• Economic and Environmental Geology
• /
• v.55 no.1
• /
• pp.53-61
• /
• 2022

The Gasado Au-Ag deposit is located within the south-western margin of the Hanam-Jindo basin. The geology of the Gasado is composed of the late Cretaceous volcaniclastic sedimentary rocks and acidic or intermediate igneous rocks. Within the deposit area, there are a number of hydrothermal quartz and calcite veins, formed by narrow open space filling along subparallel fractures in the late Cretaceous volcaniclastic sedimentary rock. Vein mineralization at the Gasado is characterized by several textural varieties such as chalcedony, drusy, comb, bladed, crustiform and colloform. The textures have been used as exploring indicators of the epithermal deposit. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz veins; stage II, barren carbonate veins) considering major tectonic fracturing event. Stage I, at which the precipitation of Au-Ag bearing minerals occurred, is further divided into three substages (early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite and pyrrhotite with minor chalcopyrite, sphalerite and electrum; middle, characterized by introduction of electrum and base-metal sulfides with minor argentite; late, marked by argentite and native silver. Au-Ag-bearing mineralization at the Gasado deposit occurred under the condition between initial high temperatures (≥290℃) and later lower temperatures (≤130℃). Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur (≈10^-10.1 to ≤10^-18.5atm) by evolution of the Gasado hydrothermal system with increasing paragenetic time. The Gasado deposit may represents an epithermal gold-silver deposit which was formed near paleo-surface.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.24 no.5
• /
• pp.470-482
• /
• 2021

Purpose: We investigated the relationship between sonographic measurements of fatty liver and body mass index standard deviation score (BMI-Z score), abdominal wall fat thickness (AWFT), and serum biochemical parameters in childhood obesity. Methods: Anthropometric, laboratory, and ultrasonography data were obtained from 174 children with BMI-Z score >1. After the qualitative grading of hepatosteatosis (grades 0-3), the quantitative liver-kidney echogenicity ratio (LKER) was calculated using a software tool. Groups according to sex, age (AG-I to AG-III), BMI-Z score (BMG-I to BMG-III), and hepatosteatosis degree (HS-I and HS-II) were formed. The differences and distributions of the variables were statistically analyzed and compared among the groups. Results: Serum transaminase and glucose levels showed a positive correlation with LKER, whereas the HDL level showed a negative correlation. BMI-Z score and AWFT showed a positive correlation with fasting insulin level and HOMA-IR value. LKER was significantly higher in girls than in boys (p=0.008). In the AG-I group (age 3-8.9 years), the BMI-Z score was significantly higher, whereas AWFT was significantly lower than in the other age groups (p<0.001). The cutoff point of LKER for predicting grade 2 or higher steatosis (HS-II group) was determined to be 1.83. Cardiovascular disease risk was significantly higher in the HS-II group (p=0.035). Conclusion: As a valuable quantitative measurement tool, LKER can be used for the sonographic screening of fatty liver. AWFT, on the basis of its correlation with fasting insulin level and HOMA-IR value, may be a useful sonographic parameter in the management of childhood obesity.

• Microbiology and Biotechnology Letters
• /
• v.14 no.6
• /
• pp.447-453
• /
• 1986

The culture filtrate of thermophilic alkalophilic Bacillus K17 strain contained two types of xylanases were purified by ammonium sulfate fractionation, DEAD-Sephadex A-50 column chromatography, CM-Sephadex C-50 column chromatography and Sephadex G-100 gel filtration. The purified enzymes were found to be homogeneous by sodium dodecyl sulfate and disc polyacrylamide gel electrophoresis. Xylanase I and II were characterized with respect to molecular weight, optimal temperature and pH, thermal and pH stability, and Michaelis constant. Xylanase II was more active and stable, and showed greater substrate affinity and molecular weight than xylanase I. The activities of xylanases I and II were inhibited by Cu$^{++}$, Ag$^+$, Hg$^{++}$ and Fe$^{++}$. Xylanase I hydrolyzed xylan to yield xylobiose and higher amount of xylooligosaccharides, but xylanase II produced xylose other than xylobiose and xylooligosacchrides.

