• 약학회지
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• 제31권2호
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• pp.112-115
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• 1987

Gypsogenin was derivatized with 2, 4-dinitrophenylhyclrazine prior to analysis with HPLC. Reversed-phase column (Du pont ODS) was used and the mobile phase was acetonitrile and water (60:40). The effluent was detected at 550nm using an U.V. detector and the retention time was approximately 9.2min. The concentration was quantitated by measuring the area and the detection limit was 0.2$\mu\textrm{g}$.

• Elastomers and Composites
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• 제14권4호
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• pp.231-252
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• 1979

Polymerization of 2-pyrrolidone was carried out through anionic mechanism using $SO_2/KOH$ as catalyst. The effects of KOH concentration, $SO_2/KOH$ mole ratio and temperature on polymerization were investigated. The conversion and viscosity of polymers were measured at various polymerization conditions. It was observed that as the concentration of KOH was increased, equilibrium conversion was also increased. It was, however, found that after the concentration of KOH was reached above 8 mole percent, the equilibrium conversion was decreased. The highest rate of polymerization and maximum conversion were obtained when $SO_2/KOH$ mole ratio was around 0.5. It was also found that the rate of polymerization and the equilibrium conversion were higher at $50^{\circ}C$. than at $30^{\circ}C$. but the viscosity of polymer solution at $50^{\circ}C$. was not so high as expected. The rate constant, $K_p$ of polymerization, was determined by least square method: the value of $K_p$ was observed as 16 liter/mole hour at $50^{\circ}C$. and 2.6 liter/mole hour at $30^{\circ}C$., respectively. The mechanism of polymerization was also discussed.

• Journal of Welding and Joining
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• 제15권4호
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• pp.126-135
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• 1997

$H_2/O_2$ 비에 따른 Hybrid HVOF 용사된 $Cr_3C_2$-7wt%(NiCr) 용사층의 특성 및 산화거동 This study was performed to investigate the influence of fuel/oxygen ratio (F/O=3.2, 3.0, 2.8) on the characteristics and the oxidation behavior of the hybrid-HVOF sprayed $Cr_3C_2$-7wt%NiCr coatings. Decomposition and the oxidation of the $Cr_3C_2$was occured during spraying. The degree of transformation from $Cr_3C_2$to $Cr_7C_3$ was increased with decreasing the F/O ratio. The microstructural differences of the as sprayed coating with F/O ratio can not be distinguished, However, large pores were diminished and then the coatings became dense by heat treatment. Microhardness of the as-sprayed specimen which sprayed with F/O=3.0 condition was hightest ($Hv_{300}$=1140) and the hardness was increased to 1500 after heat treatment at $600^{\circ}C$ for 50hrs in air. It was supposed that hardness was increased due to the formation of $Cr_2O_3$ within $Cr_3C_2$/$Cr_7C_3$matrix and the densification of coating layer during heat treatment. Apparent activation energy for oxidation was varied from 21.2 kcal$mol^{-1}K^{-1}$ to 23.8 kcal$mol^{-1}K^{-1}$ with respect to the F/O ratio. The surface morphology was changed to porous and oxide chusters were grown after oxidation $1000^{\circ}C$ for 50 hours by the aggressive evolution of gas phase ($CrO_3$ and$CO_2$). The oxide cluster was composed of Ni and Cr.

• Journal of Chest Surgery
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• 제24권3호
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• pp.229-244
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• 1991

A bioassay technique and organ bath study were performed to analyze the effects of extracellular $Ca^{2+}$ and $Ca^{2+}$-antagonists on endothelium-derived relaxing factor[s][EDRF] released from the endothelial cells of rabbit aorta. Transverse strips with intact endothelium or damaged endothelium were used for the mechanical contraction experiment using organ bath. Long segment including thoracic and abdominal aorta with endothelium [EDRF donor aorta] was perfused with Tyrode solution which was aerated with 95% $O_2-5%$ $CO_2$ mixed gas and kept at 35oC. The perfusate was bioassayed with a transverse strip of thoracic aorta with damaged endothelium. The test strip was contracted with nor-epinephrine and acetylcholine was used to stimulate the release of EDRF from endothelial cells. The results obtained were as follows; 1] The endothelium-dependent relaxation[EDR] induced by acetylcholine was biphasic; an initial rapid relaxation followed by a slow relaxation. 2] EDR induced by acetylcholine was reduced gradually with the decrease in the concentration of extracellular $Ca^{2+}$. The effect of extracellular $Ca^{2+}$ on EDR was more prominent in the late slow relaxation phase. 3] EDR to acetylcholine was not altered by acute exposure to organic $Ca^{2+}$-antagonists. Pretreatment with verapamil to the EDRF donor aortic segment did not alter the magnitude of EDR. 4] Among the inorganic $Ca^{2+}$-antagonists $Mn^{2+}$ and $Cd^{2+}$ did not inhibit EDR, whereas $Co^{2+}$ and $La^{3+}$ inhibited EDR. 5] The inhibitory response of $Co^{2+}$ to EDR developed when infused directly on the test strip. That of $La^{3+}$, however, was evoked when added to solution perfusing the donor aortic segment. The above results suggest that $Ca^{2+}$-antagonists do not affect EDR and the inhibitory effect of $Ca^{2+}$ results from influencing the action of EDRF on vascular smooth muscle, whereas that of $La^{3+}$ results from its action on the release of EDRF from endothelial cells.

