The uncoupling limit of identical Hopf bifurcations with an application to perceptual bistability

We study the dynamics arising when two identical oscillators are coupled near a Hopf bifurcation where we assume a parameter $\epsilon$ uncouples the system at $\epsilon=0$. Using a normal form for $N=2$ identical systems undergoing Hopf bifurcation, we explore the dynamical properties. Matching the normal form coefficients to a coupled Wilson-Cowan oscillator network gives an understanding of different types of behaviour that arise in a model of perceptual bistability. Notably, we find bistability between in-phase and anti-phase solutions that demonstrates the feasibility for synchronisation to act as the mechanism by which periodic inputs can be segregated (rather than via strong inhibitory coupling, as in existing models). Using numerical continuation we confirm our theoretical analysis for small coupling strength and explore the bifurcation diagrams for large coupling strength, where the normal form approximation breaks down

Appraisement of planar, bending and twisting cracks in 3D with isotropic and orthotropic damage models

This paper discusses the modeling of cracking in quasi-brittle materials using isotropic and orthotropic damage constitutive laws. A mixed strain/displacement finite element formulation is used, taking advantage of its enhanced precision and its enforced interelemental strain continuity. On the one hand, this formulation avoids the spurious mesh dependency of the computed solution associated to standard elements and does not require the use of tracking techniques. On the other hand, it greatly alleviates the spurious stress locking associated to the use of orthotropic models on standard finite elements. The performance of several isotropic and orthotropic damage constitutive laws is assessed through an extensive comparison with analytical solutions, numerical tests and experimental evidence reported in the literature. The behavior of the different damage models in terms of crack surface, collapse mechanism and force displacement curves is investigated performing 3D analyses in several conditions including Mode I, Mixed Mode and Mode III fracture. When performing the appraisement of planar, bending and twisting cracks, the enhanced accuracy of the mixed formulation allows for a distinct assessment of the several damage models considered. Aspects related to the behavior of damage models, such as the influence of Poisson’s ratio, the shape of the damage surface and the adoption of isotropic and orthotropic models are investigated and noteworthy conclusions are draw

Finite element modeling of quasi-brittle cracks in 2D and 3D with enhanced strain accuracy

This paper discusses the finite element modeling of cracking in quasi-brittle materials. The problem is addressed via a mixed strain/displacement finite element formulation and an isotropic damage constitutive model. The proposed mixed formulation is fully general and is applied in 2D and 3D. Also, it is independent of the specific finite element discretization considered; it can be equally used with triangles/tetrahedra, quadrilaterals/hexahedra and prisms. The feasibility and accuracy of the method is assessed through extensive comparison with experimental evidence. The correlation with the experimental tests shows the capacity of the mixed formulation to reproduce the experimental crack path and the force–displacement curves with remarkable accuracy. Both 2D and 3D examples produce results consistent with the documented data. Aspects related to the discrete solution, such as convergence regarding mesh resolution and mesh bias, as well as other related to the physical model, like structural size effect and the influence of Poisson’s ratio, are also investigated. The enhanced accuracy of the computed strain field leads to accurate results in terms of crack paths, failure mechanisms and force displacement curves. Spurious mesh dependency suffered by both continuous and discontinuous irreducible formulations is avoided by the mixed FE, without the need of auxiliary tracking techniques or other computational schemes that alter the continuum mechanical problem

Structural Analysis of Masonry Historical Constructions. Classical and Advanced Approaches

A review of methods applicable to the study of masonry historical construction, encompassing both classical and advanced ones, is presented. Firstly, the paper offers a discussion on the main challenges posed by historical structures and the desirable conditions that approaches oriented to the modeling and analysis of this type of structures should accomplish. Secondly, the main available methods which are actually used for study masonry historical structures are referred to and discussed. The main available strategies, including limit analysis, simplified methods, FEM macro- or micro-modeling and discrete element methods (DEM) are considered with regard to their realism, computer efficiency, data availability and real applicability to large structures. A set of final considerations are offered on the real possibility of carrying out realistic analysis of complex historic masonry structures. In spite of the modern developments, the study of historical buildings is still facing significant difficulties linked to computational effort, possibility of input data acquisition and limited realism of methods

