9,483 research outputs found
Effect of grain shape on the agglomeration of polycrystalline thin films
Grain-boundary grooving is a general phenomenon occurring in all
polycrystalline materials at the intersection between the grain-boundary and
the interface or free surface. It has been studied theoretically for some time.
Grain-boundary grooving in the context of faceted interfaces in particular has
attracted some attention. However, these works did not consider the case of
thin films and the consequences on agglomeration of the shape of the interface.
In this Letter, we compare the agglomeration of thin films with rounded and
faceted interfaces. The shape of the grains can dramatically affect the
agglomeration of polycrystalline thin films by grain-boundary grooving.
Anisotropy plays a central role in the stability against agglomeration of
faceted films. Even a small difference between the interface energies of the
facets can destabilize faceted grains or, on the contrary, it can make them
perfectly stable at any thickness. keywords: grain-boundary grooving, dihedral
angle, faceting, energy, silicide, theory, model.Comment: 3 pages, 3 figure
Phase field simulations of coupled phase transformations in ferroelastic-ferroelastic nanocomposites
We use phase field simulations to study composites made of two different
ferroelastics (e.g., two types of martensite). The deformation of one material
due to a phase transformation can elastically affect the other constituent and
induce it to transform as well. We show that the phase transformation can then
occur above its normal critical temperature and even higher above this
temperature in nanocomposites than in bulk composites. Microstructures depend
on temperature, on the thickness of the layers, and on the crystal structure of
the two constituents -- certain nanocomposites exhibit a great diversity of
microstructures not found in bulk composites. Also, the periodicity of the
martensite twins may vary over 1 order of magnitude based on geometry.
keywords: Ginzburg-Landau, martensitic transformation, multi-ferroics,
nanostructure, shape-memory alloyComment: 8 pages, 15 figure
GreenPhylDB: A Gene Family Database for plant functional Genomics
With the increasing number of genomes being sequenced, a major objective is to transfer accurate annotation from characterised proteins to uncharacterised sequences. Consequently, comparative genomics has become a usual and efficient strategy in functional genomics. The release of various annotated genomes of plants, such as _O. sativa_ and _A. thaliana_, has allowed setting up comprehensive lists of gene families defined by automated methods. However, like for gene sequence, manual curation of gene families is an important requirement that has to be undertaken. GreenPhylDB comprises protein sequences of 12 plant species fully sequenced that were grouped into homeomorphic families using similarity-based methods. Clusters are finally processed by phylogenetic analysis to infer orthologs and paralogs that will be particularly helpful to study genome evolution. Previously, each cluster has to be curated (i.e. properly named and classified) using different sources of information. A web interface for plant gene families’ curation was developed for that purpose. This interface, accessible on GreenPhylDB ("http://greenphyl.cirad.fr":http://greenphyl.cirad.fr), centralizes external references (e.g. InterPro, KEGG, Swiss-Prot, PIRSF, Pubmed) related to all gene members of the clusters and shows statistics and automatic analysis. We believe that this synthetic view of data available for a gene cluster, combined with basic guidelines, is an efficient way to provide reliable method for gene family annotations
Non-monotonic density dependence of the diffusion of DNA fragments in low-salt suspensions
The high linear charge density of 20-base-pair oligomers of DNA is shown to
lead to a striking non-monotonic dependence of the long-time self-diffusion on
the concentration of the DNA in low-salt conditions. This generic non-monotonic
behavior results from both the strong coupling between the electrostatic and
solvent-mediated hydrodynamic interactions, and from the renormalization of
these electrostatic interactions at large separations, and specifically from
the dominance of the far-field hydrodynamic interactions caused by the strong
repulsion between the DNA fragments.Comment: 4 pages, 2 figures. Physical Review E, accepted on November 24, 200
A Collection of Problems on Spectrally Bounded Operators
We discuss several open problems on spectrally bounded operators, some new,
some old, adding in a few new insights.Comment: 15 pages,; submitte
Low-rate coding using incremental redundancy for GLDPC codes
In this paper we propose a low-rate coding method, suited for application-layer forward error correction. Depending on channel conditions, the coding scheme we propose can switch from a fixed-rate LDPC code to various low-rate GLDPC codes. The source symbols are first encoded by using a staircase or triangular LDPC code. If additional symbols are needed, the encoder is then switched to the GLDPC mode and extra-repair symbols are produced, on demand. In order to ensure small overheads, we consider irregular distributions of extra-repair symbols optimized by density evolution techniques. We also show that increasing the number of extra-repair symbols improves the successful decoding probability, which becomes very close to 1 for sufficiently many extra-repair symbols
Quenched invariance principle for random walks in balanced random environment
We consider random walks in a balanced random environment in ,
. We first prove an invariance principle (for ) and the
transience of the random walks when (recurrence when ) in an
ergodic environment which is not uniformly elliptic but satisfies certain
moment condition. Then, using percolation arguments, we show that under mere
ellipticity, the above results hold for random walks in i.i.d. balanced
environments.Comment: Published online in Probab. Theory Relat. Fields, 05 Oct 2010. Typo
(in journal version) corrected in (26
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