• 한국초지조사료학회지
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• 제18권2호
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• pp.89-94
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• 1998

A field experiment was carried out to determine the effects of chemical drying agents at mowing on the field drying rate of alfalfa (cv. Vernal) and rye (cv. Koolgrazer) for hastening hay manuf8cture. In alfalfa; chemicals ($K_2CO_3$ 2% $K_2CO_3$ 3% $Na_2CO_3$ 2% $CaCO_3$, 2% $K_2CO_3$2% + $Na_2CO_3$, 1% only water spray and control) were treated at early bloom stage in 1995. Chemicals ($K_2CO_3$, 2%, $Na_2CO_3$, 2% $CaCO_3$, 2% and control) were applicated at different harvest stages (early heading, heading and bloom) in rye, 1996. The drying rate of alfalfa by $K_2CO_3$ treatment among chemicals was higher than control, and the duration of field dry was shortened by one day with $K_2CO_3$ application, but there was no difference in drying efficiency between $K_2CO_3$ 2% and $K_2CO_3$ 3%. In rye, however, no moisture reduction by chemicals was observed. The days required for field dry were 6, 4, and 3 days at warly heading heading and bloom stage respectively; regardless of chemical drying agents and conbol. The nutritive value of rye hay with chemicals at baling was very slightly higher than control, but there was no significant difference. Also, no difference of hay quality was found among drying agents. In conclusion, $K_2CO_3$can enhance the field drying rate of alfalfa hay, but the drying efficiency was not high, particularly in rye hay. Harvesting at early heading to heading stage was desirable for manufacture of high quality rye hay.

• 약학회지
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• 제30권6호
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• pp.311-316
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• 1986

A new UV labeling reagent was developed and used in HPLC for the determination of prostaglandin $E_2$ which have weak UV light-absorbing property. This reagent, 2-bromoacetyltriphenylene, was synthesized by the bromination of 2-acetyltriphenylene which was obtained from triphenylene by Friedel-Crafts reaction. The wave length maximum (${\lambda}_{max}^{CH_3CN}$ of this reagent was 268nm. Prostaglandin E$_2$ was extracted from prostaglandin E$_2$-$\beta$-cyclodextrin using a Sep-pak $C_{18}$ cartridge. The prostaglandin E$_2$ was labeled with 2-bromoacetyl-triphenylene in aectonitrite using 18-crown-6-ether as catalyst. Derivatized prostaglandins were separated on a reversed-phase column (Radial-pak) $\mu$-Bondapak $C_{18}$ using acetonitrile: water=60:40 as mobile phase. The effluent was monitored by UV detector at 254nm filter kit. Linearity of calibration curve was obtained between 30ng and 140ng, and the lower limit of detection was 5ng.

• 한국주조공학회지
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• 제2권3호
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• pp.16-24
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• 1982

For the purpose of development of domestic carburizer, when the basicity of ash in carburizer was changed from $Na_2O/Al_2O_3+SiO_2$ ; 0.06 to $Na_2O/Al_2O_3+SiO_2$ ; 0,196wt%, using $Na_2O$ as flux for domestic graphite resource (Bong Myung armorphous graphite), carburizing efficiency was improved as basicity increased, optimum basicity value was $Na_2O/Al_2O_3+SiO_2$ ; 0.151. This means that $Na_2O$ contributed to lower viscosity of slag and raise occurence probability of specific reaction surface between molten iron and carburizer. The experiment of effect of general characteristics offecting carburizing ability of this carburizer was performed, the result is that 10/30 mesh was optimum size of the carburizer and as carbon equivalent of molten iron was higher, carburizing ratio was lowered, but when si concentration was below 1.8% in general cast iron melting region, recovery showed 75-85%. As agitation rate of molten iron and temperature interval were higher, Carburizing ratio was increased and showed max, 94%. Desulfurizing phenomena of molten iron by $Na_2O$ in carburizer didn't appear.

