1,181 research outputs found
Basis of the trade off between parasitoid resistance and larval competitive ability in Drosophila melanogaster
No full textDrosophila melanogaster can be artificially selected for increased resistance against parasitoid wasps that attack the larvae. Lines selected for greater resistance are poorer larval competitors under conditions of resource scarcity. Here we investigated the mechanistic basis of this apparent trade-off. We found that resistant lines have approximately twice the density of haemocytes (blood cells) than that of controls. Haemocytes are involved in encapsulation, the chief cellular immune defence against parasitoids. We have previously shown that resistant lines feed more slowly than controls and hypothesize that limiting resources are being switched from trophic to defensive functions
Costs of counterdefenses to host resistance in a parasitoid of Drosophila
No full textAbstractThe ability of a parasitoid to evolve enhanced counterdefenses against host resistance and its possible costs were studied in a Drosophila-parasitoid system. We reared Asobara tabida (Braconidae, Hymenoptera) exclusively on D. melanogaster to impose artificial selection for improved counterdefenses against cellular encapsulation, the main host defense against parasitism. Controls were reared on D. subobscura, the main host of the population of wasps from which the laboratory culture was derived and a species that never encapsulates parasitoids. We observed improved survival and avoidance of encapsulation in all five selection lines compared to their paired control lines, although there was unexpected variation among pairs. Improved survival was associated with parasitoid eggs becoming embedded in host tissue, where they were protected from circulating haemocytes. There were no differences among lines in average adult size, fat content, egg load, or performance on D. subobscura. However, the duration of the egg stage in selection lines was longer than that of control lines, probably because of reduced nutrient and/or oxygen supply when eggs are embedded in host tissue. We suggest that this delay in hatching reduces the probability of parasitoid survival if another parasitoid egg is laid in the same host (superparasitism or multiparasitism) and hence is a cost of enhanced counterdefenses against host resistance.<br/
Afropean Journeys: A Conversation with E.C. Osondu
No full textNigeria-born and US resident author E.C. Osondu debuted with the short story collection Voice of America (2010), followed by the novel This House is Not for Sale (2015) and Alien Stories (2020). His latest novel, When the Sky is Ready the Stars Will Appear, the compelling tale of an African boy’s journey towards Rome in search of a better life, was first published in translation in Italy with the title Quando il cielo vuole spuntano le stelle (2020). Only one year later, the original version of the novel was published in Nigeria. This piece, based on a conversation with the author within the context of the “Afropean Bridges” 2021 Series, introduces E.C. Osondu and his works to the Italian audience
Ships Observing Marine Climate: a catalogue of the VOS participating in the VSOP-NA
No full textOur present knowledge of the marine climate, as represented by data sets such as COADS (Woodruff et al., 1987), is based on meteorological observations from the Voluntary Observing Ships (VOS). Because the VOS are merchant ships, rather than specially designed meteorological platforms, errors and biases exist in the data. However there is little information readily available to the climatologist either on the nature of the VOS fleet or on the observing practises which are used. This report, describing the forty-six ships that participated in the Voluntary Observing Ships' Special Observing Project - North Atlantic (VSOP-NA), therefore serves two purposes:(i) it provides a reference document to aid analysis of the VSOP-NA data set,(ii) it gives a detailed description of a subset of the VOS, which will be of value in the interpretation of marine climate data sets.This report is in two parts, Part 1 is an overall summary of the ship characteristics, Part 2 is a ship by ship description. The next section will briefly describe the VSOP-NA project, followed by a summary of the characteristics of the VSOP-NA ships (Section 3). Since these ships were specially selected (Section 2.2), the degree to which they are representative of the whole VOS fleet will be carefully considered. The meteorological instrumentation used by the VOS varies depending on which meteorological agency recruited the ships. That used on the chosen VSOP-NA ships is typical of VOS recruited by the countries bordering the North Atlantic, and will be described in Section 4. Section 5 is a summary of Part 1 of the report.Part 2 presents the VSOP-NA ship catalogue. This includes, for each ship, diagrams of the layout (indicating in particular the exposure of the sensors), a summary of the geographical positions at which observations were obtained, and details of the instrumentation used.<br/
Services in Europe: a policy for the '90s. Europe: Magazine of the European Community No. 263, January-February 1987
No full textA comparison of data-driven internal multiple elimination strategies and their consequences for imaging
No full textWe compare two data-driven internal multiple reflection elimination schemes derived from regular Marchenko equations and Inverse Scattering Series (ISS). The scheme derived from regular Marchenko equations creates a new data set without internal multiple reflections. The scheme derived from ISS is equal to the result after the second iteration of the Marchenko-based scheme. It can attenuate internal multiple reflections with residuals. We evaluate the success of two schemes with a 2D complex numerical example. It is shown that Marchenko-based data-driven scheme is relatively more robust for internal multiple reflection elimination.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic
Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)
No full textThe two main texts of the transmission lines of the treaty of Tudmīr (94 H/713 e.C. ), included by al- ‘Uḏrī and al-Ḍabbī in their respective works, are edited and translated on the basis of an new reading of the manuscripts that contain them, and after that, we reach some conclusions about its process of copy. There are compared the two texts, and are listed its textual differences. As conclusion, we propose that Al- ‘Uḏrī’s text is the oldest, because its author has copied them from the original document of the 8th. c. (or a copy transfer of this). The transmission of al-Ḍabbī is more recent and it was based in an oral transmission of the text.Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)Los dos textos principales de las líneas de transmisión del tratado de Tudmīr (94 H/713 e.C.), incluidos por al-‘Uḏrī y al-Ḍabbī en sus respectivas obras, son editados y traducidos en base a la relectura de los manuscritos que los contienen y de ello se extraen una serie de conclusiones sobre su proceso de copia. Luego son comparados los dos textos entre sí y se enumeran una serie de diferencias textuales. Finalmente, como hipótesis interpretativa se propone que el texto de al-‘Uḏrī es el más antiguo, y habría sido copiado de un traslado del original por su autor, mientras que la transmisión de al-Ḍabbī habría sido más reciente y se habría fundado en otra fuente más antigua que habría puesto por escrito un relato oral del texto
A study of phytochrome, its isolation, structure and photochemical transformations
No full textApplied Science
Cosmos: a sketch of a physical description of the universe
No full textRetrieved from "Biodiversity Heritage Library" Translated from the German by E.C. Otte. New York: Harper & Brothers - 1877 TRANSLATOR'S PREFACE I CAN not more appropriately introduce the Cosmos than by presenting a brief sketch of the life of its illustrious author.* While the name of Alexander von Humboldt is familiar to every one, few, perhaps, are aware of the peculiar circumstances of his scientific career and of the extent of his labors in almost every department of physical knowledge. He was born on the 14th'' of September, 1769, and is, therefore, now in his 80 th year. After going through the ordinary course of education at Gottingen, and having made a rapid tour through Holland, England; and France, he became a pupil of Werner at the mining school of Freyburg, and in his 21st year published an "Essay on the Basalts of the Rhine." Though he soon became officially connected with the mining corps, he was enabled to continue his excursions in foreign countries, for, during the six or seven years succeeding the publication of his first essay, he seems to have visited Austria, Switzerland, Italy, and France. His attention to mining did not, however, prevent him from devotmg his attention to other scientific pursuits, among which botany and the then recent discovery of galvanism may be especially noticed. Botany, indeed, we know from his own authority, occupied him almost exclusively for some years ; but even at this time he was practicing the use of those astronomical and physical instruments which he afterward turned to so singularly excellent an account
- …
