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981.
982.
Measurement of emerging dechloranes in human serum using modulated gas chromatography coupled to electron capture negative ionization time‐of‐flight mass spectrometry
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983.
Although the synthetic potential of the intramolecular variant of the Diels-Alder reaction has now been fully recognized3, little attention has so far been paid to this type of addition using the furan nucleus as the diene partner4–8. The presence of an oxygenated cyclohexene system in several complex natural products (e.g. gibberellic acid, morphine), the diverse possibilities of the substituted 7-oxabicyclo |2.2.1|-2-heptene system for further transformation9, the expected enhanced reactivity and stereoselectivity of the intramolecular cycloaddition and the availability of a wide variety of commercial furan derivatives make the sequence a → b → c particularly attractive in total synthesis. 相似文献
984.
A synthetic tris-(bis-(aminomethyl)pyridine) receptor was prepared in excellent yields via reversible imine condensation strategy. Catalytic activity in Henry reactions of the corresponding copper(II) complex was studied. Capitalizing on previous works by Anslyn with related receptors, the dramatic increase in basicity induced by this type of complex on diketo-derivatives was used to perform a nucleophilic addition of a deprotonated substrate onto an electrophile within the cavity. Hence, a Lewis acid stabilized nitronate was reacted with various aldehydes. A notable preference for small reactants easily accommodated in the cavity over encumbered ones was observed, thus representing an example of substrate-selectivity. 相似文献
985.
Gravitational sinking in the water column is known to affect size composition of planktonic communities. One important driver toward the reduction of plankton size is the fact that larger cells tend to sink faster below the euphotic layer. In this work, we discuss the role of gravitational sinking in driving cell size selection, showing that the outcome of phytoplankton competition is determined by the dependence of sinking velocity on cell size, shape, and on the temporal variability associated with turbulence. This opens a question on whether regional modulations of the turbulence intensity could affect size distribution of planktonic communities. 相似文献
986.
987.
Francesco De Vincentiis Giorgio Bencivenni Dr. Fabio Pesciaioli Andrea Mazzanti Dr. Giuseppe Bartoli Prof. Patrizia Galzerano Dr. Paolo Melchiorre Prof. Dr. 《化学:亚洲杂志》2010,5(7):1652-1656
The first catalytic method for the asymmetric aziridination of cyclic enones is described. The presented organocatalytic strategy is based on the use of an easily available organocatalyst that is able to convert a wide range of cyclic enones into the desired aziridines with very high enantiomeric purity and good chemical yield. Such a method may very well open up new opportunities to stereoselectively prepare complex chiral molecules that possess an indane moiety, a framework that is found in a large number of bioactive and pharmaceutically important molecules 相似文献
988.
We developed a constituent quark-diquark model for the nucleon and its resonances using a harmonic oscillator potential for
the interaction. The effects due to relativistic kinetic energy correction are studied. Finally, charge form factor of the
model is calculated and compared with experimental data.
相似文献
989.
990.
A. De Roeck A. Katre P. Mermod D. Milstead T. Sloan 《The European Physical Journal C - Particles and Fields》2012,72(4):1985
The experiments at the Large Hadron Collider (LHC) are able to discover or set limits on the production of exotic particles
with TeV-scale masses possessing values of electric and/or magnetic charge such that they behave as highly ionising particles
(HIPs). In this paper the sensitivity of the LHC experiments to HIP production is discussed in detail. It is shown that a
number of different detection methods are required to investigate as fully as possible the charge-mass range. These include
direct detection as the HIPs pass through either passive or active detectors and, in the case of magnetically charged objects,
the so-called induction method with which magnetic monopoles which stop in accelerator and detector material could be observed.
The benefit of using complementary approaches to HIP detection is discussed. 相似文献