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991.
Abstract

Kabachnik-Fields reactions of a variety of amines, phospha-Michael additions to maleimide derivatives and alcoholysis of dialkyl phosphites were studied under microwave conditions.  相似文献   
992.
The polymerization of vinyl monomers with a binary system composed of N-chlorosuccinimide (NCS) and some Lewis acids was investigated by means of kinetic and spectral determinations. It was found that the NCS-ZnCl2 system was the most effective as an initiator of radical polymerization of methyl methacrylate, and this polymerization was initiated by a radical produced via the reaction of NCS and ZnCl2, and terminated bimolecularly. By applying a spin trapping technique to the reaction of NCS with ZnCl2, it was shown that the initiating radical was N-succinimidyl radical which was obtained through a homolysis at the N-Cl bond.  相似文献   
993.
Multi‐component polymer nanomaterials have attracted great attention because of their applications in areas such as biomedicine, tissue engineering, and organic solar cells. The precise control over the morphologies of multi‐component polymer nanomaterials, however, is still a great challenge. In this work, the fabrication of poly(methyl methacrylate)(PMMA)/poly­styrene (PS) nanostructures that contain PMMA shells and encapsulated PS nanospheres is studied. The nanostructures are prepared using a triple solution wetting method with anodic aluminum oxide (AAO) templates. The nanopores of the templates are wetted sequentially by PS solutions in dimethylformamide (DMF), PMMA solutions in acetic acid, and water. The compositions and morphologies of the nanostructures are controlled by the interactions between the polymers, solvents, and AAO walls. This work not only presents a feasible method to prepare multi‐component polymer nanomaterials, but also leads to a better understanding of polymer‐solvent interactions in confined geometries.

  相似文献   

994.
An efficient synthesis of 1H-benzo[g]indazoles starting from Morita–Baylis–Hillman (MBH) adducts is disclosed. The synthesis was carried out from MBH bromide via a sequential copper-catalyzed alkynylation, one-pot synthesis of pyrazole, propargyl–allenyl isomerization, and a 6π-electrocyclization involving two aromatic π-bonds and an allenyl π-bond.  相似文献   
995.
This paper considers a diffusive ratio-dependent simple food chain model. The sufficient conditions for the existence and non-existence of coexistence states are provided. In addition, this paper investigates the uniqueness of coexistence states and examines the global attractor of the time-dependent system. Moreover, in view of extinction results, the domino effect and biological control are discussed.  相似文献   
996.
An analytical expression is proposed to the Kirkwood-Fr?hlich dipole orientation correlation parameter g. This parameter, which has been considered as a relevant guide to understanding the structuredness of supercritical fluids, had been always determined numerically. The advantage of the used protocol: the BPES, is to yield continuous and integrable expressions which can be easily incorporated in analytical models. The results have been compared to several precedent studies.  相似文献   
997.
Based on the detailed Mn L(2,3)-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO(3) or the tilted antiphase ab cycloid in Eu(3/4)Y(1/4)MnO(3). The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.  相似文献   
998.
We investigated the orbital and antiferromagnetic ordering behaviors of the half-doped bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ? 0.5) by using Mn L(2,3)-edge resonant soft x-ray scattering. Resonant soft x-ray scattering reveals the CE-type orbital order below T(oo) ? 220 K, which shows partial melting behavior below T(m) ? 165 K. We also found coexistence CE- and A-type antiferromagnetic orders. Both orders involve the CE-type orbital order with nearly the same orbital character and are coupled with each other. These results manifest that the ground state with the CE-type antiferromagnetic order is easily susceptible to destabilization into the A-type one even with a small fluctuation of the doping level, as suggested by the extremely narrow magnetic phase boundaries at x ? 0.5±0.005.  相似文献   
999.
Identifying hadronic molecular states and/or hadrons with multiquark components either with or without exotic quantum numbers is a long-standing challenge in hadronic physics. We suggest that studying the production of these hadrons in relativistic heavy ion collisions offers a promising resolution to this problem as yields of exotic hadrons are expected to be strongly affected by their structures. Using the coalescence model for hadron production, we find that, compared to the case of a nonexotic hadron with normal quark numbers, the yield of an exotic hadron is typically an order of magnitude smaller when it is a compact multiquark state and a factor of 2 or more larger when it is a loosely bound hadronic molecule. We further find that some of the newly proposed heavy exotic states could be produced and realistically measured in these experiments.  相似文献   
1000.
We report the first observation of the doubly Cabibbo-suppressed decays D(+)→K(+)η((')) using a 791 fb(-1) data sample collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. The ratio of the branching fractions of doubly Cabibbo-suppressed relative to singly Cabibbo-suppressed D(+)→π(+)η((')) decays are B(D(+)→K(+)η)/B(D(+)→π(+)η)=(3.06±0.43±0.14)% and B(D(+)→K(+)η')/B(D(+)→π(+)η')=(3.77±0.39±0.10)%. From these, we find that the relative final-state phase difference between the tree and annihilation amplitudes in D(+) decays, δ(TA), is (72±9)° or (288±9)°. We also report the most precise measurements of CP asymmetries to date: A(CP)(D(+)→π(+)η)=(+1.74±1.13±0.19)% and A(CP)(D(+)→π(+)η')=(-0.12±1.12±0.17)%.  相似文献   
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