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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 577 records · Page 32

Random sub-diffusion and capture of genes by the nuclear pore reduces dynamics and coordinates inter-chromosomal movement

Hundreds of genes interact with the yeast nuclear pore complex (NPC), localizing at the nuclear periphery and clustering with co-regulated genes. Dynamic tracking of peripheral genes shows that they cycle on and off the NPC and that interaction with the NPC slows their sub-diffusive movement. Furthermore, NPC-dependent inter-chromosomal clustering leads to coordinated movement of pairs of loci separated by hundreds of nanometers. We developed fractional Brownian motion simulations for chromosomal loci in the nucleoplasm and interacting with NPCs. These simulations predict the rate and nature of random sub-diffusion during repositioning from nucleoplasm to periphery and match measurements from two different experimental models, arguing that recruitment to the nuclear periphery is due to random sub-diffusion and transient capture by NPCs. Finally, the simulations do not lead to inter-chromosomal clustering or coordinated movement, suggesting that interaction with the NPC is necessary, but not sufficient, to cause clustering.

59 BASIC BIOLOGICAL SCIENCES↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1971 and 1972

Ephemeris data are presented for each month of 1971 and 1972 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of the Jet Propulsion Laboratory ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described.

Hartung, A. D.↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1973 and 1974

Ephemeris data are presented for each month of 1973 and 1974 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of the Jet Propulsion Laboratory ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described.

Hartung, A. D.↗

Lunar ephemeris selenographic coordinates of the earth and sun for 1975 and 1976

Ephemeris data are presented for 1975 and 1976 to provide a time history of lunar coordinates and related geometric information. A Manned Spacecraft Center modification of the Jet Propulsion Laboratory ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases.

Hartung, A. D.↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1979 and 1980

Ephemeris data are presented in sections for each month for 1979 and 1980 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of an ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described in the appendix.

Hartung, A. D.↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1977 and 1978

Ephemeris data are presented in sections for each month for 1977 and 1978 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of an ephmeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between June 30 and July 1. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described in the appendix.

Hartung, A. D.↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1981 and 1982

Ephemeris data are presented in sections for each month for 1981 and 1982 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center (MSC) modification of the Jet Propulsion Laboratory ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between June 30 and July 1. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. For 1966 to 1970, the same type of data presentation has been prepared in informal MSC documents. The data for 1971 to 1980 and 1983 and 1984 are presented. The computer program used to compute and plot the ephemeris data is described.

Hartung, A. D.↗

Lunar ephemeris and selenographic coordinates of the earth and sun for 1983 and 1984

Ephemeris data are presented in sections for each month for 1983 and 1984 to provide a time history of lunar coordinates and related geometric information. A NASA Manned Spacecraft Center modification of an ephemeris tape was used to calculate and plot coordinates of the earth, moon, and sun. The ephemeris is referenced to the mean vernal equinox at the nearest beginning of a Besselian year. Therefore, the reference equinox changes from one year to the next between 30 June and 1 July. The apparent discontinuity in the data is not noticeable in the graphical presentation, but can be observed in the digital output. The mean equator of epoch is used in all cases. The computer program used to compute and plot the ephemeris data is described in the appendix.

Hartung, A. D.↗

Hybrid coordinate formulation used for the design of attitude control systems for flexible spacecraft

Formulation combines certain advantages of discrete and distributed coordinates by using both simultaneously. In report summarizing method, theoretical development is extended as necessary for applications of practical interest. Explicit analyses are presented in sufficient detail to establish utility in flexible space vehicle control system of hybrid coordinate formulation.

Likins, P. W.↗

Tracking-station coordinates from Geos 1 and Geos 2 optical flash data.

