• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.368-368
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• 2016

그래핀(Graphene)은 탄소 원자가 6각 구조로 이루진 2차원 알려진 물질 중 가장 얇은(0.34 nm) 두께의 물질이며 그 밴드구로조 인해 우수한 전자 이동도($200000cmV^{-1}s^{-1}$)를 가지고 있며, 이외에도 기계적, 화학적으로 뛰어난 특성을 가진다. 대면적화 된 그래핀을 성장시키기 위한 방법으로는 화학적 기상 증착법(Chemical Vapor Deposition)이 있다. 하지만 실제 여러 전이금속에서 합성되는 그래핀은 다결정으로, 서로 다른 면 방향을 가진 계면에서 전자의 산란이 일어나며, 고유의 우수한 특성이 저하되게 된다. 따라서 전자소재로 사용되기 위해서는 단결정의 대면적화 된 그래핀에 대한 연구가 지속적으로 이루어지고 있다. 앞서의 두 문제점 중, 단결정의 그래핀 합성에 크게 영향을 미치는 요인으로는 크게 합성 온도, 촉매 기판의 탄소 용해도, 촉매 표면에서의 탄소 원자의 확산성이 있다. 본 연구에서는 구리, 니켈, 실리콘에 비해 탄소 용해도가 낮으며, 탄소 원자의 높은 확산성으로 인해 단결정의 단층 그래핀을 합성에 적합하다고 보고된 저마늄(Germanium) 기판을 사용하여 그래핀을 합성하였다. 단결정의 그래핀을 성장시키기 위해 메탄(Methane; $CH_4$)가스의 주입량과 수소 가스의 주입량을 제어하여 성장 속도를 조절 하였으며, 성장하는 그래핀의 면방향을 제어하고자 하였다. 표면의 산화층(Oxidized layer)을 제거하기 위하여 불산(Hydrofluoric acid)를 사용하였다. 불산 처리 후 표면의 변화는 원자간력현미경(Atomic force microscopipe)을 통하여 분석하였다. 합성된 그래핀의 특성을 저 에너지 전자현미경(Low energy electron microscopy), 광전자 현미경(Photo emission electron microscopy), 라만 분광법(Raman spectroscopy), 원자간력현미경(Atomic force microscopy)와 투과전자현미경 (transmission electron microscopy)을 이용하여 기판 표면의 구조와 결정성을 분석하였다.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.7
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• pp.979-985
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• 2001

Two experiments on commercial broiler chickens (3-37 d) and WL layers (252-364 d) were conducted to study the relative bioavailability of phosphorus (P) from different P supplements in comparison to tricalcium phosphate (TCP), at constant dietary calcium (Ca):P ratio. The P sources tested were dicalcium phosphate (DCP), steam sterilized bone meal (SSBM), commercial mineral mixture (CMM), phosphoric acid (PA) and a combination of CMM + PA. Fluorine (F) content in CMM and SSBM was 13.12 and 0.14 g/kg, respectively. In commercial broiler diets, DCP, SSBM or PA could be used as supplemental P sources without affecting (p<0.05) weight gain, feed intake, tibia ash and, P and Ca contents in tibia ash when compared to TCP. Severity of leg abnormality and deposition of F in bone were higher (p<0.05) in group fed CMM. P retention and serum inorganic P content was significantly reduced (p<0.05) in CMM fed birds compared to those fed TCP, SSBM, PA or CMM+PA. Among other P sources (TCP, SSBM, PA and CMM+PA) the serum inorganic P levels did not vary significantly (p<0.05). The P retention also significantly reduced in CMM fed groups compared to those fed DCP or PA. The P retention significantly increased from 0.183 to 0.216 units by supplementation of PA to CMM diet. In layers, egg production was not affected by replacing TCP with DCP, SSBM, PA or CMM+PA, but significantly (p<0.05) reduced with CMM. Feed (kg)/kg egg mass, egg weight, shell quality (shell weight and shell thickness) and serum Ca levels were not influenced by dietary variation in P source. The poor performance of both broilers and layers fed on CMM based diets could be attributed to the presence of hlgher levels of F (647.8 and 630.1 mg/kg, respectively) and low P utilization. Based on growth, bone mineralization and P retention it is concluded that DCP, SSBM or PA can be used as alternatives to TCP in broiler diets. In WL layer diets, in addition to above P sources, CMM can also be used as supplemental P source by replacing one half of P from CMM with PA without affecting egg production and shell quality.

• The Korean Journal of Ecology
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• v.17 no.3
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• pp.287-297
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• 1994

To elucidate the cause of growth decline of pitch pine (Pinus rigida) in Seoul, tree density, tree age and physico-chemical properties of soils were investigated at 33 sites of pitch pine forests in metropolitan Seoul, its vicinity and rural areas. The physical properties of soils except for soil texture in Seoul did not differ from those in rural areas. pH values, base saturation, and Ca and Mg contents of soils in Seoul, however, were significantly lower than those in suburbs and rural areas. In contrast, soluble Al and $S0_4^{2-}-S$ contents in Seoul were higher than those in rural areas. Low pH of forest soils in Seoul and suburbs seems to be caused by acid deposition. According to multiple regression analysis, growth of pitch pine in Seoul was affected by several factors in the following order: soil bulk density < Al content of soils < tree density < Mg contents of soil < tree age. We concluded that the acidification of forest soil can be a predisposing factor for the growth decline of pitch pine in metropolitan areas.

