Entropic stochastic resonance

We present a novel scheme for the appearance of stochastic resonance when the dynamics of a Brownian particle takes place in a confined medium. The presence of uneven boundaries, giving rise to an entropic contribution to the potential, may upon application of a periodic driving force result in an increase of the spectral amplification at an optimum value of the ambient noise level. The entropic stochastic resonance, characteristic of small-scale systems, may constitute a useful mechanism for the manipulation and control of single molecules and nanodevices.

Diffusion in stationary flow from mesoscopic nonequilibrium thermodynamics

We analyze the diffusion of a Brownian particle in a fluid under stationary flow. By using the scheme of nonequilibrium thermodynamics in phase space, we obtain the Fokker-Planck equation that is compared with others derived from the kinetic theory and projector operator techniques. This equation exhibits violation of the fluctuation-dissipation theorem. By implementing the hydrodynamic regime described by the first moments of the nonequilibrium distribution, we find relaxation equations for the diffusion current and pressure tensor, allowing us to arrive at a complete description of the system in the inertial and diffusion regimes. The simplicity and generality of the method we propose makes it applicable to more complex situations, often encountered in problems of soft-condensed matter, in which not only one but more degrees of freedom are coupled to a nonequilibrium bath.

Kinetic equations for difussion in the presence of entropic barriers

We use the mesoscopic nonequilibrium thermodynamics theory to derive the general kinetic equation of a system in the presence of potential barriers. The result is applied to a description of the evolution of systems whose dynamics is influenced by entropic barriers. We analyze in detail the case of diffusion in a domain of irregular geometry in which the presence of the boundaries induces an entropy barrier when approaching the exact dynamics by a coarsening of the description. The corresponding kinetic equation, named the Fick-Jacobs equation, is obtained, and its validity is generalized through the formulation of a scaling law for the diffusion coefficient which depends on the shape of the boundaries. The method we propose can be useful to analyze the dynamics of systems at the nanoscale where the presence of entropy barriers is a common feature.

Biased diffusion in confined media: Test of the Fick-Jacobs approximation and validity criteria

We study biased, diffusive transport of Brownian particles through narrow, spatially periodic structures in which the motion is constrained in lateral directions. The problem is analyzed under the perspective of the Fick-Jacobs equation, which accounts for the effect of the lateral confinement by introducing an entropic barrier in a one-dimensional diffusion. The validity of this approximation, based on the assumption of an instantaneous equilibration of the particle distribution in the cross section of the structure, is analyzed by comparing the different time scales that characterize the problem. A validity criterion is established in terms of the shape of the structure and of the applied force. It is analytically corroborated and verified by numerical simulations that the critical value of the force up to which this description holds true scales as the square of the periodicity of the structure. The criterion can be visualized by means of a diagram representing the regions where the Fick-Jacobs description becomes inaccurate in terms of the scaled force versus the periodicity of the structure.

A Thermokinetic approach to radiative heat transfer at the nanoscale

Radiative heat exchange at the nanoscale presents a challenge for several areas due to its scope and nature. Here, we provide a thermokinetic description of microscale radiative energy transfer including phonon-photon coupling manifested through a non-Debye relaxation behavior. We show that a lognormal-like distribution of modes of relaxation accounts for this non-Debye relaxation behavior leading to the thermal conductance. We also discuss the validity of the fluctuation-dissipation theorem. The general expression for the thermal conductance we obtain fits existing experimental results with remarkable accuracy. Accordingly, our approach offers an overall explanation of radiative energy transfer through micrometric gaps regardless of geometrical configurations and distances.

Transgene inheritances and genetic similarities of near isogenic lines of genetically modified common beans

The objective of the present work was to determine the inheritance and stability of transgenes of a transgenic bean line expressing the genes rep-trap-ren from Bean golden mosaic virus and the bar gene. Crosses were done between the transgenic line and four commercial bean cultivars, followed by four backcrosses to the commercial cultivars. Progenies from each cross were evaluated for the presence of the transgenes by brushing the leaves with glufosinate ammonium and by polymerase chain reaction using specific oligonucleotides. Advanced generations were rub-inoculated with an isolate of Bean common mosaic necrosis virus (BCMNV). The transgenes were inherited consistently in a Mendelian pattern in the four crosses studied. The analyzed lines recovered close to 80% of the characteristics of the recurrent parent, as determined by the random amplified DNA markers used, besides maintaining important traits such as resistance to BCMNV. The presence of the transgene did not cause any detectable undesirable effect in the evaluated progenies.

