Disc-shaped Particles Research Articles

Palmitic acid-mediated modulation of crystallization dynamics in amylose microparticle formation: From spherical to macaron and disc shapes

Here, we investigated the complexation of short chain amylose (SCAs) and palmitic acid (PA), serving as polymeric building blocks that alter the selectivity and directionality of particle growth. This alteration affects the shape anisotropy of the particles, broadening their applications due to the increased surface area. By modifying the concentration of PA, we were able to make spherical, macaron, and disc-shaped particles, demonstrating that PA acts as a structure-directing agent. We further illustrated the lateral and longitudinal stacking kinetics between PA-SCA inclusion complexes during self-assembly, leading to anisotropy. Transmission electron microscope (TEM) and scanning electron microscope (SEM) revealed the structural difference between the initial and final morphologies of palmitic acid-short chain amylose particles (PA-SCAPs) compared to those of short-chain amylose particle (SCAPs). The presence of PA-SCA inclusion complex in the anisotropic particles was confirmed using nuclear magnetic resonance (NMR) and powder x-ray diffraction (XRD) analysis.

Feasibility of compacted attapulgite/diatomite amended clayey soils as gas barrier materials

Compacted clay liners are extensively used as barriers to control the upward diffusion of vapors of volatile or semi-volatile organic contaminants released from unsaturated contaminated soils at industry-contaminated sites. This study aimed to investigate the gas diffusion barrier performance of compacted clayey soils amended with three agents including attapulgite and diatomite individually, and attapulgite/diatomite mixture. The properties including water retention, volumetric shrinkage, gas diffusion, and unconfined compressive strength were evaluated through a series of laboratory tests of amended compacted clayey soils. The results demonstrate that the decrease in volume proportions of inter-aggregate pores leads to an increase in unconfined compressive strength (qu). Both hydrophilic groups and microstructures of attapulgite and diatomite result in an increase in water retention percent (Wt) of compacted clayey soil specimens after amendment regardless of the type of agent or initial water content (w0). Furthermore, the ratio of the gas diffusion coefficient (De) to the gas diffusion coefficient in the air (Da) was significantly reduced owing to a decrease in volume proportions of inter-aggregate pores, hydrophilic group, and microstructures of attapulgite and diatomite. Scanning electron microscope analyses revealed that rod-shaped attapulgite filled the inter-aggregate pores formed by clay particles, whereas the disc-shaped diatomite particles, characterized by micropores, failed to obstruct the inter-aggregate pores due to their larger particle size. Mercury intrusion porosimetry (MIP) analyses showed a reduction in pore volume in the inter-aggregate pores, leading to a reduction in the total pore volume for both the attapulgite and attapulgite/diatomite mixture amended clays, which is in accordance with the scanning electron microscope (SEM) results. The findings are pertinent to the practical application of compacted clay liners as gas barriers against the upward migration of volatile or semi-volatile organic contaminants at contaminated sites.

Behaviour of RC Beam Using Concrete Mixed With Magnetically Treated Water

The most important challenge for concrete construction is to improve the performance of concrete. In the last two decades, in Russia and China, a new technology, called magnetic water technology, has been used in making concrete. As per this technology, by passing water through a magnetic field, some of its physical properties tend to change and, as a result of such changes, the number of molecules in the water cluster decreases from 13 to 5 or 6, which cause a decrease in the surface tension of water, with an improvement in the workability and strength of concrete. Magnetic treatment of water increases the ion solubility and pH. The influence of magnetic flux changes the mode of calcium carbonate precipitation such that circular disc-shaped particles are formed rather than the dendritic (branching or tree like) particles observed in non-treated water. This technique is mostly used for the softening of water and, for the first time in this research, it has been adopted by the scientists for the production of concrete with improved strength. Some researchers hypothesize that magnetic treatment affects the nature of hydrogen bonds between water molecules which increases the pH and softens the water.

Magnetic Cellular Backpacks for Spatial Targeting, Imaging, and Immunotherapy.

Adoptive cell transfer (ACT) therapies are growing in popularity due to their ability to interact with diseased tissues in a specific manner. Disc-shaped particles, or "backpacks", that bind to cellular surfaces show promise for augmenting the therapeutic potential of adoptively transferred cells by resisting phagocytosis and locally releasing drugs to maintain cellular activity over time. However, many ACTs suffer from limited tumor infiltration and retention and lack a method for real-time spatial analysis. Therefore, we have designed biodegradable backpacks loaded with superparamagnetic iron oxide nanoparticles (SPIONs) to improve upon current ACT strategies by (i) controlling the localization of cell-backpack complexes using gradient magnetic fields and (ii) enabling magnetic particle imaging (MPI) to track complexes after injection. We show that magnetic backpacks bound to macrophages and loaded with a proinflammatory drug, resiquimod, maintain anticancer phenotypes of carrier macrophages for 5 days and create cytokine "factories" that continuously release IL-12. Furthermore, we establish that forces generated by gradient magnet fields are sufficient to displace cell-backpack complexes in physiological settings. Finally, we demonstrate that MPI can be used to visualize cell-backpack complexes in mouse tumors, enabling a potential strategy to track the biodistribution of ACTs in real time.

An approach to estimating the range of wild fire firebrands transportation by wind

Forest wild fire prevention that is carried out to minimize of wild fires number and possible damage from them, is inconceivable without the development of fire-prevention procedures, which are based on data from wild fire monitoring. One of the areas of wild fires monitoring is the evaluation of forest wild fires spreading ability to transportation of firebrands by the wind. This way observed at crown-type of forest wild fires, which are formed from ground ones by transferring the flame to the trees crowns when the wind reaches a certain speed. A mathematical model has been developed for the firebrands transportation by the wind. Mathematical model adequacy was evaluated by inclusion of transfer coefficient as a ratio of firebrand speed to wind speed. The modeling of the horizontal firebrands transportation (sphere, cylinder and disc) has been carried out. Experimental conditions are firebrands have various sizes, fall off from a height of 5-20 m, at a wind speed of 1-5 m⋅s-1. Spherical and discshaped particles have the best transportation ability. The adequacy of the model of horizontal firebrands transportation has been experimentally proved by conducting our own experiments and analyzing information obtained from the literature on similar studies. The results of the experiments showed that with an increase in the air flow speed up to 10 m⋅s-1, the speed of the burning particle does not exceed the speed of the air flow that stimulates it. Thus, it is shown that within the air flow velocity of 1-10 m⋅s-1, the value of the transfer coefficient does not exceed one.

Terminal velocity and drag coefficient models for disc-shaped particles based on the imaging experiment

Terminal velocity and drag coefficient are the core parameters of particle motion, but their predictive models and measuring methods have rarely been focused. In this work, terminal velocity and drag coefficient models for disc-shaped particles are proposed based on the imaging experiment. Experimental devices include particle sedimentation and video image acquisition systems. A total of 120 disc-shaped particles sedimentation are investigated. Results show that terminal velocity closely relates to the shape, size and density of the particles. Thus, particle shape factors should be considered in the drag coefficient model. The proposed models fitted by the LM + UGO optimization algorithm, have more accuracy and stability than the published models. The present study is applicable for the disc-shaped particles in the ranges of sphericity φ = 0.56–0.77, flatness ratio da /dv = 0.65–1.21, circularity ψ = 0.59–1, and Reynolds number Re = 323–10,800. Furthermore, the imaging measurement method can be extended to other non-spherical particles.

High Adsorption of α-Glucosidase on Polymer Brush-Modified Anisotropic Particles Acquired by Electrospraying-A Combined Experimental and Simulation Study.