Center-of-mass coordinates for 28 NASA MOTS and SAO Baker-Nunn camera sites have been obtained from optical flash data from Geos 1 (1965 89A) and Geos 2 (1968 002A). More than 25,000 observations in about 100 two-day arcs were used in dynamical solutions (SAO 1969 AGU gravity model). Comparison of results with local survey solutions and with solutions from deep-space vehicle tracking suggests accuracy of about 2 meters in longitude and height and 5 meters in latitude. The relatively larger error in latitude arose from propagation of gravity-model error largely along the track of these high-inclination satellites. The results have also been compared with the solutions of the SAO 1969 standard earth for station coordinates on the North American datum. The solution obtained in the present work is much closer to the survey results in chord length between stations.

Marsh, J. G.↗

Magnetic coordinates for the Pioneer 10 Jupiter encounter

The magnetic coordinates of the Pioneer 10 spacecraft and the five innermost satellites are reported for the Jupiter encounter. The D sub 2 offset is used to make the calculations. Magnetic coordinates are needed for the interpretation of the trapped particle measurements, including the absorption effects of the satellites. Contours of constant field magnitude and magnetic latitude are given at the surface of Jupiter for the D sub 2 model. The system 3 longitude of a spacecraft at Jupiter is derived, and formulas given for the relationships between system 1, 2, and 3 longitudes. The longitude of the magnetic dipole increases by about 3 deg per year, due to the inaccurate rotation rate used to define system 3 longitude.

Mead, G. D.↗

Derivation of transformation formulas between geocentric and geodetic coordinates for nonzero altitudes

Four formulas, for the nonzero altitude transformation from geodetic coordinates (geodetic latitude and altitude) to geocentric coordinates (geocentric latitude and geocentric distance) and vice versa, are derived. The set of four formulas is expressed in each of the three useful forms: series expansion in powers of the earth's flattening; series expansion in powers of the earth's eccentricity; and Fourier series expansion in terms of the geodetic latitude or the geocentric latitude. The error incurred in these series expansions is of the order of one part in 3 x 10 to the 7th power.

Long, S. A. T.↗

Which electromagnetic equations apply in rotating coordinates

It was discovered some years ago by Schiff that two equations for fields in vacuum do not carry over without change from an inertial frame to a frame with rotating axes of space coordinates, even for a region with all velocities much lower than the speed of light. However, the belief that all four of the field equations are invariant under such conditions is still prevalent and causes misconceptions in physical applications, including astrophysical and geophysical ones. The purpose of the present paper is therefore to call attention to Schiff's discovery, discussing its basis and its extension to fields in material media, and to interpret the additional terms that must be added to the equations in order to obtain valid transformations to rotating axes of coordinates.

Webster, D. L.↗

Coordinate systems and lunar observing station positions

Satellite geodesy has yielded the locations of more than fifty stations in a single coordinate system referred to the earth's center of mass with accuracies in the five to ten meter range. The different methods used at Goddard to accomplish this are described, and estimates of the accuracies of the satellite determinations are discussed. Theoretical aspects of coordinate systems associated with the earth and the moon are also considered.

Siry, J. W.↗

Magnetic coordinates for the Pioneer 10 Jupiter encounter

The magnetic coordinates of the Pioneer 10 spacecraft and the five innermost satellites are given around the time of Jupiter encounter, Dec. 1-8, 1973. The D sub 2 offset dipole model of Smith et al. (1974) is used to make the calculations. Magnetic coordinates are needed for the interpretation of the trapped particle measurements, including the absorption effects of the satellites. Contours of constant field magnitude and magnetic latitude are given at the surface of Jupiter for the D sub 2 model. The system III longitude of a spacecraft at Jupiter is derived, and formulas are given for the relationships between system I, II, and III longitudes. The longitude of the magnetic dipole increases by about 3 deg/yr, owing to the inaccurate rotation rate used to define system III longitude.

Mead, G. D.↗

Secular variations of L, B-coordinates

The calculation results of L, B-coordinates for different years from 1957 to 1967 are given. Periodic calculations of the geomagnetic coordinates for different epochs are considered to be very urgent.

Getselev, I. V.↗