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41.
Chollet C Crousse B Ourévitch M Bonnet-Delpon D 《The Journal of organic chemistry》2006,71(8):3082-3085
In this paper, we report a simple route to accede to a new family of C-10 fluorinated derivatives of artemisinin 7. We demonstrated that nucleophilic substitution of the allylic bromide 6 with alcohols can occur at carbon 10 (compounds 7) under solvolytic conditions (S(N)'/S(N) ratio, 87:13). Furthermore, using the particular properties of hexafluoroisopropanol (HFIP), we are able to increase the selectivity of the substitution. Primary alcohols are completely selective for allylic substitution. With amines as nucleophiles, selectivity of substitution is dependent on their nucleophilicity, but attack at carbon 16 was always favored. However, the S(N)'/S(N) ratio could be slightly increased by adding HFIP, which is able to modulate their nucleophilicity through hydrogen bonding. In preliminary in vitro assessments, these new compounds, 7, exhibited a satisfying activity against malaria. 相似文献
42.
George A Knez M Hlawacek G Hagedoorn D Verputten HH van Gastel R ten Elshof JE 《Langmuir : the ACS journal of surfaces and colloids》2012,28(5):3045-3052
A simple methodology to fabricate micrometer- and nanometer-scale patterned surfaces with multiple chemical functionalities is presented. Patterns with lateral dimensions down to 110 nm were made. The fabrication process involves multistep gas-phase patterning of amine, thiol, alkyl, and fluorinated alkyl-functional organosilane molecules using PDMS molds as shadow masks. Also, a combination process of channel diffused plasma etching of organosilane molecular thin films in combination with masked gas-phase deposition to fabricate multilength scale, multifunctional surfaces is demonstrated. 相似文献
43.
A matching game is a cooperative game (N, v) defined on a graph G = (N, E) with an edge weighting
w: E? \mathbb R+{w: E\to {\mathbb R}_+}. The player set is N and the value of a coalition S í N{S \subseteq N} is defined as the maximum weight of a matching in the subgraph induced by S. First we present an O(nm + n
2 log n) algorithm that tests if the core of a matching game defined on a weighted graph with n vertices and m edges is nonempty and that computes a core member if the core is nonempty. This algorithm improves previous work based on
the ellipsoid method and can also be used to compute stable solutions for instances of the stable roommates problem with payments.
Second we show that the nucleolus of an n-player matching game with a nonempty core can be computed in O(n
4) time. This generalizes the corresponding result of Solymosi and Raghavan for assignment games. Third we prove that is NP-hard to determine an imputation with minimum number of blocking pairs, even for matching games with unit edge weights, whereas
the problem of determining an imputation with minimum total blocking value is shown to be polynomial-time solvable for general
matching games. 相似文献
44.
45.
We show that ifG is a semisimple algebraic group defined overQ and Γ is an arithmetic lattice inG:=G
R with respect to theQ-structure, then there exists a compact subsetC ofG/Γ such that, for any unipotent one-parameter subgroup {u
t} ofG and anyg∈G, the time spent inC by the {u
t}-trajectory ofgΓ, during the time interval [0,T], is asymptotic toT, unless {g
−1utg} is contained in aQ-parabolic subgroup ofG. Some quantitative versions of this are also proved. The results strengthen similar assertions forSL(n,Z),n≥2, proved earlier in [5] and also enable verification of a technical condition introduced in [7] for lattices inSL(3,R), which was used in our proof of Raghunathan’s conjecture for a class of unipotent flows, in [8]. 相似文献
46.
Kristo Michael J. Williams Ross Gaffney Amy M. Kayzar-Boggs Theresa M. Schorzman Kerri C. Lagerkvist Petra Vesterlund Anna Ramebäck Henrik Nelwamondo Aubrey N. Kotze Deon Song Kyuseok Lim Sang Ho Han Sun-Ho Lee Chi-Gyu Okubo Ayako Maloubier Didier Cardona Danièle Samuleev Pavel Dimayuga Ike Varga Zsolt Wallenius Maria Mayer Klaus Loi Elaine Keegan Elizabeth Harrison Jennifer Thiruvoth Sangeeth Stanley Floyd E. Spencer Khal J. Tandon Lav 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):425-434
Journal of Radioanalytical and Nuclear Chemistry - In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched... 相似文献
47.
We describe necessary and sufficient conditions for orbits of linear transformations onR
n
,n1, and sets arising as sums of elements from orbits, to be harmonious subsets. This is done via a generalization of the notion of Pisot-Vijayaraghavan and Salem numbers. 相似文献
48.
49.
S. G. Dani 《Israel Journal of Mathematics》2001,126(1):327-344
We show that ifG is a connected Lie group with an abelian group of automorphisms acting ergodically on it then there exists a compact central
subgroup inG such thatG/C is a vector group. Various related questions about such actions are also discussed.
Research supported by EPSRC Grant GRK99015. 相似文献
50.
Hajo Broersma Jiří Fiala Petr A. Golovach Tomáš Kaiser Daniël Paulusma Andrzej Proskurowski 《Journal of Graph Theory》2015,79(4):282-299
We prove that for all an interval graph is ‐Hamilton‐connected if and only if its scattering number is at most k. This complements a previously known fact that an interval graph has a nonnegative scattering number if and only if it contains a Hamilton cycle, as well as a characterization of interval graphs with positive scattering numbers in terms of the minimum size of a path cover. We also give an time algorithm for computing the scattering number of an interval graph with n vertices and m edges, which improves the previously best‐known time bound for solving this problem. As a consequence of our two results, the maximum k for which an interval graph is k‐Hamilton‐connected can be computed in time. 相似文献