Collection Of Dust Particles Research Articles

Height-modulating horizontal transport of dust particles in a dusty plasma ratchet

Dust particles are often electrostatically trapped and levitated within the non-electroneutral region of a sheath. The fascinating transport phenomena of dust particles strongly depend on the plasma parameters surrounding them within the sheath, whereas, that are quite difficult to obtain, leading to an unclear understanding of particle transport mechanisms. Here, we demonstrate a tunable horizontal transport of micron-sized dust particles by precisely manipulating their vertically suspended heights in an asymmetric ratchet sheath by designing dusty plasma ratchet. A collection of dust particles serves as micro-probes to detect the height-dependent transport properties and the feature of the sheath. Two methods are employed to lift or reduce the suspended heights of dust particles while maintaining the sheath unchanged. As the suspended heights of dust particles vary, their directional transport changes accordingly, including a flow reversal. A two-dimensional model of the ratchet sheath depicts the nonlinear distributions of plasma parameters and reveals that these unexpected transport phenomena can be attributed to the dependence of the electric ratchet potential and the resulting non-equilibrium net ion drag force on the suspended heights of dust particles. Our combined experimental and theoretical study provides insights into the fundamental transport properties of dust particles in an asymmetrical sheath.

Extraterrestrial dust flux monitoring at Antarctic Vostok station: New collection of extraterrestrial spherules fallen from May to September 2017

AbstractDust particles obtained by filtering fresh snow collected from May to September 2017 in the vicinity of Vostok station in Antarctica were examined using a scanning electron microscope. The collection of dust particles contains 197 spherules ranging from 0.5 to 117 μm in diameter, the most abundant ones (n = 188) by far being iron oxide spherules. Analyses of meteorological and human activity data suggest an extraterrestrial origin of most of the spherical particles. The particle size distribution histogram showed a smooth increase in their number with decreasing size and a dramatic drop at sizes smaller than 3 μm. The number of spherical particles has an uneven distribution over time, with an intense peak in July 27–28, 2017 which correlates by dates with the peak of the Southern Delta Aquariids meteor shower. The size distribution of the particles collected during the same period indicates the presence of a mechanism that accelerates their fall to the Earth. We propose that they are effective centers of condensation of ice crystals in stratospheric clouds. Our data indicate that collection of micrometeorites with sizes of several microns from the fresh snow is possible, opening a new way for sampling micrometeorites, including separate meteor showers.

Using Sterile Flocked Swabs as an Alternative Method for Rodent Health Monitoring.

Routine health monitoring is an integral part of managing SPF rodent colonies. In recent years, rack-level environmental sampling has been introduced as an adjunct method or replacement for exposure of sentinel rodents to soiled bedding. However, rack-level environmental monitoring is not compatible with rodent housing systems that have cage-level filtration. The current study investigated whether exposure of sterile flocked swabs to soiled bedding can be an alternative sampling method for routine health monitoring in mice, thus replacing the use of sentinels in soiled-bedding cages. Flocked swabs were placed in cages containing pooled samples of soiled bedding but no mice; swabs remained there for 90 d, with weekly agitation and biweekly swabbing of the cage floor to mimic the agitation of soiled bedding by sentinel mice and facilitate the collection of dust particles. Fecal samples were collected from both colony and sentinel mice. For environmental samples, exhaust debris was collected from the rack plenum, and dust samples were collected from the exhaust hose. All samples were collected on days 88 through 91 and were tested for multiple pathogens by using real-time PCR assays. To determine the diagnostic agreement of flocked swab sampling with the other methods, we used κ statistics to compare the test results from flocked swabs with those from sentinel feces, exhaust debris, and colony animal feces; we found excellent agreement between the colony feces and the flocked swab methods. The sterile flocked swab method detected all enzootic pathogens in the colonies tested. Results from flocked swab samples had the least agreement with sentinel feces, which also failed to detect the presence of fur mites. This study supports the use of sterile flocked swabs as alternative to using sentinel mice, thus conforming to the guiding principles of replacement and reduction in the use of animals for routine colony health monitoring.

