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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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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Molecular bases for unity and diversity in organic evolution

The origin of biological information has been ascribed at various times to DNA, RNA, or protein. The origin of nucleic acids without the action of prior informed protein has not been supported by plausible experiments, although such possibilities have been examined. The behavior of thermal proteins and of the microspheres selfassembled therefrom explain the origin of the first cells, the first membrane, the first reproduction cycle, ancient metabolism including ATP-aided synthesis of peptides and polynucleotides, growth, bioelectricity, and polybiofunctionality in general.

Fox, S. W.↗
NASA NTRS1989

Full-scale system impact analysis: Digital document storage project

The Digital Document Storage Full Scale System can provide cost effective electronic document storage, retrieval, hard copy reproduction, and remote access for users of NASA Technical Reports. The desired functionality of the DDS system is highly dependent on the assumed requirements for remote access used in this Impact Analysis. It is highly recommended that NASA proceed with a phased, communications requirement analysis to ensure that adequate communications service can be supplied at a reasonable cost in order to validate recent working assumptions upon which the success of the DDS Full Scale System is dependent.

Source record↗
NASA NTRS1992

Analysis of a generalized dual reflector antenna system using physical optics

Reflector antennas are widely used in communication satellite systems because they provide high gain at low cost. Offset-fed single paraboloids and dual reflector offset Cassegrain and Gregorian antennas with multiple focal region feeds provide a simple, blockage-free means of forming multiple, shaped, and isolated beams with low sidelobes. Such antennas are applicable to communications satellite frequency reuse systems and earth stations requiring access to several satellites. While the single offset paraboloid has been the most extensively used configuration for the satellite multiple-beam antenna, the trend toward large apertures requiring minimum scanned beam degradation over the field of view 18 degrees for full earth coverage from geostationary orbit may lead to impractically long focal length and large feed arrays. Dual reflector antennas offer packaging advantages and more degrees of design freedom to improve beam scanning and cross-polarization properties. The Cassegrain and Gregorian antennas are the most commonly used dual reflector antennas. A computer program for calculating the secondary pattern and directivity of a generalized dual reflector antenna system was developed and implemented at LeRC. The theoretical foundation for this program is based on the use of physical optics methodology for describing the induced currents on the sub-reflector and main reflector. The resulting induced currents on the main reflector are integrated to obtain the antenna far-zone electric fields. The computer program is verified with other physical optics programs and with measured antenna patterns. The comparison shows good agreement in far-field sidelobe reproduction and directivity.

Acosta, Roberto J.↗
NASA NTRS1992

USSR Space Life Sciences Digest, issue 32

This is the thirty-second issue of NASA's USSR Space Life Sciences Digest. It contains abstracts of 34 journal or conference papers published in Russian and of 4 Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. The abstracts in this issue have been identified as relevant to 18 areas of space biology and medicine. These areas include: adaptation, aviation medicine, biological rhythms, biospherics, cardiovascular and respiratory systems, developmental biology, exobiology, habitability and environmental effects, human performance, hematology, mathematical models, metabolism, microbiology, musculoskeletal system, neurophysiology, operational medicine, and reproductive system.

Stone, Lydia Razran↗
NASA NTRS1991

Advances in space biology and medicine. Vol. 1

Topics discussed include the effects of prolonged spaceflights on the human body; skeletal responses to spaceflight; gravity effects on reproduction, development, and aging; neurovestibular physiology in fish; and gravity perception and circumnutation in plants. Attention is also given to the development of higher plants under altered gravitational conditions; the techniques, findings, and theory concerning gravity effects on single cells; protein crystal growth in space; and facilities for animal research in space.

Bonting, Sjoerd L.↗
NASA NTRS1992

Opportunities and questions for the fundamental biological sciences in space

The nature of biological issues which can be addressed during long-term space missions is briefly discussed. These issues include structure, from cell to organ to organism; function, the regulation of systems such as immunology, neural sciences, and behavior; and reproduction and development.

Sharp, Joseph C.↗
NASA NTRS1992

Analysis of thermo-chemical nonequilibrium models for carbon dioxide flows

The aerothermodynamics of thermochemical nonequilibrium carbon dioxide flows is studied. The chemical kinetics models of McKenzie and Park are implemented in separate three-dimensional computational fluid dynamics codes. The codes incorporate a five-species gas model characterized by a translational-rotational and a vibrational temperature. Solutions are obtained for flow over finite length elliptical and circular cylinders. The computed flowfields are then employed to calculate Mach-Zehnder interferograms for comparison with experimental data. The accuracy of the chemical kinetics models is determined through this comparison. Also, the methodology of the three-dimensional thermochemical nonequilibrium code is verified by the reproduction of the experiments.

