• Applied Microscopy
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• v.18 no.1
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• pp.60-76
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• 1988

Chick embryos which have received a single injection of the organophosphate compound, malathion (0.1 mg/0.05 ml, 0.5 mg/0.05 ml, 1.0 mg/0.05 ml or 2.0 mg/0.05 ml) via the yolk sac at certain times (2 days, 4 days or 6 days after incubation) have been investigated. After 9 days of incubation, chick embryos were harvested to examine the effects of malathion on the ultrastructure and the acetylcholinesterase(AChE) activity of the developing spinal cord. The effects of simultaneous injection of malathion and nicotinamide were also compared. On ultrastructural findings, neurons in the ventral horn of spinal cord showed to be inhibited in their differentiation by malathion; nuclear irregularity, separation of nuclear membranes, reduction of ribosomal distribution, and cytoplasmic vacuoles were observed. In the younger embryos treated with relatively high doses of malathion, nucleus and cytoplasmic organelles of neurons were severely destroyed, and the neurons were shown to be necrotic. On cytochemical study of AChE by electron microscope, the positive reaction products of AChE were localized at the membranes of nucleus and endoplasmic reticulum of neurons. Inhibition of AChE activity was severe in groups treated with relatively low doses of malathion. Nicotinamide (5.0 mg/0.05 ml) alleviated malathion-induced morphological alterations. In conclusion, it is suggested that malathion changes the ultrastructure and reduces. AChE activity in differentiating neurons, and the severity of which is consistently dose- and age-dependent.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.350-352
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• 2009

The effect of porosity on the high-cycle fatigue properties of Al-Si-Mg casting aluminum alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both Al-Si-Mg casted (F) and heat-treated (T6) conditions. Porosity characteristics on the fracture surfaces of fatigue-tested samples were examined using SEM and image analysis. The microstructure observation results showed that eutectic Si particles were homogeneously dispersed in the matrix of the Al-Si-Mg casting alloys, but there were porosities formed as cast defects. The high-cycle fatigue results indicated that the fatigue strength of the 356-T6 alloy was higher than that of the 356-F alloys because of the significant reduction in volume fraction of pores by heat treatment. The SEM fractography results showed that porosity affected detrimental effect on the fatigue life: 80% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. It was found that fatigue life decreased as the size of the surface pore increased. A comparison was made between surface pore and inner pore fur its effect on the fatigue behavior. The results showed that the fatigue strength with the inner pores was higher than that of the surface pore.

• The Korean Journal of Food And Nutrition
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• v.34 no.2
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• pp.207-216
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• 2021

This study analyzed the quality characteristics of Soksungjang combined with sorghum koji, according to the amount of sorghum added and the length of the fermentation period. The moisture content of Soksungjang was the lowest in the control group when there was no sorghum koji added, but gradually increased as the amount of added sorghum koji increased. The reduction in the sugar content of sorghum Soksungjang did not change according to the fermentation period of the control group, but increased alongside the fermentation period when sorghum koji was added to Soksungjang. The amino nitrogen content increased from 67.20-80.73 mg% from the beginning of the fermentation period to 173.13-383.60 mg% at the end of the fermentation period, and the total polyphenol content increased from 260.25-351.28 mg% from the beginning of the fermentation period to 567.28 mg%-674.93 mg% to the end of the fermentation period. DPPH radical scavenging activity also increased as the fermentation period elapsed, and ABTS radical scavenging activity increased and then decreased slightly over the fermentation period. The antioxidant activity was the highest in the Soksungjang mixture with a 10% concentration of sorghum koji.

• Journal of Powder Materials
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• v.28 no.2
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• pp.134-142
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• 2021

In this study, AlSi10Mg powders with average diameters of 44 ㎛ are additively manufactured into bulk samples using a selective laser melting (SLM) process. Post-heat treatment to reduce residual stress in the as-synthesized sample is performed at different temperatures. From the results of a tensile test, as the heat-treatment temperature increases from 270 to 320℃, strength decreases while elongation significantly increases up to 13% at 320℃. The microstructures and tensile properties of the two heat-treated samples at 290 and 320℃, respectively, are characterized and compared to those of the as-synthesized samples. Interestingly, the Si-rich phases that network in the as-synthesized state are discontinuously separated, and the size of the particle-shaped Si phases becomes large and spherical as the heat-treatment temperature increases. Due to these morphological changes of Si-rich phases, the reduction in tensile strengths and increase in elongations, respectively, can be obtained by the post-heat treatment process. These results provide fundamental information for the practical applications of AlSi10Mg parts fabricated by SLM.

