WIRIS OM tools: a semantic formula editor

With the increasing reliance on computers for the automatic processing of information a new method is needed for editing mathematical formulae. We are used to WYSIWYG editors that produce beautiful presentations of formulae and store the typesetting primitives rather than the meaning of the formulas. However, new services such as database searching or calculation web-services work best if they have access to the semantic information behind a formula. This can only be done with a new generation of formula editors. In this paper we present WIRIS OM Tools [17], a semantic oriented formula editor which addresses these concerns. It is based on the OpenMath language and a suitable transformation process between OpenMath and MathML ex- pressions. Additionally, this approach adds new features for the users such as error, type and syntax checking. The editor is currently being used in the LeActiveMath and WebALT projects

Eddington-inspired Born-Infeld gravity: nuclear physics constraints and the validity of the continuous fluid approximation

In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory \kappa, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level.Comment: 3 page

Limits on Self-Interacting Dark Matter

We impose new severe constraints on the self-interactions of fermionic asymmetric dark matter based on observations of nearby old neutron stars. WIMP self-interactions mediated by Yukawa- type interactions can lower significantly the number of WIMPs necessary for gravitational collapse of the WIMP population accumulated in a neutron star. Even nearby neutron stars located at regions of low dark matter density can accrete sufficient number of WIMPs that can potentially collapse, form a mini black hole, and destroy the host star. Based on this, we derive constraints on the WIMP self-interactions which in some cases are by several orders of magnitude stricter than the ones from the bullet cluster (which are currently considered the most stringent).Comment: 5 page

Observing Radio Pulsars in the Galactic Centre with the Square Kilometre Array

The discovery and timing of radio pulsars within the Galactic centre is a fundamental aspect of the SKA Science Case, responding to the topic of "Strong Field Tests of Gravity with Pulsars and Black Holes" (Kramer et al. 2004; Cordes et al. 2004). Pulsars have in many ways proven to be excellent tools for testing the General theory of Relativity and alternative gravity theories (see Wex (2014) for a recent review). Timing a pulsar in orbit around a companion, provides a unique way of probing the relativistic dynamics and spacetime of such a system. The strictest tests of gravity, in strong field conditions, are expected to come from a pulsar orbiting a black hole. In this sense, a pulsar in a close orbit ($P_{\rm orb}$ < 1 yr) around our nearest supermassive black hole candidate, Sagittarius A* - at a distance of ~8.3 kpc in the Galactic centre (Gillessen et al. 2009a) - would be the ideal tool. Given the size of the orbit and the relativistic effects associated with it, even a slowly spinning pulsar would allow the black hole spacetime to be explored in great detail (Liu et al. 2012). For example, measurement of the frame dragging caused by the rotation of the supermassive black hole, would allow a test of the "cosmic censorship conjecture." The "no-hair theorem" can be tested by measuring the quadrupole moment of the black hole. These are two of the prime examples for the fundamental studies of gravity one could do with a pulsar around Sagittarius A*. As will be shown here, SKA1-MID and ultimately the SKA will provide the opportunity to begin to find and time the pulsars in this extreme environment.Comment: 14 pages, 5 figures, to be published in: "Advancing Astrophysics with the Square Kilometre Array", Proceedings of Science, PoS(AASKA14)04

Spatiotemporal dynamics of multiple shear-banding events for viscoelastic micellar fluids in cone-plate shearing flows

We characterize the transient response of semi-dilute wormlike micellar solutions under an imposed steady shear flow in a cone-plate geometry. By combining conventional rheometry with 2-D Particle Image Velocimetry (PIV), we can simultaneously correlate the temporal stress response with time-resolved velocimetric measurements. By imposing a well defined shear history protocol, consisting of a stepped shear flow sweep, we explore both the linear and nonlinear responses of two surfactant solutions: cetylpiridinium chloride (CPyCl) and sodium salicylate (NaSal) mixtures at concentrations of [66:40] mM and [100:60] mM, respectively. The transient stress signal of the more dilute solution relaxes to its equilibrium value very fast and the corresponding velocity profiles remain linear, even in the strongly shear-thinning regime. The more concentrated solution also exhibits linear velocity profiles at small shear rates. At large enough shear rates, typically larger than the inverse of the relaxation time of the fluid, the flow field reorganizes giving rise to strongly shear-banded velocity profiles. These are composed of an odd number of shear bands with low-shear-rate bands adjacent to both gap boundaries. In the non-linear regime long transients (much longer than the relaxation time of the fluid) are observed in the transient stress response before the fluid reaches a final, fully-developed state. The temporal evolution in the shear stress can be correlated with the spatiotemporal dynamics of the multiple shear-banded structure measured using RheoPIV. In particular our experiments show the onset of elastic instabilities in the flow which are characterized by the presence of multiple shear bands that evolve and rearrange in time resulting in a slow increase in the average torque acting on the rotating fixture

Identifying the first generation of radio powerful AGN in the Universe with the SKA

One of the most challenging and exciting subjects in modern astrophysics is that of galaxy formation at the epoch of reionisation. The SKA, with its revolutionary capabilities in terms of frequency range, resolution and sensitivity, will allow to explore the first Gyr of structure formation in the Universe, in particular, with the detection and study of the earliest manifestations of the AGN phenomenon. The tens of QSOs that are currently known out to the highest redshifts (z 7), many of them exhibiting powerful radio emission, imply that super-massive black holes can be grown on a very short timescale and support the existence of very high redshift (z &gt; 7) radio loud sources - sources that have so far escaped detection. Not only would such detections be paramount to the understanding of the earliest stages of galaxy evolution, they are necessary for the direct study of neutral hydrogen in the Epoch of Reionisation, through observations of the HI 21cm forest against such background sources. In order to understand how SKA and SKA1 observations can be optimised to reveal these earliest AGN, we have examined the effect of a hot CMB on the emission of powerful and young radio galaxies. By looking at the SKA1 capabilities, in particular in terms of wavelength coverage and resolution, we determine how the effects of "CMB-muting" of a radio loud source can be observationally minimised and how to identify the best highest-redshift radio candidates. Considering different predictions for the space density of radio loud AGN at such redshifts, we identify the survey characteristics necessary to optimize the detection and identification of the very first generation of radio loud AGN in the Universe

Edificio para viviendas, en Barcelona

This building has a garage basement, a ground floor with a communed playing zone for all the children of the block, and the entrance vestibule. The rest of the building is occupied with apartments, of about 200 m2 each, which are functionally designed, and are suitable for medium sized average income families. Special attention has been given to the external facades, which, among other things, are of extremely simple design.El edificio contiene: en el sótano, un guardacoches; en la planta baja, una zona de juegos común para los niños de todas las viviendas, además de los vestíbulos. El resto de la superficie edificada está destinado a viviendas, de unos 200 m2, construidos con distribución funcional y adecuada para familias medias ya constituidas. Fue dedicada una especial atención a la composición de las fachadas, que ofrecen, entre otros atractivos, el de su elegante sencillez