Abstracts
Here you can find the Abstracts of the talks.
Many thanks to the speakers!!
Mario.Castro.UPCo
A Bayesian approach to T-cell receptor specificity
Broadly speaking, specificity is a measure of how a molecule interacts with other molecules or discriminates among almost similar peptides that differ only in a few mutations. Although specificity has a generic meaning for any protein, the concept is central for the immune cell as it allows to understand the dilemma between being useful and being harmless for the self. In this talk I will address an empirical way to define and quantify the specificity of a T-cell receptor based on concepts borrowed from information theory and Bayesian analysis.
Pablo.Catalán.UC3M
toyLIFE reloaded: dynamics on the multiplex
Recent research on genotype networks has improved our understanding of the genotype-phenotype map. Until now, this study has been mainly limited to single environments: the phenotype associated to a genotype is computed for one environment, and assumed to be the same in different environments. However, experimental evidence shows that genotypes usually express different phenotypes in different environments, a phenomenon that has been called phenotypic plasticity. In this talk I will propose an extension of the genotype network framework for multiple environments. The result of this extension is a multiplex genotype network that facilitates the understanding of evolutionary dynamics. I will make use of toyLIFE [1], a computational model devised by our group, to explore the consequences of the multiplex structure, and to shed some light on some open issues in evolutionary biology.
[1] Arias, C. F., Catalán, P., Manrubia, S. and Cuesta, J. A. toyLIFE: a computational framework to study the multi-level organization of the genotype-phenotype map. Scientific Reports 4, 7549 (2014).
José.Cuesta.UC3M
Neutral evolution and the acceleration of the molecular clock
Large sets of genotypes give rise to the same phenotype because phenotypic expression is highly redundant. Accordingly, a population can accept mutations without altering its phenotype, as long as the genotype mutates into another one on the same set. By linking every pair of genotypes that are mutually accessible through mutation, genotypes organize themselves into neutral networks (NN). These networks are known to be heterogeneous and assortative, and these properties affect the evolutionary dynamics of the population. By studying the dynamics of populations on NN with arbitrary topology we analyze the effect of assortativity, of NN (phenotype) fitness, and of network size. We find that the probability that the population leaves the network is smaller the longer the time spent on it. This progressive “phenotypic entrapment” entails a systematic increase in the overdispersion of the process with time and an acceleration in the fixation rate of neutral mutations [1].
[1] Manrubia, S., and Cuesta, J. A. Evolution on neutral networks accelerates the ticking rate of the molecular clock. Journal of the Royal Society Interface 102, 20141010 (2015).
Luis.Dinis.UCM
Carnot engine played a crucial role in the development of thermodynamics, setting a fundamental upper limit to the efficiency of a motor operating between two thermal baths. Nowadays, micromanipulation techniques make it possible to explore the thermodynamics of small systems at scales where fluctuations cannot be neglected. In this talk, I will present an experimental realization of a Carnot engine with a single optically trapped Brownian particle as working substance. We have fully characterized the thermodynamics of the engine when operating both in and out of equilibrium, observing that our device reaches Carnot efficiency for slow driving. I will also discuss the fluctuations of the finite-time stochastic efficiency, showing that Carnot efficiency can be surpassed in individual or ensembles of a few number of non-equilibrium realizations of the engine. Finally, I'll briefly comment on the stochastic efficiency large deviation behaviour which could provide information about the fundamental characteristics of the engine.
Miguel.González.UAM
A rich variety of ordered phases —such as nematic, columnar, smectic or crystal— can be found in liquid crystal systems. Here I will present our recent work on the topic. We use density-functional theory to study patterning formation and phase behaviour of hard particles, in particular rods and plates. I will discuss how external conditions (confinement and presence of obstacles) and particles shape can lead to the formation of different phases. Equilibrium phases and dynamic evolution will be shown.
Gonzalo.Manzano.UCM
Fluctuation theorems for quantum maps
When considering small systems, quantum fluctuations, in addition to thermal ones, come into play. Furthermore, there is a wide range of phenomena without classical counterpart that cannot be neglected, such as coherence, squeezing or entanglement, in both single and many-body systems. A promising route to the understanding of thermodynamics in quantum systems are the fluctuation theorems, which establish exact statements about the fluctuations of thermodynamic quantities in systems arbitrarily far from equilibrium. In this talk I will introduce some general notions about the fluctuation theorems and their quantum extensions, then I will present a novel generalized fluctuation theorem valid for a broad range of quantum maps.
Juan.MR.Parrondo.UCM
Nonequilibrium free energy and the thermodynamics of information
The definition of entropy and free energy for non-equilibrium systems is a controversial matter. Shannon entropy has been often identified with thermodynamic entropy in an uncritical manner. Both coincide for equilibrium states, but it is not clear what happens out of equilibrium. In this talk I will try to show, using simple examples, that it makes no sense to define a thermodynamic entropy for arbitrary non-equilibrium situations. However, Shannon's entropy does have a physical meaning in some specific situations; much like the thermodynamic entropy, Shannon's determines the energy transfers in certain processes. In particular, the energetics of isothermal processes is characterized by a non-equilibrium free energy defined in terms of Shannon entropy. Finally, I will discuss how this free energy is a powerful tool to develop a thermodynamics of information processing.
Ignacio.Pascual.UC3M
Modeling paradigm shifts in cultural evolution
Cultural transmission is a process of innovation and interaction between individuals that brings about changes in societies. These changes can occur either smoothly and gradually or suddenly and abruptly. Abrupt changes are collective phenomena referred to as “paradigm shifts”. They have been described in Social Sciences, and some mechanisms, like interaction between cultural elements —that is, how the presence of an element facilitates or inhibits the presence of a second one— have been pointed as responsible of them. However, how and why these transitions occur and which are the clue elements that lead to them are questions that so far have only received an intuitive explaination. We explore how the interaction between cultural elements changes the dynamics of cultural transmission to the extent that it can explain the occurrence of paradigm shifts.
Pablo.Rodríguez.Université Paris Sud (Francia)
Casimir effect and heat transfer between 2D materials
Chern insulators are a class of two-dimensional topological materials. Their electronic properties are different from conventional materials, and lead to interesting new physics as quantum Hall effect in absence of an external magnetic field. Here I will review some of their special properties and, in particular, I will discuss the radiative heat transfer and the Casimir effect between two planar Chern Insulators sheets. Finally, I will show how to control the intensity and sign of this Casimir force as well as the requirements to observe a repulsive Casimir force in the lab with those materials.
Chantal.Valeriani.UCM
Living clusters and crystals from low density suspensions of active colloids
In our work, we study a dilute suspension of attractive self-propelling spherical particles and address the problem of the formation of living clusters and crystals of active particles [1]. We observe the formation of living clusters and explain this general feature in terms of the balance between active forces and regression to thermodynamic equilibrium [1-3].
[1] B. Mognetti, A. Šarić, S. Angioletti-Uberti, A. Cacciuto, C. Valeriani and D. Frenkel, Living clusters and crystals from low densities suspensions of active colloids, Phys. Rev. Lett. 111, 245702 (2013).
[2] Philip Ball, Focus: Particle Clustering Phenomena Inspire Multiple Explanations, Physics 6, 134 (2013).
[3] F. Alarcón, C. Valeriani and I. Pagonabarraga, Characterization of active clusters of self-propelled attractive spheres, in preparation (2015).