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1
Herrera-Velarde, Salvador, Edith C. Euán-Díaz, and Ramón Castañeda-Priego. "Ordering and Dynamics of Interacting Colloidal Particles under Soft Confinement." Colloids and Interfaces 5, no. 2 (2021): 29. http://dx.doi.org/10.3390/colloids5020029.
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Confinement can induce substantial changes in the physical properties of macromolecules in suspension. Soft confinement is a particular class of restriction where the boundaries that constraint the particles in a region of the space are not well-defined. This scenario leads to a broader structural and dynamical behavior than observed in systems enclosed between rigid walls. In this contribution, we study the ordering and diffusive properties of a two-dimensional colloidal model system subjected to a one-dimensional parabolic trap. Increasing the trap strength makes it possible to go through weak to strong confinement, allowing a dimensional transition from two- to one-dimension. The non-monotonic response of the static and dynamical properties to the gradual dimensionality change affects the system phase behavior. We find that the particle dynamics are connected to the structural transitions induced by the parabolic trap. In particular, at low and intermediate confinement regimes, complex structural and dynamical scenarios arise, where the softness of the external potential induces melting and freezing, resulting in faster and slower particle diffusion, respectively. Besides, at strong confinements, colloids move basically along one direction, and the whole system behaves structurally and dynamically similar to a one-dimensional colloidal system.
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Yu, Shi, Jiaxin Wu, Xianliang Meng, Ruizhi Chu, Xiao Li, and Guoguang Wu. "Mesoscale Simulation of Bacterial Chromosome and Cytoplasmic Nanoparticles in Confinement." Entropy 23, no. 5 (2021): 542. http://dx.doi.org/10.3390/e23050542.
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In this study we investigated, using a simple polymer model of bacterial chromosome, the subdiffusive behaviors of both cytoplasmic particles and various loci in different cell wall confinements. Non-Gaussian subdiffusion of cytoplasmic particles as well as loci were obtained in our Langevin dynamic simulations, which agrees with fluorescence microscope observations. The effects of cytoplasmic particle size, locus position, confinement geometry, and density on motions of particles and loci were examined systematically. It is demonstrated that the cytoplasmic subdiffusion can largely be attributed to the mechanical properties of bacterial chromosomes rather than the viscoelasticity of cytoplasm. Due to the randomly positioned bacterial chromosome segments, the surrounding environment for both particle and loci is heterogeneous. Therefore, the exponent characterizing the subdiffusion of cytoplasmic particle/loci as well as Laplace displacement distributions of particle/loci can be reproduced by this simple model. Nevertheless, this bacterial chromosome model cannot explain the different responses of cytoplasmic particles and loci to external compression exerted on the bacterial cell wall, which suggests that the nonequilibrium activity, e.g., metabolic reactions, play an important role in cytoplasmic subdiffusion.
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JALALZADEH, S., and H. R. SEPANGI. "BRANE GRAVITY AND CONFINEMENT OF TEST PARTICLES." International Journal of Modern Physics A 20, no. 11 (2005): 2275–81. http://dx.doi.org/10.1142/s0217751x05024493.
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The confinement of classical and quantum test particles moving on a brane is studied by employing the notion of a returning force. It is shown that for classical test particles, the effects of extra dimensions are feeble whereas for quantum particles, these effects are pronounced. We also show that confinement causes the mass of a quantum particle to be quantized. Another consequence of the confinement is that it strongly restricts the choice of the bulk geometry even in the presence of the returning force.
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Vernerey, Franck, and Tong Shen. "The mechanics of hydrogel crawlers in confined environment." Journal of The Royal Society Interface 14, no. 132 (2017): 20170242. http://dx.doi.org/10.1098/rsif.2017.0242.
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We present theoretical and experimental results regarding the development of temperature-sensitive hydrogel particles that can display self-motility in confined channels. Inspired by the motility of living organisms such as larva, the motion of the particle relies on the combination of two key mechanisms. The first, referred to as actuation, is enabled by the cyclic extension and retraction of the particle owing to oscillations of its temperature around the so-called lower critical solution temperature. The second, referred to as symmetry breaking, transforms the isotropic particle actuation into a directed motion owing to the asymmetric friction properties of the channel's surface. The role of particle confinement in these processes is, however, less intuitive and displays an optimal value at which the particle's step size is maximum. These observations are supported by a model that identifies the underlying locomotion mechanisms and predicts the dependency of the particle motion efficiency on the confinement condition, as well as frictional properties of the substrate. Our analysis suggests that the existence of a lubrication layer around the particle hinders its motion at low confinement, while an excessive degree of confinement is detrimental to the particle's overall deformation and, thus, to its locomotion efficiency.
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Mondal, Ranajit, and Madivala G. Basavaraj. "Patterning of colloids into spirals via confined drying." Soft Matter 16, no. 15 (2020): 3753–61. http://dx.doi.org/10.1039/d0sm00118j.
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The colloidal dispersions dried in parallel plate confinement leave intriguing spiral patterns. Such deposit patterns form irrespective of confinement spacing, concentration of particles, volume of the dispersion, particle shape and substrate wettability.
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Jeong, Eue-Jin. "QCD QED Potentials, Quark Confinement." International Journal of Fundamental Physical Sciences 12, no. 3 (2022): 29–34. http://dx.doi.org/10.14331/ijfps.2022.330153.
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One of the enduring puzzles in high energy particle physics is why quarks do not exist independently despite their existence inside the hadron as quarks have never been found in isolation. This problem may be solved by formulating a QCD potential for the entire range of interaction distances of the quarks. The mystery could be related to the fundamental origin of the mass of elementary particles despite the success of the quantum field theories to the highest level of accuracy. The renormalization program is an essential part of the calculation of the scattering amplitudes, where the infinities of the calculated masses of the elementary particles are subtracted for the progressive calculation of the higher-order perturbative terms. The mathematical structure of the mass term from quantum field theories expressed in the form of infinities suggests that there may exist a finite dynamical mass in the limit when the input mass parameter approaches zero. The Lagrangian recovers symmetry at the same time as the input mass becomes zero, whereas the self-energy diagrams acquire a finite dynamical mass in the 4-dimensional space when the dimensional regularization method of renormalization is utilized. We report a new finding that using the mathematical expression of the self-energy(mass) for photons and gluons calculated from this method, the complex form of the QCD and QED interaction potentials can be obtained by replacing the fixed interaction mediating particle’s mass and coupling constants in Yukawa potential with the scale-dependent running coupling constant and the corresponding dynamical mass. The derived QCD QED potentials predict the behavior of the related elementary particles exactly as verified by experimental observation.
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Fringes, Stefan, Felix Holzner, and Armin W. Knoll. "The nanofluidic confinement apparatus: studying confinement-dependent nanoparticle behavior and diffusion." Beilstein Journal of Nanotechnology 9 (January 26, 2018): 301–10. http://dx.doi.org/10.3762/bjnano.9.30.
