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  • 1
    ISSN: 1573-8248
    Keywords: Encarsia pergandiella Howard ; Trialeurodes vaporariorum (Westwood) ; autoparasitoid ; host suitability ; hyperparasite ; Encarsia pergandiella Howard ; Trialeurodes vaporariorum ; Westwood ; autoparasitoïdes ; hyperparasitoîdes ; réceptivité de l'hôte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Les femelles d'Encarsia pergandiella Howard se développent comme parasitoïdes primaires des stades larvaires d'aleurodes, alors que les ♀♀ se développent comme parasitoïdes secondaires de leur propre espèce ou d'autres parasitoïdes primaires des Aleurodes. En laboratoire à 24°C, nous avons étudié le développement des ♀♀ d'E. pergandiella en utilisant comme hôte des jeunes ♂♂ d'E. pergandiella en place à l'intérieur du corps distendu deTrialeurodes vaporariorum (Westwood) à des stades différents. Nous avons séparé les femelles d'E. pergandiella, adultes vierges pendant 24 h en les plaçant chacune sur des feuilles de plantes comportant des hôtes âgés soit de 5 jours (3c stade larvaire avancé), soit de 7 jours (fin de 3c stade à prépupe), soit enfin de 9 jours (pupe). Au cours d'un traitement de contrôle, on a laissé les hôtes se développer sans être exposés à des femelles adultes. L'éclosion des ♂♂ (hôtes) et des ♀♀ résultant de tous les traitements a été enregistrée quotidiennement. On a trouvé que les pupes (9 jours) d'E. pergandiella étaient les hôtes les plus propices au développement des ♀♀. Les hôtes de 9 et 7 jours ont été attaqués à un rythme semblable comme l'indique la faible proportion d'éclosion des hôtes, mais les ♀♀ éclosent plus rapidement dans le traitement de 9 jours que dans celui de 7 jours et ceci d'une manière significative. Le temps de développement des ♀♀ dans le traitement de 9 jours a été de 15±1 jours et de 16±1 dans le traitement de 7 jours (P〈0,005). La proportion d'hôtes éclos dans le traitement de 5 jours n'était pas vraiment différente de celle observée dans le traitement de contrôle. Ces résultats tendent à suggérer que la capacité colonisatrice d'E. pergandiella en serre serait limitée par un délai de 7 à 9 jours entre l'oviposition des œufs femelles et la réceptivité de ces femelles à l'oviposition des œufs mâles. Puisque le temps de développement des 2 sexes est semblable, ce délai devrait provoquer un manque de synchronisation dans l'éclosion et l'accouplement des femelles et des mâles F1.
    Notes: Abstract Encarsia pergandiella Howard females develop as primary parasitoids of immature whiteflies, whereas ♀♀ develop as secondary parasitoids on ♂♂ of their own species or on other primary whitefly parasitoids. In this experiment, maleE. pergandiella development was examined in the laboratory at 24°C, using different stages of immatureE. pergandiella females [enclosed within the cuticle ofTrialeurodes vaporariorum (Westwood)] as hosts. Unmated adult femaleE. pergandiella were caged individually for 24 h on leaves of plants with either 5-day (early to late 3rd instar larval), 7-day (late 3rd instar to prepupal), or 9-day (pupal) hosts. In a control treatment, hosts were allowed to complete development without exposure to unmated adult females. Subsequent emergence of ♂♂ (hosts) and ♀♀ from all treatments was recorded daily. Pupal (9-day)E. pergandiella females were found to be the most suitable hosts for development of ♀♀. Nine- and 7-day hosts were attacked at a similar rate, as indicated by a similarly low proportion of host emergence, but ♀♀ emerged at a significantly higher rate in the 9-day treatment than in the 7-day treatment. Development time of ♀♀ was 15±1 days in the 9-day treatment, and 16±1 days in the 7-day treatment (p〈0.005). The proportion of hosts emerging from the 5-day treatment was not significantly different from the control treatment. The data suggest that the colonizing ability ofE. pergandiella in greenhouses is likely to be limited by the delay of 7–9 days between oviposition of female eggs and the suitability of these ♂♂ for oviposition of male eggs. Since development time of the 2 sexes is similar this delay should cause a lack of synchrony in the emergence and mating of F1 ♂♂ and ♀♀.
