• 한국분말재료학회지
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• 제30권5호
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• pp.424-430
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• 2023

YAG phosphor powders were fabricated by the atmospheric plasma spraying method with the spray-dried spherical YAG precursor. The YAG precursor slurry for the spray drying process was prepared by the PVA solution chemical processing utilizing a domestic easy-sintered aluminum oxide (Al₂O₃) powder as a seed. The homogenous and viscous slurry resulted in dense granules, not hollow or porous particles. The synthesized phosphor powders demonstrated a stable YAG phase, and excellent fluorescence properties of approximately 115% compared with commercial YAG:Ce³⁺ powder. The microstructure of the phosphor powder had a perfect spherical shape and an average particle size of approx imately 30 ㎛. As a result of the PKG test of the YAG phosphor powder, the synthesized phosphor powders exhibited an outstanding luminous intensity, and a peak wavelength was observed at 531 nm.

• Animal cells and systems
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• 제1권2호
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• pp.371-379
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• 1997

To investigate the movement of sperm head and the role of sperm neck in forward sperm motility in the Korean striped field mouse, Apodemus agrarius coreae, the morphological characteristics of the cauda epididymal spermatozoa were examined by light microscopy and scanning and transmission electron microscopy. Spermatozoa of A. agrarius coreae were characterized by the conspicuous shape of the acrosome and the long tail compared with those of other rodents. Total length of the sperm was $133\mu{m}$. The sperm head had a curved falciform shape. The head was 8.0${\mu}$m in length, and about 4.0 ${\mu}$m in width. The shape of acrosome had an openerlike form. The sperm tail (125 ${\mu}$m) consisted of four major segments: neck (0.5 ${\mu}$m), middle piece (29.5 ${\mu}$m), and principal piece plus the end piece (95 ${\mu}$m). The outer dense fibers were arranged in a horseshoe fashion, and No. 1, 5, 6, and 9 of the outer dense fibers were larger than the others. The mitochondrial bundles of middle piece were composed of a pair of arms, which surrounded the axone of the middle piece by the 45 0 angled helical structure. The total number of mitochondrial gyres was 188. In particular, the microfilament structures existed in plasma membrane of the sperm, which was adjacent to the acrosomal region on the nuclear membrane. The segmented columns were surrounded by microfilament structures, and the microfilament bundles were adjacent to the outer membrane of the first mitochondria of middle piece. This study presents for the first time the existence of microfilament structures within the plasma membrane of sperm which is located from the adjacent acrosome region to the connecting piece in sperm neck of Korean striped field mouse, Apodemus agrarius coreae. The present result suggests that the constriction and extension of microfilament in sperm neck as well as the wave-movement of sperm tail may play a role in the movement of sperm head.

• Journal of Plant Biology
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• 제35권3호
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• pp.219-227
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• 1992

지질성 종자(해바라기, 피마자, 잣나무)와 전분성 종자(완두, 옥수수)를 대상으로 배유와 자엽세포내의 저장지질의 형성, 분포 및 구조적 변화 등과 지질가수분해효소의 활성부위 및 세포내 분포양상 등을 세포화학적 방법을 이용하여 조사하였다. 채종후의 지질 및 전분성 종자의 배유와 저장성 자엽세포에는 구형의 단백과립과 지질소구인 스페로솜, 전분과립 등의 저장물질이 널리 분포하였으며 세포내소기관은 드물게 관찰되었다. 활면소포체에서 형성되어 방출된 소포들과 스페로솜의 초기 단계로 여겨지는, 전자밀도가 낮은 막성의 과립들은 염색상이 스페로솜의 그것과 동일하였다. 조면소포체에서 방출된 전자밀도가 높은 과립들은 원형질막의 인접부위에서 관찰되었다. 지질염색반응 결과, 일반적인 미세구조의 염색상과는 상이하게 단백과립내의 단백질보다는 구형의 스페로솜의 전자밀도가 높고 균일함이 확인되어 스페로솜의 주요 구성성분은 지질임을 알 수 있었다. 스페로솜과 활면소포체에서 방출하는 물질을 함유한 소포는 염색상이 동일하였다. 지질가수분해효소는 분해과정이 진행중인 스페로솜의 기질과 막 주변부, 그리고 원형질막 부근에서 강한 활성을 보였다.

