• International Journal of Industrial Entomology and Biomaterials
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• v.33 no.2
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• pp.138-143
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• 2016

In the present study, silk fibroin (SF) was dissolved in $CaCl_2/H_2O/EtOH$ solution at $85^{\circ}C$. After the dissolution, the SF solution was cooled down and stored at $4^{\circ}C$ for 28 d. The stability of the solution's viscosity and electrospinnability was observed to examine the stability of SF molecules during storage in $CaCl_2/H_2O/EtOH$ solution. The viscosities of $SF/CaCl_2/H_2O/EtOH$ solution and SF formic acid solution did not change during 28 days' storage of SF in $CaCl_2/H_2O/EtOH$ solution. The electrospinnability of the SF solution, mean diameter of the electrospun SF fiber, and crystallinity index of electrospun SF web did not change, regardless of the length of the storage period. These results imply that SF molecules do not degrade during 28 days' storage in $CaCl_2/H_2O/EtOH$ solution.

• Bulletin of the Korean Chemical Society
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• v.24 no.7
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• pp.906-910
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• 2003

Hydrothermal reactions of Ni(NO₃)₂· 6H₂O with trans-1,2-bis(4-pyridyl)ethylene (bipyen), in the presence of a linear 2,6-naphthalene dicarboxylic acid (NDCH₂) and a bent 4,4'-oxybis(benzoic acid) (OBCH₂), gave a 2-D coordination polymer [Ni(NDC)(bipyen)(H₂O)] (1) and also a 2-D coordination polymer [Ni(OBC)(bipyen)]· H₂O (2), respectively. A reversible de-coordination and re-coordination of an aqua ligand was observed for polymer 1. Polymer 2 has an undulated 2-D network based on 50-membered rectangular grids, each of which has the dimension of 13.61 × 13.17 Å.

• Journal of the Korean Ceramic Society
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• v.30 no.11
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• pp.897-904
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• 1993

CdS doped SiO2 glass coating films which are good candidates for the nonlinear optical materials were prepared by the Sol-Gel method. TEOS, C2H5OH, H2O and HCl were used as starting materials to obtain SiO2 matrix solutions. Then Cd(NO3)2.2H2O and CS(NH2)2 were dissolved into the SiO2 matrix solutions. Coating was performed several times in order to increase the thickness of coated film by the dip-coating method. Then heat treatments were carried out to control the size of CdS microcrystals doped in SiO2 glass matrix with respect to temperatures and times. CdS-doped SiO2 transparent coating films were successfully obtained. CdS crystals were changed from cubic to hexagonal type about $600^{\circ}C$.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.80-84
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• 2006

The removal efficiency of Cu and Fe contaminants on the silicon wafer surface was examined to investigate the effect of cleaning solutions on the behavior of metallic impurities. Silicon wafers were intentionally contaminated with Cu and Fe solutions by spin coating and cleaned in different types of cleaning solutions based on $NH_4OH/H_2O_2/H_2O\;(SC1),\;H_2O_2/HCl/H_2O$ (SC2), and/or HCl/$H_2O$ (m-SC2) mixtures. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). Cu ions were effectively removed both in alkali (SC1) and in acid (SC2) based solutions. When $H_2O_2$ was not added to SC2 solution like m-SC2, the removal efficiency of Cu impurities was decreased drastically. The efficiency of Cu ions in SC1 was not changed by increasing cleaning temperature. Fe ions were soluble only in acid solution like SC2 or m-SC2 solution. The removal efficiencies of Fe ions in acid solutions were enhanced by increasing cleaning temperature. It is found that the behavior of metallic contaminants as Cu and Fe from silicon surfaces in cleaning solutions could be explained in terms of Pourbaix diagram.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.157-168
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• 1994

The surface morphology, electrical properties, and optical properties of textured $SnO_2(:F)$ films according to deposition parameters such as HF and $H_2O$ content was studies. The electron concentration, resistivity, and mobility was $3{\Times}10^{20}/cm^3$, $7{\Times}10^4~9{\Times}10^4{Omega}cm$ and $18~25cm^2/V.sec$, respectively, when HF bubbling rate over 0.9 slm. The surface morphology was sharp edged pyramid shape without bubbling $H_2O$ but changed to round edged hemispherical shape when $H_2O$ was added.

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.99-103
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• 2004

The structure of $C_{16}H_{19}O_2N_3CuCl_2\;{\cdot}\;H_2O$ has been determined by X-ray diffraction methods. The crystal system is triclinic, space group Pl, unit cell constants. $a=7.6202(9)\; \AA,\; b=8.5943(7) \AA,\; c= 8.6272(6) \AA,\; \alpha= 67.518(6)^{\circ}.\; \beta= 68.043(8)^{\circ},\; \gamma=74.370(8)^{\circ},\; V=478.89(8)\; \AA^3,\; T=295K,\; Z=1,\; D_c=1.504Mgm^{-3}$The intensity data were collected on an Enraf-Nonius CAD-4 Diffractometer with graphite monochromated $MoK\alpha$ radiation $(\alpha=0.7107\;\AA)$. The molecular structure was solved by direct method.』 and refined by full-matrix least squares to a final $R=2.47\%$ for 1659 unique observed $F_0>4\sigma(F_0)$ reflections and 234 parameters.

