GaAs MESFET characterization using least squares approximation byrational functions

The authors propose a method of characterizing active devices such as the FET by describing S-parameters with a set of rational functions of angular frequency. The set of rational functions is uniquely determined by only 27 coefficients, while the conventional method using tabulated S-parameters requires eight times the number of sampling points (a typical case might require 404 data points in floating-point notation). This drastically reduces the database size required to give adequate information for circuit design. A method for determining the equivalent circuit is described. Since the equivalent circuit is determined from the set of rational functions, no additional measurements are needed to determine extrinsic elements. In conventional methods, selection of initial values affects the final results. In the present method, reliable initial values are extracted from the rational functions' coefficients. The calculated S-parameters of three GaAs MESFETs having different gate widths agree closely with those measured by wafer-probe     

Synthesis of Nanohole‐Structured Single‐Crystalline Platinum Nanosheets Using Surfactant‐Liquid‐Crystals and their Electrochemical Characterization

Nanohole‐structured single‐crystalline Pt nanosheets have been synthesized by the borohydride reduction of Na₂PtCl₆ confined to the lyotropic liquid crystals (LLCs) of polyoxyethylene (20) sorbitan monooleate (Tween 80) with or without nonaethylene‐glycol (C₁₂EO₉). The Pt nanosheets of around 4–10 nm in central thickness and up to 500 nm or above in diameter have a number of hexagonal‐shaped nanoholes ∼1.8 nm wide. High‐resolution electron microscope images of the nanosheets showed atomic fringes with a spacing of 0.22 nm indicating that the nanosheets are crystallographically continuous through the nanoholed and non‐holed areas. The inner‐angle distributions for the hexagonal nanoholes indicate that the six sides of the nanoholes are walled with each two Pt (111), Pt (1 1) and Pt (010) planes. The formation mechanism of nanoholed Pt nanosheets is discussed on the basis of structural and compositional data for the resulting solids and their precursory LLCs, with the aid of similar nanohole growth observed for a Tween 80 free but oleic acid‐incorporated system. It is also demonstrated that the nanoholed Pt nanostructures loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction and a high performance as a cathode material for polymer‐electrolyte fuel cells, along with their extremely high thermostability revealed through the effect of electron‐irradiation.     

Present Status and Future Prospects of Laser Fusion Research at ILE Osaka University

Reviewed are the present status and future prospects of the laser fusion research at the ILE Osaka.The Gekko XII and Peta Watt laser system have been operated for investigating the implosion hydrodynamics,fast ignition, and the relativistic laser plasma interactions and so on.In particular,the fast ignition experiments with cone shell target have been in progress as the UK and US-Japan collaboration programs.In the experiments,the imploded high density plasmas are heated by irradiating 500 J level peta-watt laser pulse.The thermal neutron yield is found to increase by three orders of magnitude by injecting the peta-watt laser into the cone shell target.The Rayleigh-Taylor instability experiment results are also reviewed is this paper.     

Tiliroside, a glycosidic flavonoid, inhibits carbohydrate digestion and glucose absorption in the gastrointestinal tract

Scope Recent studies have reported that tiliroside, a glycosidic flavonoid, possesses anti‐diabetic activities. In the present study, we investigated the effects of tiliroside on carbohydrate digestion and absorption in the gastrointestinal tract. Methods and results This study showed that tiliroside inhibits pancreatic α‐amylase (IC₅₀ = 0.28 mM) in vitro. Tiliroside was found as a noncompetitive inhibitor of α‐amylase with K_i values of 84.2 μM. In male ICR mice, the increase in postprandial plasma glucose levels was significantly suppressed in the tiliroside‐administered group. Tiliroside treatment also suppressed hyperinsulinemia after starch administration. Tiliroside administration inhibited the increase of plasma glucose levels in an oral glucose tolerance test, but not in an intraperitoneal glucose tolerance test. In human intestinal Caco‐2 cells, the addition of tiliroside caused a significant dose‐dependent inhibition of glucose uptake. The inhibitory effects of both sodium‐dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2) inhibitors (phlorizin and phloretin, respectively) on glucose uptake were significantly inhibited in the presence of tiliroside, suggesting that tiliroside inhibited glucose uptake mediated by both SGLT1 and GLUT2. Conclusion These findings indicate that the anti‐diabetic effects of tiliroside are at least partially mediated through inhibitory effects on carbohydrate digestion and glucose uptake in the gastrointestinal tract.     