• 환경위생공학
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• 제15권1호
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.

• 한국수정란이식학회지
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• 제15권1호
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• pp.77-83
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• 2000

The purpose of this study was to develop a breeding technique to increase Hanwoo of superior characteristics. In the present study, reproductive status of Hanwoo such as size of farm, breeding system and gestationi length was investigated. In addition, effect of low dose administration of prostaglandin F2$\alpha$(PGF2$\alpha$) on luteolysis was examined. The size of farm was classified by the total number of cows and the number of breeding stocks, respectively. The distribution of herd size of < 5, 6~10, 11~30, 31~50 and > heads was 31%, 15%, 39%, 4% and 11%, respectively. Furthermore, the distribution of breeding stock size of <5, 6~10, 11~30, 31~50 and > 50 heads was 36%, 28%, 31%, 3% and 3%, respectively. Average parity was 2.1 in breeding stock. In breeding pattern, artificial in semination(A.I), estrus synchronization-A.I and natural mating was 92.7%, 2.4% and 4.9% respectively. Gestational length of Hanwoo was ranged 253~316 days (average length : 285 days) after estrus( estrus=0). To induce luteolysis, PGF2$\alpha$ was injected into ovarian parenchyma by a modified ovarian injector. The effect of administration of 6mg PGF2$\alpha$ on luteolysis and estrus induction was betweer (P<0.01) when PGF2$\alpha$ was administered into ovarian parechyma than when administered intramuscluarly (71 vs. 91%). When PGF2$\alpha$ was injected into ovarian parenchyma, a decreased concentration to 3 mg did not significantly decreaed its luteolytic effect(92%). When AI was performed following PGF2$\alpha$ treatment, the intraovarian injection group yielded a higher pregnancy rate(69 vs. 88%) than the IM injection groups, regardless of the dosage. In conclusion these results suggest that increasing herd size and regular reproductive management are needed to improve reproductive efficiency in Hanwoo industry. Furthermore, intraovarian administration of PGF2$\alpha$ is effective way to induce luteolysis compared with intramuscular injection.

• 한국학교보건학회지
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• 제13권2호
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• pp.319-329
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• 2000

This study suggestes that the improvement of oral care through on investigation of the effects of oral care on children by parents. This investigation was done on Sep. 29 1999 through Oct. 8 examining 376 of elementary, 1grade, 2grade, 3grade students in Kyunggi-Do. The content of the questions was analzed with a t-test and a one-way ANOVA; the relation to the oral care on children by parents with oral care behavior was analyzed by a Pearson's Correlation Coefficient. The results are as follow; 1) Statistically women were higher(F=-2.675, p<0.01). The average of the oral care of children was 2.34, man averaged 2.29, woman are raged 2.32. Statistically women were also higher(F=4.682, p<0.052). 2) The more educatior the mother had higher, the higher the grade. Statistically there was a difference(F=6.756, p<0.01. The oral care of children above Uni graduate(M=2.38), high (M=2:23), middle graduate(M=2.Z3). Statistically, the higher the academic degree, the more optimistic(F=4.114, p<0.05). 3) In the oral care on children by parents, when the conversation with the family was often 2.17, there was little difference(F=7.343, p<0.01). In the oral care of children was 2.45, there was little difference(F=7.343. p<0.01). As a result, the conversation with family affects the behavior. 4) In the oral care of children, if the food that they like was fruits, vegetables, and fresh food, the average was 2.37, very high. There was little difference in other cases(F=-3.179, p<0.05). We can conclude that fresh food affects the oral care of children. 5) In the oral care on children by parents, when the course of knowledge on the oral care was viewed by a grandfather(M=2.02), grandmother(M=2.05), father(M=2.14), mother(M=2.08). There was little difference(F=2.666, p<0.05). 6) In oral care, if the level of income was viewed high level(M=2.42), middle(M=2.34), 10w(M=1.88), there was a little difference(F=3.300, p<0.05). 7) The relation of the oral care on children by parents and the oral care was normal. In other words, the more management by parents, the more management by children.(p<0.01) Therefore in this study, the oral care on children by parents effect the oral care behavior of children. To improve the mouth health of children, the parents's interest in their children must be constant. Also, it is needed to develope an education program where parents and children can be educated.