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We clarified the chemical reaction of deposits following the electrolytic UVIO22+ to UVO2+ reduction.

Pt single-atom materials possess an ideal atom economy but suffer from limited intrinsic activity and side reaction of producing H

Internal exposure to actinides such as uranium and plutonium has been reduced using chelating agents for decorporation because of their potential to induce both radiological and chemical toxicities. This study measures uranium chemical forms in serum in the presence and absence of chelating agents based on X-ray absorption spectroscopy (XAS). The chelating agents used were 1-hydroxyethane 1,1-bisphosphonate (EHBP), inositol hexaphosphate (IP6), deferoxamine B (DFO), and diethylenetriaminepentaacetate (DTPA). Percentages of uranium–chelating agents and uranium–bioligands (bioligands: inorganic and organic ligands coordinating with uranium) dissolving in the serum were successfully evaluated based on principal component analysis of XAS spectra. The main ligands forming complexes with uranium in the serum were estimated as follows: IP6 > EHBP > bioligands > DFO >> DTPA when the concentration ratio of the chelating agent to uranium was 10. Measurements of uranium chemical forms and their concentrations in the serum would be useful for the appropriate treatment using chelating agents for the decorporation of uranium.

The reaction mechanism of the direct photoreduction of a Rh3+ ion complex to a Rh0 species induced by pulsed ultraviolet laser irradiation was studied using dispersive X-ray absorption fine structure (DXAFS) spectroscopy. The time-resolved X-ray absorption near edge structure (XANES) showed the absence of isosbestic points and suggested that more than two Rhn+ species contribute toward the direct photoreduction of Rh3+. Analysis of the time-resolved XANES data by singular value deposition showed that the direct photoreduction involves three Rhn+ species. Multivariate curve resolution by alternating least-squares analysis (MCR-ALS) of the time-resolved XANES data gave pure spectra and concentration profiles of the three Rhn+ species. The Rhn+ species were assigned to Rh3+, Rh+, and Rh0 species based on the features of the pure XANES spectra. The concentration profiles suggested that the direct photoreduction proceeds in the order of Rh3+ → Rh+ → Rh0. A reaction mechanism, which was proposed involving photoreductions of Rh3+ and Rh+, photoinduced autocatalytic reductions of Rh3+ and Rh+, and photooxidation of Rh+, well reproduced the concentration profiles of three Rhn+ species.

The discrete element method (DEM) coupled with computational fluid dynamics (CFD) is a powerful tool for exploring the detailed behaviors of dense particle–fluid interaction problems such as fluidized beds. Coarse-graining models have been proposed to decrease the computational cost by increasing the model particle size. In this study, we examine the influence of the model particle size and the spatial resolution on the average size and number of bubbles in coarse-graining DEM-CFD calculations of bubbling fluidized beds. Calculation results indicate that the bubble size is scaled by the model particle size if parameters are following similarity laws defined in a particle scale, as well as the geometric similarity of the whole system is maintained. The usage of coarse spatial resolution increases the bubble size and decreases the number of bubbles. The countervailing influence of the model particle size and the spatial resolution in a practical coarse-graining scenario results in nearly the same bubble size.

Tissue-engineered tracheae have been developed to replace defective tracheae. However, the direction of ciliated cells in the regenerated epithelium remains unclear. We investigated planar polarity formed in the regenerated airway epithelium after tracheal graft implantation. We also partially resected the rat trachea and implanted a collagen scaffold. The direction of the basal foot was assessed by transmission electron microscopy. Immunofluorescence staining was performed to examine the biased distribution of Vangl1 and Frizzled6 proteins. The direction of mucociliary transport was analyzed by video microscopy. Our results showed that the basal feet of cilia in the proximal and distal regions of the implanted areas were respectively oriented toward the proximal and distal directions. The biased distribution of Vangl1 and Frizzled6, and the directions of mucociliary transport showed that planar polarities formed in the regenerated epithelium were oriented toward the proximal, distal, left, and right directions in the proximal, distal, left, and right regions of the implanted area. These polarities persisted until nine months after implantation. Hence, the results suggest that planar polarities formed in epithelia regenerated on tracheal grafts are directed toward the nearby edges of implanted areas and are preserved for a prolonged period. The polarities can, at least partially, contribute to clearing external materials from the implanted areas by transporting them to a normal region. This article is protected by copyright. All rights reserved.