• BMB Reports
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• v.43 no.2
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• pp.140-145
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• 2010

The present study investigated whether the mammalian target of rapamycin (mTOR) signal pathway is involved in the regulation of high glucose-induced intramuscular adipogenesis in porcine muscle satellite cells. High glucose (25 mM) dramatically increased intracellular lipid accumulation in cells during the 10-day adipogenic differentiation period. The expressions of CCAAT/enhancer binding protein-$\alpha$ (C/EBP-$\alpha$) and fatty acid synthase (FAS) protein were gradually enhanced during the 10-day duration while mTOR phosphorylation and sterol-regulatory- element-binding protein (SREBP)-1c protein were induced on day 4. Moreover, inhibition of mTOR activity by rapamycin resulted in a reduction of SREBP-1c protein expression and adipogenesis in cells. Collectively, our findings suggest that the adipogenic differentiation of porcine muscle satellite cells and a succeeding extensive adipogenesis, which is triggered by high glucose, is initiated by the mTOR signal pathway through the activation of SREBP-1c protein. This process is previously uncharacterized and suggests a cellular mechanism may be involved in ectopic lipid deposition in skeletal muscle during type 2 diabetes.

• Progress in Medical Physics
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• v.28 no.3
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• pp.106-110
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• 2017

The variable density phantom fabricated with varying the infill values of 3D printer to provide more accurate dose verification of radiation treatments. A total of 20 samples of rectangular shape were fabricated by using the $Finebot^{TM}$ (AnyWorks; Korea) Z420 model ($width{\times}length{\times}height=50mm{\times}50mm{\times}10mm$) varying the infill value from 5% to 100%. The samples were scanned with 1-mm thickness using a Philips Big Bore Brilliance CT Scanner (Philips Medical, Eindhoven, Netherlands). The average Hounsfield Unit (HU) measured by the region of interest (ROI) on the transversal CT images. The average HU and the infill values of the 3D printer measured through the 2D area profile measurement method exhibited a strong linear relationship (adjusted R-square=0.99563) in which the average HU changed from -926.8 to 36.7, while the infill values varied from 5% to 100%. This study showed the feasibility fabricating variable density phantoms using the 3D printer with FDM (Fused Deposition Modeling)-type and PLA (Poly Lactic Acid) materials.

• Journal of Oriental Neuropsychiatry
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• v.12 no.2
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• pp.157-171
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• 2001

Astrocytes are glial cells that play a major role in the inflammation observed in Alzheimer's disease (AD). Upon stimulation from various agents, these cells adopt a reactive phenotype, a morphological hallmark in AD pathology, during which they themselves may produce still more inflammatory cytokines. Substance P (SP) can stimulate secretion of tumor necrosis $factor-\;{\alpha}$ $(TNF-\;{\alpha})$ from astrocytes stimulated with lipopolysaccharide (LPS). Here I report that Sunghyangjungkisan- ga- pogokyoung(Sgp) can modulate cytokines secretion from primary cultures of rat astrocytes. Sgp $(10\;to\;1000\;{\mu}g/ml)$ significantly inhibited the $TNF-\;{\alpha}$ secretion by astrocytes stimulated with LPS and SP. Interleukin-1 (IL-1) has been shown to elevate $TNF-\;{\alpha}$ secretion from LPS-stimulated astrocytes while having no effect on astrocytes in the absence of LPS. Treatment of Sgp $(10\;to\;1000\;{\mu}g/ml)$ to astrocytes stimulated with both LPS and SP decreased IL-1 secretion significantly. The secretion of $TNF-\;{\alpha}$ by LPS and SP in astrocytes was progressively inhibited with increasing amount of IL-1 neutralizing antibody. Neurodegenerative processes in AD are thought to be driven in part by the deposition of ${\beta}\;-amyloid\;(A\;{\beta})$, a 39- to 43-amino acid peptide product resulting from an alternative cleavage of amyloid precursor protein. Sgp $(10\;to\;1000\;{\mu}g/ml)$ significantly inhibited the $TNF-\;{\alpha}$ secretion by astrocytes stimulated with $A-{\beta}-$and IL-1. These results suggest that Sgp may inhibit $TNF-\;{\alpha}$ secretion by inhibiting IL-1 secretion and that Sgp has an antiinflammatory activity in AD brain

• Journal of Korea Water Resources Association
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• v.40 no.9
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• pp.723-734
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• 2007

