200 research outputs found

    Conservation of the Beira Railway Station in Mozambique: Lessons from a 20th-Century Heritage Case Study in Africa

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    The conservation of built cultural heritage is a fundamental task for modern societies. Specialized expertise is necessary to define a proper strategy to preserve a heritage that is accumulating damage due to the deterioration of materials, repeated loading, and exceptional events. This paper provides part of the work developed for the definition of the Conservation Management Plan of a 20th-century building in Africa. The monumental building, the Beira railway station, is in Mozambique and was considered among the one hundred more important 20th-century Portuguese engineering buildings. The work presented focuses on the analysis of damage, material characterization, and assessment of the comfort conditions of this concrete building—fundamental tasks for the understanding of the current condition of the building and the definition of appropriate remedial actions and maintenance tasks. The work provides a detailed definition of different approaches and techniques that can be implemented for this type of building to obtain reliable information to define measures and actions that are more in line with the reality of the building. Moreover, the work allows for a discussion on the long-term performance of Modern Movement buildings with low maintenance and the success of comfort concepts in local climatic conditions.This work is partly financed by the Getty Foundation under the Keeping It Modern Grant “Preparation of a conservation management plan for Francisco José de Castro, João Garizo do Carmo and Paulo de Melo Sampaio’s Beira Railway Station in Mozambique (Grant #: ORG-201942637). Funding provided by the Portuguese Foundation for Science and Technology (FCT) to the Research Unit ISISE (POCI-01-0145-FEDER-007633) is also gratefully acknowledged

    Scattering of graphene plasmons at abrupt interfaces: an analytic and numeric study

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    We discuss the scattering of graphene surface plasmon-polaritons (SPPs) at an interface between two semi-infinite graphene sheets with different doping levels and/or different underlying dielectric substrates. We take into account retardation effects and the emission of free radiation in the scattering process. We derive approximate analytic expressions for the reflection and the transmission coefficients of the SPPs as well as the same quantities for the emitted free radiation. We show that the scattering problem can be recast as a Fredholm equation of the second kind. Such equation can then be solved by a series expansion, with the first term of the series correspond to our approximated analytical solution for the reflection and transmission amplitudes. We have found that almost no free radiation is emitted in the scattering process and that under typical experimental conditions the back-scattered SPP transports very little energy. This work provides a theoretical description of graphene plasmon scattering at an interface between distinct Fermi levels which could be relevant for the realization of plasmonic circuitry elements such as plasmonic lenses or reflectors, and for controlling plasmon propagation by modulating the potential landscape of graphene.A.J.C. acknowledges the scholarship from the Brazilian agency CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico). B.A., Y.V.B., and N.M.R.P. acknowledge support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. No. 696656). P.A.D.G. acknowledges financial support from the VILLUM Fonden (Grant No. 16498), and from the Center for Nanostructured Graphene sponsored by the Danish National Research Foundation (project DNRF103). N.M.R.P. also acknowledges the hospitality of the MackGraphe Center, at Mackenzie Presbyterian University, where this work has started, the projects Fapesp 2012/50259-8 and 2016/11814-7, and the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2013.info:eu-repo/semantics/submittedVersio

    Bone mineral density and risk of heart failure in older adults: The Cardiovascular Health Study

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    Background Despite increasing evidence of a common link between bone and heart health, the relationship between bone mineral density ( BMD ) and heart failure ( HF ) risk remains insufficiently studied. Methods and Results We investigated whether BMD measured by dual‐energy x‐ray absorptiometry was associated with incident HF in an older cohort. Cox models were stratified by sex and interactions of BMD with race assessed. BMD was examined at the total hip and femoral neck separately, both continuously and by World Health Organization categories. Of 1250 participants, 442 (55% women) developed HF during the median follow‐up of 10.5 years. In both black and nonblack women, neither total hip nor femoral neck BMD was significantly associated with HF ; there was no significant interaction by race. In black and nonblack men, total hip, but not femoral neck, BMD was significantly associated with HF , with evidence of an interaction by race. In nonblack men, lower total hip BMD was associated with higher HF risk (hazard ratio, 1.13 [95% CI, 1.01–1.26] per 0.1 g/cm 2 decrement), whereas in black men, lower total hip BMD was associated with lower HF risk (hazard ratio, 0.74 [95% CI, 0.59–0.94]). There were no black men with total hip osteoporosis. Among nonblack men, total hip osteoporosis was associated with higher HF risk (hazard ratio, 2.83 [95% CI, 1.39–5.74]) compared with normal BMD . Conclusions Among older adults, lower total hip BMD was associated with higher HF risk in nonblack men but lower risk in black men, with no evidence of an association in women. Further research is needed to replicate these findings and to study potential underlying pathways. </jats:sec

    Massive Blooms of Chattonella subsalsa Biecheler (Raphidophyceae) in a Hypereutrophic, Tropical Estuary—Guanabara Bay, Brazil

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    Cell concentrations of the potentially harmful raphidophyte Chattonella subsalsa Biecheler were quantified in surface waters of Guanabara Bay, a heavily eutrophicated estuarine system in tropical Brazil, from February 2014 to January 2018. Cells were imaged and quantified in live samples by means of an automated imaging system (FlowCam®). Bloom episodes (&gt;0.1 × 106 cells L−1) were observed in 37 samples, mostly in a shallow (&lt;10 m) area with extremely high nutrient and organic matter loads (average total P = 19 μM and total N = 344 μM), intermediate salinity (average 24.5), and low water transparency (average Secchi depth = 0.54 m) due to continental runoff. Blooms in this area reached up to 13.3 × 106 cells L−1. C. subsalsa cell concentration was correlated with parameters linked to eutrophication of the bay. On a monthly basis, C. subsalsa abundance was correlated with a period of positive Multivariated El Niño/Southern Oscilation Index (MEI) that lasted from the beginning of 2015 to mid-2016 (known as Godzilla El Niño), indicating a potential influence of regional climate on the occurrence of C. subsalsa. Notably, at least six fish kill episodes were reported in the Bay during this period which, added to the toxicity of C. subsalsa strains isolated from the bay to Artemia nauplia (48h-LC50 = 7.3 × 106 cells L−1), highlights the threat that this HAB species poses to the environment. This is the first report of recurrent, massive C. subsalsa blooms in Guanabara Bay. Regardless of the influence of climatic forcing in favoring C. subsalsa development, reducing nutrient loads would be the best strategy to mitigate blooms of this and other potentially harmful algae in Guanabara Bay
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