46 research outputs found

    Photochemically driven polymeric network formation: Synthesis and applications

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    Polymeric networks have been intensely investigated and a large number of applications have been found in areas ranging from biomedicine to materials science. Network fabrication via light-induced reactions is a particularly powerful tool, since light provides ready access to temporal and spatial control, opening an array of synthetic access routes for structuring the network geometry as well as functionality. Herein, the most recent light-induced modular reactions and their use in the formation of precision polymeric networks are collated. The synthetic strategies including photoinduced thiol-based reactions, Diels‚ÄďAlder systems, and photogenerated reactive dipoles, as well as photodimerizations, are discussed in detail. Importantly, applications of the fabricated networks via the aforementioned reactions are highlighted with selected examples. Concomitantly, we provide future directions for the field, emphasizing the most critically required advances

    Contribution of genetics to ecological restoration

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    © 2014 John Wiley & Sons Ltd. Ecological restoration of degraded ecosystems has emerged as a critical tool in the fight to reverse and ameliorate the current loss of biodiversity and ecosystem services. Approaches derived from different genetic disciplines are extending the theoretical and applied frameworks on which ecological restoration is based. We performed a search of scientific articles and identified 160 articles that employed a genetic approach within a restoration context to shed light on the links between genetics and restoration. These articles were then classified on whether they examined association between genetics and fitness or the application of genetics in demographic studies, and on the way the studies informed restoration practice. Although genetic research in restoration is rapidly growing, we found that studies could make better use of the extensive toolbox developed by applied fields in genetics. Overall, 41% of reviewed studies used genetic information to evaluate or monitor restoration, and 59% provided genetic information to guide prerestoration decision-making processes. Reviewed studies suggest that restoration practitioners often overlook the importance of including genetic aspects within their restoration goals. Even though there is a genetic basis influencing the provision of ecosystem services, few studies explored this relationship. We provide a view of research gaps, future directions and challenges in the genetics of restoration

    Genome-wide single-generation signatures of local selection in the panmictic European eel

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    Next-generation sequencing and the collection of genome-wide data allow identifying adaptive variation and footprints of directional selection. Using a large SNP data set from 259 RAD-sequenced European eel individuals (glass eels) from eight locations between 34 and 64¬įN, we examined the patterns of genome-wide genetic diversity across locations. We tested for local selection by searching for increased population differentiation using FST-based outlier tests and by testing for significant associations between allele frequencies and environmental variables. The overall low genetic differentiation found (FST = 0.0007) indicates that most of the genome is homogenized by gene flow, providing further evidence for genomic panmixia in the European eel. The lack of genetic substructuring was consistent at both nuclear and mitochondrial SNPs. Using an extensive number of diagnostic SNPs, results showed a low occurrence of hybrids between European and American eel, mainly limited to Iceland (5.9%), although individuals with signatures of introgression several generations back in time were found in mainland Europe. Despite panmixia, a small set of SNPs showed high genetic differentiation consistent with single-generation signatures of spatially varying selection acting on glass eels. After screening 50 354 SNPs, a total of 754 potentially locally selected SNPs were identified. Candidate genes for local selection constituted a wide array of functions, including calcium signalling, neuroactive ligand‚Äďreceptor interaction and circadian rhythm. Remarkably, one of the candidate genes identified is PERIOD, possibly related to differences in local photoperiod associated with the >30¬į difference in latitude between locations. Genes under selection were spread across the genome, and there were no large regions of increased differentiation as expected when selection occurs within just a single generation due to panmixia. This supports the conclusion that most of the genome is homogenized by gene flow that removes any effects of diversifying selection from each new generation

    Species distribution models and mitochondrial DNA phylogeography suggest an extensive biogeographical shift in the high-intertidal seaweed Pelvetia canaliculata

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    Aim: Species distributions have been continuously adjusting to changing climatic conditions throughout the glacial‚Äďinterglacial cycles. In the marine realm, evidence suggests that latitudinal range shifts, involving both spatial expansions and trailingedge contractions, may represent a common response to climatic oscillations. The biogeographical histories of coastal organisms, however, have been inferred primarily using molecular markers, potentially overlooking past range dynamics beyond contemporary rear edges. In this study we combined species distribution models (SDMs) and mitochondrial DNA (mtDNA) data to investigate the biogeographical history of the high-intertidal seaweed Pelvetia canaliculata. We investigated the hypotheses that its distribution is set by both marine and terrestrial climates and that its range has shifted northwards since the Last Glacial Maximum. Location North-eastern Atlantic intertidal from Portugal to Norway. Methods: In total, 432 individuals at 27 sites covering the extant range of Pelvetia canaliculata were sampled and sequenced for a c. 500 bp mtDNA intergenic spacer. A niche model was developed using marine and terrestrial variables. Range dynamics were reconstructed based on the geographical patterns of genetic variation and on the SDM projections for the Last Glacial Maximum (LGM) and the present. Results: The best distribution models incorporated both marine and terrestrial variables. LGM projections revealed suitable habitat between southern Morocco and the periglacial shorelines of the Celtic Sea. Pelvetia canaliculata exhibited a highly structured phylogeography, being subdivided into three largely disjunct lineages, two of them endemic to Iberia. The central/northern European lineage exhibited the highest haplotypic diversity and showed a consistent decline in nucleotide diversity and haplotypic richness at higher latitudes. Main conclusions: Assuming species/climate equilibrium, SDMs supported the hypothesis of a post-glacial latitudinal range shift. Molecular variation revealed contrasting demographic behaviours in Iberian and periglacial regions. In Iberia the low haplotypic diversity suggested complex range dynamics that are not fully captured by SDM projections. Periglacial regions, identified as the source of poleward colonization, were inferred to have been comparatively more stable. Greater attention should be paid to marine range dynamics at low-latitude range margins, particularly in genetically structured low-dispersal species exhibiting southern endemic variation

