• 한국초전도ㆍ저온공학회논문지
• /
• 제16권1호
• /
• pp.9-13
• /
• 2014

Effects of neutron irradiation on the superconducting properties of the undoped $MgB_2$ and the carbon(C)-doped $MgB_2$ bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared $MgB_2$ samples were neutron-irradiated at the neutron fluence of $10^{16}-10^{18}n/cm^2$ in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature ($T_c$) and transition width were estimated from the M-T curves and critical current density ($J_c$) was estimated from the M-H curves using a Bean's critical model. The $T_cs$ of the undoped $MgB_2$ and C-doped $MgB_2$ before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The $T_cs$ decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of $7.16{\times}10^{17}n/cm^2$, and decreased to 22.6 K and 24.0 K, respectively, at $3.13{\times}10^{18}n/cm^2$. The $J_c$ cross-over was observed at the high magnetic field of 5.2 T for the undoped $MgB_2$ irradiated at $7.16{\times}10^{17}n/cm^2$. The $T_c$ and $J_c$ variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.

• 한국자기공명학회논문지
• /
• 제22권3호
• /
• pp.71-75
• /
• 2018

The CRISPR-Cas system is the adaptive immune system in bacteria and archaea against invading phages or foreign plasmids. In the type II CRISPR-Cas system, an endonuclease Cas9 cleaves DNA targets of phages as directed by guide RNA comprising crRNA and tracrRNA. To avoid targeting and destruction by Cas9, phages employ anti-CRISPR (Acr) proteins that act against host bacterial immunity by inactivating the CRISPR-Cas system. Here we report the backbone $^1H$, $^{15}N$, and $^{13}C$ resonance assignments of AcrIIA4 that inhibits endonuclease activity of type II-A Listeria monocytogenes Cas9 and also Streptococcus pyogenesis Cas9 using triple resonance nuclear magnetic resonance spectroscopy. The secondary structures of AcrIIA4 predicted by the backbone chemical shifts show an ${\alpha}{\beta}{\beta}{\beta}{\alpha}{\alpha}$ fold, which is used to determine the solution structure.

• Bulletin of the Korean Chemical Society
• /
• 제26권1호
• /
• pp.146-150
• /
• 2005

Two new barium vanadium borophosphate compounds, $(NH_4)_2(C_2H_{10}N_2)_6[Ba(H_2O)_5]_2[V_2P_2BO_{12}]_6{\cdot}8H_2O$, Ba- VBPO1 and $(NH_4)_8(C_3H_{12}N_2)_4[Ba(H_2O)_7][V_2P_2BO_{12}]_6{\cdot}17H_2O$, Ba-VBPO2 have been synthesized by interdiffusion methods in the presence of diprotonated ethylenediamine and 1,3-diaminopropane. Compound Ba-VBPO1 has an infinite chain anion (${[BaH_2O)_5]_2[V_2P_2BO_{12}]_6}$$^{14-}$, whereas Ba-VBPO2 has a discrete cluster anion {[$Ba(H_2O)_7][V_2P_2BO_{12}]_6$}$^{16-}$. Crystal Data: $(NH_4)_2(C_2H_{10}N_2)_6[Ba(H_2O)_5]_2[V_2P_2BO_{12}]_6{\cdot}8H_2O$, triclinic, space group P$\overline{1}$ (no. 2), a = 13.7252(7) $\AA$, b = 15.7548(8) $\AA$, c = 15.8609(8) $\AA$, α = 63.278(1)$^{\circ}$, $\beta$ = 75.707(1)$^{\circ}$, $\gamma$ = 65.881(1)$^{\circ}$, Z = 1; $(NH_4)_8(C_3H_{12}N_2)_4[Ba(H_2O)_7][V_2P_2BO_{12}]_6{\cdot}17H_2O$, monoclinic, space group C2/c (no. 15), a = 31.347(2) $\AA$, b = 17.1221(9) $\AA$, c = 22.3058(1) $\AA$, $\beta$ = 99.303(1)$^{\circ}$, Z = 4.

