• Polymer(Korea)
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• v.36 no.3
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• pp.287-294
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• 2012

ZnAl-LDH(layered double hydroxide) (Zn:Al=2:1 mole ratio) modified with stearic acid (SA) or oleic acid (OA) was synthesized by a coprecipitation method and compounded to SAN polymer at various contents. All the SAN composites were manufactured by a co-rotating twin-screw extruder and subsequently injection molded into several specimen. Morphology, transparency, and thermal resistance of these composites were evaluated by TEM, XRD(X-ray diffractometry), UV-Vis spectrophotometry, and thermogravimetric analysis. SAN nanocomposites containing OA-$Zn_2Al$ LDH showed better optical transmittance than SAN nanocomposites containing SA-$Zn_2Al$ LDH. All the SAN nanocomposites containing OA-$Zn_2Al$ LDH or SA-$Zn_2Al$ LDH exhibited improvement of thermal resistance at second stage of thermal oxidation. These results were explained by the fact that the interaction between organic modifier and polymer performed an important role in the property improvement of polymer nanocomposites.

• Korean Journal of Weed Science
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• v.18 no.4
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• pp.348-355
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• 1998

This study was conducted to identify allelopathic compounds in rye and oat straw extracts by HPLC analysis. These extracts were analyzed with 12 standard chemicals including salicylic acid. 11 chemicals in rye extract except for naringin and in oat extract except for catechin were identified. Salicylic acid(8.34mg/g) in rye straw extracts and naringin(7.50mg/g) in oat straw extracts among these standard chemicals were identified as the largest amount substance. The germination of Chenopodium ablum seeds was significantly inhibited by these chemicals at $10^{-3}$ and $10^{-4}M$ concentrations as compared to control. Salicylic acid in rye and naringin in oat were considered as the major allelopathic substances although allelopathy may be caused by an interaction of many substances. Yet many unidentified chemical compounds are present in both extracts.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.293-299
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• 2014

The bentonite, a buffer material, is essential for the deep geological disposal of HLW (high-level radioactive waste), and it is important to know its characteristic long-term evolution in the underground environment. With an assumption that the concentration of aqueous copper ions will increase if copper-coated materials on a metal canister are corroded, we examined some characteristic ion-exchanges and cation release phenomena occurring in the bentonite clay (montmorillonite) interacted with aqueous Cu cations. During the interaction between dissolved copper and bentonite, Na rather than Ca cations in the expandable clay were preferentially replaced by Cu ions in the experiment. In addition, the Cu-exchanged montmorillonite was characterized by an asymmetric X-ray diffracted pattern with relatively collapsed interlayers compared to the raw sample. These results indicate that the gradual change of the original bentonite property may occur in a underground disposal condition. We are going to further study the characteristic chemical and mineralogical changes of the bentonite buffer to be used for the disposal site by conducting additional experiments.

• Advances in Traditional Medicine
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• v.6 no.4
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• pp.274-285
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• 2006

Allium sativum (Family Amaryllidaceae or Liliaceae) is used worldwide for various clinical uses like hypertension, cholesterol lowering effect, antiplatelets and fibrinolytic activity etc. Due to these common house hold uses of Allium sativum, as a herbal supplements, and failure of patients to inform their physician of the over-the-counter supplements they consume leads to drugnutrient interactions with components in herbal supplements. Today these types of interactions between a herbal supplement and clinically prescribed drugs are an increasing concern. In vitro studies indicated that garlic constituents modulated various CYP (cytochrome P450) enzymes. CYP 3A4 is abundantly present in human liver and small intestine and contributes to the metabolism of more than 50% of commonly used drugs including nifedipine, cyclosporine, erythromycin, midazolam, alprazolam, and triazolam. Extracts from fresh and aged garlic inhibited CYP 3A4 in human liver microsomes. The in vivo effects of garlic constituents are found to be species depended and the dosing regimen of garlic constituents appeared to influence the modulation of various CYP isoforms. Studies have indicated that the inhibition of various CYPs by organosulfur compounds from garlic was related to their structure also. Studies using in vitro, in vivo, animal and human models have indicated that various garlic constituents can be the substrates, inhibitors and or inducers of various CYP enzymes. The modulation of CYP enzyme activity and expression are dependent on the type and chemical structure of garlic constituents, dose regime, animal species and tissue, and source of garlic thus this review throws light on the possible herb drug interaction with the use of garlic.

