• The Journal of Korean Academy of Prosthodontics
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• v.50 no.2
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• pp.92-98
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• 2012

Purpose: The aim of this study was to evaluate the effects of different abutment materials on abutment screw loosening and settling-down effect in conical connection type implant system. Materials and methods: Three types of abutment, cementation, gold UCLA, and metal UCLA abutment were used. Two UCLA groups were fabricated in a similar pattern to cementation abutment. Type III gold alloy and Nickel-Chromium alloy was used for casting gold UCLA abutment and metal UCLA abutment, respectively. Fixture and abutment were tightened to 30 Ncm by using digital torque controller and re-tightening was conducted with same force after 10 minutes. Digital torque gauge was used to measure loosening torque and fixture/abutment length was measured by digital micrometer. Dynamic loads between 25 N and 250 N were applied with $0^{\circ}$ angle to the abutment axis. After loading, fixture/abutment length was re-measured and amount of settlement was calculated. Loosening torque value was also measured for comparison Results: All three groups showed significant differences of length when comparing before and after loading, but there was no significant difference of settling amount in all groups. Loosening torque values were significantly decreased when comparing before and after loading in all groups($P$<.05). However, there was no significant difference in loss of loosening torque values when compared to groups. Conclusion: In internal conical connection type implants, dynamic load affected on settlement and loosening torque of implant, but there was no differences between abutments materials. Likewise gold UCLA abutment, metal UCLA abutment might be able to withstand functional load.

• Journal of the Korean Chemical Society
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• v.41 no.5
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• pp.223-233
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• 1997

Ultra-thin $TiO_2$ films are grown on the Mo(100) surface using evaporated Ti metal under ambient $O_2$ pressure. The thickness of the $TiO_2$ film is controlled by the dosing rate of Ti metal over Mo(100) which is determined from the Auger signal changes with dosing time. 30 ML, 5 ML, and 1.6 ML thick films are prepared and used to determine the growth mechanism, the chemical composition, and the surface structure of the films. The growth mechanism of the $TiO_2$ film on Mo(100) is observed to follow the layer-by-layer growth mechanism. The chemical composition of the film is found to be that of bulk $TiO_2$. The surface plane of the film is (001), which facets irreversibly at 1200 K. The LEED pattern obtained from the film can be explained with the faceted surface with {011} planes reconstructed to $(2\sqrt2{\times}\sqrt2)R45^{\circ}$ with respect to the $TiO_2$ (001) surface. The film is somewhat thermally unstable when annealed to 1300 K. The film sputtered with $Ar^+$ ion is also studied by XPS.

• Analytical Science and Technology
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• v.9 no.3
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• pp.270-278
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• 1996

Response mechanism for the chloride-selective membrane doped with 5, 10, 15, 20-tetraphenyl(porphyrinato)manganase(III) chloride(Mn(TPP)Cl) in PVC/DOS matrix is proposed by examining the visible spectra of the corresponding optode membrane. The visible spectra of Mn(TPP)Cl-doped membrane placed in aqueous solution show that the chloride ligand is easily replaced with water molecule. When other halogen ions, such as $F^-$, $Br^-$ and $I^-$, are added to the sample solution, they replace the water ligand, exhibiting distinctive change in the Soret band of Mn(TPP). On the other hand, bulky anions, such as SCN and salicylate, do not form a bond with the central metal. These results suggests that the potentiometric response of Mn(TPP)-based membrane results either from the ligand exchange (water with halides) at the central metal or from the counter ion exchange (chlorides with bulky lipophilic anions) around the positively charged porphyrin molecule in membrane phase. It was also noted that both hydration enthalpies of anions and their binding constants to Mn(TPP) play critical role in determining the potentiometric selectivity pattern of the membrane.

• Korean Journal of Environmental Agriculture
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• v.9 no.1
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• pp.39-45
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• 1990

We established HPLC method for MAs (mugineic acid and its analogous phytosiderophore) determination. It was found that major phytosiderophores existed in high heavy metal-induced rice roots were MA (mugineic acid) and DMA (2'-deoxymugineic acid). The two MAs (MA and DMA) were simultaneously secreted at maximum rate at 12 : 00-14 : 00. On the other hand, the secretion of amino acids gradually decreased from after sunrise (7 : 00) to sunset (21 : 00). Fluctuaton in daily MAs secretion had rhythmic variation which occurred at intervals of about 4 days. The stimulation of MAs secretion from the roots was attributed not only to the light/dark cycle but to the increase in temperature. Temperature variation played a more important role than a photoperiod in MAs secretion from the roots. The initiation time of MAs secretion was positively correlated with rising time in temperature($20-30^{\circ}$) during the dark period.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.2
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• pp.285-290
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• 1997