Entropic transport in confined media: a challenge for computational studies in biological and soft-matter systems

Transport in small-scale biological and soft-matter systems typically occurs under confinement conditions in which particles proceed through obstacles and irregularities of the boundaries that may significantly alter their trajectories. A transport model that assimilates the confinement to the presence of entropic barriers provides an efficient approach to quantify its effect on the particle current and the diffusion coefficient. We review the main peculiarities of entropic transport and treat two cases in which confinement effects play a crucial role, with the appearance of emergent properties. The presence of entropic barriers modifies the mean first-passage time distribution and therefore plays a very important role in ion transport through micro- and nano-channels. The functionality of molecular motors, modeled as Brownian ratchets, is strongly affected when the motor proceeds in a confined medium that may constitute another source of rectification. The interplay between ratchet and entropic rectification gives rise to a wide variety of dynamical behaviors, not observed when the Brownian motor proceeds in an unbounded medium. Entropic transport offers new venues of transport control and particle manipulation and new ways to engineer more efficient devices for transport at the nanoscale.

Reduced microwave losses of YBa2Cu3O7_thin films on electro-optic LiNbO3 crystals

We report on the growth of epitaxial YBa2Cu3O7 thin films on X-cut LiNbO3 single crystals. The use of double CeO2/YSZ buffer layers allows a single in-plane orientation of YBa2Cu3O7, and results in superior superconducting properties. In particular, surface resistance Rs values of 1.4 m¿ have been measured at 8 GHz and 65 K. The attainment of such low values of Rs constitutes a key step toward the incorporation of high Tc materials as electrodes in photonic and acoustic devices.

Eficacia de la inducción miofascial para el tratamiento de la espasticidad en pacientes con parálisis cerebral espástica: ensayo clínico aleatorizado

¿El tratamiento mediante la inducción miofascial disminuye la espasticidad en los pacientes con Parálisis Cerebral Espástica (PCE) mientras son intervenidos con un tratamiento convencional? Objetivos: Comprobar si la inducción miofascial disminuye la espasticidad en pacientes con parálisis cerebral espástica (PCE) y así mismo prevenir las complicaciones musculoesqueléticas y aumentar el rango de movilidad articular. Metodología: Ensayo controlado clínico aleatorizado que recoge un total de 96 casos de PCE con Grado l, ll y lll de afectación según la Escala de clasificación Gross Motor Function Measure (GMFM). Se asignará de forma aleatoria y equitativamente 48 sujetos al grupo control aplicándose el tratamiento convencional y 48 sujetos al grupo experimental, donde la inducción miofascial se complementará con tratamiento convencional. Durante 3 meses se llevará a cabo el plan de intervención, 2 días a la semana en ambos grupos. Los datos serán analizados a través de las siguientes escalas: el tono muscular (Escala de Ashworth Modificada, Escala de Tardieu, Test pendular Wartenberg) funcionalidad y actividad (Gross Motor Function Classification System, Gross Motor Function Mesurement, Pediatric Evaluation of Disability Inventory), valoración neurológica (National Institute of NEurological Disordes and Stroke Scale) y la satisfacción del paciente (Questionnaire on Pain Caused by Spasticity). Estos datos serán extraidos el primer día, el último y 3 meses más tarde a modo de seguimiento. Durante el plan de intervención también se realizarán valoraciones semanales y mensuales.

Eficacia de la terapia y/o los ejercicios terapéuticos en pacientes con trastorno temporomandibular. Alteración cóndilo-discal posterior.

