Aggregate Structure Research Articles

The dynamics of soil health

The dynamics of soil health Thomas Gumbricht from Stockholm University and xSpectre, with Sonia Meller from Digit Soil, discuss what we need to know about understanding the dynamics of soil health. Soils are formed by mineral debris, organic matter, water and living organisms. The soil ecosystem takes millennia to form and is sustained by a web of interplay both within the soil and with the vegetation ecosystem it harbours. Our human society wholly depends on soil for food, fodder, fibre, water cleaning, and climate control. But we are mismanaging soils, and in Europe, the majority of soils are considered unhealthy. Intense use of chemicals has depleted soil organisms, compaction causes water to runoff from the surface rather than infiltrate, and ploughing destroys the soil’s vital aggregate structure and oxidises soil organic carbon. The European Commission’s Soil Health and Food Mission aims to address these issues by promoting sustainable soil management practices across the continent.

Optimizing the aggregate structure and charge carrier transport performance of D‐A conjugated polymer films using nonpolar solvents

Optimizing the aggregate structure and charge carrier transport performance of D‐A conjugated polymer films using nonpolar solvents

Structural features of skeletal muscle titin aggregates

Titin is a multidomain protein of striated and smooth muscles of vertebrates. The protein consists of repeating immunoglobulin-like (Ig) and fibronectin-like (FnIII) domains, which are β-sandwiches with a predominant β-structure, and also contains disordered regions. In this work, the methods of atomic force microscopy (AFM), X-ray diffraction and Fourier transform infrared spectroscopy were used to study the morphology and structure of aggregates of rabbit skeletal muscle titin obtained in two different solutions: 0.15 M glycine-KOH, pH 7.0 and 200 mM KCl, 10 mM imidazole, pH 7.0. According to AFM data, skeletal muscle titin formed amorphous aggregates of different morphology in the above two solutions. Amorphous aggregates of titin formed in a solution containing glycine consisted of much larger particles than aggregates of this protein formed in a solution containing KCl. The “KCl-aggregates” according to AFM data had the form of a “sponge”-like structure, while amorphous “glycine-aggregates” of titin formed “branching” structures. Spectrofluorometry revealed the ability of titin “glycine aggregates” to bind to the dye thioflavin T (TT), and X-ray diffraction revealed the presence of one of the elements of the amyloid cross β-structure, a reflection of ~4.6 Å, in these aggregates. These data indicate that the “glycine-aggregates” of titin are amyloid or amyloid-like. No similar structural features were found in titin “KCl-aggregates”; they also did not show the ability to bind to thioflavin T, indicating the non-amyloid nature of these titin aggregates. Fourier transform infrared spectroscopy revealed differences in the secondary structure of the two types of titin aggregates. The data obtained demonstrate the features of structural changes during the formation of intermolecular bonds between molecules of the giant titin protein during its aggregation. The data expand the understanding of the process of amyloid protein aggregation.

Quantitative Study on Reinforcing Mechanism of Nanofiller Network in Silicone Elastomer Based on Fluorescence Labeling Technology

Although there have been many theoretical studies on the enhancement effect of nanofiller networks and their interaction with elastomer molecular chains on the mechanical properties of elastomers, its mechanism description is still not completely clear. One of the main obstacles is the lack of quantitative characterization techniques and corresponding theoretical models for the three-dimensional morphology of complex nanofiller networks. In this paper, the precipitated silica-filled silicone rubber was studied by fluorescence labeling combined with laser scanning confocal microscopy, and the real three-dimensional images of dispersion and aggregation structure of filled rubber systems were obtained. The microstructure evolution of nano-particle aggregates caused by the increase in the filler volume fraction was quantitatively described, and the reinforcement mechanism of elastomers with a distribution of aggregates and filler networks composed of nanoparticles was studied. Furthermore, a nano-composite reinforcement model based on volume fraction, particle shape, interaction, and filler dispersion has been proposed.

