Nonequilibrium thermodynamics versus model grain growth: derivation and some physical implications

Nonequilibrium thermodynamics formalism is proposed to derive the flux of grainy (bubbles-containing) matter, emerging in a nucleation growth process. Some power and non-power limits, due to the applied potential as well as owing to basic correlations in such systems, have been discussed. Some encouragement for such a discussion comes from the fact that the nucleation and growth processes studied, and their kinetics, are frequently reported in literature as self-similar (characteristic of algebraic correlations and laws) both in basic entity (grain; bubble) size as well as time scales.Comment: 8 pages, 1 figur

Potentially Harmful Microalgae from the Southern-Central Coast of Cuba

Benthic and planktic toxic microalgae from the southern-central region of Cuba were surveyed intermittently between 2007 and 2009, mainly in the estuarine Cienfuegos Bay and its adjacent coast. The highest abundance of both benthic and planktic species were recorded in dry season and at the beginning of the rainy period which is directly correlated with a higher incidence of ciguatera and other episodes associated to harmful algal blooms. Ostreopsis lenticularis and Gambierdiscus caribaeus were the dominant benthic species in the eastern coast. After heavy rain, Ostreopsis ovata and Prorocentrum lima were dominant. Moderate abundance of the potentially ciguatotoxic Prorocentrum concavum, P.rathymum and the dermatotoxic cyanophyte Lyngbya majuscula were registered on blooms of macroalgae. Gymnodinium catenatum, Pyrodinium bahamense and Dinophysis ovum were first reported in the region. Blooms of the diatom Pseudo-nitzschia multistriata have been observed in eutrophic zones. A small episode of dead fish was associated to blooms of Heterocapsa circularisquama. Other toxic or noxious species have been seen accompanying such as Cochlodinium polykrikoides, Dinophysis caudata, Gonyaulax polygramma, G. spinifera and Prorocentrum minimum. High abundance of the cyanobacteria Planktothrix isothrix, Pseudoanabaena sp., Dolichospermum solitarium and Microcystis aeruginosa were registered in the bay after hurricanes.Versión del edito

EU-LIFEHAB: Expanding the discussion on the life cycles of harmful algae

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Quantum Theory of Irreversibility

A generalization of the Gibbs-von Neumann relative entropy is proposed based on the quantum BBGKY [Bogolyubov-Born-Green-Kirkwood-Yvon] hierarchy as the nonequilibrium entropy for an N-body system. By using a generalization of the Liouville-von Neumann equation describing the evolution of a density super- operator, it is demonstrated that the entropy production for an isolated system is non-negative, which provides an arrow of time. Moreover, following the procedure of non-equilibrium thermodynamics a master matrix is introduced for which a mi- croscopic expression is obtained. Then, the quantum Boltzmann equation is derived in terms of a transition superoperator related to that master matrix

Imaging the Proton Concentration and Mapping the Spatial Distribution of the Electric Field of Catalytic Micropumps

Catalytic engines can use hydrogen peroxide as a chemical fuel in order to drive motion at the microscale. The chemo-mechanical actuation is a complex mechanism based on the interrelation between catalytic reactions and electro-hydrodynamics phenomena. We studied catalytic micropumps using fluorescence confocal microscopy to image the concentration of protons in the liquid. In addition, we measured the motion of particles with different charges in order to map the spatial distributions of the electric field, the electrostatic potential and the fluid flow. The combination of these two techniques allows us to contrast the gradient of the concentration of protons against the spatial variation in the electric field. We present numerical simulations that reproduce the experimental results. Our work sheds light on the interrelation between the different processes at work in the chemomechanical actuation of catalytic pumps. Our experimental approach could be used to study other electrochemical systems with heterogeneous electrodes