46,576 research outputs found

    Copyright, Fair Use and the Digital Age in Academic Libraries: A Review of the Literature

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    Copyright law in the United States has gained a certain notoriety for its complexity and ambiguity, which has only been compounded by the evolution (or, some would say, revolution) of print resources to electronic resources. The purpose of this literature review is to review the current understanding of copyright law within the context of academic libraries in universities and colleges. Additionally, this review will describe what issues academic librarians face in complying with copyright law in this new digital age while continuing to perform duties such as processing course reserve materials, developing an institutional repository, and maintaining a digital collection. This literature review emphasizes the need for further and continuing education about copyright law among all members of the campus community, and, in particular, academic librarians

    Studies on the release of neutrophil extracellular traps and IFN-γ as part of the innate immune response to Aspergillus fumigatus and on the fungal stress response via the hybrid sensor kinase TcsC

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    Aspergillus fumigatus is a saprophytic mold that naturally inhabits the soil. Asexual reproduction yields hardy conidia that circulate in the air and are inhaled daily by humans. The fungus seems not to have evolved distinct mechanisms of pathogenicity, but is capable of responding to many stressful environmental cues present in its naturally harsh niche. The robust conidia present no problem to a fully functioning immune system, but if the innate immune system is compromised, the conidia can become activated and differentiate within the lung tissue to form invasive and disseminating hyphae. The resulting disease is called aspergillosis and is difficult to detect and to treat. To date, scientists have yet to find the factor(s) missing during immunosuppression that allow a healthy patient to easily dispose of A. fumigatus. We explored two possibilities: the production of neutrophil extracellular traps (NETs) and the release of IFN-γ by natural killer (NK) cells. We report here that NETs alone cannot kill the fungus, but do inhibit polar growth. Elongation of hyphal tips is abrogated due to zinc starvation, likely a consequence of the zinc-chelating, NETs-associated protein calprotectin. NK cells alone are also incapable of fungicidal activity, but their release of IFN-γ upon contact with A. fumigatus abrogates hyphal growth by a yet unknown mechanism. In vitro studies of the innate immune response, though helpful, are far from representative of the in vivo response. Neither NETs nor IFN-γ alone can manage Aspergillus infection, but in combination, these and other immune assaults certainly can. The difficulty lies in identifying the precise combination of immune cells and cytokine milieu that in a healthy individual prevent infection. Additionally, we explored mechanisms by which the fungus responds to stress, namely the HOG MAPK pathway, historically involved in osmotic stress response. In filamentous fungi, certain stress signals are sensed by a cytoplasmic hybrid histidine kinase sensor and then passed through the HOG system via phosphorylation. We identified the putative hybrid sensor kinase in A. fumigatus, and generated a corresponding knockout mutant. The ΔtcsC mutant was indeed sensitive to osmotic stress, and resistant to the phenolpyrrole fungicide fludioxonil. In the wild type the addition of either osmotic stress or fludioxonil resulted in SakA phosphorylation and translocation to the nucleus. SakA, the Hog1 homolog in A. fumigatus, is located at the end of the HOG pathway, confirming the role of TcsC as the cytoplasmic sensor upstream of SakA. In hypoxia, on farnesol, and in high concentrations of divalent cations the ΔtcsC mutant exhibited a striking “fluffy” phenotype characterized by the production of tremendous aerial hyphae and little or no differentiation, i.e., no conidiation. Though the ΔtcsC mutant showed no change in virulence compared to wild type, components of the TcsC signalling pathway remain promising targets for antifungal agents

    The asymptotically flat scalar-flat Yamabe problem with boundary

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    We consider two cases of the asymptotically flat scalar-flat Yamabe problem on a non-compact manifold with boundary, in dimension n3n\geq3. First, following arguments of Cantor and Brill in the compact case, we show that given an asymptotically flat metric gg, there is a conformally equivalent asymptotically flat scalar-flat metric that agrees with gg on the boundary. We then replace the metric boundary condition with a condition on the mean curvature: Given a function ff on the boundary that is not too large, we show that there is an asymptotically flat scalar-flat metric, conformally equivalent to gg whose boundary mean curvature is given by ff. The latter case involves solving an elliptic PDE with critical exponent using the method of sub- and supersolutions. Both results require the usual assumption that the Sobolev quotient is positive.Comment: 10 page

    First Law of Black Hole Mechanics as a Condition for Stationarity

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    In earlier work [arXiv:1302.1237], we provided a Hilbert manifold structure for the phase space for the Einstein-Yang-Mills equations, and used this to prove a condition for initial data to be stationary. Here we use the same phase space to consider the evolution of initial data exterior to some closed 2-surface boundary, and establish a condition for stationarity in this case. It is shown that the differential relationship given in the first law of black hole mechanics is exactly the condition required for the initial data to be stationary; this was first argued non-rigorously by Sudarsky and Wald in 1992. Furthermore, we give evidence to suggest that if this differential relationship holds then the boundary surface is the bifurcation surface of a bifurcate Killing horizon.Comment: 20 page

    A note on mass-minimising extensions

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    A conjecture related to the Bartnik quasilocal mass, is that the infimum of the ADM energy, over an appropriate space of extensions to a compact 3-manifold with boundary, is realised by a static metric. It was shown by Corvino [Comm. Math. Phys. 214(1), (2000)] that if the infimum is indeed achieved, then it is achieved by a static metric; however, the more difficult question of whether or not the infimum is achieved, is still an open problem. Bartnik [Comm. Anal. Geom. 13(5), (2005)] then proved that critical points of the ADM mass, over the space of solutions to the Einstein constraints on an asymptotically flat manifold without boundary, correspond to stationary solutions. In that article, he stated that it should be possible to use a similar construction to provide a more natural proof of Corvino's result. In the first part of this note, we discuss the required modifications to Bartnik's argument to adapt it to include a boundary. Assuming that certain results concerning a Hilbert manifold structure for the space of solutions carry over to the case considered here, we then demonstrate how Bartnik's proof can be modified to consider the simpler case of scalar-flat extensions and obtain Corvino's result. In the second part of this note, we consider a space of extensions in a fixed conformal class. Sufficient conditions are given to ensure that the infimum is realised within this class.Comment: 17 pages. Substantial changes to Section 3. Updated to agree with published versio

    The Phase Space for the Einstein-Yang-Mills Equations and the First Law of Black Hole Thermodynamics

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    We use the techniques of Bartnik (2005) to show that the space of solutions to the Einstein-Yang-Mills constraint equations on an asymptotically at manifold with one end and zero boundary components, has a Hilbert manifold structure; the Einstein-Maxwell system can be considered as a special case. This is equivalent to the property of linearisation stability, which was studied in depth throughout the 70s. This framework allows us to prove a conjecture of Sudarsky and Wald (1992), that is, the validity of the first law of black hole thermodynamics is a suitable condition for stationarity. Since we work with a single end and no boundary conditions, this is equivalent to critical points of the ADM mass subject to variations fixing the Yang-Mills charge corresponding exactly to stationary solutions. The natural extension to this work is to prove the second conjecture of Sudarsky and Wald, which is the case where an interior boundary is present; this will be addressed in future work.Comment: 21 pages; references added. v3: typos corrected, minor formatting changes. To appear in ATMP, 18(4

    Race, Gender, Sexuality, Ability, Identity and Cycling, Blog 5

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    Student blog posts from the Great VCU Bike Race Book
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