Quantized spin wave modes in magnetic tunnel junction nanopillars

We present an experimental and theoretical study of the magnetic field dependence of the mode frequency of thermally excited spin waves in rectangular shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned from MgO-based magnetic tunnel junctions. The spin wave frequencies were measured using spectrally resolved electrical noise measurements. In all spectra, several independent quantized spin wave modes have been observed and could be identified as eigenexcitations of the free layer and of the synthetic antiferromagnet of the junction. Using a theoretical approach based on the diagonalization of the dynamical matrix of a system of three coupled, spatially confined magnetic layers, we have modeled the spectra for the smallest pillar and have extracted its material parameters. The magnetization and exchange stiffness constant of the CoFeB free layer are thereby found to be substantially reduced compared to the corresponding thin film values. Moreover, we could infer that the pinning of the magnetization at the lateral boundaries must be weak. Finally, the interlayer dipolar coupling between the free layer and the synthetic antiferromagnet causes mode anticrossings with gap openings up to 2 GHz. At low fields and in the larger pillars, there is clear evidence for strong non-uniformities of the layer magnetizations. In particular, at zero field the lowest mode is not the fundamental mode, but a mode most likely localized near the layer edges.Comment: 16 pages, 4 figures, (re)submitted to PR

Vacuum Polarization in the Spacetime of a Scalar-Tensor Cosmic String

We study the vacuum polarization effect in the spacetime generated by a magnetic flux cosmic string in the framework of a scalar-tensor gravity. The vacuum expectation values of the energy-momentum tensor of a conformally coupled scalar field are calculated. The dilaton's contribution to the vacuum polarization effect is shown explicitly.Comment: 11 pages, LATEX file, 2 eps figure

The Environment and Nature of the Class I Protostar Elias 29: Molecular Gas Observations and the Location of Ices

A (sub-)millimeter line and continuum study of the Class I protostar Elias 29 in the ρ Ophiuchi molecular cloud is presented whose goals are to understand the nature of this source and to locate the ices that are abundantly present along this line of sight. Within 15"-60" beams, several different components contribute to the line emission. Two different foreground clouds are detected, an envelope/disk system and a dense ridge of HCO^+-rich material. The latter two components are spatially separated in millimeter interferometer maps. We analyze the envelope/disk system by using inside-out collapse and flared disk models. The disk is in a relatively face-on orientation (<60°), which explains many of the remarkable observational features of Elias 29, such as its flat spectral energy distribution, its brightness in the near-infrared, the extended components found in speckle interferometry observations, and its high-velocity molecular outflow. It cannot account for the ices seen along the line of sight, however. A small fraction of the ices is present in a (remnant) envelope of mass 0.12-0.33 M_☉, but most of the ices (~70%) are present in cool (T < 40 K) quiescent foreground clouds. This explains the observed absence of thermally processed ices (crystallized H_2O) toward Elias 29. Nevertheless, the temperatures could be sufficiently high to account for the low abundance of apolar (CO, N_2, O_2) ices. This work shows that it is crucial to obtain spectrally and spatially resolved information from single-dish and interferometric molecular gas observations in order to determine the nature of protostars and to interpret Infrared Space Observatory and future Space Infrared Telescope Facility observations of ices and silicates along a pencil beam

Análise de Componentes Principais em Caracteres Morfológicos de Coffea arabica L.

Este trabalho teve como objetivo estudar quais caracteres morfológicos de maior importância na discriminação de genótipos de Coffea arabica L. Foram avaliados 250 acessos de C. arabica (cultivares, híbridos e alguns genótipos selvagens) oriundos do banco de germoplasma de café, instalado na fazenda experimental da Empresa de Pesquisa Agropecuária de Minas Gerais, em Patrocínio, MG. O delineamento utilizado foi de blocos casualizados com duas repetições, espaçamento de 3,5 x 0,8 metros, com parcelas de dez plantas. Os caracteres morfológicos foram avaliados em 2006, 12 meses após a implantação da cultura, com as plantas ainda na fase juvenil. Por meio dos resultados é possível observar que o ?comprimento do 1º ramo plagiotrópico?, ?vigor?, ?diâmetro do caule? e ?número de nós do 1º ramo plagiotrópico? são as variáveis de maior importância na distinção dos materiais. Assim, podem-se concentrar maiores esforços na avaliação das mesmas, descartando a avaliação das outras variáveis

Evaluation of Microencapsulation of The UFV-AREG1 Bacteriophage in Alginate-Ca Microcapsules using Microfluidic Devices

The indiscriminate use of antibiotics and the emergence of resistant microorganisms have become a major challenge for the food industry. The purpose of this work was to microencapsulate the bacteriophage UFV-AREG1 in a calcium alginate matrix using microfluidic devices and to study the viability and efficiency of retention. The microcapsules were added to gel of propylene glycol for use as an antimicrobial in the food industry. The technique showed the number of the phage encapsulation, yielding drops with an average 100-250 $\mu$m of diameter, 82.1 $\pm$ 2% retention efficiency and stability in the gel matrix for 21 days. The gel added to the microencapsulated phage showed efficiency (not detectable on the surface) in reducing bacterial contamination on the surface at a similar level to antimicrobial chemicals (alcohol 70%). Therefore, it was possible to microencapsulate bacteriophages in alginate-Ca and apply the microcapsules in gels for use as sanitizers in the food industry.Comment: 8 pages, 5 figure

Phenomenological viability of orbifold models with three Higgs families

We discuss the phenomenological viability of string multi-Higgs doublet models, namely a scenario of heterotic $Z_3$ orbifolds with two Wilson lines, which naturally predicts three supersymmetric families of matter and Higgs fields. We study the orbifold parameter space, and discuss the compatibility of the predicted Yukawa couplings with current experimental data. We address the implications of tree-level flavour changing neutral processes in constraining the Higgs sector of the model, finding that viable scenarios can be obtained for a reasonably light Higgs spectrum. We also take into account the tree-level contributions to indirect CP violation, showing that the experimental value of $\epsilon_K$ can be accommodated in the present framework.Comment: 31 pages, 12 figures. Comments and references added. Final version to be published in JHE

Spin 1 fields in Riemann-Cartan space-times "via" Duffin-Kemmer-Petiau theory

We consider massive spin 1 fields, in Riemann-Cartan space-times, described by Duffin-Kemmer-Petiau theory. We show that this approach induces a coupling between the spin 1 field and the space-time torsion which breaks the usual equivalence with the Proca theory, but that such equivalence is preserved in the context of the Teleparallel Equivalent of General Relativity.Comment: 8 pages, no figures, revtex. Dedicated to Professor Gerhard Wilhelm Bund on the occasion of his 70th birthday. To appear in Gen. Rel. Grav. Equations numbering corrected. References update

Reductive activation and structural rearrangement in superoxide reductase: a combined infrared spectroscopic and computational study

Superoxide reductases (SOR) are a family of non-heme iron enzymes that limit oxidative stress by catalysing the reduction of superoxide to hydrogen peroxide and, thus, represent model systems for the detoxification of reactive oxygen species. In several enzymes of this type, reductive activation of the active site involves the reversible dissociation of a glutamate from the proposed substrate binding site at the iron. In this study we have employed IR spectroscopic and theoretical methods to gain insights into redox-linked structural changes of 1Fe-type superoxide reductases, focusing on the enzyme from the archaeon Ignicoccus hospitalis. Guided by crystal structure data and complemented by spectra calculation for an active site model, the main IR difference signals could be assigned. These signals reflect redox-induced structural changes in the first coordination sphere of the iron centre, adjacent loop and helical regions, and more remote β-sheets. By comparison with the spectra obtained for the E23A mutant of Ignicoccus hospitalis SOR, it is shown that glutamate E23 dissociates reversibly from the ferrous iron during reductive activation of the wild type enzyme. Moreover, this process is found to trigger a global conformational transition of the protein that is strictly dependent on the presence of E23. Similar concerted structural changes can be inferred from the IR spectra of related SORs such as that from Archaeoglobus fulgidus, indicating a widespread mechanism. A possible functional role of this process in terms of synergistic effects during reductive activation of the homotetrameric enzyme is proposed.DFG, EXC 314, Unifying Concepts in Catalysi

Remoção e metabolização de Dexametasona por plantas da família das macrófitas

A presença de compostos farmacêuticos e seus metabolitos no ambiente aquático tornou-se nos últimos anos um problema ambiental emergente. Assim, tornou-se essencial o desenvolvimento de processos de remoção mais eficientes, como o tratamento de efluentes com leitos construídos de macrófitas (LCM) que, em muitos casos, tem permitido a obtenção de águas residuais finais de boa qualidade. Este trabalho teve como objectivo avaliar a eficiência de remoção de um anti-inflamatório de origem veterinária, a dexametasona, por um microcosmos de LCM utilizando LECA 2/4 como matriz de suporte, e plantado com Phragmites australis. Preliminarmente, foi avaliada a capacidade de adsorção da dexametasona pelo material LECA, a diversas concentrações iniciais, em água e num efluente recolhido após um tratamento secundário. A LECA demonstrou elevada capacidade de remoção da dexametasona, quer em água quer em efluente, embora neste último meio se tenha verificado um ligeira diminuição na eficiência de remoção (∼2 %). Posteriormente foi avaliada a eficiência de remoção da dexametasona alcançada pelo microcosmos de LCM, em dois ensaios realizados em estações do ano opostas (Inverno e Verão), a qual se verificou ter sido muito elevada (∼80 %) podendo a maior parte da eficiência ser atribuída à matriz de suporte através de fenómenos de adsorção. No entanto, comparando as remoções alcançadas em leitos plantados e não-plantados verificou-se que as plantas permitiram acelerar significativamente o processo de remoção. As amostras de tecidos de folhas das plantas usadas nos ensaios foram analisadas por LC-ESI-MS, tendo sido possível constatar a presença de DEXA e de dois dos seus metabolitos, o que sugere que a DEXA é absorvida e translocada para a parte área da planta, sofrendo uma rápida metabolização/transformação (num período inferior a 48h). Os resultados deste estudo apontam para o potencial de utilização dos LCMs, tendo LECA como matriz de suporte e plantados com Phragmites australis, para a remoção de DEXA de efluentes contaminados com este anti-inflamatório de origem veterinária