310 research outputs found

    Laser induced synthesis of nickel alloy (alumel) nanoparticles in liquids

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    Pulsed laser ablation in liquids (PLAL) has been growing as a powerful technique for the synthesis of multielement nanoparticles (NPs) such as metal alloys with complex composition. In consequence, there is a great necessity in expanding the current knowledge about alloy NPs formation during this method, aiming to control the chemical composition of produced NPs. In this work, a nanosecond Nd:YAG laser was used to synthesize NPs of a novel nickel (Ni) alloy, and a brief description regarding the influence of liquid media in size and stability of produced nanoparticles is presented. The results showed great stability in the colloids produced in isopropanol medium without using a surfactant, whereas this environment allowed the production of smaller nanoparticles.This work has been supported by FCT (Fundação para a Ciência e Tecnologia – Portugal) in the scope of the projects UID/EEA/04436/2013 and NORTE-01- 0145-FEDER-000018-HAMaBICo. It is also co-funded by National Funds through FCT - Portuguese Foundation for Science and Technology, Reference UID/CTM/50025/2013 and FEDER funds through the COMPETE 2020 Programme under the project number POCI-01-0145-FEDER-007688. Thank the CNPq (205791/2014-0) and CAPES for financial support

    Environmentally friendly synthesis methods to obtain the misfit [Ca2CoO3-δ]0.62[CoO2] thermoelectric material

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    This work reports the microstructural and thermoelectric characterization of the misfit [Ca2CoO3-δ]0.62[CoO2] compound obtained by a solid-state synthesis using mollusk shells and a proteic sol-gel method, which uses gelatin as a polymerizing agent. The results clearly demonstrate the capability of these routes to produce pure Ca3Co4O9 with plate-like morphology. Sintered ceramic samples show randomly oriented grains and relative densities in the range of 63–67%. The obtained microstructures provide reasonable electrical properties and result in competitive thermoelectric performance for the material prepared by the proteic sol-gel synthesis (P.F. of 205 μW/K2 m at 700 °C).publishe

    Increasing Dominance - the Role of Advertising, Pricing and Product Design

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    Despite the empirical relevance of advertising strategies in concentrated markets, the economics literature is largely silent on the effect of persuasive advertising strategies on pricing, market structure and increasing (or decreasing) dominance. In a simple model of persuasive advertising and pricing with differentiated goods, we analyze the interdependencies between ex-ante asymmetries in consumer appeal, advertising and prices. Products with larger initial appeal to consumers will be advertised more heavily but priced at a higher level - that is, advertising and price discounts are strategic substitutes for products with asymmetric initial appeal. We find that the escalating effect of advertising dominates the moderating effect of pricing so that post-competition market shares are more asymmetric than pre-competition differences in consumer appeal. We further find that collusive advertising (but competitive pricing) generates the same market outcomes, and that network effects lead to even more extreme market outcomes, both directly and via the effect on advertising

    Assessing road effects on bats: the role of landscape, road features, and bat activity on road-kills

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    Recent studies suggest that roads can significantly impact bat populations. Though bats are one of the most threatened groups of European vertebrates, studies aiming to quantify bat mortality and determine the main factors driving it remain scarce. Between March 16 and October 31 of 2009, we surveyed road-killed bats daily along a 51-km-long transect that incorporates different types of roads in southern Portugal. We found 154 road-killed bats of 11 species. The two most common species in the study area, Pipistrellus kuhlii and P. pygmaeus, were also the most commonly identified road-kill, representing 72 % of the total specimens collected. About two-thirds of the total mortality occurred between mid July and late September, peaking in the second half of August. We also recorded casualties of threatened and rare species, including Miniopterus schreibersii, Rhinolophus ferrumequinum, R. hipposideros, Barbastella barbastellus, and Nyctalus leisleri. These species were found mostly in early autumn, corresponding to the mating and swarming periods. Landscape features were the most important variable subset for explaining bat casualties. Road stretches crossing or in the vicinity of high-quality habitats for bats—including dense Mediterranean woodland (‘‘montado’’) areas, water courses with riparian gallery, and water reservoirs—yielded a significantly higher number of casualties. Additionally, more roadkilled bats were recorded on high-traffic road stretches with viaducts, in areas of higher bat activity and near known roosts

    Observation of strong two-electron-one-photon transitions in few-electron ions

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    We resonantly excite the K series of O5+ and O6+ up to principal quantum number n = 11 with monochromatic x rays, producing K-shell holes, and observe their relaxation by soft-x-ray emission. Some photoabsorption resonances of O5+ reveal strong two-electron-one-photon (TEOP) transitions. We find that for the [(1s2s)(1)5p(3)(/2)](3/2;1/2) states, TEOP relaxation is by far stronger than the radiative decay and competes with the usually much faster Auger decay path. This enhanced TEOP decay arises from a strong correlation with the near-degenerate upper states [(1s2p(3)(/2))(1)4s](3/2;1/2) of a Li-like satellite blend of the He-like K alpha transition. Even in three-electron systems, TEOP transitions can play a dominant role, and the present results should guide further research on the ubiquitous and abundant many-electron ions where electronic energy degeneracies are far more common and configuration mixing is stronger

    Seagrass and submerged aquatic vegetation (VAS) habitats off the Coast of Brazil: state of knowledge, conservation and main threats

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    Seagrass meadows are among the most threatened ecosystems on earth, raising concerns about the equilibrium of coastal ecosystems and the sustainability of local fisheries. The present review evaluated the current status of the research on seagrasses and submerged aquatic vegetation (SAV) habitats off the coast of Brazil in terms of plant responses to environmental conditions, changes in distribution and abundance, and the possible role of climate change and variability. Despite an increase in the number of studies, the communication of the results is still relatively limited and is mainly addressed to a national or regional public; thus, South American seagrasses are rarely included or cited in global reviews and models. The scarcity of large-scale and long-term studies allowing the detection of changes in the structure, abundance and composition of seagrass habitats and associated species still hinders the investigation of such communities with respect to the potential effects of climate change. Seagrass meadows and SAV occur all along the Brazilian coast, with species distribution and abundance being strongly influenced by regional oceanography, coastal water masses, river runoff and coastal geomorphology. Based on these geomorphological, hydrological and ecological features, we characterised the distribution of seagrass habitats and abundances within the major coastal compartments. The current conservation status of Brazilian seagrasses and SAV is critical. The unsustainable exploitation and occupation of coastal areas and the multifold anthropogenic footprints left during the last 100 years led to the loss and degradation of shoreline habitats potentially suitable for seagrass occupation. Knowledge of the prevailing patterns and processes governing seagrass structure and functioning along the Brazilian coast is necessary for the global discussion on climate change. Our review is a first and much-needed step toward a more integrated and inclusive approach to understanding the diversity of coastal plant formations along the Southwestern Atlantic coast as well as a regional alert the projected or predicted effects of global changes on the goods and services provided by regional seagrasses and SAV
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