• Analytical Science and Technology
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• v.7 no.3
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• pp.1069-1084
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• 1994

수 MV급 탄뎀형 가속기와 정전형, 자장형 질량분석기를 결합함으로써 존재비가 극히 작은 동위원소 측정이 가능해진다. 수 MeV로 가속이 되면 분해에 방해가 되는 모든 분자이온들이 제거되며, 탄뎀형 가속기에서는 음이온으로부터 가속이 개시되므로 몇몇 음이온을 형성하지 못하는 동중원소의 간섭으로부터 자유로워지기 때문에 고감도분석이 실현될 수 있다. 이외에 음이온을 형성하는 동중원소들은 주로 이온함인 최종 검출기에서의 유효 전하에 따른 에너지손실 차이를 이용하여 효과적으로 제거할 수 있다. 현재는 주로 장반감기 방사성동위원소인 $^{10}Be$, $^{14}C$, $^{26}Al$, $^{36}Cl$과 $^{129}I$ 등의 측정법이 확립되어 천연시료 중에서 동위원소 존재비 $10^{-12}$에서 $10^{-15}$까지의 정량이 가능하며, 원자수로 환산한 검출하한을 $10^5$개가 된다. 또한 해당 원소를 기준으로 소요 시료량은 대부분 mg 정도로 충분하다. 지금까지는 불가능했던 이러한 특징으로 인해 지난 수년간 AMS(Accelerator Mass Spectrometry)가 활용되어 온 연구분야는 지구과학(기후학, 우주화학, 빙하학, 수문학, 해양학, 퇴적학, 화산학 및 광물탐사), 인류 및 고고학(연대측정), 그리고 물리학(천체물리, 핵 및 입자물리) 등으로 다양하다. 이외에 생의학 및 재료과학 분야에서도 AMS를 활용하고자 하는 노력이 계속되고 있다. 본 해설에서는 가속기질량분석기술의 특징, 원리, 장치 및 활용분야 등을 소개하고자 하며, 이로써 관련 분야의 연구 활성화에 기여하고자 한다.

• Journal of the Korean Applied Science and Technology
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• v.19 no.1
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• pp.33-42
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• 2002

Copolymerization of ${\alpha}$-Methylstyrene(AMS) with Acrylonitrile(AN) was carried out with benzoylperoxide(BPO) as an initiator in toluene at $80^{\circ}C$ in a continuous stirred tank reactor. Reaction volume and residence time were 0.6 liters and 3 hours, respectively. The monomer reactivity ratios, $r_{AMS}$ and $r_{AN}$ determined by both the Kele$T{\"{u}}d\"{o}s$ method and the Fineman-Ross method were $r_{AMS}$=0.16(0.14), $r_{AN}$=0.04(0.06). The cross-termination factor ${\Phi}$ of the copolymer over the entire AMS composition ranged from 0.75 to 0.92. The ${\Phi}$ factors of poly(AMS-co-AN) were increased with increasing AMS content. The simulated conversions and copolymerization rates were compared with the experimental results. It was observed that the average time to reach dynamic steady-state was three times the residence time.

• The Korean Journal of Ecology
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• v.25 no.1
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• pp.45-49
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• 2002

Pollen analyses and $^{14}$ C dating of the sediments of the Akindonuma moor, which is situated in a closed depression of an old landslide, were peformed in order to study the vegetation history of the montane zone of the Miyagi Prefecture, Northeast Japan. The main results are as follows: Two forest zones have been distinguished: 1) the A-I zone, or the Fagus-Quercus-Betula forest (R I stage, before about 11,700 yrs B.P.), and 2) the A-II zone, or the Fagus-Quercus forest (R II stage, after about 11,700 yrs B.P.). By comparing the geological section with the pollen diagram of the moor, it is assumed that the deposit environment of the Middle Part, which mostly consists of peat layers, is very stable. During the period, the Ulmus/Zelfkova pollen ratio was very low and small peak was not recognized. According to the preceding research, theme is a close relationship between the fluctuation of the Ulmus/Zelkova pollen ratio and the general trend of hillslope instability in the changing balance of temporature and precipitation Actually, Zelkova serrata tends to cover the footslope and the lower sideslope. Ulmus davidiana covers the footslope and the alluvial cone. Therefore, the fact that the Ulmus/Zeikova pollen ratio was very low and small peak was not recognized, is believed to reflect the stability of the earth's surface environment, which was estimated from the geological section.

