Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MATURATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Effects of simulated weightlessness on meiosis. Fertilization, and early development in mice

The initial goal was to construct a clinostat which could support mammalian cell culture. The clinostat was selected as a means by which to simulate microgravity conditions within the laboratory, by constant re-orientation of cells with respect to the gravity vector. The effects of this simulated microgravity on in-vitro meiotic maturation of oocytes, using mouse as the model system, was investigated. The effects of clinostat rotation on fertilization in-vitro was then examined. Specific endpoints included examining the timely appearance of male and female pronuclei (indicating fertilization) and the efficiency of extrusion of the second polar body. Particular attention was paid to detecting anomalies of fertilization, including parthenogenetic activation and multiple pronuclei. Finally, for the preliminary studies on mouse embryogenesis, a key feature of the clinostat was modified, that of the position of the cells during rotation. A means was found to immobilize the cells during the clinostat reotation, permitting the cells to remain at the axis of rotation yet not interfering with cellular development.

Wolgemuth, D. J.↗
NASA NTRS1985

Observations from a prototype implementation of the Common APSE Interface Set (CAIS)

This paper presents an overview of the Common Ada Programming Support Environment (APSE) Interface Set (CAIS), its purpose, and its history. The paper describes an internal research and development effort at the Mitre Corporation to implement a prototype version of the current CAIS specification and to rehost existing Ada software development tools onto the CAIS prototype. Based on this effort, observations are made on the maturity and functionality of the CAIS. These observations support the government's current policy of publicizing the CAIS specification as a baseline for public review in support of its evolution into a standard which can be mandated for use as Ada is today.

Mcclimens, M.↗
NASA NTRS1985

Heat flow and continental breakup: The Gulf of Elat (Aqaba)

Heat flow measurements were made in the major basins of the Gulf of Elat (Aqaba), northern Red Sea. The gulf is located at the southern portion of the Dead Sea rift which is a transform plate boundary. Gradient measurements at each site were made with a probe which allows multiple penetration of the bottom during a single deployment of the instrument. Thermal conductivity was determined by needle probe measurements on sedimentary cores. The mean heat flux, about 80 mWm(-2), is significantly above the continental mean, and probably also above that from the adjacent Sinai and Arabian continental blocks. The heat flow appears to increase from north to south. Such an increase may be related to the more advanced rifting stage of the Red Sea immediately to the south, which presently includes creation of an oceanic crust. This trend also corresponds to the general trend of the deep crustal structure in the gulf. Evidence from various geophysical fields suggest a gradual thinning of the crust towards the direction of the Red Sea where a normal oceanic crust exists. The heat flow data, together with other geophysical data, indicate a propagation of mature rifting activity from the Red Sea into the Gulf of Elat. This process is acting simultaneously with the transform motion along the Dead Sea rift.

Ben-Avraham, Z.↗
NASA NTRS1985

Evolution of basin and range structure in the Ruby Mountains and vicinity, Nevada

Results from various age dating techniques, seismic reflection profiling hydrocarbon maturation studies, and structural analysis were used to evaluate the Cenozoic deformation in the Ruby Mountains and adjoining ranges (pinyon Range and Cortez Range) in Elko and Eureka Counties, Nevada. Age dating techniques used include potassium-argon ages of biotites from granites published by Kistler et al. (1981) and fission track ages from apatite and zircon. Fission track ages from apatite reflect a closing temperature of 100 plus or minus 20 deg C. Zircon fission track ages reflect a closing temperature of 175 plus or minus 25 deg C and potassium-argon ages from brotite reflect a closing temperature of 250 plus or minus 30 deg C. Thus these results allow a reasonably precise tracking of the evolution of the ranges during the Cenozoic. Seismic reflection data are available from Huntington Valley. Access to seismic reflection data directly to the west of the Harrison Pass Pluton in the central Ruby Mountains was obtained. In addition results are available from several deep exploration holes in Huntington Valley.

Blackwell, D. D.↗
NASA NTRS1986

Defining reclaimed water potability requirements

Water used during previous space missions has been either carried or made aloft. Future human space endeavors will probably have to utilize some form of water reclamation and recycling. There is little applied experience in either the US or foreign space programs with this technology. Water reclamation and recycling constitutes an engineering challenge of the broadest nature and will require an intensive research and development effort if this technology is to mature in time for practical use on the proposed US spacestation. In order for this to happen, reclaimed/recycled water specification will need to be devised to guide engineering development. Perhaps the most strigent specifications will involve water to be consumed. NASA's present Potable Water Specifications are not applicable to reclaimed or recycled potable water. No specifications for reclaimed or recycled potable water presently exist either inside or outside NASA. NASA's past experience with potable water systems is reviewed, limitations of the present Potable Water Specifications are examined, present world expertise with potable water reclamation/recycling systems and system analogs is reviewed, and an approach to developing pertinent Reclaimed/Recycled Potable Water Specifications for spacecraft is presented.

