Effect Of Particle Aggregation Research Articles

Streamlined Analysis of Maternal Plasma Indicates Small Extracellular Vesicles are Significantly Elevated in Early-Onset Preeclampsia

Preeclampsia (PE) is a leading cause of maternal and fetal mortality and morbidity. While placental dysfunction is a core underlying issue, the pathogenesis of this disorder is thought to differ between early-onset (EOPE) and late-onset (LOPE) subtypes. As recent reports suggest that small extracellular vesicles (sEVs) contribute to the development of PE, we have compared systemic sEV concentrations between normotensive, EOPE, and LOPE pregnancies. To circumvent lengthy isolation techniques and intermediate filtration steps, a streamlined approach was developed to evaluate circulating plasma sEVs from maternal plasma. Polymer-based precipitation and purification were used to isolate total systemic circulating maternal sEVs, free from bias toward specific surface marker expression or extensive subpurification. Immediate Nanoparticle Tracking Analysis (NTA) of freshly isolated sEV samples afforded a comprehensive analysis that can be completed within hours, avoiding confounding freeze–thaw effects of particle aggregation and degradation.Rather than exosomal subpopulations, our findings indicate a significant elevation in the total number of circulating maternal sEVs in patients with EOPE. This streamlined approach also preserves sEV-bound protein and microRNA (miRNA) that can be used for potential biomarker analysis. This study is one of the first to demonstrate that maternal plasma sEVs harbor full-length hypoxia inducible factor 1 alpha (HIF-1α) protein, with EOPE sEVs carrying higher levels of HIF-1α compared to control sEVs. The detection of HIF-1α and its direct signaling partner microRNA-210 (miR-210) within systemic maternal sEVs lays the groundwork for identifying how sEV signaling contributes to the development of preeclampsia. When taken together, our quantitative and qualitative results provide compelling evidence to support the translational potential of streamlined sEV analysis for future use in the clinical management of patients with EOPE.

Solar-assisted photodegradation of pesticides over pellet-shaped TiO2-kaolin catalytic macrocomposites at semi-pilot-plant scale: Elucidation of photo-mechanisms and water matrix effect

The behavior of novel pellet-shaped bulky titania-kaolin photocatalysts is herein evaluated for its application in the solar-assisted photocatalytic treatment of a bio-recalcitrant pesticide mix (imidacloprid, pyrimethanil and methomyl) in solar lab-scale and semi-pilot scale raceway pond photoreactors. The photocatalyst consists of 1 cm long titania-kaolin macro-composites that combine some advantages of both nanoparticulate and supported catalysts without being either. This opening the opportunity to extend the use of this photocatalyst to complex wastewater effluents. In addition, their stability and reusability potential was also evaluated, and reactive species leading to the solar-degradation of each pesticide were also identified using radical scavengers. Total removal of pesticides (2 mg L−1 each) with an optimal pellets dosage of 34.8 g L−1 was addressed, whether in ultrapure water (180–270 min of solar irradiation) or in two basic pH Municipal Wastewater Treatment Plant (MWWTP) effluents (≤300 min of solar irradiation) where methomyl was always the most recalcitrant pesticide. Lower Total Organic Carbon (TOC) removal (≈53–56%) was also found under the effect of these complex MWWTP effluents than in ultrapure water (>60%). Those results are very promising when comparing to the almost negligible TOC removal achieved with the Titania powder under basic MWWTP effluents due to the strong effect of particle aggregation. Very good photocatalyst stability and durability was shown along three consecutive cycles after applying a low-cost recovery protocol consisting of several washing and drying cycles without addressing a significant photoefficiency loss (TOC≈60-56%). The application of scavengers revealed that hydroxyl radical generated from photoinduced holes was the dominant species in the degradation of pyrimethanil and methomyl whereas reactive oxygen species formed from conduction band electrons were mainly involved in the photo-oxidation of imidacloprid.

