Changes In Size Distribution Research Articles

Highly stable mesoporous Ni-phyllosilicate particle under high temperature hydrothermal and base conditions towards industrial catalytic applications

Two mesoporous nickel phyllosilicate (Ni-PS) samples with Ni/Si ratios of 0.3 and 1 were used to compare high-temperature hydrothermal stability. The Ni-PS structures have well-developed porosity and pore size distributions mainly ranging from 2 to 20 nm. To assess their hydrothermal resistance as a reusable heterogeneous catalyst in high-temperature reactions, the samples were exposed to 800 °C for 7 days using steam-supplied muffle furnaces. Three types of mesoporous silica samples (i.e. MCM-41, SBA-15, and mesoporous benzene-silica) and two zeolites (i.e. ZSM-5 and zeolite-Y) were compared under the same conditions. The hydrothermal resistance was primarily confirmed based on changes in pore size distribution and surface area through nitrogen-sorption isotherm analysis. The crystal structure and the binding energy of each sample were investigated by X-ray diffraction and X-ray photoelectron spectroscopy measurements. The Ni-PS structures displayed excellent stability (i.e. BET surface area retained over 77 % and 65 % after 1-d and 7-d treatment, respectively.) compared with other mesoporous samples, and even higher stability than zeolite Y. In addition, structural stability at pH = 10 is much higher than that of ZSM-5. This suggests that it could be used for various catalytic chemical reactions including hydrogenation and cracking processes because NiO and Ni nanoparticles are uniformly distributed on the surface, maintaining their particle shape even after a reduction process.

Maintenance of Lognormal-Like Skewed Dendritic Spine Size Distributions in Dentate Granule Cells of TNF, TNF-R1, TNF-R2, and TNF-R1/2-Deficient Mice.

Dendritic spines are sites of synaptic plasticity and their head size correlates with the strength of the corresponding synapse. We recently showed that the distribution of spine head sizes follows a lognormal-like distribution even after blockage of activity or plasticity induction. As the cytokine tumor necrosis factor (TNF) influences synaptic transmission and constitutive TNF and receptor (TNF-R)-deficiencies cause changes in spine head size distributions, we tested whether these genetic alterations disrupt the lognormality of spine head sizes. Furthermore, we distinguished between spines containing the actin-modulating protein synaptopodin (SP-positive), which is present in large, strong and stable spines and those lacking it (SP-negative). Our analysis revealed that neither TNF-deficiency nor the absence of TNF-R1, TNF-R2 or TNF-R 1 and 2 (TNF-R1/R2) degrades the general lognormal-like, skewed distribution of spine head sizes (all spines, SP-positive spines, SP-negative spines). However, TNF, TNF-R1 and TNF-R2-deficiency affected the width of the lognormal distribution, and TNF-R1/2-deficiency shifted the distribution to the left. Our findings demonstrate the robustness of the lognormal-like, skewed distribution, which is maintained even in the face of genetic manipulations that alter the distribution of spine head sizes. Our observations are in line with homeostatic adaptation mechanisms of neurons regulating the distribution of spines and their head sizes.

Maximizing N-Nitrosamine Rejection via RO Membrane Plugging with Hexylamine and Hexamethylenediamine.

The rapid expansion of urban areas and the increasing demand for water resources necessitate substantial investments in technologies that enable the reuse of municipal wastewater for various purposes. Nonetheless, numerous challenges remain, particularly regarding disinfection by-products (DBPs), especially carcinogenic compounds such as N-nitrosamines (NTRs). To tackle the ongoing issues associated with reverse osmosis (RO) membranes, this study investigated the rejection of NTRs across a range of commercially available RO membranes. In addition, the research aimed to improve rejection rates by integrating molecular plugs into the nanopores of the polyamide (PA) layer. Hexylamine (HEX) and hexamethylenediamine (HDMA), both linear chain amines, have proven to be effective as molecular plugs for enhancing the removal of NTRs. Given the environmental and human health concerns associated with linear amines, the study also aimed to assess the feasibility of diamine molecules as potential alternatives. The application of molecular plugs led to changes in pore size distribution (PSD) and effective pore number, resulting in a decrease in membrane permeability (from 5 to 33%), while maintaining levels suitable for RO processes. HEX and HDMA exhibited a positive effect on NTR rejection with ACM1, ACM5 and BW30LE membranes. In particular, NDMA rejection, the smallest molecule of the tested NTRs, with ACM1 was improved by 65.5% and 70.6% after treatment with HEX and HDMA, respectively.

