2,549 research outputs found
Microscopic Conductivity of Lattice Fermions at Equilibrium - Part I: Non-Interacting Particles
We consider free lattice fermions subjected to a static bounded potential and
a time- and space-dependent electric field. For any bounded convex region
() of space, electric fields
within drive currents. At leading order, uniformly
with respect to the volume of and
the particular choice of the static potential, the dependency on
of the current is linear and described by a conductivity distribution. Because
of the positivity of the heat production, the real part of its Fourier
transform is a positive measure, named here (microscopic) conductivity measure
of , in accordance with Ohm's law in Fourier space. This finite
measure is the Fourier transform of a time-correlation function of current
fluctuations, i.e., the conductivity distribution satisfies Green-Kubo
relations. We additionally show that this measure can also be seen as the
boundary value of the Laplace-Fourier transform of a so-called quantum current
viscosity. The real and imaginary parts of conductivity distributions satisfy
Kramers-Kronig relations. At leading order, uniformly with respect to
parameters, the heat production is the classical work performed by electric
fields on the system in presence of currents. The conductivity measure is
uniformly bounded with respect to parameters of the system and it is never the
trivial measure . Therefore, electric fields generally
produce heat in such systems. In fact, the conductivity measure defines a
quadratic form in the space of Schwartz functions, the Legendre-Fenchel
transform of which describes the resistivity of the system. This leads to
Joule's law, i.e., the heat produced by currents is proportional to the
resistivity and the square of currents
Caracterização genética de bovinos da raça Nelore Variedade Vermelha por meio de marcadores microssatélites1.
Mathematical model of brain tumour with glia-neuron interactions and chemotherapy treatment
Acknowledgements This study was possible by partial financial support from the following Brazilian government agencies: Fundação Araucária, EPSRC-EP/I032606/1 and CNPq, CAPES and Science Without Borders Program Process nos. 17656125, 99999.010583/2013-00 and 245377/2012-3.Peer reviewedPreprin
Synthesis and characterization of copper coatings on polyimide membranes (PIR 003)
The formation of stable metallic/polymeric joints is a huge challenge in the materials
sciences. Adhesion requires interphase that is able to specifically interact with the metallic
phase. The primary amino groups exhibit copolymers as highly reactive to metal surfaces.
This article will give a better understanding of the mechanisms of chemo-absorption by
chemical functionalization of polyimides, as well as in the wet development of
metallization of materials based on H2 reduction in polymers. And it will be evidenced by
comparisons by measures of polymer/metal characterization.Campus Arequip
Efeitos da micorriza e do suprimento de fósforo na atividade enzimática e na resposta de espécies arbóreas ao nitrogênio.
Avaliou-se, em um experimento realizado em vasos com 5 kg de um latossolo, a influencia de micorriza arbuscular e do suprimento de fosforo na micorriza arbuscular e do suprimento de fosforo na resposta da acacia (Acacia mangium (L.), fedegoso (Senna macranthera (Collad.) I & B.), cassia verrugosa (Senna multijuga (L.C.Rich) I.&B.) e angico vermelho (Anadenanthera peregrina (L.) Speg.) a adubacao nitrogenada. Verificou-se que plantas colonizadas por Glomus etunicatum (Becker & Gerdemann), mesmo apresentando menores teores de fosforo na parte aerea, apresentaram maiores respostas em crescimento a adicao de N-mineral ao solo do que quando estas foram adubadas com 360 mg de P kg-1. Para absorcao de N, verificou-se que as plantas micorrizadas apresentaram teores deN ate 2,6 vezes maior devido a aplicacao deste nutriente, enquanto nas plantas com P esta relacao nao ultrapassou 1,5. Isto indica que o efeito da micorriza na resposta da nutricao fosfatica da planta e sim devido a melhor absrocao do N via fungo micorrizico. O conteudo de proteina soluvel na folha e a atividade da GS, Fd-GOGAT e PEPC foram pouco influenciados pelos tratamentos, sendo os valores maximos observados para o fedegoso. Alem de efeitos diretos da nutricao fosfatica, a micorriza se mostrou importante para a nutricao das especies arboreas utilizadas neste estudo
Solidification thermal parameters affecting the columnar-to-equiaxed transition
Experiments were conducted to analyze the columnar-to-equiaxed transition (CET) during the upward unsteady-state directional solidification of Al-Cu and Sn-Pb alloys, under different conditions of superheat and heat-transfer efficiencies at the metal/mold interface. A combined theoretical and experimental approach is developed to quantitatively determine the solidification thermal parameters: transient heat-transfer coefficients, tip growth rates, thermal gradients, and cooling rates. The observed results do not give support to CET criteria based individually either on tip growth rate or temperature gradients ahead of the liquidus isotherm. Rather, the analysis has indicated that a more convenient criterion should encompass both thermal parameters through the tip cooling rate. The columnar growth is expected to prevail throughout the casting for a tip cooling rate higher than a critical value, which depends only on the alloy system and was observed to be about 0.2 K/s for Al-Cu alloys and 0.01 K/s for Sn-Pb alloys in the present investigation.3372107211
Thermofield Dynamics for Twisted Poincare-Invariant Field Theories: Wick Theorem and S-matrix
Poincare invariant quantum field theories can be formulated on
non-commutative planes if the statistics of fields is twisted. This is
equivalent to state that the coproduct on the Poincare group is suitably
twisted. In the present work we present a twisted Poincare invariant quantum
field theory at finite temperature. For that we use the formalism of
Thermofield Dynamics (TFD). This TFD formalism is extend to incorporate
interacting fields. This is a non trivial step, since the separation in
positive and negative frequency terms is no longer valid in TFD. In particular,
we prove the validity of Wick's theorem for twisted scalar quantum field at
finite temperature.Comment: v1: 25 pages, no figure v2: references added; typos corrected; typo
in title correcte
Mineralização do nitrogênio de lodo de esgoto após aplicação no solo.
