Bipolar Nickel-hydrogen Batteries for Aerospace Applications

A bipolar nickel-hydrogen battery which effectively addresses all key requirements for a spacecraft power system, including long-term reliability and low mass, is discussed. The design of this battery is discussed in the context of system requirements and nickel-hydrogen battery technology in general. To achieve the ultimate goal of an aerospace application of a bipolar Ni-H2 battery several objectives must be met in the design and development of the system. These objectives include: maximization of reliability and life; high specific energy and energy density; reasonable cost of manufacture, test, and integration; and ease in scaling for growth in power requirements. These basic objectives translate into a number of specific design requirements, which are discussed

Integrated Structure and Semantics for Reo Connectors and Petri Nets

In this paper, we present an integrated structural and behavioral model of Reo connectors and Petri nets, allowing a direct comparison of the two concurrency models. For this purpose, we introduce a notion of connectors which consist of a number of interconnected, user-defined primitives with fixed behavior. While the structure of connectors resembles hypergraphs, their semantics is given in terms of so-called port automata. We define both models in a categorical setting where composition operations can be elegantly defined and integrated. Specifically, we formalize structural gluings of connectors as pushouts, and joins of port automata as pullbacks. We then define a semantical functor from the connector to the port automata category which preserves this composition. We further show how to encode Reo connectors and Petri nets into this model and indicate applications to dynamic reconfigurations modeled using double pushout graph transformation

Ultrafast spatio-temporal dynamics of terahertz generation by ionizing two-color femtosecond pulses in gases

We present a combined theoretical and experimental study of spatio-temporal propagation effects in terahertz (THz) generation in gases using two-color ionizing laser pulses. The observed strong broadening of the THz spectra with increasing gas pressure reveals the prominent role of spatio-temporal reshaping and of a plasma-induced blue-shift of the pump pulses in the generation process. Results obtained from (3+1)-dimensional simulations are in good agreement with experimental findings and clarify the mechanisms responsible for THz emission

The role of body rotation in bacterial flagellar bundling

In bacterial chemotaxis, E. coli cells drift up chemical gradients by a series of runs and tumbles. Runs are periods of directed swimming, and tumbles are abrupt changes in swimming direction. Near the beginning of each run, the rotating helical flagellar filaments which propel the cell form a bundle. Using resistive-force theory, we show that the counter-rotation of the cell body necessary for torque balance is sufficient to wrap the filaments into a bundle, even in the absence of the swirling flows produced by each individual filament

Magnetic behavior of EuCu2As2: Delicate balance between antiferromagnetic and ferromagnetic order

The Eu-based compound, EuCu2As2, crystallizing in the ThCr2Si2-type tetragonal structure, has been synthesized and its magnetic behavior has been investigated by magnetization (M), heat-capacity (C) and electrical resistivity (rho) measurements as a function of temperature (T) and magnetic field (H) as well as by 151Eu Moessbauer measurements. The results reveal that Eu is divalent ordering antiferromagnetically below 15 K in the absence of magnetic field, apparently with the formation of magnetic Brillouin-zone boundary gaps. A fascinating observation is made in a narrow temperature range before antiferromagnetism sets in: That is, there is a remarkable upturn just below 20 K in the plot of magnetic susceptibility versus T even at low fields, as though the compound actually tends to order ferromagnetically. There are corresponding anomalies in the magnetocaloric effect data as well. In addition, a small application of magnetic field (around 1 kOe at 1.8 K) in the antiferromagnetic state causes spin-reorientation effect. These results suggest that there is a close balance between antiferromagnetism and ferromagnetism in this compoundComment: Phys. Rev. B, in pres

Enraizamento de estacas de erva-mate (Ilex paraguariensis A. St. Hill.) provenientes de brotações rejuvenescidas.

A erva-mate (Ilex paraguariensis A. St.-Hill.) é espécie nativa da América do Sul, de grande importância econômica devido a seu consumo na forma de chás e também vem sendo amplamente estudada nas áreas de farmacologia e biotecnologia. No entanto, tem baixo capacidade de propagação, seja ela sexuada ou assexuada. Um dos principais efeitos da maturação é a perda da capacidade de enraizamento, desta forma, o presente trabalho teve como objetivos observar a influência do rejuvenescimento e aplicação de ácido indol butírico (IBA) no enraizamento de estacas caulinares de erva-mate. Foram confeccionadas estacas a partir de brotações do ano de árvores de 13 anos, assim como de brotos rejuvenescidos, obtidos da decepa de árvores com 17 anos. As estacas foram tratadas com IBA em solução nas seguintes concentrações: 0, 1500, 3000, 4500 e 6000 mg L-1, resultando em 5 tratamentos para cada tipo de estaca. O plantio foi realizado em caixas plásticas preenchidas com vermiculita e casca-de-arroz carbonizada na proporção de 1:1 e após 90 dias em casa-de-vegetação, foram avaliadas as seguintes variáveis: porcentagem de estacas enraizadas, número de raízes/estaca, comprimento das 3 maiores raízes/estaca, porcentagem de estacas vivas, com calos e mortas. A análise estatística mostrou que o material rejuvenescido apresentou os melhores resultados quanto à porcentagem de estacas enraizadas, assim como de número e comprimento de raízes. Já a aplicação da auxina sintética não influenciou no enraizamento das estacas de nenhum dos dois tipos, de modo que os tratamentos com IBA não diferiram entre si estatisticamente

Unraveling intra-aggregate structural disorder using single-molecule spectroscopy

Structural disorder within self-assembled molecular aggregates may have strong effects on their optical functionality. Such disorder, however, is hard to explore using standard ensemble measurements. In this paper, we report on the characterization of intra-aggregate structural disorder through a linewidth analysis of fluorescence excitation experiments on individual zinc-chlorin (ZnChl) nanotubular molecular aggregates. Recent experiments suggest an anomaly in the linewidths of the two absorption bands that dominate the spectra: the higher-energy bands on average show a smaller linewidth than the lower-energy bands. This anomaly is explored in this paper by analyzing and modeling the correlation of the two linewidths for each aggregate. We exploit a Frenkel exciton model to show that the experimentally observed correlation of linewidths and other statistical properties of the single-aggregate spectra can be explained from small variations of the molecular orientations within individual aggregates

Rights Myopia in Child Welfare

For decades, legal scholars have debated the proper balance of parents\u27 rights and children\u27s rights in the child welfare system. This Article argues that the debate mistakenly privileges rights. Neither parents\u27 rights nor children\u27s rights serve families well because, as implemented, a solely rights-based model of child welfare does not protect the interests of parents or children. Additionally, even if well-implemented, the model still would not serve parents or children because it obscures the important role of poverty in child abuse and neglect and fosters conflict rather than collaboration between the state and families. In lieu of a solely rights-based model, this Article proposes a problem-solving model for child welfare and explores one embodiment of such a model, family group conferencing. This Article concludes that a problem-solving model holds significant potential to address many of the profound theoretical and practical shortcomings of the current child welfare system