Particle Interactions Research Articles

Surface-induced interaction of colloidal particles in isotropic liquid crystals

Surface-induced interaction of colloidal particles in isotropic liquid crystals

Experimental modeling of atmospheric discharge phenomena and charged dust particle interactions

Experimental modeling of atmospheric discharge phenomena and charged dust particle interactions

Which Coverages of Arc-Shaped Proteins Are Required for Membrane Tubulation?

Arc-shaped BIN/Amphiphysin/Rvs (BAR) domain proteins generate curvature by binding to membranes and induce membrane tubulation at sufficiently large protein coverages. For the amphiphysin N-BAR domain, Le Roux et al., Nat. Commun. 2021, 12, 6550, measured a threshold coverage of 0.44 ± 0.097 for nanotubules emerging from the supported lipid bilayer. In this article, we systematically investigate membrane tubulation induced by arc-shaped protein-like particles with coarse-grained modeling and simulations and determine the threshold coverages at different particle-particle interaction strengths and membrane spontaneous curvatures. In our simulations, the binding of arc-shaped particles induces a membrane shape transition from spherical vesicles to tubules at a particle threshold coverage of about 0.5, which is rather robust to variations of the direct attractive particle interactions or spontaneous membrane curvature in the coarse-grained model. Our study suggests that threshold coverages of around or slightly below 0.5 are a general requirement for membrane tubulation by arc-shaped BAR domain proteins.

Motion of fine particles in a temperature gradient: Experiment, visualization, and numerical simulation studies

The migration and deposition processes of fine particles under the influence of temperature gradients and fluid flow are widely prevalent. Investigating the mechanisms of particle interactions in these processes contributes to the development of efficient dust removal techniques. In this work, experimental and numerical studies of particle motion in temperature gradient fields are conducted. The research encompasses both qualitative and quantitative analyses of particle motion influenced by thermophoresis and particle diameter. Qualitative analysis reveals that the motion characteristics of particles are jointly determined by gravity, drag force, and thermophoretic force, and the diameter range that exhibiting a notable influence of the thermophoretic force is 20–30 μm. Quantitative analysis shows that the manifestations of deposition and diffusion become more evident with an increasing temperature gradient. For instance, in comparison to the working condition with ΔT = 0 K and dp = 20 μm, the deposition mass increases by approximately 23% when ΔT = -15 K; conversely, it diminishes by about 11% when ΔT = 15 K. Additionally, the Discrete Phase Model (DPM) is employed to simulate the motion of gas-solid flow. This study presents a novel visualization system to observe particle motion in gas-solid systems to elucidate the mechanisms underlying the thermophoretic effect and establish a robust theoretical foundation for thermophoretic dust removal technology.

Modeling Colloidal Particle Aggregation Using Cluster Aggregation with Multiple Particle Interactions.

In this study, we investigate the aggregation dynamics of colloidal silica by generating simulated structures and comparing them to experimental data gathered through scanning transmission electron microscopy (STEM). More specifically, diffusion-limited cluster aggregation and reaction-limited cluster aggregation models with different functions for the probability of particles sticking upon contact were used. Aside from using a constant sticking probability, the sticking probability was allowed to depend on the masses of the colliding clusters and on the number of particles close to the collision between clusters. The different models of the sticking probability were evaluated based on the goodness-of-fit of spatial summary statistics. Furthermore, the models were compared to the experimental data by calculating the structures' fractal dimension and mass transport properties from simulations of flow and diffusion. The sticking probability, depending on the interaction with multiple particles close to the collision site, led to structures most similar to the STEM data.

A novel approach for Technetium-99m radioisotope transportation and storage in lead-free glass containers: A comprehensive assessment through Monte Carlo simulation technique

The primary aim of this project is to develop glass containers that are free from lead for the transportation of Tc-99m. The analysis included glass container structures characterized by the chemical formula 60B2O3-(25-x)GeO2-15BaO-xWO3 (where x ranges from 0 to 25). The rates of addition, in theory, range from 3.397 to 4.124 g/cm3. To evaluate the radiation shielding abilities of glass containers, the Phy-X/PSD software was used. The energy values employed in the evaluation varied from 0.015 MeV to 0.15 MeV, a range frequently employed in the field of medical physics. The transmission factors for the specific gamma energy of Tc-99m were determined using the Monte Carlo method MCNPX (version 2.7.0). The method simulates the motion and interaction of particles. The G6 glass container type exhibited the highest level of gamma-ray attenuation among all the investigated glass containers, primarily due to its superior shielding properties. The creation of glass containers that do not contain lead and are designed to contain the movement of Tc-99m has significant implications in the areas of radiopharmaceuticals and medical diagnostics. In light of the continuous attempts of the scientific community, it is advisable to undertake more investigations aimed at enhancing the technology of lead-free glass.