In this work, a resolved CFD–DEM coupling model for the simulation of gas-liquid-solid flows is developed: the interface capturing method based on the colour function is employed for fluids (i.e. a gas and liquid) whilst Discrete Element Method (DEM) is used for particles. The Volume Penalisation (VP) method is adopted to consider the hydrodynamic interactions between fluids and particles along with the Immersed Free Surface (IFS) method, which artificially extends the gas-liquid interface into the interior of the particle to account for the wettability. The unique point of the proposed model is that the thickness of the gas-liquid interface can be controlled by using both interface compression and diffuse interface techniques simultaneously. From the simulation results, it is presented that the accurate evaluation of the surface tension force as well as the capillary force can be achieved by appropriately controlling the interface thickness. Moreover, the major two methods in the literature to calculate the capillary force are compared in this work. The validity of the proposed model is presented for both static and dynamic cases. The behaviour of two colliding particles with a dynamic liquid bridge is then simulated to demonstrate the applicability of the proposed model to a complex three-phase system.

Float-sink of large objects (on order of cm) in a gas-solid fluidized bed of powder (on order of 100 s of microns) based on density difference has been utilized for dry density separation in industry. The air velocity u0/umf is one of the important factors operating the fluidized bed, where u0 and umf are the superficial air velocity and the minimum fluidization air velocity, respectively. It is empirically known that the sinking of heavy objects is “occasionally” unstable in the fluidized bed combustor, for which the higher air velocity u0/umf > 4 is used. Unstable sinking means heavy objects that are expected to sink but sometimes do not. However, the precise conditions at which the unstable sinking occurs are not clear. In this study, we investigated the float-sink characteristics at a given air velocity u0/umf = 2–7 using glass beads of size Dgb = 425–600 μm and 600–850 μm as the fluidized powder bed media. The float-sink experiments were carried out at the bed height hgb = 150 mm and 75 mm using density adjusted spheres (diameter = 30 mm). We found that the spheres stably float or sink based on density difference at Dgb = 425–600 μm & hgb = 150 mm and at Dgb = 600–850 μm & hgb = 75 mm. However, the unstable sinking does occur at u0/umf > 4 at Dgb = 600–850 μm & hgb = 150 mm. These results indicate that the powder size and the bed height are key factors to induce the unstable sinking at the higher air velocity.

Summary Nanozymes are promising alternatives to natural enzymes, but their use remains limited owing to poor specificity. Overcoming this and controlling the targeted enzyme-like performance of traditional nanozymes is extremely challenging due to the intrinsic structural complexity of these systems. We report theoretical design and experimental realization of a series of heterogeneous molybdenum single-atom nanozymes (named MoSA–Nx–C), wherein we find that the peroxidase-like specificity is well regulated by the coordination numbers of single Mo sites. The resulting MoSA–N3–C catalyst shows exclusive peroxidase-like behavior. It achieves this behavior via a homolytic pathway, whereas MoSA–N2–C and MoSA–N4–C catalysts have a different heterolytic pathway. The mechanism of this coordination-number-dependent enzymatic specificity is attributed to geometrical structure differences and orientation relationships of the frontier molecular orbitals toward these MoSA–Nx–C peroxidase mimics. This study demonstrates the rational design of peroxidase-specific nanozymes and precise regulation of their enzymatic properties.

A resolved CFD–DEM coupling model for the simulation of particulate flows is proposed in this work. The Volume Penalisation (VP) method, which is a family of the continuous forcing Immersed Boundary (IB) method, is employed to express the particle–fluid interaction. A smooth mask function is used to avoid sharp transition between the solid (particle) and fluid domains that may cause numerical oscillation with moving particles. Optimal permeability is employed to reduce the model error associated with the VP method. It is determined as a function of only the interface thickness and fluid kinematic viscosity. The proposed model is accurate, easy to implement with any discretisation scheme, and only requires small computational overhead for particle–fluid interaction. Several simulations are performed to test the validity of the proposed model in various systems, i.e. from dilute to relatively dense flows, and the results show good agreement with the exact solution or empirical correlation. It is found that the error can be scaled with the ratio between the gap and interface thickness. The proposed model is also applied to predict the relative viscosity of suspensions and the density segregation in fluidised beds.

The most effective treatment for retinopathy of prematurity (ROP) is considered as the laser therapy. We compared the foveal morphology of the retina in eyes with a history of ROP with that of full-term children. This was a cross-sectional comparative study. Seventy-eight patients with a history of ROP, aged 4–6 years, were included. Among them, 45 underwent laser treatment for ROP. The clinical findings and retinal morphology in these patients were compared with that of 33 patients who had spontaneous regression of ROP and 30 age-matched full-term controls. All patients with ROP had 20/40 or better best-corrected visual acuity (BCVA). The foveal thickness was significantly thicker and foveal depression was significantly shallower in laser-treated ROP eyes than in regressed ROP eyes and controls. The outer nuclear layer was significantly thicker, and the inner segment (IS) of the photoreceptors and the inner retinal layer (IRL) were significantly longer in the laser-treated ROP eyes than that in the control eyes. In ROP patients and controls, BCVA was associated with the foveal depression, foveal depression was associated with the gestational age and IS thickness was associated with ROP stage. Our results suggest that prematurity and laser treatment affect the foveal morphology and BCVA.

