• Journal of the Korean Magnetics Society
• /
• v.16 no.1
• /
• pp.92-97
• /
• 2006

A study of the adsorption site of CO in the Ni(111)$(2\times2)$-O/CO coadsorbed phase over different sample preparation temperatures revealed that the atop site is favoured. The Ni-C spacing is given by $1.77\pm0.01\;{\AA}$. A study of the adsorption site of Co in the Ni(111)$(2\times2)$-O/CO coadsorbed phase over different sample preparation temperatures revealed that the atop site is favoured. The Ni-C spacing is given by $1.77\pm0.01\;{\AA}$. The data from the sample prepared at 265 K showed atop sites, which is well consistent with vibrational spectroscopy, whilst the data from the low temperature preparation appears the mixture of atop and hop $(35\%)$. The occupation of hop hollow sites is probably due to an incorrect pre-coverage of atomic oxygen (different from 0.25ml). Similar observation of site mixture also found in recent high resolution XPS measurements using C 1s and O 1s chemical shifts.

• Proceedings of the Korean Biophysical Society Conference
• /
• 2003.06a
• /
• pp.68-68
• /
• 2003

HP(2-20) (AKKVFKRLEKLEKLFSKIQNDK) derived from the N-terminus of Helicobacter pylori Ribosomal Protein L1 shows potent antimicrobial activity against bacterial, fungi and cancer cells without cytotoxic effect. In order to investigate the relationships between antimicrobial activity and the structures, several analogues have been designed and synthesized. The structures of these peptides in SDS micelles have been investigated using NMR spectroscopy and they revealed that analogue 3 has the longest, well-defined alpha-helix from Val5 to Trp19. NOESY experiments performed on HP and its analogues in nondeuterated SDS micelles show that protons in the indole ring of Trp16 are in close contact with methylene protons of SDS micelles. In order to probe the position of HP and its analogues relative to the SDS micelles, spin-labeled stearate was added. Large effects are observed for the chemical shifts and the intensities of Phe5, Glu9, Phe12, and Trp16 within the helix region by 16-doxylstearate. This result implies that 16-doxylstearate is located in the center of the micelles and the hydrophobic phase of the amphiphilic ${\alpha}$-helix is located in contact with the acyl chains of the micelles. Also, Lys3 and Lys4 at N-terminus and Lys20 at C-terminus may produce an optimal arrangement for electrostatic interactions between the sulfate head groups of the SDS and the positively charged lysyl N$\sub$3/$\^$+/. Interactions between the indole ring of Trp and the membrane, as well as the amphiphilic ${\alpha}$-helical structure of HP induced by Trp at the C-terminus may allow HP to span the lipid bilayer. These structural features are crucial for their potent antibiotic activities.

• Archives of Pharmacal Research
• /
• v.29 no.11
• /
• pp.1055-1060
• /
• 2006

The objective of this study was to formulate itraconazole semisolid dosage forms and characterize their physicochemical properties. Itraconazole and excipients such as polysorbate 80, fatty acids, fatty alcohols, oils and organic acids were melted at $160^{\circ}C$. The fused solution was then cooled immediately at $-10^{\circ}C$ to make wax-like semisolid preparations. Their physicochemical attributes were first characterized using differential scanning calorimetry, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectrometry. The solubility of itraconazole in semisolid preparations and their dispersability in the simulated gastric fluid were also determined. Our semisolid preparations did not show any distinct endothermic peak of a crystalline form of itraconazole around $160-163^{\circ}C$. This suggested that it was changed into amorphous one, when it was formulated into semisolid preparations. In addition, the distinctive functional peaks and chemical shifts of itraconazole were well retained after processing into semisolid preparations. It could be inferred from the data that itraconazole was stable during incorporation into semisolid preparations by the hot melt technique. In particular, itraconazole semisolid preparations composed of polysorbate 80, fatty acids and organic acids showed good solubility and dissolution when dispersed in an aqueous medium. It was anticipated that the semisolid dosage forms would be industrially applicable to improving the bioavailability of poorly water-soluble drugs.

• Membrane Journal
• /
• v.5 no.2
• /
• pp.89-96
• /
• 1995

The monolayer characteristics of phosphate amphiphiles with azobenzene at air/water interface were studied by the measurment of $\pi-A$ curves and absorption spectra. Immediately after being spread on the water surface, these amphiphiles having strong intermolecular hydrogen bonding interactions showed the typical absorption spectra which resulted from domain formation. But the aggregated domains could be controlled by changing the subphase conditions (adding bulky salt and rasing pH). Addition of metal ions in subphase changes the molecular orientation of monolayer. As the metal ion charge increases ($1\leq2$ < 3 < 4 valence), the absorption maximum (310nm) of the amphiphile with azobenzene shifts to a longer wavelength (350nm) which means that the orientation of the amphiphile is tilted. These results suggest that the molecular orientation, and furthermore the aggregation state of monolayer can be possibly controlled by the interaction of metal ions with different charge types.

