Granular flow is a typical phenomenon that arises in slope disasters such as landslides and debris flows, and its runout distance is closely associated with the resulting damage. Therefore, predicting and evaluating the runout distance is essential for disaster prevention and mitigation. In recent years, the discrete element method (DEM), which can reproduce particle-scale behavior, has been widely utilized for such risk assessment. However, the runout distance of granular flow varies depending on many physical parameters and exhibits strong randomness, making its analysis challenging. The authors have previously published a study that investigated combinations of DEM parameters that are critical for efficiently estimating the maximum runout distance of granular flow through a series of DEM simulations. Specifically, dominant DEM parameters were first identified, and the relationship between their combinations and the runout distance was then analyzed. This article provides an explanatory overview of that study.

Cyclodextrin functions as a host molecule that can include external guest molecules in its hydrophobic cavity in water. In our laboratory, we have found that per-O-methylated β-cyclodextrin (TMe-β-CD) forms a stable 2:1 inclu­sion complex with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS). The inclusion complex has a strong hydrophobic cavity around the porphyrin scaffold, similar to the environment of heme in heme proteins. We have synthesized a per-O-methylated β-CD dimer having pyridine linker (Py3CD) to make a biomimetic model compound of hemoglobin (Hb) and myoglobin (Mb). The inclusion complex of Py3CD with iron complex of TPPS (FeTPPS) is the first biomimetic Hb/Mb model complex in water. The complex, hemoCD, showed a very high CO binding affinity in vivo. When hemoCD was injected to animals (mice and rats) after exposure to CO, hemoCD captured CO during circulation and was excreted in urine without showing any toxic effect. These properties seem appropriate for the use of hemoCD as an inject­able antidote against CO poisoning. We have just started the drug development to implement hemoCD as a CO antidote for clinical use.

The growing demand for lithium-ion batteries requires improved performance and productivity. The formation of electronic conduction paths by carbon nanotubes (CNTs) is an important factor influencing electrode performance. However, only a few methods have been reported to allow direct and quantitative evaluation of CNT dispersion. Conventional ion milling for cross-sectional preparation exposes only CNTs in the interstices of active materials, limiting accurate assessment. In this study, we applied a fracturing method to prepare electrode cross sections, thereby exposing more CNTs in the observation area and enabling clear visualization of CNT networks. Furthermore, low-accelerating-voltage SEM enhanced the contrast between binders and CNTs, facilitating their separation and enabling quantitative evaluation of CNT linear density when combined with machine-learning-based image analysis. This study demonstrates a direct and quantitative method for assessing CNT distribution in lithium-ion battery electrodes.

Active matter often exhibits ordered collective motion, such as in bacterial colonies or swarms of fish and birds. Understanding the mechanisms underlying the complicated collective behaviors is significant to develop innovative chemical systems. We discovered that Pt catalytic particles with simpler structures exhibit a unique collective motion, that is, repetitive cluster formation and disintegration in an aqueous ethanol solution. In this study, the collective behavior of Pt particles is demonstrated in mixtures containing inert particles. Two distinct types of cluster formation were observed by varying the mixing ratio of the Pt and Au particles: Pt/Au mosaic-like clusters and Pt/Au core–shell clusters. In contrast, no Pt/silica cluster formation was observed in the silica particles mixed with Pt particles. In the Pt/Au core–shell clusters observed in this study, the thickness of the Au particle shell could be controlled by adjusting the concentration of the Au particle. This finding suggests that the spatial separation of Pt and Au particles can be realized under controlled conditions.

As grinding progresses, powders exhibit high surface activity due to the generation of ions and radicals, and interfacial effects become pronounced. Mechanochemical reactions that effectively utilize this surface activity have been applied to the synthesis of functionalized powders. In this study, a mechanochemical polymerization process was carried out continuously modifying the surface of silica particles by grinding silica sand in the presence of methyl methacrylate (MMA) using a dry bead mill. The effects of grinding conditions on the MMA conversion, particle size distribution, specific surface area, and chemical composition were investigated. As a result, the possibility of continuously producing surface-modified particles with polymer coatings accompanied by fine grinding was demonstrated. Furthermore, it was confirmed that optimizing the milling atmosphere and grinding conditions is crucial for improving the efficiency of polymer-modified powder production in this process.

3D printing has emerged as a promising technology for the production of personalized medicines, enabling freeform design and on-demand manufacturing. Selective laser sintering (SLS) is a solvent-free powder bed fusion technique capable of simultaneously fabricating dosage forms and inducing drug amorphization. However, the optimization of printing parameters and the reuse of powder materials remain key challenges for pharmaceutical applications. In this study, printlets containing either acetaminophen or indomethacin were fabricated using an SLS 3D printer with Kollidon^® VA64 as a thermoplastic polymeric excipient. The effects of SLS process parameters on printlet formability and drug dissolution were evaluated. The results demonstrated that printing temperature strongly influenced formability, with optimal values varying between formulations. Although the reuse of powder was not feasible due to physicochemical changes in the drug upon heat exposure, high manufacturing efficiency was achieved by maximizing the number of printlets produced per batch. Furthermore, indomethacin was successfully amorphized during the printing process, leading to a marked improvement in its dissolution behavior. These findings suggest that SLS 3D printing can serve as a one-step manufacturing platform for preparing amorphous solid dispersions and enabling flexible design of dosage forms for poorly water-soluble drugs.