• Clean Technology
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• v.17 no.2
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• pp.97-102
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• 2011

The adsorption characteristics of amatanth dye by granular activated carbon were experimently investigated in the batch adsorption. Kinetic studies of adsorption of amaranth dye were carried out at 298, 308 and 318 K, using aqueous solutions with 100, 200 and 300 mg/L initial concentration of amatanth. It was established that the adsorption equilibrium of amaranth dye on granular activated carbon was successfully fitted by Langmuir isotherm equation at 298 K. The pseudo first order and pseudo second order models were used to evaluate the kinetic data and the pseudo second order kinetic model was the best with good correlation. Values of the rate constant ($k_2$) have been calculated as 0.1076, 0.0531, and 0.0309 g/mg h at 100, 200 and 300 mg/L initial concentration of amatanth, respectively. Thermodynamic parameter such as activation energy, standard enthalpy, standard entropy and standard free energy were evaluated. The estimated values for standard free energy were -5.08 - -8.10 kJ/mol over activated carbon at 200 mg/L, indicated toward a spontaneous process. The positive value for enthalpy, 38.89 kJ/mol indicates that adsorption interaction of amatanth dye on activated carbon is an endothermic process.

• Journal of Soil and Groundwater Environment
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• v.16 no.2
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• pp.61-76
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• 2011

This study was objected to provide suggestions for best management practices to restore the cultural and historical values of the wells in Palaces as well as their water qualities. Water resources in the five Palaces in Seoul Metropolitan, including Gyeongbokgung, Changdeokgung, Changgyeonggung, Jongmyo Shrine, and Deoksugung, were surveyed for their physical flows and chemical compositions from April to July in 2010. Ground waters in most wells were found at depths within 5 m from the ground surface, showing typical water-table aquifer systems. Hydraulic gradients indicate water resources in Gyeongbokgung, Changdeokgung, and Changgyeonggung flowing toward south, and toward east in Deoksugung area. Especially, water-level fluctuation data at S-10 in Deoksugung implied the influence of groundwater discharge facility. In Jongmyo Shrine, water was not detected in wells, indicating the water level was lower than the well depth. Based on the water chemistry and stable isotope analyses, water resources and their qualities appeared to be formed by the water-rock interaction along the groundwater paths. S-10 (Deoksugung) and S-14 (Changgyeonggung) samples were contaminated with nitrate ($NO_3$) in levels of higher than Korean drinking water standard, 10 mg/L as $NO_3$-N, but once in four sampling campaigns. In the situation that water resources in Palaces still maintain natural characteristics, the materials that will be used for the restoration and improvement of the Palace water supplies should be carefully selected not to disturb the natural integrity. In addition, because the wells are located in the center of metropolitan area, a systematic monitoring should be applied to detect and to manage the potential impacts of underground construction and various pollution sources.

• Korean Journal of Clinical Pharmacy
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• v.26 no.4
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• pp.324-329
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• 2016

Background: With the development of information and communication technology, there is a growing number of people looking for health information on the internet. This pilot study was performed to analyze the pattern of pharmacist consultation on the internet portal site. Methods: Questions and answers posted on the portal site "Naver Jisik-iN" from March 1st to 31th in 2016 were collected. Medications asked were categorized into prescription drugs, nonprescription drugs, sanitary aids, emergency drugs, functional health foods, and others. Medications were subcategorized into 14 according to the anatomical therapeutic chemical classification system. Questions were divided into 10 categories based on Hepler's drug-related problems. Results: Of the 955 cases, females accounted for 59.5% and inquirers from 11 to 40 years old, 89.4%. The number of prescription drugs, nonprescription drugs, sanitary aids, emergency drugs, functional health foods, and others were 428 (44.8%), 328 (34.3%), 31 (3.3%), 2 (0.2%), 122 (12.8%), and 44 (4.6%), respectively. Questions for drugs acting on alimentary tract and metabolism took up 27.4% followed by those on nervous system, 13.6% and anti-infectives for systemic use, 12.2%. Pharmacist consultation regarding drug information, drug interaction, and adverse reaction occupied 47.9%, 15.2%, and 12.3%, respectively. Conclusion: Health counseling through online is predicted to increase steadily, so pharmacists should broaden their boundaries beyond off-line pharmacies to meet social needs.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.811-817
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• 2003

