• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.709-714
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• 2003

Eu doped $Y_2$ $O_3$ nanoparticles were prepared with the solvothermal synthesis using the ethyleneglycol solvent at 20$0^{\circ}C$ for 3-5 h and then annealed in air at 1000-140$0^{\circ}C$ for 2-4 h. The X-ray diffraction pattern of annealed crystals at 100$0^{\circ}C$ for 2 h could be indexed as pure cubic cell of $Y_2$ $O_3$ phase with lattice parameters a=10.5856 $\AA$ which is very close to the reported data (JCPDS Card File, 41-1105 a=10.6041 $\AA$). Average size of prepared phosphor particles have about 100 nm, which were spherical morphology. The phosphor particle sizes decreased and the emission intensity increased at the annealing temperature. Though PL spectrum analysis, the 3% Eu doped $Y_{2-x}$ $O_3$:E $u_{x}$ $^{3+}$(x=0.06) phosphor showed the excitation spectrum at 250 nm wavelength and the maximum emission spectrum at 611 nm wavelength.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.852-856
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• 1999

The objective of this study was to prepare hydrogel beads which were useful microbial immobilization to remove nitrogen and phosphorous in the industrial wastewater. Two different polyols(PEG, PTMG) terminated with photo-crosslinkable methacrylate groups were synthesized. Structures of the prepolymers and the UV cured hydrogels were characterized by using $^1H$-NMR and FT-IR spectroscopy. Water content, mechanical strength and pore sizes of the hydrogels having different MW of polyols and different ratios of PEG/PTMG were investigated. Hydrogels prepared from PEG(MW1000) only or the mixture of PEG(MW1000) and PTMG(MW2900) with 7:3 by weight were considered as potential candidates for the matrix for the immobilization of microorganism.

• Journal of the Korean Chemical Society
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• v.32 no.2
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• pp.85-93
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• 1988

Solvolyses of t-butylhalides (X = Cl, Br, I) in quasi isodielectric solvent system, MeOH-nitromethane, MeOH-nitrobenzene and MeOH-ethyleneglycol have been studied kinetically. Methanolyses for t-butylhalides in MeOH-NM and MeOH-NB show rate maxima at 40~100 % (v/v) MeOH. The rate maxima observed have been interpreted as a result of cooperative enhancement of polarity-polarizability and hydrogen bonddonor ability of solvents. The influences of polarity-polarizability and hydrogen bonddonor ability on reactivities of substrates have been discussed in terms of Y value changes. The solvolysis rates for t-butylhalides in E.G. are more than 20 fold faster than those in MeOH and this was attributed to the solvent structure of E.G.

• Membrane Journal
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• v.24 no.6
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• pp.472-483
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• 2014

This study is preparation of microporous membranes by using macrocyclic metal ion complexes and extended cage complexes. It is a more favorable way to existing methods because polymer and metal ion-ligand complex system provides a fine control over the phase transition behavior. Chemical functionalization of the polar surface can be obtained. Metal-templated condensation of cyclohexanedione dioxime, hydroxyphenylboronic acid in the presence of metal salts proceeds cleanly in methanol to furnish the metal clathrochelate complexes. Organic/inorganic hybrid membranes were prepared with polyethersulfone (PES), polyvinylpyrrolidone (PVP), ethyleneglycol butyl ether (BE), metal clathrochelate s and DMF by using nonsolvent induced phase inversion method. The structure of membranes was characterized with scanning electron microscopy (SEM) and microflow permporometer. The addition of Fe(II) clathrochelate complex with p-hydroxyphenyl group leads to changes of membrane morphology such as narrow mean pore size distribution, increase of surface pore density and decrease of the largest pore size.

