11,349 research outputs found
Symmetry for the duration of entropy-consuming intervals
We introduce the violation fraction 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, , which can be interpreted as an entropy associated to the
fluctuations of the violation fraction.
The function , 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 .
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} 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 and the duration of the time interval . In the
large- and large- limit we show that, for ergodic and microreversible
systems, the mean value of scales as
. The
exponent is positive and generally depends on the protocol for the
external driving forces, being 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 with
and 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]
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