Uncharged Particles Research Articles

POSSIBILITIES OF SYNTHESIS OF UNCHARGED STABLE LATEX PARTICLES FOR IMMUNOANALYSIS

Objective: The objective of this study is to find a method for synthesizing uncharged polystyrene latex particles whose surface can be easily modified. Theoretical basis: The main method of latex synthesis is emulsion polymerization. Latexes for a specific purpose can be obtained by polymerization in heterogeneous monomer-water systems, without the use of emulsifiers, both with intensive mixing of the system and under static conditions. In this work, polymerization was carried out without the use of emulsifiers in a static monomer-water system. Method: To achieve the set goal, the possibility of obtaining latex particles using a hydrophobic initiator - ditrile of azoisobutyric acid - was investigated by carrying out polymerization in a diffusion mode in a three-phase system monomer - water - initiator. Results and discussion: The results of the study showed that the latex obtained in the three-phase system is stable. It is assumed that the stability is due to the presence of hydroxyl end groups groups of polymer molecules on the surface of the latex particles, which are formed as a result of the reaction of the initiator with water and initiate polymerization. The synthesized latexes retained stability for a year. Practical value: Latexes can be used in all those areas of science and technology where the absence of a charge on the surface of latex particles is required. Originality/value: The originality of the work lies in the fundamental simplicity of the synthesis and the unambiguity of the results obtained.

Extensive study of droplet dynamics with end-grafted polymer chains in Pickering emulsions: Molecular Dynamics simulation and a generic model derived from the generalized Langevin equation

This paper investigates Pickering emulsions (PEs), formed by suspending oil droplets as the dispersed phase in water as the continuous phase using uncharged particles at their interface. To prevent coalescence, the particles are grafted with polymer chains, as emulsifier, not only to provide steric repulsion forces through the excluded volume between monomers floating in water, compensating for the absence of Coulombic repulsive forces but also control emulsion stabilization/destabilization. We combined molecular dynamics (MD) simulations and a generalized Langevin equation (GLE) model to study the dynamics of hairy-droplets using two dynamic quantities: mean square displacement (MSD) and velocity autocorrelation function (VACF). The number of grafted-polymer-chains, f, was the main parameter of interest, while the other parameters of the system were kept constant. A statistical approach was used to estimate theoretical GLE-based model parameters along with their uncertainties, providing insight into the diffusion behavior of these hairy-droplets and specifically addressing the transition between different observed regimes. we capture three specific values of grafted-polymer-chains as, fb=47 and ft=185 describe the transitions of mushroom-brush conformation of grafted-polymer-chains and viscous-viscoelastic behavior of hairy-droplets, respectively, and fg=257 representing the gel-like state number.

Turbulence modulation by charged inertial particles in channel flow

Large amounts of small inertial particles embedded in a turbulent flow are known to modify the turbulent statistics and structures, a phenomenon referred to as turbulence modulation. While particle electrification is ubiquitous in particle-laden turbulence and significantly alters particle behaviour, the effects of inter-particle electrostatic forces on turbulence modulation and the underlying physical mechanisms remain unclear. To fill this gap, we perform a series of point-particle direct numerical simulations of turbulent channel flows at a friction Reynolds number of approximately 540, laden with uncharged and charged bidisperse particles. The results demonstrate that, compared to flows laden with uncharged particles, the presence of inter-particle electrostatic forces leads to substantial changes in both turbulent intensities and structures. In particular, the inner-scaled mean streamwise fluid velocity is found to shift towards lower values, indicating a noticeable increase in fluid friction velocity. Turbulent intensities appear to be further suppressed through facilitating the particles to extract momentum from the fluid phase and increasing extra turbulent kinetic dissipation by particles. Importantly, the overall drag is enhanced by indirectly strengthening the contribution of particle stress, even though the contribution of the total fluid stress is decreased. On the other hand, the magnitude of the large-scale motions is weakened by simultaneously reducing turbulent production and increasing particle feedback around the scales of the large-scale motions. Meanwhile, the average streaky fluid structures in the streamwise–spanwise planes and inclined fluid structures in the streamwise–wall-normal planes become expanded and flattened, respectively.

