Particle Transport Research Articles

Design and optimization of gradient fibrous media using the method of moments

The goal of this work is to optimize the deposition mass distribution of polydisperse particles inside the fibrous media by modifying the distribution of the fiber packing density across filter depth. Two types of gradient fibrous media with linear and exponential fiber packing density distribution along the flow direction were derived. The method of moments was employed to study the transport and deposition characteristics of polydisperse aerosol particles inside the fibrous media. The reliability of the calculated results by the method of moments was confirmed by the numerical simulations based on the discrete phase model (DPM). Results indicate that the gradient fibrous media allows more particles to transport and deposit into the interior of the fibrous media, which improves the uniformity of particle deposition distribution across filter depth. There exists an optimal fiber packing density distribution ratio for the gradient fibrous media where the non-uniformity of deposition mass distribution of polydisperse particles across filter depth is minimized. In this way, uniform deposition distribution along the flow direction can be generally achieved by optimizing the fiber packing density distribution, which will contribute to the optimal design of microstructures for the fibrous filter.

Behavior of silver tellurite glasses against gamma rays, neutrons, and ions using theoretical and the PHITS Monte Carlo method

Present work analyze the ionizing radiations attenuation behaviour, photon trajectories and dose rate reduction properties of silver tellurite glasses to investigate their potential application in radiation shielding. The shielding capability of five glass systems with different elemental compositions have been calculated with the help of theoretical software: Phy-X/PSD and NIST XCOM. For the photon energy range of 1.00 keV to 100.00 GeV, various shielding parameters are calculated, including attenuation coefficients (MAC, LAC), mean free path, half value layer, tenth value layer, effective atomic number, effective electron density, energy build up factors, energy absorption buildup factors, and fast neutron removal cross section. While the energy stopping potentials, projected range of ions (H+, He+, and C+) has been presented with the help of SRIM software. Additionally photon trajectories and dose rate attenuating behavior of 105 photons generated from 137Cs and 60Co sources with activity 200.00 GBq has been studied with the help of particle and heavy ion transport (PHITS) code. It is observed that at both low and high energy levels, the glass composition, labelled S4, (70TeO2-25Ag2O-2Nb2O5-2BaO-1PbO), exhibits comparable attenuation coefficients to previously recommended glass samples for radiation shielding applications. In addition to S4, nine different types of glass samples and polymers with comparable densities to our glass sample, along with water, were included for comparison. The findings indicate that among all the samples tested, S4 demonstrates the highest and comparable radiation-protective performance, positioning it favourably for such applications.

Conceptual design of the tail research experiment at the Space Plasma Environment Research Facility (SPERF-TREX)

The Space Plasma Environment Research Facility (SPERF) for ground simulation of the space plasma environment is a key component of the Space Environment Simulation Research Infrastructure (SESRI), a major national science and technology infrastructure for fundamental research. It is designed to investigate outstanding issues in the space plasma environment, such as energetic particle acceleration, transport, and interaction with electromagnetic waves, as well as magnetic reconnection processes, in magnetospheric plasmas. The Tail-Research EXperiment (TREX) is part of the SPERF for laboratory studies of space physics relevant to magnetic reconnection, dipolarization and hydromagnetic wave excitation in the magnetotail. SPERF-TREX is designed to carry out three types of experiments: the tail plasmoid for magnetic reconnection, dipolarization front formation, and magnetohydrodynamic waves excited by high-speed plasma jets. In this paper, the scientific goals and three scenarios of SPERF-TREX for typical processes in space plasmas are presented, and experimental plans for SPERF-TREX are also reviewed, together with the plasma sources applied to generate the plasma with the desired parameters and various magnetic configurations.

Monte Carlo simulations of x-ray energy spectra in kilovoltage radiotherapy using the PENELOPE code

The Monte Carlo method was applied using the PENELOPE code to simulate the transport of particles in two different x-ray tubes. This method is considered the most important and accurate for simulations and calculations in different branches of science, including medical physics. The tubes were modeled according to the manufacturer’s specifications, and the simulations were divided into two stages due to the computational time. The scope of the work was to obtain in greater detail photon spectra of different qualities of beams in the orthovoltage range used in radiotherapy, since few works have, yet been developed for this energy range. A detailed analysis was carried out by comparing to the spectra results obtained using the SpekCalc software for the different qualities of radiation in the two stages. Mean energy values along with the first and second half-value layers (HVLs) of each energy were determined with the respective differences between them. Different discrepancies were found in most cases, and so it is vitally important to consider each situation independently. Finally, secondary electron energy spectra in the second stage of each quality were presented with their respective mean energies, an important parameter considered in the dose deposition of the different experimental geometries that use such qualities.

