Traffic dispersion induced by noise in off-lattice model

We study the dispersion of vehicles induced by speed fluctuation on a single-lane highway under open boundary. We extend the cellular automaton model on one-dimensional lattice to the real-variable model on off-lattice (continuous-in space model) in order to take into account the fluctuation of vehicular speed. Vehicles extend over the highway when moving forward. The characteristics of traffic dispersion are derived. It is shown that vehicular traffic exhibits scaling property. When a vehicle accelerates for following the vehicle ahead, vehicles move forming a cluster without dispersion. The relationship between the width of vehicular cluster and acceleration rate is clarified.     

Membrane Organization and Dynamics of the G-Protein-Coupled Serotonin<Subscript>1A</Subscript> Receptor Monitored Using Fluorescence-Based Approaches

The G-protein-coupled receptor (GPCR) superfamily represents one of the largest classes of molecules involved in signal transduction across the plasma membrane. Fluorescence-based approaches have provided valuable insights into GPCR functions such as receptor–receptor and receptor–ligand interactions, real-time assessment of signal transduction, receptor dynamics on the plasma membrane, and intracellular trafficking of receptors. This has largely been possible with the use of fluorescent probes such as the green fluorescent protein (GFP) from the jellyfish Aequoria victoria and its variants. We discuss the potential of fluorescence-based approaches in providing novel information on the membrane organization and dynamics of the G-protein-coupled serotonin_1A receptor tagged to the enhanced yellow fluorescent protein (EYFP). These authors contributed equally to the work.     

Stochastic Ornstein–Uhlenbeck Capacitors

We introduce and study a class of random capacitor systems which are both charged and discharged stochastically. A capacitor is fed by a random inflow with stationary and independent increments. Discharging occurs according to a Markovian rate which is linear in the capacitors level. The resulting capacitor dynamics are Markovian, stochastically cyclic, and regenerative. We coin these systems Lévy-charged Ornstein–Uhlenbeck capacitors. Various random quantities associated with these systems are analyzed, including: the time-to- discharge; the duration of the charging cycle; the trajectory and the peak height of the capacitor level during a charging cycle; and, the capacitors stationary equilibrium level. Furthermore, we show that there are sharp distinctions between these capacitor systems and corresponding standard Lévy-driven Ornstein–Uhlenbeck systems.     

Membrane tube pearling induced by a coupling of osmotic pressure and nanoparticle adhesion

ABSTRACT

In this work, a coarse-grained molecular dynamics simulation method that belongs to the class of dissipative particle dynamics scheme with implicit solvent was used to indicate that adsorption of nanoparticles (NPs) inside a lipid membrane tube and pressure difference across the membrane, e.g. osmotic pressure, cooperatively induce membrane tube pearling. We demonstrate that NP adsorption and aggregation initiate the shape transformation of the lipid tube, and pressure difference provides a driving force for pearling transition. Depending on the dynamic coupling of tube shape transition and NP aggregation in the interior of the tube, different shape transitions via four kinds of pearling pathways are recognised, including pearls on a string (i.e. vesicles are interconnected via either a chain or double-chain of NPs) and tube-to-vesicle transition that is dominated kinetically either by NP-membrane attraction or by pressure difference. Considering the fact that biological membranes are semipermeable and many proteins interact with the membranes, these findings not only provide a mechanism of membrane tube pearling but also demonstrate the importance of osmotic pressure and protein–membrane interaction for many cell activities related to shape transitions of biomembrane.     

Molecular dynamics simulations of pure methane and carbon dioxide hydrates: lattice constants and derivative properties

ABSTRACT

We report extensive molecular dynamics simulation results of pure methane and carbon dioxide hydrates at pressure and temperature conditions that are of interest to various practical applications. We focus on the calculation of the lattice constants of the two pure hydrates and their dependence on pressure and temperature. The calculated lattice constants are correlated using second order polynomials which are functions of either temperature or pressure. Finally, the obtained correlations are used in order to calculate two derivative properties, namely the isothermal compressibility and the isobaric thermal expansion coefficient. The current simulation results are also compared against reported experimental measurements and other simulation studies and good agreement is found for the case of isothermal compressibility. On the other hand, for the case of isobaric thermal expansion coefficient good agreement is found only with other simulation studies, while the simulation studies are in disagreement with experiments, particularly at low temperatures.     

