4,039 research outputs found
Flexible synthesis of polyfunctionalised 3-fluoropyrroles
An efficient and selective approach for the synthesis of polyfunctionalised 3-fluoropyrroles has been developed starting from commercial aldehydes. The methodology is concise, efficient and allows for the modular and systematic assembly of polysubstituted 3-fluoropyrroles. This synthesis provides an alternative and highly convergent strategy for the generation of these chemically and biologically important units
Scaling behavior of jamming fluctuations upon random sequential adsorption
It is shown that the fluctuations of the jamming coverage upon Random
Sequential Adsorption (), decay with the lattice size
according to the power-law , with
, where is the dimension of the substrate and
is the fractal dimension of the set of sites belonging to the
substrate where the RSA process actually takes place. This result is in
excellent agreement with the figure recently reported by Vandewalle {\it et al}
({\it Eur. Phys. J.} B. {\bf 14}, 407 (2000)), namely for the
RSA of needles with and , that gives . Furthermore,
our prediction is in excellent agreement with different previous numerical
results. The derived relationships are also confirmed by means of extensive
numerical simulations applied to the RSA of dimers on both stochastic and
deterministic fractal substrates.Comment: 8 pages, 2 figures. To appear in Eur. Phys. J. B (Rapid note) (2003
Anomalous scaling in a non local growth model in the Kardar-Parisi-Zhang universality class
We study the interface dynamics of a discrete model to quantitatively
describe electrochemical deposition experiments. Extensive numerical
simulations indicate that the interface dynamics is unstable at early times,
but asymptotically displays the scaling of the Kardar-Parisi-Zhang universality
class. During the time interval in which the surface is unstable, its power
spectrum is anomalous; hence the behaviors at length scales smaller than or
comparable with the system size are described by different roughness exponents.
These results are expected to apply to a wide range of electrochemical
deposition experiments.Comment: REVTEX (4 pages) and three figures (postscript), to be published in
PRE (rapid communication, March, 1998
Dimensional reduction of the CPT-even electromagnetic sector of the Standard Model Extension
The CPT-even abelian gauge sector of the Standard Model Extension is
represented by the Maxwell term supplemented by
, where the
Lorentz-violating background tensor, , possesses
the symmetries of the Riemann tensor. In the present work, we examine the
planar version of this theory, obtained by means of a typical dimensional
reduction procedure to dimensions. The resulting planar electrodynamics
is composed of a gauge sector containing six Lorentz-violating coefficients, a
scalar field endowed with a noncanonical kinetic term, and a coupling term that
links the scalar and gauge sectors. The dispersion relation is exactly
determined, revealing that the six parameters related to the pure
electromagnetic sector do not yield birefringence at any order. In this model,
the birefringence may appear only as a second order effect associated with the
coupling tensor linking the gauge and scalar sectors.The equations of motion
are written and solved in the stationary regime. The Lorentz-violating
parameters do not alter the asymptotic behavior of the fields but induce an
angular dependence not observed in the Maxwell planar theory.Comment: 13 pages, revtex style, no figures, to appear in Physical Review
D(2011
Short and efficient synthesis of fluorinated δ-lactams
The diastereoselective synthesis of fluorinated δ-lactams has been achieved through an efficient five step process. The route can tolerate a range of functionalities, and provides a quick route for the generation of new fluorinated medicinal building blocks
Quantum transport through single and multilayer icosahedral fullerenes
We use a tight-binding Hamiltonian and Green functions methods to calculate
the quantum transmission through single-wall fullerenes and bilayered and
trilayered onions of icosahedral symmetry attached to metallic leads. The
electronic structure of the onion-like fullerenes takes into account the
curvature and finite size of the fullerenes layers as well as the strength of
the intershell interactions depending on to the number of interacting atom
pairs belonging to adjacent shells. Misalignment of the symmetry axes of the
concentric icosahedral shells produces breaking of the level degeneracies of
the individual shells, giving rise some narrow quasi-continuum bands instead of
the localized discrete peaks of the individual fullerenes. As a result, the
transmission function for non symmetrical onions are rapidly varying functions
of the Fermi energy. Furthermore, we found that most of the features of the
transmission through the onions are due to the electronic structure of the
outer shell with additional Fano-like antiresonances arising from coupling with
or between the inner shells.Comment: 16 pages, 5 figur
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