Charge exchange recombination spectroscopy on the alkali beam of Wendelstein 7-X.

Measurements of ion temperature profiles are required to assess the energy and particle transport processes in the Wendelstein 7-X stellarator. This device is equipped with a diagnostic alkali beam, which can be utilized to determine local impurity temperatures and densities by Charge Exchange Recombination Spectroscopy (CXRS). It could provide such profiles in the edge plasma, where other diagnostics are less efficient. With this contribution, first results of CXRS measurements on the sodium beam from the scientific operation phase OP2.1 are presented. The spectroscopic system was in commissioning phase lacking some of the final optical components. Thus, the aim of the diagnostics during this campaign was to explore the measurement capabilities. Based on the processed spectra, the prospects of C5+ and C6+ ion temperature and concentration measurements are discussed. The results indicate that with the final optical setup under installation, the diagnostics could provide ion temperature profiles in the edge with 3mm radial resolution and at least 1s temporal resolution.

Stokes drift in crossing windsea and swell, and its effect on near-shore particle transport in Lofoten, Northern Norway

Transport assessments near the coast are often related to particles drifting near the surface. Such “particles” may be salmon lice, cod eggs, macro plastics or ship debris. Their drift depends on the Eulerian currents and the Stokes drift associated with the wind-generated surface wave field. The Stokes drift must be parameterized, and in doing so, one will inevitably make bulk estimates of the direction and speed of the drift for the wave spectrum. This paper implements a recently proposed parameterization of the Stokes drift vertical profile, which accounts for the effect of swell and windsea that propagate in different directions, to the open-source Lagrangian particle tracking model OpenDrift. We investigate how particles drifting in the Lofoten archipelago in Northern Norway depend on the Stokes drift and how we parameterize it. The parameterization accounting for crossing windsea and swell leads to lower residence time near the coastline than other popular parameterizations in the domain we studied.

Modeling the Concentration Enhancement and Selectivity of Plastic Particle Transport in Sea Spray Aerosols

AbstractBursting bubbles transport bacteria, viruses, and other marine particles across the air‐sea interface. This effect is enhanced when particles are hydrophobic and cling to the bubbles as they rise. Recent studies suggest that plastic particles, a major ocean pollutant, can also be transported by sea spray. However, estimates of plastic transport via this pathway have large uncertainties due to limited size detection techniques in field studies and few lab studies. An understanding of the number and size of particles carried in the smallest drops, which have the longest residence time in the atmosphere, is missing from current literature. Here, we develop a modeling framework to provide bounds on the number, area, and volume transport of non‐scavenged hydrophilic and fully‐scavenged hydrophobic particles of radii between 0.1 and 100 μm for a range of jet and film drops. For droplets containing plastic particulates, we predict particle enrichment is significantly higher in jet drops than film drops. For particles in these jet drops, our results suggest that in the absence of bubble scavenging, the number distribution is dominated by smaller plastics, the mass/volume distribution by larger plastics, and surface area distribution is balanced across plastic size. Whereas for hydrophobic particles, scavenging dramatically modifies these distributions, enhancing certain particle–droplet size combinations by over four orders of magnitude. Our predictions suggest critical effects of enrichment in air‐sea particle transport and highlight the variable dependencies on bubble and particle size, improving our theoretical understanding of plastic and marine particle transport and identifying modeling assumptions to refine with experimental measurements.

On Calculating Diffusion Coefficients Numerically in Synthetic Turbulence Using Particle Pushers

Numerical simulations of test particle transport in the presence of synthetic turbulence with known properties still provide the most reliable estimations of the diffusion coefficients of charged particles in turbulent space plasmas available. The development and implementation of such simulations, however, are far from straightforward. The present study provides a comprehensive treatment of the development and testing of such a simulation code, detailing the simulation of synthetic turbulence and diffusion coefficients, as well as various numerical tests to validate code output. Furthermore, a novel test for such codes is proposed, namely, the transport of charged particles in pure slab turbulence, which proves sensitive to numerical factors prior tests remain insensitive to.

