• Bulletin of the Korean Mathematical Society
• /
• v.34 no.4
• /
• pp.549-560
• /
• 1997

For positive integers $n_i \geq 2, i = 1, 2, 3, 4$, such that $\Sigma \frac{n_i}{1} < 2$, there exists a quadrilateral $P = P_1 P_2 P_3 P_4$ in the hyperbolic plane $H^2$ with the interior angle $\frac{n_i}{\pi}$ at $P_i$. Let $\Gamma \subset Isom(H^2)$ be the (discrete) group generated by reflections in each side of $P$. Then the quotient space $H^2/\gamma$ is a differentiable orbifold of type $(^* n_1 n_2 n_3 n_4)$. It will be shown that the deformation space of $Rp^2$-structures on this orbifold can be mapped continuously and bijectively onto the cell of dimension 4 - \left$\mid$ {i$\mid$n_i = 2} \right$\mid$$.

• Journal of Life Science
• /
• v.18 no.8
• /
• pp.1147-1153
• /
• 2008

The purpose of this investigation was to determine the effect of feeding trans fat on serum and tissue lipid profiles and fatty acid composition in mice. Forty-five male mice aged at 4 weeks were fed on the 10% palm oil (n-3 deficient group), 20% dried mackerel (n-3 adequate group) and 5% trans fat (trans group) for three months. Total triglyceride, cholesterol and LDL-cholesterol levels were increased in serum, liver and heart of the n-3 deficient and trans groups compared with the n-3 adequate group, while liver HDL-cholesterol levels were lowest in the trans group (p<0.05). In liver and heart, trans group showed higher levels of total cholesterol and LDL-cholesterol compared with the n-3 deficient group (p<0.05). In fatty acid compositions of serum, heart, liver and kidney, the intake of trans fat led to increased percentages of 18:1n-9trans and 18:2n-6trans. The trans group showed similar patterns to the n-3 deficient group, except an increased percentage of 18:2n-6cis. Generally, the n-3 deficient and trans groups showed increased percentages of n-6 fatty acids and decreased percentages of n-3 fatty acids, specially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) compared to the n-3 adequate group (p<0.05). These results indicate that intake of trans fat increased total triglyceride, cholesterol and LDL-cholesterol levels, which may affect risk for cardiovascular mortality.

• Communications of the Korean Mathematical Society
• /
• v.25 no.1
• /
• pp.19-25
• /
• 2010

$3{\times}3{\times}3$ is the meaningful smallest product of three chains of each size 2n+1 since $1{\times}1{\times}1$ is a 1-element poset. The linear discrepancy of the product of three chains $2n{\times}2n{\times}2n$ is found as $6n^3-2n^2-1$. But the case of the product of three chains $(2n + 1){\times}(2n + 1){\times}(2n + 1)$ is not known yet. In this paper, we determine ld$(3{\times}3{\times}3)$ as a case to determine the linear discrepancy of the product of three chains of each size 2n + 1.

• Korean Journal of Materials Research
• /
• v.6 no.4
• /
• pp.428-435
• /
• 1996

초미립 SiC분말과 SiC platelet을 2차성으로 Si3N4에 첨가하여 SiC/Si3N4 하이브리드 복합체를 가압소결로 제조한 후 2차상의 영향을 조사한 결과핫프레스법을 이용한 경우 SiC platelet은 Si3N4 기지 복합채의 치밀화를 저해하지 않고 초미립의 SiC 첨가는 Si3N4의 입성장을 효과적으로 억제하여 미세한 $\beta$-Si3N4의 grain을 형성함을 관찰하였다. 초미립 SiC첨가를 통한 복합체의 강도 증진은 상대적으로 $\beta$-Si3N4입자의 미세화에 의한 인성의 저하를 유도하나 SiC platelet을 첨가하여 급격한 강도 저하 없이 높은 인성을 갖는 하이브리드 복합체를 제조할 수 있었으며 SiC/Si3N4 하이브리드 복합체의 인성증진은 elongated $\beta$-Si3N4와 platelet SiC의 debonding에 의한 grain pull-out 영향임을 알 수 있었다.

