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  • Populus deltoides  (3)
  • SPACECRAFT PROPULSION AND POWER  (2)
  • cable analysis  (2)
  • 1990-1994
  • 1985-1989  (7)
  • 1940-1944
  • 1988  (7)
Collection
Keywords
Publisher
Years
  • 1990-1994
  • 1985-1989  (7)
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    Leaf disc size and insect feeding preference: implications for assays and studies on induction of plant defense (1988)
    Springer
    Entomologia experimentalis et applicata 47 (1988), S. 167-172 
    Details
    ISSN: 1570-7458
    Keywords: feeding behavior ; leaf center or edge feeders ; chemical signals ; trial design ; Plagiodera versicolora ; Populus deltoides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Plagiodera versicolora Laich (Coléo., Chrysomelidae) a préféré significativement consommer les grandes rondelles (diamètre 17 mm) de Populus deltoides préalablement exposées à l'ozone ambiant, aux témoins exposés à de l'air filtré sur charbon de bois. Cependant, quand le diamètre a été réduit à 10 mm, les insectes n'ont plus préféré les feuilles soumises à l'ozone. Les préférences alimentaires de cet insecte consommant le centre des feuilles ont probablement changé parceque les signaux chimiques de la coupure ont surpassé ou masqué ceux des petits disques. Ainsi, le rapport périmètre sur surface du disque est un critère important de la procédure expérimentale. L'influence de la taille du disque dépend vraisemblablement du fait que l'insecte consomme le centre ou la pourtour de la feuille, de la taille de l'insecte et du type d'expérience. Nous en avons déduit que l'effet de la taille du disque est fréquent particulièrement chez les insectes consommant le centre des feuilles. Les modificatons du choix des insectes lorsque les plantes avaient été présentées sous forme de rondelles au lieu de feuilles ou plantes entières, peuvent être expliqués aussi par le changement des signaux provoqué par le découpage des rondelles, plutôt que par l'induction de modifications chimiques dues à la cueillette, comme cela a été précédemment indiqué par différents auteurs. Par ailleurs, dans les conditions naturelles, des changements dans les signaux chimiques des feuilles dus à une consommation antérieure par des insectes, peuvent être aussi importants dans le comportement alimentaire des insectes que n'importe quel changement chimique induit dans les feuilles par les dégâts.
    Notes: Abstract The size of cottonwood (Populus deltoides L. Bartr.) leaf discs used in insect feeding preference trials with the chrysomelid beetle, Plagiodera versicoloraLaich., was shown to affect behavior, and the outcome of the feeding trial. It is suggested that disc size has an effect because it alters the ratio of chemical signals from the cut leaf edge to those of the intact leaf center. The implications of this finding to the design of bioassays; to previously noted differences in feeding behavior for insects on discs versus leaves; and to the study of feeding preference and induction of plant defense are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367483
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Plant stress and insect performance: cottonwood, ozone and a leaf beetle (1988)
    Springer
    Oecologia 76 (1988), S. 57-61 
    Details
    ISSN: 1432-1939
    Keywords: Plagiodera versicolora ; Plant stress ; Populus deltoides ; Ozone effects ; Insect fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf area consumption rates, development rates, survivorship, and fecundity of the imported willow leaf beetle (Plagiodera versicolora Laich) were examined on two clones of eastern cottonwood which were previously exposed to ozone or charcoal-filtered air. P. versicolora consumed more ozone treated foliage, but were more fecund when reared on charcoal-filtered air treated plants. Beetle development rates and survivorship were not significantly different on treated and control cottonwoods. We concluded that: 1) Ozone fumigation of cottonwood reduced foliage quality, and the reproductive success and overall performance of P. versicolora. 2) increased foliage consumption by beetles was probably a mechanism compensating for decreases in foliage quality. 3) Reductions in beetle fecundity were due to an initial reduction in oviposition rates. 4) Beetle feeding preference did not correlate with the suitability of foliage for beetle performance. These results are discussed in relation to the impact of air pollution on plant-insect interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379600
