• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.11
• /
• pp.921-925
• /
• 2000

Characteristics of Pb(Mg, Nb)O$_3$-Pb(Zr, Ti)O$_3$system thick films fabricated by a screen printing method were investigated. The buffer layer were coated with various thickness of Ag-Pd by screen printing to investigate the effect as a diffusion barrier and deposited Pt as a electrode by sputtering on Ag-Pb layer. The printed thick films were burned out at 650$\^{C}$ and sintered at 950$\^{C}$ in O$_2$condition for each 20, 60min after printing with 350mesh screen. The thickness of piezoelectric thick film was 15∼20㎛ and Ag-Pb layer acted as a diffusion barrier above 3㎛ thickness. The PMN-PZT thick films were screen printed on Pt/Ag-Pb(6m) and sintered by 2nd step (650$\^{C}$/20min and 950$\^{C}$/1h) using paste mixed PMN-PZT and binder in the ratio of 70:30, and the remnant polarization of thick film was 9.1$\mu$C/㎠ in this conditions.

• Nuclear Engineering and Technology
• /
• v.53 no.9
• /
• pp.2926-2936
• /
• 2021

Rare-earth (RE) industries generate a massive amount of radioactive residue containing high thorium concentrations. Due to the fact that thorium is considered a non-economic element, large volume of these RE processed residues are commonly disposed of without treatment. It is essential to study an appropriate treatment that could reduce the volume of waste for final disposition. To this end, this research investigates the applicability of carbon-based adsorbent in separating thorium from aqueous phase sulphate is obtained from the cracking and leaching process of solid rare-earth by-product residue. Adsorption of thorium from the aqueous phase sulphate by carbon-based electrodes was investigated through electrosorption experiments conducted at a duration of 180 minutes with a positive potential variable range of +0.2V to +0.6V (vs. Ag/AgCl). Through this research, the specific capacity obtained was equivalent to 1.0 to 5.14 mg-Th/g-Carbon. Furthermore, electrosorption of thorium ions from aqueous phase sulphate is found to be most favorable at a higher positive potential of +0.6V (vs. Ag/AgCl). This study's findings elucidate the removal of thorium from the rare-earth residue by carbon-based electrodes and simultaneously its potential to reduce disposal waste of untreated residue.

• Journal of the Korean institute of surface engineering
• /
• v.50 no.3
• /
• pp.147-154
• /
• 2017

This research was conducted to investigate the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. Native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in seven different electrolytes containing the following anions $Cl^-$, $F^-$, $SO{_4}^{2-}$, $NO_3{^-}$, $CH_3COO^-$, $CO{_3}^{2-}$, and $PO{_4}^{3-}$. It was observed from open circuit potential (OCP) transients that the potential initially decreased before gradually increasing again in the solutions containing only $CO{_3}^{2-}$ or $PO{_4}^{3-}$ ions, indicating the dissolution or transformation of the native air-formed oxide film into new more protective surface films. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that there was growth of new surface films with immersion time on the air-formed oxide film-covered specimens in all the electrolyte. The least resistive surface films were formed in fluoride and sulphate baths whereas the most protective film was formed in phosphate bath. The potentiodynamic polarization curves illustrated that passive behaviour of AZ31 Mg alloy under anodic polarization appears only in $CO{_3}^{2-}$, or $PO{_4}^{3-}$ ions containing solutions and at more than $-0.4V_{Ag/AgCl}$ in $F^-$ ion containing solution.

