• Journal of the Korean Society of Tobacco Science
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• v.7 no.1
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• pp.85-92
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• 1985

Extraction efficienties of volatile organic acids in tobacco leaves according to several extraction methods were investigated and contents of volatile organic acids in 16 kinds of tobacco leaf varieties were compared. Extraction efficiency according to simultaneous distillation and extraction was 5 to 10 times higher than that according to solvent extraction, steam distillation, essential oil extraction or continuous extraction and distillation. Total contents of volatile organic acids were 1.62 to 12.94mg per l00g of sample in aromatic tobacco varieties,0.12 to 2.08mg in flue-cured tobacco leaves, and trace in burleys. Among the Korean aromatic tobacco varieties, total contents of volatile organic acids in ST374-3 were the highest, 4.66mg per l00g of sample, and those in Sohyang and Hyangcho were low, 1.69mg and 1.62mg, respectively. Among flue-cured tobacco varieties, those in NC2326 were the highest, 2.08mg per 100g of sample, but those in the other varieties were not more than 0.80mg per 1 00g of sample. Total contents of volatile organic acids in acidic hydrolysis with 0.1 M tartaric acid were higher than in non-acidic condition in all kinds of tobacco varieties.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.809-814
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• 2011

A method based on the TMS derivatives and acidic hydrolysis was developed for the simultaneous determination of free and conjugated steroidal hormones in surface water. A silylation of five natural and two synthetic steroidal hormones was achieved with N-methyl-N-(trimethylsilyl) trifluoroacetamide/$NH_4I$ (1000:3) under catalysis of dithioerythritol for 60 min at $80^{\circ}C$. TMS derivatives of the steroid hormones containing multifunctional groups offer a single derivative product under this condition. The accuracy of the analytes was in the range of 87 to 110% at a concentration of 20 and 50 ng/L with relative standard deviations of less than 10%. The method detection limit was in the range of 0.01 to 0.02 ng/L for surface water. Natural steroidal hormones were detected in a concentration range of 0 to 1.03 ng/L in free form and 0 to 14.6 ng/L in conjugated form, respectively. We found that most of the natural hormonal steroids exist in conjugate forms (43 to 100%) in river water.

• Journal of Soil and Groundwater Environment
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• v.26 no.1
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• pp.34-44
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• 2021

Acid mine drainage (AMD) resulting from pyrite oxidation in mining areas, subsequently leads to soil acidification accompanied by lowering pH and high concentration of metals and metalloids in its surrounding environment. Regarding to this, the microbial amelioration has been considered as a promising option for a more cost-effective and eco-friendlier countermeasure, compared to the use of alkaline chemicals. This study was aimed to evaluate influencing factors in microbially-mediated amelioration of acidic soil spiked by simulated AMD. For this, microcosm experiments were conducted by acid-neutralizing bacterial consortium (dominated by Klebsiella sp. and Raoultella sp.) under the various conditions of AMD spikes (0-2,500 mg SO42-/L), together with acidic mine soil (0-100 g) or sphagnum peat (0-5 g) in the 200 mL of nutrient medium. The employed bacterial consortium, capable of resisting to high level of sulfate concentration (up to 1,500 mg SO42-/L) in low pH, generated the ammonium while concomitantly reduced the sulfate, subsequently contributing to the effective soil stabilization with an evolution of soil pH up to neutral. Furthermore, it demonstrates that suitable condition has to be tuned for successful microbial metabolism to facilitate with neutralization during practical application.

