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排序方式: 共有80条查询结果,搜索用时 15 毫秒
1.
Stockman RA Sinclair A Arini LG Szeto P Hughes DL 《The Journal of organic chemistry》2004,69(5):1598-1602
An entirely two-directional synthesis of (+/-)-perhydrohistrionicotoxin is presented, utilizing a tandem oxime formation/Michael addition/[3 + 2] cycloaddition as the key step. This approach also constitutes formal syntheses of (+/-)-histrionicotoxin and (+/-)-histrionicotoxin 235A. 相似文献
2.
The quaternion algebraB[j] over a commutative ringB with 1 defined byS. Parimala andR. Sridharan is generalized in two directions: (1) the ringB may be non-commutative with 1, and (2)j
2 may be any invertible element (not necessarily –1). LetG={} be an automorphism group ofB of order 2, andA={b inB| (b)=b}. LetB[j] be a generalized quaternion algebra such thataj (a) for eacha inB. It will be shown thatB is Galois (for non-commutative ring extensions) overA which is contained in the center ofB if and only ifB[j] is Azumaya overA. Also,A[j] is a splitting ring forB[j] such thatA[j] is Galois overA. Moreover, we shall determine which automorphism group ofA[j] is a Galois group. 相似文献
3.
Margherita Modesti Colleen Szeto Renata Ristic WenWen Jiang Julie Culbert Keren Bindon Cesare Catelli Fabio Mencarelli Pietro Tonutti Kerry Wilkinson 《Molecules (Basel, Switzerland)》2021,26(6)
When bushfires occur near grape growing regions, vineyards can be exposed to smoke, and depending on the timing and duration of grapevine smoke exposure, fruit can become tainted. Smoke-derived volatile compounds, including volatile phenols, can impart unpleasant smoky, ashy characters to wines made from smoke-affected grapes, leading to substantial revenue losses where wines are perceivably tainted. This study investigated the potential for post-harvest ozone treatment of smoke-affected grapes to mitigate the intensity of smoke taint in wine. Merlot grapevines were exposed to smoke at ~7 days post-veraison and at harvest grapes were treated with 1 or 3 ppm of gaseous ozone (for 24 or 12 h, respectively), prior to winemaking. The concentrations of smoke taint marker compounds (i.e., free and glycosylated volatile phenols) were measured in grapes and wines to determine to what extent ozonation could mitigate the effects of grapevine exposure to smoke. The 24 h 1 ppm ozone treatment not only gave significantly lower volatile phenol and volatile phenol glycoside concentrations but also diminished the sensory perception of smoke taint in wine. Post-harvest smoke and ozone treatment of grapes suggests that ozone works more effectively when smoke-derived volatile phenols are in their free (aglycone) form, rather than glycosylated forms. Nevertheless, the collective results demonstrate the efficacy of post-harvest ozone treatment as a strategy for mitigation of smoke taint in wine. 相似文献
4.
Elnaz Miandoabchi Farzaneh Daneshzand Reza Zanjirani Farahani Wai Yuen Szeto 《The Journal of the Operational Research Society》2015,66(6):894-913
This paper aims to model and investigate the discrete urban road network design problem, using a multi-objective time-dependent decision-making approach. Given a base network made up with two-way links, candidate link expansion projects, and candidate link construction projects, the problem determines the optimal combination of one-way and two-way links, the optimal selection of capacity expansion projects, and the optimal lane allocations on two-way links over a dual time scale. The problem considers both the total travel time and the total CO emissions as the two objective function measures. The problem is modelled using a time-dependent approach that considers a planning horizon of multiple years and both morning and evening peaks. Under this approach, the model allows determining the sequence of link construction, the expansion projects over a predetermined planning horizon, the configuration of street orientations, and the lane allocations for morning and evening peaks in each year of the planning horizon. This model is formulated as a mixed-integer programming problem with mathematical equilibrium constraints. In this regard, two multi-objective metaheuristics, including a modified non-dominated sorting genetic algorithm (NSGA-II) and a multi-objective B-cell algorithm, are proposed to solve the above-mentioned problem. Computational results for various test networks are also presented in this paper. 相似文献
5.
6.
K. Y. Szeto 《Hyperfine Interactions》1986,31(1-4):87-92
A theory is developed for the calculation of zero field muon spin relaxation function for classical simple magnets (Ising,
XY, and Heisenberg) in D(=1,2,3) dimensions. The results are different from the Kubo-Toyabe theory, except for Heisenberg
system in three dimension. Relation between the relaxation function and random field distribution is dicussed and a new method
of analysing experimental data is suggested and discussed in the context of spin glasses. 相似文献
7.
Damage spreading(DS) of the random graph networks with power-law degree distributions is investigated using Glauber dynamics. Various subgraphs defined by the probability of acquaintance show distinct features in DS as measured by Hamming distance. A heuristic understanding of the long-time value of damage is achieved through an analysis of the survivor statistics. All survivors are dynamical, flipping in unison for the controlled sample and the damaged sample. Verification of these dynamic survivors is achieved through the introduction of a new measure of self-damage. 相似文献
8.
The double‐chain coordination polymer, {[Zn(H2O)6][Zn(bbtc)H2O]·4H2O}n (bbtc = 3,3′, 4,4′‐benzophenonetetracarboxylate), features two kinds of zinc center. One is octahedrally coordinated by six aqua ligands and the other is coordinated by four carboxylate oxygen atoms, derived from three bbtc ligands, and a water molecule, forming a geometry intermediate between square‐pyramidal and trigonal bipyramidal. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
General base-catalyzed double-Michael reactions of allenes with various dinucleophiles are described. The reactions are facilitated most efficiently by a catalytic amount of trimethylphosphine, affording six types of C2-functionalized benzannulated five-membered heterocycles: benzimidazolines, benzoxazolines, benzothiazolines, 1,3-benzodioxoles, 1,3-benzoxathioles, and 1,3-benzodithioles. This atom-economical reaction is operationally simple and provides the product heterocycles in good to excellent yields. Careful mechanistic studies unveiled the phosphine-triggered general base catalysis pathway. Furthermore, the double-Michael reaction can serve as an alternative method for the selective monoketalization of β-diketones. 相似文献
10.