Colonies of the Marine Cyanobacterium <i>Trichodesmium</i> Optimize Dust Utilization by Selective Collection and Retention of Nutrient-Rich Particles

Trichodesmium, a globally important, N2-fixing and colony-forming cyanobacterium employs multiple pathways for acquiring nutrients from air-borne dust, including the active collection of dust particles. Once concentrated within the colony core, dust can supply Trichodesmium with the limiting nutrients iron (Fe) and phosphorus (P). Studying particle collection by natural colonies, we recently documented a preference for Fe-rich over Fe-free particles. In this follow-up study we examined if colonies selectively collect P-rich particles. Over an entire bloom season, we incubated ~1 200 Trichodesmium colonies from the Red Sea with P-free CaCO3, P-coated CaCO 3 and dust. We utilized three discrete parameters to characterize the colony-particle interactions and integrated them to an index that describes the particle collection behavior over time. Colonies were found to preferably interact, center and retain P-coated CaCO3 in comparison to P-free CaCO3, suggesting that Trichodesmium can optimize its P-acquisition by selecting P-rich particles. In both current and former studies, colonies clearly favored dust over all other particles tested, while nutrient-free particles were barely collected or retained, indicating that Trichodesmium senses the particle composition and preferably collects nutrient-rich particles. This unique ability contributes to Trichodesmium's current ecological success and may assist it to flourish in future warmer oceans.

Design and Analysis of a Separator for Aluminium Dust Particle Collection

Cyclone separators are considered one of the most common and widely used method of separating solid particles from fluids. The focus of this paper was to design a separator that could effectively improve the air quality of an industrial working environment by considering factors such as the nature of the particles and the restrictions on the device such as size and operating condition. To do so, a sample of the dust sample was studied to determine the characteristics of the aluminum dust. An initial separator model which satisfied the separation condition was developed, and a second model was developed with the goal of optimizing and reducing the overall size of the separator. All models developed were subjected to CFD simulations to analyze the flow patterns, separation rate at various particle diameters as well as comparing against the theoretical predicted values. The simulation results showed how the change in various parameters improved the separation efficiency. The total height of the model was approximately 20% smaller than the initial proposed design to fit into the manufacturer’s workbench while the separation efficiencies improved by an average of 5% to 10% across various particle sizes. The results obtained indicated that the efficiency of the particle collection is dependent on the area of the barrel inlet of the separator and the depth of the vortex finder.

Dynamical states in two-dimensional charged dust particle clusters in plasma medium.

The formation of dynamical states for a collection of dust particles in two dimensions is shown using molecular dynamics simulations. The charged dust particles interact with each other with a Yukawa pair potential mimicking the screening due to plasma. An external radial confining force has also been applied to the dust particles to keep them radially confined. When the particle number is low (say, a few), they get arranged on the radial locations corresponding to multiple rings or shells. For specific numbers, such an arrangement of particles is stationary. However, for several cases, the cluster of dust particles relaxes to a state for which the dust particles on rings display intershell rotation. For a larger number of dust particles (a few hundred, for instance), an equilibrium state with a coherent rigid body displaying angular oscillation of the entire cluster is observed. A detailed characterization of the formation of these states in terms of particle number, coupling parameter, etc., is provided.

Efficiency of Tungsten Dust Collection of Different Types of Dust Particles by Electrostatic Probe

Formation of dust particles and clusters is observed in almost every modern thermonuclear facility. Accumulation of dust in the next generation thermonuclear installations can dramatically affect the plasma parameters and lead to the accumulation of unacceptably large amounts of tritium. Experiments on collection of dust particles by a model of electrostatic probe developed for collection of metallic dust at ITER are described in the article. Experiments on the generation of tungsten dust consisting of flakes formed during the destruction of tungsten layers formed on the walls of the plasma chamber sputtered from the surface of the tungsten target by plasma ions were conducted. The nature of dust degassing at elevated temperatures and the behavior of dust in an electric field were studied. The results obtained are compared with the results of the experiments with dust consisting of crystal particles of simple geometric shapes. The effectiveness of collection of both types of dust using the model of an electrostatic probe is determined.

Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta.

The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis.This article is part of the themed issue 'Cometary science after Rosetta'.

Observation of the Korteweg-de Vries soliton in molecular dynamics simulations of a dusty plasma medium

The excitation and evolution of Korteweg-de Vries (KdV) solitons in a dusty plasma medium are studied using Molecular Dynamics (MD) simulations. The dusty plasma medium is modelled as a collection of dust particles interacting through Yukawa potential, which takes into account dust charge screening due to the lighter electron and ion species. The collective response of such screened dust particles to an applied electric field impulse is studied here. An excitation of a perturbed positive density pulse propagating in one direction along with a train of negative perturbed rarefactive density oscillations in the opposite direction is observed. These observations are in accordance with evolution governed by the KdV equation. Detailed studies of (a) amplitude vs. width variation of the observed pulse, (b) the emergence of intact separate pulses with an associated phase shift after collisional interaction amidst them, etc., conclusively qualify the positive pulses observed in the simulations as KdV solitons. It is also observed that by increasing the strength of the electric field impulse, multiple solitonic structures get excited. The excitations of the multiple solitons are similar to the experimental observations reported recently by Boruah et al. [Phys. Plasmas 23, 093704 (2016)] for dusty plasmas. The role of coupling parameter has also been investigated here, which shows that with increasing coupling parameter, the amplitude of the solitonic pulse increases whereas its width decreases.

The development and the tests of the electrostatic probe for dust particle collection in thermonuclear reactors

Formation of dust particles in thermonuclear reactors can greatly affect the plasma parameters and lead to accumulation of tritium. The rates of formation and deposition of dust need to be measured, and the parameters of formation of dust particles and clusters need to be studied. A model of a device for collection of fine conductive particles capable of removing them from the reactor chamber for future research is proposed in this paper. The dust collector's operation is based on a principle of applied electrostatic field. The model was tested in different operating conditions: in vacuum, at the atmospheric pressure in the atmosphere of air and dry nitrogen. The experiments were conducted with a stationary system and with the dust collector in motion relative to the dusty surface. It is shown that, during the probe moving relative to the surface, it can remove up to 95% of fine tungsten particles with sizes ranging from 1 to 10 μm.

Mechanism of Collection of Dust Particles by Charged Droplet

The paper presents a numerical algorithm for simulating the trajectories of charged dust particles moving horizontally in the vicinity of an oppositely charged droplet. With taking the air drag, electrical and gravitational into account, the trajectories of charged dust particles are traced by solving the Newton equation. Calculation results show that the dust particles deposit in the whole surface of charged droplet by the effect of electrical force. Electrical force becomes the main factor for dust deposition at low Stokes.

Dust particle formation due to interaction between graphite and helicon deuterium plasmas

The collection of dust particles using divertor simulation helicon plasmas has been carried out to examine dust formation due to the interaction between a graphite target and deuterium plasmas, which are planned to operate in the large helical device (LHD) at the Japanese National Institute for Fusion Science (NIFS). The collected dust particles are classified into three types: (i) small spherical particles below 400nm in size, (ii) agglomerates whose primary particles have a size of about 10nm, and (iii) large flakes above 1μm in size. These features are quite similar to those obtained through hydrogen plasma operation, indicating that the dust formation mechanisms due to the interaction between a carbon wall and a plasma of deuterium, which is the isotope of hydrogen, is probably similar to those of hydrogen.

