104,141 research outputs found
Optimal designs for an interference model
Full text linkKunert and Martin (2000) determined optimal and efficient block designs in a model for field trials with interference effects, for block sizes up to 4. In this paper we use Kushner's method (Kushner, 1997) of finding optimal approximate designs to extend the work of Kunert and Martin (2000) to optimal designs with five or more plots per block. We give an overall upper bound a*t,b,k for the trace of the information matrix of any design and show that an universally optimal approximate design will have all its sequences from merely four different equivalence classes. We further determine the efficiency of a binary type I orthogonal array under the general p-criterion. We find that these designs achieve high efficiencies of more than 0:94. --
GÜNTER KUNERT: UOMO IN MARE
No full textSi tratta del primo studio dedicato specificatamente all'opera in prosa di uno dei protagonisti della letteratura tedesca del secondo Novecento presentandone una vasta scelta in prima traduzione italiana e che ha potuto vedere la luce per mezzo del contributo decisivo del Goethe-Institut (l'ente statale preposto alla diffusione della cultura tedesca nel mondo) e del Dipartimento Sitlec.
Il volume, che contestualizza storicamente e dal punto di vista dei generi letterari la sterminata attività di Kunert (scrittore dalla vicenda paradigmatica per la storia tedesca ed europea dagli anni Trenta fino al nuovo millenio), presenta le tante frecce di cui dispone l'arco della prosa dello scrittore berlinese: dall'omaggio alle 'storie da calendario' sotto forma di parabole ed apologhi, al racconto breve di stampo psicologico, all'elzeviro, fino alle brevissime epifanie aforistiche o epigrammatiche ricavate da quell’immane, inesaurito e inesauribile “work in progress” a cui Kunert attende giorno per giorno e che – lui, un “allegro pessi-mistico” – lo avvicinano per certi versi a un altro grande della letteratura, sempre inopportunatamente citato e sempre scomodo, il nostro Ennio Flaiano. Molti dei brani sono caratterizzati da uno stile lapidario, da una struttura dialettica, dal paradosso, da un crescendo grottesco con un finale spesso appunto aforistico o sentenzioso, in grado di illuminare fulmineamente un dato di fatto o una problematica. Talvolta lo straniamento paradossale scatta in situazioni tratteggiate in modo realistico, così da trasformare nella mente del lettore il noto e il familiare in qualcosa di lugubre e sinistro.
Come segnalato dalle recensioni allegate, la pubblicazione ha contribuito alla "scoperta" nel nostro Paese di un autore imprescindibile. Il volume si presta, inoltre, molto bene ad essere impiegato nella didattica sia dei generi letterari, sia come esemplificazione delle modalità di traduzione di differenti registri stilistici
Dealing with food shortage: larval dispersal behaviour and survival on non-prey food of the hoverfly Episyrphus balteatus
Full text link1. Predatory larvae often have to face food shortages during their development, and thus the ability to disperse and find new feeding sites is crucial for survival. However, the dispersal capacity of predatory larvae, the host finding cues employed, and their use of alternative food sources are largely unknown. These aspects of the foraging behaviour of the aphidophagous hoverfly (Episyrphus balteatus De Geer) larvae were investigated in the present study. 2. It was shown that these hoverfly larvae do not leave a plant as long as there are aphids available, but that dispersing larvae are able to find other aphid colonies in the field. Dispersing hoverfly larvae accumulated on large aphid colonies, but did not distinguish between different pea aphid race–plant species combinations. Large aphid colonies might be easier to detect because of intensified searching by hoverfly larvae following the encounter of aphid cues like honeydew that accumulate around large colonies. 3. It was further shown that non-prey food, such as diluted honey or pollen, was insufficient for hoverfly larvae to gain weight, but prolonged the survival of the larvae compared with unfed individuals. As soon as larvae were switched back to an aphid diet, they rapidly gained weight and some pupated after a few days. Although pupation and adult hatching rates were strongly reduced compared with hoverflies continuously fed with aphids, the consumption of non-prey food most probably increases the probability that hoverfly larvae find an aphid colony and complete their development
Hoverfly preference for high honeydew amounts creates enemy-free space for aphids colonizing novel host plants
No full textThe existence of an enemy-free space can play an important role in aphid host race formation processes, but little is known about the mechanisms that create an area of low predation pressure on particular host plants. In this paper, we identify a mechanism generating lower predation pressure that promotes the maintenance of the different host races of the pea aphid (Acyrthosiphon pisum) complex, a well-studied model for ecological speciation. The pea aphid consists of at least 15 genetically distinct host races which are native to specific host plants of the legume family, but can all develop on the universal host plant Vicia faba. Previous work showed that hoverfly (Episyrphus balteatus) oviposition preferences contribute to the enemy-free space that helps to maintain the different pea aphid host races, and that higher amounts of honeydew are more attractive to ovipositing hoverflies. Here we demonstrated that aphid honeydew is produced in large amounts when aphid reproduction rate was highest, and is an important oviposition cue for hoverflies under field conditions. However, on less suitable host plants, where honeydew production is reduced, pea aphids enjoy lower predation rates. A reduction in enemy pressure can mitigate the performance disadvantages of aphids colonizing a novel host and probably plays an important role in pea aphid host race formation
Is there any evidence that aphid alarm pheromones work as prey and host finding kairomones for natural enemies?
