Depletion Of Particles Research Articles

Tail Morphology of Near-Sun Comet C/2020 F3 (NEOWISE)

We study the morphological changes of bright near-Sun comet C/2020 F3 (NEOWISE) using a series of multi-color wide-field images obtained in 2020 July 8–30, as the comet receded from 0.3 to 0.8 au from the Sun. Syndyne–synchrone modeling shows that the dusts that makes up the visible tail were mostly produced at and after perihelion. The images show changes of dust size distribution throughout the observations, with a gradual depletion of micron-sized particles. We discuss caveats in using the syndyne–synchrone model to study tail dynamics of comets at small perihelion distances. The r-band images consistently show a straight, non-dust tail throughout our observations that is likely to be made by neutral sodium atoms and H2O+ molecules.

Multi-laser nanoparticle tracking analysis (NTA): A unique method to visualize dynamic (shear) and dynamic (Brownian motion) light scattering and quantify nonliving natural organic matter (NNOM) in environmental water

Application of simultaneous multi-laser nanoparticle tracking analysis (NTA) to environmental water samples to investigate nonliving natural organic matter (NNOM) is introduced as an innovative method for observing particles directly in their native media. Multi-laser NTA results of particle visualization, particle number concentration, and particle size distribution elucidated particle dynamics in low and high total dissolved solids (TDS) aqueous environmental samples. A pond water sample and concentrate from a reverse osmosis (RO) treatment process (Stage 1) had 1.3 × 108 and 5.62 × 1019 particles/mL, respectively, (at time = 0) after filtration at 0.45 μm. Beyond the traditional applications for this instrument, this research presents novel evidence-based investigations that probe the existence of supramolecular structures in environmental waters during turbulence or quiescence. The pond water sample exhibited time-dependent aggregation as the volume distribution shifted to greater diameter during quiescence, compared to turbulence. Disaggregation (increased numbers of particles over time) was noted in the >250 nm to <600 nm region, and aggregation of >450 nm particles was also noted in the quiescent RO concentrate sample, indicative of depletion of small particles to form larger ones. Multi-laser NTA and dynamic light scattering (DLS) capabilities were compared and contrasted. DLS and NTA are different (complementary) particle sizing techniques. DLS yielded more information about the physical hydrogel in the NNOM hierarchy whereas multi-laser NTA better characterized meta-chemical and chemical hydrogel characteristics. Operationalization of innovation—moving from fundamental investigations to application—is supported by implementing novel analytical instrumentation as we address issues involving climate change, drought, and the scarcity of potable water. Multi-laser NTA can be used as a tool to study and optimize complex water and wastewater treatment processes. Questions about water treatment efficiencies, membrane fouling, assistance of pollutant transport, and carbon capture cycles affected by NNOM will benefit from insights from multi-laser NTA.

Sediment sorting and transport mechanism controlled by both soil properties and hydraulic parameters on hillslopes

Understanding the sediment sorting and transport processes is is crucial for enhancing the understanding of soil erosion mechanisms and improving soil erosion prediction. However, quantitative studies based on the coupling effects of both hydraulic parameters and soil properties are still lacking. In this study, five loessial soils with varying physicochemical properties were collected in the Loess Plateau of China, and simulated rainfall experiments were carried out in a metal box with a slope of 20 degrees under rainfall intensities of 1, 1.5, and 2 mm min−1. Runoff samples were collected to analyze the variation in erosion rates and effective particle size distribution of eroded sediments during the rainfall process. The results showed that the stream power was the optimal parameter to model the erosion rate, and a power function incorporating the clay content and stream power could well predict the erosion rate of different soils. The enrichment ratio indicated the enrichment of fine particles and depletion of coarse particles. And the sediment sorting degree increased with increasing soil clay content. The critical particle size for distinguishing different transport mechanisms varied among soils, with more than 55.46 % of the total sediment transported by suspension/saltation. A linear function and power function including the original soil particle size distribution and stream power were developed to quantify the sediment clay content and the relative contribution of different transport mechanisms. This study could be helpful to improve the soil erosion prediction model and provide basic guidelines for regional soil and water conservation.

Dip-coating deposition of nanocomposite thin films based on water-soluble polymer and silica nanoparticles

Dip-coating deposition of nanocomposite thin films composed of polyvinylpyrrolidone and silica nanoparticles was studied using atomic force microscopy and scanning electron microscopy. The presence of particles (up to 5 wt%) did not modify the film thickness, which followed a classical additive law of an evaporative regime and a draining regime. Within film volume, no preferential retrieval of particles nor polymer occurred during deposition. This was consistent with the size of particles small enough so that particles were not trapped in the meniscus. For the thicker films prepared in pure capillary and draining regimes, the number of particles observed on the surface was independent of the thickness and was in full agreement with a homogenous distribution of the particles in the film. In contrast, for the thinner films (near the critical withdrawal speed) the number of particles differed in the two regimes. In the draining branch, the number followed the theoretical prediction with an increased number of particles as the thickness decreased, due to the presence of an exclusion zone at the interfaces. Unexpectedly, in the capillary branch, a depletion of particles was observed and could result from competition and interplay between time-dependent phenomena that took place during the dip-coating. This behavior will need to be carefully considered when preparing nanocomposite thin films where surface properties such as roughness or wettability need to be considered.

Hydrodynamic approximations for driven dense colloidal mixtures in narrow pores.

The system of driven dense colloid mixtures is studied in one-, two-, and three-dimensional geometries. We calculate the diffusion coefficients and mobilities for each particle type, including cross-terms, in a hydrodynamic limit, using a mean-field-type approximation. The set of nonlinear diffusion equationsare then solved. In one dimension, analytical results are possible. We show that in mixtures, the "Brazil nut" phenomenon, or depletion of larger particles by force of smaller ones, appears quite generically. We calculate the ratchet current and quantify the capability of sorting particles according to their size. We also indicate that the "Brazil nut" effect lies behind the possibility of perfect separation, where large and big particles travel in strictly opposite direction.

Characterisation of the granular dynamics at the interface between a pipe and a granular flow in a rotating drum

A new mobile bed heat exchanger is presented in this work which is composed of a flowing granular material in a rotating drum and a cylindrical pipe with potential interest in different energy applications as cooling, heating or heat recovery processes. An optimal design of the device requires a characterisation of the phenomena involved at the interface between the granular flow and the pipe. The process is modelled by the discrete element method and a global classification of the flow patterns around the pipe is presented with respect to the three main control parameters of the problem: the Froude number, the diameter ratio and the relative filling height of the drum. The second part is devoted to the characterisation of the structure of the flow at the interface (velocity field, density field) in particular in a so-called Biflow regime where granular motion occurs above as well as below the pipe which is favourable to transfer by convection. A typical behavior at the interface with the pipe consists of a zone I with high velocities of particles at the top of the pipe, a second zone with quasistatic particles or low velocity particles at the front and at the bottom of the pipe and a last zone III of depletion of particles at the back of the pipe. The Froude number has a limited effect on the features of this structure on the first layer in the range of Froude numbers considered whereas the relative height is a more determinant parameter to control the relative magnitude of velocities in zone I and zone II as well as the extent of the depletion zone. This first hydrodynamical characterisation can shed light on the dynamical regimes with improved transfer between the particles and the pipe boundary.

Роль дефензинів у неспецифічному захисті макроорганізму від інфекційних агентів при запальних захворюваннях порожнини рота і ротоглотки (огляд літератури)

The purpose of the study was to analyze literature sources containing information about defensins, cysteine-rich cationic amphipathic peptides produced by circulating white blood cells and tissue cells. This review describes the antimicrobial, antiviral, anti-inflammatory and immunomodulatory properties of defensins, as well as their molecular and cellular interactions. These substances, which are present on the epithelium and body fluids, are active against bacteria, fungi and viruses, as well as produced by immune and epithelial cells. These natural antimicrobial cationic peptides play an important role in innate and adaptive immunity. Defensins are divided into alpha and beta families. Alpha-defensins (α-defensins) are found in neutrophils, macrophages and Paneth cells in the intestine. Beta-defensins (β-defensins) are secreted by most leukocytes and epithelial cells. Extensive antimicrobial activity and multifaceted immunomodulatory functions of defensins confirm their role in innate immunity as the main protective component of the human body against bacterial, viral and fungal infections. Thus, they are key effector molecules in protecting the organism from infection due to their broad-spectrum antimicrobial activity. Their common antimicrobial function is the formation of destructive pores in the membranes of pathogens, including enveloped viruses. Antiviral activity includes the direct effect of defensin on viral envelopes, glycoproteins and capsids. Binding and modulation of host cell surface receptors and disruption of intracellular signaling by defensins may also inhibit virus replication. These peptides block infection with enveloped and non-enveloped viruses by aggregating particles, blocking receptor binding, inhibiting virus penetration or depletion of particles, inhibiting stem cell signaling, or viral gene expression. In addition, defensins may function as chemokines to enhance and alter adaptive immune responses by exhibiting an indirect antiviral mechanism. Conclusion. However, sources of scientific information have shown that defensins attract immune cells and modulate adaptive immune responses. It has also been shown that defensins can both induce inflammation and suppress inflammatory responses by acting on certain cells through various mechanisms. Due to this, they can be used as one of the markers in the development of inflammatory diseases of the mouth and oropharynx. The main drugs that activate the production of defensins are probiotics, vitamin D and leukotriene B4. This expands the possibility of their use as a new class of non-toxic antimicrobials and immunomodulators

