1,520 research outputs found

    Theory of the Injun 5 VLF Poynting flux measurements

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    VLF Poynting flux measurement technique used on Injun 5 satellit

    VLF electric and magnetic fields observed in the auroral zone with the Javelin 8.46 sounding rocket

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    VLF electric and magnetic fields observed in auroral zone with Javelin 8.46 sounding rocke

    ORION: A Small, Full Capability, General Purpose, Low Earth Orbit Satellite Bus

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    A low cost general purpose satellite bus has been designed to support a wide variety of small scientific and commercial payloads. The design provides a number of launch options, including the new NASA extended Get- Away-Special * (GAS) canister and several small expendable launch vehicles. The satellite is 48 cm. (19 in,) in diameter, 89 cm. (35 in.) high and weighs approximately 123 kg. (270 Ibs.). The satellite bus provides telemetry, attitude control, orbital boost/station keeping, electrical power, microprocessor and data storage for up to 23 kg. (50 Ibs.) of user payload. The satellite. has a hydrazine propulsion system, with up to 123 m/s (2600 ft/s) delta-V capability. On-board propulsion reduces launcher orbital insertion accuracy requirements and allows the satellite to independently achieve 1480 km. (300 nm. } circular or 4070 km, (2200 nm.) elliptic orbits from an initial orbit of 250 km. (135 nm.)

    N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels

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    The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N<sub>2</sub>O), has been re-examined, using known global atmospheric removal rates and concentration growth of N<sub>2</sub>O as a proxy for overall emissions. For both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production, we find an overall conversion factor of 3&ndash;5% from newly fixed N to N<sub>2</sub>O-N. We assume the same factor to be valid for biofuel production systems. It is covered only in part by the default conversion factor for "direct" emissions from agricultural crop lands (1%) estimated by IPCC (2006), and the default factors for the "indirect" emissions (following volatilization/deposition and leaching/runoff of N: 0.35&ndash;0.45%) cited therein. However, as we show in the paper, when additional emissions included in the IPCC methodology, e.g. those from livestock production, are included, the total may not be inconsistent with that given by our "top-down" method. When the extra N<sub>2</sub>O emission from biofuel production is calculated in "CO<sub>2</sub>-equivalent" global warming terms, and compared with the quasi-cooling effect of "saving" emissions of fossil fuel derived CO<sub>2</sub>, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), depending on N fertilizer uptake efficiency by the plants, can contribute as much or more to global warming by N<sub>2</sub>O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species, have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment

    Elevated CO\u3csub\u3e2\u3c/sub\u3e Enhances Productivity and the C/N Ratio of Grasses in the Colorado Shortgrass Steppe

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    Atmospheric CO2 concentrations have been increasing since the industrial revolution, and are projected to double within this century over today\u27s concentration of 360 µmol mol-1 . This study used six open-top chambers in the Colorado, USA shortgrass steppe to investigate how increasing CO2 will affect productivity and C and N status of indigenous perennial grasses and forbs. From March until October, chambers were placed on two plots in each of the three blocks. In each block, one chamber was assigned an ambient CO2 treatment (~360 µmol mol-1), the other an elevated CO2 treatment (~720 µmol mol-1). Each block also had an unchambered control plot. Growth under elevated CO2 increased above-ground phytomass an average 31% in 1997 and 47% in 1998, with no differences in relative growth responses of C3 and C4 grasses and forbs. Growth in chambers was greater than non-chambered control plots, presumably due to warmer temperatures in chambers and a longer growing season. Shoot N concentrations were reduced 21% and C/N ratios increased 23% in elevated compared to ambient chambers. Variation in aboveground phytomass due to year, CO2 and chamber effects correlated well to % shoot N and C/N ratios, although for both traits different regression lines were required for green plant material (harvested in July) and senescent plant material (harvested in October). Results suggest increased growth and reduced N concentrations in this mixed C3/C4 grassland in an elevated CO2 environment

    Initial observations of VLF electric and magnetic fields with the Injun 5 satellite

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    Very low frequency electric and magnetic field observations by Injun 5 satellit

    Genome of a Low-Salinity Ammonia-Oxidizing Archaeon Determined by Single-Cell and Metagenomic Analysis

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    Ammonia-oxidizing archaea (AOA) are thought to be among the most abundant microorganisms on Earth and may significantly impact the global nitrogen and carbon cycles. We sequenced the genome of AOA in an enrichment culture from low-salinity sediments in San Francisco Bay using single-cell and metagenomic genome sequence data. Five single cells were isolated inside an integrated microfluidic device using laser tweezers, the cells' genomic DNA was amplified by multiple displacement amplification (MDA) in 50 nL volumes and then sequenced by high-throughput DNA pyrosequencing. This microscopy-based approach to single-cell genomics minimizes contamination and allows correlation of high-resolution cell images with genomic sequences. Statistical properties of coverage across the five single cells, in combination with the contrasting properties of the metagenomic dataset allowed the assembly of a high-quality draft genome. The genome of this AOA, which we designate Candidatus Nitrosoarchaeum limnia SFB1, is ∼1.77 Mb with >2100 genes and a G+C content of 32%. Across the entire genome, the average nucleotide identity to Nitrosopumilus maritimus, the only AOA in pure culture, is ∼70%, suggesting this AOA represents a new genus of Crenarchaeota. Phylogenetically, the 16S rRNA and ammonia monooxygenase subunit A (amoA) genes of this AOA are most closely related to sequences reported from a wide variety of freshwater ecosystems. Like N. maritimus, the low-salinity AOA genome appears to have an ammonia oxidation pathway distinct from ammonia oxidizing bacteria (AOB). In contrast to other described AOA, these low-salinity AOA appear to be motile, based on the presence of numerous motility- and chemotaxis-associated genes in the genome. This genome data will be used to inform targeted physiological and metabolic studies of this novel group of AOA, which may ultimately advance our understanding of AOA metabolism and their impacts on the global carbon and nitrogen cycles

    Design for an 8 Meter Monolithic UV/OIR Space Telescope

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    ATLAST-8 is an 8-meter monolithic UV/optical/NIR space observatory to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V cargo launch vehicle. The ATLAST-8 will yield fundamental astronomical breakthroughs. The mission concept utilizes two enabling technologies: planned Ares-V launch vehicle (scheduled for 2019) and autonomous rendezvous and docking (AR&D). The unprecedented Ares-V payload and mass capacity enables the use of a massive, monolithic, thin-meniscus primary mirror - similar to a VLT or Subaru. Furthermore, it enables simple robust design rules to mitigate cost, schedule and performance risk. AR&D enables on-orbit servicing, extending mission life and enhancing science return

    A new look at low-energy nuclear reaction (LENR) research: a response to Shanahan

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    In his criticisms of the review article on LENR by Krivit and Marwan, Shanahan has raised a number of issues in the areas of calorimetry, heat after death, elemental transmutation, energetic particle detection using CR-39, and the temporal correlation between heat and helium-4. These issues are addressed by the researchers who conducted the original work that was discussed in the Krivit-Marwan (K&M) review paper
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