The transition to irreversibility in sheared suspensions: An analysis based on a mesoscopic entropy production

We study the shear-induced diffusion effect and the transition to irreversibility in suspensions under oscillatory shear flow by performing an analysis of the entropy production associated to the motion of the particles. We show that the Onsager coupling between different contributions to the entropy production is responsible for the scaling of the mean square displacement on particle diameter and applied strain. We also show that the shear-induced effective diffusion coefficient depends on the volume fraction and use Lattice-Boltzmann simulations to characterize the effect through the power spectrum of particle positions for different Reynolds numbers and volume fractions. Our study gives a thermodynamic explanation of the the transition to irreversibility through a pertinent analysis of the second law of thermodynamics.Comment: 17 pages, 3 figures, paper submitted tp phys rev

Pattern formation from consistent dynamical closures of uniaxial nematic liquid crystals

Pattern formation in uniaxial polymeric liquid crystals is studied for different dynamic closure approximations. Using the principles of mesoscopic non-equilibrium thermodynamics in a mean-field approach, we derive a Fokker-Planck equation for the single-particle non-homogeneous distribution function of particle orientations and the evolution equations for the second and fourth order orientational tensor parameters. Afterwards, two dynamic closure approximations are discussed, one of them considering the relaxation of the fourth order orientational parameter and leading to a novel expression for the free-energy like function in terms of the scalar order parameter. Considering the evolution equation of the density of the system and values of the interaction parameter for which isotropic and nematic phases coexist, our analysis predicts that patterns and traveling waves can be produced in lyotropic uniaxial nematics even in the absence of external driving.Comment: 34 pages, 7 figure

The Interstitial Lymphatic Peritoneal Mesothelium Axis in Portal Hypertensive Ascites: When in Danger, Go Back to the Sea

Portal hypertension induces a splanchnic and systemic low-grade inflammatory response that could induce the expression of three phenotypes, named ischemia-reperfusion, leukocytic, and angiogenic phenotypes.During the splanchnic expression of these phenotypes, interstitial edema, increased lymph flow, and lymphangiogenesis are produced in the gastrointestinal tract. Associated liver disease increases intestinal bacterial translocation, splanchnic lymph flow, and induces ascites and hepatorenal syndrome. Extrahepatic cholestasis in the rat allows to study the worsening of the portal hypertensive syndrome when associated with chronic liver disease. The splanchnic interstitium, the mesenteric lymphatics, and the peritoneal mesothelium seem to create an inflammatory pathway that could have a key pathophysiological relevance in the production of the portal hypertension syndrome complications. The hypothetical comparison between the ascitic and the amniotic fluids allows for translational investigation. From a phylogenetic point of view, the ancestral mechanisms for amniotic fluid production were essential for animal survival out of the aquatic environment. However, their hypothetical appearance in the cirrhotic patient is considered pathological since ultimately they lead to ascites development. But, the adult human being would take advantage of the potential beneficial effects of this “amniotic-like fluid” to manage the interstitial fluids without adverse effects when chronic liver disease aggravates

Adherencia al tratamiento con fármacos moduladores de la enfermedad sintéticos en la artritis reumatoide. Resultados del estudio OBSERVAR

[Abstract] Background: Treatment compliance with disease-modifying antirheumatic drugs (DMARD) is essential to achieve the therapeutic goals in rheumatoid arthritis (RA). However, despite the need for good compliance, there is evidence that patients with RA frequently fail to use DMARD for the control of RA. Thus, the main objective of the OBSERVAR study is to evaluate the reasons for the lack of therapeutic adherence to synthetic DMARD in these patients. Patients and methods: A Delphi process involving 18 randomly selected Spanish rheumatologists determined the level of agreement with 66 causes of noncompliance selected from the literature in relation to synthetic DMARD in RA. Results: The reasons for noncompliance were consistent in 75.7%, although 3 reasons (4.5%) were highly consistent: 1) not knowing what to do in the case of an adverse event with DMARD; 2) not having undergone adherence screening by health personnel for early detection of "noncompliant patients"; and 3) not having undergone interventions or strategies that improve adherence. Conclusion: In order to improve adherence to RA treatment with synthetic DMARD, the patient should be adequately informed of each new treatment introduced, the patient's compliance profile should be incorporated into the clinical routine and the patient's motivation for therapeutic compliance be reinforced through the methods available to us.[Resumen] Introducción. La cumplimentación del tratamiento modificador de la enfermedad es esencial para alcanzar los objetivos terapéuticos en la artritis reumatoide (AR). Sin embargo, y a pesar de la necesidad de una buena adherencia, existe evidencia de que muchos pacientes con AR no cumplen adecuadamente con la prescripción del tratamiento indicado con fármacos moduladores de la enfermedad de acción lenta (FAME) sintéticos o convencionales. Conscientes de la importancia de este hecho, el estudio sobre observancia terapéutica en AR (estudio OBSERVAR) tiene como objetivo principal valorar los motivos de la falta de adherencia terapéutica a los FAME sintéticos en estos pacientes. Pacientes y métodos. Mediante un proceso Delphi entre 18 reumatólogos españoles seleccionados aleatoriamente se determinó el grado de acuerdo con 66 causas de incumplimiento seleccionadas de la bibliografía, en relación con los FAME sintéticos en la AR. Resultados. Los motivos de incumplimiento fueron consistentes en el 75,7%, si bien 3 razones (4,5%) destacaron como muy consistentes: 1) desconocer qué hacer cuando se sufre un acontecimiento adverso con el FAME; 2) no llevar a cabo métodos de cribado de la adherencia por el personal sanitario para detectar a los «pacientes incumplidores» de forma temprana y 3) no aplicar intervenciones o estrategias que mejoren la adherencia terapéutica. Conclusión. Para mejorar la adherencia al tratamiento de la AR con FAME sintéticos se debe informar al paciente de cada tratamiento nuevo introducido, incorporar el perfil de cumplimiento del paciente en la rutina clínica, y reforzar la motivación del paciente al cumplimiento terapéutico mediante los métodos a nuestro alcance

