Antioxidant Activities of Free and Liposome-Encapsulated Green tea extracts on canola oil oxidation stability

In the present study, green tea extract was encapsulated in liposomes based on the Mozafari method (with no organic solvents) and characterized for its physicochemical properties (encapsulation efficiency, particle size, and Z-potential). Encapsulation efficiency, particles size, and Z-potential were determined to be 51.34, 419 nm, and -57 mV, respectively. Total polyphenol content of the green tea by Folin-Ciocalteu's phenol reagent was measured as 164.2 mg gallic acid/g extract. Free radical scavenging activities of free and liposomal extracts were 90.6 and 93.4%, respectively, using the DPPH method. Antioxidant activity of the ethanolic extract of green tea in free and liposomal forms with concentrations of 200, 600, and 1000 mg L⁻¹ were assessed on oxidative stability of the canola oil at 60 °C for 0, 4, 8, 12, 16, 20, 24, 28, and 32 days. Results were compared to results of synthetic antioxidant butylated hydroxytoluene at 200 mg L⁻¹. To assess antioxidant activity on canola oil stability, peroxide, thiobarbitoric acid, and anisidine values were assessed as well as the total oxidation value and rancimat test. Results showed that the liposomal green tea extract was more effective than the free extract. Furthermore, a 600 mg L⁻¹ concentration of the green tea extract showed a significant antioxidant activity, compared to other extract concentrations. Increasing storage time and various concentrations of the ethanolic green tea extracts included significant effects on canola oil stability (P ≤ 0.05). Results demonstrated that the green tea extract could be used as an effective antioxidant. Free and liposomal extract (at 600 mg L⁻¹) resulted in stronger functionality than the synthetic antioxidant butylated hydroxytoluene.     

Effects of Winding Attachment Positions on Output Characteristics of Flux‐Modulating Synchronous Machines

The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power.     

Carbonaceous microsphere-based superabsorbent polymer as filler for coating of NPK fertilizer: Fabrication,properties, swelling,and nitrogen release characteristics

Recently, the use of controlled release fertilizers in agriculture has resulted in huge benefits in plant growth and cultivation. Superabsorbent polymer (SAP)-coated fertilizers have the added advantage in retaining water in soil after irrigation and also reduce the nutrient release rate from soil in a controlled manner. This study aimed to produce a nitrogen–phosphorus–potassium (NPK) fertilizer coated with superabsorbent carbonaceous microspheres polymer (SPC) by inverse suspension polymerization method with water-retention and controlled release properties. Two sets of experiments were conducted: (1) three different weight percentages and (2) different materials. NPK coated with SPC showed increasing water-retention ability with respect to carbon microsphere percentages and retains >80% water at the 30th day of experiment compared with pure NPK and NPK coated with SAP. The slow release behavior of all samples was investigated by induced coupled plasma mass spectrometry spectrometry and results showed that NPK coated with SAP and SPC has a low release rate with <50% nutrient release compared with uncoated NPK at the 30th day. The release mechanism kinetics of NPK coated with SAP and SPC were studied based on the Kosmeyer–Peppas model. The mechanisms approached Fickian diffusion-controlled release as the n value for both samples was less than 0.5. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48396.     

Molecular Dynamics Study of Radial Corrugation in Carbon Nanotubes

Molecular dynamics simulations of multiwalled carbon nanotubes under hydrostatic pressure are performed to elucidate the novel class of radial buckling in the systems. It is revealed by all-atom simulations that the initial circular cross section transforms into a flower-like wavy configuration at critical pressure on the order of hundreds mega pascals or less. This kind of radial buckling, called radial corrugation, originates from the competition of the three relevant energies in the system: in-plane strain energy, van der Waals interaction energy between adjacent tubes, and out-of-plane bending energy. Their possible consequences for physical properties of carbon nanotubes are also discussed.     

Calculation of the Characteristics of Salient‐Pole Synchronous Machines Assisted by Permanent Magnets on the Basis of the Operating Principle

In this study we investigate a method for accurately calculating the characteristics of salient‐pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, a theoretical representation of the assist effect on the permanent magnets is derived based on the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. We show that the load characteristics of the proposed machine can be accurately estimated from the no‐load and short‐circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets.     

