Aggregation Behavior Research Articles

A perspective on the algae-derived dissolved organic matter and its dynamic influence on the aggregation of nanoplastics in eutrophic waters

The aggregation behavior of nanoplastics (NPs) is crucial in determining their fate in aquatic environments. Dissolved organic matter (DOM), characterized by its complex molecular structure and diverse functional groups, can spontaneously absorb on the surface of NPs, thus altering their colloidal stability. In eutrophic waters, DOM primarily originates from metabolic byproducts released by phytoplankton, and its molecular composition and hydrophilic properties change dynamically as the progression of algal blooms. This perspective aims to summarize the heterogeneity of DOM during the initiation, outbreak and recession of algal blooms. And we investigate the influence of molecular-level variations in DOM composition on the aggregation behavior of NPs. Additionally, this study provides insights into the underlying mechanisms relating to the interactions between DOM and NPs. Ultimately, it tackles the challenges and future directions, highlighting the necessity for comprehensive studies to understand the fate of NPs in eutrophic waters.

Effect of Froth on the Interaction Between Coal Particles and Cake Structures in the Dewatering Process of Clean Coal

Effective coal slurry water solid–liquid separation is indispensable for the recycling and sustainable development of coal resources. The interaction between bubble and coal particles plays a critical role in the process of dewatering for clean coal. In this study, we firstly conducted a comprehensive investigation of the impact of froth on the interactions between coal particles by rheological measurement and particle aggregation behavior. Furthermore, the macroscopic dewatering performance of coal slurry in the presence of froth and its microscopic cake structure were investigated using the filtration test and X-ray microtomography (CT). It was found that the interaction between coal particles in the presence of froth was enhanced as a result of the dynamic shear value, combined with the large floc size and compact structure, which led to a higher cake moisture and higher filtration velocity. The CT results indicated that the enhanced interaction of particles in the presence of froth also led to a dense microstructure of the filter cake. The porosity of the filter cake decreased to 2.05% when the aeration time increased from 0 s to 90 s, the throat radius in the filter cake was reduced to 1.32 μm, and the number of throat passages was reduced to one third. Multiple blind pores and low coordination numbers led to a poor connectivity of the pore network and high moisture content.

Linear and Nonlinear Rheological Investigations of Poly(3-hexylthiophene) H-Aggregated Gel Networks.

Owing to its facile synthesis and low cost, poly(3-hexylthiophene) (P3HT) has been extensively investigated in the field of organic electronics. Well-defined packing of P3HT chains and getting controlled morphologies, which solely depend on the polarity of the solvent, remain challenging. Herein, the aggregation behaviors of P3HT in organic solvents having different solvent polarities have been investigated to achieve different orderings of P3HT chains (H-type or J-type). The aggregation in the solution phase and the subsequent structural as well as morphological behaviors of P3HT chains have been investigated by absorption, X-ray powder diffraction, and topological studies, respectively. It has been noticed from absorption studies that P3HT forms H-type aggregates in anisole, phenetole, etc., whereas it produces J-type aggregates in toluene. More surprisingly, H-type aggregations of P3HT chains at low concentrations (CP3HT = 0.001 g/cm3) eventually lead to the formation of the gel network that ceases the flow of the solvents. Contrary to expectations, J-type aggregation in toluene does not produce the gel network at the said concentration. Further, to reveal the viscoelastic and microstructural properties, P3HT gel networks have been thoroughly investigated by small-amplitude oscillatory shear (SAOS) and large-amplitude oscillatory shear (LAOS) with varying concentrations, solvents, and molecular weights of P3HT. With quantitative analysis, the nonlinear rheological characteristics of higher harmonics, strain-stiffening ratio, shear-thinning ratio, dissipation ratio, intracycle transient moduli, and derivative of transient moduli have been evaluated for P3HT networks, which significantly provide the rheological information for the understanding of conducting polymer networks.