Simulation based on discrete element method (DEM) coupled with computational fluid dynamics (CFD), coupled DEM-CFD, is a powerful tool for investigating the details of dense particle–fluid interaction problems such as in fluidized beds and pneumatic conveyers. The addition of a mechanical vibration to a system can drastically alter the particle and fluid flows; however, their detailed mechanisms are not well understood. In this study, a DEM-CFD model based on a non-inertial frame of reference is developed to achieve a better understanding of the influence of vibration in a vibrated fluidized bed. Because the high computational cost of DEM-CFD calculations is still a major problem, an upscaled coarse-graining model is also employed. To realize similar behaviors with enlarged model particles, non-dimensional parameters at the particle scale were deduced from the governing equations. The suitability and limitations of the proposed model were examined for a density segregation problem of a binary system. To reduce the computational costs, we show that the ratio between the bed width and model particle size can be reduced to a minimum value of 100; to obtain similar segregation behaviors, the ratio between the bed height and model particle size is considered unchanged.

Separation of fine particulate solid materials is one of most important unit operations in industry. Utilization of gas-solid fluidized beds has been considered where particulates are released from constraints due to contacts with surrounding particulates and segregation occurs according to density, size or combination of density and size. Addition of mechanical vibration to the gas-solid fluidized bed may improve dry solid separation. In this study, we investigated the dry separation characteristics of solid particulates using a vibro-fluidized bed especially focusing on the separation of fine particulate ores (≈100 μm) with small density differences. At first, we focused on the influence of fluidizing air velocity on the efficiency of segregation. Subsequently, the influence of vibration strength, vibration amplitude and frequency on segregation behavior was investigated. We found the density segregation does not occur with either gas-fluidization or vertical vibration alone. Only the combination of these effects produces density segregation. The fluidizing air velocity is an important factor to enhance the density-segregation of the particulates with small density difference.

K. Washino, E. L. Chan, T. Tsujimoto, et al. Development of resolved CFD–DEM coupling model for three-phase flows with non-spherical particles. Chemical Engineering Science 267, 118335 (2023); https://doi.org/10.1016/j.ces.2022.118335., In this work, a resolved CFD–DEM coupling model for gas–liquid-solid three-phase flows with non-spherical particles is developed where the shape of the particle is implicitly captured by a superquadric function. Both gas–liquid and fluid–solid interfaces are smoothly represented with a specified thickness so that the interface thicknesses and CFD cell size are independent of each other. Several sensitivity studies are carried out and criteria for mesh- and thickness-independent results are proposed. It is confirmed that the proposed model can properly predict the hydrodynamic and capillary forces acting on particles with a wide range of shapes and contact angles. Finally, the model proposed is applied to perform several virtual experiments of typical chemical engineering processes: a liquid–solid fluidised bed and bubbly flow with various particle shapes. It is found that particle shape can have a significant impact on the fluid-particle interactions and resultant particle movement, leading to segregation and preferential alignment.

Particle density segregations in vibrated fluidized beds depending on gas inflow velocity under the same vertical vibration condition are studied. Coarse-graining discrete element method and computational fluid dynamics numerical simulations are employed to capture the behaviors of reverse segregation in which heavy particles are located above light particles at zero gas inflow velocity or at velocities considerably lower than the minimum fluidization velocity of light particles. Furthermore, upon increasing the gas inflow velocity slightly, the forward segregation occurs, such that heavy particles are located below light particles. The mechanisms are also elucidated using the simulation results. Because of the relative motions between the particles and bed caused by vertical vibration, negative gauge pressure is observed to be dependent on the vibration phase. In the reverse segregation case, the accumulative effect of the downward gas pressure gradient force induced by vibration overcomes the upward force of the forced air flow. The wall friction transports both the heavy and light particles in the vicinity of the sidewall to the bed bottom, where the local void fraction is comparatively high and reverse segregation mainly occurs. Reverse segregation results from the combined effects of the downward gas pressure gradient force, particle transport, and local formation of the high void region. The increase in gas inflow velocity enhances the upward pressure gradient force, resulting in forward segregation.

