Analysis of weighted networks

The connections in many networks are not merely binary entities, either present or not, but have associated weights that record their strengths relative to one another. Recent studies of networks have, by and large, steered clear of such weighted networks, which are often perceived as being harder to analyze than their unweighted counterparts. Here we point out that weighted networks can in many cases be analyzed using a simple mapping from a weighted network to an unweighted multigraph, allowing us to apply standard techniques for unweighted graphs to weighted ones as well. We give a number of examples of the method, including an algorithm for detecting community structure in weighted networks and a new and simple proof of the max-flow/min-cut theorem.Comment: 9 pages, 3 figure

Efficiency in Multi-objective Games

In a multi-objective game, each agent individually evaluates each overall action-profile on multiple objectives. I generalize the price of anarchy to multi-objective games and provide a polynomial-time algorithm to assess it. This work asserts that policies on tobacco promote a higher economic efficiency

From Anti-equilibrium to The Socialist System and Beyond

This essay attempts to understand János Kornai’s works from a political economy perspective. It argues that Kornai has significantly contributed to the formation of a new paradigm of political economy. The main endeavor of Kornai has been the combination of analytical concepts of economics with the empirical description of real economies. After a certain period of theoretical experimentation János Kornai formulated his research program that can be called the shortage economy explanation of the socialist system. The Economics of Shortage and The Socialist System have created a new theoretical paradigm in a framework in which it has become possible to establish a connection between the analytical and empirical, universal and historical aspects of the theory studying the socialist system as a real economic entity. János Kornai has built his analysis of the socialist system on the primary role of politics in the creation of economic institutions. In his present work on capitalism he has extended this thesis to the capitalist system. This seems to be an important contribution of his to a new political economy paradigm that is just in the process of formation

Angiogenesis in tissue engineering : Breathing life into constructed tissue substitutes

Long-term function of three-dimensional (3D) tissue constructs depends on adequate vascularization after implantation. Accordingly, research in tissue engineering has focused on the analysis of angiogenesis. For this purpose, 2 sophisticated in vivo models (the chorioallantoic membrane and the dorsal skinfold chamber) have recently been introduced in tissue engineering research, allowing a more detailed analysis of angiogenic dysfunction and engraftment failure. To achieve vascularization of tissue constructs, several approaches are currently under investigation. These include the modification of biomaterial properties of scaffolds and the stimulation of blood vessel development and maturation by different growth factors using slow-release devices through pre-encapsulated microspheres. Moreover, new microvascular networks in tissue substitutes can be engineered by using endothelial cells and stem cells or by creating arteriovenous shunt loops. Nonetheless, the currently used techniques are not sufficient to induce the rapid vascularization necessary for an adequate cellular oxygen supply. Thus, future directions of research should focus on the creation of microvascular networks within 3D tissue constructs in vitro before implantation or by co-stimulation of angiogenesis and parenchymal cell proliferation to engineer the vascularized tissue substitute in situ

Einstein's "Zur Elektrodynamik..." (1905) Revisited, with Some Consequences

Einstein, in his "Zur Elektrodynamik bewegter Korper", gave a physical (operational) meaning to "time" of a remote event in describing "motion" by introducing the concept of "synchronous stationary clocks located at different places". But with regard to "place" in describing motion, he assumed without analysis the concept of a system of co-ordinates. In the present paper, we propose a way of giving physical (operational) meaning to the concepts of "place" and "co-ordinate system", and show how the observer can define both the place and time of a remote event. Following Einstein, we consider another system "in uniform motion of translation relatively to the former". Without assuming "the properties of homogeneity which we attribute to space and time", we show that the definitions of space and time in the two systems are linearly related. We deduce some novel consequences of our approach regarding faster-than-light observers and particles, "one-way" and "two-way" velocities of light, symmetry, the "group property" of inertial reference frames, length contraction and time dilatation, and the "twin paradox". Finally, we point out a flaw in Einstein's argument in the "Electrodynamical Part" of his paper and show that the Lorentz force formula and Einstein's formula for transformation of field quantities are mutually consistent. We show that for faster-than-light bodies, a simple modification of Planck's formula for mass suffices. (Except for the reference to Planck's formula, we restrict ourselves to Physics of 1905.)Comment: 55 pages, 4 figures, accepted for publication in "Foundations of Physics

