52 research outputs found
Immersed nano-sized Al dispersoids in an Al matrix; effects on the structural and mechanical properties by Molecular Dynamics simulations
We used molecular dynamics simulations based on a potential model in analogy
to the Tight Binding scheme in the Second Moment Approximation to simulate the
effects of aluminum icosahedral grains (dispersoids) on the structure and the
mechanical properties of an aluminum matrix. First we validated our model by
calculating several thermodynamic properties referring to the bulk Al case and
we found good agreement with available experimental and theoretical data.
Afterwards, we simulated Al systems containing Al clusters of various sizes. We
found that the structure of the Al matrix is affected by the presence of the
dispersoids resulting in well ordered domains of different symmetries that were
identified using suitable Voronoi analysis. In addition, we found that the
increase of the grain size has negative effect on the mechanical properties of
the nanocomposite as manifested by the lowering of the calculated bulk moduli.
The obtained results are in line with available experimental data.Comment: 15 pages, 8 figures. Submitted to J. Phys: Condens. Matte
Ising models with long-range dipolar and short-range ferromagnetic interactions
We study the ground state of a --dimensional Ising model with both long
range (dipole--like) and nearest neighbor ferromagnetic (FM) interactions. The
long range interaction is equal to , , while the FM interaction
has strength . If and is large enough the ground state is FM,
while if the FM state is not the ground state for any choice of
. In we show that for any the ground state has a series of
transitions from an antiferromagnetic state of period 2 to --periodic
states of blocks of sizes with alternating sign, the size growing when
the FM interaction strength is increased (a generalization of this result
to the case is also discussed). In we prove, for , that the dominant asymptotic behavior of the ground state energy agrees
for large with that obtained from a periodic striped state conjectured to
be the true ground state. The geometry of contours in the ground state is
discussed.Comment: 16 pages; references added, minor changes in the introduction and one
remark added after theorem 3. Final version, to appear in Phys. Rev.
Energy Landscape and Global Optimization for a Frustrated Model Protein
The three-color (BLN) 69-residue model protein was designed to exhibit frustrated folding. We investigate the energy landscape of this protein using disconnectivity graphs and compare it to a Go model, which is designed to reduce the frustration by removing all non-native attractive interactions. Finding the global minimum on a frustrated energy landscape is a good test of global optimization techniques, and we present calculations evaluating the performance of basin-hopping and genetic algorithms for this system.Comparisons are made with the widely studied 46-residue BLN protein.We show that the energy landscape of the 69-residue BLN protein contains several deep funnels, each of which corresponds to a different β-barrel structure
Salmonella-Induced Mucosal Lectin RegIIIβ Kills Competing Gut Microbiota
Intestinal inflammation induces alterations of the gut microbiota and promotes overgrowth of the enteric pathogen Salmonella enterica by largely unknown mechanisms. Here, we identified a host factor involved in this process. Specifically, the C-type lectin RegIIIβ is strongly upregulated during mucosal infection and released into the gut lumen. In vitro, RegIIIβ kills diverse commensal gut bacteria but not Salmonella enterica subspecies I serovar Typhimurium (S. Typhimurium). Protection of the pathogen was attributable to its specific cell envelope structure. Co-infection experiments with an avirulent S. Typhimurium mutant and a RegIIIβ-sensitive commensal E. coli strain demonstrated that feeding of RegIIIβ was sufficient for suppressing commensals in the absence of all other changes inflicted by mucosal disease. These data suggest that RegIIIβ production by the host can promote S. Typhimurium infection by eliminating inhibitory gut microbiota
Safe-and-sustainable-by-design chemicals and advanced materials: a paradigm shift towards prevention-based risk governance is needed
Identification and evaluation of the immunogenic tissue antigens TTR and S100A9 in primary brain tumors by automated two-dimensional protein fractionation
Activated carbons from waste biomass and low rank coals as catalyst supports for hydrogen production by methanol decomposition
Activated carbons with different textural and chemical surface characteristics were synthesized from waste biomass and low rank coals, and furthermore used as a host matrix for cobalt species, varying the preparation and modification methods. The obtained activated carbons and modified samples were characterized by complex of various physicochemical methods, such as: low temperature physisorption of nitrogen, XRD, EPR, XPS, UV–Vis and TPR with hydrogen. Boehm method was applied for qualitative and quantitative determination of oxygen-containing groups on the carbon surface before and after cobalt deposition. The catalytic properties of cobalt modifications were tested in methanol decomposition. The dominant effect of activated carbon texture over the surface chemistry on the state and catalytic behavior of cobalt species was discussed.Financial support from Bulgarian Academy of Sciences and Bulgarian Ministry of Education (Projects DFNI-Е01/7/2012 and DFNI-E02/2/2014) is gratefully acknowledged.Peer reviewe
THE RELATIONSHIP BETWEEN TOLERANCE OF AMBIGUITY AND CREATIVITY IN ARCHITECTURAL DESIGN STUDIO
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