マイクロ波帯における電場と磁場が平行なベルトラミ場の研究

京都大学新制・課程博士博士(工学)甲第24584号工博第5090号新制||工||1975(附属図書館)京都大学大学院工学研究科電気工学専攻(主査)教授 篠原 真毅, 教授 大村 善治, 教授 小嶋 浩嗣, 教授 引原 隆士学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDGA

Quarter-wavelength E‖H Beltrami cavity resonators

In this paper, we present the design and implementation methods of quarter-wavelength resonators accommodating Beltrami standing waves with parallel electric and magnetic (E‖H) fields. The resonator is bounded by the quarter-wavelength longitudinal electromagnetic conductor (LEMC), the circumferential electromagnetic conductor (CMEC), and the radial electromagnetic conductor (REMC). The LEMC, CEMC, and REMC boundaries are artificially implemented by the circumferentially aligned corrugation, concentrically aligned circular fins, and axisymmetrically aligned radial fins, respectively. The coupling control methods by introducing slots in the CEMC and REMC with the external TM01 and TE01 circular waveguides are presented. We design the quarter-wavelength resonators with the implemented LEMC, CEMC, and REMC boundaries with controlled external couplings and numerically demonstrate their E‖H properties, which confirms the validity of the proposed design method

Zero Poynting vector E∥H Beltrami field cylindrical cavity resonators

In this paper, we present novel cylindrical cavity resonators accommodating spatially and temporally zero Poynting vector Beltrami standing waves with the parallel electric and magnetic fields (E∥H). We introduce the special boundary conditions, i.e., longitudinal electromagnetic conductor (LEMC) on which zero longitudinal electromagnetic components are enforced and circumferential electromagnetic conductor (CEMC) on which zero circumference electromagnetic components are enforced in an axisymmetric waveguide system, and show that the zero Poynting vector E∥H Beltrami standing wave is generated as a superposition of dual degenerated axisymmetric TM and TE standing waves in a cylindrical resonator using the LEMC and CEMC boundary conditions. We present physical implementation methods of the LEMC and CEMC boundary conditions composed of the circumferentially arranged corrugations and the concentrically aligned cylindrical thin fins, respectively. In addition, we numerically demonstrate the Beltrami standing field generation and reveal its peculiar electromagnetic properties: the spatially and temporally E∥H with zero Poynting vector distribution, identical electric and magnetic energy density distributions, and zero local reactive energy flow

Efficient depolymerization of polyethylene terephthalate (PET) and polyethylene furanoate by engineered PET hydrolase Cut190

The enzymatic recycling of polyethylene terephthalate (PET) can be a promising approach to tackle the problem of plastic waste. The thermostability and activity of PET-hydrolyzing enzymes are still insufficient for practical application. Pretreatment of PET waste is needed for bio-recycling. Here, we analyzed the degradation of PET films, packages, and bottles using the newly engineered cutinase Cut190. Using gel permeation chromatography and high-performance liquid chromatography, the degradation of PET films by the Cut190 variant was shown to proceed via a repeating two-step hydrolysis process; initial endo-type scission of a surface polymer chain, followed by exo-type hydrolysis to produce mono/bis(2-hydroxyethyl) terephthalate and terephthalate from the ends of fragmented polymer molecules. Amorphous PET powders were degraded more than twofold higher than amorphous PET film with the same weight. Moreover, homogenization of post-consumer PET products, such as packages and bottles, increased their degradability, indicating the importance of surface area for the enzymatic hydrolysis of PET. In addition, it was required to maintain an alkaline pH to enable continuous enzymatic hydrolysis, by increasing the buffer concentration (HEPES, pH 9.0) depending on the level of the acidic products formed. The cationic surfactant dodecyltrimethylammonium chloride promoted PET degradation via adsorption on the PET surface and binding to the anionic surface of the Cut190 variant. The Cut190 variant also hydrolyzed polyethylene furanoate. Using the best performing Cut190 variant (L136F/Q138A/S226P/R228S/D250C-E296C/Q123H/N202H/K305del/L306del/N307del) and amorphous PET powders, more than 90 mM degradation products were obtained in 3 days and approximately 80 mM in 1 day

Non-touch, Quick Removal of an Occluding Intratracheal Balloon Using High Intensity Focused Ultrasound and Limonene Emulsion

In recent years, fetal endoscopic tracheal occlusion （FETO） using a balloon has been clinically employed for promoting prenatal lung growth to ameliorate postnatal respiratory failure caused by severe in utero lung hypoplasia. After a successful FETO, in some limited fetal centers, planned or emergency balloon removal using another fetoscopy is performed to release the tracheal occlusion immediately before delivery. To overcome this additional fetoscopy, we previously reported an innovative simple procedure to remove the occluding balloon by bursting it with a pre-planned sequence of high intensity focused ultrasound （HIFU） irradiation. In that previous study, which used rabbits euthanized and submerged in degassed water, we inflated the balloon by injecting a mixture of perfluorocarbon and ultrasound contrast medium through a fetoscopically-guided catheter. The rate of successful balloon burst and deflation using HIFU irradiation was high enough （100％）, but the mode and timing of tracheal reopening （i.e., sudden burst or slow shrinkage of the balloon） was rather varied and collateral damage to the dermal/tracheal tissue was identified in 72.7％ of the experimental animals. Accordingly, to standardize the HIFU irradiation sequence and to achieve a reliable and secure balloon burst, we conducted another series of animal experiments in which the mixture of perfluorocarbon was replaced with “limonene emulsion” （D-limonene micelle emulsified in physiological saline） as the balloon injection fluid. In all 6 animals, we succeeded in reopening the airway by achieving an instantaneous and timely balloon burst without definite skin/tracheal damage. We conclude that HIFU irradiation together with injecting the balloon with “limonene emulsion” is an improved method for safe tracheal release from a balloon occlusion