각종 인체 암조직의 당의 산화경로 분석

이봉기,이상돈,Lee, Bong-Kee,Lee, Sang-Don 대한생리학회 1968 대한생리학회지 Vol.2 No.1

Tissue homogenates of 12 kinds of human cancer tissues were incubated separately in medium containing $C^{14}-1-glucose$ and $C^{14}-6-glucose$ as a substrate in order to observe the oxidative pathway of glucose in the tumor tissues. At the end of 3 hours incubation in the Dubnuff metabolic shaking incubator, respiratory $CO_2$ samples trapped by alkaling which was placed in the center well of incubation flask were analysed for total $CO_2$ production rates and their radioactivities. The tissue homogenate samples after incubation were analyzed for their concentrations of glucose, lactate and pyruvate. Calculations were made on the glucose consumption rate and accumulation rates of lactate and pyruvate. Fractionation of oxidative pathway of glucose was carried out by calculating $C^{14}O_2 yields from C-1 and C-6 carbon of glucose. The following results were obtained. 1. In 12 kinds of human cancer, total $CO_2$ production rates were less than $8{\mu}M/gm$ except 2 cases. These lower values impressed that oxidative metabolism in the tumor tissues generally inhibited as compared with that in normal tissues. On the other hand, fractions of $CO_2$ derived from glucose to total $CO_2$ production rates (RSA) were less than 10% in every case. These facts showed that oxidation of glucose into $CO_2$ was remarkably inhibited in the tumor tissues. 2. Factions of glucose disappeared into $CO_2\;(RGD_{CO_2})$, lactate $(RGD_L)$, pyruvate $(RGD_P)$ to glucose consumption rates were as follows. $RGD_{CO_2}$ were less than 2% in cases of in this experiment and $RGD_L$ showed more than 5% except in 2 cases. These facts showed that anaerobic degradation of glucose into 3 carbon compounds was easily proceeded but further degradation into $CO_2$ via the TCA cycle was greatly inhibited resulting in accumulation of lactate. There are large variation in values of $RGD_P$ in different kinds of tumor tissue but relatively higher values in $RGD_{CO_2}$ were obtained in the tumor tissues as compared with those of normal tissues. 3. The oxidative pathway of glucose in tumor tissues were analyzed from the values of RSA which were obtained in $C^{14}-1\;and\;C^{14}-6-glucose$ incubation experiments. It was found that 3% of $CO_2$ derived from glucose were oxidized via the principal EMP-TCA cycle and the remainder were via alternate pathway such as HMP in the liver cancer and values in other cancer tissues were as follows; 4% in the tongue cancer, 6% in the colon cancer, 6% in the lung cancer, 9% in the stomach cancer, 11% in the ovarian cancer, 12% in the neck tumor, 22% in the uterine cancer, 22% in the bladder tumor, 32% in the spindle cell sarcoma and 65% in the brain tumor. These values except later 2 cases showed less than 30% which is the lowest value among the normal tissues. Even in the brain tumor in which showed highest value in the tumor group. It is reasonable to suppose that this fraction was remarkably decreased because values in normal brain tissue was more than 90%. From the above data, it was concluded that in tumor tissues, oxidation of glucose via TCA cycle was greatly inhibited but correlation between degree of inhibited oxidation of glucose via TCA cycle and malignancy of tumor were not clarified in this experiments.

미세유체 칩의 초소형 사출성형 공정에 대한 수치적 연구

이봉기(Bong-Kee Lee),강석원(Seok Won Kang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

In the present study, a numerical study was carried out to investigate a melt flow behavior and effects of processing parameters in an injection molding process of a novel microfluidic chip platform. The platform mainly consisted of upper and lower plates, which included several basic components such as T-shaped microchannels, through-holes, interconnecting ports, and guiding elements. In order to manufacture the platform plates efficiently, an injection mold core having two distinct cavities was designed and employed in the molding experiments. Based on the numerical simulations for the designed mold structures, the detailed melt flow behaviors inside the mold cavities, for instance flow balance, filling pattern, and relevant defects, were inspected. Also, the effects of important processing parameters were investigated, which could be used as a stepping-stone toward an optimized injection molding process for the microfluidic chip platform.

Numerical Analysis of the Filling Stage in Insert Injection Molding of Microfluidic Chip with Metal Electrodes

이봉기(Bong-Kee Lee),나승식(Seung-Sik Na) Korean Society for Precision Engineering 2015 한국정밀공학회지 Vol.32 No.11

In the present study, a numerical investigation of an insert injection molding process was carried out for the development of thermoplastic microfluidic chip plates with metal electrodes. Insert injection molding technology enables efficient realization of a plastic-metal hybrid structure and various efforts have been undertaken to produce novel components in several application fields. The microfluidic chip with metal inserts was proposed as a representative example and its molding process was analyzed. The important characteristics of the filling stage, such as the effects of filling time and thickness of the part cavity, were characterized. Furthermore, the detailed distributions of pressure and temperature at the end of the filling stage were investigated, revealing the significance of metal insert temperature.

