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81.
Sungmo Moon 《Journal of Solid State Electrochemistry》2014,18(2):341-346
Corrosion behavior and resistance of plasma electrolyte oxidation (PEO)-treated AZ31 Mg alloy were investigated by immersion and potentiodynamic polarization tests in 0.5 M NaCl solution in view of the PEO film thickness and sealing treatment of the PEO films in boiling water. The PEO films were formed using pulse current for various durations in 1 M NaOH?+?0.5 M NaF solution. Filiform corrosion was observed during the immersion test while pitting corrosion occurred during the potentiodynamic polarization test, irrespective of sealing treatment of the PEO films. Corrosion resistance of AZ31 Mg alloy was improved remarkably by the formation of thicker PEO films and their sealing treatments. 相似文献
82.
Spectroscopic Monitoring of the Acidity of Water Films on Ru(0001): Orientation‐Specific Acidity of Adsorbed Water
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Youngsoon Kim Sunghwan Shin Dr. Eui‐Seong Moon Prof. Heon Kang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3376-3383
We examined the acid–base properties of water films adsorbed onto a Ru(0001) substrate by using surface spectroscopic methods in vacuum environments. Ammonia adsorption experiments combined with low‐energy sputtering (LES), reactive ion scattering (RIS), reflection–absorption infrared spectroscopy (RAIRS) and temperature‐programmed desorption (TPD) measurements showed that the adsorbed water is acidic enough to transfer protons to ammonia. Only the water molecules in an intact water monolayer and water clusters larger than the hexamer exhibit such acidity, whereas small clusters, a thick ice film or a partially dissociated water monolayer that contains OH, H2O and H species are not acidic. The observations indicate the orientation‐specific acidity of adsorbed water. The acidity stems from water molecules with H‐down adsorption geometry present in the monolayer. However, the dissociation of water into H and OH on the surface does not promote but rather suppresses the proton transfer to ammonia. 相似文献
83.
Dr. Cheng‐Chung Lee Dr. Manuel Maestre‐Reyna Dr. Kai‐Cheng Hsu Prof. Dr. Hao‐Ching Wang Prof. Dr. Chia‐I Liu Prof. Dr. Wen‐Yih Jeng Li‐Ling Lin Richard Wood Dr. Chia‐Cheng Chou Prof. Dr. Jinn‐Moon Yang Prof. Dr. Andrew H.‐J. Wang 《Angewandte Chemie (International ed. in English)》2014,53(48):13054-13058
Crown ethers are small, cyclic polyethers that have found wide‐spread use in phase‐transfer catalysis and, to a certain degree, in protein chemistry. Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. We elucidated the crystal structures of several protein‐crown ether co‐crystals grown in the presence of 18‐crown‐6. We then employed biophysical methods and molecular dynamics simulations to compare these complexes with the corresponding apoproteins and with similar complexes with ring‐shaped low‐molecular‐weight polyethylene glycols. Our studies show that crown ethers can modify protein surface behavior dramatically by stabilizing either intra‐ or intermolecular interactions. Consequently, we propose that crown ethers can be used to modulate a wide variety of protein surface behaviors, such as oligomerization, domain–domain interactions, stabilization in organic solvents, and crystallization. 相似文献
84.
Dr. Guobin Wen Dr. Bohua Ren Dr. Moon G. Park Dr. Jie Yang Dr. Haozhen Dou Dr. Zhen Zhang Dr. Ya-Ping Deng Prof. Zhengyu Bai Prof. Lin Yang Prof. Jeff Gostick Prof. Gianluigi A. Botton Prof. Yongfeng Hu Prof. Zhongwei Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12960-12967
Simultaneously improving energy efficiency (EE) and material stability in electrochemical CO2 conversion remains an unsolved challenge. Among a series of ternary Sn-Ti-O electrocatalysts, 3D ordered mesoporous (3DOM) Sn0.3Ti0.7O2 achieves a trade-off between active-site exposure and structural stability, demonstrating up to 71.5 % half-cell EE over 200 hours, and a 94.5 % Faradaic efficiency for CO at an overpotential as low as 430 mV. DFT and X-ray absorption fine structure analyses reveal an electron density reconfiguration in the Sn-Ti-O system. A downshift of the orbital band center of Sn and a charge depletion of Ti collectively facilitate the dissociative adsorption of the desired intermediate COOH* for CO formation. It is also beneficial in maintaining a local alkaline environment to suppress H2 and formate formation, and in stabilizing oxygen atoms to prolong durability. These findings provide a new strategy in materials design for efficient CO2 conversion and beyond. 相似文献
85.
Wooseup Hwang Jejoong Yoo In‐Chul Hwang Jiyeon Lee Young Ho Ko Hyun Woo Kim Younghoon Kim Yeonsang Lee Moon Young Hur Kyeng Min Park Jongcheol Seo Kangkyun Baek Kimoon Kim 《Angewandte Chemie (International ed. in English)》2020,59(9):3460-3464
Hierarchical self‐assembly of building blocks over multiple length scales is ubiquitous in living organisms. Microtubules are one of the principal cellular components formed by hierarchical self‐assembly of nanometer‐sized tubulin heterodimers into protofilaments, which then associate to form micron‐length‐scale, multi‐stranded tubes. This peculiar biological process is now mimicked with a fully synthetic molecule, which forms a 1:1 host‐guest complex with cucurbit[7]uril as a globular building block, and then polymerizes into linear poly‐pseudorotaxanes that associate laterally with each other in a self‐shape‐complementary manner to form a tubular structure with a length over tens of micrometers. Molecular dynamic simulations suggest that the tubular assembly consists of eight poly‐pseudorotaxanes that wind together to form a 4.5 nm wide multi‐stranded tubule. 相似文献
86.
