Comments on the ophiuroid family Protasteridae and description of a new genus from the Lower Devonian of the Fox Bay Formation, Falkland Islands

Asterozoan fossils are comparatively rare in Gondwana compared with Laurentia, especially in the Devonian. We examined the only fossil ophiuroid yet known from the Falkland Islands and assess its significance for the evolution of the clade. This ophiuroid, herein distinguished as a new genus and species, Darwinaster coleenbiggsae, belongs to the same suprageneric group as Protaster, which was established on a series of Middle–Upper Ordovician taxa and persisted into the late Palaeozoic remarkably little changed in morphology. This single example is part of a much wider fauna that includes fossils from the Bokkeveld Group, South Africa and the Precordillera of Argentina. Existing palaeobiogeographic reconstructions confirm that these faunas once existed on contiguous terranes and characterized a distinct suite of similar palaeoenvironments within the Malvinokaffric Realm. This study reviews the existing record of Devonian asterozoans and revises Protasteridae

On the age of the Ballantrae Complex, SW Scotland

The Ballantrae Complex, SW Scotland, is an ophiolitic assemblage of mostly Early and early Middle Ordovician age (Tremadoc–Arenig in terms of the British Ordovician Series). Its varied components were generated and assembled in the Iapetus Ocean, then obducted on to the Laurentian continental margin by the earliest Llanvirn. The timing of obduction is constrained by biostratigraphic and radiometric data. It was most probably a polyphase process initiated at about the beginning of the Arenig, at around 478 Ma. However, parts of the Complex are significantly younger, with some recent evidence taken to suggest an earliest Llanvirn age of about 464 Ma for the emplacement of some of the volcanic and pelagic sedimentary rocks. The oldest strata in the succession that now unconformably overlies the Ballantrae Complex were deposited at about 463 Ma. Hence there may have been as little as one million years available for the final stages of the Complex's tectonic assembly, obduction, uplift, erosion and downfaulting. Obduction of the Complex has been invoked as a factor in the initiation of the Grampian Orogeny and, whilst there is a broad correlation in timing, the detail from Ballantrae militates against a causal relationship

Charles Darwin's discovery of Devonian fossils in the Falkland Islands, 1833, and its controversial consequences

In March 1833 Charles Darwin discovered Devonian fossils in the Falkland Islands. He was excited by his find but could have had little premonition of the long-running geological controversy that he was initiating. Darwin's fossils matched a coeval South African fauna, and as further collections were made the association was apparently strengthened. A particularly important contribution arose around 1910 through collaborations between a local collector, Constance Allardyce, and professional palaeontologists: Ernest Schwarz in South Africa and John Clarke in the USA. The accumulating evidence was seized upon by the early proponents of ‘displacement theory’ - continental drift - notably Alexander Du Toit, who relocated the Falkland Islands northward for his 1927 South Atlantic reconstruction. A more radical, but geologically sounder proposal arose in 1952 when Ray Adie suggested that the Falkland Islands, rotated through 180°, had originated as the eastward culmination of the Cape Fold Belt and Karoo Basin. In effect, Adie had presciently described a rotated microplate, perhaps the first on record. An opposing view saw the Falkland Islands as part of a fixed, South American promontory, and argument around these two contrasting interpretations of South Atlantic geology continues to the present day

Technological Devices in the Archives: A Policy Analysis

Doing research in the archive is the cornerstone of humanities scholarship. Various archives institute policies regarding the use of technological devices, such as mobile phones, laptops, and cameras in their reading rooms. Such policies directly affect the scholars as the devices mediate the nature of their interaction with the source materials in terms of capturing, organizing, note taking, and record keeping for future use of found materials. In this paper, we present our analysis of the policies of thirty archives regarding the use of technology in their reading rooms. This policy analysis, along with data from interviews of scholars and archivists, is intended to serve as a basis for developing mobile applications for assisting scholars in their research activities. In this paper we introduce an early prototype of such a mobile application— AMTracker.Informatio

Dispersion in low-loss liquid-core optical fibres

Measurements of pulse dispersion in liquid-core multimode fibres have been made for different fibre curvatures and core diameters. The results indicate the presence of mode-conversion effects, and a mode-filtering mechanism is demonstrated with a probing beam of narrow angular width. By measuring transmission loss as a function of angle of incidence, the loss in the cladding material is obtained

A synopsis of the Ordovician System in its birthplace - Britain and Ireland

Rock successions in Britain and Ireland, and more especially those in North Wales, were instrumental in the founding and naming of the Ordovician System, and the Anglo-Welsh series established both initially and subsequently were used widely as a standard for Ordovician chronostratigraphy. Although now largely superseded in the global scheme of series and stages, they retain their local and regional importance. The Ordovician System in Britain and Ireland documents the history of a segment of the Earth's crust that incorporated opposing peri-Gondwanan and peri-Laurentian/Laurentian margins of the Iapetus Ocean during its closure, and is accordingly complex. The complexity arises from the volcanic and tectonic processes that accompanied oceanic closure coupled with the effects of eustatic sea-level changes, including the far-field effects of the Late Ordovician glaciation. For the past three decades, Ordovician successions in Britain and Ireland have been discussed in terms of terranes. Here we review Ordovician successions in each terrane, incorporating the results of recent research and correlating those successions via biostratigraphical schemes and radiometric dates to the global Ordovician series and stages

Green function techniques in the treatment of quantum transport at the molecular scale

The theoretical investigation of charge (and spin) transport at nanometer length scales requires the use of advanced and powerful techniques able to deal with the dynamical properties of the relevant physical systems, to explicitly include out-of-equilibrium situations typical for electrical/heat transport as well as to take into account interaction effects in a systematic way. Equilibrium Green function techniques and their extension to non-equilibrium situations via the Keldysh formalism build one of the pillars of current state-of-the-art approaches to quantum transport which have been implemented in both model Hamiltonian formulations and first-principle methodologies. We offer a tutorial overview of the applications of Green functions to deal with some fundamental aspects of charge transport at the nanoscale, mainly focusing on applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references, submitted to Springer series "Lecture Notes in Physics

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe