• Korean Journal of Environment and Ecology
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• v.28 no.5
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• pp.510-515
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• 2014

Duckweed (Lemna perpusilla J. Torrey) is a typical floating aquatic macrophyte that has been used for evaluating phytotoxicity of toxicants. In this study, we evaluated the responses of duckweed to PAHs and ammonium as toxicants that frequently affect the growth of plants in polluted industrial and agricultural areas. As the duckweed is growing in aquatic environment, the PAHs and ammonium were incorporated into nutrient solution and the fronds were cultured hydroponically. Frond growth was responded differentially to the concentration and type of PAHs. The severe inhibition of frond growth was observed in the treatment of fluorene. Fluoranthene and pyrene, however, showed weak inhibition of frond growth. The latter PAHs that showed weak inhibition did not reduced frond number at the low concentration of 30 ppm. Pigment contents were also responded differentially. Phenanthrene and fluorene reduced chlorophyll content more strongly than fluoranthene and pyrene. Carotenoids, well-known antioxidative compound, was relatively increased at the low concentration of PAHs up to 30 ppm by the treatment of fluoranthene and pyrene, suggesting an increased antioxidative activity in fronds. Ammonium treatment showed higher inhibitory effect even low concentration of 3 mM.

• Korean Journal of Soil Science and Fertilizer
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• v.21 no.2
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• pp.149-159
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• 1988

This study was made to investigate the effect of pesticides on microflora to nitrogen metabolism, nitrification and nitrogen fixing activity in the submerged soil. The results are summarized as follows; Pesticides treatment leaded to the inhibition of $NH_4{^-}$-oxdizers, $NO_3{^-}$-reducer, and denitrifying bacteria population. $NO_2{^-}$-oxdizers were inhibited by cabamate compounds, carbofuran and MIPC. Simetryne seemed to stimulate the denitrifying bacteria at 60 days after incubation. Generally, formation of $NO_2{^-}$ and $NO_3{^-}$ tended to decrease by pesticides application. Pesticides application stimulated Azotobacter and Clostridia populations, while simetryne inhibited Athiorhodaceae and Thiorhodaceae. However acephate seemed to be stimulatory to blue-geen algae. $C_2H_2$-reducing activity by acephate was clearly appeared. The change of $C_2H_2$-reducing activity did not seems to be affected by pesticides application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.255-261
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• 2016

$CaCO_3$ was applied in various industries including rubber, plastics, paint, paper, food additives, and acid neutralizer, etc., owing to its excellent physical and chemical characteristics as well as various appearances of crystals and many reserves. In particular, research on controlling the structure and shape of $CaCO_3$ has attracted considerable attention recently, because the whiteness and physical characteristics of $CaCO_3$ depend on the size and shapes of the particles. In this study, $CaCO_3$ was synthesized using $CaCl_2$ and $(NH4)_2CO_3$, which has multi-shapes and structures, using a self-assembly method with a hydrothermal method. The structure and morphology of the $CaCO_3$ could be controlled by adjusting the pH and precursor concentration. In particular, the pH adjustment appeared to be a critical factor for the morphology and crystal form. In addition, the calcite and cubic shape were obtained at pH 7, while the mixed calcite, aragonite structure, and rod shapes appeared at pH 7 and over. Through an analysis of the particle formation process, the formation of the calcium carbonate particles was confirmed. The physicochemical properties of the synthesized $CaCO_3$ were analyzed by SEM, XRD, EDS, FTIR, and TG/DTA.

• Journal of environmental and Sanitary engineering
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• v.16 no.4
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• pp.55-61
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• 2001

There are many reservoirs used as the source of water supply and they show various specific characteristics in water quality depend seasonal. Especially, there were not a little variations of water quality in summer, as a natural consequence it follows that stratification occured phenomenon and changed anaerobic condition in the bottom of reservoir, and then accumulated Fe and Mn substance in soil and sediment were resolved into water, it attributes to coloration. G purification plant located in Y gun is very small plant in which coloration occurs by Fe and Mn in every summer. Using this plant as a model, the removal methods of Fe and Mn were studied. After prechlorination plus LAS coagulation, Fe, Mn, $NH_3-N$ were decreased from 7.290 mg/l to 0.080 mg/l, from 0.480 mg/l to 0.075 mg/l, from 0.55 mg/l to 0.04 mg/l. But $THM_{s}$ was increased from 0.050 mg/l to 0.044 mg/l. It shows that the prechlorination plus LAS coagulation treatment process in purification plant is effective to remove Fe and Mn ion.