• Archives of Obesity and Metabolism
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• v.1 no.1
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• pp.4-13
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• 2022

Currently, pharmacotherapy is becoming essential for obesity, owing to its expanding and increasing epidemiology. In this review, novel peptide-based drugs of four classes are covered: GLP-1 receptor agonist, GIP/GLP-1 receptor dual agonist, glucagon/GLP-1 receptor dual agonist, and a combination of amylin receptor agonist/GLP-1 receptor agonist. Semaglutide is a next-generation GLP-1 receptor agonist with a longer duration and stronger weight and glucose reduction effects than liraglutide and dulaglutide. In the STEP1 trial, semaglutide 2.4 mg reduced body weight by approximately 15% in people with obesity with similar or milder adverse events than liraglutide 3.0 mg. Tirzepatide, a GIP/GLP-1 receptor dual agonist, also has a long duration and strong weight- and glucose-lowering effect. According to SURPASS-2, 3, and 4, in patients with BMI≥25 kg/m² and type 2 diabetes mellitus (T2DM), tirzepatide 15 mg reduced the initial body weight by >13%. Cotadutide, a glucagon/GLP-1 receptor dual agonist, showed weaker weight-lowering effects than semaglutide and tirzepatide, while it was comparable to that of liraglutide in a phase 2 clinical trial for non-alcoholic fatty liver disease in patients with BMI≥25 kg/m² and T2DM. Additionally, its effect on the liver was noticeable. The long-acting amylin receptor agonist cargrilintide combined with semaglutide can be another effective option for obesity treatment. Even in a small phase 1 trial with a short study period of 20 weeks, cargrilintide 2.4 mg/semaglutide 2.4 mg reduced by 17% of initial body weight in people with BMI 27-39.9 kg/m². In coming several years, semaglutide, tirzepatide, and cargrilintide/semaglutide will become available for obesity treatment in Korea.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.2
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• pp.148-157
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• 2022

Research on hydrogen storage is active to properly deal with hydrogen, which is considered a next-generation energy medium. In particular, research on metal hydride with excellent safety and energy efficiency has attracted attention, and among them, magnesium-based hydrogen storage alloys have been studied for a long time due to their high storage density, low cost, and abundance. However, Mg-based alloys require high temperature conditions due to strong binding enthalpy, and have many difficulties due to slow hydrogenation kinetics and reduction in hydrogen storage capacity due to oxidation, and various strategies have been proposed for this. This research manufactured Mg₂Ni to improve hydrogenation kinetics and synthesize about 5, 10, 20 wt% of CaF₂ as a catalyst for controlling oxidation. Mg₂NiHx-CaF₂ produced by hydrogen induced mechanical alloying analyzed hydrogenation kinetics through an automatic PCT measurement system under conditions of 423 K, 523 K, and 623 K. In addition, material life cycle assessment was conducted through Gabi software and CML 2001 and Eco-Indicator 99' methodology, and the environmental impact characteristics of the manufacturing process of the composites were analyzed. In conclusion, it was found that the effects of resource depletion (ARD) and fossil fuels had a higher burden than other impact categories.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.313-321
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• 2000

This research is to remove heavy metals from AMD(Acid Mine Drainage) using AFMR(Anaerobic Floating Media Reactor) process. Two AFMR were operated at HRT(hydraulic retention time) of 3 days. COD/sulfate ratio from 0.3 to 0.8, temperature from $30^{\circ}C$ to $35^{\circ}C$, and alkalinity of 1.000mg/l(as $CaCO_3$). At COD/sulfate($SO{_4}^{2-}$) ratio of 0.5 and temperature of $35^{\circ}C$, the ratio of reduced sulfate($SO{_4}^{2-}$)/removed COD(mg/mg) kept about 1 and the reactor achieved 99.99% of Cr, Pb anee Fe, 98% of Cd, and 90% of Mn removal efficiencies, respectively. Decreasing temperature to $30^{\circ}C$ increased the ratio of reduced sulfate($SO{_4}^{2-}$)/removed COD(mg/mg) to 1.37. Amount of sulfate reduction maximized at the temperature of $30^{\circ}C$ and the COD/sulfate ratio of 0.4 in the influent and then removal efficiencies of heavy metals were 99.99% of Fe, 99.99% of Pb, 99,99% of Cr, 97.3% of Mn, 99.9% of Zn, 99.9% of Cd and 99.9% of Cu.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.1
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• pp.17-22
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• 2013