Wave–particle interactions in tokamaks

Transport consequences of the wave–particle interactions in the quasilinear plateau (QP) regime are presented. Eulerian approach is adopted to solve the drift kinetic equation that includes the physics of the nonlinear trapping (NT) and QP regimes. The localization of the perturbed distribution simplifies the test particle collision operator. It is shown that a mirror force like term responsible for the flattening of the distribution in the NT regime is subdominant in the QP regime, and controls the transition between these two regimes. Transport fluxes, flux-power relation, and nonlinear damping or growth rate are all calculated. There is no explicit collision frequency dependence in these quantities; however, the width of the resonance does. Formulas that join the asymptotic results of these two regimes to facilitate thermal and energetic particle transport, and nonlinear wave evolution of a single mode are presented.

Acoustic manipulation of multi-body structures and dynamics.

Sound can exert forces on objects of any material and shape. This has made the contactless manipulation of objects by intense ultrasound a fascinating area of research with wide-ranging applications. While much is understood for acoustic forcing of individual objects, sound-mediated interactions among multiple objects at close range gives rise to a rich set of structures and dynamics that are less explored and have been emerging as a frontier for research. We introduce the basic mechanisms giving rise to sound-mediated interactions among rigid as well as deformable particles, focusing on the regime where the particles' size and spacing are much smaller than the sound wavelength. The interplay of secondary acoustic scattering, Bjerknes forces, and micro-streaming is discussed and the role of particle shape is highlighted. Furthermore, we present recent advances in characterizing non-conservative and non-pairwise additive contributions to the particle interactions, along with instabilities and active fluctuations. These excitations emerge at sufficiently strong sound energy density and can act as an effective temperature in otherwise athermal systems.

Unusually Low-frequency Whistler-mode Waves and Their Association with High-energy Protons Observed Upstream of Martian Bow Shock

Whistler-mode waves upstream of planetary bow shock are often referred to as “1-Hz waves” due to the center of their observed frequency range being at ∼1 Hz. A series of whistler-mode waves were observed upstream of the Martian bow shock by MAVEN on 2015 August 14, with unusually low frequencies centered at ∼0.4 Hz. These waves were accompanied (though not synchronized) by the significant flux enhancement of high-energy protons up to ∼10 keV. By analyzing the wave dispersion property and the wave–particle interaction condition, we find that the observed whistler-mode waves have the potential of resonating with protons of ∼1 keV with large pitch angles up to nearly perpendicular to the background magnetic field, thereby providing a feasible means of accounting for proton acceleration. Our results indicate the possible origin of energized protons in the Martian environment through the interaction with whistler-mode waves, and their potential relationship with the unique upstream conditions.

Towards complex dynamic physics system simulation with graph neural ordinary equations

The great learning ability of deep learning facilitates us to comprehend the real physical world, making learning to simulate complicated particle systems a promising endeavour both in academia and industry. However, the complex laws of the physical world pose significant challenges to the learning based simulations, such as the varying spatial dependencies between interacting particles and varying temporal dependencies between particle system states in different time stamps, which dominate particles’ interacting behavior and the physical systems’ evolution patterns. Existing learning based methods fail to fully account for the complexities, making them unable to yield satisfactory simulations. To better comprehend the complex physical laws, we propose a novel model – Graph Networks with Spatial–Temporal neural Ordinary Differential Equations (GNSTODE) – that characterizes the varying spatial and temporal dependencies in particle systems using a united end-to-end framework. Through training with real-world particle–particle interaction observations, GNSTODE can simulate any possible particle systems with high precisions. We empirically evaluate GNSTODE’s simulation performance on two real-world particle systems, Gravity and Coulomb, with varying levels of spatial and temporal dependencies. The results show that GNSTODE yields better simulations than state-of-the-art methods, showing that GNSTODE can serve as an effective tool for particle simulation in real-world applications. Our code is made available at https://github.com/Guangsi-Shi/AI-for-physics-GNSTODE.

Plasmonic excitations in double-walled carbon nanotubes

The interactions of charged particles moving paraxially in multi-walled carbon nanotubes may excite electromagnetic modes. This wake effect has recently been proposed as a potential novel method of short-wavelength high-gradient particle acceleration and for obtaining brilliant radiation sources. In this work, the excitation of wakefields in double-walled carbon nanotubes is studied by means of the linearized hydrodynamic theory. General expressions have been derived for the excited longitudinal and transverse wakefields and related to the resonant wavenumbers which can be obtained from the dispersion relation. In the absence of friction, the stopping power of the wakefield driver, modelled here as a charged macroparticle, can be written solely as a function of these resonant wavenumbers. The dependencies of the wakefields on the radii of the double-walled carbon nanotubes and the driving velocity have been studied. Double-walled carbon nanotubes with inter-wall distances much smaller than the internal radius may be a potential option to obtain higher wakefields for particle acceleration compared to single-walled carbon nanotubes.