• Journal of Life Science
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• v.13 no.1
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• pp.90-98
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• 2003

An allium rhizobacterium Serratia plymuthica AL-1 was previously selected as a biocontrol agent of allium white rot. The chitinase from S. plymuthica AL-1 produced in medium containing colloidal chitin was purified by ammonium sulfate precipitation (40~70%), affinity adsorption, column chromatography on DEAE-sephadex A-50 and sephadex C-200 gel filtration. The enzyme was purified 10.8-fold with a yield of 7.3% from the starting culture broth. The purified chtinase gave a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis, it's molecular weight was estimated to be 55 kDa. The optimum pH and temperature of the purified enzyme were pH 5.5 and $55^{\circ}C$, respectively and it is stable up to $50^{\circ}C$ and maintains around 90% of its activity for 60min. The enzyme were activated by $Ca^{2+}$, $Mn^{2+}$ and $Mg^{2+}$ and inhibited by $Cu^{2+}$, SDS, $\rho$-CMB, MIA, respectively. The purified chitinase showed broad spectrum of antifungal activities against plant pathogenic fungi Sclerotium cepivoruin, Alternana alternnta, Colletotrichum glceosporioidrs, Phoma sp., Sclerotinia sclerotiorum, Stemphylium solani, Fusarium oxysporium f. sp. niveum but rarely inhibited Phytophthora capsici and Pythium ultimum.. The purified chitinase from S. plymuthica AL-1 caused swelling, lysis, deceleration and degradation of the hyphal tips of S. sczerotiorum causing allium white rot. It suggest that S. prymuthica AL-1 chitinase play an important part in the bifunctional chitinase / lysozyme activity.

• Journal of Periodontal and Implant Science
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• v.30 no.3
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• pp.491-504
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• 2000

In clinical therapy, the current goal of dental implants is to enhance quantity and quality of osseointegration. Surface roughness and oxide structure are considered to influence the behavior of adherent cells. The purpose of this study is to evaluate the effect of different surface treatment on cellular response. The attachment and proliferation of osteoblast-like cell on sandblasted, sandblasted and etched, thermal oxidated surfaces have been compared. Sandblasting was done with $Al_2O_3$ particles(grain size of $50{\mu}m$), etching was processed with $NH_4OH$ : $H_2O_2$ : $H_2O(1:1:5)$ at $90^{\circ}C$ for 1 minute. Thermal oxidation was followed sandblasting and etching at $400^{\circ}C$, $600^{\circ}C$, $800^{\circ}C$ for 2 hours. Measurement of surface roughness after the different treatment did not show any differences of Ra value between terated surfaces. Cell attachment and proliferation were increased during experiment period, but no difference was observed. SEM evaluation revealed a similar pattern of osteoblast-like cells, well attached with dendritic extension and producing numerous matrix vesicles on cell surface. The results of this study showed that oxide layer alteration by thermal oxidation did not affect the attachment and proliferation of osteoblast-like cells. This suggests the possibility that the cellular responses are further influenced by surface roughness than titaniun oxide structure.