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  • 3
    Electronic Resource
    Electronic Resource
    Plant stress and insect behavior: cottonwood, ozone and the feeding and oviposition preference of a beetle (1988)
    Springer
    Oecologia 76 (1988), S. 51-56 
    Details
    ISSN: 1432-1939
    Keywords: Plagiodera versicolora ; Populus deltoides ; Clones ; Damage distribution ; Community structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Adults and larvae of the beetle Plagiodera versicolora preferred to feed on and consumed more of cottonwood, Populus deltoides, plant material that had been previously exposed to an acute dose of ozone (0.20 ppm, 5 h), compared to controls in choice experiments. However, females preferred to oviposit on the unexposed controls. Results were consistent for 2 cottonwood clones over 3 years in disc, leaf and whole-plant choice tests. The differential feeding and oviposition response of this insect to stressed plants could have at least 3 unexpected consequences: 1. An immediate increase in damage to stressed trees, but a subsequent decrease in damage. 2. A subsequent increase in damage to unstressed adjacent trees. 3. Changes in the insect and pathogen communities of both stressed and unstressed trees. These complex scenarios show that predicting outcomes of plant stress on plant-insect interactions will require comprchensive examination of behavioral, growth and reproductive responses of insects to stressed plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379599
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  • 4
    Electronic Resource
    Electronic Resource
    Voltage- and time dependence of apical membrane conductance during current clamp inNecturus gallbladder epithelium (1988)
    Springer
    The journal of membrane biology 103 (1988), S. 191-204 
    Details
    ISSN: 1432-1424
    Keywords: voltage-dependent K+ channel ; TEA+ ; barium ; circuit analysis ; cable analysis ; current-voltage relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of short (1 sec) and long (1 min) transepithelial current clamps on membrane voltages and resistances ofNecturus gallbladder were investigated. Transepithelial and cell membrane current-voltage relationships determined from 1-sec clamps revealed that: a) depolarization of the apical membrane voltage (V mc) results in a marked decrease in apical membrane fractional resistance (fR a), whereas hyperpolarization ofV mc results in either no change infR a or a small increase, and b) the voltage-dependent changes infR a are essentially complete within 500 msec. Exposure of the tissue to 5mm TEA+ on the mucosal side caused no significant change in baselineV mc (−69±2 mV) and yet virtually abolished the voltage dependence offR a. A possible interpretation of these results is that two types of K+ channels exist in the apical membrane, with different voltage dependencies and TEA+ sensitivities. Acidification or Ba2+ addition to the mucosal solution also reduced the voltage-dependent changes infR a. The time courses of the changes infR a and in the cable properties of the epithelium were assessed during 1-min transepithelial current clamps (±200 μA/cm2). No secondary change infR a was observed with mucosa-to-serosa currents, but a slow TEA+-sensitive decrease infR a (half-time of seconds) was evident with serosa-to-mucosa currents. Cable analysis experiments demonstrated that the initial (〈500 msec) voltage-dependent decrease infR a is due to a fall in apical membrane resistance. The later decrease infR a is due to changes in both cell membrane resistances attributable to the increase in transcellular current flow resulting from a fall in paracellular conductance. The voltage dependence of the apical membrane conductance is a more significant problem in estimatingfR a than the current-induced effects on the lateral intercellular spaces. In principle, TEA+ can be used to prevent the nonlinear behavior ofR a during measurements of the voltage divider or membrane resistance ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870949
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  • 5
    Electronic Resource
    Electronic Resource
    Dependence of cell membrane conductances on bathing solution HCO 3 − /CO2 inNecturus gallbladder (1988)
    Springer
    The journal of membrane biology 102 (1988), S. 163-174 
    Details
    ISSN: 1432-1424