Mineralogía de los materiales detríticos de la Fm. Escucha (Albiense inferior) en el distrito minero de Teruel (sector Suroriental de la Cordillera Ibérica)

The present study focuses on the determination of the source areas of the Escucha Fm. (Albian) sediments in the Teruel Mining District (NE Spain). To this en4 we have carried out a detailed study of the heavy mineral fraction of the sandstone beds from this sedimentary unit at three stratigraphic successions at the Ariño-Oliete and Utrillas subbasins. The minerals found in the stratigraphic successions studied are in low proportions and a few mineral phases are present. Quartz is the dominant phase in the light mineral association, whereas potassium feldspars and plagioclase are in trace amounts. The opaque heavy minerals are hematite and goethite with minor amounts of pyrite. Finally, the transparent heavy minerals may be divided into the three following major associations: a) turmaline, zircon and rutile (resistant minerals); b) kyanite, staurolite and almandine (metamorphic association); and c) metamorphic mineral association from the Ctrillas sub-basin, characterised by very low heavy mineral proportions, and by the absence of one or various mineral phases from the association b. The flow directions from paleochannels and the absence of metarnorphic minerals in the sandstone levels of the upper unit of the Escucha Fm at the northern areas point to the "Platuforma del Ebro" as a possihle source area The minerals with this origin, with variable morphoscopy, could proceed from sedimentary recycling The metamorphic assemblage found in the southern areas may proceed from the "Macizo Castellano", where gneiss and mica-schists are present. It is not possible to precisse exactly the age of the source areas of the detrital sediments of the Escucha Fm This is due to the fact that these may have been different through the basin evolution, and also to the evidence of recycling processes The middle and lower units of the Escucha Fm at Ariño and Oliete, where the workable coa1 seams are present, show a metamorphic assemblage which demonstrate the Paleozoic age of the source lands Consequently, the Triassic units could also supply detrital minerals to the delta system of the Escucha Fm. These results are consistent with the hypothesis of the Triassic origin of the sulphur enrichment of the coals from the Ariño-Oliete area The recycling of detrital sediments from the Escucha Fm or a different source lana could account for the proteciion of the Utrillas sub-basin against the Triassic sulphate supply, and consequently for the lower sulphur content of the coals from this area.

Producción científica nacional e internacional en drogas de diseño (1988-1997)

Rafael Aleixandre Benavent: [email protected]ón: El conocimiento de las fuentes de información científica es imprescindible para el abordaje del problema del consumo de drogas de diseño. El objetivo de este trabajo es analizar la producción científica nacional e internacional sobre esta conducta, a partir del análisis bibliométrico de las publicaciones. Material y método: La producción científica sobre drogas de diseño se ha obtenido de las bases de datos IME, MEDLINE, ISOC y teseo durante el período 1988-1997. También se revisaron las referencias bibliográficas de los artículos recuperados en la base de datos IME. Los artículos obtenidos se distribuyeron por años, tipo documental, revista de publicación y temática, instituciones y países de procedencia, idiomas y temas tratados. Resultados: En las revistas españolas se publicaron 34 artículos y en las extranjeras 2.181. Los principales aspectos tratados se refieren a la toxicidad, concepto y clasificación y actividad farmacológica de las drogas de diseño. Las áreas temáticas más productivas son la neuropsiquiatría, la farmacología y la medicina general e interna. Conclusiones: El análisis muestra que existen escasos estudios experimentales y epidemiológicos publicados en España. Las revistas son de drogodependencias, temática general, neuropsiquiatría y farmacología, lo que pone de relieve la multidisciplinariedad de esta conducta adictiva. Predominan los estudios sobre la 1-metil-4-fenil-1,2,3,6-tetrahidropiridina y los análogos y derivados de la MDMA.Introduction: The knowledge of the scientific information sources is essential to approach the problem of the design drugs consumption. The objective of this work is directed to analyse the national and international scientific production about such behaviour, starting from the analysis bibliometric of the publications. Material and method: The scientific production on design drugs is being obtained from the data base IME, MEDLINE, ISOC and teseo during the 1988/1997 begin_of_the_skype_highlighting              1988/1997      end_of_the_skype_highlighting begin_of_the_skype_highlighting              1988/1997      end_of_the_skype_highlighting period. It has been done checking the bibliographic references of the articles recovered from the data base IME. The articles obtained have been separated by year, documentation type, journals thematic, institutions, country of origin, language and subject-matter. Results: In the spanish journals there has been published 34 articles and 2.181 in foreing journals. The main aspects treated make reference to toxicity, concept, classification and pharmacological activity of the design drugs. The thematic areas more productive are neuropsychiatry, pharmacological and general and internal medicine. Conclusions: The analysis points out that its does exist minimal experimental and epidemiological studies published in Spain. The journals more productives are specialised in drug addiction, general thematic, neuropsychiatry and pharmacological, what underlines the multidisciplinary of this addictive behaviour. The studies of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and of analogues and derived of MDMA predominate

