• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.681-688
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• 1998

The purpose of this study was to evaluate the effects of the surface treatments of resin bases in indirect bracket bonding technique by study of shear bond strengths and failure patterns. Ninety metal brackets were bonded to the stone models of specimens involving bovine lower incisor with light-cured adhesive(Light-Bond). After removal of brackets with the resin base from the stone models, the surfaces of resin bases in thirty brackets were treated with Plastic Conditioner and the surfaces of resin bases in another thirty brackets were treated with sandblaster and the remaining thirty brackets were served as controls. All brackets were transferred to the specimens and bonded using sealant. The shear bond strength was tested on universal testing machine, and failure pattern was assessed with the adhesive remnant index(ARI). The results were as follows: 1. Surface treatments of resin bases with Plastic Conditioner or sandblasting showed statistically higher shear bond strengths than no treatment group. 2. No significant difference in shear bond strength was found between Plastic Conditioner treatment and sandblasting treatment groups. 3. No significant difference in ARI scores was found among the three groups. 4. As the result of correlation analysis between shear bond strengths and hnl scores, failure at adhesive/bracket base interface tends to increase when the shear bond strength was high, but it was not significant statistically. The above results suggest that improvement of bond strength can be obtained by surface treatment of resin base in the indirect bonding technique.

• Economic and Environmental Geology
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• v.3 no.2
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• pp.55-73
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• 1970

The district investigated covers the central and southern portions of the Uiryong Quadrangle amounting to $40km^2$ in area and is bounded approximately by geographical coordinates of $128^{\circ}$ 28' $40^{{\prime}{\prime}}{\sim}128^{\circ}$ 24' 25"E in longitude and $35^{\circ}10{\prime}{\sim}35^{\circ}14^{\prime}06^{{\prime}{\prime}}N$ in latitude. The purpose of this investigation was to provide basic information in drawing up a comprehensive development plan of the copper ore deposits known to exist in the HamanKumbuk district with special emphasis given to the ascertainment of geological and paragenetic characteristics. The area consists chiefly of shale, sandy shale and chert, all belong to Kyongsang System of Cretaceous age. Intruded into these rocks are andesite, granodiorite, basic dikes, and acidic dikes. The mineralization which took place in the area, consists of mostly fissure-filling vein deposits, numbering several tens, with varying magnitudes. The fissures and shear zones created in rocks, such as chert and granodiorite, hosted the deposition of mineralizing vapors and/or hydrothermal solutions along their openings. The strike lengths of these veins vary from 50 to 600 meters in extension and 0.1 to 3 meters in width. Although the degree of fluctuation in width is great, it averages 0.3m. The stuctural patterns, which apparently affected the deposition of veins, are fissure patterns, trend NS to $N30^{\circ}W$, and steep-pitching tension fractures as well as normal fault pattern. Ore minerals associated with vein matters are primarily chalcopyrite and small amounts of scheelite, cobaltiferous arsenopyrite, and gold and silver intimately associated with sulphide minerals. Associated with these ore mineral are pyrite, pyrrhotite, magnetite, specularite and arsenopyrite. Gangue minerals noted are quartz, calcite, chlorite, tourmaline and hornblende. In terms of the compositions of associated minerals, the vein deposits in the district could be grouped under the following four categories: 1. Pyrrhoitite, Arsenopyrite, Gold and Silver Bearing Copper Vein (Type I) 2. Calcite-Scheelite-Copper Vein (Type II) 3. Magnetite-Pyrite-Copper Vein (Type III) 4. Tourmaline Copper Vein (Type IV) Of the four types, the first and the fourth are presently yielding relatively higher grades: of copper ores and concentrates. The estimated ore reserves total some 222,000 metric tons with the following breakdown in terms of metal contents: Name of Mines Au(g/t) Ag(g/t) Cu(%) Reserves(M/T) Kunbuk 15.92 78.69 6,074 60.498 Cheil Kunbuk - - 1.040 60,847 Haman - - 2.688 101,204 222,549 As rehabilitation of old workings and/or exploration of veins at depth proceed, additional estimation of ore reserves may become apparent and necessary. With regard to the problem of beneficiation and upgrading of low-grade ores in the district, it would be advisable to make decisions on location, treating capacity and mill flowsheet after sufficient amount of exploration is completed as suggested in the report.

