Effect Of Interparticle Interactions Research Articles

High-fidelity composite adiabatic passage in nonlinear two-level systems

We investigate the composite adiabatic passage (CAP) reported by B. T. Torosov et al. [Phys. Rev. Lett. 106, 233001 (2011)] in a nonlinear two-level system in which the level energies depend on the occupation of the levels, representing a mean-field type of interaction between the particles. A high-fidelity, fast, and robust quantum manipulation is achieved in the system. We consider the effect of interparticle interaction and find that it tends to increase the number of the pulse sequences. The CAP technique can suppress the nonadiabatic oscillations below the quantum-information benchmark ${10}^{\ensuremath{-}4}$, as long as there exist sufficiently long composite sequences. We analyze the robustness against the variations in the field parameters. The difference between the nonlinear and linear systems on the CAP technique is also discussed.

Self-subdiffusion in solutions of star-shaped crowders: non-monotonic effects of inter-particle interactions

We examine by extensive computer simulations the self-diffusion of anisotropic star-like particles in crowded two-dimensional solutions. We investigate the implications of the area coverage fraction ϕ of the crowders and the crowder–crowder adhesion properties on the regime of transient anomalous diffusion. We systematically compute the mean squared displacement (MSD) of the particles, their time averaged MSD, and the effective diffusion coefficient. The diffusion is ergodic in the limit of long traces, such that the mean time averaged MSD converges towards the ensemble averaged MSD, and features a small residual amplitude spread of the time averaged MSD from individual trajectories. At intermediate time scales, we quantify the anomalous diffusion in the system. Also, we show that the translational—but not rotational—diffusivity of the particles D is a nonmonotonic function of the attraction strength between them. Both diffusion coefficients decrease as the power law with the area fraction ϕ occupied by the crowders and the critical value Our results might be applicable to rationalising the experimental observations of non-Brownian diffusion for a number of standard macromolecular crowders used in vitro to mimic the cytoplasmic conditions of living cells.

Effect of interparticle interaction on magnetic hyperthermia in ferrofluids

The work deals with the theoretical study of effect of magnetic interaction between single-domain ferromagnetic particles on the hyperthermia effect produced by these particles under the action of oscillating magnetic field. We consider a homogeneous (without heterogeneous aggregates) ferrofluid consisting of identical spherical Brownian particles. Effects of the particles diameter and their magnetic properties on the intensity of the heat production are studied.

Effect of Inter-particle Interactions on Pair Correlations of One-Dimensional Anyon Gases

The pair correlation function of the one-dimensional interacting anyonic system in its ground state is investigated based on the exact Bethe ansatz solution for arbitrary coupling constant (\(0\le c\le \infty \)) and statistics parameter (\(0\le \kappa \le \pi \)). We discuss the effects of the inter-particle interactions and the fractional statistics on the pair correlations in both position and momentum spaces. The pair correlations of anyons with coupling constant c and statistical parameter \(\kappa \) in position space are identical to that of the Lieb–Liniger Bose model with effective coupling constant \(c^{^{\prime }}=c/\cos \left( \kappa /2\right) \). Besides the effect of renormalized coupling, the correlations in momentum space reveal more effects induced by the statistics parameter. The anyonic statistics results in the nonsymmetric correlation when the statistics parameter deviates from 0 (Bose statistics) and \(\pi \) (Fermi statistics) for any coupling constant c. The correlations display peaks and dips, representing the bunching and antibunching of atoms, respectively. The correlations show crossover from bunching behavior of bosons to antibunching behavior of fermions as \(\kappa \ \) varies from 0 to \(\pi \) for arbitrary coupling constant. Besides the fractional effect, we also observe the effects induced by the inter-particle interactions in the momentum correlations. With the increase of the coupling constant, the bunching effect between particles weakens and the antibunching points in the correlations shift.

