Sn/SnO_x-loaded uniform-sized hollow carbon spheres on graphene nanosheets as an anode for lithium-ion batteries

Lee, Jeongyeon,Hwang, Taejin,Oh, Jiseop,Kim, Jong Min,Jeon, Youngmoo,Piao, Yuanzhe Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.736 No.-

<P><B>Abstract</B></P> <P>To meet the increasing demands for large-scalable application required high capacity and energy density, Sn-based materials as a promising anode for lithium-ion batteries have been widely studied. In this work, a carbon nanostructure of uniform-sized hollow carbon spheres on a graphene nanosheet was prepared by a facile synthesis process. The obtained nanostructure has numerous uniform-sized hollow carbon spheres with a diameter of ∼20 nm attached on graphene nanosheets, and mass production is considerably easy. Then, Sn/SnO<SUB>x</SUB> was loaded into the carbon nanostructure by a typical melt diffusion process, and its electrode delivers the high rate capability of 290.0 mA g<SUP>−1</SUP> at 3.0 A g<SUP>−1</SUP> and the good cyclability of 284.1 mA h g<SUP>−1</SUP> after 1000 cycles at 1.0 A g<SUP>−1</SUP>. The excellent electrochemical performance is attributed to the unique carbon nanostructure, which mitigates the volume expansion of Sn by the physical barrier of uniform-sized hollow carbon spheres and enables Li-ions or electrons to easily move by the improving electrical conductivity during discharge/charge process. Thus, the Sn loaded nanocomposite is expected to be a promising anode material for lithium-ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A strategy is established for the synthesis of hollow carbon spheres on graphene nanosheets. </LI> <LI> The hollow carbon spheres were used as Sn/SnO<SUB>x</SUB> hosts for lithium ion battery. </LI> <LI> The carbon nanostructure could mitigate the volume expansion of Sn during the cycling. </LI> <LI> The electrode delivers an excellent reversible capacity even after 1000 cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Sn/SnO<SUB>x</SUB>-loaded uniform-sized hollow carbon spheres on graphene nanosheets is fabricated from a facile solventless method and delivers good cycle ability for lithium-ion batteries.</P> <P>[DISPLAY OMISSION]</P>

GluA1 phosphorylation at serine 831 in the lateral amygdala is required for fear renewal

Lee, Sukwon,Song, Beomjong,Kim, Jeongyeon,Park, Kyungjoon,Hong, Ingie,An, Bobae,Song, Sangho,Lee, Jiwon,Park, Sungmo,Kim, Jihye,Park, Dongeun,Lee, C Justin,Kim, Kyungjin,Shin, Ki Soon,Tsien, Richard W Nature Publishing Group, a division of Macmillan P 2013 NATURE NEUROSCIENCE Vol.16 No.10

Fear renewal, a widely pursued model of post-traumatic stress disorder and phobias, refers to the context-specific relapse of conditioned fear after extinction. However, its molecular mechanisms are largely unknown. We found that renewal-inducing stimuli, generally believed to be insufficient to induce synaptic plasticity, enhanced excitatory synaptic strength, activity of synaptic GluA2-lacking AMPA receptors and Ser831 phosphorylation of synaptic surface GluA1 in the lateral nucleus of the amygdala (LAn) of fear-extinguished rats. Consistently, the induction threshold for LAn synaptic potentiation was considerably lowered after extinction, and renewal occluded this low-threshold potentiation. The low-threshold potentiation (a potential cellular substrate for renewal), but not long-term potentiation, was attenuated by dialysis into LAn neurons of a GluA1-derived peptide that competes with Ser831-phosphorylated GluA1. Microinjections of the same peptide into the LAn attenuated fear renewal, but not fear learning. Our findings suggest that GluA1 phosphorylation constitutes a promising target for clinical treatment of aberrant fear-related disorders.

Impairment of fear memory consolidation in maternally stressed male mouse offspring: evidence for nongenomic glucocorticoid action on the amygdala.

