Spherical Particles Research Articles

A Refractive Index Matched Experimental Investigation Of The Dynamics Of Inertial Spheres Across Round Pipes And Buoyancy-Driven Flows

A series of refractive index-matched time-resolved tomographic PIV experiments are performed to study the dynamics of motion of solid spheres in flow. The refractive index matching of acrylic spheres with the working fluid facilitates unobstructed optical access around the spheres, enabling the simultaneous estimation of both the 3D flow field and the fluid-structure interactions governing the kinematics of the spheres. Additionally, using normal tracers as well as fluorescent tracers for PIV helps identify the most suitable approach for multiphase index-matched PIV studies. Two different test cases are presented: (1) solid spheres moving in a round channel with an abrupt area expansion and, (2) solid spheres rising in a quiescent flow at terminal velocity. Despite both falling under the category of solid-liquid flows, these cases exhibit entirely different mechanisms and flow characteristics. Nonetheless, refractive index matching provides a valuable tool that can be used to characterize the flow as well as the motion dynamics of the free spherical particles in a liquid. These time-resolved 3D experiments offer a comprehensive insight into the transient evolution of the flow fields and the pressure forces on the spheres, providing a complete picture of the dynamic process. The emphasis of the present paper lies in the experimental methodologies, challenges and data analysis techniques used for refractive index-matched multiphase flow studies.

Particle Tracking of Orientation and Velocity Of Arbitrary Shape

Dispersions or particulate systems are prevalent in numerous natural and practical applications. Characterisation of such multiphase systems usually involves measuring size, spatial location, velocity and number density, which is usually non-trivial. The 'Depth from Defocus' (DFD) technique provides an imaging-based volumetric approach for estimating the size and position of dispersed spherical particles using the blurring information from a shadowgraph image. The two-image DFD approach involves two cameras to capture simultaneous images at different degrees of blur, which, although simpler, requires a mandatory calibration procedure. This study proposes a single-image DFD technique that provides a calibration-free size estimation using theoretical functions while evaluating position requires a simple calibration. The efficacy of this technique is demonstrated for various sparse spherical dispersions, including target dots, dispersed glass beads, liquid droplets in sprays and surface bubble rupture, and pollen grains. The method further enables precise determination of the measurement volume, which is crucial, allowing for bias-free estimates of the size distribution and volume concentration. The simple optical configuration and semi-automatic calibration procedure make this method easily deployable and accessible for diverse applications. The pixelation effect on the limiting value of the degree of blur is also estimated theoretically and compared with experiments. This effect is of interest concerning any typical discrete sensor imaging system in general.

Depth from Defocus Technique For High Number Density Particle Images

The Depth from Defocus (DFD) imaging technique is used to measure the size and number concentration of particles in dispersed two-phase flows, but until now it has primarily been applied to low concentration particle images. This study explores how the technique can be extended to handle overlapping images caused by neighboring particles, significantly broadening the application scope of the DFD technique and enabling measurements at higher particle number/volume concentrations. The processing algorithms are experimentally validated using a dedicated apparatus that can systematically vary particle size, shape, and degree of image overlap. Additionally, this study explores the use of Convolutional Neural Networks (CNN) for this task, comparing these results with those obtained using conventional analyses in terms of accuracy, tolerable concentration limits, and computational speed. This approach requires a large teaching dataset of images, which is only practical and feasible if the dataset can be synthetically generated. An image generation procedure for out-of-focus neighboring spherical particles, resulting in a known blurred image overlap, is therefore first developed. This procedure is validated using laboratory images with known particle size distribution, position, and image overlap before creating the teaching dataset. The trained processing scheme is then applied to both synthetic datasets and experimental data, allowing the evaluation of the technique’s limits in terms of image overlap and tolerable volume concentration, as a function of particle size distribution.