    Convergent evolutionary processes driven by foraging opportunity in two sympatric morph pairs of Arctic charr with contrasting post-glacial origins

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    The expression of two or more discrete phenotypes amongst individuals within a species (morphs) provides multiple modes upon which selection can act semi-independently, and thus may be an important stage in speciation. In the present study, we compared two sympatric morph systems aiming to address hypotheses related to their evolutionary origin. Arctic charr in sympatry in Loch Tay, Scotland, exhibit one of two discrete, alternative body size phenotypes at maturity (large or small body size). Arctic charr in Loch Awe segregate into two temporally segregated spawning groups (breeding in either spring or autumn). Mitochondrial DNA restriction fragment length polymorphism analysis showed that the morph pairs in both lakes comprise separate gene pools, although segregation of the Loch Awe morphs is more subtle than that of Loch Tay. We conclude that the Loch Awe morphs diverged in situ (within the lake), whereas Loch Tay morphs most likely arose through multiple invasions by different ancestral groups that segregated before post-glacial invasion (i.e. in allopatry). Both morph pairs showed clear trophic segregation between planktonic and benthic resources (measured by stable isotope analysis) but this was significantly less distinct in Loch Tay than in Loch Awe. By contrast, both inter-morph morphological and life-history differences were more subtle in Loch Awe than in Loch Tay. The strong ecological but relatively weak morphological and life-history divergence of the in situ derived morphs compared to morphs with allopatric origins indicates a strong link between early ecological and subsequent genetic divergence of sympatric origin emerging species pairs. The emergence of parallel specialisms despite distinct genetic origins of these morph pairs suggests that the effect of available foraging opportunities may be at least as important as genetic origin in structuring sympatric divergence in post-glacial fishes with high levels of phenotypic plasticity

    A1_2 Duck, duck... Spruce!

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    The H-4 Hercules was a prototype aircraft built in 1947 which was never properly flight tested. This report explores a theory that this aircraft would never have been able to fly more than a few hundred feet off of the ground due to the ground effect and that the plane was not viable for the purpose of transporting heavy military equipment. By exploring the pressure difference over the wing surfaces, the aircraft is shown to be able to reach a maximum altitude of 9,660 m and to require a minimum takeoff speed of 113.6 km/h. It is therefore shown that the aircraft would have been able to takeoff fully loaded and could have reached a high altitude successfully.√ā

    A1_9 The solar contract?

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    This report examines the claim by the 'Institute for Creation Research' that the Sun is contracting by about 5 ft per hour. It is determined that the gravitational potential energy released from the Sun contracting from its currently established radius to a radius 2.5 ft smaller would be larger than the Sun's current luminosity. It has also been shown that this would result in Earth being hotter than the current surface temperature of Venus and the Sun's peak of radiation would be in the ultra violet range rather than the visible

    A1_7 The Neutrino Problem

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    This report examines the premise from the movie "2012" (2009) that solar neutrinos start interacting with the core of the Earth, causing it to melt. A lower energy limit required for this interaction is found to be 9.55*10^4 GeV√ā¬† and it is shown that the source of such energetic neutrinos is unlikely to be from within the solar system

    An integrated genetic-demographic model to unravel the origin of genetic structure in European eel (Anguilla anguilla L.)

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    The evolutionary enlightened management of species with complex life cycles often requires the development of mathematical models integrating demographic and genetic data. The genetic structure of the endangered European eel (Anguilla anguilla L.) has been thoroughly analyzed in several studies in the past years. However, the interpretation of the key demographic and biologic processes that determine the observed spatio-temporal genetic structure has been very challenging owing to the complex life cycle of this catadromous species. Here, we present the first integrated demographic-genetic model applied to the European eel that explicitly accounts for different levels of larval and adult mixing during oceanic migrations and allows us to explore alternative hypotheses on genetic differentiation. Our analyses show that (i) very low levels of mixing occurring during larval dispersal or adult migration are sufficient to erase entirely any genetic differences among sub-populations; (ii) small-scale temporal differentiation in recruitment can arise if the spawning stock is subdivided in distinct reproductive groups; and (iii) the geographic differentiation component might be overestimated if a limited number of temporal recruits are analyzed. Our study can inspire the scientific debate on the interpretation of genetic structure in other species characterized by complex life cycle and long-range migrations
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