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  • COMMUNICATIONS AND RADAR  (6)
  • Lower Carboniferous  (2)
  • Myrmecophytes  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Zircon dating of North Bohemian granulites, Czech Republic: further evidence for the Lower Carboniferous high-pressure event in the Bohemian Massif (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 154-161 
    Details
    ISSN: 1437-3262
    Keywords: HP granulites ; Zircon dating ; Rutile dating ; Lower Carboniferous ; N Bohemia Czech Republic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract U-Pb zircon and rutile multigrain ages and 207Pb/206Pb zircon evaporation ages are reported from high-pressure felsic and metapelitic granulites from northern Bohemia, Czech Republic. The granulites, in contrast to those from other occurrences in the Bohemian Massif, do not show evidence of successive HT/MPLP overprints. Multigrain size fractions of nearly spherical, multifaceted, metamorphic zircons from three samples are slightly discordant and yield a U-Pb Concordia intercept age of 348 ± 10 Ma, whereas single zircon evaporation of two samples resulted in 207Pb/206Pb ages of 339 ± 1.5 and 339 ± 1.4 Ma, respectively. A rutile fraction from one sample has a U-Pb Concordia intercept age of 346 ± 14 Ma. All ages are identical, within error, and a mean age of 342 ± 5 Ma was adopted to reflect the peak of HP metamorphism. Because rutile has a lower closing temperature for the U-Pb isotopic system than zircon, the results and the P-T data imply rapid uplift and cooling after peak metamorphism. The above age is identical to ages for high-grade metamorphism reported from the southern Bohemian Massif and the Granulite Massif in Saxony. It can be speculated that all these granulites were part of the same lower crustal unit in early Carboniferous, being separated later due to crustal stacking and subsequent late Variscan orogenic collapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192073
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Studies of a South East Asian ant-plant association: protection of Macaranga trees by Crematogaster borneensis (1989)
    Springer
    Oecologia 79 (1989), S. 463-470 
    Details
    ISSN: 1432-1939
    Keywords: Ant/plant interaction ; Myrmecophytes ; Protection ; Macaranga ; Crematogaster borneensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the humid tropics of SE Asia there are some 14 myrmecophytic species of the pioneer tree genus Macaranga (Euphorbiaceae). In Peninsular Malaysia a close association exists between the trees and the small, non-stinging myrmicine Crematogaster borneensis. These ants feed mainly on food bodies provided by the plants and have their colonies inside the hollow internodes. In a ten months field study we were able to demonstrate for four Macaranga species (M. triloba, M. hypoleuca, M. hosei, M. hulletti) that host plants also benefit considerably from ant-occupation. Ants do not contribute to the nutrient demands of their host plant, they do, however, protect it against herbivores and plant competition. Cleaning behaviour of the ants results in the removal of potential hervivores already in their earliest developmental stages. Strong aggressiveness and a mass recruiting system enable the ants to defend the host plant against many herbivorous insects. This results in a significant decrease in leaf damage due to herbivores on ant-occupied compared to ant-free myrmecophytes as well as compared to non-myrmecophytic Macaranga species. Most important is the ants' defense of the host plant against plant competitors, especially vines, which are abundant in the well-lit pioneer habitats where Macaranga grows. Ants bite off any foreign plant part coming into contact with their host plant. Both ant-free myrmecophytes and non-myrmecophytic Macaranga species had a significantly higher incidence of vine growth than specimens with active ant colonies. This may be a factor of considerable importance allowing Macaranga plants to grow at sites of strongest competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378662
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  • 3
    Electronic Resource
    Electronic Resource
    Diversity of ant-plant interactions: protective efficacy in Macaranga species with different degrees of ant association (1994)
    Springer
    Oecologia 97 (1994), S. 186-192 
    Details
    ISSN: 1432-1939
    Keywords: Ant-plant interactions ; Herbivory Macaranga ; Mutualism ; Myrmecophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pioneer tree Macaranga in SE Asia has developed manyfold associations with ants. The genus comprises all stages of interaction with ants, from facultative relationships to obligate myrmecophytes. Only myrmecophytic Macaranga offer nesting space for ants and are associated with a specific ant partner. The nonmyrmecophytic species are visited by a variety of different ant species which are attracted by extrafloral nectaries (EFN) and food bodies. Transitional Macaranga species like M. hosei are colonized later in their development due to their stem structure. Before the colonization by their specific Crematogaster partner the young plants are visited by different ant species attracted by EFN. These nectaries are reduced and food body production starts as soon as colonization becomes possible. We demonstrated earlier that obligate ant partners can protect their Macaranga plants against herbivore damage and vine cover. In this study we focused on nonspecific interactions and studied M. tanarius and M. hosei, representing a non-myrmecophyte and a transitional species respectively. In ant exclusion experiments both M. tanarius and M. hosei suffered significantly higher mean leaf damage than controls, 37% versus 6% in M. hosei, 16% versus 7% in M. tanarius. M. tanarius offers both EFN and food bodies so that tests for different effects of these two food rewards could be conducted. Plants with food bodies removed but with EFN remaining had the lowest mean increase of herbivore damage of all experimental groups. Main herbivores on M. hosei were mites and caterpillars. Many M. tanarius plants were infested by a shootborer. Both Macaranga species were visited by various ant species, Crematogaster spp. being the most abundant. We found no evidence for any specific relationships. The results of this study strongly support the hypothesis that non-specific, facultative associations with ants can be advantageous for Macaranga plants. Food bodies appear to have lower attractive value for opportunistic ants than EFN and may require a specific dietary adaptation. This is also indicated by the fact that food body production in the transitional M. hosei does not start before stem structure allows a colonization by the obligate Crematogaster species. M. hosei thus benefits from facultative association with a variety of ants until it produces its first domatia and can be colonized by its obligate mutualist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323148
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  • 4
    Electronic Resource
    Electronic Resource
    Zircon dating of North Bohemian granulites, Czech Republic: further evidence for the Lower Carboniferous high-pressure event in the Bohemian Massif (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 154-161 
    Details
    ISSN: 0016-7835