Lee, Eun Jeong,Son, Gi Hoon,Chung, Sooyoung,Lee, Sukwon,Kim, Jeongyeon,Choi, Sukwoo,Kim, Kyungjin The Society 2011 The Journal of neuroscience Vol.31 No.19

<P>The environment in early life elicits profound effects on fetal brain development that can extend into adulthood. However, the long-lasting impact of maternal stress on emotional learning remains largely unknown. Here, we focus on amygdala-related learning processes in maternally stressed mice. In these mice, fear memory consolidation and certain related signaling cascades were significantly impaired, though innate fear, fear memory acquisition, and synaptic NMDA receptor expression in the amygdala were unaltered. In accordance with these findings, maintenance of long-term potentiation (LTP) at amygdala synapses, but not its induction, was significantly impaired in the maternally stressed animals. Interestingly, amygdala glucocorticoid receptor expression was reduced in the maternally stressed mice, and administration of glucocorticoids (GCs) immediately after fear conditioning and LTP induction restored memory consolidation and LTP maintenance, respectively, suggesting that a weakening of GC signaling was responsible for the observed impairment. Furthermore, microinfusion of a membrane-impermeable form of GC (BSA-conjugated GC) into the amygdala mimicked the restorative effects of GC, indicating that a nongenomic activity of GC mediates the restorative effect. Together, these findings suggest that prenatal stress induces long-term dysregulation of nongenomic GC action in the amygdala of adult offspring, resulting in the impairment of fear memory consolidation. Since modulation of amygdala activity is known to alter the consolidation of emotionally influenced memories allocated in other brain regions, the nongenomic action of GC on the amygdala shown herein may also participate in the amygdala-dependent modulation of memory consolidation.</P>

How Does The Creative Industry Cluster in Shoreditch Impact on The Entrepreneurial Activity in terms of Running their Businesses?

LEE, JEONGYEON 한국문화산업학회 2018 문화산업연구 Vol.18 No.4

This research focuses on the relationship between creative clusters and entrepreneurial activity within their businesses. The emergence of Florida (2004)’s study on the creative class has had a number of implications for how we perceive urban regeneration. It has attracted the attention of numerous studies particularly regarding creative clusters in the cities which have recently become a major focus of attention due to the significance in which they are evidently held in both academic and political circles. Most of the studies highlight the importance of local concentrations in relation to the development of the regional economy in the creative industry, however, only few studies have centred on individual entrepreneurs in terms of their businesses in the locality. This study therefore, will present concrete evidences by means of entrepreneurs’ experience to prove how the creative industry clusters contributes that may well affect entrepreneurial activity in many aspects as well. Also, It will demonstrate that there is an important link between clustering creative industry and entrepreneurial activities that play a pivotal part in change and development within businesses. On the fundamental basis established by the qualitative research; mainly throughout the interviews carried out with the entrepreneurs in the creative clusters located on the neighbourhood of Shoreditch, UK, this research will indicate the implications of urban regeneration that distinguish places, then analyse how the factors of a local environment are significant.

A multichannel neural probe with embedded microfluidic channels for simultaneous in vivo neural recording and drug delivery.

Lee, Hyunjoo J,Son, Yoojin,Kim, Jeongyeon,Lee, C Justin,Yoon, Eui-Sung,Cho, Il-Joo Royal Society of Chemistry 2015 Lab on a chip Vol.15 No.6

<P>Multi-functional neural probes integrated with various stimulation modalities are becoming essential tools in neuroscience to study the brain more effectively. In this paper, we present a new multi-functional neural probe that allows chemical stimulation through drug delivery and simultaneous recording of individual neuron signals through a microelectrode array. By embedding microchannels in silicon using a proposed glass reflow process, we successfully fabricated 40 μm thick silicon neural probes suitable for small animal experiments. The electrochemical impedance spectroscopy confirms that impedance of iridium microelectrodes is low enough (<1 Mω at 1 kHz) to measure neural signals. Flow rate characterization in a 0.9% w/v agarose gel shows the capability to deliver a small volume of drugs (<1 μl) at a controlled flow rate. We demonstrate the viability and potential of this new probe by conducting in vivo experiments on mice. Because of the proposed compact structure, both action potentials of individual neurons and local field potentials (LFP) at the thalamus region of a mouse brain were successfully detected with a noise level of ~30 μVpp. Furthermore, we successfully induced absence seizure by injecting seizure-inducing drugs (baclofen) at a local target region and observed distinctive changes in neural signal patterns. Specifically, spike-wave discharge (SWD), which is an indicative signal pattern of absence seizure, was successfully recorded. These signals were also directly compared to SWD detected after inducing absence seizure through direct injection of baclofen through the abdomen. This work demonstrates the potential of our multi-functional neural probes for use in effective investigation of brain functions and disorders by using widely available mouse models.</P>

Multi-Heteroatom-Doped Hollow Carbon Attached on Graphene Using LiFePO₄ Nanoparticles as Hard Templates for High-Performance Lithium-Sulfur Batteries