• Economic and Environmental Geology
• /
• v.42 no.3
• /
• pp.177-193
• /
• 2009

The Samgwang deposit consists of eight massive mesothermal quartz veins that filled NE and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. The mineralogy and paragenesis of the veins allow two separate discrete mineralization episodes(stage I=quartz and calcite stage, stage II-calcite stage) to be recognized, temporally separated by a major faulting event. The ore minerals are contained within quartz and calcite associated with fracturing and healing of veins that occurred during both mineralization episodes. The hydrothermal alteration of stage I is sericitization, chloritization, carbonitization, pyritization, silicification and argillization. Sericitic zone occurs near and at quartz vein and include mainly sericite, quartz, and minor illite, carbonates and chlorite. Chloritic zone occurs far from quartz vein and is composed of mainly chlorite, quartz and minor sericite, carbonates and epidote. Fe/(Fe+Mg) ratios of sericite and chlorite range 0.45 to 0.50(0.48$\pm$0.02) and 0.74 to 0.81(0.77$\pm$0.03), and belong to muscovite-petzite series and brunsvigite, respectiveIy. Calculated $Al_{IV}$-FE/(FE+Mg) diagrams of sericite and chlorite suggest that this can be a reliable indicator of alteration temperature in Au-Ag deposits. Calculated activities of chlorite end member are $a3(Fe_5Al_2Si_3O_{10}(OH)_6$=0.0275${\sim}$0.0413, $a2(Mg_5Al_2Si_3O_{10}(OH)_6$=1.18E-10${\sim}$7.79E-7, $a1(Mg_6Si_4O_{10}(OH)_6$=4.92E-10${\sim}$9.29E-7. It suggest that chlorite from the Samgwang deposit is iron-rich chlorite formed due to decreasing temperature from high temperature(T>450$^{\circ}C$). Calculated ${\alpha}Na^+$, ${\alpha}K^+$, ${\alpha}Ca^{2+}$, ${\alpha}Mg^{2+}$ and pH values during wallrock alteration are 0.0476($400^{\circ}C$), 0.0863($350^{\circ}C$), 0.0154($400^{\circ}C$), 0.0231($350^{\circ}C$), 2.42E-11($400^{\circ}C$), 7.07E-10($350^{\circ}C$), 1.59E-12($400^{\circ}C$), 1.77E-11($350^{\circ}C$), 5.4${\sim}$6.4($400^{\circ}C$), 5.3${\sim}$5.7($350^{\circ}C$)respectively. Gain elements(enrichment elements) during wallrock alteration are $TiO_2$, $Fe_2O_3(T)$,CaO, MnO, MgO, As, Ag, Cu, Zn, Ni, Co, W, V, Br, Cs, Rb, Sc, Bi, Nb, Sb, Se, Sn and Lu. Elements(Ag, As, Zn, Sc, Sb, Rb, S, $CO_2$) represents a potential tools for exploration in mesothermal and epithermal gold-silver deposits.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.30 no.4
• /
• pp.283-290
• /
• 2010

Guineagrass (Panicum maximum Jacq.) is an important warm-season forage grass as well as biomass crop. It has both sexual and asexual mode of reproduction (apomictic) depending on cultivar. We developed efficient plant regeneration system for an apomictic (cv. Natsukaze) and a non-apomictic (Noh-PL1) guineagrass by optimizing the level of L-proline in the callus induction and that of $AgNO_3$ in plant regeneration medium. Among the L-proline concentrations tested, the best callus induction was achieved by using 2g/L L-proline in both the genotypes. Immature embryos proved to be the best explant source for tissue culture of guineagrass. The highest frequency of shoot regeneration was obtained on MS plant regeneration medium supplemented with 2 mg/L $AgNO_3$. These results provide a foundation for efficient tissue culture and genetic improvement of guineagrass.

