Iron K-alpha Emission from X-ray Reflection: Predictions for Gamma-Ray Burst Models

Recent observations of several gamma-ray burst (GRB) afterglows have shown evidence for a large amount of X-ray line emitting material, possibly arising from ionized iron. A significant detection of an X-ray spectral feature, such as that found in the Chandra observation of GRB 991216, may provide important constraints on the immediate environment of the burst and hence on progenitor models. The large Fe K-alpha equivalent widths inferred from the X-ray observations favor models in which the line is produced when the primary X-ray emission from the source strikes Thomson-thick material and Compton scatters into our line of sight. We present such reflection spectra here, computed in a fully self-consistent manner, and discuss the range of ionization parameters that may be relevant to different models of GRBs. We argue that the presence of a strong hydrogen-like K-alpha line is unlikely, because Fe-XXVI photons would be trapped resonantly and removed from the line core by Compton scattering. In contrast, a strong narrow emission line from He-like Fe-XXV is prominent in the model spectra. We briefly discuss how these constraints may affect the line energy determination in GRB 991216.Comment: 8 pages, 3 figures, Ap.J. Letters accepte

Regulation and deregulation in industrial countries : some lessons for LDCs

The United States'experience with antitrust and with directive regulation in the rail, trucking, airline, and telephone sectors offers useful lessons for developing countries. The experience highlights the realities both of market failure and of the difficulties of implementing regulation to control it - and reveals that imperfect regulation may be no better than imperfect competition. Antitrust measures to regulate price fixing and to require approval for mergers above some threshold level of industrial concentration are straightforward to implement and have provided some gains in economic welfare. The regulation of price discrimination, restrictive vertical practices, and predatory pricing is administratively more difficult, and the potential gains are less clearly evident. In many situations, import competition can be an efficient alternative. Direct regulation of rail, trucking, airline, and telephone was frequently inefficient, the regulatory apparatus often lost sight of its original objectives, and the regulators were captured by the regulated. For rail and trucking regulation, the regulatory outcome probably was worse than it would have been under laissez-faire.Administrative&Regulatory Law,Economic Theory&Research,National Governance,Knowledge Economy,Environmental Economics&Policies

Phi-four solitary waves in a parabolic potentia: existence, stability, and collisional dynamics

We explore a φ4 model with an added external parabolic potential term. This term dramatically alters the spectral properties of the system. We identify single and multiple kink solutions and examine their stability features; importantly, all of the stationary structures turn out to be unstable. We complement these with a dynamical study of the evolution of a single kink in the trap, as well as of the scattering of kink and anti-kink solutions of the model. We observe that some of the key characteristics of kink-antikink collisions, such as the critical velocity and the multi-bounce windows, are sensitively dependent on the trap strength parameter, as well as the initial displacement of the kink and antikink.Accepted manuscrip

Simple algorithm for the correction of MRI image artefacts due to random phase fluctuations

Grant support: This work was supported by EPSRC [grant numbers EP/E036775/1, EP/K020293/1] and received funding from the European Union's Horizon 2020 research and innovation programme [grant agreement No 668119, project “IDentIFY”]Peer reviewedPublisher PD

Trans-Atlantic Correlation of Upper Cretaceous Marine Sediments

Upper Cretaceous marine deposits from the Mid-Atlantic region of North America (Delaware, Maryland, and New Jersey) and the Maastricht area (southern Netherlands, and nearby Belgium and Gennany) are correlated across the Atlantic using a variety of macro invertebrates, nannofossils, and sequence stratigraphy. Four late Cretaceous Mid-Atlantic sequences, the Marshalltown, Englishtown, Merchantville, and Navesink, span the upper Santonian to lowennost Danian, and have direct correlatives in the Maastricht area. Correlations between the Mid-Atlantic and the Maastricht regions (respectively) are as follows: the upper Santonian to lower Campanian Merchantville and Matawan formations with the Achen and lower Vaals fonnations; the middle Campanian upper Englishtown F onnation with the upper Vaals F onnation; the uppermost middle Campanian to upper Campanian Marshalltown, Wenonah, and Mount Laurel fomlations with the lower Gulpen Fonnation; the Navesink and lower Severn fonnations with the middle Gulpen Fonnation; and the New Egypt and upper Severn fonnations with the upper Gulpen and Maastricht fonnations. Additionally, deposits of the Maastricht area also provide support for several proposed subdivisions in the Marshalltown and Navesink sequences. The correlations proposed here can serve to refine the biostratigraphy oflarge marine vertebrates known from both sides of the Atlantic

Population Dynamics, Impacts, and Integrated Management of Forest Defoliating Insects

Pine plantations on Typic Quartzipsamments in East Texas are difficult to establish. Forest management options following clearcutting are limited. An 8-year regeneration study of the growth and survival of loblolly, Pinus taeda, L. shortleaf, P. echinata Mill., slash, P. elliotii Engelm and longleaf pines P. palustris Mill. was conducted to determine optimum tree species and treatments for reforestation, and to recommend practical alternative land uses and management strategies for Typic Quartzipsamments. Successful regeneration provides new opportunities for insects and pathogens. Impacts of the Nantucket pine tip moth, R}iyacionia frustrana (Comstock), the Deodar weevil, Pissodes nemorensis, Germar, Annosus root rot, Heterobasidion annosum (Fr: Fr) Bref, fusiform rust, Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme (hedge and N. Hunt) Burdsall and G. Snow and the Texas leaf-cutting ant, Atta texana, (Buckley) will be discussed in the context of droughty site management

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David R. Low, Ross L. Chapman and Terry R. Sloan explore innovation and market orientation in Australian manufacturing SMEs

Truthmakers and modality

This paper attempts to locate, within an actualist ontology, truthmakers for modal truths: truths of the form or . In section 1 I motivate the demand for substantial truthmakers for modal truths. In section 2 I criticise Armstrong’s account of truthmakers for modal truths. In section 3 I examine essentialism and defend an account of what makes essentialist attributions true, but I argue that this does not solve the problem of modal truth in general. In section 4 I discuss, and dismiss, a theistic account of the source of modal truth proposed by Alexander Pruss. In section 5 I offer a means of (dis)solving the problem

Site/stand factors influencing Nantucket pine tip moth in loblolly pine plantations

Tip moth infestation and loblolly pine growth were examined on sandy, loamy and clayey sites in 2-3 year old plantations. Infestations were greatest on loamy sites. Following fertilizer and herbicide applications, tip moth infestations were lowest on fertilized plots following application of phosphorus