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The behavior of nanoparticles under nanofluidic confinement depends strongly on their distance to the confining walls; however, a measurement in which the gap distance is varied is challenging. Here, we present a versatile setup for investigating the behavior of nanoparticles as a function of the gap distance, which is controlled to the nanometer. The setup is designed as an open system that operates with a small amount of dispersion of ≈20 μL, permits the use of coated and patterned samples and allows high-numerical-aperture microscopy access. Using the tool, we measure the vertical position (termed height) and the lateral diffusion of 60 nm, charged, Au nanospheres as a function of confinement between a glass surface and a polymer surface. Interferometric scattering detection provides an effective particle illumination time of less than 30 μs, which results in lateral and vertical position detection accuracy ≈10 nm for diffusing particles. We found the height of the particles to be consistently above that of the gap center, corresponding to a higher charge on the polymer substrate. In terms of diffusion, we found a strong monotonic decay of the diffusion constant with decreasing gap distance. This result cannot be explained by hydrodynamic effects, including the asymmetric vertical position of the particles in the gap. Instead we attribute it to an electroviscous effect. For strong confinement of less than 120 nm gap distance, we detect the onset of subdiffusion, which can be correlated to the motion of the particles along high-gap-distance paths.
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Kawaguchi, Misa, Tomohiro Fukui, and Koji Morinishi. "Contribution of Particle–Wall Distance and Rotational Motion of a Single Confined Elliptical Particle to the Effective Viscosity in Pressure-Driven Plane Poiseuille Flows." Applied Sciences 11, no. 15 (2021): 6727. http://dx.doi.org/10.3390/app11156727.
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Rheological properties of the suspension flow, especially effective viscosity, partly depend on spatial arrangement and motion of suspended particles. It is important to consider effective viscosity from the microscopic point of view. For elliptical particles, the equilibrium position of inertial migration in confined state is unclear, and there are few studies on the relationship between dynamics of suspended particles and induced local effective viscosity distribution. Contribution of a single circular or elliptical particle flowing between parallel plates to the effective viscosity was studied, focusing on the particle–wall distance and particle rotational motion using the two-dimensional regularized lattice Boltzmann method and virtual flux method. As a result, confinement effects of the elliptical particle on the equilibrium position of inertial migration were summarized using three definitions of confinement. In addition, the effects of particle shape (aspect ratio and confinement) on the effective viscosity were assessed focusing on the particle–wall distance. The contribution of particle shape to the effective viscosity was found to be enhanced when the particle flowed near the wall. Focusing on the spatial and temporal variation of relative viscosity evaluated from wall shear stress, it was found that the spatial variation of the local relative viscosity was larger than temporal variation regardless of the aspect ratio and particle–wall distance.
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Light, Adam D., Hariharan Srinivasulu, Christopher J. Hansen, and Michael R. Brown. "Counterintuitive Particle Confinement in a Helical Force-Free Plasma." Plasma 8, no. 2 (2025): 20. https://doi.org/10.3390/plasma8020020.
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The force-free magnetic field solution formed in a high-aspect ratio cylinder is a non-axisymmetric (m=1), closed magnetic structure that can be produced in laboratory experiments. Force-free equilibria can have strong field gradients that break the usual adiabatic invariants associated with particle motion, and gyroradii at measured conditions can be large relative to the gradient scale lengths of the magnetic field. Individual particle motion is largely unexplored in force-free systems without axisymmetry, and it is unclear how the large gradients influence confinement. To understand more about how particles remain confined in these configurations, we simulate a thermal distribution of protons moving in a high-aspect-ratio force-free magnetic field using a Boris stepper. The particle loss is logarithmic in time, which suggests trapping and/or periodic orbits. Many particles do remain confined in particular regions of the field, analogous to trapped particles in other magnetic configurations. Some closed flux surfaces can be identified, but particle orbits are not necessarily described by these surfaces. We show examples of orbits that remain on well-defined surfaces and discuss the statistical properties of confined and escaping particles.
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Teich, Erin G., Greg van Anders, Daphne Klotsa, Julia Dshemuchadse, and Sharon C. Glotzer. "Clusters of polyhedra in spherical confinement." Proceedings of the National Academy of Sciences 113, no. 6 (2016): E669—E678. http://dx.doi.org/10.1073/pnas.1524875113.
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Dense particle packing in a confining volume remains a rich, largely unexplored problem, despite applications in blood clotting, plasmonics, industrial packaging and transport, colloidal molecule design, and information storage. Here, we report densest found clusters of the Platonic solids in spherical confinement, for up to N=60 constituent polyhedral particles. We examine the interplay between anisotropic particle shape and isotropic 3D confinement. Densest clusters exhibit a wide variety of symmetry point groups and form in up to three layers at higher N. For many N values, icosahedra and dodecahedra form clusters that resemble sphere clusters. These common structures are layers of optimal spherical codes in most cases, a surprising fact given the significant faceting of the icosahedron and dodecahedron. We also investigate cluster density as a function of N for each particle shape. We find that, in contrast to what happens in bulk, polyhedra often pack less densely than spheres. We also find especially dense clusters at so-called magic numbers of constituent particles. Our results showcase the structural diversity and experimental utility of families of solutions to the packing in confinement problem.
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Helden, Laurent, Ralf Eichhorn, and Clemens Bechinger. "Direct measurement of thermophoretic forces." Soft Matter 11, no. 12 (2015): 2379–86. http://dx.doi.org/10.1039/c4sm02833c.
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Thermophoretic forces acting on spherical colloidal particles in confinement are obtained from single particle measurements. This allows to characterize so far inaccessible particle sizes and materials.
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Hedin, Eric R. "Extradimensional confinement of quantum particles." Physics Essays 25, no. 2 (2012): 177–90. http://dx.doi.org/10.4006/0836-1398-25.2.177.
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Anisovich, V. V. "Color effective particles and confinement." JETP Letters 92, no. 6 (2010): 421–28. http://dx.doi.org/10.1134/s0021364010180128.
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Cheung, P., M. F. Choi, and P. M. Hui. "Classical interacting particles in confinement." Solid State Communications 103, no. 6 (1997): 357–60. http://dx.doi.org/10.1016/s0038-1098(97)00200-7.
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Becton, Matthew, Jixin Hou, Yiping Zhao, and Xianqiao Wang. "Dynamic Clustering and Scaling Behavior of Active Particles under Confinement." Nanomaterials 14, no. 2 (2024): 144. http://dx.doi.org/10.3390/nano14020144.