Janik, D. S.↗
NASA NTRS1986

Controlled environment life support system: Growth studies with potatoes

Results of experiments conducted to maximize the productivity of potatoes grown under controlled environmental conditions are discussed. A variety of parameters is examined which affect potato growth, specifically, photoperiod, light intensity, temperature, nitrogen nutrition, carbon dioxide concentration and culture techniques. These experiments were conducted using five different cultivars, Russet Burbank, Norchip, Superior, Kennebec and Norland. To achieve high productivity, three specific objectives were explored: (1) to develop effective cultural procedures, (2) to determine the most effective photoperiod and (3) to develop a mist culture system. It is felt that the productivity obtained in this study is below the maximum that can be obtained. High irradiance levels coupled with tuber-promoting conditions such as cooler temperatures, increased CO2 levels and lowered nitrogen concentrations should allow increases in tuber production. Tuberization appears to be accelerated by short daylengths although final yields are not increased. Mist culture techniques have not yet produced fully developed tubers. The use of supporting media and alteration of the nitrogen content of the mist solution are being explored as a way to allow tubers to develop to maturity.

Tibbitts, T. W.↗
NASA NTRS1985

Sun-view angle effects on reflectance factors of corn canopies

The effects of sun and view angles on reflectance factors of corn (Zea mays L.) canopies ranging from the six leaf stage to harvest maturity were studied on the Purdue University Agronomy Farm by a multiband radiometer. The two methods of acquiring spectral data, the truck system and the tower systrem, are described. The analysis of the spectral data is presented in three parts: solar angle effects on reflectance factors viewed at nadir; solar angle effects on reflectance factors viewed at a fixed sun angle; and both sun and view angles effect on reflectance factors. The analysis revealed that for nadir-viewed reflectance factors there is a strong solar angle dependence in all spectral bands for canopies with low leaf area index. Reflectance factors observed from the sun angle at different view azimuth angles showed that the position of the sensor relative to the sun is important in determining angular reflectance characteristics. For both sun and view angles, reflectance factors are maximized when the sensor view direction is towards the sun.

Ranson, K. J.↗
NASA NTRS1985

Radio emission from the sun and stars

Radio astronomy of the sun has reached a high level of maturity, while radio astronomy of the stars is now a burgeoning new field of study. The present review is mainly concerned with radiation which is emitted by 'normal' stars, defined here to include those appearing on classical Hertzsprung-Russell diagrams. The mechanisms for both steady, quiescent emission and intense, strongly varying outbursts are discussed. Included are discussions of bremsstrahlung, gyrosynchrotron emission, electron-cyclotron masers, and plasma radiation. The manifestation of these mechanisms in various kinds of solar radiation are considered along with stellar manifestations.

Dulk, G. A.↗
NASA NTRS1984

Microwave remote sensing of soil moisture

Because of the large contrast between the dielectric constant of liquid water and that of dry soil at microwave wavelength, there is a strong dependence of the thermal emission and radar backscatter from the soil on its moisture content. This dependence provides a means for the remote sensing of the moisture content in a surface layer approximately 5 cm thick. The feasibility of these techniques is demonstrated from field, aircraft and spacecraft platforms. The soil texture, surface roughness, and vegetative cover affect the sensitivity of the microwave response to moisture variations with vegetation being the most important. It serves as an attenuating layer which can totally obscure the surface. Research indicates that it is possible to obtain five or more levels of moisture discrimination and that a mature corn crop is the limiting vegetation situation.

Schmugge, T. J.↗
NASA NTRS1985

Hydrogen and water desorption on the moon - Approximate, on-line simulations

The basic models that have been used over the last 15 years to describe the accumulation and release of solar wind-related species at lunar conditions at the lunar surface are reviewed. Recent results which show that these models are not totally valid are discussed. It is suggested that mature lunar surface soils may act as efficient converters for transforming the flux of energetic solar wind protons into a flux of low-energy hydrogen and water molecules continuously injected into the lunar atmosphere.

Blanford, G. E.↗
NASA NTRS1985

Skeletal mass change as a function of gravitational loading

The hypothesis that increased loading on an animal by chronic centrifugation results in an increase in skeletal mass was tested, using metabolically mature hamsters, rats, guinea pigs, Dutch rabbits and New Zealand rabbits representing a body mass range from 0.15 to 3.8 kg. Groups of 12 male animals of each species were subjeted to 2.0 g for 6 weeks on a 2.74 radius centrifuge with one degree of freedom. Subsequently, six of the animals were killed to measure whole body composition, while the rest comprised the control group, recovering for four weeks at 1.0 g prior to composition analysis. Results show a significant increase in bone mineral mass at 2.0 g. These centrifuge experiment results were then compared with the results of the USSR Cosmos Biosatellite experiment, whereby five rats experienced osteoporosis after 18.5 days of weightlessness. The opposing nature of effects that occurred at 0 g and 2.0 g is indicated schematically of particular interest is the fact that the bone mineral mass of the Cosmos 1129 flight rats was 17 pct less than that of the 1.0 g controls; whereas the bone mineral mass of the centrifuge rats was 18 pct greater than that of their 1.0 g controls. It is concluded that the bone mineral mass of the rat is directly proportional to gravitational loading over the range of 0 g to 2.0 g.

