Marine microplastics

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordGalloway and Lewis discuss marine microplastics and their devastating effects on ocean ecosystems

A population study of type II bursts in the Rapid Burster

Type II bursts are thought to arise from instabilities in the accretion flow onto a neutron star in an X-ray binary. Despite having been known for almost 40 years, no model can yet satisfactorily account for all their properties. To shed light on the nature of this phenomenon and provide a reference for future theoretical work, we study the entire sample of Rossi X-ray Timing Explorer data of type II bursts from the Rapid Burster (MXB 1730-335). We find that type II bursts are Eddington-limited in flux, that a larger amount of energy goes in the bursts than in the persistent emission, that type II bursts can be as short as 0.130 s, and that the distribution of recurrence times drops abruptly below 15-18 s. We highlight the complicated feedback between type II bursts and the NS surface thermonuclear explosions known as type I bursts, and between type II bursts and the persistent emission. We review a number of models for type II bursts. While no model can reproduce all the observed burst properties and explain the source uniqueness, models involving a gating role for the magnetic field come closest to matching the properties of our sample. The uniqueness of the source may be explained by a special combination of magnetic field strength, stellar spin period and alignment between the magnetic field and the spin axis.Comment: Accepted 2015 February 12. Received 2015 February 10; in original form 2014 December 1

Charmonium properties from lattice QCD + QED: hyperfine splitting, J/ψJ/\psi leptonic width, charm quark mass and aμca_{\mu}^c

We have performed the first $n_f = 2+1+1$ lattice QCD computations of the properties (masses and decay constants) of ground-state charmonium mesons. Our calculation uses the HISQ action to generate quark-line connected two-point correlation functions on MILC gluon field configurations that include $u/d$ quark masses going down to the physical point, tuning the $c$ quark mass from $M_{J/\psi}$ and including the effect of the $c$ quark's electric charge through quenched QED. We obtain $M_{J/\psi}-M_{\eta_c}$ (connected) = 120.3(1.1) MeV and interpret the difference with experiment as the impact on $M_{\eta_c}$ of its decay to gluons, missing from the lattice calculation. This allows us to determine $\Delta M_{\eta_c}^{\mathrm{annihiln}}$ =+7.3(1.2) MeV, giving its value for the first time. Our result of $f_{J/\psi}=$ 0.4104(17) GeV, gives $\Gamma(J/\psi \rightarrow e^+e^-)$=5.637(49) keV, in agreement with, but now more accurate than experiment. At the same time we have improved the determination of the $c$ quark mass, including the impact of quenched QED to give $\overline{m}_c(3\,\mathrm{GeV})$ = 0.9841(51) GeV. We have also used the time-moments of the vector charmonium current-current correlators to improve the lattice QCD result for the $c$ quark HVP contribution to the anomalous magnetic moment of the muon. We obtain $a_{\mu}^c = 14.638(47) \times 10^{-10}$, which is 2.5$\sigma$ higher than the value derived using moments extracted from some sets of experimental data on $R(e^+e^- \rightarrow \mathrm{hadrons})$. This value for $a_{\mu}^c$ includes our determination of the effect of QED on this quantity, $\delta a_{\mu}^c = 0.0313(28) \times 10^{-10}$.Comment: Added extra discussion on QED setup, some new results to study the effects of strong isospin breaking in the sea (including new Fig. 1) and a fit stability plot for the hyperfine splitting (new Fig. 7). Version accepted for publication in PR

Dissolution and bandgap paradigms for predicting the toxicity of metal oxide nanoparticles in the marine environment: an in vivo study with oyster embryos

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordDissolution and bandgap paradigms have been proposed for predicting the ability of metal oxide nanoparticles (NPs) to induce oxidative stress in different in vitro and in vivo models. Here, we addressed the effectiveness of these paradigms in vivo and under conditions typical of the marine environment, a final sink for many NPs released through aquatic systems. We used ZnO and MnO2 NPs as models for dissolution and bandgap paradigms, respectively, and CeO2 NPs to assess reactive oxygen radical (ROS) production via Fenton-like reactions in vivo. Oyster embryos were exposed to 0.5-500 μM of each test NP over 24 h and oxidative stress was determined as a primary toxicity pathway across successive levels of biological complexity, with arrested development as the main pathological outcome. NPs were actively ingested by oyster larvae and entered cells. Dissolution was a viable paradigm for predicting the toxicity of NPs in the marine environment, whereas the surface reactivity based paradigms (i.e. bandgap and ROS generation via Fenton-like reaction) were not supported under seawater conditions. Bio-imaging identified potential cellular storage-disposal sites of solid particles that could ameliorate the toxicological behavior of non-dissolving NPs, whilst abiotic screening of surface reactivity suggested that the adsorption-complexation of surface active sites by seawater ions could provide a valuable hypothesis to explain the quenching of the intrinsic oxidation potential of MnO2 NPs in seawater.This project was funded by the European Union Horizon 2020 research and innovation program under Marie Sklodowska-Curie grant agreement No 655134 and NERC FENAC access grant No PR120021. TG acknowledges support from NERC grant NE/N006178/1