• 한국환경농학회지
• /
• 제15권2호
• /
• pp.179-187
• /
• 1996

실험실에서 주택용 소형 퇴비화용기로 사용 가능성이 확인된 이중 벽으로 만든 퇴비화용기를 단독주택의 가족이 4인인 한 가정에 설치하여 적용 가능성을 실험하였다. 그 결과를 요약하면 다음과 같다 : 1) 계절별 실험한 결과 퇴비 내에서 상승한 최고온도는 봄철 $31^{\circ}C$, 여름철 $36^{\circ}C$, 겨울철 $50^{\circ}C$였다. 2) 60일 후 생산된 퇴비의 pH는 겨울철 7.94, 봄철 8.21 그리고 여름철 8.29였다. 퇴비화기간의 경과에 따라 퇴비중 유기물함량은 감소 그리고 회분 함량은 증가하였음에도 불구하고 퇴비 중 각종 무기성분 및 중금속은 축적되지 않았다. 60일 후 회분함량은 겨울철 73.8%, 봄철 55.8% 그리고 여름철 57.0%였다. 질소함량은 0.2-5.8%의 범위였으며 겨울철에 가장 높았고 그리고 여름철에 가장 낮았다. 특히 높은 수분과 Cd의 함량은 퇴비화 가능한 가정쓰레기의 퇴비화에 문제점으로 지적되었다. 60일 후 계절 평균 약 58.5%의 무게가 감소하였다. 퇴비화과정 중 무기성분들의 함량범위는 3 계절 $P_2O_5\;1.50{\sim}4.41%$, $K_2O\;0.02{\sim}1.31%$, CaO $0.13{\sim}1.68%$, MgO $0.05{\sim}1.22%$였다. 또한 중금속성분들의 함량은 Zn $13{\sim}89mg/kg$, Cu $4{\sim}62mg/kg$, Cd $1{\sim}21mg/kg$, Pb $N.D.{\sim}97mg/kg$, Cr $N.D.{\sim}37mg/kg$, Hg $N.D.{\sim}1,38mg/kg$의 범위였다.

• 한국식품과학회지
• /
• 제46권1호
• /
• pp.39-43
• /
• 2014

상산나무 잎의 항미생물 활성을 알아보기 위하여 상산나무 잎을 메탄올, 70% 에탄올, $65^{\circ}C$ 열수로 추출하였고 각각의 추출물에 대하여 13종의 미생물에 대하여 항미생물 활성을 paper disc diffusion법으로 측정하였다. 그 결과 4개 균주 S. mutans, B. cereus, S. aureus, P. aeruginosa가 메탄올 추출물, 70% 에탄올 추출물에서 clear zone을 형성하여 추출물에 의하여 생육이 저해되는 것을 확인할 수 있었고 methanol 추출물이 70% ethanol 추출물에 비하여 항균활성이 크게 나타났다. 이에 methanol 추출물을 극성이 다른 여러 용매로 분획추출하고 항균활성을 측정한 결과 dichloromethane 분획물에서 항균활성을 나타냈으며 다른 분획물인 n-hexane, ethyl acetate, butanol, water 분획물에서는 항균활성이 나타나지 않았다. 가장 활성이 크게 나타났던 메탄올 추출물의 항균활성을 보인 4개의 균에 대하여 최소저해농도를 측정한 결과 S. mutans, S. aureus, P. aeruginosa는 추출물의 농도가 49.22 mg/mL에서 항균활성이 나타났으며 B. cereus의 경우 24.61 mg/mL에서 항균활성을 나타내었으며 S. mutans, B. cereus, S. aureus, P. aeruginosa에 대한 dichloromethane 분획물의 최소저해농도는 각각 3.31, 0.21, 1.7, 1.7 mg/mL으로 나타났다. 메탄올 추출물의 pH에 대한 안정성을 알아보기 위하여 pH 3, 7, 11로 조절하여 1-3시간 동안 처리한 결과 항균활성에는 영향을 주지 않았고 열에 대한 안정성을 확인하기 위하여 80, $100^{\circ}C$에서 1-6시간 동안 처리한 결과 대조군과 차이가 없었고 $120^{\circ}C$ 처리한 경우 항균활성이 약간 저하되었으나 항균활성이 완전히 실활 되지 않은 것으로 보아 상산나무 잎 methanol 추출물은 열과 pH에 비교적 안정하여 식품의 가공 처리에도 적합한 천연 식품첨가물로 유용하게 이용될 수 있을 것으로 사료된다.

