The influence of wall interaction on dynamic particle modelling of magneto-rheological suspensions between shearing plates

We report on the modelling of a magneto-rheological (MR) suspension bound between shearing parallel plates using a particle-level numerical simulation. The simulation is similar to an approach used previously but includes particle hydrodynamic interaction using elements of the Stokesian-dynamic method. Observations of initially chain-like aggregations are reported, and the evolving morphology of suspension particle clusters is explored. Our early-strain observations concur with the prevailing ideas of experimentalists on the important role that the microstructure has on bulk viscosity. We then study in particular the effects of simulation size and strain on viscosity. While initial viscous response is similar to previously reported observations in the literature, when left to run for longer strains, suspensions evolved into markedly different microstructures from those observed experimentally, or in electro-rheological suspensions, or MR simulations with artificial wall interaction. Substantial qualitative and quantitative divergence was observed over long strains. We argue that this divergence is due to the lack of a particle–wall interaction model for MR fluids. While current theories in MR modelling do not justify the requirement for a particle–wall interaction, these results suggest that one is required in order to match experimental observations.

Comparison of Fatty Acid Contents and MMP-1 Inhibitory Effects of the Two Antarctic Fish,Notothenia rossii and Champsocephalus gunnari

Total fatty-acid (FA) contents of different organs (stomach, liver, brain, and skin) of two Antarctic fish, marbled rockcod (Notothenia rossii) and mackerel icefish (Champsocephalus gunnari), were examined using gas chromatography–mass spectrometry (GC–MS). N. rossii possessed higher contents of total omega-3, where eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the most represented omega-3 FAs, were distributed throughout all parts of the fish. The highest level of EPA was observed in the skin and that of DHA was observed in the brain of N. rossii. C. gunnari showed organ peculiarity in that most of the omega-3 FAs were found in stomach and skin. Specifically, the highest levels of EPA and DHA were both observed in the stomach. Although N. rossii and C. gunnari both inhabit the Antarctic Southern Oceans, their characteristics in terms of the composition of fatty acids were shown to vary. The extracts were also evaluated for matrix metalloproteinase-1 (MMP-1)-inhibitory activities in UVB-induced human dermal fibroblasts, where extracts of the skin and liver of N. rossii showed the most significant inhibition upon MMP-1 production. These findings provide experimental evidence that the extracts of the Antarctic fish could be utilized as bioactive nutrients, particularly in the enhancement of skin health.     

Functional Characterization of an Arabidopsis Profilin Protein as a Molecular Chaperone under Heat Shock Stress

Profilins (PFNs) are actin monomer-binding proteins that function as antimicrobial agents in plant phloem sap. Although the roles of Arabidopsis thaliana profilin protein isoforms (AtPFNs) in regulating actin polymerization have already been described, their biochemical and molecular functions remain to be elucidated. Interestingly, a previous study indicated that AtPFN2 with high molecular weight (HMW) complexes showed lower antifungal activity than AtPFN1 with low molecular weight (LMW). These were bacterially expressed and purified to characterize the unknown functions of AtPFNs with different structures. In this study, we found that AtPFN1 and AtPFN2 proteins have LMW and HMW structures, respectively, but only AtPFN2 has a potential function as a molecular chaperone, which has never been reported elsewhere. AtPFN2 has better protein stability than AtPFN1 due to its higher molecular weight under heat shock conditions. The function of AtPFN2 as a holdase chaperone predominated in the HMW complexes, whereas the chaperone function of AtPFN1 was not observed in the LMW forms. These results suggest that AtPFN2 plays a critical role in plant tolerance by increasing hydrophobicity due to external heat stress.     

1H NMR titration study of stimuli-responsive supramolecular assemblies: inclusion complexes between PEG–b-PEI copolymer-grafted dextran and naphthalene-appended γ-cyclodextrin via double-strand inclusion

We have previously prepared a stimuli-responsive inclusion complex between PEG–b-PEI–g-dextran graft copolymer (PEG–PEI–dex) and γ-cyclodextrin (γ-CD) in order to investigate unique inclusion phenomena, double-axle inclusion. For further study, a γ-CD derivative, mono-6-O-(2-sulfonato-6-naphthyl)-γ-CD (SN-γ-CD) was additionally synthesized for ¹H NMR titration study, which is expected to induce the competition of pendant naphthyl group with external polymer guests. Consequently, ¹H NMR titration results of the inclusion complex of PEG–PEI–dex with SN-γ-CD showed stoichiometric changes, temperature-dependence, and reversibly pH-responsive properties of the inclusion complexes in terms of chemical shift variation.     

Development of pH sensor based on aromatic polyurethane matrix

The synthesized aromatic polyurethane (APU)-based all-solid-state (ASS) pH sensor was developed with the same APU-based reference site in an ASS multi sensing electrode. The best analytical performance (the linear range of pH 3.0–11.5, slopes of 57 mV pH⁻¹) was obtained with the membrane composition of 33:66:1 (wt.%) of APU/plasticizer (NPOE)/ionophore (N,N-dioctadecylmethylamine) with the addition of lipophilic additive (KTpClPB, 5 mol.%). This ASSE exhibits more advantages of increasing stability, reducing membrane resistance and reducing anion interference.     

Influence of substrate temperature on the optical and piezoelectric properties of ZnO thin films deposited by rf magnetron sputtering

In this study, ZnO thin films were fabricated using the rf magnetron sputtering method and their piezoelectrical and optical characteristics were investigated for various substrate temperatures. The ZnO thin film has the largest crystallization orientation for the (0 0 2) peak and the smallest FWHM value of 0.56° at a substrate temperature of 200 °C. The surface morphology shows a relatively dense surface structure at 200 °C compared to the other substrate temperatures. The surface roughness shows the smallest of 1.6 nm at a substrate temperature of 200 °C. The piezoelectric constant of the ZnO thin film measured using the pneumatic loading method (PLM) has a maximum value of 11.9 pC/N at a substrate temperature of 200 °C. The transmittance of the ZnO thin film measured using spectrophotometry with various substrate temperatures ranged from 75 to 93% in the visible light region. By fitting the refractive index from the transmittance to the Sellmeir dispersion relation, we can predict the refractive index of the ZnO thin film according to the wavelength. In the visible light range, the refraction index of the ZnO thin film deposited at a substrate temperature of 200 °C is the range of 1.88-2.08.     

Redox reaction kinetics of UO2+x

Oxidation and reduction kinetics of UO_2+x was investigated in CO₂/CO gas mixtures at elevated temperatures of 1000°C to 1300°C by monitoring the electrical conductivity relaxation induced by an abrupt change of ambient oxygen partial pressure. By fitting the experimental relaxation data to theoretical equations, the oxidation and reduction kinetics was found to be controlled mostly by the surface reaction step in the ranges of oxygen partial pressure and temperature examined and the surface reaction rate constants were derived therefrom.