• Journal of the Korean institute of surface engineering
• /
• v.38 no.5
• /
• pp.202-206
• /
• 2005

Nitriding treatments were conducted on tool steel (SKD 61) at a temperature of $500^{\circ}C$ for 5 hr using high vacuum direct current (DC) plasma, with ammonia and argon as source gases. The structural and compositional changes produced in the nitrided layers by applying different ratios of Ar to $NH_{3}\;(n_{Ar}/n_{NH3}) were investigated using glancing x-ray diffraction (GXRD), optical microscopy, atomic force microscopy (AFM), micro-Vickers hardness testing, and pin-on-disc type tribometer. Nitriding case depths of around of $50{\mu}m$ were produced, varying slightly with different ratios of $n_{Ar}/n_{NH3}. It was found that the specimen surface hardness was 1150 Hv with $n_{Ar}/n_{NH3}=1, increasing to a maximum value of 1500 Hv with $n_{Ar}/n_{NH3}=5. With a further increase in ratio to $n_{Ar}/n_{NH3}=10, the surface hardness of the specimen reduced slightly to a value of 1370 Hv. These phenomena were caused by changes of the crystallographic structure of the nitride layers, i.e the $\gamma'-Fe_{4}N$ phase only was observed in the sample treated with $n_{Ar}/n_{NH3}$=1, and the intensity of the $\gamma'-Fe_{4}N$ phase were reduced but new phase of $\varepsilon'-Fe_{3}N$, which was known as a high hardness, with increasing $n_{Ar}/n_{NH3}. Also, the relative weight loss of counterface of the pin-on-disc with unnitrided steel was 0.2. And that of nitrided steel at a gas mixture ($n_{Ar}/n_{NH3}) of 1, 5, 7, and 10 was 0.4, 0.7, 0.6, and 0.5 mg, respectively. This means that the wear resistance of the nitrided samples could be increased by a factor of 2 at least than that of unnitrided steel.

• Journal of the Korean Chemical Society
• /
• v.36 no.1
• /
• pp.81-86
• /
• 1992

The electrophilic and nucleophilic reactions of M(S-S,ph)(N-N,H) (M = Ni(II), Pd(II), Pt(II); (S-S,ph) = 1,2-diphenylethylenedithiolate; (N-N,H)=1,10-phenanthroline) complexes have been investigated. Reaction with norbornadiene depended upon the back donating ability of the central metal ion and produced 2,5-dithia-3,4-diphenyl-tricyclo[4,4,1,0]-undeca-3,8-diene. In the reaction with methyl iodide, the effect of cleavage of (N-N,H) ligand affected the yield of methylated $M(S-S,ph)_2$ product. The structure of the thermolysis product, ${\alpha},{\alpha}{\prime}$-bismethylthiostibene $(CH_3S-SCH_3,ph)$ of methylated complexes indicates that the main product of the nucleophilic reaction is $M(CH_3S-SCH_3,ph)(S-S,ph)$. We have synthesized a new mixed-ligand complex M(S-S,CN)(N-N,H)((S-S,CN) = 1,2-dicyanoethylenedithiolate) through the nucleophilic reaction of ligand.

• Journal of the Korean Ceramic Society
• /
• v.27 no.6
• /
• pp.799-807
• /
• 1990

In this study, effects of oxide additives on mechanical properties and microstructure of A1N and A1N polytype ceramics were investigated. Fine A1N powder was synthesized by nitriding alumiuim hydroxide prepared from Al-isopropoxide, at 1350$^{\circ}C$ for 10h in N2 atmosphere. By adding 3w/o Y2O3, 0.56w/o CaO, and 10w/o SiO2 to AlN powder, AlN and AlN polytype ceramics were prepared by hot-pressing under the pressure of 30 MPa at 1800$^{\circ}C$ for 1h. AlN ceramics with no additives formed considerable amount of AlON phase, while AlN ceramics doped with Y2O3 or CaO decreased AlON phase and formed Y-Al or Ca-Al oxide compound. AlN＋10w/o SiO2(＋3w/o Y2O3) composition produced AlON and AlN polytype compound having 21R as a major phase. Room temperature flexural strength of AlN ceramics with no additive was 246MPa, and room temperature flexural strength and critical temperature difference by thermal shock(ΔTc) of AlN ceramics dooped with Y2O3 or CaO were 532MPa/340$^{\circ}C$ and 423MPa/300$^{\circ}C$, respectively. Y2O3 and CaO used as sintering agent played roles of densification and oxygen removal of AlN ceramics, and affected grain growth/grain morphologies of AlN ceramics.

