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.

This review presents new techniques for the measurement of ceramic slurries. First, we have developed a scanning electron-assisted dielectric microscope (SE-ADM) system with energy-dispersive X-ray spectrometry (EDS) that enables direct observation and elemental analysis of nanoparticles in solution. This system facilitates the understanding of alumina particle dispersion states in solution, binder distribution, and silica and magnesium particle bonding states. Furthermore, we demonstrate a dynamic approach to evaluate adsorptive interactions between ceramic particles and polymeric binders entangled in a slurry by utilizing differential centrifugal sedimentation (DCS). The settling of particles under a centrifugal force field exerts significant viscous resistance on the adsorbed binder, leading to its detachment, influenced by particle size and density. This behavior directly reflects the particle-binder interactions, and detailed DCS spectrum analysis enables the quantitative assessment of nano-Newton-order adsorption forces.

Calcium carbonate nanoparticles are widely used in various composite materials across industrial sectors. However, previously synthesized calcite nanoparticles have typically been rhombohedral with an aspect ratio of ~1. This study investigates the microscopic evolutions of particle morphologies during the formation of calcite rhombohedral nanoparticles. By better understanding these changes, methods involving the addition of Ca(OH)₂ and Mg(OH)₂ have been developed to produce high-aspect-ratio 1D chain-like particles. Controlling the primary particle morphology significantly enhances solid-liquid separation in slurries after liquid-phase synthesis and improves the mechanical properties when these particles are used as fillers in composite materials.