1,241,775 research outputs found

    Bonehead Non-Proliferation

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    The Review and Extension Conference of the Non-Proliferation Treaty (NPT) will convene in 1995. The primary issue to be considered at the Extension Conference is whether the NPT, universally regarded as the most important bulwark against the spread of nuclear weaponry, should remain in force. In this article, David A. Koplow argues that the United States must negotiate a Comprehensive Test Ban Treaty (CTBT) in order to maintain the non-proliferation regime and promote its own long-run security interest

    Applications of hydrodynamic models for modeling drifting jellyfish blooms around the Maltese Islands

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    Within the ambit of the MED-JELLYRISK project, the IOI-Malta Operational Centre is coordinating the development of a jellyfish dispersion model capable of generating both a hindcast and a forecast (extending up to a maximum of 4 days following day of sighting) output for the dispersion trajectory taken by a jellyfish bloom of specified densities and sighted at a specified location. The numerical tool is based on a high resolution hydrodynamic finite element coastal ocean model (SHYFEM) coupled with a particles tracking lagrangian model for reproducing both the surface water circulation and the transport and diffusion of numerical particles inside the area of interest. The coastal model is nested into an Open Ocean sub-regional 3D hydrodynamic model (ROSARIO), having a resolution of 1/640 and which reproduces daily the 3D hydrodynamic fields needed for predicting the fate of released numerical particles. The model domain was reproduced by means of a finite element mesh that was designed to accurately reproduce both the bathymetric features and the complex geometry of the Maltese archipelago coastlines. The system will be integrated into a Graphical User Interface (GUI) which will allow the user to define the position in time and space of a hypothetical bloom found in the Maltese waters, to select the amount of particles to simulate the jellyfish biomass and to launch the trajectory model run. The model will be partly validated by using the trajectories followed by a series of open water and coastal water drifters whose dispersion is geo-referenced and which have been regularly released by the IOI-MOC within Maltese coastal waters.peer-reviewe

    Countering CBW Proliferation

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    No alternative to proliferation

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    We reflect on the nature, role and limits of non-empirical theory assessment in fundamental physics, focusing in particular on quantum gravity. We argue for the usefulness and, to some extent, necessity of non-empirical theory assessment, but also examine critically its dangers. We conclude that the principle of proliferation of theories is not only at the very root of theory assessment but all the more necessary when experimental tests are scarce, and also that, in the same situation, it represents the only medicine against the degeneration of scientific research programmes.Comment: 15 pages; contribution to the volume "Why trust a theory?", edited by: R. Dardashti, R. Dawid, K. Thebault, to be published by Cambridge University Pres

    Pmp27 Promotes Peroxisomal Proliferation

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    Peroxisomes perform many essential functions in eukaryotic cells. The weight of evidence indicates that these organelles divide by budding from preexisting peroxisomes. This process is not understood at the molecular level. Peroxisomal proliferation can be induced in Saccharomyces cerevisiae by oleate. This growth substrate is metabolized by peroxisomal enzymes. We have identified a protein, Pmp27, that promotes peroxisomal proliferation. This protein, previously termed Pmp24, was purified from peroxisomal membranes, and the corresponding gene, PMP27, was isolated and sequenced. Prop27 shares sequence similarity with the Pmp30 family in Candida boidinii. Pmp27 is a hydrophobic peroxisomal membrane protein but it can be extracted by high pH, suggesting that it does not fully span the bilayer. Its expression is regulated by oleate. The function of Pmp27 was probed by observing the phenotype of strains in which the protein was eliminated by gene disruption or overproduced by expression from a multicopy plasmid. The strain containing the disruption (3B) was able to grow on all carbon sources tested, including oleate, although growth on oleate, glycerol, and acetate was slower than wild type. Strain 3B contained peroxisomes with all of the enzymes of β-oxidation. However, in addition to the presence of a few modestly sized peroxisomes seen in a typical thin section of a cell growing on oleate-containing medium, cells of strain 3B also contained one or two very large peroxisomes. In contrast, cells in a strain in which Pmp27 was overexpressed contained an increased number of normal-sized peroxisomes. We suggest that Pmp27 promotes peroxisomal proliferation by participating in peroxisomal elongation or fission.