Pregunta: ¿Qué tipo de terapia manual y/o ejercicios terapéuticos son más eficaces en pacientes con trastorno temporomandibular? Objetivo: Evaluar y comparar la eficacia de la terapia manual y/o los ejercicios terapéuticos en pacientes con trastorno temporomandibular. Metodología: la presente revisión bibliográfica se centra en bases de datos Medline, Scopus, PEDro y Google Scholar. Los artículos obtenidos fueron publicados entre los años 2004 y 2014. Se incluyen un total de 12 ensayos clínicos aleatorios. La literatura consta de pacientes con trastorno temporomandibular que hayan sido intervenidos con técnicas de terapia manual y/o ejercicios terapéuticos aplicados por un fisioterapeuta. Resultados: fueron seleccionados 10 estudios de alta evidencia científica para demostrar que la terapia manual combinada con ejercicio terapéutico disminuye el dolor, aumenta la abertura de la boca y corrige la anteversión de la cabeza. Conclusiones: la terapia manual combinada con ejercicios terapéuticos es efectiva para disminuir los síntomas en pacientes con trastornos temporomandibulares.

Coarse-graining and thermodynamics in far-from-equilibrium systems

Lying at the core of statistical physics is the need to reduce the number of degrees of freedom in a system. Coarse-graining is a frequently-used procedure to bridge molecular modeling with experiments. In equilibrium systems, this task can be readily performed; however in systems outside equilibrium, a possible lack of equilibration of the eliminated degrees of freedom may lead to incomplete or even misleading descriptions. Here, we present some examples showing how an improper coarse-graining procedure may result in linear approaches to nonlinear processes, miscalculations of activation rates and violations of the fluctuation-dissipation theorem.

Hardness of FRHC-Cu determined by statistical analysis

A statistical indentation method has been employed to study the hardness value of fire-refined high conductivity copper, using nanoindentation technique. The Joslin and Oliver approach was used with the aim to separate the hardness (H) influence of copper matrix, from that of inclusions and grain boundaries. This approach relies on a large array of imprints (around 400 indentations), performed at 150 nm of indentation depth. A statistical study using a cumulative distribution function fit and Gaussian simulated distributions, exhibits that H for each phase can be extracted when the indentation depth is much lower than the size of the secondary phases. It is found that the thermal treatment produces a hardness increase, due to the partly re-dissolution of the inclusions (mainly Pb and Sn) in the matrix.

Evaluación de la efectividad de las Técnicas de Activación Muscular® en la resolución de la fasciosis plantar en corredores habituales: ensayo clínico aleatorizado.

Pregunta clínica de investigación: ¿es efectiva la Técnica de Activación Muscular® (MAT®) en la resolución de la fasciosis plantar (FP) en personas corredoras habituales? Objetivo: determinar si la terapia combinada mediante ejercicios de MAT® mejora los resultados obtenidos con el procedimiento convencional en el tratamiento de la FP en personas deportistas en la ciudad de Lleida. Metodología: En este ensayo clínico experimental ha participado un total de 264 pacientes, corredores habituales con FP de más de un mes y menos de un año de evolución, que han sido derivados por sus médicos de atención primaria. La muestra se ha dividido de forma aleatoria en dos grupos, uno control que sigue un protocolo convencional (educación sanitaria, AINEs y estiramietos) y el grupo experimental, al que se le ha aplicado la intervención de MAT®. La duración del estudio es de dos años, y cada intervención dura 4 semanas con un seguimiento a 6 y 12 meses. Un analista externo es el encargado del análisis de la información mediante el programa SPSS 15.0. Los resultados se miden mediante las variables de: dolor a la presión, grosor de la aponeurosis, percepción del estado de los pies, rango de movimiento articular (RMA) de tobillo y 1era metetarsofalángica (MTF) y tiempo de vuelta a la carrera entre otras.

Determinacion de las propiedades mecanicas y mecanismos de fractura de electrolitos soportados de YSZ y GDC mediante ensayos de indentacion instrumentada

El objetivo del presente trabajo es evaluar las propiedades mecánicas, así como los diferentes mecanismos de fractura activados mediante ensayos de indentación instrumentada, de electrolitos basados en circona estabilizada con itria ("yttria stabilized zirconia",YSZ) y ceria dopada con gadolinia ("gadolinia doped ceria", GDC), para pilas de combustible de óxido sólido, SOFCs. Ambos materiales, con un espesor final de 200 ¿m, se conformaron mediante prensado uniaxial a 500 MPa y se sinterizaron a 1400ºC. Propiedades mecánicas tales como la dureza (H) y el módulo de Young (E) han sido estudiadas a diferentes profundidades de penetración utilizando el algoritmo de Oliver y Pharr.