The tetrapod Caerorhachis bairdi Holmes and Carroll from the Lower Carboniferous of Scotland

The tetrapod Caerorhachis bairdi, probably from the Pendleian Limestone Coal Group in the Scottish Midland Valley, is redi agnosed and redescribed, and its affinities are discussed. Caerorachis was originally interpreted as a temnospondyl amphibian, based on characters that are now regarded as primitive for tetrapods, or of uncertain polarity. Several features of Caerorhachis (e.g. gastrocentrous vertebrae, curved trunk ribs, reduced dorsal iliac blade, L-shaped tarsal intermedium) are observed in certain primitive amniotes. In particular, Caerorhachis resembles ‘anthracosaurs’, generally considered to be among the most primitive of stem-group amniotes. The phylogenetic position of Caerorhachis is considered in the light of recently published cladistic analyses of Palaeozoic tetrapods. Most analyses place Caerorhachis at the base of, or within, ‘anthra- cosaurs’. When multiple, equally parsimonious solutions are found, its ‘anthracosaur’ affinities are shown in at least some trees, and are supported by several informative and, generally, highly consistent characters. Alternative phylogenetic placements (e.g. sister taxon to temnospondyls) are usually less well corroborated. If the fundamental evolutionary split of most early tetrapods into stem-group lissamphibians (e.g. temnospondyl s) and stem-group amniotes (e.g. ‘anthracosaurs’) is accepted, then the revised interpretation of Caerorhachi s sheds light on near-ancestral conditions for Amniota

Ultrarelativistic boost of the black ring

We investigate the ultrarelativistic boost of the five-dimensional Emparan-Reall non-rotating black ring. Following the classical method of Aichelburg and Sexl, we determine the gravitational field generated by a black ring moving ``with the speed of light'' in an arbitrary direction. In particular, we study in detail two different boosts along axes orthogonal and parallel to the plane of the ring circle, respectively. In both cases, after the limit one obtains a five-dimensional impulsive pp-wave propagating in Minkowski spacetime. The curvature singularity of the original static spacetime becomes a singular source within the wave front, in the shape of a ring or a rod according to the direction of the boost. In the case of an orthogonal boost, the wave front contains also a remnant of the original disk-shaped membrane as a component of the Ricci tensor (which is everywhere else vanishing). We also analyze the asymptotic properties of the boosted black ring at large spatial distances from the singularity, and its behaviour near the sources. In the limit when the singularity shrinks to a point, one recovers the well known five-dimensional analogue of the Aichelburg-Sexl ``monopole'' solution.Comment: 10 pages, 2 figures, REVTeX 4. v2: added boost in an arbitrary direction, one new figure, one new reference. To appear in Phys. Rev.

Language, identity and translation: Brian Friel’s Translations in Catalan

Translations, de Brian Friel, és una de les obres més conegudes d’aquest dramaturg irlandès i es pot descriure com una reflexió sobre el valor simbòlic de les llengües com a dipositàries de la cultura i sobre les relacions de poder desiguals que s’estableixen entre cultures en contacte.Ha estat traduïda dues vegades al català: la primera el 1984 per Josep M. Balanyà i la segona el 2013 per Joan Sellent, versió representada durant la temporada 2013-2014 arreu de Catalunya. En aquest article, després de reflexionar com es reflecteixen conceptes com ara la dominació, el poder i la ideologia en el discurs sobre la identitat cultural, s’analitza el tractament que ha rebut en totes dues traduccions un grup d’elements culturals i estilístics de què l’autor fa ús per parlar de la llengua, l’educació i la cultura. Es conclou que hi ha una relació entre la recerca de naturalitat que fan els traductors, sobretot Sellent, i la transmissió d’un determinat missatge ideològic.The drama Translations (1981), one of Brian Friel’s best-known works, can be described as a reflection on the symbolic value of languages as depositories of culture and on unequal power relations between cultures in contact. It has been translated twice into Catalan, the first time in 1984 by Josep M. Balanyà, and the second in 2013 by Joan Sellent; the latter version was performed in 2013-14 around Catalonia. In this paper we first discuss the presence of concepts such as domination, power and ideology in the discourse on cultural identity, and we then analyze what treatment a group of cultural and stylistic elements related to language, education and culture have received in the two translations. It is concluded that there is a relationship between the translators’ pursuit of fluency and a certain ideological message

Philosophy and updating of the asteroid photometric catalogue

The Asteroid Photometric Catalogue now contains photometric lightcurves for 584 asteroids. We discuss some of the guiding principles behind it. This concerns both observers who offer input to it and users of the product

Excursion Sets and Non-Gaussian Void Statistics

Primordial non-Gaussianity (NG) affects the large scale structure (LSS) of the universe by leaving an imprint on the distribution of matter at late times. Much attention has been focused on using the distribution of collapsed objects (i.e. dark matter halos and the galaxies and galaxy clusters that reside in them) to probe primordial NG. An equally interesting and complementary probe however is the abundance of extended underdense regions or voids in the LSS. The calculation of the abundance of voids using the excursion set formalism in the presence of primordial NG is subject to the same technical issues as the one for halos, which were discussed e.g. in arXiv:1005.1203. However, unlike the excursion set problem for halos which involved random walks in the presence of one barrier $\delta_c$, the void excursion set problem involves two barriers $\delta_v$ and $\delta_c$. This leads to a new complication introduced by what is called the "void-in-cloud" effect discussed in the literature, which is unique to the case of voids. We explore a path integral approach which allows us to carefully account for all these issues, leading to a rigorous derivation of the effects of primordial NG on void abundances. The void-in-cloud issue in particular makes the calculation conceptually rather different from the one for halos. However, we show that its final effect can be described by a simple yet accurate approximation. Our final void abundance function is valid on larger scales than the expressions of other authors, while being broadly in agreement with those expressions on smaller scales.Comment: 28 pages (18+appendices), 7 figures; v2 -- minor changes in sec 3.2, version published in PR

