Effective Particle Diameter Research Articles

Structural Changes of the Lipid Model Systems in the Presence of Enzymes or Silver Nanoparticles

This work aimed to study the interaction of silver nanoparticles (AgNP) and lipases with models of biological membranes based on natural phospholipid and cholesterol. The crude phosphatidylcholine from egg yolk (PCe1) and synthetic cholesterol (Chol) were obtained from Sigma-Aldrich. Porcine pancreatic lipase (PPL) was obtained by purification from the hog pancreas. AgNP dispersion was prepared by the well-known citrate method. Measurement of surface tension (ST) was carried out using a BPA-1P device. The equilibrium surface tension (eST) was obtained by calculating the ST-time isotherms using the ADSA program. The particle sizes were determined by the dynamic light scattering method. An addition of AgNPs led to a pronounced decrease in both ST and eST (whereas almost no changes occurred by lipase addition), and AgNPs destructed the large lipid particles. The average lipid particle diameter values changed drastically, whereas the effective particle diameter values were almost the same by lipase addition. Thus, the interactions of AgNPs or lipase with the mixture of natural phospholipid and cholesterol have had entirely different features. These effects are interesting for modeling the interactions of inorganic and organic compounds with biological membranes.

Screening of frozen-thawed conditions for keeping nutritive compositions and physicochemical characteristics of goat milk

Frozen milk can help producers overcome the seasonality of goat milk production, low goat production and short lactation periods, and avoid discarding milk during some special periods. We investigated effects of combination between freezing (cryogenic refrigerator of -16 to -20°C or ultra-cryogenic refrigerator of -76 to -80°C) and thawing (homeothermy of 20 to 25°C or refrigeration of 2 to 4°C) on nutritive compositions and physicochemical characteristics of raw goat milk during storage period (80 d). Compared with fresh goat milk, the frozen-thawed milk decreased contents of fat, protein, and lactose, as well as surface tension and stability coefficient, whereas increased effective diameter and polydispersity index. The average values of color values (L*, a*, and b*) in 4 group samples changed from 83.01 to 82.25, -1.40 to -1.54, 3.51 to 3.81, respectively, and the ΔE of most samples did not exceed 2. In contrast to the other 3 frozen-thawed treatments, goat milk treated with ultra-cryogenic freezing-homeothermic thawing (UFHT) possessed higher fat (5.20 g/100 g), smaller effective particle diameter (0.32 µm), and the lowest polydispersity index value (0.26). The color and confocal laser scanning microscopy images of UFHT were similar to those of fresh goat milk, illustrating UFHT was the optimal approach to maintain the natural quality of goat milk. Our finding provides a theoretical basis for producers to freeze surplus milk.

Passive Remote Sensing of Ice Cloud Properties at Terahertz Wavelengths Based on Genetic Algorithm

Ice clouds play a critical role in the balance of the earth–atmosphere radiation system, but there are some limitations in the existing remote sensing methods for ice clouds. Terahertz wave is expected to be the best waveband for retrieving ice clouds, with terahertz wavelengths in the order of the size of typical ice cloud particles. An inversion method for the remote sensing of ice clouds at terahertz wavelengths based on genetic algorithm is proposed in this paper. First, suitable channel sets in the terahertz band, which are mainly a combination of absorption lines and window regions, are determined. Then, to improve the efficiency of the generation of the retrieval database, based on the brightness temperature simulated by the atmospheric radiative transfer simulator (ARTS) for different cloud parameters, a fast forward operator is constructed using three-dimensional interpolation to simulate the brightness temperature difference between clear sky and a cloudy scene. Finally, an inversion model to retrieve the ice cloud base height, the effective particle diameter and the ice water path is established based on the genetic algorithm, and an analysis of the inversion errors is performed. The results show that the forward operator, constructed by the nearest interpolation, can accurately calculate the brightness temperature difference at a high speed. The proposed inversion method at terahertz wavelengths based on the genetic algorithm can achieve the expected scientific requirement. The absolute error of the cloud height is around 0.2 km, and the absolute error of the low ice water path (below 20 g/m2) is small, while the relative error of the high ice water path is generally maintained at around 10%, and the absolute error of the effective particle diameter is mostly around 4 μm.

