Biodegradation of Poly(butylene succinate) Powder in a Controlled Compost at 58 ��C Evaluated by Naturally-Occurring Carbon 14 Amounts in Evolved CO2 Based on the ISO 14855-2 Method

The biodegradabilities of poly(butylene succinate) (PBS) powders in a controlled compost at 58 °C have been studied using a Microbial Oxidative Degradation Analyzer (MODA) based on the ISO 14855-2 method, entitled “Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions—Method by analysis of evolved carbon dioxide—Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test”. The evolved CO₂ was trapped by an additional aqueous Ba(OH)₂ solution. The trapped BaCO₃ was transformed into graphite via a serial vaporization and reduction reaction using a gas-tight tube and vacuum manifold system. This graphite was analyzed by accelerated mass spectrometry (AMS) to determine the percent modern carbon [pMC (sample)] based on the ¹⁴C radiocarbon concentration. By using the theory that pMC (sample) was the sum of the pMC (compost) (109.87%) and pMC (PBS) (0%) as the respective ratio in the determined period, the CO₂ (respiration) was calculated from only one reaction vessel. It was found that the biodegradabilities determined by the CO₂ amount from PBS in the sample vessel were about 30% lower than those based on the ISO method. These differences between the ISO and AMS methods are caused by the fact that part of the carbons from PBS are changed into metabolites by the microorganisms in the compost, and not changed into CO₂.     

Raman Scattering Study of Cubic–Tetragonal Phase Transition in Zr1−xCexO2 Solid Solution

A structural phase transition between the cubic (space group, Fm 3 m) and tetragonal (space group, P 4₂ /nmc) phases in a zirconia–ceria solid solution (Zr_1−xCe_xO₂) has been observed by Raman spectroscopy. The cubic–tetragonal ( c–t" ) phase boundary in compositionally homogeneous samples exists at a composition X₀ (0.8 < X₀ < 0.9) at room temperature, where t " is defined as a tetragonal phase whose axial ratio c/a equals unity. The axial ratio c/a decreases with an increase of ceria concentration and becomes 1 at a composition X'₀ (0.65 < X'₀ < 0.7) at room temperature. The sample with a composition between X₀ and X'₀ is t " ZrO₂. By Raman scattering measurements at high temperatures, the tetragonal ( t" ) → cubic and cubic → tetragonal phase transitions occur above 400°C in Zr_0.2 Ce_0.8O₂ solid solution.     

A predictive instantaneous-current PWM controlled rectifier withAC-side harmonic current reduction

A new single-phase bridge rectifier controlled by a predictive instantaneous-current PWM control scheme for reducing AC-side harmonic currents and improving power factor is proposed. The rectifier can operate at the unity displacement power factor and has fast response to an input signal as a current reference. The effect of the DC-side voltage ripples is taken into account. The paper describes three digital control schemes for such rectifiers and presents experimental and simulation studies on steady-state and dynamic performances of the rectifier. The effectiveness of the control schemes is confirmed by experiments and simulations. The proposed rectifier can be used for applications such as UPS systems and static VAr compensators     

Room-Temperature Preparation of Crystallized Ba1-χSrχWO4 Solid-Solution Films by an Electrochemical Method

Films of a complete series of solid-solution oxides, Ba^1-χSr^χWO⁴ (O ≥ X ≥ 1), have been prepared on tungsten substrates in an electrolytic solution containing Ba²⁺ and Sr²⁺ ions by an electrochemical method at room temperature (25°C). The composition X could easily be controlled by the concentrations of Ba and Sr species in the starting solutions. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that a complete series of well-crystallized solid-solution oxides was formed even at room temperature.     

Transient Tests on a Voltage-Regulated Controlled-Current PWM Converter

The controlled-current PWM converter has the capability of delivering near sinusoidal current waveforms with unity and even leading power factors. This paper describes its transient characteristics when operated with a simple proportional feedback control to ensure regulated dc voltage output. Experimental tests show that it has fast step response and that it survives abnormal operational conditions such as brown-outs and loss of a single phase.     

Catalytic Hydrogenation of Fullerenes in the Presence of Metal Catalysts in Toluene Solution

The catalytic hydrogenation of fullerenes was studied in the presence of various metal catalysts in toluene solution under several conditions. Fullerenes were found to be catalytically hydrogenated in toluene solution in the presence of the Ru/carbon, Pdharbon, NiDiatomaceous Earth or Ptharbon as the catalysts. The reactivity of catalytic hydrogenation of the Ru/C was the highest for the among the used metal catalysts.     

Recognition of amino acids by membrane potential and circular dichroism of immobilized albumin membranes

The shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α-helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.     

Design of a 1.65-μm-band optical time-domain reflectometer

The design and performance of a 1.65-μm-band single-mode optical time-domain reflectometer (OTDR) with a laser diode source are described. The approach employs a high-power laser diode with a strained-layer InGaAs/InGaAsP multiple-quantum-well (MQW) structure which is grown by metalorganic vapor phase epitaxy (MOVPE), an InGaAs avalanche photodiode, and methods for reducing the optical wiring loss in an optical unit. A 1.65-μm-band OTDR is realized with a single-way dynamic range of 25 dB at a pulse width of 1.0 μs