• Title/Summary/Keyword: Molecular structures

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Microstructural Characteristics of III-Nitride Layers Grown on Si(110) Substrate by Molecular Beam Epitaxy

  • Kim, Young Heon;Ahn, Sang Jung;Noh, Young-Kyun;Oh, Jae-Eung
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.327.1-327.1
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    • 2014
  • Nitrides-on-silicon structures are considered to be an excellent candidate for unique design architectures and creating devices for high-power applications. Therefore, a lot of effort has been concentrating on growing high-quality III-nitrides on Si substrates, mostly Si(111) and Si(001) substrates. However, there are several fundamental problems in the growth of nitride compound semiconductors on silicon. First, the large difference in lattice constants and thermal expansion coefficients will lead to misfit dislocation and stress in the epitaxial films. Second, the growth of polar compounds on a non-polar substrate can lead to antiphase domains or other defective structures. Even though the lattice mismatches are reached to 16.9 % to GaN and 19 % to AlN and a number of dislocations are originated, Si(111) has been selected as the substrate for the epitaxial growth of nitrides because it is always favored due to its three-fold symmetry at the surface, which gives a good rotational matching for the six-fold symmetry of the wurtzite structure of nitrides. Also, Si(001) has been used for the growth of nitrides due to a possible integration of nitride devices with silicon technology despite a four-fold symmetry and a surface reconstruction. Moreover, Si(110), one of surface orientations used in the silicon technology, begins to attract attention as a substrate for the epitaxial growth of nitrides due to an interesting interface structure. In this system, the close lattice match along the [-1100]AlN/[001]Si direction promotes the faster growth along a particular crystal orientation. However, there are insufficient until now on the studies for the growth of nitride compound semiconductors on Si(110) substrate from a microstructural point of view. In this work, the microstructural properties of nitride thin layers grown on Si(110) have been characterized using various TEM techniques. The main purpose of this study was to understand the atomic structure and the strain behavior of III-nitrides grown on Si(110) substrate by molecular beam epitaxy (MBE). Insight gained at the microscopic level regarding how thin layer grows at the interface is essential for the growth of high quality thin films for various applications.

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Performance Evaluation of Multi-Friction Dampers for Seismic Retrofitting of Structures (구조물 내진보강을 위한 다중 마찰댐퍼의 성능 평가)

  • Kim, Sung-Bae;Kwon, Hyung-O;Lee, Jong-Suk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.6
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    • pp.54-63
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    • 2022
  • This paper is a study on the friction damper, which is one of the seismic reinforcement devices for structures. This study developed a damper by replacing the internal friction material with ultra high molecular weight polyethylene (UHMWPE), a type of composite material. In addition, this study applied a multi-friction method in which the internal structure where frictional force is generated is laminated in several layers. To verify the performance of the developed multi-friction damper, this study performed a characteristic analysis test for the basic physical properties, wear characteristics, and disc springs of the material. As a result of the wear test, the mass reduction rate of UHMWPE was 0.003%, which showed the best performance among the friction materials based on composite materials. Regarding the disc spring, this study secured the design basic data from the finite element analysis and experimental test results. Moreover, to confirm the quality stability of the developed multi-friction damper, this study performed an seismic load test on the damping device and the friction force change according to the torque value. The quality performance test result showed a linear frictional force change according to the torque value adjustment. As a result of the seismic load test, the allowable error of the friction damper was less than 15%, which is the standard required by the design standards, so it satisfies the requirements for seismic reinforcement devices.