Magnetic coupling properties of multiple metal wear particles for high-precision electromagnetic debris detection applications

The electromagnetic wear particle detector is one of effective method to monitor wear debris in lubricating oil for assessing the wear condition of mechanical equipment. However, the motion of wear particles, especially the aggregation behavior in both fluid field and magnetic field, may make the particle detector generate false wear signals. Therefore, to estimate the impact on the detection accuracy of wear debris by the particle aggregation effect, the magnetic coupling model of multiple wear particles is established for studying the magnetic coupling effect between adjacent metal particles. The research results show that the effect changes the total magnetic energy variation induced by the particles and then affects the amplitude of particle signal. Meanwhile, the variation degree is closely associated with the frequency of magnetic field of particle detectors. Overall, the aggregation of wear particles with the same magnetic properties (both ferromagnetic or non-ferromagnetic) leads to false alarms of particle detectors; and the aggregation of wear particles with different magnetic properties causes missing alarms of particle detectors. Meanwhile, increasing the field frequency may increases the probability of missing alarm failure of particle detectors.

Intense green UCL in KAlF4:Ho3+ / Yb3+ nanoparticles for bioimaging applications

Fluorides host is more biocompatible for medical diagnostics and doping of trivalent rare earth ions help to produce efficient near-infrared to visible upconversion. Here we reported the KAlF4 upconversion nanocrystal doped with Ho3+/Yb3+ for the first time, which has been synthesized by precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, transmission electron microscopy (TEM) and Photoluminescence (PL) measurements were carried out to study the crystalline phase, morphology, upconversion luminescence (UCL) properties and surface area of nanocrystals. BET and SEM analysis show the effects of particle aggregation and average particle size found at around 42 nm. UCL properties were studied by using 980 nm laser excitation, where KAlF4:Ho3+/Yb3+ phosphor shows the intense green band at 540 nm. Thus, reported host may have the potential scope for bioimaging applications.

Particle Aggregation Effect on Electron Density Distribution and Propagation of Electron Avalanche

Particles will aggregate in the presence of dense mist in the wet electrostatic precipitator (WESP), and larger size particles with changed distribution make discharge more significant. This article puts forward the simulation of corona discharge with the existence of particle aggregation effect, which shows the characteristics of electron density distribution during the propagation. Besides, we also provide propagation patterns of branching and quenching phenomenon of plasma channels in the presence of particle aggregation. The results indicate that particle aggregation will considerably influence the plasma patterns. When the electron avalanche reaches the particle distributing areas, there will be several plasma channels formed and a narrow diffusion radius around the aggregated particles. When particles gather around the electrode, which means dense particle distribution, corona quenching happens with dense particle distribution.

Role of bacterial motility in differential resistance mechanisms of silver nanoparticles and silver ions.

Unlike conventional antimicrobials, the study of bacterial resistance to silver nanoparticles (AgNPs) remains in its infancy and the mechanism(s) through which it evolves are limited and inconclusive. The central question remains whether bacterial resistance is driven by the AgNPs, released Ag(I) ions or a combination of these and other factors. Here, we show a specific resistance in an Escherichia coli K-12 MG1655 strain to subinhibitory concentrations of AgNPs, and not Ag(I) ions, as indicated by a statistically significant greater-than-twofold increase in the minimum inhibitory concentration occurring after eight repeated passages that was maintained after the AgNPs were removed and reintroduced. Whole-population genome sequencing identified a cusS mutation associated with the heritable resistance that possibly increased silver ion efflux. Finally, we rule out the effect of particle aggregation on resistance and suggest that the mechanism of resistance may be enhanced or mediated by flagellum-based motility.

