• Analytical Science and Technology
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• v.6 no.1
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• pp.39-45
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• 1993

We have examined Raman spectra of cis-peptide model complex, diketopiperazine in water and $D_2O$ with 320 nm through 218 nm excitation. Our study examines assignment of the resonance enhanced amide vibrations and characterizes their enhancement mechanism. Three resonance enhaned cis-peptide marker bands were observed in aqueous solution at 1676, 1533 and $806cm^{-1}$, which were assigned to the cis-amide I, II and S band, respectively. The $1533cm^{-1}$ amide II band, which is almost pure C-N stretching, was most dominant in water and shifted to $1520cm^{-1}$ upon N-deuteration. This band will be probably a potential probe band for cis-peptide moieties in proteins. The excitation profile data and an Albrecht A-term fit indicated that the cis-peptide vibrations derive their intensities from the 188 nm cis-peptide ${\pi}-{\pi}^*$ electronic transition. We Propose that the geometry of cis-peptide ${\pi}^*$ excited state is C-N bond displacement relative to that of electronic ground state.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.447-452
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• 2020

In this work, α-Fe₂O₃ nanocrystals are synthesized by co-precipitation method and used as adsorbent to remove Cr⁶⁺, Cd²⁺, and Pb²⁺ from wastewater at room temperature. The prepared sample is evaluated by XRD, BET surface area, and FESEM for structural and morphological characteristics. XRD patterns confirm the formation of a pure hematite structure of average particle size of ~ 40 nm, which is further supported by the FESEM images of the nanocrystals. The nanocrystals are found to have BET specific surface area of ~ 39.18 m² g^-1. Adsorption experiments are carried out for the different values of pH of the solutions, contact time, and initial concentration of metal ions. High efficiency Cr⁶⁺, Cd²⁺, and Pb²⁺ removal occur at pH 3, 7, and 5.5, respectively. Equilibrium study reveals that the heavy metal ion adsorption of the α-Fe₂O₃ nanocrystals followed Langmuir and Freundlich isotherm models. The Cr⁶⁺, Cd²⁺, and Pb²⁺ adsorption equilibrium data are best fitted to the Langmuir model. The maximum adsorption capacities of α-Fe₂O₃ nanocrystals related to Cr⁶⁺, Cd²⁺, and Pb²⁺ are found to be 15.15, 11.63, and 20 mg g^-1, respectively. These results clearly suggest that the synthesized α-Fe₂O₃ nanocrystals can be considered as potential nano-adsorbents for future environmental and health related applications.

• Macromolecular Research
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• v.17 no.9
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• pp.688-696
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• 2009

In this study, a new class of polyurethane (PU) nanofibers containing silver (Ag) nanoparticles (NPs) was synthesized by electrospinning. A simple method that did not depending on additional foreign chemicals was used to self synthesize the silver NPs in/on PU nanofibers. The synthesis of silver NPs was carried out by exploiting the reduction ability of N,N-dimethylformamide (DMF), which is used mainly to decompose silver nitrate to silver NPs. Typically, a sol-gel consisting of $AgNO_3$/PU was electrospun and aged for one week. Silver NPs were created in/on PU nanofibers. SEM confirmed the well oriented nanofibers and good dispersion of pure silver NPs. TEM indicated that the Ag NPs were 5 to 20 nm in diameter. XRD demonstrated the good crystalline features of silver metal. The mechanical properties of the nanofiber mats showed improvement with increasing silver NPs content. The fixedness of the silver NPs obtained on PU nanofibers was examined by harsh successive washing of the as-prepared mats using a large amount of water. The results confirmed the good stability of the synthesized nanofiber mats. Two model organisms, E. coli and S. typhimurium, were used to check the antimicrobial influence of these nanofiber mats. Subsequently, antimicrobial tests indicated that the prepared nanofibers have a high bactericidal effect. Accordingly, these results highlight the potential use of these nanofiber mats as antimicrobial agents.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.4
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• pp.266-273
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• 2008

Natural gas hydrates are ice-like solid substances, which are composed of water and natural gas, mainly methane. They have three kinds of crystal structures of five polyhedra formed by hydrogen-bonded water molecules, and are stable at high pressures and low temperatures. They contain large amounts of organic carbon and widely occur in deep oceans and permafrost regions. Therefore, they are expected as a potential energy resource in the future. Especially, $1m^3$ natural gas hydrate contains up to $172Nm^3$ of methane gas, de pending on the pressure and temperature of production. Such large volumes make natural gas hydrates can be used to store and transport natural gas. In this study, three-phase equilibrium conditions for forming natural gas hydrate were numerically obtained in pure water and single electrolyte solution containing 3 wt% NaCl. The results show that the predictions match the previous experimental values very well, and it was found that NaCl acts as an inhibitor. Also, help gases such that ethane, propane, i-butane, and n-butane reduce the hydrate formation pressure at the same temperature.