• Journal of Environmental Science International
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• v.18 no.1
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• pp.9-14
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• 2009

Pfiesteriaand Pfiesteria-like organisms were reported to be linked to major fish kills(involving well over a billion fish) in North Carolina and Maryland estuaries on the U.S. east coast during the 1990s. Occurrences of these species have been recently reported from Korean waters including Chinhae Bay and the coast of Yeosu. In this study, the life cycle of Cryptoperidiniopsis brodyi and Pfiesteria piscicida were examined using DAPI staining. Their excystment and growth were stimulated directly by the addition of prey cells such as Rhodiminas salina. Amoeboid stages in C. brodyi and P. piscicida were never observed in culture, even after addition of filter-sterile fish mucus and tissue. The dominant life cycle stages consisted of motile flagellated zoospores and cysts. A typical dinoflagellate life cycle was demonstrated by direct observation and DAPI staining.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.571-574
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• 2013

To determine an efficient growth system for algal cultivation and to develop adequate culture system utilizing LED light, we investigated the effects of fluorescent and light emitting diode (LED) light source on the growth of Ulva pertusa. U. pertusa was cultured at $17^{\circ}C$ under a light intensity of 35 ${\mu}mol$ photons $m^{-2}s^{-1}$ and a 10L:14D photoperiod using either fluorescent or LED lamps. After 1 week of incubation under the same environmental condition, the length and width of Ulva pertusa grown under LED light were 1.5- and 1.9-fold greater, respectively, than the length and width of algae grown under fluorescent light. After two weeks, length and width were 2.6- and 2.0-fold greater, respectively, in algae grown under LED light. Total length and width of Ulva pertusa after three weeks of incubation were 1.7- and 1.2-fold greater in algae grown under LED light than those grown under fluorescent light. Therefore, the LED light induced significantly higher growth of Ulva pertusa than fluorescent light.

• BMB Reports
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• v.35 no.6
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• pp.576-582
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• 2002

Collagenase from the internal organs of a mackerel was purified using acetone precipitation, ion-exchange chromatography on a DEAE-Sephadex A-50, gel filtration chromatography on a Sephadex G-100, ion-exchange chromatography on DEAE-Sephacel, and gel filtration chromatography on a Sephadex G-75 column. The molecular mass of the purified enzyme was estimated to be 14.8 kDa by gel filtration and SDS-PAGE. The purification and yield were 39.5-fold and 0.1% when compared to those in the starting-crude extract. The optimum pH and temperature for the enzyme activity were around pH 7.5 and $55^{\circ}C$, respectively. The $K_m$ and $V_{max}$ of the enzyme for collagen Type I were approximately 1.1 mM and 2,343 U, respectively. The purified enzyme was strongly inhibited by $Hg^{2+}$, $Zn^{2+}$, PMSF, TLCK, and the soybean-trypsin inhibitor.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.7
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• pp.1063-1069
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• 1999

Wheat straw samples (3-4 cm) were sprayed with solutions of urea (U) alone or with a dry addition of garden soil (GS), midden soil (MS), soya bean meal (SM) or jack bean meal (JM) as crude urease sources and with a pure urease (UR) enzyme. Each of the urease sources was included at two levels: 30 and 60 g/kg except pure urease, which was added at a level of 2.5 & 5.0 g/kg treated straw dry matter. Untreated straw without urease source was used as a control. After treatment, samples were sealed in polythene bags and stored for 2, 7, 14, 21 and 35 days at $19{^{\circ}C}$. The urease sources, their levels and treatment time produced significant effects on ammonia production (p<0.01). The addition of urease offered more flexibility in hydrolyzing urea in the shortest possible time. Incorporation of soya bean and jack bean meal was effective in reducing the modified acid detergent fiber (MADF) content of straw and the same time increasing organic matter (OM) digestibility. Overall effect, addition of soya bean to urea at a ratio of 1:1 appeared to be the most satisfactory urease source for the treatment of urea and wheat straw.