Effect of increasing the Blaine fineness of Metakaolin on its chemical reactivity

Metakaolin (MK) is widely used as a partial substitute for cement in concrete, mainly due to its high reactivity. MK exhibits simultaneously a chemical reactivity known as pozzolanicity and a physical one, principally linked to the material's fineness. The chemical reactivity of MK depends on its chemical and mineralogical compositions, its dehydroxylation/amorphization degree but also on its fineness. The present study attempts to clarify the effect of increasing the Blaine fineness of MK on its chemical reactivity assessed by chemical tests of Frattini, modified Chapelle and saturated lime and the 28-day compressive strength. Thermal treatment of Kaolin at 800 °C for 5 h was used to obtain MK; however the uncalcined kaolin was used, at the same proportion and fineness, as an inert material for comparison purposes. It has been observed that chemical tests are more sensitive to fineness of MK than mechanical test. Chemical reactivity increases with fineness in the case of chemical tests, however, it does not appear to be influenced in the case of compressive strength test, since the strength activity index remains unchanged although the Blaine fineness increases from 4290 to 8220 cm2/g. It has been concluded that the fineness of MK has promoted its lime consumption in the case of chemical tests, but factors such as MK content, amount of reactive phases and the depletion of fine particles did not allow improving the chemical reactivity in the case of compressive strength test.

Microstructural examination of carbonated 3D-printed concrete.

The recent interest in 3D printing with concrete has generated great interest on how inhomogeneities arise and affect performance parameters, in particular strength and durability. With respect to durability, of particular interest is how 3D‐printed layer interfaces can impact transport of species of interest, such as moisture, chlorides or carbon dioxide in carbonation processes. This is of particular interest considering that the primary use case of 3D‐printed concrete has been as a lost formwork for a cast structural concrete, and thus it is of interest to determine the carbonation resistance. This study consists of a preliminary look at the microstructure after accelerated carbonation of a 3D‐printed concrete used as a lost formwork. Preferential carbonation is observed in the layer interfaces compared to the bulk of the printed filaments, possibly related to porosity from air voids or a locally high capillary porosity corresponding to the lubrication layer.

Directional manipulation of diffusio-osmosis flow by design of solute-wall and solvent-wall interactions

Understanding of diffusio-osmosis, the flow induced by a solute gradient acting in narrow interfacial layers at a nanoscale solid-liquid interface, is of great value in view of the increasing importance of micro- and nano-fluidic devices and self-propelling particles. Using molecular dynamics simulations, we employ an appropriate strategy for direct simulation of diffusio-osmosis flows, mimicking a realistic experiment without any assumed external forces. It allows us to obtain reliable flow details, which are hard to obtain in experiments. We found that the solvent-wall interaction, previously overlooked in the classical paradigm, plays a critical role in the diffusio-osmosis process. In particular, diffusio-osmosis is controlled by the interaction difference between the solute-wall and solvent-wall. When the solute-wall interaction is stronger (weaker) than the solvent-wall, a surface excess (depletion) of solute particles on the solid-liquid interface is formed, which induces diffusio-osmosis flow towards a low (high) concentration. We modified the classical Derjaguin expression to include the effect of nanoscale hydrodynamics boundary conditions for the accurate prediction of diffusio-osmosis characteristics. Overall, our results provide clear guidance for controlling fluid flow and manipulating the motion of colloids under tunable solute concentrations.

Degradation Mechanisms of Solid Oxide Fuel Cells under Various Thermal Cycling Conditions.