Abelmoschus manihot gum improves the water retention capacity of low-salt myofibrillar protein gels: Perspective on aggregation behaviour and conformational changes during heating

This study aimed to investigate the effect of Abelmoschus manihot gum (AMG) on the water retention capacity of low-salt myofibrillar protein (MP) gel by analysing its aggregation behaviour and conformational changes during heating (30–80 °C). The results revealed that AMG significantly increased the water holding capacity and facilitated the formation of a more uniform gel network structure in low-salt MP gel (P < 0.05). During the heat-induced gelation process, the solubility of low-salt MP significantly decreased, whereas its turbidity evidently increased as the level of added AMG increased (P < 0.05). Furthermore, the dynamic rheological behaviours indicated that low-salt MP-AMG gels underwent early denaturation and unfolded at 58 °C, finally forming an irreversible three-dimensional network at 80 °C. Moreover, adding AMG promoted α-helix-to-β-sheet transition in low-salt MP and decreased its fluorescence intensity during the heating process. Hydrophobic interactions and disulfide bonds were the two dominant forces governing the formation and maintenance of low-salt MP gel. The present study provides theoretical guidance for the production of novel low-salt healthy meat products.

Aggregation unveiled: A sequential modelling approach to bark beetle outbreaks

Tree-killing bark beetle infestations are a cause of massive coniferous forest mortality impacting forest ecosystems and the ecosystem services they provide. Models predicting bark beetle outbreaks are crucial for forest management and conservation, necessitating studies of the effect of epidemiological traits on the probability and severity of outbreaks. Due to the aggregation behaviour of beetles and host tree defence, this epidemiological interaction is highly non-linear and outbreak behaviour remains poorly understood, motivating questions about when an outbreak can occur, what determines outbreak severity, and how aggregation behaviour modulates these quantities. Here, we apply the principle of distributed delays to create a novel and mathematically tractable model for beetle aggregation in an epidemiological framework. We derive the critical outbreak threshold for the beetle emergence rate, which is a quantity analogous to the basic reproductive ratio, R0, for epidemics. Beetle aggregation qualitatively impacts outbreak potential from depending on the emergence rate alone in the absence of aggregation to depending on both emergence rate and initial beetle density when aggregation is required. Finally, we use a stochastic model to confirm that our deterministic model predictions are robust in finite populations.

Effects of interaction between wheat bran dietary fiber and gluten protein on gluten protein aggregation behavior.

Effects of wheat bran dietary fiber (WBDF) as a nutritional additive on flour products quality mainly depends on the interaction between WBDF and gluten protein. In this study, the effects and mechanisms of WBDF with different particle sizes and additive amounts on gluten protein aggregation behavior were investigated. The results showed that the addition of WBDF led to a decrease in free sulfhydryl content, particle size, molecular weight and gluten macromer (GMP) content, an increase in zeta potential and SDS-extractable protein content, and a deterioration in the gluten network morphology compared to the control group, suggesting that the aggregation behavior of gluten protein was inhibited. When WBDF was added at 3 % and 6 %, dilution effect, mechanical shear, steric hindrance, and non-covalent binding were the main mechanisms leading to depolymerization. Further addition of WBDF (9 %, 12 %) inhibited the depolymerization of gluten protein due to competitive hydration and non-covalent binding. However, when WBDF was added at 15 %, the dilution effect, mechanical shear and steric hindrance of WBDF (88 μm < particle size<150 μm) dominated, and their inhibitory of aggregation induced the formation of a loose gluten network structure. In contrast, the weaker mechanical shear and steric hindrance effects of WBDF (particle size<88 μm) mitigated the degradation of gluten network structures by WBDF.

Thermodynamics study and micellization behavior of surface active ionic liquid choline oleate in presence and absence of naproxen drug in alcoholic media at different temperatures: A conductometric and physicochemical analysis

Surface active ionic liquids (SAILs) have attracted significant interest as promising substitutes for conventionally available surfactants owing to their exceptionally favorable physicochemical features. Herein, the aggregation behavior of SAIL choline oleate (SAIL[Cho][Ole]) in the presence and absence of naproxen (NAP) drug and its interaction with alcohol such as methanol, ethanol, 2-propanol and 1-butanol at different concentrations and temperatures have been investigated by conductivity method. For alcohol-water systems at a fixed temperature, the critical micelle concentration (CMC) at a specific temperature was found to increase in the presence of alcoholic media. Finally, numerous thermodynamic parameters like standard Gibbs free energy of micellization (), standard enthalpy (), and standard entropy of micellization () were calculated as well as explained thoroughly. The obtained negative values of and indicate that micellization is spontaneous and exothermic, respectively. The molar heat capacity ( was also evaluated as well as explained.

