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In this work, the particle dynamics within a rotary granulator will be investigated using a novel measurement technique that allows the tracking of magnetic tracer particles. In particular, the influence of liquid on the dynamics will be investigated, since rotary granulators are often used for the production of agglomerates or for spheronization, where a binder liquid is used in these processes. The particle dynamics are defined by means of 2D cross-sectional diagrams and distributions of the particle velocities. In addition, models for the evaluation of the particle dynamics are applied and compared. Apart from the influence of the liquid, whereby the influence of the volume ratio and the viscosity is examined, operating parameters of the rotary granulator are varied as well.

The effect of the concentration and chain length of the copolymer AB with sequence length τ = 8 on the interfacial properties of the ternary mixtures A 10 /AB/B 10 are investigated by the dissipative particle dynamics (DPD) simulations. It is found that: i) As the copolymer concentration varies from 0.05 to 0.15, increasing the copolymer enrichment at the center of the interface enlarges the interface width ω and reduces the interfacial tension. However, as the concentration of the sequence copolymers further increases to 0.2, because the interface has formed micelles and the micellization could lower the efficiency of copolymers as a compatibilizer, the interfacial tension exhibits a slightly increase; ii) elevating the copolymer chain length, the copolymer volumes vary from a cylinder shape to a pancake shape. The blends of the copolymer with chain length N cp = 24 exhibit a wider interfacial width w and a lower interfacial tension γ , which indicates that the sequenced copolymer N cp = 24 exhibits a better performance as the compatibilizers. This study illustrates the correlations between the reduction in interfacial tension produced by the sequence copolymers and their molecular parameters, which guide a rational design of an efficient compatibilizer.

The self-assembly of particles at fluid interfaces, driven by the reduction in interfacial energy, is well established. However, for nanoscopic particles, thermal fluctuations compete with interfacial energy and give rise to a particle-size-dependent self-assembly. Ligand-stabilized nanoparticles assembled into three-dimensional constructs at fluid-fluid interfaces, where the properties unique to the nanoparticles were preserved. The small size of the nanoparticles led to a weak confinement of the nanoparticles at the fluid interface that opens avenues to size-selective particle assembly, two-dimensional phase behavior, and functionalization. Fluid interfaces afford a rapid approach to equilibrium and easy access to nanoparticles for subsequent modification. A photoinduced transformation is described in which nanoparticles, initially soluble only in toluene, were transported across an interface into water and were dispersed in the water phase. The characteristic fluorescence emission of the nanoparticles provided a direct probe of their spatial distribution.

Understanding the behaviour of particles suspended in a fluid has many important applications across a range of fields, including engineering and geophysics. Comprising two main parts, this book begins with the well-developed theory of particles in viscous fluids, i.e. microhydrodynamics, particularly for single- and pair-body dynamics. Part II considers many-body dynamics, covering shear flows and sedimentation, bulk flow properties and collective phenomena. An interlude between the two parts provides the basic statistical techniques needed to employ the results of the first (microscopic) in the second (macroscopic). The authors introduce theoretical, mathematical concepts through concrete examples, making the material accessible to non-mathematicians. They also include some of the many open questions in the field to encourage further study. Consequently, this is an ideal introduction for students and researchers from other disciplines who are approaching suspension dynamics for the first time.

The influence of molecular fragmentation and parameter settings on a mesoscopic dissipative particle dynamics (DPD) simulation of lamellar bilayer formation for a C 10 E 4 /water mixture is studied. A “bottom-up” decomposition of C 10 E 4 into the smallest fragment molecules (particles) that satisfy chemical intuition leads to convincing simulation results which agree with experimental findings for bilayer formation and thickness. For integration of the equations of motion Shardlow’s S1 scheme proves to be a favorable choice with best overall performance. Increasing the integration time steps above the common setting of 0.04 DPD units leads to increasingly unphysical temperature drifts, but also to increasingly rapid formation of bilayer superstructures without significantly distorted particle distributions up to an integration time step of 0.12. A scaling of the mutual particle–particle repulsions that guide the dynamics has negligible influence within a considerable range of values but exhibits apparent lower thresholds beyond which a simulation fails. Repulsion parameter scaling and molecular particle decomposition show a mutual dependence. For mapping of concentrations to molecule numbers in the simulation box particle volume scaling should be taken into account. A repulsion parameter morphing investigation suggests to not overstretch repulsion parameter accuracy considerations.

Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing to a higher passenger density in bus cabins. We developed a numerical prediction method for the spatial distribution of airborne transmission risks inside bus cabins. For a computational fluid dynamics analyses, targeting two types of bus cabins, sophisticated geometries of bus cabins with realistic heating, ventilation, and air-conditioning were reproduced. The passengers in bus cabins were reproduced using computer-simulated persons. Airflow, heat, and moisture transfer analysis were conducted based on computational fluid dynamics, to predict the microclimate around passengers and the interaction between the cabin climate and passengers. Finally, droplet dispersion analysis using the Eulerian–Lagrangian method and an investigation of the spatial distribution of infection/spread risks, assuming SARS-CoV-2 infection, were performed. Through parametric analyses of passive and individual countermeasures to reduce airborne infection risks, the effectiveness of countermeasures for airborne infection was discussed. Partition installation as a passive countermeasure had an impact on the human microclimate, which decreased infection risks. The individual countermeasure, mask-wearing, almost completely prevented airborne infection.

The splitting of zero-energy Majorana modes in a tunnel-coupled InAs nanowire with epitaxial aluminium is exponentially suppressed as the wire length is increased, resulting in protection of these modes; this result helps to establish the robust presence of Majorana modes and quantifies exponential protection in nanowire devices. Majorana modes get more real There are three known fundamental types of fermions called Dirac, Weyl and Majorana. Until recently, the latter two had escaped observation, but evidence for the existence of Weyl and Majorana modes was found in condensed matter systems. In particular, signatures for Majorana modes were identified in semiconductor–superconductor nanowire devices, and this sparked significant interest because non-trivial topological properties had been predicted. Charles Marcus and colleagues present the next essential piece of evidence for the robust presence of Majorana modes in such devices, namely the exponential protection of Majorana modes in the form of a suppression of energy splitting with increasing nanowire length. The observations open a path to the next step of controlling Majorana modes and establishing topological properties. Majorana zero modes are quasiparticle excitations in condensed matter systems that have been proposed as building blocks of fault-tolerant quantum computers 1 . They are expected to exhibit non-Abelian particle statistics, in contrast to the usual statistics of fermions and bosons, enabling quantum operations to be performed by braiding isolated modes around one another 1 , 2 . Quantum braiding operations are topologically protected insofar as these modes are pinned near zero energy, with the departure from zero expected to be exponentially small as the modes become spatially separated 3 , 4 . Following theoretical proposals 5 , 6 , several experiments have identified signatures of Majorana modes in nanowires with proximity-induced superconductivity 7 , 8 , 9 , 10 , 11 and atomic chains 12 , with small amounts of mode splitting potentially explained by hybridization of Majorana modes 13 , 14 , 15 . Here, we use Coulomb-blockade spectroscopy in an InAs nanowire segment with epitaxial aluminium, which forms a proximity-induced superconducting Coulomb island (a ‘Majorana island’) that is isolated from normal-metal leads by tunnel barriers, to measure the splitting of near-zero-energy Majorana modes. We observe exponential suppression of energy splitting with increasing wire length. For short devices of a few hundred nanometres, sub-gap state energies oscillate as the magnetic field is varied, as is expected for hybridized Majorana modes. Splitting decreases by a factor of about ten for each half a micrometre of increased wire length. For devices longer than about one micrometre, transport in strong magnetic fields occurs through a zero-energy state that is energetically isolated from a continuum, yielding uniformly spaced Coulomb-blockade conductance peaks, consistent with teleportation via Majorana modes 16 , 17 . Our results help to explain the trivial-to-topological transition in finite systems and to quantify the scaling of topological protection with end-mode separation.