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A systematic investigation of the dynamic clustering behavior of active particles under confinement, including the effects of both particle density and active driving force, is presented based on a hybrid coarse-grained molecular dynamics simulation. First, a series of scaling laws are derived with power relationships for the dynamic clustering time as a function of both particle density and active driving force. Notably, the average number of clusters N¯ assembled from active particles in the simulation system exhibits a scaling relationship with clustering time t described by N¯∝t−m. Simultaneously, the scaling behavior of the average cluster size S¯ is characterized by S¯∝tm. Our findings reveal the presence of up to four distinct dynamic regions concerning clustering over time, with transitions contingent upon the particle density within the system. Furthermore, as the active driving force increases, the aggregation behavior also accelerates, while an increase in density of active particles induces alterations in the dynamic procession of the system.
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Pineda-Ríos, Erick Manuel, and Rosario Paredes. "Cooper Pairs in 2D Trapped Atoms Interacting Through Finite-Range Potentials." Atoms 13, no. 1 (2025): 4. https://doi.org/10.3390/atoms13010004.
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This work deals with the key constituent behind the existence of superfluid states in ultracold fermionic gases confined in a harmonic trap in 2D, namely, the formation of Cooper pairs in the presence of a Fermi sea in inhomogeneous confinement. For a set of finite-range models representing particle–particle interaction, we first ascertain the simultaneity of the emergence of bound states and the divergence of the s-wave scattering length in 2D as a function of the interaction potential parameters in free space. Then, through the analysis of two particles interacting in 2D harmonic confinement, we evaluate the energy shift with respect to the discrete harmonic oscillator levels for both repulsive and attractive cases. All of these results are the basis for determining the energy gaps of Cooper pairs arising from two particles interacting in the presence of a Fermi sea consisting of particles immersed in a 2D harmonic trap.
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Laribi, Elias, Shun Ogawa, Guilhem Dif-Pradalier, Alexei Vasiliev, and Xavier Garbet and Xavier Leoncini. "Influence of Toroidal Flow on Stationary Density of Collisionless Plasmas." Fluids 4, no. 3 (2019): 172. http://dx.doi.org/10.3390/fluids4030172.
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Starting from the given passive particle equilibrium particle cylindrical profiles, we built self-consistent stationary conditions of the Maxwell-Vlasov equation at thermodynamic equilibrium with non-flat density profiles. The solutions to the obtained equations are then discussed. It appears that the presence of an azimuthal (poloidal) flow in the plasma can ensure radial confinement, while the presence of a longitudinal (toroidal) flow can enhance greatly the confinement. Moreover in the global physically reasonable situation, we find that no unstable point can emerge in the effective integrable Hamiltonian of the individual particles, hinting at some stability of the confinement when considering a toroidal geometry in the large aspect ratio limit.
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Liu, Bing-Rui, Jian-Zhong Lin, and Xiao-Ke Ku. "Migration and Alignment of Three Interacting Particles in Poiseuille Flow of Giesekus Fluids." Fluids 6, no. 6 (2021): 218. http://dx.doi.org/10.3390/fluids6060218.
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Effect of rheological property on the migration and alignment of three interacting particles in Poiseuille flow of Giesekus fluids is studied with the direct-forcing fictitious domain method for the Weissenberg number (Wi) ranging from 0.1 to 1.5, the mobility parameter ranging from 0.1 to 0.7, the ratio of particle diameter to channel height ranging from 0.2 to 0.4, the ratio of the solvent viscosity to the total viscosity being 0.3 and the initial distance (y0) of particles from the centerline ranging from 0 to 0.2. The results showed that the effect of y0 on the migration and alignment of particles is significant. The variation of off-centerline (y0 ≠ 0) particle spacing is completely different from that of on-centerline (y0 = 0) particle spacing. As the initial vertical distance y0 increased, the various types of particle spacing are more diversified. For the off-centerline particle, the change of particle spacing is mainly concentrated in the process of cross-flow migration. Additionally, the polymer extension is proportional to both the Weissenberg number and confinement ratio. The bigger the Wi and confinement ratio is, the bigger the increment of spacing is. The memory of shear-thinning is responsible for the reduction of d1. Furthermore, the particles migrate abnormally due to the interparticle interaction.
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Liu, Peng, Hongwei Zhu, Ying Zeng, et al. "Oscillating collective motion of active rotors in confinement." Proceedings of the National Academy of Sciences 117, no. 22 (2020): 11901–7. http://dx.doi.org/10.1073/pnas.1922633117.
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Due to its inherent out-of-equilibrium nature, active matter in confinement may exhibit collective behavior absent in unconfined systems. Extensive studies have indicated that hydrodynamic or steric interactions between active particles and boundary play an important role in the emergence of collective behavior. However, besides introducing external couplings at the single-particle level, the confinement also induces an inhomogeneous density distribution due to particle-position correlations, whose effect on collective behavior remains unclear. Here, we investigate this effect in a minimal chiral active matter composed of self-spinning rotors through simulation, experiment, and theory. We find that the density inhomogeneity leads to a position-dependent frictional stress that results from interrotor friction and couples the spin to the translation of the particles, which can then drive a striking spatially oscillating collective motion of the chiral active matter along the confinement boundary. Moreover, depending on the oscillation properties, the collective behavior has three different modes as the packing fraction varies. The structural origins of the transitions between the different modes are well identified by the percolation of solid-like regions or the occurrence of defect-induced particle rearrangement. Our results thus show that the confinement-induced inhomogeneity, dynamic structure, and compressibility have significant influences on collective behavior of active matter and should be properly taken into account.
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Sunol, Alp M., and Roseanna N. Zia. "Confined Brownian suspensions: Equilibrium diffusion, thermodynamics, and rheology." Journal of Rheology 67, no. 2 (2023): 433–60. http://dx.doi.org/10.1122/8.0000520.
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We examine the impact of confinement on the structure, dynamics, and rheology of spherically confined macromolecular suspensions, with a focus on the role played by entropic forces, by comparing the limits of strong hydrodynamics and no hydrodynamics. We present novel measurements of the osmotic pressure, intrinsic viscosity, and long-time self-diffusivity in spherical confinement and find confinement induces strong structural correlations and restrictions on configurational entropy that drive up osmotic pressure and viscosity and drive down self-diffusion. Even in the absence of hydrodynamics, confinement produces distinct short-time and long-time self-diffusion regimes. This finding revises the previous understanding that short-time self-diffusion is a purely hydrodynamic quantity. The entropic short-time self-diffusion is proportional to an entropic mobility, a direct analog to the hydrodynamic mobility. A caging plateau following the short-time regime is stronger and more durable without hydrodynamics, and entropic drift—a gradient in volume fraction—drives particles out of their cages. The distinct long-time regime emerges when an entropic mobility gradient arising from heterogeneous distribution of particle volume drives particles out of local cages. We conclude that entropic mobility gradients produce a distinct long-time dynamical regime in confinement and that hydrodynamic interactions weaken this effect. From a statistical physics perspective, confinement restricts configurational entropy, driving up confined osmotic pressure, viscosity, and (inverse) long-time dynamics as confinement tightens. We support this claim by rescaling the volume fraction as the distance from confinement-dependent maximum packing, which collapses the data for each rheological measure onto a single curve.
