Unfolding designable structures

Among an infinite number of possible folds, nature has chosen only about 1000 distinct folds to form protein structures. Theoretical studies suggest that selected folds are intrinsically more designable than others; these selected folds are unusually stable, a property called the designability principle. In this paper we use the 2D hydrophobic-polar lattice model to classify structures according to their designability, and Langevin dynamics to account for their time evolution. We demonstrate that, among all possible folds, the more designable ones are easier to unfold due to their large number of surface-core bonds.Comment: 10 pages, 4 figures, Proceeding of the 3rd International Conference NEXT-SigmaPh

Intra-group Light in Hickson Compact Groups

We have analyzed the intra-group light component of 3 Hickson Compact Groups (HCG 79, HCG 88 and HCG 95) with detections in two of them: HCG 79, with $46\pm11$ of the total $B$ band luminosity and HCG 95 with $11\pm26$. HCG 88 had no component detected. This component is presumably due to tidally stripped stellar material trapped in the group potential and represents an efficient tool to determine the stage of dynamical evolution and to map its gravitational potential. To detect this low surface brightness structure we have applied the wavelet technique OV\_WAV, which separates the different components of the image according to their spatial characteristic sizes.Comment: Small update on the associated institutions lis

Los escritos de Alfred Schütz desde la perspectiva de una teoría de la 'creatividad' de la acción

La ponencia presenta un esbozo de los aportes de Schütz a una reflexión sobre la 'creatividad' de la acción. La cuestión no fue planteada en forma sistemática por Schütz pero puede abordarse mediante conceptos claves de su obra, lo que implica también, indirectamente, un aporte a la renovación de su lectura. Se establecen en concreto cuatro campos de interés: la capacidad de los actores para innovar con y en el 'acervo de conocimiento'; la capacidad de 'fantasear' proyectos de acción; la capacidad de simbolizar y de producir mediante símbolos mundos 'imaginarios'; la capacidad de dar nacimiento constante a nuevas 'vivencias'. Se aporta también, al comienzo, una precisión de la palabra 'creatividad', a partir de la cual se organiza la lectura. Y se ofrece como conclusión una lista de aspectos de la obra que exigen investigación fenomenológica complementari

Males involuntarios. Para una reapropiación del concepto de «efectos perversos»

Este trabajo intenta hacer, a la vez, una restricción y una ampliación del concepto de «efectos perversos» (Raymond Boudon). Restricción, porque trata de circunscribir la noción a un conjunto más específico de fenómenos que los considerados por Boudon bajo su órbita, concibiéndolos como un tipo particular de «consecuencias no intencionadas» de la acción social. Pero al mismo tiempo ampliación, porque se intenta recuperar el concepto por fuera del presupuesto de una agencia y una interacción «racional».Unintended wrong. For a reformulation of the concept of «perverse effects» This paper aims at both a limiting and at the same time broadening of the «perverse effects» concept (Raymond Boudon). A limiting, since the factors encompassed by this notion are reduced to a more specific group of social facts. Thus, they are seen as a particular kind of unintended consequences of social action. At the same time its a broadening, as it tries to recuperate the «perverse effects» concept but outside of agency and «rational» interaction model

Microscopic mechanism for cold denaturation

We elucidate the mechanism of cold denaturation through constant-pressure simulations for a model of hydrophobic molecules in an explicit solvent. We find that the temperature dependence of the hydrophobic effect is the driving force/induces/facilitates cold denaturation. The physical mechanism underlying this phenomenon is identified as the destabilization of hydrophobic contact in favor of solvent separated configurations, the same mechanism seen in pressure induced denaturation. A phenomenological explanation proposed for the mechanism is suggested as being responsible for cold denaturation in real proteins

Spatial and spectral shape of inhomogeneous non-equilibrium exciton-polariton condensates

We develop a mean-field theory of the spatial profile and the spectral properties of polariton condensates in nonresonantly pumped semiconductor microcavities in the strong coupling regime. Predictions are obtained for both the continuous-wave and the pulsed excitation regimes and the specific signatures of the non-equilibrium character of the condensation process are pointed out. A striking sensitivity of the condensate shape on the optical pump spot size is demonstrated by analytical and numerical calculations, in good quantitative agreement with recent experimental observations.Comment: 5 pages, 3 figure

Stochastic properties of systems controlled by autocatalytic reactions II

We analyzed the stochastic behavior of systems controlled by autocatalytic reaction A+X -> X+X, X+X -> A+X, X -> B provided that the distribution of reacting particles in the system volume is uniform, i.e. the point model of reaction kinetics introduced in arXiv:cond-mat/0404402 can be applied. Assuming the number of substrate particles A to be kept constant by a suitable reservoir, we derived the forward Kolmogorov equation for the probability of finding n=0,1,... autocatalytic particles X in the system at a given time moment. We have shown that the stochastic model results in an equation for the mean value of autocatalytic particles X which differs strongly from the kinetic rate equation. It has been found that not only the law of the mass action is violated but also the bifurcation point is disappeared in the well-known diagram of X particle- vs. A particle-concentration. Therefore, speculations about the role of autocatalytic reactions in processes of the "natural selection" can be hardly supported.Comment: 17 pages, 6 figure

Quantum theory of intersubband polarons

We present a microscopic quantum theory of intersubband polarons, quasiparticles originated from the coupling between intersubband transitions and longitudinal optical phonons. To this aim we develop a second quantized theory taking into account both the Fr\"ohlich interaction between phonons and intersubband transitions and the Coulomb interaction between the intersubband transitions themselves. Our results show that the coupling between the phonons and the intersubband transitions is extremely intense, thanks both to the collective nature of the intersubband excitations and to the natural tight confinement of optical phonons. Not only the coupling is strong enough to spectroscopically resolve the resonant splitting between the modes (strong coupling regime), but it can become comparable to the bare frequency of the excitations (ultrastrong coupling regime). We thus predict the possibility to exploit intersubband polarons both for applied optoelectronic research, where a precise control of the phonon resonances is needed, and also to observe fundamental quantum vacuum physics, typical of the ultrastrong coupling regime