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Thermo-osmotic flows - flows generated in micro and nanofluidic systems by thermal gradients - could provide an alternative approach to harvest waste heat. However, such use would require massive thermo-osmotic flows, which are up to now only predicted for special and expensive materials. There is thus an urgent need to design affordable nanofluidic systems displaying large thermo-osmotic coefficients. In this paper we propose a general model for thermo-osmosis of aqueous electrolytes in charged nanofluidic channels, taking into account hydrodynamic slip, together with the different solvent and solute contributions to the thermo-osmotic response. We apply this model to a wide range of systems, by studying the effect of wetting, salt type and concentration, and surface charge. We show that intense thermo-osmotic flows can be generated using slipping charged surfaces. We also predict for intermediate wettings a transition from a thermophobic to a thermophilic behavior depending on the surface charge and salt concentration. Overall, this theoretical framework opens an avenue for controlling and manipulating thermally induced flows with common charged surfaces and a pinch of salt., 7 pages, 3 figures

The discovery of ultrastable glasses raises novel challenges about glassy systems. Recent experiments studied the macroscopic devitrification of ultrastable glasses into liquids upon heating but lacked microscopic resolution. We use molecular dynamics simulations to analyze the kinetics of this transformation. In the most stable systems, devitrification occurs after a very large time, but the liquid emerges in two steps. At short times, we observe the rare nucleation and slow growth of isolated droplets containing a liquid maintained under pressure by the rigidity of the surrounding glass. At large times, pressure is released after the droplets coalesce into large domains, which accelerates devitrification. This two-step process produces pronounced deviations from the classical Avrami kinetics and explains the emergence of a giant lengthscale characterizing the devitrification of bulk ultrastable glasses. Our study elucidates the nonequilibrium kinetics of glasses following a large temperature jump, which differs from both equilibrium relaxation and aging dynamics, and will guide future experimental studies.

Introduction: The prevalence of heart failure is on the rise. In its advanced stage (AHF) the condition manifests with incapacitating symptoms. Exacerbations, frequent admissions, and high morbidity and mortality represent conditions amenable to palliative care. A cardiology palliative care (CPC) program was designed to monitor symptoms, deepen communication, establish advanced directives, and adjust therapeutic efforts. The goal of the study was to compare the care of patients who died from AHF before and after CPC program implementation. Material and methods: This was an observational, comparative study. CPC was offered to patients with AHF, and these subjects were compared to a control group without CPC because of unavailability (preCPC). In the statistical analysis categorical variables were evaluated using non-parametric tests. Continuous variables were compared using the Mann-Whithey U-test. Results: Seventy-seven patients were included in the preCPC group, and 65 in the CPC group. They all had similar demographic characteristics: age (median), 75 years; male gender, 70 %. A decrease in duration (27.3 vs. 7.2; p < 0.001) and in number of hospital admissions (2.64 vs. 1.51; p < 0.001) was found in the CPC group as compared to the control group. Invasive procedures within the final 5 days of life predominated in the preCPC group; assisted mechanical ventilation (52.7 % vs. 7.8 %; p < 0.001), hemodialysis (41 % vs. 5.5 %; p < 0.001), cardiopulmonary resuscitation (88.2 % vs. 11 %; p < 0.001), central vascular access (75.7 % vs. 26.5 %, p < 0.01), and use of inotropics (70.5 % vs. 20 %; p < 0.001). Non-invasive, comfort interventions predominated in the CPC group: palliative sedation (3 % vs. 25 %), opioid use (35 % vs. 58.3 %), deactivation of implantable cardiac defibrillator (0 vs. 37,5 %), and do-not-resuscitate orders (3 % vs. 77 %; p < 0.001). Mortality in critical care settings predominated in the preCPC group (51 % vs. 26 %; p < 0.005). Discussion: CPC improves quality of care for patients with AHF, and ensures adequacy of therapeutic efforts, thus preventing disproportionate, unnecessary interventions.

The search for materials with high thermal resistance has promising applications in thermoelectric devices and boiling crisis retardation. In this paper, we study the interfacial heat transfer between water and gold, nanostructuring the gold surface and coating it with graphene. By trapping air (or vacuum in our simulations) between graphene and the nanopatterned surface, we observe a considerable increase in the interfacial resistance compared to the planar gold situation, which is shown to scale with the effective graphene–gold contact surface for both monolayer and multilayer graphene. With the massive thermal resistances we predict (up to 200 nm in terms of Kapitza length), the system proposed here represents a robust alternative to superhydrophobic Cassie materials. Moreover, since the low thermal conductance is achieved primarily due to geometry (vacuum trapping), it is straightforward to extend our results to any material with a structure equivalent to that of the nanopatterned gold wall considered here.

Cecilia Herrero, Takeshi Omori, Yasutaka Yamaguchi, and Laurent Joly, "Shear force measurement of the hydrodynamic wall position in molecular dynamics", The Journal of Chemical Physics 151, 041103 (2019) https://doi.org/10.1063/1.5111966., Flows in nanofluidic systems are strongly affected by liquid-solid slip, which is quantified by the slip length and by the position where the slip boundary condition applies. Here, we show that the viscosity, slip length, and hydrodynamic wall position (HWP) can be accurately determined from a single molecular dynamics (MD) simulation of a Poiseuille flow, after identifying a relation between the HWP and the wall shear stress in that configuration. From this relation, we deduce that in gravity-driven flows, the HWP identifies with the Gibbs dividing plane of the liquid-vacuum density profile. Simulations of a generic Lennard-Jones liquid confined between parallel frozen walls show that the HWP for a pressure-driven flow is also close to the Gibbs dividing plane (measured at equilibrium), which therefore provides an inexpensive estimate of the HWP, going beyond the common practice of assuming a given position for the hydrodynamic wall. For instance, we show that the HWP depends on the wettability of the surface, an effect usually neglected in MD studies of liquid-solid slip. Overall, the method introduced in this article is simple, fast, and accurate and could be applied to a large variety of systems of interest for nanofluidic applications.

Se presenta un modelo en dos pasos que predice la probabilidad de presencia de necromasa en pinares de repoblación y rebollares del norte de España y cuantifica el área basimétrica de los árboles muertos en pie y el volumen de los árboles caídos. Por otra parte se presenta un modelo lineal que cuantifica la fijación de carbono en la necromasa caída en el suelo.