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Cao, Juanhua, and Yafang Zhang. "Analysis and Investigation of Diffusion-Induced Stress in Lithium-Ion Particle Through Elastic-Viscoplastic Model of Binder." Batteries 11, no. 4 (2025): 132. https://doi.org/10.3390/batteries11040132.
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During the charging and discharging process of lithium-ion batteries, lithium-ions are embedded and removed from the active particles, leading to volume expansion and contraction of the active particles, and hence diffusion-induced stress (DIS) is generated. DIS leads to fatigue damage of the active particles during periodic cycling, causing battery aging and capacity degradation. This article establishes a two-dimensional particle-binder system model in which a linear elastic model is used for the active particle, and an elastic-viscoplastic model is used for the binder. The state of charge, stress, and strain of the particle-binder system under different charge rates are investigated. The simulation results show that the location of particle crack excitation is related to two factors: the concentration gradient of lithium-ion and the binder confinement effect. Under a lower charge rate, the crack excitation position of the particle located at the edge of the particle-binder interfacial (PBI) is mainly attributed to the binder confinement effect, while under a higher charge rate, the crack excitation position occurs at the center of the particle due to the dominance of concentration gradient effect. Furthermore, analysis reveals that the binder undergoes plastic deformation due to the traction force caused by particle expansion, which weakens the constraint on the particle and prevents PBI debonding. Finally, a binder with lower stiffness and higher yield strength behavior is recommended for rapid stress release of particles and could reduce plastic deformation of the binder.
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Ninomiya, H., K. Tobita, U. Schneider, G. Martin, W. W. Heidbrink, and Ya I. Kolesnichenko. "Energetic particles in magnetic confinement systems." Nuclear Fusion 40, no. 7 (2000): 1287–91. http://dx.doi.org/10.1088/0029-5515/40/7/201.
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Günter, S. "Energetic particles in magnetic confinement systems." Nuclear Fusion 48, no. 8 (2008): 080201. http://dx.doi.org/10.1088/0029-5515/48/8/080201.
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Zhang, Yichao, Haifeng Liu, Jie Huang та ін. "Suppression of non-axisymmetric field-induced α-particle loss channels in a quasi-axisymmetric stellarator". AIP Advances 12, № 5 (2022): 055214. http://dx.doi.org/10.1063/5.0079827.
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In future fusion reactors, the confinement of α-particles is a crucial issue. The perfect omnigenity may be difficult to achieve in the quasi-isodynamic and quasi-symmetric stellarators when a multi-objective optimization is considered. Non-axisymmetric field can result in collisionless particles’ transport via localized trapping by ripples. Specific loss channels have been revealed to essentially exist in quasi-axisymmetric stellarators [Yang et al., Europhys. Lett. 129, 35001 (2020)] and W7-X [J. M. Faustin et al., Nucl. Fusion 56, 092006 (2016)]. It indicates a drastic loss of collisionless ions through these channels. This paper is devoted to investigate the effects of axisymmetry-breaking magnetic fields on collisionless α-particle transport in the CFQS (Chinese First Quasi-axisymmetric Stellarator) -like reactor configuration. A semi-analytic representation of radial and poloidal drifts in Boozer coordinates is given, by which we found an effective route to mitigate α-particle losses, i.e., adjusting the location of the quasi-axisymmetric radial position. Such a route enables the enhancement of the poloidal drift and decrease of radial drift in peripheral regions of the identified loss channels. The particles launched inside the quasi-axisymmetric radial surface can be well confined because localized particles that may fall in loss channels can transit into blocked particles near the quasi-axisymmetric surface, escaping from loss channels, which is beneficial for the improvement of the particle confinement. Moreover, this paper may provide a set of proxy functions for suppression of energetic particle losses to optimize stellarator configurations.
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Kang, Dong Woo, Mina Lee, Kyung Hak Kim, Ming Xia, Sang Hyuk Im, and Bum Jun Park. "Electrostatic interactions between particles through heterogeneous fluid phases." Soft Matter 13, no. 37 (2017): 6647–58. http://dx.doi.org/10.1039/c7sm01309d.
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Mosiori, Cliff Orori. "Effects of Quantum Confinements in Tin Sulphide Nanocrystals Produced by Wet-Solution Technique." Asia Pacific Journal of Energy and Environment 6, no. 1 (2019): 37–42. http://dx.doi.org/10.18034/apjee.v6i1.261.
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In thin film nano-crystals studies, electron energy levels are known not continuous in the bulk thin films but are rather discrete(finite density of states) because of confinement of their electron wave functions to the physically dimensions of the particles. This phenomenon is called Quantum confinement and therefore nano-crystals are also referred to Quantum dots. The quantum confinement effect is mainly observed when the size of the particle involved is too small to be comparable to the wavelength of the electron. To understand this effect, this study broke the words confinement to mean to confine the motion of randomly moving electron to restrict its motion in specific energy levels (discreteness) and the term quantum to reflect the atomic realm of particles involved in this study. So as the size of a particle decrease to a nano scale, then the decrease in confining dimension causes the particle energy levels to be too discrete and at the same time widens up the band gap. As a result the ultimately effect is that the band gap energy increases. In this study, nanocrystalline tin sulphide (SnS) powder was prepared using tin chloride (SnCl2) as a tin ion (Sn+2) source and sodium sulfide (Na2S) as a sulfur (S-2) ion source using solution magneto DC sputtering technique. The as-synthesized thin film in form of nanoparticles were then qualitatively and quantitatively analyzed and characterized in terms of their morphological, structural and optical properties and found to have an orthorhombic structure whose direct band gap had blue shifted (1.74 eV) and was confirmed using theoretical calculations of exciton energy based on the potential morphing method (PMM) in the Hartree Fock approximation.
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STICHEL, P. C., and W. J. ZAKRZEWSKI. "POSSIBLE CONFINEMENT MECHANISMS FOR NONRELATIVISTIC PARTICLES ON A LINE." Modern Physics Letters A 16, no. 29 (2001): 1919–32. http://dx.doi.org/10.1142/s0217732301005278.
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The gauge model of nonrelativistic particles on a line interacting with nonstandard gravitational fields5 is supplemented by the addition of a (non)-Abelian gauge interaction. Solving for the gauge fields we obtain equations, in closed form, for a classical two-particle system. The corresponding Schrödinger equation, obtained by the Moyal quantization procedure, is solved analytically. Its solutions exhibit two different confinement mechanisms — dependent on the sign of the coupling λ to the nonstandard gravitational fields. For λ >0 confinement is due to a rising potential, whereas for λ<0 it is due to the dynamical (geometric) bag formation. Numerical results for the corresponding energy spectra are given. For a particular relation between two coupling constants, the model fits into the scheme of supersymmetrical quantum mechanics.
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Ordonez, C. A. "Magnetic confinement of effectively unmagnetized plasma particles." Physics of Plasmas 27, no. 12 (2020): 122501. http://dx.doi.org/10.1063/5.0030215.