방사광 X-선을 이용한 정밀 마이크로 금형 제작

이봉기(Bong-Kee Lee) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.5-2

In the present study, a precise micromold was developed by a deep X-ray lithography using a synchrotron radiation and a subsequent nickel electroforming for a mass replication of plastic microstructured surfaces. The micromold consisted of several modules, each having different cross-sectional microfeatures on its top side. A PMMA mother structure of the various modules with the precise cross-sectional microfeatures was realized by utilizing the advantages of the synchrotron X-ray. The nickel electroforming onto the obtained mother structure was subsequently carried out, resulting in the precise micrmold modules. By assembling the modules in a mold core, the micromold having the complex microfeatures on its surface was prepared. Finally, the plastic injection molding process was employed in order to replicate the various microstructured surfaces.

모듈화된 초소형 몰드 시스템(MSMS)을 이용한 다단 마이크로 구조물의 초소형 사출성형 공정

이봉기(Bong-Kee Lee),권태헌(Tai Hun Kwon) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.7

본 연구에서는 다단 마이크로 구조물의 대량성형을 위하여, 모듈화된 초소형몰드 시스템(MSMS)을 이용한 초소형 사출성형 공정을 수행하였다. 본 연구에서 적용된 초소형몰드 시스템은 여러 모듈들로 구성되어 있으며, 각 모듈들은 다양한 단면 마이크로 구조물을 가지고 있다. 초소형몰드 시스템의 모듈들은 X-선 리소그래피 공정 및 니켈 전주도금 공정으로 제작되었으며, 다양한 모듈들을 조합 및 결합함으로써 복잡한 형상을 가지는 초소형몰드 시스템을 효과적으로 구현할 수 있다. 이와 같은 초소형몰드 시스템을 적용함으로써, 본 연구에서는 다단 구조물의 표면에 마이크로 삼각 프리즘이 주기적으로 배열되어 있는 다단 마이크로 구조물의 초소형 사출성형 공정을 성공적으로 수행하였다. In this study, microinjection molding process using the newly developed micromold system, namely modularized and sectioned micromold system (MSMS), has been carried out for a replication of multi-level microstructures. The present MSMS consisted of several micromold modules, each having cross-sectional microstructures on the top surface. The micromold modules were precisely fabricated by deep X-ray lithography and subsequent nickel electroforming. By assembling the micromold modules, an MSMS having multi-level microstructures, which could be used as a mold system in micromolding processes, was obtained. In this manner, polymeric multi-level microstructures, such as the triangular prism microstructures on a stepped surface, were successfully replicated by the microinjection molding process.

전기장 해석을 통한 다중노즐 전기방사 공정 연구

이봉기(Bong-Kee Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.5

이중 전기방사된 TPU/PVDF-HFP 멤브레인의 인장 특성 평가

이봉기(Bong-Kee Lee),노재관(Jae-Gwan Rho),허은정(Eun-Jeong Heo),오채은(Chae-Eun Oh) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11

균일한 고분자 나노섬유 매트 제작을 위한 다중 노즐 전기방사 공정 연구

이봉기(Bong-Kee Lee),박재한(Jae-Han Park),박건중(Geon-Jung Park),박광련(Kwang-Ryun Park) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.3

In the present study, the multi-nozzle electrospinning process is investigated for the fabrication of uniform polymer nanofiber mats. Electrospinning has been one of the simple and efficient methods to manufacture polymer nanofibers and their mats. Although a typical electrospinning has many advantages such as simple system and operation, various materials, and cost-effectiveness, a relatively low productivity prevents it from being used in practical applications. Thus, the multi-nozzle electrospinning system with the adjustable nozzle position and rotating drum collector is designed and produced in this study. In particular, the effects of the inter-nozzle distance and spatial arrangement of nozzles on the uniformity of the electrospun nanofibers are investigated. With this multi-nozzle electrospinning process, the maximum flow rate of the supplied polymer solution for a uniform electrospinning increases, which indicates the enhanced productivity.

미세사출성형에서의 유동성에 대한 실험 및 수치적 연구

이봉기(Bong-Kee Lee),이재구(Jae Gu Lee),권태헌(Tai Hun Kwon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

In this study, the moldability in micro injection molding is investigated both numerically and experimentally. A numerical analysis system, which is based on a domain decomposition of the whole part, has been developed for the injection mold filling of microstructures. Along with the numerical analysis, various injection molding experiments with micro-rib structures are also carried out in order to investigate the moldability in micro injection molding. The melt front advancements in micro-rib structures are measured in detail. Due to a rapid cooling of polymer melt through the thin micro-rib structures, not only the ‘shot shot’ but also the ‘flow back’ phenomena are observed. Furthermore the effects of processing conditions on the moldability in micro-rib structures are also investigated.

초소형사출성형 공정을 이용한 마이크로 구조 표면의 성형

이봉기(Bong-Kee Lee),김영배(Young-Bae Kim),권태헌(Tai Hun Kwon) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.9

In the present study, replication of microstructured surfaces by microinjection molding was carried out. For a fabrication of mold inserts, nickel microstructures having various characteristic dimensions were fabricated by nickel electroforming onto Si mother microstructures. In addition, reverse nickel microstructures based on the electroformed nickel microstructures were successfully realized by electroforming with passivation process. The fabricated nickel microstructures were used as mold inserts for a replication of microstructured surfaces by microinjection molding. Microinjection molding experiment was carried out under three different processing conditions, which revealed effects of a packing stage and mold wall temperature. The microinjection-molded microstructured surfaces were characterized by using an atomic force microscope (AFM). It was found that mold wall temperature could enhance replication quality, resulting in the precise microstructured surfaces.