Remediation of Pb and Cd contaminated sediments by wheat straw biochar and microbial community analysis

Wheat straw biochar (BC) or modified wheat straw biochar (MBC) could affect the aggregate structure of soil, effectively adsorb heavy metal and reduce the bioavailability of heavy metals in soil. TGA, BET, FTIR and SEM were used to characterize the surface morphology and structure of BC and MBC. The adsorption properties of BC and MBC on Pb(‌II) and Cd(‌II) in solution systems were investigated by batch experiments, and the remediation performance of Pb and Cd contaminated sediment by BC or MBC were studied by pot experiments. The results showed that MBC had a larger specific surface area of 46.04 m2/g and total pore volume 0.0555 cm3/g; the adsorption isotherms of Pb(II) and Cd(II) for BC and MBC were more suitable for Langmuir model (R2 over 0.91), and the maximum adsorption capacities of Pb(II) and Cd(II) by MBC could reach 71.14 and 115.64 mg/g, respectively. BC or MBC promoted the transformation of Pb and Cd from the extractable acid fraction to the oxidizable and residual fraction, reduced the migration of heavy metals and enhanced the stability of aggregates. Therefore, the results provided a perspective for the dredged contaminated sediments used as planting soil. In addition, BC or MBC, as soil amendments, could improve the abundance of microbial community. At the phylum level, the main dominant bacteria were Proteobacteria and Bacteroidetes.

Particle aggregation and the grinding limit in high energy ball mill

Dust aggregates — clusters of individual particles — are formed during mechanochemical processing of brown coal in a planetary ball mill. The aggregate structure can be identified by comparing the average sizes of aggregates and individual particles. We showed that dust aggregates are generally arranged in a regular way: the number of individual particles located along the aggregate coincides with the number of particles located across the aggregate. Power of power-law distribution of the monomers per aggregate revealed that individual particles stick together in extremely dense clusters. The average number of monomers per claster is ~104. In addition, it turned out that the dependence of the monomer's “stickiness” on applied energy dose has a kink simultaneously with other characteristics of the mechanochemical process (the monomer size and the chemical reaction depth). Speaking using mechanochemistry terms, it corresponds to transition from the brittle grinding mode to the plastic deformation mode after reaching the grinding limit.

Exploration of the regulatory mechanism of pulsed electric field on the aggregation behavior of soybean protein isolates

As an emerging protein modification technology, pulsed electric field (PEF) technology in modifying soybean protein isolates (SPI) suffers from unclear mechanism and controversial changes in aggregation structure. To address these issues, the effects of PEF treatment with different electric field intensities (5–30 kV/cm) on the aggregation behavior and spatial structure of SPI were investigated. The results showed that the SPI aggregates exhibited a trend of depolymerization followed by reaggregation with the increase of PEF intensity. At 10 and 15 kV/cm, the polarization effect of PEF induced the unfolding of the tertiary structure of SPI, leading to the enhancement of the electronegativity of the side chains, and the electrostatic repulsive force between the molecules promoted the depolymerization of SPI aggregates. However, with the withdrawal of PEF, the structure of the SPI was partially reversible, resulting in a limited depolymerization effect. When the PEF intensity reached 20 kV/cm and above, SPI underwentstructure unfolding, subunit dissociation, continuous exposure of hydrophobic groups and sulfhydryl groups, and ultimately reaggregation mediated by hydrophobic interactions and disulfide bonding, resulting in the formation of high molecular weight soluble and insoluble protein aggregates. In addition, the formation of free radicals under strong electric fields (≥20 kV/cm) accelerated the oxidation of SPI and promoted the rapid formation of disulfide bonds. This study provides a theoretical basis for the targeted regulation of SPI aggregation structure by PEF.

A bi-component model to assess the rheology of soft cellular aggregates probed using the micropipette aspiration technique