• Asian Journal of Turfgrass Science
• /
• v.9 no.3
• /
• pp.207-212
• /
• 1995

This experiment was conducted to investigate the effect of the nitrogen fertilization levels on the content of $NH_4^+$-N in soil of 'Suffolk' Kentucky bluegrass and zoysiagrass. The results obtained are summarized as follows : 1.According to the nitrogen fertilization levels, the content of $NH_4^+$-N in soil of Kentucky blue-grass and zoysiagrass was not significantly different. The content of $NH_4^+$-N in soil of Kentucky bluegrass and zoysiagrass was highest in June and December and lowest in March and September. 2.The content of $NH_3^-$-N in soil was increased by increasing the nitrogen fertilization levels in both Kentucky bluegrass and zoysiagrass. However, the deeper the depth of soil the less the content of $NO_3^-$-N in soil. In 40~60cm soil depth, the content of $NO_3^-$-N in soil was lower than 10ppm in average. Even in June, which was the highest month of the content of $NO_3^-$-N in soil, the content of $NO_3^-$-N in soil was not overpassed the degree of 20ppm.

• Journal of Yeungnam Medical Science
• /
• v.19 no.1
• /
• pp.39-48
• /
• 2002

Background: The treatment of rheumatoid arthritis still depend on conserve therapy in major. Recent studies report that n-3 polyunsaturated fatty acids(PUFA) could modulate the incidence and progress of arthritis. The purpose of this study was to investigate the effects of n-3 PUFA on the development of collagen-induced arthritis in rats. Materials and Methods: Female Louvain rats were used for this experiment. Rats were randomly assigned into either normal (n=8) or collagen-immunized groups, and collagen immunized groups were divided into control(n=8, normal diet) and n-3 PUFA(n=8, 5% n-3 PUFA in diet) groups. One week after feeding n-3 PUFA to rats, they were immunized with type II collagen emulsified in incomplete Freund's adjuvant into tail and back. Development of arthritis was confirmed by x-ray and microscopic examination. Results: Incidence of arthritis at the 5th week after immunization was 38% in control and 0% in n-3 PUFA. Rats with arthritis showed edema in hind paws and inflammation in synovial membrane of the knee joint. Plasma glucose and insulin were not changed by both of immunization and diet. Plasma triglycerides and cholesterol concentrations were decreased by n-3 PUFA. Conclusion: n-3 PUFA may prevent or treat collagen-induced arthritis m rats. Further studies are needed for action mechanism of it.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.8
• /
• pp.1190-1196
• /
• 2005

Halopyrroles, N-substituted 2-halopyrroles were prepared by halogenation of N-substituted pyrroles with NBS, NCS, or surfuryl chloride. N-Substituted 3-halopyrroles were synthesized by acid-catalyzed thermal and photochemical isomerization reactions of N-substituted 2-halopyrroles. Both the thermal and photochemical reactions were acid-catalyzed. For the acid-catalyzed isomerization, a mechanism of [1,3] bromine shift followed by deprotonation is operated. For the acid-catalyzed photoisomerization, an excited triplet state of 2-protonated N-benzyl-2-halopyrrole produces an intermediate N-substituted pyrrole complex with halonium ion which is equilibrated with N-substituted pyrrole plus halonium ion, and then the halonium ion newly adds to 3-position of N-substituted pyrrole followed by deprotonation to afford N-benzyl-3-halopyrrole.