1,538 research outputs found
Multifractal analysis of electronic states on random Voronoi-Delaunay lattices
We consider the transport of non-interacting electrons on two- and
three-dimensional random Voronoi-Delaunay lattices. It was recently shown that
these topologically disordered lattices feature strong disorder
anticorrelations between the coordination numbers that qualitatively change the
properties of continuous and first-order phase transitions. To determine
whether or not these unusual features also influence Anderson localization, we
study the electronic wave functions by multifractal analysis and finite-size
scaling. We observe only localized states for all energies in the
two-dimensional system. In three dimensions, we find two Anderson transitions
between localized and extended states very close to the band edges. The
critical exponent of the localization length is about 1.6. All these results
agree with the usual orthogonal universality class. Additional generic
energetic randomness introduced via random potentials does not lead to
qualitative changes but allows us to obtain a phase diagram by varying the
strength of these potentials
Vision-Based Localization Algorithm Based on Landmark Matching, Triangulation, Reconstruction, and Comparison
Many generic position-estimation algorithms are vulnerable to ambiguity introduced by nonunique landmarks. Also, the available high-dimensional image data is not fully used when these techniques are extended to vision-based localization. This paper presents the landmark matching, triangulation, reconstruction, and comparison (LTRC) global localization algorithm, which is reasonably immune to ambiguous landmark matches. It extracts natural landmarks for the (rough) matching stage before generating the list of possible position estimates through triangulation. Reconstruction and comparison then rank the possible estimates. The LTRC algorithm has been implemented using an interpreted language, onto a robot equipped with a panoramic vision system. Empirical data shows remarkable improvement in accuracy when compared with the established random sample consensus method. LTRC is also robust against inaccurate map data
Developing Algorithms for Quantifying the Super Resolution Microscopic Data: Applications to the Quantification of Protein-Reorganization in Bacteria Responding to Treatment by Silver Ions
Histone-like nucleoid structuring proteins (HNS) play significant roles in shaping the chromosomal DNA, regulation of transcriptional networks in microbes, as well as bacterial responses to environmental changes such as temperature fluctuations. In this work, the intracellular organization of HNS proteins in E. coli bacteria was investigated utilizing super-resolution fluorescence microscopy, which surpasses conventional microscopy by 10–20 fold in spatial resolution. More importantly, the changes of the spatial distribution of HNS proteins in E. coli, by addition of silver ions into the growth medium were explored. To quantify the spatial distribution of HNS in bacteria and its changes, an automatic method based on Voronoi diagram was implemented. The HNS proteins localized in super-resolution fluorescence microscopy were segmented and clustered based on several quantitative parameters, such as molecular areas, molecular densities, and mean inter-molecular distances of the k-th rank, all of which were computed from the Voronoi diagrams. These parameters, as well as the associated clustering analysis, allowed us to quantify how the spatial organization of HNS proteins responds to silver, and provided insight into understanding how microbes adapt to new environments
Relativistic-dft study of the electronic structure, bonding and energetic of the [ref8]־ and [uf8]2- ions
Indexación: ScieloABSTRACT
In this study we evaluated the importance of the relativistic effects (scalar and spin-orbit) on the description of the electronic structure, bonding and the energetic of the [ReF8]- and [UF8]2- ions. We described the bonding interaction between ligands and metal center using the energy decomposition analysis (EDA) proposed by Morokuma and Ziegler, in which it can be appreciated a strong ionic behavior for both ions since the electrostatic interaction energy (∆Ezlestat) is greater than the orbitalic interaction energy (∆EOrb). Furthermore, a qualitative analysis using the mapping of the electrostatic potential over the total electronic density evidence an increase of the ionic character, as well as, the polarization of the electronic density as U > Re. The electron localization function (ELF) corroborates the bonding analysis because of the lack of di-synaptic basins on the metal-ligand bonding region
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Multicolor 3D-dSTORM Reveals Native-State Ultrastructure of Polysaccharides' Network during Plant Cell Wall Assembly.
The plant cell wall, a form of the extracellular matrix, is a complex and dynamic network of polymers mediating a plethora of physiological functions. How polysaccharides assemble into a coherent and heterogeneous matrix remains mostly undefined. Further progress requires improved molecular-level visualization methods that would gain a deeper understanding of the cell wall nanoarchitecture. dSTORM, a type of super-resolution microscopy, permits quantitative nanoimaging of the cell wall. However, due to the lack of single-cell model systems and the requirement of tissue-level imaging, its use in plant science is almost absent. Here we overcome these limitations; we compare two methods to achieve three-dimensional dSTORM and identify optimal photoswitching dyes for tissue-level multicolor nanoscopy. Combining dSTORM with spatial statistics, we reveal and characterize the ultrastructure of three major polysaccharides, callose, mannan, and cellulose, in the plant cell wall precursor and provide evidence for cellulose structural re-organization related to callose content
RELATIVISTIC-DFT STUDY OF THE ELECTRONIC STRUCTURE, BONDING AND ENERGETIC OF THE [ReF8]־ AND [UF8]2- IONS
Indexación: Web of Science; Scielo.In this study we evaluated the importance of the relativistic effects (scalar and spin-orbit) on the description of the electronic structure, bonding and the energetic of the [ReF8]- and [UF8]2- ions. We described the bonding interaction between ligands and metal center using the energy decomposition analysis (EDA) proposed by Morokuma and Ziegler, in which it can be appreciated a strong ionic behavior for both ions since the electrostatic interaction energy (∆Ezlestat) is greater than the orbitalic interaction energy (∆EOrb). Furthermore, a qualitative analysis using the mapping of the electrostatic potential over the total electronic density evidence an increase of the ionic character, as well as, the polarization of the electronic density as U > Re. The electron localization function (ELF) corroborates the bonding analysis because of the lack of di-synaptic basins on the metal-ligand bonding region.http://ref.scielo.org/jcbd4
Kibble-Zurek mechanism in curved elastic surface crystals
Topological defects shape the material and transport properties of physical
systems. Examples range from vortex lines in quantum superfluids,
defect-mediated buckling of graphene, and grain boundaries in ferromagnets and
colloidal crystals, to domain structures formed in the early universe. The
Kibble-Zurek (KZ) mechanism describes the topological defect formation in
continuous non-equilibrium phase transitions with a constant finite quench
rate. Universal KZ scaling laws have been verified experimentally and
numerically for second-order transitions in planar Euclidean geometries, but
their validity for discontinuous first-order transitions in curved and
topologically nontrivial systems still poses an open question. Here, we use
recent experimentally confirmed theory to investigate topological defect
formation in curved elastic surface crystals formed by stress-quenching a
bilayer material. Studying both spherical and toroidal crystals, we find that
the defect densities follow KZ-type power laws independent of surface geometry
and topology. Moreover, the nucleation sequences agree with recent experimental
observations for spherical colloidal crystals. These results suggest that KZ
scaling laws hold for a much broader class of dynamical phase transitions than
previously thought, including non-thermal first-order transitions in non-planar
geometries.Comment: 8 pages, 3 figures; introduction and typos correcte
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