• Korean Journal of Materials Research
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• v.5 no.5
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• pp.575-582
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• 1995

Al 8090합금의 퇴화처리시에 나타나는 금속간화합물 변화과정과 PFZ 생성 및 입계석출물의 거동을 TEM을 사용하여 조사하였다. 기지에서는 $\delta$상, T$_{1}$ 상과 S'상이 모든 시편에서 관찰되었고, 입계어슨 PFZ이 형성되었다. 본 연구에 사용된 Al합금의 초기PFZ의 생성 기구는 입계의 임계공공 농도에 의한 것으로 나타났다. 2단계 열처리시 시간이 2분 이상이면 입계에 석축물이 형성되었다. 입계에는 중간단계로 5회전대칭축을 가지는 준안전상의 icosahedral상의 생성되었다. 평형 입계석출물은 사방정의 $Al_{13}$Fe$_{4}$였다.

• Korean Journal of Veterinary Research
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• v.46 no.1
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• pp.21-25
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• 2006

Iridovirus is an icosahedral cytoplasmic double-stranded DNA virus with a genome size of 170-200kb. Outbreaks of fish iridovirus infection are characterized by their wide geographic distribution and broad host spectrum, especially in water temperatures of $25-27^{\circ}C$ Recently, the causative agent of high mortalities in flounder (Paralichthys olivaceus) was identified as fish iridovirus in Korea. Iridoviral infection repeatedly occurs in the same area for long periods, suggesting the possibility of viral infection in nursery. To examine this, the existence of iridovirus in juvenile flounders was detected by PCR using virus-specific primers. Antibodies induced against this virus were also examined using ELISA. As a result, juvenile fish in nursery were found to be previously infected with iridovirus, suggesting that proper prevention systems are required.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.51-52
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• 2006

[ $Ti_{45}Zr_{38}Ni_{17}$ ] powders were thermally sprayed onto mild steel substrates in air and under a reduced pressure of argon. Several oxides were formed after thermally-spraying the mechanically-alloyed powders in air. After spraying in a reduced pressure of argon, the coating layers obtained from the gently mixed powders consisted of the elemental metals, but an amorphous phase primarily appeared in the thermally-sprayed mechanically-alloyed powders, which transformed into the icosahedral quasicrystal phase and a minor $Ti_2Ni-type$ crystal phase after annealing at 828 K. The Vickers hardness and the contact angle with pure water for the quasicrystal layers were about 7 GPa and $92^{\circ}$ respectively.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1112-1117
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• 1996

The electronic structures of twenty-seven isomers of a macrocyclic fulleropyrrolidine are investigated with semi-empirical extended Huckel (EH) molecular orbital method. The geometry of each isomer is determined by the molecular mechanics and dynamics methods based on UFF (universal force field) empirical force field. The calculated geometries, such as the carbon-carbon distances of the fullerene moiety, are in good agreement with those of related fullerene derivatives. The EH calculation shows that the formation of macrocyclic pyrrolidine ring on fullerene moiety results in the reduction of the HOMO-LUMO energy gap. From the graphical analysis of the DOS (density of states), PDOS (projected DOS), and MOOP (molecular orbital overlap population) curves, we can find that this reduction is due to splitting of the HOMO of fullerene moiety, which results from the symmetry-breaking and the distortion of the buckminsterfullerene framework from its ideal icosahedral structure.

• Journal of the Korean Mathematical Society
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• v.56 no.5
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• pp.1173-1246
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• 2019

We find all P-resolutions of quotient surface singularities (especially, tetrahedral, octahedral, and icosahedral singularities) together with their dual graphs, which reproduces (a corrected version of) Jan Steven's list [Manuscripta Math. 1993] of the numbers of P-resolutions of each singularities. We then compute the dimensions and Milnor numbers of the corresponding irreducible components of the reduced base spaces of versal deformations of each singularities. Furthermore we realize Milnor fibers as complements of certain divisors (depending only on the singularities) in rational surfaces via the semi-stable minimal model program for 3-folds. Then we compare Milnor fibers with minimal symplectic fillings, where the latter are classified by Bhupal and Ono [Nagoya Math. J. 2012]. As an application, we show that there are 6 pairs of entries in the list of Bhupal and Ono [Nagoya Math. J. 2012] such that two entries in each pairs represent diffeomorphic minimal symplectic fillings.

• Journal of Korea Foundry Society
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• v.40 no.2
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• pp.7-15
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• 2020

