Hairpin-based state machine and conformational addressing: Design and experiment

In this paper, we propose a new architecture for a multi-state DNA machine whose conformation of repeated hairpin structures changes sequentially in response to input oligomers. As an application of the machine, we also propose molecular memory in which the machine is used as a memory unit. Addressing in the memory is realized through state transitions of the machine. We then describe a method for designing DNA sequences of the machine, which exhaustively checks conformational changes of the machine by dividing its secondary structure into hairpin units. The method is based on the minimum free energy of the structure, the structure transition paths, and the total frequency of optimal and suboptimal structures. DNA sequences designed by the method were tested in a chemical experiment in which a machine consisting of two hairpins was actually constructed. As a result, we verified that the multi-state DNA machine realized the expected changes in its secondary structure.     

Flexible microelectronics: New application for thin‐film transistors in fingerprint sensors

Abstract— Thin‐film transistors (TFTs) are field‐effect transistors that can be used to create large‐scale‐integrated (LSI) circuits. The combination of high‐performance TFTs and transfer technology of the TFTs has the potential to foster the rise of a new flexible microelectronics industry. This paper discusses the current status of flexible microelectronics, using a TFT fingerprint sensor (FPS) as an example. Technology used in active‐matrix displays can easily be applied to the TFT FPS. TFT technology should not be confined to the display industry; its use should be expanded into the semiconductor industry. With the result presented in this paper, we declare a new era of flexible microelectronics open.     

Internal oxidation in gold alloys containing small amounts of Fe and Sn

Internal oxidation was observed in gold-rich alloys as substrates for porcelain veneers in dental restorations, which contain small amounts of Fe and Sn. The internal oxidation proceeded with oxygen ions diffusing to the inner part of the alloy through Fe₂O₃ formed at the grain boundaries of the alloy matrix. SnO₂ was formed internally together with the Fe₂O₃. The external oxidation zone was composed of only Fe₂O₃ in a wide range of Fe and Sn concentrations. Fe₃O₄ was formed with Fe₂O₃ in the Sn-rich composition range by reduction of Fe₂O₃ in the presence of Sn. A band mainly composed of SnO₂ was formed at the inside of the internal oxidation zone in the composition range where Fe₃O₄ formed. In the Sn-rich alloys this internal oxidation band of SnO₂ moved to the external oxidation zone.     

Optical topography: practical problems and new applications

We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity.     

Microstructure and anodic polarization behavior of experimental Ag–18Cu–15Pd–12Au alloy in aqueous sulfide solution

The anodic corrosion behavior of an experimental Ag–15Pd–18Cu–12Au alloy in 0.1% Na₂S solution in relation to its microstructure was investigated using potentiodynamic and potentiostatic polarization techniques with analyses of corrosion products by X-ray diffractometry, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The role of Pd in improvement of the corrosion resistance was also investigated. In the potential/current density curve, three distinct current peaks, at –520 mV (peak I), –425 mV (peak II) and –175 mV (peak III), were observed. The Ag-rich ₂ matrix with coarse Cu and Pd-rich lamellae was the most corrosion-susceptible region, and this region was preferentially corroded at peak I with the formation of granular deposits of Ag₂S. A small amount of Ag–Cu mixed sulfide deposited on the Cu and Pd-rich coarse particles and dissolution of Ag as AgO^– might have occurred in parallel with Ag₂S formation at peak II. Enrichment of Pd on the alloy surface occurred at peak III due to preferential dissolution of Ag and Cu. A high level of corrosion resistance was attained with the formation of a thin Pd-rich sulfide film, which enhanced the passivity of the alloy in an alkaline sulfide solution. It was found that passivity is an important phenomenon not only for base metal alloys but also for noble metal alloys to maintain high levels of resistance to corrosion and tarnishing in sulfide environments.     

Surface acoustic wave based sensors employing ionic liquid for hydrogen sulfide gas detection

This paper describes a new type hydrogen sulfide (H₂S) gas sensor using ionic liquid (IL). In this sensor, a reservoir for the IL was integrated on a surface acoustic wave (SAW) resonator. The IL serves as an absorber for H₂S gas. Mass change due to this absorption is detected as shift in the resonant frequency. In this study, we fabricated and demonstrated the sensor using the lithium niobate (LiNbO₃) SAW resonator with the resonant frequency of 38 MHz. The integrated reservoir was filled by the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]-[PF₆]). As an experimental result, we observed the linear correlation between the frequency-shift and the exposure time of the sensor to the H₂S gas.     

High-pressure studies on Tc and crystal structure of iron chalcogenide superconductors

The superconducting transition temperature, T_c, in iron-based solids can be enhanced by applied pressure: T_c increases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se_1−xTe_x) and Fe(Se_1−xS_x). In the case of Fe(Se_1−xTe_x), the maximum T_c under high pressure did not exceed the T_c of FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se_1−xS_x) (0 < x < 0.3), T_c exhibited a significant increase with pressure; however, the maximum T_c under high pressure did not exceed the T_c of FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect on T_c for the 1111-type superconductor Ca(Fe_1−xCo_x)AsF. The T_c of Fe(Se_1−xS_x) showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, the T_c (P) curve was correlated with the local structural parameter.     

Gas analysis of the CVD process for high yield growth of carbon nanotubes over metal-supported catalysts

Changes in the gas composition during the methane chemical vapor deposition growth of single- and double-walled carbon nanotubes over metal-supported MgO catalysts were investigated in an attempt to increase the nanotube yield. Monitoring the gas composition by gas chromatography as a function of the reaction time provides information on the activity and lifetime of the catalyst. The degree of methane decomposition, i.e., the C-H bond dissociation, was closely related to the nanotube yield, and the Fe-Mo binary catalyst exhibited a high activity. The effects of water vapor on the catalytic nanotube growth were also studied by introducing water vapor in the inlet gas. An appropriate amount of water prolonged the lifetime of the catalyst and increased the nanotube yield by 35%.     

The characteristics of the external‐electrode mercury fluorescent lamp for backlighting liquid‐crystal‐television displays

Abstract— A reliable external‐electrode mercury fluorescent lamp (EEFL) has been developed for backlighting a liquid‐crystal‐television (LC‐TV) display. This involved the investigation of the EEFL characteristics and the improvement in the construction of the EEFL and drive waveforms, in the frequency range of 50–200 kHz, that affects the EEFL characteristics. The results showed that a sinusoidal waveform is suitable for driving the EEFL, and EEFL's voltage decreases when the frequency of the drive waveform is increased.