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21.
Efficient and accurate integration of stochastic (partial) differential equations with multiplicative noise can be obtained through a split-step scheme, which separates the integration of the deterministic part from that of the stochastic part, the latter being performed by sampling exactly the solution of the associated Fokker-Planck equation. We demonstrate the computational power of this method by applying it to the most absorbing phase transitions for which Langevin equations have been proposed. This provides precise estimates of the associated scaling exponents, clarifying the classification of these nonequilibrium problems, and confirms or refutes some existing theories. 相似文献
22.
We apply the nonperturbative renormalization group method to a class of out-of-equilibrium phase transitions (usually called "parity-conserving" or, more properly, "generalized voter" class) which is out of the reach of perturbative approaches. We show the existence of a genuinely nonperturbative fixed point, i.e., a critical point that does not seem to be Gaussian in any dimension. 相似文献
23.
The phase transitions to absorbing states of the branching-annihilating reaction-diffusion processes mA-->(m+k)A, nA-->(n-l)A are studied systematically in one space dimension within a new family of models. Four universality classes of nontrivial critical behavior are found. This provides, in particular, the first evidence of universal scaling laws for pair and triplet processes. 相似文献
24.
Alessandro Massi Alberto CavazziniOmar Pandoli Valentina CostaLuisa Pasti Pier Paolo Giovannini 《Tetrahedron letters》2011,52(5):619-622
The activity and stability under flow conditions of covalently and non-covalently silica supported proline and proline-like organocatalysts is herein described. The slow aldol reaction of cyclohexanone with p-nitro benzaldehyde and the fast α-amination of isovaleraldehyde with dibenzyl azodicarboxylate have been selected as model reactions for this study. Prospects and limitations of the disclosed continuous-flow organocatalytic approach are widely discussed. 相似文献
25.
26.
Tacchi S Montoncello F Madami M Gubbiotti G Carlotti G Giovannini L Zivieri R Nizzoli F Jain S Adeyeye AO Singh N 《Physical review letters》2011,107(12):127204
The dispersion curves of collective spin-wave excitations in a magnonic crystal consisting of a square array of interacting saturated nanodisks have been measured by Brillouin light scattering along the four principal directions of the first Brillouin zone. The experimental data are successfully compared to calculations of the band diagram and of the Brillouin light scattering cross section, performed through the dynamical matrix method extended to include the dipolar interaction between the disks. We found that the fourfold symmetry of the geometrical lattice is reduced by the application of the external field and therefore equivalent directions of the first Brillouin zone are characterized by different dispersion relations of collective spin waves. The dispersion relations are explained through the introduction of a bidimensional effective wave vector that characterizes each mode in this magnonic metamaterial. 相似文献
27.
Analysis methodology for 3C-PIV data of rotary wing vortices 总被引:1,自引:0,他引:1
3C-PIV data from tip vortices of either fixed-wing or rotating wing experiments are challenging from an analysis point of view. Model motion, vortex wander, spurious vectors, periodic and aperiodic effects, turbulence, and other disturbing effects are all present in the data. In most cases the vortices are not measured perpendicular to their axis as well. Engineers need time-averaged properties from the vortex in the vortex axis system for a proper modelization within simulation codes. This article describes the methods needed to deal with all the mentioned problem areas, including the conditional averaging and rotation into the vortex axis system. The methods are validated by using numerically generated vortex vector fields, and finally applied to experimental data from a hover condition of a model rotor. 相似文献
28.
P. Solokha M. Giovannini N.R. Lee-Hone D.H. Ryan 《Journal of solid state chemistry》2011,184(9):2498-2505
The crystal structure of the ternary intermetallic compound Yb3Pd2Sn2 has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7) nm. Yb3Pd2Sn2 is composed of a complex ∞[Pd2Sn2]δ− polyanionic network in which the Yb ions are embedded. A comparison between this structure and those of Eu3Pd2Sn2 and Ca3Pd2Sn2, other novel polar intermetallic compounds, was made. DC susceptibility and 170Yb Mössbauer spectroscopic measurements indicate a close-to divalent Yb behavior. Moreover, a hybridization between 4f and conduction electrons is suggested by electronic structure calculations and heat capacity measurements. 相似文献
29.
Laguri C Sapay N Simorre JP Brutscher B Imberty A Gans P Lortat-Jacob H 《Journal of the American Chemical Society》2011,133(25):9642-9645
Heparan sulfate (HS), a polysaccharide of the glycosaminoglycan family characterized by a unique level of complexity, has emerged as a key regulator of many fundamental biological processes. Although it has become clear that this class of molecules exert their functions by interacting with proteins, the exact modes of interaction still remain largely unknown. Here we report the engineering of a (13)C-labeled HS-like oligosaccharide with a defined oligosaccharidic sequence that was used to investigate the structural determinants involved in protein/HS recognition by multidimensional NMR spectroscopy. Using the chemokine CXCL12α as a model system, we obtained experimental NMR data on both the oligosaccharide and the chemokine that was used to obtain a structural model of a protein/HS complex. This new approach provides a foundation for further investigations of protein/HS interactions and should find wide application. 相似文献
30.
Bortolini O Fantin G Fogagnolo M Giovannini PP Massi A Pacifico S 《Organic & biomolecular chemistry》2011,9(24):8437-8444
An efficient method for the N-heterocyclic carbene (NHC)-catalyzed conjugate addition of acetyl anions to various α,β-unsaturated acceptors (Stetter reaction) has been optimized by using 2,3-butandione (biacetyl) as an alternative surrogate of acetaldehyde. The disclosed procedure proved to be compatible with microwave dielectric heating for reaction time reduction and with the use of different linear α-diketones as acyl anion donors (e.g. 3,4-hexanedione for propionyl anion additions). Moreover, the unprecedented umpolung reactivity of cyclic α-diketones in the atom economic nucleophilic acylation of chalcones is herein presented. Mechanistic aspects of the thiazolium-based catalysis involving linear and cyclic α-diketone substrates are also discussed. 相似文献