Capturing Aerosol Particles in a Device with a Regular Pulsating Nozzle

The paper is dedicated to reducing the technogenic impact on the environment of using highly efficient apparatus for the complex exhaust gas treatment, operating in the advanced turbulence regime – an apparatus with a regular pulsating nozzle (RPN). Devices with on-load tap-changers are characterized by high efficiency of capturing solid particles of different dispersion (e.g., fog, dust, and smoke), the possibility of self-cleaning of contact elements from sticky dust, low material consumption, and high reliability in operation. Purpose of the study – to obtain analytical solutions for assessing the efficiency of capturing polydisperse aerosols in an apparatus with an on-load tap-changer due to diffusion and inertial mechanisms. The paper proposes a new solution for the minimum effective diameter of aerosol particles that can be captured in devices with an on-load tap-changer and can be used for a wide range of diameters of absorbing liquid droplets and their number in the volume of the apparatus. The calculations allow us to say that the minimum effective diameter of aerosol particles captured by liquid drops in an apparatus with an on-load tap-changer is less than 0.3 microns.

Interaction of Lipase with Lipid Model Systems

The aim of this work was to study the interaction of lipases (as an important biopolymer) with models of biomembranes based on the phospholipid and cholesterol. Lipases (triacylglycerolacyl hydrolases) are widely distributed enzymes and well-known by their hydrolytic activity. The study of the lipase interactions with lipid vesicles in aqueous dispersions is of fundamental and practical interest. The pure phosphatidylcholine from egg yolk (ePC) and cholesterol (Chol) were obtained from Sigma-Aldrich. Lipase was obtained from hog pancreas. Measurements of the current and equilibrium surface tension (ST and eST) values were carried out using a BPA-1P device and ADSA program. The particle sizes in the prepared colloidal solutions were determined by the method of dynamic light scattering. An addition of lipase led to some decrease both, of ST and eST for the samples of ePC:Chol (in the ratios from19:1 to 1:1). The mean particle diameter (MPD) and effective particle diameter (EPD) values for the samples of ePC:Chol changed drastically by lipase addition. The EPD/MPD ratios increased from 1.7 to 2.0, from 1.8 to 2.6, from 2.3 to 6.5, from 1.5 to 2.9 for the samples of ePC:Chol at the ratios of 19:1, 14:1, 9:1, 7:1, respectively by lipase concentration increase. This general tendency can be explained by strong interaction of lipase with lipid membrane that leads to the formation of the mixed particles ePC:Chol:lipase with more narrow particle size distribution as compared to the initial EPD/MPD ratio (for the ePC:Chol mixture without lipase).

Effects of pressure, shear, temperature, and their interactions on selected milk quality attributes

The effects of pressure, temperature, shear, and their interactions on selected quality attributes and stability of milk during ultra-shear technology (UST) were investigated. The UST experiments include pressure (400 MPa) treatment of the milk sample preconditioned at 2 different initial temperatures (25°C and 15°C) and subsequently depressurizing it via a shear valve at 2 flow rates (low: 0.15-0.36 g/s; high: 1.11-1.22 g/s). Raw milk, high-pressure processed (HPP; 400 MPa, ~40°C for 0 and 3 min) and thermal treated (72°C for 15 s) milk samples served as the controls. The effect of different process parameters on milk quality attributes were evaluated using particle size, zeta potential, viscosity, pH, creaming, lipase activity, and protein profile. The HPP treatment did not cause apparent particle size reduction but increased the sample viscosity up to 3.08 mPa·s compared with 2.68 mPa·s for raw milk. Moreover, it produced varied effects on creaming and lipase activity depending on hold time. Thermal treatment induced slight reduction in particle size and creaming as compared with raw milk. The UST treatment at 35°C reduced the effective diameter of sample particles from 3,511.76 nm (raw milk) to 291.45 nm. This treatment also showed minimum relative lipase activity (29.93%) and kept milk stable by preventing creaming. The differential effects of pressure, shear, temperature, and their interactions were evident, which would be useful information for equipment developers and food processors interested in developing improved food processes for dairy beverages.

