• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.209-212
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• 2004

In this paper, The stress induced leakage currents of thin silicon oxides is investigated in the nano scale structure implementation for Soc. The stress and transient currents associated with the on and off time of applied voltage were used to measure the distribution of high voltage stress induced traps in thin silicon oxide films. The stress and transient currents were due to the charging and discharging of traps generated by high stress voltage in the silicon oxides. The channel current for the thickness dependence of stress current, transient current, and stress induced leakage currents has been measured in oxides with thicknesses between $41\square\;and\;113.4\square,$ which have the channel width x length 10x1um, respectively. The stress induced leakage currents will affect data retention and the stress current, transient current is used to estimate to fundamental limitations on oxide thicknesses. The weight value of synapse transistor was caused by the bias conditions. Excitatory state and inhitory state according to weighted values affected the channel current. The stress induced leakage currents affected excitatory state and inhitory state.

• Applied Microscopy
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• 제30권2호
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• pp.121-139
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• 2000

망막 발육에 관한 연구는 광수용세포와 외망상층에 대해서 집중적으로 연구되어 왔고 내망상층의 연구는 초기 발육에 관한 연구가 보고된 바 있다. 본 연구는 태생 초기부터 말기까지의 인태아를 대상으로 내핵층의 신경모세포의 분화, 발육과 내망상층에서 신경연접 형성 과정을 전자현미경으로 관찰하여 다음과 같은 결과를 얻었다. 좌고 30mm(태령 9주)때 망막은 외신경모세포와 내신경모세포로 분화, 발육하였고 외신경모세포의 분열은 90mm(태령 14주)때까지 진행되었다. Chievitz층은 30mm때, 내망상층은 50mm(태령 11주)때, 외망상층은 150 mm때 각각 형성되었다. 신경절세포는 자유리보솜이 세포 전역에 분포하고 있었고 조면내형질망, 골지장치, 미세소관 및 농소체를 함유하고 있었다. 30mm때 뮐러세포는 신경절세포의 축삭사이로 돌기를 내고 있었고 초자체쪽에서 내경계막을 형성하였으며 90mm때는 뮐러세포의 돌기는 방사상으로 배열하고 있으며 다량의 활면내형질망을 함유하고 있었다. 신경연접은 50mm때 연접막비후는 존재하면서 연접소포를 내포하고 있지 않은 연접이 관찰되었고, 연접소포를 내포하고 있는 보통연접이 90mm때, 리본연접은 150mm때 각각 출현하였다. 260mm(태령 30주)때 연접소포가 없는 연접, 보통연접 및 리본연접 등 성인에서 출현하는 세 가지 연접이 모두 관찰되었다.

• 한국통신학회논문지
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• 제18권1호
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• pp.57-68
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• 1993

본 논문에서는 pended 프로토콜을 가지는 HiPi버스와 다중 캐쉬 메모리를 사용하는 멀티프로세서 시스템을 기술하고, 캐쉬 코히어런스 프로토콜에 따라 프로세서의 효율 측면에서 시스템의 성능을 평가하였다. HiPi 버스는 ETRI에서 개발된 행정전산망용 주전산기인 TICOMII의 공유 버스로 사용되기 위하여 개발되었다. HiPi버스는 고속의 데이타 전송 능력을 가지고 있으나, 캐쉬 간의 데이타 전송을 허용하지 못하는 단점을 가지고 있다. 캐쉬 간의 데이타 전송이 전체 시스템의 성능에 미치는 영향을 측정하고, HiPi버스에 적합한 캐쉬 코히어런스 프로토콜을 선택하기 위하여 두가지 시뮬레이션을 실시하였다. 첫째, HiPi 버스를 사용하는 멀티프로세서 시스템에 다양한 캐쉬 코히어런스 프로토콜을 적용하고 시뮬레이션을 통하여 프로세서 효율에 따른 성능 분석을 실시하였다. 각각으니 프로토콜은 상태 천이도록 나타내었으며, Markov정적 상태도를 이용하여 각 상태의 확률 갑을 구하였다. 각 상태의 확률은 시뮬레이션에서 입력 값으로 사용되었고, 모델링과 시뮬레이션은 SLAMII심볼과 언어를 사용하였다. 둘째, 캐쉬 간의 데이타 전송을 갖는 HiPi버스를 제안하였고, 제안된 HiPi버스를 사용하는 멀티프로세서 시스템에 다양한 캐쉬 코히어런스 프로토콜을 적용하고 시뮬레이션을 통하여 프로세서 효율에 따른 성능 분석을 실시하였다. 고려된 캐쉬 코히어런스 프로토콜은 Write-through, Write-once, Berkely, Synapse. Illinois, Firefly, Dragon이다.