Novel griseofulvin zinc nanohybrid emulsion for intensifying the antimicrobial control of dermatophytes and some opportunistic pathogens

Dermatophytosis is a critical sort of skin infection caused by dermatophytes. The long-term treatment of such skin infections may be improved through the application of nanotechnology. This study aimed to prepare griseofulvin zinc Nanohybrid emulsion (GF-Zn–NHE) to improve griseofulvin activity against dermatophytes and some opportunistic pathogenic yeasts and bacteria. The GF-Zn-NHE is prepared by ultra-homogenization ultra-sonication strategies and validated by UV–visible spectroscopy analysis that confirms presences of griseofulvin and Zn-NPs peaks at 265 and 360 nm, respectively. The GF-Zn-NHE has mean distribution size 50 nm and zeta potential in the range from -40 to -36 mV with no significant changes in size distribution and particle size within 120 day ageing. Fourier transform infrared spectroscopy spectrum confirmed the presence of griseofulvin and Zn-NPs stretching vibration peaks. Gamma ray has a negative influence on GF-Zn-NE production and stability. GF-Zn-NHE drug release 95% up to 24 h and 98% up to 72 h of GF was observed and Zinc 90% up to 24 h and 95% up to 72 h, respectively. High antimicrobial activity was observed with GF-Zn–NHE against dermatophytic pathogens in compare with GF, GF-NE, zinc nitrate and ketoconazole with inhibition zone ranged from 14 to 36 mm. The results have shown that the MIC value for Cryptococcus neoformans, Prophyromonas gingivalis and Pseudomonas aeruginosa is 0.125 mg ml −1 and for Trichophyton rubrum, L. bulgaricus and Escherichia coli value is 0.25 mg ml −1 and for Candida albicans, Malassezia furfur and Enterococcus faecalis is 0.5 mg ml −1 and finally 1 mg ml −1 for Streptococcus mutans. TEM of treated Cryptococcus neoformans cells with GF-Zn-NHE displayed essentially modified morphology, degradation, damage of organelles, vacuoles and other structures.

Influence of chemical pretreatment on the pozzolanicity of recycled glass microparticles used as a substitute for Portland cement

This research investigated the influence of using chemically treated glass microparticles as a partial replacement for cement in Portland cement pastes and mortars. The microparticles were obtained by grinding glass waste into three different particle size fractions (< 75 µm, < 45 µm, and < 25 µm), treated with calcium hydroxide (CH), and characterized using SEM/EDS and a laser particle size analyzer. Samples prepared with the incorporation of glass were characterized using XRD, TGA/DTG, and SEM/EDS. The pretreatment with calcium hydroxide induced the formation of C-S-H with different morphologies on the surface of the particles, in addition to causing changes in particle size distribution due to the formation of agglomerates. The pastes prepared with treated particles had lower amounts of CH and higher levels of hydrated silicates. However, when indirectly measuring the pozzolanicity of treated particles through the compressive strength of mortars, no significant differences were observed in the strengths of mortars made with treated and untreated particles.

Characterization of Respirable Coal Mine Dust Recovered from Fibrous Polyvinyl Chloride Filters by Scanning Electron Microscopy