• Korean Journal of Animal Reproduction
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• v.23 no.1
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• pp.75-84
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• 1999

This study assessed development in vitro of pronuclear(PN) stage embryos cryopreserved by the method of either vitrification or slow freezing, by using of different cryoprotectants, and equilibration and cooling rate, in rabbit. Ethyleneglycol- ficoll- sucrose(EFS) or ethyleneglycol- polyvinylpyrrolidone - galactose- (EPG-I) for vitrification, and EPG- II for slow freezing as cryoprotectant were used. The pronuclear embryos were exposed to EFS for 0 to 5 min and diluted with D-PBS and/or pre-dilution with 0.5 M sucrose. To examine the viability of frozen-thawed embryos, PN embryos were co-cultured with bovine oviductal epitherial cell(BOEC) for 5 days to hatching blastocyst stage in 39 $^{\circ}C$ 5% $CO_2$incubator. The results obtained were as follows: The dilution with 0.5 M sucrose and D-PBS after the exposure to EFS for 1.0 min resulted in no significant(P＜0.05) decrease in the development of PN embryos to hatching blastocyst(72.0%), compared with controls. The development of PN embryos cryopreserved to hatching blastocyst was not significantly (P＜0.05) different between EFS for 1.0 min(72.0%), EPG-I for 1.0 min(72.0%) and EPG-II for 30 min(66. 7%). The post-thaw development of PN embryos to hatching blastocyst was similarly very low as 6.1% and 11.5% in vitrification with EFS and slow freezing with EPG-II, respectively. The incidence of post-thaw zona-crack in PN embryos cryopreserved by slow freezing with plunging to liquid nitrogen at －35$^{\circ}C$ was signicantly(P＜0.05) higher(25.0%), compared with －85$^{\circ}C$ (1.9%). These results indicated that the rabbit PN embryos could be cryopreserved with either vitrification or slow freezing procedure, and frozen PN embryos could be successfully developed in vitro to haching blastocyst. but the post-thaw development of cryopreserved PN embryos was still very low under the present conditions.

• Membrane Journal
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• v.14 no.3
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• pp.250-257
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• 2004

PEG(poly(ethylene glycol)) acrylate/PPG(poly(propylene glycol)) acrylate (PEG/PPG) was prepared using UV induced photopolymerization method to investigate gas permeation properties of the membrane. The effect of PPG content on the solubility, diffusivity, and permeability of $CO_2$, $O_2$, and $N_2$ in PEG/PPG membrane is reported at $25^{\circ}C$ and $35^{\circ}C$. PEG/PPG (9:1) membrane exhibits $CO_2$ permeability coefficient of 28.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 57.9 at $25^{\circ}C$. Permeability coefficient of increased with increasing with PPG content in the membrane. PEG/PPG (5:5) membrane shows $CO_2$ permeability coefficient of 78.9 barrer and $CO_2$/$N_2$ pure gas selectivity of 33.2 at $25^{\circ}C$.

• Korean Journal of Animal Reproduction
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• v.22 no.2
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• pp.187-194
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• 1998

In order to determine suitable conditions for rapid freezing of porcine embryos, the kind and concentration of cryoprotectants, sucrose concentrations, equilibration time and thawing temperature in freezing medium were examined in relation to the survival of frozen-thawed oocyte and embryos. The results obtained are as follows : 1. The suitable concentrations of cryoprotoctant in the freezing medium which consisted of TCM-199+20% FCS were 1.5M for glycerol, 2.0M for DMSO, 2.5M for ethylene glycol, and 2.0M for propanediol. The sucrose concentration of 0.25M in the medium was found to optimal because the survival rate was markedly higher at this concentration when compared to the others. The survival rate was relatively high when the frozen embryos were thawed at 30$^{\circ}C$ in the freezing medium containing 2.5M cryoprotectants. The equilibration periods of 2.0 and 5.0 minutes revealed the higher survival in the media containing 1.5 or 2.1M glycerol when compared to 10 and 15 minutes. 2. The fertilization rates of frozen-thawed follicular oocytes which matured in vitro for 1, 12, 24 and 48 hours were 6.7~26.7% depending on the maturation time, and the rates were relatively high for those matured for a short period of time. The survival rates of frozen-thawed oocytes which matured in vitro for certain periods and fertilized were 10.0~30.0% depending on the maturation time.

