Convective stability of carbon sequestration in anisotropic porous media

© 2014 The Author(s) Published by the Royal Society. All rights reserved. The stability of convection in an anisotropic porous medium, where the solute concentration is assumed to decay via a first-order chemical reaction, is studied. This is a simplified model for the interactions between carbon dioxide and brine in underground aquifers; the instability of which is essential in reducing reservoir mixing times. The key purpose of this paper is to explore the role porous media anisotropy plays in convective instabilities. It is shown that varying the ratio of horizontal to vertical solutal diffusivites does not significantly affect the behaviour of the instability. This is also the case for changes of permeability when the diffusion rate dominates the solute reaction rate. However, interestingly, when the solute reaction rate dominates the diffusion rate a change in the permeability of the porous material does have a substantial effect on the instability of the system. The region of potential subcritical instabilities is shown to be negligible, which further supports the novel instability behaviour

Thermal convection in a Brinkman–Darcy–Kelvin–Voigt fluid with a generalized Maxwell–Cattaneo law

We investigate thoroughly a model for thermal convection of a class of viscoelastic fluids in a porous medium of Brinkman–Darcy type. The saturating fluids are of Kelvin–Voigt nature. The equations governing the temperature field arise from Maxwell–Cattaneo theory, although we include Guyer–Krumhansl terms, and we investigate the possibility of employing an objective derivative for the heat flux. The critical Rayleigh number for linear instability is calculated for both stationary and oscillatory convection. In addition a nonlinear stability analysis is carried out exactly

Antioxidants: real medicines?

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Thermal convection in a higher-gradient Navier–Stokes fluid

We discuss models for flow in a class of generalized Navier–Stokes equations. The work concentrates on producing models for thermal convection, analysing these in detail, and deriving critical Rayleigh and wave numbers for the onset of convective fluid motion. In addition to linear instability theory we present a careful analysis of fully nonlinear stability theory. The theories analysed all possess a bi-Laplacian term in addition to the normal spatial derivative term. The theories discussed are Stokes couple stress theory, dipolar fluid theory, Green–Naghdi theory, Fried–Gurtin–Musesti theory, and a second theory of Fried and Gurtin. We show that the Stokes couple stress theory and the Fried–Gurtin–Musesti theory involve the same partial differential equations while those of Green–Naghdi and dipolar theory are similar. However, we concentrate on boundary conditions which are crucial to understand all five theories and their differences

Balance, In All Things

This poem is a vent for the inherent frustration felt from trying to find a career in and bridge the transition between politics and medicine. It reflects a stubborn determination to not give in to critics\u27 never-enough-ism while also trying to be open to improvement and not give in to pride nor cynicism

A Computational Comparison of the Hydrophobic Pocket of Neural and Epithelial Cadherins for the Purpose of Identifying a Selective Inhibitor

Classical cadherins are a subfamily of calcium-dependent cellular adhesion molecules that play an important role in the formation of cellular junctions in many tissues. The extracellular portion of cadherins consists of five tandem-repeated domains (EC1-EC5). The critical first step in cadherin-mediated cellular adhesion occurs at the interface between two adjacent EC1 domains in which the transition from monomer to dimer is accomplished by docking the W2 residue of the N-terminal β-strand of one EC1 domain into the hydrophobic pocket of its partner domain. Cancer and many other diseases have been linked to the aberrant expression of Epithelial (E-cad) and Neural Cadherins (N- cad). Due to the importance of cadherins in the study of cancer, the hydrophobic pocket of the EC1 domain is of interest because it provides a possible site for the selective inhibition of dimerization as an anti-cancer treatment. Furthermore, if the shape of the hydrophobic pocket is different in E-cad and N-cad, then perhaps these differences may be exploited to target a specific tissue or specific form of cancer. In order to study the significance of the hydrophobic pocket, we studied the crystal structures of the EC1-EC2 domains of E-cad and N-cad using the imaging software Chimera. First, we compared the position of critical hydrophobic pocket residues in two identical crystal structures of N- cad and likewise for E-cad. Second, we used a specific function in Chimera to obtain area and volume measurements of the hydrophobic pocket and its opening in each structure. Subsequently, a database of indole derivatives were docked into the hydrophobic pocket using the software OpenEye to identify potential ligands that could selectively bind a single Cadherin subtype. Results indicate that there is indeed a difference in the size and shape of the hydrophobic pockets of N-cad and E-cad that leads to differences in the optimal indole derivatives predicted to bind to N-cad and E-cad. These critical results suggest that the hydrophobic pockets of these two proteins are different and may be exploited for selective inhibition of dimerization by cadherin subtypes. Future studies will be directed toward developing these unique indole structures as possible cancer therapies