The characterization of respirable dust on the basis of constituent fractions and particle sizes is increasingly of concern for evaluating exposure hazards. For high-resolution particle analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) can be an effective tool. However, it requires particles to be deposited on a smooth, uniform substrate such as a polycarbonate (PC) filter for optimal results. While direct sampling onto PC is possible, this is not the standard approach in many situations. For example, in coal mines, respirable dust samples have typically been collected onto polyvinyl chloride (PVC) filters because they are intended for gravimetric and/or infrared spectroscopy analysis. Such fibrous substrates are not ideal for SEM-EDX (or other microscopy), but an effective method to recover and redeposit the dust particles could render such samples suitable for the additional analysis. Here, we present a simple method and compare SEM-EDX results for paired samples analyzed directly on PC and following recovery from PVC and redeposition on PC. Both laboratory-generated dust samples (n = 10 pairs) and field samples of respirable coal mine dust (n = 44 pairs) are included in this study. Although some changes in particle size distributions were observed between samples analyzed directly and those that were recovered and redeposited prior to analysis, the results indicate the dust recovery method generally yields a representative sample in terms of mineral constituents. That said, results also highlighted the effects of high particle loading density on individual particle analysis. Considering all sample pairs, those with similar loading density between the directly analyzed and recovered sample tended to exhibit similar mineralogy distributions. This was generally the case for the lab-generated sample pairs, and the Freeman-Halton exact test of independence indicated that the samples in just three (of 10) pairs were in disagreement in terms of their mineralogy distributions. On the other hand, for the field samples, the directly analyzed sample often had higher loading density than the recovered sample; and the Freeman-Halton test showed that 25 (of 44) pairs were in disagreement. However, the effect of possible particle agglomeration on the directly analyzed samples cannot be ruled out—and exploration of this factor was beyond the scope of the current study.

Intra-decadal increase in globally-spread Magallana gigas in southern California estuaries.

Introduction and establishment of non-indigenous species (NIS) has been accelerated on a global scale by climate change. NIS Magallana gigas' (formerly Crassostrea gigas') global spread over the past several decades has been linked to warming waters, specifically during summer months, raising the specter of more spread due to predicted warming. We tracked changes in density and size distribution of M. gigas in two southern California, USA bays over the decade spanning 2010-2020 using randomly placed quadrats across multiple intertidal habitats (e.g., cobble, seawalls, riprap) and documented density increases by 2.2 to 32.8 times at 7 of the 8 sites surveyed across the two bays. These increases in density were coincident with 2-4° C increases in median monthly seawater temperature during summer months, consistent with global spread of M. gigas elsewhere. Size frequency distribution data, with all size classes represented across sites, suggest now-regular recruitment of M. gigas. Our data provide a baseline against which to compare future changes in density and abundance of a globally-spread NIS of significant concern.

An Image-based method for evaluating changes in particle size and morphology distributions of aggregate materials after vibratory compaction test

Particle breakage and abrasion of aggregate materials can be induced by field compaction during construction, which adversely affects their mechanical properties. However, current compaction quality control testing does not evaluate changes in particle size distribution and particle morphology of aggregate materials due to the lack of fast and inexpensive testing methods. In this study, a modified watershed-based segmentation image analysis method and computational geometry algorithms were used to quickly quantify changes in particle size and morphology distributions of a large amount of contacting aggregate particles. The accuracy and required minimum sample size of the image analysis method were statistically evaluated. Compared to the conventional ASTM C136 aggregate sieve analysis test, the image analysis method conducted on a 40% sample size of the conventional method yielded less than 6% difference between the results, which can meet the ASTM C136 test repeatability criteria. In addition, demonstration tests were conducted to incorporate the image analysis method into a laboratory vibratory compaction test for evaluating the overall particle size and morphology changes of an aggregate material after compaction. Results indicate that the initial gradation and water content of the aggregate material can influence the particle breakage and abrasion characteristics of aggregate materials under compaction.

Investigation on the anti-carbonation properties of alkali-activated slag concrete: Effect of activator types and dosages

In this paper, three alkaline activators, namely sodium hydroxide (SH), calcium oxide and sodium carbonate (COSC), calcium hydroxide and sodium sulfate (CHSS), and the influence of different alkali equivalents on the carbonation resistance of alkali-activated slag concrete (AASC) were investigated. By testing the mechanical properties at different carbonation ages of AASC with three types of activators at varying alkali equivalents (4%, 6%, and 8%), along with the changes in carbonation depth, this study aims to characterize hydration products and porosity through microstructural analysis. The objective is to explain the mechanism by which carbonation affects the AASC structure. The findings showed that the carbonation rate (i.e., the growth rate of the carbonation depth) of AASC was CHSS > COSC > SH when the exciter dosages were the same, and the carbonation rate of all samples tended to slow down as the alkali components increased. Calcite and spherulite were the calcium carbonate morphologies after SH, COSC, and CHSS carbonation according to XRD, TG/DSC, and pore structure tests; the calcium carbonate content decreased with increasing alkali equivalent after carbonation. Since the pore-increasing effect of carbonation due to the destruction of C–S–H is weaker than the filling effect produced by calcium carbonate, the total pore volume of SH, COSC, and CHSS decreased due to the activator effect after carbonation. Specifically, the calcium carbonate created by carbonation repairs pores and cracks of matrix, but its presence also reduces the calcium hydroxide concentration, leading to a decrease in the alkalinity of the pore solution, which disrupts the structure of the hydration products and loosens the matrix. The focus is on which aspect is more decisive. Interestingly, small pores however decreased, while there was an increase in larger pore sizes resulting in a change in pore size distribution. However, this negative impact on pore distribution decreased with increasing alkali dosage.

