• Toxicological Research
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• v.23 no.1
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• pp.79-86
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• 2007

The isolated plantamajoside from Plantago asiatica that is often used as a marker compound in chemotaxonomic studies has various bioactivites such as the inhibitions of cyclic AMP phosphodi-esterase and 5-lipoxygenase, microbial growth and inflammation, and currently demands the generation of toxicity data. The purpose of this study was to examine the toxicities of the single and 14 days repeated dose toxicity in Sprague-Dawley rats orally administrated with plantamajoside at dose levels of 0, 500, 1000, and 2000 mg of dried material/kg body weight/day. The results showed that there was no difference in body weight change, food intake, water consumption, or relative organ weight among different dose groups. Also we observed no death and abnormal clinical signs were observed during the experimental period. Between the groups orally administered Plantago asiatica and the control group, there was no statistical significance in hematological test or serum biochemical values. There were no gross findings at final sacrifice. There was no evidence of histopathological alteration mediated by 14 days treatment with Plantago asiatica. These results suggest that no observed adverse effect level (NOAEL) of the oral application was considered to be more than 2000 mg/kg in rats under the conditions employed in this study. Another observation was performed to investigate the safety of Plantago asiatica in respect of genotoxicity. This substance was examined that Salmonella typhimurium reversion assay (Ames test) in strain TA98, TA100, TA1535. In the reverse mutation test, Plantago asiatica did not induce mutagenicity in Samonella typhimurium with and without metabolic activation. These results indicated that Plantago asiatica had no genotoxicity.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.1
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• pp.87-91
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• 2005

Dental plaque is a film of microorganisms on the tooth surface that plays an important part in the development of caries and periodontal diseases. Streptococcus mutans (S. mutans) is present in almost all types of dental plaque. Teeth and their supporting structure, the gums (gingiva) are subjected to infection by S. mutans that causes cavities and pyorrhea which, if left untreated, can eventually lead to gingivitis. Various chemical agents have been evaluated over the years with respect to their antimicrobial effects in the oral cavity; however, all are associated with side effects that prohibit regular long-term use. The present study was designed to investigate the effect of Aralia continentalis (Araliaceae) extracts on the growth, acid production, adhesion, and insoluble glucan synthesis of S. mutans. The methanol extract of A. continentalis showed concentration dependent inhibitory activity against the growth and acid production of S. mutans, and produced significant inhibition at the concentration of 0.25, 0.5, 1, 2 and 4 mg/ml compared to the control group. The extracts markedly inhibited S. mutans adherence to HA treated with saliva, and cell adherence was repressed by more than 60% at the concentration of 0.25 mg/ml and complete inhibition was observed at the concentration of 4 mg/ml. On the activity of glucosyltransferase which synthesizes water insoluble glucan from sucrose, methanol extract of A. continentalis showed more than 10% inhibition over the concentration of 0.25 mg/ml. The synthesis of insoluble glucan was decreased in the presence of 0.25 - 4 mg/ml of the methanol extract of A. continentalis. Hence, we conclude that A. continentalis might be a candidate of anticaries agent.

• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.165-173
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• 1986

Accumulation of Pseudomonas sp., P. fluorescens and Erwinia carotovora in 60 min treatment was greater in extracts from soil, exudate from ginseng root and solutions than distilled water. In bacterial movement toward rubber tube soil from chamber, accumulation of P. fluorescens in response to soil supplemented with soil extracts, exudate and solutions was generally greater in soil extracts compared to control and other solutions, but Pseudomonas sp. and E. carotovora were not much response to supplemented extracts, exudate and solutions. Accumulation of the bacteria in capillaries containing various exudates from fungal propagules with not attracted to the exudates. For an accumulation of bacteria in rubber tubes containing soil inoculated with fungal propagules, the Pseudomonas sp. was not attracted in soil inoculated by the organisms as attractant but P. fluorescens and E. carotovora to fungi were attracted to F. solani, F. oxysporum and mixed organism Alternaria panax did not affect on bacterial movement except E. carotovora. The organic matter conten in Kangwha and Kimpo soil were low in diseased and healthy soil. The K content was especially high in Kimpo healthy soil. Bacterial population in Goesan and Kangwha were more abundant than other soil. The number actinomycetes was populated abundant in healthy soil of Goesan and diseased soil of Poonggi.