Pace, N.↗
NASA NTRS1985

Early mammalian development under conditions of reorientation relative to the gravity vector

A clinostat was used to assess the effects of reorientation relative to the gravity vector on mammalian germ cells cultured in vitro. Previous studies using this system revealed an inhibition of meiotic maturation of mouse oocytes. In the present study, the effects of clinostat rotation on in vitro fertilization were examined. The frequency of fertilization of experimental cultures did not vary from that of the clinostat vertical control cultures at either of the rotation rates examined. Importantly, no abnormalities of fertilization, such as parthenogenetic activation, fragmentation, or polyspermy were seen. It is concluded that the initial events of fertilization were unaffected by this treatment, although the developmental potential of these embryos remains to be assessed.

Wolgemuth, D. J.↗
NASA NTRS1985

Morphogenesis and calcification of the statoconia in the chick (Gallus domesticus) embryo - Implications for future studies

The morphogenesis of the statoconia in the chick, Gallus domesticus, injected with a carbon anhydrase inhibitor is studied. The preparation of the embryo specimens for analysis is described. The early, middle, and late stages of embryonic development are examined. The data reveal that acetozolamide inhibits statoconia formation in the middle stage of development and the calcification process follows statoconia formation. The spatial relationship between the development of type 1 and type 2 hair cells and the appearance and maturation of the statoconia is investigated.

Fermin, C. D.↗
NASA NTRS1985

Space Station Advanced Development Program

The Space Station Advanced Development Program has the objective to transform promising new techniques into mature proven concepts to enable design options for the initial Space Station. It is pointed out that the options should improve system performance and reduce operational costs. Attention is given to the approach employed in the implementation of the program, the technology issues, aspects of Space Station evolution and growth, a Space Station technology overview, and subsystem technologies. The Advanced Development Power Program is considered along with the advanced development of auxiliary propulsion, the program dealing with attitude control and stabilization, and developments related to data management. Other developments are concerned with communication, system operation, manned systems technology, structures, and environmental control and life support.

Carlisle, R. F.↗
NASA NTRS1986

The SIR-B observations of microwave backscatter dependence on soil moisture, surface roughness, and vegetation covers

An experiment was conducted from an L-band SAR aboard Space Shuttle Challenger in October 1984 to study the microwave backscatter dependence on soil moisture, surface roughness, and vegetation cover. The results based on the analyses of an image obtained at 21-deg incidence angle show a positive correlatlion between scattering coefficient and soil moisture content, with a sensitivity comparable to that derived from the ground radar measurements reported by Ulaby et al. (1978). The surface roughness strongly affects the microwave backscatter. A factor of two change in the standard deviation of surface roughness height gives a corresponding change of about 8 dB in the scattering coefficient. The microwave backscatter also depends on the vegetation types. Under the dry soil conditions, the scattering coefficient is observed to change from about -24 dB for an alfalfa or lettuce field to about -17 dB for a mature corn field. These results suggest that observations with a SAR system of multiple frequencies and polarizations are required to unravel the effects of soil moisture, surface roughness, and vegetation cover.

Wang, J. R.↗
NASA NTRS1985

The status of low-energy gamma-ray astronomy and the Gamma-Ray Observatory

A brief sketch of the objectives and status of the various subdisciplines in gamma-ray astronomy (below 10 GeV) are presented. The Gamma-Ray Observatory planned for launch in 1988 is described. This NASA observatory and several planned French-Soviet spacecraft are expected to elevate gamma-ray astronomy into a mature observational science for the Space Station era.

Fishman, G. J.↗
NASA NTRS1986

Transportation mode performance comparison for a sustained manned Mars base

The results of a study performed to characterize the propellant mass requirements of two new types of orbit transfers between earth and Mars are discussed. These new orbit types, called VISIT and Up/Down Escalators, cycle continuously between the two planets, allowing a large crew facility, or CASTLE, to remain in this orbit with smaller crew transfer vehicles, or Taxis, used to shuttle between planetary orbits and this vehicle. Trajectory options and infrastructure elements are discussed along with the assumptions made in this study. The latter include the existence of a mature Martian base and the production and use of extraterrestrial propellants. Performance results from each of the three orbit transfer options presented here are discussed.

Hoffman, S. J.↗
NASA NTRS1986

Orbit determination for the Voyager II Uranus encounter

The Voyager II flyby of Uranus in January 1986 was the most distant planetary encounter ever attempted, and presented unique challenges to the process of orbit determination. Long light-times and spacecraft receiver difficulties hampered the collection of two-way radiometric data and helped bring about the maturation of a Very Long Baseline Interferometry navigational data type during the long cruise from Saturn. Planet and satellite ephemeris uncertainties necessitated the use of the onboard spacecraft optical system for Uranus-relative navigation. During the close approach phase, these optical data were combined with radiometric data to drive the Uranus system-relative uncertainties down to the level of a few tens of kilometers. This paper contains qualitative and quantitative results and conclusions based on orbit determination experience during Uranus cruise and encounter. Topics include an overview of the navigation-related mission events and requirements, and a review of the salient orbit determination results.

Taylor, T. H.↗