Effects of Silicon Concentration and Synthesis Duration on Lignin Structure: A Spectroscopic and Microscopic Study.

Silicon (Si) is a highly abundant mineral in Earth's crust. It plays a vital role in plant growth, providing mechanical support, enhancing grain yield, facilitating mineral nutrition, and aiding stress response mechanisms. The intricate relationship between silicification and lignin chemistry significantly impacts cell wall structure. Yet, the precise influence of Si on lignin synthesis remains elusive. This study investigated the interaction between Si and lignin model compounds during invitro synthesis. Employing spectroscopic and microscopic analyses, we delineated how Si concentrations modulate lignin polymerization dynamics, particularly affecting molecular conformation and aggregation behavior over time. Fluctuations in the polymer structure are directly related to both the synthesis time and the concentration of silica. Our results demonstrate that lower Si concentrations promote the aggregation of lignin oligomers into larger particles, while higher concentrations increase the possibility of oligomer repulsion, thus preventing particle growth. These findings elucidate the intricate interplay between Si and lignin, which is crucial for understanding plant cell wall structure and stress resilience. Moreover, the results provide insights for developing lignin-silica materials with increasing applications in industry and medicine.

Enhancing the efficiency of novel PCNF demulsifier for oil-contaminated wastewater treatment through numerical simulation optimization of demulsification mechanism

This study used COMSOL simulation software to simulate the aggregation behavior of oil droplets under the action of a direct current electric field. Moreover, in-depth research was conducted on the aggregation process of oil droplets and the dynamic changes of the water oil micro interface. Research has found that the interfacial tension between water and oil is an important factor affecting the deformation of oil droplets. In this work, a new type of magnetic demulsifier (PCNF) was prepared using nano-Fe3O4 as the condensed core, sodium carboxymethyl cellulose (CMC-Na) as the binder, and polyferric sulfate (PFS), and this demulsifier was coupled with an electroflocculation process. The results indicate that the addition of PCNF can effectively reduce the interfacial tension between water and oil, promoting the demulsification process. Compared with traditional flocculants, the combination of electrochemical action and the optimal 2 g/L PCNF dosage provides higher purification efficiency. By introducing calcium chloride, the dosage of PCNF can be reduced. When the dosage is adjusted to 1.5 g PCNF + 0.5 g calcium chloride, the electrolysis time can be shortened from 180 min to 90 min. Under these treatment conditions, the COD in the emulsified oil wastewater is reduced to 46 mg/L and the oil content is reduced to 5.08 mg/L. Economic calculations show that compared to using PCNF alone, this reduction method can reduce operating costs by 39.83 %. This strategy achieves efficient demulsification and oil removal, lowers economic costs, and provides a solid foundation for guiding the development of practical technology.

Unveiling the chemical and behavioural ecology of Tribolium castaneum (Herbst, 1797) in wheat flour: Alterations in flour metabolic content and the role of chemical cues in modulating beetles' behaviour and regulating population growth

Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae) is a notorious secondary pest of stored grains and flours, accounting for 10–15% of global annual losses in stored products. This study first evaluated the impact of T. castaneum infestation on the nutritional parameters of stored wheat flour. Infested flour exhibited reductions in total soluble sugars, triacylglycerol levels, and unsaturated fatty acids, particularly Oleic and Linoleic acid, while secondary metabolites such as phenolics, flavonoids, and tannins were increased. Behavioural assays revealed that adult beetles were significantly more attracted towards infested flour odour due to the presence of 4,8-Dimethyldecanal (4,8-DMD), an aggregation pheromone of T. castaneum. Another key compound in infested flour, 1-Pentadecene, derived from the beetles' cuticular wax, was found to influence adult beetle behaviour. At higher concentrations, 1-Pentadecene acted as a repellent for the species. Molecular docking studies suggested that 1-Pentadecene competes with 4,8-DMD for binding to the odorant receptor TcOR1, which could potentially inhibit aggregation behaviour and reduce population growth. The docking analysis revealed that 1-Pentadecene interacts with the same binding pocket on TcOR1, sharing key amino acids (MET49, PHE69, THR72, GLN73, THR134, VAL135, TYR138, LEU154, ILE177, GLY180, ALA181, TYR286) and forming similar intermolecular bonds, such as a pi-alkyl bond, with a binding affinity (ΔG = −5.7) comparable to 4,8-DMD (ΔG = −5.8). Additionally, beetles reared in wheat flour containing higher concentrations of 1-Pentadecene exhibited lower population growth compared to those reared in flour with lower concentrations of this compound.

