Mutational Synergism Between Radiations and Methylated Purines in Escherichia Coli
Mutational synergism between ultraviolet radiation and purines in escherichia coli
MUTATION↗
SEARCH · Engineering Papers
Results for “SYNERGISM”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Synergism between hyperoxia and antibiotics for pseudomonas aeruginosa.
Synergism between hyperoxia and antibiotics for pseudomonas aeruginosa
HYPEROXIA↗
Synergism between NOAA-AVHRR and Meteosat data for studying vegetation development in semi-arid West Africa
Rainfall estimates, based on cold cloud duration estimated from Meteosat data, are compared with vegetation development depicted by data of the normalized difference vegetation index (NDVI) from the NOAA AVHRR for part of the Sahel. Decadal data from the 1985 and 1986 growing seasons are examined to determine the synergism of the datasets for rangeland monitoring. There is a general correspondence between the two datasets with a marked lag between rainfall and NDVI of between 10 and 20 days. This time lag is particularly noticeable at the beginning of the rainy season and in the more northern areas where rainfall is the limiting factor for growth. Principal component analysis was used to examine deviations from the general relationship between rainfall and the NDVI. Areas of low NDVI values for a given input of rainfall were identified: at a regional scale, they give an indication o areas of low production potential and possible degradation of ecosystems.
Justice, C. O.↗
Synergic inversion technique for active and passive microwave remote sensing of the ocean
A unified approach for combining active and passive microwave measurements for remote sensing applications is described. A synergic inversion technique has been developed and applied to the retrieval of geophysical parameters of the ocean surface and of the atmosphere. It is based on the combination of radiometric and radar measurements at the electromagnetic and cell level and not only on the correction of radar measurements by radiometric measurements, or conversely. Such a combination is performed through a common quantity: the bistatic scattering coefficient of the observed surface. This is used in a direct model to simulate combined measurements from active and passive sensors. It requires a rather complete and accurate calculation of the scattering of microwaves by the rough sea surface. Comparisons with experimental models derived for scatterometers and radar altimeters or with data derived from radiometric measurements show that the results of this unified approach are consistent with those from separate microwave sensors, at least for a foam-free sea surface.
Sobieski, Piotr↗
Diurnal change in trees as observed by optical and microwave sensors - The EOS Synergism Study
The EOS (Earth Observing System) Synergism Study examined the temporal variability of the optical and microwave backscatter due to diurnal change in canopy properties of interest to ecosystem modelers. The experiment was designed to address diurnal changes in canopy water status that relate to transpiration. Multispectral optical and multifrequency, multipolarization microwave measurements were acquired using boom-truck-based systems over a two-week period. Sensor and canopy properties were collected around the clock. The canopy studied was a walnut orchard in the San Joaquin Valley of California. The results demonstrate a large diurnal variation in the dielectric properties of the tree that in turn produces significant diurnal changes in the microwave backscatter. The results suggest that permanently orbiting spaceborne sensors such as those on EOS should be placed in orbits that are optimized for the individual sensor and need not be tied together by a tight simultaneity requirement on the order of minutes to hours for the purpose of monitoring ecosystem properties.
Way, Jobea↗
Orbit selection for the EOS mission and its synergism implications
The fundamentals of orbital mechanics are presented and applied to show how the baseline Earth Observing System orbits were selected. Scientific goals, spacecraft limitations, and instrument requirements are examined. Instrument synergism issues related to satellite orbits are discussed. It is concluded that, within constraints imposed by the Earth's atmosphere, launch vehicle capability, and other factors, an orbit can be designed to accomplish the Mission to Planet Earth.
Casey, Daren↗
21st Century Extravehicular Activities: Synergizing Past and Present Training Methods for Future Spacewalking Success
Neil Armstrong's understated words, "That's one small step for man, one giant leap for mankind." were spoken from Tranquility Base forty years ago. Even today, those words resonate in the ears of millions, including many who had yet to be born when man first landed on the surface of the moon. By their very nature, and in the the spirit of exploration, extravehicular activities (EVAs) have generated much excitement throughout the history of manned spaceflight. From Ed White's first space walk in June of 1965, to the first steps on the moon in 1969, to the expected completion of the International Space Station (ISS), the ability to exist, live and work in the vacuum of space has stood as a beacon of what is possible. It was NASA's first spacewalk that taught engineers on the ground the valuable lesson that successful spacewalking requires a unique set of learned skills. That lesson sparked extensive efforts to develop and define the training requirements necessary to ensure success. As focus shifted from orbital activities to lunar surface activities, the required skill-set and subsequently the training methods, changed. The requirements duly changed again when NASA left the moon for the last time in 1972 and have continued to evolve through the Skylab, Space Shuttle; and ISS eras. Yet because the visits to the moon were so long ago, NASA's expertise in the realm of extra-terrestrial EVAs has diminished. As manned spaceflight again shifts its focus beyond low earth orbit, EVA success will depend on the ability to synergize the knowledge gained over 40+ years of spacewalking to create a training method that allows a single crewmember to perform equally well, whether performing an EVA on the surface of the Moon, while in the vacuum of space, or heading for a rendezvous with Mars. This paper reviews NASA's past and present EVA training methods and extrapolates techniques from both to construct the basis for future EVA astronaut training.
