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  • Time  (2)
  • Coordinating Committee  (1)
  • Ginkgo biloba  (1)
  • Man/System Technology and Life Support  (1)
  • 2000-2004  (4)
  • 1
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    Geology of the eastern Himalayan syntaxis. The 19th Himalaya-Karakorum-Tibet Workshop (2004)
    In:  Himalayan Journal of Sciences, Special Issue, pp. 197, vol. 2
    Details
    Publication Date: 2004
    Keywords: CC 1/1 ; Coordinating Committee ; Himalayas
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    BIBLIOGRAPHY ILP
  • 2
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    Paleobotanical evidence for near present-day levels of atmospheric Co2 during part of the tertiary (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-06-26
    Description: Understanding the link between the greenhouse gas carbon dioxide (CO(2)) and Earth's temperature underpins much of paleoclimatology and our predictions of future global warming. Here, we use the inverse relationship between leaf stomatal indices and the partial pressure of CO(2) in modern Ginkgo biloba and Metasequoia glyptostroboides to develop a CO(2) reconstruction based on fossil Ginkgo and Metasequoia cuticles for the middle Paleocene to early Eocene and middle Miocene. Our reconstruction indicates that CO(2) remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the Paleocene/Eocene boundary. These results suggest that factors in addition to CO(2) are required to explain these past intervals of global warmth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Royer, D L -- Wing, S L -- Beerling, D J -- Jolley, D W -- Koch, P L -- Hickey, L J -- Berner, R A -- New York, N.Y. -- Science. 2001 Jun 22;292(5525):2310-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geology and Geophysics, Yale University, Post Office Box 208109, New Haven, CT 06520-8109, USA. dana.royer@yale.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11423657" target="_blank"〉PubMed〈/a〉
    Keywords: *Atmosphere ; *Carbon Dioxide ; Climate ; *Fossils ; Ginkgo biloba ; Gymnosperms/*cytology ; Partial Pressure ; Plant Leaves/cytology ; Plants, Medicinal ; Temperature ; Time
    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
  • 3
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    Paleoclimate. CO2 and climate change (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-05-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crowley, T J -- Berner, R A -- New York, N.Y. -- Science. 2001 May 4;292(5518):870-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Oceanography, Texas A&M University, College Station, TX 77843, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11341284" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Atmosphere ; *Carbon Dioxide ; *Climate ; Eukaryota ; Fossils ; Geologic Sediments ; Oceans and Seas ; Oxygen Isotopes ; Plants ; Time
    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
  • 4
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    Reduction of Phase Ambiguity in an Offset-QPSK Receiver (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Proposed modifications of an offset-quadri-phase-shift keying (offset-QPSK) transmitter and receiver would reduce the amount of signal processing that must be done in the receiver to resolve the QPSK fourfold phase ambiguity. Resolution of the phase ambiguity is necessary in order to synchronize, with the received carrier signal, the signal generated by a local oscillator in a carrier-tracking loop in the receiver. Without resolution of the fourfold phase ambiguity, the loop could lock to any of four possible phase points, only one of which has the proper phase relationship with the carrier. The proposal applies, more specifically, to an offset-QPSK receiver that contains a carrier-tracking loop like that shown in Figure 1. This carrier-tracking loop does not resolve or reduce the phase ambiguity. A carrier-tracking loop of a different design optimized for the reception of offset QPSK could reduce the phase ambiguity from fourfold to twofold, but would be more complex. Alternatively, one could resolve the fourfold phase ambiguity by use of differential coding in the transmitter, at a cost of reduced power efficiency. The proposed modifications would make it possible to reduce the fourfold phase ambiguity to twofold, with no loss in power efficiency and only relatively simple additional signal-processing steps in the transmitter and receiver. The twofold phase ambiguity would then be resolved by use of a unique synchronization word, as is commonly done in binary phase-shift keying (BPSK). Although the mathematical and signal-processing principles underlying the modifications are too complex to explain in detail here, the modifications themselves would be relatively simple and are best described with the help of simple block diagrams (see Figure 2). In the transmitter, one would add a unit that would periodically invert bits going into the QPSK modulator; in the receiver, one would add a unit that would effect different but corresponding inversions of bits coming out of the QPSK demodulator. The net effect of all the inversions would be that depending on which lock point the carrier-tracking loop had selected, all the output bits would be either inverted or non-inverted together; hence, the ambiguity would be reduced from fourfold to twofold, as desired.
    Keywords: Man/System Technology and Life Support
    Type: NPO-30384 , NASA Tech Briefs, May 2004; 13-14
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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