• Clean Technology
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• v.28 no.4
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• pp.301-308
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• 2022

Since nanoporous silica aerogel was first synthesized in 1931, its potential as an ultra-lightweight superinsulation material has been steadily attracting attention. Silica aerogel is the best thermal insulation material to date. However, the potential applications of this lightweight material have so far been hindered by its inherent fragibility and brittleness arising from its ultra-porous nature. Although the monolithic form of silica aerogel has the best ultra-lightweight superinsulation properties, it cannot be used in this form. Instead it is used in the form of powders, particles, and blankets. However, these forms still have shortcomings. Silica aerogel is most widely applied in the form of a fiber-reinforced aerogel blanket, but this form is likely to generate dust when handled. Although silica aerogel particles have been proven to be non-toxic to humans, dust formation remains a major barrier to the widespread application of silica aerogel blankets. This paper will investigate the unique properties of silica aerogel and determine what fields it can be used in or potentially be used in due to its unique properties. In addition, we will review the important advances in silica aerogel synthesis technology and its commercialization so far, and then consider the problems that exist for its widespread commercialization in the future and how to overcome them.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.701-716
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• 2023

Microplastics (<5 mm diameter) in aquatic environments adsorb heavy metals, potentially exposing humans to their toxic effects via food chains. We investigated factors influencing the adsorption of heavy metals on microplastics in aquatic environments, examining their adsorption processes and mechanisms. Adsorption characteristics vary with polymer type, crystallinity, particle size, and environmental conditions (pH, temperature, weathering), and the adsorption capacity for heavy metals increases with weathering and reduction in polymer particle size. However, correlations between environment temperature, polymer crystallinity, and adsorption capacity for heavy metals could not be confirmed. The adsorption behavior of heavy metals can be explained in terms of physicochemical adsorption processes and evaluated through adsorption kinetics and isothermal studies, with multiple mechanisms usually being involved. An understanding of the adsorption of heavy metals by microplastics should aid evaluation of the potential risks of microplastics in aquatic environments.

• Nutrition Research and Practice
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• v.17 no.5
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• pp.899-916
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• 2023

BACKGROUND/OBJECTIVES: Oxidative stress is a fundamental neurodegenerative disease trigger that damages and decimates nerve cells. Neurodegenerative diseases are chronic central nervous system disorders that progress and result from neuronal degradation and loss. Recent studies have extensively focused on neurodegenerative disease treatment and prevention using dietary compounds. Heseperetin is an aglycone hesperidin form with various physiological activities, such as anti-inflammation, antioxidant, and antitumor. However, few studies have considered hesperetin's neuroprotective effects and mechanisms; thus, our study investigated this in hydrogen peroxide (H₂O₂)-treated SH-SY5Y cells. MATERIALS/METHODS: SH-SY5Y cells were treated with H₂O₂ (400 µM) in hesperetin absence or presence (10-40 µM) for 24 h. Three-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assays detected cell viability, and 4',6-diamidino-2-phenylindole staining allowed us to observe nuclear morphology changes such as chromatin condensation and apoptotic nuclei. Reactive oxygen species (ROS) detection assays measured intracellular ROS production; Griess reaction assays assessed nitric oxide (NO) production. Western blotting and quantitative polymerase chain reactions quantified corresponding mRNA and proteins. RESULTS: Subsequent experiments utilized various non-toxic hesperetin concentrations, establishing that hesperetin notably decreased intracellular ROS and NO production in H₂O₂-treated SH-SY5Y cells (P < 0.05). Furthermore, hesperetin inhibited H₂O₂-induced inflammation-related gene expression, including interluekin-6, tumor necrosis factor-α, and nuclear factor kappa B (NF-κB) p65 activation. In addition, hesperetin inhibited NF-κB translocation into H₂O₂-treated SH-SY5Y cell nuclei and suppressed mitogen-activated protein kinase protein expression, an essential apoptotic cell death regulator. Various apoptosis hallmarks, including shrinkage and nuclear condensation in H₂O₂-treated cells, were suppressed dose-dependently. Additionally, hesperetin treatment down-regulated Bax/Bcl-2 expression ratios and activated AMP-activated protein kinase-mammalian target of rapamycin autophagy pathways. CONCLUSION: These results substantiate that hesperetin activates autophagy and inhibits apoptosis and inflammation. Hesperetin is a potentially potent dietary agent that reduces neurodegenerative disease onset, progression, and prevention.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.23-28
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• 2024

Cesium is a potential toxic contaminant due to its high solubility, which allows it to easily penetrate the human body and potentially induce cancer or DNA mutations. In this study, oxygen functional groups were introduced on activated carbons (ACs) by ozone treatment to enhance the cesium adsorption capacity. As the ozone treatment time increased, the oxygen content on the ACs surface increased. Subsequently, the electrostatic interaction between ACs and cesium enhanced, resulting in higher cesium ion adsorption efficiency across all samples. In particular, the sample treated with ozone for 7 minutes at an internal ozone concentration of 50000 ppm had roughly 12% greater oxygen functional group content and the highest cesium removal effectiveness (97.6%). Meanwhile, samples treated for 5 minutes showed a 0.3% cesium removal rate difference compared to those treated for 7 minutes, which was caused by the surface chemical similarity of the two samples due to the reactive characteristics of ozone gas. However, the cesium adsorption performance of ozonated activated carbon seems to be mainly influenced by the amount of oxygen functional groups introduced to the surface, although the specific surface area and pore structure of the activated carbon are also important.

• Asian Journal of Atmospheric Environment
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• v.8 no.1
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• pp.35-47
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• 2014

The purpose of the study is to evaluate the pollution level (gaseous and particle phase) in the public facilities for the PAHs, non-regulated materials, forecast the risk level by the health risk assessment (HRA) and propose the guideline level. PAH assessments through sampling of particulate matter of diameter < 2.5 ${\mu}m$ ($PM_{2.5}$). The user and worker exposure scenario for the PAHs consists of 24-hour exposure scenario (WIES) assuming the worst case and the normal exposure scenario (MIES) based on the survey. This study investigated 20 PAH substances selected out of 32 substances known to be carcinogenic or potentially carcinogenic. The risk assessment applies major toxic equivalency factor (TEF) proposed from existing studies and estaimates individual Excess Cancer Risk (ECR). The study assesses the fine dusts ($PM_{2.5}$) and the exposure levels of the gaseous and particle PAH materials for 6 spots in each 8 facility, e.g. underground subway stations, child-care facilities, elderly care facilities, super market, indoor parking lot, terminal waiting room, internet caf$\acute{e}$ (PC-rooms), movie theater. For internet caf$\acute{e}$ (PC-rooms) in particular, that marks the highest $PM_{2.5}$ concentration and the average concentration of 10 spots (2 spots for each cafe) is 73.3 ${\mu}g/m^3$ (range: 6.8-185.2 ${\mu}g/m^3$). The high level of $PM_{2.5}$ seen in internet cafes was likely due to indoor smoking in most cases. For the gaseous PAHs, the detection frequency for 4-5 rings shows high and the elements with 6 rings shows low frequency. For the particle PAHs, the detection frequency for 2-3 rings shows low and the elements with 6 rings show high frequency. As a result, it is investigated that the most important PAHs are the naphthalene, acenaphthene and phenanthrene from the study of Kim et al. (2013) and this annual study. The health risk assessment demonstrates that each facility shows the level of $10^{-6}-10^{-4}$. Considering standards and local source of pollution levels, it is judged that the management standard of the benzo (a)pyrene, one of the PAHs, shall be managed with the range of 0.5-1.2 $ng/m^3$. Smoking and ventilation were considered as the most important PAHs exposure associated with public facility $PM_{2.5}$. This study only estimated for inhalation health risk of PAHs and focused on the associated cancer risk, while multiple measurements would be necessary for public health and policy.