Breakage dynamics and scaling of wet aggregates of rigid particles

The mechanical behaviour of wet particle aggregates is crucial in many granular processes such as wet granulation and soil degradation. However, the interplay of capillary and viscous forces for aggregate stability and breakage have remained elusive due to the complexity of granular dynamics. We use particle dynamics simulations to analyse the deformation and breakage of wet aggregates colliding with a flat wall. The aggregates are composed of spherical particles and the effect of liquid bonds is modelled through capillary and lubrication forces acting between particles. We perform an extensive parametric study by varying surface tension, impact velocity and liquid viscosity in a broad range of values. We show that when lubrication force is neglected, aggregate breakage is fully controlled by the reduced kinetic energy $\xi$ , defined as the ratio of incident kinetic energy to the initial capillary energy. At low values of $\xi$ , the aggregate deforms without breakage due to inelastic energy loss induced by rearrangements and loss of capillary bonds, whereas above a critical value of $\xi$ it breaks into smaller aggregates due to the transfer of kinetic energy from aggregate to fragments. In the presence of lubrication forces, the crossover from capillary to viscous regime is controlled by the capillary number, defined as the ratio of viscous dissipation to capillary energy. We find that the critical value of $\xi$ for aggregate breakage in the viscous regime increases as a power law with capillary number while the effective restitution coefficient follows the same trend as in the capillary regime.

Formation of dimer and higher aggregates of methylene blue in alcohol

This study investigates MB aggregation in propanol, ethanol, butanol, and methanol using UV–Visible, steady-state, and time-resolved fluorescence spectroscopy at room temperature. This work reveals the presence of monomers, dimers, and higher aggregates across various concentrations, affecting both the absorption spectra and fluorescence intensity. Characteristic peaks for monomeric, dimeric, and higher aggregates of MB are identified, with shifts in emission peak intensity and lifetime as a function of concentration, solvent polarity, and viscosity. A strong correlation between fluorescence lifetime and solvent properties, such as dielectric constant and viscosity, suggests that solvent polarity and viscosity significantly influence the stabilization of excited states and the deactivation dynamics of methylene blue. The critical concentration for MB aggregation is identified for each solvent and is found to be higher in solvents with a greater dielectric constant, likely due to Van der Waals forces dominating over Coulombic interactions in the aggregation process. The findings indicate that MB aggregation in alcohols differs from that in aqueous solutions, underscoring the importance of the solvent environment in MB’s aggregation and fluorescence behavior, with implications for optimizing its use in laser and photomedicine applications.

Fine‐Tuning Thickness‐Dependent Molecular Aggregation for Enhanced Performance in Semitransparent Organic Photovoltaics

Semitransparent organic photovoltaics (ST‐OPV) exhibit tremendous potential for application in integrated photovoltaic architecture. The reduction of the ratio of wide‐bandgap donors in the active layer is crucial for enhancing both the power conversion efficiency (PCE) and the average visible light transmittance (AVT), which are key performance indicators for ST‐OPV. Herein, successful suppression of the thickness‐dependent transition from H‐aggregates to J‐aggregates in PM6 films was achieved through temperature control, significantly improving charge transport and extraction efficiency, thereby markedly enhancing the PCE of sequential processed pseudo p‐i‐n devices employing the Y6 acceptor. With ≈30% AVT maintained, the PCE increases from 6.50% to 11.10%, while the light utilization efficiency rises from 1.98% to 3.40%. Unlike previous studies primarily focused on optical coupling structure design, this research underscores the precise control of molecular aggregation behavior in the active layer material, demonstrating the innovativeness of material and structural design and offering new avenues and methodologies for the development of future semitransparent photovoltaic materials.

