34,742 research outputs found
An approach to the multidimensional assessment of food security and environmental sustainability: a vulnerability framework for the Mediterranean region
Poster presented at First International Conference on Global Food Security. Noordwijkerhout (The Netherlands), 29 Sep - 2 Oct 201
Multidimensional assessment of food security and environmental sustainability: a vulnerability framework for the Mediterranean Region [Poster]
Poster presented at Tropentag 2013. International Research on Food Security, Natural Resource Management and Rural Development. "Agricultural development within the rural-urban continuum". Stuttgart-Hohenheim (Germany), Sep 17-19 2013
Evolution: Complexity, uncertainty and innovation
Complexity science provides a general mathematical basis for evolutionary thinking. It makes us face the inherent, irreducible nature of uncertainty and the limits to knowledge and prediction. Complex, evolutionary systems work on the basis of on-going, continuous internal processes of exploration, experimentation and innovation at their underlying levels. This is acted upon by the level above, leading to a selection process on the lower levels and a probing of the stability of the level above. This could either be an organizational level above, or the potential market place. Models aimed at predicting system behaviour therefore consist of assumptions of constraints on the micro-level – and because of inertia or conformity may be approximately true for some unspecified time. However, systems without strong mechanisms of repression and conformity will evolve, innovate and change, creating new emergent structures, capabilities and characteristics. Systems with no individual freedom at their lower levels will have predictable behaviour in the short term – but will not survive in the long term. Creative, innovative, evolving systems, on the other hand, will more probably survive over longer times, but will not have predictable characteristics or behaviour. These minimal mechanisms are all that are required to explain (though not predict) the co-evolutionary processes occurring in markets, organizations, and indeed in emergent, evolutionary communities of practice. Some examples will be presented briefly
An approach to the multidimensional assessment of food security and environmental sustainability: a vulnerability framework for the Mediterranean region
Poster presented at First International Conference on Global Food Security. Noordwijkerhout (The Netherlands), 29 Sep - 2 Oct 201
Hard Spheres: Crystallization and Glass Formation
Motivated by old experiments on colloidal suspensions, we report molecular
dynamics simulations of assemblies of hard spheres, addressing crystallization
and glass formation. The simulations cover wide ranges of polydispersity s
(standard deviation of the particle size distribution divided by its mean) and
particle concentration. No crystallization is observed for s > 0.07. For 0.02 <
s < 0.07, we find that increasing the polydispersity at a given concentration
slows down crystal nucleation. The main effect here is that polydispersity
reduces the supersaturation since it tends to stabilise the fluid but to
destabilise the crystal. At a given polydispersity (< 0.07) we find three
regimes of nucleation: standard nucleation and growth at concentrations in and
slightly above the coexistence region; "spinodal nucleation", where the free
energy barrier to nucleation appears to be negligible, at intermediate
concentrations; and, at the highest concentrations, a new mechanism, still to
be fully understood, which only requires small re-arrangement of the particle
positions. The cross-over between the second and third regimes occurs at a
concentration, around 58% by volume, where the colloid experiments show a
marked change in the nature of the crystals formed and the particle dynamics
indicate an "ideal" glass transition
Mean properties and Free Energy of a few hard spheres confined in a spherical cavity
We use analytical calculations and event-driven molecular dynamics
simulations to study a small number of hard sphere particles in a spherical
cavity. The cavity is taken also as the thermal bath so that the system
thermalizes by collisions with the wall. In that way, these systems of two,
three and four particles, are considered in the canonical ensemble. We
characterize various mean and thermal properties for a wide range of number
densities. We study the density profiles, the components of the local pressure
tensor, the interface tension, and the adsorption at the wall. This spans from
the ideal gas limit at low densities to the high-packing limit in which there
are significant regions of the cavity for which the particles have no access,
due the conjunction of excluded volume and confinement. The contact density and
the pressure on the wall are obtained by simulations and compared to exact
analytical results. We also obtain the excess free energy for N=4, by using a
simulated-assisted approach in which we combine simulation results with the
knowledge of the exact partition function for two and three particles in a
spherical cavity.Comment: 11 pages, 9 figures and two table
Nernst effect, quasiparticles, and d-density waves in cuprates
We examine the possibility that the large Nernst signal observed in the
pseudogap regime of hole-doped cuprates originates from quasiparticle transport
in a state with d-density wave (DDW) order, proposed by S. Chakravarty et al.
[Phys. Rev. B 63, 094503 (2001)]. We find that the Nernst coefficient can be
moderately enhanced in magnitude by DDW order, and is generally of negative
sign. Thus, the quasiparticles of the DDW state cannot account for the large
and positive Nernst signal observed in the pseudogap phase of the cuprates.
However, the general considerations outlined in this paper may be of broader
relevance, in particular to the recent measurements of Bel et al. in NbSe_2 and
CeCoIn_5 [Phys. Rev. Lett. 91, 066602 (2003); ibid. 92, 217002 (2004)].Comment: 9 pages, 3 figures; published versio
Theory and simulation of the nematic zenithal anchoring coefficient
Combining molecular simulation, Onsager theory and the elastic description of
nematic liquid crystals, we study the dependence of the nematic liquid crystal
elastic constants and the zenithal surface anchoring coefficient on the value
of the bulk order parameter
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Fatalism, Social Support and Mental Health in Four Former Soviet Cultures
Research on social support has identified differences in levels of support between cultures, but has provided only a limited explanation of the role of values or beliefs in accounting for such variations. In this paper we examine the relationship between fatalism and perceived support amongst 2672 respondents in four former Soviet States (Russia, Georgia, Ukraine and Belorussia), with participants drawn from groups of manual workers, managers, civil servants, students and the retired in these four countries. We also examine the consequences of such social support for mental health across these nations. Findings indicate a small but significant moderator effect for fatalism on the relationship between social support and mental health. These results are discussed in the context of the continuing economic and social challenges facing the citizens of these nations
The Interactive Influence of Ambition and Sociability on Performance in a Behavior Description Interview
The purpose of this study was to present and empirically test the potential influence on ratings in a behavior description interview (BDI) of the personality traits ambition and sociability, two facets of extraversion. Results suggest a relatively strong role for ambition in the administration and outcomes of BDIs in organizational selection, particularly when its interaction with sociability is taken into consideration. In a sample of 85 participants working in entry-level positions, the correlation with BDI ratings was .22 for ambition alone, which increased to .44 when sociability and its interaction with ambition were added. Adding sociability by itself to ambition without the interaction term resulted in a minimal increase in predictability of BDI ratings. Implications of these results include the possibility of a general BDI performance factor, one that may tend to capture maximal (rather than typical) behavior
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