In this study, a pH control method by carbon dioxide ($CO_2$) was applied to coagulation process in water treatment plant (WTP) to investigate the coagulation efficiency and residual dissolved aluminum when high pH raw water is flowing into the plant during algal blooming. Existing coagulant dose (1 mg/L in raw water) resulted in the pH reduction of 0.0384 by LAS, 0.0254 by PAC, 0.0201 by A-PAC, and 0.0135 by PACS2, respectively. And then the concentration of dissolved aluminum was 0.02 mg/L at pH 7.44, 0.07 mg/L at pH 7.96, 0.12 mg/L at pH 8.16, 0.39 mg/L at pH 8.38 showing the concentration increase with pH in the coagulation process. It was noteworthy that rapid increase was observed at pH above 8.0 next the rapid mixing. Therefore it is necessarily required to control pH below 7.8 in the coagulation process in order to meet drinking water quality standard of aluminum for high pH raw water into WTP, $CO_2$ injection could control pH successfully at about 7.3 even for the raw water of high pH above 8.0. In addition it was found that the pH control by $CO_2$ injection was significantly effective for coagulation in terms of turbidity removal, coagulant dosage, and residual dissolved aluminum concentration.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.389-397
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• 1992

Workability and aging behavior of Mg-Li-Al alloys hate been investigated with variation of Li and Al contents. It was found that ${\alpha}$(HCP) + ${\beta}$(BCC) two phase structure reveals better workability than ${\alpha}$(HCP) single phase structure. Increase of workability is attributed to the additional slip on pyramidal and prism planes besides the slip on basal plane of HCP Mg. Workability of ${\alpha}$+${\beta}$ two phase structure is improved with increased amount of Al. Among alloys studied in the present study, reduction limit up to 62 % was obtained for Mg-8.08Li-4.26Al. MgL$i_2$Al(${\theta}$) aging precipitation was observed in ${\alpha}$+ ${\beta}$ two phase structure, while it was not in a single phase structure. Result of microhardness reveals peak hardness for ${\alpha}$ +${\beta}$ two phase structure due to $\theta$ precipitate in ${\theta}$ phase. In ${\alpha}$+${\beta}$ two phase Mg-Li-Al alloys, hardness increased with increasing amount of Al. It is believed that addition of Al raised the amount Al partition in u phase and ${\theta}$ precipitation in ${\beta}$ phase.

• Korean Journal of Environmental Biology
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• v.31 no.3
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• pp.204-212
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• 2013

This study analyzed the occurrence of tunic softness, survival rate, metabolic rate and histopathologic changes arising from the effect of hypoxic environment in order to find the causes of occurrences of tunic softness, which manifests as the key phenomenon of mass mortality of Halocynthia roretzi. Regarding the survival of H. roretzi with reduction in dissolved oxygen, all the entities died on the 4th day of exposure to the dissolved oxygen concentration of $2mg\;L^{-1}$ while 50% mortality was observed on the 5th day of exposure to the dissolved oxygen concentration of $3mg\;L^{-1}$. Therefore the 5 days-$LC_{50}$ was found to be $3.55mg\;L^{-1}$ (1.86~$4.96mg\;L^{-1}$). However, occurrence of tunic softness was not observed during the period of exposure to low oxygen concentration. The oxygen consumption rate significantly decreases at the dissolved oxygen concentration of less than $5mg\;L^{-1}$ in comparison to the control group. Therefore, it is presumed that H. roretzi controls the respiration rate for prescribed period of time when exposed to hypoxic environment. Regarding the histopathologic changes in the gill, digestive gland and cyst of H. roretzi due to hypoxic environment, necrosis of epithelial layer, in filtration of blood cells, and condensation of nucleus that compose each of the organs were observed. Regarding morphological changes, the decrease in volume with shrinking of the tunic, discoloration of the internal organs and necrosis of gill and hepatopancreas were observed.