• Polymer(Korea)
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• v.31 no.3
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• pp.201-205
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• 2007

Biodegradable polymers such as polylactide, polyglycolide and poly (lactide- co-glycolide) (PLGA) have been extensively investigated because of easily controlled drug release rate, completely degradable materials without the toxic by-product, and good biocompatibility. But, according to the bulk erosion property of PLGA in vitro test, it had the disadvantage that first-order release reduced releasing amount slowly after excessive initial burst. In this study we used PLGA powder obtained through recrystallization to revise bulk erosion property of PLGA. The PLGA used in this study was prepared by vacuum drying method and to estimate release profiles of BCNU loaded PLGA wafer. We also evaluated the release profile of drug with the water soluble additive. It was found that the drug loaded PLGA recrystallized by vacuum drying method exhibited the initial burst and the constant rate of drug release compared to that prepared by a conventional method.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.555-561
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• 2005

A new graphical method was developed to separate two distinctive decay rate coefficients($k_1$ and $k_2$) at their respective degradable substrate fractions($S_1 and $S_2$). The mesophilic batch reactor showed $k_1$ of $0.151\;day^{-1}$ for wasted activated sludge(WAS), $0.123\;day^{-1}$ for thickened sludge(T-S), $0.248{\sim}0.358\;day^{-1}$ at S/I ratio of $1{\sim}3$ for sorghum and $0.155{\sim}0.209\;day^{-1}$ at S/I ratio $0.2{\sim}1.0$ for swine waste, whereas their long term batch decay rate coefficients($k_2$) were $0.021\;day^{-1}$, $0.001\;day^{-1}$, $0.03\;day^{-1}$ and $0.04\;day^{-1}$ respectively. At least an order of magnitude difference between $k_1$ and $k_2$ was routinely observed in the batch tests. The portion of $S_1$, which degrades with each $k_1$ appeared 71% for WAS, 39% for T-S, 90% for sorghum, and $84{\sim}91%$ at S/I ratio of $0.2{\sim}1.0$ for swine waste. Ultimate biodegradabilities of 50% for WAS, 40% of T-S, $82{\sim}92%$ for sorghum, and $81{\sim}89%$ for swine waste were observed.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.3 s.47
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• pp.295-305
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• 2004

Colloid and surface chemistry have been focused on surface area and surface energy. Local surface properties such as surface density, interaction, molecular orientation and reactivity have been one of interesting subjects. Systems of such surface energy being important would be listed as association colloid, emulsion, particle dispersion, foam, and 2-D surface and film. Such nanoparticle systems would be applied to drug delivery systems and functional cosmetics with biocompatible and degradable materials, while nanoparticles having its size of several nm to micron, and wide surface area, have been accepted as a possible drug carrier because their preparation, characteristics and drug loading have been inves-tigated. The biocompatible carriers were also used for the solubilization of insoluble drugs, the enhancement of skin absorption, the block out of UV radiation, the chemical stabilization and controlled release. Nano/micro emulstion system is classified into nano/microsphere, nano/microcapsule, nano/microemulsion, polymeric micelle, liposome according to its prep-aration method and size. Specially, the preparation method and industrial applications have been introduced for polymeric micelles self-assembled in aqueous solution, nano/microapsules controlling the concentration and activity of high concen-tration and activity materials, and monolayer or multilayer liposomes carrying bioactive ingredients.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.5
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• pp.711-720
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• 2009

Leaf fibers have many good properties; they are strong, long, cheap, abundant and bio-degradable. Since they, however, contain a great quantity of non-cellulose components, they have been used for the materials of mats, ropes, bags and nets rather than those of clothing. In this study, we investigated the characteristics of leaf fibers in order to promote the use of leaf fibers for the materials of clothing as well as develop the high value-added textile fibers. Leaf fiber plants including New Zealand Flax, Henequen and Banana plant, which have various nature and shape, were used. New Zealand Flax and Henequen leaves were cut from lower part of plants. Banana leaves and pseudo-stems were peeled and cut from the stem of Banana plants. First, the thin outer skins like film of leaves, veins and stems were removed before retting. The chemical retting had been processed for 1hour, at 100 in 0.4% $H_2SO_4$ aqueous solution(liquid ratio 50:1). Then, the retted leaf fibers had been soaked for 1hour, at room temperature in 0.5% NaClO solution(v/v) to remove the miscellaneous materials. We investigated the physical characteristics of three leaf fibers including the transversal and longitudinal morphology, the contents(%) of pectin, lignin and hemicellulose, the length and diameter of fibers, the tensile strength of the fiber bundles, and the fiber crystallinity and the moisture regain(%). The lengths of fiber from three leaf fibers were similar to their leaf lengths. The fiber bundles were composed of the cellulose paralleled to the fiber axis and the non-cellulose intersecting at right angle with the fiber axis. The diameters of New Zealand Flax, Henequen and Banana fibers were $25.13{\mu}m$, $18.16{\mu}m$ and $14.01{\mu}m$, respectively and their tensile strengths were 19.40 Mpa, 32.16 Mpa and 8.45 Mpa, respective. The non-cellulose contents of three leaf fibers were relatively as high as 40%. If the non-cellulose contents of leaf fibers might be controlled, leaf fibers could be used for the materials of textile fiber, non-wovens and Korean traditional paper, Hanjee.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.91-101
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• 2000

