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  • AIRCRAFT STABILITY AND CONTROL  (7)
  • Life and Medical Sciences  (4)
  • Meteorology and Climatology  (3)
  • ASTRONOMY  (1)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 14 (1989), S. 435-445 
    ISSN: 0886-1544
    Keywords: flagella ; dynein heavy chains ; flagellar ATPase ; sequence homology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We previously cloned portions of the alpha and beta dynein heavy chain genes of Chlamydomonas reinhardtii by screening a genomic expression library with monoclonal antibodies (Williams et al.: Journal of Cell Biology 103:1-11, 1986). Here we provide further evidence of the identity of these clones and describe the selection of adjacent regions from a large insert genomic library. Southern blots indicate that only a single copy of each gene is present in the Chlamydomonas genome, while Northern blots show that both heavy chains are encoded by 13.5 kilobase mRNAs and that the corresponding transcription units each span approximately 20 kilobase-pairs of genomic DNA. No similarities were detected between restriction maps of the alpha and beta dynein genes, but extensive regions of sequence similarity were identified by the cross-hybridization of cloned gene fragments.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 510-520 
    ISSN: 0886-1544
    Keywords: flagella ; motility ; dynein substructure ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When outer-row dynein arms are extracted from Chlamydomonas flagellar axonemes, they dissociate into two ATPase complexes with sedimentation coefficients of 12S and 18S. We immunized mice with 18S dynein and generated a library of monoclonal antibodies against the polypeptides in this complex. Antibodies were selected which specifically recognize the 18S α- and β-heavy chains and the 83,000-dalton and 70,000-dalton intermediate chains. These antibodies were isolated and characterized for their ability to recognize determinants on both denatured antigens and native 18S dynein; 18S dynein was dissociated in stepwise fashion into smaller aggregates with ionic and nonionic detergents and the resulting subcomplexes were isolated by precipitation with specific monoclonal antibodies. The smallest aggregates isolated were heterodimers between the α-chain and a 16,000-dalton light chain and between the two intermediate chains. Additional close associations of the β-heavy chain with an 18,000-dalton light chain and 70,000-dalton intermediate chain, and a weaker interaction between the intermediate chain heterodimer and light chains of 21,000 daltons and 12,500 daltons, were also observed. We present a model of 18S dynein substructure based upon this information.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 12 (1990), S. 74-79 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: DNA repair is important in such phenomena as carcinogenesis and aging. While much is known about DNA repair in single-cell systems such as bacteria, yeast, and cultured mammalian cells, it is necessary to examine DNA repair in a developmental context in order to completely understand its processes in complex metazoa such as man. We present data to support the notion that proliferating cells from organ systems, tumors, and embryos have a greater DNA repair capacity than terminally differentiated, nonproliferating cells. Differential expression of repair genes and accessibility of chromatin to repair enzymes are considered as determinants in the developmental regulation of DNA repair.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 715-722 
    ISSN: 0749-503X
    Keywords: Gene fusion ; protein purification ; glutathione S-transferase ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A rapid and convenient method of protein purification involves creating a fusion protein with glutathione S-transferase (GST) (Smith and Johnson, Gene 67, 31-40, 1988). In this report, we describe two vectors for the conditional expression of GST fusions in Saccharomyces cerevisiae. The parent plasmid is based on a high-copy, galactose-inducible shuttle vector previously described (Baldari et al., EMBO J. 6, 229-243, 1987). We have demonstrated the use of this system by creating fusions between GST and the yeast RAS2 gene. GST-Ras2 fusion proteins undergo the post-translational modifications required for Ras2p to become membrane localized. These vectors provide a useful system for the expression an dpurification of eukaryotic proteins requiring post-translational modification.
    Additional Material: 4 Ill.
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  • 5
    Publication Date: 2013-08-31
    Description: The pilot's perceptions of aircraft handling qualities are influenced by a combination of the aircraft dynamics, the task, and the environment under which the evaluation is performed. When the evaluation is performed in a groundbased simulator, the characteristics of the simulation facility also come into play. Two studies were conducted on NASA Ames Research Center's Vertical Motion Simulator to determine the effects of simulator characteristics on perceived handling qualities. Most evaluations were conducted with a baseline set of rotorcraft dynamics, using a simple transfer-function model of an uncoupled helicopter, under different conditions of visual time delays and motion command washout filters. Differences in pilot opinion were found as the visual and motion parameters were changed, reflecting a change in the pilots' perceptions of handling qualities, rather than changes in the aircraft model itself. The results indicate a need for tailoring the motion washout dynamics to suit the task. Visual-delay data are inconclusive but suggest that it may be better to allow some time delay in the visual path to minimize the mismatch between visual and motion, rather than eliminate the visual delay entirely through lead compensation.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA. Ames Research Center, Piloting Vertical Flight Aircraft: A Conference on Flying Qualities and Human Factors; p 341-359
    Format: application/pdf
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  • 6
    Publication Date: 2018-06-11
    Description: The large horizontal extent, location in the cold upper troposphere, and ice composition make cirrus clouds important modulators of the earth's radiation budget and climate. Cirrus cloud microphysical properties are difficult to measure and model because they are inhomogeneous in nature and their ice crystal size distribution and habit are not well characterized. Accurate retrievals of cloud properties are crucial for improving the representation of cloud scale processes in large-scale models and for accurately predicting the earth's future climate. A number of passive and active remote sensing retrieval algorithms exist for estimating the microphysical properties of upper tropospheric clouds. We believe significant progress has been made in the evolution of these retrieval algorithms in the last decade, however, there is room for improvement. Members of the Atmospheric Radiation measurement program (ARM) Cloud properties Working Group are involved in an intercomparison of optical depth(tau), ice water path, and characteristic particle size in clouds retrieved using ground-based instruments. The goals of this intercomparison are to evaluate the accuracy of state-of-the-art algorithms, quantify the uncertainties, and make recommendations for improvement.
    Keywords: Meteorology and Climatology
    Format: application/pdf
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  • 7
    Publication Date: 2019-06-28
    Description: A study aimed at determining the effects of simulator characteristics on perceived handling qualities is discussed. Evaluations were conducted with a baseline set of rotorcraft dynamics, using a simple transfer-function model of an uncoupled helicopter, under different conditions of visual and overall time delays. As the visual and motion parameters were changed, differences in pilot opinion were found reflecting a change in the pilots' perceptions of handling qualities, rather than changes in the aircraft model itself. It is concluded that it is necessary to tailor the motion washout dynamics to suit the task, with reduced washouts for precision maneuvering as compared to aggressive maneuvering. Visual-delay data suggest that it may be better to allow some time delay in the visual path to minimize the mismatch between visual and motion, rather than eliminate the visual delay entirely through lead compensation.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 91-2892
    Format: text
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  • 8
    Publication Date: 2019-06-28
    Description: This report presents the results of analysis of cockpit lateral control feel-system studies. Variations in feel-system natural frequency, damping, and command sensing reference (force and position) were investigated, in combination with variations in the aircraft response characteristics. The primary data for the report were obtained from a flight investigation conducted with a variable-stability airplane, with additional information taken from other flight experiments and ground-based simulations for both airplanes and helicopters . The study consisted of analysis of handling qualities ratings and extraction of open-loop, pilot-vehicle describing functions from sum-of-sines tracking data, including, for a limited subset of these data, the development of pilot models. The study confirms the findings of other investigators that the effects on pilot opinion of cockpit feel-system dynamics are not equivalent to a comparable level of added time delay, and until a more comprehensive set of criteria are developed, it is recommended that feel-system dynamics be considered a delay-inducing element in the aircraft response. The best correlation with time-delay requirements was found when the feel-system dynamics were included in the delay measurements, regardless of the command reference. This is a radical departure from past approaches.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-4443 , H-1769 , NAS 1.26:4443
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  • 9
    Publication Date: 2019-06-28
    Description: A fixed base simulation has been performed to investigate the handling qualities requirements for the mid-term pitch response of a helicopter at hover and in low-speed flight. Pilot rating results from this simulation were compared with those from previous experiments to develop handling qualities limits on the frequency and damping of the oscillatory mode in the hovering cubic. Pilot performance data obtained during the experiment were used to confirm the pilot rating results. These data show the pilot performance to closely match that predicted by the theory of piloted control. A means of predicting pilot ratings from the open-loop aircraft dynamics is presented.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 87-2533
    Format: text
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  • 10
    Publication Date: 2019-06-28
    Description: A flight experiment has been conducted using the Canadian National Aeronautical Establishment's variable-stability airborne simulator to define the dynamic response requirements for operations at hover and low speeds. Fourteen Attitude Command/Attitude Hold, Rate, and Rate Command/Attitude Hold configurations were evaluated by six pilots using both conventional controls and a four-axis integrated sidestick over a low-speed course consisting of precision hover, landing, sidestep, and dash/quickstop tasks. The results indicate that with conventional controls all three response-types were acceptable as long as their response bandwidth was sufficiently high, and higher bandwidths were required in roll than in pitch. With the four-axis sidestick, there was a preference for the Rate systems. The range of acceptable bandwidths was lower, and the spread in pilot ratings smaller, than were found in a similar ground-based simulation.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 87-2285
    Format: text
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