Numerical analysis on the behaviour of concrete masonry walls subjected to fire

This paper presents a numerical study on the structural behaviour of concrete masonry at elevated temperatures. Based on an experimental research previously performed on half-scale walls in fire situations, numerical models were developed and validated. The heat transfer models led to thermal fields with good agreement with the temperatures measured by thermocouples installed in the wall, a bigger scatter of temperatures was found in the experimental research. The mechanical analysis led to vertical and out-of-plane displacements in good agreement with the displacements measured by LVDTs. The numerical model was validated and will be used in future researches to perform parametric studies

Normal and tangential behaviour of dry joints in refractory masonry

Industrial vessels used in high temperature processes of steel and cement production are protected by refractory linings built with mortarless joints. These dry joints, formed by stacked bricks have a crucial importance on the mechanical behaviour of the lining. The stiffness and consequently the stresses generated by thermal expansion are reduced due to the joints. The present article presents the results of experimental and numerical tests on the thermomechanical behaviour of these joints. The compressive strength of the brick was assessed at ambient and high temperatures and a statistical analysis of the distribution of the bricks’ shape imperfections was carried out. Several studies were carried out on the normal behaviour of the joints: classical joint closure test; bed joint closing action in a masonry wallet measured with a DIC; effects of brick’s height imperfections on its loadbearing capacity; effects of brick’s height imperfections on the wall’s behaviour at ambient and high temperatures and a comparison between the bed and head joints behaviour. To characterize the joint’s tangential behaviour at high temperatures a novel device was developed and presented.The authors would like to thank the support of European Commission under the framework of Marie Sklodowska-Curie Actions Innovative Training Networks, project ATHOR -Advanced THermomechanical multiscale mOdelling of Refractory linings 764987 Grant

Experimental and numerical analysis on the structural fire behaviour of three-cell hollowed concrete masonry walls

Preprint versionMasonry is one of the oldest and most traditional materials in building construction. Nevertheless, the knowledge on the structural fire behaviour of masonry elements is not yet well consolidated. The literature on the load-bearing capacity of masonry walls in case of fire showed an enhanced performance of these elements, however the lack of normative documents, characterization of material properties at high temperatures and experimental results, for calibrating and validating the numerical models, indicates the need of further research. A research study on the structural fire behaviour of three-cell hollowed concrete masonry walls subjected to fire is presented based on results of experimental and numerical studies. First, several loadbearing capacity tests at high temperatures and fire resistance tests on the walls, were carried out in order to assess their behaviour, critical times, failure modes and temperature distribution. The specimens were built with three cell concrete blocks and M10 mortar and were then subjected to an in-plane serviceability load during test. The temperatures, loads and displacements were measured. Second, finite element models were developed and validated with the experimental results. The experimental and numerical results were also compared with the ones given by EN1996-1–2 provisions.European Union (European Commission), Marie Skłodowska-Curie Actions Innovative Training Networks in the frame of the project ATHOR - Advanced THermomechanical multiscale modelling of Refractory linings 764987 Gran

Combined use of a new SNP-based assay and multilocus SSR markers to assess genetic diversity of Xylella fastidiosa subsp. pauca infecting citrus and coffee plants

Two haplotypes of Xylella fastidiosa subsp. pauca (Xfp) that correlated with their host of origin were identified in a collection of 90 isolates infecting citrus and coffee plants in Brazil, based on a single-nucleotide polymorphism in the gyrB sequence. A new single-nucleotide primer extension (SNuPE) protocol was designed for rapid identification of Xfp according to the host source. The protocol proved to be robust for the prediction of the Xfp host source in blind tests using DNA from cultures of the bacterium, infected plants, and insect vectors allowed to feed on Xfp- infected citrus plants. AMOVA and STRUCTURE analyses of microsatellite data separated most Xfp populations on the basis of their host source, indicating that they were genetically distinct. The combined use of the SNaPshot protocol and three previously developed multilocus SSR markers showed that two haplotypes and distinct isolates of Xfp infect citrus and coffee in Brazil and that multiple, genetically different isolates can be present in a single orchard or infect a single tree. This combined approach will be very useful in studies of the epidemiology of Xfp- induced diseases, host specificity of bacterial genotypes, the occurrence of Xfp host jumping, vector feeding habits, etc., in economically important cultivated plants or weed host reservoirs of Xfp in Brazil and elsewhere [Int Microbiol 2015; 18(1):13-24].We acknowledge financial support from the EU grant ICA4-CT-2001-10005 and an ‘Intramural Project’ to B. B. Landa from the Spanish National Research Council (CSIC), as well as CNPq for a scholarship to J. R. S. Lopes in Brazil.Peer reviewe

Estudo numérico de paredes de alvenaria estrutural de blocos de concreto em situação de incêndio

[Excerto] As paredes de alvenaria estrutural de blocos de concreto tem sido usadas mundialmente como elementos portantes e de partição. Para garantir a segurança destas estruturas em situação de incêndio, alguns requisitos relacionados com o isolamento, a integridade e a capacidade portante devem ser atendidos. Na Europa, a norma europeia EN 1996-1-2 (2005) [1] preconiza que paredes de alvenaria estrutural devem atender aos seguintes quesitos quando expostas ao fogo: I para isolamento térmico, E para integridade (evitar a proliferação de fumos e gases através da parede), R para capacidade portante e M para impacto mecânico. Em situações de incêndio, as paredes de alvenaria são geralmente submetidas a aquecimento em uma face, o que leva a um gradiente térmico através de sua espessura. Em paredes sem restrições, o alongamento térmico diferencial resulta em curvatura térmica em direção ao fogo, um fenômeno complexo que depende das propriedades térmicas e mecânicas do material, que são variáveis com a temperatura [2]. A degradação das propriedades dos materiais causada por temperaturas elevadas associadas às tensões térmicas e mecânicas pode levar ao colapso estrutural da parede [3-6]. Portanto, a estabilidade estrutural da alvenaria durante o incêndio é necessária para evitar o colapso, prevenir a propagação do incêndio, mitigar o colapso da estrutura local e garantir a evacuação segura dos ocupantes do edifício [4-8]. [...

