Volume-weighted Mean Size Research Articles

A Production and Fractionation Protocol for Polyvinyl Chloride Microplastics

Concerns about the presence of microplastics in the environment has increased in recent years, prompting more attention from scientists. Thorough exposure studies using artificially produced microplastics containing additives are required to assess their potentially hazardous effects. Therefore, an efficient microplastic production and fractionation protocol was established using a cryogenic grinding and wet-sieving approach. The developed cryogenic grinding method was able to produce (20-40 g/h) polyvinyl chloride (PVC) microplastics having a volume-weighted mean particle size of 391 µm and a span of 2.12. Performing a second grinding cycle on the same particles resulted in microplastics which were smaller (volume-weighted mean size = 219 μm) and had a narrower particle size distribution (span = 1.59). In addition, the microplastics were also fractionated into different particle size ranges using a vibrating wet-sieving tower. The latter technique allowed separating 10 g of PVC microplastics into seven different fractions using six sieves (Ø 200 mm) for 30 min while shaking. By using the developed method, PVC microplastics could easily be made and fractionated into desired particle-size ranges. The proposed protocol could also be adjusted to produce and fractionate microplastics of other plastics.

Magnetic nanoparticles of Ga‐substituted ε‐Fe2O3 for biomedical applications: Magnetic properties, transverse relaxivity, and effects of silica‐coated particles on cytoskeletal networks

Magnetic nanoparticles of ε-Fe1.76 Ga0.24 O3 with the volume-weighted mean size of 17 nm were prepared by thermal treatment of a mesoporous silica template impregnated with metal nitrates and were coated with silica shell of four different thicknesses in the range 6-24 nm. The bare particles exhibited higher magnetization than the undoped compound, 22.4 Am2 kg-1 at 300 K, and were characterized by blocked state with the coercivity of 1.2 T at 300 K, being thus the very opposite of superparamagnetic iron oxides. The relaxometric study of the silica-coated samples at 0.47 T revealed promising properties for MRI, specifically, transverse relaxivity of 89-168 s-1 mmol(f.u.)-1 L depending on the shell thickness was observed. We investigated the effects of the silica-coated nanoparticles on human A549 and MCF-7 cells. Cell viability, proliferation, cell cycle distribution, and the arrangement of actin cytoskeleton were assessed, as well as formation and maturation of focal adhesions. Our study revealed that high concentrations of silica-coated particles with larger shell thicknesses of 16-24 nm interfere with the actin cytoskeletal networks, inducing thus morphological changes. Consequently, the focal adhesion areas were significantly decreased, resulting in impaired cell adhesion.

Application of vacuum membrane distillation for small scale drinking water production

This study evaluated the applicability of a modified design vacuum enhanced-multi effect membrane distillation (V-MEMD) for drinking water production with feed solution containing NaCl and CaSO4. The applicability was studied in terms of flux, scale formation and ease of cleaning. A slight flux decline (18–20%) was observed with loosely deposited crystals in the membrane module during the 920min of the operation. Larger formation of crystal (volume weighted mean size, D[4,3]) was observed in the final feed brine (D[4,3]brine feed=455.96μm) compared to that inside the module (D[4,3]brine module=62.68μm). The loose crystal deposition was attributed to the absence of hydraulic pressure, low feed temperature, high turbulence (Re=5665.6) and short membrane retention time (21.6s). The crystal formation in the membrane module, D[4,3]brine module increased with reduced permeate side vacuum and lower feed velocity. Periodic DI water flushing was found to be efficient to remove the scaling. The feed component mass balance showed that most of the components were able to be removed with 2L DI water flushing. A 70% recovery ratio was projected for a scaled-up unit, highlighting the suitability of the V-MEMD as a small scale system for drinking water production.

Co-delivery of hydrophobic curcumin and hydrophilic catechin by a water-in-oil-in-water double emulsion

Curcumin and catechin are naturally occurring phytochemicals with extreme sensitivity to oxidation and low bioavailability. We fabricated a water-in-oil-in-water (W/O/W) double emulsion encapsulating hydrophilic catechin and hydrophobic curcumin simultaneously. The co-loaded emulsion was fabricated using a two-step emulsification method, and its physicochemical properties were characterised. Volume-weighted mean size (d43) of emulsion droplets was ≈3.88μm for blank emulsions, whereas it decreased to ≈2.8–3.0μm for curcumin and/or catechin-loaded emulsions, which was attributed to their capacity to act as emulsifiers. High entrapment efficiency was observed for curcumin and/or catechin-loaded emulsions (88–97%). Encapsulation of catechin and curcumin within an emulsion increased their stability significantly in simulated gastrointestinal fluid, which resulted in a four-fold augmentation in their bioaccessibility compared to that of freely suspended curcumin and catechin solutions. Co-loading of curcumin and catechin did not have adverse effects on either compound’s stability or bioaccessibility.

