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  • 1
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The respiration of both castes ofFormica polyctena (Foerster) during the larval development was investigated manometrically. The distribution of mitochondria and their structure in the fat body cells were measured simultaneously by electron-microscopy to ascertain if caste-specific differences of the intensity of respiration were recognizable by the content of mitochondria. The following results were obtained: At 20°C larvae of sexuals weighing 1 to 5 mg per individual consumed 860–910 μl O2/g/h, which was double the oxygen amount used by larvae of workers weighing up to 1.5 mg per individual. At the end of the larval development this difference disappeared, with values stabilizing at 410–420 μl O2/g/h. The volume density of mitochondria in 8 mg-sexual larvae was 12.2%, and in 60 mg-larvae or 1.9 mg — and 12.5 mg — worker larvae only 8.2–8.6% of the cytoplasm (without nucleus). The numeric density of the mitochondria was calculated as 840 per mm3 in larvae of 8 mg-sexuals, and in those of 60 mg or in 1.9 mg — and 12,5 mg — worker larvae only as 570–625 per mm3. No caste-specific and stage-dependent differences could be found in the size and microstructure of the mitochondria. An increased respiration was associated with a higher numeric and volume density of the mitochondria.
    Notes: Zusammenfassung Die Atmung wurde während der Larvalentwicklung beider Kasten vonFormica polyctena (Foerster) manometrisch untersucht. Parallel dazu wurde nach elektronenoptischer Präparation die Mitochondrienverteilung und Mitochondrienstruktur in Fettkörperzellen ermittelt, um festzustellen, ob kastenspezifische Unterschiede in der Atmungsintensität auch im Mitochondriengehalt zu erkennen sind. Folgende Resultate wurden erhalten: Geschlechtstierlarven von 1–5 mg/Tier verbrauchten mit 860–910 μl O2/g/h bei 24°C mehr als doppelt so viel Sauerstoff wie Arbeiterinlarven bis 1,5 mg/Tier. Am Ende der Larvalentwicklung war dieser Unterschied bei 410–420 μl O2/g/h ausgeglichen. Die CO2-Abgabe verhielt sich ähnlich. Die Volumendichte der Mitochondrien betrug bei 8 mg-Geschlechtstierlarven 12,2%, bei solchen von 60 mg sowie Arbeiterinlarven von 1,9 mg und 12,5 mg nur 8-2-8,6% des Cytoplasmas (ohne Kern). Die numerische Dichte der Mitochondrien betrug bei 8 mg-Geschlechtstierlarven 840/mm3, bei solchen von 60 mg sowie Arbeiterinlarven von 1,9 mg und 12,5 mg nur 570–625/mm3. In der Größe und Feinstruktur der Mitochondrien konnten keine kastenspezifischen und stadiumabhängigen Unterschiede festgestellt werden. Eine erhöhte Atmungstätigkeit war verbunden mit höherer numerischer und Volumendichte der Mitochondrien.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Insectes sociaux 24 (1977), S. 277-278 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Insectes sociaux 32 (1985), S. 86-95 
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary Queens ofF. polyctena kept with workers in small groups under laboratory conditions laid eggs up to four months. The rate of egg deposition depended on the proportion of queen and workers. At a given size of the growing boxes an optimum was reached at about 100 workers per queen. An increase of the protein content of the artificial standard diet did not noticeably influence the rate of oviposition and the size of the eggs. After a vernalization in the laboratory the queens produced eggs of different sizes as they do after hibernation in the forest nests. But queens kept at constant high room temperature during the whole year laid eggs of similar size only. As in nature after experimental vernalization the queens at first produced big, later on smaller eggs similar to the known w- and s-eggs of the queens of this ant species.
    Notes: Zusammenfassung Königinnen vonF. polyctena, die mit Arbeiterinnen im Laboratorium in kleinen Gruppen gehalten wurden, legten bis über vier Monate hinweg Eier ab. Die Ablagerate wurde vom Verhältnis Königin/Arbeiterinnen beeinflußt. Bei vorgegebener Behältergröße erreichte sie ein Optimum bei ca. 100 Arbeiterinnen pro Königin. Eine Erhöhung des Proteingehaltes der künstlichen Standard-Diät beeinflußte die Eiablagerate und die Eigröße nicht merklich. Im Laboratorium eingewinterte legten wie solche im Winter aus Freilandnestern entnommene Königinnen Eier von unterschiedlicher Größe, während ganzjährig bei konstant hohen Raumtemperaturen gehaltene Königinnen Eier einheitlicher Größe produzierten. Auch nach experimenteller Vernalisation wurden zunächst große, später kleinere Eier abgelegt, die als W- und S-Eier betrachtet werden.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1612-4766
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Prostephanus truncatus (Horn) wurde zu Beginn der 80er Jahre mit Importmais aus tropischen Regionen Amerikas nach West- und Ostafrika eingeschleppt und breitet sich nun unufhaltsam im Gebiet südlich der Sahara aus. Seine Hauptnahrung ist Mais. Er vermehrt sich besonders zahlreich in Maiskolben, in denen der Mais gelagert wird. Da die Populationsdichte anderer Schädlinge mit ätherischen Pflanzenölen oft erfolgreich reduziert werden konnte, wurden Untersuchungen mit Kalmusöl und seinem Hauptbestandteil β-Asaron durchgeführt. Bedampfung der Käfer auf losem Mais und Maiskolben war erfolglos. In einigen Fällen führte die Applikation von Kalmusöldampf sogar zu signifikanter Steigerung des Körnerfraßes und der Reproduktion. Hungernde Käfer wurden dagegen innerhalb von 3 Tagen abgetötet. Kürzere Behandlungszeiten führten zu hoher Sterblichkeit und bei den Überlebenden zu Fraßreduktion und verringerter Reproduktion. Direktbehandlung von Maiskolben konnte eine Besiedlung durch den Schädling nicht verhindern. In die Kolben eingedrungene Tiere vermehrten sich ungehemmt. Dagegen ließ sich Körnermais durch Besprühen mit Kalmusöl gut schützen. Eine Menge von 750 mg Öl pro kg Mais reichte aus, um den Käferfraß auf 5% zu reduzieren.