A Single Camera Calibration-Free Approach For Dispersion Size Measurement Using Depth From Defocus

The Depth from Defocus (DFD) imaging technique is used to measure the size and number concentration of particles in dispersed two-phase flows, but until now it has primarily been applied to low concentration particle images. This study explores how the technique can be extended to handle overlapping images caused by neighboring particles, significantly broadening the application scope of the DFD technique and enabling measurements at higher particle number/volume concentrations. The processing algorithms are experimentally validated using a dedicated apparatus that can systematically vary particle size, shape, and degree of image overlap. Additionally, this study explores the use of Convolutional Neural Networks (CNN) for this task, comparing these results with those obtained using conventional analyses in terms of accuracy, tolerable concentration limits, and computational speed. This approach requires a large teaching dataset of images, which is only practical and feasible if the dataset can be synthetically generated. An image generation procedure for out-of-focus neighboring spherical particles, resulting in a known blurred image overlap, is therefore first developed. This procedure is validated using laboratory images with known particle size distribution, position, and image overlap before creating the teaching dataset. The trained processing scheme is then applied to both synthetic datasets and experimental data, allowing the evaluation of the technique’s limits in terms of image overlap and tolerable volume concentration, as a function of particle size distribution.

Exploring the influence of pore shape on conductance and permeation

There are increasing numbers of ion channel structures featuring heteromeric subunit assembly, exemplified by synaptic α1βB glycine and α4β2 nicotinic receptors. These structures exhibit inherent pore asymmetry, but the relevance of this to function is unknown. Furthermore, molecular dynamics simulations performed on symmetrical homomeric channels often lead to thermal distortion whereby conformations of the resulting ensemble are also asymmetrical. When functionally annotating ion channels, researchers often rely on minimal constrictions determined via radius-profile calculations performed with computer programs, such as HOLE or CHAP, coupled with an assessment of pore hydrophobicity. However, such tools typically employ spherical probe particles, limiting their ability to accurately capture pore asymmetry. Here, we introduce an algorithm that employs ellipsoidal probe particles, enabling a more comprehensive representation of the pore geometry. Our analysis reveals that the use of nonspherical ellipsoids for pore characterization provides a more accurate and easily interpretable depiction of conductance. To quantify the implications of pore asymmetry on conductance, we systematically investigated carbon nanotubes with varying degrees of pore asymmetry as model systems. The conductance through these channels shows surprising effects that would otherwise not be predicted with spherical probes. The results have broad implications not only for the functional annotation of biological ion channels but also for the design of synthetic channel systems for use in areas such as water filtration. Furthermore, we make use of the more accurate characterization of channel pores to refine a physical conductance model to obtain a heuristic estimate for single-channel conductance. The code is freely available, obtainable as pip-installable python package and provided as a web service.

Polyaniline microspheres using potassium polyvinyl sulfate as template for large-area broadband electrochromic device with large infrared emissivity variation

In the development of polyaniline (PANI) based large-area broadband electrochromic devices, we employed a controlled deposition process using potassium polyvinyl sulfate (PVSK) as a template to regulate the morphology of PANI. This resulted in consistent spherical particle morphology and heightened electrochemical activity in PVSK-PANI films. The simple structure of PVSK, coupled with its similar IR absorption to polyethylene and sulfuric acid, mitigated any detrimental effects on the broadband electrochromic properties. In small-area (2 × 2 cm²) PVSK-PANI electrochromic devices, we observed maximum emissivity changes of 0.47, 0.51, and 0.49 in the 3-5 μm, 8-14 μm, and 2.5-15 μm ranges, respectively. Expanding our approach to large-area devices (20 × 20 cm2), we achieved even more promising results. The PVSK-PANI based electrochromic devices achieved maximum emissivity changes of 0.55, 0.46, and 0.46 within the same spectral ranges of 3-5 μm, 8-14 μm, and 2.5-15 μm, respectively. Notably, these large-area electrochromic devices demonstrated a remarkable capacity to modulate infrared temperature by up to 10.4 °C at a background temperature of 70 °C.

