An agar-agar chamber for study of electromagnetic waves in an inhomogeneous medium

A medium for the propagation of electromagnetic waves whose dielectric constant or loss tangent has a prescribed profile was fabricated by using a large quantity of agar-agar in simulation chambers. The dielectric constant of the agar-agar could be changed continuously by means of a controlled diffusion of ethyl alcohol. The loss tangent of the same medium could be changed continuously by means of a controlled diffusion of NaCl. This paper is concerned with the design and characteristics of the simulation chamber. Topics to be considered include the properties of agar-agar in a wide frequency spectrum, the diffusion profiles, a reexamination of the principle of simulation, and the construction of various types of probes and simulation chambers.     

An experimental study of the insulated dipole antenna immersed in a conducting medium

The driving-point admittance and the amplitude and phase distributions of the current referred to the driving-point were measured for an insulated cylindrical antenna immersed in a conducting medium. The ratiosigma/omegaepsilon_{r}epsilon_{0}of the conducting medium was varied fromsigma/omegaepsilon_{r}epsilon_{0}= 0.036to 8.8, a range which includes a variety of media such as poor insulators, the ionosphere, plasmas, dry earth, wet earth, lake water and sea water. The antenna heightbeta hin radians was varied frombeta h=0.1throughbeta h=2piat intervals of 0.1. The thickness of the insulator was varied fromb/a = 1.25tob/a = 12.0whereais the radius of the antenna andbthe radius of the insulator. Measurements have also been made of the admittance, current and phase distributions along an insulated antenna with a conductive top load, that is, one whose tip is in direct contact with the conducting medium. It is found that when the tip of the antenna is in direct contact with the conducting medium, the current increases almost linearly as the end of the antenna is approached. This is quite unlike the decaying sinusoidal distribution on the completely insulated antenna. In a general sense, the experimental results are in fair agreement with an approximate theoretical expression for the admittance of an insulated antenna immersed in a highly conducting solution. The approximate theory is based on the driving-point admittance of a coaxial line whose outer conductor is imperfectly conducting and infinite in extent.     

Enhancement of the activities with feedstream doping by tetrachloromethane in the oxidative dehydrogenation of propane on α-magnesium pyrovanadate

The oxidative dehydrogenation of propane to propylene has been investigated on -magnesium pyrovanadate (Mg₂V₂O₇) at 723 K in the presence and absence of tetrachloromethane (TCM). Under the present conditions, the conversion of propane and the selectivity to propylene were 5.0 and 74.5%, respectively, in the absence of TCM while those were 14.0 and 70.2%, respectively, upon addition of a small amount of TCM (P(TCM) = 0.34 kPa) into the feedstream on the catalyst. The conversion of propane on Mg₂V₂O₇ without oxidant in the presence and absence of TCM revealed that a contribution of lattice oxygen in the catalyst to the oxidation was strongly controlled by the addition of TCM, resulting in the enhancement of the activity with TCM.     

A 385–500 GHz SIDEBAND-SEPARATING (2SB) SIS MIXER BASED ON A WAVEGUIDE SPLIT-BLOCK COUPLER

We have developed a 385–500 GHz sideband-separating (2SB) mixer, which is based on a waveguide split-block coupler at the edge of the H-plane of the 508 μm × 254 μm (WR 2.0) waveguide, for the Atacama Large Millimeter/submillimeter Array (ALMA). An RF/LO coupler, which contains an RF quadrature hybrid, two LO couplers, and an in-phase power divider, was designed with the issue of mechanical tolerance taken into account. The RF/LO coupler was measured optically with a microscope and electrically with a submillimeter vector network analyzer. The image rejection ratio (IRR) and the single-sideband (SSB) noise temperature of the receiver using the RF/LO coupler have also been measured. The IRR was found to be larger than 8 dB and typically ～ 12 dB in the 385–500 GHz band. The SSB noise temperature of this receiver is 80 K at the band center, which corresponds to 4 times the quantum noise limit (hf/k) in SSB, and 250 K at the band edges.     

