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  • 1
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    Inhibition of the EGF-activated MAP kinase signaling pathway by adenosine 3',5'-monophosphate (1993)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1993-11-12
    Description: Mitogen-activated protein (MAP) kinases p42mapk and p44mapk are activated in cells stimulated with epidermal growth factor (EGF) and other agents. A principal pathway for MAP kinase (MAPK) activation by EGF consists of sequential activations of the guanine nucleotide exchange factor Sos, the guanosine triphosphate binding protein Ras, and the protein kinases Raf-1, MAPK kinase (MKK), and MAPK. Because adenosine 3',5'-monophosphate (cAMP) does not activate MAPK and has some opposing physiologic effects, the effect of increasing intracellular concentrations of cAMP with forskolin and 3-isobutyl-1-methylxanthine on the EGF-stimulated MAPK pathway was studied. Increased concentrations of cAMP blocked activation of Raf-1, MKK, and MAPK in Rat1hER fibroblasts, accompanied by a threefold increase in Raf-1 phosphorylation on serine 43 in the regulatory domain. Phosphorylation of Raf-1 in vitro and in vivo reduces the apparent affinity with which it binds to Ras and may contribute to the blockade by cAMP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wu, J -- Dent, P -- Jelinek, T -- Wolfman, A -- Weber, M J -- Sturgill, T W -- CA39076/CA/NCI NIH HHS/ -- DK41077/DK/NIDDK NIH HHS/ -- New York, N.Y. -- Science. 1993 Nov 12;262(5136):1065-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Internal Medicine, University of Virginia, Health Sciences Center, Charlottesville 22908.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7694366" target="_blank"〉PubMed〈/a〉
    Keywords: 1-Methyl-3-isobutylxanthine/pharmacology ; 3T3 Cells ; Amino Acid Sequence ; Animals ; Cell Line ; Colforsin/pharmacology ; Cyclic AMP/*metabolism ; Cyclic AMP-Dependent Protein Kinases/metabolism ; Enzyme Activation/drug effects ; Epidermal Growth Factor/*pharmacology ; Mice ; Mitogen-Activated Protein Kinase 1 ; Mitogen-Activated Protein Kinase Kinases ; Molecular Sequence Data ; Phosphorylation ; Protein Kinases/metabolism ; Protein-Serine-Threonine Kinases/*metabolism ; Protein-Tyrosine Kinases/*metabolism ; Proto-Oncogene Proteins/metabolism ; Proto-Oncogene Proteins c-raf ; Proto-Oncogene Proteins p21(ras)/*metabolism ; Rats ; *Signal Transduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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    PAPER CURRENT
  • 2
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    Minimizing selective availability error on satellite and ground global positioning system measurements (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 15; 5, Se; 1306-130
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Equivalent GPS measurements for efficient estimation process (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Dual-frequency pseudorange and carrier phase data streams can be analytically combined into a single equivalent data stream, reducing the data volume and computing time in the filtering process for parameter estimation by a factor of 2 to 4. The resulting single data stream is that of carrier phase measurements with both data noise and bias uncertainty strictly defined. Based on these analytical formulas the equivalent GPS measurements can be formed by simple and efficient numerical calculations without any degradation in data strength. Formulation for the equivalent GPS measurements and their covariances are given in closed form; and a numerical simulation is performed to demonstrate the validity and effectiveness of the equivalent measurements.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 91-538 , AAS/AIAA Astrodynamics Conference; Aug 19, 1991 - Aug 22, 1991; Durango, CO; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Effects of antenna orientation on GPS carrier phase (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The observed carrier phase in the Global Positioning System depends on the orientation of the antennas of the transmitter and the receiver as well as the direction of the line of sight. Two equivalent analytic formulas are derived for the correction based on the property of circularly polarized wave. The magnitude of the correction is evaluated with a simulation. Result from a GPS experiment is shown for the effect of the phase correction. A general formula useful for qualitative evaluation of the differenced measurements is given in terms of the solid angles subtended at the center of the earth by the receivers and transmitters involved.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 91-537 , AAS/AIAA Astrodynamics Conference; Aug 19, 1991 - Aug 22, 1991; Durango, CO; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Gravity field improvement using GPS data from Topex/Poseidon - A covariance analysis (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A covariance analysis is performed using a realistic scenario for processing 10 days of GPS data, to obtain the expected improvement to the GEM-T2 gravity field. The gravity bin technique has been refined to compute the covariance matrix associated with the spherical harmonic gravity field. It is shown that the GPS data from one ten-day arc of Topex/Poseidon with no a priori can improve medium degree and order (3-26) sigmas for the parameters in the GEM-T2 gravity field by more than an order of magnitude.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 90-2944 , AIAA/AAS Astrodynamics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Minimizing selective availability error on Topex GPS measurements (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: GPS measurements made at Topex/Poseidon and the accompanying ground tracking sites will be affected by the selective availability. Although in principle the effects may be removed by differencing between receivers observing the same GPS satellites, this requires accurate synchronization of all receiver clocks. In the case of Topex/Poseidon application, there are two sources of imperfect clock synchronization. The first and larger is due to the constantly drifting clock onboard Topex, which may cause a residual effect as large as 10 cm on Topex carrier phase and 1 m on Topex pseudorange. The second is due to light-time differences between receivers observing the same GPS satellites, which may amount to a few mm error. In this paper a data reduction scheme which incorporates a low-order polynomial interpolation and carrier phase smoothing on pseudorange acquired at Topex and ground receivers is described; a simulation analysis is given demonstrating the effectiveness of the scheme for reducing the GPS S/A effects; and comparison with other schemes is discussed.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 90-2942 , AIAA/AAS Astrodynamics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
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    NASA TECHNICAL REPORTS
  • 7
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    How well can gravity be recovered using Topex and GPS data? (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: When Topex is launched in mid-1992 it will carry a high quality GPS receiver which will operate in concert with a worldwide network of precision GPS ground receivers. The data from these receivers can be used to recover new information about the earth's gravity field at longer wavelengths. Software and algorithms have been developed which will allow this gravity field information to be recovered with much greater efficiency than with traditional techniques. The basis for these algorithms is the gravity bin formulation and related filtering techniques that exploit the repeat orbit of Topex and the sparse matrix structure of the problem. This new software has been used to evaluate the expected improvement in the gravity field using multiple ten-day arcs of GPS data from Topex.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 89-360 , AAS/AIAA Astrodynamics Conference 1989; Aug 07, 1989 - Aug 10, 1989; Stowe, VT; United States
    Format: text
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    NASA TECHNICAL REPORTS
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