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Exploring the democratic potential of online social networking: The scope and limitations of e-participation
Copyright © 2012 by the Association for Information Systems.The availability and promise of social networking technologies with their perceived open philosophy has increasingly inspired citizens around the world to participate in political activity on the Web. Recent examples range from opposing public policies, such as government funding cuts, to organizing revolutionary social movements, such as those in the Middle East and North Africa. Although online spaces create remarkable opportunities for various forms of political action, there are concerns over the power of existing institutions to control and even censor such interaction spaces. The objective of this article is to draw together different insights on the online engagement phenomenon, highlighting both its potential and limitations as a mechanism for fostering democratic debate and influencing policy making. We examine recent examples from Europe, the Middle East and Latin America. Finally, we summarize the implications of our work and outline directions for further research
Structural and magnetic properties of Ru/Ni multilayers
International audienceRu/Ni multilayers of different Ni thickness have been fabricated using magnetron sputtering. The structure of the multilayers has been determined by grazing incidence X-ray diffraction and X-ray reflectivity and their magnetic properties by magnetization and polarized neutron reflectivity measurements. The presence of Ru leads to the formation of a hexagonal Ni structure within interfacial layer ~1 nm above each Ru layer, while the rest of the Ni layer relaxes to the equilibrium fcc structure. The hcp Ni interfacial layer has a substantially increased cell volume is ferromagnetic with an atomic magnetic moment that increases with Ni layer thickness but remains lower than the value predicted from ab initio calculations
Crowding of Polymer Coils and Demixing in Nanoparticle-Polymer Mixtures
The Asakura-Oosawa-Vrij (AOV) model of colloid-polymer mixtures idealizes
nonadsorbing polymers as effective spheres that are fixed in size and
impenetrable to hard particles. Real polymer coils, however, are intrinsically
polydisperse in size (radius of gyration) and may be penetrated by smaller
particles. Crowding by nanoparticles can affect the size distribution of
polymer coils, thereby modifying effective depletion interactions and
thermodynamic stability. To analyse the influence of crowding on polymer
conformations and demixing phase behaviour, we adapt the AOV model to mixtures
of nanoparticles and ideal, penetrable polymer coils that can vary in size. We
perform Gibbs ensemble Monte Carlo simulations, including trial
nanoparticle-polymer overlaps and variations in radius of gyration. Results are
compared with predictions of free-volume theory. Simulation and theory
consistently predict that ideal polymers are compressed by nanoparticles and
that compressibility and penetrability stabilise nanoparticle-polymer mixtures.Comment: 18 pages, 4 figure
Maximum Valency Lattice Gas Models
We study lattice gas models with the imposition of a constraint on the
maximum number of bonds (nearest neighbor interactions) that particles can
participate in. The critical parameters, as well as the coexistence region are
studied using the mean field approximation and the Bethe-Peierls approximation.
We find that the reduction of the number of interactions suppresses the
temperature-density region where the liquid and gas phases coexist. We confirm
these results from simulations using the histogram reweighting method employing
grand Canonical Monte Carlo simulations
Total arterial revascularization on OPCABG with the exclusive use of two internal mammary arteries â a single center ten-year study analysis
Universality class of criticality in the restricted primitive model electrolyte
The 1:1 equisized hard-sphere electrolyte or restricted primitive model has
been simulated via grand-canonical fine-discretization Monte Carlo. Newly
devised unbiased finite-size extrapolation methods using temperature-density,
(T, rho), loci of inflections, Q = ^2/ maxima, canonical and C_V
criticality, yield estimates of (T_c, rho_c) to +- (0.04, 3)%. Extrapolated
exponents and Q-ratio are (gamma, nu, Q_c) = [1.24(3), 0.63(3); 0.624(2)] which
support Ising (n = 1) behavior with (1.23_9, 0.630_3; 0.623_6), but exclude
classical, XY (n = 2), SAW (n = 0), and n = 1 criticality with potentials
phi(r)>Phi/r^{4.9} when r \to \infty
Coexistence and Criticality in Size-Asymmetric Hard-Core Electrolytes
Liquid-vapor coexistence curves and critical parameters for hard-core 1:1
electrolyte models with diameter ratios lambda = sigma_{-}/\sigma_{+}=1 to 5.7
have been studied by fine-discretization Monte Carlo methods. Normalizing via
the length scale sigma_{+-}=(sigma_{+} + sigma_{-})/2 relevant for the low
densities in question, both Tc* (=kB Tc sigma_{+-}/q^2 and rhoc* (= rhoc sigma
_{+-}^{3}) decrease rapidly (from ~ 0.05 to 0.03 and 0.08 to 0.04,
respectively) as lambda increases. These trends, which unequivocally contradict
current theories, are closely mirrored by results for tightly tethered dipolar
dimers (with Tc* lower by ~ 0-11% and rhoc* greater by 37-12%).Comment: 4 pages, 5 figure
Dipolar origin of the gas-liquid coexistence of the hard-core 1:1 electrolyte model
We present a systematic study of the effect of the ion pairing on the
gas-liquid phase transition of hard-core 1:1 electrolyte models. We study a
class of dipolar dimer models that depend on a parameter R_c, the maximum
separation between the ions that compose the dimer. This parameter can vary
from sigma_{+/-} that corresponds to the tightly tethered dipolar dimer model,
to R_c --> infinity, that corresponds to the Stillinger-Lovett description of
the free ion system. The coexistence curve and critical point parameters are
obtained as a function of R_c by grand canonical Monte Carlo techniques. Our
results show that this dependence is smooth but non-monotonic and converges
asymptotically towards the free ion case for relatively small values of R_c.
This fact allows us to describe the gas-liquid transition in the free ion model
as a transition between two dimerized fluid phases. The role of the unpaired
ions can be considered as a perturbation of this picture.Comment: 16 pages, 13 figures, submitted to Physical Review
Advanced ultra-light multifunctional metallic-glass wave springs
We show that, using thermo -elastic processing, metallic -glass foils can be shaped, without being embrittled, into linear and annular wave springs. These springs exhibit an undulatory behaviour, unique to metallic -glass foils, in which under compression the number of arcs in the spring increases, increasing the load -bearing capacity and the spring constant. We evaluate the performance limits of the metallic -glass wave springs, and consider how the undulatory behaviour can be exploited. The metallic -glass springs can operate over the same load -ranges as commercially available crystalline wave springs, but have material volumes (and therefore weights) that are one to two orders of magnitude less. Their energy storage per unit material volume is as high as 2600 kJ m â 3 . We suggest that the undulatory behaviour is important in rendering the springs fail -safe in case of overload. We discuss the range of applicability of thermo -elastic processing, the likely working limit of metallic -glass wave springs, and the potential for application of metallic -glass springs in MEMS devices
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