Rock, Stacey G.↗
NASA NTRS1992

Effects of microgravity or simulated launch on testicular function in rats

Reproductive toxicology and cellular and molecular biology approaches were used to evaluate testicular function in rats from Cosmos 2044. It is found that concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced in flight rates to less than 20 percent of values for simulated-launch or vivarium controls. Spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed.

Amann, R. P.↗
NASA NTRS1991

Embryogenic plant cells in microgravity

In view of circumstantial evidence for the role of gravity (g) in shaping the embryo environment, normal embryo development may not occur reliably and efficiently in the microgravity environment of space. Attention must accordingly be given to those aspects of higher plant reproductive biology in space environments required for the production of viable embryos in a 'seed to seed to seed' experiment. It is suggested that cultured cells can be grown to be morphogenetically competent, and can be evaluated as to their ability to simulate embryogenic events usually associated with fertilized eggs in the embryo sac of the ovule in the ovary.

Krikorian, Abraham D.↗
NASA NTRS1992

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 23: Information technology and aerospace knowledge diffusion: Exploring the intermediary-end user interface in a policy framework

Federal attempts to stimulate technological innovation have been unsuccessful because of the application of an inappropriate policy framework that lacks conceptual and empirical knowledge of the process of technological innovation and fails to acknowledge the relationship between knowled reproduction, transfer, and use as equally important components of the process of knowledge diffusion. It is argued that the potential contributions of high-speed computing and networking systems will be diminished unless empirically derived knowledge about the information-seeking behavior of the members of the social system is incorporated into a new policy framework. Findings from the NASA/DoD Aerospace Knowledge Diffusion Research Project are presented in support of this assertion.

Pinelli, Thomas E.↗
NASA NTRS1992

Integrated software package STAMP for minor planets

The integrated software package STAMP allowed for rapid and exact reproduction of the tables of the year-book 'Ephemerides of Minor Planets.' Additionally, STAMP solved the typical problems connected with the use of the year-book. STAMP is described. The year-book 'Ephemerides of Minor Planets' (EMP) is a publication used in many astronomical institutions around the world. It contains all the necessary information on the orbits of the numbered minor planets. Also, the astronomical coordinates are provided for each planet during its suitable observation period.

Kochetova, O. M.↗
NASA NTRS1993

Digest of Russian Space Life Sciences, issue 33

This is the thirty-third issue of NASA's USSR Space Life Sciences Digest. It contains abstracts of 55 papers published in Russian journals. The abstracts in this issue have been identified as relevant to the following areas of space biology and medicine: biological rhythms, body fluids, botany, cardiovascular and respiratory systems, developmental biology, endocrinology, equipment and instrumentation, gastrointestinal system, genetics, hematology, human performance, metabolism, microbiology, musculoskeletal system, neurophysiology, nutrition, operational medicine, psychology, radiobiology, and reproductive system.

Stone, Lydia Razran↗
NASA NTRS1993

Parametric motion control of robotic arms: A biologically based approach using neural networks

A neural network based system is presented which is able to generate point-to-point movements of robotic manipulators. The foundation of this approach is the use of prototypical control torque signals which are defined by a set of parameters. The parameter set is used for scaling and shaping of these prototypical torque signals to effect a desired outcome of the system. This approach is based on neurophysiological findings that the central nervous system stores generalized cognitive representations of movements called synergies, schemas, or motor programs. It has been proposed that these motor programs may be stored as torque-time functions in central pattern generators which can be scaled with appropriate time and magnitude parameters. The central pattern generators use these parameters to generate stereotypical torque-time profiles, which are then sent to the joint actuators. Hence, only a small number of parameters need to be determined for each point-to-point movement instead of the entire torque-time trajectory. This same principle is implemented for controlling the joint torques of robotic manipulators where a neural network is used to identify the relationship between the task requirements and the torque parameters. Movements are specified by the initial robot position in joint coordinates and the desired final end-effector position in Cartesian coordinates. This information is provided to the neural network which calculates six torque parameters for a two-link system. The prototypical torque profiles (one per joint) are then scaled by those parameters. After appropriate training of the network, our parametric control design allowed the reproduction of a trained set of movements with relatively high accuracy, and the production of previously untrained movements with comparable accuracy. We conclude that our approach was successful in discriminating between trained movements and in generalizing to untrained movements.

