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Leakage current limit of time domain reflectometry in ultrathin dielectric characterization
Kim, Yonghun,Baek, Seung-heon Chris,Jeon, Changhoon,Lee, Young Gon,Kim, Jin Ju,Jung, Ukjin,Kang, Soo Cheol,Park, Woojin,Lee, Seok Hee,Lee, Byoung Hun Institute of Pure and Applied Physics 2014 Japanese Journal of Applied Physics Vol. No.
Extraction of the Interface State Density of Top-Gate Graphene Field-Effect Transistors
Ukjin Jung,Yun Ji Kim,Yonghun Kim,Young Gon Lee,Byoung Hun Lee IEEE 2015 IEEE electron device letters Vol.36 No.4
<P>Novel electrical measurement method, discharge current analysis (DCA), is introduced to extract the density and energy distribution of charge traps at the dielectric interface of top-gate graphene field-effect transistors. Using DCA method, the highest charge trap density ~10<SUP>13</SUP> (cm<SUP>-2</SUP> · eV<SUP>-1</SUP>) is extracted at Fermi level ~0.4 eV. This is the first quantitative estimation of trap density at a specific Fermi level of graphene.</P>
Kim, Jin,Kim, C-yoon,Oh, Hanseul,Ryu, Bokyeong,Kim, Ukjin,Lee, Ji Min,Jung, Cho-Rok,Park, Jae-Hak Elsevier 2019 The Science of the total environment Vol.653 No.-
<P><B>Abstract</B></P> <P>Trimethyltin chloride (TMT), one of the most widely used organotin compounds in industrial and agricultural fields, is widespread in soil, aquatic systems, foodstuffs and household items. TMT reportedly has toxic effects on the nervous system; however, there is limited information about its effects on eye development and no clear associated mechanisms have been identified. Therefore, in the present study, we investigated eye morphology, vison-related behavior, reactive oxygen species (ROS) production, apoptosis, histopathology, and gene expression to evaluate the toxicity of TMT during ocular development in zebrafish embryos. Exposure to TMT decreased the axial length and surface area of the eye and impaired the ability of zebrafish to recognize light. 2′,7′-dichlorofluorescein diacetate and acridine orange assays revealed dose-dependent increases in ROS formation and apoptosis in the eye. Furthermore, pyknosis of retinal cells was confirmed through histopathological analysis. Antioxidative enzyme-related genes were downregulated and apoptosis-inducing genes were upregulated in TMT-treated zebrafish compared to expression in controls. Retinal cell-specific gene expression was suppressed mainly in retinal ganglion cells, bipolar cells, and photoreceptor cells, whereas amacrine cell-, horizontal cell-, and Müller cell-specific gene expression was enhanced. Our results demonstrate for the first time the toxicity of TMT during eye development, which occurs through the induction of ROS-mediated apoptosis in retinal cells during ocular formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TMT causes microphthalmia and impairs visual function in zebrafish embryo. </LI> <LI> TMT induces dose-dependent increases in ROS formation and apoptosis in the eye. </LI> <LI> TMT is toxic to specific retinal cells and leads histopathological abnormalities. </LI> <LI> TMT affected the expression of genes related to above changes. </LI> <LI> This is the first study to confirm the ocular developmental toxicity of TMT. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Jin,Oh, Hanseul,Ryu, Bokyeong,Kim, Ukjin,Lee, Ji Min,Jung, Cho-Rok,Kim, C-yoon,Park, Jae-Hak Elsevier 2018 Environmental pollution Vol.236 No.-
