• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2299-2303
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• 2014

Two diastereoisomers of cyclo(Pro-Tyr) have been synthesized simultaneously. The crystal structures and conformations of both cyclo($\small{L}$-Pro-$\small{L}$-Tyr) and a racemic mixture of cyclo($\small{D}$-Pro-$\small{L}$-Tyr) and cyclo($\small{L}$-Pro-$\small{D}$-Tyr), abbreviated as rac-cyclo($\small{D}$-Pro-$\small{L}$-Tyr/$\small{L}$-Pro-$\small{D}$-Tyr), have been determined by a single-crystal X-ray diffraction study at low temperature. The crystals of rac-cyclo($\small{D}$-Pro-$\small{L}$-Tyr/$\small{L}$-Pro-$\small{D}$-Tyr) belong to orthorhombic space group $Pna2_1$ with a = 10.755 (1), b = 12.699 (1), c = 9.600 (1) ${\AA}$ and Z = 4. The tyrosine side chain is folded towards the diketopiperazine (DKP) ring. The DKP ring adopts a twist boat conformation with pseudo symmetry $C_{2v}$. The pyrrolidine ring has an envelope conformation with the N5, C4, C7 and C8 atoms in a plane. The crystal of rac-cyclo($\small{D}$-Pro-$\small{L}$-Tyr/$\small{L}$-Pro-$\small{D}$-Tyr) is stabilized by hydrogen bonds between amide N2-H2 and carbonyl oxygen O2 in the neighbor. The hydroxyl group of tyrosine residue is also hydrogen bonded to the oxygen of the carbonyl group of the DKP ring in the next molecule. The spectroscopic properties of both isomers are also described.

• Proceedings of the Korea Crystallographic Association Conference
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• 2001.05a
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• pp.13-13
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• 2001

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.577-580
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• 2007

분자 크기가 너무 커 가스 하이드레이트를 형성하지 않는다고 알려진 n-펜탄과 n-헥산이 다른 구조-H 형성 화합물과 혼합되어 사용될 경우 구조-H 동공 내에 함께 포접되는 것으로 확인되었다. 구조-H 하이드레이트의 형성 및 미세구조 분석은 고체 NMR 및 X-선 회절 분광법을 이용하여 확인하였다. 이러한 혼합 화합물에서 보이는 구조-H 하이드레이트 형성은 전체적인 구조-H 형성 화합물에서 나타나는 일반적 특징인 것으로 여겨진다.

• Journal of the Chungcheong Mathematical Society
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• v.19 no.4
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• pp.319-324
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• 2006

Let K be a finite cyclic extension of $k=\mathbb{F}_q(T)$ of prime degree ${\ell}$. Let ${\tilde{\mathcal{C}}}l_{K,{\ell}}$ be the Sylow ${\ell}$-subgroup of the ideal class group ${\tilde{\mathcal{C}}}l_K$ of $\mathcal{O}_K$. The structure of ${\tilde{\mathcal{C}}}l_{K,{\ell}}$ as $\mathbb{Z}_{\ell}[G]$/<$N_G$>-module is determined the dimensions $${\lambda}_i\;:=dim_{\mathbb{F}_{\ell}}({\tilde{\mathcal{C}}}l_{K,{\ell}}^{({\sigma}-1)^{i-1}}/{\tilde{\mathcal{C}}}l_{K,{\ell}}^{({\sigma}-1)^i})$$ for $i{\geq}1$. In this paper we investigate the dimensions ${\lambda}_1$ and ${\lambda}_2$.

• Journal of the Mineralogical Society of Korea
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• v.16 no.3
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• pp.223-232
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• 2003

The co-precipitation method is applied to synthesize the cathode material Li[L $i_{x}$M $n_{1-x-y}$C $r_{y}$ ] $O_2$ for lithium rechargeable batteries at $650^{\circ}C$ (CR650) and 8$50^{\circ}C$ (CR850), respectively. Rietveld indices indicate that $R_{wp}$ with respect to $R_{exp}$ ( $R_{wp}$/ $R_{exp}$) are 9.2%/10.1% for CR650 and 15.9%/9.76% for CR850, respectively. $R_{B}$ and S (GofF) shows 10.9%, 8.54% and 1.9, 1.6, respectively. Rietveld structure refinement reveals that layer structure of LiMn $O_2$ (R3m) coexists with lower symmetry of Li[L $i_{1}$3/M $n_{2}$3/] $O_2$ (C2/c) due to superlattice ordering of Li and Mn in metal-transition containing layers. Unit-cell parameters are calculated as a=2.8520(2)$\AA$, c=14.248(2)$\AA$, V=100.40(l)$\AA^3$ for CR650, and a=2.8504(1)$\AA$, c=14.2371(7)$\AA$, V=100.179(8)$\AA^3$ for CR850. Final chemistry is obtained as Li[L $i_{0.35}$M $n_{0.56}$C $r_{0.09}$] $O_2$ (CR650) and Li[L $i_{0.27}$M $n_{0.61}$C $r_{0.13}$] $O_2$ (CR850), respectively.y...y..vely.y...y..