A critical issue to tackle before successful commercialization of solid oxide fuel cells (SOFCs) can be achieved is the long-term thermal stability required for SOFCs to operate reliably without significant performance degradation despite enduring thermal cycling. In this work, the impact of thermal cycling on the durability of NiO-yttria-stabilized zirconia-based anode-supported cells is studied using three different heating/cooling rates (1, 2, and 5 °C min-1) as the temperature fluctuated between 400 and 700 °C. Our experiments simulate time periods when power from SOFCs is not required (e.g., as might occur at night or during an emergency shutdown). The decay ratios of the cell voltages are 8.8% (82 μV h-1) and 19.1% (187 μV h-1) after thermal cycling testing at heating/cooling rates of 1 and 5 °C min-1, respectively, over a period of 1000 h. The results indicate SOFCs that undergo rapid thermal cycling experience much greater performance degradation than cells that experience slow heating/cooling rates. The changes in total resistance for thermally cycled cells are determined by measuring the Rpol of the electrodes (whereas the ohmic resistances of the cells remain unchanged from their initial value), signifying that electrode deterioration is the main degradation mechanism for SOFCs under thermal cycling. In particular, fast thermal cycling leads to severe degradation in the anode part of SOFCs with substantial agglomeration and depletion of Ni particles seen in our characterizations with field emission-scanning electron microscopy and electron probe microanalysis. In addition, the mean particle size in the cathode after thermal cycling testing increases from 0.104 to 0.201 μm for the 5 °C min-1 cell. Further, the presence of Sr-enriched regions is more significant in the La0.6Sr0.4Co0.2Fe0.8O3-δ cathode after fast thermally cycled SOFCs.

Tempered fractional Brownian motion on finite intervals

Diffusive transport in many complex systems features a crossover between anomalous diffusion at short times and normal diffusion at long times. This behavior can be mathematically modeled by cutting off (tempering) beyond a mesoscopic correlation time the power-law correlations between the increments of fractional Brownian motion. Here, we investigate such tempered fractional Brownian motion confined to a finite interval by reflecting walls. Specifically, we explore how the tempering of the long-time correlations affects the strong accumulation and depletion of particles near reflecting boundaries recently discovered for untempered fractional Brownian motion. We find that exponential tempering introduces a characteristic size for the accumulation and depletion zones but does not affect the functional form of the probability density close to the wall. In contrast, power-law tempering leads to more complex behavior that differs between the superdiffusive and subdiffusive cases.

Diffusion and thermalization in a boundary-driven dephasing model

We study a model of noninteracting spinless fermions coupled to local dephasing and boundary drive and described within a Lindblad master equation. The model features an interplay between infinite temperature thermalization due to bulk dephasing and a nonequilibrium stationary state due to the boundary drive and dissipation. We revisit the linear and nonlinear transport properties of the model, featuring a crossover from ballistic to diffusive scaling, and compute the spectral and occupation properties encoded in the single-particle Green's functions, that we compute exactly using the Lindblad equations of motion in spite of the interacting nature of the dephasing term. We show that the distribution function in the bulk of the system becomes frequency independent and flat, consistent with infinite temperature thermalization, while near the boundaries it retains strong nonequilibrium features that reflect the continuous injection and depletion of particles due to driving and dissipation.

Electron dynamics for high-intensity hollow electron beams

Hollow Electron Lenses (HEL) will be installed at the High Luminosity Large Hadron Collider to provide a continuous and controlled depletion of beam halo particles by interaction with a superimposed hollow electron beam, of intensity as high as 5 A, and radii 1.1–2.2 mm for 7 TeV LHC operations. In this paper, issues related to the propagation of high intensity hollow electron beams are discussed and the simulations of the electron beam dynamics with feedback to the HEL design are presented. The main results are the rise of the electron beam accelerating voltage from 10 kV, as in the initial proposal, to 15 kV and the validation of the 5 T magnetic field at the main solenoids as being sufficient to guarantee a stable electron beam.

Effect of Particle Concentration on Surfactant-Induced Alteration of the Contact Line Deposition in Evaporating Sessile Droplets.