Effect of Interparticle Interaction on Magnetic Hyperthermia—A Theoretical Study

Effect of Interparticle Interaction on Magnetic Hyperthermia—A Theoretical Study

Maximum entropy-based stochastic micromechanical model for a two-phase composite considering the inter-particle interaction effect

A maximum entropy-based stochastic micromechanical framework considering the inter-particle interaction effect is proposed to characterize the probabilistic behavior of the effective properties of two-phase composite materials. Based on our previous work, the deterministic micromechanical model of the two-phase composites is derived by introducing the strain concentration tensors considering the inter-particle interaction effect. By modeling the volume fractions and properties of constituents as stochastic, we extend the deterministic framework to stochastics, to incorporate the inherent randomness of effective properties among different specimens. A distribution-free method is employed to get the unbiased probability density function based on the maximum entropy principle. Further, the normalization procedures are utilized to make the probability density functions more stable. Numerical examples including limited experimental validations, comparisons with existing micromechanical models, commonly used probability density functions and the direct Monte Carlo simulations indicate that the proposed models provide an accurate and computationally efficient framework in characterizing the effective properties of two-phase composites.

Magnetic Anisotropy of Maghemite Nanoparticles Probed by RF Transverse Susceptibility

We present radio frequency magnetic transverse susceptibility measurements on γ-Fe2O3 nanoparticles, which yield an estimation of their effective anisotropy constant, Keff as a function of nanoparticle size. The resulting values range from 4 to 8 × 104 erg/cm3, being on the order of the magnetocrystalline anisotropy in bulk maghemite. Keff values increase as the particle diameter increases. Evidences of anisotropy field distribution given by the size distribution in the samples, and interparticle interactions that increase as the particle size increases, are also observed in the TS measurements. The effects of such interparticle interaction overcome those of thermal fluctuations, in contrast with the behavior of other iron oxide particles.

The accurate assessment of small-angle X-ray scattering data.

Small-angle X-ray scattering (SAXS) has grown in popularity in recent times with the advent of bright synchrotron X-ray sources, powerful computational resources and algorithms enabling the calculation of increasingly complex models. However, the lack of standardized data-quality metrics presents difficulties for the growing user community in accurately assessing the quality of experimental SAXS data. Here, a series of metrics to quantitatively describe SAXS data in an objective manner using statistical evaluations are defined. These metrics are applied to identify the effects of radiation damage, concentration dependence and interparticle interactions on SAXS data from a set of 27 previously described targets for which high-resolution structures have been determined via X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. The studies show that these metrics are sufficient to characterize SAXS data quality on a small sample set with statistical rigor and sensitivity similar to or better than manual analysis. The development of data-quality analysis strategies such as these initial efforts is needed to enable the accurate and unbiased assessment of SAXS data quality.

Correlation of superparamagnetic relaxation with magnetic dipole interaction in capped iron-oxide nanoparticles

Six nanometer sized iron-oxide nanoparticles capped with an organic surfactant and/or silica shell of various thicknesses have been synthesized by a microemulsion method to enable controllable contributions of interparticle magnetic dipole interaction via tunable interparticle distances. Bare particles with direct surface contact were used as a reference to distinguish between interparticle interaction and surface effects by use of Mössbauer spectroscopy. Superparamagnetic relaxation behaviour was analyzed by SQUID-magnetometry techniques, showing a decrease of the blocking temperature with decreasing interparticle interaction energies kBT0 obtained by AC susceptibility. A many-state relaxation model enabled us to describe experimental Mössbauer spectra, leading to an effective anisotropy constant Keff ≈ 45 kJm−3 in case of weakly interacting particles, consistent with results from ferromagnetic resonance. Our unique multi-technique approach, spanning a huge regime of characteristic time windows from about 10 s to 5 ns, provides a concise picture of the correlation of superparamagnetic relaxation with interparticle magnetic dipole interaction.

Intra- and interparticle magnetism of cobalt-doped iron-oxide nanoparticles encapsulated in a synthetic ferritin cage

We present an in-depth examination of the composition and magnetism of cobalt $({\mathrm{Co}}^{2+})$-doped iron-oxide nanoparticles encapsulated in Pyrococcus furiosus ferritin shells. We show that the ${\mathrm{Co}}^{2+}$ dopant ions were incorporated into the $\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}/{\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ core, with small paramagnetic-like clusters likely residing on the surface of the nanoparticle that were observed for all cobalt-doped samples. In addition, element-specific characterization using M\ossbauer spectroscopy and polarized x-ray absorption indicated that ${\mathrm{Co}}^{2+}$ was incorporated exclusively into the octahedral B sites of the spinel-oxide nanoparticle. Comparable superparamagnetic blocking temperatures, coercivities, and effective anisotropies were obtained for 7%, 10%, and 12% cobalt-doped nanoparticles, and were only slightly reduced for 3% cobalt, indicating a strong effect of cobalt incorporation, with a lesser effect of cobalt content. Due to the regular particle size and separation that result from the use of the ferritin cage, a comparison of the effects of interparticle interactions on the disordered assembly of nanoparticles was also obtained that indicated significantly different behaviors between undoped and cobalt-doped nanoparticles.