ОЦІНКА СТРУКТУРИ ШЛАКОВИХ РОЗПЛАВІВ НА ПІДСТАВІ АНАЛІЗУ ТЕМПЕРАТУРНИХ ЗАЛЕЖНОСТЕЙ В’ЯЗКОСТІ ТА ЕЛЕКТРОПРОВІДНОСТІ З ВИКОРИСТАННЯМ АДАПТИВНОЇ СЕГМЕНТНОЇ РЕГРЕСІЙНОЇ МОДЕЛІ

The expediency of using an adaptive segmented regression model for the analysis of logarithmic dependences of viscosity and electrical conductivity on temperature to assess the structure of slag melts is shown. Calculated values of the activation energies of viscosity ( ) and electrical conductivity ( ) in different temperature ranges. The obtained calculation results confirm that the viscosity and electrical conductivity of slag melts characterize the interaction of various structural particles (ions and/or their groups) and can be used in the study of the structure of slag melts. It was established that the activation energy of viscosity and electrical conductivity decreases as the temperature of slag melts increases. The performed calculations of the indicator n=En/Ex indicate that it can be a criterion for evaluating the structure of the slag melt, when n >1, the slag melt is a heterogeneous system, and when n < 1, it is a homogeneous system. Viscosity and electrical conductivity are interdependent properties and can be predicted if there is data on one of the properties, provided the value of n is known.

Calibration of particle interactions for discrete element modeling of powder flow

Calibration of particle interactions for discrete element modeling of powder flow

Enhanced fully resolved CFD-DEM-PBFM simulation of non-spherical particle–fluid interactions during hydraulic collection

The interactions between non-spherical particles and fluids are commonplace in both nature and engineering applications, such as deep-sea nodules hydraulic collection. However, accurately simulating granular particles with non-spherical shapes and gaining a deep understanding of the intricate mechanisms involved in fluid–particle interactions still pose significant challenges. In this study, the superquadric model and the Gaussian curvature model are introduced in the Discrete Element Method to describe particle shapes and characterize their nonlinear contact behavior, respectively. Simultaneously, the Fictitious Domain-Immersed Boundary Method (FD-IBM) and the Particle Boundary Field Method (PBFM) are employed to enhance the stability and accuracy of numerical simulations. Building upon these advancements, an extended resolved CFD-DEM-PBFM method is developed. The validation and superiority of this resolved CFD-DEM-PBFM method are rigorously verified by comparing its results with the experimental and other research results across various scenarios, including non-spherical particle collision and packing, particle settling, drafting-kissing-tumbling test, and flow around non-spherical particles. Subsequently, the application of our novel model has been further conducted by a case study that simulates the hydraulic collection of nodules with different aspect ratios l/d. Concurrently, the influences of the nodule shapes on the hydraulic collection mechanism of the hydraulic collection are unveiled in terms of suction forces, trajectory of the particle, and flow field characteristics. Our findings demonstrate that the extended resolved CFD-DEM-PBFM method excels at accurately characterizing multiphase interaction mechanisms at both macro and micro scales, presenting considerable advantages in simulating fluid-particle systems involving non-spherical particles.

Thermodynamic signatures and phase transitions in high-energy Au-Au collisions

Abstract In this study, we systematically investigate the dynamics of various particles namely π+, π−, K+, K−, p, ̄p, Λ, ̄Λ, Ξ− and ̄Ξ+ produced in central Au-Au collisions. We analyze data of AGS and RHIC, which span a broad range of collision energies, ranging from √sN N = 1.9 to 200 GeV. To analyze the transverse momentum (pT ) and transverse mass (mT ) distributions, we employ a two-component standard distribution function, achieving a very good representation of the experimental data across these energy regimes. We extract key thermodynamic parameters, including the effective temperature T , the mean transverse momentum ⟨pT ⟩, and the initial temperature Ti, and analyze their dependence on the values of collision energy and particle mass. Our findings reveal a distinct transition behaviour around √sN N = 19.6 GeV. Below √sN N = 19.6 GeV, the values of T , ⟨pT ⟩, and Ti increase monotonically for all particles due to higher energy transfer into the system. Above this energy threshold, these extracted parameters plateau, suggesting that the additional energy is utilized as latent heat for phase transition rather than increasing the system’s temperature. These observations delineate two distinct regions: a baryon-dominated region at lower energies and a parton-dominated region at higher energies, each potentially indicative of different phases of matter, with the latter possibly signalling the onset of a Quark-Gluon Plasma (QGP). The study thus provides critical insights into the complex interplay of thermodynamics, phase transitions, and particle interactions in high-energy Au-Au collisions.

