Evolutionary lability of a complex life cycle in the aphid genus Brachycaudus

<p>Abstract</p> <p>Background</p> <p>Most aphid species complete their life cycle on the same set of host-plant species, but some (heteroecious species) alternate between different hosts, migrating from primary (woody) to secondary (herbaceous) host plants. The evolutionary processes behind the evolution of this complex life cycle have often been debated. One widely accepted scenario is that heteroecy evolved from monoecy on woody host plants. Several shifts towards monoecy on herbaceous plants have subsequently occurred and resulted in the radiation of aphids. Host alternation would have persisted in some cases due to developmental constraints preventing aphids from shifting their entire life cycle to herbaceous hosts (which are thought to be more favourable). According to this scenario, if aphids lose their primary host during evolution they should not regain it. The genus <it>Brachycaudus </it>includes species with all the types of life cycle (monoecy on woody plants, heteroecy, monoecy on herbs). We used this genus to test hypotheses concerning the evolution of life cycles in aphids.</p> <p>Results</p> <p>Phylogenetic investigation and character reconstruction suggest that life cycle is evolutionary labile in the genus. Though ancestral character states can be ambiguous depending on optimization methods, all analyses suggest that transitions from monoecy on herbs towards heteroecy have occurred several times. Transitions from heteroecy towards monoecy, are also likely. There have been many shifts in feeding behaviour but we found no significant correlation between life cycle changes and changes in diet.</p> <p>Conclusions</p> <p>The transitions from monoecy on herbs towards heteroecy observed in this study go against a widely accepted evolutionary scenario: aphids in the genus <it>Brachycaudus </it>seem to be able to recapture their supposedly ancestral woody host. This suggests that the determinants of host alternation are probably not as complicated as previously thought. Definitive proofs of the lability of life cycle in <it>Brachycaudus </it>will necessitate investigation of these determinants. Life cycle changes, whether corresponding to the loss or acquisition of a primary host, necessarily promote speciation, by inducing shifts of the reproductive phase on different plants. We suggest that the evolutionary lability of life cycle may have driven speciation events in the <it>Brachycaudus </it>genus.</p

Notes sur quelques pâturages camélins et la cure de sel dans l'Adrar des Iforas et la région de Tombouctou

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Remembering turbulent times: accounting for Adult ADHD through the reconstruction of childhood.

This thesis explores the diagnosis of ADHD among adults in the UK. The condition has only recently been defined as a lifelong disorder and extended from childhood to adulthood. Through ethnographic research in a specialist psychiatric clinic and with a patient organisation, this thesis traces the diagnostic process as it takes place in both sites and also between them. It highlights the role of memory practices in the many versions of ADHD that circulate. I outline clinical and lay practices of identifying ADHD. Individuals in the support groups identified with the diagnosis through recognising themselves in other people, as if in a mirror, which I describe as ‘moments of recognition’. In the clinic, the elicitation of medical histories brought contrasting memory practices to the fore, as patients sought evidence from their childhood necessary to a formal diagnosis. Although these memory practices appear distinct, they are combined in practice. This fieldwork led me to concentrate less on the potentially negative medicalisation of human experiences, the main topic of social science research in the field, than the ways in which memory practices were mobilised. These practices were key to the production of evidence-based diagnosis in the clinic and to collective archives in the support groups. Moreover, both types of memory practices informed wider relations. Thus, I explore unexpected ways of making kin such as the manner in which children, more commonly diagnosed with ADHD than adults, ‘made’ their parents in the light of a shared condition. Furthermore, concepts of neurobiology led some research participants to recognise strangers as ‘family’, linked by a common factor and celebrated as neurodiversity. This thesis attends not only to the emerging and mostly unexamined lived experiences of adults with ADHD, but it also contributes to an anthropological exploration of social and caring practices more broadly

Estudios sobre las maderas su explotación, clasificación, etc.