• Biomolecules & Therapeutics
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• 제20권1호
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• pp.27-35
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• 2012

Oroxylin A is a flavone isolated from a medicinal herb reported to be effective in reducing the inflammatory and oxidative stresses. It also modulates the production of brain derived neurotrophic factor (BDNF) in cortical neurons by the transactivation of cAMP response element-binding protein (CREB). As a neurotrophin, BDNF plays roles in neuronal development, differentiation, synaptogenesis, and neural protection from the harmful stimuli. Adenosine $A2_A$ receptor colocalized with BDNF in brain and the functional interaction between $A2_A$ receptor stimulation and BDNF action has been suggested. In this study, we investigated the possibility that oroxylin A modulates BDNF production in cortical neuron through the regulation of $A2_A$ receptor system. As expected, CGS21680 ($A2_A$ receptor agonist) induced BDNF expression and release, however, an antagonist, ZM241385, prevented oroxylin A-induced increase in BDNF production. Oroxylin A activated the PI3K-Akt-GSK-$3{\beta}$ signaling pathway, which is inhibited by ZM241385 and the blockade of the signaling pathway abolished the increase in BDNF production. The physiological roles of oroxylin A-induced BDNF production were demonstrated by the increased neurite extension as well as synapse formation from neurons. Overall, oroxylin A might regulate BDNF production in cortical neuron through $A2_A$ receptor stimulation, which promotes cellular survival, synapse formation and neurite extension.

• 전자공학회논문지
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• 제52권4호
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• pp.80-87
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• 2015

멤리스터는 인가된 전하의 크기에 따라 저항의 크기가 변화하고, 외부 전원이 끊겨도 이전의 저항 상태를 계속 기억하는 새로운 형태의 메모리소자이다. 일반적인 멤리스터는 직류 전압을 인가할 경우, 시간에 대해서 저항의 크기가 비선형적으로 프로그램밍되는 특성을 갖고 있다. 멤리스터에 대한 용이한 프로그램을 위해서는 시간에 대해서 저항의 크기가 선형적으로 증가 혹은 감소하는 것이 바람직하다. 본 연구팀은 과거 +, - 및 0 에 대한 가중치 프로그램이 가능한 멤리스터 브릿지 회로 구조를 제안한 바 있다. 멤리스터 브릿지 회로에서 두 개의 멤리스터는 서로 다른 극성으로 직렬 연결되고, 반대 극성의 멤리스터들 간의 상호 보완 관계에 의해 강력한 선형화 효과를 갖는다. 본 논문에서는 브릿지 회로의 시간에 대한 멤리스터의 선형적 프로그램 특성을 연구하였고, HP 사의 $TiO_2$ 멤리스터와 윈도우 기반 비선형성 멤리스터 모델을 사용하여 선형화 효과를 검증하였다. 멤리스터 브릿지 회로는 멤리스터를 이용한 시냅스 회로에서 시냅스의 가중치 프로그램을 수행할 경우, 유용하게 사용될 것으로 전망된다.

• BMB Reports
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• 제48권5호
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• pp.249-255
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• 2015

PTPRT/RPTPρ is the most recently isolated member of the type IIB receptor-type protein tyrosine phosphatase family and its expression is restricted to the nervous system. PTPRT plays a critical role in regulation of synaptic formation and neuronal development. When PTPRT was overexpressed in hippocampal neurons, synaptic formation and dendritic arborization were induced. On the other hand, knockdown of PTPRT decreased neuronal transmission and attenuated neuronal development. PTPRT strengthened neuronal synapses by forming homophilic trans dimers with each other and heterophilic cis complexes with neuronal adhesion molecules. Fyn tyrosine kinase regulated PTPRT activity through phosphorylation of tyrosine 912 within the membrane-proximal catalytic domain of PTPRT. Phosphorylation induced homophilic cis dimerization of PTPRT and resulted in the inhibition of phosphatase activity. BCR-Rac1 GAP and Syntaxin-binding protein were found as new endogenous substrates of PTPRT in rat brain. PTPRT induced polymerization of actin cytoskeleton that determined the morphologies of dendrites and spines by inhibiting BCR-Rac1 GAP activity. Additionally, PTPRT appeared to regulate neurotransmitter release through reinforcement of interactions between Syntaxin-binding protein and Syntaxin, a SNARE protein. In conclusion, PTPRT regulates synaptic function and neuronal development through interactions with neuronal adhesion molecules and the dephosphorylation of synaptic molecules. [BMB Reports 2015; 48(5): 249-255]

