Effect of bacterial population density on germination wheat seeds and dynamics of simple artificial ecosystems.

Effect of the size of rhizospheric bacterial populations on germination of seeds and development of simple terrestrial "wheat plants--rhizospheric microorganisms--artificial soil" and "wheat plants-artificial soil" systems has been studied. Experiments demonstrated that within specify ranges in the inoculate, the rhizospheric bacteria are capable of increasing the yield of germinated seeds and stimulate the growth of plantlets. Germination of seeds inoculated with bacteria was either stimulated, or inhibited or remained at control levels depending on the amount of bacteria. Plant biomass growth and total photoassimilation has been found to depend on the amount of bacteria on the plant roots: the higher the amount of bacteria on plant roots, the smaller is the biomass of plants but the total photoassimilation is, higher. Thus, depending on the amount of bacteria on the roots of plants the system either increases the biomass of plants or increases the total photoassimilation, i.e. "pumps" carbon through itself involving bacteria. Grant numbers: N99-04-96017, N15.     

EUVITA — An extreme UV imaging telescope array with spectral capability

EUVITA is a set of 8 extreme UV normal incidence imaging telescopes, each of them sensitive in a narrow band (λ/Δλ = 15 to 80), centered at wavelengths between 50 and 175 Å. Each telescope has an effective area of a few cm²; a field of view of 1.2° and a spatial resolution of 10 arcsec.

EUVITA will be flown on the Russian mission SPECTRUM X-G. This satellite will be launched in a highly eccentric orbit with a period of 4 days, allowing long, uninterrupted observations (e.g. 10⁵ seconds). EUVITA's narrow spectral bands allow the measurement of source parameters such as temperature or power law index as well as interstellar absorption, and will resolve groups of strong lines emitted by optically thin hot plasmas.     

Accessing NASA technology with the World Wide Web

NASA Langley Research Center (LaRC) began using the World Wide Web (WWW) in the summer of 1993, becoming the first NASA installation to provide a center-wide home page. This coincided with a reorganization of LaRC to provide a more concentrated focus on technology transfer to both aerospace and non-aerospace industry. Use of WWW and NCSA Mosaic not only provides automated information dissemination, but also allows for the implementation, evolution and integration of many technology transfer and technology awareness applications. This paper describes several of these innovative applications, including the on-line presentation of the entire Technology Opportunities Showcase (TOPS), an industrial partnering showcase that exists on the Web long after the actual 3-day event ended. The NASA Technical Report Server (NTRS) provides uniform access to many logically similar, yet physically distributed NASA report servers. WWW is also the foundation of the Langley Software Server (LSS), an experimental software distribution system which will distribute LaRC-developed software. In addition to the more formal technology distribution projects, WWW has been successful in connecting people with technologies and people with other people     

Design for testability for future digital avionics systems

The authors describe an integrated testing approach called the Maintenance and Diagnostic System (MADS), which was developed for digital avionics systems using VHSIC and semicustom devices. Mission/operational requirements dictate high availability with capability to detect 98% of all faults and isolate 90% of these faults to a line replacement module (LRM) or 95% of the faults to two LRMs. MADS achieves these goals by defining a module maintenance node (MMN) chip set for each LRM in the system and the design for testability concepts for hardware. The MMN aids parallel, high-speed testing of LRMs, isolating the fault(s) to a module/chip level while incurring less than 10% overhead. It uses the concepts of scan set design, pseudorandom test vector generation, output response compression, and separate scan set loops to test the SSI-MSI logic on the LRM. It also stores interim test results and run-time fault information to isolate the hard-to-reproduce failures and performs verification of interchip and intermodule wiring     

Saturn's equatorial haze

We have measured the amount of Raman scattering in Saturn's equatorial zone and polar regions near the central meridian at the wavelengths of the H and K Ca II solar lines, 3934 Å and 3969 Å. Approximately 2.1% of the sunlight in this wavelength range is Raman scattered out of this range in Saturn's equatorial zone. Modeling the aerosol particle distribution as a clear, Rayleigh- and Raman-scattering gas over a dense haze yields an H₂ column abundance of about 40 km-Amagats. Comparison with results obtained by Pioneer 11 suggests that either the equatorial haze was 2.5 times deeper at the time of these observations (May, 1981) than at the time of the Pioneer 11 flyby (Sept., 1979); or the haze particles are much more strongly polarizing in blue light than they are in red light.     

Effects of Modulation Nonlinearity on the Range Response of FM Radars

The effect of modulation nonlinearity on the range response of FM radars with harmonic processing and ?triangle? modulation is derived. The nonlinearity may be desirable or undesirable; that is, the sidelobe level of the range response may be decreased or increased depending on the shape and amount of nonlinearity. The results of this paper may be used to predict the actual range laws of existing ?linear? FM radars; or, alternately, to specify the desired amount of modulation nonlinearity for new FM radars so that superior sidelobe suppression can be realized.     

Analysis of a Long-Distance System Measuring the Concentration of Atmospheric Gaseous Pollutants

A detailed inaccuracy and sensitivity analysis of a long-distance air pollution detection system, using a laser measuring the resonance absorption of polluting molecules, is introduced. The noise and the dynamic range of the radiation detectors used, the atmospheric inhomogeneities, and the atmospheric propagation losses of the electromagnetic radiation are considered. In addition, the best measuring path length as a function of a molecule density and atmospheric transparency and irregularity is discussed.     

The Synthetic-Array Radar Image of a Flat Plate

The radar cross section of a flat plate has a sin x/x lobe structure. If a synthetic-array radar flies past the plate the resulting image is dependent upon what part of this lobe structure is sampled. When the plate is parallel to the flight path, the image is a line as wide as the plate. If the plate is not parallel, only the discontinuities at the ends of the plate are visible in the image.