• Journal of Life Science
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• v.27 no.2
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• pp.139-148
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• 2017

The inhibition of tyrosinase, a key enzyme in mammalian melanin synthesis, plays an important role in preventing skin pigmentation and melanoma. Therefore, tyrosinase inhibitors are very important in the fields of medicine and cosmetics. However, only a few tyrosinase inhibitors are currently available because of their toxic effects on skin or lack of selectivity and stability. Therefore, we synthesized a novel series of (E)-2-(substituted benzylidene)-2,3-dihydro-1H-cyclopenta[a]naphthalen-1-one derivatives and evaluated their inhibitory effects on mushroom tyrosinase, with the aim of discovering a novel tyrosinase inhibitor. Among 19 derivatives, MHY3655 ($IC_{50}=0.1456{\mu}M$) showed the strongest inhibitory effect on tyrosinase activity compared to kojic acid ($IC_{50}=17.2{\mu}M$), a well-known tyrosinase inhibitor. In addition, MHY3655 showed competitive inhibition on Lineweaver-Burk plots. We confirmed that MHY3655 strongly interacts with mushroom tyrosinase residues through the docking simulation. Substitutions with a hydroxy group at both R2 and R4 in the phenyl ring indicated that these groups play a major role in the high binding affinity to tyrosinase. Further, MHY3655 did not show cytotoxicity at the concentrations tested in B16F10 melanoma cells. In conclusion, the novel compound MHY3655 potentially shows tyrosinase inhibitory activity, and it could be used as an ingredient in whitening cosmetics.

• Journal of Dairy Science and Biotechnology
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• v.32 no.2
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• pp.77-92
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• 2014

Fermented foods have often been implicated as causative agents in poisoning due to toxic levels of biogenic amines. Cheese, a milk-based fermented food, is the product most likely to contain potentially harmful levels of biogenic amines, such as tyramine, histamine, putrescine, and so on. Recently, the risk awareness of a dietary uptake of high loads of biogenic amines has increased. Hence, we here review the published literature on several factors known to affect the biosynthesis of biogenic amines and their accumulation in milk-based foods. Furthermore, with regard to risk analysis, we discuss the control of factors related to the synthesis and accumulation of biogenic amines as a means to reduce their incidence in milk-based products, and thus to increase food safety.

• Journal of Environmental Impact Assessment
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• v.32 no.2
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• pp.123-133
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• 2023

Wastewater generated in the secondary battery production process contains lithium and high-concentration sulfate. Recently, as demand as demand for high-Ni precursors with high-energy density has surged, nickel emission is also a concern. Lithium and sulfate are not included in the current water pollutant discharge standard, so if they are not properly processed and discharged, the negative effect on future environment may be great. Therefore, in this study, the ecotoxicity of lithium, nickel, and sulfate, which are potential contaminants that can be discharged from the secondary battery production process, was evaluated using water flea (Daphnia magna) and luminescent bacteria (Aliivibrio fischeri). As a result of the ecotoxicity test, 24-hour and 48-hour D. magna EC₅₀ values of lithium were 18.2mg/L and 14.5mg/L, nickel EC50 values were 7.2mg/L and 5.4mg/L, and sulfate EC₅₀ values were 4,605.5mg/L and 4,345.0mg/L, respectively. In the case of D. magna, it was found that there was a difference in ecotoxicity according to the contaminants and exposure time (24 hours, 48 hours). Comparing the EC₅₀ of D. magna for lithium, nickel, and sulfate, the EC₅₀ of nickel at 24h and 48h was 39.6-37.2% compared to lithium and 0.1-0.2% compared to sulfate, which was the most toxic among the three substances. The difference appeared to be at a similarlevelregardless of the exposure time. The EC₅₀ of sulfate was 253.0-299.7% and 639.5-804.6%, respectively, compared to lithium and nickel, showing the least toxicity among the three substances. The 30-minute EC₅₀ values of luminescent bacteria forlithium, nickel, and sulfate were 2,755.8mg/L, 7.4mg/L, and 66,047.3mg/L,respectively. Unlike nickel, it was confirmed that there was a difference in sensitivity between D. magna and A. fischeri bacteria to lithium and sulfate. Studies on the mixture toxicity of these substances are needed.