<P><B>Abstract</B></P> <P>Triclosan (TCS) is an organic compound with a wide range of antibiotic activity and has been widely used in items ranging from hygiene products to cosmetics; however, recent studies suggest that it has several adverse effects. In particular, TCS can be passed to both fetus and infants, and while some evidence suggests <I>in vitro</I> neurotoxicity, there are currently few studies concerning the mechanisms of TCS-induced developmental neurotoxicity. Therefore, this study aimed to clarify the effect of TCS on neural development using zebrafish models, by analyzing the morphological changes, the alterations observed in fluorescence using HuC-GFP and Olig2-dsRED transgenic zebrafish models, and neurodevelopmental gene expression. TCS exposure decreased the body length, head size, and eye size in a concentration-dependent manner in zebrafish embryos. It increased apoptosis in the central nervous system (CNS) and particularly affected the structure of the CNS, resulting in decreased synaptic density and shortened axon length. In addition, it significantly up-regulated the expression of genes related to axon extension and synapse formation such as <I>α1-Tubulin</I> and <I>Gap43</I>, while decreasing <I>Gfap</I> and <I>Mbp</I> related to axon guidance, myelination and maintenance. Collectively, these changes indicate that exposure to TCS during neurodevelopment, especially during axonogenesis, is toxic. This is the first study to demonstrate the toxicity of TCS during neurogenesis, and suggests a possible mechanism underlying the neurotoxic effects of TCS in developing vertebrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TCS changes craniofacial morphology and neural structures in zebrafish embryos. </LI> <LI> TCS affects the expression of apoptosis and neurogenesis related genes. </LI> <LI> TCS is toxic to neurodevelopmental stages, especially in axonogenesis. </LI> <LI> This is the first study to confirm the developmental neurotoxicity of TCS. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Yonghun Kim,Young Gon Lee,Ukjin Jung,Jin Ju Kim,Minhyeok Choe,Kyong Taek Lee,Sangwoo Pae,Jongwoo Park,Byoung Hun Lee IEEE 2015 IEEE transactions on electron devices Vol.62 No.4
<P>The effective mobility (μ<SUB>eff</SUB>) of MOSFETs with ultrathin high-k gate dielectric (EOT = 0.85 nm) has been successfully extracted using a time domain reflectometry method. A ground-signal-ground-ground probe configuration is used to analyze the gate-to-channel capacitance (C<SUB>gc</SUB>), gate-to-bulk capacitance (C<SUB>gb</SUB>), and total gate capacitance (C<SUB>g</SUB>) without a complex RF test structure. Using this method, the effective mobility can be extracted even in the presence of a high gate leakage current (~30 A/cm<SUP>2</SUP>) when the conventional split capacitance-voltage method using an impedance analyzer cannot be applied.</P>
Hot-Carrier Instability of nMOSFETs Under Pseudorandom Bit Sequence Stress
Yonghun Kim,Soo Cheol Kang,Sang Kyung Lee,Ukjin Jung,Seung Mo Kim,Byoung Hun Lee IEEE 2016 IEEE electron device letters Vol.37 No.4
<P>Hot-carrier instability under stress conditions emulating a random logic operation (random ON and OFF) has been investigated using pseudorandom bit sequence (PRBS) stress patterns. Furthermore, the impacts of PRBS stress on circuit-level operation have been compared with the conventional dc (static) and ac (periodic) stress conditions using hot-carrier-induced random timing jitter. It was observed that the recovery achieved by charge trapping and detrapping under dynamic stress conditions significantly affects the degree of hot-carrier degradation.</P>
Improved human hematopoietic reconstitution in HepaRG co-transplanted humanized NSG mice
Jin Kim,유보경,Ukjin Kim,Chang-Hwan Kim,Gyeung-Haeng Hur,김경설,Jae-Hak Park 생화학분자생물학회 2020 BMB Reports Vol.53 No.9
Several humanized mouse models are being used to study humanspecific immune responses and diseases. However, the pivotal needs of fetal tissues for the humanized mice model have been huddled because of the demand for ethical and medical approval. Thus, we have verified the hematopoietic and immunomodulatory function of HepaRG and developed a new and easy humanized mouse model to replace the use of fetal liver tissue. HepaRG co-transplanted Hu-NSG mice significantly increased CD45+ lymphocytes and CD19+ B cells and CD3+ T cells than normal Hu-NSG, suggesting enhanced reconstitution of the human immune system. These results have improved the applicability of humanized mice by developing new models easily accessible.