Effect of cyclic heat treatment process on the pitting corrosion resistance of EN-1.4405 martensitic, EN-1.4404 austenitic, and EN-1.4539 austenitic stainless steels in chloride-sulfate solution.

The effect of high temperature variation on the corrosion resistance of EN-1.4405, EN-1.4404, and EN-1.4539 stainless steels in 2 M H2SO4/3.5% NaCl solution was studied. Untreated EN 1.4405 exhibited the highest corrosion rate at 4.775 mm/year compared to untreated EN 1.4539 with the lowest corrosion rate (1.043 mm/year). Repetitive heat treatment significantly decreased the corrosion rate of the steels by 54.61%, 27.83%, and 50.28% to 2.167, 1.396, and 0.519 mm/year. EN-1.4539 steel exhibited the shortest metastable pitting activity among the untreated steels due to higher resistance to transient pit formation while heat treated EN-1.4404 and EN-1.4539 steels exhibited double metastable pitting activity. Heat treated EN-1.4405 was unable to passivate after anodic polarization signifying weak corrosion resistance. Pitting current of heat-treated steels was generally higher than the untreated counterparts. Heat treatment extended the passivation range value of EN-1.4405 and EN-1.4539 steels compared to those of the untreated steels. The corrosion potential of heat-treated steels significantly shifted to electronegative values. The optical image of untreated and heat treated EN-1.4404 and EN-1.4539 steels were generally similar while the images for EN-1.4405 significantly contrast each other

Root architecture governs plasticity in response to drought

Aims: Root characteristics are important for predicting plant and ecosystem responses to resource scarcity. Simple, categorical traits for roots could be broadly applied to ecosystem function and restoration experiments, but they need to be evaluated for their role and behaviour under various stresses, including water limitation. We hypothesised that more complex root architectures allow more plastic responses to limited water than do tap roots. Methods: We carried out two greenhouse experiments: one with a range of grassland plant species; the other with only species of Asteraceae to test the responsiveness of root architectural classes to location of limited water in the soil column. Using trait screening techniques and X-ray tomography, we measured the plasticity of the roots in response to water location. Results: Plasticity of root biomass was lowest in tap rooted species, while fibrous and rhizomatous roots allocated biomass preferentially to where the soil was wettest. X-ray tomography indicated that root morphology was least plastic in rhizomatous species. Conclusions: Our results provide a starting point to effective categorisation of plants in terms of rooting architecture that could aid in understanding drought tolerance of grassland species. They also demonstrate the utility of X-ray tomography in root analyses

Ten millennia of hepatitis B virus evolution

Hepatitis B virus (HBV) has been infecting humans for millennia and remains a global health problem, but its past diversity and dispersal routes are largely unknown. We generated HBV genomic data from 137 Eurasians and Native Americans dated between ~10,500 and ~400 years ago. We date the most recent common ancestor of all HBV lineages to between ~20,000 and 12,000 years ago, with the virus present in European and South American hunter-gatherers during the early Holocene. After the European Neolithic transition, Mesolithic HBV strains were replaced by a lineage likely disseminated by early farmers that prevailed throughout western Eurasia for ~4000 years, declining around the end of the 2nd millennium BCE. The only remnant of this prehistoric HBV diversity is the rare genotype G, which appears to have reemerged during the HIV pandemic

Brane effective actions, kappa-symmetry and applications

This is a review on brane effective actions, their symmetries and some of their applications. Its first part covers the Green–Schwarz formulation of single M- and D-brane effective actions focusing on kinematical aspects: the identification of their degrees of freedom, the importance of world volume diffeomorphisms and kappa symmetry to achieve manifest spacetime covariance and supersymmetry, and the explicit construction of such actions in arbitrary on-shell supergravity backgrounds. Its second part deals with applications. First, the use of kappa symmetry to determine supersymmetric world volume solitons. This includes their explicit construction in flat and curved backgrounds, their interpretation as Bogomol’nyi–Prasad–Sommerfield (BPS) states carrying (topological) charges in the supersymmetry algebra and the connection between supersymmetry and Hamiltonian BPS bounds. When available, I emphasise the use of these solitons as constituents in microscopic models of black holes. Second, the use of probe approximations to infer about the non-trivial dynamics of strongly-coupled gauge theories using the anti de Sitter/conformal field theory (AdS/CFT) correspondence. This includes expectation values of Wilson loop operators, spectrum information and the general use of D-brane probes to approximate the dynamics of systems with small number of degrees of freedom interacting with larger systems allowing a dual gravitational description. Its final part briefly discusses effective actions for N D-branes and M2-branes. This includes both Super-Yang-Mills theories, their higher-order corrections and partial results in covariantising these couplings to curved backgrounds, and the more recent supersymmetric Chern–Simons matter theories describing M2-branes using field theory, brane constructions and 3-algebra considerations