• Parasites, Hosts and Diseases
• /
• v.42 no.4
• /
• pp.175-183
• /
• 2004

To evaluate the role of nitric oxide (NO) in $IFN-{\gamma}$ production and apoptosis of splenocytes in genetically different strains of mice with toxoplasmosis, BALB/c (a toxoplasmosis resistant strain) and C57BL/6 (a toxoplasmosis susceptible strain) mice were infected with Toxoplasma gondii cysts orally and subsequently injected intraperitoneally with aminoguanidine, an iNOS inhibitor (AG; 35 mg/kg per mouse daily for 14 days). When BALB/c or C57BL/6 mice were infected with T. gondii without AG treatment, number of brain cysts, NO and IFN-y production by splenocytes, and percentages of apoptotic splenocytes were increased compared to uninfected control mice without AG treatment. AG treatment increased the number of brain cysts, and reduced NO and $IFN-{\gamma}$ production in T. gondii-infected C57BL/6 mice. In contrast, in T. gondii-infected BABL/c mice, the number of brain cysts, and NO and $IFN-{\gamma}$ production of splenocytes was not altered by treatment with AG. However, the percentages of apoptotic splenocytes in T. gondii-infected BALB/c or C57BL/6 mice were not affected by AG treatment. These results suggest that NO modulates $IFN-{\gamma}$ production in T. gondii-infected C57BL/6 mice, and that NO is involved in mediating a protective response in toxoplasmosis susceptible, but not resistant, mice strain during acute infection.

• YAKHAK HOEJI
• /
• v.44 no.1
• /
• pp.1-8
• /
• 2000

Effects of Astragali radix extract (AG) on the humoral immunotoxic responses of zinc chloride (Zn) were studied in ICR mice. Mice were divided into 4 groups (10 mice/group), and Zn was given to the mice, 1 hr after i.p. injection with 0.5 g/kg of AG, by i.p. injection daily for 10 days at a dose of 25 mg/kg. Mice were immunized and challenged with sheep red blood cells (SRBC). Zn treatment increased the relative weight of spleen compared with those in controls, but decreased the hemagglutination (HA) titer 2-mercaptoethanol-resistant HA (MER-HA) titer and splenic plaque forming cells (PFC). AG treatment significantly increased the relative weight of spleen, HA titer and PFC compared with those in controls. Combination of Zn and AG significantly increased the relative weight of spleen compared with those in controls, but decreased the HA titer, MER-HA titer and PFC. The relative weight of spleen was significantly increased in the Zn and AG combination group than those in Zn alone treatment group. But the HA titer, MER-HA titer and PFC were slightly increased in the group of combination. These results suggest that AG might slightly restore humoral immune responses lowered by an excess of zinc.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.23 no.4
• /
• pp.311-318
• /
• 2020

Chronic hepatitis B viral (HBV) infection remains a major health threat, especially in high-prevalence areas. Most infants infected by mother-to-infant HBV transmission become chronic carriers. In Taiwan, many important preventive interventions have been implemented to block the perinatal transmission of HBV in the past 35 years. The first nationwide universal HBV vaccination program was launched in Taiwan in July 1984. The three-dose HBV vaccine completion rate reached 98.1% in 2018. The prevalence of Hepatitis B surface antigen (HBsAg) decreased from 9.8% in pre-vaccinated period in 1984 to 0.5% in the vaccinated cohort in 2014. The incidence of hepatocellular carcinoma in children aged 6-9 years significantly declined from 0.52 to 0.13 per 100,000 children born before and after 1984, respectively. Furthermore, we have performed a maternal HBV screening program during pregnancy since 1984, with the screening rate peaked at 93% in 2012. The HBsAg- and HBeAg-seropositive rate in pregnant women declined from 13.4% and 6.4% in 1984-1985 to 5.9% and 1.0% in 2016, respectively. To closely control perinatal HBV infection, we have administered hepatitis B immunoglobulin immediately after birth and checked the serum level of HBsAg and anti-HBs in high-risk babies born to HBsAg-seropositive mothers, irrespective of their HBeAg status, since July 2019. We have also adopted short-term antiviral treatments such as tenofovir 300 mg daily in the third trimester for highly viremic mothers and reduced the perinatal infection rates from 10.7 to 1.5%. Through all these efforts, we expect to meet the global goal of eliminating HBV infection by 2030.