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.

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.

The flexible metal-organic frameworks (MOFs), which are a new type of porous material, exhibit unique adsorption behavior, and are expected to have a wide range of applications. However, to overcome the issue of low handling performance of flexible MOFs, it is necessary to establish a molding process. Although it is predicted that the flexible MOF particles and their aggregate structure should strongly affect the molding process, the effect on the particularly unique adsorption behavior is still unknown. In this study, the effect of the aggregate structure of flexible MOF particles on the uniaxial compression process was investigated experimentally and numerically. It was demonstrated that hollow-structured aggregates maintained the best adsorption properties. In addition, numerical analysis revealed that the force applied to the particles was reduced in hollow-structured aggregates. These would be useful results for the practical application of flexible MOF particles.

Cerium oxide nanoparticles were synthesized using the Forced Thin-Film Type Reactor (FTFR). The precipitation solution was changed from aqueous sodium hydroxide to ammonia solutions. By adjusting the mixing ratio of trivalent and tetravalent cerium ions in the solutions and varying the cerium ion concentration, the shape of the particles varied from spherical to truncated octahedron and irregular shape to cuboidal to truncated octahedral. It was estimated that the change in particle shape could be attributed to the difference in the concentration of dissolved oxygen and hydroxide ion in each solution.

Nanoemulsions have been employed as one of the methods for nano-dispersing poorly water-soluble drugs in mucus. However, most liquid suspension such as the emulsions is washed by the clearance effect on the mucus surface. This study examined the spontaneous emulsification formulation using porous polymer microparticles with mucosal adhesion as the technology for drug permeation enhancement. The nanoemulsion formation expected in this technology could be realized using medium-chain fatty acid triglyceride as the oil component. Moreover, the spontaneous emulsification and the diffusion of the nanoemulsion in mucus proceeded smoothly by using porous particles composed of anionic polymers that have little interaction with mucus components, because mucus is composed of anionic polymer, mucin. It was anticipated that the fine emulsions prepared by this method would enhance drug transport in mucus.

Flowability of wet granules is an important indicator for design and control of manufacturing processes. In this study, we aimed to develop a method to evaluate the flowability with simple equipment and operation. We measured the stirring torque under constant normal stress and the resistance force acting on the plate penetrating into the granules layer. The stirring operation did not properly measure the flowability of strongly cohesive wet granules because voids around the stirring impeller were generated. The penetration operation was able to evaluate the flowability over a wide range of water content conditions by two different indices. Furthermore, the theory of bearing capacity was applied to the penetration tests.

Our study described a new annealing approach for dry-coated formulations, which includes heating of the dosage forms in plasticizer vapor. First, coated tablets were produced by V-shaped blending of tablets and polymer particles without any solvents. Second, these tablets were placed in a desiccator, in which triethyl citrate in liquid state was pre-charged, followed by heating at various temperatures. The resulting tablets were characterized. The polymer particles layered on the surface of tablets coalesced by heating at 80°C or more in plasticizer vapor, indicating that using plasticizer vapor could lower heating temperature required for film formation of coated polymer. The weight of polymer compacts increased by heating in plasticizer vapor as heating temperature increased. These data were correlated with vaporization rate of the plasticizer, indicating that plasticizer in gas state was absorbed in polymer particles, promoting film formation due to a decrease in glass transition temperature of the polymer.

In this study, core-shell type particles with a membrane-like shell layer were prepared using a planetary ball mill. Tg = 63°C particles (8.7 μm) and Tg = 32°C particles (7.4 μm) containing a low melting point material were used for the core particles, and water suspension of acrylic particles (150 nm) were used for the shell material. Cross-sectional observation showed a membrane-like shell layer with no visible interfaces was produced on the core surface. This is because the shell particles uniformly adhered to the core particle surface, followed by the close packing and deformation due to the capillary force and curing during the vacuum drying. When the processed particles were heated in an oven at the temperature of the Tg of processed particles, no thermal aggregation and seepage of the low melting point material were observed. It was found that the shell layer effectively protected the core particles.

Hollow particles are widely used because they have different properties from solid particles, such as low density and high specific surface area. Here, we investigated the effects of the presence or absence of ultrasound irradiation and the amount of ammonia added in the synthesis process of hollow silica particles using calcite nanoparticles as a template. As a result, particles with thicker shells, higher particle density, and smaller specific surface area and pore volume can be synthesized by stirring with a stirrer while being irradiated with ultrasonic waves than by stirring with a stirrer alone. Furthermore, by increasing the amount of ammonia added, particles with thick shells can be synthesized.