2,756 research outputs found
Basal-plane Incommensurate Phases in HCP Structures
An Ising model with competing interaction is used to study the appearance of
incommensurate phases in the basal plane of an hexagonal closed-packed
structure. The calculated mean-field phase diagram reveals various
1q-incommensurate and lock-in phases. The results are applied to explain the
basal-plane incommensurate phase in some compounds of the A'A"BX_4 family, like
K_2MoO_4, K_2WO_4, Rb_2WO4 and to describe the sequence of high-temperature
phase transitions in other compounds of this family.Comment: 8 pages, RevTeX + 4 ps figure
Utilização de carvão e subprodutos da carbonização vegetal na agricultura: aprendendo com as Terras Pretas de Índio.
A Carbonização Vegetal. Físico química da carbonização vegetal. Características e propriedades do carvão e de subprodutos da carbonização vegetal. Carvão. Alcatrão vegetal. Ácido pirolenhoso. A produção de carvão vegetal e subprodutos da carbonização vegetal no Brasil. Potencial produção de fertilizantes e condicionadores de solos a partir de carvão e subprodutos da carbonização vegetal. Síntese de ácidos húmicos a partir de carvão vegetal. Utilização de carvão na produção de fertilizantes orgânicos e substratos. Produção de condicionadores orgânicos. Utilização de fino de carvão como substrato para mudas. Próximos passos para a pesquisa, desenvolvimento e inovação
Experimental observation of fractional topological phases with photonic qudits
Geometrical and topological phases play a fundamental role in quantum theory.
Geometric phases have been proposed as a tool for implementing unitary gates
for quantum computation. A fractional topological phase has been recently
discovered for bipartite systems. The dimension of the Hilbert space determines
the topological phase of entangled qudits under local unitary operations. Here
we investigate fractional topological phases acquired by photonic entangled
qudits. Photon pairs prepared as spatial qudits are operated inside a Sagnac
interferometer and the two-photon interference pattern reveals the topological
phase as fringes shifts when local operations are performed. Dimensions and were tested, showing the expected theoretical values.Comment: 6 pages, 4 figure
The Yang-Baxter equation for PT invariant nineteen vertex models
We study the solutions of the Yang-Baxter equation associated to nineteen
vertex models invariant by the parity-time symmetry from the perspective of
algebraic geometry. We determine the form of the algebraic curves constraining
the respective Boltzmann weights and found that they possess a universal
structure. This allows us to classify the integrable manifolds in four
different families reproducing three known models besides uncovering a novel
nineteen vertex model in a unified way. The introduction of the spectral
parameter on the weights is made via the parameterization of the fundamental
algebraic curve which is a conic. The diagonalization of the transfer matrix of
the new vertex model and its thermodynamic limit properties are discussed. We
point out a connection between the form of the main curve and the nature of the
excitations of the corresponding spin-1 chains.Comment: 43 pages, 6 figures and 5 table
Structural correlations in heterogeneous electron transfer at monolayer and multilayer graphene electrodes
As a new form of carbon, graphene is attracting intense interest as an electrode material with widespread applications. In the present study, the heterogeneous electron transfer (ET) activity of graphene is investigated using scanning electrochemical cell microscopy (SECCM), which allows electrochemical currents to be mapped at high spatial resolution across a surface for correlation with the corresponding structure and properties of the graphene surface. We establish that the rate of heterogeneous ET at graphene increases systematically with the number of graphene layers, and show that the stacking in multilayers also has a subtle influence on ET kinetics. © 2012 American Chemical Society
Avaliação da citopatologia como diagnóstico precoce em melanomas de pele
O artigo não apresenta resumo.
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