Gyrokinetic simulations of electrostatic microturbulence in ADITYA-U tokamak with argon impurity

The effect of impurity on the electrostatic microturbulence in ADITYA-U tokamak is assessed using global gyrokinetic simulations. The realistic geometry and experimental profiles of the ADITYA-U are used, before and after argon gas seeding, to perform the simulations. Before the impurity seeding, the simulations show the existence of the trapped electron mode (TEM) instability in three distinct regions on the radial-poloidal plane. The mode is identified by its linear eigenmode structure and its characteristic propagation in the electron diamagnetic direction. The simulations with Ar1+ impurity ions in the outer-core region show a significant reduction in the turbulence and transport due to a reduction in the linear instability drive, with respect to the case without impurity. A decrease in particle and heat transport in the outer-core region modifies the plasma density profile measured after the impurity seeding. It, thus, results in the stabilization of the TEM instability in the core region. Due to the reduced turbulence activity, the electron and ion temperatures in the central region increase by about 10%.

Comprehensive new insights on the potential use of SiC as plasma-facing materials in future fusion reactors

The performance of silicon carbide as an alternative plasma facing material (PFM) was studied at various irradiation conditions relevant to ion energies and fluxes of a fusion reactor. This analysis involves detailed modeling of subsurface plasma/material interactions, sputtered particle transport above the surface and redeposition, and related changes in material composition and microstructure induced by steady-state and Edge Localized Mode ion fluxes. Transition of a crystalline SiC surface to semi-crystalline and amorphous phases was analyzed based on advanced modeling of DIII-D tokamak experiments where SiC was irradiated in single- and multiple- L-mode and H-mode discharges. This analysis shows that displacement damage, particle deposition/redeposition, and D accumulation on the SiC divertor surface can lead to significant microstructural changes that result in enhanced sputtering erosion in comparison with the original crystalline material. However, the resulting total net erosion rate for a full-coverage, advanced tokamak, SiC coated divertor may well be acceptably low. Moreover, the C sputtering yield from the evolved SiC surface can be seven times lower than from a pure graphite surface; this would imply significantly reduced tritium co-deposition rates in a D-T tokamak reactor, compared with a pure carbon surface. It was also determined that chemical sputtering of both C and Si should not result in any noticeable effect on the net erosion, for attached plasma regimes. Our results thus show encouraging results overall for use of SiC as a PFM in tokamaks.

Identification of dust sources inside and outside of Iran affecting air quality in the Tehran region

Introduction: Recent climate changes and droughts have exacerbated the impact of dust sources globally, necessitating a thorough understanding of their influence on air quality. In Tehran, the interaction between internal dust sources from Iran and external sources from neighboring countries significantly affects air quality. Materials and methods: This study spans a 20-year period (2003-2022), utilizing satellite data and advanced algorithms to analyze dust event trends and patterns. The material and methods section outlines the use of Aqua satellite MODIS sensor data alongside two algorithms to identify dust sources, focusing on Aerosol Optical Depth (AOD) data during peak dust event seasons. Statistical analysis of dust events in 2022 supplements the investigation. Results: The analysis reveals distinct patterns in dust particle origin and transport, highlighting the predominant contribution of internal dust sources from Iran's southern Semnan province and significant input from external sources in Iraq and northern Saudi Arabia. Examining meteorological conditions during severe dust events highlights the role of synoptic conditions, particularly the presence of a tropospheric trough, in facilitating dust transport. Increased convective motions and downburst occurrences in specific regions further exacerbate the spread of dust particles, particularly those originating from external countries and provinces. Conclusion: The conclusion emphasizes the complex interplay between internal and external dust sources and the necessity of understanding dust emission dynamics for effective mitigation strategies. It calls for proactive measures involving local and regional cooperation to mitigate dust pollution's adverse effects on air quality in Tehran and similar urban centers.