Thermal convection with a Cattaneo heat flux model

The problem of thermal convection in a layer of viscous incompressible fluid is analysed. The heat flux law is taken to be one of Cattaneo type. The time derivative of the heat flux is allowed to be a material derivative, or a general objective derivative. It is shown that only one objective derivative leads to results consistent with what one expects in real life. This objective derivative leads to a Cattaneo–Christov theory, and the results for linear instability theory are in agreement with those for a material derivative. It is further shown that none of the theories allow a standard nonlinear, energy stability analysis. A further heat flux due to P.M. Mariano is added and then an analysis is performed for stationary convection, oscillatory convection, and fully nonlinear theory. For the material derivative case, the analysis proceeds and global nonlinear stability is achieved. For Cattaneo–Christov theory, it appears necessary to add a regularization term in the equation for the heat flux, and even then the analysis only works in two space dimensions, and is conditional upon the size of the initial data. For the three-dimensional situation, it is shown how a nonlinear stability analysis may be achieved with a Navier–Stokes–Voigt fluid rather than a Navier–Stokes one

Mussel Community Studies [Year One].

Mytilus californianus communities (mussel beds) were examined from six geographic localities in Southern California. These included two mainland sites, Coal Oil Point and San Diego; and four island sites, San Miguel, Santa Cruz, San Nicholas, and Santa Barbara Islands. Optimal sample sizes were determined for each locality. In general, a sample, size of 1500 cm2 (five cores) was optimal for the "typical" mussel bed. However, structurally unique mussel beds required individual consideration. Community biomass, diversity, species richness, and species evenness were calculated quarterly for the island localities and biannually for mainland locations. The molluscs, primarily the mussels, accounted for 90% of the total biomass while all other groups combined accounted for 10% or less of the total biomass. The mussel communities from all localities contributed to the master species list which conservatively contained 346 species. The most diverse localities were Coal Oil Point and Santa Cruz Island with an average number of 73 and 74 species/O.lS m respectively. No overall seasonal patterns existed in community composition. The community similarity analyses showed the mainland localities biotically dissimilar from the islands and both groups were characterized by distinct faunal assemblages. In addition, San Miguel Island biota were unique among the island sites. The most important mussel bed structural attributes provided habitats for the associated community and included sediment and coarse fraction features. Food-related resources provided by the mussel bed were secondarily important. Community diversity generally increased with the quantity of habitat and food resources. (PDF contains 138 pages

Phases of a Man Called \u27Moon\u27: Mayor Landrieu and Race Relations in New Orleans, 1960-1974

This study examines the political career of Maurice Edwin Moon Landrieu from his election to the Louisiana legislature in 1960 to the end of his first term as mayor of New Orleans in 1974. Landrieu was a white southern liberal who vigorously supported the agenda of the civil rights movement. He succeeded in building an unprecedented coalition between liberal, middle-class whites and a large segment of the black community. As the 1970s unfolded, however, he found his coalition increasingly threatened not just by disgruntled white conservatives, which might be expected, but also by angry black radicals of the Black Panther Party. This study argues that Landrieu\u27s firm commitment to opening up political and economic opportunity to all citizens enabled him to keep his progressive, biracial coalition together and to help pave the way for the 1978 election of Ernest Dutch Morial, the first black mayor of New Orleans