Effects of non-isothermal annealing on the microstructure of pure and potassium-doped tungsten sheets

Within this study, the effects of non-isothermal annealing procedures, especially different heating rates, were studied for cold rolled pure and potassium doped tungsten sheets. The sheets had a thickness of 0.2 mm. The microstructure was studied via etching of polished cross sections as well as electron backscatter diffraction. The potassium-bubble distribution in the doped tungsten sheets was investigated using scanning electron microscopy.Regarding the microstructure, the doped tungsten sheets presented an elongated, layered microstructure, that was considerably affected by the heating rate. A decrease of the heating rate from 14,400 K/min to 20 K/min resulted in a grain size shift in rolling direction from 70 to 513 μm. On the other hand, pure tungsten sheets showed no significant dependence on the heating rate. Moreover, additional isothermal annealing periods at 2400 °C did generally not affect the microstructure of doped tungsten sheets, which in turn led to a significant increase of the grain size in pure tungsten. This difference was attributed to the grain growth mechanisms, normal grain growth for pure and secondary recrystallization for K-doped tungsten.However, the potassium bubble structure, being responsible for the microstructural differences, was in turn only affected by the maximum annealing temperature. The heating rate differences led to no significant changes in the bubble size distribution. Furthermore, additional isothermal annealing at 2400 °C led to comparably minor changes in the average bubble diameter.

Preparation of fine suspensions using stirred media bead mill

Preparation of fine suspensions using stirred media bead mill

Machine Learning Assisted Experimental Characterization of Bubble Dynamics in Gas-Solid Fluidized Beds.

This study introduces a machine learning (ML)-assisted image segmentation method for automatic bubble identification in gas-solid quasi-2D fluidized beds, offering enhanced accuracy in bubble recognition. Binary images are segmented by the ML method, and an in-house Lagrangian tracking technique is developed to track bubble evolution. The ML-assisted segmentation method requires few training data, achieves an accuracy of 98.75%, and allows for filtering out common sources of uncertainty in hydrodynamics, such as varying illumination conditions and out-of-focus regions, thus providing an efficient tool to study bubbling in a standard, consistent, and repeatable manner. In this work, the ML-assisted methodology is tested in a particularly challenging case: structured oscillating fluidized beds, where the spatial and time evolution of the bubble position, velocity, and shape are characteristics of the nucleation-propagation-rupture cycle. The new method is validated across various operational conditions and particle sizes, demonstrating versatility and effectiveness. It shows the ability to capture challenging bubbling dynamics and subtle changes in velocity and size distributions observed in beds of varying particle size. New characteristic features of oscillating beds are identified, including the effect of frequency and particle size on the bubble morphology, aspect, and shape factors and their relationship with the stability of the flow, quantified through the rate of coalescence and splitting events. This type of combination of classic analysis with the application of the ML assisted techniques provides a powerful tool to improve standardization and address the reproducibility of hydrodynamic studies, with the potential to be extended from gas-solid fluidization to other multiphase flow systems.

Starch-Based Polysaccharide Systems with Bioactive Substances: Physicochemical and Wettability Characteristics.