Phase stability of stress-sensitive Ag2CO3 silver carbonate at high pressures and temperature

Silver carbonate (Ag2CO3) is a material currently used for artificial carbon storage. In this work, we report synchrotron X-ray powder diffraction (XRD) experiments under high pressure and high temperature in combination with density-functional theory (DFT) calculations on silver carbonate up to 13.3 GPa. Two pressure-induced phase transitions were observed at room temperature: at 2.9 GPa to a high-pressure (HP1) phase and at 10.5 GPa to a second high-pressure phase (HP2). The facts that a) the HP2 phase can be indexed with the initial P21/m structure, b) our DFT calculations predict the initial structure is stable in the entire pressure range, and c) the HP2 phase is stable under decompression suggest that the intermediate HP1 phase is a product of the appearance of non-hydrostatic stresses in the sample. The observed structural transformations are associated to a high sensitivity of this compound to non-hydrostatic conditions. The compressibility of Ag2CO3 has also been determined, showing the c axis is the most compressible and that the bulk modulus increases quickly with applied pressure. We attribute both observations to the weak nature of the closed-shell Ag–Ag interactions in this material. The behavior of Ag2CO3 under heating at approximately 3 GPa was also studied. No temperature-induced phase transitions were found at this pressure, and the thermal expansion was determined to be relatively high for a carbonate.Authors thank the financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) and the Agencia Estatal de Investigación under projects MALTA Consolider Ingenio 2010 network (RED2018-102612-T) and PGC2021-125518NB-I00 (cofinanced by EU FEDER funds), and from the Generalitat Valenciana under projects CIAICO/2021/241 and MFA/2022/007. A.O.R. acknowledges the financial support of the Spanish MINECO RyC-2016-20301 Ramón y Cajal Grant and the project AYUD/2021/51036 of the Principality of Asturias (cofinanced by EU FEDER funds). Authors also thank the MALTA Consolider supercomputing centre and Compute Canada for computational resources and ALBA-CELLS synchrotron for providing beamtime under experiments 2020084419 and 2021024988. These experiments were performed at the MSPD beamline with the collaboration of ALBA staff

A Novel Approach to Study the Variability of NGC 5548

Understanding the properties of the continuum radiation and broad emission lines of active galactic nuclei provides significant information not only to model the radiation mechanism and constrain the geometry and kinematics of the broad-line region (BLR) but also to probe the central engine of the sources. Here we investigate the multifractal behavior of the Hβ emission line and the 5100 Å continuum flux light curves of NGC 5548. The aim is to search for multiscaling signatures in the light curves and heck if there is a possible nonlinear relationship between them. To this end, we use a multifractality analysis technique called the Multifractal Detrended Moving Average analysis. We detect multifractal (nonlinear) signatures in the full monitoring and densely sampled period of the Hβ line and 5100 Å continuum light curves of NGC 5548, possibly indicating the presence of complex and nonlinear interaction in the 5100 Å continuum and Hβ emission line regions. Moreover, the degree of multifractality of the Hβ line is found to be about twice that of the 5100 Å continuum. The nonlinearity of both emissions could be generated when the BLR reprocesses the radiation from the central compact source. Finally, we found that antipersistent long-range temporal correlation is the main source of the multifractality detected in both light curves.We warmly thank the anonymous referee for valuable suggestions and comments. A.B. acknowledges a CAPES PhD fellowship. L.J.G. acknowledges support by the MINECO/AEI/FEDER-UE grant AYA2017-89815-P and the University of Cantabria

Symmetries in Classical Field Theory

The multisymplectic description of Classical Field Theories is revisited, including its relation with the presymplectic formalism on the space of Cauchy data. Both descriptions allow us to give a complete scheme of classification of infinitesimal symmetries, and to obtain the corresponding conservation laws.Comment: 70S05; 70H33; 55R10; 58A2

The rheology of hard sphere suspensions at arbitrary volume fractions: An improved differential viscosity model

We propose a simple and general model accounting for the dependence of the viscosity of a hard sphere suspension at arbitrary volume fractions. The model constitutes a continuum-medium description based on a recursive-differential method that assumes a hierarchy of relaxation times. Geometrical information of the system is introduced through an effective volume fraction that approaches the usual filling fraction at low concentrations and becomes one at maximum packing. The agreement of our expression for the viscosity with experiments at low- and high-shear rates and in the high-frequency limit is remarkable for all volume fractions.Comment: 16 pages, 6 figures, submitte