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Active ROP2 GTPase inhibits ABA‐ and CO<sub>2</sub>‐induced stomatal closure
HWANG, JAE‐,UNG,JEON, BYEONG WOOK,HONG, DAEWOONG,LEE, YOUNGSOOK Blackwell Publishing Ltd 2011 Plant, cell and environment Vol.34 No.12
<P><B>ABSTRACT</B></P><P>ROP GTPases function as molecular switches in diverse cellular processes. Previously, we showed that ROP2 GTPase is activated upon light irradiation, and thereby negatively regulates light‐induced stomatal opening. Here we studied the role of ROP2 during stomatal closure. The expression of a constitutively active form of ROP2 (CA‐rop2) in <I>Arabidopsis thaliana</I> and <I>Vicia faba</I> resulted in slower and reduced stomatal closure in response to abscisic acid (ABA) and CO<SUB>2</SUB>. In contrast, the expression of a dominant‐negative form of ROP2 (DN‐rop2) and the knockout mutation of ROP2 (<I>rop2 KO</I>) promoted ABA‐induced stomatal closure in <I>Arabidopsis</I>. As early as 10 min after ABA treatment, ROP2 was inactivated and translocated to the cytoplasm of the stomatal guard cells. To elucidate the mechanism by which active ROP2 suppresses stomatal closure, we monitored endocytotic membrane trafficking, which is regulated by Rho GTPases in animal cells. We found that the endocytosis of plasma membrane (PM), as tracked by FM4‐64, was lower in CA‐rop2‐expressing guard cells than in those of wild‐type plants, which suggests that active ROP2 suppresses the endocytotic internalization of PM, a process required for stomatal closure. Together, our results suggest that ROP2 is inactivated by ABA, and that this inactivation is required for the timely stomatal closure.</P>
Roh, Eun,Hwang, Byeong-Ung,Kim, Doil,Kim, Bo-Yeong,Lee, Nae-Eung American Chemical Society 2015 ACS NANO Vol.9 No.6
<P>Interactivity between humans and smart systems, including-wearable, body-attachable, or implantable platforms, can be enhanced by realization of multifunctional human machine interfaces, where a variety of sensors collect information about the surrounding environment, intentions, or physiological conditions of the human to which they are attached. Here, we describe a stretchable, transparent, ultrasensitive, and patchable strain sensor that is made of a novel sandwich-like stacked piezoresisitive nanohybrid film of single-wall carbon nanotubes (SWCNTs) and a conductive elastomeric composite of polyurethane (PU)-poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS). This sensor, which can detect small strains on human skin, was created using environmentally benign water-based solution processing. We attributed the tunability of strain sensitivity (i.e., gauge factor), stability, and optical transparency to enhanced formation of percolating networks between conductive SWCNTs and PEDOT phases at interfaces in the stacked PU-PEDOT:PSS/SWCNT/PU-PEDOT: PSS structure. The mechanical stability, high stretchability of up to 100%, optical transparency of 62%, and gauge factor of 62 suggested that when attached to the skin of the face, this sensor would be able to detect small strains induced by emotional expressions such as laughing and crying, as well as eye movement, and we confirmed this experimentally.</P>
Do-Il Kim,Byeong-Ung Hwang,Nguyen Thanh Tien,Il-Jin Kim,이내응 대한금속·재료학회 2012 ELECTRONIC MATERIALS LETTERS Vol.8 No.1
In this report, the electrical properties of both pentacene thin-film and pentacene organic thin-film transistors (OTFTs) under static and dynamic bending were investigated. From the responses to the applied static strain,the piezoresistivity coefficient of pentacene thin-film was determined to be 12.5. Significant changes in the field-effect mobility, µ, and the channel current, which were ascribed to the piezoresistivity of the pentacene channel in OTFTs, were observed while other parameters, such as contact resistance and gate capacitance,appear invariant up to the bending radius of 4.3 mm. Hysteresis in cyclic bending, which was assumed to be caused by local defects of pentacene thin-film, was observed to be independent of bending speed during dynamic bending tests.