Computational investigation of dust settlement effect on power generation of three solar tracking photovoltaic modules using a modified angular losses coefficient

Providing a suitable method for predicting the effect of particle aggregation on photovoltaic (PV) performance can be one of the best ways to make better use of solar energy. In this study, a mathematical method was used and modified to provide a better prediction of angular losses coefficient (αr). The modified coefficient as well as a computational method were used to find the performance of dusty modules equipped with one-axis (East-West (EW), North-South (NS)), and dual-axis (DAT) solar tracking systems. The modified αr, which here is called the degree of surface dirtiness, can be used to estimate the area covered by particles per cm2, i.e. A∗C(θ). A better prediction of αr causes a better prediction of power loss due to dust settlement. Results showed that A∗C(θ) is the factor that shows the role of incidence angle in visualizing the type of dust cover, while αr shows the effect of slope angle on dust deposition density. Furthermore, combination of αr with the computational model revealed that the dirty DAT module has the least daily power loss which is 9% of the clean counterpart power. The power losses for the NS and EW dusty modules are 13% and 20.5% lower than the clean counterparts, respectively. It should be noted that the obtained results in this study are in a good compromise with the experimental and computational data available in the literature.

Adsorption and foaming properties of edible egg yolk peptide nanoparticles: Effect of particle aggregation

The adsorption and foaming properties of an edible colloidal nanoparticle (EYPNs), self-assembled from the food-derived, amphiphilic egg yolk peptides, were investigated, with the aim of evaluating their potential as efficient particulate stabilizers for development of aqueous food foams. The influence of particle aggregation induced by the changes of environmental conditions (mainly the pH) on these properties of EYPN systems was determined. Our results showed that the EYPNs are a highly pH-responsive system, showing the pH-dependent particle aggregation behavior, which is found to strongly affect the interfacial adsorption and macroscopic foaming behaviors of systems. Compared to high pH (6.0–9.0), the EYPNs at low pH (2.0–5.0) showed higher surface activity with a lower equilibrated surface tension as well as a higher packing density of particles and particle aggregates at the interface, probably due to the reduced electrostatic adsorption barrier. Accordingly, the EYPNs at these low pH values exhibited significantly higher foamability and foam stability. The presence of large particle clusters and/or aggregates formed at low pH in the continuous phase may contribute to the foam stability of EYPNs. These results indicate that our edible peptide-based nanoparticle EYPNs can be used as a new class of Pickering-type foam stabilizer for the design of food foams with controlled material properties, which may have sustainable applications in foods, cosmetics, and personal care products.

Particle Size Characterization in Liquid–Solid Dispersion With Aggregates by Broadband Ultrasound Attenuation

Ultrasound attenuation methods for particle size characterization generally assume that the dispersed phases are uniformly dispersed in the continuous phase. However, the aggregation of particles in dispersions affects ultrasound attenuation, which limits the estimation accuracy of the attenuation model. A broadband ultrasound method is proposed, which utilizes a fractal approach to address the acoustic attenuation influence of particle aggregation. First, a chirp-based swept-frequency mode is designed to demodulate the ultrasonic attenuation at a low time cost to ensure the consistency of multifrequency attenuation. Next, considering the effect of particle aggregation on attenuation, the ultrasound attenuation model based on Faran scattering theory is modified by the fractal approach. Then, the inversion of particle size characterization is formulated as an optimization problem of nonlinear and nonconvex functions. An iterative optimization method is proposed to solve the ill-posed inverse problem, in which covariance matrix adaptive evolutionary strategy (CMA-ES) is developed as its inverse solver, and the fractal modified attenuation model is developed as its forward solver. Finally, the experiments were carried out with a mixture of micron-sized polystyrene particles and water. Experimental results indicate that the attenuation predicted by the proposed attenuation model is in good agreement with that measured in liquid–solid dispersion with particle aggregation, and the effectiveness of CMA-ES based on multiple distribution functions is verified for the inversion of particle size characterization.

