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  • 1
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Wir haben das Zusammenleben von meheren Weibchen in Nestern vonXylocopa suspecta, X. frontalis undX. grisescens, den häufigsten Arten in der Region von Ribeirão Preto, S.P., Brasilien, untersucht. Nahrungssammeln und Fortpflanzung der Weibchen wurde als Maß für das Sozialverhalten gewertet. Die Bildung einer Gemeinschaft begann am Ende des biologischen Zyklus', wenn die Nester erneut benutzt wurden. Zu Beginn bestanden die Gemeinschaften aus der Mutter und ihren Töchtern. Anschließend waren nur die Töchter im Nest, von denen eine, gewöhnlich das älteste Weibchen, Eier legte (erste Phase). Im nächsten Stadium waren zwei oder mehr Weibchen in der Lage, Eier zu legen; sie versorgten gemeinsam dieselben Zellen mit Nahrung und legten Eier. In der dritten Phase legten alle Weibchen Eier, jede versorgte aber ihre eigenen Zellen. Das Sozialverhalten in der ersten Phase wird als semisozial, das Verhalten in der zweiten Phase als quasisozial angesehen. Diese Verhaltensmuster traten jedoch nur vorübergehend auf, denn im letzten Stadium zeigten die Weibchen ein kommunales Sozialverhalten.
    Notes: Summary We have investigated the occurrence of cohabitation of several females in the same nest ofXylocopa suspecta, X. frontalis andX. grisescens which are the most common species in the region of Ribeirão Preto, S.P., Brazil. The study of social behaviour of these species involved, as a general procedure, the identification of each associated female in relation to its foraging and reproductive activity. It was observed that in each species the association of females started at the final phase of the biological cycle, when the reactivation of the nests began. Initially the association was observed to occur among mother and daughters. Subsequently only daughters remained in the nest and in the first phase of this association only one female (generally the eldest), was able to realize oviposition. Next, two ore more females were in the same condition, provisioning and ovipositing in only one cell. In the third phase the females had all the same condition, each one of them provisioning and ovipositing in their own cells. So, in the first and second phases the social behaviour corresponds to the semisocial and quasisocial levels, respectively. Nevertheless, this behaviour was transitory and the final pattern attained was communal.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-9098
    Keywords: Nest re-use ; communal nesting ; nest defense ; Microthurge corumbae ; Megachilidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Observations on the nesting activities ofMicrothurge corumbae, carried out at the University Campus of Ribeirão Preto, São Paulo, Brazil, from 1977 to 1981, indicated that 61.9 % of nests were re-used by succeeding generations. Re-use by one generation was more frequent than by two generations, and re-use by a third was observed only once. Nests were re-used by one or several females. Single females were more frequently in the first re-use. In these cases nest re-use did not differ essentially from the solitary foundation of a new nest, except for the adoption of a pre-existing nest without excavation. In multifemale nests, analysis of relative age (wing wear), ovarian and spermathecal conditions of associated females and the content of nests at excavation indicated that the social pattern in such colonies is communal. There is some evidence that the associated females are relatives. The chalcidoid waspLeucospis was the principal nest parasite, and ants of the genusCrematogaster were nest predators. In multifemale nests, the rate of parasitism was significantly lower than in solitary nests, indicating that nest-sharing resulted in improved nest defense. On the other hand, the absence of predation on immatures of the first generation of M.commbae in multifemale nests suggests that such nests are also more resistant to attack by predators.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2017-03-08
    Description: The purpose of this study is to evaluate the abundance and preservation state of the tests of Hoeglundina elegans , with the goal to propose a new preservation index for deep-sea sediments. In seawater, aragonite is more soluble than calcite; the benthic foraminiferal species H. elegans produces aragonitic tests, thereby providing potential proxies for subtle variations in carbonate preservation. Using two proxies based on H. elegans , as well as three other carbonate-dissolution proxies, we interpret the main drivers of carbonate dissolution in the western South Atlantic Ocean from a core, GL-854 (water depth 2220 m) from the western South Atlantic Ocean, Santos Basin. The H. elegans (〉150 μm) abundance and the HelP Index ( Hoeglundina elegans Preservation Index), based on five test-preservation degrees, were assessed to determine the state of aragonite preservation. Images were taken using SEM to demonstrate each degree of preservation and to observe the ultrastructural breakdown of the tests’ walls. The other parameters determined were planktonic foraminiferal Fragmentation Index (FI), %CaCO 3 and sand fraction (〉63 μm). The H. elegans abundance, HelP Index, and sand fraction correlated positively, and those proxies correlated inversely with the FI. The weakest correlations were between %CaCO 3 , and the other proxies. Subtle differences in proxy responses were consistent with specific stages of carbonate dissolution, ranging from the aragonite lysocline to the Calcite Compensation Depth. The results revealed alternating modes of high and low carbonate preservation throughout the core and the primary driver of carbonate dissolution appeared to be variation in the aragonite saturation state influenced by circulation-induced changes in water masses. The carbonate dissolution observed in specific intervals, probably due to shoaling of the Aragonite Compensation Depth, suggests a mixing zone with more corrosive southern-sourced water and less corrosive northern-sourced water at the depth where the core was located.
    Print ISSN: 0096-1191
    Topics: Geosciences
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  • 4
    Publication Date: 2019-07-13
    Description: A preliminary study on arc-melted samples has indicated that ruthenium silicide has the potential to obtain figure-of-merit values four times higher than that of conventional silicon-germanium material. In order to realize the high figure-of-merit values, high-quality crystal from the melt is needed. A Bridgman-like method has been employed and has realized much better crystals than arc-melted ones.
    Keywords: SOLID-STATE PHYSICS
    Type: IECEC ''91: Intersociety Energy Conversion Engineering Conference; Aug 04, 1991 - Aug 09, 1991; Boston, MA; United States
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  • 5
    Publication Date: 2019-07-12
    Description: Inelastic scattering of laser light found to indicate onset of gas-phase polymerization in plasma-enhanced chemical-vapor deposition (PECVD) of photoconductive amorphous hydrogenated silicon/germanium alloy (a-SiGe:H) film. In PECVD process, film deposited from radio-frequency glow-discharge plasma of silane (SiH4) and germane (GeH4) diluted with hydrogen. Gas-phase polymerization undesirable because it causes formation of particulates and defective films.
    Keywords: PHYSICAL SCIENCES
    Type: NPO-17779 , NASA Tech Briefs (ISSN 0145-319X); 14; 7; P. 47
    Format: text
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