulatory system in a dose-dependent manner and potentially impact thrombosis and hemostasis. To investigate the direct effects of microplastics on fibrin clot formation, a simplified ex vivo human thrombin/fibrinogen clot model was utilized. The 100 nm polystyrene particles (non-functionalized [nPS] and aminated [aPS]) were preincubated (0-200 µg/mL) with either thrombin or fibrinogen, and fibrin clot formation was characterized via turbidity and thromboelastography (TEG). When the particles were preincubated with fibrinogen, little effect was observed for aPS or nPS on turbidity or TEG up through 100 µg/mL. TEG results demonstrated a significant impact on clot formation rate and strength, in the case of nPS preincubated with thrombin exhibiting a significant dose-dependent inhibitory effect. In conclusion, the presence of microplastics can have inhibitory effects on fibrin clot formation that are dependent upon both particle surface charge and concentration. Negatively charged nPS exhibited the most significant impacts to clot strength, turbidity, and rate of fibrin formation when first incubated with thrombin, with its impact being greatly diminished when preincubated with fibrinogen in this simplified fibrin clot model.

Addressing the Surface Concentration Discontinuity of the Core-Shell Model for Lithium Iron Phosphate Batteries

This communication addresses the limitation of core-shell enhanced single particle model for lithium iron-phosphate recently published by the authors. In this model, the positive particle surface concentration has a jump discontinuity that forms at the transition from the one-phase to the two-phase region, which is responsible for the positive particle overpotential and open circuit potential jumps seen in the cell output voltage. Such a discontinuity is eliminated by proposing a modification of the core-shell enhanced single particle model based on the bulk-normalized lithium concentration. Simulation results show the effectiveness of the new solution against the previously published one.

Main Results Of The Analysis Of The HOMER Lagrangian Particle Tracking And Data Assimilation Database

In this work, we extend the analysis of Lagrangian Particle Tracking (LPT) and Data Assimilation (DA) algorithms, presented at the ISPIV21 conference, to the case of a turbulent wall-bounded flow interacting with a moving panel. The work is conducted within the European project HOMER and the data is processed by the partners of the project consortium. A synthetic experiment is performed that reproduces the air flow around a cylinder in ground effect, whereby a flexible panel is placed undergoing periodic oscillations. The database comprises two different panel's materials, namely metal and rubber, different marker densities on the panel’s surface and different concentrations of tracer particles in the flow. Images of the flow tracers and of the surface markers are acquired either with a four-camera volumetric imaging setup or with a dual setup composed of four LPT cameras and two Digital Image Correlation (DIC) cameras. Additionally, three image acquisition modes are simulated, namely time-resolved, two-pulse and four-pulse. The data are analyzed in terms of percentages of correctly reconstructed, missed and ghost particles, errors of the measured particles’ positions, velocities and accelerations (LPT analysis) and errors of the reconstructed flow fields, panel’s positions and surface pressures (DA analysis).

Baseline of Surface and Column-Integrated Aerosol Loadings in the Pearl River Delta Region, China

Much attention has been paid to the rapid variation of aerosol loading in the urban areas of the Pearl River Delta (PRD) region. The baseline of aerosol loading in this rapidly developing region is critical in evaluating how and why the aerosol level has evolved, which absolutely requires long-term observations. Based on long-term observations of aerosol optical depth (AOD), visibility, and particulate matter (PM) mass concentrations at Xichong (114.56°E, 22.49°N), a background site in the PRD region, the variabilities of aerosol loading at multiple temporal scales are revealed. The means (±σ) of AOD, visibility, PM10, PM2.5, and PM1 are 0.38 ± 0.07, 12.6 ± 2.3 km, 23.7 ± 12.6 μg/m3, 19.7 ± 11.0 μg/m3, and 16.1 ± 10.1 μg/m3, respectively, which show that aerosol loading at the Xichong site is much lower than that in urban and suburban sites. Significant decreases in PM10, PM2.5, and PM1 mass concentrations are observed with magnitudes up to −2.13, −1.82, and −1.37 yr−1, respectively, at a 95% confidence level. The decrease in aerosol loadings at Xichong is attributed to the strict environmental regulations for improving air quality. Higher AOD and PM (lower visibility) values are observed during the early spring months as a result of long-range transport of biomass burning from Southeastern Asia. Diurnal variations of PM and visibility are dominantly determined by those of boundary layer height and relative humidity. PM mass concentrations show a generally negative (positive) correlation with visibility (AOD) at Xichong, but the correlations are weak with the R2 of 0.22 and 0.54, respectively. Low visibility and high aerosol loading are generally associated with very weak easterly and southerly winds. Understanding of variability of surface particle concentration and column-integrated aerosol loading at this background site in the PRD region would provide a scientific basis for the adoption of pollution prevention and control measures.

