Understanding Biofilm Formation in Ecotoxicological Assays With Natural and Anthropogenic Particulates

Fossil-made polymers harbor unique bacterial assemblages, and concerns have been raised that ingested microplastic may affect the consumer gut microbiota and spread pathogens in animal populations. We hypothesized that in an ecotoxicity assay with a mixture of polystyrene (PS) and clay: (1) microbiome of the test animals inoculates the system with bacteria; (2) relative contribution of PS and the total amount of suspended solids (SS) select for specific bacterial communities; and (3) particle aggregation is affected by biofilm community composition, with concomitant effects on the animal survival. Mixtures of PS and clay at different concentrations of SS (10, 100, and 1000 mg/L) with a varying microplastics contribution (%PS; 0–80%) were incubated with Daphnia magna, whose microbiome served as an inoculum for the biofilms during the exposure. After 4-days of exposure, we examined the biofilm communities by 16S rRNA gene sequencing, particle size distribution, and animal survival. The biofilm communities were significantly different from the Daphnia microbiota used to inoculate the system, with an overrepresentation of predatory, rare, and potentially pathogenic taxa in the biofilms. The biofilm diversity was stimulated by %PS and decreased by predatory bacteria. Particle aggregate size and the biofilm composition were the primary drivers of animal survival, with small particles and predatory bacteria associated with a higher death rate. Thus, in effect studies with solid waste materials, ecological interactions in the biofilm can affect particle aggregation and support potentially harmful microorganisms with concomitant effects on the test animals.

Viscoelastic Equivalent Creep Behavior and Its Influencing Factors of Basalt Fiber-Reinforced Asphalt Mixture under Indirect Tensile Condition

The aim of this study is to further investigate the effect of different basalt fiber (BF) factors on the viscoelastic equivalent creep behavior of fiber-reinforced asphalt mixture (FRAM) under indirect tensile (IDT) condition. A two-dimension mesostructural model composed of different components including fiber mortar polymer and coarse particle aggregate is constructed via the section image processing for the IDT FRAM specimen, where BF is considered as random distribution in the mortar polymer. Furthermore, the stress distribution and equivalent creep of the IDT mesostructural model in simulation software are analyzed to discuss the influence of components on the creep behavior of FRAM. Moreover, the laboratory creep test of IDT specimens under 0% and 0.3% BF contents for FRAM is carried out to validate the simulated values. Research results indicate that the simulated creep deformation of the IDT mesostructural model is in agreement with that of the experiment. Finally, creep simulations are further conducted to discuss the effect of BF (e.g., fiber content, length-diameter ratio, and fiber modulus) and aggregate on the creep characteristic of FRAM. The increase of fiber content and length-diameter ratio has a significant reinforcing effect on the equivalent mechanical behavior, but the change in the modulus of fiber and aggregate has slight effects.

Impact of Oxygenated Additives on Soot Properties during Diesel Combustion

Emissions from diesel engines can be limited and potentially decreased by modifying the fuel chemical composition through additive insertion. One class of additives that have shown to be particularly efficient in the reduction of the particulates from the combustion of diesel fuels are oxygenated compounds. In the present study we investigate the effect of tripropylene glycol methyl ether (TPGME) and two polyoxymethylene dimethyl ethers (POMDME or OMEs) on soot formation in a laminar diesel diffusion flame. From the evaluation of soot volume fraction by laser-induced incandescence (LII) measurements we could observe that OME additives have a substantial capability (higher compared to TPGME) to decrease the particle concentration, which drops by up to 36% with respect to the pure diesel fuel. We also note a reduction in particle aggregate size, determined by wide-angle light scattering (WALS) measurements, which is more pronounced in the case of OME–diesel blends. The effects we observe can be correlated to the higher amount of oxygen content in the OME molecules. Moreover, both additives investigated seem to have almost no impact on the local soot temperature which could in turn play a key role in the production of soot particles.

