• Korean Journal of Microbiology
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• v.25 no.2
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• pp.157-164
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• 1987

A new endo-$\beta$-1, 4-glucanase was purified from the culture filtrate of thermophilic anaerobic Clostridium thermocellum. The purification procedure included two steps of ion exchange chromatography with DEAD-Sephadex A-50 and gel filtration chromatography with Sephadex G-75. Even though the 56 fold increase in CMCase specific activity was obtained, the actually recovered enzyme activity was relatively lower level of 0.7%. Judging from the two bands in SDS-polyacrylamide gel electrophoresis, the endo-$\beta$-1, 4-glucanase consists of two subunits whose M.W. are 38,000 and 58,000, respectively. The optimum pH and temperature were determined to be 5.0 and $65^{\circ}C$, respectively. The enzyme was stable up to $70^{\circ}C$, but inactivated at $80^{\circ}C$. The kinetic parameters of the separated fraction were also determined. The purified enzyme did not show any significant hydrolytic activity against the highly ordered crystalline cellulose as well as filter paper.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.99-104
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• 2005

In this study, the effects of C and Si on damping capacity and mechanical properties of as-cast and as-rolled Fe-17%Mn alloys were investigated as a basic study for the purpose of the commercialization of the alloy. The $M_s$ temperature of ${\gamma}{\rightarrow}{\varepsilon}$ martensitic transformation in Fe-17%Mn alloy was decreased with increasing C and Si contents, resulting in the less volume fraction of ${\varepsilon}$ martensite. The damping capacity was also decreased with increasing alloying content because of less ${\varepsilon}$ amount and the reduction in mobility of the damping sources such as the stacking fault boundaries and ${\gamma}/{\varepsilon}$ interfaces due to the pinning effect by alloying elements. The mechanical properties of as-rolled alloys were superior to those of as-cast alloys probably because of finer ${\gamma}$ grains, larger amount of ${\varepsilon}$ martensite, and chemical homogeneity.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.3
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• pp.342-347
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• 2003

The enzyme $20{\alpha}$-hydroxysteroid dehydrogenase ($20{\alpha}$-HSD) catabolizes progesterone to $20{\alpha}$-dihydroprogesterone ($20{\alpha}$-OHP), and is appeared in rat corpora luteal and placenta. A polled samples of 10-15 placental and ovarian tissues collected from each individual rat were subjected to measurement of $20{\alpha}$-HSD activity. A $20{\alpha}$-HSD activity in the cytosol fraction was based on the generation of NADPH. In this study, it is designed to study cytosolic $20{\alpha}$-HSD activity in rat ovarian and placenta during pregnancy, and its relationship to embryonic mortality. It was found that from days 5 to 18 of pregnancy the $20{\alpha}$-HSD activities steady by decreased but at parturition time rapidly increased in ovary. On the other hand, placental cytosolic $20{\alpha}$-HSD activities were high detected from days 8 to 10 of pregnancy, not detectable from days 11 to 20 of pregnancy, but again very high at the time of parturition. Analysis of DEAE column chromatography revealed that two different types of $20{\alpha}$-HSD (HSD-1 and HSD-2) were found with similar activity in the placental cytosol on day 10 of pregnancy. The number of fetuses on day 10 of pregnancy was 15.4 and decreased significantly to 12.9 on day 12. The results suggested that expression of $20{\alpha}$-HSD in the placental tissues seems to be related the number of fetal survived in the specific time (days 11 and 12) which spontaneous fetal loss occurs.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.4
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• pp.295-304
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• 1998

The effects of retained austenite and carbon content in the retained austenite on the tensile strength-elongation balance and spot weldability of TRIP high strength steel sheet have been investigated. The retained austenite of granular type increased with increasing intercritical annealing and austempering temperature, and film type was increased with the increase of austempering time. The volume fraction of retained austenite increased with decreasing intereritical annealing temperature, and the maximum value was obtained at austempering temperature of $400^{\circ}C$. The values of tensile strength-elongation balance increased with decreasing intercritical annealing temperature and maximum value was obtained at austempering temperature of $400^{\circ}C$. The maximum value of tensile strength-elongation balance was obtained at a retained austenite content of about 12%. Tensile shear strength of the specimens with retained austenite was higher than that of the normalizing specimens. With increasing welding current and time, the tensile shear strengh and nugget diameter increased, while nugget thickness showed the peak value and then decreased. The optimum range of welding condition at the given welding pressure of 350kgf was 7~11kA and 10~15 cycles.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.5
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• pp.215-221
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• 2017