Controlling and suppressing the so-called "coffee-ring effect" (CRE) is an issue of cardinal importance and intense interest in many industries and scientific fields. Here, the combined effect of the particle and surfactant concentration on the CRE is investigated by gradually adding Triton X-100 surfactant to colloidal suspensions of SiO2 nanoparticles in ethanol for various particle concentrations. First, the effect of particle concentration on the contact line dynamics during the evaporation of a sessile droplet is investigated. It is shown that increasing the particle concentration leads to an increase in pinning time and ring width, whereas the droplet's initial and dynamic contact angle remains unchanged. Afterward, the effect of different concentrations of surfactant is studied for different particle concentrations. It is concluded that the surfactant concentration at which the CRE is suppressed is dependent on the initial particle concentration of the colloid, and it increases as the particle concentration increases. Furthermore, as adding surfactant with a concentration lower than this critical concentration results in an unsuppressed CRE, it is shown that surpassing this concentration will result in a depletion of particles in the contact line. Moreover, it is demonstrated that this critical surfactant concentration has no significant effect on the droplet's geometry and the total evaporation time.

Mechanisms influencing particle depletion in and around mussel farms in different environments

Through the mechanisms of particle immobilization and subsequent depletion of particles, mussel cultivation has a direct effect on chlorophyll-a concentrations and Secchi depth; both of which are primary indicators of marine ecological status and metrics for water quality management. As such, mussel cultivation has been proposed as a measure to mitigate the effects of coastal eutrophication. However, the extent to which this ecosystem service, and relatedly, biomass accumulation, are affected by ambient environmental conditions involves complex interactions. To explore the interacting mechanisms underpinning depletion dynamics under various biophysical conditions along the salinity gradient in the Baltic Sea, we used an updated Dynamic Energy Budget (DEB) model with field data from the western Baltic Sea, accommodating osmotic stress. We use the DEB model to drive a 3D farm-scale model within a novel precompiled hydrodynamic framework (FlexSem) to evaluate the effects of different environmental conditions and farm configuration on the intensity and extent of the chlorophyll-a depletion signal. We also report on extensive in situ monitoring of chlorophyll-a and Secchi depth within and around mussel farms, from several cultivation areas from around the western Baltic Sea to evaluate site-specific characteristics of depletion. Monitoring reflected the high degree of spatio-temporal variability in the quantification of this ecosystem service; with relative differences in chlorophyll-a from −14 to 69% and Secchi depth from 0 to 75%. We find that the extensive in situ measurements in different environmental conditions can be represented by the integrated farm model in terms of mussel biomass accumulation and depletion, providing insight on the interactions of current velocity, farm orientation to predominant current direction, ambient chlorophyll-a concentrations, and total biomass loads on the intensity and spatial extent of the depletion signal. Furthermore, the model has been calibrated to cover a variety of environmental contexts and permits fine-resolution simulation of multiple environmental interactions on mussel energetics, which can be used to evaluate potentials for optimizing mussel mitigation culture and the associated ecosystem services of phytoplankton depletion under local conditions without extensive recalibration from field growth data. The general interactions exhibited here and model will be useful for evaluating depletion and planning the establishment of mitigation farms in regions where national environmental monitoring programs can provide basic data. This can also reduce the need for extensive and costly in situ monitoring programs.

Individual particle investigation on the chloride depletion of inland transported sea spray aerosols during East Asian summer monsoon

Inland transported sea spray aerosol (SSA) particles along with multiphase reactions are essential to drive the regional circulation of nitrogen, sulfur and halogen species in the atmosphere. Specially, the physicochemical properties of SSA will be significantly affected by the displacement reaction of chloride. However, the role of organic species and the mixing state on the chloride depletion of SSA during long-range inland transport remains unclear. Hence, a single particle aerosol mass spectrometer (SPAMS) was employed to investigate the particle size and chemical composition of individual SSA particles over inland southern China during the East Asian summer monsoon. Based on the variation of chemical composition, SSA particles were clustered into SSA-Aged, SSA-Bio and SSA-Ca. SSA-Aged was regarded as the aged Na-rich SSA particles. In comparison to the SSA-Aged, SSA-Bio involved some extra organic species associated with biological origin (i.e., organic nitrogen and phosphate). Each type occupies for approximately 50% of total detected SSA particles. Besides, SSA-Ca may relate to organic shell of Na-rich SSA particles, which is negligible (~3%). Tight correlation between Na and diverse organic acids was exhibited for the SSA-Aged (r2 = 0.52, p < 0.01) and SSA-Bio (r2 = 0.61, p < 0.01), reflecting the impact of organic acids to the chloride displacement during inland transport SSA particles. The chloride depletion occupied by organic acids is estimated to be up to 34%. It is noted that distinctly different degree of chloride depletion was observed between SSA-Aged and SSA-Bio. It is more likely to be attributed to the associated organic coatings for the SSA-Bio particles, which inhibits the displacement reactions between acids and chloride. As revealed from the mixing state of SSA-Bio, defined hourly mean peak area ratio of Cl / Na increases with the increasing phosphate and organic nitrogen. This finding provides additional basis for the improvement of modeling simulations in chlorine circulation and a comprehensive understanding of the effects of organics on chloride depletion of SSA particles.