• Journal of Pharmacopuncture
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• v.19 no.4
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• pp.319-328
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• 2016

Objectives: Advancements in nanotechnology have led to nanoparticle (NP) use in various fields of medicine. Although the potential of NPs is promising, the lack of documented evidence on the toxicological effects of NPs is concerning. A few studies have documented that homeopathy uses NPs. Unfortunately, very few sound scientific studies have explored the toxic effects of homeopathic drugs. Citing this lack of high-quality scientific evidence, regulatory agencies have been reluctant to endorse homeopathic treatment as an alternative or adjunct treatment. This study aimed to enhance our insight into the impact of commercially-available homeopathic drugs, to study the presence of NPs in those drugs and any deleterious effects they might have, and to determine the distribution pattern of NPs in zebrafish embryos (Danio rerio). Methods: Homeopathic dilutions were studied using high-resolution transmission electron microscopy with selected area electron diffraction (SAED). For the toxicity assessment on Zebrafish, embryos were exposed to a test solution from 4 - 6 hours post-fertilization, and embryos/larvae were assessed up to 5 days post-fertilization (dpf ) for viability and morphology. Toxicity was recorded in terms of mortality, hatching delay, phenotypic defects and metal accumulation. Around 5 dpf was found to be the optimum developmental stage for evaluation. Results: The present study aimed to conclusively prove the presence of NPs in all high dilutions of homeopathic drugs. Embryonic zebrafish were exposed to three homeopathic drugs with two potencies (30CH, 200CH) during early embryogenesis. The resulting morphological and cellular responses were observed. Exposure to these potencies produced no visibly significant malformations, pericardial edema, and mortality and no necrotic and apoptotic cellular death. Conclusion: Our findings clearly demonstrate that no toxic effects were observed for these three homeopathic drugs at the potencies and exposure times used in this study. The embryonic zebrafish model is recommended as a well-established method for rapidly assessing the toxicity of homeopathic drugs.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.250-254
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• 2011

We have synthesized bluish-green, highly-efficient $BaSi_2O_2N_2:Eu^{2+}$ and $(Ba,Sr)Si_2O_2N_2:Eu^{2+}$ phosphors through a conventional solid state reaction method using metal carbonate, $Si_3N_4$, and $Eu_2O_3$ as raw materials. The X-ray diffraction (XRD) pattern of these phosphors revealed that a $BaSi_2O_2N_2$ single phase was obtained. The excitation and emission spectra showed typical broadband excitation and emission resulting from the 5d to 4f transition of $Eu^{2+}$. These phosphors absorb blue light at around 450 nm and emit bluish-green luminescence, with a peak wavelength at around 495 nm. From the results of an experiment involving Eu concentration quenching, the relative PL intensity was reduced dramatically for Eu = 0.033. A small substitution of Sr in place of Ba increased the relative emission intensity of the phosphor. We prepared several white LEDs through a combination of $BaSi_2O_2N_2:Eu^{2+}$, YAG:$Ce^{3+}$, and silicone resin with a blue InGaN-based LED. In the case of only the YAG:$Ce^{3+}$-converted LED, the color rendering index was 73.4 and the efficiency was 127 lm/W. In contrast, in the YAG:$Ce^{3+}$ and $BaSi_2O_2N_2:Eu^{2+}$-converted LED, two distinct emission bands from InGaN (450 nm) and the two phosphors (475-750 nm) are observed, and combine to give a spectrum that appears white to the naked eye. The range of the color rendering index and the efficiency were 79.7-81.2 and 117-128 lm/W, respectively. The increased values of the color rendering index indicate that the two phosphor-converted LEDs have improved bluish-green emission compared to the YAG:Ce-converted LED. As such, the $BaSi_2O_2N_2:Eu^{2+}$ phosphor is applicable to white high-rendered LEDs for solid state lighting.

