• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1190-1197
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• 2016

The acid response of Bifidobacterium longum subsp. longum BBMN68 has been studied in our previous study. The fab gene, which is supposed to be involved in membrane fatty acid biosynthesis, was demonstrated to be induced in acid response. In order to investigate the relationship between acid response and cell membrane fatty acid composition, the acid adaptation of BBMN68 was assessed and the membrane fatty acid composition at different adaptation conditions was identified. Indeed, the fatty acid composition was influenced by acid adaptation. Our results showed that the effective acid adaptations were accompanied with decrease in the unsaturated to saturated fatty acids ratio (UFA/SFA) and increase in cyclopropane fatty acid (CFA) content, which corresponded to previous studies. Moreover, both effective and non-effective acid adaptation conditions resulted in decrease in the C_18:1 cis-9/C_18:1 trans-9 ratio, indicating that the C_18:1 cis-9/C_18:1 trans-9 ratio is associated with acid tolerance response but not with acid adaptation response. Taken together, this study indicated that the UFA/SFA and CFA content of BBMN68 were involved in acid adaptation and the C_18:1 cis-9/C_18:1 trans-9 ratio was involved in acid tolerance response.

• Journal of Korea Foundry Society
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• v.18 no.6
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• pp.593-603
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• 1998

Commercial ductile iron was coated with titanium and aluminum powders by low pressure plasma spraying and then irradiated with a $CO_2$ laser to produce anti-corrosive TiC composite layer. TiC carbides were precipitated homogeneously in a laser alloyed layer by in-situ reaction between carbon existed in the base metal and titanium with thermal sprayed coating. The formation of gas pores and brittle limited mixing zone with ledeburite microstructure in TiC composite layer were surpressed by the complementary alloying of aluminum. The hardness of TiC composite layer obtained by addition of titanium and aluminum was between 600 and 660 Hv, which was three times as high as the hardness of ferritic ductile iron. From the results of isothermal oxidation at 1123k for 24 hours in air, high temperature oxidation resistance of the TiC composite layer with aluminum was improved and doubled when compared with the TiC composite layer without aluminum.

• Journal of Powder Materials
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• v.18 no.3
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• pp.297-302
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• 2011

Colloidal stability is one of crucial factors for many applications of nanodiamond. Despite recent development, nanodiamonds available on the market often exhibit a high impurity content, wide size distribution of aggregates and low resistance to sedimentation. In the current study, four commercial nanodiamond powders synthesized by detonation synthesis were surface modified and then separated with respect to the size into six fractions by centrifugation. The fractions were evaluated by zeta potential, particle size distribution and elemental composition. The results showed that the modified nanodiamonds form stable colloidal suspensions without sedimentation for a long time.

• Journal of the Korean Institute of Gas
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• v.26 no.2
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• pp.1-8
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• 2022

The purpose of this study is to prepare GPTMS((3-Glycidoxypropyl) trimethoxysilane)-SiO₂ nanofluid and analyze the effect of nanofluid injection on carbonate reservoirs. Structural analysis of silica nanoparticles modified by GPTMS was investigated by FTIR(Fourier transform infrared spectroscopy). C-H stretching vibrations at 2,950 cm^-1 indicating the silica surface modification with GPTMS were observed when the silane feed was over 0.5 mmol/g. Also, the coreflooding test by nanofluid injection on the aged limestone and dolomite plug samples was carried out with different particle concentration and flow rate. The incremental oil recovery was up to 18.9%, and contact angle and permeability of carbonate samples were changed by the effect of nanoparticle adsorption on pore which caused wettability alteration and pore size change. Therefore, the prepared nanofluid will be utilized as an injection fluid for enhancing oil recovery and modifying fluid flow properties such as change of rock wettability and permeability in carbonate reservoirs.

• Fibers and Polymers
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• v.3 no.1
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• pp.18-23
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• 2002

The structure development and dynamic properties of fibers produced by high-speed spinning of P(EN-ET) random copolymers were investigated. The as-spun fibers were found to remain amorphous up to the spinning speed of 1500 m/min, and subsequent increases in speed resulted in the crystalline domains containing primarily $\alpha$ crystalline modification of PEN. The f modification was not found up to spinning speeds of 4500 m/min. On the other hand, annealing of constrained fibers spun at the 2100 m/min at 180,200, and 240^{\circ}C$ exhibited $\beta$-form crystalline structure, while the annealed fibers spun in 600-1500 m/min range exhibited dominantly $\alpha$-form. However $\beta$-form crystals disappeared above the spinning speed of 3000 m/min. With increasing spinning speeds from 600 to 4500 m/min, the storage modulus of as-spun fibers increased continuously and reached a value of about 10.4 spa at room temperature. The tan $\delta$curves showed the $\alpha$-relaxation peak at about 155-165^{\circ}C$, which is considered to correspond to the glass transition. The $\alpha$-relaxation peaks became smaller and broader, and shift to higher temperatures as the spinning speed increases, meaning that molecular mobility in the amorphous region is restricted by increased crystalline domain.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.1
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• pp.51-58
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• 2002

Destruction process of toluene using a wire-cylindrical BBD (Dielectric Barrier Discharge) reactor packed with catalysts was investigated to characterize the synergetic effects of non-thermal plasma and catalyst process. The catalysts used in the present study were ${\gamma}$-Al$_2$BO$_3$ and Pt/${\gamma}$-Al$_2$O$_3$. Under the numerous test conditions, specific energy density (SED (J/L)) and the conversion of toluene, defined as (1 -[C$_{f}$]/[C$_{i}$]), were measured. The test results showed that toluene decomposition efficiency followed the pseudo-first order in the case of plasma only process. The pseudo-first order process, however, was modified to pseudo-zeroth order reaction in the case of catalyst-assisted plasma process. This modification of the reaction order was verified based on a simple kinetic model proposed in the present study. Owing to the modification of reaction order, which resulted from the catalytic process, the specific energy to achieve the high removal efficiencies, i.e. 80~90%, was reduced significantly.y.y.

