Recent advances in bead mill design have been achieved through optimization using the Discrete Element Method (DEM). This is because the impact energy of beads calculated by DEM is well correlated with the actual grinding performance of bead mills. However, wear is inevitable in bead mills, leading to a decline in grinding performance and making it difficult to maintain the effectiveness of the optimized shape over time. In this study, we propose a shape optimization system that accounts for wear. The proposed system integrates the Design of Experiments (DOE) for analyzing shape parameters and the Interface Capturing Wear Model (ICWM) for accurate and robust wear simulation. The effectiveness of optimized bead mill is validated through comparison with actual grinding experiments.

The goal of this research is to prepare polymethyl methacrylate (PMMA) nanoparticles with an average particle diameter of less than 100 nm in which a functional dye that absorbs near-infrared light is immobilized. In the experimental conditions used in this study, the liquid-in-drying method was employed to prepare the nanoparticles by dissolving the polymer as the wall material and the functional dye in an organic solvent and dispersing the O/W emulsion in water. As a result, the particle size tended to decrease as the concentration of nonionic surfactant added to the dispersed phase was increased, and nanoparticles with functional dyes below 100 nm could be prepared under conditions of 15 wt% or higher. However, as the surfactant concentration increased, the functional dye content decreased. In the dispersion stability tests of the prepared nanoparticles had a high dispersion stability under a static condition for 7 days expect for the nanoparticles prepared with Tween80 concentration of 1 wt%.

We numerically investigate the stability of a cylindrical column composed of wet granular materials under gravity using the discrete element method. When the column height exceeds a critical value H_c, the column collapses under its own weight. From the phase diagram for stability, we demonstrate that the critical height depends on the surface tension γ. Applying the Mohr-Coulomb yield criterion, we theoretically determine the critical height H_c, which is subsequently validated through numerical simulations.

In many clinically-approved nucleic acid products, transfection agents, including viral vectors and lipid nanoparticles, have been applied for high transfection efficiency, whereas they have major concerns about severe systemic adverse action. Inhaled dry powder formulations for naked nucleic acids without transfection agents are highly attractive because of many practical advantages, such as direct and noninvasive delivery to the lungs where nuclease activity is low, easy usage, good device portability, and high storage stability. However, various physical stresses generated in the production process can destabilize nucleic acids, and there are few articles demonstrating the efficacy of the naked nucleic acid powders produced. The present article introduces our outcomes about the stability of naked nucleic acids under several types of physical treatment or powder formation and about the successful development of inhaled dry naked nucleic acid powders with high aerosol performance and superior pulmonary transfection efficiency.

The purpose of this study is to investigate the effects of acoustic streaming and acoustic radiation force on particles motion in an ultrasonic standing wave. A flexural vibration plate with 4 nodes was designed, and it was shown that the amplitude at the antinode is proportional to the voltage. This means it is possible to conduct experiments with any amplitude. After confirming that a standing wave field was generated in closed space, an experiment was carried out to visualize acoustic streaming. Eight vortices were observed in the horizontal direction, indicating a Rayleigh acoustic flow. In addition, a vortex in perpendicular direction against the plate was generated when the height between vibration plate and acrylic surface was set at half wavelength. Then two vortexes were obtained at a wave length for the height. Simulations for acoustic pressure and streaming agreed with this experimental result. Finally, simulations on particle motion showed that acoustic flow dominates when particle diameter is less than 20 μm. On the other hand, the motion of over 20 μm particle is influenced by acoustic radiation force.