Confinement-induced alternating interactions between inclusions in an active fluid.

In a system of colloidal inclusions suspended in an equilibrium bath of smaller particles, the particulate bath engenders effective, short-ranged, primarily attractive interactions between the inclusions, known as depletion interactions, that originate from the steric depletion of bath particles from the immediate vicinity of the inclusions. In a bath of active (self-propelled) particles, the nature of such bath-mediated interactions can qualitatively change from attraction to repulsion, and they become stronger in magnitude and range of action as compared with typical equilibrium depletion interactions, especially as the bath activity (particle self-propulsion) is increased. We study effective interactions mediated by a bath of active Brownian particles between two fixed, impenetrable, and disk-shaped inclusions in a planar (channel) confinement in two dimensions. Confinement is found to strongly influence the effective interaction between the inclusions, specifically by producing alternating interaction profiles with possible attractive and repulsive regions in sufficiently narrow channels. We study the dependence of the ensuing interactions on different system parameters and the orientational (parallel versus perpendicular) configuration of the inclusion pair relative to the channel walls. The confinement effects are largely regulated by the layering of active particles next to the surface boundaries, both of the inclusions and the channel walls that counteract one another in accumulating the active particles in their own proximities. In narrow channels, the combined effects due to the channel walls and the inclusions lead to peculiar structuring of active particles (reminiscent of wavelike interference patterns) within the channel.

Mass flux decay timescales of volcanic particles due to aeolian processes in the Argentinian Patagonia steppe

We investigate the timescales of the horizontal mass flux decay of wind remobilised volcanic particles in Argentina, associated with the tephra-fallout deposit produced by the 2011–2012 Cordón Caulle (Chile) eruption. Particle removal processes are controlled by complex interactions of meteorological conditions, surface properties and particle depletion with time. We find that ash remobilisation follows a two-phase exponential decay with specific timescales for the initial input of fresh ash (1–74 days) and the following soil stabilisation processes (3–52 months). The characteristic timescales as a function of particle size shows two minimum values, identified for sizes around 2 and 19–37 upmum, suggesting that these size-range particles are remobilised more easily, due to the interaction between saltation and suspension-induced processes. We find that in volcanic regions, characterised by a sudden release and a subsequent depletion of particles, the availability of wind-erodible particles plays a major role due to compaction and removal of fine particles. We propose, therefore, a simple and reproducible empirical model to describe the mass flux decay of remobilised ash in a supply-limited environment. This methodology represents an innovative approach to link field measurements of multi-sized and supply-limited deposits with saltation erosion theory.

Bidensity particle-laden exchange flows in a vertical duct

Buoyancy-driven exchange flow in a vertical duct is studied theoretically for a light pure fluid and a heavy fluid. The latter is a suspension composed of a Newtonian fluid and two populations of negatively buoyant particles of the same size but different densities (bidensity). In a previous study (Mirzaeian & Alba, J. Fluid Mech., vol. 847, 2018, pp. 134–160), the authors developed a lubrication model for monodensity suspension of particles of uniform size. The main observation of the monodensity study was the discovery of particle-enriched zones near heavy and light fluid fronts due to the relative motion of particles and the fluid. Distinct from the previous work, here, mismatched densities instigate a relative motion of lighter and heavier particles in addition to the movement of fluids. Other than the previously observed enrichment case, the bidensity case gives rise to a novel flow regime where there is enrichment of heavy particles but depletion of light particles near the interface. The transition to this regime is governed by a balance between the densities of heavy and light particles as well as those of light and carrying fluids for a given choice of initial volume fractions of particles. Such density balance is characterized by two dimensionless parameters comprising light and heavy particle-to-carrying-fluid density ratios. The transition mechanism is studied through additional simulations, revealing that the former increases with initial volume fraction of particles of either type, while the latter contrarily decreases. The effect of other parameters on the flow are discussed within the context of the paper.