Are Neutron-Rich Elements Produced in the Collapse of Strange Dwarfs ?

The structure of strange dwarfs and that of hybrid stars with same baryonic number is compared. There is a critical mass (M~0.24M_sun) in the strange dwarf branch, below which configurations with the same baryonic number in the hybrid star branch are more stable. If a transition occurs between both branches, the collapse releases an energy of about of 3x10^{50} erg, mostly under the form of neutrinos resulting from the conversion of hadronic matter onto strange quark matter. Only a fraction (~4%) is required to expel the outer neutron-rich layers. These events may contribute significantly to the chemical yield of nuclides with A>80 in the Galaxy, if their frequency is of about one per 1500 years.Comment: Accepted for publication in IJMP

Deployment characterization of a floatable tidal energy converter on a tidal channel, Ria Formosa, Portugal

This paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). A baseline marine geophysical, hydrodynamic and ecological study based on the experience collected on the test site is presented. The collected data was used to validate a hydro-morphodynamic model, allowing the selection of the installation area based on both operational and environmental constraints. Operational results related to the description of power generation capacity, energy capture area and proportion of energy flux are presented and discussed, including the failures occurring during the experimental setup. The data is now available to the scientific community and to TEC industry developers, enhancing the operational knowledge of TEC technology concerning efficiency, environmental effects, and interactions (i.e. device/environment). The results can be used by developers on the licensing process, on overcoming the commercial deployment barriers, on offering extra assurance and confidence to investors, who traditionally have seen environmental concerns as a barrier, and on providing the foundations whereupon similar deployment areas can be considered around the world for marine tidal energy extraction.Acknowledgements The paper is a contribution to the SCORE project, funded by the Portuguese Foundation for Science and Technology (FCT e PTDC/ AAG-TEC/1710/2014). Andre Pacheco was supported by the Portu- guese Foundation for Science and Technology under the Portuguese Researchers' Programme 2014 entitled “Exploring new concepts for extracting energy from tides” (IF/00286/2014/CP1234). Eduardo GGorbena has received funding for the OpTiCA project from the ~ Marie Skłodowska-Curie Actions of the European Union's H2020- MSCA-IF-EF-RI-2016/under REA grant agreement n [748747]. The authors would like to thank to the Portuguese Maritime Authorities and Sofareia SA for their help on the deployment.info:eu-repo/semantics/publishedVersio

A bright nanowire single photon source based on SiV centers in diamond

The practical implementation of many quantum technologies relies on the development of robust and bright single photon sources that operate at room temperature. The negatively charged silicon-vacancy (SiV-) color center in diamond is a possible candidate for such a single photon source. However, due to the high refraction index mismatch to air, color centers in diamond typically exhibit low photon out-coupling. An additional shortcoming is due to the random localization of native defects in the diamond sample. Here we demonstrate deterministic implantation of Si ions with high conversion efficiency to single SiV- centers, targeted to fabricated nanowires. The co-localization of single SiV- centers with the nanostructures yields a ten times higher light coupling efficiency than for single SiV- centers in bulk diamond. This enhanced photon out-coupling, together with the intrinsic scalability of the SiV- creation method, enables a new class of devices for integrated photonics and quantum science.Comment: 15 pages, 5 figure

Alguns contributos da nanotecnologia para a sustentabilidade dos materiais de construção

Os avanços nanotecnológicos atingem inúmeras áreas da ciência, mas no âmbito da sustentabilidade dos materiais de construção os progressos embora importantes são escassos e acima de tudo objeto de reduzida divulgação. O presente artigo sintetiza uma avaliação do estado da arte relativa a alguns dos contributos da nanotecnologia para a sustentabilidade dos materiais de construção. No mesmo se aborda a compreensão dos compostos gerados durante a hidratação do cimento Portland, o aumento da resistência e da durabilidade de argamassas e betões pela adição de nanopartículas e nanotubos e de que forma a adição de nanopartículas pode contribuir para a autolimpeza, a purificação do ar e a capacidade bactericida em materiais construtivos por via do efeito fotocatalítico. O presente artigo aborda ainda os últimos desenvolvimentos da nanotecnologia com vista à eficiência energética, nomeadamente pela produção de isolamentos térmicos de elevado desempenho, janelas com baixa condutibilidade térmica, vidros com transmitância variável e materiais de mudança de fase mais eficientes