• Journal of the Korean Wood Science and Technology
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• v.26 no.1
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• pp.14-18
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• 1998

A low density polyethylene(LDPE) was examined as an additive in phenol-formaldehyde(PF) resin adhesive for bonding radiata pine plywood. The LDPE was supplied by the commercial manufacturer. The LDPE was compared to a commercial filler commonly used in structural plywood adhesives in the United States. The adhesive mixes were made by following the recommended procedure of Georgia-Pacific Resins Inc.. using plywood-type PF resin. A total of 48 three-ply plywoods. 6.3 mm nominal thickness and 30 by 30 em in size, were made at two press times (4 and 5 min). two press temperatures (150 and $160^{\circ}C$) and 30 minute assembly times for four adhesive mixing types. Evaluations of the LDPE addition were carried out by performance tension shear tests after two cycle boil aging tests on plywood per the U.S. Product Standard PS I-83. After accelerated-aging tests. plywoods were exhibited no delamination. The test results included tension shear strength and estimated wood failure values. The plywood test results support the use of polyethylene as an additive in plywood adhesives.

• YAKHAK HOEJI
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• v.43 no.1
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• pp.68-76
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• 1999

Phenoxazinone synthase catalyzes the oxidative condensation of two molecules of substituted o-aminophenol to the phenoxazinone chromophore of actinomycin. Mutant strain, Streptomyces sp. V-8-M-1 producing higher phenoxazinone synthase, was obtained from Streptomyces sp. V-8 by treatment of N-methyl-N'-nitro-N-nitrosoguanidine. The phenoxazinone synthase was purified from extract of mutant strain of Streptomyces sp. V-8-M-l by successive steps of streptomycin sulfate, ammonium sulfate precipitation. DEAE-cellulose and Sephadex G-200 column chromatography. Molecular weight of the enzyme was 360,000 daltons. The enzyme was composed of octamer of a single subunit of 45,000 daltons. The Km value and Vmax value for 3-HAA were $14.9{\;}{\mu}M$ and 9.5 mg/U, respectively. The optimal pH and temperature for the enzyme activity were 9.0 and $25~30^{\circ}C$, respectively. Treatment of the enzyme with group specific reagents, phenylglyoxal, p-hydroxymercury-benzoate, Nbromosuccinimide, 5.5'-dithiobis-nitrobenzoic acid and ethylmaleimide resulted in loss of enzyme activity, which shows arginine and cysteine residues are at or near the active site.

• Computers and Concrete
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• v.25 no.1
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• pp.1-14
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• 2020

This study presents applications of the multivariate adaptive regression splines (MARS) method for predicting the ultimate loading carrying capacity (N_u) of rectangular concrete-filled steel tubular (CFST) columns subjected to eccentric loading. A database containing 141 experimental data was collected from available literature to develop the MARS model with a total of seven variables that covered various geometrical and material properties including the width of rectangular steel tube (B), the depth of rectangular steel tube (H), the wall thickness of steel tube (t), the length of column (L), cylinder compressive strength of concrete (f'_c), yield strength of steel (f_y), and the load eccentricity (e). The proposed model is a combination of the MARS algorithm and the grid search cross-validation technique (abbreviated here as GS-MARS) in order to determine MARS' parameters. A new explicit formulation was derived from MARS for the mentioned input variables. The GS-MARS estimation accuracy was compared with four available mathematical methods presented in the current design codes, including AISC, ACI-318, AS, and Eurocode 4. The results in terms of criteria indices indicated that the MARS model was much better than the available formulae.