    Notes: Abstract In the early 1980s,Prostephanus truncatus (Horn) spread out uncontrollably in aras south of the Sahara, having been brought in by imported maize from tropical regions of America. Its main diet is maize; it reproduces at a great rate in stored maize cobs. Attempts were made to control this pest usingAcorus calamus oil and its main ingredient β-asarone, as the use of similar oils has been shown to arrest the development of other insects. Vapourising the maize kernels and cobs was unsuccessful and in some cases led to a significant increase in the destruction of maize and the reproduction of beetles. However vapourisation killed hungry beetles within 3 days; short periods of treatment achieved a high rate of pest destruction, leaving the survivors with a reduced appetite and reproductive rate. Spraying of maize cobs did not prevent infestation; beetles able to infect these cobs reproduced normally. Success was only achieved by spraying maize kernels, usingAcorus calamus oil dosed at 750 mg per kilo maize; damage was then restricted to 5%.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 689-691 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Mouse embryo aggregation chimaeras were prepared at the MRC Laboratories, Carshalton, as described previously4. The mosaic cell populations in the intestinal epithelium of the chimaeras were demonstrated using H-2 antigens4,5 and a carbohydrate polymorphism recognized by Dolichos biflorus ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 332 (1988), S. 482-482 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-The commentary by Beverley Halstead emphasizes the importance of publishing parts of the thesis before the PhD is awarded, a view I fully support. However, the space permitted for a publication often varies between journals, the most contested journals generally requiring the author to be ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 36 (1999), S. 405-414 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Heavy metals present in the soil get differently accumulated in organisms and show different rates of toxicity at different stages of the life cycle of any organism living there. To see whether such toxicants get accumulated during the embryonic development and/or change the normal developmental processes of organisms exposed to heavy metals, freshly laid eggs and egg pods of two acridids, Aiolopus thalassinus and Eyprepocnemis plorans, were tested against different concentrations of Hg2+, Cd2+, and Pb2+. At increasing Hg2+ concentration in the substrate, an increased egg mortality and reduced nymphal hatching in A. thalassinus were observed, yet no change in the normal duration for embryonic development was noticed. A higher hatching rate of E. plorans nymphs than that of A. thalassinus could possibly be due to the higher tolerance, contributed by larger egg volume and thicker foam around the egg pods of the former. Treated concentrations of Hg2+ could be of sublethal (0.121 μg Hg2+/g substrate) to lethal (0.605 μg and more Hg2+/g substrate) doses. The mortality of eggs did not always increase with increasing substrate concentration of Cd2+ and Pb2+, and the hatching rates of both grasshopper species in many cases were even higher than that in the control. Still, lower accumulation factors of Cd2+ and Pb2+ than that of Hg2+ were found coupled with not increased mortality. The tested concentrations of Cd2+ and Pb2+ in the substrates, thus, could be of subacute doses. The embryonic development was found prolonged due to Cd2+ and Pb2+. During parallel egg and egg pod treatments, higher metal concentrations were found in not developed eggs than that in fresh nymphs hatching from the same substrates. This indicated the role of foam around the egg pods as “protective filter” against the toxic substances in the soil.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 80 (1993), S. 379-380 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 29 (1995), S. 473-496 
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract A multigrid method for an elliptic linear boundary value problem is presented. A consistent lowest-order mixed-finite-element discretisation is used on Cartesian locally refined grids in up to three space dimensions. The solution of the indefinite system of equations is reformulated as a problem of constrained minimisation. The constraint is satisfied exactly after one multigrid cycle; the functional is reduced iteratively by smoothing and coarse-grid corrections. By a suitable choice of prolongation and restriction operators, all corrections on coarser levels also reduce the functional within the constraint. This approach leads to a non-standard convergence proof which also holds for the variable-coefficient case. The proof does not predict the actual convergence rate, but shows that the functional will never increase after a multigrid cycle, while the constraint is satisfied exactly after the first multigrid cycle. The conditions required for convergence allow some freedom in choosing the restriction and prolongation operators, which can be used to improve the convergence rate. This leads to operator weighed restriction and prolongation operators in a novel manner. Some numerical examples are presented to demonstrate the robustness of the method.
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