Ion‐Pairing: A Bygone Treatment of Electrolyte Solutions?

AbstractThe field of battery research has advanced significantly in the past 50 years. Despite the importance of electrolyte solutions for these devices, the battery community's perception of this essential component arguably aligns more with the 19th century reasoning than the 20th centuries advancements. This paper traces the historical evolution of electrolyte theories, emphasizing the consequences of an overly ion‐pairing‐centric view, and the benefits of a more nuanced analysis. A quantitative example is provided. It will be shown that an association constant of can be obtained from conductivity measurements of sodium acetate in water. However, studying the activity coefficients of this electrolyte reveals that this association constant would result in an unreasonable scenario where the free ions behave as uncharged particles at low concentrations. The aim is to promote a nuanced perspective on electrolyte solutions within the battery community, while also providing a collection of reputable references for the interested readers further studies.

Motion of particles around a magnetically charged Euler–Heisenberg black hole with scalar hair and the Event Horizon Telescope

We study the motion of uncharged particles and photons in the background of a magnetically charged Euler–Heisenberg (EH) black hole (BH) with scalar hair. The spacetime can be asymptotically (A)dS or flat. After investigating particle motions around the BH and the behavior of the effective potential of the particle radial motion, we determine the contribution of the BH parameters to the geodesics. Photons follow null geodesics of an effective geometry induced by the corrections of the EH non-linear electrodynamics. Thus, after determining the effective geometry, we calculate the shadow of the BH. We also analyze in detail the case of extremal BH spacetimes and we find that the radius of both the event horizon and shadow exhibits discontinuities when varying with respect to either the magnetic charge or the scalar charge. These extremal scenarios exist for sufficiently small values of the EH parameter, and imply the formation of a second photon ring around the BH shadow. Upon comparing the theoretically calculated BH shadow to the images of the shadows of M87* and Sgr A* observed by the Event Horizon Telescope collaboration, we impose constraints on the BH parameters, namely the scalar hair (ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}), the magnetic charge (Qm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q_{m}$$\\end{document}) and the EH parameter (α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}). For sufficiently large values of the EH parameter, our model is in agreement with the EHT observations for approximately every value for the BH magnetic charge.

Effects of polycarboxylate superplasticizer and hydroxypropyl methylcellulose on the properties of ferric-rich sulfoaluminate cement

Ferric-rich sulfoaluminate cement (FR-SAC) is a promising low-carbon cement and is usually used to prepare precast products due to its short setting time. However, the fast setting of FR-SAC paste also leads to its poor fluidity and workability. Polycarboxylate superplasticizer (PCE) and hydroxypropyl methylcellulose (HPMC) can improve the fluidity and viscosity but may affect other properties of FR-SAC products. To get a suitable performance of FR-SAC by adding PCE or HPMC, the properties of FR-SAC paste with PCE and HPMC added and their influence mechanism were explored. The results indicate that PCE adsorbs on the surface of positively charged ettringite in the slurry under the electrostatic attraction, which makes the negatively charged or uncharged FR-SAC particles uniformly dispersed in the slurry, thus regulating the rheology and other properties of FR-SAC paste. The compressive strength of FR-SAC paste increases with the increase of PCE addition. PCE slightly retard the early hydration rate of FR-SAC but does not affect the formation of later hydration products. Adding HPMC to FR-SAC paste can decrease the fluidity and increase the viscosity of FR-SAC paste but has little effect on its hydration properties. Therefore, when PCE and HPMC are used to modulate the rheology of FR-SAC paste, it is necessary to combine the utilization process and compressive strength requirements to keep both the rheological parameters and compressive strength in the suitable condition.

Glassy-like Transients in Semiconductor Nanomaterials.

