Preparation and characterization of Z-type hexaferrites, Ba3(1−x)Sr3x Co2Fe24O41 with x = 0–0.5, via a two-step calcination with an intermediate wet milling

Z-type hexaferrites (Ba_{3(1 − x)}Sr_3x Co₂Fe₂₄O₄₁with x = 0–0.5, Z-hex) were prepared in a nearly phase pure state by a two-step calcination with an intermediate wet milling. The first calcination of the starting mixture comprising oxides or hydroxides at temperatures below 1100^∘C brought about a mixture of layer-structured M and Y-type hexaferrite phases, together with a spinel phase of Co ferrite. Z-hex was fully crystallized after the second calcination up to 1230^∘C. Wet milling between the two calcination steps was decisive for the phase purity. Emphasis was laid on the quantitative analyses of Z-hex, together with the evaluation of anisotropic growth of the crystallites. Sr addition stabilizes Z-hex, while decreases degree of anisotropy simultaneously.     

Intracellular recovery of gold by microbial reduction of AuCl4 ions using the anaerobic bacterium Shewanella algae

Microbial reduction and intracellular precipitation of gold was achieved at 25 °C and pH 7 by using the mesophilic anaerobic bacterium Shewanella algae with H₂ as the electron donor. The reductive precipitation of gold by S. algae was a fast process: 0.1–1 mol/m³ AuCl₄⁻ ions were completely reduced to insoluble gold within 30 min. The biogenic precipitates were crystalline gold nanoparticles of 10–20 nm present in the periplasmic space. The reducing power of S. algae at 3.2 × 10¹⁵ cells/m³ and 25 °C was comparable to that of aqueous citric acid solution (chemical reductant) at 20 mol/m³ and 50 °C. The intracellular recovery of gold is potentially attractive as an environmentally friendly alternative to conventional methods.     

Effect of gravity on InGaSb crystal growth

The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In_0.1Ga_0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth.     

"Residence times difference" fluxgate magnetometers

We present analytical and experimental results on fluxgate magnetometers that make use of a readout technique based on residence times. This approach allows for enhancing sensitivity to weak target signals in particular when the reduction of the sensor dimensions are considered. Our approach, exploiting the inherent nonlinear character of the bistable core dynamics, is based on the time domain characterization of the transitions between the two saturation states of the hysteresis loop that is inherent in the ferromagnetic core dynamics. This readout technique can be implemented with bias signals having lower amplitude and frequency than those used in conventional fluxgate processing schemes, thus reducing the device power requirements. The efficacy of this strategy is shown through an analytical approach and via experimental results which suggests guidelines for optimal device design and realization. The experiments have been carried out on a miniaturized laboratory fluxgate prototype; this device shows numerous desirable characteristics, including very good sensitivity and resolution, as well as ease of operation and a very low cost.     

Applications of Thermoelectric Power Measurement to Deterioration Diagnosis of Nuclear Material and Its Principle

In order to non-destructively evaluate changes in toughness of cast duplex stainless steel, which is frequently used in main coolant pipes of PWR type nuclear power plants, due to thermal aging, we tried to apply thermoelectric power (TEP) measurement. because TEP is sensitive to microstructural material changes, and to clarify the mechanism behind TEP changes due to thermal aging. As a result, TEP of cast duplex stainless steel increased with aging time, and good correlations were found between TEP and toughness. Concerning the mechanism, TEP of high and low Cr content alloys was higher than that of intermediate Cr content alloys. Because high and low Cr areas are created in the ferrite phase due to thermal aging. TEP of the entire material increased. Furthermore, when each Cr fluctuating area acted in parallel, the increase in TEP became larger. According to the Mott-Jones theory, TEP is largely related to the electron density of states at the Fermi level. The electron density of states of Fe–Cr–Ni alloys in the valence band was measured with X-ray photoelectron spectroscopy (XPS). As a result, there was a high correlation between the TEP calculated from the XPS spectrum and the measured TEP. Therefore, we showed experimentally that the electron density of states changed due to variations in Cr concentration, which also affect TEP.     

