Collective motion of polar active particles on a sphere

Collective motion of active particles with polar alignment is investigated on a sphere.We discussed the factors that affect particle swarm motion and define an order parameter that can show the degree of particle swarm motion.In the model,we added a polar alignment strength,along with Gaussian curvature,affecting particles swarm motion.We find that when the force exceeds a certain limit,the order parameter will decrease with the increase of the force.Combined with our definition of order parameter and observation of the model,the reason is that particles begin to move side by side under the influence of polar forces.In addition,the effects of velocity,rotational diffusion coefficient,and packing fraction on particle swarm motion are discussed.It is found that the rotational diffusion coefficient and the packing fraction have a great influence on the clustering motion of particles,while the velocity has little influence on the clustering motion of particles.

Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles

The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma. It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field Eo has also been studied in this paper.

Generation of polarized particle beams at relativistic laser intensities

The acceleration of polarized electrons,positrons,protons and ions in strong laser and plasma fields is a very attractive option for obtaining polarized beams in the multi-mega-electron volt range.Recently,there has been substantial progress in the understanding of the dominant mechanisms leading to high degrees of polarization,in the numerical modeling of these processes and in their experimental implementation.This review paper presents an overview on the current state of the field,and on the concepts of polarized laser–plasma accelerators and of beam polarimetry.

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three-step emulsion polymerization using poly（butyl acrylate-methyl metbacrylate-methacrylic acid-ethylene glycol dimethacrylate） （P（BA-MMA-MAA- EGDMA）） as core, poly（methyl methacrylate-methacrylic acid-styrene） （P（St-MMA-MAA）） as interlayer and polystyrene （PSt） as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy （TEM）, dynamic light scattering （DLS） and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two-layer core/interlayer and three-layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl-containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage