Avaliação do efeito de gases poluentes na corrosão metálica: um experimento para o ensino da corrosão

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Magnetoresistance and transistor-like behavior of a double quantum-dot via crossed Andreev reflections

The electric current and the magnetoresistance effect are studied in a double quantum-dot system, where one of the dots QD(a) is coupled to two ferromagnetic electrodes (F-1; F-2), while the second QD(b) is connected to a superconductor S. For energy scales within the superconductor gap, electric conduction is allowed by Andreev reflection processes. Due to the presence of two ferromagnetic leads, non-local crossed Andreev reflections are possible. We found that the magnetoresistance sign can be changed by tuning the external potential applied to the ferromagnets. In addition, it is possible to control the current of the first ferromagnet (F-1) through the potential applied to the second one (F-2). We have also included intradot interaction and gate voltages at each quantum dot and analyzed their influence through a mean field approximation. The interaction reduces the current amplitudes with respect to the non-interacting case, but the switching effect still remains as a manifestation of quantum coherence, in scales of the order of the superconductor coherence length. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4723000]

Adsorção dos gases NH3, NO e H2S em fosfato de vanadila, hidrogeno fosfato de vanadila e fosfatos de vanadila dopados por Al, Co, Mn e Cr

In this work were synthesized the materials called vanadyl phosphate, hydrogen vanadyl phosphate and vanadyl phosphate doped by transition metals with the aim in adsorption the following compounds: ammonia, hydrogen sulfide and nitrogen oxide. To characterize the starting compounds was used DRX, FTIR, FRX and TG analysis. After the characterization of substrates, proceeded de adsorption of NH3 and H2S gases in reactor, passing the gases with continuous flow for 30 min and room temperature. Gravimetric data indicate that the matrices of higher performance in adsorption of ammonia was those doped by aluminum and manganese, obtaining results of 216,77 mgNH3/g and 200,40 mgNH3/g of matrix, respectively. The matrice of higher performance in adsorption of hydrogen sulfide was that doped by manganese, obtaining results of 86,94 mgH2S/g of matrix. The synthesis of substrates VOPO4.2H2O and MnVOPO4.2H2O with nitrogen oxide was made in solution, aiming the final products VOPO4.G.nH2O and MnVOPO4.G.nH2O (G = NO and n = number of water molecules). The thermo analytical behavior and the infrared spectroscopy are indicative of formation of VOPO4.2,5NO.3H2O compound. Results of scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS) of materials vanadyl phosphate and vanadyl phosphate modified after reaction in solid state or in solution with the gases show morphology changes in substrates, beyond the formation of orthorhombic sulfur crystals over their respective hosts when these adsorb hydrogen sulfide

Umidificação e aquecimento do gás inalado durante ventilação artificial com baixo fluxo e fluxo mínimo de gases frescos

JUSTIFICATIVA E OBJETIVOS: em pacientes sob intubação traqueal ou traqueostomia, a umidificação e o aquecimento do gás inalado são necessários para a prevenção de lesões no sistema respiratório, conseqüentes ao contato do gás frio e seco com as vias aéreas. O objetivo da pesquisa foi avaliar o efeito do sistema respiratório circular com absorvedor de dióxido de carbono do aparelho de anestesia Cícero da Dräger, quanto à capacidade de aquecimento e umidificação dos gases inalados, utilizando-se fluxo baixo (1 L.min-1) ou mínimo (0,5 L.min-1) de gases frescos. MÉTODO: O estudo aleatório foi realizado em 24 pacientes, estado físico ASA I, com idades entre 18 e 65 anos, submetidos à anestesia geral, utilizando-se a Estação de Trabalho Cícero da Dräger (Alemanha), para realização de cirurgias abdominais, os quais foram distribuídos aleatoriamente em dois grupos: grupo de Baixo Fluxo (BF), no qual foi administrado 0,5 L.min-1 de oxigênio e 0,5 L.min-1 de óxido nitroso e fluxo mínimo (FM), administrando-se somente oxigênio a 0,5 L.min-1. Os atributos estudados foram temperatura, umidade relativa e absoluta da sala de operação e do gás no sistema inspiratório. RESULTADOS: Os valores da temperatura, umidade relativa e umidade absoluta no sistema inspiratório na saída do aparelho de anestesia e junto ao tubo traqueal não apresentaram diferença significante entre os grupos, mas aumentaram ao longo do tempo nos dois grupos (BF e FM), havendo influência da temperatura da sala de operação sobre a temperatura do gás inalado, nos dois grupos estudados. Níveis de umidade e temperatura próximos dos ideais foram alcançados, nos dois grupos, a partir de 90 minutos. CONCLUSÕES: Não há diferença significante da umidade e temperatura do gás inalado utilizando-se baixo fluxo e fluxo mínimo de gases frescos.

Larynx and cervical trachea in humidification and heating of inhaled gases

To evaluate the participation of the larynx and cervical trachea in conditioning inspired gases, we randomly allocated 16 mixed-breed dogs to two groups: group TT (tracheal tube; n = 8) and group LMA (laryngeal mask airway; n = 8). The dogs were anesthetized with pentobarbital sodium and mechanically ventilated for 3 hours. The parameters studied were temperature and absolute humidities of ambient, inhaled, and tracheal air. There was a small increase in tracheal air temperature compared to inhaled air temperature, but no significant difference between groups. The absolute humidity of tracheal air was greater in group LMA than in group TT (23 mg H2O center dot L-1 and 14 mg H2O center dot L-1, respectively; p < .0001). The difference in absolute humidity between the tracheal air and the inhaled air was higher in group LMA at all times (p < .0001). We conclude that the larynx and cervical trachea of the dog participate in humidification and heating of inhaled air by means of air contact with mucosa in this airway segment.

Adaptação da máscara do analisador de gases VO2000 para mensuração de parâmetros cardiorrespiratórios em natação

O objetivo do presente estudo foi desenvolver um snorquel (SNQ) de baixo custo para mensuração de parâmetros cardiorrespiratórios em natação. Para isso, a máscara do analisador de gases VO2000 (MASC) foi adaptada a um SNQ desenvolvido artesanalmente com espaço morto de 250ml. Oito participantes foram submetidos a dois testes incrementais (TI) em cicloergômetro utilizando a MASC e o SNQ. Os TI foram realizados até a exaustão voluntária e foram compostos por estágios de 3min com carga inicial e incrementos de 35W. em ambas as situações, amostras gasosas foram coletadas em intervalos de 10s para determinação dos volumes de oxigênio (VO2), gás carbônico (VCO2), ventilatório (VE) e mensuração da freqüência cardíaca (FC). A comparação dos parâmetros cardiorrespiratórios (VO2, VE, VCO2 e FC) mensurados com o SNQ e a MASC foi realizada com o teste t de Student para amostras dependentes, enquanto que o teste de correlação de Pearson e a análise gráfica de Bland e Altman foram utilizados para verificar as associações e concordância entre parâmetros. em todos os casos, o nível de significância foi de P < 0,05. A adequação das equações de correção para os valores provenientes do SNQ foi verificada pelos erros sistemáticos (bias), aleatórios (precisão) e acurácia (ac). Não foram observadas diferenças significativas entre os valores de VO2, VCO2 e FC obtidos com a MASC e SNQ. Os valores de VE mensurados com o SNQ foram significativamente superiores aos obtidos com a MASC. No entanto, todos os parâmetros apresentaram elevada concordância e coeficiente de correlação (0,88 a 0,97). Além disso, foram verificados reduzidos valores de bias (VO2 = 0,11L/min; VE = 4,11L/min; VCO2 = 0,54L/min; 8,87bpm), precisão (VO2 = 0,24L/min; VE = 11,02L/ min; VCO2 = 0,18L/min; 7,42bpm) e ac (VO2 = 0,27L/min; VE = 11,76L/min; VCO2 = 0,56L/min; 11,56bpm). Desse modo, pode-se concluir que o SNQ desenvolvido neste estudo possibilita a mensuração válida de parâmetros cardiorrespiratórios em natação.

Effects of temperature on lung and blood gases in the South American rattlesnake Crotalus durissus terrificus

The effects of temperature on lung and blood gases were measured in the South American rattlesnake (Crotalus durissus terrificus). Arterial blood and lung gas samples were obtained from chronically cannulated animals at 15, 25, and 35 degrees C. As expected for reptiles, arterial pH fell with increased temperature (0.018 U degrees C-1 between 15 and 25 degrees C and 0.011 U degrees C-1 between 25 and 35 degrees C) while lung gas PCO2 rose from 5.8 mmHg at 15 degrees C to 13.2 mmHg at 35 degrees C. Concurrently, lung gas PO2 declined from 132 mmHg at 15 degrees C to 120 mmHg at 35 degrees C, and arterial PO2 increased from 33 to 76 mmHg in that temperature range. Arterial haemoglobin O-2 saturation rose from 0.53 at 15 degrees C to 0.83 at 25 degrees C but became slightly reduced (0.77) with a further elevation of temperature to 35 degrees C. Arterial haemoglobin concentration increased from 1.96 to 2.53 mM between 15 and 35 degrees C, consistent with higher demands on oxygen delivery to tissues at elevated temperatures. Moreover, the substantial increase of haemoglobin O-2 saturation between 15 and 25 degrees C conforms to the idea that reduction of the central vascular right-to-left shunt (pulmonary bypass of systemic venous return) is associated with high metabolic demands. (C) 1998 Elsevier B.V. All rights reserved.