Influence of ultrasonically assisted synthesis on particle size of magnetic nanoparticles

Poly(methacrylic acid)(PMAA) coated magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in aqueous solution with the use of conventional magnetic stirring and ultrasonic agitation. It has been shown that the ultrasonic agitation during the synthesis of magnetite particles decreased the size of PMAA-coated magnetic agglomerates significantly. The primary particle size of iron oxide particles was determined as approximately 10nm by X-ray diffraction method (Scherer's equation). The volume weighted mean size (D[4,3]) of PMAA coated magnetite particles was determined as about 80nm using laser diffraction technique.

Spray-dried encapsulation of chia essential oil (Salvia hispanica L.) in whey protein concentrate-polysaccharide matrices

Eight chia essential oil-in-water fresh emulsions (E) variations were prepared using biopolymers blends whey protein concentrate (WPC) with mesquite gum (MG) or gum Arabic (GA), core to wall material ratios (Co:Wa) of 1:2 and 1:3, and total solids contents (TSC) of 30 and 40wt%. All E variations displayed volume-weighted mean size (d4,3) droplet sizes that fell within 2.32 and 3.35μm and rates of droplet coalescence (kC) of 10−8s−1. E variations were spray-dried and the resulting microcapsules (M) had d4,3 falling within the range of 13.17–28.20μm. The encapsulation efficiency (EE) was higher than 70% for all M, but those obtained from E with lower TSC and higher Co:Wa displayed higher EE and lower surface oil, independently of M particle size. The reconstituted emulsions (RE) exhibited significantly higher d4,3 and kC values of the same magnitude as E variations.

Preparation and characterization of polymer coated superparamagnetic magnetite nanoparticle agglomerates

In order to produce magnetic microparticles (agglomerates), magnetite (Fe 3O 4) particles were synthesized using coprecipitation of FeSO 4·7H 2O and FeCl 3·6H 2O with the presence of poly(methacrylic acid) (PMAA) in aqueous solution.. Transmission electron microscopy (TEM), X-ray diffraction, and vibrating sample magnetometry (VSM) methods were used to characterize the PMAA coated superparamagnetic agglomerates. The influences of various processing parameters such as the process temperature, PMAA content, and the addition of surfactant on the agglomerate size and size distribution of produced magnetic microparticles were investigated. The particle size and size distribution characteristics, (the volume weighted mean size ( D[4,3], surface weighted mean size D[3,2], the geometric standard deviation, and span value) of the magnetic agglomerates were determined using the laser diffraction technique. The PMAA coated magnetic agglomerates with surface weighted mean sizes ranging from 1.5 to 3 μm were produced successfully.

Kinetics Estimation and Single and Multi-Objective Optimization of a Seeded, Anti-Solvent, Isothermal Batch Crystallizer

The nucleation and growth kinetic parameters of paracetamol in an isopropanol−water antisolvent batch crystallizer were estimated by nonlinear regression in terms of the moments of the crystal population density. The moments were calculated using the measured chord length distribution (CLD) generated by the FBRM. The measured supersaturation by ATR-FTIR spectroscopy was also used to calculate the nucleation and growth rates using power law correlations. Using the estimated kinetic parameters, the crystallization model based on the population and mass balance, was validated using the open-loop experimental particle size distribution and supersaturation results. Subsequently, the solution to the optimal antisolvent flow-rate profiles was obtained by applying nonlinear constrained single- and multiobjective optimization on the validated model. These profiles were implemented on the crystallizer and crystal-size distributions were compared with the open-loop experiments. The bimodality in the particle size distribution (PSD), which was present in the open-loop experiments, was either minimized or completely eliminated with the optimal profile policies. The results of the multiobjective optimization showed an improvement of 27.5 μm and 3% in the volume weighted mean size and yield, respectively, in comparison to the best results obtained from the open-loop experiments.

Fuzzy logic and rigid control of a seeded semi-batch, anti-solvent, isothermal crystallizer

The objective of this study was to investigate the closed-loop control strategy for a batch crystallizer using two different control methods. The isothermal crystallization of paracetamol (PA) in isopropanol–water mixtures at 20 °C was used as the model system. The annuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and the focus beam reflectance measurement (FBRM) were used for in situ measurement of the concentration of paracetamol and chord length counts, respectively. The controlled variables were the supersaturation and the difference in the chord length counts between two sampling intervals and the manipulated variable was the anti-solvent (water) flow rate. The rigid logic control (RLC) and the fuzzy logic control (FLC) were applied. The direct objective of this study was to maintain the controlled variables inside their predetermined ranges. The indirect objectives were minimization of the batch time and maximizing the final crystals size and they were closely related to the meeting of the direct objectives. The experiments conducted with FLC resulted in approximately 30% reduction of time of the experiment and an increase of 80 μ m in the final volume weighted mean size.