An experimental investigation on dynamic and mechanical characterization of olive pomace-filled glass/epoxy composite laminates

The waste of olive pomace (OP) particle filler was incorporated with glass fiber-reinforced composites (GFRP)/epoxy resin to manufacture OP particles-modified GFRP composites. Different weight ratios (0.5, 1, 2, 5, 10, and 15 wt%) of OP particles were incorporated within the common matrix of epoxy resin to investigate the effects of OP particles on tensile, flexural, and vibration damping properties on GFRP composites. In the mechanical tests, addition of OP filler contributed the significantly enhancement in tensile and flexural modulus, and samples at 5 wt% of OP filler showed highest flexural and tensile strength, while further addition of OP filler resulted in reduction of maximum elongation value at breaking point. In dynamic tests, it was found that damping ratios of the OP particles included samples were improved by 70% at OP content of 10 wt%, while first-mode natural frequency was reached optimum value at 5 wt% of OP particles, indicating better chemical compatibility at this weight content, and further incorporation of OP particles into the epoxy resin resulted in reduction for both of mechanical and dynamic properties as a result of particle aggregation effects between OP particles–epoxy resin–fiber interfaces.

Induction heating response of iron oxide nanoparticles in varyingly viscous mediums with prediction of brownian heating contribution

ABSTRACT This study examines the effects of nanoparticle concentration, magnetic field frequency, and carrier fluid viscosity on the induction heating response of nanofluids exposed to an alternating magnetic field. Uncapped iron-oxide nanoparticles with a mean diameter 14.42 nm were sonically dispersed into mixtures of deionized water and ethylene glycol (WEG) as well as highly viscous oil blends. The resulting nanofluids were exposed to an alternating magnetic field with a strength of 72.6 kA/m at frequencies of 217, 303, and 397 kHz with the heating response characterized calorimetrically through the specific absorption rate (SAR). Concentration and frequency effects mirror those found in literature with SAR reduction and enhancement, respectively. Additionally, SAR output is characterized across a wide range of viscosities showing a consistent decrease in heating output as viscosity increases through the WEG regime, however, the SAR was found to be relatively consistent across the oil blends. The effects of particle aggregation were measured through dynamic light scattering denoting particle clustering as a function of viscosity. Viscosity trends with SAR are accounted for by the viscous inhibition of particles reducing their Brownian heating, as well as clustering effects potentially inhibiting heat production in the low viscosity range where aggregation is pronounced. Lastly, a model predicting the Brownian contribution to heating as a function of frequency, concentration, and viscosity is proposed. This study provides a broad view of the effects on heating output for suspensions of commercially available iron oxide nanoparticles for several concentrations and field frequencies across an expansive range of viscosity.

Scattering of light by a large, densely packed agglomerate of small silica spheres.

We model the measured phase function and degree of linear polarization of a macroscopic agglomerate made of micrometer-scale silica spheres using the methodology of multiple scattering. In the laboratory work, the agglomerate is produced ballistically, characterized by scanning electron microscopy, and measured with the $ {\text{PROGRA}^{2}} $PROGRA2 instrument to obtain the light scattering properties. The model phase function and degree of polarization are in satisfactory agreement with the experimental data. To our best knowledge, this is the first time the degree of linear polarization has been modeled well for a large, densely packed agglomerate composed of small particles with known sizes and shapes. The study emphasizes the relevance of the degree of linear polarization and gives insights into the effects of particle aggregation on the scattering characteristics.

Effect of particle aggregation on thermal conductivity of nanofluids: Enhancement of phonon MFP

Particle aggregation in nanofluids is a common phenomenon. Some studies indicated that aggregation can increase the thermal conductivity of nanofluids due to the formation of an “efficient heat channel,” while the underlying mechanism is still unclear. In this study, an effective medium model considering phonon scattering is applied to explore the effect of particle aggregation on nanofluid thermal conductivity. The aggregation is simulated by a diffusion-limit-cluster-aggregation model, where the effects of nanoparticle size, concentration, and number in a cluster on the aggregation structure are studied. Results show that nanoparticle aggregation can dramatically increase the thermal conductivity of nanofluids, and aggregation puts up stronger effects for the case of smaller nanoparticles and lower concentrations. The main mechanism is that the aggregation raises the phonon MFP in the solid phase, which further results in the thermal conductivity enhancement of nanoparticles.