The insulin-like growth factors(IGFs) are bound to several binding proteins(IGFBPs) that appear to regulate IGF transport, receptor binding, and its action. The concentration of these peptides are altered by catabolic conditions. To determine IGF-I and IGFBP levels in noninsulin-dependent diabetes mellitus (NIDDM), sera was obtained from 5 patients and 7 controls. Serum levels of IGF-I in NIDDM were lower than those in either of the controls. By western immunoblot analysis, especially IGFBP-1 levels are increased, whereas IGFBP-3 levels decreased and their fragments was increased in NIDDM serum. IGFBP-3 proteolytic activity in NIDDM sera was inhibited by phenylmethylsulfonylfluoride (PMSF), aprotinin, and ethylenediaminetetraacetic acid(EDTA). This pattern of inhibition was consistent with a metal-dependent serine protease. By gelatin zymography, these proteolytic enzymes were identified as the size of 97 and 69 kDa. IGFBP-1, which is primarily insulin regulated, was increased in NIDDM and may modulate circulating IGF-I levels by regulating capillary passage of IGF-I. IGFBP-3 proteolysis markedly reduces its affinity for the IGFs, particularly for IGF-I. This accelerates their kinetics of dissociation, thereby increasing the proportions of IGF-I in free form and its availability to the cells.

• Journal of the Korean Society of Radiology
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• v.9 no.1
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• pp.39-45
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• 2015

$La_2W_3O_{12}:Eu^{3+}$ phosphors were prepared by solid state reaction method. The crystal structure was characterized by XRD pattern and ICSD card (78180). Luminescence properties of $La_2W_3O_{12}:Eu^{3+}$ are investigated by optical and laser-excitation spectroscopy in which emission and excitation spectra and time-resolved spectra are measured. The 1 mol % $Eu^{3+}$-doped $La_2W_3O_{12}$ phosphor exhibits broad excitation band peaking at 286 nm due to the ligand-to-metal charge transfer transition. The excitation lines due to the $^7F_0{\rightarrow}{^5D_4},{^5D_4},{^5L_6},{^5G_4},{^5D_3},{^5D_2}$ transitions of $Eu^{3+}$ are observed in the wavelength region 350-500 nm. The strong line emission is observed at 618 nm corresponding to the due to the $^5D_0{\rightarrow}^7F_2$ transition. The lifetime of 618 nm emission decreases with increasing temperature as 7 K ($114{\mu}s$), 100 K ($94{\mu}s$), 200 K ($10{\mu}s$) and 300 K ($0.5{\mu}s$).

• Journal of the Korean earth science society
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• v.24 no.5
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• pp.477-490
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• 2003

Bottom sediments from Youngil Bay, East Coast of Korea, were analyzed for grain composition as well as elemental compositions and total organic carbon (TOC) content in order to investigate the spatial variability and content of metal elements. Grain size distribution of the sediments seems to be controlled by anticlockwise current pattern with bottom topography of the study area. Spatial variability of TOC and all elemental contents reflects those of grain size, but an exception was found in the harbor area (Old-Port): their contents are high in the central part of the bay with the muddy sediment and decrease toward the sand-dominated coastal zone. However, contents of Ca, Sr, K are high in the sand-dominated coastal zone and contents of some heavy metals (Cd, Cu, Zn) are high in the Old-Port area and the mouth of Hyeongsan River. The correlation matrix and R-mode factor analyses reveal that four important factors controlling the distribution of metals in the bay are sediment grain size (or quartz dilution effect), the formation of sulfide minerals associated with decomposition of organic matters under anoxic geochemical environment, calcium carbonate (mainly shell fragments) and coarse-grained feldspar mineral. According to the metal content of labile fraction an CER (concentration enrichment ratio) value, high accumulation of some heavy metals in the harbor area seems to result not formed by early diagenetic processes under anoxic environment.

• Journal of Environmental Health Sciences
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• v.21 no.1
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• pp.56-67
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• 1995