The effect of austenitizing temperature on the degree of carbides re-solutionizing, mean graine size, hardness and the volume fraction of retaind austenite ($V_{\gamma}$) etc., has been studied by means of metallography, X-ray diffractometry and hardness measurement in STD 11 tool steel. As austenitizing temperature increases, the amount of alloying elements which is re-dissolved into matrix increases, resulting in increase of $V_{\gamma}$, due to the chemical stabilization of austenite. The Vickers hardness value decreases with increasing austenitizing temperature, which is attributed to grain size as well the volume fractions of $V_{\gamma}$ and carbides. Theoretical diffraction intensity of (200) ${\alpha}^{\prime}$, (211) ${\alpha}^{\prime}$ (200) ${\gamma}$ and (220) ${\gamma}$ peaks obtained by $CuK_{\alpha}$ chracteristics X-ray (${\lambda}=0.15429nm$) was calculated, and quantitative analysis of $V_{\gamma}$ could be carried out by X-ray diffraction method. The resultant value is well coincided with the value obtained by image analysis method. When the quenched specimen is tempered above $200{\sim}400^{\circ}C$ for 30 min, the transition carbides i.e., MC and $M_2C$ in the size of about 20 nm begin to precipitate at $300^{\circ}C$.

• Progress in Superconductivity and Cryogenics
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• v.19 no.3
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• pp.27-32
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• 2017

The effects of artificial holes on the trapped magnetic fields and magnetic levitation forces of very large single-grain $Y_{1.5}Ba_2Cu_3O_{7-y}$ (Y1.5) bulk superconductors were studied. Artificial holes were made for Y1.5 powder compacts by die pressing using cylindrical dies with a diameter of 30 mm or 40 m, or rectangular dies with a side length of 50 mm. The single grain Y1.5 bulk superconductors (25 mm, 33 mm in diameter and 42 mm in side length) with artificial holes were fabricated using a top-seeded melt growth (TSMG) process for the die-pressed Y1.5 powder compacts. The magnetic levitation forces at 77 K of the 25 mm single grain Y1.5 samples with one (diameters of 4.2 mm) or six artificial holes (diameters of 2.5 mm) were 10-17% higher than that of the Y1.5 sample without artificial holes. The trapped magnetic fields at 77 K of the Y1.5 samples with artificial holes were also 9.6-18% higher than that of the Y1.5 sample without artificial holes. The 33 mm and 42 mm single grain Y1.5 samples with artificial holes (2.5 mm and 4.2 mm in diameter) also showed trapped magnetic fields 10-13% higher than that of the Y1.5 samples without artificial holes in spite of the reduced superconducting volume fraction due to the presence of artificial holes. The property enhancement in the large single grain Y1.5 bulk superconductors appears to be attributed to the formation of the pore-free regions near the artificial holes and the homogeneous oxygen distribution in the large Y123 grains.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.423-423
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• 2007

In this study, the effects of annealing conditions on the structural and optical properties of ZnO films were investigated. ZnO oxide (ZnO) films were deposited onto $SiO_2$/Si substrates by RF magnetron sputtering from a ZnO target. The substrate was not heated during deposition. ZnO films were annealed in temperature ranges of $500{\sim}650^{\circ}C$ in the $O_2$ flow for 5 ~ 20 min. The film average thicknesses were in the range of 291 nm. The surface morphologies and structures of the samples were characterized by SEM and XRD, respectively. The optical properties were evaluated by PL measurement at room temperature using a He-Cd 325 nm laser. According to the results, the optimal annealing conditions for the best photoluminescence (PL) characteristics were found to be oxygen fraction, ($O_2/O_2+Ar$) of 20%, RF power of 240W, substrate temperature of RT (room temperature), annealing condition of $600^{\circ}C$ for 20 min, and sputtering pressure of 20 mTorr. The obtained wavelength of light emission was found at 379 nm (ultraviolet-UV region). However, the optimal parameters for the best PL characteristics of ZnO thin films were not consistent with those obtained from the (002) intensities of XRD analyses. As a result, XRD pattern was not considered as the key issue concerning the intensity of PL of ZnO thin film. The intensity of the emitted UV light will correspond to the grain size of ZnO film.