Diffusion of ellipsoidal granular particles in shear flow

AbstractThe diffusion of nonspherical particles has not been well understood due to the complexity of their contact mechanics and self‐organization of their orientations. We perform discrete element method simulations of monodisperse ellipsoids in a shear flow with Lees‐Edwards boundary conditions to quantify the relation between the diffusion coefficient and the flow parameters. The results indicate that the particle aspect ratio strongly affects the diffusion coefficient by influencing the particle orientation and alignment. We develop a scaling law for the diffusion coefficient perpendicular to the flow direction, Dyy, which combines the influences of the shear rate , the solids fraction f, the effective particle diameter deff and the particle aspect ratio Z. We show that , where kd is a dimensionless pre‐factor, and a fit is obtained for the functional form of χ(f, Z). This scaling law will be useful in developing continuum transport models for applications.

The role of DME addition on the evolution of soot and soot precursors in laminar ethylene jet flames

Dimethyl ether (DME) has received considerable attention as a fuel additive to reduce the emission of particulate matter (PM) due to its low-temperature chemistry, molecularly bound oxygen atom and the absence of CC bonds. However, the effect of DME addition on the evolution of soot and particularly soot precursors is not entirely understood. This study aims to shed light on this issue by blending different proportions of DME with diffusion, E60, and partially premixed, PP12, base cases of laminar ethylene flames using the Yale benchmark burner. Laser-induced fluorescence (LIF) intensity and decay time are used to characterize the structure and evolution of soot precursors, while laser-induced incandescence (LII) is utilized to determine the soot volume fraction (SVF) and the effective primary particle diameter (Dp). For the diffusion flames, the addition of 10% DME increases the concentrations of both soot and soot precursors. With the further addition of DME to 20%, the SVF decreases to levels similar to those of E60 and then decreases further with 30% DME addition. All diffusion flames with DME addition exhibit higher concentrations of soot precursors than those of the reference E60 case. For PP12, the addition of 10% DME shows similar concentrations of soot precursors and a slight reduction in the SVF which continues to decrease with further increases in DME additions to the PP12 flame. The addition of DME seems to have little effect on the soot particle diameters for all the studied flames. Overall, the PP flames result in smaller mean particle diameters than the diffusion flame counterparts.

Model of destruction of montmorillonite crystal structure in a microwave field

We address amorphization of montmorillonite crystal structure. Powdered montmorillonite samples with an effective particle diameter 630 micrometers were treated by a microwave field with frequency 2,45 GHz and power 750 W for ten minutes in different environments. The first sample was treated in an air environment, the second one in a humid environment. The third sample was a ceramic mass with 10 percent concentration of mixing water (with respect to the total mass). The model describing amorphization is based on results of X-ray analysis. Activation energies were evaluated for covalent and ionic bounds of oxygen ions, hydroxyl groups, and silicon (aluminum) ions. It is shown that the amorphization is carried out in four stages. In fractions of the energy consumption of the last stage the first one consumes 7-9 percent, the second one takes 13-15 percent, and the third one takes 49-59 percent.

Vertical characteristics of aerosol hygroscopicity and impacts on optical properties over the North China Plain during winter