• Journal of Ginseng Research
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• v.38 no.1
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• pp.28-33
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• 2014

Background: Panax notoginseng has been used as a general tonic agent to invigorate human body for millennia in China and continued to be used until present. Methods: Some chromatographic methods were performed to isolate pure triterpenoids, and their structures were determined by nuclear magnetic resonance (NMR) experiments. Anti-diabetes activities of isolated compounds were evaluated through their inhibitory activity of protein tyrosine phosphatase 1B (PTP1B) enzyme. Results and Conclusion: Three new dammarane-type triterpenoids, notoginsenoside-LX (1), notoginsenoside-LY (2), and notoginsenoside-FZ (3) together with eighteen known compounds were isolated from the Panax notoginseng leaves. The structure-activity relationship of the compounds with dammaranetype triterpenoids and their PTP1B inhibitory activity were also reported. Results showed that compounds 2, 15, 20, and 21 can significantly inhibit the enzyme activity of PTP1B in a dose-dependent manner, with inhibitory concentration 50 ($IC_{50}$) values of $29.08{\mu}M$, $21.27{\mu}M$, $28.12{\mu}M$, and $26.59{\mu}M$, respectively. The results suggested that Panax notoginseng leaves might have potential as a new therapeutic agent for the treatment of diabetes.

• Journal of the Korean Chemical Society
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• v.20 no.6
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• pp.486-493
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• 1976

The PVC mixed silver iodide pellet was prepared by means of the Infrared Pellet presser and the pellet was used as an indicating membrane electrode, to measure the potentials for various silver ion activities, ranging from $10^{-1}$ to $10^{-6}$ M. The potential responses to silver ion activities were linear and the slope was much close to Nernstian relation as compared with that of the pure silver iodide pellet membrane electrode and the PVC coated silver iodide pellet membrane electrode. The mechanical property and chemical durability of this electrode were found much better than the others. This electrode did not show significant response to the other except silver ion, but had good response to halide ions, i.e., iodide, chloride, bromide and cyanide ions, in the concentration range $10^{-1}$ to $10^{-6}$ M. This electrode could be used as an indicating electrode in potentiometric titrations of single halide ion and also halide mixture with standard solution of silver nitrate.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1733-1739
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• 2017

Molecular dynamics simulations were performed to investigate the uniaxial tensile properties of nanocrystalline $U_{0.5}Th_{0.5}O_2$ solid solution with the Born-Mayer-Huggins potential. The results indicated that the elastic modulus increased linearly with the density relative to a single crystal, but decreased with increasing temperature. The simulated nanocrystalline $U_{0.5}Th_{0.5}O_2$ exhibited a breakdown in the Halle-Petch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of $U_{1-y}Th_yO_2$ solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline $U_{0.5}Th_{0.5}O_2$ was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure $UO_2$.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.153-165
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• 1999

In order to trace the lateral-torsional post-bucking behaviors of thin-walled space frames with non-symmetric cross sections, a geometrically non-linear finite element formulation is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for non-symmetric thin-walled cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, tangent stiffness matrices of thin-walled space frame element are derived by using the Hermition polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines and incremental member forces.

• Journal of Microbiology and Biotechnology
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• v.24 no.4
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• pp.534-544
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• 2014

The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, $SO_4{^{2-}}$ in the inoculated red earth soil decreased acutely after incubation. The shift in the microbial community composite in the inoculated soil was analyzed through denaturing gradient gel electrophoresis. Results revealed the potential cooperative effect of microbial Fe(III) reduction and sulfate reduction on copper immobilization. After exposure to air for 144 h, more than 50% of the immobilized Cu was remobilized from the anaerobic matrices; aqueous sulfate increased significantly. Sequential extraction analysis demonstrated that the organic matter/sulfide-bound Cu increased by 52% after anaerobic incubation relative to the abiotic treatment but decreased by 32% after oxidation, indicating the generation and oxidation of Cu-sulfide coprecipitates in the inoculated red earth soil. These findings suggest that the immobilization of copper could be enhanced by mediating microbial Fe(III) reduction with sulfate reduction under anaerobic conditions. The findings have an important implication for bioremediation in Cu-contaminated and Fe-rich soils, especially in acid-mine-drainage-affected sites.

• Journal of Microbiology and Biotechnology
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• v.26 no.11
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• pp.1855-1862
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• 2016

Cronobacter sakazakii (C. sakazakii) is a foodborne pathogen, posing a high risk of disease to infants and immunocompromised individuals. In order to develop a quick, easy, and sensitive assay for detecting C. sakazakii, a rabbit anti-C. sakazakii immunoglobulin G (IgG) was developed using sonicated cell protein from C. sakazakii. The developed anti-C. sakazakii (IgG) was of good quality and purity, as well as species-specific. The developed rabbit anti-C. sakazakii IgG was attached to the surface of a sulforhodamine B-encapsulated liposome to form an immunoliposome. A test strip was then prepared by coating goat anti-rabbit IgG onto the control line and rabbit anti-C. sakazakii IgG onto the test line, respectively, of a plastic-backed nitrocellulose membrane. A purple color signal both on the test line and the control line indicated the presence of C. sakazakii in the sample, whereas purple color only on the control line indicated the absence of C. sakazakii in the sample. This immunochromatographic strip assay could produce results in 15 min with a limit of detection of $10^7CFU/ml$ in C. sakazakii culture. The immunochromatographic strip assay also showed very good specificity without cross-reactivity with other tested Cronobacter species. Based on these results, the developed immunochromatographic strip assay is efficient for the detection of C. sakazakii and has high potential for on-site detection.