CuI and H2O2 Inactivate and FeII Inhibits [Fe]‐Hydrogenase at Very Low Concentrations

[Fe]‐Hydrogenase (Hmd) catalyzes reversible hydride transfer from H₂. It harbors an iron‐guanylylpyridinol as a cofactor with an Fe^II that is ligated to one thiolate, two COs, one acyl‐C, one pyridinol‐N, and solvent. Here, we report that Cu^I and H₂O₂ inactivate Hmd (half‐maximal rates at 1 μM Cu^I and 20 μM H₂O₂) and that Fe^II inhibits the enzyme with very high affinity (K_i=40 nM ). Infrared and EPR studies together with competitive inhibition studies with isocyanide indicated that Cu^I exerts its inhibitory effect most probably by binding to the active site iron‐thiolate ligand. Using the same methods, it was found that H₂O₂ binds to the active‐site iron at the solvent‐binding site and oxidizes Fe^II to Fe^III. Also it was shown that Fe^II reversibly binds away from the active site iron, with binding being competitive to the organic hydride acceptor; this inhibition is specific for Fe^II and is reminiscent of that for the [FeFe]‐hydrogenase second iron, which specifically interacts with H₂.     

The effect of microencapsulated phase change materials on the rheology of geopolymer and Portland cement mortars

The effect of microencapsulated phase-change materials (MPCM) on the rheological properties of pre-set geopolymer and Portland cement mortars was examined. Microcapsules with hydrophilic and hydrophobic shells were compared. The shear rate dependency of the viscosities fitted well to a double Carreau model. The zero shear viscosities are higher for geopolymer mortar, illustrating poorer workability. The time evolution of the viscosities was explored at shear rates of 1 and 10 s⁻¹. New empirical equations were developed to quantify the time-dependent viscosity changes. The highest shear rate disrupted the buildup of the mortar structures much more than the lower shear rate. Microcapsules with a hydrophobic shell affect the rheological properties much less than the microcapsules with a hydrophilic shell, due to the higher water adsorption onto the hydrophilic microcapsules. Shear forces was found to break down the initial structures within geopolymer mortars more easily than for Portland cement mortars, while the geopolymer reaction products are able to withstand shear forces better than Portland cement hydration products. Initially, the viscosity of geopolymer mortars increases relatively slowly during due to formation of geopolymer precursors; at longer times, there is a steeper viscosity rise caused by the development of a 3D-geopolymer network. Disruption of agglomerates causes the viscosities of portland cement mortars to decrease during the first few minutes, after which the hydration process (increasing viscosities) competes with shear-induced disruption of the structures (decreasing viscosities), resulting in a complex viscosity behavior.     

Transmission Electron Microscopy-Based Analysis of Electrically Conductive Surface Defects in Large Area GaSb Homoepitaxial Diodes Grown Using Molecular Beam Epitaxy

We investigate a mechanism causing shorting of large area GaSb diodes grown on GaSb substrates using molecular beam epitaxy (MBE). The source of these shorts is determined to be large crystallographic defects on the surface of the diodes that are formed around droplets of gallium ejected from the gallium Knudsen cells during MBE. The gallium droplets cause defects in the crystal structure, and, as the epitaxy continues, the gallium is incorporated into the surrounding material. The shape of the defects is pyramidal with a central void extending from the epi-surface to the gallium core. Processing a GaSb diode with these surface defects results in the top-side contact metal migrating into the defect and shorting the diode. This prevents realization of large area diodes that are critical to applications such as photovoltaics and detectors. The diodes in this study are electrically characterized and the defect formation mechanism is investigated using cross-section transmission electron microscopy and electron dispersive spectroscopy.     

A Study on the Effect of Air on the Dynamic Motion of a MEMS Device and Its Shape Optimization

The authors propose a new design concept for controlling the deflection of a micro-membrane with the aid of its thickness distribution for realizing a prescribed design in the MEMS. As an example, the authors treat a micro air pump that comprises a micro-membrane. The membrane is actuated by an electrostatic force. The membrane deflects and thus the deflection is influenced by the air pressure and the electrostatic field. This is a highly complicated system. To find out a proper thickness distribution, the authors use the genetic algorithm that is appropriate to reduce the searching space of solution.