Recovery of deformation substructure and coarsening of particles on annealing severely plastically deformedAl–Mg–Si alloy and analysis of strengthening mechanisms

An Al–Mg–Si alloy was annealed to various solutionized and aged states and was then severely plastically deformed by equal channel angular pressing (ECAP). These materials were subsequently annealed for a range of times and temperatures to induce precipitation, dislocation recovery, and grain growth, with changes of mechanical behavior followed by tensile testing. Precipitation of excess solute was seen to occur in all cases, independent of the initial heat treated state, but the particles present appear to play only a small role in stabilizing the deformation substructure, at least until significant particle and grain coarsening has occurred, when discontinuous grain coarsening can be provoked. The strength of materials is examined, and the respective contributions of loosely arranged dislocations, many grain boundaries, and dispersed particles are deduced. It is shown that dislocation strengthening is significant in as-deformed, as well as lightly annealed materials, with grain boundary strengthening providing the major contribution thereafterComunidad de Madrid (CAM) under Contract No. 07N/0087/2002Peer reviewe

Matrix grain refinement in Al-TiAl composites by severe plastic deformation: influence of particle size and processing route

The microstructure and mechanical behaviour of Al-based composites reinforced with TiAl intermetallic particles has been examined in the as-extruded state and after processing by equal channel angular pressing (ECAP). The latter produces a grain size reduction in the aluminium matrix to values of 500 nm, using route A, and 750 nm, using route C. The ECAP produces up to a 75% increase in the yield stress of the composites, being more rapid when route A is used. The strengthening effect by ECAP is much larger than that obtained by increasing the volume fraction of reinforcement particles from 25 to 50% in these compositesThanks to the Spanish Ministry of Education and Science for financing this study under project number MAT2003-01540.Peer reviewe

Susceptibility of different life stages of Blattella germanica (Blattodea: Blattellidae) and Periplaneta fuliginosa (Blattodea: Blattidae) to entomopathogenic fungi

The susceptibility of nymphs and adults of the German cockroach, Blattella germanica Linnaeus (Blattodea: Blattellidae) and the smokybrown cockroach, Periplaneta fuliginosa Serville (Blattodea: Blattidae) to Argentinian isolates of the entomopathogenic fungi Metarhizium anisopliae (Metschn.) Sorokin (CEP 085) and Beauveria bassiana (Bals.-Criv.) Vuill. (CEP 077) was evaluated. Fungi were tested by using two different methods: bait and direct contact. Mortality was monitored daily for twenty days to obtain LT50. M. anisopliae produced 60 and 93% mortality in nymphs and adults of B. germanica, respectively, when conidia were applied by direct contact. The LT50 for adults was 3.8 days, and 8.6 days for nymphs. Direct contact of B. bassiana produced 80% mortality on adults of B. germanica with a LT50 of 4.9 days, and for nymphs 40 % mortality in 10 days. When B. germanica was exposed to bait, the level of mortality was significant in adults. Nymphs of P. fuliginosa were treated with bait with M. anisopliae and B. bassiana and they caused 50% mortality with a LT50 of 22 days, and LT50 of 27 days respectively. Nymphs and adults of P. fuliginosa treated by direct contact and adults treated with bait showed that mortality level was not significantly different as compared to the control. Results showed differences in susceptibility between the two species of cockroaches and between nymphs and adults of the same species. In addition, different responses to the fungal species with the two methods that were used in the bioassays have been demonstrated. This is the first report of susceptibility of P. fuliginosa to entomopathogenic fungi. This study demonstrates the potential of fungi as biocontrol agents against this pest.Fil: Gutierrez, Alejandra Concepción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); Argentina. Universidad Nacional de La Plata; ArgentinaFil: García, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); Argentina. Universidad Nacional de La Plata; ArgentinaFil: Alzogaray, Raul Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; ArgentinaFil: Urrutia, María I.. Universidad Nacional de La Plata; ArgentinaFil: Lopez Lastra, Claudia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); Argentina. Universidad Nacional de La Plata; Argentin

Enhanced synthesis of medium-chain-length poly(3-hydroxyalkanoates) by inactivating the tricarboxylate transport system of Pseudomonas putida KT2440 and process development using waste vegetable oil

Indexación: Scopus.The use of waste materials as feedstock for biosynthesis of valuable compounds has been an intensive area of research aiming at diminishing the consumption of non-renewable materials. In this study, P. putida KT2440 was employed as a cell factory for the bioconversion of waste vegetable oil into medium-chain-length Polyhydroxyalkanoates. In the presence of the waste oil this environmental strain is capable of secreting enzymes with lipase activities that enhance the bioavailability of this hydrophobic carbon substrate. It was also found that the oxygen transfer coefficient is directly correlated with high PHA levels in KT2440 cells when metabolizing the waste frying oil. By knocking out the tctA gene, encoding for an enzyme of the tripartite carboxylate transport system, an enhanced intracellular level of mcl-PHA was found in the engineered strain when grown on fatty acids. Batch bioreactors showed that the KT2440 strain produced 1.01 (g⋅L −1 ) of PHA whereas the engineered ΔtctA P. putida strain synthesized 1.91 (g⋅L −1 ) after 72 h cultivation on 20 (g⋅L −1 ) of waste oil, resulting in a nearly 2-fold increment in the PHA volumetric productivity. Taken together, this work contributes to accelerate the pace of development for efficient bioconversion of waste vegetable oils into sustainable biopolymers. © 2018 Elsevier Ltd.https://www.sciencedirect.com/science/article/pii/S135951131831451X?via%3Dihu