Electrode reaction of the Np3+/Np couple in LiCl–KCl eutectic melts

The electrochemical behaviour of the Np³⁺/Np couple in the LiCl–KCl eutectic salt was investigated by electromotive force measurements, cyclic voltammetry and chronopotentiometry in the temperature region between 723 and 823 K. The standard redox potential of the Np³⁺/Np couple vs Ag/AgCl (1.00 wt %) was measured and given by the equation, E _Np ³⁺ _/Np ^° = –2.0298 + 0.000706 T, where E is in V and T in K. The electrode reaction of the Np³⁺/Np couple was almost reversible under the conditions studied. The diffusion coefficient of Np³⁺, D _Np ³⁺, in the LiCl–KCl eutectic melts between 723 and 823 K was represented by the equation, D _Np ³⁺ = 2.22 × 10^–6 – 6.88 × 10^–9 T + 5.60 × 10^–12 T ² cm² s^–1. The adsorption and desorption peaks of Np at the Mo working electrode caused by underpotential deposition were also observed in the cyclic voltammograms, and the work function of Np was evaluated as 3.04 eV by peak analysis of the cyclic voltammograms.     

Cloning and sequencing of cDNA and genomic DNA encoding serine carboxypeptidase of Fusarium moniliforme that was copurified with phosphatase

A previous study [Yoshida, H. et al., J. Biochem., 140, 813-823 (2006)] revealed that a protein of unknown nature was copurified with PDM phosphatase of Fusarium moniliforme. In this study, the identity of this protein was investigated. The results of homology search for the tryptic peptides derived from the purified preparation of PDM phosphatase strongly suggested that it might be serine carboxypeptidase. In fact, carboxypeptidase activity was demonstrated in the preparation and partial separation of carboxypeptidase from PDM phosphatase was achieved by gel filtration high-performance liquid chromatography. Cloning and sequencing of the full-length cDNA encoding the carboxypeptidase was successfully conducted. The cDNA possessed an open reading frame for a protein of 575 amino acid residues with a molecular mass of 64,650 Da, which was highly homologous to certain fungal serine carboxypeptidases. Comparison of the deduced amino acid sequence with the N-terminal sequence of the separated carboxypeptidase revealed that the mature enzyme starts at serine 56 of the precursor and has a molecular mass of 58,487 Da. Cloning and sequencing of the genomic DNA corresponding to the cDNA demonstrated that the gene of carboxypeptidase consists of four exons. A limited number of close homologs of F. moniliforme carboxypeptidase were detected among fungi by homology search and their evolutionary relationship was discussed.     

Improvement of carbon monoxide analysis in fish meat

Carbon monoxide (CO) treatment of fish meat of tuna, yellowtail, tilapia etc. is not allowed in Japan, since it can maintain the red color for a longer period than the microbiological shelf life of fish meat. The official method for quantification of CO has a problem, in that a part of the CO is lost during the preparation of the fish sample. To solve this problem, we modified the official method in this study. We also applied this modified method to survey the contents of CO in tuna, yellowtail, young yellowtail, and tilapia. As a result, the modified method was found to be more suitable for CO quantification than the official method. An inter-laboratory study by 4 laboratories confirmed that the CO content of many samples of tilapia exceeded the regulation value, apparently due to the higher recovery of CO, compared to the official method. Therefore, it was suggested that the regulation value in the case of tilapia should be changed if this method is introduced as an official method.     

A model of the high-temperature deformation of metallic materials with ellipsoidal second-phase particles

A micromechanics model developed in the previous work which incorporated the effect of dynamic recovery by diffusion of atoms was applied to the interpretation of the high-temperature deformation of metallic materials with ellipsoidal second-phase particles. A theoretical discussion based on this model was made on the effect of several factors including shape, particle size, orientation and elastic modulus of second phase on the work-hardening behaviour of the materials at high temperature. A good correlation was found between the result of the calculations and those of the experiments obtained by the present authors or other investigators of several kinds of metallic materials with ellipsoidal second-phase particles. The dynamic recovery model used in this study can be applied to the understanding of high-temperature deformation behaviour or to the prediction of the possible recovery mechanism of the materials.     

Microstructure Development in RuO2-Glass Thick-Film Resistors and Its Effect on the Electrical Resistivity

Microstructure development in RuO₂-glass thick-film resistors has been studied by optical microscopy with special emphasis on the effect of glass particle size and mixing and firing conditions. The microstructure development has been characterized by the coalescence of glass grains, infiltration of glass into RuO₂ particle aggregates, and agglomeration of RuO₂ particles. The resistivity-firing temperature relationship has been correlated with the microstructure development.