Moore, Sandra K.↗
Space Station benefits from ECLS - Propulsion system synergism
Benefits of integrating the Space Station Environmental Control and Life Support (ECLS) system with the propulsion system are addressed in this paper for various levels of ECLS closure. Effluents generated by the ECLS system are used to augment or even supplement the propulsion system. Potential benefits include reductions in logistic weights and volumes, fixed weights and volumes, power requirements, and in total station systems cost.
Brennan, S. M.↗
Science synergism study for EOS on evolution of desert surfaces
The effectiveness of EOS data as a basis for the study of desert surfaces' evolution is presently evaluated for both long and short term geomorphic evolution. Attention is given to the usefulness of such sensor systems planned for EOS as MODIS for regional vegetation distribution/variability monitoring, HIRIS for visible-near IR observations, TIMS for lithological identification, HMMR and SSMI for soil characteristics, LASA for atmospheric profiles, SAR for surface roughness, ALT for two-dimensional topography, ACR for the calibration of imaging sensors, and ERBE for climate modeling and regional surface albedo variation determinations.
Farr, Tom G.↗
Synergism requirements and concepts for SAR and HIRIS on EOS
A study is conducted to ascertain the synergistic advantages obtainable by combining, in the EOS orbital instrument platform, instruments for the optical and microwave measurements of biophysical properties important in ecosystem modeling. Attention is given to the comparative coverages of the SAR, HIRIS, TIMS and MODIS instruments that will be carried by the platform, and to the ongoing development of joint inversion algorithms for the modeling of the ecosystems-related data thus obtained. A three-dimensional characterization of the physical attributes of the vegetation canopy and its background surface will be attempted.
Cimino, J. B.↗
Synergism of He-3 acquisition with lunar base evolution
It is shown how acquisition of He-3 affects Lunar Base development and operation. A four phase evolutionary Lunar Base scenario is summarized with initial equipment mass and resupply requirements. Requirements for various He-3 mining operations are shown and available by-products are identified. Impacts of mining He-3 on Lunar Base development include increases in equipment masses to be delivered to the lunar surface and a reduction of Lunar Base resupply based on availability of He-3 acquisition by-products. It is concluded that the acquisition of this valuable fusion fuel element greatly enhances the commercial potential of a Lunar Base.
Crabb, Thomas M.↗
The three R's of training: Recording, Retaining, and Reporting - The training management system that synergizes
NASA's Kennedy Space Center employs a Training and Certification Record System (TCRS) which tracks and maintains records for each of its employees, encompassing all aspects of training history: training courses, physical examinations, proficiency tests, on-the-job training, standboards, and certifications with completions and expiration dates. TCRS, which is fully automated, includes an expiration-alert notification capability to project recurring expirations, thereby functioning as a forecasting tool for training budgets.
Ingram, Dick D.↗
Vacuum ultraviolet radiation/atomic oxygen synergism in materials reactivity
Experimental results are presented which indicate that low fluxes of vacuum UV (VUV) radiation exert a pronounced influence on the atomic oxygen reactivity of such fluorocarbon and fluorocarbon spacecraft materials as the FEP Teflon and PCTFE that are under consideration for the Space Station Freedom. With simultaneous exposure to VUV fluxes comparable to those experienced in LEO, the reactivity of these materials becomes comparable to that of Kapton; VUV radiation has also been shown to increase the reactivity of Kapton with thermal-energy oxygen atoms.
Koontz, Steven↗
Vacuum ultraviolet radiation/atomic oxygen synergism in fluorinated ethylene propylene Teflon erosion
A micrographic investigation is reported of samples of the fluorinated ethylene propylene (FEP) Teflon thermal-blanketing materials recovered from the Long-Duration Exposure Facility (LDEF) satellite. The samples are taken from the trailing edge and row 8 which correspond to exposures to vacuum UV (VUV) and VUV + atomic O, respectively. Data are taken from SEM and IR-spectra observations, and the LDEF leading-edge FEP shows a high degree of erosion, roughening, and sharp peaks angled in the direction of the flow of atomic O. The trailing edge sample influenced primarily by VUV shows a hard brittle layer and some cracked mosaic patterns. Comparisons to a reference sample suggest that the brittle layer is related to exposure to VUV and is removed by atomic-O impingement. Polymers that are stable to VUV radiation appear to be more stable in terms of atomic oxygen.