Lee, Jeongyeon,Oh, Jiseop,Jeon, Youngmoo,Piao, Yuanzhe American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.31

<P>P, O, and N heteroatom-doped hollow carbon on graphene (PONHC/G) from nanosized LiFePO<SUB>4</SUB> (LFP) as a hard template is shown to be a very efficient sulfur host for lithium-sulfur (Li-S) batteries. The PONHC/G made from LFP nanoparticles as hard materials provides sufficient voids with various pore sizes for sulfur storage, and doping of the carbon structures with various heteroatoms minimized dissolution/diffusion of the polysulfides. The obtained PONHC/G can store sulfur and mitigate diffusion of the dissolved polysulfide owing to the well-organized host structure and the strong chemical affinity for polysulfides because of the polarization effect of the heteroatom dopants. As a cathode, S@PONHC/G shows excellent cycle stability and rate capability, as confirmed by polysulfide adsorption analysis. Therefore, PONHC/G may show high potential as a sulfur scaffold in the commercialization of Li-S batteries through additional modification and optimization of these host materials.</P> [FIG OMISSION]</BR>

S-423 Plasma aldosterone level and its metabolic implications in patients with type 2 diabetes

( Jeongyeon Won ),( Soyeon Yoo ),( Sang Ah Lee ),( Gwanpyo Koh ),( Dae Ho Lee ) 대한내과학회 2016 대한내과학회 추계학술대회 Vol.2016 No.1

Aldosterone is involved in not only the regulation of blood pressure and renal sodium handling, but also the pathogenesis of insulin resistance, suggesting the clinical relevance of the inhibition of renin-angiotensin-aldosterone system (RAAS) in insulin resistant conditions. To better characterize metabolic implication of RAAS, we measured plasma renin activity (PRA) and aldosterone (PA) level in patient with type 2 diabetes. All other treatments and metabolic evaluations were performed at the discretion of the responsible physicians according to local guidelines. In the present study, we analyzed the data of 628 patients aged 18 or more years. Major exclusion criteria included renal failure, severe hepatic dysfunction, the use of spironolactone, and other severe systemic illnesses. Both PRA and PA were correlated with the circulating levels of serum sodium, apolipoprotein B (ApoB), high sensitivity CRP (hsCRP), and ALT. On a multivariate analysis, PA showed a significant association with ApoB (β=0.580, p=<0.001), ALT (β=0.305, p=0.006), and sodium (β=-0.224, p=0.035) after adjusting for multiple factors. In subgroup analyses according to the type of RAAS inhibition, the association of PA with ApoB and hsCRP was markedly attenuated in patient treated with angiotensin-converting enzyme inhibitor (ACEi) (n=53) compared with that in patients treated with angiotensin receptor blocker (n=187) or with no RAAS inhibitor therapy (n=388). Our results show that aldosterone has important implications for the pathophysiology of type 2 diabetes. Further studies are required to determine whether ACEi therapy is a metabolically better RAAS inhibition in patients with type 2 diabetes.

Surface Modification of Sulfur Cathodes with PEDOT:PSS Conducting Polymer in Lithium-Sulfur Batteries

Lee, Jeongyeon,Choi, Wonchang The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.6

<P>Sulfur powder was coated with poly(3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT:PSS) using a wet mixing process in water. The modified sulfur material was investigated for use as a cathode in lithium-sulfur (Li-S) batteries. The surface modification with the conducting polymer was identified with Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) analyses. Electrochemical evaluation revealed that surface modification with PEDOT:PSS leads to increases in initial capacity and improvements in the rate capability and cyclability of sulfur electrodes. Electrochemical impedance spectroscopy (EIS) measurements certified a decreased resistance of the PEDOT:PSS-coated sulfur electrode compared to a pure sulfur electrode, indicating that surface modification with a conducting polymer effectively enhanced the electrochemical performance of sulfur electrodes in Li-S batteries.</P>

An Aqueous Extract of Herbal Medicine ALWPs Enhances Cognitive Performance and Inhibits LPS-Induced Neuroinflammation via FAK/NF-κB Signaling Pathways

Lee, Ju-Young,Joo, Bitna,Nam, Jin Han,Nam, Hye Yeon,Lee, Wonil,Nam, Youngpyo,Seo, Yongtaek,Kang, Hye-Jin,Cho, Hyun-Ji,Jang, Young Pyo,Kim, Jeongyeon,We, Young-Man,Koo, Ja Wook,Hoe, Hyang-Sook Frontiers Media S.A. 2018 FRONTIERS IN AGING NEUROSCIENCE Vol.10 No.-