• 한국세라믹학회지
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• 제43권6호
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• pp.358-361
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• 2006

A two-step plasma-assisted boronizing process was carried out on the AISI 1045 steel substrate to reduce the pore density introduced by a conventional single plasma boronizing process. The specimens were plasma boronized for 1 h at $650^{\circ}C$ and subsequently far 7 h at $800^{\circ}C$ in an atmosphere of $BCl_3-H_2-Ar$. The boride layer thickness was parabolic in boronizing time, a high HV reading of 1540 was found up to the boride layer thickness of $25{\mu}m$. It was found that the morphology of the boride layer prepared by the two-step boronizing process was changed from a columnar to a tooth-like structure and the pores in the borided steel were eliminated completely in comparison to those synthesized by the conventional single boronizing process, implying that it is highly applicable for enhancing the dense and compact coating properties of the low-alloy steel.

• 멤브레인
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• 제20권4호
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• pp.297-303
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• 2010

폴리올레핀 중합공정에서 발생되는 미반응 올레핀 모노머를 회수하기 위한 분리막/냉각응축 공정에 적용할 복합막을 용액 코팅공정과 플라즈마 중합공정의 두가지 방법으로 제조하였다. Polysulfone (PSF) 지지체 위에 poly(dimethylsiloxane) (PDMS) 용액을 코팅하였고 코팅 용액에서 prepolymer의 함량이 높을수록 올레핀 모노머의 선택도는 증가하였으나 막이 치밀하여지는 관계로 절대 투과량은 감소하는 경향을 보였다. 유기물의 복합막 투과는 용액확산 메커니즘에 의한 것으로서 임계온도가 높을수록 분리효율은 향상되고 molar volume이 증가할수록 투과도가 향상되었다. 또한 가교시간에 siloxane 계열의 물질을 plasma 종합하여 복합막을 제조하였는데 PSF 및 polypropylene (PP) 지지체를 사용하였다. 특히 지지체로 기존의 용액코팅 공정에서 사용되기 어렵던 PP 지지체 위에도 복합막을 코팅할 수 있었으며 용액코팅 공정으로 제조된 복합막과 유사한 성능을 나타내었다.

• 한국분말재료학회지
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• 제17권1호
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• pp.13-22
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• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• Applied Microscopy
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• 제20권2호
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• pp.12-22
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• 1990

The morphological characteristics and changes of the foregut in the grasshopper (Oxya sinuosa Mistshenko) have been studied with the special reference to the developmental stage. In light microscope level, the epithelia are seen the cuboidal shape in the 5th instar nymph and the adult. A number of pigment granules are appeared in the cuboidal epithelium of the 5th instar nymph, however the pigment granules were a few in the adult. Indistinct or undifferentiated folds of the epithelial layer were appeared in the 5th instar nymph, whereas the well-developed folds were in the adult. The well-developed muscular layers are seen in the 5th instar nymph, however in the adult the muscular layers are appeared thin or a few layer except the crop. In electron microscope level, in the foregut epithelium, a few round or oval shaped mitochondria, well-developed rER, Golgi complex, lysosome and a number of vacuoles were appeared in the cytoplasm. Two types of pigment granules, electron dense or homogenous and low electron dense or lamellar profiles, are seen in the esophageal epithelium. The crystalline profiles and plasma membrane infoldings were also appeared. In the foregut epithelium of the 5th instar nymph, however the cell organelles were generally undifferentiated and in the crop two types of pigment granules as the adult esophageal epithelium were also found.