The micro-pipette aspiration technique is a classical experiment used to characterize the physical properties of inert fluids and biological soft materials such as cellular aggregates. The physical parameters of the fluid, as viscosity and interfacial tension, are obtained by studying how the fluid enters the pipette when the suction pressure is increased and how it relaxes when the suction pressure is put to zero. A mathematical model representative of the experiment is needed to extrapolate the physical parameters of the fluid-like matter; however, for biological materials as cells or cell aggregates these models are always based on strong starting hypotheses that impact the significance of the identified parameters. In this article, starting from the bi-constituent nature of the cell aggregate, we derive a general mathematical model based of a Cahn-Hilliard-Navier-Stokes set of equations. The model is applied to describe quantitatively the aspiration-retraction dynamics of a cell-aggregate into and out of a pipette. We demonstrate the predictive capability of the model and highlight the impact of the assumptions made on the identified parameters by studying two cases: one with a non-wetting condition between the cells and the wall of the pipette (classical assumption in the literature) and the second one, which is more realistic, with a partial wetting condition (contact angle θs = 150°). Furthermore, our results provide a purely physical explanation to the asymmetry between the aspiration and retraction responses which is alternative to the proposed hypothesis of an mechano-responsive alteration of the surface tension of the cell aggregate. Statement of SignificanceOur study introduces a general mathematical model, based on the Cahn-Hilliard-Navier-Stokes equations, tailored to model micro-pipette aspiration of cell aggregates. The model accounts for the multi-component structure of the cell aggregate and its intrinsic viscoelastic rheology. By challenging prevailing assumptions, particularly regarding perfect non-wetting conditions and the mechano-responsive alteration of cell surface tension, we demonstrate the reliability of the mathematical model and elucidate the mechanisms at play, offering a purely physical explanation for observed asymmetries between the aspiration and retraction stages of the experiment.

Long‐Term Biochar Application Improved Aggregate K Availability by Affecting Soil Organic Carbon Content and Composition

ABSTRACTStraw biochar is an effective amendment at improving soil aggregate structure and increasing soil carbon and potassium (K) content. However, little information is available on the relationship between soil organic carbon (SOC) and aggregate‐associated K distribution under long‐term biochar application conditions. To address this, a field trial established in 2013 was used to examine the impact of biochar (B0: 0 and B1: 2.625 t ha−1 year−1) and K fertilizer (K0: 0 and K1: 60 kg ha−1 year−1) on the variation in soil aggregate K and reveal the associated influencing factors. A total of four treatments (B0K0, B0K1, B1K0, and B1K1) were included in this study. The soil analysis results obtained in 2021 showed that after 9 years' amendment, B1K1 increased the aggregate exchangeable K (EK) and nonexchangeable K (NEK) pools by 27.40% and 39.55%, respectively, and the increment was primarily because biochar enhanced > 0.25 mm aggregate fractions and strengthened soil K+ adsorption capacity, which benefit from a synergistic increase in SOC and humic acid (HA) content by biochar. 13C NMR analysis showed that long‐term biochar applications altered the chemical composition of SOC, with an outcome of increased aromaticity and hydrophobicity but decreased the lipidation of SOC, indicating that the complexity of SOC molecular structure was enhanced and eventually contributed to strengthening the macroaggregates stability and soil K+ adsorption capacity. The correlation analysis revealed that soil aggregate EK and NEK contents were positively correlated with SOC and HA contents, which further proved that increase of SOC and soil HA is a significant mechanism for biochar ameliorate soil aggregate‐associated K availability.

A biosensor based on carbon dots-protein interactions for specific and sensitive detection of pepsin in saliva

Salivary pepsin has emerged as a promising biomarker for rapid screening and diagnosis of gastroesophageal reflux disease (GERD). Pepsin mainly exists in strongly acidic environments and exhibits its highest activity. However, the poor stability of most fluorescent sensors in strong acidic environments brings a significant challenge for pepsin detection. Herein, an innovative biosensor was developed for the highly specific and sensitive detection of pepsin on the basis of green-emitting ionic liquid-based carbon dots (G-IL-CDs) conjugated with whey proteins (WPs). The G-IL-CDs exhibited aggregation-induced fluorescence enhancement when interacting with WP, and the fluorescence intensity decreased after incubation with pepsin due to the disruption of the aggregation structure. This strategy is highly selective for pepsin due to the strongly acidic environment in which other proteases are inactivated. Under optimal experimental conditions, this biosensor successfully detected pepsin in real human saliva with a satisfying recovery. Furthermore, this study not only developed a CDs-based sensor for detecting pepsin but also laid a solid theoretical foundation for the future development of novel biosensors combining CDs and proteins.

