1,065 research outputs found
Self-similar solutions to the mean curvature flow in
In this paper we make an analysis of self-similar solutions for the mean
curvature flow (MCF) by surfaces of revolution and ruled surfaces in
. We prove that self-similar solutions of the MCF by
non-cylindrival surfaces and conical surfaces in are trivial.
Moreover, we characterize the self-similar solutions of the MCF by surfaces of
revolutions under a homothetic helicoidal motion in in terms
of the curvature of the generating curve. Finally, we characterize the
self-similar solutions for the MCF by cylindrical surfaces under a homothetic
helicoidal motion in . Explicit families of exact solutions for
the MCF by cylindrical surfaces in are also given
Fixed Points of the Dissipative Hofstadter Model
The phase diagram of a dissipative particle in a periodic potential and a
magnetic field is studied in the weak barrier limit and in the tight-biding
regime. For the case of half flux per plaquette, and for a wide range of values
of the dissipation, the physics of the model is determined by a non trivial
fixed point. A combination of exact and variational results is used to
characterize this fixed point. Finally, it is also argued that there is an
intermediate energy scale that separates the weak coupling physics from the
tight-binding solution.Comment: 4 pages 3 figure
Programming phenomenology: proof of concept on adaptivity
Phenomenology is the empirical study of mind and consciousness. Considering programming activity as a cognitive procedure, phenomenology may be applied to address some of its issues. A particular issue of interest is how one programming approach differs from others, i.e. the cognition performed when using an approach differs from the one performed using another? If they are similar the two approaches are like to be the same, otherwise essentially different. Since adaptive computing proposal is Turing-equivalent it may be discussed about the actual differences among those approaches. As an example, λ-calculus is also Turing-equivalent but since the cognition performed is different it justifies the several λ-based existing approaches. In order to accomplish such analysis, bergsonism will be used as phenomenological method to be applied in particular adaptive structure called adaptive-graph. As a result it will be argued cognition performed using adaptive-graph is different from the one performed when using non-adaptive one. Then it will generalized suggesting adaptive computing cognition shall be further explored.This paper has been supported by COMPETE: POCI-01-0145-FEDER-0070 43 and FCT Fundac ̧ ̃ao para a Ciˆencia e Tecnologia - Project UID/CEC/00319/2013
Resilient Quantum Computation in Correlated Environments: A Quantum Phase Transition Perspective
We analyze the problem of a quantum computer in a correlated environment
protected from decoherence by QEC using a perturbative renormalization group
approach. The scaling equation obtained reflects the competition between the
dimension of the computer and the scaling dimension of the correlations. For an
irrelevant flow, the error probability is reduced to a stochastic form for long
time and/or large number of qubits; thus, the traditional derivation of the
threshold theorem holds for these error models. In this way, the ``threshold
theorem'' of quantum computing is rephrased as a dimensional criterion.Comment: 4.1 pages, minor correction and an improved discussion of Eqs. (4)
and (14
Properties of magnetic nanodots with perpendicular anisotropy
Nanodots with magnetic vortices have many potential applications, such as
magnetic memories (VRAMs) and spin transfer nano-oscillators (STNOs). Adding a
perpendicular anisotropy term to the magnetic energy of the nanodot it becomes
possible to tune the vortex core properties. This can be obtained, e.g., in Co
nanodots by varying the thickness of the Co layer in a Co/Pt stack. Here we
discuss the spin configuration of circular and elliptical nanodots for
different perpendicular anisotropies; we show for nanodisks that micromagnetic
simulations and analytical results agree. Increasing the perpendicular
anisotropy, the vortex core radii increase, the phase diagrams are modified and
new configurations appear; the knowledge of these phase diagrams is relevant
for the choice of optimum nanodot dimensions for applications. MFM measurements
on Co/Pt multilayers confirm the trend of the vortex core diameters with
varying Co layer thicknesses.Comment: 7 pages, 8 figure
Adubação fosfatada em algumas culturas nos Estados de Minas Gerais, Espírito Santo e Rio de Janeiro.
Diversidade de fungos micorrízicos arbusculares em áreas revegetadas após a mineração de bauxita.
A contribuição da diversidade dos FMAs para manutenção da diversidade e funcionalidade de ecossistemas naturais tem sido pouco estudada. Neste trabalho objetivou-se avaliar a diversidade de FMAs em áreas revegetadas em diferentes momentos. Com base na morfologia de esporos 13 espécies distintas foram encontradas, com predomínio de espécies dos gêneros Glomus e Acaulospora. Glomus macrocarpum foi a espécies mais freqüente e abundante e as parcelas das áreas revegetadas nos anos de 1985A1, 1998A1, 2002-1, 2002A1, 2004FP e 2006-1 apresentaram os maiores valores do índice de diversidade Shannon. Não foi observada relação entre o tempo de revegtação e a diversidade de FMAs
Implementation of Micromundo@UPorto: an educacional project based on service-learning promoting antimicrobial resistance awareness among university and school students
Atypical Non-H2S-Producing Monophasic Salmonella Typhimurium ST3478 Strains from Chicken Meat at Processing Stage Are Adapted to Diverse Stresses
Poultry products are still an important cause of Salmonella infections worldwide, with an increasingly reported expansion of less-frequent serotypes or atypical strains that are frequently multidrug-resistant. Nevertheless, the ability of Salmonella to survive antimicrobials promoted in the context of antibiotic reducing/replacing and farming rethinking (e.g., organic acids and copper in feed/biocides) has been scarcely explored. We investigated Salmonella occurrence (conventional and molecular assays) among chicken meat at the processing stage (n = 53 batches/29 farms) and characterized their tolerance to diverse stress factors (antibiotics, copper, acid pH, and peracetic acid). Whole-genome sequencing was used to assess adaptive features and to perform comparative analysis. We found a low Salmonella occurrence (4%) and identified S. Enteritidis/ST11 plus atypical non-H2S-producing S. 1,4,[5],12:i:-/ST3478. The ST3478 presented the ability to grow under diverse stresses (antibiotics, copper, and acid-pH). Comparative genomics among ST3478 isolates showed similar antibiotic/metal resistance gene repertoires and identical nonsense phsA thiosulfate reductase mutations (related to H2S-negative phenotype), besides their close phylogenetic relationship by cgMLST and SNPs. This study alerts for the ongoing national and international spread of an emerging monophasic Salmonella Typhimurium clonal lineage with an enlarged ability to survive to antimicrobials/biocides commonly used in poultry production, being unnoticed by conventional Salmonella detection approaches due to an atypical non-H2S-producing phenotype
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