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Chen, Wei, and Zheng-Xiong Wang. "Energetic Particles in Magnetic Confinement Fusion Plasmas." Chinese Physics Letters 37, no. 12 (2020): 125001. http://dx.doi.org/10.1088/0256-307x/37/12/125001.
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Bonofiglo, P. J., D. W. Dudt, and C. P. S. Swanson. "Fast ion confinement in quasi-axisymmetric stellarator equilibria." Nuclear Fusion 65, no. 2 (2025): 026050. https://doi.org/10.1088/1741-4326/ada56d.
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Abstract This report presents an initial analysis of the fast ion confinement and losses within quasi-axisymmetric stellarator equilibria in consideration by Thea Energy. The equilibria have not yet been explicitly optimized for fast particle confinement and require validation. Modeling with the ASCOT5 code is used to directly examine the fast ion transport. The particle tracking simulations are purely (neo)classical in nature and simply contain the supplied equilibrium and collisions (pitch-angle, energy slowing, and velocity diffusion) from supplied thermal profiles. Uniform marker deposition is used to probe the general confinement properties of the equilibria while a realistic beam-born population is provided from the BEAMS3D code and an alpha particle population is calculated from a fusion source integrator. A first wall is included and defines the loss boundary. Analysis for NBI ions within Thea Energy’s conceptual Eos neutron source are presented along with alpha particles in an enlarged DT-plasma. The fast ions are assessed in regards to their confinement time, pitch, energy, and spatial coordinates. For each population, the impact of collisions and orbit drifts are discussed. It is found that NBI born ions in Eos are strongly confined until slowing-down, owing largely to the tangential injection geometry, while 22% of DT-born alpha energy is lost in the scaled device, indicating that any fusion pilot plant design optimization should include metrics for fast ion confinement.
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Corral Arroyo, Pablo, Grégory David, Peter A. Alpert, Evelyne A. Parmentier, Markus Ammann, and Ruth Signorell. "Amplification of light within aerosol particles accelerates in-particle photochemistry." Science 376, no. 6590 (2022): 293–96. http://dx.doi.org/10.1126/science.abm7915.
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Optical confinement (OC) structures the optical field and amplifies light intensity inside atmospheric aerosol particles, with major consequences for sunlight-driven aerosol chemistry. Although theorized, the OC-induced spatial structuring has so far defied experimental observation. Here, x-ray spectromicroscopic imaging complemented by modeling provides direct evidence for OC-induced patterning inside photoactive particles. Single iron(III)–citrate particles were probed using the iron oxidation state as a photochemical marker. Based on these results, we predict an overall acceleration of photochemical reactions by a factor of two to three for most classes of atmospheric aerosol particles. Rotation of free aerosol particles and intraparticle molecular transport generally accelerate the photochemistry. Given the prevalence of OC effects, their influence on aerosol particle photochemistry should be considered by atmospheric models.
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Xiao, Mufei, and Nikifor Rakov. "Size and temperature dependent plasmons of quantum particles." International Journal of Modern Physics B 29, no. 21 (2015): 1550146. http://dx.doi.org/10.1142/s0217979215501465.
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This work reports on the influences of temperature changes on plasmons of metallic particles that are so small that electric carriers in the conduction band are forced to be at discrete sub-bands due to quantum confinement. In the framework of the electron-in-a-box model and with an every-electron-count computational scheme, the spatial electric distribution inside the particle is calculated. In the calculations, the intra-subband fluctuations are taken into account. The numerical results have shown that the small-particle plasmon frequency shifts with the temperature. The findings suggest that it would be possible to control the plasmons of quantum particles externally.
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Giuliatti Winter, S. M., G. Madeira, and R. Sfair. "Neptune’s ring arcs confined by coorbital satellites: dust orbital evolution through solar radiation." Monthly Notices of the Royal Astronomical Society 496, no. 1 (2020): 590–97. http://dx.doi.org/10.1093/mnras/staa1519.
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ABSTRACT Here, we report the results of a set of numerical simulations of the system formed by Neptune, Galatea, dust ring particles, and hypothetical co-orbital satellites. This dynamical system depicts a recent confinement mechanism formed by four co-orbital satellites being responsible for the azimuthal confinement of the arcs. After the numerical simulations, the particles were divided into four groups: particles that stay in the arcs, transient particles, particles that leave the arcs, and particles that collide with the co-orbital satellites. Our results showed that the lifetime of the smaller particles is 50 yr at most. After 100 yr, about $20{{\ \rm per\ cent}}$ of the total amount of larger particles are still present in the arcs. From our numerical simulations, the particles should be present in all arcs after 30 yr. Analysis of the dust production ruled out the hypothesis that small satellites close to or in the arc structure could be its source.
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ZHANG Shuchen and WAN Duanduan. "Effects of Allowing Temporary Overlaps During Compression on the Packing Density and Configuration of Hard Particle Systems." Acta Physica Sinica 74, no. 16 (2025): 0. https://doi.org/10.7498/aps.74.20250552.
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The dense packing of hard particles in confined spaces is of broad interest in both mathematics and statistical physics. It relates to classical packing problems under geometric constraints, plays a central role in understanding the self-assembly of microscopic particles such as colloids and nanoparticles, and inspires studies across a wide range of physical systems. However, achieving high packing densities under confinement remains challenging due to anisotropic particle shapes, the discontinuous nature of hard-core interactions, and geometric frustration. In this work, we develop a Monte Carlo scheme that combines boundary compression with controlled, temporary particle overlaps. Specifically, we allow a limited number of overlaps during the compression of a circular boundary, which are subsequently removed via standard Monte Carlo relaxation before further compression steps. We apply this strategy to three types of two-dimensional particles—disks, squares, and rectangles with an aspect ratio of 5:1—confined within a circular boundary. As a control, we also perform simulations using a conventional method that strictly prohibits overlaps throughout. The final configurations from both methods exhibit similar structural features. For hard disks, central particles form a triangular lattice, while those near the boundary become more disordered to accommodate the circular geometry. For hard squares, particles at the center organize into a square lattice, whereas those near the boundary form concentric layers. For rectangles, particles in the central region display local smectic-like alignment within clusters that are oriented nearly perpendicular to one another. Near the boundary, some particles align tangentially along the circular edge. Quantitatively, the temporary-overlap strategy consistently yields denser packings across all particle types. Analysis of 10 independent samples shows higher average and maximal packing densities compared to the conventional method. Further analysis of the radial distribution functions and orientational order parameters reveals that, although both methods produce similar structural features, the overlap-allowed method yields a larger central region exhibiting lattice-like or cluster-like ordering. Our findings suggest that allowing temporary particle overlaps is an effective strategy for generating dense configurations of hard particles under confinement. This approach may be extended to more complex systems, including three-dimensional particles or mixtures with different shapes confined within restricted geometries.