Resumo: Lodos de esgoto podem ser reciclados em solo agrícola para fornecimento de nutrientes às plantas, principalmente nitrogênio (N), cuja concentração média nesse tipo de resíduo é de 2 a 4%. O presente trabalho teve como objetivo estudar a mineralização do nitrogênio aplicado no solo via doses de lodo de esgoto. O lodo de esgoto foi aplicado na área experimental da Embrapa Meio Ambiente entre os anos de 1999 e 2010, sendo a última aplicação em 2012. Foram testadas doses de lodo para fornecimento de 120, 240, 480 e 960 kg ha-1 de N, além de controle (0N). Tubos de PVC foram inseridos no solo (0 - 20 cm) e posteriormente retirados em duas épocas para quantificação do N inorgânico. No tempo inicial de avaliação os teores de amônio foram superiores aos de nitrato e após 45 dias estes se aproximaram. O amônio aumentou linearmente com a dose de lodo, enquanto o nitrato variou no tempo, com incremento de 407 mg kg-1 de N-NO3- em 45 dias. A taxa de mineralização do N do lodo nesse período foi igual a 92% do total de N aplicado, ou seja, houve disponibilidade excessiva de N em comparação com a demanda pelo milho
Finding a minimal set of SNPs for paternity identification in Nelore cattle.
Cattle breeding programs often demand pedigree information to associate the herdability of genetic markers to animal performance, like milk and beef quality or disease predisposition. Paternity mistakes are a common problem in cattle herds and genetic markers have been used in parentage exclusion tests for resolving pedigree disagreements. The most common markers used in these tests are microsatellites and SNPs (Single Nucleotide Polymorphisms). SNPs have also been used in GWAS (Genome Wide Association Studies) based on the novel commercial high density bovine SNP chips. Such platforms possess around 770k SNPs which can be used also as a rich resource for paternity exclusion tests. However genotyping such a large amount of SNPs for individuals of a whole flock to perform paternity exclusion tests is not economically feasible. Furthermore, many of these SNPs are non-informative because of high levels of linkage disequilibrium among them and because of low levels of minimum allele frequency (MAF), call rate and genotyping accuracy (GC score). In this work we devised a method to select a minimal set of SNPs from Nelore cattle samples, which are highly informative and are independent, so they could be used in a small genotyping panel for paternity exclusion tests. Samples from 32 Nelore sires chosen to represent the main genealogies marketed in Brazil and 762 nelore bulls produced by artificial insemination were genotyped. The platform used was Illumina BovineHD Genotyping Beadchip that has ~770k SNPs. The algorithm developed first run a quality control filter that selected, from the starting 770k SNPs, only markers that: i) were in Hardy Weinberg equilibrium, ii) had MAF>0.4, iii) had Illumina's accuracy GC Score > 0.8, iv) had call rate >=0.95 and v) had a D?<0.5 with other marker. 126 pairs of father-sons (151 samples), with the paternity already resolved, were selected to compose the test set. The other 643 animals that were left composed the training set. From the training set, 325 SNPs passed the quality control filter. The selected 325 SNPs were used in the test set to perform paternity tests, following the methodology adapted from Fung et al., 2002. The results show that values of the combined power of exclusion (Q) for all markers, between 0.2 and 0.7, gives the correct paternity answer for all pairs of individuals. We believe that this set of 325 SNPs could be used in a small genotyping chip to perform paternity exclusion tests for Nelore cattle; a low-cost solution to be used by cattle producers to correct paternity disagreements. All procedures were performed using the R language in a local linux server machine.X-MEETING, 2011
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