Particle Retention Research Articles

Effect of tortuosity on retention of aerosol particles through small curved concrete cracks

In the case of incomplete failure of concrete containment, penetration of aerosol through concrete cracks is an important influence factor for the radiological assessment released from concrete containment. The small concrete cracks with curved flow channel have good retention effect on the aerosol penetration. However, a conservative method, aerosol assumed as pure gas leakage without any retention, is used for source term evaluation for nuclear power plant, due to the lack of the knowledge of the aerosol retention with concrete cracks. In this paper, one artificial straight crack and three curved cracks with tortuosity of 1.09, 1.13 and 1.36 formed by tensile shear, are studied in the airflow characterization tests and aerosol penetration tests. The flow characteristic height of concrete crack is obtained by the Suzuki flow formula to solve the problem that the tiny height of concrete crack cannot be measured directly. Compared with the straight crack, increasing the tortuosity is of great significance to the penetration of submicron particles. Larger particle diameter and higher pressure-difference will reduce the penetration of particles due to the increase of particle inertia. Based on the mechanism of inertial deposition, an empirical correlation expressed with the leakage flow rate and tortuosity has been proposed to evaluate the particle penetration, which is validated with the results of aerosol retention inside concrete crack with a tortuosity of 1.27.

Sensitivity analysis of a particle retention model and application to a pressurised sand bed filter for drip irrigation

Sensitivity analysis of a particle retention model and application to a pressurised sand bed filter for drip irrigation

Motion characteristics and residence time of particles in the new cross structure under constant-pulse condition

The residence time of particles in the flow field is highly sensitive to the fluid’s flow characteristics and the particles’ motion. We proposed a dynamic entry mode with the constant-pulse (CP) condition in response to the conditions of symmetric impinging streams and asymmetric impinging streams. Single-particle motion behaviors and particle residence time in a novel cross-type structure reactor we designed were studied and discussed in this article. This was done by looking at how these variables changed depending on the impulse inlet velocity conditions, the reactor geometry, and the particle properties. The results demonstrate that when particle relaxation time is short, those particles without oscillatory motions were directly accelerated to leave the active area. When its relaxation time is reasonably set, even a single particle can hugely elevate the oscillatory motions. With the structure of the novel cross type, the particle merely exhibits three oscillatory under the condition of the symmetric pulse inlet flow and asymmetric pulse inlet flow, notwithstanding, CP contains at least three oscillatory motions. The t tot is the duration that an individual particle spends in the working region. The t tot and active area were affected by inlet velocity, parameters of particles and the shape of the reactor parameters of particles and the shape of the reactor. The t tot raised with τ* increased in a certain range. T is the inlet velocity variation period. The particle resides time at T = T b reaches a maximum in the CP. The maximum residence times T b was affected by particle relaxation time, under CP with a diameter ratio of 5 and inlet velocity difference of 0.8. The particle retention time in the novel cross-type structure reactor was heightened by 7 times. The CP and the novel cross-type structure reactor can improve the retention time of particles in the flow field.

Euler-Euler CFD simulation of high velocity gas injection at pool scrubbing conditions

Pressure relief by blowdown is one of the most important measures to prevent excessive pressures in the primary circuit or containment in severe nuclear accidents. Pool scrubbing can significantly reduce the release of radioactive materials, e.g., aerosols, to the environment during the pressure relief. The decontamination factor indicating the particle retention efficiency depends, among other factors, on the hydrodynamic conditions of the gas-liquid two-phase flow inside the pool. In the present work, the hydrodynamics in two typical pool scrubbing experiments is investigated with the two-fluid model, and the influence of some key factors including bubble diameter, nozzle submergence as well as interaction models are analysed. One case is a rectangular pool and the other is a cylindrical column, and their injection Weber number is around 2×103 and 4×105, respectively. The numerical results show that as the distance from the nozzle exit increases, the void fraction and velocity field expand from the central region, where the nozzle is located, to the whole cross section. The profile and its development depends largely on the bubble size and the interaction force model. It reveals that in the monodisperse simulation, the tuning of bubble diameter is necessary for achieving good agreement, although it is difficult for high velocity gas injection. More information is required to properly describe the bubble size distribution as well as its evolution in pool scrubbing conditions. Furthermore, the experimental data show clear drag reduction in the bubble swarm generated by the gas jet, and the mechanism and model improvement possibilities need to be investigated.