Abstract. The water uptake of aerosol influences its optical depth and capacity for cloud formation, depending on the vertical profile of aerosol hygroscopicity because of different solar radiation received and supersaturation (SS) conditions at different atmospheric levels. Such information is lacking over the polluted East Asian region. This study presents aircraft-based in situ measured aerosol size distributions and chemical compositions by a series of flights over the Beijing area in wintertime. Under high relative humidity (hRH) conditions (surface RH > 60 %), a significant enhancement of aerosol hygroscopicity parameter (κ) in the planetary boundary layer (PBL) was observed to increase by 50 % from 0.20 up to 0.34 from the surface to the top of the PBL (vertical gradient of ∼0.13 km−1), along with the dry particle effective diameter (Deff) being increased by 71 % and activation ratio up to 0.23 (0.64) at SS =0.05 % (0.1 %). However, a lower vertical gradient of κ (0.05 km−1) and smaller Deff was exhibited under low RH (lRH, surface RH < 60 %). This suggests that the aqueous processes played an important role in promoting the enhancement of particle hygroscopicity in the PBL. The κ in the lower free troposphere (LFT) was relatively stable at 0.24±0.03 with a slight increase during regional transport. The enhancement of aerosol optical depth (AOD) due to water uptake ranged 1.0–1.22 for the PBL under lRH and LFT, but it reached as high as 6.4 in the PBL under hRH. About 80 % and 18 % of the AOD were contributed to by aerosol hygroscopic growth under hRH and lRH, respectively. These results emphasize the important evolution of aerosol water-uptake capacity in the PBL, especially under the high RH condition.

Full‐Field Modeling of Heat Transfer in Asteroid Regolith: 1. Radiative Thermal Conductivity of Polydisperse Particulates

AbstractCharacterizing the surface material of an asteroid is important for understanding its geology and for informing mission decisions, such as the selection of a sample site. Diurnal surface temperature amplitudes are directly related to the thermal properties of the materials on the surface. We describe a numerical model for studying the thermal conductivity of particulate regolith in vacuum. Heat diffusion and surface‐to‐surface radiation calculations are performed using the finite element (FE) method in three‐dimensional meshed geometries of randomly packed spherical particles. We validate the model for test cases where the total solid and radiative conductivity values of particulates with monodisperse particle size frequency distributions (SFDs) are determined at steady‐state thermal conditions. Then, we use the model to study the bulk radiative thermal conductivity of particulates with polydisperse, cumulative power law particle SFDs. We show that for each polydisperse particulate geometry tested, there is a corresponding monodisperse geometry with some effective particle diameter that has an identical radiative thermal conductivity. These effective diameters are found to correspond very well to the Sauter mean particle diameter, which is essentially the surface area‐weighted mean. Next, we show that the thermal conductivity of the particle material can have an important effect on the radiative component of the thermal conductivity of particulates, especially if the particle material conductivity is very low or the spheres are relatively large, owing to non‐isothermality in each particle. We provide an empirical correlation to predict the effects of non‐isothermality on radiative thermal conductivity in both monodisperse and polydisperse particulates.

Experimental study of the intrinsic permeability of municipal solid waste

Changing patterns of municipal solid waste (MSW) management, for example sorting for recycling and mechanical–biological treatment (MBT), will change the nature of the residual material going to landfill and in particular its intrinsic permeability. This is an important parameter, not least because of its influence on gas and leachate flows and the ramifications for gas and leachate management. This paper reports the results of laboratory permeability tests on specimens of MSW recovered from boreholes drilled in a Chinese landfill, under both liquid and gas flow. The test results are used to assess the intrinsic permeability of the waste, and are compared with corresponding data from raw and MBT municipal solid wastes from developed countries in the context of differences in waste composition, porosity and particle size. For the Chinese waste, the intrinsic permeability decreased with depth, while at a given depth the permeability determined with gas flow was consistently larger than that determined with liquid flow. Intrinsic permeabilities determined in liquid flow showed no clear trend of variation with effective particle diameter d10, but reduced with drainable porosity (the drainable porosity, ne, being a more appropriate and useful measure than the total porosity, n). Conversely, intrinsic permeabilities determined in gas flow showed a clear decrease with decreasing d10, but no consistent variation with porosity. These differences are potentially significant in assessing the impacts and interactions between gas and liquid flows; some reasons for them are suggested.

The effect of fine particle influence on numerical simulation of bidisperse fluidized bed

In this paper, we consider methods for choosing the effective diameter of solid particles for fluidized bed modeling using the Euler-Euler approach to describing a multiphase medium. Calculations are carried out for the modal average diameter Dmod and average diameter of Sauter D32. Studies have also been conducted for the bidisperse composition of particles, with separation into large and small fractions. The results of numerical simulation were compared with experimental data.

