The saturation of decaying counterflow turbulence in helium II

We are concerned with the problem of the decay of a tangle of quantized vortices in He II generated by a heat current. Direct application of Vinen's equation yields the temporal scaling of vortex line density $L \sim t^{-1}$. Schwarz and Rozen [Phys. Rev. Lett. {\bf 66}, 1898 (1991); Phys. Rev. B {\bf 44}, 7563 (1991)] observed a faster decay followed by a slower decay. More recently, Skrbek and collaborators [Phys. Rev. E {\bf 67}, 047302 (2003)] found an initial transient followed by the same classical $t^{-3/2}$ scaling observed in the decay of grid-generated turbulence. We present a simple theoretical model which, we argue, contains the essential physical ingredients, and accounts for these apparently contradictory results.Comment: 19 pages, 5 figure

Localization of Electronic States in Chain Model Based on Real DNA Sequence

We investigate the localization property of an electron in the disordered two-chain system (ladder model) with long-range correlation as a simple model for electronic property in DNA sequence. The chains are constructed by repetition of the sugar-phosphate sites, and the inter-chain hopping at the sugar sites come from nucleotide pairs, i.e., $A-T$ or $G-C$ pairs. It has been found that some DNA sequences have long-range correlation. In this paper we use some actual DNA sequences such as bacteriophages of escherichia coli, human omosome 22 and histone protein as the correlated sequence for the interchain hopping at the sugar sites. We will present some numerical results for the Lyapunov exponent (inverse localization length) of the wave function in the cases in comparison to the results for artificial sequence generated by an asymmetric modified Bernoulli map. It is shown that the correlation and asymmetry of the sequence affect on the localization in both the artificial and real DNA sequences.Comment: 12 pages, 4 figure

Electrons in Dry DNA from Density Functional Calculations

The electronic structure of an infinite poly-guanine - poly-cytosine DNA molecule in its dry A-helix structure is studied by means of density-functional calculations. An extensive study of 30 nucleic base pairs is performed to validate the method. The electronic energy bands of DNA close to the Fermi level are then analyzed in order to clarify the electron transport properties in this particularly simple DNA realization, probably the best suited candidate for conduction. The energy scale found for the relevant band widths, as compared with the energy fluctuations of vibrational or genetic-sequence origin, makes highly implausible the coherent transport of electrons in this system. The possibility of diffusive transport with sub-nanometer mean free paths is, however, still open. Information for model Hamiltonians for conduction is provided.Comment: 8 pages, 4 figure

Quasiparticle band structure of infinite hydrogen fluoride and hydrogen chloride chains

We study the quasiparticle band structure of isolated, infinite HF and HCl bent (zigzag) chains and examine the effect of the crystal field on the energy levels of the constituent monomers. The chains are one of the simplest but realistic models of the corresponding three-dimensional crystalline solids. To describe the isolated monomers and the chains, we set out from the Hartree-Fock approximation, harnessing the advanced Green's function methods "local molecular orbital algebraic diagrammatic construction" (ADC) scheme and "local crystal orbital ADC" (CO-ADC) in a strict second order approximation, ADC(2,2) and CO-ADC(2,2), respectively, to account for electron correlations. The configuration space of the periodic correlation calculations is found to converge rapidly only requiring nearest-neighbor contributions to be regarded. Although electron correlations cause a pronounced shift of the quasiparticle band structure of the chains with respect to the Hartree-Fock result, the bandwidth essentially remains unaltered in contrast to, e.g., covalently bound compounds.Comment: 11 pages, 6 figures, 6 tables, RevTeX4, corrected typoe

Ab initio Green's function formalism for band structures

Using the Green's function formalism, an ab initio theory for band structures of crystals is derived starting from the Hartree-Fock approximation. It is based on the algebraic diagrammatic construction scheme for the self-energy which is formulated for crystal orbitals (CO-ADC). In this approach, the poles of the Green's function are determined by solving a suitable Hermitian eigenvalue problem. The method is not only applicable to the outer valence and conduction bands, it is also stable for inner valence bands where strong electron correlations are effective. The key to the proposed scheme is to evaluate the self-energy in terms of Wannier orbitals before transforming it to a crystal momentum representation. Exploiting the fact that electron correlations are mainly local, one can truncate the lattice summations by an appropriate configuration selection scheme. This yields a flat configuration space; i.e., its size scales only linearly with the number of atoms per unit cell for large systems and, under certain conditions, the computational effort to determine band structures also scales linearly. As a first application of the new formalism, a lithium fluoride crystal has been chosen. A minimal basis set description is studied, and a satisfactory agreement with previous theoretical and experimental results for the fundamental band gap and the width of the F 2p valence band complex is obtained.Comment: 20 pages, 3 figures, 1 table, RevTeX4, new section on lithium fluorid

Estudo de viabilidade econômica de uma empresa de reciclagem de plásticos de origem industrial

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Ambiental.Estudo de viabilidade econômica para a montagem de uma empresa de reciclagem de resíduos plásticos industriais, enfocando os plásticos de engenharia, caracterizados pelo alto valor agregado. A pesquisa preliminar quantificou e qualificou os resíduos plásticos industriais do Estado de Santa Catarina e posteriormente fez-se referência aos de plásticos de engenharia. Os resultados da recicladora são apresentados através dos indicadores de resultados, como lucratividade, rentabilidade, ponto de equilíbrio e prazo de retorno do investimento. É calculada também a melhor localização desta empresa segundo as empresas fornecedoras de refugos e os potenciais clientes. Torna-se importante salientar as principais barreiras a este mercado, que é crescente mais ainda pouco incentivado nos âmbitos político, econômico e tributário

Tecnologias Produtivas, Design e Pesquisa Participativa - Estudo de Caso do Artesanato de Cipó Imbé em Garuva, SC: Dados e Indicadores de Produção

Garuva, município da região Nordeste de Santa Catarina, tem como uma das principais atividades econômicas locais o artesanato em fibras naturais. Entre as fibras mais utilizadas na região, destaca-se o cipó imbé, que é extraído da Mata Atlântica e seu artesanato é comercializado por intermediários em diversos estados do Brasil. Em pesquisas realizadas no município, através de instituições como a Universidade do Estado de Santa Catarina – UDESC e a Empresa de Pesquisa Agropecuária e Extensão Rural S.A. – EPAGRI, foram identificadas e diagnosticadas diversas demandas relacionadas à cadeia produtiva do artesanato, principalmente nas etapas de extração, beneficiamento e projeto de produtos e comercialização. Neste sentido a presente pesquisa tem como tema central a investigação sobre o desenvolvimento participativo de novas tecnologias sociais de produção nas comunidades de Palmital e Mina Velha, ambas em Garuva. Pretende-se assim, avaliar o processo metodológico participativo das ações de design de novas tecnologias. Neste breve relato, são apresentadas as análises de dados obtidos mediante o acompanhamento de produção artesanal e seu cruzamento com os dados coletados no pré-cadastramento realizado no município. Alguns aspectos ambientais e indicadores econômicos ficam evidentes, como a produção média mensal por artesão, sua renda com essa produção e a caracterização dos resíduos gerados na localidade. Tais dados mostram-se fundamentais no estabelecimento de estratégias metodológicas para a solução dos problemas