Probing the geometry and motion of AGN coronae through accretion disc emissivity profiles

To gain a better understanding of the inner disc region that comprises active galactic nuclei it is necessary to understand the pattern in which the disc is illuminated (the emissivity profile) by X-rays emitted from the continuum source above the black hole (corona). The differences in the emissivity profiles produced by various corona geometries are explored via general relativistic ray tracing simulations. Through the analysis of various parameters of the geometries simulated it is found that emissivity profiles produced by point source and extended geometries such as cylindrical slabs and spheroidal coronae placed on the accretion disc are distinguishable. Profiles produced by point source and conical geometries are not significantly different, requiring an analysis of reflection fraction to differentiate the two geometries. Beamed point and beamed conical sources are also simulated in an effort to model jet-like coronae, though the differences here are most evident in the reflection fraction. For a point source we determine an approximation for the measured reflection fraction with the source height and velocity. Simulating spectra from the emissivity profiles produced by the various geometries produce distinguishable differences. Overall spectral differences between the geometries do not exceed 15 per cent in the most extreme cases. It is found that emissivity profiles can be useful in distinguishing point source and extended geometries given high quality spectral data of extreme, bright sources over long exposure times. In combination with reflection fraction, timing, and spectral analysis we may use emissivity profiles to discern the geometry of the X-ray source.Comment: 15 pages, 12 figures. Accepted for publication in MNRA

Kinetic Studies of the Formation of Iron (III) Ethylenediaminetetraacetate-Hydrogen Peroxide Complex

The formation of· a red-purple iron (III) ethylenediaminetetraacetate mono hydrogen peroxide species obeys the kinetic express ion rate= k LFe(EDTA) (OH)2 3-J [H 202] over the range pH 9.0-11.0. The Arrhenius equation, k = 1.9 X 10 7 exp (-6,700/RT) holds and at 25°, k = 2.5 X 10 2 M - 1 sec-1• An enhanced rate above pH = 11 .0 may be associated with enhanced reactivity of [Fe(EDTA) (0H)3] 4- or H02-. A brief compar ison is made of the results with data for pe roxidase and catalase reactions with hydrogen peroxide

Management of the Rice Tungro Virus Vector \u3ci\u3eNephotettix virescens\u3c/i\u3e (Homoptera: Cicadellidae) with Controlled-Release Formulations of Carbofuran

Field trials were conducted in lowland flooded rice in the Philippines to evaluate a number of carbofuran controlled-release formulations in comparison with commercial formulations. The test formulations were based on a biodegradable matrix of pine kraft lignin and were used as granules of different sizes and also in the form of small strips. The release rates were assessed under field conditions by bioassaying rice plants in the field, using adult rice green leafhopper, Nephotettix virescens Distant. The lignin formulations with a high level of active ingredient (15–45% by weight) gave as good or better control than the commercial 3% granules in tests based on three application techniques: broadcast into the floodwater, soil incorporation, and root zone injection. The improvements in control levels of green leafhoppers were most marked with soil incorporation and root zone application. The best lignin-based formulation reduced levels of tungro virus infection from 23% for a conventional flowable carbofuran formulation to 1.0% at an application rate of 0.5 kg (AI)/ha. At the same rate, the grain yield was increased from 3.56 t/ha to 5.5 t/ha, using the controlled-released formulation

Change in Grassland Science: Implications for Training, Research and Grassland Societies

In most of the world the priority for production-oriented research has been succeeded by the need for grassland research to focus on systems which satisfy requirements relating to the stability and protection of land, water and atmospheric resources and to biodiversity, in addition to production efficiency. This dictates not only a new approach to research, but also new approaches for the organisation of research, the training and development of research scientists and the activities of Grassland Societies and associated organisations