Non-Existence of Black Holes in Certain Λ<0\Lambda<0 Spacetimes

Assuming certain asymptotic conditions, we prove a general theorem on the non-existence of static regular (i.e., nondegenerate) black holes in spacetimes with a negative cosmological constant, given that the fundamental group of space is infinite. We use this to rule out the existence of regular negative mass AdS black holes with Ricci flat scri. For any mass, we also rule out a class of conformally compactifiable static black holes whose conformal infinity has positive scalar curvature and infinite fundamental group, subject to our asymptotic conditions. In a limited, but important, special case our result adds new support to the AdS/CFT inspired positive mass conjecture of Horowitz and Myers.Comment: 17 pages, Latex. Typos corrected, minor changes to the text. Accepted for publication in Classical and Quantum Gravit

Summary of the recent short-haul systems studies

The results of several NASA sponsored high density short haul air transportation systems studies are reported as well as analyzed. Included are the total STOL systems analysis approach, a companion STOL composites study conducted in conjunction with STOL systems studies, a STOL economic assessment study, an evaluation of STOL aircraft with and without externally blown flaps, an alternative STOL systems for the San Francisco Bay Area, and the quiet, clean experimental engine studies. Assumptions and results of these studies are summarized, their differences, analyzed, and the results compared with those in-house analyses performed by the Systems Studies Division of the NASA-Ames Research Center. Pertinent conclusions are developed and the more significant technology needs for the evaluation of a viable short haul transportation system are identified

A uniqueness theorem for the adS soliton

The stability of physical systems depends on the existence of a state of least energy. In gravity, this is guaranteed by the positive energy theorem. For topological reasons this fails for nonsupersymmetric Kaluza-Klein compactifications, which can decay to arbitrarily negative energy. For related reasons, this also fails for the AdS soliton, a globally static, asymptotically toroidal $\Lambda<0$ spacetime with negative mass. Nonetheless, arguing from the AdS/CFT correspondence, Horowitz and Myers (hep-th/9808079) proposed a new positive energy conjecture, which asserts that the AdS soliton is the unique state of least energy in its asymptotic class. We give a new structure theorem for static $\Lambda<0$ spacetimes and use it to prove uniqueness of the AdS soliton. Our results offer significant support for the new positive energy conjecture and add to the body of rigorous results inspired by the AdS/CFT correspondence.Comment: Revtex, 4 pages; Matches published version. More detail in Abstract and one equation corrected. For details of proofs and further results, see hep-th/020408

Gravity Dual of Gauge Theory on S^2 x S^1 x R

We (numerically) construct new static, asymptotically AdS solutions where the conformal infinity is the product of time and S^2 x S^1. There always exist a family of solutions in which the S^1 is not contractible and, for small S^1, there are two additional families of solutions in which the S^1 smoothly pinches off. This shows that (when fermions are antiperiodic around the S^1) there is a quantum phase transition in the gauge theory as one decreases the radius of the S^1 relative to the S^2. We also compare the masses of our solutions and argue that the one with lowest mass should minimize the energy among all solutions with conformal boundary S^2 x S^1 x R. This provides a new positive energy conjecture for asymptotically locally AdS metrics. A simple analytic continuation produces AdS black holes with topology S^2 x S^1.Comment: 17 pages, 4 figures, v2: minor changes, added reference

Type I X-ray bursts and burst oscillations in the accreting millisecond X-ray pulsar IGR J17511-3057

We report the discovery of burst oscillations at the spin frequency in ten thermonuclear bursts from the accreting millisecond X-ray pulsar (AMXP) IGR J17511-3057. The burst oscillation properties are, like those from the persistent AMXPs SAX J1808.4-3658 and XTE J1814-338, anomalous compared to burst oscillations from intermittent pulsars or non-pulsing LMXBs. Like SAX J1808.4-3658 they show frequency drifts in the rising phase rather than the tail. There is also evidence for harmonic content. Where IGR J17511-3057 is unusual compared to the other two persistent pulsars is that oscillations are not detected throughout all bursts. As accretion rate drops the bursts get brighter and their rise/decay time scales become shorter, while the oscillation amplitude falls below the detection threshold: first in the burst peak and then also in the rise. None of the bursts from IGR J17511-3057 show evidence for photospheric radius expansion (which might be expected to suppress oscillation amplitude) which allow us to set an upper limit to the distance of 6.9 kpc. We discuss the implications of our results for models of the burst oscillation mechanism.Comment: 11 pages, 5 figures, MNRAS in pres