Elasto-inertial focusing and particle migration in high aspect ratio microchannels for high-throughput separation

The combination of flow elasticity and inertia has emerged as a viable tool for focusing and manipulating particles using microfluidics. Although there is considerable interest in the field of elasto-inertial microfluidics owing to its potential applications, research on particle focusing has been mostly limited to low Reynolds numbers (Re<1), and particle migration toward equilibrium positions has not been extensively examined. In this work, we thoroughly studied particle focusing on the dynamic range of flow rates and particle migration using straight microchannels with a single inlet high aspect ratio. We initially explored several parameters that had an impact on particle focusing, such as the particle size, channel dimensions, concentration of viscoelastic fluid, and flow rate. Our experimental work covered a wide range of dimensionless numbers (0.05 < Reynolds number < 85, 1.5 < Weissenberg number < 3800, 5 < Elasticity number < 470) using 3, 5, 7, and 10 µm particles. Our results showed that the particle size played a dominant role, and by tuning the parameters, particle focusing could be achieved at Reynolds numbers ranging from 0.2 (1 µL/min) to 85 (250 µL/min). Furthermore, we numerically and experimentally studied particle migration and reported differential particle migration for high-resolution separations of 5 µm, 7 µm and 10 µm particles in a sheathless flow at a throughput of 150 µL/min. Our work elucidates the complex particle transport in elasto-inertial flows and has great potential for the development of high-throughput and high-resolution particle separation for biomedical and environmental applications.

Density and porosity analyses of porous hybrid microparticles containing gas in closed pores using centrifugal liquid sedimentation-dynamic light scattering combined analytical method.

Porous hybrid microparticles are characterized by their densities and porosities. Consequently, the evaluation for density and porosity of porous hybrid microparticles in liquids is crucial for predicting the transport of particles in the atmosphere, human body, and industrial processes. However, direct measurement of the density and porosity of porous hybrid microparticles in liquids remains a challenge. In this study, we investigated the centrifugal sedimentation of polystyrene-silica hybrid microparticles with and without gas-containing closed pores. A centrifugal liquid sedimentation-dynamic light scattering combined analytical method was employed to determine the apparent densities of hybrid microparticles with and without gas-containing closed pores. The porosity of the hybrid microparticles with gas-containing closed pores was elucidated based on the inner buoyancy, which is a centrifugal force generated by the presence of low-density gas inside numerous closed pores. Further, the inner gas buoyancy was analyzed to estimate the particle porosity in liquids. The results obtained in this study confirmed the feasibility of utilizing the proposed method to determine the apparent density and porosity of porous hybrid microparticles in liquids.

MR-PVHEE: A novel magnetic resonance-guided parallel-beam very high-energy electron radiotherapy system

PurposeMR-guided very high-energy electron (VHEE) radiotherapy can combine the imaging advantages of MR with the dosimetry advantages of VHEE radiotherapy, which is of significant clinical value. However, VHEEs are highly susceptible to the Lorentz force generated by the MR magnetic field, and coupling MR and VHEEs is challenging. Here, we present a novel MR-guided parallel-beam VHEE (MR-PVHEE) radiotherapy system and confirm its feasibility and effectiveness. MethodThe proposed MR-PVHEE radiotherapy system includes an ingenious coupling model of MR and VHEEs and an electromagnetic steering parameters commissioning (ESP-COM) method for accurate delivery. First, by generating parallel VHEE (PVHEE) beamlets that point in the same direction as the MR main magnetic field, the coupling model based on triple-stage electromagnetic steering can significantly lessen the twisting and deflecting of the VHEE beamlets' delivery trajectory caused by the MR magnetic field. The dosimetric advantage of VHEEs will be enhanced by delicately utilizing the MR magnetic field to constrain lateral scatter. Then, the ESP-COM method based on Bayesian black-box optimization for the PVHEE beamlets is designed by constructing a cost function using the position and direction information of particles in phase space and optimizing the parameters to deliver the beamlets accurately to the target spots. Finite element electromagnetic modeling and Monte Carlo particle transport simulation are used to validate the MR-PVHEE. ResultsMR-PVHEE can generate the PVHEE beamlets in the same direction as the MR magnetic field and accurately deliver them to the target spots. The average position error is within 0.5 mm, and the average direction error is about 0.5°, which can meet the requirements of clinical treatment accuracy. MR-PVHEE can reduce the VHEE lateral penumbra and increase the dose drop gradient. ConclusionFor the first time, MR and VHEE radiotherapy are successfully coupled in this study, and the innovative MR-PVHEE radiotherapy system can elicit new modalities for MR-guided charged particle radiotherapy and spatially fractionated radiotherapy.