Real-time optimal control of an anti-solvent isothermal semi-batch crystallization process

This study presents a novel approach for the implementation of a real-time dynamic optimal control methodology on a seeded, anti-solvent batch crystallization process. The novel features of the approach include online estimation of the nucleation, growth rates and moments of paracetamol in isopropanol–water solution using the FBRM ® probe, and the real-time single and multi-objective optimization. In addition, the supersaturation was measured by ATR-FTIR spectroscopy. The crystallization model, which involved population and mass balance, was solved based on the finite difference method. The results of the multi-objective optimization showed a substantial improvement of the end of batch properties expressed in terms of the volume-weighted mean size and yield. The effect of mean size of seeds was studied as well, and it was found that the seeds with smaller mean volume-weighted mean size promoted the growth rate. The multi-objective optimal control resulted in an increase in the volume-weighted mean size by 120.8 μ m compared to the seeds and 51% of theoretical yield, which showed better performance compared to other optimal control policies.

Adaptive MIMO neuro-fuzzy logic control of a seeded and an unseeded anti-solvent semi-batch crystallizer

This study explores the implementation of a two input/two output adaptive neuro-fuzzy logic controller on an anti-solvent semi-batch crystallization process. The solution concentration and the solubility curve of paracetamol (PA) in a mixture of water and isopropanol in the range of temperatures between 10 and 40 ∘ C were determined using attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy. The in situ chord length distribution of crystals was obtained from laser backscattering by focus beam reflectance measurement (FBRM) probe. The controlled variables were the supersaturation and the difference in the chord length counts between two sampling times, and the manipulated variables were the cooling rate and anti-solvent flow rate. The ‘direct’ objectives of this study were to keep the controlled variables inside their predetermined ranges. The ‘indirect’ objectives were to improve the end-of-batch properties that included batch time, yield, and particle size distribution. Performance of the adaptive neuro-fuzzy logic controller for the closed-loop system was evaluated based on meeting the ‘direct’ and ‘indirect’ objectives. The best results in terms of batch time and product yield for unseeded experiments were 280 min and 95%, respectively. However, the most significant improvement was noted in the seeded set of experiments that resulted in 225 min batch time, an increase of the volume weighted mean size by 275.1 μ m , and 99% product yield.

Line profile analysis: pattern modellingversusprofile fitting

Powder diffraction data collected on a nanocrystalline ceria sample within a round robin conducted by the IUCr Commission on Powder Diffraction were analysed by two alternative approaches: (i) whole-powder-pattern modelling based upon a fundamental microstructural parameters approach, and (ii) a traditional whole-powder-pattern fitting followed by Williamson–Hall and Warren–Averbach analysis. While the former gives results in close agreement with those of transmission electron microscopy, the latter tends to overestimate the domain size effect, providing size values about 20% smaller. The origin of the discrepancy can be traced back to a substantial inadequacy of profile fitting with Voigt profiles, which leads to systematic errors in the following line profile analysis by traditional methods. However, independently of the model, those systematic errors seem to have little effect on the volume-weighted mean size.

Tumour embolization of the Vx2 rabbit head and neck cancer model with Dextran hydrogel and Holmium-poly(L-lactic acid) microspheres: a radionuclide and histological pilot study

Introduction: Intra-arterial embolization of unresectable malignant tumours with biodegradable microspheres is an effective way of selective anti-tumour therapy. Promising candidates are Dextran hydrogel (Dex) microspheres for chemo-embolization and Holmium-166 poly(L-lactic acid) (166HoPLA) microspheres for radio-embolization. This study was performed to investigate the distribution of intra-arterially injected microspheres both in vivo and histologically in order to establish an optimal size of particles for embolization of head and neck tumours. Material: Twenty rabbits with Vx2 auricular tumours were embolized via the caudal auricular artery with 4 different batches of microspheres: Radioactive166HoPLA microspheres sieved between 20 and 50 μm and Dextran hydrogel microspheres sieved between 20 and 100μm (Dex20), 30 and 100 μm (Dex30) or 50 and 100 μm (Dex50). Dex20 and Dex50 microspheres were labelled with99mTechnetium in six cases. Methods: The average particle size of the microspheres was determined. The proportion of microspheres entrapped in the tumour was measured with a gamma camera. The distribution of microspheres around the primary tumour and spill of particles over into lungs or other organs was analysed from histological sections. Results: The mean particle diameter varied from 19 to 66 μm:166HoPLA 19±11 μm, Dex20 40±19 μm, Dex30 50±19 μm, Dex50 66±21 μm. The 19 μm166HoPLA particles proved inadequate for embolization as 51% spilled over into the lungs, whereas over 95% of the 40–66 μm Dex microspheres were retained within the primary tumour area. Particle density in lung tissues proved significantly lower for the Dex50 group. Stray emboli to the brain occurred in two rabbits. Conclusion: The results of this investigation show that both Dextran hydrogel and holmium-166 poly(L-lactic acid) microspheres are potential candidates for embolization of head and neck cancer. In future studies, arterio-arteriolar anastomoses which might confound treatment should be identified and occluded. Particles with a number weighted mean diameter of at least 40 μm and a volume weighted mean size up to 70 μm should be used.