Coupled non-equilibrium fluctuations in a polymeric ternary mixture.

We investigate by dynamic shadowgraphy the non-equilibrium fluctuations at the steady state of a thermodiffusion experiment in a polymeric ternary mixture of polystyrene-toluene-n-hexane. The structure function of the refractive index reveals the existence of quite different decay times, thus requiring the analysis of a wide range of correlation times. This is related to the simultaneous presence of three distinct decay modes corresponding to (from fastest to slowest) the relaxation of temperature fluctuations, of the concentration fluctuations of the mixed solvent, and of the concentration fluctuations of the polymer in the binary solvent. An investigation of the decay times at the corresponding diffusive regimes provides a measurement of the thermal diffusivity and the two eigenvalues of the mass diffusion matrix of the ternary mixture. Similar experiments were performed in the past but here, to suppress the confinement effect and obtain a more direct comparison with the theory, a thicker sample is studied. Moreover, also a faster camera is used allowing the experimental observation of faster modes, like the propagative ones. The experimental values of the decay times are eventually compared with those predicted by different available theories. Finally, we present a more complete theoretical model to describe the non-equilibrium fluctuations in the bulk of a ternary mixture at the steady state of a thermodiffusion experiment.

Nonequilibrium Casimir pressures in liquids under shear.

In stationary nonequilibrium states coupling between hydrodynamic modes causes thermal fluctuations to become long ranged inducing nonequilibrium Casimir pressures. Here we consider nonequilibrium Casimir pressures induced in liquids by a velocity gradient. Specifically, we have obtained explicit expressions for the magnitude of the shear-induced pressure enhancements in a liquid layer between two horizontal plates that complete and correct results previously presented in the literature. In contrast to nonequilibrium Casimir pressures induced by a temperature or concentration gradient, we find that in shear nonequilibrium contributions from short-range fluctuations are no longer negligible. In addition, it is noted that currently available computer simulations of model fluids in shear observe effects from molecular correlations at nanoscales that have a different physical origin and do not probe shear-induced pressures resulting from coupling of long-wavelength hydrodynamic modes. Even more importantly, we find that in actual experimental conditions, shear-induced pressure enhancements are caused by viscous heating and not by thermal velocity fluctuations. Hence, isothermal computer simulations are irrelevant for the interpretation of experimental shear-induced pressure enhancements.

European Space Agency experiments on thermodiffusion of fluid mixtures in space.

This paper describes the European Space Agency (ESA) experiments devoted to study thermodiffusion of fluid mixtures in microgravity environment, where sedimentation and convection do not affect the mass flow induced by the Soret effect. First, the experiments performed on binary mixtures in the IVIDIL and GRADFLEX experiments are described. Then, further experiments on ternary mixtures and complex fluids performed in DCMIX and planned to be performed in the context of the NEUF-DIX project are presented. Finally, multi-component mixtures studied in the SCCO project are detailed.

Estudio observacional transversal para la evaluación de la adherencia en personas mayores: ESTUDIO NAGUSI / Cross-sectional, observational study for the evaluation of adherence in elderly people: NAGUSI STUDY