The impact of size-segregated particle properties on daily mortality in Seoul, Korea.

To investigate the causative component for certain health outcomes, the associations between the properties of ambient particles and cause-specific mortality (all-cause, cardiovascular, and respiratory-related mortality) measured in Seoul, Korea, from January 1, 2013, to December 31, 2016, were evaluated with a quasi-Poisson generalized additive model (GAM). The total mass of PM10 and PM2.5 moderately affected respiratory-related mortality but had almost no impact on all-cause and cardiovascular-related mortality. Among PM2.5 mass compositions, ammonium sulfate, which is in generally 300-500nm as a secondary species, showed the most statistically significant effect on respiratory-related mortality at lag 4 (p < 0.1) but not for other mortalities. However, from the size-selective investigations, cardiovascular-related mortality was impacted by particle number concentrations (PNCs), particle surface concentrations (PSCs), and particle volume concentrations (PVCs) in the size range from 50 to 200nm with a statistically significant association, particularly at lag 1, suggesting that mass is not the only way to examine mortality, which is likely because mass and chemical composition concentrations are generally controlled by larger-sized particles. Our study suggests that the size-specific mortality and/or impacts of size-resolved properties on mortalities need to be evaluated since smaller particles get into the body more efficiently, and therefore, more diverse size-dependent causes and effects can occur.

Exploring the relationships between ground-measured particulate matter and satellite-retrieved aerosol parameters in China.

In this study, the PM2.5 and PM10 concentrations from 367 cities in China were integrated with MODIS-retrieved aerosol optical depth (AOD) and Angstrom exponent (AE) data to explore the relationship between ground-measured surface particle concentrations and remote-sensing aerosol parameters. The impact of meteorological and topographical factors and seasonality were also taken into consideration and the partial least squares (PLS) regression model was adopted to evaluate the effects of surface particulate matter (PM) concentration and meteorological factors on the variation of aerosol parameters. PM concentrations and aerosol parameters all presented strong spatial disparity and seasonal patterns in China. After implementation of stringent clean air actions and policies, both the ground-measured and satellite-retrieved aerosol parameters revealed that the concentrations of suspended particles in China's cities declined dramatically from 2015 to 2018. The PM/AOD ratio showed conspicuous south-north and west-east differences. The ratio was strongly correlated to meteorological and topographic factors, and it tended to be higher in arid and less polluted regions. Moreover, the dominant factors affecting seasonal PM/AOD ratios varied among China's five regions. The correlations of daily PM-AOD were always strong in southwest China and in basin terrain (e.g., Sichuan Basin and Tarim Basin). In contrast, the PM-AOD correlation was found to be negative in some cities on the Tibetan Plateau because local relative humidity makes a greater contribution to AOD variation. Since the climate is arid and the ratio of coarse particles (e.g., PM10) is much higher, PM tended to have a significantly negative correlation with AE in northwestern cities. Whereas in many southern cities, PM was positively correlated with AE because of the area's high relative humidity and aerosol hygroscopic properties.