The high-temperature stability of Mg-8.0Zn-1.6Y (wt.%) alloys upon the addition of Ca has been investigated by characterizing the ignition temperature, microstructure, tensile and creep properties. The ignition temperature increases with an increase in the Ca content, indicating that an addition of Ca enhances the ignition resistance of the Mg-Zn-Y alloy. The as-cast microstructures of all tested alloys mainly consisted of the dendritic α-Mg matrix and I-phase (Mg₃Zn₆Y) at the grain boundaries. In the Ca-added Mg-8.0Zn-1.6Y alloys, the Ca₂Mg₆Zn₃ phase forms, with this phase fraction increasing with an increase in the Ca contents. However, a high volume fraction of the Ca₂Mg₆Zn₃ phase rather deteriorates the mechanical properties. Therefore, a moderate amount of Ca element in Mg-8.0Zn-1.6Y alloys is effective for improving the tensile and creep properties of the Mg-Zn-Y alloy. The Mg-8.0Zn-1.6Y-0.3Ca alloy exhibits the highest tensile strength and the lowest creep strain among the alloys investigated in the present study. The creep resistance of Mg-Zn-Y-Ca alloys depends on the selection of the secondary solidification phase; i.e., when Ca₂Mg₆Zn₃ forms in an alloy containing a high level of Ca, the creep resistance deteriorates because Ca₂Mg₆Zn₃ is less stable than the I-phase at a high temperature.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.265-271
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• 1985

The classification of bacteriophage could be followed by several criteria. In this study three criteria were used for classification of Lactobacillus casei bacteriophag. In serological classification. antiserum was prepared by rabbit and used for classification. The inactivation effect of phage by antiserum was exponential and L. casei phage was classified in to three serological groups by inactivation rate (K-values). The Lac Y group was proved as a new serological group but the Lac J and Lac S group were shown the same results as previous reports. From the comparison of restriction enzyme pattern of phage DNA, Lac J group was divided into four sub-groups. According to the difference of host range, Lac J-II group was further subdivided into three groups. These results were shown that L. casei strains S-1 bacteriophage was classified into 8 sub-groups. The phage YK of Lac Y group was shown to consist of a icosahedral head about 95nm in diameter, a contractile tail about 150nm in length and 20nm in width. The tail of YK phage is composed of stacked disks(4nm repeat)and a hexagonal baseplate. The molecular weight of YK phage DNA was approximately 85.6 Mdalton.

• The Journal of Korean Society of Virology
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• v.26 no.2
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• pp.269-272
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• 1996

Adenovirus group consists of over 100 related viruses which have been isolated from respiratory or gastro-intestinal tract of primate, cattle, dog and mice. Approximately 40 serologic types of adenovirus producing a variety of human respiratory and conjunctival infections were identified. Adenoviruses are icosahedral virions containing double-stranded linea DNA. They are 70nm to 90nm in diameter and each of capsid is composed of 252 capsomeres. Several numbers of this group, including types commonly associated with respiratory disease in man, are capable of producing malignant tumors in young hamsters and a few types have been shown to be on-cogenic in young rat. Previous report involving effect of Hormone on replication of adenovirus(9) has been carried out. The present report represents a continuation of previous study. To obtain evidence concerning the effect of caffeine on the transformation, investigation of adenovirus type 12 of this group was undertaken. For practical consideration it was desirable to investigation of the effect of caffeine on the adenovirus type 12-induced transformation in L cell. Results were as follows; 1. Adenovirus type 12-induced transformation was inhibited in the presence of caffeine. 2. Yields of adeoovirus type 12 in L cell were slightly inhibited by treatment of caffeine.

• Korean Journal of Veterinary Research
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• v.29 no.2
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• pp.99-108
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• 1989

In order to observe the pathological changes of kidney in rabbits infected with the viral haemorrhagic disease, the kidney tissues from the 91 rabbits infected with the viral haemorrhagic disease were examined by light and electron microscopy. The results observed were as follows: 1. On light microscopic observation, the kidney lesions were identified as haemorrhagic glomerular necrosis(33.0%), membranous glomerulonephritis(20.9%), thrombotic glomerulopathy(19.8%), membranoproliferative glomerulonephritis(8.8%), mesangial proliferative glomerulonephritis(8.8%) ischemic acute tubular necrosis(7.7%), and acute serous glomerulitis(6.6%). 2. On electron microscopic observation, cytoplasmic degeneration of mesangial cells, and irregular thickening of basement membranes with electron dense granular materials were observed. In podocytes swelling of mitochondria, dilatation of endoplasmic reticulum and extensive fusion of foot processes were also observed. Nonenveloped round icosahedral picornaviral particles with a diameter of 28~33nm were detected in the cytoplasm of degenerative endothelial cells, polymorphonuclear leucoytes, and monocytes.

• Journal of Microbiology and Biotechnology
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• v.23 no.8
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• pp.1147-1153
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• 2013

Pectobacterium carotovorum subsp. carotovorum (formerly Erwinia carotovora subsp. carotovora) is a plant pathogen that causes soft rot and stem rot diseases in several crops, including Chinese cabbage, potato, and tomato. To control this bacterium, we isolated a bacteriophage, PP1, with lytic activity against P. carotovorum subsp. carotovorum. Transmission electron microscopy revealed that the PP1 phage belongs to the Podoviridae family of the order Caudovirales, which exhibit icosahedral heads and short non-contractile tails. PP1 phage showed high specificity for P. carotovorum subsp. carotovorum, and several bacteria belonging to different species and phyla were resistant to PP1. This phage showed rapid and strong lytic activity against its host bacteria in liquid medium and was stable over a broad range of pH values. Disease caused by P. carotovorum subsp. carotovorum was significantly reduced by PP1 treatment. Overall, PP1 bacteriophage effectively controls P. carotovorum subsp. carotovorum.