Side Chain Phenyl Isomerization-Induced Spatial Conjugation for Achieving Efficient Near-Infrared II Phototheranostic Agents.

The contradiction of near-infrared II (NIR-II) emission and photothermal effects limits the development of phototheranostic agents (PTAs) in many emerging cutting-edge applications. Organic aggregates present a promising opportunity for the balance of competitive relaxation processes through the manipulation of molecular structure and packing. Herein, side chain phenyl isomerization-induced spatial conjugation was proposed for constructing A-D-A type NIR-II PTAs with simultaneous enhancement of fluorescence brightness and photothermal properties. Three pairs of mutually isomeric fluorophores, whose phenyls respectively located at the outside (o-series) and inside (i-series) of the side chain, were designed and synthesized. The positional isomerization of the phenyl endows the o-series crystals with strong spatial conjugation between the phenyl group on the side chain and the backbone, as well as interlocked planar network, which is different to that observed in the i-series. Thus, all o-series nanoparticles (NPs) exhibit red-shifted absorption, enhanced NIR-II emission, and superior photothermal properties than their i-series counterparts. A prominent member of the o-series, o-ITNP NPs, demonstrated efficacy in facilitating NIR-II angiography, tumor localization, and NIR-II imaging-guided tumor photothermal therapy. The success of this side chain phenyl isomerization strategy paves the way for precise control of the aggregation behavior and for further development of efficient NIR-II PTAs.

Side Chain Phenyl Isomerization‐Induced Spatial Conjugation for Achieving Efficient Near‐Infrared II Phototheranostic Agents

AbstractThe contradiction of near‐infrared II (NIR‐II) emission and photothermal effects limits the development of phototheranostic agents (PTAs) in many emerging cutting‐edge applications. Organic aggregates present a promising opportunity for the balance of competitive relaxation processes through the manipulation of molecular structure and packing. Herein, side chain phenyl isomerization‐induced spatial conjugation was proposed for constructing A‐D‐A type NIR‐II PTAs with simultaneous enhancement of fluorescence brightness and photothermal properties. Three pairs of mutually isomeric fluorophores, whose phenyls respectively located at the outside (o‐series) and inside (i‐series) of the side chain, were designed and synthesized. The positional isomerization of the phenyl endows the o‐series crystals with strong spatial conjugation between the phenyl group on the side chain and the backbone, as well as interlocked planar network, which is different to that observed in the i‐series. Thus, all o‐series nanoparticles (NPs) exhibit red‐shifted absorption, enhanced NIR‐II emission, and superior photothermal properties than their i‐series counterparts. A prominent member of the o‐series, o‐ITNP NPs, demonstrated efficacy in facilitating NIR‐II angiography, tumor localization, and NIR‐II imaging‐guided tumor photothermal therapy. The success of this side chain phenyl isomerization strategy paves the way for precise control of the aggregation behavior and for further development of efficient NIR‐II PTAs.

Numerical study of the dynamic aggregation behaviors of oil droplets in the porous filter media consisting of basalt particles

Porous granular media based on the gravity-driven principle have been proven to be efficient for the separation of oil-water emulsions. However, the complexity of the relevant parameters and the intricate structure of porous media pose great challenges to the design and optimization of the separation process. In this study, the dynamic behavior of oil droplets within the porous structure was numerically analyzed based on the Euler-Euler model and the coupling of the two-phase flow and level set method. The oil-water separation efficiency and droplet trajectory were analyzed under different conditions, considering the deformation of the droplets, kinetic viscosity, and interactions among the droplets. The simulation results show the real-time movement, aggregation, and detachment of oil droplets within the porous filter. The results are useful for understanding the demulsification in a microscopic perspective and provide theoretical guidance for designing more efficient oil-water separation systems.