Introducción: La baja adherencia conlleva importantes problemas y es importante medirla para abordar intervenciones farmacéuticas para mejorarla. El test de Morisky-Green es la principal herramienta para ello, pero en nuestro medio hay pocos estudios realizados con él en personas mayores del ámbito comunitario que son quienes acuden a las farmacias. Objetivo: Conocer la adherencia a los tratamientos farmacológicos de las personas mayores que acuden al principal evento orientado al envejecimiento activo en Euskadi, de cara a emprender posibles actuaciones desde la farmacia comunitaria. Material y Métodos: Estudio observacional transversal de adherencia mediante el test de Morisky-Green a todas las personas mayores que acudieron al stand del COFBI durante el Salón Nagusi. Resultados: Se realizaron 498 encuestas. 480 sujetos tomaban algún medicamento (73,1% mujeres, 26,9% hombres). Su edad media era 74,6 años (±5,9) y el 34% vivían solos. De media tomaban 3,2 medicamentos (±2,1). El número medio de tomas diarias era 2,0 (±0,8). 457 sujetos completaron el test, obteniéndose un 49,5% de adherencia. No se hallaron diferencias significativas entre el grupo adherente y el incumplidor en ninguna de las variables independientes. Conclusiones: Las personas mayores que acuden al salón Nagusi muestran un nivel de adherencia al tratamiento farmacológico similar al descrito por la OMS y al detectado en otros estudios en los que se empleó la misma herramienta de medida. Las variables independientes estudiadas, no influyen significativamente en el grado de adherencia, lo que facilitaría el diseño de intervenciones desde la farmacia comunitaria para optimizarla en este tipo de población

Introduction: Low adherence involves significant problems. It is important to measure it in order to set out pharmaceutical interventions to improve it. The Morisky-Green test is the main tool designed for this purpose. Nevertheless, in our environment there are few studies done with this test in elderly people living in the community who are the ones that come to the pharmacies. Objective: To determine the adherence to pharmacological treatments of the elderly people who attend the main event aimed to promote active aging in Euskadi. The objective is to set out possible interventions from the community pharmacy. Material and Methods: Cross-sectional observational study of adherence using the Morisky-Green test in the elderly people who attended the COFBI stand during the Nagusi Hall. Results: 498 surveys were carried out. 480 subjects were taking medication (73.1% women, 26.9% men). Their average age was 74.6 years (± 5.9) and 34% lived alone. On average, they took 3.2 medicines (± 2.1). The mean number of daily intakes was 2.0 (± 0.8). 457 subjects completed the test, obtaining 49.5% of adherence. There were no significant differences between the adherent group and the non-compliant group in any of the independent variables. Conclusions: Elderly people attending Nagusi show a rate of adherence to pharmacological treatment similar to the one described by WHO and to those found in other studies done with the same measurement tool. The independent variables studied did not influence significantly the adherence degree, which would make easier to undertake actions from the community pharmacy to improve adherence in this population

Non-local fluctuation phenomena in liquids.

Fluids in non-equilibrium steady states exhibit long-range fluctuations which extend over the entire system. They can be described by non-equilibrium thermodynamics and fluctuating hydrodynamics that assume local equilibrium for the thermophysical properties as a function of space and time. The experimental evidence for the consistency between this assumption of local equilibrium in the equations and the non-local fluctuation phenomena observed is reviewed.

Nonequilibrium fluctuation-induced Casimir pressures in liquid mixtures.

In this article we derive expressions for Casimir-like pressures induced by nonequilibrium concentration fluctuations in liquid mixtures. The results are then applied to liquid mixtures in which the concentration gradient results from a temperature gradient through the Soret effect. A comparison is made between the pressures induced by nonequilibrium concentration fluctuations in liquid mixtures and those induced by nonequilibrium temperature fluctuations in one-component fluids. Some suggestions for experimental verification procedures are also presented.

Physical origin of nonequilibrium fluctuation-induced forces in fluids.

Long-range thermal fluctuations appear in fluids in nonequilibrium states leading to fluctuation-induced Casimir-like forces. Two distinct mechanisms have been identified for the origin of the long-range nonequilibrium fluctuations in fluids subjected to a temperature or concentration gradient. One is a coupling between the heat or mass-diffusion mode with a viscous mode in fluids subjected to a temperature or concentration gradient. Another one is the spatial inhomogeneity of thermal noise in the presence of a gradient. We show that in fluids fluctuation-induced forces arising from mode coupling are several orders of magnitude larger than those from inhomogeneous noise.

Fickian Diffusion in Ternary Mixtures Composed by 1,2,3,4-Tetrahydronaphthalene, Isobutylbenzene, and n-Dodecane.

