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341.
Anna Prodi Claudio Chiorboli Franco Scandola Elisabetta Iengo Enzo Alessio 《Chemphyschem》2006,7(7):1514-1519
The molecular box 1 comprises of two zinc-porphyrin metallacycles connected by two free-base 4'-trans-dipyridylporphyrins, axially coordinated to the zinc centers. The photophysics of 1 were studied in chloroform by emission and ultrafast absorption spectroscopy. In the molecular box, fast singlet energy transfer (main component, tau=32 ps) is observed to occur from the zinc-porphyrin metallacycles to the free-base chromophores. From wavelength-dependent spectrofluorimetric data, the efficiency of the energy-transfer (ET) process is estimated as 0.5. The lower-than-unity value is tentatively attributed to the possibility of a competing electron-transfer quenching pathway. Molecular box 1 can be considered to be a simple, self-assembling, six-chromophore antenna system. It has an inner cavity, 11.4 Angstrom wide, that could be used, in principle, to host a variety of guest molecules and obtain higher-order assemblies. 相似文献
342.
Lorenzo Bertini Emilio N.M. Cirillo Enzo Olivieri 《Communications in Mathematical Physics》2006,261(2):323-378
We analyze the block averaging transformation applied to lattice gas models with short range interaction in the uniqueness
region below the critical temperature. We prove weak Gibbsianity of the renormalized measure and convergence of the renormalized
potential in a weak sense. Since we are arbitrarily close to the coexistence region we have a diverging characteristic length
of the system: the correlation length or the critical length for metastability, or both. Thus, to perturbatively treat the
problem we have to use a scale–adapted expansion. Moreover, such a model below the critical temperature resembles a disordered
system in the presence of Griffiths' singularity. Then the cluster expansion that we use must be graded with its minimal scale
length diverging when the coexistence line is approached.
The authors acknowledge the support of Cofinanziamento MIUR. 相似文献
343.
Elizabeth Y. Elgueta Joaquín Barberá Jorge M. Vergara Mohamed Dahrouch Enzo W. Díaz 《Liquid crystals》2016,43(11):1649-1658
Two new series of columnar liquid crystal materials based on tetra- and hexacatenar Schiff bases were synthesised by reaction of 4-aminophenyl-1,3,4-thiadiazole derivatives with terephthalaldehyde (series 2a–f) and with 2,5-thiophenedicarbaldehyde (series 3a–f). The mesomorphic properties of these compounds were studied by differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction (XRD). The mesomorphic behaviour was found to be dependent on the nature of the central ring (benzene in series 2a–f, thiophene in series 3a–f), on length and on number of alkoxy chains. Both tetra- and hexacatenar compounds in series 2a–f display an enantiotropic hexagonal columnar phase. Whereas, in the case of the series 3, only the tetracatenar Schiff bases (3a, 3c and 3e) display enantiotropic hexagonal columnar mesomorphism, hexacatenar Schiff bases (3b, 3d and 3f) do not show mesomorphic properties. Photophysical studies were realised in solution and in solid state. Also, a thermogravimetric analysis was performed. A fibre obtained from compound 3b was analysed by POM showing that the mesophase is maintained in the fibre. 相似文献
344.
Ilaria Maccari Andrea Maiorano Enzo Marinari Juan Jesus Ruiz-Lorenzo 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(5):127
We analyze a system of interacting islands of XY spins on a triangular lattice. This model has been introduced a few years ago by Eley et al. [Nat. Phys. 8, 59 (2012)] to account for the phenomenology in experiments on tunable arrays of proximity coupled long superconductor-normal metal-superconductor junctions. The main features of the model are the separation of a local and a global interaction energy scale and the mesoscopic character of the spin islands. Upon lowering the temperature the model undergoes two crossovers corresponding to an increasing phase coherence on a single island and to the onset of global coherence across the array; the latter is a thermodynamical phase transition in the Ising universality class. The dependence of the second transition on the island edge-to-edge spacing is related to the proximity-effect of the coupling constant. 相似文献
345.