    Proliferation Resistant Reprocessing Methods

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    Induction of endothelial cell proliferation by recombinant and microparticle-tissue factor involves β1-integrin and extracellular signal regulated kinase activation

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    Objective: Increased levels of circulating tissue factor (TF) in the form of microparticles increase the risk of thrombosis. However, any direct influence of microparticle-associated TF on vascular endothelial cell proliferation is not known. In this study, the influence of recombinant and microparticle- associated TF on endothelial cell proliferation and mitogen-activated protein kinase signaling mechanisms was examined. Methods and Results: Incubation of human coronary artery endothelial cells with lipidated recombinant full-length TF, or TF-containing microparticles (50 to 200 pmol/L TF), increased the rate of cell proliferation and induced phosphorylation of extracellular signal regulated kinase 1 in a TF-dependent manner. Inhibition of extracellular signal regulated kinase 1/2 using PD98059 or extracellular signal regulated kinase 1/2 antisense oligonucleotides or inhibition of c-Jun N-terminal kinase reduced recombinant TF-mediated cell proliferation. PD98059 also reduced cell proliferation in response to TF-containing microparticles. Inclusion of FVIIa (5 nmol/L) and FXa (10 nmol/L) or preincubation of cells with an inhibitory anti-FVIIa antibody had no additional influence on TF-mediated cell proliferation. However, preincubation of exogenous TF with a β1-integrin peptide (amino acids 579 to 799) reduced TF-mediated proliferation. Conclusion: High concentrations of recombinant or microparticle-associated TF stimulate endothelial cell proliferation through activation of the extracellular signal regulated kinase 1/2 pathway, mediated through a novel mechanism requiring the interaction of exogenous TF with cell surface β1-integrin and independent of FVIIa. © 2010 American Heart Association, Inc

    Stat3/Cdc25a-dependent cell proliferation promotes embryonic axis extension during zebrafish gastrulation

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    Cell proliferation has generally been considered dispensable for anteroposterior extension of embryonic axis during vertebrate gastrulation. Signal transducer and activator of transcription 3 (Stat3), a conserved controller of cell proliferation, survival and regeneration, is associated with human scoliosis, cancer and Hyper IgE Syndrome. Zebrafish Stat3 was proposed to govern convergence and extension gastrulation movements in part by promoting Wnt/Planar Cell Polarity (PCP) signaling, a conserved regulator of mediolaterally polarized cell behaviors. Here, using zebrafish stat3 null mutants and pharmacological tools, we demonstrate that cell proliferation contributes to anteroposterior embryonic axis extension. Zebrafish embryos lacking maternal and zygotic Stat3 expression exhibit normal convergence movements and planar cell polarity signaling, but transient axis elongation defect due to insufficient number of cells resulting largely from reduced cell proliferation and increased apoptosis. Pharmacologic inhibition of cell proliferation during gastrulation phenocopied axis elongation defects. Stat3 regulates cell proliferation and axis extension in part via upregulation of Cdc25a expression during oogenesis. Accordingly, restoring Cdc25a expression in stat3 mutants partially suppressed cell proliferation and gastrulation defects. During later development, stat3 mutant zebrafish exhibit stunted growth, scoliosis, excessive inflammation, and fail to thrive, affording a genetic tool to study Stat3 function in vertebrate development, regeneration, and disease

    Functional Integration of Ecological Networks through Pathway Proliferation

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    Large-scale structural patterns commonly occur in network models of complex systems including a skewed node degree distribution and small-world topology. These patterns suggest common organizational constraints and similar functional consequences. Here, we investigate a structural pattern termed pathway proliferation. Previous research enumerating pathways that link species determined that as pathway length increases, the number of pathways tends to increase without bound. We hypothesize that this pathway proliferation influences the flow of energy, matter, and information in ecosystems. In this paper, we clarify the pathway proliferation concept, introduce a measure of the node--node proliferation rate, describe factors influencing the rate, and characterize it in 17 large empirical food-webs. During this investigation, we uncovered a modular organization within these systems. Over half of the food-webs were composed of one or more subgroups that were strongly connected internally, but weakly connected to the rest of the system. Further, these modules had distinct proliferation rates. We conclude that pathway proliferation in ecological networks reveals subgroups of species that will be functionally integrated through cyclic indirect effects.Comment: 29 pages, 2 figures, 3 tables, Submitted to Journal of Theoretical Biolog
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