Copyright and cultural work: an exploration

This article first discusses the contemporary debate on cultural “creativity” and the economy. Second, it considers the current state of UK copyright law and how it relates to cultural work. Third, based on empirical research on British dancers and musicians, an analysis of precarious cultural work is presented. A major focus is how those who follow their art by way of “portfolio” work handle their rights in ways that diverge significantly from the current simplistic assumptions of law and cultural policy. Our conclusions underline the distance between present top-down conceptions of what drives production in the cultural field and the actual practice of dancers and musicians

Inductive Construction of 2-Connected Graphs for Calculating the Virial Coefficients

In this paper we give a method for constructing systematically all simple 2-connected graphs with n vertices from the set of simple 2-connected graphs with n-1 vertices, by means of two operations: subdivision of an edge and addition of a vertex. The motivation of our study comes from the theory of non-ideal gases and, more specifically, from the virial equation of state. It is a known result of Statistical Mechanics that the coefficients in the virial equation of state are sums over labelled 2-connected graphs. These graphs correspond to clusters of particles. Thus, theoretically, the virial coefficients of any order can be calculated by means of 2-connected graphs used in the virial coefficient of the previous order. Our main result gives a method for constructing inductively all simple 2-connected graphs, by induction on the number of vertices. Moreover, the two operations we are using maintain the correspondence between graphs and clusters of particles.Comment: 23 pages, 5 figures, 3 table

Library Design in Combinatorial Chemistry by Monte Carlo Methods

Strategies for searching the space of variables in combinatorial chemistry experiments are presented, and a random energy model of combinatorial chemistry experiments is introduced. The search strategies, derived by analogy with the computer modeling technique of Monte Carlo, effectively search the variable space even in combinatorial chemistry experiments of modest size. Efficient implementations of the library design and redesign strategies are feasible with current experimental capabilities.Comment: 5 pages, 3 figure

Notions of Connectivity in Overlay Networks

International audience" How well connected is the network? " This is one of the most fundamental questions one would ask when facing the challenge of designing a communication network. Three major notions of connectivity have been considered in the literature, but in the context of traditional (single-layer) networks, they turn out to be equivalent. This paper introduces a model for studying the three notions of connectivity in multi-layer networks. Using this model, it is easy to demonstrate that in multi-layer networks the three notions may differ dramatically. Unfortunately, in contrast to the single-layer case, where the values of the three connectivity notions can be computed efficiently, it has been recently shown in the context of WDM networks (results that can be easily translated to our model) that the values of two of these notions of connectivity are hard to compute or even approximate in multi-layer networks. The current paper shed some positive light into the multi-layer connectivity topic: we show that the value of the third connectivity notion can be computed in polynomial time and develop an approximation for the construction of well connected overlay networks

IKKbeta Deficiency in Myeloid Cells Ameliorates Alzheimer's Disease-Related Symptoms and Pathology

Alzheimer's disease (AD) is characterized by extracellular amyloid-beta (Abeta) deposits and microglia-dominated inflammatory activation. Innate immune signaling controls microglial inflammatory activities and Abeta clearance. However, studies examining innate immunity in Abeta pathology and neuronal degeneration have produced conflicting results. In this study, we investigated the pathogenic role of innate immunity in AD by ablating a key signaling molecule, IKKbeta, specifically in the myeloid cells of TgCRND8 APP-transgenic mice. Deficiency of IKKbeta in myeloid cells, especially microglia, simultaneously reduced inflammatory activation and Abeta load in the brain and these effects were associated with reduction of cognitive deficits and preservation of synaptic structure proteins. IKKbeta deficiency enhanced microglial recruitment to Abeta deposits and facilitated Abeta internalization, perhaps by inhibiting TGF-beta-SMAD2/3 signaling, but did not affect Abeta production and efflux. Therefore, inhibition of IKKbeta signaling in myeloid cells improves cognitive functions in AD mice by reducing inflammatory activation and enhancing Abeta clearance. These results contribute to a better understanding of AD pathogenesis and could offer a new therapeutic option for delaying AD progression