• Journal of the Korean Chemical Society
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• v.41 no.9
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• pp.465-470
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• 1997

A chiral pentadentate ligand, 1,9-bis(S)-prolyl-1,9-dioxo-2,5,8-triaza-nonane, (S,S-prochen) which shows the stereospecific reaction was synthesized from the reaction of S-proline and diethylenetriamine (dien). The red-violet $[Co(SS-prodien)H_2O]ClO_4$ was prepared by the oxidation of the aqueous solution dissolving $CoCl_2{\cdot}6H_2O$ and S,S-prodien. Elemental analysis, electronic absorption spectroscopy, and $^{13}C-NMR$ spectroscopy suggest that the geometrical structure of the Co(III) complex to be an ${\alpha}{\beta}$ (ffm) form, where the dien moiety of the ligand chelates the metal center to comprise a facial isomer, and an aqua ligand coordinates a cis site to the secondary nitrogens of the dien. Based upon the CD spectroscopic analysis, it seems that the absolute configuration of the ${\alpha}{\beta}$(ffm)-$[Co(SS-prodien)H_2O]ClO_4$ has the ${\Lambda}$-form.

• Reproductive and Developmental Biology
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• v.35 no.3
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• pp.221-225
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• 2011

This study was undertaken to evaluate the relationship between in vitro maturation and plasminogen activators (PAs) activity on porcine cumulus-oocytes complexes (COCs) exposed to oxidative stress. When COCs were cultured in maturation medium with hydrogen peroxide ($H_2O_2$), the proportion of the germinal vesicle breakdown (GVBD) and oocytes maturation were decrease with addition of $H_2O_2$, and were significantly (p<0.05) lower in medium with 0.1 mM $H_2O_2$ than control group. Also, the rate of degenerated oocytes was increased in as $H_2O_2$ concentration in eased. When COCs were cultured for 48 h, three plasminogen-dependent lytic bands were observed: tissue-type PA (tPA); urokinase-type PA (uPA); and tPA-PA inhibitor (tPA-PAI). PA activity was quantified using SDS-PAGE and zymography. When $H_2O_2$ concentration was increased, tPA and tPA-PAI activities also increased in porcine oocytes cultured for 48 h, but not uPA. In other experiment, embryos were divided into three groups and cultured in (1) control medium, (2) control medium with 1.0 mM $H_2O_2$ and (3) control medium with 1.0 mM $H_2O_2$ along with catalase in concentrations of 0.01, 0.1, and 1.0 mg/ml, respectively. $H_2O_2$ decreased the rate of GVBD and maturation in porcine COCs but catalase revealed protective activity, against oxidative stress caused by $H_2O_2$. In this experiment, tPA and tPA-PAI activities were higher in media with 1.0 mM $H_2O_2$ alone. Increasing concentration of catalase decreased tPA and tPA-PAI activities in porcine oocytes. These results indicate that the exposure of porcine follicular oocytes to ROS inhibits oocytes maturation to metaphase-II stage and increase the oocytes degeneration. Also, we speculated that increased ROS level may trigger tPA and tPA-PAI activities in porcine oocytes matured in vitro.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.731-736
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• 2019

In this article, Pt/TiO₂ was manufactured in the form of powder and honeycomb, and the influence of SO₂, which is a poisonous substance to catalyst, and regeneration method were investigated. The catalytic activity of Pt/TiO₂ before and after the exposure to SO₂ was also compared. The initial activity of Pt/TiO₂ was proportional to the injected H₂ concentration (1~5%). And the optimum temperature of the catalyst and conversion rate of H₂ were 183 ℃ and 95%, respectively. It was confirmed that when exposing 2,800 ppm of SO₂ to the powder and honeycomb Pt/TiO₂, the performance of catalyst was not measurable and also 0.69% sulfur (S) remained on the catalyst surface. As a result of the cleaning and heat treatment for the poisoning catalyst, the activity of the powder catalyst exhibited a conversion rate of H₂ greater than 96%. Whereas, the honeycomb catalyst showed a conversion rate of H₂ greater than 95% when it was regenerated through the heat treatment of H₂ or air atmosphere.

• Journal of Hydrogen and New Energy
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• v.30 no.3
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• pp.201-208
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• 2019

Recently, a fuel reforming plant for supplying high purity hydrogen is being applied to submarines. Since steam reforming is an endothermic reaction, it is necessary to continuously supply heat to the reactor. A fuel reforming plant for a submarine needs a multi-stage burner (MSB) to acquire heat and convert the combustion gas to $CO_2+H_2O$. The MSB has problems that the combustion imbalance occurs during start-up due to the temperature restriction of the combustion gas. This problems can be solved by burning $H_2O$ together with fuel and $O_2$. In this study, the simulation results of MSB were analyzed to determine the optimum flow rate of $H_2O$ supplied to the 6-stage burner. When the flow rate of $H_2O$ was low, combustion was concentrated on the burner#6 in comparison with the burner#1-#5. This combustion concentration improved as the supply amount of $H_2O$ increased. As a results, it was necessary to supply at least 4.9 kmol/h of $H_2O$ (per 1 kmol/h of fuel) to burner#1 in order to maintain the combustion gas temperature of each stage at $750^{\circ}C$ and to convert the final stage burner gas composition to $CO_2+H_2O$.