85 research outputs found

    X-ray spectral and eclipsing model of the clumpy obscurer in active galactic nuclei

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    We present a unification model for a clumpy obscurer in active galactic nuclei (AGN) and investigate the properties of the resulting X-ray spectrum. Our model is constructed to reproduce the column density distribution of the AGN population and cloud eclipse events in terms of their angular sizes and frequency. We developed and released a generalised Monte Carlo X-ray radiative transfer code, XARS, to compute X-ray spectra of obscurer models. The geometry results in strong Compton scattering, causing soft photons to escape also along Compton-thick sight lines. This makes our model spectra very similar to our TORUS previous model. However, only if we introduce an additional Compton-thick reflector near the corona, we achieve good fits to NuSTAR spectra. This additional component in our model can be interpreted as part of the dust-free broad-line region, an inner wall or rim, or a warped disk. It cannot be attributed to a simple disk because the reflector must simultaneously block the line of sight to the corona and reflect its radiation. We release our model as an Xspec table model and present corresponding CLUMPY infrared spectra, paving the way for self-consistent multi-wavelength analyses

    Utilisation and valorisation of distillery whisky waste streams via biomass electrolysis : electrosynthesis of hydrogen

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    Fuel-flexible hydrogen generation methods, such as electrochemical conversion of biomass, offer a route for sustainable production of hydrogen whilst valorising feedstocks that are often overlooked as waste products. This work explores the potential of a novel, two-stage electrolysis process to convert biomass-containing solid (draff/spent barley) and liquid (pot ale and spent lees) whisky co-products, from the Isle of Raasay Distillery, into hydrogen, using a phosphomolybdic acid (H3[PMo12O40] or PMA) catalyst. Characterization of whisky distillery co-products was conducted by thermogravimetric, differential scanning calorimetric, CHN elemental, total organic carbon and chemical oxygen demand analysis. The results indicated that the characteristics of these co-products align well with those reported across the Scotch Whisky distillation sector. Subsequently, the concept of thermal digestion of each co-product type, using the Keggin-type polyoxometalate PMA catalyst to abstract protons and electrons from biomass, will be outlined. UV-visible spectrophotometry was employed to assess the extent of reduction of the catalyst, after digestion of each co-product, and indicated that draff and pot ale offer the largest scope for hydrogen production, whilst digestion and electrolysis of spent lees is not viable due to the low biomass content of this distillation co-product. Finally, details of electrolysis of the PMA-biomass solutions using a proton exchange membrane electrolysis cell (PEMEC) will be provided, including electrochemical data which help to elucidate the performance-limiting processes of the PEMEC operating on digested biomass-PMA anolytes

    A Comparison of Embedded and Nonembedded Print Coverage of the U.S. Invasion and Occupation of Iraq

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    This study examines the impact of embedded versus nonembedded (unilateral) news coverage during the U.S. invasion and occupation of Iraq. A content analysis was conduycted of the Washington Post, New York Times, Los Angeles Times, and Chicago Tribune news coverage of the invasion and occupation examining whether embedded and nonembedded new reports were different and, if so, how. News reports were examined for differences in tone toward the military, trust in the military, framing, and authoritativeness. The results of the study revealed significant differences in overall tone toward the military, trust in military personnel, framing, and authoritativeness between embedded and nonembedded articles.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

    The Panchromatic Afterglow of GW170817: The full uniform dataset, modeling, comparison with previous results and implications

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    We present the full panchromatic afterglow light curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all archival data, and reprocessing a subset of it, we have ensured that the panchromatic dataset is uniform and therefore immune to the differences in data processing or flux determination methods used by different groups. Simple power-law fits to the uniform afterglow light curve indicate a t^(0.86±0.04) rise, a t^(−1.90±0.12) decline, and a peak occurring at 155±4 days. The afterglow is optically thin throughout its evolution, consistent with a single spectral index (−0.569±0.002) across all epochs. This gives a precise and updated estimate of the electron power-law index, p=2.138±0.004. By studying the diffuse X-ray emission from the host galaxy, we place a conservative upper limit on the hot ionized ISM density, <0.01 cm⁻³, consistent with previous afterglow studies. Using the late-time afterglow data we rule out any long-lived neutron star remnant having magnetic field strength between 10^(10.4) G and 10¹⁶ G. Our fits to the afterglow data using an analytical model that includes VLBI proper motion from Mooley et al (2018), and a structured jet model that ignores the proper motion, indicates that the proper motion measurement needs to be considered while seeking an accurate estimate of the viewing angle

    Negative feedback regulation of the ERK1/2 MAPK pathway

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    The extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signalling pathway regulates many cellular functions, including proliferation, differentiation, and transformation. To reliably convert external stimuli into specific cellular responses and to adapt to environmental circumstances, the pathway must be integrated into the overall signalling activity of the cell. Multiple mechanisms have evolved to perform this role. In this review, we will focus on negative feedback mechanisms and examine how they shape ERK1/2 MAPK signalling. We will first discuss the extensive number of negative feedback loops targeting the different components of the ERK1/2 MAPK cascade, specifically the direct posttranslational modification of pathway components by downstream protein kinases and the induction of de novo gene synthesis of specific pathway inhibitors. We will then evaluate how negative feedback modulates the spatiotemporal signalling dynamics of the ERK1/2 pathway regarding signalling amplitude and duration as well as subcellular localisation. Aberrant ERK1/2 activation results in deregulated proliferation and malignant transformation in model systems and is commonly observed in human tumours. Inhibition of the ERK1/2 pathway thus represents an attractive target for the treatment of malignant tumours with increased ERK1/2 activity. We will, therefore, discuss the effect of ERK1/2 MAPK feedback regulation on cancer treatment and how it contributes to reduced clinical efficacy of therapeutic agents and the development of drug resistance

    Hierarchy and conflict in mutual being

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