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  • 2
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The removal of nitrilotriacetic acid (NTA) following acclimatization in an activated sludge pilot plant has been studied during transient changes in operating conditions. These changes included increases in hydraulic loading and influent chemical oxygen demand (COD) and such phenomena in combination with transient temperature reductions. Short-term increases in hydraulic loading from 1 to 2 dry weather flow (dwf) had a very limited effect on NTA removal. Increasing the influent COD had a slight effect on NTA removal. Short term increases in hydraulic loading combined with transient reductions in temperature significantly reduced NTA removal. The effect of these combined changes on NTA removal was synergistic, rather than additive. Increases in influent COD combined with transient temperature reductions also caused a significant reduction of NTA removal. The effect of such combined changes on NTA removal was at most only additive.
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  • 3
    ISSN: 1572-9958
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract Within the broad context of Singapore's IT2000 Project, an exploratory research project was conducted as part of an on-going program to identify the perceptions of what constitutes the qualities of an “excellent” systems analyst. A grounded theory approach (theory building) was adopted using Kelly's RepGrid technique to conduct interviews with stakeholders in the systems analyst's performance in a large organization based in Singapore. In reviewing the constructs which emerged from the stakeholder interviews, 12 universal Themes were identified, such as Attitude, Knowledge, Communicate, including a number of sub-Themes. Each stakeholder group had its own interpretation of the relative importance of each Theme. These results have implications for the selection, training and development of systems analysts. Suggestions are made for further research to compare the cross-cultural perceptions of “excellent” systems analysts, as well as the testing of specific hypotheses derived from the results of this research project.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1935-1937 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y2O3 has a relatively high dielectric constant (13–17) leading to several potential applications. In this work, pulsed-laser deposition was used to grow epitaxial Y2O3 films on Si(111) substrates. Structural characterization indicated two-dimensional growth without the formation of an amorphous interfacial layer. Annealing in either Ar or O2 was found to induce an O2 diffusion reaction resulting in the formation of two interfacial amorphous layers. Electrical characterization by capacitance–voltage and current–voltage indicated that the as-grown samples were poor insulating films. Annealing the samples improved the electrical performance by lowering leakage currents and exhibiting inversion during capacitance–voltage testing. This epitaxial growth points toward the possibility of the heteroepitaxial growth of silicon on insulator device structures. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 8
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report detailed vibrational, rotational, and electronic (V,R,E) distributions of nascent NO(X 2Π1/2,3/2) deriving from monoenergetic unimolecular reactions of expansion-cooled NO2. Near UV excitation above dissociation threshold (25 130.6 cm−1) prepares molecular eigenstates which are admixtures of the optically active 1 2B2 state and the ground X˜ 2A1 electronic state. The strong mixings among the vibronic states result in vibrational predissociation from states of predominantly ground state character, and the NO product state distributions (PSDs) are compared with the predictions of several statistical theories. The PSDs are combined with previously measured O(3PJ) distributions and unimolecular reaction rates, thereby providing a complete description of the decomposition of NO2 at these excess energies. All the rotational distributions show prominent fluctuations and structures, but tend on average to follow the statistical distributions predicted by phase space theory (PST). This behavior is observed in both NO(v=0) and NO(v=1) channels, although the relative population in NO(v=1) was always greater than expected by PST. The NO(v=1) fractional population is bounded by the predictions of the separate statistical ensembes (SSE) method, and recent variational Rice–Ramsperger–Kassel–Marcus (RRKM) calculations are in agreement with the experimental results. Prior distributions underestimate the degree of vibrational excitation even more than PST does, and also the relative populations of the lower NO rotational levels. The observed NO spin–orbit states are always colder than statistical. We conclude that a significant interplay between dynamical biases and statistical expectations is manifest from the onset of dissociation, and is particularly evident when the initial parent rotational state is well defined.
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  • 9
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 73 (1951), S. 3798-3803 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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