• Korean Journal of Environmental Agriculture
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• v.20 no.4
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• pp.238-243
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• 2001

Mass reduction and physicochemical properties of the produced compost were investigated during composting domestic food wastes without additive. A small composter used in this study had the height of 15 cm from the center of bottom half circle (diameter 24 cm) up to under the lid, the side length of 50 cm and the horizontal lid angle of $50^{\circ}$ and was operated at the heating unit temperature of $85^{\circ}$. It was mixed by the rotating arm for two minutes in every half hour while supplied with air flow at 3 L/min for 10 minutes in every half hour. This condition was found in a preliminary experiment as optimal for keeping the water content of composting material in the optimal range without adding any bulking materials. The domestic food wastes were added into the composter at the rate of 1 kg/day without additives during composting. The results were as follows; during the composting process, water content maintained in the range of $51.0{\sim}53.5%$. Hemicellulose and lignin contents did not show any tendency, but cellulose content decreased. During the composting process, $NH_3-N$ and $NO_2-N$ were not detected due to nitrification. The contents of inorganic compounds did not increase during the composting process. They were in the range of $1.32{\sim}1.71%\;P_2O_5$, $1.29{\sim}1.48%\;CaO$, $0.41{\sim}0.49%\;MgO$, and $0.38{\sim}0.74%\;K_2O$. For 20 days, weight reduction rate was 67.5% in wet basis, and decomposition rate was 48% in dry basis. Concentration of heavy metals (Cu, Cr, Cd, Pb, Zn, Hg, As) was less than the limiting value of the compost. Maturity of the produced compost was 3 grade through reaching maximum temperature of $46{\sim}48^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.224-232
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• 2000

Aluminum metal process in surface micromachining enables to fabricate Al electrodes or Al structures, which improve electrical characteristics by reducing contact- and line-resistance or makes the whole process to be simple by using oxide as sacrificial layer. However, it is not possible to use conventional sacrificial layer etching process, because HF solution attacks aluminum as well as sacrificial oxide. The mixed solution of BHF and glycerine as an alternative shows the adequate properties to meet with this end. The exact etching properties, however, are sensitively depends on the geometry of the released structure, because the most etching process of sacrificial layer proceeds to the lateral direction in narrow space. Also, the surface roughness of aluminum affects to the etching characteristics. This paper reports experimental results on the effect of microstructure and surface roughness of aluminum to the etching properties. Considering these effects, we propose the optimized etching condition, which can be used practically for the fabrication of aluminum electrodes and microstructures by using standard surface micromachining process without modification or additional process.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.18 no.1
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• pp.47-52
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• 2013

Despite the usefulness of nitrogen isotope tracer experiments in nitrogen cycling studies, there are not such many measurement data mainly due to the difficulties in analytical methods. Although Gardner et al. (1996) developed a relatively simple and accurate method that can measure ammonium isotope using HPLC and used it widely in various N dynamics studies, the technique was not adopted to other laboratories. An HPLC-RTS system using updated HPLC pumps that can perform the same measurements as that of Gardner et al. (1996) was built. The result of standard sample showed linear increase of RTS with the $^{15}N$ proportions. Centroid retention times calculated with Matlab$^{(R)}$ program enhanced the linearity of the response. In a sea water incubation experiment spiked with $^{15}NH_4{^+}$, the uptake and regeneration of ammonium could be separately estimated using the temporal change of $^{15}N/^{14}N$.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.3
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• pp.136-142
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• 2004

Though diverse methods have been developed to characterize surface charge of soils and pure minerals, there is not still a reliable and rapid method for differentiating permanent charge from variable charge. Thus, it is needed to find out a reasonable method for measuring permanent and pH-dependent charge of soils. In this study various methods such as Cs-adsorption method, Hybrid model, $NH_4{^+}$-adsorption method and theoretical calculation of lattice charge were applied to measure permanent charge of montmorillonite and illite. Calculated lattice charge was $71.82cmol\;kg^{-1}$ and $14.20cmol\;kg^{-1}$ for montmorillonite and illite, respectively. The permanent charge measured by Cs-adsorption method were $78.23cmol\;kg^{-1}$ and $11.13cmol\;kg^{-1}$ for montmorillonite and illite, respectively. The differences between the values measured by Cs-adsorption method and the calculated lattice charge were not different significantly as $6.41cmol\;kg^{-1}$ and $3.07cmol\;kg^{-1}$. But, Hybrid model showed an underestimated values when applied to clay minerals with predominant amounts of permanent charge. The experimental results showed Cs-adsorption method was more reasonable for permanent charge measurement than the Hybrid model for illlte or montmorillonitetype clays.