<P>Recent studies have shown that Liuwei Dihuang pills (LWPs) can positively affect learning, memory and neurogenesis. However, the underlying molecular mechanisms are not understood. In the present study, we developed ALWPs, a mixture of <I>Antler</I> and LWPs, and investigated whether ALWPs can affect neuroinflammatory responses. We found that ALWPs (500 mg/ml) inhibited lipopolysaccharide (LPS)-induced proinflammatory cytokine IL-1β mRNA levels in BV2 microglial cells but not primary astrocytes. ALWPs significantly reduced LPS-induced cell-surface levels of TLR4 to alter neuroinflammation. An examination of the molecular mechanisms by which ALWPs regulate the LPS-induced proinflammatory response revealed that ALWPs significantly downregulated LPS-induced levels of FAK phosphorylation, suggesting that ALWPs modulate FAK signaling to alter LPS-induced IL-1β levels. In addition, treatment with ALWPs followed by LPS resulted in decreased levels of the transcription factor NF-κB in the nucleus compared with LPS alone. Moreover, ALWPs significantly suppressed LPS-induced BV2 microglial cell migration. To examine whether ALWPs modulate learning and memory <I>in vivo</I>, wild-type C57BL/6J mice were orally administered ALWPs (200 mg/kg) or PBS daily for 3 days, intraperitoneally injected (i.p.) with LPS (250 μg/kg) or PBS, and assessed in Y maze and NOR tests. We observed that oral administration of ALWPs to LPS-injected wild-type C57BL/6J mice significantly rescued short- and long-term memory. More importantly, oral administration of ALWPs to LPS-injected wild-type C57BL/6J mice significantly reduced microglial activation in the hippocampus and cortex. Taken together, our results suggest that ALWPs can suppress neuroinflammation-associated cognitive deficits and that ALWPs have potential as a drug for neuroinflammation/neurodegeneration-related diseases, including Alzheimer’s disease (AD).</P>

SiC UMOSFET 구조에 따른 온도 신뢰성 분석

이정연(Jeongyeon Lee),김광수(Kwang-Soo Kim) 한국전기전자학회 2020 전기전자학회논문지 Vol.24 No.1

SiC 기반 소자는 silicon 소자 대비 1200V 이상의 고전압 환경에서 우수하게 동작하며 특히 매우 높은 온도에서 안정적인 특성을 보여준다. 따라서 최근 1700V급 UMOSFET이 전기 자동차, 항공기 등의 전력시스템의 사용을 목표로 활발하게 연구개발 되고 있다. 본 논문에서는 최근 연구되고 있는 세 종류의 1700급 UMOSFET-Conventional UMOSFET (C-UMOSFET), Source Trench UMOSFET (ST-UMOSFET), Local Floating Superjunction UMOSFET (LFS-UMOSFET)-에 대해 온도변화(300K-600K)에 따른 전력소자에서 중요한 변수 (breakdown voltage(BV), on-resistance(Ron), threshold voltage(vth), transconductance(gm))의 신뢰성 특성을 비교 분석하였다. 세 소자 모두 온도 증가에 따른 BV 증가, Ron 증가, vth 감소, gm 감소를 확인하였다. 그러나 세 소자의 구조 차이에 따라 BV, Ron vth, gm 변화에 차이가 있어 그 정도 및 원인에 대해 비교 분석하였다. 모든 결과는 sentaurus TCAD을 통해 simulation 되었다. SiC-based devices perform well in high-voltage environments of more than 1200V compared to silicon devices, and are particularly stable at very high temperatures. Therefore, 1700V UMOSFET has been actively researched and developed for the use of electric power systems such as electric vehicles and aircrafts. In this paper, we analysed thermal variations of critical variables (breakdown voltage (BV), on-resistance (Ron), threshold voltage (vth), and transconductance (gm)) for the three type 1700V UMOSFETs-Conventional UMOSFET (C-UMOSFET), Source Trench UMOSFET (STUMOSFET), and Local Floating Superjunction UMOSFET (LFS-UMOSFET). All three devices showed BV increase, Ron increase, vth decrease, and gm decrease with increasing temperature. However, there are differences in BV, vth, gm, according to the structural differences of the three devices, and the degree and cause of the analysis were compared. All results were simulated using sentaurus TCAD.