The combination of interparticle interactions and a synthetic gauge field leads to chirality in the propagation dynamics of particles in a ladder-like lattice. Gauging two-body interactions Simulating topological band structures, the corresponding edge states, and the quantum Hall effect with neutral atoms requires the introduction of artificial gauge fields. Although challenging, various groups have recently demonstrated artificial gauge fields in ultracold neutral-atom systems. However, up to now, these simulations have been limited to single-particle effects, meaning that many fascinating condensed-matter phenomena, such as the fractional quantum Hall effect, could not be studied. Here, the authors subject a two-dimensional Bose–Einstein condensate of rubidium-87 atoms to an artificial gauge field and use a quantum gas microscope to investigate how two-body interactions affect the chiral dynamics. If extended to many-body interactions, this strategy could enable the simulation of the interplay between many-body interactions and topology in condensed-matter physics. The interplay between magnetic fields and interacting particles can lead to exotic phases of matter that exhibit topological order and high degrees of spatial entanglement 1 . Although these phases were discovered in a solid-state setting 2 , 3 , recent innovations in systems of ultracold neutral atoms—uncharged atoms that do not naturally experience a Lorentz force—allow the synthesis of artificial magnetic, or gauge, fields 4 , 5 , 6 , 7 , 8 , 9 , 10 . This experimental platform holds promise for exploring exotic physics in fractional quantum Hall systems, owing to the microscopic control and precision that is achievable in cold-atom systems 11 , 12 . However, so far these experiments have mostly explored the regime of weak interactions, which precludes access to correlated many-body states 4 , 13 , 14 , 15 , 16 , 17 . Here, through microscopic atomic control and detection, we demonstrate the controlled incorporation of strong interactions into a two-body system with a chiral band structure. We observe and explain the way in which interparticle interactions induce chirality in the propagation dynamics of particles in a ladder-like, real-space lattice governed by the interacting Harper–Hofstadter model, which describes lattice-confined, coherently mobile particles in the presence of a magnetic field 18 . We use a bottom-up strategy to prepare interacting chiral quantum states, thus circumventing the challenges of a top-down approach that begins with a many-body system, the size of which can hinder the preparation of controlled states. Our experimental platform combines all of the necessary components for investigating highly entangled topological states, and our observations provide a benchmark for future experiments in the fractional quantum Hall regime.

In non-Hermitian systems, spectral degeneracies can arise that can cause unusual, counter-intuitive effects; here exciton-polaritons—hybrid light–matter particles—within a semiconductor microcavity are found to display non-trivial topological modal structure exclusive to such systems. Non-Hermitian dynamics in a quantum chaotic exciton-polariton system In non-Hermitian systems, which are open and subject to gain and loss, exceptional points can arise, spectral degeneracies that can cause unusual, counter-intuitive effects. Recent efforts to observe non-Hermitian physics have concentrated on various optical systems, but not yet on exciton-polaritons. These are hybrid light–matter particles, formed by strongly interacting photons and excitons (electron–hole pairs) in semiconductor microcavities. Such systems require constant pumping of energy and continuously decays releasing coherent radiation, so are a profoundly open quantum system. In a striking experiment involving a chaotic exciton-polariton billiard —a two-dimensional area enclosed by a curved potential barrier — these authors demonstrate this non-Hermitian nature for the first time. The experiment reveals the non-trivial topological modal structure exclusive to non-Hermitian systems. These findings open the way for novel types of operating principles for polariton-based optoelectronic devices. Exciton-polaritons are hybrid light–matter quasiparticles formed by strongly interacting photons and excitons (electron–hole pairs) in semiconductor microcavities 1 , 2 , 3 . They have emerged as a robust solid-state platform for next-generation optoelectronic applications as well as for fundamental studies of quantum many-body physics. Importantly, exciton-polaritons are a profoundly open (that is, non-Hermitian 4 , 5 ) quantum system, which requires constant pumping of energy and continuously decays, releasing coherent radiation 6 . Thus, the exciton-polaritons always exist in a balanced potential landscape of gain and loss. However, the inherent non-Hermitian nature of this potential has so far been largely ignored in exciton-polariton physics. Here we demonstrate that non-Hermiticity dramatically modifies the structure of modes and spectral degeneracies in exciton-polariton systems, and, therefore, will affect their quantum transport, localization and dynamical properties 7 , 8 , 9 . Using a spatially structured optical pump 10 , 11 , 12 , we create a chaotic exciton-polariton billiard—a two-dimensional area enclosed by a curved potential barrier. Eigenmodes of this billiard exhibit multiple non-Hermitian spectral degeneracies, known as exceptional points 13 , 14 . Such points can cause remarkable wave phenomena, such as unidirectional transport 15 , anomalous lasing/absorption 16 , 17 and chiral modes 18 . By varying parameters of the billiard, we observe crossing and anti-crossing of energy levels and reveal the non-trivial topological modal structure exclusive to non-Hermitian systems 9 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 . We also observe mode switching and a topological Berry phase for a parameter loop encircling the exceptional point 23 , 24 . Our findings pave the way to studies of non-Hermitian quantum dynamics of exciton-polaritons, which may uncover novel operating principles for polariton-based devices.