• Economic and Environmental Geology
• /
• v.29 no.3
• /
• pp.235-246
• /
• 1996

Placer gold in collected heavy minerals from several localities in Huongkhe area, is consistently very finegrained (${\leq}100$ to $400{\mu}m$). The size and size distribution show somewhat differences at Dongdo and Hoahai : at Dongdo, predominant relatively larger and wide distribution; at Hoahai, characteristic relatively finer and narrow distribution range. The morphology of gold grains is divided into the four groups assumed by the dimension ratio : spherical, subprismoidal, prismoidal, and irregular. The gold grains at Dongdo show wide morphological distribution, whereas, at Hoahai, spherical form is predominant (${\approx}75%$). Three main types of gold are classified based on their chemical composition and mode of occurrence: type I (electrum; fineness=568~931), type II (amalgam; fineness=671~927), and type III (native gold; fineness=923~999). Type I gold contains, relatively high and variable silver contents (${\approx}11$ to 58 atomic % Ag), and has been classified into two subtypes based on their silver contents (type IA, ${\approx}11{\sim}39$ atomic % Ag; type IB, ${\approx}40{\sim}58$ atomic % Ag). However, type I gold would have been generally original compositions of electrum which originated at the provenance deposits. Mercury reacts with gold and silver to form amalgam (type II gold) which has variable Hg contents (1.2~30.5 atomic % Hg). The mercury contents in gold grains at Hoahai (10.9~30.5 atomic % Hg) are higher than those at Dongdo (5.8~21.1 atomic % Hg). The gold grains from the area generally exhibit a high-purity gold (type III) rim. The individual rims on the various grains range from <1 to $80{\mu}m$ in thickness and have silver contents of <10 atomic percent Ag, even though the core compositions range from ${\approx}11$ to 58 atomic percent Ag. The rim of gold most likely is responsible for the commonly cited cases of gold from placer deposits assaying at higher values of fineness than the gold in the corresponding source lode. The gold-rich rim in the Huongkhe area apparently forms by a combination of self-electrorefining and preferential dissolution of silver under oxidizing nature during the weathering and transport process. All data of gold grains in the Huongkhe area suggest that the transport distances and/or time of placer gold at Hoahai are generally farther than those at Dongdo. The mercurian gold bearing provenance deposits at Dongdo and Hoahai would be suggest nearest epithermal gold-silver vein-type.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.11
• /
• pp.967-971
• /
• 1994

The stability constants, log K of the 1 : 1 complexation for IA ions, $Ag^+$, and $Tl^+$ with a series of podands having different aromatic end-groups (I-IV) have been determined conductometrically in methanol at 25.0 $^{\circ}$C. Exceptionally the equivalent conductivity, ${\lambda}_{eq}\;of\;Li^+\;and\;Na^+$ were increased by the addition of I, because the complexed ions are less mobile than solvated ions. The order of log K values for I was $Ag^+{\gg}Tl^+>K^+>Na^+>Rb^+>Cs6+>Li^+$. The log K sequence of the podands for the certain cations was I>II>III${\geq}$IV. And every podands except IV showed the maximum selectivity for $Ag^+$ among the cations. These results were discussed in terms of the aromatic end-group effects, such as hetero-donor atoms or conformational changes by ${\pi}-{\pi}$ stacking interactions. The detailed conformations of ${\pi}-{\pi}$ stacking were also discussed by the observations of upfield shifts of some aromatic protons upon complexation from $^1H$ NMR spectra.

• Journal of Food Hygiene and Safety
• /
• v.27 no.4
• /
• pp.479-486
• /
• 2012

This study was conducted to demonstrate quality characteristics of ginger by making aged ginger( AG) with two methods, the frist method was that ginger was aged at constant temperature and humidity chamber for the duration of 10, 20 and 30 days, and the other method was drying the ginger just after steaming it for 3 hours. As the age was being processed, the volume of ginger's appearance decreased rapidly and its color seemed to be darker because of the decrease in moisture. In the case of general components, the content of crude ash was depended on aged periods while the content of crude fat was independent with aged periods, and according to the content of crude protein, there was not any significant differences. The main valuable ingredient which is 6-gingerol showed the decreasing trend as it was exposed to heat with more time, and 6-shogaol which is also one of the main valuable ingredients showed high content at T-II(AG-10days). Free sugar and free amino acid of AG decreased as aged period goes by, and this study found that there were lots of essential amino acid (threonine, glutamic acid, alanine, valine, leucine and tyrosine) in ginger. The amount of unsaturated fatty acid of AG was significantly higher than the amount of saturated fatty acid of AG with the approximate ratio of 60:40, and the amount of free fatty acid of AG did not seem any big differences between AG and none AG. Considering both valuable ingredients and nutritive components, T-I (steamed ginger, SG) and T-II which was aged for 10 days were evaluated excellently.