In this particular contribution, we aim to immobilize a model enzyme such as α-glucosidase onto poly(DMAEMA) [poly(2-dimethyl amino ethyl methacrylate)] brush-modified anisotropic (cup- and disc-shaped) biocompatible polymeric particles. The anisotropic particles comprising a blend of PLA [poly(lactide)] and poly(MMA-co-BEMA) [poly((methyl methacrylate)-co-(2-(2-bromopropionyloxy) ethyl methacrylate)] were acquired by electrospraying, a scalable and convenient technique. We have also demonstrated the role of a swollen polymer brush grafted on the surface of cup-/disc-shaped particles via surface-initiated atom transfer radical polymerization in immobilizing an unprecedentedly high loading of enzyme [441 mg/g (cup)-589 mg/g (disc) of particles, 15-20 times higher than that of the literature-reported system] as compared to non-brush-modified particles. Circular dichroism spectroscopy was used to predict the structural changes of the enzyme upon immobilization onto the carrier particles. An enormously high amount of enzymes with preserved activity (∼85 ± 13% for cups and ∼78 ± 15% for discs) was found to adhere onto brush-modified particles at pH 7 via electrostatic adsorption. These findings were further explored at the atomistic level using a coarse-grained dissipative particle dynamics simulation approach, which exhibited excellent correlation with experimental results. In addition, accelerated particle separation was also achieved via magnetic force-induced aggregation within 20 min (without a centrifuge) by incorporating magnetic nanoparticles into disc-shaped particles while electrojetting. This further strengthens the technical feasibility of the process, which holds immense potential to be applied for various enzymes intended for several applications.

Smoldering and Flaming of Disc Wood Particles Under External Radiation: Autoignition and Size Effect

Wildfires are global issues that cause severe damages to the society and environment. Wood particles and firebrands are the most common fuels in wildfires, but the size effect on the flaming and smoldering ignitions as well as the subsequent burning behavior is still poorly understood. In this work, a well-controlled experiment was performed to investigate smoldering and flaming ignitions of stationary disc-shaped wood particles with different diameters (25–60 mm) and thicknesses (15–25 mm) under varying radiant heat flux. The ignition difficulty, in terms of the minimum heat flux, increases from smoldering ignition to piloted flaming ignition and then to flaming autoignition. As the sample thickness increases, the minimum heat flux, ignition temperature, and burning duration for flaming autoignition all increase, while the peak burning flux decreases, but they are insensitive to the sample diameter. During ignition and burning processes, the disc particle is deformed due to the interaction between chemical reactions and thermomechanical stresses, especially for smoldering. The characteristic thickness of the smoldering front on wood is also found to be 10–15 mm. This study sheds light on the size effect on the ignition of wood particles by wildfire radiation and helps understand the interaction between flaming and smoldering wildfires.

Criteria for Determining the Genesis of Placers and Their Different Sources Based on the Morphological Features of Placer Gold

Based on the identified typomorphic features of placer gold, a set of determined morphogenetic criteria is proposed to identify the genesis of placer gold content and different sources in the platform areas, which allow more correctly selecting search methods and improving the efficiency of forecasting ore and placer gold deposits. Gold particles larger than 0.25 mm with signs of wind-worn processing indicate the formation of autochthonous aeolian placers. Gold particles with signs of wind-worn processing with a size of 0.1–0.25 mm, forming an extensive halo of dispersion, indicate the formation of allochthonous placers in Quaternary deposits. Deflationary (autochthonous) placers of native gold can be found by the halo of its distribution of toroidal and spherical hollow forms, which, of course, are the search morphogenetic criterion of aeolian placers. The presence of disc-shaped and lamellar gold particles with ridgelike edges in alluvial placers is typical for placers of heterogeneous origin, formed due to deflation of proluvial placers. The discovery of pseudo-ore gold in alluvial placers indicates the arrival of gold from intermediate gold-bearing sources of different ages and not from primary sources, which is a morphogenetic criterion for determining different sources of the placer. In modern gold placers, the presence of gold of a pseudo-ore appearance can serve as a search criterion for the discovery of gold-bearing conglomerates with high gold content. The developed method for diagnosing the genotype of placer gold by its morphological characteristics (alluvial, aeolian, pseudo-ore) can be successfully used by industrial geological organizations to search and explore ore and placer gold deposits.