Nam Sook Kim Sun Hee Moon Hwan Seong Choi Ji Hyun Lee Seongsoo Park Hoil Kang 《Journal of separation science》2020,43(14):2750-2765
An analytical method for the simultaneous and reliable determination of 20 antigout and antiosteoporosis pharmaceutical compounds in adulterated health food products was developed using liquid chromatography with electrospray ionization tandem mass spectrometry and liquid chromatography with quadrupole‐time‐of‐flight mass spectrometry. The method was validated through the determination of specificity, linearity, limit of detection, and limit of quantification, method detection limit, method quantitation limit, precision, accuracy, recovery, and stability. The matrix effect was also determined. The validation results of the developed method are as follows: for solid and liquid blank samples, limits of detection ranged from 0.05 to 5.00 ng/mL and limits of quantification ranged from 0.15 to 15.00 ng/mL. Linearity was acceptable, and the correlation coefficients (R2) were ≥0.99 for all target compounds. Both intra and interday precision were less than 9.16% RSD, and accuracies ranged from 95.31 to 116.68%. Mean recoveries for different types of dietary supplements classified as powders, liquids, tablets, and capsules were found to be 80.81 to 117.62% with less than 15.00% relative standard deviation. The stability of the standard mixture solution was less than 11.72% relative standard deviation after 48 h. By the proposed method, the presence of dexamethasone was determined in seized herbal food products at concentrations that ranged from 126 to 215 µg/g. 相似文献
87.
Dokyung Yoon Daekwang Woo Jung Heon Kim Moon Ki Kim Taesung Kim Eung-Soo Hwang Seunghyun Baik 《Journal of nanoparticle research》2011,13(6):2543-2551
The cytotoxicity of alumina nanoparticles (NPs) was investigated for a wide range of concentration (25–200 μg/mL) and incubation
time (0–72 h) using floating cells (THP-1) and adherent cells (J774A.1, A549, and 293). Alumina NPs were gradually agglomerated
over time although a significant portion of sedimentation occurred at the early stage within 6 h. A decrease of the viability
was found in floating (THP-1) and adherent (J774A.1 and A549) cells in a dose-dependent manner. However, the time-dependent
decrease in cell viability was observed only in adherent cells (J774A.1 and A549), which is predominantly related with the
sedimentation of alumina NPs in cell culture medium. The uptake of alumina NPs in macrophages and an increased cell-to-cell
adhesion in adherent cells were observed. There was no significant change in the viability of 293 cells. This in vitro test
suggests that the agglomeration and sedimentation of alumina NPs affected cellular viability depending on cell types such
as monocytes (THP-1), macrophages (J774A.1), lung carcinoma cells (A549), and embryonic kidney cells (293). 相似文献
88.
Jeong Won Lee Joongwoo Brian Park Hang-Hyun Jo Jae-Suk Yang Hie-Tae Moon 《Physica A》2009,388(2-3):137-144
The entropy density is an intuitive and powerful concept to study the complicated nonlinear processes derived from physical systems. We develop the minimum entropy density method (MEDM) to detect the structure scale of a given time series, which is defined as the scale in which the uncertainty is minimized, hence the pattern is revealed most. The MEDM is applied to the financial time series of Standard and Poor’s 500 index from February 1983 to April 2006. Then the temporal behavior of structure scale is obtained and analyzed in relation to the information delivery time and efficient market hypothesis. 相似文献
89.
Yong Sam Chung Sun Ha Kim Gwang Min Sun Jong Myoung Lim Jong Hwa Moon Kye Hong Lee Young Jin Kim Jong Il Choi Ju Woon Lee 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(1):223-229
The analysis of mineral contents in space foods is needed to obtain an information on a comprehensive elemental composition
as well as the investigation on the effects of human nutrition and health based on the dietary intake of mineral elements.
Recently, six items of new Korean space foods (KSFs) such as kimchi, bibimbap, bulgogi, a ramen, a mulberry beverage and a
fruit punch which was developed by the KAERI, and the contents of more than 15 elements in the samples were examined by using
instrumental neutron activation analysis (INAA). Five biological certified reference materials, NIST SRM were used for analytical
quality control. The results were compared with those of common Korean foods reported, and these results will be applied toward
the identification of irradiated foods. 相似文献
90.
Detoxification of Chemical Warfare Agents Using a Zr6‐Based Metal–Organic Framework/Polymer Mixture
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Dr. Su‐Young Moon Emmanuel Proussaloglou Gregory W. Peterson Dr. Jared B. DeCoste Morgan G. Hall Dr. Ashlee J. Howarth Prof. Joseph T. Hupp Prof. Omar K. Farha 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):14864-14868
Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium‐based metal–organic frameworks (Zr6‐MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant, dimethyl 4‐nitrophenylphosphate (DMNP), in buffered solutions. A hurdle to using MOFs for this application is the current need for a buffer solution. Here the destruction of the simulant DMNP, as well as the chemical warfare agents (GD and VX) through hydrolysis using a MOF catalyst mixed with a non‐volatile, water‐insoluble, heterogeneous buffer is reported. The hydrolysis of the simulant and nerve agents in the presence of the heterogeneous buffer was fast and effective. 相似文献