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201.
202.
203.
Hyuk Yoon Seunghyun Ahn Doseok Hwang Geunhyeong Jo Dong Woon Kim Sang Ho Kim Dongsoo Koh Yoongho Lim 《Magnetic resonance in chemistry : MRC》2012,50(11):759-764
Several types of chalcones containing 2H‐chromen group were synthesized. Claisen–Schmidt condensation of 2H‐chromen‐3‐carbaldehydes (I) with methoxy substituted acetophenones afforded (E)‐3‐(2H‐chromen‐3‐yl)‐1‐(methoxyphenyl)prop‐2‐en‐1‐ones (chromenylchalcones, 1–7). Other types of chromenylchalcone, (E)‐1‐(6‐methoxy‐2H‐chromen‐3‐yl)‐3‐(methoxyphenyl)prop‐2‐en‐1‐ones (8–13) were also obtained between reaction of methoxy substituted benzaldehydes and 1‐(6‐methoxy‐2H‐chromen‐3‐yl)ethanone (II). Dichromenylchalcones (14–16) were also synthesized through the same reaction between aldehydes (I) and ketone (II). Their complete 1H‐NMR and 13C‐NMR assignments are reported here and more polysubstituted chromenylchalcones synthesized or isolated from the natural sources in the future can be identified on the basis of the NMR data reported here. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
204.
205.
Yoon Yeol Yoon Kil Yong Lee Kyung Seok Ko 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):591-595
The contents of H-3 and C-14 in groundwater and surface waters around low and medium-level atomic waste repository site in
Korea were determined. The concentrations of C-14 were in the range 0.186–0.287 Bq/L. The H-3 concentration of the groundwaters
and surface waters were <0.06–5.75 and 1.22–4.74 Bq/L. The average H-3 contents of west, north and south direction were 1.18 ± 0.12,
1.11 ± 0.78 and 2.85 ± 2.66. H-3 and C-14 concentrations in the south direction were relatively higher than west and north
direction samples. The surface waters sampled from catchment were four times higher than average H-3 concentration in precipitation.
The concentrations of H-3 and C-14 within 5 km area samples were much higher than other samples. 相似文献
206.
Let X be a closed, oriented Riemannian 4-manifold. Suppose that a cyclic group Z(
p
(p is prime) acts on X by an orientation preserving isometry with an embedded Riemann surface as fixed point set. We study the representation of Z
p
on the Spinc-bundles and the Z
p-invariant moduli space of the solutions of the Seiberg–Witten equations for a Spinc-structure X. When the Z
p
action on the determinant bundle det L acts non-trivially on the restriction L| over the fixed point set , we consider -twisted solutions of the Seiberg-Witten equations over a Spinc-structure ' on the quotient manifold X/Z
p
X', (0,1). We relate the Z
p
-invariant moduli space for the Spinc-structure on X and the -twisted moduli space for the Spinc-structure on X'. From this we induce a one-to-one correspondence between these moduli spaces and calculate the dimension of the -twisted moduli space. When Z
p
acts trivially on L|, we prove that there is a one-to-one correspondence between the Z
p
-invariant moduli space M(
Zp
and the moduli space M (") where ' is a Spinc-structure on X' associated to the quotient bundle L/Z
p
X'. vskip0pt When p = 2, we apply the above constructions to a Kahler surface X with b
2
+
(X) > 3 and H
2(X;Z) has no 2-torsion on which an anti-holomorphic involution acts with fixed point set , a Lagrangian surface with genus greater than 0 and []2H
2(H ;Z). If
K
X
2 > 0 or K
X
2
= 0 and the genus g()> 1, we have a vanishing theorem for Seiberg–Witten invariant of the quotient manifold X'. When K
X
2
= 0 and the genus g()= 1, if there is a Z
2-equivariant Spinc-structure on X whose virtual dimension of the Seiberg–Witten moduli space is zero then there is a Spinc-structure " on X' such that the Seiberg-Witten invariant is ±1. 相似文献
207.
Song CE Jung DU Roh EJ Lee SG Chi DY 《Chemical communications (Cambridge, England)》2002,(24):3038-3039
In Os-catalysed asymmetric dihydroxylation using NMO as a co-oxidant, the combination of an ionic liquid and the new bis-cinchona alkaloid 2 generated in situ from (QN)2PHAL during reaction provided a simple and practical approach to the recycling of both catalytic components (osmium tetraoxide and chiral ligand). 相似文献
208.
[reaction: see text] 2'-Deoxy-2'-C-difluoromethylene-4'-thiocytidine (4) as a potential antitumor agent was synthesized starting from L-xylose via 2-deoxy-2-C-difluoromethylene-4-thiosugar as a key intermediate. An elimination product, 8, was always formed as the major product during removal of the protecting groups under acidic or basic conditions. However, utilizing neutral reaction conditions to remove the protecting groups afforded the desired product 4 exclusively. 相似文献
209.
Bréchignac C Cahuzac P Carlier F Colliex C Leroux J Masson A Yoon B Landman U 《Physical review letters》2002,88(19):196103
Formation and evolution of fragmentation instabilities in fractal islands, obtained by deposition of silver clusters on graphite, are studied. The fragmentation dynamics and subsequent relaxation to the equilibrium shapes are controlled by the deposition conditions and cluster composition. Sharing common features with other materials' breakup phenomena, the fragmentation instability is governed by the length-to-width ratio of the fractal arms. 相似文献
210.
We employ kinetic theory for a binary mixture to study segregation by size and/or mass in a gravitational field. Simple segregation criteria are obtained for spheres and disks that are supported by numerical simulations. 相似文献