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Polarization Dependence of the Optical Modal Gain in ZnO
Bumjin Kim,김광석,조채용 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1
The modal gain spectrum due to the electron-hole plasma in ZnO was measured using a variablestripe-length method. A modal gain contour map for energy and stripe length allowed the modal gain saturation to be analyzed in terms of the spectral and the stripe length dependences. The modal gain was observed to be more significant in the TE mode than in the TM mode due to the polarization asymmetry of the wurtzite structure. We also found that the degree of polarization are enhanced as the stripe length increased, despite of modal gain saturation.
Kim, Young-Kook,Yu, Jieun,Han, Tae Su,Park, Seong-Yeon,Namkoong, Bumjin,Kim, Dong Hyuk,Hur, Keun,Yoo, Moon-Won,Lee, Hyuk-Joon,Yang, Han-Kwang,Kim, V. Narry Oxford University Press 2009 Nucleic acids research Vol.37 No.5
<P>microRNAs (miRNAs) play integral roles in diverse processes including tumorigenesis. miRNA gene loci are often found in close conjunction, and such clustered miRNA genes are transcribed from a common promoter to generate polycistronic primary transcript. The primary transcript (pri-miRNA) is then processed by two RNase III proteins to release the mature miRNAs. Although it has been speculated that the miRNAs in the same cluster may play related biological functions, this has not been experimentally addressed. Here we report that the miRNAs in two clusters (miR-106b∼93 ∼ 25 and miR-222 ∼ 221) suppress the Cip/Kip family members of Cdk inhibitors (p57<SUP>Kip2</SUP>, p21<SUP>Cip1</SUP> and p27<SUP>Kip1</SUP>). We show that miR-25 targets p57 through the 3′-UTR. Furthermore, miR-106b and miR-93 control p21 while miR-222 and miR-221 regulate both p27 and p57. Ectopic expression of these miRNAs results in activation of Cdk2 and facilitation of G1/S phase transition. Consistent with these results, both clusters are abnormally upregulated in gastric cancer tissues compared to the corresponding normal tissues. Ectopic expression of miR-222 cluster enhanced tumor growth in the mouse xenograft model. Our study demonstrates the functional associations between clustered miRNAs and further implicates that effective cancer treatment may require a combinatorial approach to target multiple oncogenic miRNA clusters.</P>
ECgene: genome annotation for alternative splicing
Kim, Pora,Kim, Namshin,Lee, Younghee,Kim, Bumjin,Shin, Youngah,Lee, Sanghyuk Oxford University Press 2005 Nucleic acids research Vol.33 No.1
<P>ECgene provides annotation for gene structure, function and expression, taking alternative splicing events into consideration. The gene-modeling algorithm combines the genome-based expressed sequence tag (EST) clustering and graph-theoretic transcript assembly procedures. The website provides several viewers and applications that have many unique features useful for the analysis of the transcript structure and gene expression. The summary viewer shows the gene summary and the essence of other annotation programs. The genome browser and the transcript viewer are available for comparing the gene structure of splice variants. Changes in the functional domains by alternative splicing can be seen at a glance in the transcript viewer. We also provide two unique ways of analyzing gene expression. The SAGE tags deduced from the assembled transcripts are used to delineate quantitative expression patterns from SAGE libraries available publically. Furthermore, the cDNA libraries of EST sequences in each cluster are used to infer qualitative expression patterns. It should be noted that the ECgene website provides annotation for the whole transcriptome, not just the alternatively spliced genes. Currently, ECgene supports the human, mouse and rat genomes. The ECgene suite of tools and programs is available at http://genome.ewha.ac.kr/ECgene/.</P>
Optical Modal Gain Saturation of Exciton-Exciton Scattering and Electron-Hole Plasma in ZnO
Bumjin Kim,김광석 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.5
The optical modal gain spectrum for a ZnO thin film was measured by using a variable stripe length method. Using the differential equation for amplified spontaneous emission in a stripe geometry, we obtained stripe-length-dependent gain spectra, which enabled us to investigate the gain saturation in long stripe lengths. When the stripe was shorter than the saturation length, our analysis was in a good agreement with the gain obtained by commonly-used analysis\cite{1}. For intermediate density ($<$$n_{\rm{Mott}}\sim 3.7~\times~10^{19}~$cm$^{-3}$), the gain was attributed to inelastic exciton-exciton scattering while both exciton-exciton scattering and the electron-hole plasma contribute beyond the Mott densities ($>$$n_{\rm{Mott}}$). Both gains saturate with increasing stripe length, but the electron-hole plasma becomes relatively dominant for long stripe lengths ($\geq$$1000~\rm\mu m$) while the exciton-exciton scattering is relatively suppressed. This result suggests that exciton-exciton scattering gain saturation is more vulnerable to increase in the stripe length increase since the excitonic stimulated emission occurs on a coherence scale of the localized area.
TFT LCD의 고속응답 속도 달성을 위한 LC, TFT 구조 및 구동회로에 대한 연구
김범진(Bumjin Kim),이준신(Junsin Lee),강승재(Seungjae Kang) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
본 연구는 LCD 화질의 중요 Issue중 하나인 고속 응답 속도를 달성하기 위해 액정의 물성 및 TFT 구조 그리고 구동회로에 있어 필요한 조건을 찾기 위한 연구로서 응답속도에 관련된 주요 인자 중 특히 pixel에 인가되는 전압에 관련된 구동회로 조건과 TFT 구조에 초점을 맞추고 있다. 소비전류 Issue가 없는 Monitor 향 제품과 달리 Note 향 LCD 제품의 경우 액정의 유전율을 상승시켜 고속응답을 달성하고 있는데 이로 인해 Cst/Clc의 비율이 응답속도의 중요 인자로 작용하며 이에 최적 응답속도 달성을 위한 Cst/Clc 비율을 시뮬레이션 및 Test SPL 제작을 통해 제안하며 실제 pixel에 인가되는 Offset 전압에 의한 응답속도 유의차 및 Cusp 현상에 대해 논하였다.