• 한국환경과학회지
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• 제14권6호
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• pp.605-611
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• 2005

The aim of this study was to analyze the local distribution of the heavy metal concentration in Daegu and Ulsan which were divided into the residual areas, the traffic dense areas and the industrial areas. The Inductively Coupled Plasma(ICP) was used to analyze heavy metals, such as As, Cr, Hg, Zn, Cd, Pb, Cu and minor metals, such as Fe, Si, Mg, Ca, AI, Na, K. The results of this analysis showed that the content of heavy metals which was classified by districts in Daegu and Ulsan was the highest in the industrial areas followed by the traffic dense areas and the residual areas. Compared to the level of heavy metals of national and local soil survey network in 2003, contamination of heavy metals in Daegu was lower than national average. However, the content of Cd, As, Zn in Ulsan was respectively 13.38 times, 472 times and 2.65 times higher than national average contamination. In addition, compared to the soil pollution level of the environmental protection law, contamination of all areas in Daegu was lower. But the content of As at the industrial areas in Ulsan was 10.71 times higher than standard of soil pollution and 4.28 times higher than standard of measures against soil contamination.

• The Plant Pathology Journal
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• 제28권4호
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• pp.401-408
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• 2012

Initial subcellular responses in susceptible (PI 274420) and resistant (cv. Hartwig) soybeans infected with the soybean cyst nematode (SCN) were examined 2 and 4 days after inoculation (DAI). Subcellular features common to both soybeans at 2 DAI included hypertrophied initial syncytial cells (ISCs) and syncytium-component cells (SCs) with a dense cytoplasm containing proliferated rough and smooth endoplasmic reticulum (RER and SER), a hypertrophied nucleolus, and reduced vacuoles, suggesting that the nematode-infected cells were dedifferentiated. In the resistant soybean, a striking initial subcellular difference from the susceptible soybean was the dilation of the RER, indicating ER dysfunction and leading to cell death. This disturbed nematode feeding, as evidenced by disrupted feeding tubes. In PI 274420, the ISC cytoplasm was depleted, with the exception of ER membranes, at 4 DAI, while the SC cytoplasm was dense with proliferation of starch-containing plastids around multiple nuclei that might be derived from the congregation of nuclei in the neighboring SCs and in part by nuclear division without cytokinesis. In cv. Hartwig, syncytia were necrotized with secondary cell wall thickening outside the plasma membrane and an extremely dense cytoplasm containing a nucleus with an electron-lucent nucleolus, accompanied by the proliferation of closely stacked parallel RER and ribosomes. These results suggest that syncytia develop continuously in PI 274420 to produce and store nutritional substances in SCs, providing for the nematode through ISC until maturation, but in cv. Hartwig, syncytia degenerate early due to excessive metabolism, blocking nematode feeding and cytoplasmic connections with adjacent intact cells.

• Journal of Digestive Cancer Research
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• 제6권1호
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• pp.1-5
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• 2018

Eosinophilic gastrointestinal disease (EGID), a chronic allergic condition characterized by dense infiltration of eosinophils in the digestive tract, is classified into two types, eosinophilic esophagitis (EoE), which features dense infiltration of eosinophils in the esophageal epithelial layer, and eosinophilic gastroenteritis (EGE), in which the entire digestive tract including the esophagus may be involved. Patients with EoE only have esophageal symptoms, since the other parts of the digestive tract are not involved. On the other hand, 80% of EGE patients have lesions in the small intestine. The esophageal epithelial layer in healthy individuals has no or negligible infiltration by eosinophils, while the small intestinal mucosal layer, especially the distal small intestinal mucosa, can show dense eosinophil infiltration even in the absence of disease. Therefore, histological changes observed in cases of EGE are not qualitative but rather quantitative, as compared to EoE, which has qualitative histopathological changes, indicating important pathogenetic differences between the types. Comparisons of clinical, laboratory, and morphological characteristics between EoE and EGE have revealed several interesting differences. Both EoE and EGE patients are frequently affected by atopic diseases, such as bronchial asthma and allergic rhinitis, and elevated plasma levels of Th2 type cytokines and chemokines are also similarly seen in both. On the other hand, age at diagnosis differs, as the former is generally found in individuals from 30 to 50 years old, while the latter appears in all age groups. Additionally, 80% of patients with EoE are male as compared to only 50% of those with EGE. Furthermore, approximately 60% of patients with EoE respond favorably to proton pump inhibitor (PPI) administration, whereas EGE patients rarely show a response to PPIs. Nevertheless, both diseases show a similarly favorable response to a six foods elimination diet and glucocorticoid administration. These similarities and differences of EoE and EGE provide important clues for understanding the pathogenesis of these EGID types.