On better quasi-ordering countable trees

AbstractThe main result is that the class of countable trees is better-quasi-ordered under embeddability. R. Laver proved before that a certain class of well-founded trees is b.q.o. Actually our better-quasi-ordered class is larger than the countable class but does not contain Suslin like-trees nor certain Galvin trees of height ω + 1

On better quasi-ordering countable trees

AbstractThe main result is that the class of countable trees is better-quasi-ordered under embeddability. R. Laver proved before that a certain class of well-founded trees is b.q.o. Actually our better-quasi-ordered class is larger than the countable class but does not contain Suslin like-trees nor certain Galvin trees of height ω + 1

Nuevas perspectivas de la orientación profesional para responder a los cambios y necesidades de la sociedad de hoy

En el siguiente artículo se presenta una breve síntesis del origen y desarrollo de la orientación profesional en el siglo XX y se elabora un sumario de los cambios en la sociedad en las últimas décadas que afectan de manera directa o indirecta la orientación profesional y exigen modificaciones en la intervención orientadora. Asimismo, se hace un esbozo de nuevas perspectivas para afrontar dichos cambios recogiendo aportaciones de diversos autores y se sugieren algunas de las competencias necesarias en la actuación de los orientadores en los distintos niveles de intervención

On the origin of ambiguity in efficient communication

This article studies the emergence of ambiguity in communication through the concept of logical irreversibility and within the framework of Shannon's information theory. This leads us to a precise and general expression of the intuition behind Zipf's vocabulary balance in terms of a symmetry equation between the complexities of the coding and the decoding processes that imposes an unavoidable amount of logical uncertainty in natural communication. Accordingly, the emergence of irreversible computations is required if the complexities of the coding and the decoding processes are balanced in a symmetric scenario, which means that the emergence of ambiguous codes is a necessary condition for natural communication to succeed.Comment: 28 pages, 2 figure

Computational modelling of hydrogen assisted fracture in polycrystalline materials

We present a combined phase field and cohesive zone formulation for hydrogen embrittlement that resolves the polycrystalline microstructure of metals. Unlike previous studies, our deformation-diffusion-fracture modelling framework accounts for hydrogen-microstructure interactions and explicitly captures the interplay between bulk (transgranular) fracture and intergranular fracture, with the latter being facilitated by hydrogen through mechanisms such as grain boundary decohesion. We demonstrate the potential of the theoretical and computational formulation presented by simulating inter- and trans-granular cracking in relevant case studies. Firstly, verification calculations are conducted to show how the framework predicts the expected qualitative trends. Secondly, the model is used to simulate recent experiments on pure Ni and a Ni-Cu superalloy that have attracted particular interest. We show that the model is able to provide a good quantitative agreement with testing data and yields a mechanistic rationale for the experimental observations

The BTB-zinc finger transcription factor abrupt acts as an epithelial oncogene in drosophila melanogaster through maintaining a progenitor-like cell state

The capacity of tumour cells to maintain continual overgrowth potential has been linked to the commandeering of normal self-renewal pathways. Using an epithelial cancer model in Drosophila melanogaster, we carried out an overexpression screen for oncogenes capable of cooperating with the loss of the epithelial apico-basal cell polarity regulator, scribbled (scrib), and identified the cell fate regulator, Abrupt, a BTB-zinc finger protein. Abrupt overexpression alone is insufficient to transform cells, but in cooperation with scrib loss of function, Abrupt promotes the formation of massive tumours in the eye/antennal disc. The steroid hormone receptor coactivator, Taiman (a homologue of SRC3/AIB1), is known to associate with Abrupt, and Taiman overexpression also drives tumour formation in cooperation with the loss of Scrib. Expression arrays and ChIP-Seq indicates that Abrupt overexpression represses a large number of genes, including steroid hormone-response genes and multiple cell fate regulators, thereby maintaining cells within an epithelial progenitor-like state. The progenitor-like state is characterised by the failure to express the conserved Eyes absent/Dachshund regulatory complex in the eye disc, and in the antennal disc by the failure to express cell fate regulators that define the temporal elaboration of the appendage along the proximo-distal axis downstream of Distalless. Loss of scrib promotes cooperation with Abrupt through impaired Hippo signalling, which is required and sufficient for cooperative overgrowth with Abrupt, and JNK (Jun kinase) signalling, which is required for tumour cell migration/invasion but not overgrowth. These results thus identify a novel cooperating oncogene, identify mammalian family members of which are also known oncogenes, and demonstrate that epithelial tumours in Drosophila can be characterised by the maintenance of a progenitor-like state