Multiscale formulation for material failure accounting for cohesive cracks at the macro and micro scales

This contribution presents a two-scale formulation devised to simulate failure in materials with het- erogeneous micro-structure. The mechanical model accounts for the activation of cohesive cracks in the micro-scale domain. The evolution/propagation of cohesive micro-cracks can induce material instability at the macro-scale level. Then, a cohesive crack is activated in the macro-scale model which considers, in a homogenized sense, the constitutive response of the intricate failure mode taking place in the smaller length scale.The two-scale model is based on the concept of Representative Volume Element (RVE). It is designed following an axiomatic variational structure. Two hypotheses are introduced in order to build the foundations of the entire two-scale theory, namely: (i) a mechanism for transferring kinematical information from macro- to-micro scale along with the concept of “Kinematical Admissibility”, relating both primal descriptions, and (ii) a Multiscale Variational Principle of internal virtual power equivalence between the involved scales of analysis. The homogenization formulae for the generalized stresses, as well as the equilibrium equations at the micro-scale, are consequences of the variational statement of the problem.The present multiscale technique is a generalization of a previous model proposed by the authors and could be viewed as an application of a general framework recently proposed by the authors. The main novelty in this article lies on the fact that failure modes in the micro-structure now involve a set of multiple cohesive cracks, connected or disconnected, with arbitrary orientation, conforming a complex tortuous failure path. Tortuosity is a topic of decisive importance in the modelling of material degradation due to crack propagation. Following the present multiscale modelling approach, the tortuosity effect is introduced in order to satisfy the “Kinematical Admissibility” concept, when the macro-scale kinematics is transferred into the micro-scale domain. There- fore, it has a direct consequence in the homogenized mechanical response, in the sense that the proposed scale transition method (including the tortuosity effect) retrieves the correct post-critical response.Coupled (macro-micro) numerical examples are presented showing the potentialities of the model to sim- ulate complex and realistic fracture problems in heterogeneous materials. In order to validate the multiscale technique in a rigorous manner, comparisons with the so-called DNS (Direct Numerical Solution) approach are also presented

Revista de Vertebrados de la Estación Biológica de Doñana

Tiempo y orden de aparición de las escamas en el salmón del Atlántico (Salmo salar)Estudios sobre el sapo corredor (Bufo calamita) en el sur de España.III. ReproducciónInfluencia de las carecterísticas del medio acuático sobre las poblaciones de larvas de anfibios en lala Reserva Biológica de Doñana(Huelva, EspañaDieta de la cigüeñuela (Himantopus himantopus) en las salinas del estuario del GuadianaOrientación y selección del lugar del nido en el gorrión moruno (Passer hispaniolensis)la avifauna de las Vegas Bajas del Guadianala reproducción de la malvasía (Oxyura leucocephala) en el sur de la provincia de Córdoba, España.La alimentación de la curruca cabecinegra (Sylvia melanocephala, Gmelin 1788) en olivares de la provincia de Jaén (otoño-invierno)Consideraciones sobre el efecto de los conejos y los grandes herbívoros en los pastizales de la Vera de DoñanaAnálisis factorial de las expresiones faciales del babuino sagrado (Papio hamadryas)Contaminación xenobiótica del Parque Nacionalde Doñana. II. Residuos de insecticidas organoclorados, bifenilos policlorados, (PGBs) y metales pesados en Falconiformes y StrigiformesTransferencia total y del y bioacumulación de mercurio y metilmercurio en ecosistemas del Parque Nacional de DoñanaNota sobre la alimentación de larvas de anfibios: I. Pleurodeles waltl en charcas temporaleNota sobre nuevas especies parasitada por el críalo (Clamator glandarius) en EspañaEstructura de la jerarquización en la predación de huevos y pichones en Spheniscus magellanicusPasser domesticus, nueva specie para Bolivia¿Están realmente subalimentados los cernícalos primilla en el valle del Guadalquivir durante el periodo no reproductor?.Nidificación del paiño común (Hydrobates pelagicus) en las Islas Canarias.Nuevos datos sobre la presencia del visón europeo (Mustela lutreola L.) en NavarraLa población de gamos del Parque Nacional de Doñana en 1979Puntualización a la nota "predacción de Falco peregrino y Falco subbuteo sobre quirópteros" de Aymerich y García de Castro aparecida en el vol. 9 de esta revista.Peer reviewe

Cellular and molecular mechanisms of chronic rhinosinusitis and potential therapeutic strategies: review on cytokines, nuclear factor kappa B and transforming growth factor beta

Background: Chronic rhinosinusitis is characterised by persistent inflammation of the sinonasal mucosa. Multiple pathophysiological mechanisms are likely to exist. Previous research has focused predominantly on T-helper type cytokines to highlight the inflammatory mechanisms. However, proteins such as nuclear factor kappa B and transforming growth factor beta are increasingly recognised to have important roles in sinonasal inflammation and tissue remodelling

Contrasting genetic structures across two hybrid zones of a tropical reef fish, Acanthochromis polyacanthus (Bleeker 1855)

Hybrid zones are natural laboratories offering insights into speciation processes. Narrow hybrid zones are less common in the sea than on land consistent with higher dispersal among marine populations. Acanthochromis polyacanthus is an unusual bony marine fish with philopatric dispersal that exists as allopatric stocks of white, bicoloured and black fish on the Great Barrier Reef (GBR). At two latitudes, different morphs coexist and hybridize at narrow contact zones. Sequence data from mitochondrial Hypervariable Region 1 revealed contrasting patterns of introgression across these zones. At the northern hybrid zone, a single clade of mitochondrial haplotypes was found in all white fish, hybrids and tens of kilometres into pure bicoloured stock. At the southern hybrid zone, there was no introgression of mitochondrial genes into black fish and hybrids shared the bicoloured haplotypes. Based on this asymmetry, we postulate that black fish from the southern GBR have experienced a selective sweep of their mitochondrial genome, which has resulted in almost total reproductive isolation

Effect of lysine antifibrinolytics and cyclooxygenase inhibitors on the proteolytic profile of breast cancer cells interacting with macrophages or endothelial cells

Extracellular matrix (ECM) proteases play a key role in the regulation of tumour invasion, growth, and transendothelial migration. The expression of ECM proteases and their endogenous inhibitors by cancer cells is regulated by stromal cells. We investigated the effect of commonly used perioperative medications on this regulation