Low-Gradient Magnetophoresis of Nanospheres and Nanorods through a Single Layer of Paper.

The possible magnetophoretic migration of iron oxide nanoparticles through the cellulosic matrix within a single layer of paper is challenging with its underlying mechanism remained unclear. Even with the recent advancements of theoretical understanding on magnetophoresis, mainly driven by cooperative and hydrodynamics phenomena, the contributions of these two mechanisms on possible penetration of magnetic nanoparticles through cellulosic matrix of paper have yet been proven. Here, by using iron oxide nanoparticles (IONPs), both nanospheres and nanorods, we have investigated the migration kinetics of these nanoparticles through grade 4 Whatman filter paper with a particle retention of 20-25 μm. By performing droplet tracking experiments, the real-time stained area growth of the particle droplet on the filter paper, under the influences of a grade N40 NdFeB magnet, were recorded. Our results show that the spatial and temporal expansion of the IONP stain is biased toward the magnet and such an effect is dependent on (i) particle concentration and (ii) particle shape. The kinetics data were first analyzed by treating it as a radial wicking fluid, and later the IONP distribution within the cellulosic matrix was investigated by optical microscopy. The macroscopic flow front velocities of the stained area ranged from 259 μm/s to 16 040 μm/s. Moreover, the microscopic magnetophoretic velocity of nanorod cluster was also successfully measured as ∼214 μm/s. Findings in this work have indirectly revealed the strong influence of cooperative magnetophoresis and the engineering feasibility of paper-based magnetophoretic technology by taking advantage of magnetoshape anisotropy effect of the particles.

Impact Deposition Behavior of Al/B4C Cold-Sprayed Composite Coatings: Understanding the Role of Porosity on Particle Retention.

This study explores the role of porosity in the impact deposition of a ceramic-reinforced metal-matrix (i.e., Al/B4C) composite coating fabricated via cold spraying. The Johnson-Holmquist-Beissel constitutive law and the modified Gurson-Tvergaard-Needleman model were used to describe the high strain-rate behavior of the boron carbide and the aluminum metal matrix during impact deposition, respectively. Within a finite element model framework, the Arbitrary Lagrangian-Eulerian technique is implemented to explore the roles of reinforcement particle size and velocity, and pore size and depth in particle retention by examining the post-impact crater morphology, penetration depth, and localized plastic deformation of the aluminum substrate. Results reveal that some degree of matrix porosity may improve particle retention. In particular, porosity near the surface facilitates particle retention at lower impact velocities, while kinetic energy dominates particle retention at higher deposition velocities. Altogether, these results provide insights into the effect of deposition variables (i.e., particle size, impact velocity, pore size, and pore depth) on particle retention that improves coating quality.

The importance of resolving nearshore currents in coastal dispersal models

Biophysical models often require shelf-scale domains to map larval dispersal over several weeks, presenting a computational challenge. This can be overcome by decreasing model spatial resolution; however, nearshore processes, which potentially play a significant role in larval dispersal, will inevitably be unresolved. Here, we evaluate how simulated larval dispersal in the nearshore is sensitive to model spatial resolution. We use an unstructured, finite element, hydrodynamic model of a topographically-complex coastline in North Wales, UK (which includes headlands, bays and channels) at four different spatial scales (50, 100, 250, 500 m) to compare the influence of spatial resolution on transport and dispersal patterns of particles released within the nearshore region (within 1 km of the shore). In the higher resolution (50 and 100 m) simulations, particles generally travelled offshore more quickly and further (∼18%) than in the coarser (250 and 500 m) simulations. This had important implications for potential connectivity along the coast: for the lower resolution simulations, retention of particles near source sites was increased by ∼50% and, whilst the magnitude of connectivity among discrete regions along the coast was also increased (by ∼27%), the number of connected regions was reduced (by ∼9%), compared with the higher resolution simulations. Our results, based on a case study in a highly energetic and topographically complex region, suggest that model spatial resolution of ≤100 m should be used for dispersal studies in the nearshore zone. These findings add to growing evidence of the importance of using appropriately scaled models when simulating the transport of material within – and out of – the coastal zone, with many applications, such as marine ecology, marine biosecurity, marine spatial planning and marine pollution.

Cyclosporine A-Loaded Ternary Solid Dispersion Prepared with Fine Droplet Drying Process for Improvement of Storage Stability and Oral Bioavailability

This study aimed to develop a cyclosporine A (CsA)-loaded ternary solid dispersion (tSD/CsA) to improve the storage stability of a solid dispersion (SD) system and the oral absorbability of CsA. Hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose acetate succinate (HPMCAS) were selected as carrier materials of tSD, and tSD/CsA was prepared with a fine droplet drying process, a powderization technology that employs an inkjet head. The physicochemical properties of tSD/CsA were evaluated in terms of morphology, storage stability, dissolution behavior, and mucoadhesive property. After the oral administration of CsA samples (10 mg-CsA/kg) to rats, the plasma concentration of CsA was monitored to estimate oral absorbability. tSD/CsA comprised uniform shriveled particles with a diameter of 3.4 mm and span factor of 0.4, which is a parameter to estimate the particle size distribution. Although HPC-based binary SD showed marked aggregation of the particles after storage under 40 °C/75% relative humidity, there were no significant aggregations of tSD/CsA, due to the relatively low hygroscopic property of HPMCAS. The pH-dependent release of CsA with improved dissolution was observed in tSD/CsA. In the in vitro mucoadhesive evaluation using a mucin disk, tSD/CsA exhibited a better mucoadhesive property than HPC-based SD, possibly leading to prolonged retention of tSD particles in the gastrointestinal tract after oral administration. Orally-dosed tSD/CsA in rats resulted in significantly improved oral absorption of CsA, as evidenced by a 27-fold higher bioavailability than amorphous CsA. tSD/CsA may be a promising dosage option to improve the storage stability of a SD system and the biopharmaceutical properties of CsA.

Airway mucus in pulmonary diseases: Muco-adhesive and muco-penetrating particles to overcome the airway mucus barriers

Airway mucus is a complex viscoelastic gel that provides a defensive physical barrier and shields the airway epithelium by trapping inhaled foreign pathogens and facilitating their removal via mucociliary clearance (MCC). In patients with respiratory diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), non-CF bronchiectasis, and asthma, an increase in crosslinking and physical entanglement of mucin polymers as well as mucus dehydration often alters and typically reduces mucus mesh network pore size, which reduces neutrophil migration, decreases pathogen capture, sustains bacterial infection, and accelerates lung function decline. Conventional aerosol particles containing hydrophobic drugs are rapidly captured and removed by MCC. Therefore, it is critical to design aerosol delivery systems with the appropriate size and surface chemistry that can improve drug retention and absorption with the goal of increased efficacy. Biodegradable muco-adhesive particles (MAPs) and muco-penetrating particles (MPPs) have been engineered to achieve effective pulmonary delivery and extend drug residence time in the lungs. MAPs can be used to target mucus as they get trapped in airway mucus by steric obstruction and/or adhesion. MPPs avoid muco-adhesion and are designed to have a particle size smaller than the mucus network, enhancing lung retention of particles as well as transport to the respiratory epithelial layer and drug absorption. In this review, we aim to provide insight into the composition of airway mucus, rheological characteristics of airway mucus in healthy and diseased subjects, the most recent techniques to study the flow dynamics and particle diffusion in airway mucus (in particular, multiple particle tracking, MPT), and the advancements in engineering MPPs that have contributed to improved airway mucus penetration, lung distribution, and retention.

Particle uptake by filter-feeding macrofoulers from the Mar Grande of Taranto (Mediterranean Sea, Italy): potential as microplastic pollution bioremediators

Microplastics (MPs) are a serious threat to the marine environment affecting ecosystem functioning and biodiversity. There is a vast literature about the uptake of MPs at different trophic levels, mainly focused on ecotoxicological effects in commercially relevant species. Little is still known about possible strategies to face MP pollution. Bioremediation is recently gaining attention in this framework. The clearance rate and particle retention of Sabella spallanzanii, Mytilus galloprovincialis, Phallusia mammillata, Paraleucilla magna at three MP concentrations (C1: 1.4 · 101 p/L; C2: 1.4 · 102 p/L; C3: 1.4 · 103 p/L) were investigated to test their potential as MP remover. Digestion protocol removed 98 % of tissues simplifying the MP quantification. P. magna clearance rate decreased with increasing concentration while P. mammillata showed no significant variations. S. spallanzanii and M. galloprovincialis instead exhibited the highest values of clearance rate. Yet, unlike mussels, S. spallanzanii can inhibit particle return to the surrounding water storing them in the tube, resulting to be the best candidate for bioremediation purposes.

Is there a difference in ruminal fermentation control between cattle and sheep? A meta-analytical test of a hypothesis on differential particle and fluid retention

Ruminant species differ in digestive physiology. The species-specific ratio of mean retention time of particles and fluid (MRTparticle/MRTfluid) in the reticulorumen has been interpreted as controlling ruminal fermentation: a higher ratio indicates of a more distinct ‘washing’ of particulate digesta by liquid. This should increase the harvest of microbes from the reticulorumen, and keep the microbiome in a state of more intense growth; at the same time, this should increase the metabolic losses of faecal nitrogen of microbial origin, leading to lower values for the apparent digestibility of crude protein (aD CP). A systematic difference has been hypothesized between cattle (higher ratio) and sheep (lower ratio), with a lower MRTfluid in cattle due to a higher saliva production. Here, we test these hypotheses in a meta-analysis, using only studies that investigated cattle and sheep simultaneously. The datasets included 12 studies on MRT (of which 11 contained information on feed intake), yielding 102 (or 89) individual data; and 26 studies on protein digestibility (of which 18 contained information on intake), yielding 349 individual data. Cattle had a higher MRTparticle/MRTfluid (2.1) than sheep (1.7), mainly due to longer MRTparticle; only if body mass was included in the model, MRTfluid was significantly shorter in cattle in the larger MRT dataset (and tended to be shorter in the slightly smaller dataset). Cattle had a significantly lower aD CP than sheep, while there was no such difference in overall (dry or organic matter) digestibility. The dataset confirms a shift in fermentation strategy towards microbial production in cattle. While this has been suggested for ruminants in general, cattle appear particularly far on an evolutionary trajectory of maximizing microbial yield from the forestomach. The application of more specific digestive physiology data (like endogenous losses) gained from sheep to cattle should be done bearing these differences in mind.

Determination of running temperature in entrained flow gasifier in regard to coal ash melting thermal kinetic effects

The operating temperature of entrained flow gasifier is one of the important parameters to determine its gasification efficiency, which is empirically estimated by ash fusion temperatures (AFTs) in the industry. However, the measurements of AFTs in labs are conducted at a very low heating rate (5–10 °C/min) compared to industrial entrained flow gasifiers (several hundred °C/s). The melting behaviors of coal ash under such huge varied conditions are different due to thermo-kinetic effects. Here, the factors concerning coal ash melting thermo-kinetics including heating rate, particle size, and retention time are explored by AFTs analyzer, thermal mechanical analysis, in-situ hot stage microscope and differential scanning calorimetry. The results of the investigation demonstrated that ash particle size and retention time showed limited influence on ash fusion behavior, while the influence of heating rates can not be ignored. Furthermore, an Arrhenian-based regression model covering major thermo-kinetics was developed to quantitatively predict the running temperature. The developed model suggested using the temperature that shrinkage corresponds to 75% to extrapolate the running temperature. The model can help to determine the operating temperature of slagging gasifiers.

Influence of Rock Structure on Migration of Radioactive Colloids from an Underground Repository of High-Level Radioactive Waste

Studies of leaching of vitrified simulated high-level radioactive waste (HLW) evidence that most of actinides or their simulators enter leaching water in a colloidal form. In this paper, we consider a mechanism of colloid-facilitated migration of radionuclides from an underground repository of HLW located at a depth of a few hundreds of meters in fractured crystalline rocks. The comparison between data of field and laboratory measurements showed that the bulk permeability of the rock massif in field tests is much greater than the permeability of rock samples in laboratory experiments due to an influence of a network of fractures in the rock massif. Our theoretical analysis presents evidence that this difference can take place even in a case when the network is not continuous, and the fractures are isolated with each other through a porous low-permeable matrix of the rock. Results of modelling revealed a possibility of mechanical retention of radionuclide-bearing colloid particles in the frame of rock during their underground migration.

Restored tufa-depositing streams: a dynamic interface between terrestrial and aquatic ecosystems

Stream periphyton has implications for ecosystem processes, yet little is known about its function in response to restoration efforts. In this study, we compared the taxonomic and functional composition of periphytic ciliates between restored and unrestored (control) streams for two different immersion periods to identify species with indicator potential, identify ciliate functional traits that differ between the two stream types, and examine the effects of environmental parameters on species and functional trait composition. Our study showed that restored streams differed from control streams in terms of species and functional trait composition. In restored streams, better competitors, i.e., omnivorous and bacterivorous free-swimming ciliates predominated, utilizing a wider range of different niches created by the greater microhabitat complexity due to retention of allochthonous organic matter particles and precipitation of calcite crystals, i.e., tufa. One of these species was Platyophrya vorax, which was identified as a species with indicator potential for restored tufa-depositing streams. The relationship between habitat heterogeneity, ciliate functional traits, and organic matter dynamics suggests that restoration of tufa-depositing streams affects ecosystem functioning by influencing its functional components, highlighting the need to investigate such ecosystems through the prism of connected lotic and terrestrial ecosystems rather than isolated ecosystems.

Comparative study of filtration parameters depending on the nature of the filter material

The paper presents a comparative study of the filtration parameters in the case of passenger compartment filters designed for commercial vehicles. The research is aimed to determine the materials characteristic that may improve the quality of the air breathed by passengers in the given conditions of increasing the degree of pollution due to heavy traffic in large cities. Two dimensionally similar types of cabin filters were considered, having as filtering medium two types of materials: microporous cardboard and microporous cardboard with activated carbon insertion. In order to determine the filtration parameters, the particle retention capacity and the filtration efficiency.

An insight on mechanism and management of kidney stones and its recurrence

Kidney stones (calculi) comprise mineral concretions which can form in both renal calyces and pelvis and can be free floating or associated with the renal papillae. It is an emerging urological condition that affects around 12% of the world’s population. Globally, the prevalence and recurrence of kidney stone disease are increasing, and there are limited effective treatment options. I manifest a brief general overview and then concentrate on risk factors, pathophysiology, and medical treatment of kidney stones. The major component of most stones is calcium oxalate, and many of them develop on a foundation of calcium phosphate known as Randall’s plaques, which are located on the renal papillary surface. The mechanism of stone formation is a complicated process that involves multiple physicochemical phenomena such as supersaturation, nucleation, growth, aggregation, and retention of urinary stone ingredients inside tubular cells. Cellular damage is also thought to enhance particle retention on renal papillary surfaces. There is currently no effective treatment or prevention for kidney stone recurrence. Recurrence prevention required behavioral and nutritional interventions, as significantly as pharmaceutical therapies tailored to the kind of stone. There is a great demand for recurrence prevention, which necessitates a deeper knowledge of the processes involved in the development of stones to design more effective medications. Open surgical lithotomy has given way to minimally invasive endourological procedures for the treatment of symptomatic kidney stones, resulting in lower patient morbidity, increased stone-free rates, and enhanced quality of life. As a result, furthering our knowledge of the biology of kidney stone development is a research focus for treating urolithiasis with novel medications.

Numerical study of the filtering barriers influence to contain aerated particulate systems

Since the high rate of viral proliferation caused by Covid-19, it was observed that microdroplets with a pathogenic load can remain floating when in confined environments due to their low densities. They are also subject to being transported very easily when in open environments, becoming potential agents of infection. It has motivated several researchers in the field of particulate systems to try understand how particles behave in more extreme conditions. Bearing in mind that the materials currently used have a low retention yield for liquid droplets, and that protection barriers against pathogens are present both in daily use in hospital application, from diagnosis to treatment, this work simulated computationally, in a Eulerian-Eulerian approach, fluid particle retention efficiency in filter films. The simulated results indicated the high degree of retention of the filtering medium and the dependence of its saturation on the particle diameter and flow velocity, in which the greater the initial flow velocity and larger particles, the faster the saturation and detachment of particles, reducing the filter medium containment capacity. However, the results indicated that even so, retainer materials are efficient in reducing the proliferation of pathogenic loads.