Interaction of a quantum particle with gravitational wave in modified gravity theory

We present the formal solution for a quantum mechanical particle responding to gravitational wave (GW) in the framework of modified theories of gravity (MTG) where, apart from the two standard tensorial modes of polarization of GW, we have considered an additional scalar mode. The presence of this longitudinal scalar mode makes it necessary to extend the usual two-dimensional description of matter-GW interaction to a three-dimensional one. Naturally this requires non-trivial changes in the quantum mechanical treatment which we elaborate in this paper.

A methodology for alpha particles identification in liquid scintillation using a cost-efficient Artificial Neural Network

The discrimination of α/β-particles based on Liquid Scintillation (LS) is a measurement technique that can be applied for environmental monitoring. This technique relies on the specific feature of the scintillation process yielding two decay components (fast and delayed) of the photon emission following a particle interaction in a LS sample; indeed, the intensity of the delayed component is higher for α-particles than for β-particles. When operating with a photon detector such as a PhotoMultiplier Tube (PMT), the Pulse-Shape Discrimination (PSD) is the traditional approach, relying on low-pass filtered signals allowing pulse-tail analysis for an α-particle identification. This paper presents a new α-particle detection method based on an Artificial Neural Network (ANN) that directly processes fast pulse trains produced by the delayed scintillation component of a single detector. The ANN is trained using an experimental dataset obtained with a single PMT channel connected in a 3-PMTs detection system from which triple coincidences resulting from α-interactions (241Am) in a LS source are used for the single detector labeling. As we target a real-time implementation, the ANN is designed to minimize the computational resources. The classifier can operate with good performances (91.0% of correct classification, 8.5% false negative and 0.5% false positive) on a single-channel detector.

A case study of enhanced flotation of coal gasification fine slag by multiple compound collectors

ABSTRACT The flotation mechanism of multiple compound collectors called ZKC-I for coal gasification fine slag (CGFS) was revealed from the flotation kinetics, adsorption properties, bubble–particle interaction, and froth properties. The results were compared to dodecane, which represents the conventional nonpolar hydrocarbon oil collector. The flotation concentrates yield and rate constant of CGFS treated by ZKC-I were 2–3 times than those of CGFS treated by dodecane. Fourier transform infrared spectroscopy and wrap angle results showed that ZKC-I improved the hydrophobicity of residual carbon because of the synergistic adsorption of fatty acids, esters, and aromatic hydrocarbons in the ZKC-I on the heterogeneous surface of residual carbon particles, which enhanced the adhesion between residual carbon particles and bubble. Due to the strong carrying capacity of the bubble to residual carbon particles, the number of residual carbon particles in the froth treated by ZKC-I was more than that of the CGFS froth treated by dodecane. The high content of carbon particles in the froth resulted in great stability of the flotation froth, and the maximum height and half-life of the froth were higher than that of CGFS treated by dodecane. This study has practical and theoretical significance for the separation of coal-based solid waste.

Changes of surface properties of sucrose particles during grinding in a cocoa butter-based suspension and their influence on the macroscopic behavior of the suspension

AbstractChocolate mass is a cocoa butter-based suspension, which mainly consists of sugar and cocoa particles dispersed in a continuous lipid phase. During chocolate manufacturing, sugar particles have to be ground to sizes below 25–30 µm. Such a fine grinding is carried out either by five roll refiners or by ball mills. Despite obtaining similar particle size distributions at the end, the grinding procedures result in different chocolate mass properties. The reasons for that are not fully understood, so far. Therefore, changes in particle sizes and surface properties of sucrose particles as well as their interactions with surrounding cocoa butter during the different grinding processes were investigated including atomic force microscopy techniques to characterize local surface states. It was found that especially the alteration of surfaces during continued grinding differed. In the case of roller grinding, surface states became more inhomogeneous and different surfaces states at microscopic level existed in parallel. More homogenous surfaces but with a higher degree of amorphous states were formed during grinding in the ball mill. Variations in macroscopic behavior of the suspension can be explained by the differences in interaction of particles with each other and with the surrounding lipid phase.

An Overview of the Antimatter-Matter Asymmetry Problem

This literature review delves into the heart of the Matter-Antimatter Asymmetry Problem, a fundamental puzzle that challenges our understanding of the early universe and the dynamics of particle interactions. A few new innovative theories and experimental investigations exist to approach this problem and are elucidated in this paper, specifically charge-parity violation (CPV) and Baryogenesis. The paper begins with exploring the historical development of the Matter-Antimatter Asymmetry Problem. It then examines the theoretical constructs necessary for generating the observed imbalance, such as Sakharov's conditions. This is followed by an analysis of the experimental evidence and ongoing research efforts, coupled with advancements in theoretical frameworks of CPV and baryogenesis mechanisms that offer promising avenues to unlock the secrets of matter-antimatter asymmetry. However, these theories still need to fully answer the question of the asymmetry problem, pushing us to explore the potential extensions to the Standard Model that may provide a resolution.