Fast and efficient method to evaluate the potential of eutectic solvents to dissolve lignocellulosic components

The application of eutectic solvents (ESs) in lignocellulosic biomass fractionation has been demonstrated as a promising approach to accomplish efficient and environmentally friendly biomass valorization. In general, ESs are a combination of two components, a hydrogen-bonding donor and a hydrogen-bonding acceptor, in which the melting point of the mixture is lower than that of the individual components. However, there are plenty of possible combinations to form ESs with the potential to apply in biomass processing. Therefore, the development of fast and effective screening methods to find combinations capable to dissolve the main biomass components—namely cellulose, hemicelluloses, and lignin—is highly required. An accurate and simple technique based on optical microscopy with or without polarized lenses was used in this study to quickly screen and monitor the dissolution of cellulose, xylose (a monomer of hemicelluloses), and lignin in several ESs. The dissolution of these solutes were investigated in different choline-chloride-based ESs (ChCl:UREA, ChCl:PROP, ChCl:EtGLY, ChCl:OXA, ChCl:GLY, ChCl:LAC). Small amounts of solute and solvent with temperature control were applied and the dissolution process was monitored in real time. The results obtained in this study showed that cellulose was insoluble in these ESs, while lignin and xylose were progressively dissolved.publishe

A study on the immunological basis of the dissociation between type I-hypersensitivity skin reactions to Blomia tropicalis antigens and serum anti-B. tropicalis IgE antibodies

<p>Abstract</p> <p>Background</p> <p>Two conditions are used as markers of atopy: the presence of circulating anti-allergen IgE antibodies and the presence of positive skin prick test (SPT) reactions to allergenic extracts. The correlation between these conditions is not absolute. This study aimed at investigating immunological parameters that may mediate this lack of correlation. Individuals whose sera contained anti-<it>B. tropicalis </it>extract IgE antibodies (α<it>-Bt</it>E IgE) were divided into two groups, according to the presence or absence of skin reactivity to <it>B. tropicalis </it>extract (<it>Bt</it>E). The following parameters were investigated: total IgE levels; α<it>-Bt</it>E IgE levels; an arbitrary α<it>-Bt</it>E IgE/total IgE ratio; the proportion of carbohydrate-reactive α<it>-Bt</it>E IgE; the proportion of α<it>-Bt</it>E IgE that reacted with <it>Ascaris lumbricoides </it>extract (<it>Al</it>E); the production of IL-10 by <it>Bt</it>E- and <it>Al</it>E-stimulated peripheral blood cells (PBMC).</p> <p>Results</p> <p>Total IgE levels were similar in the two groups, but α<it>-Bt</it>E IgE was significantly higher in the SPT-positive group (SPT<b>+</b>). A large overlap of α<it>-Bt</it>E IgE levels was found in individuals of both groups, indicating that these levels alone cannot account for the differences in SPT outcome. Individuals of the two groups did not differ, statistically, in the proportion of α-<it>Bt</it>E IgE that reacted with carbohydrate and in the production of IL-10 by <it>Bt</it>E- and <it>Al</it>E-stimulated PBMC. Both groups had part of α-<it>Bt</it>E IgE activity absorbed out by <it>Al</it>E, indicating the existence of cross-reactive IgE antibodies. However, the α-<it>Bt</it>E IgE from the SPT-negative individuals (SPT-) was more absorbed with <it>AlE </it>than the α-<it>Bt</it>E IgE from the SPT+ individuals. This finding may be ascribed to avidity differences of the α-<it>Bt</it>E IgE that is present in the two groups of individuals, and could occur if at least part of the α-<it>Bt</it>E IgE from the SPT- individuals were elicited by <it>A. lumbricoides </it>infection.</p> <p>Conclusion</p> <p>The present results suggest that a low ratio of specific IgE to total IgE levels (in a minority of individuals), and differences in α-<it>Bt</it>E IgE avidities (which would have high affinities for <it>A. lumbricoides </it>antigens in SPT- than in SPT<b>+ </b>individuals) may play a role in the down-modulation of type-I hypersensitivity reaction against aeroallergens described in helminth-infected individuals.</p

Identification and analysis of seven effector protein families with different adaptive and evolutionary histories in plant-associated members of the Xanthomonadaceae.

The Xanthomonadaceae family consists of species of non-pathogenic and pathogenic γ-proteobacteria that infect different hosts, including humans and plants. In this study, we performed a comparative analysis using 69 fully sequenced genomes belonging to this family, with a focus on identifying proteins enriched in phytopathogens that could explain the lifestyle and the ability to infect plants. Using a computational approach, we identified seven phytopathogen-enriched protein families putatively secreted by type II secretory system: PheA (CM-sec), LipA/LesA, VirK, and four families involved in N-glycan degradation, NixE, NixF, NixL, and FucA1. In silico and phylogenetic analyses of these protein families revealed they all have orthologs in other phytopathogenic or symbiotic bacteria, and are involved in the modulation and evasion of the immune system. As a proof of concept, we performed a biochemical characterization of LipA from Xac306 and verified that the mutant strain lost most of its lipase and esterase activities and displayed reduced virulence in citrus. Since this study includes closely related organisms with distinct lifestyles and highlights proteins directly related to adaptation inside plant tissues, novel approaches might use these proteins as biotechnological targets for disease control, and contribute to our understanding of the coevolution of plant-associated bacteria