Oil refinery dusts: morphological and size analysis by TEM

The objectives of this work were to develop a means of sampling atmospheric dusts on the premises of an oil refinery for electron microscopic study to carry out preliminary morphological analyses and to compare these dusts with those collected at sites beyond the refinery limits. Carbon and collodion membranes were used as a support for collection of dust particles straight on transmission electron microscopy (TEM) grids. Micrographs of the dust particles were taken at magnifications from ×4,000 to ×80,000 with a Tesla BS500 transmission electron microscope. Four parameters were defined on the basis of the micrographs: surface area, Feret diameter, circumference, and shape coefficient. The micrographs and literature data were used to classify the atmospheric dusts into six groups: particles with an irregular shape and rounded edges; particles with an irregular shape and sharp edges; soot and its aggregates; spherical particles; singly occurring, ultrafine dust particles; and particles not allocated to any of the previous five groups. The types of dusts found in all the samples were similar, although differences did exist between the various morphological parameters. Dust particles with the largest Feret diameter were present in sample 3 (mean, 0.739 μm)-these were collected near the refinery's effluent treatment plant. The particles with the smallest diameter were found in the sample that had been intended to be a reference sample for the remaining results (mean, 0.326 μm). The dust particles collected in the refinery had larger mean Feret diameters, even 100% larger, than those collected beyond it. Particles with diameters from 0.1 to 0.2 μm made up the most numerous group in all the samples collected in the refinery.

Wet Electroscrubbers for State of the Art Gas Cleaning

Current trends observed in air pollution control technology are closely related to the development of new, more efficient hybrid systems, i.e., those, which simultaneously utilize two or more physical mechanisms for dust or gaseous contaminants removal. These systems can operate more economically than conventional devices, especially in the removal of PM2.5 particles. The electrostatic scrubber (electroscrubber), discussed in this paper, is one of such types of devices, which combines advantages of electrostatic precipitators and inertial wet scrubbers, and removes many shortcomings inherent to both of these systems operating independently. The electroscrubber is a device in which Coulomb attraction or repulsion forces between electrically charged scrubbing droplets (collector) and dust particles are utilized for the removal of particles from a gas. Unlike wet electrostatic precipitators in which particles are precipitated only on the collection electrode, in electroscrubbers, the collection of dust particles takes place in the entire precipitator chamber. Compared to inertial scrubbers, the electroscrubbers can operate at lower droplet velocities, but the collection efficiency for a single droplet can be larger than 1. The paper reviews the state-of-the-art of wet electrostatic scrubbing (electroscrubbing) technique used for gas cleaning from dust or smoke particles. Three groups of problems are discussed: (1) The fundamental problems concerning the charged dust particle deposition on a charged collector, usually a drop, with a focus on different models describing the process. (2) The experimental works of fundamental importance to our knowledge referring to the scrubbing process, which can be used for validating the theory. (3) The laboratory demonstrations and industrial tests of different constructions of electroscrubbers designed for effective gas cleaning. The electroscrubber is not designed to replace wet or dry electrostatic precipitators but can be used as a complementary device following the last stage of conventional electrostatic precipitator, which helps to remove submicron particles. It was shown in the paper that a higher collection efficiency of an electroscrubber could be obtained for higher values of Coulomb number (i.e., higher electric charges on the collector and particle), and for a Stokes number lower than5 (i.e., low particle-collector relative velocity).

Electrohydrodynamic gas flow in a positive polarity wire-plate electrostatic precipitator and the related dust particle collection efficiency

In this paper, the results of the particle image velocimetry measurements of the flow velocity fields in an intermediate spacing wire-to-plate type electrostatic precipitator (ESP) with a single positive polarity wire electrode are presented. The observation plane was placed perpendicular to the wire electrode at its half-length. The investigation showed significant influence of the electric field and charge on the flow patterns in the intermediate spacing ESP under an extreme large electrohydrodynamic (EHD) number. The EHD forces cause the formation of strong vortex pairs in the upstream and downstream ESP regions for Ehd/ Re 2>1.