Surface-enhanced Raman scattering enhancement due to localized surface plasmon resonance coupling between metallic nanoparticles and substrate

In this study, gold nanostructures (AuNSs) and silver nanoparticles (AgNPs) were integrated with a silver micro-flower-like structure deposited on a screen-printed carbon electrode (AgMF-SPCE) for enhancing surface-enhanced Raman scattering (SERS) by using 4-mercaptobenzoic acid (4-MBA) as a Raman reporter. SERS was enhanced by approximately 3.6–52.1-fold, depending on the frequency of the incident laser, the localized surface plasmon resonance frequency of metallic NPs, and particle–particle aggregation effects. Compared with AgNP/SPCE and AgMF-SPCE substrates, the AgNP/AgMF-SPCE substrate showed high temperature tolerance and long-term durability. Furthermore, the proposed substrates easily obtained hot spots for other Raman reporters such as 4-aminothiophenol, 5,5′-dithiobis-2-nitrobenzoic acid, and 4-chlorothiophenol. A linear relationship was found between the Raman signal and the concentration of Raman reporters in the range 10 nM–100 μM, with the limit of detection in the range of 6.19–77.2 nM at a signal-to-noise ratio of 3.0. These results suggest that the AgNP/AgMF-SPCE substrate will be well suited for quantitative analysis.

Effects of magnetic field strength and particle aggregation on relaxivity of ultra-small dual contrast iron oxide nanoparticles

This study aims to compare the relaxivities of ultra-small dual positive and negative contrast iron oxide nanoparticles (DCION) at different magnetic field strengths ranging from 4.7 to 16.4 T at physiological temperatures; and to investigate the effect of particle aggregation on relaxivities. Relaxivities of DCIONs were determined by magnetic resonance imaging scanners at 4.7, 7, 9.4, and 16.4 T. Both longitudinal (T1) and transverse relaxation times (T2) were measured by appropriate spin-echo sequences. It has been found that both longitudinal and transverse relaxivities are significantly dependent on the magnetic field strength. Particle aggregation also strongly affects the relaxivities. Awareness of the field strength and particle colloid stability is crucial for the comparison and evaluation of relaxivity values of these ultra-small iron oxide nanoparticles, and also for their medical applications as contrast agents.

The effects of nanoparticle aggregation on the convection heat transfer investigated by a combined NDDM and DPM method

ABSTRACTIn this study, convective heat transfer of Al2O3-water nanofluids (NFs) of various concentrations under laminar flow in a horizontal circular tube with and without considering particle aggregation was numerically investigated by a combined nanoparticle diameter distribution model (NDDM) with the Discrete Phase Model (DPM). Heat transfer coefficient (h), temperature distribution in axial and radial direction, and pressure drop (ΔP) were studied. It turns out that beside a slight pressure drop, heat transfer near the wall will significantly deteriorate when particle aggregation occurs. With an increase in Re numbers, the effects of particle aggregation on the heat transfer performance of the fluid will decrease.

Optical Simulations of Self-assembly Relevant Gold Aggregates: A Comparative Study

In this study, visible light extinction spectra of different gold nanoparticle assemblies were simulated using boundary element method (BEM) in order to investigate the optical properties of structures which determine the experimentally measured spectra during the self-assembly of the particles. Numerous different optically dominant particle arrangements can evolve depending on the underlying physicochemical mechanism of the clustering process itself: one-dimensional chains, two-dimensional arrays or three-dimensional clusters can be formed in the solutions or at interfaces. Experimentally the aggregation or clustering of gold nanoparticles can be conveniently followed by spectroscopic techniques due to the plasmon coupling related profound effect of particle aggregation on the visible extinction spectrum. However, the measured spectra usually contain the optical response of various aggregate structures. Additionally, small changes of the interparticle distance can have a significant impact on the frequency of the coupled mode. In order to assess the contribution of the different structures to the experimentally measurable extinction spectra during particle clustering, different model structures (chains, array and 3D-cluster) have been simulated, where the distance between the particles was varied as well.