Revealing structure and evolution within the corona of the Seyfert galaxy I Zw 1

X-ray spectral timing analysis is presented of XMM-Newton observations of the narrow line Seyfert 1 galaxy I Zwicky 1 (I Zw 1) taken in 2015 January. After exploring the effect of background flaring on timing analyses, X-ray time lags between the reflection-dominated 0.3-1.0keV energy and continuum-dominated 1.0-4.0keV band are measured, indicative of reverberation off the inner accretion disc. The reverberation lag time is seen to vary as a step function in frequency; across lower frequency components of the variability, 3e-4 to 1.2e-3Hz a lag of 160s is measured, but the lag shortens to (59 +/- 4)s above 1.2e-3Hz. The lag-energy spectrum reveals differing profiles between these ranges with a change in the dip showing the earliest arriving photons. The low frequency signal indicates reverberation of X-rays emitted from a corona extended at low height over the disc while at high frequencies, variability is generated in a collimated core of the corona through which luminosity fluctuations propagate upwards. Principal component analysis of the variability supports this interpretation, showing uncorrelated variation in the spectral slope of two power law continuum components. The distinct evolution of the two components of the corona is seen as a flare passes inwards from the extended to the collimated portion. An increase in variability in the extended corona was found preceding the initial increase in X-ray flux. Variability from the extended corona was seen to die away as the flare passed into the collimated core leading to a second sharper increase in the X-ray count rate.Comment: 18 pages, 11 figures. Accepted for publication in MNRA

The effects of sitaxentan on sildenafil pharmacokinetics and pharmacodynamics in healthy subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: * Endothelin-A receptor antagonists (ETRAs) and phosphodiesterase-type 5 inhibitors are approved monotherapies for the treatment of pulmonary arterial hypertension; combining agents from these two drug classes could be beneficial. * There is a significant pharmacokinetic (PK) interaction between the ETRA bosentan and the phosphodiesterase-type 5 inhibitor sildenafil. * This study assessed whether the ETRA sitaxentan similarly impacts the PK of sildenafil. WHAT THIS STUDY ADDS: * This study demonstrates that sitaxentan has little effect on sildenafil PK and pharmacodynamics and that no dose adjustment of either agent is required upon co-administration of sildenafil with sitaxentan. AIMS: This study evaluated the effects of sitaxentan on the pharmacodynamic [systemic blood pressure (BP)] and pharmacokinetic (PK) parameters of sildenafil in healthy volunteers. METHODS: Healthy subjects (18-60 years, n= 24) were randomized into two sequence groups. Group 1 received sitaxentan sodium 100 mg daily (7 days), followed by placebo (7 days). Group 2 received placebo (7 days), followed by sitaxentan sodium 100 mg (7 days). On day 7 of each treatment period, participants received sildenafil 100 mg. PK parameters and BP were analysed on day 7 in each treatment period. RESULTS: Sildenafil exposure was slightly higher [AUC(infinity) geometric mean ratio (GMR), 128%] when co-administered with sitaxentan 100 mg vs. placebo, demonstrating a weak, but statistically significant interaction (90% confidence interval 115.5%, 141.2%). The mean maximum positive (E(max)+) and maximum negative (E(max)-) changes from baseline in both systolic and diastolic BP were comparable for sitaxentan and placebo (range 4.8-7.3 mmHg) with three of four geometric mean ratios falling within the equivalence window, suggesting that the drug interaction was not clinically significant. Adverse events were similar between sitaxentan 100 mg (39%) and placebo (30%). No deaths or serious adverse events occurred during the study. CONCLUSION: The dose of sildenafil does not need to be adjusted when co-administered with sitaxentan

On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra

The spin of Cygnus X-1 is measured by fitting reflection models to Suzaku data covering the energy band 0.9-400 keV. The inner radius of the accretion disc is found to lie within 2 gravitational radii (r_g=GM/c^2) and a value for the dimensionless black hole spin is obtained of 0.97^{+0.014}_{-0.02}. This agrees with recent measurements using the continuum fitting method by Gou et al. and of the broad iron line by Duro et al. The disc inclination is measured at 23.7^{+6.7}_{-5.4} deg, which is consistent with the recent optical measurement of the binary system inclination by Orosz et al of 27+/-0.8 deg. We pay special attention to the emissivity profile caused by irradiation of the inner disc by the hard power-law source. The X-ray observations and simulations show that the index q of that profile deviates from the commonly used, Newtonian, value of 3 within 3r_g, steepening considerably within 2r_g, as expected in the strong gravity regime.Comment: 7 pages, 10 figures, MNRAS in pres