We report the Fickian diffusion coefficients in 20 ternary mixtures formed by 1,2,3,4-tetrahydronaphthalene (THN), isobutylbenzene (IBB) and n-dodecane (nC12) measured by the Taylor dispersion technique at 298.1 K and atmospheric pressure. Four diffusion coefficients of the ternary mixtures were measured along six concentration paths starting on one binary subsystem and moving toward the other one. We found expressions for the diffusion matrix of a ternary mixture approaching to the binary limits. The measured diffusion coefficients were thoroughly verified by comparison with the theoretical asymptotic behavior. The main diffusion coefficients vary smoothly over the entire concentration space and D11 is always larger than D22. One of the two cross-diffusion coefficients is of the same order of magnitude as the main ones and, hence, not negligible, whereas the other one is close to zero. The investigated mixtures also comprise compositions that were examined in microgravity experiments in the ESA DCMIX1 project.

Non-equilibrium concentration fluctuations in binary liquids with realistic boundary conditions.

Because of the spatially long-ranged nature of spontaneous fluctuations in thermal non-equilibrium systems, they are affected by boundary conditions for the fluctuating hydrodynamic variables. In this paper we consider a liquid mixture between two rigid and impervious plates with a stationary concentration gradient resulting from a temperature gradient through the Soret effect. For liquid mixtures with large Lewis and Schmidt numbers, we are able to obtain explicit analytical expressions for the intensity of the non-equilibrium concentration fluctuations as a function of the frequency ω and the wave number q of the fluctuations. In addition we elucidate the spatial dependence of the intensity of the non-equilibrium fluctuations responsible for a non-equilibrium Casimir effect.

Nonequilibrium Casimir-like Forces in Liquid Mixtures.

In this Letter, we consider a liquid mixture confined between two thermally conducting walls subjected to a stationary temperature gradient. While in a one-component liquid nonequilibrium fluctuation forces appear inside the liquid layer, nonequilibrium fluctuations in a mixture induce a Casimir-like force on the walls. The physical reason is that the temperature gradient induces large concentration fluctuations through the Soret effect. Unlike temperature fluctuations, nonequilibrium concentration fluctuations are also present near a perfectly thermally conducting wall. The magnitude of the fluctuation-induced Casimir force is proportional to the square of the Soret coefficient and is related to the concentration dependence of the heat and volume of mixing.

Investigation of Fickian diffusion in the ternary mixture of 1,2,3,4-tetrahydronaphthalene, isobutylbenzene, and dodecane.

We present a comprehensive analysis of experimental results obtained for Fickian diffusion in the benchmark ternary liquid mixture of 1,2,3,4-tetrahydronaphthalene, isobutylbenzene, and dodecane (nC12) with equal mass fractions. Isothermal diffusion coefficients have been measured by two independent experimental methods: by Taylor dispersion technique, and by a counter flow cell fitted with an optical interferometry device. The experimental diffusion matrices have been critically analyzed regarding the Onsager reciprocal relations, for which we introduce a matrix asymmetry index s(2) that is independent of the frame of reference and the component order.

Giant Casimir effect in fluids in nonequilibrium steady states.

In this Letter, we consider the fluctuation-induced force exerted between two plates separated by a distance L in a fluid with a temperature gradient. We predict that for a range of distances L, this nonequilibrium force is anomalously large compared to other Casimir forces. The physical reason is that correlations in a nonequilibrium fluid are generally of longer range than other correlations, even than those near an equilibrium critical point. This giant Casimir force is related to a divergent Burnett coefficient that characterizes an Onsager cross effect between the pressure and the temperature gradient. The predicted Casimir force should be detectable with currently available experimental techniques.

Concentration fluctuations in non-isothermal reaction-diffusion systems. II. The nonlinear case.