Lipid-bound ApoE3 self-assemble into elliptical disc-shaped particles

Apolipoproteins are vital to lipid metabolism and cholesterol transport in the human body. Here we present a structural study of the lipid-bound particles formed by ApoE3 in a full-length and a truncated version. The particles are formed with, respectively, POPC and DMPC and investigated by small-angle X-ray scattering and negative stain electron microscopy. We find that lipid-bound ApoE3 particles are elliptical, disc-shaped particles composed of a central lipid bilayer encircled by two amphipathic ApoE3 proteins. We went on to investigate a truncated form of ApoE3 containing only residue 80 to 255 (ApoE380–255), which is the central helical repeat segment of ApoE3. The lipid-bound ApoE380–255 particles are found to have the same morphology as the particles with full-length ApoE3. However, they are larger, and form more heterogeneous discoidal structures with four proteins per particle. This behavior is in contrast to ApoA1 where the highly similar helical repeat domain determines the size and stoichiometry of the formed particles both in the case of full-length and truncated ApoA1. Our data hence points towards different mechanisms for lipid bilayer structural modulation by ApoA1 and ApoE3 due to different roles of the non-repeat segments.

On the potential of particle engineered anti-erosion coatings for leading edge protection of wind turbine blades: Computational studies

The potential of particle and fiber reinforced anti-erosion coatings for the protection of wind turbine blades is explored through computational modelling. A hypothesis that stiff disc-shaped particle or fiber reinforcements embedded in viscoelastic coatings ensure better erosion protection is validated numerically, and mechanisms of this effect are analyzed. A computational unit cell model of coatings with embedded fibers (fiber pulp) or disc particles subject to rain droplet impact is developed, and series of computational experiments is carried out. The distribution and scattering of stress waves from the rain droplet impact and damping properties are analyzed for homogeneous viscoelastic polyurethane coatings, coatings with discshaped particles, and fiber pulp. It is shown that the stress waves are increasingly scattered, and the damping is increased with higher volume percentage of the fibers. The mechanism of such increased energy dissipation is found to be related to the high local viscoelastic deformation in the regions between closely located fibers and the higher stiffness of the unit cell. The current work demonstrates the high potential of fiber engineered coatings for the improvement of anti-erosion protection of wind turbine blades.

Quantitative assessment of multi-scale second phase particles and their roles in the deformation response of ZK60 alloy

The quantification and visualization of the multi-scale particles and their roles in the deformation response of the ZK60 magnesium alloy are investigated in this study. The three-dimensional (3D) characters of multi-scale second phase particles, including size, shape and distribution, are visualized and quantified using X-ray computed tomography (CT) technology. Results show that rod-shaped Mg4Zn7 particles are only distributed at the submicron scale, while disc-shaped MgZn2 particles are distributed at various scales. 3D finite element structural models, constructed using CT imaging, show competitive effects between submicron Mg4Zn7 particles and micron MgZn2 particles on the plastic deformation. According to the detailed fracture surface analysis, the fracture initiation is observed to occur close to the rod-shaped Mg4Zn7 particles.

Polymer Discs with High Interfacial Adhesion Fabricated from Hot-Pressing of Microspheres

Owing to the large contact surface area in geometry, disc-shaped polymer particles and their fascinating properties compared to those of spherical particles have received increasing attention. Alth...

Blank roasting kinetics of illite type vanadium bearing stone coal

Vanadium bearing stone coal is an important vanadium resource in China, and roasting is the foundation for extracting vanadium from stone coa1. In this paper, the blank roasting kinetics of illite type vanadium bearing stone coal is studied using the derived kinetics equations of disc-shaped particles. Stone coal samples were roasted at the set temperature and time, the roasted clinker was leached with sulfuric acid. The roasting effect was judged by the leaching rate of vanadium, and the kinetics and mechanism of the roasting reaction were discussed. The results show that the blank roasting process of stone coal is divided into two stages. The first stage activation energy is 159.50kJ/mol, which follows the control of chemical reaction kinetics; the second stage activation energy is 256.45kJ/mol, which belongs to diffusion control. In addition, As the roasting reaction proceeds, it can be noted that chemical reaction control can be quickly transformed into diffusion control. The apparent activation energy of the diffusion control is greater than that of the chemical reaction control, which indicates that diffusion is the controlling factor that affects the conversion efficiency of vanadium during the blank roasting process of stone coal. The results of blank roasting kinetics model of disc-shaped particles established in this study are in good agreement with the experimental analysis results, which also verifies the accuracy of this model.

Variations in structural, optical, and dielectric properties of CuO nanostructures with thermal decomposition

Herein, we report the characterization of CuO nanostructures annealed at different temperatures, synthesized by chemical co-precipitation method. It is found in the XRD patterns that the peaks were broader at low temperatures due to increased defect density and poor crystallization suggesting that increasing annealing temperature enhances the degree of crystallization of the samples. Scanning electron microscopy (SEM) suggests that the CuO nanostructures change with increasing annealing temperature from rods to disc-shaped particles. It is observed in PL that with the increase in annealing temperature, the emission intensities increase for the same morphology due to the increase in oxygen vacancies (O.Vs) and improvement of crystallization. The dielectric constant has been increased with increasing temperature for the same morphology and is maximum for the sample annealed at 600 °C which is mainly due to the RDP and SCP. The relaxation peaks are shifted to the higher frequencies due to defect dipoles. Enhancement in conductivity is due to the growth of conducting grains. Our findings may provide comprehensive insight in designing high-performance electronic devices.

One-pot fabrication of polymer micro/nano-discs via phase separation and a roll-to-roll coating process

Disc-shaped particles are one of the unique and promising shapes that can improve adhesion to interfaces and can function as the key feature in various applications; e.g. injectable drug carriers. However, most of these methods include the shape deformation process from spheres to discs using various external stimuli or require multiple processing steps, which is complicated and has limitations in terms of continuous fabrication. We herein propose a novel method combining polymer blend phase separation and a roll-to-roll coating process to continuously fabricate polymer micro/nano-discs in a one-pot manner on a large-scale. The evaporation of solvent during a roll-to-roll coating process encourages the formation of homogenous island-like domains composed of the minor component dispersed in a matrix of the major component on a water-soluble polyvinyl alcohol (PVA) film. In fact, polyvinylpyrrolidone (PVP) was chosen as the major component since it dissolves in both water and chloroform. Another polymer, polystyrene (PS), as a minor component was dissolved in chloroform with PVP. A PVP and PVA matrix film can be easily washed out by water, and micro/nano-discs of the PS minor component can be obtained in a one-pot manner. This method is shown to be capable of continuously fabricating PS micro/nano-discs at a very high rate of ∼108 particles/min. The effects of fabrication conditions, such as the blend ratio and total polymer concentration on the dimensions of the PS discs were investigated, and a maximum aspect ratio (ratio between diameter and thickness) of 6.3 (diameter ∼830 nm, thickness ∼130 nm) was demonstrated. The method proposed in this study could provide a straightforward and time-saving way to continuously fabricate micro/nano-discs via polymer phase separation and a roll-to-roll coating process.

Small-angle X-ray and neutron scattering demonstrates that cell-free expression produces properly formed disc-shaped nanolipoprotein particles.