No full textGigahertz pulse source by compression of mode-locked VECSEL pulses coherently broadened in the normal dispersion regime
Full text linkWe report the coherent spectral broadening of the output of a mode-locked VECSEL emitting 455 fs pulses at 1007 nm in the normal-dispersion regime. Subsequent compression of the fiber outputs using a transmission grating compressor produced 1.56 GHz trains of 150 fs pulses at 270 mW average power or 220 fs pulses at 520 mW average power. The system approaches the performance needed for a pump for coherent supercontinuum generation. This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-10-12096. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.</p
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Enemy-free space promotes maintenance of host races in an aphid species
No full textThe enormous biodiversity of herbivorous insects may arise from ecological speciation via continuous host-plant switches. Whether such switches are successful depends on the trade-off between different selection pressures that act on herbivores. Decreased herbivore performance due to suboptimal nutrition might be compensated for by a reduced natural enemy pressure. As a consequence, an "enemy-free space" on a certain plant might facilitate host-plant switches and maintain biotypes. To test this hypothesis, we used the pea aphid (Acyrthosiphon pisum) complex, which consists of at least 11 genetically distinct host races that are native to specific legume host plants but can all develop on the universal host plant Vicia faba. Three A. pisum host races native to Trifolium pratense, Pisum sativum, and Medicago sativa were investigated in experiments on their respective host plants and on the universal host plant V. faba. We found that hoverflies preferred to oviposit on P. sativum and the universal host V. faba. Since feeding by hoverfly larvae suppressed aphid population growth on these host plants, the native hosts M. sativa and T. pratense provided enemy-free space for the respective A. pisum races. Mobile predators, such as ants and ladybird beetles, preferred Pisum race aphids on V. faba over P. sativum. Thus, all three of the native host plants studied supply enemy-free space for A. pisum compared to the universal host V. faba. Reducing encounters between aphid races on V. faba would reduce gene flow among them and could contribute to maintaining the host races
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
On Nearly Balanced Designs for Sensory Trials
Full text linkIn sensory experiments, often designs are used that are balanced for carryover effects. It is hoped that this controls for possible carryover effects, like, e.g., a lingering taste of the products. Proper randomization is essential to guarantee the usual model assumption of independent identically distributed (i.i.d.) errors. We consider a randomization procedure that permutes treatment labels and assessors. This restricted randomization leaves the neighbour structure unchanged and validates the assumption of i.i.d. errors if the design used is a Generalized Youden Design (GYD). However, the use of a neighbour balanced GYD may require too many assessors. The question arises, whether nearly balanced designs may be used without grossly violating the validity of the analysis. We therefore do a simulation study to assess the properties (under this restricted randomization) of nearly balanced designs like, e.g., the ones proposed by Périnel and Pag?s (2004, Food Quality and Preference 15, 439?446). We observe that, if there are no carryover effects, the variance estimates for treatment contrasts are not significantly biased whenever we use designs that are nearly GYD. Additionally, designs that are nearly carryover balanced still produce conservative variance estimates, even in the presence of large carryover effects. In all, ?nearly neighbour balanced nearly GYD? as proposed by Périnel and Pag?s (2004) appear to be useful in experimental situations where the use of GYD is too restrictive. It should be stressed, however, that these results are true only if randomization is used as a protection against effects unaccounted for in the statistical model. --carryover balance,nearly balanced designs,randomization,validity
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