Polysaccharide-based systems have very good emulsifying and stabilizing properties, and starch plays a leading role. Their modifications should add new quality features to the product to such an extent that preserves the structure-forming properties of native starch. The aim of this manuscript was to examine the physicochemical characteristics of the combinations of starch with phospholipids or lysozymes and determine the effect of starch modification (surface hydrophobization or biological additives) and preparation temperature (before and after gelatinization). Changes in electrokinetic potential (zeta), effective diameter, and size distribution as a function of time were analyzed using the dynamic light scattering and microelectrophoresis techniques. The wettability of starch-coated glass plates before and after modification was checked by the advancing and receding contact angle measurements, as well as the angle hysteresis, using the settle drop method as a complement to profilometry and FTIR. It can be generalized that starch dispersions are more stable than analogous n-alkane/starch emulsions at room and physiological temperatures. On the other hand, the contact angle hysteresis values usually decrease with temperature increase, pointing to a more homogeneous surface, and the hydrophobization effect decreases vs. the thickness of the substrate. Surface hydrophobization of starch carried out using an n-alkane film does not change its bulk properties and leads to improvement of its mechanical and functional properties. The obtained specific starch-based hybrid systems, characterized in detail by switchable wettability, give the possibility to determine the energetic state of the starch surface and understand the strength and specificity of interactions with substances of different polarities in biological processes and their applicability for multidirectional use.

Forecasting the effect of HIV-targeted interventions on the age distribution of people with HIV in Kenya.

To provide accurate forecasts of the age distribution of people with HIV (PWH) in Kenya from 2025 to 2040. Development of a compartmental model of HIV in Kenya, calibrated to historical estimates of HIV epidemiology. We forecasted changes in population size and age distribution of new HIV infections and PWH under the status quo and under scale-up of HIV services. Without scale-up, new HIV infections were forecasted to fall from 34 000 (28 000-41 000) in 2,025 to 29 000 (15 000-57 000) in 2,040; the percentage of new infections occurring among persons over 30 increased from 33% (20-50%) to 40% (24-62%). The median age of PWH increased from 39 years (38-40) in 2025 to 43 years (39-46) in 2040, and the percentage of PWH over age 50 increased from 26% (23-29%) to 34% (26-43%). Under the full intervention scenario, new infections were forecasted to fall to 6,000 (3,000-12 000) in 2,040. The percentage of new infections occurring in people over age 30 increased to 52% (34-71%) in 2,040, and there was an additional shift in the age structure of PWH [forecasted median age of 46 (43-48) and 40% (33-47%) over age 50]. PWH in Kenya are forecasted to age over the next 15 years; improvements to the HIV care continuum are expected to contribute to the growing proportion of older PWH.

A simple gradation-state-dependent model for granular materials

This paper proposes a gradation-state-dependent constitutive model to capture the granular materials' mechanical behaviours considering the granular crushing's influence. Firstly, a gradation evolution law is developed to reflect the change in grain size distribution (GSD) with the growth of stress levels, and then, based on the evolution law, the elastic compliance matrix is modified to reflect the effects of particle breakage. Secondly, as the critical state line (CSL) exhibits gradation dependence, a novel method is developed to describe the family of CSLs under different fixed gradations. Subsequently, by combining the gradation evolution law with the CSL equation, the paper explains the steepening of the slope of the critical state line when the crushing is activated. With the improvement of CSL, the material's shear dilatancy and contraction properties are better reflected, assisting in establishing a plastic compliance matrix. Employing the derived elastic and plastic compliance matrix, the elastic–plastic model reflecting the influence of gradation and state effects is established and verified with a series of experimental and discrete element method (DEM) simulation results.

Surface Modification of Magnetoactive Elastomers by Laser Micromachining.

It has been recently demonstrated that laser micromachining of magnetoactive elastomers is a very convenient method for fabricating dynamic surface microstructures with magnetically tunable properties, such as wettability and surface reflectivity. In this study, we investigate the impact of the micromachining process on the fabricated material's structural properties and its chemical composition. By employing scanning electron microscopy, we investigate changes in size distribution and spatial arrangement of carbonyl iron microparticles dispersed in the polydimethylsiloxane (PDMS) matrix as a function of laser irradiation. Based on the images obtained by a low vacuum secondary electron detector, we analyze modifications of the surface topography. The results show that most profound modifications occur during the low-exposure (8 J/cm2) treatment of the surface with the laser beam. Our findings provide important insights for developing theoretical models of functional properties of laser-sculptured microstructures from magnetoactive elastomers.