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Langdon, A. Bruce. "Computer simulations of absorption and scattering." Canadian Journal of Physics 64, no. 8 (1986): 993–97. http://dx.doi.org/10.1139/p86-169.
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This paper discusses computer simulation of absorption and scattering of laser light, under conditions relevant to laboratory achievement of thermonuclear fusion by laser-driven inertial-confinement methods. We enumerate the principal absorption and scattering processes and their requirements for accurate mathematical modelling. The principal tool, so-called particle-in-cell simulation, tracks particles through electromagnetic fields calculated self-consistently from the charge and current densities of the particles themselves, external sources, and boundaries. Many references are given. Special attention is given to two-plasmon decay.
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Xiao, Yun-Feng. "Microcavity-enhanced photoacoustic vibrational spectroscopy of single particles." Journal of the Acoustical Society of America 155, no. 3_Supplement (2024): A158. http://dx.doi.org/10.1121/10.0027152.
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Confinement and manipulation of photons using microcavities have triggered intense research interest in both fundamental and applied photonics for more than two decades. Prominent examples are ultrahigh-Q whispering gallery microcavities which confine photons using continuous total internal reflection along a curved and smooth surface. The long photon lifetime, strong field confinement, and in-plane emission characteristics make them promising candidates for enhancing light-matter interactions on a chip. In this talk, I will focus on single-particle photoacoustic vibrational spectroscopy using optical microcavities.
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Vegt, Wim. "The Transformation of LIGHT into MATTER." European Journal of Engineering Research and Science 4, no. 11 (2019): 52–69. http://dx.doi.org/10.24018/ejers.2019.4.11.1631.
Full textAbstract:
Within the scope of this article, LIGHT has been considered as any arbitrary Electromagnetic Radiation within a very wide frequency range, because during the transformation from Visible Light into the Gravitational Electromagnetic Confinement, the frequency changes in a very wide range. This frequency transformation is possible because of the combined Lorentz / Doppler-Effect transformation during the collapse (contraction) of the radiation when the Gravitational Electromagnetic Confinement has been formed (Implosion of Visible Light). Within the scope of this article MATTER is considered to be any kind of 3-dimensional confined (Electromagnetic) energy. The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.
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Vegt, Wim. "Transformation of LIGHT into MATTER." European Journal of Engineering and Technology Research 4, no. 11 (2019): 52–69. http://dx.doi.org/10.24018/ejeng.2019.4.11.1631.
Full textAbstract:
Within the scope of this article, LIGHT has been considered as any arbitrary Electromagnetic Radiation within a very wide frequency range, because during the transformation from Visible Light into the Gravitational Electromagnetic Confinement, the frequency changes in a very wide range. This frequency transformation is possible because of the combined Lorentz / Doppler-Effect transformation during the collapse (contraction) of the radiation when the Gravitational Electromagnetic Confinement has been formed (Implosion of Visible Light). Within the scope of this article MATTER is considered to be any kind of 3-dimensional confined (Electromagnetic) energy. The inner structure of a photon is based on a 3-dimensional anisotropic equilibrium within the electromagnetic pulses in which an equilibrium does exist for the Electric and the Magnetic Fields separately generated by the pulses. A photon cannot be considered as a particle. Because particles are 3-dimensional confinements. Photons are anisotropic (in 1st and 2nd dimension a particle and in the 3rd dimension a wave) confinements of electromagnetic pulses, generated during the energy transitions within the atoms. Photons are 2-dimensional confinements of electromagnetic energy and demonstrate the property of inertia (electromagnetic mass) in the 2 directions of confinement. In the 3rd direction, the direction of propagation, photons can only be considered as an electromagnetic wave and for that reason do not demonstrate the property of inertia. Electromagnetic waves cannot be accelerated or decelerated because the speed of light is a universal constant. For that reason, photons interact with a gravitational field in an anisotropic way. Due to a gravitational field, photons can be accelerated or decelerated in the directions perpendicular to the direction of propagation and follow a curved path. But a gravitational field in the direction of propagation will have no impact on the speed of the photons, which will remain the unchanged universal constant, the speed of light. Photonics is the physical science of light based on the concept of “photons” introduced by Albert Einstein in the early 20th century. Einstein introduced this concept in the “particle-wave duality” discussion with Niels Bohr to demonstrate that even light has particle properties (mass and momentum) and wave properties (frequency). That concept became a metaphor and from that time on a beam of light has been generally considered as a beam of particles (photons). Which is a wrong understanding. Light particles do not exist. Photons are nothing else but electromagnetic complex wave configurations and light particles are not like “particles” but separated electromagnetic wave packages, 2-dimensionally confined in the directions perpendicular to the direction of propagation and in a perfect equilibrium with the radiation pressure and the inertia of electromagnetic energy in the forward direction, controlling the speed of light. This new theory will explain how electromagnetic wave packages demonstrate inertia, mass and momentum and which forces keep the wave packages together in a way that they can be measured like particles with their own specific mass and momentum. All we know about light, and in generally about any electromagnetic field configuration, has been based only on two fundamental theories. James Clerk Maxwell introduced in 1865 the “Theory of Electrodynamics” with the publication: “A Dynamical Theory of the Electromagnetic Field” and Albert Einstein introduced in 1905 the “Theory of Special Relativity” with the publication: “On the Electrodynamics of Moving Bodies” and in 1913 the “Theory of General Relativity” with the publication ”Outline of a Generalized Theory of Relativity and of a Theory of Gravitation”. However, both theories are not capable to explain the property of electromagnetic mass and in specific the anisotropy of the phenomenon of electromagnetic mass presented e.g. in a LASER beam. To understand what electromagnetic inertia and the corresponding electromagnetic mass is and how the anisotropy of electromagnetic mass can be explained and how it has to be defined, a New Theory about Light has to be developed. A part of this “New Theory about Light”, based on Newton’s well- known Equation in 3 dimensions will be published in this article in an extension into 4 dimensions. Newton’s 4-dimensional law in the 3 spatial dimensions results in an improved version of the classical Maxwell equations and Newton’s law in the 4th dimension (time) results in the quantum mechanical Schrödinger wave equation (at non-relativistic velocities) and the relativistic Dirac equation.
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Fily, Yaouen, Aparna Baskaran, and Michael F. Hagan. "Dynamics of self-propelled particles under strong confinement." Soft Matter 10, no. 30 (2014): 5609–17. http://dx.doi.org/10.1039/c4sm00975d.
Full text
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Williams, Ian, Erdal C. Oğuz, Hartmut Löwen, Wilson C. K. Poon, and C. Patrick Royall. "The rheology of confined colloidal hard disks." Journal of Chemical Physics 156, no. 18 (2022): 184902. http://dx.doi.org/10.1063/5.0087444.