Biochar filters as an on-farm treatment to reduce pathogens when irrigating with wastewater-polluted sources

Microbial contamination of vegetables due to irrigation with wastewater-polluted streams is a common problem around most cities in developing countries because wastewater is an available source of water and nutrients but wastewater treatment is often inadequate. On-farm treatment of polluted water is a feasible option to manage microbial risks in a multi-barrier approach. Current evidence indicates good suitability of biochar filters for microbe removal from wastewater using the hydraulic loading rate (HLR) designed for sand filters, but their suitability has not been tested under on-farm conditions. This study evaluated the combined effect of several variables on removal of microbial indicators from diluted wastewater by biochar filtration on-farm and the correlations between removal efficiency and HLR. Columns of biochar with three different effective particle diameters (d10) were fed with diluted wastewater at 1x, 6x, and 12x the design HLR and two levels of water salinity (electrical conductivity, EC). Influent and effluent samples were collected from the columns and analyzed for bacteriophages (ɸX174 and MS2), Escherichia coli, Enterococcus spp., and Saccharomyces cerevisiae. Microbe removal decreased with increasing HLR, from 2 to 4 to 1 log10 for bacteria and from 2 to 0.8 log10 for viruses, while S. cerevisiae removal was unaffected. Effective particle diameter (d10) was the main variable explaining microbe removal at 6x and 12x, while EC had no effect. Correlation analysis showed removal of 2 log10 bacteria and 1 log10 virus at 3x HLR. Thus biochar filters on-farm would not remove significant amounts of bacteria and viruses. However, the design HLR was found to be conservative. These results, and some technical and management considerations identified, can assist in the development of a scientific method for designing biochar filters for on-farm and conventional wastewater treatment.

A physical model of the high‐frequency seismic signal generated by debris flows

AbstractWe propose a physical model for the high‐frequency (>1 Hz) spectral distribution of seismic power generated by debris flows. The modeled debris flow is assumed to have four regions where the impact rate and impulses are controlled by different mechanisms: the flow body, a coarser‐grained snout, a snout lip where particles fall from the snout on the bed, and a dilute front composed of saltating particles. We calculate the seismic power produced by this impact model in two end‐member scenarios, a thin‐flow and thick‐flow limit, which assume that the ratio of grain sizes to flow thicknesses are either near unity or much less than unity. The thin‐flow limit is more appropriate for boulder‐rich flows that are most likely to generate large seismic signals. As a flow passes a seismic station, the rise phase of the seismic amplitude is generated primarily by the snout while the decay phase is generated first by the snout and then the main flow body. The lip and saltating front generate a negligible seismic signal. When ground properties are known, seismic power depends most strongly on both particle diameter and average flow speed cubed, and also depends on length and width of the flow. The effective particle diameter for producing seismic power is substantially higher than the median grain size and close to the 73rd percentile for a realistic grain size distribution. We discuss how the model can be used to estimate effective particle diameter and average flow speed from an integrated measure of seismic power. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.

Simulation of Remote Sensing of Clouds and Humidity From Space Using a Combined Platform of Radar and Multifrequency Microwave Radiometers

AbstractThis study presents a simulated simultaneous retrieval of mass mean cloud ice particle effective diameter, ice water content, water vapor, and temperature profiles using a combination of a 94‐GHz cloud radar and multifrequency (118, 183, 240, 310, 380, 664, and 850 GHz) millimeter‐ and submillimeter‐wave radiometers from a space platform. The retrieval capabilities and uncertainties of the combined radar and microwave radiometers are quantified. We show that this combined active and passive remote sensing approach with SmallSat technologies addresses a gap in the current state‐of‐the‐art remote sensing measurements of ice cloud properties, especially deriving vertical profiles of ice cloud particle sizes in the atmosphere together with the ambient thermodynamic conditions. Therefore, this new approach can serve as a plausible candidate for future missions that target cloud and precipitation processes to improve weather forecasts and climate predictions.