The emission sources of volatile organic compounds (VOCs) are wastewater treatment plants. sanitary landfills, automobile industries, and so on. The VOCs are harmful to human beings because of their toxicity and carcinogenicity, and cause the serious air pollution problem producing ozone ($O_3$) as a result of photochemical reaction. To investigate the emission of VOCs from wastewater treatment plant, aeration basins at the City of Los Angeles' Hyperion Treatment Plant were selected and measured flux was compared with calculated flux. For compounds commonly associated with wastewater (DCM, TCM, PCE, UM, DCB, UND) and not expected in vehicle exhaust or ambient air coming off the ocean, concentrations immediately downwind of the aeration basins were a factor of ten or higher than those measured in the upwind air. The airborne flux of less degradable or non-biodegradable compounds, e.g., DCE, DCM, TCA, DCA, TCM, PCE, DCB, through an imaginary plane at the downwind side of the aeration basins was in agreement with the estimated flux from measured liquid phase concentrations. Henry's constant. aeration rate, and an assumption of bubble saturation. For several compounds (PCE, DCE, TCA), the ratio (measured flux/calculated flux) is almost unity.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.291-298
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• 2016

Electrochemical water treatment process as a useful treatment method for the removal of non-degradable matter has been consistently studied for several decades. Key process of electrochemical water treatment are oxidation reaction from an anode and reduction from a cathode. In this study, the effect of pre-treatment methods in the insoluble electrode manufacturing process for the water treatment has been evaluated for the life time of electrode The results of this study showed that pre-treatment methods of a base metal such as surface roughness, clean method and interlayer formation influenced to life time of electrode when the same condition (catalyst electrode layer coating method and material system) was applied for pre-treatment methods. This study was conducted by using $IrO_2/Ti$ electrode In the test of sand-blasting process, an electrode manufactured by using sanding media of different sizes resulted in the most effective electrode life time when the size of alumina was used for $212{\sim}180{\mu}m$ praticle size (#80). The most effective method was considered using arc plasma in the additional roughness control and cleaning process, sputtering method to form Ta type interlayer formation process.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.1
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• pp.7-15
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• 2004

Nitric oxide (NO) system has been implicated in a wide range of physiological functions in the nervous system. However, the role of NO in regulating the neural activity in the gustatory zone of nucleus tractus solitarius (NTS) has not been established. The present study was aimed to investigate the role of NO in the gustatory NTS neurons. Sprague-Dawley rats, weighing about 50 g, were used. Whole cell patch recording and immunohistochemistry were done to determine the electrophysiological characteristics of the rostral gustatory nucleus of the tractus solitaries and distribution of NO synthases (NOS). Neuronal NOS (nNOS) immunoreactivity was strongly detected along the solitary tract extending from rostral to caudal medulla. Resting membrane potentials of NTS neurons were $-49.2{\pm}2\;mV$ and action potential amplitudes were $68.5{\pm}2\;mV$ with a mean duration measured at half amplitude of $1.7{\pm}0.3\;ms$. Input resistance, determined from the response to a 150 ms, -100 pA hyperpolarizing current pulse, was $385{\pm}15\;M{\Omega}$, Superfusion of SNAP or SNP, NO donors, produced either hyperpolarization (68%), depolarization (5%), or no effect (27%). The hyperpolarization was mostly accompanied by a decrease in input resistance. The hyperpolarization caused by SNAP or SNP increased the time to initiate the first action potential, and decreased the number of action potentials elicited by current injection. SNP or SNAP also markedly decreased the number of firing neural discharges of the spontaneous NTS neural activity under zero current. Superfusion of L-NAME, a NOS inhibitor, slightly depolarized the membrane potential and increased the firing rate of NTS neurons induced by current injection. ODQ, a soluble guanylate cyclase inhibitor, ameliorated the SNAP-induced changes in membrane potential, input resistance and firing rates. 8-Br-cGMP, a non-degradable cell-permeable cGMP, hyperpolarized the membrane potential and decreased the number of action potentials. It is suggested that NO in the gustatory NTS has an inhibitory role on the neural activity of NTS through activating soluble guanylate cyclase.

