単一または複数気泡によって誘起される飽和核沸騰熱伝達

京都大学0048新制・課程博士博士(工学)甲第22894号工博第4791号新制||工||1749(附属図書館)京都大学大学院工学研究科原子核工学専攻(主査)教授 横峯 健彦, 教授 佐々木 隆之, 講師 河原 全作学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDGA

CYP105-diverse structures, functions and roles in an intriguing family of enzymes in 'Streptomyces'

The cytochromes P450 (CYP or P450) are a large superfamily of haem-containing enzymes found in all domains of life. They catalyse a variety of complex reactions, predominantly mixed-function oxidations, often displaying highly regio- and/or stereospecific chemistry. In streptomycetes, they are predominantly associated with secondary metabolite biosynthetic pathways or with xenobiotic catabolism. Homologues of one family, CYP105, have been found in all Streptomyces species thus far sequenced. This review looks at the diverse biological functions of CYP105s and the biosynthetic/catabolic pathways they are associated with. Examples are presented showing a range of biotransformative abilities and different contexts. As biocatalysts capable of some remarkable chemistry, CYP105s have great biotechnological potential and merit detailed study. Recent developments in biotechnological applications which utilize CYP105s are described, alongside a brief overview of the benefits and drawbacks of using P450s in commercial applications. The role of CYP105s in vivo is in many cases undefined and provides a rich source for further investigation into the functions these enzymes fulfil and the metabolic pathways they participate in, in the natural environment

Influence of hydrodynamic interactions among multiple bubbles on convective heat transfer in nucleate boiling

To clear the effects of the hydrodynamic interactions among neighboring vapor bubbles on the saturated pool boiling heat transfer, artificial nucleation sites with several cavity arrangements were manufactured on the substrate surface and measured liquid temperatures near heated substrate by a miniature thermocouple probe with 10 kHz. The surface temperature of heated substrate was measured by an infrared camera with 1 kHz and bubble dynamics were simultaneously visualized by a high-speed video camera with 5 kHz and 10 kHz, respectively. The liquid temperature fluctuations, measured with micro thermocouple 100 %m and 10 %m above the substrate surface, were compared among each other and with the transient temperature fields obtained through IR measurements. Results showed that the hydrodynamic interaction among neighboring bubbles causes the liquid convection, that was only detected 100 %m above the boiling surface. Generally, the degree of liquid temperature fluctuations at 10 %m height and different arrangements of nucleation sites was under 1 K. Here the superheated sublayer in the vicinity of the boiling surface was generally not affected by the convection. Only when the coalescence from two neighboring nucleation sites occurred and the liquid-vapor interface nearly reached the substrate, a steep temperature drop over 2 K was detected. It was concluded that the viscous sublayer stably exists during boiling of water in lower heat flux conditions. To enhance the convective heat transfer in nucleate boiling, coalesced bubble needs to peel off the viscous sublayer during its deformation. Based on the measurements in this study, this peel-off effect only happens when the coalescence point is less than 1 mm above the heated surface