103,471 research outputs found

    Potential benefits and risks of clinical xenotransplantation

    Get PDF
    The transplantation of organs and cells from pigs into humans could overcome the critical and continuing problem of the lack of availability of deceased human organs and cells for clinical transplantation. Developments in the genetic engineering of pigs have enabled considerable progress to be made in the experimental laboratory in overcoming the immune barriers to successful xenotransplantation. With regard to pig organ xenotransplantation, antibody- and cell-mediated rejection have largely been overcome, and the current major barrier is the development of coagulation dysregulation. This is believed to be due to a combination of immune activation of the vascular endothelial cells of the graft and molecular incompatibilities between the pig and primate coagulation-anticoagulation systems. Pigs with new genetic modifications specifically directed to this problem are now becoming available. With regard to less complex tissues, such as islets (for the treatment of diabetes), neuronal cells (for the treatment of Parkinson's disease), and corneas, the remaining barriers are less problematic, and graft survival in nonhuman primate models extends for > 1 year in all three cases. In planning the initial clinical trials, consideration will be concentrated on the risk-benefit ratio, based to a large extent on the results of preclinical studies in nonhuman primates. If the benefit to the patient is anticipated to be high, eg, insulin-independent control of glycemia, and the potential risks low, eg, minimal risk of transfer of a porcine infectious agent, then a clinical trial would be justified. © 2012 Cooper and Ayares, publisher and licensee Dove Medical Press Ltd

    Operation of a forced circulation, haynes alloy no. 25, mercury loop to study corrosion product separation techniques

    Get PDF
    Forced circulation, Haynes alloy 25, mercury loop to study corrosion product separatio

    Prediction of acidification and recovery on a landscape scale. Progress report 26.9.97

    Get PDF

    New England reservoir management

    Get PDF
    There are no author-identified significant results in this report

    Finite-volume Hyperbolic 3-Manifolds contain immersed Quasi-Fuchsian surfaces

    Full text link
    The paper contains a new proof that a complete, non-compact hyperbolic 33-manifold MM with finite volume contains an immersed, closed, quasi-Fuchsian surface.Comment: Final version to appear in AGT. Some typos corrected, particularly def (3.6). Rewording of 4 paragraphs in proof of (4.2) for added clarity. Final section added comparing this paper to the approach of Masters and Zhan

    Inhibition and young children's performance on the Tower of London task

    Get PDF
    Young children, when performing problem solving tasks, show a tendency to break task rules and produce incomplete solutions. We propose that this tendency can be explained by understanding problem solving within the context of the development of “executive functions” – general cognitive control functions, which serve to regulate the operation of the cognitive system. This proposal is supported by the construction of two computational models that simulate separately the performance of 3–4 year old and 5–6 year old children on the Tower of London planning task. We seek in particular to capture the emerging role of inhibition in the older group. The basic framework within which the models are developed is derived from Fox and Das’ Domino model [Fox, J., & Das, S. (2000). Safe and sound: Artificial intelligence in hazardous applications. Cambridge, MA: MIT Press] and Norman and Shallice’s [Norman, D.A., & Shallice, T. (1986). Attention to action: Willed and automatic control of behaviour. In R. Davidson, G. Schwartz, & D. Shapiro (Eds.), Consciousness and Self Regulation (Vol. 4). New York: Plenum] theory of willed and automatic action. Two strategies and a simple perceptual bias are implemented within the models and comparisons between model and child performance reveal a good fit for the key dependent measures (number of rule breaks and percentage of incomplete solutions) of the two groups
    corecore