Double fermiophobic Higgs boson production at the LHC and LC

We consider the phenomenology of a fermiophobic Higgs boson (h_f) at the Large Hadron Collider (LHC) and a e+e- Linear Collider (LC). At both machines the standard production mechanisms which rely on the coupling h_fVV (V=W,Z) can be very suppressed at large tan beta. In such cases the complementary channels pp to H^\pm h_f, A^0 h_f and e+e- to A^0 h_f offer promising cross-sections. Together with the potentially large branching ratios for H^\pm to h_fW* and A^0 to h_fZ*, these mechanisms would give rise to double h_f production, leading to signatures of gamma gamma gamma gamma, gamma gamma VV and VVVV.Comment: 19 pages, 9 figures, expanded discussion, fig.1 changed slightly, version to appear in Phys.Rev.

Efeito do dano mecânico na qualidade fisiológica e na capacidade de expansão de sementes de milho pipoca.

Com o objetivo de dar subsidio aos produtores de sementes e/ou graos de milho pipoca, para melhorar a qualidade fisiologica da producao, sementes da cultivar CMS-43 foram submetidas a tres niveis de danificacao mecanica (sem danos, com danos e com danos dobrados), e avaliadas pelos testes de germinacao, vigor (condutividade eletrica) e capacidade de expansao. Os resultados demonstraram que sementes danificadas reduzem significativamente a germinacao, o vigor e a capacidade de expansao das sementes. Concluiu-se que indiferente a finalidade da producao, sementes e/ou graos, a colheita do milho pipoca precisa ser feita com o minimo de danificacao mecanica possivel, para propiciar um produto com maxima qualidade

Eco-concrete: one-part geopolymer mixes

The geopolymerization of alumino-silicate materials is a complex chemical process evolving dissolution of raw materiais, transportation or orientation and polycondensation of the reaction products. Publications on the field of geopolymeric binders, state that this new material is likely to have high potential to become an altemative to Portland cement composites, Classical two part geopolymers could be made more eco-efficient with a lower carbon dioxide footprint if the use of sodium silicate is avoided. Besides current geopolymeric mixes can suffer from efflorescence originated by the fact that alkaline and/or soluble silicates that are added during processing cannot be totally consumed during geopolymerisation. Therefore new geopolymer mixes are needed. This paper presents experimental results on a novel kind of mixes termed one-part geopolymers. Compressive strength results and efflorescences observations show that the new mixes already analyzed are promissing

Development of foam one-part geopolymers with enhanced thermal insulation performance and low carbon dioxide emissions

Buildings are responsible for more than 40% of the energy consumption and greenhouse gas emissions. Thus, increasing building energy efficiency is one the most cost-effective ways to reduce emissions. The use of thermal insulation materials could constitute the most effective way of reducing heat losses in buildings by minimising heat energy needs. These materials have a thermal conductivity factor, k (W/m.K) lower than 0.065 while other insulation materials such as aerated concrete can go up to 0.11. Current insulation materials are associated with negative impacts in terms of toxicity. Polystyrene, for example contains anti-oxidant additives and ignition retardants. In addition, its production involves the generation of benzene and chlorofluorocarbons. Polyurethane is obtained from isocyanates, which are widely known for their tragic association with the Bhopal disaster. Besides current insulation materials releases toxic fumes when subjected to fire. This paper presents experimental results on one-part geopolymers. It also includes global warming potential assessment and cost analysis. The results show that only the use of aluminium powder allows the production mixtures with a high compressive strength however its high cost means they are commercially useless when facing the competition of commercial cellular concrete. The results also show that one-part geopolymer mixtures based on 26%OPC +58.3%FA +8%CS +7.7%CH and 3.5% hydrogen peroxide constitute a promising cost efficient (67 euro/m3), thermal insulation solution for floor heating systems with low global warming potential of 443 KgCO2eq/m3