34 research outputs found

    Villa de Noheda (Cuenca, Spain): a multi-analytical approach for mortar characterization

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    Villa de Noheda (Cuenca, Spain): a multi-analytical approach for mortar characterization Cristina Galacho(1), Patrícia Moita(2), Miguel Tévar(3), António Candeias(1) José Mirão(2) (1) Laboratory Hercules, Dpt. of Chemistry, Univ. of Évora, Portugal ([email protected]) (2) Laboratory Hercules, Dpt. of Geosciences, Univ. of Évora, Portugal . (3) Universidad de Castilla la Mancha, Spain The Roman architectural ensemble of Noheda, known by the fantastic dimensions of the tile panels have been classified as Cultural Heritage in 2012 and open to the public since 2015. Located at 500m of the homonymous village in Spain, corresponds to a roman Villa, dated from 4th to 5th century, which evidences an agricultural use trough a constructive complex with several functions. Until now there are two exhumed areas of the rural complex: some structures belonging to the pars rustica and on the other hand, a sector of the pars urbana, composed of some balneary outbuildings and various rooms of the residential building. It is in this last one that stands out the so-called Triabsid Room, not only for its imposing dimensions of 290.64m2, and its extraordinary pavements, but also for its complex architectural articulation and its careful walls decoration composed by marble plaques and mural painting. Under the framework of a bilateral Iberian project, several mortar samples were analysed for their compositional and textural characterization. The studied mortars cover a wide spectrum of architecture contexts (triclinium and its access areas, octagonal room and baths), inside and outside walls, and also later added walls. The data acquisition techniques consisted of X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDS) and thin-section optical microscopy. The mortars are mainly composed by quartz aggregates, with semi-angular to semi-rounded grains, and very small amounts of K-feldspars. A generalized feature is the presence of numerous lime nodules, sometimes of centimeter-size, with calcitic composition. Lithic, ceramic and coal were occasionally observed. According to XRD analyses, the raw materials are very similar between samples suggesting a similar provenance, probably a river sand. The binder is an aerial calcite lime that was used mainly with a binder:aggregate ratio of 1:2 as determined by TG-DTA. The mortar from the baths have a smaller amount of binder (1:4) as well as an external wall (1:3) interpreted as a late enlargement after abandonment of the Villa. The results obtained point out to a considerable similarity not only at the level of the raw materials but also in the production technique used in the different areas of the residential building of the pars urbana, which would not have been altered in subsequent interventions. Differences were found only for the different functionalities; whether in the baths or when dealing with external walls

    The use of administrative data sources for measurement of angiotensinreceptor blockers therapeutic adherence

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    RESUMO - A recente evolução do registo informático dos atos de prescrição e levantamento de medicação disponibiliza um conjunto de dados que possibilita a mensuração dos comportamentos de adesão terapêutica, por recurso a Fontes administrativas de dados. Pretendeu-se caracterizar o comportamento de adesão terapêutica, no subgrupo fármaco-terapêutico dos antagonistas dos recetores da angiotensina, dos doentes hipertensos residentes na região de saúde do Alentejo nos anos de 2010-2011. Constatou-se que a adesão terapêutica primária foi de 61,2% e que a adesão terapêutica total se situou entre 55,7-69,5%, com elevada variabilidade nos padrões comportamentais por idade, sexo e área geográfica.ABSTRACT - tThe recent development in electronic pharmacy records made possible the measure ofpatients’ adherence behavior using administrative data sources. The overall objective ofthe study was to characterize the adherence behavior to Angiotensin Receptor Blockers ofhypertensive patients living in Alentejo, Portugal, in 2010 and 2011. The results revealedthat primary adherence stood at 61.2% and total adherence was situated between 55.7%and 69.5% with high variability on behavioral patterns for age, gender and geographic area.info:eu-repo/semantics/publishedVersio

    Thermal conductivity of nanofluids: a review on prediction models, controversies and challenges

