Angular Momentum and Energy-Momentum Densities as Gauge Currents

If we replace the general spacetime group of diffeomorphisms by transformations taking place in the tangent space, general relativity can be interpreted as a gauge theory, and in particular as a gauge theory for the Lorentz group. In this context, it is shown that the angular momentum and the energy-momentum tensors of a general matter field can be obtained from the invariance of the corresponding action integral under transformations taking place, not in spacetime, but in the tangent space, in which case they can be considered as gauge currents.Comment: RevTeX4, 7 pages, no figures. Presentation changes; version to appear in Phys. Rev.

Analysis of decomposition parameters of green manure in the Brazilian Northeast with Association Rules Networks.

Modern agricultural processes are increasingly looking at the use of chemicals, so the constant search for organic alternatives to fertilization becomes frequent. The use of data mining using association rule networks (ARN) can aid in the analysis of the parameters involved in choosing which plant to use as green manure. In this work, an analysis of the parameters of green manures used in the Brazilian Northeast is presented, demonstrating the applicability of the computational technique as well as its use to gain in productivity

Higher lattices, discrete two-dimensional holonomy and topological phases in (3+1)D with higher gauge symmetry

Higher gauge theory is a higher order version of gauge theory that makes possible the definition of 2-dimensional holonomy along surfaces embedded in a manifold where a gauge 2-connection is present. In this paper, we study Hamiltonian models for discrete higher gauge theory on a lattice decomposition of a manifold. We show that a construction for higher lattice gauge theory is well-defined, including in particular a Hamiltonian for topological phases of matter in 3+1 dimensions. Our construction builds upon the Kitaev quantum double model, replacing the finite gauge connection with a finite gauge 2-group 2-connection. Our Hamiltonian higher lattice gauge theory model is defined on spatial manifolds of arbitrary dimension presented by slightly combinatorialized CW-decompositions (2-lattice decompositions), whose 1-cells and 2-cells carry discrete 1-dimensional and 2-dimensional holonomy data. We prove that the ground-state degeneracy of Hamiltonian higher lattice gauge theory is a topological invariant of manifolds, coinciding with the number of homotopy classes of maps from the manifold to the classifying space of the underlying gauge 2-group. The operators of our Hamiltonian model are closely related to discrete 2-dimensional holonomy operators for discretized 2-connections on manifolds with a 2-lattice decomposition. We therefore address the definition of discrete 2-dimensional holonomy for surfaces embedded in 2-lattices. Several results concerning the well-definedness of discrete 2-dimensional holonomy, and its construction in a combinatorial and algebraic topological setting are presented

Ciência na Ponta dos Dedos: Scientific Activities for Children under 10

In the context of the “Projeto” of the 3rd year of “Licenciatura em Biologia Aplicada” it was proposed to develop experimental activities connected with science for 1st to 4th grade students. This initiative was named Ciência na Ponta dos Dedos and was presented in the scope of “Festa da Ciência 2014”, an event of the Escola de Ciências of Universidade do Minho, which happens every year during May (and lasted this year from 12th to 14th of May). The first edition of Ciência na Ponta dos Dedos was offered to 1st grade students (6-7 years old). A mini laboratory where children could see, try and participate in scientific hands-on activities was created for the initiative. The experimental activities were designed and settled in accordance with curricular guidelines, age [1,2,3] and in the scope of the theme “water source of life” through the development of six different activities where the children, organized in groups, had the opportunity to explore aspects connected with the (i) reaction of an acid with sodium bicarbonate in water, (ii) dissolution of different substances in water,(iii) permeability of different soils, (iv) water cycle through the observation of a mini ecosystem, (v) observation on the microscope of the stoma of the plants and (vi) the colouring of carnations by capillarity using several dyes. These activities were carried out in such an environment that kids’ eyes had light up as brightly when doing the science lab activities Children could feel free to express their ideas and participate in the activities to build applicable knowledge in the context of experimental science. This kind of learning comes easier to children if they can touch and make the experiments by themselves, though with a proper supervision, allowing the children to think and to learn that “if I do this, that will happen“, so “in order that to happen, I will have to make this” [2]. In the sequence of these experimental activities, children were asked to fill in an inquiry, previously prepared in order to know their opinion about the activities they performed, including their favourite ones. This survey will also provide some new ideas to improve future similar events.The present communication intends to present the project and its success near the children and their teachers, as well as to highlight the importance of scientific knowledge. Quoting some children: “the activities were very funny and I learned new things”, “I learned why oil does not mix with water” and “I learned that the noses of the plants are in their leaves”. In a developing society it is more and more important that the education system makes science stand out from the early years of school in order to form citizens able to deal efficiently with the challenges and the necessities of the current society [2].info:eu-repo/semantics/publishedVersio

