Optical second-harmonic generation study of incorporation of nitrogen atoms at Si(1 0 0) surfaces

The kinetics of N incorporation into Si layers has been studied on the Si(1 0 0) surface probing surface dangling bonds with an optical second-harmonic (SH) generation during surface exposure to N atoms generated by a radio frequency N₂ plasma. It is observed that SH intensity decreases with N dose. The rate of decrease in SH intensity apparently decreases with surface temperature, whereas total amount of N atoms taken on the surface remains constant. This fact suggests that N atoms are incorporated at the subsurface layers at higher temperatures. It is shown that the N incorporation at the subsurface layers proceeds by the indiffusion of N atoms either directly or indirectly via intermediate, metastable adsorption at the first surface layer. Applying Kisliuk adsorption model, activation energies of the N indiffusion are evaluated to be 0.30 ± 0.03 and 0.34 ± 0.05 eV for the indirect and direct path, respectively.     

Unified origin for the 3D magnetism and superconductivity in NaxCoO2

We analyze the origin of the three-dimensional (3D) magnetism observed in nonhydrated Na-rich Na(x)CoO2 within an itinerant spin picture using a 3D Hubbard model. The origin is identified as the 3D nesting between the inner and outer portions of the Fermi surface, which arise due to the local minimum structure of the a(1g) band at the Gamma-A line. The calculated spin wave dispersion strikingly resembles the neutron scattering result. We argue that this 3D magnetism and the spin fluctuations responsible for superconductivity in the hydrated systems share essentially the same origin.     

Promotion of Turbulent Thermal Mixing of Hot and Cold Airflows in T-junction

An experimental study has been conducted on the promotion and control of turbulent thermal mixing of hot and cold airflows in a T-junction with rectangular cross sections, which simulates the HVAC unit for automobile air-conditioning system. In order to promote the turbulent thermal mixing, small jets have been blown into the main channel at the upstream edge of the T-junction in the direction of 45° against the main flow. Turbulence intensity in the upper part of the thermal mixing layer can be increased with these jets, and consequently the turbulent mixing of hot and cold airflows is promoted effectively. Moreover, it has been found that the degree of thermal mixing can be controlled by changing the jet velocity.     

Image analysis of the spatial distribution of paramagnetic Pr3+ ions in a polymer gel by a 1H-chemical shift NMR imaging method

¹H-chemical shift NMR imaging patterns of a poly(methacrylic acid) gel containing water with paramagnetic praseodymium ions(Pr³⁺) were successfully observed, in order to elucidate spatial distribution of Pr³⁺ ions in the gel. The ¹H chemical shift of water associated with Pr³⁺ ions in the gel moves largely downfield. By analyzing these experimental results, the immersion process of Pr³⁺ ions into the network of the polymer gel was spatially clarified. Further, it is shown that the chemical shift NMR imaging method is a useful means for determining the spatial distribution of paramagnetic metal ions in polymer gels.     

Living polymerizations of acrylic monomers with aluminioporphyrin

Aluminioporphyrin was found to be an excellent initiator for the living polymerizations of methacrylates, acrylates, and methacrylonitrile. Porphinatoaluminium thiolate and enolate were effective in the dark, different from methylporphinatoaluminium which requires irradiation by visible light. The addition of pyridine was necessary for the polymerization of methacrylonitrile, which was accelerated by visible light. By using the living polymer of methyl methacrylate as initiator, block copolymers from acrylic monomers could be synthesized. A system composed of aluminioporphyrin and trialkylaluminium was found highly active for the polymerization of methacrylates.     

Aquaphotomics Research of Cold Stress in Soybean Cultivars with Different Stress Tolerance Ability: Early Detection of Cold Stress Response

The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in the near infrared (NIR) range (588–1025 nm) from five cultivars genetically engineered to have different levels of cold stress tolerance. The spectra were acquired at the optimal growing temperature 27 °C and when the temperature was decreased to 22 °C. In this paper, we report the results of the aquaphotomics analysis performed with the objective of understanding the role of the water molecular system in the early cold stress response of all cultivars. The raw spectra and the results of Principal Component Analysis, Soft Independent Modeling of Class Analogies and aquagrams showed consistent evidence of huge differences in the NIR spectral profiles of all cultivars under normal and mild cold stress conditions. The SIMCA discrimination between the plants before and after stress was achieved with 100% accuracy. The interpretation of spectral patterns before and after cold stress revealed major changes in the water molecular structure of the soybean leaves, altered carbohydrate and oxidative metabolism. Specific water molecular structures in the leaves of soybean cultivars were found to be highly sensitive to the temperature, showing their crucial role in the cold stress response. The results also indicated the existence of differences in the cold stress response of different cultivars, which will be a topic of further research.     

Improvement of an Automated Sample Injection System for Pillar Array Columns to Increase Analytical Reproducibility

In our previous study, we developed an automatic sample injection system for pillar array columns for quantitative analysis. An autosampler was used to maintain a constant sample injection volume. However, the sample was diluted during injection using the autosampler, thus deteriorating the analytical reproducibility. In this study, we have substituted the autosampler with a syringe pump to overcome the abovementioned problem and improve the system. Sample dilution was avoided by filling the entire capillary with the sample at a constant rate. This improved system also increased the analytical reproducibility. In the previous system, the relative standard deviation (RSD) exceeded 17% of the peak height for coumarin dyes. In contrast, the improved system decreased the RSD to the range 1.2–1.8%. The analytical reproducibility was evaluated by using five types of amino acids. The RSD of each peak height was within 3.0%, confirming good reproducibility. These results indicate that the sample injection method developed in this study can be applied to biological sample analyses as a simple quantitative analysis method for pillar array columns.     

Development of porous silica production by hydrothermal method

Abstract

A new process for porous silica production has been developed using a hydrothermal method. Hydrothermally synthesized calcium silicate was used as the starting material in this study, which was produced from a mixture of Ca(OH)₂ and amorphous silica (white carbon) under hydrothermal conditions of 140°C and 0.4 MPa, for 8 hours. The calcium silicate was subsequently treated with an acid solution, facilitating the leaching of Ca ions. After washing with pure water, the multant Ca²⁺ -free silica powder was allowed to dry. The Ca²⁺ -free silica powder was found to have an amorphous structure, with 0.9 ml/g pore volume, up to 610m²/g BET specific surface area, and an average 5 ～ 8 nm pore size. Our hydrothermal process is simple and low cost, and is anticipated to have numerous applications to the petrochemical industry.