Ionized Reflection Spectra from Accretion Disks Illuminated by X-Ray Pulsars

X-ray reflection signatures are observed around multiple classes of accreting compact objects. Modelling these features yield important constraints on the physics of accretion disks, motivating the development of X-ray reflection models appropriate for a variety of systems and illumination conditions. Here, constant density ionized X-ray reflection models are presented for a disk irradiated with a very hard power-law X-ray spectrum (\Gamma \u3c 1) and a variable high-energy cutoff. These models are then applied to the Suzaku data of the accreting X-ray pulsar LMC X-4, where very good fits are obtained with a highly ionized reflector responsible for both the broad Fe K line and the soft excess. The ionized reflector shows strong evidence for significant Doppler broadening and is redshifted by ~10^4 km/s. These features indicate that the reflecting material is associated with the complex dynamics occurring at the inner region of the magnetically-truncated accretion disk. Thus, reflection studies of X-ray pulsar spectra may give important insights into the accretion physics at the magnetospheric radius

Environmental Baseline Monitoring Project. Phase II, final report

This report is submitted in compliance with the conditions set out in the grant awarded to the British Geological Survey (BGS), for the period April 2016 – March 2017, to support the jointly-funded project "Science-based environmental baseline monitoring". It presents the results of monitoring and/or measurement and preliminary interpretation of these data to characterise the baseline environmental conditions in the Vale of Pickering, North Yorkshire and for air quality, the Fylde in Lancashire ahead of any shale gas development. The two areas where the monitoring is taking place have seen, during the project, planning applications approved for the exploration for shale gas and hydraulic fracturing. It is widely recognised that there is a need for good environmental baseline data and establishment of effective monitoring protocols ahead of any shale gas/oil development. This monitoring will enable future changes that may occur as a result of industrial activity to be identified and differentiated from other natural and man-made changes that are influencing the baseline. Continued monitoring will then enable any deviations from the baseline, should they occur, to be identified and investigated independently to determine the possible causes, sources and significance to the environment and public health. The absence of such data in the United States has undermined public confidence, led to major controversy and inability to identify and effectively deal with impact/contamination where it has occurred. A key aim of this work is to avoid a similar situation and the independent monitoring being carried out as part of this project provides an opportunity to develop robust environmental baseline for the two study areas and monitoring procedures, and share experience that is applicable to the wider UK situation. This work is internationally unique and comprises an inter-disciplinary researcher-led programme that is developing, testing and implementing monitoring methodologies to enable future environmental changes to be detected at a local scale (individual site) as well as across a wider area, e.g. ‘shale gas play’ where cumulative impacts may be significant. The monitoring includes: water quality (groundwater and surface water), seismicity, ground motion, soil gas, atmospheric composition (greenhouse gases and air quality) and radon in air. Recent scientific and other commissioned studies have highlighted that credible and transparent monitoring is key to gaining public acceptance and providing the evidence base to demonstrate the industry’s impact on the environment and importantly on public health. As a result, BGS and its partners initiated in early 2015, a co-ordinated programme of environmental monitoring in Lancashire that was then extended to the Vale of Pickering in North Yorkshire after the Secretary of State for Energy and Climate Change (BEIS) awarded a grant to the British Geological Survey (BGS). The current duration of the grant award is to 31st March 2018. It has so far enabled baseline environmental monitoring for a period of more than 12 months. With hydraulic fracturing of shale gas likely to take place during late 2017/early 2018, the current funding will allow the environmental monitoring to continue during the transition from baseline to monitoring during shale gas operations. This report presents the monitoring results to April 2017 and a preliminary interpretation. A full interpretation is not presented in this report as monitoring is continuing and it is expected that there will be at least six months of additional baseline data before hydraulic fracturing takes place. This represents up to 50% more data for some components of the montoring, and when included in the analysis will significantly improve the characterisation and interpretation of the baseline. In addition to this report, the BGS web site contains further information on the project, near real-time data for some components of the monitoring and links to other projects outputs, e.g. reports and videos (www.bgs.ac.uk/research/groundwater/shaleGas/monitoring/home.html)

Two--Electron Atoms in Short Intense Laser Pulses

We discuss a method of solving the time dependent Schrodinger equation for atoms with two active electrons in a strong laser field, which we used in a previous paper [A. Scrinzi and B. Piraux, Phys. Rev. A 56, R13 (1997)] to calculate ionization, double excitation and harmonic generation in Helium by short laser pulses. The method employs complex scaling and an expansion in an explicitly correlated basis. Convergence of the calculations is documented and error estimates are provided. The results for Helium at peak intensities up to 10^15 W/cm^2 and wave length 248 nm are accurate to at least 10 %. Similarly accurate calculations are presented for electron detachment and double excitation of the negative hydrogen ion.Comment: 14 pages, including figure

Grain boundary pinning and glassy dynamics in stripe phases

We study numerically and analytically the coarsening of stripe phases in two spatial dimensions, and show that transient configurations do not achieve long ranged orientational order but rather evolve into glassy configurations with very slow dynamics. In the absence of thermal fluctuations, defects such as grain boundaries become pinned in an effective periodic potential that is induced by the underlying periodicity of the stripe pattern itself. Pinning arises without quenched disorder from the non-adiabatic coupling between the slowly varying envelope of the order parameter around a defect, and its fast variation over the stripe wavelength. The characteristic size of ordered domains asymptotes to a finite value $R_g \sim \lambda_0\ \epsilon^{-1/2}\exp(|a|/\sqrt{\epsilon})$, where$\epsilon\ll 1$is the dimensionless distance away from threshold,$\lambda_0$the stripe wavelength, and$a$ a constant of order unity. Random fluctuations allow defect motion to resume until a new characteristic scale is reached, function of the intensity of the fluctuations. We finally discuss the relationship between defect pinning and the coarsening laws obtained in the intermediate time regime.Comment: 17 pages, 8 figures. Corrected version with one new figur