Texture Variations and Cyclic Softening Mechanisms on ZRY-4 at Room Temperature. Part I: Cyclic behavior

RESUMEN El presente trabajo informa sobre experimentos de fatiga, y su correspondiente interpretación, efectuados en Zry-4 con el objeto de estudiar los fenómenos de ablandamiento cíclico que este material presenta a temperatura ambiente. El endurecimiento cíclico es un fenómeno habitual en materiales recocidos en tanto que fenómenos de reacomodamiento de defectos pueden dar lugar a ablandamiento en deformación cíclica en materiales endurecidos por deformación previa. Estos fenómenos se encuentran bastante bien estudiados en materiales de estructura FCC y BCC. En el caso de materiales HCP, como las aleaciones de Zr y Ti, la información existente es mucho más escasa. El principal propósito es analizar la confiabilidad de modelos que pretenden explicar estos fenómenos de ablandamiento como efecto de reorientaciones cristalinas inducidas por la deformación cíclica. Ha sido propuesto que esta reorientación, o cambio en la textura del material, produciría un ablandamiento debido a la disminución del factor de Taylor por reorientación de planos de deslizamiento prismático. La Parte I del trabajo presenta, además de los ensayos de fatiga, un análisis y modelos alternativos de interpretación de los resultados. La Parte II presenta experimentos de medición de texturas, además de ensayos de fatiga complementarios, y simulaciones mediante modelos auto consistentes que permiten evaluar el comportamiento en fatiga de las distintas texturas medidas. Palabras clave: Fatiga de bajo número de ciclos, difracción de rayos x, textura, modelos micro mecánicos, ablandamiento cíclico. ABSTRACT The current paper presents fatigue experiments, and its interpretations, performed in Zry-4 to study cyclic softening behavior shown by this material at room temperature. Cyclic hardening is a usual phenomena in well-annealed materials while defect re-arrangement phenomena can lead to cyclic softening in previously deformation hardened materials. These phenomena are well studied in FCC and BCC materials. For HCP materials, like Zr and Ti alloys, the current information is much more scanty. The main purpose of the current paper is the analysis of the reliability of some models proposing crystal reorientation during cyclic deformation as the main cause for cyclic softening. According to those models, that reorientation, or texture change, would induce softening due to diminishing Taylor factors because of prismatic slip system rotations. Part I of the paper presents, besides fatigue tests, analysis of the results and alternative models for interpretation. Part II shows texture experiments, together with complementary fatigue experiments, and selfconsistent micromecanical simulations to evaluate expected fatigue behavior of the measured textures

Polycrystalline modeling of the cyclic hardening/softening behavior of an austenitic-ferritic stainless steel

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Initiation and growth of short cracks during cycling in an aged superduplex stainless steel

The kinetics of short crack growth during cycling has been studied in a superduplex stainless steel in aged condition. After few cycles, slip lines appear distributed in both phases but the preferred phase for microcrack nucleation is the ferrite. Contrary to the exponential behavior observed in the as-received material, the growth rate of microcracks in aged condition follows a rather linear law. Internal dislocation structures were studied in the near surface region; microbands that sometimes extend over several grains were found at approximately 45º of the tensile axis on ferrite grains. The origin of the microbands has been analyzed and correlated with the microcracks.Fil: Balbi, Marcela Ángela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Hereñu, Silvina Andrea Noemi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Proriol Serre, I.. Université de Lille; FranciaFil: Vogt, J. B.. Université de Lille; FranciaFil: Armas, A. F.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Alvarez Armas, I.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentin