Search Results (3,831)

Quasicrystals are ordered phases without periodicity. They are often found in aluminium and other alloys. They can appear in different sizes. Therefore, several metallographic and characterisation techniques are required to fully determine their shape, size, crystallography, and chemical composition. This review paper gives special attention to identifying quasicrystals in aluminium alloys using classical metallographic techniques, such as etching, deep etching, and particle extraction, which allow the investigation of larger areas by light and scanning electron microscope, giving additional information by combining with complementary high-resolution techniques. Full article

This study investigated the physicochemical and rheological properties of floury rice powder (FRP) with different particle sizes and their effects on the quality characteristics of gluten-free butter sponge cake. Soft rice grain (Baromi2 variety) was dry-milled and sieved into four fractions: FR1 (60 mesh overs), FR2 (60–80 mesh), FR3 (80–100 mesh), and FR4 (100 mesh throughs). FRP fractions were analyzed for chemical composition, swelling power, solubility, gelatinization, pasting viscosity, and viscoelastic property. Gluten-free cakes made using a whole-egg foam method were evaluated for morphological structure, baking loss, moisture, specific volume and firmness. With decreasing FRP particle size, there were increasing trends in solubility, pasting viscosity, resistance to deformation, viscoelastic attributes (G′ and G″), and gel rigidity. FR3 and FR4 cakes exhibited flat and puffy loaves compared to FR1 and FR2 cakes with loaf collapses. The finer FRP enhanced the morphological balances of the cakes. Increasing trends in specific volume and firmness were observed as FRP particle size decreased. These results paralleled the solubility, pasting, rheological, and gelling properties of FRP itself. Overall, the results suggest that the rheological and gelling properties of FRP may play a role in determining the quality of gluten-free sponge cakes. In addition, FRP with a particle size of 80–100 mesh appears most appropriate for gluten-free sponge cake. Full article

Soil contamination with heavy metals (HM) poses a risk to human health and can impact different soil functions. This study aimed to determine the influence of heavy metal pollution on the physical and physicochemical characteristics of the two profiles of alluvial–deluvial soil under grassland located at different distances from the Aurubis-Pirdop Copper smelter in Bulgaria. Data for soil particle-size distribution, soil bulk and particle densities, mineralogical composition, soil organic carbon contents, cation exchange properties, surface charge, soil water retention curves, pore size distribution—obtained by mercury intrusion porosimetry (MIP)—and thermal properties were obtained. The contents of Pb, Cu, As, Zn, and Cd were above the maximum permissible level in the humic horizon and decreased with depth and distance from the Copper smelter. Depending on HM speciation, the correlations are established with SOC and most physicochemical parameters. It can be concluded that the HMs impact the clay content, specific surface area, distribution of pores, and the water stability of soil aggregate fraction 1–3 mm to varying degrees. Full article

This research evaluates the stabilization of a clay collected from the northern expansion zone of Cartagena de Indias, Colombia. Laboratory analyses, including particle size distribution, Atterberg limits, compaction, specific gravity, and XRF/XRD, classified the soil as a highly plastic clay (CH) with moderate dispersivity, as confirmed by pinhole and crumb tests. The soil was treated with 3–9% lime, with and without the addition of NaCl (0% and 2%), and tested for unconfined compressive strength (q_u), small-strain stiffness (G_o), and microstructural properties under curing periods of 14 and 28 days at two compaction densities. Results showed that lime significantly improved mechanical behavior, while the inclusion of NaCl further enhanced q_u (up to 185%) and G_o (up to 3-fold), particularly at higher lime contents and curing times. Regression models demonstrated that both q_u and G_o follow power-type relationships with the porosity-to-lime index, with consistent exponents (−4.75 and −5.23, respectively) and high coefficients of determination (R² > 0.79). Normalization of the data yielded master curves with R² values above 0.90, confirming the robustness of the porosity-to-lime framework as a predictive tool. The G_o/q_u ratio obtained (3737.4) falls within the range reported for cemented geomaterials, reinforcing its relevance for comparative analysis. SEM observations revealed the transition from a porous, weakly aggregated structure to a dense matrix filled with C–S–H and C–A–H gels, corroborating the macro–micro correlation. Overall, the combined use of lime and NaCl effectively converts dispersive clays into non-dispersive, mechanically improved geomaterials, providing a practical and sustainable approach for stabilizing problematic coastal soils in tropical environments. Full article

The High Temperature Gas-cooled Reactor (HTGR) is characterized by a high output temperature and inherent safety due to its fuel design. However, the double heterogeneity of the reactor component structure poses a challenge in thermal analyses, where fuel temperature is a key safety parameter. In this paper, a methodology for coupled thermal and neutron calculations with power discretization is developed to accurately reflect the spatial phenomena occurring in the moderator. The method is based on the point generation of power in the thermal model, and these points are determined based on the location of the fuel in the neutron model. The multi-physics interface capabilities of the Serpent code were used to investigate several configurations of the thermal model mesh and its alignment with the fuel. The impact of the radial discretization of power density was further analyzed in detail. The study revealed that the highest accuracy was achieved when the thermal model mesh was aligned with the TRi-structural ISO-tropic (TRISO) fuel particle size, and the TRISO particle arrangement was centered relative to the mesh cells. Moreover, it was found that due to the power–temperature feedback phenomena, the power is shifted outwards within a range of 1% of the relative power density. Full article

This article presents the results of a comprehensive investigation into geopolymer composites synthesized from fly ash, incorporating ground asphalt derived from reclaimed road pavement and quartz sand. The primary objective of this study was to elucidate the influence of mixture composition on the mechanical, physical, and microstructural characteristics of the developed materials. The innovative aspect of this research lies in the integration of two distinct filler types—mineral (quartz sand) and organic-mineral (milled asphalt)—within a single geopolymer matrix, while preserving key performance parameters required for engineering applications, including compressive and flexural strength, density, water absorption, and abrasion resistance. The experimental methodology encompassed the characterization of the raw materials by X-ray diffraction (XRD), chemical composition analysis via X-ray fluorescence (XRF), and assessment of particle size distribution. Additionally, the produced geopolymer materials underwent density determination, compressive and flexural strength measurements, abrasion testing, and mass water absorption evaluation. The chemical composition was further examined using XRF, and the surface morphology of the specimens was analyzed by scanning electron microscopy (SEM). The findings demonstrate that the incorporation of quartz sand enhances the density and mechanical strength of the composites, whereas the addition of recycled asphalt, despite causing a modest reduction in mechanical performance at elevated dosages, augments water resistance. Moreover, ternary composite material provide an optimal compromise between mechanical strength and durability under humid conditions. Overall, the results substantiate the feasibility of utilizing asphalt waste for the fabrication of functional and sustainable geopolymer materials suitable for construction applications. Full article

This study explores the formulation of chitosan microparticles through ionic gelation and presents detailed physicochemical characterization, release studies, and the utility and potential uses for drug delivery. Three formulations were prepared under rate-controlled conditions (stirring at 800 rpm and pH maintained at 4.6) with and without stabilizers to examine the effects of formulation parameters on particle morphology and structural stability. To determine different structural and chemical characteristics, Attenuated Total Reflectance Fourier-Transform Infrared spectroscopy (ATR–FTIR), Scanning Electron Microscopy (SEM), and dynamic light scattering (DLS) were utilized, which confirmed that the particles formed and assessed size distribution and structural integrity. Atomic force microscopy (AFM) was used to quantify surface roughness and potential nanomechanical differences that may derive from the use of different modifiers. Coformulation of bovine serum albumin (BSA) permitted assessment of encapsulation efficiency and drug release capacity. Based on in vitro release evidence, the protein released at a different rate, and the dispersion of formulations under physiological conditions (PBS, pH 7.4, 37 °C) confirmed the differences in stability between formulations. The tunable physical characteristics, mild fabrication conditions, and controlled drug release demonstrated that the chitosan particles could have useful relevance as a substrate for localized drug delivery and as a bioactive scaffold for tissue regenerative purposes. Full article

In the marine environment, plastic fragments are constantly engaged in a complex degradation process under exposure to various physical and chemical factors, one of which is ultraviolet (UV) radiation. These processes result in the formation of smaller micro- and nano-sized plastic particles, which are highly bioavailable to marine organisms. To clarify the toxicological effects of the exposure of degraded plastic on the marine organisms, the model used in this study was the Pacific mussel Mytilus trossulus and polymethylmethacrylate (PMMA), which is commonly found in marine debris. Using molecular and biochemical markers (DNA damage, lysosomal membrane stability, integral antiradical activity (IAA) of biological samples, and malondialdehyde (MDA) as a product of lipid peroxidation), the toxicity of pristine PMMA and photoaged (PMMA-UV) particles was assessed. Using Fourier transform infrared spectroscopy, the characteristics of the macromolecular changes in the chemical structure of PMMA-UV were obtained, with an oxidation index of 6.83 ± 0.46, compared to the pristine PMMA of 5.15 ± 0.54. Using a laser analyzer, the sizes of PMMA particles were determined, and it was found that after UV irradiation, the ratio of size groups changed—the proportion of particles with sizes of 500–1000 μm decreased, and the number of particles with sizes of 50–125 μm increased twofold. Analysis of mussel cell viability showed that after exposure to both types of PMMA microparticles, there was a decrease in the ability to retain neutral red dye in lysosomes: PMMA and PMMA-UV had a similar effect on hemocytes, reducing dye retention in cells to 55.2 ± 3.24% and 61.1 ± 1.99%, respectively. In gill and digestive gland cells, PMMA-UV particles reduced the stability of lysosomal membranes to a greater extent than PMMA. After PMMA and PMMA-UV particle exposure, the levels of DNA damage were as follows: in hemocytes, 10.1 ± 1.4% and 12.7 ± 0.8%, respectively; in gills, 7.8 ± 1.1% and 14.4 ± 2.9%, respectively; and in the digestive gland, 19.0 ± 1.3% and 21.9 ± 2.8%, respectively, according to the control values 3.6 ± 1.3%, 4.6 ± 1.1%, 5.1 ± 1.5%, respectively. According to the results of biochemical markers, the reaction of mussels to the presence of PMMA and PMMA-UV particles in the environment was tissue-specific: in the cells of the digestive gland, the level of IAA increased by 2 and 1.3 times compared to the control group of mussels (76.22 ± 6.77 nmol trolox/g wet weight and 52.43 ± 2.36 nmol trolox/g wet, respectively), while in the gill cells, the non-significant increase in antiradical activity was noted. An increase in MDA content was also observed in gill cells (255.8 ± 9.12 nmol MDA/g wet weight and 263.46 ± 9.45 nmol MDA/g wet weight, respectively) compared with the control group. This study showed that UV irradiation of PMMA microparticles increases their bioavailability and toxicity to M. trossulus. Full article

Colquiri is one of several deposits from the Central Andean tin belt, where sphalerite and cassiterite are mined. Although this is a high-grade Zn-Sn deposit, processing results in a low overall yield, with significant amounts of zinc and tin being discarded as tailings. In this study, mineralogical research was conducted to identify the causes of the low yield, so that the flow diagram could be modified to improve recovery. Particle size was measured, and chemical and mineralogical analyses were performed using optical and electron microscopy and X-ray diffraction. The mineral chemistry of the ores was determined using electron probe microanalysis (EPMA), and mineral liberation analyses were performed to complete the characterization. Mineralization occurred in four stages: (1) formation of silicates and oxides; (2) main precipitation of sulfides, including pyrrhotite, sphalerite, and stannite; (3) precipitation of fluorite and the replacement of pyrrhotite by pyrite, which was then replaced by siderite; and (4) weathering of previously formed minerals. The run-of-mine material contains approximately 12 wt.% ZnO and 1.5 wt.% SnO₂. The Zn concentrate contains up to 43.90 wt.% ZnO, and the Sn concentrate contains 52 wt.% SnO₂. The final tailings still retain more than 3–4.5 wt.% ZnO and 1.2 wt.% SnO₂. The average grain size of sphalerite is 200 µm, while that of cassiterite and stannite is 45 µm. The liberated fraction of sphalerite is 51.43%, and binary particles of sphalerite plus stannite account for 60 wt.%. Cassiterite is liberated at 54.68 wt.%. To increase the recovery of sphalerite (with stannite) and cassiterite, as well as the grade of the concentrates, it is necessary to reduce the particle size of the processed ores to less than 100 µm. Full article

