1,373 research outputs found
The suburban question: grassroots politics and place making in Spanish suburbs
Manuel Castells spoke of the urban as a unit of collective consumption, yet much of the politics of collective consumption he documented was evident in the suburbs. The tendency for suburbs of most complexions to lack services and amenities has been and continues to be a focus of politics in Europe. In Spain, as elsewhere in Europe, a grassroots politics surrounding the making good of these deficits in basic services and amenities has broadened and formalised somewhat to become part of a competitive local representative politics concerned with shaping a sense of place. Here we consider this legacy of grassroots politics as it has played out more recently in a politics of place making in Getafe and Badalona in metropolitan Madrid and Barcelona, respectively. In conclusion, we suggest that this enduring suburban question—of making the suburban urban—places them at the centre of contemporary metropolitan governance and politics. However, it also raises further issues for study—notably, the scalar politics in which suburban place making is empowered or constrained, the role of political parties and individual politicians on the place-making process, and the point at which grassroots politics of collective consumption becomes urban entrepreneurialism
Growth in systems of vesicles and membranes
We present a theoretical study for the intermediate stages of the growth of
membranes and vesicles in supersaturated solutions of amphiphilic molecules.
The problem presents important differences with the growth of droplets in the
classical theory of Lifshitz-Slyozov-Wagner, because the aggregates are
extensive only in two dimensions, but still grow in a three dimensional bath.
The balance between curvature and edge energy favours the nucleation of small
planar membranes, but as they grow beyond a critical size they close themselves
to form vesicles. We obtain a system of coupled equations describing the growth
of planar membranes and vesicles, which is solved numerically for different
initial conditions. Finally, the range of parameters relevant in experimental
situations is discussed.Comment: 13 pages and 5 postscript figures. To appear in Phys. Rev
Free energies, vacancy concentrations and density distribution anisotropies in hard--sphere crystals: A combined density functional and simulation study
We perform a comparative study of the free energies and the density
distributions in hard sphere crystals using Monte Carlo simulations and density
functional theory (employing Fundamental Measure functionals). Using a recently
introduced technique (Schilling and Schmid, J. Chem. Phys 131, 231102 (2009))
we obtain crystal free energies to a high precision. The free energies from
Fundamental Measure theory are in good agreement with the simulation results
and demonstrate the applicability of these functionals to the treatment of
other problems involving crystallization. The agreement between FMT and
simulations on the level of the free energies is also reflected in the density
distributions around single lattice sites. Overall, the peak widths and
anisotropy signs for different lattice directions agree, however, it is found
that Fundamental Measure theory gives slightly narrower peaks with more
anisotropy than seen in the simulations. Among the three types of Fundamental
Measure functionals studied, only the White Bear II functional (Hansen-Goos and
Roth, J. Phys.: Condens. Matter 18, 8413 (2006)) exhibits sensible results for
the equilibrium vacancy concentration and a physical behavior of the chemical
potential in crystals constrained by a fixed vacancy concentration.Comment: 17 pages, submitted to Phys. Rev.
Lattice density-functional theory of surface melting: the effect of a square-gradient correction
I use the method of classical density-functional theory in the
weighted-density approximation of Tarazona to investigate the phase diagram and
the interface structure of a two-dimensional lattice-gas model with three
phases -- vapour, liquid, and triangular solid. While a straightforward
mean-field treatment of the interparticle attraction is unable to give a stable
liquid phase, the correct phase diagram is obtained when including a suitably
chosen square-gradient term in the system grand potential. Taken this theory
for granted, I further examine the structure of the solid-vapour interface as
the triple point is approached from low temperature. Surprisingly, a novel
phase (rather than the liquid) is found to grow at the interface, exhibiting an
unusually long modulation along the interface normal. The conventional
surface-melting behaviour is recovered only by artificially restricting the
symmetries being available to the density field.Comment: 16 pages, 6 figure
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