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Search Results: 1 - 10 of 15489 matches for " Christian Peeters "
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Male Biology in the Queenless Ponerine Ant Ophthalmopone Berthoudi (Hymenoptera: Formicidae)
Christian Peeters,Robin Crewe
Psyche , 1986, DOI: 10.1155/1986/90827
Foraging and Recruitment inPonerine Ants: Solitary Hunting inthe Queenless Ophthalmopone Berthoudi(Hymenoptera: Formicidae)
Christian Peeters,Robin Crewe
Psyche , 1987, DOI: 10.1155/1987/74592
Cooperation Between Dealate Queens DuringColony Foundation in the Green Tree Ant,Oecophylla Smaragdina
Christian Peeters,Alan N. Andersen
Psyche , 1989, DOI: 10.1155/1989/12368
Caste and Reproduction in Ants: Not All Mated Egg-Layers are “Queens”
Christian Peeters,Ross H. Crozier
Psyche , 1988, DOI: 10.1155/1988/52368
Notes on the Morphology of the Sticky "Doorknobs" of Larvae in an AustralianHypoponera SP. (Formicidae; Ponerinae)
Christian Peeters,Bert Hölldobler
Psyche , 1992, DOI: 10.1155/1992/96238
Bigger Helpers in the Ant Cataglyphis bombycina: Increased Worker Polymorphism or Novel Soldier Caste?
Mathieu Molet, Vincent Maicher, Christian Peeters
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084929
Abstract: Introduction The mechanisms by which development favors or constrains the evolution of new phenotypes are incompletely understood. Polyphenic species may benefit from developmental plasticity not only regarding ecological advantages, but also potential for evolutionary diversification. For instance, the repeated evolution of novel castes in ants may have been facilitated by the existence of alternative queen and worker castes and their respective developmental programs. Material and Methods Cataglyphis bombycina is exceptional in its genus because winged queens and size-polymorphic workers occur together with bigger individuals having saber-shaped mandibles. We measured seven body parts in more than 150 individuals to perform a morphometric analysis and assess the developmental origin of this novel phenotype. Results Adults with saber-shaped mandibles differ from both workers and queens regarding the size of most body parts. Their relative growth rates are identical to workers for some pairs of body parts, and identical to queens for other pairs of body parts; critical sizes differ in all cases. Conclusions Big individuals are a third caste, i.e. soldiers, not major workers. Novel traits such as elongated mandibles are combined with a mix of queen and worker growth rates. We also reveal the existence of a dimorphism in the queen caste (microgynes and macrogynes). We discuss how novel phenotypes can evolve more readily in the context of an existing polyphenism. Both morphological traits and growth rules from existing queen and worker castes can be recombined, hence mosaic phenotypes are more likely to be viable. In C. bombycina, such a mosaic phenotype appears to function both for defense (saber-shaped mandibles) and fat storage (big abdomen). Recycling of developmental programs may have contributed to the morphological diversity and ecological success of ants.
Selection against Aerial Dispersal in Ants: Two Non-Flying Queen Phenotypes in Pogonomyrmex laticeps
Christian Peeters, Roberto A. Keller, Robert A. Johnson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0047727
Abstract: The South American seed-harvester ant Pogonomyrmex laticeps has dimorphic queens: ergatoid (permanently wingless) and brachypterous (short, non-functional wings). Surveys in western Argentina indicated that colonies near Chilecito, La Rioja Province, produced only ergatoid queens, while those near Punta Balasto, Catamarca Province (263 km away), produced only brachypterous queens. Brachypterous queens were significantly larger than ergatoid queens for 10 of 11 external characters, but both phenotypes had comparable reproductive potential, i.e., a spermatheca and a similar number of ovarioles. Using normal winged queens of the closely related P. uruguayensis for comparison, we determined that both queen phenotypes in P. laticeps had a full set of dorsal thoracic sclerites, albeit each sclerite was much reduced, whereas workers had a thorax without distinct dorsal sclerites. Sclerites were fused and immobile in ergatoid queens, while they were separable and fully articulated in brachypterous queens. Both phenotypes lacked the big indirect flight muscles, but brachypterous queens retained the tiny direct flight muscles. Overall, this dimorphism across populations indicates that there are alternative solutions to selective pressures against flying queens. We lack field data about colony founding strategy (independent or dependent) for either queen phenotype, but colonies at both sites produced numerous gynes, and we infer that all foundresses initiate colonies independently and are obligate foragers.
Measurement of temperature changes during cavitation generated by an erbium, chromium: Yttrium, scandium, gallium garnet laser  [PDF]
Harry Huiz Peeters, Latief Mooduto
Open Journal of Stomatology (OJST) , 2012, DOI: 10.4236/ojst.2012.24050
Abstract: Aim: The present study evaluated the magnitude of temperature changes in the tooth during cavitation produced by an Er,Cr:YSGG laser. Methods: The root canal of a single extracted maxillary canine was enlarged to a size 30/.02 file. Four thermocouples were attached to the tooth: one to the surface of the root and three inserted into the canal at 3, 9, and 15 mm from the apical foramen, respectively. The tooth was placed in a plastic container at room temperature around 25°C. The tooth was processed as follows. In the EDTA condition, the tooth was irrigated with 17% EDTA; in the NaOCl condition, the tooth was irrigated with 3% NaOCl; and to analyse the effect of different thicknesses of dentin, the tooth was irrigated with tap water. In all conditions, the irrigants were activated at 2 W for 120 seconds. Results: The mean temperature was 25.2°C to 27.1°C and the temperature ranged from 25.0°C to 29.6°C. The temperature elevation measured during cavitation generated by the laser didnot exceed 5°C. Conclusions: The magnitude of the temperature changes in the root canal and at the surface of the tooth did not exceed 5°C when laser-driven irrigation was used to produce cavitation in the root canal.
Introducing Cadabra: a symbolic computer algebra system for field theory problems
Peeters, Kasper
High Energy Physics - Phenomenology , 2007,
Abstract: Cadabra is a new computer algebra system designed specifically for the solution of problems encountered in field theory. It has extensive functionality for tensor polynomial simplification taking care of Bianchi and Schouten identities, for fermions and anti-commuting variables, Clifford algebras and Fierz transformations, implicit coordinate dependence, multiple index types and many other field theory related concepts. The input format is a subset of TeX and thus easy to learn. Both a command-line and a graphical interface are available. The present paper is an introduction to the program using several concrete problems from gravity, supergravity and quantum field theory.
a va ? vs How are you ? Remarques ethnophraséologiques
Bert Peeters
Synergies Royaume-Uni et Irlande , 2008,
Abstract: Dans cet article, qui se situe dans le prolongement de deux autres textes publiés au cours de la deuxième moitié des années 90, il est montré, à travers une étude ethnophraséologique (Peeters, 2006a), qu’un examen approfondi des conditions d’usage du a va ? fran ais aussi bien que des réactions qu’il peut susciter permet de postuler une valeur culturelle fran aise (la franchise), dont une étude ethnoaxiologique devra corroborer la réalité. L’approche est contrastive : nous essayons de mieux comprendre le fonctionnement du a va ? fran ais en établissant des comparaisons avec le How ARE ya ? australien, ce qui révèle notamment qu’il y a des différences de fréquence et que la fa on dont on réagit à des énoncés de ce genre n’est pas forcément la même d’une langue à l’autre.
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