Experimental study on evaluation of effective diameter for non-spherical particles in predicting pressure gradients of water/air two-phase flow in particle beds

To evaluate the adequacy of the effective diameter (dsd and deq) of non-spherical particles in predicting pressure gradients of upward air/water two-phase flow through well-packed beds, a set of experiments were performed using four kinds of cylindrical particles under isothermal conditions varying the superficial air velocity (0–0.8 m/s) with no water inflow at the bottom. The measured pressure gradients were compared with the existing models and the proposed model from our previous study adopting dsd or deq. Consequently, the proposed model adopting deq predicts the pressure gradients of two-phase flow through non-spherical particle beds much better than the existing models, which is reducing the uncertainty in evaluating long-term coolability of ex-vessel debris bed composed of irregular shaped particles.

Pressure Drops and Dryout Heat Fluxes of Packed Beds with Cylindrical Particles

Motivated by reducing the uncertainties in coolability analysis of a debris bed formed in severe accident of nuclear reactors, the pressure drops of single-/two-phase flow and dryout heat fluxes of the packed beds with non-spherical particles are investigated in the present study. Both adiabatic single-/two-phase flow tests and boiling tests are performed on a particulate porous bed packed with cylindrical particles separately, the pressure drops and dryout heat fluxes under different conditions are measured to identify and validate the debris coolability analysis models. The results show that for a particulate bed packed with non-spherical particles such as cylinders, the effective particle diameter can be represented by the equivalent diameter of the particles, which is the product of Sauter mean diameter and the shape factor. Given this diameter, the measured pressure drops and the dryout heat fluxes are comparable with the predictions of Reed model. Comparing with the cooling scheme of top-flooding case, the bottom injection improves the dryout heat flux significantly.

An Equivalent Spherical Particle System to Describe Characteristics of Flow in a Dense Packing of Non-spherical Particles

Effective characteristics, such as the effective particle diameter and hydraulic radius, are usually used to determine the pressure loss associated with single-phase flow through an isotropic, dense non-spherical granular packing. These quantities can be considered as those of an equivalent spherical particle system. This paper reviews different methods to select effective particle diameters taking into account the effect of particle shape. A new method is proposed to determine an equivalent spherical particle system with both the hydraulic radius and the pressure loss equivalent to those in the actual non-spherical particle packing. This equivalent system can be used to determine the characteristics of flow in the actual system. The analyses provide theoretical justification for adoption of proper effective particle diameters and porosity as well as the dependency of Ergun–Kozeny constant on the shape factor of particles. It is also shown theoretically that the critical Reynolds number for Darcian flow depends on the porosity and the shape factor of particles.

Defining the optimal morphology of Rhn nanoparticles for efficient hydrazine adsorption: a DFT-D3 study

The catalytic decomposition of hydrazine using metallic nanoparticles has recently attracted considerable attention as this provides a promising means for highly efficient hydrogen release desired for a cleaner economy; however, the efficient catalytic nanoparticles model is still controversial. To shed further light on the optimal morphology of rhodium nanoparticles reported as the most efficient catalyst for this reaction, a more realistic nanocluster (Rhn) model is implemented here to compare the adsorption energies of hydrazine on these nanoclusters using the density functional theory. These nanoclusters (Rhn) comprise a varied number of Rh atom (n = 13–201), with their pre-constructed shapes but further defined by the highest energy optimization. Our calculations unravel that the vertex atoms of an Rhn nanocluster are the most favoured sites for N2H4 adsorption, in comparison with edge atoms or inner atoms of facets. Notably, the computed adsorption energies (Eads) clearly exhibit a linear dependence on their sizes effective particle diameter (r), with the equation Eads = − 1.30 + (− 0.24) r established. Further calculations on the introduction of adatoms to the regular nanoclusters demonstrated that the stepped facet plays a decisive role in determining the adsorption energy. Moreover, the electronic structure and charge transfer calculations revealed the dative-type binding nature of the N–Rh bond. These results highlight the importance of a more realistic particle model used for such adsorption studies and provide new insights into the design and development of nanocatalysts for the decomposition of hydrazine.