HOx observations over West Africa during AMMA: impact of isoprene and NOx

Aircraft OH and HO2 measurements made over West Africa during the AMMA field campaign in summer 2006 have been investigated using a box model constrained to observations of long-lived species and physical parameters. "Good" agreement was found for HO2 (modelled to observed gradient of 1.23 ± 0.11). However, the model significantly overpredicts OH concentrations. The reasons for this are not clear, but may reflect instrumental instabilities affecting the OH measurements. Within the model, HOx concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O(1D) with water vapour, and loss processes dominated by HO2 + HO2 and HO2 + RO2. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NOx and high isoprene environments, we do not observe any dependence of model success for HO2 on isoprene and attribute this to efficient recycling of HOx through RO2 + NO reactions under the moderate NOx concentrations (5–300 ppt NO in the boundary layer, median 76 ppt) encountered during AMMA. This suggests that some of the problems with understanding the impact of isoprene on atmospheric composition may be limited to the extreme low range of NOx concentrations

X-Linked Immunodeficient Mice With No Functional Bruton's Tyrosine Kinase Are Protected From Sepsis-Induced Multiple Organ Failure

We previously reported the Bruton's tyrosine kinase (BTK) inhibitors ibrutinib and acalabrutinib improve outcomes in a mouse model of polymicrobial sepsis. Now we show that genetic deficiency of the BTK gene alone in Xid mice confers protection against cardiac, renal, and liver injury in polymicrobial sepsis and reduces hyperimmune stimulation (“cytokine storm”) induced by an overwhelming bacterial infection. Protection is due in part to enhanced bacterial phagocytosis in vivo, changes in lipid metabolism and decreased activation of NF-κB and the NLRP3 inflammasome. The inactivation of BTK leads to reduced innate immune cell recruitment and a phenotypic switch from M1 to M2 macrophages, aiding in the resolution of sepsis. We have also found that BTK expression in humans is increased in the blood of septic non-survivors, while lower expression is associated with survival from sepsis. Importantly no further reduction in organ damage, cytokine production, or changes in plasma metabolites is seen in Xid mice treated with the BTK inhibitor ibrutinib, demonstrating that the protective effects of BTK inhibitors in polymicrobial sepsis are mediated solely by inhibition of BTK and not by off-target effects of this class of drugs

Scattering length of the ground state Mg+Mg collision

We have constructed the X 1SIGMAg+ potential for the collision between two ground state Mg atoms and analyzed the effect of uncertainties in the shape of the potential on scattering properties at ultra-cold temperatures. This potential reproduces the experimental term values to 0.2 inverse cm and has a scattering length of +1.4(5) nm where the error is prodominantly due to the uncertainty in the dissociation energy and the C6 dispersion coefficient. A positive sign of the scattering length suggests that a Bose-Einstein condensate of ground state Mg atoms is stable.Comment: 15 pages, 3 figures, Submitted Phys. Rev.

Influence of Coulomb and Phonon Interaction on the Exciton Formation Dynamics in Semiconductor Heterostructures

A microscopic theory is developed to analyze the dynamics of exciton formation out of incoherent carriers in semiconductor heterostructures. The carrier Coulomb and phonon interaction is included consistently. A cluster expansion method is used to systematically truncate the hierarchy problem. By including all correlations up to the four-point (i.e. two-particle) level, the fundamental fermionic substructure of excitons is fully included. The analysis shows that the exciton formation is an intricate process where Coulomb correlations rapidly build up on a picosecond time scale while phonon dynamics leads to true exciton formation on a slow nanosecond time scale.Comment: 18 pages, 7 figure

Radio Frequency Spectra of 388 Bright 74 MHz Sources

As a service to the community, we have compiled radio frequency spectra from the literature for all sources within the VLA Low Frequency Sky Survey (VLSS) that are brighter than 15 Jy at 74 MHz. Over 160 references were used to maximize the amount of spectral data used in the compilation of the spectra, while also taking care to determine the corrections needed to put the flux densities from all reference on the same absolute flux density scale. With the new VLSS data, we are able to vastly improve upon previous efforts to compile spectra of bright radio sources to frequencies below 100 MHz because (1) the VLSS flux densities are more reliable than those from some previous low frequency surveys and (2) the VLSS covers a much larger area of the sky (declination >-30 deg.) than many other low frequency surveys (e.g., the 8C survey). In this paper, we discuss how the spectra were constructed and how parameters quantifying the shapes of the spectra were derived. Both the spectra and the shape parameters are made available here to assist in the calibration of observations made with current and future low frequency radio facilities.Comment: Accepted to ApJ

The Second Cambridge Pulsar Survey at 81.5 MHz

We have searched the northern sky for pulsars at the low radio frequency of 81.5 MHz, using the 3.6-hectare array at Cambridge, England. The survey covered most of the sky north of declination -20 deg and provided sensitivities of order 200 mJy for pulsars not too close to the galactic plane. A total of 20 pulsars were detected, all of them previously known. The effective post-detection sampling rate was 1.3 kHz, and the sensitivity to low-dispersion millisecond pulsars was sufficient to allow the detection of objects similar to PSR J0437-4715 (period 5.7 ms, dispersion measure 2.6 cm^-3 pc, mean flux density 1 Jy). No such pulsars were found.Comment: 19 pages, 5 figure