    Keywords: chloride transport ; equivalent circuit ; cable analysis ; fluid transport ; ouffers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effects of bathing solution HCO 3 − /CO2 concentrations on baseline cell membrane voltages and resistances were measured inNecturus gallbladder epithelium with conventional intracellular microelectrode techniques. Gallbladders were bathed in either low HCO 3 − /CO2 Ringer's solutions (2.4mm HCO 3 − /air or 1mm HEPES/air) or a high HCO 3 − /CO2 Ringer's (10mm HCO 3 − /1% CO2). The principal finding of these studies was that the apical membrane fractional resistance (fR a) was higher in tissues bathed in the 10mm HCO 3 − /CO2 Ringer's, averaging 0.87±0.06, whereasfR a averaged 0.63±0.07 and 0.48±0.08 in 2.4mm HCO 3 − and 1mm HEPES, respectively. Intraepithelial cable analysis was employed to obtain estimates of the individual apical (R a) and basolateral membrane (R b) resistances in tissues bathed in 10mm HCO 3 − /1% CO2 Ringer's. Compared to previous resistance measurements obtained in tissues bathed in a low HCO 3 − /CO2 Ringer's, the higher value offR a was found to be due to both an increase inR a and a decrease inR b. The higher values offR a and lower values ofR b confirm the recent observations of others. To ascertain the pathways responsible for these effects, cell membrane voltages were measured during serosal solution K+ and Cl− substitutions. The results of these studies suggest that an electrodiffusive Cl− transport mechanism exists at the basolateral membrane of tissues bathed in a 10mm HCO 3 − /1% CO2 Ringer's, which can explain in part the fall inR b. The above observations are discussed in terms of a stimulatory effect of solution [HCO 3 − /PCO2 on transepithelial fluid transport, which results in adaptive changes in the conductive properties of the apical and basolateral membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870454
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  • 6
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    Performance and lifetime assessment of MPD arc thruster technology (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A summary of performance and lifetime characteristics of pulsed and steady-state magnetoplasmadynamic (MPD) thrusters is presented. The technical focus is on cargo vehicle propulsion for exploration-class missions to the Moon and Mars. Relatively high MPD thruster efficiencies of 0.43 and 0.69 have been reported at about 5000 s specific impulse using hydrogen and lithium, respectively. Efficiencies of 0.10 to 0.35 in the 1000 to 4500 s specific impulse range have been obtained with other propellants (e.g., Ar, NH3, N2). Thermal efficiency data in excess of 0.80 at MW power levels using pulsed thrusters indicate the potential of high MPD thruster performance. Extended tests of pulsed and steady-state MPD thrusters yield total impulses at least two to three orders of magnitude below that necessary for cargo vehicle propulsion. Performance tests and diagnostics for life-limiting mechanisms of megawatt-class thrusters will require high fidelity test stands which handle in excess of 10 kA and a vacuum facility whose operational pressure is less than 3 x 10 to the -4 torr.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-101293 , E-4274 , NAS 1.15:101293 , AIAA PAPER 88-3211
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Performance and lifetime assessment of MPD arc thruster technology (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A summary of performance and lifetime characteristics of pulsed and steady-state magnetoplasmadynamic (MPD) thrusters is presented. The technical focus is on cargo vehicle propulsion for exploration-class missions to the Moon and Mars. Relatively high MPD thruster efficiencies of 0.43 and 0.69 have been reported at about 5000 s specific impulse using hydrogen and lithium, respectively. Efficiencies of 0.10 to 0.35 in the 1000 to 4500 s specific impulse range have been obtained with other propellants (e.g., Ar, NH3, N2). Thermal efficiency data in excess of 0.80 at MW power levels using pulsed thrusters indicate the potential of high MPD thruster performance. Extended tests of pulsed and steady-state MPD thrusters yield total impulses at least two to three orders of magnitude below that necessary for cargo vehicle propulsion. Performance tests and diagnostics for life-limiting mechanisms of megawatt-class thrusters will require high fidelity test stands which handle in excess of 10 kA and a vacuum facility whose operational pressure is less than 3 x 10 to the -4 torr.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 88-3211
    Format: text
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    NASA TECHNICAL REPORTS
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