Bock, O.↗
NASA NTRS1993

A laboratory study of subjective response to sonic booms measured at White Sands Missile Range

The Sonic Boom Simulator of the Langley Research Center was used to quantify subjective loudness response to boom signatures consisting of: (1) simulator reproductions of booms recently recorded at White Sands Missile Range; (2) idealized N-waves; and (3) idealized booms having intermediate shocks. The booms with intermediate shocks represented signatures derived from CFD predictions. The recorded booms represented those generated by F15 and T38 aircraft flyovers and represented a variety of waveforms reflecting the effects of propagation through a turbulent atmosphere. These waveforms included the following shape categories: N-waves, peaked, rounded, and U-shaped. Results showed that Perceived Level and Zwicker Loudness Level were good estimators of the loudness of turbulence modified sonic booms. No significant differences were observed between loudness responses for the several shape categories when expressed in terms of Perceived Level. Thus, Perceived Level effectively accounted for waveform differences due to turbulence. Idealized booms with intermediate shocks, however, were rated as being approximately 2.7 dB(PL) less loud than the recorded signatures. This difference was not accounted for by PL.

Sullivan, Brenda M.↗
NASA NTRS1993

Growing wheat to maturity in reduced gas pressures

The main objective of this project was to determine assimilation of CO2 and efficiency of water use in wheat grown to maturity in a low pressure total gas pressure environment. A functional test of the low pressure plant growth chamber system was accomplished in February and March of 1993 wherein this objective was partially achieved. Plants were grown to maturity in the chambers. Data were actively collected during the first 29 days. The plants were allowed to maintain themselves at the CO2 compensation point until day 45 of the study at which point active atmospheric regulation was resumed. This provided data at the vegetative and reproductive stages of the life cycle of the plants. However, this information may not be representative of the performance of the plants due to the loss of low pressure on a number of days during the study, which affected the plants by changing the pressure potential of the tissues. The performance of the system will be discussed on a component by component basis. The maintenance of the plants at the CO2 compensation point was driven by the failure of the computer program operating the system. The software problems that arose during the functional test have since been corrected. Results from the functional test also indicated that the plants were not receiving adequate light and nutrients. The growth chambers have been relocated and the growth room modified to compensate for these deficiencies.

Rykiel, Edward J., Jr.↗
NASA NTRS1992

Comparison of numerical oblique detonation solutions with an asymptotic benchmark

In order to have confidence in a numerical method, the verification of its reproduction of known benchmark analytic solutions for simple model problems is of great importance. Attention is presently given to a novel benchmarking procedure for numerical models of high speed, reactive 2D flows. The procedure is illustrated by comparing asymptotic and numerical solutions for oblique detonations in which an attached oblique shock is followed by an exothermic reaction with a thick reaction zone.

Grismer, Matthew J.↗
NASA NTRS1987

Melatonin in human preovulatory follicular fluid

Melatonin, the major hormone of the pineal gland, has antigonadotrophic activity in many mammals and may also be involved in human reproduction. Melatonin suppresses steroidogenesis by ovarian granulosa and luteal cells in vitro. To determine if melatonin is present in the human ovary, preovulatory follicular fluids (n = 32) from 15 women were assayed for melatonin by RIA after solvent extraction. The fluids were obtained by laparoscopy or sonographically controlled follicular puncture from infertile women undergoing in vitro fertilization and embryo transfer. All patients had received clomiphene citrate, human menopausal gonadotropin, and hCG to stimulate follicle formation. Blood samples were obtained by venipuncture 30 rain or less after follicular aspiration. All of the follicular fluids contained melatonim, in concentrations substantially higher than those in the corresponding serum. A positive correlation was found between follicular fluid and serum melatonin levels in each woman; these observations indicate that preovulatory follicles contain substantial amounts of melatonin that may affect ovarian steroidogenesis.

Brzezinski, Amnon↗
NASA NTRS1987

Melatonin in human preovulatory follicular fluid

Melatonin, the major hormone of the pineal gland, has antigonadotrophic activity in many mammals and may also be involved in human reproduction. Melatonin suppresses steroidogenesis by ovarian granulosa and luteal cells in vitro. To determine if melatonin is present in the human ovary, preovulatory follicular fluids (n = 32) from 15 women were assayed for melatonin by RIA after solvent extraction. The fluids were obtained by laparoscopy or sonographically controlled follicular puncture from infertile women undergoing in vitro fertilization and embryo transfer. All patients had received clomiphene citrate, human menopausal gonadotropin, and hCG to stimulate follicle formation. Blood samples were obtained by venipuncture 30 min or less after follicular aspiration. All of the follicular fluids contained melatonin, in concentrations (35.6 plus or minus 4.8 (plus or minus SEM) pg/mL) substantially higher than those in the corresponding serum (10.0 plus or minus 1.4 pg/mL). A positive correlation was found between follicular fluid and serum melatonin levels in each woman (r = 0.770; P less than 0.001). These observations indicate that preovulatory follicles contain substantial amounts of melatonin that may affect ovarian steroidogenesis.

Brzezinski, Amnon↗