    Keywords: Key words HP granulites ; Zircon dating ; Rutile dating ; Lower Carboniferous ; N Bohemia ; Czech Republic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  U–Pb zircon and rutile multigrain ages and 207Pb/206Pb zircon evaporation ages are reported from high-pressure felsic and metapelitic granulites from northern Bohemia, Czech Republic. The granulites, in contrast to those from other occurrences in the Bohemian Massif, do not show evidence of successive HT/MP-LP overprints. Multigrain size fractions of nearly spherical, multifaceted, metamorphic zircons from three samples are slightly discordant and yield a U–Pb Concordia intercept age of 348±10 Ma, whereas single zircon evaporation of two samples resulted in 207Pb/206Pb ages of 339±1.5 and 339±1.4 Ma, respectively. A rutile fraction from one sample has a U–Pb Concordia intercept age of 346±14 Ma. All ages are identical, within error, and a mean age of 342±5 Ma was adopted to reflect the peak of HP metamorphism. Because rutile has a lower closing temperature for the U–Pb isotopic system than zircon, the results and the P–T data imply rapid uplift and cooling after peak metamorphism. The above age is identical to ages for high-grade metamorphism reported from the southern Bohemian Massif and the Granulite Massif in Saxony. It can be speculated that all these granulites were part of the same lower crustal unit in early Carboniferous, being separated later due to crustal stacking and subsequent late Variscan orogenic collapse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192073
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  • 5
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    A digitally implemented communications experiment utilizing the Hermes /CTS/ satellite (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Attention is given to an investigation being conducted by NASA-Lewis and Comsat Laboratories which uses the Hermes (CTS) satellite to explain digital link implementation and the advantages it provides over conventional analog systems. The experiment concentrates on developing several video, audio, and data digital communications techniques.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium on Hermes (Communications Technology Satellite): Its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Utilization of NASA Lewis mobile terminals for the Hermes satellite (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper describes the portable earth terminal (PET) and the transportable earth terminal (TET) which enable two-way television and voice communication. Both terminals were developed by NASA and utilize the high power of the Hermes satellite. PET is a bus-type vehicle which has receiving equipment for full duplex color television and which can transmit programs originating in either the on-board PET studio or in nearby buildings. PET has a collapsible 2.4-m diameter parabolic antenna interfacing with a 500-watt 14-GHz wideband TV transmitter and a 12-GHz wideband TV receiver system. TET uses two parabolic reflector antennas, 3 m and 1.2 m in diameter, mounted on a flat trailer towed by a truck. TET can receive and relay color TV signals, and its narrowband transmitter can serve as a return audio link permitting a question-and-answer format. Also described are uplink and downlink performance characteristics, operation procedures, and field demonstrations which enabled personnel at several hospitals to participate in a distant medical conference.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium on Hermes (Communications Technology Satellite): Its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa; Canada
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Performance characteristics of the 12 GHz, 200 watt Transmitter Experiment Package for CTS (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Measured performance characteristics from ground test of the Transmitter Experiment Package (TEP) for the Communications Technology Satellite are presented. The experiment package consists of a 200 W Output Stage Tube (OST) powered by a Power Processing System (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 per cent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 per cent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, intermodulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center).
    Keywords: COMMUNICATIONS AND RADAR
    Type: EASCON ''75; Electronics and Aerospace Systems Convention; Sep 29, 1975 - Oct 01, 1975; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    A digitally implemented communications experiment utilizing the Hermes (CTS) satellite (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Hermes (CTS) experiment program made possible a significant effort directed toward new developments which will reduce the costs associated with the distribution of satellite services. Advanced satellite transponder technology and small inexpensive earth terminals were demonstrated as part of the Hermes program. Another system element that holds promise for reduced transmission cost is associated with the communication link implementation. An experiment is described which uses CTS to demonstrate digital link implementation and its advantages over conventional analog systems. A Digitally Implemented Communications experiment which demonstrates the flexibility and efficiency of digital transmission of television video and audio, telephone voice and high-bit-rate data is also described. Presentation of the experiment concept which concentrates on the evaluation of full-duplex digital television in the teleconferencing environment is followed by a description of unique equipment that was developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73827 , Symp. on Hermes (Comm. Technol. Satellite) its Performance and Appl.; Nov 29, 1977 - Dec 01, 1977; Ottawa, Ontario; Canada
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Performance characteristics of the 12 GHz, 200 watt transmitter experiment package for CTS (1975)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: The experiment package consists of a 200 W output stage tube (OST) powered by a power processing system (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 percent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 percent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, inter-modulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center).
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-71773 , E-8426
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Utilization of NASA Lewis mobile terminals for the Hermes satellite (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The high power of the Hermes satellite enables two-way television and voice communication with small ground terminals. The Portable Earth Terminal (PET) and the Transportable Earth Terminal (TET) were developed and built by NASA-Lewis to provide communications capability to short-term users. The NASA-Lewis mobile terminals are described in terms of vehicles and onboard equipment, as well as operation aspects, including use in the field. The section on demonstrations divides the uses into categories of medicine, education, technology and government. Applications of special interest within each category are briefly described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73859 , E-9448 , Symp. of Hermes, Commun. Technol. Satellite: Its Performance and Appl.; Nov 29, 1977 - Dec 01, 1977; Ottawa
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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