Some boundary effects in quantum field theory

We have constructed a quantum field theory in a finite box, with periodic boundary conditions, using the hypothesis that particles living in a finite box are created and/or annihilated by the creation and/or annihilation operators, respectively, of a quantum harmonic oscillator on a circle. An expression for the effective coupling constant is obtained showing explicitly its dependence on the dimension of the box.Comment: 12 pages, Late

Effect of phonon scattering by surface roughness on the universal thermal conductance

The effect of phonon scattering by surface roughness on the thermal conductance in mesoscopic systems at low temperatures is calculated using full elasticity theory. The low frequency behavior of the scattering shows novel power law dependences arising from the unusual properties of the elastic modes. This leads to new predictions for the low temperature depression of the thermal conductance below the ideal universal value. Comparison with the data of Schwab et al. [Nature 404, 974 (2000)] suggests that surface roughness on a scale of the width of the thermal pathway is important in the experiment.Comment: 6 pages, 3 figure

Barragem subterranea: um estudo de caso.

O armazenamento de água em aquíferos artificiais, por meio de barragens subterrâneas, pode ser uma alternativa para suprir as necessidades de água no meio rural, principalmente para consumo vegetal. Em Alexandria - RN, em uma barragem subterrânea com área de 2,0 ha, verificou-se um aumento significativo na produção das culturas de milho, feijão e arroz, permitindo ao produtor comercializar o excedente da produção e aumentar a renda familiar

Low-temperature heat transfer in nanowires

The new regime of low-temperature heat transfer in suspended nanowires is predicted. It takes place when (i) only ``acoustic'' phonon modes of the wire are thermally populated and (ii) phonons are subject to the effective elastic scattering. Qualitatively, the main peculiarities of heat transfer originate due to appearance of the flexural modes with high density of states in the wire phonon spectrum. They give rise to the $T^{1/2}$ temperature dependence of the wire thermal conductance. The experimental situations where the new regime is likely to be detected are discussed.Comment: RevTex file, 1 PS figur

Alternativa tecnológica para aumentar a disponibilidade de agua no Semi-Árido.

Armazenar agua em aquiferos artificiais, por meio de barragens subterraneas, pode ser uma alternativa capaz de suprir as necessidades de agua do meio rural, principalmente para consumo vegetal. Na construcao dessas barragens pode-se utilizar material disponivel na propria regiao, como argila, alvenaria, concreto ou lona plastica. Este trabalho objetivou analisar a viabilidade tecnico-economica de uma barragem subterranea construida no municipio de Alexandria, RN, utilizando-se lona plastica de polietileno, confirmando-se que, mesmo na estacao seca, o conteudo de agua disponivel no solo foi suficiente para suprir as necessidades de agua das culturas, possibilitando a exploracao agricola durante todo o ano. Nestas condicoes, verificou-se aumento significativo na producao das culturas de milho, feijao e arroz, quando comparada com os anos anteriores, em condicoes de solo e clima semelhantes. O aumento da produtividade permitiu ao agricultor comercializar o excedente da producao, aumentar sua renda familiar e dispor de restos culturais para complementar a alimentacao do rebanho

Soroprevalência da infecção por Chlamydophila abortus em pequenos ruminantes explorados na Microrregião HOmogênea de Teresina, Piauí, Brasil.

[Seroprevalence of Chlamydophila abortus infection in small ruminants exploited the Teresina homogeneous microregion, Piaui, Brazil]. Abstract: Aimed to conduct epidemiological survey of Chlamydophila abortus in productive and reproductive losses in sheep and goat flocks in homogeneous microregion of Teresina, Piauí, Brazil. 450 samples, 150 sheep and 300 goats were examined. Blood serum samples was stored at -20 ° C and 10 samples from each farm were randomly selected for analysis. The overall prevalence of Chlamydophila abortus in sheep and goats in homogeneous micro region of Teresina was 10.66% (48/450). The overall prevalence of infection by C. abortus in sheep flocks in the region analyzed was 11.3% (17/150) and 7% (21/300) of the overall prevalence of infection in the herd goats. The Chlamydophila abortus agent is present in sheep and goat flocks in homogeneous micro region of Teresina recording the first occurrence of this infection in goats and sheep exploited in the state of Piaui, Brazil.Trabalho apresentado nos Anais do VII Congresso Norte Nordeste de Reprodução Animal (CONERA), Mossoró, maio, 2014

Avaliação de cultivares de gergelim no outono - inverno na região Norte-Fluminense.

bitstream/CNPA/18341/1/BOLETIM73.pd