• 한국환경성돌연변이발암원학회지
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• 제8권1호
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• pp.13-21
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• 1988

Mutagenic actions of aflatoxin B$_1$ (AFB$_1$) in the presence of various concentrations of L-ascorbIc acid (AA) in Salmonella typhimurium strains TA 100 and TA98 were studied. Spontaneous revertants per plate of the tester strains TA100 and TA98 were 121-125 and 25-30 with or without S9 mix, respectively. The negative controls used in the study did not show any mutagenesis in the tester strains. AFB$_1$ revealed strong mutagenicity at the dose levels of 0.05, 0.1 and 0.25 ${\mu}$g/plate with metabolic activation system in both strains. However, it showed a toxic effect when the levels were more than 0.5 ${\mu}$g/plate. When lower concentrations of AA (5-20 ${\mu}$g/plate) were added to AFB$_1$ in the Ames assay system with S9 mix the mutagenic action of AFB$_1$ decreased in both strains. About 70-90% of mutagenicity of AFB$_1$ disappeared in strain TA100 when 20${\mu}$g of AA was added to 0.05 ${\mu}$g of AFB$_1$. The inhibitory effect was greatly increased by the addition of higher concentrations of AA to AFB$_1$ in TA100 strain. The mutagenicity of AFB$_1$ was completely inhibited when 100 ${\mu}$g and 500 ${\mu}$g of AA were added to 0.05 ${\mu}$g and 0.1 ${\mu}$g of AFB$_1$, respectively, However, this protective effect of AA on AFB$_1$ mediated mutagenesis was less effective in TA98 strain than that in TA100.

• Environmental Engineering Research
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• 제16권3호
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• pp.165-173
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• 2011

The equilibrium and kinetic adsorption of arsenic on six different adsorbents were investigated with one synthetic and four natural types (two surface and two ground) of water. The adsorbents tested included magnetic ion exchange resins (MIEX), hydrous ion oxide particles (HIOPs), granular ferric hydroxide (GFH), activated alumina (AA), sulfur modified iron (SMI), and iron oxide-coated microsand (IOC-M), which have different physicochemical properties (shape, charge, surface area, size, and metal content). The results showed that adsorption equilibriums were achieved within a contact period of 20 min. The optimal doses of adsorbents determined for a given equilibrium concentration of $C_{eq}=10\;{\mu}g/L$ were 500 mg/L for AA and GFH, 520-1,300 mg/L for MIEX, 1,200 mg/L for HIOPs, 2,500 mg/L for SMI, and 7,500 mg/L for IOC-M at a contact time of 60 min. At these optimal doses, the rate constants of the adsorbents were 3.9, 2.6, 2.5, 1.9, 1.8, and 1.6 1/hr for HIOPs, AA, GFH, MIEX, SMI, and IOC-M, respectively. The presence of silicate significantly reduced the arsenic removal efficiency of HIOPs, AA, and GFH, presumably due to the decrease in chemical binding affinity of arsenic in the presence of silicate. Additional experiments with natural types of water showed that, with the exception of IOC-M, the adsorbents had lower adsorption capacities in ground water than with surface and deionized water, in which the adsorption capacities decreased by approximately 60-95%.

• 대한전자공학회논문지SD
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• 제37권12호
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• pp.18-23
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• 2000

본 논문에서는 유리기판 위에 공액고분자 물질인 MEH-PPV를 스핀 코팅한 후 Al 전극 사이에 초박막의 CsF층을 진공증착으로 삽입한 유기발광소자를 제안하였다. 이러한 구조에서 CsF층은 음극을 통해 주입된 전자들이 원활히 발광층으로 전송되어 유기발광소자의 발광효율을 증대시켰다. 또한 CsF층의 두께변화를 $2{\AA},\;4{\AA},\;8{\AA},\;10{\AA},\;20{\AA},\;50{\AA},\;75{\AA}$으로 변화를 주어 전류- 전압- 발광 특성을 조사하였다. 그리고 CsF/Al와 CsF/Au 및 Cs/Au 전극을 각각 진공증착하여 비교하였다. CsF층 두께가 $4{\AA}$에서 양자효율이 0.6%로 최대값을 나타냈고 $8{\AA}$ 이상에선 효율이 감소하였지만 CsF층이 없는 순수한 Al전극층에서 효율이 0.01%인 것에 비해 높은 양자효율 값을 유지하였다.

• Bulletin of the Korean Chemical Society
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• 제17권5호
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• pp.433-436
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• 1996

Cobalt(Ⅲ) complexes of trifunctional amino acid and N,N'-diethylethylenediamine-N,N'-di-α-butyrate(deedba), s-cis-[Co(deedba)(L-aa)] (L-aa=S-methyl-L-cysteine, L-aspartic acid, L-glutamic acid) have been prepared from the reaction between the s-cis-[Co(deedba)(Cl2)]- complex and the corresponding amino acid. The amino acids have been found to coordinate through the amine and carboxylate groups. The S-methyl-L-cystene is coordinated not by the sulfur donor atom, but by the nitrogen and oxgen donor atoms, and the L-aspartic and L-glutamic acids are coordinated to the cobalt(Ⅲ) ion via formation of the five-membered glycinate chelate ring. Relatively small optical activity shown by the complexes is due to the chiral center present in the amino acids.

• 한국식품저장유통학회지
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• 제19권3호
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• pp.323-327
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• 2012

신선절단 '쓰가루' 사과의 갈변과 미생물 성장 저해에 대해 ascorbic acid와 초음파 처리의 효과를 조사하였다. 사과를 8조각으로 자르고, 1분간 증류수에 침지(Cont), 1분 동안 1% ascorbic acid에 침지(AA), 1분 동안 초음파 처리(US), 또는 1분 동안 1% ascorbic acid용액으로 초음파 처리(AA+US) 후 0.04 mm polypropylnene film으로 열접합 포장하고, 8일 동안 $10^{\circ}C$에서 저장하면서 품질 변화를 분석하였다. AA+US 처리구에서 저장 마지막 날까지 가장 높은 $L^*$값과 낮은 $a^*$, $b^*$값을 보였고, polyphonoloxidase 활성 또한 가장 억제 된 것으로 나타났다. 총균수의 변화는 저장 초기부터 마지막 날까지 AA+US 처리구에서 미생물 성장이 가장 저해된 것으로 나타났다. 가용성 고형분 함량, 적정산도 및 pH 등은 처리조건에 따른 큰 차이를 보이지 않았다. 따라서 ascorbic acid와 초음파의 병용 처리는 신선 절단 사과의 효소적 갈변을 억제하고, 미생물 성장을 저해하는 효과를 가지는 것으로 확인되었다.

• The Korean Journal of Physiology and Pharmacology
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• 제1권4호
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• pp.435-443
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• 1997

We employed the whole-cell patch clamp technique to investigate the effects of arachidonic acid (AA) on barium inward current through the L-type calcium channels ($I_{Ba}$) and on osmotic stretch-induced increase of $I_{Ba}$ in guinea-pig antral gastric myocytes. Under isosmotic condition, AA inhibited $I_{Ba}$ in a dose-dependent manner to $91.1{\pm}1.4,\;72.0{\pm}3.2,\;46.0{\pm}1.8,\;and\;20.3{\pm}2.3%$ at 1, 5, 10, 30 mM, respectively. The inhibitory effect of AA was not affected by 10 ${\mu}M$ indomethacin, a cyclooxygenase inhibitor. Other unsaturated fatty acids, linoleic acid (LA) and oleic acid (OA) were also found to suppress $I_{Ba}$ but stearic acid (SA), a saturated fatty acid, had no inhibitory effect on $I_{Ba}$. The potency sequence of these inhibitory effects was AA ($79.7{\pm}2.3%$) ＞ LA ($43.1{\pm}2.7%$) ＞ OA ($14.2{\pm}1.1%$) at 30 ${\mu}M$. On superfusing the myocyte with hyposmotic solution (214 mOsm) the amplitude of $I_{Ba}$ at 0 mV increased ($38.0{\pm}5.5%$); this increase was completely blocked by pretreatment with 30 mM AA, but not significantly inhibited by lower concentrations of AA (1, 5 and 10 ${\mu}M$) (P＞0.05). Unsaturated fatty acids shifted the steady-state inactivation curves of $I_{Ba}$ to the left; the extent of shift caused by AA was greater than that caused by LA. The activation curve was not affected by AA or LA. The results suggest that AA and other unsaturated fatty acids directly modulate L-type calcium channels and AA might modulate the hyposmotic stretch- induced increase of L-type calcium channel current in guinea-pig gastric smooth muscle.

• 한국식품영양과학회지
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• 제37권1호
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• pp.20-26
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• 2008

