The Limitations and Possibilities of Co-Creation in the Public Domain of Rotterdam

A group of undergraduate bachelor students engaged in a project that focused on finding new co-creation methods for the public domain in Rotterdam. This paper describes the context in which the students worked, the findings they\ud made and the solutions they proposed. Their working process is compared with the work of the Freehouse foundation, a professional artist-run organization that focuses on empowering locals, socially and economically, by enlarging their involvement in the public domain. Subsequently the specifics of the discussed public domain, Rotterdam South, are pointed out. This is required because a very specific context is created by the combination of working class pride, lack of involved citizenship and severe social issues in the area. To conclude, the effect of the co-creative methods employed by the students and Freehouse on the\ud redistribution of power is compared with more traditional forms of citizen participation

Compression of tetrahedrally bonded SiO2 liquid and silicate liquid‐crystal density inversion

We have investigated the response to pressure of liquid SiO2 by performing a quantitatively realistic Monte Carlo simulation. The model liquid was restricted to at most four‐fold Si‐O coordination by the effective imposition of an infinite potential barrier to a fifth bond. We thus obtained an unambiguous comparison of the compression mechanisms of solid and liquid tetrahedral networks. In spite of this restriction, the density of the simulated liquid exceeds that of the corresponding models of quartz, coesite and cristobalite at high pressure. The efficient compression of the liquid results from a continuous restructuring of the network that leaves the mean Si‐Si distance virtually unchanged and does not require an increase in the coordination number. The restructuring is effected by local breaking and reconnecting of bonds, a mechanism that is not available to a perfect crystal

Interdisciplinary Science and Policy

I am a mathematician by education and a manager of interdisciplinary policy research by experience. In this paper, I want to use the style of my discipline to express the lessons of my profession. Through a series of propositions, corollaries, and theorems I will try to demonstrate my thesis of relationship between interdisciplinary science and policy: interdisciplinary science is a necessary aid to policy, and special policies are needed, in turn, to achieve useful interdisciplinary science. Strengthening this symbiosis should be a basic goal of science policy in the '80s

Coalescent processes emerging from large deviations

The classical model for the genealogies of a neutrally evolving population in a fixed is environment is due to Kingman. Kingman's coalescent process, which produces a binary tree, universally emerges from many microscopic models in which the variance in the number of offspring is finite. It is understood that power-law offspring distributions with infinite variance can result in a very different type of coalescent structure with merging of more than two lineages. Here we investigate the regime where the variance of the offspring distribution is finite but comparable to the population size. This is achieved by studying a model in which the logarithm offspring sizes has a stretched exponential form. Such offspring distributions are motivated by biology, where they emerges from a toy model of growth in a heterogenous environment, but also mathematics and statistical physics, where limit theorems and phase transitions for sums over random exponentials have seen considerable attention due to their appearance in the partition function of the Random Energy Model (REM). We find that the limit coalescent is a $\beta$-coalescent -- a previously studied model emerging from evolutionary dynamics models with heavy-tailed offspring distributions. We also discuss the interpretation of these results in terms of the REM

Direct Wolf summation of a polarizable force field for silica

We extend the Wolf direct, pairwise r^(-1) summation method with spherical truncation to dipolar interactions in silica. The Tangney-Scandolo interatomic force field for silica takes regard of polarizable oxygen atoms whose dipole moments are determined by iteration to a self-consistent solution. With Wolf summation, the computational effort scales linearly in the system size and can easily be distributed among many processors, thus making large-scale simulations of dipoles possible. The details of the implementation are explained. The approach is validated by estimations of the error term and simulations of microstructural and thermodynamic properties of silica.Comment: See http://link.aip.org/link/?JCP/132/194109 - 8 pages, 6 figures. Changes in v3: Copyright notice added, minor typographical changes. Changes in v2: 1. Inserted Paragraph in Sec. IV B describing the limitations of the TS potential. 2. We corrected transcription errors in Tab. II, and adjusted the deviation percentages mentioned in Sec. IV B, first paragraph, accordingl

On balance relations for irreversible chemical reaction networks

We investigate a class of irreversible networks whose chemical species can be partitioned into two disjoint sets S1 and S2, resulting in a weakly reversible subnetwork G2 involving only the species S2, and a semi-weaklyreversible network G1; the latter reduces to a weakly reversible network on formally eliminating the chemical species S2. We introduce a generalized flux balance condition that can be understood as the natural analogue of the complex balance condition for weakly reversible networks, and which serves as a tool for investigating how irreversible networks differ from reversible ones. We also make a connection between the generalized balance condition and the theory of multiscale networks by taking S1 to consist of high copy number species (O(N)), where N is the system size, and S2 to consist of low copy number species (O(1)). We show how the generalized balance condition of the full stochastic model is related to a moment balance condition of the corresponding piecewise deterministic Markov process (PDMP) obtained in the thermodynamic limit N → ∞