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Lee, Jiyoon,Jang, Hosung,Shin, Hosub,Choi, Woo Lee,Mok, Young Geun,Huh, Jin Hoe Oxford University Press 2014 Nucleic acids research Vol.42 No.18
<P>DNA methylation is a primary epigenetic modification regulating gene expression and chromatin structure in many eukaryotes. Plants have a unique DNA demethylation system in that 5-methylcytosine (5mC) is directly removed by DNA demethylases, such as DME/ROS1 family proteins, but little is known about the downstream events. During 5mC excision, DME produces 3′-phosphor-α, β-unsaturated aldehyde and 3′-phosphate by successive β- and δ-eliminations, respectively. The kinetic studies revealed that these 3′-blocking lesions persist for a significant amount of time and at least two different enzyme activities are required to immediately process them. We demonstrate that <I>Arabidopsis</I> AP endonucleases APE1L, APE2 and ARP have distinct functions to process such harmful lesions to allow nucleotide extension. <I>DME</I> expression is toxic to <I>E. coli</I> due to excessive 5mC excision, but expression of <I>APE1L</I> or <I>ARP</I> significantly reduces DME-induced cytotoxicity. Finally, we propose a model of base excision repair and DNA demethylation pathway unique to plants.</P>
Principal Component Regression by Principal Component Selection
Lee, Hosung,Park, Yun Mi,Lee, Seokho The Korean Statistical Society 2015 Communications for statistical applications and me Vol.22 No.2
We propose a selection procedure of principal components in principal component regression. Our method selects principal components using variable selection procedures instead of a small subset of major principal components in principal component regression. Our procedure consists of two steps to improve estimation and prediction. First, we reduce the number of principal components using the conventional principal component regression to yield the set of candidate principal components and then select principal components among the candidate set using sparse regression techniques. The performance of our proposals is demonstrated numerically and compared with the typical dimension reduction approaches (including principal component regression and partial least square regression) using synthetic and real datasets.
A Method of Substrate Shaping to Improve Gain of Active-Element Pattern for Small Arrays
Lee, Taekki,Lee, Dae-Heon,Choo, Hosung,Byun, Gangil IEEE 2017 IEEE antennas and wireless propagation letters Vol.16 No.-
<P>This letter proposes a method of substrate subtraction to improve the gain of an active-element pattern for individual elements in a small array. The proposed method is applied to a three-element controlled reception pattern antenna array, whose radiating elements are printed on a high-dielectric ceramic substrate. Then, three identical fan-shaped areas, placed between the array elements, are subtracted from the substrate, and their shapes are adjusted to avoid unnecessary power losses caused by the fringing field effect, leakage fields, and surface currents. The effects of the subtracted areas are also investigated as parametric studies to demonstrate the effectiveness of the proposed substrate shaping method. The results show that the gain can be increased by 0.7 dB due to lower effective dielectric loss compared to the full substrate.</P>
Angiopoietin-2 exacerbates cardiac hypoxia and inflammation after myocardial infarction
Lee, Seung-Jun,Lee, Choong-kun,Kang, Seok,Park, Intae,Kim, Yoo Hyung,Kim, Seo Ki,Hong, Seon Pyo,Bae, Hosung,He, Yulong,Kubota, Yoshiaki,Koh, Gou Young American Society for Clinical Investigation 2018 The Journal of clinical investigation Vol.128 No.11
Signal characteristic and test exploitation for intermittent nanometer-scale cracks
Lee, Hosung,Baeg, Sanghyeon Elsevier 2018 Microelectronics reliability Vol.84 No.-
<P><B>Abstract</B></P> <P>This paper analyzes signal distortion caused by nanometer-scale solder ball fractures. A solder ball fracture causes an intermittent open circuit on the transmission line. The resulting basic failure mechanism is a drop in signal voltage, due to the capacitance-induced Alternating Current (AC)-coupling effect (which is induced by the fractured solder ball). The two major contributing factors to this error are fracture height and the persisting duration of the consecutive same-logic-value signal. The required signal that induces a voltage drop, sufficient to detect nanometer-scale solder ball fractures, can be composed by repetition of certain signal patterns even for the I/O connections with run-length restrictions. The