Capacitive Performance of Reduced Graphene Oxide Modified Sodium Ion-Intercalated Manganese Oxide Composite Electrode

The reduced graphene oxide modified sodium ion-intercalated manganese oxide (RGO-NaxMnO2) is designed as a supercapacitor electrode material. The layered intercalation compound NaxMnO2 is prepared through a solid-state reaction process. RGO-NaxMnO2 is then formed by the chemical reduction of graphene oxide coated NaxMnO2 through a hydrothermal process. RGO-NaxMnO2 is supported on the substrate of nickel form (NF) and titanium nitride (TiN) to form RGO-NaxMnO2/NF and RGO-NaxMnO2/TiN composite electrodes. NaxMnO2 has a particle aggregate structure with the individual particle size of 1–2 µm. RGO-NaxMnO2 composite shows the densely packed arrangement of particles with the particle aggregate size of 8 µm. RGO modification can well improve the electrical conductivity of RGO-NaxMnO2. The current response is highly enhanced from 0.127 A g−1 for NaxMnO2/NF to 0.372 A g−1 for RGO-NaxMnO2/NF at 2 mV s−1. Furthermore, the TiN substrate with superior electrical conductivity and electrochemical anti-corrosion contributes to improving the electrochemical capacitance and cycle stability of RGO-NaxMnO2. RGO-NaxMnO2/TiN reveals higher specific capacitance (244.2 F g−1 at 2.0 A g−1) and higher cycling capacitance retention (99.7%) after 500 cycles at 2.0 A g−1 than RGO-NaxMnO2/NF (177.1 F g−1, 43.6%). So, RGO-NaxMnO2/TiN exhibits much higher capacitive performance than RGO-NaxMnO2/NF, which presents a potential application for electrochemical energy storage.

Laser Induced Aggregation of Light Absorbing Particles by Marangoni Convection

Laser induced Marangoni convection can be used to accumulate micro-particles. In this paper, a method is developed to control and accumulate the light absorbing particles dispersed in a thin solution layer. The particles are irradiated by a focused laser beam. Due to the photothermal effect of the particles, the laser heating generates a thermal gradient and induces a convective flow around the laser’s heating center. The convective flow drives the particles to accumulate and form a particle aggregate close to the laser’s heating center. The motion of particles is dominated by the Marangoni convection. When the laser power is high, the vapor bubbles generated by laser heating on particles strengthen the convection, which accelerates the particles’ aggregation.

Formation of the properties of the structure of disperse-filled polymer composites

The influence of the structure on the properties of the metal-polymer composite consisting of a polymer matrix in the form of epoxy resin (ED-20) with butadiene-styrene rubber (BSK), dispersedly filled with copper nanoparticles, is investigated. In the framework of fractal analysis, the real diameter of the aggregates of the initial filler particles was calculated for various concentrations and size of the filling particles and for different compositions of the polymer matrix. The concept of the structure of a polymer composite as a combination of two fractals (multifractals) was substantially used, which allows to determine the principles of the polymer matrix plasticity changes and to reveal the main factors affecting the degree of perturbation of its structure. Using fractal analysis methods, the influence of factors on the fractal dimension of the surface of initial filler particles aggregates and on the pattern of its dependence both on the degree of aggregation and on the fractal dimension of the frame of the particle aggregate is investigated The proposed approach enables prediction the fi nal parameters of aggregates of nanoparticles as a function of the size of the initial particles, their concentration and chemical properties of the surface of the polymer matrix.

Active particle aggregate on complex bubble surfaces

Recently, colloids have been shown to form complex structures on bubble surfaces on demand. With the help of a high power pulse laser shining on a thin water film, water bubbles can be formed and heat unbalance creates a convective flow, which carries colloids on the surface of these water bubbles to form aggregates. Here, active particles are studied in a similar setup and conditions are laid out to form aggregates on water bubble surfaces. The effect of motility and chirality of active particles on formation of aggregate are discussed. The simulation results obtained here will hopefully help the experimental endeavors in future.