• 천문학회보
• /
• 제38권2호
• /
• pp.66.1-66.1
• /
• 2013

We present various observational results toward a small group of Young Stellar Objects (YSOs), L1251C. Observations by Spitzer Space Telescope legacy program "From Molecular Cores to Planet Forming Disks" (c2d; Evans et al. 2003) revealed that there are three YSOs within ~15" in L1251C: IRS1 (Class I), IRS2 (Class II), and IRS3 (Class II). In order to understand the molecular environment around these YSOs, we carried out the KVN single-dish observations in $HCO^+$ J=1-0, $H^{13}CO^+$ J=1-0, $N_2H^+$ J=1-0 and HCN J=1-0. $^{12}CO$ J=1-0 was also mapped in L1251C with the TRAO 14m telescope. Integrated intensity maps of high density tracers such as $H^{13}CO^+$ J=1-0, $N_2H^+$ J=1-0 and HCN J=1-0 show similar emission distributions, whose peaks are off the positions of YSOs. A compact $HCO^+$ J=1-0 outflow and an extended $^{12}CO$ J=1-0 outflow were observed, but their outflow axes are not cosistent ($HCO^+$: NW-SE, $^{12}CO$: EW). However, the highest velocity component of the $^{12}CO$ J=1-0 outflow shows similar morphology to the $HCO^+$ J=1-0 outflow, and ~ 23 % of $^{12}CO$ outflow momentum flux is loaded onto this high velocity component. Furthermore, continuum emission has been observed at 350, 450, 850 ${\mu}m$, and 1.3mm. With the KVN single dish, the 22 GHz $H_2O$ maser emission has been also monitored toward L1251C to find variations of the systemic velocity and intensity with time.

• 한국대기환경학회지
• /
• 제13권1호
• /
• pp.9-18
• /
• 1997

Precipitation samples were collected by the wet- only event sampling method from Seoul during September 1991 to April 1995. These samples were analyzed for the concentrations of the major ionic components (N $O_3$$^{[-10]}$ , N $O_2$$^{[-10]}$ , S $O_4$$^{2-}$, C $l^{[-10]}$ , $F^{[-10]}$ , N $a^{＋}$, $K^{+}$, $Ca^{2＋}$, $Mg^{2＋}$, and N $H_4$$^{＋}$), pH, and electric conductivity. During the study period, a total of 182 samples were collected, but only 163 samples were used for the data analysis via quality assurance of precipitation chemistry data. The volume-weighted pH was found to be 4.7. The major acidifying species from our precipitation studies were identified to be non-seasalt sulfate (84$\pm$9 $\mu$eq/L) and nitrate (24$\pm$2 $\mu$eq/L) except for chloride. Because the Cl/Na ratio in the precipitation was close to the ratio in seawater. If all of the non-seasalt sulfate and nitrate were in the form of sulfuric and nitric acids, the mean pH in the precipitation could have been as low as 3.7 lower than the computed value. Consequently, the difference between two pH values indicate that the acidity of precipitation was neutralized by alkaline species. The equivalent concentration ratio of sulfate to nitrate was 3.5, indicating that sulfuric and nitric acids can comprise 78％ and 22％ of the precipitation acidity, respectively. Analysis of temporal trend in the measured acidity and ionic components were also performed using the linear regression method. The precipitation acidity generally showed a significantly decreasing trend, which was compatible with the pattern of the ratio (N $H_4$$^{＋}$＋C $a^{2＋}$)/ (nss-S $O_4$$^{2-}$＋N $O_3$$^{[-10]}$ ).).

