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991.
Seo WD Curtis-Long MJ Ryu YB Lee JH Yang MS Lee WS Park KH 《The Journal of organic chemistry》2006,71(13):5008-5011
The high diastereoselectivity of the base-catalyzed epimerization of oxazolidin-2-ones 7 and 8 is shown to depend on the nature of the N-substituent (R group); when R = Bn, the 4,5-trans-product (4S,5R)-9 is formed, whereas when R = H the 4,5-cis-product (4S,5S)-10 is formed, both with >99:1 dr. The successful hydrolysis of the oxazolidin-2-one group in both cis- and trans-derivatives show this to be a stereodivergent route to enantiopure alpha-hydroxy-beta-amino isopentanoic acids (2R,3S)-1 and (2S,3S)-2. 相似文献
992.
The paper studies strategy-proof cost sharing rules for public good provision based on referenda with different threshold quotas. By appropriately relaxing the assumptions of individual rationality and anonymity we provide a complete characterization of the family of quota rules with (possibly) unequal pricing. We prove that these quota rules are the only cost sharing rules satisfying four conditions: strategy-proofness, non-bossiness, weak continuity and weak anonymity. In addition, the specification of the degree to which individual rationality may be violated results in the selection of a specific “quota” for the referendum. While all these rules are “almost” always efficient when providing the public good and they are also almost everywhere coalitionally strategy-proof, only one family of rules from this class satisfies these two properties everywhere. The rules satisfying these two properties are Moulin’s Conservative Equal Costs Rule and unequal cost sharing variants of Moulin’s rule. 相似文献
993.
Keomkyo Seo 《Archiv der Mathematik》2010,94(2):173-181
We prove that if an n-dimensional complete minimal submanifold M in hyperbolic space has sufficiently small total scalar curvature then M has only one end. We also prove that for such M there exist no nontrivial L
2 harmonic 1-forms on M. 相似文献
994.
Shaoqiang Chen Akira UedonoJongwon Seo Junji SawahataKatsuhiro Akimoto 《Journal of Crystal Growth》2009,311(10):3097-3099
The density of the vacancy-type defect in Er doped GaN was measured by positron annihilation spectrometry (PAS) and the correlation between the intensity of the Er-related luminescence was studied. A luminescence peak at 558 nm originating from 4S3/2 to 4I15/2 transition of Er3+ was observed in Er-doped GaN. The intensity of the luminescence increased with increasing Er concentration and showed the maximum with the Er concentration of around 4.0 at%. The PAS measurements showed that the vacancy-type defect density increased with increasing Er concentration up to 4 at%, and around 4 at% of Er, the formation of defect complex such as VGa–VN was suggested. The contribution of the defect to the radiative recombination of intra-4f transition of Er is discussed. 相似文献
995.
We report on the selective area growth (SAG) of GaN nanorods on Si substrates masked with W or SiO2 and also on bare Si substrates by RF plasma-assisted molecular beam epitaxy (RF-MBE). The growth of GaN (i.e. irradiation of Ga and RF plasma-activated N2) on the W mask layer results in the appearance of a ring reflection high-energy electron diffraction (RHEED) pattern coming from α-W. In contrast, broken ring RHEED patterns from GaN nanorods are clearly observed on SiO2 and Si surfaces. Ex-situ scanning Auger microscopy analysis confirms that no growth of GaN takes place on W. Utilizing this phenomenon, we have demonstrated the SAG of GaN nanorods on Si substrates partly masked with W. We will discuss this phenomenon in terms of the difference in the desorption energy of Ga on W, SiO2, and Si. 相似文献
996.
S.-Y. Seo C.-H. Kwak S.-H. Kim B.-H. Kim C.-I. Park S.-H. Park S.-W. Han 《Journal of Crystal Growth》2010,312(14):2093-2097
High quality Zn1−xFexO thin films were deposited on α-sapphire substrates by RF magnetron sputtering. X-ray absorption fine structure measurements showed that the chemical valence of Fe ions in the films was a mixture of 2+ and 3+ states, and Fe ions substituted mainly for the Zn sites in the films. DC-magnetization measurements revealed ferromagnetic properties from 5 to 300 K. The photoluminescence measurements at 15 K showed a sharp main transition peak at 3.35 eV along with a broad impurity peak at 2.45 eV. The structural and magnetization analyses of the Zn1−xFexO films strongly suggested that the ferromagnetism was the intrinsic properties of the films. 相似文献
997.
Jiwon Seo 《Tetrahedron letters》2006,47(24):4069-4073
The syntheses of arginine-containing hydroxamates using various peptide coupling methods are described. Fmoc-Arg(NO2)-Cl prepared at low temperature did not undergo intramolecular δ-lactam formation and effectively provided desired hydroxamates (8 and 10) in good yields. Fmoc and N-nitro protecting groups can be easily removed. Therefore, this report provides a facile synthesis of arginine-containing peptidomimetic compounds. 相似文献
998.
Young Jun Seo 《Tetrahedron letters》2006,47(24):4037-4039
We appended pyrene units covalently onto adenosine and uridine nucleosides (forming AP and UP units, respectively) and then incorporated them into oligonucleotides such that they were positioned in complementary locations in opposite strands in the middle positions of hairpin stems. Systems 1 (APUP) and 3 (APAP) individually exhibit aromatic stacking between the opposing pyrene units in the stems of their hairpins and display in their spectra the photophysical properties of strongly red-shifted bands; in contrast, the UPUP system 2 exhibits quenching spectra. Systems 1 (APUP) and 3 (APAP) behave as effective molecular beacons (MBs) that change color from green to blue upon duplex formation, whereas 2 (UPUP) is an effective MB that changes the intensity of its fluorescence upon forming its perfectly matched duplex. 相似文献
999.
1000.
Kim YJ Lee Y Kang MJ Huh JS Yoon M Lee J Choi YW 《Biomedical chromatography : BMC》2006,20(11):1172-1177
A highly sensitive high-performance liquid chromatographic quantification method with fluorescence detection was developed and validated for the determination of doxazosin in human plasma. The developed method employed one-step extraction of doxazosin from plasma matrix with ethyl acetate using propranolol as an internal standard. Chromatographic separation was obtained within 8.0 min using a reverse-phase Capcell-Pak C(18) column (150 x 4.6 mm i.d., 5 microm) and the mobile phase consisted of methanol-water containing 10 mM perchloric acid and 1.8 mM sodium heptane sulfonic acid (50:50, v/v) and was set at a flow rate of 1.5 mL/min. The calibration curve constructed was linear in the range of 0.3-50.0 ng/mL. The proposed method achieved a lower limit of quantification of 0.3 ng/mL, better than the reported HPLC methods. Average recoveries of doxazosin and the internal standard from human plasma matrix were 87.0 and 85.9%, respectively. The present method was validated by evaluating the precision and accuracy for inter- and intraday variation in the concentration range 0.3-50 ng/mL. The precision values expressed as relative standard deviations in the inter- and intraday validation were 1.17-6.29 and 0.84-5.94%, respectively. This method was successfully applied to the bioequivalence study of two doxazosin controlled release tablets in healthy, male human subjects. 相似文献