Remarkable improvement of the signal-to-noise ratio of Mn/Fe in-beam Mössbauer spectroscopy

In-beam Mössbauer spectroscopy utilizing unstable ⁵⁷Mn beams is a powerful method to extract physical and chemical properties at the atomic scale. A parallel plate avalanche counter (PPAC), optimized to detect conversion electrons generated by the Mössbauer effect, can be employed to suppress higher-energy background γ rays. However, β rays are emitted by the ⁵⁷Mn parent nuclei of ⁵⁷Fe, which can significantly degrade the spectrum quality. In the present work, we have developed a new anti-coincidence-detection system with a thin plastic scintillation counter (0.5 mmt), which can be used to detect β rays and reject them from the recorded PPAC events. To demonstrate the anti-coincidence system, we carried out Mössbauer spectroscopy utilizing ⁵⁷Mn nuclei that were implanted into a non-magnetic aluminum metal plate at room temperature. Using the anti-coincidence method, we obtained a typical Mössbauer spectrum of high quality, despite a very low number of implanted ⁵⁷Mn atoms, of ∼5 × 10⁹. The signal to noise ratio of the obtained spectrum was increased remarkably, and the relative peak height above the baseline increased from 10% to 220% using the anti-coincidence method. The developed detection system is applicable to investigation of in situ properties, and avoids the potentially problematic agglomeration of probes in a sample.     

A filter immunobinding technique for the rapid detection and simultaneous identification of avian and bovine mycoplasmas

A filter immunobinding (FIB) method was developed for the detection and identification of mycoplasmas. Type strains of a total of 18 avian and bovine mycoplasma species propagated in broth media were diluted and immobilized on a nitrocellulose membrane as antigens for investigating the specificity with rabbit hyperimmune sera. Non-specific FIB reactions were easily eliminated by the procedure of absorbing rabbit hyperimmune sera in the broth. Absorbed rabbit hyperimmune sera exhibited clear species-specificity with mycoplasma antigens by the FIB. These specific reactions always agreed with the results of identification by tests of biochemical properties and growth inhibition for the isolates of M. bovirhinis, M. bovis, M. columbinum, M. columborale, M. gallisepticum and M. synoviae. Some bovine mycoplasma species, which were impossible to identify by growth inhibition test, because of their strong production of film and spots on the agar, specifically reacted with absorbed rabbit hyperimmune sera against M. bovis in the FIB. The detection limit of mycoplasmas by this method was about 10(4)-10(5) colony-forming units/ml, which is lower than that of colony determination on agar. The FIB seems to be a useful technique for rapid detection and simultaneous identification of mycoplasmas.     

Analytical evaluation of unstable deformation criterion of atomic structure and its application to nanostructure

An analytical method for evaluating the unstable deformation modes of atomic structure is proposed. The instability criterion is given as positiveness of the minimum eigenvalue of the matrix, which consists of second order differential of potential energy with respect to atomic coordinates. The eigenvector for the minimum eigenvalue indicates the relative displacement of atoms at the instability (unstable deformation mode). The method is applied to tensile strengths of (1) thin film and (2) cracked body. The thin film with the thickness under 10 nm is weaker than bulk. The crack propagation mode in (2) is dependent on the boundary condition, and the mode is successfully distinguished by the method.     

An approach to develop space solar power as a new energy system for developing countries

The idea of space solar power proposed by Glaser was explained as a set of a solar power power station in geostationary earth orbit to transmit microwave power and a ground station to receive the microwave power. Most of the ideas and concepts since Glaser used the same context. On the other hand, Collins et al. (Proceedings SPS '91, pp. 132–141, 1991) introduced the concept of microwave “fuel” to assess the commercial relations of power from space, in which space solar power stations are considered to sell microwave power to any unspecified rectenna. This concept changed the theoretical context of “power from space” to an industrial and economic relation of producers and buyers of an industrial product. This new context has been applied to the SPS 2000 conceptual study. As a result, if 2.45 GHz microwave power transmission is used, each rectenna can be planned and engineered independently from the space sector by local users, especially in developing countries, who are familiar with such activities as introducing solar energy systems.     

Time-dependent dielectric breakdown (TDDB) distribution in n-MOSFET with HfSiON gate dielectrics under DC and AC stressing

This paper discusses time-dependent dielectric breakdown (TDDB) in n-FETs with HfSiON gate stacks under various stress conditions. It was found that the slope of Weibull distribution of T_bd, Weibull β, changes with stress conditions, namely, DC stress, unipolar AC stress and bipolar AC stresses. On the other hand, the time evolution component of stress-induced leakage current (SILC) was not changed by these stresses. These experimental results indicate that the modulation of electron trapping/de-trapping and hole trapping/de-trapping by stress condition changes the defect size in high-k gate dielectrics. Therefore, the control of injected carrier and the characteristics of trapping can provide the steep Weibull distribution of T_bd, leading to long-term reliability in scaled CMOS devices with high-k gate stacks.