Recently, application fields of non-metallic minerals by utilizing their structure properties are broadening. Especially, layered minerals have not only excellent shielding or covering ability but also absorbing and storing characteristics of chemical elements between a layers. We considered about the above mentioned characteristics and added functional substances onto their surfaces for the preparation of new environmentally friendly functional materials. In this study, natural graphite and sericite were mainly used to produce for the new environmentally friendly functional building materials. Graphite surfaces were modified with a surfactant (Alkyl Benzyle Demethyle Ammonium Chloride) for anti-bacillus and penicillium. Surface modification mechanism are that primary adsorption by differential zeta potential between graphite and ABDM and secondary adsorption by interaction between surfactant chains take place. Surfactant layers were fully formed and it was expected up to 99.7% up the efficiency of anti-bacillus and penicillium. Also the prepared functional samples have a effect to improve a various efficiency such as electromagnetic wave shield(up to 95%), deodorization(up to 80%), heat storage(5%) etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.150-150
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• 2010

Carbon nanotubes have drawn attention as one of the most promising emitter materials ever known not only due to their nanometer-scale radius of curvature at tip and extremely high aspect ratios but also due to their strong mechanical strength, excellent thermal conductivity, good chemical stability, etc. Some applications of CNTs as emitters, such as X-ray tubes and microwave amplifiers, require high current emission over a small emitter area. The field emission for high current density often damages CNT emitters by Joule heating, field evaporation, or electrostatic interaction. In order to endure the high current density emission, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects: highly crystalline CNT materials, low gas emission during electron emission in vacuum, optimal emitter distribution density, optimal aspect ratio of emitters, uniform emitter height, strong emitter adhesion onto a substrate, etc. We attempted a novel approach to fabricate CNT emitters to meet some of requirements described above, including highly crystalline CNT materials, low gas emission, and strong emitter adhesion. In this study, CNT emitters were fabricated by filtrating an aqueous suspension of highly crystalline thin multiwalled CNTs (Hanwha Nanotech Inc.) through a metal mesh. The metal mesh served as a support and fixture frame of CNT emitters. When 5 ml of the CNT suspension was engaged in filtration through a 400 mesh, the CNT layers were formed to be as thick as the mesh at the mesh openings. The CNT emitter sample of $1{\times}1\;cm^2$ in size was characteristic of the turn-on electrical field of 2.7 V/${\mu}m$ and the current density of 14.5 mA at 5.8 V/${\mu}m$ without noticeable deterioration of emitters. This study seems to provide a novel fabrication route to simply produce small-size CNT emitters for high current emission with reliability.

• Journal of Environmental Science International
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• v.22 no.10
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• pp.1263-1271
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• 2013

Graphene oxide (GO)-titania composites have emerged as an attractive heterogeneous photocatalyst that can enhance the photocatalytic activity of $TiO_2$ nanoparticles owing to their potential interaction of electronic and adsorption natures. Accordingly, $TiO_2$-GO mixtures were synthesized in this study using a simple chemical mixing process, and their heterogeneous photocatalytic activities were investigated to determine the degradation of airborne organic pollutants (benzene, ethyl benzene, and o-xylene (BEX)) under different operational conditions. The Fourier transform infrared spectroscopy results demonstrated the presence of GO for the $TiO_2$-GO composites. The average efficiencies of the $TiO_2$-GO mixtures for the decomposition of each component of BEX determined during the 3-h photocatalytic processes were 26%, 92%, and 96%, respectively, whereas the average efficiencies of the unmodified $TiO_2$ powder were 3%, 8%, and 10%, respectively. Furthermore, the degradation efficiency of the unmodified $TiO_2$ powder for all target compounds decreased during the 3-h photocatalytic processes, suggesting a potential deactivation even during such a short time period. Two operational conditions (air flow entering into the air-cleaning devices and the indoor pollution levels) were found to be important factors for the photocatalytic decomposition of BEX molecules. Taken together, these results show that a $TiO_2$-GO mixture can be applied effectively for the purification of airborne organic pollutants when the operating conditions are optimized.