Transport behavior of particles and evolution of plugging zones in rough fractures: Insights from a novel coupled CFD-DEM model

The meso-mechanism of particle bridging and plugging in rough fractures remains unclear. Therefore, this study explores a novel meso-model for simulating particle transport in rough fractures by combining Computational Fluid Dynamics and Discrete Element Method (CFD-DEM). The dynamic behavior of particles and the corresponding evolution mechanism of plugging zones are investigated. The simulation innovatively uses particle boundaries to correct fluid flow, greatly simplifying the fluid mesh partitioning while ensuring accuracy. The results reveal the connection between particles’ transport and bridging behavior in rough fracture spaces, the distribution characteristics of plugging zones, and fluid flow characteristics. The distribution of bridging favorable zones determines the position and pattern of the front edge of subsequent plugging zones. The stress accumulated by particles has little effect on the strong force chain of the front edge. The force chain strength of the double-particle bridging structure is greater than that of the single-particle bridging structure. Due to weak shear planes, the double-particle bridging structure is more prone to shear failure and instability under external loads. Improving the particle size distribution range can reduce bridging blind zones and achieve better sealing performance. The results provide theoretical help for the design of field operation processes.

Triazole derivatives inhibit the VOR complex-mediated nuclear transport of extracellular particles: Potential application in cancer and HIV-1 infection

Extracellular vesicles (EVs) appear to play an important role in intercellular communication in various physiological processes and pathological conditions such as cancer. Like enveloped viruses, EVs can transport their contents into the nucleus of recipient cells, and a new intracellular pathway has been described to explain the nuclear shuttling of EV cargoes. It involves a tripartite protein complex consisting of vesicle-associated membrane protein-associated protein A (VAP-A), oxysterol-binding protein (OSBP)-related protein-3 (ORP3) and late endosome-associated Rab7 allowing late endosome entry into the nucleoplasmic reticulum. Rab7 binding to ORP3-VAP-A complex can be blocked by the FDA-approved antifungal drug itraconazole. Here, we design a new series of smaller triazole derivatives, which lack the dioxolane moiety responsible for the antifungal function, acting on the hydrophobic sterol-binding pocket of ORP3 and evaluate their structure–activity relationship through inhibition of VOR interactions and nuclear transfer of EV and HIV-1 cargoes. Our investigation reveals that the most effective compounds that prevent nuclear transfer of EV cargo and productive infection by VSV-G-pseudotyped HIV-1 are those with a side chain between 1 and 4 carbons, linear or branched (methyl) on the triazolone region. These potent chemical drugs could find clinical applications either for nuclear transfer of cancer-derived EVs that impact metastasis or viral infection.

Random walk characteristics of particles in slurry pipeline transportation

During the pumping of wet shotcrete in a pipe, the aggregate migrates under various forces. In order to investigate the random walking characteristics of particles in slurry pipeline transportation, particle tracking platform for half-open tubes was constructed. Cement-like slurry colloids were prepared. The particle capture function of high-speed camera was utilized to track the particle movement. Random walk theory was used to analyze the transport trajectories of aggregates with different particle sizes. The transport properties of the particles were quantitatively analyzed. The experimental results showed that cement-like slurry colloids were obtained by using a mixture of powder of xanthan gum, carbomer, polyacrylamide and water mixed in a certain proportion. The trajectory of particle transportation in the slurry pipe had a large correlation with the particle size. In a straight pipe, the smoothest particle trajectories were found in the range of 4.17–6.25 % of the pipe diameter. The spectral dimension was positively correlated with tortuosity and more highly correlated with particle size in pipeline transport. The number of spectral dimensions and tortuosity were negatively correlated with axial walking steps of the particles. This paper provided a new way of thinking to study the particle transportation law in concrete pipeline.

