2,363 research outputs found
Cold-water coral reef frameworks, megafaunal communities and evidence for coral carbonate mounds on the Hatton Bank, north east Atlantic
Offshore banks and seamounts sustain diverse megafaunal communities, including framework reefs formed by cold-water corals. Few studies have quantified environmental effects on the alpha or beta diversity of these communities. We adopted an interdisciplinary approach that used historical geophysical data to identify topographic highs on Hatton Bank, which were surveyed visually. The resulting photographic data were used to examine relationships between megafaunal communities and macrohabitat, the latter defined into six categories (mud, sand, cobbles, coral rubble, coral framework, rock). The survey stations revealed considerable small-scale variability in macrohabitat from exposed Late Palaeocene lava flows to quiescent muddy habitats and coral-built carbonate mounds. The first reported evidence for coral carbonate mound development in UK waters is presented, which was most pronounced near present-day or former sites of topographic change, suggesting that local current acceleration favoured coral framework growth and mound initiation. Alpha diversity varied significantly across macrohabitats, but not between rock and coral rubble, or between smaller grain sized categories of cobbles, sand and mud. Community composition differed between most macrohabitats, and variation in beta diversity across Hatton Bank was largely explained by fine-scale substratum. Certain megafauna were clearly associated with particular macrohabitats, with stylasterid corals notably associated with cobble and rock habitats and coral habitats characterized by a diverse community of suspension-feeders. The visual surveys also produced novel images of deep-water megafauna including a new photographic record of the gorgonian coral Paragorgia arborea, a species not previously reported from Rockall Plateau. Further interdisciplinary studies are needed to interpret beta diversity across these and other environmental gradients on Hatton Bank. It is clear that efforts are also needed to improve our understanding of the genetic connectivity and biogeography of vulnerable deep-water ecosystems and to develop predictive models of their occurrence that can help inform future conservation measures
A Renormalization Group Analysis of Coupled Superconducting and Stripe Order in 1+1 Dimensions
In this paper we perform a renormalization group analysis on the 1+1
dimensional version of an effective field theory (previously proposed by
Dung-Hai Lee, cond-mat/011393) describing (quantum) fluctuating stripe and
superconductor orders. We find four possible phases corresponding to stripe
order/disorder combined with superconducting order/disorder.Comment: 8 pages, 3 figures, revte
Structures in the Gauge/Gravity Duality Cascade
We study corrections to the anomalous mass dimension and their effects in the
Seiberg duality cascade in the Klebanov-Strassler throat, where
supersymmetric gauge theory with bifundamental chiral
superfields and a quartic tree level superpotential in four dimensions is dual
to type IIB string theory on background. Analyzing the
renormalization group flow of the couplings on the gauge theory side, we
propose specific corrections to the anomalous mass dimension. Applying
gauge/gravity duality, we then show that the corrections reveal structures on
the supergravity side with steps appearing in the running of the fluxes and the
metric. The "charges" at the steps provide a gravitational source for Seiberg
duality transformations. The finiteness of these corrections suggests that the
theory flows to a baryonic branch rather than to a confining branch. The
cosmological implication of the duality cascade and the gauge/gravity duality
on the brane inflationary scenario and the cosmic microwave background
radiation is pointed out.Comment: v3: 40 pages, minor changes and typos fixe
Sedimentation-consolidation of a double porosity material
This paper studies the sedimentation-consolidation of a double porosity
material, such as lumpy clay. Large displacements and finite strains are
accounted for in a multidimensional setting. Fundamental equations are derived
using a phenomenological approach and non-equilibrium thermodynamics, as set
out by Coussy [Coussy, Poromechanics, Wiley, Chichester, 2004]. These equations
particularise to three non-linear partial differential equations in one
dimensional context. Numerical implementation in a finite element code is
currently being undertaken
Little String Theory from Double-Scaling Limits of Field Theories
We show that little string theory on S^5 can be obtained as double-scaling
limits of the maximally supersymmetric Yang-Mills theories on RxS^2 and
RxS^3/Z_k. By matching the gauge theory parameters with those in the gravity
duals found by Lin and Maldacena, we determine the limits in the gauge theories
that correspond to decoupling of NS5-brane degrees of freedom. We find that for
the theory on RxS^2, the 't Hooft coupling must be scaled like ln^3(N), and on
RxS^3/Z_k, like ln^2(N). Accordingly, taking these limits in these field
theories gives Lagrangian definitions of little string theory on S^5.Comment: 16 pages, 5 figures. Minor change
Stability of Stationary Solutions of Extended Reaction-Diffusion-Convection Equations on a Finite Segment
A simple geometric criterion on the linear stability of stationary solutions of nonlinear second order parabolic equations on a finite segment is stated and proved
The forgotten '45 : Donald Dubh's rebellion in an archipelagic context
The final rebellion of Donald Dubh, heir to the forfeited MacDonald lordship of the Isles, is usually examined within the context of Highland rebellions that occurred in the half century after forfeiture. However, the factors that motivated the Islesmen to rise in rebellion in 1545 are multi-faceted and can only be fully understood by placing the rising in a wider context, which considers national and archipelagic events. The discussion that follows explores the reasons why the Islesmen, almost unanimously, entered into agreement with Henry VIII to attack Scotland from the west and why this endeavour failed. At the same time, the article highlights Henry’s recognition of the strategic importance of the west which led him into alliance with Donald Dubh and his supporters
Soaking up the oil: Biological impacts of dispersants and crude oil on the sponge Halichondria panicea
Used during an oil spill to minimise the formation of an oil slick, dispersants have negative biological effects on marine model organisms. However, no study has investigated the impacts of dispersants on adult sponge individuals. Here, we examine the effects of water accommodated oil fraction (WAF - oil in seawater), chemically enhanced WAF (CEWAF - oil and dispersant in seawater) and Benzo[A]Pyrene on sponge Halichondria panicea at physiological and molecular levels. Sponge clearance rate decreased sharply when exposed to WAF and CEWAF but the oil loading at which the clearance rate was reduced by 50% (ED50) was 39-fold lower in CEWAF than in WAF. Transcriptomic analysis revealed a homogenous molecular response with the greatest number of differentially expressed genes identified in CEWAF samples (1,461 genes). Specifically, genes involved in stress responses were up-regulated. This study presents evidence that the use of dispersants should be considered carefully in areas where sponges are present
Carotid arterial remodeling - A maladaptive phenomenon in type 2 diabetes but not in impaired glucose metabolism: The Hoorn Study
Background and Purpose-Deteriorating glucose tolerance is associated with an increased cardiovascular disease (CVD) risk. The underlying mechanisms remain unclear. Arterial remodeling is the change in structural properties through time in response to atherogenic and/or hemodynamic alterations and aims to maintain circumferential wall stress constant (
Mild renal insufficiency is associated with increased cardiovascular mortality: The Hoorn Study
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