6,789 research outputs found

    Going nuclear: gene family evolution and vertebrate phylogeny reconciled

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    Gene duplications have been common throughout vertebrate evolution, introducing paralogy and so complicating phylogenctic inference from nuclear genes. Reconciled trees are one method capable of dealing with paralogy, using the relationship between a gene phylogeny and the phylogeny of the organisms containing those genes to identify gene duplication events. This allows us to infer phylogenies from gene families containing both orthologous and paralogous copies. Vertebrate phylogeny is well understood from morphological and palaeontological data, but studies using mitochondrial sequence data have failed to reproduce this classical view. Reconciled tree analysis of a database of 118 vertebrate gene families supports a largely classical vertebrate phylogeny

    The university as a site of socialisation for sustainability education

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    This chapter reports on an innovative approach to in-service teacher education focusing on Education for Sustainable Development (ESD) aimed at faculty in a UK university. Building on the underpinning philosophies that characterise sustainability education: participation, experiential learning and authenticity, a module on ESD was designed which at first flipped and then moved beyond the classroom. An online resource was developed to house the necessary declarative content which student-teachers accessed before the class. Class time was then spent within deliberative, dialogic and ‘walkabout’ learning spaces. These included a critically informed tour of the university campus and community exploring the ‘unseen university’, following energy and waste processes, evaluating accessibility and inclusivity and considering the university as an example of an organisation in transition. They also afforded the opportunity for student-teachers to meet key sustainability individuals from procurement, estates, marketing and finances, as well as curriculum champions and of course students themselves. Discussions took place in boiler rooms, on stairwells, in coffee shops and in parks. Following an action research strategy for change leadership, student-teachers collaboratively and critically dissected these experiences and negotiated assignments which were not only informed by these experiences but that sought to address specific sustainability needs identified on our journeying through the university as a manifold learning space. At the end of the course, student-teachers used the UNECE (2012) framework for Competences in Education for Sustainable Development to assess what had been learnt and where to focus ongoing CPD. The course has proved popular in its home institution and has been showcased as an example of good practice by the European Communion through their ‘Lifelong Learning Programme’ (Mader et al. 2014)

    Endoscopic Treatment of a Bile Duct Stone Containing a Surgical Staple

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    We report a case of a pigmented gallstone which formed around a surgical staple in the bile duct. The stone was removed and retrieved endoscopically. A brief review of bile duct foreign bodies and gallstones is presented

    Magnetoelectric birefringence revisited

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    Electromagnetic wave propagation inside isotropic material media characterized by dielectric coefficients εμν(E,B)\varepsilon_{\mu\nu}(E,B) and μμν(E,B)\mu_{\mu\nu}(E,B) is examined. The regime of the eikonal approximation is considered. The Hadamard method of field disturbances is used and the dispersion relations are obtained by solving the Fresnel equation. Some applications of the formalism are presented. Particularly, birefringence phenomena induced by applied external fields are derived and discussed. It is shown that magnetoelectric birefringence effect can occur even without the presence of Kerr and Cotton-Mouton effects, provided the physical system satisfies certain conditions.Comment: 9 pages, 1 figure, LaTe

    The Einstein 3-form G_a and its equivalent 1-form L_a in Riemann-Cartan space

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    The definition of the Einstein 3-form G_a is motivated by means of the contracted 2nd Bianchi identity. This definition involves at first the complete curvature 2-form. The 1-form L_a is defined via G_a = L^b \wedge #(o_b \wedge o_a). Here # denotes the Hodge-star, o_a the coframe, and \wedge the exterior product. The L_a is equivalent to the Einstein 3-form and represents a certain contraction of the curvature 2-form. A variational formula of Salgado on quadratic invariants of the L_a 1-form is discussed, generalized, and put into proper perspective.Comment: LaTeX, 13 Pages. To appear in Gen. Rel. Gra

