Comparative study of single-atom gold and iridium on CeO2{111}.

Oxide-supported single-atom catalysts have shown promise for a variety of heterogeneous processes. In addition to their inherent activity and selectivity, these materials come at much lower financial cost, avoiding the use of full-bodied precious-metal catalysts, but at the conceptual expense that more complex structural and electronic considerations need to be understood if we are to exploit their full potential. Here, we focus on the adsorption of single-atom iridium at both stoichiometric and defective CeO2{111} surfaces, by means of first-principles density functional theory. Reference calculations for the adsorption of single-atom gold, on the same set of substrates, provide a valuable set of benchmarks against which to interpret our iridium results.Winston Churchill Foundation of the United State

Similarity and Diversity in Macrophage Activation by Nematodes, Trematodes, and Cestodes

This review summarizes current knowledge of macrophages in helminth infections, with a focus not only on delineating the striking similarities in macrophage phenotype between diverse infections but also on highlighting the differences. Findings from many different labs illustrate that macrophages in helminth infection can act as anti-parasite effectors but can also act as powerful immune suppressors. The specific role for their alternative (Th2-mediated) activation in helminth killing or expulsion versus immune regulation remains to be determined. Meanwhile, the rapid growth in knowledge of alternatively activated macrophages will require an even more expansive view of their potential functions to include repair of host tissue and regulation of host metabolism

Energy landscapes and dynamics of glycine on Cu(110).

Amino acids adsorbed on single-crystal metal surfaces have emerged as prototypical systems for exploring the properties that govern the development of long-range chirality in self-assembled monolayers (SAM) and supramolecular 2D networks. In this study, we characterise the self-assembly mechanism for glycine on the Cu(110) surface. This process occurs on a time scale that is too fast for most atomically resolved microscopic techniques, so the mechanism we propose here provides new insight for an important unexplored surface phenomenon

Lifting of Ir{100} reconstruction by CO adsorption: An ab initio study

The adsorption of CO on unreconstructed and reconstructed Ir{100} has been studied, using a combination of density functional theory and thermodynamics, to determine the relative stability of the two phases as a function of CO coverage, temperature and pressure. We obtain good agreement with experimentaldata. At zero temperature, the (1X5) reconstruction becomes less stable than the unreconstructed (1X1) surface when the CO coverage exceeds a critical value of 0.09 ML. The interaction between CO molecules is found to be repulsive on the reconstructed surface, but attractive on the unreconstructed, explaining the experimental observation of high CO coverage on growing (1X1) islands. At all temperatures and pressures, we find only two possible stable states: 0.05 ML CO c(2X2) overlayer on the (1X1) substrate, and the clean (1$\times$5) reconstructed surface.Comment: 31 page

Trends in antibacterial resistance among Streptococcus pneumoniae isolated in the USA: update from PROTEKT US Years 1–4

© 2008 Jenkins et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

The influence of mussel-modified habitat on Fucus serratus L. a rocky intertidal canopy-forming macroalga

The influence of habitat modification by Mytilus edulis L. on the settlement and development of Fucus serratus populations was investigated on rocky shores of the Isle of Anglesey, North Wales. Settlement of fucoids was higher inside mussel habitat than outside on one of two shores studied. The effect of microhabitat on survival of fucoid germlings was examined by transplanting the germlings into and outside mussel habitats, each with and without the exclusion of grazers. Observation showed that periwinkles and top shells were abundant in mussel habitat, while limpets dominated bare rock. Exclusion of grazers greatly enhanced the survival of fucoid germlings in both habitats, indicating that while mussel habitat supports a different grazer assemblage to bare rock, both assemblages are important in limiting fucoid recruitment. The risk of dislodgement was assessed and compared between fucoids growing on mussel shells and bare rock. In situ pull-tests showed that less force was required to detach large fertile thalli growing on mussel shells than those growing on the rock. Adhesion was generally broken between the mussel and the rock rather than between the holdfast and the mussel. These observations indicate that mussels provide an unstable substrate for mature fucoids. Overall results suggest that a negative effect of mussel-modified habitat on fucoids is profound in adults; but the effect is context-dependent in juveniles and can be positive at settlement. Results from a survey on population structure of fucoids across two shores showed that there were greater numbers of large fertile fucoids growing directly attached to rock than on mussel shells, while there was no difference for juvenile fucoids confirming the experimental results. Moreover thalli larger than 60 cm were found only on the rock but not on shells. This finding suggests that a mussel dominated habitat may have a significant impact on reproductive output in fucoid populations

Surface Chirality Influences Molecular Rotation upon Desorption.

Chiral surfaces offer great potential as a medium for enantioselective synthesis or separation, yet their dynamic enantiospecific interactions with adsorbates are not well understood. Here, the influence of chiral surfaces on the molecular rotations of desorbing molecules is investigated. Formic acid desorption from Cu{531} and Cu{110} serve as model systems for desorption processes of an achiral adsorbate from a chiral and an achiral surface. Our first-principles molecular dynamics study reveals a much larger and more directed angular momentum for molecules desorbing from the chiral surface and a clear preference for one sense of rotation. This result provides new insight into desorption and adsorption processes and propensities on chiral surfaces

Diophantine Approach to the Classification of Two-Dimensional Lattices: Surfaces of Face-Centered Cubic Materials.

The long-range periodic order of a crystalline surface is generally represented by means of a two-dimensional Bravais lattice, of which only five symmetrically distinct types are possible. Here, we explore the circumstances under which each type may or may not be found at the surfaces of face-centered cubic materials and provide means by which the type of lattice may be determined with reference only to the Miller indices of the surface; the approach achieves formal rigor by focusing on the number theory of integer variables rather than directly upon real geometry. We prove that the {100} and {111} surfaces are, respectively, the only exemplars of square and triangular lattices. For surfaces exhibiting a single mirror plane, we not only show that rectangular and rhombic lattices are the only two possibilities, but also capture their alternation in terms of the parity of the indices. In the case of chiral surfaces, oblique lattices predominate, but rectangular and rhombic cases are also possible and arise according to well-defined rules, here partially recounted