• Title/Summary/Keyword: Structural Transition

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Oxidative Addition Reaction of Mono(aryl)cyanoplatinum(Ⅱ) Complex with Two Amino Ligands with the Dihalogens

  • Ko Jaejung;Kim Moonsik;Kim Seho;Shin Yookil
    • Bulletin of the Korean Chemical Society
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    • v.13 no.2
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    • pp.135-139
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    • 1992
  • The mono(aryl)cyanoplatinum(II) complex $[Pt(CN)(C_6H_3{CH_2NMe_2}_2-26)]$, reacts with the dihalogens to yield the mono(aryl)cyanoplatinum complexes $[PtX_2(CN)(C_6H_3{CH_2NMe_2}_2-26)]$, (X = Cl, Br, I). The structural configuration of the two halogen atoms for a square planar platinum complex was studied by 1H-NMR spectroscopy and led to a mixture of trans and cis orientation. The trans orientation was found to be more stable in energy (1.33 kcal/mol) than the cis orientation by means of Extended H ckel calculations. On the base of a combination of the analysis of $^1H-NMR$, $^{13}C-NMR spectra and computational calculations it is assumed that the intermediate consists of an initial attack in the linear transition state, leading to the $S_{N}2$ type mechanism.

Fabrication of Fe3O4 Thin Film using Reactive DC Magnetron Sputtering (반응성 DC 마그네트론 스퍼터링으로 Fe3O4 박막 제조에 관한 연구)

  • Jung, Minkyung;Park, Sungmin;Park, Daewon;Lee, Seong-Rae
    • Korean Journal of Metals and Materials
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    • v.47 no.6
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    • pp.378-382
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    • 2009
  • We investigated the effects of deposition conditions on the fabrication of $Fe_{3}O_{4}$ thin films using a reactive DC magnetron sputtering at room temperature. The structural, electrical, and magnetic properties of Fe oxide films dependence on the film thickness, oxygen flow rate, and the substrate crystallinity were also studied. We have successfully fabricated $Fe_{3}O_{4}$ film with thickness of about 10 nm under optimal reactive sputtering conditions. The saturation magnetization, resistivity, and Verwey transition of the $Fe_{3}O_{4}$ film were298 emu/cc, $4.0{\times}10^{-2}{\Omega}cm$, and 125 K, respectively.

A New Synthetic Route to Wustite

  • 박정철;김돈;이충섭;김동국
    • Bulletin of the Korean Chemical Society
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    • v.20 no.9
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    • pp.1005-1009
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    • 1999
  • Wustite with NaCl structure is successfully synthesized in a quartz tube sealed under vacuum ( ≒1×10 -3 torr). Hematite in an evacuated quartz tube progressively loses oxide ion at 1373 K. XRD patterns disclose that α-Fe2O3 is transformed into the Fe3O4 after heat treatment at 1373 K for 32 h, and the poorly crystallized FeO is appeared after heat treatment for 48 h. Finally, α-Fe2O3 is completely transformed into the well crystallized Fe 0.935O after heat treatment for 84 h. The electrical resistivity, ac-susceptibility measurement, Mossbauer spectroscopy, and x-ray absorption spectroscopy corroborate the structural phase transition on the iron oxides prepared in a sealed quartz tube depending on the heating time at 1373 K.

X-ray Structure and Electrochemical Properties of Ferrocene-Substituted Metalloporphyrins

  • Kim, Jin Won;Lee, Seok U;Na, Yong Hwan;Lee, Gi Pyeong;Do, Yeong Gyu;Jeong, Se Chae
    • Bulletin of the Korean Chemical Society
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    • v.22 no.12
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    • pp.1316-1322
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    • 2001
  • Transition metal complexes of novel mono- and di-ferrocene-substituted porphyrins have been synthesized and characterized by structural and electrochemical methods. The X-ray structures of Mn(FPTTP)Cl and Mn(DFTTP)Cl showed the distorted square pyramidal coordination geometry with syn configuration of chloride and ferrocenyl substituents. The electrochemistry of ferrocene-substituted porphyrins and their metal complexes has been determined to elucidate the ${\pi}-conjugation$ effect of the porphyrin ring. The ferrocenyl group of H2FPTTP underwent a reversible one-electron transfer process at 0.30 V, indicating the good electron donating effect of the phorphyrin ring to the ferrocene substituent. The redox potential of the ferrocenyl subunit and porphyrin ring was affected by the central metal ions of the metalloporphyrins, that is, Zn(II) and Ni(II) made the oxidation of ferrocene much easier and Mn(III) made it harder. The ferrocene subunits of H2DFTTP interacted electrochemically with each other with peak splitting of 0.21 V. The strength of the electrochemical interactions between the two ferrocenyl substituents can be controlled by central metal ions of metalloporphyrins.