Stiegman, A. E.↗
Synergism of He-3 acquisition with lunar base evolution
Researchers have discovered that the lunar surface contains a valuable fusion fuel element that is relatively scarce on Earth. This element, He-3, originates from the solar wind that has bombarded the surface of the Moon over geologic time. Mining operations to recover this resource would allow the by-product acquisition of hydrogen, water, carbon dioxide, carbon monoxide, methane, and nitrogen from the lunar surface with relatively minimal additional resource investment when compared to the costs to supply these resources from Earth. Two configurations for the He-3 mining system are discussed, and the impacts of these mining operations on a projected lunar base scenario are assessed. We conclude that the acquisition of He-3 is feasible with minimal advances in current state-of-the-art technologies and could support a terrestrial nuclear fusion power economy with the lowest hazard risk of any nuclear reaction known. Also, the availability of the by-products of He-3 acquisition from the Moon could significantly reduce the operational requirements of a lunar base and increase the commercialization potential of the base through consumable resupply of the lunar base itself, other components of the space infrastructure, and other space missions.
Crabb, T. M.↗
Extended ecosystem signatures with application to Eos synergism requirements
The primary objective is to define the advantages of synergistically combining optical and microwave remote sensing measurements for the determination of biophysical properties important in ecosystem modeling. This objective was approached in a stepwise fashion starting with ground-based observations of controlled agricultural and orchard canopies and progressing to airborne observations of more natural forest ecosystems. This observational program is complemented by a parallel effort to model the visible reflectance and microwave scattering properties of composite vegetation canopies. The goals of the modeling studies are to verify our basic understanding of the sensor-scene interaction physics and to provide the basis for development of inverse models optimized for retrieval of key biophysical properties. These retrieval algorithms can then be used to simulate the expected performance of various aspects of Eos including the need for simultaneous SAR and HIRIS observations or justification for other (non-synchronous) relative timing constraints and the frequency, polarization, and angle of incidence requirements for accurate biophysical parameter extractions. This program completed a very successful series of truck-mounted experiments, made remarkable progress in development and validation of optical reflectance and microwave scattering models for vegetation, extended the scattering models to accommodate discontinuous and periodic canopies, developed inversion approaches for surface and canopy properties, and disseminated these results widely through symposia and journal publications. In addition, the third generation of the computer code for the microwave scattering models was provided to a number of other US, Canadian, Australian, and European investigators who are currently presenting and publishing results using the MIMICS research code.
Ulaby, Fawwaz T.↗
Synergism of active and passive microwave data for estimating bare surface soil moisture
Active and passive microwave sensors were applied effectively to the problem of estimating the surface soil moisture in a variety of environmental conditions. Research to date has shown that both types of sensors are also sensitive to the surface roughness and the vegetation cover. In estimating the soil moisture, the effect of the vegetation and roughness are often corrected either by acquiring multi-configuration (frequency and polarization) data or by adjusting the surface parameters in order to match the model predictions to the measured data. Due to the limitations on multi-configuration spaceborne data and the lack of a priori knowledge of the surface characteristics for parameter adjustments, it was suggested that the synergistic use of the sensors may improve the estimation of the soil moisture over the extreme range of naturally occurring soil and vegetation conditions. To investigate this problem, the backscattering and emission from a bare soil surface using the classical rough surface scattering theory were modeled. The model combines the small perturbation and the Kirchhoff approximations in conjunction with the Peak formulation to cover a wide range of surface roughness parameters with respect to frequency for both active and passive measurements. In this approach, the same analytical method was used to calculate the backscattering and emissivity. Therefore, the active and passive simulations can be combined at various polarizations and frequencies in order to estimate the soil moisture more actively. As a result, it is shown that (1) the emissivity is less dependent on the surface correlation length, (2) the ratio of the backscattering coefficient (HH) over the surface reflectivity (H) is almost independent of the soil moisture for a wide range of surface roughness, and (3) this ratio can be approximated as a linear function of the surface rms height. The results were compared with the data obtained by a multi-frequency radiometer-scatterometer system working at frequencies between 3.0 GHz to 11.0 GHz. The data were acquired over bare soil surfaces with moisture variations due to freezing and thawing and roughness changes due to rain and erosion. The model predictions are shown to be in reasonable agreement with the data. In addition, it was shown that the same ratio when calculated from the data shows almost no dependence on the soil moisture. Finally, a simple technique which combines the backscattering coefficient at HH polarization (active sensing) with the emissivity at H polarization (passive sensing) is suggested for retrieving the soil moisture from bare soil surfaces.
Saatchi, Sasan S.↗
Synergism of SLR and GPS
The launch of GPS-35 (RPN 5) with a laser retroreflector has provided an opportunity to compare SLR-determined orbits of a GPS satellite with those determined by GPS receivers operated with the transmitted radio signals on the L(sub 1) and L(sub 2) frequencies. Operational considerations of the SLR and hardware design have influenced the amount and quality of SLR data collected on this satellite. As of February 1, 1994, all of the collected SLR data have been collected from northern hemisphere stations. Adequate southern hemisphere coverage is required to fully compare the results obtained from L(sub 1)/L(sub 2) and from SLR.
Schutz, Bob E.↗