Mineralogía de los materiales detríticos de la Fm. Escucha (Albiense inferior) en el distrito minero de Teruel (sector Suroriental de la Cordillera Ibérica)

The present study focuses on the determination of the source areas of the Escucha Fm. (Albian) sediments in the Teruel Mining District (NE Spain). To this en4 we have carried out a detailed study of the heavy mineral fraction of the sandstone beds from this sedimentary unit at three stratigraphic successions at the Ariño-Oliete and Utrillas subbasins. The minerals found in the stratigraphic successions studied are in low proportions and a few mineral phases are present. Quartz is the dominant phase in the light mineral association, whereas potassium feldspars and plagioclase are in trace amounts. The opaque heavy minerals are hematite and goethite with minor amounts of pyrite. Finally, the transparent heavy minerals may be divided into the three following major associations: a) turmaline, zircon and rutile (resistant minerals); b) kyanite, staurolite and almandine (metamorphic association); and c) metamorphic mineral association from the Ctrillas sub-basin, characterised by very low heavy mineral proportions, and by the absence of one or various mineral phases from the association b. The flow directions from paleochannels and the absence of metarnorphic minerals in the sandstone levels of the upper unit of the Escucha Fm at the northern areas point to the "Platuforma del Ebro" as a possihle source area The minerals with this origin, with variable morphoscopy, could proceed from sedimentary recycling The metamorphic assemblage found in the southern areas may proceed from the "Macizo Castellano", where gneiss and mica-schists are present. It is not possible to precisse exactly the age of the source areas of the detrital sediments of the Escucha Fm This is due to the fact that these may have been different through the basin evolution, and also to the evidence of recycling processes The middle and lower units of the Escucha Fm at Ariño and Oliete, where the workable coa1 seams are present, show a metamorphic assemblage which demonstrate the Paleozoic age of the source lands Consequently, the Triassic units could also supply detrital minerals to the delta system of the Escucha Fm. These results are consistent with the hypothesis of the Triassic origin of the sulphur enrichment of the coals from the Ariño-Oliete area The recycling of detrital sediments from the Escucha Fm or a different source lana could account for the proteciion of the Utrillas sub-basin against the Triassic sulphate supply, and consequently for the lower sulphur content of the coals from this area.

Phenotypic diversity of Thuridilla hopei (Verany, 1853) (Gastropoda Heterobranchia Sacoglossa). A DNA-barcoding approach

The sacoglossan Thuridilla hopei (Verany, 1853) shows highly diverse chromatic patterns. Based on the morphological examination of specimens from different Mediterranean localities, we have observed that in spite of this great variability in colours of T. hopei, two major chromatic morphotypes are related to bathymetry. Specimens from deeper water exhibit blue darker and more uniform patterns than individuals from shallower water, which show a more variable, dashed and spotted arrangement of light blue, yellow, orange, white and black pigmentation. A molecular genetic analysis using the mitochondrial COI and 16S rDNA markers has confirmed that all these extremely different chromatic morphotypes belong to a single specific entity, i.e. T. hopei, a sacoglossan with a wide distribution, from Macaronesia in the Atlantic, to the easternmost Mediterranean Sea