• Journal of Soil and Groundwater Environment
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• v.13 no.6
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• pp.93-102
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• 2008

Experimental studies were conducted to characterize the synthesized nanoscale zero-valent iron (NZVI) which is resistant to oxidation in the atmospheric environment. XRD, XPS, and TEM analyses revealed that the oxidation-resistant NZVI particles formed under various controlled air contact conditions (4, 8 and 12 mL/min) have shells with ${\sim}$5 nm thickness. The shells consist of magnetite (${Fe_3}{O_4}$) and maghemite (${\gamma}-{Fe_2}{O_3}$), predominantly. No substantial differences were found in the shell components and thickness among NZVI particles formed under the various air flow rates. On the other hand, shell was not detected in the TEM image of rapidly oxidized NZVI particles. NZVI particles synthesized under the various air flow rates showed similar TCE degradation performances ($k_{obs}$= 0.111, 0.102, and 0.086 $hr^{-1}$), which are equivalent to approximately 80% of those obtained by the fresh NZVI particles. TCE degradation efficiencies of the NZVI particles(fresh, controlled air contact and rapidly oxidized) were improved after equilibrating with water for one day, indicating that depassivation of the shells occurred. The performances of NZVI particles decreased to 90% and 50% of those of the fresh NZVI particles, when they were equilibrated with the atmosphere for a week and two months, respectively. The NZVI particles synthesized under the controlled air contact would have advantages over traditional NZVI particles in terms of practical application into the site, because of their inertness toward atmospheric oxygen.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.55-61
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• 2015

Based on the literature study for the determination of perchlorate in soil we chose the ion chromatography as a measurement method and decided to use 70 mM KOH as an eluent to avoid the interference derived from the co-elution of pyrophosphate (P₂O₇⁴⁻), tripolyphosphate (P₃O₁₀⁵⁻). Also we proposed to use air dried soil through 0.15 mm sieve and distilled water as an extractant. Under the these basic concepts, we carried out the experiments to set up the detail procedure like solid to liquid ratio (S/L ratio), extraction time, device for extraction and indicating factors for quality control (e.g. precision, accuracy, MDL, LOQ). In case of time and device for extraction, 5 hours of mechanical shaking or 1 hour of centrifugation showed better precision and accuracy than that of sonication for 1 hour According to these results, we proposed the extraction method combining 5 hours of mechanical shaking with 1 hour of centrifugation. From the aspect of S/L ratio, the ratio of 1/2 or 1/3 showed resonable precision and accuracy. In case of the ratio of 1/2, there would be some problems in the separation process when the proportion of fine particle is high. Therefore, we proposed the extraction ratio of solid to liquid as 1/3 instead of 1/2. With the consideration of cost effectiveness and soil salinity, we proposed the use of cartridge for removing the interfering anions like chloride, sulfate and carbonate in specific sample such as saline soil.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.30-35
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• 2016

Rice cultivation in paddy field affects the global balance of methane ($CH_4$) as a key greenhouse gas. To evaluate a potential use of by-product gypsum fertilizer (BGF) in reducing $CH_4$ emission from paddy soil, $CH_4$ fluxes from a paddy soil applied with BGF different levels (0, 2, 4 and $8Mg\;ha^{-1}$) were investigated by closed-chamber method during rice cultivation period. $CH_4$ flux significantly decreased (p<0.05) with increasing level of BGF application. $8Mg\;ha^{-1}$ of BGF addition in soil reduced $CH_4$ flux by 60.6% compared to control. Decreased soil redox potential (Eh) resulted in increasing $CH_4$ emission through a $CO_2$ reduction reaction. The concentrations of dissolved calcium (Ca) and sulfate ion (${SO_4}^{2-}$) in soil pore water were significantly increased as the application rate of BGF increased and showed negatively correlations with $CH_4$ flux. Decreased $CH_4$ flux with BGF application implied that ${SO_4}^{2-}$ ion led to decreases in electron availability for methanogen and precipitation reaction of Ca ion with inorganic carbon including carbonate and bicarbonate as a source of $CH_4$ formation under anoxic condition. BGF application also increased rice grain yield by 16% at $8Mg\;ha^{-1}$ of BGF addition. Therefore, our results suggest that BGF application can be a good soil management practice to reduce $CH_4$ emission from paddy soil and to increase rice yield.