Prof. Enzo Cadoni Dr. Giulio Ferino Dr. Patrizia Pitzanti Dr. Francesco Secci Dr. Claudia Fattuoni Prof. Francesco Nicolò Prof. Giuseppe Bruno 《ChemistryOpen》2015,4(2):161-168
The aim of this study is to describe and compare the supramolecular interactions, in the solid state, of chloro-, bromo-, and iodobenzothiophene diols. The compounds were obtained through organo-catalyzed reactions starting from 3-substituted halobenzothiophene carbaldehydes. Energies of the noncovalent interactions were obtained by density functional theory calculations. Bond distances and angles were found to be in accordance with those determined by X-ray structure analysis. anti-Bromobenzothiophene derivatives showed strong halogen⋅⋅⋅π interactions between bromine and the heterocyclic phenyl ring, corresponding to an energy of 7.5 kcal mol−1. syn-Bromo and syn-iodo derivatives appeared to be isostructural, showing X⋅⋅⋅O (carbonyl) interactions, π stacking, and formation of extended hydrogen bonding networks. In contrast, the chloro derivatives displayed no halogen bonding interactions. 相似文献
346.
347.
Lorenzo D’Ambrosio Enzo Mitidieri 《Proceedings of the Steklov Institute of Mathematics》2013,283(1):3-19
We prove general a priori estimates of the solutions of a class of quasilinear elliptic systems on Carnot groups. As a consequence, we obtain several nonexistence theorems. The results are new even in the Euclidean setting. 相似文献
348.
Fernando G. Basombrío Enzo A. Dari Gustavo C. Buscaglia Raúl A. Feijóo 《International Journal of Computational Fluid Dynamics》2013,27(4):231-246
Numerical experiments for non-trivial flows, close to realistic situations in hæmodynamics, are described and interpreted. Two geometries have been selected: an axisymmetric corrugated tube (with periodic boundary conditions) and a 3D bifurcation with an obstructed end (anastomosis). Results concern sensitivity of errors associated to the time-step size and mesh refinement, but essentially consist of the quantitative estimation of non-Newtonian effects based on Casson's rheological model, treated in retarded form. The time-step lag of such effects is the main reason for evaluating the sensitivity of errors. Due to the high computational cost characterizing the problems to be faced, we expect that the present results will be useful when real geometries should be modeled. The main conclusions are that non-Newtonian effects may be relevant (especially for secondary flows) and that, in most cases, for the same level of errors the use of Casson's law does not generate excessive additional computational costs. Thus, within this strategy, the user can accurately solve the problem using this rheological model without having to worry if the non-Newtonian effects are important or not. 相似文献
349.
Pavel Vlad Elena Gorincioi Aculina Aricu Alic Barba Ada Manzocchi Enzo Santaniello 《Tetrahedron: Asymmetry》2010,21(17):2108-2116
The asymmetric dihydroxylation of drim-7-en-11-ol was studied in detail and diastereomerically pure driman-7α,8α,11- and driman-7β,8β,11-triols were prepared. Further elaboration of driman-7α,8α,11-triol afforded 14,15-bisnorlabd-7α,8α-isopropylidenedioxy-11,13-dione from which a novel chlorinated bisnorlabdanic compound (14,15-bisnorlabd-12-ene-12-chloro-8α,13-epoxy-7α-ol-11-one) and an unusual dichloro-derivative, 13,14,15,16-tetranorlabd-12-dichloro-7α-acetoxy-8α-ol-11-one, were obtained. 相似文献
350.
Gustavo C. Buscaglia Enzo A. Dari J. Ezequiel Martín Daniela L. Arnica Fabián J. Bonetto 《International Journal of Computational Fluid Dynamics》2013,27(5):355-365
A finite element simulation of flow and heat transfer in the moderator cell of a cold-neutron source (CNS), in which liquid deuterium subject to internal heat generation is flowing, is reported. The numerical scheme consists of a stabilized equal-order method. A time-accurate approach is adopted to resolve the large-scale eddies of the flow, with a Smagorinsky's model for the subgrid-scale effects. The thermal coupling follows a staggered strategy, with SUPG-type upwinding. A specific wall-law is developed that accounts for the correct partition of the heat deposited at the wall by radiation between the liquid deuterium and the helium gas flowing at the outer side of the wall. The average flow and thermal structure are presented. The turbulent fluctuations are both illustrated in physical space and decomposed into spectral components. The wavenumber spectrum suggests that adequate resolution of the large-scale eddies has been attained with just 200,000 nodes, while a DNS analysis would have required at least 1010 nodes. Usefulness of the approach in the design process of the CNS is highlighted. 相似文献