Search

Abstract: The aim of this work was to probe for the first time the back-spillover of labile O and OH species during steam reforming of phenol towards H2 production over Rh and Fe supported on MgO, Mg-Ce-O and Mg-Ce-Zr-O metal oxides. This was made possible through SSITKA and other transient isotopic experiments (use of D2O and 18O2). The size of the active pool of H-containing species (H and/or OH) present under reaction conditions as a function of reaction T and catalyst composition, and deuterium kinetic isotope effects were measured. [Copyright &y& Elsevier]

Although silver nanoparticles (AgNPs) appear to be promising for certain medical/pharmaceutical applications, they present significant disadvantages when it comes to environmental applications due to the need for recovery of the metal (Ag) which is considered hazardous for the environment. The present study examines the antimicrobial properties and mechanism of action of immobilized (on Al 2 O 3) silver nanoparticles' (1 wt% Ag-iNPs) regarding the treatment of E. coli microbial solutions. Antimicrobial experiments were conducted in semi-batch mode using a three-phase continuous flow stirred tank reactor. Every treated sample was taken from the outlet of the reactor for the time intervals of 0, 5 and 25 min. To ensure that the bactericidal property of Ag-iNPs is not attributed to the dissolution of surface silver (as free Ag+), a suitable Ag+ scavenger was used as already described in our earlier studies. Regarding the molecular analysis performed under this study, the regulation of key enzymes involved in bactericidal activity of E. coli, was examined , after their treatment either with immobilized silver nanoparticles (Ag-iNPs) or AgNO 3. Specifically, 50 mL sample for each case was centrifuged (10 min at 10,000 rpm) and the pellet (≈109 cells) was immediately subjected to total RNA extraction. For real-time RT-qPCR analyses, 1 μg of total RNA was converted into cDNA. It was found that PldA gene, which encodes outer membrane's phospholipase A (OMPLA), was up-regulated after 5 and 25 min of treatment with Ag-iNPs. OMPLA's activation appears to be the initial step of Ag-iNPs bactericidal mechanism that ultimately leads to the creation of holes on the outer membrane (OM), irreversibly disturbing the cells' respiration cycle. In addition, after treatment with Ag-iNPs, Blue copper oxidase CueO (encoded by cueO gene) was found to be over-produced and appears to play a key-role in the oxidative transfer of silver from the surface of Ag-iNPs to the cell. This leads to the Ag-induced displacement of copper from its native protein sites such as CusS/CusR, a fact that causes the release of labile copper and ROS inside the cell. In addition, TEM analysis of bacteria treated with Ag-iNPs revealed severe morphological changes ("holes") on bacterial outer membrane, indicating that there is an intermediate step in the proposed antimicrobial mechanism which takes place on the surface of Ag-iNPs. [Display omitted] • Immobilized AgNPs activity is not exclusively attributed to free Ag+ ions. • Ag-iNPs' interaction with OMPLA and CueO enzymes are decisive mechanistic steps. • OMPLA's activation appears to be the initial step of Ag-iNPs bactericidal mechanism. • Ag-induced displacement of Cu from its native proteins leads to ROS overproduction. • TEM studies revealed the formation of Ag-NPs induced "holes" on bacterial outer membrane. [ABSTRACT FROM AUTHOR]

• Controversies in the classification of siliceous aggregates were found. • Latin American concretes tend to use granite and basalt as siliceous aggregates. • Granitic and basaltic concretes performed better than other siliceous concretes. • Factors such as porosity and the type of silica change the aggregate behavior. • It is necessary to include more data of structures after fires in the standards. The exposure of concrete to high temperatures affects its mechanical properties, reducing its compressive strength, tensile strength and modulus of elasticity. The reduction factors of these properties have been the target of several studies over the years, producing conflicting results. This article addresses the key factors related to such disparity, highlighting the influence of standardization and types of coarse aggregates, as well as an overview of the study of the mechanical properties of concrete exposed to high temperatures in the last years, foregrounding research in several countries and Latin American experience. This article also shows results from a Brazilian experimental study concerning the residual mechanical strength of concrete (NSC and HSC) exposed to temperatures from 100 to 900 °C at 1 °C/min, with or without preheating, in which three types of coarse aggregates—basaltic, granitic and limestone—were used, as well as RILEM recommendations. There is no precedent in Latin America for a study conducted for this purpose and which has applied such international recommendations. Through comparison with bibliographic references and statistical analysis, the effects of the type of coarse aggregate, preheating of samples and types of addition being used were evaluated, contributing to the structural analyses of burning structures. [ABSTRACT FROM AUTHOR]

