88 research outputs found
Solution of voter model dynamics on annealed small-world networks
An analytical study of the behavior of the voter model on the small-world
topology is performed. In order to solve the equations for the dynamics, we
consider an annealed version of the Watts-Strogatz (WS) network, where
long-range connections are randomly chosen at each time step. The resulting
dynamics is as rich as on the original WS network. A temporal scale
separates a quasi-stationary disordered state with coexisting domains from a
fully ordered frozen configuration. is proportional to the number of
nodes in the network, so that the system remains asymptotically disordered in
the thermodynamic limit.Comment: 11 pages, 4 figures, published version. Added section with extension
to generic number of nearest neighbor
A semantical approach to equilibria and rationality
Game theoretic equilibria are mathematical expressions of rationality.
Rational agents are used to model not only humans and their software
representatives, but also organisms, populations, species and genes,
interacting with each other and with the environment. Rational behaviors are
achieved not only through conscious reasoning, but also through spontaneous
stabilization at equilibrium points.
Formal theories of rationality are usually guided by informal intuitions,
which are acquired by observing some concrete economic, biological, or network
processes. Treating such processes as instances of computation, we reconstruct
and refine some basic notions of equilibrium and rationality from the some
basic structures of computation.
It is, of course, well known that equilibria arise as fixed points; the point
is that semantics of computation of fixed points seems to be providing novel
methods, algebraic and coalgebraic, for reasoning about them.Comment: 18 pages; Proceedings of CALCO 200
Thinking about growth : a cognitive mapping approach to understanding small business development
School of Managemen
Motion of influential players can support cooperation in Prisoner's Dilemma
We study a spatial Prisoner's dilemma game with two types (A and B) of
players located on a square lattice. Players following either cooperator or
defector strategies play Prisoner's Dilemma games with their 24 nearest
neighbors. The players are allowed to adopt one of their neighbor's strategy
with a probability dependent on the payoff difference and type of the given
neighbor. Players A and B have different efficiency in the transfer of their
own strategy therefore the strategy adoption probability is reduced by a
multiplicative factor (w < 1) from the players of type B. We report that the
motion of the influential payers (type A) can improve remarkably the
maintenance of cooperation even for their low densities.Comment: 7 pages, 7 figure
A terminal assessment of stages theory : introducing a dynamic states approach to entrepreneurship
Stages of Growth models were the most frequent theoretical approach to understanding entrepreneurial business growth from 1962 to 2006; they built on the growth imperative and developmental models of that time. An analysis of the universe of such models (N=104) published in the management literature shows no consensus on basic constructs of the approach, nor is there any empirical confirmations of stages theory. However, by changing two propositions of the stages models, a new dynamic states approach is derived. The dynamic states approach has far greater explanatory power than its precursor, and is compatible with leading edge research in entrepreneurship
Penguin and Box Diagrams in Unitary Gauge
We evaluate one-loop diagrams in the unitary gauge that contribute to
flavor-changing neutral current (FCNC) transitions involving two and four
fermions. Specifically, we deal with penguin and box diagrams arising within
the standard model (SM) and in nonrenormalizable extensions thereof with
anomalous couplings of the W boson to quarks. We show explicitly in the SM the
subtle cancelation among divergences from individual unitary-gauge
contributions to some of the physical FCNC amplitudes and derive expressions
consistent with those obtained using R_xi gauges in the literature. Some of our
results can be used more generally in certain models involving fermions and
gauge bosons which have interactions similar in form to those we consider.Comment: 11 pages, 2 figures, to appear in EPJ
Using a normative framework to explore the prototyping of wireless grids
The capacity for normative frameworks to capture the essential features of interactions between components in open architectures suggests they might also be of assistance in an early, rapid prototyping phase of system development, helping to refine concepts, identify actors, explore policies and evaluate feasibility. As an exercise to examine this thesis, we investigate the concept of the wireless grid. Wireless grids have been proposed to address the energy issues arising from a new generation of mobile phones, the idea being that local communication with other mobile phones, being cheaper, can be used in combination with network communication to achieve common goals while at the same time extending the battery duty cycle. This results in a social dilemma, as it is advantageous for rational users to benefit from the energy savings without any contribution to the cooperation, as every commitment has its price. We present a necessarily simplified model, whose purpose is to provide us with the foundation to explore issues in the management of such a framework, policies to encourage collaborative behaviour, and the means to evaluate the effects on energy consumption
Wnt signalling and cancer stem cells
[Abstract] Intracellular signalling mediated by secreted Wnt proteins is essential for the establishment of cell fates and proper tissue patterning during embryo development and for the regulation of tissue homeostasis and stem cell function in adult tissues. Aberrant activation of Wnt signalling pathways has been directly linked to the genesis of different tumours. Here, the components and molecular mechanisms implicated in the transduction of Wnt signal, along with important results supporting a central role for this signalling pathway in stem cell function regulation and carcinogenesis will be briefly reviewed.Ministerio de Ciencia e Innovación; SAF2008-0060
Mitochondrial pharmacology.
Mitochondria are being recognized as key factors in many unexpected areas of biomedical science. In addition to their well-known roles in oxidative phosphorylation and metabolism, it is now clear that mitochondria are also central to cell death, neoplasia, cell differentiation, the innate immune system, oxygen and hypoxia sensing, and calcium metabolism. Disruption to these processes contributes to a range of human pathologies, making mitochondria a potentially important, but currently seemingly neglected, therapeutic target. Mitochondrial dysfunction is often associated with oxidative damage, calcium dyshomeostasis, defective ATP synthesis, or induction of the permeability transition pore. Consequently, therapies designed to prevent these types of damage are beneficial and can be used to treat many diverse and apparently unrelated indications. Here we outline the biological properties that make mitochondria important determinants of health and disease, and describe the pharmacological strategies being developed to address mitochondrial dysfunction
Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures
Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo
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