• The Korean Journal of Physiology and Pharmacology
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• v.11 no.2
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• pp.37-43
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• 2007

Adenosine has been reported to provide cytoprotection in the central nervous systems as well as myocardium by activating cell surface adenosine receptors. However, the exact target and mechanism of its action still remain controversial. The present study was performed to examine whether adenosine has a protective effect against $A{\beta}$-induced injury in neuroglial cells. The astrocyte-derived human neuroglioma cell line, A172 cells, and $A{\beta}_{25{\sim}35}$ were employed to produce an experimental $A{\beta}$-induced glial cell injury model. Adenosine significantly prevented $A{\beta}$-induced apoptotic cell death. Studies using various nucleotide receptor agonists and antagonists suggested that the protection was mediated by $A_1$ receptors. Adenosine attenuated $A{\beta}$-induced impairment in mitochondrial functional integrity as estimated by cellular ATP level and MTT reduction ability. In addition, adenosine prevented $A{\beta}$-induced mitochondrial permeability transition, release of cytochrome c into cytosol and subsequent activation of caspase-9. The protective effect of adenosine disappeared when cells were pretreated with 5-hydroxydecanoate, a selective blocker of the mitochondrial ATP-sensitive $K^+$ channel. In conclusion, therefore we suggest that adenosine exerts protective effect against $A{\beta}$-induced cell death of A172 cells, and that the underlying mechanism of the protection may be attributed to preservation of mitochonarial functional integrity through opening of the mitochondrial ATP-sensitive $K^+$ channels.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1673-1681
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• 2015

A low dropout (LDO) regulator with a wide-bandwidth is proposed in this paper. The regulator features a Human Body Model (HBM) 8kV-class high robustness ElectroStatic Discharge (ESD) protection circuit, and two error amplifiers (one with low gain and wide bandwidth, and the other with high gain and narrow bandwidth). The dual error amplifiers are located within the feedback loop of the LDO regulator, and they selectively amplify the signal according to its ripples. The proposed LDO regulator is more efficient in its regulation process because of its selective amplification according to frequency and bandwidth. Furthermore, the proposed regulator has the same gain as a conventional LDO at 62 dB with a 130 kHz-wide bandwidth, which is approximately 3.5 times that of a conventional LDO. The proposed device presents a fast response with improved load and line regulation characteristics. In addition, to prevent an increase in the area of the circuit, a body-driven fabrication technique was used for the error amplifier and the pass transistor. The proposed LDO regulator has an input voltage range of 2.5 V to 4.5 V, and it provides a load current of 100 mA in an output voltage range of 1.2 V to 4.1 V. In addition, to prevent damage in the Integrated Circuit (IC) as a result of static electricity, the reliability of IC was improved by embedding a self-produced 8 kV-class (Chip level) ESD protection circuit of a P-substrate-Triggered Silicon Controlled Rectifier (PTSCR) type with high robustness characteristics.

• Journal of Industrial Technology
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• v.24 no.B
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• pp.193-198
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• 2004

We propose and analyse a flexible secure file sharing scheme which can be used for data sharing among members in P2P environment. When a member wants to share data, notification messages are sent to the members with whom the member wants to share data. Each notification message includes one-time password encrypted with the receiver's public key. A member who received the notification message can download the data by using the one-time password. The proposed scheme provides selective sharing, download confirmation and efficient memory management. In terms of security, the proposed scheme supports authentication, entity privacy, replay attack protection and disguise prevention.

• Transactions on Electrical and Electronic Materials
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• v.2 no.2
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• pp.5-15
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• 2001

The experiment established optimal conditions for over-carbonization. With the use of the electron microscopy and X-ray phase analysis the regularities of carbon deposit formation in process of methane and propane pyrolysis on the zeolites, Kazakhstan natural clays, chrome and bauxite sludge containing metal oxides of iron subgroup, have been studied. In process of over-carbonization the trivalent iron was reduced to metal form. In addition, the carbon tubes of divers morphology had been impregnated with ultra-dispersed metal particles. The kinetic parameters of carbon formation in process of methane decomposition on the zeolite - CoO mixture surface were investigated by method of thermo-gravimetric analysis. The morphology and structure of formed carbon fibrils, with the metal particles fixed at their ends, have been investigated, the formation of branched carbon fibrils pattern, so called octopus, being found. Also, the walnut shells and grape kernel carbonization, their immobilization by the cells of selective absorption of heavy metal and sulfur dioxide ions have been studied. The example of metal-carbon composites used as adsorbents for wastewater purification, C$_3$- C$_4$ hydrocarbon cracking catalysts and refractory materials with improved properties have been considered.