Enhanced Accumulation of Colloidal Particles in Microgrooved Channels via Diffusiophoresis and Steady-State Electrolyte Flows.

The delivery of colloidal particles in dead-end microstructures is very challenging, since these geometries do not allow net flows of particle-laden fluids; meanwhile, diffusive transport is slow and inefficient. Recently, we introduced a novel particle manipulation strategy, based on diffusiophoresis, whereby the salt concentration gradient between parallel electrolyte streams in a microgrooved channel induces the rapid (i.e., within minutes) and reversible accumulation, retention, and removal of colloidal particles in the microgrooves. In this study, we investigated the effects of salt contrast and groove depth on the accumulation process in silicon microgrooves and determined the experimental conditions that lead to a particle concentration peak of more than four times the concentration in the channel bulk. Also, we achieved an average particle concentration in the grooves of more than twice the concentration in the flowing streams and almost 2 orders of magnitude larger than the average concentration in the grooves in the absence of a salt concentration gradient. Analytical sufficient and necessary conditions for particle accumulation are also derived. Finally, we successfully tested the accumulation process in polydimethylsiloxane microgrooved channels, as they are less expensive to fabricate than silicon microgrooved substrates. The controlled and enhanced accumulation of colloidal particles in dead-end structures by solute concentration gradients has potential applications in soft matter and living systems, such as drug delivery, synthetic biology, and on-chip diagnostics.

A pore-scale investigation of microplastics migration and deposition during unsaturated flow in porous media

Microplastics are ubiquitous in the natural environment and have the potential to endanger the natural environment, ecology and even human health. A series of microfluidic experiments by using soft lithography technology were carried out to investigate the effect of flow rate, particle volume fraction, particle size and pore/throat ratio on microplastics migration and deposition at the pore scale. We discovered a range of deposition patterns of the spherical microplastics from no particle deposition, to discontinuous particle layer, and to continuous particle layers in the retained liquid in the pores, depending on the particle size and volume fraction. Several metrics, including air saturation, probability of particle detainment, expansion ratio and thickness of residual liquid, were quantified to examine the role of various parameters on particle migration and retention of microplastics. At low flow rate (Q = 0.05 μL/min), microplastics migration and deposition were sensitive to changes in particle volume fraction, particle size and pore/throat ratio. In contrast, at high flow rates (Q > 5 μL/min), the migration and retention of particles were mainly controlled by strongly channelized air invasion pattern, while the particle volume fraction, particle size and pore/throat size ratio have only secondary influence. At intermediate range of flow rates, microplastics migration and deposition were dramatically impacted by flow rate, particle volume fraction, particle size and pore/throat ratio. This work improves the understanding of the mechanisms of particle migration and retention in porous media and can provide a reference for more accurate assessment of the exposure levels and times of microplastics in soil and groundwater systems.

Influence of exposure history on the particle retention capacity and physiological responses of Euonymus japonicus Thunb. var. aurea-marginatus Hort.

Green plants in urban environments experience cyclical particulate matter stress. And this history of exhaust exposure may generate stress memory in plants, which may alter their subsequent response. Studies combining urban pollution characteristics and stress memory are limited. Therefore, we selected E. japonicus var. aurea-marginatus, a common urban greening tree species in the Yangtze River Delta, and conducted an experiment in three periods: the initial pollution period (S1: 28 days), the recovery period (R: 14 days) and the secondary pollution period (S2: 28 days). The experimental design consisted of an elevated pollution treatment (173 μg•cm−3) and an ambient control (34 μg•cm−3) with three replicates. In S2, the net total particle retention and saturated particle retention decreased by 11.5% and 19.3%, respectively, while PM10 and PM2.5 did not change significantly. E. japonicus var. aurea-marginatus exhibited recovery of chlorophyll levels, slower degradation of carotenoid, faster accumulation of ASA, lower accumulation of MDA, reduced activity of SOD under the second pollution period, and the period had a significant effect on the physiological indicators. Collectively, the effect of autoexhaust exposure history on the particle retention capacity of selected plant varied across particle sizes, and stress memory may confer plant resistance to recurrent exhaust pollution via combined regulations of physiological responses. Fine particles which pose a great risk to human health arise predominantly from vehicular traffic and energy production. So, E. japonicus tends to play a stabilising role in particle retention in industrial, traffic and residential areas.