Chlorella vulgaris is a nutrient-dense microalga with recognized antioxidant, anti-inflammatory, and metabolic regulatory properties, making it an attractive candidate for functional food applications. In such contexts, both chemical composition and particle size can influence dispersibility, bioactive release, and physiological effects. In this study, two commercial C. vulgaris powders from India (Sample 1) and the UK (Sample 2) were compared with respect to particle size, metabolite composition, and biological activity. Sample 1 exhibited finer particles, while Sample 2 was coarser. GC–MS profiling revealed distinct compositional differences: Sample 1 displayed a higher relative abundance of saturated fatty acids, β-sitosterol, β-amyrin, and glucitol, whereas Sample 2 contained higher levels of unsaturated fatty acids, betulin, salicylic acid, and specific carbohydrates. In vitro assays showed stronger inhibition of albumin denaturation by Sample 1 compared with Sample 2 and prednisolone. Ex vivo tests indicated that both samples induced tonic contraction of gastric smooth muscle through muscarinic acetylcholine receptors (mAChRs) and L-type calcium channels, as evidenced by the marked reduction in responses after atropine and verapamil treatment, with Sample 1 producing a more pronounced effect. Immunohistochemistry further demonstrated broader IL-1β upregulation with Sample 1 and localized nNOS modulation with Sample 2. Overall, the results demonstrate that the interplay between composition and particle size shapes the bioactivity of C. vulgaris, supporting its targeted use in digestive, neuroimmune, and cardiometabolic health. Full article

Background/Objectives: Optimizing drug deposition to the olfactory region is key in Nose-to-brain drug delivery strategies. However, findings from computational fluid dynamics (CFD) studies remain inconsistent concerning the parameters influencing olfactory deposition, limiting clinical translation and device optimization. This systematic review aims to identify robust CFD parameters for optimizing drug delivery to the olfactory region. Methods: A systematic review and meta-analysis were conducted following PRISMA guidelines, selecting studies reporting CFD simulations of nasal drug delivery with evaluation of olfactory deposition efficiency. The primary outcome was the correlation between each CFD parameter and olfactory deposition rate. Parameters included particle size, impaction parameter, flow rate, spray cone angle, insertion angle, injection velocity, head position, release position, and breathing pattern. Data were extracted and standardized, and statistical methods were used to assess correlations, heterogeneity, and potential biases in study results. Results: Smaller particle size (pooled r = −0.42) and lower impaction parameter (r = −0.39) were significantly associated with higher olfactory deposition. No consistent correlation was observed with breathing flow rate. Heterogeneity across studies was high (I² > 90%). Funnel plots asymmetry suggested potential publication bias in particle-related outcomes. Conclusions: Particle characteristics, especially size and inertia, are the most critical determinants of olfactory deposition in CFD simulations. These findings support design optimization of nasal delivery devices targeting the olfactory region and underscore the need for standardized reporting and validation across CFD studies. Full article

Nanocrystalline CoWO₄ sampled were synthesized using a simple mechanochemical approach and a solid-state reaction, respectively. The formation of nanocrystalline CoWO₄ was characterized by X-ray diffraction (XRD) and infrared spectroscopy (IR). The optical properties of the obtained samples were explored by diffuse reflectance UV–visible (DRS) and photoluminescence (PL) techniques. A milling speed of 850 rpm led to the direct synthesis of monoclinic CoWO₄ with a short reaction time (1 h). The complete reaction did not occur in the solid-state synthesis. The obtained samples had monoclinic crystal systems with different lattice parameters. The average crystallite sizes of CoWO₄ were in the range of 20 to 180 nm. The TEM investigation showed that the morphology of the CoWO₄ particles differed depending on the preparation conditions. The values of the determined optical bandgap of CoWO₄ were the range of 1.89 to 2.18 eV, according to diffusion reflectance spectroscopy in the ultraviolet-to-visible range. Broader blue–green emission spectra with peaks at 430 nm were observed for samples prepared via both routes. The CIE color coordinates of the CoWO₄ samples lay in the blue and purple regions. The quantum yields of the CoWO₄ samples synthesized after 1 h and 5 h milling times at 850 rom were 0.34 and 0.67%, respectively. This study proposes an affordable mechanochemical approach for blue–green phosphors that could possibly be used in various light-emitting diodes (LEDs). Full article

Three-dimensional concrete printing (3DCP) is advancing rapidly, yet its sustainable adoption requires alignment with circular-economy principles. This study evaluates the substitution of natural aggregates with recycled constituents, 3DCP waste, brick debris, glass cullet, mixed rubble, fly ash, and slag, and the use of lightweight fillers (expanded perlite, lightweight expanded clay aggregate (LECA), and expanded polystyrene (EPS)) to reduce density and improve insulation. Key properties, such as particle-size distribution, printability, mechanical performance, thermal conductivity, and water absorption, were determined. Results indicate that grading strongly affected mixture behavior. Narrow distributions (fly ash, milled 3DCP waste) enhanced extrudability, while broader gradings (glass, rubble, slag) increased water demand and extrusion risks. Despite these differences, all systems remained within the printable window: flow spread decreased with most recycled additions (lowest for brick) and increased with glass. Mechanical responses were composition-dependent. Flexural strength typically decreased. Compressive strength benefited from broader gradings, with replacement levels up to ~6% enhancing strength due to improved packing. Loading anisotropy typical of 3DCP was observed, with perpendicular compressive strength reaching up to 13% higher values than parallel loading. Lightweight fillers significantly reduced thermal conductivity. LECA provided the best compromise between strength and insulation, perlite showed intermediate behavior, and EPS achieved the lowest thermal conductivity but induced significant strength penalties due to weak matrix-EPS interfaces. Water absorption decreased in recycled-aggregate mixes, whereas lightweight systems, particularly with perlite, retained higher uptake. The results demonstrate that non-reactive recycled aggregates and lightweight insulating fillers can be successfully integrated into extrusion-based 3DCP without compromising printability. Full article

The current study examines the feasibility of Ultrasint PP nat 01 polypropylene material in powder bed fusion through powder characterisation. The results obtained are also deemed to be pertinent when developing or validating analytical and numerical models of Polymer Laser Sintering, which were not within the scope of this paper. The following critical characteristics were examined: powder morphology, powder particle size distribution (PSD), bulk density, tapped density, melt flow index, thermal characteristics of the material, degree of crystallinity, and optical properties. Ultrasint PP nat 01 powder has a PSD in the range of 20–80 µm, which is within the recommended particle size distribution. The Hausner ratio, tapped density, and bulk density of the material were calculated and measured as 1.230 ± 0.05, 0.455 ± 0.02 g/cm³, and 0.370 ± 0.03 g/cm³, respectively. The melt flow index of Ultrasint PP nat 01 was measured as 15.8 g/10 min. The initial melting point of the material was determined to be 133.8 °C. The powder used had a relatively high sintering window of 30.7 °C, a degree of crystallinity of around 31.8%, and a high thermal stability of around 461.52 °C. The material was found to attain full fusion of particles at around 170 °C. Fourier Transform Infrared Spectroscopy indicated that Ultrasint PP nat 01 powder has poor radiation absorption, but high transmission properties. Full article

Polymeric nanocomposites have been extensively investigated due to their potential for enhancing the mechanical and tribological properties of polymer composites. In this study, the mechanical performance of carbon fiber-reinforced epoxy composites modified with nano-sized ferrochrome slag particles, an industrial by-product from stainless steel manufacturing, was evaluated. Composite laminates were fabricated using a vacuum-assisted hand lay-up process, with consistent carbon fiber reinforcement and uniformly dispersed nanofillers in the epoxy matrix. Mechanical properties such as tensile, flexural, impact, and Shore D hardness were evaluated as per ASTM and ISO standards. At 2 wt.% nanofiller loading, enhanced tensile strength and hardness by 33.02% and 8.92%, respectively, were achieved, while flexural strength and impact strength increased by 3.70% and 3.62% at 1 wt.% compared to the neat composite. Higher filler contents (>3 wt.%) resulted in reduced performance due to particle agglomeration and microstructural inhomogeneity. A scanning electron microscope was used to determine the uniform dispersion and agglomeration of nanofillers. The results demonstrated the potential of ferrochrome slag as a sustainable and cost-effective nanofiller for advanced composite applications. Full article