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.2031-2035
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• 2010

A triple-probe channel type chemosensor based on an $NO_2S_2$-macrocycle functionalized with phenyltricyanovinyl group was synthesized and its sensing characteristics were examined. The pink-red solution of L changed selectively to pale yellow upon addition of $Hg^{2+}$. The selective fluorometric response of L to all the tested metal ions was studied. The results showed that a large enhancement of the fluorescence of L was observed only in the case of $Hg^{2+}$. In addition, L showed large anodic shift (~ 0.3 V) for the addition of excess $Hg^{2+}$. Through above three observed results by the different techniques, we confirmed that the proposed chemosensor acts as the multiple-probe channel sensing material. The crystal structure of mercury(II) nitrate complexs of L which shows a 1-D polymer network with a formula $[Hg_2(L)_2(NO_3)_2({\mu}-NO_3)_2]_n$ was also reported.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1333-1335
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• 1994

The nitrification of pure iron powders is found to occur even at room temperature by high energy ball milling in $NH_3$ gas atmosphere. The powders of metastable iron nitrides ($0<at.%N{\le}23.3$) thus produced are identified as the super-saturated bee structure for the N content below 14.9 at.%N and the high temperature phase of the hcp structure above 19.4 at.%N. The atomic volume of Fe in the bcc phase is found to be smaller than that of the N-martensite reported in the literature. Magnetization at room temperature gradually decreases with increasing the N concentration in contrast to the enhancement reported for the bet nitrides. Neutron diffraction experiment also provide detailed information about the local structure surrounding the nitrogen atom. The coordination number of Fe atom around a nitrogen atom for the iron nitride containing 9.5 at.%N turns out to be 3.9 atoms.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.171-172
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• 2015

$Ni-W-Si_3N_4$ alloy composite coatings were prepared by pulse electro-deposition method using nickel sulfate bath with different contents of tungsten source, $Na_2WO_4.2H_2O$, and dispersed $Si_3N_4$ nano-particles. The structure and micro-structure of coatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicated that nano $Si_3N_4$ and W content in alloy had remarkable effect on micro-structure, micro-hardness and scratch resistant properties. Tungsten content in Ni-W and $Ni-W-Si_3N_4$ alloy ranged from 7 to 14 at.%. Scratch test results suggest that as compared to Ni-W only, $Ni-W-Si_3N_4$ prepared from Ni/W molar ratio of 1:1.5 dispersed with 20 g/L $Si_3N_4$ has shown the best result among different samples.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2125-2130
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• 2013

A new nickel(II) complex $[NiL^1]^{2+}$ ($L^1$ = 1-(2-aminoethyl)-3-(N-{2-aminoethyl}aminomethyl-1,3-diazacyclohexane) containing one 1,3-diazacyclohexane ring has been prepared selectively by the metal-template condensation of formaldehyde with N-(2-aminoethyl)-1,3-propanediamine and ethylenediamine at room temperature. The complex reacts with nitroethane and formaldehyde to yield the pentaaza macrocyclic complex $[NiL^2]^{2+}$ ($L^2$ = 8-methyl-8-nitro-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one C-$NO_2$ pendant arm. The reduction of $[NiL^2]^{2+}$ by using Zn/HCl produces $[NiL^3(H_2O)]^{2+}$ ($L^3$ = 8-amino-8-methyl-1,3,6,10,13-pentaazabicyclo[13.3.1]heptadecane) bearing one coordinated C-$NH_2$ pendant arm that is readily protonated in acid solutions. The hexaaza macrocyclic complex $[NiL^4]^{2+}$ ($L^4$ = 8-phenylmethyl-8-nitro-1,3,6,8,10,13-hexaazabicyclo[13.3.1]heptadecane) bearing one N-$CH_2C_6H_5$ pendant arm has also been prepared by the reaction of $[NiL^1]^{2+}$ with benzylamine and formaldehyde. The nickel(II) complexes of $L^1$, $L^2$, and $L^4$ have square-planar coordination geometry in the solid states and in nitromethane. However, they exist as equilibrium mixtures of the square-planar $[NiL]^{2+}$ (L = $L^1$, $L^2$, or $L^4$) and octahedral $[NiL(S)_2]^{2+}$ species in various coordinating solvents (S); the proportion of the octahedral species $[NiL(S)_2]^{2+}$ is strongly influenced by the ligand structure and the nature of the solvent. Synthesis, spectra, and chemical properties of the nickel(II) complexes of $L^1-L^4$ are described.

• Membrane and Water Treatment
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• v.8 no.6
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• pp.613-623
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• 2017

We report the novel thin film composite RO membrane modified by graphene oxide. The thin film composite RO membrane was exposed to 2000 mg/l sodium hypochloride; thereafter it was subjected to different graphene oxide concentration ranging from 50 mg/l to 1000 mg/l in water. The resultant membrane was crosslinked with 5000 mg/l N-hydroxysuccinimide. The performance of different membranes were analysed by solute rejection and water-flux measurement. It was found that 100 mg/l graphene oxide exposure followed by 5000 mg/l N-hydroxysuccinimide treatment resulted in the membrane with the highest solute rejection of 97.78% and water-flux of 4.64 Liter per sqm per hour per bar g. The membranes were characterized by contact angle for hydrophilicity, scanning electron micrographs for surface morphology, energy dispersive X-Ray for chemical composition of the surface, Atomic force microscope for surface roughness, ATR-FTIR for chemical structure identification. It was found that the graphene oxide modified membrane increases the salt rejection performance after exposure to high-fouling water containing albumin. Highly hydrophilic, antifouling surface formation with the nanomaterial led to the improved membrane performance. Moreover, the protocol of incorporating nanomaterial by this post-treatment is simple and can be applied to any RO membrane after it is manufactured.