• Microbiology and Biotechnology Letters
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• v.37 no.1
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• pp.33-41
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• 2009

The crushed fruiting body of Alaskan Porodaedalea pini (Brot.) Murrill (syn. Phellinus pini) was extracted in boiling water for 4 h with the yield of 20.5% in dry mass. This hot-water extract showed significant antiviral activity by inhibiting the plaque formation in HeLa cells by coxackievirus B3 (CVB3) and also showed highest inhibitory effect against neuraminidase activity among water extracts of various mushrooms. From the water extract, the ethanol precipitate (EP) and supernatant fraction (ES) were obtained through 75% ethanol precipitation with the yield of 43.3% and 28.3% in dry mass, respectively. Whereas ES did not show any detectable level of antiviral activity, EP showed significant dose-dependent inhibition of plaque formation by CVB3 in HeLa cells with an $EC_{50}$ (50% effective concentration) of 0.45 mg/mL. The cytotoxicity on HeLa cells by EP was relatively low with the $CC_{50}$ (50% cytotoxic concentration) of 2.25 mg/mL. EP also effectively inhibited neuraminidase activity in a dose-dependent manner showing up to 75% inhibition at 1.7 mg/mL. These results suggest that the hot-water extract and its EP of P. pini fruiting body can be a candidate for the development of a potent broad-range antiviral agent against influenza virus(Flu) as well as CVB3. The major active component of EP was shown to be a heteropolysaccharide-protein complex containing glucose as the main sugar residue with mole percentage of 79.8% and other sugars like galactose (19.2%), xylose (17%), mannose (5.8%), and fucose (4.6%) and a small portion (12.7%, in mass) of protein.

• Korean Journal of Food Science and Technology
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• v.51 no.5
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• pp.480-485
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• 2019

The present study was conducted to compare antioxidant capacities of protein hydrolysates from four different edible insects (Protaetia brevitarsis larvae, Allomyrina dichotoma larvae, Gryllus bimaculatus imago, and Tenebrio molitor larvae) which have recently been registered as food varieties in Korea. Protein hydrolysates were prepared from each insect using enzymatic hydrolysis using alcalase, and were then separated into a fraction containing ${\leq}3kDa$. According to $RC_{50}$ values and trolox equivalent antioxidant capacity results obtained from five different antioxidant analyses, the Gryllus bimaculatus (GB) hydrolysate showed relatively high levels of antioxidant capacity and, in particular, the GB hydrolysate showed considerably strong antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and in ferric reducing antioxidant power (FRAP) assays. The GB hydrolysate also showed the strongest inhibitory effect on peroxidation of linoleic acid, and its rate of inhibition at $100{\mu}g/mL$ on day 3 of treatment was 60.26%. These results suggest that protein hydrolysates from edible insects including GB represent potential sources of natural antioxidants.

• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.66-71
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• 2003

Pt/AlGaN Schottky-type UV photodetectors were designed and fabricated. A low-temperature AlGaN interlayer buffer was grown between the AlGaN and GaN film in the diode structure epitaxy to obtain crack-free AlGaN active layers. A comparison was then made of the structural, electrical, and optical characteristics of two different diodes: one with an AlGaN($0.5\;{\mu}m$)/n+-GaN(2 nm) structure (type 1) and the other with an AlGaN($0.5\;{\mu}m$)/AlGaN interlayer($150\;{\AA}$)/n+-GaN($3\;{\mu}m$) structure(type 2). A crack-free AlGaN film was obtained by the insertion of a low-temperature AlGaN interlayer with an aluminum mole fraction of 26% into the $Al_xGa_{1-x}N$ layer. The fabricated Pt/$Al_{0.33}Ga_{0.67}N$ photodetector had a leakage current of 1 nA for the type 1 diode and $0.1\;{\mu}A$ for the type 2 diode at a reverse bias of -5 V. For the photoresponse measurement, the type 2 diode exhibited a cut-off wavelength of 300 nm, prominent responsivity of 0.15 A/W at 280 nm, and UV-visible extinction ratio of $1.5{\times}10^4$. Accordingly, the Pt/$Al_{0.33}Ga_{0.67}N$ Schottky-type ultraviolet photodetector with an AlGaN interlayer exhibited superior electrical and optical characteristics and improved UV detecting properties.