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101.
Using a representation of multichannel quantum defect theory in terms of a quantum Poincaré map for bound Rydberg molecules, we apply Jung's scattering map to derive a generalized quantum map, that includes the continuum. We show that this representation not only simplifies the understanding of the method, but moreover produces considerable numerical advantages. Finally we show under what circumstances the usual semi-classical approximations yield satisfactory results. In particular we see that singularities that cause problems in semi-classics are irrelevant to the quantum map. 相似文献
102.
103.
Giraud N Blackledge M Goldman M Böckmann A Lesage A Penin F Emsley L 《Journal of the American Chemical Society》2005,127(51):18190-18201
A detailed analysis of nitrogen-15 longitudinal relaxation times in microcrystalline proteins is presented. A theoretical model to quantitatively interpret relaxation times is developed in terms of motional amplitude and characteristic time scale. Different averaging schemes are examined in order to propose an analysis of relaxation curves that takes into account the specificity of MAS experiments. In particular, it is shown that magic angle spinning averages the relaxation rate experienced by a single spin over one rotor period, resulting in individual relaxation curves that are dependent on the orientation of their corresponding carousel with respect to the rotor axis. Powder averaging thus leads to a nonexponential behavior in the observed decay curves. We extract dynamic information from experimental decay curves, using a diffusion in a cone model. We apply this study to the analysis of spin-lattice relaxation rates of the microcrystalline protein Crh at two different fields and determine differential dynamic parameters for several residues in the protein. 相似文献
104.
C-H bond activation has been extensively studied with (Cp*)M(L)n (M = Ir, Rh), but cobalt, the third member of this triad, has not previously been shown to activate sp3 C-H bonds. Further, practical functionalization of the metal alkyl products of oxidative addition has not been fully explored. Toward these ends, we have developed catalytic dehydrogenation of alkyl amines with a Co(I) catalyst. Amine substrates are protected with vinyl silanes, followed by catalytic transfer hydrogenation, to yield a broad range of stable protected enamines and 1,2-diheteroatom-substituted alkenes, including several unprecedented heterocycles. (Cp*)Co(VTMS)2 catalyzes transfer hydrogenation under surprisingly mild conditions with high chemo-, regio-, and diastereoselectivity, while tolerating additional functionality. 相似文献
105.
Maurice Dubois 《Experimental Mechanics》1981,21(11):401-407
ONERA, the French Aerospace Research Institute, currently design, manufacture and calibrate the many dynamometers and balances, measuring one or several components, necessary for the tests in the large wind tunnels and other installations of its Modane-Avrieux and Le Fauga-Mauzac Centers, as well as those requested by external organizations, in France or abroad. The number of dynamometric sensors realized since 1955 amounts to several hundreds. Their capacities range from 0.01 N to 1000 kN. Their precision is usually about 10?3, but may reach 10?4. This paper describes the problems concerning the metallic architecture of the multicomponent balances, their strain-gage and electric equipment, thermal effects and their compensation it presents the general principles and the means used for the calibration of these balances. 相似文献
106.
Dissolution and Seepage Coupling Effect on Transport and Mechanical Properties of Glauberite Salt Rock 总被引:1,自引:0,他引:1
Weiguo Liang Yangsheng Zhao Suguo Xu Maurice B. Dusseault 《Transport in Porous Media》2008,74(2):185-199
Potential high rates of aqueous dissolution are characteristic of salt rocks, and solute and mass flux through a soluble porous
medium are functions of solute concentration gradients and pressure gradients. Due to different dissolution properties for
different mineral components in glauberite salt rock, an interaction between mineral dissolution and solvent seepage arises,
driven by the hydraulic pressure gradient in the rock. The originally almost impermeable glauberite rock becomes an increasingly
permeable porous medium with dissolution, changing the transport and mechanical properties because of the progressive removal
of solid sodium sulfate (Na2SO4), one of the constitutive components of glauberite salt rock. Glauberite is often found in bedded salt rock deposits, and
the mineral glauberite has economic value and has been mined for many years in China. More economic and safe technologies,
such as controlled solution mining, are inherently attractive. Thus, investigations into relevant physical and mechanical
properties of glauberite in the context of solution mining have value, and to clarify glauberite behaviour, a series of experiments
were performed. It is observed through experiments that the permeability of the rock mass during dissolution of glauberite
is a function of the dissolution duration and the hydraulic pressure gradient applied to the system. For example, in laboratory
tests, after 49, 53 and 70 h of dissolution, the relationships between permeability (k—cm2) and pressure gradient (Δp—MPa across the specimen of length 100 mm) of the glauberite specimens were observed to be k = 0.24 for a Δp of 0.10, k = 0.30 for a Δp of 0.12, and k = 0.41 for a Δp of 0.18, with the empirical functional relationship becoming gradually steeper with pressure. Also, the triaxial compression
(mechanical) characteristics of glauberite salt rock change substantially after a period of dissolution: the compressive strength
under a confining stress of σ3 = 2.0 MPa changes initially from 46 to 11 MPa after 70 h of dissolution and seepage. Along with strength degradation, the
Young’s modulus (stiffness) changed from 4.6 to 0.5 GPa. Evidently, coupled dissolution and seepage rate greatly impact both
transport and mechanical properties of the rock as fabric evolves in a time-dependent manner. 相似文献
107.
Gerd Finke Pierre Lemaire Jean-Marie Proth Maurice Queyranne 《European Journal of Operational Research》2009,199(3):702-705
In this paper, we present a new objective function for scheduling on parallel machines: minimizing the number of machines for schedules of minimum length. We study its complexity and we prove the NP-completeness of this problem, even if there is no precedences or for unitary execution times. We propose several polynomial algorithms for various particular cases. 相似文献
108.
109.
New 4-aminoquinolines having a -CF2CH-(heteroaryl)-OH moiety are obtained in moderate yields from the electrochemical catalyzed reaction of the corresponding 4-amino-3-chlorodifluoroacetyl-2-methoxyquinoline in the presence of heteroaryl aldehydes. A one-pot intramolecular zinc mediated aromatic nucleophilic substitution also gave access to novel difluorinated 5-aminodihydropyrano[2,3-b]quinolin-4-ones. 相似文献
110.