Evaluation of Equivalent Thermal Conductivity for Carbon Fiber-Reinforced Bentonite through Experimental and Numerical Analysis

Bentonite is widely used as a water-proof material in engineering, and fibers are added to reduce the crack development of bentonite after drying. Carbon fiber can reinforce bentonite in heat-sensitive projects because of its high thermal conductivity and potential inhibition of bentonite cracking. Thus, it is important to determine the thermal conductivity of carbon fiber-reinforced bentonite. This study evaluated the thermal conductivity of carbon fiber-reinforced bentonite by analytical solution, experiment, and finite element method (FEM) simulation and discussed the effects of carbon fiber content, fiber length, fiber distribution, and the porosity of bentonite on the thermal conductivity of reinforced bentonite. The results show that the addition of carbon fiber can effectively improve the thermal conductivity of bentonite, and the thermal conductivity of the mixture is positively correlated with the content of fibers and the dry density of bentonite. When the content of carbon fiber with a thermal conductivity of 1000 W/(m K) is 1.0 %, and the porosity of bentonite is 0.4, the thermal conductivity of the composite can be increased by up to 390 %. At the same time, the distribution of fibers plays a vital role in thermal conductivity, and the thermal conductivity in the case of parallel distribution is 1.48 and 2.91 times that of random distribution and serial distribution. In addition, longer fiber length will help improve the thermal conductivity of the mixture. The thermal conductivity of the mixture for 1-inch fibers is 1.11 and 1.29 times that of 1/2-inch and 1/4-inch fibers. This study provides evidence of the possibility of improving the thermal conductivity of carbon fiber-reinforced bentonite

Friends matter. The relationship between Korean international students\u27 friendship networks and study abroad outcomes

This study examined the determinants of international students\u27 interactions with different friendship networks and the relationships of these interactions with study abroad outcomes, using data from 482 Korean college students who had participated in international student exchange programs. The results showed that students\u27 participation in extracurricular and off-campus activities while studying abroad was significantly related to their interactions with local and other international students. The results also showed that students\u27 interactions with co-national, local, and other international students while studying abroad were positively associated with their intercultural competence, personal development, and career development, even after controlling for other variables. We discuss the policy implications of these findings beyond the Korean context. (DIPF/Orig.

Highly oxygen-stable CO2 reductase-catalyzed bioconversion of carbon dioxide into formate in electrochemical reactor

Electrochemical reduction of carbon dioxide (CO2) into value-added chemicals have been one of promising issues to utilize greenhouse gas for the storage of hydrogen, bioplastic, fuel cell et al. Among many potential candidates such as formate, alcohols, ethylene, etc., formate was known one of most promising chemicals through the addition of two elections and one proton during electro-catalytic reduction of CO2. Here, our group has developed efficient CO2 reductase-catalyzed conversion of CO2 into formate in electrochemical reactor. Electro-biocatalytic reduction of CO2 into formate have three main challenges. Formate dehydrogenase(FDH) have been one of potential CO2 reductase candidates but the activity of many FDHs for formate oxidation was superior than that of CO2 reduction. However, recombinant MeFDH1 in our study showed significantly higher preference for CO2 reduction with 209 (±10.66) s-1 of turnover rate than that of formate oxidation with 85.62 (± 5.76) s-1. In addition, the value of kinetic equilibrium constant (Keq), which determines the direction of reaction in reversible catalysis, implied that kinetic preference for CO2 reduction is 62.3-folds higher than that for formate oxidation. This kinetics analysis allowed MeFDH1 to be referred to as the CO2 reductase. As another challenge, Mo- or W-containing formate dehydrogenase was known vulnerable against oxygen molecule. As contrasted with the high oxygen-sensitivity of FDHs from other strains, MeFDH1 was not deactivated even under 0.13 mM of dissolved oxygen. At a range of oxygen level (0.1 % to 4 %) in the composition of Carbon Capture and Storage (CCS) gas, MeFDH1 was consequently stable without considerable decreased activity. Lastly, the long-term stability of CO2 reduction reaction system has been indispensable issue in both biocatalysts and chemical catalysts. Through the immobilization of MeFDH1, the enhanced stability for long-term operation leaded the formate formation over 500 mM with high volumetric productivity for several days

Topically administered bevacizumab had longer standing anti-angiogenic effect than subconjunctivally injected bevacizumab in rat corneal neovacularization

<b>AIM:</b> To compare the effect of topically administered and subconjunctivally injected bevacizumab on experimental corneal neovascularization in rats for two weeks after treatment.<b>METHODS:</b> Twenty-eight Sprague-Dawley rats were divided into four groups of 7 animals. Each corneal center of right eye was cauterized with silver/potassium nitrate for 8s. After corneal burning, bevacizumab (12.5mg/mL) was topically administered three times per day (TB group) for two weeks or subconjunctivally injected on days 2 and 4 after cauterization (0.02mL; SB group). As negative controls, rats received 0.9% saline topically three times per day (TS group) or subconjunctivally on days 2 and 4 (0.02mL; SS group). Digital photographs of the cornea were taken 1 and 2 weeks after treatment and analyzed to determine the area of cornea covered by neovascularization as the percentage of corneal neovascularization.<b>RESULTS:</b> One week after treatment, the percentage of corneal neovascularization was significantly lower in the TB and SB groups than in the TS and SS groups (all <i>P</i><0.05). Two weeks after treatment, the percentage of corneal neovascularization was significantly lower in the TB group than in the TS group (<i>P</i><0.05). In all groups, the percentage of neovascularization was decreasing as time passed (all <i>P</i><0.05)<b>CONCLUSION:</b> Topically administered bevacizumab has longer standing anti-angiogenic effect than subconjunctivally injected bevacizumab in corneal neovascularization following chemical injury in rats