Tracheal epithelia have barrier and mucociliary clearance functions that prevent invasion of extraneous particles and infectious materials. Hence, following tracheal reconstructions, functional and morphological regeneration of epithelia is required to prevent respiratory declines and infectious diseases. Although growth factors (GFs) promote the regeneration of tracheal epithelial morphologies, it remains unclear whether tracheal grafts containing GFs are beneficial for regeneration of tracheal epithelial functions. Thus, we fabricated collagen sponge scaffolds containing insulin-like GF-1 (IGF-1) and the basic fibroblast, hepatocyte, and epidermal GFs (bFGFs, HGFs, and EGFs, respectively), and we evaluated the effects of the grafts on the functional regeneration of tracheal epithelia. Partial tracheal defects were imposed surgically, and collagen sponges containing IGF-1, bFGF, HGF, or EGF were then transplanted to defect sites. Subsequent immunofluorescence studies suggested that EGF and bFGF contribute to regular distributions of tight junction molecules, and tracer permeability assays suggested that EGF and bFGF promote regeneration of barrier function. Increased ciliogenesis was also observed using scanning electron microscopy in reconstructed regions treated with EGF- and bFGF-supplemented collagen sponges. However, bFGF-supplemented collagen sponges led to greater microsphere transport than did EGF-supplemented sponges. The present data suggested that collagen sponge scaffold containing bFGF promotes functional regeneration of tracheal epithelial tissues.

Previously, we showed that the irradiation of a nanosecond pulsed UV laser with high pulse energy into the Pd(II) solution forms the Pd particle with submicron size (100–500 nm), which has not been generated in the photo-induced particle formation using a UV lamp. It indicates that the laser irradiation with high pulse energy promotes the Pd particle growth, the mechanism of which is unclear. In this work, we studied the particle formation in the Pd(II) solution in the laser irradiation with high pulse energy using time-resolved X-ray absorption fine structure (XAFS) spectroscopy., 6th International Conference on Advanced Nanoparticle Generation & Excitation by Lasers in Liquids

Objects released into a granular packing close to incipient fluidization may float or sink depending on their density. Contrary to intuition, earlier work reported that under certain conditions, a lighter sphere can sink further and slower than a heavier one. In this study, we reveal the mechanism of this intriguing phenomenon using both magnetic resonance imaging and discrete particle simulation. Our findings suggest that local fluidization around the sinking sphere and the formation and detachment of gas bubbles play a critical role in driving this anomaly.

Hu Y., Chan E.L., Tsuji T., et al. Geometric similarity on interparticle force evaluation for scaled-up DEM particles. Powder Technology, 404, 117483. https://doi.org/10.1016/j.powtec.2022.117483., The scaled-up particle model, which is also commonly known as the coarse grain model or discrete parcel model, is frequently used to reduce the computational cost in Discrete Element Method (DEM). In the direct force scaling approach, the forces acting on original particles are first estimated and then directly scaled to apply to scaled-up particles. It is therefore crucial to appropriately evaluate the variables of the original particles, e.g. overlap and separation distance, from the scaled-up particles particularly when estimating complex interparticle forces. The present work proposes the use of geometric similarity for the evaluation of the original particle overlap and separation distance. It is demonstrated that the proposed method can provide an almost identical stress-strain curve between the original and scaled-up particles during uniaxial compression of a packed particle bed, whilst the conventional method in the literature gives significant overestimation of the stress. In addition, the scaled-up particles can reasonably replicate the original velocity distributions of cohesive particles with both liquid bridge and JKR surface adhesion forces in a dynamic flow system (vertical mixer). The simulation results suggest that the method proposed can be applied to any type of interparticle forces. A scaling of time step limit is also derived theoretically and discussed.

We measured X-ray absorption fine structure (XAFS) and Raman spectra of isopolymolybdates(VI) in highly concentrated HNO3 solution (0.15 - 4.0 M), which change their geometries depending on the acid concentration, and performed the simultaneous resolution of the XAFS and Raman data using a multivariate curve resolution by alternating least-squares (MCR-ALS) analysis. In iterative ALS optimization, initial data matrices were prepared by two different methods. For low sensitivity of the XAFS spectra to the geometrical change of the isopolymolybdates, the MCR-ALS result of single XAFS data matrix shows a large dependence on the preparation method of the initial data matrices. This problem is improved by the simultaneous resolution of the XAFS and Raman data: the MCR-ALS result of an augmented matrix of these data has little dependence on the initial data matrices. This indicates that the augmentation method effectively improves the rotation ambiguities in the MCR-ALS analysis of the XAFS data.