methodology is newly proposed to determine potential ranges of solder ball fractures. Test pattern generation is made by maximally exploiting the compounding effect of various sizes of same data bits to generate effective run-length that is larger than maximum run length for the purpose of detecting intermittent solder ball fractures. In DDR3 memory systems with 5-nm solder ball fractures, at least 29 bits of consecutive logic “1” or “0” signals are required to detect fractures. If the system has a maximum run-length of 10, 20, or 30 bits, the test signal—which has the equivalent voltage-dropping effect as 29-consecutive bits—can be generated with six, two, or one repetition of the test pattern, respectively; the test pattern is in the form of concatenated N-1 bits of consecutive logic “1” and 1 bit of logic “0” where N is the maximum run length. In addition, a SPICE simulation was conducted to confirm correlation between calculations and actual results. In the simulation, in order to detect a 5-nm solder ball fracture, at least 37 bits of consecutive signal were required.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The basic mechanism of the error by the nano-meter scale solder ball fracture </LI> <LI> The compounding effects of the switching signal for the fractured solder ball </LI> <LI> The methodology for selecting the target solder-ball-fracture range </LI> <LI> The methodology for generating the test pattern for the solder ball fracture </LI> </UL> </P>
Tumor metastasis to lymph nodes requires YAP-dependent metabolic adaptation
Lee, Choong-kun,Jeong, Seung-hwan,Jang, Cholsoon,Bae, Hosung,Kim, Yoo Hyung,Park, Intae,Kim, Sang Kyum,Koh, Gou Young American Association for the Advancement of Scienc 2019 Science Vol.363 No.6427
<P><B>Fueling lymph node metastases</B></P><P>Metastatic cells can migrate from a primary tumor to distant organs through two routes: They can enter the bloodstream directly, or they can enter a lymph node adjacent to the primary tumor. Little is known about the biological mechanisms that allow tumor cells to survive and grow within lymph nodes. Studying mouse models, Lee <I>et al.</I> found that tumor cells adapt to the lymph node microenvironment by shifting their metabolism toward fatty acid oxidation. This occurs through activation of a signaling pathway driven by the yes-associated protein (YAP) transcription factor. Importantly, inhibition of fatty acid oxidation or YAP signaling suppressed lymph node metastasis in the mice.</P><P><I>Science</I>, this issue p. 644</P><P>In cancer patients, metastasis of tumors to sentinel lymph nodes (LNs) predicts disease progression and often guides treatment decisions. The mechanisms underlying tumor LN metastasis are poorly understood. By using comparative transcriptomics and metabolomics analyses of primary and LN-metastatic tumors in mice, we found that LN metastasis requires that tumor cells undergo a metabolic shift toward fatty acid oxidation (FAO). Transcriptional coactivator yes-associated protein (YAP) is selectively activated in LN-metastatic tumors, leading to the up-regulation of genes in the FAO signaling pathway. Pharmacological inhibition of FAO or genetic ablation of YAP suppressed LN metastasis in mice. Several bioactive bile acids accumulated to high levels in the metastatic LNs, and these bile acids activated YAP in tumor cells, likely through the nuclear vitamin D receptor. Inhibition of FAO or YAP may merit exploration as a potential therapeutic strategy for mitigating tumor metastasis to LNs.</P>
가시화 엔진을 이용한 스월과 분사압력이 직분식 디젤엔진의 연소에 미치는 영향에 대한 연구
남호성(Hosung Nam),정해영(Haeyoung Jeong),이기형(Kihyung Lee),이창식(Changsik Lee) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11
The objective of this work is to investigate the effect of swirl and injection pressure on D.I. diesel combustion by<br/> using a transparent engine system. The test engine is equipped with common rail injection system to obtain high<br/> pressure and adjust injection timing and duration. In this study, the combustion analysis and steady flow test were<br/> conducted to obtain the heat release rate from in-cylinder pressure and the swirl ratio, respectively. In addition, the<br/> spray and diffusion flame images were investigated by a high speed camera. As the results, injection pressure was<br/> found to shorten ignition delay as well as enhance peak pressure and heat release rate at premixed combustion region.<br/> However, this effect was reduced in case of swirl flow. The swirl effect was found to shorten ignition delay at certain<br/> injection timing and generally enhance heat release rate