11,598 research outputs found
Lightweight nickel electrode for nickel hydrogen cells and batteries
The nickel electrode was identified as the heaviest component of the nickel hydrogen (NiH2) battery. The NASA Lewis Research Center is developing nickel electrodes for NiH2 battery devices which will be lighter in weight and have higher energy densities when cycled under a low Earth orbit regime at deep depths of discharge. Lightweight plaques are first exposed to 31 percent potassium hydroxide for 3 months to determine their suitability for use as electrode substrates from a chemical corrosion standpoint. Pore size distribution and porosity of the plaques are then measured. The lightweight plaques examined are nickel foam, nickel felt, nickel plastic and nickel plated graphite. Plaques are then electrochemically impregnated in an aqueous solution. Initial characterization tests of the impregnated plaques are performed at five discharge levels, C/2, 1.0 C, 1.37 C, 2.0C, and 2.74 C rates. Electrodes that passed the initial characterization screening test will be life cycle tested. Lightweight electrodes are approximately 30 to 50 percent lighter in weight than the sintered nickel electrode
Study of the Decay $\Lambda_c \to \Lambda l^+ \nu_{l}
Using the CLEO II detector at CESR, we observe 500 pairs
consistent with the semileptonic decay . We
measure pb. Combining with the charm semileptonic
width and the lifetime of the , we also obtain . We find no evidence for final states
in which there are additional decay products. We measure the
decay asymmetry parameter of to be
$\alpha_{\Lambda_c} =-0.89\pm{^{0.17}_{0.11}}\pm{^{0.09}_{0.06}}.Comment: 18 pages uuencoded compressed postscript (process with uudecode then
gunzip). hardcopies with figures can be obtained by sending mail to:
[email protected]
Electrolyte management in porous battery components. Static measurements
The interaction between the porous hydrogen and nickel electrodes and microporous separator with respect to electrolyte management in nickel/hydrogen cells has been investigated. The distribution of electrolyte among the components has been measured and correlated with the pore size distributions, total void volume, and resistance of a variety of electrodes and separators. Calculations are used to show the effects of systematically varying these properties
Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries
Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders
Development of a lightweight nickel electrode
Nickel electrodes made using lightweight plastic plaque are about half the weight of electrodes made from state of the art sintered nickel plaque. This weight reduction would result in a significant improvement in the energy density of batteries using nickel electrodes (nickel hydrogen, nickel cadmium and nickel zinc). These lightweight electrodes are suitably conductive and yield comparable capacities (as high as 0.25 AH/gm (0.048 AH/sq cm)) after formation. These lightweight electrodes also show excellent discharge performance at high rates
Protostellar Feedback Processes and the Mass of the First Stars
We review theoretical models of Population III.1 star formation, focusing on
the protostellar feedback processes that are expected to terminate accretion
and thus set the mass of these stars. We discuss how dark matter annihilation
may modify this standard feedback scenario. Then, under the assumption that
dark matter annihilation is unimportant, we predict the mass of stars forming
in 12 cosmological minihalos produced in independent numerical simulations.
This allows us to make a simple estimate of the Pop III.1 initial mass function
and how it may evolve with redshift.Comment: 6 pages, Proceedings of 'The First Stars and Galaxies: Challenges for
the Next Decade", Austin, TX, March 8-11, 201
microRNAs of parasitic helminths – identification, characterization and potential as drug targets
microRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional gene regulation. They were first identified in the free-living nematode Caenorhabditis elegans, where the miRNAs lin-4 and let-7 were shown to be essential for regulating correct developmental progression. The sequence of let-7 was subsequently found to be conserved in higher organisms and changes in expression of let-7, as well as other miRNAs, are associated with certain cancers, indicating important regulatory roles. Some miRNAs have been shown to have essential functions, but the roles of many are currently unknown. With the increasing availability of genome sequence data, miRNAs have now been identified from a number of parasitic helminths, by deep sequencing of small RNA libraries and bioinformatic approaches. While some miRNAs are widely conserved in a range of organisms, others are helminth-specific and many are novel to each species. Here we review the potential roles of miRNAs in regulating helminth development, in interacting with the host environment and in development of drug resistance. Use of fluorescently-labeled small RNAs demonstrates uptake by parasites, at least in vitro. Therefore delivery of miRNA inhibitors or mimics has potential to alter miRNA activity, providing a useful tool for probing the roles of miRNAs and suggesting novel routes to therapeutics for parasite control
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