• Korean Journal of Agricultural Science
• /
• v.46 no.2
• /
• pp.405-416
• /
• 2019

Weeds are a serious problem in crop production. Use of synthetic herbicides is rapidly increasing in weed management worldwide including Korea. Herbicide application reduces the time spent on weed control. However, the evolution of resistance to herbicides in weeds has become widespread as a natural response to selection pressure imposed by agricultural management activities. If an herbicide with the same mechanisms of action is used repeatedly and intensively, it can rapidly select for a weed biotype that shifts toward difficult-to-control becoming a more tolerant weed and lead to the evolution of herbicideresistant weeds. Moreover, agricultural and biological factors have an important role in the development of herbicide-resistant weed populations. Mitigating the evolution of herbicide resistance in weeds relies on reducing selection through the diversification of weed control techniques. The resistance management of weeds in the future will strongly depend on intensive cropping systems. The current situation of intensive cropping systems with their heavy reliance on the efficacy of chemical weed control will not lead to significant containment of this problem. Therefore, management strategies need to overcome the further spread of herbicide resistance in weeds in Korean crop production. This review presents the current information on herbicide resistance in Korea and factors controlling the development of herbicide resistant weeds.

• Applied Chemistry for Engineering
• /
• v.22 no.4
• /
• pp.348-352
• /
• 2011

In this research, we have synthesized new pendant-type polyurethane polymers by introducing various chromophores with stilbene derivatives in the side-chain of the polymer backbone. The Stilbene monomers, N,N-bis(2-hydroxyethyl) amino-4'-cyanostilbene, N,N-bis(2-hydroxyethyl)amino-4'-methoxy stilbene, N,N-bis(2-hydroxyethyl)amino-4'-acetylstilbene, and N,N-bis(2-hydroxyethyl) amino stilbene, were synthesized by Wittig reaction. Another stilbene monomer, N,N-bis(2-hydroxyethyl)amino-4'-nitrostilbene, was synthesized by Knoevenagel condensation. By the measurement of UV-Vis absorption and Photoluminescence (PL) spectrum, we found that introduction of the electron-withdrawing group as a substituent shifts both UV-Vis and PL spectra to longer wavelength, and the introduction of the electron-donating group results in blue-shift of the spectrum. In case of polymer with $NO_2$ group as a substituent, PL is quenched.

• Analytical Science and Technology
• /
• v.20 no.6
• /
• pp.483-487
• /
• 2007

Electrochemistry of 1.0 mM bis(1,10-phenanthroline)copper(II) $(Cu(ph){_2}^{2+})$ in 100 mM NaCl solution including 27 mM $MgCl_2$ with and without sodium dodecyl sulfate (SDS) is studied. In the presence of SDS, $E_{pa}$ and $E_{1/2}$ of $Cu(ph){_2}^{2+}$ by adding $Mg^{2+}$ shifts to a positive direction compared to the SDS free. The intersection of two lines on ${\Delta}E_p$ vs -log[SDS] plot is determined as a critical micelle concentration (CMC). When $Mg^{2+}$ is added, it seems that the double layer became more compact. And the formation of micelles is retarded.

• Journal of the Korean Chemical Society
• /
• v.42 no.6
• /
• pp.607-617
• /
• 1998

Au was dosed on $TiO_2(001)$ film grown epitaxially on Mo(100) surface in about 90 ${\AA}$ thickness. The growth mode of Au, thermal behavior and stability of the Au clusters, and the binding energy shift of Au 4f with the change in the amount of Au loading were studied by Auger Electron Spectroscopy (AES), Temperature Programmed Desorption (TPD) spectroscopy, Ion Scattering Spectroscopy (ISS), and X-ray Photoelectron Spectroscopy (XPS). Au grows three dimensionally on $TiO_2(001)$ film and the average size of Au clusters prepared at low temperature is smaller than those at higher temperature and the size increases with temperature irreversibly. Au clusters on $TiO_2(001)/Mo(100)$ start evaporation at 1000 K. TPD spectra of Au show very asymmetric peaks with the same leading edges irrespective of the amount of Au loading. The temperature at the peak maximum increases with the amount of Au. The desorption energy of Au obtained from the leading edge analysis of the TPD spectra is about 50 kcal/mol. The initial sticking coefficient of Au on $TiO_2(001)$ is constant in the temperature range of 200-600 K. The binding energy of Au 4f for the Au loaded on the film less than 2.0 MLE shifts to higher energy compared with the bulk Au. The shift is +0.3 eV at 0.1 MLE Au amount.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.264-264
• /
• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.

• Journal of the Mineralogical Society of Korea
• /
• v.19 no.4 s.50
• /
• pp.347-353
• /
• 2006

The atomic-nano scale structures of multi-component aluminosilicate glasses have not been well understood in spite of its implications fur dynamics and generation of magma in the natural system due to lack of suitable spectroscopic and scattering experiments. Here, we report O-17 MAS and isotropic projection of 3QMAS NMR spectra for quaternary Na-Ca silicate glasses $[(CaO)_x(Na_2O)_{1-x}]\;(A1_2O_3)_{0.5}(SiO_2)_6,\;CNAS)$ at 14.1 Tesla where atomic configurations around bridging oxygen (Si-O-Si, Si-O-Al) and non bridging oxygen (Na-O-Si, Ca-O-Si, (Na, Ca)-O-Si) are partially resolved. With increasing Na content, the fraction of Na-O-Si increases while those for bridging oxygens remain constant. The Na/Ca ratio apparently affects the peak widths of bridging oxygen peaks (e.g., Si-O-Si)) and thus the topological entropy as well as chemical shifts of the bridging oxygen peaks, implying that both BOs and NBOs are strongly interacting with network modifying cations The effect of cation field strength on the degree of Al-avoidance was also discussed.