This study was to investigate the settling velocity which is an important factor for the prediction of cohesive deposition under the various densities of particle and dissolved ion addition$(Na^+,\;Cl^-,\;OH^-,\;H^+)$ in rivers, ports, reservoirs and lakes. Settling velocity of suspended fine particles in still water was measured with a pressure sensor (maximum 10 mbar). At the initial concentration of 20g/l of alumina and quartz the average settling velocities were high due to the aggregation behaviour of particles. At this point it was 0.185 mm/s (alumina) and 0.022 mm/s (quartz). Above this initial concentration it was on the decrease owing to the hindered settling. The higher the salinity is, the faster the settling velocity of alumina and quartz is. Furthermore, in an acid condition the average settling velocity of alumina was on the decrease. In an alkaline water, which causes strong flocculation, the average settling velocity of alumina it was observed on the increase. However, in an alkaline medium the low average settling velocity of quartz powder was measured.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.250-253
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• 2007

An evaporated Ti/Pd/Ag contact system is most widely used to make high-efficiency silicon solar cells, however, the system is not cost effective due to expensive materials and vacuum techniques. Commercial solar cells with screen-printed contacts formed by using Ag paste suffer from a low fill factor and a high shading loss because of high contact resistance and low aspect ratio. Low-cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Ni/Cu alloy is plated on a silicon substrate by electro-deposition of the alloy from an acetate electrolyte solution, and nickel-silicide formation at the interface between the silicon and the nickel enhances stability and reduces the contact resistance. It was, therefore, found that nickel-silicide was suitable for high-efficiency solar cell applications. The Ni contact was formed on the front grid pattern by electroless plating followed by anneal ing at $380{\sim}400^{\circ}C$ for $15{\sim}30$ min at $N_{2}$ gas to allow formation of a nickel-silicide in a tube furnace or a rapid thermal processing(RTP) chamber because nickel is transformed to NiSi at $380{\sim}400^{\circ}C$. The Ni plating solution is composed of a mixture of $NiCl_{2}$ as a main nickel source. Cu was electroplated on the Ni layer by using a light induced plating method. The Cu electroplating solution was made up of a commercially available acid sulfate bath and additives to reduce the stress of the copper layer. The Ni/Cu contact was found to be well suited for high-efficiency solar cells and was successfully formed by using electroless plating and electroplating, which are more cost effective than vacuum evaporation. In this paper, we investigated low-cost Ni/Cu contact formation by electroless and electroplating for crystalline silicon solar cells.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.5
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• pp.491-498
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• 1998

Fog water samples were collected at Chunchon, Korea, by using active fog sampler during foggy Period in fall of 1996 and 1997. The average annual foggy days at Chunchon increased from 37 days, for the yearn 1963 ∼ 1973, to 63 days , for the year 1974∼1993 that followed the construction of Lake Soyang. Volume weighted mean pH of fog water was 5.5 with a range of 4.8 to 7.0 in 1996, and 5.0 with a range of 4.1 to 6.6 in 1997. These pH values were higher than those of rain water sampled in corresponding years. However the concentration of ionic species in fog water were 26 times higher than those of rain water. The major anions in fog water were in order of SO42-, NO3- and Cl-, and their average concentrations were 1770.6meq/ml, 346.2 meq/ml, 216 meq/ml in 1996, and 901.8meq/ml, 269.6meq/ml, 141.0meq/ml in 1997, respectively. The major cations were Ca2+, NH4+, Mg2+ and K+, and their average concentrations frere 408.5meq/ml, 280.0meq/ml, 43.8meq/ml, 45.2meq/ml in 1996, and 400.4 meq/ml, 299.0meq/ml, 73.1meq/ml, 44.5meq/ml in 1997, respectively. The fraction acidity of fog water was 0.006 and that of rain water was 0.2, which means fog water was much more neutralized than rain water.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.5
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• pp.615-621
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• 2007

AMP-activated protein kinase alpha 2 (PRKAA2) plays a key role in regulation of fatty acid and cholesterol metabolism. This study investigated the porcine PRKAA2 gene as a positional candidate for intramuscular fat and backfat thickness traits in pig chromosome 6. A partial fragment of the porcine PRKAA2 gene, amplified by PCR, contained a putative intron 3 including a part of exon 3 and 4, comparable with that of human PRKAA2 gene. Within the fragment, several single nucleotide polymorphisms were identified using multiple sequence alignments. Of these, TaqI restriction enzyme polymorphism was used for genotyping various pig breeds including Korean reference family. Using linkage and physical mapping, the porcine PRKAA2 gene was mapped in the region between microsatellite markers SW1881 and SW1680 on chromosome 6. Allele frequencies were quite different among pig breeds. The full length cDNA of the porcine PRKAA2 (2,145 bp) obtained by RACE containing 1,656 bp open reading frame of deduced 552 amino acids, had sequence identities with PRKAA2 of human (98.2%), rat (97.8%), and mouse (97.5%). These results suggested that the porcine PRKAA2 is a positional candidate gene for fat deposition trait at near telomeric region of the long arm of SSC 6.