Vertical distributions of aerosol microphysical and optical properties based on aircraft measurements made over the Loess Plateau in China

Aerosol microphysical properties, scattering and absorption characteristics, and in particular, the vertical distributions of these parameters over the eastern Loess Plateau, were analyzed based on aircraft measurements made in 2020 during a summertime aircraft campaign in Shanxi, China. Data from six flights were analyzed. Statistical characteristics and vertical distributions of aerosol concentration, particle size, optical properties, including aerosol scattering coefficient (σsp), backscattering ratio (βsc), Ångström exponent (α), single-scattering albedo (SSA), partially-integrated aerosol optical depth (PAOD), and black carbon concentration (BCc), were obtained and discussed. Mean values of aerosol particle number concentration (Na), particle volume concentration (Va), mass concentration (Ma), surface concentration (Sa), and particle effective diameter (EDa) were 854.92 cm−3, 13.37 μm3 cm−3, 20.06 μg/m3, 170.08 μm3 cm−3, and 0.47 μm, respectively. Mean values of BCc, σsp(450, 525, 635 nm), βsp(525 nm), α(635/450), and SSA were 1791.66 ng m−3, 82.37 Mm−1 at 450 nm, 102.57 Mm−1 at 525 nm, 126.60 Mm−1 at 635 nm, 0.23, 1.47, and 0.92, respectively. Compared with values obtained in 2013, Na decreased by 60% and Ma decreased by 45%, but the scattering coefficients increased in different degrees. In the vertical direction, aerosol concentrations were higher at lower altitudes, decreasing with height. Vertical profiles of σsp, βsp, α(635/450), and BCc measured during the six flights were examined. Two peaks in Na were identified near the top of the boundary layer and between 2000 and 2200 m. Fine particles with EDa smaller than 0.8 μm are dominant in the boundary layer and coarse aerosols existed aloft. Aerosol scattering properties and BCc in the lowest layer of the atmosphere contributed the most to the total aerosol radiative forcing. SSA values were greater than 0.9 below 2500 m, with lower values at higher levels of the atmosphere. On lightly foggy days, SSA values were greater than 0.9, and aerosols played a cooling role in the atmosphere. On hazy days, lower-level SSA values were generally greater than 0.85, with aerosols likely having a warming effect on the atmosphere. 48-hour backward trajectories of air masses during the observation days showed that the majority of aerosol particles in the lower atmosphere originated from local or regional pollution emissions, contributing the most to the total aerosol loading and leading to high values of aerosol concentration and radiative forcing.

A new solution to the spherical particle surface concentration of lithium-ion battery electrodes

The lithium-ion concentration of a solid phase is essential to solve the electrochemical model of a lithium-ion battery. Based on the analytic solution of a convolution infinite series, a new algorithm is proposed to efficiently and accurately solve the partial differential equation for the lithium-ion diffusion behavior of electrode particles. Under galvanostatic profiles, the analytic solution is an infinite time series transformed into a converged sum function by using the monotone convergence theorem. Under dynamic profiles, the infinite series solution is simplified to a finite discrete convolution of both the input and the sum function. Meanwhile, the discrete step is determined by the amplitude-frequency characteristic curve, and the sum function is truncated by its characteristic monotonic decay approaching zero over time. Compared with using a professional finite element analysis software, it takes less time to use this discrete convolution algorithm, and it yields less error. And, it has the least solution time with medium accuracy in comparison with two commonly used approximations. Not only that, the proposed algorithm has only two parameters to be determined with little computation, thus promoting the electrochemical models built in battery management systems.

Hydrochemical interactions of phoretic particles: a regularized multipole framework

Abstract

Improving the sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosols of the Weather Research and Forecasting-Chemistry (WRF-Chem) model with the revised Gridpoint Statistical Interpolation system and multi-wavelength aerosol optical measurements: the dust aerosol observation campaign at Kashi, near the Taklimakan Desert, northwestern China