Type III and N Einstein spacetimes in higher dimensions: general properties

The Sachs equations governing the evolution of the optical matrix of geodetic WANDs (Weyl aligned null directions) are explicitly solved in n-dimensions in several cases which are of interest in potential applications. This is then used to study Einstein spacetimes of type III and N in the higher dimensional Newman-Penrose formalism, considering both Kundt and expanding (possibly twisting) solutions. In particular, the general dependence of the metric and of the Weyl tensor on an affine parameter r is obtained in a closed form. This allows us to characterize the peeling behaviour of the Weyl "physical" components for large values of r, and thus to discuss, e.g., how the presence of twist affects polarization modes, and qualitative differences between four and higher dimensions. Further, the r-dependence of certain non-zero scalar curvature invariants of expanding spacetimes is used to demonstrate that curvature singularities may generically be present. As an illustration, several explicit type N/III spacetimes that solve Einstein's vacuum equations (with a possible cosmological constant) in higher dimensions are finally presented.Comment: 19 page

Production of a novel medium chain length Poly(3-hydroxyalkanoate) using unprocessed biodiesel waste and its evaluation as a tissue engineering scaffold

This study demonstrated the utilisation of unprocessed biodiesel waste as a carbon feedstock for Pseudomonas mendocina CH50, for the production of PHAs. A PHA yield of 39.5% CDM was obtained using 5% (v/v) biodiesel waste substrate. Chemical analysis confirmed that the polymer produced was poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate-co-3- hydroxydecanoate-co-3-hydroxydodecanoate) or P(3HHx-3HO-3HD-3HDD). P(3HHx-3HO- 3HD-3HDD) was further characterised and evaluated for its use as a tissue engineering scaffold (TES). This study demonstrated that P(3HHx-3HO-3HD-3HDD) was biocompatible with the C2C12 (myoblast) cell line. In fact, the % cell proliferation of C2C12 on the P(3HHx-3HO-3HD-3HDD) scaffold was 72% higher than the standard tissue culture plastic confirming that this novel PHA was indeed a promising new material for soft tissue engineering

Robinson-Trautman spacetimes in higher dimensions

As an extension of the Robinson-Trautman solutions of D=4 general relativity, we investigate higher dimensional spacetimes which admit a hypersurface orthogonal, non-shearing and expanding geodesic null congruence. Einstein's field equations with an arbitrary cosmological constant and possibly an aligned pure radiation are fully integrated, so that the complete family is presented in closed explicit form. As a distinctive feature of higher dimensions, the transverse spatial part of the general line element must be a Riemannian Einstein space, but it is otherwise arbitrary. On the other hand, the remaining part of the metric is - perhaps surprisingly - not so rich as in the standard D=4 case, and the corresponding Weyl tensor is necessarily of algebraic type D. While the general family contains (generalized) static Schwarzschild-Kottler-Tangherlini black holes and extensions of the Vaidya metric, there is no analogue of important solutions such as the C-metric.Comment: 11 page

Position controlled self-catalyzed growth of GaAs nanowires by molecular beam epitaxy

GaAs nanowires are grown by molecular beam epitaxy using a self-catalyzed, Ga-assisted growth technique. Position control is achieved by nano-patterning a SiO2 layer with arrays of holes with a hole diameter of 85 nm and a hole pitch varying between 200 nm and 2 \mum. Gallium droplets form preferentially at the etched holes acting as catalyst for the nanowire growth. The nanowires have hexagonal cross-sections with {110} side facets and crystallize predominantly in zincblende. The interdistance dependence of the nanowire growth rate indicates a change of the III/V ratio towards As-rich conditions for large hole distances inhibiting NW growth.Comment: 9 pages, 4 figure

The radio/gamma-ray connection from 120 MHz to 230 GHz

Radio loud active galactic nuclei are composed of different spatial features, each one characterized by different spectral properties in the radio band. Among them, blazars are the most common class of sources detected at gamma-rays by Fermi, and their radio emission is dominated by the flat spectrum compact core. In this contribution, we explore the connection between emission at high energy revealed by Fermi and at radio frequencies. Taking as a reference the strong and very highly significant correlation found between gamma rays and cm-λ radio emission, we explore the different behaviours found as we change the energy range in gamma rays and in radio, therefore changing the physical parameters of the zones involved in the emitted radiation. We find that the correlation weakens when we consider (1) gamma rays of energy above 10 GeV (except for high synchrotron peaked blazars) or (2) low frequency radio data taken by the Murchison Widefield Array; on the other hand, the correlation strengthens when we consider mm-λ data taken by Atacama Large Millimeter Array (ALMA)