Long-term Chinese milk vetch incorporation promotes soil aggregate stability by affecting mineralogy and organic carbon

Soil aggregates profoundly impact soil sustainability and crop productivity, and they are influenced by complex interactions between minerals and organics. This study aimed to elucidate the alterations in mineralogy and soil organic carbon (SOC) following long-term green manure incorporation and the effect on soil aggregates. Based on 5- and 36-year field experiments, surface soil samples (0-20 cm) were collected from Alfisol and Ferrisol soils subjected to rice-rice-winter fallow (CK) and rice-rice-Chinese milk vetch (MV) treatments to investigate aggregate stability, mineralogy, SOC composition, and soil microstructural characteristics. The results showed that high clay-content Ferrisol exhibited greater aggregate stability than low clay-content Alfisol. The phyllosilicates in Alfisol primarily comprised illite and vermiculite, whereas those in Ferrisol with high-content free-form Fe oxides (Fed) were dominated by kaolinite. Additionally, the clay fraction in Ferrisol contained more aromatic-C than the clay fraction in Alfisol. The 36-year MV incorporation significantly increased the Ferrisol macroaggregate stability (9.57-13.37%), and it also facilitated the transformation of vermiculite into kaolinite and significantly increased the clay, Fed, and aromatic-C contents in Ferrisol. Backscattered electron (BSE)-scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) revealed a compact aggregate structure in Ferrisol with co-localization of Fe oxides and kaolinite. Moreover, the partial least path model (PLS-PM) revealed that clay content directly improved macroaggregate stability, and that kaolinite and Fed positively and directly affected clay or indirectly modulated clay formation by increasing the aromatic-C levels. Overall, long-term MV incorporation promotes clay aggregation by affecting mineral transformation to produce more kaolinite and Fe oxides and retain aromatic-C, and it ultimately improves aggregate stability..

A structural and optical modification of ZnO-Fe2O3 nanocomposite for enhancing catalytic activity

This study investigates the photocatalytic degradation of organic Methyl Blue (MB) using a ZnO-Fe2O3 composite prepared via the sol-gel technique. FTIR analysis elucidates the substantial impact of Fe2O3 addition, as evidenced by shifts in the ZnO absorption bands, notably observed at 631 cm-1 and 919.74 cm-1 peaks. X-ray diffraction (XRD) corroborates heightened crystallinity due to interactions between ZnO and Fe2O3. SEM analysis unveils a highly aggregated structure, showcasing promising capabilities for efficient dye degradation and environmental applications. Photoluminescence (PL) spectra exhibit an intensified peak at 377 nm, indicative of efficient charge separation and electron transfer, offering potential in optoelectronic applications. The composite's distinctive refractive index (n) of 2.33, extinction coefficient (k) of 2.12, optical electronegativity (∆X*) of 0.75, and dielectric constants (εr of 0.40 and εi of 9.92) underscore its versatile bonding and broad application prospects. Evaluating the photocatalytic activity (PCA) reveals that among all samples, the nanocomposite ZnO-Fe2O3 synthesized at 500°C exhibits superior performance, showcasing heightened degradation of MB dye under 90 minutes of sunlight irradiation.

Process-induced protein aggregates influenced pea globulins’ structure formation upon heating

Pea protein ingredients play key role in formulations of plant-based foods. However, functional properties of pea ingredients are inconsistent depending on extraction process. Protein aggregation occurs simultaneously during protein extraction, thus examining the protein aggregated states as induced by processing is essential for better process design. This study investigated the influence of process-induced protein aggregated states on structure formation upon heating of pea protein ingredients. Combining rheological, spectroscopic, and microscopic techniques, the mechanisms underlining heat-induced structure formation have been unveiled from microscopic to macroscopic scales. The salt-extracted isolate (PPI*) where protein aggregation was minimized, developed mesh-like structure through intermolecular protein-protein interaction upon gelling similar to commercial protein concentrate (PPC). In turn, commercial isolate (PPI) as appeared as microscopic particles, formed gel through accumulation of protein particles with no structure development. The aggregated states of PPI* and PPI seemed to dictate vicilin and legumin purification by means of anion exchange chromatography. Purification process promoted intermolecular protein aggregate structures. However, these purified fractions regardless of parent isolates showed similar structure development as PPC and PPI* during gelling. Monitoring protein aggregation during extraction process can be a key to limit functional property variation in pea protein ingredients.