This study was carried out to observe how composting reaction proceed in the optimum composting condition and to understand the characteristics of final compost, when swine feces was amended with different bulking material. Sawdust, rice straw, and rice hull were selected as bulking materials and each of these was mixed with swine feces to obtain the optimum range of moisture contents and C:N ratio. To grasp the influence of newspaper on cornposting reaction when it flew into the composting site intentionally or accidentally, another composting reaction using newspaper as a bulking material was studied. In this experiment, raw material mixes containing the same amount of organic materials were put into 4 composting reactors and composted in the same environmental condition for 3 weeks from Aug. 1, 1994 to Aug. 22, 1994. The followings are the main results of this study. 1. The maximum temperatures reached at during cornposting reaction were 53.8$\circ$C, 51.9$\circ$C, 52.7$\circ$C, and 52.1$\circ$C in the reactor using sawdust, rice straw, rice hull, and newspaper as a bulking material respectively: Thermophilic temperatures were maintained for 72, 108, 108, and 111 hours in each reactor. Mean temperatures of reactors using sawdust, rice straw, rice hull, or newspaper as a bulking materials were 39.7$\circ$C, 39.5$\circ$C, 41.3$\circ$C, and 40.3$\circ$C, but no significant difference between these mean temperatures was observed(p>0.05). Each composter showed significant difference from room temperature(p<0.01), and the mean difference between them was 9.4$\circ$C. 2. Ash contents of each reactor increased rapidly in order of rice straw, rice hull, newspaper, and sawdust according to the pattern of second order function. This rate of increase seemed to result from structural characteristics of a bulking material. The absolute values of second order coefficient of these regression functions were 0.0199, 0.0159, 0.0157, and 0.0144 in each reactor using rice straw, rice hull, newspaper, or sawdust as a bulking material. 3. C:N ratio decreased as the reaction proceeded. Degree of decrease was in order of rice straw, rice hull, newspaper, and sawdust. This sequence was consistent with the increase rate of ash content. The ratios of initial C:N ratio to final C:N ratio were 0.45, 0.53, 0.64, and 0.75 in each reactor using rice straw, rice hull, newspaper, and sawdust as a bulking material respectively. From this ratios, it was possible to infer that all the composting reactions were completed. 4. Fertilizer content containing in the final compost was 1.61~2.20% of N, and 0.35~0.54% of P in dry weight base. According to the classification standard for compost constituent by Higgins, all composts had the intermediate grade of N, but below the low grade of P excepting the newspaper amended compost(fall into the range of the low grade). 5. Heavy metal contents contained in the composts were analyzed. In case of Cd, the range of 0.58~1.11 $\mu$g/g was observed, and in case of Pb, the range of 24.76~39.53 $\mu$g/g was observed(in wet weight base). These values are below the permissible heavy metal level for compost of foreign countries.

• The Journal of Advanced Prosthodontics
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• v.9 no.4
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• pp.244-251
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• 2017

PURPOSE. The purpose of this study was to determine fracture resistance and failure modes of three-unit fixed dental prostheses (FDPs) made of lithium disilicate pressed on zirconia (LZ), monolithic lithium disilicate (ML), and monolithic zirconia (MZ). MATERIALS AND METHODS. Co-Cr alloy three-unit metal FDPs model with maxillary first premolar and first molar abutments was fabricated. Three different FDPs groups, LZ, ML, and MZ, were prepared (n = 5 per group). The three-unit FDPs designs were identical for all specimens and cemented with resin cement on the prepared metal model. The region of pontic in FDPs was given 50,000 times of cyclic preloading at 2 Hz via dental chewing simulator and received a static load until fracture with universal testing machine fixed at $10^{\circ}$. The fracture resistance and mode of failure were recorded. Statistical analyses were performed using the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni's correction (${\alpha}=0.05/3=0.017$). RESULTS. A significant difference in fracture resistance was found between LZ ($4943.87{\pm}1243.70N$) and ML ($2872.61{\pm}658.78N$) groups, as well as between ML and MZ ($4948.02{\pm}974.51N$) groups (P<.05), but no significant difference was found between LZ and MZ groups (P>.05). With regard to fracture pattern, there were three cases of veneer chipping and two interfacial fractures in LZ group, and complete fracture was observed in all the specimens of ML and MZ groups. CONCLUSION. Compared to monolithic lithium disilicate FDPs, monolithic zirconia FDPs and lithium disilicate glass ceramics pressed on zirconia-based FDPs showed superior fracture resistance while they manifested comparable fracture resistances.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.207-216
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• 2009

In this study, water quality variation in borehole groundwaters and surface leachate waters were investigated on a seasonal sampling and remote monitoring basis within the waste impoundments at the Geopung mine site where previous rehabilitation measures were unsuccessful to prevent acidic drainage. All groundwaters were typical acidic drainage with acidic pH (3.3${\sim}$4.6) and high TDS (338${\sim}$3330 mg/L) values during the dry season, but increases in metal contents (TDS 414${\sim}$4890 mg/L) and decrease of pH (2.7${\sim}$3.6) were observed during the rainy season. Surface leachate waters showed a similar pattern in water quality variation. Surface runoff waters during rain events had acidic pH (3.0${\sim}$3.4) through direct reactions with waste rocks. Good correlations were found between major and trace elements measured in water samples, but no significant seasonal variation in chemical compositions was shown except relative changes in contents. It can be suggested that dissolution of soluble secondary salts caused by flushing of weathered waste rocks and tailings directly influenced the water quality within the waste impoundments. Increases in acid and metal concentrations and their loadings from mine wastes are anticipated in the rainy season. More appropriate cover systems on waste rocks and tailings necessitate consideration of more extreme conditions in the study mine.