BEEF MEAT TRACEABILITY. CAN NIRS COULD HELP\ulcorner

  • Cozzolino, D.
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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    • 2001.06a
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    • pp.1246-1246
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    • 2001
  • The quality of meat is highly variable in many properties. This variability originates from both animal production and meat processing. At the pre-slaughter stage, animal factors such as breed, sex, age contribute to this variability. Environmental factors include feeding, rearing, transport and conditions just before slaughter (Hildrum et al., 1995). Meat can be presented in a variety of forms, each offering different opportunities for adulteration and contamination. This has imposed great pressure on the food manufacturing industry to guarantee the safety of meat. Tissue and muscle speciation of flesh foods, as well as speciation of animal derived by-products fed to all classes of domestic animals, are now perhaps the most important uncertainty which the food industry must resolve to allay consumer concern. Recently, there is a demand for rapid and low cost methods of direct quality measurements in both food and food ingredients (including high performance liquid chromatography (HPLC), thin layer chromatography (TLC), enzymatic and inmunological tests (e.g. ELISA test) and physical tests) to establish their authenticity and hence guarantee the quality of products manufactured for consumers (Holland et al., 1998). The use of Near Infrared Reflectance Spectroscopy (NIRS) for the rapid, precise and non-destructive analysis of a wide range of organic materials has been comprehensively documented (Osborne et at., 1993). Most of the established methods have involved the development of NIRS calibrations for the quantitative prediction of composition in meat (Ben-Gera and Norris, 1968; Lanza, 1983; Clark and Short, 1994). This was a rational strategy to pursue during the initial stages of its application, given the type of equipment available, the state of development of the emerging discipline of chemometrics and the overwhelming commercial interest in solving such problems (Downey, 1994). One of the advantages of NIRS technology is not only to assess chemical structures through the analysis of the molecular bonds in the near infrared spectrum, but also to build an optical model characteristic of the sample which behaves like the “finger print” of the sample. This opens the possibility of using spectra to determine complex attributes of organic structures, which are related to molecular chromophores, organoleptic scores and sensory characteristics (Hildrum et al., 1994, 1995; Park et al., 1998). In addition, the application of statistical packages like principal component or discriminant analysis provides the possibility to understand the optical properties of the sample and make a classification without the chemical information. The objectives of this present work were: (1) to examine two methods of sample presentation to the instrument (intact and minced) and (2) to explore the use of principal component analysis (PCA) and Soft Independent Modelling of class Analogy (SIMCA) to classify muscles by quality attributes. Seventy-eight (n: 78) beef muscles (m. longissimus dorsi) from Hereford breed of cattle were used. The samples were scanned in a NIRS monochromator instrument (NIR Systems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced presentation to the instrument were explored. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

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Plant Regeneration from Leaf and Root Cultures of Lycoris chejuensis via Bulblet Formation (제주상사화 (Lycoris chejuensis K. Tae et S. Ko) 잎 및 뿌리 절편으로부터 소자구 형성을 통한 식물체 재생안)

  • Oh, Myung-Jin;Park, Jong-Mi;Tae, Kyoung-Hwan;Liu, Jang-Ryol;Kim, Suk-Weon
    • Journal of Plant Biotechnology
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    • v.34 no.3
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    • pp.223-227
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    • 2007
  • Plant regeneration system from leaf and root segments of Lycoris chejuensis via bulblet formation was established. Surface-sterilized leaf and root segments were cultured on the B5 medium containing 2,4-D. After 12 weeks of culture onto B5 medium containing 2,4-D, white globular structures and white calluses were formed on the cut surface of the explants. The highest frequency of globular structures and calluses formation from leaf explants was 32.1% when leaf explants were cultured onto B5 medium supplemented with 1 mg/L of 2,4-D. However, the higher concentration of 2,4-D (over than 3 mg/L) resulted in decrease of the frequency. In comparison to leaf explants, root segments showed the highest frequency at a rate of 36.1% when root explants were cultured onto B5 medium supplemented with 3 mg/L of 2,4-D. These structures and calluses were sub-cultured and proliferated onto the same culture medium. Upon transfer to B5 basal medium, white globular structures were developed into bulblets and normal plantlets. After 4 weeks of incubation in the light, plantlets were successfully rooted over the frequency of approximately 90%. Rooted plantlets were successfully transferred to potting soil and acclimatized in the growth chamber. The plant regeneration system of Lycoris chejuensis established in this study, might be applied to mass proliferation, conservation of genetic resources and genetic transformation for molecular breeding.

Optical transition dynamics in ZnO/ZnMgO multiple quantum well structures with different well widths grown on ZnO substrates