Ionic Polymerization-Based Synthesis of Bioinspired Adhesive Hydrogel Microparticles with Tunable Morphologies from Microfluidics.

Shape-anisotropic hydrogel microparticles have attracted considerable attention for drug-delivery applications. Particularly, nonspherical hydrogel microcarriers with enhanced adhesive and circulatory abilities have demonstrated value in gastrointestinal drug administration. Herein, inspired by the structures of natural suckers, we demonstrate an ionic polymerization-based production of calcium (Ca)-alginate microparticles with tunable shapes from Janus emulsion for the first time. Monodispersed Janus droplets composed of sodium alginate and nongelable segments were generated using a coflow droplet generator. The interfacial curvatures, sizes, and production frequencies of Janus droplets can be flexibly controlled by varying the flow conditions and surfactant concentrations in the multiphase system. Janus droplets were ionically solidified on a chip, and hydrogel beads of different shapes were obtained. The in vitro and in vivo adhesion abilities of the hydrogel beads to the mouse colon were investigated. The anisotropic beads showed prominent adhesive properties compared with the spherical particles owing to their sticky hydrogel components and unique shapes. Finally, a novel computational fluid dynamics and discrete element method (CFD-DEM) coupling simulation was used to evaluate particle migration and contact forces theoretically. This review presents a simple strategy to synthesize Ca-alginate particles with tunable structures that could be ideal materials for constructing gastrointestinal drug delivery systems.

Adsorption on a Spherical Colloidal Particle from a Mixture of Nanoparticles with Competing Interactions.

Adsorption of nanoparticles on a spherical colloidal particle is studied by molecular dynamics simulations. We consider a generic model for a mixture of nanoparticles with energetically favored self-assembly into alternating layers of the two components. When both components are attracted to the colloidal particle, the adsorbed nanoparticles self-assemble either into alternating parallel tori and clusters at the two poles of the colloidal particle, or into alternating spirals wrapped around the spherical surface. The long-lived metastable states obtained in simulations follow from the spherical shape of the adsorbing surface and the requirement that the neighboring chains of the nanoparticles are composed of different components. A geometrical construction leading to all such patterns is presented. When the second component particles are repelled from the colloidal particle and the attraction of the first component is strong, the attracted particles form a monolayer at the surface of the colloidal particle that screens the repulsion of the second component. The subsequent adsorbed alternating spherical layers of the two components form together a thick shell. This structure leads to the adsorption that is larger than in the case of the same attraction of the two components to the colloidal particle.

Effect of Spherical Silver Particles Size of the Catalyst Bed on Hydrogen Peroxide Monopropellant Thruster Performance

Effect of Spherical Silver Particles Size of the Catalyst Bed on Hydrogen Peroxide Monopropellant Thruster Performance

Tribological properties of GO/modified SiO2 combination as lubricant additive for bearings

This study investigates the tribological performance of GO/modified SiO2 (GMS) as a composite additive and elucidates their synergistic mechanism. A four-ball friction testing machine and a Timken friction testing machine were used to evaluate the tribological performance of the GMS lubricating oil. The results show that the addition of 0.03 wt% GO and 0.12 wt% modified SiO2 (Mod-SiO2) in the oil resulted in a 48.70 % reduction in average friction coefficient, a 60.56 % decrease in wear, and a 1.43 % increase in PB, compared to pure GO oil. Compared to pure Mod-SiO2 oil, the average friction coefficient decreased by 46.09 %, wear decreased by 51.40 %, and PB increased by 1.38 %. Furthermore, under different loads, the GMS lubricating oil exhibited outstanding capability in reducing frictional noise between the bearing rollers and outer ring, as well as mitigating the trend of temperature variation. The worn surfaces of the test rollers were analyzed using EDS, SEM, CLSM, TEM and Raman spectrum. The spherical Mod-SiO2 particles adhere to the flake-like GO, preventing agglomeration and facilitating better dispersion in the lubricating oil. Therefore, GMS exhibits its significant advantages and potential as a lubricant additive.