Según PALAU, VII, 125169 fechado en 185

Méthodologie pour la génération d'opérations d'ébauche 5 axes

International audiencela définition des opérations d'ébauche de formes complexes est un élément clé pour l'amélioration du processus de fabrication des pièces. Ces opérations doivent maximiser le débit de matière retiré et réduire le temps global de fabrication en supprimant les reprises d'ébauches avant les opérations de finition. Dans ce contexte, le recours aux opérations 5 axes permet d'améliorer l'accessibilité de l'outil dans des zones en contre-dépouille, minimisant ainsi le volume de matière restant. Nous proposons donc une étude de différentes techniques de génération des trajectoires d'ébauche en fraisage 5 axes de pièces complexes de l'industrie aéronautique afin d'établir une optimisation des stratégies pour ce type d'opération. Ayant défini l'ébauche comme le balayage d'un volume de matière à retirer de la pièce, une première étape consiste à extraire ce volume à partir de la géométrie des pièces brutes et finies. Chacune des faces du volume extrait est alors analysée puis classée selon qu'elle permette l'accessibilité de l'outil sans collisions ou non. L'étape suivante aborde le partitionnement du volume extrait en sous-volumes afin d'évaluer la stratégie de balayage utilisée. Ce découpage s'appuie sur des surfaces telles que des offsets des bords du volume et des surfaces canoniques (plans, cylindres, etc.) générées par les mouvements articulaires. La dernière étape analyse alors les techniques de balayage d'un sous-volume en intégrant l'accessibilité des faces par l'outil et ainsi définir la solution adaptée en se basant sur des critères tels que le volume restant, la longueur de la trajectoire d'ébauche ou le débit de copeau. Mots clés : usinage 5 axes, ébauche, partitionnement de volume, génération de trajectoires

Time-domain Compressed Sensing

Ultrashort time-domain spectroscopy, particularly field-resolved spectroscopy, are established methods for identifying the constituents and internal dynamics of samples. However, these techniques are often encumbered by the Nyquist criterion, leading to prolonged data acquisition and processing times as well as sizable data volumes. To mitigate these issues, we have successfully implemented the first instance of time-domain compressed sensing, enabling us to pinpoint the primary absorption peaks of atmospheric water vapor in response to tera-hertz light transients that exceed the Nyquist limit. Our method demonstrates successful identification of water absorption peaks up to 2.5 THz, even for sampling rates where the Nyquist frequency is as low as 0.75 THz, with a mean squared error of 12*10-4. Time-domain sparse sampling achieves considerable data compression while also expediting both the measurement and data processing time, representing a significant stride towards the realm of real-time spectroscop

Ability to gall: The ultimate basis of host specificity in fig wasps?

1. Fig trees (Ficus spp.) and their host-specific pollinator fig wasps (Agaonidae) are partners in an obligate mutualism. Receptive phase figs release specific volatiles to attract their pollinators, and this is generally effective in preventing pollinator species from entering figs of the wrong hosts. 2. If entry is attempted into atypical host figs, then ostiole size and shape and style length may also prevent reproduction. In spite of these barriers, there is increasing evidence that fig wasps enter atypical hosts, and that this can result in hybrid seed and fig wasp offspring. 3. This study examines the basis of pollinator specificity in two dioecious fig species from different geographical areas. Kradibia tentacularis pollinates Ficus montana in Asia. Ficus asperifolia from East Africa is closely related but is pollinated by a different species of Kradibia. 4. In glasshouses, K. tentacularis was attracted to its normal host, F1s and backcrosses, but only rarely entered figs of F. asperifolia. Foundresses were able to lay eggs in hybrids, backcrosses, and F. asperifolia, although flower occupancy was lowest in F. asperifolia figs and intermediate in hybrids. 5. The fig wasp failed to reproduce in female F. montana, male F. asperifolia, and male F1s, and most but not all backcrosses to F. montana. This was a result of the failure to initiate gall production. 6. Host specificity in this fig wasp is strongly influenced by host volatiles, but the ability to gall may be the ultimate determinant of whether it can reproduce