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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 11 (1998), S. 131-139 
    ISSN: 1432-2145
    Keywords: Key words Calmodulin ; mRNA ; Calcium ; Pollen tube ; Agapanthus umbellatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pollen tube growth is a vital process for angiosperm fertilisation and is dependent on the presence of a tip-focused gradient of cytosolic free calcium ([Ca2+]c). In order to clarify some of the target molecules which convey the Ca2+ signal information, we investigated calmodulin distribution during tube growth. Fluorescently labelled calmodulin was pressure microinjected into pollen tubes and its distribution monitored by confocal microscopy. Calmodulin distributes evenly throughout the cell, but some of its binding sites form a V-shaped collar behind the apical region. This specific association dissipates upon growth arrest, and suggests an interaction of calmodulin with cytoskeletal-bound target proteins. The distribution of calmodulin mRNA was also analysed by microinjection of fluorescently labelled mRNA. No specific pattern was observed, with an even localisation in the body of tube and a lower concentration in the cell apex. Studies with localised application of inhibitors/activators indicate that calmodulin plays a crucial role in tip elongation but does not direct tube orientation.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-06-27
    Description: The Multispectral Scanner (MSS) was launched on the Earth Resources Technology Satellite (ERTS-1) on July 23, 1972. The MSS has two calibration systems, one internal and one external. Both calibration systems have shown strong, spectrally dependent performance degradation since launch. This paper presents details on the optical system of the MSS and data on the performance degradation as a function of both spectral interval and time in orbit. The history of the MSS during tests is traced, and it is shown that hydrocarbons from an external source may have been deposited on optical surfaces in the instrument. It is postulated that these contaminant coatings may have polymerized as a result of the exposure to UV light from the sun, increasing their blue absorbtion and accounting for the observed performance degradation.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 13; May 1974
    Format: text
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  • 3
    Publication Date: 2019-06-27
    Description: Sun calibration data from Landsat-2 are presented and compared with those from Landsat-1 (ERTS-1). The data support the hypothesis that organic contamination caused the poor performance of the Landsat-1 sun calibration mirror, since extra cleanliness precautions were taken with the Landsat-2 mirror. These precautions are described; of particular importance was the aluminum foil covering kept close to the reflective surfaces of the second mirror during the prelaunch period.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 14; Sept
    Format: text
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  • 4
    Publication Date: 2019-07-27
    Description: An automatic support system concept that isolated faults in an existing nonavionics subsystem was flight tested up to a Mach number of 3. The adaptation of the automated support concept to an existing system (the jet engine automatic inlet control system) caused most of the problems one would expect to encounter in other applications. These problems and their solutions are discussed. Criteria for integrating automatic support into the initial design of new subsystems are included in the paper. Cost effectiveness resulted from both the low maintenance of the automated system and the man-hour saving resulting from the real time diagnosis of the monitored subsystem.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Format: text
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  • 5
    Publication Date: 2019-07-13
    Description: The Multispectral Scanner carried by the ERTS-1 satellite (launched on July 23, 1972) is a very high resolution line scanning imaging radiometer operating in the visible and near infrared spectral regions. The instrument contains optical surfaces that are exposed to both direct and reflected sunlight, and the reflectivity and transmission of some of these surfaces have decreased in orbit. Details of the optical system are explained, and data on the degradation are reviewed as a function of both spectral interval and time in orbit. The history of the scanner during testing (when hydrocarbons from an external source may have been deposited on the optical surfaces) is also examined, and a mechanism is postulated for the observed degradation in orbit.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Spring Meeting of the Optical Society of America; Mar 13, 1973 - Mar 16, 1973; Denver, CO
    Format: text
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