Glassy behavior is manifested by three time-dependent characteristics of a dynamic physical property. Such behaviors have been found in the electrical conductivity transients of various disordered systems, but the mechanisms that yield the glassy behavior are still under intensive debate. The focus of the present work is on the effect of the quantum confinement (QC) and the Coulomb blockade (CB) effects on the experimentally observed glassy-like behavior in semiconductor nanomaterials. Correspondingly, we studied the transient electrical currents in semiconductor systems that contain CdSe or Si nanosize crystallites, as a function of that size and the ambient temperature. In particular, in contrast to the more commonly studied post-excitation behavior in electronic glassy systems, we have also examined the current transients during the excitation. This has enabled us to show that the glassy behavior is a result of the nanosize nature of the studied systems and thus to conclude that the observed characteristics are sensitive to the above effects. Following this and the temperature dependence of the transients, we derived a more detailed macroscopic and microscopic understanding of the corresponding transport mechanisms and their glassy manifestations. We concluded that the observed electrical transients must be explained not only by the commonly suggested principle of the minimization of energy upon the approach to equilibrium, as in the mechanical (say, viscose) glass, but also by the principle of minimal energy dissipation by the electrical current which determines the percolation network of the electrical conductivity. We further suggest that the deep reason for the glassy-like behavior that is observed in the electrical transients of the nanomaterials studied is the close similarity between the localization range of electrons due to the Coulomb blockade and the caging range of the uncharged atomic-size particles in the classical mechanical glass. These considerations are expected to be useful for the understanding and planning of semiconductor nanodevices such as corresponding quantum dot memories and quantum well MOSFETs.

Observation of a Photonic Orbital Gauge Field.

Gauge field is widely studied in natural and artificial materials. With an effective magnetic field for uncharged particles, many intriguing phenomena are observed in several systems like photonic Floquet topological insulator. However, previous researches about the gauge field mostly focus on limited dimensions such as the Dirac spinor in graphene materials. Here, an orbital gauge field based on photonic triangular lattices is first proposed and experimentally observed. Disclination defects with Frank angle Ω created on such lattices breaks the original lattice symmetry and generates purely geometric gauge field operating on orbital basis functions. Interestingly, it is found that bound states near zero energy with the orbital angular momentum (OAM) l = 2 are intensively confined at the disclination as gradually expanding Ω. Moreover, the introduction of a vector potential field breaks the time-reversal symmetry of the orbital gauge field, experimentally manifested by the chiral transmission of light on helical waveguides. The orbital gauge field further suggests fantastic applications of manipulating the vortex light in photonic integrateddevices.

Moment tracking and their coordinate transformations for macroparticles with an application to plasmas around black holes

Particle-in-cell (PIC) codes usually represent large groups of particles as a single macroparticle. These codes are computationally efficient but lose information about the internal structure of the macroparticle. To improve the accuracy of these codes, this work presents a method in which, as well as tracking the macroparticle, the moments of the macroparticle are also tracked. Although the equations needed to track these moments are known, the coordinate transformations for moments where the space and time coordinates are mixed cannot be calculated using the standard method for representing moments. These coordinate transformations are important in astrophysical plasma, where there is no preferred coordinate system. This work uses the language of Schwartz distributions to calculate the coordinate transformations of moments. Both the moment tracking and coordinate transformation equations are tested by modelling the motion of uncharged particles in a circular orbit around a black hole in both Schwarzschild and Kruskal–Szekeres coordinates. Numerical testing shows that the error in tracking moments is small, and scales quadratically. This error can be improved by including higher order moments. By choosing an appropriate method for using these moments to deposit the charge back onto the grid, a full PIC code can be developed.