• The Korean Journal of Zoology
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• v.18 no.3
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• pp.107-114
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• 1975

This study was performed in order to know the histochemical changes of mucosubstances in granular secretions of the serous gland under normal and dry conditions. The frogs were collected near Jinju and the experimental groups were retained under dry conditions for 24, 48, 72 and 96 hours to make a comparison with normal group. The results obtained were as follows: 1. The secreting granules in serous gland of the frog skin contained neutral and weakly acidic mucosubstances. 2. the secreting granules in serous gland of the frog skin were significantly decreased under dry conditions, as is evident from the histochemical properties. The neutral mucosubstances were decreased more than acidic mucosubstances. 3. Histochemical compositions of the mucosubstances of secreting granules in the lumen of the serous gland were not changed according to dry condition.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.2
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• pp.141-153
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• 2009

$PM_{2.5}$ samples were collected from December 2005 through November 2007 in two cities including Chuncheon and Seoul in order to investigate the characteristics of carbonaceous aerosol. The average $PM_{2.5}$ concentration in Seoul ($43.2{\mu}g/m^3$) was approximately 1.2 times higher than that measured in Chuncheon ($36.1{\mu}g/m^3$), however there was no statistical difference on $PM_{2.5}$ concentration between those two cities. Backward trajectories were passing through Seoul area before arriving Chuncheon for about half of the samples, and $PM_{2.5}$ largely increased in Chuncheon when back-trajectories originated from Seoul area. Total carbon (TC) was calculated as sum of OC and EC, contributing 20.5% and 29.2% to total $PM_{2.5}$ mass in Chuncheon and Seoul, respectively. The average ratio of secondary organic carbon (SOC) to total OC was 40% at both sites, and the highest SOC concentration was observed in summer probably due to enhanced volatilization of organic species and active photochemical reaction. J value was calculated to determine if acidic condition affected the increase of secondary organic carbon. In both Chuncheon and Seoul SOC/OC ratios were fairly enhanced when J<100% of acidic condition.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.483-491
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• 2016

Even though the antifogging property of nanosilica coated glass surface is highly increased due to the hydrophilic hydroxyl groups on nanosilica surface, the durability of this property on outdoor glass was diminished rapidly after rain washing. In addition the topology of nanosilica coated glass surface plays very important roles to control an light transmittance or antireflection property. To improve these coating durability and characteristics a hydrophilic nanosilica coating on glass was prepared by coating with 1.5 wt% of nanosilica (Ludox) suspension in the presence of hydrolyzed tetraethylorthosilicate (TEOS). The optimum hydrolysis condition of TEOS in acidic or basic aqueous solution was also examined by contact angle measurement. The final transparent hydrophilic coating layer coated with nanosilica-TEOS in acidic condition (pH=4) showed much improved durability of hydrophilic surface as well as higher visible light transmittance than original uncoated glass by 2 % point.

• The Korean Journal of Ecology
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• v.21 no.5_3
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• pp.633-648
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• 1998

The forest vegetation of Mt. Nam Nature Park was investigated according to the phytosociological method. The vegetation in this study area was classified into 5 communities Quercus mongolica (Acer pseudo-sieboldianum subcommunity, Prunus sargentii subcommunity), P. sargentii, Pinus densiflora (Q. mongolica subcommunity, Stephanandra incisa subcommunity) and 5 afforestations Robinia pseudo-acacia, Populus tomentoglandulosa, P. koraiensis, P. rigida, Metasequoia glyptostroboides. Generally, were P. densiflora forest at the Southern slope and Q. mongolica forest at Northern slope dominant species from the top zone standing in Namsan tower. The dominance sequences on each stratum determined by the R-NCD (Relative net Contribution Degree) showed Q. mongolica and P. densiflora in tree-1 layer, Styrax japonica and Corbus alnifolia in tree-2 layer, S. incisa, S. japonica and rhododendron schlipenbachii in shrub layer, and Oplismenus undulatifolius, Eupatorium rugosum, Parthenocissus tricuspidata and Disporum smilacinum in herb layer. The soil was analyzed to investigate the soil conditions and fertility. The pHs of soil collected in each sites appeared strongly acidic with the range of 4.34 to 5.01 each community and especially, was the lowest value 4.34 in P. rigida afforestation. And Q. mongolica-P. sargentii subcommunity was distributed at the area with relative mesic conditions and high organic matters. Nitrogen was highest at P. sargentii community, phosphate at P. densiflora-S. incisa subcommunity, calcium, potasium and magnesium of exchangeble cation at R. pseudo-acacia afforestation. Especially, the level of calcium in R. pseudo-acacia afforestation, P. koraiensis afforestation and P. densiflora community was shown the highest (0.38-1.48 mg/100g) compared to other communities, because of the influence of lime fertilization used to improve acidic soil.