Nano particle distribution in blood via electroosmotic peristaltic flow in a non-uniform wavy membrane base capillaries

ObjectiveThe primary purpose of this article is to undertake a mathematical investigation into the electro osmotically thermally driven transport of solute particles, which are typically on a micro to nano-meter scale, suspended in blood. The study is conducted within a non-uniform porous channel for a Williamson fluid. The main objective of this research is to explore the interactions and consequences of solute particles and nanoparticles in the Esophagus, particularly regarding their potential applications in drug delivery and biomedical engineering, especially in the context of electroosmotic non-Newtonian fluids. SignificanceThis research also has significant implications for microscale physiological phenomena. In this investigation, blood serves as the base fluid, and a nanofluid is created by introducing Nickel and Cobalt nanoparticles into the blood. Both nanoparticles have critical medical applications, especially in drug delivery and cancer treatment. To delve deeper into the study of nanomedicine delivery, Nickel and Cobalt nanoparticles are introduced into the blood alongside other smaller solute particles. MethodologyThe mathematical modeling is conducted in a rectangular coordinate system, and the governing flow equations are linearized using approximations that consider low Reynolds numbers and large wavelengths. The numerical solution is computed for a coupled set of nonlinear equations that describe the profiles of fluid-particle velocity, temperature, and fluid-particle composition. The study explores the influence of various key parameters and presents these effects through graphical representations. FindingsIt is observed that an increase in the suspension concentration and the Williamson fluid parameter leads to higher fluid velocity, while the temperature distribution exhibits the opposite trend. The introduction of nanoparticles into the fluid decelerates the flow and raises the temperature.

The hazardous protective glass material for gamma, neutrons, and behaviors of charged particles: Results of adding barium oxide concentrations

The objective of this research is to examine the effectiveness of gamma and neutron shielding, as well as to investigate the behavior of charged particles in glass compositions with the formula xBaO:5SnO2:10Na2O:10CaO:10Li2O: (65-x)SiO2. These glass compositions will be created using the melt quenching technique (MQT). The findings indicated that the physical characteristics, such as density and molar volume, exhibited a comparable pattern. The gamma-ray shielding capacity of the glass system was assessed by comparing it with theoretical, simulation, and experimental values obtained using WinXCom, PHITS (Particle and Heavy Ion Transport Code System) Monte Carlo simulation, and Compton scattering technique (CST), respectively. The results revealed that the total attenuation (μm), effective atomic number (Zeff), and electron density (Nel) exhibited a consistent increase with higher BaO contents. Additionally, this increase led to a decrease in scattering energy within the Compton energy range. The half-value layer (HVL) exhibited superior shielding characteristics compared to alternative substances. Furthermore, the addition of more BaO atoms in the glass structure results in an increased ability of the material to stop the motion of charged particles with larger mass. Conversely, lower concentrations of BaO demonstrate an efficient barrier against fast neutrons. The simulation revealed that BaO can be utilized as an additive in glass materials to enhance their radiation shielding properties in environments with high levels of radiation.

Diagnosing the Particle Transport Mechanism in the Pulsar Halo via X-Ray Observations

Pulsar halos (also termed “TeV halos”) are a new class of γ-ray sources in the Galaxy, which manifest as extended γ-ray emission around middle-aged pulsars, as discovered around the Geminga pulsar, the Monogem pulsar, and PSR J0622+3749 by the High-Altitude Water Cherenkov Observatory and the Large High-Altitude Air Shower Observatory. A consensus has been reached that the teraelectronvolt emission comes from the inverse Compton scattering of escaping electrons/positrons from the pulsar wind nebula of the soft background radiation field, while the particle transport mechanism in the halo is still in dispute. Currently, there are mainly three interpretations: the isotropic, suppressed diffusion model; the isotropic, unsuppressed diffusion model that considers the ballistic propagation of newly injected particles; and the anisotropic diffusion model. While the predicted γ-ray surface brightness profiles of all three models can be more or less consistent with the observations, the implications of the three models for cosmic-ray transport mechanisms and the properties of the interstellar magnetic field are quite different. In this study, we calculate the anticipated X-ray emission of pulsar halos under the three models. We show that the synchrotron radiation of these escaping electrons/positrons can produce a corresponding X-ray halo around the pulsar and that the expected surface brightness profiles are distinct in the three models. We suggest that sensitive X-ray detectors of a large field of view (such as eROSITA and the Einstein Probe) with a reasonably long exposure time are crucial to understanding the formation mechanism of pulsar halos and can serve as a probe of the properties of interstellar turbulence.