Effects of a modified Reissner-Nordström spacetime

A modified Reissner-Nordström spacetime is considered here, where the central object (for example, a black hole or naked singularity) possesses a mass, with an “ordinary”, i.e., Standard Model (SM) electric charge, along with a “dark” electric charge associated with dark matter (DM). The inclusion of this dark charge modifies the gravitational properties of the spacetime, while not affecting ordinary electrodynamics. Geodesic motions of both charged and uncharged SM test particles are modified due to the presence of dark charge. The modifications may allow the detection and measrement of the dark charge. In particular, (1) the effective potential for orbiting particles is modified, and consequently, (2) the angular momenta and ISCOs of test masses in circular orbits are changed from those for the usual Reissner-Nordström case. (3) In the case of a naked singularity, it is possible that a “levitating atmosphere”, due to short distance repulsive gravity, forms at the zero gravity radius, which depends upon both SM and DM charges. A levitating atmosphere may then cloak the naked singularity.

Sedimentation of a Charged Spherical Particle in a Viscoelastic Electrolyte Solution.

When a charged particle translates through an electrolyte solution, the electric double layer around it deforms in response to the fluid motion and creates an electric force opposite the direction of motion, decreasing the settling velocity. This is a multidisciplinary phenomenon that combines fluid mechanics and electrodynamics, differentiating it from the classical problem of an uncharged sedimenting particle. It has many applications varying from mechanical to biomedical, such as in drug delivery in blood through charged microparticles. Related studies so far have focused on Newtonian fluids, but recent studies have proven that many biofluids, such as human blood plasma, have elastic properties. To this end, we perform a computational study of the steady sedimentation of a spherical, charged particle in human blood plasma due to the centrifugal force. We used the Giesekus model to describe the rheological behavior of human blood plasma. Assuming axial symmetry, the governing equations include the momentum and mass balances, Poisson's equation for the electric field, and the species conservation. The finite size of the ions is considered through the local-density approximation approach of Carnahan-Starling. We perform a detailed parametric analysis, varying parameters such as the ζ potential, the size of the ions, and the centrifugal force exerted upon the particle. We observe that as the ζ potential increases, the settling velocity decreases due to a stronger electric force that slows the particle. We also conduct a parametric analysis of the relaxation time of the material to investigate what happens generally in viscoelastic electrolyte solutions and not only in human blood plasma. We conclude that elasticity plays a crucial role and should not be excluded from the study. Finally, we examine under which conditions the assumption of point-like ions gives different predictions from the Carnahan-Starling approach.

Medical imaging applied to heritage.

The use of imaging has transformed the study of cultural heritage artefacts in the same way that medical imaging has transformed medicine. X-ray-based techniques are common in both medical and heritage imaging. Optical imaging, including scientific photography and spectral imaging techniques, is also common in both domains. Some common medical imaging methods such as ultrasound and MRI have not yet found routine application in heritage, whereas other methods such as imaging with charged and uncharged particles and 3D surface imaging are more common in heritage. Here, we review the field of heritage imaging from the point of view of medical imaging and include some classic challenges of heritage imaging such as reading the text on burnt scrolls, identifying underdrawings in paintings, and CT scanning of mummies, an ancient calculating device and sealed documents. We show how hyperspectral imaging can offer insight into the drawing techniques of Leonardo da Vinci and explain how laparoscopy has identified the method of construction of a 500-year-old pop-up anatomical text book.

Sedimentation of a Fine Aerosol in the Acoustic Fieldand with the Electrostatic Charge of Particles

Finding an efficient way to eliminate fine dust (particle diameter of 1–15 μm) from a room can be a challenging problem. Acoustic radiation emitters are widely used to accelerate particle coagulation and sedimentation. In this study, we propose one more method for depositing harmful particles – dispersion of electrostatically charged particles. These particles attract uncharged particles from the air and accelerate coagulation. The paper is devoted to a comparison of methods for the acoustic and electrostatic sedimentation of aerosols. The mathematical model for the coagulation of aerosols on the basis of Smoluchowski’s equation is proposed in the options corresponding to acoustic and electrostatic coagulation. A number of conclusions about the most effective conditions of sedimentation were made on the basis of the analysis of a kernel type of Smoluchowski’s integral equation. The results of the experiments on acoustic and electrostatic sedimentation of the model aerosol media (coal dust) are given. The results of the calculations according to the mathematical model of coagulation taking into account the proposed mechanisms for the sedimentation of aerosols in the acoustic field and electrostatic charging of particles are given.