• KSBB Journal
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• v.23 no.6
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• pp.546-550
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• 2008

Basic characteristics of astaxanthin including solubility and stability were investigated. Astaxanthin showed a very poor solubility in water, but it was highly soluble in organic solvents such as acetone and acetic acid. The solubility of astaxanthin in acidic condition was 10-20 times higher than those in neutral and basic conditions. Astaxanthin was very unstable in acidic condition under UV irradiation and in the presence of oxygen. Also, heating even for a very short time accelerated the degradation of astaxanthin. In conclusion, it is required to enhance the water-solubility and stability of astaxanthin for industrial application in food and cosmetic area.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.301-306
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• 2016

The effects of nanotexturing and post-etching on the reflection and quantum efficiency properties of diamond wire sawn (DWS) multicrystalline silicon (mc-Si) solar cell have been investigated. The chemical solutions, which are acidic etching solution (HF-$HNO_3$), metal assisted chemical etching (MAC etch) solutions ($AgNO_3$-HF-DI, HF-$H_2O_2$-DI) and post-etching solution (diluted KOH at $80^{\circ}C$), were used for micro- and nano-texturing at the surface of diamond wire sawn (DWS) mc-Si wafer. Experiments were performed with various post-etching time conditions in order to determine the optimized etching condition for solar cell. The reflectance of mc-Si wafer texturing with acidic etching solution showed a very high reflectance value of about 30% (w/o anti-reflection coating), which indicates the insufficient light absorption for solar cell. The formation of nano-texture on the surface of mc-Si contributed to the enhancement of light absorption. Also, post-etching time condition of 240 s was found adequate to the nano-texturing of mc-Si due to its high external quantum efficiency of about 30% at short wavelengths and high short circuit current density ($J_{sc}$) of $35.4mA/cm^2$.

• Archives of Pharmacal Research
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• v.27 no.1
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• pp.61-67
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• 2004

When ginseng water extract was incubated at $60^{\circ}C$ in acidic conditions, its protopanaxadiol ginsenosides were transformed to ginsenoside $Rg_3$ and ${\Delta}^{20}$-ginsenoside $Rg_3$. However, protopanaxadiol glycoside ginsenosides $Rb_1, Rb_2$ and Rc isolated from ginseng were mostly not transformed to ginsenoside $Rg_3$ by the incubation in neutral condition. The transformation of these ginsenosides to ginsenoside $Rg_3$ and ${\Delta}^{20}$-ginsenoside $Rg_3$ was increased by increasing incubation temperature and time in acidic condition: the optimal incubation time and temperature for this transformation was 5 h and $60^{\circ}C$ resepectively. The transformed ginsenoside $Rg_3$ and ${\Delta}^{20}$-ginsenoside $Rg_3$ were metabolized to ginsenoside $Rh_2$ and $\Delta^{20}$--ginsenoside $Rh_2$, respectively, by human fecal microflora. Among the bacteria isolated from human fecal microflora, Bacteroides sp., and Bifidobacterium sp. and Fusobacterium sp. potently transformed ginsenoside $Rg_3$ to ginsenoside $Rh_2$. Acid-treated ginseng (AG) extract, fermented AG extract, ginsenoside $Rh_2$ and protopanaxadiol showed potent cytotoxicity against tumor cell lines. AG extract, fermented AG extract and protopanaxadiol potently inhibited the growth of Helicobacter pylori.