Dissipative particle dynamics simulations of polymer chains: scaling laws and shearing response compared to DNA experiments

Dissipative particle dynamics simulations of several bead-spring representations of polymer chains in dilute solution are used to demonstrate the correct static scaling laws for the radius of gyration. Shear flow results for the wormlike chain simulating single DNA molecules compare well with average extensions from experiments, irrespective of the number of beads. However, coarse graining with more than a few beads degrades the agreement of the autocorrelation of the extension.     

Pattern formation and fluctuation-induced transitions in protein crystallization

A kinetic model of protein crystallization accounting for the nucleation stage, the growth and competition of solid particles and the formation of macroscopic patterns is developed. Different versions are considered corresponding successively, to a continuous one-dimensional crystallization reactor, a coarse grained two-box model and a model describing the evolution of the space averaged values of fluid and solid material. The analysis brings out the high multiplicity of the patterns. It provides information on their stability as well as on the kinetics of transitions between different states under the influence of the fluctuations.     

Interactions between polymers and carbon nanotubes: a molecular dynamics study

We used force-field-based molecular dynamics to study the interaction between polymers and carbon nanotubes (CNTs). The intermolecular interaction energy between single-walled carbon nanotubes and polymers was computed, and the morphology of polymers adsorbed to the surface of nanotubes was investigated. Furthermore, the "wrapping" of nanotubes by polymer chains was examined. It was found that the specific monomer structure plays a very important role in determining the strength of interaction between nanotubes and polymers. The results of our study suggest that polymers with a backbone containing aromatic rings are promising candidates for the noncovalent binding of carbon nanotubes into composite structures. Such polymers can be used as building blocks in amphiphilic copolymers to promote increased interfacial binding between the CNT and a polymeric matrix.     

Calculation of nonlinear modes guided by multilayer dielectric structures using the resonance technique

A simple and easily programmable approach based on the resonance method has been developed for analysing optical waves guided by complicated configurations such as multilayer dielectric structures with arbitrary nonlinear media. In this formulation both TE and TM polarizations are considered. In the present paper, as an example of the resonance technique application, the five-layer waveguiding configuration, including two arbitrary nonlinear media along with a linear film of arbitrary profile, is treated. Numerical results are presented in the form of guided power versus propagation constant for various parameters of the problem.     

Experimental and theoretical studies of a high repetition rate fiber laser, mode-locked by external optical modulation

An experimental and theoretical study of a high repetition rate laser source operating on a novel mode-locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A complete mathematical model of the fiber ring laser is presented describing the mode-locking process in the laser oscillator and providing solutions for the steady-state mode-locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode-locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of its critical parameters.     

Near IR Bandgap Semiconducting 2D Conjugated Metal-Organic Framework with Rhombic Lattice and High Mobility

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs) are emerging as a unique class of electronic materials. However, 2D c-MOFs with band gaps in the Vis-NIR and high charge carrier mobility are rare. Most of the reported conducting 2D c-MOFs are metallic (i.e. gapless), which largely limits their use in logic devices. Herein, we design a phenanthrotriphenylene-based, D_2h-symmetric π-extended ligand ( OHPTP ), and synthesize the first rhombic 2D c-MOF single crystals ( Cu₂(OHPTP) ). The continuous rotation electron diffraction (cRED) analysis unveils the orthorhombic crystal structure at the atomic level with a unique slipped AA stacking. The Cu₂(OHPTP) is a p-type semiconductor with an indirect band gap of ≈0.50 eV and exhibits high electrical conductivity of 0.10 S cm⁻¹ and high charge carrier mobility of ≈10.0 cm² V⁻¹ s⁻¹. Theoretical calculations underline the predominant role of the out-of-plane charge transport in this semiquinone-based 2D c-MOF.     

Improved particle filters for multi-target tracking

We present a novel approach for improving particle filters for multi-target tracking. The suggested approach is based on drift homotopy for stochastic differential equations. Drift homotopy is used to design a Markov Chain Monte Carlo step which is appended to the particle filter and aims to bring the particle filter samples closer to the observations while at the same time respecting the target dynamics. We have used the proposed approach on the problem of multi-target tracking with a nonlinear observation model. The numerical results show that the suggested approach can improve significantly the performance of a particle filter.