• Journal of the Korean Wood Science and Technology
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• v.40 no.4
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• pp.257-267
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• 2012

In this study, the method for heat treating wood using superheated steam (SHS) was designed and applied. The physical and mechanical properties of Korean Pine (Pinus koraiensis Siebold & Zucc.) lumber heat-treated by SHS at $170^{\circ}C$ and 0.4 MPa for 10 hours were compared with those of non-treated and normal heat-treated wood. The amount of adsorbed water and equilibrium moisture content of the SHS treated wood were lower than non-treated wood. On the other hand the compressive strength parallel to grain and the bending strength of SHS treated wood were higher than those of non-treated wood. The hygroscopicity of SHS treated wood was similar to normal heat treated wood at $220^{\circ}C$. Internal checks that often occur during normal heat treatment were not developed at SHS treatment. Also, SHS treatment are effective in control of internal checks occurrence and resin exudation.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.149-156
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• 2019

Assessing the hydrological safety of existing dams against climate change and providing appropriate adaptation measures are important in terms of sustainable water supply and management. Korean major dams ensure their safety through periodic inspections and maintenance according to 'Special Act on the safety control and maintenance of establishments'. Especially when performing a full safety examination, principal engineer must assess the hydrological safety and prepare for potential risks. This study employed future probable maximum precipitation (PMP) estimated using outputs of regional climate models based on RCP4.5 and RCP8.5 greenhouse-gas emission scenarios to assess climate change impact on existing dam's future hydrological safety. The analysis period was selected from 2011 to 2040, from 2041 to 2070, and from 2071 to 2100. Evaluating the potential risk based on the future probable maximum flood (PMF) for four major dams (A, B, C, I) showed that climate change could induce increasing the overflow risk on three dams (A, B, I), although there are small differences depending on the RCP scenarios and the analysis periods. Our results suggested that dam managers should consider both non-structural measures and structural measures to adapt to the expected climate change.

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.95-108
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• 2015

Nano-sized iron colloids are formed as acid mine drainage is exposed to surface environments and is introduced into surrounding water bodies. These iron nanomaterials invoke aesthetic contamination as well as adverse effects on aqueous ecosystems. In order to control them, the characteristics of their behaviour should be understood first, but the cumulative research outputs up to now are much less than the expected. Using zero-valent iron (ZVI) and magnetite, this study aims to investigate the behaviour of iron nanomaterials according to the change in the composition and pH of background electrolyte and the concentration of natural organic matter (NOM). The size and surface zeta potential of iron nanomaterials were measured using dynamic light scattering. Characteristic behaviour, such as aggregation and dispersion was compared each other based on the DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory. Whereas iron nanomaterials showed a strong tendency of aggregation at the pH near point of zero charge (PZC) due to electrostatic attraction between particles, their dispersions became dominant at the pH which was higher or lower than PZC. In addition, the behaviour of iron nanomaterials was likely to be more significantly influenced by cations than anions in the electrolyte solutions. Particularly, it was observed that divalent cation influenced more effectively than monovalent cation in electrostatic attraction and repulsion between particles. It was also confirmed that the NOM enhanced the dispersion nanomaterials with increasing the negative charge of nanomaterials by coating on their surface. Under identical conditions, ZVI aggregated more easily than magnetite, and which would be attributed to the lower stability and larger reactivity of ZVI.

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.27-32
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• 2010

We used phototrophic bacteria to remove low concentrated organic materials (CODCr), nitrogen and phosphorus. We applied $COD_{Cr}$ 37.3 mg/L, $NH_3-N$ 4.0 mg/L, and $PO_4^{3-}-P$ 1.0 mg/L (C:N:P=100:10:1) in the batch test, and the removal efficiencies were shown as follow: $COD_{Cr}$ 87.4%, $NH_3-N$ 46.3%, $PO_4^{3-}-P$ 79.7%. The aerobic process with mixed phototrophic bacteria, ceramic media, and media KSP01 showed the removal efficiencies of $COD_{Cr}$, $NH_3-N$, and $PO_4^{3-}-P$, each as 72.7% and 79.2%, respectively in the lab-scale reactor. The maximum $PO_4^{3-}-P$ removal efficiency reached 92.6% by adjusting pH. There were three conditions used to remove $NH_3-N$. The highest removal efficiency was 98.5% with 10.2 L/min of aeration in 1-2 reactors, and the result of applying river-water showed the high removal efficiency of $NH_3-N$ (82.8%). Therefore, this purification system may be useful to control nitrogen and phosphorus at low concentration in field.