Direct Evidence for Structural Transition Promoting Shear Thinning in Cylindrical Colloid Assemblies

In this paper, we describe stimuli‐responsive hydrogels prepared from a rigid rod‐like polyelectrolyte ‘imogolite’ and a dicarboxylic acid. The hydrogel exhibited thixotropy in response to mechanical shock within the order of seconds or sub‐seconds. Here, using the latest structural/rheological characterisation techniques, the relationship between the structural transition processes and the shear thinning was estimated. The evidence obtained by the experiments revealed for the first time the direct relationship between the microscopic structural change and the macroscopic thixotropic behavior that have been extensively discussed. The thixotropic hydrogel has the hierarchical architecture in the combination of imogolite and dicarboxylic acid, i.e., sheathed nanotubes/hydroclusters of cross‐bridged nanotubes/frameworks. The formation and disintegration of the network structure upon resting and agitating, respectively, were the origin of gel/sol transition (thixotropy), although the hydroclusters of cross‐bridged nanotubes were maintained throughout the transition.     

Bringing out the Potential of Wild-type Cytochrome P450s using Decoy Molecules: Oxygenation of Nonnative Substrates by Bacterial Cytochrome P450s

To bring out the potential of wild-type cytochrome P450s, we have developed a series of “decoy molecules” to change their high substrate specificity without any mutagenesis. Decoy molecules are inert dummy substrates with structures that are very similar to those of natural substrates. The decoy molecules force long-alkyl-chain fatty acid hydroxylases (P450_BSβ, P450_SPα, and P450BM3) to generate the active species and to catalyze oxidation of various substrates other than fatty acids. Interestingly, the catalytic activity was highly dependent on the structure of decoy molecules. Furthermore, the enantioselectivity of reactions catalyzed by P450_BSβ and P450_SPα was also dependent on the structure of decoy molecules. The decoy molecule system allows us to control reactions catalyzed by wild-type enzymes by designing decoy molecules.     

Surface Diffusivity under High-Pressure Gas

The sintering behavior of TiO₂ under high-pressure gas (100 MPa) was studied with respect to densification rate, decreasing rate of specific surface area, and narrowing rate of pore size distribution. At the low sintering temperature (800°C) used in this study, the densification rate under high- pressure gas was similar to that under low (i.e., 1 atm) pressure. The specific surface area decreased and the pore size distribution narrowed at a faster rate under high- pressure gas than under low-pressure gas. These results imply that high-pressure gas enhances surface diffusion.     

Direct observation of X-ray induced atomic motion using scanning tunneling microscope combined with synchrotron radiation

X-ray induced atomic motion on a Ge(111)-c(2 x 8) clean surface at room temperature was directly observed with atomic resolution using a synchrotron radiation (SR)-based scanning tunneling microscope (STM) system under ultra high vacuum condition. The atomic motion was visualized as a tracking image by developing a method to merge the STM images before and after X-ray irradiation. Using the tracking image, the atomic mobility was found to be strongly affected by defects on the surface, but was not dependent on the incident X-ray energy, although it was clearly dependent on the photon density. The atomic motion can be attributed to surface diffusion, which might not be due to core-excitation accompanied with electronic transition, but a thermal effect by X-ray irradiation. The crystal surface structure was possible to break even at a lower photon density than the conventionally known barrier. These results can alert X-ray studies in the near future about sample damage during measurements, while suggesting the possibility of new applications. Also the obtained results show a new availability of the in-situ SR-STM system.     

Room-temperature formation of low refractive index silicon oxide films using atmospheric-pressure plasma

This study aims to apply atmospheric-pressure (AP) plasma to the fabrication of single-layer anti-reflection (AR) coatings with porous silicon oxide. 150 MHz very high-frequency (VHF) excitation of AP plasma permits to enhance the chemical reactions both in the gas phase and on the film-growing surface, increasing deposition rate significantly. Silicon oxide films were prepared from silane (SiH4) and carbon dioxide (CO2) dual sources diluted with helium. The microstructure and refractive index of the films were studied using infrared absorption and ellipsometry as a function of VHF power density. It was shown that significant increase in deposition rate at room temperature prevented the formation of a dense SiO2 network, decreasing refractive index of the resulting film effectively. As a result, a porous silicon oxide film, which had the lowest refractive index of 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave AR coating of a glass plate.     