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    In recent years, the nanofluids (NFs) have become the main candidates for improving or even replacing traditional heat transfer fluids. The possibility of NFs to be used in various technological applications, from renewable energies to nanomedicine, has made NFs and their thermal conductivity one of the most studied topics nowadays. Hence, this review presents an overview of the most important advances and controversial results related to the NFs thermal conductivity. The different techniques used to measure the thermal conductivity of NFs are discussed. Moreover, the fundamental parameters that affect the NFs thermal conductivity are analyzed, and possible improvements are addressed, such as the increase of long-term stability of the nanoparticles (NPs).The most representative prediction classical models based on fluid mechanics, thermodynamics, and experimental fittings are presented. Also, the recent statistical machine learning-based prediction models are comprehensively addressed, and the comparison with the classical empirical ones is made, whenever possible.This work has been funded by Portuguese national funds of FCT/MCTES (PIDDAC) through the base funding from the following research units: UIDB/00532/2020 (Transport Phenomena Research Center–CEFT), UIDB/04077/2020 (MEtRICs) and UIDP/04436/2020.The authors are also grateful for the funding of FCT through the projects POCI-01-0145-FEDER-016861, POCI-01- 0145-FEDER-028159, NORTE-01-0145-FEDER-029394, NORTE-01-0145-FEDER-030171, funded by COMPETE2020, NORTE2020, PORTUGAL2020, and FEDER

    Caranguejos que correm, crinóides que caminham, gastrópodes que se alimentam: diversidade comportamental no Lagerstätte do Cabeço da Ladeira e suas implicações evolutivas (Jurássico Médio, Portugal)

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    Ichnology is a powerful tool for understanding the evolutionary paths of animal clades, through the paleobiology of behavior preserved in Lagerstätten such as the Cabeço da Ladeira (Portugal) site. Here, the peritidal carbonates of the Chão das Pias Formation (Middle Jurassic, upper Bajocian) record the development of microbial mats in a tidal flat. Episodically, the flat was expanded during periods of equinoctial spring tides that may have been responsible for the in situ killing of several members of echinoderm clades, and the fine preservation of their endoskeleton, in addition to the behavior of an arthropod-dominated endo- and epifauna. Mat-preserved shallow tiers with a moderate ichnodiversity attributed to the Cruziana ichnofacies include trackways of crabs (Laterigradus lusitanica igen. nov., isp. nov.) and shrimps ( Diplopodichnus isp.); trails of fishes (?Undichna), gastropods (Archaeonassa fossulata), isocrinid crinoids (Krinodromos bentou igen. nov., isp. nov.) and insects (Haplotichnus indianensis); and burrows of shrimps or lobsters (Thalassinoides suevicus) and other arthropods (Asterosoma ludwigae, Gyrochorte comosa), or polychaetes (Rhizocorallium commune ). This is implied already above (igen. nov., etc.) and seems not needed. The crab trackways and gastropod bulldozing trails, extending up to 12.3 m, are among the longest invertebrate cursorial traces ever found in the fossil record. The mortichnial crawling trail of a crinoid is the first evidence of locomotion for this group in the fossil record, and a rare unambiguous example of this ethology. Extensive continuous trackways attributed to amphibious crabs record, with great detail, typical gaits of underwater punting and walking sideways on dry land. The earliest evidences of sidewalking behavior may also be evidence for the development of the crab form during their rise in the Jurassic.A Icnologia é um poderoso instrumento para a compreensão das etapas evolutivas de clados de animais através da paleobiologia do comportamento inscrito em sítios paleontológicos excepcionais, como o Cabeço da Ladeira (Portugal). O Jurássico Médio (Bajociano superior) da Formação de Chão das Pias é formado por uma sequência de carbonatos peritidais que regista o desenvolvimento de tapetes microbianos numa planície de maré. Episodicamente, esta terá tido um desenvolvimento extraordinário através de marés equinociais que poderão ter sido responsáveis pela morte in situ de diversos grupos de equinodermes e pela preservação com excelente detalhe dos seus esqueletos articulados, além das formas de comportamento de uma endo- e epifauna dominada pelos artrópodes. Os níveis superficiais, com uma moderada icnodiversidade preservada pelos tapetes microbianos e atribuível à icnofácies de Cruziana, incluem trilhos de caranguejos (Laterigradus lusitanica nov. igén.) e de outros crustáceos (Diplopodichnus isp.), assim como eventualmente de peixes (?Undichna), pistas de gastrópodes (Archaeonassa fossulata), crinóides isocrinídeos (Krinodromos bentou nov. igén.) e insectos (Haplotichnus indianensis), além de galerias de lagostins ou de lagostas (Thalassinoides suevicus), e de outros artrópodes (Asterosoma ludwigae, Gyrochorte comosa) ou poliquetas (Rhizocorallium commune). Laterigradus lusitanicus e Krinodromos bentou são novos icnogéneros e icnoespécies definidos neste trabalho. Os trilhos de caranguejos e as pistas de gastrópodes são algumas das mais extensas evidências de locomoção encontradas no registo fóssil dos invertebrados até ao momento. A “marcha para a morte” de um crinóide é o primeiro registo fóssil de locomoção para este grupo, e um raro exemplo desta categoria etológica. Extensos trilhos contínuos também evidenciam com grande detalhe os estilos de locomoção “salto com vara” subaquático e “caminhada de lado” em terra emersa característicos dos caranguejos anfíbios. Os mais antigos indícios da locomoção “de lado” poderão ser também a evidência da evolução da forma de caranguejo com a diversificação dos Brachyura durante o Jurássico, um clado bem-sucedido que culminou com a colonização de habitats terrestres devido às suas exaptações motoras

