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901.
A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time. 相似文献
902.
Fan Liu Qing Li Hong Yang Xiao‐Ling Cai Xue‐Kui Xia Sheng‐Ping Chen Meng‐Feng Li Zhi‐Gang She Yong‐Cheng Lin 《Magnetic resonance in chemistry : MRC》2009,47(5):453-455
Two new natural products, tenelate A ( 1 ) and B ( 2 ), together with the known compound, tenellic acid C ( 3 ), were isolated from the mangrove endophytic fungus Talaromyces sp. (SBE‐14), from the South China Sea. Their structures were elucidated by spectroscopic methods, mainly 1D and 2D NMR techniques. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
903.
Pan Peng Yi‐Zhang Chen Yan‐Fang Gao Jian Yu Zhao‐Xia Guo 《Journal of Polymer Science.Polymer Physics》2009,47(19):1853-1859
Polyoxymethylene/thermoplastic polyurethane (POM/TPU) blends containing 10–30 wt % of TPU were electrospun using hexafluoroisopropanol as the solvent. The average fiber diameter increases with the increase in TPU content from 0.68 μm for neat POM fibers to 0.92 μm for POM/TPU 7:3 blend fibers due to the increase in solution viscosity. Core/sheath structure with the major component POM as the core and the minor component TPU as the sheath was observed by transmission electron microscopy and further confirmed by surface N contents of the blend fiber mats. The crystalline melting point and the degree of crystallinity of POM have no obvious change by coelectrospinning with TPU due to lack of interaction between POM and TPU as revealed by Fourier transform infrared spectroscopy. Tensile tests showed that the unusual high ductility of POM fiber mat could be further increased by coelectrospinning with 10 or 20 wt % TPU without significantly decreasing the stiffness and strength. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1853–1859, 2009 相似文献
904.
In this paper, a new one-step explicit method of fourth order is derived. The new method is proved to be A-stable and L-stable, and it gives exact results when applied to the test equation y'=λy with Re(λ)<0, Also several numerical examples are included. 相似文献
905.
906.
X. W. Zhang Y. H. Zhu J. B. Xia 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):133-142
The Hamiltonian in the framework of eight-band effective-mass
approximation of the zinc-blende nanowires and nanorods in the
presence of external homogeneous magnetic field is given in the
cylindrical coordinate. The electronic structure, optical
properties, magnetic energy levels, and g factors of the nanowires
and nanorods are calculated. It is found that the electron states
consist of many hole-state components, due to the coupling of the
conduction band and valence band. For the normal bands which are
monotone functions of |kz|, long nanorods can be modeled by the
nanowires, the energy levels of the nanorods approximately equal
the values of the energy band E(kz) of the nanowires with the
same radius at a special kz, where kz is the wave vector
in the wire direction. Due to the coupling of the states, some of
the hole energy bands of the nanowires have their highest points
at kz≠0. Especially, the highest hole state of the InSb
nanowires is not at the kz=0 point. It is an indirect band
gap. For these abnormal bands, nanorods can not be modeled by the
nanowires. The energy levels of the nanorods show an interesting
plait-like pattern. The linear polarization factor is zero, when
the aspect ratio L/2R is smaller than 1, and increases as the
length increases. The gz and gx factors as functions of
the kz, radius R and length L are calculated for the
wires and rods, respectively. For the wires, the gz of the
electron ground state increases, and the gz of the hole
ground state decreases first, then increases with the kz
increasing. For the rods, the gz and gx of the electron
ground state decrease as the R or the L increases. The gx
of the hole ground state decreases, the gz of the hole ground
state increases with the L increasing. The variation of the
gz of the wires with the kz is in agreement with the
variation of the gz of the rods with the L. 相似文献
907.
In this paper we will provide a theory for an extrapolation algorithm of band-limited signals with sampling errors or low
noises. The main result is as follows: Suppose thatf(t) is in L2 and is a continuous Ω band-limited signal. Then for any positive numbers T, A(>T) and ε, there exists a δ>0 such that when
the sampling errors (or noises) off(t) on [−T, T] is less than δ we can extrapolate the values off(t) on the interval [−A, A] such that the difference between the extrapolated value and the exact value off(t) does not exceed ε. 相似文献
908.
Bulk viscosity for interacting strange quark matter and r-mode instability windows for strange stars
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We investigate the bulk viscosity of strange quark matter in the framework of the equivparticle model,where analytical formulae are obtained for certain temperature ranges,which can be readily applied to those with various quark mass scalings.In the case of adopting a quark mass scaling with both linear confinement and perturbative interactions,the obtained bulk viscosity increases by 1-2 orders of magnitude compared with those in bag model scenarios.Such an enhancement is mainly due to the large quark equivalent masses adopted in the equivparticle model,which are essentially attributed to the strong interquark interactions and are related to the dynamical chiral symmetry breaki ng.Due to the high bulk viscosity,the predicted damping time of oscillatio ns for a can on ical 1.4 M⊙ strange star is less than one millisecond,which is shorter than previous findings.Consequently,the obtained r-mode instability window for the canonical strange stars well accommodates the observational frequencies and temperatures for pulsars in low-mass X-ray binaries(LMXBs). 相似文献
909.
The phase state of dense matter in the intermediate density range (\begin{document}$\sim$\end{document} ![]()
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1-10 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit (\begin{document}$c_s/c=1/\sqrt{3}$\end{document} ![]()
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) at high densities and should also fulfill the causality limit (\begin{document}$c_s/c<1$\end{document} ![]()
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). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future high-precision radius measurements of pulsar-like objects. 相似文献
910.
By means of collision models(CMs) where the environment is simulated by a collection of ancillas consisting of two entangled qubits, we investigate the effects of entanglement in the environment on the non-Markovianity of an open quantum system. Two CMs are considered in this study, in the first one the open quantum system S directly collides with the environment,while in the second one the system interacts with two intermediate qubits which, in turn, are coupled to the environment. We show that it is possible to enhance the non-Markovianity by environment entanglement in both models. In particular, in the second model, we show that the initial state of the auxiliary qubits can also affect the non-Markovianity of the system and there exists the optimal combination of the initial environmental state and the initial state of auxiliary qubits. In this case, the non-Markovianity can be greatly enhanced. 相似文献