Creeping flow of a couple stress fluid past a semipermeable spherical particle consisting of a solid core: magnetic field effect

Creeping flow of a couple stress fluid past a semipermeable spherical particle consisting of a solid core: magnetic field effect

Computational modeling of the physical features that influence breast cancer invasion into adipose tissue.

Breast cancer invasion into adipose tissue strongly influences disease progression and metastasis. The degree of cancer cell invasion into adipose tissue depends on both biochemical signaling and the mechanical properties of cancer cells, adipocytes, and other key components of adipose tissue. We model breast cancer invasion into adipose tissue using discrete element method simulations of active, cohesive spherical particles (cancer cells) invading into confluent packings of deformable polyhedra (adipocytes). We quantify the degree of invasion by calculating the interfacial area At between cancer cells and adipocytes. We determine the long-time value of At vs the activity and strength of the cohesion between cancer cells, as well as the mechanical properties of the adipocytes and extracellular matrix in which adipocytes are embedded. We show that the degree of invasion collapses onto a master curve as a function of the dimensionless energy scale Ec , which grows linearly with the cancer cell velocity persistence time and fluctuations, is inversely proportional to the system pressure, and is offset by the cancer cell cohesive energy. When , cancer cells will invade the adipose tissue, whereas for , cancer cells and adipocytes remain de-mixed. We also show that At decreases when the adipocytes are constrained by the ECM by an amount that depends on the spatial heterogeneity of the adipose tissue.

Effects of Co on Mechanical Properties and Precipitates in a Novel Secondary-Hardening Steel with Duplex Strengthening of M2C and β-NiAl.

Synergistic strengthening of nano-scaled M2C and β-NiAl has become a new route to develop ultra-high secondary-hardening steel. At present, the effect of Co on the synergistic precipitation behavior of duplex phases of M2C and β-NiAl has been rarely reported. This paper revealed the effects of Co on the mechanical properties and duplex precipitates of M2C and β-NiAl in a novel 2.5 GPa ultra-high strength secondary-hardening steel. The tensile tests indicated that a 10% Co-alloy steel achieved a much stronger secondary-hardening effects compared to a Co-free steel during aging process, especially in the early-aging state. Needle-shaped M2C and spherical β-NiAl particles were observed in both Co-alloy and Co-free steels. However, the number density, and volume fraction of M2C were significantly enhanced in the 10% Co-alloy steel. The Mo contents in M2C carbide and α-Fe after aging treatment were both analyzed through experimental determination and thermodynamic calculation, and the results indicated that Co decreased the solubility of Mo in α-Fe, thus promoting the precipitation of Mo-rich carbides.

Preparation and microwave absorption properties of FeS2/Co-BTC composite nanomaterials

Nanocomposite materials are multiphase materials with rich interfacial nanoscale features and adjustable microstructures, which are widely used in various fields. This paper describes the synthesis of FeS2 nanospheres, Co-BTC microcrystals, and FeS2/Co-BTC nanocomposite using a solvothermal method, with SEM, XRD, and other techniques characterizing their microstructure, and tests on their magnetic, ultraviolet, and wave-absorbing properties. The results show that FeS2 is composed of nanosheets of 10 to 20 nm that form spherical particles with a diameter of 1 µm,and FeS2/Co-BTC has a well-mixed composite structure. XRD results indicate that the samples are relatively pure. The magnetic experiments indicate that among the three samples, FeS2 exhibits the highest magnetic field intensity, followed by FeS2/Co-BTC. The magnetic permeability of Co-BTC can be approximated as close to zero. The absorption results indicate that FeS2 possesses strong energy storage and dissipation capabilities. FeS2/Co-BTC exhibits strong magnetic energy storage and dissipation capabilities, as well as a larger optimal absorption bandwidth. These materials demonstrate excellent electromagnetic properties suitable for electromagnetic wave absorption applications.