Choi, Tae Young,Hwang, Byeong-Ung,Kim, Bo-Yeong,Trung, Tran Quang,Nam, Yun Hyoung,Kim, Do-Nyun,Eom, Kilho,Lee, Nae-Eung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.21
<P>Stretchable and transparent touch sensors are essential input devices for future stretchable transparent electronics. Capacitive touch sensors with a simple structure of only two electrodes and one dielectric are an established technology in current rigid electronics. However, the development of stretchable and transparent capacitive touch sensors has been limited due to changes in capacitance resulting from dimensional changes in elastomeric dielectrics and difficulty in obtaining stretchable transparent electrodes that are stable under large strains. Herein, a stretch-unresponsive stretchable and transparent capacitive touch sensor array was demonstrated by employing stretchable and transparent electrodes with a simple selective-patterning process and by carefully selecting dielectric and substrate materials with low strain responsivity. A selective-patterning process was used to embed a stretchable and transparent silver nanowires/reduced graphene oxide (AgNWs/rGO) electrode line into a polyurethane (PU) dielectric layer on a polydimethylsiloxane (PDMS) substrate using oxygen plasma treatment. This method provides the ability to directly fabricate thin film electrode lines on elastomeric substrates and can be used in conventional processes employed in stretchable electronics. We used a dielectric (PU) with a Poissons ratio smaller than that of the substrate (PDMS), which prevented changes in the capacitance resulting from stretching of the sensor. The stretch-unresponsive touch sensing capability of our transparent and stretchable capacitive touch sensor has great potential in wearable electronics and humanmachine interfaces.</P>
Choi, Young-In,Hwang, Byeong-Ung,Meeseepong, Montri,Hanif, Adeela,Ramasundaram, Subramaniyan,Trung, Tran Quang,Lee, Nae-Eung The Royal Society of Chemistry 2019 Nanoscale Vol.11 No.9
<P>Creating stretchable and transparent conductive electrodes for stretchable and transparent electronics is very challenging due to difficulties in obtaining adequate optical and mechanical properties simultaneously. Here, we designed a stretchable and transparent nanofiber-networked electrode (STNNE) based on a networked structure of electrospun stretchable nanofibers made from a mixture of polyurethane (PU)/reduced graphene oxide (rGO)/silver nanoparticles (AgNPs). The STNNE showed a sheet resistance as small as 210 Ω sq<SUP>−1</SUP> at an optical transparency of ∼83%. In addition, the STNNE has up to 40% mechanical stretchability and relatively high electrical stability (<I>i.e.</I>, a resistance change of 83% at 40% stretching). The good electrical conductance, mechanical stretchability, and electrical stability under static/dynamic stretching or after cyclic stretching are attributed to the high dispersion of AgNPs in the nanofibers, which creates more electrically conductive pathways and forms fused junctions at the intersections between nanofibers during electrospinning. As a demonstration, an STNNE with a simple selective-patterning process was employed to fabricate a stretchable capacitive touch sensor with a stretchable and transparent dielectric (PU) on a polydimethylsiloxane substrate. The signal output of the touch sensor upon touching under stretched conditions was nearly unchanged. This STNNE has great potential in stretchable and transparent electronics.</P>
금속분리판의 Electro Polishing 및 CrN 코팅을 통한 PEMFC 성능 향상을 위한 연구
황성택(Sung Tack Hwang),천승호(Seung Ho Cheon),송준석(Jun Seok Song),윤영훈(Younghoon Yun),김병헌(Byeong Heon Kim),장하(Xia Zhang),김대웅(Dae-Ung Kim),현덕수(Deoksu Hyon),오병수(Byeong Soo Oh) 한국자동차공학회 2013 한국자동차공학회 지부 학술대회 논문집 Vol.2013 No.5-1
As an important component of a fuel cell, the bipolar plate comprises a large proportion in the fuel cell’s volume, weight and price. The bipolar plate is the most widely used; however, graphite bipolar plate is large in volume, brittle and therefore easily broken during assembling. In addition, due to its poor machinability, production costs a lot, unless mass production. Compared with the graphite bipolar plate, the metal bipolar plate has good machinability, high electric conductivity and strong mechanical strength; however, it corrodes easily and has a high contact resistance, so in order to prevent corrosion and reduce the contact resistance, the basic metal needs to be processed by use of electro polishing and coating. The water which is produced by electrochemical reactions in the fuel cell must be discharged smoothly. In this study, in order to prevent corrosion the processes of electro polishing and CrN coating were used. According to the presence or absence of these processes, the contact angles can be measured and different metal bipolar plates can be made, these plates can be used for comparing and analyzing the performance of the fuel cell.
치료계획시스템에서 전산화단층촬영과 자기공명영상의 영상융합 재현성 및 선량평가
안병혁,최재혁,황재웅,박지연,이두현,Ahn, Byeong Hyeok,Choi, Jae Hyeok,Hwang, Jae ung,Bak, Ji yeon,Lee, Du hyeon 대한방사선치료학회 2017 대한방사선치료학회지 Vol.29 No.2
목 적: 종양에는 최대한의 선량을 부여하고 주변의 정상조직에는 최소한의 선량이 조사되도록 부작용을 줄이는 목적으로 방사선 치료기술이 발전함에 따라 다양한 치료계획 및 치료 방법이 개발되고 있다. 방사선 치료 시 CT(Computed tomography)와 MRI(Magnetic resonance imaging)영상의 융합은 종양에 선량을 전달하는데 커다란 역할을 한다. 본 연구의 목적은 치료계획 시 자체 제작한 팬톰을 이용하여 CT와 MRI영상들의 융합을 통해 영상의 재현성 및 유용성을 평가하고 획득한 영상에서 타겟 선량을 비교, 분석해보고자 한다. 대상 및 방법: 자체 제작한 팬톰을 이용하여 CT 촬영을 하고, 자장의 세기가 다른 1.5T 와 3.0T의 MRI 촬영을 하여 영상을 획득한다. CT 촬영을 한 팬톰의 영상과 각기 다른 자장의 세기로 촬영한 팬톰의 MRI영상에서 팬톰 내에 존재하는 작은 홀의 크기 및 용적의 재현성을 비교하고, 임의의 타겟에서 선량 변화를 비교, 분석한다. 결 과: 13개의 작은 홀 직경은 CT 촬영에서 최대 31 mm, 최소 27.54 mm를 나타냈으며, 실제 제작한 것과 비교하여 평균 29.28 mm 1 % 이내로 측정되었다. 1.5T MRI 퓨전 영상에서는 최대 31.65 mm, 최소 24.3 mm를 나타냈으며, 평균 28.8 mm 1 % 이내로 측정되었다. 3.0T MRI 퓨전 영상에서는 최대 30.2 mm, 최소 27.92 mm를 나타냈으며, 평균 29.41 mm 1.3 % 이내로 측정되었다. 타겟의 조사된 선량변화는 CT에서 95.9-102.1 %, CT-1.5T MRI 퓨전영상에서 93.1-101.4 %, CT-3.0T MRI 퓨전영상에서는 96-102 %의 선량변화를 보였다. 결 론: CT 및 MRI는 영상획득 시 다른 알고리즘이 적용된다. 또한 인체의 장기는 각기 다른 밀도를 가지고 있으므로 영상 획득 시 이미지 왜곡이 발생할 수 있다. 이러한 부정확한 영상의 묘사는 타겟의 용적범위 및 선량에 영향을 주기 때문에 정확한 타겟의 용적과 위치는 불필요한 선량이 조사되는 것을 방지하며, 치료계획 시 오차를 방지할 수 있다. 즉 CT와 MRI 영상이 가지고 있는 영상 표출 알고리즘의 장점을 이용하여 치료계획에 적용해야 할 것이다. Objectives: The aim of this study is to evaluate the reproducibility and usefulness of the images through the fusion of CT(Computed tomography) and MRI(Magnetic resonance imaging) using a self-manufactured phantom. We will also compare and analyze the target dose from acquired images. Materials and Methods: Using a self-manufactured phantom, CT images and MRI images are acquired by 1.5T and 3.0T of different magnetic fields. The reproducibility of the size and volume of the small holes present in the phantom is compared through the image from CT and 1.5T and 3.0T MRI, and dose changes are compared and analyzed on any target. Results: 13 small hole diameters were a maximum 31 mm and a minimum 27.54 mm in the CT scan and the were measured within an average of 29.28 mm 1 % compared to actual size. 1.5 T MRI images showed a maximum 31.65 mm and a minimum 24.3 mm, the average is 28.8 mm, which is within 1 %. 3.0T MRI images showed a maximum 30.2 mm and a minimum 27.92 mm, the average is 29.41 mm, which is within 1.3 %. The dose changes in the target were 95.9-102.1 % in CT images, 93.1-101.4 % in CT-1.5T MRI fusion images, and 96-102 % in CT-3.0T MRI fusion images. Conclusion: CT and MRI are applied with different algorithms for image acquisition. Also, since the organs of the human body have different densities, image distortion may occur during image acquisition. Because these inaccurate images description affects the volume range and dose of the target, accurate volume and location of the target can prevent unnecessary doses from being exposed and errors in treatment planning. Therefore, it should be applied to the treatment plan by taking advantage of the image display algorithm possessed by CT and MRI.