  • Li, Song-Mei;Kwon, Bong-Joon;Kwack, Ho-Sang;Jin, Li-Hua;Cho, Yong-Hoon;Park, Young-Sin;Han, Myung-Soo;Park, Young-Sik
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.121-121
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    • 2010
  • ZnO is a promising material for the application of high efficiency light emitting diodes with short wavelength region for its large bandgap energy of 3.37 eV which is similar to GaN (3.39 eV) at room temperature. The large exciton binding energy of 60 meV in ZnO provide provides higher efficiency of emission for optoelectronic device applications. Several ZnO/ZnMgO multiple quantum well (MQW) structures have been grown on various substrates such as sapphire, GaN, Si, and so on. However, the achievement of high quality ZnO/ZnMgO MQW structures has been somehow limited by the use of lattice-mismatched substrates. Therefore, we propose the optical properties of ZnO/ZnMgO multiple quantum well (MQW) structures with different well widths grown on lattice-matched ZnO substrates by molecular beam epitaxy. Photoluminescence (PL) spectra show MQW emissions at 3.387 and 3.369 eV for the ZnO/ZnMgO MQW samples with well widths of 2 and 5 nm, respectively, due to the quantum confinement effect. Time-resolved PL results show an efficient photo-generated carrier transfer from the barrier to the MQWs, which leads to an increased intensity ratio of the well to barrier emissions for the ZnO/ZnMgO MQW sample with the wider width. From the power-dependent PL spectra, we observed no PL peak shift of MQW emission in both samples, indicating a negligible built-in electric field effect in the ZnO/$Zn_{0.9}Mg_{0.1}O$ MQWs grown on lattice-matched ZnO substrates.

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Inhibitory Effects of Oriental Medicinal Herbs on Enzymatic Activity of Sialyltransferases (ST3Gal I and ST6Gal I) Associated with Cancer

  • Kim, Kyoung-Sook;Kim, Cheorl-Ho;Kim, June-Ki;Lee, Young-Choon
    • Journal of Life Science
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    • v.10 no.1
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    • pp.51-56
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    • 2000
  • In many cases of human cancer, the appearance of hypersialylated glycan structures is related to a precise stage of the disease ; this may depend on the elebated sialyltransferase activity during carcinogenesis. The aim of this study was to investigate the inhibitory effects of Oriental medicinal herbs on enzymatic activities of two kinds ofsialyltransferase, Gal $\beta$ 1,3GalNAc$\alpha$2,3-sialyltransferase(ST3Gal I) and Gal $\beta$ 1,4GlcNAc $\alpha$2,6-sialyltransterases(ST6Gal I), which are well known as glycosyltransterases associated with cancer. The aqueous extracts of Scutellaria Baicalensis Georgi, Coptidis Rhizoma, Glycyrrhiza urlensis Fisch, Bupleuri Radix and Platycodi Radix were prepared and tested, respectively. At concentration of 100$\mu$g, Glycyrrhiza uralensis Fisch showed the highest inhibitory effects(about 42% and 57%, respectively) on ST3Gal Iand ST6Gal Iactivities. ST3GAl I was inhibited about 23% by Scutellaria baicalensi G댁햐, but not by the other samples, whereas ST6Gal I was inhibited about 20% and 40%,respectively, by Scutellaria baicalensis Georgi and Bupleuri Radix. All inhibitory effects were obtained in a concentration-dependent manner.

Liquid Crystalline Properties of Dimers Having o-, m- and p- Positional Molecular Structures

  • Park, Joo-Hoon;Choi, Ok-Byung;Lee, Hwan-Myung;Lee, Jin-Young;Kim, Sung-Jo;Cha, Eun-Hee;Kim, Dong-Hyun;Ramaraj, B.;So, Bong-Keun;Kim, Kyung-Hwan;Lee, Soo-Min;Yoon, Kuk-Ro
    • Bulletin of the Korean Chemical Society
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    • v.33 no.5
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    • pp.1647-1652
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    • 2012
  • With the objective to design and synthesis of Schiff's base symmetrical liquid crystal dimmers and to study the effect of molecular structure variation ($o-ortho$, $m-meta$, $p-para$) and change in alkoxy terminal chain length on mesomorphic properties of liquid crystals, We have synthesized Schiff base dimers from dialdehyde derivative containing 2-hydroxy-1,3-dioxypropylene as short spacer with aniline derivatives having different lengths of terminal alkoxy chains ($n$ = 5, 7, 9). The chemical structure of the final products was characterized by proton nuclear magnetic resonance ($^1H$ NMR) spectroscopy and fourier transform infrared (FT-IR) spectroscopy. The mesomorphic properties and optical textures of the resultant dimers were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The existence of smectic A phase transition was confirmed by the observation of batonnets and fan shaped textures in optical microscopy when compound were heated from crystalline phase. All of the dimers of this series, with the exception of $\mathbf{2S_5}$ -ortho, -meta, -para, were thermotropic liquid crystal. The compound $\mathbf{2S_9}$ -meta was monotropic, while the rest were enantiotropic. It was found that the change in terminal alkoxy chain length has pronounced effect on the mesomorphic properties. The temperature range of smectic A phase window widens with increasing alkoxy chain length.