Extraction and structural analysis of mannoproteins from different species of yeast: Bitter suppression and the potential mechanisms for wine

To rich the research for mannoproteins (MPs) suppressive effect on the bitterness of wine, this study distinguished bitterness into initial bitterness and bitter aftertaste. By utilizing the thermal alkali extraction method, MPs were extracted from three different yeast species: Saccharomyces cerevisiae (CECA), Lachancea thermotolerans (A38), and Torulaspora delbrueckii (2082). Their basic structures, addition concentrations, and correlation with bitter suppression ability were characterized. CECA exhibited stronger initial bitterness suppression ability, may attributed to its more branches and lack of a triple-helix structure. 2082 showed greater bitter aftertaste suppression and might due to smaller particle aggregation, fewer branches, and triple-helix structure. Additionally, it was noteworthy that due to the unique structure of 2082, it may bound more monomer and oligomeric proanthocyanidins (MOPC) on MPs surface, reducing its initial bitterness suppression ability. Concerning concentration, the increase in polysaccharide chain polymerization hindered further interaction with MOPC, leading to a decrease in its initial bitterness suppression ability. Bitter aftertaste exhibited different behaviors. As the concentration of CECA increased, there was an increase in oral adhesion instead.

Transitions between Localised Patterns with Different Spatial Symmetries in Non-Local Hyperbolic Models for Self-Organised Biological Aggregations

Pattern formation in biological aggregations is a topic of great interest, due to the complex spatial structure of various aggregations of cells/bacteria/animals that can be observed in nature. While many such aggregations look similar at the macroscopic level, they might differ in their microscopic spatial structure. However, the complexity of the non-linear and sometimes non-local interactions among individuals inside these aggregations makes it difficult to investigate these spatial structures. In this study, we investigate numerically the transitions between different spatial patterns of animal aggregations with various symmetries (even, odd or no symmetry) that characterise the microscopic distribution of individuals inside these aggregations. To this end, we construct a bifurcation diagram starting with perturbations of spatially homogeneous solutions with low, medium, and high amplitudes. For perturbations with low amplitudes, the bifurcating structures show transitions among even-symmetric, odd-symmetric, and non-symmetric solutions. For perturbations with large amplitudes, there are wide parameter regions with non-convergent solutions, characterised by oscillatory transitions between different relatively similar solutions. These numerical results emphasize: (i) the effect of nonlinear and non-local interactions on the microscopically different symmetric/non-symmetric structures of macroscopically similar ecological aggregations; (ii) the difficulty of developing continuation algorithms for this class of non-local models.

Langmuir adsorption model to assess the impact of silane coupling on nano-dispersion of silica in SBR

Surface active agents are often used to improve dispersion of nanoparticles. Quantitative correlation between these surface-active molecules and nanoscale dispersion is absent from the literature partly because a quantitative measure of nanoscale dispersion does not exist. Recently, we have developed the Virial-van der Waals method to quantify dispersion in nanocomposites using virial coefficients. In this paper, the Langmuir adsorption model is used to quantify the influence of surface-active agents on nano-scale dispersion in terms of the effective second virial coefficient B2∗. The impact of silane coupling agent on the nano-dispersion and silica aggregate structure in precipitated silica/SBR nanocomposites is demonstrated. It is shown that the higher viscosity SBR matrix led to a greater silica aggregate structural breakup, while lower viscosity matrix improved surface silanization. The isomeric content of the SBR, which impacts the dielectric behavior, impacted whether the system could be modeled through a mean-field or specific interactions. We earlier showed that larger aggregates improve dispersion, and this is reaffirmed in these results. After account is made for aggregate size, nano-scale dispersion improves with the addition of silane coupling agent. The behavior is well modeled using Langmuir monolayer adsorption.

Aggregate structure of agro-gray soils of Vladimir Opolye: composition and strength of aggregates