The uniaxial strain test - a simple method for the characterization of porous materials

  • Fiedler, T.;Ochsner, A.;Gracio, J.
    • Structural Engineering and Mechanics
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    • v.22 no.1
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    • pp.17-32
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    • 2006
  • The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

A Comparative Anatomy of the Secondary Xylem in the Roots and Stems of Some Pinus Plants (수종 소나무속 식물에 있어서 뿌리와 줄기의 이기목부에 관한 비교해부)

  • 임동옥
    • Journal of Plant Biology
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    • v.29 no.3
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    • pp.185-196
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    • 1986
  • Anatomical characteristics of the secondary xylem in the roots and the stems of genus Pinus including nine species growing naturally in Korea have been studied to elucidate the structural differences between two organs. The results, comparing the root woods with the stem woods, are as follows; The transition from the early-wood to the late-wood occurs more gradually in the root woods. In the root woods, the bordered pits on the radial wall of tracheid are frequent in the two rows. The spiral thickening on the radial and tangential wall of the tracheid can be seen in the only stem woods of four species such as P. koraiensis, P. rigida, P. rigitaeda and P. banksiana. In the majority of the species studied, the length of the tracheid is longer in the root woods, but in some species such as P. strobus, P. densiflora, P. rigida and P. sylvestris, this length is almost sam ein both organs. The diameter of the tracheid in the root woods is wider. The wall thickness of the tracheid in the early wood is thicker in the root woods, but vice versa in the late woods. More rays per unit area can be seen in the root woods.

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Understanding Senior Tourists' Well-Being: The Moderating Effect of Travel Patterns

  • Kim, Hyelin (Lina)
    • Asia-Pacific Journal of Business
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    • v.9 no.4
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    • pp.1-11
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    • 2018
  • Retiring from work is a major personal and professional transition and has a major influence on one's life. Tourism researchers have been aware of the importance of seniors' tourism and leisure activities to enhance their well-being. The study examines the effect of tourism experience on leisure life domain, which in turn influences overall quality of life. Moreover, the moderating effect of travel patterns is also tested. A final sample of 328 was used for data analysis including Structural equation modeling (SEM) and multi-group analysis to test the hypotheses. The findings revealed that tourism experience positively influences satisfaction with leisure life domain and overall quality of life. Findings also indicated that there are moderating effects of the travel patterns on the relationship between satisfaction with leisure life domains and overall quality of life. The study also provided managerial implications for tourism marketers and destination managers.

Role of Type 1 Inositol 1,4,5-triphosphate Receptors in Mammalian Oocytes

  • Yoon, Sook Young
    • Development and Reproduction
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    • v.23 no.1
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    • pp.1-9
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    • 2019
  • The ability of oocytes to undergo normal fertilization and embryo development is acquired during oocyte maturation which is transition from the germinal vesicle stage (GV), germinal vesicle breakdown (GVBD) to metaphase of meiosis II (MII). Part of this process includes redistribution of inositol 1, 4, 5-triphosphate receptor (IP3R), a predominant $Ca^{2+}$ channel on the endoplasmic reticulum membrane. Type 1 IP3R (IP3R1) is expressed in mouse oocytes dominantly. At GV stage, IP3R1 are arranged as a network throughout the cytoplasm with minute accumulation around the nucleus. At MII stage, IP3R1 diffuses to the entire cytoplasm in a more reticular manner, and obvious clusters of IP3R1 are observed at the cortex of the egg. This structural reorganization provides acquisition of $[Ca^{2+}]_i$ oscillatory activity during fertilization. In this review, general properties of IP3R1 in somatic cells and mammalian oocyte are introduced.

Theoretical Studies on the Base-Catalyzed Deprotonation of Sulfonyl-Activatec Carbon Acids

  • 김왕기;류완선;손창국;이본수;김창곤;이익준
    • Bulletin of the Korean Chemical Society
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    • v.18 no.2
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    • pp.208-212
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    • 1997
  • Theoretical AM1 MO studies are reported on the gas-phase deprotonations of N-methyl 4-((Y-phenylsulfonyl)pyridinium cations (Ⅳ) and N-(Y-benzyl) 4-((phenylsulfonyl)methyl pyridinium cations (Ⅴ) using NH3 as a base. Bronsted α values for deprotonation of Ⅳ and Ⅴ are 0.18 and 0.17, respectively. Bronsted β value of 0.53 is found for the deprotonation of Ⅳ and Ⅴ by substituted aniline bases. The negative transition state (TS) imbalances, Ⅰ(=α-β) < 0, are rationalized by the negative distance factor, Δd (=dp-dTS) < 0, where dp and dTS are the distance between anionic charge center and substituents in the product and in the TS, respectively. The inability of d-pπ-conjugation in Ⅳ, where instead n-σ* type sigma delocalization occurs, causes very little lag in the structural reorganization in the TS.

Magnetic and Electrical Properties of High-Tc Superconductor $YBa_2Cu_3O_{6.87}$

  • Kim, Don;Kang, Chang-Kwon;Kim, Keu-Hong;Choi, Jae-Shi
    • Bulletin of the Korean Chemical Society
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    • v.9 no.5
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    • pp.280-282
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    • 1988
  • The structural, electrical and magnetic properties were investigated for the high-Tc superconductor $YBa_2Cu_3O_{7-x}$, where x was 0.13. The results of temperature dependence of the resistivity and the magnetization in $YBa_2Cu_3O_{6.87}$ whose structure and phase are confirmed by arialysis of X-ray powder diffraction pattern have been reported. A very sharp superconductivity transition appears at 92K in the specimen whose chemical composition is determined from redox titration, strongly suggesting that this specimen consists of a single-phase superconductor. From the results of X-ray diffraction analysis, magnetization curves, levitation and resistance measurements, it is suggested that the observed superconductivity is bulk property in nature and that the $YBa_2Cu_3O_{6.87}$ phase is responsible for the superconductivity of the present reproducible specimen.