The Impact of o-Toluidinyl Structure of 2-Methyl-4-(2-methylphenyldiazenyl)phenyl picolinamide on the AHR Antagonistic Activity (2-Methyl-4-(phenyldiazenyl)phenyl picolinamide의 o-toluidinyl 구조가 AHR 길항저해 활성에 미치는 영향)

  • Lee, Hyosung
    • Journal of the Korea Convergence Society
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    • v.8 no.1
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    • pp.115-121
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    • 2017
  • AHR is a transcription factor activated by aryl hydrocarbons, regulating the expression of XMEs (xenobiotics Metabolizing Enzymes). Even though the role of AHR in human physiology has been intensively investigated for the past decades, our understandings are still largely limited due to the deficiency of adequate chemical agents. In addition, it has been demonstrated that AHR correlates to pathogeneses for some diseases. Furthermore, emerging data suggest that the study on the AHR may provide a valid therapeutic target. Classical antagonists in current use are reported to be partial agonistic whereas a pure antagonist is demanded. In this study, o-toluidinyl ring structure of 2-methyl-4-(2-methylphenyldiazenyl)phenyl picolinamide has been modified into various structures to optimize the AHR antagonistic activity by means of convergence study of organic synthesis and molecular biology.

Molecular Hydrogen Outflow in Infrared Dark Cloud Core MSXDC G53.11+00.05

  • Kim, Hyun-Jeong;Koo, Bon-Chul;Pyo, Tae-Soo;Davis, Christopher J.
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.41.4-42
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    • 2015
  • Outflows and jets from young stellar objects (YSOs) are prominent observational phenomena in star formation process. Indicating currently ongoing star formation and directly tracing mass accretion, they provide clues about the accretion processes and accretion history of YSOs. While outflows of low-mass YSOs are commonly observed and well studied, such studies for high-mass YSOs have been so far rather limited owing to their large distances and high visual extinction. Recently, we have found a number of molecular hydrogen (H2 1-0 S(1) at 2.12 micron) outflows in the long, filamentary infrared dark cloud (IRDC) G53.2 located at 1.7 kpc from UWISH2, the unbiased, narrow-band imaging survey centered at 2.12 micron using WFCAM/UKIRT. In IRDC G53.2 which is an active star-forming region with ~300 YSOs, H2 outflows are ubiquitously distributed around YSOs along dark filaments. In this study, we present the most prominent H2 outflow among them identified in one of the IRDC cores MSXDC G53.11+00.05. The outflow shows a remarkable bipolar morphology and has complex structures with several flows and knots. The outflow size of ~1 pc and H2 luminosity about ~1.2 Lsol as well as spectral energy distributions of the Class I YSOs at the center suggest that the outflow is likely associated with a high-mass YSO. We report the physical properties of H2 outflow and characteristics of central YSOs that show variability between several years using the H2 and [Fe II] images obtained from UWISH2, UWIFE and Subaru/IRCS+AO188 observations. Based on the results, we discuss the possible origin of the outflow and accretion processes in terms of massive star formation occurring in IRDC core.

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The Pharmacology of Botulinum Toxin (보툴리눔 독소의 약리)

  • Lee, Sang Hyuk;Lee, Hyun Sub;Jin, Sung Min
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.23 no.2
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    • pp.93-98
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    • 2012
  • Botulinum toxins are the most potent toxins known to mankind. Botulinum toxin acts by blocking the cholinergic neuromuscular or the cholinergic autonomic innervation of exocrine glands and smooth muscles. Seven distinct antigenic botulinum toxins (A, B, C, D, E, F and G) produced by different strains of Clostridium botulinum have been described and only A and B type of botulinum toxins were clinically used. Toxins were consisted of a heavy chain with a molecular weight of 100 kD and a light chain with a molecular weight of 50 kD. Toxins are bound with an astounding selectivity to glycoprotein structures located on the cholinergic nerve terminal. Subsequently light chain of toxin is internalized and cleaves different proteins of the acetylcholine transport protein cascade transporting the acetylcholine vesicle from the intracellular space into the synaptic cleft. After a decade of therapeutic application of the toxin, no anaphylaxis or deaths have been reported and systemic adverse effects have not been reported so far. However the toxin's immunologic properties can lead to the stimulation of antibody production, potentially rendering further treatments ineffective. Botulinum toxin is a safe and effective treatment. Use of botulinum toxin in clinical medicine has grown exponentially in recent years, and many parts of the human body are now being targeted for therapeutic purposes.

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