Myopic oligopoly pricing

This paper examines capacity-constrained oligopoly pricing with sellers who seek myopic improvements. We employ the Myopic Stable Set solution concept and establish the existence of a unique pure-strategy price solution for any given level of capacity. This solution is shown to coincide with the set of pure-strategy Nash equilibria when capacities are large or small. For an intermediate range of capacities, it predicts a price interval that includes the mixed-strategy support. This stability concept thus encompasses all Nash equilibria and offers a pure-strategy solution when there is none in Nash terms. It particularly provides a behavioral rationale for different pricing patterns, including Edgeworth price cycles and states of hyper-competition with supply shortages. We also analyze the impact of a change in firm size distribution. A merger among the biggest firms may lead to more price dispersion as it increases the maximum and decreases the minimum myopically stable price.

Study on Preparation Technology and Heat Conduction Mechanism of High-Purity & Ultra-Fine Alumina Powder from Scrap Aluminum Cans

In view of the increasing scarcity of bauxite resources in China, the high energy consumption and high pollution of electrolytic aluminum, and the requirements for energy conservation and environmental protection, aluminum recycling and high-value utilization of its derivatives have evolved into a crucial development requirement for the aluminum industry in the future. As an important part of the development of recycled aluminum resources, the high-value application of scrap aluminum cans has always been a hot research topic in various recycled aluminum processing enterprises and scientific research units. The traditional regeneration system of waste cans includes a series of complex technological processes such as pretreatment, paint removal, smelting system and casting system, which is difficult to control in the middle of the process. Most of the recycled scrap aluminum cans are cast and downgraded for later use, except for a part of them used as alloy materials for new cans. In this paper, combined with the research on the preparation of metal aluminum alkoxide, combined with recrystallization heat conduction to further study the effective dissolution or adsorption how to remove impurity elements to obtain high-purity aluminum alcohol salt mechanism research, and thermal effect of alcohols with different carbon chains on the synthesis of high-purity aluminum alkoxide was further investigated. Moreover, the changes in morphology and pore size distribution of hydrolyzed alumina precursor materials under different hydrothermal temperature conditions were discussed by means of the alkoxide hydrolysis-sol-gel process. Eventually, the aluminum alkoxide was obtained by the reaction of waste cans with isopropanol and heavy crystal thermal conductivity, and the high-purity aluminum alkoxide was purified by vacuum distillation. Under the hydrothermal condition of 160°C, the high-purity alumina material with a purity of 99.99% and an original crystal size of 200nm was prepared.

Dissipative Particle Dynamics Study on the Phase Region of Spatial Gradient Materials Produced by Photoinduced Isomerization

AbstractSpatial gradient materials occupy an important research position in the field of functional materials with their unique porous structure. Gradient changes in pore size and density distribution have received extensive attention in the fields of biomimetic and smart materials. The gradient transition law is mathematically related to the driving force of isomerization reaction and component phase separation. In this study, a dissipative particle dynamics simulation is used to introduce photoisomerization reactions into the system. Lambert's law is used to construct a reaction model for the variation of light intensity with irradiation depth, and a gradient structure with a spatial transition law is obtained. The effects of the extinction coefficient ε, the initial reaction probability Pr0, and the interactions α(A,B) between the isomerized molecules as well as the viscosity on the formation of the gradient structure are investigated in detail. Furthermore, the mathematical proportionality between the size of the phase region and interfacial energy of the two phases is elucidated. This study provides preliminary computational insights into the factors affecting the photoinduced phase separation process of polymeric gradient materials. It may help to develop effective strategies to improve the phase separation and properties of polymer gradient materials in subsequent studies.

Deep learning-based online image analysis of the water suspension granulation process for 1,3,5-trinitro-1,3,5-triazacyclohexane-based polymer-bonded explosives

Polymer-bonded explosives (PBXs) are typically prepared via water suspension granulation (WSG). However, few studies have reported on online monitoring during WSG. In this study, the WSG process for 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)-based PBXs was monitored using online imaging and infrared detection technology. The images of the particles and droplets obtained during the WSG process were then identified by employing the Mask Region-based Convolutional Neural Network (Mask R-CNN). The characteristic peak of ethyl acetate identified in the online infrared spectra during the WSG process is a key indicator for binder concentration. The experimental results show that the changes in the particle size distribution and particle morphology of the explosive modeling powders are consistent with the actual results, online infrared detection can provide effective guidance for the addition of the binder solution. This new and effective approach can be used to study WSG and has considerable potential for process optimization and quality control.