Dynamic wetting characteristics of two droplets impacting a spherical dust particle

The removal of dust based on water misting is one of the most effective measures for dust control, and the basis of this method lies in the liquid–solid impact behavior. To further improve the dust removal efficiency, in this work, the removal mechanism was studied at the microscopic level, and the dynamic impact between two water droplets and a spherical dust particle was simulated using the coupled level-set/volume-of-fluid (CLSVOF) method. The optimal parameter ranges for micron-level dust removal were determined through the method of variable control, and the reliability of the obtained results was experimentally verified. When two droplets continuously or simultaneously impact a spherical particle, the liquid film formed undergoes deformation phenomena such as fusion, rupture, stretching, contraction, and fragmentation. The liquid film is more likely to break at higher droplet velocities, leading to the filling of the gas film and hindering the wetting process. The optimum contact angle and velocity range of the liquid droplets to completely encapsulate the dust particles were found to be θ = 2 and V = 10–20 m/s, respectively. The experimental results also showed that for the same dust particle size, the dust removal efficiency initially increased but then decreased with increasing dust concentration. The optimum dust removal efficiency of 98.1 % was achieved for θ = 2 and V = 10 m/s. This study sheds new light on the dust removal mechanism of water mist-based dust removal technologies and can aid in the design and parameter optimization of more effective dust suppression systems.

Comparing novel small-angle x-ray scattering approaches for absolute size and number concentration measurements of spherical SiO2 particles to established methods

Biomedical analytical applications, as well as the industrial production of high-quality nano- and sub-micrometre particles, require accurate methods to quantify the absolute number concentration of particles. In this context, small-angle x-ray scattering (SAXS) is a powerful tool to determine the particle size and concentration traceable to the Système international d’unités (SI). Therefore, absolute measurements of the scattering cross-section must be performed, which require precise knowledge of all experimental parameters, such as the electron density of solvent and particles, whereas the latter is often unknown. Within the present study, novel SAXS-based approaches to determine the size distribution, density and number concentrations of sub-micron spherical silica particles with narrow size distributions and mean diameters between 160 nm and 430 nm are presented. For the first-time traceable density and number concentration measurements of silica particles are presented and current challenges in SAXS measurements such as beam-smearing, poorly known electron densities and moderately polydisperse samples are addressed. In addition, and for comparison purpose, atomic force microscopy has been used for traceable measurements of the size distribution and single particle inductively coupled plasma mass spectrometry with the dynamic mass flow approach for the accurate quantification of the number concentrations of silica particles. The possibilities and limitations of the current approaches are critically discussed in this study.

Updating the Loth Drag Model to Include Nonspherical Particle Effects

Sophisticated drag models have been developed over the past few decades that are based on ballistic range and other experimental data. These drag models are applicable over a wide range of particle-flow environments and include compressibility and rarefaction effects. One drawback of these sophisticated drag models is that they assume spherical particles. However, Martian dust particles and materials used in ground-based dusty-flow experiments such as Al2O3 or BN are known to be nonspherical. It is well known that nonspherical particles, in general, will experience higher drag forces compared to spherical particles. There has also been a considerable amount of research developing drag models that account for nonspherical particle shapes, but most of these models are restricted to incompressible, continuum particle-flow conditions. This paper presents a simple way to include nonspherical particle effects into the widely used Loth particle drag model. This updated drag model is used to simulate dust-laden flow experiments performed in the German Aerospace Center the multiple phase flow facility (GBK) experimental facility and in the shock layer of a Martian-entry spacecraft to assess the effectiveness and range of applicability of this new drag model. In the GBK experiment simulations, the modified Loth drag model, which includes both compressibility and nonspherical particle effects, showed improved comparison to the experimental data.