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.385-385
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• 2012

Understanding the thermodynamics and structural transformation during the Metal-Insulator Transition (MIT) is critical to better understand the underlying physical origin of phase transition in the vanadiumdioxide ($VO_2$). Here, through the temperature-dependent in-situ high resolutiontransmission electron microscopy (HR-TEM), and systematic electrical transport study, we have shown that the tunable MIT transition of $VO_2$ nanowires is strongly affected by interplay between strain and domain nucleation by ion beam irradiation. Surprsingly, we have also observed that the $VO_2$ rutile (R) metallic phase could form directly in a strain-induced metastable monoclinic (M2) phase. These insights open the door toward more systematic approaches to synthesis for $VO_2$ nanostructures in desired phase and to use for applications including ultrafast optical switching, smart window, metamaterial, resistance RAM and synapse devices.

• BMB Reports
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• 제51권8호
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• pp.369-370
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• 2018

In previous studies, memory storage was localized to engram cells distributed across the brain. While these studies have provided an individual cellular profile of engram cells, their synaptic connectivity, or whether they follow Hebbian mechanisms, remains uncertain. Therefore, our recent study investigated whether synapses between engram cells exhibit selectively enhanced structural and functional properties following memory formation. This was accomplished using a newly developed technique called "dual-eGRASP". We found that the number and size of spines on CA1 engram cells that receive inputs from CA3 engram cells were larger than at other synapses. We further observed that this enhanced connectivity correlated with induced memory strength. CA3 engram synapses exhibited increased release probability, while CA1 engram synapses produced enhanced postsynaptic responses. CA3 engram to CA1 engram projections showed strong occlusion of long-term potentiation. We demonstrated that the synaptic connectivity of CA3 to CA1 engram cells was strengthened following memory formation. Our results suggest that Hebbian plasticity occurs during memory formation among engram cells at the synapse level.

• Molecules and Cells
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• 제27권1호
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• pp.89-97
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• 2009

We investigate the molecular and cellular etiologies that underlie the deletion of the six amino acid residues (${\Delta}F323-Y328$; ${\Delta}FY$) in human torsin A (HtorA). The most common and severe mutation involved with early-onset torsion dystonia is a glutamic acid deletion (${\Delta}E$ 302/303; ${\Delta}E$) in HtorA which induces protein aggregates in neurons and cells. Even though ${\Delta}FY$ HtorA forms no protein clusters, flies expressing ${\Delta}FY$ HtorA in neurons or muscles manifested a similar but delayed onset of adult locomotor disability compared with flies expressing ${\Delta}E$ in HtorA. In addition, flies expressing ${\Delta}FY$ HtorA had fewer aberrant ultrastructures at synapses compared with flies expressing ${\Delta}E$ HtorA. Taken together, the ${\Delta}FY$ mutation in HtorA may be responsible for behavioral and anatomical aberrations in Drosophila.

• The Korean Journal of Physiology and Pharmacology
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• 제16권2호
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• pp.139-144
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• 2012

It has been reported that activation of metabotropic glutamate receptor 1 (mGluR1) can mediate endocannabinoid-induced short-term depression of synaptic transmission in cerebellar parallel fiber (PF)-Purkinje cell (PC) synapse. mGluR1 has signaling pathways involved in intracellular calcium increase which may contribute to endocannabinoid release. Two major mGluR1-evoked calcium signaling pathways are known: (1) slow-kinetic inward current carried by transient receptor potential canonical (TRPC) channel which is permeable to $Ca^{2+}$; (2) $IP_3$-induced calcium release from intracellular calcium store. However, it is unclear how much each calcium source contributes to endocannabinoid signaling. Here, we investigated whether calcium influx through mGluR1-evoked TRPC channel contributes to endocannabinoid signaling in cerebellar Purkinje cells. At first, we applied SKF96365 to inhibit TRPC, which blocked endocannabinoid-induced short-term depression completely. However, an alternative TRP channel inhibitor, BTP2 did not affect endocannabinoid-induced short-term depression although it blocked mGluR1-evoked TRPC currents. Endocannabinoid signaling occurred normally even though the TRPC current was mostly blocked by BTP2. Our data imply that TRPC current does not play an important role in endocannabinoid signaling. We also suggest precaution in applying SKF96365 to inhibit TRP channels and propose BTP2 as an alternative TRPC inhibitor.