Evolution of the Antarctic Peninsula lithosphere: evidence from Mesozoic mafic rocks

New geochronology from a thick (> 800m) basaltic succession along the eastern margin of the Antarctic Peninsula confirm a Middle Jurassic age (178 ± 1 Ma). This marginally postdates the adjacent Ferrar large igneous province of the Transantarctic Mountains and predates the extensive silicic volcanism of the Mapple Formation (~ 170 Ma) of the Antarctic Peninsula. The geochemistry of other rare, but broadly contemporaneous, basaltic successions of the Antarctic Peninsula, along with Cretaceous-age mafic dykes, are used to interpret the influences of lithospheric and asthenospheric mantle sources during the Mesozoic. Two significant high magmatic addition rate events occurred along the Antarctic Peninsula continental margin at 170 and 110 Ma and can be correlated to events along the South American Cordillera. These ‘flare-up’ events are characterised by extensive silicic (mostly ignimbrite) volcanism of the Chon Aike Province (V2 event: 170 Ma) and significant granitoid batholith emplacement of the Lassiter Coast intrusive suite (110 Ma). The 170 Ma event is exposed across large parts of the northern Antarctic Peninsula, whilst the 110 Ma event is more widespread across the southern Antarctic Peninsula. The basaltic volcanism described here precedes the ‘flare-up’ event at 170 Ma and has geochemical characteristics that indicate a thickened lithosphere prevailed. A major dyke swarm that followed the 170 Ma event indicates that extensive lithospheric thinning had occurred, which allowed the ascent of depleted mafic melts. The thinning was the direct result of widespread lower crustal/upper lithospheric melting associated with the silicic volcanism. In the southern Antarctic Peninsula, the lithosphere remained over thickened until the emplacement of the major batholiths of the Lassiter Coast intrusive suite at 110 Ma and was then immediately followed by the emplacement of more asthenosphere-like melts indicating extensive lithospheric thinnin

Temperature, inocula and substrate: contrasting electroactive consortia, diversity and performance in microbial fuel cells

The factors that affect microbial community assembly and its effects on the performance of bioelectrochemical systems are poorly understood. Sixteen microbial fuel cell (MFC) reactors were set up to test the importance of inoculum, temperature and substrate: Arctic soil versus wastewater as inoculum; warm (26.5°C) versus cold (7.5°C) temperature; and acetate versus wastewater as substrate. Substrate was the dominant factor in determining performance and diversity: unexpectedly the simple electrogenic substrate delivered a higher diversity than a complex wastewater. Furthermore, in acetate fed reactors, diversity did not correlate with performance, yet in wastewater fed ones it did, with greater diversity sustaining higher power densities and coulombic efficiencies. Temperature had only a minor effect on power density, (Q10: 2 and 1.2 for acetate and wastewater respectively): this is surprising given the well-known temperature sensitivity of anaerobic bioreactors. Reactors were able to operate at low temperature with real wastewater without the need for specialised inocula; it is speculated that MFC biofilms may have a self-heating effect. Importantly, the warm acetate fed reactors in this study did not act as direct model for cold wastewater fed systems. Application of this technology will encompass use of real wastewater at ambient temperatures

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 µm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures

Mathematical modelling of contact dermatitis from nickel and chromium

Dermal exposure to metal allergens can lead to irritant (ICD) and allergic contact dermatitis (ACD). In this paper we present a mathematical model of the absorption of metal ions, hexavalent chromium and nickel, into the viable epidermis and compare the localised irritant and T-lymphocyte (T-cell) mediated immune responses. The model accounts for the spatial-temporal variation of skin health, extra and intracellular allergen concentrations, innate immune cells, T-cells, cytokine signalling and lymph node activity up to about 6 days after contact with these metals; repair processes associated with withdrawal of exposure to both metals is not considered in the current model, being assumed secondary during the initial phases of exposure. Simulations of the resulting system of PDEs are studied in one-dimension, i.e. across skin depth, and three-dimensional scenarios with the aim of comparing the responses to the two ions in the cases of first contact (no T-cells initially present) and second contact (T-cells initially present). The results show that on continuous contact, chromium ions elicit stronger skin inflammation, but for nickel, subsequent re-exposure stimulates stronger responses due to an accumulation of cytotoxic T-cell mediated responses which characterise ACD. Furthermore, the surface area of contact to these metals has little effect on the speed of response, whilst sensitivity is predicted to increase with the thickness of skin. The modelling approach is generic and should be applicable to describe contact dermatitis from a wide range of allergens

Tracking the tempo of a continental margin arc: insights from a forearc succession in West Antarctica