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.208-213
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• 2002

The present study describe the electrical performance of amorphous T $a_2$ $O_{5-X}$ fabricated on the buffer layers Ti and Ti $O_2$. T $a_2$ $O_{5-X}$ thin films were grown on the Ti and Ti $O_2$ layers as a capacitor layer using reactive sputtering method. The X-ray pattern analysis indicated that the two as-deposited films were amorphous and the amorphous state was kept stable on the RTA(rapid thermal annealing) at even $700^{\circ}C$. Measurements of dielectric properties of the reactive sputtered T $a_2$ $O_{5-X}$ thin films fabricated in two simple MIS(metal insulator semiconductor), structures, (Cu/T $a_2$ $O_{5}$ Ti/Si and CuT $a_2$ $O_{5}$ Ti $O_2$Si) show that the amorphous T $a_2$ $O_{5}$ grown on Ti showed high dielectric constant (23～39) and high leakage current density(10$^{-3}$ ～10$^{-4}$ (A/$\textrm{cm}^2$)), whereas relatively low dielectric constant (～15) and tow leakage current density(10$^{-9}$ ～10$^{-10}$ (A/$\textrm{cm}^2$)) were observed in the amorphous T $a_2$ $O_{5}$ deposited on the Ti $O_2$ layer. The electrical behaviors of the T $a_2$ $O^{5}$ thin films were attributed to the contribution of Ti- $O_2$ and the compositionally gradient Ta-Ti-0, being the low dielectric layer and high leakage current barrier. In additional, The T $a_2$ $O_{5}$ Ti $O_2$ thin films exhibited dominant conduction mechanism contributed by the Poole-Frenkel emission at high electric field. In the case of T $a_2$ $O_{5}$ Ti $O_2$ thin films were related to the diffusion of Ta, Ti and O, followed by the creation of vacancies, in the rapid thermal treated thin films.films.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.276-284
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• 2000

Distributions of organic carbon (Co$_{org}$), organic nitrogen (N$_{org}$), and heavy metals (Zn, Pb, Cr, Cu, Mn) were investigated in Lake Shihwa sediments. Surface and core samples were collected in April and September, 1997 and March, 1998 for the study. The results show that these components contents are variable with sampling timeand station. In surface sediments, both Co$_{org}$ and N$_{org}$ have similar distribution pattern in which their high contents found in stations located near the land, indicating that the streams and industrial wastes seem to act as point sources. The C$_{org}$ contents are linearly related with those of heavy metals. It appears, therefore, that the distribution of heavy metals may be partly controlled by a complex interplay of biogenic, terrestial, and anthropogenic factors. The C/N ratios from three stations are in the range of 3-32, with an average of 13.2. Vertical profiles of heavy metals in sediment cores are similar to those of C$_{org}$ and N$_{org}$. Copper content of sediments is enriched compared to that of reported value before dike construction, but Zn and Mn are not deposited considerably. Especially, Pb content show less variable. Currently, anthropogenic effects of industrial complex may not reached to drainage gate area where heavy metal contents are comparable with those adjacent to coastal sediments.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.399-399
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• 2013