Alternating magnetic field energy absorption in the dispersion of iron oxide nanoparticles in a viscous medium

Magnetic iron oxide nanoparticles were obtained by a coprecipitation method in a controlled growth process leading to the formation of uniform highly crystalline nanoparticles with average size of 13 nm, which corresponds to the superparamagnetic state. Nanoparticles obtained are a mixture of single-phase nanoparticles of magnetite and maghemite as well as nanoparticles of non-stoichiometric magnetite. The subsequent annealing of nanoparticles at 300 °C in air during 6 h leads to the full transformation to maghemite. It results in reduced value of the saturation magnetization (from 56 emu g −1 to 48 emu g −1 ) but does not affect the heating ability of nanoparticles. A 2–7 wt% dispersion of as-prepared and annealed nanoparticles in glycerol provides high heating rate in alternating magnetic fields allowed for application in magnetic hyperthermia; however the value of specific loss power does not exceed 30 W g −1 . This feature of heat output is explained by the combined effect of magnetic interparticle interactions and the properties of the carrier medium. Nanoparticles coalesce during the synthesis and form aggregates showing ferromagnetic-like behavior with magnetization hysteresis , distinct sextets on Mössbauer spectrum , blocking temperature well about room temperature, which accounts for the higher energy barrier for magnetization reversal. At the same time, low specific heat capacity of glycerol intensifies heat transfer in the magnetic dispersion. However, high viscosity of glycerol limits the specific loss power value, since predominantly the Neel relaxation accounts for the absorption of AC magnetic field energy. • Mixed phase iron oxide magnetic nanoparticles were obtained by coprecipitation. • A part of nanoparticles was annealed at 300 °C to achieve the single-phase γ-Fe 2 O 3 . • Nanoparticles revealed ferromagnetic-like behavior due to interparticle interactions. • Nanoparticles glycerol dispersions showed rapid heating at moderate field amplitudes. • Interparticle interactions and carrier medium properties determine heat generation.

Understanding dynamics of interacting magnetic nanoparticles: from the weak interaction regime to the collective superspin glass state

A brief review of the investigations on interparticle interaction effects (weak and strong interactions regimes) is reported with a special emphasis on the critical behaviour in the static and dynamical properties and on the out of equilibrium dynamics of the collective superspin glass (SSG) state. The results of the investigation of aging and memory effects in two peculiar SSG systems are discussed: MnFe2O4 nanoparticles, in powder form, with very strong dipolar interactions, and a diluted system, consisting of a film of Co particles dispersed (5% volume fraction) in a Mn matrix, where interparticle interactions are mainly mediated by the matrix.

Effects of hydrodynamic retardation and interparticle interactions on the self-assembly in a drying droplet containing suspended solid particles.

Self-assembly of particles, suspended in a drying droplet, were studied by the Monte Carlo method. The Brownian diffusion of particles was simulated accounting for the effect of hydrodynamic retardation and interparticle interactions. The model allowed for explaining formation of the "coffee ring" patterns even without accounting for the radial flows towards the three-phase contact line. Morphologies of the drying patterns and their dependence on interparticle interactions and concentration of particles are discussed.

Effects of size and interparticle interaction of silica nanoparticles on dispersion and electrical conductivity of silver/epoxy nanocomposites

The agglomeration of nanoparticles (NPs) occurs due to attractive interaction between NPs and worsens the physical properties of materials such as electrical conductivity. When the attractive interaction is sufficiently strong, the agglomerates of NPs may be arrested dynamically in non-equilibrium state with a large relaxation time. We show that when conductive silver NPs form agglomerates in epoxy matrices, one can tune the effective interaction between silver NPs in epoxy matrices by introducing auxiliary non-conductive silica NPs and may prevent the agglomeration easily. More interestingly, as the size of the auxiliary silica NPs decreases, the silver NPs disperse better, thus increasing the electrical conductivity by orders of magnitude. We also perform Monte Carlo simulations and show that the auxiliary silica NPs influence the morphology of silver NPs not entropically but energetically.

