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Genevieve S. Walsh 《Topology》2005,44(5):947-958
We show that all two-bridge knot and link complements are virtually fibered. We also show that spherical Montesinos knot and link complements are virtually fibered. This is accomplished by showing that such manifolds are finitely covered by great circle link complements. 相似文献
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We prove a Bruckner–Garg type theorem for the fiber structure of a generic map from a continuum X into the unit interval I. We also study the specific case of X=S2. We show that each nondegenerate component of each fiber of a generic map in C(S2,I) is figure-eight-like. This together with a result by Krasinkiewicz and Levin gives that each nondegenerate component of each fiber of a generic map in C(S2,I) is hereditarily indecomposable and figure-eight-like. We also show that pseudoarcs, pseudocircles and Lakes of Wada appear in abundance in fibers of a generic map in C(S2,I). We also exhibit a general method for proving when a P-like hereditarily indecomposable continuum is Q-like when Q is a certain graph containing P. 相似文献
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Didier Revel Pierre Loubeyre Alexandra Delignette Philippe Douek Michel Amiel 《Magnetic resonance imaging》1993,11(8):1101-1105
The authors propose a new imaging approach for studying thoracic great vessels, using high-speed MR imaging combined with intravenous rapid bolus injection of a paramagnetic contrast media. The decrease of the T1 relaxation time of flowing blood induced by the contrast agent (Gd-DOTA) caused an increased signal intensity within the vessel lumen for a time period allowing multiplanar imaging of various vascular structures. The intraluminal signal enhancement is mainly related to the blood concentration of the contrast agent as in conventional X-ray angiography. Information on the aorta and pulmonary arteries obtained by the so-called contrast-enhanced magnetic resonance tomoangiography appears complementary to that obtained with other vascular MR imaging procedures such as cine-MRI and magnetic resonance angiography (MRA). 相似文献
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J.Mansel DaVies Sakarindr Bhumiratana R.Byron Bird 《ournal of non Newtonian Fluid Mechanics》1978,3(3):237-259
In the earlier theoretical work of Barnes, Townsend, and Walters on pulsatile flow of viscoelastic fluids, it was found that an Oldroyd model predicted that flow enhancement should decrease with increasing frequency of pulsation, whereas their experimental data showed an increase. Their calculations have been repeated for the Goddard—Miller model using two different expressions for the relaxation modulus; it is found that the Goddard—Miller model leads to the same discrepancy between theory and experiment. It is tentatively concluded that secondary-flow effects are playing an important role. The role of the elastic and inertial effects and the role of the shape of the viscosity vs. shear rate curve are discussed. 相似文献
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Novel semi-synthetic derivatives of penicillin and cephalosporin have been prepared in which the conventional phenyl or heteroaromatic group has been replaced by a ferrocene moiety, and in which the metal atom is in close proximity to the β-lactam ring of the antibiotic; several of the compounds exhibit high antibiotic activity and others are potent β-lactamase inhibitors. 相似文献
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The photochemical reaction of tricarbonyl-η6-1,3,5-cycloheptatriene-chromium(0) (I) with tricyclo[6.3.0.02,7]undeca-3,5-diene (II) in n-pentane at 248 K yields the [4 + 6]-cycloadduct tricarbonyl-η6-pentacyclo[7.6.2.110,15.02,8.03,7]octadeca-11,13,16-triene-chromium(0) (III). Detachment of the pentacyclic triene ligand from chromium can be achieved with trimethylphosphite. The constitutions of complex III and of the pentacyclic hydrocarbon IV were determined by spectroscopic means. 相似文献
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大数定律和中心极限定理在保险业中的重要应用 总被引:4,自引:0,他引:4
王东红 《数学的实践与认识》2005,35(10):128-133
结合《车祸赔付倍涨,车险保额不涨?》报道,阐述了大数法则和中心极限理论在保险中的重要作用.经过分析计算,当机动车第三者保险金额不超过20万元时,保险公司的预期利润最有保障,这就说明了目前机动车第三者责任险最高只能投保20万元的根本原因. 相似文献