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Colloids may be treated as “big atoms” so that they are good models for atomic and molecular systems. Colloidal hard disks are, therefore, good models for 2d materials, and although their phase behavior is well characterized, rheology has received relatively little attention. Here, we exploit a novel, particle-resolved, experimental setup and complementary computer simulations to measure the shear rheology of quasi-hard-disk colloids in extreme confinement. In particular, we confine quasi-2d hard disks in a circular “corral” comprised of 27 particles held in optical traps. Confinement and shear suppress hexagonal ordering that would occur in the bulk and create a layered fluid. We measure the rheology of our system by balancing drag and driving forces on each layer. Given the extreme confinement, it is remarkable that our system exhibits rheological behavior very similar to unconfined 2d and 3d hard particle systems, characterized by a dynamic yield stress and shear-thinning of comparable magnitude. By quantifying particle motion perpendicular to shear, we show that particles become more tightly confined to their layers with no concomitant increase in density upon increasing the shear rate. Shear thinning is, therefore, a consequence of a reduction in dissipation due to weakening in interactions between layers as the shear rate increases. We reproduce our experiments with Brownian dynamics simulations with Hydrodynamic Interactions (HI) included at the level of the Rotne–Prager tensor. That the inclusion of HI is necessary to reproduce our experiments is evidence of their importance in transmission of momentum through the system.
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Liu, Zhaogang, Mei Li, Yanhong Hu, Hai Fu, Mitang Wang, and Zaiyong Jiang. "DISPERSION AND MECHANICAL PROPERTIES OF CERIUM OXIDE FILLED INTO RUBBER COMPOSITES." Rubber Chemistry and Technology 87, no. 2 (2014): 340–47. http://dx.doi.org/10.5254/rct.13.86993.
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ABSTRACT Rubber composites were synthesized by natural rubber filled with cerium oxide with different particle diameters. The dispersion morphology of cerium oxide in rubber matrix and the mechanical properties of composites were studied, and the contrast experiment of reinforcing rubber with cerium oxide was performed. The results showed that the small particles of cerium oxide had better disparity than the large particles of cerium oxide in NR. The mechanical properties of rubber filled with small particles of cerium oxide were better than those of rubber filled with large particles of cerium oxide. The crystalline rubber was measured by X-ray diffraction, which indicated that the CeO2 accelerated crystallization capacity and confined the rubber chain movement. The tensile strength of rubber was increased by this confinement.
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Chow, Edmond, and Jeffrey Skolnick. "Effects of confinement on models of intracellular macromolecular dynamics." Proceedings of the National Academy of Sciences 112, no. 48 (2015): 14846–51. http://dx.doi.org/10.1073/pnas.1514757112.
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The motions of particles in a viscous fluid confined within a spherical cell have been simulated using Brownian and Stokesian dynamics simulations. High volume fractions mimicking the crowded interior of biological cells were used. Importantly, although confinement yields an overall slowdown in motion, the qualitative effects of motion in the interior of the cell can be effectively modeled as if the system were an infinite periodic system. However, we observe layering of particles at the cell wall due to steric interactions in the confined space. Motions of nearby particles are also strongly correlated at the cell wall, and these correlations increase when hydrodynamic interactions are modeled. Further, particles near the cell wall have a tendency to remain near the cell wall. A consequence of these effects is that the mean contact time between particles is longer at the cell wall than in the interior of the cell. These findings identify a specific way that confinement affects the interactions between particles and points to a previously unidentified mechanism that may play a role in signal transduction and other processes near the membrane of biological cells.
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Zhang, Jianping, and Baodong Ren. "Influence of magnetic field and working voltage on the tripping performance in spherical cylindrical ECP." E3S Web of Conferences 261 (2021): 02033. http://dx.doi.org/10.1051/e3sconf/202126102033.
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In order to further improve the trapping effect of fine particles, a new electrostatic cyclone precipitator (ECP) with magnetic confinement was proposed, the overall efficiencies of fine particles under different operating conditions were numerically simulated, and the influence of working voltage on the dust-removal effect of fine particles with and without magnetic field were discussed. The results show that increasing working voltage or magnetic induction intensity improves the trapping performance of spherical cylindrical magnetically confinement ECP, and the lifting effect gradually weakens while increasing the same amplitude. The results can offer technical reference for the optimization design of greatly improving the ECP dust-removal performance.
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Misconi, Nebil Y. "New technique for levitating solid particles using a proton beam." Laser and Particle Beams 14, no. 3 (1996): 501–10. http://dx.doi.org/10.1017/s026303460001017x.
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A new technique for levitating solid particles inside a vacuum chamber is developed using a proton beam. This new technique differs from the classical laser-levitation technique invented by Ashkin in that it does not heat up light-absorbing levitated particles to vaporization. This unique property of the method will make it possible to levitate real interplanetary dust particles in a vacuum chamber and study their spin-up dynamics in a ground-based laboratory. It is found that a flux of protons from a proton gun of ~1015 cm–2 sec–1 is needed to levitate a 10-mm particle. Confinement of the levitated particle can be achieved by a Z or θ pinch to create a gravity well, or by making the beam profile doughnut in shape.
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Kremeyer, Thierry, R. König, S. Brezinsek, et al. "Analysis of hydrogen fueling, recycling, and confinement at Wendelstein 7-X via a single-reservoir particle balance." Nuclear Fusion 62, no. 3 (2022): 036023. http://dx.doi.org/10.1088/1741-4326/ac4acb.
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Abstract A single-reservoir particle balance for the main plasma species hydrogen has been established for W7-X. This has enabled the quantitative characterization of the particle sources in the standard island divertor configuration for the first time. Findings from attached scenarios with two different island sizes with a boronized wall and turbo molecular pumping are presented. Fueling efficiencies, particle flows and source locations were measured and used to infer the total particle confinement time τ p. Perturbative gas injection experiments served to measure the effective particle confinement time τ p * . Combining both confinement times provides access to the global recycling coefficient R ¯ . Hydrogen particle inventories have been addressed and the knowledge of particle sources and sinks reveals the core fueling distribution and provides insight into the capability of the magnetic islands to control exhaust features. Measurements of hydrogen fueling efficiencies were sensitive to the precise fueling location and measured between 12% and 31% with the recycling fueling at the strike line modeled at only 6%, due to much higher densities. 15% of the total 5.2 × 1022 a/s recycling flow ionizes far away from the recycling surfaces in the main chamber. It was shown that 60% of recycled particles ionize above the horizontal and 18% above the vertical divertor target, while the remainder of the recycling flow ionizes above the baffle (7%). Combining these source terms with their individual fueling efficiencies resolves the core fueling distribution. Due to the higher fueling efficiency in the main chamber, up to 51% of the total 5.1 × 1021 s−1 core fueling particles are entering the confined plasma from the main chamber. τ p values in the range of 260 ms were extracted for these discharges. Together with τ p, the global recycling coefficient R ¯ was resolved for every τ p * measurement and a typical value close to unity was obtained. An increase of the island size, resulted in no change of τ p, but doubled τ p * , indicating the feasibility of the control coils as an actuator to control exhaust features without affecting core confinement properties.