    Plate-impact loading of cellular structures formed by selective laser melting

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    Porous materials are of great interest because of improved energy absorption over their solid counterparts. Their properties, however, have been difficult to optimize. Additive manufacturing has emerged as a potential technique to closely define the structure and properties of porous components, i.e. density, strut width and pore size; however, the behaviour of these materials at very high impact energies remains largely unexplored. We describe an initial study of the dynamic compression response of lattice materials fabricated through additive manufacturing. Lattices consisting of an array of intersecting stainless steel rods were fabricated into discs using selective laser melting. The resulting discs were impacted against solid stainless steel targets at velocities ranging from 300 to 700 m s-1 using a gas gun. Continuum CTH simulations were performed to identify key features in the measured wave profiles, while 3D simulations, in which the individual cells were modelled, revealed details of microscale deformation during collapse of the lattice structure. The validated computer models have been used to provide an understanding of the deformation processes in the cellular samples. The study supports the optimization of cellular structures for application as energy absorbers. © 2014 IOP Publishing Ltd

    Patches in a side-by-side configuration: a description of the flow and deposition fields

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    In the last few decades, a lot of research attention has been paid to flow-vegetation interactions. Starting with the description of the flow field around uniform macrophyte stands, research has evolved more recently to the description of flow fields around individual, distinct patches. However, in the field, vegetation patches almost never occur in isolation. As such, patches will influence each other during their development and interacting, complex flow fields can be expected. In this study, two emergent patches of the same diameter (D = 22 cm) and a solid volume fraction of 10% were placed in a side-by-side configuration in a lab flume. The patches were built as an array of wooden cylinders, and the distance between the patches (gap width Delta) was varied between Delta = 0 and 14 cm. Flow measurements were performed by a 3D Vectrino Velocimeter (Nortek AS) at mid-depth of the flow. Deposition experiments of suspended solids were performed for selected gap widths. Directly behind each patch, the wake evolved in a manner identical to that of a single, isolated patch. On the centerline between the patches, the maximum velocity U-max was found to be independent of the gap width Delta. However, the length over which this maximum velocity persists, the potential core L-j, increased linearly as the gap width increased. After the merging of the wakes, the centerline velocity reaches a minimum value U-min. The minimum centerline velocity decreased in magnitude as the gap width decreased. The velocity pattern within the wake is reflected in the deposition patterns. An erosion zone occurs on the centerline between the patches, where the velocity is elevated. Deposition occurs in the low velocity zones directly behind each patch and also downstream of the patches, along the centerline between the patches at the point of local velocity minimum. This downstream deposition zone, a result of the interaction of neighbouring patch wakes, may facilitate the establishment of new vegetation, which may eventually inhibit flow between the upstream patches and facilitate patch merger

    Magnetic Linear Birefringence Measurements Using Pulsed Fields

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    In this paper we present the realization of further steps towards the measurement of the magnetic birefringence of the vacuum using pulsed fields. After describing our experiment, we report the calibration of our apparatus using nitrogen gas and we discuss the precision of our measurement giving a detailed error budget. Our best present vacuum upper limit is Dn < 5.0x10^(-20) T^-2 per 4 ms acquisition time. We finally discuss the improvements necessary to reach our final goal.Comment: submitted to Phys. Rev.

    90GHz and 150GHz observations of the Orion M42 region. A sub-millimeter to radio analysis

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    We have used the new 90GHz MUSTANG camera on the Robert C. Byrd Green Bank Telescope (GBT) to map the bright Huygens region of the star-forming region M42 with a resolution of 9" and a sensitivity of 2.8mJy/beam. 90GHz is an interesting transition frequency, as MUSTANG detects both the free-free emission characteristic of the HII region created by the Trapezium stars, normally seen at lower frequencies, and thermal dust emission from the background OMC1 molecular cloud, normally mapped at higher frequencies. We also present similar data from the 150GHz GISMO camera taken on the IRAM telescope. This map has 15" resolution. By combining the MUSTANG data with 1.4, 8, and 21GHz radio data from the VLA and GBT, we derive a new estimate of the emission measure (EM) averaged electron temperature of Te = 11376K by an original method relating free-free emission intensities at optically thin and optically thick frequencies. Combining ISO-LWS data with our data, we derive a new estimate of the dust temperature and spectral emissivity index within the 80" ISO-LWS beam toward OrionKL/BN, Td = 42K and Beta=1.3. We show that both Td and Beta decrease when going from the HII region and excited OMC1 interface to the denser UV shielded part of OMC1 (OrionKL/BN, Orion S). With a model consisting of only free-free and thermal dust emission we are able to fit data taken at frequencies from 1.5GHz to 854GHz.Comment: 18 pages, 8 figures, submitted to the Astrophysical Journa
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