The Fossil Bluff Group of eastern Alexander Island records the exceptional preservation of more than 8 km of Mesozoic sedimentary rocks deposited into an accretionary forearc basin that developed unconformably above a late Paleozoic accretionary complex, and in proximity to a continental margin arc during a prolonged phase of enhanced magmatism. Through the Mesozoic, the Fossil Bluff Group evolved from a trench-slope environment to a forearc basin sourced from the continental margin arc. During this period, the Antarctic Peninsula’s convergent margin was characterized by episodes of magmatic flare-ups that developed during tectonic compression, crustal thickening, extension, and uplift. U-Pb and Lu-Hf detrital zircon data are used to determine the provenance of the forearc succession and as a monitor of arc magmatic tempos during the late Mesozoic. The magmatic record in the adjacent arc is poorly preserved or partially absent, but the sedimentary record of the forearc basin preserves a largely uninterrupted record of arc magmatism that can be studied with detrital zircon geochronology and geochemistry. The basal succession of the Fossil Bluff Group is sourced from the adjacent accretionary complex, but thereafter it is strongly controlled by the proximal arc in western Palmer Land and is characterized by a mixed arc/recycled signature during episodes of renewed sedimentation. However, the main phases of deposition during the Early Jurassic (ca. 180 Ma), Early Cretaceous (141–131 Ma), and mid-Cretaceous (125–102 Ma) are dominated by arc-only sources. The Lu-Hf isotopic record supports a transition from convergence to extension and a return to convergence during the Mesozoic, which is consistent with accretionary orogens from elsewhere along the West Gondwanan margin. The provenance record during the depositional history of the basin points overwhelmingly to an autochthonous origin; as such, models for parts of the western province of the Antarctic Peninsula being allochthonous are unsupported

Mixed configuration-interaction and many-body perturbation theory calculations of energies and oscillator strengths of J=1 odd states of neon

Ab-initio theory is developed for energies of J=1 particle-hole states of neutral neon and for oscillator strengths of transitions from such states to the J=0 ground state. Hole energies of low-Z neonlike ions are evaluated.Comment: 5 pages, 1 figure, 4 table

Family stories, public silence: Irish identity construction amongst the second-generation Irish in England

Formal narratives of history, especially that of colonial oppression, have been central to the construction of national identities in Ireland. But the Irish diasporic community in Britain has been cut off from the reproduction of these narratives, most notably by their absence from the curriculum of Catholic schools, as result of the unofficial 'denationalisation' pact agreed by the Church in the 19th century (Hickman, 1995). The reproduction of Irish identities is largely a private matter, carried out within the home through family accounts of local connections, often reinforced by extended visits to parent/s 'home' areas. Recapturing a public dimension has often become a personal quest in adulthood, 'filling in the gaps'. This paper explores constructions of narratives of nation by a key diasporic population, those with one or two Irish-born parents. It places particular emphasis on varying regional/national contexts within which such constructions take place, drawing on focus group discussions and interviews for the ESRC-funded Irish 2 Project in five locations — London, Glasgow, Manchester, Coventry and Banbury

Effects of unidirectional flow shear stresses on the formation, fractal microstructure and rigidity of incipient whole blood clots and fibrin gels

Incipient clot formation in whole blood and fibrin gels was studied by the rheometric techniques of controlled stress parallel superposition (CSPS) and small amplitude oscillatory shear (SAOS). The effects of unidirectional shear stress on incipient clot microstructure, formation kinetics and elasticity are reported in terms of the fractal dimension (df ) of the fibrin network, the gel network formation time (TGP ) and the shear elastic modulus, respectively. The results of this first haemorheological application of CSPS reveal the marked sensitivity of incipient clot microstructure to physiologically relevant levels of shear stress, these being an order of magnitude lower than have previously been studied by SAOS. CSPS tests revealed that exposure of forming clots to increasing levels of shear stress produces a corresponding elevation in df , consistent with the formation of tighter, more compact clot microstructures under unidirectional flow. A corresponding increase in shear elasticity was recorded. The scaling relationship established between shear elasticity and df for fibrin clots and whole blood confirms the fibrin network as the dominant microstructural component of the incipient clot in terms of its response to imposed stress. Supplementary studies of fibrin clot formation by rheometry and microscopy revealed the substantial additional network mass required to increase df and provide evidence to support the hypothesis that microstructural changes in blood clotted under unidirectional shear may be attributed to flow enhanced thrombin generation and activation. CSPS also identified a threshold value of unidirectional shear stress above which no incipient clot formation could be detected. CSPS was shown to be a valuable haemorheological tool for the study of the effects of physiological and pathological levels of shear on clot properties

The structure of blocks with a Klein four defect group

We prove Erdmann’s conjecture [16] stating that every block with a Klein four defect group has a simple module with trivial source, and deduce from this that Puig’s finiteness conjecture holds for source algebras of blocks with a Klein four defect group. The proof uses the classification of finite simple groups