• YAKHAK HOEJI
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• v.45 no.6
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• pp.575-581
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• 2001

The galactolipid M-5, which showed anti-inflammatory activity is glycoglycerolipid isolated from the Okinawa marine sponge Phyllospongia foliascens. Glycolipids have been synthesized by various methods, especially it were generally known that synthetic method of M-5 analogue and synthetic method of various glycolipids by glycosidation after synthesis of glycerolipid part. The others, it was not suggested that synthetic method via glycosylglycerol obtained by degradation from diglycoside. This study was carried out to investigate the synthesis of galactosylglycerol from melibiose as M-5 intermediate. Synthesis of galactosylglycerol was accomplished by selective protection of hydroxy group of sugar and diol cleavage by Pb(OAc)$_4$. As a result, galactosylglycerol was synthesized by 8 steps pathway and their structures were elucidated by analysis instrument.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.878-884
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• 2006

Grounding fault and short of the DC power supply systems are detected and protected by high-speed circuit breaker, linked breaking device, ground relay and fault selective device, all of which are installed and operated in substaions. however, there have been many cases in which the protective devices did not detect grounding of of the over head catenary systems on concrete support for an extended period of time. Such cases often cause severe damages to the supports with high grounding resistances. If grounding accidents occur repetitively, the earth current and the rise of earth potential can damage not only passenger and staff but also electric facilities and equipment, necessitating high cost and endeavor to restore. The following study points out various problems that can be occurred occur as a result of high impedance grounding accident, and proposes a new system which can protect and intercept them.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1059-1063
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• 1998

Regiospecific total syntheses of (±)-11-deoxy-4-methoxy-10-oxo-βrhodomycinone (21a) and (±)-11-deoxy-1-methoxy-10-oxo-β-rbodomycinone (21b) are described. 2-(2-Bromoethyl)-1,3-dioxane (6) was transformed to naphthalenone 12, which was condensed with (phenylsulfonyl)-isobenzofuranone 13 to afford 7,8-dihydro-9-ethyl-6-hydroxy-4-methoxynaphthacen-5,12-dione (15). Epoxide 16 prepared from olefinic compound 15, reacted with HF/Pyr (7:3) to give 17. Dihydroxylation of 17 with t-BuOK/P(OMe)3/O2, selective cis-diol protection of mixed compounds 18 with phenylboronic acid in toluene, separation of cis-boronate 19 and trans-diol 20 by column chromatography on silica gel, and cleavage of the boronate group of 19 with 2-methylpentane-2,4-diol in acetic acid completed the construction of 21.

• Archives of Pharmacal Research
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• v.24 no.6
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• pp.503-507
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• 2001

trans-Metanicotine, a subtype (${\alpha}_4{\beta}_2$)-selective ligand for neuronal nicotinic acetylcholine receptor, is under clinical phase for Alzheimer's disease. An efficient synthetic route for ($\pm$)-methyl-(1-aryl-4-pyridin-3-yl-but-3-enyl)-am ices, derivatives of tracts-metanicotine, was explored. Allylation reaction of aryl aldimines with allylmagnesium bromide in THF gave ($\pm$)-methyl-(1-aryl-but-3-enyl)-amines. Protection of the amines with the Boc group and following Heck reaction of the N-Boc amines with 3-bromopyridine gave ($\pm$)-methyl-(1-aryl-4-pyridin-3-yl-but-3-enyl)-carbamic acid tert-butyl esters. Deprotection of the N-Boc group in aqueous 1 N-HCI solution gave the titled amines in good yields. Thus, trans-metanicotine analogues modified at the ${\alpha}-position$ of the methylamino group with amyl groups were obtained in 5 steps.

• CORROSION AND PROTECTION
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• v.12 no.1
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• pp.12-23
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• 2013

원자력 발전소 주요 부품에 사용되는 Alloy 600의 PWSCC 개시와 전파기구를 살펴보고 그 억제 기술을 소개하였다. ○ 균열은 경화된 표면 산화층이 깨질 경우, 입계부식, 공식(pitting), 열처리 또는 물속에 노출되었을 때 일어나는 선택부식(selective corrosion), MnS등 게재물의 용출등에 의해 시작된다. ○ 균열의 전파는 '느린 성장'과 '빠른 성장'으로 구별해 볼 수 있는데 빠른 균열성장은 균열 선단에서의 응력확대 계수(K_I)가 균열이 전파하는 임계값(K_Iscc)을 넘는 경우에 일어난다. ○ Slip Dissolution/Film Rupture Model, Enhanced surface mobility model, Hydrogen assisted creep rupture, Internal oxidation 등의 모델이 제시되어 있으며 Internal oxidation 모델이 여러 실험자료로 잘 뒷 받침되고 있다. ○ PWSCC 억제 방안으로는 부식환경과의 격리 및 보수용접이 대표적이며 부품의 교체를 통한 안전 확보의 방안도 있다. 수소량 조절을 통한 억제 방안도 제시되어 있다. ○ Alloy 600 PWSCC열화 관리 전략프로그램은 결함 발생 가능성이 높은 부위 선정, 우선 순위에 따른 계획적인 검사, 결함이 발견될 경우 완화조치를 취하거나 필요시 교체/보수를 실시하고 그 운영프로그램을 지속적으로 갱신관리하는 방안으로 유지되어야 한다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.5
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• pp.224-228
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• 2014

Recently, the demands for separation/recovery of valuable metals such as nickel or tin from copper based alloys has been attracting much attention from the viewpoints of environmental protection and resource utilization. In this report, experimental results on concentration increasement of nickel and tin compared to the previous report are investigated. Ni is successfully separated by a organic solvent and reduced to the metal powder whose concentration is over 98 %. Sn is separated by a selective solution method and its concentration is increased to 97.5 % by three consecutive solution and reduction process. Crystal structure, surface morphology and microstructure of the separated samples are studied.