• The Journal of Korean Academy of Prosthodontics
• /
• v.39 no.4
• /
• pp.417-432
• /
• 2001

The pcf metal primers on the bond strength and durability of 4-META/MMA-TBB resins adhered to an Au-Ag-Pd alloy. For this study, the specimens were divided into 8 groups as follows: Thermocyle 0 : (1) control group : sandblast, (2) Group I : sandblast + Cesead Opaque Primer; (3) Group II : sandblast + Metal Primer; (4) Group III : sandblast + V-Primer; Thermocyle 10,000 (5) control sandblast: (6) Group I : sandblast + Cesead Opaque Primer: (7) Group II : sandblast + Metal Primer; (8) Group III sandblast + V-Primer. The shear bond strength was determined using an Instron were observed with the use of scanning electron microscope. Finally, the strengths of bonded joints were evaluated with regard to their adherence energy using a wedge test. The results obtained were as follows ; (1) The shear bond strength of 4-META/MMA-TBB resin to the Au-Ag-Pd alloy was significantly improved in all the groups treated with the primers (p<0.05). (2) Regardless of the adhesive primers used, a significant difference was observed in the bond strength of the thermocycle 0 groups and 10,000 groups (p<0.05). (3) Both before and after thermocycling, the strongest bond strength between the resin an the alloy was obtained after treatment with a metal primer containing MEPS (p<0.05). (4) In the wedge test, the adherence energies of the control group and Group III decreased more rapidly than those of Group I and II during the 2nd day of storage in water.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.3C no.6
• /
• pp.211-215
• /
• 2003

Alternating current (AC) losses of two Bi-2223 ([Bi, Pb] : Sr : Ca : Cu :O = 2:2:2:3) tapes [one untwisted (Tape I, twist-pitch of $\infty$ mm) and the other with a twist-pitch of 8mm (Tape II) ] were measured and compared. These samples, produced by the powder-in-tube (PIT) method, are multi-filamentary and have a Ag/Au and Ag matrix, respectively. Susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation.

• Journal of Technologic Dentistry
• /
• v.20 no.1
• /
• pp.37-49
• /
• 1998

The specimens used were Ag-25 Pd-15 Cu ternary alloy and Au addition alloy. These alloys were melted and casted by induction electric furnace and centrifugal casting machine in Ar atmosphere. These specimens were solution treated for 2hr at $800^{\circ}C$ and were then quenched into iced water, and aged at $350{\sim}550^{\circ}C$ Age- hardening characteristics of the small Au-containing Ag-Pd-Cu dental alloys were investigated by means of hardness testing. X-ray diffraction and electron microscope observations, electrical resistance, ergy dispersed spectra and electron probe microanalysis. Principal results are as follows : Hardening occured in two stages, i.e., stage I in low temperature and stage II in high temperature regions, during continuous aging. The case of hardening in stage I was due to the formation of the $L1_0$ type face-centered tetragonal PdCu-ordered phase in the grain interior and hardening in stage I was affected by the Cu concentration. In stage II, decomposition of the ${\alpha}$ solid solution to a PdCu ordered phase($L1_0$ type) and an Ag-rich ${\alpha}2$ phase occurred and a discontinuous precipitation occurred at the grain boundary. From the electron microscope study, it was conclued that the cause of age-hardening in this alloy is the precipitation of the PdCu ordered phase, which has AuCu I type face-centered tetragonal structure. Precipetation procedure was ${\alpha}{\to}{\alpha}+{\alpha}_2+PdCu {\to}{\alpha}_1+{\alpha}_2+PdCu$ at Pd/Cu = 1.7 Ag-Pd-Cu alloy is more effective dental alloy as ageing treatment and is suitable to isothermal ageing at $450^{\circ}C$.

• Economic and Environmental Geology
• /
• v.54 no.6
• /
• pp.753-765
• /
• 2021

The Dongwon Au-Ag deposit is located within the Paleozoic Taebaeksan province, Okcheon belt. Mineral paragenesis can be divided into two stages (stage I, ore-bearing quartz veins; stage II, barren carbonate veins) by major tectonic fracturing. Stage I, at which the precipitation of major ore minerals occurred, is further divided into three substages(early, middle and late) with paragenetic time based on minor fractures and discernible mineral assemblages: early, marked by deposition of pyrite with minor magnetite, pyrrhotite and arsenopyrite; middle, characterized by introduction of electrum and base-metal sulfides with minor sulfosalts; late, marked by argentite, Cu-As (and/or Sb) and Ag-Sb sulfosalts with base-metal sulfides. Fluid inclusion data show that stage I ore mineralization was deposited between initial high temperatures (≥430℃) and later lower temperatures (≤230℃) from fluids with salinities between 6.0 to 0.4 wt. percent equiv. NaCl. The relationship of salinity and homogenization temperature suggest that ore mineralization at Dongwon was deposited mainly due to fluid boiling, cooling and dilution via influx of cooler, more dilute meteoric waters. Changes in stage I vein mineralogy reflect decreasing temperature and fugacity of sulfur by evolution of the Dongwon hydrothermal system with increasing paragenetic time. The Dongwon deposit may represents a Korean-type and/or Au-Ag type mesothermal/epithermal gold-silver deposit.