Particle-stabilized foams with fatty acid salts as stabilizers triggered by transition metal ions

Particle-stabilized foams have been becoming the focus on foaming field because of their excellent stability due to the high stiffness of interface membrane. However, the modification of particle surfaces to reach an appropriate wettability needs complicated process, resulting in accompanied inconvenient foaming-defoaming regulation. In this work, we reported a series of foams stabilized by insoluble particles generated from fatty acid anions with metal ions. Different hydrocarbon chains endowed the formed particles diverse wettability and different aggregation behaviors at the gas–liquid interface, e.g., different foamability and the formation of the “dry water”. The foams exhibited ultra-stable properties and were responsive to environmental acidity, thus possessing a smart foaming-defoaming transition tuned by pH. The combination ability of fatty acid anions with metal ions changed with the chain-length and the nature of metal ions, leading to a choice for the extraction or separation of some metal ions in a fast and simple way. This new aggregation behavior of fatty acid salts can be explored to expand the practical applications.

Flock size does not influence escape decisions of urban lawn-foraging birds

Context Predator avoidance is considered a key evolutionary driver shaping aggregation behavior. An overlooked aspect in the study of predator avoidance is whether individuals can make better escape decisions (i.e. gain greater benefits) when in larger groups. Escape decisions encompass when to flee (FID: the distance at which an animal moves away from approaching threats), how far to flee (distance fled, DF), flight direction (FD) and whether to seek refuge. Aim This study evaluates the influence of flock size on the FID, DF and FD in urban birds. Methods We studied a series of escape behaviors of eight urban lawn-foraging bird species in Huaibei city, China, approached by one, two or three persons representing varying levels of predation risk. Key results We found that flock size had a limited effect on birds’ escape decisions, including FID, DF, FD and refuge-seeking behavior, with some species-specific effects. Predation risk (number of approachers) also had a subtle influence on birds’ escape decisions. Conclusions Urban birds generally exhibit consistent escape behavior regardless of flock size or predation risk. Implications Urban birds might maintain a minimum antipredator response to approaching humans due to their extensive habituation to human occurrence. Future research should examine how urban birds’ responses to humans compare with their reactions to natural predators, and investigate the varying impacts of urbanization on these behaviors.

Effects of material and structure types on drifting speed of fish aggregation devices (FADs) in tuna purse seine fishery

The drifting speed and trajectory of fish aggregation devices (FADs) influence tuna aggregation behavior. Based on expertise, fishermen modify FAD structures to slow down drifting speed, but few studies quantify material and structure effects on this speed. To address this, 14 different types of FAD models were tested under 5 different current velocities in a flume tank and compared drifting using pairwise Wilcoxon tests. Results indicate that 1) FAD models covered with netting exhibited higher drifting speeds than the others. 2) It is feasible that replacing the netting bundle with the cotton rope of the same diameter for constructing submerged structure effectively slows down the drifting speeds of FADs. 3) Additionally, FAD models with a floating structure aspect ratio close to 1 exhibited slower drifting speeds compared to other designs when the submerged structure is the same.

Cotransport of fullerene nanoparticles and clay colloids in porous media: The relation between aggregation and transport

In the study, cotransport of fullerene nanoparticles (nC60) and mobile clay colloids (illite (ILL), kaolinite (KL), montmorillonite (ML)) in aquifer porous media and its relation to the aggregative interaction between these two types of particles was investigated. Minimal interaction occurred between nC60 and ILL, resulting in unaffected transport. Strong heteroaggregation between ML and nC60 resulted in not only significant retention of both particles during their cotransport but also the retention of nC60 in the media pre-injected with ML. Strong homoaggregation of KL caused strong straining effect and consequently retention of both KL and nC60 during their cotransport, however, the pre-emplacement of KL did not cause retention of nC60 during the sequential injection of KL and nC60. Such aggregation behaviors were well demonstrated by the adsorption-sedimentation experiment, microscopic observation, the size and zeta-potential test, and model simulation. Based on the surface chemistry analysis, divalent-cation bridging between ML and nC60 and hydrogen bonding between KL particles were responsible for the heteroaggregation and the homoaggregation, respectively. The study demonstrated the specificity of the aggregation between the mobile clays and nC60 to the chemistry of the clays and its consequent effect on the cotransport of the particles, which is critical for assessment of the environmental risk of nC60.