• 한국자기공명학회논문지
• /
• 제22권4호
• /
• pp.115-118
• /
• 2018

Dipyrromethane 2 functionalized with 3-chloropropyl group on the meso carbon undergoes an unusual intramolecular electrophilic aromatic substitution reaction in the presence of $NaN_3$ instead of a simple nucleophilic substitution reaction. As a result, a new chiral dipyrromethane 1 was synthesized. In this reaction, the ${\beta}$-carbon of the pyrrole ring functions as a nucleophile while the carbon next to the chlorine atom acts as an electrophile. Interestingly, this reaction progresses even in the absence of an acid catalyst. Compound 1 was fully characterized by $^1H-^1H$ and $^1H-^{13}C$ COSY NMR spectroscopic analyses and the high resolution EI mass spectrometry.

• 한국수산과학회지
• /
• 제47권2호
• /
• pp.144-153
• /
• 2014

Both docosahexaenoic acid (DHA, 22:6n-3) and eicosapentaenoic acid (EPA, 20:5n-3) have attracted increasing attention since the first epidemiological report on the importance of n-3 essential fatty acids. Lipids in microbial cells play various biological roles and, consequently, much research has been carried out on their role in cell physiology. The lipid composition of microorganisms can exhibit considerable variations depending on environment. The effects of culture conditions, temperature (15, 20, 24, 28, 32 and $36^{\circ}C$), salinity (10, 20, 30, 40 and 50 psu), pH (pH5, 6, 7, 8 and 9), rotation speeds (50, 100, 150 and 200 rpm), carbon sources, nitrogen sources and C/N ratio on the production of docosahexaenoic acid, fatty-acid profiles, and acids secreted to the broth culture by the oleaginous microorganism, Schizochytrium mangrovei (KCTC 11117BP), were studied. Temperature (initially $28^{\circ}C$), salinity (20 psu), pH (pH7), rotation speeds (100 rpm), organism fatty acids, and secreted acids in the broth were varied during cultivation of S. mangrovei. At pH 7.0, S. mangrovei was able to accumulate lipids up to 40% of its biomass, with 13% (w/w) DHA content. The monosaccharides glucose and fructose, and yeast extract were suitable carbon and nitrogen sources, respectively. The primary omega-3 polyunsaturated fatty acid produced was docosahexaenoic acid.

• 대한화학회지
• /
• 제33권2호
• /
• pp.156-163
• /
• 1989

사염화탄소 용액중에서 thiopropionamide(TPA)와 N,N-dimethylalkylamides(DMF, DMA, DMP)간의 수소결합에 관한 열역학적 상수를 구하기 위하여 TPA의 근적외선 영역의 흡수띠 중에서 $ν_a+amide II$조합띠를 사용하여 5${\sim}$55$^{\circ}C$ 범위에서 실험하였다. TPA 단위체와 수소결합을 하고 있는 TPA의 혼합 흡수띠를 Lorentzian-Gaussian product function을 사용하여 개개의 띠로 분리하였다. 컴퓨터로 분해하여 얻은 개개의 흡수띠의 면적을 사용하여 단위체 및 1 : 1 복합체의 농도를 계산하였고 이로부터 평형상수를 구하였다. 열역학적 상수들은 온도의존 흡수띠를 분석하여 구하였다. TPA와 DMF, DMA 및 DMP간의 1 : 1 복합체의 ${\Delta}$$H^{\circ}$는 각각 -12.5, -13.5, -14.1kJ/mol이었고.${\Delta}$$S^{\circ}$는 각각 -15.2, -17.9, -22.3kJ/mol${\cdot}$deg이었다.