Structural approach to nanoscience: a case study of complex and cluster formation in ZnBr2–ZnCl2 melts

Although the melt structure of glass-forming ZnCl₂ has so far been well studied, there exists quite little information on the structural change due to anion-substitution. In the present work, the short-range structure of ZnCl₂–ZnBr₂ mixture melts was analyzed systematically by time-of-flight pulsed neutron diffraction techniques, Raman spectroscopy, molecular orbital calculations, and molecular dynamics simulations. According to radial distribution analysis, it was found that there were tetrahedral structural units of ligand-substituted [ZnCl_nBr_4−n]²⁻ (n=0–4) in these melts, not implying the simple mixing of [ZnCl₄]²⁻ and [ZnBr₄]²⁻ units. Further detailed estimation indicated that the ligand-substituted complex anions were linked with each other by sharing a common anion.     

Development of dual-probe atomic force microscopy system using optical beam deflection sensors with obliquely incident laser beams

We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The deflection of each cantilever is measured by the optical beam deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.     

Mutagenicity and DNA-damaging activity of decomposed products of food colours under UV irradiation

Five synthetic food colours Food Red Nos 3, 40 and 102 and Food Blue Nos 1 and 2, and their UV irradiated products were tested for mutagenic activity by means of the Ames test using Salmonella typhimurium strains TA98 and TA100. Food colours were irradiated with UV light for 14 days. Food Red Nos 3, 40 and 102 and Food Blue No. 1 were non-mutagenic before and after irradiation. UV irradiated products of Food Blue No. 2 were mutagenic in TA98 with or without S-9 mix. The mutagenic activity increased with increasing irradiation period, reached maximum potency on day 6, and then decreased. Moreover, Food Blue No. 2 showed DNA-damaging activity after 14 days of irradiation in rec-assay using Bacillus subtilis strains H17 and M45. The capillary electrophoresis was applied for the analysis of UV irradiated products of Food Blue No. 2. The original peak of Food Blue No. 2 was decomposed into seven peaks after UV irradiation.     

Out‐of‐Plane Strain Induced in a Moiré Superstructure of Monolayer MoS2 and MoSe2 on Au(111)

Making contact of transition metal dichalcogenides (TMDCs) with a metal surface is essential for fabricating and designing electronic devices and catalytic systems. It also generates strain in the TMDCs that plays significant role in both electronic and phonon structures. Therefore, detailed understanding of mechanism of the strain generation is important to fully comprehend the modulation effect for the electronic and phonon properties. Here, MoS₂ and MoSe₂ monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out‐of‐plane strain in both MoS₂ and MoSe₂ layers, whereas no strain generation is observed on polycrystalline Au or SiO₂/Si surfaces. Scanning tunneling microscopy analysis provides information regarding consequent specific adsorption sites between lower S (Se) atoms in the S? Mo? S (Se? Mo? Se) structure and Au atoms via unique moiré superstructure formation for MoS₂ and MoSe₂ layers on Au(111). This observation indicates that the specific adsorption sites give rise to out‐of‐plane strain in the TMDC layers. Furthermore, it also leads to effective modulation of the electronic structure of the MoS₂ or MoSe₂ layer.     

Design of a 1-MW,CW coaxial gyrotron with two gaussian beam outputs

The design of a 170 GHz, 1 MW-CW gyrotron for electron cyclotron heating of nuclear fusion plasmas is presented. The designed gyrotron incorporates a coaxial cavity to reduce mode competition, and a coaxial electron gun to support the cavity inner conductor. A new mode converter splits the generated wave into two beams and radiates them in different directions. The radiated beams are transmitted to two output windows through two mirror systems, being transformed into Gaussian-like beams. A single-stage depressed collector improves the overall efficiency of the gyrotron and reduces the heat flux to the collector surface.     

Analysis of a new configuration of coplanar stripline

A new configuration of coplanar stripline is presented and analyzed. This configuration is derived by augmenting coplanar stripline (CPS) with electrically wide lateral ground planes on either side of the balanced pair of signal lines. The ground planes should replace line-to-line coupling in complex circuits and eliminate the TE₀ parasitic dielectric slab waveguide mode. Also, the spacing from signal lines to ground planes can be adjusted to change the characteristic impedance. Spectral domain analysis is used to calculate the dispersion characteristics of this transmission line. Analytical expressions for quasi-static values of the line are presented. This configuration of CPS should be useful for balanced high-impedance lines in monolithic microwave integrated circuit (MMIC) and high speed digital circuits     

Iron–Nitrogen‐Doped Vertically Aligned Carbon Nanotube Electrocatalyst for the Oxygen Reduction Reaction

A highly active iron–nitrogen‐doped carbon nanotube catalyst for the oxygen reduction reaction (ORR) is produced by employing vertically aligned carbon nanotubes (VA‐CNT) with a high specific surface area and iron(II) phthalocyanine (FePc) molecules. Pyrolyzing the composite easily transforms the adsorbed FePc molecules into a large number of iron coordinated nitrogen functionalized nanographene (Fe–N–C) structures, which serve as ORR active sites on the individual VA‐CNT surfaces. The catalyst exhibits a high ORR activity, with onset and half‐wave potentials of 0.97 and 0.79 V, respectively, versus reversible hydrogen electrode, a high selectivity of above 3.92 electron transfer number, and a high electrochemical durability, with a 17 mV negative shift of E _1/2 after 10 000 cycles in an oxygen‐saturated 0.5 m H₂SO₄ solution. The catalyst demonstrates one of the highest ORR performances in previously reported any‐nanotube‐based catalysts in acid media. The excellent ORR performance can be attributed to the formation of a greater number of catalytically active Fe–N–C centers and their dense immobilization on individual tubes, in addition to more efficient mass transport due to the mesoporous nature of the VA‐CNTs.     

Slippage of 4He Films and Precursor Phenomenon of Superfluidity

We have carried out quartz crystal microbalance (QCM) experiments for ⁴He films on an exfoliated single-crystalline graphite using a 32 kHz tuning fork, and have measured the temperature dependence of the resonance frequency and the Q value for various areal densities and oscillation amplitudes. Comparing with the previous experiments for Grafoil, the decoupling of the films due to the slippage or the superfluidity was larger than that of Grafoil, and the competition between the slippage and the superfluidity was observed in three-atom thick films. Furthermore, it was found that the slippage is suppressed gradually at higher temperature than the superfluid onset T _c , and that the relaxation time decreases at low temperatures while it obeys the Arrhenius law at high temperatures. These results suggest a precursor to the superfluidity of ⁴He films.     

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