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61.
Gilles Casano Maxime Robin Pascale Barbier Vincent Peyrot Robert Faure 《Magnetic resonance in chemistry : MRC》2010,48(9):738-744
The complete 1H and 13C NMR assignment of 9 acetamidochalcones, 18 acetamidoflavones, 18 aminoflavones, 9 acetamidoflavonols and 9 aminoflavonols has been performed using one‐ and two‐dimensional NMR techniques including COSY, HMQC and HMBC experiments. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
62.
Quantifying the nonlinear mode competition in the flow over an open cavity at medium Reynolds number 总被引:1,自引:0,他引:1
L. R. Pastur F. Lusseyran T. M. Faure Y. Fraigneau R. Pethieu P. Debesse 《Experiments in fluids》2008,44(4):597-608
Our purpose is to quantify the rate of intermittency of nonlinearly competing modes, in a dominantly mode-switching scenario. What is the rate of presence of each mode? Can they simultaneously appear in, or disappear from the signal? The study is done in the context of open flows, exhibiting self-sustained oscillations, where air is here flowing over an open cavity. Reynolds numbers are of the order of 14,000. Velocity measurements downstream of the cavity are based on a laser Doppler velocimetry technique. We propose two methods to estimate the rate of presence of each mode: one based on a complex demodulation technique, the other on the distribution of the state vectors in the phase portrait of the signal. 相似文献
63.
From a previous study in one dimension, precise estimates are deduced for the star discrepancy of some generalized Hammersley sequences in two dimensions, giving the lower constants presently known; also general bounds are obtained, and it is shown that these bounds are reached by the usual Hammersley sequences. 相似文献
64.
Ina Reiche Matthieu Lebon Céline Chadefaux Katharina Müller Anne-Solenn Le Hô Michael Gensch Ulrich Schade 《Analytical and bioanalytical chemistry》2010,397(6):2491-2499
Archaeological bone materials record characteristic markers of life in prehistoric times (dating, climate, environment, diet, human migration) in their isotopic and chemical composition in addition to palaeontological, archaeozoological, anthropological and palaeogenetic information. Thus, the discovery and conservation of archaeological bone materials is of great importance to get access to this information. However, archaeological materials are altered by different postmortem processes and it appears necessary to estimate if the archaeological information is still reliable or if it has been modified during burial. As archaeological bone materials present a high structural hierarchy at the micro- and nanoscale, changes induced by diagenetic phenomena have to be observed at these scales. One method for revealing post mortem changes of the bone structure and composition at the microscale is synchrotron radiation micro-FTIR imaging (SR micro-FTIR). Thus, thin sections of about 5,000-year-old archaeological bones have been analysed in transmission mode at the IRIS beamline (BESSY II, HZB Berlin) to determine markers of the state of bone preservation at the microscale. The archaeological bone material comes from station 19 of the Neolithic site of the Chalain Lake. By using SR micro-FTIR it was possible to image characteristic bone structures, e.g. osteons (the constitutive histological unit of cortical bone), using the absorption band ratios corresponding to different chemical bone constituents (collagen content and quality, phosphate crystallinity, carbonate content). These data allow us to precisely evaluate the state of preservation of a 5,000-year-old bone at the histological level. Figure
Chemical mapping of a thin section of the archaeological bone AB_CH19nb1 from the Neolithic station 19 at Chalain Lake 相似文献
65.
In order to develop a portable and disposable instrument for on-site analysis of neutral compounds, a lauryl methacrylate monolith has been synthesized into a cyclic olefin copolymer microdevice for reversed-phase electrochromatography purposes. This monolith was tested in capillary to evaluate electrochromatographic performances in terms of electroosmotic flow (EOF) mobility, retention and efficiency prior to its transfer into the microfluidic device. The produced monolithic bed exhibited a good run-to-run repeatability, column-to-column reproducibility and batch-to-batch reproducibility, with relative standard deviation (RSD) values below 9% for EOF mobility, retention factors and heights of theoretical plate. The electrochromatographic performances of the monolith were optimized by reducing irradiation time. Photopolymerization time of 10 min was found to be the best process in order to obtain a robust, retentive and efficient system. The on-chip performances of this monolith were evaluated in detail for the reversed-phase electrochromatographic separation of polycyclic aromatic hydrocarbons, with plate heights reaching down to 15 μm when working at optimal velocity. Aiming at the maximum simplification of instrumental fabrication and operation, a direct injection from a 2 μL droplet was compared with more conventional dynamic injection process. 相似文献
66.
Using a semiclassical approach we show that the spectrum of a smooth Anosov vector field V on a compact manifold is discrete (in suitable anisotropic Sobolev spaces) and then we provide an upper bound for the density
of eigenvalues of the operator (−i)V, called Ruelle resonances, close to the real axis and for large real parts. 相似文献
67.
We provide a resolution of one of the long-standing puzzles in the theory of disordered systems. By reformulating the functional renormalization group for the critical behavior of the random field Ising model in a superfield formalism, we are able to follow the associated supersymmetry and its spontaneous breaking along the functional renormalization group flow. Breaking is shown to occur below a critical dimension d(DR) ? 5.1 and leads to a breakdown of the "dimensional reduction" property. We compute the critical exponents as a function of dimension and give evidence that scaling is described by three independent exponents. 相似文献
68.
69.
We study in this paper the movement of a rigid solid inside an incompressible Navier‐Stokes flow within a bounded domain. We consider the case where slip is allowed at the fluid/solid interface through a Navier condition. Taking into account slip at the interface is very natural within this model, as classical no‐slip conditions lead to unrealistic collisional behavior between the solid and the domain boundary. We prove for this model existence of weak solutions of Leray type, up to collision, in three dimensions. The key point is that, due to the slip condition, the velocity field is discontinuous across the fluid/solid interface. This prevents obtaining global H1 bounds on the velocity, which makes many aspects of the theory of weak solutions for Dirichlet conditions inappropriate. © 2014 Wiley Periodicals, Inc. 相似文献
70.
Matthieu Gendulphe 《Mathematische Annalen》2011,350(4):919-951
We introduce a new tool, the contiguity graph, which enables us to determine the Bers’s constant in genus two. 相似文献