1,143 research outputs found

    Synthesis of a [2]rotaxane through first- and second-sphere coordination

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    In an effort to expand the application of a new template from interpenetrated to interlocked molecular species, we report the synthesis of a new [2]rotaxane by means of both first- and second-sphere coordination of a palladium(II) dichloride subunit

    Discovery-dominance trade-off among widespread invasive ant species.

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    Ants are among the most problematic invasive species. They displace numerous native species, alter ecosystem processes, and can have negative impacts on agriculture and human health. In part, their success might stem from a departure from the discovery-dominance trade-off that can promote co-existence in native ant communities, that is, invasive ants are thought to be at the same time behaviorally dominant and faster discoverers of resources, compared to native species. However, it has not yet been tested whether similar asymmetries in behavioral dominance, exploration, and recruitment abilities also exist among invasive species. Here, we establish a dominance hierarchy among four of the most problematic invasive ants (Linepithema humile, Lasius neglectus, Wasmannia auropunctata, Pheidole megacephala) that may be able to arrive and establish in the same areas in the future. To assess behavioral dominance, we used confrontation experiments, testing the aggressiveness in individual and group interactions between all species pairs. In addition, to compare discovery efficiency, we tested the species' capacity to locate a food resource in a maze, and the capacity to recruit nestmates to exploit a food resource. The four species differed greatly in their capacity to discover resources and to recruit nestmates and to dominate the other species. Our results are consistent with a discovery-dominance trade-off. The species that showed the highest level of interspecific aggressiveness and dominance during dyadic interactions

    Intrinsic and extrinsic factors drive ontogeny of early-life at-sea behaviour in a marine top predator

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    Young animals must learn to forage effectively to survive the transition from parental provisioning to independent feeding. Rapid development of successful foraging strategies is particularly important for capital breeders that do not receive parental guidance after weaning. The intrinsic and extrinsic drivers of variation in ontogeny of foraging are poorly understood for many species. Grey seals (Halichoerus grypus) are typical capital breeders; pups are abandoned on the natal site after a brief suckling phase, and must develop foraging skills without external input. We collected location and dive data from recently-weaned grey seal pups from two regions of the United Kingdom (the North Sea and the Celtic and Irish Seas) using animal-borne telemetry devices during their first months of independence at sea. Dive duration, depth, bottom time, and benthic diving increased over the first 40 days. The shape and magnitude of changes differed between regions. Females consistently had longer bottom times, and in the Celtic and Irish Seas they used shallower water than males. Regional sex differences suggest that extrinsic factors, such as water depth, contribute to behavioural sexual segregation. We recommend that conservation strategies consider movements of young naïve animals in addition to those of adults to account for developmental behavioural changes

    Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Current and advanced act control system definition study. Volume 2: Appendices

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    The current status of the Active Controls Technology (ACT) for the advanced subsonic transport project is investigated through analysis of the systems technical data. Control systems technologies under examination include computerized reliability analysis, pitch axis fly by wire actuator, flaperon actuation system design trade study, control law synthesis and analysis, flutter mode control and gust load alleviation analysis, and implementation of alternative ACT systems. Extensive analysis of the computer techniques involved in each system is included

    Screening disability insurance applications

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    This paper investigates the effects of stricter screening of disability insurance applications. A large-scale experiment was setup where in two of the 26 Dutch regions case workers of the disability insurance administration were instructed to screen applications more stringently. The empirical results show that stricter screening reduces long-term sickness absenteeism and disability insurance applications. We find evidence for direct effects of stricter screening on work resumption during the period of sickness absence and for self-screening by potential disability insurance applicants. Stricter screening seems to improve targeting efficiency, without inducing negative spillover effects to the inflow into unemployment insurance. The costs of stricter screening are only a small fraction of the monetary benefits.Disability insurance; experiment; policy evaluation; sickness absenteeism; self-screening

    Epidermal Mosaicism and Blaschko\u27s Lines

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    To test the hypothesis that epidermal rather than dermal mosaicism determines Blaschko\u27s lines in hypomelanosis of Ito (HI), we studied the distribution of chromosomal mosaicism in four patients. In two, mosaicism had not been detected in lymphocytes or dermal fibroblasts, but was clearly shown in epidermal keratinocytes; furthermore, the abnormal cell line was confirmed to the hypopigmented epidermis and the normal epidermis contained only normal cells. Negative findings in the other two patients might be because of mosaicism which was undetected either because it was submicroscopic or because it was present in melanocytes, which have not yet been studied. These preliminary results support the ideas that (1) Blaschko\u27s lines represent single clones of epidermal cells; (2) in patients with HI and severe neurological involvement mosaicism, if detectable, is best shown in keratinocytes; and (3) the cytogenetic defect in epidermal cells may be directly responsible for the failure of pigmentation in HI

    Variation in the level of aggression, chemical and genetic distance among three supercolonies of the Argentine ant in Europe.