The Lippmann–Schwinger Formula and One Dimensional Models with Dirac Delta Interactions

We show how a proper use of the Lippmann–Schwinger equation simplifies the calculations to obtain scattering states for one dimensional systems perturbed by N Dirac delta equations. Here, we consider two situations. In the former, attractive Dirac deltas perturbed the free one dimensional Schrödinger Hamiltonian. We obtain explicit expressions for scattering and Gamow states. For completeness, we show that the method to obtain bound states use comparable formulas, although not based on the Lippmann–Schwinger equation. Then, the attractive N deltas perturbed the one dimensional Salpeter equation. We also obtain explicit expressions for the scattering wave functions. Here, we need regularisation techniques that we implement via heat kernel regularisation

Luta contra o oídio da videira. Eficácia relativa de um fungicida sistémico e um enxofre molhável simples ou misturado com ureia

Apresentam-se os resultados de dois ensaios de campo de luta contra o oídio da videira, Oidium tuckeri Berk. Comparam-se: um fungicida sistémico, o triadimefão, em quatro modalidades diferentes, um enxofre molhável e a mistura deste com ureia a 1/200. Os ensaios foram estabelecidos em blocos casualizados com quatro repetições. Nos dois anos consecutivos, eu mesma repetição localizou-se sempre na mesma parcela. Avaliou-se o efeito dos produtos pela determinação da eficácia nos cachos e completou-se com a notação do peso médio dos bagos, teor de açúcar do mosto e evolução da queda das folhas no Outono. O triadimefão assegurou uma protecção absoluta, nos moldes de avaliação usados, nas modalidades A, B e C e permitiu um ligeiro ataque (médias de 0,5 e 1 % para cada ano) na modalidade D, onde se fizeram apenas quatro tratamentos. O enxofre molhável quer simples (10 kg/ha — modalidade E) quer misturado com ureia (5 kg+20 g/ha— modalidade F) manteve sempre o nível de ataque inferior a 26 %, salvo num caso, que parece devido a um foco primário surgido antes do início dos tratamentos. Exceptuando o mesmo caso, não houve diminuição significativa na eficácia quando se reduziu a quantidade de enxofre para metade e se lhe juntou ureia a 1/200. A queda das folhas, no Outono, foi retardada por um período maior em relação à testemunha, nas modalidades tratadas com enxofre (E e F), apesar da menor eficácia deste fungicida, provavelmente devido ao seu maior efeito residual ou a modificações fisiológicas e de estrutura dos tecidos provocadas pelos produtosinfo:eu-repo/semantics/publishedVersio

Torsion and the Gravitational Interaction

By using a nonholonomous-frame formulation of the general covariance principle, seen as an active version of the strong equivalence principle, an analysis of the gravitational coupling prescription in the presence of curvature and torsion is made. The coupling prescription implied by this principle is found to be always equivalent with that of general relativity, a result that reinforces the completeness of this theory, as well as the teleparallel point of view according to which torsion does not represent additional degrees of freedom for gravity, but simply an alternative way of representing the gravitational field.Comment: Version 2: minor presentation changes, a reference added, 11 pages (IOP style

IFNγ and iNOS-mediated alterations in the bone marrow and thymus and its impact on Mycobacterium avium-induced thymic atrophy [preprint]

Disseminated infection with the high virulence strain of Mycobacterium avium 25291 lead to progressive thymic atrophy. We previously uncovered that M. avium-induced thymic atrophy is due to increased levels of glucocorticoids synergizing with nitric oxide (NO) produced by interferon gamma (IFNγ) activated macrophages. Where and how these mediators are playing, was yet to be understood. We hypothesized that IFNγ and NO might be affecting bone marrow (BM) T cell precursors and/or T cell differentiation in the thymus. We show that M. avium infection causes a reduction on the percentage of lymphoid-primed multipotent progenitors (LMPP) and common lymphoid progenitors (CLP). Additionally, BM precursors from infected mice are unable to reconstitute thymi of RAGKO mice in an IFNγ-dependent way. Thymi from infected mice presents a NO-dependent inflammation. When transplanted under the kidney capsule of non-infected mice, thymic stroma from infected mice is unable to sustain T cell differentiation. Finally, we observed increased thymocyte death via apoptosis after infection, independent of both IFNγ and iNOS, and a decrease on activated caspase-3 positive thymocytes, that was not observed in the absence of iNOS expression. Together our data suggests that M. avium-induced thymic atrophy results from a combination of impairments, mediated by IFNγ and NO, affecting different steps of T cell differentiation from T cell precursor cells in the BM to the thymic stroma and thymocytes