Choice of appropriate aggregation radius for the descriptions of different properties of the nanofluids

Nanofluids with suspensions containing nanoparticles, have been considered to have great potential in the application of energy conversion, chemical technology or heat transfer enhancement. Due to the high surface energy, nanoparticles in nanofluid tend to form large secondary aggregates. The aggregation and the size increase could lead to significant change in various physical properties of the suspension. It is well known that many kinds of equivalent radii can be potentially employed in the description of the particle aggregates, such as hydrodynamic radius (Rh), gyration radius (Rg) and smallest sphere enclosing radius (Rs) etc. However, in most of previous study, only hydrodynamic radius was used to study the effect of the aggregation on the properties of the nanofluids. Systematic study on the appropriate choice of the equivalent radii for the description of the different properties of the nanofluids, is rare. In this study, the three representative equivalent radii of nanoparticle aggregates, Rh, Rg and Rs, were studied. It was found that for both diffusion limited cluster–cluster aggregation (DLCA) and reaction limited cluster–cluster aggregation (RLCA), the general sequence is Rh<Rg<Rs. The three equivalent radii were correlated with each other by Monte Carlo method using an off-lattice cluster–cluster aggregation algorithm. The relationship is useful because hydrodynamic radius can be obtained experimentally from light scattering technique, while the other two are difficult to obtain experimentally. In our study, based on hydrodynamic radius obtained by DLS method, the other two equivalent radii were successfully obtained based on the proposed relationship. By comparing the experimental results with theoretical prediction, it was found that Rh, Rg and Rs showed the better accuracy when predicting viscosity, thermal conductivity and absorption coefficient, respectively. Based on these findings, in the last part, we propose a criterion for the choice of appropriate aggregation radii in predicting different physical properties of nanofluid. Our study is expected to provide a valuable guidance for the study of the effect of particle aggregation on the various properties of the nanofluids.

Evaluation of the Flow Behavior in a Large-Scale Polydisperse Particle Fluidized System by an Energy Minimization Multiscale-Eulerian Combined Model

The Eulerian–Eulerian model with kinetic theory of granular flow was applied to evaluate the gas–solid flow behavior in a large-scale polydisperse fluidized system for polysilicon chemical vapor deposition growth. The uniform particle system was well validated on the basis of the empirical correlations and experimental data after parametric analysis on drag force, particle–particle collision, and wall boundary condition, and furthermore the fluidization quality in the polydisperse system by the validated computational fluid dynamics model was basically the same as that in the uniform one. The results showed that the energy minimization multiscale-based drag model had remarkable advantages in the prediction of the “core-annular” flow structure and mesoscale flow characteristics in a large-diameter fluidized bed, as compared to the Gidaspow model. Moreover, effects of particle aggregation and the fluidization ratio on solid distribution in the polydisperse system were also investigated, revealing an accumul...

Integration of host strain bioengineering and bioprocess development using ultra-scale down studies to select the optimum combination: an antibody fragment primary recovery case study.

An ultra scale-down primary recovery sequence was established for a platform E. coli Fab production process. It was used to evaluate the process robustness of various bioengineered strains. Centrifugal discharge in the initial dewatering stage was determined to be the major cause of cell breakage. The ability of cells to resist breakage was dependant on a combination of factors including host strain, vector, and fermentation strategy. Periplasmic extraction studies were conducted in shake flasks and it was demonstrated that key performance parameters such as Fab titre and nucleic acid concentrations were mimicked. The shake flask system also captured particle aggregation effects seen in a large scale stirred vessel, reproducing the fine particle size distribution that impacts the final centrifugal clarification stage. The use of scale-down primary recovery process sequences can be used to screen a larger number of engineered strains. This can lead to closer integration with and better feedback between strain development, fermentation development, and primary recovery studies. Biotechnol. Bioeng. 2014;111: 1971–1981. © 2014 Wiley Periodicals, Inc.