Abstract. The Gridpoint Statistical Interpolation data assimilation (DA) system was developed for the four size bin sectional Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) aerosol mechanism in the Weather Research and Forecasting-Chemistry (WRF-Chem) model. The forward and tangent linear operators for the aerosol optical depth (AOD) analysis were derived from WRF-Chem aerosol optical code. We applied three-dimensional variational DA to assimilate the multi-wavelength AOD, ambient aerosol scattering coefficient, and aerosol absorption coefficient, measured by the sun–sky photometer, nephelometer, and aethalometer, respectively. These measurements were undertaken during a dust observation field campaign at Kashi in northwestern China in April 2019. The results showed that the DA analyses decreased the model aerosols' low biases; however, it had some deficiencies. Assimilating the surface particle concentration increased the coarse particles in the dust episodes, but AOD and the coefficients for aerosol scattering and absorption were still lower than those observed. Assimilating aerosol scattering coefficient separately from AOD improved the two optical quantities. However, it caused an overestimation of the particle concentrations at the surface. Assimilating the aerosol absorption coefficient yielded the highest positive bias in the surface particle concentration, aerosol scattering coefficient, and AOD. The positive biases in the DA analysis were caused by the forward operator underestimating aerosol mass scattering and absorption efficiency. As compensation, the DA system increased particle concentrations excessively to fit the observed optical values. The best overall improvements were obtained from the simultaneous assimilation of the surface particle concentration and AOD. The assimilation did not substantially change the aerosol chemical fractions. After DA, the clear-sky aerosol radiative forcing at Kashi was −10.4 W m−2 at the top of the atmosphere, which was 55 % higher than the radiative forcing value before DA.

Biotin-NeutrAvidin Mediated Immobilization of Polymer Micro- and Nanoparticles on T Lymphocytes.

Cells are powerful carriers that can help to improve the delivery of nanomedicines. One approach to use cells as carriers is to immobilize the nanoparticulate cargo on the cell surface. While a plethora of chemical conjugation strategies are available to bind nanoparticles to cell surfaces, only relatively little is known about the effects of particle size and cell type on the surface immobilization of nanoparticles. This study investigates the biotin-NeutrAvidin mediated immobilization of model polymer nanoparticles with sizes ranging from 40 nm to 1 μm on two different T cell lines, viz., human Jurkat cells as well as mouse SJL/PLP7 T cells, which are of potential interest for drug delivery across the blood-brain barrier. The nanoparticle cell surface immobilization and the particle surface concentration and distribution were analyzed by flow cytometry and confocal microscopy. The functional properties of nanoparticle-modified SJL/PLP7 T cells were assessed in an ICAM-1 binding assay as well as in a two-chamber setup in which the migration of the particle-modified T cells across an in vitro model of the blood-brain barrier was studied. The results of these experiments highlight the effects of particle size and cell line on the surface immobilization of nanoparticles on living cells.

Evidence of inter-particles collision effect in airflow resuspension of poly-dispersed non-spherical tungsten particles in monolayer deposits

Poly-dispersed particle resuspension by turbulent airflow was experimentally studied in a wind tunnel called BISE. The set-up was carefully validated to produce reference airflows with three absolute pressures and friction velocities values. Monolayer deposits of poly-dispersed tungsten particles on tungsten surfaces were used for the experiments. The fraction of detached particles by size bin from 1 μm to 50 μm was quantified to analyze the effects of friction velocity, absolute pressure and particles concentration on surface. Comparison of the results with Rock'n Roll and Monte-Carlo resuspension modeling revealed discrepancies for particles behavior with diameter below 4.5 μm. These discrepancies could not be understood by assessment of particle-surface adhesion force distribution carried out with Atomic Force Microscopy analysis. For particle surface concentrations ranging from 35 to 100 mm−2, a collision effect was identified due to the concentration and poly-dispersion of particles deposited on the surface. Indeed, when analyzing the experimental data, a good linear correlation is obtained between the fraction of the small particles detached and a collision parameter, demonstrating that collisions could be responsible for the unexpectedly high resuspended fraction observed for particle size below 4.5 μm in diameter. The experimental data and the analysis presented in the paper show that particle surface concentration and collision effects are clearly relevant and should be considered in the above-mentioned resuspension models, especially for poly-dispersed particles assessment.