In this paper, we consider a simple reaction-diffusion system, namely, a binary fluid mixture with an association-dissociation reaction between two species. We study fluctuations at hydrodynamic spatiotemporal scales when this mixture is driven out of equilibrium by the presence of a temperature gradient, while still being far away from any chemical instability. This study extends the analysis in our first paper on the subject [J. M. Ortiz de Zárate, J. V. Sengers, D. Bedeaux, and S. Kjelstrup, J. Chem. Phys. 127, 034501 (2007)], where we considered fluctuations in a non-isothermal reaction-diffusion system but still close to equilibrium. The present extension is based on mesoscopic non-equilibrium thermodynamics that we recently developed [D. Bedeaux, I. Pagonabarraga, J. M. Ortiz de Zárate, J. V. Sengers, and S. Kjelstrup, Phys. Chem. Chem. Phys. 12, 12780 (2010)] to derive the law of mass action and fluctuation-dissipation theorems for the random contributions to the dissipative fluxes in the nonlinear macroscopic description. Just as for non-equilibrium fluctuations close to equilibrium, we again find an enhancement of the intensity of the concentration fluctuations in the presence of a temperature gradient. The non-equilibrium concentration fluctuations are in both cases spatially long ranged, with an intensity depending on the wave number q. The intensity exhibits a crossover from a ∝q(-4) to a ∝q(-2) behavior depending on whether the corresponding wavelength is smaller or larger than the penetration depth of the reacting mixture. This opens a possibility to distinguish between diffusion- or activation-controlled regimes of the reaction experimentally. The important conclusion overall is that non-equilibrium fluctuations in non-isothermal reaction-diffusion systems are always long ranged.

Mesoscopic non-equilibrium thermodynamics of non-isothermal reaction-diffusion.

We show how the law of mass action can be derived from a thermodynamic basis, in the presence of temperature gradients, chemical potential gradients and hydrodynamic flow. The solution gives the law of mass action for the forward and the reverse contributions to the net chemical reaction. In addition we derive the fluctuation-dissipation theorem for the fluctuating contributions to the reaction rate, heat flux and mass fluxes. All these results arise without any other assumptions than those which are common in mesoscopic non-equilibrium thermodynamics; namely quasi-stationary transport across a high activation energy barrier, and local equilibrium along the reaction coordinate. Arrhenius-type behaviour of the kinetic coefficients is recovered. The thermal conductivity, Soret coefficient and diffusivity are significantly influenced by the presence of a chemical reaction. We thus demonstrate how chemical reactions can be fully reconciled with non-equilibrium thermodynamics.

[Demand for dispensing of medicines without medical prescription]. / Demanda de medicamentos de prescripción sin receta médica.

OBJECTIVES: To study the request for drugs and their dispensing without the necessary prescription form. DESIGN: Cross-sectional, observational study. SETTING: Volunteer community pharmacies in Spain. MAIN MEASUREMENTS: Percentages of request and dispensation of drugs without prescription. Reasons given by people requesting the medicines and pharmacists' reasons for dispensing them. RESULTS: 11.1% of prescription drugs were requested without a prescription form: 69.7% of these requests were for chronic medication or acute treatment and 20% were for self-medication. The drugs without prescription form were dispensed in 10.8% and refused in 0.3% of cases. The reasons given by pharmacists for dispensing without the compulsory prescription form were: "drugs recommended by a doctor" (33.3%), "advance on prescriptions" (24.1%), and "the pharmacist knew the patient's pharmaco-therapeutic record" (17.5%). CONCLUSIONS: Dispensing drugs without the necessary prescription form is a very frequent practice (10.8%) and is not restricted to any particular drug therapy group. Doctors, dentists, nurses, pharmacists, patients and health service management must all assume their share of responsibility if this problem is to be solved. The system of prescription and dispensing of chronic medicine (repeat prescription in long-term treatment) needs to be improved and strengthened.

Utilidad de las prótesis autoexpandibles recubiertas en la enfermedad benigna gastroesofágica / Utility of covered self-expanding prostheses in benign gastroesophageal disease

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