• Journal of Food Hygiene and Safety
• /
• v.38 no.5
• /
• pp.319-331
• /
• 2023

Aminoglycoside antibiotics, also known as aminoglycosides (AGs), are veterinary drugs effective against a wide range of gram-negative and gram-positive bacteria. Owing to their recent use in cultured meats, it has become essential to establish an analytical method for safety management. AGs are highly polar compounds, and ion-pair reagents (IPRs) are used to ensure component separation. Owing to the high possibility of potential mechanical problems resulting from IPR addition to the mobile phase, an analytical method in which IPRs are added directly to the vial was explored. In this study, methods for analyzing 10 AGs via liquid chromatography-tandem mass spectrometry (LC-MS/MS) with the addition of two IPRs were validated for selectivity, detection limit, quantitation limit, recovery, and precision. The detection limit was 0.0001-0.0038 mg/kg, the quantification limit was 0.004-0.011 mg/kg, and the linearity (R²) within the concentration range of 0.01-0.5 mg/kg was over 0.99. Recovery and precision (expressed as relative standard deviation) evaluated in the two matrices (beef and cell culture media) ranged from 70.7% to 120.6% and 0.2% to 24.7%, respectively. The validated AG analytical method was then applied to 15 meats prepared from chicken, beef, and pork, and 6 culture media and additives used in cultured meat. No AGs were detected in any of the 15 meats distributed in Korea; however, streptomycin and dihydrostreptomycin were detected at levels ranging from 695.85 to 1152.71 mg/kg and 6.35 to 11.11 mg/kg, respectively, in the culture media additives. The LC-MS/MS method coupled with direct addition of IPRs to the vial can provide useful basic data for AG analysis and safety evaluation of meats as well as culture media and additives for cultured meats.

• Pediatric Gastroenterology, Hepatology & Nutrition
• /
• v.11 no.2
• /
• pp.137-142
• /
• 2008

Purpose: Interferon is a widely used treatment for chronic hepatitis B in children. However, additional treatment options are needed because more than 50% of hepatitis B patients are unresponsive to interferon. Although lamivudine is widely used to treat hepatitis B, there are few studies on the effect of lamivudine in hepatitis B patients unresponsive to interferon. Methods: Eight interferon unresponsive patients (6 males and 2 females) were treated with lamivudine (3 mg/kg/day, maximum 100 mg/day) from 6~12 months after interferon treatment was discontinued among 33 children with chronic hepatitis B. They were treated with interferon (interferon ${\alpha}$-2b, 10 MU/$m^2$ or pegylated interferon $1.5{\mu}g/kg$) for 6 months from January 2000 to December 2007 at the Pusan National University Hospital. The medical records were analyzed retrospectively. Results: The age at treatment with interferon and lamivudine was 4.9${\pm}$3.1 and 6.1${\pm}$3.2 years, respectively. The serum ALT level before treatment with interferon was 148.1${\pm}$105.8 IU/L and the log HBV-DNA PCR mean value was 6.95${\pm}$0.70 copies/mL. The serum ALT level after treatment with interferon was 143.1${\pm}$90.4 IU/L and the log HBV-DNA mean PCR value was 6.46${\pm}$2.08. HBeAg negativization occurred in 2 patients. For all patients, normalization of the serum ALT levels and HBeAg seroconversion (except 2 patients with HBeAg negativization) occurred at 7.4${\pm}$2.1 and 7.9${\pm}$2.1 months respectively after lamivudine treatment. The HBV-DNA PCR became negative in 7 patients (87.5%) at 2.4${\pm}$2.8 months. Complete response was achieved in 7 patients and no recurrence was observed in 2 patients for 3 years after the completion of treatment. Five patients are still under treatment for a mean treatment duration of 24.4${\pm}$9.1 months. In one patient, viral breakthrough occurred and the treatment was stopped. Conclusion: The number of patients was small, however, lamivudine treatment in patients with chronic hepatitis B who were unresponsive to interferon was highly effective.