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991.
threo-β-Hydroxy-l-glutamic acid 1 is an attractive target as a biologically active compound and as a chiral synthon. The required β-hydroxyl group in 1 was efficiently and stereoselectively introduced via an intramolecular conjugate addition of the N-hydroxymethyl group of γ-amino-α,β-unsaturated (Z)-ester 4. While the corresponding (E)-ester 3 gave a lower selectivity of ca. 5:1 in the intramolecular conjugate addition, a selectivity of up to 70:1 was shown with (Z)-ester 4. The tandem (Z)-olefination-conjugate addition could be achieved by simply changing the reaction conditions to give a selectivity of >20:1. Thus, the target compound 1 was obtained as its hydrochloride salt in 70% overall yield over four steps from lactol 2. 相似文献
992.
Kwang Soo Kim Eun Jin Jun Sook Kyung Kim Jaeduk Yoo Myung Ho Hyun Juyoung Yoon 《Tetrahedron letters》2007,48(14):2481-2484
Two new binaphthyl-azacrown-anthracene fluorophores were synthesized. These new fluorescent receptors exhibited large fluorescent changes with aqueous Hg2+, Cu2+ and Zn2+. Interestingly, the fluorescent emissions from the binaphthyl and anthracene groups using different excitation wavelengths showed different patterns in the presence of metal ions. The chiral recognitions of these receptors with chiral ammonium guests were also examined. 相似文献
993.
Jae Keun Yoo 《Journal of multivariate analysis》2008,99(8):1825-1839
Recent sufficient dimension reduction methodologies in multivariate regression do not have direct application to a categorical predictor. For this, we define the multivariate central partial mean subspace and propose two methodologies to estimate it. The first method uses the ordinary least squares. Chi-squared distributed statistics for dimension tests are constructed, and an estimate of the target subspace is consistent and efficient. Moreover, the effects of continuous predictors can be tested without assuming any model. The second method extends Iterative Hessian Transformation to this context. For dimension estimation, permutation tests are used. Simulated and real data examples for illustrating various properties of the proposed methods are presented. 相似文献
994.
In this paper, we propose a memory state feedback model predictive control (MPC) law for a discrete-time uncertain state delayed system with input constraints. The model uncertainty is assumed to be polytopic, and the delay is assumed to be unknown, but with a known upper bound. We derive a sufficient condition for cost monotonicity in terms of LMI, which can be easily solved by an efficient convex optimization algorithm. A delayed state dependent quadratic function with an estimated delay index is considered for incorporating MPC problem formulation. The MPC problem is formulated to minimize the upper bound of infinite horizon cost that satisfies the sufficient conditions. Therefore, a less conservative sufficient conditions in terms of linear matrix inequality (LMI) can be derived to design a more robust MPC algorithm. A numerical example is included to illustrate the effectiveness of the proposed method. 相似文献
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Yong-Seong Byeon Eun Jeong Hong Seungryul Yoo Taihyeop Lho Sung-Young Yoon Seong Bong Kim Suk Jae Yoo Seungmin Ryu 《Plasma Chemistry and Plasma Processing》2017,37(5):1405-1416
We demonstrated a pilot-scaled underwater plasma discharge device for the treatment of ballast water (5 ton/h). Phytoplankton and microorganisms in the ballast water were successfully removed using underwater plasma with capillary electrodes. Microorganisms between 10 and 50 μm in the ballast water were eliminated with an efficiency of 99.9% as well as heterotrophic bacteria with an efficiency of 92.7%. 相似文献
999.
Oxidation of various carbohydrates into ammonium formate was investigated in the presence of hydrogen peroxide and ammonium hydroxide. Most of the examined carbohydrates except nonreducing sugars were efficiently converted into ammonium formate under environment friendly and mild conditions in aqueous media. 相似文献
1000.
The aim of this article is to link Schubert varieties in the flag manifold with hyperplane arrangements. For a permutation, we construct a certain graphical hyperplane arrangement. We show that the generating function for regions of this arrangement coincides with the Poincaré polynomial of the corresponding Schubert variety if and only if the Schubert variety is smooth. We give an explicit combinatorial formula for the Poincaré polynomial. Our main technical tools are chordal graphs and perfect elimination orderings. 相似文献