2,041 research outputs found

    Krill biomass and aggregation structure in relation to tidal cycle in a penguin foraging region off the Western Antarctic Peninsula

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    Antarctic krill are a key component of the diet of Adlie penguins inhabiting the Western Antarctic Peninsula (WAP), yet our understanding of the variability of krill distribution patterns within nearshore penguin feeding grounds is limited. A recent study of the foraging patterns of penguins breeding in the northern WAP suggests that tidal phase plays a role in foraging distance. We used acoustics to examine biomass and aggregation structure of krill in the penguin foraging grounds off Palmer Station during diurnal and semi-diurnal tides. Nearshore, integrated krill biomass during diurnal tides was significantly higher than during semi-diurnal tides. Krill aggregations were also shallower, closer together, and larger in dimension during diurnal tides. Conversely, krill aggregations had higher volumetric biomass and abundance during semi-diurnal tides. Further offshore, at the head of the Palmer Deep canyon, krill aggregations were similar to those observed nearshore during diurnal tides (i.e. shallow, close together, and large in dimension). Since krill aggregation structure strongly influences availability as a potential prey source, we suggest that foraging behavior of Adlie penguins in this region is strongly linked to the variability in nearshore krill aggregation structure as well as biomass

    Yangians, Integrable Quantum Systems and Dorey's rule

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    We study tensor products of fundamental representations of Yangians and show that the fundamental quotients of such tensor products are given by Dorey's rule.Comment: We have made corrections to the results for the Yangians associated to the non--simply laced algebra

    Two-pulse interference and superluminality

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    We examine how the interference of a coherent light-pulse with its slightly time-delayed copy may generate a pulse nearly identical to the original one and ahead of it. The simplicity of this 2-pulse system enabled us to obtain exact analytic expressions of the pulse distortion, valid for a wide class of pulse shapes. Explicit results are given for the pulses usually considered (gaussian, hyperbolic secant) but also for more realistic pulses of strictly limited duration. We finally show that the efficiency of the 2-pulse system is comparable to that of the other superluminal systems, at least for the pulse advancements actually demonstrated in the optical experiments

    Penguin biogeography along the West Antarctic Peninsula: Testing the canyon hypothesis with Palmer LTER observations

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    The West Antarctic Peninsula (WAP) is home to large breeding colonies of the ice-dependent Antarctic Adélie penguin (Pygoscelis adeliae). Although the entire inner continental shelf is highly productive, with abundant phytoplankton and krill populations, penguin colonies are distributed heterogeneously along the WAP (Ducklow et al., 2013, in this issue). This ecological conundrum targets a long-standing question of interest: what environmental factors structure the locations of Adélie penguin "hot spots" throughout the WAP

    Local P Violation Effects and Thermalization in QCD: Views from Quantum Field Theory and Holography

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    We argue that the local violation of P and CP invariance in heavy ion collisions and the universal thermal aspects observed in high energy collisions are in fact two sides of the same coin, and both are related to quantum anomalies of QCD. We argue that the low energy relations representing the quantum anomalies of QCD are saturated by coherent low dimensional vacuum configurations as observed in Monte Carlo lattice studies. The thermal spectrum and approximate universality of the temperature with no dependence on energy of colliding particles in this framework is due to the fact that the emission results from the distortion of these low dimensional vacuum sheets rather than from the colliding particles themselves. The emergence of the long- range correlations of P odd domains (a feature which is apparently required for explanation of the asymmetry observed at RHIC and LHC) is also a result of the same distortion of the QCD vacuum configurations. We formulate the corresponding physics using the effective low energy effective Lagrangian. We also formulate the same physics in terms of the dual holographic picture when low-dimensional sheets of topological charge embedded in 4d space, as observed in Monte Carlo simulations, are identified with D2 branes. Finally, we argue that study of these long range correlations in heavy ion collisions could serve as a perfect test of a proposal that the observed dark energy in present epoch is a result of a tiny deviation of the QCD vacuum energy in expanding universe from its conventional value in Minkowski spacetime.Comment: final version to appear in Nucl.Phys.

    P and CP Violation and New Thermalization Scenario in Heavy Ion Collisions

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    The violation of local P and CP invariance in QCD, as it is observed at RHIC, has been a subject of intense discussions for the last couple of years.Separately, a new thermalization scenario for heavy ion collisions through the event horizon as a manifestation of the Unruh effect, has been also suggested. In this paper we argue that these two, naively unrelated phenomena, are actually two sides of the same coin as they are deeply rooted into the same fundamental physics related to some very nontrivial topological features of QCD. We formulate the universality conjecture for P and CP odd effects in heavy ion collisions analogous to the universal thermal behaviour observed in all other high energy interactions.Comment: Matches the journal versio

    Use and Outcomes Associated With Bridging During Anticoagulation Interruptions in Patients With Atrial Fibrillation: Findings From the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF)

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    BACKGROUND: Temporary interruption of oral anticoagulation for procedures is often required, and some propose using bridging anticoagulation. However, the use and outcomes of bridging during oral anticoagulation interruptions in clinical practice are unknown. METHODS AND RESULTS: The Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) registry is a prospective, observational registry study of US outpatients with atrial fibrillation. We recorded incident temporary interruptions of oral anticoagulation for a procedure, including the use and type of bridging therapy. Outcomes included multivariable-adjusted rates of myocardial infarction, stroke or systemic embolism, major bleeding, cause-specific hospitalization, and death within 30 days. Of 7372 patients treated with oral anticoagulation, 2803 overall interruption events occurred in 2200 patients (30%) at a median follow-up of 2 years. Bridging anticoagulants were used in 24% (n=665), predominantly low-molecular-weight heparin (73%, n=487) and unfractionated heparin (15%, n=97). Bridged patients were more likely to have had prior cerebrovascular events (22% versus 15%; P=0.0003) and mechanical valve replacements (9.6% versus 2.4%; P/=2 in 94% versus 95%; P=0.5). Bleeding events were more common in bridged than nonbridged patients (5.0% versus 1.3%; adjusted odds ratio, 3.84;
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