Computation of Neutron Coefficients for B2O3 reinforced Composite

Radiation is an important phenome and has been used in many different fields since its discovery. Although there are different types of radiation, neutron is one of the most interesting types as it is an uncharged particle. This character made neutron is more dangerous radiation types than others and thus protection from neutron effect requires more care. In this paper neutron attenuation coefficients of B2O3 reinforced composite have been investigated using Phy-X/PSD software.

Technical note: Simplified approaches to estimate the output of particle mass analyzers paired with unipolar chargers

Particle mass analyzers (PMAs) classify particles by their mass-to-charge ratio. PMAs are often paired with bipolar chargers, which produce charge distributions that consist of positively-, negatively, and neutrally-charged particles, which greatly limits the transmission efficiency of PMAs and allows small, uncharged particles to be classified erroneously. These limitations provide an opportunity for unipolar chargers, which impart several charges per particle. However, the PMA setpoint (mass-to-charge ratio) loses physical meaning when the average number of charges per particle mass is unknown. The average charge of the PMA classified particles can be inferred from downstream size distribution measurements or by running detailed models. However, downstream measurements are often practically infeasible and detailed models require knowledge of the unclassified aerosol size and density. These challenges motivate a need for simplified approaches. Using simulations, we show that the unipolar charger-PMA average charge can be estimated to within ±20% for a reasonable range of parameters for typical aerosol scenarios. The most significant uncertainties behind the simplified approach are related to particle morphology (e.g., fractal versus spheroidal particles). Our simplified approach relies on the derivation of an empirical power-law relationship between the particle average charge and particle diameter, which is consistent with several previous experimental studies and existing models. The approaches described in this work improve the capabilities of unipolar charger-PMA systems to classify a known average mass (rather than a known mass-to-charge ratio) which is valuable for characterizing and calibrating the response of optical and mass instruments.

Rotating black hole in 4D Einstein–Gauss–Bonnet massive gravity: Shadow and center of mass energy

This work comprises the derivation of a rotating black hole metric by applying the modified Newman-Janis algorithm to a static four dimensional black hole in Einstein-Gauss–Bonnet massive gravity. We choose several parametric values to study the influence of graviton mass m and the Gauss–Bonnet parameter α on the horizon radii and photon sphere’s radii of the rotating and non-rotating black holes, respectively. By considering the Hamilton–Jacobi method, we construct the geodesic equations and by using Bardeen’s procedure of impact parameters, we study the effect of graviton mass on the effective potential, shadow, distortion and energy emission rate. We find that the graviton mass has a very significant effect on the shadow and related physical observables. In the vicinity of the black hole, we investigate the collision of two uncharged particles. We compute the energy of the particles in the center of mass frame for the static and rotating BH cases. Finally, the shadow diameter is compared with Sgr. A* to obtain the constraints on the black hole parameters.

The performance evaluation of pleated electret filters enhanced by electrostatic enhanced method

The filtration efficiency deterioration over operating time due to exposure to particles, organic solvents and other factors is an obvious defect of electret filter, especially during the coronavirus pandemic. Electrostatic enhanced method has been proposed as a promising way to improve the filtration efficiency and service time of electret filters without increasing the pressure drop. In this work, the effect of discharge electrode structure and operation mode of the electrostatic enhanced structure(EES) on the filtration efficiency of commercial pleated electret filters were studied firstly, then the EES was installed in a special designed prototype air purifier, two key indicators of air purifiers(clean air delivery rate (CADR) and cumulate clean mass (CCM)) were tested to evaluate the actual performance improvement of electret filters by the electrostatic enhanced method. It was found that the discharge electrode structure had significant influence on the filtration efficiency and multi-wire array electrode was more suitable for the discharge electrode to pleated filter to ground mesh structure used in this paper. The decayed electrostatic charges of pleated electret filter cannot be recharged again through the EES in actual operation condition. The filtration efficiency improvement of the test pleated electret filters was dominantly contributed by particle charging. The filter polarizing induced by the external electric field was helpful in increasing the filtration efficiency when the particles were charged while its effect on uncharged particles was almost negligible. Besides, the actual performance of the prototype air purifier indicated that the EES can alleviate the filtration efficiency deterioration of test electret filters and extend the service life of H11 and H13 filters by more than 3 and 1.5 times respectively according to the CCM test results.

Effect of drag force modeling on the flow of electrostatically charged particles

In CFD simulations of two-phase flows, accurate drag force modeling is essential for predicting particle dynamics. However, a generally valid formulation is lacking, as all available drag force correlations have been established for specific flow situations. In particular, these correlations have not been evaluated for particle-laden flows subjected to electrostatic forces. The paper reports the effect of drag force modeling on the flow of electrically charged particles. To this end, we implemented different drag force correlations to the open-source CFD tool pafiX. Then, we performed highly-resolved Direct Numerical Simulations (DNS) using the Eulerian–Lagrangian approach of a particle-laden channel flow with the friction Reynolds number of 180. The simulations generally revealed a strong influence of the precise drag correlation on particles in the near-wall region and a minor effect on the particles far from the walls. Due to their turbophoretic drift, particles accumulate close to the channel walls. For uncharged particles, the simulations show large deviations of the particle concentration profile in the near-wall region depending on the drag force correlation. Therefore, the disturbance of the flow surrounding a particle by a nearby wall or other particles is important for its drag. Driven by electrostatic forces, charged particles accumulate even closer to the wall. Contrary to the uncharged cases, when the particles carry a high charge (in our case one femto-coulomb), we found minor effects of drag force modeling on particle concentration profiles. In conclusion, for the investigated conditions, we propose to account for the effect of nearby particles and walls on the drag of low- or uncharged particles.

Numerical study of airborne particle dynamics in vortices near curved electrode surfaces

A study is formulated to identify unique features in the dynamical behavior of airborne particles near curved surfaces, subject to a combination of aerodynamic and electrostatic influences. Particle tracing investigation is conducted in numerically fabricated steady vortices distorted near curved electrodes. The effect of direction and strength of air circulation on uncharged airborne particles is studied relative to that of the externally induced electric field, for a range of particle sizes and inertia. Unique features such as (a) improvement, deterioration, and controlled cutoff of electrostatic capture of particles; (b) segregation of particles expelled onto the domain walls selectively based on their size and inertia; and (c) particle flight manipulation with airborne trapping in inertial limit cycle trajectories and inverse cyclonic separation are observed. These phenomena are characterized by suitably identified dimensionless numbers Stv and ξv representing the ratio of the aerodynamic drag and the dielectrophoretic force to the particle inertia, respectively.

Radar Cross-section of a target and attenuation of electromagnetic waves in sandstorms

The sand particles suspended in the atmosphere can cause the attenuation of electromagnetic waves (EWs) and affect the electromagnetic scattering properties of a target during sandstorms. In this study, a theoretical analysis is offered for the prediction of the EWs attenuation and the radar cross section (RCS) of a target in sandstorms. In the model, an equivalent medium approximation is performed by considering the non-uniform charge distribution on the sand particles, and the effect of the charged sand particles on the scattering characteristics of a target is also taken into account. Numerical results show that the RCS of a target is severely affected in sandstorms. Besides, the charged sand particles have a much greater effect on the target's RCS than the case of the uncharged sand particles. It can be found that the average variation value of the target's RCS decreases nearly exponentially with the increase of visibility, and increases nearly linearly with the distance between the target and incident wave source. Finally, an empirical formula is presented to calculate the RCS of an arbitrarily shaped metal target in a homogeneous lossy medium. These investigations will be of significant benefit to radar detection technology in sandstorms.