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Pol, Antonio, Riccardo Artoni, Patrick Richard, Paulo Ricardo Nunes da Conceição, and Fabio Gabrieli. "Kinematics and shear-induced alignment in confined granular flows of elongated particles." New Journal of Physics, June 30, 2022. http://dx.doi.org/10.1088/1367-2630/ac7d6d.
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Abstract The kinematics and the shear-induced alignment of elongated particles in confined, heterogeneous flow conditions are investigated experimentally. Experiments are conducted in an annular shear cell with a rotating bottom wall and a top wall permitting confinement of the flow. Flow kinematics and particle orientation statistics are computed by particle tracking using optical imaging. Translational velocity profiles show an exponential decay, and surprisingly, only the slip velocity at the bottom is influenced by the particle shape. Rotations are highly frustrated by particle shape, more elongated particles showing, on average, a lower angular velocity. In addition, a clear shear-rate dependency of the proneness of a particle to rotate is observed, with a stronger inhibition in low shear zones. The average orientation of the particles does not correspond to the main flow direction, they are slightly tilted downwards. The corresponding angle decreases with the particles' elongation. Orientational order was observed to increase with particles' elongation, and surprisingly was not affected by the applied confinement. A weak but systematic decrease of the orientational order was observed in regions of higher shear rate. At the particle-scale, angular velocity fluctuations show a strong correlation with local particle orientation, particles being strongly misaligned with the preferential particles' orientation rotating faster. This correlation becomes stronger for more elongated particles, while is almost unaffected by the applied confinement.
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Boyd, Jarrett, Gram Hepner, Maxwell Ujhazy, Shawn Bliss, and Melikhan Tanyeri. "Dual hydrodynamic trap based on coupled stagnation point flows." Physics of Fluids 35, no. 6 (2023). http://dx.doi.org/10.1063/5.0150089.
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Recent advancements in science and engineering have allowed for trapping and manipulation of individual particles and macromolecules within an aqueous medium using a flow-based confinement method. In this work, we demonstrate the feasibility of trapping and manipulating two particles using coupled planar extensional flows. Using Brownian dynamics simulations and a proportional feedback control algorithm, we show that two micro/nanoscale particles can be simultaneously confined and manipulated at the stagnation points of a pair of interconnected planar extensional flows. We specifically studied the effect of strain rate, particle size, and feedback control parameters on particle confinement. We also demonstrate precise control of the interparticle distance by manipulating the strain rates at both junctions and particle position at one of the junctions. We further discuss the advantages and limitations of the dual hydrodynamic trap in comparison to existing colloidal particle confinement methods and outline some potential applications in polymer science and biology. Our results demonstrate the versatility of flow-based confinement and further our understanding of feedback-controlled particle manipulation.
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Miron, Asaf. "Local resetting with geometric confinement." Journal of Physics A: Mathematical and Theoretical, November 11, 2022. http://dx.doi.org/10.1088/1751-8121/aca22e.
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Abstract "Local resetting" was recently introduced to describe stochastic resetting in interacting systems where particles independently try to reset to a common "origin". Our understanding of such systems, where the resetting process is itself affected by interactions, is still very limited. One ubiquitous constraint that is often imposed on the dynamics of interacting particles is geometric confinement, e.g. restricting rigid spherical particles to a channel so narrow that overtaking becomes difficult. We here explore the interplay between local resetting and geometric confinement in a system consisting of two species of diffusive particles: "bath" particles, and "tracers" which undergo local resetting. Mean-field analysis and numerical simulations show that the resetting tracers, whose stationary density profile exhibits a typical "tent-like" shape, imprint this shape onto the bath density profile. Upon varying the ratio of the degree of geometric confinement over particle diffusivity, the system is found to transition between two states. In one tracers expel bath particles away from the origin, while in the other they ensnare them instead. Between these two states, we find a special case where the mean field approximation becomes exact.
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Lauricella, Giuseppe, Jian Zhou, Qiyue Luan, Ian Papautsky, and Zhangli Peng. "Computational study of inertial migration of prolate particles in a straight rectangular channel." Physics of Fluids, July 28, 2022. http://dx.doi.org/10.1063/5.0100963.
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Inertial migration of spherical particles has been investigated extensively using experiments, theory, and computational modeling. Yet, a systematic investigation of the effect of particle shape on inertial migration is still lacking. Herein, we numerically mapped the migration dynamics of a prolate particle in a straight rectangular microchannel using smoothed particles hydrodynamics (SPH), at moderate Reynolds number flows. After validations, we applied our model to 2:1 and 3:1 shape aspect ratio particles at multiple confinement ratios. Their effects on the final focusing position, rotational behavior, and transitional dynamics were studied. In addition to the commonly reported tumbling motion, for the first time, we identified a new logrolling behavior of a prolate ellipsoidal particle in the confined channel. This new behavior occurs when the confinement ratio is above an approximate threshold value of K = 0.72. Our microfluidic experiments using cell aggregates with similar shape aspect ratio and confinement ratio confirmed this new predicted logrolling motion. We also found that the same particle can undergo different rotational modes, including kayaking behavior, depending on its initial cross-sectional position and orientation. Furthermore, we examined the migration speed, angular velocity, and rotation period, as well as their dependence on both particle shape aspect ratio and confinement ratio. Our findings are especially relevant to the applications where particle shape and alignment are used for sorting and analysis, such as the use of barcoded particles for biochemical assays through optical
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Samukcham, Jimpaul, Thokchom Premkumar Meitei, and Lenin S. Shagolsem. "Energy polydisperse fluid under cylindrical confinement." Physics of Fluids 36, no. 9 (2024). http://dx.doi.org/10.1063/5.0218639.
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The thermodynamic melting/freezing transition (T∗) behavior and particle dynamics under cylindrical confinement of a model energy polydisperse (EP) fluid are investigated by means of molecular dynamics simulations. All the particles in the system are different whose identity is characterized by the interaction energy parameter εi drawn randomly from a uniform distribution, and thus, the system represents an extreme limit of a multi-component system. It is observed that confinement induces shift in T∗ for both the EP and reference one-component (1C) fluid systems from their respective bulk values, and the direction of the shift is sensitive to the density. Although the trend of shift is similar for both the systems, the value of T∗ for the EP system is consistently above the 1C system for the considered different degrees of confinement. Neighborhood identity ordering (NIO) driven by the preferential interaction among the particles is observed in EP systems which is more pronounced near/below T∗. Unlike in bulk, confinement driven morphology of NIO in the form of alternate rings of higher/lower εi particles is observed. The particles with εi values near and below the mean show hopping motion between these annular regions. We believe that the observed complex dynamics in confined EP fluid could be utilized in practical applications where the mid εi particles can be used as carriers between the core and the curve surface of the narrow confinement for efficient and even distribution of substance of interest which needs to be adsorbed on the surface of a long narrow channel.