Acetylcholine Induces Hyperpolarization Mediated by Activation of K<SUB>(Ca)</SUB> Channels in Cultured Chick Myoblasts

Doyun Lee,Jaehee Han,Jae-Yong Park 대한생리학회-대한약리학회 2005 The Korean Journal of Physiology & Pharmacology Vol.9 No.1

Our previous report demonstrated that chick myoblasts are equipped with Ca<SUP>2⁢</SUP>-permeable stretch- activated channels and Ca<SUP>2⁢</SUP>-activated potassium channels (K<SUB>Ca</SUB>), and that hyperpolarization-induced by K<SUB>Ca</SUB> channels provides driving force for Ca<SUP>2⁢ </SUP>influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for Ca<SUP>2⁢</SUP> influx. Under cell-attatched patch configuration, ACh increased the open probability of K<SUB>Ca</SUB> channels from 0.007 to 0.055 only when extracellular Ca<SUP>2⁢</SUP> was present. Nicotine, a nAChR agonist, increased the open probability of K<SUB>Ca</SUB> channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of K<SUB>Ca</SUB> channel is sensitive to intracellular Ca<SUP>2⁢</SUP> level, nAChR seems to be capable of inducing Ca<SUP>2⁢</SUP> influx. Using the Ca<SUP>2⁢</SUP> imaging analysis, we were able to provide direct evidence that ACh induced Ca<SUP>2⁢</SUP> influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from ⁣12.5⁑3 to ⁣31.2⁑5 mV by generating the outward current through K<SUB>Ca</SUB> channels. These results suggest that activation of nAChR increases Ca<SUP>2⁢</SUP> influx, which activates K<SUB>Ca</SUB> channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

Reward learning improves social information processing in the medial prefrontal cortex

Doyun Lee 한국실험동물학회 2022 한국실험동물학회 학술발표대회 논문집 Vol.2022 No.7

Development of Automated Welding System for Construction: Focused on Robotic Arm Operation for Varying Weave Patterns

Doyun Lee,Guang-Yu Nie,Aman Ahmed,Kevin Han Council on Tall Building and Urban Habitat Korea 2022 International journal of high-rise buildings Vol.11 No.2

Welding is a significant part of the construction industry. Since most high-rise building construction structures rely on a robust metal frame welded together, welding defect can damage welded structures and is critical to safety and quality. Despite its importance and heavy usage in construction, the labor shortage of welders has been a continuous challenge to the construction industry. To deal with the labor shortage, the ultimate goal of this study is to design and develop an automated robotic welding system composed of a welding machine, unmanned ground vehicle (UGV), robotic arm, and visual sensors. This paper proposes and focuses on automated weaving using the robotic arm. For automated welding operation, a microcontroller is used to control the switch and is added to a welding torch by physically modifying the hardware. Varying weave patterns are mathematically programmed. The automated weaving is tested using a brush pen and a ballpoint pen to clearly see the patterns and detect any changes in vertical forces by the arm during weaving. The results show that the weave patterns have sufficiently high consistency and precision to be used in the actual welding. Lastly, actual welding was performed, and the results are presented.

Identifying Sustainable Development Patterns of Nations and Cities in Three Asian Regions with Unsupervised Learning

Doyun Lee,Jiyeon Park,Danbi Kim,Steven Jige Quan 한국환경정책학회 2022 環境政策 Vol.30 No.-

Asia, the largest and most populous continent in the world, is in dire need of sustainable development due to its rapid urbanization; particularly, the Southeast, South, and West Asia regions demand the most attention. However, previous studies have been limited in examining sustainable development patterns in the three regions. This study identified sustainability development patterns in 23 countries and 33 major cities in three Asian regions using time series clustering, an unsupervised learning technique. Considering the three pillars of sustainability, three clusters were identified at both national and city levels based on three variables: population, GDP per capita, and total energy/electricity consumption per capita. The identified clusters suggested diverse sustainable development patterns in each of the three regions. The largest clusters at national and city levels exhibited a rapid development trend in all three aspects, indicating an urgent need to pursue sustainable development. Other clusters revealed complex trends that were closely linked to local development characteristics. Overall, the clusters at both national and city levels transcend the regions significantly, suggesting that future policymaking in the three regions should be tailored to local issues and take cues from regions with similar patterns rather than adhering to the conventional notion of Asian regions. The results provide fresh insights into sustainable development patterns in the three regions, thereby helping policymakers make better policy comparisons and more targeted policy execution decisions.

Transient effect of mossy fiber stimulation on spatial firing of CA3 neurons

Lee, Joonyeup,Yun, Miru,Cho, Eunjae,Lee, Jong Won,Lee, Doyun,Jung, Min Whan John Wiley Sons, Inc. 2019 Hippocampus Vol.29 No.7

<P><B>Abstract</B></P><P>Strong hippocampal mossy fiber synapses are thought to function as detonators, imposing “teaching” signals onto CA3 neurons during new memory formation. For an empirical test of this long‐standing view, we examined effects of optogenetically stimulating mossy fibers on spatial firing of CA3 neurons in freely‐moving mice. We found that spatially restricted mossy fiber stimulation drives novel place‐specific firing in some CA3 pyramidal neurons. Such neurons comprise only a minority, however, and many more CA3 neurons showed inhibited spatial firing during mossy fiber stimulation. Also, changes in spatial firing induced by mossy fiber stimulation, both activated and inhibited, reverted immediately upon stimulation termination, leaving CA3 place fields unaltered. Our results do not support the traditional view that mossy fibers impose teaching signals onto CA3 network, and show robustness of established CA3 spatial representations.</P>

Screening for<i>Escherichia coli</i>K-12 genes conferring glyoxal resistance or sensitivity by transposon insertions