• Journal of Sericultural and Entomological Science
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• v.49 no.1
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• pp.24-27
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• 2007

Silkworm fed on the mulberry leaf mixed with silver nanoparticle to produce silver-nanoparticle embedded cocoon. Comparative analysis of silver content of cocoon shell, percentage of pupation and percentage of cocoon-shell weight showed that the optimum concentration and the feeding period of mulberry leaf mixed with silver nanoparticle were 500 ppm and the period from 3 day 5 instar to mounting of silkworm. The silver content of cocoon was observed variously by silkworm breedings. C212 variety makes pale yellow cocoon with the highest silver content(69%). Using the scanning electron microscope, we showed that the size of silver nanoparticles in silk was observed from 26.98 to 99.81nm. Silver-nanoparticle embedded silk is expected to use as high valuable application owing to the different functional properties including antibiotic characteristics and mechanical and electronic properties. The applicable fields expected is antistatic and/or electronic products with biological degradable natural materials.

• Korean Journal of Environmental Agriculture
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• v.40 no.3
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• pp.219-230
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• 2021

BACKGROUND: Biochar is a solid material converted from agricultural biomass such as crop residues and pruning branch through pyrolysis under limited oxygen supply. Biochar consists of non-degradable carbon (C) double bonds and aromatic ring that are not readily broken down by microbial degradation in the soils. Due to the recalcitrancy of C in biochar, biochar application to the soils is of help in enhancing soil carbon sequestration in arable lands that might be a strategy of agricultural sector to mitigate climate change. METHODS AND RESULTS: Data were collected from studies on the effect of biochar application on soil C content conducted in East Asian countries including China, Japan and Korea under different experimental conditions (incubation, column, pot, and field). The magnitude of soil C storage was positively correlated (p < 0.001) with biochar application rate under field conditions, reflecting accumulation of recalcitrant black C in the biochar. However, The changes in soil C contents per C input from biochar (% per t/ha) were 6.80 in field condition, and 12.58 in laboratory condition. The magnitude of increment of soil C was lower in field than in laboratory conditions due to potential loss of C through weathering of biochar under field conditions. Biochar production condition also affected soil C increment; more C increment was found with biochar produced at a high temperature (over 450℃). CONCLUSION: This review suggests that biochar application is a potential measures of C sequestration in agricultural soils. However, as the increment of soil C biochar was affected by biochar types, further studies are necessary to find better biochar types for enhanced soil C storage.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.23-33
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• 2020

Marine algae(Macro algae) are easily bio-degradable, and by-products are available as feed and fertilizer. The biomass of marine algae has higher CO2 absorption capacity than the wood system, and is highly valuable in use due to its fast growth speed and wide cultivation area without special cost for raw material production. In 2018, Marine algae production was 1,722,486ton, such as Saccharina japonica, Undaria pinnatifida and Porphyra tenera, the large amounts of by-products have been generated in the food processing facilities for commercialization. In this study, Saccharina japonica, Undaria pinnatifida were collected in the south coast region and Porphyra tenera was collected in the west coast region. The theoretical methane potential and biochemical methane potential(BMP) were analyzed, and Modified Gompertz model and Parallel first order kinetics model were adopted for the interpretation of the cumulative methane production curves. The theoretical methane potential of Saccharina japonica, Undaria pinnatifida and Porphyra tenera were 0.393, 0.373 and 0.435 N㎥/kg-VS, respectively. BMP obtained by the Modified gompertz model 0.226, 0.227, and 0.241 N㎥/kg-VS for Saccharina japonica, Undaria pinnatifida and Porphyra tenera, respectively. And BMP obtained by the Parallel first order kinetics model were 0.220, 0.243, and 0.240 N㎥/kg-VS for Saccharina japonica, Undaria pinnatifida and Porphyra tenera, respectively.