Liposome co-delivery of quercetin and doxorubicin in inhibiting retinoblastoma by regulating epithelial-mesenchymal transition process

Regulating the process of epithelial-mesenchymal transition(EMT) is an essential strategy to inhibit tumor growth and metastasis. This study is based on the EMT process of retinoblastoma and constructs quercetin(QUE) and doxorubicin(DOX) co-loaded liposome(QD Lipo) to investigate the therapeutic effect and mechanisms of combined QUE and DOX treatment on retinoblastoma. Single-factor experiments were conducted to optimize the prescription process of QD Lipo. Eventually, spherical particles with a diameter of(108.87±1.93) nm, a PDI of 0.13±0.02, and a Zeta potential of(-34.83±1.92) mV were obtained. The encapsulation rates of QUE and DOX were 96.20%±4.40% and 91.17%±4.41%, respectively. Y79 human retinoblastoma cells were used as an in vitro cellular model, and confocal microscopy demonstrated that QD Lipo could enhance Y79 uptake efficiency. The CCK-8 assay confirmed that the optimal combination therapy effect of QUE and DOX occurred at a mass ratio of 1∶1 to 1∶2. Flow cytometry showed that QD Lipo enhanced the induction of apoptosis in Y79 cells. Western blot analysis revealed that QD Lipo significantly reduced the expression of EMT pathway-related proteins vimentin and α-SMA. Fluorescence assays detected a significant decrease in ROS levels in Y79 cells after treatment with QD. These results indicated that liposomal co-delivery of QUE and DOX can enhance drug delivery efficiency to retinoblastoma cells, inhibit the EMT process in retinoblastoma by downregulating ROS levels, and enhance the cytotoxicity of DOX against retinoblastoma.

Performance and mechanism of sulfadiazine and norfloxacin adsorption from aqueous solution by magnetic coconut shell biochar.

In this study, magnetic coconut shell biochar loaded with spherical Fe3O4 and γ-Fe2O3 particles was successfully synthesized using a chemical coprecipitation method. The magnetic biochar exhibited a good magnetic separability and environmental security. The maximum sulfadiazine (SDZ) and norfloxacin (NOR) removal efficiencies were 94.8% and 92.3% at pH 4 and 25°C with adsorbent dosage of 2.5g/L, respectively. When antibiotic concentrations ranged from 5 to 50mg/L, the theoretical maximum adsorption capacities of SDZ and NOR were 16.7mg/g and 25.8mg/g, respectively. The Langmuir isotherm and pseudo-second-order kinetic models could better describe the adsorption process of both antibiotics, implying the monolayer chemical adsorption. The thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. The ionic strength had no significant effect on the adsorption behavior of either antibiotic. Combined with BET, FTIR, and XPS results, the dominant mechanisms for SDZ and NOR adsorption were pore filling, π-π electron-donor-acceptor interaction, hydrogen bonds and surface complexation. Moreover, Lewis acid-base interaction also contributed to SDZ adsorption.

Influence of WC particle size and morphology on the performance of NiCu-based composite coatings deposited by laser direct energy deposition

NiCu alloys are commonly utilized due to their outstanding plasticity, toughness, corrosion resistance, and thermal conductivity. Nevertheless, their limited hardness and wear resistance have hindered their further development. In this study, 24CrNiMo alloy brake disc was coated with NiCu-based composite coatings containing different sizes and shapes of tungsten carbide, in order to investigate the effects of tungsten carbide particle characteristics on the microstructure, microhardness and wear resistance of Nickel‑copper composite coating. The results show that the microstructure of the coatings was minimally affected by the size and morphology of the WC particles, while non-spherical WC particles exhibited superior uniformity within the coatings. In terms of microhardness, smaller WC particles demonstrated a more consistent distribution. The ball-disk wear tests revealed that coatings with larger WC particles displayed better wear resistance in sizes, while those with non-spherical WC particles exhibited excellent resistance to wear in morphologies. Additionally, in abrasive wear tests, composite coatings containing spherical WC particles demonstrated superior wear resistance compared to those containing non-spherical WC particles. The diverse wear resistance observed in different wear experiments among the various WC coatings can be attributed primarily to differences in the distribution and preparation methods of the WC particles. Consequently, these findings hold significant promise for the practical application of NiCu-based composite coatings in industry.