Enhanced conduction-corrected modified effective temperature as the outdoor thermal environment evaluation index upon the human body

This paper aims to clarify the handling technique of the solar radiation in an element of the thermal environment evaluation indices and to add expansions and improvements to conduction-corrected modified effective temperature ETF (Kurazumi et al., 2009) that can quantify the comprehensive effect on sensational and physiological sense and the effect of individual meteorological elements on the same evaluation axis applicable to an outdoor environment. Mean radiant temperature and radiant heat transfer coefficient of the outdoor space was defined. Enhanced conduction-corrected modified effective temperature ETFe that is ETF including short-wave solar radiation in outdoor space was defined. This sensational and physiological climatic environment index can make temperature convert each effect of difference in posture; air velocity; long-wave radiation in the outdoor space; short-wave solar radiation; contact surface temperature and humidity into individual meteorological elements. The addition of each temperature-converted factor is possible and quantifying the composite effect on sensational and physiological sense in the outdoor spaces as well as the discrete effect of each meteorological element is possible on the same evaluation axis. Consequently, it is possible to make the climate modification effects due to tree shade and areas of water that improve the urban thermal environment quantitatively explicit.     

Low-power wake-up receiver with subthreshold CMOS circuits for wireless sensor networks

We developed a wake-up receiver comprised of subthreshold CMOS circuits. The proposed receiver includes an envelope detector, a high-gain baseband amplifier, a clock and data recovery (CDR) circuit, and a wake-up signal recognition circuit. The drain nonlinearity in the subthreshold region effectively detects the baseband signal with a microwave carrier. The offset cancellation method with a biasing circuit operated by the subthreshold produces a high gain of more than 100 dB for the baseband amplifier. A pulse-width modulation (PWM) CDR drastically reduces the power consumption of the receiver. A 2.4-GHz detector, a high-gain amplifier and a PWM clock recovery circuit were designed and fabricated with 0.18-μm CMOS process with one poly and six metal layers. The fabricated detector and high-gain amplifier achieved a sensitivity of ?47.2 dBm while consuming only 6.8 μW from a 1.5 V supply. The fabricated clock recovery circuit operated successfully up to 500 kbps.     

Synthesis, Thermal Stability and Photochemical Properties of DNA Containing Fluorescent Biaryl-Type Nucleoside Surrogates

A major goal of research in biotechnology and nanotechnology is to develop assemblies of novel biomaterials that can be used in analytical, industrial, and therapeutic applications. The synthesis of DNA （oligodeoxyribonucleotide） has been described containing the biaryl-type nucleoside surrogates, 6-deamino-2＇-deoxy-6-（l-naphthyl） adenosine （AN） and 6-deamino-2＇-deoxy-6-（1-pyrenyl） adenosine （AP）. It is found that incorporation of multiple ATM or AP residues in the middle of DNA duplexes does not significantly destabilize the duplexes and that the fluorescence intensities of the oligonucleotides containing AN or Ap significantly increases in the duplexes formed.     

Improvement of capacitance value as the electrode of an electrochemical capacitor by mixing starch with guanidine phosphate

Starch or starch mixed with phosphoric acid, guanidine carbonate, or guanidine phosphate is heat-treated for use as an electrode in an electrochemical capacitor. In the case of starch, the capacitance value is low (31.2 F g⁻¹ at 50 mA g⁻¹). However, the capacitance value significantly increases with the addition of guanidine phosphate, which can act as a flame-retardant (124.1F g⁻¹ at 50 mA g⁻¹). The method used in this study, which involves mixing with a flame-retardant by immersion, should be a promising candidate for improving of the capacitance value of starch-derived carbon.