Metal silicides는 Si 기반의microelectronic devices의 interconnect와 contact 물질 등에 사용하기 위하여 그 형성 mechanism과 전기적 특성에 대한 연구가 많이 이루어지고 있다. 이 중 Rare-earth(RE) silicides는 저온에서 silicides를 형성하고, n-type Si과 낮은 Schottky Barrier contact (~0.3 eV)을 이룬다. 또한 낮은 resistivity와 Si과의 작은 lattice mismatch, 그리고 epitaxial growth의 가능성, 높은 thermal stability 등의 장점을 갖고 있다. RE silicides 중 ytterbium silicide는 가장 낮은 electric work function을 갖고 있어 n-channel schottky barrier MOSFETs의 source/drain으로 주목받고 있다. 또한 Silicon 기반의 CMOSFETs의 성능 향상 한계로 인하여 germanium 기반의 소자에 대한 연구가 이루어져 왔다. Ge 기반 FETs 제작을 위해서는 낮은 source/drain series/contact resistances의 contact을 형성해야 한다. 본 연구에서는 저접촉 저항 contact material로서 ytterbium germanide의 가능성에 대해 고찰하고자 하였다. HRTEM과 EDS를 이용하여 ytterbium germanide의 미세구조 분석과 면저항 및 Schottky Barrier Heights 등의 전기적 특성 분석을 진행하였다. Low doped n-type Ge (100) wafer를 1%의 hydrofluoric (HF) acid solution에 세정하여 native oxide layer를 제거하고, 고진공에서 RF sputtering 법을 이용하여 ytterbium 30 nm를 먼저 증착하고, 그 위에 ytterbium의 oxidation을 방지하기 위한 capping layer로 100 nm 두께의 TiN을 증착하였다. 증착 후, rapid thermal anneal (RTA)을 이용하여 N2 분위기에서 $300{\sim}700^{\circ}C$에서 각각 1분간 열처리하여 ytterbium germanides를 형성하였다. Ytterbium germanide의 미세구조 분석은 transmission electron microscopy (JEM-2100F)을 이용하였다. 면 저항 측정을 위해 sulfuric acid와 hydrogen peroxide solution (H2SO4:H2O2=6:1)에서 strip을 진행하여 TiN과 unreacted Yb을 제거하였고, 4-point probe를 통하여 측정하였다. Yb germanides의 면저항은 열처리 온도 증가에 따라 감소하다 증가하는 경향을 보이고, $400{\sim}500^{\circ}C$에서 가장 작은 면저항을 나타내었다. HRTEM 분석 결과, deposition 과정에서 Yb과 Si의 intermixing이 일어나 amorphous layer가 존재하였고, 열처리 온도가 증가하면서 diffusion이 더 활발히 일어나 amorphous layer의 두께가 증가하였다. $350^{\circ}C$ 열처리 샘플에서 germanide/Ge interface에서 epitaxial 구조의 crystalline Yb germanide가 형성되었고, EDS 측정 및 diffraction pattern을 통하여 안정상인 YbGe2-X phase임을 확인하였다. 이러한 epitaxial growth는 면저항의 감소를 가져왔으며, 열처리 온도가 증가하면서 epitaxial layer가 증가하다가 고온에서 polycrystalline 구조의 Yb germanide가 형성되어 면저항의 증가를 가져왔다. Schottky Barrier Heights 측정 결과 또한 면저항 경향과 동일하게 열처리 증가에 따라 감소하다가 고온에서 다시 증가하였다.

• Applied Biological Chemistry
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• v.48 no.1
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• pp.53-59
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• 2005

The effect of various stressors such as reductant ascorbic acid, signalling molecules (salicylic acid and methyl jasmonic acid), heavy metals $(NiCl_2,\;and\;MnSO_4)$ and NaCl on the glutathione peroxidase (GPX) activities and isoenzyme expression patterns were investigated in rice seedling roots. Total GPX activity increased according to the increase of ascorbic acid concentration. Prominent enhancement of GPX1 isozyme due to ascorbic acid contributed to the increase of total GPX activity. GPX showed different reactivity toward salicylic acid and methyl jasmonic acid. GPX activity increased at 0.1 mM salicylic acid, and then decreased thereafter. However, GPX increased gradually in a methyl jasmonic acid concentration-dependent manner, and 3 fold increase of GPX activity was found at 1 mM methyl jasmonic acid. Moreover, GPX1 isozyme increased according to the increase of salicylic acid, while GPX1 isozyme decreased according to the increase of methyl jasmonic acid. When metal ions were treated, GPX activity increased considerably according to the increase of $NiCl_2$ concentration, however, GPX activity increased about 2 fold at 0.5 mM $CuSO_4$ and then decreased. Enhancement of GPX1 isozyme contributed to the increase of total GPX activities in $NiCl_2-treated$ and $MnSO_4-treated$ rice seedlings. Total GPX activity increased 1.7 fold in response to 300 mM NaCl. Especially GPX2 isozyme showed gradual increase according to the increase of NaCl concentration.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.4
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• pp.221-228
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• 1992