    Pool boiling of nanofluids on biphilic surfaces: An experimental and numerical study

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    This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.This work was funded by Portuguese national funds of FCT/MCTES (PIDDAC) through the base funding from the following research units: UIDB/00532/2020 (Transport Phenomena Research Center, CEFT), UIDB/04077/2020 (MEtRICs) and UIDP/04436/2020. The authors are also grateful for the funding of FCT through the projects LISBOA-01-0145-FEDER-030171/NORTE-01-0145-FEDER-030171 (PTDC/EME-SIS/30171/2017), funded by COMPETE2020, NORTE2020, PORTUGAL2020 and FEDER. The authors also acknowledge FCT for partially financing the research under the framework of the project UTAP-EXPL/CTE/0064/2017, financiado no ambito do Projeto 5665-Parcerias Internacionais de Ciencia e Tecnologia, UT Austin Programme. Mr Pedro Pontes also acknowledgesFCT for his fellowship ref. SFRH/BD/149286/2019

    Phytoplankton dynamics in relation to seasonal variability and upwelling and relaxation patterns at the mouth of Ria de Aveiro (West Iberian Margin) over a four-year period

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    From June 2004 to December 2007, samples were weekly collected at a fixed station located at the mouth of Ria de Aveiro (West Iberian Margin). We examined the seasonal and inter-annual fluctuations in composition and community structure of the phytoplankton in relation to the main environmental drivers and assessed the influence of the oceano-graphic regime, namely changes in frequency and intensity of upwelling events, over the dynamics of the phytoplankton assemblage. The samples were consistently handled and a final subset of 136 OTUs (taxa with relative abundance > 0.01%) was subsequently submitted to various multivariate analyses. The phytoplankton assemblage showed significant changes at all temporal scales but with an overriding importance of seasonality over longer-(inter-annual) or shorter-term fluctuations (upwelling-related). Sea-surface temperature, salinity and maximum upwelling index were retrieved as the main driver of seasonal change. Seasonal signal was most evident in the fluctuations of chlorophyll a concentration and in the high turnover from the winter to spring phytoplankton assemblage. The seasonal cycle of production and succession was disturbed by upwelling events known to disrupt thermal stratification and induce changes in the phytoplankton assemblage. Our results indicate that both the frequency and intensity of physical forcing were important drivers of such variability, but the outcome in terms of species composition was highly dependent on the available local pool of species and the timing of those events in relation to the seasonal cycle. We conclude that duration, frequency and intensity of upwelling events, which vary seasonally and inter-annually, are paramount for maintaining long-term phytoplankton diversity likely by allowing unstable coexistence and incorporating species turnover at different scales. Our results contribute to the understanding of the complex mechanisms of coastal phytoplankton dynamics in relation to changing physical forcing which is fundamental to improve predictability of future prospects under climate change.Portuguese Foundation for Science and Technology (FCT, Portugal) [SFRH/BPD/ 94562/2013]; FEDER funds; national funds; CESAM [UID/AMB/50017]; FCT/MEC through national funds; FEDERinfo:eu-repo/semantics/publishedVersio

    The Pool-Boiling-Induced Deposition of Nanoparticles as the Transient Game Changer—A Review