Diverging electrophoretic and dynamic mobility of model silica colloids at low ionic strength in ethanol

Electroacoustics and laser Doppler electrophoresis were employed to measure the mobility of surface-modified silica colloids in ethanol as a function of the ionic strength. Sufficiently low volume fractions were chosen to exclude effects of interparticle interactions. At high ionic strength, the electrophoretic mobility μe is equal to the (electroacoustic) dynamic mobility μd at 3.3MHz. However, the ratio μd/μe increases significantly to ∼5 at low ionic strength. This increase may be related to the porous outer layer of the surface-modified silica spheres.

Structure and Interaction of Poly(ethylene glycol) in Aqueous Solutions. Small‐Angle Neutron Scattering Data

SummaryBehavior of low molecular mass poly(ethylene glycol) (PEG) polymer, i.e. molar masses Mn = 400 and 1000, in heavy water is studied by small‐angle neutron scattering (SANS). Some part of the polymer molecules in concentrated solutions is found to form aggregates with size exceeding 30 nm. The form‐factor of Gaussian coil is used to describe low concentrated PEG solutions. Virial coefficients are obtained from approximation of experimental SANS data for PEG solutions with concentration higher than 3% where the interparticle interaction effect is well observed.

Effect of Interparticle Interaction on Particle Deposition in a Crossflow Microfilter

Recent studies show that interparticle interaction can affect particle trajectories and particle deposition causing fouling in the microfilters used for metal working fluids (MWFs). Interparticle interaction depends on various factors: particle geometry and surface properties, membrane pore geometry and surface properties, MWF's properties and system operating conditions, etc. A mathematical model with a Langevin equation for particle trajectory and a hard-sphere model for particle deposition has been used to study the effect of particle's size, particle's surface zeta potential, interparticle distance, and shape of membrane pore wall surface on particle trajectory and its deposition on membrane pore wall. The study reveals the microlevel force phenomena behind bigger particles having a lesser tendency to be deposited on membrane pore walls than smaller particles. Deposition of particles on pore walls with asperities such as previously deposited particles is also examined and it is found that such cases can reduce repulsive electrostatic forces and lead to a higher probability of particle capture.

Erratum: Effect of interparticle interaction in a free-oscillation atomic interferometer [Phys. Rev. A87, 043630 (2013)

Received 5 November 2013DOI:https://doi.org/10.1103/PhysRevA.88.059903©2013 American Physical Society

Colloids in light fields: Particle dynamics in random and periodic energy landscapes

The dynamics of colloidal particles in potential energy landscapes have mainly been investigated theoretically. In contrast, here we discuss the experimental realization of potential energy landscapes with the help of light fields and the observation of the particle dynamics by video microscopy. The experimentally observed dynamics in periodic and random potentials are compared to simulation and theoretical results in terms of, e.g. the mean-squared displacement, the time-dependent diffusion coefficient or the non-Gaussian parameter. The dynamics are initially diffusive followed by intermediate subdiffusive behaviour which again becomes diffusive at long times. How pronounced and extended the different regimes are, depends on the specific conditions, in particular the shape of the potential as well as its roughness or amplitude but also the particle concentration. Here we focus on dilute systems, but the dynamics of interacting systems in external potentials, and thus the interplay between particle-particle and particle-potential interactions, is also mentioned briefly. Furthermore, the observed dynamics of dilute systems resemble the dynamics of concentrated systems close to their glass transition, with which it is compared. The effect of certain potential energy landscapes on the dynamics of individual particles appears similar to the effect of interparticle interactions in the absence of an external potential.

Bosonic transport through a chain of quantum dots

The particle transport through a chain of quantum dots coupled to two bosonic reservoirs is studied. For the case of reservoirs of non-interacting bosonic particles, we derive an exact set of stochastic differential equations, whose memory kernels and driving noise are characterised entirely by the properties of the reservoirs. Going to the Markovian limit an analytically solvable case is presented. The effect of interparticle interactions on the transient behaviour of the system, when both reservoirs are instantaneously coupled to an empty chain of quantum dots, is approximated by a semiclassical method, known as the Truncated Wigner approximation. The steady-state particle flow through the chain and the mean particle occupations are explained via the spectral properties of the interacting system.