Lee, Changhan,Kim, Jihong,Kwon, Minsuk,Lee, Kihyun,Min, Haeyoung,Kim, Seong Hun,Kim, Dongkyu,Lee, Nayoung,Kim, Jiyeun,Kim, Doyun,Ko, Changmin,Park, Chankyu,Calendar, Richard Published by Elsevier/North Holland on behalf of t 2016 FEMS microbiology letters Vol.363 No.18

Whole-Cell Recording in the Awake Brain

Lee, Doyun,Lee, Albert K. Cold Spring Harbor Laboratory Press 2017 Cold Spring Harbor protocols Vol.2017 No.4

<P>Intracellular recording is an essential technique for investigating cellular mechanisms underlying complex brain functions. Despite the high sensitivity of the technique to mechanical disturbances, intracellular recording has been applied to awake, behaving, and even freely moving, animals. Here we summarize recent advances in these methods and their application to the measurement and manipulation of membrane potential dynamics for understanding neuronal computations in behaving animals.</P>

Identifying Sustainable Development Patterns of Nations and Cities in Three Asian Regions with Unsupervised Learning

( Doyun Lee ),( Jiyeon Park ),( Danbi Kim ),( Steven Jige Quan ) 한국환경연구원 2022 環境政策 Vol.30 No.5

Asia, the largest and most populous continent in the world, is in dire need of sustainable development due to its rapid urbanization; particularly, the Southeast, South, and West Asia regions demand the most attention. However, previous studies have been limited in examining sustainable development patterns in the three regions. This study identified sustainability development patterns in 23 countries and 33 major cities in three Asian regions using time series clustering, an unsupervised learning technique. Considering the three pillars of sustainability, three clusters were identified at both national and city levels based on three variables: population, GDP per capita, and total energy/electricity consumption per capita. The identified clusters suggested diverse sustainable development patterns in each of the three regions. The largest clusters at national and city levels exhibited a rapid development trend in all three aspects, indicating an urgent need to pursue sustainable development. Other clusters revealed complex trends that were closely linked to local development characteristics. Overall, the clusters at both national and city levels transcend the regions significantly, suggesting that future policymaking in the three regions should be tailored to local issues and take cues from regions with similar patterns rather than adhering to the conventional notion of Asian regions. The results provide fresh insights into sustainable development patterns in the three regions, thereby helping policymakers make better policy comparisons and more targeted policy execution decisions.

High performance microthruster with ammonium-dinitramide-based monopropellant

Lee, Doyun,Kim, Juwon,Kwon, Sejin Elsevier 2018 Sensors and actuators. A Physical Vol.283 No.-

<P><B>Abstract</B></P> <P>A high performance environmentally friendly ammonium dinitramide (ADN) based liquid monopropellant was used to develop a thruster with improved performance compared to a conventional hydrogen peroxide propellant microthruster. Compared to regular thrusters, microthrusters have high heat loss due to the higher reactor surface area to volume ratio. A high enthalpy propellant needs to be used to increase the decomposition temperature in order to enhance the thruster performance. There is a need to increase the heat tolerance of the catalyst given the increased reactor temperature. A lanthanum doped Pt/Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was fabricated and applied to increase the heat resistance performance against the ADN-based propellant with a theoretical adiabatic decomposition temperature of 1630 °C. The microthruster was manufactured using a MEMS process. A total of five layers of photosensitive glass with different shapes were fabricated by wet etching and stacked and adhered, and sensors were assembled to measure the pressure and temperature. A combustion experimentation was carried out. 90 wt.% hydrogen peroxide was injected in advance for catalyst preheating and then the ADN-based propellant was injected. In the experimental results, ignition was observed within the reactor and the combustion temperature was 983 ℃. The thrust and specific impulse performances were obtained. Compared to a microthruster using 90 wt.% hydrogen peroxide, the ADN-based propellant enhanced thrust by 19% while the specific impulse increased by 86%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An ammonium dinitramide based monopropellant was used to develop a microthruster. </LI> <LI> The microthruster was manufactured using a MEMS process. </LI> <LI> A lanthanum doped Pt/Al2O3 catalyst was applied to increase the heat resistance. </LI> <LI> The thrust and specific impulse increased compared to H2O2 microthruster. </LI> </UL> </P>

전술유도무기용 소형 유압식 구동장치의 모델링 및 시뮬레이션

이도윤(Doyun Lee),이호성(Hosung Lee),안성용(Sungyong An),박연정(Yeonjung Park) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.4

최근 전술유도무기 분야는 대부분 전기식 구동장치를 채용하고 있으나 주어진 공간조건과 무게 제한 아래 상대적으로 부하가 크며 작동시간이 짧고 동시에 빠른 응답성이 요구될 경우에는 무게 및 공간 조건을 맞추기 위해서 반드시 유압식 구동장치를 적용해야 할 경우가 발생한다. 본 논문에서는 소형 유압식 구동장치 시스템을 대상으로 수학적 모델링과 시뮬레이션을 수행하였다. 수학적 모델은 고압용기, 압력조절밸브, 저유기, 유압작동기로 나누어 구성하였으며 실험 결과와 비교하여 모델의 타당성을 검증하고 고찰하였다. 본 연구를 통하여 소형 유압식 구동장치 시스템 설계에 유용한 수학적 모델을 수립하였다. If an actuation system of the tactical missile is required very fast response time on conditions of short operating time and big loads on the actuator, we would prefer to adopt a small hydraulic system. In this paper, a mathematical model is proposed to analyze and simulate the small hydraulic actuation system. The mathematical model consists of a high pressure vessel model, a pressure regulator model, a hydraulic reservoir model and a actuator model. The suggested model is validated by comparison of simulation results with experimental data. The simulation results show that the mathematical model could be useful for designing a hydraulic actuation system.