• Polymer(Korea)
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• v.30 no.6
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• pp.478-485
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• 2006

Physical properties and flammability of polyhydroxyamides (PHAs) haying poly (ethylene-glycol) methyl ether (MPEG) and/or dimethylphenoxy pendants were studied by using DSC, TGA, FTIR, pyrolysis combustion flow calorimeter (PCFC), and X-ray diffractometer. The degradation temperatures of the polymers were recorded in the ranges of $276{\sim}396^{\circ}C$ in air. PCFC results showed that the heat release (HR) capacity and total heat release (total HR) values of the PHAs were increased with in-creasing molecular weight of MPEG. In case of M-PHA 2 annealed at $290^{\circ}C$, the values of HR capacity were siginificantly decreased from 253 to 42 J/gK, and 60% weight loss temperatures increased from 408 to $856^{\circ}C$ with an annealing temperature. The activation energy for the decomposition reaction of the PHAs showed in the range of $129.3{\sim}235.1kJ/mol$, which increased with increasing conversion. Tensile modulus of PHAs were decreased as increasing chain of MPEG, and showed an increase more than initial modulus after converted to PBOs.

• KSBB Journal
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• v.9 no.3
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• pp.246-252
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• 1994

Enzyme-catalyzed polycondensatlon reaction of aliphatic polyesters with several repeating units was studied using the biocatalytic activities of lipases from different sources. Porcine pancreatic lipase (PPL) was found to be best in utilizing bls(2,2,2-trichloroethyl) glutarate and 1,4-butanediol as substrafes. The reaction was also catalyzed to some extent by the lipases from Humicola lanuginos and Psudomonas sp. In the series of short-chain diols(C2-C4), bis(2,2,2-trichloroethyl) glutarate was iransesterified fastest with 1,4-butanediol and for the long-chain diols (PEG-300-PEG-1000), the reaction was fastest with PEG-400. With PEGs, only monoesterification product was obtained. PPL functioned well in relatively hydrophilic organic solvents such as tetrahydrofuran(THF), ether and acetonitrile. The reaction rate was accelerated as the reaction temperature was raised from $20^{\circ}C$ to $60^{\circ}C$ while Mn values of the reaction products were not affected by the reaction temperature. End group analysis by NMR showed that Mn values of the polymer were in the range of 1500-4000 daltons.

• Korean Journal of Veterinary Research
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• v.42 no.1
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• pp.35-43
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• 2002

Cryopreservation is commonly used for an efficient utilization of semen, oocytes and embryos but has disadvantage in the survival, development of the post-thawed eggs. The high risk in the survival, development of eggs after thawing is thought to be caused by inappropriate internal regulation of $Ca^{2+}$ and/or formation of intracellular ice crystals. In this experiment, we tested whether the $Ca^{2+}$ current (iCa), a decisive factor to $Ca^{2+}$ entry, was altered in post-thawed oocytes by using whole cell voltage clamp technique. The quality and survival rates of the oocytes derived from both fresh and frozen groups were examined by morphology and FDA-test. Vitrified oocytes (VOs) were incubated for 4 hr after thawing and then donated to this experiment. Ethyleneglycol-ficoll-galactose (EFG) was used as a cryoprotectant for vitrification. The membrane potential was held at -80 mV and step depolarizations of 250 ms were applied from -50 mV to 50 mV in 10 mV increments. The survival rates showed a higher in VOs vitrified with EFG containing $Ca^{2+}$ than in VOs vitrified with EFG under the $Ca^{2+}$-free condition (82.0% vs 14%). In group with/without $Ca^{2+}$, the survival rates were significantly (P<0.01) difference. In the fresh metaphase II oocytes (FOs), current-voltage (I-V) relationship showed that iCa began to activate at -40 mV and reached its maximum at -10 mV. With same voltage pulses, inward currents were elicited in VOs. I-V relationships observed in VOs were similar to those in FOs. Time constants of activation and inactivation of the inward current shown in VOs were not different to those in FOs. This accordance in I-V relations and time constants in FOs with those in VOs indicates that the inward currents in FOs are unaltered by vitrification and thawing. Therefore, vitrification with EFG does not play as a factor to deteriorate $Ca^{2+}$ entry across the membrane of the oocytes.