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    In their invasive ranges, Argentine ant populations often form one geographically vast supercolony, genetically and chemically uniform within which there is no intraspecific aggression. Here we present regional patterns of intraspecific aggression, cuticular hydrocarbons (CHCs) and population genetics of 18 nesting sites across Corsica and the French mainland. Aggression tests confirm the presence of a third European supercolony, the Corsican supercolony, which exhibits moderate to high levels of aggression, depending on nesting sites, with the Main supercolony, and invariably high levels of aggression with the Catalonian supercolony. The chemical analyses corroborated the behavioural data, with workers of the Corsican supercolony showing moderate differences in CHCs compared to workers of the European Main supercolony and strong differences compared to workers of the Catalonian supercolony. Interestingly, there were also clear genetic differences between workers of the Catalonian supercolony and the two other supercolonies at both nuclear and mitochondrial markers, but only very weak genetic differentiation between nesting sites of the Corsican and Main supercolonies (F(ST) = 0.06). A detailed comparison of the genetic composition of supercolonies also revealed that, if one of the last two supercolonies derived from the other, it is the Main supercolony that derived from the Corsican supercolony rather than the reverse. Overall, these findings highlight the importance of conducting more qualitative and quantitative analyses of the level of aggression between supercolonies, which has to be correlated with genetic and chemical data

    Potential novel habitat created by holdfasts from cultivated Laminaria digitata : assessing the macroinvertebrate assemblages

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    A.M.W. is currently funded by the Dr. Tony Ryan Research Trust, NUI Galway.Interest in the cultivation of native kelp species is increasing within Europe. Observations of seaweed farms suggest that they may act as a habitat for associated species, potentially altering the richness of the local area. Previous studies have generally focused on species associated with wild kelps, showing the holdfast to be relatively species-rich. Little research has, however, been conducted on the species associated with cultivated kelps. The habitat created by cultivated kelp holdfasts may act as a novel habitat and not simply an expansion of existing kelp habitat, due to differences in holdfast age, holdfast morphology and holdfast position in the water column. Laminaria digitata from the west of Ireland were examined to test if these differences result in the fauna of cultivated (suspended) holdfasts being distinct from wild (benthic) stands. To place the results in a broader context, patterns were compared to holdfast-richness relationships observed in comparable studies from the NE Atlantic. Total abundance of holdfast epifauna was similar across benthic and suspended holdfasts from the west of Ireland, although species richness was higher in suspended samples. Richness and abundance in suspended kelp holdfasts were consistent with the range of values recorded in other wild kelp studies. There were significant differences in assemblage composition between holdfast types (ANOSIM; R = 0.383, p <0.05). The distributions of faunal feeding types did not, however, vary between suspended and benthic kelps. Suspended holdfasts in the west of Ireland represented a novel habitat with higher species richness and a different species assemblage when compared to adjacent benthic kelps.Publisher PDFPeer reviewe

    The future of the oceans past : toward a global marine historical research initiative

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    Historical research is playing an increasingly important role in marine sciences. Historical data are also used in policy making and marine resource management, and have helped to address the issue of shifting baselines for numerous species and ecosystems. Although many important research questions still remain unanswered, tremendous developments in conceptual and methodological approaches are expected to contribute to a comprehensive understanding of the global history of human interactions with life in the seas. Based on our experiences and knowledge from the "History of Marine Animal Populations' project, this paper identifies the emerging research topics for future historical marine research. It elaborates on concepts and tools which are expected to play a major role in answering these questions, and identifies geographical regions which deserve future attention from marine environmental historians and historical ecologists

    2,6-Diamino­pyridinium tetra­phenyl­borate–1,2-bis­(5,7-dimethyl-1,8-naphthyridin-2-yl)diazene (1/1)

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    In the title compound, C5H8N3 +·C24H20B−·C20H18N6, the 1,2-bis­(5,7-dimethyl-1,8-naphthyridin-2-yl)diazene mol­ecule is essentially planar (r.m.s. deviation = 0.0045 Å) and aligned in nearly coplanar manner with the 2,6-diamino­pyridinium ion, making a dihedral angle of 5.19 (5)°. The diamino­pyridine mol­ecule is protonated on the central pyridine N atom and the B atom bears the counter-charge. The amine groups of the diamino pyridinium cation form intra­molecular N—H⋯N hydrogen bonds, resulting in linear and bent inter­actions with the naphthyridine ring system
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