Nonlinear Lattice Within Supersymmetric Quantum Mechanics Formalism

In the last decades, the study of nonlinear one dimensional lattices has attracted much attention of the scientific community. One of these lattices is related to a simplified model for the DNA molecule, allowing to recover experimental results, such as the denaturation of DNA double helix. Inspired by this model we construct a Hamiltonian for a reflectionless potential through the Supersymmetric Quantum Mechanics formalism, SQM. Thermodynamical properties of such one dimensional lattice are evaluated aming possible biological applications.

Equivalence of many-photon Green's functions in the Duffin-Kemmer-Petiau and Klein-Gordon-Fock statistical quantum field theories

Using the functional integral formalism for the statistical generating functional in the statistical (finite temperature) quantum field theory, we prove the equivalence of many-photon Greens functions in the Duffin-Kennner-Petiau and Klein-Gordon-Fock statistical quantum field theories. As an illustration, we calculate the one-loop polarization operators in both theories and demonstrate their coincidence.

Quantum coherent tunneling between two atomic-molecular Bose-Einstein condensates

We study the quantum coherent tunneling dynamics of two weakly coupled atomic-molecular Bose-Einstein condensates (AMBEC). A weak link is supposed to be provided by a double-well trap. The regions of parameters where the macroscopic quantum localization of the relative atomic population occurs are revealed. The different dynamical regimes are found depending on the value of nonlinearity, namely, coupled oscillations of population imbalance of atomic and molecular condensate, including irregular oscillations regions, and macroscopic quantum self trapping regimes. Quantum means and quadrature variances are calculated for population of atomic and molecular condensates and the possibility of quadrature squeezing is shown via stochastic simulations within P-positive phase space representation method. Linear tunnel coupling between two AMBEC leads to correlations in quantum statistics.

Combinatorial identities and quantum state densities of supersymmetric sigma models on N-folds

There is a remarkable connection between the number of quantum states of conformal theories and the sequence of dimensions of Lie algebras. In this paper, we explore this connection by computing the asymptotic expansion of the elliptic genus and the microscopic entropy of black holes associated with (supersymmetric) sigma models. The new features of these results are the appearance of correct prefactors in the state density expansion and in the coefficient of the logarithmic correction to the entropy.

Momentum-space non-hydrogenic wavefunction of quantum defect theory

We derive a closed-form analytic expression in momentum space for the asymptotic non-hydrogenic wavefunction of the quantum defect theory (QDT) due to Seaton and compare it with a widely used QDT-approximate wavefunction for the Rydberg states Li-3(2s), Mg-24(6s) and Rb-37(5s).

Quantum description of spin tunneling in magnetic molecules

Starting from a phenomenological Hamiltonian originally written in terms of angular momentum operators we derive a new quantum angle-based Hamiltonian that allows for a discussion on the quantum spin tunneling. The study of the applicability of the present approach, carried out in calculations with a soluble quasi-spin model, shows that we are allowed to use our method in the description of physical systems such as the Mn12-acetate molecule, as well as the octanuclear iron cluster, Fe8, in a reliable way. With the present description the interpretation of the spin tunneling is seen to be direct, the spectra and energy barriers of those systems are obtained, and it is shown that they agree with the experimental ones. (c) 2006 Elsevier B.V. All rights reserved.

Nonequilibrium dynamics of quantum fields

The nonequilibrium effective equation of motion for a scalar background field in a thermal bath is studied numerically. This equation emerges from a microscopic quantum field theory derivation and it is suitable to a Langevin simulation on the lattice. Results for both the symmetric and broken phases are presented.

Quantization rules for bound states in quantum wells

An algebraic reformulation of the Bohr-Sommerfeld (BS) quantization rule is suggested and applied to the study of bound states in one-dimensional quantum wells. The energies obtained with the present quantization rule are compared to those obtained with the usual BS and WKB quantization rules and with the exact solution of the Schrodinger equation. We find that, in diverse cases of physical interest in molecular physics, the present quantization rule not only yields a good approximation to the exact solution of the Schrodinger equation, but yields more precise energies than those obtained with the usual BS and/or WKB quantization rules. Among the examples considered numerically are the Poeschl-Teller potential and several anharmonic oscillator potentials. which simulate molecular vibrational spectra and the problem of an isolated quantum well structure subject to an external electric field.