In order to evaluate the degree of air pollution, soils from 125 and 60points of main streets of Seoul and Daejeon, respectively, were sampled and analyzed for the contents of lead, copper, iron and zinc by nitric acid($HNO_3$) extraction followed by atomic absorption spectrophotometry during June and September, 1990. The Pb contents of Seoul and Daejeon were 350.2$\mu$g/g and 175.9$\mu$g/g, respectively, which were 14.5times and 7.3times respectively higher than the control(24.0). In Seoul, the commercial area gave the highest value followed by resdential and industrial areas in the decreasing order, while the order in Daejeon was Industrial, commercial and residential areas. The Cu contents in Seoul and Daejeon were very similar(236.6 and 234.6, respectively) each other, and about 11times higher than the control(20.9). The concentration was highest in industrial, followed by commercial and the lowest in residential areas in Seoul, while the order in Daejeon was industrial, residential and commercial areas. The Fe contents were 25716.5 in Seoul and 22838.6 in Daejeon, both being similar to the control value(22537.0). The value was highest in industrial and next in commercial areas and the lowest in residential area both in Seoul and Daejeon. The Zn contents in Seoul and Daejeon were 728.2 and 404.0, respectively, wihch were 6.3 and 3.6times higher than the control(113.3). The value was highest in commercial and next in industrial areas and the lowest in residental area in Seoul, while the order was industrial, residential and commercial areas in Daejeon. The heavy metal content was higher in the soil of main streets than that of minor streets in Seoul. The content of lead in Seoul was higher in the streets of Chongro-ku(525.9) and Chung-ku(684.8), the central area of the city which had a heavy traffic, than those in Nowon-ku(320.3) and Kwanak-ku(312.6) which had relatively less traffic crowd. The similar pattern was observed in the content of zinc; it was higher in Chongro-ku(1305.0) and Chung-ku(1335.4) than in Nowon-ku(489.1) and Kwanak-ku(569.8). In Daejeon, the contents of lead and zinc were decreasing as the distance from Daejeon Railroad Station increased : they were respectively 157.8 and 447.7 within 2km from the station, 157.6 and 235.7 with in 2-4km, and 63.5 and 156.2 within 4-6km and 58.7 and 142.2 within 6-8km. In summary, the contents of lead, copper and zinc were generally higher in the central area of the city, areas of heavy traffic and areas of industry and commerce.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.6
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• pp.915-921
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• 1996

An alkaline pretense Producing microorganism was isolated from Korean traditional soy sauce and identified as Bacillus subtilis CCKS-111. The optimum culture condition of Bacillus subtilis CCKS-111 for the production of alkaline pretense was as follow: 2% soluble starch, 0.2% peptone, 0.1% (NB$_4$)$_2$S$_2$O$_{8}$ , 0.2% MgSO$_4$, pH 7.0, 35$^{\circ}C$ and 24hrs. The optimum pH and temperature for the enzyme activity of alkaline pretense producing Bacillus subtilis CCKS-111 were pH 9.0 and 5$0^{\circ}C$, respectively. The enzyme was relatively stable at pH 6.0~11.0 and at temperature below 4$0^{\circ}C$. The activity of the enzyme was inhibited by $K^{+}$ and Hg$^{2+}$, whereas Cu$^{2+}$ exhibited rather activating effects on the enzyme activity. Ethylenediaminetetraacetic acid and phenylmethanesulfonyl fluoride inhibited the enzyme activity. This indicates that this is serine pretense which requires metal ion group for the enzyme activity. Km value was 2.313$\times$10$^{-4}$ M/L, V$_{max}$ value was 39.216$\mu\textrm{g}$/min. This enzyme hydrolyzed casein more rapidly than the hemoglobin.lobin.