Comparison of isolation methods using commercially available kits for obtaining extracellular vesicles from cow milk

Extracellular vesicles (EV) are important for delivering biologically active substances to facilitate cell-to-cell communication. Milk-derived EV are widely known because of their potential for immune enhancement. However, procedures for isolating milk-derived EV have not been fully established. To obtain pure milk-derived EV and accurately reveal their function, such procedures must be established. The aim of the present study was to compare methods using commercially available kits for isolating milk-derived EV. Initially, we investigated procedures to remove casein, which is the major obstacle in determining milk-derived EV purity. We separated whey using centrifugation only, acetic acid precipitation, and EDTA precipitation. Then, we isolated milk-derived EV by ultracentrifugation, membrane affinity column, size exclusion chromatography (SEC), polymer-based isolation, or phosphatidylserine-affinity isolation. Using EV count per milligram of protein, which is a good indicator of purity, we determined that acetic acid precipitation was the best method for removing casein. Using nanoparticle tracking analysis, protein quantity analysis, and RNA quantity analysis, we comprehensively compared each isolation method for its purity and yield. We found that SEC-based qEV column (Izon Science) could collect purer milk-derived EV at higher quantities. Thus, a combination of acetic acid precipitation and qEV can effectively isolate high amounts of pure extracellular vesicles from bovine milk.     

Improvement of lysozyme recovery method from the precipitate of protein-anionic surfactant complexes

A new protein separation process using a surfactant and a polar organic solvent consists of a precipitation step and a recovery step. In the precipitation step, a protein-surfactant complex is precipitated from an aqueous solution, when an ionic surfactant, sodium di(2-ethylhexyl) sulfosuccinate (AOT), is added to an aqueous solution, including protein (lysozyme). In the recovery step, the precipitate is dissolved in a polar organic solvent, such as acetone, and the protein is recovered as precipitates when a very small amount of salt solution was added to remove surfactants from the protein-surfactant complex. However, the details of the protein recovery step from precipitate have not been studied yet. In this study, the improvement of the protein recovery step was examined from the viewpoint of a recovery ratio of protein and a remaining ratio of surfactant. The optimum NaCl concentration in the feed for the protein recovery was in the range of 0.05–0.2 kmol/m³. As the NaCl concentration in the feed increased to more than 0.2 kmol/m³, the precipitation ratio decreased due to the electrostatic screening effect of NaCl. It was found that the addition of a very small amount of NaCl solution to acetone was unnecessary when NaCl was included in the feed lysozyme solution. On the other hand, as the NaCl concentration decreased to less than 0.05 kmol/m³, the precipitation ratio was decreased due to the low re-precipitation of protein by the addition of a small amount of NaCl solution in acetone. In the case of the feed containing no salt, the desired NaCl concentration added to acetone was in the range above 0.2 kmol/m³. In addition, the most suitable volume ratio of acetone to feed was found to be 0.2.     

Decomposition Characteristics of an Artificial Biogas in a Low‐Pressure DC Glow Discharge

The decomposition characteristics of an artificial biogas, which is a mixture of CH ₄, CO ₂, and H ₂ S, using a low‐pressure DC glow discharge have been investigated. It is found that H ₂, CO, C ₂ H ₂, H ₂ O, CS ₂, and COS are produced from the artificial biogas in the glow discharge. About 65% of the hydrogen atoms in CH ₄ are converted into H ₂ at an input energy of 800 J, at which CH ₄ is completely decomposed, and the decomposition characteristics of the artificial biogas are minimally dependent on the H ₂ S additive. Further, H ₂ S has a tendency to be decomposed earlier than the other components of the artificial biogas. When the glow discharge is generated in the artificial biogas with H ₂ S, some of the carbon atoms are found to deposit on the electrodes and the wall of the discharge chamber. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 26–33, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22304     

Intestinal absorption and biological effects of orally administered amorphous silica particles

Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.