A complex of soils characteristic of the Vladimir Opole region was studied: agro-gray typical deep-arable soil, tongue-shaped agrozem and agro-gray gleyic soil. The high contrast of soil properties, which is due to the genesis of field landscapes, can be traced in the differences in the arable and subarable horizons of agro-gray soils at the aggregate and microaggregate levels. The soils have an excellent structural condition, high water resistance and mechanical strength of aggregates. In the aggregate structure of arable horizons, dependences on the position in the relief were found: down the slope the content of agronomically valuable aggregates decreases, the weighted average diameter of aggregates increases, the water resistance of aggregates and the mechanical strength of aggregates at capillary saturation decreases. However, the distribution and size of microaggregates, as well as the strength of aggregates in an air-dry state, reflects the complex genesis of the landscape and retains the influence of paleorelief with depressions and elevations. The weighted average diameter of microaggregates of arable horizons of the soils of the Vladimir Opole region is close to the chernozems of the Kursk region. The granulometric composition of the studied soils is typical of Vladimir Opolye soils and close to each other. In accordance with the classification of N.A. Kachinsky arable horizons are medium loamy, coarse silt, BT horizons are heavy loamy, coarse silt. The most structural is the arable horizon of agro-gray typical deep-arable soil, it has large microaggregates, it also has high water resistance and the highest content of agronomically valuable aggregates. The most homogeneous in terms of aggregate composition is tongue-shaped agrozem; the average diameter of aggregates and microaggregates in the arable and subarable horizons are equal and similar in the content of microaggregates and agronomically valuable aggregates. This soil is also highly water resistant. Agro-gray gleyic soil contains fewer agronomically valuable aggregates and its water stability is unsatisfactory.

Modulation of retrogradation properties by removal and retention of starch granule-associated lipids: A case study on buckwheat and wheat starches

The objective of this research was to investigate the influence of starch granule-associated lipids (SGALs) on retrogradation properties of buckwheat and wheat starches. According to the results, the removal of SGALs led to remarkable increase in the retrogradation enthalpy change of all starches and the strength of starch gels, as well as the density and short-range ordered structure of starch aggregates. The strength of starch gel experienced a rise from 3139.39 g to 3718.18 g in Tartary buckwheat, 2924.12 g to 3551.13 g in common buckwheat, and 1887.55 g to 2555.24 g in wheat, respectively. The removal of SGALs contributed to a decrease in the thermal stability of starches and an augmentation of amylose leaching during gelatinization process, which would strengthen the hydrogen bond interaction between starch molecules during cooling process, and promoting the rearrangement of the order structure of starch molecules. In general, these results indicated that the retention of SGALs could limit amylose leaching, then inhibited rearrangement and recrystallization of dissolved starch molecules, and ultimately delayed the short-term and long-term retrogradation process. This work further supplemented theoretical knowledge about SGALs in buckwheat and wheat starches, also provided a new perspective for regulating the physicochemical properties of starches.

Three-Dimensional Nanoscale Imaging of SiO2 Nanofiller in Styrene-Butadiene Rubber with High-Resolution and High-Sensitivity Ptychographic X-ray Computed Tomography.

SiO2 aggregates in styrene-butadiene rubber (SBR) were observed using ptychographic X-ray computed tomography (PXCT). The rubber composites were illuminated with X-rays focused by total reflection focusing mirrors, and the ptychographic diffraction patterns were collected using a CITIUS detector in the range of -75° to +75° angle of incidence. The projection images of the rubber composites were reconstructed with a two-dimensional resolution of 76 nm, and no significant structural changes were observed during the PXCT measurements. A three-dimensional image of the rubber composite was reconstructed with an isotropic resolution of 98 nm. Segmentation of SiO2 from the SBR, based on a histogram analysis of the phase shift, revealed a fragmented network structure of interconnected SiO2 aggregates.

MAFormer: A cross-channel spatio-temporal feature aggregation method for human action recognition

Human action recognition has been widely used in fields such as human–computer interaction and virtual reality. Despite significant progress, existing approaches still struggle with effectively integrating hierarchical information and processing data beyond a certain frame count. To address these challenges, we introduce the Multi-AxisFormer (MAFormer) model, which is organized in terms of spatial, temporal, and channel dimensions of the action sequence, thereby enhancing the model’s understanding of correlations and intricate structures among and within features. Drawing on the Transformer architecture, we propose the Cross-channel Spatio-temporal Aggregation (CSA) structure for more refined feature extraction and the Multi-Axis Attention (MAA) module for more comprehensive feature aggregation. Moreover, the integration of Rotary Position Embedding (RoPE) boosts the model’s extrapolation and generalization abilities. MAFormer surpasses the known state-of-the-art on multiple skeleton-based action recognition benchmarks with the accuracy of 93.2% on NTU RGB+D 60 cross-subject split, 89.9% on NTU RGB+D 120 cross-subject split, and 97.2% on N-UCLA, offering a novel paradigm for hierarchical modeling in human action recognition.