Nano-mechanical properties of Fe-Mn-Al-C lightweight steels

High Al Low-density steels could have a transformative effect on the light-weighting of steel structures for transportation and achieving the desired properties with the minimum amount of Ni is of great interest from an economic perspective. In this study, the mechanical properties of two duplex low-density steels, Fe-15Mn-10Al-0.8C-5Ni and Fe-15Mn-10Al-0.8C (wt.%) were investigated through nano-indentation and simulation through utilization of ab initio formalisms in Density Functional Theory (DFT) in order to establish the hardness resulting from two critical structural features (ߢ-carbides and B2 intermetallic) as a function of annealing temperature (500 − 1050 ℃) and the addition of Ni. In the Ni-free sample, the calculated elastic properties of kappa-carbides were compared with those of the B2 intermetallic Fe3Al − L12, and the role of Mn in the kappa structure and its elastic properties were studied. The Ni-containing samples were found to have a higher hardness due to the B2 phase composition being NiAl rather than FeAl, with Ni-Al bonds reported to be stronger than the Fe-Al bonds. In both samples, at temperatures of 900 ℃ and above, the ferrite phase contained nano-sized discs of B2 phase, wherein the Ni-containing samples exhibited higher hardness, attributed again to the stronger Ni-Al bonds in the B2 phase. At 700 ℃ and below, the nano-sized B2 discs were replaced by micrometre sized needles of kappa in the Ni-free sample resulting in a lowering of the hardness. In the Ni-containing sample, the entire alpha phase was replaced by B2 stringers, which had a lower hardness than the Ni-Al nano-discs due to a lower Ni content in B2 stringer bands formed at 700 ℃ and below. In addition, the hardness of needle-like kappa-carbides formed in alpha phase was found to be a function of Mn content. Although it was impossible to measure the hardness of cuboid kappa particles in gamma phase because of their nano-size, the hardness value of composite phases, e.g. gamma + kappa was measured and reported. All the hardness values were compared and rationalized by bonding energy between different atoms

Channelling carbon flux through the meta-cleavage route for improved poly(3-hydroxyalkanoate) production from benzoate and lignin-based aromatics in Pseudomonas putida H

Indexación: Scopus.Lignin-based aromatics are attractive raw materials to derive medium-chain length poly(3-hydroxyalkanoates) (mcl-PHAs), biodegradable polymers of commercial value. So far, this conversion has exclusively used the ortho-cleavage route of Pseudomonas putida KT2440, which results in the secretion of toxic intermediates and limited performance. Pseudomonas putida H exhibits the ortho- and the meta-cleavage pathways where the latter appears promising because it stoichiometrically yields higher levels of acetyl-CoA. Here, we created a double-mutant H-ΔcatAΔA2 that utilizes the meta route exclusively and synthesized 30% more PHA on benzoate than the parental strain but suffered from catechol accumulation. The single deletion of the catA2 gene in the H strain provoked a slight attenuation on the enzymatic capacity of the ortho route (25%) and activation of the meta route by nearly 8-fold, producing twice as much mcl-PHAs compared to the wild type. Inline, the mutant H-ΔcatA2 showed a 2-fold increase in the intracellular malonyl-CoA abundance – the main precursor for mcl-PHAs synthesis. As inferred from flux simulation and enzyme activity assays, the superior performance of H-ΔcatA2 benefited from reduced flux through the TCA cycle and malic enzyme and diminished by-product formation. In a benzoate-based fed-batch, P. putida H-ΔcatA2 achieved a PHA titre of 6.1 g l‒1 and a volumetric productivity of 1.8 g l‒1 day‒1. Using Kraft lignin hydrolysate as feedstock, the engineered strain formed 1.4 g l- 1 PHA. The balancing of carbon flux between the parallel catechol-degrading routes emerges as an important strategy to prevent intermediate accumulation and elevate mcl-PHA production in P. putida H and, as shown here, sets the next level to derive this sustainable biopolymer from lignin hydrolysates and aromatics.https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/1751-7915.1370

Modular reorganization of the global network of gene regulatory interactions during perinatal human brain development.

BACKGROUND During early development of the nervous system, gene expression patterns are known to vary widely depending on the specific developmental trajectories of different structures. Observable changes in gene expression profiles throughout development are determined by an underlying network of precise regulatory interactions between individual genes. Elucidating the organizing principles that shape this gene regulatory network is one of the central goals of developmental biology. Whether the developmental programme is the result of a dynamic driven by a fixed architecture of regulatory interactions, or alternatively, the result of waves of regulatory reorganization is not known. RESULTS Here we contrast these two alternative models by examining existing expression data derived from the developing human brain in prenatal and postnatal stages. We reveal a sharp change in gene expression profiles at birth across brain areas. This sharp division between foetal and postnatal profiles is not the result of pronounced changes in level of expression of existing gene networks. Instead we demonstrate that the perinatal transition is marked by the widespread regulatory rearrangement within and across existing gene clusters, leading to the emergence of new functional groups. This rearrangement is itself organized into discrete blocks of genes, each targeted by a distinct set of transcriptional regulators and associated to specific biological functions. CONCLUSIONS Our results provide evidence of an acute modular reorganization of the regulatory architecture of the brain transcriptome occurring at birth, reflecting the reassembly of new functional associations required for the normal transition from prenatal to postnatal brain development