무모쥐의 피부에 도포한 애엽 추출물과 positive 비교군인 아스코르브산이 피부 조직에 미치는 항산화효과를 조사하였다. 활성산소인 과산화수소의 생성량은 애엽 추출물과 아스코르브산 2%와 5% 도포군에서 유의적으로 감소하였다. 히드록시 라디칼의 생성량은 애엽 추출물 2%와 5% 도포군에서만 유의적인 감소효과가 있었다. 산화적 스트레스의 지표인 산화 단백질의 함량은 모든 애엽 추출물 도포군에서 대조군에 비해 유의적으로 감소($14.6%{\sim}18.5%$)하였으나, 아스코르브산의 경우는 2% 도포군에서만 저해효과가 인지되었다. 과산화지질 생성량은 대조군에 비해 애엽 추출물과 아스코르브산 도포그룹 모두에서 크게 감소하였다. 항산화효소인 카탈라아제의 활성은 애엽 추출물과 아스코르브산 모든 그룹에서 첨가 농도가 증가함에 따라 크게 증가하였으며, 글루타치온 퍼옥시다아제의 활성은 애엽 추출물 도포군은 2%와 5%에서, 아스코르브산의 경우는 모든 그룹에서 유의적인 활성 증가를 보였다. 이상의 결과는 피부 노화 억제기능성 화장품 소재로서 애엽 추출물의 활용 가능성을 제시한다.

• 소성∙가공
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• 제22권4호
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• pp.204-215
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• 2013

As a pressure vessel, a small seamless aluminum liner with inner volume of about 6.75L is made from an initial billet material of AA6061-O. To produce the aluminum liner, warm forging including backward extrusion and head nosing was numerically simulated using a billet initially pre-heated to about $480^{\circ}C$. Compression tests on the billet material were performed at various temperatures and strain rates, and the measured mechanical properties were used in the numerical simulations. For the backward extrusion and the head nosing, the tool geometries were designed based on the desired configuration of the aluminum liner. Furthermore, the structural integrity of the tooling was evaluated to ensure adequate tool life. The seamless aluminum liner has an endurance limit of about 1.47MPa ($15Kg_f/cm^2$), estimated based on the required inner pressure. The results confirm that the small seamless aluminum liner of AA6061-O can be successfully made by using the two stage warm forging procedures without any bursting failures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.33-35
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• 2008

We have fabricated and evaluated new high efficiency green light emitting phosphorescent devices with an emission layer of $[TCTA_{1/3}TAZ_{2/3}/TAZ]:Ir(ppy)_3$. The whole experimental devices have the basic structure of $2-TNATA(500 {\AA})/NPB(300{\AA})/EML(300{\AA})/BCP(50{\AA})/SFC137(500{\AA})$ between anode and cathode. We have also fabricated conventional phosphorescent devices with emission layers of $(TCTA_{1/3}TAZ_{2/3}):Ir(ppy)_3$ and $(TCTA/TAZ):Ir(ppy)_3$ and compared their electroluminescence characteristics with those of the device with an emission layer of $(TCTA/TCTA_{1/3}TAZ_{2/3}/TAZ):Ir(ppy)_3$. The current density(J), luminance(L), and current efficiency($\eta$) of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ were 95 $mA/cm^2$, 25000 $cd/m^2$, and 27 cd/A at an applied voltage of 10V, respectively. The maximum current efficiency was 52 cd/A under the luminance of 400 $cd/m^2$. The peak wavelength and FWHM(full width at half maximum) in the electroluminescence spectral were 513nm and 65nm, respectively. The color coordinate was (0.30, 0.62) on the CIE (Commission Internationale de l'Eclairage) chart. Under the luminance of 15000 $cd/m^2$, the current efficiency of the device with an emission layer of $(80{\AA}-TCTA/90{\AA}-TCTA_{1/3}TAZ_{2/3}/130{\AA}-TAZ):10%-Ir(ppy)_3$ was 34 cd/A, which has been improved 1.7 times and 1.4 limes compared to those of the devices with emission layers of $(300{\AA}-TCTA_{1/3}TAZ_{2/3}): 10%-Ir(ppy)_3$ and $(100{\AA}-TCTA/200{\AA}-TAZ):10%-Ir(ppy)_3$, respectively.

• Bulletin of the Korean Chemical Society
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• 제11권4호
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• pp.354-357
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• 1990

Synthesis of dichloro cobalt (Ⅲ) complexes of a flexible $N_2O_2-type$ tetradentate ligand, ethylenediamene-N,N'-di-${\alpha}$-isobutyric acid (eddib), has yielded two geometrical isomers, s-cis-$(Co(eddib)Cl_2)- and uns-cis-(Co(eddib)Cl_2)-.$ A series of substitution reactions, $(Co(eddib)Cl_2)^- {\to} (CO(eddib)Cl H_2O) {\to} (Co(eddib)CO_3)^- {\to} (Co(eddib(H_2O)_2)^+$ have been run for each of the two geometrical isomers. The reaction between the s-cis-(Co(eddib)Cl_2)^-$ complex and L-alanine (L-als) or S-methyl-L-cysteine (L-mcy) gave the meridional s-cis-[Co(eddib)(aa)) (aa = L-ala or L-mcy) complex. The S-methyl-L-cysteine was found to coordinate to cobalt (Ⅲ) ion via the nitrogen and oxygen donor atoms.