Surface Waves on Superfluid <Superscript>4</Superscript>He Under Reduced Gravity

Superfluid ⁴He was produced on a small jet plane for the first time using a small GM-refrigerator to condense the liquid and a scroll pump to get the superfluid by evaporation. The surface wave on superfluid under 0.5g _E, 0.1g _E and 0.05g _E, together with 2g _E and 1g _E, was successfully examined by an optical method utilizing parabolic flight. Here, g _E is the gravitational constant on the ground. Assuming that only the fundamental mode was excited as determined by the sample cell width, the resonance peak in the frequency domain was well reproduced by the gravity wave with corresponding gravity constant.     

Practical equalizer for a perpendicular magnetic disk

We have developed a readback equalizer for a perpendicular magnetic disk with a commercial anisotropic magnetoresistive head for use with a PR4ML read channel with 8-9 coding. The transfer function of the perpendicular magnetic disk, derived by Fourier analysis, has a phase lag of 90/spl deg/ from that of the longitudinal magnetic disk. We defined the parameters of the equalizer by simulation. The equalized readback signal nearly satisfied Nyquist's first criterion. Using resistor-capacitor circuits that correspond to the simulated function, we obtained a byte-error rate of below 10/sup -7/. Comparing the effect of incorporating PR4 or PR1 as part of the equalizer, we observed that PR4 gave a lower bit-error rate than PR1. Thus, PR4 is an effective detection method for a perpendicular magnetic disk. It is suitable not only for longitudinal magnetic disks, but also for perpendicular magnetic disks.     

Thermal conductivity of RAlO3(R = Dy, Er and Ho) in liquid helium temperatures

The thermal conductivities of rare earth ortho-aluminate, DyAlO₃, ErAlO₃ and HoAlO₃, single crystals were measured between 2 and 20 K at magnetic fields between 0 and 5T. In zero magnetic field, the thermal conductivities show a typical dielectric behaviour and there are large differences in the peak values of the thermal conductivities. This suggests that the resonant phonon scattering by rare earth ions already exists at zero magnetic field in those perovskites. Two types of magnetic field dependencies are observed. The thermal conductivities of DyAlO₃ and ErAlO₃ decrease with increasing magnetic field; however, HoAlO₃ gives the opposite result. These dependencies can be qualitatively explained by using an energy level scheme on the ground state in Kramer or non-Kramer ions.     

Solid state phase transformation of BaB2O4 during the isothermal annealing process

Solid-state phase transformation of BaB₂O₄ during the isothermal annealing process for both to and to were investigated using a platinum crucible. For the -phase crystal at the -phase stable temperature (> 925 °C), the phase transforms to the phase perfectly below the melting temperature of 1100 °C. Meanwhile, for the -phase crystal at the -phase stable temperature (< 925 °C), the phase transforms to the phase perfectly above 800 °C. There is some difference in phase transformation behaviour between bulk-shape crystals and the powder, caused by thermal stress.     

A new control method for the relative dielectric constant of 1–3 piezoelectric composites realized with the LIGA process

 A plasma treatment for controlling the relative dielectric constant (ɛ_r) of fine-scale lead zirconate titanate (PZT) rods was developed. This new method made it easy to control ɛ_r of 1-3 piezoelectric composites, which were made up of fine-scale PZT rods in epoxy resin. The PZT rods were fabricated using the LIGA process, realizing an array of PZT rods with a cross section, height and volume fraction of 25 μm square, 250 μm and 25%, respectively. The new method consists of a plasma treatment applied before sintering of the PZT rods. By controlling the output RF power and duration of the plasma treatment, ɛ_r could be controlled between 250 and 400. Although extended plasma etching reduced ɛ_r, there were no changes in the piezoelectric properties and no defects in the sintered body. The ability to control ɛ_r of piezoelectric composites allows good electrical impedance matching with the electric circuit of diagnostic systems, thereby reducing signal transmission losses. Changing ɛ_r by varying the piezoelectric material or the sintering conditions requires lengthy process optimization. In contrast, controlling ɛ_r to establish a good impedance match can be done relatively easily with this new plasma technique because the piezoelectric properties are not affected.     

Development of LIGA process using a superconducting compact synchrotron light source

This paper describes the LIGA process using a 600-MeV superconducting compact synchrotron light source. Deep-etch X-ray lithography is conducted using a new resist and mask. The resist is composed of a copolymer of methyl methacrylate (MMA) and methacrylic acid (MAA). Its main benefit is its high sensitivity, which is one order of magnitude greater than that of polymethyl methacrylate (PMMA) conventionally used in the LIGA process. The mask is composed of a 2-μm-thick silicon nitride membrane with high transparency, supporting a 5-μm-thick tungsten absorber. Experimental results for deep-etch X-ray lithography, electroplating, and molding techniques are presented. A micro-ultrasonic transmitter obtained using these techniques is also described. The purpose of this study is the realization of low-cost microcomponents for a variety of industrial applications. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 40–48, 1997     

Mechanism for aromatase inactivation by a suicide substrate, androst-4-ene-3,6,17-trione. The 4 beta, 5 beta-epoxy-19-oxo derivative as a reactive electrophile irreversibly binding to the active site

Aromatase is a cytochrome P450 enzyme complex that catalyzes the conversion of androst-4-ene-3,17-dione to estrone through three sequential oxygenations of the 19-methyl group. Androst-4-ene-3,6,17-trione (1) is a suicide substrate of aromatase. The inactivation mechanism for steroid 1 has been studied to show that the inactivation reaction proceeds through the 19-oxo intermediate 3. To further clarify the mechanism, 4 beta, 5 beta-epoxyandrosta-3,6,17,19-tetraone (6) was synthesized as a candidate for a reactive electrophile involved in irreversible binding to the active site of aromatase, upon treatment of compound 3 with hydrogen peroxide in the presence of NaHCO3. The epoxide 6 inhibited human placental aromatase in a competitive manner (Ki = 30 microM); moreover, it inactivated the enzyme in an active-site-directed manner in the absence of NADPH (K1 = 88 microM, kinact = 0.071 min-1). NADPH and BSA both stimulated the inactivation rate without a significant change of the K1 in either case (kinact: 0.133 or 0.091 min-1, in the presence of NADPH or BSA, respectively). The substrate androst-4-ene-3,17-dione protected the inactivation, but a nucleophile, L-cysteine, did not. When both the epoxide 6 and its 19-methyl analog 4 were subjected separately to reaction with N-acetyl-L-cysteine in the presence of NaHCO3, the 19-oxo steroid 6 disappeared from the reaction mixture more rapidly (T1/2 = 40 sec) than the 19-methyl analog 4 (T1/2 = 3.0 min). The results clearly indicate that the 4 beta, 5 beta-epoxy-19-oxo compound 6, which is possibly produced from 19-oxo-4-ene steroid 3 through the 19-hydroxy-19-hydroperoxide intermediate, is a reactive electrophile that irreversibly binds to the active site of aromatase.