Symmetry for the duration of entropy-consuming intervals

We introduce the violation fraction $\upsilon$ as the cumulative fraction of time that a mesoscopic system spends consuming entropy at a single trajectory in phase space. We show that the fluctuations of this quantity are described in terms of a symmetry relation reminiscent of fluctuation theorems, which involve a function, $\Phi$, which can be interpreted as an entropy associated to the fluctuations of the violation fraction. The function $\Phi$, when evaluated for arbitrary stochastic realizations of the violation fraction, is odd upon the symmetry transformations which are relevant for the associated stochastic entropy production. This fact leads to a detailed fluctuation theorem for the probability density function of $\Phi$. We study the steady-state limit of this symmetry in the paradigmatic case of a colloidal particle dragged by optical tweezers through an aqueous solution. Finally, we briefly discuss on possible applications of our results for the estimation of free-energy differences from single molecule experiments.Comment: 11 pages, 4 figures. Last revised. Version accepted for publication in Phys. Rev.

Duration of local violations of the second law of thermodynamics along single trajectories in phase space

We define the {\it violation fraction} $\nu$ as the cumulative fraction of time that the entropy change is negative during single realizations of processes in phase space. This quantity depends both on the number of degrees of freedom $N$ and the duration of the time interval $\tau$. In the large-$\tau$ and large-$N$ limit we show that, for ergodic and microreversible systems, the mean value of $\nu$ scales as $\langle\nu(N,\tau)\rangle\sim\big(\tau N^{\frac{1}{1+\alpha}}\big)^{-1}$. The exponent $\alpha$ is positive and generally depends on the protocol for the external driving forces, being $\alpha=1$ for a constant drive. As an example, we study a nontrivial model where the fluctuations of the entropy production are non-Gaussian: an elastic line driven at a constant rate by an anharmonic trap. In this case we show that the scaling of $\langle \nu \rangle$ with $N$ and $\tau$ agrees with our result. Finally, we discuss how this scaling law may break down in the vicinity of a continuous phase transition.Comment: 8 pages, 2 figures, Final version, as accepted for publication in Phys. Rev.

Interplay between optical, viscous and elastic forces on an optically trapped Brownian particle immersed in a viscoelastic fluid

We provide a detailed study of the interplay between the different interactions which appear in the Brownian motion of a micronsized sphere immersed in a viscoelastic fluid measured with optical trapping interferometry. To explore a wide range of viscous, elastic and optical forces, we analyze two different viscoelastic solutions at various concentrations, which provide a dynamic polymeric structure surrounding the Brownian sphere. Our experiments show that, depending of the fluid, optical forces, even if small, slightly modify the complex modulus at low frequencies. Based on our findings, we propose an alternative methodology to calibrate this kind of experimental set-up when non-Newtonian fluids are used. Understanding the influence of the optical potential is essential for a correct interpretation of the mechanical properties obtained by optically-trapped probe-based studies of biomaterials and living matter.Comment: Accepted for publication in Applied Physics Letter

Sufficient conditions for controllability and observability of serial and parallel concatenated linear systems

This paper deals with the sufficient conditions for controllability and observability characters of finitedimensional linear continuous-time-invariant systems of serial and parallel concatenated systems. The obtained conditions depend on the controllability and observability of the systems and in some cases, the functional output-controllability of the first one.Peer ReviewedPostprint (published version

Temas selectos de biomedicina en Ciencias de la Salud

trabajos de investigación en forma de capítulos individuales, los cuales abordan temas de aplicación de la nanotecnología en las ciencias odontológicas, cómo mejorar la experiencia del paciente que acude a la consulta odontológica, los efectos de la dieta en caries dental y enfermedades crónicas degenerativas como la diabetes mellitus; asimismo, la actividad física en la condición de salud y nutrición de los adolescentes, microbiología médica y diversos tópicos relacionados con la psicología de la salud, desde el comportamiento de los médicos y estudiantes de medicina con respecto a sus pacientes, hasta la relación de pareja, la salud mental laboral, la actitud de los pacientes ante la presencia de enfermedades crónico-degenerativas y la recuperación de la salud mental después del abuso sexual

Discursos para gobernarlos a todos

Recensión de: García Cardiel, Jorge, 2016, Los discursos del poder en el mundo ibérico del sureste (siglos VII-I a.C.), CSIC, Bibliotheca Praehistorica Hispana 32, Madrid. Entrevista con el auto

Fluorokinolona antibiotikoen analisia ingurumeneko uretan: metodo analitikoaren garapena eta aplikazioa

[EUS] Gaur egun, konposatu kimiko jakin batzuek (adibidez, hidrokarburo polizikliko aromatikoak, bifenilo polikloratuak, ftalatoak, etab.) ingurumenean eragin ditzaketen kalteak ezagunak dira eta ondorioz, hainbat legedien bidez arautuak izan dira [1]. Hala ere, badaude urte askotan kutsatzailetzat hartu ez diren hainbat konposatu eta haiek ingurumenean izan ditzaketen eraginak aztertzen hasi dira. Kutsatzaile berri hauen artean, jatorri eta ezaugarri kimiko desberdineko konposatuak daude; esate baterako, abusuzko drogak, norbere higienerako produktuak, industria erabilerarako produktuak, etab. Kutsatzaile izendatu berri guztien artean kezka handienetakoa eragiten dutenak sendagaiak dira. Izatez, azken urteetan konposatu farmazeutiko berrien garapenak gaixotasun desberdinak gainditzeko aukera paregabea eman dute. Haien kontsumoa mundu osoan hedatu eta zabaldu da, baina alde batera utzi izan dira ingurumenean izan ditzaketen eraginak kontutan hartu gabe [2]. Horregatik, osasun publikoaren eta ingurumenaren babesean jarduten duten erakunde nagusiek (Osasunaren Mundu Erakundea, Ingurumena Babesteko Agentzia edo Europako Batzordea) lehentasunezko lerro bihurtu dute konposatu horien ikerketa [3]