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    It is widely known by the scientific community that the suspended nanoparticles of nanofluids can enhance the thermophysical properties of base fluids and maximize pool-boiling heat transfer. However, the nanoparticles may undergo extended boiling times and deposit onto the heating surfaces under pool-boiling conditions, thus altering their intrinsic characteristics such as wettability and roughness over time. The present study reviews the fundamental mechanisms and characteristics of nanoparticle deposition, and its impact on surface roughness and wettability, density of vaporized core points, and thermal resistance, among other factors. Moreover, the effect of the nanoparticle layer in long-term thermal boiling performance parameters such as the heat transfer coefficient and critical heat flux is also discussed. This work attempts to highlight, in a comprehensive manner, the pros and cons of nanoparticle deposition after extended pool-boiling periods, leading the scientific community toward further investigation studies of pool-boiling heat-transfer enhancement using nanofluids. This review also attempts to clarify the inconsistent results of studies on heat transfer parameters using nanofluids

    An Overview of the Molten Salt Nanofluids as Thermal Energy Storage Media

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    The research in the field of the nanofluids has experienced noticeable advances since its discovery two decades ago. These thermal fluids having minimal quantities of nano-scaled solid particles in suspension have great potential for thermal management purposes because of their superior thermophysical properties. The conventional water-based nanofluids have been extensively investigated so far with emphasis in their improved thermal conductivity. A novel class of nanofluids based on inorganic salts has been developed in the last few years with the goal of storing and transferring thermal energy under high temperatures. These molten salt-based nanofluids can in general be recognized by an enhanced specific heat due to the inclusion of the nanoparticles. However, it should be emphasized that this does not always happen since this thermophysical property depends on so many factors, including the nature of the molten salts, different preparation methods, and formation of the compressed layer and secondary nanostructures, among others, which will be thoroughly discussed in this work. This peculiar performance has caused a widespread open debate within the research community, which is currently trying to deal with the inconsistent and controversial findings, as well as attempting to overcome the lack of accurate theories and prediction models for the nanofluids in general. This review intends to present an extensive survey of the published scientific articles on the molten salt nanofluids. Other important realities concerning the development and thermal behavior of the molten salt nanofluids, such as the stability over time of the nanoparticles dispersed in the molten salts, latent heat, viscosity, and thermal conductivity, will be reviewed in the current work. Additionally, special focus will be given to concentrated solar power technology applications. Finally, the limitations and prospects of the molten salts nanofluids will be addressed and the main concluding remarks will be listed

    Nanofluids for the Next Generation Thermal Management of Electronics: A Review

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    Nowadays, the thermal management of electronic components, devices and systems is one of the most important challenges of this technological field. The ever-increasing miniaturization also entails the pressing need for the dissipation of higher power energy under the form of heat per unit of surface area by the cooling systems. The current work briefly describes the use on those cooling systems of the novel heat transfer fluids named nanofluids. Although not intensively applied in our daily use of electronic devices and appliances, the nanofluids have merited an in-depth research and investigative focus, with several recently published papers on the subject. The development of this cooling approach should give a sustained foothold to go on to further studies and developments on continuous miniaturization, together with more energy-efficient cooling systems and devices. Indeed, the superior thermophysical properties of the nanofluids, which are highlighted in this review, make those innovative fluids very promising for the aforementioned purpose. Moreover, the present work intends to contribute to the knowledge of the nanofluids and its most prominent results from the typical nanoparticles/base fluid mixtures used and combined in technical and functional solutions, based on fluid-surface interfacial flows

    Nanofluids as a Waste Heat Recovery Medium: A Critical Review and Guidelines for Future Research and Use

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    The thermal energy storage and conversion process possesses high energy losses in the form of waste heat. The losses associated with energy conversion achieve almost 90% of the worldwide energy supply, and approximately half of these losses are waste heat. Hence, waste heat recovery approaches intend to recuperate that large amount of wasted heat from chimneys, vehicles, and solar energy systems, among others. The novel class of thermal fluids designated by nanofluids has a high potential to be employed in waste heat recovery. It has already been demonstrated that nanofluids enhance energy recovery efficiency by more than 20%. Also, the use of nanofluids can improve the energy capacity of steelworks systems by around three times. In general, nanofluids can improve efficiency and reduce exergy destruction and carbon emissions in devices like heat exchangers. The current work summarizes the application of nanofluids in waste heat recovery and discusses the involved feasibility factors. Also, the critical survey of more than one hundred scientific papers enabled the overview of the environmental aspects of the nanofluid’s waste heat recovery. Finally, it discusses the main limitations and prospects of the use of nanofluids in waste heat recovery processes
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