• Journal of the Korean Vacuum Society
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• v.18 no.1
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• pp.1-8
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• 2009

Hydrophilic Surface modification of Polysarene (PS) was performed by Atmospheric Pressure Plasma (APP). Air or 0, gases were used for carrier gases and RF power was changed from 150 to 350 W. We controlled the treatment time as 1 time to 4 time passing through the plasma region. when the carrier gas was air, the water contact angle on the PS surface was decreased from $91^{\circ}$ to $20^{\circ}$. And the surface energy increased from 45.74 dyne/cm to 68.48 dyne/cm. In case of the $O_2$ plasma treatment, at 300 W of RF power and 4 times treatment, the water contact angle on the PS. Surface was decreased from $91^{\circ}$ to $17^{\circ}$ and the surface energy was increased from 45.74 dyne/cm to 69.73 dyne/cm. The surface energy was increased by polar force not by dispersion force. Improvement of surface properties can be explained by the formation of new hydrophilic groups which is identified as C-O, C=O by XPS analysis. The contact angle of APP treated PS surface kept in air was increased with time elapse, but maintained same value when it was kept in water. We treated the PS surface by APP and deposited Cu as $4,000\;{\AA}$ and $8,000\;{\AA}$ by thermal evaporation. The adhesion between sample and Cu thin film improvement of treated PS surface against untreated sample. could be verifiable by Tape test (ASTM D3359)

• Elastomers and Composites
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• v.48 no.1
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• pp.18-23
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• 2013

Nylon 12 elastomer was slightly crosslinked in molten state by the addition of small amount of dicumyl peroxide (DCP) as a crosslink agent and triallycyanuate (TAC) as a co-agent during melt compounding at $160^{\circ}C$ in an internal mixer. The effect of the peroxide crosslinking on mechanical, dynamic mechanical and rheological properties of the nylon 12 elastomer was investigated by means of tensile testing, dynamic mechanical analysis (DMA) and small amplitude oscillating rheometer, respectively. With modification, there is an improvement in tensile modulus and Young's modulus with decease in elongation at break. DMA results for peroxide modified nylon 12 elastomers demonstrated that the glass transiaiton temperature of PTMG segment shifted to higher temperature and the storage modulus remained constant above the melting temperature of nylon 12 segments. Melt rheological studies revealed that the peroxide modified nylon 12 elastomer exhibited a more solid like behavior and stronger shear thinning behavior compared to neat nylon 12 elastomer, which was more prominent at higher TAC content in the polymer matrix. The peroxide modified nylon 12 elastomer exhibited good elastic recoverability and improved mechanical properties without sacrificing melt processibilty, and especially the service temperature range increased as compared to neat nylon 12 elastomer.

• Polymer(Korea)
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• v.32 no.5
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• pp.497-500
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• 2008

Polystyrene foam (styrofoam) was treated with low-temperature oxygen plasma by means of immobilization and grafting techniques in order to modify its hydrophobic surface property to hydrophilic one using hydrophilic monomers of acrylic acid and acrylamide, and its surface chemical structure, morphology, and hydrophilicity were examined by ESCA, field emission scanning electron microscope (FESEM), and contactangle meter. The experimental evidences, such as the increases of O/C and N/C ratios in ESCA spectrum, thin film deposition, decrease in contact-angle, strongly suggested that the plasma treatments were useful methods for the preparation of hydrophilic surface. Contact angle diminished drastically from $84^{\circ}$ to $18{\sim}19^{\circ}$. Acrylamide, compared to acrylic acid, appeared to play a decisive role, and to be more powerful agent for improving its surface hydrophilicity.

• Journal of Life Science
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• v.19 no.2
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• pp.198-205
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• 2009

The purpose of this study was to find out the effects of a 12-week aerobic exercise plus lifestyle modification on obese-induced metabolic syndrome in obese adolescent girls. A total of 52 obese adolescent girls (13-14 years old; body mass index (BMI) ${\geq}$95th percentiles for age and sex) purposely assigned to aerobic exercise group (AEG, n=15), aerobic exercise plus lifestyle modification group (ALG, n=18), or control group (CG, n=19). The AEG completed 12 weeks of walking exercise (30-60 min/day, 65-75% HRmax, 6 days/week), the ALG completed 12 weeks of walking exercise (30-60 min/day, 65-75% HRmax, 6 days/week) and behavior modification (60 min/day, 1 day/week), and the CG continued their normal life. The presence of the metabolic syndrome and component risk factors were determined before and after 12-week programs. The total prevalence of the metabolic syndrome was 48.1% in this sample (25/52) of participants at baseline. After the programs the prevalence of the metabolic syndrome was improved in the AEG and ALG 33.3, 27.8%, respectively. Group analyses showed significant difference in risk factors of the metabolic syndrome such that the AEG and ALG had significantly greater improvements in waist circumference, triglycerides, blood glucose and systolic blood pressure than the CG, while there were no significant difference in HDL cholesterol and diastolic blood pressure. Also there was no group difference between AEG and ALG in all measured metabolic risk factors after the programs. These results indicate that the positive changes of the ALG were not associated with lifestyle modification (behavior modification) but associated with aerobic exercise. However, long-term follow up studies are necessary to clarify the additive effect of the behavior modification on the metabolic syndrome.