Brownian and advective dynamics in microflow studied by coherent X‐ray scattering experiments

Combining microfluidics with coherent X‐ray illumination offers the possibility to not only measure the structure but also the dynamics of flowing samples in a single‐scattering experiment. Here, the power of this combination is demonstrated by studying the advective and Brownian dynamics of colloidal suspensions in microflow of different geometries. Using an experimental setup with a fast two‐dimensional detector and performing X‐ray correlation spectroscopy by calculating two‐dimensional maps of the intensity auto‐correlation functions, it was possible to evaluate the sample structure and furthermore to characterize the detailed flow behavior, including flow geometry, main flow directions, advective flow velocities and diffusive dynamics. By scanning a microfocused X‐ray beam over a microfluidic device, the anisotropic auto‐correlation functions of driven colloidal suspensions in straight, curved and constricted microchannels were mapped with the spatial resolution of the X‐ray beam. This method has not only a huge potential for studying flow patterns in complex fluids but also to generally characterize anisotropic dynamics in materials.     

Quantum Zeno dynamics in atoms and cavities

Quantum Zeno Dynamics restricts the evolution of a system in a tailorable subspace of the Hilbert space by repeated measurements of a proper observable. This restricted dynamics can be counterintuitive and lead to the generation of interesting nonclassical states. We describe an experiment implementing the Zeno dynamics in an atomic Rydberg level manifold, and we propose an implementation in the cavity quantum electrodynamics context. Both systems open promising perspectives for quantum-enabled metrology and decoherence studies.     

Dynamics of charge transfer at Au/Si metal-semiconductor nano-interface

An ab initio analysis of the periodic array of Au/Si nanostructure composed of gold clusters linked to silicon quantum dot (QD) co-doped by aluminium and phosphorus along [111] direction is presented in this paper. The density functional theory (DFT) is used to compute the electronic structure of the simulated system. Non-adiabatic coupling implemented in the form of dissipative equation of motion for reduced density matrix is used to study the phonon-induced relaxation in the simulated system. The density of states clearly shows that the formation of Au–Si bonds contributes states to the band gap of the model. Dynamics of selected photo-excitations shows that hole relaxation in energy and in space is much faster than electron relaxation, which is due to the higher density of states of the valence band.     

Strain rate effects on compressive behavior of covalently bonded CNT networks

In this study, strain rate effects on the compressive mechanical properties of randomly structured carbon nanotube (CNT) networks were examined. For this purpose, three-dimensional atomistic models of CNT networks with covalently-bonded junctions were generated. After that, molecular dynamics (MD) simulations of compressive loading were performed at five different strain rates to investigate the basic deformation characteristic mechanisms of CNT networks and determine the effect of strain rate on stress–strain curves. The simulation results showed that the strain rate of compressive loading increases, so that a higher resistance of specimens to deformation is observed. Furthermore, the local deformation characteristics of CNT segments, which are mainly driven by bending and buckling modes, and their prevalence are strongly affected by the deformation rate. It was also observed that CNT networks have superior features to metal foams such as metal matrix syntactic foams (MMSFs) and porous sintered fiber metals (PSFMs) in terms of energy absorbing capabilities.     

Reconstructing the relaxation dynamics induced by an unknown heat bath

In quantum state tomography, one potential source of error is uncontrolled contact of the system with a heat bath whose detailed properties are not known, and whose impact on the system moreover varies between different runs of the experiment. Precisely these variations provide a handle for reconstructing the system?s effective relaxation dynamics. I propose a pertinent estimation scheme which is based on a steepest-descent ansatz and maximum likelihood. After reconstructing the relaxation dynamics, the original quantum state of the system can be constrained to a curve in state space.