A singularity-free solution of Friedmann universe in the discrete spacetime

An idealized Friedmann cosmological model in the discrete spacetime is consist of collection of dust particles obtained in paper［1］ and proved to be singu larity-free.

16.P.15 Dust particle collection efficiency of cold precharger and pulse energized electrostatic precipitator under heavy dust loadings

16.P.15 Dust particle collection efficiency of cold precharger and pulse energized electrostatic precipitator under heavy dust loadings

Levitation and dynamics of a collection of dust particles in a fully ionized plasma sheath

Examines the dynamics of a collection of charged dust particles in the plasma sheath above a large body in a fully ionized space plasma when the radius of the large body is much larger than the sheath thickness. The dust particles are charged by the plasma, and the forces on the dust particles are assumed to be from the electric field in the sheath and from gravitation only. These forces will often act in opposite directions and may balance, making dust suspension and collection possible. The dust particles are supplied by injection or by electrostatic levitation. The ability of the sheath to collect dust particles, will be optimal for a certain combination of gravitation and plasma and dust particle parameters. In a dense dust sheath, the charges on the dust particles contribute significantly to the total space charge, and collective effects become important. These effects will reduce the magnitude of the sheath electric field strength and the charge on the dust particles. As dust particles are collected, the dust sheath is stretched and the largest dust particles may drop out, because the sheath is no longer able to suspend them. In a tenuous dust sheath, the inner layer, from the surface and about one Debye length thick, will be unstable for dust particle motion, and dust will not collect there. In a dense dust sheath, collective effects will decrease the thickness of this inner dust-free layer, making dust collection closer to the surface possible. By linearization of the force and current equations, the necessary and sufficient conditions for a stable dust sheath are found. The authors consider conditions which resemble those of planetary system bodies, but the results may also be of relevance to some laboratory plasmas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

STATIC ELECTRICITY (SE) IN NEONATAL INTENSIVE CARE UNIT (NICU) ENVIRONMENT

The presence of SE and its potential hazard to infants in NICU is not well recognized. We therefore quantified the SE generated on equipment, patients and personnel in our NICU. A specially designed isolated plate monitor was used consisting of a 6″ square steel plate whose potential is monitored by an electrostatic field meter probe. (SIMCO CORP IIATFIELD, Pa). The monitor is chopper stabilized to provide drift free readings. 45 sets of SE measurements taken on different days in our NICU are shown in Kilovolts (KV). x ± SD). Relative humidity ranged from 40 to 62% during study.Wiping isolettes, monitors, tubing, saran wrap, etc, increased SE many folds. Static changes of upto 14 KV were recorded from isolettes and saran wraps wiped with dry cloth. We further studied effects of discharge of SE from surface charged up to IKV on skin of 3 premature baboons under continuous monitoring of central BP, CVP and EKG. No recordable changes were produced in these. A study into effects of sudden discharge of larger amounts of SE in the vicinity of indwelling catheters in sick premature baboons is now in progress. We conclude that large amounts of SE exist in the NICU. Besides having the potential for causing injury to sick newborns, SE promotes collection of dust particles in close proximity to the newborn, thus increasing the risk of nosocomial infections. Precautions should be taken to decrease SE in NICU.

Studies of the dynamic behaviour of charged dust particles in high electric fields using laser Doppler velocimetry

As a preliminary study for the collection of dust particles in an electrostatic precipitator, laser Doppler velocimetry has been used to measure the velocity of small dust particles charged in the high electric field of a model electrostatic precipitator. A differential optical system is adopted for the velocimeter. The period-measuring system is used to analyse Doppler beat signals and to obtain velocity data from them. By means of the laser Doppler velocimeter, the dynamic behaviour of the velocity and direction of moving dust particles is fully revealed as a function of the applied electric voltage in the entire collecting space of the model electrostatic precipitator, and is shown in vectorial flow diagrams of particle velocity.