• Bond behavior between NSM CFRP and concrete after exposure to elevated temperatures was investigated. • Beam pullout tests were used to evaluate bond properties. • Before reaching T g , bond properties presented a slight increase, due to post-curing effects. • After T g , bond properties significantly decreased. • Semi-empirical model was used to fit experimental values. This study evaluated the effect of elevated temperatures on the residual bond (i.e., after cooling) of concrete strengthened with carbon fiber reinforced polymer (CFRP) laminate installed according to the near surface mounted (NSM) technique. Bond was evaluated using the beam pullout test, based on the test method proposed by RILEM RC 05. Initially, tests were conducted at room temperature to determine the influence of bond length. Next, samples were heated at different target temperatures (50 °C to 250 °C). Lastly, bond after heating was evaluated to determine the reduction of bond properties in relation to temperature. In relation to room temperature, higher bond strength was obtained with an anchorage length of 120 mm – the value used for following experimental parts. Regarding the thermal program, it was verified that T g was reached in the resin at the target temperature of 100 °C. Color changes in the resin were observed at the target temperatures of 200 °C and 250 °C. Regarding bond after heating, bond stress varied according to the temperature reached. At 50 °C, before reaching T g , the system presented an increase of 7,3% in bond strength, mostly due to post-curing promoted by cooling. After that, bond strength significantly decreased, reaching 45,1% of the initial value at 150 °C. [ABSTRACT FROM AUTHOR]

The multiple-lactation autoregressive test-day (AR) model is the adopted model for the national genetic evaluation of dairy cattle in Portugal. Under this model, animals' permanent environment effects are assumed to follow a first-order autoregressive process over the long (auto-correlations between parities) and short (auto-correlations between test-days within lactation) terms. Given the relevance of genomic prediction in dairy cattle, it is essential to include marker information in national genetic evaluations. In this context, we aimed to evaluate the feasibility of applying the single-step genomic (G)BLUP to analyze milk yield using the AR model in Portuguese Holstein cattle. In total, 11,434,294 test-day records from the first 3 lactations collected between 1994 and 2017 and 1,071 genotyped bulls were used in this study. Rank correlations and differences in reliability among bulls were used to compare the performance of the traditional (A-AR) and single-step (H-AR) models. These 2 modeling approaches were also applied to reduced data sets with records truncated after 2012 (deleting daughters of tested bulls) to evaluate the predictive ability of the H-AR. Validation scenarios were proposed, taking into account young and proven bulls. Average EBV reliabilities, empirical reliabilities, and genetic trends predicted from the complete and reduced data sets were used to validate the genomic evaluation. Average EBV reliabilities for H-AR (A-AR) using the complete data set were 0.52 (0.16) and 0.72 (0.62) for genotyped bulls with no daughters and bulls with 1 to 9 daughters, respectively. These results showed an increase in EBV reliabilities of 0.10 to 0.36 when genomic information was included, corresponding to a reduction of up to 43% in prediction error variance. Considering the 3 validation scenarios, the inclusion of genomic information improved the average EBV reliability in the reduced data set, which ranged, on average, from 0.16 to 0.26, indicating an increase in the predictive ability. Similarly, empirical reliability increased by up to 0.08 between validation tests. The H-AR outperformed A-AR in terms of genetic trends when unproven genotyped bulls were included. The results suggest that the single-step GBLUP AR model is feasible and may be applied to national Portuguese genetic evaluations for milk yield. [ABSTRACT FROM AUTHOR]

Abstract: Mixed oxides of the general formula La0.8Sr0.2FeO3−x were prepared by ceramic and surfactant methods and tested towards the NO/H2/O2 and NO/CH4/O2 lean-deNO x reactions in the 200–450°C range. The materials were characterized for their bulk and surface composition by XRD, Mössbauer and XPS techniques. The main crystal phases detected were perovskites LaFeO3 and SrFeO3−x , and α-Fe2O3. The Mössbauer technique allowed the precise determination of the composition of Fe-containing phases in the solids prepared by both the ceramic and surfactant methods. Significant differences in the composition of the phases and the surface chemical states of Fe, Sr and La were revealed among the two solid compositions. For the CH4 lean-deNO x reaction at 350°C, the La0.8Sr0.2FeO3−x solid composition (LSF-2) prepared by the surfactant method exhibited an increase by 50% in the rate of NO conversion and by 30% in the rate of N2 formation (per gram basis) as compared to the solid prepared by the ceramic method (LSF-1). An opposite relative catalytic activity behavior was observed for the two solids when tested towards the H2 lean-deNO x reaction. At 375°C (maximum activity observed) the solid prepared by the ceramic method (LSF-1) exhibited an increase by 83% in the rate of N2 formation as compared to the solid prepared by the surfactant method (LSF-2). It is suggested that the mobility of surface lattice oxygen, the concentration of oxygen vacant sites, and the mixed valences of metal cations present in the La0.8Sr0.2FeO3−x solid all influenced by the preparation method used are the main parameters that largely influenced the catalytic behavior observed over the LSF-1 and LSF-2 solids. [Copyright &y& Elsevier]