Generation of Closed Timelike Curves with Rotating Superconductors

The spacetime metric around a rotating SuperConductive Ring (SCR) is deduced from the gravitomagnetic London moment in rotating superconductors. It is shown that theoretically it is possible to generate Closed Timelike Curves (CTC) with rotating SCRs. The possibility to use these CTC's to travel in time as initially idealized by G\"{o}del is investigated. It is shown however, that from a technology and experimental point of view these ideas are impossible to implement in the present context.Comment: 9 pages. Submitted to Classical and Quantum Gravit

Biogas production from dairy cattle manure, under organic and conventional production systems.

The purpose of this study was to evaluate the production of biogas, as well as the biogas production potential resulting from the anaerobic biodigestion of dairy cattle manure under organic (CMOS) and conventional (CMCS) production system. Also, the concentration of thermotolerant coliforms was evaluated after the biodigestion process. Therefore, bench biodigesters prototypes were supplied with CMOS and CMCS for 30 weeks. The experimental design was completely randomized with four repetitions for each treatment. Analysis of total solids (TS), volatile solids (VS), biogas production potential, most probable number (MPN) of thermotolerant coliforms were made. The cumulative biogas production was 6.18 L and 11.15 L, when using the CMOS and CMCS, respectively. Average biogas production potential of CMCS were 0.2; 2.6 and 2.9 L kg-1 substrate, ST and SV added, respectively and for CMOS 0.1; 1.4 and 1.9 L kg-1substrate, ST and SV added, respectively. After the anaerobic biodigestion process of CMOS and CMCS, it was observed that the concentrations of thermotolerant coliforms were well below than the limit established by law

Quantum mechanical counterpart of nonlinear optics

Raman-type laser excitation of a trapped atom allows one to realize the quantum mechanical counterpart of phenomena of nonlinear optics, such as Kerr-type nonlinearities, parametric amplification, and multi-mode mixing. Additionally, huge nonlinearities emerge from the interference of the atomic wave function with the laser waves. They lead to a partitioning of the phase space accompanied by a significantly different action of the time evolution in neighboring phase-space zones. For example, a nonlinearly modified coherent "displacement" of the motional quantum state may induce strong amplitude squeezing and quantum interferences.Comment: 6 pages, 4 figures, to be published in Phys. Rev. A 55 (June

Exact inflationary solutions

We present a new class of exact inflationary solutions for the evolution of a universe with spatial curvature, filled with a perfect fluid, a scalar field with potential $V_{\pm}(\phi)=\lambda(\phi^2\pm\delta^2)^2$ and a cosmological constant $\Lambda$. With the $V_+(\phi)$ potential and a negative cosmological constant, the scale factor experiments a graceful exit. We give a brief discussion about the physical meaning of the solutions.Comment: 10 pages, revtex file, 6 figures included with epsf. To be published in IJMP-

Diagnóstico de sistemas de dessalinização de água salobra subterrânea em municípios do Estado da Paraíba-Brasil.

Embora, no Semi-Árido brasileiro, predomine o embasamento cristalino, com poços apresentando qualidade comprometida por sais, à tecnologia da dessalinização permite a potabilização dessas águas. Desde 1996 vem sendo implantados, equipamentos de dessalinização por osmose inversa visando o atendimento da demanda hídrica para consumo humano. No entanto, dificuldades estão presentes na implantação dos equipamentos, tais como a falta de operação e manutenção adequadas que causam a paralisação dos mesmos, e como a produção de rejeitos, os quais são água com elevados teores de sais, normalmente despejados ao solo sem qualquer critério, cujo maior impacto tem sido a erosão e a salinidade do solo. Assim, considerando que a Embrapa Semi-Árido pesquisa manejos dos rejeitos, a Fundação Banco do Brasil realizou parceria com a Embrapa, com o objetivo de avaliar 21 sistemas de dessalinização implantados no Estado da Paraíba. O presente artigo tem por objetivo apresentar um diagnóstico da atual situação dos sistemas da Paraíba, principalmente quanto aos aspectos de conservação, manutenção e operacionalização; aos parâmetros técnicos, à qualidade de água e aos impactos ambientais causados pelos rejeitos

Seleção para resistência de linhagens de arroz de terras altas aos nematóides-das-galhas (Meloidogyne incognita).

A avaliação da resistência de linhagens aos nematóides formadores de galhas radiculares é onerosa e demanda muito trabalho. Como os programas de melhoramento trabalham com a avaliação de um grande número de linhagens, a avaliação da resistência pode se tornar mais prática utilizando-se como parâmetro a massa de ovos. Dessa forma, o presente trabalho teve como objetivo verificar se o índice massa de ovos pode ser utilizado como parâmetro de avaliação de resistência ao nematóide de galhas (Meloidogyne incognita) em linhagens de arroz de terras altas