Nanolipoprotein particles (NLPs), composed of membrane scaffold proteins and lipids, have been used to support membrane proteins in a native-like bilayer environment for biochemical and structural studies. Traditionally, these NLPs have been prepared by the controlled removal of detergent from a detergent-solubilized protein-lipid mixture. Recently, an alternative method has been developed using direct cell-free expression of the membrane scaffold protein in the presence of preformed lipid vesicles, which spontaneously produces NLPs without the need for detergent at any stage. Using SANS/SAXS, we show here that NLPs produced by this cell-free expression method are structurally indistinguishable from those produced using detergent removal methodologies. This further supports the utility of single step cell-free methods for the production of lipid binding proteins. In addition, detailed structural information describing these NLPs can be obtained by fitting a capped core-shell cylinder type model to all SANS/SAXS data simultaneously.

Reversed compressive yield anisotropy in magnesium with microlaminated structure

To investigate the effect of grain morphology on the mechanical properties of polycrystalline Mg, two types of bulk Mg samples with equiaxed and microlaminated grain structures were fabricated by spark plasma sintering (SPS) of as-received Mg powder and cryomilled disc-shaped Mg powder particles, respectively. Based on a detailed microstructural investigation, the mechanisms by which microstructure evolves and texture development occurs were identified and are discussed. The basal fiber textures in the SPS consolidated samples allow the plastic anisotropy in such textured Mg to be investigated. Compression tests at room temperature parallel and perpendicular to the SPS compaction axis determined that, in comparison to the conventional anisotropy observed in the equiaxed sample, the anisotropy of yield strength is reversed in the microlaminated sample, with the yield strength for c-axis extension being higher than that for c-axis contraction. The reversed compressive yield strength anisotropy observed in the sample that was cryomilled is related to the low twinning activity, limited twinning growth and the anisotropy induced by the microlaminated grain structure, which offers an opportunity to reduce or even reverse the intrinsic plastic anisotropy of hexagonal close packed Mg.

Thermal Hysteresis and Seeding of Twisted Fibers Formed by Achiral Discotic Particles.

In this paper, molecular dynamics simulations of simple disc-shaped particles are used to investigate the free self-assembly of defect-free fibers. Depending on the choice of particle shape and interaction strength, the formed fibers are reproducibly either straight or, for reasons of packing efficiency, spontaneously chiral. As they grow radially, increasing stresses cause chiral fibers to untwist either continuously or via morphological rearrangement. It is also found that, due to the kinetics of fiber initiation, the isotropic solution has to be significantly supercooled before aggregation takes place. As a result, the thermal hysteresis of one formed fiber extends to 13.9% of the formation temperature. In the presence of a three-thread seed cluster of 15 particles, however, monotonic fiber growth is observed 9.3% above the normal formation temperature. Thus, as in many experimental systems, it is the kinetic pathway, rather than the thermodynamic stability of the final assembly, that dominates the observed behavior.

Size-dependent mechanical behavior of an intergranular bond revealed by an analytical model

The size of intergranular bonds significantly affects the macroscopic mechanical properties of geomaterials. A size-dependent bond contact model is desired in the distinct element method (DEM) for geomaterials formed by aggregates of bonded particles. This paper proposes an analytical solution of highly-precise stress fields of a biconcave bond between two identical disc-shaped particles under different loading paths based on Dvorkin’s solution. The Unified Strength theory is then introduced to obtain the initial failure domain in the bond. The proposed solution is consistent with results predicted by finite element simulations and experimental observations. The functions of bond stiffness with respect to all influencing parameters, i.e. bond width/thickness, particle radius and elastic parameters of bond material, are provided by the solution and empirically formulated by fitting a large number of analytical results. Additionally, the failure criterion or envelope under different combined loads is formulated for typical brittle bonds. The resulting failure criterion, approximated as an ellipsoid, depends on the size and material properties of the bonds. The proposed solution and equation can be implemented into a bond contact model used in DEM simulations of a geomaterial, where variation of bond sizes is significant and size-dependent contact model is important.