Control of complex networks requires both structure and dynamics

The study of network structure has uncovered signatures of the organization of complex systems. However, there is also a need to understand how to control them; for example, identifying strategies to revert a diseased cell to a healthy state, or a mature cell to a pluripotent state. Two recent methodologies suggest that the controllability of complex systems can be predicted solely from the graph of interactions between variables, without considering their dynamics: structural controllability and minimum dominating sets. We demonstrate that such structure-only methods fail to characterize controllability when dynamics are introduced. We study Boolean network ensembles of network motifs as well as three models of biochemical regulation: the segment polarity network in Drosophila melanogaster, the cell cycle of budding yeast Saccharomyces cerevisiae, and the floral organ arrangement in Arabidopsis thaliana. We demonstrate that structure-only methods both undershoot and overshoot the number and which sets of critical variables best control the dynamics of these models, highlighting the importance of the actual system dynamics in determining control. Our analysis further shows that the logic of automata transition functions, namely how canalizing they are, plays an important role in the extent to which structure predicts dynamics.Comment: 15 pages, 6 figure

The Real Anatomy of Complex Linear Superfields

Recent work on classicication of off-shell representations of N-extended worldline supersymmetry without central charges has uncovered an unexpectedly vast number--trillions of even just (chromo)topology types--of so called adinkraic supermultiplets. Herein, we show by explicit analysis that a long-known but rarely used representation, the complex linear supermultiplet, is not adinkraic, cannot be decomposed locally, but may be reduced by means of a Wess-Zumino type gauge. This then indicates that the already unexpectedly vast number of adinkraic off-shell supersymmetry representations is but the proverbial tip of the iceberg.Comment: 21 pages, 4 figure

Analyses of the dynamic docking test system for advanced mission docking system test programs

Results are given of analytical studies performed in support of the design, implementation, checkout and use of NASA's dynamic docking test system (DDTS). Included are analyses of simulator components, a list of detailed operational test procedures, a summary of simulator performance, and an analysis and comparison of docking dynamics and loads obtained by test and analysis

Economic Benefits of American Lobster Fishery Management Regulations

A simulation model is used to compare measures for future management identified in the American lobster fishery management plan; specifically, increases in the minimum legal size and a modest reduction in aggregate fishing mortality are evaluated. The analysis differs from previous work in that the distributional aspects of the alternative management regulations are quantified. The results indicate that (1) both an increased minimum size and a reduction in fishing mortality are economically justified in the sense that net benefits are positive; (2) increasing the minimum size without an adjunct regulation to prohibit entry will cause present fishermen to suffer an initial short-term reduction in revenues for which there will be no long-term gain; (3) because increased minimum size can be justified on the basis of consumer benefits alone, arguments favoring its increase to prevent recruitment failure are moot as far as a test of national economic efficiency is concerned; and (4) a program of effort reduction which reduces by 20% the fraction of available lobsters captured annually is projected to generate SI of producer benefits for every pound of lobster landed. Reducing the annual harvest fraction by 20% results in a level of fishery benefits greater than increasing the minimum size to 89 mm (3^-in.), and increases the coincidence of short-run costs and long-term benefits among those impacted by fishery management.Environmental Economics and Policy, Resource /Energy Economics and Policy,

Modularity and the spread of perturbations in complex dynamical systems

We propose a method to decompose dynamical systems based on the idea that modules constrain the spread of perturbations. We find partitions of system variables that maximize 'perturbation modularity', defined as the autocovariance of coarse-grained perturbed trajectories. The measure effectively separates the fast intramodular from the slow intermodular dynamics of perturbation spreading (in this respect, it is a generalization of the 'Markov stability' method of network community detection). Our approach captures variation of modular organization across different system states, time scales, and in response to different kinds of perturbations: aspects of modularity which are all relevant to real-world dynamical systems. It offers a principled alternative to detecting communities in networks of statistical dependencies between system variables (e.g., 'relevance networks' or 'functional networks'). Using coupled logistic maps, we demonstrate that the method uncovers hierarchical modular organization planted in a system's coupling matrix. Additionally, in homogeneously-coupled map lattices, it identifies the presence of self-organized modularity that depends on the initial state, dynamical parameters, and type of perturbations. Our approach offers a powerful tool for exploring the modular organization of complex dynamical systems

Nanocrystal seeding: A low temperature route to polycrystalline Si films

A novel method is presented for growth of polycrystalline silicon films on amorphous substrates at temperatures of 540–575 °C. Grain nucleation and grain growth are performed in two steps, using Si nanocrystals as nuclei ("seeds"). The nanocrystal seeds are produced by excimer laser photolysis of disilane in a room temperature flow cell. Film (grain) growth occurs epitaxially on the seeds in a separate thermal chemical vapor deposition (CVD) step, with growth rates 10–100 times higher than similar CVD growth rates on crystal Si. Grain size and CVD growth rates are dependent on seed coverage, for seed coverage <0.2 monolayers

Comparison of Some Exact and Perturbative Results for a Supersymmetric SU(NcN_c) Gauge Theory

We consider vectorial, asymptotically free ${\cal N}=1$ supersymmetric SU($N_c$) gauge theories with $N_f$ copies of massless chiral super fields in various representations and study how perturbative predictions for the lower boundary of the infrared conformal phase, as a function of $N_f$, compare with exact results. We make use of two-loop and three-loop calculations of the beta function and anomalous dimension of the quadratic chiral super field operator product for this purpose. The specific chiral superfield contents that we consider are $N_f$ copies of (i) $F+\bar F$, (ii) $Adj$, (iii) $S_2+\bar S_2$, and (iv) $A_2 + \bar A_2$, where $F$, $Adj$, $S_2$, and $A_2$ denote, respectively, the fundamental, adjoint, and symmetric and antisymmetric rank-2 tensor representations. We find that perturbative results slightly overestimate the value of $N_{f,cr}$ relative to the respective exact results for these representations, i.e., slightly underestimate the interval in $N_f$ for which the theory has infrared conformal behavior. Our results provide a measure of how closely perturbative calculations reproduce exact results for these theories.Comment: 16 pages, 3 figure

Marriage, Registration and Dissolution by Same-Sex Couples in the U.S.

This study analyzes data from states that have extended legal recognition to same-sex couples. Analyses show that same-sex couples want and use these new legal statuses. Furthermore, they react more enthusiastically when marriage is possible. More than 40% of same-sex couples have formed legal unions in states where such recognition is available. Same-sex couples prefer marriage over civil unions or domestic partnerships. In the first year that marriage was offered in Massachusetts, 37% of same-sex couples there married. In states that offered civil unions, only 12% of same-sex couples took advantage of this status in the first year and only 10% did so in states with domestic partnership registrie